United States Patent [19]
Brison. et ale
[11] Patent Number:
[45] Date of Patent:
4,754,953
Jut 5, 1988
[54] UTILIZATION OF OXYGEN IN LEACHING
AND/OR RECOVERY PROCEDURES
EMPLOYING CARBON
Related U.S. Application Data
Division of Ser. No. 732,637, May 10, 1985, abandoned.
Int. Cl.4 C22B 11/04
U.S. Cl 266/101; 266/168;
266/170; 75/101 R; 75/105; 75/108; 75/109;
75/118 R; 423/27; 423/29; 423/30; 423/31
Field of Search 423/27,29, 30, 31;
75/105, 101 R, 108, 109, 118 R; 266/101, 168,
170; 422/129, 211, 232
References Cited
U.S. PATENT DOCUMENTS
4,251,352 2/1981 Shoemaker 209/45
4,331,472 5/1982 King, Jr 266/170 5 Claims, 3 Drawing Sheets
[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-Ieach (CIL) processes and
related processes using resins. Deaeration of the ore
slurry can be practiced prior to the introduction of the
oxygen.
4,416,774 1111983 Taylor 210/236
4,457,495 7/1984 Eder et al. 266/170
FOREIGN PATENT DOCUMENTS
0899119 111982 U.S.S.R 266/168
Primary Examiner-Robert L. Stoll
Attorney, Agent, or Firm-Nixon & Vanderhye
Robert J. Brison, Golden, Colo.; Carl
L. Elmore; Phillip Mitchell, both of
Glens Falls, N.Y.
Kamyr, Inc., Glens Falls, N.Y.
900,687
Aug. 27, 1986
Assignee:
Appl. No.:
Filed:
[75] Inventors:
[73]
[21]
[22]
[58]
[62]
[51]
[52]
[56]
ORE FEED
FROM
THICKENER
SO%SOUDS
-ISO MESH
LOADED
CARBON
TO GOLD
RECOVERY
..5"8 I
LOADED
CARBON
TO GOLD
RECOVERY
ORE FEED
FROM
THICKENER
50 % SOLIDS
-/50 MESH
WASTE
/3/
/4
/7
//
;:2
zz"
~.L
CARBON
ADDITION
COARSE PARTICLES+30
MESH
II
II
I~ I
49
./
~
CFl •
~a~
sa.
~F-
",UI ....
\0
00
00
en
0'"
rt>
~....
~w
-..A.
-..l
lJl
-..A.
\0
lJl
W
u.s. Patent
ORE,
CYANIDE
SLURRY
Jul. 5, 1988
DEAERATE
Sheet 2 of 3
02
INJECTION
4,754,953
60
1SLURRY
FLOW
DIRECTION
ICARBON
GRANULE
DIRECTION
LOADED CARBON
TO STRIPPING,
ACID WASHING.
THERMAL
REGENERATION
AND REUSE
6/
66 70
RESIDUE;
.....-.~:J----------l:::JCYANIDE DESTRUCT
oN a 01 SPOSAL
r.JJ
::r'
t't>
~
W
o
~
w
~
E=-
...A.
-.l
til
...A.
\0
til
t;..)
VI
.....
\0
00
00
~
U'J •
~
§
I""+-
TAILING
CARBON
LOADED
CARBON
TO GOLD
RECOVERY
~a
CIP
RECOVERY
7.f"
83
as-
78
76
77
FIBER
15 tt / TON
7.5 T /0
FLOCCULANT
.25 IS- /TON
250#/0
MILL WATER
169 GPM
OVERSIZE RETURN
TO REGRIND
NaCN IT/D
ORE FEED
FROM CLASSIFIER
1000
T/D 35%
SOLIDS
r,
-~-i
I 02 /400 il /0 I 1i1r-E-tikJl 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
actuated carbon results in an extremely efficient
5process for treatment ofgold 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 significantly
higher proportion of oxygen than is found in air.
Although activated carbon is well known to be a
catalyst in decomposition of cyanideion 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 has a higher proportion of oxygen
than natural air; it will also have a significantly lower
proportion of carbon dioxide than normal air. Reduced
carbon dioxide also increases carbonadsorption 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
omy 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-fifth 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-fifth 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 significantly decreased.
Compared to conventional CIL processes, the process
according to the invention would reduce the agitated
tank size by a factor of about five 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
4,754,953
1
UTILIZATION OF OXYGEN IN LEACHING
AND/OR RECOVERY PROCEDURES
EMPLOYING CARBON
This is a division 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 regovery of gold
and/or silver from ores, and the like, are the carbon-inpulp
(CIP), and carbon-in-leach (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
these vessels, which are open to the atmosphere, and in 25
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 first 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 ofabout 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
gold 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 significantly 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.
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
ofthe detailed description ofthe invention, and
from the appended claims.
BRIEF DESCRIPTION OF THE DRAWINGS 10
FIG. 1 is a schematic view, with parts of some components
shown in cross-section, of exemplary apparat1ls
for practicing a eIP process according to the present
invention;
FIG. 2 is a schematic view of exemplary apparat1ls 15
for practicing a CIL process according to the invention;
and
FIG. 3 is a schematic view of exemplary apparat1ls
for increased efficiency of ore leaching which can precede
the adsorption tanks of the enhanced ClP process 20
according to the invention.
4,754,953
DETAILED DESCRIPTION
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 decreased proportion of carbon
dioxide compared to normal air, which also results
in decreased cyanide consumption and reduced formation
of CaC03.
In the embodiment actually illustrated in FIG. I, 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
The invention will be herein described with respect
to the recovery of gold and/or silver from gold and/or 25 level, and in accordance with the present invention it is
silver containing ores or the like. The term "ore or the desirable to provide a cover for the solution to minimize
like" as used in the present specification and claims the transfer of oxygen from the slurry to the air, and
means all materials conventionally considered as gold also to minimize the t:ansfer o~ nitrogen from the air to
__ .and silver ores, and other materials such as tailings, the s~urry.A conven~lonal stan~nary c?ver tank may be
from which gold and/or silver may be recovered. Also, 30 p~oVlded, or, a floatIng c~ver IS provlde.d, such as the
the invention has applicability to the recovery of other disc-shaped cover 26 which has. a- generally flat top
.-metals. . surface 27, and a generally concave bottom surface 28
In the preferred embodiment according to the present which is actually in con~ct with the sl~, and which
invention, activated charcoal (also known as activated has an a~e 29 therem thr~ugh which the shaft 24
carbon, carbon, and the like) is used as the material for 35 passes. If desl1'ed, a permane~t hd 30 may a:tso be ~laced
adsorbing the gold and/or silver from the solution. on the tank 22, and the enure tank prOVided With an
However it is.to be understood that other materials can oxygen atmosphere at about one atmosphere pressure,
!:Ie utilized, besides activated charcoal granules or parti- or provided with an oxygen atmosphere at significantly
ccles, for adsorbing the gold and/or silver, such as ion greater than one atmospher~ pressure. .
_.-exchange resins (i.e. a resin-in-pulp process, as de- 40 Only one leach tank 22 IS shown..TypI~ally th~r~
':;.scribed in U.S. Pat. No. 4,502,952). would be about 4 to 6 more such tanks m senes to mml-
-~::: .In the utilization ofthe apparat1ls illustrated in FIG. 1 mize short-circ~ting of ~e sl~ particles.
for the practice ofa CIP process according to the inven- After the desl1'ed retennon t1me m the leach tank 22,
tion, the ore is milled in the presence of lime and possi- the. slurry overflows from tank 22, or thr~ugh.cut-out
bly cyanide, and ultimately fed through the flow con- 45 31 m the cover 26, and through the condUit 32 Into the
trol valve 11 to a separating screen assembly 12 which flI'St carbon adsorption tank 34 of a series of such tanks.
screens out the particles that are too large, and is Three tanks are shown in series in FIG. 1, however any.
dumped in discharge 13. If desired, the ore slurry may desired number of tanks may be provided.
be thickened by conventional means to remove part of Conventional components of the tank 34 include the
the solution, which may be treated separately for gold 50 mechanical agitator including blades 35 and shaft 36,
and/or silver recovery. The ore slurry that passes the slurry inlet 37, the slurry outlet 38 covered by a
through the screen 12 passes to the level control tank carbon screen 39 (e.g. see U.S. Pat. No. 4,416,774),
14, and is withdrawn from the tank 14 by the pump 15. carbon inlet 40 connected up to carbon pump 41, and
If desired, the ore slurry can be deaerated as by any carbon outlet 42. The pumps 41, 41' may be placed near
type of conventional deaeration means (such as a vac- 55 the top of the tank. The tank 34 may be a conventional
uum system) 16. covered tank, or may include a non-conventional float-
After the ore slurry passes through pump 15, a con- ing cover 44 which is substantially identical to the cover
ventional basic cyanide solution (such as NaCN) is 26 (except there is no necessity for the cut-out 31),
added to the ore from source 17, additional lime may be which floats on the top of the slurry within the tank 34.
added as needed, and oxygen containing gas from 60 The floating cover can be a plurality of floating balls.
source 18 is added through the flow control valve 19, Non-conventional components of the tank 34 also
and oxygen injector 20. If desired the cyanide solution include the sparger 46 located adjacent the bottom of
and the oxygen containing gas can be added to the the tank for sparging oxygen into the tank from the
slurry utilizing mixers, although since significant mixing source 18. The sparger 46. in addition to introducing the
will take place in subsequent vessels a separate mixer at 65 oxygen into the solution that is necessary for the inthis
point is not essential. creased efficiency according to the invention, also ef-
The oxygen containing gas from source 18 preferably fects some agitation oftile solution, facilitating efficient
comprises generally pure oxygen (that is a gas contain- dissolution of the oxygen.
4,754,953
5
Another non-conventional component of the tank 34
comprises the top 47. The top 47, as does the top 30, can
seal the tank so that an oxygen atmosphere (either at
one atmosphere pressure, or significantly greater than
one atmosphere pressure) may be maintained in the 5
tank.
The further tanks 48, 49, etc. in the adsorption system
are each substantially identical to the tank 34 except
that in the last tank 49 in the series the cover 44/ has
disposed therein a valved opening 50 which allows the 10
addition of activated charcoal particles, which are
coarser than the ore particles in the slurry [the difference
in coarseness allowing effective screening].
The slurry discharged through outlet 38' of the tank
49 goes to tank 52, and from tank 52 is withdrawn by 15
pump 53 and ultimately passed to a disposal site 54 for
the ore tailings (which is what the pulp has been reduced
to). The carbon particles outlet 42 from the first
tank 34 passes through flow control valve 55 to chute
56, and ultimately to the carbon screen 57, with sepa- 20
rated loaded carbon being passed to the gold and/or
silver recovery station 58, and separated slurry in conduit
59 being recirculated.
The apparatus of FIG. 1 can also be utilized for a
carbon-in-leach process merely by elimination of the 25
tank 22. Such an arrangement is especially advantageous,
and the size and/or number of tanks 34, 48, 49
would be less than for conventional CIL processes.
FIG. 2 schematically illustrates another form the
apparatus according to the invention can take for the 30
practice of a CIL process. The ore slurry, mixed with
oxygen, passes into the top of vertical vessel 60, and
flows continuously downwardly therein. Typical conditions
of the ore slurry would be 50 percent solids
(minus 100 mesh), 0.3 gil NaCN, solids specific gravity 35
of 2.7, and a slurry specific gravity of 1.46. The activated
charcoal granules would be introduced from
source 61 into the bottom of the vessel 60 at point 62,
and would flow upwardly in the vessel. Typically the
carbon granules would be relatively large, about 6-16 40
mesh, and would have a lower specific gravity than the
slurry (e.g. 1.2). The slurry density, carbon density and
size, and other factors (such as the addition offlocculent
or fibers to the slurry) could be adjusted to optimize the
carbon upflow rate relative to the slurry downflow rate. 45
The loaded carbon, with some entrained slurry, would
be withdrawn from adjacent the top of the vessel 60 at
point 63, and passed to a carbon screen 64, with the
loaded carbon stripped and regenerated for reuse in the
carbon injection system 61, and with separated slurry in 50
conduit 65 returning to the top of the vessel 60. The
residue withdrawn at the bottom 66 of the vessel 60 by
the pump 67 would either pass into conduit 68 to be
used as part of the liquid for carrying the recycled carbon
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 CIP recovery in station 75. Utilizing the
6
apparatus of FIG. 3, the slurried ore in conduit 76 is
mixed with cyanide from conduit 77, and ultimately
mixed with oxygen from conduit 78 in a mixer 79. The
mixer may be any suitable mixer capable of mixing
components of a medium consistency slurry, such as an
MC® mixer sold by Kamyr, Inc, of Glens Falls, N.Y.
Also, as generally disclosed in U.S. Pat. No. 4,501,721;
flocculent and/or fiber can be added to the slurry to
facilitate locking of the particulized ore in a stable network
in the slurry. For instance cellulosic fibers, fiberglass
fibers, or the like are mixed with liquid in tank 80
and then metered to the inlet to mixer 79, while flocculents,
such as synthetic polymers of anionic, cationic, or
nonionic types are mixed with mill water in tanks 81,
and then ultimately passed to conduit 82 prior to introduction
into upflow 83. The leached slurry that is discharged
from the top 84 of vessel 83 will then pass to
the CIP recovery station 75, which can be as illustrated
in FIG. 1 (without the tank 22). The vessel 83 can also
be pressurized, as by utilizing pressure control valve 85,
and a one atmosphere, or super-atmospheric, oxygen
atmosphere maintained therein, or the vessel can be
completely slurry filled.
Utilizing the apparatus heretofore described, according
to the present invention a process of gold and/or
silver recovery from ore and the like may be practiced.
The process comprises the steps of: leaching gold and/
or silver from the ore or the like, to dissolve the gold
and/or silver, utilizing a basic cyanide solution; and (b)
recovering the leached gold and/or silver in solution by
contacting the solution with solid material for adsorbing
the gold and/or silver from the solution; wherein
step (b) is practiced by providing oxygen gas in the
solution in an amount significantly greater than can be
obtained by contacting the solution with air so as to
greatly increase the solution rate of the gold and/or
silver, and by minimizing the amount of carbon dioxide
in the solution so that it is significantly less than would
be obtained by contacting the solution with air, so as to
possibly increase the gold and/or silver adsorption efficiency
of the adsorbing material, and certainly to reduce
the production of CaC03. Preferably step (b) is
practiced by substantially saturating the solution with
oxygen, and preferably by utilizing generally pure oxygen.
The following table I indicates the results achieved
by preparing a gold cyanide solution by leaching a
common gold ore sample (the gold ore sample, as is
typical, also contained a small amount of silver), and
then exposing the solution to carbon adsorption in a
rotating bottle for six hours, with atmospheres of air,
oxygen, and nitrogen, respectively.
TABLE I
Atmosphere
Oxygen Air Nitrogen
Approx. % 02 100 21 0
in atmosphere
Leach solution 4.14 4.14 4.14
assay, Au, mgII
Final solution assay, 0.032 0.041 0.079
Au. mgll
Final carbon assay, 23.4 23.1 23.1
AU,oz/ton
Au adsorption, %1 99.23 99.01 98.10
Leach solution assay, 1.8 1.8 1.8
Ag, mgll
Final solution 0.2 0.2 0.2
assay, Ag, mgII
Final carbon assay, 8.77 8.97 8.36
Test #1 Test #2
Conditions 65
Grind 77.9%-200 77.9%-200
% Solids 27 27
pH: initial/adj. 8.7/10.9 8.7/10.9
In the following table III, further bottletype tests 50
were conducted for a carbon-in-leach cyanidation, confirming
that simultaneous leaching and carbon adsorption
in an oxygenated slurry results in rapid high gold
extraction with low cyanide consumption. The ore
tested in each of the two tests in table III was Gencor's 55
Buffelsfontein 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
O.19-0.271bs. per ton. The low cyanide consumption is
very unexpected and advantageous.
TABLE III
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. 1), Leslie (No.2), and 81. 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
atomsphere 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 elP process.
TABLE II
20 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 25
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, tola1
CaO,g 0.12 0.12 0.12 30
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 35 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. m1 1414 1453 1399 40
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 0.16 0.33 0.26 45
NaCN, 1b/ton
Extraction. % 92.0 94.7 89.8
Au
Oxygen Air Nitrogen
8
TABLE III-continued
Test #1 Test #2
NaCN, initial gil 0.3 0.3
Time, hr 61 62
Feed
Weight, g 399.9 399.9
Au? oz/ton 0.217 0.217
Reagents added, total
CaO,g 0.12 0.12
NaCN, g 0.25 0.25
Carbon
Mesh size Tyler 6 X 14 6 X 14
Initial wt, g 22.00 22.00
Final wt, g 22.26 22.07
AU,ozlton 2.684 2.695
Sol'n, end of test 10.5 10.6
pH
Filtrate. total
Volume, mI 1412.67 1417.76
NaCN, gil 0.24 0.22
Residue
Weight, g 298.24 298.48
AU,oz/ton 0.019 0.018
Reagents consumed 0.37 0.47
NaCN, 1b/ton
Extraction, % 91.3 91.7
Au
Calculated heads 0.219 0.217
AU,oz/ton
Ipre-saturated with 02 at ambo press. for 16 hours previous to leach.
2During 6-hr elP leach, purge with 02 at T = 0 ht and T = 1 hr. Also add 11 g
carbon at each of these times.
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
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 mddiflcations may be made
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 a leach-adsorpton system for the recovery of
one of gold and silver from ore slurry containing the
same and also a gas containing a substantially higher
proportion of oxygen than is contained in natural air
wherein one of the gold and silver is leached from the
ore and recovered by contacting the slurry with solid
material for adsorbing the one of said sold and silver
from solution, apparatus therefor comprising:
a vessel having an inlet for the introduction of the ore
slurry and an outlet for the ore slurry;
means for controlling the level of slurry within the
vessel;
floating cover means disposed at the top of the slurry
level of the vessel for reducing the transfer of oxygen
out ofthe slurry and the transfer of nitrogen or
carbon dioxide into the slurry; and
a mechanical agitator disposed in said vessel, said
mechanical agitator including a central shaft, and
said floating cover means comprising means defining
an aperture therein for receipt of said shaft so
that said shaft may pass therethrough into the
slurry.
2. Apparatus as recited in claim 1 further comprising
sparger means for sparging oxygen into the slurry adjacent
the bottom of the vessel.
5
4,754,953
88.6 88.6 88.1
Atmosphere
7
TABLE I-continued
Ag,oz/ton
Ag adsorption, %1
'Based on final carbon and final solution.
4,754,953
9
3. Apparatus as recited in claim 2 further comprising
means for introducing activated charcoal particles into
the vessel, means for withdrawing said particles from
the vessel, and screening means at said slurry outlet for
screening the particles out of the slurry passing through 5
said outlet.
4. Apparatus as recited in claim 3 wherein said floating
cover means comprises a bed of floating balls.
5. In a leach-adsorption system for the recovery of 10
one of gold and silver from ore slurry containing the
same and also a gas containing a substantially higher
proportion of oxygen than is contained in natural air
wherein one of the gold and silver is leached from the
ore and recovered by contacting the slurry with solid 15
10
material for adsorbing the one of said gold and silver
from solution, apparatus therefor comprising:
a vessel having an inlet for the introduction of the ore
slurry and an outlet for the ore slurry;
means for controlling the level of slurry within the
vessel; and
floating cover means disposed at the top of the slurry
level of the vessel for reducing the transfer of oxygen
out of the slurry and the transfer of nitrogen or
carbon dioxide into the slurry, said floating cover
means comprising a disc-shaped cover having a top
substantially flat surface, and having a bottom surface
that is substantially concave, said substantially
convcave bottom in contact with the slurry.
... ... ... ... ...
20
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30
35
40
45
50
55
60
65