United States Patent
Lowenhaupt et al.
[19] [11]
[45]'
Patent Number:
Date of Patent:
4,548,794
* Oct. 22, 1985
[54] METHOD OF RECOVERING NICKEL FROM
LATERITE ORES
[75] Inventors:· E. Harris Lowenhaupt, Gasquet,
Calif.; John E. Litz, Lakewood;
Dennis L. Howe, Broomfield, both of
Colo.
[73] Assignee:.. California Nickel Corporation,
Crescent City, Calif.
[ *] Notice: The portion of the term of this patent
subsequent to Sep. 17,2002 has been
disclaimed.
3,809,549 5/1974 Opratko 75/101 R
3,991,159 11/1976 Queneau et al. 423/150
4,012,484 3/1977 Lussiez 423/53
4,044,096 8/1977 Queneau et al. 423/150
4,065,542 12/1977 Subramanian et al. 423/35
4,097,575 6/1978 Chou et al. 423/150
4,098,870 7/1978 Fekete et al. 423/123
4,195,065 3/1980 Duyvesteyn 423/150
4,410,498 10/1983 Hatch et al. 423/150
4,415,542 11/1983 Queneau et al. 423/150
Primary Examiner-John Doll
Assistant Examiner-Robert L. Stoll
Attorney, Agent, or Firm-Sheridan, Ross & Mcintosh
21 Claims, 2 Drawing Figures
According to the present invention, processes are provided
for recovery of nickel, cobalt and like metal values
from laterite ores wherein the ores are separated
into high and low magnesium containing fractions, the
low magnesium fraction is leached with sulfuric acid at
elevated temperatures and pressure to solubilize the,
metal values. The pregnant liquor resulting from the
high pressure which also contains solubilized Fe, Al and
acid is then contacted with a low magnesium fraction of
the ore in a low pressure leach under conditions such
that at least some of the acid is neutralized and substantially
all of the solubilized Fe and Al is removed as'
hematite and alunite precipitate.
In one embodiment, the pregnant liquor from the high
pressure leach and the high magnesium fraction are
contacted at atmospheric pressure and a temperature of
about 80° C. prior to low pressure leaching. In other
embodiments, various process streams are separated by
size and otherwise, and recycled to within the processes.
In another embodiment, all leached values, including
magnesium and sulfuric acid, are recovered, resulting in
a dischargeless process which is environmentally and
economically acceptable. Elimination of prior art iron
and aluminum contaminants by the low pressure leach
provides a simplified method of recovery of all elements
in the leachate.
[21] Appl. No.: 516,236
[22] Filed: JuI. 22, 1983
[51] Int. CI.4 C01G 53/00; COlG 55/00;
C22B 3/00
[52] U.S. Cl. 423/123; 423/128;
423/131; 423/146; 423/141; 423/150; 423/159;
423/161; 423/166; 75/101 R; 75/108; 75/115;
75/119; 75/121
[58] Field of Search 423/123, 140, 141, 146,
423/150,155,530,128, 131, 159, 161, 166;
75/101 R, 108, 115, 119, 121
[56] References Cited
U.S. PATENT DOCUMENTS
2,842,427 7/1958 Reynaud et al. 23/183
2,872,306 2/1959 Morrow 75/101
2,971,836 2/1961 Hall 75/119
3,082,080 3/1963 Simons 75/115
3,086,846 3/1958 Clark 423/530
3,093,559 6/1963 White 204/123
3,293,027 12/1966 Mackiw et al. 75/119
3,333,924 8/1967 Hazen et al. 23/165
3,365,341 1/1968 Fitzhugh, Jr. et al. 75/119
3,466,144 9/1969 Kay 23/183
3,473,920 10/1969 Fitzhugh, Jr. et al. 75/109
3,720,749 3/1973 Taylor et al. 423/141
3,737,307 6/1973 Fitzhugh, Jr. et al. 75/109
3,761,566 9/1970 Michal 423/141
3,773,891 11/1973 O'Neill 423/139
3,793,430 2/1974 Weston 423/36
3,793,432 2/1974 Weston 423/143
3,804,613 4/1974 Zundel et aI. 75/101 R
[57] ABSTRACT
u.s. Patent Oct 22, 1985
LATERITE
Sheet 1 of2 4,548,794
t--~... DISCARD
5
M 9O--t1...-_--.,.--_--.J
303
CHROMITE
REcovERY
PROCES5
24 ,..-'3-_....L-_--,
Fig- 1
u.s. Patent Oct 22,1985 Sheet 2 of2 4,548,794
LATERITE
2.4
25
I---.r-~ DISCARD
M90-~
f 'L.----r----4
Co Ni M9
Fig, 2
.BRIEF DESCRIPTION OF THE PRIOR ART
METHOD OF RECOVEltING NICKEL FROM
LATERITE ORES
FIELD OF INVENTION
This invention relates to the recovery of nickel and
cobalt from lateritic ores and, in particular, to a method
of sequentially leaching ore fractions to effectively solubilize
the nickel and cobalt while adjusting the iron,
aluminum and other trivalent ions to acceptably low
levels.
4,548,794
1 2
leach liquor. The scalping is effected by physical means,
i.e. screening and classifying including the use of screw
and rake type classifers.
Prior art processes heretofore have separated the iron
5 and aluminum present in ores such as laterite by precipitating
them out of the nickel and cobalt containing
pregnant liquor during neutralization. Upon the addition
of MgO, Mg(OHh or other alkaline neutralizing
agent, at the conditions of the prior art processes, alumi-
10 num and iron values precipitate out primarily as hydroxides
and basic sulfates. Such compounds are gelatinous
in nature and upon separation from the nickel and
cobalt containing liquors were merely discarded. For
A wide variety of processes are known for the recov- example, U.S. Pat. No. 3,991,159 teaches the desirability
ery of nickel and/or cobalt from various nickel-bearing 15 of effecting rejection of acid, Al and Fe by neutralizaores
including laterite and serpentine ores. Basic to one tion but has no teaching regarding the Fe and Al save
such process is the solubilizing of the nickel and/or that they are discarded. U.S. Pat. No. 3,804,613 simicobalt
by sulfuric acid leaching followed by neutraliza- lady teaches the advantages of process conditions
tion. which maximize the hydrolyzing of Al and Fe and
While the sulfuric acid leach process obtains a high 20 thereby precipitate each out of solution in hydroxide
extraction of nickel and cobalt, in the prior art it has form.
been environmentally unsound due to coextraction of The prior art generally teaches that at high pressure
iron, aluminum, and the like, and has often been uneco- leaching the formation of gelatinous hydrolyzed iron
nomical when ores contain large amounts of magnesium 25 oxides is minimized, i.e. at temperatures above about
which consumes excessive sulfuric acid. 260· C., but there is an increase in the amount of solubi-
Because in prior art practice iron and aluminum are lized iron sulfates which lead to detrimental scaling.
present in relatively large quantities, i.e. several grams U.S. Pat. No. 3,809,549 teaches a process directed to
per liter of each, removal by precipitation as hydroxides the elimination of scale forming iron salts from the
or basic sulfates is not easily accomplished as will be nickel containing liquor by the presence of sufficient
recognized by those familiar with the gelatinous nature 30 of such precipitates. quantities of pyrite during the initial acid leach. HowIf
iron, aluminum, and other triva-
1ent I·ons are present'III the 1eachate, they WI'11 cause ever, hydrolyzed iron oxide is formed with the attensevere
damage to aquatic systems if the spent leachate is dant problems of liquid/solid separation and a method
discarded to natural waters such as an ocean. of increasing the settling rate results. U.S. Pat. No.
Alternatively, if the impure leachate is to be pro- 35 4,098,870 addresses the same problem, but teaches incessed
further, e.g. "l'or recovery 0 f magnesI.Um va1ues, cremental addition of sulfuric acid as a solution. After
the presence of large amounts of trivalent ions creates neutralization and a difficult solid-liquid separation, the
substantial process difficulties and costs due to the ge- residue containing AI and Fe hydroxides and the like is
latinous character of these precipitates. merely discarded as waste.
Prior art practices did not efficiently reject iron and 40 It is known that AI and Fe can be removed from the
aluminum impurities, and were not always economical nickel/cobalt containing solutions without the formawhen
high magnesium dissolution was encountered. tion of hydroxides and the attendant difficulties of liq-
U.S. Pat. No. 3,991,159 is representative of prior art uid-solid separation if the AI and Fe can be made into
processes wherein sulfuric acid leaching is carried out insoluble jarosites, alunites and/or other crystalline
at elevated temperatures, e.g. 200·-300· C., and ele- 45 basic sulfates. U.S. Pat. No.4, 195,065, for example,
vated pressures, e.g. 225 psig to 1750 psig. Other exam- teaches the addition of water-soluble alkali metal or
pIes of high pressure acid leaches are disclosed in U.S. ammonium salts during the pressure leaching of gamier-
Pat. Nos. 4,195,065; 3,804,613; and 4,044,096. itic ores to improve liquid/solid separation by reacting
It is known to minimize consumption of both H2S04 the solubilized iron and aluminum with the alkali andand/
or the neutralizing agent, e.g. MgO, by separating 50 lor ammonium cations to form jarosites. Other referthe
nickel bearing ore into high and low magnesium ences disclosing the separation of AI and Fe as jarosites
fractions. By treating only the low magnesium fraction and alunites from Ni/Co containing liquors are U.S.
acid consumption can be reduced. By using the high Pat. Nos. 3,466,144 and 4,044,096. Similarly, iron oxmagnesium
fraction or raw ore itself as some or all of ides, e.g. Fe203, can be precipitated if formed under
the neutralizing agent, use of sulfuric acid is minimized. 55 conditions which do not result in hydrolysis and forma-
U.S. Pat. No. 3,991,159 teaches the use of high magne- tion of hydroxides. •
sium serpentine ore to neutralize acid leach slurries of It is an object of the present invention to produce a
limonite ore. U.S. Pat. No. 4,097,575 teaches separating leachate which is low in iron, aluminum, and similar
high magnesium ore into high and low nickel fractions concentrations, thereby minimizing the need to precipiby
screening and converting the low nickel fraction to 60 tate appreciable amounts of such metals, while at the
a neutralizer by roasting it under oxidizing conditions. same time minimizing the consumption of sulfuric acid
U.S. Pat. No. 3,804,613 teaches preconditioning high and attendant magnesium dissolution and attendant
magnesium ore by preleaching it with spent H2S04 consumption of sulfuric acid.
leach liquor prior to the standard high pressure H2S04 It is another object of the present invention to proleach.
U.S. Pat. No. 4,044,096 is specifically directed to 65 vide a process wherein dissolved magnesium values are
scalping laterite ore, i.e. removing the coarse, magnesi- recovered as magnesium sulfate, which is then calcined
urn-rich fraction to effect savings in acid consumption to magnesium oxide and sulfur dioxide. The S02 is recyand
for use in neutralizing the high pressure H2S04 cled to make sulfuric acid for use in leaching. By reduc0.7-
0.8
0.07-0.09
28-30
7-10
2-3
0.3-0.4
Element Approximate Assay Range (%)
Nickel
Cobalt
Iron
Magnesium
Aluminum
Manganese
50
4
accomplished by use of a low pressure, preferably dual
temperature, leach subsequent to a primary H2S04
leach. Typically, the ore is separated into at least two
fractions, one finer and with a lower magnesium con-
5 tent than the other. The low magnesium fraction in
combination with recycled residue undergoes high
pressure leaching in the presence of excess H2S04 to
dissolve Ni, Co and Mg. The high pressure leach liquor
containing high levels of excess acid, iron and alumi-
10 num, is contacted with the high magnesium fraction(s)
and undergoes low pressure leaching. In the low pressure
leach the magnesium serves to neutralize at least a
portion of the acid present and precipitation of the Fe
and Al present an insoluble hematite, jarosite and alunite
also results.
Residue from the low pressure leach, containing cobalt
and nickel may go to the high pressure leach where
the metals can be solubilized for recovery. Alternatively,
residues from the low pressure leach or leaches
may be discarded in part or in total to further reduce the
magnesium dissolution and H2S04 consumption. The
low pressure leach liquor contains relatively little Fe
and AI, which may be precipitated without difficulty.
The metal values are recoverable from the liquor. In
another embodiment (not shown), an overall process is
provided wherein the dissolved magnesium values after
neutralization are recovered as magnesium sulfate
which is calcined to S02 and MgO. The S02 is recycled
into H2S04 for use in the high pressure leach and the
MgO is recycled as needed as a neutralizing agent or
sold.
In one embodiment depicted in FIG. 2 the high pressure
leach liquor, a recycle portion of the low pressure
35 leach residue, and a high magnesium fraction of the ore
are contacted in an atmospheric leach prior to the low
pressure leach.
Referring to FIG. 1, laterite ore is prepared by conventional
methods and separated by a classifier 2 into at
least two, preferably three fractions. The coarsest of the
three fractions 3, i.e. that above about !" are typically
discarded. Lateritic ores useful in the practice of the
present invention are nickel-, cobalt- and magnesiumcontaining
ores in a matrix of natural hydrated oxides of
45 iron and aluminum. Such ores are typically ocher red
products of decay having relatively high contents of
oxides and hydroxides of iron and aluminum. Laterites
are typically composed of some or all of the following
major constituents:
Peridotite-An igneous rock high in iron and magnesium
minerals, especially olivine;
Saprolite-Partly altered igneous rock, peridotite
Geothite-FeO(OH)
Hematite-Fe203
Magnetite-Fe304
Maghemite-A magnetic ferrous oxide similar to
magnetite
Aluminum Oxides-Mixed aluminum oxide materials
Typical laterite ore has an analysis such as the follow60
ing:
4,548,794
SUMMARY OF THE INVENTION
DETAILED DESCRIPTION OF THE
INVENTION
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a schematic flow diagram of a process according
to the present invention.
FIG. 2 is a schematic flow diagram of a second embodiment
of the present invention.
3
ing the amount of magnesium dissolved, the process of
this invention provides the added advantage of reducing
the capital and operating costs of magnesium sulfate
recovery, and of its calcination and conversion of S02
to acid.
By incorporating the novel practices of the present
invention, an acid leach process which is environmentally
and economically acceptable is for the first time
available. By using the teachings of the present invention,
clean leachates, which require only minimal purification,
are obtained, and recovery of Ni, Co and Mg is
greatly simplifed.
The present invention provides for improved economical
methods of recovering the metal values, i.e.
nickel and cobalt, from laterite ores wherein the aluminum
and iron from such ores are precipitated as insolu- 55
ble alunites and hematite thereby improving solid-liquid
separation rates and, in addition, the high magnesium
fraction of the ore is used for neutralization thereby
minimizing the need for independent neutralizing agents
while nevertheless permitting metal value recovery
from the high magnesium fraction. In general, the methods
of the present invention provide for a two-stage
process in which the natural characteristics of laterite
ore are used to consume the excess acid needed for high
percentage dissolution of nickel and cobalt at high tem- 65
perature and pressure, and the pregnant liquor from the
high temperature leach is purified at moderate process
pressures and temperatures. The process objectives are
The present invention provides novel processes for 15
recovering Ni/Co from laterite ore which utilize a low
pressure leach, preferably at two different temperatures
to preferentially precipitate Al and Fe, as alunite and
hematite respectively, while maximizing extraction of
the Ni and Co into solution for later recovery. 20
According to the present invention, processes are
provided for recovery of nickel, cobalt and like metal
values from laterite ores wherein the ores are separated
into high and low magnesium containing fractions. The
low magnesium fraction is leached with sulfuric acid at 25
elevated temperature and pressure to solubilize the
metal values. The pregnant liquor resulting from the
high pressure leach which also contains solubilized Fe,
Al and residual acid is then contacted with a high magnesium
fraction of the ore in a low pressure leach under 30
conditions such that at least some of the acid is neutralized
and substantially all of the solubilized Fe and Al is
removed as hematite, jarosite, alunite and/or other
basic sulfate precipitate which settles rapidly and is not
gelatinous.
In one embodiment, the pregnant liquor from the
high pressure leach and the high magnesium fraction
are contacted at atmospheric pressure and a temperature
of about 80· C. prior to low pressure leaching. In
other embodiments, various process streams are sepa- 40
rated by size and otherwise, and recycled to within the
processes.
6
200· C. for about 20 to about 30 minutes. Alternatively,
the LPL 12 can be at the higher temperature first.
Additional amounts of base, e.g. MgO, Mg(OHh, or
acid-consuming ore needed to complete neutralization
5 of the free acid in the LPL slurry 28 from the HPL
liquor 113 may be added during and/or subsequent to
the low pressure leach 12. Following neutralization 25
the LPL liquor 30 is again separated from the solids,
typically in a cyclone 16 and/or thickener 18 and con-
10 centrated by an evaporator. The overflow 32 from cyclone
16 and/or thickener 18 goes to metal recovery 24
and the residue or underflow 31 is recycled to the high
pressure leach 6 or discarded if low in Ni and Co.
In one embodiment the neutralized low pressure
leach slurry 30 is separated in cyclone 16 with the + 200
mesh underflow 29 being filtered 20. The filtrate 21
joins the pregnant liquor 32 stream going to metal recovery
either before or after thickening and the filter
cake 303 is processed for chromite recovery. In this
embodiment any nickel or cobalt present in the coarser
fines (+200 mesh) 29 from the neutralized low pressure
leachate 30 is rejected through the filter cake 303 and
chromite recovery. In another embodiment, depicted in
FIG. 2, such values may be totally or at least partially
recovered by contact with excess acid in leach liquor
113, from the high pressure leach 6, within atmospheric
leach 40.
Referring to FIG. 2, a process is presented in which
the + 200 mesh fraction of the LPL slurry 28 is recycled
to a low temperature atmospheric leach 40. The high
magnesium fraction 5 from the classifier 2 and the high
pressure leach liquor 113 are also contacted in atmospheric
leach 40. The atmospheric leachate 41 is separated,
typically by cyclone 22, with the + 200 mesh
underflow 41B going to chromite recovery and the
-200 mesh overflow 41A proceeding to the low pressure
leach 12. The -200 mesh overflow 41A contains
Ni- and Co-rich fines liberated during leaching. The
-325 overflow 14 in FIGS. 1 and 2, is separated and
optionally thickened, and then passes to the HPL 6,
while the + 325 fraction or underflow 15 from cyclone
4, goes to low pressure leach 12.
In an embodiment not depicted in the Figures, Mg
and S are recovered after purification and Ni-Co ·recovery
by crystalizing magnesium sulfate (MgS04), which
is then calcined to MgO and 802. Some MgO may be
recycled to the process for neutralization purposes, and
the balance sold. The 802 may be converted to sulfuric
acid for recycle to high pressure leach.
Prior art processes which dump spent leach liquor to
an ocean do not recover Mg or S values, and pollute the
aquatic environment with Fe, Al and other impurities.
55 Prior art processes which include recovery ofMg and 8
values do not teach the removal of trivalent ions by the
novel process of this invention. As a result, they produce
leachates which are high in Fe and AI, and are
costly and difficult to process as has' been described
hereinbefore.
As described hereinbefore the laterite ore useful for
purposes of the present invention is first separated into
at least two, preferably three or more fractions of relatively
higher and lower magnesium content. During
typical ore preparation, classification into appropriately
sized fractions is effected, e.g. first by wet screening on
the vibrating grizzly. Typically 95% or more of most
metals reports to the minus 3-inch fraction. Only mag-
4,548,794
1.0-1.5
5
Approximate Assay Range (%)
-continued
Element
Chromium
The cobalt and nickel tend to concentrate in the relatively
soft iron oxide materials, the magnesium in the
coarser peridotite and saprolite particles, and the chromite
in the relatively hard granular materials of intermediate
size range.
Referring again to FIG. 1, the -100 mesh fraction,
i.e. the overflow 11 from the classifier 2 which is rich in
nickel and cobalt and low in magnesium content is further
separated, e.g. by cyclone 4, into a - 325 mesh
overflow 14 and a +325 mesh underflow 15. The over- 15
flow 14 is optionally thickened further and then proceeds
to a high pressure sulfuric acid leach 6.
The high pressure leach is in the presence of steam,
and sulfuric acid 101 and is typically at conditions
known in the art, i.e. at temperatures of from about 200· 20
C. to about 300· C., preferably at about 220· C. to about
270· C., at pressures of from about 200 to about 820 psig
and for a time period sufficient to solubilize or leach
substantially all of the nickel and cobalt present, typically
from about 30 to about 60 minutes or more. In one 25
embodiment improved recovery of Ni and Co is
achieved by adding the H2804101 to the slurry prior to
heating.
The leached slurry 106 comprising a high pressure
leach residue and a high pressure leach liquor is sepa- 30
rated by countercurrent decantation 8. The liquor 113 is
then advantageously concentrated by an evaporator 10,
and the underflow or leach residue 105 goes to waste.
The high pressure leach (HPL) liquor 113 from the
evaporator 10 then advances to the low pressure leach 35
(LPL) 12. The +325 mesh underflow 15 from cyclone
4 and the high magnesium, low nickel- and cobalt-containing
fraction, Le. the + 100 mesh underflow 5 from
classifier 2, also advance to the low pressure leach 12
where they are contacted with the HPL liquor 113 40
which is high in acid, Fe and AI.
The low pressure leach 12 of the present invention
results in two major advantages. First of all, the magnesium
present from the + 100 mesh sands 5 and, to a
lesser extent, from the + 325 underflow 15 serve to 45
neutralize a portion of the acid present in the high pressure
leach liquor 113, reducing the acid concentration
and thus minimizing or eliminating the amount of neutralizing
agent, e.g. MgO, Mg(OHh, which must be
utilized in the downstream neutralization 25. Secondly, 50
the conditions of the low pressure leach (LPL) 12 are
such that Al and Fe present are precipitated as insoluble
alunites and hematite thereby enhancing the rate of
subsequent liquid-solid separations by minimizing formation
of gelatinous hydroxides or basic sulfates.
The low pressure leach 12 is typically carried out at
moderate to low temperatures and pressures, e.g. from
about 140· C. to about 200· C. and from about 90 to
about 300 psig. Precipitation of iron oxide, i.e. hematite
(Fe203). is preferably carried out at temperatures of 60
from about 140· to about 180· C., most preferably at
about 160· C., whereas precipitation of aluminum sulfate
product, e.g. alunite, is preferably at temperatures
of about 180· to about 200· C. Accordingly, the low
pressure leach 12 is performed at two different tempera- 65
tures, at 140· C. to about 180· C., preferably at about
160· C. for about I hour, preferably for about 30 to
about 40 minutes and at from about 180· C. to about
EXAMPLE II
I 40 19 15
2 49 23 17
3 49 24 17
4 Not Measured
5 Not Measured
6 Not Measured
7 Not Measured
G solids Final Filtrate
Test per liter Free Acid Fe Al Dissolved, %
No. evaporate g H2S04/1 gil gil Ni Co Mg
Evaporate Test Nos. 1-3: 19 gil Fe, 5.1 gil AI, 19.7 gil H,S04
I 400 7.2 1.8 1.9 28 62 39
2 482 5.4 1.6 1.3 22 60 38
3 597 1.2 0.9 0.4 12 53 31
Evaporate Test No.4: 8.4 gil Fe, 1.9 gil AI, 63 gil H2S04
4 400 10.3 0.47 0.7\
Evaporate Test No.5: 5.0 gil Fe, 2.2 gil AI, 60.3 gil H2S04
5 480 2.34 0.26 0.80
Evaporate Test No.6: 15.3 gil Fe, 4.9 gil AI, 77.7 gil H2S04
6 480 2.\ 0.16 0.32
Evaporate Test No.7: 2.9 gil Fe, 0.1 gil AI, 56.7 gil H,S04
7 400 7.4 0.11 0.92
Distribution of Values in Residue
% of Hnch by 325-mesh Feed Content in - 200 mesh
Test No. Nickel Cobalt Magnesium
8
-100 mesh and the -100 mesh further classified into
+325 mesh and -325 mesh. The + 100 mesh ore fraction
and the + 325 mesh ore fraction were mixed with
an evaporate, i.e. a high pressure leachate.
The mixture of ore fractions and evaporate was then
leached in a low pressure leach at 180· C. for 40 minutes
and at 160· C,. for 20 minutes and at 300 Ibs. total pressure.
No gelatinous materials were observed and the
leach residue settled and filtered rapidly. The residue
and filtrate were analyzed and the results are provided
in 'Table I. The bottom half of the table shows the percentage
of the Ni, Co and Mg in the insoluble material
reporting to the plus 200-mesh portion of the residue.
TABLE I
Two series of four tests were performed similar to
those of Example I but wherein the +100 mesh ore
fraction was contacted with the HPL evaporate in an
atmospheric leach prior to advancing to the low pressure
leach. In the first series (Nos. 8-11) the atmospheric
leach was at 80· C. for 8 hours, although most of
the reaction occurred during the first 2 hours. The filtrate
and residue from the atmospheric leach were analyzed
and the data is provided in the top halfofTable II.
In the second series (Nos. 12-15) leaching was at 80· C.
for 2 hours. The filtrate and residue were analyzed and
the results provided in the bottom half of Table II. In
both series there was no apparent reduction in the Fe
55 and Al level in solution and no obvious Al or Fe precipitate
was formed whereas free acid level in the solution
decreased.
4,548,794
EXPERIMENTAL
7
nesium, a major acid consumer, is rejected in any quantity.
The minus three inch mesh or other sized initial fraction
is further divided, typically into plus and minus one
inch fractions, and then the minus one inch fraction is 5
further separated into plus and minus! inch fractions by
wet screening on a vibrating screen.
The minus ! inch fraction is further separated, typically
in a spiral classifier. When waterflow in the spiral
classifier is adjusted to wash out the fines (approxi- 10
mately minus 270 mesh) the fines contained an average
of about 85 percent of the nickel and 89 percent of the
cobalt and amount to about 74 percent by weight of the
minus 3 inch feed.
As will be known and understood by those skilled in 15
the art the purpose of classifying the ore by size is in the
distribution of important metals in the various ore fractions
and that distribution is in large part dependent
upon the specific ore. In general, however, by initially
rejecting about 10 weight percent of the initial ore, 20
some ofthe metal values are lost. However, this is compensated
for by the fact that a significantly larger portion
of the magnesium, the main acid consumer, is also
rejected. In a preferred embodiment, +! inch fractions
are rejected despite the fact that about 10 percent each 25
of the initial cobalt and nickel may be contained therein
because of the high proportion of acid-consuming magnesium.
Of note is that nickel and cobalt values tend to
concentrate in the fines and the magnesium in the coarse
ore fractions. Depending upon the mill product in- 30
volved, cobalt also concentrates somewhat in the coarse
or intermediate sizes.
In operation an advantageous separation of the laterite
feed has been into at least a high magnesium, lower
nickel fraction of from ! inch to about 65 mesh, most 35
preferably between ! inch and 100 mesh and a lower
magnesium, higher nickel fines fraction of finer than
about 65 mesh, preferably about minus 100 mesh. The
optimum size division of the fraction is in large part
determined by the specific ore(s) being treated and by 40
the process steps and parameters to which the fractions
will be exposed.
As will also be known and understood by those
skilled in the art these fractions could proceed respectively
to the low pressure leach and high pressure leach 45
according to the present invention. Alternatively, as
depicted in the flowsheets of FIGS. 1 and 2, it has been
found advantageous to further separate the high nickel,
low magnesium fines fraction into two fractions, one
higher in magnesium which reports directly to the low 50
pressure leach along with the initial high magnesium cut
and a lower magnesium fraction which reports to the
high pressure leach. Typically, this second separation is
at about 150 to about 400 mesh preferably from about
200 to about 325 mesh.
8
9
65 10
II'
A series of tests simulating the steps of the processes
of the present invention as depicted in each of FIGS. 1
and 2 were performed. The ore tested was from Gas- 60
quet Mountain laterite deposits obtained from test sampling
pits.
EXAMPLE I
A series of tests were performed to demonstrate that
low pressure leaching of the present invention decreases
acid and removes Al and Fe from solution as non-gelatinous
precipitates. Ore was classified into + 100 and
Test
No.
TABLE II
Final Filtrate
Free Acid Fe AI Dissolved, %
Solids % g H2S04/1 gil gil Ni Co Mg
Evaporate: 20 gil Fe, 5.43 gil AI, 36 gil H,S04
5 14.7 21 5.4 44. I 56.4 46.0
10 10.3 23 5.5 35.8 50.6 42.5
15 11.7 22 5.6 43.2 55.3 39.4
10 6.2 20 5.5 41.3 57.4 41.6
Evaporate: 22.7 gil Fe, 4.99 gil AI. 35 gil H,S04
9.1 10.2 19 4.3 39 58 23
9
TABLE II-continued
4,548,794
10
TABLE V
Test No. 18 LPL Residue (wi Atm Leach)
Nickel Cobalt Magnesium
Disl. % Disl. % Disl. % Disl.
% Ni % Co % Mg %
+65- 7.94 0.335 5.60 0.022 5.61 11.00 14.61
mesh
65 X 150 22.68 0.334 15.95 0.023 16.76 8.38 31.79
150 X 24.23 0.391 19.96 0.027 21.03 6.96 28.22
270
-270 45.15 0.615 58.49 0.039 56.59 3.36 25.38
Total 100.00 0.475 100.00 0.031 100.00 5.98 100.00
The data of Table V show, for example, that if the
residue is split at 270-mesh, about 56-58% of the nickel
and cobalt is recovered in the minus 270-mesh fraction
and about 75% of the magnesium is rejected into the
plus 270-mesh fraction.
EXAMPLE IV
Tests Nos. 12-15 of Example II demonstrate the advantages
of the atmospheric leach of the high magnesium,
coarse sands fraction with the high pressure leach
liquor (as depicted in the process'of FIG. 2) prior to the
low pressure leach. In addition to partial neutralization
of the free acid in the liquor, the nickel and cobalt present
in the sands is recoverable.
The residue of these atmospheric leaches was analyzed
and demonstrates that magnesium can be rejected
30 in the coarse fraction, i.e. about plus 200 mesh, whereas
nickel and cobalt concentrate in the - 200 mesh fracEXAMPLE
III tions. The screen analysis data is provided in Table VI.
Atmospheric Leach Filtrate: 21 gil Fe. 5.0 gil AI, 15 gil H2SO4
g solidsl Final Filtrate
liter Free Acid Fe AI Dissolved, % 25
Test No. filtrate g H2S04/1 gil gil Ni Co Mg
16 538 0.3 1.4 0.23 4 57 35
17 484 1.0 0.8 0.46 15 57 37
18 430 1.4 1.7 0.73 24 65 40
Final Filtrate
Test Free Acid Fe AI Dissolved, %
No. Solids % g H2S04!1 gil gil Ni Co Mg 5
132 7.7 11.8 20 4.9 33 53 24
142 6.3 10.8 22 5.1 37 55 26
152 4.8 12.0 20 4.8 38 57 30
tground to pass 35~mesh
2ground to pass 20~mesh 10
The filtrate, Le. leach liquor, from the atmospheric
leach of Test Nos. 8-11 was composited and was low
pressure leached at the same conditions as the LPL of
Example I. The LPL filtrate and residue were analyzed 15
and the results obtained are provided in Table III. As
indicated, the free acid level was reduced further and
the LPL resulted in removal of AL and Fe from solution
as non-gelatinous precipitates which settled and
filtered rapidly. 20
TABLE III
The data of Table IV show, for example, that if the
residue is split at 200-mesh, about 50-55% of the nickel
and cobalt is recovered and about 76% of magnesium is 65
rejected. The minus 200-mesh fraction is advanced to
the high pressure leach where most of the nickel and
cobalt are dissolved.
TABLE VI
Distribution of Values in Atmospheric Leached Residue
Test No. 12 13
Screen Size +200 -200 +200 -200
Weight, % 76.4 77.1
ANALYSIS
Nickel, % 0.26 0.43 0.30 0.43
Distr, % 66.1 68.2
Cobalt, % 0.021 0.033 0.024 0.034
Distr, % 68.4 66.7
Iron, % 23.2 30.4 26.3 30.9
D'istr, % 71.2 74.1
Magnesium, 9.09 6.59 8.95 6.53
%
Distr, % 81.7 82.1
Manganese, % 0.15 0.16 0.16 0.17
Dislr, % 75.0 77.3
Chromium, % 3.02 1.71 3.04 • 1.59
Distr, % 85.2 86.4
Aluminum, % 3.54 3.56 3.53 3.54
Distr, % 76.3 77.0
Test No. 14 IS
Screen Size +200 -200 +200 -200
Weight, % 77.9 78.8
ANALYSIS
Nickel, % 0.28 0.43 0.29 0.43
Dislr, % 69.7 70.8
Cobalt, % 0.023 0.036 0.023 0.034
Distr, % 66.7 72.5
Iron. % 25.1 31.4 25.1 30.8
Distr, % 83.4 84.3
Manganese, % 0.16 0.18 0.16 0.17
Distr, % 76.5 76.9
Chromium, % 2.97 1.57 2.80 1.65
Dislr, % 87.1 86.3
Aluminum, % 3.52 3.54 3.37 3.37
Distr, % 78.0 78.9
50
55
60
Low pressure leach residues from Test No.3 of Example
I and Test No. 18 from Example II were ana- 3
lyzed and demonstrate that nickel and cobalt tend to be 5
upgraded in the fine fraction and magnesium tends to be
upgraded in the coarse fraction of the LPL residue in
the proceses of both FIG. 1 and FIG. 2. The analysis of
the residues from Test No.3 and Test No. 18 are pro- 40
vided in Tables IV and V, respectively.
Low pressure leaching with and without prior atmospheric
leaching results in depletion of the Ni and Co
values from the coarser fraction which fraction contains
the bulk of the insoluble magnesium. As such only the 45
Ni/Co enriched fines fraction, Le. minus 200 mesh in the
Examples, need be advanced to the high pressure leach
(HPL) to obtain high Ni/Co recovery while advancing
a minimum of magnesium of the HPL.
TABLE IV
Test No.3 LPL Residue (w/o Atm Leach)
Nickel Cobalt Magnesium
Disl. % Dist. % % Disl.
% Ni % grams Co Mg %
+20-mesh 11.65 0.502 11.76 0.042 13.56 7.67 13.05
20 X 48 13.30 0.351 9.39 0.029 10.68 9.35 18.15
48 X 100 16.48 0.308 10.21 0.026 11.87 9.79 23.56
100 X 200 18.10 0.363 13.21 0.029 14.54 8.04 21.25
-200 40.47 0.681 55.43 0.044 49.34 4.06 23.99
Total 59.53 0.497 100.00 0.036 100.00 6.85 100.00
TABLE IX
60
Combined Recovery of Ni. Co,
and Mg for Low Pressure Leach Tests
g Solids
per Dis- % in Combined
Test Liter solved 200-mesh Recovery,
No. Lixiviant % Residue % 65
Nickel
16 538 4.05 65.2 69.3
17 484 15.0 57.8 72.8
Residue
S04
%
H2S04 Fe Al
gil gil gil
Filtrate
12
TABLE IX-continued
Combined Recovery of Ni. Co.
and Mg for Low Pressure Leach Tests
g Solids
per Dis- % in Combined
Liter solved 2oo-mesh Recovery.
Lixiviant % Residue %
430 24.1 51.6 75.7
538 57.2 28.3 85.4
484 57.4 28.1 85.5
430 64.6 23.4 88.0
538 35.4 22.6 58.0
484 37.0 22.1 59.1
430 39.6 21.1 60.7
grams solidsl
liter
evaporate
Test Nos. 19-26 Evaporate: 15 gil Fe 5.2 gil Al 85 gil H2S04
19 480 3.4 2.7 0.63 7.6
20 480 2.4 1.7 0.97 10.3
21 480 2. I 0.2 0.32 2.3
22 480 8.2 3.1 4.5 3.5
23 480 8.5 4.7 3.6 3.7
24 564 8.2 3.4 2.6 6.2
25 706 5.9 2.2 1.9 10.4
26 706 13.0 2.6 10.3
Test No. 27 Evaporate: 5 gil Fe. 2.2 gil Al 60 gil H2S04
27 450 2.3 0.7 0.80 3.6
Test
No.
Test
No.
5
35
18
Cobalt
10 16
17
18
Magnesium
16
17
IS _18 _
EXAMPLE VII
A second series of low pressure leaches were per-
20 formed and the residues analyzed for sulfate, Al and Fe
to demonstrate removal of iron and aluminum as hematite
and alunite, respectively. Conditions and residue
analyses for the various tests are provided in Table VII.
In each of the tests the absence of Fe and Al hydroxides
25 was observable since no obviously gelatinous particles
were formed and the residues settled and filtered rapidly.
.
TABLE IX
30
Although the foregoing invention has been described
45 in some detail by way of illustration and example for
purposes of clarity of understanding, it will be obvious
that certain changes and modifications may be practiced
within the scope of the invention, as limited only by the
scope of the appended claims.
50 What is claimed is:
1. A method of recovering metal values from iron-.
aluminum-, magnesium-, nickel- and cobalt-containing
laterite ore comprising:
(a) separating said ore into at least a first and second
55 fraction, said second fraction containing more of
said magnesium than said first fraction;
(b) contacting said first fraction with sulfuric acid in
a high pressure leach at elevated temperature and
pressure sufficient to solubilize nickel and cobalt to
form a solubilized nickel- and cobalt-containing
high pressure leachate and a high pressure leach
residue;
(c) separating said high pressure leach residue from
said high pressure leachate;
(d) contacting at least a portion of said separated high
pressure leachate, and at least a portion of said
second fraction ofstep (a) in a low pressure leach at
a pressure above atmospheric and below about 300
40
4,548,794
Combined
Recovery,
%
% in
2oo-mesh
Residue
Dissolved
%
400 27.9 39.7 67.6
482 22.0 49.4 71.5
597 11.5 48.7 60.2
400 61.5 19.3 80.8
482 59.7 23.0 82.7
597 53.1 23.5 76.6
400 38.7 15.3 54.0
482 37.7 17.1 54.8
597 31.0 17.2 48.2
Combined Recovery for LPL Tests
g Solids
per
Liter
Lixiviant
EXAMPLE VI
For tests of Table III of Example II with an atmospheric
leach (Test Nos. 16-18), the combined recoveries
for three tests are shown in Table IX.
11
Assuming that only the minus 2oo-mesh fraction of
the residue is advanced to the low pressure leach from
the atmospheric leach, the combined recoveries for the
atmospheric leach are shown below in Table VII.
TABLE VII
Nickel
1
2
3
Cobalt
1
2
3
Magnesium
1
2
3
Test No. 12 13 14 15
Nickel Dissolved, % 39.2 33.0 36.7 37.6
In -200 mesh 20.6 -l2:.L ...!2L ...ll:L
Total 59.8 52.8 55.9 55.8
Cobalt Dissolved, % 57.8 53.4 54.9 56.5
In -200 mesh ~ ~ ~ -11i...
Total 71.1 68.9 69.9 69.1
Iron Dissolved. % 14.6 6.1 10.6 12.5
In -200 mesh 24.6 24.3 ~ -1!1...
Total 39.2 30.4 34.0 34.3
Magnesium Dissolved. % 23.4 24.3 26.0 29.5
In -200 mesh J!Q ---!.1.L 12.3 -l!:.L
Total 37.4 37.8 38.3 40.6
Manganese Dissolved. % 58.5 54.1 55.3 56.0
In -200 mesh 10.4 10.4 10.5 10.2
Total 68.9 64.5 65.8 66.2
Chromium Dissolved. % 5.2 5.2 8.4 13.4
In -200 mesh J.!.! 12.6 11.9 11.9
Total 19.3 17.8 20.3 25.3
Aluminum Dissolved. % 11.9 12.1 13.8 18.8
In -200 mesh 20.9 20.2 19.2 17.2
Total 32.8 32.3 33.0 36.0
EXAMPLE V
For the three tests of Example I without an atmospheric
leach, whose residues were screened and tested
at 200 mech (Test Nos. 1-3), the combind recoveries,
Le. nickel and cobalt dissolved plus nickel and cobalt in
the fine fraction of the low pressure leach residue, are
shown in Table VIII.
TABLE VIII
Test
No.
* * * * *
14
11. A method according to claim 7 wherein said contacting
with sulfuric acid in step (b) at elevated temperature
further comprises contacting said first fraction
and said low pressure leach residue with sulfuric acid
before heating to said elevated temperature.
12. A method according to claim 1 further comprising
recycling at least a portion of said low pressure
leach residue to the high pressure leach of step (b).
13. A method according to claim 12 wherein at least
a portion of said; high pressure leachate of step (b), at
least a portion of said second fraction of step (a) and at
least a portion of the said low pressure leach residue of
step (d) are contacted in an atmospheric leach at atmospheric
pressure and at a temperature below about 100·
C. to form an atmospheric leachate prior to contact in
the low pressure leach of step (d).
14. A method according to claim 1, or claim 2, or
claim 3, or claim 4, or claim 5, further comprising recovering
MgS04 from at least a portion of said low
pressure leachate.
15. A method according to claim 14 further comprising
calcining said MgS04 to produce MgO and S02.
16. A method according to claim 15 further comprising
recycling said MgO to neutralize said low pressure
leachate.
17. A method according to claim 15 further comprising
producing H2S04 from said S02, and recycling said
H2S04 to said high pressure leach.
18. A method of enhancing recovery of nickel and
cobalt from aluminum-, iron-, nickel-, cobalt- and magnesium-
containing laterite ore comprising:
(a) sulfuric acid leaching a low magnesium fraction of
said ore at high pressure and temperature to solubilize
said nickel, cobalt and iron and aluminum into
a first acid leach liquor, and subsequently
(b) contacting said leach liquor at a low pressure
above atmospheric in the presence of at least one
high magnesium fraction of said ore at a temperature
whereby at least a portion of the acid is neutralized,
said iron is precipitated as hematite and
said aluminum is precipitated as alunite.
19. A method according to claim 18 wherein said
contacting in step (b) is at a temperature of about 140·
C. to 180· C. for about 1 hour to precipitate said iron,
and then at a temperature of about 180· C. to 200· C. for
about 1 hour to precipitate said aluminum.
20. A method according to claim 18 wherein said
contacting in step (b) is performed at a temperature of
about 180· C. to 200· C. for about I hour to precipitate
said aluminum, and then at a temperature of about 140·
C. to 180· C. for about 1 hour to precipitate said iron.
21. A method according to claim 19 or claim 20,
wherein said contacting in step (b) to precipitate said
iron is carried out at about 160· C. for about 30 to 40
55 minutes, and wherein said contacting in step (b) to precipitate
said aluminum is carried out at about 180· C. for
about 20 to 30 minutes.
4,548,794
13
psig and at temperature conditions that precipitate
said iron and said aluminum in crystalline form
producing a low pressure leachate and a low pressure
leach residue; and
(e) recovering metal values from said Fe- and Al-dep- 5
leted low pressure leachate and from at least a
portion of said low pressure leach residue in a
leaching step.
2. A method according to claim 1 further comprising
separating from said first fraction a coarser third frac- 10
tion, said third fraction containing more magnesium
than said first fraction and less than said second fraction;
and contacting at least a portion of said third fraction
and at least a portion of said high pressure leachate in
the low pressure leach of step (d). 15
3. A method according to claim 1 wherein at least a
portion of said high pressure leachate of step (c) and at
least a portion of said second fraction of step (a), are
contacted in an atmospheric leach at atmospheric pressure
and at a temperature below about 100· C. to form 20
an atmospheric leach residue and an atmospheric leachate
prior to contact in the low pressure leach of step (d).
4. A method according to claim 3 further comprising
separating from said first fraction a coarser third frac- 25
tion, said third fraction containing more magnesium
than said first fraction and less than said second fraction,
and contacting at least a portion of said third fraction
and at least a portion of said atmospheric leachate in the
low pressure leach of step (d). 30
5. A method according to claim 1 further comprising
separating from said first fraction a coarser third fraction,
said third fraction containing more magnesium
than said first fraction and less than said second fraction,
and contacting at least a portion of said third fraction in 35
the low pressure leach of step (d).
6. A method according to claim 1 or claim 3, wherein
at least a portion ofsaid low pressure leachate is neutralized
by the addition of a neutralization agent selected
from the group consisting of alkali and alkaline earth 40
oxides and alkali and alkaline earth hydroxides to form
a neutralized low pressure leachate.
7. A method according to claim 1, or claim 2, or claim
3, or claim 4, wherein at least a portion of said low
pressure leach residue is recycled to said high pressure 45
leach.
8. A method according to claim 3 or claim 4, wherein
at least a portion of said low pressure leach residue is
recycled to said atmospheric leach.
9. A method according to claim 8 wherein a coarser 50
fraction of said atmospheric leach residue is separated
from said atmospheric leachate and the remainder of
said atmospheric leach residue, and further comprising
filtering said coarser fraction into a filtrate and a filter
cake from which chromite is recovered.
10. A method according to claim 9 wherein at least a
portion of said filtrate is recycled to said atmospheric
leach.
60
65