PAPER
SOCIETYOF PETROLEUM ENGINEERS OF’AIME
6200 North Central Expressway
Dallas, Texas 75206
NUMBER
SPE
3456
THIS IS A PREPRINT--- SUBJECTTO CORRECTION
.
DE? SEtlii7~ti
.
Oi’1
c?
R~9~ki=h
u I Wu . . . .. Waters
by
Ion
Exchange
By
A. C. Epstein and M. B. Yeligar, Permuitit Co.
American
@ Copyright 1971
Institute of Mining, Metallurgical, and Petroleum
Engineers,
Inc.
This paper was prepared for the 46thAnnual Fall Meeting of the Society of Petroleum Engineers
of AIIv?X,
to be held in New Orleans, La., Oct. 3-6, 1971.
to an
Permission to copy is restricted
abstractof not more than 300 words. Illustrations
may not be copied. The abstractShotidcontain
conspicuous acknowledgment of where and by whom the paper is presented. Publication elsewhere after
publication in the JOURNAL OF PETROLEUM TECHNOLOGY or the SOCIETY OF PETROLEUM ENGINEERS JOURNAL is
usually granted upon request to the Editor of the appropriate journal provided agreement to give
proper credit is made.
+.
Discussion of this paper is invited. Three copies of any discussion should be sent to the
Society of Petroleum Engineers office. Such discussion may be presented at the above meetingand,
with the paper, may be considered for publication in one of the two SPE magazines.
ABSTRACT
Recent developments in ion
exchange tec’nnology &laV-e
made It
economically feasible to desalt brackish waters. Four ion exchange systems
capable of desaiting brackish waters
containing 1000 to 3000 ppm of TDS
are reviewed with respect to their
technology, operating results and
operatirlg costs. ~ah~ratory and
field studies of these systems show
that desalination of brackish water
is technically feasible and that the
most economical systems depend on
the characteristics of the brackish
water, the characteristics of the
desalted water and the required
quality of the product water
(desalted water blended with brackish water) for its end use.
INTRODUCTION
The petroleum industry is second,
only to the steel industry, as a consumer of water. The water, whose
a~~eptab~e qlua~ity varies from poor
to excellent, is needed both at
References and illustrations at end of 1
refineries and in the field. Many
of these sites are located where
the only major source of water is
brackish.
Demineralization by ion exchange
of wat~r~ containing less than 500 ppm
has been an accepted practice for many
years. For this type of water, the
chemical cost, capital cost, labor
cost and.maintenance cost compare
favorably with other systems, such as
reverse osmosis, distillation, etc.
In addition, ion exchange processes
are usually easier to build, simpler
to operate and produce water qualities
as good as those obtained from other
systems.
Ion exchange demineralization of
waters containing greater than 500 ppm
TDS has been infrequent. As the
salinity increases, the capital cost
and operating costs increase. This
is because large volumes of ion
exchange resins are necessary and
high consumption of regenerants are
required. Also, as the salinity
.. amc-tintof %=-..
.v-ch
wa+er
increases, rne
... ...
DESALINATION OF BRACKISH
WATERS
BY-ION EXCUGE
required for rinsing increases. If
treated water must be used to wash
the resins, the process becomesunrealistic since practically the
entire production of treated water
is required. On the other hand, if
tGrJFrece=Sedwaker is employed? the
resin could be exhausted in the
process of rinsing the regenerants.
Recently several processes have
been invented which can treat brackish waters economically because they
reduce one or more of the above
effects. The paper reviews three of
these processes. !rwoof these
systems, the Desal Process and the
SUL-biSUL Process, have been tested
in both the laboratory and the field.
The last process, the RDI Process,
has been tested in the laboratory on
both a laboratory and pilot plant
scale.
Desal Process
The Desal ProcessI-s was invented
by Dr. Robert Kunin of the Rohm and
Haas Company. The basic process
(see Fig. 1) is a three-bed system
containing a weak-base resin in the
bicarbonate form in the first column,
a weak-acid resin in the hydrogen
form in the second column and a weakbase resin in the free-base form in
the third column. The weak-base
resin in the first and third columns
is the Rohm and Haas resin type IRA-68.
The weak-acid resin is IRC-84. The
first column is called the alkalization column because passage of brackish water through the column converts
neutral salts to their respective
bicarbonates:
Cl-+
1
ca’+ *’
wg”+ l-tco~
HZO
(Rae)
The neutral salt leakage from the
first column passes through the
second column unaltered.
The effluent from the dealkalization column (second column) Passes
into the carbonation column (third
cc~&T,PL)m-mwarting
----.-- -—.-4~he weak-base
resin from the free-base form to
the bicarbonate form.
R.N+
H2C03
RNHCI
~
R.r4H.HCOS+
H20
CDesd+d~
1
Leak
The brackish water has been desalted
with the exception of a small amount
of neutral salt leakage.
Three-Bed System
i?-NHHCo3+ti’
3456
acid and exchanges the cation of the
bicarbonate salts onto the resin:
HaO
NaCl
Na~*
PROCESS DESCRIPTIONS
SPE
+ AL3Hc03
::;)s04
CaCnC031z
@g
CHC03)2
%0
NaCl
Na2%
Leak-&
)
These bicarbonate salts plus
some leakage of neutral salts are
then passed through the second column
or dealkalization column which converts the bicarbonates to carbonic
Upon completion of the service
cycle, the first column is in the
chloride, sulfate and bicarbonate
forms; the second column is in the
sodium, magnesium and calcium forms
and the last column is in the bicarbonate and free-base forms.
Regeneration of the first column
with aqueous ammonia converts the
resin to the free-base form. -
To prevent the precipitation of
magnesium hydroxide during anion
regeneration, the regenerant dilution
water and rinse water must be softened
water. In some cases, this softening
can be accomplished by passing the
raw brackish water through the
exhausted dealkalization column,
taking advantage of the softening
capacity of that
part of the weakacid resin which is in the sodium
form. This scheme is shown in
Fig. 2. If this is not feasible or
it is necessary to minimize the
regeneration time by simultaneously
regenerating the alkalization and
PE
A. C. EPSTEIN and M. B. YELIGAR
3456
dealkalization columns, a separate
softener is necessary.
Regeneration of the dealkalization column is with sulfuric acid.
To prevent precipitation of calcium
sulfate in the columns, the initial
---~=..-~=-4A ~~n~entration should
suALuLAb
uti..be no greater than 0.5%. If this
concentration is maintained throughout the entire regeneration, the
waste volume is large and the regeneration time is long. Therefore,
standard practice is to start the
regeneration with the 0.5% concentration and gradually increase the
sulfuric acid concentration to 4%
as the regeneration proceeds.
All the bicarbonate on the resin
in the first column is not exchanged
during service. Also, leakage of
bicarbonate from the last column
occurs. These effects are equivalent t~ losses of carbonic acid
during service and result in
incomplete conversion of the resin
in the third column from the freebase to the bicarbonate form.”
Make-up or supplemental carbon
dioxide is used to complete the
carbonation of the last column.
Because most of the resin is in
the bicarbonate form, demineralized
water should be used for the carbonation step. However, reuse of the
demineralized water is feasible.
When the regeneration of the
system is completed, the third column
is in the bicarbonate form; the
second column is in the hydrogen
form and the first column is in the
free-base form. If the flow pattern
iS
reversed
for the next service
cycle (i.e. through the third coiumn
first), the third column acts as the
alkalization column and the first
column acts as the carbonation
column. The second column is still
the dealkalization column.
Two-Bed System
A second Desal Process is also
available. This consists of a two
column system as shown in Fig. 3.
In this system, the carbonation
column of the three-bed system is
replaced by a decarbonator. The
main advankage of this design Ss
the reduction in capital costs due
to the elimination of the resin and
equipment associated with the
carbonation column. The description
of the process is similar to the
three-bed system, with the exception
that the effluent from the cation
column is passed through a decarbonator
for removal of carbon dioxide.
The regenerations of the weakbase and weak-acid col’umns in the
two-bed system are also similar to
the regenerations of the three-bed
system. However, after conversion
of the weak-base resin to the freebase form, it must be converted to
the bicarbonate form by carbonation
with carbon dioxide. For this system,
the carbonation requirement is six
times the carbonation requirement of
the three-bed system because the
carbon dioxide is not recovered in
a carbonation column.
SUL-biSUL Process
The basic SUL-biSUL Process’-s
is a &W-O=!XXlsystem (see Fig. 5)
consisting of a column containing
a strong-acid resin in the hydrogen
form in series with a column containing a strong-base resin in the
sulfate form. Passage of brackish
water through the first column
~o.n.:ertsp.el~tralsalts to their
respective strong acids and bicarbonates to carbonic acid:
R-bla
+
licl
U H + lQa* CI-~
HZSQ
s+=
Czi++
R
Ca
J
rl~?”
HzC03
J ~@
AO
(RaU>
~>q
R
HZO
FJac I
blaa-
Leak
)
There is also some leakage of
neutral salts from the first column.
The effluent fr~m the first column
is passed through the second column
in which the strong acid converts
the strong-base resin from the
sulfate form to the bisulfate form
and to the form associated with the
anion of the acid:
+ RzsQ~Q.Hsq+
R-cl+H2c03
Hcl
HaS~
NaCl
Leak
NJ2S J
l’tzco3
/420(=-1+
HZO
tdaC/
Nazsq 1
Lealc
The carbonic acid and neutral
.
n~f~~~nt
from
salt Iea’kage ill +ha
b..--the first column pass through the
second column and into a decarbonator in which the carbon dioxide
DESALINATION OF BRACKISH
EXCHANGE
WATERS BY I
4
SPE 3456
is removed. Upon completion of the
service cycle, the first column is
in the sodium, magnesium and ca”lcium
forms. The second column is in the
chloride and bisulfate forms.
The regeneration of the first
column is accomplished with sulfuric
acid using increasing concentrations.
This converts the resin to the
~Ydrogen for~.and releases sulfates
in the regenerant waste.
2f3.iNa
+
1izso4~
212-i-I
+
The bicarbonates now pass into
the second column through the weakacid resin and are converted to
carbonic acid:
R-l-i +
Na2s04
Ca S04
mg S04
2 R-ca
2.e-ml
NaHC03
~
~-N~
+
2R-Q
c~CHQi..=
H2cc)3
1420
H Zo
The key economic feature of the
SUL-biSUL Process is the ability to
use raw water to regenerate the anion
column. The use of raw water reverses
the sulfate/bisulfate equilibrium:
2tda2C03
+
2.1-\=SC4-2waHC03
2CaCo3
C03
2 r-lg
+
Ca(HCa3)2
&lcJ(.co&
Nazs%
Ca S04
;:::
and converts the chloride form of
the resin to the sulfate form due
to the resin’s higher selectivity
for sulfate.
RDI Process
Nacl
Leuk
which passes through the third column
=.~ the fourth COIU~ and into the
us.decarbonator.
The operation of the first two
columns is similar to that of the
Desal Process. However, whereas
efficient operation of the Desal
Process is not achieved when there
is high neutral salt leakage from
the first column, the efficient
operation of the RDI Process
actually depends on neutral salt
leakage from the first column.
The neutral salt leakage passes
unaltered through the second column
and into the third column in which
the cations exchange with the
strong-acid resin and converts the
neutral salt leakage to free mineral
acidity:
Q-H+
blzC03 ~
Naci
Na2so
The third desalting process is
the RDI ProcessLO~ll invented by
Dr. Mori-Tavani of the Resindion
Company of Italy. This system (see
Fig. 7) is a four-bed process consisting of a column of strong-base
resin in the bicarbonate form, a
~o~t~qun~f Weak-acid resin in the
hydrogen form, a column of strongacid resin in the hydrogen form, a
column of weak-base resin in the
free-base form and a decarbonator.
Brackish
water enters the first
,.
unit iii ‘W-ll~eFI rle.utral
salts
are
converted to their equivalent
bicarbonate salts:
1
tiaz%
H20
Leak
J
~-~a +
Hcl
HZSCW
HzC03
H20
The free mineral acidity is
then absorbed by the free-base form
of the weak-base resin in the fourth
column:
Q-Nf+Cl
+ H2C03
R-N+HcI
~
R-NH.
!+2SQ
~-N H )*4
H2C03
\4ao
Whereas conventional demineralization processes using strong-base
and strong-acid resins utiiize oniy
25-50% of the resin’s theoretical
capacity, the RDI Process utilizes
A. C. EPSTEIN and M. B. YELIGAR
SPE 3456
the maximum capacity of the resins.
This is because of its ability to
tolerate leakage without affecting
the product water quality combined
with the high capacity of a weakbase resin in the free-base form
for free mineral acidity. This
reduces the size of the columns,
the initial resin loading, the
required resin inventory and, hencel
the cost.
To produce good quality effluents,
regenerant requirements of strongbase or strong-acid resins are two
to three times the chemical equivalent
of the resin’s capacity. However,
weak-base or weak-acid resins require
approximately stoichiometric quantities of regenerants. Therefore, if
a strong-base or strong-acid resin
is regenerated firstl the excess
regenerant contained in the regenerant waste can be used to regenerate
a weak-base or weak-acid resin. This
technique results in efficient regenerant utilization and is used in the
regeneration of the RDI Process.
Regeneration of the cation
through
the strong-acid column and then
downflow through the weak-acid
column . The regenerant is sulfuric
acid. In the strong-acid column,
the resin is converted to the
hydrogen form:
Col”&iuIl
o .
1=
=av+nwm-d
&G.L*”
.
. ----
upf~~w
M$J SO+
R-da
Ca .S04
~=sm.
The effluent containing the excess
acid then passes through the weakacid column converting this resin
to the hydrogen form:
The anion columns are regenerated downflow through the strongbase anion column and then upflow
through the weak-base anion column.
The regenerant is sodium bicarbonate.
However, ammxiuii bicarbonate can be
used if regenerant recovery is
desirable. Passage of the fresh
regenerant through the strong-base
anion column converts the resin to
the bicarbonate form:
R-cl
+ tQaHC~3 ~R-HCC)3+
NJac~
NaaS04
:>*
Na H033
The subsequent passage of excess
sodium bicarbonate through the weakbase anion resin converts the resin
to the free-base form:
Q.Nkl.ci -1-Nacl ~
G?-~ + 2Na@Q
2 rlac I
H2C03
One additional feature of this
regeneration technique is that the
strong-acid and weak-base resins are
regenerated countercurrent to the
service flow. This is a common
technique used to obtain excellent
quality product water.
EFFECT OF WATER COMPOSITIONS
ON-BLENDING
For a particular water, the
chemical operating costs are not a
function of plant size, but can be
decreased if blending of raw water
and desalted water is possible. The
amount of blending and, hencel the
chemical operating cost depends on
the composition and total dissolved
solids (TDS) of the brackish water,
the composition and total dissolved
solids of the desalted water and the
required water quaiity. The ef~ects
of these parameters On blending and
cost are shown in Table I in which
the end use is potable water
(TDS ~500 mg/1 with neither chloride
nor sulfate greater than 250 mg/1).
Table I shows that the best brackish
water for blendirlg is a low TDS water
evenly
divided between chloride and
sulfate. For example, the cost to
desalt a 1000 mg/1 TDS water (with
500 mg/1 of chloride and 500 mg/1
of sulfate) blended with desalted
water containing 100 mg/1 TDS is
62.5@/Kgal versus 75#/Kgal for a
1000 mg/1 TDS brackish water containing all chloride, which is blended
with a zero TDS desalted water.
OPERATING RESULTS AND CHEMICAL
OPERATING COSTS
The tables referred to in this
section present typical operating
results and chemical costs for the
different processes. These are
based on desalting iOOO gaiions of
brackish water without any blending
of raw water and desalted water.
Capital costs are not presented
since they vary with the size of the
plant. However, a general rule is
6
DESALINATION OF BRACKISH
WATERS BY ION EXCHANGE
that, as the plant size increases,
the cost per thousand gallons of
product water decreases.
The purchase price of the regenerants used to calculate the chemical
costs are 2.754/lb. for ammonia,12
1.57Q/lb. for sulfuric acid and
4.14/lb. for carbon dioxide. The
carbon dioxide cost is a typical
=+mfi=the CQSt
of carbon
i?~~~~ -----dioxide varies with the annual
requirement.6 For example, carbon
dioxide costs .6.5$/lb. for an annual
requirement between 12.5 - 25 tons
and only 1.6254\lb. for an annual
requirement between 1500 - 2500 tons.
The costs shown in the tables
do not include costs for neutralizing any regenerant wastes.
Table 11A shows the composition
of two similar waters at the low TDS
range for which desalination would
be necessary. The waters are both
high hardness, high sulfate waters=
The SUL-biSUL Process and Three-Bed
Desal Process will desalt these
waters and produce a desalted water
of the composition shown in Table IIB.
The operating results which are
shown in Table III are based on
pilot plant tests of both processes.
Table III shows the chemical operating cost for treating a relatively
low TDS water, without any blending
of the raw water and desalted water,
is in the range of 25-306/Kgal.
Although Table III shows that
the chemicai operating cost of the
SUL-biSUL Process is less than the
chemical operating cost of the
Three-Bed Desal Process, the
SUL-biSUL Process requires more
resin (larger columns) and greater
quantities of regenerants. This
indicates the total operating costs
(including capital cost) of both
processes may not be significantly
different.
The composition of another water
is shown in Table IVA. The TDS of thi,
water is near the upper range for
waters which can be treated by ion
exchange. In this case, the water.
..- a lligll
~hlnride
water,
SOdlURl
_.AAw.-_~s
Because of this, the SUL-biSUL Process
cannot be used. Also, the Two-Bed
Desal Process should be used instead
SPE 3456
of the Three-Bed Desal Process. In
Table IVB are shown the desalted
water compositions obtained after
treatment with the two desalting
processes. The chemical operating
costs for this high TDS water are
shown in Table V. They are on the
order of $1.60/Kgal to $1.90/Kgal.
As previously stated, these costs
can be reduced somewhat by blending.
Further reduction in costs may be
----..,
: .
obtained by the recovery of eIIUIIUJJAa
and carbon dioxide in the Desal
Process and by the use of recoverable
ammonium bicarbonate for regeneration
of the anion columns in the RDI
Process. Recovering 80% of the
ammonium bicarbonate will reduce
the total cost for the RDI Process
to $1.00/Kgal.
Table V shows the high capacities, and efficiency of regeneration
obtained with the RDI Process. This
means that, although the RDI Process
requires more columns than the other
processes, these columns are much
smaller than those used in either
the SUL-biSL’L or Desal Pro~cesses.
Hence, its capital’ cost may be less
than the capital costs of the other
processes.
If the RDI Process had been
used to treat the low TDS water, the
cost would have been between
33$/Kgal and 624/Kgal depending
upon
which
regenerant
was
used.
The operating results and costs
for treating waters with a TDS
between 1100 ppm and 2700 ppm will
& between the numbers shown in
Table 111 and Table V.
PROCESS ADVANTAGES AND DISADVANTAGES
The three major ion exchange
processes described in this paper
are generally applicable from a
technical standpoint to waters
whose TDS is less than 3000 ppm as
CaC03. The economic feasibility
of each ion exchange process is
governed not only by the chemical
composition of the brackish water,
but also by the required effluent
quality of the water needed for
4n-n7an+
Aa.—yA
----- Il=e.
-.-7-.
M described earlier,
each ion exchange process utilizes
a combination of anion and cation
resins. The chemical nature of
these resins significantly regulates
APE 3456
A. C. EPSTEIN a
the performance and costs of the
process. Therefore, in SeleC.tin9
a particular process for brackish
water treatment, it is important
to take into consideration the
chemical composition of the water,
rather than just the TDS of the
water.
TWO other parameters of economic
significance are the amount of resin
required and size of the columns.
Both of these parameters are governed
by the capacity of the resin. Higher
capacity means less resin is required
to remove an equivalent amount of
ions from an equai volui-meof ‘water.
Hence, less resin must be purchased
and the columns in which this resin
is contained can be smaller.
Certain advantages and disadvantages of each of the processes
are summarized below.
Desal PrOCeSS
Three-Bed Process
Advantages
The primary advantage of the
three-bed process is the recovery
of most of the carbon dioxide used
to carbonate the anion column. This
minimizes the carbon dioxide requirement and cost. Since the recovery
is accomplished by carbonation of the
anion resin, the carbonation time is
reduced which allows lower resin
volumes to be employed in the process.
Another major advantage of the Desal
Process is the use of weak-base and
weak-acid resins which can be regenerated more efficiently than strongbase or strong-acid resins. Although
it has not been demonstrated, recovery
of ammonia from the regenerant waste
is probably economically feasible.
Finally, the regenerant dilution
water and rinse water for both
columns does not have to be product
water.
Disadvantages
Of the four processes described
in this paper, the three-bed process
yields the poorest quality desalted
water.
There is a possibility of precipitating caicium carlxmate in the
alkalinization column. This cannot
M. B. YELIGAR
7
be tolerated because it increases
pumping costs, causes poor flow
distribution through the resin bed,
reduces anion exchange capacity of
the resin and consumes carbon dioxide.
Finally, to eliminate the possibility
of precipitation of magnesium hydroxide
in the anion column during regeneration
with ammonia, the regenerant dilution
water and rinse water must be softened
water.
Desal Process
Two-Bed Svstem
The primary advantage of the
Two-Bed Desal Process is the
reduction in capital cost
and resin
cost when compared with the threebed process. Furthermore, the
capacities of both resins are greater
than those used in the SUL-biSUL
Process, which means the cdurtn
sizes are smaller. Also, the quality
of the desalted water is better than
that obtained with the Three-Bed
Desal Process. Finally, if precipitation of calcium carbonate does
occur in the first column, it will
be dissolved during the carbonation
step.
Disadvantages
The major disadvantage of the
Two-Bed Desal Process is the increased
cost for the carbon dioxide needed
to carbonate the anion column. In
addition, the increased carbonation
L:..
.
....=..
~Ags~e=~_j&~~~
~~.~
USe
of more
LA1lLC
Allay
resin and larger columns to produce
a continuous supply of product water.
The two-bed process also requires
softened anion regenerant dilution
and rinse water for the ammonia
regeneration.
SUL-biSUL Process
Advantages
The major advantage of the
SUL-biSUL Process is the strong-base
resin does not require a purchased
regenerant. Regeneration is
accomplished by using raw water.
This feature results in this process
having the lowest chemical operating
cost
●
DESALINATION OF BRACKISH
WATERS BY ION EXCHANGE
8
The use of raw water as a regenerant eliminates the need for rinse
water. A weak-acid column can be
inserted prior to the strong-acid
column at no additional chemical
cost . This increases the capacity
of the strong-acid column.
Disadvantages
Although the SUL-biSUL Process
is attractive from a chemical cost
standpoint, there are several disThe
advantages to t&liS
p~OC=SS.
---major disadvantage is its limitation
to waters containing a sulfate to
chloride ratio of 9 to 1 or more.
The operating capacities of both
resins used in this process are
relatively low. This necessitates
the use of either large columns or
frequent regenerations. Alsor the
regeneration with raw water results
in large
‘waste VG~UIT,eS wb.~c~- mntain
sulfuric acid and, therefore, must
be neutralized.
RDI Process
Advantages
The major advantage of this
process is its capability to produce
the best quality desalted water of
all the processes described in this
paper. This may offset the high
cost of the anion regenerant.
Although the process requires more
columns than the other processes,
the columns are smaller because of
the very high capacities of the resins
employed. The high capacities
combined with relatively low rinse
requirements allow the use of raw
water for regenerant dilution water
and rinse water without incurring a
significant decrease in the capacities. Furthermore, the efficient
use of regenerants”means a relatively
low excess of reqeners?.t xwill be i.nthe regenerant wastes.
Disadvantaqes
The primary disadvantage of the
RDI Process is the high cost of
scdium.~i~=yhnnake
needed to regenZ-W-----crate the anion columns. Although
a substantial chemicai cost reduction
can be obtained through the use of
a recoverable regenerant (ammonium
bicarbonate), its use complicates
the system and increases the capital
costs .
SPE 3456
CONCLUSIONS
mL.
*llC
.aInfl++on
a=.L==ti.-A
of
technically
applicable desalting processes
depends on the water characteristics.
For example, the SUL-biSUL Process
is not suitable for waters containing
relatively high chloride concentrations
with respect to sulfate concentrations.
The sulfate to chloride ion ratio
should be approximately 9 to 1 or
more. The alkalinity of the brackish
water should be at least 10% of the
total anions present. Waters containing high hardness and iow sodium
are particularly suitable for treatment by the SUL-biSUL Process.
The Three-Bed Desal Process is
technically suitable for the above
characterized water. However, it is
not limited to a sulfate to chloride
ratio of 9 to 1. The Two-Bed Desal
Process becomes more applicable as
the sulfate to chioride ratio
approaches 1 to 1. For both Desal
Processes, high alkalinity is
desirable (though not necessary)
because it does not use anion
capacity.
TuneRDI Process is teehr.ically
app~i~able to all types of waters.
However, the anion ~egenerant is
more expnsive than those used for
other processes. High alkalinity
“is also desirable in this process
because it does not use the strongbase anion capacity. Of the three
processes, the RDI Process produces
the best quality desalted water
which may allow a greater quantity
of raw water to be blended with the
desalted product water.
After the selection of the
desalting systems which are technically applicable to the particular
brackish water, consideration must
be given to all costs (capital and
operating) associated with these
systems to determine the most
economical process.
in S-uiiUYiary,
w’eha%’e skm?n-kb-at
the state of the art for demineralizing high TDS waters has been
developed to the extent %“here
~e%,era~pr~~esses are technically
and economically feasible. However,
all the processes are not technically
applicable to all brackish waters.
When the chemical composition of the
brackish water is known, the selection
JE 3456
9
A. C. EPSTEIN a ~ M. B. YELIGAR
me
or
mre
tedmimlly
applicable
desalting processes can be made.
Then the most economical system can
be determined from an analysis Of
the operating costs and capital costs.
of
Ion Exchange Resin - An insoluble
materiai whlcn has the CapaC~@
of exchanging one ion for another”
NOMENCLATURE
Alkalinity - Capacity of water to
neutralize acids~ a property
imparted by the water’s-con~ent
of carbonates, bicarbonates and
hydroxides. Usually expressed
in parts per million as calcium
carbonate.
Anion - A negatively charged ion
Bed - The ion exchange resin con‘tained
in a column
%&%L%n%xn$
::::::”ent
which may be high quality water,
with raw water
Brackish Water - A water containing
dissolved salts from 1000 ppm to
5000 ppm
mg~i
- A iinitof
“
which
concen +w=++m
----equals the milligrams of the
constituent dissolved in a liter
of solution. This term is
replacing parts per million to
which it is approximately equal.
Neutral Salts - Salts which do not
change the pH of a solution
EE?!!l- Parts per million. A measure
of concentration used in the
water treating field.
Strong-Acid Resin - Refers to sulphonic resins, capable of salt
splitting
Strong-Base Resin - Resins with
quaternary ammonium groups
capable of exchange with weakly
ionized salts
Capacitm
- Adsorption capacity
possessed in varying degree by
ion exchange materials. This
quality is expressed as kilograins per cubic foot, where the
numerator represents the weight
of the ions adsorbed and the
denominator, the volume of resin.
Countercurrent Operation - The operation of an ion exchange column
in which the service cycle and
regeneration are performed in
opposite directions
Decarbonator - A vessel within which
water IS cascaded countercurrent
to a flow of air, resulting in
the removal of carbon dioxide
from the water
Total Dissolved Solids - The sum of
dissolved constituents in water
usually expressed in milligrams
per liter
a solution
column ,
‘*;$l::::K::EG:
i.e., in at the bottom, out at
the top of the column
Weak-Acid
Resin Refers
to carboxylic
—~.
~,..
n.hln of
resins generd-~y lr~Car--.splitting salts
Weak-Base Resin - Refers to reSins
containing amine exchange groups
which will not exchange with
weakly ionized salts
REFERENCES
Desalination - Removal of dissolved
salts from brackish water
Downflow - Conventional direction of
solutions to be processed in ion
exchange column operation, i.e.~
in at the top, out at the bottom
of the column
1.
Kunin, R., “New Deionization
Techniques Based Upon Weak
Electrolyte Ion Exchange Resins,”
Ind. Eng. Chem. Proc. Des. Dev. ~,
404-409(1964)
.
2. Kunin, R., U. S. Patent 3,156,644
(November 10, 1964).
DESALINATION OF BRACKISH
WATERS BY ION EXCHANGE
10
-.
8. Schmidt, K., “Field Operating
Experience with the Sul-biSul
Process for Brackish Water Treatment, “ Proceedings of the 29th
International Water Conference,
Engineer’s Society of Western
Pennsylvania, Nov&nber 1968,
pp. 69-72.
3. Kunin, R., “A New Ion-Exchange
Desalination Technique,” Proceedings of the First International
Symposium on Water Desalination,
VO1.
2 (U. S. Govt. Printing
Office, Washington, D. C., 1965) ~
PP 69-80.
●
4,
Kunin~ R., “Further Studies on
the Weak Electrolyte Ion Exchange
Resin Desalination Process (DeSal
Process) ,“ Desalination ~, 38-44
(1968).
5.
Desal Process (Rohm and Haas Co.~
Philadelphia, Pa.) .
6.
Epsteir., A. P-a and Yeligar~ M. B.,
“Ion Exchange - Field Evaluation
of DeSal Process,” OffiCe of
Saline Water, Research and Development Report No. 631, November 1970.
7.
Odland, K., “Desalination by the
Sul-biSul Process, Part I - The
Technology,” Proceedings of the
26th Internat~onal Water Conference, Engineer’s Society of
w~ern
Pennsylvania, October
1965, pp. 143-146. .
10
SPE 3456
a
J.
K., Senqer, D., schwark~ Dt
and Dalaly, H.1 ‘iSul-biSulIon
Exchange Process: Field Evaluation
on Brackish Watersr” Office of
Saline Water, Research and Develop-.
ment Report No. 446, May 1969.
‘A*
sc!’mn-.;
10. Watson, C. I., “TechnicalEconomic Survey of the Ion
Exchange Process for ‘~.e
Desalination of Brackish Water,”
(Control Systems Research Inc.,
Arlington, Vs.), April 1970.
11. Personal communications between
Dr. Mori-Tavani and Permutit
personnel.
12.
Oil, Paint and Drug Reporter,
July 19, 1971.
Ispx x9q teo3
*Z936W b931639a
x93sW fiaiS3sxEl
g
2aT
_
00?
00?
0001
0
0001 0001
@
0001 0
0001
ooa
00.1?
0
Ool
001
00?! 00?! 0001
ooa
00.1?
Ool
0
001
00?! 00?
00s
00.1.?
0
001
001
0
00s
00.1?
001
0
001
0001 0
&c&
00.s?
000
es
00.s?.
0
0001
0001 0001
0001
0001 0001 000s
00s
00s
o
000s 000s
- ,kATE:Cc ?cSIZ IO:.:
TA?Y>
. a.;,1:. :ABLE :-
A.
Brackish
Water
Compositions
Desal
SUL-biSUL
~m
Anions
PP m as
as CaC03
CaCO~
279
372
HC03-
20
700
cl-
!30g
X34=
-_!!
TOTAL
1082
Desalted
Resin
Type
cation
Resin
Quantity
Cation
Capacity
Cation
Regenerant
Regenerant
Cation
1099
Ca++
660
4s0
Mg++
220
342
316
Na+
— 202
—
TOTAL
1082
1138
Water
Acid
8.38
7.55
- H+
Quantity
Level
Anion
Resin
Type
Anion
Resin
Quantity
Anion
Capacity
Anion
Reqenerant
Weak
17.3
Kgr/cu. ft.
2.78
17.1$ /Kgal
Form
Cu. ft.
Kgr/cu. ft.
Raw
Acid
lbs.
1313%
- SQ4=
14.1
Form
Cu. ft.
10.9
lbs.
24.6$ /Kgal
Base
- H+
Sulfuric
Acid
i9i%
strong
Desal
Acid
3.45
Cu. ft.
15.6
Regeneratmn
Form
Kgr/cu. ft.
Sulfuric
Cation
Regenerant
Cost
per Kgal of Desalted
Water
Cations
B.
Three-Bed
SUL-bi SUL
Strong
Cation
Weak
Bas~
- HC033.15
15.2
Form
Cu. ft.
Kgr/cu. ft.
Water
Ammonia
Compositions
Regenerant
suL-bi SUL
ppm
Anions
DeSal
ppm
as CaC03
as CaC03
20
98
4
1
s04=
—55
— 37
TOTAL
79
136
Hco ~ cl-
Regeneran
83 gal/c u. ft.
Quantity
Anion Regenerant
Cost
per Kgal of Desalted
Water
Quantity
C02
Regeneration
Pumping
Level
COZ Cost per Kgal
Desalted
Water
lbs.
126%
8C/Kgal
Costs
--
COZ
2.9
_-
t Level
1.1
lbs.
--
19%
--
4.7 C/Kgal
of
Cations
Ca++
30
124
M9++
18
16
Na+
31
—
— 1
TOTAL
79
141
TABLE L.- WATER CO[.TOSITIOITS
TOTAL
CHEMICAL
OPEPATING
COSTS
24.6 C/Kgal
TABLE 5 - OPERATING RESULTS BASED Ot:PRODUCLNG 1000 GAL OF DESALTEL MATZP OF COITPOSITIOP1
SHOW
A.
Brackish
Water
Resin
Type
200
cl-
2500
—
Cation
Resin
Quantity
TOTAL
2700
Water
+ Mg++
12.84
- H+
RDI
—
Form
270
Na+
2430
—
ToTAL
2700
Cation
cu. ft.
Kgr/cu.
Sulfuric
Regenerant
Regenerant
Ca +-lons
Desalted
De Sal
Acid
12.29
Cati OJ-,Capaci V,,
Cation
B.
Weak
Cation
PP m as C.C03
HC03-
Ca++
IllTABLE 46
Two-Bed
Compositions
AnIons
29.8 C/Kgal
4.84
(total of
ft.
Acid
32.5
Kgr/cU. ft.
24.2
Cation
Regenerant
Cost
per Kgal of Desalted
water
Acid
lbs.
iii38
130%
Level
cu. ft.
two resins)
Sulfuric
2B .72 lbs.
Quantity
Regeneration
weak Acid - H+ Form
Strong Acid - H+ Form
45.3’$/Kgal
35.6 C/Kgal
Composition*
Two-Bed
Am
ppm
as
DeSal
CaC03
RDI
—
Weak
Anion
Resin
Type
Anion
Resin
Quantity
Base
- HC03-
9.58
FOEm
Cu. ft.
@p m as CaCOJ
15.25
HC03-
83
--
Anion
Capacity
cl-
—8
~
~,-’~on
p>ege,qeran.
TOTAL
91
10
Regenerant
Quantity
Regenerant
Level
~
Kgr/Cu.
Ammonia
9.22
lbs.
ft.
Weak Base - Free-Base
Strong Base - HC03-
4.94 C“. ft.
(total of two resins)
29.5
KgK/cU. ft.
Sodium
Bicarbonate
38.5
lbs,
110%
130%
Cations
Na+
51
10
Anion Regenerant
Cost
per Kgal of Desalted
Water
25. 4$/’Kg Fil
C02
Quantity
22.03
C02
Regeneration
Level
C02 Cost per Kgal
Desalted
Water
TOTAL
CHEMICAL
lbs.
OPERATING
COSTS
150 C/Kqal
--
120%
--
90.3 C/Kgal
-.
of
161 C/Kgal
Form
Form
185.66 /Kgal
RAW
MA:EJP
WATER
. . . . . . . ..-
lcl -
No+, Mg
so:
++
f
HCO:
co++
1
@
WEAK
ACIO
CATION
WEAK
BASE
ANION
R-H+
R-HCO;
“Rf[J
ANION
REGENERATION
MH, CI
(NH,)?
SOFTENED
RAW wATER
SO.
H2C03
1
H2 SO,
NoCI
CATION
Regeneration
NO cl (LEAKAGE)
NO(HC03)
CO(HCOS)t
I
wEAK
ACID
CATION
I
R-No+
WEAK
BASE
ANION
;>
co”
o
N02 S04
co so.
.
-—--o III ‘tl’r
Mg SO,
z -
Fig.
Fig.
1
-
3-bed
service
Desal
cycle.
Process,
Desal
RAW WATER
co++ f Mg””
NH,
C02
s-bed
*-_-*_
ANION
REGENERATION
L-l
D
WEAK
WEAK
1
k----,
‘2
I
cl-
SOZ
BASE
ACID
CATION
R-Cl-
R- NO+
R>so:
R
R> Ca++
SO$TA:t4:D
HCO:
Ca++
STRONG
ACl O
CATION
STRONG
BASE
ANION
R-H+
R so:
R>
RAw
(NH4)2S04
u
NoCI
C02
WEAK
u“--~~H4c,
H2C0,
NO c1 (LEAKAGE)
CO(HC03)2
WEAK
ANION
R-H+
R- HCO;
regeneration.
NO+ Mg++
I
ACID
CATION
BASE
ANION
Process,
C02
H Cl
H2S04
Hz CO,
WEAK
ACl O
CATION
REGENERATION
CATION
11
R- NO+
;> co++
OECARB.
] DECARB.I
Noz S04
1-----1
co S04
MgSOe
Fig.
Fig,
3
Fig.
-
2-bed
De Sal
service
4
-
Regeneration
f’recess,
Desal
of
the
5
SiJL-bi
-
SUL
tWO-bed
Process,
cycle.
ANION
REGENERATION
Nocl
H2C03
NOZS04
No HC03
CO(H:OJ2
n
BASE
ANION
ANION
REGENERATION
H.#04
I
00
R-Cl-
;>
N02S04
1
Na2S04 MgS04
Ca s 04
NaCl
h4g Clz
co so,
H2S04
Ma
,.. . SO.
---
HzCO,
-?
Cp
+
Cp
r’
Mg++
1
NaCl
Ca(HC03)Z
NaHc03
NacI(LEAKAGE)
R-HSO~
co++
R-H+
I
I
R- No+
R
R>
0
WEAK
ACIO
RESIN
R-H CO;
RAW wATER
/HCO~/SO~
STA::;G
WEAK
EASE
RESIN
DECARB.
RESIN
R-H+
H2C03
J
-
SUL-bi
regenrat
SUL
iOn.
R> H2S04
i
@
@
nO
00
I
4
NoCI
process,
7
-
Rol
Process,
/ N02S04
CATION
/NIJH’J%
REGENERATION
NO C1/COC12/HCl
(
?
STRONG
ACIO
CATION
WEAK
ACIO
CATION
R-No”
:>
service
co++
-r
2
NoCI
COC12
Fig.
Fig.
Ij
R>so
R-HCI
R
R
COC12
Fig.
R-ClR
R>ca”+
H Cl
H:C03
H20
BASE
ANION
BASE
ANION
R-Na+
%
R-OHQ
@
WEAK
c)
STRONG
--1
I
sTRONG
CATION
REGENERATION
Service
cycle.
F’r Ocess.
cycle.
8
-
RDI
regeneration.
prOCess!