Influence of the Reduction Rate of Slag from Oxidation Process of Cu–Fe–Pb Alloy During Reduction (De-coppering) on Its Viscosity

Abstract The production of copper based on a direct-to-blister flash smelting process made it necessary to introduce the technology for the reduction of flash smelting slag and subsequent refining of the resulting Cu–Fe–Pb alloy. Refining of Cu–Fe–Pb alloy produces a converter slag containing 7 ÷ 25 wt pct Cu, 3 ÷ 20 wt pct Fe , and 15 ÷ 45 wt pct Pb. This material is directed to the reduction (de-coppering) process, which allows the recovery of copper in the form of Cu–Pb alloy as well as the removal of lead from the copper material cycle in the form of lead-bearing material. The copper recovery rate in the form of Cu–Pb alloy depends on a number of factors, of which one of the primary ones is the viscosity of the medium (slag), which determines the rate of coalescence and sedimentation of the reduced metal droplets. The investigations on how the degree of reduction of metal oxides from the converter slag affects its viscosity are presented in the study. Viscosity tests were conducted in the range of 1000 ÷ 1450 °C and showed that the main factor affecting viscosity is the Cu 2 O content in the slag. Slags directed to the reduction process with a high Cu 2 O content have a lower viscosity than slags after the reduction process, which is due to a decrease in the copper oxide content of the slag. The viscosity of slags after reduction depends on the PbO content, the higher the PbO content the lower the slag viscosity. Furthermore, studies have shown that the viscosity of slags can be reduced by adding CaO to the slag.