In this study influence of selected parameters on the process of reduction of converter slag from refining of Cu-Pb-Fe alloy was numerically examined. The process of the slag reduction is carried out in Q 80 converters of Hoboken type for copper removal. Converter slags show high concentration of lead therefore they can be seen as an important component for further processing in rotary-rocking furnaces together with other lead-bearing materials. Three-dimensional simulation was performed using the IPSA (Inter Phase Slip Algorithm) module of two-phase flow from PHOENICS package. Numerical simulations have forecasted influence of changes in the slag chemical composition and the process time on the process course.