Laboratory-scale smelting of copper-anode slimes

摘要

Anode slimes produced during the electrorefining of copper are a valuable source of silver, gold, selenium and tellurium. The conventional pyrometallurgical process for treating slimes involves preliminary leaching of the slimes in sulphuric acid followed by smelting in a reverberatory furnace with fluxes, but it is slow and has many recycle streams. The chemistry of the phases and the reactions that occur in slimes smelting are poorly understood and this prevents major improvements to the process. AS a first attempt to gain insight into slimes smelting, laboratory-scale experiments were conducted using unleached slimes, with and without the addition of fluxes and under neutral, oxidizing and reducing conditions. The results show that selenium is readily removed as gaseous selenium dioxide and that molten Cu -Ag-Se-O phases form when fluxes are added. Oxidation-refining of these phases by injection of air and addition of fluxes can result in the formation of silver that is suitable for further electrorefining. The phase relations in the Cu-Ag-Se-O system were not established in the investigation and require further study.