United States Patent [19]
Brison et ale
[11] Patent Number:
[45] Date of Patent:
4,816,234
Mar. 28, 1989
[54] UTILIZATION OF OXYGEN IN LEACHING
AND/OR RECOVERY PROCEDURES
EMPLOYING CARBON
U.S. PATENT DOCUMENTS
4,173,519 11/1979 Parker et al ; 75/105
4,174,997 0/1979 Richter.
4,251,352 211981 Shoemaker 209/45
4,289,532 9/1981 Matson et al 75/105
4,416,774 1111983 Taylor 210/236
4,438,076 3/1984 Pietsch et al 423/30
4,501,721 2/1985 Sherman et al 423/27
4,502,952 3/1985 Naden et al 210/86
4,510,721 211985 Sherman et al 423/27
4,557,905 1211985 Sherman et al 423/27
FOREIGN PATENT DOCUMENTS
85559/82 6/1983 Australia.
18928/83 9/1983 Australia.
3126234 111983 Fed. Rep. of Germany.
76/6476 1011976 South Africa.
77/1778 3/1977 South Africa.
78/1184 311978 South Africa.
8111215 211981 South Africa.
987406 3/1965 United Kingdom.
OTHER PUBLICATIONS
Headley, N. and Tabachnick, H. "Chemistry of Cyan-
References Cited
Related U.S. Application Data
Continuation of Ser. No. 732,637, May 10, 1985, abandoned.
20 Claims, 3 Drawing Sheets
dation. Mineral Dressing Notes", American Cyanamid
Co., Jun. 1958, No. 23.
Davidson R. Brown, G. A. Schmidt, C. G. et al "The
Inventive Cyanidation of Gold-Plant Gravity Concentrates",
J. S. Afr. Inst. Min. Metall. 1978, pp. 146-165.
"On the Dissolution of Precious Metals ... ," Tronev et
al., Comptes Rendus (Doklady) de l'Academie des Sciences
(1937), vol. 16, No.5, pp. 281-284.
"The Kamyr Process for Leaching Gold and Silver
Ores," Elmore et al., First International Symposium on
Precious Metals Recovery, Reno, Nev., Jun. 1984.
"The Chemistry of the Extraction of Gold ... ," Gold
Metallurgy in South Africa, Finkelstein, Chapter 10, p.
309 (1972).
"Research on Pressure Leaching of Ores ... ," Pietsch
et al., Erzmetall, Jun. 1983, pp. 261-265.
"The Treatment of Refractory Gold-Bearing ... ,"
Muir et al., Precious Metals: Mining Extraction and
Processing, 1984, pp. 309-322.
"Solubilities of Inorganic and Metal-Organic Compounds
(Seidel)", Linke, 4th Ed., 1958, vol. 1, p. 250,
vol. 2, pp. 1228-1230.
(List continued on next page.)
Primary Examiner-Gary P. Straub
Attorney, Agent, or Firm-Nixon & Vanderhye
[57] ABSTRACT
In gold and/or silver cyanide leaching-adsorption processes
employing solid adsorbents such as activated
charcoal, the overall efficiency in the recovery of gold
and/or silver from ores or the like is greatly increased
by contacting the cyanide slurry containing the gold
and/or silver, with oxygen gas instead of normal air. A
generally pure oxygen gas can be bubbled into a vessel
containing the slurry, and a cover (e.g. a floating cover)
may be provided on the vessel to reduce the oxygen
transfer out of the solution and to facilitate pressurization
of the system with an oxygen atmosphere. The
procedures of the invention are applicable to carbon-inpulp
(CIP), and carbon-in-leach (CIL) processes and
related processes using resins. Deaeration of the ore
slurry can be practiced prior to the introduction of the
oxygen.
Robert J. Brison, Golden, Colo.; Carl
L. Elmore; Phillip Mitchell, both of
Glens Falls, N.Y.
Kamyr, Inc., Glens Falls, N.Y.
102,742
Sep. 23, 1987
Inventors:
Int. Cl.4 BOlD 11/00; C22B 3/00
U.S. Cl 423/29; 423/27;
75/105; 75/108; 75/118 R
Field of Search 423/27,29,30, 31;
75/105, 101 R, 108, 118 R
Assignee:
Appl. No.:
Filed:
[75]
[73]
[21]
[22]
[63]
[51]
[52]
[58]
[56]
4,816,234
Page 2
OTHER PUBLICATIONS
No. 72/3211, Extract from South Africa Patent Journal.
No. 72/6051, Extract from South Africa Patent Journal.
No. 72/8222, Extract from South Africa Patent Journal.
No. 73/1753, Extract from South Africa Patent Journal.
No. 73/2941, Extract from South Africa Patent Journal.
No. 68/2047, Extract from South Africa Patent Journal.
No. 68/6142, Extract from South Africa Patent Journal.
McDougall et al, "Activated Carbons and Go1d-A
Literature Survey", Minerals Sci. Engng. vol. 12, No.2,
Apr. 1980 pp. 85-99.
Laxen et al, "The Carbon-in-Pulp Gold Recovery
Process-A Major Breakthrough", S. A. Mining &Engineering
Journal, Jul. 1979, vol. 90.
Tsuchida et al, "Studies on the Mechanism of Gold
Absorption on Carbon", Mineral Chemistry Research
Unit, Murdoch University, Perth, W. Australia, 1984.
Newrick et al, "Carbon-in-Pu1p Versus Carbon-
in-Leach", World Mining, Jun. 1983, pp. 48-51.
Laxen et al, "A Review of Pilot-Plant TestworkConducted
on the Carbon-in-Pu1p Process for the Recovery
of Gold", Proceedings, 12th CMMI Congress, 1982,
pp. 551-561.
"Principles of Extractive Metallurgy," Fatha Habashi,
vol. 2, pp. 15-16, 24-30.
Lehrbuch der Metallhiittenkunde, Dr. Ing. Victor Tafel
et al., pp. 17, 31-34.
"Some Studies on the Gold-Dissolution rate in Cyanide
Solutions," Engineering and Mining Journal, pp. 44-47,
vol. 140, No.1, Jan. 1939.
"Unit Operations", G. G. Brown & Associates, John
Wiley & Sons, Inc. (1956), p. 290.
~
(D a
~
~w
~
~
~
rJ1 •
~
foo+. g
l"""fo.
~ --..
00
~
--0.. \
~
~
54
~
~
~
\C
oc
\C
i •
.58 I
LOADED
CARBON
TO GOLD
RECOVERY
I
III
r=----rn 49
I~/
CARBON
ADDITION
COARSE PARTICLES+30
MESH
~./
//
/4
WASTE
/'
/3
/7
ORE FEED
. FROM
THICKENER
50% SOLIDS
-/50 MESH
u.s. Patent
ORE,
CYANIDE
SLURRY
Mar. 28, 1989
DEAERATE
Sheet 2 of 3
02
INJECTION
4,816,234
60
'1 SLFULRORWY
DIRECTION
1CARBON
GRANULE
DIRECTION
LOADED CARBON
TO STRIPPING,
ACID WASHING,
THERMAL
REGENERATION
AND REUSE
6/
~e 70
RESIDUE ~
~~:l---------.GJ CYANIDE DESTRUCTION
a DISPOSAL
g2
t'D a
~
S,
~
... ....
00
~
0'\
~...
~
fJ1 •
~a~
a
CARBON
LOADED
CARBON
TO GOLD
RECOVERY
~
N
",010
~
\C
~ TAILING I~
~o
7..r
83
80
78
76
77
FLOCCULANT
.25 ;- ITON
250lD
MILL WATER
169 GPM
OVERSIZE RETURN
TO REGRIND
FIBER
15 'It I TON
7.5 TID
NaCN IT/D
ORE FEED
FROM CLASSIFIER
1000
TID 35%
SOLIDS
~-l
I
J 02 14001£ /0 ~ IIH:kI I
2
According to the present invention, it has been found
that the combination of (1) the use of oxygen or oxygenenriched
air and (2) a leach-adsorption system employing
activated carbon results in an extremely efficient
5 process for treatment of gold and/or silver ores, or the
like.
It has been found that not only does oxygen increase
the rate of dissolution of gold and/or silver, but that the
overall efficiency. of processes employing carbon ad10
sorption in gold and/or silver recovery is significantly
increased by the use of a gas containing a signiftcantly
higher proportion of oxygen than is found in air. .
Although activated carbon is well known to be a
catalyst in decomposition of cyanide' ion by oxygen,
surprisingly, it has been found that the use of oxygen
rather than air in CIP or CIL systems does not result in
unacceptable cyanide consumption, the cyanide consumption
being unexpectedly low.
It has been found that the increased efficiency that
results from the practice of the present invention has a
number of contributing factors. In CIL and CIP processes,
the oxygen increases the dissolution rate, which
therefore makes the gold and/or silver more readily
available for adsorption by the carbon. Also, since the
gas that is introduced as a higher proportion of oxygen
than natural air, it will also have a signiftcantly lower
proportion of carbon dioxide than normal air. Reduced
carbon dioxide also increases carbon adsorption efficiency
since carbon dioxide reacts with lime in the
cyanide solution to form CaC03 (as well as causing
other problems), which deposits on the carbon granules.
Practicing the invention one can either get a higher
percentage of gold and/or silver extraction, or get the
same percentage extraction as in conventional facilities
only using much less, and/or smaller, equipment, or a
combination of these advantages. For instance in a conventional
CIL plant, all of the CIL tanks could be reduced
to about one-ftfth their normal size if oxygen
were utilized instead of air to contact the solution. Further,
if oxygen is utilized in a leaching process followed
by CIP the large agitated leach tanks can each be reduced
to about one-ftfth their usual size (with commensurate
reduction in the residence time in each).
Compared to conventional CIP processes, according
to the invention since the gold would be adsorbed almost
as soon as it was leached, the driving force for
leaching of the gold would be increased, and the "preg"
robbing effects in the case of carbonaceous ores would
be minimized. Also the tie-up of gold in the in-process
inventory would be signiftcantly decreased.
Compared to conventional CIL processes, the process
according to the invention would reduce the agitated
tank size by a factor of about ftve or more, reduce
the carbon and gold loss due to abrasion of the carbon,
reduce the tie-up of gold in the in-process inventory,
and reduce the. carbon inventory.
The process according to the invention also has the
potential for optimizing the leach time for differences in
the types of ore utilized. For instance for slow leaching
ores, a pressurized leach-adsorption system could be
utilized to obtain higher oxygen concentration in the
solution. For fast leaching ores, oxygen enriched air
could be utilized to provide only a moderate increase in
leach rate since little is gained by reducing the leach
time below the time required for carbon adsorption
(about 4-6 hours). In any event, the practice of the
process according to the invention, and the utilization
4,816,234
1
UTILIZATION OF OXYGEN IN LEACHING
AND/OR RECOVERY PROCEDURES
EMPLOYING CARBON
This is a continuation of application Ser. No. 732,637
ftled May 10, 1985, now abandoned.
BACKGROUND AND SUMMARY OF THE
INVENTION
Procedures that have been gaining increasing acceptance
and widespread usage for the recovery of gold
and/or silver from ores, and the like, are the carbon-inpulp
(CIP), and carbon-in-Ieach (CIL) processes. These
procedures are versatile, and effect efficient recovery of 15
the gold and/or silver from the ore.
In a typical CIP process,milled ore is leached in a
series of agitated vessels (typically approximately six
vessels each having a retention time of about four
hours). In the leach vessels the gold and/or silver is 20
largely dissolved from the pulp. After leaching, the
pulp moves to the CIP adsorption system, which typically
contains about six vessels each having a retention
time of about one hour. The pulp is agitated in each of 25
these vessels, which are open to the atmosphere, and in
each vessel the pulp is contacted by activated charcoal
particles (i.e. carbon granules) that preferentially adsorb
gold and silver from the solution. The inventory of
carbon granules is continuously or periodically trans- 30
ferred from one vessel to the next in the opposite direction
of the flow of the pulp, with carbon discharged
from the ftrst vessel in the series ultimately being passed
to a gold and/or silver recovery station, while the pulp
discharged from the last vessel in the series is leach 35
residue, which can be disposed of.
Resin-in-pulp processes are similar to carbon-in-pulp
processes except that an ion exchange resin is used in
place of carbon granules. Such processes have not yet
received commercial acceptance for Au/Ag leaching. 40
Conventional CIL processes are similar to CIP processes
except that the dissolution and the adsorption of
the gold and silver are practiced essentially simultaneously.
In a typical CIL procedure, the ground and
thickened ore slurry typically passes to a series of about 45
six agitated leach-adsorption vessels, each having a
retention time of about four hours. In the agitated leachadsorption
vessels the carbon and ore flow in countercurrent
paths in basically the same manner as in the CIP
process, with the loaded carbon passed to a recovery 50
stage and the discharged leach residue is disposed of. As
in most cyanidation operations, part of the gold and/or
silver is typically dissolved in the grinding circuit and in
other preliminary processing steps, such as thickening.
Although the proportion of the total metal dissolved in 55
these steps is often substantial, subsequent treatment in a
series of leach vessels, or leach-adsorption vessels, is
typically practiced in order to obtain more complete
golc;l and/or silver recovery.
It has been known for many years that, under certain 60
limiting conditions, the rate of gold dissolution in a
cyanide solution is approximately proportional to the
partial pressure of oxygen, and that the rate of dissolution
can be signiftcantly increased if generally pure
oxygen gas (e.g. gas having an oxygen content of about 65
99 percent or greater) is used instead of air to effect
oxidation during the cyanidation process. However this
fact has not been taken advantage of commercially.
4
ing about 99 percent or more oxygen). However the
desired results according to the invention, of increased
carbon adsorption efficiency, and the like, can sometimes
be achieved even when generally pure oxygen is
not utilized, but rather merely a gas having a significantly
increased proportion of oxygen compared to
normal air. The gas from source 18 also desirably, and
usually inherently (merely by the increase in the proportion
of oxygen), has a determined proportion of
10 carbon dioxid compared to normal air, which also results
in decreased cyanide consumption and reduced
formation of CaC03.
In the embodiment actually illustrated in FIG. 1, a
single leach (or pre-leach) tank 22 is illustrated. In the
tank 22 no carbon is present, but rather only leaching
takes place. As described above, however, the presence
of the oxygen containing gas in the leach· tank 22 also
increases the efficiency of the dissolution of the gold
and/or silver into the cyanide solution.
The tank 22 is preferably an agitated tank, having a
conventional mechanical agitator including blades 23
and shaft 24, powered by a powering device 25 or the
like. The slurry within the tank 22 will achieve a certain
level, and in accordance with the present invention it is
desirable to provide a cover for the solution to minimize
the transfer of oxygen from the slurry to the air, and
also to minimize the transfer of nitrogen from the air to
the slurry. A conventional stationary cover tank may be
provided, or, a floating cover is provided, such as the
disc-shaped cover 26 which has a generally flat top
surface 27, and a generally concave bottom surface 28
wliich is actually in contact with the slurry, and which
has an aperture 29 therein through which the shaft 24
passes. If desired, a permanent lid 30 may also be placed
on the tank 22, and the entire tank provided with an
oxygen atmosphere at about one atmosphere pressure,
or provided with an oxygen atmosphere at significantly
greater than one atmosphere pressure.
Only one leach tank 22 is shown. Typically there
would be about 4 to 6 more such tanks in series to minimize
short-circuiting of the slurry particles.
After the desired retention time in the leach tank 22,
the slurry overflows from tank 22, or through cut-out
31 in the cover 26, and through the conduit 32 into the
first carbon adsorption tank 34 of a series of such tanks.
Three tanks are shown in series of FIG. I, however any
desired number of tanks may be provided.
Conventional components of the tank 34 include the
mechanical agitator including blades 35 and shaft 36,
the slurry inlet 37, the slurry outlet 38 covered by a
carbon screen 39 (e.g. see U.S. Pat. No. 4,416,774),
carbon inlet 40 connected up to carbon pump 41, and
carbon outlet 42. The pumps 41, 41' may be placed near
the top of the tank. The tank 34 may be a conventional
covered tank, or may include a non-conventional floating
cover 44 which is substantially identical to the cover
26 (except there is no necessity for the cut-out 31),
which floats on the top of the slurry within the tank 34.
The floating cover can be a plurality of floating balls.
Non-conventional components of the tank 34 also
include the sparger 46 located adjacent the bottom of
the tank for sparging oxygen into the tank from the
source 18. The sparger 46, in addition to introducing the
oxygen into the solution that is necessary for the increased
efficiency according to the invention, also effects
some agitation of the solution, facilitating efficient
dissolution of the oxygen.
4,816,234
DETAILED DESCRIPTION
BRIEF DESCRIPTION OF THE DRAWINGS
3
of the apparatus according to the present invention, is
extremely advantageous.
It is the primary object of the present invention to
provide for the increased efficiency of the recovery of
gold and/or silver from ores or the like. This and other 5
objects of the invention will become clear from an inspection
of the detailed description ofthe invention, and
from the appended claims.
FIG. 1 is a schematic view, with parts of some components
shown in cross-section, of exemplary apparatus
for practicing a CIP process according to the present
invention;
FIG. 2 is a schematic view of exemplary apparatus 15
for practicing a CIL process according to the invention;
and
FIG. 3 is a schematic view of exemplary apparatus
for increased efficiency of ore leaching which can precede
the adsorption tanks of the enhanced CIP process 20
according to the invention.
The invention will be herein described with respect
to the recovery of gold and/or silver from gold and/or 25
silver containing ores or the like. The term "ore or the
like" as used in the present specification and claims
means all materials conventionally considered as gold
and silver ores, and other materials such as tailings,
from which gold and/or silver may be recovered. Also, 30
the invention has applicability to the recovery of other
metals.
In the preferred embodiment according to the present
invention, activated charcoal (also known as activated
carbon, carbon, and the like) is used as the material for 35
adsorbing the gold and/or silver from the solution.
However, it is to be understood that other materials can
be utilized, besides activated charcoal granules or particles,
or adsorbing the gold and/or silver, such as ion
exchange resins (i.e. a resin-in-pulp process, as de- 40
scribed in U.S. Pat. No. 4,502,952).
In the utilization of the apparatus illustrated in FIG. 1
for the practice of a CIP process according to the invention,
the ore is milled in the presence of lime and possibly
cyanide, and ultimately fed through the flow con- 45
trol valve 11 to a separating screen assembly 12 which
screens out the particles that are too large, and is
dumped in discharge 13. If desired, the ore slurry may
be thickened by conventional means to remove part of
the solution, which may be treated separately for gold 50
and/or silver recovery. The ore slurry that passes
through the screen 12 passes to the level control tank
14, and is withdrawn from the tank 14 by the pump 15.
If desired, the ore slurry can be deaerated as by any type
of conventional deaeration means (such as a vacuum 55
system) 16.
After the ore slurry passes through pump 15, a conventional
basic cyanide solution (such as NaCN) is
added to the ore from source 17, additionalHme may be
added as needed, and oxygen containing gas from 60
source 18 is added through the flow control valve 19,
and oxygen injector 20. If desired the cyanide solution
and the oxygen containing gas can be added to the
slurry utilizing mixers, although since significant mixing
will take place in subsequent vessels a separate mixer at 65
this point is not essential.
The oxygen containing gas from source 18 preferably
comprises generally pure oxygen (that is a gas contain8.36
4.14
0.2
0.079
o
98.10
1.8
23.1
Nitrogen
8.97
4.14
0.041
0.2
Air
21
23.1
99.01
1.8
Atmosphere
8.77
4.14
0.2
0.032
23.4
99.23
1.8
100
Oxygen
Approx. % 02
in atmosphere
Leach solution
assay. Au, mg/l
Final solution assay.
Au, mg/l
Final carbon assay,
Au, oz/ton
Au adsorption. %1
Leach solution assay,
Ag, mg/l
Final solution
assay. Ag, mg/l
Finill carbon assay.
4,816,234
5 6
Another non-conventional component of the tank 34 the apparatus of FIG. 3, the slurried ore in conduit 76 is
comprises the top 47. The top 47, as does the top 30, can mixed with cyanide from conduit 77, and ultimately
seal the tank so that an oxygen atmosphere (either at mixed with oxygen from conduit 78 in a mixer 79. The
one atmosphere pressure, or significantly greater than mixer may be any suitable mixer capable of mixing
one atmosphere pressure) may be maintained in the 5 components of a medium consistency slurry, such as an
tank. MC ® mixer sold by Kamyr, Inc. of Glens Falls, N.Y.
The further tanks 48,49, etc. in the adsorption system Also, as generally disclosed in U.S. Pat. No. 4,501,721,
are each substantially identical to the tank 34 except flocculent and/or fiber can be added to the slurry to
that in the last tank 49 in the series the cover 44' has facilitate locking of the particulized ore in a stable netdisposed
therein a valved opening 50 which allows the 10 work in the slurry. For instance cellulosic fibers, fiberaddition
of activated charcoal particles, which are glass fibers, or the like are mixed with liquid in tank 80
coarser than the ore particles in the slurry [the differ- and then metered to the inlet to mixer 79, while floccuence
in coarseness allowing effective screening]. lents, such as syntheti~ poly~ers o! anionic".cationic, or
The slurry discharged through outlet 38' of the tank nonionic types are 1l1lXed With mill water m tanks 81,
49 goes to tank 52, and from tank 52to withdrawn by 15 and then ultimately passed to conduit 82 prior to intropump
53 and ultimately passed to a disposal site 54 for duction into upflow 83. The leached slurry that is disthe
ore tailings (which is what the pulp has been re- charged from the top 84 of vessel 83 will then pass to
duced to). The carbon particles outlet 42 from the first the CIP recovery station 75, which can be as illustrated
tank 34 pas~ through flow control valve 55 to chute in FIG.l (without the tank 22). The vessel 83 can also
56, and ultimately to the carbon screen 57, with sepa- 20 be pressurized, as by utilizing pressure control valve 85,
rated loaded carbon being passed to the gold and/or and a one atmosphere, or super-atmospheric, oxygen
silver recovery station 58, and separated slurry in con- atmosphere maintained therein, or the vessel can be
duit 59 being recirculated. completely slurry filled.
The apparatus of FIG. 1 can also be utilized for a Utilizing the apparatus heretofore described, accordcarbon-
in-leach process merely by elimination of the 25 ing to the present invention a process of gold and/or
tank 22. Such an arrangement is especially advanta- silver recovery from ore and the like may be practiced.
geous, and the size and/or number of tanks 34, 48, 49 The process comprises the steps of: leaching gold andwould
be less than for conventional CIL processes. lor silver from the ore or the like, to dissolve the gold
FIG. 2 schematically illustrates another form the and/or silver, utilizing a basic cyanide solution; and (b)
apparatus according to the invention can take for the 30 recovering the leached gold and/or silver in solution by
practice of a CIL process. The ore slurry, mixed with contacting the solution with solid material for adsorboxygen,
passes into the top of vertical vessel 60, and ing the gold and/or silver from the solution; wherein
flows continuously downwardly therein. Typical con- step (b) is practiced by providing oxygen gas in the
ditions of the ore slurry would be 50 percent solids solution in an amount significantly greater than can be
(minus 100 mesh), 0.3 gil NaCN, solids specific gravity 35 obtained by contacting the solution with air so as to
of 2.7, and a slurry specific gravity of 1.46. The acti- greatly increase the solution rate of the gold and/or'
vated charcoal granules would be introduced from silver,and by minimizing the amount of carbon dioxide
source 61 into the bottom of the vessel 60 at point 62, in the solution so that it is significantly .less than would
and would flow· upwardly in the vessel. Typically the be obtained by contacting the solution with air, so as to
carbon granules would be relatively large, about 6-16 40 possibly increase the gold and/or silver adsorption effimesh,
and would have a lower specific gravity than the ciency of the adsorbing material, and certainly toreslurry
(e.g. 1.2). The slurry density, carbon density and duce the production of CaC03. Preferably step (b) is
size, and other factors (such as the addition of flocculent practiced by substantially saturating the solution with
or fibers to the slurry) could be adjusted to optimize the oxygen, and preferably by utilizing generally pure oxycarbon
upflow rate relativ to the slurry downflow rate. 45
The loaded carbon, with some entrained slurry, would ge~e following table I indicates the results achieved
be .withdrawn from adjacent the top of the vess:l 60 at by preparing a gold cyanide solution by leaching a
pomt 63, and p~d to a carbon screen 64, Wlt~ the common gold ore sample (the gold ore sample, as is
loaded carbon stopped and regenerated for reuse m the typo al al contained a small amount of silver) and
carbo~ injection s~stem 61, and with separated slurry in 50 the~c e~po:~g the solution to carbon adsorption' in a
co~dwt 6~ returnmg to the top of the vessel 60. The rotatin bottle for six hours, with atmospheres of air,
reSidue Withdrawn at t.he bottom.66 of the v~ssel 60 by x e: and nitrogen respectively.
the pump 67 would eIther pass mto condwt 68 to be 0 yg , ,
used as part of the liquid for carrying the recycled car- TABLE I
bon into the column within the vessel 60, or would pass 55
to conduit 69 and ultimately to cyanide destruction and
disposal site 70.
The vessel 60 may be operated at atmospheric pressure,
or at super-atmospheric pressure, and an oxygen
atmosphere may be provided at the top thereof in either 60
case. Also, the system could be operated so that the
slurry flowed upwardly and the carbon granules flowed
downwardly, if denser carbon were utilized, and/or if
the slurry solids had a lower specific gravity.
FIG. 3 schematically illustrates other exemplary ap- 65
paratus that can be utilized for effectively and efficiently
dissolving the gold and/or silver in the leaching
stage prior to the CIP recovery in station 75. Utilizing
7
TABLE I-continued
4,816,234
8
TABLE III-continued
Atmosphere Test #1 Test #2
IPre-saturated with 02 at ambo press. for 16 hours previous to leach.
2During 6-hr elP leach, purge with 02 at T = 0 hr and T= 1 hr. Also add II g
30 carbon at each of these times.
8.7/10.9
0.3
62
399.9
0.217
6 X 14
22.00
22.07
2.695
10.6
0.12
0.25
91.7
1417.76
0.22
298.48
0.018
0.47
8.7/10.9
0.3
61
399.9
0.217
10.5
0.12
0.25
6 X 14
22.00
22.26
2.684
298.24
0.019
91.3
1412.67
0.24
0.37
pH: initial/adj.
NaCN, initial gil
Time, hr
Feed
Weight, g
Au, oz/ton
Reagents added, lotal
Cao, g
NaCN, g
~
Mesh size Tyler
Initial wi, g
Final wt, g
Au, oz/ton
Sol'n, end of lest
pH
Filtrate, total
Volume, ml
NaCN, gil
~
Weight, g
Au, oz/ton
Reagents consumed
NaCN, 1b/ton
Extraction, %
Au
Calculated heads
Au, oz/ton 0.219 0.217
5
25
In conclusion, according to the present invention, a
method and apparatus are provided for the extremely
efficient and effective recovery of gold and/or silver
35 from ore or the like. While the invention has been
herein shown and described in what is presently conceived
to be the most practical and preferred embodiment
thereof, it will be apparent to those of ordinary
skill in the art that many modifications may be made
40 thereof within the scope of the invention, which scope
is to be accorded the broadest interpretation of the
appended claims so as to encompass all equivalent process
and apparatus.
What is claimed is:
1. In the recovery of gold or silver from an ore slurry,
an adsorbent-in-leach process comprising the steps of
simultaneously, in the same vessel: (a) leaching gold or
silver from the ore slurry, to dissolve the gold or silver,
utilizing a basic cyanide solution; and (b) recovering the
leached gold or silver in solution by contacting the
slurry with an adsorbing material selected from the
group consisting essentially of activated charcoal granules
and ion-exchange resins for adsorbing the gold or
silver from the solution; wherein
steps (a) and (b) are practiced at about atmospheric
pressure by providing a dissolved oxygen concentration
in the slurry that is significantly greater
thana dissolved oxygen concentration in the slurry
if the slurry is contacted with air under identical
pressure conditions such that increased gold or
silver extraction per unit time occurs as compared
with contacting the slurry with air, wherein steps
(a) and (b) are further practiced by introducing
generally pure oxygen into the slurry in contact
with the adsorbing material.
2. A process as recited in claim 1 comprising the
further step of degassing the slurry before practicing
steps (a) and (b).
45
88.1
Air Nitrogen
88.6
Ag,ozlton
Ag adsorption, %1 88.6
Oxygen
Test #1 Test #2 65
Conditions
Grind 77.9% ·200 77.9% - 200
% Solids 27 27
IBased on fmal carbon and fmal solution.
The following table II indicates the results from a
carbon-in-pulp cyanidation test utilizing three different 10
types of Gencor ore samples from, respectively, Buffeisfontein
(No. I), Leslie (No.2), and St. Helena (No.3).
The tests indicate high gold extractions (in the range of
90-95%), and, surprisingly, low cyanide consumption.
All tests were performed in rotated bottles with oxygen 15
atmosphere at the local atmospheric pressure of 12.1
psia. The time in each case (total of 10 hours) was a six
hour cyanide leach plus a four hour eIP process.
TABLE II
-------~;;.;;;;;..;;;;;~;....-------20
In the following table III, further bottle-type tests 50
were conducted for a carbon-in-leach cyanidation, confirming
that simultaneous leaching and carbon adsorption
in an oxygenated slurry results in rapid higli gold
extraction with low cyanide consumption. The ore
tested in each of the two tests in table III was Gencor's 55
Buffiesfontein ore. With gold extractions of about
91-92%, in six hours, cyanide consumption was only
0.37-0.47 Ibs. per ton. If the pulp density and carbon
concentration was closer to expected plant conditions,
cyanide consumption is expected to be as little as 60
0.19-0.27 lbs. per ton. The low cyanide consumption is
very unexpected and advantageous.
TABLE III
Test #1 Test #2 Test #3
Conditions
Grind 77.9% - 200 80%·200 80% - 200
% Solids 27 27 27
pH: initial/adj. 8.7/10.9 9.0/10/8 9.0/10.7
NaCN, initial gil 0.3 0.3 0.3
Time, hr. 10 10 10
Feed
Weight, g 300.0 300.0 300.0
AU,oz/ton 0.217 0.110 0.186
Reagents added, total
Cao,g 0.12 0.12 0.12
NaCN, g 0.25 0.25 0.25
Carbon
Mesh size Tyler 6 X 14 6 X 14 6 X 14
Initial wt, g 22.00 22.00 22.00
Final wt, g 22.05 22.11 22.09
Au,oz/ton 2.631 0.966 1.779
. Sol'n, end of test
NaCN, gil 0.276 0.245 0.264
pH 10.6 10.6 10.4
Filtrate, total
Volume, ml 1414 1453 1399
Au, mgll 0.004 0.002 0.003
Residue
Weight, g 298.7 298.6 298.6
Au, oz/ton 0.017 0.004 0.015
0.015 rerun
Reagents consumed
NaCN, 1b/ton 0.16 0.33 0.26
Extraction, %
Au 92.0 94.7 89.8
4,816,234
9
3. A process according to claim 1 wherein said generally
pure oxygen has an oxygen content of about 99%.
4. A process as recited in claim 1 wherein steps (a)
and (b) are practiced in a covered vented vessel so as to
decrease the transfer of oxygen out of solution and 5
decrease the transfer of nitrogen or carbon dioxide into
the slurry.
5. A process as recited in claim 1 wherein steps (a)
and (b) are further practiced by providing the slurry
and adsorbing material in a vessel, and maintaining an 10
oxygen atmosphere in the top of the vessel.
6. A process as recited in claim 1 wherein steps (a)
and (b) are practiced by directing the flow of the ore
slurry in a fIrst direction, and directing a flow ofadsorbing
material in a second direction, opposite the fIrst 15
direction.
7. A process as recited in claim 1 wherein steps (a)
and (b) are further practiced by agitating the slurry and
adsorbing material.
8. A process as recited in claim 7 wherein said agitat- 20
ing step is practiced by mechanically agitating the
slurry and adsorbing material.
9. A process as recited in claim 7 wherein said agitating
step is practiced by introducing oxygen gas under
pressure into the bottom of a vessel containing the 25
slurry and the adsorbing material.
10. A process as recited in claim 1 such that the consumption
of the cyanide is decreased by using said
greater dissolved oxygen concentration in the slurry as
compared with using the dissolved oxygen concentra- 30
tion in the slurry ifthe slurry is contacted with air under
identical pressure conditions for the same amount of
gold or silver extracted from the ore.
11. A process as recited in claim 1 wherein steps (a)
and (b) are carried out in each of a plurality of serially 35
connected vessels and including the further steps of
directing the flow of the ore slurry in a fIrst direction
serially through said vessels and directing a flow of
adsorbing material in a second direction serially
through said vessels opposite the fIrst direction. 40
12. A process according to claim 11 such that the
consumption of the cyanide is decreased by using said
greater dissolved oxygen concentration in the slurry as
compared with using the dissolved oxygen concentration
in the slurry ifthe slurry is contacted with air under 45
10
identical pressure conditions for the same amount of
gold or silver extracted from the ore.
13. A process according to claim 12 comprising the
further step of degassing the slurry before practicing
steps (a) and (b), and wherein the step of recovering the
leached gold or silver in solution includes contacting
the slurry with activated carbon granules for adsorbing
the gold or silver from the solution.
14. A process according to claim 13 wherein the
activated carbon granules are non-deoxygenated prior
to contact with the slurry.
15. A process according to claim 1 wherein steps (a)
and (b) are practiced by directing the flow of the ore
slurry in a fIrst direction, and directing a flow of adsorbing
material in a second direction, opposite the fIrst
direction and such that the consumption of the cyanide
is decreased by using said greater dissolved oxygen
concentration in the slurry as compared with using the
dissolved oxygen concentration in the slurry if the
slurry is contacted with air under identical pressure
conditions for the same amount of gold or silver extracted
from the ore.
16. A process according to claim 15 wherein steps (a)
and (b) are practiced in a covered vented vessel so as to
decrease the transfer of oxygen out of solution and
decrease the transfer of nitrogen or carbon dioxide into
the slurry.
17. A propess according to claim 15 wherein steps (a)
and (b) are further practiced by providing the slurry
and adsorbing material in a vessel, and maintaining an
oxygen atmosphere in the top of the vessel.
18. A process according to claim 17 wherein the
dissolved oxygen concentration is provided by introducing
oxygen gas under pressure into the bottom of
the vessel containing the slurry and the adsorbing material.
19. A process according to claim 18 comprising the
further step of degassing the slurry before practicing
steps (a) and (b).
20. A process according to claim 1 including introducing
oxygen gas under pressure into the bottom of
the vessel containing the slurry and the adsorbing material.
* * * * *
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60
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