I
I
I
I
I
. . ~ .'
.. . . . . . .
I
I
I
I
I
I
I
I
I
I
I
I
I
I
UNITED NUCLEAR
- HDMESTAKE.PARTNERS
URANIUM WlLLING OPERATIONS
GRANTS, NEW MEXICO
..... ..: .. i. .
...
.
.
.
,.
.
I
I
1
I
I
I
I.
I
1
I
I
I
1
I'
I
I
I
I
I
URANIUM ORE MINING AND MILLING
. .
'..
UNITED NUCLEAR
AT
- HOMESTAKE
PARTNERS
,.
GRANTS, NEW MEXICO
Homestake Mining Company and United Nuclear Corporation
i n a major uranium mining
'
'
'
.. ; ': . 8
. .
.',,
.a
aFB partners
aqd milling venture in New Mexico formerly called
Homestake-Sapin Partners and recently renamed United Nuclear
Partners.
. .
. . . .' ,. ,
.' . . . ,
The Partnershiphas
beena
- Homestake
major producer.of uranium cince 1458
wheh a contract
was signed in 1957 with the U. S. Atomic Energy Commission.
Since that time
i t and another partnership,
Homestake
(closed November 1961) have delivered approtrlmately
- New
Mexico Partners'
27,000,000 pounds o f U3O8
to the Conraission plus approximately 628,000 pounds of U308 t o t h e c o m r c i a l
market.
The Partnership currently opeFates
six mines,a
t t u t k h g rdWki3ion
and a 3,500 ton per day alkaline leach miZ1.. Recently the pavmers
a Eevised Partomship agreement that providea for distribution
of uranium concentrate produced
exfsring SF: co#fracts and
&ti.
t6 the pwk!%ers
iequjiienmt needed t a f u l f i l 3
Cor t h e ,par%trrwrJFCQ share in the available mill
capaciey OS fhtir itrdivkduaX
a basis f o r
tn '&Wcsrso i
annouriced,
~GCQUR~.S,
T&$a new arrangements will insure
it.8a rang-term o p e k i o n o f khnese mining end processing faC&LiC&6
a t a time, when wbstantia;k EuZwo growth is anticipated gor the uraafum
tadurrrry.
.
. . ..
.I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I I
. .
UNITED NUCLEAR
- HOMESTAKE PARTNERS
CURRENT MILLING OPERATIONS
During the ten years since operations
werebegun a t the &itt%d Wwlear
-
Homestake Partners uranium m i l l , $he, processing flowsheet has undesgom gradual
changes u n t i l the present flowsheet has
beenevolved.
ORE PREPARATION
Ore Receiving.
Ore forprocessing
which a r e 10 to 52 miles distant
€nom the'milS.
22 t o 28 tons. .Control
loadsof
i s t8CaiVed from varioue m%es $S%hed i s t r i c t
of the ore
The' @re i s delivered %%x Wuck
i s by consecwtive lot
which vary from 200 to 1,500 tons, usually consist
ore lots,
from one mine in one day.
The o r e i s then dumped
empty truck i s weighed.
is taken for a
sf the
.and
oFe received
the milit, f t 'is weighed; and tRe ore ka aesigned
As each truck arrives at
to a lot.
xiiuri1&2%
in 'a
on che ore pad, and 'the
specified area
A sampie fr@n the dump p i l e of each truck load ~ l are
f
moistujce determinatton kiRLch is used t o calc&lbte the dry &is
o f ore in each l o t .
Crushing. .
The concrete p0r&~ri o f
i s coveredwitha
the ore must pastf.
s3se ora pad coatainsasub-gradehopper
that
griaz;l;y; Tho ga%ezlp has164nchsquaneopeningsthrou,gh
The oee horpper d b e h a r g e s onto
t(r$
aprorr feeder which Bas a
variable speed dwive and is controlled by tbe crusher operabr.
a.
discharges through
an anchor chain cwt.a&,
a42-inchconveyor
belt,
The crusher
.
t
which
The apron' feeder
ovgk a statlonaary gtieely, afid cttv6a
feed belk disehargee %heore oiuto a v i e a t i n g
grizzly which al%owBthe m h a a &wb&wh Ififactimn oT
eke ?$e
The orusheher i s a twin rotov Universal Impact BreaktM:.
t~ bppae.U $Ire enifdter.
.
..
The crusher discharge and the Wbrating grizzly ugdeosiar: &%e@~3lobLt&
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
and elevated bymeans
o f conveyor b e l t s t o two, 6 by 12-foot vibrating screens
which a r e coveredwith a 1/2-inch by 4-inch slotted
f a l l s o n t o a r e t u r n b e l t for recycle
to
the crusher,
dropsonto
a conveyor and is t r a n s f e r r e d t o t h e
Drying.
Ores thatcontain
ca t h e
Samplin%:.
.
a t 5% moisture,onto
rocating samplers that cut all
retaw
and thg c m h e r
CfMveybt b e l t
The dtyer burner bas a capacity o f 10
COQSiStS
0
r
fu62 &l.
of four s t a g e s o f Geary-iaaingB, ZeCiZp-
of the ore stream pave
of t h e time.The
on the ettcisc crushing plant output
sample into a small surge bin.
%his
for the di.96t FQ Supplied
and i t can be f i r e d with e i t h e r n a t u r a l g a s
The samplingplant
stage sampler operates
co-currently fired,
vibrating screens. Draft
by two, 45W Rotoclone dust collectoxs.
million Btu per hour,
sampling plant.
8O-foot,
The dryerdischargestheore,
wtrlch returns thp. ore
and the sereen undersize
is the vibrating grizzly uudersize
The feed to the dryer
discharge.
The screen oversize
more than 8 t o 9% moisturerequixedf2hg.
is accomplished i n a 10-foot diameter by
dryer.
screer!,
The sorgo
$fa
ocllotatw a
A
and disicharges tbe
lima sensing device
which controls the speed of the belts feeding the remaining
a steady stream o f f a l l f P g ore for ea& rampler.
f&sC
sampikers tQinawe
r@Ucrusher inserted in
the sample l i o e b e t v e e a t h e second m d W s d sanp&ers reduces the p a r t i c l e s i z e
from I f 2 t o l ' f 4 - t ~ . c k ~
The f h a Z aampze i a ~ 0 D e c t a din a drsrm in a quantftig apulvalent to (one
pound of sampde E m ea& faur cow o f Q F ~ - . %e sample
t o a 100-pound lot sample.
d r i e d aa& s p l i t down
The lot ~anqhaiei~Ehea prepared f o r asray using a
procedure approved by t h e Atomic Ene%$y Cammiartlmk.
,2
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
A conveyor b e l t t r a n s p o r t s t h e o r e
of t h e o r e p r i o r t o m i l l i n g ;
plant to the top
the ore into
of t h e f i n e o r e b i n s ,
anyone
..
i s very l i t t l e blending
i t s i d e n t i t yu n t i lt h eo r er e a c h e st h eo r eb i n s ,t h e r e
from t h e sample
and a b e l t t r i p p e r i s used to discharge
of four ore bins or into
a truck hopper f o r return t o t h e
o r e pad.
Grinding.
bymeans
The f e e dt ot h eg r i n d i n gc i r c u i t s
is withdrawn from the f i n e orebins
One feeder i s manuallycontrolled
of two belt feeders inder each bin.
i s automaticallyconttolled.
and theotherfeeder
collecting belt for transfer to the ball
the ore roasting circuit,
The feedersdischargeonto
m i l l feed belt or onto
The b a l l mill feed belts contain
which supply the load signals for the
a belt feeding
weigh sections
Condo-Weigh weightometers.
meters in turn vary the speed of the automatic feeders to maiatain
feedtotheball
mills.
a
The weightoa constant
Two ore bins supply the feed for each grinding cir-
cuit.
The g r i n d i n g c i r c u i t c o n s i s t s
Hardinge c o n i c a l b a l l mills.
WEMCO s p i r a l c l a s s i f i e r .
of two, 10-foot diameter
by 66-inch,
The mills operate in closed circuit with
A t a f e e d r a t e of 73 tonsperhour,
48 mesh and 35% minus 200 mesh i s produced.
a grind of
steel b a l l s .
5%
plus
The b a l l charge i n each m i l l is
approximately 22 tons, and the ba15 make-up c o n s i s t s of equal weights
2-1/2-inchforged
a 72-inch
o f 2 aiad
Each bas1 m i l l i s driven by a 400 hp, 4,160-
. v o l t , wound r o t o r motor d i r e c t l y g e a r e d t o t h e b a l l
a t 20 rpm o r 83% of critical speed, Grinding
mill.
The b a l l mills operate
is conducted a t 65% s o l i d s i n a
sodium carbonate and bicarbonate m i l l solution containing 37 grams Na2C03 per
l i t e r and 7 grams NaHC03 per liter.
Roasting.
The c l a s s i f i e r s overflow a t 20% s o l i d s .
The l e a c h i n gc h a r a c t e r i s t i c so fc e r t a i no r e s
jectingtheseoresto
canbe
a low-temperature roast. These ores are placed
3
improved by sub-
i n one ore
of 20 t o 25 tonsper
bin and f e d t o t h e r o a s t i n g c i r c u i t a t a r a t e
roasting i s accomplished i n an 8-footdiameter
i s raised slowly to
temperature of the ore
minute.
The ore is thencooled
by 80-foot rotary kiln.
Exhaust i s provided by a 36W Rotoclone.
the kiln.
conveyor which elevates
The cooler i s 8 f e e t i n
of a Baker type cooler.
and o p e r a t e s i n a c o n c r e t e b a s i n p a r t i a l l y f i l l e d w i t h
mill solution. Mill solution
transfers the ore to the ball
insure adequbte
is also sprayed over the cooler to
The cooled ore discharges
Thickenins.
a t 225O.F onto a high-temperature belt
pump t o a20-inchKrebscyclone.
A polyacrylamideflocculent
cyclonesandsby-passthethickener.
preheattank
and the
i s mixed with
in s e t t l i n g and c l a r i f i c a t i o n . The thickenedslurry
i s removed from the thickener with a
thickenerunderflow
is pumped'with
The cycloneoverflow
is discharged into the feed launder of a 100-foot diameter thickener,
thethickenerfeedtoaid
which
mill feed circuit.
The c l a s s i f i e r overflow from eachgrindingcircuit
a six-inch Wilfley slurry
at the dis-
combustion of the burner gas, ind the
The roaster discharges onto a drag
diameter by 55 feet long,
coaling,
l i f t e r s t o provide for efficient
A 20-foot brick-lined section
charge end of the kiln provides for
the hot ore to the feed chute
The
and s e n t t o t h e g r i n d i n g c i r c u i t .
contact of the ore with the hot air.
dust collector.
The
600° F a t a r a t e of 15 t o 20' F per
The r o a s t i n g k i l n i s equipped with angle
burners f i r e d i r e c t l y i n t o
hour.
Dorrcodiaphragm
and the cyclone sands are
a t 52-54% s o l i d s .
pump a t 40% s o l i d s .
recombined i n t h e l e a c h c i r c u i t
The overflow from thethickeners
t o a m i l l solution storage tank for recycle to
The
flow by gravity
t h e grinding and roasting circuits.
LEACHING
The exWaction of the
circuit consisting of
a18-hour
uranium from t h e o r e is ae&mplished i n a two-stage
a 4.5-hour leach a t 65 psig pressure and 200' F followed by
leach a t atmosphericpressure
and 185O F.
4
Leaching is accomplished i n
.
I
I
I
I
I
I
,,:, .
an aerated solution containing
liter.
and 7 grams NaHC03 p e r
37 grams Na2C03 p e r l i t e r
The extraction obtained from pressure leaching varies
depending on thetype
and gradeoftheore.
increases the extraction
tion ofonly
from 85 t o 95%
of theleach
The atmosphericportion
7 t o 10% f u r o r e s t h a t
85%. The grade o f the ore averages
'
produce a pressure leach extrac0.21% U308 and t h e leach residue
averages .011% U308.
o€
The chemistry of the alkaline leaching system involves the oxidation
I
any t e t r a v a l e n t uranium to the hexavalent state using the
I
I
I
I
I
I
I
I
I
I
I
I
l i n i t y t o form a uranyl tricarbonate complex ion according to the following
the air.
The hexavalent uranium d i s s o l v e s i n t h e
oxygen a v a i l a b l e i n
presemce o f carbonatealkare-
action *
2U02
iO2 i6Na2C03
+
2H20 ___o_ 2Na4U02(C03)3
The uranium w i l l not dissolve in
a l k a l i n i t y formed with the
+ 4 MaOH
a sodium carbomate solution because the hydroxide
complex ion causes the ion to
c o n t a l i n g sodium bicarbonate, the hydroxide alkalinity
In a solution
decompose.
i s neutralized immediately;
and the reaction proceeds as follows:
2U02 i0 2
-!-
+ 4Na2CO3 -!-
6Na2C03 i4Na2HCO3-2NA4U02(C03)3
2H20
. I
is accomplished in two s e p a r a t ec i r c u i t s
PressureLeaching..PressurePeaching
each containing
eight
autoclaves,
eight autoclaves. but
Each c i r c u i t can
be
operated
as
'1
The f i r s t unit i n each leachikg circuit
underflow and thecyclonesandsare
i s a preheat tank
A two stage
c e n t r i f u g a l pumping system is &sed t o pump the preheated s l u r r y i n t o a s p l i t t e r
tank where t h e s l u r r y is divided into two streams for feed to the autoclaves,
tanksequippedwith
bf 16-foot high,
a top-mounted '"Lightrdn" mixer,
5
$
'1.
i m which the thickener
recombined and heated t o 150° F .
The autoclaves are 12-foot diameter
.+
a s e r i eos f
i s Gormally divided fnto two eircuits of four autoclaves.
'.I
'
domed, pressure
Each task has two, turbine
.
imFellers moumted on a l%-foot, &inch dfameter s h a f t .
type,42-inchdiameter
b o t t m of the autoclaves through a 30-incb bubble-
Oxidation a i r is fed iato the
Fn an atetoclaw cizeuit is maintaimed by an automatic
cap diffuser, Pressure
on thepipeheaderconnected
bleed-offvalve
.
t o eachautoclave.
leachimg is supplied by three set8 oE 2-inch- 6 t e m coils
Heat f o r
ia the f i c s t autoclave
in each c i r c u i t of four:. Theremaiarfarg aatoclaves M e only one stem !@il
which is used t o hold operating temperature
an autoclave i s removed fgom service, the
series of seven autoclaves;
Tempezature and
are maintained by allefamsztie coatrols,
pressure in the autoclave circuit
event that
i f necessary,
'La the
c%zmP%fa azranrged into a
attd the tonnage is redwed t o iuain&aha ron8fant
retention time.
i s by gravity, amd the feed
The flow through the autoelwes
clave enters at the slurry surface
i n t e r n a l riser.
t o each aurto-
and diaaharges from the battom through an
A s i x d n c h d r o p between au%eebavesprovides the head for flow
through the six-inch
pipimg in t h e a5rcof,t,
The diacharge from thelest.azBtocliwe
clave i s approximatelyll,000gafla&s.
i n each c i r c a f t of four flows
The operating voO%ume
of each auto-
ilato B %eCdowa tank,
'
The l e v e l in t%hel e t d o m
tank is maintained by a capaeita#s@ type probe and. level conttwd&er. .From the
letdown tank, the leached
s'kwry d f s e b r g e s t h r o u g i
exchanger t h a t coola t h e s l a r r 2 &nu
system provides the energy
20@
P eo
280°
B
coeacmtlrie tube heat
B, The pressure
a%?the
t o push the p a r t i a l l y leached s l u r i y &rough the
letdown control valve,. the heat exchanger,
and 900 f e e t of pipe t o the atmos-
pheric leach circuit.
AtmosphericLeachins.
The atmosphetfcleaching
Pachuca tanks 19 f e e t fn diameter by 38 f e e t deep.
leach circuit
c i r c u i tc o n s i s t s
of
The s l u r r y from
nine
the pressure
16 added to the top of the f i r s t Pachuca tank; from wbich i.t.flows
1
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
by gravity through the tanks
Four,ten-inch
pumpsump.
a i r l i f t s provide agitation for each
i s providedthmughsteamjacketsonthe
the circuit
air for oxidation
Pachuca; and h e a t f o r
a i r l i f t pipes. Additionai
is suppliedthroughfive,3/4*inchpipessuspendedfronthe
topofeachtank.
'
and into an elevated
The air enters the slurry approximately three feet
from tho
bottom of the tank,
LIQUID-SOLIDS SEPARATION
Filtratioh.
Theremoval
uranium values from t h e l e a c h c i r c u i t
of.thesoluble
discharge i s accomplishedwtththreestagesofcountercurrentfiltration.
filter stage contains five,
drumvacuum
filters,
Back
650 square-foot and two, 570 square-foot, rotary
The filters a r e 11-1LZ f e e t i n diameter, and a r e equipped
with polypropylene grids.
A -huvy dutynylon
f i l t e r c l a t h i s used
t d cover the
f i l t e r s , and 14-gauge s t a i n l e s a eteel wire is wound on t h e f i l t e r s t o retain the
fiiter cloth.
i
I
The discharge from the sLIcor&daryl e a c h i n g c i r c u i t i s pumped t o t h e f i l t e r
feed tank
bymeans
of four-inch Wilfley
feed to the first stage of
a pipe-loop
by means of a five-inch Wiafley slurry
pump;
Each of the
and r e t u r n s t o t h e f i l t e r
f i r s t stage f i l t e r tubshas a level c o n t r o l l e r which
operates a valve on thg feed line.
into the filter feed line
A dilute solution of flocculent
on the discharge side
of the pump.
and flocculent are mixed by flow through the piping
asmallmixing
chamber og each filter tub.
enters at the center
The pipe-loop feeds
into the bottom of a head tank which provldes
feedpressure.Excessfeedoverflswstheheadtank
feedtank.
The
filters is pumped from the f i l t e r feed tank through
each f i l t e r and then discharges
I
pumps and 800 f e e t o f p4pipeline.
of the tub.
7
is pumped
The f i l t e r feed
and the feed valves
The feedtoeach
and i n
first s t a g e f i l t e r
'
i
,
cake i s washed with a h o t f i l t r a t e s o l u t i o n
The f i r s t s t a g e f i l t e r
The f i l t r a t e i s s e n t t o c l a r i f i c a t i o n ,
thethirdstageoffilters.
from
and the
f i r s t s t a g e f i l t e r cake discharges into repulpers for repulping with third
stage filtrate.
and i n t o t h e
The repulpedslurryflows
by gravitythrough
second s t a g e o f f i l t e r s , F l o c c u l e n t
solution to aid in
an a g i t a t e d sump
is added to the repulper
second s t a g e f i l t r a t i o n .
The second and t h i r d s t a g e of filters are operated in much t h e same manner
as the first stage; 'except that recarbonated barren solution
from the precipi-
t a t i o n c i r c u i t i s used as a f i l t e r wash and in the repulpers on t h e second stage
and t a i l i n g s pond solution or water
is used as a washon
wash s o l u t i o n f o r e a c h s t a g e ' o f f i l t e r s
s t a g e f i l t r a t e is sent to the
t r a t e i s usedas
wash and repulper solution
of filters
on t h e f i r s t s t a g e
Clarification.
.
The
Is repulpedand slurried f o r t a i l i n g s
0.8% of t h e
,
The f i l t r a t e produced by t h ef i r s ts t a g eo ff i l t e r s
pregnant solution for the precipitation circuit,
fied before precipitation
fil-
of f i l t e r s .
The loss of soluble uranium.in the tailings slurry averages
uranium i n t h e mill feed.
The
i s maintained a t 150° F, Thesecond
m i l l s o l u t i o n c i r c u i t , and the third stage
f i l t e r cake from t h e t h i r d s t a g e
disposal.
the third stage,.
is the
but the solution must b e c l a r i -
t o remove slimes t h a t . h a v e p e n e t r a t e d t h e f i l t e r c l o t h s .
The c l a r i f i c a t i o n i s conducted in a t h i c k e n e r i n which the major portion of the
contaminants settle.
TailingsDisposal.
The f i l t e r cake from t h et h i r ds t a g eo ff i l t e r s
with recycle solution
from t h e t a i l i n g s
a t a i l i n g s s l u r r y t a n k whichoverflows
reciprocating sample c u t t e r .
i s repulped
pond and transferred through launders to
i n t o a 1aunder.and over a Geary-Jennings.
The t a i l i n g s sampleroperratescontfnuously
8
and d i s -
'.
charges into a small W-ilfley pump f o r ' t r a n s f e r t o asecofidsampler.
The second
and is used t o o b t a i n t h e f i n a l t a i l i n g s
sampler operates intermittently
The t a i l i n g s d i s p o s a l a r e a
sample.
is a:.llO*acre pond enclosed within an a r t i f i c i a l
in 'the pond a r e a t o a height
o f 10 f e e t .
Dike construction i s now accomplished by pumping t h e t a i l i n g s s l u r r y a t
40% s o l i d s
dike originally constructed from the clay
throqghthree,
truck-mounted,10-inch
cyclones.
and the slimes and t a i l i n g s s o l u t i o n
thedike,
flow i n t o t h e pond,
pumps i n s e r i e s and a cyclone truck.
cyclones services each half of the
The pre$eDt
pond.
Thepumping
One s e t o f pumps and
capacity is 959 gpm of
through 4;OOO f e e t of nine-knch pipeline
t a i l i n g s s l u r r y whenpumping
on
The disposal o f t a i l i n g s i s handled by 'Cwo,
dike is approaching 80 f e e t i n h e i g h t .
eight-inchHydroseal
The cyclone6depositthesands
and three
cyclones.
The slimes in the cyclone overflow settle i n t h e t a i l i n g s pond, and the
t a i l i n g ss o l u t i o n
i s recoveredthrough
two centrallylocateddecant
tcwers.
The
underground i n t o a pump basin and i s returned to the
recovered solution flows
m i l l by means of a 900 gpm pump and 2,Sm feet of eight-inch pipeline. Tailings
recycle solution is used
in
t h e . f i l t e r b u i l d i n g f o r washon
filters and for repulping of the f i n a l ' t a i l s .
used to preheat the tailings
pondwash
A waste heat recovery circuit
the tailings slurry to
pondwash
of
ik
water.Four,tube-and-shellheatexchanaers
i n t h e powerhouse cool the diesel engine jacket water
preheat the tailings
the third stage
from 180° F t o 150' Fand
water &om 80° I to 130° F. Raw water i s added to
make up for evaporation and tie-up i n t h e t a i l i n g s pond.
PRODUCT ReCOVERY
Precipitation.
The uranium e x i s t s in thepregnantsolutionasthe
tricarbonate ion which i s s t a b l e a t a pH lower than11.0.
complex, qranyl
When the pY i s sqiaed
t o above 12.0 with c a u s t i c sod#, the complex ion decomposes t o form sodium
carbonate and sodium diuranate.
The l a t t e r s a l t ,
is
ayellowprecipitate,
commonly called yellowcake.
2NA4U02(C03)3
+ 6NaOH -.
Na2U207
Precipitation i s conducted i n atwo-stage
+
6Na2C03 + 3H20
c i r c u i t i n which the pregnant solution
i s mixed'with recycled yellowcake to increase the soluble
uranium content and
then mixed with caustic soda t o p r e c i p i t a t e t h e uranium as yellowcake.
The pregnanr solution for precipitation
i s pumped from a storage tank
through a concentric tube heat exchanger to heat the solution
from 325' F t o
1500 F. The heat i s obtained by cooling the pressure leach discharge
t o 180° F. The temperature of the preheated solution is.raised to
tube-and-shell heat exchanger before flowing into the first of
from ZOO0 F
F in a
180'
two yellowcake
dissolving tanks.
The technique of. recycling yellowcake-to a redissolving tank
to achieve a
solution.
more complete precipitation of the
was developed
uranium in the original pregnant
The dissolvingtanksoperatewithayellowcakerecycleequivalentto
500% of the uranium i n t h e incoming pregnant solution, In five hours of contact
with the pregnant solution, a portion of the yellowcake dissolves;
soluble grade of the solution increases
liter toapproximately
from approximately 3.5 grams of U308 per
7.5 grams of IT308 per liter. The p r e c i p i t a t i o n e f f i c i e n c y
of t h e c i r c u i t v a r i e s w i t h t h e l e v e l o f s o l u b l e
the grade of the
and the
uranium
i n the feed.
Based on
incoming pregnant solution, .the precipitation efficiency
vary from 92 to 94% on straight pregnant solution
i n c r e a s ei nt h es o l u b l e
will
t o b e t t e r t h a n 98% with a 100%
qranium i n thepregnantsolution.Undissolvedyellow-
cake i n c i r c u l a t i o n does not appreciably effect the precipitatgon.
The p r e c i p i t a t i o n c i r c u i t c o n s i s t s o f e i g h t a g i t a t e d t a n k s
whichhave
a
r e t e n t i o n time of six hours.' A solution of 50% c a u s t i c soda i s metered i n t o t h e
10
I
I
I
I
I
I'
I
I
1
I
I
I
I
I
I
I
I
I
I
f i r s t tank to effect fhe precipitation
of theyellowcake.
be added to the pipeline feeding the tank
t o change t h e c h a r a c t e r i s t i c s of the
p r e c i p i t a t e and the efficiency of precipitation,
of addition.
The c a u s t i c may a l s o
which a r e a f f e c t e d by the paint
A s u f f i c i e n t q u a n t i t y of caustic is added t o t h e c i r c u i t t o n e q t t a l -
i z e t h e sodium bicarbonate in the pregnant solution
and to maintain an exceqs
og
5.5 grams of NaOH per l i t e r of barren solution.
a 4tO-foof
The yellowcake s l u r r y from t h e p r e c i p i t a t i o n c i r c u i t f l o w s i n t o
diameter by 12-foot deep thickener
8-foot deep feedwell.
The thickener i s insulated with a floating.
two-inch
on the sides.
Styrofoam l i d and two inchesofFiberglassinsulation
thickener operates a t 170 t o 180'
by
which i s equipped with a 12-foot diameter
Because the
F, t h e i n s u l a t i o n i s necessary to prevent
evaporation and heat ,loss which create thermal ,currents that hinder settling.
The thickener underf,low is pumped a t 39-49% s o l i d s t o t h e
section or to the yellowcake dissolving tank for recycle.
vanadium removal
The tbickenerover-
flow is pumped t h r o u g h t h r e e f i l t e r p r e s s e s f o r f i n a l c l a r i f i c a t i o n
and then to
caustic barren storage.
Recarbonation.
The causticbarrensolution
produced i n t h ep r e c i p i t a t i o nc i r -
c u i t c o n t a i n s sodium carbonate and a small quantity of
reuse the barren solution, the
sodium hydrexide.
caust3.c must'be converted to
and sodium bicarbonate.Thisconversion
sodium carbonate
i s accomplished i n two packed towers
i n which t h e c a u s t i c barcren solution is contacted with boiler flue gas.
CO2
in t h e f l u e gas ne,utralizes the
carbonate to bicarbonate.
The
sodium hydroxide and converts some o f the
The recarbonated barren solution with
NaHCO3 p e r l i t e r i s s e n t t o t h e f i l t e r b u i l d i n g f o r
stage of filters.
11
..
To
use as
washon
two grams of
the second.
I
1
I
I
VanadiumRemoval.The
I
moval of the excess
I
I
I
I
I
I
I
I
I
I
I
I
I
I
primary precipitationofyellowcakeproducesaproduct
which, when washed and d r i e d , w i l l assay 75 t o 77% U3O8, 5 t o 6% V2O5, and 2
t o 2.5% CO3.
Although the uranium content is satisfactory, both the
and carbonatecontentoftheprecipitate
vanadium
exceed contract specifications.
Re-
vanadium and carbonate i s required before the yellowcake
is acceptable to the
Atomic Energy Commission.
The removalof
t h e vanadium and, quite incidentally, the carbonate
the yellowcake i s accomplished by roasting followed by water leaching.
yellowcakethickenerunderflow
i s .pumped t o a d i s c f i l t e r t o
from
The
dewater t h e s l u r r y ,
and t h e f i l t e r cake is agitated with a small quantity of sodium'carbonate before
being fed to the yellowcake roaster.
Yellowcake r o a s t i n g is accomplished i n an 8-foot 6-inch diameter,
hearth, Pacific furnace,
and reaches 1,600'
The feedtothefurnace
charges into a
200'
i s dried on thetophearth
F by the time i t leaves the fourth hearth.
sixthhearthsholdtheyellowcakeattemperature.
water cooledscrewconveyor
F before discharging into
which cools the calcine to approximately
Water is used t o d i s s o l v e
the vanadium and carbonatecontaminants i n theyellowcake.
thickener. overflow containing the
storage.
The f i f t h and
The calcinedyellowcake dis-
a b a l l m i l l conveyor.
cake s l u r r y is collected in a 16-fooa diameter
six-
.The leachedyellow-
by 10-foot deep thickener, and the
vanadium is f i l t e r e d and sent to vanadium
The vanadium solution containing 8% V2O5 i s presently sold to a nearby
vanadium producer,
ProductHandling.
Vanadium solutioninthesecondaryyellowcakethickener
underflow i s removedontwo,
drum f i l t e r s .
eight-foot diameter by eight-foot long,
The f i r s t f i l t e r cake is repulpedwithwater
on the second f i l t e r .
vacuum,
arld theri f i l t e r e d
Water is used as a wash on each f i l t e r , but h o s t of the
12
I
I
I
I
I
I
1
I
I
I
I
I
I
I
I
I
I
I
I
washing is accomplished in the dewatering action of the filters.
The.filter cake from the second yellowcake filter discharges into the
extruder mechanismof a Proctor-Schwartz steam dryer and is forced through the
extruder screen as 3/16-inch diameter noodles.
The yellowcake dryer is heated with steam, and the yellowcake is dried
by circulation of hot air through
a slotted stainless steel
belt passing con.
I
tinuously through the dryer,
' The dried yellowcake, containing'less than one
percent moisture, is reduced to minus
1/8 inch ina modified roll crusher and
then carried to drum loading by of
means
a screw conveyor.
Yellowcake is packaged in 55-gallou, open headatdrums
three drum
loading stations. The screw conveyor discharges the
intofirst drum until the
drum and the feed chute are filled, The screw then carries the material to the
next drum. A vibrator under the first loading station is used to settle the
contents of each drum. After the drums are sampled and weighed, the head is
sealed in placeand the drumis cleaned and placed in storage for shipment.
Each drum contains
a maximum of1,000 pounds and40 drums of yellowcake comprise
a lot. The average lot of yellowcake assays
85.5% u308, 0.4%V205, and 0.4%
C03; and a normal
lot of yellowcake contains 34,000 pounds
U308. of
LOW SODIUM CIRCUIT
In order to meet specifications
for sodium contenti n yellowcake if
processed into uranium hexafluoride by the Allied Chemical Corporation for
commercial sales an additional processing step had to be added to the flowshee
After
removalof vanadium the yellowcake containing approximately
7.5% sodium
is
dissolved with sulfuric acid aat
pH of 2.2 in a ten-foot diameter by twelvefoot deep tank. The overflow from this tank discharges ainto
ten-foot by
twelve-foot tank where
amonia is added to maintain
a pH of 7.4. The uranium
13
I
I
I
reprecipitates as yellowcake containing less 0.5%
than sodium.. This product.is
I
I
I
I
dried by the Procter-Schwartz steam dryer and packaged
as described under the
filtered by the two eight-foot diameter by 'eight-foot long, vacuum, drum filters,
section
on
ANCILLARY
Product
Handling.
FACILITIES
Powerhouse. The electrical generation equipment and a portion of tk? steam
.
..
generating and air compressing equipment are located in a.centra1 powerhouse.'
The elctrical equipment consists of seven, diesel engine driven generators,
I
which supply all of the electrical energy requirements for the mill. The diesel
I
gas and diesel fuel. The generators are rated
at 1,000 kw. The generation. and
I
I
I
I
I
I
I
I
I
I
engines are rated 1,400
at
horsepower and are operated aon
mixture of natural
distribution
voltageis 4,160 volts.
The steam generating equipment consists
of three, 7,500-pound per hour,
package boilers which generate steam
at 125 psig.
The boilers provide the steam
requirements far the secondary leach circuit and supplemental steam for heating
wash solutionsin the filter section..Three &350 scfm, 45 psig compressorsLn
the powerhouse supply the air requirements the
forsecgndary leach circriit and
sypplemental airfor the filter buildip&
14
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I