Separation of Hydrogen Isotopes
H o w a r d K . Rae,
EDITOR
Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.fw001
Atomic Energy of Canada, Limited
A symposium co-sponsored by the
Physical Chemistry Division of the
Chemical Institute of Canada and
the Canadian Society for Chemical
Engineering at the 2nd Joint
Conference of the Chemical Institute
of Canada and the American
Chemical Society, Montreal,
May 30-June 1,
1977.
ACS SYMPOSIUM SERIES 68
AMERICAN
CHEMICAL
WASHINGTON, D. C.
SOCIETY
1978
In Separation of Hydrogen Isotopes; Rae, H.;
ACS Symposium Series; American Chemical Society: Washington, DC, 1978.
Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.fw001
Library of Congress CIP Data
Main entry under title:
Separation of hydrogen isotopes.
(ACS symposium series; 68 ISSN 0097-6156)
Includes bibliographies and index.
1. Deuterium oxide—Congresses. 2. Hydrogen—Isotopes—Congresses. 3. Isotope separation—Congresses. 4.
Heavy water reactors—Congresses.
I. Rae, Howard K . , 1925. II. Chemical Institute
of Canada. Physical Chemistry Division. III. Canadian
Society for Chemical Engineering. IV. Series: American
Chemical Society. ACS symposium series; 68.
TK9350.S46
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In Separation of Hydrogen Isotopes; Rae, H.;
ACS Symposium Series; American Chemical Society: Washington, DC, 1978.
ACS Symposium Series
Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.fw001
Robert F. G o u l d , Editor
Advisory Board
Kenneth B. Bischoff
Nina I. McClelland
Donald G. Crosby
John B. Pfeiffer
Jeremiah P. Freeman
Joseph V. Rodricks
E. Desmond Goddard
F. Sherwood Rowland
Jack Halpern
Alan C. Sartorelli
Robert A. Hofstader
Raymond B. Seymour
James P. Lodge
Roy L. Whistler
John L. Margrave
Aaron Wold
In Separation of Hydrogen Isotopes; Rae, H.;
ACS Symposium Series; American Chemical Society: Washington, DC, 1978.
Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.fw001
FOREWORD
The ACS SYMPOSIUM SERIES was founded in 1974 to provide
a medium for publishing symposia quickly in book form. The
format of the SERIES parallels that of the continuing ADVANCES
IN CHEMISTRY SERIES except that in order to save time the
papers are not typeset but are reproduced as they are submitted by the authors in camera-ready form. As a further
means of saving time, the papers are not edited or reviewed
except by the symposium chairman, who becomes editor of
the book. Papers published in the ACS SYMPOSIUM SERIES
are original contributions not published elsewhere in whole or
major part and include reports of research as well as reviews
since symposia may embrace both types of presentation.
In Separation of Hydrogen Isotopes; Rae, H.;
ACS Symposium Series; American Chemical Society: Washington, DC, 1978.
Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.pr001
PREFACE
'"phis volume describes process development and plant performance
-•- for the separation of deuterium from hydrogen, tritium from hydrogen, and tritium from deuterium. All of the important processes that
are recognized today are included although not necessarily in equal
detail or appropriate relative emphasis. Nonetheless, this volume forms
a valuable, up-to-date report on the status of hydrogen isotope separation.
Obviously heavy water production is essential to a program of
nuclear power production that is based on natural uranium-fueled and
heavy water-moderated reactors. Canada and India have selected this
route to nuclear power, and both are establishing an industrial heavy
water production capability.
The Canadian design of a heavy water power reactor, the C A N D U
design, requires 0.85 Mg of heavy water per electrical M W of installed
capacity. The heavy water is not consumed by reactor operation so that
the demand for heavy water is set by the rate at which new nuclear
power stations are built. A small make-up of less than 1% of the inventory per year is needed to replace losses by leakage.
With 4000 M W of nuclear-electric generating capacity in operation
and with 15,000 M W committed for operation by 1988, Canada has a
very substantial demand for heavy water. Several large production plants
are in operation and more are being built. Thus, it is not surprising that
one-half of the papers in this volume are from Canada; the chapters
report on plant performance and on the development of alternative
processes to the established water-hydrogen-sulfide exchange method.
Tritium is produced by neutron capture in deuterium and by uranium fission. Thus, heavy water in reactors contains a gradually increasing concentration of T D O , and aqueous wastes from any water-cooled
reactor and from fuel reprocessing contain T H O . Tritium recovery from
these sources is desirable to minimize the release of tritium to the biosphere, and such tritium separation plants will become increasingly
common. Tritium separation on a much larger scale will be necessary
when fusion reactors are developed successfully.
Atomic Energy of Canada, Limited
Ontario, Canada
December, 1977
HOWARD K . R A E
vii
In Separation of Hydrogen Isotopes; Rae, H.;
ACS Symposium Series; American Chemical Society: Washington, DC, 1978.
1
Selecting Heavy Water Processes
H . K . RAE
Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch001
Chalk River Nuclear Laboratories, Atomic Energy of Canada Ltd.,
Chalk River, Ontario, Canada K0J 1J0
Hundreds o f methods have been proposed f o r the p r o d u c t i o n o f
heavy water, b u t o n l y a few show any real promise. This paper
will
d i s c u s s the important
characteristics
which define
relative
process a t t r a c t i v e n e s s and will compare s e v e r a l chemical exchange
and
distillation
processes.
In this way it will show why the GS
( G i r d l e r - S u l f i d e ) process has dominated heavy water p r o d u c t i o n
f o r 25 y e a r s .
I t will a l s o review the c u r r e n t s t a t u s o f s e v e r a l
promising
alternatives.
A brief review o f heavy water process development and heavy
water p r o d u c t i o n will s e t the background. Deuterium was first
separated by the fractional e v a p o r a t i o n o f hydrogen in 1932 by
Urey, Brickwedde and Murphy (1). Over the next few years water
electrolysis,
water
distillation
and hydrogen
distillation
were
i n v e s t i g a t e d as hydrogen-deuterium s e p a r a t i o n methods. During
World War II in the USA, and t o l e s s e r extent in Germany, there
was a very l a r g e e f f o r t t o evaluate and develop methods f o r heavy
water p r o d u c t i o n ( 2 , 3 ) . Two p r o m i s i n g chemical exchange p r o ­
cesses were defined—water-hydrogen and w a t e r - h y d r o g e n - s u l f i d e .
The former was the b a s i s o f the first heavy water p r o d u c t i o n a t a
reasonable c o s t from industrial s c a l e p l a n t s . The latter eventu­
ally became known as the GS p r o c e s s , and the b a s i s o f all l a r g e
heavy water p l a n t s .
Throughout the f i f t i e s and the s i x t i e s hundreds o f methods
were c o n s i d e r e d , dozens were i n v e s t i g a t e d in the l a b o r a t o r y and
in p i l o t p l a n t s , but o n l y a handful were used in p r o d u c t i o n (4_) .
Major research and development to i n v e s t i g a t e heavy water p r o ­
cesses (A) was done in n e a r l y a l l the c o u n t r i e s t h a t b u i l t p r o t o ­
type heavy water power r e a c t o r s : Canada, F r a n c e , Germany, I n d i a ,
I t a l y , Sweden, S w i t z e r l a n d and U n i t e d Kingdom.
Despite this l a r g e e f f o r t i n v o l v i n g hundreds o f man-years by
chemists, p h y s i c i s t s and e n g i n e e r s , no other method has reached
the stage where it can challenge the GS process as the major
source o f heavy water.
©
0-8412-0420-9/78/47-068-001$10.00/0
In Separation of Hydrogen Isotopes; Rae, H.;
ACS Symposium Series; American Chemical Society: Washington, DC, 1978.
2
SEPARATION O F
HYDROGEN
ISOTOPES
Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch001
Heavy Water Plants
So f a r p l a n t o p e r a t i n g experience has been obtained with
f i v e processes, as shown in Table I.
Monothermal water-vapour-hydrogen exchange, with the
e n r i c h e d hydrogen r e f l u x p r o v i d e d by e l e c t r o l y s i s , was used a t
T r a i l in Canada (5) and in Norway (5); the l a t t e r p l a n t i s s t i l l
in o p e r a t i o n . An improved v e r s i o n o f this process using exchange
with l i q u i d water i s d e s c r i b e d by Hammerli (<S) and r e f e r r e d to as
combined e l e c t r o l y s i s and chemical exchange (CECE). The o r i g i n a l
p l a n t in Norway simply used e l e c t r o l y s i s to produce heavy water.
Water-hydrogen exchange u n i t s were being added to the p l a n t in
1943 d u r i n g the German occupation o f Norway when it was destroyed
by A l l i e d r a i d s ; the p l a n t was r e b u i l t and expanded a f t e r the
war.
Water
distillation
was used as a p r o d u c t i o n method b r i e f l y
in three s m a l l p l a n t s during World War II
(2).
In the USA in 1950 there was a need f o r a l a r g e heavy water
p r o d u c t i o n c a p a c i t y and the GS process was chosen as the p r e f e r red method (7). Two 500 Mg/a p l a n t s were b u i l t .
One t h i r d of
the Savannah R i v e r p l a n t i s s t i l l o p e r a t i n g a f t e r twenty-five
y e a r s . The GS process was adopted in Canada in the m i d - s i x t i e s
to supply the CANDU* power r e a c t o r program. Current o p e r a t i n g
c a p a c i t y in Canada i s 1600 Mg/a in three p l a n t s and three more
are being b u i l t (8). In I n d i a a 100 Mg/a GS p l a n t i s a t an
advanced stage o f c o n s t r u c t i o n .
F i v e small hydrogen
distillation
p l a n t s have been operated.
The p l a n t in I n d i a , of 13 Mg/a c a p a c i t y , continues in o p e r a t i o n
(9).
The s i z e of the Russian p l a n t has not been reported; it
a l s o probably continues in o p e r a t i o n .
A 25 Mg/a ammonia-hydrogen p l a n t operated f o r s e v e r a l years
in France (10) . The first o f three Indian ammonia-hydrogen
p l a n t s , each about 65 Mg/a,
(11,12) i s being commissioned.
Heavy Water Production
The cumulative world production o f heavy water to May
1977
i s 11 Gg (excluding USSR and China). This i s d i s t r i b u t e d by
process as f o l l o w s : GS - 93.2%, H2O/H2 exchange - 4.4%,
H D i s t i l l a t i o n - 1.3%, NH /H exchange - 0.9% and H 0 D i s t i l l a t i o n - 0.2%.
By country, 59% has been produced in the USA, 35%
in Canada, 4% in Norway, 1% in India and 1% in France.
By about 1982 the Canadian heavy water p r o d u c t i o n c a p a c i t y
will be 4000 Mg/a.
This will c o n s i s t o f the three o p e r a t i n g
p l a n t s — P o r t Hawkesbury in Nova S c o t i a with a nominal design
c a p a c i t y o f 400 Mg/a, Bruce A in Ontario o f 800 Mg/a and Glace
Bay in Nova S c o t i a o f 400 Mg/a—and three p l a n t s now being b u i l t 2
3
2
2
*Canada Deuterium Uranium
In Separation of Hydrogen Isotopes; Rae, H.;
ACS Symposium Series; American Chemical Society: Washington, DC, 1978.
1.
RAE
Selecting
Heavy
Water
3
Processes
B r u c e Β a n d D, e a c h o f 800 Mg/a n o m i n a l c a p a c i t y , a n d L a P r a d e in
Quebec o f 800 Mg/a.
T h i s c a p a c i t y i s e x p e c t e d t o meet demands
u n t i l a b o u t 1990
(8).
Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch001
General Process
Characteristics
Before c o n s i d e r i n g the v a r i o u s i n d i v i d u a l processes and
c o m p a r i n g t h e i r c h a r a c t e r i s t i c s , it i s i m p o r t a n t t o l o o k a t t h e
g e n e r a l nature o f the deuterium-hydrogen s e p a r a t i o n problem which
d e r i v e s from the low d e u t e r i u m c o n t e n t o f a l l p o t e n t i a l s o u r c e
materials.
The c o n s e q u e n c e s o f this f o r a n y p r o c e s s c a n be
r e a d i l y s e e n in t e r m s o f i t s a f f e c t o n t h e d e s i g n o f GS h e a v y
water p l a n t s .
T h i s v e r y l o w v a l u e o f t h e d e u t e r i u m - t o - h y d r o g e n r a t i o in
n a t u r e *of a b o u t 150 ppm i s t h e m a i n f a c t o r r e s p o n s i b l e f o r t h e
h i g h c o s t o f heavy water.
I t i s necessary t o process a t l e a s t
8000 m o i s o f f e e d p e r m o l o f p r o d u c t f o r a l l p r o c e s s e s , a n d f o r
t h e GS p r o c e s s t h e r a t i o o f f e e d t o p r o d u c t i s n e a r l y 40,000 t o 1.
R e a c t o r g r a d e h e a v y w a t e r i s 99.75 m o l % D2O.
Thus, the o v e r ­
a l l c o n c e n t r a t i o n r a t i o from feed t o p r o d u c t i s about 3 x l O .
T h i s means t h a t h u n d r e d s o f s e p a r a t i v e e l e m e n t s in s e r i e s a r e
n e e d e d t o go f r o m n a t u r a l w a t e r t o r e a c t o r g r a d e h e a v y w a t e r .
The c o m b i n a t i o n o f a v e r y l a r g e f e e d f l o w a n d a v e r y l a r g e
number o f s e p a r a t i v e e l e m e n t s means t h a t h e a v y w a t e r p l a n t s a r e
v e r y l a r g e in r e l a t i o n t o most o t h e r c h e m i c a l p l a n t s . A s a
consequence heavy water i s an e x t r e m e l y c a p i t a l i n t e n s i v e p r o d u c t .
F i g u r e 1 shows t h e G l a c e Bay Heavy Water P l a n t .
The first s t a g e
t o w e r s a r e a b o u t 7 m in d i a m e t e r a n d 60 m h i g h . F e e d w a t e r goes
t o s i x o f t h e s e t o w e r s in p a r a l l e l a t a t o t a l f l o w r a t e o f a b o u t
40,000 m /d ( 1 0 US g a l l o n s / d a y ) . T o t a l h e a t r e j e c t i o n b y t h e
p l a n t i s 300 t h e r m a l MW, m a i n l y b y c o o l i n g t o w e r s a t t h e r i g h t o f
the photograph.
The e f f l u e n t w a t e r i s c o o l e d b y s p r a y m o d u l e s in
the e f f l u e n t channel a t the l e f t o f the photograph.
The c o m b i n a t i o n o f a d i l u t e f e e d a n d a l a r g e o v e r a l l c o n c e n ­
t r a t i o n r a t i o means t h a t c a s c a d i n g c o n f e r s v e r y i m p o r t a n t a d v a n ­
tages. F i g u r e 2 i l l u s t r a t e s three cascade arrangements f o r a
t y p i c a l GS p r o c e s s d e s i g n . I n e a c h c a s e t h e p r o d u c t i s 2 0 % D2O.
I n t h e t w o - s t a g e a r r a n g e m e n t t h e first s t a g e g i v e s a t e n - f o l d
enrichment.
I n the t h r e e - s t a g e arrangement the
first
stage gives
a f o u r - f o l d enrichment w h i l e the second stage p r o v i d e s a f u r t h e r
s i x - f o l d enrichment.
The r e l a t i v e t o w e r v o l u m e s show a 30%
decrease f o r the two-stage case and a f u r t h e r 10% r e d u c t i o n f o r
t h e t h r e e - s t a g e c a s e . The change in h e a v y w a t e r i n v e n t o r y i s
more d r a m a t i c .
I n the s i n g l e stage case the i n v e n t o r y approaches
t h e a n n u a l p l a n t c a p a c i t y . F o r two s t a g e s this i s r e d u c e d b y a n
o r d e r o f magnitude and f o r t h r e e stages i s reduced f u r t h e r by a
f a c t o r o f two.
A d d i n g more s t a g e s i s n o t w o r t h w h i l e s i n c e e a c h
s t a g e adds e x t r a e q u i p m e n t a n d i n c r e a s e s p l a n t c o m p l e x i t y .
I n a l l c a s e s t h e first s t a g e d o m i n a t e s p l a n t c o s t s .
Thus,
when c o m p a r i n g p r o c e s s e s it i s g e n e r a l l y o n l y
this
first
stage
6
3
7
In Separation of Hydrogen Isotopes; Rae, H.;
ACS Symposium Series; American Chemical Society: Washington, DC, 1978.
4
SEPARATION OF HYDROGEN ISOTOPES
Table I
HEAVY WATER PRODUCTION PLANTS
First
Plant
Operating
Capacity
1977
Mg/a
19 34
30
Number o f P l a n t s
Process
H 0/H
2
Country
P
e r a
.
9
l n
Being
Built
NOR.,* CAN
2
H2O D i s t n
Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch001
Shut
Down
GS
H2 D i s t n
USA
1944
USA, CAN, IND
1952
1800
W. GER, RUS
FR, SWIT, IND
1958
>13
NH3/H2
FR,
* electrolysis
1968
IND
o n l y u n t i l 1948.
Figure 1.
Glace Bay heavy water plant
In Separation of Hydrogen Isotopes; Rae, H.;
ACS Symposium Series; American Chemical Society: Washington, DC, 1978.
1.
RAE
Selecting
Heavy
Water
5
Processes
Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch001
t h a t needs t o be c o n s i d e r e d .
F i g u r e 3 i l l u s t r a t e s a t h r e e - s t a g e GS p r o c e s s d e s i g n s h o w i n g
t h e r e l a t i v e m o l a r f l o w r a t e s o f w a t e r a n d h y d r o g e n s u l f i d e in
e a c h s t a g e a n d t h e v a r i o u s i n t e r s t a g e c o n n e c t i o n s . The r e l a t i v e
tower s i z e s a r e a l s o i l l u s t r a t e d .
Because o f t h e v e r y l a r g e
f l o w s r e q u i r e d in t h e first s t a g e it i s n e c e s s a r y t o have s e v e r a l
l a r g e t o w e r s in p a r a l l e l ; t h r e e a r e shown in this e x a m p l e . The
p r o d u c t f r o m t h e t h i r d GS s t a g e i s 2 0 % D2O. I t i s b r o u g h t t o
r e a c t o r grade by water
distillation
w h i c h i s a much s i m p l e r p r o cess o p e r a t i n g a t low p r e s s u r e w i t h a low p o t e n t i a l f o r leakage.
T h i s f i n a l e n r i c h m e n t u n i t r e p r e s e n t s l e s s t h a n 5% o f t h e t o t a l
p l a n t i n v e s t m e n t . N e a r l y a l l h e a v y w a t e r p l a n t s have b e e n
designed w i t h d i f f e r e n t p r o c e s s e s f o r p r i m a r y enrichment and
f i n a l enrichment (13).
Types o f P r o c e s s e s
Table I I i s a p a r t i a l l i s t o f the types o f processes t h a t
have been c o n s i d e r e d f o r heavy w a t e r p r o d u c t i o n .
D i s t i l l a t i o n i s one o f t h e s i m p l e s t .
However, t o w e r volume
i s e x c e s s i v e f o r a l l p o t e n t i a l working substances except hydrogen
itself.
The most p r o m i s i n g p r o c e s s e s a r e b a s e d o n c h e m i c a l e x c h a n g e .
I r r e v e r s i b l e p r o c e s s e s l i k e d i f f u s i o n have h i g h e n e r g y c o s t s
and v e r y l a r g e membrane o r b a r r i e r a r e a s a r e n e e d e d . B o t h e l e c t r o l y s i s and g r a v i t a t i o n a l processes, w h i l e o f f e r i n g f a i r l y h i g h
s e p a r a t i o n f a c t o r s , a r e v e r y e n e r g y i n t e n s i v e a n d f o r this r e a s o n
unattractive.
Adsorption processes are not p a r t i c u l a r l y s e l e c t i v e f o r
deuterium and t h e r e f o r e r e q u i r e v e r y l a r g e volumes o f a d s o r b e n t .
B i o l o g i c a l p r o c e s s e s have t h e same s h o r t c o m i n g s a s a d s o r p t i o n ,
Table I I
POSSIBLE HEAVY WATER PROCESSES
P r o c e s s Type
Distillation
C h e m i c a l Exchange
Diffusion
Electrolysis
Gravitational
Adsorption
Biological
Crystallization
S e l e c t i v e Photochemical
Status
S i z e E x c e s s i v e E x c e p t H2
Most P r o m i s i n g
B a r r i e r o r Membrane C o s t s
E x c e s s i v e ; High Energy
E x c e s s i v e Energy
E x c e s s i v e Energy
H i g h A d s o r b e n t Volume
E x c e s s i v e Volume
I m p r a c t i c a l on Large S c a l e
Promising i f S e l e c t i v i t y
A p p r o a c h e s 10
In Separation of Hydrogen Isotopes; Rae, H.;
ACS Symposium Series; American Chemical Society: Washington, DC, 1978.
Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch001
SEPARATION O F H Y D R O G E N ISOTOPES
SINGLE
STAGE
TWO
STAGES
THREE
STAGES
RELATIVE
TOWER
VOLUME
1
0.7
0.6
RELATIVE
PROCESS
INVENTORY
1
0.12
Figure 2.
0.05
GS process cascades
Figure 3.
GS flowsheet
In Separation of Hydrogen Isotopes; Rae, H.;
ACS Symposium Series; American Chemical Society: Washington, DC, 1978.
1.
RAE
Selecting
Heavy
Water
7
Processes
Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch001
and h e n c e r e q u i r e t h e p r o d u c t i o n o f e x c e s s i v e amounts o f
deuterium-depleted organisms.
C o u n t e r c u r r e n t c r y s t a l i z a t i o n systems ( i c e - w a t e r ) c a n con­
c e i v a b l y h a v e v e r y l a r g e numbers o f s e p a r a t i n g e l e m e n t s in a
r e a s o n a b l e volume a n d h a v e a l o w e n e r g y r e q u i r e m e n t ; h o w e v e r , a
r e a s o n a b l e p r o c e s s i n g r a t e c a n o n l y be a c h i e v e d w i t h an i m practically small crystal size
(14).
S e l e c t i v e photochemical processes are a t too e a r l y a stage
to assess p r o p e r l y .
I f s u c c e s s i s t o be a c h i e v e d f o r d e u t e r i u m hydrogen s e p a r a t i o n , a v e r y h i g h s e l e c t i v i t y i s needed t o o f f s e t
t h e d i s a d v a n t a g e o f t h e low n a t u r a l abundance o f d e u t e r i u m .
The r e m a i n d e r o f t h e p a p e r will r e v i e w
distillation
and
c h e m i c a l e x c h a n g e p r o c e s s e s in more d e t a i l .
Separation Factor
One o f t h e m o s t i m p o r t a n t p a r a m e t e r s in d e f i n i n g t h e
a t t r a c t i v e n e s s o f a process i s the s e p a r a t i o n f a c t o r .
It is
d e f i n e d as
α = (D/H) /(D/H)
Β
A
where A a n d Β a r e e n r i c h e d a n d d e p l e t e d s t r e a m s f r o m a s e p a r a t i n g
d e v i c e , a r e t w o p h a s e s in p h y s i c a l e q u i l i b r i u m , o r a r e two com­
p o u n d s in c h e m i c a l e q u i l i b r i u m .
The s e p a r a t i o n f a c t o r i s f r e q u e n t l y t h e first p a r a m e t e r t o
be d e t e r m i n e d in s t u d y i n g a new h e a v y w a t e r p r o c e s s .
Values
r a n g e f r o m u n i t y (no s e p a r a t i o n ) t o a b o u t 30 (low t e m p e r a t u r e
e l e c t r o l y s i s o f ammonia).
Distillation
T a b l e I I I compares f o u r
distillation
p r o c e s s e s based on
h y d r o g e n , methane, ammonia a n d w a t e r .
I n e a c h c a s e optimum c o n ­
d i t i o n s have been s e l e c t e d .
For water the pressure i s h i g h e r
than i s used f o r f i n a l enrichment.
T h i s i s because the p r o c e s s ,
as o p t i m i z e d f o r p r i m a r y e n r i c h m e n t , i s b a s e d o n v a p o u r recom­
p r e s s i o n t o conserve energy.
The l o w s e p a r a t i o n f a c t o r s f o r t h e
Table I I I
D I S T I L L A T I O N PROCESSES
Temperature
k
Hydrogen
Methane
Ammonia
Water
24
112
2 39
378
Pressure
kPa
250
100
100
120
Separation
Factor
1.5
1.00 35
1.036
1.024
In Separation of Hydrogen Isotopes; Rae, H.;
ACS Symposium Series; American Chemical Society: Washington, DC, 1978.
8
SEPARATION
O F HYDROGEN
ISOTOPES
three substances other than hydrogen are an overwhelming d i s ­
advantage. This can be seen by comparing tower volumes. The
r e l a t i v e tower volume i s p r o p o r t i o n a l t o TP" (ot-1) " m~ f o r a
given gas v e l o c i t y and HETP (height e q u i v a l e n t to a t h e o r e t i c a l
p l a t e ) where Τ i s absolute temperature, Ρ i s pressure, α i s
s e p a r a t i o n f a c t o r and m i s the number o f hydrogen atoms p e r
molecule.
C l e a r l y ( a - l ) ~ dominates this expression. F i g u r e 4
shows this r e l a t i v e tower volume as a f u n c t i o n o f p r e s s u r e .
There i s a three t o four orders o f magnitude d i f f e r e n c e in tower
volume between the compounds o f hydrogen and molecular hydrogen
itself.
The c a p i t a l c o s t a s s o c i a t e d with the former as d i s t i l l a ­
t i o n working substance would be f a r too high f o r these t o be
a t t r a c t i v e heavy water production processes. However, as already
i n d i c a t e d , water
distillation
i s used e x t e n s i v e l y f o r f i n a l en­
richment from a D/H r a t i o o f about 0.1.
Hydrogen
distillation,
on the other hand, i s a p o t e n t i a l l y a t t r a c t i v e process. As will
be d i s c u s s e d l a t e r , it i s c l o s e t o being competitive with the GS
process.
1
2
1
Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch001
2
Chemical Exchange
The GS process i s the archetype o f chemical exchange pro­
cesses. Deuterium i s t r a n s f e r r e d from a water molecule t o a
hydrogen s u l f i d e molecule and v i s a - v e r s a :
H 0 + H D S ^ ± H D O + H S.
2
2
The s e p a r a t i o n f a c t o r i s roughly equal t o the e q u i l i b r i u m con­
s t a n t f o r this r e a c t i o n . At 303 Κ α = 2.33 and a t 403 Κ it i s
1.82.
T h i s d i f f e r e n c e i s the b a s i s o f the b i t h e r m a l concentra­
t i o n process t o be d e s c r i b e d l a t e r .
The l a r g e flows and l a r g e energy input have already been
d i s c u s s e d q u a l i t a t i v e l y . F o r the GS process the feed r a t e p e r
kg D 0 i s 35 Mg and the energy r e q u i r e d per kg D 0 i s 25 GJ o f
thermal energy and 700 kWh o f e l e c t r i c a l energy.
The three other chemical exchange processes d i s c u s s e d in
this paper are water-hydrogen, ammonia-hydrogen and aminehydrogen:
2
2
H 0 + HD ^ HDO + H ,
NH + H D ^ N H D + H ,
CH NH + HD^CH NHD + H .
2
2
3
3
2
2
3
2
2
In each case the gas i s hydrogen and the other component i s the
liquid.
F i g u r e 5 i l l u s t r a t e s the simplest chemical exchange flow­
sheet - that f o r monothermal exchange as used in Norway o r a t
Trail.
The l i q u i d feed i s enriched in deuterium as it flows
down the tower and encounters p r o g r e s s i v e l y r i c h e r gas. A t the
bottom o f the tower the l i q u i d i s t o t a l l y converted t o the gas,
In Separation of Hydrogen Isotopes; Rae, H.;
ACS Symposium Series; American Chemical Society: Washington, DC, 1978.
1.
RAE
Selecting
E
Heavy
10
Water
9
Processes
E
ο- 1 0 ' h
S
10 h
4
<
oc
1
0
AMMONIA
3
Ρ Η , Ο = Pc
D
10
2
Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch001
Q
2
Ο
ÛC
ÛH 0 =1
ONE
ATM -H
10
D
HYDROGEN
OC
0.1
1
10
10
2
10
3
10
4
10
5
PRESSURE, kPa
Figure 4.
Relative tower volume for
Figure 5.
distilhtion
Simple monothermal process
In Separation of Hydrogen Isotopes; Rae, H.;
ACS Symposium Series; American Chemical Society: Washington, DC, 1978.
Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch001
10
SEPARATION OF HYDROGEN ISOTOPES
e x c e p t f o r t h a t f r a c t i o n which forms the f e e d t o h i g h e r s t a g e s
in t h e c a s c a d e .
T h i s phase c o n v e r t e r i s analogous t o a r e b o i l e r
in
distillation.
P h a s e c o n v e r s i o n i s e x p e n s i v e in m o s t e x c h a n g e
systems.
However, w a t e r e l e c t r o l y s i s u s e d f o r c o m m e r c i a l h y d r o gen p r o d u c t i o n c a n be a s p e c i a l c a s e .
Then h e a v y w a t e r r e c o v e r y
becomes a b y p r o d u c t o p e r a t i o n . O t h e r h y d r o g e n p r o d u c t i o n t e c h n i q u e s c a n f u n c t i o n in a s i m i l a r manner ( 1 5 ) .
Ammonia-hydrogen e x c h a n g e i s most r e a d i l y a d a p t e d t o monothermal o p e r a t i o n because the heat o f f o r m a t i o n from hydrogen
and n i t r o g e n i s r e l a t i v e l y l o w .
I n this c a s e ammonia s y n t h e s i s
gas i s t h e d e u t e r i u m s o u r c e , so t h e f e e d i s a g a s .
The ammonia
e x c h a n g e l i q u i d i s n o t o n l y c r a c k e d in t h e p h a s e c o n v e r t e r a t
t h e b o t t o m o f t h e e x c h a n g e c o l u m n as in F i g u r e 5, b u t i s a l s o
s y n t h e s i z e d f o r r e f l u x a t t h e t o p o f t h e c o l u m n - in this f o r m
the monothermal f l o w s h e e t i s c o m p l e t e l y analogous t o a d i s t i l l a t i o n process.
S u c h a m o n o t h e r m a l ammonia-hydrogen e x c h a n g e p r o c e s s was
first
u s e d a t M a z i n g a r b e in F r a n c e and i s t h e b a s i s o f
two p l a n t s in I n d i a ( 1 1 ) .
P r a c t i c a l monothermal p r o c e s s e s a r e u n f o r t u n a t e l y r a r e because phase c o n v e r s i o n i s g e n e r a l l y too complex o r too c o s t l y .
I n s t e a d , t h e b i t h e r m a l a r r a n g e m e n t i s u s e d as i l l u s t r a t e d in
F i g u r e 6 f o r t h e GS p r o c e s s .
The p h a s e c o n v e r t e r o f F i g u r e 5 i s
r e p l a c e d by a h o t t o w e r .
I n this i l l u s t r a t i o n , and in s e v e r a l
o f t h e GS p l a n t s , t h e h o t and c o l d t o w e r s a r e c o m b i n e d in a
single vessel:
t h e y a r e t h e n r e f e r r e d t o as h o t and c o l d t o w e r
sections.
I n t h e GS p r o c e s s t h e w a t e r i s e n r i c h e d in d e u t e r i u m
in t h e c o l d s e c t i o n and i s d e p l e t e d in t h e h o t s e c t i o n .
The
w a t e r c o n t a c t s t h e same gas a t t h e t o p o f t h e c o l d s e c t i o n as a t
t h e b o t t o m o f t h e h o t s e c t i o n , and t h e f l o w s a r e c o n t r o l l e d s o
gas and w a t e r t e n d t o a p p r o a c h e q u i l i b r i u m w i t h e a c h o t h e r a t
t h e s e two l o c a t i o n s .
T h e r e f o r e , the deuterium-to-hydrogen r a t i o
in t h e d e p l e t e d e f f l u e n t w a t e r a p p r o a c h e s a v a l u e e q u a l t o
o t h / o t c (~0.8
f o r t h e GS p r o c e s s ) o f t h a t in t h e f e e d .
The c o u n t e r c u r r e n t gas and w a t e r f l o w s , i f a p p r o p r i a t e l y c o n t r o l l e d a t c l o s e
t o t h e c o r r e c t f l o w r a t i o , c a u s e a n e t t r a n s p o r t o f d e u t e r i u m up
t h e h o t s e c t i o n and down t h e . c o l d s e c t i o n t o p r o v i d e e n r i c h e d gas
and w a t e r a t t h e c e n t r e o f t h e t o w e r .
Here a s m a l l e n r i c h e d
s t r e a m i s f e d f o r w a r d t o a n o t h e r t o w e r w o r k i n g in a h i g h e r c o n c e n t r a t i o n r a n g e (a h i g h e r s t a g e ) and i s m a t c h e d by a p a r t i a l l y
d e p l e t e d r e t u r n i n g stream.
The n e t t r a n s p o r t o f d e u t e r i u m t o
the h i g h e r stage i s c o n t r o l l e d t o equal the e x t r a c t i o n r a t e from
the feed water.
The c o n n e c t i o n b e t w e e n t h e
first
s t a g e and t h e
h i g h e r s t a g e c a n be gas as in F i g u r e 6, o r w a t e r o r b o t h .
The h o t t o w e r o f t h e b i t h e r m a l p r o c e s s c a n be t h o u g h t o f as
a n a l o g o u s t o an i m p e r f e c t r e b o i l e r , and so p r o v i d e s gas t o t h e
c o l d tower a t a c o n s i d e r a b l y lower deuterium c o n c e n t r a t i o n than
i s a c h i e v e d by the phase c o n v e r t e r o f the monothermal p r o c e s s .
As a c o n s e q u e n c e , n o t o n l y does t h e h o t t o w e r and i t s a s s o c i a t e d
h e a t i n g and c o o l i n g e q u i p m e n t o f t h e b i t h e r m a l p r o c e s s r e p l a c e
the phase c o n v e r t e r o f the monothermal p r o c e s s , b u t the
In Separation of Hydrogen Isotopes; Rae, H.;
ACS Symposium Series; American Chemical Society: Washington, DC, 1978.
1.
RAE
Selecting
Heavy
Water
11
Processes
b i t h e r m a l p r o c e s s r e q u i r e s a much l a r g e r c o l d t o w e r .
The m o n o t h e r m a l a n d b i t h e r m a l p r o c e s s a r r a n g e m e n t s a r e com­
p a r e d i n F i g u r e 7 i n t h e f o r m o f M c C a b e - T h i e l e d i a g r a m s . The
e q u i l i b r i u m l i n e s h a v e s l o p e s o f 1/ot.
The o p e r a t i n g l i n e f o r
the monothermal case has a s l o p e o f u n i t y , e q u a l t o t h e l i q u i d to-gas f l o w r a t i o (L/G).
The l a r g e d i v e r g e n c e b e t w e e n t h e
o p e r a t i n g and e q u i l i b r i u m l i n e s a l l o w s a s u b s t a n t i a l enrichment
(e.g. 5 times t h e f e e d c o n c e n t r a t i o n ) t o be reached w i t h o n l y a
few t h e o r e t i c a l t r a y s .
The d i f f e r e n c e i n d e u t e r i u m c o n c e n t r a ­
t i o n b e t w e e n t h e f e e d (F) a n d t h e w a s t e (W), i . e . t h e r e c o v e r y
f r o m t h e f e e d , c a n be l a r g e ; a s a f r a c t i o n i t a p p r o a c h e s
(α-1)/α. F o r t h e b i t h e r m a l c a s e L/G, t h e s l o p e o f t h e o p e r a t i n g
l i n e s , m u s t be b e t w e e n l / a a n d 1/oth. C o n s e q u e n t l y , b o t h h o t
and c o l d c o l u m n s a r e s e v e r e l y p i n c h e d a n d many t h e o r e t i c a l t r a y s
a r e r e q u i r e d f o r t h e same f i v e - f o l d e n r i c h m e n t .
The r e c o v e r y ,
as a l r e a d y n o t e d , i s s m a l l ; l e s s t h a n ( a - a h ) / o t .
Thus, t h e
p e n a l t y f o r c i r c u m v e n t i n g t h e need f o r phase c o n v e r s i o n i s a
l a r g e i n c r e a s e i n f l o w s a n d a n e v e n l a r g e r i n c r e a s e i n column
v o l u m e . N o n e t h e l e s s , b i t h e r m a l i s g e n e r a l l y t h e more a t t r a c t i v e
a r r a n g e m e n t t o s e l e c t b e c a u s e f e a s i b l e r e a c t i o n s f o r a monothermal process a r e r a r e and r e q u i r e l a r g e energy i n p u t s .
A l t h o u g h t h e s i m p l e f l o w s h e e t s d i s c u s s e d so f a r have
l i m i t e d r e c o v e r i e s s e t b y t h e above r e l a t i o n s h i p s , i t i s p o s s i b l e
t o add s t r i p p i n g s e c t i o n s t o t h e process and achieve h i g h r e ­
coveries approaching u n i t y i n the l i m i t .
T h i s means a d d i n g more
c o l u m n volume a s shown i n F i g u r e 8, f o r a g a s - f e d b i t h e r m a l p r o ­
cess.
T h i s i s t h e arrangement o f t h e amine-hydrogen p r o c e s s
w h i c h h a s been s t u d i e d e x t e n s i v e l y b y A t o m i c Energy o f Canada
L i m i t e d ( 1 6 ) . To s t r i p t h e g a s t o a l o w d e u t e r i u m c o n t e n t r e ­
q u i r e s a l i q u i d s u f f i c i e n t l y l e a n i n deuterium.
This i s pro­
d u c e d b y r e c y c l i n g some l e a n g a s t o t h e h o t t o w e r a n d l e n g t h e n i n g
the h o t tower c o r r e s p o n d i n g l y .
I n t h e simple case w i t h o u t
s t r i p p i n g , t h e gas feed would e n t e r t h e bottom o f t h e h o t tower
and n o t r e q u i r e a g a s r e c y c l e . A n o t h e r v e r s i o n o f a g a s - f e d
b i t h e r m a l flowsheet w i t h s t r i p p i n g i s d e s c r i b e d by N i t s c h k e ( 1 2 ) .
F i g u r e 9 d e s c r i b e s the s e p a r a t i o n f a c t o r as a f u n c t i o n o f
temperature f o r t h e f o u r systems b e i n g c o n s i d e r e d .
The l a r g e r
a b s o l u t e v a l u e s f o r t h e hydrogen-based systems a r e e v i d e n t , as
a r e t h e p o s s i b i l i t i e s o f much l a r g e r v a l u e s o f o t / a n .
non-aqueous s y s t e m s c a n r e a c h v e r y l o w t e m p e r a t u r e s w i t h a c o n ­
sequent l a r g e i n c r e a s e i n s e p a r a t i o n f a c t o r .
In this respect
t h e amine s y s t e m (17) i s p a r t i c u l a r l y a t t r a c t i v e .
Relative to
t h e GS s y s t e m , t h e much l a r g e r s e p a r a t i o n f a c t o r s f o r t h e
h y d r o g e n - b a s e d s y s t e m s mean t h a t r e c o v e r i e s a r e h i g h e r , f l o w s
per u n i t product lower and fewer t h e o r e t i c a l t r a y s a r e r e q u i r e d .
A l l these advantages c o u l d l e a d t o s u b s t a n t i a l l y s m a l l e r tower
volume f o r t h e h y d r o g e n - b a s e d p r o c e s s e s , b u t t h i s c a n o n l y b e
a s s e s s e d a f t e r r a t e s o f exchange a r e c o n s i d e r e d which r e l a t e
actual trays to theoretical trays.
Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch001
c
c
c
T
n
c
In Separation of Hydrogen Isotopes; Rae, H.;
ACS Symposium Series; American Chemical Society: Washington, DC, 1978.
e
t
w
o
Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch001
12
SEPARATION OF HYDROGEN ISOTOPES
Figure 6.
Exchange tower with gas feed forward
Figure 7.
McCabe-Thiele
diagrams
In Separation of Hydrogen Isotopes; Rae, H.;
ACS Symposium Series; American Chemical Society: Washington, DC, 1978.
Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch001
1.
RAE
Selecting
Heavy
Figure
ι
ι
Water
8.
Gas-fed bithermal
stripping
I
ι ι
13
Processes
1 1 ι
-
\H -CH
" Η
2
2
- Ν Η ^ Λ
:
>
ι
N
I
process with
I
ι ι ι ι
11 1 1
I
1 1 11
—
2
H
ν
H
2
- H
2
-
0
H
2
S - H
2
0
o°c
1 1 1 1
200
11
250
1 ι
ι I
300
ι
ι ι
ι
1
100°C
I 1 I I I I
350
400
I
I
I
450
TEMPERATURE,°K
Figure 9.
Liquid^gas separation factors
In Separation of Hydrogen Isotopes; Rae, H.;
ACS Symposium Series; American Chemical Society: Washington, DC, 1978.
Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch001
14
SEPARATION O F
HYDROGEN ISOTOPES
Because exchange r a t e s are g e n e r a l l y f a s t a t h o t tower con­
d i t i o n s f o r a l l four processes being c o n s i d e r e d , the important
mass t r a n s f e r and k i n e t i c l i m i t a t i o n s o c c u r i n t h e c o l d t o w e r .
These w i l l now be d i s c u s s e d i n some d e t a i l .
The f i r s t s t e p i n c o m p a r i n g r a t e s o f d e u t e r i u m e x c h a n g e i s
t o d e f i n e p r a c t i c a l p r o c e s s c o n d i t i o n s f o r e a c h s y s t e m , and t h i s
i s done i n T a b l e IV.
B e c a u s e o f t h e low s o l u b i l i t y o f h y d r o g e n ,
g i v e n as t h e r e c i p r o c a l o f H e n r y ' s Law c o n s t a n t i n t h e T a b l e ,
the hydrogen-based processes operate a t high p r e s s u r e .
The
t e m p e r a t u r e r a n g e s a r e p r i m a r i l y d i c t a t e d by v a p o u r p r e s s u r e f o r
t h e u p p e r v a l u e and by a minimum p r a c t i c a l e x c h a n g e r a t e f o r t h e
l o w e r v a l u e . The amine p r o c e s s i s r e s t r i c t e d i n h o t t o w e r
t e m p e r a t u r e by t h e r m a l s t a b i l i t y o f t h e c a t a l y s t (16_). The GS
p r o c e s s i s r e s t r i c t e d i n c o l d t o w e r t e m p e r a t u r e by t h e f o r m a t i o n
of a s o l i d hydrate.
Each o f the hydrogen-based p r o c e s s e s r e ­
q u i r e s a c a t a l y s t - homogeneous f o r t h e non-aqueous o n e s and
heterogeneous for'water-hydrogen.
Even so t h e v a l u e s o f t h e
k i n e t i c r a t e c o n s t a n t s w h i c h can be a c h i e v e d a r e low (18, 1 9 ) .
The v a l u e g i v e n i n T a b l e IV f o r w a t e r - h y d r o g e n i s f o r t h e
c a t a l y s t as a c o l l o i d a l s l u r r y (20) ; h i g h e r e f f e c t i v e r a t e s can
be a c h i e v e d w i t h a f i x e d - b e d c a t a l y s t as w i l l be d i s c u s s e d l a t e r .
F o r the purposes o f comparison exchange r a t e s are e v a l u a t e d
h e r e f o r g a s - l i q u i d c o n t a c t i n g on a s i e v e t r a y , even t h o u g h t h i s
i s n o t t h e most p r a c t i c a l c o l d t o w e r c o n t a c t i n g e q u i p m e n t f o r a l l
four processes.
As i l l u s t r a t e d s c h e m a t i c a l l y i n F i g u r e 10, t h e
gas f l o w s up t h e t o w e r t h r o u g h a m u l t i t u d e o f h o l e s i n e a c h t r a y .
The l i q u i d f l o w s a c r o s s e a c h t r a y , o v e r a w e i r and down t o t h e
n e x t t r a y ; t h e gas p r e s s u r e d r o p a c r o s s a t r a y h o l d s t h e l i q u i d
on t h e t r a y .
Thus, t h e r e i s c o n t i n u o u s , m u l t i - c o n t a c t , c o u n t e r c u r r e n t o p e r a t i o n . The g a s - l i q u i d m i x i n g on e a c h t r a y g e n e r a t e s
a l a r g e i n t e r f a c i a l a r e a b e t w e e n them i n t h e f o r m o f b u b b l e and
d r o p l e t s u r f a c e s . The gas and l i q u i d t h e n must s e p a r a t e b e f o r e
each phase passes t o i t s subsequent t r a y .
Table
IV
CHEMICAL EXCHANGE PROCESSES
GS
7
230
330
2
H 0/H
2
and a p r a c t i c a l v a l u e o f
catalyst
Catalyst
Rate Constant* s"
Gas S o l u b i l i t y * mol/(m .MPa)
*at c o l d tower temperature
concentration.
7
220
315
3
15
10
2
30 3
400
3
NH /H
10
300
440
Pt/C
1
8
P r e s s u r e MPa
Temperature Κ
1
Amine
-
5000
830
CH3NHK
130
24
NH2K
In Separation of Hydrogen Isotopes; Rae, H.;
ACS Symposium Series; American Chemical Society: Washington, DC, 1978.
2
1.
RAE
Selecting
Heavy
Water
15
Processes
I n s i m p l e t e r m s t h e t o w e r volume i s g i v e n b y :
Volume = GRTN/(PK a)
G
where G i s the gas f l o w i n m o l s / s , R i s the gas law c o n s t a n t
(MPa.m /(mol.Κ)), Τ i s t h e t e m p e r a t u r e i n Κ, Ν i s t h e number o f
t h e o r e t i c a l t r a y s , Ρ i s t h e p r e s s u r e i n MPa, K G i s t h e o v e r a l l
mass t r a n s f e r c o e f f i c i e n t i n m/s a n d a i s t h e i n t e r f a c i a l a r e a
p e r u n i t volume ( m / m ) . The o v e r a l l mass t r a n s f e r c o e f f i c i e n t
can be r e l a t e d t o t h e g a s p h a s e mass t r a n s f e r c o e f f i c i e n t , k^,
and t h e l i q u i d p h a s e mass t r a n s f e r c o e f f i c i e n t , k , b y :
3
2
3
Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch001
L
1__
Κ
G
=
1_
k
G
H
k RT
L
3
where H i s t h e H e n r y ' s Law c o n s t a n t (MPa.m /mol).
For a s o l u b l e gas l i k e hydrogen s u l f i d e the v a l u e o f H i s
s m a l l ( T a b l e IV) a n d t h e g a s p h a s e r e s i s t a n c e i s i m p o r t a n t a n d
p o s s i b l y c o n t r o l l i n g . F o r h y d r o g e n H i s l a r g e r b y two o r d e r s o f
magnitude and k g i s a l s o i n c r e a s e d ; t h u s , o n l y the l i q u i d phase
r e s i s t a n c e need be c o n s i d e r e d .
The v a l u e o f k L depends o n b o t h
mass t r a n s f e r a n d c h e m i c a l r e a c t i o n s o t h a t t h e k i n e t i c r a t e
constant, k , enters i n t o i t s determination.
I t i s beyond the scope o f t h i s paper t o t r e a t the e v a l u a t i o n
o f k i n any d e t a i l .
F o l l o w i n g the e x p o s i t i o n o f A s t a r i t a (21),
F i g u r e 11 shows how k L , t h e mass t r a n s f e r c o e f f i c i e n t f o r t h e
l i q u i d phase f o r combined a b s o r p t i o n and c h e m i c a l r e a c t i o n , i s
r e l a t e d t o kg, the l i q u i d phase c o e f f i c i e n t f o r p h y s i c a l ab­
s o r p t i o n w i t h o u t r e a c t i o n , as a f u n c t i o n o f k . I n e x p r e s s i n g
t h i s f u n c t i o n t h e r a t i o o f k / s i s u s e d where s i s t h e f r a c t i o n a l
rate o f surface renewal ( s " ) .
A t y p i c a l value o f s for a sieve
t r a y i s 50 s " .
I f D i s the d i f f u s i v i t y o f the d i s s o l v e d gas
( m / s ) , t h e n k g = (Ds)°« . The p a r a m e t e r i n t h i s f i g u r e ,
e s ° * / a D - , a l l o w s f o r t h e e f f e c t o f t h e volume f r a c t i o n o f
l i q u i d c o n t a i n e d i n t h e t o t a l u n i t v o l u m e , ε, w h i c h i s i m p o r t a n t
i n the slow r e a c t i o n regime.
I n t h e s l o w r e a c t i o n r e g i m e i n F i g u r e 11, t h e e x c h a n g e
r e a c t i o n occurs i n the bulk l i q u i d .
k i s l e s s than k g and
equals ek /a.
I n t h e c a s e o f t h e e j e c t o r c o n t a c t o r (15) where
a i s very l a r g e and s i s l i k e l y a l s o i n c r e a s e d r e l a t i v e t o a
s i e v e t r a y , t h e low v a l u e o f e s ° - / a D - c o u l d b r i n g b o t h t h e
w a t e r - h y d r o g e n a n d t h e ammonia-hydrogen s y s t e m s i n t o t h e s l o w
r e a c t i o n regime.
When k s k g t h e e x c h a n g e r a t e i s c o n t r o l l e d p r i m a r i l y b y
physical absorption.
This i s a t r a n s i t i o n r e g i o n o r the d i f ­
f u s i o n r e g i m e w h e r e k < s . The r e a c t i o n o c c u r s p r i m a r i l y i n t h e
bulk l i q u i d , but s u f f i c i e n t l y r a p i d l y that p h y s i c a l absorption i s
the r a t e c o n t r o l l i n g s t e p .
Both the s l u r r y - c a t a l y z e d w a t e r h y d r o g e n s y s t e m a n d t h e ammonia-hydrogen s y s t e m a r e i n t h i s
r e g i o n f o r c o n t a c t i n g on a s i e v e t r a y .
r
L
r
r
1
1
2
5
5
0
5
L
r
5
0
5
L
r
In Separation of Hydrogen Isotopes; Rae, H.;
ACS Symposium Series; American Chemical Society: Washington, DC, 1978.
16
SEPARATION O F H Y D R O G E N ISOTOPES
Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch001
COLD
SECTION O F E X C H A N G E
WATER
Figure 10.
Figure 11.
TOWER
E N R I C H E D IN D E U T E R I U M
Sieve tray operation
Cold tower mass transfer coefficients
In Separation of Hydrogen Isotopes; Rae, H.;
ACS Symposium Series; American Chemical Society: Washington, DC, 1978.
1.
RAE
Selecting
Heavy
Water
17
Processes
The f a s t r e a c t i o n r e g i m e i n F i g u r e 11 b e g i n s when k > k^,
and c h e m i c a l r e a c t i o n e n h a n c e s t h e mass t r a n s f e r r a t e .
Once
k / s e x c e e d s a b o u t 3, t h e n k]^ i s e q u a l t o ( k D ) - .
Here t h e
r e a c t i o n zone i s l i m i t e d t o f r e s h e l e m e n t s o f l i q u i d b r o u g h t t o
the i n t e r f a c i a l s u r f a c e by t u r b u l e n t e d d i e s ; d i f f u s i o n and
r e a c t i o n o c c u r s i m u l t a n e o u s l y a t the s u r f a c e w h i l e the b u l k
l i q u i d i s a l w a y s a t e q u i l i b r i u m . The a m i n e - h y d r o g e n p r o c e s s i s
c l e a r l y i n t h i s regime.
F o r a n y g i v e n c o n t a c t o r s y s t e m t h e f a s t r e a c t i o n r e g i m e ends
once t h e g a s p h a s e mass t r a n s f e r r a t e b e g i n s t o c o n t r o l ; t h i s i s
t h e i n s t a n t a n e o u s r e a c t i o n r e g i m e . A s shown i n F i g u r e 11 t h e GS
p r o c e s s i s a l m o s t i n t h i s r e g i m e . The v a l u e o f k f o r t h i s
s y s t e m g i v e n i n T a b l e IV i s o n l y a p p r o x i m a t e ; no r e l i a b l e
measurement h a s b e e n made. However, 5000 s " p r o b a b l y i s a
lower l i m i t .
A s d i s c u s s e d above t h e l o w v a l u e o f H f o r t h e
H2O-H2S s y s t e m means t h e g a s p h a s e r e s i s t a n c e must be c o n s i d e r e d
e v e n a t modest v a l u e s f o r k . P i l o t p l a n t d a t a f o r GS s i e v e t r a y
e f f i c i e n c y a r e c o n s i s t e n t w i t h kgH/RTkg e q u a l t o 6. The d o t t e d
l i n e i n F i g u r e 11 r e p r e s e n t s KçH/RTk^ when k H / R T k ° = 6 f o r
v a r i o u s v a l u e s o f k and hence k .
U s i n g t h e d a t a i n T a b l e I V a n d F i g u r e 11, t h e o v e r a l l
v o l u m e t i c mass t r a n s f e r c o e f f i c i e n t s , Kça, a n d t h e t o w e r v o l u m e s
have b e e n e s t i m a t e d a s shown i n T a b l e V a s s u m i n g a * 300 m" f o r
L
0
r
5
r
r
Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch001
1
r
G
r
L
1
H2O-H2S a n d H2O-H2,
1
a n d a * 600 m"
f o r NH3-H2 a n d C H N H - H .
3
2
2
F o r t h e p r o c e s s e s b a s e d on h y d r o g e n t h e low v a l u e s o f Kça a r e
c o m p e n s a t e d f o r b y t h e f e w e r number o f t h e o r e t i c a l t r a y s , t h e
h i g h e r p r e s s u r e and the lower gas f l o w r a t e .
Thus, f o r t h e
amine p r o c e s s t h e t o w e r volume i s l e s s t h a n f o r t h e GS p r o c e s s .
However, t h e h i g h e r p r e s s u r e f o r t h e f o r m e r r e s u l t s i n a v e s s e l
w e i g h t w h i c h i s s i m i l a r t o t h a t f o r t h e GS p r o c e s s .
K^a c a n be
enhanced by u s i n g mechanical energy t o i n c r e a s e the i n t e r f a c i a l
area very c o n s i d e r a b l y , as i n the e j e c t o r c o n t a c t o r (15), and so
t o r e d u c e t o w e r volume s i g n i f i c a n t l y a t t h e e x p e n s e o f c o m p l e x
and c o s t l y i n t e r n a l s .
The o v e r a l l e x c h a n g e r a t e i s o f c o u r s e d e p e n d e n t o n c a t a l y s t
c o n c e n t r a t i o n a n d on t h e f o r m o f c a t a l y s t u s e d . F o r t h e w a t e r h y d r o g e n p r o c e s s t h e v a l u e s o f Kça g i v e n i n T a b l e V a r e f o r a
hydrophobic p l a t i n u m c a t a l y s t supported on the s u r f a c e o f a
p a c k i n g i n a t r i c k l e - b e d r e a c t o r (22) . T h i s new c a t a l y s t d e v e l o p e d b y A t o m i c E n e r g y o f Canada L i m i t e d p r o v i d e s a h i g h e r
v o l u m e t r i c mass t r a n s f e r r a t e t h a n t h e s l u r r y c a t a l y s t r e f e r r e d
to e a r l i e r .
The b i t h e r m a l p r o c e s s a r r a n g e m e n t r e q u i r e s a h i g h
p r e s s u r e (10 MPa) s o t h a t K^a i s l o w a n d t h e t o w e r volume i s
large.
F o r t h e m o n o t h e r m a l CECE a r r a n g e m e n t t h e p r e s s u r e i s
l o w e r (1.5 MPa) a n d Kça i s a n o r d e r o f m a g n i t u d e h i g h e r g i v i n g a
somewhat l a r g e r v a l u e f o r PKça; t h e much s m a l l e r t o w e r volume r e s u l t s m a i n l y f r o m t h e r e d u c t i o n i n Ν a n d G. The same a d v a n t a g e
f o r t h e m o n o t h e r m a l f l o w s h e e t c a n a l s o be s e e n f o r t h e ammoniahydrogen system.
In Separation of Hydrogen Isotopes; Rae, H.;
ACS Symposium Series; American Chemical Society: Washington, DC, 1978.
18
SEPARATION O F
HYDROGEN ISOTOPES
Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch001
T u r n i n g now t o c o n s i d e r h o t t o w e r v o l u m e s , t h e r e i s no
l o n g e r a p r o b l e m o f low exchange r a t e s .
F o r t h e GS p r o c e s s t h e
r a t e s i n t h e c o l d and h o t t o w e r s a r e r o u g h l y s i m i l a r , b o t h c o n ­
trolled
by mass t r a n s f e r i n t h e gas p h a s e .
F o r the hydrogenb a s e d p r o c e s s e s t h e r a t e s o f e x c h a n g e a r e much f a s t e r i n t h e h o t
tower than i n the c o l d tower.
Thus, i n p r i n c i p l e the h o t tower
v o l u m e s f o r t h e s e p r o c e s s e s c o u l d be s m a l l e r t h a n f o r t h e GS
p r o c e s s . However, i n p r a c t i c e t h e b i t h e r m a l d e s i g n i n t h e s e
c a s e s i s o p t i m i z e d t o c o n c e n t r a t e s e p a r a t i v e work i n t h e h o t
t o w e r and so l i m i t demands on t h e c o l d t o w e r ; as a r e s u l t b o t h
t e n d t o have a b o u t t h e same v o l u m e . The v a l u e s o f Ν u s e d i n
T a b l e V r e f l e c t t h i s o p t i m i z i n g p r o c e s s , and so t h e r e l a t i v e c o l d
tower volumes a r e r e p r e s e n t a t i v e o f the r e l a t i v e t o t a l tower
volumes f o r t h e b i t h e r m a l f l o w s h e e t s .
Transfer Processes
A s p e c i a l c a t e g o r y o f c h e m i c a l exchange r e a c t i o n i s h i g h
temperature p r o c e s s e s which t r a n s f e r deuterium from a source
m a t e r i a l a v a i l a b l e as l a r g e s i n g l e s t r e a m s , s u c h as w a t e r o r
methane, t o h y d r o g e n .
Thus, the v e r y l a r g e s c a l e p o s s i b l e w i t h
t h e s e s o u r c e m a t e r i a l s c a n be c o m b i n e d w i t h t h e i n h e r e n t a d ­
vantages o f u s i n g a hydrogen-based p r o c e s s w h i c h can c o n c e n t r a t e
d e u t e r i u m more e f f i c i e n t l y .
H y d r o g e n i t s e l f i s an a b u n d a n t
s o u r c e ( w o r l d p r o d u c t i o n e q u i v a l e n t t o 30,000 Mg D20/a b u t i t
i s d e r i v e d f r o m a v a s t number o f i n d i v i d u a l u n i t s , w i t h a
t y p i c a l l a r g e u n i t b e i n g e q u i v a l e n t t o o n l y 70 Mg D20/a.
The s t e a m - h y d r o g e n p r o c e s s i l l u s t r a t e d i n F i g u r e 12 l i n k s
a w a t e r f e e d t o t h e amine-hydrogen p r o c e s s . Water i s e v a p o r a t e d
i n t o d e p l e t e d h y d r o g e n and t h e m i x t u r e i s h e a t e d t o 870 Κ where
the exchange r e a c t i o n o c c u r s o v e r a n i c k e l o x i d e c a t a l y s t t o
t r a n s f e r d e u t e r i u m from t h e steam t o the hydrogen.
The s t e a m i s
c o n d e n s e d and t h e h y d r o g e n r e t u r n e d t o t h e b i t h e r m a l a m i n e hydrogen u n i t .
Two s t e a m - h y d r o g e n e q u i l i b r a t i o n s i n s e r i e s a r e
r e q u i r e d , and e v e n so t h e d e u t e r i u m c o n t e n t o f t h e r e p l e n i s h e d
h y d r o g e n i s s i g n i f i c a n t l y b e l o w n a t u r a l . F l o w s a r e l a r g e and
energy requirements are h i g h ; the steam-hydrogen t r a n s f e r p r o c e s s
by i t s e l f i s e q u i v a l e n t i n c o s t p e r k g o f h e a v y w a t e r e x t r a c t e d
t o more t h a n h a l f t h e c o s t o f t h e h e a v y w a t e r p r o d u c e d by t h e GS
p r o c e s s . A l t h o u g h some i m p r o v e m e n t s i n t h i s t r a n s f e r p r o c e s s
may be p o s s i b l e , i t w i l l be d i f f i c u l t t o a c h i e v e a c o m p e t i t i v e
combination w i t h amine-hydrogen o r o t h e r hydrogen-based p r o c e s s .
A s i m i l a r t r a n s f e r p r o c e s s w h i c h c a n be u s e d t o e x t r a c t
d e u t e r i u m f r o m methane (2_3) has b e e n s t u d i e d a t t h e G u l f R e s e a r c h
and D e v e l o p m e n t Company. D e p l e t e d h y d r o g e n i s m i x e d w i t h
methane f e e d and t h e e x c h a n g e r e a c t i o n i s c a r r i e d o u t o v e r a
c a t a l y s t a t a b o u t 1000 K.
The two components a r e s e p a r a t e d by
l i q u e f y i n g t h e methane. The r e p l e n i s h e d h y d r o g e n f e e d s a d i s ­
t i l l a t i o n u n i t which separates the deuterium.
T h i s p r o c e s s com­
b i n a t i o n i s i l l u s t r a t e d i n F i g u r e 13. A g a i n two e q u i l i b r a t i o n s
In Separation of Hydrogen Isotopes; Rae, H.;
ACS Symposium Series; American Chemical Society: Washington, DC, 1978.
RAE
Selecting
Heavy Water
Processes
Table V
RELATIVE COLD TOWER VOLUMES
Gas F l o w
Theoretical
k m o l / m o l D2O
Trays
H 0 -H2S
74
2
CH3NH2
-
H
24
2
;
Kça
s^
1
Relative
Volume
1
27
0.9
1
10
0.04
0.6
5
10
0.008
0.008
0.9
4
0.08*
0.008^
0.3
5
NH3-H2
14
31
Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch001
monothermal
bithermal
H 0 - H
CECE
bithermal
2
2
*For a 4 - f o l d
2
3
9
50
enrichment.
V o l u m e = GNT/PK a; s e e T a b l e I V f o r Ρ a n d Τ e x c e p t f o r
CECE w h i c h h a s Ρ =1.5 MPa.
G
3
Weighted average f o r s t r i p p i n g and e n r i c h i n g
(see F i g u r e 8 ) .
*For t h e f i x e d - b e d
columns
hydrophobic platinum c a t a l y s t .
Figure 12.
Steam-Η
-amine process
2
In Separation of Hydrogen Isotopes; Rae, H.;
ACS Symposium Series; American Chemical Society: Washington, DC, 1978.
20
SEPARATION OF HYDROGEN ISOTOPES
Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch001
with countercurrent flow o f hydrogen and methane between them are
needed.
Energy consumption i s h i g h , most o f i t f o r r e f r i g e r a t i o n .
The methane-hydrogen p a r t o f the process i s probably s i m i l a r i n
cost t o steam-hydrogen t r a n s f e r .
I t should be noted t h a t s e l e c t i v e photochemical processes
based on the use o f l a s e r s w i l l r e q u i r e a s i m i l a r t r a n s f e r step
to l i n k the s e p a r a t i o n process t o an abundant feed.
Depending
on the molecules i n v o l v e d , high temperature may not be needed t o
achieve a s e p a r a t i o n f a c t o r near u n i t y f o r the t r a n s f e r r e a c t i o n ,
but unusually low p r e s s u r e s may be a requirement. C e r t a i n l y ,
t h i s can be a c o s t l y o p e r a t i o n because o f the l a r g e volume o f
m a t e r i a l t o be handled and the n e c e s s i t y t o recover the r e c i r c u l a t i n g deuterium c a r r i e r from the waste stream with a h i g h
efficiency .
Process
Comparison
While the s e p a r a t i o n f a c t o r i s a key p r o p e r t y f o r r a n k i n g
the economic a t t r a c t i v e n e s s o f p r o c e s s e s , energy consumption i s
almost o f equal importance. A convenient c h a r t to i l l u s t r a t e
t h i s i s shown i n Figure 14. An expanded s c a l e o f l o g ( a - l ) i s
used f o r the s e p a r a t i o n f a c t o r .
E l e c t r i c a l o r mechanical energy
i s converted t o e q u i v a l e n t thermal energy u s i n g 40% e f f i c i e n c y
and added t o the a c t u a l thermal energy requirement t o give t o t a l
e q u i v a l e n t thermal energy i n GJ/kg.
The GS process r e q u i r e s
30 GJ/kg which i s e q u i v a l e n t to about 5 b a r r e l s o f o i l per
kilogram.
The energy consumption f o r a process i s d i f f i c u l t t o d e f i n e
without a d e t a i l e d d e s i g n . I t depends on the degree o f energy
recovery which i n turn depends on such f a c t o r s as the i n g e n u i t y
of the designer, the r e l a t i v e cost o f energy and c a p i t a l equipment, and how the p l a n t i s t o be f i n a n c e d . T o t a l energy i f o f t e n
under-estimated i n p r e l i m i n a r y process e v a l u a t i o n s because o f the
s i m p l i f y i n g assumptions that are u s u a l l y made.
Processes i n the uneconomic region o f Figure 14 have too low
a s e p a r a t i o n f a c t o r (water c r y s t a l l i z a t i o n ) , too high an energy
consumption (hydrogen d i f f u s i o n ) o r both (water d i s t i l l a t i o n ) .
E l e c t r o l y s i s ranks h i g h e s t i n s e p a r a t i o n f a c t o r and h i g h e s t i n
energy consumption unless i t i s undertaken f o r hydrogen production.
In t h a t case about one t h i r d o f the deuterium cont a i n e d i n the feed water can be recovered as a hydrogen stream
enriched t o three times n a t u r a l a t p r a c t i c a l l y zero c o s t (9_) .
The G u l f process (23) i s d e s c r i b e d i n F i g u r e 13; while i t s
energy consumption i s high, i t has many i n h e r e n t advantages
which are l i k e l y t o permit an a t t r a c t i v e l y low c a p i t a l c o s t .
However, not only i s i t s energy consumption about twice t h a t o f
the GS process, but t h i s energy i s p r i m a r i l y mechanical and
t h e r e f o r e expensive. Under e s p e c i a l l y favourable circumstances
the G u l f process might become competitive with GS.
In Separation of Hydrogen Isotopes; Rae, H.;
ACS Symposium Series; American Chemical Society: Washington, DC, 1978.
Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch001
Selecting
Heavy
Water
Processes
Figure 13.
C,-H
2
process
Figure 14
In Separation of Hydrogen Isotopes; Rae, H.;
ACS Symposium Series; American Chemical Society: Washington, DC, 1978.
22
SEPARATION
O F HYDROGEN
The CECE process i s shown twice - a t the high energy con­
sumption f o r the case where there i s no market f o r the e l e c t r o ­
l y t i c hydrogen and a t the low energy consumption where the heavy
water i s a by-product o f the hydrogen p r o d u c t i o n . The l a t t e r i s a
p a r t i c u l a r l y favourable s i t u a t i o n .
The value o f α used i n F i g u r e 14 f o r the s e p a r a t i o n f a c t o r
of the b i t h e r m a l exchange processes i s α / α ^ i n order t o
c h a r a c t e r i z e each o f them by a s i n g l e v a l u e .
The GS process has a lower s e p a r a t i o n f a c t o r and a h i g h e r
energy consumption than s i x other processes i n Figure 14. I t
even has the d i s t i n c t l y u n d e s i r a b l e f e a t u r e o f using hydrogen
s u l f i d e which i s c o r r o s i v e , smelly and t o x i c . Yet the GS process
dominates heavy water p r o d u c t i o n and i s s t i l l the p r e f e r r e d
method o f p r o d u c t i o n . Why? Table VI compares i t with two o f i t s
p o t e n t i a l competitors:
- the GS process uses an abundant feed and t h e r e f o r e enjoys
the advantage o f a l a r g e s c a l e ; hydrogen-fed p l a n t s are
l i m i t e d to l e s s than 100 Mg/a c a p a c i t y and the hydrogenbased processes are expensive t o l i n k to water o r methane,
- while the GS process energy consumption i s higher than
the other two, i t i s not e x c e s s i v e ,
- the GS process enjoys f a s t mass t r a n s f e r r a t e s , b u t so
does hydrogen d i s t i l l a t i o n ,
- the temperature which c o n t r o l s GS process energy i n p u t i s
moderate, whereas both hydrogen d i s t i l l a t i o n and aminehydrogen r e q u i r e expensive r e f r i g e r a t i o n ,
- the GS process pressure i s not high enough t o i n c u r a
large cost penalty,
- while the GS process s e p a r a t i o n f a c t o r i s not as h i g h as
f o r the other processes, i t i s reasonable.
The major reason f o r the success o f the GS process i s the s c a l e
effect.
α
Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch001
ISOTOPES
Table VI
PROCESS COMPARISON
GS
Feed
Energy GJ/kg D 2 O
Mass T r a n s f e r
Temperature* Κ
Pressure MPa
Separation F a c t o r
H0
30
Fast
400
2
1.3
2
Amine
Hydrogen
Distillation
H2
H2
11
Slow
220
7
2.2
22
Fast
24
0.25
1.5
C o n t r o l l i n g major energy i n p u t
In Separation of Hydrogen Isotopes; Rae, H.;
ACS Symposium Series; American Chemical Society: Washington, DC, 1978.
Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch001
1.
RAE
Selecting
Heavy Water Processes
Figure 15.
Key factors in process evaluation
In Separation of Hydrogen Isotopes; Rae, H.;
ACS Symposium Series; American Chemical Society: Washington, DC, 1978.
23
24
SEPARATION O F HYDROGEN ISOTOPES
Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch001
The k e y f a c t o r s i n p r o c e s s e v a l u a t i o n a r e o u t l i n e d i n
F i g u r e 15. The i n h e r e n t p r o c e s s c o n d i t i o n s a n d p r o p e r t i e s o f
p r e s s u r e , t e m p e r a t u r e , mass t r a n s f e r r a t e and s e p a r a t i o n f a c t o r
a r e a l l i m p o r t a n t . P r e s s u r e and t e m p e r a t u r e c a n be v a r i e d t o
o p t i m i z e the c o n d i t i o n s , b u t u s u a l l y o n l y a r e l a t i v e l y narrow
range i s p r a c t i c a l .
These c o n d i t i o n s s e t t h e v a l u e s o f α a n d
Kça. Knowing α i t i s p o s s i b l e t o s e l e c t t h e r e c o v e r y , t h e f l o w
r a t e , G, a n d t h e number o f t r a n s f e r u n i t s o r t h e o r e t i c a l t r a y s ,
N. The p r e s s u r e and t e m p e r a t u r e s e t t h e a l l o w a b l e v e l o c i t y , V.
Then G, N, Kça and V combine t o d e f i n e t o w e r v o l u m e .
The m a j o r
p a r a m e t e r s d e t e r m i n i n g e n e r g y c o n s u m p t i o n a r e f l o w and t e m p e r a t u r e , b u t as a l r e a d y n o t e d t h e d e t a i l e d p r o c e s s f l o w s h e e t i s
important here.
Summary
The GS p r o c e s s i s t h e o n l y l a r g e - s c a l e i n d e p e n d e n t p r o c e s s
w i t h a d i r e c t w a t e r f e e d and t h i s i s l a r g e l y r e s p o n s i b l e f o r i t s
p r e - e m i n e n t p o s i t i o n i n heavy w a t e r p r o d u c t i o n .
Water-hydrogen exchange i s o n l y a t t r a c t i v e i n c o m b i n a t i o n
w i t h e l e c t r o l y t i c hydrogen p r o d u c t i o n - t h e combined e l e c t r o l y s i s
and c a t a l y t i c exchange (CECE) p r o c e s s .
T h r e e h y d r o g e n - b a s e d p r o c e s s e s , a m i n e - h y d r o g e n , ammoniah y d r o g e n and h y d r o g e n d i s t i l l a t i o n , a r e a l l c l o s e t o b e i n g comp e t i t i v e w i t h t h e GS p r o c e s s .
Of t h e s e , a m i n e - h y d r o g e n i s l i k e l y
t o be t h e c h e a p e s t . H y d r o g e n d i s t i l l a t i o n l i n k e d t o n a t u r a l gas
as t h e d e u t e r i u m s o u r c e , w h i l e d i s t i n c t l y e n e r g y i n t e n s i v e , may
be a n e a r c o m p e t i t o r u n d e r some c i r c u m s t a n c e s .
Hydrogen i s a p o t e n t i a l l y abundant heavy w a t e r s o u r c e , b u t
i n d i v i d u a l p l a n t s are small.
However, h y d r o g e n - b a s e d h e a v y w a t e r
p l a n t s a r e b e i n g b u i l t a n d more w i l l be c o m m i t t e d . N o n e t h e l e s s ,
t h e GS p r o c e s s w i l l c o n t i n u e as t h e d o m i n a n t one f o r a n o t h e r 10
o r 20 y e a r s .
Nomenclature
a
D
(D/H)
G
H
G
KQ
~
-
k
kg
-
k
-
k
L
L
r
-
i n t e r f a c i a l a r e a p e r u n i t volume o f m i x e d p h a s e s , m"
d i f f u s i v i t y o f d i s s o l v e d g a s , m /s
atom r a t i o o f d e u t e r i u m t o h y d r o g e n
gas f l o w r a t e , mol/s
H e n r y ' s Law c o n s t a n t , MPa.m /kmol
9
p h a s e mass t r a n s f e r c o e f f i c i e n t , m/s
o v e r a l l mass t r a n s f e r c o e f f i c i e n t b a s e d on gas p h a s e
c o n c e n t r a t i o n s , m/s
l i q u i d p h a s e mass t r a n s f e r c o e f f i c i e n t , m/s
l i q u i d p h a s e mass t r a n s f e r c o e f f i c i e n t f o r p h y s i c a l
a b s o r p t i o n , m/s
psuedo f i r s t o r d e r r a t e c o n s t a n t f o r c o n v e r s i o n o f
m o n o d e u t e r a t e d d i s s o l v e d gas t o m o n o d e u t e r a t e d s o l v e n t , s "
l i q u i d f l o w r a t e , mol/s
2
3
a s
In Separation of Hydrogen Isotopes; Rae, H.;
ACS Symposium Series; American Chemical Society: Washington, DC, 1978.
1
1.
Selecting
RAE
m
Ν
Ρ
R
s
Τ
V
α
ε
Water
-
25
Processes
number o f hydrogen atoms i n the molecule
number o f t h e o r e t i c a l t r a y s
p r e s s u r e , MPa
gas law constant = 8.2 χ 10"" m .MPa/ (kmol .K)
f r a c t i o n a l r a t e o f surface renewal, s "
temperature, Κ
gas v e l o c i t y based on the a c t i v e area o f the t r a y , i . e .
tower cross s e c t i o n a l area minus t o t a l downcomer area,
m/s
- deuterium s e p a r a t i o n f a c t o r
- volume f r a c t i o n o f l i q u i d on a t r a y
Subscripts :
Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch001
Heavy
3
3
1
c - c o l d tower;
h - h o t tower
Literature Cited
(1)
(2)
(3)
(4)
(5)
(6)
(7)
(8)
(9)
(10)
(11)
(12)
Urey, H . C . , Brickwedde, F . G . , Murphy, G.M., Phys. Rev.,
(1932), 39, 164.
Murphy, G.M., Urey, H . C . , Kirshenbaum, I . , "Production of
Heavy Water", McGraw-Hill Book Co., Inc., New York, 1955.
Clusius, K . , et al., "Nuclear Physics and Cosmic Rays,
Part II", FIAT Rev. Ger. S c i . , (1948), p.182-188.
Lavrencic, D . , Comitato Nazionale Energia Nucleare Report
RT/ING(74)9, (1974), Rome.
Benedict, M . , Pigford, T . H . , "Nuclear Chemical Engineering",
McGraw-Hill Book Co., Inc., New York, 1957.
Hammerli, Μ., Stevens, W.H., Butler, J.P., "Separation of
Hydrogen Isotopes", p.110, American Chemical Society,
Washington, 1978.
Bebbington, W.P., Proctor, J.F., Scotten, W.C., Thayer, V.R.,
Third United Nations International Conference on the Peace­
ful Uses of Atomic Energy, (1964), Proceedings 12, 334
United Nations, Geneva.
Dahlinger, Α . , Lockerby, W.E., Rae, H . K . , IAEA Inter­
national Conference on Nuclear Power and i t s Fuel Cycle,
(1977), Salzbury, Austria, Paper IAEA-CN-36/183; Atomic
Energy of Canada Limited Report 5710 (1977).
Gami, D . C . , Rapial, A . S . , Third United Nations Inter­
national Conference on the Peaceful Uses of Atomic Energy,
(1964), Proceedings 12, 421 United Nations, Geneva.
Roth, E., Bedhome, Α . , Lefrancois, B . , LeChatelier, J.,
Tillol,
Α . , Energie Nucleaire, (1968), 10, 214.
Roth, Ε . , Traourouder, R., V i r a t e l l e , J., Lefrancois, B . ,
Fourth United Nations Conference on the Peaceful Uses of
Atomic Energy, (1971), Proceedings 9, 69, United Nations,
Geneva.
Nitschke, E., Ilgner, H . , Walter, S., "Separation of
Hydrogen Isotopes", p. 77, American Chemical Society,
Washington, 1978.
In Separation of Hydrogen Isotopes; Rae, H.;
ACS Symposium Series; American Chemical Society: Washington, DC, 1978.
SEPARATION OF HYDROGEN ISOTOPES
26
(13)
(14)
(15)
(16)
(17)
(18)
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(19)
(20)
(21)
(22)
(23)
Nitschke, E., Atomwirtschaft, (1973), 18, 297.
Kuhn, W., Thurkauf, Μ., Helv. Chem. Acta, (1958), 41, 938.
Wynn, N.P., "Separation of Hydrogen Isotopes", p. ,
American Chemical Society, Washington, 1978.
Holtslander, W . J . , Lockerby, W.E., "Separation of Hydrogen
Isotopes", p. 4 0 , American Chemical Society, Washington,
1978.
Rolston, J.H., Butler, J.P., Denhartog, J., "A Deter­
mination of the Isotopic Separation Factor Between
Hydrogen and Liquid Methylamine", to be published.
Bourke, P.J., Lee, J.C., Trans. Inst. Chem. Engrs.,
(1961), 39, 280.
Kalra, H . , Otto, F . D . , Can. J. Chem. Eng., (1974), 52, 258.
Becker, E.W., Hubener, R., Kessler, R., Chemie Ing. Tech.,
(1958), 30, 288.
Astarita, G . , "Mass Transfer with Chemical Reaction",
Elsevier, 1967.
Butler, J.P., Rolston, J.H., Stevens, W.H., "Separation of
Hydrogen Isotopes", p. 9 3 , American Chemical Society,
Washington, 1978.
Pachaly, R.W., "Process for Obtaining Deuterium from
Hydrogen-Containing Compounds and the Production of Heavy
Water Therefrom", Canadian Patent 943742, (1974).
RECEIVED December 16, 1977
In Separation of Hydrogen Isotopes; Rae, H.;
ACS Symposium Series; American Chemical Society: Washington, DC, 1978.
2
Bruce Heavy Water Plant Performance
G. D. DAVIDSON
Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch002
Bruce Heavy Water Plant, Ontario Hydro, Box 2000,
Triverton, Ontario, CanadaN0G2T0
To satisfy the Canadian demand f o r heavy water
which is used as a moderator and heat t r a n s p o r t medium
in CANDU r e a c t o r s , Atomic Energy o f Canada L i m i t e d
c o n t r a c t e d the Lummus Company o f Canada L i m i t e d in
1969 t o d e s i g n and c o n s t r u c t Bruce Heavy Water P l a n t
' A ' a t the Bruce N u c l e a r Power Development.
The 9.5 square k i l o m e t e r (2300 a c r e s ) s i t e had
p r e v i o u s l y been p u r c h a s e d by O n t a r i o Hydro f o r the
Douglas P o i n t N u c l e a r G e n e r a t i n g S t a t i o n .
I t is
l o c a t e d in the County o f Bruce on the e a s t e r n shore o f
Lake Huron, midway between the towns o f K i n c a r d i n e and
P o r t Elgin, a p p r o x i m a t e l y 240 k i l o m e t e r s (150 m i l e s )
northwest o f T o r o n t o .
O n t a r i o Hydro was r e s p o n s i b l e f o r commissioning
and o p e r a t i n g the p l a n t which has a d e s i g n c a p a c i t y o f
96.6 k g / h o f 99.75% purity heavy water (D2O).
Commissioning o f P l a n t ' Α ' commenced in 1971 and
proceeded w i t h o u t any major
difficulty
t h r o u g h 1972
and 1973.
On 28 June, 1973, O n t a r i o Hydro p u r c h a s e d
the p l a n t from AECL and d e c l a r e d the p l a n t
in-service.
D e s i g n p r o d u c t i o n c a p a c i t y was r e a c h e d in April, 1974
after
e l e v e n months o f o p e r a t i o n .
Production rates
and c a p a c i t y f a c t o r s have s t e a d i l y been i n c r e a s e d such
t h a t the
official
capacity
was i n c r e a s e d t o 100.6 k g / h
in 1976.
As a r e s u l t o f t h e e a r l y o p e r a t i n g s u c c e s s o f
BHWP A, O n t a r i o Hydro announced t h e c o n s t r u c t i o n o f
t h r e e a d d i t i o n a l and e s s e n t i a l l y i d e n t i c a l heavy water
p l a n t s a t Bruce (BHWP B, C and D ) . A c u t b a c k in t h e
N u c l e a r G e n e r a t i o n c o n s t r u c t i o n program in 1976
r e s u l t e d in one o f t h e s e , BHWP C, b e i n g c a n c e l l e d and
the s c h e d u l e f o r a n o t h e r , BHWP D, b e i n g d e f e r r e d by
two y e a r s .
©
0-8412-0420-9/78/47-068-027$05.00/0
In Separation of Hydrogen Isotopes; Rae, H.;
ACS Symposium Series; American Chemical Society: Washington, DC, 1978.
28
SEPARATION O F H Y D R O G E N
ISOTOPES
Bruce Heavy Water Plant uses the proven Dual
Temperature Hydrogen Sulphide - Water Exchange Process
to separate deuterium. This process has been in use
on a commercial scale in North America f o r 25 years.
Following a b r i e f d e s c r i p t i o n of the production
process, BHWP A performance from in-service to the end
of 1976 is described in terms of the following key
performance c r i t e r i a : Employee Safety, Care of the
Environment, R e l i a b i l i t y and Manpower Development.
F i n a l l y , commissioning progress to date of BHWP Β is
described.
Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch002
Production Process
Water is pumped from Lake Huron (see "Figure 1")
with a deuterium i s o t o p i c content of 148 mg/kg. I t is
f i l t e r e d to remove s o l i d s and preheated to 29°C. The
pH is lowered to 3.8 - 4.2 by the addition of sulphuric
acid to decompose carbonates, the water is degassed of
oxygen and carbon dioxide, and then the pH is raised
to 6.0 - 6.5 by the addition of caustic to avoid
corrosion to carbon s t e e l processing equipment.
This
treated water is then fed to the Enriching Units.
Each of the heavy water plants consists of two
i d e n t i c a l enriching units and one f i n i s h i n g u n i t .
Each Enriching Unit can be divided broadly into three
sections: the absorption and desorption section, the
extraction section and the enriching section.
The absorption and desorption section serves two
functions: removal of H2S from the depleted water be­
fore i t is returned to the lake, and removal of H2S in
the purge gas before i t is f l a r e d . As the feed water
passes through t h i s section, i t is p a r t i a l l y saturated
with H2S.
In the extraction section (see "Figure 2") water
passes counter-current to a r e c i r c u l a t i n g stream of
hydrogen sulphide (H2S) gas in three large sieve tray
towers operating in p a r a l l e l which are the f i r s t stage.
By making use of a two temperature exchange reaction
(see "Figure 3") between hydrogen sulphide (H2S) and
water - at 30°C deuterium is concentrated in the l i q u i d
phase and a t 130°C deuterium is concentrated in the gas
phase. The three f i r s t stage towers (see "Figure 2")
each have two d i s t i n c t process temperature sections the top being a cold section and the bottom being a hot
section. Deuterium is c a r r i e d forward to the second
stage only in the gas phase while anything not
extracted from the water is returned to the lake from
the f i r s t stage a f t e r i t has been stripped of H2S and
cooled. I f H2S in the e f f l u e n t is not within the
In Separation of Hydrogen Isotopes; Rae, H.;
ACS Symposium Series; American Chemical Society: Washington, DC, 1978.
2.
DAVIDSON
Bruce
Heavy Water Plant
29
Performance
Water
Treating
D
2
0
Enrichingj
20-30%
D
2
0
Finishing
99.73%
Product
Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch002
Treating
Candu
Reactors
Figure 1.
BHWP-AD 0
Figure 2.
2
production
Enriching section
30°C
H
2
0
(i> +
P D S (g) ^
±
P D O
(£) +
H
2
S
(g)
130°C
Figure 3.
GS process
In Separation of Hydrogen Isotopes; Rae, H.;
ACS Symposium Series; American Chemical Society: Washington, DC, 1978.
SEPARATION OF HYDROGEN ISOTOPES
Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch002
30
r e g u l a t o r y l i m i t s i t is d i v e r t e d t o a e r a t e d lagoons
where the gas is removed and the water is s e n t t o t h e
lake.
One p a r t in 7000 coming o u t o f t h e l a k e is deuterium.
But i t is o n l y e c o n o m i c a l t o remove about 20%
or one p a r t in 35000.
The second and t h i r d s t a g e s o n l y e n r i c h o r conc e n t r a t e t h e d e u t e r i u m which has been e x t r a c t e d . The
second s t a g e is a s i n g l e tower whose o p e r a t i o n is
s i m i l a r t o t h e f i r s t s t a g e towers.
However, t h e r e is
no h e a t i n g s e c t i o n a t the bottom o f the h o t tower as
the gas is a l r e a d y hot coming forward from the f i r s t
stage.
To m a i n t a i n l i q u i d c i r c u l a t i o n in the second
s t a g e , water is pumped from t h e bottom o f the h o t
tower, t h r o u g h a c o o l e r t o t h e top o f the c o l d tower.
The t h i r d s t a g e c o n s i s t s o f two s e p a r a t e towers - one
c o l d tower, t h e o t h e r a hot tower. T h i r d s t a g e o p e r a t i o n a l s o d i f f e r s from the p r e v i o u s two.
Enriched
l i q u i d from the bottom o f t h e c o l d tower is t a k e n f o r ward f o r f u r t h e r p r o c e s s i n g . The H 2 S in t h i s e n r i c h i n g
u n i t l i q u i d p r o d u c t is s t r i p p e d out and r e t u r n e d t o t h e
t h i r d s t a g e gas l o o p .
E n r i c h e d water a t 20 - 30% D 0 c o n c e n t r a t i o n from
b o t h e n r i c h i n g u n i t s is f e d t o t h e f i n i s h i n g u n i t .
The f i n i s h i n g u n i t is a t h r e e s t a g e , f o u r tower steam
vacuum d i s t i l l a t i o n system t h a t c o n c e n t r a t e s t h e
p r o d u c t from t h e e n r i c h i n g u n i t s i n t o the f i n a l r e a c t o r
grade heavy water. A l l f i n i s h i n g u n i t towers c o n t a i n
sieve trays.
The heavy water is then t r e a t e d in e i t h e r o f two
p o t a s s i u m permanganate b a t c h k e t t l e s t o o x i d i z e o r g a n i c
impurities.
The p r o d u c t is e i t h e r drummed o r s h i p p e d
in b u l k t o CANDU r e a c t o r s .
T r a n s l a t e d i n t o r e a l i t y , the process u n i t s a r e
shown in t h e a e r i a l view o f BHWP (see " F i g u r e 4 " ) .
BHWP A water i n t a k e is shared w i t h the Douglas P o i n t
Nuclear Generating S t a t i o n .
The f i g u r e shows t h e
b u i l d i n g h o u s i n g t h e sand f i l t e r s , t h e d e g a s s i n g towe r s , the main s w i t c h y a r d , t h e steam s u p p l y from
Douglas P o i n t N u c l e a r G e n e r a t i n g S t a t i o n and t h e Bruce
Steam P l a n t , t h e H S s t o r a g e b u l l e t s , t h e f l a r e (145 m
or 475 f e e t above g r a d e ) , t h e l a g o o n s , t h e a b s o r p t i o n
and d e s o r p t i o n s e c t i o n c o n s i s t i n g o f an Absorber tower,
Purge tower and an E f f l u e n t S t r i p p e r tower, t h e t h r e e
f i r s t s t a g e towers, the second s t a g e tower, the t h i r d
s t a g e and t h e f o u r tower, t h r e e s t a g e F i n i s h i n g U n i t .
The f i g u r e a l s o shows the bank o f heat exchangers
a c r o s s the f r o n t o f each u n i t , used t o a c h i e v e t h e
two p r o c e s s temperatures and o p t i m i z e steam u t i l i z a tion .
2
2
In Separation of Hydrogen Isotopes; Rae, H.;
ACS Symposium Series; American Chemical Society: Washington, DC, 1978.
2.
DAVIDSON
Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch002
Employee
Bruce
Heavy
Water
Plant
Performance
31
Safety
One m a j o r d i s a d v a n t a g e o f t h e D u a l T e m p e r a t u r e
Hydrogen S u l p h i d e - Water Exchange Process i s t h e
t o x i c i t y o f the H2Sgas and the p o t e n t i a l s a f e t y
hazards i t poses.
The g r e a t e s t d a n g e r f r o m t h e i n h a l a t i o n o f hydrogen sulphide i s from i t s acute e f f e c t s ;
i t i s n o tcumulative i n a c t i o n . Exposure t o moderate
c o n c e n t r a t i o n s causes headaches, d i z z i n e s s , nausea and
vomiting i n that order.
C o n t i n u e d e x p o s u r e may c a u s e
l o s s o f consciousness, r e s p i r a t o r y f a i l u r e and death i f
the gas c o n c e n t r a t i o n i s h i g h enough.
Hydrogen S u l phide i s a l s o flammable and i n c e r t a i n mixtures w i t h
a i r i t c a nbe e x p l o s i v e .
From t h e o u t s e t , O n t a r i o Hydro o p e r a t i n g s t a f f
e s t a b l i s h e d rigorous s a f e t y p o l i c i e s and procedures
f o r a l l a s p e c t s o f c o m m i s s i o n i n g a n d o p e r a t i n g P l a n t A,
w i t h s p e c i a l emphasis on the h a n d l i n g o f H2S and equipment c o n t a i n i n g i t .
S a f e t y p e r f o r m a n c e a t B r u c e Heavy Water P l a n t i s
p r e s e n t e d i n terms o f "H2S I n c i d e n t s " (see " F i g u r e 5")
o r t h e number o f e m p l o y e e s t e m p o r a r i l y a f f e c t e d b y t h e
t o x i c o l o g i c a l p r o p e r t i e s o f h y d r o g e n s u l p h i d e , number
of l o s t time accidents and l o s t time accident
frequency
(see " F i g u r e 6").
"H2S I n c i d e n t s " are d e f i n e d as "sub-acute" o r
"acute".
B r i e f l y , a "sub-acute" i n c i d e n t i s one i n
w h i c h a p e r s o n e x p o s e d t o H y d r o g e n S u l p h i d e shows s i g n s
of b e i n g a f f e c t e d b u t does n o tr e q u i r e r e s u s c i t a t i o n
or a s s i s t a n c e t o e x i t from the area a f f e c t e d by H2S,
w h i l e an "acute" i n c i d e n t i s one i n which a person
overcome by Hydrogen S u l p h i d e r e q u i r e s r e s u s c i t a t i o n
and/or a s s i s t a n c e t o e x i t from the area a f f e c t e d by
Hydrogen S u l p h i d e .
Only one H2S I n c i d e n t has r e s u l t e d i na l o s t time
a c c i d e n t ( i n 1975) when t h e a f f e c t s o f H 2 S c a u s e d a n
employee t o f a l l and b r u i s e h i s r i b s .
I n t h e t w o y e a r p e r i o d f r o m May 1 9 7 2 t o May 1 9 7 4 ,
w h i c h c o v e r e d t h e b u l k o f c o m m i s s i o n i n g , t h e r e was n o t
a s i n g l e l o s t time accident.
The two l o s t t i m e
a c c i d e n t s i n 1976 were b o t h b a c k i n j u r i e s c a u s e d b y
improper l i f t i n g
techniques.
F a c t o r s c o n t r i b u t i n g t o BHWP s a f e w o r k p e r f o r m a n c e
( s e e " F i g u r e 7") h a v e b e e n g r o u p e d u n d e r t h e b r o a d
h e a d i n g s o f Management P o l i c i e s , S a f e t y T r a i n i n g ,
General T r a i n i n g , Procedures, Employee R e l a t i o n s ,
P l a n t I n t e g r i t y , P e r s o n a l P r o t e c t i v e Equipment and
S a f e t y Equipment.
A l l a r eimportant t o a successful
s a f e t y program.
A t no t i m e d u r i n g the h i s t o r y o f B r u c e Heavy Water
In Separation of Hydrogen Isotopes; Rae, H.;
ACS Symposium Series; American Chemical Society: Washington, DC, 1978.
Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch002
SEPARATION OF HYDROGEN ISOTOPES
Figure 4. Aerial view of BHWP
1973
74
75
76
Figures. BHWP—History of H S incidents
t
In Separation of Hydrogen Isotopes; Rae, H.;
ACS Symposium Series; American Chemical Society: Washington, DC, 1978.
2.
3
Bruce
DAVIDSON
Heavy
Water
Plant
Performance
33
·
Lost T i m e
ι:·:·:·:·:.·ι
:
Accidents
Frequency
(/10
6
Rate
Manhours)
Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch002
1 ·
Manhours
1973
74
75
76
772,575
737,906
965,870
1,230,626
Figure 6.
1.
Management
BHWP—Safety
4.
Policies
- the b u d d y s y s t e m
environment
- training
- work on H2S systems
- procedural approach
- control of work
- equipment inspections.
- plant m o d i f i c a t i o n c o n t r o l
- equipment
maintenance
5.
Safety
- communications.
orientation
6.
- emergency procedures
Plant
Integrity
- b u d d y training
- isolating circuits a n d devices
- r e s c u e training
- equipment design
- p r o t e c t i o n training - fire,
- e m e r g e n c y p o w e r , s t e a m , w a t e r a n d air
- equipment inspections.
c h e m i c a l , electrical, etc.
- W o r k Protection C o d e
7.
Personal Protective
- t a n k c a r repairs
- conventional
- v e s s e l entry
- breathing
- first aid
- rescue stations.
- regular m e e t i n g s .
3.
Relations
- Personal Hygiene
Training
- new employee
Employee
- Medicals
- event reporting.
2.
Procedures
- plant a c c e s s control
- n u m b e r 1 priority
- work
performance
8.
Safety
Equipment
equipment
Equipment
General Training
- fire f i g h t i n g
- science fundamentals
- H2S detectors and monitors
- e q u i p m e n t / s y s t e m s principles
- gas detectors
- plant s y s t e m s
- rescue vehicle
- field skills.
- survey vehicles
- first aid r o o m .
Figure 7.
Factors contributing to safe work performance
In Separation of Hydrogen Isotopes; Rae, H.;
ACS Symposium Series; American Chemical Society: Washington, DC, 1978.
34
SEPARATION
P l a n t has i t s o p e r a t i o n p r e s e n t e d
and s a f e t y o f the p u b l i c .
Care o f t h e
O F HYDROGEN
a r i s k t o the
health
Environment
Bruce Heavy Water P l a n t has two major e n v i r o n mental c o n s i d e r a t i o n s - H 2 S e m i s s i o n s t o atmosphere
and H 2 S e m i s s i o n s t o water.
On the f i r s t o f t h e s e ,
Hydrogen S u l p h i d e i s an odourous m a t e r i a l . I f concent r a t i o n s r e a c h more than 2 0 0 yg/m (micrograms per
metre cubed) H 2 S can be s m e l l e d by most p e o p l e and i s
c o n s i d e r e d by v i r t u a l l y a l l as an u n a c c e p t a b l e odour.
The p l a n t i s s i t u a t e d i n a r u r a l and summer r e s o r t
area.
C o m p l a i n t s o f odour s t a r t e d t o be r e c e i v e d
s h o r t l y a f t e r H S was i n t r o d u c e d i n t o the u n i t s i n
1973.
By y e a r end, a t o t a l o f 56 c o m p l a i n t s were
r e g i s t e r e d (see " F i g u r e 8").
A t a s k f o r c e was formed
to r e c t i f y t h i s u n s a t i s f a c t o r y s i t u a t i o n .
Several
a c t i o n s were t a k e n :
e f f o r t s were d i r e c t e d toward r e d u c i n g the amount o f H 2 S r e l e a s e d ; s t e p s were taken t o
i n s u r e a c o m b u s t i b l e m i x t u r e o f s t a c k gas a t a l l t i m e s ;
d r a i n water t o be s t r i p p e d o f H 2 S was m i n i m i z e d ; r e l e a s e s o f steam o r n i t r o g e n and o t h e r i n e r t s t o t h e
f l a r e were accompanied by i n c r e a s e d propane f l o w s t o
the f l a r e .
In 1974, t h r e e odour r e p o r t s came i n , i n
1975 f o u r odour r e p o r t s were r e c e i v e d and i n 1976
t h e r e were two.
R e l a t i o n s w i t h t h e p u b l i c a r e no
l o n g e r a problem as f a r as H 2 S odours a r e c o n c e r n e d .
An H 2 S r e c o v e r y system t o m i n i m i z e H 2 S and p r o pane usage i s b e i n g b u i l t as p a r t o f t h e p l a n t
expansion.
As a r e s u l t , H 2 S r e l e a s e s t o the f l a r e
w i l l be f u r t h e r r e d u c e d .
On the second e n v i r o n m e n t a l c o n s i d e r a t i o n , H 2 S
e m i s s i o n s t o water, a l l water streams c o n t a i n i n g H 2 S
must be s t r i p p e d o f i t b e f o r e the water i s r e t u r n e d
to the l a k e .
" F i g u r e 8" shows the number o f times the
r e g u l a t o r y l i m i t f o r hydrogen s u l p h i d e i n water was
exceeded by y e a r .
U n s t a b l e f l o w s i n the towers were
q u i t e f r e q u e n t i n 1973.
T h i s i n s t a b i l i t y caused the
e f f l u e n t s t r i p p e r operating conditions to f l u c t u a t e
d e t e r r i n g i t s e f f e c t i v e n e s s . P h y s i c a l changes t o
tower t r a y w e i r s and the a d d i t i o n o f a n t i f o a m t o t h e
p r o c e s s water s t e a d i e d o p e r a t i n g c o n d i t i o n s and t h e r e f o r e improved the e f f e c t i v e n e s s o f the s t r i p p e r .
Replacement o f u n r e l i a b l e i n s t r u m e n t a t i o n and b e t t e r
p r o c e s s c o n t r o l d u r i n g s t a r t u p s and shutdowns have
improved performance.
A continuous H2S-in-water
m o n i t o r which has p r o v e n r e l i a b l e w i t h q u i c k r e s p o n s e
was i n s t a l l e d on the s t r i p p e r o u t l e t .
This monitor
p l u s o t h e r e f f l u e n t s t r i p p e r p r o c e s s parameters o f
3
Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch002
ISOTOPES
2
In Separation of Hydrogen Isotopes; Rae, H.;
ACS Symposium Series; American Chemical Society: Washington, DC, 1978.
2.
DAVIDSON
Bruce
Heavy
Water
Plant
Performance
35
f e e d temperature, l e v e l and p r e s s u r e have a l l been
interlocked to automatically d i v e r t e f f l u e n t to the
lagoons i f a p r e s e t c o n c e n t r a t i o n o f H 2 S i s exceeded
o r t h e measured v a r i a b l e s exceed d e f i n e d l i m i t s .
Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch002
Reliability
The r e l i a b i l i t y o f BHWP A has g e n e r a l l y been good f o r
a p l a n t o f i t s s i z e w i t h m i n i m a l redundancy i n i t s
o p e r a t i n g equipment.
" F i g u r e 9" shows downtime
e x p e r i e n c e t o d a t e . P l a n n e d u n i t t u r n - a r o u n d s have
been r e d u c e d from 10 weeks i n 1973 t o 4 weeks i n 1975.
An outage p l a n n e d f o r September, 1976 was advanced t o
t a k e advantage o f an unplanned outage i n J u l y .
Another f a c t o r o f r e l i a b i l i t y i s production r a t e .
" F i g u r e 10" shows i n s t a n t a n e o u s p r o d u c t i o n r a t e s i n
k i l o g r a m s p e r hour t h a t t h e p l a n t was o p e r a t i n g , i . e .
shutdown p e r i o d s have been e x c l u d e d . The o r i g i n a l Des i g n C a p a c i t y was 48.3 kg/h f o r each e n r i c h i n g u n i t .
F o l l o w i n g s t a r t up i n 1973, t r a y f l o o d i n g problems
caused by foaminess o f t h e p r o c e s s and a d e f i c i e n c y i n
t r a y d e s i g n were e x p e r i e n c e d .
C o r r e c t i o n o f these
problems by t h e a d d i t i o n o f a n t i f o a m t o t h e feedwater
and m o d i f i c a t i o n o f t h e t r a y s r e s u l t e d i n d r a m a t i c
improvements i n p r o d u c t i o n r a t e s .
P r o d u c t i o n r a t e s have c o n t i n u e d t o improve, r e s u l t i n g i n a r e - r a t i n g o f t h e p l a n t c a p a c i t y i n 1976
t o 100.6 kg/h.
C a p a c i t y F a c t o r s (based on D e s i g n C a p a c i t y f o r
1973 t o 1975 and based on Demonstrated C a p a c i t y f o r
1976) and a n n u a l p r o d u c t i o n a r e shown i n " F i g u r e 11".
These do n o t i n c l u d e about 99 Mg t h a t were " e n r i c h e d "
t o 20% i s o t o p i c p u r i t y d u r i n g 1974/1975/1976, o f
which 31 Mg were " f i n i s h e d " t o r e a c t o r grade elsewhere
i n 1975 and 42 Mg were " f i n i s h e d " elsewhere i n " 1976.
I f t h e s e " f i n i s h e d " q u a n t i t i e s were c o m p l e t e l y
c r e d i t e d t o BHWP A, t h e apparent C a p a c i t y F a c t o r s i n
1975 and 1976 would be 71.7% and 90.9% r e s p e c t i v e l y .
Manpower Development
The purpose o f t r a i n i n g i s t o e n s u r e t h a t each
p o s i t i o n i n t h e p l a n t i s f i l l e d by a p e r s o n w i t h
a p p r o p r i a t e knowledge and s k i l l s so t h a t t h e p l a n t i s
o p e r a t e d s a f e l y , e f f e c t i v e l y and e f f i c i e n t l y .
T r a i n i n g i s therefore a part o f the plant's p e r f o r mance o b j e c t i v e s .
Formal t r a i n i n g i s p r o v i d e d by l e c t u r e d c o u r s e s
and demonstrated s k i l l s i n t h e c l a s s r o o m and t h e f i e l d .
F o r each j o b , t h e l e v e l and p r o f i c i e n c y which must be
In Separation of Hydrogen Isotopes; Rae, H.;
ACS Symposium Series; American Chemical Society: Washington, DC, 1978.
36
SEPARATION
O F HYDROGEN
Odour
ΓΤ!Τ·!·!·!·!·!·!:!:Ι
i.'.',.„'.'.'.'.'.'|
ι
ISOTOPES
Reports
•!
Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch002
H2S E m i s s i o n s t o W a t e r
mam
Figure 8.
%
rnmrn
74
1973
75
76
Environmental performance to date
Downtime
Enriching
Finishing
Units
Planned
E$:$:$:3 F o r c e d
Unit
V////A T o t a l
Outages
Outages
Outages
ρ
m
ϋ
m
S
1973
74
Figure 9.
75
76
BHWP—Reliability
In Separation of Hydrogen Isotopes; Rae, H.;
ACS Symposium Series; American Chemical Society: Washington, DC, 1978.
Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch002
2.
DAVIDSON
Bruce
Heavy
Water
Plant
Performance
37
a t t a i n e d are s p e c i f i e d i n each o f the f o l l o w i n g :
Management, S c i e n c e Fundamentals, Equipment and System
P r i n c i p l e s , F i e l d S k i l l s , S p e c i f i c P l a n t Systems, AECB
Operating License, Protection T r a i n i n g .
T r a i n i n g i s p r o v i d e d by the N u c l e a r T r a i n i n g De­
partment o f O n t a r i o Hydro a t R o l p h t o n , by the Manpower
Development Department o f O n t a r i o Hydro a t O r a n g e v i l l e ,
by the Bruce T r a i n i n g C e n t r e a t the s i t e and by the
BHWP T r a i n i n g S e c t i o n .
BHWP T r a i n i n g S e c t i o n i s s t a f f e d by e i g h t T r a i n ­
i n g T e c h n i c i a n s , two e n g i n e e r s and a T r a i n i n g O f f i c e r .
BHWP o p e r a t e s a f i v e s h i f t system i n s t e a d o f t h e
t r a d i t i o n a l f o u r , so t h a t o p e r a t o r s , m a i n t a i n e r s and
c o n t r o l t e c h n i c i a n s on s h i f t spend t e n t o f o u r t e e n
p e r c e n t o f t h e i r time i n t r a i n i n g .
I n 1975 t h e r e were
6,822 man c o u r s e s g i v e n and i n 1976 t h e r e were 11,400
man c o u r s e s g i v e n a t BHWP.
Commissioning P r o g r e s s Report - BHWP Β
A s s e m b l i n g a commissioning team o f e n g i n e e r s ,
o p e r a t o r s , m a i n t a i n e r s and c o n t r o l t e c h n i c i a n s f o r
P l a n t Β began i n 1975.
A nucleus o f personnel with
o p e r a t i n g e x p e r i e n c e i n P l a n t A i s b e i n g augmented
w i t h new employees. The commissioning group i s p r e ­
p a r i n g commissioning e s t i m a t e s and p r o c e d u r e s , and
i n s p e c t i n g and w i t n e s s i n g equipment t e s t s as the p l a n t
i s being b u i l t .
T h i s group i s commissioning and
o p e r a t i n g the v a r i o u s p l a n t systems as t h e y a r e t u r n e d
o v e r from c o n s t r u c t i o n .
The a i r compressor system f o r P l a n t Β and t h e
u t i l i t i e s f o r F i n i s h i n g U n i t F2 were t u r n e d o v e r from
c o n s t r u c t i o n and commissioned i n the l a s t q u a r t e r o f
1976.
The l a s t t u r n o v e r o f the F i n i s h i n g U n i t p r o c e s s
system was on 6 J a n u a r y , 1977.
P r e - s t a r t u p checks o f
equipment and i n s t r u m e n t a t i o n were completed by 18
F e b r u a r y , 1977.
O p e r a t i o n o f F2 on d e m i n e r a l i z e d
water f o l l o w e d and t h i s program was completed by the
end o f A p r i l .
Equipment i n s p e c t i o n s f o l l o w i n g t h i s
run and minor d e f i c i e n c y c o r r e c t i o n s were completed
by 10 May, 1977 and s t a r t u p on i n t e r m e d i a t e p r o d u c t
from P l a n t A commenced. F i r s t r e a c t o r grade p r o d u c t
from F2 was produced on 23 May, 1977.
The p l a n (see " F i g u r e 12") shows l a s t t u r n o v e r o f
E n r i c h i n g U n i t E4 equipment f o r commissioning 1 May,
1978.
E n r i c h i n g U n i t E3 l a s t t u r n o v e r i s s c h e d u l e d
f o r 15 December, 1978.
T h i s p l a n a l s o shows P l a n t D
F i n i s h i n g U n i t F4 l a s t t u r n o v e r f o r commissioning a t
the end o f September, 1979 w i t h E n r i c h i n g U n i t s 7 and
In Separation of Hydrogen Isotopes; Rae, H.;
ACS Symposium Series; American Chemical Society: Washington, DC, 1978.
38
SEPARATION
OF
HYDROGEN
ISOTOPES
Extraction
kg D 0 / h
2
60·
Hot Tower
Clarifier Tests
Alum Addition
June 74
40<
^
^
: Q u e n c h W a t e r ·:·
1 s t A n t ifo a m
: Addition
Addition
May
Temp.
Raised J a n .7 6
Stopped
June
'73
E1 W e i r
:
Starts
75
Cuts:
Sept. 7 3
:
:
Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch002
20
1973
74
10.
Figure
76
75
Enriching
unit extraction
D 0/h)
(kg
2
Production
Megagrams
Capacitor
Factor
%
57
249
1974
76
640
1975
68
574
1976
86
758
74
2221
1973
(6 mo.)
Figure
11.
BHWP-A
BHWP Β
E4
<3>—©
F2
E3
First R / G
D
2
Φ
0
®Φ-®
BHWP D
E7
φ
Last Turnover ( L u m m u s to O . H . )
@
First E x t r a c t i o n o f D 0
F4
E8
( § ) First R e a c t o r G r a d e
@
1976
-®
2
D 0
2
First R / G
D
2
0
In S e r v i c e
77
Figure
78
12.
Commissioning
79
80
milestones
In Separation of Hydrogen Isotopes; Rae, H.;
ACS Symposium Series; American Chemical Society: Washington, DC, 1978.
81
2.
DAVIDSON
Bruce Heavy
Water
Plant
Performance
8 t o f o l l o w i n 1980.
Conclusion
The c o - o p e r a t i o n o f AECL and O n t a r i o Hydro has
brought s u c c e s s t o Bruce Heavy Water P l a n t t o d a t e .
Comparable r e s u l t s a r e expected i n t h e f u t u r e .
September
12, 1977
Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch002
RECEIVED
In Separation of Hydrogen Isotopes; Rae, H.;
ACS Symposium Series; American Chemical Society: Washington, DC, 1978.
3
Hydrogen-Amine Process for Heavy Water Production
W. J. HOLTSLANDER
Atomic Energy of Canada Ltd., Chemical Engineering Branch,
Chalk River Nuclear Laboratories, Chalk River, Ontario
W. E . LOCKERBY
Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch003
Atomic Energy of Canada Ltd., Heavy Water Projects,
Tunney's Pasture, Ottawa, Ontario
Ammonia-hydrogen or amine-hydrogen exchange is one of the
three major chemical systems considered u s e f u l f o r deuterium
enrichment processes. The other two being the water-hydrogen
sulfide
system (GS process) p r e s e n t l y being used to produce the
major f r a c t i o n o f the w o r l d ' s heavy water supply and the hydrogen­
-water system which is c u r r e n t l y under a c t i v e development. Heavy
water p l a n t s based on ammonia-hydrogen exchange have operated in
France and are being commissioned in I n d i a . The usefulness of
amines in place of ammonia was shown by B a r - E l i and K l e i n (_1) in
1962.
This work showed amines, p a r t i c u l a r l y methylamine had
f a s t e r exchange r a t e s than the comparable ammonia-based system.
A t Chalk R i v e r , a f t e r work w i t h the ammonia-hydrogen system
showed a water-fed p l a n t d i d not o f f e r any advantage over the GS
p r o c e s s , development was s t a r t e d on the amine-hydrogen system.
A p a r a l l e l development program f o r the amine process was a l s o
i n i t i a t e d by the Commissariat a L ' E n e r g i e Atomique in France and
d e t a i l s of the exchange r e a c t i o n work were reported by Rochard and
Ravoire ( 2 ) . The amine chosen was methylamine (MA). The advan­
tages of methylamine over ammonia are f a s t e r deuterium exchange
r a t e s , higher hydrogen s o l u b i l i t y and a low vapour pressure. The
choice of methylamine over other amines was discussed in d e t a i l
by Bancroft and Rae ( 3 ) . The o r i g i n a l c a t a l y s t was the potassium
s a l t of methylamine, potassium methylamide (PMA), because of i t s
favourable exchange r a t e coupled w i t h reasonable c o s t .
Subsequent
work forced a m o d i f i c a t i o n o f the c a t a l y s t and the reasons f o r
t h i s w i l l be d i s c u s s e d .
T h e d e v e l o p m e n t o f t h e amine p r o c e s s a t CRNL p r o c e e d e d in
three major areas:
c o n t a c t o r development, p r o c e s s c h e m i s t r y and
p r o c e s s d e s i g n . Development o f e f f i c i e n t g a s - l i q u i d c o n t a c t o r s
was r e q u i r e d t o p r o v i d e h i g h mass t r a n s f e r r a t e s p e r u n i t volume
in t h e c o l d t o w e r s (-50°C) where t h e e x c h a n g e r e a c t i o n r a t e is
r e l a t i v e l y slow.
T h i s program evolved through a s e r i e s o f p i l o t
p l a n t c o n t a c t o r s r a n g i n g in s i z e f r o m 5 t o 15 cm d i a m e t e r a t l o w
©
0-8412-0420-9/78/47-068-040$05.00/0
In Separation of Hydrogen Isotopes; Rae, H.;
ACS Symposium Series; American Chemical Society: Washington, DC, 1978.
3.
HOLTSLANDER
AND
LOCKERBY
Hydro gen-Amine
Process
41
Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch003
p r e s s u r e in g l a s s t o a 25 cm s t a i n l e s s s t e e l c o n t a c t o r t h a t
o p e r a t e d a t 2 MPa (300 p s i ) f o r b o t h c o l d t o w e r a n d h o t t o w e r
testing.
F u r t h e r i n f o r m a t i o n on c o n t a c t o r development and process
d e s i g n was o b t a i n e d in c o o p e r a t i o n w i t h S u l z e r B r o s . , S w i t z e r l a n d
who h a d i n d e p e n d e n t l y c o n s t r u c t e d a p i l o t p l a n t u s i n g a f u l l s c a l e
contactor operating a t f u l l process pressure (4).
E x t e n s i v e p r o c e s s d e s i g n work and economic e v a l u a t i o n s were
done a t CRNL a n d u n d e r c o n t r a c t w i t h i n d u s t r i a l e n g i n e e r i n g
f irms.
The v e r y e x t e n s i v e c h e m i s t r y p r o g r a m c o n s i s t e d o f d e t e r m i n ing the p h y s i c a l and chemical p r o p e r t i e s o f the system,
d e v e l o p i n g h a n d l i n g and a n a l y t i c a l t e c h n i q u e s , d e t e r m i n i n g the
r e a c t i v i t y o f the system w i t h p o t e n t i a l i m p u r i t i e s , examining
f a c t o r s which a f f e c t the deuterium exchange r a t e , l o o k i n g f o r
b e t t e r c a t a l y s t s t o improve the exchange r a t e and s t u d y i n g the
s t a b i l i t y o f the c a t a l y s t s o l u t i o n a t process c o n d i t i o n s . This
p r o g r a m was v e r y much o f a p i o n e e r i n g one b e c a u s e o f t h e s c a r c i t y
o f i n f o r m a t i o n o n s o l u t i o n s o f a l k a l i m e t a l a l k y l a m i d e in a m i n e s
in t h e l i t e r a t u r e .
I t was n e c e s s a r y t o f i r s t d e v e l o p s u i t a b l e
l a b o r a t o r y t e c h n i q u e s t o handle such a r e a c t i v e system s a f e l y
and in t h e a b s e n c e o f a t m o s p h e r i c c o n t a m i n a n t s t o o b t a i n
meaningful q u a n t i t a t i v e data.
The a b s e n c e o f p r e v i o u s l y
p u b l i s h e d i n f o r m a t i o n o n r e l a t e d s y s t e m s meant t h a t l i t t l e
g u i d a n c e was a v a i l a b l e f o r p r e d i c t i o n o f t h e c h e m i c a l b e h a v i o u r
and a l l a s p e c t s o f t h e w o r k had t o b e e x p e r i m e n t a l l y d e t e r m i n e d .
D e v e l o p m e n t o f a c o m p l e t e r a n g e o f a n a l y t i c a l m e t h o d s was a
m a j o r component o f t h e p r o g r a m . W i t h t h i s l a c k o f b a c k g r o u n d
i n f o r m a t i o n , u n f o r e s e e n r e s u l t s were o f t e n observed.
A prime
e x a m p l e in t h i s w o r k was t h e d i s c o v e r y t h a t h y d r o g e n a t p r o c e s s
p r e s s u r e is a r e a c t i v e s p e c i e s ; n o t o n l y in t h e d e u t e r i u m
e x c h a n g e r e a c t i o n b u t a l s o c h e m i c a l l y . T h i s is n o t s oint h e
c o m p a r a b l e ammonia s y s t e m and was t o t a l l y u n e x p e c t e d .
I t was t h i s
d i s c o v e r y t h a t n e c e s s i t a t e d t h e d e v e l o p m e n t o f a new c a t a l y s t t o
make t h e p r o c e s s v i a b l e .
Because the process operates a t h i g h
p r e s s u r e (6-13 MPa, d i c t a t e d b y t h e h o s t ammonia p l a n t ) t o o b t a i n
e f f e c t i v e mass t r a n s f e r r a t e s , much o f t h e c h e m i s t r y h a d t o b e
done a t c o n d i t i o n s w h i c h s i m u l a t e d t h e p r o c e s s .
T h i s added t h e
c o m p l i c a t i o n o f having t o develop s p e c i a l experimental techniques.
T h i s w o r k i l l u s t r a t e s t h e i m p o r t a n c e o f c h e m i s t r y s t u d i e s in
p r o c e s s d e v e l o p m e n t . A l t h o u g h d e u t e r i u m e x c h a n g e is t h e c e n t r a l
f e a t u r e o f a heavy water process, s u c c e s s f u l development r e q u i r e s
d e t a i l e d knowledge o f a l l a s p e c t s o f p r o c e s s c h e m i s t r y .
I n many
c a s e s t h e s e a r e l a r g e l y unknown b e f o r e h a n d .
The c h e m i s t r y w o r k was done b y a number o f g r o u p s a t CRNL
and t h r o u g h c o n t r a c t s w i t h t h e U n i v e r s i t y o f A l b e r t a , T r e n t
U n i v e r s i t y , R a y l o C h e m i c a l s L t d . in A l b e r t a a n d C h e m i c a l P r o j e c t s
L t d . in T o r o n t o .
A more d e t a i l e d r e v i e w o f t h i s c h e m i c a l w o r k
forms the major p o r t i o n o f t h i s paper.
In Separation of Hydrogen Isotopes; Rae, H.;
ACS Symposium Series; American Chemical Society: Washington, DC, 1978.
42
S E P A R A T I O N O F H Y D R O G E N ISOTOPES
Process
Chemistry
The p r o c e s s l i q u i d , m e t h y l a m i n e , must c o n t a i n a d i s s o l v e d
c a t a l y s t t o p r o v i d e an a c c e p t a b l e d e u t e r i u m e x c h a n g e r a t e .
This
c a t a l y s t is p r e p a r e d b y d i s s o l v i n g p o t a s s i u m m e t a l in t h e m e t h y l ­
amine. The p o t a s s i u m s l o w l y d i s s o l v e s t o g i v e a b l u e s o l u t i o n
t y p i c a l o f a l k a l i m e t a l s in ammonia o r a m i n e s .
Blue
Yellow
+
Κ + C H N H + K , K~, e" - + KNHCH + % H
3 2
*
' solv
3
2
Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch003
0
0
0
I n a m i n e s w i t h p o t a s s i u m F l e t c h e r e t a l Ç5,6) a t CRNL h a v e shown
t h i s c o l o u r t o be due t o a n e q u i l i b r i u m b e t w e e n p o t a s s i u m a n i o n s
and s o l v a t e d e l e c t i o n i o n p a i r s .
The b l u e c o l o u r e d s o l u t i o n
s l o w l y decomposes t o g i v e t h e y e l l o w p o t a s s i u m m e t h y l a m i d e
s o l u t i o n and hydrogen.
A l k a l i m e t a l a l k y l a m i d e s d i s s o l v e d in a m i n e s a r e s t r o n g
b a s e s and a r e v e r y r e a c t i v e c h e m i c a l l y . They r e a c t v i g o r o u s l y
w i t h a i r and w a t e r s o t h a t s p e c i a l t e c h n i q u e s a r e r e q u i r e d when
h a n d l i n g and s t u d y i n g t h e s e s y s t e m s .
Some o f t h e more i m p o r t a n t
r e a c t i o n s w i t h i m p u r i t i e s e n c o u n t e r e d in t h e p r o c e s s a r e l i s t e d
below.
CH^NHK + H 0
CH NH
2
CH^NHK + 0
3
2
+ ΚΟΗΨ
-> KCN+, CH NCH=NCH , ΚΟΗΨ
2
3
3
Κ
Potassium
D ime t h y 1 f ο rmamid i d e
0
π
CH NHK + CO
CH^NHK + C 0
HC-lji- CH Ψ ( p o t a s s i u m N - m e t h y l f ormamide)
Κ
0
2
-> C^NHC-ΟΚΨ(carbamate)
0
2CH NH
3
2
+ C0
CH NHK + N H
3
0
2
3
·> CH NHC-O CH NH®(carbamate)
3
-> C H N H
3
3
2
+ KNH^
A l l o f t h e s e r e a c t i o n s h a v e b e e n s t u d i e d in v a r y i n g d e g r e e s
o f d e t a i l t o d e t e r m i n e t h e i d e n t i t y o f t h e p r o d u c t s and t h e
e f f e c t t h e y h a v e on t h e p r o c e s s . The m a j o r c o n s e q u e n c e o f t h e s e
r e a c t i o n s is d e s t r u c t i o n o f c a t a l y s t t h u s r e d u c i n g t h e e x c h a n g e
r a t e , and p r o d u c i n g i n s o l u b l e s o l i d s t h a t may c a u s e d e p o s i t i o n
In Separation of Hydrogen Isotopes; Rae, H.;
ACS Symposium Series; American Chemical Society: Washington, DC, 1978.
3.
HOLTSLANDER
H y dro gen-Amine
A N D LOCKERBY
Process
43
and b l o c k a g e o f e q u i p m e n t .
I t is t h e r e f o r e a r e q u i r e m e n t t h a t
t h e s e i m p u r i t i e s b e m a i n t a i n e d a t an a c c e p t a b l y l o w l e v e l in t h e
process t o a v o i d these problems.
An a r e a o f p r o c e s s c h e m i s t r y t h a t was e x t e n s i v e l y s t u d i e d
b o t h a t C h a l k R i v e r and by S a n f o r d , P r e s c o t t and Lemieux a t Raylo
C h e m i c a l s , Edmonton was t h e t h e r m a l s t a b i l i t y o f t h e PMA-MA
system.
Thermal decomposition occurs t o y i e l d t h r e e major
p r o d u c t s : h y d r o g e n , p o t a s s i u m d i m e t h y l f o r m a m i d i d e (PDMFA) a n d
ammonia,
2CH NH
Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch003
3
2
+ CH^NHK + 2 H + CH N=CHNKCH + N H ^
2
3
3
The r a t e o f t h i s r e a c t i o n h a s b e e n d e t e r m i n e d o v e r t h e r a n g e
of p r o c e s s c o n d i t i o n s .
A s a r e s u l t t h e optimum h o t t o w e r
t e m p e r a t u r e o r i g i n a l l y s e t a t 70°C ( 3 ) b a s e d on p r e l i m i n a r y
d e c o m p o s i t i o n d a t a was r e d u c e d t o 40^C. The d e c o m p o s i t i o n
r e a c t i o n h a s two p r o c e s s e f f e c t s ; i t r e s u l t s in a l o s s o f c a t a l y s t
t h a t r e q u i r e s make-up and i t p r o d u c e s ammonia and PDMFA b o t h o f
w h i c h must be removed. The ammonia must b e removed b e c a u s e o f
i t s r e a c t i o n w i t h PMA f o r m i n g p o t a s s i u m amide w h i c h h a s a l i m i t e d
s o l u b i l i t y (0.06 mmoles/g). Removal o f PDMFA is o f l e s s
importance b u t i t w i l l e v e n t u a l l y b u i l d up t o a c o n c e n t r a t i o n t h a t
e x c e e d s i t s s o l u b i l i t y (3.3 mmoles/g @ -40°C) a n d w i l l p r e c i p i t a t e .
I n t h e s t u d y o f ways t o r e d u c e t h e d e c o m p o s i t i o n r a t e a n
u n e x p e c t e d s i d e r e a c t i o n was d i s c o v e r e d . S i n c e h y d r o g e n was a
p r o d u c t o f t h e d e c o m p o s i t i o n , one o f t h e p o s t u l a t e d f i r s t s t e p s
w a s d e h y d r o g e n a t i o n o f t h e PMA t o a m e t h y l e n i m i n e ,
CH NHK t CH =NK +
3
2
I f t h i s p o s t u l a t e d i n t e r m e d i a t e s t e p was r e v e r s i b l e t h e n a h i g h
hydrogen p a r t i a l p r e s s u r e might i n h i b i t t h e d e c o m p o s i t i o n .
Since
t h e p r o c e s s o p e r a t e s most e f f e c t i v e l y a t h i g h h y d r o g e n p r e s s u r e i t
was e s s e n t i a l t o i n v e s t i g a t e t h e d e c o m p o s i t i o n r e a c t i o n o v e r t h e
f u l l p r e s s u r e range.
High hydrogen p r e s s u r e d i d reduce t h e
d e c o m p o s i t i o n r a t e b u t t h e r e s u l t s were v e r y e r r a t i c and t h e
e x p e r i m e n t s were p l a g u e d b y t h e i r r e p r o d u c i b l e a p p e a r a n c e a n d
disappearance of white p r e c i p i t a t e s .
Workers a t Raylo Chemicals
showed t h e h y d r o g e n was r e a c t i n g w i t h t h e PMA-MA s o l u t i o n t o g i v e
p o t a s s i u m h y d r i d e w h i c h was i n s o l u b l e .
CH NHK + H
3
2
t CH NH
3
2
+ ΚΗΨ
The a p p a r e n t r e d u c t i o n in t h e r m a l d e c o m p o s i t i o n r a t e was due t o
r e m o v a l o f PMA f r o m s o l u t i o n .
T h i s r e a c t i o n t o f o r m KH does n o t
o c c u r in t h e ammonia s y s t e m and was n o t e x p e c t e d in m e t h y l a m i n e .
A r e a c t i o n b e t w e e n KNH2 a n d h y d r o g e n d o e s o c c u r in ammonia a t v e r y
h i g h hydrogen p r e s s u r e , b u t g i v e s t h e s o l v a t e d e l e c t r o n (the b l u e
s o l u t i o n ) r a t h e r than a h y d r i d e p r e c i p i t a t e (7,8).
In Separation of Hydrogen Isotopes; Rae, H.;
ACS Symposium Series; American Chemical Society: Washington, DC, 1978.
Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch003
44
SEPARATION
OF
HYDROGEN
ISOTOPES
The gas l i q u i d c o n t a c t o r w o r k a t C h a l k R i v e r was done a t 2 MPa and
m i s s e d t h e h y d r i d e r e a c t i o n . A l o w p r e s s u r e c o n t a c t o r was u s e d
b e c a u s e t h e mass t r a n s f e r c o e f f i c i e n t was l i q u i d phase c o n t r o l l e d
and c o u l d be r e l i a b l y e x t r a p o l a t e d t o h i g h e r p r e s s u r e s .
I t was
o n l y through the chemistry study the r e a c t i v i t y of hydrogen w i t h
p o t a s s i u m m e t h y l a m i d e came t o l i g h t .
The h y d r i d e r e a c t i o n had m a j o r p r o c e s s i m p l i c a t i o n s . B e c a u s e
o f t h e l o w KH s o l u b i l i t y t h e n e t r e a c t i o n a t p r o c e s s h y d r o g e n
p r e s s u r e s was t o t h e r i g h t so t h a t t h e m a j o r p o r t i o n o f t h e
c a t a l y s t was t a k e n o u t o f s o l u t i o n as t h e h y d r i d e .
T h i s is shown
in F i g u r e 1.
T h e r e is l i t t l e t e m p e r a t u r e e f f e c t on t h e r e a c t i o n ,
w h i c h o c c u r s t o g i v e a s i m i l a r shape o f s o l u b i l i t y v e r s u s p r e s s u r e
f r o m -30°C t o +50°C. The e f f e c t o f t h e l o w maximum c a t a l y s t
s o l u b i l i t y in s o l u t i o n s a t p r o c e s s p r e s s u r e was t o r e d u c e t h e c o l d
t o w e r e x c h a n g e e f f i c i e n c y t o a b o u t h a l f t h a t m e a s u r e d a t 2 MPa.
A f t e r d i s c o v e r y o f t h e h y d r i d e r e a c t i o n an e x t e n s i v e p r o g r a m
was i n i t i a t e d t o f i n d a method o f i n h i b i t i n g t h e r e a c t i o n . A v e r y
l a r g e number o f c h e m i c a l a d d i t i v e s and a l t e r n a t i v e s y s t e m s were
investigated.
Work a t C h a l k R i v e r showed t h e a n a l o g o u s r e a c t i o n
o c c u r r e d w i t h s o d i u m m e t h y l a m i d e in m e t h y l a m i n e and w i t h s o d i u m
and p o t a s s i u m d i m e t h y l a m i d e in d i m e t h y l a m i n e .
I t d i d not occur
w i t h l i t h i u m methylamide or w i t h cesium methylamide, but l i t h i u m
m e t h y l a m i d e is a v e r y p o o r c a t a l y s t f o r d e u t e r i u m e x c h a n g e and
c e s i u m is e x p e n s i v e .
I t was f o u n d , h o w e v e r , t h a t when l i t h i u m was
added t o PMA in m e t h y l a m i n e t h e r e a c t i o n w i t h h y d r o g e n d i d n o t
o c c u r , a t l e a s t in t h e r a n g e o f h y d r o g e n p a r t i a l p r e s s u r e s o f
i n t e r e s t to the heavy water p r o c e s s .
T h i s is shown in F i g u r e 2
where PLMA r e p r e s e n t s e q u i m o l a r p o t a s s i u m - l i t h i u m m e t h y l a m i d e .
T h i s d i s c o v e r y s o l v e d one o f t h e m a j o r p r o c e s s p r o b l e m s b u t
r e q u i r e d t h e answer t o many q u e s t i o n s s u c h as t h e e f f e c t o f added
l i t h i u m on t h e e x c h a n g e r e a c t i o n , t h e r e a c t i o n s w i t h i m p u r i t i e s ,
t h e t h e r m a l d e c o m p o s i t i o n r e a c t i o n , and t h e optimum l i t h i u m
concentration.
E x c h a n g e r a t e s w e r e s t u d i e d in t h e l a b o r a t o r y a t C h a l k R i v e r
u s i n g a s m a l l r a p i d l y s t i r r e d e x c h a n g e c e l l where t h e t r a n s f e r o f
d e u t e r i u m f r o m h y d r o g e n t o m e t h y l a m i n e was m o n i t o r e d w i t h an onl i n e mass s p e c t r o m e t e r .
L a r g e - s c a l e e x c h a n g e w o r k was done in t h e
25 cm p i l o t p l a n t c o n t a c t o r . K i n e t i c e x c h a n g e d a t a u s i n g a
s i n g l e - s p h e r e a b s o r b e r was a l s o o b t a i n e d by P r o f e s s o r F.D. O t t o a t
t h e U n i v e r s i t y o f A l b e r t a . I n i t i a l w o r k showed t h e PLMA e x c h a n g e
c a t a l y s t gave e q u a l o r somewhat h i g h e r r a t e c o n s t a n t s and t r a y
e f f i c i e n c i e s t h a n PMA.
However, s u b s e q u e n t more d e t a i l e d w o r k has
shown t h e e x c h a n g e r a t e c o n s t a n t is d e p e n d e n t on t h e amount o f
l i t h i u m added and d e c r e a s e s w i t h i n c r e a s i n g l i t h i u m c o n c e n t r a t i o n .
T h i s is shown in F i g u r e 3.
The t e m p e r a t u r e c o e f f i c i e n t o f t h e e x c h a n g e r e a c t i o n was
f o u n d t o be t h e same f o r b o t h t h e PMA and PLMA s y s t e m s w i t h an
a c t i v a t i o n e n e r g y o f 28 k j o u l e s / m o l e , t h e same a s was f o u n d
e a r l i e r by R o c h a r d f o r t h e PMA s y s t e m ( 2 ) .
In Separation of Hydrogen Isotopes; Rae, H.;
ACS Symposium Series; American Chemical Society: Washington, DC, 1978.
3.
HOLTSLANDER
Hydrogen-Amine
A N D LOCKERBY
45
Process
MAXIMUM
CATALYST
CONCENTRATION
Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch003
(m moles/g)
8
10
12
14
16
18
20
22
24
26
28
30
PRESSURE (MPa)
Figure 1.
Effect of hydrogen on PMA solutions at 296°Κ
MAXIMUM
CATALYST
CONCENTRATION
(m moles/g)
12
14
16
18
20
22
24
26
28
30
PRESSURE (MPa)
Figure 2.
Effect of hydrogen on PMA and PLMA
catalyst solutions at 296°Κ
In Separation of Hydrogen Isotopes; Rae, H.;
ACS Symposium Series; American Chemical Society: Washington, DC, 1978.
Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch003
46
SEPARATION O F H Y D R O G E N ISOTOPES
Figure 3.
Effect of lithium-potassium mole ratio on exchange rate.
Stirred exchange cell at 203°K.
In Separation of Hydrogen Isotopes; Rae, H.;
ACS Symposium Series; American Chemical Society: Washington, DC, 1978.
Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch003
3.
HOLTSLANDER
AND
LOCKERBY
Hydrogen-Amine
Process
47
A s e c o n d exchange r e a c t i o n t h a t o c c u r s in b o t h t h e PMA and
PLMA s y s t e m is d e u t e r i u m e x c h a n g e b e t w e e n t h e amino- and m e t h y l groups o f methylamine.
T h i s r e a c t i o n was s t u d i e d in d e t a i l b y
H a l l i d a y and B i n d n e r (9) a t CRNL and is more t h a n 1000 t i m e s
s l o w e r than the amino-group-molecular hydrogen exchange. W h i l e i t
d o e s r e s u l t in a s l o w b u i l d u p o f d e u t e r i u m in t h e m e t h y l g r o u p o f
t h e p r o c e s s l i q u i d , i t does n o t c o n s t i t u t e a p r o c e s s p r o b l e m .
The s o l u b i l i t y - t e m p e r a t u r e r e l a t i o n s h i p o f PLMA ( F i g u r e 4)
is o p p o s i t e t o t h a t o f e i t h e r PMA o r LMA ( l i t h i u m m e t h y l a m i d e ) ,
s h o w i n g a somewhat l o w e r s o l u b i l i t y a t t h e l o w t e m p e r a t u r e and a
much h i g h e r s o l u b i l i t y a t h i g h t e m p e r a t u r e s .
The s o l u b i l i t y is
a l s o m a r k e d l y d e p e n d e n t on t h e l i t h i u m c o n c e n t r a t i o n a s shown in
F i g u r e 5.
A s t h e amount o f l i t h i u m i n c r e a s e s t h e t o t a l s o l u b i l i t y
increases rapidly.
I n f a c t systems w i t h h i g h l i t h i u m r a t i o s
y i e l d e d c l e a r s o l u t i o n s w i t h a s a l t c o n t e n t c l o s e t o 30% by w e i g h t .
The e f f e c t o f added l i t h i u m on t h e t h e r m a l s t a b i l i t y o f t h e
s o l u t i o n is shown in F i g u r e 6. The s o l u t i o n is more s t a b l eint h e
presence of l i t h i u m w i t h the h a l f - l i f e f o r an equimolar potassiuml i t h i u m s o l u t i o n b e i n g h i g h e r (100 d a y s ) a t 40°C t h a n a PMA
s o l u t i o n (25 d a y s ) . I n t h e h e a v y w a t e r p r o c e s s w h e r e t h e s o l u t i o n
is c i r c u l a t i n g b e t w e e n c o l d and h o t t o w e r s t h e t i m e s p e n t a t 40°C
is o n l y a f r a c t i o n o f a c t u a l t i m e in t h e p r o c e s s so t h a t t h e
p r a c t i c a l h a l f - l i f e o f t h e s o l u t i o n is g r e a t e r t h a n t h e 100 d a y s
m e a s u r e d in t h e l a b o r a t o r y .
The p r o d u c t s o f d e c o m p o s i t i o n a r e t h e
same as f r o m PMA w i t h t h e a d d i t i o n o f l i t h i u m d i m e t h y l f o r m a m i d i d e .
The ammonia formed r e a c t s i n d i s c r i m i n a t e l y w i t h l i t h i u m and
p o t a s s i u m s a l t s t o p r e c i p i t a t e L i N H 2 and KNH2. I n a d d i t i o n , i t
was f o u n d t h a t t h e amide s a l t s c o - p r e c i p i t a t e d m e t h y l a m i d e a l o n g
w i t h them t h u s f u r t h e r r e m o v i n g a c t i v e c a t a l y s t f r o m t h e s o l u t i o n .
F o r t h i s r e a s o n t h e p u r i f i c a t i o n s y s t e m m u s t m a i n t a i n t h e ammonia
a t a c o n c e n t r a t i o n b e l o w 0.06 mmole/g w h i c h c o r r e s p o n d s t o t h e
amide s o l u b i l i t y .
S a n f o r d a t R a y l o has demonstrated a s i m p l e
p u r i f i c a t i o n method b a s e d o n d i s t i l l a t i o n o f a s i d e s t r e a m t o
remove ammonia and c o n v e r t a m i d e s b a c k t o m e t h y l a m i d e s .
MNH
+ CH NH
2
3
2
-> CH^NHM + N H ^
From t h e f u n d a m e n t a l p o i n t o f v i e w t h e q u e s t i o n a r i s e s o f
how l i t h i u m m o d i f i e s t h e p r o p e r t i e s o f t h e s o l u t i o n . L i t h i u m
m e t h y l a m i d e b y i t s e l f in m e t h y l a m i n e s o l u t i o n is a v e r y p o o r
c a t a l y s t w i t h a n e x c h a n g e r a t e l e s s t h a n 1% o f t h a t o f PMA. The
w o r k r e p o r t e d in t h i s p a p e r s u g g e s t s t h a t p o t a s s i u m and l i t h i u m
m e t h y l a m i d e e x i s t in s o l u t i o n a s a c o m p l e x r a t h e r t h a n a s i m p l e
m i x t u r e o f t h e two s a l t s in s o l u t i o n .
S u c h a c o m p l e x in e q u i l i b r i u m w i t h t h e two m e t h y l a m i d e s is shown b e l o w .
K Li (NHCH ) ^±2KNHCH
2
2
3
4
3
+ 2LiNHCH
2
E v i d e n c e f o r s u c h a c o m p l e x in s o l u t i o n is s u m m a r i z e d in
F i g u r e 7. The t o t a l l y o p p o s i t e s o l u b i l i t y - t e m p e r a t u r e r e l a t i o n s h i p
American Chemfcar
Society Library
1155 of Hydrogen
16th St.Isotopes;
N. w.Rae, H.;
In Separation
ACS Symposium Series;
American Chemical
Washington, DC, 1978.
Washington,
D. C.Society:
20038
Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch003
SEPARATION O F HYDROGEN ISOTOPES
Figure 4.
Solubility of methylamides
In Separation of Hydrogen Isotopes; Rae, H.;
ACS Symposium Series; American Chemical Society: Washington, DC, 1978.
Hydrogen-Amine
A N D LOCKERBY
Process
Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch003
HOLTSLANDER
Figure
5. Solubility
of
potassium-lithium
methylamine
methylamide
in
In Separation of Hydrogen Isotopes; Rae, H.;
ACS Symposium Series; American Chemical Society: Washington, DC, 1978.
SEPARATION
O F HYDROGEN ISOTOPES
Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch003
1000
Figure 7.
Evidence that PLMA is a complex
In Separation of Hydrogen Isotopes; Rae, H.;
ACS Symposium Series; American Chemical Society: Washington, DC, 1978.
3.
HOLTSLANDER
AND
LOCKERBY
Hydrogen
Amine
Process
51
i n d i c a t e s a c o m p l e x r a t h e r t h a n a m i x t u r e . The I R a n d X - r a y
s p e c t r a obtained i n Glinthard's l a b o r a t o r y i n t h e Swiss F e d e r a l
I n s t i t u t e o f T e c h n o l o g y u n d e r c o n t r a c t t o S u l z e r shows u n i q u e
s p e c t r a f o r PLMA r a t h e r t h a n a sum o f a l l t h e l i n e s f r o m PMA a n d
LMA.
C o n d u c t i v i t y d a t a o b t a i n e d a t CRNL shows a d i f f e r e n t
t e m p e r a t u r e b e h a v i o u r f o r PLMA t h a n f o r PMA o r LMA. The r e a c t i v i t y
i s d i f f e r e n t t h a n PMA a n d t h e v a p o u r p r e s s u r e d a t a o b t a i n e d b y
Sanford a t Raylo Chemicals i n d i c a t e s a d i f f e r e n t species i n s o l u t i o n t h a n e i t h e r o f t h e two component s a l t s .
A l l o f these
o b s e r v a t i o n s a r e c o n s i s t e n t w i t h a complex r a t h e r than a s i m p l e
mixture.
Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch003
Conclusion
I t h a s been demonstrated t h a t p o t a s s i u m - l i t h i u m methylamide
i s a s u p e r i o r c a t a l y s t f o r t h e amine-hydrogen heavy water p r o c e s s .
I t does n o t r e a c t w i t h hydrogen, and I t has a f a v o u r a b l e deuterium
e x c h a n g e r a t e , good s o l u b i l i t y a n d a n a c c e p t a b l e t h e r m a l decomposition rate.
A p a t e n t h a s b e e n g r a n t e d f o r t h i s new c a t a l y s t (10).
The a m i n e - h y d r o g e n p r o c e s s i s r i c h i n c h e m i s t r y , much o f i t
p r e v i o u s l y unknown. The p r a c t i c a l a s p e c t s o f t h e c h e m i s t r y w h i c h
d i r e c t l y affect theprocess, i . e . , the preparation of catalyst,
t h e r e a c t i v i t y o f t h ec a t a l y s t s o l u t i o n w i t h process ingredients
and p r o c e s s i m p u r i t i e s , t h e d e u t e r i u m e x c h a n g e p r o p e r t i e s , t h e
t h e r m a l s t a b i l i t y have been t h o r o u g h l y i n v e s t i g a t e d .
The p r o c e s s
c h e m i s t r y s t u d i e s p r o v i d e a f i r m b a s i s f o r t h e p r o c e s s , however
t h e r e i s s t i l l many f u n d a m e n t a l a s p e c t s o f c h e m i s t r y o f t h e s y s t e m
w h i c h c o u l d be a f e r t i l e a r e a f o r f u r t h e r b a s i c r e s e a r c h .
As a r e s u l t o f t h e s u c c e s s a c h i e v e d i n t h e t h r e e a r e a s o f
development, t h a t o f g a s - l i q u i d c o n t a c t o r s , p r o c e s s c h e m i s t r y and
p r o c e s s d e s i g n , t h e amine-hydrogen heavy water p r o c e s s h i s reached
t h e p o s i t i o n w h e r e t h e n e x t s t a g e i s commitment o f a p r o t o t y p e
p l a n t , and t h u s i s now b e i n g p u r s u e d .
Acknowledgement s
We a c k n o w l e d g e t h e c o n t r i b u t i o n s o f D r . H.K. Rae a n d
A.R. B a n c r o f t who d i r e c t e d t h e p r o c e s s d e v e l o p m e n t p r o g r a m a n d
for t h e i r review of t h i s manuscript.
We a l s o a c k n o w l e d g e
D r s . J . F . P r e s c o t t a n d E.C. S a n f o r d a t R a y l o C h e m i c a l s a n d
R.E. J o h n s o n a n d R.P. D e n a u l t o f t h e C h e m i c a l E n g i n e e r i n g B r a n c h ,
CRNL f o r t h e i r m a j o r c o n t r i b u t i o n t o t h e e x p e r i m e n t a l w o r k a n d t o
D r . J.P. M i s l a n a n d c o - w o r k e r s o f t h e G e n e r a l C h e m i s t r y B r a n c h ,
CRNL, who d i d much o f t h e a n a l y t i c a l m e t h o d s d e v e l o p m e n t .
Abstract
The hydrogen-amine process f o r heavy water p r o d u c t i o n employs
a deuterium i s o t o p e exchange r e a c t i o n between hydrogen and m e t h y l amine c o n t a i n i n g a d i s s o l v e d alkali metal methylamide c a t a l y s t .
In Separation of Hydrogen Isotopes; Rae, H.;
ACS Symposium Series; American Chemical Society: Washington, DC, 1978.
52
SEPARATION OF HYDROGEN ISOTOPES
This system is c h e m i c a l l y v e r y r e a c t i v e and a d e t a i l e d understand­
ing o f all aspects of the process chemistry was r e q u i r e d . T h i s
understanding was made more
difficult
by the l a c k of i n f o r m a t i o n
in the
literature
on this o r similar systems.
The m a j o r i t y of the
work was of a p i o n e e r i n g n a t u r e . For example, a h i t h e r t o unknown
s i d e r e a c t i o n of hydrogen at process pressure w i t h the
original
exchange c a t a l y s t was d i s c o v e r e d . The s u c c e s s f u l development
of a new c a t a l y s t r e s t o r e d the
viability
of the process so that
commercial a p p l i c a t i o n is now f e a s i b l e and is being pursued.
Literature
Cited
Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch003
(1)
(2)
Bar-Eli,
K . and Klein, F.S., J. Chem. S o c . , 3803, (1962).
Rochard, E . and R a v o i r e , J., J. Chem. P h y s . , 68, 1183,
(1971).
(3) B a n c r o f t , A . R . and Rae, H.K., Atomic Energy of Canada L i m i t e d ,
Report AECL-3684, (1970).
(4) Wynn, Ν . , paper no. 57 Isotope Separation Symposium ACS/CIC
C o n f . , (June 1977).
(5) F l e t c h e r , J.W., Seddon, W . A . , Jevcak, J. and Sopchyshyn, F.C.,
Chem. Phys. Lett., 18, 592, (1973).
(6) F l e t c h e r , J.W., Seddon, W.A. and Sopchyshyn, F.C., Can. J.
Chem., 51, 2975, (1973).
(7) K i r s c h k e , E.J. and Jolly, W . L . , I n o r g . Chem. 6, 855, (1967).
(8) Bödddeker, K . W . , Land, G . , and Schindewolf, U., Angew Chem.
( I n t . E d . ) 8, 138, (1969).
(9) H a l l i d a y , J.D. and B i n d n e r , P.E., Can. J. Chem. 54, 3775
(1967).
(10) H o l t s l a n d e r , W.J., and Johnson, R.E., U n i t e d States P a t e n t ,
3995017, (November 30, 1976).
RECEIVED September 7, 1977
In Separation of Hydrogen Isotopes; Rae, H.;
ACS Symposium Series; American Chemical Society: Washington, DC, 1978.
4
AECL-Sulzer Amine Process for Heavy Water
N. P. WYNN
Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch004
Sulzer Brothers Ltd., P.O. Box 210, Pointe Claire, Quebec, Canada H9R
4N9
The purpose o f t h i s paper is t o o u t l i n e the d e s i g n o f
the AECL - S u l z e r amine p r o c e s s f o r heavy water, t o
demonstrate why the p r o c e s s is a t t r a c t i v e compared t o
e x i s t i n g p r o c e s s e s and t o summarise the s t e p s which
have been taken t o p r e p a r e the p r o c e s s f o r commercial
exploitation.
Work on p r o c e s s development was s t a r t e d independ e n t l y by Atomic Energy o f Canada and by S u l z e r B r o t h e r s . AECL were e v a l u a t i n g a l t e r n a t i v e s t o the e s t a b l i s h e d GS s e p a r a t i o n p r o c e s s and conducted
experiments
to compare exchange r a t e s f o r ammonia-hydrogen and
amine-hydrogen. S u l z e r were i n t e r e s t e d in the amine-hydrogen p r o c e s s as a s u c c e s s o r t o the s e r i e s o f hydrogen f e d heavy water p l a n t s w i t h which they had been inv o l v e d . T h i s i n v o l v e m e n t had s t a r t e d in 1956 w i t h the
c o n s t r u c t i o n o f a p l a n t u s i n g l i q u e f a c t i o n and d i s t i l l a t i o n o f e l e c t r o l y t i c hydrogen a t Ems in S w i t z e r l a n d
(1) and has c o n t i n u e d w i t h the c o n s t r u c t i o n o f t h r e e
p l a n t s u s i n g the monothermal ammonia-hydrogen p r o c e s s .
The p r o t o t y p e p l a n t was b u i l t a t Mazingarbe (2/3,4) in
F r a n c e in 1967 and was f o l l o w e d by two p l a n t s s u p p l i e d
to I n d i a by the GELPRA c o n s o r t i u m (5,6). The f i r s t o f
t h e s e p l a n t s , a t Baroda, is c u r r e n t l y b e i n g s t a r t e d up
and the second, a t T u t i c o r i n , is in the f i n a l s t a g e o f
c o n s t r u c t i o n . The o t h e r ammonia-hydrogen p l a n t a t
T a l c h e r (6),
a l s o in I n d i a , uses a f i n a l enrichment
system d e s i g n e d and s u p p l i e d by S u l z e r and is a l s o in
the l a t t e r s t a g e s o f c o n s t r u c t i o n . S i m i l a r f i n a l enr i c h m e n t systems u s i n g vacuum d i s t i l l a t i o n o f water
have been s u p p l i e d by S u l z e r f o r a m a j o r i t y o f the Can a d i a n GS heavy water p l a n t s
{J)In 1973 S u l z e r and AECL agreed t o exchange i n f o r mation on amine p r o c e s s development. A heavy water p r o c e s s was d e s i g n e d u s i n g a f l o w s h e e t development from
S u l z e r s e x p e r i e n c e w i t h the f i v e ammonia p l a n t based
1
© 0-8412-0420-9/78/47-068-053$05.00/0
In Separation of Hydrogen Isotopes; Rae, H.;
ACS Symposium Series; American Chemical Society: Washington, DC, 1978.
Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch004
54
SEPARATION
O F HYDROGEN ISOTOPES
heavy water p l a n t s ment, oned above t o g e t h e r w i t h the
AECL owned c a t a l y s t d e v e l o p e d a t C h a l k R i v e r N u c l e a r
l a b o r a t o r i e s . Advantages o v e r e x i s t i n g p r o c e s s e s were
a p p a r e n t and s u f f i c i e n t f o r S u l z e r t o commit themselves
to d e v e l o p the p r o c e s s t o a s t a g e a t which a t u r n k e y
p l a n t c o u l d be b u i l t w i t h known c o s t s and guaranteed
performance.
The s t i m u l u s b e h i n d t h i s development was the r e c o g n i t i o n t h a t the p r o c e s s can produce heavy water
u s i n g c o n s i d e r a b l y l e s s equipment and l e s s energy than
e x i s t i n g p r o c e s s e s . There a r e two p r i n c i p a l reasons
f o r t h i s . The f i r s t depends on the d e u t e r i u m exchange
p r o p e r t i e s o f methylamine and hydrogen and can b e s t be
i l l u s t r a t e d by comparing t h i s c h e m i c a l exchange p a i r
w i t h the two o t h e r exchange p a i r s commonly used in ind u s t r i a l heavy water p l a n t s : hydrogen s u l p h i d e - w a t e r
and ammonia-hydrogen (8,9). The second f a c t o r is t i e d
up w i t h the use o f hydrogen, in the form o f ammonia
s y n t h e s i s gas, as d e u t e r i u m f e e d s t o c k . T h i s w i l l be dem o n s t r a t e d by d i s c u s s i n g the way in which the heavy
water p l a n t is c o u p l e d w i t h the s y n t h e s i s gas product i o n system o f the ammonia p l a n t .
B i t h e r m a l Enrichment u s i n g Amine-Hydrogen Exchange
Most o f the d e u t e r i u m s e p a r a t i o n in the amine-hydrogen p r o c e s s is a c h i e v e d u s i n g the b i t h e r m a l (dual
temperature) enrichment t e c h n i q u e (10). T h i s t e c h n i q u e
is a l s o used in the GS p l a n t s and in the ammonia-hydrogen p l a n t b e i n g b u i l t a t T a l c h e r
(6).
The t e c h n i q u e makes use o f a temperature dependent
d e u t e r i u m exchange r e a c t i o n between a l i q u i d and a gas.
In the amine-hydrogen p r o c e s s d e u t e r i u m is exchanged
between the amino group o f l i q u i d monomethylamine and
gaseous hydrogen a c c o r d i n g t o the r e a c t i o n :
A s i m p l e gas f e d b i t h e r m a l enrichment l o o p is
shown in F i g u r e 1. Feed gas is s u c c e s s i v e l y passed
through hot and c o l d exchange towers in c o u n t e r c u r r e n t
to a c l o s e d l o o p o f l i q u i d . In t h e h o t tower the e q u i l i b r i u m f o r the above r e a c t i o n is t o the l e f t , t h e r e f o r e d e u t e r i u m passes from the l i q u i d t o the gas. In
the c o l d tower the e q u i l i b r i u m s h i f t s t o the r i g h t so
t h a t d e u t e r i u m passes from the gas t o the l i q u i d . The
gas l e a v i n g the h o t tower is e n r i c h e d in d e u t e r i u m and
a p o r t i o n o f i t is used as f e e d f o r a h i g h e r enrichment
s t a g e . T h i s gas r e t u r n s d e p l e t e d and j o i n s the main
stream o f gas which is d e u t e r i u m s t r i p p e d in the c o l d
In Separation of Hydrogen Isotopes; Rae, H.;
ACS Symposium Series; American Chemical Society: Washington, DC, 1978.
4.
W Y N N
AECL-Sulzer
Amine
55
Process
tower.
The s e p a r a t i o n power o f such a b i t h e r m a l l o o p depends on the d i f f e r e n c e in the exchange e q u i l i b r i a in
the h o t and c o l d towers. The s e p a r a t i o n f a c t o r ,
is
d e f i n e d as the r a t i o o f D/D+H in l i q u i d t o D/D+H in
the gas. E f f i c i e n t d e u t e r i u m e x t r a c t i o n and e n r i c h m e n t
is a c h i e v e d w i t h a low v a l u e o f t h e s e p a r a t i o n f a c t o r
in the h o t tower i ^ ) and a h i g h v a l u e in the c o l d
tower (oCç).
The s i m p l e s t s t a n d a r d o f comparison f o r b i t h e r m a l
e n r i c h m e n t p r o c e s s e s is t h e maximum r e c o v e r y a v a i l a b l e
u s i n g a s i n g l e e n r i c h m e n t l o o p w i t h an i n f i n i t e number
o f t h e o r e t i c a l p l a t e s in h o t and c o l d towers, g i v e n by
the term l-oCh/<=*c. T h i s v a l u e is a rough i n d i c a t i o n
o f t h e amount o f p r o d u c t heavy water s e p a r a t e d by
p l a n t s p r o c e s s i n g the same molar q u a n t i t y o f f e e d s t o c k ,
be i t water o r hydrogen. F o r the same p r o d u c t i o n r a t e
t h e r e f o r e , the f e e d s t o c k q u a n t i t y t o be p r o c e s s e d is
r o u g h l y p r o p o r t i o n a l t o t h e r e c i p r o c a l o f t h i s number.
The s e p a r a t i o n f a c t o r s t h a t can be r e a l i s e d in
a b i t h e r m a l l o o p depend upon the p r o p e r t i e s o f the exchange p a r t n e r s . F i g u r e 2 shows t h e v a r i a t i o n in the
s e p a r a t i o n f a c t o r , * * , as a f u n c t i o n o f t e m p e r a t u r e f o r
the f o l l o w i n g exchange r e a c t i o n s :
Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch004
0
1
HDO
+ HS
«=-t
2
HD
+ NH
4 = £ H
3
HD
+ CH NH
2
3
3
2
i=?
H0
H
2
+
HDS
2
+ NH D
2
+ CH^HD
2
The c u r v e s a r e o n l y shown f o r the temperature
range in which an i n d u s t r i a l heavy water p r o c e s s can
o p e r a t e w e l l . F o r the GS p r o c e s s the h o t tower o p e r a t e s a t 130 °C t o l i m i t t h e amount o f water vapour in
the gas phase. C o l d tower temperature i g l i m i t e d by
the f o r m a t i o n o f a s o l i d h y d r a t e a t 28
C. F o r the
ammonia-hydrogen p r o c e s s a h o t tower temperature
around 60 °C l i m i t s the ammonia vapour c o n c e n t r a t i o n
in t h e gas phase. C o l d tower t e m p e r a t u r e is l i m i t e d t o
about -25 °C by the poor k i n e t i c s o f the exchange a t
low t e m p e r a t u r e s . Amine-hydrogen h o t tower t e m p e r a t u r e
is l i m i t e d t o +40 °C t o m i n i m i s e the r a t e o f c a t a l y s t
d e c o m p o s i t i o n . The c o l d tower can o p e r a t e a t -50
C
however, because o f the f a r s u p e r i o r k i n e t i c s o f the
c h e m i c a l exchange r e a c t i o n , compared w i t h ammonia-hydrogen exchange. However, the use o f s p e c i a l g a s - l i q u i d c o n t a c t o r s is n e c e s s a r y t o t a k e f u l l advantages o f
the amine-hydrogen exchange k i n e t i c s a t -50
C.
L i s t e d below a r e the h o t and c o l d tower o p e r a t i n g
In Separation of Hydrogen Isotopes; Rae, H.;
ACS Symposium Series; American Chemical Society: Washington, DC, 1978.
56
SEPARATION
O F HYDROGEN
ISOTOPES
DEPLETED GAS
LIQUID
ICOLDj
GAS RETURN
FROM NEXT STAGE
ENRICHED GAS
Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch004
TO NEXT STAGE
HOT
Jf
FEED GAS
Figure 1.
Gas-fed bithermal enrichment stage
SEPARATION
FACTOR dC
10
Figure 2.
Deuterium exchange equilibria for bithermal enrichment processes
In Separation of Hydrogen Isotopes; Rae, H.;
ACS Symposium Series; American Chemical Society: Washington, DC, 1978.
4.
W Y N N
AECL-Sulzer
Amine
Process
57
c o n d i t i o n s , s e p a r a t i o n f a c t o r s and maximum p o s s i b l e
y i e l d f o r the t h r e e systems.
System
H S/H 0
2
Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch004
c o l d tower o p e r a t i n g
temperature (°C)
c o l d tower s e p a r a t i o n
factor
hot tower o p e r a t i n g
temperature (°C)
hot tower s e p a r a t i o n
factor
maximum p o s s i b l e y i e l d
2
NH /H
3
2
CH NH /H
3
2
+ 30
-25
-50
2.22
5.3
7.9
+130
+60
+40
1.76
0.21
2.9
0.45
3.6
0.55
T h i s s i m p l e comparison i n d i c a t e s t h a t f o r t h e same
d e u t e r i u m e x t r a c t i o n t h e ammonia-hydrogen system o n l y
needs t o p r o c e s s about h a l f as much f e e d s t o c k as the
GS system and the amine-hydrogen system o n l y about
40 % as much.
A more r e a l i s t i c comparison is t o l o o k a t t h e
performance o f t h e systems w i t h a f i n i t e number o f
t h e o r e t i c a l s t a g e s in the exchange towers. A t t a i n m e n t
of t h e h i g h s e p a r a t i o n f a c t o r in the c o l d towers o f
the hydrogen based p r o c e s s e s is n e c e s s a r y t o a c h i e v e
a h i g h y i e l d . T h i s can o n l y be a c h i e v e d by o p e r a t i n g
a t low c o l d tower t e m p e r a t u r e s where the slow i s o t o p i c
exchange r e q u i r e s the use o f s p e c i a l c o n t a c t i n g d e v i c e s
to a c h i e v e r e a s o n a b l e t r a y e f f i c i e n c i e s . Each o f t h e s e
s p e c i a l c o n t a c t o r s r e q u i r e s more tower volume t h a n a
s i e v e t r a y which g i v e s a r e a s o n a b l e t r a y e f f i c i e n c y in
the GS c o l d towers. C o n s e q u e n t l y , f o r t h e same o u t l a y
in equipment, l e s s t h e o r e t i c a l s t a g e s w i l l be a v a i l a b l e
in the c o l d towers o f the hydrogen based p r o c e s s e s .
F i g u r e 3 compares the performance o f t h e t h r e e b i t h e r m a l systems u s i n g a f i n i t e number o f t r a n s f e r s t a ges in the h o t and c o l d exchange columns. GS p e r f o r mance has been computed f o r h o t and c o l d towers each
with f i f t y sieve trays using tray e f f i c i e n c i e s reported in the l i t e r a t u r e (11). The performance o f t h e
amine-hydrogen and ammonia hydrogen system has been
computed f o r h o t towers w i t h f i f t y s i e v e t r a y s and
c o l d towers w i t h f i v e s p e c i a l c o l d c o n t a c t o r s . Stage
e f f i c i e n c i e s a r e based on S u l z e r and AECL p i l o t t e s t s .
The c o l d towers w i t h f i v e c o l d c o n t a c t o r s r o u g h l y
c o r r e s p o n d in tower h e i g h t t o the f i f t y s i e v e t r a y s
used in the GS c o l d tower c o n s i d e r e d h e r e . Hence the
comparison is f o r enrichment l o o p s w i t h r o u g h l y s i m i l a r
equipment c o s t s , b u t o p e r a t i n g w i t h d i f f e r e n t exchange
fluids.
In Separation of Hydrogen Isotopes; Rae, H.;
ACS Symposium Series; American Chemical Society: Washington, DC, 1978.
Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch004
58
SEPARATION
O F HYDROGEN
ISOTOPES
The performance o f t h e s e systems cannot a c c u r a t e l y be
compared u s i n g t h e s i n g l e v a r i a b l e o f d e u t e r i u m r e c o v e r y s i n c e t h i s is dependent on t h e e n r i c h m e n t p r o d u c e d .
F i g u r e 3 shows t h e e n r i c h m e n t / y i e l d c h a r a c t e r i s t i c s f o r
t h e t h r e e systems. A t an e n r i c h m e n t f a c t o r o f 1 (no e n richment) t h e y i e l d s a r e t h e maximum t h e o r e t i c a l v a l ues o f l - c * h / c * c . As t h e e n r i c h m e n t f a c t o r i n c r e a s e s
the y i e l d is r e d u c e d . T h i s e f f e c t is more marked f o r
the hydrogen based p r o c e s s e s because l e s s c o n t a c t i n g
s t a g e s a r e a v a i l a b l e in t h e c o l d tower. T h i s is t h e
p e n a l t y f o r t h e c o m p a r a t i v e l y poor exchange k i n e t i c s o f
the hydrogen based p r o c e s s e s a t low t e m p e r a t u r e s .
An e n r i c h m e n t f a c t o r o f about f o u r c o r r e s p o n d s t o
o p e r a t i n g c o n d i t i o n s in t h e GS p l a n t s (11) and in t h e
amine-hydrogen p r o c e s s . A t t h i s p o i n t t h e y i e l d f o r
the ammonia-hydrogen l o o p is no more than t h a t f o r t h e
GS l o o p . The y i e l d from t h e amine-hydrogen l o o p is howe v e r t w i c e as g r e a t , i . e . u n i t p r o d u c t from t h e aminehydrogen l o o p r e q u i r e s o n l y h a l f t h e amount o f f e e d s t o c k o f t h e o t h e r two p r o c e s s e s .
The amount o f f l u i d r e q u i r i n g p r o c e s s i n g is a key
parameter in d e t e r m i n i n g t h e c o s t o f a p r o c e s s . Heavy
water is e x p e n s i v e because huge q u a n t i t i e s o f f e e d s t o c k
r e q u i r e p r o c e s s i n g t o produce a r e l a t i v e l y s m a l l amount
o f p r o d u c t . A p r o c e s s b u i l t from a c a s c a d e o f h i g h
y i e l d e n r i c h m e n t l o o p s is l i k e l y t o be c h e a p e r . Not
o n l y tower volumes b u t equipment and energy c o s t s f o r
p u r i f i c a t i o n , h u m i d i f i c a t i o n and d e - h u m i d f i c a t i o n a r e
all p r o p o r t i o n a l t o t h e amount o f gas and l i q u i d r e q u i r i n g p r o c e s s i n g in t h e e n r i c h m e n t l o o p s .
The p r o c e s s i n g c o s t s p e r mole o f c i r c u l a t i n g gas
a r e d i f f i c u l t t o compare f o r t h e amine-hydrogen and GS
p r o c e s s e s a s t h e problems a r e o f a d i f f e r e n t n a t u r e .
Problems o f c o r r o s i o n and t h e t o x i c p r o p e r t i e s o f hydrogen s u l p h i d e add t o t h e c o s t s o f t h e GS p r o c e s s . I n
the amine p r o c e s s c o s t s a r i s e from t h e use o f low temp e r a t u r e r e f r i g e r a t i o n and low t e m p e r a t u r e s t e e l s .
Comparison between ammonia-hydrogen and amine-hydrogen
is e a s i e r . These p r o c e s s e s o p e r a t e a t s i m i l a r p r e s s u r e s
and use s i m i l a r equipment. The amine p r o c e s s o p e r a t e s
a t a lower temperature so r e f r i g e r a t i o n is more expens i v e . On t h e o t h e r hand l e s s r e f r i g e r a t i o n is r e q u i r e d
p e r mole o f hydrogen c i r c u l a t e d because t h e vapour
p r e s s u r e o f amine is o n l y h a l f t h a t o f ammonia. T h e r e f o r e l e s s r e f r i g e r a t i o n is r e q u i r e d f o r d e h u m i d i f y i n g
the c i r c u l a t i n g gas. P r o c e s s i n g c o s t s p e r mole o f gas
c i r c u l a t e d a r e u n l i k e l y t o be s i g n i f i c a n t l y d i f f e r e n t .
The above comparison u s i n g t h e d e u t e r i u m exchange
p r o p e r t i e s o f t h e t h r e e systems shows t h a t an aminehydrogen b i t h e r m a l l o o p need o n l y be h a l f t h e s i z e o f
In Separation of Hydrogen Isotopes; Rae, H.;
ACS Symposium Series; American Chemical Society: Washington, DC, 1978.
4.
W Y N N
AECL-Sulzer
Amine
Process
59
an ammonia-hydrogen l o o p o f e q u i v a l e n t performance.
T h i s is one o f the key reasons f o r the economy o f the
amine-hydrogen p r o c e s s and i t has p r o v i d e d the s t i m u l u s
f o r S u l z e r t o s h i f t development from the ammonia-hydrogen t o the amine-hydrogen p r o c e s s .
Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch004
Special Cold Contactors
The achievement o f h i g h i s o t o p i c exchange e f f i c i e n c i e s a t low temperature was the f i r s t g o a l o f the
amine-hydrogen p r o c e s s development program. E a r l y
t e s t s made by AECL show a s i e v e t r a y e f f i c i e n c y o f
o n l y 0.7 % a t -50 °C (.12). Subsequent development work
has produced c o n t a c t o r s w i t h e f f i c i e n c i e s r a n g i n g up
to 70 % a t t h i s temperature. Success in t h i s key a r e a
l e d t o a more g e n e r a l development e f f o r t which has
brought the p r o c e s s t o i t s c u r r e n t mature s t a t e .
Deuterium exchange between methylamine and hydrogen o c c u r s v i a the c a t a l y s t d i s s o l v e d in the l i q u i d
phase. In p r i n c i p l e the r a t e o f i s o t o p i c exchange is
dependent on both the i n t r i n s i c c h e m i c a l k i n e t i c s o f
the exchange r e a c t i o n and the r a t e o f d i f f u s i o n a l mass
t r a n s f e r o f r e a c t a n t s and p r o d u c t s . Because o f the
low s o l u b i l i t y o f hydrogen in amine and the h i g h a c t i v i t y o f the c a t a l y s t , even a t the low c o l d tower tempe r a t u r e o f -50 °C, the r e a c t i o n is in the f a s t regime
(11).
T h i s means t h a t s i m u l t a n e o u s mass t r a n s f e r and
c h e m i c a l r e a c t i o n o c c u r o n l y in f r e s h elements o f l i q u i d brought near the g a s - l i q u i d i n t e r f a c e .
I n c r e a s e s in exchange r a t e have been produced by
i n c r e a s i n g both the g a s - l i q u i d i n t e r f a c i a l a r e a and the
r a t e o f s u r f a c e renewal by p r o d u c i n g a t u r b u l e n t gas
l i q u i d m i x t u r e . Exchange e f f i c i e n c i e s in the s p e c i a l l y
d e v e l o p e d c o n t a c t o r s a r e a l s o h i g h e r than f o r the s i e v e
t r a y because o f g r e a t e r r e s i d e n c e time, i . e . the cont a c t o r s c o n t a i n more l i q u i d in which exchange is o c c u r r i n g . F i g u r e 4 shows two s u i t a b l e low temperature cont a c t o r s . The c o c u r r e n t
bed c o n t a c t o r is b a s i c a l l y a
deep s i e v e t r a y which is f i l l e d w i t h a k n i t t e d mesh
p a c k i n g t o reduce bubble c o a l e s c e n c e . The f l o w p a t t e r n
is m a i n l y c o n c u r r e n t because o f the h i g h o v e r f l o w w e i r .
T h i s c o n t a c t o r has been d e v e l o p e d by Chalk R i v e r Nuc l e a r L a b o r a t o r i e s (11,13).
The e j e c t o r c o n t a c t o r , shown s c h e m a t i c a l l y in
F i g u r e 4, was d e v e l o p e d by S u l z e r o r i g i n a l l y f o r use in
the monothermal ammonia heavy water p r o c e s s (14,4). In
each s t a g e gas is expanded through n o z z l e s and l i q u i d
is sucked i n t o the h i g h v e l o c i t y gas stream g i v i n g a
v e r y i n t i m a t e g a s / l i q u i d m i x t u r e . The m i x t u r e passes
up a r e a c t i o n tube and is then s e p a r a t e d in a c e n t r i -
In Separation of Hydrogen Isotopes; Rae, H.;
ACS Symposium Series; American Chemical Society: Washington, DC, 1978.
Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch004
60
SEPARATION O F HYDROGEN ISOTOPES
Figure 3.
Comparison of bithermal enrichment fluids
Figure 4.
Cold-contacting devices
In Separation of Hydrogen Isotopes; Rae, H.;
ACS Symposium Series; American Chemical Society: Washington, DC, 1978.
4,
AECL-Sulzer
W Y N N
Amine
61
Process
f u g a l s e p a r a t o r , gas p a s s i n g on t o t h e n e x t s t a g e and
l i q u i d b e i n g r e c y c l e d t o t h e e j e c t o r s . The l i q u i d
throughput in t h e tower is pumped from s t a g e t o s t a g e
t o overcome t h e p r e s s u r e d i f f e r e n c e caused by t h e p r e s s u r e drop in t h e e j e c t o r d r i v i n g n o z z l e .
The d e s i g n f e a t u r e s and performance o f t h e s p e c i a l
c o n t a c t o r s on amine-hydrogen exchange a t -50 C a r e
c o n t r a s t e d w i t h t h o s e o f a normal s i e v e t r a y below:
contactor
type
^ ^ ^ - ^
property
Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch004
flow p a t t e r n
gas phase
residence
superficial
(s)
time,u,
sieve
tray
packed
bed
ejector
cross
current
cocurrent
recycle
co-current
7.6
1
6.7
s p e c i f i c energy
dissipation (watts/liter)
1
1
10
stage e f f i c i e n c y
0.7
22
70
(%)
r a t i o o f mass
transfer rates
i n t e r f a c i a l area
1
2 3
(m /m )
250
5.7
1300
23
6000
The packed bed c o n t a c t o r d e v e l o p e d by AECL p e r f o r m s
b e t t e r than t h e s i e v e t r a y f o r two r e a s o n s . F i r s t l y
the packed bed is deeper so t h e gas phase r e s i d e n c e
time is h i g h e r . S e c o n d l y t h e r a t e o f mass t r a n s f e r in
the m i x t u r e is h i g h e r . T h i s is a t t r i b u t a b l e t o t h e
high voidage packing i n c r e a s i n g g a s - l i q u i d i n t e r f a c i a l
a r e a by p r e v e n t i n g b u b b l e c o a l e s c e n c e . I t is a l s o p r o b a b l e t h a t t h e upper r e g i o n s o f t h e s i e v e t r a y were
o p e r a t i n g in t h e s p r a y regime where l i q u i d phase t u r b u l e n c e would be r e l a t i v e l y p o o r . The s p e c i f i c energy
d i s s i p a t i o n is d e f i n e d as t h e gas phase p r e s s u r e d r o p
m u l t i p l i e d by t h e gas f l o w r a t e and d i v i d e d by t h e r e a c t i o n m i x t u r e volume. Both t h e s i e v e t r a y and t h e
packed bed a r e d e s i g n e d t o keep t h e p r e s s u r e drop
a c r o s s t h e s i e v e p l a t e low so as t o reduce l i q u i d backup in t h e downcomers and r e d u c e t r a y s p a c i n g . T h i s r e s u l t s in t h e s p e c i f i c energy d i s s i p a t i o n b e i n g low and
s i m i l a r f o r both d e v i c e s .
The e j e c t o r shows more than a t h r e e f o l d improvement in e f f i c i e n c y compared t o t h e packed bed. The r e s i d e n c e times f o r t h e two d e v i c e s a r e s i m i l a r . The
In Separation of Hydrogen Isotopes; Rae, H.;
ACS Symposium Series; American Chemical Society: Washington, DC, 1978.
Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch004
62
S E P A R A T I O N O F H Y D R O G E N ISOTOPES
b e t t e r performance is a t t r i b u t a b l e t o t h e h i g h e r r a t e
o f energy d i s s i p a t i o n in t h e e j e c t o r p r o d u c i n g a much
more i n t i m a t e g a s - l i q u i d m i x t u r e . The h i g h e r energy input is caused by t h e p r e s s u r e drop in t h e gas n o z z l e s
o f t h e e j e c t o r which r e q u i r e s t h e use o f pumps f o r
p a s s i n g l i q u i d s t a g e w i s e down t h e tower. The r e d u c t i o n
in tower volume by a f a c t o r o f o v e r t h r e e when u s i n g
the e j e c t o r more than makes up f o r t h e c o s t o f t h e s e
pumps. Energy c o s t s in t h e form o f i n c r e a s e d gas
stream p r e s s u r e drop a r e s m a l l . In f a c t t h e e j e c t o r
c o n t a c t o r s use l e s s energy than t h e s i e v e t r a y s f o r a
g i v e n mass t r a n s f e r d u t y . Though t h e r a t e o f energy
d i s s i p a t i o n p e r u n i t r e a c t i o n volume f o r t h e e j e c t o r
is h i g h e r than f o r t h e s i e v e t r a y , a tower u s i n g e j e c t o r s w i l l r e q u i r e o n l y 75 % o f t h e energy in t h e form
o f p r e s s u r e drop compared w i t h a s i e v e t r a y tower o f
equal performance.
There a r e o t h e r advantages in u s i n g t h e e j e c t o r
contactor. Multiple units consisting of nozzles, eject o r s , r e a c t i o n tubes and s e p a r a t o r s a r e i n s t a l l e d in
p a r a l l e l i n s i d e each s t a g e o f t h e c o l d tower. P i l o t
t e s t i n g o f one f u l l s i z e u n i t e l i m i n a t e s t h e n e c e s s i t y
f o r and a v o i d s t h e r i s k s o f s c a l e - u p . A n o t h e r advantage
is t h a t gas and l i q u i d a r e mixed and s e p a r a t e d u s i n g
i n e r t i a l f o r c e s . These a r e l a r g e compared t o t h e normal
i n t e r f a c i a l f o r c e s a c t i n g in a two phase m i x t u r e . V a r i a t i o n s in t h e foaminess o f t h e p r o c e s s l i q u i d s c a u s e d
by a c o n c e n t r a t i o n o f i m p u r i t i e s a r e l e s s l i k e l y t o
a f f e c t t h e h y d r a u l i c performance o f t h e e j e c t o r s .
The use o f t h e s e s p e c i a l c o n t a c t o r s is t o a l a r g e
e x t e n t r e s p o n s i b l e f o r t h e p o t e n t i a l o f t h e amine p r o c e s s . Because o f t h e s t r o n g temperature dependence o f
the exchange e f f i c i e n c y , t h e i r use e f f e c t i v e l y lowers
the optimum c o l d tower temperature a l l o w i n g t h e p r o c e s s
the economies o f h i g h d e u t e r i u m r e c o v e r y mentioned
earlier.
Link-Up w i t h t h e Ammonia
Plant
Ammonia p l a n t s y n t h e s i s gas has been used as f e e d s t o c k f o r a number o f heavy water p l a n t s (6,15). The
gas is s t r i p p e d o f d e u t e r i u m in t h e heavy water p l a n t
and r e t u r n e d t o t h e s y n t h e s i s l o o p o f t h e ammonia
p l a n t . One advantage o f u s i n g s y n t h e s i s gas is t h a t
the gas is r e l a t i v e l y p u r e . The main contaminant,
n i t r o g e n , is i n e r t and does n o t i n t e r f e r e w i t h t h e
heavy water p r o c e s s . The main d i s a d v a n t a g e o f u s i n g
s y n t h e s i s gas as a d e u t e r i u m s o u r c e is t h a t t h e s i z e
o f t h e heavy water p l a n t is l i m i t e d by t h e s i z e o f t h e
ammonia p l a n t t o which i t is c o n n e c t e d . S y n t h e s i s gas
In Separation of Hydrogen Isotopes; Rae, H.;
ACS Symposium Series; American Chemical Society: Washington, DC, 1978.
Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch004
4.
W Y N N
AECL-Sulzer
Amine
Process
63
from a one thousand t o n p e r day ammonia p l a n t c a n o n l y
y i e l d about 65 t o n s p e r y e a r o f heavy water. T h i s l i m i t s t h e s c a l e economies p o s s i b l e f o r t h e heavy water
plant.
C o n n e c t i o n o f t h e amine-hydrogen p r o c e s s t o t h e
ammonia p l a n t has been d e s i g n e d so t h a t a p r e - e n r i c h ment in d e u t e r i u m o c c u r s b e f o r e t h e s y n t h e s i s gas
r e a c h e s t h e heavy water p l a n t , so r e d u c i n g t h e e n r i c h ment n e c e s s a r y in t h e heavy water p l a n t i t s e l f . T h i s
is the second r e a s o n why t h e amine-hydrogen p r o c e s s is
a b l e t o produce heavy water c h e a p l y .
In an o p e r a t i n g ammonia p l a n t t h e hydrogen in t h e
s y n t h e s i s gas has a d e u t e r i u m c o n c e n t r a t i o n w e l l below
the average v a l u e o f t h a t o f t h e hydrogen in t h e f e e d s t o c k , which is n o r m a l l y around 130 ppm. The s y n t h e s i s
gas is d e p l e t e d in d e u t e r i u m by t h e l a r g e e x c e s s o f
steam r e q u i r e d in t h e r e f o r m e r s where t h e s y n t h e s i s
gas is produced. A t t h e h i g h temperatures r e q u i r e d t h e
steam and p r o d u c t hydrogen r e a c h i s o t o p i c e q u i l i b r i u m ;
the e q u i l i b r i u m p r o d u c i n g a d e u t e r i u m enrichment in t h e
steam and a d e p l e t i o n in t h e hydrogen g a s . When t h e unr e a c t e d steam is condensed o u t o f t h e gas and dumped
the d e u t e r i u m c o n t e n t is l o s t . The d i s t r i b u t i o n o f
d e u t e r i u m in t h e main p r o c e s s streams o f an ammonia
p l a n t is shown in F i g u r e 5.
Most ammonia p l a n t s which have been c o u p l e d w i t h
heavy water p l a n t s have been m o d i f i e d t o a v o i d t h i s
d e u t e r i u m d e p l e t i o n in t h e s y n t h e s i s g a s . Two methods
have been used, b o t h e f f e c t i v e l y r e c y c l i n g d e u t e r i u m
from t h e e n r i c h e d p r o c e s s condensate back i n t o t h e
r e f o r m e r steam s u p p l y . F i g u r e 6 shows one o f t h e s e
methods. The steam d e s t i n e d f o r t h e r e f o r m e r s is passed
t h r o u g h a column in c o u n t e r c u r r e n t t o t h e p r o c e s s cond e n s a t e and s t r i p s o u t t h e e n r i c h e d w a t e r . The o t h e r
method is t o use t h e e n r i c h e d condensate, a f t e r s u i t a b l e t r e a t m e n t , as feedwater f o r t h e b o i l e r which
g e n e r a t e s r e f o r m e r steam.
A f l o w s h e e t has been used f o r t h e amine-hydrogen
p r o c e s s which goes one s t e p f u r t h e r ; i n s t e a d o f r e s t o r i n g t h e d e u t e r i u m c o n t e n t in t h e s y n t h e s i s gas t o
i t s natural l e v e l i t increases i t s t i l l further. This
p r e - e n r i c h m e n t r e d u c e s s u b s t a n t i a l l y t h e number o f
b i t h e r m a l enrichment s t a g e s r e q u i r e d in t h e r e s t o f
t h e p l a n t . F i g u r e 7 shows in p r i n c i p l e how t h i s is
done. Some o f t h e d e u t e r i u m e x t r a c t e d from t h e s y n t h e s i s gas stream is t r a n s f e r r e d v i a a s e r i e s o f i s o t o p i c exchange columns t o t h e r e f o r m e r steam f e e d t o g e t h e r w i t h t h e d e u t e r i u m from t h e e n r i c h e d p r o c e s s
condensate. In t h e f i r s t t r a n s f e r column, t h e t o p one
in the f i g u r e , d e u t e r i u m is t r a n s f e r r e d i n t o c a t a l y s t
In Separation of Hydrogen Isotopes; Rae, H.;
ACS Symposium Series; American Chemical Society: Washington, DC, 1978.
SEPARATION O F H Y D R O G E N ISOTOPES
AMMONIA SYNTHESIS
LOOP
AMMONIA
PRODUCT
CONDENSATE
Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch004
AIR
GAS
|SYNTHESI9|
GAS
jGENERAT.
STEAM
Ν = 135 PPM D/D + H
(ALBERTA)
Figure 5. Deuterium concentrations in an ammonia plant
Figure 6.
Concentrations with deuterium recycle from condensate
In Separation of Hydrogen Isotopes; Rae, H.;
ACS Symposium Series; American Chemical Society: Washington, DC, 1978.
Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch004
4.
W Y N N
AECL-Sulzer
Amine
Process
65
l a d e n l i q u i d methy1amine. In the n e x t column the deut e r i u m e n r i c h e d amine is t r a n s f e r r e d i n t o an amine
vapor stream. In the t h i r d column d e u t e r i u m is t r a n s f e r r e d from amine vapor t o water which is p a s s e d , t o g e t h e r w i t h the e n r i c h e d p r o c e s s condensate, i n t o the
condensate s t r i p p i n g column. T h i s e n r i c h e s the r e f o r m e r
steam which in t u r n e n r i c h e s the s y n t h e s i s gas produced
in the r e f o r m e r .
Deuterium t r a n s f e r from the hydrogen in the s y n t h e s i s gas back t o the r e f o r m e r steam is p o s s i b l e because the s e p a r a t i o n f a c t o r between water and hydrogen
is g r e a t e r than 1. I f water and hydrogen o f e q u a l deut e r i u m c o n c e n t r a t i o n a r e brought i n t o i s o t o p i c e q u i l i brium t h e n d e u t e r i u m w i l l pass from the hydrogen t o
the water. The d e u t e r i u m in the hydrogen is, in e f f e c t ,
more a v a i l a b l e . I f hydrogen is produced from t h i s water
by removing oxygen, t h e n i t w i l l a l s o be e n r i c h e d and
can s e r v e t o e n r i c h more water by i s o t o p i c exchange.
T h i s is the monothermal o r d e c o m p o s i t i o n enrichment
t e c h n i q u e which has been used w i t h water and hydrogen
in the heavy water p l a n t s a t T r a i l and Rjukan and w i t h
ammonia and hydrogen in t h e p l a n t s a t Mazingarbe, Baroda and T u t i c o r i n (5).
The d i s a d v a n t a g e o f the p r o c e s s
is the c o s t o f the d e c o m p o s i t i o n s t e p ; e l e c t r o l y s i s o f
water o r t h e r m a l c r a c k i n g o f ammonia (15). However, in
the amine-hydrogen p r o c e s s the d e c o m p o s i t i o n s t e p
o c c u r s in the r e f o r m e r s o f the ammonia p l a n t . Where
s y n t h e s i s gas is used as a d e u t e r i u m s o u r c e the ammonia
p l a n t is n o r m a l l y m o d i f i e d t o r e c y c l e d e u t e r i u m from
the p r o c e s s condensate t o the r e f o r m e r steam. The e x t r a
c o s t o f r e c y c l i n g d e u t e r i u m from the s y n t h e s i s gas t o
the r e f o r m e r steam is s m a l l .
D e t a i l e d d e s i g n o f the l i n k - u p depends on the des i g n o f the ammonia p l a n t . K e l l o g g Canada have c o l l a b o r a t e d w i t h S u l z e r in t h i s a r e a and the d e s i g n package f o r the 65 t o n s p e r y e a r heavy water p l a n t is spec i f i c a l l y t a i l o r e d t o the K e l l o g g ammonia p l a n t d e s i g n .
The degree o f p r e - e n r i c h m e n t p o s s i b l e u s i n g such
a system is l i m i t e d by the l e a k s o f steam, water and
s y n t h e s i s gas o c c u r r i n g in the ammonia p l a n t r e f o r m e r s .
However, s u f f i c i e n t p r e - e n r i c h m e n t can be a c h i e v e d t o
more than h a l v e the amount o f equipment used in the
subsequent b i t h e r m a l amine-hydrogen enrichment s e c t i o n
o f the heavy water p l a n t .
Deuterium Enrichment
System
F i g u r e 8 shows s c h e m a t i c a l l y the i s o t o p i c e n r i c h ment scheme used in the p r o c e s s . A c a s c a d e o f two
amine-hydrogen b i t h e r m a l enrichment l o o p s is used
In Separation of Hydrogen Isotopes; Rae, H.;
ACS Symposium Series; American Chemical Society: Washington, DC, 1978.
SEPARATION
Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch004
66
Figure 7.
Figure 8.
O F HYDROGEN ISOTOPES
Concentrations with deuterium recycle from condensate
and synthesis gas
Isotopic enrichment scheme
HEAVY WATER
In Separation of Hydrogen Isotopes; Rae, H.;
ACS Symposium Series; American Chemical Society: Washington, DC, 1978.
Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch004
4.
W Y N N
AECL-Sulzer
Amine
Process
67
c o u p l e d w i t h f i n a l enrichment by water d i s t i l l a t i o n .
T h i s scheme is used t o reduce l o s s e s o f d e u t e r i u m enr i c h e d s u b s t a n c e s and t o m i n i m i z e the d e u t e r i u m i n v e n t o r y o f the p l a n t .
P r e - e n r i c h e d s y n t h e s i s gas from the ammonia p l a n t
is t r e a t e d t o remove water and c a r b o n o x i d e s and t h e n
fed t h r o u g h the main b i t h e r m a l enrichment l o o p . Dep l e t e d amine from the h o t tower is f u r t h e r s t r i p p e d by
the p r e - e n r i c h m e n t d e u t e r i u m t r a n s f e r column b e f o r e
b e i n g f e d t o the f i r s t s t a g e c o l d column. The f i r s t
stage e n r i c h e s gas t o about 20 t i m e s n a t u r a l c o n c e n t r a t i o n . E n r i c h e d l i q u i d is b l e d from between the c o l d
and h o t columns and f e d t o the second b i t h e r m a l enrichment stage.
The second s t a g e e n r i c h e s gas t o about 300 t i m e s
n a t u r a l c o n c e n t r a t i o n g i v i n g a deuterium concentration
in methylamine o f about f o u r t e e n p e r c e n t . Condensed
amine vapor from the second s t a g e d e h u m i d i f i e r is cont a c t e d w i t h water in a t r a n s f e r column. T h i s e n r i c h e d
water is then d i s t i l l e d under vacuum t o g i v e the heavy
water p r o d u c t o f 99.8 % d e u t e r i u m c o n c e n t r a t i o n .
Process Status
The amine-hydrogen p r o c e s s f o r heavy water o u t l i n e d here has been d e v e l o p e d o v e r t h e p a s t t e n y e a r s ,
s t a r t i n g w i t h bench t e s t s o f amine-hydrogen d e u t e r i u m
exchange by Atomic Energy o f Canada L i m i t e d (16)
and
c u l m i n a t i n g in the g e n e r a t i o n by S u l z e r o f a complete
d e s i g n package f o r a 65 t o n s p e r y e a r p l a n t l i n k e d t o
an ammonia p l a n t in A l b e r t a .
L a b o r a t o r y work has c e n t r e d around i m p r o v i n g the
low temperature k i n e t i c s o f the amine-hydrogen exchange
r e a c t i o n . Three f u l l s c a l e e j e c t o r c o n t a c t o r s have
been p i l o t e d and s u c c e s s i v e m o d i f i c a t i o n s have improved
exchange e f f i c i e n c y by a f a c t o r o f f o u r . A l l o t h e r u n i t
p r o c e s s e s n o t used in i n d u s t r i a l heavy water p l a n t have
been p i l o t e d e i t h e r by AECL o r by S u l z e r .
AECL have d e v e l o p e d the homogeneous c a t a l y s t used
to promote exchange and have measured r a t e s o f c a t a l y s t
d e c o m p o s i t i o n (17). S u l z e r have p i l o t e d p r o c e s s e s t o
remove t h e s e d e c o m p o s i t i o n p r o d u c t s from the p l a n t inventory.
P r o c e s s d e s i g n has p r o g r e s s e d from the g e n e r a l
o u t l i n e o f the p r o c e s s g i v e n above t o d e t a i l e d h e a t ,
mass and i s o t o p i c b a l a n c e s f o r the complete p r o c e s s .
D e s i g n is based on equipment performance d e t e r m i n e d
d u r i n g p i l o t t e s t s o r on m a n u f a c t u r e r s ' quoted guarant e e s f o r s t a n d a r d equipment i t e m s . The s e n s i t i v i t y o f
the p r o c e s s t o equipment m a l f u n c t i o n o r o p e r a t i n g
In Separation of Hydrogen Isotopes; Rae, H.;
ACS Symposium Series; American Chemical Society: Washington, DC, 1978.
68
SEPARATION O F HYDROGEN
ISOTOPES
Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch004
e r r o r s has been a s s e s s e d by computer m o d e l l i n g and
s u i t a b l e d e s i g n margins i n c o r p o r a t e d . In g e n e r a l t h e
p r o c e s s is much l e s s s e n s i t i v e t o such d i s t u r b a n c e s
than o t h e r b i t h e r m a l heavy water p r o c e s s e s because o f
the b i g d i f f e r e n c e in h o t and c o l d tower s e p a r a t i o n
factors
(11).
E n g i n e e r i n g d e s i g n has been pursued s i m u l t a n e o u s l y
w i t h t h e above a c t i v i t i e s . Equipment items have been
s p e c i f i e d and b i d s r e c e i v e d from s e l e c t e d v e n d o r s .
P r e l i m i n a r y d e s i g n o f c i v i l work has been c o n c l u d e d by
l o c a l companies. A s a f e t y r e p o r t has been p r e p a r e d as
a guide t o s i t e s e l e c t i o n . The p l a n t c a p i t a l c o s t has
been c a l c u l a t e d based on b i d s f o r equipment and e n g i n eering.
Conclusion
Amine-hydrogen p r o c e s s development was t r i g g e r e d
by p r o c e s s c o n s i d e r a t i o n s i n d i c a t i n g c o n s i d e r a b l e a d vantages o v e r e s t a b l i s h e d p r o d u c t i o n p r o c e s s e s
(16).
S u c c e s s f u l development, i n c l u d i n g l a b o r a t o r y and p i l o t
work, has in t u r n s t i m u l a t e d t h e g e n e r a t i o n by S u l z e r
of a complete d e s i g n package f o r a 65 t o n / y r heavy
water p l a n t a t t a c h e d t o a K e l l o g g ammonia p l a n t in
Western Canada. E s t i m a t e s o f heavy water p r o d u c t i o n
c o s t from t h i s p l a n t a r e based on a s o l i d f o u n d a t i o n
and f a v o u r t h e e x p l o i t a t i o n o f t h e p r o c e s s in t h e near
future.
Abstract
A heavy water p r o c e s s
based on
isotopic
exchange
between hydrogen and methylamine and methylamine and
water
has been d e v e l o p e d by S u l z e r and Atomic Energy
of Canada. Deuterium s o u r c e is the s y n t h e s i s gas stream
of an ammonia p l a n t . Deuterium enrichment is a c h i e v e d
by b i t h e r m a l amine-hydrogen exchange, however, p r e l i m i nary enrichment is made t o o c c u r in the r e f o r m e r s o f
the ammonia p l a n t by u s i n g the steam r e f o r m i n g p r o c e s s
as the d e c o m p o s i t i o n s t e p o f a monothermal enrichment
s t a g e . T h i s f e a t u r e , c o u p l e d w i t h the h i g h v a l u e o f the
s e p a r a t i o n f a c t o r a c h i e v a b l e w i t h hydrogen-amine exchange, a l l o w s a h i g h d e u t e r i u m yield w i t h o u t the use
of hydrogen r e c y c l e in the e x t r a c t i o n s t a g e . D e s i g n
work has been based on pilot t e s t s o f the key p r o c e s s
steps using
industrial
c o n t a c t i n g equipment.
Literature
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Cited
J.,
"A Low-Temperature P l a n t f o r the Production
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4.
WYNN
2
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Roth E., " I s o t o p i c Exchange o f Deuterium Between
Ammonia and Hydrogen - A New Method o f P r o d u c i n g
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Technique de C o m m i s s a r i a t a L ' E n e r g i e Atomique (1968)
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L e f r a n c o i s Β., "Mazingarbe Heavy Water P l a n t ,
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P r o d u z i o n e de Acque P e s a n t e , p . 199, Comitato N a z i o n a l e E n e r g i a N u c l e a r e Rome (1971)
Roth E., T r a o u r o u d e r R., Viratelle J. and L e f r a n c o i s
B., " S t u d i e s o f P r o d u c t i o n P r o c e s s e s and Heavy Water
P l a n t s U s i n g the F r e n c h P r o c e s s " , F o u r t h U n i t e d
N a t i o n s Conference on the P e a c e f u l Uses o f Atomic
E n e r g y , P r o c e e d i n g s 9, 69 U n i t e d N a t i o n s , Geneva
(1971).
N i t s c h k e E., "Processes and Research in the
Produc­
tion o f Heavy Water", A t o m w i r t s c h a f t 18 (1973) 297
Zmasek R., " S u l z e r R e c t i f y i n g P l a n t s f o r E n r i c h i n g
Heavy Water", S u l z e r T e c h n i c a l Review S p e c i a l I s s u e
f o r Nuclex 72 (1972)
S c h i n d e w o l f U . and Lang G . " O p t i m i z a t i o n o f a Heavy
Water P r o d u c t i o n P l a n t w i t h the Ammonia-Hydrogen
Dual Temperature Exchange System", T e c n i c a ed E c o n o ­
mia della P r o d u z i o n e de Acque P e s a n t e , p . 75, Comi­
t a t o N a z i o n a l e E n e r g i a N u c l e a r e , Rome (1971)
W a l t e r S. and N i t s c h k e E., "Problems o f the D e s i g n
and C o n s t r u c t i o n o f a P l a n t f o r Heavy Water
Produc­
tion U s i n g the Dual Temperature Ammonia-Hydrogen
Exchange System" T e c n i c a ed Economia della P r o d u ­
z i o n e di Acque P e s a n t e , p . 173, Comitato N a z i o n a l e
E n e r g i a N u c l e a r e , Rome (1971).
B e n e d i c t M. and P i g f o r d T.H., "Nuclear C h e m i c a l
E n g i n e e r i n g " , M c G r a w - H i l l Book C o . Inc., New York
(1957)
Rae H.K., "Mass T r a n s f e r in Heavy Water P r o d u c t i o n " ,
paper p r e s e n t e d a t 25th Canadian C h e m i c a l E n g i n ­
e e r i n g C o n f e r e n c e , M o n t r e a l (November 1975).
L o c k e r b y W.E., private communication.
Miller A.I. and Voyer R.D., "Improved G a s - L i q u i d
C o n t a c t i n g in C o - C u r r e n t F l o w " , C a n . J. Chem. E n g .
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Hartmann F. and Roeck G., Chemie Ingen. T e c h . (1965)
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proved Heavy Water P r o c e s s " , paper p r e s e n t e d a t 24th
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ACS Symposium Series; American Chemical Society: Washington, DC, 1978.
70
SEPARATION OF HYDROGEN ISOTOPES
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16 Bancroft A.R. a n d R a e H.K., " H e a v y W a t e r
Production
by Amine-Hydrogen E x c h a n g e " ,
Tecnica
ed Economia
della
P r o d u z i o n e di A c q u a
Pesante,
p . 47, C o m i t a t o
Nazionale
Energia
Nucleare,
Rome (1971); a n d Atomic
E n e r g y of C a n a d a
Limited
Report,
AECL-3684 (1970).
17
Holtslander
W.J.
and
Lockerby
W.E.,
"Chemistry
of
the H y d r o g e n - A m i n e Process for H e a v y W a t e r
Produc­
tion",
t o be
published.
Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch004
RECEIVED September 6, 1977
In Separation of Hydrogen Isotopes; Rae, H.;
ACS Symposium Series; American Chemical Society: Washington, DC, 1978.
5
Heavy Water Production by Isotopic Exchange between
Hydrogen and Methylamine
M. BRIEC, J. RAVOIRE, M. ROSTAING, and E . ROTH
Commissariat à l'Energie Atomique, Division de Chimie,
Centre D'Études Nucléaires De Saclay, République Française
B. LEFRANCOIS
Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch005
Sté. Chimique des Charbonnages
Isotopic exchange between water and hydrogen sulphide was
the f i r s t chemical process used on a large scale for the production of heavy water, and is still employed in the big
Canadian plants.
Isotopic exchange between liquid ammonia and hydrogen,
discovered by Wilmarth and Dayton(1) which offers a much
higher separation factor than the former process, has been
studied in French CEA laboratory, since 1956, and developed
using available sources of hydrogen in the ammonia industry.
However, to extract deuterium from hydrogen, especially
from NH3 synthesis gases, Bar-Eli and Klein (2) then J. Ravoire
and E . Rochard (3 and 4)studied the exchange between hydrogen
and a primary or secondary amine, catalysed by an alkaline
derivative of the amine used. Kinetic measurements showed
that the exchange is much faster than that between hydrogen
and ammonia, the separation factors being similar (7 at - 6 0 ° C
and 3.5 at +30° C). The hydrogen-monomethylamine system
(MMA) can thus be used for productions of the same order
as those of the NH -H exchange process, as shown by detailed
studies on a laboratory, p i l o t unit and plant project scale.
3
2
Laboratory Studies
I t is easy t o imagine the use o f the amine-H exchange
in a dual-temperature process, t u r n i n g t o account the v a r i a t i o n
in the separation f a c t o r α with temperature. Once the α
values were determined the p o i n t s t o be s t u d i e d were as f o l l o w s :
2
1. Exchange K i n e t i c s . The exchange is c a t a l y s e d by
a l k a l i n e methylamides, the most e f f i c i e n t being C H 3 N H K ; the
chemical r a t e is much f a s t e r than in the case o f ammonia under
the same temperature and c a t a l y s t c o n c e n t r a t i o n c o n d i t i o n s .
© 0-8412-0420-9/78/47-068-071$05.00/0
In Separation of Hydrogen Isotopes; Rae, H.;
ACS Symposium Series; American Chemical Society: Washington, DC, 1978.
72
SEPARATION O F H Y D R O G E N ISOTOPES
2. S o l u b i l i t y o f Hydrogen. Hydrogen is more s o l u b l e in
monomethylamine (MMA) than in ammonia (2.5 times a t -50° C ) .
T h i s helps t o speed up the exchange r a t e .
Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch005
3. Thermal S t a b i l i t y o f the C a t a l y s t . Potassium methylamide is s t a b l e a t low temperatures, but in s o l u t i o n a t high
temperature i t is thermolysed and converted t o a potassium s a l t
of Ν,Ν'-dimethylformamidine, s o l u b l e in MMA.
By long duration
t e s t s in p i l o t u n i t s , the s t a b i l i t y was proved s a t i s f a c t o r y
under present working c o n d i t i o n s .
4. S o l u b i l i t y o f the C a t a l y s t . I t s s o l u b i l i t y decreases
as the temperature r i s e s .
In the presence o f hydrogen the con­
c e n t r a t i o n o f potassium methylamide is l i m i t e d by the formation
of potassium hydride:
CH NHK + H
3
2
*
>
CH NH
3
2
+ HK.
The methylamide concentration a t e q u i l i b r i u m is i n v e r s e l y
p r o p o r t i o n a l t o the hydrogen pressure and is about 0.1 mol/kg
amine f o r a hydrogen pressure o f 50 bars.
The e q u i l i b r i u m
depends l i t t l e on temperature; i t is s e t up slowly and the
hydride formation r a t e is bound up with the nature o f the con­
tainer walls.
5. Adjuvant E f f e c t o f Trimethylamine (TMA). I t was
discovered t h a t a n o n - c a t a l y t i c a d d i t i v e t o the c a t a l y s t can
speed up the exchange r a t e ; thus, a m u l t i p l i c a t i o n f a c t o r o f
1.7 was obtained by a d d i t i o n o f about 7% (molar) o f TMA t o the
MMA.
P i l o t Plant
Tests
The c h i e f problem was t o f i n d a h i g h l y e f f i c i e n t contact
system. F i n e l y p e r f o r a t e d p l a t e s , with s u i t a b l e heights o f
l i q u i d , are s a t i s f a c t o r y s i n c e a 60 cm spacing is enough f o r
the p l a t e s t o f u n c t i o n w e l l .
P r e l i m i n a r y D r a f t o f a Factory (in c o l l a b o r a t i o n with l a
Société Chimique des Charbonnages)
1. D e s c r i p t i o n o f the Process. The r e s u l t s presented here
concern research on the p r e l i m i n a r y d r a f t o f a 60 Τ p e r year
heavy water p l a n t attached t o a 1000 Τ per day ammonium s y t h e s i s
u n i t ; the exchange takes place by a dual temperature process,
as mentioned above, t o avoid any chemical transformation o f the
amine. As shown on Figure 1, the synthesis mixture (N + 3 H ) ,
f r e e d o f oxygenated i m p u r i t i e s by hydrogénation (A), dehydration
(B) and f i n a l l y by washing in the tower (C), t r a n s f e r s i t s
deuterium t o a c u r r e n t o f MMA in a low-temperature TT tower
(the only tower t o c o n t a i n a nitrogen-hydrogen mixture, enabling
2
In Separation of Hydrogen Isotopes; Rae, H.;
ACS Symposium Series; American Chemical Society: Washington, DC, 1978.
2
B R i E C ET AL.
and
Methyhmine
Isotopic
Exchange
Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch005
Hydrogen
A
methanation
TF2
cold
BB'
dehydration
TC2
h o t tower
(2nd
stage)
stage)
CC
1
TT
purification
transfer
tower
DD'
deamination
TEP
s t r i p p i n g tower
(1st stage)
TEN
enrichment
TC
hot toner ( 1 s t sta^e)
tower
TH
humidification
tower
(2nd
r
compressor(2nd
F
f i n i s h i n g plant
abed
hydrogen
efgh
liquid
stage)
loop (1st stage)
loop (1st stage)
(1st stage)
tower
(1st stage)
Figure 1.
Heavy water production unit
In Separation of Hydrogen Isotopes; Rae, H.;
ACS Symposium Series; American Chemical Society: Washington, DC, 1978.
74
SEPARATION O F
HYDROGEN ISOTOPES
Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch005
p u r e h y d r o g e n t o be u s e d in t h e r e s t o f t h e s y s t e m ) .
After
r e c u p e r a t i o n of the methylamine
t h e gas is s e n t t o t h e
ammonia s y n t h e s i s u n i t .
The l i q u i d is f e d t h r o u g h a s e r i e s
o f h o t and c o l d t o w e r s in w h i c h i t a c c u m u l a t e s d e u t e r i u m
a g a i n s t t h e c o u n t e r - f l o w o f a h y d r o g e n l o o p . The p r o c e s s
i n v o l v e s two e n r i c h m e n t s t a g e s b e f o r e a f i n i s h i n g p l a n t w h i c h
can be e i t h e r a h y d r o g e n r e c t i f i c a t i o n o r a w a t e r r e c t i f i c a t i o n
a f t e r e x c h a n g e b e t w e e n t h e w a t e r and t h e amine.
2. D e t e r m i n a t i o n o f W o r k i n g C o n d i t i o n s . The p r e s s u r e
and t e m p e r a t u r e c o n d i t i o n s were d e t e r m i n e d on t h e b a s i s o f
p h y s i c o - c h e m i c a l f a c t o r s s u c h as t h e r m a l s t a b i l i t y o f t h e
c a t a l y s t , s o l u b i l i t y in t h e p r e s e n c e o f h y d r o g e n , f a c t o r s
r e l a t i v e t o a s s o c i a t i o n w i t h ammonia s y s t h e s i s s u c h as t h e
a v a i l a b l e p r e s s u r e o f f e e d - g a s , and e c o n o m i c c o n s i d e r a t i o n s .
The c h o i c e o f t h e p r e s s u r e is t h e r e s u l t o f many c o m p r o m i s e s ;
t h e p r e s s u r e must be l o w enough t o a l l o w a r e a s o n a b l e c a t a l y s t
c o n c e n t r a t i o n , so as t o o b t a i n good p l a t e e f f i c i e n c i e s and t h e
use o f more c o n v e n t i o n a l m a t e r i a l t h a n in h i g h p r e s s u r e
ammonia s y n t h e s i s ; on t h e o t h e r hand i t must be f a i r l y h i g h
in o r d e r t o a v o i d undue gas r e c o m p r e s s i o n and t o m a i n t a i n
t h e l o w MMA v a p o u r p r e s s u r e w h i c h a f f e c t s t h e e n e r g y consump­
t i o n (amine s a t u r a t i o n o f t h e gas and c o n d e n s a t i o n o f t h i s
amine b e t w e e n t h e h o t a n d c o l d t o w e r s ) . The h i g h e r t e m p e r a t u r e
c h o s e n is l o w enough t o r e t a i n s a t i s f a c t o r y b e h a v i o u r o f t h e
catalyst.
I n c h o o s i n g t h e c o l d t e m p e r a t u r e i t was n e c e s s a r y
t o d e c i d e b e t w e e n l o w e r f l o w s a t l o w e r t e m p e r a t u r e on t h e one
hand and l e s s f a v o u r a b l e k i n e t i c s , h i g h e r c o o l i n g c o s t s and
more e l a b o r a t e s t e e l s on t h e o t h e r . A f t e r a d e t a i l e d e c o n o m i c
s t u d y a c o l d t e m p e r a t u r e o f -50° C was a d o p t e d .
3. Economy o f t h e P r o c e s s . T a b l e I shows t h e m a i n s p e c i ­
f i c a t i o n s o f the u n i t :
dimensions o f the i s o t o p i c exchange
towers, d i s t r i b u t i o n of investments according t o the d i f f e r e n t
i t e m s , and p r i n c i p a l c o n s u m p t i o n s .
Where i n v e s t m e n t s a r e
c o n c e r n e d t h e two m a i n i t e m s o f e x p e n s e a r e t h e h e a t t r a n s f e r
e q u i p m e n t ( c o o l i n g s t a t i o n + e x c h a n g e r s + i n s u l a t i o n ) and t h e
exchange towers equipped w i t h t h e i r p l a t e s .
The c a p i t a l c o s t
f o r t h i s p r o c e s s r e p r e s e n t s $460 p e r k g o f h e a v y w a t e r p e r
y e a r . The p r e s s u r e b e l o w t h a t o f t h e s y n t h e s i s c a n i n v o l v e
an i n c r e a s e o f gas r e c o m p r e s s i o n c o s t s and o f c e r t a i n c o o l i n g
costs.
I n s p i t e o f a l l t h e s e f a c t o r s the energy expenses are
lower than those o f o t h e r p r o c e s s e s , H S - H 0 f o r example,
u n d e r t h e e c o n o m i c c o n d i t i o n s p u b l i s h e d f o r t h e P o r t Hawkesbury
and B r u c e s i t e s {5)
(where 60% o f t h e e n e r g y is r e c o v e r e d ) .
The c o n s u m p t i o n s f o r o u r p r o c e s s
a r e 0.7 Τ s t e a m (60 p s i ^ k g D 0
and 700 k W h A g a g a i n s t 11 Τ s t e a m (330 p s i ) / k g D 0 and 550 kWh/kg.
2
2
2
2
In Separation of Hydrogen Isotopes; Rae, H.;
ACS Symposium Series; American Chemical Society: Washington, DC, 1978.
In Separation of Hydrogen Isotopes; Rae, H.;
ACS Symposium Series; American Chemical Society: Washington, DC, 1978.
1000 T/day N2 + 3H2
(H2) = 1,4
piping + valves
e l e c t r i c i t y + control
compressors + pumps
b u i l d i n g , engineering
H2preparation tanks +
catalyst preparation
2nd stage
dehydration + deamination
c o o l i n g s t a t i o n + exchanger +
insulation
towers + p l a t e s
18, 46%
17, 34%
1 1 , 30%
13, 60%
r
10, 00%
7, 18%
4,44%
5, 59%
1 1 , 98%
Coolant water:
Steam
o f which
Electricity
1164 m /hour
2292 : 1 s t stage com­
pressors
2245 : c o o l i n g s t a t i o n
6 tons/hour
5893 kWh
Consumptions
75
73,8
51
55,5
2 χ 49,8
28
2,35
2,44
2,44
2,94
1,22
1,47
Principal
h e i g h t (m)
130 ppm
Diameter (m)
Deuterium content o f the hydrogen:
t r a n s f e r tower
s t r i p p i n g tower
enrichment tower
hot tower
c o l d tower
hot tower
D i s t r i b u t i o n o f investments (%)
2nd tower
1 s t stage:
1000 (25 f o r the 1 s t stage)
Tower dimension
Enrichment:
Loop gas flow-rate/supply gas f l o w - r a t e
Feeding r a t e :
Main s p e c i f i c a t i o n s o f the heavy water p r o d u c t i o n p l a n t
(production: 58,5 T/year)
TABLE I
Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch005
76
SEPARATION OF HYDROGEN ISOTOPES
Conclusion
The exchange r a t e s in the H -MMA system are extremely
f a s t in view o f the a c t i v i t y o f the c a t a l y s t and the s o l u b i l i t y
of hydrogen. The development o f a s u f f i c i e n t l y s t a b l e and
s o l u b l e c a t a l y s t means t h a t the c o n s t r u c t i o n o f heavy water
p l a n t s is f e a s i b l e under f i n a n c i a l l y competitive c o n d i t i o n s .
The production o f appreciable q u a n t i t i e s o f heavy water from
the hydrogen used f o r synthesis o f ammonia is now p o s s i b l e
in many c o u n t r i e s .
I f the use o f hydrogen in the future as an
energy v e c t o r is developed, the MMA-hydrogen process w i l l p r o f i t
from the s c a l e e f f e c t in the b u i l d i n g o f u n i t s , and the low
p r i c e s o f thermal and e l e c t r i c a l s u p p l i e s a v a i l a b l e a t the
proximity o f hydrogen chemical-nuclear generators.
Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch005
2
Literature Cited
(1)
(2)
(3)
(4)
(5)
Wilmarth, W . , . and Dayton, J.C., JACS (1953) 75.4553.
B a r - E l i , Ε . , and Klein, F . S . , J. Chem. Soc. (1962) 3083.
Rochard, E., and Ravoire, J., Rapport C . E . A . (1969) 3835.
Rochard, Ε., and Ravoire, J., J. Chem. Phys. (1971) 1183.
Rae, H . K . , "Heavy Water", Atomic Energy of Canada Limited
Report No. 3866, Geneva, 1971.
RECEIVED October 17, 1977
In Separation of Hydrogen Isotopes; Rae, H.;
ACS Symposium Series; American Chemical Society: Washington, DC, 1978.
6
U H D E Process for the Recovery of Heavy Water from
Synthesis Gas
E. NITSCHKE, H. ILGNER, and S. WALTER
Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch006
Friedrich Uhde GmbH, Dortmund, West Germany
Heavy water, or deuterium o x i d e , has been used up t o now,
on an industrial s c a l e , only as a moderator in nuclear r e a c t o r s .
Due to the good
utilization
of neutrons in heavy water r e a c t o r s ,
n a t u r a l uranium can be used as f u e l . A t the end o f the
fifties,
when the
feasibility
of the v a r i o u s types o f r e a c t o r s was
examined, the heavy water r e a c t o r was found t o have very good
prospects.
Heavy water r e a c t o r s are of particular i n t e r e s t to
c o u n t r i e s which have uranium d e p o s i t s , but do not have t h e i r
own uranium enrichment p l a n t s . Canada has c o n s i s t e n t l y centred
the development of the nuclear energy generation on heavy water
and has assumed a l e a d i n g r o l e in this field (1). A l s o , in
I n d i a , A r g e n t i n a and P a k i s t a n heavy water r e a c t o r s are used as
nuclear power p l a n t s .
Deuterium can a l s o be used as f u e l f o r f u s i o n r e a c t o r s .
Intensive research is being made i n t o the development of these
r e a c t o r s , but there are still s e v e r a l fundamental p h y s i c a l and
t e c h n i c a l problems t o be s o l v e d . There are f o r e c a s t s t h a t some
time in the f u t u r e , the f u s i o n r e a c t o r will supersede the
fission
r e a c t o r in energy p r o d u c t i o n . However, it is difficult
to p r e d i c t when this will happen.
The h e a v y w a t e r r e q u i r e m e n t o f a h e a v y w a t e r r e a c t o r is
0.7 t D2O/MW; in o t h e r w o r d s , a 600 MW f i s s i o n r e a c t o r r e q u i r e s
a p p r o x i m a t e l y 400 t D 0 a s a n i n i t i a l c h a r g e . L o s s e s o f one t o
two p e r c e n t p e r y e a r o f t h e i n i t i a l c h a r g e c a n be e x p e c t e d , i . e .
the make-up r e q u i r e m e n t is 4 - 8 t D2O p e r y e a r . I n t h e c a s e o f
f u s i o n r e a c t o r s , t h e a n n u a l heavy water r e q u i r e m e n t f o r a t y p i c a l
2000 MW f u s i o n r e a c t o r w o u l d be no more t h a n a f e w t D2O.
There a r e two f u n d a m e n t a l c o n c e p t s t o s e p a r a t e t h e d e u t e r i u m
isotope:
one i n v o l v i n g t h e p h y s i c a l c h a r a c t e r i s t i c s o f h y d r o g e n
and w a t e r a n d t h e o t h e r , t h e c h e m i c a l i s o t o p e e x c h a n g e c h a r a c t e r i s t i c s w h i c h o f f e r some f a v o u r a b l e f a c t o r s f o r c o m m e r c i a l
plant design.
Under t h i s c a t e g o r y t h r e e s y s t e m s h a v e b e e n
a p p l i e d f o r commercial a p p l i c a t i o n :
hydrogen s u l f i d e system,
h y d r o g e n - w a t e r e x c h a n g e , a n d t h e hydrogen-ammonia e x c h a n g e .
2
© 0-8412-0420-9/78/47-068-077$05.00/0
In Separation of Hydrogen Isotopes; Rae, H.;
ACS Symposium Series; American Chemical Society: Washington, DC, 1978.
SEPARATION OF
78
HYDROGEN ISOTOPES
The H2O/H2S p r o c e s s u s e s w a t e r a s a f e e d s t o c k and is u s e d
f o r i n d u s t r i a l h e a v y w a t e r p l a n t s in t h e U.S.A. and in Canada.
The f e a s i b l e s i z e o f a p l a n t is a t a p r o d u c t i o n o f more t h a n
200 t p e r y e a r .
I n c o n t r a s t t o t h i s , t h e H / H 0 and H / NH
systems are
b a s e d on h y d r o g e n . When u s i n g h y d r o g e n t h e p r o d u c t i o n c a p a c i t y
is l i m i t e d by t h e amount o f h y d r o g e n a v a i l a b l e . T h i s l i m i t a t i o n
was o f t e n c o n s i d e r e d as a p r i n c i p a l d i s a d v a n t a g e .
T h i s argument
is n o t v a l i d any more, a s t h e c a p a c i t y o f i n d u s t r i a l h y d r o g e n
p r o d u c t i o n p l a n t s , f o r e x a m p l e ammonia s y n t h e s i s , has i n c r e a s e d
in r e c e n t y e a r s by a f a c t o r o f 5 - 10.
A 1500 t p e r day
NH
s y n t h e s i s p l a n t is c a p a b l e o f p r o d u c i n g more t h a n 100 t p e r y e a r
D 0 a t a y i e l d o f 80%.
2
2
2
3
3
Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch006
2
P r i n c i p l e s of Isotope
Separation
The a t t a i n a b l e e l e m e n t a r y s e p a r a t i o n f a c t o r is s m a l l in
c h e m i c a l i s o t o p e e x c h a n g e . The n e c e s s a r y m u l t i p l i c a t i o n o f t h e
e l e m e n t a r y s e p a r a t i o n f a c t o r by c o u n t e r c u r r e n t o f t h e l i q u i d
and t h e g a s e o u s p h a s e c a n be a c h i e v e d by v a r i o u s schemes (2) .
The p r i n c i p a l schemes a r e shown in F i g u r e 1.
Schemes a and b
c o m p r i s e o n l y one c o l u m n , w h i c h is c o u p l e d t o a s o - c a l l e d p h a s e
conversion unit.
I n a r e c t i f i c a t i o n p r o c e s s p h a s e c o n v e r s i o n is
a c h i e v e d in a r e l a t i v e l y s i m p l e way, by means o f , r e s p e c t i v e l y ,
t h e r e b o i l e r and t h e o v e r h e a d c o n d e n s e r . F o r c h e m i c a l s y s t e m s
s u c h p h a s e c o n v e r s i o n i n v o l v e s a more c o m p l i c a t e d s t e p - i n a
water/hydrogen system, f o r instance, a water e l e c t r o l y s i s .
In
an ammonia/hydrogen s y s t e m , p h a s e c o n v e r s i o n w o u l d be e f f e c t e d
by t h e s y n t h e s i s o f t h e ammonia o r t h e c r a c k i n g o f ammonia t o
h y d r o g e n and n i t r o g e n . T h i s i n v o l v e s c o n s i d e r a b l e p r o b l e m s
f r o m t h e d e s i g n and o p e r a t i o n p o i n t o f v i e w , as t h e c a t a l y s t
must be s e p a r a t e d and f e d b a c k t o t h e t o p o f t h e e n r i c h m e n t
column.
Ammonia c r a c k i n g means a r e l a t i v e l y h i g h a d d i t i o n a l i n v e s t ment and e n e r g y c o n s u m p t i o n , as t h e e n e r g y r e l e a s e d d u r i n g
s y n t h e s i s is o b t a i n e d a t a d i f f e r e n t l e v e l f r o m t h e e n e r g y w h i c h
is r e q u i r e d f o r ammonia c r a c k i n g .
When u s i n g t h e h o t - c o l d p r i n c i p l e , t h e p h a s e - c o n v e r s i o n
is
r e p l a c e d by a h o t c o l u m n ( F i g u r e 1 c ) . Due t o n e g a t i v e d e p e n dence o f the e q u i l i b r i u m c o n s t a n t , t h e d i r e c t i o n o f the i s o t o p e
t r a n s p o r t is r e s e r v e d .
H o t - c o l d processes are a l s o c a l l e d
b i t h e r m a l o r d u a l t e m p e r a t u r e exchange p r o c e s s e s .
The maximum
y i e l d w h i c h is t h e o r e t i c a l l y p o s s i b l e is shown in t h e f i r s t l i n e
o f t h e d i a g r a m . F o r t h e b i t h e r m a l s y s t e m , t h e y i e l d is l i m i t e d
by t h e g i v e n s e p a r a t i o n f a c t o r s a t t h e o p e r a t i n g t e m p e r a t u r e o f
t h e h o t and c o l d c o l u m n . The y i e l d c a n be i n c r e a s e d by a d d i n g
a s t r i p p i n g system.
Such a s t r i p p i n g s y s t e m is a r e v e r s e h o t c o l d s y s t e m , i . e . a c o l d c o l u m n is f o l l o w e d by a h o t column
( F i g u r e I d ) . F o r t h i s p u r p o s e i t is n e c e s s a r y t o c i r c u l a t e an
a d d i t i o n a l gas and l i q u i d s t r e a m t h r o u g h t h e s y s t e m .
In Separation of Hydrogen Isotopes; Rae, H.;
ACS Symposium Series; American Chemical Society: Washington, DC, 1978.
In Separation of Hydrogen Isotopes; Rae, H.;
ACS Symposium Series; American Chemical Society: Washington, DC, 1978.
^«1
LIT
4"
a
Ρο
c
o
2
τ«
Ρ,
u
2
Τ, α ,
Pi
Τ,or
Figure 1.
C o n d l f i o n s
Principal schemes for chemical isotope exchange
T£
m
n
s
Λ* double phase conversion. c- Hot-coldsystem d-Hot-coldsystem with, e Hot-colasystem with
Stripping system
Transfer column
A - depleted stream
^ ^^
f ^
/
RU^phase-conversbn
catalyst separation
^conditions of fyof columns
P.U.
Τι«ι
pu.
Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch006
SEPARATION O F
80
H Y D R O G E N ISOTOPES
I n t h e b i t h e r m a l s y s t e m t h e t e m p e r a t u r e o f t h e h o t column is
l i m i t e d f o r p r o c e s s and e c o n o m i c r e a s o n s - t h e p a r t i a l p r e s s u r e
o f t h e l i q u i d p h a s e in t h e h o t column s h o u l d be s m a l l in r e l a t i o n
t o t h e t o t a l p r e s s u r e ; h i g h p r e s s u r e o f a b o u t 300 k g / c m is
t h e r e f o r e r e q u e s t e d in t h e s y s t e m . T h e r e f o r e , i f t h e f e e d
m a t e r i a l , h y d r o g e n , is o n l y a v a i l a b l e a t a r e l a t i v e l y l o w p r e s s u r e (100 - 200 k g / c m ) , one c a n add a t r a n s f e r column w h i c h
o p e r a t e s a t a low temperature upstream o f the enrichment system
(Figure l e ) .
The e n r i c h m e n t s y s t e m i t s e l f is t h e n c o u p l e d t o
t h e t r a n s f e r column o n l y v i a t h e l i q u i d p h a s e .
A t r a n s f e r column
a l s o g i v e s a d d i t i o n a l a d v a n t a g e s w h i c h w i l l be shown l a t e r .
The
UHDE p r o c e s s is a c o m b i n a t i o n o f a s t r i p p i n g s y s t e m w i t h a t r a n s f e r column ( F i g u r e 2 ) .
F e a s i b i l i t y s t u d i e s o f t h e s y s t e m have c l e a r l y shown t h a t
due t o t h e i m p r o v e d r e c o v e r y , t h e i n c r e a s e in c a p a c i t y more t h a n
compensates f o r t h e e x t r a c o s t o f t h e s t r i p p i n g s y s t e m .
The
e c o n o m i c optimum is a p p r o x i m a t e l y 80% y i e l d .
L i k e t h e w a t e r / h y d r o g e n s y s t e m , t h e ammonia/hydrogen s y s t e m
a l s o r e q u i r e s a c a t a l y s t f o r the d e u t e r i u m exchange.
Potassium
amide (KNH2) is a c a t a l y s t s u i t a b l e f o r t h i s p u r p o s e . T h i s
c a t a l y s t has t h e s p e c i a l a d v a n t a g e t h a t i t is h o m o g e n e o u s l y d i s s o l v e d in ammonia. A number o f o t h e r c a t a l y s t s and c a t a l y s t
g r o u p s have been t e s t e d , b u t up t o now i t is t h e o n l y c a t a l y s t
u s e d in t h e c o m m e r c i a l a p p l i c a t i o n .
2
Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch006
2
D e s i g n o f Heavy Water P l a n t
The p l a n t a s shown on t h e s i m p l i f i e d f l o w d i a g r a m ( F i g u r e 3)
c o n s i s t s o f f i v e e s s e n t i a l s e c t i o n s , t h e gas p u r i f i c a t i o n s e c t i o n
w i t h t r a n s f e r column, the f i r s t stage w i t h s t r i p p i n g system, t h e
s e c o n d a n d t h i r d s t a g e and l a s t l y , t h e f i n a l c o n c e n t r a t i o n
s e c t i o n c o m p r i s i n g t h e exchange column and t h e w a t e r d i s t i l l a t i o n
section.
A n o t h e r i m p o r t a n t p l a n t s e c t i o n n o t shown on t h e f l o w d i a grams is t h e r e f r i g e r a t i o n u n i t .
The r e f r i g e r a t i o n c o m p r e s s o r
w i t h two d i f f e r e n t t e m p e r a t u r e l e v e l s is d r i v e n by a s t e a m
t u r b i n e o f t h e e x t r a c t i o n c o n d e n s i n g t y p e . B a c k - p r e s s u r e steam
is u s e d f o r h e a t i n g and s a t u r a t i n g t h e gas o r l i q u i d s t r e a m s .
D e p e n d i n g on t h e c o o l i n g w a t e r c o n d i t i o n s t h e t u r b i n e c a n a l s o
be o p e r a t e d w i t h o u t t h e c o n d e n s i n g p a r t .
P u r i f i c a t i o n System.
The s y n t h e s i s gas p a s s e s t h r o u g h a
gas p u r i f i c a t i o n s e c t i o n in w h i c h a l l o x y g e n - b e a r i n g gas comp o n e n t s s u c h as H2O, C 0 , CO and 0 a r e removed (<5) . A l l t h e s e
s u b s t a n c e s r e a c t w i t h t h e p o t a s s i u m amide, f o r m i n g s u b s t a n c e s
w h i c h a r e i n s o l u b l e in l i q u i d ammonia. T h i s w o u l d r e s u l t n o t
o n l y in a r e d u c t i o n o f t h e c a t a l y s t e f f i c i e n c y , b u t a l s o i n t r o d u c e s t h e r i s k o f c l o g g i n g in t h e c o l u m n .
Water a n d c a r b o n d i o x i d e a r e removed in a f i r s t s t a g e by
l i q u i d ammonia s c r u b b i n g . The ammonia is t a k e n f r o m t h e ammonia
2
2
In Separation of Hydrogen Isotopes; Rae, H.;
ACS Symposium Series; American Chemical Society: Washington, DC, 1978.
NiTscHKE ET AL.
UHDE
81
Process
Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch006
6.
Figure 2.
Transfer-stripping-enrichment
system
In Separation of Hydrogen Isotopes; Rae, H.;
ACS Symposium Series; American Chemical Society: Washington, DC, 1978.
Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch006
82
SEPARATION
O F H Y D R O G E N ISOTOPES
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In Separation of Hydrogen Isotopes; Rae, H.;
ACS Symposium Series; American Chemical Society: Washington, DC, 1978.
NiTscHKE ET AL.
6.
UHDE
Process
83
Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch006
s y n t h e s i s u n i t and r e t u r n e d t o i t a f t e r p a s s i n g t h e p u r i f i c a t i o n
unit.
C a r b o n monoxide and a l s o o x y g e n , i f t h e l a t t e r is p r e s e n t
in t h e g a s , a r e removed b y s c r u b b i n g w i t h p o t a s s i u m amide
solution.
A special design o f the trays eliminates the r i s k o f
c l o g g i n g . The r e a c t i o n p r o d u c t s f o r m e d in t h i s s t a g e a r e r e moved o u t s i d e t h e c o l u m n and t h e p o t a s s i u m amide s o l u t i o n is f e d
to t h e t o p a g a i n .
T r a n s f e r Column. The g a s t h e n p a s s e s t h r o u g h t h e t r a n s f e r
c o l u m n where t h e d e u t e r i u m is t r a n s f e r r e d t o t h e ammonia a n d t h e
s y n g a s is r e t u r n e d t o t h e ammonia s y n t h e s i s u n i t .
I n washing
t r a y s a t t h e t o p o f t h e t r a n s f e r column e n t r a i n e d p o t a s s i u m
amide is removed. The e n r i c h e d ammonia l e a v i n g t h e b o t t o m o f
t h e t r a n s f e r c o l u m n is p r e s s u r i z e d t o t h e p r e s s u r e o f t h e downstream f i r s t stage.
F i r s t S t a g e a n d S t r i p p i n g System. The f i r s t s t a g e c o n s i s t s
o f t h e b i t h e r m a l s e c t i o n p r o p e r a n d t h e s t r i p p i n g s y s t e m . The
o p e r a t i o n o f t h e i n d i v i d u a l s e c t i o n s o f t h e f i r s t stage might
b e s t be e x p l a i n e d w i t h t h e a i d o f t h e M c C a b e - T h i e l e
diagrams
( F i g u r e 4 ) . H e r e , N ( 0 ) is t h e c o n c e n t r a t i o n o f t h e l i q u i d
ammonia f e d f r o m t h e b o t t o m o f t h e t r a n s f e r c o l u m n t o t h e t o p
o f t h e c o l d column o f t h e e n r i c h m e n t s y s t e m .
In t h e c o l d c o l u m n , d e u t e r i u m is t r a n s f e r r e d f r o m t h e g a s
t o t h e l i q u i d ; in o t h e r w o r d s , we a r e g o i n g up t h e w o r k i n g l i n e .
A t t h e b o t t o m o f t h e c o l d c o l u m n , d e u t e r i u m - b e a r i n g h y d r o g e n is
removed a n d t r a n s f e r r e d t o t h e n e x t s t a g e a n d a c o r r e s p o n d i n g
s t r e a m is r e t u r n e d ; h o w e v e r , w i t h a l o w e r d e u t e r i u m c o n c e n t r a tion.
The c o n c e n t r a t i o n c h a n g e s f r o m N ( z ) t o N ( z ) a n d we f o l l o w
the w o r k i n g l i n e o f t h e h o t column as f a r as t o t h e bottom o f
t h e h o t c o l u m n . Here t h e g a s s t r e a m is s p l i t .
On t h e McCabeT h i e l e d i a g r a m , t h i s means a change in t h e s l o p e o f t h e w o r k i n g
line.
I n t h e h o t s t r i p p i n g c o l u m n d e u t e r i u m c o n t i n u e s t o be
t r a n s f e r r e d t o t h e gas and t h e l o w e s t deuterium c o n c e n t r a t i o n
N ( Z ) is f i n a l l y r e a c h e d a t t h e b o t t o m o f t h e h o t s t r i p p i n g
column. P r i o r t o e n t e r i n g t h e c o l d s t r i p p i n g column, t h e
ammonia, w h i c h is b e i n g r e t u r n e d t o t h e t o p o f t h e t r a n s f e r
column, is removed. T h i s a l t e r s t h e s l o p e o f t h e w o r k i n g l i n e
a g a i n a n d in t h e c o l d s t r i p p i n g c o l u m n we come b a c k t o t h e
feeding point.
T h i s d i a g r a m a l s o shows t h a t t h e s l o p e o f t h e
w o r k i n g l i n e is l i m i t e d b y t h e s l o p e o f t h e two e q u i l i b r i u m
l i n e s a t t h e t e m p e r a t u r e o f t h e h o t a n d c o l d c o l u m n . When
d e s i g n i n g t h e p l a n t , t h e s l o p e o f t h e w o r k i n g l i n e s must be
d e t e r m i n e d in s u c h a way t h a t o n l y a minimum o f t r a y s is r e quired.
As t h e t r a y e f f i c i e n c y in t h e h o t and c o l d c o l u m n s is
d i f f e r e n t , t h i s minimum r e f e r s t o t h e number o f a c t u a l t r a y s ;
in o t h e r w o r d s , t h e c o l u m n volume o f t h e s y s t e m is t o be m i n i m i z e d .
1
2
In Separation of Hydrogen Isotopes; Rae, H.;
ACS Symposium Series; American Chemical Society: Washington, DC, 1978.
In Separation of Hydrogen Isotopes; Rae, H.;
ACS Symposium Series; American Chemical Society: Washington, DC, 1978.
Figure 4.
McCabe-Thiele
diagram of the first stage
Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch006
W
§
W
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M
Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch006
6.
NiTscHKE ET AL.
UHDE
Process
85
I n t h e f i r s t s t a g e t h e r e a r e two s u p e r i m p o s e d gas c y c l e s .
However, o n l y one c i r c u l a t i n g c o m p r e s s o r is s u f f i c i e n t as t h e
d i f f e r e n t p r e s s u r e d r o p s in b o t h c y c l e s c a n be u s e d f o r c o n t r o l l i n g t h e gas r a t e s .
When b e i n g t r a n s f e r r e d f r o m t h e h o t c o l u m n
t o t h e c o l d c o l u m n and v i c e v e r s a , t h e gas and l i q u i d s t r e a m s
are h e a t e d and c o o l e d r e s p e c t i v e l y .
I t is o b v i o u s t h a t t h i s
must be done in a way t o c o n s e r v e t h e h e a t in o r d e r t o r e d u c e t h e
energy consumption.
F i g u r e 5 shows t h e e n t h a l p y / t e m p e r a t u r e d i a g r a m f o r s y n t h e s i s gas w h i c h is s a t u r a t e d w i t h ammonia and t h e a r r a n g e m e n t
of the h e a t exchanges f o r c o o l i n g
t h e s y n t h e s i s gas from the
h o t column.
Downstream o f a d i r e c t h e a t e x c h a n g e r , w h i c h is
a r r a n g e d i n s i d e t h e h o t c o l u m n , t h e h e a t is t r a n s f e r r e d t o
l i q u i d ammonia a t a r e l a t i v e l y h i g h t e m p e r a t u r e w h i c h t h e n
t r a n s f e r s t h i s h e a t t o t h e gas f o r s a t u r a t i o n .
The gas t h e n
f l o w s t h r o u g h a water c o o l e r and t h e n t h r o u g h a gas/gas exchanger.
The r e m a i n i n g gap t o come down t o t h e t e m p e r a t u r e o f t h e c o l d
c o l u m n is p r o v i d e d by t h e r e f r i g e r a t i o n p l a n t and t r a n s f e r r e d f r o m
the gas in two h e a t e x c h a n g e r s , c o n n e c t e d in s e r i e s .
These
o p e r a t e a t d i f f e r e n t t e m p e r a t u r e s in o r d e r t o r e d u c e t h e e n e r g y
consumption f o r the r e f r i g e r a t i o n compressor.
Altogether,
a l m o s t 70% o f t h e h e a t r e l e a s e d d u r i n g c o o l i n g is u t i l i z e d .
The a r r a n g e m e n t o f t h e h e a t e x c h a n g e r s and t h e d e t e r m i n a t i o n
o f t h e w o r k i n g r a n g e is n o t a r b i t r a r y , b u t is d e t e r m i n e d by t h e
e n e r g y c o s t s and t h e c a p i t a l i n v e s t m e n t f o r h e a t e x c h a n g e r s ,
t a k i n g i n t o account the s p e c i a l c o n d i t i o n s a t the s i t e .
T h i s p r o b l e m o f o p t i m i z a t i o n was r e s o l v e d s i m u l t a n e o u s l y
w i t h t h e p r o b l e m o f m i n i m i z i n g t h e c o l u m n v o l u m e by s e t t i n g up
a p p r o p r i a t e computer programs.
T h i s work was done in a v e r y
c l o s e c o o p e r a t i o n w i t h the I n s t i t u t e f o r Nuclear Technology a t
K a r l s r u h e U n i v e r s i t y (4).
The c o o p e r a t i o n is n o t c o n f i n e d t o
t h i s s u b j e c t b u t a l s o t o s o l v i n g o t h e r p r o b l e m s , in p a r t i c u l a r
the p e r f o r m a n c e o f p i l o t p l a n t t e s t s w h i c h s u p p l i e d t h e r e s u l t s
on w h i c h t h e d e s i g n o f t h e p r o c e s s is b a s e d ( 3 ) , C5) .
Second and T h i r d S t a g e . The a r r a n g e m e n t o f t h e s e c o n d and
t h i r d s t a g e is a n a l o g u e t o t h e f i r s t s t a g e . I n e a c h s t a g e t h e
d e u t e r i u m c o n t e n t is i n c r e a s e d by a f a c t o r a r o u n d 9.
Ammonia
w h i c h h a s b e e n e n r i c h e d t o 15-20% d e u t e r i u m c a n t h e n be t a k e n
o u t b e t w e e n t h e h o t and c o l d c o l u m n o f t h e t h i r d and l a s t s t a g e .
Since the streams are s m a l l e r , i . e . i n v e r s e l y p r o p o r t i o n a l t o the
e n r i c h m e n t f a c t o r , t h e h e a t r e c o v e r y s y s t e m b e t w e e n h o t and c o l d
c o l u m n is made s i m p l e r .
F i n a l C o n c e n t r a t i o n . A f t e r c a r e f u l e x a m i n a t i o n Uhde d e c i d e d
f o r a w a t e r d i s t i l l a t i o n as f i n a l c o n c e n t r a t i o n . W a t e r d i s t i l l a t i o n is a w e l l - p r o v e n p r o c e s s and c a n be o p e r a t e d u n d e r n o r m a l
p r e s s u r e and t e m p e r a t u r e .
F o r t h i s , i t is n e c e s s a r y t o t r a n s f e r t h e d e u t e r i u m f r o m
the ammonia t o w a t e r . The e n r i c h e d ammonia w h i c h h a d b e e n
In Separation of Hydrogen Isotopes; Rae, H.;
ACS Symposium Series; American Chemical Society: Washington, DC, 1978.
SEPARATION OF HYDROGEN ISOTOPES
Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch006
86
-30
-20
-10
Figure 5. Enthalpy-temperature
diagram for synthesis gas (3 N
NH
2
+ H ) saturated with
2
3
In Separation of Hydrogen Isotopes; Rae, H.;
ACS Symposium Series; American Chemical Society: Washington, DC, 1978.
6.
N i T S C H K E ET AL.
UHDE
Process
87
s e p a r a t e d f r o m t h e c a t a l y s t t h r o u g h e v a p o r a t i o n , is t h u s b r o u g h t
i n t o contact w i t h water.
Both r e a c t i o n p a r t n e r s a r e separated
a g a i n in a d i s t i l l a t i o n s e c t i o n a t t o p and b o t t o m o f t h e c o l u m n ,
t h e ammonia is f e d b a c k t o t h e t h i r d s t a g e .
The e n r i c h e d w a t e r
is f e d t o a s i n g l e - s t a g e d i s t i l l a t i o n c o l u m n . The h e a v y w a t e r
w i t h a c o n t e n t o f o v e r 9 9 . 8 % D 0 c a n f i n a l l y be w i t h d r a w n f r o m
the bottom o f t h e d i s t i l l a t i o n column.
B a s e d on t h i s c o n s i d e r a t i o n t h e f i n a l c o n c e n t r a t i o n h a s b e e n
d e s i g n e d and s u p p l i e d by S u l z e r B r o s . , W i n t e r t h u r .
Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch006
2
O p e r a t i o n o f t h e P l a n t . The d i f f e r e n t s e c t i o n s o f t h e
p l a n t - t h e gas p u r i f i c a t i o n s e c t i o n w i t h t r a n s f e r column, t h e
f i r s t s t a g e w i t h s t r i p p i n g s y s t e m , t h e s e c o n d and t h i r d s t a g e
and l a s t l y , t h e f i n a l p u r i f i c a t i o n s e c t i o n , c a n be o p e r a t e d
i n d e p e n d e n t l y ; t h a t means i f one o f them h a s t o be s h u t down,
t h e o t h e r s c a n still be o p e r a t e d .
This reduces the process
c o n t r o l p r o b l e m s and i n c r e a s e s p l a n t r e l i a b i l i t y .
I t is a
c h a r a c t e r i s t i c f e a t u r e o f the process t h a t the steady s t a t e
c o n d i t i o n s , i . e . t h e f i n a l c o n c e n t r a t i o n p r o f i l e in t h e c o l u m n s ,
a r e r e a c h e d o n l y a f t e r a p e r i o d o f a few d a y s .
Also therefore
e a c h s e c t i o n is p r o v i d e d w i t h a s e p a r a t e c o l l e c t i n g t a n k f o r t h e
l i q u i d h o l d up in o r d e r t o a v o i d m i x i n g o f l i q u i d s w i t h d i f f e r e n t
i s o t o p e c o n c e n t r a t i o n s , and so t o f a c i l i t a t e r e - s t a r t i n g .
Engineering
Problems
Apart from q u e s t i o n s d e a l i n g w i t h t h e process d e s i g n
e n g i n e e r i n g t h e r e were a l s o s e v e r a l m e c h a n i c a l e n g i n e e r i n g
p r o b l e m s t o be s o l v e d . The p l a n t is d e s i g n e d f o r much t h e
same p r e s s u r e a n d t e m p e r a t u r e r a n g e as an ammonia s y n t h e s i s
p l a n t ; c o n s e q u e n t l y , t h e same s o r t o f t e c h n i q u e s c a n be u s e d
for the design. This a p p l i e s p a r t i c u l a r l y t o the heat exchangers as w e l l as t h e c h o i c e o f o t h e r equipment.
The h i g h - p r e s s u r e c o l u m n s i n v o l v e new p r o b l e m s .
The
d i a m e t e r o f t h e c o l d c o l u m n in t h e f i r s t s t a g e is 2 m and t h e
d i a m e t e r o f t h e c o r r e s p o n d i n g h o t c o l u m n s is l a r g e r
still
due
t o t h e g r e a t e r g a s and l i q u i d l o a d . The c o l u m n s a r e up t o
40 m h i g h . The c o l d c o l u m n s o f t h e e n r i c h m e n t s y s t e m a n d o f
t h e t r a n s f e r s e c t i o n a r e d i v i d e d in two p a r t s in s e r i e s .
A t an o p e r a t i n g p r e s s u r e o f 325 k g / c m t h e c o l u m n w e i g h t
is c o n s i d e r a b l e .
The l a r g e s t c o l u m n , w h i c h h a s a d e a d w e i g h t
o f 270 t , must be t r a n s p o r t e d t o t h e p l a n t s i t e in one p i e c e
and e r e c t e d t h e r e . T h e r e f o r e t h e t r a n s p o r t a t i o n c o n d i t i o n s
s h o u l d be r e v i e w e d c a r e f u l l y b e f o r e d e c i d i n g o n t h e l o c a t i o n f o r
a plant of this kind.
A l l towers are equipped w i t h s i e v e t r a y s , which p r o v i d e a
good mass t r a n s f e r b e t w e e n t h e p h a s e s . A c c o r d i n g t o t h e s p e c i a l
f e a t u r e s o f the system w i t h regard t o the k i n e t i c s o f the
r e a c t i o n and t h e h y d r o d y n a m i c c h a r a c t e r i s t i c s o f t h e f l u i d s , t h e
d e s i g n o f t h e s i e v e t r a y s d i f f e r s from t h e d e s i g n n o r m a l l y used
2
In Separation of Hydrogen Isotopes; Rae, H.;
ACS Symposium Series; American Chemical Society: Washington, DC, 1978.
88
SEPARATION OF
H Y D R O G E N ISOTOPES
Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch006
for
d i s t i l l a t i o n or a b s o r p t i o n towers.
O x y g e n - b e a r i n g s u b s t a n c e s a r e c o m p l e t e l y removed f r o m t h e
gas due t o t h e p r e s e n c e o f p o t a s s i u m amide. I t is w e l l known
t h a t hydrogen o f extreme p u r i t y reduces the n o t c h impact s t r e n g t h
of high-grade s t e e l s .
T e s t s have shown, h o w e v e r , t h a t s u c h a
r i s k is u n l i k e l y u n d e r t h e c o n d i t i o n s p r e v a i l i n g h e r e .
For
s a f e t y r e a s o n s s t e e l s a r e p r e f e r r e d , w h i c h h a v e a r e l a t i v e l y low
s t r e n g t h and good d u c t i l i t y , e v e n a t low t e m p e r a t u r e s , a s is t h e
case f o r higher n i c k e l - a l l o y e d s t e e l s .
P o t a s s i u m amide in ammonia a c t s v e r y s t r o n g l y on o r g a n i c
m a t e r i a l s , so e v e n m a t e r i a l s l i k e T e f l o n c o r r o d e w i t h i n a
short time.
A v a r i e t y o f m a t e r i a l s were e x a m i n e d in a u t o c l a v e
t e s t s in o r d e r t o f i n d m a t e r i a l s w h i c h a r e r e s i s t a n t t c p o t a s s i u m
amide a t t h e p r e v a i l i n g o p e r a t i n g c o n d i t i o n s . L a t e r t h e s e
m a t e r i a l s a r e t e s t e d u n d e r o p e r a t i n g c o n d i t i o n s in a s p e c i a l
facility.
Even t o d a y t h i s is done t o t e s t m a t e r i a l f o r pump
s e a l s and s t u f f i n g b o x e s w h i c h a r e new on t h e m a r k e t . A l l t h e s e
q u e s t i o n s have b e e n e x a m i n e d v e r y c a r e f u l l y , f i r s t on a l a b o r a t o r y s c a l e and t h e n on a p i l o t - p l a n t s c a l e in o r d e r t o f i n d a
r e l i a b l e s o l u t i o n f o r the design of a commercial p l a n t .
I n t e g r a t i o n o f Heavy W a t e r P l a n t and Ammonia
Synthesis
T h i s p r o c e s s is b a s e d on h y d r o g e n as t h e s o u r c e o f d e u t e r i u m .
T h i s h y d r o g e n can be o b t a i n e d f o r example f r o m t h e g a s i f i c a t i o n
u n i t o f t h e ammonia p l a n t . The h e a v y w a t e r p l a n t is s t r i p p i n g
t h e d e u t e r i u m f r o m t h e s y n g a s , w h i c h is t h e n r e t u r n e d t o t h e
ammonia s y n t h e s i s l o o p .
T h i s c o u p l i n g is o f v i t a l i m p o r t a n c e
f o r t h e o p e r a t i o n o f ammonia p l a n t s .
I t must be c e r t a i n t h a t
t h e p r o d u c t i o n and a l s o t h e o n - s t r e a m t i m e o f t h e ammonia p l a n t
are not a f f e c t e d .
F i g u r e 6 shows t h e
scheme o f i n t e g r a t i o n o f a h e a v y w a t e r
p l a n t w i t h an ammonia p l a n t .
1.
2.
The s y n t h e s i s gas p r o d u c e d in t h e g a s i f i c a t i o n s e c t i o n is
p u r i f i e d in t h e u s u a l way and f e d t o t h e s y n t h e s i s gas
c o m p r e s s o r , where i t is b r o u g h t up t o t h e p r e s s u r e o f t h e
ammonia s y n t h e s i s u n i t and a d m i x e d t o t h e s y n t h e s i s gas
c y c l e as f e e d g a s .
A f t e r the l a s t stage o f the syngas
c o m p r e s s o r , t h e s y n t h e s i s gas is d i v e r t e d t o t h e h e a v y
w a t e r p l a n t . The s y n t h e s i s gas w h i c h is d e p l e t e d o f d e u t e r i u m is t h e n r e t u r n e d t o t h e ammonia s y n t h e s i s u n i t .
The h e a v y w a t e r p l a n t in f a c t c o n s t i t u t e s a b y - p a s s t o t h e
ammonia s y n t h e s i s u n i t .
The s y n t h e s i s gas p a s s e s o n l y t h r o u g h t h e gas p u r i f i c a t i o n
c o l u m n and t h e t r a n s f e r column o f t h e h e a v y w a t e r p l a n t
r e s u l t i n g in a c e r t a i n p r e s s u r e d r o p . T h i s p r e s s u r e d r o p
w o u l d have t o be made up by t h e s y n t h e s i s gas c o m p r e s s o r .
However, i t is b e t t e r t o i n s t a l l an a d d i t i o n a l b o o s t e r comp r e s s o r w h i c h compensates f o r t h i s p r e s s u r e drop.
In the
In Separation of Hydrogen Isotopes; Rae, H.;
ACS Symposium Series; American Chemical Society: Washington, DC, 1978.
In Separation of Hydrogen Isotopes; Rae, H.;
ACS Symposium Series; American Chemical Society: Washington, DC, 1978.
Figure 6.
Integration of heavy water plant with ammonia plant
Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch006
CD
92
es
S?
Ci
-*
ο
ft
>
w
90
SEPARATION OF
HYDROGEN ISOTOPES
e v e n t o f f a i l u r e o f t h e NH
s y n t h e s i s u n i t , t h e gas p u r i f i c a t i o n c o l u m n and t h e t r a n s f e r c o l u m n can be o p e r a t e d in
a closed c i r c u i t .
A l s o in t h i s c a s e t h e r e is no n e e d f o r
a v a l v e in t h e b y - p a s s l i n e , t h u s e s t a b l i s h i n g an open bypass.
I n t h e c a s e o f f l u c t u a t i o n in t h e gas f l o w t h e h e a v y
water p l a n t runs under c o n s t a n t c o n d i t i o n s ; o n l y the d i r e c t i o n f l o w in t h e b y - p a s s l i n e w i l l be c h a n g e d . The f l o w
can s l o w l y be a d j u s t e d t o new c o n d i t i o n s a c c o r d i n g l y .
The
same is t h e c a s e i f t h e r e a r e d i s t u r b a n c e s in t h e h e a v y
water p l a n t .
The s y n t h e s i s gas w h i c h is r e t u r n e d t o t h e s y n t h e s i s u n i t
is s a t u r a t e d w i t h ammonia a t a dew p o i n t o f -28° C c o r r e sponding t o the temperature a t the top o f the c o l d t r a n s f e r
c o l u m n . A t a p r e s s u r e o f 200 k g / c m in t h e s y n t h e s i s u n i t ,
t h e ammonia c o n t e n t o f t h i s s t r e a m is t h u s a p p r o x i m a t e l y
1.2%.
I f t h i s gas is a d m i x e d t o t h e r e c y c l e gas o f t h e
s y n t h e s i s u n i t u p s t r e a m o f t h e f i r s t s e p a r a t o r , i t has no
e f f e c t on t h e s y n t h e s i s c y c l e . However, i f t h e gas is f e d
t o t h e r e c y c l e gas d i r e c t l y u p s t r e a m o f t h e c o n v e r t e r , as
is t h e c a s e sometimes in s y n t h e s i s u n i t s where n i t r o g e n
s c r u b b i n g is u s e d f o r gas p u r i f i c a t i o n , t h e gas e n t e r i n g
t h e c o n v e r t e r w o u l d have a s l i g h t l y h i g h e r ammonia c o n t e n t
and t h i s w o u l d r e s u l t in a c o r r e s p o n d i n g d e c r e a s e in t h e
N H 3 c o n v e r s i o n r a t e in t h e c o n v e r t e r .
T h i s can be compens a t e d by i n c r e a s i n g t h e p r e s s u r e o f t h e s y n t h e s i s l o o p ,
b u t i t is b e t t e r t o compensate t h i s h i g h e r ammonia c o n t e n t
by s l i g h t l y i n c r e a s i n g t h e c o l d d u t y o f t h e l a s t s e p a r a t o r
o f t h e ammonia s y n t h e s i s u n i t , in o r d e r t o k e e p t h e d e s i g n
c o n d i t i o n s of the converter constant.
The t e m p e r a t u r e o f t h e r e t u r n gas is l o w e r t h a n t h a t o f t h e
f e e d g a s , b e c a u s e t h e h e a t e x c h a n g e r must have a c e r t a i n
temperature gradient.
F u r t h e r m o r e , t h e gas c o n t a i n s no t r a c e s o f e i t h e r CO o r
o x y g e n w h i c h u s u a l l y have a d e t r i m e n t a l e f f e c t on t h e
ammonia c a t a l y s t .
The l a s t two f a c t o r s m e n t i o n e d have a
f a v o u r a b l e e f f e c t on t h e o p e r a t i o n o f t h e ammonia s y n t h e s i s
u n i t , a l t h o u g h t h e b e n e f i t s c a n n o t be d e f i n e d q u a n t i t a t i v e l y .
An e s s e n t i a l p o i n t o f t h e i n t e g r a t i o n c o n c e r n s t h e g a s i f i c a t i o n s e c t i o n . The gas p u r i f i c a t i o n s h o u l d be d e s i g n e d
in s u c h a way as t o k e e p t h e c o n t e n t o f o x y g e n - b e a r i n g
i m p u r i t i e s as low as p o s s i b l e in o r d e r t o r e d u c e t h e l o a d
on t h e gas p u r i f i c a t i o n s e c t i o n o f t h e h e a v y w a t e r p l a n t .
However, t h e d e u t e r i u m c o n t e n t in t h e gas is more i m p o r t a n t
and s h o u l d , o f c o u r s e , be k e p t as h i g h as p o s s i b l e .
The
d e u t e r i u m c o n t e n t is d e t e r m i n e d by t h e d e u t e r i u m c o n t e n t
o f t h e f e e d s t o c k s u s e d f o r t h e ammonia, e.g. methane and
w a t e r ; b u t , as we h a v e s e e n f r o m numerous measurements o f
the d e u t e r i u m content o f samples taken a t v a r i o u s p a r t s o f
ammonia p l a n t s , i t c a n be n e g a t i v e l y i n f l u e n c e d by p r o c e s s e s
w i t h i n t h e g a s i f i c a t i o n s e c t i o n . A d e u t e r i u m e x c h a n g e can
3
3.
Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch006
2
4.
5.
6.
In Separation of Hydrogen Isotopes; Rae, H.;
ACS Symposium Series; American Chemical Society: Washington, DC, 1978.
Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch006
NiTscHKE ET AL.
Figure 7.
UHDE
Process
Model of a heavy water plant (capacity 631/yr)
In Separation of Hydrogen Isotopes; Rae, H.;
ACS Symposium Series; American Chemical Society: Washington, DC, 1978.
Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch006
92
SEPARATION OF HYDROGEN ISOTOPES
take p l a c e between the hydrogen and the excess steam i n the
CO s h i f t conversion,the deuterium being t r a n s f e r r e d t o
the steam. The hydrogen thus becomes depleted o f deuterium
and the steam becomes e n r i c h e d . This steam i s condensed
upstream o f the CO2 scrubbing u n i t and i s discharged from
the p l a n t .
The condensate i s u s u a l l y not returned t o the
p l a n t and the deuterium contained i n i t would be l o s t and
t h i s would r e s u l t i n a p r o p o r t i o n a t e r e d u c t i o n i n the
p r o d u c t i o n o f the heavy water p l a n t .
These l o s s e s can be
avoided i f t h i s enriched condensate i s transformed t o
steam and t h i s steam i s then used as process steam i n the
steam reformer. However, t h i s i n v o l v e s a g r e a t e r load on
the steam system o f the ammonia p l a n t which cannot be
r e a l i z e d i n the case o f e x i s t i n g ammonia p l a n t s .
This
problem can be avoided by an isotope exchange o f the
enriched condensate with the process steam which i s being
fed t o the steam reformer o r t o the s h i f t conversion.
The e q u i l i b r i u m between water and water vapour i s n e a r l y
equal t o u n i t y ; t h a t means the condensate l e a v i n g the
exchange system has the normal deuterium c o n c e n t r a t i o n
again.
These p o i n t s show t h a t an ammonia p l a n t and a heavy water
p l a n t can be i n t e g r a t e d without any p a r t i c u l a r d i f f i c u l t i e s .
Conclusion
A heavy water p l a n t with a c a p a c i t y o f 63 t D 0 p e r year
w i l l be b u i l t a t T a l c h e r / I n d i a .
The p l a n t i s coupled w i t h a
900 t per day ammonia p l a n t and w i l l be put on stream beginning
1978.
F i g u r e 7 i s a photo o f the model.
A comparison o f the p r o d u c t i o n costs based on the c a l c u l a t i o n f o r t h i s p l a n t shows with regard t o the investment as w e l l
as t o the o p e r a t i n g c o s t s t h a t t h i s process can compete with
other processes o r may even be s u p e r i o r .
2
Literature
(1)
(2)
(3)
(4)
(5)
(6)
Cited
Lumb, P.B.; J. B r . N u c l . Energy Soc. (1976) 15, pp. 35-46.
Becker, E . W . ; IAEA R e v . , S e r i e s No. 21 (1962) V i e n n a .
W a l t e r , S., N i t s c h k e , E.; "Tecnica ed Economia d e l l a
Produzione d i Acqua Pesante", p . 173, Comitato Nazionale
Energia Nucleare, Rome (1971).
Schindewolf, U., Lang, G.; "Tecnica ed Economia d e l l a
Produzione d i Acqua Pesante", p . 75, Comitato Nazionale
Energia N u c l e a r e , Rome (1971).
Walter, S., Schindewolf, U . ; Chem. Ing. Techn. (1965), 37,
pp. 1185-91.
Schindewolf, U., Hornke, S . ; Chem. Ing. Techn. (1969), 41,
p p . 645-648.
RECEIVED October 28, 1977
In Separation of Hydrogen Isotopes; Rae, H.;
ACS Symposium Series; American Chemical Society: Washington, DC, 1978.
7
Novel Catalysts for Isotopic Exchange between
Hydrogen and Liquid Water
J. P. BUTLER, J. H . ROLSTON, and W. H . STEVENS
Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch007
Atomic Energy of Canada Ltd., Chalk River Nuclear Laboratories,
Physical Chemistry Branch, Chalk River, Ontario K0J 1J0
Canada's atomic power program r e q u i r e s l a r g e
q u a n t i t i e s o f heavy water t h a t a r e c u r r e n t l y produced
by t h e G i r d l e r - S u l p h i d e o r GS p r o c e s s .
This process
i s based on exchange o f hydrogen i s o t o p e s between
hydrogen s u l p h i d e gas and l i q u i d w a t e r as g i v e n by t h e
f o l l o w i n g c h e m i c a l exchange r e a c t i o n :
HDS
g
+ H 0,. s
liq
N
HDO . + H S
l i q
g
z 2
n
(1)
z 2
At Chalk R i v e r we have a s t r o n g i n t e r e s t i n t r y i n g t o
d e v e l o p new and more e f f i c i e n t p r o c e s s e s f o r t h e p r o ­
d u c t i o n o f heavy w a t e r . A v e r y a t t r a c t i v e p r o c e s s and
one w i t h many i n h e r e n t p o t e n t i a l advantages i s based
on t h e h y d r o g e n - l i q u i d w a t e r i s o t o p i c exchange
reaction.
HD + H 0
2
l i q
N
^
H
D
0
H
l i q
+ 2
(2>
The hydrogen-water i s o t o p i c exchange r e a c t i o n i s more
a t t r a c t i v e p r i m a r i l y because i t has a h i g h e r s e p a r ­
a t i o n f a c t o r , a , d e f i n e d i n terms o f t h e d e u t e r i u m (D)
to p r o t i u m (H) atom r a t i o s i n t h e two s p e c i e s a t
equilibrium.
α
= (D/H)
l i q
j/(D/H)
(3)
g
A t low d e u t e r i u m c o n c e n t r a t i o n s , α i s e q u a l t o t h e
e q u i l i b r i u m c o n s t a n t f o r b o t h o f t h e s e exchange
reactions.
Figure 1 gives the separation f a c t o r f o r the
h y d r o g e n - l i q u i d water (1) and t h e hydrogen s u l p h i d e l i q u i d water (2) exchange r e a c t i o n s i n t h e temperature
range 0-200°C.
Over t h e e n t i r e temperature range, t h e
s e p a r a t i o n f a c t o r , a , f o r t h e H - H 0 system i s about a
f a c t o r o f 2 h i g h e r than t h a t f o r t h e H S - H 0
2
2
2
©
2
0-8412-0420-9/78/47-068-093$05.00/0
In Separation of Hydrogen Isotopes; Rae, H.;
ACS Symposium Series; American Chemical Society: Washington, DC, 1978.
Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch007
SEPARATION O F HYDROGEN ISOTOPES
Figure 1.
Separation factor, a, as a function of temperature for the
hydrogen-water and hydrogen sulfide—water systems
In Separation of Hydrogen Isotopes; Rae, H.;
ACS Symposium Series; American Chemical Society: Washington, DC, 1978.
7.
BUTLER ET
AL.
Novel
Catalysts
for
Isotopic
Exchange
95
exchange r e a c t i o n .
As a r e s u l t , a p r o c e s s based on
the H 2 - H 2 O r e a c t i o n w i l l have a h i g h e r r e c o v e r y o f
d e u t e r i u m from n a t u r a l w a t e r and, as a consequence, a
s m a l l e r p l a n t w i l l be r e q u i r e d . T h e o r e t i c a l r e ­
c o v e r i e s o f 50% are p o s s i b l e f o r a b i t h e r m a l p r o c e s s
based on the hydrogen-water r e a c t i o n compared t o 21%
f o r the GS p r o c e s s .
Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch007
C a t a l y s t Development
A l t h o u g h the hydrogen-water i s o t o p i c exchange
r e a c t i o n i s v e r y d e s i r a b l e f o r the s e p a r a t i o n o f
hydrogen i s o t o p e s , the d i f f i c u l t y has been t o o b t a i n
a c a t a l y s t t h a t can o p e r a t e e f f i c i e n t l y i n the
p r e s e n c e o f l i q u i d w a t e r (3) . E f f e c t i v e n o b l e metal
c a t a l y s t s f o r the vapour exchange r e a c t i o n have been
known f o r many y e a r s b u t t h e s e c a t a l y s t s l o s e t h e i r
a c t i v i t y i n contact with water.
Our new approach i s t o use a c a t a l y s t s u i t a b l e
f o r the vapour exchange r e a c t i o n , such as h i g h l y
d i s p e r s e d p l a t i n u m metal d e p o s i t e d on γ-alumina, and
t o c o a t the c a t a l y s t body w i t h a v e r y t h i n l a y e r o f a
water r e p e l l e n t m a t e r i a l , such as a s i l i c o n e polymer,
t o p r e v e n t w e t t i n g (4) . To i l l u s t r a t e the e f f e c t i v e ­
ness o f the s i l i c o n e w e t p r o o f i n g , F i g u r e 2 shows what
happens when c a t a l y s t p e l l e t s o f p l a t i n u m on alumina,
a commercial c a t a l y s t produced by E n g e l h a r d
I n d u s t r i e s , a r e immersed i n water.
The u n t r e a t e d p e l ­
l e t s r e l e a s e a stream o f s m a l l b u b b l e s o f a i r as w a t e r
immediately e n t e r s the p o r e s o f the alumina.
The
p e l l e t s become j e t b l a c k , i n d i c a t i n g t h a t the s u r f a c e
i s completely wetted.
In c o n t r a s t , the s i l i c o n e
t r e a t e d p e l l e t s shown i n F i g u r e 3 have l a r g e gas
b u b b l e s a d h e r i n g t o t h e i r s u r f a c e and the s u r f a c e
remains l i g h t grey i n c o l o u r , which i s c h a r a c t e r i s t i c
o f the w e t p r o o f i n g a c t i o n o f the s i l i c o n e .
These
s i l i c o n e t r e a t e d , o r w e t p r o o f e d , c a t a l y s t s are q u i t e
e f f e c t i v e f o r the h y d r o g e n - l i q u i d water i s o t o p i c
exchange r e a c t i o n .
S u b s e q u e n t l y , c a t a l y s t s were p r e p a r e d by d e p o s i t ­
i n g p l a t i n u m on porous p o l y t e t r a f l u o r o e t h y l e n e i n an
attempt t o p r o v i d e an improved h y d r o p h o b i c environment
f o r t h e p l a t i n u m c r y s t a l l i t e s (5) . A more s u c c e s s f u l
approach has been t o d e p o s i t p l a t i n u m on h i g h s u r f a c e
a r e a carbon and t o bond the p l a t i n i z e d carbon t o a
v a r i e t y o f column p a c k i n g s o r c a r r i e r s u s i n g T e f l o n as
b o t h the b o n d i n g and the w e t p r o o f i n g agent.
These
l a i t t e r c a t a l y s t s have proven v e r y e f f e c t i v e f o r the
h y d r o g e n - l i q u i d w a t e r exchange r e a c t i o n .
In Separation of Hydrogen Isotopes; Rae, H.;
ACS Symposium Series; American Chemical Society: Washington, DC, 1978.
96
Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch007
SEPARATION O F H Y D R O G E N ISOTOPES
Figure
2.
Untreated 0.5% Pt-Al O
Engelhard
mersed in water
2
s
catalyst im-
In Separation of Hydrogen Isotopes; Rae, H.;
ACS Symposium Series; American Chemical Society: Washington, DC, 1978.
Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch007
BUTLER E T A L .
Figure 3.
0.5%
Novel
Catalysts for Isotopic
Exchange
Pt-Al 0
Engelhard catalyst treated with Dow
773 Silicone and immersed in water
2
3
Corning
In Separation of Hydrogen Isotopes; Rae, H.;
ACS Symposium Series; American Chemical Society: Washington, DC, 1978.
98
SEPARATION O F H Y D R O G E N ISOTOPES
Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch007
C a t a l y s t Performance
To measure the performance, o r the a c t i v i t y , o f
t h e s e c a t a l y s t s we have used a s i n g l e pass t r i c k l e bed
r e a c t o r shown d i a g r a m m a t i c a l l y i n F i g u r e 4. A known
q u a n t i t y o f c a t a l y s t i s packed i n a 2.5 cm d i a m e t e r
g l a s s column t o depths v a r y i n g from 5 t o 75 cm.
About
15 cm o f n o n - c a t a l y t i c p a c k i n g i s p l a c e d d i r e c t l y
below the c a t a l y s t bed t o a i d i n e s t a b l i s h i n g u n i f o r m
gas flow p a t t e r n s through the bed.
The e n t i r e p a c k i n g
i s s u p p o r t e d on a s t a i n l e s s s t e e l s c r e e n (mesh s i z e ,
40 χ 40). N a t u r a l w a t e r (D/H = 144 ppm) i s i n t r o d u c e d
a t the top o f the column through a w a t e r d i s t r i b u t o r
and flows downward through the c a t a l y s t bed assembly.
P u r i f i e d d r y hydrogen, e n r i c h e d i n d e u t e r i u m
(D/H = 300 ppm), flows c o u n t e r c u r r e n t l y upward through
the h u m i d i f i e r where i t becomes s a t u r a t e d w i t h w a t e r
vapour which i s i n i s o t o p i c e q u i l i b r i u m w i t h the
l i q u i d water l e a v i n g the c a t a l y s t bed.
The gas and
water vapour then c o n t i n u e upward t h r o u g h the c a t a l y s t
bed.
The d e u t e r i u m c o n c e n t r a t i o n i n the i n l e t and
o u t l e t hydrogen gas streams i s measured w i t h an on­
l i n e mass s p e c t r o m e t e r {6) . F o r the o p e r a t i n g con­
d i t i o n s d e s c r i b e d , the e n r i c h e d hydrogen gas becomes
d e p l e t e d i n d e u t e r i u m i n p a s s i n g through the column
w h i l e the n a t u r a l water f e e d i s e n r i c h e d .
For
example, f o r a g i v e n c a t a l y s t o p e r a t i n g a t 25°C where
the s e p a r a t i o n f a c t o r , a, i s 3.81, the hydrogen gas
s t r e a m l e a v i n g the top o f the column may have a
D/H = 150 ppm, w h i l e i f e q u i l i b r i u m had been
e s t a b l i s h e d between the two phases the c o n c e n t r a t i o n
would be 37.8 ppm.
The a c t i v i t y o f the v a r i o u s c a t a l y s t s f o r the
i s o t o p i c exchange r e a c t i o n i n the hydrogen-water
system i s d e t e r m i n e d by the nearness o f approach t o
i s o t o p i c e q u i l i b r i u m between the two phases a f t e r
p a s s i n g through the column.
T h i s degree o f approach
i s e x p r e s s e d i n terms o f a column e f f i c i e n c y , η ,
d e f i n e d as the r a t i o o f the a c t u a l change i n the
d e u t e r i u m c o n c e n t r a t i o n o f the hydrogen t o the change
t h a t would have o c c u r r e d had the hydrogen gas stream
r e a c h e d e q u i l i b r i u m w i t h the f e e d water.
With
m i x t u r e s o f hydrogen and water a t low d e u t e r i u m
i s o t o p i c c o m p o s i t i o n , the column e f f i c i e n c y , η , f o r
the c a t a l y s t bed i s g i v e n by the e x p r e s s i o n
η = F r a c t i o n a l Approach t o E q u i l i b r i u m
Between the Two Phases
In Separation of Hydrogen Isotopes; Rae, H.;
ACS Symposium Series; American Chemical Society: Washington, DC, 1978.
7.
BUTLER ET AL.
Novel
Catalysts
for Isotopic
Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch007
NATURAL WATER
FEED (D/H)=l44ppm
>
WATER
DISTRIBUTOR
—
PACKED
CATALYST BED
—
NON-CATALYTIC
PACKING
—
H
2°LIQ Ψ
Exchange
H -(D/H)=l50ppm
2
(AT EQUIL= 37.8ppm)
T=
25°C
a= 3.806
H - SATURATED
WITH H 0
H (D/H)= 300ppm
2
ι
2
V A P
2
PACKED BED
HUMIDIFIER
—
PURIFIED^DRY
ENRICHED
H
2
(D/H)=300ppm
Figure 4. Trickle bed reactor used for hydrogenliquid water isotopic exchange studies
In Separation of Hydrogen Isotopes; Rae, H.;
ACS Symposium Series; American Chemical Society: Washington, DC, 1978.
99
100
SEPARATION O F H Y D R O G E N ISOTOPES
(D/H),
-
(D/H)
(D/H)^ "
(D/H)
Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch007
b
t
(4)
eq
where (D/H) i s the atom r a t i o and the s u b s c r i p t s , b
and t , r e f e r t o the i n l e t and o u t l e t hydrogen gas
streams a t the bottom and top r e s p e c t i v e l y o f the
exchange column.
The s u b s c r i p t , eq, r e f e r s t o the
d e u t e r i u m c o n c e n t r a t i o n o f the hydrogen i n e q u i l i ­
b r i u m w i t h the l i q u i d w a t e r . From a measurement o f
the column e f f i c i e n c y , η , the o v e r a l l t r a n s f e r o f
d e u t e r i u m from hydrogen t o l i q u i d w a t e r can be
calculated.
F o r hydrogen and water f l o w i n g c o u n t e r c u r r e n t l y i n a packed column, the t r a n s f e r o f
d e u t e r i u m from the hydrogen t o the w a t e r i s c h a r a c ­
t e r i z e d by an o v e r a l l gas-phase mass t r a n s f e r
c o e f f i c i e n t , Tya, e x p r e s s e d i n gram atoms p e r u n i t
t i m e , p e r u n i t volume o f bed, f o r u n i t d i s p l a c e m e n t o f
the d e u t e r i u m mole f r a c t i o n from the e q u i l i b r i u m
value.
F o r a s m a l l t e s t r e a c t o r where the concen­
t r a t i o n o f d e u t e r i u m i n the water does n o t v a r y
s i g n i f i c a n t l y t h r o u g h o u t the r e a c t o r , the r a t e o f
d e u t e r i u m t r a n s f e r from the gas t o the l i q u i d phase i n
a s m a l l volume element o f the r e a c t o r , dV, o f c r o s s
s e c t i o n a l a r e a A and h e i g h t dh,
i s g i v e n by the
following d i f f e r e n t i a l equation:
-G-A-dy = T a ( y - y*)A-dh
y
(5)
where G i s the molar f l o w r a t e o f hydrogen p e r second
p e r u n i t a r e a , y i s the a c t u a l mole f r a c t i o n o f
d e u t e r i u m i n the hydrogen a t a g i v e n h e i g h t , h , and y*
i s the v a l u e a t e q u i l i b r i u m w i t h the l i q u i d w a t e r .
I n t e g r a t i n g e q u a t i o n 5 o v e r the h e i g h t o f the c a t a l y s t
bed, h, g i v e s
(6)
Τ a =
= g £-ln(l - n)
y
S i n c e gas flow r a t e s are n o r m a l l y measured i n terms o f
volume, we have found i t c o n v e n i e n t t o use a volume
t r a n s f e r c o e f f i c i e n t , Κ a g i v e n by the e x p r e s s i o n
K a
y
= ~
I -ln(l
-
n)
(7)
where F
- s u p e r f i c i a l hydrogen flow r a t e , m-s
a t STP
h
- h e i g h t o f the c a t a l y s t bed, m
Κ a - gas-phase volume t r a n s f e r c o e f f i c i e n t , m
(of H
at STP)-s" -m" (of c a t a l y s t bed).
Y
1
3
2
In Separation of Hydrogen Isotopes; Rae, H.;
ACS Symposium Series; American Chemical Society: Washington, DC, 1978.
:
BUTLER ET AL.
7.
Novel
Catalysts
for
Isotopic
Exchange
101
The r a t e o f the o v e r a l l i s o t o p i c exchange r e a c t i o n i s
f i r s t o r d e r i n the approach o f the d e u t e r i u m concent r a t i o n o f any o f the s p e c i e s t o i t s f i n a l e q u i l i b r i u m
v a l u e and thus Kya i s a f i r s t o r d e r r a t e c o n s t a n t and
d i m e n s i o n a l l y i t has the u n i t s o f s " .
We have s t u d i e d the e f f e c t o f many parameters on
the a c t i v i t y o f the c a t a l y s t , Kya, and F i g u r e 5 shows
the e f f e c t o f hydrogen gas flow r a t e and temperature
f o r a 0.37% P t - C - T e f l o n c a t a l y s t on 6.1 mm c e r a m i c
spheres.
F o r t h i s c a t a l y s t , Kya i n c r e a s e s a p p r o x i mately as the 0.3 power o f the hydrogen flow r a t e i n
the range 0.05 t o 1.4 m/s a t STP.
We a r e d e a l i n g h e r e
w i t h a v e r y f a s t i s o t o p i c exchange r e a c t i o n : f o r
example, a t a temperature o f 25°C and a hydrogen flow
r a t e o f 1.0 m/s a t STP, Kya = 1.2.
This i s equivalent
t o a h a l f - t i m e f o r the exchange r e a c t i o n o f 0.18 s.
The h a l f - t i m e i s c a l c u l a t e d u s i n g the a c t u a l hydrogen
f l o w r a t e which i s 3.1 times the s u p e r f i c i a l flow r a t e
f o r t h i s p a r t i c u l a r c a t a l y s t bed assembly (the volume
f r a c t i o n o f gas i n the o p e r a t i n g column i s 0.32).
The
s o l i d p o i n t s i n F i g u r e 5 were o b t a i n e d u s i n g e n r i c h e d
hydrogen (D/H = 250 ppm), where the d e u t e r i u m i s
t r a n s f e r r e d from the hydrogen gas t o the l i q u i d w a t e r ,
w h i l e the open p o i n t s were o b t a i n e d u s i n g e n r i c h e d
water (D/H = 1130 ppm),where d e u t e r i u m i s t r a n s f e r r e d
from the l i q u i d water t o the hydrogen gas.
From the
d a t a no d i f f e r e n c e can be d e t e c t e d i n the r a t e o f
d e u t e r i u m t r a n s f e r f o r the n e t r e a c t i o n o c c u r r i n g i n
either direction.
The e f f e c t o f temperature on the
a c t i v i t y o f the c a t a l y s t i s a l s o i l l u s t r a t e d i n F i g u r e
5.
F o r an i n c r e a s e i n temperature from 25° t o 60°C,
K a i n c r e a s e s by a f a c t o r o f 2.4.
The temperature
c o e f f i c i e n t o f Kya f o r t h i s c a t a l y s t i n the range 15°
t o 60°C i s e q u i v a l e n t t o an A r r h e n i u s a c t i v a t i o n
energy o f 21 k J - m o l " o r about 5 k c a l - m o l " .
The e f f e c t o f p l a t i n u m m e t a l s u r f a c e a r e a on the
a c t i v i t y o f the c a t a l y s t i s shown i n F i g u r e 6 where
Kya, the volume t r a n s f e r r a t e c o n s t a n t , i s p l o t t e d
a g a i n s t the p l a t i n u m m e t a l s u r f a c e a r e a , measured by
hydrogen c h e m i s o r p t i o n , and e x p r e s s e d as m
p e r cm
of
packed bed.
A l t h o u g h Kya i n c r e a s e s w i t h m e t a l a r e a ,
the i n c r e a s e i s not d i r e c t l y p r o p o r t i o n a l t o the a r e a .
F o r m e t a l areas below 0.06 m -cm" , Kya i n c r e a s e s as
the 0.75 power o f the m e t a l s u r f a c e a r e a and a t h i g h e r
m e t a l areas the r a t e o f i n c r e a s e o f Kya i s l e s s .
The
curve appears t o be a p p r o a c h i n g a maximum v a l u e .
These r e s u l t s i n d i c a t e t h a t a n o t h e r r e a c t i o n b e s i d e s
the c a t a l y t i c one i s l i m i t i n g the o v e r a l l exchange
reaction rate.
Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch007
1
y
1
1
2
2
3
In Separation of Hydrogen Isotopes; Rae, H.;
ACS Symposium Series; American Chemical Society: Washington, DC, 1978.
3
102
SEPARATION
O F HYDROGEN
-
-
6
*
0
^ ^ ^ - P - 4 5
Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch007
C
°
e
C
^0 •
^
-
2
5
^
OOo-—°*
-
CARRIER
-
6 . 1 mm C E R A M I C
SPHERES
CATALYST BED
0. 5
HEIGHT
-
20.3
cm
AREA
-
4.80
cm*
PRESSURE
-
106 k P a
H 0
2
FLOW -
2. 1 k g - m (60
•
m
ο
•
1
0.2
A
1
0 . 4
HYDROGEN
Figure
^
5.
ENRICHED Η
ENRICHED
2
- °/H
Η 0
2
0 . 6 . 0.8
FLOW
RATE
= 2 5 0 ppm
- D/H
1
1
· $•'
2
g/m i n )
= 1 1 3 0 ppm
1
1
1.0
1.2
- m/s ( A T
1.4
STP)
Effect of hydrogen gas flow rate and temperature on the
activity, K a , of α 0.37% Pt-C-Teflon
y
catalyst
In Separation of Hydrogen Isotopes; Rae, H.;
ACS Symposium Series; American Chemical Society: Washington, DC, 1978.
ISOTOPES
Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch007
7.
BUTLER ET AL.
Figure 6.
Novel Catalysts
for Isotopic
Exchange
103
Dependence of the transfer rate constant, K a, on the platinum metal area o)
Pt-C-Teflon catalysts
y
In Separation of Hydrogen Isotopes; Rae, H.;
ACS Symposium Series; American Chemical Society: Washington, DC, 1978.
104
SEPARATION
O F HYDROGEN
ISOTOPES
Mechanism o f the Exchange R e a c t i o n
As a f i r s t a p p r o x i m a t i o n , t h e o v e r a l l r a t e o f
transfer of
d e u t e r i u m between streams o f hydrogen
and l i q u i d water o v e r these w e t p r o o f e d c a t a l y s t s can
be c o n s i d e r e d i n terms o f two t r a n s f e r s t e p s . The
f i r s t corresponds t o the c a t a l y t i c r a t e o f t r a n s f e r o f
d e u t e r i u m from an e n r i c h e d hydrogen stream t o water
vapour and t h e second c o r r e s p o n d s t o the t r a n s f e r r a t e
from water vapour t o l i q u i d as shown i n e q u a t i o n s [8]
and [ 9 ] .
Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch007
HD
HDO
vap
+ H zo O
vap
+
Ηz
2
Ο
η
.
liq
ν
^
N
s
HDO
vap
HDO,.
l i q
+
+ Hz
(8)
H
0
z
(9)
2
2
vap
The c a t a l y t i c r e a c t i o n [8] o c c u r s on a c t i v e c a t a l y s t
s i t e s w h i l e t h e v a p o u r - l i q u i d t r a n s f e r r e a c t i o n [9]
o c c u r s on any s u r f a c e . The l a t t e r t r a n s f e r s t e p can
be c o n s i d e r e d as a c o n d e n s a t i o n - e v a p o r a t i o n r e a c t i o n .
Techniques have been d e v e l o p e d so t h a t , i n a t r i c k l e
bed r e a c t o r , t h e o v e r a l l r a t e and t h e i n d i v i d u a l
t r a n s f e r r a t e s ( r e a c t i o n s [8] and [9]) can be d e t e r ­
mined s i m u l t a n e o u s l y (7) . The magnitudes o f t h e s e
s e p a r a t e d r a t e s a r e b o t h about a f a c t o r o f 2 l a r g e r
than v a l u e s from d i r e c t measurements made on these
two r e a c t i o n s i n d e p e n d e n t l y .
These r e s u l t s have l e d
to t h e c o n c l u s i o n t h a t t h e o v e r a l l mechanism f o r t h e
exchange r e a c t i o n i s n o t as s i m p l e as f i r s t assumed
and t h a t t h e r e i s a t h i r d p r o c e s s independent o f t h e
w a t e r vapour i n v o l v e d i n the t r a n s f e r o f deuterium
from hydrogen gas t o l i q u i d w a t e r .
The e x a c t n a t u r e
of t h i s t h i r d p r o c e s s i s n o t y e t known.
S t u d i e s have been made o f t h e e f f e c t o f some 20
d i f f e r e n t parameters on t h e a c t i v i t y o f t h e c a t a l y s t s
and t h e s e w i l l be d i s c u s s e d i n f u t u r e p u b l i c a t i o n s .
Improvements i n C a t a l y s t Performance
I n n o v a t i o n s r e s u l t i n g i n improved c a t a l y s t p e r ­
formance a r e summarized i n T a b l e 1. The a c t i v i t y ,
Kya, o f each c a t a l y s t i n a t r i c k l e bed r e a c t o r i s
g i v e n f o r a column o p e r a t i n g a t 25°C, a t about 1
atmosphere p r e s s u r e (0.106 MPa) and a s u p e r f i c i a l
hydrogen gas flow r a t e o f 1.0 m/s a t STP. A l s o
l i s t e d i n T a b l e 1 i s t h e s p e c i f i c a c t i v i t y o f each
c a t a l y s t , Kya*, d e f i n e d as t h e o v e r a l l t r a n s f e r r a t e
per u n i t c o n c e n t r a t i o n o f platinum i n the c a t a l y s t
bed,
In Separation of Hydrogen Isotopes; Rae, H.;
ACS Symposium Series; American Chemical Society: Washington, DC, 1978.
In Separation of Hydrogen Isotopes; Rae, H.;
ACS Symposium Series; American Chemical Society: Washington, DC, 1978.
0.14% P t - C - T e f l o n
0.087% P t - C - T e f l o n
0.39% P t - C - T e f l o n
Ordered Packing
6.
7.
8.
0.98
2.40
1.20
0.58
0.20
0.22
0.005
0.017
K^a
m^'S 1 ·itT3
C a l c u l a t e d from d a t a g i v e n i n r e f e r e n c e
0.4% P t - C - T e f l o n
5.
Teflon
0.4% P t - P o r o u s
3
4.
2
0.5% P t - A l 0
S i l i c o n e Treated
3
3.
2
0.05% P t - A l 0
Untreated
2.
Taylor
Pt-Charcoal,
1.
Catalyst
(8) .
a
2.18
2.84
1.44
0.146
0.064
0.046
0.0011
0.0022
K
Performance
a
y *
m3*s~Mkg Pt)"^-
Improvement i n C a t a l y s t
TABLE 1
Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch007
1980
2580
1300
133
58
42
1.0
2.0
Rel. Specific
Activity
106
SEPARATION
Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch007
/
O F HYDROGEN
ISOTOPES
Κ a* =
(10)
kg P t p e r m bed
y
The s p e c i f i c a c t i v i t y g i v e s a measure o f how e f f e c ­
t i v e l y t h e p l a t i n u m i s b e i n g used i n a g i v e n c a t a l y s t .
The l a s t column g i v e s t h e s p e c i f i c a c t i v i t y r e l a t i v e
t o c a t a l y s t #2, an u n t r e a t e d , 0 . 5 % P t c a t a l y s t on
3.2 mm p e l l e t s o f γ-alumina. C a t a l y s t #1, p l a t i n u m on
powdered c h a r c o a l , was p a t e n t e d by T a y l o r f o r t h i s
exchange r e a c t i o n i n 1954 (8) . Treatment o f c a t a l y s t
#2 w i t h s i l i c o n e (Cat. #3) improved t h e performance by
a f a c t o r o f 40. In an attempt t o f u r t h e r improve t h e
h y d r o p h o b i c environment o f t h e p l a t i n u m c r y s t a l l i t e s ,
p l a t i n u m was d e p o s i t e d on porous T e f l o n (Cat. #4) and
t h i s enhanced the a c t i v i t y s l i g h t l y .
Depositing
p l a t i n u m on h i g h s u r f a c e a r e a carbon and b o n d i n g t h i s
t o a c a r r i e r w i t h T e f l o n (Cat. #5) made a s i g n i f i c a n t
improvement i n the s p e c i f i c a c t i v i t y .
By d e c r e a s i n g
the p l a t i n u m l o a d i n g and i n c r e a s i n g i t s d i s p e r s i o n on
the carbon b l a c k (Cat. #6) t h e r e l a t i v e s p e c i f i c
a c t i v i t y was i n c r e a s e d by a f a c t o r o f 10. By f u r t h e r
d e c r e a s i n g t h e p l a t i n u m l o a d i n g t o 0.0 87% (Cat. #7) a
f u r t h e r i n c r e a s e was o b t a i n e d .
This l a t t e r c a t a l y s t
has a s p e c i f i c a c t i v i t y about 2000 times h i g h e r than
the u n t r e a t e d 0.5% P t - A l 0 c a t a l y s t , #3, and i s about
1000 times more a c t i v e than the c a t a l y s t p a t e n t e d by
T a y l o r (8) f o r t h i s exchange r e a c t i o n (Cat. #1). In
c a t a l y s t #8, the p l a t i n i z e d carbon was bonded w i t h
T e f l o n t o c o r r u g a t e d m e t a l s h e e t s a r r a n g e d i n an
o r d e r e d f a s h i o n i n t h e exchange column. A l t h o u g h t h i s
c a t a l y s t has a h i g h e r p l a t i n u m c o n t e n t , 0.39%, t h e
c o n c e n t r a t i o n o f p l a t i n u m p e r u n i t volume o f b e d i s
e s s e n t i a l l y the same as c a t a l y s t #6. However as a
r e s u l t o f t h e improved g e o m e t r i c c o n f i g u r a t i o n o f t h e
c a t a l y s t , b o t h t h e a c t i v i t y and t h e s p e c i f i c a c t i v i t y
are t w i c e t h a t o f c a t a l y s t #6. S i n c e the h e i g h t o f
the column r e q u i r e d f o r a g i v e n s e p a r a t i o n i s
i n v e r s e l y p r o p o r t i o n a l t o Kya, t h e s p e c t a c u l a r
improvements i n c a t a l y s t a c t i v i t y r e p o r t e d here make a
hydrogen-water exchange p r o c e s s f o r d e u t e r i u m e n r i c h ­
ment l o o k v e r y p r o m i s i n g .
3
2
Process
3
F e a t u r e s o f Hydrogen-Water Exchange
P r o c e s s e s based on the hydrogen-water exchange
r e a c t i o n p o t e n t i a l l y have many a t t r a c t i v e f e a t u r e s
f o r t h e s e p a r a t i o n o f hydrogen i s o t o p e s r e l a t i v e t o
the GS p r o c e s s .
In Separation of Hydrogen Isotopes; Rae, H.;
ACS Symposium Series; American Chemical Society: Washington, DC, 1978.
7.
BUTLER ET AL.
Novel Catalysts
for Isotopic
Exchange
107
ADVANTAGES OF HYDROGEN-WATER PROCESSES
Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch007
1.
2.
3.
4.
5.
6.
7.
8.
9.
HIGHER SEPARATION FACTOR
HIGHER RECOVERY
LOWER WATER AND GAS FLOWS
SMALLER EXCHANGE COLUMNS
SIMPLE CHEMISTRY
NON-CORROSIVE SYSTEM
NON-TOXIC
LOW ENVIRONMENTAL IMPACT, POLLUTION-NIL
USES ONLY ONE EXCHANGE REACTION
These g e n e r i c advantages a r e g e n e r a l l y a p p l i c a b l e
t o any p r o c e s s based on the hydrogen-water exchange
r e a c t i o n and a r e p a r t i c u l a r l y r e l e v a n t t o t h e Combined
Electrolysis
C a t a l y t i c Exchange (CECE) p r o c e s s . The
CECE p r o c e s s which c o u p l e s a hydrogen-water c a t a l y t i c
exchange column t o the hydrogen gas stream
from an
e l e c t r o l y s i s c e l l o f f e r s a v e r y e f f e c t i v e system f o r
the enrichment o f deuterium.
The p r o c e s s i s d i s c u s s e d
i n more d e t a i l by Hammerli, e t a^L. (9) i n the next
paper.
S i n c e t h e s e p a r a t i o n f a c t o r , a , f o r the
hydrogen-water exchange r e a c t i o n i s h i g h e r than t h a t
f o r the GS system, a h i g h e r deuterium r e c o v e r y i s
p o s s i b l e , 70% from n a t u r a l water compared t o 19% f o r
the GS p r o c e s s .
H i g h e r r e c o v e r y p e r m i t s lower water
and gas flow r a t e s i n t h e p l a n t . The v e r y a c t i v e
c a t a l y s t s t h a t have been d e v e l o p e d mean t h a t the
exchange columns w i l l be q u i t e s m a l l . A l t h o u g h most
o f t h e s e p a r a t o r y work i s a c c o m p l i s h e d i n these
columns, t h e i r volume would o n l y be about 4% o r 1/25
o f t h e exchange volume i n c u r r e n t GS p l a n t s f o r t h e
same p r o d u c t i o n o f heavy water.
The c h e m i s t r y o f the hydrogen-water system i s
s i m p l e and o p e r a t i n g c o n d i t i o n s o f the CECE p r o c e s s
are n e a r ambient.
The system i s n o n - c o r r o s i v e , an
i m p o r t a n t f e a t u r e s i n c e many o f the shut-downs i n GS
p l a n t s r e s u l t from c o r r o s i o n . The system i s nont o x i c and n o n - p o l l u t i n g and would have a v e r y low
e n v i r o n m e n t a l impact.
The CECE p r o c e s s y i e l d s two
v a l u a b l e p r o d u c t s - heavy water and l a r g e q u a n t i t i e s
o f hydrogen, a v e r y u s e f u l c h e m i c a l .
Electrolytic
oxygen may a l s o be c o n s i d e r e d as an a d d i t i o n a l
product.
F i n a l l y the p r o c e s s u t i l i z e s o n l y one
exchange r e a c t i o n f o r t h e complete enrichment o f
d e u t e r i u m from n a t u r a l water t o r e a c t o r grade heavy
w a t e r , 99.8% D 0 . T h i s removes many o f the comp l e x i t i e s o f o t h e r heavy water p r o c e s s e s which r e q u i r e
d i f f e r e n t processes a t various stages i n the
enrichment.
2
In Separation of Hydrogen Isotopes; Rae, H.;
ACS Symposium Series; American Chemical Society: Washington, DC, 1978.
108
SEPARATION OF HYDROGEN ISOTOPES
Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch007
The major d i s a d v a n t a g e s o f t h e p r o c e s s a r e t h a t
i t r e q u i r e s a l a r g e amount o f e l e c t r i c a l power f o r t h e
e l e c t r o l y s i s c e l l s and i t r e q u i r e s a s t a b l e p l a t i n u m
c a t a l y s t which i s somewhat e x p e n s i v e .
However a c t i v e
c a t a l y s t s have been d e v e l o p e d w i t h low p l a t i n u m
l o a d i n g s so t h a t the p l a t i n u m r e p r e s e n t s o n l y about
30% o f the c o s t o f t h e f i n i s h e d c a t a l y s t .
Further,
the amount o f c a t a l y s t r e q u i r e d i s s m a l l and i t has
been e s t i m a t e d t h a t t h e c a t a l y s t c o s t w i l l be o n l y a
v e r y s m a l l p e r c e n t a g e o f the t o t a l c a p i t a l c o s t o f a
heavy water p l a n t .
L i k e w i s e c a t a l y s t replacement i s
n o t e x p e c t e d t o add s i g n i f i c a n t l y t o t h e o p e r a t i n g
costs.
Acknowledgements
We thank J. den H a r t o g and F.W. Molson f o r t h e i r
a s s i s t a n c e i n t h e development o f these w e t p r o o f e d
catalysts.
We e x p r e s s o u r thanks t o W.M. T h u r s t o n f o r
the development o f an a u t o m a t i c mass s p e c t r o m e t e r
system f o r o n - l i n e a n a l y s i s o f d e u t e r i u m i n hydrogen
gas streams, a t n e a r n a t u r a l abundance. Only w i t h
h i s equipment and a s s i s t a n c e i n the a n a l y s i s o f
thousands o f gas samples has t h i s r e s e a r c h been
feasible.
Abstract
Catalytic
i s o t o p i c exchange between hydrogen and
liquid
water o f f e r s many i n h e r e n t p o t e n t i a l advantages
f o r the s e p a r a t i o n o f hydrogen i s o t o p e s which i s o f
g r e a t importance i n the Canadian n u c l e a r program.
Active catalysts for
isotopic
exchange between
hydrogen and water vapour have l o n g been a v a i l a b l e ,
but these c a t a l y s t s are
essentially
i n a c t i v e i n the
presence o f liquid w a t e r .
New, water r e p e l l e n t
p l a t i n u m c a t a l y s t s have been p r e p a r e d b y :
1) t r e a t i n g
supported c a t a l y s t s with
silicone,
2) d e p o s i t i n g
p l a t i n u m on
i n h e r e n t l y hydrophobic polymeric
s u p p o r t s , and 3) t r e a t i n g
platinized
carbon with
T e f l o n and b o n d i n g to a
carrier.
The
activity
of
these c a t a l y s t s f o r i s o t o p i c exchange between c o u n t e r - c u r r e n t streams o f liquid water and hydrogen s a t u r a t e d
w i t h water vapour has been measured in a packed
trickle
bed
integral
reactor.
The performance o f
t h e s e h y d r o p h o b i c c a t a l y s t s i s compared w i t h non-wetproofed
catalysts.
The mechanism o f the
overall
exchange r e a c t i o n i s
briefly
discussed.
In Separation of Hydrogen Isotopes; Rae, H.;
ACS Symposium Series; American Chemical Society: Washington, DC, 1978.
7.
BUTLER ET AL.
Literature
1.
2.
3.
4.
Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch007
5.
6.
7.
8.
9.
Novel
Catalysts
for Isotopic
Exchange
109
Cited
R o l s t o n , J.H., den H a r t o g , J. and B u t l e r ,
J.P.,
J.
Phys. Chem., (1976), 80,
1064.
P o h l , H.Α., J. Chem. & E n g . D a t a , (1961), 6,
(4),
515.
Murphy, G.M., U r e y , H . C . and Kirshenbaum,
I.,
Editors,
" P r o d u c t i o n o f Heavy Water, N a t i o n a l
Energy S e r i e s " , C h a p t e r 2, p . 16, M c G r a w - H i l l ,
New Y o r k , 1955.
S t e v e n s , W . H . , Canadian P a t e n t No. 907,292,
August 15,
1972.
Rolston,
J.H.,
den H a r t o g , J. and B u t l e r ,
J.P.,
U . S . P a t e n t No. 4 , 0 2 5 , 5 6 0 , May 24,
1977.
T h u r s t o n , W . M . , Rev. Sci. I n s t r u m e n t s , (1970),
41, 963 and (1971), 42, 700.
Butler,
J.P.,
den H a r t o g , J., G o o d a l e , J.W. and
Rolston,
J.H.,
"Proceedings o f the S i x t h I n t e r ­
n a t i o n a l Congress on
Catalysis,
London 1976",
Vol.
2, p . 747, The C h e m i c a l S o c i e t y , London,
1977.
T a y l o r , H.S., U . S . P a t e n t No. 2 , 6 9 0 , 3 8 0 ,
September 28,
1954.
Hammerli, Μ . , S t e v e n s , W . H . , and
Butler,
J.P.,
P r o c e e d i n g s o f the Symposium on " S e p a r a t i o n o f
Hydrogen I s o t o p e s " , M o n t r e a l 1977, p . 110 ,
American Chemical S o c i e t y , Washington,
1977.
RECEIVED October 10, 1977
In Separation of Hydrogen Isotopes; Rae, H.;
ACS Symposium Series; American Chemical Society: Washington, DC, 1978.
8
Combined Electrolysis Catalytic Exchange (CECE)
Process for Hydrogen Isotope Separation
M. HAMMERLI, W. H . STEVENS, and J. P. BUTLER
Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch008
Atomic Energy of Canada Ltd., Chalk River Nuclear Laboratories,
Chalk River, Ontario, Canada K0J 1J0
In t h e p r e c e d i n g p a p e r ( J ) a n o v e l p l a t i n u m - c a r b o n
- T e f l o n c a t a l y s t for e f f i c i e n t s e p a r a t i o n o f the hydro­
gen
i s o t o p e s i n t h e p r e s e n c e o f l i q u i d w a t e r has been
discussed.
T h i s p a p e r d e a l s w i t h the Combined
E l e c t r o l y s i s C a t a l y t i c E x c h a n g e (CECE) p r o c e s s e s w h i c h
use t h i s c a t a l y s t f o r s e p a r a t i n g t h e h y d r o g e n i s o t o p e s ,
n a m e l y t h e CECE-HWP ( - H e a v y W a t e r p r o c e s s ) and t h e
CECE-TRP ( - T j i t i u m R e c o v e r y p r o c e s s ) .
The
i s o t o p i c s e p a r a t i o n p r i n c i p l e s i n h e r e n t i n the
CECE p r o c e s s e s
are:
(a) the e q u i l i b r i u m i s o t o p e e f f e c t i n r e a c t i o n s o f the
type :
H D
and
gas
+
i t s isotopic
H
*
0
l i q u i d ^ % a s
+
H
D
0
l i q u i d
analogues, and
™
(b)
the k i n e t i c isotope e f f e c t
(2) i n h e r e n t i n t h e
e l e c t r o l y t i c hydrogen e v o l u t i o n r e a c t i o n .
There are
thus two r e l a t i v e l y
large isotopic separation
factors
i n v o l v e d i n t h e s e p r o c e s s e s w h i c h , as we m i g h t e x p e c t ,
l e a d t o many o f t h e i r a d v a n t a g e s , d i s c u s s e d
later.
Both s e p a r a t i o n f a c t o r s favour c o n c e n t r a t i o n o f the
heavier isotope i n the l i q u i d water r e l a t i v e to the
hydrogen g a s .
T h e CECE-HWP i s a n e w , y e t o l d p r o c e s s , f o r i t
u t i l i z e s t h e same b a s i c p r i n c i p l e s as C a n a d a ' s
first
i n d u s t r i a l heavy w a t e r p l a n t o p e r a t e d by C o n s o l i d a t e d
M i n i n g a n d S m e l t i n g Company f r o m 1 9 4 3 t o 1956 a t T r a i l ,
B.C.
(J3 ) .
The T r a i l p r o c e s s was a l s o a c o m b i n a t i o n o f
e l e c t r o l y s i s and hydrogen-water exchange, but the
e x c h a n g e r e a c t i o n h a d t o be c a r r i e d o u t i n t h e gas
phase because l i q u i d water p o i s o n e d the c a t a l y s t .
In
the e x c h a n g e c o l u m n , d e u t e r i u m was t r a n s f e r r e d
from
hydrogen to water vapour i n a heated c a t a l y s t bed, and
then a p a i r o f bubble cap t r a y s promoted d e u t e r i u m
©
0-8412-0420-9/78/47-068-110$05.00/0
In Separation of Hydrogen Isotopes; Rae, H.;
ACS Symposium Series; American Chemical Society: Washington, DC, 1978.
Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch008
8.
HAMMERLI ET AL.
Combined
Electrolysis
Catalytic
Exchange
111
exchange between the w a t e r vapour and l i q u i d w a t e r .
T h i s s e q u e n c e w a s r e p e a t e d many t i m e s t h r o u g h o u t t h e
column.
Heavy w a t e r p r o d u c e d by t h e T r a i l p r o c e s s was
too c o s t l y because o f the s i z e and c o m p l e x i t y o f t h e
exchange columns and t h e e x c e s s i v e energy r e q u i r e d f o r
the steam preheaters
t o r e p e a t e d l y v a p o u r i z e any l i q u i d
w a t e r i n the gas s t r e a m .
I t s h o u l d be n o t e d t h a t t h e
c a t a l y s t beds o c c u p i e d o n l y 4 p e r c e n t o f t h e t o t a l
volume o f the t o w e r s .
If a catalyst
c o u l d be d e v e l o p e d t h a t w o u l d
remain
a c t i v e i n the presence of l i q u i d w a t e r , the need f o r
t h e c o m p l e x T r a i l - t y p e c o l u m n s c o u l d be e l i m i n a t e d , a n d
p a c k e d l i q u i d - v a p o u r c o n t a c t o r s c o u l d be u s e d .
Becker
and c o - w o r k e r s
(£) developed a s l u r r y c a t a l y s t
cons i s t i n g o f p l a t i n u m on f i n e l y d i v i d e d c h a r c o a l f o r t h e
hydrogen l i q u i d water exchange r e a c t i o n .
The e x c h a n g e
r a t e f o r t h e i r c a t a l y s t d e p e n d e d p r i m a r i l y on t h e
d i s s o l v e d hydrogen c o n c e n t r a t i o n so t h a t t h e c a t a l y s t
c o u l d o n l y be u s e d a t v e r y h i g h p r e s s u r e s , 20 M P a .
Low
c a t a l y s t a c t i v i t y , h i g h i n v e n t o r y o f p l a t i n u m and l o s s e s
of the f i n e l y d i v i d e d c a t a l y s t
are t h e main reasons the
process proved uneconomic.
With Stevens'
i n v e n t i o n of the wetproofed
catalyst
(5>) , i t b e c a m e p o s s i b l e t o e f f e c t a v e r y
efficient
d e u t e r i u m exchange between hydrogen and l i q u i d w a t e r a t
low p r e s s u r e s ,
t h i s c a t a l y s t allows the very
close
c o u p l i n g o f t h e two e x c h a n g e r e a c t i o n s .
Preheaters
and
b u b b l e cap t r a y s become u n n e c e s s a r y and t h e e x c h a n g e
c o l u m n c a n be o p e r a t e d a t l o w e r ( a m b i e n t )
temperatures
where the s e p a r a t i o n f a c t o r i s l a r g e r ( 6 ) .
Thus t h e
v o l u m e o f t h e c o l u m n f o r t h e CECE-HWP i s r e d u c e d b y a
f a c t o r o f a b o u t 20 r e l a t i v e
to the T r a i l
process.
B e c a u s e t h e w e t p r o o f e d c a t a l y s t i n t h e CECE-HWP
has d r a s t i c a l l y a l t e r e d t h e e x c h a n g e column o f t h e
T r a i l - t y p e p r o c e s s , t h e d e s i g n a t i o n CECE w i l l
only
apply t o processes i n c o r p o r a t i n g t h i s type o f c a t a l y s t ,
e v e n t h o u g h t h e same b a s i c i s o t o p e s e p a r a t i o n p r i n c i p l e s
a p p l y to b o t h .
B e f o r e d i s c u s s i n g t h e CECE-HWP i n m o r e d e t a i l , i t
is worth mentioning that this process involves
three
p r o d u c t s , H , D 0 and 0 , o f w h i c h t h e f i r s t two have
considerable commercial value at present.
The l a r g e
amount o f e l e c t r i c a l e n e r g y r e q u i r e d t o p r o d u c e one
k i l o g r a m o f r e a c t o r g r a d e h e a v y w a t e r can be o f f s e t
s o m e w h a t b y t h e v a l u e o f t h e h y d r o g e n , e i t h e r as a
c h e m i c a l o r as a f u e l
(equivalent
t o ^ 2 0 MWh/kg D 0 ) .
N e v e r t h e l e s s , i t m u s t be u n d e r s t o o d a t t h e o u t s e t
that
t h e m a j o r d i s a d v a n t a g e o f t h e CECE-HWP i s i t s r e l a tively
l a r g e s p e c i f i c e n e r g y r e q u i r e m e n t ( ^ 5 0 MWh/kg
D 0),
t h e energy b e i n g o f the h i g h e s t grade and c o s t .
2
2
2
2
2
In Separation of Hydrogen Isotopes; Rae, H.;
ACS Symposium Series; American Chemical Society: Washington, DC, 1978.
112
SEPARATION OF
H Y D R O G E N ISOTOPES
T h e CECE-HWP w i l l b e c o m e i n c r e a s i n g l y m o r e
attractive
f o r the l a r g e s c a l e p r o d u c t i o n of D 0 from n a t u r a l
water,
to the degree t h a t the c o s t of f o s s i l
fuels
escalates
f a s t e r t h a n t h e c o s t o f CANDU* n u c l e a r p o w e r .
2
Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch008
The
CECE-HWP
B a s i c D e s c r i p t i o n of the P r o c e s s .
I n t h e CECE-HWP
(see
F i g u r e 1) t h e e l e c t r o l y t i c h y d r o a e n ,
already
depleted in deuterium r e l a t i v e
to the e l e c t r o l y t e
by
v i r t u e o f the k i n e t i c i s o t o p e e f f e c t i n h e r e n t i n
the
hydrogen e v o l u t i o n r e a c t i o n , s t e a d i l y loses most of
its
r e m a i n i n g d e u t e r i u m as i t m o v e s up t h e c a t a l y s t
column
in c o u n t e r - c u r r e n t flow w i t h the feed water t r i c k l i n g
down i n t o t h e e l e c t r o l y s i s c e l l .
The w a t e r becomes e n r i c h e d i n d e u t e r i u m a c c o r d i n g t o r e a c t i o n 1 as
it
p a s s e s down t h e c a t a l y s t b e d .
The o v e r a l l
deuterium
p r o f i l e i s one i n w h i c h t h e d e u t e r i u m c o n c e n t r a t i o n
in
the w a t e r i n c r e a s e s a l o n g t h e l e n g t h o f the column from
top to b o t t o m , w h i l e i n the gas phase t h e
deuterium
concentration decreases
from the bottom to top.
The d e h u m i d i f i e r i s n e c e s s a r y i f t h e
depleted
h y d r o g e n g a s m u s t be d r y .
This unit also transfers
the
d e u t e r i u m i n t h e w a t e r v a p o u r c a r r i e d by t h e
hydroaen
gas to the f e e d w a t e r .
The s c r u b b e r b e t w e e n t h e c a t a l y s t c o l u m n and t h e
e l e c t r o l y s i s c e l l serves
the f o l l o w i n g f u n c t i o n s :
(a)
removes e n t r a i n e d e l e c t r o l y t e i n t h e hydrogen g a s ,
(b)
a d j u s t s the h u m i d i t y of the h y d r o g e n gas to t h e
c o n d i t i o n s p r e v a i l i n g i n t h e c o l u m n , w h i c h n e e d n o t be
t h e same as t h o s e i n t h e
cell,
(c)
t h e r m o s t a t s t h e h u m i d i f i e d gas t o t h e c o l u m n t e m perature,
and
(d)
t r a n s f e r s deuterium from the w a t e r vapour e n t r a i n e d
i n t h e h y d r o g e n gas to the l i q u i d
water.
The l a t t e r f u n c t i o n i s v e r y i m p o r t a n t s i n c e
the
deuterium c o n c e n t r a t i o n of the water vapour in the
h y d r o g e n gas s t r e a m l e a v i n g t h e e l e c t r o l y s i s
cell
c o u l d e a s i l y be a b o u t 3 t o 10 t i m e s l a r g e r t h a n
that
in the w a t e r at the b o t t o m o f the e x c h a n q e c o l u m n .
T h i s d i f f e r e n c e i s m a i n l y d e p e n d e n t on t h e m a g n i t u d e o f
t h e e f f e c t i v e e l e c t r o l y t i c H/D s e p a r a t i o n f a c t o r ,
which
i n t u r n d e p e n d s on t h e c a t h o d e m a t e r i a l a n d t h e o p e r a ting conditions of the e l e c t r o l y s i s
cell.
Any t y p e o f e l e c t r o l y s i s c e l l i n c o r p o r a t i n g a
s e p a r a t o r between the anode and c a t h o d e
compartments
may b e u s e d i n t h e C E C E - H W P .
If the c e l l contains a
l i q u i d e l e c t r o l y t e , s u c h as 2 5 w e i g h t % s o l u t i o n o f K O H ,
t h e s a l t o f t h e e l e c t r o l y t e m u s t be r e m o v e d f r o m t h e
w
*CANada
Deuterium
I U r a n i urn
In Separation of Hydrogen Isotopes; Rae, H.;
ACS Symposium Series; American Chemical Society: Washington, DC, 1978.
Combined
HAMMERLI ET AL.
Electrolysis
FEED WATER
Catalytic
Exchange
HYDROGEN GAS TO
f s T Ô R AGF ÔVENÊRGY '
[l48 ppm]
DEHUMIDIFIER
CONVERTER ETC.
Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch008
1
H /H 0
DEUTERIUM
EXCHANGE
CATALYST
TOWER
2
OXYGEN GAS TO
STORAGEJDR ENERGY
CONVERTER
ETC.
2
~!
SCRUBBER
DRYER
H0
2
τ.
,H
2
1
ELECTROLYS IS CELLS
ANODE
COMPARTMENT ,
1
CATHODE
COMPARTMENT
SALT OF
ELECTROLYTE
ELECTROLYTE
SEPARATOR
DEUTERIUM ENRICHED
WATER TO HEAVY WATER
PLANT
Figure 1.
Combined Electrolysis Catalytic Exchange-Heavy
"Process (CECE-HWP)
Water
In Separation of Hydrogen Isotopes; Rae, H.;
ACS Symposium Series; American Chemical Society: Washington, DC, 1978.
114
SEPARATION O F HYDROGEN ISOTOPES
Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch008
p r o d u c t s t r e a m b e f o r e i t c a n be f e d t o t h e n e x t h i g h e r
stage.
Electrolyte
r e m o v a l may b e s t b e a c c o m p l i s h e d
b y f l a s h e v a p o r a t i o n (_7) * w h i c h w o u l d a l s o
remove
s i m u l t a n e o u s l y the excess heat generated in the c e l l .
It i s i m p o r t a n t t o dry the c o - l i b e r a t e d oxygen
b e c a u s e t h e f i r s t s t a g e p r o d u c t c o u l d e a s i l y be a b o u t
20 t i m e s r i c h e r i n d e u t e r i u m t h a n t h e f e e d w a t e r a t
the top o f the column ( 8j , so t h a t l o s s e s w o u l d o t h e r ­
w i s e be i n t o l e r a b l e .
Results from L a b o r a t o r y U n i t .
The s m a l l
labora­
t o r y u n i t used to demonstrate the p r i n c i p l e s of the
CECE-HWP c o n s i s t s o f a c a t a l y s t
c o l u m n , 36 cm l o n g a n d
2 . 5 4 cm i n d i a m e t e r , a n d a G . E . e l e c t r o l y s i s
module
containing 2-unit c e l l s .
The a p p a r a t u s i s shown
s c h e m a t i c a l l y in Figure 2.
Because the G.E.
e l e c t r o l y s i s module c o n t a i n s a s o l i d polymer
electrolyte
(SPE), the e l e c t r o l y t e s e p a r a t o r
(see
F i g u r e 1) i s n o t r e q u i r e d .
The e l e c t r o l y s i s c e l l was
o p e r a t e d a t a c u r r e n t o f 2 χ 2 0 = 40 A .
With o p e r a t i n g c o n d i t i o n s such that the feed water
r a t e i s a d j u s t e d t o e q u a l t h e e l e c t r o l y s i s r a t e and no
p r o d u c t i s w i t h d r a w n ( t o t a l r e f l u x ) , one w o u l d e x p e c t
to see a l i n e a r i n c r e a s e i n the deuterium
concentration
i n t h e c e l l - w a t e r c i r c u i t as a f u n c t i o n o f e l e c t r o l y s i s
time p r o v i d i n g the f o l l o w i n g c o n d i t i o n s p e r t a i n :
(a) t h e c e l l c u r r e n t remains
constant,
(b) t h e d e u t e r i u m c o n c e n t r a t i o n s i n both t h e feed w a t e r
and t h e e f f l u e n t h y d r o g e n r e m a i n c o n s t a n t , and
(c) t h e r e are no e x t r a n e o u s d e u t e r i u m l o s s e s i n t h e
system.
C o n d i t i o n (a) i s e a s i l y s a t i s f i e d w i t h a c o n s t a n t
c u r r e n t power s u p p l y .
The d e u t e r i u m c o n c e n t r a t i o n i n
the f e e d w a t e r i s a l s o easy to keep c o n s t a n t , b u t t h a t
i n t h e e f f l u e n t h y d r o g e n gas i s a f u n c t i o n o f the
c o l u m n p a r a m e t e r s i n c l u d i n g c a t a l y s t a c t i v i t y , as w e l l
as t h e d e u t e r i u m c o n c e n t r a t i o n i n t h e e l e c t r o l y t i c
hydrogen.
However, the c a t a l y s t bed parameters
were
c h o s e n so t h a t t h e column o p e r a t e d a t n e a r 100%
e f f i c i e n c y f o r a p r o d u c t c o n c e n t r a t i o n up t o a b o u t 0 . 1 % .
T h i s c a n be s e e n b y t h e a l m o s t h o r i z o n t a l l i n e f o r t h e
d e u t e r i u m c o n c e n t r a t i o n i n t h e d e p l e t e d h y d r o q e n gas i n
F i g u r e 3.
The d e v i a t i o n o f t h e d e u t e r i u m b u i l d - u p i n
the w a t e r from the t h e o r e t i c a l l i n e i s thus
mainly
a t t r i b u t a b l e to l o s s e s a s s o c i a t e d w i t h
incomplete
d r y i n g o f the oxygen g a s .
These l o s s e s
naturally
b e c o m e l a r g e r as t h e d e u t e r i u m c o n c e n t r a t i o n
increases
in the c e l l
water.
The s l o p e o f t h e c a l c u l a t e d l i q u i d p h a s e l i n e i n
F i g u r e 3 i s a f u n c t i o n o f t h e volume o f w a t e r i n the
In Separation of Hydrogen Isotopes; Rae, H.;
ACS Symposium Series; American Chemical Society: Washington, DC, 1978.
In Separation of Hydrogen Isotopes; Rae, H.;
ACS Symposium Series; American Chemical Society: Washington, DC, 1978.
Laboratory CECE-HWP
demonstration unit. The unit incorporates a General Electric solid
polymer electrolyte electrolysis module.
Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch008
Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch008
SEPARATION O F HYDROGEN ISOTOPES
Figure 3. Deuterium concentration in the electrolysis cell water
circuit as a function of electrolysis time. The feed water flow
rate equals the electrolysis rate, and the product flow rate is zero.
The dashed line is calculated assuming no deuterium loss from
the system (see text).
In Separation of Hydrogen Isotopes; Rae, H.;
ACS Symposium Series; American Chemical Society: Washington, DC, 1978.
8.
HAMMERLI ET AL.
Combined
Electrolysis
Catalytic
Exchange
117
c e l l - w a t e r c i r c u i t , the deuterium concentration i n the
feed water,
the operating temperature o f the column,
and t h e r a t e o f e l e c t r o l y s i s .
Thus i t h a s no f u n d a mental
significance.
It i s worth e m p h a s i z i n g that both t h e w a t e r and
h y d r o g e n l i n e a r f l o w r a t e s a r e a b o u t two o r d e r s o f
magnitude s m a l l e r than t h e optimum flow rates f o r t h e
2 . 5 4 cm d i a m e t e r c o l u m n , b e c a u s e o f t h e l o w c u r r e n t ,
40 A , i n t h e e l e c t r o l y s i s c e l l .
L i n e a r hydroaen
flow
r a t e s o f 1 to 2 m - s " at S . T . P . appear optimum f o r
e f f i c i e n t u t i l i z a t i o n o f the novel c a t a l y s t
Q ) for a
column o p e r a t i n g at near a t m o s p h e r i c p r e s s u r e .
This
c o l u m n w o u l d r e q u i r e an e l e c t r o l y s i s c u r r e n t o f 4 , 3 6 5 A
to 8,730 A t o produce t h e r e q u i r e d l i n e a r hydrogen
flow
rates.
These f i g u r e s p o i n t to t h e f a c t t h a t t h e
e l e c t r o l y s i s p l a n t w i l l be c o n s i d e r a b l y l a r g e r t h a n t h e
c o r r e s p o n d i n g c a t a l y s t c o l u m n i n an o p t i m u m C E C E - H W P
pi ant.
Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch008
1
De u t e r i urn R e c o v e r y .
In t h e CECE-HWP, t h e
theoretical
f r a c t i o n o f t h e d e u t e r i u m w h i c h c a n be
r e c o v e r e d from t h e f e e d w a t e r i s g o v e r n e d s o l e l y by t h e
v a l u e o f t h e e q u i l i b r i u m c o n s t a n t o f r e a c t i o n 1, and
hence t h e t e m p e r a t u r e o f t h e top o f t h e c o l u m n .
I t may
be e x p r e s s e d i n t e r m s o f t h e s e p a r a t i o n f a c t o r f o r t h e
column, aç, which i s i d e n t i c a l to the e q u i l i b r i u m cons t a n t , as f o l 1 o w s :
Theoretical
Recovery
=
D
p
-
D /a
p
c
(2)
w h e r e Dp i s t h e d e u t e r i u m c o n c e n t r a t i o n i n t h e f e e d
wate r.
In p r a c t i c e , i t i s p r u d e n t t o c h o o s e a d e u t e r i u m
c o n c e n t r a t i o n i n the e f f l u e n t hydrogen gas which i s
a b o u t 10% l a r g e r than t h e c a l c u l a t e d e q u i l i b r i u m v a l u e ,
Dp/aQ.
Then c a t a l y s t r e q u i r e m e n t s , w h i c h w o u l d
otherwise
approach i n f i n i t y , are reasonable.
The p r a c t i c a l
range
of deuterium recoveries
f o r t h e CECE-HWP w i l l
probably
be i n t h e r a n g e 6 6 - 7 5 % c o r r e s p o n d i n g t o a t e m p e r a t u r e
range o f about 60°C t o 15°C r e s p e c t i v e l y .
This i s a
h i g h r e c o v e r y f o r a d e u t e r i u m p r o d u c t i o n p r o c e s s (9).
S y n e r q i s t i c Ε f fe c t s .
Several synergistic
effects
r e s u l t from combining e l e c t r o l y s i s with H /H 0 deuterium
exchange r e l a t i v e t o e i t h e r cascaded
conventional
e l e c t r o l y s i s alone or cascaded H /H 0 exchange
alone.
In t h e l a t t e r c a s e , a b i t h e r m a l e x c h a n g e p r o c e s s m u s t
be u s e d , s i m i l a r i n p r i n c i p l e t o t h e p r e s e n t
GirdlerS u l p h i d e ( G S ) p r o c e s s (9) b a s e d on t h e H S / H 0 e x c h a n g e
2
2
2
2
2
2
In Separation of Hydrogen Isotopes; Rae, H.;
ACS Symposium Series; American Chemical Society: Washington, DC, 1978.
118
SEPARATION O F
HYDROGEN ISOTOPES
re a c t i o n .
The s y n e r g i s t i c e f f e c t s o f t h e CECE-HWP a r e
s u m m a r i z e d i n T a b l e s I and
II.
I n T a b l e I,
e l e c t r o l y s i s a l o n e , o p e r a t i n g a s an
i d e a l c a s c a d e , i s c o m p a r e d to e l e c t r o l y s i s i n
the
CECE-HWP a s s u m i n g t h e e l e c t r o l y t i c H/D s e p a r a t i o n
f a c t o r , CL£
is 6 for both.
This value is
certainly
attainable in p r a c t i c e .
For e x a m p l e , the
electrolytic
h e a v y w a t e r U p g r a d i n a P l a n t a t CRNL h a s o p e r a t e d
for
s e v e r a l y e a r s w i t h an e f f e c t i v e a p o f 8 t o 9 a t
cell
t e m p e r a t u r e s f r o m 35°C t o 25°C r e s p e c t i v e l y .
However,
these c e l l s incorporate mild steel cathodes
and
operate at lower temperatures than i s the
current
p r a c t i c e in commercial c e l l s .
S i n c e the t r e n d is
to­
w a r d s h i g h e r o p e r a t i n g t e m p e r a t u r e s and o t h e r
cathode
m a t e r i a l s * , i n c l u d i n g p r e c i o u s m e t a l s , an a£ o f s a y ,
3,
m i g h t be m o r e r e a l i s t i c i n t h e f u t u r e .
A n y v a l u e o f ap
less than 6 w o u l d , of c o u r s e , i n c r e a s e the
differences
in Table
I.
The f a c t o r s w h i c h l e a d t o a r e d u c t i o n i n
catalyst
r e q u i r e m e n t s f o r t h e CECE-HWP v e r s u s t h e b i t h e r m a l
H /
H 0-HWP are t a b u l a t e d i n T a b l e II.
S i n c e the s p e c i f i c
c a t a l y s t r e q u i r e m e n t (amount o f c a t a l y s t r e q u i r e d p e r
unit of D 0 production per unit of time) is
directly
p r o p o r t i o n a l to t h e gas f l o w r a t e but t h e
deuterium
p r o d u c t i o n i s d i r e c t l y p r o p o r t i o n a l to the l i q u i d
flow
r a t e , i n c r e a s i n g t h e L/G r a t i o ( L a n d G a r e t h e m o l a r
w a t e r and gas f l o w r a t e s r e s p e c t i v e l y )
decreases
the
catalyst requirement d i r e c t l y .
D a t a i n T a b l e II
serve
to i l l u s t r a t e the e f f e c t s of the d i f f e r e n t
parameters
on t h e c a t a l y s t v o l u m e f o r a g i v e n D 0 p r o d u c t i o n
rate
and are n o t n e c e s s a r i l y optimum v a l u e s .
For the b i t h e r m a l H /H 0-HWP, the d e u t e r i u m r e ­
c o v e r y i s l i m i t e d by t h e d i f f e r e n c e i n t h e
practical
c o l d and hot column t e m p e r a t u r e a t t a i n a b l e , s i n c e
it
i s b a s e d on t h e t e m p e r a t u r e c o e f f i c i e n t o f α ς .
For a
g i v e n d e u t e r i u m c o n c e n t r a t i o n i n the f e e d , the
specific
v o l u m e o f w a t e r w h i c h m u s t be p r o c e s s e d p e r u n i t o f D 0
p r o d u c e d i s d i r e c t l y d e p e n d e n t on t h e
recovery.
The t h i r d p a r a m e t e r w h i c h i s c o m p a r e d i n T a b l e
II
i s the number of t r a n s f e r u n i t s ( N . T . U . ) r e q u i r e d f o r
a deuterium c o n c e n t r a t i o n in the product of 0.1%
[ 1 0 0 0 ppm D/(H + D ) ] w h e n a£ = 6 , a n d t h e f e e d w a t e r
con­
t a i n s 1 4 8 ppm d e u t e r i u m , w h i c h c o i n c i d e s w i t h
the
Great Lakes w a t e r s ( 1 0 ) .
The s p e c i f i c c a t a l y s t
volume
f o r a g i v e n c a t a l y s t i s d i r e c t l y d e p e n d e n t on t h e
N.T.U.'s (£).
It i s i m p o r t a n t to p o i n t out that
only
Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch008
9
2
2
2
2
2
2
2
* I r o n o r m i l d s t e e 1 c a t h o d e s y i e l d t h e l a r g e s t aE
values f o r a given set of operating conditions
relat i ve t o o t h e r m e t a l s .
In Separation of Hydrogen Isotopes; Rae, H.;
ACS Symposium Series; American Chemical Society: Washington, DC, 1978.
In Separation of Hydrogen Isotopes; Rae, H.;
ACS Symposium Series; American Chemical Society: Washington, DC, 1978.
a
F
No.
of
Reflux,
F
Stages
n
Parameter
Cascade
1.7
^17
Ideal
Electrolysis
Compared
CECE-HWP
3
1.0
CECE-HWP
Cascade)
CECE-HWP
OF THE
I
Size of
electrolysis plant
not
affected
the
(Ideal
in
EFFECTS
Size of
electrolysis plant
d i r e c t l y dependent
on ac
Conventional
SYNERGISTIC
Table
in
plant
volume
increases
a s α^· d e c r e a s e s
complicated
Catalyst
somewhat
Less
costs
reduction
Remarks
Electrolysis
energy
^70%
to
Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch008
In Separation of Hydrogen Isotopes; Rae, H.;
ACS Symposium Series; American Chemical Society: Washington, DC, 1978.
for
the
cold
FACTOR
^1
=
6
MPa
7.4
^66
1
CECE-HWP
E
the
Bithermal
since
= 265
the
ppm
^24
^2
Λ
^15
deuterium
instead of
1 .66
2
2.3
C a t a l y s t R e d u c t i on
Factor
versus
CECE-HWP
CECE-HWP
THE
^ T h e N . T . U . ' s f o r t h e CECE-HWP a r e r e d u c e d by t h i s f a c t o r
c o n c e n t r a t i o n i n t h e c o l u m n l i q u i d p r o d u c t n e e d s o n l y be
1 0 0 0 ppm i f a
is 6 instead of
unity.
on1y
REDUCTION
Calculated
TOTAL
column
12.3*
^33
Nil
Separation
2
0.43
2
H /H 0-HWP
Electrolytic
ppm
OF
II
Requirements
f o r the
H2/H2O-HWP
Bithermal
Catalyst
7 MP a
1000
in
EFFECTS
Pressure
for
Recovery
N.T.U.
%
L/G
Ρ aramete r
Reduction
SYNERGISTIC
Table
Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch008
Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch008
8.
HAMMERLI ET AL.
Combined
Electrolysis
Catalytic
Exchange
121
catalyst
f o r t h e c o l d column i n the b i t h e r m a l
process
is considered here.
A d d i t i o n a l c a t a l y s t would of
c o u r s e be r e q u i r e d f o r t h e h o t c o l u m n i n t h e b i t h e r m a l
p r o c e s s b u t n o t i n t h e CECE-HWP.
On t h e o t h e r h a n d ,
e l e c t r o l y s i s c e l l s a r e r e q u i r e d i n t h e CECE-HWP.
The b i t h e r m a l p r o c e s s must o p e r a t e a t h i g h
p r e s s u r e s t o a v o i d an e x c e s s i v e l y l a r g e h o t c o l u m n a s
a r e s u l t o f t h e vapour l o a d a t t h e hot column t e m p e r a ­
ture (^200°C).
On t h e o t h e r h a n d , t h e c a t a l y s t
column
i n t h e CECE-HWP c o u l d o p e r a t e a t a b o u t a t m o s p h e r i c
p r e s s u r e , a l t h o u g h 1 t o 2 M P a may b e p r e f e r a b l e i n t h e
1st stage.
S e v e r a l p r e s s u r e e f f e c t s combine t o produce
t h e a p p r o x i m a t e f a c t o r shown i n T a b l e
II.
A s s u m i n g f o r t h e m o m e n t t h a t ot£ i s u n i t y , a v a l u e
w h i c h w o u l d be a p p r o a c h e d i n a h i g h
temperature
(~1000°C) e l e c t r o l y s i s c e l l , t h e c a t a l y s t
requirements
f o r t h e C E C E - H W P w o u l d be a b o u t 1 5 t i m e s l e s s t h a n
that
f o r only t h e c o l d column of the b i t h e r m a l H /H 0-HWP.
I f aE i s 6 , t h e o v e r a l l
catalyst reduction factor is
approximately 24.
In the above a n a l y s i s , t h e 2nd and
3 r d s t a g e s have been i g n o r e d .
This i s j u s t i f i a b l e
s i n c e t h e s e s t a g e s w o u l d t o g e t h e r r e q u i r e o n l y 10%
a d d i t i o n a l c a t a l y s t o r l e s s d e p e n d i n g on t h e d e u t e r i u m
c o n c e n t r a t i o n o f t h e 1 s t s t a g e p r o d u c t (8;).
2
Applications
o f t h e CECE-HWP
2
and CECE-TRP
T h e d e v e l o p m e n t o f b o t h t h e CECE-HWP a n d t h e
CECE-TRP i s b a s e d m a i n l y on a b o u t 7 y e a r s o f l a b o r a t o r y
r e s e a r c h (]_).
The r e s u l t s f r o m t h i s w o r k h a v e l e d t o
commitments o f s m a l l p i l o t p l a n t s f o r both p r o c e s s e s .
T h e CECE-HWP p i l o t p l a n t w i l l b e l o c a t e d a t C h a l k
River
Nuclear Laboratories
(CRNL).
The CECE-TRP p i l o t
plant
i s a c o o p e r a t i v e p r o j e c t b e t w e e n CRNL a n d t h e E n e r g y
Research
and D e v e l o p m e n t A d m i n i s t r a t i o n (ERDA) o f t h e
U.S.
G o v e r n m e n t , and i s l o c a t e d at t h e Mound L a b o r a t o r y ,
Miamisburg, Ohio.
P r e l i m i n a r y r e s u l t s f r o m t h e Mound
p i l o t p l a n t have been r e p o r t e d by Rogers e t a l . ( Π ) .
D e s p i t e t h e s u c c e s s a c h i e v e d i n t h e c a t a l ys t H J e v e l o p m e n t p r o g r a m , we h a v e n o t y e t p r e p a r e d a p l a t i n u m carbon-TefIon
catalyst
(J_) w i t h s u f f i c i e n t a c t i v i t y t o
make a f u l l s c a l e b i t h e r m a l H - H 0 h e a v y w a t e r p l a n t
economically feasible.
With our present catalysts the
amount r e q u i r e d w o u l d be t o o l a r g e .
Furthermore, a
s a t i s f a c t o r y h y d r o p h o b i c c a t a l y s t f o r the h o t column
has n o t been d e v e l o p e d .
Our present c a t a l y s t s are
s u f f i c i e n t l y a c t i v e , however, to perform e f f e c t i v e l y i n
t h e CECE-HWP w h e r e t h e c a t a l y s t r e q u i r e m e n t s a r e r e l a ­
t i v e l y s m a l l , o n l y a b o u t 4% o f t h a t r e q u i r e d i n t h e
c o l d column o f a b i t h e r m a l p l a n t .
Several small
scale
2
2
In Separation of Hydrogen Isotopes; Rae, H.;
ACS Symposium Series; American Chemical Society: Washington, DC, 1978.
122
SEPARATION OF HYDROGEN ISOTOPES
a p p l i c a t i o n s o f t h e CECE-HWP a n d t h e C E C E - T R P
that
c o u l d now b e u s e d i n t h e n u c l e a r p o w e r i n d u s t r y
are
outlined
below.
(1)
U p g r a d i n g o f D 0 - T h e h e a v y w a t e r u s e d i n CANDU
reactors
as m o d e r a t o r a n d c o o l a n t t h a t h a s b e c o m e d o w n g r a d e d w i t h l i g h t w a t e r c a n be r e - e n r i c h e d t o
reactor
g r a d e , 9 9 . 8 % D 0 , by t h e C E C E - H W P .
(2)
F i n a l E n r i c h m e n t S t a g e f o r GS P l a n t s
- T h e GS
system
produces 10-20% D 0 which i s c u r r e n t l y e n r i c h e d
to
r e a c t o r g r a d e by w a t e r d i s t i l l a t i o n .
T h i s c o u l d be
done more e f f e c t i v e l y
by t h e
CECE-HWP.
(3)
Recovery
o f T r i t i u m f r o m t h e D 0 i n CANDU R e a c t o r s T r i t i u m b u i l d s up i n t h e h e a v y w a t e r d u r i n g t h e
operat i o n o f CANDU r e a c t o r s .
The r e c o v e r y
of this
tritium
w o u l d r e d u c e t h e r a d i a t i o n f i e l d i n some a r e a s
of
the
p o w e r s t a t i o n and i t s
r e m o v a l may b e c o m e an e n v i r o n mental n e c e s s i t y .
T r i t i u m may a l s o b e c o m e a s a l e a b l e
commodity f o r the d e v e l o p m e n t o f e x p e r i m e n t a l
nuclear
fusion
reactors.
(4)
T r i t i u m Recovery
f r o m L i g h t W a t e r - T r i t i u m c a n be
recovered from l i g h t water wastes
f r o m ERDA
contractors
in the U.S.A.
As a l r e a d y n o t e d , p i l o t s t u d i e s o f
this
a p p l i c a t i o n a r e b e i n g made a t t h e M o u n d L a b o r a t o r y
(11).
This a p p l i c a t i o n w i l l
a l s o be r e q u i r e d i n n u c l e a r
fuel
reprocessing plants since t r i t i u m is a product of
the
fission
process.
The d i s a d v a n t a g e o f t h e h i g h e n e r g y
requirement
for
t h e f u l l s c a l e p r o d u c t i o n o f h e a v y w a t e r by t h e
CECEHWP d o e s n o t a p p l y t o t h e s e a p p l i c a t i o n s , p r i m a r i l y
b e c a u s e o f t h e much s m a l l e r l i q u i d f l o w s .
F o r t h e CECE-HWP a p p l i c a t i o n s 1 a n d 2 , t h e
overall
separation
required is considerably less
(enrichment
f a c t o r of ^10)
than t h a t r e q u i r e d to p r o d u c e pure
D 0
from natural water
(enrichment
f a c t o r 'WOOO ) .
Thus
the
e l e c t r o l y s i s energy
r e q u i r e d i s r e d u c e d by a f a c t o r
of
a b o u t 7 0 0 f r o m 50 MWh t o 70 kWh p e r k i l o g r a m o f
D 0.
F o r the CECE-TRP a p p l i c a t i o n s 3 and 4, t h e
water
f l o w s w i l l be a t l e a s t a t h o u s a n d t i m e s s m a l l e r
than
f o r a f u l l s c a l e heavy w a t e r p l a n t .
Furthermore,
the
energy
requirements
f o r the CECE-TRP are s m a l l e r
than
f o r other processes c u r r e n t l y being c o n s i d e r e d , such
as
w a t e r and h y d r o g e n d i s t i l l a t i o n , because the
separation
factors
are
larger.
L a r g e r s c a l e a p p l i c a t i o n s o f t h e CECE-HWP, i f
pilot
plant studies warrant
these, would i n c l u d e :
(1)
Small
D 0 Plant
- A s m a l l ('WO
Mg/a)
complete
D 0
p l a n t w o u l d be e c o n o m i c a l l y f e a s i b l e w h e r e a m a r k e t
e x i s t s f o r the e l e c t r o l y t i c h y d r o g e n and the heavy
water.
(2) S i m u l t a n e o u s
D 0 and P e a k P o w e r P r o d u c t i o n - The
CECE-HWP c o u l d be c o u p l e d w i t h e i t h e r H / 0
gas
turbine2
2
2
Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch008
2
2
2
2
2
2
2
2
In Separation of Hydrogen Isotopes; Rae, H.;
ACS Symposium Series; American Chemical Society: Washington, DC, 1978.
8.
HAMMERLI ET AL.
Combined
Electrolysis
Catalytic
Exchange
123
generators
or fuel
c e l l s through appropriate H
and 0
s t o r a g e f a c i l i t i e s to produce D 0 ( d u r i n g the
off-peak
periods)
and peak p o w e r .
This load l e v e l l i n g
scheme
(8.) i s b e i n g c o n s i d e r e d b y O n t a r i o H y d r o ,
Canada's
l a r g e s t e l e c t r i c u t i l i t y , as o n e a l t e r n a t i v e
for
their
future load-level l i n g requi rements.
(3) E l e c t r o l y t i c H
as N a t u r a l G a s S u p p l e m e n t
or
C h e m i c a l - I t m i g h t be f e a s i b l e t o u s e e x c e s s
hydro
e l e c t r i c power, w h e r e v e r i t e x i s t s , to produce
hydrogen
and D 0 u s i n g t h e CECE-HWP.
T h e h y d r o g e n c o u l d be u s e d
as a n a t u r a l
gas s u p p l e m e n t i n a p i p e l i n e and a f e a s i b i l i t y s t u d y o f a 1 0 0 MW p r o t o t y p e p l a n t i s
underway.
A l t e r n a t i v e l y t h e h y d r o g e n c o u l d b e u s e d as a c h e m i c a l ,
e . g . hydrogénation o f bitumen or chemical
intermediate,
e . g . m e t h a n o l p r o d u c t i o n w h i c h c o u l d s e r v e as a g a s o line
supplement.
2
2
2
2
Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch008
2
A l l of the above p o t e n t i a l
a p p l i c a t i o n s must a w a i t
p i l o t p l a n t s t u d i e s b e f o r e p l a n t s c a n be c o m m i t t e d .
Furthermore, the r e l a t i v e
economics of
electrolytic
hydrogen versus hydrogen produced from f o s s i l
fuels
w i l l p l a y a m a j o r r o l e i n any d e c i s i o n t o p r o c e e d
in
each of these a p p l i c a t i o n s .
The c u r r e n t v a l u e o f
the
D 0 by-product w i l l
a l s o be i m p o r t a n t a n d t o a l e s s e r
e x t e n t , the v a l u e and m a r k e t a b i l i t y o f the
co-liberated
oxygen.
I t n e e d h a r d l y be s a i d t h a t s u c c e s s f u l
development of e f f i c i e n t , r e l a t i v e l y
low c o s t
electrol y z e r s i s a l s o a key r e q u i r e m e n t f o r these
larger
applications.
Moreover,
c u r r e n t emphasis to
conserve
a l l our non-renewable
resources w i l l increase
the
s t i m u l u s t o d e v e l o p t h e CECE p r o c e s s o v e r t h e
next
decade or s o .
When f o s s i l
r e s o u r c e s become s u f f i c i e n t l y
s c a r c e , a n d / o r e x p e n s i v e , t h e move t o w a r d s
a hybrid
h y d r o g e n - e l e c t r i c e c o n o m y w i l l be a c c e l e r a t e d
and
c o n s e q u e n t l y l a r g e r amounts o f b y - p r o d u c t heavy w a t e r
c o u l d be p r o d u c e d b y t h e C E C E - H W P .
2
Summary
The CECE p r o c e s s i s a v e r y e f f i c i e n t m e t h o d f o r
the s e p a r a t i o n of hydrogen i s o t o p e s .
The
catalytic
exchange columns where most o f the s e p a r a t o r y work
is
a c c o m p l i s h e d w o u l d be v e r y s m a l l c o m p a r e d t o t h e e x change column used i n e i t h e r a b i t h e r m a l H / H 0 p r o c e s s
o r t h e p r e s e n t b i t h e r m a l H S / H 0 (GS)
process.
Laborat o r y s t u d i e s have d e m o n s t r a t e d the s a l i e n t f e a t u r e s
of
t h e CECE p r o c e s s a n d i f p i l o t p l a n t s t u d i e s a t CRNL
and
Mound L a b o r a t o r y
are s u c c e s s f u l , the process w i l l
und o u b t e d l y be u s e d i n t h e n u c l e a r p o w e r i n d u s t r y i n a
number of the s m a l l s c a l e a p p l i c a t i o n s d i s c u s s e d i n
this paper.
As l a r g e h y d r o g e n g a s s t r e a m s
become
2
2
2
2
In Separation of Hydrogen Isotopes; Rae, H.;
ACS Symposium Series; American Chemical Society: Washington, DC, 1978.
124
SEPARATION O F HYDROGEN
ISOTOPES
a v a i l a b l e t h e p r o c e s s c o u l d a l s o be u s e d f o r t h e f u l l
s c a l e p r o d u c t i o n o f l a r g e q u a n t i t i e s , 70-100 M g / a , o f
heavy w a t e r .
Acknowledgements
Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch008
We t h a n k A . S . D e n o v a n f o r t e c h n i c a l a s s i s t a n c e i n
operatinq the laboratory demonstration unit of the
CECE p r o c e s s a n d f o r p e r f o r m i n g t h e d e u t e r i u m a n a l y s e s
i n gas and w a t e r s a m p l e s .
We a l s o t h a n k W.M. T h u r s t o n
and M.W.D. James f o r c o n s t r u c t i n g and m a i n t a i n i n g t h e
mass- and i n f r a r e d - s p e c t r o m e t e r s y s t e m s used f o r the
d e u t e r i urn an a l y s e s .
Abstract
Hydrogen i s o t o p e s can be s e p a r a t e d
efficiently
by a process which combines an
electrolysis
c e l l with a
trickle
bed column packed with a hydrophobic p l a t i n u m
catalyst.
The column e f f e c t s i s o t o p i c exchange between
c o u n t e r - c u r r e n t streams o f
electrolytic
hydrogen and
liquid
water w h i l e the
electrolysis
c e l l contributes
to i s o t o p e s e p a r a t i o n by v i r t u e of the k i n e t i c i s o t o p e
e f f e c t i n h e r e n t i n the hydrogen e v o l u t i o n r e a c t i o n .
The main f e a t u r e s of the CECE process f o r heavy water
p r o d u c t i o n are p r e s e n t e d as w e l l as a d i s c u s s i o n of
the i n h e r e n t p o s i t i v e s y n e r g i s t i c
effects,
and o t h e r
advantages and disadvantages of the p r o c e s s .
S e v e r a l p o t e n t i a l a p p l i c a t i o n s o f the process in
the n u c l e a r power i n d u s t r y are d i s c u s s e d .
Literature
1.
2.
3.
4.
5.
Cited
B u t l e r , J.P., R o l s t o n , J.H. and S t e v e n s , W.H.,
Proceedings of the Symposium on " S e p a r a t i o n of
Hydrogen I s o t o p e s " , Montreal 1977, p. 93 ,
American Chemical S o c i e t y , Washington, 1977.
Hammerli, M., M i s l a n , J.P. and Olmstead, W.J.,
J. E l e c t r o c h e m . Soc., ( 1 9 7 0 ) , 117, 751 (and
references t h e r e i n ) .
B a r l o w , E . A , Atomic Energy of Canada r e p o r t
no. CRE-374, March 8, 1948; D e c l a s s i f i e d and r e i s s u e d as r e p o r t no. A E C L - 1 6 3 , February 22, 1955.
B e c k e r , H . W . , Bier, K . , Hubener, R . P . and
K e s s e l e r , R.W., " P r o c e e d i n g s of 2nd I n t e r n a t i o n a l
Conference on P e a c e f u l Uses of Atomic E n e r g y " ,
( 1 9 5 9 ) , 4, 543, U n i t e d N a t i o n s .
S t e v e n s , W.H., U . S . Patent no. 3 , 8 8 8 , 9 7 4 , June 10,
1975.
In Separation of Hydrogen Isotopes; Rae, H.;
ACS Symposium Series; American Chemical Society: Washington, DC, 1978.
8.
6.
7.
8.
9.
10.
Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch008
11.
HAMMERLI ET AL.
Combined Electrolysis Catalytic Exchange
125
Rolston,
J.H.,
den H a r t o g , J. and B u t l e r ,
J.P.,
J. Phys. Chem., (1976), 80,
1064.
Winter,
E.E.,
p r i v a t e communications.
Hammerli, Μ., S t e v e n s , W.H., B r a d l e y , W.J. and
Butler,
J.P.,
Atomic Energy of Canada r e p o r t no.
AECL-5512, A p r i l
1976.
Rae, H . K . , Proceedings of the Symposium on
" S e p a r a t i o n o f Hydrogen I s o t o p e s " , Montreal
1977,
p. 1 , American Chemical S o c i e t y , Washington,
1977.
Brown, R . M . , R o b e r t s o n , E . and T h u r s t o n , W.M.,
Atomic Energy of Canada L t d . r e p o r t no. AECL-3800,
January 1971.
Rogers, M.L., Lamberger,
P.H.,
Ellis,
R . E . and
Mills,
T.K.,
Proceedings of the Symposium on
" S e p a r a t i o n of Hydrogen I s o t o p e s " , Montreal
1977,
p. 171, American Chemical S o c i e t y , Washington,
1977.
RECEIVED October 18, 1977
In Separation of Hydrogen Isotopes; Rae, H.;
ACS Symposium Series; American Chemical Society: Washington, DC, 1978.
9
Heavy Water Distillation
G. M. KEYSER, D. B. McCONNELL, N. ANYAS-WEISS, and P. KIRKBY
Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch009
Ontario Hydro Research Div., 800 Kipling Ave., Toronto, Canada
The m o t i v a t i o n f o r t h e c u r r e n t heavy water r e s e a r c h program a t O n t a r i o Hydro comes from o u r growing
dependence on CANDU-based n u c l e a r power p l a n t s .
About
15% o f t h e c a p i t a l c o s t o f t h e s e p l a n t s i s f o r t h e
heavy water moderator and c o o l a n t . We hope t o be a b l e
to p r o v i d e e c o n o m i c a l l y and t e c h n i c a l l y v i a b l e o p t i o n s
f o r heavy water p r o d u c t i o n i n t h e 1990 s by d e v e l o p i n g
a l t e r n a t i v e p r o d u c t i o n methods t o an i n d u s t r i a l l y usef u l degree by t h a t t i m e .
The Heavy Water Group a t Hydro Research D i v i s i o n
has a s s i s t e d i n e s t a b l i s h i n g t h e s c i e n t i f i c
feasibili t y o f two heavy water p r o d u c t i o n methods : l a s e r i n d u c e d d i s s o c i a t i o n o f formaldehyde, and low-temperat u r e water d i s t i l l a t i o n u s i n g waste h e a t and hopes t o
c o n t i n u e development o f b o t h t h e s e methods.
In t h i s t a l k , I w i l l d e s c r i b e t h e experiments
c a r r i e d o u t t o demonstrate t h e f e a s i b i l i t y o f lowtemperature d i s t i l l a t i o n w i t h a p a r a l l e l - s h e e t p a c k i n g
d e v e l o p e d a t t h e Research D i v i s i o n .
The c o s t e n v i r o n ment o f heavy water d i s t i l l a t i o n w i l l a l s o be d i s cussed.
1
Distillation
Systems
- Physical
To r e f r e s h your memory, I w i l l show i n F i g u r e 1 (a)
a s c h e m a t i c r e p r e s e n t a t i o n o f a d i s t i l l a t i o n system.
The main f e a t u r e s o f t h e system a r e upward moving v a pour streams and f a l l i n g l i q u i d f i l m s i n c l o s e p r o x i m i t y , m a i n t a i n e d by a temperature g r a d i e n t between t h e
h e a t s o u r c e ( b o i l e r ) a t t h e bottom and t h e heat s i n k
(condenser) a t t h e t o p o f t h e system. A c o n v e n i e n t
way o f b r i n g i n g t h e c o u n t e r - f l o w i n g phases c l o s e t o
each o t h e r i s t o p r o v i d e v e r t i c a l s h e e t s o f m a t e r i a l
o v e r which t h e l i q u i d f l o w s as a t h i n f i l m , w h i l e t h e
vapour r i s e s i n narrow c h a n n e l s between t h e s h e e t s , as
©
0-8412-0420-9/78/47-068-126$05.00/0
In Separation of Hydrogen Isotopes; Rae, H.;
ACS Symposium Series; American Chemical Society: Washington, DC, 1978.
9.
KEYSER ET AL.
Heavy
Water
127
Distillation
Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch009
shown i n F i g u r e 1 ( b ) .
What makes a heavy water system " d i f f e r e n t " i s
t h a t the component t o be s e p a r a t e d o u t , HDO, i s p r e s e n t
i n v e r y low c o n c e n t r a t i o n , about one p a r t i n 3500, i n
n a t u r a l water f e d t o the system, so t h a t enormous v o l umes o f vapour must be p a s s e d t h r o u g h the s e p a r a t i n g
system t o e x t r a c t s u f f i c i e n t HDO.
C o s t Components. From our e s t i m a t e (and those o f
many p r i o r workers) o f the c o s t o f heavy water from a
d i s t i l l a t i o n p l a n t , i f we were t o pay f o r f o s s i l f u e l s ,
or i f we used the heat from a n u c l e a r r e a c t o r which
would o t h e r w i s e be g e n e r a t i n g e l e c t r i c i t y , the c o s t o f
t h i s energy would i t s e l f amount t o w e l l o v e r the c u r r e n t c o s t o f heavy water.
S i n c e t h e r m a l g e n e r a t i n g s t a t i o n s are o n l y about
40% e f f i c i e n t i n c o n v e r t i n g the t h e r m a l energy r e l e a s e d from f u e l i n t o e l e c t r i c i t y , ~ 6 0 % o f i t i s a v a i l a b l e as low grade heat (water a t about 26°C) c o s t i n g
o n l y the p r i c e o f t r a n s p o r t i n g i t t o the p o i n t o f use.
Our o b j e c t i v e , t h e n , has been t o u t i l i z e t h i s
waste h e a t , by o p e r a t i n g between about 26°C and the
l a k e water temperature which i s t y p i c a l l y 20° lower.
I f we can u t i l i z e waste h e a t , then the r e m a i n i n g h i g h c o s t components a r e the m a t e r i a l , o r p a c k i n g , used t o
b r i n g the l i q u i d and vapour i n t o c l o s e p r o x i m i t y , the
s t r u c t u r e s (vacuum b u i l d i n g s ) used t o house the packi n g , and the h e a t exchangers and b o i l e r s f o r m a i n t a i n i n g the f l o w o f h e a t t h r o u g h the system.
The r e l a t i v e
magnitudes o f t h e s e components, based on D 0 a t $200/kg
i s shown i n F i g u r e 2.
The g r e a t e s t c o s t component, by
f a r , i s the p a c k i n g f o r the columns.
2
400 Ton P l a n t C o n c e p t i o n
F i g u r e 3 shows our p r e s e n t c o n c e p t i o n o f a lowtemperature d i s t i l l a t i o n p l a n t c a p a b l e o f p r o d u c i n g 400
tons o f heavy water per y e a r . I t i s d i v i d e d i n t o s e v e r a l hundred u n i t s housed i n s e p a r a t e towers, each o p e r a t i n g i n d e p e n d e n t l y to d i s t i l l the heavy water out o f
c l e a n l a k e water and b r i n g i t t o a c o n c e n t r a t i o n o f about 1%.
The subsequent c o n c e n t r a t i o n s t e p t o 99.8%
f o r r e a c t o r use c o s t s o n l y 15% t o 20% t h a t o f p e r f o r m i n g the f i r s t s t e p , and i s c a r r i e d o u t i n a s e p a r a t e
d i s t i l l a t i o n "finishing" unit.
Experimental Packing
The major gap i n the p l a n t c o n c e p t was the p a c k i n g .
Heavy Water d i s t i l l a t i o n p a c k i n g s f o r the low-tempera-
In Separation of Hydrogen Isotopes; Rae, H.;
ACS Symposium Series; American Chemical Society: Washington, DC, 1978.
SEPARATION OF HYDROGEN ISOTOPES
H E A T SINK
AT T E M P E R A T U R E T
2
DIFFUSIVE
DEUTERIUM TRANSPORT
FROM VAPOR T O
LIQUID
Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch009
FALLING
LIQUID
RISING
VAPOUR
HEAT SOURCE
A T T E M P E R A T U R E T,
(a)
(b)
Figure 1.
Elements of a distilhtion system
COMPONENT
WASTE
RELATIVE COST
$ / k g D2O
6.5
HEAT
COOLING
20
V A C U U M BUILDINGS
AND PLUMBING
5.5
CONDENSERS
AND BOILERS
14
PACKING AND SUPPORTING
STRUCTURES
OPERATION AND
MISCELLANEOUS*
96
58
200
•WATER CLEANUP,
COMMISSIONING
Figure 2.
INSTRUMENTATION,
CONSTRUCTION LABOR,
Rehtive component costs in heavy water distilhtion
In Separation of Hydrogen Isotopes; Rae, H.;
ACS Symposium Series; American Chemical Society: Washington, DC, 1978.
9.
KEYSER ET AL.
Heavy
Water
129
Distillation
Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch009
GENERATING STATION
(3000 MW)
COOLING W A T E R
FROM L A K E
35 - 5 0 ° F
150 ppm
0O
125 rn /s
REJECT HEAT
TO LAKE
* ~ 55 - 7 0 ° F
149 ppm
X
9
3
60°F
90°F
HEATING
OUT
COOLING
HEATING
IN
IN
COOLING
OUT
DISTILLATION PLANT
S E V E R A L HUNDRED TOWERS
W O R K I N G V O L U M E - 3 0 000 m
F O R 400 T O N N E S / Y E A R
3
\\%
D 0
2
τ
FINISHER
Τ
PRODUCT
(45 Kg/h )
REACTOR GRADE
Figure 3.
0 0
£
Concept for a heavy water distillation plant using waste heat from a
generating station. 400 tonne/year D 0 plant.
2
In Separation of Hydrogen Isotopes; Rae, H.;
ACS Symposium Series; American Chemical Society: Washington, DC, 1978.
SEPARATION OF HYDROGEN ISOTOPES
Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch009
130
t u r e and p r e s s u r e regime had not been developed com­
mercially.
A t h e o r y o f the p r o c e s s p r e d i c t e d t h a t a
u s e f u l degree o f s e p a r a t i v e power c o u l d be a c h i e v e d
u s i n g simple p a r a l l e l s h e e t s c a r r y i n g downward-moving
water f i l m s , w i t h upward-moving vapour between them.
The p a c k i n g developed a t the Research D i v i s i o n i s
based on t h i s concept, and i s shown s c h e m a t i c a l l y i n
F i g u r e 4.
A s e r i e s of tubes c a r r i e s condensed water
t o the tops of the s h e e t s t o f l o w downward over t h e i r
s u r f a c e s , w h i l e vapour moves up between them.
The
s h e e t s used t o date have been n y l o n f a b r i c under t e n ­
s i o n , w i t h a s u r f a c e treatment t o improve the u n i f o r m ­
i t y o f the water f i l m .
The performance of t h i s module
i s expected t o depend on the two mass and d e u t e r i u m
f l o w parameters, the v e l o c i t y , and the d i f f u s i o n time
i n each phase.
P a c k i n g Performance -
Experimental
The b a s i c mechanism which causes i s o t o p i c s e p a r a ­
t i o n i n d i s t i l l a t i o n systems i s the d i f f e r e n c e i n v a ­
pour p r e s s u r e of H 0 and HDO, a t the same temperature.
In d i s t i l l a t i o n , the r a t i o o f the e q u i l i b r i u m vapour
p r e s s u r e s of H 0 and HDO i s c a l l e d a, as shown i n
F i g u r e 5.
2
2
P
a(T) =
H- 0
,
HDO
1
t y p i c a l l y , α i s around 1.08 i n t h i s
temperature r e g i o n , r i s i n g a t lower
temperatures towards 1.10.
We can gauge the performance by measuring the i s o ­
t o p i c enrichment o f the water f l o w i n g out the bottom
Bottonw the d e p l e t i o n o f the vapour l e a v i n g at. the
top Or/op' t a k i n g the n a t u r a l l o g a r i t h m o f t h e i r r a t i o
and d i v i d i n g by the n a t u r a l l o g a r i t h m of the average
α v a l u e f o r the system; t h i s i s a measure of the num­
ber o f s t a g e s , each c a r r y i n g out a s e p a r a t i o n o f a, i n
the column. The number o f such s t a g e s per metre of
column h e i g h t i s a performance parameter f o r the pack­
ing :
~ In
In [I ^Bottomjl / H l n a , where Η i s
Ν (number of stages/m) «
c
C
\ T"Top
o p // the column h e i g h t .
C u r r e n t e x p e r i m e n t a l v a l u e s o f Ν run from 2.5 t o over
3 s t a g e s per metre.
U s i n g t h i s parameter, and the c o r r e s p o n d i n g mass
flow r a t e , we can e s t i m a t e the t o t a l s u r f a c e a r e a o f
the s h e e t s r e q u i r e d t o produce 400 tons of D 0 per
year.
The f i g u r e a l s o shows the " e a r n i n g power" o f
our e x p e r i m e n t a l p a c k i n g and the t h e o r e t i c a l l i m i t t o
i t as a f u n c t i o n o f the F-number ( r e l a t e d t o the mass
2
In Separation of Hydrogen Isotopes; Rae, H.;
ACS Symposium Series; American Chemical Society: Washington, DC, 1978.
Heavy
Water
Distillation
Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch009
KEYSER ET AL.
Figure 4.
Parallel plate packing module (without glass
envelope)
In Separation of Hydrogen Isotopes; Rae, H.;
ACS Symposium Series; American Chemical Society: Washington, DC, 1978.
132
Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch009
SEPARATION O F HYDROGEN ISOTOPES
Figure 5.
Earning power of two experimental packings
In Separation of Hydrogen Isotopes; Rae, H.;
ACS Symposium Series; American Chemical Society: Washington, DC, 1978.
9.
KEYSER ET AL.
Heavy
Water
Distillation
133
flow) i n t h e system.
Each square metre o f p a c k i n g can
be c o n s i d e r e d t o produce about 0 . 2 k i l o g r a m s ( - 4 0 d o l l a r s worth) o f D 0 p e r y e a r . The upper c u r v e i s t h e
p r e d i c t e d maximum e a r n i n g power f o r t h i s type o f packi n g system. As you can see, o u r r e s u l t s w h i l e showing
t h a t t h e system works, c a n s t i l l be c o n s i d e r a b l y improved.
The t r i a n g l e s show more r e c e n t work w i t h a
d i f f e r e n t m a t e r i a l ; as o u r u n d e r s t a n d i n g o f t h e d e s i r a b l e and u n d e s i r a b l e f e a t u r e s o f t h e s e m a t e r i a l s grows,
we b e l i e v e we c a n come s t i l l c l o s e r t o t h e t h e o r e t i cal limit.
T h i s would b r i n g our heavy water c o s t e s t i m a t e down towards $2 0 0 / k g .
F u r t h e r work on a l a r g e r
s c a l e would a l s o be r e q u i r e d t o study how w e l l t h e
p a c k i n g u n i t c a n be s c a l e d up t o an i n d u s t r i a l l y useful
size.
Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch009
2
Summary
I c a n summarize what we have l e a r n e d as f o l l o w s :
r e c e n t work a t t h e R e s e a r c h D i v i s i o n has demonstrated
the f e a s i b i l i t y o f p e r f o r m i n g heavy water s e p a r a t i o n
by d i s t i l l a t i o n a t low t e m p e r a t u r e , u s i n g a newly dev e l o p e d p a c k i n g system. We b e l i e v e t h a t t h e c u r r e n t
performance can be c o n s i d e r a b l y improved, and t h a t t h e
c o s t o f heavy water from d i s t i l l a t i o n can be made comp a r a b l e t o t h a t from t h e c u r r e n t p r o d u c t i o n method.
T e s t s on a l a r g e r s c a l e w i l l be r e q u i r e d t o demons t r a t e t h a t t h i s performance can be s u c c e s s f u l l y
s c a l e d up t o an i n d u s t r i a l l y u s e f u l d e g r e e .
Abstract
A review of
distillation
as a heavy water
separation method has
identified
a r e a s o f h i g h c o s t : energy
and p a c k i n g
material.
A t t e m p e r a t u r e s around 2 5 ° C ,
l a r g e amounts o f energy are a v a i l a b l e as waste heat
from t h e r m a l g e n e r a t i n g s t a t i o n s .
I f a s u i t a b l e low- c o s t p a c k i n g can be d e v e l o p e d f o r use i n
this
temperature r e g i o n ,
distillation
c o u l d become e c o n o m i c a l l y
competitive.
Results of
theoretical
p a c k i n g work, and e x p e r i ments on a p r o t o t y p e p a c k i n g f o r heavy water p l a n t s
are d i s c u s s e d .
RECEIVED August 30, 1977
In Separation of Hydrogen Isotopes; Rae, H.;
ACS Symposium Series; American Chemical Society: Washington, DC, 1978.
10
Deuterium Isotope Separation via Vibrationally
Enhanced Deuterium Halide—Olefin Addition Reactions
J. B . M A R L I N G and J. R. S I M P S O N
University of California, Lawrence Livermore Laboratory, Livermore, C A
Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch010
M. M . M I L L E R
Francis Bitter National Magnet Laboratory, Massachusetts Institute of Technology,
Cambridge, M A
Over t h e past few y e a r s , t h e r e has been much excitement i n
the s c i e n t i f i c community about the prospects f o r e f f i c i e n t sep­
a r a t i o n o f i s o t o p e s , p a r t i c u l a r l y uranium-235 and deuterium,
using l a s e r techniques. Of t h e v a r i o u s l a s e r methods which have
been suggested, those which i n v o l v e t h e use o f IR photons t o
enhance t h e r a t e o f i s o t o p i c a l l y s e l e c t i v e photochemical r e a c t i o n s
have r e c e i v e d much a t t e n t i o n , and t h i s paper d i s c u s s e s one
e x a m p l e — v i b r a t i o n a l l y enhanced gas phase deuterium h a l i d e a d d i ­
t i o n i n t o o l e f i n s . The i n c e n t i v e f o r u s i n g IR photons i s c l e a r ;
t o quote from a recent review a r t i c l e (l_) : "The a t t r a c t i v e
f e a t u r e o f v i b r a t i o n a l photochemistry f o r i s o t o p e s e p a r a t i o n i s
the promise o f u s i n g low energy IR photons from an e f f i c i e n t
molecular l a s e r t o get a good y i e l d o f product. Since 1 mole of
photons at 3000 cm" i s 1 0 kwh and some IR l a s e r s are about 10
per cent e f f i c i e n t , p r o c e s s i n g o f b u l k chemicals might even be
economic." Thus, a deuterium s e p a r a t i o n process w i t h 1% quantum
e f f i c i e n c y t h a t u t i l i z e d 2000 cm" photons from a 10 per cent
e f f i c i e n t CO l a s e r would r e q u i r e a l a s e r process energy o f 6 . 6
kwh/mole D, e q u i v a l e n t t o a l a s e r o p e r a t i n g cost o f 13^/mole
D Ξ $13/kg D 0, assuming e l e c t r i c i t y at 20 m i l l s per kwh. The
s p e c i f i c l a s e r c a p i t a l investment, assuming a p r i c e o f $20 per
o p t i c a l watt o f 10 per cent e f f i c i e n t l a s e r power, would be
roughly $152/kg D 0/yr., e q u i v a l e n t t o approximately $30/kg D 0
at a c a p i t a l charge r a t e o f 20 per cent/year. To put these
numbers i n p e r s p e c t i v e , we note t h a t t h e current Canadian p r i c e
f o r heavy water made by the H S/H 0 exchange (G-S) process i s
about $150/kilogram, o f which 60 per cent i s due t o c a p i t a l
charges, 25 per cent due t o energy, and 15 per cent f o r operations
and maintenance (2). Since heavy water i s a much cheaper commod­
i t y than U-235, t h i s approximate c a l c u l a t i o n i l l u s t r a t e s t h e
challenge i n developing a l a s e r deuterium s e p a r a t i o n process which
i s economically c o m p e t i t i v e w i t h the e x i s t i n g technology ( 3_).
In t h i s paper we i l l u s t r a t e t h e problems and prospects
i n v o l v e d by examining i n some d e t a i l a s p e c i f i c deuterium
separation process based on deuterium h a l i d e - o l e f i n a d d i t i o n
1
- 2
1
2
2
2
2
©
2
0-8412-0420-9/78/47-068-134$05.00/0
In Separation of Hydrogen Isotopes; Rae, H.;
ACS Symposium Series; American Chemical Society: Washington, DC, 1978.
10.
MARLING ET AL.
Deuterium
Isotope
Separation
135
r e a c t i o n s . I n S e c t i o n I I we describe t h e b a s i c r e a c t i o n mechan­
ism, w i t h p a r t i c u l a r a t t e n t i o n t o the problem o f e x c i t i n g t h e
deuterium h a l i d e w i t h e x i s t i n g l a s e r s . S e c t i o n I I I i s devoted
t o t h e c r u c i a l question o f the expected e f f e c t i v e n e s s o f v i b r a ­
t i o n a l e x c i t a t i o n f o r t h i s c l a s s o f r e a c t i o n s . I n S e c t i o n IV, we
focus on t h e "back-end" o f t h i s separation scheme i n the context
of a p o s s i b l e flow-sheet f o r t h e o v e r a l l process. We conclude
w i t h a summary o f our r e s u l t s and the i m p l i c a t i o n s t h e r e o f i n
S e c t i o n V.
Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch010
II.
Hydrogen H a l i d e - O l e f i n A d d i t i o n Reactions
An i d e a l i s o t o p i c a l l y s e l e c t i v e l a s e r photochemical process
would use a s i n g l e IR photon t o e x c i t e t h e fundamental mode o f
the i s o t o p i c molecule o f i n t e r e s t , f o l l o w e d by a gas phase,
v i b r a t i o n a l l y - e n h a n c e d b i m o l e c u l a r r e a c t i o n , l e a d i n g t o an i s o ­
t o p i c a l l y enriched r e a c t i o n product which could e a s i l y be
separated. A primary c o n s i d e r a t i o n i n t h e choice o f r e a c t i o n i s
the a c t i v a t i o n energy. I t must be high enough t o minimize t h e
(thermal) r e a c t i o n r a t e i n t h e absence o f v i b r a t i o n a l e x c i t a t i o n ,
but low enough so that t h e r e a c t i o n r a t e o f the v i b r a t i o n a l l y
e x c i t e d species exceeds t h e r a t e o f scrambling r e a c t i o n s , e.g.,
V-V and V-T energy t r a n s f e r s , which l e a d t o the l o s s o f i s o t o p i c
s e l e c t i v i t y . I n t h i s s e c t i o n we d i s c u s s a c l a s s o f r e a c t i o n s ,
deuterium h a l i d e - o l e f i n a d d i t i o n s , w i t h thermal e q u i l i b r i u m
a c t i v a t i o n energies i n the range 15-^0 kcal/mole.
The i n i t i a l step o f t h i s process i n v o l v e s s e q u e n t i a l absorp­
t i o n o f s e v e r a l quanta near 5 microns from a pulsed CO l a s e r t o
e x c i t e DBr o r DC1 up t h e i r v i b r a t i o n a l ladders t o t h e ν >_ 3
v i b r a t i o n a l l e v e l . A l t e r n a t e l y , a pulsed DF l a s e r near h microns
can s e q u e n t i a l l y e x c i t e DF or EDO t o ν > 3. I n pure DX, c o l l i ­
sions o f the type DX(v = l ) + DX(v = l ) •> DX(v = 2) + DX(v = 0)
can a l s o e x c i t e higher v i b r a t i o n a l l e v e l s , but t h i s mechanism i s
not f e a s i b l e i n n a t u r a l HX c o n t a i n i n g only 0.015% DX. The v i ­
b r a t i o n a l l y e x c i t e d DX molecule (X = B r , C l , F, OH) then w i l l
p r e f e r e n t i a l l y r e a c t w i t h unsaturated hydrocarbons ( f o r example,
DBr r e a c t i n g w i t h ethylene) t o y i e l d a deuterium-tagged a d d i t i o n
product, e.g., e t h y l bromide-d}. These steps may be w r i t t e n
DX + nhv + DX* (v=n)
η >_ 3
(pulsed CO o r DF l a s e r e x c i t a t i o n )
DX* +
(R
(1)
(2)
l5
R
2
= H, CH , CH=CH , etc.)
3
2
This type o f a d d i t i o n r e a c t i o n i n t o unsaturated hydrocarbons
i n t h e gas phase occurs by a homogeneous, b i m o l e c u l a r , f o u r - o r
s i x - c e n t e r process (^,5.). Both the forward r e a c t i o n (2) and t h e
In Separation of Hydrogen Isotopes; Rae, H.;
ACS Symposium Series; American Chemical Society: Washington, DC, 1978.
SEPARATION OF HYDROGEN ISOTOPES
136
reverse r e a c t i o n (unimolecular e l i m i n a t i o n o f HX) have been very
w e l l s t u d i e d i n the gas p h a s e ( 6 l ) . K i n e t i c parameters f o r the
gas phase thermal a d d i t i o n r e a c t i o n are w e l l represented by the
Arrhenius r a t e e x p r e s s i o n
,
-E /RT
k(sec
) = [C]-Ae
(3)
9
a
where
[c] = o l e f i n c o n c e n t r a t i o n ( m o l e s / l i t e r )
A = frequency f a c t o r ( l i t e r / m o l e - s e c )
Ε = thermal a c t i v a t i o n energy (kcal/mole)
a
A r r h e n i u s parameters f o r HX a d d i t i o n i n t o simple and con­
jugated o l e f i n s are given i n Table I , which i l l u s t r a t e s the
v a r i a t i o n o f a c t i v a t i o n energy E and frequency f a c t o r A,
according t o the choice o f reagents.
Examination o f Table I r e v e a l s t h a t a c t i v a t i o n energies i n
the range 10-50 kcal/mole are a v a i l a b l e , depending on the choice
o f reagents. Lowest a c t i v a t i o n energies occur f o r HI a d d i t i o n
w i t h i n c r e a s i n g a c t i v a t i o n energy f o r l i g h t e r HX, such t h a t
E ( H l ) < E ( H B r ) < E (HCl) < E (HF) < E ( H 0 ) . Table I a l s o
shows t h a t a c t i v a t i o n energy decreases w i t h i n c r e a s i n g s u b s t i ­
t u t i o n , w i t h E decreasing by about 5 kcal/mole per methyl
(-CH3) group and by about 9 kcal/mole per v i n y l (-CH=CH2) group
on the a- or h a l o g e n - r e c e i v i n g carbon atom. Among
olefins,
2-methylpropene and 1,3-butadiene have n e a r l y i d e n t i c a l a c t i v a ­
t i o n e n e r g i e s , but 1,3-butadiene i s a f a r s u p e r i o r reagent choice
because of i t s approximately 2 0 0 - f o l d higher frequency f a c t o r
(A v a l u e ) .
Although HI has the lowest a c t i v a t i o n energies f o r r e a c t i o n ,
i t i s probably not an acceptable choice i n a l a r g e s c a l e process
because of i t s tendency t o decompose. HF and H 0 are probably
r e l a t i v e l y u n a t t r a c t i v e , s i n c e they have s i g n i f i c a n t l y higher
a c t i v a t i o n e n e r g i e s ; t h i s l e a v e s HBr or HC1 as the most l i k e l y
reagent c h o i c e . A l s o , use of HF or H 0 would r e q u i r e e x c i t a t i o n
by a DF chemical l a s e r , which i s an i n h e r e n t l y more expensive
and l e s s e f f i c i e n t device than the CO l a s e r , p r i m a r i l y due t o
the cost of r e g e n e r a t i n g the f l u o r i n e . The CO l a s e r i s an e f f i ­
c i e n t , well-developed device ( l l ) which i s q u i t e s u i t a b l e f o r a
l a r g e - s c a l e i n d u s t r i a l process.
To evaluate the s u i t a b i l i t y o f the CO l a s e r f o r e x c i t a t i o n
o f DBr or DC1, a computer comparison was made o f the c a l c u l a t e d
wavelengths of CO emission l i n e s and DBr or DC1 a b s o r p t i o n l i n e s .
For these diatomic molecules, accurate frequencies may be gener­
ated from a Dunham equation f o r the energy l e v e l s :
Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch010
a
a
a
a
a
a
2
a
2
2
kj j+i
*™ = Z\*K)\î
In Separation of Hydrogen Isotopes; Rae, H.;
ACS Symposium Series; American Chemical Society: Washington, DC, 1978.
(u)
10.
MARLING ET AL.
Deuterium
Isotope
137
Separation
TABLE I
A r r h e n i u s Parameters
Olefins:
Frequency
Factor
Unsaturated
Hydrocarbon
LogipA
propylene^
3
Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch010
t
2-methylpropene
Phenyl e t h y l e n e
X = I , B r , C l , F, OH
A c t i v a t i o n Energy Ε (kcal/mole)
a
HBr
HCl
HF
HI
H 0
tot7
2
8.3°
ethylene
f o r HX A d d i t i o n t o
28.5
ko
50
57
U5
52
7.9
C
23.5
28.5
3k
6.5
C
18.5
23.5
28
20
2k
30
13
1,3-butadiene
2-methyl-l,3butadiene
1 5 3-pentadiene
3k
18.7
1
Q.k
h
7-7
I5
s
1
26
g
20
1
25
s
2k
20
f
ih.T
h
2-methyl-l,3 .
pentadiene
l.k*
11
16
21
H-methyl-1,3-.
pentadiene
6.3
10
15
20
J
U n i t s o f A are l i t e r s - m o l e
f o r a l l HX compounds.
b
Ε
a
l e
38
29
1
e
kg
sec \
L o g A i s constant ± 0 . 3
10
values from Reference 6.
c
Reference k.
d
Computed from A o f back r e a c t i o n .
See Reference 7 ·
Reference 8.
Computed from k i n e t i c data o f Reference 5 .
Computed from k i n e t i c s o f back r e a c t i o n .
See Reference 9 ·
Reference 1 0 .
Estimated Ε
value.
Probable accuracy:
Estimated v a l u e f o r L o g ^ A .
± 2 kcal/mole.
Probable accuracy: ± O.k.
In Separation of Hydrogen Isotopes; Rae, H.;
ACS Symposium Series; American Chemical Society: Washington, DC, 1978.
SEPARATION OF HYDROGEN ISOTOPES
138
Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch010
For normal and i s o t o p i c
y i e l d computed emission
(Ref. 12) or even a few
measured values f o r the
carbon monoxide, the c o e f f i c i e n t s Y
frequencies accurate t o 0.001
cm"
megahertz (13). For D ^ ^ c i , d i r e c t l y
Υ „ were a v a i l a b l e ( l U ) . For D^Tci the
£k
ntr
—
Y
were computed from
D ^ C l u s i n g the Dunham i s o t o p e
r e l a t i o n s (15) and the a p p r o p r i a t e atomic reduced masses ( l 6 ) .
For D^^Br and D^lBr the e a r l i e r r e p o r t e d a b s o r p t i o n f r e q u e n c i e s
(IT) were not s u f f i c i e n t l y accurate. T h e r e f o r e , accurate Y
were generated f o r HBr u s i n g the accurate r o t a t i o n a l constants
(l8) and recent higher l e v e l v i b r a t i o n a l constants (19.). The
a p p r o p r i a t e reduced masses (l6) and Dunham i s o t o p e relation§^(15)
then were used t o d e r i v e a l l Y
except Y ^ f o r D Br and D Br.
Y-|_Q was then f i x e d by r e q u i r i n g the computed 1-0 band t o be
0.25 cm" higher than i t s measured value (17) > according t o the
c o r r e c t i o n suggested i n Ref. 20.
The d e r i v e d Dunham c o e f f i c i e n t s f o r DC1 and DBr thus p r o ­
v i d e d c a l c u l a t e d a b s o r p t i o n l i n e center frequencies f o r a
computer search t o f i n d near-coincidences w i t h CO l a s e r emission
f r e q u e n c i e s . For each near c o i n c i d e n c e , the a b s o r p t i o n co­
e f f i c i e n t was computed u s i n g a standard Lorentz l i n e shape f o r ­
mula, equation (5)> which a l s o i n c l u d e d the temperature depen­
dence o f the r o t a t i o n a l l e v e l p o p u l a t i o n :
-3m(m+l)/kT
1
Λ
1
α ( Δ ν )
= lV
(Λν/0. Ρ)
5Ύ
( 5 )
2
In equation ( 5 ) , α(Δν) i s the a b s o r p t i o n ( i n cm" ) at a d i s t a n c e
Av(cm~l) from DX l i n e center at a pressure o f Ρ atmospheres.
The values f o r the pressure-broadened l i n e w i d t h γ(cm atm" )
depend on r o t a t i o n a l number m, and were taken from Ref. 21_ f o r
DC1 broadening by HC1.
The r o t a t i o n a l number i s m = J - l f o r
R-branch and m = J f o r P-branch t r a n s i t i o n s . DBr values f o r γ
were d e r i v e d from the r e p o r t e d values f o r HBr(22). The parameters
Κ and 3 i n equation (5) were a d j u s t e d t o match the r e p o r t e d DC1
a b s o r p t i o n l i n e s t r e n g t h s ( 2 3 ) , and DBr values f o r Κ and 3 were
d e r i v e d from the HBr values (22) by assuming K(DBr) = l/k K(HBr)
and 3(DBr) Ξ 2 3(HBr), assumptions found t o be reasonable f o r
the DC1/HC1 data (23).
Equation (5) thus permits reasonably accurate e s t i m a t i o n of
a b s o r p t i o n i n the 1-0 band o f DC1 and DBr by CO l a s e r l i n e s .
A b s o r p t i o n s t r e n g t h of the higher v i b r a t i o n a l bands (2-1 through
5-U i n t h i s study) w i l l i n c r e a s e approximately p r o p o r t i o n a l t o
ν (Réf. 2*0, but decrease due t o the d i s t r i b u t i o n o f p o p u l a t i o n
over the s e v e r a l l e v e l s . As a f i r s t approximation, a b s o r p t i o n
s t r e n g t h f o r higher v i b r a t i o n a l bands was thus taken t o be the
same as the 1-0 band.
Tables I I and I I I summarize the computed a b s o r p t i o n o f
-^C-^O l a s e r emission l i n e s by the v a r i o u s i s o t o p e s of DC1 and
DBr.
Data f o r Tables I I and I I I were computed f o r atmospheric
pressure and room temperature (298°K), and i l l u s t r a t e the ease
1
-1
In Separation of Hydrogen Isotopes; Rae, H.;
ACS Symposium Series; American Chemical Society: Washington, DC, 1978.
1
10.
MARLING ET AL.
Deuterium
Isotope
139
Separation
TABLE I I
ABSORPTION OF
C O
DC1 T r a n s i t i o n * ·
ν ( cm" )
Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch010
1
1-0
1-0
1-0
1-0
2-1
2-1
2-1
2-1
3-2
3-2
3-2
3-2
U-3
h-3
h-3
h-3
5-U
P(T)
P(3)37
P(T)37
P(U)
P(2)
p(n)
P(U)
3 5
3 5
3 5
3 5
3 7
2011.Ohl
2055-1^6
2008.282
20U6.609
2016.033
1909.678
1991.iih
R(3)
2077.3k0
P(2)
1963.IUO
P(ll)
1858.853
P(6)
1918.799
P(2)
1960.51^
P ( 5 ) 5 1878.238
R(5)
1986.873
P(2)
1910.507
P(3)
1897.518
P ( 7 ) 5 I80U.358
p(i)
1868.160
3 5
3 5
3 5
3 5
3 7
3
3 5
3 5
3 7
3
5-U
5-U R ( 2 )
3 5
3 7
1903.939
LASER LINES BY D ^ C l and D^'Cl, a t P=l ATM.
1 2
l 6
c o
LASER LINE
5-h P ( 7 )
3-2 P ( 9 )
3-2 P ( 2 0 )
3-2 P ( l l )
2 - 1 F(2k)
6-5 P ( 2 5 )
5-U P ( 1 2 )
2 - 1 P(10)
7-6 P ( 6 )
1 0 - 9 P(13)
7-6 P ( 1 7 )
h-3 P ( 2 5 )
10-9 P(8)
5-U P ( 1 3 )
7-6 P ( 1 9 )
7-6 P ( 2 2 )
12-11 P(lU)
9-8 P ( 1 7 )
9-8 P(8)
v
Vi- co
( c n r l )
ABSORPTION
COEF. (cm" )
-0.0i+9
-0.012
-O.I38
-0.3^9
0.007
-0.001
0.090
0.201
0.058
-O.Okh
-0.179
0.103
-O.OI7
-0.037
-0.02U
-0.101
0.026
0.03U
0.058
* S u b s c r i p t 35 o r 37 r e f e r s t o D ^ C l o r D
respectively.
1
11.8
l.U
1.1
12.6
5.1
3.0
2.9
8.7
3.6
3Λ
1.7
18.5
15.2
11.8
2.3
Ik.k
6.0
3.7
Cltransitions,
In Separation of Hydrogen Isotopes; Rae, H.;
ACS Symposium Series; American Chemical Society: Washington, DC, 1978.
SEPARATION OF HYDROGEN ISOTOPES
140
TABLE I I I
ABSORPTION OF
1 2
C
l 6
0 LASER LINES BY D
Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch010
TRANSITION*
v ( cm*" )
1
B r and D
C C 0
LASER LINE
1 2
DBr
T 9
8 l
B r a t P=l ATM.
1 6
v
v
DBr- C0
( c m
"
1 )
ABSORPTION
(cm" )
1
1-0
R ( 2 ) 81
1863.999
9-8
P(l8)
0.011
3.2
1-0
R(3) 79
18T2.3T8
8-7
P(22)
0.0U8
2.5
1-0
P(9) 79
1757.851
lU-13 P(13)
1-0
P(3) 81
1813.573
11-10
2-1
R ( 6 ] 81
I8U7.I63
9-8
2-1
P(8] 81
1722.606
2-1
R ( 9 ! 79
1867.966
8-7
2-1
P ( 9 ! 79
1713.U97
15-lh
3-2
P(6) 81
1696.517
3-2
R ( 2 ; 81
3-2
P(l8)
2.1
0.057
1.9
P(22)
0.0U6
3.0
16-15 P(9)
0.003
3.8
-0.032
2.0
P(l8)
-0.0U6
2.0
16-15
P(l6)
0.008
h.3
1771.3h3
13-12
P(l6)
0.017
3.1
P ( 9 l 79
1669.172
18-17
P(10)
0.07^
1.3
h-3
p(u; 81
1669.H5
18-17
P(10)
0.017
3.7
h-3
R(3
79
1732.808
15-lU P(13)
0.0U3
2.7
5-U
P(T ) g
1598.386
21-20 P ( 9 )
0.016
u.o
5-U
P(T '81
1597.983
20-19
P(l6)
0.0^9
2.9
Br o r D
Br t r a n s i t i o n s ,
7
* S u b s c r i p t 79 o r 8 l r e f e r s t o D
P(23)
respectively.
In Separation of Hydrogen Isotopes; Rae, H.;
ACS Symposium Series; American Chemical Society: Washington, DC, 1978.
10.
MARLING ET AL.
Deuterium
Isotope
141
Separation
i n a c h i e v i n g s e q u e n t i a l a b s o r p t i o n o f CO l a s e r quanta t o e x c i t e
DC1 o r DBr up t h e i r v i b r a t i o n a l l a d d e r s t o ν - 5·
Examination o f Table I I i n d i c a t e s t h a t the best matches o f
12^1 ο l a s e r emission w i t h D^^ci y i e l d a b s o r p t i o n c o e f f i c i e n t s
of about 12 cm" a t 1 atmosphere. S i m i l a r l y , the best CO
laser-DBr a b s o r p t i o n c o e f f i c i e n t s are about 3 cm" . At higher
p r e s s u r e s , r a d i a t i o n from CO l a s e r l i n e s i s e a s i l y absorbed w i t h ­
out need f o r CO l a s e r l i n e s e l e c t i o n .
For example, a t 5 atmo­
spheres pressure any CO l a s e r l i n e i n the U.9—5·1 micron r e g i o n
i s c a l c u l a t e d t o experience an average DC1 a b s o r p t i o n c o e f f i c i e n t
of 2 cm" f o r the 1-0 band, which i n c r e a s e s t o about 10 cm"
when a b s o r p t i o n from DC1 v i b r a t i o n a l l y e x c i t e d s t a t e s i s i n c l u d ­
ed. Only the "best" matches were given i n Tables I I and I I I f o r
each l e v e l o f v i b r a t i o n a l e x c i t a t i o n . Table I I shows t h a t most
DC1 a b s o r p t i o n o f C " 0 l a s e r emission w i l l occur i n the U . 9 micron r e g i o n , and u s e f u l DBr a b s o r p t i o n w i l l occur i n the
5.^-6.2 micron r e g i o n . At n a t u r a l deuterium abundance, t h e
1/e a b s o r p t i o n depth would be about 5 meters f o r DC1 and 20
meters f o r DBr.
Since a t y p i c a l r e a c t i o n mixture would a l s o c o n t a i n an
o l e f i n a t near-atmospheric p r e s s u r e , i t would be important t o
i n s u r e t h a t the o l e f i n i s s u f f i c i e n t l y t r a n s p a r e n t a t these
wavelengths (a < 0.1 m e t e r " ) .
This i s e s s e n t i a l t o a l l o w the
CO l a s e r emission t o e x c i t e p r i m a r i l y DBr o r DC1, and not waste
photons by o p t i c a l l y h e a t i n g the o l e f i n . Examination o f simple
and conjugated o l e f i n a b s o r p t i o n bands (25) i n the 5-6 micron
r e g i o n r e v e a l s q u i t e strong C = C s t r e t c h a b s o r p t i o n a t 6.0-6.2
micron. P o t e n t i a l l y troublesome combination band a b s o r p t i o n
occurs a t 5·1*Μ and e s p e c i a l l y a t 5 · 6 μ i n 1,3-butadiene and i s o prene, probably the best reagent choices from Table I .
Gas phase a b s o r p t i o n s p e c t r a were examined and showed an
a b s o r p t i o n c o e f f i c i e n t ( t o base e) o f about 0 . 5 cm" A t m f o r
both 1,3-butadiene and isoprene near 5 · 6 micron. This i s about
2-3 orders o f magnitude stronger than n a t u r a l l y o c c u r r i n g DBr
a b s o r p t i o n , r e n d e r i n g photon e f f i c i e n t e x c i t a t i o n o f DBr
i m p o s s i b l e . The s i t u a t i o n i s somewhat improved a t 5·1 micron,
where the a b s o r p t i o n c o e f f i c i e n t s o f these two o l e f i n s are about
0.05 cm"" atm" , s t i l l about an order o f magnitude stronger than
DC1 a b s o r p t i o n a t n a t u r a l abundance. T h i s suggests t h a t l i n e a r
conjugated o l e f i n s w i l l be e x c e s s i v e l y absorbing, and prevent
e f f i c i e n t CO-laser e x c i t a t i o n o f DC1 and e s p e c i a l l y DBr.
Cyclopentadiene and 1 , 3 - c y c l o h e x a d i e n e should a l s o e x h i b i t low a c t i v a ­
t i o n energies f o r hydrogen h a l i d e a d d i t i o n , s i m i l a r t o the l i n e a r
conjugated o l e f i n s l i s t e d i n Table I , and o p t i c a l a b s o r p t i o n
s p e c t r a are somewhat more promising. Cyclopentadiene (26)
appears t r a n s p a r e n t i n the 5 . 0 - 5 . 3 μ r e g i o n , p o t e n t i a l l y s u i t ­
able f o r use w i t h DC1, and 1 , 3 - c y c l o h e x a d i e n e (27) appears
t r a n s p a r e n t i n the 5 · ^ - 5 · 7 5 y r e g i o n , making i t p o t e n t i a l l y
s u i t a b l e f o r use w i t h DBr.
E l i m i n a t i o n of o l e f i n absorption w i l l
be e s s e n t i a l f o r e f f i c i e n t photon u t i l i z a t i o n a t low deuterium
Ό
1
1
Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch010
1
1
1 2
1
1
1
1
1
In Separation of Hydrogen Isotopes; Rae, H.;
ACS Symposium Series; American Chemical Society: Washington, DC, 1978.
- 1
SEPARATION OF HYDROGEN ISOTOPES
142
c o n c e n t r a t i o n s . Only ethylene (25) shows extreme t r a n s p a r e n c y ,
w i t h no d e t e c t a b l e a b s o r p t i o n from 1550 cm- t o 1750 cm"" , making
i t o p t i c a l l y s u i t a b l e f o r use w i t h DBr.
Non-reactive quenching o f v i b r a t i o n a l l y e x c i t e d deuterium
h a l i d e w i l l be an important p r o c e s s , as i t competes w i t h r e a c t i v e
a d d i t i o n o f t h e e x c i t e d s p e c i e s i n t o t h e o l e f i n . The r e a c t i o n
e f f i c i e n c y φ w i l l be simply t h e r a t i o o f r e a c t i v e quenching t o
t o t a l quenching, or
1
1
R [c]
v
φ
=
( V Q ) [ c ] + Q [x]
c
(6)
x
Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch010
where
[c] = Olefin concentration
[x] = Hydrogen h a l i d e c o n c e n t r a t i o n
R
= Deuterium h a l i d e r e a c t i v i t y i n
vibrational level ν
Q
= Quenching r a t e / u n i t c o n c e n t r a t i o n
°
of olefin
Q
= Quenching r a t e / u n i t c o n c e n t r a t i o n
of hydrogen h a l i d e
In a d d i t i o n t o r e a c t i o n , t h e v i b r a t i o n a l l y e x c i t e d
deuterium h a l i d e w i l l experience n o n - r e a c t i v e v i b r a t i o n a l
quenching by both t h e o l e f i n and t h e hydrogen h a l i d e .
Q
denotes v i b r a t i o n a l quenching o f deuterium h a l i d e by hydrogen
h a l i d e and has been measured f o r quenching o f t h e DX v = l l e v e l
(28-31). For DBr, a value o f Q = 0.2 (μsec · atm)" was d e t e r ­
mined (28) f o r quenching by HBr. For DC1 quenching by HC1, a
value of Q = O.h {\isec · atm)"" may be i n f e r r e d (29). Nonr e a c t i v e v i b r a t i o n a l quenching by t h e o l e f i n may be 10-100 times
f a s t e r than these r a t e s , based on t h e observed r a p i d quenching
of HBr ( 3 0 ) , HC1 (31) and DC1 (31) by water and methane.
Quenching r a t e s o f higher DX v i b r a t i o n a l l e v e l s w i l l be f a s t e r
than f o r the v = l l e v e l , r i s i n g approximately p r o p o r t i o n a l t o ν
(Ref. 2 9 ) . Thus, equation (6) reduces t o a simpler form when
the o l e f i n c o n c e n t r a t i o n [θ] i s r a i s e d t o o p t i m i z e φ,
x
1
x
1
x
φ ifc R /(R +Q ) i f [C] % [X]
v
v
c
and Q » Q
c
χ
(7)
since v i b r a t i o n a l quenching by HX i s slow compared t o t h e
expected o l e f i n quenching r a t e s . The upper l i m i t o f t h e DX r e ­
a c t i o n r a t e w i t h a given o l e f i n i s simply the frequency A
(Table I ) and i s expected t o be approached as t h e DX l a s e r s u p p l i e d v i b r a t i o n a l energy exceeds t h e r e a c t i o n - a c t i v a t i o n
energy Ε . T h i s assumption was examined f o r other r e a c t i o n
systems ( 3 2 ) , and i s d i s c u s s e d f u r t h e r i n S e c t i o n I I I . T h i s
p l a c e s an upper l i m i t on t h e r e a c t i o n e f f i c i e n c y
In Separation of Hydrogen Isotopes; Rae, H.;
ACS Symposium Series; American Chemical Society: Washington, DC, 1978.
10.
MARLING ET AL.
Deuterium
Isotope
143
Separation
(8)
max
when one assumes (32) t h a t A f o r a b i m o l e c u l a r r e a c t i o n i s i n d e ­
pendent o f reagent v i b r a t i o n a l e x c i t a t i o n . The best value o f A
from Table I occurs f o r 1 , 3 - b u t a d i e n e , A - 25 (μsec•atm) . I f
o l e f i n n o n - r e a c t i v e v i b r a t i o n a l quenching i s comparable t o HX
quenching r a t e s by methane ( 3 j 0 , 3 l ) , o r Q = 10-60 (μεβο •atm)*"" ,
then the maximum r e a c t i o n e f f i c i e n c y , from equation ( 8 ) , c o u l d
l i e i n the range 0.1%-50%, w i t h the higher r e a c t i o n e f f i c i e n c i e s
corresponding t o use o f o l e f i n s w i t h h i g h values o f A, such as
1,3-butadiene o r ethylene.
The problem o f n o n - r e a c t i v e quenching o f v i b r a t i o n a l l y
e x c i t e d DX by the o l e f i n i s r e l a t e d t o the problem o f e x c e s s i v e
o p t i c a l a b s o r p t i o n by the o l e f i n , namely the presence o f o l e f i n
energy resonances near DX a b s o r p t i o n f r e q u e n c i e s . DX v i b r a t i o n a l
quenching by v-v energy t r a n s f e r processes becomes very r a p i d
near energy resonance (30,33), but should drop t o acceptably low
v a l u e s , i f the nearest resonances have an energy discrepancy o f
more than about 1000 cm" . Lower n o n - r e a c t i v e quenching can be
achieved by u s i n g f u l l y halogenated o l e f i n s (3*0, which may a l s o
y i e l d h i g h o l e f i n transparency a t DX a b s o r p t i o n f r e q u e n c i e s .
However, t y p i c a l f l u o r i n a t e d o l e f i n reagent c h o i c e s , such as
h e x a f l u o r o - l , 3 - b u t a d i e n e (35.), hexafluoropropene (36), o r
f l u o r i n a t e d ethylenes (36) have e x c e s s i v e o p t i c a l a b s o r p t i o n i n
the 5-6 micron r e g i o n (35.,36) , and hence are not s u i t a b l e . But
when i n the course o f t h i s work t e t r a c h l o r o e t h y l e n e o p t i c a l
a b s o r p t i o n was examined i n the gas phase, i t was found t o be
h i g h l y transparent i n the H.2-5-2 μ r e g i o n , and i s thus poten­
t i a l l y s u i t a b l e f o r use w i t h HC1.
Experimental k i n e t i c data on
a c t i v a t i o n energies are not r e p o r t e d , but c a l c u l a t e d values o f
E f o r HF o r HC1 r e a c t i n g w i t h perhalogenated ethylene are 5
kcal/mole lower than w i t h normal ethylene (6). Some p e r f l u o r i n a ­
t e d o l e f i n s are v e r y t o x i c ( 3T_), and p e r c h l o r i n a t e d o l e f i n s
r e q u i r e o p e r a t i n g temperatures 100-200°C higher than normal
o l e f i n s t o achieve u s e f u l vapor pressure. N e v e r t h e l e s s , t h e
p o t e n t i a l f o r h i g h IR transparency and low v i b r a t i o n a l quenching
makes t h i s c l a s s o f reagents (and t e t r a c h l o r o e t h y l e n e i n
p a r t i c u l a r ) a t t r a c t i v e t o c o n s i d e r f o r a p r a c t i c a l process.
There i s p r e s e n t l y very l i t t l e experimental data on l a s e r e x c i t e d HX a d d i t i o n i n t o o l e f i n s . However, r e a c t i o n was observed
between 2-methylpropene and HCl(v=6) produced by i n t r a c a v i t y dye
l a s e r e x c i t a t i o n o f the HC1 f i f t h overtone ( 3 8 ) . Quantum y i e l d s
f o r r e a c t i o n were estimated (38.) t o l i e i n the range 0.01-0.1%,
c o n s i s t e n t w i t h the very l o w frequency f a c t o r f o r t h i s o l e f i n
(see Table I ) . Use o f 1,3-butadiene i n t h i s same experiement
( i n s t e a d o f 2-methylpropene) was not t r i e d , but should have
y i e l d e d a r e a c t i o n quantum y i e l d o f 2-20%, based on i t s 2 0 0 - f o l d
higher frequency f a c t o r . Economic a n a l y s i s o f l a s e r - r e l a t e d
c o s t s i n heavy water p r o d u c t i o n by the D X - o l e f i n process
l
1
Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch010
c
1
a
In Separation of Hydrogen Isotopes; Rae, H.;
ACS Symposium Series; American Chemical Society: Washington, DC, 1978.
SEPARATION OF HYDROGEN ISOTOPES
Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch010
144
d i s c u s s e d here i n d i c a t e t h a t r e a c t i o n e f f i c i e n c i e s must exceed
5% f o r t h i s process t o be economically v i a b l e (39)·
Additional
c o s t s due t o the "back-end" of t h i s process (see S e c t i o n IV) w i l l
probably set a p r a c t i c a l lower l i m i t of 10% f o r an acceptable
r e a c t i o n e f f i c i e n c y . In t h i s c o n t e x t , the c l a s s i c a l quantum
e f f i c i e n c y i s the r e a c t i o n e f f i c i e n c y φ d i v i d e d by n, the average
number of absorbed quanta per DX molecule. The assumption of
η = 5 p l a c e s an approximate lower l i m i t of 2% on an economically
acceptable quantum e f f i c i e n c y f o r deuterium h a l i d e a d d i t i o n i n t o
o l e f i n s as a p o t e n t i a l photochemical route t o heavy water pro­
duction.
In t h i s s e c t i o n we have shown t h a t the CO l a s e r permits
s e q u e n t i a l e x c i t a t i o n of DBr or DC1 up the v i b r a t i o n a l ladder t o
at l e a s t the ν = 5 v i b r a t i o n a l l e v e l . At n a t u r a l deuterium
abundance, the l / e a b s o r p t i o n depth f o r s e l e c t e d CO l a s e r l i n e
r a d i a t i o n i s about 5 meters f o r DC1 and about 20 meters f o r DBr,
at a hydrogen h a l i d e o p e r a t i n g pressure of one atmosphere. At
5 atmospheres o p e r a t i n g p r e s s u r e , u n r e s t r i c t e d m u l t i l i n e opera­
t i o n of the CO l a s e r i s s u f f i c i e n t , but some l i n e t u n i n g
(according t o Tables I I and I I I ) f a c i l i t a t e s DX a b s o r p t i o n at one
atmosphere pressure. Troublesome o l e f i n o p t i c a l a b s o r p t i o n and
v i b r a t i o n a l quenching may be reduced by u s i n g t e t r a c h l o r o e t h y l e n e .
Unwanted o l e f i n o p t i c a l a b s o r p t i o n may a l s o be avoided by u s i n g
e t h y l e n e , cyclopentadiene, or 1,3-cyclohexadiene.
The l a r g e
choice of Arrhenius parameters a v a i l a b l e f o r t y p i c a l reagent
choices (Table I ) permits reagent o p t i m i z a t i o n f o r acceptable
process r e a c t i o n e f f i c i e n c y . Experimental e v a l u a t i o n of the
deuterium h a l i d e / o l e f i n process f o r heavy water p r o d u c t i o n i s i n
progress at the Lawrence Livermore Laboratory.
I I I . E f f e c t i v e n e s s of V i b r a t i o n a l E x c i t a t i o n
In the preceding s e c t i o n , we have shown t h a t e x c i t a t i o n of
l o w - l y i n g v i b r a t i o n a l l e v e l s of deuterated h a l i d e s should l e a d
t o s i g n i f i c a n t enrichments v i a i s o t o p i c a l l y s e l e c t i v e a d d i t i o n
r e a c t i o n s , I f the h a l i d e v i b r a t i o n and r e a c t i o n coordinates are
e s s e n t i a l l y i d e n t i c a l . That v i b r a t i o n a l e x c i t a t i o n of hydrogen
h a l i d e s l e a d s t o enhanced r a t e s f o r diatomic-atom exchange
r e a c t i o n s of the type
K f
A + BC
t
t
AB
+ C
(9)
have been e x p e r i m e n t a l l y confirmed; perhaps the most s t r i k i n g
example i s the f a c t t h a t HC1 (v = 2) was found t o r e a c t w i t h
bromine approximately 1 0
times f a s t e r than HC1 (ν = 0)
(kO).
The t h e o r e t i c a l e x p l a n a t i o n o f these r a t e enhancements runs
as f o l l o w s : Since the forward, exoergic r e a c t i o n leaves the
product AB i n a h i g h l y v i b r a t i o n a l l y e x c i t e d s t a t e (AB ), then
1 1
In Separation of Hydrogen Isotopes; Rae, H.;
ACS Symposium Series; American Chemical Society: Washington, DC, 1978.
10.
MARLING ET AL.
Deuterium
Isotope
145
Separation
microscopic r e v e r s i b i l i t y a t the same t o t a l energy i m p l i e s t h a t
the r a t e o f the r e v e r s e , endoergic r e a c t i o n - w i l l be enhanced more
e f f e c t i v e l y when energy i s put i n t o AB v i b r a t i o n r a t h e r than i n t o
r e l a t i v e t r a n s l a t i o n o f AB and C. I n c o n s i d e r i n g more general
r e a c t i o n s i n v o l v i n g v i b r a t i o n a l l y e x c i t e d reagents, i t i s impor­
t a n t t o note t h a t the r e v e r s i b i l i t y argument can be a p p l i e d inde­
pendent o f whether the r e a c t i o n which leads t o a v i b r a t i o n a l l y
e x c i t e d product i s endoergic o r exoergic. We s t r e s s t h i s because,
w h i l e i t i s g e n e r a l l y b e l i e v e d t h a t t h e endoergic r e a c t i o n s u t i ­
l i z e v i b r a t i o n a l energy more e f f e c t i v e l y than exoergic r e a c t i o n s
(hi), t h e e x i s t i n g experimental evidence, as analyzed by B i r e l y
and Lyman (32.) does not show any strong c o r r e l a t i o n between the
e f f e c t i v e n e s s o f reagent v i b r a t i o n i n lowering the a c t i v a t i o n
energy and r e a c t i o n e x o e r g i c i t y . I t f o l l o w s t h a t i n s i g h t i n t o
the e f f e c t o f v i b r a t i o n a l e x c i t a t i o n o f hydrogen h a l i d e s on the
r a t e o f exoergic a d d i t i o n r e a c t i o n s can best be gleaned from t h e
experimental data on the energy d i s p o s a l o f the reverse r e a c t i o n s ,
i . e . , unimolecular hydrogen h a l i d e e l i m i n a t i o n s from, e.g., h a l o alkanes and h a l o o l e f i n s , f o l l o w i n g chemical o r photochemical a c t i ­
v a t i o n . There i s an extensive l i t e r a t u r e i n t h i s area: The
experimental evidence i s summarized by Berry (h2) who concludes
t h a t , i r r e s p e c t i v e o f the a c t i v a t i o n mechanism, the t o t a l a v a i l ­
able energy ( E ) , o r t h e molecular complexity o f the r e a c t a n t , a l l
HX e l i m i n a t i o n products acquire ^ 15-h0% o f t h e p o t e n t i a l energy
(E ) a v a i l a b l e t o t h e r e a c t a n t s (defined as t h e t h r e s h h o l d energy
fo? HX e l i m i n a t i o n minus t h e r e a c t i o n e n d o e r g i c i t y ) as v i b r a t i o n a l
energy. The remaining energy i s channeled i n t o HX r o t a t i o n , o l e ­
f i n product r o t a t i o n and v i b r a t i o n and r e l a t i v e t r a n s l a t i o n a l
energy o f t h e r e c o i l i n g products.
We note t h a t a l l t h e data per­
t a i n s t o experiments i n which E^ >> Ε . Of g r e a t e r relevance as
f a r as e f f e c t i v e n e s s o f HX v i b r a t i o n §n t h e r a t e o f t h e i n v e r s e
a d d i t i o n would be data on HX e l i m i n a t i o n s f o r which E - Ε .
Τ
ρ
Nevertheless, t h e a v a i l a b i l i t y o f many i n t e r n a l degrees o f f r e e ­
dom o f t h e product o l e f i n makes i t improbable t h a t r a t e enhance­
ments f o r HX a d d i t i o n r e a c t i o n comparable t o those f o r HX-atom
exchange r e a c t i o n s can be achieved.
Experiments t o t e s t t h i s conjecture are i n progress a t t h e Lawrence Livermore Laboratory.
IV. "Back-End" o f the Separation Cycle
Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch010
5
T
m
In common w i t h most other deuterium separation schemes, t h e
economic v i a b i l i t y o f an enrichment process based on l a s e r
enhanced deuterium h a l i d e a d d i t i o n r e a c t i o n s n e c e s s i t a t e s p r o ­
v i s i o n f o r r e c y c l i n g t h e working f l u i d . That i s , i t i s not
f e a s i b l e t o use, e.g., h y d r o c h l o r i c a c i d , on a once-through b a s i s
as feed f o r a deuterium separation p l a n t since even i f a l l t h e D
i n n a t u r a l HC1 ( n a t u r a l abundance - 1 . 5 x 10" ) were removed
w i t h 100% e f f i c i e n c y , t h e HC1 feed cost alone would be
4
In Separation of Hydrogen Isotopes; Rae, H.;
ACS Symposium Series; American Chemical Society: Washington, DC, 1978.
SEPARATION OF HYDROGEN ISOTOPES
146
$0.1
36
kgHCl
kg mole HC1
1 mole D 0
kg HC1
(1)
Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch010
2 mole DC1
$2U00/kg
20 kg
2
X
^
'
to
D_0
2
kg mole D 0
2
assuming HC1 c o s t s 10φ p e r k i l o g r a m . Thus, t h e economic v i a b i l ­
i t y o f t h i s process depends on the a b i l i t y t o redeuterate t h e HC1
which has been depleted o f D by t h e i s o t o p i c a l l y s e l e c t i v e a d d i ­
t i o n r e a c t i o n . The "obvious" way t o accomplish t h e r e d e u t e r a t i o n
i s by i s o t o p i c exchange o f HC1 w i t h n a t u r a l water (k3). For
s p e c i f i c i t y , we d i s c u s s t h i s r e f l u x o p e r a t i o n i n t h e context o f
the prototype system shown i n F i g u r e 1. The deuterated product
of t h e a d d i t i o n r e a c t i o n (DACl) i s t h e r m a l l y d i s s o c i a t e d t o p r o ­
duce i s o t o p i c a l l y pure DC1 (and e v e n t u a l l y D2O through exchange
with n a t u r a l water), while the o l e f i n i s r e c i r c u l a t e d t o the
l a s e r i r r a d i a t i o n area. The m a t e r i a l flows i n t h e r e f l u x tower
assume e q u i l i b r i u m o p e r a t i o n a t 108°C (hh). At t h i s temperature
the s e p a r a t i o n f a c t o r α f o r t h e exchange r e a c t i o n
DC1 + H 0 $ HC1 + HDO
(2)
2
is
(U3)
(H)H^O
2
(I)
1.9
Ή01
Besides t h e f a c t t h a t a l l t h e hydrogen h a l i d e - w a t e r exchange r e ­
a c t i o n s are c h a r a c t e r i z e d by an unfavorable e q u i l i b r i u m as f a r as
r e f l e x i s concerned, i . e . , t h e deuterium tends t o concentrate i n
the water, t h e r e a r e two other p r a c t i c a l d i f f i c u l t i e s a s s o c i a t e d
w i t h t h e use o f these systems: ( l ) they are h i g h l y c o r r o s i v e ,
n e c e s s i t a t i n g t h e use o f s p e c i a l m a t e r i a l s , e.g., Monel, and, (2)
they form constant b o i l i n g ( a z e o t r o p i c ) mixtures.
The s i g n i f i c a n c e o f t h e l a t t e r i s t h a t i t i s i m p o s s i b l e by
s u c c e s s i v e d i s t i l l a t i o n s a t a given pressure (or a t a given
temperature) t o o b t a i n both components as pure products from a
hydrogen halide-water mixture. At some p o i n t i n t h e d i s t i l l a t i o n
p r o c e s s , the a z e o t r o p i c c o n c e n t r a t i o n w i l l be reached (kk) ; when
t h i s a z e o t r o p i c feed i s p a r t i a l l y v a p o r i z e d , t h e vapor has t h e
same composition as t h e l i q u i d and no f u r t h e r s e p a r a t i o n o f com­
ponents i s p o s s i b l e . One convenient way t o break t h e azeotrope
and separate t h e phases a f t e r t h e i s o t o p i c exchange process has
been completed i s t o make use o f t h e s o - c a l l e d " s a l t e f f e c t " i n
v a p o r - l i q u i d e q u i l i b r i u m . The a d d i t i o n o f a n o n - v o l a t i l e s a l t
such as c a l c i u m c h l o r i d e , CaCl2, t o t h e HCl/H 0 mixture has t h e
e f f e c t o f s i m u l t a n e o u s l y i n c r e a s i n g t h e vapor pressure o f t h e HC1
v i a t h e common i o n effect, and decreasing t h e vapor pressure o f
the water, thus generating vapor o f higher HC1 c o n c e n t r a t i o n than
t h a t c h a r a c t e r i s t i c o f t h e azeotrope. We have not been able t o
2
In Separation of Hydrogen Isotopes; Rae, H.;
ACS Symposium Series; American Chemical Society: Washington, DC, 1978.
10.
MARLING ET AL.
Deuterium
Isotope
147
Separation
1mA
DC1 + A
1 m DAC1
DAC1
addition
dissociation
Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch010
Carbon monoxide
laser
13,500
m HC1
1 m DC1
1 m DC1
+
13,500
m HC1
13,501
HC1
reflux
| l m HC1
m HC1
D
2°
production
0.5m
D 0
2
t
Feed:
3500 m
n a t u r a l H^O
Waste :
3500 m H 0
2
Feed: 0.5 m
n a t u r a l H^O
LEGEND :
m = Mole
A = Olefin
DAC1 = DC1 + O l e f i n a d d i t i o n product
Figure 1.
Process flow diagram for DO production by laser-augmented deuteriumchloride addition into olefins
American Chemfcaf
Society Library
1155 16th St. N. W.
In Separation of Hydrogen Isotopes; Rae, H.;
ACS Symposium Series; American Chemical
Washington, DC, 1978.
1. D. C.Society:
20038
SEPARATION O F HYDROGEN ISOTOPES
148
f i n d i n f o r m a t i o n i n the l i t e r a t u r e on t h e HCl/H O/CaCl^ system;
however, from data on Isopropanol/H^O/CaCl^
(^5.) and
HCl/H^O/H^SO^ mixtures (U6_)(HpS0^, w h i l e not a common i o n , be­
haves s i m i l a r l y t o a n o n - v o l a t i l e s a l t i n reducing the vapor
pressure o f H^O), we c o n j e c t u r e t h a t t h e c o n c e n t r a t i o n o f CaCl^
r e q u i r e d w i l l be approximately 2-k wt.%.
A d e t a i l e d d i s c u s s i o n o f t h e design o f t h e HC1/H 0 exchange
process i n c o r p o r a t i n g t h e equipment necessary t o generate r e deuterated, anhydrous HC1 f o r r e f l u x t o the l a s e r tower would
c a r r y us too f a r a f i e l d (Vf) ; however, t h e b a s i c concept i s as
f o l l o w s . The i s o t o p i c exchange takes p l a c e on a s e r i e s o f t r a y s
w i t h the HC1 bubbling up and H 0 f l o w i n g down i n a countereurrent
f a s h i o n . The l i q u i d stream from t h e exchange column, and a s a l t
s o l u t i o n are f e d t o a concentrated s t r i p p e r which produces vapor
of h i g h p u r i t y (> 99 mole % H C l ) ; t h i s i s r e c y c l e d t o t h e bottom
o f t h e i s o t o p i c exchange column. The l i q u i d from t h e concentra­
ted s t r i p p e r , having a c o n c e n t r a t i o n lower than t h e azeotrope,
passes t o an evaporator where t h e s a l t i s recovered f o r r e c y c l e
to t h e concentrated s t r i p p e r , and vapor i s produced which i s
subsequently s t r i p p e d t o produce two streams: a water stream
which i s washed before d i s c h a r g e , and an a z e o t r o p i c HC1/H 0
mixture. The l a t t e r , mixed w i t h incoming f r e s h water, i s f e d t o
the t o p o f t h e i s o t o p i c exchange column. Many v a r i a t i o n s o f t h e
above are probably f e a s i b l e ; our main p o i n t here i s t o i n d i c a t e
t h a t w h i l e t h e use o f hydrogen h a l i d e s i n t r o d u c e s c o m p l i c a t i o n s
i n the design o f the "back-end" o f t h e s e p a r a t i o n scheme, these
can be overcome.
2
Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch010
2
2
V.
Conclusion
O p t i c a l p r o d u c t i o n o f heavy water i s beginning t o r e c e i v e
s e r i o u s c o n s i d e r a t i o n . L a b o r a t o r y - s c a l e photochemical s e p a r a t i o n
of deuterium v i a d i s s o c i a t i o n o f deuterated formaldehyde (HDCO)to
y i e l d HD and CO has a l r e a d y been demonstrated i n t h e UV(3_) u s i n g
a s i n g l e photon, and i n t h e IR at 10.6 microns u s i n g multi-photon
a b s o r p t i o n (kO). To be economically v i a b l e , t h e former process
awaits e f f i c i e n t low cost tunable u l t r a v i o l e t l a s e r s near 3^0 nm
(39,^9) w h i l e the l a t t e r process r e q u i r e s s i g n i f i c a n t improve­
ment i n photon u t i l i z a t i o n (^ 1 0 photons are p r e s e n t l y r e q u i r e d
per separated HD {kQ)). A l l photochemical deuterium enrichment
processes w i l l probably r e q u i r e deuterium o p t i c a l i s o t o p i c
s e l e c t i v i t y o f 1000-fold or b e t t e r f o r e f f i c i e n t photon u t i l i z a ­
t i o n (3£,^9), about an order o f magnitude higher than has been
demonstrated (3,^8).
The deuterium s e p a r a t i o n process j u s t presented proposes t o
u t i l i z e e x i s t i n g , e f f i c i e n t , h i g h average power CO l a s e r t e c h ­
nology t o promote deuterium h a l i d e a d d i t i o n i n t o unsaturated
hydrocarbons.
Spectroscopic s t u d i e s o f CO l a s e r s and deuterium
h a l i d e s have shown t h a t both DC1 and DBr can be s e q u e n t i a l l y
e x c i t e d by t h e CO l a s e r near 5-6 microns t o a t l e a s t the ν = 5
9
6
In Separation of Hydrogen Isotopes; Rae, H.;
ACS Symposium Series; American Chemical Society: Washington, DC, 1978.
Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch010
10.
MARLING E T A L .
Deuterium
Isotope
149
Separation
l e v e l , as summarized i n Tables I I and I I I . A d d i t i o n i n t o
unsaturated hydrocarbons should occur w i t h a c t i v a t i o n energies i n
the range of 15-^0 kcal/mole u s i n g HC1 or HBr as the working gas,
as i n d i c a t e d i n Table I . The e f f e c t i v e n e s s of hydrogen h a l i d e
v i b r a t i o n a l energy toward l o w e r i n g the a d d i t i o n r e a c t i o n a c t i v a t i o n b a r r i e r is not known, but probably l i e s i n the range of
30-100%, suggesting t h a t perhaps 5-8 quanta of DX v i b r a t i o n a l
e x c i t a t i o n w i l l be r e q u i r e d f o r u s e f u l l y f a s t r e a c t i o n t o occur.
Two s i g n i f i c a n t problems t o be r e s o l v e d are photon l o s s by o l e f i n combination band absorption i n the 5 - 6 micron r e g i o n and
p o t e n t i a l l y low r e a c t i o n quantum y i e l d s due t o non-reactive
v i b r a t i o n a l quenching by the o l e f i n . These problems appear
s o l v a b l e by s u i t a b l e o l e f i n s t r u c t u r a l design.
The problems a t
the "back-end" of t h e s e p a r a t i o n c y c l e , s p e c i f i c a l l y the
breaking of the HX/H 0 azeotrope, a l s o appear s o l v a b l e . Research
c u r r e n t l y underway w i l l examine the e f f e c t i v e n e s s of v i b r a t i o n a l
c a t a l y s i s on the r e a c t i o n r a t e and r e a c t i o n quantum y i e l d as a
f u n c t i o n of o l e f i n s t r u c t u r e .
2
Acknowledgement
One of the authors (M.M.M.) would l i k e t o thank
M. Benedict and J. E. V i v i a n f o r h e l p f u l d i s c u s s i o n .
Professors
Abstract
The feasibility of a gas phase deuterium s e p a r a t i o n process
is examined which would use IR l a s e r s t o augment a d d i t i o n re­
actions between HX (X = Br, Cl, F , OH) and unsaturated hydro­
carbons. High
vibrational
levels
(V ≥ 4) of DF or HDO may be
e x c i t e d by a p u l s e d DF laser. S i m i l a r h i g h
vibrational
excitation
of DCl o r DBr may be achieved by a p u l s e d CO laser and s p e c t r o ­
scopic d e t a i l s f o r excitation up t o V = 5 are examined. The
thermal r e a c t i o n between HX and unsaturated hydrocarbons is
c h a r a c t e r i z e d by activation exergies between 15 and 57 k c a l / m o l e ,
depending on olefin s t r u c t u r e and choice of HX. The e f f e c t i v e n e s s
of HX/DX vibrational energy in l o w e r i n g the r e a c t i o n b a r r i e r is
d i s c u s s e d . Primary emphasis is g i v e n t o an overall deuterium
s e p a r a t i o n process utilizing HCl as a c l o s e d c y c l e working gas
w i t h aqueous phase r e d e u t e r a t i o n .
P r e f e r r e d olefin reagents are
i n d i c a t e d compatible w i t h CO laser e x c i t a t i o n of DCl at a wave­
l e n g t h of 4.9-5.3 m i c r o n .
Literature Cited
1.
2.
Letokhov, V . S . and Moore, C.B., Sov. J. Quant. E l e c t r o n
(1976) 6, 129 and 259.
Miller,
A . I. and Rae, H.K., Chemistry in Canada (1975), 27,
25.
We note t h a t ERDA's current
(April,
1977) p r i c e f o r
heavy water is $213/kg, a p r i c e i n c r e a s e due t o the
In Separation of Hydrogen Isotopes; Rae, H.;
ACS Symposium Series; American Chemical Society: Washington, DC, 1978.
150
3.
4.
Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch010
5.
6.
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8.
9.
10.
11.
12.
13.
14.
15.
16.
17.
18.
19.
20.
21.
22.
23.
SEPARATION OF HYDROGEN ISOTOPES
diseconomy of small s c a l e p r o d u c t i o n . N e v e r t h e l e s s , a heavy
water cost of approximately $200/kg f o r d e l i v e r y in 1980 is
probably a conservative estimate.
The possibility of deuterium separation
via
photopredissociation of formaldehyde has been demonstrated by J. B . M a r l i n g .
See J. B . M a r l i n g , "Laser Isotope Separation of Deuterium,"
Chem. Phys. Lett., (1974) 34, 84, and "Isotope Separation of
Oxygen-17, Oxygen-18, Carbon-13, and Deuterium by Ion Laser
Induced Formaldehyde P h o t o p r e d i s s o c i a t i o n , " J. Chem. Phys.
(1977) 66, 4200.
Benson, S. W., and Bose, A . N., J. Chem. Phys. (1963), 39
3463.
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Tschuikow-Roux, Ε., and Maltman, F . R., I n t . J. Chem. Kin.
(1975), Vol. VII, 363.
Benson, S. W., and O ' N e a l , Η. Ε., " K i n e t i c Data on Gas Phase
Unimolecular R e a c t i o n s , " (1970), NSRDS-NBS 21.
Kubota, Η . , Rev. Phys. Chem., Japan (1967) 37, 25, and (1967)
37, 32.
Harding, C. J., M a c c o l l , Α., and Ross, R. Α., J. Chem. Soc. B,
(1969), 634.
Egger, K. W . , and Benson, S. W., J. Phys. Chem. (1967), 71,
1933.
Boness, M. J. W . , and Center, R. E., J. A p p l . Phys. (1977), 48,
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Quant. E l e c t r o n . (1973), 2, 305.
Todd, T. R., C l a y t o n , C. Μ . , Telfair, W. Β., McCubbin, Τ. Κ . ,
Jr., and Pliva, J., J. M o l . Spect. (1976), 62, 201.
Ross, A . H . M., Eng, R. S., and Kildal, Η . , Opt. Comm. (1974),
12, 433.
Rank, D. Η . , Eastman, D. P., Rao, B . S., and Wiggins, Τ. Α.,
J. Opt. Soc. Am. (1962), 52, 1.
Dunham, J. L., Phys. Rev. (1932), 41, 721.
Townes, C. Η . , and Shawlow, A . L., "Microwave Spectroscopy,"
p. 644, McGraw-Hill Brook Company, Inc., New York, New York
(1955).
Keller, F . L., and N i e l s e n , A . H., J. Chem. Phys. (1954), 22,
294.
Rank, D. Η . , F i n k , Uwe, and Wiggins, Τ. Α., J. M o l . Spect.
(1965), 18, 170.
Bernage, P., N i a y , P., Bockuet, Η . , and Houdart, R., Revue de
Phys. A p p l . (1973), 8, 333.
Mould, Η. Μ., Price, W. C., and W i l k i n s o n , G. R., S p e c t r o chimica A c t a (1960), 16, 479.
James, T. C., and T h i b a u l t , R. J., J. Chem. Phys. (1964), 40,
534.
Babrov, H. J., J. Chem. Phys. (1964), 40, 831.
B e n e d i c t , W. S., Herman, R., and S i l v e r m a n , S., J. Chem. Phys.
(1957), 26, 1671.
In Separation of Hydrogen Isotopes; Rae, H.;
ACS Symposium Series; American Chemical Society: Washington, DC, 1978.
10.
MARLING ET AL.
Deuterium
Isotope
24. Smith, F. G., J. Quant. Spectrosc. R a d i a t . T r a n s f e r
13,
25.
151
Separation
(1973),
717.
26.
Rasmussen, R.S.,and Brattain, R. R., J. Chem. Phys. ( 1 9 4 7 ) ,
120 and 131.
Gallinella, Ε., F o r t u n a t o , Β., and Mirone, P., J. Mol. Spect.
27.
28.
DiLauro, C., and Neto, N., J. Mol. S t r u c t u r e ( 1 9 6 9 ) , 3, 219.
Chen, M. Y.-D., and Chen, H. -L., J. Chem. Phys. ( 1 9 7 2 ) ,
29.
Weitz, Ε., and F l y n n , G., Ann. Rev. Phys. Chem. ( 1 9 7 4 ) , 25,
15,
(1967),
56,
24, 345.
3315.
275.
30. Hopkins, Β. M., and Chen, H. -L., J. Chem. Phys. ( 1 9 7 3 ) , 5 9 ,
1495.
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31.
Zittel,
P. F., and Moore, C. B.,J.Chem. Phys. ( 1 9 7 3 ) ,
58,
2004.
32. Birely, J. H., and Lyman, J. L., J. Photochem. ( 1 9 7 5 ) , 4, 2 6 9 .
33. Zittel, P. F., and Moore, C. B., J. Chem. Phys. ( 1 9 7 3 ) , 5 8 ,
2922.
34. Moore, C. Β., private communication.
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36.
26,
(1957),
370.
N i e l s o n , J. R., C l a s s e n , H. H., and Smith, D. C., J. Chem.
Phys. ( 1 9 5 0 ) , 1 8 , 485 and 8 1 2 ; ibid ( 1 9 5 2 ) , 2 0 , 1 9 1 6 .
37. C l a y t o n , J. W., Jr., Fluorine Chem. Rev. ( 1 9 6 7 ) , 1, 197.
38. B e r r y , M. J., paper presented a t t h e T h i r d Winter Colloquium
on Laser Induced Chemistry, Park City, Utah, Feb. 14-16, 1977.
39. M a r l i n g , J. Β., Wood, L. L., and Daugherty, J. D., "The LaserR e l a t e d Costs of Some Approaches to Laser Isotope S e p a r a t i o n
of Deuterium," Univ. Calif. Lawrence Livermore Laboratory
I n t e r n a l Document, Feb., 1977.
40. Arnoldi, D., Kaufmann, Κ., and Wolfrum, J., Phys. Rev. L e t t .
(1975),
34, 1 5 9 7 .
41. See, e.g., L e v i n e , R. D., and Manz, J., J. Chem. Phys.
63,
(1975),
4280.
42.
B e r r y , M. J., J. Chem. Phys. (1974), 61, 3114, and r e f e r e n c e s
cited t h e r e i n .
43. B e n e d i c t , Μ., and Pigford, Τ. Η., "Nuclear Chemical Engineer­
i n g , " p. 454, Table II-9, McGraw-Hill, New York, New York
(1957).
44. For HCl/H O the constant boiling mixture is 11.13 mole%HCl.
It boils at 108.5°C under a pressure of one atmosphere.
45. Ohe, S., Japan Chem. Quart. ( 1 9 6 9 ) , 4, 2 0 .
46. Chu, J u Chin, e tal.,"Vapor L i q u i d E q u i l i b r i u m Data," 2nd
Edition,
p. 6 3 9 , Edwards, Ann Arbor ( 1 9 5 6 ) .
47. A d e t a i l e d f l o w sheet is a v a i l a b l e from one of the authors
(M.M.M.).
48. Koren, G., Oppenheim,P.,Tal,D., Okon, Μ., and W e i l , R.,
A p p l . Phys. L e t t . ( 1 9 7 6 ) , 2 9 , 40.
49. Vanderleeden, J. C., "Laser S e p a r a t i o n of Deuterium," Laser
Focus (June, 1 9 7 7 ) , 1 3 , 51.
2
RECEIVED September 12, 1977
In Separation of Hydrogen Isotopes; Rae, H.;
ACS Symposium Series; American Chemical Society: Washington, DC, 1978.
11
Proposed H / D / T Separations Based on Laser-Augmented
A + B = C Reactions
S. H . BAUER
Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch011
Department of Chemistry, Cornell University, Ithaca, NY 14853
The separationofH/D/T by laser photolysisofselected congeners
in the infrared does not require high spectral resolution but does depend
on the retentionofselective excitation and rapid reactionofthe species
which initially absorb the photolyzing radiation. Except for the vibra­
tion augmentationofthree center abstraction reactions
[A + B*C — AB + C], all isotope fractionations achieved to date involving
polyatomics are based on fragmentationofthe irradiated species by co­
herent absorption of a large numberofphotons under essentially colli­
sion free conditions, to excited states considerably above the critical
level for dissociation. A thermodynamic and kinetic analysis, which
constitutes the first partofthis report indicates that the inverse process
i.e. the bimolecular association should also be isotopically selective.
In the second partofthis report several specific cases are proposed for
testing this concept. The emphasis hereison chemical properties, not
on spectroscopy, sinceitappears that the required irradiating frequen­
cies are either available now or shortly will be from sufficiently power­
ful lasers. All the systems considered are presumed to beinthe gas
phase at pressures sufficiently low such that individually each species
behaves ideally. Whileinsome respects the analysis appears elemen­
tary,itisbasic and merits formulation in a consistent manner.
Thermodynamic and Kinetic Relations
Consider the direct synthesisofan adduct:
A + Β < " >.
C
(M)
v
(1)
C
Reference to Figure 1 provides definitionsofthe conventional symbols
used. For a system whichisinstatistical equilibrium N^. ( E , T)
represent a normalized Boltzmann distributionofpopulationsofthe
reactants; the hashed levels represent the weighted mean energies of
B
©
0-8412-0420-9/78/47-068-152$05.00/0
In Separation of Hydrogen Isotopes; Rae, H.;
ACS Symposium Series; American Chemical Society: Washington, DC, 1978.
11.
BAUER
Proposed
H/D/T
153
Separations
the reactants, transition state, and products. The zero of energy for
each species, per convention, is measured from the corresponding zeropoint level. Thus,
00
Δ
Τ =
Ε
Δ
Ε
ο
JΟ
+
00
E
< '
A; Β A; Β
Ε
N
"J
T) d E
ΔΗ° = (ΔΕ° - RT) < 0
;
E
N
C
ο
( E
C
'
T ) d E
( 2 )
Δβ° < 0
Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch011
These are thermodynamically favored reactions.
K
p,eq
'
Ρ
=
4
?V
μ
}
Α Ί
=
E
eq
"
L
E
X
P { - | A S ° | /
R
|ΔΕ°|/ΚΤ}
+
1
(«»)
-1 \
= (RT) — ·
X
2
—
-1
3 -1
The units of κ-^ and ^
* molecule cm s .
Clearly, on raising the
temperature, i.e. for T^ > T,both distribution functions get steeper and
eq( l> eq< >For a system which is in statistical equilibrium at the temperature
T, except for a steady burning of a hole at level Eg and maintenance of
an overpopulation at E ^ , most of the reactant populations are unchanged,
Figure 2. The magnitude of the second term in the right member of (2)
is obviously increased and K^(T) is greater than Kp q(T). The reverse
applies when the hole in the population is burned at fe and the over­
population established at Ε . These qualitative relations apply inde­
pendentlyofthe magnitude of E , which can be positive or zero. For
example, the steady state irradiation of a mixture of B(CH3>3 and N H
with a C O 2 laser should increase the magnitude of the "perturbed equili­
brium constant" for the reaction (1),
a
K
T
<K
r
e
n
T
e
p
σ
a
3
NH* + B ( C H )
3
3
* (CH ) B:NH
3
3
AR°
3
QQ
=
-14.2 kcal/mole
(unirradiated)
even though the adduct is presumed to be generated without an activation
energy. A similar argument applies to the adsorption of gases onto a
solid surface, where the amount adsorbed under steady state irradiation
should increase when either the adsorber or the adsorbate undergo a
resonant transition which is matched by the irradiating frequency. Here,
the equivalent of the condition κ Ι Μ
ι * P i d intrasurface-layer
vibrational relaxation.
2
>
κ
s
r a
In Separation of Hydrogen Isotopes; Rae, H.;
ACS Symposium Series; American Chemical Society: Washington, DC, 1978.
Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch011
SEPARATION OF HYDROGEN ISOTOPES
Figure 2. Change in population distribution at steady state because of
pumping by β -> « = (E — Ε )/1ι or + = (Ε — E )/h, assuming
the statistical temperature remains at Τ
a
β
Vp
σ
σ
p
In Separation of Hydrogen Isotopes; Rae, H.;
ACS Symposium Series; American Chemical Society: Washington, DC, 1978.
11.
BAUER
Proposed H/D/T
155
Separations
The kinetic formulation provides addition details for the above
analysis. To eliminate the dependence on [M] we must stipulate that
X2ÎM] > κ ^ . Then the unidirectional rate of production of from the
reagent is determined by the product of the individual state densities and
the cross sections for association:
j)
P
(i) (J)
A B
at stat.
equil. *
P
Γ A B
&
/
&
V
E
° A , BL
lQ
Q: e x p v - " k F ~ ) J
o 7- o
A
(4)
B M
B
P
A B
P
i,3
-1
with
Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch011
-1
r ψ « ι/L ( 1 +
(5)
skT /
where s is the equivalent number of classical oscillators assigned to the
transition state (C*) and,
ν* = Π u . ( Π
+
C
1=1
ι \j i
=
ν* )
3 /
Similar expressions apply to the second step in the conversion. Hence
for a system at steady state, with a hole burned at E and overpopulated
Q
se Β
ρ ' is the molecular density at Eg at statistical equilibrium. Because
the perturbed system is generated by direct pumping, the increments in
densities at a and 3 are equal but of opposite sign; however,
< κ£°^
and (R^-R^) > 0. The net rate (fà^-ift.j) is larger than ( ^ - i ^ ) since the
reverse rate is minimally affected by pumping β — a; recall Ή^[Μ.] > κ ^ .
Note that the sign of the increment in the unidirectional flux is determined
by the perturbed population, again, irrespective of the magnitude of E .
However, the size of the increment depends on (κ^-κ^) which is small
when Eg > E (2).
Clearly, to maintain the spiked distribution at the steady state, with­
out allowing the system temperature to rise indefinitely, one must
continually remove as much energy as is pumped into it by radiation.
Imagine that the reactants and the reactor s walls are initially at a uni­
form temperature, T < T . Upon turning on the radiation there will be
a transient condition wherein, on a time scale of T(vib)
(transi), the
reactant temperature rises, but on a longer time scale ( T ) it levels off,
due to conduction and convection, to the operating temperature Τ which
a
R
T
Q
r
In Separation of Hydrogen Isotopes; Rae, H.;
ACS Symposium Series; American Chemical Society: Washington, DC, 1978.
156
SEPARATION OF HYDROGEN ISOTOPES
is determined by the rate of heat transfer to the walls, maintained at Τ .
Thus the gas temperature tends toward, but does not attain a uniform
distribution (3). The steady state populationinlevel a is established by
the balance between the pumping rate and the combined loss by relaxation
and reaction. The efficiency of any LIS will be determined by the
selectivity and intensity of pumping (β — a) and limited by v(i)
v(3)
transfer efficiencies among the congeners, as well as by ν —• R, Τ pro­
cesses which raise the operating temperature.
Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch011
Classification of Adduct Production
To select suitable systems for isotope separations based on the above
relations a broad range of criteria must be considered, but the principal
step is to find conditions under which laser radiation does augment the
rate of adduct production. In many cases the apparently simple reaction
indicated in Eq. (1) proves to follow a much more complex mechanism.
Toward this end it is useful to compile proposed reactions according to
the magnitudes of their activation energies (E ). Values of (30-40)
kcal/mole are typical for the additionofmineral acids, water and hydro­
gen sulfide to olefins (4); these are the inverse of (α, β) eliminations.
The additionofmineral acids or water to aldehydes and ketones require
(12-18) kcal/mole. Also the additionofHBr and HI to conjugated dienes
are in this group. Lewis acid-base adducts and hydrogen bonded com­
plexes are generated with little or no activation energy (0-5 kcal/mole).
A small sub-s et of the first group which is the largest and the most
extensively investigated, is the addition of HF to H C = C F and other
variously substituted fluoroethylenes, illustrated in Figure 3. Many
lower activation energy pairs in this category are cited by Marling (5).
Numerical values for the pertinent energy parameters for the HF/ethylene
additions are listed in Table I. The estimated lowest activation energy is
that for H F / C F ^ . Indeed, one may anticipate that excitation of H F
would accelerate its addition across the double bondinview of the ob­
served vibrationally excited HF generated from mixtures of C H 3 and CF^
radicals. However, it appears (6) that of the 72 kcal/mole which the
a
2
2
2
level], about 30 kcal/mole are statistically distributed prior to H F *
elimination. Hence the application of detailed balance suggest that
C H F ^ excitation may be just as essential as that of the H F to promote
significant enhancement of the rate. Indeed we reached that conclusion
after obtaining negative results by simply exposing mixtures of HF and
various olefins to a pulsed HF laser with the cell at room temperature
(Table H). Thus, the conditions outlinedinthe preceeding section are
necessary but not sufficient, particularly for combinations which consist
of a sizeable polyatomic acceptor and a strongly bonded intruder (HF;
2
n
n
In Separation of Hydrogen Isotopes; Rae, H.;
ACS Symposium Series; American Chemical Society: Washington, DC, 1978.
11.
BAUER
Proposed
H/D/T
TABLE I.
HF/Ethylene
x
-1
kcal mol
57
11
31
46
-93
62
24
33
38
CH FCH F
89.6
62
10
28
52
CH CF
99
69
27
30
42
92
71
-28
21
43
91
69
-26
22
43
94
72
-40
22
31
2
2
3
Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch011
2
e
kcal mol
kcal mol
88
2
3
Ε
kcal mol * kcal mol
CH CH F
CH CHF
Values of Parameters for Figure 3
D(C-C)
Adduct
3
157
Separations
3
CH FCF
2
3
CHF CHF
2
CHF CF
2
2
3
T A B L E II. Attempts to Augment HF Addition
HF laser operation: pulsed, 2/s; & 150 mj/p
ο
p(HF)/p(substrate):
3/1 to 1/3; 10 pulses
P(HF) = 0.5 torr; cell temp
f\
/TTT.v
c
n
±
^
Γ
25°
^
C
(low
^
T)
Mass spectral analysis for products
Compounds tested, no reaction with H F *
C F
2
<*,h); C H = C F (H); H ^ - C H - C O O E t (h)
4
2
2
C H - c p d (h); C H -allene (ft); H CC=CH (*)
5
6
3
6
3
c - C H O (h); c - C H 0
4
g
4
6
2
(h); COC^ (*,h)
2
SiH (h); C D (h); HC£CF (h)
4
HF
4
2
reacts with the following, on mixing
;
Ο
H C=CO
1
H C=CH* OCH
0
Q
\
Ο
In Separation of Hydrogen Isotopes; Rae, H.;
ACS Symposium Series; American Chemical Society: Washington, DC, 1978.
158
SEPARATION OF HYDROGEN ISOTOPES
H 0 ; CHgOH). Then vibrational activation of the acceptor is probably
essential for significant augmentation of the rate of addition across the
double bond.
An interesting combination of reagents which is related to, but is
not strictly a member of, the first category involves an (a, a) elimi­
nation of DCS. from OC&C F . This is diagramed in Figure 4 and conceived as
a by-pass attached to a polyfluoroethylene production plant (7).
There are relatively few members of the second group of addition
reactions. Also only sparse data are available on their thermochemistry
and kinetic behavior. We looked for combinations which fitted the
following criteria as closely as possible:
(a) One or both of the combining reagents (if one uses two irradiation
frequencies) should have strong ir absorption bands in the region of
currently developed, high powered lasers.
(b) The thermal recombination rate should be limited by an activation
energy which
equals the equivalent of a few photons of the#irradiating frequency, such that addition of DX* would be favored strongly
over HX.
(c) The adduct can be separated from the mixture rapidly enough to
avoid H/D exchange with the residual X H .
(d) The system is scalable for large throughput. This implies that the
H/D carrier can be readily equilibrated with a natural source of
deuterium (natural gas or water).
We found several combinations which satisfy criteria (a) and (b) and thus
constitute good candidates for laser augmented rate trials, but as yet no
such tests have been made. The equilibrium constants at room temper­
ature for the addition of HF to tetrahydrofurane [C^HgO] is substantial
(1.1 χ 10 , M " ) ; addition to dimethylformamide [Me NCHO] is even
larger, 4. 6 χ 10** M * ; however, no kinetic data are available. It has
been reported that perfluorocyclobutanon [ C 4 F 4 O ] readily adds H F but
only qualitative observations have been mde. We selected for our initial
experiments the production of gaseous hydrates of perfluoroacetone and
trifluoroacetaldehyde. Their infrared spectra are shown in Figures 5
and 6, respectively. These compounds do satisfy criterion (a). Several
rates of hydration and of decomposition of the adducts were measured (8)
to check whether these comply with criterion (b).
2
Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch011
2
3
1
2
-
For:
H
F.C-CHO + H O
* -,
> FC-CH(OH)
Q
a
In Separation of Hydrogen Isotopes; Rae, H.;
ACS Symposium Series; American Chemical Society: Washington, DC, 1978.
BAUER
Proposed
H/D/T
Separations
H3C+CF3 ^ = = :
Radicals
by
generated
Photolysis
F
3
of
C ^
H Ç = ÇF
2
-HF(4)
2
H--F
D(C-C)
— HF(3)
Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch011
—
HF(2)
-HF(I)
H C = CF +
2
ΙΛΠ
HF(0)
-r
L
H3C-CF3
Figure 3.
2
Energy level diagram for
pairs
HF/ethylene
ν selected
to d e c o m p o s e
D C I C F 2 but not H C I C F 2
HF—η
CHCI -4
3
[CDCI j^
3
PHOTOLYTIC
C F
CELL
2
4
STRIPPER
Figure 4. Flow chart for selective laser photolysis of DCICF to generate
DCl from natural abundance of D in chloroform, incorporated in a perfiuoroethylene plant. Based on the total annual C>F production (USA), an
optimum yield of 400 tons of D 0 could be developed. Recirculation of
CF
F
F , and F
to generate larger supplies of chloroform (via HCl)
would be energy intensive.
2
h
2
2
h
lï}
12
23
In Separation of Hydrogen Isotopes; Rae, H.;
ACS Symposium Series; American Chemical Society: Washington, DC, 1978.
SEPARATION OF HYDROGEN ISOTOPES
Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch011
fui W
Figure 5.
IR transmission spectra of perfiuoroacetone, its mono-and hemihy drat es
6
7
8
9
10
12
15
WAVELENGTH
Figure 6.
IR transmission spectra of trifluoroacetaldehyde and its monohydrate
In Separation of Hydrogen Isotopes; Rae, H.;
ACS Symposium Series; American Chemical Society: Washington, DC, 1978.
11.
BAUER
k
k
a
d
Proposed
2
3
S
1
Ε
(77°C) = 6.23 χ 10~
s"
1
3
(137°C) = 3.75 χ 10~
s"
1
3
a
1
4
(F C) CO
k
161
Separations
(75°C) - 1.3 χ 10 mole c m
For:
Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch011
H/D/T
2
+
Ε
H 0
a
d
= 19 ± 3 kcal/mole
= 29.2 ± 1 kcal/mole
(F C) C(OH)
2
3
(25°C) = 1.5 χ 10 mole c m s
3
1
3
2
2
1
Measurement of laser augmented rates will be made after our low
pressure intracavity reactor (9) has been modified to minimize adsorp­
tion of these reagents on the cell walls.
We anticipate that the rates of adduct production in the third
category, characterized by very low activation energies, would be
slightly if at all augmented by laser irradiation of the precursors but the
"perturbed equilibrium" composition of the adduct (at steady state,
Figure 2) should be reduced upon its irradiation. Conceptually this can
be utilized for an H/D separation in the following scheme, wherein the
particular Lewis acid and base shown are examples selected from a large
class of possible combinations (1) :
Β Me
k
< " >
+ MeNH
ο
Δ
GaEt + MeNH
3
2
0
κ
<
t
Me B:NH Me
S
>
k
2
2
Δ
Et Ga NH Me
3
2
:
ΔΗ°
=-18.2 kcal/mole
oUU
= -19.8
Whereas both k^ and ko are presumed to be large (?^10 mole c m s
and temperature insensitive, the reverse steps are much slower since
and k have Arrhenius exponential factors with (-18.2/RT) and
(-19.9/RT), respectively. Thus, were an equilibrium mixture of
methylamine, the two Lewis acids, and the corresponding adducts in
equilibrium, exposed to radiation which is selectively absorbed by
EtgGa:NHDMe, the deuterium would be selectively trapped as
MegBHDMe, possibly for a sufficient time to achieve separation. Other
means for trapping laser shifted concentrations of dissociation products
are conceivable. For example, the irradiation of matrix isolated
samples followed by adjusted diffusion rates of the products (careful
12
2
In Separation of Hydrogen Isotopes; Rae, H.;
ACS Symposium Series; American Chemical Society: Washington, DC, 1978.
1
3
162
SEPARATION O F HYDROGEN ISOTOPES
temperature control) but these applications appear of little practical
utility.
Abstract
Thermodynamic and kinetic analyses of adduct production:
Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch011
indicate how the steady state composition and rates (forward vs reverse) can be perturbed by absorbable
radiation which generates a "spiked" steady state population distribution
for one of the species.
Three classes of reactions were considered,
wherein E ranges from (30-40) kcal/mole; (12-16) kcal/mole; and
(0-5) kcal/mole. These are of particular interest for H/D/T
separation, in that one of the adducts can be water, a mineral acid
(which rapidly equilibrates with water) or hydrogen. Our analysis
and preliminary experiments indicate that the intermediate case
( E ~ 15 kcal/mole) is particularly attractive for LIS.
a
a
Literature Cited
1.
2.
3.
4.
5.
6.
7.
8.
9.
Drago, R. S., Vogel, G. C. and Needham, T . E., J. Am. Chem.
Soc (1971) 93, 6014, have compiled extensive tables of enthalpies
for adduct formation.
Levine, R. D. and Manz, J., J. Chem. Phys. (1975) 63, 4280.
Shaub, W. and Bauer, S. Η . , Int. J. Chem. Kin. (1975) 7, 509.
Tschuikow-Roux, E . and Maltman, Κ. A., Int. J. Chem. Kin.
(1975) 7, 363, have compiled extensive tables for the inverse
processes.
Marling, J. Β., Joint Conference CIC and ACS, Montreal, 1977,
Physical Chemistry Division, Abst. 081.
Clough, P. N., Polanyi, J. C. and Tagudu, R. Τ., Can. J. Chem.
(1970) 48, 2919.
Data from Petrochemical Handbood, 1976.
Bell, R. P. and McDougall, Α. Ο . , Trans. Farad. Soc. (1960) 56,
1285 give useful data on hydration equilibria of aldehydes and
ketones.
My sincere thanks to Dr. Kuei-Ru Chien for performing measure­
ments on the perfluoro compounds.
Lory, E . R . , Manuccia, T . and Bauer, S. H., J. Phys. Chem.
(1975) 79, 545.
RECEIVED
August 31, 1977
In Separation of Hydrogen Isotopes; Rae, H.;
ACS Symposium Series; American Chemical Society: Washington, DC, 1978.
12
Operating Experience with the Tritium and Hydrogen
Extraction Plant at the Laue—Langevin Institute
PH.
PAUTROT
Institute Max Von Laue-Paul Langevin, 38000, Grenoble, France
M. DAMIANI
Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch012
Sulzer Brothers L t d . , Dept. 6162, CH-8401 Winterthur, Switzerland
The I n s t i t u t e Max Von LAUE - P a u l LANGEVIN in
GRENOBLE is a s o c i e t y founded in 1967 by a government
agreement between FRANCE and GERMANY.
In 1974 GREAT
BRITAIN a l s o j o i n e d the I n s t i t u t e .
The I n s t i t u t e o p e r a t e s the High F l u x R e a c t o r
whose purpose is a l a r g e programme of n u c l e a r p h y s i c s
r e s e a r c h u s i n g the n e u t r o n s produced by the r e a c t o r .
T h i s High F l u x R e a c t o r has a t h e r m a l performance
of 57 MW w i t h a s i n g l e heavy water c o o l e d and moderated
circuit.
Heavy water h o l d - u p is about 40 m . The
mean f l u x of t h e r m a l n e u t r o n s in the heavy water is
e q u a l t o 1,8 .
10
n / c m s e c , which l e a d s t o f o r m a t i o n
of tritium w i t h a s a t u r a t i o n activity of more than
80 C u r i e per
litre
( a f t e r 10 y e a r s about 30
Curie/1).
T h i s is s i m i l a r t o the v a l u e e x p e c t e d in the moderator
circuit
of
the CANDU type r e a c t o r .
For s a f e t y r e a s o n s ,
tritium
c o n c e n t r a t i o n in
heavy water s h o u l d not exceed 3 C u r i e per litre and in
o r d e r t o m a i n t a i n moderator
efficiency
of
heavy w a t e r ,
its
fractional
c o n c e n t r a t i o n s h o u l d not be lower than
99,6 mol %. The
installation
fulfilling
the mentioned
d u t i e s was built by CCM/SULZER* in c l o s e c o - o p e r a t i o n
w i t h the
C.E.A.
(Commissariat ā l'Energie A t o m i q u e ) .
SULZER a l r e a d y had e x p e r i e n c e in the low temperature
distillation
of
hydrogen from a s m a l l heavy water
p l a n t in EMS S w i t z e r l a n d .
The
installation
a t the LAUE-LANGEVIN I n s t i t u t e
on the Grenoble N u c l e a r C e n t r e site is the
first
known
p l a n t in o p e r a t i o n f o r the s i m u l t a n e o u s e x t r a c t i o n of
hydrogen and tritium from heavy w a t e r .
3
14
*
is L i c e n s e e
process
of
©
2
a patent
owned by the CEA for t h i s
0-8412-0420-9/78/47-068-163$05.00/0
In Separation of Hydrogen Isotopes; Rae, H.;
ACS Symposium Series; American Chemical Society: Washington, DC, 1978.
164
SEPARATION OF HYDROGEN ISOTOPES
Design Data.
- T r i t i u m c o n c e n t r a t i o n of heavy
water has t o be s t a b i l i z e d a t 1,7 C i / 1 by an annual
e x t r a c t i o n of 160 000 C u r i e , e q u i v a l e n t t o about
60 N l of pure t r i t i u m .
- C o n t e n t of heavy water has t o be m a i n t a i n e d a t 99,6
mol % by an a n n u a l e x t r a c t i o n of 160 l i t r e s of l i g h t
water, e q u i v a l e n t t o about 2 00 Nm
of hydrogen.
3
Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch012
P r i n c i p l e of O p e r a t i o n . F i g u r e 1 shows the mass
f l o w s w i t h the c o r r e s p o n d i n g c o n t e n t s a t normal opera t i o n c o n d i t i o n s in 1976, and f u r t h e r m o r e , t h a t the
p l a n t is made up of two main p a r t s :
1.
C a t a l y t i c exchange between heavy water vapour and
d e u t e r i u m gas a t 200°C and about 1,2 b a r , which
a l l o w s the mass t r a n s f e r of hydrogen and t r i t i u m
from heavy water t o d e u t e r i u m t o r e a c h e q u i l i b r i u m
a c c o r d i n g t o the f o l l o w i n g r e a c t i o n s :
HDO
+ D2
D2O
+
HD
2.
Low temperature r e c t i f i c a t i o n of the hydrogen
i s o t o p e s HD/D2/DT/T2 a t about 1,5 bar in two
columns w i t h e x t r a c t i o n of HD a t the top of the
f i r s t column and pure t r i t i u m a t the bottom of the
second column.
The f l o w s h e e t F i g . 2 shows t h a t the heavy water
coming from the r e a c t o r is e v a p o r a t e d , s u p e r h e a t e d ,
and mixed w i t h the d e u t e r i u m t o pass through the c a t a l y t i c r e a c t o r where the i s o t o p i c exchange r e a c t i o n s
o c c u r ; it is then recondensed t o be s e p a r a t e d from
the d e u t e r i u m and t r a n s f e r r e d t o the second and then
t o the t h i r d s t a g e of the c a t a l y t i c exchange.
The d e u t e r i u m coming out of the c a t a l y t i c exchange
is d r i e d and p u r i f i e d b e f o r e b e i n g s e n t i n t o a d i s t i l l a t i o n column c o n t a i n i n g S u l z e r p a c k i n g s .
The p a r t i a l l y
t r i t i u m and hydrogen s t r i p p e d d e u t e r i u m coming out of
the column r e t u r n s t o the c a t a l y t i c exchange t h r o u g h
an e x p a n s i o n v e s s e l .
The d e u t e r i u m h y d r i d e drawn o f f
w i t h a c o n t e n t of about 80 mol % a t the head is s e n t
to a burner.
The t r i t i a t e d d e u t e r i u m a t the f o o t of
the column is s e n t t o a second column w i t h d i x o n r i n g
packing.
In the m i d d l e of t h i s column, DT is w i t h drawn in a tank t o g e t t r i t i u m a c c o r d i n g t o e q u i l i b r i u m
r e a c t i o n 2 DT <r ^ T 2 + D 2 . At the bottom of t h i s
column, pure t r i t i u m of about 9 8 mol % is drawn o f f
periodically.
In Separation of Hydrogen Isotopes; Rae, H.;
ACS Symposium Series; American Chemical Society: Washington, DC, 1978.
In Separation of Hydrogen Isotopes; Rae, H.;
ACS Symposium Series; American Chemical Society: Washington, DC, 1978.
D2
HDO +
2
D
+
DTO
= ^ ·
XHDO
10"'
+
D 0
HYDROGEN
TRITIUM
DEUTERIUM
2
+
2
Nm*.h
Nr^.h-
D 0
45
45
EXCHANGE
FLOW
OW
CATALYTIC
- 1.34.
XDTO
;
Ci I
2.15
ACTIVITY ;
2
D 0
21 I h "
;
FLOW
INPUT
1
2
D 0
HD
DT
Ι
J
M<^y
COMPRESSOR
(f^.
D
T
=
XHO=
X
XHD^9
XHO=0.01
11
0,69
1
0"
3
6
10-
10 "
XQJ ΖΟ,Μ 10 '
«02=0,996
2
5,6.ΙΟ­
10-
APPOINT D =2Nm /we*k
XH
3
Ci I -
X T O =. 0.3S
ACTIVITY ; 0.56
OUTPUT .
Figure 1
165 I h"'
COLUMN
θ 2
N°1
=0,8
=a2
CIRCULATOR
XHD
χ
=*0
6
10-
X Q T = 1β0.10"»
XQT
Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch012
T
X 2 = 0,9β
~ 2 Ν I /week
COLUMN N°2
STORAGE
-••"j DP AWING OFF
OF TRITIUM
S*
a
<?•+.
H
C*l
-*
ο
ft
>
>
3
ο
>
Ο
Η
Η
»
ο
>
SEPARATION O F HYDROGEN ISOTOPES
Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch012
166
In Separation of Hydrogen Isotopes; Rae, H.;
ACS Symposium Series; American Chemical Society: Washington, DC, 1978.
12.
PAUTROT AND DAMiANi
Tritium
and
Hydrogen
Extraction
Plant
167
R e f r i g e r a t i o n power r e q u i r e d t o l i q u i f y d e u t e r i u m
is o b t a i n e d by an a u x i l i a r y h e l i u m c i r c u i t .
Helium is
compressed t o 15 bar and then expanded t o 4 bar through
a gas expansion t u r b i n e w i t h o i l b e a r i n g s .
Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch012
P l a n t S a f e t y P r e c a u t i o n s . The r i s k s of e x p l o s i o n
and r a d i o a c t i v e c o n t a m i n a t i o n formed the b a s i c c r i t e r i a
f o r the d e s i g n , c o n s t r u c t i o n and o p e r a t i o n of the
installation.
Very s t r i c t measures were adopted:
1.
L o c a t i o n of the i n s t a l l a t i o n o u t s i d e of the r e a c t o r
but n o t in the open a i r . The e x t e r n a l w a l l s of the
b u i l d i n g are blowable t o an open a r e a t o l i m i t
e x p l o s i o n damage.
2.
C o n s t r u c t i o n of the p l a n t a c c o r d i n g t o
standards".
3.
C o n s t a n t v e n t i l a t i o n of the p r e m i s e s .
4.
C o n s t a n t t r i t i u m and d e u t e r i u m c o n t r o l of the
a t m o s p h e r i c a i r of the p r e m i s e s .
5.
Oxygen c o n t e n t in d e u t e r i u m c i r c u i t is permanently
r e g i s t e r e d a t the i n l e t t o the d i s t i l l a t i o n column
in o r d e r t o have an i n d i c a t i o n about the q u a n t i t y
of ozone which c o u l d be formed by β - r a d i a t i o n of
oxygen. Ozone in l i q u i d or s o l i d phase may decom­
pose in an e x p l o s i v e manner.
6.
In case of a l a r m from d e u t e r i u m o r t r i t i u m l e a k a g e ,
the p l a n t is stopped and i s o l a t e d in f i v e p a r t s .
Each of t h e s e can be e v a c u a t e d and r i n s e d auto­
m a t i c a l l y by n i t r o g e n b e f o r e r e p a i r works s t a r t .
7.
A two stage membrane compressor can draw o f f the
d e u t e r i u m hold-up and f i l l i n t o b o t t l e s under 200
bar.
8.
Some main alarms and a main s w i t c h are r e p e a t e d in
the main c o n t r o l p a n e l of the r e a c t o r .
"hydrogen
S t a r t - U p of the P l a n t and O p e r a t i n g E x p e r i e n c e
The f i r s t t e s t s w i t h hydrogen began in August 1971.
S t a r t - u p w i t h d e u t e r i u m and n o n t r i t i a t e d heavy water
f o l l o w e d q u i c k l y and s e p a r a t i o n performances between
hydrogen and d e u t e r i u m were c o n t r o l l e d .
I t was o n l y in
August 1972 t h a t the f i r s t i n t r o d u c t i o n of t r i t i a t e d
heavy water from the High F l u x R e a c t o r was t r e a t e d .
In Separation of Hydrogen Isotopes; Rae, H.;
ACS Symposium Series; American Chemical Society: Washington, DC, 1978.
Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch012
168
SEPARATION OF HYDROGEN ISOTOPES
By J u l y 19 73 the a c c u m u l a t i o n of t r i t i u m o n l y r e a c h e d
5 000 C u r i e . By the end of 1976 t h e r e was a t r i t i u m
hold-up of 220 000 C u r i e in the p l a n t and 230 000
l i t r e s of heavy water had been t r e a t e d .
About 85 000
C u r i e of pure t r i t i u m w i t h an average molar c o n t e n t of
98% had been e x t r a c t e d in gaseous phase.
S i n c e t r i t i u m p r o d u c t i o n of the r e a c t o r is about
35 % lower and the a d m i s s i b l e t r i t i u m c o n c e n t r a t i o n is
now about 10 % h i g h e r compared w i t h d e s i g n d a t a , and
f u r t h e r m o r e p l a n t performance c o u l d be i n c r e a s e d by
about 25 % by v a r i a t i o n of the r a t i o between heavy
water and d e u t e r i u m streams in the c a t a l y t i c exchange,
the p l a n t is a b l e t o f u l f i l r e a c t o r r e q u i r e m e n t s in
o n l y f i v e months per y e a r .
That means p l a n t o v e r c a p a c i t y a l l o w s the treatment of t r i t i a t e d water from
other r e a c t o r s .
The I n s t i t u t e has a l r e a d y t r e a t e d about 16 000 1
of heavy water w i t h a c o n c e n t r a t i o n of about 6 C u r i e
per l i t r e f o r a F r e n c h c l i e n t .
A t p r e s e n t , p l a n t performance r e a c h e s an e x t r a c t i o n of 240 000 C u r i e per y e a r s t a r t i n g from a f e e d
c o n c e n t r a t i o n of 2 C u r i e per l i t r e .
Tritium analysis
made on the r e c t i f i c a t i o n columns showed t h a t about
400 t h e o r e t i c a l s t a g e s are i n s t a l l e d .
S i n c e leakage of l i g h t water i n t o the heavy water
c i r c u i t is s m a l l e r than presumed, the heavy water molar
c o n t e n t has n o t reached 99,6 % up t o now, and conseq u e n t l y l i g h t water e x t r a c t i o n has been s m a l l e r than
160 l i t r e s per y e a r .
D i f f i c u l t i e s Encountered
During
Operation
C o n c e r n i n g the p r i n c i p a l r u n n i n g of t h i s p r o c e s s c a t a l y t i c exchange w i t h d e u t e r i u m r e c t i f i c a t i o n - no
p a r t i c u l a r d i f f i c u l t i e s have been encountered.
The main d i f f i c u l t i e s which o c c u r r e d d u r i n g opera t i o n were:
Two t e c h n o l o g i c a l i n c i d e n t s on the h e l i u m c i r c u i t ,
the major b e i n g an a c c i d e n t a l d i s p l a c e m e n t of the
m o l e c u l a r s i e v e , w i t h subsequent d i s t r i b u t i o n of i t s
c o n s t i t u e n t s through the whole h e l i u m c i r c u i t . T h i s
r e q u i r e d complete c l e a n i n g of the h e l i u m c i r c u i t ,
p a r t i c u l a r l y of the heat exchangers and caused a
p l a n t shutdown of s e v e r a l months.
The o t h e r i n c i d e n t was the p r e s e n c e of mud and
o r g a n i c a l g a e in the r i v e r water, which c l o g g e d the
h e l i u m water c o o l e r .
C h l o r i n a t i o n in the c o o l i n g
water k i l l e d o f f the a l g a e , but r e s u l t e d in c o r r o s i o n
In Separation of Hydrogen Isotopes; Rae, H.;
ACS Symposium Series; American Chemical Society: Washington, DC, 1978.
PAUTROT AND D A M i A N i
Tritium
and
Hydrogen
Extraction
Plant
169
Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch012
of the welds on the carbon s t e e l h e l i u m c o o l e r s , so
t h a t leakages of h e l i u m and i n g r e s s of water p r e ­
vented the r e q u i r e d r e f r i g e r a t i o n power b e i n g
reached.
F i n a l l y , new s t a i n l e s s s t e e l c o o l e r s and
a c l o s e d c o o l i n g water c i r c u i t were i n s t a l l e d t o
get s a t i s f a c t o r y c o n d i t i o n s .
The presence of alumina p a r t i c l e s in the heavy water
a r r i v i n g from the r e a c t o r s e r v e d as s u p p o r t f o r
a c t i v a t i o n p r o d u c t s - m a i n l y c o b a l t and chrome - and
r e s u l t e d in h i g h a c t i v i t y in the e n t r a n c e of the
c a t a l y t i c exchange.
The alumina p a r t i c l e s have a
s i z e of 0,01 t o 0, lM
and pass through e x i s t i n g
0,22 ΛΑ f i l t e r .
To p r e v e n t the presence of t h e s e
a c t i v a t e d alumina p a r t i c l e s in t r i t i u m e x t r a c t i o n
p l a n t , a supplementary s e p a r a t i o n p l a n t has been
i n s t a l l e d in the r e a c t o r . T h i s p l a n t was put i n t o
o p e r a t i o n s a t i s f a c t o r i l y some months ago.
F i s s u r e phenomena have appeared in the p i p i n g work
c o n t a i n i n g heavy water vapor a t the e n t r a n c e in the
f i r s t stage of c a t a l y t i c exchange. The o r i g i n of
t h e s e c o r r o s i o n s is not e x a c t l y known.
Different
e x p e r t s t h i n k t h a t these c o r r o s i o n s are due t o the
a c t i o n of m e c h a n i c a l f o r c e s , caused by v i b r a t i o n and
t h e r m a l e x p a n s i o n , a c t i n g in c o n j u n c t i o n w i t h a
c o r r o s i v e agent p r e s e n t in the heavy water.
This
agent may be c h l o r i n e .
However, t h i s f a c t is not
yet proved.
At the b e g i n n i n g n i t r o g e n was used as c o v e r gas in
the r e a c t o r .
N i t r o g e n d i s s o l v e d in heavy water
passed even through a c t i v a t e d c h a r c o a l a d s o r b e r and
was c o n c e n t r a t e d in the column e v a p o r a t o r r e d u c i n g
d e u t e r i u m vapor l o a d due t o d e t e r i o r a t i o n in heat
transfer.
Furthermore, a pH v a l u e of about 1 was
noted in the heavy water l e a v i n g the b u r n e r , caused
by n i t r i c a c i d formed due t o the presence of n i t r o ­
gen coming from the n i t r o g e n a d s o r b e r d u r i n g i t s
regeneration cycle.
These i n c o n v e n i e n c e s were
r e s o l v e d by r e p l a c i n g n i t r o g e n by h e l i u m as r e a c t o r
cover gas.
D u r i n g commissioning, d i f f e r e n t r e g u l a t i o n systems
c o u l d be improved but none of t h e s e improvements
r e s u l t e d from major problems.
A f t e r about 23 000 hours of o p e r a t i o n of the p l a n t ,
the e f f i c i e n c y of c a t a l y s t s has s t i l l n o t d e c r e a s e d .
In Separation of Hydrogen Isotopes; Rae, H.;
ACS Symposium Series; American Chemical Society: Washington, DC, 1978.
Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch012
170
SEPARATION OF HYDROGEN ISOTOPES
In t h e f o l l o w i n g I w i l l i n d i c a t e some o p e r a t i o n
conditions :
P l a n t o p e r a t i o n is semiautomatic. P e r s o n n e l a r e
r e q u i r e d t o c a r r y o u t v a r i o u s adjustments and mainten­
ance concerned w i t h t h e movement of heavy water and
r e g e n e r a t i o n of t h e a d s o r b e r s and c a r r y i n g o u t v a r i o u s
analyses.
D u r i n g working h o u r s , o p e r a t i o n is ensured
by f o u r p e r s o n s ; o u t s i d e working hours r e q u i r e d super­
v i s i o n is t r a n s f e r r e d t o t h e r e a c t o r main c o n t r o l room.
A t a s t o p , p l a n t goes a u t o m a t i c a l l y i n t o a s a f e t y p o s i ­
tion.
O p e r a t i o n of t h e p l a n t is c o n t i n u o u s , s t a r t up
l a s t s about 12 hours and another 3 o r 4 days a r e r e ­
q u i r e d t o reach steady s t a t e c o n d i t i o n s before t r e a t i n g
t r i t i a t e d heavy water.
The main consumptions a r e :
- Electricity
- C o o l i n g water
- Deuterium
- Compressed
air
800 KW
25 m /h
2 Nm /week a t todays
conditions
50 Nm /h
3
3
3
Hold-ups :
1 000 l i t r e s of
85 Nm
of
200 000 C i
of
35 Nm
of
3
3
Bibliography:
heavy water
deuterium
tritium
helium
(1) PAUTROT, P h . , ARNAULD, J.P.
American N u c l e a r S o c i e t y , (1975)
V o l 20, 202-205
(2) DAMIANI, M . , GETRAUD, R., SENN, Α.,
S u l z e r T e c h . Revue, (1972) V o l 4
RECEIVED August 22, 1977
In Separation of Hydrogen Isotopes; Rae, H.;
ACS Symposium Series; American Chemical Society: Washington, DC, 1978.
13
Catalytic Detritiation of Water
M. L. ROGERS, P. H . LAMBERGER, R. E . ELLIS, and T. K. MILLS
Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch013
Monsanto Research Corp., Mound Laboratory*, Miamisburg, O H 45342
Mound L a b o r a t o r y has, d u r i n g t h e p a s t f o u r y e a r s ,
been a c t i v e l y i n v o l v e d i n the development o f methods t o
c o n t a i n and c o n t r o l t r i t i u m d u r i n g i t s p r o c e s s i n g and t o
r e c o v e r i t from waste s t r e a m s . I n i t i a l b e n c h - s c a l e
r e s e a r c h was d i r e c t e d m a i n l y toward removal o f t r i t i u m
from gaseous e f f l u e n t s t r e a m s . The gaseous e f f l u e n t
i n v e s t i g a t i o n has p r o g r e s s e d t h r o u g h t h e development
s t a g e and has been implemented i n r o u t i n e o p e r a t i o n s .
A t e s t l a b o r a t o r y embodying many o f t h e r e s u l t s o f t h e
r e s e a r c h phase has been d e s i g n e d and i t s c o n s t r u c t i o n
has been completed.
As t h e program a t Mound L a b o r a t o r y has p r o g r e s s e d ,
the scope o f t h e e f f o r t has been expanded t o i n c l u d e
r e s e a r c h c o n c e r n e d w i t h h a n d l i n g t r i t i a t e d l i q u i d s as well.
A program i s p r e s e n t l y under way t o i n v e s t i g a t e
the d e t r i t i a t i o n o f aqueous wastes u s i n g the Combined
E l e c t r o l y s i s C a t a l y t i c Exchange (CECE) p r o c e s s , a p r o c e s s v e r y s i m i l a r t o the CECE-TRP p r o c e s s d i s c u s s e d a t
t h i s symposium by Dr. Hammerli.
As i n the CECE-TRP
p r o c e s s , the key t o o u r CECE p r o c e s s i s a p r e c i o u s m e t a l
h y d r o p h o b i c c a t a l y s t d e v e l o p e d by Dr. John B u t l e r a t
Chalk R i v e r .
Dr. B u t l e r , who d i s c u s s e d t h i s t y p e o f
c a t a l y s t e a r l i e r i n the symposium, made t h e c a t a l y s t f o r
our system.
Catalytic
Exchange
The c a t a l y t i c
c e n t e r s around two
arranged i n s e r i e s
and lower s e c t i o n s
exchange s e c t i o n o f the p r o c e s s
c a t a l y s t - p a c k e d columns, which a r e
t o o p e r a t e as i f they were t h e upper
o f a s i n g l e column.
(See F i g u r e 1.)
*Mound L a b o r a t o r y is o p e r a t e d by Monsanto R e s e a r c h
C o r p o r a t i o n f o r t h e U.S. Energy R e s e a r c h and Development
A d m i n i s t r a t i o n under C o n t r a c t No. EY-76-C-04-0053.
©
0-8412-0420-9/78/47-068-171$05.00/0
In Separation of Hydrogen Isotopes; Rae, H.;
ACS Symposium Series; American Chemical Society: Washington, DC, 1978.
SEPARATION
172
O F HYDROGEN ISOTOPES
Each column i s 7.5 m i n l e n g t h and has an i n s i d e diame t e r o f 2.5 cm, which r e s u l t s i n a s u p e r f i c i a l c r o s s s e c t i o n a l a r e a o f 5 cm
and a g r o s s column volume o f
3800 cm .
The p a c k i n g i n each column c o n s i s t s o f 4300
g o f 0.6-cm d i a m e t e r c a t a l y s t s p h e r e s . L i q u i d r e d i s t r i b u t i o n r i n g s a r e p l a c e d a t 45-cm i n t e r v a l s t h r o u g h out the l e n g t h o f each column t o l i m i t c h a n n e l i n g i n
the packed s e c t i o n s .
In o p e r a t i o n , the l i q u i d t o be d e t r i t i a t e d i s
s u p p l i e d a t a p p r o x i m a t e l y 5 cm /min.
I t i s combined
w i t h the l i q u i d stream e x i t i n g the upper column, and
i n t r o d u c e d a t the t o p o f the lower column. The 10
cm /
min l i q u i d stream from the bottom o f the lower column
i s r o u t e d t o the e l e c t r o l y s i s s e c t i o n o f the p r o c e s s
where i t i s used as f e e d .
C u r r e n t l y , the l i q u i d stream
e n t e r i n g a t the top o f the upper column i s made up o f
d i s t i l l e d water, s u p p l i e d from o u t s i d e the p r o c e s s .
U l t i m a t e l y , however, t h i s stream i s e x p e c t e d t o be a
r e f l u x stream, p r o v i d e d by a recombiner o r f u e l c e l l
which would i n t u r n be f e d by the hydrogen p r o d u c t from
the upper column.
The hydrogen stream from t h e e l e c t r o l y s i s s e c t i o n
i s f e d t o the bottom o f the lower column and t h e n i s
r o u t e d t o t h e bottom o f the upper column. Upon e x i t i n g
t h e upper column, i t i s c u r r e n t l y v e n t e d t o the a t mosphere t h r o u g h a s t a c k . As mentioned p r e v i o u s l y ,
however, i t i s a n t i c i p a t e d t h a t t h i s stream w i l l l a t e r
be f e d t o e i t h e r a f u e l c e l l o r a recombiner t o p r o v i d e
r e f l u x t o the p r o c e s s and a d e t r i t i a t e d l i q u i d p r o d u c t .
C o n t r o l o f the c a t a l y t i c exchange s e c t i o n o f the
p r o c e s s c o n s i s t s o f f i v e l o o p s , s e r v i c e d by a s i n g l e
microprocessor.
In each o f the l o o p s t h e c o n t r o l
element i s a m e t e r i n g v a l v e , d r i v e n by a s t e p p i n g
motor. F o r the gas stream p a s s i n g through the columns,
the s e n s i n g element i s a t u r b i n e meter l o c a t e d downstream from the columns.
The two l i q u i d f e e d s t o the
p r o c e s s are sensed by h o t - w i r e anemometers, and the
l e v e l s m a i n t a i n e d i n the bottom o f each column a r e
m o n i t o r e d by c a p a c i t i v e l e v e l s e n s o r s . A l t h o u g h not
used i n the c o n t r o l o f the p r o c e s s , t r i t i u m c o n c e n t r a t i o n s a r e m o n i t o r e d a t v a r i o u s p o i n t s by l i q u i d
s c i n t i l l a t i o n c o u n t e r s f o r l i q u i d streams and i o n
chambers f o r gas streams.
2
3
3
Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch013
3
Electrolysis
The p r i n c i p a l items o f equipment i n the e l e c t r o l y s i s s e c t i o n are f o u r G e n e r a l E l e c t r i c e l e c t r o l y s i s
stacks.
(See F i g u r e 2.)
Each s t a c k c o n s i s t s o f e i g h t
c e l l s , each o f which has an a c t i v e a r e a o f 46.45 cm .
In Separation of Hydrogen Isotopes; Rae, H.;
ACS Symposium Series; American Chemical Society: Washington, DC, 1978.
13.
ROGERS
E T
Catalytic
AL.
Detritiation
of
173
Water
DEPLETED
H TO STACK
2
DISTILLED
WATER
ENRICHED
H FROM
ELECTROLYSIS
Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch013
2
TRITIATED
LIQUID
FEED
ENRICHED
LIQUID T O
ELECTROLYSIS
Figure 1.
Catalytic exchange section
PHASE
SEPARATOR
ENRICHED
LIQUID
_
FROM
CATALYTIC
EXCHANGE
OXYGEN
TO EX­
HAUST
Ho TO
PHASE
SEPARATOR
ft
ι
I
I
ι
cb
-
DEIONIZER
\
|ELECTROLYSIS|
CELLS
Figure 2. Electrolysis section
In Separation of Hydrogen Isotopes; Rae, H.;
ACS Symposium Series; American Chemical Society: Washington, DC, 1978.
CATALYTIC
EXCHANGE
174
SEPARATION O F
HYDROGEN
ISOTOPES
C u r r e n t d e n s i t y i s 1.076 amp/cm f o r the maximum r a t e d
c u r r e n t o f 50 amps. Rated s t a c k v o l t a g e i s 16.8
VDC.
O p e r a t i n g a t t h e s e c o n d i t i o n s , each s t a c k e l e c t r o l y z e s
2.45 cm
water/min t o produce a p p r o x i m a t e l y 3000 cm
hydrogen/min and 1500 cm
oxygen/min. The maximum
p r e s s u r e i s 100 p s i g and the upper l i m i t temperature i s
66°C.
Proper s t a c k o p e r a t i o n r e q u i r e s t h a t f e e d water
r e s i s t i v i t y be m a i n t a i n e d a t g r e a t e r than 500,000 ohmcm, and t h a t a water c i r c u l a t i o n r a t e o f a p p r o x i m a t e l y
400 cm /min p e r 8 - c e l l s t a c k be m a i n t a i n e d .
Feed t o the e l e c t r o l y s i s s e c t i o n i s s u p p l i e d from
a f e e d tank, which a l s o p r o v i d e s r e c i r c u l a t i o n
capacity.
From the f e e d tank, the water i s pumped
through a d e i o n i z e r , and then t o the c e l l s .
From the
c e l l s , the hydrogen stream p a s s e s through a c o o l e r and
a phase s e p a r a t o r , and i s r e t u r n e d t o the c a t a l y t i c
exchange s e c t i o n . The oxygen stream, a f t e r b e i n g
r o u t e d through a c o o l e r and a phase s e p a r a t o r , i s
c u r r e n t l y s e n t t o the a i r d e t r i t i a t i o n system f o r
p u r i f i c a t i o n and d i s p o s a l . I t i s a n t i c i p a t e d , however,
t h a t t h i s stream w i l l u l t i m a t e l y be f e d t o a recombiner
o r a f u e l c e l l s u p p l y i n g r e f l u x t o the c a t a l y t i c
exchange columns. The water removed from both the
oxygen and hydrogen streams i n the phase s e p a r a t o r s i s
mixed w i t h the f r e s h f e e d upstream from the d e i o n i z e r ,
and r e c i r c u l a t e d through the system.
3
3
3
Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch013
3
Preliminary
Results
The CECE system was r e c e n t l y o p e r a t e d c o n t i n u o u s l y
f o r a p e r i o d o f a p p r o x i m a t e l y 48 h r .
Water was f e d
both t o the top o f the f i r s t column and i n between the
columns, each a t a r a t e o f 3 cm /min. The top f e e d had
a c o n c e n t r a t i o n o f 0.028 y C i / l i t e r w h i l e the mid-column
f e e d , which can be c o n s i d e r e d the "hot" f e e d , had a
t r i t i u m c o n c e n t r a t i o n o f 304 y C i / l i t e r .
The t o t a l
e l e c t r o l y s i s stream, 7.2 l i t e r s / m i n , was r e t u r n e d t o
the bottom o f the second column.
The d e p l e t e d hydrogen stream e x i t s the system a t
the top o f t h e f i r s t column, where a p o r t i o n o f t h i s
stream i s o x i d i z e d t o water, c o l l e c t e d i n an e t h y l e n e
g l y c o l " b u b b l e r " , and a n a l y z e d f o r t r i t i u m u s i n g l i q u i d
s c i n t i l l a t i o n counting.
A t the end of t h i s 48-hr r u n ,
the water formed from t h i s d e p l e t e d hydrogen had a
c o n c e n t r a t i o n o f 0.006 y C i / l i t e r , w h i l e the e l e c t r o l y s i s water l o o p had been e n r i c h e d t o 386 y C i / l i t e r .
These r e s u l t s a r e summarized i n F i g u r e 3.
3
In Separation of Hydrogen Isotopes; Rae, H.;
ACS Symposium Series; American Chemical Society: Washington, DC, 1978.
ROGERS
E T
Catalytic
AL.
H 0
3 cm /min
0.028 MCi/liter
Detritiation
of
Water
2
3
H (depleted in T )
7.2 liter/min (6 cm /min H 0)
burn ^ 100 cm /min to water
and sample
2
2
3
2
3
After ^28
^39
^42
^46
hr
hr
hr
hr
0.021 juCi/liter
0.012 MCi/liter
0.011 MCi/liter
0.006 MCi/liter
Equilibrium value 0.004
μΟ\/\\Χβτ
Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch013
7.5-m Stripping Section
HTO
3 cm /min
304 MCi/liter
3
7.5-m Enriching Section
HTO
Electrolysis Cells
0 to Stack via Air
Detritiation System
2
HTO in Cell Loop
386 MCi/liter After 48 hr
Equilibrium Value ν 2 Ci/liter
Figure 3.
Preliminary results combined electrolysis catalytic exchange sys­
tem (CECE)
In Separation of Hydrogen Isotopes; Rae, H.;
ACS Symposium Series; American Chemical Society: Washington, DC, 1978.
176
Future
SEPARATION
O F HYDROGEN ISOTOPES
Plans
The p i l o t CECE system w i l l c o n t i n u e t o be
operated with goals of obtaining operating experience,
d e t e r m i n i n g s c a l e - u p parameters, and i m p r o v i n g system
dependability.
Mound L a b o r a t o r y a l s o t e n t a t i v e l y
p l a n s t o b u i l d a l a r g e r system b e g i n n i n g i n l a t e 1 9 7 8 .
T h i s system would be used t o t r e a t aqueous t r i t i a t e d
waste f o r ERDA.
Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch013
Abstract
A
pilot-scale
system has been used a t Mound
L a b o r a t o r y t o i n v e s t i g a t e the
catalytic
detritiation
of w a t e r .
A hydrophobic, precious metal c a t a l y s t i s
used t o promote the exchange o f tritium between
liquid
water and gaseous h y d r o g e n .
T h i s c a t a l y s t was
d e v e l o p e d a t C h a l k R i v e r N u c l e a r L a b o r a t o r i e s and i s
operated at 6 0 ° C .
The
catalyst
i s packed in two
columns, each 7.5 m l o n g by 2 . 5 cm
i.d.
Water flow i s
5 - 1 0 c m / m i n and c o u n t e r c u r r e n t hydrogen flow i s 9 0 0 0 12,000
cm /min.
The equipment, e x c e p t f o r the columns,
is housed i n an inert atmosphere glovebox and i s
computer
controlled.
The hydrogen i s o b t a i n e d by
electrolysis
of a p o r t i o n o f the water s t r e a m .
E n r i c h e d gaseous tritium i s withdrawn f o r f u r t h e r
enrichment.
T h i s paper d e s c r i b e s the system and
o u t l i n e s its o p e r a t i o n , i n c l u d i n g e x p e r i m e n t a l d a t a .
3
3
RECEIVED August 10, 1977
In Separation of Hydrogen Isotopes; Rae, H.;
ACS Symposium Series; American Chemical Society: Washington, DC, 1978.
INDEX
A
Absorption of C 0 laser lines
139,140
Absorption coefficients, C O laser-DBr 141
Acids, mineral
156
Addition reactions, deuterium isotope
separation via vibrationally
enhanced deuterium halide olefin 134
Adduct production, classification of .. 156
Adsorption
5
AECL—Sulzer amine process
53
Algae, presence of mud and organic .. 168
Alumina, catalyst pellets of platinum
on
95
Alumina particles, presence of
169
Amine-hydrogen exchange
8, 40
bithermal enrichment using
54
Amine-hydrogen process 11, 17, 40, 53, 63
Amine, steam hydrogen
19
Amino groups of methylamine
47
Ammonia
advantages of methylamine over ....
40
catalyst
90
cracking
78
exchange, hydrogen8-10, 40, 77
and hydrogen, isotopic exchange
between liquid
71
hydrogen process
15,53,58,80
plant
63,67,89
deuterium concentrations in an ..
64
link-up with the
62
synthesis
88
system
43
Argentina
77
Arrhenius parameters for H X addition 136
Atmosphere, H S emissions to
34
Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ix001
1 2
1 6
2
Β
Back-end of the separation cycle
Bed contactor, packed
Bed reactor, trickle
BHWP
aerial view
II,S incidents
reliability
safety performance
training section
BHWP-A
deuterium production
reliability of
145
61
99
32
32
36
33
37
38
29
35
BIIWP-B
37
Bimolecular association
152
Bimolecular reaction
143
Biological
5
Bithermal
enrichment using amine-hydrogen
exchange
54
enrichment
fluids
60
enrichment process
54—56
exchange processes
78
hydrogen-water— H W P
118
process
10-13,121
systems
57
Bruce heavy water plant
27, 28
"Bubbler," ethylene glycol
174
Canada
1, 2, 53, 77, 78, 93, 110
Canada Deuterium Uranium power
reactor program ( C A N D U )
2
C A N D U reactors
27-30, 122, 163
Capacity factors
35
Carbamate
42
Carbon monoxide absorption
coefficients
141
Carbon-Teflon catalyst, platinum
121
Catalyst(s)
44
activity, effect of hydrogen gas flow
rate and temperature on
102
ammonia
90
concentration
17
development
95
effect of platinum metal surface
area on the activity of the
101
efficiency of
169
Engelhard
96
for isotopic exchange between
hydrogen and liquid water,
novel
93
metal hydrophobic
171
pellets of platinum on alumina
95
performance
98, 104, 105
platinum carbon-Teflon catalyst .... 121
solubility of the
72
thermal stability of the
72
Catalytic detritiation of water
171
Catalytic exchange
171-173
between heavy water vapor and
deuterium gas
164
177
In Separation of Hydrogen Isotopes; Rae, H.;
ACS Symposium Series; American Chemical Society: Washington, DC, 1978.
SEPARATION O F HYDROGEN ISOTOPES
Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ix001
178
Catalytic exchange process, com­
bined electrolysis ( C E C E )
110
Cesium methylamide
44
Chalk River
40
Chemical exchange
5—8
combined electrolysis and ( C E C E )
2
processes
1, 14
China
2
Cold principle, hot—
78
Column efficiency
100
Combined electrolysis and chemical
exchange ( C E C E )
2, 110, 175
arrangement, monothermal
17
HWP
112
applications of the
121
block diagram of the
113
demonstration unit laboratory .... 115
synergistic effects of the
119, 120
process
22,171
T R P , applications of the
121
Commissioning progress report
37
Components, cost
127,128
Concentration
in an ammonia plant, deuterium ....
64
catalyst
17
in the electrolysis cell water
circuit, deuterium
116
Condensate and synthesis gas,
deuterium recycle from
66
Conditions, determination of working
74
Coefficients, mass transfer
16
Contacting devices, cold
60
Contactons)
development
40
ejector
61, 62
packed bed
61
sieve tray
61
special cold
59
Countercurrent crystallization systems
7
Crystallization
5
systems, countercurrent
7
water
20
Cycle, back-end of the separation
145
D
D.O
in C A N D U reactors, recovery of
tritium from the
and peak power production,
simultaneous
plant, small
upgrading of
Decomposition, thermal
Design data
Detritiation of water, catalytic
Deuterium
concentrations in an ammonia plant
Deuterium (continued)
concentration in the electrolysis
cell water circuit
116
enrichment system
65
exchange
between hydrogen and liquid
water
Ill
between the water vapor and
liquid water
Ill
equilibria
56
properties
54, 58
rate
14,42
gas, catalytic exchange between
heavy water vapor and
164
halide, vibrationally excited
142
-to-hydrogen ratio
3,10
isotope separation via vibrationally
enhanced deuterium halide
olefin addition reactions
134
plant
82
production, B H W P - A
29
recovery
117
recycle from condensate and
synthesis gas
66
separation methods, hydrogen
1
uranium power reactor program,
Canada ( C A N D U )
2
Development, reliability and
manpower
28
Diagram, enthalpy-temperature
85, 86
Diagram, McCabe-Thiele
11, 83, 84
Diffusion
5
hydrogen
20
D i e t h y l a m i d e , potassium
44
Dimethylformamidide, lithium
47
Dimethylformamidide ( P D M F A ) ,
potassium
42, 43
Distillation
5-9
component costs in heavy water .... 128
heavy water
126
system, elements of a
128
systems—physical
126
water
20
Draft of a factory, preliminary
72
Dunham isotope relations
138
Ε
122
122
122
122
43
164
171
64
Effects of the C E C E - H W P ,
synergistic
119, 120
Effects, synergistic
117
Ejector contactor
61, 62
Electrolysis
5, 172,173
catalytic exchange process,
combined ( C E C E )
2, 110
cell water circuit, deuterium
concentration in the
116
Elimination of H X , unimolecular
136
In Separation of Hydrogen Isotopes; Rae, H.;
ACS Symposium Series; American Chemical Society: Washington, DC, 1978.
179
INDEX
Emissions to atmosphere, IL.S
34
Emissions to water, H »S
34
Energy consumption
20
Energy diagram, potential
154
Engineering problems
87
Enrichment system
81
Enthalpy-temperature diagram
85, 86
Environment, care of the
28, 34
Environmental performance
36
Equilibrium
constant, perturbed
153
isotope effect
110
perturbed
161
statistical
152
Ethylene
142
additions, H F 156
pairs, H F 195
Exchange
amine-hydrogen
8,40
ammonia-hydrogen
8-10, 40
between heavy water vapor and
deutrium gas, catalytic
164
between hydrogen and liquid water,
deuterium
Ill
between hydrogen and liquid water,
novel catalysts for isotopic
93
between hydrogen and methyl­
amine, isotopic
71
between liquid ammonia and
hydrogen, isotopic
71
between water and hydrogen
sulfide, isotopic
71
between the water vapor and
liquid water, deuterium
111
bithermal enrichment using
amine-hydrogen
54
catalytic
171-173
chemical
5-8
combined electrolysis and chemical
(CECE)
2
efficiencies, isotopic
59
equilibria, deuterium
56
hydrogen-ammonia
77
of HC1 with natural water, isotopic 146
isotope
79
kinetics
71
process ( es)
bithermal
78
chemical
1, 14
combined electrolysis catalytic
(CECE)
110
design of the H C l - H . O
148
dual temperature
78
features of hydrogen-water
106
hydrogen sulfide-water
31
water
28
properties, deuterium
54, 58
rate, deuterium
14,42
Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ix001
L
Exchange (continued)
rate, effect of lithium-potassium
mole ratio on
reaction, hydrogen halide-water ...
reaction, mechanism of the
water-hydrogen
water-hydrogen sulfide
water-vapor—hydrogen
Excitation, effectiveness of vibrational
Extraction plant, operating experience
with the tritium hydrogen
46
146
104
2,8
8
2
144
163
F
Factors, capacity
35
Factory, preliminary draft of a
72
Fissure phenomena
169
Flash evaporation
114
Fluoroethylenes
156
Fragmentation
152
France
1,2,10,40,53,163
G
Gas
catalytic exchange between heavy
water vapor and deuterium .... 164
deuterium recycle from condensate
and synthesis
66
fed bithermal process
11
flow rate and temperature on
catalyst activity, effect of
hydrogen
102
reactor cover
169
supplement, electrolytic H as
natural
123
synthesis
62, 63, 85
Gaseous effluent streams, removal of
tritium from
171
Germany
1, 163
Girdler-Sulfide ( G S ) plants, final
enrichment stage for
122
GS process
1-10,14,17-22, 29, 55-58, 93
Glace Bay heavy water plant
3, 4
Glycol 'limbbler," ethylene
174
Gravitational
5
Great Britain
163
Gulf process
20
2
H
H C l - Η . , Ο exchange process, design
of the
148
H F addition
156, 157
HF-ethylene pairs
159
H S emissions
34
H S incidents
31
H X addition, Arrhenius
parameters for
136, 137
H X , unimolecular elimination of
136
2
2
In Separation of Hydrogen Isotopes; Rae, H.;
ACS Symposium Series; American Chemical Society: Washington, DC, 1978.
Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ix001
180
SEPARATION O F HYDROGEN ISOTOPES
Halide-olefin addition reactions .134, 135
Halide, vibrationally excited
deuterium
142
Heavy water
plant
applications of the C E C E
121
bithermal Η - , - Η , Ο
118
block diagram of the C E C E
113
Bruce
27,28
CECE
112
demonstration unit, laboratory
CECE
115
design of
80
Glace Bay
3, 4
model of a
91
synergistic effects of the
CECE
119,120
processes
1
production
2
from synthesis gas, U H D E
process for the recovery of
77
Henry's Law
14, 15
Hot-cold principle
78
Hydrates of perfluoroacetone, gaseous 158
Hydrates of trifluoroacetaldehyde,
gaseous
158
Hydrogen
7, 42, 43
amine process
40
amine, steam19
ammonia exchange
77
ammonia systems
15
-based processes
14, 18
deuterium separation methods
1
deuterium-tritium separations
based on laser augmented
A - f B = C reactions proposed 152
diffusion
20
exchange
amine
8, 40
ammonia
8-10. 40
bithermal enrichment using
amine54
water
2, 8
extraction plant, operating experi­
ence with the tritium and
163
gas flow rate and temperature on
catalyst activity, effect of
102
halide-olefin addition reactions
135
halide-water exchange reactions .... 146
isotopic exchange between liquid
ammonia and
71
and liquid water, deuterium
exchange between
Ill
and liquid water, novel catalysts
for isotopic exchange between
93
and methylamine, isotopic exchange
between
71
monomethylamine system ( M M A )
71
Hydrogen (continued)
as natural gas supplement,
electrolytic
123
on P L M A solutions, effect of
45
on P M A solutions, effect of
45
process
amine
11, 17,18, 53-58, 63-67
ammonia
53, 58
methane
20,21
steam
18
water
1
ratio, deuterium-to3, 10
solubility of
72
sufide
dual temperature
28
exchange, water
8
isotope exchange between water
and
71
process, water
1
system
77
water
40
toxicologic^ properties of
31
water exchange process
31
water system
94
system, ammonia80
system, water14, 15, 80, 94
transfer, steam
20
water exchange
77
water-HWP, bithermal
118
water processes, advantages of
107
Hydrophobic catalyst, metal
171
Ice-water systems
7
Impurities, oxygen-bearing
90
Incidents, I L S
31
India
1, 2, 10, 40, 53, 77
IR photons
134
Institute, Laue-Langevin
163
Isotope
effect, equilibrium
110
enrichment
66
exchange
79
of HC1 with natural water
146
between hydrogen and liquid
water, novel catalysts for
93
between hydrogen and
methylamine
71
between liquid ammonia and
hydrogen
71
between water and hydrogen
sulfide
71
relations, Dunham
138
separation, principles of
78
separation via vibrationally
enhanced deuterium halide
olefin addition reactions
134
Italy
1
In Separation of Hydrogen Isotopes; Rae, H.;
ACS Symposium Series; American Chemical Society: Washington, DC, 1978.
181
INDEX
Κ
Kinetics, exchange
71
Monothermal process
M u d and organic algae, presence of ..
Ν
L
Laboratory unit, results from
114
Lake Huron
28
Laser
augmented A + Β = C reactions,
proposed H / D / T separation
based on
152
lines, absorption of C O
139, 140
methods
134
photolysis
159
Laue-Langevin Institute
163
Law, Henry's
14,15
Cithium
47
dimethylformamidide
47
methylamide
44
potassium
44
solubility of potassium
49
potassium mole ratio on exchange
rate, effect of
46
Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ix001
1 2
9-11
168
Natural gas supplement,
electrolytic H as
North America
Norway
2
123
28
2,8
Ο
i e
M
Manpower development, reliability
and
28,35
McCabe-Thiele diagrams
11,12, 83, 84
Metal
hydrophobic catalyst
171
surface area on the activity of the
catalyst, effect of platinum
101
transfer rate constant dependence
on platinum
103
Methane
7
-hydrogen process
20
Methyl groups of methylamine
47
Methylamide
cesium
44
lithium
44
potassium-lithium
44
sodium
44
solubility of
48, 49
solution, potassium
42
Methylamine
42-44, 65
amino groups of
47
over ammonia, advantages of
40
isotopic exchange between
hydrogen and
71
methyl groups of
47
Methylenimine
43
N-Methylformamide, potassium
42
Mineral acids
156
Molecular sieve, displacement of the
168
Monomethylamine system, hydrogen
(MMA)
71
Monothermal C E C E arrangement ....
17
Olefin addition reactions, hydrogen
halide
134,135
Olefins, Arrhenius parameters for
H X addition to
137
Operating experience
167
Operation, difficulties encountered
during
168
Operation, principle of
164
Oxygen-bearing impurities
90
Ρ
Packed bed contactor
61
Packing(s)
earning power of two experimental
132
experimental
127
performance—experimental
130
Sulzer
164
Pakistan
77
Perfluoroacetone
160
Photochemical, selective
5
Photolysis, laser
159
Photons, ir
134
Pilot plant tests
72
Plant(s)
ammonia
63-67, 89
Bruce heavy water
28
conception, 400 ton
127
design of heavy water
80
deuterium
82
concentration in an ammonia
64
final enrichment stage for GS
122
Glace Bay heavy water
3
heavy water
2
link-up with the ammonia
62
model of a heavy water
91
operating experience with the
tritium and hydrogen extraction
163
operation of the
87
packing module, parallel
131
performance, Bruce heavy water ....
27
polyfluoroethylene production
158
safety precautions
164
small DX>
122
start-up of the
167
400-ton
129
In Separation of Hydrogen Isotopes; Rae, H.;
ACS Symposium Series; American Chemical Society: Washington, DC, 1978.
182
SEPARATION O F HYDROGEN
Platinum
on alumina, catalyst pellets of
95
carbon-Teflon catalyst
121
metal surface area on the activity
of the catalyst, effect of
101
metal, transfer rate constant
dependence on
103
PLMA
44-50
Polyfluoroethylene production plant.. 158
Potassium amide ( K N H )
80
Potassium dimethylamide
44
Potassium dimethylformamidide
(PDMFA)
42,43
Potassium hydride
43
Potassium-lithium methylamide
44, 49
Potassium methylamide ( P M A )
40-47
Potassium N-methylformamide
42
Potassium mole ratio on exchange
rate, effect of lithium
46
Potential energy diagram
154
Power
of experimental packings
132
production, simultaneous D 0
and peak
122
reactor program, Canada deuterium
uranium ( C A N D U )
2
Principle, hot-cold
78
Problems, engineering
87
Process (es)
advantages of hydrogen water
107
amine-hydrogen .11,17,18, 53-58, 63-67
basic description of the
112
bithermal
10-13, 121
enrichment
56
exchange
78
CECE
22, 171
characteristics, general
3
chemical exchange
1,14
chemistry
40-42
comparison
20-22
design
40,67
GS
3
of the H C 1 - H 0 exchange
148
development
41
dual temperature exchange
78
economy of the
74
evaluation
23,24
features of hydrogen-water
exchange
106
gas-fed bithermal
11
Girdler-Sulfide
( GS )
1, 5-10,17-22, 29, 55-59,93
gulf
20
heavy water
1
hydrogen-amine
40
hydrogen-based
14,18
hydrogen sulfide—water exchange
31
methane-hydrogen
20, 21
Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ix001
2
2
2
ISOTOPES
Process ( es ) ( continued )
monothermal
10,11
production
28
for the recovery of heavy water
from synthesis gas, U H D E ..
77
steam-hydrogen
18
transfer
18
types of
5
water exchange
28
water—hydrogen
1
Production
heavy water
2
process
28
rate
35
unit diagram
73
Program, Canada deuterium uranium
power reactor ( C A N D U )
2
Properties, deuterium exchange
54
Properties of hydrogen sulfide,
toxicological
31
Purification system
80
Q
Quenching, vibrational
142
R
Rate(s)
constant dependence on platinum
metal, transfer
103
deuterium exchange
14, 42
effect of lithium—potassium mole
ratio on exchange
46
expression, Arrhenius
136
of methylamide solutions,
thermolysis
50
production
35
and temperature on catalyst
activity, effect of hydrogen
gas
flow
102
Ratio, deuterium-to-hydrogen
3, 10
Reaction(s)
bimolecular
143
deuterium isotope separation via
vibrationally enhanced deuterium halide olefin addition .... 134
hydrogen halide—water exchange . . . 146
mechanism of the exchange
104
proposed H / D / T separations based
on laser augmented A + B = C 152
Reactor
C A N D U type
27-30, 163
cover gas
169
high
flux
163
program ( C A N D U )
2
trickle bed
99
Recovery of heavy water from synthesis gas, U H D E process for the ....
77
In Separation of Hydrogen Isotopes; Rae, H.;
ACS Symposium Series; American Chemical Society: Washington, DC, 1978.
183
INDEX
Reliability of B H W P - A
Reliability and manpower
development
Results, preliminary
Russia
35
28
172
2
S
Safety, employee
28—31
Safety performance, B H W P
33
Safety precautions, plant
167
Selective photochemical
5
Separation(s)
based on laser augmented A -f- Β
= C reactions, proposed
H/D/T
152
cycle, back-end of the
145
factors
7-13, 20, 57, 65, 71, 93 94
methods, hydrogen-deuterium
1
Sieve
displacement of the molecular
168
tray(s)
87
contactor
61
operation
16
Silicone-treated pellets
95
Sodium methylamide
44
Solubility
44
of the catalyst
72
of hydrogen
72
Stability of the catalyst, thermal
72
Statistical equilibrium
152
Steady state
154
Steam-hydrogen-amine
19
Steam-hydrogen process
18
Steam-hydrogen transfer
20
Stripping system
81—83
Sulfide
dual temperature hydrogen
28
process, Girdler-Sulfide (GS)
1
process, water-hydrogen
1
system, hydrogen
77
system, water-hydrogen
40
toxicological properties of hydrogen
31
water exchange process, hydrogen ..
31
Sulzer packings
164
Surfaoe area on the activity of the
catalyst, effect of platinum metal
101
Sweden
1
Switzerland
1, 41, 163
Synergistic effects
117-120
Synthesis, ammonia
88
Synthesis gas
62r-67, 80, 85, 90
deuterium recycle from condensate
and
66
U H D E process for the recovery of
heavy water from
77
System
ammonia hydrogen
80
deuterium enrichment
65
System (continued)
elements of a distillation
enrichment
GS
hydrogen—monomethylamine
(MMA)
hydrogen—sulfide
hydrogen sulfide-water
hydrogen-water
physical, distillation
purification
stripping
transfer
water-hydrogen
water-hydrogen sulfide
71
77
94
94
126
80
81-83
81
80
40
Τ
;
Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ix001
128
81
11
Teflon catalyst, platinum carbon
121
Temperature
on catalyst activity, effect of
hydrogen gas flow rate and .... 102
diagram, enthalpy
85, 86
dual
31
exchange processes, dual
78
hydrogen sulfide, dual
28
Tetrahydrofurane, addition of H F to
158
Thermal decomposition
43
Thermal stability of the catalyst
72
Thermodynamic and kinetic relations
152
Thermolysis rate of methylamide
solutions
50
Thiele diagrams, M c C a b e 11, 83, 84
Thylene glycol "bubbler"
174
Toxicological properties of hydrogen
sulfide
31
Training section, B H W P
37
Transfer
coefficients, mass
16
column
83
processes
18
rate constant dependence on
platinum metal
103
steam—hydrogen
20
system
81
Trays, sieve
16, 87
Trickle bed reactor
99
Trifluoroacetaldehyde
160
Trimethylamine ( T M A ) , adjuvant
effect of
72
Tritium
from the D 0 in C A N D U reactors,
recovery of
122
from gaseous effluent streams,
removal of
171
and hydrogen extraction plant,
operating experience with the . 163
recovery from light water
122
T R P , applications of the C E C E
121
2
In Separation of Hydrogen Isotopes; Rae, H.;
ACS Symposium Series; American Chemical Society: Washington, DC, 1978.
184
SEPARATION O F HYDROGEN ISOTOPES
u
U H D E process for the recovery of
heavy water from synthesis gas ..
77
United Kingdom
1
Uranium power reactor program,
Canada deuterium ( C A N D U ) ....
2
USA
2,77
USSR
2
Water (continued)
exchange
hydrogen—
77
process
28
design of the H C 1 148
features of hydrogen106
hydrogen sulfide31
reactions, hydrogen halide146
H W P , bithermal H 118
H S emissions to
34
hydrogen
14, 15
exchange
2, 8
process
1
sulfide exchange
1,8,71
sulfide system
40, 94
system
80, 94
isotopic exchange of HC1 with
natural
146
novel catalysts for isotopic exchange
between hydrogen and liquid ..
93
processes, advantages of hydrogen 107
system, ice
7
tritium recovery from light
122
vapor and deuterium gas, catalytic
exchange between heavy
164
vapor-hydrogen exchange
2
vapor and liquid water, deuterium
exchange between the
Ill
Working conditions, determination of
74
2
V
Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ix001
Vapor-hydrogen exchange, water
Vibrational excitation, effectiveness of
Vibrational quenching
Vibrationally enhanced deuterium
halide olefin addition reactions,
deuterium isotope separation via
2
2
144
142
134
W
Water
catalytic detritiation of
circuit, deuterium concentration in
the electrolysis cell
crystallization
deuterium exchange between
hydrogen and liquid
distillation
component costs in heavy
heavy
171
116
20
Ill
20
128
126
In Separation of Hydrogen Isotopes; Rae, H.;
ACS Symposium Series; American Chemical Society: Washington, DC, 1978.