8,012,318 Process for multiple stage direct electrowinning of copper

Patent Number/Link:

111111111111111111111111111111111111111111111111111111111111111111111111111

US008012318B2

(12) United States Patent

Marsden et al.

(10) Patent No.:

(45) Date of Patent:

US 8,012,318 B2

*Sep.6,2011

(54) PROCESS FOR MULTIPLE STAGE DIRECT

ELECTROWINNING OF COPPER

(73) Assignee: Freeport-McMoran Corporation,

Phoenix, AZ (US)

(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)

(56) References Cited

(57) ABSTRACT

U.S. PATENT DOCUMENTS

4,632,738 A * 12/1986 Beattie et al. 205/347

5,670,035 A * 9/1997 Virnig et al. 205/345

7,462,272 B2 * 12/2008 Marsden et al. 205/580

7,476,308 B2 * 112009 Marsden et al. 205/580

7,722,756 B2 * 5/2010 Marsden et al. 205/580

* cited by examiner

(52) U.S. Cl. 204/236; 204/232; 204/233; 204/234;

205/584; 205/580; 205/586; 75/740; 75/743

(58) Field of Classification Search 204/232,

204/233,234,236; 205/580,581,584,585,

205/586, 574; 75/740, 743

See application file for complete search history.

Primary Examiner - Bruce F Bell

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

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 terminal disclaimer.

( *) Notice:

11 Claims, 3 Drawing Sheets

A system and process for recovering copper from a coppercontaining

ore, concentrate, or other copper-bearing material

to produce high quality cathode copper from a leach solution

without the use of copper solvent/solution extraction techniques

or apparatus. A process for recovering copper from a

copper-containing ore generally includes the steps of providing

a feed stream containing comminuted copper-containing

ore, concentrate, or other copper-bearing material, leaching

the feed stream to yield a copper-containing solution, conditioning

the copper-containing solution through one or more

physical or chemical conditioning steps, and electrowinning

copper directly from the copper-containing solution in multiple

electrowinning stages, without subjecting the coppercontaining

solution to solvent/solution extraction prior to

electrowinning.

Aug. 19,2010

(2006.01)

Prior Publication Data

Filed: Apr. 29, 2010

US 2010/0206741 Al

(21) Appl. No.: 121769,884

(22)

(65)

Related U.S. Application Data

Continuation of application No. 12/274,035, filed on

Nov. 19, 2008, now Pat. No. 7,722,756, which is a

continuation of application No. 111163,761, filed on

Oct. 28, 2005, now Pat. No. 7,462,272.

Provisional application No. 60/623,199, filed on Oct.

29,2004.

(51) Int. Cl.

e25B 15/08

(63)

(60)

u.s. Patent Sep.6,2011 Sheet 1 of 3 US 8,012,318 B2

1010,,-

~ --Iy101

Cu SEPARATION

(OPTIONAL) \

109

111

V 102

1020"-.1r--_-------- -----------:

I s L t--r---'\~

I I

1_ - - - - -1~;1- - -V-103 - - - - - - • 110

127 I

\ 1030~ 1 ---~.1....-_~~J PRESSURE LEACHING I \

\ 1--\--------------------1 118

112 1031 V 104

1040

J Cu

119

I ~120

ATMOSPHERIC FLASH

FIRST STAGE DIRECT

ELECTROWINNING

1070",,-

108

1080",

1051 ~105

1050 r--\-------------------, ~ - I ---.-.......... L S 1-'-1--,--

~/----------V106-- - -: ~4

I.. 115

128 ; ELECTROLYTE

RECYCLE TANK l-- - - - - - - - - - - - - - - - 1

1060../ll..-----.--------' :

~107 :

- - - .....

-+ ---

I- - - -

125",

1\ 1090~

y-122

( Cu )

FIG. 1

u.s. Patent Sep.6,2011 Sheet 2 of 3 US 8,012,318 B2

202

203

201

ATMOSPHERIC LEACHI

PRESSURE LEACH

2020

126~

:I 126.110 208 204 J204

I _~__ --------------------- 1

I I

I 2030 I

1 ELECTROWINNING I

: 203 I

: ~ 1 ~ 205 r 2_0~ j

1 I I

- - - - - - - - - - - - - - - -1- - - - - -,... - - - - - t- - - - - - - - - - - - - - - - I

I I I

I I

1 I

1 206 209 211 I

I I

I 2070 I

I I

I 212 I

: 210 :

I 1

~------------------------------------- I

FIG. 2

u.s. Patent Sep.6,2011 Sheet 3 of 3 US 8,012,318 B2

Cu ORE: OR

CONCENTRATE

1 !

ATMOSPHERIC}

PRESSURE LEACH

1~ V 101 I

\ 1010, Cu SEPARATION 203

(OPTIONAL) r 102

1020 s---- L

- - l \ y103 110

1030

----x------- PRESSURE LEACH

I 1..7 104

1 1040

I ATMOSPHERIC FLASH

I v i OS I

'-.

1 1050 l-- I ___5

1 \

I -<----1--'

\oc - -1- ______________ V iD6 114

108~ 1060,

I t-l----. ELECTROLYTE RECYCLE TANK

: 108 V i07 - --- ....I

I 1070,,- I FIRST STAGE DIRECT ( I- - - - --lc- - -\- -- ELECTROWINNING / \. Cu )

108 1./120 116

1\ 1080".] ELECTROLYTE

RECYCLE TANK

123

y121 )2

\ 1090,"",,- SECOND STAGE DIRECT / Cu ) ELECTROW'NNING \.

123

FIG. 3

US 8,012,318 B2

SUMMARY OF THE INVENTION

niques have shown the ability for direct electrowinning of

copper to produce a relatively low-quality copper product.

An effective and efficient method to recover copper from

metal-bearing materials, such as, for example, chalcopyrite,

chalcocite, bornite, covellite, digenite, and enargite, that

enables high copper recovery to be achieved at a reduced cost

over conventional processing techniques would be advantageous.

While the way in which the present invention addresses the

deficiencies and disadvantages of the prior art is described in

greater detail hereinbelow, in general, according to various

aspects of the present invention, a process for recovering

copper and other metal values from a copper-containing

material includes obtaining a copper-containing solution

from, for example, a pressure leaching system, and then

20 appropriately conditioning the copper-containing solution for

electrowinning. In an exemplary aspect of the invention, the

composition of the copper-containing solution is similar to

the composition of the electrolyte produced by a solvent/

solution extraction circuit, for example, with respect to acid

25 and copper concentrations. In accordance with various

embodiments of the present invention, however, the coppercontaining

solution is not subjected to solvent/solution

extraction prior to electrowinning.

In accordance with an exemplary embodiment of the

30 present invention, a process for recovering copper from a

copper-containing material generally includes the steps of: (i)

providing a feed stream containing copper-containing material;

(ii) optionally, subjecting the copper-containing feed

stream to a copper separation stage; (iii) subjecting the cop-

35 per-containing feed stream to atmospheric leaching or pressure

leaching to yield a copper-containing solution; (iv) conditioning

the copper-containing solution through one or more

chemical or physical conditioning steps; (v) electrowinning

40 copper directly from the copper-containing solution, without

subjecting the copper-containing solution to solvent/solution

extraction; (vi) optionally, treating at least a portion ofa lean

electrolyte stream from the electrowinning step in a solvent/

solution extraction and electrowinning operation; and (vii)

45 recycling at least a portion ofthe lean electrolyte stream to the

atmospheric or pressure leaching step to provide some or all

ofthe acid requirement of the leaching operation.

In accordance with another exemplary embodiment ofthe

present invention, a process for recovering copper from a

50 copper-containing material generally includes the steps of: (i)

providing a feed stream containing copper-containing material;

(ii) optionally, subjecting the copper-containing feed

stream to a copper separation stage; (iii) subjecting the copper-

containing feed stream to atmospheric leaching or pres-

55 sure leaching to yield a copper-containing solution; (iv) conditioning

the copper-containing solution through one or more

chemical or physical conditioning steps; (v) electrowinning

copper directly from the copper-containing solution, without

subjecting the copper-containing solution to solvent/solution

60 extraction; (vi) optionally, treating at least a portion ofa lean

electrolyte stream from the electrowinning step in a solvent/

solution extraction and electrowinning operation; and (vii)

recycling at least a portion ofthe lean electrolyte stream to the

atmospheric or pressure leaching step to provide some or all

65 of the acid requirement of the leaching operation. As used

herein, the term "pressure leaching" shall refer to a metal

recovery process in which material is contacted with a liquid

FIELD OF THE INVENTION

CROSS-REFERENCE TO RELATED

APPLICATIONS

BACKGROUND OF THE INVENTION

PROCESS FOR MULTIPLE STAGE DIRECT

ELECTROWINNING OF COPPER

This application claims priority to U.S. patent application

Ser. No. 12/274,035, entitled "Process for Multiple Stage

Direct Electrowinning of Copper" filed on Nov. 19, 2008,

now U.S. Pat. No. 7,722,756. The '035 application claims 10

priority to U.S. patent application Ser. No. 11/163,761,

entitled "Process for Multiple Stage Direct Electrowinning of

Copper" filed on Oct. 28, 2005 (now U.S. Pat. No. 7,462,272

issued on Dec. 9, 2008). The '761 application claims priority 15

to U.S. Provisional Patent Application Ser. No. 60/623,199,

entitled "Process for Multiple Stage Direct Electrowinning of

Copper" filed Oct. 29, 2004. All these references are hereby

incorporated by reference in their entirety.

The present invention relates generally to a process for

recovering copper from a copper-containing ore, concentrate,

or other copper-bearing material, and more specifically, to a

process using super-fine grinding, a copper separation operation,

and pressure leaching to produce cathode copper from a

multiple-stage direct electrowinning process.

Hydrometallurgical treatment of copper-containing materials,

such as copper ores, concentrates, and other copperbearing

materials, has been well established for many years.

Currently, there exist many creative approaches to the hydrometallurgical

treatment ofthese materials; however, common

to almost all of the processes either now known or under

development is the use of solvent/solution extraction and

electrowinning (SX-EW) operations for solution purification

and copper recovery.

The traditional hydrometallurgical process for copper

recovery involves first leaching copper-containing material

with sulfuric acid solution, either atmospherically or under

conditions of elevated temperature and pressure. The resultant

liquid stream-the so-called pregnant leach solution-is

collected and processed in a solvent/solution extraction stage,

in which the leach solution is mixed with an organic solvent

(i.e., an extractant mixed with a suitable diluent, such as

kerosene). The organic phase selectively removes the copper

from the pregnant leach solution. The copper-loaded organic

phase is then mixed with an aqueous acid solution, which

strips the copper from the extractant, producing a solution

stream suitable for electrowinning. This resultant solution is

highly concentrated in copper, is relatively pure, and typically

is processed in an electrowinning circuit to yield high quality

copper cathode.

Purification of copper from the pregnant leach solution by

solvent/solution extraction has proven to be a successful

means of providing a concentrated copper solution suitable

for electrowinning of highly pure copper metal. Direct electrowinning

ofcopper-that is, plating ofcopper directly from

the pregnant leach solution without the intervening step of

purification by solvent/solution extraction-is known. However,

the copper recovered by such so-called direct electrowinning

processes often is too impure for sale or use as is, and

thus, generally must be further refined at an additional cost, or

may be sold at a discount. More specifically, prior art techUS

8,012,318 B2

3 4

uct quality and process efficiency. Moreover, existing copper

recovery processes that use a conventional atmospheric or

pressure leaching, solvent/solution extraction, and electrowinning

process sequence may, in many instances, be easily

retrofitted to exploit the many commercial benefits the

present invention provides.

In one optional aspect of an exemplary embodiment ofthe

invention, at least a portion of the acid generated during the

electrowinning stage as a copper-containing electrolyte

stream is transported out ofthe copper recovery process after

an optional separation step in which substantially all of the

copper is removed from the copper-containing electrolyte

stream. It is generally economically advantageous to utilize

this generated acid in some way, rather than to attenuate or

dispose ofit. Thus, as discussed in greater detail hereinbelow,

embodiments of the present invention incorporating these

optional aspects may find particular utility in combination

with conventional atmospheric leaching operations, such as,

for example, heap leaching, vat leaching, dump or stockpile

leaching, pad leaching, agitated tank leaching, and bacterial

leaching operations, which often require a substantially continuous

acid supply.

In accordance with one aspect of an exemplary embodiment

of the present invention, a feed stream containing copper-

containing material is provided for processing. In accordance

with various embodiments of present invention, the

copper-containing material may be an ore, a concentrate, or

any other copper-bearing material from which copper and/or

other metal values may be recovered. The copper in the copper-

containing material may be in the form ofcopper oxides,

copper sulfides, and/or other copper minerals, and the coppercontaining

material may include any number of a variety of

other metals, such as, for example, gold, platinum group

metals, silver, zinc, nickel, cobalt, molybdenum, rare earth

metals, rhenium, uranium and mixtures thereof. Various

aspects and embodiments ofthe present invention prove especially

advantageous in connection with the recovery of copper

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

chalcopyrite (CuFeS2), chalcocite (Cu2S), bornite

(Cu5FeS4), covellite (CuS), enargite (Cu3AsS4), digenite

(Cu9S5), and/or mixtures thereof.

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.

45 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,

50 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

55 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

60 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-

65 cations.

In accordance with an exemplary aspect of the invention,

the particle size of the copper-containing feed material is

DETAILED DESCRIPTION

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention exhibits significant advancements

over prior art processes, especially other so-called "direct

electrowinning" processes, particularly with regard to prod-

(e.g., an acidic solution, water, etc.) and oxygen under conditions

of elevated temperature and pressure (i.e., above

ambient).

In one optional aspect ofan exemplary embodiment ofthe

invention, one or more processing steps are used to separate

copper from the acid in a recycled portion of the lean electrolyte

from the direct electrowinning process, thus rejecting

a portion of the acid and impurities from the process circuit

without rejecting a significant portion of the copper. As discussed

in greater detail hereinbelow, a number of conven- 10

tional or hereafter devised processes may be utilized to separate

copper from acid in the feed stream. For example, in

accordance with one aspect of an exemplary embodiment of

the invention, a copper precipitation step may be utilized to

precipitate solubilized copper from a lean electrolyte stream 15

onto the surfaces of solid particles in a copper-containing

material (e.g., finely ground chalcopyrite) stream in advance

of the pressure leaching step, thereby separating the copper

from the acid solution.

In accordance with various exemplary aspects of the 20

present invention, by providing for the electrowinning of

copper directly from a copper-containing solution without

first subjecting the copper-containing solution to solvent/solution

extraction, the present invention enables lower-cost

recovery of copper and reduces the expenses associated with 25

solvent/solution extraction, such as expenses associated with

reagents, process apparatus and equipment, and energy

resources. Furthermore, in accordance with one exemplary

aspect ofthe invention, careful control ofthe composition and

the dispersion ofthe copper-containing solution entering the 30

electrowinning circuit enables production of high quality,

uniformly-plated cathode copper. However, in accordance

with still other aspects of the present invention, one or more

process "bleed" streams may be subjected to solvent/solution

extraction or treatment in one or more liberator cells or other 35

similar processes, preferably following the electrowinning of

copper therefrom.

These and other advantages of a process according to vari0us

aspects and embodiments ofthe present invention will be

apparent to those skilled in the art upon reading and under- 40

standing the following detailed description with reference to

the accompanying figures.

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 an exemplary embodiment ofthe

present invention;

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

copper recovery process in accordance with an alternative

embodiment of the present invention; and,

FIG. 3 illustrates a flow diagram of a copper recovery

process in accordance with an alternative embodiment ofthe

present invention.

US 8,012,318 B2

5 6

niques may be useful to achieve the separation ofcopper from

acid in the lean electrolyte stream. For example, separation

processes and/or techniques such as precipitation, low temperature

pressure leaching, acid solvent/solution extraction!

ion exchange, membrane separation, cementation, pressure

reduction, sulfiding, and/or the use of liberator cells may be

useful for this purpose.

The optional separation aspect of an exemplary embodiment

ofthe invention contributes to providing a resultant acid

10 stream from copper separation step 1010 that contains a relatively

small fraction of copper, which can be used for leaching,

pH control, and/or other applications. Moreover, utilization

of a separation process may advantageously enable

removal of certain impurities. For example, because the

15 resultant acid stream is preferably removed from the metal

recovery process and utilized in remote operations, disposed

of, or attenuated, the impurities contained therein are likewise

removed from the metal recovery process and are thus prevented

from accumulating in the process stream. This may be

20 a significant advantage in that such impurities, particularly

metal impurities, typically have a deleterious effect on the

effectiveness and efficiency of the desired metal recovery

process. For example, metal impurities and other impurities

in the process stream, ifnot carefully controlled and/or mini-

25 mized, 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 optional

30 aspect ofan exemplary embodiment ofthe invention, coppercontaining

material stream 101 is subjected to a separation

step, such as, for example, a precipitation step, which, in this

exemplary process, serves to precipitate solubilized copper

from a recycled lean electrolyte stream. As discussed in detail

35 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 significant

economic benefits.

In accordance with an exemplary embodiment ofthe invention,

an optional precipitation step involves copper-containing

material stream 101 being combined with a lean electrolyte

stream 125 and, optionally, a sulfur dioxide (S02) stream

109 in a suitable processing vessel. For example, in the

45 embodiment illustrated in FIG. 1, lean electrolyte stream 125

may comprise a recycled acidic copper sulfate stream generated

during an electrowinning operation. Other streams, however,

preferably acidic streams, may also be used. While the

use of such other streams will be described in greater detail

50 hereinbelow, in accordance with various aspects of the

present invention, processing streams, preferably from electrowinning

operations, may be used. For example, in the

embodiments illustrated in FIGS. 1 and 3, multiple stage

electrowinning follows pressure leaching. While two such

55 electrowinning stages are illustrated, it will be appreciated

that additional stages may also be utilized in various applications.

However, lean electrolyte from either the first or second

electrowinning stage may be used as the recycled electrolyte

used in optional copper separation step 1010. Preferably,

60 however, and as is illustrated best in FIG. 3, a stream 123 from

the second electrowinning circuit 1090 is recycled to copper

separation step 1010. In one aspect of an embodiment ofthe

invention, lean electrolyte stream 125 has an acid concentration

of from about 20 to about 200 grams/liter, preferably

65 from about 70 to about 180 grams/liter, and most preferably

from about 140 to about 170 grams/liter. In a further aspect of

this embodiment ofthe invention, lean electrolyte stream 125

reduced to optimize the processing steps of atmospheric or

pressure leaching and subsequent metal recovery processes.

A variety of acceptable techniques and devices for reducing

the particle size of the copper-containing 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

area ofthe material to be processed. With regard to one aspect

ofan exemplary embodiment ofthe invention, such a result is

desired because the reaction rate during precipitation and/or

leaching may increase as the surface area of the coppercontaining

material increases.

In accordance with one aspect of an exemplary embodiment

of the invention, satisfactory grinding of chalcopyrite

concentrate with an as-received particle size of approximately

98 percent passing about 172 microns may be

achieved using a grinding apparatus such as, for example, a

stirred horizontal shaft mill with baffles or a vertically stirred

mill without baffles. Exemplary apparatus include the Isamill

developed jointly by Mount Isa Mines (MIM), Australia, and

Netzsch Feinmahltechnik, Gennany 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 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, and the like. Exemplary media

include, for example, sand, silica, metal beads, ceramic

beads, and ceramic balls.

In another optional aspect ofan exemplary embodiment of

the present invention, all or part ofthe metal-bearing material

feed stream may be combined with a liquid prior to entering

optional copper separation stage 1010 (described hereinbelow)

or copper leaching stage 1030. Preferably, the liquid

comprises water, but any suitable liquid may be employed,

such as, for example, raffinate, pregnant leach solution, or 40

lean electrolyte. For example, a portion of lean electrolyte

stream 125 from the direct electrowinning process may be

combined with metal-bearing material to fonn metal-bearing

material feed stream 10l.

The optional combination of a liquid with the metal-bearing

material can be accomplished using anyone or more of a

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 ofan embodiment

ofthe invention, the concentration of solid metal-bearing

material 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 another optional aspect of an exemplary

embodiment ofthe present invention, at least a portion

of the copper in a recycled stream of, lean electrolyte from

electrowinning is separated from the acid in the stream,

thereby reducing the amount of impurities in the portion of

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

such 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 solid or

soluble impurities from the copper-containing feed stream

and the recycled lean electrolyte stream. Any number ofconventional

or hereafter devised separation processes and techUS

8,012,318 B2

7 8

1070, and second electrowinning stage 1090, and any acid

generated in optional copper separation stage 1010 as a result

ofS02.

In accordance with an exemplary aspect of the invention,

the copper-containing material stream entering the pressure

leaching stage contains from about 10 and about 50 percent

solids by weight, preferably from about 20 to about 40 percent

solids by weight. To adjust the solids concentration of

product stream 102 in accordance with the desired parameters

10 and to separate the acid-bearing solution from the coppercontaining

solids, in accordance with an exemplary embodiment

of the invention, product stream 102 is sent to a solidliquid

separation circuit 1020. In one aspect of an exemplary

embodiment of the invention, solid-liquid separation circuit

15 1020 preferably includes a thickener circuit 1021 comprising

at least one thickener that will effectuate solid-liquid separation.

In the illustrated embodiment, the underflow of thickener

circuit 1021 is pressure leaching feed stream 103 and the

overflow is acid stream 110. Preferably, acid stream 110

20 contains only a negligible amount of copper.

Process effluent acid stream 110 may be utilized, processed,

attenuated, impounded, and/or disposed of in a variety

ofways, the appropriate choice ofwhich is largely dependent

upon economic and regulatory factors. In one aspect of

25 the illustrated embodiment, the acid stream can be beneficially

used in, for example, a leaching operation, such as an

atmospheric leaching operation, where acid is required to

leach copper oxide, copper sulfide, or other metal oxide/

sulfur minerals. Such a leaching operation may be a heap

30 leach, a vat leach, a tank leach, a pad leach, or any other

similar operation or may be a medium or low-temperature

pressure leaching operation. Acid is consumed in these operations

through reaction with acid-consuming constituents in

the ore.

In FIG. 2, acid stream 110 from thickener circuit 1021

(FIG. 1) is sent to an atmospheric pressure leach operation

2010. In accordance with one aspect ofan exemplary embodiment

ofthe invention, leach operation 2010 is a conventional

acid-consuming heap leach operation, wherein a copper ore

40 201 is contacted with acid stream 110 and, optionally, other

process streams, such as raffinate stream 206 from downstream

solvent/solution extraction unit 2020. In the example

of leach operation 2010 as a heap leach operation, the acid

percolates downward through the ore heap, solubilizing the

45 copper in the copper-containing ore in the form of copper

sulfate, to form a copper-rich pregnant leach solution (PLS)

stream 203. In the example of leach operation 2010 as a

pressure leach operation, acid aids in the solubilization of

copper in the feed material to form a PLS stream. PLS stream

50 203 is sent to a solvent/solution extraction unit, such as solvent/

solution extraction unit 2020 in FIG. 2, to produce a high

concentration and relatively pure copper sulfate solution suitable

for electrowinning of copper. In accordance with an

alternative aspect ofthe present invention illustrated in FIG.

55 2, PLS stream 203 may not be subjected to solvent/solution

extraction, but may instead be blended with other coppercontaining

process streams, and the resultant stream then sent

to a copper electrowinning circuit. For example, all or a

portion ofPLS stream 203 (broken line) may be blended with

60 copper-containing solution stream 106 and lean electrolyte

stream 115 in electrolyte recycle tank 1060 (from FIG. 1) to

form a resultant product stream suitable for copper electrowinning

in an electrowinning circuit.

Ifeffluent acid stream 110 is not used as an acid-containing

65 by-product or otherwise utilized, the acid may be attenuated

using, for example, acid-consuming gangue (i.e., mineral

processing tailings) or an attenuating agent, such as limestone

CuFeS2+Cu+2->Fe+2+2CuS

has a copper concentration of from about 20 to about 55

grams/liter, preferably from about 25 to about 50 grams/liter,

and most preferably from about 30 to about 45 grams/liter. If

utilized, in copper precipitation stage 1010, copper from lean

electrolyte stream 125 precipitates to form a desired copperrich

concentrate. Preferably, when used, precipitation is carried

out such that the copper from the lean electrolyte precipitates,

at least in part, in the form of a copper sulfide, such

as, for example, CuS. While not wishing to be bound by any

particular theory, the chemical reaction during this exemplary

copper precipitation step-wherein, for example, the coppercontaining

material is primarily chalcopyrite-is believed to

be as follows:

Other copper minerals and other sulfides react to varying

degrees according to similar reactions, producing copper precipitates

and a weak sulfuric acid by-product. In accordance

with an optional aspect of the invention, 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, such as with

steam, electric heating coils, a heat blanket, process fluid heat

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

the exemplary process of FIG. 1, steam generated in other

process areas, such as stream 119 from flash tank 1040 or

stream 118 from pressure leaching stage 1030, may be

directed to the processing vessel in copper separation stage

1010 to provide the heat desired to enhance the precipitation

process.

The residence time for the optional copper separation pro- 35

cess can vary, depending on factors such as the operating

temperature ofthe processing vessel and the size distribution!

surface area of the composition of the copper-containing

material, but typically ranges from about two (2) minutes to

about six (6) hours. Preferably, conditions are selected such

that significant amounts of copper are precipitated. For

example, precipitation rates on the order of about 98% precipitation

ofcopper have been achieved in processing vessels

maintained at about 90° C. for about 4 hours.

Other parameters to consider when conditioning the copper-

containing material feed stream for processing are (i) the

ratio ofsolid particles in the feed stream to the total volume of

the copper-containing solution feed stream; (ii) the ratio of

copper in solution to copper-containing material; (iii) temperature;

(iv) pressure; (v) viscosity; (vi) slurry density ofthe

feed stream; and (vii) other factors may be suitably addressed.

Although these parameters mayor may not be significant to

the overall efficiency ofprocessing operations downstream in

all cases, these parameters can affect equipment size and

material specifications, energy requirements, and other

important aspects ofprocess design. Thus, calculated adjustment

of these stream parameters in advance of complex or

resource-intensive processing stages can positively affect the

economic efficiency ofthe chosen process. Solid-liquid separation

systems, such as, for example, filtration systems,

counter-current decantation (CCD) circuits, thickeners, and

the like are useful in adjusting these parameters and are

widely used in the industry.

In one aspect ofthe embodiment ofthe invention illustrated

in FIG. 1, product stream 102, which generally contains covellite/

chalcopyrite particles and acid, contains acid generated

in pressure leaching stage 1030, first electrowinning stage

US 8,012,318 B2

9 10

2CuS+2H2S04+02->2Cu+2+2S04-2+2H20+2S0

CuS+202->CuS04

2Cu2S+502+2H2S04->4CuS04+2H20

4CuFeS2+1702+4H20->4CuS04+4H2S04+2Fe203

4CuFeS2+4H2S04+502->4CuS04+2Fe203+8So+

4H20

Pressure leaching, for example in pressure leaching vessel

1031, preferably occurs in a manner suitably selected to promote

the solubilization of copper using these (or other) processes.

In general, temperature and pressure in the pressure

leaching vessel should be carefully controlled. For example,

in accordance with one aspect of the invention, the temperature

of pressure leaching vessel 1031 is maintained at from

about 100° C. to about 250° c., preferably from about 140° C.

to about 235° C. In accordance with one aspect of one

embodiment of the invention, the temperature of pressure

leaching vessel 1031 is advantageously maintained at from

Ifdesired, conditions during pressure leaching can be controlled

such that a portion ofthe sulfide sulfur contained in the

feed stream is converted to elemental sulfur instead ofsulfate.

50 The fraction of chalcopyrite and covellite that fonn sulfur

instead of sulfate are believed to react according to the following

reactions:

about 40 to about 60 percent solids by weight, the balance

being a dilute acid solution. The general composition of the

dilute acid solution is dependent upon the ratio of process

water to acid introduced in the thickener circuit.

In a further aspect ofthe present invention, the conditioned

copper-containing feed stream preferably is subjected to a

suitable process, such as pressure leaching, to produce product

slurry 104, which comprises a copper-containing solution

106 and a residue 114. The process may be selected as

10 desired, but, in general, enables production of a copper-containing

solution 106 that exhibits copper and acid concentrations

similar to an electrolyte stream resulting from a solvent/

solution extraction circuit-that is, the copper-containing

solution preferably is suitable for processing in an electrow-

15 inning circuit. Any suitable technique or combination oftechniques

that yields an appropriate copper-containing solution

without employing solvent/solution extraction techniques

may be used. In an exemplary embodiment of the invention,

as illustrated in FIG. 1, pressure leaching feed stream 103 is

20 subjected to a pressure leaching stage 1030 to yield coppercontaining

product slurry 104.

In accordance with one aspect of this embodiment of the

present invention, pressure leaching feed stream 103 is transported

to a suitable vessel for pressure leaching, which can be

25 any vessel suitably designed to contain the process components

at the desired temperature and pressure conditions for

the requisite processing residence time. In an exemplary

embodiment, a pressure leaching vessell 031 is employed for

this purpose. Pressure leaching vessel 1031 is preferably a

30 horizontal multi-compartment, agitated vessel; however,

other vessel configuration and agitation alternatives now

known or hereafter devised may be employed. It should be

appreciated that any pressure leaching vessel that suitably

permits pressure leaching feed stream 103 to be prepared for

35 copper recovery may be utilized within the scope of the

present invention.

Generally, the chemical conversions that occur during

pressure leaching stage 1030 under certain conditions for the

solubilization of the copper in copper-containing materials,

40 such as chalcopyrite, chalcocite, or covellite are as follows:

or lime. Attenuating with acid-consuming gangue can be

relatively inexpensive, as the attenuating reagent is essentially

free. On the other hand, attenuating with limestone or

lime may be less desirable economically, as both these

reagents will incur cost. Nevertheless, should attenuation be

desired, any method for acid attenuation now known or hereafter

devised may be employed.

In accordance with a further aspect ofthis embodiment of

the present invention, as previously briefly mentioned, acid

stream 110 advantageously may remove impurities from the

process, for example, the electrowinning process. Such impurities

include, without limitation, iron, aluminum, manganese,

magnesium, sodium, potassium, and other metal ions,

often present as sulfates. In the absence of removal, such

impurities may accumulate to deleterious levels, and, as such

negatively impact production efficiencies and product (i.e.,

copper cathode) quality. The presence of such impurities in

acid stream 110 generally does not negatively impact the

aforementioned handling of acid stream 110.

In accordance with one aspect of an exemplary embodiment

of the invention illustrated in FIG. 2, solvent/solution

extraction unit 2020 purifies copper-bearing PLS stream 203

from the heap leach in two unit operations-an extraction

operation, which may have multiple stages, followed by a

stripping operation. In the extraction stage, PLS stream 203 is

contacted with an organic phase consisting of a diluent (e.g.,

kerosene) in which a copper selective extractant reagent (i.e.,

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

the organic extractant chemically removes the copper from

the PLS, forming an 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 of the aqueous phase (stream 206) is typically

returned to one or more leaching operations to be

reloaded with copper from the ore in the atmospheric leaching

step 2010 to fonn the PLS. Optionally, a portion ofraffinate

stream 206 may be recycled to copper separation step

1010. The organic stream passes on to the second unit operation

of the solvent/solution extraction process, the stripping

operation. In the 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 of copper. At least a

portion of the loaded strip solution aqueous phase (stream

204) is advanced to an electrowinning plant 2030 as a copper 45

"rich" solution. Aqueous stream 204 is processed in electrowinning

plant 2030 to yield cathode copper 207 and a coppercontaining

lean electrolyte stream 208, which, in one aspect

of an exemplary embodiment of the invention, may be

recycled in part to solvent/solution extraction unit 2020.

In accordance with one alternative aspect ofthe invention,

aqueous stream 204 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 55

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

stream 204 (broken line) may be blended with coppercontaining

solution stream 106 and lean electrolyte stream

115 in electrolyte recycle tank 1060 (from FIG. 1) to fonn a

resultant product stream suitable for electrowinning in an 60

electrowinning circuit 1070. In such cases the stripping solutions

used in solvent/solution extraction 2020 likely will be

comprised of spent electrolyte from electrowinning circuit

1070.

Referring again to FIG. 1, the underflow slurry from thick- 65

ener circuit 1021, pressure leaching feed stream 103 in this

preferred embodiment of the invention, has a composition of

US 8,012,318 B2

11 12

tion sufficient to achieve the desired result. In one aspect ofan

exemplary embodiment ofthe invention, favorable results are

achievable during pressure leaching of chalcopyrite using

calcium lignosulfonate in an amount of about 2 to about 20

kilograms per tonne, and more preferably in an amount of

about 4 to about 12 kilograms per tonne; and more preferably

in an amount of about 6 to about 10 kilograms per tonne of

chalcopyrite concentrate.

In another aspect of the present invention, the copper-

10 containing solution is conditioned for electrowinning through

one or more chemical and/or physical processing steps. In

much the same way that the copper-containing material feed

stream is conditioned for processing in accordance with

above-described aspects ofthe invention, the copper-contain-

15 ing solution intended to be utilized in the electrowinning

circuit of the present invention is conditioned to adjust the

composition, component concentrations, volume, temperature,

and/or other physical and/or chemical parameters to

desired values. Generally, a properly conditioned copper-

20 containing solution will contain a relatively high concentration

of copper in an acid solution and will contain relatively

few impurities. Preferably, the conditions of copper-containing

solution entering the electrowinning circuit are kept at a

constant level to enhance the quality and nniformity of the

25 cathode copper product.

In an exemplary aspect of the invention, conditioning of a

copper-containing solution for electrowinning begins by

adjusting certain physical parameters of the product slurry

from the previous processing step. In an exemplary embodi-

30 ment ofthe invention wherein the previous processing step is

pressure leaching, it is desirable to reduce the temperature

and pressure ofthe product slurry.An exemplary method ofso

adjusting the temperature and pressure characteristics of the

preferred product slurry is atmospheric flashing.

Thus, in accordance with an exemplary aspect of the

embodiment illustrated in FIG. 1, product slurry 104 from

pressure leaching vessel 1031 is flashed in an atmospheric

flash tank 1040 or other suitable atmospheric system to

release pressure and to evaporatively cool the product slurry

40 104 through the release of steam to form a flashed product

slurry 105. Flashed product slurry 105 preferably has a temperature

ranging from about 90° C. to about 101° c., a copper

concentration of from about 40 to about 120 grams/liter, and

an acid concentration of from about 10 to about 60 grams/

45 liter. In one aspect ofthe invention, however, flashed product

slurry 105 also contains a particulate solid residue containing,

for example, the iron oxide by-product of pressure leaching,

elemental sulfur, precious metals and other components that

are nndesirable for a feed stream to an electrowinning circuit.

50 Thus, in accordance with the same principles discussed

above, it is 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 solution-preferably

is separated from the solid portion of the slurry, which

55 may be subjected to further processing.

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

the invention flashed product slurry 105 is directed to a solidliquid

separation stage 1050, such as a CCD circuit 1051. In

an alternative embodiment ofthe invention, solid-liquid sepa-

60 ration stage 1050 may comprise, for example, a thickener or

a filter. 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, a thickener, a filter, or

65 other suitable device in solid-liquid separation stage 1050. In

one aspect of an exemplary embodiment of the invention,

CCD circuit 1051 uses conventional countercurrent washing

about 140° C. to about 180° C. or in the range of from about

150° C. to about 175° C. In accordance with anotherembodiment

of the invention, the temperature of pressure leaching

vessel 1031 is advantageously maintained between from

about 200° C. to about 235° C. or in the range of from about

210° C. to about 225° C.

In accordance with one aspect of the present invention,

during pressure leaching in pressure leaching vessel 1031,

sufficient oxygen 112 is injected into the vessel to maintain an

oxygen partial pressure from about 50 to about 250 psig,

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

from about 150 to about 200 psig. Furthermore, due to

the nature ofmedium temperature pressure leaching, the total

operating pressure (including oxygen partial pressure and

steam pressure) in the pressure leaching vessel is generally

superatmospheric, preferably 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.

Because pressure leaching of many metal sulfides is a

highly exothermic process and the heat generated is generally

greater than that required to heat pressure leaching feed

stream 103 to the desired operating temperature, cooling liquid

111 is preferably contacted with pressure leaching feed

stream 103 in pressure leaching vessel 1031 during pressure

leaching. Cooling liquid 111 is preferably process water, but

can be any suitable cooling fluid from within the refining

process or from an outside source. In an exemplary embodiment

of the invention, a sufficient amount of cooling liquid

111 is added to pressure leaching vessel 1031 to yield a solids

content in the product slurry 104 ranging from about 3 to

about 15 percent solids by weight. In accordance with one

aspect of the present invention, and with momentary reference

to FIG. 3, cooling ofthe pressure leaching vessel can be

accomplished by recycling lean electrolyte 123 from one or

more of the subsequent electrowinning stages. For example, 35

as illustrated in FIG. 3, preferably a lean electrolyte stream

108 is directed from the first electrowinning circuit 1070 to

pressure leaching step 1031.

The residence time for pressure leaching generally

depends on a number offactors, including the composition of

the copper-containing feed stream, its particle size, 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 pressure leaching of

chalcopyrite ranges from about 30 to about 180 minutes,

more preferably from about 60 to about 150 minutes, and

most preferably on the order of about 80 to about 120 minutes.

In accordance with an exemplary aspect of the present

invention, medium temperature pressure leaching of stream

103 is performed in the presence of a dispersing agent 127.

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 alkyIbenzene

sulfonates, and combinations ofthe above. Dispersing

agent 127 may be any compound that resists degradation

in the temperature range of medium temperature pressure

leaching (i.e., from about 140° C. to about 180° 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 127 may be introduced to the

pressure leaching vessel in an amount and/or at a concentraUS

8,012,318 B2

13 14

2CuS04+2H20->2Cuo+2H2S04+02

Cathode half-reaction: Cu2 ++2e-->Cuo

Anode half-reaction: 2H20->4H++02+4e-

Turning again to FIG. 1, in an exemplary embodiment the

invention, product stream 107 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

Referring briefly to an alternative embodiment of the

invention illustrated in FIG. 2, an additional lean electrolyte

stream 205 may be blended with lean electrolyte stream 115

and copper-containing solution stream 106 in electrolyte

recycle tank 1060 to produce product stream 107 in accordance

with the process control principles discussed in connection

with the embodiment illustrated in FIG. 1. In one

aspect ofthis alternative embodiment, lean electrolyte stream

205 preferably has a composition similar to that of lean elec-

10 trolyte stream 115. Further, as discussed above, other streams

may be introduced to electrolyte recycle tank 1060 for blending,

such as, for example, PLS stream 203 (FIG. 2) or a

portion oflean electrolyte stream 123 from second electrow-

15 inning circuit 1090 (FIG. 3).

Referring again to FIG. 1, preferably, the copper composition

of product stream 107 is maintained substantially constant.

While product stream 107 may contain a copper concentration

up to the copper solubility limit under the

20 prevailing conditions, preferably product stream 107 has a

copper concentration ofabout IS to about 80 grams/liter, and

more preferably ofabout 20 to about 60 grams/liter, and often

above 30 grams/liter. In one aspect of an exemplary embodiment

ofthe invention, control valves are positioned on each of

25 the pipelines feeding lean electrolyte stream 115 and coppercontaining

solution stream 106 to electrolyte recycle tank

1060 to facilitate blending control within the tank. With reference

to FIG. 1, copper from the product stream 107 is

suitably electrowon to yield a pure, cathode copper product.

30 In accordance with various aspects ofthe invention, a process

is provided wherein, upon proper conditioning of a coppercontaining

solution, a high quality, uniformly-plated cathode

copper product 116 may be realized without subjecting the

copper-containing solution to a solvent/solution extraction

35 process prior to entering the electrowinning circuit.

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-

40 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

45 configured to operate in a conventional manner. 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.

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

for example at one end, to flow perpendicular 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 with the application of current.

55 The primary electro chemical reactions for electrowinning

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

ofthe residue stream with wash water 113 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 residue disposal. Preferably,

large washratios are used to enhance the effectiveness of

solid-liquid separation stage 1050-that is, relatively large

amounts ofwash water 113 are added to the residue in CCD

circuit 1051. Preferably, the solution portion of the residue

slurry stream is diluted by wash water 113 in CCD circuit

1051 to a copper concentration of from about 5 to about 200

parts per million (ppm) in the solution portion of residue

stream 114. In accordance with one aspect of an exemplary

embodiment ofthe invention, addition of a chemical reagent

to solid-liquid separation stage 1050 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 remove other undesirable

species from the process stream. One such suitable chemical

reagent is POLYOXTM WSR-301, available from Dow

Chemical.

Depending on its composition, residue stream 114 from

solid-liquid separation stage 1050 may be impounded, disposed

of, or subjected to further processing, such as, for

example, precious metal recovery. For example, if residue

stream 114 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 now known or hereafter

devised. If gold or other precious metals are to be recovered

from residue stream 114 by cyanidation techniques, the content

ofimpurities in the stream, such as elemental sulfur, iron

precipitates, unreacted copper minerals, acid, and soluble

copper and soluble impurities, is preferably minimized. Such

materials may promote high reagent consumption in the cyanidation

process and thus increase the expense ofthe precious

metal recovery operation. As mentioned above, it is therefore

preferable to use a large amount ofwash water or other diluent

during the solid-liquid separation process to maintain low

copper and acid levels in the solids-containing residue stream

in an attempt to optimize the conditions for subsequent precious

metal recovery. As previously noted, careful control of

the conditions of a copper-containing solution entering an

electrowinning circuit-especially maintenance ofa substantially

constant copper composition---can enhance the quality

of the electrowon copper by, among other things, enabling

even plating of copper on the cathode and avoidance of surface

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.

Referring again to FIG. 1, in an exemplary aspect of the

invention, copper-containing solution stream circuit 106

from solid-liquid separation stage 1050 is sent to an electrolyte

recycle tank 1060. Electrolyte recycle tank 1060 suitably

facilitates process control for first electrowinning circuit

1070, as will be discussed in greater detail below. Copper- 60

containing solution stream 106, which generally contains

from about 40 to about 120 grams/liter of copper and from

about 10 to about 60 grams/liter acid, is preferably blended

with a lean electrolyte stream 115 in electrolyte recycle tank

1060 at a ratio suitable to yield a product stream 107, the 65

conditions ofwhich may be controlled to optimize the resultant

product of first electrowinning circuit 1070.

US 8,012,318 B2

15 16

taining acid, designated in FIG. 1 as lean electrolyte stream

123. In accordance with one exemplary embodiment, at least

a portion oflean electrolyte stream 123 is directed to electrolyte

recycle tank 1080 in an amount suitable to yield a product

stream 121, the conditions of which may be chosen to optimize

the resultant product of second electrowinning circuit

1090. Optionally, a portion oflean electrolyte stream 123 may

be recycled to copper separation stage 1010 via stream 125

(which may also comprise a portion of the lean electrolyte

10 produced in first electrowinning circuit 1070).

In accordance with various exemplary embodiments ofthe

invention as illustrated in FIG. 3, lean electrolyte stream 123

is directed optionally, wholly or in part to electrolyte recycle

tank 1080, electrolyte recycle tank 1060, and/or to copper

15 precipitation stage 1010. Those skilled in the art will appreciate

the ability to effectively manage stream flow control to

other streams and operations of the invention. Although not

illustrated as such in FIGS. 1 and 3, at least a portion oflean

electrolyte stream 123 may optionally be directed for further

20 processing in accordance with a process such as that illustrated

in FIG. 2.

The present invention has been described above with reference

to a number of exemplary embodiments. It should be

appreciated that the particular embodiments shown and

25 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 be made

to the exemplary embodiments without departing from the

30 scope of the present invention. For example, although reference

has been made throughout to copper, it is intended that

the invention also be applicable to the recovery of other

metals from metal-containing materials. Further, although

certain preferred aspects of the invention, such as techniques

35 and apparatus for conditioning process streams and for precipitation

of copper, for example, are described herein in

tenns of exemplary embodiments, such aspects ofthe invention

may be achieved through any number of suitable means

now known or hereafter devised. Accordingly, these and other

40 changes or modifications are intended to be included within

the scope of the present invention.

The invention claimed is:

1. A system for recovering copper from a copper-bearing

material, comprising:

a pressure leaching vessel configured to pressure leach a

feed stream comprising a copper-containing material

and an acid at a temperature offrom about 100° C. about

250° C. to yield a product slurry comprising a copperbearing

solution and a residue;

a first electrowinning apparatus configured to receive said

copper-bearing solution and to produce copper cathode

and a first stage lean electrolyte stream;

a second electrowinning apparatus configured to receive a

portion of said first stage lean electrolyte stream and to

produce copper cathode and a second stage lean electrolyte

stream; and

a recycling conduit configured to conduct at least a portion

of said first stage lean electrolyte stream to said pressure

leaching vessel.

2. The system of claim 1, wherein said feed stream comprises

at least one of a copper-bearing sulfide ore, a concentrate,

and a precipitate.

3. The system of claim 1, wherein said feed stream comprises

at least one of chalcopyrite, chalcocite, bornite, covel65

lite, digenite, enargite, or mixtures or combinations thereof.

4. The system of claim 1, further comprising a separation

vessel configured to separate at least a portion ofsaid copperwith

the above-referenced reactions or otherwise, is within

the scope of the present invention.

In accordance with an exemplary aspect of the invention,

electrowinning circuit 1070 yields a cathode copper product

116, optionally, an off gas stream 117, and a relatively large

volume of copper-containing acid, herein designated as lean

electrolyte streams 108 and 115. As discussed above, in the

embodiment illustrated in FIG. 1, lean electrolyte stream 108

may be directed to copper precipitation stage 1010 via lean

electrolyte stream 125 (which, as discussed hereinbelow, may

comprise a portion oflean electrolyte stream 123 from second

electrowinning circuit 1090), and lean electrolyte stream 115

is directed to electrolyte recycle tank 1060.As those skilled in

the art are aware, it may be preferable to regulate the flow

amount, flow direction or other aspects ofthe lean electrolyte

streams directed from electrowinning circuit 1070 to further

maximize the efficiency of the described invention.

In accordance with an exemplary aspect of an alternative

preferred embodiment, a portion of lean electrolyte stream

108 is directed to pressure leaching feed stage 1031. Lean

electrolyte stream 108 may exhibit copper concentration sufficient

to combine with pressure leaching feed stream 103 to

further maximize the operational and economic efficiency of

the present invention. In addition, as briefly noted above,

stream 108 may provide suitable cooling liquid to pressure

leaching step 1031.

Again referring to FIG. 3, in an exemplary alternative to an

aspect of the invention, all of copper-containing stream 106

may not be directed to electrolyte recycle tank 1060. To

achieve optimum operational and economic efficiency in

accordance with various embodiments of the present invention,

it may be desirable to direct a portion ofcopper-containing

feed stream 106 to operations other than electrowinning.

As depicted in FIG. 3, a portion of copper-containing stream

106 may be directed to pressure leaching feed stream 103.

Moreover, a portion ofcopper-containing stream 106 may be

directed to precipitation stage 1010.

Referring back again to FIG. 1, electrolyte stream 120 from

first electrowinning circuit 1070-which comprises at least a

portion of the lean electrolyte produced in first electrowinning

circuit 1070 that is not recycled to other process operations-

is subjected to further processing in a second electrowinning

circuit 1090. In an exemplary aspect of the

embodiment, lean electrolyte stream 120 is sent to electrolyte

recycle tank 1080.

Electrolyte recycle tank 1080 suitably facilitates process

control for electrowinning circuit 1090, as will be discussed

in greater detail below. Lean electrolyte stream 120, which

generally contains from about 20 to about 40 grams/liter of

copper and from about 100 to about 180 grams/liter ofacid, is 50

preferably blended with lean electrolyte stream 123 from

second electrowinning circuit in electrolyte recycle tank 1080

at a ratio suitable to yield a product stream 121, the conditions

ofwhich may be chosen to optimize the resultant product of

electrowinning circuit 1090.

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

121 is suitably electrowon to yield a pure, cathode copper

product. In accordance with various aspects ofthe invention,

a process is provided wherein, upon proper conditioning of a

copper-containing solution, a high quality, unifonnly-plated 60

cathode copper product 122 may be realized without subjecting

the copper-containing solution to a solvent/solution

extraction process prior to entering the electrowinning circuit.

In furtherance of an exemplary aspect of the embodiment,

second electrowinning circuit 1090 yields a cathode copper

product 122, offgas, and a remainder volume of copper-con17

US 8,012,318 B2

containing material from said acid in said feed stream to yield

a copper-containing feed stream comprising a copper-bearing

material.

5. The system of claim 4, wherein said separation vessel is

configured to house a precipitation process comprising reacting

at least a portion of the copper in a copper-containing

electrolyte stream with a precipitant to precipitate at least a

portion of said copper in said copper-containing electrolyte

stream as copper sulfide in said feed stream.

6. The system of claim 4, wherein said separation vessel is

configured to react at least a portion ofthe copper in a coppercontaining

electrolyte stream in the presence of sulfur dioxide,

whereby at least a portion of said copper in said coppercontaining

electrolyte stream precipitates as copper sulfide in

said feed stream.

7. The system of claim 1, wherein said pressure leaching

vessel is configured to pressure leach said feed stream in the

presence ofa surfactant selected from the group consisting of

lignin derivatives, orthophenylene diamine, alkyl sulfonates,

and mixtures thereof.

8. The system of claim 1, wherein said pressure leaching

vessel is configured to pressure leach said feed stream in the

presence ofa surfactant in an amount offrom about 2 to about

20 kilograms per tonne ofconcentrate in the copper-containing

feed stream.

9. The system of claim 1, wherein said second electrowinning

apparatus is configured to electrowin copper from at

least a portion of said first stage lean electrolyte stream without

subjecting said first stage lean electrolyte stream to solvent/

solution extraction.

10. The system of claim 4, wherein said second electrowinning

apparatus is configured to electrowin copper from at

least a portion of said first stage lean electrolyte stream without

subjecting said first stage lean electrolyte stream to sol-

10 vent/solution extraction.

11. A method comprising:

pressure leaching a feed stream comprising a copper-containing

material and an acid at a temperature of from

about 100° C. about 250° C. to yield a product slurry

15 comprising a copper-bearing solution;

electrowinning copper from said copper-bearing solution

in a first electrowinning stage to produce a first stage

lean electrolyte stream;

electrowinning copper from said first stage lean electrolyte

20 stream in a second electrowinning stage to produce a

second stage lean electrolyte stream; and

recycling at least a portion of said first stage lean electrolyte

stream to said pressure leaching.

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