4,606,764 Method of recovering metals from ores using a formate reducing agent

Patent Number/Link:

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

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.

4,606,764

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

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

800

26.8

25.1

30.1

6.9

0.33

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

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

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

EMF. mv

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

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

4,606,764

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.

200

400

1.6

70.8

86.4

3.2

1.2

9.2

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

Atmospheric

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

Adjusted to pH 1.5 with H2S04

200° C.

320 psig total (02 + steam)

Downcast impeller, 600 rpm

98-99%

Test I

Leach conditions

% solids

Acidity

Temperature

30 Pressure

Agitation

Cu extraction

Precipitation

Reductant

Temperature, °C.

35 Pressure, psig

Time, min

Flotation

No. of stages

Reagents

40 Cu distribution, %

Concentrates

Cleaner tails

Rougher tails

Solutions

Cu concentrates assay

45 % Cu

%Fe

% 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

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!.

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

adjusted to pH 1.5

with H2S04

ambient - 22" C.

atmospheric

45 min.

800 rpm

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

1.1 1.15

43.5 39.5 37.7 35.6

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

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

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