15 Claims, No Drawings
The invention comprises the treatment of metal oxides
and mixed metal oxides and metal sulfides in a vertical
tube reactor system having a downcomer section and a
riser section in order to oxidize and dissolve the metal
values in aqueous slurry primarily in the downcomer
section and introducing a reducing agent comprising a
formate species and reducing the dissolved metal values
in the riser section. The reduced metal values are then
separated with the gangue values from the product
solution downstream from the vertical tube reactor
system. The reduced metal values may then be separated
from the gangue material by conventional solid
separation techniques, such as flotation.
3,606,999 9/1971 Lawless 210/63 R X
3,640,703 2/1972 Cooper 75/101 R
3,853,759 1211974 Titmas 210/63 R
3,917,519 1111975 Fisher et aI 423/37
4,008,076 2/1977 Junghauss et al. 423/36
4,116,488 9/1978 Hsueh et aI 75/117
4,234,560 1111980 Kuerten et aI 423/659
4,272,383 6/1981 McGrew 210/741
4,322,390 3/1982 Tolley et al. 423127
4,350,599 9/1982 Chowdhury 4231206 R
OTHER PUBLICATIONS
Considine, Van Nostrand's Scientific Encyclopedia, 6th
ed. p. 1262.
Primary Examiner-John Doll
Assistant Examiner-Robert L. Stoll
Attorney, Agent, or Firm-Sheridan, Ross & McIntosh
United States Patent [19]
Hazen et al.
[54] METHOD OF RECOVERING METALS
FROM ORES USING A FORMATE
REDUCING AGENT
[75] Inventors: Wayne C. Hazen, Denver; Enzo L.
Coltrinari, Arvada; John E. Litz,
Lakewood; David L. Thompson,
Golden, all of Colo.
[73] Assignee: Resource Technology Associates,
Boulder, Colo.
[21] Appl. No.: 690,743
[22] Filed: Jan. 11, 1985
Related U.S. Application Data
[63] Continuation-in-part of Ser. No. 524,025, Aug. 17,
1983.
[51] Int. Cl.4 C22B 5/00
[52] U.S. Cl•....................................... 75/101 R; 75/2;
75/108; 75/115; 75/119; 75/117; 423/26;
423/36; 423/41; 423/42; 423/45; 423/146;
423/150
[58] Field of Search 423/27, 26, 42, 36,
423/41, 140, 145, 146, 150; 75/108, 101 R, 115,
117, 119,2
[56] References Cited
U.S. PATENT DOCUMENTS
1,472,115 10/1923 Clark 75/108
1,686,391 10/1928 Muller et aI 75/108
2,239,519 8/1941 Gurwood 75/108
2,690,425 9/1954 Moses et aI 423!DIG. 18
3,464,885 9/1969 Land et al. 166/61 X
[57]
[11] Patent Number:
[45] Date of Patent:
ABSTRACT
4,606,764
Aug. 19, 1986
SUMMARY OF THE INVENTION
DESCRIPTION OF THE PREFERRED
EMBODIMENTS
The process of the present invention utilizes a vertical
tube reactor system, particularly the hydrostatic head
pressures inherent therein, in order to process various
metal oxides and mixed metal oxides and metal sulfides.
The reactor design is typically vertical, with a downcomer
portion, which is generally a cylindrical pipe,
and a riser portion, which is also generally a cylindrical
pipe. A preferred configuration is a U-tube wherein one
leg comprises the downcomer and the adjacent leg
comprises the riser. Another preferred configuration is
an annular piping arrangement wherein the downcomer
generally comprises an internal cylindrical pipe and the
riser comprises the concentric outside annular ring. It is
not necessary that the reactor configuration be truly
vertical, as long as the feed material is introduced into
the reactor system at a location sufficiently elevated
from the primary reaction zone portion of the system so
as to generate sufficient hydrostatic head pressure.
The dimensions of the downcomer and riser portions
of the reactor system are designed so as to accomplish a
2
be particularly helpful if the non-gaseous reducing
agent had the the effect of releasing a hydrogen species.
In addition, copper metal cannot be produced by
hydrogen reduction of copper sulfate solutions in the
presence of elemental sulfur or sulfides (pyrite) due to
the formation of cupric sulfide. Accordingly, it would
be advantageous to have a process wherein the solubilized
copper from a mixture of copper sulfide/oxide
feed material can nevertheless undergo hydrogen re-
10 duction to copper metal. These and other advantages
are provided by practice of the processes of the present
invention.
15
4,606,764
1
FIELD OF INVENTION
METHOD OF RECOVERING METALS FROM
ORES USING.A FORMATE REDUCING AGENT
This application is a continuation-in-part of U.S. pa- 5
tent application Ser. No. 524,025, filed Aug. 17, 1983.
This invention relates to the processing of metal oxides
and mixed metal oxides and metal sulfides, particularly
copper oxides and mixed copper oxides and copper
sulfides, in a vertical tube reactor in order to accomplish
both oxidation and reduction of the metal values.
BRIEF DESCRIPTION OF THE PRIOR ART The invention comprises the treatment of metal ox-
Many metallurgical processes include the dissolution ides and mixed metal oxides and metal sulfides in a
of valuable constituents such as copper at elevated tem- vertical tube reactor system having a downcomer secperatures
and pressures. The majority of these processes tion and a riser section in order to oxidize and dissolve
react the metal values of the ore or concentrate with the metal values in aqueous slurry, preferably in the
acid or alkali in an agitated pressure vessel, sometimes 20 downcomer section and introducing a formate reducing
in the presence of an oxidizing or a reducing gas. In agent so as to reduce the dissolved metal values preferaaddition,
a large number of metallurgical processes bly in the riser section. The reduced metal values are
begin with furnace oxidation of sulfides or carbonifer- then separated with the gangue values from the product
ous materials. Such a step is quite often environmentally solution downstream from the vertical tube reactor
restrictive and may require significant energy input. 25 system. The reduced metal values may then be sepa-
Reaction systems are disclosed which accomplish the rated from the gangue material by conventional solid
oxidated dissolution of various materials in a vertical separation techniques, such as flotation.
tube reactor configuration. U.S. Pat. No. 4,272,383 to The invention is particularly applicable to copper
McGrew, along with various references cited therein, oxides and mixed copper oxides and copper sulfides
disclose such systems, along with particular processing 30 wherein the feed material is slurried and injected into
conditions deemed suitable for accomplishing their par- the downcomer of the vertical tube reactor system in
ticular results. the presence of sulfuric acid and/or oxygen. The system
Upon completion of the processing such as disclosed becomes increasingly pressurized as the reactants travel
in McGrew, the resultant leach liquor products are through the downcomer portion of the reactor system,
removed from the reaction vessel and further processed 35 and are permitted to travel to a depth sufficient to oxias
desired for metal recoveries. The present application dize and solubilize the copper values. A reducing agent,
deals with techniques whereby the metal values are not specifically a formate species, is introduced into the
only oxidized and dissolved in the reaction system, but system following completion of the oxidation reaction,
the metal values are also subsequently reduced and preferably in the riser section ofthe reactor. The copper
precipitated in their elemental form prior to leaving the 40 values are then reduced to elemental copper during the
reaction vessel. upflow of the product slurry. Upon exiting the vertical
Many commonly used reductants are in a gaseous tube reactor system, the leach solution is separated from
phase at ambient temperatures and atmospheric pres- the precipitated copper and residual gangue material,
sures. Thus a high-pressure gas handling system and and the solids are further processed by flotation in order
high-pressure gas lines within the reactor are typically 45 to separate the copper from the gangue material.
required by prior methods. Such a system is expensive
and presents safety problems which must be dealt with.
Accordingly, it would be advantageous to have a
method which enhances the reactivity of the copper
contained in CuFeS2 in order to decrease the ineffi- 50
ciency experienced when treating CuFeS2 for copper
recovery. Similarly, it would be advantageous to have a
process system wherein mixtures of copper oxide and
disseminated copper sulfide could be effectively treated
to recover all of the copper without the need for envi- 55
ronmentally unacceptable methods of eliminating the
sulfides such as by roasting. Non-sulfide copper ores
leach readily in sulfuric acid solutions and present no
particular leaching problems. However, many oxide
ores contain significant amounts of sulfide mineraliza- 60
tion. These ores do not respond readily to conventional
acid leaching and as such it would be advantageous to
have a process from which all of the copper could be
recovered.
Further, it would be advantageous to provide a re- 65
ducing agent which is in a non-gaseous phase at ambient
temperatures and atmospheric pressures. Since copper
reduction by hydrogen gas is well understood, it would
COOH--C02+HExamples
of formate species are: potassium formate,
sodium formate, carbon monoxide (in basic solution),
and formic acid.
The formate ion can produce hydrogen by a reaction,
similar to the "water-gas shift" reaction. According to
this reaction, an aqueous solution of formate ions decomposes
under certain conditions to form an active
hydrogen species, carbon dioxide and hydroxyl ions.
A reducing agent which produces hydrogen such as a
formate ion is particularly useful when sulfur is present
in the ore. The formate ion is also particularly useful as
a reductant since it is a polar ion which can react in
ways that non-polar molecular hydrogen cannot. It
produces the equivalent of a hydride ion:
Formate ions can be produced by dissolution of such
formate compounds as potassium formate, sodium formate,
and formic acid. Potassium is particularly useful
because of its high solubility in water. Formate ions are
also formed by introducing carbon monoxide to a basic
water solution. Carbon monoxide can thus be converted
under mild conditions to a low volatility reducing agent
that does not involve a high partial pressure of gas.
The present process, then, makes possible introduction
of a hydrogen-producing reducing agent which
avoids the necessity of a high-pressure gas handling
system. This avoidance is advantageous for reactions
carried out in a vertical tube reactor and particularly in
a subterranean reactor because it avoids both the surface
high-pressure gas handling system, and the necessity
for down-hole high-pressure gas lines and other
systems required for introduction of a high-pressure
gas. The reducing agent is preferably introduced directly
into the riser section of the reactor.
As will be known and understood by those skilled in
the art, formate species may be employed in processes
other than recovery of precious metals from ores, as
either a reducing agent or a hydrogen-producing reagent
and are are particularly useful as such in a subterranean
vertical reactor environment.
The mixture of the formate with the slurry containing
dissolved, oxidized metal values is conveyed to a second
"reducing" section of the reactor, preferably the
riser section, having a reduction-effective temperature
and pressure. As used, herein, a "reduction-effective
temperature and pressure" is a temperature and pressure
The vertical tube reactor system is preferably designed
so as to complete the oxidative dissolution of the
metal values in the downcomer portion of the reactor
design. A reducing agent is then introduced into a re-
5 duction zone within the reactor in order to accomplish
the reduction and precipitation of the dissolved metal
values. According to the process of this invention, the
reducing agent is a formate species. As used herein,
"formate species" refers to a species, which at the reduction
zone temperatures and pressures, produces
formate ions. A formate ion is an ion with the structural
formula:
4,606,764
3
feed slurry flow rate and reactor residence time sufficient
to accomplish the oxidative dissolution reaction
and the metal precipitate reduction reaction. The reactor
length is primarily a function of the desired reaction
pressure.
Feed materials suitable for the process of the present
invention include metal-containing ores, primarily
metal oxide ores and mixed metal oxide and metal sulfide
ores, along with scrap metal values, which are
amenable to oxidative pressure leaching and subsequent 10
slurry reduction. Metal values particularly suitable for
the present process include nickel and cobalt values
from laterite ores and copper values from copper oxide
ores and mixed copper oxide/copper sulfide ores. Suitable
feed materials also include unreacted metal values 15
which are recycled from previous processing.
Ore feed materials which contain significant amounts
of acid consuming impurities are preferably concentrated,
such as by flotation, prior to being introduced
into the reactor system. The ore and/or concentrate 20
may be pre-treated in order to obtain a more preferred
balance of oxides to sulfides ratio. For example, when
treating chalcopyrite ore, which is primarily a refractory
mixed copper-iron sulfide ore, the chalcopyrite is 25
preferably initially leached with a copper sulfate solution
under processing conditions suitable to produce
simple copper sulfides, such as chalcocite, covellite and
digenite. These sulfides may then be blended with copper
oxide feed materials. 30
The feed material prior to entering the reaction system
is crushed and sized to a slurriable size. A slurry is
formed of the crushed, sized ore. The particular selection
of particle sizes and slurry solids contents are functions
of the selection of the balance of the processing 35
variables, as is appreciated in the art.
The oxidizing agent is mixed with the slurry, generally
prior to conveying the slurry to a first "oxidizing"
section of the reaction system. If the feed material contains
sufficient sulfide values, the oxidizing agent is 40
preferably oxygen, as sulfuric acid is then formed in
situ. When processing feed materials with insufficient
sulfides content, the desired oxidizing agent, for example,
sulfuric acid, is mixed with the feed material prior
to introduction into the reaction system. Alternatively, 45
it may be convenient or desirable to introduce the oxidizing
agent after the slurry enters the reactor.
The temperature and pressure in the oxidizing section
must be an oxidation-effective temperature and pressure.
As used herein, an "oxidation-effective tempera- 50
ture and pressure" is a temperature and pressure which
is sufficient to oxidize substantially all the metal in the
slurry after the oxidizing agent has been added. Preferred
temperature and pressure conditions are dependent
upon the feed material, the oxidizing agent, reac- 55
tion residence time, degree of metal dissolution desired,
and the selection of the balance of processing variables.
When dealing with feed materials containing sulfides, it
is generally preferred to maintain the process at a temperature
in excess ofthe melting point of sulfur, i.e. 1190 60
C., as below this temperature elemental sulfur forms and
interferes with the subsequent reduction reaction. Processing
pressures of from about 50 to about 800 psig are
generally suitable, depending upon the selection of the
other processing variables. The slurry is maintained at 65
an oxidation-effective temperature and pressure for a
time sufficient to substantially oxidize the metal in the
ore.
200
2
800
%
26.8
25.1
30.1
6.9
0.33
Cu
Fe
S
Zn
Pb
Temperature, 'c.
Time, hour
Agitation, rpm
Leaching Results
I 2
7 3 5 6 2 4
110 110 110 ISO 200 110 110
200 450 600 500 700 450 600
18 70 30 41 50 27 87
50 75 62 64 99 84 79
72 81 74 87 99 91 91
Pressure Leach of Copper Concentrates
Conversion conditions:
Summary of Results
Ore concentrate head assay Element
6
Tests I, 3, 5, 6 and 7 the copper sulfate to sulfide ratio
was one. Table I summarizes the test data, while Table
I(a) provides the information in detail.
TABLE I
CuS04/Cu
mole ratio
Test No.
20 Temperature. 'C.
Pressure. psig
Cu extracted. % at:
I hour
2 hours
3 hours
4,606,764
EXAMPLE 1
5
which is sufficient to substantially reduce the dissolved
metal values in the presence of formate ions, whereby
elemental metal is formed. The remainder of the slurry
forms a gangue material. The mixture is maintained at a
reduction-effective temperature and pressure for a time 5
sufficient to reduce substantially all the metal values.
Upon exiting the riser portion of the reaction system
the metal values amenable to the processing exist in
precipitated form in the slurry. The process liquor is
preferably separated from the solids, and the solids may 10
then be treated for the further recovery of the metal
values. One particularly preferred technique, particularly
with respect to the processing of copper ores,
includes flotation. The. resulting gangue material from
this separation may then be further processed for the 15
recovery of residual values or otherwise suitably discarded.
The following examples are provided by way of illustration
and not by way of limitation.
Two series of tests were performed to evaluate pressure
leaching. time, temperature and oxygen partial
pressure on the copper dissolution after pretreatment
with copper sulfate. Tests 2 and 4 reacted two moles of 25
copper sulfate for each mole of copper as sulfide. For
TABLE l(a)
Test Data: Pressure Leaching Copper Sulfide Concentrate
Feed Ore Concentrate: 26.8% Cu. 25.1% Fe. 30.5% S. 6.9% Zn, 0.3% Pb
Ground to 8.7% on 325-mesh. 82% passing 4OO-mesh
Test Number:
Conversion Leach
Mole Ratio: Cu + + ICu
Solution:
Cu, gil
Fe++. gil
H2S04. gil
Pulp Density. % solids
Temperature, C.
Sample Time. hours
Filtrate:
Cu, gil
Fe. gil
H2S04. gil
Vapor phase odor
Oxidation Leach
Temperature. C.
Oxygen Pressure, psi
Oxygen Consumption, Iblt
Sample Time, hours
Copper Extraction %
Residue: Cu, %
Filtrate:
Cu, gil
Fe. gil
H2S04. gil
pH
EMF. mv
4
2 2
23 33 22 31
8.2 7.3 7.5 7.6
38 39 39 39
8 6 8 6
200 200 200 200
2 2 2 2
0.98 0.001 1.14 0.001 0.23 0.001 1.07 0.001
22.0 19.1 18.5 19.5 21.3 22.6 19.1 20.3
42.2 50.6 62.4 65.2 44.2 42.9 63.2 66.9
strong H2S some H2S some H2S some H2S
110-115 110-115 110-115 110-115
450 450 600 600
640 320 340 340
I 2 3 I 2 3 I 2 3 I 2 3
70 75 81 27 84 91 30 62 74 87 79 91
16.0 6.9 5.6 32.5 4.8 2.8 50.2 40.9 8.0 58.4 6.7 2.9
30.8 40.0 43.0 39.5 47.3 50.0 8.5 20.0 40.8 22.2 45.5 48.5
12.5 4.0 3.5 13.9 6.6 6.1 23.3 23.3 6.7 20.8 11.2 9.5
4.4 6.3 6.9 2.4 6.2 7.4 27.9 5.4 4.1 31.9 5.1 4.4
1.4 1.4 1.4 1.5 1.3 1.2 0.6 1.2 1.4 0.5 1.4 1.4
400 440 480 443 463 478 347 405 479 375 445 490
Test Number: 5 6
Conversion Leach
Mole Ratio: Cu++/Cu
Solution:
Cu, gil 22 22 22
Fe++. gil 8.0 8.0 8.0
H2S04. gil 40 40 40
Pulp Density. % solids 8 8 8
Temperature, C. 200 200 200
Sample Time. hours 2 2 2
Filtrate:
Cu. gil 0.32 0.001 0.19 0.001 0.15 0.001
Fe. gil 23.5 21.1 20.7 22.3 22.3 21.7
H2S04. gil 42.9 42.6 43.9 43.2 46.0 42.2
i
4,606,764
TABLE l(a)-continued
Test Data: Pressure Leaching Copper Sulfide Concentrate
Feed Ore Concentrate: 26.8% Cu, 25.1% Fe, 30.5% S, 6.9% Zn, 0.3% Pb
Ground to 8.7% on 325-mesh, 82% passing 400-mesh
Vapor phase odor some H2S some H2S some H2S
Oxidation Leach
Temperature, C. 150 200 110-115
Oxygen Pressure, psi 500 700 200
Oxygen Consumption, Ib/t 1680 1060 280
Sample Time, hours 1 2 3 1 2 3 1 2 3
Copper Extraction % 41 64 87 50 99 99 18 50 72
Residue: Cu, % 50.2 44.4 4.1 24.9 0.68 0.41 50.5 43.5 8.2
Filtrate:
Cu, gil 13.8 26.8 43.8 42.6 46.1 49.5 4.4 14.6 39.2
Fe, gil 22.2 23.1 20.3 24.5 8.4 5.2 22.8 21.7 5.1
H2S04, gil 28.3 26.5 9.9 31.7 58.9 73.2 34.6 15.4 2.7
pH 0.7 0.7 1.0 0.6 0.25 0.1 0.6 1.0 1.7
EMF, mv 346 379 520 354 470 560 274 395 454
EXAMPLE 2 20 EXAMPLE 3
A series of tests was performed to evaluate sulfuric A series of tests were performed to establish the effect
acid-oxygen pressure leaching of a mixed sulfide-oxide of the hydrogen overpressure when hydrogen reducing
ore. The results of these tests are summarized in Table 2. copper sulfate solutions simulating the filtrate from a
pressure leach of concentrates. The data from these
TABLE 2 25 tests are tabulated in Table 3.
Pressure Leaching Mixed Sulfide-Oxide Copper Ore TABLE 3
Ore: 0.52% total Cu Hydrogen Reduction Tests at 160' C.
0.22% oxide Cu Feed solution assays: 7.3% Fe Element gil Element gil
0.07% S 30 Cu 45.0 H2SO4 6.9
Conditions: 50% solids, 110' C. FeTol 3.5 pH I.3
(except Test 3 = 160' C.) Fe+2 0.30 emf, mv -470
0.75 initial pH, 2 hours
Test No. 2 3 4 5 Test No. 1 2 3 4 5 6
Grind, mesh 65 65 65 65 100 100 Pressure, psig 150 225 300 400 225
Oxygen pressure, psi 50 200 200 450 50 2001 35 Cu, gil:
Copper solubilized 56 54 53 55 54 58 Sample 1 hour 37.6 32.6 24.5 22.2 22.2
Residue: 2 32.6 27.8 11.8 9.3 9.32
Copper, % 0.23 0.24 0.25 0.24 0.24 0.24 3 30.4 22.7 7.65 6.60 6.60
Oxide copper, % 0.02 0.02 0.D3 0.03 0.02 0.03 4 28.3 17.4 6.05 5.21 5.21
5 26.6 11.9 4.42 3.62 3.62
1Added 5 g ferric ionlliter to feed pulp. 40 ISeeded with 2 gil Cu'. Copper plating prevailed.
Most of the tests were performed at 110° C.; however,
Test 3 was performed at 160° C. 5 grams per liter
of ferric ion were added to the leach feed in Test 6 to
determine whether the oxidation of sulfides was cata- 45
lyzed by the presence of soluble iron. The residual sulfide
copper content from this 110° C. pressure leach was
about 90% of the value in an identical test without
added iron (Test 2).
EXAMPLE 4
A series of tests were run to compare the effect on
copper extraction when chalcopyrite was treated before
leaching with copper sulfate and temperatures below
the melting point of S are used. The test conditions and
results are provided in Table 4 without pre-leach and in
Table 5 when a pre-leach is employed.
TABLE 4
Pressure Leach of Chalcopyrite Concentrates
Chalcopyrite concentrates 24.2% Cu, 26.6% Fe, 28.4% S
Autoclave 2-liter Parr
Slurry volume 1-1.2 liter
Temperature 108-117' C.
Time 4 hours
Test 2 4 6 7
Feed, Wt %
Concentrate 75 75 75 75 33.32 75 100
Pyrite 25 25 25 25 11.I2 25 0
Sand 55.63
Grind, mesh -200 -325 -200 -325 -325 -325 -325
Solution,
gil H2SO4 30 30 30 61 61 pH 8.5 pH 8.5
gil Fe 60.5 58.0
Pulp density, gil solids 167 167 167 167 375 83 62.5
Oxidant 02 02 02 02 02 Fe+3 Fe+3
Pressure, Fsig total 420 415 420 420 410 20 20
Agitation Mild Mild Vigorous Mild Mild Mild Mild
% Cu extracted 42 53 47 58 34 41 39
9
4,606,764
10
TABLE 4-continued
Pressure Leach of Chalcopyrite Concentrates
Chalcopyrite concentrates 24.2% Cu, 26.6% Fe, 28.4% S
Autoclave 2-liter Parr
Slurry volume 1-1.2 liter
Temperature 108-117° C.
Time 4 hours
Test I 2 3 4 6 7
13.2 14.1 13.7 14.5 9.20 6.08
11.5 8.1 11.6 30.0 21.3 74.8
26.5
1.3 1.2 1.2 0.65 0.55 0.4
465 465 465 485 490 407
Residue, % Cu 12.3 11.5 10.8 14.4 4.72 15.0 20.8
Solution,
~~ ~
gil Fe 66.8
g/I Fe+3 29.7
~ M
emf, mv 420
IMild = downcast impeller at 800 rpm; vigorous = turbine impeller at 1000 rpm.
2Acetone wash to remOve flotation reagents.
3Silica sand, 20- X 3D-mesh.
TABLE 6
Leach·Precipitation.Flotation Tests Using Synthetic Ore
Cu Recovery from Concentrate by
Pretreatment/Pressure Leach and
H2 Reduction of CUS04 Leach Solution
_ duction. Other test conditions and results are provided _______T_A_B_L_E_5________ in Table 6.
20
H2
200
400
90
1.6
70.8
86.4
3.2
1.2
9.2
Test 2
Test 2
0.7
28.7
By weight %
1.9% total Cu
1.3% oxide Cu
0.6% sulfide Cu,
(primarily as CU2S)
TABLE 7
EXAMPLE 6
Fe powder
23
Atmospheric
9
4.4
Same for all tests
Rougher and one cleaner
Minerec A, Aerofloat 242, Dowfroth 250
3-5
Test I
24.5
60.5
94.9
4.1
1.0
0.1
Synthetic Ore 1.0% Cu mixture of (in wt %) 2.1 cone.
of Table 4, 2.5 FeS2, 1.4 chrysocolla,
0.40 azurite/malachite, and 93.6
silica sand; minus 200-mesh
Same for all tests
50
Adjusted to pH 1.5 with H2S04
200° C.
320 psig total (02 + steam)
Downcast impeller, 600 rpm
98-99%
Test I
25
50
Leach conditions
% solids
Acidity
Temperature
30 Pressure
Agitation
Cu extraction
Precipitation
Reductant
Temperature, °C.
35 Pressure, psig
Time, min
pH
Flotation
No. of stages
Reagents
pH
40 Cu distribution, %
Concentrates
Cleaner tails
Rougher tails
Solutions
Cu concentrates assay
45 % Cu
%Fe
%S
% acid insol
A test was performed to evaluate sulfuric acid leaching
of a natural mixed copper oxide-copper sulfide ore
at ambient temperature and atmospheric pressure fol-
55 lowed by hydrogen reduction of the solubilized copper
to the elemental metal and froth flotation recovery of
the copper. Samples of the fluid portion and solid portion
of the slurry was assessed for copper content after
the 45 minute leach and after one hour and two hours of
60 hydrogen reduction. Test conditions and results are
given in Table 7.
EXAMPLE 5
24.2% Cu, 26.6% Fe, 28.4% S
In 2-liter Parr autoclave
90 g, minus 325-mesh
1200 ml; 20.2 gil Cu (as CUS04) +
5.0 gil H2S04
200°C.
230 psig (steam only)
2 hours
Downcast impeller, 800 rpm
52.1% Cu, 10.2% Fe; containing major CU9SS
(digenite) CuFeS2 and subordinate CuS
(covellite) and FeS2
Less than 0.001 gil Cu, 12.6 gil Fe, 18.9 gil
H2S04, emf = 280 mv
3 CuFeS2 + 6 CUS04 + 4 H20 ~
CU9SS + 3 FeS04 + 4 H2S04
CuFeS2 + CUS04 ~ 2 CuS + FeS04
In 2-liter Parr autoclave
From pretreatment, 1177 g (80 g solids, 1.0
liter solution)
42 g
106-109° C.
425 psig (02 + steam), no bleed
Downcast impeller, 800 rpm
73% at I hr, 92% at 2 hr, 92% at 3 hr
CU9SS + 9 H2S04 + 4.5 02 ~
9 CUS04 + 5 So + 9 H20
CuFeS2 + H2S04 + 1.25 02 + 0.5 H20 ~
CUS04 + Fe(OH)) + 2 So
CuS + H2S04 + 0.5 02 ~
CUS04 + So + H20
6 FeS04 + 1.5 02 + 9 H20 ~
2 HFe3(S04h(OH)6 + 2 H2S04
In 2-liter Parr autoclave
Filtrate from leach; 980 rnl - 30.7 gil Cu,
8 gil H2S04, 7.18 gil Fe, emf = 480 mv
200°C.
400 psig (H2 + steam)
79% at 15 min, 88% at I hr, 94% at 1.5 hr
1.99 gil Cu, 7.14 gil Fe, 59 gil H2S04,
emf = 310 mv
98% Cu, 0.004% Fe, 0.02% S
Majority of precipitated Cu plated to metal
(Ti) parts in autoclave.
Leach
Slurry
Reactions
Temperature
Pressure
Time
Agitation
Treated solids
Concentrates:
Pretreatment
Concentrate
Solution
Solution
H2S04 added
Temperature
Pressure
Agitation
Cu extraction
Reactions
Cu precipitate
Comment
H2 reduction
Solution
Temperature
Pressure
Cu precipitated
Solution (1.5 hr)
Two tests were performed to evaluate sulfuric acidoxygen
pressure leaching of a synthetic mixed sulfideoxide
ore followed by reduction of the solubilized copper
to metal utilizing three different reductants and 65
froth flotation recovery of the metals. Test 2 demonstrates
the recovery of metallic copper by flotation after
strongly oxidative pressure leaching and hydrogen reJ!.
Jl
TABLE 7-continued
100 mesh size
4,606,764
Leach Conditions
% solids
Acidity
Temperature
Pressure
Time
Agitation
Precipitation
Reductant
Temperature 0c.
Pressure, psig
Time
45 min Leach
50
adjusted to pH 1.5
with H2S04
ambient - 22" C.
atmospheric
45 min.
800 rpm
5
I 2
PF Residue
pH 1.6
wI/vol 36.2 35.1
(gil)
Cu 11.6 0.725
Fe 3.30
Flotation
Reagents
rpm
pH
1.1 1.15
43.5 39.5 37.7 35.6
20
0.93 0.37
7.62 7.90
Ca(OHh, Mineric A,
Aero 242,
Dow Froth 250, Aero
404,1%
900
3.5, except Ca(OHh
1.9 to 3.5
55
Distri· 30 Dry Assay Units bution
Copper weight (g) % Cu (g) %
I. Cleaner concentrate 3.00 85 2.55 84.4
2. Cleaner tails 4.13 2.30 .095 3.1
3. Scavenger 1.83 1.77 .067 2.9
concentrate 35
4. Scavenger tails 140.8 0.11 .155 5.1
5. Scavenger tails 1370 ml 0.102 gil 0.137 4.5
solution (0.801
gil Fe)
Total 149.8 2.01 3.024 100.0
40
Although the foregoing invention has been described
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 45
scope of the appended claims.
What is claimed is:
1. A process for producing metal values from a metalcontaining
ore comprising metal oxide ores or mixed
metal oxide and metal sulfide ores in a vertical tube 50
reactor having downcomer and riser sections comprising:
crushing and sizing said ore to a slurriable size;
forming a slurry with said crushed and sized ore;
adding an oxidizing agent to said slurry;
conveying said slurry to a first section of said reactor,
having a first pressure of above about 50 p.s.i.g.; to
produce a first mixture of dissolved metal and solid
gangue material;
adding a reducing agent comprising formate species 60
to said first mixture producing a second mixture;
conveying said second mixture to a second section of
said reactor, having a second pressure of above
about 50 p.s.i.g.;
maintaining said second mixture at above about 65
p.s.i.g. for a time sufficient to reduce substantially
all said dissolved metal values and produce a third
UNITED STATES PATENT ANL TRADEMARK OFFICE
CERTIFICATE OF CORRECTION
PATENT NO. :
DATED
INVENTOR(S) :
4,606,764
August 19, 1986
Hazen et ale
It is certified that error appears in the above-identified patent and that said Letters Patent
is hereby corrected as shown below:
Column 8, line 33, Test No.5 should read -- 51 -indicating
the footnote.
Column II, line 66, insert -- 50 -- before p.s.i.g.
Signed and Sealed this
Seventeenth Day of March, 1987
Attest:
DONALD J. QUIGG
Attesting Officer Commissioner of Parents and Trademarks