111111111111111111111111111111111111111111111111111111111111111111111111111
US007736487B2
(12) United States Patent
Marsden et al.
(10) Patent No.:
(45) Date of Patent:
US 7,736,487 B2
*Jun.15,2010
(21) Appl. No.: 11/743,034
(73) Assignee: Freeport-McMoran Corporation,
Phoenix, AZ (US)
(54) PROCESS FOR RECOVERY OF COPPER
FROM COPPER-BEARING MATERIAL
USING PRESSURE LEACHING, DIRECT
ELECTROWINNING AND SOLUTION
EXTRACTION
(75) Inventors: John O. Marsden, Paradise Valley, AZ
(US); John C. Wilmot, Anthem, AZ
(US); Christy Green, Morenci, AZ
(US); Wayne W. Hazen, Lakewood, CO
(US); David R. Baughman, Golden, CO
(US)
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(Continued)
FOREIGN PATENT DOCUMENTS
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
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May 1, 2007
This patent is subject to a tenninal disclaimer.
Subject to any disclaimer, the term ofthis
patent is extended or adjusted under 35
U.S.c. 154(b) by 308 days.
(22) Filed:
( *) Notice:
(65) Prior Publication Data AU 0219785 3/1957
Related U.S. Application Data
(63) Continuation-in-part of application No. 10/976,482,
filed on Oct. 29, 2004, now abandoned, which is a
continuation-in-part of application No. 11/163,762,
filed on Oct. 28, 2005, now Pat. No. 7,485,216.
(60) Provisional application No. 601746,122, filed on May
1,2006.
(51) Int. Cl.
C2SC 1/00 (2006.01)
(52) U.S. Cl. 205/580; 423/24; 205/581;
205/582; 205/583
(58) Field of Classification Search 423/24,
423/27; 205/580-583; 241/23; 75/743
See application file for complete search history.
US 2008/0023342 Al Jan. 31, 2008 (Continued)
OTHER PUBLICATIONS
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.
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Non-Final Office Action for U.S. Appl. No. 11/163,762 dated Dec.
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Notice of Allowance for U.S. Appl. No. 11/163,762 dated Jul. 21,
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Notice of Allowance for U.S. Appl. No. 11/163,762 dated Oct. 9,
200S.
(Continued)
Primary Examiner-Steven Bos
(74) Attorney, Agent, or Firm-Snell & Wilmer L.L.P.
(56) References Cited
U.S. PATENT DOCUMENTS
(57) ABSTRACT
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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. In accordance with one aspect
of the process, at least a portion of the residue from the
pressure leaching operation is directed to a heap, stockpile or
other leaching operation.
19 Claims, 4 Drawing Sheets
US 7,736,487 B2
Page 2
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5,902,474 A
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5,989,311 A
5,993,635 A
6,083,730 A
6,146,444 A
6,149,883 A
RE37,251 E
6,319,389 Bl
6,428,604 Bl
6,451,089 Bl
6,503,293 Bl
6,537,440 Bl
6,569,224 B2
6,660,059 B2
6,663,689 B2
6,676,909 B2
6,680,034 B2
6,972,107 B2
7,341,700 B2
7,485,216 B2
2003/0019331 Al
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2005/0109163 Al
2005/0126923 Al
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CL
GB
WO
WO
u.s. Patent Juo.15,2010 Sheet 1 of 4 US 7,736,487 B2
COPPER RECOVERY
(SEE E.G., FIG. 2)
V 101
CONTROLLED,
V 1010A
FINE GRINDING
V10
13.../ IMPURITY REMOVAL
(OPTIONAL) """-- 1015
/102
L~ 1020
119
\ V 103
~105 •
1 J C"- 106
,--126
PRESSURE LEACHING ~1030
V107
1035
ATMOSPHERIC FLASHING /110
123
V108 \ •
j j j I c::=- 1251 109 ;0
122 ~S~1040 124 \ • _y111 / ;4
~ ELECTROLYTE RESIDUE
120 TREATMENT ~1050
TREATMENT
. \ I V 113 1080
• ELECTROLYTE /1060
RECYCLE TANK
/121 /115 Y 1070 116
119 ELECTROWINNING ! ( Cu ) \ "r117 118
! TO ADDITIONAL
119
100
~
FIG. 1
u.s. Patent Juo.15,2010 Sheet 2 of 4 US 7,736,487 B2
11
CONTROLLED, 1010A
FINE GRINDING
- - - - - - - - - - - - - - - - - - - - - ~- - - - - - - - - - - - - - - - - - I I
I 101 I
I I
I I
I
I
I
I
I
I
I
I
I
~ 1010
SIZE CLASSIFICATION 1010B
(OPTIONAL)
I
I
1
: ~2 i :
~102
S 1010C
I
I
- - - - - - - - - - - - - - - - - __ I
1..------1 L
FIG. 1A
u.s. Patent Juo.15,2010 Sheet 3 of 4 US 7,736,487 B2
(FROM FIG. 1)
10~
11 Q-..... I I
- '-.1 I ;202
114 I I I
"\ I I I I ........201
'1 I I V 1 I I I
: : 1- - - -~'----.%.A-T-M-0-S-P-H-E-R..LIC-0-R----'V2020
I ------»
L ~~P_R_E_S_SU_R_E~LE-A-C-H-IN-G~
/204
,-__-L-__---, /""2010 205
SOLVENT/SOLUTION'/ - -J
EXTRACTION r
c-S-O-L-L-V-EN-T-rS-O-L-U-T--'-O, -N--;/2015
~-~
STRIPPING
LEAN
I--~--- ELECTROLYTE
BLEED
ELECTROWINNING
~208
...------Z---_V2030
TO
t-----'--------I
FIG. 1
[/207
( Cu
FIG. 2
FIG 3
Residue Copper vs. Total Acid Addition
160 deg. C, 90 min, P(98) =15 micron
~
7J).
•
~
~
~
~=~
2.0 I i
1.8 ~ I II II i i
~ 1.6 I I I I I I
2'
?....
~Ul
No
.... o
Total Acid Addition, kg/tonne
rFJ =('
D
(..'D...
,j;o,.
o....
,j;o,.
d
rJl
-l
':w..:J
0'1
~
QO
-l =N
500 550 600
• ••
350 400 450
~ 1.4 I I I • I 1 1--
! ~:~1 I I' I · I. · I I cP :2 0.8
~ 0.6 -+--- I I +-- I I I
0:= 0.4 I I I I .. I I -------j
0.2 I I I I I I
0.0 I I I I I I I
300
US 7,736,487 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:
Iyte bleed stream from electrowinning that may be further
processed in a solvent/solution extraction and electrowinning
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) subjecting
the copper-bearing feed stream to controlled fine grind-
10 ing; (iii) pressure leaching the copper-bearing feed stream to
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 electrow-
15 inning operation; (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; and, (vii) directing at least a portion ofthe pressure
leaching residue to a heap, stockpile or other leaching opera-
20 tion.
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.
In accordance with another aspect of an exemplary
embodiment ofthe invention, a bleed stream oflean electrolyte
from the electrowinning stage advantageously removes
at least a portion of the excess acid from the metal recovery
process and also impurities contained therein, thus preventing
30 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
embodiment ofthe invention, excess acid removed in the lean
electrolyte bleed stream may be utilized in other copper
35 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 containing
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
leaching step and provides acid needed for effective leaching
of copper. In this way, the use of recycled acid-containing
45 solution, rather than concentrated sulfuric acid, is economically
advantageous.
In accordance with another aspect of an exemplary
embodiment of the invention, residual solids from the pres50
sure leaching step are applied to heaps (crushed or
uncrushed), run-of-mine dumps, stockpiles, other leaching
operations and/or the like.
These and other advantages ofa process according to vari0us
aspects of the present invention will be apparent to those
55 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
ELECTROWINNINGAND 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 is a continuation-in-part application of, and claims
priority to U.S. patent application Ser. No. 10/976,482,
entitled "Process for recovery ofcopper from copper-bearing
material using medium temperature pressure leaching, direct
electrowinning and solvent/solution extraction" and filed
Oct. 29, 2004 now abandoned: and is a continuation-in-part
of, and claims priority to U.S. patent application Ser. No.
11/163,762, entitled "Process for recovery of copper from
copper-bearing material using pressure leaching, direct electrowinning
and solvent/solution extraction" and filed Oct. 28,
2005 now U.S. Pat. No. 7,485,216: and claims priority to U.S.
Provisional Application Ser. No. 60/746,122, entitled "Process
for recovery of copper from copper-bearing material
using pressure leaching, direct electrowinning and solvent/
solution extraction" and filed May I, 2006; all of which
applications, in their entirety, are hereby incorporated by 25
reference herein.
40
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 temperature
(as will be defined hereinbelow) pressure leaching, 60
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
use of an intermediate solvent/solution extraction step. Fur- 65
ther, at least a portion ofthe impurities and excess acid in the
process stream are removed through the use ofa lean electroUS
7,736,487 B2
3 4
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
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.
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,
15 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
20 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
25 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-
30 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
35 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
40 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-
45 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
50 area of the material to be processed.
For example, metal-bearing material 101 may be prepared
for metal recovery processing by controlled fine grinding.
Preferably, it is advantageous not only to reduce the size ofthe
metal-bearing material particles in the process stream, but
55 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 inven-
60 tion, 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. Pref-
65 erably, grinding in accordance with this aspect of the present
invention proceeds in a staged or closed-circuit manner. That
is, preferably the coarsest particles of metal-bearing material
DETAILED DESCRIPTION OF EXEMPLARY
EMBODIMENTS
FIG. 1 illustrates a flow diagram of a copper recovery
process in accordance with one exemplary embodiment ofthe
present invention;
FIG. 1A 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,
FIG. 3 is a graph plotting copper concentration in the
pressure leaching residue as a function of acid addition in 10
accordance with various aspects of an exemplary embodiment
of the invention.
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; (vi)
recycling at least a portion ofthe lean electrolyte stream to the
pressure leaching step; and, (vii) directing at least a portion of
the pressure leaching residue to a heap or other leaching
operation.
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, platinum
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
(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
present invention, metal-bearing material 101 may comprise
US 7,736,487 B2
5 6
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.
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
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
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 material
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
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
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
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
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
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
this aspect ofthe invention may be particularly advantageous
in that it may enable contaminants from the unrefined copper-
55 containing 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 uti-
1ized 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
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 10
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. 15
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 20
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 separa- 25
tion 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 30
leaching operation 1030 to optimize slurry density.
Grinding step 1010 preferably results in material 110 being
finely gronnd, 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 35
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 40
material 110 being finely gronnd 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 45
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 50
passing about 25 microns is preferable, and more preferably,
the metal-bearing material stream has a particle size distribution
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 marmer, 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 60
include the Isamill developed jointly by Mount Isa Mines
(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 Colo- 65
rado sand, available from Oglebay Norton Industrial Sands
Inc., Colorado Springs, Colo. However, any grinding medium
US 7,736,487 B2
(1)
(2)
4CuFeS2+1702+4H20~2Fe203+4Cu2++8H++
8soi-
8
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
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:
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
30 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
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
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 200° C. to about 210° 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
7
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 10
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- 15
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 20
electrolyte stream 108 in a suitable processing vessel. For
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 25
also be used. Preferably, precipitation is carried out such that
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,
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 nec- 35
essary, can be effectuated through any conventional means,
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 40
copper separation stage 1010 to provide the heat desired to
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 typi- 45
cally ranges from about thirty (30) minutes to about 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 of copper
have been achieved in processing vessels maintained at about 50
90° C. for about 4 hours.
Referring to FIG. 1, after metal-bearing material stream
103 has been suitably prepared for processing by controlled
fine grinding, liquid addition, and, optionally, other physical
and/or chemical conditioning processes, it is subjected to a 55
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 60
operating at a temperature in the range of about 140° C. to
about 230° C. In accordance with one embodiment, pressure
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. 65
In accordance with another embodiment, pressure leaching is
conducted at temperatures above 180° c., and preferably in
US 7,736,487 B2
9
(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(l)~Fe203(S)+3H2S04(aq)
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
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
10
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
process.
In accordance with various aspects of the present invention,
the pressure leaching process occurs in a manner suitably
designed to promote substantially complete solubiliza-
10 tion 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
15 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 of
medium temperature pressure leaching, the total operating
pressure (including oxygen partial pressure) in the pressure
20 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.
The residence time for pressure leaching can vary, depend-
25 ing on factors such as, for example, the characteristics of the
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
30 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.
Control ofthe pressure leaching process, including control
of the temperature in the pressure leaching vessel, may be
35 accomplished by any conventional or hereafter devised
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
40 leaching vessel is maintained at a temperature in the range of
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
45 in the range ofabout 1800 C. to about 2200 C. As such, a wide
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
50 leaching is generally more than that needed to heat the feed
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 vessel
during pressure leaching. In accordance with one aspect of
55 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
60 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
65 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
US 7,736,487 B2
11 12
containing 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 values
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
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
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 number
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,
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
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
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
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
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
suitably treated, for example, by use of a venturi scrubber
wherein water may be recovered and hazardous materials
55 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, connter-current
decantation (CCD) circuits, thickeners, and the like. As illusdensity
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, 10
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 15
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 com- 20
binations 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 25
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 30
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 35
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 40
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 45
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 50
copper recovery, hematite, gangue, and the like-that may
otherwise tend to partially or completely encapsulate the
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 60
may be desirable for economic reasons, and using a seeding
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 65
hematite, is either present in the metal-bearing material or is
produced as a by-product, introduction of recycled hematite13
US 7,736,487 B2
14
trated 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 10
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 15
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, 20
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 25
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 30
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 35
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 40
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 by- 45
products, 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 por- 50
tion of the slurry-the desired copper-containing solutionis
separated from the solid portion of the slurry-the nndesired
residue.
Referring still to FIG. 1, in the illustrated embodiment of
the invention, flashed product slurry 108 is directed to a 55
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 embodiment
ofthe invention, a CCD circuit uses conventional coun- 60
tercurrent 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
residue disposal. Preferably, large wash ratios and/or several 65
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,
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,
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
remove other nndesirable species from the process stream.
One such suitable chemical reagent is POLYOXTMWSR-30I,
available from Dow Chemical.
Depending on its composition, residue stream 110 from
liquid/solid separation stage 1040 may be neutralized,
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
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
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
increase the expense of the precious metal recovery operation.
As mentioned above, it is therefore preferable to use a
large amonnt 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
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
further condition and/or refine process stream 111 from solidliquid
separation stage 1040, such as, for example, through
filtration, thickening, connter-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,
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 accordance
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.
In accordance with one embodiment of the present invention,
and with momentary reference to FIG. 2, residue stream
108, residue stream 110, and/or residue stream 114 can be
used in augmenting a heap or dump leaching process, the PLS
of which may be processed in connection with respective
solution extraction step 2010, stripping step 2015 and electrowinning
step 2030, as will hereinafter be described. Copper-
containing solution stream 113 from electrolyte treatment
stage 1050 is then preferably subjected to copper
recovery; in accordance with one aspect of an exemplary
US 7,736,487 B2
15 16
electrolyte stream 117 (lean electrolyte recycle stream 119 in
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-especially maintenance of a substantially constant
copper composition in the stream---can 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
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
50 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 nnit 1070 (FIG. 1) is sent to a solvent/
55 solution extraction stage 2010. In accordance with one
embodiment of the invention, solvent/solution extraction
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
60 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.
65 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
Cathode half-reaction: Cu2++2e---""CUO
2CUS04+2H2--<>2Cu'+2H2S04+02
Anode half-reaction: 2H20--<>4H++02+4e-
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
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 of the invention, a portion oflean
embodiment, however, a portion of copper-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 electrowinning circuit
1070, as will be discussed in greater detail below. Coppercontaining
solution stream 113, is preferably blended with a 10
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
electrowinning circuit 1070.
With continued reference to FIG. 1, copper from the prod- 15
uct 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
proper conditioning of a copper-containing solution, a high
quality, uniformly-plated cathode copper product 116 may be 20
realized without subjecting the copper-containing solution to
a solvent/solution extraction 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 25
and other metal values, any ofwhich may be suitable for use
in accordance with the present invention, provided the requisite
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 30
useful in connection with various embodiments ofthe invention
may comprise an electrowinning circuit, constructed and
configured to operate in a conventional marmer. The electrowinning
circuit may include electrowinning cells constructed
as elongated rectangular tanks containing suspended 35
parallel flat cathodes ofcopper alternating with flat anodes of
lead alloy, arranged perpendicular to the long axis ofthe tank.
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 40
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. Other electrolyte distribution
and flow profiles may be used.
The primary electrochemical reactions for electrowinning 45
of copper from acid solution is believed to be as follows:
US 7,736,487 B2
17 18
31.6
30.5
34.2
15
160
90
450
10
200
290
Chalcopyrite
TABLE I
Example I
Concentrate Type
Concentrate Analyses, %
FEED
Cli
Fe
S
Grind Size. P9S, )Jill
PRESSURE LEACHING
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
45 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.
tially depleted ofcopper. At least a portion ofthe loaded strip
solution aqueous phase (stream 206) is advanced to an electrowinning
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.
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
15 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
a resultant product stream suitable for electrowinning in an
20 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
25 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
removed from the process, for example, the electrowinning
30 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
impact production efficiencies and product (e.g. copper cath-
35 ode) 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
intended to exemplifY various aspects of the invention, and
40 are not intended to limit the scope of the claimed invention.
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
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 10
stage 2010 as process stream 204.
As discussed hereinabove, and with further reference to
FIG. 2, leach operation 2020 may be augmented through the
addition of pressure leaching residue. In accordance with
various exemplary embodiments ofthis aspect of the present
invention, all or part ofthe pressure leaching residue may be
agglomerated with ore material, or may be added to the heap
feed material before, during, and/or after agglomeration, or
may be added to the ore or other leach material used in leach
operation 2020.
Notwithstanding the foregoing, it should be appreciated
that residue addition to leach operation 2020 may be carried
out in any now known or hereafter devised method. As such,
the pressure leaching residue may be pretreated, processed, or
otherwise handled in any suitable manner, for example, by
using flotation to upgrade the sulfur content of the residue.
Residue addition is believed to enhance the performance
parameters ofleach operation 2020.
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
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, followed
by a stripping operation. In the extraction stage, pro- 50
cess 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 55
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
operations to be reloaded with copper from the ore in the 60
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
stripping operation, the organic stream is contacted with a 65
strongly acidic electrolyte. This acidic solution "strips" the
copper from the extractant, leaving the organic phase substanUS
7,736,487 B2
19 20
65
and pressure to yield a product slurry comprising a copper-
bearing 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
from said conditioning step to yield cathode copper
and a copper-bearing lean electrolyte stream;
(f) recycling a portion ofsaid lean electrolyte stream to said
pressure leaching step;
(g) treating at least a portion of said lean electrolyte stream
from said electrowinning step using solvent/solution
extraction techniques; and
(h) directing at least a portion of a residue from said pressure
leaching step to a heap, stockpile or other leaching
operation.
2. The method ofclaim 1, wherein said step (h) ofdirecting
at least a portion of a residue from said pressure leaching
stage to a heap, stockpile or other leaching operation com20
prises the transfer of a residue comprising a sulfur-bearing
material to such operation.
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 chalcopy25
rite, 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 mate30
rial and a solution stream comprising copper and acid.
5. The method ofclaim 1, 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 such
that substantially all ofthe particles in said feed stream react
35 substantially completely during pressure leaching.
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
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
45 least a portion of said feed stream to controlled fine grinding
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
50 comprises reducing the particle size of said feed stream to a
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
55 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
60 about 100 psi to about 750 psi.
12. The method ofclaim 1, wherein said step (h) comprises
directing said residue by agglomerating said residue with ore
material to be used in said heap, stockpile or other leaching
operation.
13. 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
15
10
10.3
20
7.4
1.5
35.9
96.6
69
27
34
3.3
135
88
84
102
4.6
11.6
308
50
3.0
10
334
TABLE I-continued
Current Density, Alm2
Cell Temperature, 0 c.
Specific Flow, L/min-m2
FC-lllO (Mist Control), gal/106 lb Cu
PD-4201 (Leveling Agent), gitonne Cu
Lean Electrolyte, giL
Cu
Fe
ell Extraction, %
Sulfide Oxidized to Elemental Sulfur, %
Sulfide Oxidation to Sulfate, %
ELECTROWINNING
Feed Solids to Compartment 1, %
Weight Loss, %
Discharge Solids, %
Discharge Solution, giL
Cu
Fe
H2S04
Discharge Solids, %
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 electrow- 40
inning 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
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 tenns of exemplary embodiments, such aspects of the
invention may be achieved through any number of suitable
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) pressure leaching at least a portion of said feed stream
in an oxidizing environment at an elevated temperature
21
US 7,736,487 B2
22
group conslstmg of lignin derivatives, orthophenylene
diamine, alkyl sulfonates, and mixtures thereof.
14. The method ofclaim 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.
15. The method ofclaim 14, wherein said conditioning step
further comprises blending at least a portion of said copperbearing
solution with at least a portion ofone or more copperbearing
streams to achieve a copper concentration of from 10
about 15 grams/liter to about 80 grams/liter in said copperbearing
solution.
16. The method of claim 14, wherein a portion of said
copper-bearing solution from said conditioning step is
recycled to said pressure leaching step.
17. The method of claim 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.
18. 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 said pressure leaching step.
19. The method of claim 1, further comprising the step of
(i) using a portion of said lean electrolyte stream from said
electrowinning step in a leaching operation.
* * * * *