Sep 5, 2000 - cited by examiner. Primary ExaminerâMelvyn Andrews. (74) Attorney ...... W. DUDAS. Director ofthe United States Patent and Trademark O?'i'ce.
US006833020B1
(12) United States Patent
(10) Patent N0.:
Dew et al.
(54)
(45) Date of Patent:
RECOVERY OF COPPER FROM COPPER
(58)
BEARING SULPHIDE MINERALS BY BIOLEACHING WITH CONTROLLED OXYGEN FEED
266/79, 580
(56)
References Cited
U'S' PATENT DOCUMENTS
Petrus Basson, Randburg (ZA);
5,007,620 A
Deborah Maxine Miller, Johannesburg
5,021,069 A
(ZA)
5,413,624 A
4/1991 Emmett, Jr. et al. *
5,462,720 A 5,919,674 A
(73) Assignee: Billiton Intellectual Property, B.V., The Hague (NL) Notice:
Dec. 21, 2004
Field of Search .......... .. 75/743, 712; 423/DIG. 17;
(75) Inventors: David William Dew, Randburg (ZA);
(*)
US 6,833,020 B1
6,733,567 B1 *
Subject to any disclaimer, the term of this patent is extended or adjusted under 35
USC 154(b) by 65 days.
6/1991
Whellock et al. ........... .. 446/22
5/1995 Rusin et al.
10/1995 Aragonés 7/1999 Tunley 5/2004
Dew et al. .................. .. 75/743
FOREIGN PATENT DOCUMENTS EP FR GB
0 004 431 B1 2 640 284 A1 2 225 256 A
9/1981 6/1990 5/1990
(21) Appl. No.:
10/069,948
W0
(22) PCT Filed:
Sep. 5, 2000
* cited by examiner
(86) PCT No.:
PCT/ZA00/00163
Primary Examiner—Melvyn Andrews
§ 371 (9X1), (2), (4) Date:
PC.
(57)
ABSTRACT
A method of recovering copper from a copper bearing
PCT Pub. Date: Mar. 15, 2001
sulphide mineral Which includes the steps of subjecting the
Foreign Application Priority Data
Sep. 7, 1999
2/1997
(74) Attorney, Agent, or Firm—Jones, Tullar & Cooper,
Jul. 19, 2002
(87) PCT Pub. No.: WO01/18269
(30)
W0 97/0592
(ZA) ............................................ .. 99/5746
(51)
Int. Cl.7 ................................................ .. C22B 3/18
(52)
US. Cl. ......................... .. 75/712; 75/743; 205/580;
slurry to a bioleaching process, supplying a feed gas Which contains in excess of 21% oxygen by volume, to the slurry, and recovering copper from a bioleach residue of the
bioleaching process.
266/79; 423/DIG. 17
28 Claims, 6 Drawing Sheets
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US 6,833,020 B1 1
2 The said slurry may contain at least one of the folloWing:
RECOVERY OF COPPER FROM COPPER BEARING SULPHIDE MINERALS BY BIOLEACHING WITH CONTROLLED OXYGEN FEED
arsenical copper sulphides, and copper bearing sulphide minerals Which are refractory to mesophile leaching. The slurry may contain chalcopyrite concentrates. As used herein the expression “oxygen enriched gas” is intended to include a gas, eg. air, Which contains in excess
of 21% oxygen by volume. This is an oxygen content greater than the oxygen content of air. The expression “pure oxy gen” is intended to include a gas Which contains in excess of
BACKGROUND OF THE INVENTION
This invention relates to the recovery of copper from
copper bearing sulphide minerals. Commercial bioleach plants Which are currently in opera
10
contains in excess of 85% oxygen by volume ie. is substan
tion treating sulphide minerals, typically operate Within the temperature range of 40° C. to 50° C. and rely on sparging air to the bioleach reactors to provide the required oxygen. Operation at this relatively loW temperature and the use of air to supply oxygen, limit the rate of sulphide mineral oxidation that can be achieved. For example carrolite and
tially pure oxygen. The method may include the step of maintaining the dissolved oxygen concentration in the slurry Within a desired 15
20
greatly increases the rate of sulphide mineral leaching. The solubility of oxygen is hoWever limited at high temperatures and the rate of sulphide mineral leaching becomes limited. In the case of using air for the supply of oxygen, the effect of limited oxygen solubility is such that the rate of sulphide mineral leaching becomes dependent on and is limited by the rate of oxygen transfer from the gas to
the liquid phase. The bioleaching of secondary copper bearing sulphide
range Which may be determined by the operating conditions and the type of microorganisms used for leaching. The applicant has established that a loWer limit for the dissolved
enargite are relatively sloW leaching at temperatures beloW 50° C., and treatment at or beloW this temperature Would result in poor and sub-economic metal extraction. The use of high temperatures betWeen 50° C. and 100° C.
85% oxygen by volume. Preferably the feed gas Which is supplied to the slurry
oxygen concentration to sustain microorganism groWth and mineral oxidation, is in the range of from 0.2>60%) of the
On the other hand the dissolved oxygen concentration
oxygen to Warrant the additional expense; and
b) if the oxygen level in solution becomes too high
55 must not exceed an upper threshold value at Which micro
microorganism groWth is prevented and sulphide mineral bioleaching stops. Therefore, in order to realise the bene?ts of high rates of sulphide mineral leaching at high temperatures in commer cial bioleaching plants, the draWbacks of requiring expen
organism groWth is prevented. It is pointed out that the upper threshold concentration depends on the genus and strain of
microorganism used in the bioleaching process. A typical upper threshold value is in the range of from 4x10‘3 kg/m3 60
sive oxygen and the risk of failure if the dissolved oxygen levels become too high must be overcome. The bioleaching of sulphide minerals at an elevated temperature results in a high rate of sulphide mineral
oxidation, but is dependent on the supply of oxygen and carbon dioxide to maintain high rates of sulphide mineral oxidation and of microorganism groWth at adequate rates.
65
to 10x10“3 kg/m3. As has been previously indicated the rate of sulphide mineral oxidation, Which can be achieved When operating at a relatively loW temperature of the order of from 40° C. to 55° C., is limited. In order to increase the rate of oxidation it is desirable to make use of thermophiles and to operate at temperatures in excess of 60° C. Any suitable microorgan
ism capable of operating Within this temperature range may
US 6,833,020 B1 8
7 be used. The optimum operating temperature is dependent on the genus and type of microorganism used. Thus mod erate thermophiles of the type Sulfobacillus are suitable for operating at a temperature of up to 65° C. Thermophiles of the type Sulfolobus are suitable for operating at temperatures of from 60° C. to at least 85° C. Sulfolobus metallicus, for
TABLE 1 Commercial Bioreactor Performance Results
example, shoWs optimal groWth in the temperature range of
Reactor temperature
° C.
10 Oxygen mass transfer coefficient
bioleaching process, using a gas enriched With oxygen, or pure oxygen, as the oxidant, at elevated temperatures of
from 40° C. to 85° C.: increases the speci?c sulphide oxidation duty of the reactor considerably; results in an unexpected and signi?cantly enhanced oxygen mass transfer rate; increases the oxygen utilisation, providing that the dissolved oxygen concentration is controlled above the point Where microorganism groWth and mineral oxidation are prevented and beloW the point at Which microorganism groWth is inhibited; and the overall poWer required for the oxidation of sulphide minerals is signi?cantly reduced. The method of the invention represents a signi?cant improvement compared to a bioleach operation carried out
Units
Plant A Plant B
Reactor operating volume In3 Oxygen utilisation % Typical dissolved oxygen concentration mg/l
from 65° C. to 70° C.
The applicant has established that the operation of the
Description
15
s’1
0.047
0.031
Speci?c oxygen demand
kg/m3/day
21.6
14.8
Speci?c sulphide oxidation duty Speci?c poWer consumption per kg sulphide oxidised
kg/m3/day kWh/kgSZ’
8.9 1.7
5.7 1.8
At loW temperatures (40° C.—50° C.), With air as the inlet gas, Which applies to the results for the commercial reactors, Plant A and Plant B, presented in Table 1, the oxygen
transfer coef?cients (M) correspond to the applicant’s design 20
oxygen directly into the bioreactor improves the oxygen
value. The applicant has determined that if the method of the invention Were to be applied to Plant A, the plant perfor mance Would be signi?cantly increased, as indicated by the results presented in Table 2. TABLE 2 Predicted Improvement In Commercial Bioreactor Performance
utilisation ef?ciency. The oxygen utilisation for a conven
operating at from 40° C. to 45° C. With air may be expected to achieve a maximum oxygen utilisation factor of from 40% to 50%. Consequently only 40% to 50% of the total mass of oxygen supplied to the bioleach plant is used to oxidise the sulphide minerals. With the method of the invention the oxygen utilisation is signi?cantly higher, of the order of from 60% to 95%. The higher oxygen utilisation is achieved by controlled oxygen addition and results from the enhanced oxygen mass transfer rate and by operating at loW dissolved oxygen concentrations in the solution phase.
40
896 43.6 2.7
utilisations achieved are expected and the oxygen mass
25 at a temperature of from 40° C. to 45° C. With air. The controlled addition of oxygen enriched air or pure
tional commercial bioleach plant (at least 100 m3 in volume)
42
471 37.9 2.5
Plant A — using
Units
30
Plant A — typical
the method of
operation
the invention
42 Acidithiobacillus
77 Sulfolobus
Reactor temperature Microbial type strain
° C. —
Inlet gas oxygen
% by volume
20.9
90.0
Oxygen utilisation
%
37.9
93.0
Typical dissolved
mg/l
2.5
2.5
kg/m°/day
21.6
59.5
Speci?c sulphide oxidation duty
kg/m3/day
8.9
24.5
Speci?c poWer
kWh/kgSZ’
1.7
1.2
content
35
oxygen concentration
Speci?c oxygen demand 40
consumption per kg sulphide oxidised
It Will be appreciated that although high oxygen demand in bioleach reactors has come about primarily by the use of
higher temperatures, rapidly leaching sulphide minerals at temperatures beloW 60° C., using mesophile or moderate
The results clearly shoW the bene?t of the invention in
gen demands. The method of the invention is therefore not restricted to suit thermophiles or extreme thermophiles, but
achieving higher rates of reaction by the combination of bioleaching at high temperature, adding oxygen enriched gas and by controlling the dissolved oxygen concentration to a predetermined loW level (eg 0.2>