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US006893482B2
(12) United States Patent
Marsden et al.
(10) Patent No.:
(45) Date of Patent:
US 6,893,482 B2
*May 17, 2005
(54) METHOD FOR IMPROVING METALS
RECOVERY USING HIGH TEMPERATURE
PRESSURE LEACHING
(56) References Cited
U.S. PATENT DOCUMENTS
OTHER PUBLICATIONS
(Continued)
FOREIGN PATENT DOCUMENTS
21924/56
0047076
WO 02/08474
(75)
(73)
Inventors: John O. Marsden, Phoenix, AZ (US);
Robert E. Brewer, Safford, AZ (US);
Joanna M. Robertson, Thatcher, AZ
(US); David R. Baughman, Golden,
CO (US); Philip Thompson, West
Valley City, UT (US); Wayne W.
Hazen, Lakewood, CO (US); Roland
Schmidt, Golden, CO (US)
Assignee: Phelps Dodge Corporation, Phoenix,
AZ (US)
AU
EP
WO
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This patent is subject to a terminal disclaimer.
Novoa, C. "Notification of Transmittal of The International
Preliminary Examination Report", Nov. 10,2003, pp. 1-12.
Evans, et aI., "International Symposium of Hydrometallurgy,"
Mar. 1, 1973, 2 pages.
(Continued)
Primary Examiner-Melvyn Andrews
(74) Attorney, Agent, or Firm---8nell & Wilmer, LLP
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 crystallization and/or growth of solid
species which otherwise tend to passivate the reactive process
or otherwise encapsulate the metal value, thereby
reducing the amount of desired metal values partially or
completely encapsulated by such material. The seeding
agent may be generated in a number of ways, including the
recycling of residue or the introduction of foreign substances.
Systems embodying aspects of the 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.
(21) Appl. No.: 10/650,167
(22) Filed: Aug. 27, 2003
(65) Prior Publication Data
us 2004/0045406 A1 Mar. 11,2004
Related U.S. Application Data
(63) 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. 09/912,967, filed on Jul. 25, 2001, now Pat.
No. 6,451,088.
(51) Int. CI? C22B 3/06
(52) U.S. Cl. 75/739; 75/740; 75/743;
75/744; 423/122; 423/658.3; 205/560
(57) ABSTRACT
(58) Field of Search 75/739, 740, 743,
75/744; 423/122, 658.5, 658.3; 205/560 21 Claims, 2 Drawing Sheets
TOFIG.3
U.S. PATENT DOCUMENTS
US 6,893,482 B2
Page 2
OTHER PUBLICATIONS
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6,626,979 B2 *
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1998.
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and Concentrate," COPPER 1999, Fourth International Conference,
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* cited by examiner
u.s. Patent May 17, 2005 Sheet 1 of 2 US 6,893,482 B2
2
METAL-BEARING MATERIAL
4 ~\.- P_R_O_C_E~S_S_IN_G _
{
6 ~L__M_ET_A_L_R_E_C_~O_V_E_R_Y _
FIG. 1
2
METAL-BEARING MATERIAL
18
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
ElECTROWINNING
FIG. 2
u.s. Patent May 17, 2005 Sheet 2 of 2 US 6,893,482 B2
10 10
64
62
70
60
68
66
20
) 22
LIQUID-SOLID PHASE I
SEPARATION
NEUTRALIZATION &
pH ADJUSTMENT
HOT LIME BOIL
(OPTIONAL)
I
PRECIOUS METALS
CYANIDE LEACHING
PRECIOUS METALS
RECOVERY
(LIQUID} LIQUID-SOLID PHASE
SEPARATION (OPTIONAl)
--_ .... --------
CYANIDE V
DESTRUCTION
------------
( TAILINGS 72
DISPOSAL
FIG. 3
US 6,893,482 B2
2
DETAILED DESCRIPTION
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
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
may be recovered. Metal values such as, for example,
65 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 an exemplary embodiment of the
present invention, a process for recovering metal from a
metal-bearing material generally includes the steps of (i)
subjecting a concentrate containing a metal value to a
5 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 of an alternative embodiment of the invention, the
seeding agent may be recycled residue that is introduced to
10 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 solution in which the reactive process occurs. In a further
aspect of the present invention, other foreign material may
15 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 of the present invention,
copper is recovered from a metal-bearing material. The
20 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 preferably is a multi-compartment pressure leaching
vessel. The pressure leaching product may then undergo one
25 or more subsequent conditioning and/or refining processes
such that copper and/or other metal values may be recovered
from the pressure leaching product or products.
The advantages of a process according to the various
aspects of the present invention will be apparent to those
30 skilled in the art upon reading and understanding the following
detailed description with reference to the accompanying
drawing figures.
FIELD OF INVENTION
SUMMARY OF THE INVENTION
BACKGROUND OF THE INVENTION
1
METHOD FOR IMPROVING METALS
RECOVERY USING HIGH TEMPERATURE
PRESSURE LEACHING
CROSS REFERENCE TO RELATED
APPLICATIONS
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 35
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, 40
thus offsetting the costs associated with purchased acid.
On the other hand, the application of pressure leaching
may 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 45
present in the pressure leaching vessel, such as, for example,
hematite 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 50
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 and that enhances the
recovery of precious metals from metal-bearing materials 55
would be advantageous.
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.
While the way in which the present invention addresses
the deficiencies and disadvantages of the prior art is 60
described in greater detail below, in general, according to
various aspects of the present invention, a process for
recovering copper and other metal values from a metalbearing
material includes various reactive and recovery
processes. In a preferred aspect of the invention, a seeding
agent is introduced to the metal recovery process, most
preferably, during a pressure leaching process.
This application is a continuation of U.S. Ser. No. 10/238,
088, filed on Sep. 9, 2002 now U.S. Pat. No. 6,626,979,
which is a continuation of U.S. Ser. No. 09/912,967, filed on
Jul. 25, 2001 and issued as U.S. Pat. No. 6,451,088 on Sep.
17, 2002, the disclosures of which are hereby incorporated
by reference.
US 6,893,482 B2
3 4
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
5 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
10 passivate the reactive process and/or encapsulate a metal or
metals to be recovered Through use of the 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
15 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
20 of the metal recovery process or may be provided by the
addition of substances that are foreign to the metal recovery
process. In some cases, the seeding agent comprises any
material that promotes crystallization, precipitation, and/or
growth of unwanted materials-for example in the preferred
25 case of copper recovery, hematite, gangue, and the likethat
may otherwise tend to partially or completely encapsulate
the desired metal values, rendering the desired metal
values (e.g., copper and gold) generally unavailable or less
accessible to a lixiviant solution. As is known, in
30 precipitation, seed particles tend to grow in size through
deposition of materials from solution. Accordingly, nonpreferential
precipitation onto other (i.e., non-seed) material
surfaces may also occur.
One source of suitable seeding agents useful in accor-
35 dance 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 of the recycled pressure leaching vessel
discharge may be desirable for economic reasons, and using
40 a seeding agent that is similar or identical to unwanted
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-
45 bearing material or is produced as a by-product, introduction
of recycled hematite-containing residue from previous pressure
leaching processes likely will tend to provide newly
formed or liberated hematite a preferential nucleation site. In
the absence of this nucleation site, unreactive particles may
50 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.
Another source of suitable seeding agents useful in accordance
with various aspects of the 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
60 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
65 use of cyanide leaching. In such a case, the cyanideattenuated
cyanide leach tailings may suitably be used as a
seeding agent in accordance with the present invention.
in accordance with various embodiments of the present
invention. Various aspects and embodiments of the present
invention, however, prove especially advantageous in connection
with the recovery of copper and gold from goldbearing
copper sulfide ores, such as, for example, goldbearing
chalcopyrite (CuFeS2), chalcocite (Cu2S), bornite
(Cu5FeS4), and covellite (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 manner that enables the conditions
of metal-bearing material 2-such as, for example,
particle size, composition, and component concentrationto
be suitable for the chosen processing method, as such
conditions may affect the overall effectiveness and efficiency
of processing operations. 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
of the chosen processing scheme, equipment cost and material
specifications. For example, metal-bearing material 2
may undergo 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
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-bearing material 2. In accordance with one embodiment
of the present invention, processing step 4 comprises
pressure leaching, either at medium temperatures (e.g., from
about 120° C. to about 190° C.) or high temperatures (e.g.,
greater than about 200° 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 170° C. to about 235° C., more preferably from about
200° C. to about 230° c., and optimally above about 200° C.
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, 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 of the present invention.
Processing step 4 may occur in any pressure leaching
vessel suitably designed to contain the pressure leaching 55
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, 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 of the present invention.
In accordance with a preferred aspect of the 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
US 6,893,482 B2
5
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/or jarosite may be
used. Still further, generally unreactive particulate materials
such as, for example, low grade concentrate, tailings, or
intermediate 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 of the present invention, any material that is
capable of forming 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 of a 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
by-products, 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 of preparatory 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 metalbearing
solution 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 uniformity 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 of the product slurry
from the reactive processing step. In a preferred aspect of
this embodiment of the invention, wherein the reactive
processing step is high temperature pressure leaching, it is
desirable to reduce the temperature and pressure of the
product slurry. A preferred method of so adjusting the
temperature and pressure characteristics of the coppercontaining
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
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
6
filtration systems, counter-current decantation (CCD)
circuits, thickeners, centrifuges, and the like. A variety of
factors, such as the process material balance, environmental
regulations, residue composition, economic considerations,
5 and the like, may affect the decision whether to employ a
CCD circuit, a thickener, a filter, or any other suitable device
in a solid-liquid separation apparatus. However, it should be
appreciated that any technique of conditioning the product
slurry for later metal value recovery is within the scope of
10 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,
15 nickel, cobalt, molybdenum, zinc, rhenium, uranium, rare
earth metals, and the like. Alternatively, the separated solids
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 appa-
20 ratus may also undergo a series of conditioning steps to
prepare the metal values solubilized therein for metal recovery.
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
25 susceptible to metal recovery techniques. Further, subsequent
conditioning and/or processing steps may be undertaken
such that recovery rates are as efficient as possible.
After any desired preparation steps, the pressure leaching
30 product stream may undergo the desired metal recovery step.
The metal value recovery method may include any suitable
conventional method of removing the desired metal values
from solutions, such as, for example, electrowinning,
precipitation, solvent extraction, cyanidation, ion exchange,
35 and/or ion flotation, and preferably results in a relatively
pure metal product.
In an exemplary embodiment of the present invention
illustrated in FIG. 2, a copper-containing feed stream 4
containing a copper-containing material 2 is provided for
40 metal value recovery. The copper in copper-containing
material 2 may be in any form from which copper may be
extracted, such as copper oxide or copper sulfide, for
example chalcopyrite (CuFeS2), chalcocite (Cu2S), bornite
(Cu5FeS4), and covellite (CuS). Copper-containing material
45 2 also may include any number of a variety of other metals,
such as gold, silver, platinum group metals, zinc, nickel,
molybdenum, cobalt, rare earth metals, rhenium, uranium,
and/or mixtures thereof.
In accordance with one embodiment of the present
50 invention, feed stream 4 is combined with a liquid 6, which
may comprise water, to form a feed slurry 5. Feed slurry 5
is then subjected to a pressure leaching step 10.
Alternatively, feed stream 4 may be directly fed into a
pressure leaching device (step 10), such as a pressure
55 leaching vessel, together with other feed streams, namely
feed stream 6.
In one embodiment (not shown in FIG. 2), coppercontaining
material feed stream 4 is prepared for pressure
leaching by comminuting a copper-containing material and
60 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
65 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
US 6,893,482 B2
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the exothermic nature of pressure leaching of many metal
sulfides, the heat generated by high temperature pressure
leaching is generally more than that needed to heat feed
slurry 5 to the desired operating temperature. Thus, in order
5 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
of the present invention, a cooling liquid is preferably
contacted with the feed stream in pressure leaching vessel 10
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 phase from the product slurry, neutralized
raffinate solution 32, or a mixture of cooling fluids. Cooling
15 liquid may be introduced into pressure leaching vessel 10
through the same inlet as feed slurry, or alternatively in any
manner that effectuates cooling of feed slurry 5. The amount
of cooling liquid added to feed slurry 5 during pressure
leaching may vary according to the amount of sulfide
20 minerals in and the pulp density of the feed slurry 5, as well
as other parameters of the pressure leaching process. In a
preferred aspect of this embodiment of the invention, a
sufficient amount of cooling liquid is added to pressure
leaching vessel 10 to yield a solids content in product slurry
25 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 of the present invention, an
unreactive seeding agent is introduced into a high tempera-
30 ture pressure leaching process to assist in metal recovery.
Referring to FIGS. 2 and 3, in accordance with a preferred
aspect of this embodiment of the present invention, residue
22 may be recycled to pressure leaching vessel 10 and used
as a seeding agent. Residue 22 may be divided such that a
35 portion is directed back to pressure leaching vessel 10 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 portion of residue stream 22 that is not
40 recycled as a seeding agent to pressure leaching vessel 10
may undergo 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 accumulation sites for precipitation of
45 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 suitable intermediate location. It
50 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.
In accordance with a preferred aspect of the embodiment
of the invention illustrated in FIG. 2, product slurry 18 from
pressure leaching vessel 10 may be flashed in an atmospheric
flash tank 16 or other suitable vessel to release
pressure and to evaporatively cool product slurry 18 through
60 the release of 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 product slurry 24 preferably has a temperature
ranging from about 90° C. to about 105° c., a
65 copper concentration of from about 35 to about 60 grams/
liter, and an acid concentration of from about 10 to about 60
grams/liter.
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, multicompartment
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% of the concentrated coppercontaining
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 of the 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 of the sulfide
minerals in the feed slurry. However, it should be appreciated
that any method of providing for the solubilization of
copper 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 of the 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 superatmospheric, 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 55
example, the characteristics of the metal-bearing material
and the operating pressure and temperature of the 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 of the 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 200° C. to about 235° c., and
more preferably from about 215° C. to about 230° C. Due to
US 6,893,482 B2
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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 of a preferred 5
embodiment of the 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 coppercontaining
solution product and to minimize the amount of 10
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 15
circuit 20 to form a copper-containing solution having a
copper concentration of from about 15 to about 60 grams/
liter.
Depending on its composition, residue stream 22 from
solid-liquid separation apparatus 20, as discussed above, 20
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 25
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 30
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 of wash water or other 35
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 40
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 45
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 liquid- 50
solid 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 55
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 of the gold present in the 60
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., hematite) during pressure leaching enabled labo- 65
ratory gold extractions from the residue ranging from about
89 to about 91%.
10
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 extraction/electrowinning (SXIEW)
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 of
the separated 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 embodiment of the invention, sufficient
amount of solution 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 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 further
processed in a solvent extraction step 30. During solvent
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
copper-containing organic stream 34 and a raffinate solution
32. Raffinate 32 from solvent extraction step 30 may be used
in a 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 thereof. The use of
raffinate 32 in heap leaching operations may be beneficial
because the 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
of raffinate 32 may be used to optimize the Eh and pH
of heap leaching operations. It should be appreciated that the
properties of raffinate 32, such as component concentrations,
may be adjusted in accordance with the desired use of
raffinate 32.
Copper-containing organic stream 34 is then subjected to
a solvent stripping phase 40, wherein more acidic conditions
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
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
provide 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 tank may
suitably facilitate process control for electrowinning stage
46, as will be discussed in greater detail below. Coppercontaining
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 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
US 6,893,482 B2
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60
3. A process for recovering a metal value from a metalbearing
material 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 from a metalbearing
material according to claim 1, further comprising the
step of recovering metals which are present in said residue
from said reactive process before using said residue as said
seeding agent.
10 5. A process for recovering a metal value from a metalbearing
material according to claim 1, wherein said seeding
agent is not a by-product of said reactive process.
6. A process for recovering a metal value from a metalbearing
material according to claim 1, wherein said metal
value is selected from the group consisting of copper, gold,
15 silver, nickel, cobalt, molybdenum, zinc, rhenium, uranium,
rare earth metals, and platinum group metals.
7. A process for recovering a metal value from a metalbearing
material according to claim 3, wherein said metal
present in said residue is selected from the group consisting
20 of copper, gold, silver, nickel, cobalt, molybdenum, zinc,
rhenium, uranium, rare earth metals, and platinum group
metals.
8. A process for recovering a metal value from a metalbearing
material according to claim 1, further comprising the
25 step of extracting said metal value from said product of said
reactive process using electrowinning.
9. A process for recovering a metal value from a metalbearing
material according to claim 1, wherein said reactive
process comprises pressure leaching.
30 10. A process for recovering a metal value from a metalbearing
material according to claim 9, wherein said reactive
process comprises pressure leaching at a temperature of
about 170° C. to about 235° C.
11. A process for recovering a metal value from a metal-
35 bearing material according to claim 1, wherein said step of
subjecting a metal-bearing material to a reactive process
produces acid, and further comprising the step of utilizing at
least a portion of the acid produced by said reactive process
in a heap leaching operation or an agitated leaching opera-
40 tion.
12. A process for recovering a metal value from a metalbearing
material 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
45 product.
13. A process for recovering a metal value from a metalbearing
material according to claim 1, wherein said step of
extracting at least one metal value from said product comprises
extracting gold from said product.
50 14. A process for recovering a metal value from a metalbearing
material comprising the steps of
a. subjecting a metal-bearing material to a reactive process
to liberate at least one metal value from said
metal-bearing material;
b. incorporating hematite as at least one seeding agent into
said reactive process;
c. obtaining a product from said reactive process, wherein
at least one metal value is present in said product; and
d. extracting said at least one metal value from said
product.
15. A process for recovering a metal value from a metalbearing
material according to claim 14, wherein said metal
value is selected from the group consisting of copper, gold,
silver, nickel, cobalt, molybdenum, zinc, rhenium, uranium,
65 rare earth metals, and platinum group metals.
16. A process for recovering a metal value from a metalbearing
material according to claim 14, further comprising
a. subjecting a metal-bearing material to a reactive process
to liberate at least one metal value from said
metal-bearing material;
b. incorporating at least one seeding agent into said
reactive process, said seeding agent at least partially 55
preventing said reactive process from passivating or
encapsulating said at least one metal value by urging at
least one passivating or encapsulating species to at least
partially crystallize, precipitate or otherwise form on or
in proximity to said seeding agent;
c. obtaining a product from said reactive process, wherein
at least one metal value is present in said product; and
d. extracting said at least one metal value from said
product.
2. A process for recovering a metal value from a metalbearing
material according to claim 1, wherein said at least
one seeding agent comprises hematite.
recycle tank 44 at a ratio suitable to yield a product stream
50, the conditions of which may be chosen to optimize the
resultant product of metal recovery 46.
Preferably, the copper composition of product stream 50 5
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 process wherein, upon proper conditioning of
the copper-containing solution, a high quality, uniformlyplated
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 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 of
which may be suitable for use in accordance with the present
invention, provided the requisite process parameters for the
chosen method or apparatus are satisfied.
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
mode and are not intended to limit in any way the scope of
the 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 of the present
invention. For 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
of other materials that may be recovered through reactive
processing that incorporate use of a seeding agent. Further,
although certain preferred aspects of the 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 changes or modifications are
intended to be included within the scope of the present
invention, as expressed in the following claims.
What is claimed is:
1. A process for recovering a metal value from a metalbearing
material comprising the steps of:
13
US 6,893,482 B2
14
the step of extracting said metal value from said product of
said reactive process using electrowinning.
17. A process for recovering a metal value from a metalbearing
material according to claim 14, wherein said reactive
process comprises pressure leaching.
18. A process for recovering a metal value from a metalbearing
material according to claim 17, wherein said reactive
process comprises pressure leaching at a temperature of
about 170° C. to about 235° C.
19. A process for recovering a metal value from a metalbearing
material according to claim 14, wherein said step of
subjecting a metal-bearing material to a reactive process
produces acid, and further comprising the step of utilizing at
least a portion of the acid produced by said reactive process
in a heap leaching operation or an agitated leaching operation.
20. A process for recovering a metal value from a metal-
S bearing material according to claim 14, wherein said step of
extracting at least one metal value from said product comprises
extracting at least one precious metal from said
product.
21. A process for recovering a metal value from a metal10
bearing material according to claim 14, wherein said step of
extracting at least one metal value from said product comprises
extracting gold from said product.
* * * * *