Gold mine operations and gold refineries produce some by-products that are recovered by pyrometallurgical processes embracing the use of molten lead as the collector of the gold and silver. Basically these by-products are processed in the refinery plant where a sinter plant, an arc furnace (some time ago, a blast furnace was employed) and a cupellation furnace are in operation. The plant is divided in six areas: sampling, blending, sinterization, arc furnace, cupellation and fume collection.
On arrival each consignment has its mass determined and is then sampled to provide gold and silver assays of the material and to obtain a chemical assay of the main constituents. The more refractory materials are blended with suitable fluxes and recycled products, together with lead oxide such as litharge. The blend is first sintered to form porous lumps and then smelted in an arc furnace where the lead compounds are reduced to metallic lead that acts as a collector of the gold and silver and finally forms a molten bullion at the bottom of the furnace. During the process the more fusible materials are blended and smelted where the lead compounds are reduced by metallic iron where after the gold and silver are similarly collected by the molten lead. The lead bullion is treated in a cupel furnace where lead is removed as lead oxide. The resultant gold/silver alloy is cast into anodes and delivered to the silver refinery for electrolysis. The lead oxide is recovered for reuse in a subsequent blend. Next figure shows the processes employed to recover by-products.
By-Products Recovery Flowsheet