Oxidation process for releasing metal values in which nitric acid is regenerated in situ
AssigneeHydrochem Developments Ltd.
InventorsJohn C. Schneider, Gezinus Van Weert, Kenneth J. Fair
Life of this patent
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Abstract
An oxidation process for releasing a metal of interest in an ore is described. The process is especially useful for releasing a metal of interest entrapped in a refractory ore. The process comprises reacting the ore with nitric acid until sufficient oxidation has occurred to release the metal of interest so that it may be recovered by conventional techniques. Nitric acid is regenerated in situ by aerating the liquid medium and contacting it with the off gases generated by the oxidation. The process is continuous and the nitric acid is recycled to the reactor preferably after removal of accumulated sulfate.
Claims22
A process conducted at ambient pressure for oxidizing an ore to enable recovery of at least one metal of interest, comprising:
- continuously reacting the crushed ore in an aqueous slurry with nitric acid, thereby oxidizing the ore to render the metals of interest susceptible to recovery and generating nitrogen oxide gases comprising NO, the slurry being continuously agitated by at least one agitation means to maintain the crushed ore in suspension;
- continuously contacting the nitrogen oxide gases with oxygen to oxidize the NO contained in the gases to NO.sub.2 ;
- and
- continuously contacting the NO.sub.2 containing gases with water for a sufficient time to regenerate a major portion of the nitric acid consumed in the oxidation of the ore, the water being provided as a discontinuous liquid phase in the NO.sub.2 containing gas phase by means of at least one agitator, comprising a first impeller mounted on a rotatable shaft, providing sufficient agitation at the liquid surface.
A continuous process conducted at ambient pressure for oxidizing a sulfidic ore to enable recovery of at least one metal of interest, comprising:
- slurrying the crushed ore in an aqueous solution containing calcium ions;
- adjusting the pH of the slurry using aqueous process liquid containing nitric and sulfuric acids, thereby causing the precipitation of soluble sulfate as gypsum;
- oxidizing the slurry of crushed ore with nitric acid, thereby rendering the metals of interest susceptible to recovery and generating nitrogen oxide gases comprising NO;
- contacting the gaseous nitrogen oxides with oxygen to oxidize the NO contained therein to NO.sub.2 ;
- and
- contacting the NO.sub.2 containing gases with water for a sufficient time to regenerate a major portion of the nitric acid consumed in the oxidation of the ore, the water being provided as a discontinuous liquid phase in the NO.sub.2 containing gas phase by means of at least one agitator, comprising an impeller mounted on a rotatable shaft, providing sufficient agitation at the liquid surface.
Dependencies are inferred from the claim text.