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US007666371B2
(12) United States Patent
Marsden et al.
(10) Patent No.:
(45) Date of Patent:
US 7,666,371 B2
*Feb.23,2010
(54) METHOD FOR RECOVERING METAL
VALUES FROM METAL-CONTAINING
MATERIALS USING HIGH TEMPERATURE
PRESSURE LEACHING
(75) Inventors: John 0 Marsden, Phoenix, AZ (US);
Robert E Brewer, Safford, AZ (US);
Joanna M Robertson, Thatcher, AZ
(US); Wayne W Hazen, Lakewood, CO
(US); Philip Thompson, West Valley
City, UT (US); David R Baughman,
Golden, CO (US)
(73) Assignee: Freeport-McMoran Corporation,
Phoenix, AZ (US)
(60) Provisional application No. 60/220,622, filed on Jul.
25,2000.
(51) Int. Cl.
COIG 3/00 (2006.01)
(52) U.S. Cl. 423/24; 423/26; 423/27;
205/580; 205/581
(58) Field of Classification Search 423/24,
423/26,27, 8, 22, 49, 54, 109, 139,21.5;
205/580,581,589,590,604,605,564,568
See application file for complete search history.
(56) References Cited
U.S. PATENT DOCUMENTS
( *) Notice: Subject to any disclaimer, the term ofthis
patent is extended or adjusted under 35
U.S.c. 154(b) by 81 days.
This patent is subject to a tenninal disclaimer.
5,698,170 A * 12/1997 King 423/24
5,895,633 A * 4/1999 King 423/24
* cited by examiner
Primary Examiner-Steven Bos
(74) Attorney, Agent, or Firm-Snell & Wilmer L.L.P.
(21) Appl. No.: 11/952,726 (57) ABSTRACT
Prior Publication Data
Filed: Dec. 7, 2007
Related U.S. Application Data
Division of application No. 101758,755, filed on Jan.
16,2004, now Pat. No. 7,473,413, which is a continuation
of application No. 09/912,922, filed on Jul. 25,
2001, now Pat. No. 6,680,034.
(22)
(65)
(60)
US 2008/0156656 Al Jul. 3, 2008
The present invention relates generally to a process for recovering
copper and other metal values from metal-containing
materials through pressure leaching operations. In accordance
with the various aspects ofthe present invention, metalcontaining
pregnant leach solutions from pressure leaching
operations need not be significantly diluted to facilitate effective
metal recovery using solvent extraction and electrowinning.
4 Claims, 3 Drawing Sheets
u.s. Patent Feb. 23,2010 Sheet 1 of 3 US 7,666,371 B2
100
)
102
104
~ METAL-BEARING MATERIAL
l'
~ REACTIVE PROCESSING
l'
106 ~",---__M_ET_A_L_R_E_C_O_V_E_R_Y _
FIG. 1
u.s. Patent Feb. 23,2010 Sheet 2 of 3 US 7,666,371 B2
200---i METAL-BEARING MATERIAL I
t
202___( COMMINUTION )
t
204~1 COMMINUTED MATERIAL I t
208
FLOTATION
210~ CONCENTRATED COPPER
SULFIDE-BEARING MATERIAL
212----( LIGHT REGRIND )
t
214~1 PRODUCT SLURRY I t
220----( PRESSURE LEACHING )
t
222~1 PRODUCT SLURRY I t
224___( FLASH )
t 282
226~1 FLASHED PRODUCT SLURRY I 280
( SM~LTER ) • 228 LIQUID/SOLID SEPARATION
METALS
L RECOVERY
TO FIG 2B 284
FIG.2A
230
FROM FIG 2A i
COPPER-CONTAINING
SOLUTION -----------------------------------------~
TO FIG 2A
~
7J).
•
~
~
~
~=~
232 CHEMICAL pH ADJUST
268
AGITATED TANK LEACH
rFJ =('
D
(..'D...
(.H
o....
(.H
""f'j
('D
?'
N
(.H
~
No
.... o
d
rJl
......:J
0-.,
0'1
0'1
W
......:J
="""'" N
254
""" /262 l HEAP LEACH )
FIG. 28
IIII
I
IIII
,,,
,
+ t
236
266
264
CHEMICAL pH ADJUST
US 7,666,371 B2
2
incomplete, resulting in the formation of ferrous sulfate, an
undesirable reaction by-product.
In high temperature pressure leaching, the sulfur contained
in the metal-bearing material (e.g., concentrate) typically is
converted to sulfate. In connection with such pressure leaching
processing operations, the copper typically is recovered
from the resulting solution by solvent extraction and electrowinning
techniques to provide a cathode copper product of
high purity.
In solvent extraction (or solution extraction or liquid ion
exchange, as it is sometimes called), the pregnant leach solution
typically is mixed with an organic solvent (i.e., an extractant),
which selectively removes the copper from the pregnant
leach solution. The copper-loaded extractant is then mixed
15 with an aqueous acid solution, which strips the copper from
the extractant, producing a solution stream suitable for electrowinning.
This resultant solution stream is highly concentrated
in copper and relatively pure, and typically is processed
into high quality cathode copper in an electrowinning circuit.
In general, electrowinning of copper consists of the electrolytic
deposition (sometimes called "plating") of copper
onto a cathode and the evolution of oxygen at an anode. In a
simple design of an exemplary electrowinning unit, a set of
cathodes and anodes are set in a reaction chamber containing
25 the copper-containing electrolyte. When the unit is energized,
copper ions are reduced onto the cathode (i.e., plated). Plating
ofcopper typically occurs on copper starter sheets or stainless
steel blanks. Anodes are quasi-inert in the electrolyte and
provide a surface for oxygen evolution. The copper plates
30 produced by the electrowinning unit can be in excess of99.99
percent pure.
Purification of copper from the pregnant leach solution by
solvent extraction has proven to be a successful means of
providing a concentrated copper solution suitable for elec-
35 trowinning of highly pure copper metal. However, prior art
teachings suggest the importance of ensuring that the acid
concentration of the pregnant leach solution is appropriately
controlled, often through neutralization, such as through the
use of lime or acid-consuming ore.
Still others have recognized that the use oflime to neutralize
the acid in the solution not only increases operating costs
due to lime consumption but also may result in the formation
of a low pulp density slurry, thus tending to make it more
difficult to recover the copper from that slurry. In response,
45 Placer Dome, Inc., ofVancouver, British Columbia, Canada,
has proposed in, for example, U.S. Pat. Nos. 5,698,170 and
5,895,633 methods to recover copper from copper-containing
materials, especially copper from copper sulfides such as
chalcopyrite, wherein a copper-containing solution contain-
50 ing an acid is contacted, that is, diluted, with an aqueous
diluent containing no more than about 5 grams/liter acid to
yield a diluted copper-containing solution having an acid
concentration ranging from about 2 to about 8 grams/liter
prior to the step of solvent extracting the copper from the
55 diluted copper-containing solution. In their patents, Placer
Dome requires the significant use of a diluting solution to
lower acid levels in the copper-containing solution sufficiently
for favorable equilibrium conditions during solvent
extraction, which technique Placer Dome suggests signifi-
60 cantly reduces copper losses relative to many existing processes
in which neutralization of the acid in the solution
before solvent extraction is employed.
To achieve these results, Placer Dome teaches that the
desired acid concentration ranges can be obtained when a
65 sufficient amount of diluting solution is contacted with the
copper-containing solution to yield the diluted copper-containing
solution. Specifically, Placer Dome teaches that the
(1)
FIELD OF INVENTION
CROSS-REFERENCE TO RELATED
APPLICATIONS
BACKGROUND OF THE INVENTION
1
METHOD FOR RECOVERING METAL
VALUES FROM METAL-CONTAINING
MATERIALS USING HIGH TEMPERATURE
PRESSURE LEACHING
The present invention relates generally to a process for
recovering copper and other metal values from metal-containing
materials, and more specifically, to a process for
recovering copper and other metal values from metal-containing
materials using high temperature pressure leaching
processes.
This application is a divisional application of U.S. patent
application Ser. No. 10/758,755 entitled "Method for Recov- 10
ering Metal Values from Metal-Containing Materials Using
High Temperature Pressure Leaching" filed on Jan. 16,2004
which is a continuation application ofU.S. patent application
Ser. No. 091912,922, entitled "Method for Recovering Metal
Values from Metal-Containing Materials Using High Temperature
Pressure Leaching," filed Jul. 25, 2001, now U.S.
Pat. No. 6,680,034, which claims priority to U.S. Provisional
Patent Application Ser. No. 60/220,622 entitled "Methods for
Recovering Copper and Other Metal. Values from Copper
Sulfide Concentrate Using High Temperature Pressure Oxi- 20
dation" filed on Jul. 25, 2000, all ofwhich are incorporated by
reference herein.
Smelting is one approach for recovering a metal, such as
copper, from a metal-bearing sulfide material. However, due
to the high cost of smelting, the copper sulfide minerals in an
ore body typically are first concentrated by flotation techniques
to provide a smaller volume for smelting. The concentrate
is then shipped to a smelter, which processes the con- 40
centrate pyrometallurgically at high temperatures to form a
crude copper product that is subsequently refined to a highly
pure metal.
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 able to
be used in adjacent heap leaching operations, thus offsetting
some of the costs associated with purchased acid.
The mechanism by which pressure leaching processes
effectuate the release ofcopper from sulfide mineral matrices,
such as chalcopyrite, is generally dependent on temperature,
oxygen availability, and process chemistry. In high temperature
pressure leaching processes, that is, pressure leaching
processes operating above about 2150 c., the dominant oxidation
reaction is believed to be as follows:
If insufficient oxygen is present in the process vessel, the
conversion of iron to hematite (Fe20 3 ) generally will be
3
US 7,666,371 B2
4
ratio ofthe volume of copper-containing solution to the volume
ofdiluting solution must range from about I: 10 to about
I :500. In this manner, the acid generated in pressure leaching
is neutralized after, and preferably not before, solvent extraction
and electrowinning.
While Placer Dome's patented process is usable in many
situations, in cases where it is desirable to reduce operating
costs and/or the metal-bearing ore at a particular site does not
warrant such conditions, it would be desirable to obtain high
metal recovery in processes where such dilution is not
required.
SUMMARY OF THE INVENTION
While the way in which the present invention provides
these advantages over the prior art is described in greater
detail hereinbelow, in general, the process for recovering
copper and other metal values from a metal-bearing material
is improved, according to various aspects of the present
invention, in that the pressure leach solution need not be
significantly diluted before the copper and/or other metal
values are recovered, for example, through solvent extraction,
electrowinning, or other processes. In this manner, capital and
operating costs can be reduced without sacrificing the extraction
of copper or other metals.
Thus, in accordance with an exemplary embodiment ofthe
present invention, a process for recovering copper from a
copper-containing material generally includes the steps of: (i)
providing a feed stream containing copper-containing material;
(ii) pressure leaching the copper-containing feed stream
to yield a copper-containing solution; and (iii) recovering
cathode copper from the copper-containing solution using
solvent extraction and electrowinning without significantly
diluting the copper-containing solution. In general, recovery
processes in accordance with the present invention yield high
copper recovery, for example in excess of 98%, while at the
same time yielding various other important benefits.
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 general flow diagram of a metal recovery
process in accordance with one general embodiment of
the present invention;
FIG. 2A illustrates a more detailed flow diagram ofa metal
recovery process in accordance with one exemplary embodiment
of the present invention; and,
FIG. 2B illustrates further aspects of the metal recovery
process of FIG. 2A.
DETAILED DESCRIPTION
The present invention exhibits significant advancements
over prior art processes, particularly with regard to metal
recovery ratios and process cost advantages. Moreover, existing
metal recovery processes that utilize a conventional atmospheric
or pressure leaching/solvent extraction/electrowinning
process sequence may, in many instances, be easily
retrofitted to exploit the many commercial benefits the
present invention provides.
Referring to FIG. 1, in accordance with various aspects of
the present invention, a metal-bearing material 102 is provided
for processing in accordance with metal recovery process
100. Metal-bearing material 102 may be an ore, a concentrate,
or any other material from which metal values 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
10 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 from copper sulfide concentrates and/or ores,
such as, for example, chalcopyrite (CuFeS2 ), chalcocite
15 (Cu2 S), bornite (CusFeS4 ), and covellite (CuS). Thus, metalbearing
material 102 preferably is a copper ore or concentrate,
and most preferably, is a copper sulfide ore or concentrate.
Metal-bearing material 102 may be prepared for metal
20 recovery processing in any manner that enables the conditions
of metal-bearing material102-such as, for example,
composition and component concentration-to be suitable
for the chosen processing method, as such conditions may
affect the overall effectiveness and efficiency of processing
25 operations. Desired composition and component concentration
parameters can be achieved through a variety ofchemical
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
30 example, as discussed in some detail hereinbelow, metalbearing
material 102 may undergo comminution, flotation,
blending, and/or slurry formation, as well as chemical and/or
physical conditioning.
With continued reference to FIG. 1, after metal-bearing
35 material 102 has been suitably prepared, metal-bearing material
is subjected to reactive processing (step 104) to put a
metal value or values in metal-bearing material 102 in a
condition such that they may be subjected to later metal
recovery steps, namely metal recovery step 106. For example,
40 exemplary suitable processes include reactive processes that
tend to liberate the desired metal value or values in the metal
bearing material 102 from the metal-bearing material 102. In
accordance with a preferred embodiment of the present
invention, processing step 104 comprises pressure leaching,
45 preferably, high temperature pressure leaching. As used
herein, the term "pressure leaching" refers to a metal recovery
process in which material is contacted with an acidic solution
and oxygen under conditions of elevated temperature and
pressure. In accordance with various aspects of the present
50 invention, processing step 104 may comprise any type of
pressure leaching process.
As previously briefly noted, pressure leaching processes
are generally dependent upon, among other things, temperature,
oxygen availability, and process chemistry. While vari-
55 ous parameters for each may be utilized, in accordance with
preferred aspects of the present invention, the temperature
during pressure leaching preferably is maintained in the range
of about 170° C. to about 235° c., most preferably in the
range from about 200° C. to about 230° c., and optimally on
60 the order of about 225° C.
To maintain the temperature in this desired range, a cooling
liquid may be employed. As will be appreciated, pressure
leaching of many metal sulfides tends to be an exothermic
reaction, and the heat generated is generally more than that
65 required to heat the feed slurry to the desired operating temperature.
Excess heat may be removed and the desired operating
temperature maintained by contacting cooling liquid
US 7,666,371 B2
5 6
due to the lower volume of fluids which need to be handled
within metal recovery process 100.
Referring now to FIGS. 2A and 2B, a further exemplary
embodiment of the present invention is illustrated. In accordance
with this embodiment, a metal-bearing material 200,
preferably a copper-bearing material, is comminuted in step
202 to form a comminuted material 204. Preferably, metalbearing
material 200 comprises a copper sulfide-bearing
material.
Preferably, comminuted material 204 is subjected to froth
flotation (step 208) to separate copper sulfide-bearing materials
from gangue minerals. The flotation concentrate, namely
the concentrated copper sulfide-bearing material 210, is
obtained and preferably contains copper and other metals.
Further comminution ofconcentrated copper sulfide-bearing
material 210 may be necessary to yield a desired size
distribution for pressure leaching. As will be appreciated,
increasing the fineness of material 210 tends to increase the
reaction rate during pressure leaching, and thus may permit
the use of smaller, more economical pressure leaching apparatus.
Accordingly, material 210 has a particle size of about
80% passing less than about 150 microns, more preferably
less than about 100 microns, and optimally between about 30
to about 75 microns. In some instances, in order to achieve the
optimal particle size, or to expose fresh surfaces or to break up
lumps, a regrinding step 212 may be employed. During
regrinding step 212, solution (e.g., feed slurry 206 or otherwise)
may be added to the flotation concentrate 210 to facilitate
the grinding process.A product slurry 214 is then formed,
preferably with the addition of, for example, sulfuric acid,
dispersants, and the like prior to high temperature pressure
leaching (step 220). Preferably, product slurry 214 has less
than about 50% solids by weight.
Product slurry 214 is next subjected to high temperature
pressure leaching (step 220), preferably at a temperature in
the range of about 210° C. to about 235° C. in a sealed,
agitated, multi-compartment pressure leaching vessel with
oxygen overpressure of at least about 70 psig for about 1-3
hours. During pressure leaching step 220, oxygen preferably
is added continuously to the pressure leaching vessel to maintain
the oxygen overpressure optimal for the desired chemical
reactions to proceed That is, sufficient oxygen is suitably
injected to preferably maintain an oxygen partial pressure in
the pressure leaching vessel ranging from about 50 to about
45 300 psig, and more preferably in the range of about 60 to
about 150 psig. The total pressure in the sealed pressure
leaching vessel is superatmospheric, and can range from
about 300 to about 750 psig, and is preferably in the range of
about 400 to about 600 psig. A product slurry 222 is obtained
in a conventional manner therefrom.
Product slurry 222 may be flashed (step 224) to release
pressure and evaporatively cool product slurry 222 through
release of steam to form a flashed product slurry 226. Flashed
product slurry 226 preferably thereafter has a temperature
ranging from about 85° C. to about 100° C. Solution recovered
from steam generated from flashing step 224 may be
cooled and used as process make-up solution (not shown).
In accordance with further aspects of this preferred
embodiment, after product slurry 222 has been subjected to
atmospheric flashing (step 224) using, for example, a flash
tank, to achieve approximately ambient conditions of pressure
and temperature, flashed product slurry 226 may be
further conditioned in preparation for later metal-value recovery
steps. In some cases, use of a heat exchanger may be
advantageous to cool the slurry such that solid-liquid phase
separation may take place. Preferably, one or more solidliquid
phase separation stages (step 228) may be used to
with the feed slurry in the reactor vessel. The cooling liquid
can be recycled liquid phase from the product slurry, neutralized
raffinate solution, fresh make-up water, or mixtures
thereof, or may be provided by any other suitable source. The
amount ofcooling liquid added during pressure leaching will
vary according to the amount of sulfide minerals reacted (and
thus the heat generated by the pressure leaching reaction).
The duration of pressure leaching in any particular application
depends upon a number of factors, including, for
example, the characteristics ofthe metal-containing material 10
and the pressure leaching process pressure and temperature.
Preferably, the duration of pressure leaching in accordance
with various aspects of the present invention ranges from
about less than I hour to about 3 hours, and optimally is on the
order of about forty-five (45) to ninety (90) minutes. While 15
any reactor vessel for pressure leaching may be used, preferably
an agitated, multiple-compartment pressure leaching
vessel is employed.
In accordance with various aspects of the present invention,
processing step 104 via pressure leaching of metal- 20
bearing material 104 produces a product slurry having a relative
y high acid and metals content, and is characterized by
high metal (e.g., copper) recoveries through metal recovery
step 106. For example, no less than about 98% of the metal
(e.g., copper) in the preferred chalcopyrite and other copper 25
sulfides can generally be recovered through pressure oxidation
utilizing the above-described conditions.
Contrary to prior art processes, such as for example the
aforementioned Placer Dome processes, where significant
amounts of diluting solution are combined with the pressure 30
leaching liquor to reduce the acid concentration, in accordance
with various aspects ofthe present invention, dilution is
not used, or if used, relatively low dilution ratios are used. In
cases where low dilution of the pressure leaching product
slurry is employed, dilution ratios of less than about I: 10 35
metal containing solution to make-up solution are employed.
Preferably, dilution is conducted such that the dilution ratio is
on the order of between about 1:4 and about 1:8 of metalcontaining
solution to make-up solution.
40
With continued reference to FIG. 1, in accordance with
various aspects ofthe present invention, metal recovery step
106 preferably comprises conventional solvent extraction and
electrowinning (SX/EW). It should be appreciated, however,
that other metal recovery processes may be used.
Where metal recovery step 106 comprises SX/EW, such
processing preferably is conducted in a conventional manner.
As such, suitable extraction reagents should be employed.
Preferably, such extraction reagents include aldoxime,
aldoxime/ketoxime mixtures and/or modified aldoximes. For 50
example, particularly preferred solvent extraction reagents
include LIX reagents, such as, for example, LIX 622N, which
comprises a mixture of 5-dodecylsalicylaldoxime and tridecanol
in a high flash point hydrocarbon diluent, available
from Cognis Corporation; LIX 984, also available from Cog- 55
nis Corporation, which is a mixture of 5-dodecylsalicylaldoxime
and 2-hydroxy-5-nonylacetophenoneoxime in a high
flash point hydrocarbon diluent; or M-5774, available from
Avecia, an Acorga™ solvent extraction reagent, which comprises
a modified aldoxime (5-nonyl salicylaldoxime). Other 60
suitable solvent extraction reagents, however, may be
employed.
As will be appreciated by the disclosure set forth herein,
metal recovery process 100 enables various advantages over
recovery processes wherein more significant dilution is 65
required. For example, by using relatively low dilution ratios,
lower operation costs potentially can be obtained, primarily
US 7,666,371 B2
7 8
ditions are selected such that the solvent extraction reagents
collect the copper in copper-containing solution 230. The
copper-bearing reagents are then subjected to more acidic
conditions to shift the equilibrium conditions to cause the
copper to be exchanged for the acid in a highly acidic acid
stripping solution (not shown). Various process stages may be
used, as necessary, to provide a suitable stream to feed the
electrowinning process and to yield a substantially barren
solvent for re-use in the extraction process. During solvent
10 extraction 252, copper from copper-containing solution 230
may be loaded selectively onto an organic chelating agent,
such as the aforementioned aldoximes or aldoxime/ketoxime
blends. Preferably, an extraction reagent, such as LIX 984 or
Acorga® M-5774, is dissolved in an organic diluent to result
15 in the extraction of copper from metal-containing solution
which can be recovered through conventional electrowinning
(step 254) to yield the desired metal product 256. As previously
mentioned, LIX 984 is a mixture of 5-dodecylsalicylaldoxime
and 2-hydroxy-5-nonylacetophenone oxime in a
20 high flash point hydrocarbon diluent, which forms complexes
with various metal cations, such as Cu2
+. Other solvent
extraction reagents may be used in accordance with various
aspects of the present invention. Such extraction reagents
should, however, be selected to facilitate suitable extraction
25 and subsequent stripping operations.
Solvent extraction step 252 and electrowinning step 254
may also involve various solvent stripping and recycle operations
(both ofwhich are not shown) which can be operated in
a conventional manner. Preferably, no less than about 98% of
30 the copper in copper-containing solution 230 is recovered as
cathode copper product 256 by solvent extraction 252 and
electrowinning 254.
With continued reference to FIG. 2B, electrowinning step
35 254 also preferably proceeds in a conventional manner to
yield a pure, cathode copper product 256. In accordance with
the various aspects of this embodiment of the present invention,
a high-quality, uniformly plated cathode copper product
256 may be realized without subjecting copper-containing
40 solution 230 to significant dilution prior to solvent extraction.
As those skilled in the art will appreciate, a variety ofmethods
and apparatus are available for the electrowinning of copper
and other metal values, any ofwhich may be suitably used in
accordance with this embodiment of the present invention.
Raffinate solution 260 from solvent-extraction step 252
may be used in a number of ways. For example, all or a
portion ofraffinate 260 may be used in heap leaching operations
262. In some cases, in accordance with various aspects
of this embodiment of the present invention, use of raffinate
50 260 in heap leaching operations 262 may be desirable inasmuch
as raffinate 260 may have higher acid levels and in some
cases thereby more advantageously affecting heap leaching
operations 262. Alternatively, the pH ofraffinate solution 260
may be chemically adjusted, such as is shown in step 264 and
55 the resulting product sent to impoundment (step 266). In
accordance with yet another aspect ofthis embodiment ofthe
present invention, raffinate solution 260 may be agitated in a
tank leach operation (step 268).
With reference again to FIG. 2A, ifthe metal content ofthe
60 washed solids, that is residue 280, from solid-liquid separation
step 228 is sufficiently high to warrant further processing,
the metals contained therein may be recovered through conventional
means such as, for example, through smelting (step
282) or established precious metals recovery processing (step
65 284). If, however, the metals content ofresidue 280 is too low
to justifY further treatment, the residue may be sent to an
impoundment area (step 286).
separate solubilized metal solution from solid particles. This
may be accomplished in any conventional manner, including
use of filtration systems, counter-current decantation (CCD)
circuits, thickeners, and the like. A variety offactors, such as
the process material balance, environmental regulations, residue
composition, economic considerations, and the like, may
affect the decision whether to employ a CCD circuit, a thickener,
a filter, or any other suitable device in a solid-liquid
separation apparatus. However, it should be appreciated that
any technique of conditioning flashed product slurry 226 for
later metal value recovery is within the scope of the present
invention. Preferably, flashed product slurry 226 is subjected
to solid-liquid phase separation (step 228) to yield a resultant
liquid phase copper-containing solution 230 and a solid phase
residue 280.
Flashed product slurry 226 is suitably subjected to solidliquid
phase separation (step 228), by multiple stages of
counter current decantation (CCD) washing in thickeners.
Wash solution and a suitable flocculent may be added as
desired during step 228. In accordance with one alternative
aspect of this embodiment of the present invention, flashed
product slurry 226 may be thickened in a primary thickener to
recover approximately 95% or more of the soluble copper in
a high grade pregnant leach solution. In this case, primary
thickener underflow then proceeds to a multiple-stage CCD
washing circuit, and wash solution and a suitable flocculent
may be added as required (not illustrated).
Referring now to FIG. 2B, in order to optimize solution
extraction ofthe copper, the pH ofcopper-containing solution
230 from solid-liquid phase separation step 228, in accordance
with various aspects ofthis embodiment ofthe present
invention, preferably is adjusted to a pH of about 1 to about
2.2, more preferably to apH ofabout 1.2 to about 2.0, and still
more preferably to a pH of about 1.4 to about 1.8. This
adjustment may be accomplished in a variety of mauners. In
accordance with one aspect of the present invention, coppercontaining
solution 230 is subjected to a chemical pH adjustment
step 232, which optionally can be followed by further
solid-liquid separation (step 234) to yield a final metal-containing
solution 236 for solvent extraction. In such case, the
residue 238 from step 234 can be impounded (step 240) or
otherwise disposed of.
Alternatively, or in combination with the method described
above, the pH of copper-containing solution 230 may be
adjusted through dilution (step 250). In contradistinction to 45
the prior art methods that rely on significant dilution, in
accordance with the present invention, when dilution is
employed, low dilution ratios ofmake-up solution to coppercontaining
solution 230 are used. Dilution step 250 may be
accomplished by dilution with process solution, fresh water
or any other suitable liquid vehicle at dilution ratios of copper-
bearing solution to make-up solution of less than about
1: 10, and more preferably on the order of between about 1:4
to about 1:8. Once the pH of the copper-containing solution
230 has been appropriately adjusted, metal recovery preferably
is achieved by solvent extraction (step 252), ifnecessary,
using relatively high concentrations of extractants in the
organic diluent, followed by electrowinning (step 254).
In accordance with the present invention, in some instances
copper-containing solution may be directly electrowon. Ifthe
properties of solution 230 permit, electrowinning step 254
may be performed directly (that is, without first subjecting
solution 230 to solvent extraction).
When appropriate, solvent extraction, in accordance with
preferred aspects ofthis embodiment ofthe present invention,
is conducted prior to electrowinning and is conducted in a
generally conventional fashion. Typically, equilibrium con9
US 7,666,371 B2
10
The present invention has been described above with reference
to various exemplary embodiments. It should be
appreciated that the particular embodiments shown and
described herein are illustrative of the invention and not
intended to limit in any way the scope ofthe invention as set
forth in the appended claims. For example, although reference
has been made throughout this disclosure primarily to
copper recovery, it is intended that the invention also be
applicable to the recovery of other metal values.
What is claimed is:
1. A metal recovery process comprising the steps of:
a) providing a metal-bearing material in a slurry fonn;
b) subjecting said slurry to flotation to fonn a concentrated
metal-bearing material;
c) pressure leaching said concentrated metal-bearing material
at a temperature in the range of about 170° C. to
about 235° C. in an oxygen-containing atmosphere in a
pressure leaching vessel to fonn a product slurry;
d) separating said product slurry into a metal-bearing solution
and a solids-containing residue;
e) adjusting the pH of said metal-bearing solution to a pH
ofless than about 2.2 by combining said metal-bearing
solution with a make-up diluting solution to yield a
pH-adjusted metal-bearing solution, wherein the ratio of
said metal-bearing solution to said make-up diluting
solution is in the range of from about 1:4 to about 1:8;
f) solvent extracting and electrowinning said pH-adjusted
metal-bearing solution to yield an acid-containing raffinate
solution;
g) applying said acid-containing raffinate solution in a heap
leaching operation.
2. The process of claim 1 wherein said step of providing a
metal-bearing material comprises providing a copper con10
taining material.
3. The process of claim 2 wherein said step of solvent
extracting and electrowinning comprises solvent extracting
and electrowinning said pH-adjusted copper containing solution
to yield an acid containing raffinate solution and copper
15 cathode.
4. The process ofclaim 3, wherein said step ofadjusting the
pH of said metal-bearing solution comprises combining said
metal-bearing solution with a make-up diluting solution to
yield a pH-adjusted metal-bearing solution wherein the ratio
20 of said metal-bearing solution to said make-up diluting solution
is in the range of from about 1:4 to about 1:8 and the pH
of said pH-adjusted metal-bearing solution is from about 1.4
to about 1.8.
* * * * *
w Roma�v�sr�^D��areast-font-family: HiddenHorzOCR'>Plaster of Paris, 1% 70 No Change
Pitch Coal, 1% 76 12% Decrease
Na3P04012H20,1% 75 10% Decrease
Toner
1Higher value indicates less dust.
2Untreated raw coal light transmittance was 68% at 60 sec. Less than 5%
change after treatment was indicated as no change.
Dust Suppression
Agent
48- by 200-mesh
PRB Coal
Plaster of Paris
Na3P04012H20
11
US 7,208,023 B2
12
imparting a second electrostatic charge to the first fraction,
wherein the second electrostatic charge is opposite
the first electrostatic charge; and
mixing the first and second fractions.
2. The method, as claimed in claim 1, wherein the first
fraction is less than about 20% by weight of the total bulk
material.
3. The method, as claimed in claim 1, further comprising
reducing the particle size of the first fraction before the step
of imparting. 10
4. The method, as claimed in claim 1, wherein the step of
imparting comprises,
placing the first fraction in an electrostatic field of at least
about I kV/cm;
raising the temperature of the first fraction in the electro- 15
static field to between about 30° C. and about 300° c.;
and
maintaining the first fraction in the electrostatic field and
at the raised temperature for between about 5 minutes
and about 600 minutes. 20
5. The method, as claimed in claim 1, wherein the step of
imparting comprises treating the first fraction with a corona
discharge.
6. The method, as claimed in claim 1, wherein the bulk
material is a bulk fuel material. 25
7. The method, as claimed in claim 1, wherein the bulk
material is coal selected from the group consisting of
bituminous coal, subbituminous coal and lignite.
8. A method of treating a solid particulate material,
comprising: 30
a. separating the material into first and second fractions,
wherein the first fraction comprises less than about
10% of the total material;
b. reducing the particle size of the first fraction;
c. placing the first fraction in an electrostatic field of at
least about I kV/cm;
d. raising the temperature of the first fraction in the
electrostatic field to between about 30° C. and about
300° c.;
e. maintaining the first fraction in the electrostatic field
and at the raised temperature for between about 5
minutes and about 600 minutes;
f. cooling the first fraction to ambient temperature while
maintaining the electrostatic field;
g. removing the first fraction from the electrostatic field
when the material temperature is at ambient temperature;
and
h. mixing the first and second fractions.
9. A method to control dusting in a bulk material having
a first electrostatic charge, comprising:
placing a charge control agent in an electrostatic field of
at least about I kV/cm;
raising the temperature of the charge control agent in the
electrostatic field to between about 30° C. and about
300° c.;
maintaining the charge control agent in the electrostatic
field and at the raised temperature for between about 5
minutes and about 600 minutes; and,
mixing the bulk material with a charge control agent
having a second electrostatic charge opposite the first
electrostatic charge, wherein the amount of the charge
control agent is between about 0.1% and about 20% by
weight of the bulk material.
* * * * *
fam�� H�^D��OCR'>a) providing a feed stream comprising an elemental
sulfur-bearing material and a dispersant wherein said
dispersant comprises at least one of a surfactant,
ground sand, mineral processing tailings, or combination
thereof, and wherein said elemental sulfur-bearing 25
material comprises an elemental sulfur-containing residue
from a pressure leaching operation carried out at a
temperature in the range of about 1400 C. to about 1800
c.;
b) pressure leaching at least a portion of said feed stream 30
at a temperature in the range of about 2200 C. to about
275 0 C. in an oxygen-containing atmosphere in an
agitated multiple-compartment pressure leaching vessel
to form a product slurry comprising a sulfuric acid
solution;
c) separating at least a portion of said sulfuric acid 35
solution from said product slurry to yield a residue;
d) recovering at least one metal value from said residue.
2. The process of claim 1 wherein said step of recovering
at least one metal value from said residue comprises recovering
at least one precious metal from said residue.
3. The process of claim 1 wherein said step of pressure
leaching at least a portion of said feed stream comprises
pressure leaching at temperatures above about 2350 C.
4. A treatment process comprising the steps of:
a) providing a feed stream comprising an elemental 45
sulfur-bearing material-wherein said elemental sulfurbearing
material comprises an elemental sulfur-containing
residue from a pressure leaching operation
carried out at a temperature in the range of about 1400
C. to about 1800 c.; 50
b) pressure leaching at least a portion of said feed stream
in the presence of a dispersant wherein said dispersant
comprises at least one of a surfactant, ground sand,
mineral processing tailings, or combination thereof, at
a temperature in the range of about 2200 C. to about
275 0 C. in an oxygen-containing atmosphere in an 55
agitated multiple-compartment pressure leaching vessel
to form a product slurry comprising a sulfuric acid
solution;
c) separating at least a portion of said sulfuric acid
solution from said product slurry to yield a residue;
d) recovering at least one metal value from said residue.
5. The process of claim 4 wherein said step of recovering
at least one metal value from said residue comprises recovering
at least one precious metal from said residue.
6. A process for recovering metal values from an elemental
sulfur-bearing solid residue of a pressure leaching pro
='fo�`�ie�^D��nt-family:"Times New Roman","serif";mso-fareast-font-family: HiddenHorzOCR'>at a temperature in the range of about 220° C. to
about 275° C. in an oxygen-containing atmosphere in
an, agitated multiple-compartment pressure leaching
vessel to form a product slurry comprising a sulfuric
acid solution;
c) adding a dispersant during said pressure leaching step;
d) separating at least a portion of said sulfuric acid
solution from said product slurry to yield a solid
residue;
e) recovering at least one precious metal value from said
solid residue.
17. The process of claim 16 wherein said step of providing
an elemental sulfur-bearing material comprises providing an
5 elemental sulfur-containing residue from a pressure leaching
operation carried out at a temperature in the range of about
140° C. to about 180° C.
18. The process of claim 16 wherein said step of pressure
10 leaching comprises pressure leaching at a temperature of
about 235° C.
* * * * *