Specialized metallurgical processes – compositions for use therei – Processes – Free metal or alloy reductant contains magnesium
Reexamination Certificate
1999-09-15
2001-06-12
Andrews, Melvyn (Department: 1742)
Specialized metallurgical processes, compositions for use therei
Processes
Free metal or alloy reductant contains magnesium
C205S583000, C423S139000, C423SDIG001
Reexamination Certificate
active
06245125
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to the recovery of at least copper and nickel from a concentrate containing copper and nickel minerals.
The specification of U.S. Pat. No. 5,919,674 describes a process for the recovery of copper which includes the following steps:
(a) biologically oxidising copper sulphide concentrate in slurry form to dissolve copper as soluble copper sulphate;
(b) subjecting the slurry to solid/liquid separation to produce a solution with a high copper concentration;
(c) treating the solution with a solvent extraction reagent so that copper ions are exchanged by the reagent for hydrogen ions to produce a raffinate which is high in sulphuric acid and low in copper sulphate;
(d) stripping the solvent extraction reagent with a sulphuric acid solution;
(e) electrowinning copper from the sulphuric acid solution; and
(f) using at least a portion of the raffinate from step (c) in step (a).
SUMMARY OF THE INVENTION
The present invention is concerned with a process for the recovery of at least copper and nickel.
The invention provides a process for the recovery of at least copper and nickel from a concentrate containing copper and nickel minerals which includes the following steps:
(a) biologically oxidising the mineral concentrate in slurry form to dissolve copper as soluble copper sulphate and nickel as nickel sulphate;
(b) subjecting the slurry to solid/liquid separation to produce a solution with a high copper and nickel concentration;
(c) treating the solution with a solvent extraction reagent so that copper ions are exchanged by the reagent for hydrogen ions to produce a raffinate which is high in sulphuric acid and low in copper sulphate;
(d) stripping the solvent extraction reagent with a sulphuric acid solution;
(e) electrowinning copper from the sulphuric acid solution;
(f) using a portion of the raffinate from step (c) in step (a); and
(g) recovering nickel from the raffinate which remains after step (f).
The ratio of concentrate to solution prior to the solvent extraction step (c), i.e. in the feed to the solvent extraction step, may be adjusted e.g. by altering the ratio of raffinate to concentrate in step (a), to give a copper concentration in solution, as feed to step (c), in excess of 10 grams per litre, preferably in excess of 20 grams per litre and desirably of from 25 to 30 grams per litre.
To achieve this desired high level of copper concentration the leachate from step (a), must be concentrated beforehand to a higher level, for the leachate is filtered and washed and this dilutes the concentrate.
The biological oxidation in step (a) may be carried out using any suitable bacterium, bacteria, archaea (or archaebacteria), or other similar microorganism. Depending on the mineral type, use may for example be made of one or more mesophiles or moderate thermophiles or thermophiles such as the following: mesophiles: Thiobacillus ferrooxidans (ATCC 23270), Thiobacillus thiooxidans (ATCC 19377), Leptospirrilum ferrooxidans (ATCC29047); moderate thermophiles: Thiobacillus caldus (ATCC 51756), acidimicrobium (DS M2 10 331) and strains Sulfobacillus (DSMZ 10332 and ATCC 51911); thermophiles: strains Sulfolobus (DSMZ 639, DSMZ 1616, DSMZ 1651,DSMZ 5389, DSMZ 6482 and DSMZ 7519).
A combination of mesophiles such as
Thiobacillus ferrooxidans, Thiobacillus thiooxidans
and
Leptospirrilum ferrooxidans
may be used for the oxidation of many sulphide minerals including pentlandite, chalcocite, bornite, covellite, digenite, enargite and tetrahedrite. If these bacteria are used then the temperature in the tank used for carrying out step (a) may be maintained at a value of from 30° C. up to about 45° C.
Moderate thermophiles such as
Thiobacillus caldus, acidimicrobium
and the type strain Sulfobacillus may be used for the leaching of pentlandite, chalcocite, bornite, covellite, digenite, enargite, tetrahedrite and chalcopyrite. The temperature of the tank used for carrying out step (a) may then be maintained at a value of from about 45° C. to 65° C. The predominant bacterial strain in such a mixed culture will depend at least on the operating temperature. Thermophiles of the type Sulfolobus may be used for leaching the same minerals as the moderate thermophiles, and are particularly effective for leaching chalcopyrite. The temperature of the tank used for carrying out step (a) may then be maintained at a value of from 60° C. to 90° C., the optimum temperature again being dependent on the strain used. The strain
Sulfolobus metallicus
, for example, shows optimal growth in the temperature range 65° C. to 78° C.
Step (b) may be carried out in any suitable way and, for example, use may be made of settling or filtration.
Wash water may be introduced in step (b) to ensure that the solid residue is washed free of copper sulphate and nickel sulphate.
Step (c) may be carried out using any appropriate solvent extraction reagent such as an oxime-type reagent.
Preferably steps (b) and (c) are controlled so that the raffinate contains from 30 to 40 grams per litre free sulphuric acid. The copper content of the raffinate may lie in the range of from 2 to 5 grams per litre. This copper content is not necessarily disadvantageous for as much as possible of the raffinate is recycled.
The concentration level of sulphuric acid in the raffinate is dependent at least on the nature of the solvent extraction reagent which is used in step (c). This level should, within reason, be as high as possible. However solvent extraction reagents which are currently available and which are known to the applicant do not readily permit a concentration of sulphuric acid materially in excess of 40 grams per litre to be attained.
The aforementioned process may be modified by using the high copper concentration solution produced in step (b) to chemically pre-leach the mineral concentrate, subjecting the leachate to a solid/liquid separation step, directing the separated liquid to the solvent extraction step (c), and subjecting the separated solids to the biological oxidation step (a).
Prior to step (g), iron may be removed e.g. by precipitation from the raffinate which remains after step (f). Copper may also be removed by precipitation; preferably as a sulphide.
Iron may also be removed by precipitation prior to step (b) or prior to step (c). The pH of the slurry or the solution may be adjusted to a pH value in the range of from 2,0 to 3,5 at a temperature of from 30° C. to 90° C. Suitable neutralisation agents for iron precipitation include limestone, lime and magnesium oxide.
Nickel sulphate may be removed, e.g. by ion exchange or solvent extraction from the said remaining effluent, in step (g), or from the liquid which is directed to the solvent extraction step (c) (referring to the modified process).
Nickel may alternatively be recovered by precipitation as an hydroxide, carbonate or sulphide.
REFERENCES:
patent: 5919674 (1999-07-01), Tunley
patent: 5948375 (1999-09-01), Stallknecht
patent: 1422792 (1992-10-01), None
Dew David William
Miller Deborah Maxine
Andrews Melvyn
Billiton S.A. Limited
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