REDUCTION OF LIME CONSUMPTION WHEN TREATING REFRACTORY GOLD ORES OR CONCENTRATES

• US 20100024603A1
• Filed: 10/13/2009
• Published: 02/04/2010
• Est. Priority Date: 12/22/2004
• Status: Active Grant

• Current Assignee: Placer Dome Technical Services Limited
• Original Assignee: Placer Dome Technical Services Limited
• Inventors: Ji, Jinxing, Fleming, Christopher Andrew, Ferron, Cesare Giosue, King, James A.
• Granted Patent: US 8,029,751 B2
• Time in Patent Office: Days
• US Class Current: 75/744
• CPC Class Codes: C22B 11/04 by wet processes extraction of metal compounds by leaching in organic solutions C22B3/16; treatment or purification of solutions by liquid-liquid extraction C22B3/26
• CPC Class Codes: C22B 3/08 Sulfuric acid , other sulfurated acids or salts thereof
• CPC Class Codes: C22B 3/44 by chemical processes treatment or purification of solutions by liquid-liquid extraction C22B3/26, by ion-exchange extraction C22B3/42
• CPC Class Codes: Y02P 10/20 Recycling

Abstract

The present invention is directed to a precious metal recovery process in which basic ferric sulphates and/or jarosites are controlled by a number of mechanisms, including control of the oxidation reaction conditions in the first autoclave compartment, hot curing of the autoclave discharge slurry, and/or contacting of the autoclave feed slurry with the hot cured discharge liquid.

Claims

1-14. -14. (canceled)

15. A precious metal recovery process, comprising:

inputting a precious metal-containing feed slurry into a first compartment of a multi-compartment autoclave, the precious metal-containing feed slurry comprising a precious metal-containing material comprising sulphide sulphur;

providing, in the first compartment a slurry temperature that is at least about 5°

C. less than a slurry temperature in a second compartment of the autoclave, the second compartment being adjacent to and downstream of the first compartment;

removing, from the autoclave, an aqueous discharge slurry comprising discharge solids and aqueous discharge liquid, the discharge solids comprising at least a portion of the precious metal and basic iron sulphate, wherein at least most of the sulphide sulphur is oxidized to sulphate sulphur, wherein the aqueous discharge slurry comprises sulphuric acid, and wherein the discharge slurry comprises less than 10 wt. % (dry basis) of the basic iron sulphate;

contacting the discharge solids with an acid consumer to consume at least a portion of the sulphuric acid and dissolved metal sulphates; and

contacting a lixiviant, at a pH above about pH 7.0, with the discharge solids to solubilize at least most of the precious metal; and

recovering the solubilized precious metal.

16. The process of claim 15, wherein at least most of the iron in the discharge slurry is in the form of hematite.

17. The process of claim 15, wherein at least most of the basic iron sulphate in the aqueous discharge solids is basic ferric sulphate and further comprising before the lixiviant contacting step:

(g) allowing at least most of the basic ferric sulphate in the aqueous discharge solids to react with the sulphuric acid to form ferric sulphate solubilized in the aqueous discharge liquid; and

(h) separating at least most of the aqueous discharge liquid from the discharge solids, wherein at least most of the solubilized ferric sulphate is in the separated aqueous discharge liquid and wherein the separated aqueous discharge solids comprise sulphuric acid; and

(i) contacting the separated discharge solids with an acid consumer to consume at least most of the sulphuric acid and dissolved metal sulphates.

18. The process of claim 15, wherein the slurry temperature in the first compartment is at least about 10°

C. less than the slurry temperature in the second compartment.

19. The process of claim 15, wherein the slurry temperature in the first compartment ranges from about 5 to about 30°

C. less than the slurry temperature in the second compartment.

20. The process of claim 15, wherein from about 0.05 to about 0.90 (molar ratio of equivalent CaO to S) laterite is contacted with the feed slurry prior to or during sulphide oxidation in the first autoclave compartment.

21. The process of claim 15, further comprising before step (a):

(g) contacting at least a portion of the separated aqueous discharge liquid with unoxidized precious metal-containing material, wherein the recycled aqueous discharge liquid comprises dissolved ferric sulphate and free sulphuric acid to partially oxidize sulphide sulphur in the unoxidized material.

22. The process of claim 15, wherein acid consumers are added in the first compartment and wherein the molar ratio of total acid consumers (as equivalent CO₃) to sulphides in the first compartment is no more than about 0.26.

23. The process of claim 22, wherein the molar ratio ranges from about 0.1 to about 0.225.

24. A precious metal recovery process, comprising:

(a) inputting a precious metal-containing feed slurry into a first compartment of a multi-compartment autoclave, the precious metal-containing feed slurry comprising a precious metal-containing material comprising sulphide sulphur;

(b) operating the first compartment, but not at least a second autoclave compartment downstream of the first autoclave compartment, under conditions favoring hematite formation;

(c) removing, from the autoclave, an aqueous discharge slurry comprising discharge solids and aqueous discharge liquid, the discharge solids comprising at least a portion of the precious metal and basic iron sulphate, wherein at least most of the sulphide sulphur is oxidized to sulphate sulphur, wherein the aqueous discharge slurry comprises sulphuric acid, and wherein the discharge slurry comprises less than 10 wt. % (dry basis) basic iron sulphate;

(d) contacting the discharge solids with an acid consumer to consume at least a portion of the sulphuric acid and dissolved metal sulphates; and

(e) contacting a lixiviant, at a pH above about pH 7.0, with the discharge solids to solubilize at least most of the precious metal; and

(f) recovering the solubilized precious metal.

25. The process of claim 24, wherein, in the operating step, the first compartment has a slurry temperature that is at least about 5°

C. less than a slurry temperature in the second compartment.

26. The process of claim 24, wherein the first compartment is the initial compartment in the autoclave and wherein, in the operating step, no more than about 70% of the sulphide sulphur in the first compartment is oxidized.

27. The process of claim 24, wherein the first compartment is the initial compartment in the autoclave and wherein, in the operating step, a total acid concentration in the first compartment ranges from about 5 to about 30 g/l.

28. The process of claim 24, wherein acid consumers are added to the first but not the second compartments and wherein a molar ratio of total acid consumers to sulphides in the first compartment ranges from about 0.10 to about 0.225.

29. The process of claim 24, wherein at least most of the iron in the discharge slurry is in the form of hematite and wherein at least most of the basic iron sulphate in the aqueous discharge solids is basic ferric sulphate and further comprising before the lixiviant contacting step:

(g) allowing at least most of the basic ferric sulphate in the aqueous discharge solids to react with the sulphuric acid to form ferric sulphate solubilized in the aqueous discharge liquid; and

(h) separating at least most of the aqueous discharge liquid from the discharge solids, wherein at least most of the solubilized ferric sulphate is in the separated aqueous discharge liquid and wherein the separated aqueous discharge solids comprise sulphuric acid; and

(i) contacting the separated discharge solids with an acid consumer to consume at least most of the sulphuric acid and dissolved metal sulphates.

30. The process of claim 25, wherein the slurry temperature in the first compartment is at least about 10°

C. less than the slurry temperature in the second compartment.

31. The process of claim 25, wherein the slurry temperature in the first compartment ranges from about 5 to about 30°

C. less than the slurry temperature in the second compartment.

32. The process of claim 24, wherein from about 0.05 to about 0.90 (molar ratio of equivalent CaO to S) laterite is contacted with the feed slurry prior to or during sulphide oxidation in the first autoclave compartment.

33. The process of claim 24, further comprising before step (a):

(g) contacting at least a portion of the separated aqueous discharge liquid with unoxidized precious metal-containing material, wherein the recycled aqueous discharge liquid comprises dissolved ferric sulphate and free sulphuric acid to partially oxidize sulphide sulphur in the unoxidized material.

34. The process of claim 24, wherein acid consumers are added in the first compartment and wherein the molar ratio of total acid consumers (as equivalent CO₃) to sulphides in the first compartment is no more than about 0.26.

35. The process of claim 24, wherein the first compartment is the initial compartment in the autoclave and wherein, in the operating step, a total acid concentration in the first compartment is at least about 5 30 g/l less than a total acid concentration in a last downstream autoclave compartment.

36. A process, comprising:

(a) inputting a valuable metal-containing feed slurry into a first compartment of a multi-compartment autoclave, the valuable metal-containing feed slurry comprising a valuable metal-containing material comprising sulphide sulphur;

(b) at least partially oxidizing the sulphide sulphur to sulphate sulphur in the first compartment to form a first oxidized slurry;

(c) transporting the first oxidized slurry to an adjacent second compartment of the autoclave, wherein the first oxidized slurry passes through a lower portion of a first weir separating the first and second compartments; and

(d) thereafter recovering the valuable metal from a slurry output by a final compartment of the autoclave.

37. The process of claim 36, wherein the multi-compartment autoclave comprises a plurality of weirs separating a plurality of adjacent autoclave compartments, a lower portion of each of the weirs comprising a passage for slurry flow between adjacent compartments.

38. The process of claim 36, wherein a final weir separates the final compartment from an adjacent preceding compartment and wherein a lower portion of the final weir does not comprise a passage for slurry flow.

39. The process of claim 38, wherein the final weir is configured to permit the slurry to flow over an upper portion of the weir.

40. The process of claim 38, wherein the first weir is not configured to permit the slurry to flow over an upper portion of the first weir.

41. The process of claim 38, wherein each of the weirs preceding the final weir, including the first weir, is not configured to permit the slurry to flow over an upper portion of the weir.