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US007517384B2
(12) United States Patent
Marsden et al.
(10) Patent No.:
(45) Date of Patent:
US 7,517,384 B2
*Apr. 14,2009
FOREIGN PATENT DOCUMENTS
U.S. PATENT DOCUMENTS
U.S. Cl. 75/739; 75/743; 75/744
Field of Classification Search 75/739,
75/743,744
See application file for complete search history.
References Cited
(54) METHOD FOR IMPROVING METALS
RECOVERY USING HIGH TEMPERATURE
PRESSURE LEACHING
(75) Inventors: John O. Marsden, Phoenix, AZ (US);
Robert E. Brewer, Park City, UT (US);
Joanna M. Robertson, Thatcher, AZ
(US); David R. Baughman, Golden, CO
(US); Philip Thompson, West Val1ey
City, UT (US); Wayne W. Hazen,
Lakewood, CA (US); Roland Schmidt,
Golden, CO (US)
(73) Assignee: Phelps Dodge Corporation, Phoenix,
AZ (US)
(52)
(58)
(56)
4,304,644 A
6,626,979 B2 *
6,660,059 B2 *
6,746,512 B1 *
6,893,482 B2 *
7,125,436 B2 *
12/1981 Victorovich
9/2003 Marsden et al. 75/739
12/2003 Ji et al. 75/744
6/2004 Shaw.......................... 75/743
5/2005 Marsden et al. 75/739
10/2006 Marsden et al. 75/724
(21) Appl. No.: 11/551,907
* cited by examiner
Primary Examiner-Roy King
Assistant Examiner-Tima M McGuthry-Banks
(74) Attorney, Agent, or Firm-Snel1 & Wilmer, L.L.P.
ABSTRACT
( *) Notice: Subject to any disclaimer, the term ofthis
patent is extended or adjusted under 35
U.S.c. 154(b) by 32 days.
This patent is subject to a tenninal disclaimer.
WO W09707248 D9
(57)
2/1997
(51) Int. Cl.
C22B 3/04 (2006.01)
Prior Publication Data
Filed: Oct. 23, 2006
The present invention is directed to a system for recovering
metal values from metal-bearing materials. During a reactive
process, a seeding agent is introduced to provide a nucleation
site for the crystal1ization and/or growth of solid species
which otherwise tend to passivate the reactive process or
otherwise encapsulate the metal value, thereby reducing the
amount ofdesired metal values partial1y or completely encapsulated
by such material. The seeding agent may be generated
in a number ofways, including the recycling ofresidue or the
introduction of foreign substances. Systems embodying
aspects ofthe present invention may be beneficial for recovering
a variety of metals such as copper, gold, silver, nickel,
cobalt, molybdenum, zinc, rhenium, uranium, rare earth metals,
and platinum group metals from any metal-bearing material,
such as ores and concentrates.
19 Claims, 2 Drawing Sheets
US 2007/0039420 Al Feb. 22,2007
Related U.S. Application Data
Continuation of application No. 10/907,324, filed on
Mar. 29, 2005, now Pat. No.7, 125,436, which is a
continuation of application No. 10/650,167, filed on
Aug. 27, 2003, now Pat. No. 6,893,482, which is a
continuation of application No. 10/238,088, filed on
Sep. 9, 2002, now Pat. No. 6,626,979, which is a continuation
of application No. 091912,967, filed on luI.
25, 2001, now Pat. No. 6,451,088.
(22)
(65)
(63)
, METAL..BEARING MATERIAL
'-... PROCESSING
'"" METAL RECOVERY
4
2
6
u.s. Patent Apr. 14,2009 Sheet 1 of2 US 7,517,384 B2
"- METAL·BEARING MATERIAL
!
"-.. PROCESSING
1
~ METAL RECOVERY
4
2
6
FIG. 1
2
METAl·6EARING MATERIAL
6
4
5
PRESSURE LEACHING
./'8
16
ATMOSPHERIC FLASHING
24
22
20 LIQUID-SOLID PHASE SEPARATION TO FIG. 3
26
28
29
32
30
SOLVENT EXTRACTION
34
SOLVENT STRIPPING
42 48
ELECTROLYTE RECYCLE TANK
50
-46
ELECTROWINN1NG
FIG. 2
u.s. Patent
10
Apr. 14,2009 Sheet 2 of2
10
US 7,517,384 B2
20
/ 22
lIQUID-SOUD )
PHASE J...--L-----.............---,
SEPARATION
NEUTRALIZATION & ./ 60
pH ADJUSTMENT
HOT LIME SOil V 62
(OPTIONAL)
1
PRECIOUS METALS ~ 64
CYANIDE LEACHING
PREC10US METALS V 66
RECOVERY
CYANIDE
DESTRUCTION
(LIQUID) LIQUID-SOLID PHASE V 68
SEPARAT10N (OPTIONAL)
~------.---~------~••I
I
II
I
I
I
~-----------------
TAILINGS 72
DISPOSAL
FIG. 3
US 7,517,384 B2
1
METHOD FOR IMPROVING METALS
RECOVERY USING HIGH TEMPERATURE
PRESSURE LEACHING
2
ventional processing techniques and that enhances the recovery
ofprecious metals from metal-bearing materials would be
advantageous.
CROSS-REFERENCE TO RELATED
APPLICATIONS
SUMMARY OF THE INVENTION
BRIEF DESCRIPTION OF THE DRAWINGS
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 and claims when considered in
connection with the drawing figures, wherein like numerals
denote like elements and wherein:
FIG. 1 illustrates a flow diagram of a metal recovery process
in accordance with an exemplary embodiment of the
present invention;
FIG. 2 illustrates a flow diagram of an exemplary metal
recovery process in accordance with an alternative embodiment
of the present invention; and
35
While the way in which the present invention addresses the
deficiencies and disadvantages of the prior art is described in
10 greater detail below, in general, according to various aspects
ofthe present invention, a process for recovering copper and
other metal values from a metal-bearing material includes
various reactive and recovery processes. In a preferred aspect
of the invention, a seeding agent is introduced to the metal
15 recovery process, most preferably, during a pressure leaching
process.
In accordance with an exemplary embodiment of the
present invention, a process for recovering metal from a
metal-bearing material generally includes the steps of: (i)
20 subjecting a concentrate containing a metal value to a pressure
leaching process, wherein the pressure leaching vessel is
seeded with a seeding agent; and (ii) extracting the metal
value from the product of the reactive process. In one aspect
25 of an alternative embodiment of the invention, the seeding
agent may be recycled residue that is introduced to the pressure
leaching vessel. In general, the seeding agent is selected
to enable the formation of a nucleation site for the crystallization
and/or growth of solid species derived from the solu-
30 tion in which the reactive process occurs. In a further aspect of
the present invention, other foreign material may be used as a
seeding agent during pressure leaching. In an additional
aspect of the present invention, a combination of seeding
agents may be used during pressure leaching.
In yet another embodiment ofthe present invention, copper
is recovered from a metal-bearing material. The copper-containing
material is subjected to high temperature pressure
leaching in a pressure leaching vessel, wherein a seeding
agent is introduced into the pressure leaching vessel, which
40 preferably is a multi-compartment pressure leaching vessel.
The pressure leaching product may then undergo one or more
subsequent conditioning and/or refining processes such that
copper and/or other metal values may be recovered from the
45 pressure leaching product or products.
The advantages of a process according to the various
aspects of the present invention will be apparent to those
skilled in the art upon reading and understanding the following
detailed description with reference to the accompanying
50 drawing figures.
FIELD OF INVENTION
BACKGROUND OF THE INVENTION
This application is a continuation of U.S. patent application
Ser. No. 10/907,324, filed on Mar. 29, 2005 and issued as
U.S. Pat. No. 7,125,436 on Oct. 24, 2006, which is a continuation
ofU.S. patent application Ser. No. 10/650,167, filed on
Aug. 27, 2003 and issued as U.S. Pat. No. 6,893,482 on May
17,2005, which is a continuation of U.S. patent application
Ser. No. 10/238,088, filed on Sep. 9, 2002 and issued as U.S.
Pat. No. 6,626,979 on Sep. 30, 2003, which is a continuation
of U.S. patent application Ser. No. 091912,967, filed on luI.
25,2001 and issued as U.S. Pat. No. 6,451,088 on Sep. 17,
2002, the disclosures and contents ofwhich are hereby incorporated
by reference.
This process relates generally to a process for recovering
metals from metal-bearing materials, and more specifically, a
process for recovering copper and other metals through high
temperature pressure leaching in a pressure leaching vessel
wherein a seeding agent is added to the pressure leaching
vessel during the oxidation process.
This process relates generally to a process for recovering
metals from metal-bearing materials, and more specifically, a
process for recovering copper and other metals through high
temperature pressure leaching in a pressure leaching vessel
wherein a seeding agent is added to the pressure leaching
vessel during the oxidation process.
The recovery of copper from copper sulfide concentrates
using pressure leaching has proven to be a potentially economically
attractive alternative to smelting. Pressure leaching
operations generally produce less fugitive emissions than
smelting operations, and thus, environmental benefits may be
realized. Further, pressure leaching circuits may be more
cost-effectively constructed on-site at a concentrator, eliminating
the expense associated with concentrate transportation
that smelting operations may require. Further, any by-product
acid produced in the pressure leaching circuit may be used in
adjacent heap leaching operations, thus offsetting the costs
associated with purchased acid.
Onthe other hand, the application ofpressure leaching may 55
result in unacceptably high copper and precious metal losses.
A significant cause of such metal losses has been identified
when metal values become occluded by materials present in
the pressure leaching vessel, such as, for example, hematite
60 and/or other materials, rendering these metal values unavailable
to subsequent processing, which results in these metal
values being lost.
An effective and efficient method to recover copper from
copper-containing materials, especially copper from copper 65
sulfides such as chalcopyrite and chalcocite, that enables high
copper recovery to be achieved at a reduced cost over conUS
7,517,384 B2
suitably permits metal-bearing material to be prepared for
metal recovery may be utilized within the scope ofthe present
invention.
4
Processing step 4 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. Preferably, the
pressure leaching vessel used in processing step 4 is an agitated,
multi-compartment pressure leaching vessel. However,
10 it should be appreciated that any pressure leaching vessel that
suitably permits metal-bearing material to be prepared for
metal recovery may be utilized within the scope ofthe present
invention.
In accordance with a preferred aspect ofthe present invention,
a seeding agent is introduced to the reactive process
during processing step 4, prior to metal value recovery. While
a seeding agent may be utilized, care should be taken to
ensure that it does not negatively impact the overall metal
recovery process. A suitable seeding agent preferably comprises
any material capable of forming a nucleation site for
the crystallization and/or growth of solid species. For
example, in accordance with various aspects of the present
invention, as discussed hereinabove, a metal to be recovered
is liberated in connection with the reactive process. The
present inventors have found that often materials that precipitate
or crystallize from solution tend to passivate the reactive
process and/or encapsulate a metal or metals to be recovered.
Through use ofthe inventive seeding agent, such species are
urged to crystallize, precipitate or otherwise form at or in
proximity to the seeding agent, instead of the metal value,
thus leaving the metal value exposed and amenable to subsequent
leaching or other recovery.
Accordingly, the seeding agent may be any particle which
acts as a site for particle accumulation and/or precipitation,
and may originate from recycled materials from other stages
of the metal recovery process or may be provided by the
addition of substances that are foreign to the metal recovery
process. In some cases, the seeding agent comprises any
material that promotes crystallization, precipitation, and/or
growth ofunwanted materials-for example in the preferred
case ofcopper 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. As is known, in precipitation, seed particles
tend to grow in size through deposition of materials from
solution. Accordingly, non-preferential precipitation onto
other (i.e., non-seed) material surfaces may also occur.
One source ofsuitable seeding agents useful in accordance
with various aspects of the present invention 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
55 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
hematite, is either present in the metal-bearing material or is
produced as a by-product, introduction ofrecycled hematitecontaining
residue from previous pressure leaching processes
likely will tend to provide newly formed or liberated hematite
a preferential nucleation site. In the absence ofthis nucleation
site, unreactive particles may occlude the desired metal values
to solubilization by precipitating on the surface of the
metal values, rendering the metal values unrecoverable.
DETAILED DESCRIPTION
3
FIG. 3 illustrates a flow diagram of further aspects of the
exemplary metal recovery process of FIG. 2.
The present invention relates to a metal recovery process
that implements pressure leaching vessel seeding. Generally,
a material bearing a metal value is subjected to a pressure
leaching process wherein a seeding agent is utilized. Metal
values may then be recovered and processed in accordance
with various recovery processes.
Referring to FIG. 1, in accordance with various aspects of
the present invention, a metal-bearing material 2 is provided
for processing. Metal-bearing material 2 may be an ore, a
concentrate, or any other material from which metal values 15
may be recovered. Metal values such as, for example, copper,
gold, silver, zinc, 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. 20
Various aspects and embodiments of the present invention,
however, prove especially advantageous in connection with
the recovery of copper and gold from gold-bearing copper
sulfide ores, such as, for example, gold-bearing chalcopyrite
(CuFeS2 ), chalcocite (Cu2 S), bornite (CusFeS4 ), and covel- 25
lite (CuS). Thus, metal-bearing material 2 preferably is a
gold-bearing copper ore or concentrate, and most preferably,
is a gold-bearing copper sulfide ore or concentrate.
Metal-bearing material 2 may be prepared for pressure
leaching processing in any mannerthat enables the conditions 30
of metal-bearing material 2-such as, for example, particle
size, composition, and component concentration-to be suitable
for the chosen processing method, as such conditions
may affect the overall effectiveness and efficiency ofprocessing
operations. Desired composition and component concen- 35
tration 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 specifications.
For example, metal-bearing material 2 may undergo 40
comminution, flotation, blending, and/or slurry formation, as
well as chemical and/or physical conditioning.
Referring again to FIG. 1, after metal-bearing material 2
has been suitably prepared for processing, it is subjected to a
processing step 4. Processing step 4 may be any suitable 45
process or reaction that puts a metal value in metal-bearing
material 2 in a condition such that it may be subjected to later
recovery steps. For example, exemplary suitable processes
include reactive processes which tend to liberate a desired
metal value in the metal bearing material 2 from the metal- 50
bearing material 2. In accordance with one embodiment ofthe
present invention, processing step 4 comprises pressure
leaching, either at medium temperatures (e.g., from about
1200 C. to about 1900 C.) or high temperatures (e.g., greater
than about 2000 C.).
In accordance with another embodiment of the invention,
processing step 4 comprises a high temperature pressure
leaching process operating at a temperature in the range of
about 1700 C. to about 235 0 C., more preferably from about
2000 C. to about 2300 c., and optimally above about 2000 C. 60
Processing step 4 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. Preferably, the
pressure leaching vessel used in processing step 4 is an agi- 65
tated, multi-compartment pressure leaching vessel. However,
it should be appreciated that any pressure leaching vessel that
US 7,517,384 B2
5 6
the temperature and pressure of the product slurry. A preferred
method of so adjusting the temperature and pressure
characteristics ofthe copper-containing product slurry from a
high temperature pressure leaching stage is atmospheric
flashing.
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, the
product slurry may be further conditioned in preparation for
10 later metal-value recovery steps. For example, one or more
solid-liquid phase separation stages may be used to separate
solubilized metal solution from solid particles. This may be
accomplished in any conventional manner, including use of
filtration systems, counter-current decantation (CCD) cir-
15 cuits, thickeners, centrifuges, and the like. A variety of factors,
such as the process material balance, enviroumental
regulations, residue composition, economic considerations,
and the like, may affect the decision whether to employ a
CCD circuit, a thickener, a filter, or any other suitable device
20 in a solid-liquid separation apparatus. However, it should be
appreciated that any technique of conditioning the product
slurry for later metal value recovery is within he scope ofthe
present invention.
As further discussed hereinbelow, the separated solids may
25 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,
nickel, cobalt, molybdenum, zinc, rhenium, uranium, rare
earth metals, and the like. Alternatively, the separated solids
30 may be used for seeding purposes during reactive processing
as described above, or may be subject to disposal.
The liquid separated from a liquid-solid separation apparatus
may also undergo a series of conditioning steps to prepare
the metal values solubilized therein for metal recovery.
35 For example, the separated liquid may undergo various
reagent additions and/or solvent extraction stages to put the
metal values in a state such that the metal values are susceptible
to metal recovery techniques. Further, subsequent conditioning
and/or processing steps may be undertaken such
40 that recovery rates are as efficient as possible.
After any desired preparation steps, the pressure leaching
product stream may undergo the desired metal recovery step.
The metal value recovery method may include any suitable
45 conventional method of removing the desired metal values
from solutions, such as, for example, electrowinning, precipitation'
solvent extraction, cyanidation, ion exchange, and/or
ion flotation, and preferably results in a relatively pure metal
product.
In an exemplary embodiment ofthe present invention illustrated
in FIG. 2, a copper-containing feed stream 4 containing
a copper-containing material 2 is provided for metal value
recovery. The copper in copper-containing material 2 may be
in any fonn from which copper may be extracted, such as
55 copper oxide or copper sulfide, for example chalcopyrite
(CuFeS2 ), chalcocite (Cu2 S), bornite (CusFeS4 ), and covellite
(CuS). Copper-containing material 2 also may include
any number of a variety of other metals, such as gold, silver,
platinum group metals, zinc, nickel, molybdenum, cobalt,
60 rare earth metals, rhenium, uranium, and/or mixtures thereof.
In accordance with one embodiment of the present invention,
feed stream 4 is combined with a liquid 6, which may
comprise water, to fonn a feed slurry 5. Feed slurry 5 is then
subjected to a pressure leaching step 10. Alternatively, feed
65 stream 4 may be directly fed into a pressure leaching device
(step 10), such as a pressure leaching vessel, together with
other feed streams, namely feed stream 6.
Therefore, introducing a seeding agent to prevent such occlusion
may assist in providing better metal recovery.
Another source of suitable seeding agents useful in accordance
with various aspects ofthe present invention are other
by-products of the recovery process. For example, in cases
where the metal-bearing material selected for use in connection
with the recovery process of the present invention comprises
multiple metal values, for example, copper, gold, and/
or silver, it may be desirable to recover the metals in
sequential recovery steps. For example, if copper is initially
recovered through a pressure leaching process, gold and silver
may be thereafter recovered, for example, through the use
of cyanide leaching. In such a case, the cyanide-attenuated
cyanide leach tailings may suitably be used as a seeding agent
in accordance with the present invention.
A seeding agent suitable in accordance with a further
aspect of the present invention may also be a material that is
not a by-product of any reactive processing. For example,
particles that are foreign to the recovery process, such as
hematite, sand, silica sand, clays, and/orjarositemay be used.
Still further, generally unreactive particulate materials such
as, for example, low grade concentrate, tailings, or intennediate
product streams from mineral processing activities, may
be added to the pressure leaching vessel. It should be appreciated,
however, that in accordance with various aspects ofthe
present invention, any material that is capable of fonning a
nucleation site for the crystallization and/or growth of solid
species is within the scope of the invention.
In accordance with still further aspects of the present
invention, the seeding agent may be suitably selected and
varied during operation ofa continuous recovery process. For
example, again for purposes of illustration only, in cases
where the metal-bearing material selected contains copper
and other precious metals, such as gold and/or silver, the
seeding material initially may be a generally unreactive additive,
for example, hematite, and thereafter processing byproducts,
such as, for example solid-liquid separation residue,
cyanide-attenuated cyanide leach tailings, and the like,
may be recycled to the reactive process and serve as the
seeding agent during continued operation of the recovery
process.
Subsequent to metal-bearing material 2 undergoing the
reactive processing of step 4, the metal values that have been
made available by the reactive process may undergo various
recovery processes. Referring again to FIG. 1, recovery process
6 may be any process for recovering metal values, and
may include any number ofpreparatory or conditioning steps.
For example, a metal-bearing solution may be prepared and
conditioned for metal recovery through one or more chemical
and/or physical processing steps. The metal-bearing solution 50
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. Generally, a properly conditioned metal-bearing solution
will contain a relatively high concentration of soluble
metal, for example, copper ions and sulfate in solution and
preferably will contain few impurities. Moreover, the conditions
of the metal-bearing solution preferably are kept substantially
constant to enhance the quality and unifonnity of
the metal product ultimately recovered.
In one aspect of a preferred embodiment of the present
invention, conditioning of a copper-containing solution for
copper recovery in an electrowinning circuit begins by adjusting
certain physical parameters ofthe product slurry from the
reactive processing step. In a preferred aspect ofthis embodiment
of the invention, wherein the reactive processing step is
high temperature pressure leaching, it is desirable to reduce
7
US 7,517,384 B2
8
In one embodiment (not shown in FIG. 2), copper-containing
material feed stream 4 is prepared for pressure leaching by
comminuting a copper-containing material and subjecting it
to flotation. In this case, feed stream 4 is combined with a
liquid, preferably water, to form feed slurry 5, is subjected to
pressure leaching (step 10 in FIG. 2). The combination of
liquid with feed stream 4 can be effectuated 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. The combined material may then be subjected
to a flotation processing step (not shown), and the flotation
product thereafter may be filtered, air dried, and repulped
before being subjected to pressure leaching.
With continued reference to FIG. 2, feed slurry 5 is suitably
introduced to a pressure leaching vessel to undergo high
temperature pressure leaching; as such, the pressure leaching
vessel preferably comprises a sealed, multi-compartment
pressure leaching vessel 10. Feed slurry 5 may have a solid
particle size on the order of less than about 100 microns,
preferably ranging from about 45 to about 60 microns. More
preferably, the solid particle size of feed slurry 5 is suitably
dimensioned such that the size distribution of no more than
about 20% ofthe concentrated copper-containing materials is
larger than about 60 microns. In accordance with a preferred
aspect of this embodiment, feed slurry 5 has a preferred
solid-liquid ratio ranging from about 5 percent to about 50
percent solids by weight, and preferably from about 10 percent
to about 35 percent solids by weight.
Any agent capable of assisting in the solubilization of the
metal value to be recovered (e.g., copper), such as, for
example, sulfuric acid, may be provided during the pressure
leaching process in a number of ways. For example, such
acids may be provided in a cooling stream provided by the
recycle ofthe raffinate solution 32 from the solvent extraction
step 30 (before or after solubilization, see FIG. 3), and/or the
recycle of a portion of the liquid phase of the product slurry
18, and/or by the production during pressure leaching of a
sulfuric acid from the oxidation ofthe sulfide minerals in the
feed slurry. However, it should be appreciated that any
method ofproviding for the solubilization ofcopper is within
the scope of the present invention.
In accordance with one aspect of this exemplary embodiment,
the high temperature pressure leaching process in pressure
leaching vessel 10 preferably occurs in a manner suitably
selected to promote the solubilization ofthe metal value to be
recovered (e.g., copper). Various parameters may influence
the high temperature pressure leaching process. For example,
during pressure leaching, it may be desirable to introduce
materials to enhance the pressure leaching process. In accordance
with one aspect of the present invention, during pressure
leaching in the pressure leaching vessel, sufficient oxygen
14 may be injected into the vessel to maintain an oxygen
partial pressure from about 50 to about 200 psi, preferably
from about 75 to about 150 psi, and most preferably from
about 100 to about 125 psi. Furthermore, due to the nature of
high temperature pressure leaching, the total operating pressure
in the pressure leaching vessel is generally superatnospheric,
preferably from about 250 to about 750 psi, more
preferably from about 300 to about 700 psi, and most preferably
from about 400 to about 600 psi.
The residence time for the high temperature pressure
leaching process can vary, depending on factors such as, for
example, the characteristics ofthe metal-bearing material and
the operating pressure and temperature ofthe reactor. In one
aspect of the invention, the residence time for the high temperature
pressure leaching process ranges from about 30 to
about 120 minutes.
Control ofthe pressure leaching process, including control
of the temperature in pressure leaching vessel 10, may be
accomplished by any conventional or hereafter devised
method. For example, in accordance with one aspect of the
invention, the temperature of the pressure leaching vessel 10
is maintained at from about 2000 C. to about 2350 c., and
more preferably from about 2150 C. to about 2300 C. Due to
the exothermic nature of pressure leaching of many metal
sulfides, the heat generated by high temperature pressure
10 leaching is generally more than that needed to heat feed slurry
5 to the desired operating temperature. Thus, in order to
maintain preferable feed slurry temperature, a cooling liquid
may be contacted with the feed slurry during pressure leaching.
In accordance with one aspect of this embodiment ofthe
15 present invention, a cooling liquid is preferably contacted
with the feed stream in pressure leaching vessel 10 during
pressure leaching. Cooling liquid may comprise make-up
water, but can be any suitable cooling fluid from within the
process or from an outside source, such as recycled liquid
20 phase from the product slurry, neutralized raffinate solution
32, or a mixture of cooling fluids. Cooling liquid may be
introduced into pressure leaching vessel 10 through the same
inlet as feed slurry, or alternatively in any manner that effectuates
cooling offeed slurry 5. The amount of cooling liquid
25 added to feed slurry 5 during pressure leaching may vary
according to the amount of sulfide minerals in and the pulp
density ofthe feed slurry 5, as well as other parameters ofthe
pressure leaching process. In a preferred aspect of this
embodiment of the invention, a sufficient amount of cooling
30 liquid is added to pressure leaching vessell0 to yield a solids
content in product slurry 18 on the order of less than about
50% solids by weight, and more preferably ranging from
about 3 to about 35% solids by weight.
In accordance with one aspect ofthe present invention, an
35 unreactive seeding agent is introduced into a high temperature
pressure leaching process to assist in metal recovery.
Referring to FIGS. 2 and 3, in accordance with a preferred
aspect ofthis embodiment ofthe present invention, residue 22
may be recycled to pressure leaching vessel 10 and used as a
40 seeding agent. Residue 22 may be divided such that a portion
is directed backto pressure leaching vessell0 and the remainder
may be either discarded or subjected to further metal
recovery (such as, for example, as illustrated in an exemplary
fashion in FIG. 3). For example, and as is shown in FIG. 3, the
45 portion ofresidue stream 22 that is not recycled as a seeding
agent to pressure leaching vessel 10 may nndergo precious
metal recovery using cyanidation or any other metal recovery
technique. Particles in the portion of residue stream 22 that
are recycled to pressure leaching vessel 10 may act as accu-
50 mulation sites for precipitation of other materials, such as
hematite, as described above, thus enhancing the amount of
copper that may be recovered. Recycled residue 22 may be
delivered to pressure leaching vessel 10 by pumping and
piping to the pressure leaching vessel, a feed tank, or other
55 suitable intermediate location. It should be appreciated that
numerous other unreactive and/or reactive materials may be
used as seeding agents in accordance with the present invention
and may be used in combination with the feed stream to
the pressure leaching vessel.
60 In accordance with a preferred aspect ofthe embodiment of
the invention illustrated in FIG. 2, product slurry 18 from
pressure leaching vessell0 may be flashed in an atmospheric
flash tank 16 or other suitable vessel to release pressure and to
evaporatively cool product slurry 18 through the release of
65 steam to form a flashed product slurry 24. Depending upon
the specific process equipment configurations and specifications,
more than one flash stage may be employed. Flashed
US 7,517,384 B2
9
product slurry 24 preferably has a temperature ranging from
about 90° C. to about 105° c., a copper concentration offrom
about 35 to about 60 grams/liter, and an acid concentration of
from about 10 to about 60 grams/liter.
Referring still to FIG. 2, flashed product slurry 24 may be
directed to a solid-liquid separation apparatus 20, such as a
counter-current decantation (CCD) circuit. Alternatively, the
solid-liquid separation apparatus may comprise, for example,
a thickener or a filter. In one aspect ofa preferred embodiment
ofthe invention, solid-liquid phase separation step 20 may be
carried out with a conventional CCD utilizing conventional
counter-current washing of the residue stream to recover
leached copper to the copper-containing solution product and
to minimize the amount of soluble copper advancing to precious
metal recovery processes or storage. Preferably, large
wash ratios are utilized to enhance the effectiveness of the
solid-liquid separation stage-that is, relatively large
amounts of wash water are added to the residue stream in
CCD circuit 20. Preferably, flash product slurry 24 is diluted
by the wash water in CCD circuit 20 to form a coppercontaining
solution having a copper concentration of from
about IS to about 60 grams/liter.
Depending on its composition, residue stream 22 from
solid-liquid separation apparatus 20, as discussed above, may
be used as a seeding agent during pressure leaching, may be
disposed of or subjected to further processing, such as, for
example, precious metal recovery. For example, if residue
stream 22 contains an economically significant fraction of
gold, it may be desirable to recover this gold fraction don
through a cyanidation process or other suitable recovery process.
If gold and/or other precious metals are to be recovered
from residue stream 22 by cyanidation techniques, the content
of contaminants in the stream, such as elemental sulfur,
iron precipitates, and unreacted copper minerals, is preferably
minimized. Such materials generally promote high
reagent consumption in the cyanidation process and thus
increase the expense of the precious metal recovery operation.
Additionally, as mentioned above, it is preferable to use
a large amount ofwash water or other diluting solution during
the solid-liquid separation process to maintain low copper
and acid levels in the CCD residue in an attempt to optimize
the residue stream conditions for precious metal recovery.
Referring now to FIG. 3, residue 22 from solid-liquid separation
step 20 may be subjected to various further processing.
Depending on the characteristics of residue 22, it may be
advantageous to subject it to neutralization and/or pH adjustment,
such as is illustrated in step 60. The residue once so
treated may be recycled to pressure leaching 10, or subjected
to further processing.
Such processing may include, with continued reference to
FIG. 3, an optional hot lime boil (step 62) followed by precious
metal recovery (step 66), such as through the use of
conventional cyanide leaching (step 64) followed by liquidsolid
phase separation (step 68). If cyanide leaching is used,
the resultant tailings may be recycled to pressure leaching 10,
as shown, to be used as a seeding agent, preferably after the
cyanide is destroyed or attenuated (step 70), or alternatively
disposed of (step 72). As illustrated in FIG. 3, various alternative
processing routes may be utilized.
In accordance with various aspects of the present invention,
even when there is little gold present in the residue, use
of a seeding agent in the pressure leaching process can
increase the recovery ofthe gold present in the residue stream.
For example, although extraction of gold from the residue in
pilot plant experiments was on the order of from about 73 to
about 82% when a seeding agent was not introduced into the
pressure leaching vessel, use of a seeding agent (e.g., hema-
10
tite) during pressure leaching enabled laboratory gold extractions
from the residue ranging from about 89 to about 91 %.
Referring back to FIG. 2, in accordance with various
aspects of the present invention, the recovery of the desired
metal value (e.g., copper) may be accomplished through conventional
solvent extractionlelectrowinning (SX/EW) techniques.
For example, a diluting solution 26 may be contacted
with the separated liquid 28 from solid-liquid separation
apparatus 20 to reduce the acid concentration ofthe separated
10 liquid 28 sufficiently to provide desirable equilibrium conditions
for solvent extraction 30. Solution 26 may be any suitable
liquid, for example, water or atmospheric leach effluent
solution, that sufficiently reduces the copper and acid concentrations
to desired levels. In a preferred aspect of this
15 embodiment ofthe invention, sufficient amount ofsolution 26
is contacted with the separated liquid stream 28 to yield an
acid concentration in the diluted copper-containing solution
preferably ranging from about 2 to about 25 grams/liter, and
more preferably from about 4 to about 7 grams/liter and a pH
20 preferably ranging from about pH 1.5 to about pH 2.5 and
more preferably from about pH 1.8 to about pH 2.2, and
optimally in the range of about pH 2.0.
The diluted copper-containing solution 29 may be farther
processed in a solvent extraction step 30. During solvent
25 extraction 30, copper from copper-containing solution 29
may be loaded selectively onto an organic chelating agent, for
example, an aldoxime/ketoxime blend, resulting in a coppercontaining
organic stream 34 and a raffinate solution 32.
Raffinate 32 from solvent extraction step 30 may be used in a
30 number ways. For example, all or a portion of raffinate 32
maybe recycled to pressure leaching vessel 10 for temperature
control or may be used in heap leaching operations, or
may be used for a combination thereofThe use ofraffinate 32
in heap leaching operations may be beneficial because the
35 acid and ferric/ferrous iron values contained in raffinate 32
can act to optimize the potential for leaching oxide and/or
sulfide ores that commonly dominate heap leaching operations.
That is, the ferric and acid concentration ofraffinate 32
may be used to optimize the Eh and pH of heap leaching
40 operations. It should be appreciated that the properties of
raffinate 32, such as component concentrations, may be
adjusted in accordance with the desired use ofraffinate 32.
Copper-containing organic stream 34 is then subjected to a
solvent stripping phase 40, wherein more acidic conditions
45 may shift the equilibrium conditions to cause the copper in the
reagents to be exchanged for the acid in a highly acidic
stripping solution. As shown in FIG. 2, an acid-bearing
reagent 38, preferably sulfuric acid, and optionally, lean electrolyte
48, are contacted with copper-containing organic
50 stream 34 during solvent stripping phase 40. Sulfuric acid is
a preferred acid-bearing reagent and is a desirable copper
matrix for electrowinning operations. The acid-bearing
reagent is contacted with the copper-containing organic
stream to effectuate the exchange of acid for copper to pross
vide copper for metal recovery 46.
Referring still to FIG. 2, copper-containing solution stream
42 from solvent stripping phase 40 may be sent to an electrolyte
recycle tank 44. The electrolyte recycle tankmay suitably
facilitate process control for electrowinning stage 46, as will
60 be discussed in greater detail below. Copper-containing solution
stream 42, which generally contains from about 35 to
about 50 grams/liter of copper and from about 160 to about
180 grams/liter acid, is preferably blended with a lean electrolyte
48 (i.e., electrolyte that has already been through the
65 metal recovery phase and has had a portion of its dissolved
copper removed) and make-up fluid 52, such as, for example,
water, in the electrolyte recycle tank 44 at a ratio suitable to
US 7,517,384 B2
11 12
60
5. A process for recovering a metal value according to
claim 4, wherein said metal present in said residue is selected
from the group consisting of copper, gold, silver, nickel,
cobalt, molybdenum, zinc, rhenium, uranium, rare earth metals,
and platinum group metals.
6. A process for recovering a metal value according to
claim 1, wherein said step ofsubjecting a metal-bearing material
to a reactive process produces acid, and further comprising
the step ofutilizing at least a portion ofthe acid produced
by said reactive process in a heap leaching operation or an
agitated leaching operation.
7. A process for recovering a metal value according to
claim 1, wherein said step of extracting at least one metal
value from said product comprises extracting at least one
precious metal from said product.
8. A process for recovering a metal value according to
claim 1, wherein said step of extracting at least one metal
value from said product comprises extracting gold from said
product.
9. A process for recovering a metal value according to
claim 1, wherein said step of incorporating a seeding agent
into said reactive process comprises incorporating a seeding
agent into said reactive process at a temperature from about
170° C. to about 235° C.
10. A process for recovering a metal value according to
claim 1, wherein said step ofsubjecting a metal-bearing material
to a reactive process comprises subjecting the metalbearing
material to leaching.
11. A process for recovering a metal value according to
claim 1, wherein said leaching process is accomplished with
at least one of elevated pressure, elevated temperature, and
acid addition.
12. A process for recovering a metal value comprising:
subjecting a metal-bearing material to a conditioning process;
subjecting said conditioning process product to a reactive
process to liberate a metal value;
incorporating at least one seeding agent into said reactive
process, wherein said seeding agent provides a nucleation
site; and
extracting at least one metal value from said reactive process
product using electrowinning.
13. A process for recovering a metal value according to
45 claim 12, wherein said step of subjecting a metal-bearing
material to a conditioning process comprises subjecting the
metal-bearing material to at least one of comminution, flotation,
blending and slurry formation.
14. A process for recovering a metal value according to
50 claim 12, wherein said step of incorporating at least one
seeding agent into said reactive process comprises the incorporation
of a seeding agent, which nucleates a species other
than the metal value.
15. A process for recovering a metal value according to
55 claim 12, wherein said step of incorporating at least one
seeding agent into said reactive process comprises the incorporation
of a seeding agent, which nucleates the metal value.
16. A process for recovering a metal value comprising:
subjecting a metal-bearing material to a separation process;
subjecting said separation process product to a reactive
process to liberate a metal value;
incorporating at least one seeding agent into the reactive
process wherein said seeding agent provides a nucleation
site; and
extracting at least one metal value from said reactive process
product using electrowinning.
What is claimed is:
1. A process for recovering a metal value comprising:
subjecting a metal-bearing material to a reactive process;
incorporating at least one seeding agent into said reactive
process at a temperature greater than about 120° c.;
obtaining a product from said reactive process wherein at
least one metal value is present in said product and
wherein said metal value comprises at least one of copper,
gold, silver, nickel, cobalt, molybdenum, zinc, rhenium,
uranium, rare earth metal, and platinum group
metal; and
extracting said at least one metal value from said product
using electrowinning.
2. A process for recovering a metal value according to
claim 1, wherein said at least one seeding agent comprises
hematite.
3. A process for recovering a metal value according to
claim 1, wherein said seeding agent comprises at least a
portion of a residue from said reactive process.
4. A process for recovering a metal value according to
claim 3, further comprising the step ofrecovering at least one 65
metal present in said residue from said reactive process before
using said residue as said seeding agent.
yield a product stream 50, the conditions of which may be
chosen to optimize the resultant product ofmetal recovery 46.
Preferably, the copper composition ofproduct stream 50 is
maintained substantially constant at a value from about 20 to
about 60 grams/liter, more preferably at a value from about 30
to about 50 grams/liter. Copper values from the copper-containing
product stream 50 are removed during metal recovery
step 46, preferably using electrowinning, to yield a pure,
cathode copper product. It should be appreciated that in
accordance with the various aspects of the invention, a pro- 10
cess wherein, upon proper conditioning of the copper-containing
solution, a high quality, nniformly-plated cathode
copper product may be realized without subjecting the copper-
containing solution to solvent extraction prior to entering
the electrowinning circuit is within the scope of the present 15
invention. 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
requisite process parameters for the chosen method or appa- 20
ratus are satisfied.
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
described herein are illustrative of the invention and its best 25
mode and are not intended to limit in any way the scope ofthe
invention as set forth in the claims. 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 ofthe present invention. For 30
example, although reference has been made throughout to
various metal value recovery examples, it is intended that the
invention also be applicable to the recovery ofother materials
that may be recovered through reactive processing that incorporate
use of a seeding agent. Further, although certain pre- 35
ferred aspects ofthe invention, such as materials for seeding
the reactive process, for example, are described herein in
terms 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 40
changes or modifications are intended to be included within
the scope ofthe present invention, as expressed in the following
claims.
13
US 7,517,384 B2
14
17. A process for recovering a metal value according to
claim 16, wherein said step of subjecting a metal-bearing
material to a separation process comprises subjecting the
metal-bearing material to at least one of flash distillation,
filtration, counter-current decantation circuits (CCD) and
centrifuges.
18. A process for recovering a metal value according to
claim 16, wherein said step of incorporating at least one
seeding agent into said reactive process comprises the incorporation
of a seeding agent, which nucleates a species other
than the metal value.
19. A process for recovering a metal value according to
claim 16, wherein said step of incorporating at least one
seeding agent into said reactive process comprises the incorporation
of a seeding agent, which nucleates the metal value.
* * * * *