Reduction of lime consumption when treating refractor gold ores or concentrates
First Claim
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1. A precious metal recovery process, comprising:
- (a) oxidizing an aqueous feed slurry in an autoclave, the feed slurry comprising a precious metal-containing material and sulphide sulphur, wherein at least most of the sulphide sulphur is oxidized to sulphate sulphur and wherein at least a portion of the sulphate sulphur is in the form of a reactive iron-containing precipitate;
(b) 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 at least most of the reactive iron-containing precipitate, and wherein the aqueous discharge slurry comprises an acid;
(c) prior to contact of an acid consumer other than the reactive iron-containing precipitate with at least most of the discharge solids, allowing at least most of the reactive iron-containing precipitate in the discharge solids to react with the acid in the aqueous discharge liquid to form a hot cured slurry, the hot cured slurry comprising the discharge solids and a dissolved iron-containing species derived from the reaction of the acid and reactive iron-containing species;
(d) after step (c), contacting the discharge solids with the acid consumer;
(e) leaching at least most of the precious metal from the discharge solids to form a dissolved precious metal; and
(f) recovering the dissolved precious metal.
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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.
206 Citations
60 Claims
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1. A precious metal recovery process, comprising:
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(a) oxidizing an aqueous feed slurry in an autoclave, the feed slurry comprising a precious metal-containing material and sulphide sulphur, wherein at least most of the sulphide sulphur is oxidized to sulphate sulphur and wherein at least a portion of the sulphate sulphur is in the form of a reactive iron-containing precipitate; (b) 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 at least most of the reactive iron-containing precipitate, and wherein the aqueous discharge slurry comprises an acid; (c) prior to contact of an acid consumer other than the reactive iron-containing precipitate with at least most of the discharge solids, allowing at least most of the reactive iron-containing precipitate in the discharge solids to react with the acid in the aqueous discharge liquid to form a hot cured slurry, the hot cured slurry comprising the discharge solids and a dissolved iron-containing species derived from the reaction of the acid and reactive iron-containing species; (d) after step (c), contacting the discharge solids with the acid consumer; (e) leaching at least most of the precious metal from the discharge solids to form a dissolved precious metal; and (f) recovering the dissolved precious metal. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 15, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 57)
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11. A precious metal recovery process, comprising:
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(a) oxidizing sulphide sulphur in an aqueous feed slurry in an autoclave, the feed slurry comprising a precious metal-containing material, wherein at least most of the sulphide sulphur is oxidized to sulphate sulphur and wherein at least a portion of the sulphate sulphur is in the form of basic iron sulphate in a solid phase; (b) 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 at least most of the solid-phase basic iron-sulphate, and wherein the aqueous discharge slurry comprises sulphuric acid; (c) allowing at least most of the solid-phase basic iron sulphate in the aqueous discharge solids to react with the sulphuric acid in the aqueous discharge liquid to form a hot cured slurry comprising ferric sulphate dissolved in the aqueous discharge liquid, wherein the allowing step (c) is performed in one or more hot cure vessels and wherein a residence time of the at least most of the solid-phase basic iron sulfate in the one or more hot cure vessels ranges from about 1 hour to about 24 hours; (d) thereafter separating the aqueous discharge liquid from the aqueous discharge solids, wherein at least most of the dissolved ferric sulphate is in the separated aqueous discharge liquid and wherein the separated aqueous discharge solids comprise sulphuric acid; (e) contacting an acid consumer with at least one of the separated aqueous discharge liquid and the separated discharge solids to form at least one of neutralized aqueous discharge liquid and neutralized aqueous discharge solids, respectively; (f) contacting a lixiviant, at a pH above about pH 7.0, with the neutralized discharge solids to dissolve at least most of the precious metal; and (g) recovering the dissolved precious metal. - View Dependent Claims (12, 13, 16, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 41, 42, 43, 44, 45, 46, 47, 58)
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14. A precious metal recovery process, comprising:
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(a) oxidizing an aqueous feed slurry in an autoclave, the feed slurry comprising a precious metal-containing material and sulphide sulphur, wherein at least most of the sulphide sulphur is oxidized to sulphate sulphur and wherein at least a portion of the sulphate sulpur is in the form of a reactive iron-containing precipitate; (b) 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 at least most of the reactive iron-containing precipitate, wherein the reactive iron-containing precipitate comprises basic iron sulphate, and wherein the aqueous discharge slurry comprises an acid; (c) allowing at least most of the reactive iron-containing precipitate in the aqueous discharge solids to react with the acid to form a dissolved iron-containing species, wherein the dissolved iron-containing species comprises dissolved ferric sulphate, and wherein the acid comprises sulphuric acid; (d) after step (c), contacting the discharge solids with an acid consumer, wherein the acid consumer is predominantly lime, wherein liquid in contact with the discharge solids has a discharge solids pH, wherein the discharge solids pH is increased from a first pH in the range of from about pH 2.0 to about pH 5.0 to a second pH in the range of from about pH 9.0 to about pH 11.0; (e) contacting the dissolved ferric sulphate in the aqueous discharge liquid with lime and/or limestone to convert at least most of the dissolved ferric sulphate to ferric hydroxide; (f) leaching at least most of the precious metal from the discharge solids to form a dissolved precious metal; and (g) recovering the dissolved precious metal. - View Dependent Claims (53, 54, 55, 56, 59)
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- 39. The process of 38, wherein the first acid consumer is limestone and wherein the neutralized separated aqueous liquid comprises ferric hydroxide and gypsum solids.
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48. A precious metal recovery process, comprising:
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(a) oxidizing sulphide sulphur in an aqueous feed slurry in an autoclave, the feed slurry comprising a precious metal-containing material, wherein at least most of sulphide sulphur is oxidized to sulphate sulphur and wherein at least a portion of the sulphate is in the form of basic iron sulphate in a solid phase; (b) 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 at least most of the solid-phase basic iron sulphate, and wherein the aqueous discharge slurry comprises sulphuric acid; (c) allowing at least most of the solid-phase basic iron sulphate in the aqueous discharge solids to react with the sulphuric acid to form ferric sulphate dissolved in the aqueous discharge liquid; (d) thereafter separating the aqueous discharge liquid from the discharge solids, wherein at least most of the dissolved ferric sulphate is in the separated aqueous discharge liquid and wherein the separated aqueous discharge solids comprise sulphuric acid; (e) contacting the separated discharge solids with an acid consumer to consume at least most of the sulphuric acid and dissolved metal sulphates to form a neutralized discharge solids, wherein the acid consumer is predominantly lime and/or limestone, wherein the separated discharge solids have a discharge solids pH, wherein the discharge solids pH is increased from a first pH in the range of from about pH 2.0 to about pH 5.0 to a second pH in the range of from about pH 9.0 to about pH 11.0; (f) contacting the dissolved ferric sulphate in the aqueous discharge liquid with lime and/or limestone to convert at least most of the dissolved ferric sulphate to ferric hydroxide; (g) contacting a lixiviant, at a pH above about pH 7.0, with the neutralized discharge solids to dissolve at least most of the precious metal; and (h) recovering the dissolved precious metal. - View Dependent Claims (49, 50, 51, 52, 60)
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Specification