Outotec outlines plans for dewatering centre in Finland

Abstract

This chapter discusses the process of direct-to-copper smelting that is the smelting of concentrate directly to molten copper in one furnace. In 2011, it was practiced in three smelters: Olympic Dam (Australia), Glogo´w II (Poland), and Chingola (Zambia). All of these plants use an Outotec flash furnace. The main advantage of the process is its restriction of SO2 evolution to a single, continuous source of high SO2-strength gas. In principal, the energy, operating, and capital costs of producing metallic copper are also minimized by the single-furnace process. Metallic copper is obtained in a flash furnace by setting the ratio of oxygen input in the blast to concentrate feed rate to the point where all the Fe and S in the input concentrate are oxidized. The ratio must be precisely controlled to avoid the production of Cu2S or Cu2O. Avoiding formation of a molten Cu2S layer in the furnace is critical. Reactions between Cu2S layers and oxidizing slag may cause rapid SO2 evolution and slag foaming. Direct-to-copper flash smelting has proven effective for SO2 capture. However, about 25% of the Cu in the input concentrate is oxidized, ending up as copper oxide dissolved in slag. This copper oxide must be reduced back to metallic copper, usually with coke. The expense of recovering Cu from slag will probably restrict future direct-to-copper smelting to concentrates that produce little slag. Chalcopyrite concentrates will probably continue to be treated by multi-furnace processes, either by conventional smelting and converting or by continuous multi-furnace processing.