111111111111111111111111111111111111111111111111111111111111111111111111111

US007736488B2

(12) United States Patent

Marsden et al.

(10) Patent No.:

(45) Date of Patent:

US 7,736,488 B2

*Jun.15,2010

(73) Assignee: Freeport-McMoran Corporation,

Phoenix, AZ (US)

(54) PROCESS FOR RECOVERY OF COPPER

FROM COPPER-BEARING MATERIAL

USING PRESSURE LEACHING, DIRECT

ELECTROWINNING AND

SOLVENT/SOLUTION EXTRACTION

(75) Inventors: John 0 Marsden, Phoenix, AZ (US);

Robert E Brewer, Park City, UT (US);

Susan R Brewer, Park City, UT (US);

Joanna M Robertson, Thatcher, AZ

(US); David R Baughman, Golden, CO

(US); Philip Thompson, West Valley

City, UT (US); Wayne W Hazen,

Lakewood, CO (US); Christel M. A.

Bemelmans, Indian Hills, CO (US)

( *) Notice: Subject to any disclaimer, the term ofthis

patent is extended or adjusted under 35

U.S.c. 154(b) by 0 days.

This patent is subject to a tenninal disclaimer.

3,985,553 A

3,991,159 A

4,017,309 A

4,020,106 A

4,028,462 A

4,029,733 A

4,039,405 A

4,039,406 A

4,046,851 A

4,067,802 A *

4,069,119 A

4,091,070 A

4,093,526 A

4,120,935 A

4,150,976 A

4,157,912 A

4,165,362 A

4,256,553 A

4,266,972 A

4,272,341 A

4,338,168 A

4,405,569 A

4,415,540 A

4,442,072 A

4,507,268 A

4,571,264 A

10/1976 Kunda et al.

11/1976 Queneau et al.

4/1977 Johnson

4/1977 Ackerley et al.

6/1977 Domic et al.

6/1977 Faugeras et al.

8/1977 Wong

8/1977 Stanley et al.

9/1977 Subramanian et al.

1/1978 Cronberg et al 205/586

1/1978 Wong

5/1978 Riggs et al.

6/1978 Blanco et al.

10/1978 Fountain et al.

4/1979 Dain

6/1979 Weir et al.

8/1979 Reynolds

3/1981 Baczek et al.

5/1981 Redondo-Abad et al.

6/1981 Lamb

7/1982 Stanleyet al.

9/1983 Dienstbach

11/1983 Wilkomirsky et al.

4/1984 Baglin et al.

3/1985 Kordosky et al.

2/1986 Weir et al.

(21) Appl. No.: 12/344,842

(22) Filed: Dec. 29, 2008

(Continued)

FOREIGN PATENT DOCUMENTS

3/1957

11/2002

5/1983

12/2000

1/2001

(Continued)

OTHER PUBLICATIONS

0219785

1657-2000

2108480

WO 00/73520

WO 01/00889

AU

CL

GB

WO

WO

Apr. 23, 2009

Prior Publication Data

US 2009/0101518 Al

(63)

(65)

Related U.S. Application Data

Continuation of application No. 111163,762, filed on

Oct. 28, 2005, now Pat. No. 7,485,216.

(60) Provisional application No. 60/623,453, filed on Oct.

29,2004.

(51) Int. Cl.

C2SC 1/12 (2006.01)

(52) U.S. Cl. 205/580; 205/584; 205/574;

205/575; 205/576

(58) Field of Classification Search 205/574,

205/575,576,580,584

See application file for complete search history.

(56) References Cited

U.S. PATENT DOCUMENTS

20 Claims, 4 Drawing Sheets

(Continued)

Primary Examiner-Bruce F Bell

(74) Attorney, Agent, or Firm-Snell & Wilmer L.L.P.

Non-Final Office Action mailed on Mar. 21, 2008 in U.S. Appl. No.

10/976,482.

Final Office Action mailed on Oct. 15, 2008 in U.S. Appl. No.

10/976,482.

Non-Final Office Action mailed on Apr. 28, 2009 in U.S. Appl. No.

10/976,482.

(57) ABSTRACT

The present invention relates generally to a process for recovering

copper and/or other metal values from a metal-bearing

ore, concentrate, or other metal-bearing material using pressure

leaching and direct electrowinning. More particularly,

the present invention relates to a substantially acid-autogenous

process for recovering copper from chalcopyrite-containing

ore using pressure leaching and direct electrowinning

in combination with a leaching, solvent/solution extraction

and electrowinning operation.

7/1966 Zimmerleyet al.

9/1970 Green

1/1972 Mackiw et al.

4/1972 Barry et al.

6/1972 Spedden et al.

11/1973 Coffield et al.

2/1975 Lindblad et al.

7/1975 Dubeck et al.

11/1975 Fisher et al. 205/584

4/1976 Pawlek et al.

5/1976 Anderson

6/1976 Parker et al.

6/1976 Touro

7/1976 Coffield et al.

3,260,593 A

3,528,784 A

3,637,371 A

3,656,888 A

3,669,651 A

3,775,099 A

3,868,440 A

3,896,208 A

3,917,519 A *

3,949,051 A

3,958,985 A

3,961,028 A

3,962,402 A

3,967,958 A

US 7,736,488 B2

Page 2

u.s. PATENT DOCUMENTS WO

WO

WO 02/08125

WO 2006/049632

1/2002

5/2006

4,606,764 A 8/1986 Hazen et al.

4,619,814 A 10/1986 Salter et al.

4,775,413 A 10/1988 Horton et al.

4,814,007 A 3/1989 Lin et al.

4,875,935 A 10/1989 Gross et al.

4,880,607 A 1111989 Horton et al.

4,892,715 A 111990 Horton

4,895,597 A 111990 Lin et al.

4,971,662 A 1111990 Sawyer et al.

4,992,200 A 2/1991 Lin et al.

5,028,259 A 7/1991 Lin et al.

5,059,403 A 10/1991 Chen

5,073,354 A 12/1991 Fuller et al.

5,176,802 A 111993 Duyvesteyn et al.

5,223,024 A 6/1993 Jones

5,232,491 A * 8/1993 Corrans et al. ................ 75/743

5,316,567 A 5/1994 Jones

5,356,457 A 10/1994 Alvarez et al.

5,431,717 A 7/1995 Kohr

5,573,575 A 1111996 Kohr

5,628,817 A * 5/1997 Fugleberg et al. ............. 75/743

5,645,708 A 7/1997 Jones

5,650,057 A 7/1997 Jones

5,670,035 A 9/1997 Virnig et al.

5,676,733 A 10/1997 Kohr

5,698,170 A 12/1997 King

5,730,776 A 3/1998 Collins et al.

5,770,170 A 6/1998 Collins et al.

5,849,172 A 12/1998 Allen et al.

5,869,012 A 2/1999 Jones

5,874,055 A 2/1999 Jones

5,895,633 A 4/1999 King

5,902,474 A 5/1999 Jones

5,914,441 A 6/1999 Hunter et al.

5,917,116 A 6/1999 Johnson et al.

5,985,221 A 1111999 Knecht

5,989,311 A * 1111999 Han et al. ..................... 75/743

5,993,635 A 1111999 Hourn et al.

6,083,730 A 7/2000 Kohr

6,146,444 A 1112000 Kohr

6,149,883 A 1112000 Ketcham et al.

RE37,251 E 7/2001 Jones

6,319,389 Bl 1112001 Fountain et al.

6,428,604 Bl 8/2002 Kerfoot et al.

6,451,089 Bl 9/2002 Marsden et al.

6,503,293 Bl 112003 Dempsey et al.

6,537,440 Bl 3/2003 Richmond et al.

6,569,224 B2 5/2003 Kerfoot et al.

6,660,059 B2 12/2003 Ji et al.

6,663,689 B2 * 12/2003 Marsden et al. ............... 75/744

6,676,909 B2 * 112004 Marsden et al. ............... 423/28

6,680,034 B2 112004 Marsden et al.

6,972,107 B2 12/2005 Marsden et al.

7,341,700 B2 * 3/2008 Marsden et al. ............... 423/28

7,485,216 B2 * 2/2009 Marsden et al. ............. 205/584

2003/0019331 Al 112003 Marsden et al.

2004/0146438 Al 7/2004 Marsden et al.

2004/0146439 Al 7/2004 Marsden et al.

2005/0109163 Al 5/2005 Marsden et al.

2005/0126923 Al * 6/2005 Marsden et al. ............. 205/580

2005/0155459 Al 7/2005 Marsden et al.

2006/0016697 Al 112006 Gilbert et al.

2006/0144717 Al 7/2006 Marsden et al.

2006/0196313 Al 9/2006 Marsden et al.

2008/0023342 Al * 112008 Marsden et al. ............. 205/772

FOREIGN PATENT DOCUMENTS

WO WO 01100890 1/2001

OTHER PUBLICATIONS

IPER for PCTIUSO1123366 dated Oct. 23, 2002.

ISR for PCTIUS02/23454 dated Jun. 12, 2003.

Written Opinion for PCTlUS01l23468 dated Jul. 17,2002.

IPER for PCTlUS01l23468 dated Dec. 17,2002.

ISR/Written Opinion for PCTIUS07/67943 dated Aug. 29, 2007.

IPRP for PCTIUS07/067943 dated Nov. 04, 2008.

ISR/Written Opinion for PCTIUS04/042038 dated Jun. 15,2005.

IPRP for PCTIUS04/042038 dated May 10, 2007.

Beckstead, L.W., et al., "Acid Ferric Sulfate Leaching of AttritorGround

Chalcopyrite Concentrate," 11 Extractive Metallurgy of

Copper 31:611-32 (American Institute ofMining, Metallurgical, and

Petroleum Engineers, Inc.) (1976).

Berezowsky, R.M.G.S., "The Commercial Status of Pressure Leaching

Technology," JOM, 43:2, 9-15 (Feb. 1991) (abstract only).

Chmielewski, T., "Pressure Leaching of a Sulphide Copper Concentrate

with Simultaneous Regeneration of the Leaching Agent,"

Hydrometallurgy, 13:1,63-72 (1984) (no month).

Dalton, et aI., "The CUPREX Process-a new chloride-based

hydrometallurgical process for the recovery ofcopper from sulphidic

ores," 11 pages (1987).

Dannenberg, R.O., "Recovery of Cobalt and Copper from Complex

Sulfide Concentrates," Government Report, 20 pages, Report No.

BM RI 9138, U.S. Dept. Of Interior (1987) No Month (Abstract

Only).

Dreisinger, D.E., etal., "The Total Pressure Oxidation ofEI Indio Ore

and Concentrate," Copper 1999, vol. IV: Hydrometallurgy ofCopper,

pp. 181-195 (Oct. 1999).

Duyvesteyn, et aI., "The Escondida Process for Copper Concentrates,"

The Paul E. Queneau International Symposium Extractive

Metallurgy of Copper, Nickel, and Cobalt, vol. 1, Fundamental

Aspects, pp. 881-885 (1998) No month.

Evans, et aI., International Symposium of Hydrometallurgy (Mar. 1,

1973) 2 pages.

Hackl, R.P., "Effect of Sulfur-Dispersing Surfactants on the Oxygen

Pressure Leaching ofChalcopyrite," (paper from Copper 95) vol. III,

559-577, Met. Soc. OfCIM (Nov. 1995).

Hackl, R.P., "Passivation ofChalcopyrite During Oxidative Leaching

in Sulfate Media," Hydrometallurgy 39; pp. 25-48 (1995).

Hirsch, H.E., "Leaching of Metal Sulphides," Patents UK No.

1,598,454,7 pages (Sep. 23, 1981) (Abstract only).

Hoffman, J.E., "The Purification of Copper Refinery Electrolytes,"

JOM, The Society, TMS, Warrendale, PA, US, vol. 56, No.7, Jul.

2004, pp. 30-33.

King, Jim A., Autoclaving of Copper Concentrates (paper from Copper

95), vol. III, Electrorefining and Hydrometallurgy ofCopper, Int'I

Conference held in Santiago, Chile (Nov. 1995) (Abstract only).

King, Jim A., "The Total Pressure Oxidation of Copper Concentrates,"

The Paul E.Q. Int'! Symposium extractive Metallurgy of

Copper, Nickel and Cobalt vol. I, Fundamental Aspects, Minerals,

Metals & Materials Society, pp. 735-757 (Oct. 1993).

Mackiw, VN., Direct Acid Pressure Leaching of Chalcotite Concentrate,

JOM 19:2, (Feb. 1967) (Abstract only).

Opposition to CL 1767-2001 by Anglo American PLC (with accompanying

English translation of substantive assertions) (no date).

Richmond, G.D., The Commissioning and Operation of a Copper

Sulphide Pressure Oxidation Leach Process at Mt. Gordon, Alta

Copper 1999: Copper Sulphides Symposium & Copper Hydrometallurgy

Forum (Gold Coast, Queensland, Australia Conference)

(1999).

Ritcey, G.M., et aI., "Solvent Extraction, Principles and Applications

to Process Metallurgy, Part II", pp. 218-221 (1979).

Szymanowski, 1., "Dydroxyoximes and Copper Hydrometallurgy,"

(CRC Press) 6 pages (no date).

* cited by examiner

u.s. Patent Juo.15,2010 Sheet 1 of 4 US 7,736,488 B2

119

105

126

PRESSURE LEACHING

107

1030

1035

ATMOSPHERIC FLASHING 110

123

109

122

/124

119 ELECTROLYTE RESIDUE

120 TREATMENT TREATMENT

113

1080

ELECTROLYTE 1060

RECYCLE TANK

121 115

119 ( Cu )

TO ADDITIONAL

COPPER RECOVERY

(SEE E.G., FIG. 2)

FIG. 1

u.s. Patent Juo.15,2010 Sheet 2 of 4 US 7,736,488 B2

1010A

1010B

s 1010C

101

11

------------------,I

J

!

I

I

I

I

I

I

I

I

I

I

I

I/1010

I

I

r

I

I

I

I

I

I

I

I

t

I

I

I

I

I

I

I

- J~

CONTROLLED,

FINE GRINDING

SIZE CLASSIFICATION

(OPTIONAL)

r----------- ---------------~

I

t

I

I

I

I

I

I 12

I I

L '

10

'-- --I L

r-------------------

I

I

I

I

I

J

I

I

I

I

I

I

I,

I

: 13

J

I

I

I

I,

I

I

I

I

I

I

I

I

I

I

I

I

I

FIG. 1A

u.s. Patent Juo.15,2010 Sheet 3 of 4 US 7,736,488 B2

ATMOSPHERIC OR

PRESSURE LEACHING

203

/

(FROM FIG. 1)

V 118

V201 1

202

!

/2020

/204

205

SOLVENTfSOLUTION V2010 I

EXTRACTION t---------l----.I

TO

FIG. 1

/208

SOLVENTfSOLUTION

STRIPPING

V 206

/2015

/207

( Cu )

r-------i~-----,v 2030

ELECTROWINNING LEAN

I..--__----,r--__---'t------ ELECTROLYTE

BLEED

FIG. 2

FIG 3

Residue Copper vs. Total Acid Addition

160 deg. C, 90 min, P(98) =15 micron

~

7J).

•

~

~

~

~=~

•

•

• • • •

.-

Total Acid Addition, kg/tonne

2.0

1.8

~ 1.6

:i 1.4

Q.

Co 1.2 o

(,) 1.0

CD

.~- 0.8 ~ 0.6

0: 0.4

0.2

0.0

300 350 400 450 500 550 600

2'

?....

~Ul

No

.... o

rFJ =('

D

(..'D...

,j;o,.

o....

,j;o,.

d

rJl

......:J

~W

0'1

~

QO

QO =N

US 7,736,488 B2

2

BRIEF DESCRIPTION OF THE DRAWING

The subject matter of the present invention is particularly

pointed out and distinctly claimed in the concluding portion

of the specification. A more complete understanding of the

present invention, however, may best be obtained by referring

to the detailed description when considered in connection

with the drawing figures, wherein like numerals denote like

elements and wherein:

FIG. 1 illustrates a flow diagram of a copper recovery

process in accordance with one exemplary embodiment ofthe

present invention;

FIG. lA illustrates a flow diagram ofan aspect ofan exemplary

embodiment of the present invention;

FIG. 2 illustrates a flow diagram of various aspects of a

copper recovery process in accordance with an exemplary

embodiment of the present invention; and,

yield a copper-containing solution; (iv) recovering cathode

copper from the copper-containing solution; (v) treating at

least a portion of a lean electrolyte stream from the copper

recovery step in a solvent/solution extraction and electrowinning

operation; and (vi) recycling at least a portion of the

lean electrolyte stream to the pressure leaching step to provide

some or all of the acid requirement of the pressure

leaching operation.

In accordance with another exemplary embodiment, a pro-

10 cess for recovering copper includes the steps of: (i) providing

a feed stream of copper-containing material; (ii) subjecting

the copper containing feed stream to atmospheric leaching or

pressure leaching to yield a copper-containing solution; (iii)

conditioning the copper-containing solution through one or

15 more chemical or physical conditioning steps; and (iv) electrowinning

copper directly from the copper-containing solution,

without subjecting the copper-containing solution to

solvent extraction. As used herein, the term "pressure leaching"

shall refer to a metal recovery process in which material

20 is contacted with an acidic solution and oxygen under conditions

of elevated temperature and pressure.

In accordance with another aspect of an exemplary

embodiment ofthe invention, a bleed stream oflean electrolyte

from the electrowinning stage advantageously removes

25 at least a portion of the excess acid from the metal recovery

process and also impurities contained therein, thus preventing

such impurities from accumulating to deleterious levels in the

process and negatively impacting production efficiencies and

product (e. g., copper cathode) quality. In accordance with one

30 embodiment ofthe invention, excess acid removed in the lean

electrolyte bleed stream may be utilized in other copper

extraction processes, or the acid may be consumed by using

suitable materials, such as, for example, low grade copper

ore, mining waste products, and/or other rock products con-

35 taining acid neutralizing minerals, such as limestone, dolomite,

feldspar, and the like.

In accordance with another aspect of an exemplary

embodiment of the invention, acid generated in the pressure

leaching and electrowinning steps is recycled to the pressure

40 leaching step and provides acid needed for effective leaching

of copper. In this way, the use of recycled acid-containing

solution, rather than concentrated sulfuric acid, is economically

advantageous.

These and other advantages ofa process according to vari-

45 ous aspects of the present invention will be apparent to those

skilled in the art upon reading and understanding the following

detailed description with reference to the accompanying

figures.

FIELD OF INVENTION

SUMMARY OF THE INVENTION

CROSS-REFERENCE TO RELATED

APPLICATIONS

BACKGROUND OF THE INVENTION

1

PROCESS FOR RECOVERY OF COPPER

FROM COPPER-BEARING MATERIAL

USING PRESSURE LEACHING, DIRECT

ELECTROWINNING AND

SOLVENT/SOLUTION EXTRACTION

The present invention relates generally to a process for

recovering copper and other metal values from a metal-bearing

material using pressure leaching and direct electrowinning.

More particularly, the present invention relates to a

process using fine grinding, pressure leaching, and direct

electrowinning in combination with solvent/solution extraction

to recover metal from the metal-bearing material.

This application is a continuation of and claims priority to

U.S. patent application Ser. No. 11/163,762, filed Oct. 28,

2005, entitled "Process for Recovery of Copper From Copper-

Bearing Material Using Pressure Leaching, Direct Electrowinning

and Solvent/Solution Extraction." The Ser. No.

11/163,762 application is a non-provisional of and claims

priority to U.S. Provisional Patent Application Ser. No.

60/623,453, filed Oct. 29, 2004. All these references are

hereby incorporated by reference in their entirety.

Hydrometallurgical treatment of copper-containing materials,

such as copper ores, copper-bearing concentrates, and

other copper-bearing materials, has been well established for

many years. However, an effective and efficient method to

recover copper from copper-containing materials, especially

copper from copper sulfides such as chalcopyrite and chalcocite,

that enables high copper recovery to be achieved at a

reduced cost over conventional processing techniques would

be advantageous.

In general, according to various aspects of the present

invention, a process for recovering copper and other metal

values from a metal-bearing material includes various physical

conditioning, reaction, and recovery processes. For

example, in accordance with the various embodiments ofthe

present invention, fine grinding ofthe metal-bearing material

prior to reactive processing, such as by medium or high tem- 50

perature (as will be defined hereinbelow) pressure leaching,

results in enhanced metal value recovery and various other

advantages over prior art metal recovery processes. Moreover,

proper conditioning enables direct electrowinning of

copper from a pressure leaching product stream without the 55

use of an intermediate solvent/solution extraction step. Further,

at least a portion ofthe impurities and excess acid in the

process stream are removed through the use ofa lean electrolyte

bleed stream from electrowinning that may be further

processed in a solvent/solution extraction and electrowinning 60

operation.

In accordance with one exemplary embodiment of the

present invention, a process for recovering copper from a

copper-bearing material includes the steps of: (i) providing a

feed stream containing copper-bearing material; (ii) subject- 65

ing the copper-bearing feed stream to controlled fine grinding;

(iii) pressure leaching the copper-bearing feed stream to

US 7,736,488 B2

3

FIG. 3 is a graph plotting copper concentration in the

pressure leaching residue as a function of acid addition in

accordance with various aspects of an exemplary embodiment

of the invention.

DETAILED DESCRIPTION OF EXEMPLARY

EMBODIMENTS

Various embodiments ofthe present invention exhibit significant

advancements over prior art processes, particularly

with regard to copper recovery and process efficiency. In

accordance with an exemplary embodiment of the present

invention, a process for recovering copper from a copperbearing

material includes the steps of: (i) providing a feed

stream containing copper-bearing material; (ii) subjecting at

least a portion ofthe copper-bearing feed stream to controlled

fine grinding; (iii) pressure leaching the copper-bearing feed

stream to yield a copper-containing solution; (iv) recovering

cathode copper from the copper-containing solution by electrowinning;

(v) treating at least a portion ofa lean electrolyte

stream from the copper recovery step by solvent/solution

extraction followed by an electrowinning operation; and (vi)

recycling at least a portion ofthe lean electrolyte stream to the

pressure leaching step.

Various embodiments ofthe present invention exhibit significant

advancements over prior art processes, particularly

with regard to copper recovery and process efficiency. In

accordance with another exemplary embodiment of the

present invention, a process for recovering copper from a

metal-bearing material includes the steps of: (i) providing a

feed stream containing copper-bearing material; (ii) subjecting

at least a portion of the copper-bearing feed stream to

controlled fine grinding; (iii) pressure leaching the copperbearing

feed stream to yield a copper-containing solution; (iv)

recovering cathode copper from the copper-containing solution

by electrowinning; (v) treating at least a portion ofa lean

electrolyte stream from the copper recovery step by solvent/

solution extraction followed by an electrowinning operation;

and (vi) optionally, recycling at least a portion of the lean

electrolyte stream to the pressure leaching step.

In accordance with another exemplary embodiment, a process

for recovering copper includes the steps of: (i) providing

a feed stream of copper-containing material; (ii) subjecting

the copper containing feed stream to atmospheric leaching or

pressure leaching to yield a copper-containing solution; (iii)

conditioning the copper-containing solution through one or

more chemical or physical conditioning steps; and (iv) electrowinning

copper directly from the copper-containing solution,

without subjecting the copper-containing solution to

solvent extraction. As used herein, the term "pressure leaching"

shall refer to a metal recovery process in which material

is contacted with an acidic solution and oxygen under conditions

of elevated temperature and pressure.

Existing copper recovery processes that utilize conventional

atmospheric or pressure leaching, solvent/solution

extraction and electrowinning process steps may, in many

instances, be easily retrofitted to exploit the many commercial

benefits the present invention provides. Medium or high

temperature pressure leaching processes for chalcopyrite are

generally thought ofas those processes operating at temperatures

from about 1200 C. to about 1900 C. or up to 2200 C.

Referring first to FIG. 1, in accordance with various aspects

ofthe present invention, a metal-bearing material 101 is provided

for processing. Metal-bearing material 101 may be an

ore, a concentrate, a precipitate, or any other material from

which copper and/or other metal values may be recovered.

Metal values such as, for example, copper, gold, silver, plati-

4

num group metals, nickel, cobalt, molybdenum, rhenium,

uranium, rare earth metals, and the like, may be recovered

from metal-bearing materials in accordance with various

embodiments of the present invention. The various aspects

and embodiments of the present invention, however, prove

especially advantageous in connection with the recovery of

copper from copper-bearing sulfide ores, such as, for

example, ores and/or concentrates and/or precipitates containing

chalcopyrite (CuFeS2 ), chalcocite (Cu2 S), bornite

10 (CusFeS4 ), covellite (CuS), enargite (Cu3AsS4 ), digenite

(Cu9 SS ) and mixtures thereof. Thus, metal-bearing material

101 preferably is a copper ore, concentrate or precipitate, and,

more preferably, is a copper-bearing sulfide ore, concentrate

or precipitate. In accordance with yet another aspect of the

15 present invention, metal-bearing material 101 may comprise

a concentrate that is not a flotation concentrate or precipitate

thereof. For ease of discussion, the description of various

exemplary embodiments of the present invention hereinbelow

generally focuses on the recovery ofdesired metal values

20 from chalcopyrite-containing ore or concentrate, however,

any suitable metal bearing material may be utilized.

In accordance with an exemplary embodiment of the

present invention, copper is the metal to be recovered from a

metal-bearing material, such as a copper sulfide concentrate.

25 One aspect of this exemplary embodiment involves use of a

copper sulfide concentrate produced by froth flotation. In

preparation for froth flotation, the metal-bearing material

feed stream is ground to a particle size suitable to liberate

mineral-bearing particles from gangue materials. However,

30 as noted above, other concentrates may also be utilized.

Metal-bearing material 101 may be prepared for metal

recovery processing in any manner that enables the conditions

of metal-bearing material 101 to be suitable for the

chosen processing method, as such conditions may affect the

35 overall effectiveness and efficiency ofprocessing operations.

For example, feed stream conditions such as particle size,

composition, and component concentrations can affect the

overall effectiveness and efficiency of downstream processing

operations, such as, for example, atmospheric leaching or

40 pressure leaching. Desired composition and component concentration

parameters can be achieved through a variety of

chemical and/or physical processing stages, the choice of

which will depend upon the operating parameters ofthe chosen

processing scheme, equipment cost and material specifi-

45 cations.

It is generally known that hydrometallurgical processes,

particularly pressure leaching processes, are sensitive to particle

size. Thus, it is common practice in the area ofextractive

hydrometallurgy to finely divide, grind, and/or mill mineral

50 species to reduce particle sizes prior to processing by pressure

leaching. It generally has been appreciated that reducing the

particle size of a mineral species, such as, for example, a

copper sulfide, enables pressure leaching under less extreme

conditions of pressure and temperature to achieve the same

55 metal extraction as achieved under conditions ofhigher temperature

and pressure. The particle size distribution can also

affect other leaching conditions, such as, for example, acid

concentration and oxygen overpressure.

A variety of acceptable techniques and devices for reduc-

60 ing the particle size of the metal-bearing material are currently

available, such as ball mills, tower mills, superfine

grinding mills, attrition mills, stirred mills, horizontal mills

and the like, and additional techniques may later be developed

that may achieve the desired result of increasing the surface

65 area of the material to be processed.

For example, metal-bearing material 101 may be prepared

for metal recovery processing by controlled fine grinding.

US 7,736,488 B2

5 6

tion of approximately 98 percent passing from about 10 to

about 23 microns, and optimally from about 13 to about 15

mIcrons.

While, as noted, grinding step 1010 may be conducted in

any manner, satisfactory controlled fine grinding may be

achieved using a fine grinding apparatus, such as, for

example, a stirred horizontal shaft mill with baffles or a vertically

stirred mill without baffles. Such exemplary apparatus

include the Isamill developed jointly by Mount Isa Mines

10 (MIM), Australia, and Netzsch Feinmahltechnik, Germany

and the SMD or Detritor mill, manufactured by Metso Minerals,

Finland. Preferably, if a horizontal mill is utilized, the

grinding medium would be 1.2/2.4 mm or 2.4/4.8 mm Colorado

sand, available from Oglebay Norton Industrial Sands

15 Inc., Colorado Springs, Colo. However, any grinding medium

that enables the desired particle size distribution to be

achieved may be used, the type and size of which may be

dependent upon the application chosen, the product size

desired, grinding apparatus manufacturer's specifications,

20 and the like. Exemplary media include, for example, sand,

silica, metal beads, ceramic beads, and ceramic balls.

The comminuted metal-bearing material may be combined

with a liquid prior to entering reactive processing stage 1030

(described hereinbelow). Preferably, if employed, the liquid

25 comprises water, but any suitable liquid may be employed,

such as, for example, raffinate, pregnant leach solution, or

lean electrolyte. For example, a portion ofthe lean electrolyte

from the direct electrowinning process (for example, stream

119) may be combined with comminuted metal-bearing

30 material to form metal-bearing material stream 103 for delivery

to reactive processing stage 1030. In this way, acid is

recycled to the process stream such that it helps to satisfy the

acid demand of reactive processing stage 1030.

The combination of a liquid with the metal-bearing mate-

35 rial can be accomplished using anyone or more ofa variety of

techniques and apparatus, such as, for example, in-line blending

or using a mixing tank or other suitable vessel. In accordance

with an exemplary aspect of an embodiment of the

invention, the concentration of solid metal-bearing material

40 in the material stream (i.e., the slurry density) is on the order

ofless than about fifty (50) percent by weight of the stream,

and preferably about forty (40) percent by weight of the

stream. Other slurry densities that are suitable for transport

and subsequent processing may, however, be used.

In accordance with one aspect ofthe present invention, it is

desirable to separate the copper in a recycled stream of lean

electrolyte from electrowinning from the acid, and also to

reduce the amount of contaminants in the portion of the

stream to be subjected to the metal recovery process. In such

50 a separation process, the acid that is removed from the

recycled lean electrolyte stream may be rejected from the

process circuit, taking with it at least a portion of the metal

contaminants and other soluble impurities from the coppercontaining

feed stream and the recycled lean electrolyte

55 stream. Any number of conventional or hereafter devised

separation processes and techniques may be useful to achieve

the separation of copper from acid in the feed stream. For

example, separation processes and/or techniques such as precipitation,

low temperature pressure leaching, acid solvent

60 extraction/ion exchange, membrane separation, cementation,

pressure reduction, sulfiding, and/or the use of liberator cells

may be useful for this purpose.

The separation aspect of a preferred embodiment of the

invention contributes to providing a resultant acid stream that

65 contains a relatively small fraction of copper, which can be

used for leaching, pH control, or other applications. Moreover,

utilization of a separation process in accordance with

Preferably, it is advantageous not only to reduce the size ofthe

metal-bearing material particles in the process stream, but

also to ensure that the weight proportion of the coarsest particles

is minimized. Significant advantages in processing efficiency

and copper recovery are achievable by enabling substantially

all particles to react substantially completely.

In accordance with one embodiment of the present invention,

and with reference to FIG. 1 and FIG. lA, while controlled

fine grinding may utilize any now known or hereafter

devised methodology, in general, grinding step 1010 includes

controlled, fine grinding step 1010A, optional size classification

step 1010B and solid liquid separation step 1010C. Preferably,

grinding in accordance with this aspect of the present

invention proceeds in a staged or closed-circuit manner. That

is, preferably the coarsest particles ofmetal-bearing material

101 are suitably ground to the desired level, while particles

already at or below the desired level are subjected to little or

no additional grinding. As such, cost savings can be obtained

in connection with grinding operations, while at the same

time limiting the size and weight proportion of the coarsest

particles. However, open-circuit grinding may also produce

an acceptable product.

With continued reference to FIG. lA, preferably cyclone

technology, such as, for example, use of cyclones, or minicyclones,

is utilized to facilitate size classification step 1010B

by separating relatively coarse materials from relatively fine

materials. That is, after material 101 is ground in controlled

fine grinding step 1010A, the coarse material 10 is suitably

separated from the fine material 12, such that coarse material

10 may be further ground, as shown in FIG. 1A in stream 11.

Similarly, in accordance with one aspect of an exemplary

embodiment of the invention wherein the chosen grinding

method and apparatus utilize a liquid processing agent (such

as, for example, process water) to facilitate grinding in superfine

grinding stage 1010, an optional solid-liquid separation

stage 1010C may be utilized to remove excess processing

liquid 13 from the process stream 102 prior to pressure leaching,

and preferably recycle excess process liquid 13 to superfine

grinding stage 1010A for reuse. Depending upon the

configuration of the grinding apparatus, solid-liquid separation

stage 1010C mayor may not be required. If, however,

process liquid is added to copper-containing material 101

prior to or during super-fine grinding 1010, it may be desirable

to remove at least a portion of the added process liquid

from copper-containing material stream 102 prior to pressure 45

leaching operation 1030 to optimize slurry density.

Grinding step 1010 preferably results in material 110 being

finely ground, such that the particle size ofthe material being

processed is reduced such that substantially all ofthe particles

are small enough to react substantially completely during

pressure leaching.

Various particle sizes and particle size distributions may be

advantageously employed in accordance with various aspects

ofthe present invention. For example, in accordance with one

aspect of the present invention grinding step 1010 results in

material 110 being finely ground to a P80 on the order ofless

than about 25 microns, and preferably on the order of a P80

between about 13 and about 20 microns.

In accordance with another aspect ofthe present invention,

the copper-containing material has a P80 of less than about

250 microns, preferably a P80 from about 75 to about 150

microns, and more preferably a P80 on the order of from

about 5 to about 75 microns.

In accordance with yet another aspect ofthe present invention,

a particle size distribution of approximately 98 percent

passing about 25 microns is preferable, and more preferably,

the metal-bearing material stream has a particle size distribuUS

7,736,488 B2

7 8

(2)

(1)

4CuFeS2+1702+4H20~2Fe203+4Cu2++8H++

8soi-

Preferably, in accordance with the present invention, the

conditions (temperature, acid concentration) for the pressure

leaching step are suitably selected to achieve an advantageous

balance between reactions (1) and (2), but tending to reduce

or eliminate fresh make-up acid consumption and thus the

costs associated with acid make-up, but without sacrificing

copper extraction to any significant extent.

The amount of acid introduced into the pressure leaching

vessel varies depending upon the reaction parameters, particularly,

reaction temperature, iron dissolution, copper

extraction, and sulfide oxidation. Make-up acid may be introduced

into the pressure leaching vessel in the form of fresh

acid or recycled acid from the same recovery process or

another process. In certain cases, make-up acid is introduced

on the order of from about 300 to about 650 kilograms per

tonne ofconcentrate, or less; however, lower make-up acid is

required at higher temperatures.

The present inventors have discovered that operating

parameters ofthe metal recovery process ofthe present invention

may be optimized to achieve any number of economic,

processability, or production objectives. Generally speaking,

for example, at a fixed acid recycle rate, as the temperature in

the pressure leaching stage is increased, more oxygen is consumed,

more acid is produced, and less elemental sulfur is

produced. Iron dissolution can be controlled at higher temperatures

by reducing recycled acid from stream 119. Moreover,

keeping all other parameters constant, as the temperature

in the pressure leaching stage is increased, copper

recovery may be maximized. Thus, at increased temperatures

and a fixed acid recycle rate, more acid may be produced

during pressure leaching (i.e., excess acid that must be consumed)

and more oxygen may be consumed, but higher copper

recovery may be possible. At lower temperatures (e.g.,

140-150° C.), the pressure leaching operation may require

more recycled acid and copper recovery may be reduced, but

less oxygen is demanded and the cost of consuming excess

65 acid is reduced. Within a temperature range of from about

150° C. to about 170° c., however, an acid autogenous process

may be possible-that is, the pressure leaching operation

fine grinding, liquid addition, and, optionally, other physical

and/or chemical conditioning processes, it is subjected to a

reactive processing step 1030, for example, metal extraction

via pressure leaching. In accordance with one embodiment of

the present invention, reactive processing step 1030 comprises

pressure leaching. Preferably, reactive processing step

1030 is a medium temperature pressure leaching process

operating at a temperature in the range of about 140° C. to

about 230° C. In accordance with one embodiment, pressure

10 leaching preferably is conducted in the range ofabout 140° C.

to about 180° c., and generally, above about 160° C., and

more preferably in the range ofabout 160° C. to about 170° C.

In accordance with another embodiment, pressure leaching is

conducted at temperatures above 180° c., and preferably in

15 the range ofabout 180° to about 220° c., and more preferably

in the range of about 190° C. to about 210° C.

In accordance with various aspects of the present invention,

the optimum temperature range selected for operation

will tend to maximize the extraction of copper and other

20 metals, optimize production of elemental sulfur (SO), minimize

fresh acid consumption, and thereby minimize make-up

acid requirements. Acid and sulfur are made from oxidation

of sulfide according to the following reactions:

this aspect ofthe invention may be particularly advantageous

in that it may enable contaminants from the unrefined coppercontaining

material stream to be removed from the coppercontaining

material stream and incorporated into the resultant

acid stream. Because the resultant acid stream is preferably

removed from the metal recovery process altogether and utilized

in remote operations, disposed of, or neutralized, the

contaminants contained therein are likewise removed from

the metal recovery process and are thus prevented from accumulating

in the process stream. This may be a significant

advantage in that such contaminants, particularly metal contaminants,

typically have a deleterious effect on the effectiveness

and efficiency ofthe desired metal recovery process. For

example, metal contaminants and other impurities in the process

stream, ifnot carefully controlled and/or minimized, can

contribute to diminished physical and/or chemical properties

in the cathode copper produced by electrowinning, and can

thus degrade the copper product and diminish its economic

value.

Referring again to FIG. 1, in accordance with one aspect of

a preferred embodiment of the invention, copper-containing

material stream 101 is subjected to a separation, such as, for

example, a precipitation step, which, in this exemplary process,

serves to precipitate solubilized copper from a recycled

lean electrolyte stream onto the surfaces of solid particles in 25

the copper-containing material stream. As discussed in detail

above, this aspect offers an important advantage in that it

enables recovery ofcopper from a lean electrolyte stream that

otherwise may have been lost or would have required additional

processing to recover, potentially resulting in signifi- 30

cant economic benefits.

In this preferred aspect of the invention, the precipitation

step involves the copper-containing material stream being

combined with a sulfur dioxide (S02) stream 109 and a lean

electrolyte stream 108 in a suitable processing vessel. For 35

example, in the embodiment illustrated in FIG. 1, lean electrolyte

stream 108 may comprise a recycled acidic copper

sulfate stream generated during an electrowinning operation.

Other streams, however, preferably copper-rich streams, may

also be used. Preferably, precipitation is carried out such that 40

the copper from the lean electrolyte precipitates, at least in

part, onto the surface ofunreacted copper-containing material

particles within stream 101 in the form of copper sulfides,

such as, for example, CuS.

In accordance with a preferred aspect of the invention, 45

copper separation stage 1010 is carried out at a slightly

elevated temperature, such as from about 70° C. to about 180°

c., preferably from about 80° C. to about 100° c., and most

preferably at a temperature of about 90° C. Heating, if necessary,

can be effectuated through any conventional means, 50

such as electric heating coils, a heat blanket, process fluid heat

exchange, and other ways now known or later developed. In

an exemplary process, steam may be generated in other process

areas, and may be directed to the processing vessel in

copper separation stage 1010 to provide the heat desired to 55

enhance the precipitation process. The residence time for the

copper precipitation process can vary, depending on factors

such as the operating temperature ofthe processing vessel and

the composition of the copper-containing material, but typically

ranges from about thirty (30) minutes to about 6 hours. 60

Preferably, conditions are selected such that significant

amounts of copper are precipitated. For example, precipitation

rates on the order of about 98% precipitation of copper

have been achieved in processing vessels maintained at about

90° C. for about 4 hours.

Referring to FIG. 1, after metal-bearing material stream

103 has been suitably prepared for processing by controlled

9

US 7,736,488 B2

10

(aq) 25

may produce approximately the acid that it requires. As such,

it may be possible to reduce or eliminate the costs ofmake-up

acid and acid attenuation while achieving acceptable copper

recovery and moderate oxygen consumption. However, in

accordance with other embodiments ofthe present invention

higher temperatures may be utilized. For example, on the

order of about 2000 C. to about 2100 C. may tend to enhance

copper recovery.

It should be noted that any of the above scenarios may be

desirable under certain circumstances. That is, extrinsic factors-

such as power and raw material costs or the market

price of copper and/or other recoverable metal values-may

dictate whether it would be most economically desirable to

operate the pressure leaching operation at lower temperatures

(e.g., if cost of acid attenuation is higher than acid purchase,

if oxygen is expensive, if power costs are high, and/or if

copper price is low), or higher temperatures (e.g., if cost of

acid attenuation is lower than acid purchase, if acid can be

used beneficially elsewhere, if oxygen is inexpensive, if

power costs are low, and/or if copper price is high).

At medium temperature conditions (i.e., between about

1400 C. and about 1800 C.), ferric ion in solution will hydrolyze

in the pressure leaching vessel to form hematite and

sulfuric acid by the following reaction:

Fe2(S04h(aq)+3H20(1)~Fe203(S)+3H2S04

As the iron concentration in the pressure leaching vessel

increases, the iron concentration in the rich electrolyte stream

(i.e., the pressure leaching discharge liquor) also increases.

Increasing iron in the pressure leaching discharge generally

results in an undesirable drop in the current efficiency in

subsequent electrowinning operations. Decreased current

efficiency in electrowinning results in increased operating

costs per unit of copper recovered through electrowinning.

The total acid addition (free acid in solution plus ironequivalent

acid content of solution) to the pressure leaching

step is preferably controlled to optimize the copper extraction

(as indicated by the copper in the residue) and iron in the rich

electrolyte for direct electrowinning. In general, the residue

copper content decreases with increasing total acid addition

to the pressure leaching step, while the amount of iron in

solution tends to increase with increasing total acid addition.

In accordance with an exemplary embodiment ofthe invention,

a process for recovering copper from copper-bearing

material is operated such that the highest total acid addition to

the pressure leaching vessel is utilized above which there is

little or no additional benefit to the residue copper content. In

accordance with one embodiment of the invention, the total

acid addition to the pressure leaching vessel is in the range of

from about 400 to about 500 kg/tonne.

Turning again to FIG. 1, reactive processing step 1030 may

occur in any pressure leaching vessel suitably designed to

contain the pressure leaching mixture at the desired temperature

and pressure conditions for the requisite pressure leaching

residence time. In accordance with one aspect ofan exemplary

embodiment of the invention, the pressure leaching

vessel used in processing step 1030 is an agitated, multicompartment

horizontal pressure leaching vessel. However, it

should be appreciated that any pressure leaching vessel that

suitably permits metal-bearing material stream 103 to be

prepared for copper recovery may be utilized within the scope

of the present invention.

During reactive processing step 1030, copper and/or other

metal values may be solubilized or otherwise liberated in

preparation for later recovery processes. Any substance that

assists in solubilizing-and thus liberating-the metal value,

and thus releasing the metal value from a metal-bearing material,

may be used. For example, where copper is the metal

being recovered, an acid, such as sulfuric acid, may be contacted

with the copper-bearing material such that the copper

may be liberated for later recovery steps. However, it should

be appreciated that any suitable method of liberating metal

values in preparation for later metal recovery steps may be

utilized within the scope of this invention.

Any agent capable of assisting in the solubilization of the

copper, such as, for example, sulfuric acid, may be provided

10 during the reactive processing step 1030, such as, for

example, medium temperature pressure leaching, in a number

ofways. For example, such acid may be provided in a cooling

stream provided by the recycle of lean electrolyte 119 from

electrowinning stage 1070. However, it should be appreciated

15 that any method of providing for the solubilization ofcopper

is within the scope of the present invention. The amount of

acid added during pressure leaching preferably is balanced

according to the acid needed to optimize copper extraction

and, if desired, to achieve a substantially acid autogenous

20 process.

In accordance with various aspects of the present invention,

the pressure leaching process occurs in a marmer suitably

designed to promote substantially complete solubilization

ofthe copper, it may be desirable to introduce additional

materials to enhance the pressure leaching process. In accordance

with one aspect of the present invention, during pressure

leaching in a pressure leaching vessel, sufficient oxygen

105 is injected into the vessel to maintain an oxygen partial

pressure from about 50 to about 250 psig, preferably from

30 about 75 to about 220 psig, and most preferably from about

ISO to about 200 psig. Furthermore, due to the nature of

medium temperature pressure leaching, the total operating

pressure (including oxygen partial pressure) in the pressure

leaching vessel is generally superatmospheric, preferably

35 from about 100 to about 750 psig, more preferably from about

250 to about 400 psig, and most preferably from about 270 to

about 350 psig.

The residence time for pressure leaching can vary, depending

on factors such as, for example, the characteristics of the

40 copper-bearing material and the operating pressure and temperature

of the pressure leaching vessel. In one aspect of an

exemplary embodiment of the invention, the residence time

for the medium temperature pressure leaching ofchalcopyrite

ranges from about 30 to about 180 minutes, more preferably

45 from about 60 to about ISO minutes, and most preferably on

the order of about 80 to about 120 minutes.

Control ofthe pressure leaching process, including control

of the temperature in the pressure leaching vessel, may be

accomplished by any conventional or hereafter devised

50 method. For example, with respect to temperature control,

preferably the pressure leaching vessel includes a feedback

temperature control feature. For example, in accordance with

one aspect of the invention, the temperature of the pressure

leaching vessel is maintained at a temperature in the range of

55 about 1400 C. to about 1800 C. and more preferably in the

range of about 1500 C. to about 1750 C. In accordance with

another aspect of the invention, the temperature may be suitably

selected to be above about 1800 c., and more preferably

in the range ofabout 1800 C. to about 2200 C. As such, a wide

60 range of temperatures may be useful in connection with the

various aspects ofthe present invention.

Due to the exothermic nature ofpressure leaching ofmetal

sulfides, the heat generated by medium temperature pressure

leaching is generally more than that needed to heat the feed

65 stream to the desired operating temperature. Thus, in order to

maintain preferable pressure leaching temperature, a cooling

liquid 106 may be introduced into the pressure leaching vesUS

7,736,488 B2

11 12

desired metal values, rendering the desired metal values (e.g.,

copper and gold) generally nnavailable or less accessible to a

lixiviant solution.

One source ofsuitable seeding agents useful in accordance

with an aspect ofthis exemplary embodiment are those materials

which can be found in the pressure leaching vessel

discharge, which materials may be recycled for seeding purposes.

Use ofthe recycled pressure leaching vessel discharge

may be desirable for economic reasons, and using a seeding

10 agent that is similar or identical to nnwanted particles in the

pressure leaching process slurry may tend to encourage the

accumulation of unwanted material. For example, in metal

recovery processes where an unwanted material, such as

hematite, is either present in the metal-bearing material or is

15 produced as a by-product, introduction ofrecycled hematitecontaining

residue from previous pressure leaching processes

likely will tend to provide newly formed or liberated hematite

a preferential nucleation site. In the absence ofthis nucleation

site, unreactive particles may occlude the desired metal val-

20 ues to solubilization by precipitating on the surface of the

metal values, rendering the metal values unrecoverable.

Therefore, introducing a seeding agent to prevent such occlusion

may assist in providing better metal recovery. In accordance

with the exemplary embodiment illustrated in FIG. 1, a

25 portion of the solid residue stream 110 from solid-liquid

separation step 1040 provides a suitable seeding material to

reactive processing step 1030.

Subsequent to metal-bearing material stream 103 undergoing

reactive processing step 1030, the copper and/or other

30 metal values that have been made available by the reactive

process nndergo one or more of various metal recovery processes.

Referring again to FIG. 1, metal recovery process

1070 (discussed hereinbelow) is a process for recovering

copper and/or other metal values, and may include any num-

35 ber of preparatory or conditioning steps. For example, a copper-

bearing solution may be prepared and conditioned for

metal recovery through one or more chemical and/or physical

processing steps. The product stream from reactive processing

step 1030 may be conditioned to adjust the composition,

40 component concentrations, solids content, volume, temperature,

pressure, and/or other physical and/or chemical parameters

to desired values and thus to form a suitable copperbearing

solution. Generally, a properly conditioned copperbearing

solution will contain a relatively high concentration

45 ofsoluble copper in, for example, an acid sulfate solution, and

preferably will contain few impurities. In accordance with

one aspect of an exemplary embodiment of the invention,

however, impurities in the conditioned copper-bearing solution

ultimately may be decreased through the use ofa separate

50 solvent/solution extraction stage and discussed in connection

with the embodiment illustrated in FIG. 2. Moreover, the

conditions ofthe copper-bearing solution preferably are kept

substantially constant to enhance the quality and uniformity

ofthe copper product ultimately recovered.

In one aspect of an exemplary embodiment of the present

invention, conditioning of a metal-bearing solution for copper

recovery in an electrowinning circuit begins by adjusting

certain physical parameters of the product slurry from the

reactive processing step. In an exemplary aspect of this

60 embodiment of the invention, it may be desirable to reduce

the temperature and pressure ofthe product slurry to approximately

ambient conditions. An exemplary method of so

adjusting the temperature and pressure characteristics of the

metal-bearing product slurry from a medium temperature

65 pressure leaching stage is atmospheric flashing (such as

atmospheric flashing stage 1035 shown in FIG. 1). Further,

flashed gases, solids, solutions, and steam may optionally be

sel during pressure leaching. In accordance with one aspect of

an embodiment ofthe present invention, cooling liquid 106 is

preferably contacted with the feed stream in the pressure

leaching vessel during pressure leaching. Cooling liquid 106

may comprise make-up water, but can be any suitable cooling

fluid from within the process or from an outside source, such

as recycled liquid from the product slurry, lean electrolyte, or

a mixture of cooling fluids. Cooling liquid 106 may be introduced

into the pressure leaching vessel through the same inlet

as feed slurry, or alternatively in any manner that effectuates

cooling of the feed slurry. The amount of cooling liquid 106

added to the feed slurry during pressure leaching may vary,

depending on the copper and acid concentration ofthe liquid,

the amount of sulfide minerals in the feed slurry and the pulp

density of the feed slurry, as well as other parameters of the

pressure leaching process. In an exemplary aspect of this

embodiment of the invention, a sufficient amount of cooling

liquid is added to the pressure leaching vessel to yield a solids

content in product stream 108 on the order ofless than about

50% solids by weight, more preferably ranging from about 3

to about 35% solids by weight, and most preferably ranging

from about 6 to about 15% solids by weight. In accordance

with one embodiment of the invention, the cooling liquid is

added as lean electrolyte, which effectively controls the acid,

iron and copper concentrations in the discharge slurry.

In accordance with an exemplary aspect of the present

invention, pressure leaching ofstream 103 is performed in the

presence ofa dispersing agent 126. Suitable dispersing agents

useful in accordance with this aspect ofthe present invention

include, for example, organic compounds such as lignin

derivatives, such as, for example, calcium and sodium lignosulfonates,

tannin compounds, such as, for example, quebracho,

orthophenylene diamine (OPD), alkyl sulfonates, such

as, for example, sodium alkylbenzene sulfonates, and combinations

of the above. Dispersing agent 126 may be any

compound that resists degradation in the temperature range of

medium temperature pressure leaching (i.e., from about 1400

C. to about 1800 C.) long enough to disperse the elemental

sulfur produced during the medium temperature pressure

leaching process and that achieves the desired result of preventing

elemental sulfur from passivating copper values,

which may reduce copper extraction. Dispersing agent 126

may be introduced to the pressure leaching vessel in an

amonnt and/or at a concentration sufficient to achieve the

desired result. In one aspect of an exemplary embodiment of

the invention, favorable results are achievable during pressure

leaching of chalcopyrite using calcium lignosulfonate in an

amonnt ofabout 2 to about 20 kilograms per tonne, and more

preferably in an amonnt ofabout 4 to about 12 kilograms per

tonne; and more preferably in an amonnt of about 6 to about

10 kilograms per tonne of chalcopyrite concentrate.

In accordance with another exemplary embodiment of the

present invention, a seeding agent may be introduced into

reactive processing step 1030. A suitable seeding agent may 55

comprise any material capable offorming a nucleation site for

the crystallization and/or growth of solid species. Accordingly,

the seeding agent may be any particle which acts as a

site for particle accumulation and/or precipitation, and may

originate from recycled materials from other stages of the

metal recovery process or may be provided by the addition of

substances that are foreign to the metal recovery process. In

some cases, the seeding agent comprises any material that

promotes crystallization, precipitation, and/or growth of

unwanted materials-for example in the preferred case of

copper recovery, hematite, gangue, and the like-that may

otherwise tend to partially or completely encapsulate the

13

US 7,736,488 B2

14

suitably treated, for example, by use of a venturi scrubber

wherein water may be recovered and hazardous materials

may be prevented from entering the environment.

In accordance with further aspects of this preferred

embodiment, after the product slurry has been subjected to

atmospheric flashing using, for example, a flash tank, to

achieve approximately ambient conditions of pressure and

temperature, the product slurry may be further conditioned in

preparation for later metal-value recovery steps. For example,

one or more solid-liquid phase separation stages (such as

solid-liquid separation stage 1040 illustrated in FIG. 1) may

be used to separate solubilized metal solution from solid

particles. This may be accomplished in any conventional

manner, including use of filtration systems, counter-current

decantation (CCD) circuits, thickeners, and the like. As illustrated

in FIG. 1, in accordance with one embodiment of the

invention, conditioning ofthe product slurry for metal recovery

comprises a solid-liquid separation step 1040 and an

optional electrolyte treatment step 1050, which further conditions

product liquid 111 such as, for example, through

filtration, to remove fine solid particles and colloidal matter,

such as, for example, silica and/or silica-bearing material. A

variety of factors, such as the process material balance, environmental

regulations, residue composition, economic considerations,

and the like, may affect the decision whether to

employ a CCD circuit, one thickener or multiple thickeners,

one filter or multiple filters, and/or any other suitable device

or combination of devices in a solid-liquid separation apparatus.

However, it should be appreciated that any technique of

conditioning the product slurry for later metal value recovery

is within the scope of the present invention.

As further discussed hereinbelow, the separated solids may

further be subjected to later processing steps, including precious

metal or other metal value recovery, such as, for

example, recovery of gold, silver, platinum group metals,

molybdenum, zinc, nickel, cobalt, uranium, rhenium, rare

earth metals, and the like, by cyanidation or other techniques.

Later processing steps may also include treatment processes

to remove or recover other mineral constituents from the

separated solids. Alternatively, the separated solids may be

subject to impoundment or disposal, or, as noted hereinabove,

a portion of the separated solids may be introduced into the

reactive processing stage as a seeding agent.

Thus, in accordance with an exemplary aspect of the

embodiment illustrated in FIG. 1, product slurry 107 from

reactive processing step 1030 is subjected to atmospheric

flashing 1035 in one or more atmospheric flash tanks or any

other suitable atmospheric system to release pressure and to

evaporatively cool the product slurry 107 through the release

of steam to form a flashed product slurry 108. The flashed

product slurry preferably has a temperature ranging from

about 90° C. to about 101 ° c., a copper concentration offrom

about 40 to about 120 grams/liter, and an acid concentration

of from about 16 to about 50 grams/liter. In accordance with

an aspect of an exemplary embodiment of the invention, a

portion of flashed product slurry 108 (stream 123 in FIG. 1),

is recycled to pressure leaching stage 1030.

Flashed product slurry 108 also may contain a particulate

solid residue containing, for example, the iron oxide byproduct

of pressure leaching, elemental sulfur and other byproducts,

precious metals and other components that are

undesirable for a feed stream to an electrowinning circuit.

Thus, in accordance with the same principles discussed

above, it may be desirable to subject the flashed product slurry

to a solid-liquid separation process, such that the liquid portion

of the slurry-the desired copper-containing solutionis

separated from the solid portion of the slurry-the undesired

residue.

Referring still to FIG. 1, in the illustrated embodiment of

the invention, flashed product slurry 108 is directed to a

solid-liquid separation stage 1040, such as a CCD circuit. In

an alternative embodiment ofthe invention, solid-liquid separation

stage 1040 may comprise, for example, a thickener or

one or more filters. In one aspect of an exemplary embodi-

10 ment ofthe invention, a CCD circuit uses conventional countercurrent

washing ofthe residue stream with wash water 109

to recover leached copper to the copper-containing solution

product and to minimize the amount of soluble copper

advancing to either precious metal recovery processes or

15 residue disposal. Preferably, large wash ratios and/or several

CCD stages are utilized to enhance the effectiveness of solidliquid

separation stage 1040-that is, relatively large

amounts of wash water 109 are added to the residue in the

CCD circuit and/or several CCD stages are used. Preferably,

20 the solution portion ofthe residue slurry stream is diluted by

wash water 109 in the CCD circuit to a copper concentration

of from about 5 to about 200 parts per million (ppm) in the

solution portion of residue stream 110. In accordance with

another aspect ofan exemplary embodiment ofthe invention,

25 addition ofa chemical reagent to liquid/solid separation stage

1040 may be desirable to remove deleterious constituents

from the process stream. For example, a polyethylene oxide

may be added to effectuate removal of silica by precipitation,

or other flocculants and/or coagulants might be utilized to

30 remove other undesirable species from the process stream.

One such suitable chemical reagent is POLYOXTMWSR-301,

available from Dow Chemical.

Depending on its composition, residue stream 110 from

liquid/solid separation stage 1040 may be neutralized,

35 impounded, disposed of, or subjected to further processing,

such as, for example, precious metal recovery, treatment to

recover other metal values, treatment to attenuate or remediate

metals ofconcern, or other treatment to recover or remove

other mineral constituents from the stream. For example, if

40 residue stream 110 contains economically significant

amounts of gold, silver, and/or other precious metals, it may

be desirable to recover this gold fraction through a cyanidation

process or other suitable recovery process. If gold or

other precious metals are to be recovered from residue stream

45 110 by cyanidation techniques, the content ofcontaminants in

the stream, such as elemental sulfur, amorphous iron precipitates,

unreacted copper minerals and dissolved copper, is

preferably minimized. Such materials may promote high

reagent consumption in the cyanidation process and thus

50 increase the expense of the precious metal recovery operation.

As mentioned above, it is therefore preferable to use a

large amount ofwash water or other diluent or several stages

during the solid-liquid separation process to maintain low

copper and acid levels in the solids-containing residue stream

55 in an attempt to optimize the conditions for subsequent precious

metal recovery.

Optionally, as illustrated in FIG. 1 as an aspect of one

exemplary embodiment of the invention, one or more additional

electrolyte treatment stages 1050 may be utilized to

60 further condition and/or refine process stream 111 from solidliquid

separation stage 1040, such as, for example, through

filtration, thickening, counter-current decantation, or the like.

Moreover, a portion of process stream 111 (stream 122 in

FIG. 1) may be recycled to pressure leaching stage 1030,

65 either directly or through combination with lean electrolyte

recycle stream 119 (as shown) and/or other suitable process

streams entering the pressure leaching operation. In accorUS

7,736,488 B2

15 16

60

with the above-referenced reactions or otherwise, is within

the scope of the present invention.

In accordance with a preferred aspect of the invention,

electrowinning circuit 1070 yields a cathode copper product

116, optionally, an offgas stream (not shown), and a relatively

large volume of copper-containing acid solution, herein designated

as lean electrolyte stream 117. As discussed above, in

the illustrated embodiment ofthe invention, a portion oflean

electrolyte stream 117 (lean electrolyte recycle stream 119 in

10 FIG. 1) is preferably recycled to pressure leaching stage 1030

and/or to electrolyte recycle tank 1060. Optionally, a portion

ofcopper-containing solution stream 113 (stream 120 in FIG.

1) from electrolyte treatment stage 1050 is combined with

lean electrolyte recycle stream 119 and is recycled to pressure

leaching stage 1030. Moreover, in accordance with one

aspect of an exemplary embodiment of the invention, a portion

of lean electrolyte stream 117 (lean electrolyte bleed

stream 118 in FIG. 1) is removed from process 100 for the

removal of impurities and acid and/or residual copper recovery

operations, such as, for example, those illustrated in FIG.

2.

Preferably, lean electrolyte recycle stream 119 comprises

at least about 50 percent by weight oflean electrolyte stream

117, more preferably from about 60 to about 95 percent by

weight of lean electrolyte stream 117, and more preferably

from about 80 to about 90 percent by weight of lean electrolyte

stream 117. Preferably, lean electrolyte bleed stream 118

comprises less than about 50 percent by weight oflean electrolyte

stream 118, more preferably from about 5 to about 40

percent by weight of lean electrolyte stream 117, and more

preferably from about 10 to about 20 percent by weight of

lean electrolyte stream 117.

Copper values from the metal-bearing product stream 115

are removed during electrowinning step 1070 to yield a pure,

cathode copper product. It should be appreciated that in

accordance with the various aspects of the invention, a process

wherein, upon proper conditioning ofthe metal-bearing

solution, a high quality, uniformly-plated cathode copper

product may be realized without subjecting the metal-bearing

solution to solvent/solution extraction prior to entering the

electrowinning circuit is within the scope of the present

invention. As previously noted, careful control of the conditions

of the metal-bearing solution entering an electrowinning

circuit-specially maintenance of a substantially constant

copper composition in the stream-an enhance the

quality of the electrowon copper by, among other things,

enabling even plating ofcopper on the cathode and avoidance

ofsurface porosity in the cathode copper, which degrades the

copper product and thus may diminish its economic value. In

accordance with this aspect of the invention, such process

control can be accomplished using any of a variety of techniques

and equipment configurations, so long as the chosen

system and/or method maintains a sufficiently constant feed

stream to the electrowinning circuit. As those skilled in the art

55 are aware, a variety ofmethods and apparatus are available for

the electrowinning of copper and other metal values, any of

which may be suitable for use in accordance with the present

invention, provided the requisite process parameters for the

chosen method or apparatus are satisfied.

In accordance with an exemplary embodiment ofthe invention

illustrated in FIG. 2, lean electrolyte bleed stream 118

from electrowinning unit 1070 (FIG. 1) is sent to a solvent/

solution extraction stage 2010. In accordance with one

embodiment of the invention, solvent/solution extraction

65 stage 2010 is configured to treat materials from atmospheric

and/or pressure leach operations 2020 as well as lean electrolyte

bleed stream 118. Leach operation 2020 may utilize any

Cathode half-reaction: Cu2

++2e---""CUO

Turning again to FIG. 1, in a preferred embodiment of the

invention, product stream 115 is directed from electrolyte

recycle tank 1060 to an electrowinning circuit 1070, which

contains one or more conventional electrowinning cells. It

should be understood, however, that any method and/or apparatus

currently known or hereinafter devised suitable for the

electrowinning of copper from acid solution, in accordance

dance with an exemplary embodiment, residue stream 114

from electrolyte treatment stage 1050 is subjected to further

treatment 1080, wherein, depending on the conditions of

residue stream 114, all or a portion of the stream may be

neutralized, impounded, disposed of, or subjected to further

processing as described above. Copper-containing solution

stream 113 from electrolyte treatment stage 1050 is then

preferably subjected to copper recovery; however, a portion

ofcopper-containing solution stream 113 (stream 120 in FIG.

1) may be recycled to pressure leaching stage 1030.

Referring again to FIG. 1, in accordance with one aspect of

an embodiment of the invention, copper-containing solution

stream 113 from electrolyte treatment stage 1050 is sent to an

electrolyte recycle tank 1060. Electrolyte recycle tank 1060

suitably facilitates process control for electrowiuning circuit 15

1070, as will be discussed in greater detail below. Coppercontaining

solution stream 113, is preferably blended with a

lean electrolyte stream 121 in electrolyte recycle tank 1060 at

a ratio suitable to yield a product stream 115, the conditions of

which may be chosen to optimize the resultant product of 20

electrowinning circuit 1070.

With continued reference to FIG. 1, copper from the product

stream 115 is suitably electrowon to yield a pure, cathode

copper product (stream 116). In accordance with the various

aspects ofthe invention, a process is provided wherein, upon 25

proper conditioning of a copper-containing solution, a high

quality, uniformly-plated cathode copper product 116 may be

realized without subjecting the copper-containing solution to

a solvent/solution extraction process prior to entering the

electrowinning circuit. 30

As those skilled in the art are aware, a variety of methods

and apparatus are available for the electrowinning of copper

and other metal values, any ofwhich may be suitable for use

in accordance with the present invention, provided the requi- 35

site process parameters for the chosen method or apparatus

are satisfied. For the sake of convenience and a broad understanding

of the present invention, an electrowinning circuit

useful in connection with various embodiments ofthe invention

may comprise an electrowinning circuit, constructed and 40

configured to operate in a conventional marmer. The electrowinning

circuit may include electrowinning cells constructed

as elongated rectangular tanks containing suspended

parallel flat cathodes ofcopper alternating with flat anodes of

lead alloy, arranged perpendicular to the long axis ofthe tank. 45

A copper-bearing leach solution may be provided to the tank,

for example at one end, to flow perpendicular (referring to the

overall flow pattern) to the plane of the parallel anodes and

cathodes, and copper can be deposited at the cathode and

water electrolyzed to form oxygen and protons at the anode 50

with the application of current. Other electrolyte distribution

and flow profiles may be used.

The primary electrochemical reactions for electrowinning

of copper from acid solution is believed to be as follows:

US 7,736,488 B2

17 18

31.6

30.5

34.2

15

1.5

35.9

102

4.6

11.6

160

90

450

10

200

290

10.3

20

7.4

Chalcopyrite

TABLE I

Example I

Cu

Fe

S

Grind Size. P9S,)llll

PRESSURE LEACHING

FEED

Copper was recovered from chalcopyrite-containing concentrate

using continuous medium temperature pressure

leaching and direct electrowinning in accordance with an

exemplary embodiment ofthe invention. Table I, below, sets

forth the process conditions and operating parameters utilized.

Temperature, 0 c.

Time, min

Acid Addition Rate, kg acid/tonne feed

CLS Addition Rate, kg CLS/tonne feed

Oxygen Overpressure, psi

Total Pressure, psi

Feed Solids to Compartment 1, %

Weight Loss, %

Discharge Solids, %

Discharge Solution, giL

Cu

Fe

H2S04

Discharge Solids, %

65 Cu

Fe

45 Concentrate Type

Concentrate Analyses, %

In accordance with one alternative aspect ofthe invention,

aqueous stream 206 may not be subjected to electrowinning

immediately after leaving the solvent/solution extraction

unit, but may instead be blended with other copper-containing

process streams, and the resultant stream then sent to an

electrowinning circuit. For example, all or a portion of aqueous

stream 206 may be blended with a copper-containing

solution stream (not shown) and a lean electrolyte stream (not

shown) in electrolyte recycle tank 1060 (from FIG. 1) to form

10 a resultant product stream suitable for electrowinning in an

electrowinning circuit. In such cases the stripping solutions

used in solvent/solution extraction 2010 likely will be comprised

of spent electrolyte from electrowinning circuit 1070

(from FIG. 1).

Impurity removal may be further facilitated by suitable

processing in advance of pressure leaching, such as by the

aforementioned separation and/or precipitation step. In

accordance with this further aspect ofthe present invention as

previously mentioned, advantageously impurities may be

20 removed from the process, for example, the electrowinning

process. Such impurities include, without limitation, iron,

aluminum, magnesium, sodium, potassium and the like, often

present as sulfates. In the absence ofremoval, such impurities

may accumulate to deleterious levels, and, as such negatively

25 impact production efficiencies and product (e.g. copper cathode)

quality.

The Example set forth hereinbelow is illustrative ofvarious

aspects of a preferred embodiment of the present invention.

The process conditions and parameters reflected therein are

30 intended to exemplifY various aspects of the invention, and

are not intended to limit the scope of the claimed invention.

conventional or hereinafter developed atmospheric or pressure

leaching method, including, for example, heap leaching,

stockpile leaching (also sometimes referred to in the art as

"dump leaching"), vat leaching, tank leaching, agitated tank

leaching, in situ leaching, pressure leaching, or other process.

In accordance with one aspect of a preferred embodiment of

the invention, leach operation 2020 is a conventional acidconsuming

heap leach operation, wherein a low grade ore 201

is contacted with an acid-containing stream 202 and, optionally,

other process streams, such as raffinate stream 205 from

solvent/solution extraction unit 2010. In leach operation

2020, the acid percolates downward through the ore heap,

solubilizing the copper in the copper-containing ore in the

form of copper sulfate, to form a copper-rich pregnant leach

solution (PLS) stream 203. In accordance with one aspect of 15

a preferred embodiment of the invention, PLS 203 from a

heap leach operation 2020 is combined with lean electrolyte

bleed stream 118 prior to entering solvent/solution extraction

stage 2010 as process stream 204.

In accordance with a further aspect ofthis embodiment of

the present invention, as previously briefly mentioned, lean

electrolyte bleed stream 118 advantageously may remove

impurities from the process, for example the electrowinning

process. Such impurities include, without limitation, iron,

aluminum, silica, selenium, magnesium, manganese,

sodium, potassium and others. In the absence of removal,

such impurities may accumulate to deleterious levels, and, as

such negatively impact production efficiencies and product

(e.g., copper cathode) quality. The presence of such impurities

in lean electrolyte bleed stream 118 generally does not

negatively impact the aforementioned handling of lean electrolyte

bleed stream 118.

As will be discussed in further detail hereinbelow, in a

further embodiment ofthe present invention, impurities may

be removed prior to pressure leaching through any suitable 35

means, such as precipitation or other steps.

With further reference to FIG. 2, solvent/solution extraction

stage 2010 and solution stripping stage 2015 purifY copper-

bearing process stream 204 in two unit operations-an

extraction operation, which may have multiple stages, fol- 40

lowed by a stripping operation. In the extraction stage, process

stream 204 is contacted with an organic phase consisting

of a diluent in which a copper selective reagent (i.e., the

extractant) is admixed. When the solutions are contacted, the

organic extractant chemically removes the copper from

stream 204, forming a copper-depleted aqueous raffinate

stream. The raffinate and organic streams are subsequently

separated in a settler. After separation of the organic and

aqueous phases in the settler, a portion ofthe aqueous phase

(stream 205) is typically returned to one or more leaching 50

operations to be reloaded with copper from the ore in the

atmospheric leach to form the PLS, or may be recycled to

other process areas or appropriately disposed of. The organic

stream passes on to the second unit operation ofthe solvent/

solution extraction process, the stripping operation. In the 55

stripping operation, the organic stream is contacted with a

strongly acidic electrolyte. This acidic solution "strips" the

copper from the extractant, leaving the organic phase substantially

depleted ofcopper. At least a portion ofthe loaded strip

solution aqueous phase (stream 206) is advanced to an elec- 60

trowinning plant 2030 as a copper "rich" solution. Aqueous

stream 206 is processed in electrowinning plant 2030 to yield

cathode copper 207 and a copper-containing lean electrolyte

stream 208, which, in one aspect of a preferred embodiment

of the invention, may be recycled in part to solvent/solution

extraction unit 2010 and/or to pressure leaching stage 1030

(stream 209 to FIG. 1) and/or to other process areas.

US 7,736,488 B2

19 20

65

2. The method ofclaim 1, wherein said step of providing a

feed stream comprising a copper-bearing material comprises

providing a feed stream comprising a copper-bearing sulfide

ore, concentrate, or precipitate.

3. The method ofclaim 1, wherein said step of providing a

feed stream comprising a copper-bearing material comprises

providing a feed stream comprising at least one of chalcopyrite,

chalcocite, bornite, covellite, digenite, and enargite, or

mixtures or combinations thereof.

4. The method ofclaim 1, wherein said step of providing a

feed stream comprising a copper-bearing material comprises

providing a feed stream comprising a copper-bearing material

and a solution stream comprising copper and acid.

5. The method ofclaim 1, wherein said step ofsubjecting at

15 least a portion of said feed stream to controlled fine grinding

comprises reducing the particle size of said feed stream such

that substantially all ofthe particles in said feed stream react

substantially completely during pressure leaching.

20 6. The method ofclaim 5, wherein said step ofsubjecting at

least a portion of said feed stream to controlled fine grinding

comprises reducing the particle size of said feed stream to a

P80 of less than about 25 microns.

7. The method ofclaim 5, wherein said step ofsubjecting at

25 least a portion of said feed stream to controlled fine grinding

comprises reducing the particle size of said feed stream to a

P80 of from about 13 to about 20 microns.

8. The method ofclaim 5, wherein said step ofsubjecting at

least a portion of said feed stream to controlled fine grinding

30 comprises reducing the particle size of said feed stream to a

P98 of less than about 25 microns.

9. The method ofclaim 5, wherein said step ofsubjecting at

least a portion of said feed stream to controlled fine grinding

comprises reducing the particle size of said feed stream to a

35 P98 of from about 10 to about 23 microns.

10. The method ofclaim 5, wherein said step of subjecting

at least a portion of said feed stream to controlled fine grinding

comprises reducing the particle size of said feed stream to

a P98 of from about 13 to about 15 microns.

11. The method of claim 1, wherein said leaching step

comprises leaching at least a portion of said feed stream in a

pressure leaching vessel at a temperature offrom about 1400

C. to about 2300 C. and at a total operating pressure of from

about 100 psi to about 750 psi.

12. The method of claim 1, wherein said leaching step

comprises leaching at least a portion of said feed stream in a

pressure leaching vessel at a temperature offrom about 1600

C. to about 1700 C. and at a total operating pressure of from

about 100 psi to about 750 psi.

50

13. The method of claim 1, wherein said leaching step

comprises leaching at least a portion of said feed stream in a

pressure leaching vessel at a temperature offrom about 1800

C. to about 2200 C. and at a total operating pressure of from

55 about 100 psi to about 750 psi.

14. The method of claim 1, wherein said step of pressure

leaching said feed stream comprises pressure leaching said

feed stream in the presence of a surfactant selected from the

group consisting of lignin derivatives, orthophenylene

60 diamine, alkyl sulfonates, and mixtures thereof.

15. The method of claim 1, wherein said conditioning step

comprises subjecting at least a portion of said product slurry

to solid-liquid separation, wherein at least a portion of said

copper-bearing solution is separated from said residue.

16. The method ofclaim 15, wherein said conditioning step

further comprises blending at least a portion of said copperbearing

solution with at least a portion ofone or more copper-

10

96.6

69

27

34

3.3

135

88

84

308

50

3.0

10

334

TABLE I-continued

Current Density, Alm2

Cell Temperature, C C.

Specific Flow, L/min-m2

FC-1110 (Mist Control), gal/106 lb Cu

PD-4201 (Leveling Agent), gltonne Cu

Lean Electrolyte, giL

ell Extraction, %

Sulfide Oxidized to Elemental Sulfur, %

Sulfide Oxidation to Sulfate, %

ELECTROWINNING

Cu

Fe

H2S04

Current Efficiency, %

Copper Removed by Electrowinning, %

An effective and efficient method to recover copper from

metal-bearing materials, especially copper from copper sulfides,

such as chalcopyrite, that enables high copper recovery

at a reduced cost over conventional processing techniques has

been presented herein. In accordance with the present invention,

it has been shown that copper recovery in excess ofabout

96 to about 98 percent is achievable while realizing various

important economic benefits ofmediumtemperature pressure

leaching and circumventing processing problems historically

associated with medium temperature pressure leaching.

Moreover, the present invention provides a substantially acidautogenous

process for recovering copper from chalcopyritecontaining

ore using pressure leaching and direct electrowinning

in combination with an atmospheric leaching, solvent/

solution extraction, and electrowinning steps.

The present invention has been described above with reference

to a number ofexemplary embodiments and examples.

It should be appreciated that the particular embodiments

shown and described herein are illustrative of the invention

and its best mode and are not intended to limit in any way the

scope ofthe invention. Those skilled in the art having read this

disclosure will recognize that changes and modifications may 40

be made to the exemplary embodiments without departing

from the scope of the present invention. Further, although

certain preferred aspects ofthe invention are described herein

in terms of exemplary embodiments, such aspects of the

invention may be achieved through any number of suitable 45

means now known or hereafter devised. Accordingly, these

and other changes or modifications are intended to be

included within the scope ofthe present invention.

What is claimed is:

1. A method of recovering copper from a copper-bearing

material, comprising the steps of:

(a) providing a feed stream comprising a copper-bearing

material;

(b) subjecting at least a portion of said feed stream to

controlled fine grinding;

(c) leaching at least a portion of said inlet stream in an

oxidizing environment at an elevated temperature and

pressure to yield a product slurry comprising a copperbearing

solution and a residue;

(d) conditioning said product slurry without the use of

solvent/solution extraction techniques to yield a copperbearing

solution suitable for electrowinning;

(e) electrowinning copper from said copper-bearing solution

to yield cathode copper and a copper-bearing lean

electrolyte stream; and

(f) treating at least a portion of said lean electrolyte stream

using solvent/solution extraction techniques.

21

US 7,736,488 B2

22

bearing streams to achieve a copper concentration of from

about 15 grams/liter to about 80 grams/liter in said copperbearing

solution.

17. The method of claim 15, wherein a portion of said

copper-bearing solution is recycled to step (c).

18. The method ofclaim 1, wherein said conditioning step

comprises subjecting at least a portion of said product slurry

to filtration, wherein at least a portion of said copper-bearing

solution is separated from said residue.

19. The method of claim 1, wherein said conditioning step

comprises separating at least a portion of said residue from

said copper-bearing solution in said product slurry, and further

comprises using at least a portion of said residue as a

seeding agent in step (c).

20. The method of claim 1, further comprising the step of

(g) using a portion ofsaid lean electrolyte stream in a leaching

operation.

* * * * *