Nov. 29, 1966 A, V. HENRICKSON ETAL
PROCESS FOR THE RECOVERY OF METALS
3,288,569
Filed Aug. 12, 1963
RAW LIGNITE ORE
~
2 Sheeto-Sheet 1
1-4--- ACID
AGGLOMERATION
1-4--- WATER
I
NODULES
TAILS
t
PERCOLATION
LEACHING
PREG~ANT
L1Q~OR
SOLVENT
EXTRACTION RAFFI
I
ACID
NATE
NoOH
CARBONATE
STRIP LIQUOR
t
YELLOW CAKE
----;~ PRECIPITATION !------i-YELLOW CAKE
I
FILTRATE
t
TO Mo RECOVERY
INVE?\'TOR5'
ANGUS V HENRICKSON
6£OR6£ C kANE
BY
5/i~u~cIafl a.,a ~o
ATTORNEYS
Nov. 29, 1966 A. V. HENRICKSON ETAL
PROCESS FOR THE RECOVERY OF METALS
3,288,569
Filed Aug. 12, 1963 2 Sheets-Sheet 2
RAW LIGNITE
AGGLOMERATION
NODULES
ADSORPTION
TOWER
RATE
t
PERCOLATION
LEACH
C
f--NH3---.
BOIL
i--C02-
rl PRECIPITATE f----NH3
J
FILTER FILT
I
STEAM
OXIDANT
LIME
CALCINE
f
U30S CONCENTRATE
APPROX. 5% U30S
2 INVPJTORS
AN6IJS V HENRICKSON
GE.OR6£ C KANE
BY
S~a-d~~
ATTORNEYS
United States Patent Office 3,288,569
Patented Nov. 29, 1966
1 2
Ash CaC03
.096 _
Zr
Percent
.224
Mo
---~336- ---~629- ---68:6' ::::::::::
..003975 .095 58.5 8.57_
.263
.404
.066
.350
.144
.243
U30S
9.9
12.3
7.8
27.7
47.3
7.2
MoIsture
TABLE I.-ANALYSIS OF SA:\IPLES
Sample
In making samples A, B ·and C, twelve samples were
taken from widely separated areas in North and South
Dakota. These twelve samples were ,composited into
three different samples; sample B, a composite of equal
weight of the six highest grade of the twelve; s~mple C,
a c{)mposite of equal wei,ght of the six lowest grade of the
twelve and sample A, referred to as the "master composite,"
a .composite of equal weight of each of the
twelve. Sample A is believed to include some of almost
every kind ·of lignite that is potentially mill feed. Sam-
A _
B _
C _
D _
E _
F _
----1---1-----------
It is another object of this invention to provide a process
for the formation from carbonaceous minerals of
nodules which have the stability and porosity required to
permit leaching of the metals therefrom by the required
5 leaching agents.
It is another object of this invention to provide a method
for the recovery of uranium from carbonaceous material
by percolation leaching in which either an acid or
an alkaline leach can be used.
It has been found that the above and other objects can
be accomplished by first agglomerating the raw carbonaceous
ore to form nodules by a novel process to be described,
forming a bed of the nodules and leaching the
ore from the nodules by percolation leaching with either
15 an acid or alkaline leaching agent. The nodules are
formed by cascading the ore particles under moist conditions
and the formed nodules are cured under high humidity
conditions to prevent drying. The preferred leaching
agents are sulfuric acid and ammonium carbonate.
20 In the preferred procedure, a portion of the leaching
agent, acid or basic, is added in the nodulizing step as
the nodules are being formed. The metal is recovered
from the acid leach liquor or soluton by conventional
ion exchange or solvent extraction processes. An im-
25 provement in the ammonium carbonate leach modification
is the precipitation of uranium from the pregnant
leach solution with lime followed by calcining the precipitated
uranium and dissolving it in sulfuric acid from
which it can be recovered by conventional methods.
One principal inventive step in the method is the formation,
prior to percolation leaching, of nodules having
suitable characteristics for the formation therewith of a
stable and permeable ore bed through which the leach
solution will readily pass to leach the uranium from the
35 ore into a clear liquor suitable for direct feed to a recovery
system. The formation of suitable nodules from
the carbonaceous containing ore converts the ore to a
form in which it cannot clog the bed, and supports it in
a manner so that it can be effectively contacted by the
40 leaching agent.
The invention will now be described in conjunction with
the flow sheets of FIGS. 1 and 2 by its application to
uranium ore associated with a large percentage of lignite,
referred to herein as lignite ore. The ores used in the
45 tests for most of the results in the tables given below were
made from a sampling of lignite ores from various areas
in the United States in order to provide samples having a
representative composition of lignite ores in general. The
chemical analyses of the ores are given in the following
50 table:
Filed Aug. 12, 1963, Ser. No. 301,359
24 Claims. (CI. 23-319)
3,288,569
PROCESS FOR THE RECOVERY OF METALS
Angus V. Henrickson and George C. Kane, Golden, Colo.,
assignors, by mesne assignments, to SusqnehannaWestern,
Inc., Denver, Colo., a corporation of Wisconsin
This invention relates to a process for the recovery of 10
metals from their ores; more particularly, it relates to a
process for the recovery of metals from carbonaceous
minerals.
The invention is illustrated herein by a description of its
application to the recovery of uranium from lignite as
an example of a carbonaceous material containing uranium.
The inventive method is not limited to this applicaton
as it can be effectively applied to the recovery of
uranium from other type ores and to the recovery of other
metals from their ores in general. The preferred use of
the invention is for recovering metals from ores which
are associated with organic materials, these materials making
reooveryof the metals difficult or impractical by conventional
recovery processes.
Ore grade uraniferous lignite exists in commercial
quantities in carbonaceous fuel deposits in various areas
of the United States, particularly the Dakotas and Montana.
The high carbonaceous content of the material has,
in the past, made it commercially unfeasible to recover
uranium values from the relatively low grade uranium 30
ore associated with the lignite by conventional methods.
For example, attempts to concentrate the ore by percolation
leaching result in prohibitive clogging of the bed
due to the presence of organic slimes and other organic
materials. Prior to this invention no method was available
for forming carbonaceous ores into nodules for percolation
leaching which were sufficiently stable and porous
to permit leaching by the required leaching agents. Prior
attempts to form nodules of such ores have met with
failure in that the nodules were not sufficiently stable to
withstand the leaching, or were not sufficiently porous to
permit percolation so that clogging of the ore beds resulted.
One approach has been to burn the ore to reduce
it to ash and then leach the ash with acid by conventional
agitation leaching methods. Because of the
high acid consumption, however, this method of uranium
recovery offers only a marginal profit potential. The
reagent cost is an extremely important factor in any method
for recovering uranium from relatively low grade ores.
Prior art practices for the recovery of certain metals
from their ores have included suspension of the ground
ore in a matrix followed by leaching. This procedure
has proved unsatisfactory for recovering uranium from
carbonaceous minerals due to the interference of organic
materials. As mentioned above, the cost of reagents in 55
acid leaching of low grade carbonaceous uranium ores by
agitation methods has proved prohibitive. Alkaline agitaton
leach methods for recovery of uranium from these
ores have not proved successful mainly because of high
reagent costs and because of the interference of organic 60
materials. Accordingly, it is an object of this invention
to provide a new method for the recovery of metals from
their ores by percolation leaching.
It is another object of this inventon to provide a method
for the recovery of metals from ores associated with or- 65
ganic or carbonaceous materials.
It is still another object of this invention to provide a
commercially feasible method for the recovery of uranium
values from lignite contaning uranium.
,It is a further object of this invention to provide a 70
method for the recovery of uranium from carbonaceous
material by percolation leaching.
3,288,569
4,
nodulizing process by allowing a rapid and even distribution
of moistme around and through the particles.
The method of achieving rugglomeraHon in the examples
given herein was to tumble the material in a
5 tilted rotating cylinder. The angle of tilt and rotating
speed must be such that the ore will :cascade freely over itself.
Motion of the ,ore partides and nodules over themselves
imparts a iorging action !by virtue of the particles
.colliding withea·ch other.
It has been found that flocculants are helpful, in the
case of some ores, in achieving nodule formation and
stability by causing the particles to adhere. Various binders
may be used to impart rigidity to the nodule structure.
The binder material acts to fill in the interparticle void
15 and then harden into a rigid nodule structure. Any
binder material used must necessarily be compatible with
both the material being agglomerated and with the reagents
and conditions employed in the subsequent leaching
steps. Examples· of suitable binder materials for
20 forming nodules are resins, soil stabilizing agents, silicates,
plaster of Paris, or even cement. Of course the
use of such agglomerating agents as surface active or wetting
agents, flocculants or binders are variants of the invention
which are quite often unnecessary as nodules of
25 suitable porosity, coherence, homogeneity, and rigidity
can be formed without the use of the agents. I
It has been found that the method of curing the nodules
is a very important factor in achieving a stable agglomerate
structure. By "curing" is meant treating the nodules
·30 under humid conditions but not permitting them to dry.
A minimum curing time is required for the nodules to
reach homogeneity with respect to both contained liquid
and any binder material which may be present. The curing
period also allows a setting action to occur within the
35 nodules. If agglomerated nodules are allowed to completely
dry out after agglomeration, they will shrink.
Subsequent wetting, as in a leach, will then cause swelling
and the nodules will physically disintegrate as the swelling
action breaks the bonds present. The swelling when
40 wetted is primarily caused by the particles being forced
apart as the liquid enters the interparticle voids under
capillary action. It has been found that curing under
saturated humidity conditions is a method of avoiding
drying and the resulting nodule instability. Nodules are
45 formed into the percolation leach bed while they still
have a high content of moisture.
An additional cause ·of nodule breakdown during percolation
leaching is 'gas formation. This is seen when
acid solution is used for leaching nodules containing cal-
50 cium carbonate. It is avoided by adding acid during
agglomeration. A curing period then permits formation
of CO2 and evolution thereof before the percolation
step. Accordingly, an important feature of the invention
is' the addition of a portion of the leach solution during
55 the nodule formation step.
Among the criteria used to assess the stability of nodules
are apparent extent of disintegration during leach,
extent of reaction with leach liquor, slump, and flow
rate.
60 Stable nodules are uniform in size and spherically
shaped as opposed to being flattened or flaky in appearance.
Distinct nodules after leaching are a definite indication
of stability. Unstable nodules will crack, spall ot
flatten during the flooding or leaching cycle of a perco1a-
65 tion leach. Visible disintegration is indicative of instability.
Visible reaction with the leach solution will usually
destroy the stability of nodules. Observations indicating
poor stability may include effervescense, formation of a
precipitate, or a change in color of the nodules. Slump,
70 or the measurement of the amount of settling or slump of
a column of agglomerated ore, is a good quantitative test
of stability. Slump is best expressed as a percent of the
original ore bed depth, measured after leaching but before
draining the final liquor. Less than 15% slump is
75 generally indicative of a stable structure. Flow rate, the
3
pIes D and Fare fwm Wyoming, and sample E is a composite
'Of 27 samples from Billings County, North Dakota.
Nodule formation
It has been found that the agglomemtion '01' the raw
lignite 'Or other me to form nodules of the pmper type
is a highly Important prerequisite t'O the percolation leaching
of the ore for a number ·of reasons. Among the many
factors whkh influence a per.colation leach pro.cess are
particle size and distribution, particle porosity, percola- 10
ti'On rate, peI'oolation direction -and washing. Particle size
and distribution affect the permeability 'Of an ore bed. An
e:xccessive amount ·of fines or sILmes in the ore bed wJ1l
reduce its permeability, sometimes to the extent of complete
flow stoppage. Ideal peDmeability would be achieved
by an me of uniformly sized particles. Proper agglomeration
of an 'Ore produces this ideal ,condition.
The porosity of the ,individual ore particles will directly
affect diff'usion 'Of the leach solution into particles and the
leach liquor out 'Of the particles. This factor is common
to all extraction processes, and the are grind is contr
·oIled primar,ily by the nature 'Of the specific are being
treated. Properly agglomemted nodules are sufficiently
porous to allow rapid leaching rates.
The primary requisite 'Of a percolation rate is that
sufficient time be allowed for diss'Olution and diffusion
of the material being extracted. Normal per.colation rates
are ,of the mder ,of 1 bed volume of liquid per 8 hours.
Too ·great a peroolation rate will physicallyoomprei>s an
ore bed and cause clogging unless the bed is extremely
stable. Percolation rates must be adjusted to pr'Ovide all
'Optimum condition of value extraction versus bed sta'bility
and reagent ,oonsumption. Downward pewola,tion leaching
will normally produce a dear liquor. In cer.tain
cases, however, upward peroolation may be used to prevent
slimes ,from settling and plugging the bed. Flow
rates in such .cases must be kept low enough to prevent
solids from being carried into the liquO'fs. Upward perc'Olation
-is also quite useful in removing gas 1'Ock,ing by
either acoumulated air ·or eV'olved gas. The initial flood
of an ore be,d is invariably upward percolation. Both
downward and upward perc'Olation pr'Ovide an almost
positive displacement of the solution from the ore bed.
The final washing of the percolation leached ore bed
is readily aocomplished by flushing water through the bed.
Washing efficiency is high and percolating one bed volume
of wash solution through the ore, followed by drainirug
of the wash solution will normally wash the bed sufficiently.
To be successful, the percolation leach process must
(1) produce a stable permeable or bed through which
the leach s'Olution will readily pass, (2) leach the uranium
'Or other metalfmm the me into a dear liquor suitable
·ior direct feed toa recovery system, and (3) recover
the uranium, and any valuable by-products, from the
leach liquor. Successful agglomeration ,for peroolation
1eaohing to give the above results must (1) effectively
c·oagulate the slimes from the me, (2) produce nodules
which are physically stable in ,oontact with leach solution,
and (3 ) produce a permeable or bed,
It has been iound that an optimum moisture content
and moisture homogeneity must be achieved before carbonaceous
fine material will agglomerate when tumbled or
'cascaded over itself. Excess moisture will decrease
capillary action by decreasing the surface tension holding
the par,ticles together. Deficient moisture will weaken the
bonding becruuse of insufficient liquid to ,complete the
liquid bridge in the ,gaps between partides. The rate of
moisture addition, an important factor an achieving homogeneity,
should be slow enough to <allow ,the moisture to
absorb evenly throughout the mass of the material. Rapid
addition of water results in poor stability. It has been
found as a feautre of this invention that the addivion of
a surface active or wetting agent sometimes aids the
3,288,569
TABLE n.-HoSO. PERCOLATION LEACH
Sample A:
Assay: .263% U30 S; .224% Mo; .096% Zr.
Moisture: 9.9%; Grind: -1;4".
Agglomeration procedure: Agglomerated at 23 0 C., 52
r.p.m. in 5-gallon bucket. 77.9 gm. (346 lb./ton) of
H2S04 added directly from beaker and then ore
sprayed with tap 'water. Nodules 25.1% moisture.
Cure: 68 hrs., 23 0 c., 100% relative humidity.
Leaching vessel: 1.85" LD. x l' column.
Leaching procedure: Constant flow, downward percolation,
one bed-volume removed every 8 hours.
Flood solution: 5% H2S04, pH 0.65.
Liquid volume in are bed: 310 ml.
Leaching temperature: 23 0 C.
Leach solution: Same as flood.
6
of the column of the percolation vessel to maintain saturated
moisture conditions during the cure period. The
nodules must be cured under high relative humidity conditions,
preferably about 100% R.H. The curing period
5 will again depend upon the material of the nodules but
the nodules must be allowed to set properly. A curing
period of about 24 hours was found to be adequate for
lignite material.
The above agglomerating procedure was used success-
10 fully in percolation leaching performed in I-foot and 4foot
percolation columns. For greater are bed depths,
the ore grind and nodule size may possibly be adjusted
toward the coarser side with no detrimental effects.
However, nodule porosity and diffusion rates will nec-
15 essarily be a consideration if larger nodules are used.
Also, in a commerci\lL agglomerating process the .. ore
may be wetted to just below the preferred moisture content
before entering the agglomerating machine.
It was found that lignite could be satisfactorily agglo-
20 merated for percolation leaching without the use of any
wetting, flocculating or binding agents but by merely
cascading with addition of leach solution to the particles
under the proper conditions of temperature and moisture,
followed by curing under the proper humidity condi-
25 tions. As a result of a large number of tests on lignite
ores the following general preferred process was established.
The ore, ground to four mesh, is agglomerated
slowly by spraying with water containing the leaching
agent, such as sulfuric acid or ammonium carbonate.
30 Wetting agents, such as, "Aerosol" and flocculating
agents such as "Separan," or, equivalents thereof can be
added if necessary to improve stability. The acid or base,
depending upon which is used for leaching, "Aerosol,"
and "Separan" content of the agglomerating solution
35 should be adjusted to give about 100 pounds of acid or
base and about 0.1 pound each of "Aerosol" and
"Separan" per dry ton of ore in the nodules. The nodules
should be cured about 24 hours at about 100% relative
humidity prior to leaching. The nodules are not
40 permitted to dry out and are used in the bed in the moist
condition while containing a high percentage of moisture.
The are bed should be flooded by upward percolation
and leached with three bed volumes of leaching
solution every 24 hours. A temperature below about 500
45 C. is preferred for the nodulizing step.
A large number of complete runs from agglomeration
to final recovery were made on samples from A-F, inclusive,
and others, using acid and alkaline leaching
agents, representative results being recorded in Tables
50 II-VII, inclusive. In these runs the agglomerating procedure
described above was used. Representative agglomerating
procedure and results from these runs as respects
nodule formation is set forth in Tables II, III and
IV which are based respectively, on procedure for
55 H2S04, (NH4hC03 and NA2C03 leaches. The results
shown in Tables II and III were obtained On samples
A and C. The analysis for the sample of Table IV is
given in the table.
most definitive, and in practice, the most determinative
factor of stability, is dependent upon the permeability of
the ore bed. The rate of flow of leach liquor through the
ore bed is, therefore, a very good measure of stability.
Minimum flow rate should be at least one bed volume
per 8 hours for a stable agglomerate, and one volume per
hour is more common for stable I-foot and 4-foot bed
depths. Flow rates can be measured either during the
leach cycle or during the final drain; Poor stability will
usually result in plugging and total restriction of the flow
rate.
In addition to being stable, the nodules must have a
proper degree of porosity. before they can be treated by
percolation leaching. In order to extract a mineral, the
leaching chemicals must diffuse into the nodule, and the
mineral solution must diffuse out of the nodule into the
liquor. The nodulizing process by virtue of its effect on
nodule density is quite important in controlling porosity.
Since each nodule is composed of an aggregation of
smaller particles, the density of the nodule will indicate
the amount of passageway which exists between the
particles.
The agglomeration apparatus used for the examples
illustrating this invention consisted of a rotary cement
mixture which utilizes an ordinary five gallon bucket as a
mixing chamber. The bucket was rotated at either 18
r.p.m. or at 52 r.p.iffi., the latter speed being employed for
most of the work. An important factor in proper agglomerating
action is the peripheral speed of the cylinder and
its relationship to the cylinder diameter. The mixer frame
was mounted on a tilting table so that the incline of the
bucket could be changed to give the best tumbling action
for the particular charge being agglomerated. The bucket
was normally inclined to an angle of 25 to 30 degrees
from the horizontal. Agglomerating liquid was added by
an air spray device which sprayed a fine stream of liquid
onto the cascading surface of the ore.
The following agglomerating procedure was used for
the examples given and for all tests for which results are
given. The ore is first ground to the required fineness
which will be largely dependent upon the leaching characteristics
of the ore. Granular, inorganic ore may require
a fine grind to achieve reasonable extraction (10 or
20 mesh has been sufficient in most cases). Lignite and
other high content organic material may require only
-.;4" sizing, or perhaps no sizing at all, to provide nodules
permitting diffusion of the leach solution throughout
the ore mass.
The are charge for a five gallon bucket should be approximately
500 grams minimum and 2000 grams maximum
for most material. It is added to the bucket and
rotated at 52 r.p.m. and inclined 25 to 30 degrees from
horizontal. The tilt of the bucket can be adjusted to
provide good cascading action. Additives such as binders
and oxidants are added to the ore and thoroughly
blended before it is charged into the agglomeration apparatus.
The required anlount of agglomerating fluid is
added during cascading by s,praying onto the cascading
ore particles. The fluid will ordinarily be a water base
fluid and preferably contains a portion of the leaching 60
agent to be used in the leaching step. The liquid must
be added slowly enough to provide homogeneity in the
product. The preferred final moisture content will d~pend
upon the type material being agglomerated. Ordlnarily,
it should be in a range of 10'-20% for granu.lar 65
material and about 40-60% for carbonaceous matenal.
Final moisture content should give nodule size in a
range from about VB" to ;4" in diameter.
Tumbling is continued 10 to 15 minutes after liquid
addition. Forging action during this period will harden 70
the nodules and produce a stable structure. The agglomerate
is then removed from the bucket, observed and
the nodule size distribution recorded. A weighed amount
is charged into a sealed percolation vessel for curing. A
small amount of water is placed in the bottom and top 75
3,288,569
Chemicals Added, Ib./Ton
NaClO, "Aero- "Separan"
sol 2610 Na,CO, NaIlCO,
OT"
Agglomeration _ 5.0 .03 .03 100 40 Leach__________ 1. 61 1. 61 820 328 ---
TotaL___ 5.0 1. 94 1. 94 920 368
30
Slump (before drain) fmm 12" to 11%"=1.0% of
original.
Dilution (vol.-ton liquor/dry ton ore) =9.8: 1:
Mineral extracted UsGs
Percent ext,raction 88.2
Material balance, percent ~------------ -16.8
Remarks: Nodules very stable. Final flow rate, 150
mI.lmin. (3140 gaI.lsq. ft./day).
The nodules in each case were very stable and the
permeability of the beds excellent as indicated by the
flow rates obtained. No gassing of the ore beds was exexcessive
and the slump values 'Observed indicated high
stabiHty of the nodules. The 'leach liquors from tests
45 on Tables II and III were perfectly clear.
hlthough the limits 'of the various process limitations
used to obtain nodues 'Of the ifequired characteristics will
vary with the ore within the scope of the invention, it
can be said that the objective of the process is to pmvide
nodules having a stability and porosity adequate to withstand
effective percolation leaching of ore therefrom in
feasibk amounts with a suitable leaching agent.
Pmper wetting and cascading are important and the
application of liquid by spraying during cascading pro-
55 vides the most uniform distribution of moisture on the
particles. However, the most important factors in the
process are the application of part of the Jeach solution
during nodulizing, and curing for an adequate pe'riod
under the proper humidity conditions. The addition of
the leaching agent to the ore starts the leac'hing process,
stabilizes the nodules and insures' the completion before
nodule formation 'of any chemical reaction which otherwise
may 'Occur in the nodules after formation and cause
disintegration. Curing the nodules under the propeif humidity
conditions is a critical factor in the :formation of
stable nodules. Drying the nodules with curing in a low
humidity atmosphere will cause them to shrink and later
expand with cracking upon contact with moisture in the
ore bed.
As used in the specification and olaims the term "agglomerating"
means treatment of the ore to form suitable
nodules. By "agglomerating agents" as used herein is
meant agents such as wetting, flocculating and binding
agents or other agents which are added in the agglomerat-
75 ing step to improve the stabHity and porosity of the
8
20
25
TABLE IV.-Na,COs PERCOLATION LEACH DATA
Sample assay: .153% U30 S; Moisture: 41.5%; Grind:
-~".
hgglomeration ,procedure: Agglomerated at 23 0 C., 52
5 r.p.m. in 5-gallon bucket. Added Na2C03 and NaHCO
dry. Sprayed with solution containing .5 g./l. each
"Aerosol OT" and "Separan" 2610.
Cure: 4 days, 23 0 C., 100% humidity.
Leaching 'Vessel: 1.85" J.D. x l' column.
10 Leaching procedure: Quiescent leach. Five-bed V'olumes
removed at 24-hour intervals. Water flush after fifth
bed-volume.
Flood solution: 50 g.ll. Na2C03, 20g./!. NaHC03, .1
'gJl. each "Aerosol" and "Separan."
15 Liquid volume in ore bed: 308 ml.
Leaching temperature: 23 0 C.
Leach solution: Same as flood.
Dry ore wt.: kgglomeration, 585 gm. Leach, 186.1 gm.
293
83
11
393
NIT,
Zr
376
28
(6.9%) 65
-371..18 39.5_
Mo
92.6
+4.6
"Separan"
2610
Chemical Consumption, Lb./Ton
"Aerosol
OT"
Slump (before drain) from 13" to 11Y2"=11.5% of
original.
Dilution (vol.-ton liquor/dry ton ore): 12.2: 1 liquor;
1.7: 1 wash water: 70
Mineral extracted -------- U30 S Percent extraction 90.2
Material balance, percent +11.4
Remarks: Good stability. Final flow rate 31.2 gaI.lsq.
ft./day (1.5 mI.lmin.)..
ExceLsisq:uors • "_' _
TaiL _
TotaL " _
Unaccounted for Loss _
Remarks: Column very stable. Final flow rate 6480
gal.lsq. ft./day.
TABLE III.-(NH4hCOs AGGLOMERATION AND
PERCOLATION LEACH
Sample B:
Assay: .464% UsOs; Moisture: 12.3%; Grind:
-¥<til.
Agglomeration procedure: Agglomerated at 200 C., 52
T.p.m. in 5-gallon bucket. Sprayed with solution con- 35
taining 42 g./l. (NH4hCOs and .5 g./l. each "Aerosol
OT" and "Separan" 2610. Nodules 38.7% moisture.
Cure: 22 hrs., 23 0 C., 100% relative humidity.
Leaching vessel: 1.85" J.D. x l' column.
Leaching procedure: Quiescent leach, one bed-volume re- 40
moved every 24 hours.
Flood solution: 50 g./l. (NH4hCOs+.l g./l. each "Aerosol"
and "Separan."
Liquid volume in ore bed: 250 ml.
Leaching temperature: 23 0 C.
Leach solution: Same as flood; pH 8.7; 15.86 g./l. NH3.
Dry ore wt.: Agglomeration, 438.5 gill. Leach, 256:0
gm.
Lb. dry ore/cu. ft.: Crushed ore, 43.3 percolation bed,
~~ 00
Mineral Extracted______________________ U,O,
Percent Extraction _
Material Balance, Percent _
Chemical
Consumption,
Lb./Ton
Slump (before drain) from 12" to 12"=0% of original.
Dilution (vol.-ton liquor/dry ton ore).-10.6:1 liquor;
5.6: 1 wash water:
7
Dry ore wt.: Agglomer'l.tion, 450.5 gm. Leach, 208.4
gm.
Lb. dry ore/cu. ft.: Crushed ore, 45. Percolation bed,
25.
Additives:
Agglomeration_________________________________ 346
Leach_ 1,006
TotaL _ 1,352
Excess ____ ________ ___________ __ __ ______________ ____ 845
Consumption______________________________________ 507
". .... .'
-----------1---------
9
nodules. By "leaching agent" is meant the liquid medium
used for percolation leaching to dissolve the metal out
of the nodules. By the term "carbonaceous" is me,ant
organic material containing broadly as wdl as carbon
containing.
3,288,569
10
at a flow rate of 1.5 ft/hr. This helped to avoid any
air pockets or gas locking caused by evolved gas. Upward
percolation was continued until liquid level was the
desired distance above the ore bed (1 inch for 1 ft.
5 column, 2 inches for 4 ft. column). All flow rates were
Percolation leaching of nodules controlled in the feed line. If gas evolution was en-
For the examples of percolation leaching given herein countered the ,flow rate was reduced to allow gas to
the nodules used to form the ,beds were made in accord- escape.
(b) If downward percolation was used, a jack-leg tube
ance with the nodulizing procedure described above. was attached to the bottom column outlet to control the
The stability, porosity and other desirable required prop- 10 liquid level above the are bed. Leach solution was meerties
of the nodules formed is attested by the recovery tered through a feed line in the top of the colunm at
results obtained. The ,are beds of nodules all gave high the rate and time interval prescribed by specific test conflow
rates with acid percolation ,leaching as well as with ditions.
alkaline percolation leaching. It was found that it is 15 (c) After the leaching cycle was completed the last
important in the ammonium carbonate leaching that the volume of liquor was drained from the ore bed and
acidic constituents 'Of the lignite be neutralized during the bed was washed with at least one bed volume of wash
agglomeration by addition of a portion of the leaching liquid (usually water) by upward percolation and drainsolution,
otherwise initial contact with ammonium car- ing.
'bonate wBl cause evolution of carbon dioxide. Like- 20 Cd) If a tail assay was required, the tail was dried
wise, it is important for acid leaching that acid be added to constant weight at 110° C., ground to 100 mesh and
during agglomeration so that any 'gas forming reaction sampled for assay.
,between acid and ore constituents wiII be completed A complete test of the acid percolation leach flow
'before nodule formation. sheet of FIGURE 1 was made using samples A, B, C,
The percolation leac,h equipment used for the examples 25 D, E and F and the results are summarized in Table V.
TABLE V.-SULFURIC ACID PERCOLATION LEACHING OF AGGLOMERATED
URANIFEROUS LIGNITE ORES
Ore agglomerated and leached with H,SO, in I' column, except TEst E
in \vhich 4' column was used
Sample No_ . A
2
B C D
3
E F
------------------------
Head Sample:
Percent U,os_ •• ____ . ____ ._. .263 .263 .464 .066 .350 .350 .350 .144 .243 Percent Mo•• 0_._._..._____ . .224 .224 Percent Zr__________________ -------- -------- .336 .336 .336 .095 .037 .096 .090 -------- -------- .029 .029 .029 .095
Lb. dry ore/cu. It.:
Crushed ore .._.• _____ ..... __ 45 45 43 40 44 44 41 21 64 Nodules_. __ ... __________ . __ 25 25 27 31 26 27 26 20 30
Leach: Head solution, Percent
H,SO._________ ." ________ ..... 5 5 1 1 5 5 (I) 5 1
Tons liquor/ton ore__ . ____ .... _. 10.0 9.3 12.5 6.4 14.1 13.2 7.5 19.4 4.7
1'otal leach time, hL___________ 132 49 210 168 171 137 OS 88 97 Final flow rate ___ "__ ..... _______ 6,480 (') (3) (3) 6,900 6,080 6,100 400 (3)
PercZern_t_ E. _x.t.ra__c_t_io__n_:__ . _____ .. ___ 39.5 34.2 -------- -------- 32.8 35.9 9.0 Mo_________________ ..... ____ 31.8 34.9 -------- -------- 23.4 23.7 52.9 46.2 U3Os.... -___ ... _. __________ . 92.6 91. 4 82.1 SO. 1 93.6 92.3 S9.2 92.7 90.5
1 Solvent extraction raffinate.
2 Trickle leach.
"High (>1,000).
consisted of two different sized columns and associated 50
liquor transfer apparatus. The smaHer scale tests were
performed in standard 50 m!. by 400 m!. test tu'bes fitted
with an outlet tube on the :bottom and a stoppered inlet
tube on top. The effective are bed volume was 1.85" in
diameter and 12" deep. The ore bed was supported on a 55
stainless stee'l wire screen (20 mesh) with a Y<l" to Y:z"
layer of glass wool above the screen as a filter.
The lar,ge colunms were 2%" I.D. x 53" cylindrical
Lucite tubes fitted with stoppered Y<l" inlet 'and outlet
tubes. A 3 mesh wire screen coveTed by a double layer 60
of duck cloth was used as a bed support and filter.
Leach solution was normally gravity fed from a reser·
voir to the top of the column for downward percolation
and to the bottom of the column for upward percolation.
The liquid was controlled to a constant level, and reo 65
moved from the column 'by a jack·leg for downward percolation
and by a siphon for upward percolation.
Constant flow ,rates were attained by the use of a constant
head apparatus and capiHary tubes, or by use of
a metering pump. Liquor recycling was done with a 70
metering pump. All leaches weTe performed by flooding
the ore bed with the leach solution, except in one instance
where the ,leach solution was trickled through the bed.
The normal leach cycle involved the following steps:
(a) The ore bed was flooded by upward percolation 75
The uranium recoveries are around 90% and above
for most of the tests. No difficulties were encountered
in solvent extraction and yeIlow cake precipitation.
AIl solvent extraction data reported herein was obtained
using conventional amine solvent extraction techniques.
After percolation leaching with sulfuric acid,
uranium is extracted from the pregnant leach solution
by conventional solvent extraction or ion exchange procedures.
For extraction of uranium from the leach
Hquors formed in the above examples, a tri·fatty amine
was used as the organic extractant. The organic extracted
carbonaceous material as well as the metals dissolved
in the acid leach, leaving the raffinate clear and
available for reuse. The organic was then stripped with
soda ash solution which stripped the carbonaceous material
as well as uranium and molybdenum and zirconium
from the amine, and left the organic perfectly dear for
use. Excess caustic soda was used to precipitate the
yellow cake from the soda ash pregnant solution and
much of the carbonaceous material precipitated with the
yellow cake. This carbonaceous material was burned
off from the filtered precipitate and gave a yeIlow cake
that met all AEC specifications.
The high recoveries of uranium and the other metals
illustrated by the data in Table V proves the effectiveness
of the agglomeration step in the percolation leach
3,288,569
-------------------D--E- C
.464 .066 .144
------ ------ ------
------ ------ ------
43 46 21
28 22 19
50 50 50
24 24 24
12.2 7.4 15.4
1.7 1.3 3,5
276 97 240
31 31 2,000
Head Assay:
Pereent UaOs_ _ .263
Pereent Mo .224
Percent Zr .096
Lb. Dry Ore/Cu. Ft.:
Crushed Ore_____________________________ 45
N odules______ 27
Leaeh:
Head Solution, g./I. (NH4),COa__________ 50
Solution Flow Rate, hrs, per bed-voL____ 8
Tons Liquor/Ton Ore 17.4
Tons Wash Water/Ton Ore _
Total Leaeh Time, Hrs__________________ 139
Final Flow Rate, gal./sq. it./day 52
PercZernt Extraction: 41. 2 _
Mo 48.8 _
UaOs 87.2 90.2 74.4 80.0
55 Sample_______________________________________ A
12
is effective without them. The significantly high perc
ccntage yield of 88.2 for uranium demonstrates the effectiveness
of alkali metal carbonate leaching agents.
Ammonium carbonate is the preferred carbonate as an
5 alkaline leaching agent because it is less reactive than
strong alkali metal carbonates toward the organic constituents
in carbonaceous ores,and ammonia can be recovered
for reuse in the process, these advantages resulting
in drastic reduction in reagent costs.
10 Experimental results demonstrated that uranium in lignite
ore is mostly in an adsorbed form, and as such can
be extracted by an "ion exchange" elution mechanism.
Because of this mechanism, ammonium carbonate leaching
does not require elevated temperatures and air oxida-
15 tion to dissolve the uranium. Due to the volatility of ammonia
and ammonium -compounds the use of ammonium
carbonate provides optimum reagent recovery from solution
and possibly from solid residue by the combination
of heat and addition of lime. Lime acts to liberate the
20 ammonia from any non-volatile chemical compound, such
as ammonium sulfate which may be present. The underlying
principle of ammonium carbonate percolation leaching,
therefore, is that the uranium can be extracted by an
ion exchange type mechanism, and the ammonia can be
25 reoovered for reuse. In theory, actual reagent consumption
can be restricted to lime in an amount equivalent to
the sum of the acidic constituents and cationic ion exchange
capacity of the lignite.
FIG. 2 shows the flow sheet for ammonium carbonate
30 percolation leaching. This flow sheet was used for the
tests for which results are reported in Table VI. In accordance
with the invention, the ore was agglomerated by
the method disclosed above, with addition during agglomeration
of either ammonium carbonate and/or wetting or
35 flocculating agents. Table III above presents data on the
agglomeration procedure used for alkaline leaching.
In accordance with the flow sheet of FIG. 2, the leach
liquor was boiled to remove ammonia gas and carbon
dioxide, and to partially precipitate the uranium. Com-
40 plete precipitation of uranium and complete removal of
ammonia is accomplished by the addition of an oxidant
and lime. The uranium is precipitated as U30 S mixed
with organic material, and the final product is obtained
by removing the organic material in a calcination step.
45 The carbon dioxide and ammonia gas are collected and
resued. The overall reagent consumption ,is in theory
confined to the use of lime and carbon dioxide since the
ammonia is recycled.
Data from ammonium carbonate percolation leaching
50 of lignite ore samples A, C, D and E agglomerated and
leached at 23 0 C. is shown in Table VI.
TABLE VI.-AMMONIUM CARBONATE PERCOLATION
LEACHING OF URANIFEROUS LIGNITE ORES AGGLOMERATED
AND LEACHED AT 23° C.
11
process. Leaching ,characteristics in all respects, inoluding
ore bed stability -and permeability were entirely satisfactory.
It was found that the solvent extraction raffinate
could, in most cases, be re-used as leach liquor.
This shows the effectiveness of the bed for removing
organic material and is in itself a large contributing factor
to reduction in -add consumption.
The best solution flow rate for acid percolation leaching
of lignite was found to be one bed volume every 8
hours (approximately 100 gallons per square foot per
day for a 10 foot bed depth). A continuous flow at
this, rate usually gives 90% U30 a extmction within a
total leach time of four days. Using the agglomeration
and leaching methods presented above, the ores tested
all gave high flow rates.
All of the examples presented herein were made using
either I-foot or 4-foot percolation columns. The data
indicates, however, that stability would carry through
into larger production size units and that the nodules
would not be crushed appreciably by the weight of the
ore bed, even with a 10-foot bed depth.
Tests were made to determine the effects of pH on
percolation leach of lignite ores. Two tests were run
using sample B to determine (1) uranium extmction
as a function of pH, and (2) uranium extraction with
sodium nitrate leach at pH 2.5 (sodium nitrate is a
good ion exchange eluent). Amine solvent extraction
was used. These two tests gave relatively poor uranium
extraction except in the range of pH 1 or lower. It was
concluded from these and other tests that acid leaching
of lignite ores should be conducted in a range of pH 1
or lower in order to obtain best yields of uranium extraction.
Solvent extraction tests made on a composite liquor
sample made from samples Band D showed that no difficult
operation problems occur during solvent extraction
of the acid leach liquors, such as, emulsion formation or
indaequate phase separation. The solvent used was a trifatty
amine in kerosene modified with 2 volume percent
of isodecanol. Caloulated extraction coefficients based on
the results were high enough to provide for complete extraction
in three stages, indicating the complete feasibility
of the recovery of uranium from the acid percolatioI} leach
liquors. Additional evaluation tests of amine solvent
extraction from the standpoint of operability and reagent
C:onsumption conclusively demonstrated that the recovery
of uranium by this method is entirely feasible from reagent
consumption standpoint and that it produces yellow '
cake from acid percolation leach liquors meeting all requirement
specifications.
Alkaline percolation leach
The use of alkali metal and ammonium carbonates as
agglomerating and leaching agents in the overall process
was extensively tested. As set forth below, ammonium
carbonate is the preferred leaching agent from a commercial
standpoint; however, tests demonstrated that alkali
metal carbonates, such as, sodium carbonate and bicarbonate,
are highly effective. Other alkali metal carbonates,
such as, potassium ,carbonate and bicarbonates are opera- 60
tive for the process.
Table IV above presents results of a representative test
in which sodium carbonate and sodium bicarbonate were
used as agglomeration and leaching agents in the process.
The results in Table IV indicate the stability of the 65
nodules formed. This is supported by flow rates, slump
value and absence of gassing. Although sodium bicarbonate
was added it is obvious that sodium carbonate alone
can be used. The definition of sodium carbonate and ammonium
carbonate as used in the claims includes either 70 ---------_------'----'------'------'--
the carbonate alone or the combination of sodium carbo- As seen from Table VI, uranium extraction from the
nate and bicarbonate. Although the wetting agent "Aero- four lignite samples ranges from 74.4% to 90.2%. The
sol OT" and the flocoulating agent "Separan" were used lower extractions were obtained in 'accelerated tests with
in the test and it has been found that their use is bene- lower dilution and shorter leach time, so over-all extracficial
in some cases, their use is not critical and the process 75 tions would probably be in the 85% to 90% range for
3,288,569
13
completed leach tests. Sample A, the most typical of the
available ore supply, gave 87.2% uranium extraction, and
41.2% zirconium extraction. An optimum leach rate in
time is estimated to be a maximum flow rate of I-bed
volume every 8 hours for a total 'Continuous leach time
of five or six days.
The ore was agglomerated with a solution of ammonium
carbonate and sufficient cure time was allowed for
complete evaluation of CO2 gas. Flow rates, obtained
were more than sufficient for mill use, in which a flow
rate of 10 gal./sq. ft.!{lay (l-bed volume/8 hours) is
adequate.
The uranium was precipitated from the ammonium
14
destroy ammonia. Tests showed conclusively that a high
percentage of ammonia can be recovered quite easily
from the liquor and from the tails by raising the pH and
steam sparging, and that there is no apparent chemical
5 destruction of the ammonium compound to destroy the
ammonia. Tests performed by percolating an ammonium
carbonate solution through a percolation leach system
for four days with no ore in the system showed that
ammonia losses by volatilization are all within 1%, well
10 within the limits of experimental error. Ammonia material
balances on ammonium carbonate percolation leach
tests of samples of various lignites are given in Table
VII.
TABLE VII.-AMMONIA BALANCE ON AMMONIUM CARGONATE
PERCOLATION LEACH TESTS
4
7
8
Ammonia Added, Amnlonia Recovered,
lb,fton lb,fton NH,
Guin (+)
Sample or Loss (-) Percent
Agglom- Leach Total Liqnor Tail Total lb./ton ore
eration
---- --------------
A-(1) ______ 51 554 605 486 86 572 -33 -5.
A-(2) ______ 60 173 233 170 67 237 +4 +1.
B ___ "______ 11 393 404 293 83 376 -28 -6.9
C __________ E __________ 27 235 262 211 49 260 -2 - None 401 491 405 51 456 -35 -7.1
carbon~te leach liquor in accordance with the flow sheet
shown in FIG. 2. Ordinarily, if ammonium carbonate
'solution containing uranium is boiled 'and sparged with
steam, the ammonium carbonate is volatilized and uranium
precipitates as U03; however, the presence of organic
compounds in lignite leach liquor prevents the precipitation
of uranium by this simple method, probably because
of the formation of complex ,compounds. In accordance
with the process of the invention, a small
amount of a strong oxidizing agent was added to the
solution after boiling off the ammonium carbonate and
the pH raised to 12 with lime. This precipitates the
uranium completely as a low grade material containing
organics as well as some gypsum and a small amount of
calcium carbonate. The addition of lime has the added
advantage of liberating any ammonia which is present in
the liquor as a non-volatile compound such as ammonium
sulfate. The uranium precipitate was then calcined to
produce a uranium 'Concentrate assaying approximately
5% U30 8• The oxidant used to complete uranium precipitation
was sodium hypochlorite; however, other strong
oxidizing agents can be used. This may not be necessary
for all leach solutions.
In order to test the effect of an oxidizing agent in the
precipitation of uranium, duplicate precipitations were
made on similar solutions at pH 12. The first was a
control run, and the second contained the equivalent of
.2 gram sodium hypochlorite per liter. Recovery of
U30 8 in the control test was 77.5% compared to 100%
in the test containing hypochlorite. The tests showed the
effectiveness of an oxidizing agent for this ore; however,
for other ores an oxidizing agent may not be required.
Other tests indicated a preferred pH range of about 10
to 12 for conducting the precipitation. Tests indicated
that reagent consumption for the overall process is favorable
as respects economic commercial utilization of the
process.
Information as to the grade of the concentrate was
obtained from several lime precipitation tests using varying
grades of liquor. The tests showed that the concentrate
meets required specifications.
The economic feasibility of the ammonium carbonate
leaching system depends largely upon the recovery and
re-use of ammonia in the same sense that sodium must
bere-used in leaching with sodium carbonate. Three
possible ways in which ,ammonia can be lost in a percolation
leach process are (l) in the leach liquor, (2) in
the solid tails, and (3) a chemical att~ck which would
The material balances given in Table VII indicate that
all of the ammonia from an ammonium carbonate percolation
leach can be recovered. These test results demon-
30 strate that (1) lignite ores can be readily agglomerated
into nodules for ore beds from which uranium can be successfully
leached by ammonium carbonate percolation
leaching, (2) uranium can be recovered from the leach
solution at low cost as a concentrate capable of further
35 treatment to produce specification grade yellow cake and
(3) ammonia can be recovered from solution and residues
by heating and lime addition to drastically reduce reagent
cost.
40 If selective recovery of uranium, molybdenum and zirconium
from the carbonate strip liquor is required, this
can be acomplished by a process disclosed in copending
application Serial No. 302,627 filed in the U.S. Patent
Office on August 16, 1963 entitled "Process for the Selec-
45 tive Recovery of Uranium, Zirconium and Molybdenum."
It is thus seen from the above description that the invention
provides a process for the percolation leaching of
carbonaceous ores of uranium and other ores which is
commercialIy feasible. The process broadly includes the
50 steps of nodulizing the carbonaceous ore and removing
uranium from the nodules by percolation leaching. An
important feature of the invention which makes possible
the percolation leaching of carbonaceous ore is the nodulizing
procedure by which nodules are formed which are
55 sufficiently stable and porous to permit leaching in an ore
bed with the required leaching agent. The nodules are
made by cascading the ore particles accompanied by spraying
the cascading ore with a water base mixture which
preferably includes a portion of the leaching agent and
60 may include an agglomerating agent, such as, wetting a!ld
flocculating agents. The nodules must be cured under
high humidity conditions. The nodules are formed into
a bed in the percolation leach step. Percolation leaching
may be performed with either an acidic or basic agent.
65 Preferred basic agents for uranium leaching are alkali
metal carbonates and bicarbonates and ammonium carbonate
and bicarbonate. Preferred acids are dilute solutions
of strong mineral acids, such as sulfuric acid. Ammonium
carbonate is the preferred basic leach agent and
70 sulfuric acid is the preferred acidic leaching agent.
The acid leach is preferably performed at a pH between
about 1 and 2. Uranium is recovered from the acid leach
liquor by conventional solvent extraction processes.
Uranium is recovered from the ammonium carbonate
75 leach liquor by boiling off the ammonium carbonate £01-
3,288,569
2,982,602
M. J. SCOLNJCK, Assistant Examiner.
References Cited by the Examiner
UNITED STATES PATENTS
5/1961 Sherk et al. 23-14.5
OTHER REFERENCES
Clegg and Foley, Uranium Ore Processing, AddisonWesley
Co., 1958, pp. 115-136, 153-169, 197-199, 301,
393-394.
70 BENJAMIN R. PADGETT, ,Primary Examiner.
CARL D. QUARFORTH, Examiner.
16
14. The process of claim 12 in which the alkaline leaching
agent is a material from the class consisting of alkali
metal carbonates and bicarbonates and ammonium carbonate
and bicarbonate.
15. The process of claim 14 in which the leaching agent
is sodium carbonate.
16. The process of claim 14 in which the leaching agent
is ammonium carbonate.
17. The process of claim 16 in which uranium is re10
covered from the leach liquor by boiling off ammonium
carbonate followed by precipitation of the uranium with
lime.
18. The process of claim 17, in which the uranium is
precipitated at a pH between about 10 and 12.
19. -The process of claim 17 in which an oxidizing agent
is added to the solution after removal of ammonium carbonate
to aid in the precipitation of uraniuIIl.
20. The process for the recovery of metals selected
from the group consisting of uranium, zirconium and
20 molybdenum from ores of said metals contained in carbonaceous
material which comprises: agglomerating the
material into porous nodules sufficiently porous and stable
to permit percolation leaching with an ammonium carbonate
solution; forming a percolation leach bed of the
25 nodules; percolation leaching the metal from the nodules
with an ammonium carbonate leach solution; boiling the
leach solution to remove ammonium carbonate therefrom
and recovering the ammonia for re-use; precipitating the
metal from the soluton with lime at a pH of between
30 about 10 and 12; and calcining the precipitated metal to
purify it.
21. The process for the recovery of metals selected from
the group consisting of uranium, zirconium and molybdenum
from ores of said metals contained in carbonaceous
35 material which. comprises: grinding the material to fine
particles; cascading the particles in the presence of moisture
to form porous nodules; curing the nodules in a humid
atmosphere; forming a percolation leach bed from the
nodules while moist; and percolation leaching the metal
40 from the ore in the nodules with a leaching agent.
22. The process of claim 21 in which said particles are
sprayed with a portion of the leaching agent during cascading.
23. The process of claim 22 in which the nodules are
45 cured in an atmosphere of high relative humidity.
24. The process for the recovery of metals selected
from the group consisting of uranium, zirconium and
molybdenum from ores of said metals contained in
50 carbonaceous materials which comprises: grinding the
material into small particles; cascading the particles
to form porous nodules while adding thereto from
10 to about 60 percent of a leaching agent based
on the weight of the material; curing said nodules in an
55 atmosphere in which the relative humidity is from about
80 to 100 percent; forming said nodules into a bed; and
percolation leaching the metal from the nodules with said
leaching· agent.
15
lowed by raising the pH of the solution to between about
10 and 12 with lime. A small amount of a strong oxidizing
agent is added to aid the precipitation. The ammonia
removed in the recovery process is recovered and re-used.
The precipitated uranium is calcined to produce a urani- 5
um concentrate assaying approximately 5% UgOs. The
material balances for the sulfuric acid and ammonium
carbonate leach processes show that reagent consumption
is favorable for commercial requirements.
.The broad process is not restricted to the recovery of
uranium from carbonaceous ores as the invention applies
to the nodulizing of carbonaceous materials containing
ores of metals in general for the purpose of removing the
metals by percolation leaching, regardless of the percolation
leaching reagents and procedures peculiar to the metal 15
being recovered. This feature is illustrated by the per-
·centageyields oCzirconium and molybdenum recovered
in the leach liquors even though the leaching was directed
to the recovery of uranium.
Although the invention has been illustrated and described
with reference to the preferred embodiments thereof,
it is to be understood that it is in no way limited to the
details of such embodiments, but is capable of numerous
modifications with the scope of the appended claims.
What is claimed is:
1. The process for the recovery of metals selected from
the group consisting of uranium, zirconium and molybdenum
from ores of said metals contained in carbonaceous
material which comprises: agglomerating the ore-containing
material to form porous nodules; forming a percolation
leach bed of the nodules; leaching the metal from
the nodules by percolation leaching with a leaching agent;
and recovering the metal from the leach liquor.
2. The process of claim 1 in which a portion of the
leaching agent is added to the are during agglomeration.
3. The process of claim 1 in which the nodules are
cured without drying under high relative humidity conditions.
4. The process of claim 2 in which the nodules are
cured without drying under high relative humidity conditions.
5. The process of claim 1 in which an agglomeration
agent is added to the ore during the agglomeration step.
6. The process of claim 5 in which the agglomeration
agentis a wetting agent.
7. The process of claim 5 in which the agglomeration
agent is a flocculating agent.
S. The process for the recovery of metals selected from
the group consisting of uranium, zirconium and molybdenum
from ores of said metals contained in carbonaceous
material which comprises: forming porous stable nodules
of rthe ore-containing carbonaceous material; forming
a percolation leach bed of the nodules; and percolation
leaching the metal from the nodules with acid leaching
solution.
9. The process of claim 8 in which the acid is sulfuric
acid.
10. The process of claim 9 in which the uranium is recovered
from the leach liquor by solvent extraction. 60
11. The process of claim 8 in which the leaching step
is performed at a pH of less than about two.
12. The process of recovering metals selected from the
group consisting of uranium, zirconium and molybdenum
from ores of said metals contained in carbonaceous mate- 65
rial which comprises: forming the ore-containing carbonaceous
material into stable, porous nodules; forming a
percolation leach bed of the nodules; percolation leaching
the metal from the nodules with an alkaline leaching solution;
and recovering the metal from the leach liquor.
13. The process of claim 12 in which a portion of the
leaching agent is added during forming of the nodules and
the nodules are cured without drying under high relative
humidity conditions.