US4979987A — Precious metals recovery from refractory carbonat…

Claim 1

Independent Claim 192 words

A method for liberating precious metal values from refractory carbonate ores which contain inorganic sulfides and acid consumers, said method comprising: (a) adjusting a molar ratio of sulfide to total acid consumers to within a range of about 1.2 to about 3.2 to provide an adjusted ore feed, wherein said molar ratio of sulfide to total acid consumers is adjusted by contacting said ore feed with sulfuric acid to convert carbonate to carbon dioxide; and (b) contacting an aqueous slurry of said adjusted ore feed with oxygen at a slurry temperature of at least about 360° F. in a first oxidation zone and at least one subsequent oxidation zone, each of said oxidation zones having a slurry phase and a gas phase, to form a final oxidized pulp slurry and convert at least a portion of said sulfide to sulfuric acid wherein at least about 65 percent of said conversion occurs in the first oxidation zone, wherein sulfuric acid is generated in an amount sufficient to react with said acid consumers and also form at least about 5 grams of free sulfuric acid per liter of slurry in said first oxidation zone.

Claim 2

Independent Claim 192 words

A method for liberating precious metal values from refractory carbonate ores which contain inorganic sulfides and acid consumers, said method comprising: (a) adjusting a molar ratio of sulfide to total acid consumers to within a range of about 1.2 to about 3.2 to provide an adjusted ore feed, wherein said molar ratio of sulfide to total acid consumers is adjusted by contacting said ore feed with sulfuric acid to convert carbonate to carbon dioxide; and (b) contacting an aqueous slurry of said adjusted ore feed with oxygen at a slurry temperature of at least about 360° F. in a first oxidation zone and at least one subsequent oxidation zone, each of said oxidation zones having a slurry phase and a gas phase, to form a final oxidized pulp slurry and convert at least a portion of said sulfide to sulfuric acid wherein at least about 65 percent of said conversion occurs in the first oxidation zone, wherein sulfuric acid is generated in an amount sufficient to react with said acid consumers and also form at least about 5 grams of free sulfuric acid per liter of slurry in said first oxidation zone.

Claim 3

Independent Claim 182 words

A method for liberating precious metal values from refractory carbonate ores which contain inorganic sulfides and acid consumers, said method comprising: (a) adjusting a molar ratio of sulfide to total acid consumers to within a range of about 1.2 to about 3.2 to provide an adjusted ore feed; and (b) contacting an aqueous slurry of said adjusted ore feed with oxygen at a slurry temperature of at least about 360° F. in a first oxidation zone and at least one subsequent oxidation zone, each of said oxidation zones having a slurry phase and a gas phase, to form a final oxidized pulp slurry and convert at least a portion of said sulfide to sulfuric acid wherein at least about 65 percent of said conversion occurs in the first oxidation zone, wherein sulfuric acid is generated in an amount sufficient to react with said acid consumers and also form at least about 5 grams of free sulfuric acid per liter of slurry in said first oxidation zone, and wherein said final oxidized pulp slurry has an EMF of at least about 500 millivolts.

Claim 4

Independent Claim 182 words

A method for liberating precious metal values from refractory carbonate ores which contain inorganic sulfides and acid consumers, said method comprising: (a) adjusting a molar ratio of sulfide to total acid consumers to within a range of about 1.2 to about 3.2 to provide an adjusted ore feed; and (b) contacting an aqueous slurry of said adjusted ore feed with oxygen at a slurry temperature of at least about 360° F. in a first oxidation zone and at least one subsequent oxidation zone, each of said oxidation zones having a slurry phase and a gas phase, to form a final oxidized pulp slurry and convert at least a portion of said sulfide to sulfuric acid wherein at least about 65 percent of said conversion occurs in the first oxidation zone, wherein sulfuric acid is generated in an amount sufficient to react with said acid consumers and also form at least about 5 grams of free sulfuric acid per liter of slurry in said first oxidation zone, and wherein said final oxidized pulp slurry has an EMF of at least about 500 millivolts.

Claim 5

Independent Claim 185 words

A method for liberating precious metal values from refractory carbonate ores which contain inorganic sulfides and acid consumers, said method comprising: (a) adjusting a molar ratio of sulfide to total acid consumers to within a range of about 1.2 to about 3.2 to provide an adjusted ore feed; and (b) contacting an aqueous slurry of said adjusted ore feed with oxygen at a slurry temperature of at least about 360° F. in a first oxidation zone and at least one subsequent oxidation zone, each of said oxidation zones having a slurry phase and a gas phase, to form a final oxidized pulp slurry and convert at least a portion of said sulfide to sulfuric acid wherein at least about 65 percent of said conversion occurs in the first oxidation zone, wherein sulfuric acid is generated in an amount sufficient to react with said acid consumers and also form at least about 5 grams of free sulfuric acid per liter of slurry in said first oxidation zone, and wherein said final oxidized pulp slurry contains at least about 10 grams of free sulfuric acid per liter.

Claim 6

Independent Claim 185 words

A method for liberating precious metal values from refractory carbonate ores which contain inorganic sulfides and acid consumers, said method comprising: (a) adjusting a molar ratio of sulfide to total acid consumers to within a range of about 1.2 to about 3.2 to provide an adjusted ore feed; and (b) contacting an aqueous slurry of said adjusted ore feed with oxygen at a slurry temperature of at least about 360° F. in a first oxidation zone and at least one subsequent oxidation zone, each of said oxidation zones having a slurry phase and a gas phase, to form a final oxidized pulp slurry and convert at least a portion of said sulfide to sulfuric acid wherein at least about 65 percent of said conversion occurs in the first oxidation zone, wherein sulfuric acid is generated in an amount sufficient to react with said acid consumers and also form at least about 5 grams of free sulfuric acid per liter of slurry in said first oxidation zone, and wherein said final oxidized pulp slurry contains at least about 10 grams of free sulfuric acid per liter.

Claim 7

Independent Claim 168 words

A method for liberating precious metal values from refractory carbonate ores which contain inorganic sulfides and acid consumers, said method comprising: (a) adjusting a molar ratio of sulfide to total acid consumers to within a range of about 1.2 to about 3.2 to provide an adjusted ore feed; and (b) contacting an aqueous slurry of said adjusted ore feed with oxygen at a slurry temperature of at least about 360° F. in a first oxidation zone and at least one subsequent oxidation zone, each of said oxidation zones having a slurry phase and a gas phase, to form a final oxidized pulp slurry and convert at least a portion of said sulfide to sulfuric acid wherein at least about 70 percent of said conversion of sulfide occurs in said first oxidation zone, wherein sulfuric acid is generated in an amount sufficient to react with said acid consumers and also form at least about 5 grams of free sulfuric acid per liter of slurry in said first oxidation zone.

Claim 8

Independent Claim 168 words

A method for liberating precious metal values from refractory carbonate ores which contain inorganic sulfides and acid consumers, said method comprising: (a) adjusting a molar ratio of sulfide to total acid consumers to within a range of about 1.2 to about 3.2 to provide an adjusted ore feed; and (b) contacting an aqueous slurry of said adjusted ore feed with oxygen at a slurry temperature of at least about 360° F. in a first oxidation zone and at least one subsequent oxidation zone, each of said oxidation zones having a slurry phase and a gas phase, to form a final oxidized pulp slurry and convert at least a portion of said sulfide to sulfuric acid wherein at least about 70 percent of said conversion of sulfide occurs in said first oxidation zone, wherein sulfuric acid is generated in an amount sufficient to react with said acid consumers and also form at least about 5 grams of free sulfuric acid per liter of slurry in said first oxidation zone.

Claim 9

Independent Claim 214 words

A method for liberating precious metal values from refractory carbonate ores which contain inorganic sulfides and acid consumers, said method comprising: (a) adjusting a molar ratio of sulfide to total acid consumers to within a range of about 1.2 to about 3.2 to provide an adjusted ore feed; (b) contacting an aqueous slurry of said adjusted ore feed with oxygen at a slurry temperature of at least about 360° F. in a first oxidation zone and at least one subsequent oxidation zone, each of said oxidation zones having a slurry phase and a gas phase, to form a final oxidized pulp slurry and convert at least a portion of said sulfide to sulfuric acid wherein at least about 65 percent of said conversion occurs in the first oxidation zone, and wherein sulfuric acid is generated in an amount sufficient to react with said acid consumers and also form at least about 5 grams of free sulfuric acid per liter of slurry in said first oxidation zone; and (c) contacting said final oxidized pulp slurry with an alkaline solution containing cyanide to solubilize precious metal values, wherein said solubilized metal values are adsorbed on activated charcoal, said charcoal is separated from said pulp, and said metal values are then stripped from said charcoal and recovered.

Claim 10

Independent Claim 214 words

A method for liberating precious metal values from refractory carbonate ores which contain inorganic sulfides and acid consumers, said method comprising: (a) adjusting a molar ratio of sulfide to total acid consumers to within a range of about 1.2 to about 3.2 to provide an adjusted ore feed; (b) contacting an aqueous slurry of said adjusted ore feed with oxygen at a slurry temperature of at least about 360° F. in a first oxidation zone and at least one subsequent oxidation zone, each of said oxidation zones having a slurry phase and a gas phase, to form a final oxidized pulp slurry and convert at least a portion of said sulfide to sulfuric acid wherein at least about 65 percent of said conversion occurs in the first oxidation zone, and wherein sulfuric acid is generated in an amount sufficient to react with said acid consumers and also form at least about 5 grams of free sulfuric acid per liter of slurry in said first oxidation zone; and (c) contacting said final oxidized pulp slurry with an alkaline solution containing cyanide to solubilize precious metal values, wherein said solubilized metal values are adsorbed on activated charcoal, said charcoal is separated from said pulp, and said metal values are then stripped from said charcoal and recovered.

Claim 11

Independent Claim 167 words

A method for liberating precious metal values from refractory carbonate ores which contain inorganic sulfides and acid consumers, said method comprising: (a) adjusting a molar ratio of sulfide to total acid consumers to within a range of between about 1.4 and about 1.7 to provide an adjusted ore feed; and (b) contacting an aqueous slurry of said adjusted ore feed with oxygen at a slurry temperature of at least about 360° F. in a first oxidation zone and at least one subsequent oxidation zone, each of said oxidation zones having a slurry phase and a gas phase, to form a final oxidized pulp slurry and convert at least a portion of said sulfide to sulfuric acid wherein at least about 65 percent of said conversion occurs in the first oxidation zone, wherein sulfuric acid is generated in an amount sufficient to react with said acid consumers and also form at least about 5 grams of free sulfuric acid per liter of slurry in said first oxidation zone.

Claim 12

Independent Claim 167 words

A method for liberating precious metal values from refractory carbonate ores which contain inorganic sulfides and acid consumers, said method comprising: (a) adjusting a molar ratio of sulfide to total acid consumers to within a range of between about 1.4 and about 1.7 to provide an adjusted ore feed; and (b) contacting an aqueous slurry of said adjusted ore feed with oxygen at a slurry temperature of at least about 360° F. in a first oxidation zone and at least one subsequent oxidation zone, each of said oxidation zones having a slurry phase and a gas phase, to form a final oxidized pulp slurry and convert at least a portion of said sulfide to sulfuric acid wherein at least about 65 percent of said conversion occurs in the first oxidation zone, wherein sulfuric acid is generated in an amount sufficient to react with said acid consumers and also form at least about 5 grams of free sulfuric acid per liter of slurry in said first oxidation zone.

Claim 13

Independent Claim 180 words

A method for liberating precious metal values from refractory carbonate ores which contain inorganic sulfides and acid consumers, said method comprising: (a) adjusting a molar ratio of sulfide to total acid consumers to within a range of about 1.2 to about 3.2 to provide an adjusted ore feed, wherein at least about 90 mole percent of said acid consumers is carbonate; and (b) contacting an aqueous slurry of said adjusted ore feed with oxygen at a slurry temperature of at least about 360° F. in a first oxidation zone and at least one subsequent oxidation zone, each of said oxidation zones having a slurry phase and a gas phase, to form a final oxidized pulp slurry and convert at least a portion of said sulfide to sulfuric acid wherein at least about 65 percent of said conversion occurs in the first oxidation zone and wherein sulfuric acid is generated in an amount sufficient to react with said acid consumers and also form at least about 5 grams of free sulfuric acid per liter of slurry in said first oxidation zone.

Claim 14

Independent Claim 180 words

A method for liberating precious metal values from refractory carbonate ores which contain inorganic sulfides and acid consumers, said method comprising: (a) adjusting a molar ratio of sulfide to total acid consumers to within a range of about 1.2 to about 3.2 to provide an adjusted ore feed, wherein at least about 90 mole percent of said acid consumers is carbonate; and (b) contacting an aqueous slurry of said adjusted ore feed with oxygen at a slurry temperature of at least about 360° F. in a first oxidation zone and at least one subsequent oxidation zone, each of said oxidation zones having a slurry phase and a gas phase, to form a final oxidized pulp slurry and convert at least a portion of said sulfide to sulfuric acid wherein at least about 65 percent of said conversion occurs in the first oxidation zone and wherein sulfuric acid is generated in an amount sufficient to react with said acid consumers and also form at least about 5 grams of free sulfuric acid per liter of slurry in said first oxidation zone.

Claim 15

Independent Claim 207 words

A method for liberating precious metal values from refractory carbonate ores which contain inorganic sulfides and acid consumers, said method comprising: (a) adjusting a molar ratio of sulfide to total acid consumers to within a range of about 1.2 to about 3.2 to provide an adjusted ore feed; and (b) contacting an aqueous slurry of said adjusted ore feed with oxygen in a first oxidation zone and at least one subsequent oxidation zone, each of said oxidation zones having a slurry phase and a gas phase, to form a final oxidized pulp slurry and convert at least a portion of said sulfide to sulfuric acid wherein at least about 65 percent of said conversion occurs in the first oxidation zone, wherein sulfuric acid is generated in an amount sufficient to react with said acid consumers and also form at least about 5 grams of free sulfuric acid per liter of slurry in said first oxidation zone, and wherein the slurry in said oxidation zones is between about 360° F. and about 440° F., said oxygen is present in said gas phase with a partial pressure of at least 25 psia, and the total gas pressure in said first oxidation zone is about 300 to about 500 psia.

Claim 16

Independent Claim 207 words

A method for liberating precious metal values from refractory carbonate ores which contain inorganic sulfides and acid consumers, said method comprising: (a) adjusting a molar ratio of sulfide to total acid consumers to within a range of about 1.2 to about 3.2 to provide an adjusted ore feed; and (b) contacting an aqueous slurry of said adjusted ore feed with oxygen in a first oxidation zone and at least one subsequent oxidation zone, each of said oxidation zones having a slurry phase and a gas phase, to form a final oxidized pulp slurry and convert at least a portion of said sulfide to sulfuric acid wherein at least about 65 percent of said conversion occurs in the first oxidation zone, wherein sulfuric acid is generated in an amount sufficient to react with said acid consumers and also form at least about 5 grams of free sulfuric acid per liter of slurry in said first oxidation zone, and wherein the slurry in said oxidation zones is between about 360° F. and about 440° F., said oxygen is present in said gas phase with a partial pressure of at least 25 psia, and the total gas pressure in said first oxidation zone is about 300 to about 500 psia.

Claim 17

Dependent Claim 34 words

The method of claim 8 wherein the temperature in said oxidation zones is between about 400° F. and about 420° F. and the partial pressure of said oxygen is at least about 80 psia.

Claim 18

Independent Claim 417 words

A method for liberating gold and silver present in refractory carbonate ores, said method comprising: (a) adding sufficient sulfuric acid to a water slurry containing particlized ore to convert a portion of inorganic carbonates in said ore to carbon dioxide and react with other acid consumers in said ore to provide a slurry of pretreated ore having a molar ratio of sulfide to total acid consumers in said pretreated ore of between about 1.2 and about 3.2; (b) heating said slurry of pretreated ore pulp to a temperature of at least about 260° F. to provide a heated pulp slurry; (c) subjecting said heated pulp slurry to a pressure oxidation process in which said slurry is added to a first oxidation zone and is then passed sequentially through at least four subsequent oxidation zones wherein at least 50 volume percent of the total volume of all the slurry contained in all the oxidation zones is contained in the first oxidation zone, wherein each oxidation zone has a gas phase and a slurry phase in which at least a portion of the sulfide in said pulp is oxidized to sulfuric acid by introducing oxygen into said slurry to provide an oxygen partial pressure of at least about 25 psia in a gas phase above said slurry; (d) maintaining said pulp in said first oxidation zone to allow at least about 65 percent of the sulfide oxidation to occur in said first oxidation zone to generate an amount of sulfuric acid sufficient to react with the remainder of said inorganic carbonates and said other acid consumers and also form at least about 5 grams of free sulfuric acid per liter in said first zone and wherein the temperature of the slurry in said first oxidation zone is between about 360° F. to about 440°; (e) introducing additional oxygen into the slurry phase of each subsequent oxidation zone while maintaining an oxygen partial pressure of at least about 25 psia in each of said gas phases and while maintaining the temperature of said slurry in each of said subsequent oxidation zones in the range of about 360° F. to about 440°F.; (f) removing a slurry containing a final oxidized slurry, said slurry having an EMF of at least about 500 millivolts; and (g) removing a gas stream from the gas phase of at least said first oxidation zone, cooling the gas stream, separating carbon dioxide from the oxygen in said cooled gas, and recycling said oxygen to said oxidation zones.

Claim 19

Independent Claim 417 words

A method for liberating gold and silver present in refractory carbonate ores, said method comprising: (a) adding sufficient sulfuric acid to a water slurry containing particlized ore to convert a portion of inorganic carbonates in said ore to carbon dioxide and react with other acid consumers in said ore to provide a slurry of pretreated ore having a molar ratio of sulfide to total acid consumers in said pretreated ore of between about 1.2 and about 3.2; (b) heating said slurry of pretreated ore pulp to a temperature of at least about 260° F. to provide a heated pulp slurry; (c) subjecting said heated pulp slurry to a pressure oxidation process in which said slurry is added to a first oxidation zone and is then passed sequentially through at least four subsequent oxidation zones wherein at least 50 volume percent of the total volume of all the slurry contained in all the oxidation zones is contained in the first oxidation zone, wherein each oxidation zone has a gas phase and a slurry phase in which at least a portion of the sulfide in said pulp is oxidized to sulfuric acid by introducing oxygen into said slurry to provide an oxygen partial pressure of at least about 25 psia in a gas phase above said slurry; (d) maintaining said pulp in said first oxidation zone to allow at least about 65 percent of the sulfide oxidation to occur in said first oxidation zone to generate an amount of sulfuric acid sufficient to react with the remainder of said inorganic carbonates and said other acid consumers and also form at least about 5 grams of free sulfuric acid per liter in said first zone and wherein the temperature of the slurry in said first oxidation zone is between about 360° F. to about 440°; (e) introducing additional oxygen into the slurry phase of each subsequent oxidation zone while maintaining an oxygen partial pressure of at least about 25 psia in each of said gas phases and while maintaining the temperature of said slurry in each of said subsequent oxidation zones in the range of about 360° F. to about 440°F.; (f) removing a slurry containing a final oxidized slurry, said slurry having an EMF of at least about 500 millivolts; and (g) removing a gas stream from the gas phase of at least said first oxidation zone, cooling the gas stream, separating carbon dioxide from the oxygen in said cooled gas, and recycling said oxygen to said oxidation zones.

Claim 20

Dependent Claim 21 words

The method of claim 10 wherein said temperature in said oxidation zones is between about 400° F. and about 420° F.

Claim 21

Dependent Claim 24 words

The method of claim 10 wherein ratio of moles of sulfide to moles of total acid consumers is between about 1.4 and about 1.7.

Claim 22

Dependent Claim 21 words

The method of claim 11 wherein at least about 70 percent of the sulfide oxidation occurs in said first oxidation zone.

Claim 23

Dependent Claim 21 words

The method of claim 10 wherein said partial pressure of oxygen in each oxidation zone is at least about 80 psia.

Claim 24

Dependent Claim 22 words

The method of claim 10 wherein the free acid in said final oxidized slurry is at least about 10 grams per liter.

Claim 25

Independent Claim 206 words

A method for liberating precious metal values from refractory carbonate ores which contain inorganic sulfides and acid consumers, said method comprising: (a) adjusting a molar ratio of sulfide to total acid consumers to within a range of about 1.2 to about 3.2 to provide an adjusted ore feed; (b) contacting an aqueous slurry of said adjusted ore feed with oxygen at a slurry temperature of at least about 360° F. in a first oxidation zone and at least one subsequent oxidation zone, each of said oxidation zones having a slurry phase and a gas phase, to form a final oxidized pulp slurry and convert at least a portion of said sulfide to sulfuric acid wherein at least about 65 percent of said conversion occurs in the first oxidation zone, wherein sulfuric acid is generated in an amount sufficient to react with said acid consumers and also form at least about 5 grams of free sulfuric acid per liter of slurry in said first oxidation zone; and (c) removing a portion of a gas phase containing oxygen and carbon dioxide from at least one of said oxidation zones and separating substantially all of the carbon dioxide from said oxygen before recycling the oxygen to the oxidation zones.

Claim 26

Independent Claim 206 words

A method for liberating precious metal values from refractory carbonate ores which contain inorganic sulfides and acid consumers, said method comprising: (a) adjusting a molar ratio of sulfide to total acid consumers to within a range of about 1.2 to about 3.2 to provide an adjusted ore feed; (b) contacting an aqueous slurry of said adjusted ore feed with oxygen at a slurry temperature of at least about 360° F. in a first oxidation zone and at least one subsequent oxidation zone, each of said oxidation zones having a slurry phase and a gas phase, to form a final oxidized pulp slurry and convert at least a portion of said sulfide to sulfuric acid wherein at least about 65 percent of said conversion occurs in the first oxidation zone, wherein sulfuric acid is generated in an amount sufficient to react with said acid consumers and also form at least about 5 grams of free sulfuric acid per liter of slurry in said first oxidation zone; and (c) removing a portion of a gas phase containing oxygen and carbon dioxide from at least one of said oxidation zones and separating substantially all of the carbon dioxide from said oxygen before recycling the oxygen to the oxidation zones.

Claim 27

Dependent Claim 23 words

The method of claim 16 wherein said carbon dioxide is separated from said oxygen by contacting said gas phase with hot potassium carbonate.

Annuity Stage	Window Opens	Payment Deadline	Surcharge Period Until	Estimated Fee	Status
3.5 Years (Year 4)	1993-12-24	1994-06-25	1994-12-25	$2000.00	Window Closed / Lapsed
7.5 Years (Year 8)	1997-12-24	1998-06-25	1998-12-25	$3760.00	Window Closed / Lapsed
11.5 Years (Year 12)	2001-12-24	2002-06-25	2002-12-25	$7700.00	Window Closed / Lapsed

Precious metals recovery from refractory carbonate ores

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