OUTOKUMPU BLISTER FLASH SMELTING PROCESSES

Copper smelting to form blister in one single step has been feasible for a long time, particularly from low-grade concentrates. Despite its evident advantages, economic viability has been limited to a few special raw materials that possess favorable Cu/Fe and Cu/S ratios. Currently, Outokumpu Blister Flash Smelting is implemented at three operations, with three additional ones scheduled for commissioning soon. The use of typical chalcopyrite concentrates has faced two significant challenges that hinder wider adaptation of direct blister processing: the formation of slag and the generation of excess heat. High oxygen potential in the reaction shaft is essential to produce blister with sulfur content below 1%. However, extensive oxidation of iron and sulfur results in the unavoidable oxidation of copper into slag, which complicates downstream recovery operations. The oxidation of sulfur and iron also releases a substantial amount of heat, traditionally managed by decreasing oxygen enrichment, resulting in oversized off-gas lines and acid plants. Another concern is the corrosion of furnace refractory linings by high-copper slag. In the Outokumpu Direct Blister Flash Smelting process, strategies to manage these challenges are discussed, highlighting advancements in equipment and process development.