Gold recovery using controlled oxygen distribution pressure oxidation

A process for recovering gold from a refractory auriferous ore containing sulfide sulfur comprising the steps of:

• forming an aqueous ore slurry comprising said refractory auriferous ore;
• determining the sulfide sulfur content of the ore which forms the aqueous ore slurry;
• subjecting the aqueous ore slurry to pressure oxidation in an autoclave having at least three compartments comprising a first compartment, a last compartment, and one or more intermediate compartments, said pressure oxidation comprising passing said aqueous ore slurry in series through said compartments and introducing oxygen into said compartments while agitating the aqueous ore slurry therein and maintaining said aqueous ore slurry at a temperature of greater than about 180.degree. C.;
• controlling the flow of oxygen to said first compartment on the basis of said sulfide sulfur content so that the molar ratio of oxygen introduced into the first compartment to sulfide sulfur in the ore introduced into the autoclave is at least about 0.8 and distributing the flow of oxygen among said compartments so that the flowrate of oxygen to the first compartment is between about 0.1 and about 0.5 times the flowrate of oxygen to all of said compartments and to achieve at least about 70% oxygen utilization, thereby forming an oxidized ore slurry;
• and
• recovering gold from said oxidized ore slurry.

A process for recovering gold from a refractory auriferous ore containing sulfide sulfur comprising the steps of:

• forming an aqueous ore slurry comprising said refractory auriferous ore;
• determining the sulfide sulfur content of the ore which forms the aqueous ore slurry;
• subjecting the aqueous ore slurry to pressure oxidation in an autoclave having at least three compartments comprising a first compartment, a last compartment, and one or more intermediate compartments, said pressure oxidation comprising passing said aqueous ore slurry in series through said compartments and introducing oxygen into said compartments while agitating the aqueous ore slurry therein and maintaining said aqueous ore slurry at a temperature of greater than about 180.degree. C.;
• adjusting the flow of oxygen to said first compartment on the basis of said sulfide sulfur content so that the molar ratio of oxygen introduced into the first compartment to sulfide sulfur in the ore introduced into the autoclave being maintained between about 0.8 and about 1.3 and distributing the flow of oxygen among said compartments to achieve at least about 70% oxygen utilization, thereby forming an oxidized ore slurry;
• and
• recovering gold from said oxidized ore slurry.

A process for recovering gold from a refractory auriferous ore containing sulfide sulfur comprising the steps of:

• forming an aqueous ore slurry comprising said refractory auriferous ore;
• determining the sulfide sulfur content of the ore which forms the aqueous ore slurry;
• subjecting the aqueous ore slurry to pressure oxidation in an autoclave having at least three compartments comprising a first compartment, a last compartment, and one or more intermediate compartments, said pressure oxidation comprising passing said aqueous ore slurry in series through said compartments and introducing oxygen into said compartments while agitating the aqueous ore slurry therein, maintaining said aqueous or slurry at a temperature of greater than about 180.degree. C., and controlling the ratio of total oxygen to sulfide sulfur and controlling the distribution of oxygen among said compartments such that at least about 75% of the total oxygen introduced into said compartments is consumed by oxidation of sulfide sulfur in the ore and at least about 90% of the sulfide sulfur in the ore is oxidized, thereby forming an oxidized ore slurry;
• and
• recovering gold from said oxidized ore slurry.

A process for recovering gold from a refractory auriferous ore containing sulfide sulfur comprising the steps of:

• forming an aqueous ore slurry comprising said refractory auriferous ore;
• determining the sulfide sulfur content of the ore which forms the aqueous ore slurry;
• contacting the aqueous ore slurry with sulfuric acid to remove natural carbonates from the ore;
• subjecting the aqueous ore slurry to pressure oxidation in an autoclave having at least three compartments comprising a first compartment, a last compartment, and one or more intermediate compartments, said pressure oxidation comprising passing said aqueous ore slurry in series through said compartments and introducing oxygen into said compartments while agitating the aqueous ore slurry therein and maintaining said aqueous ore slurry at a temperature of greater than about 180.degree. C.;
• controlling the flow of oxygen to said compartments on the basis of said sulfide sulfur content so that the molar ratio of total oxygen introduced into said compartments to sulfide sulfur in the ore introduced into the autoclave is between about 2 and about 4, the molar ratio of oxygen introduced into said first compartment to sulfide sulfur in the ore introduced into the autoclave is maintained below about 0.9, and oxygen utilization in all of said compartments is between about 75% and about 85%, thereby forming an oxidized ore slurry;
• cooling the oxidized ore slurry to a temperature between about 90.degree. F. and 140.degree. F. to form a cooled oxidized slurry;
• neutralizing the cooled oxidized slurry to a pH of between about 9 and about 11.5;
• and
• recovering gold from said cooled oxidized slurry by adding cyanide to said slurry to form a gold-cyanide complex and adsorbing said gold-cyanide complex onto a source of added carbon.