Study of limestone and mill scale as fluxing agents for the recovery of tin from slag concentrates

Tin-slags with significant Sn and ZrO 2 levels are stored in Brazilian smelters and present potential to provide a Sn alloy to the market without additional cassiterite mining, thus contributing to minimizing environmental and social impacts.Some of these slags contain occluded metallic phases, so improving coalescence and sedimentation conditions during pyrometallurgical processing could enhance the recovery of Sn from these sources.However, critical information for process optimization, such as the melting temperature and viscosity of high ZrO 2 slags, is scarce.This research measured the melting temperatures of these slags using a softening and melting microscope under air atmosphere and used models to infer their viscosity.Based on results and optimization studies, the addition of mill scale and limestone as fluxes was proposed.The aim was to modify the properties of the slag, enhancing the recovery of Sn as a metallic button.The recovery of Sn as a metallic button was achieved at 1573K using combined additions of limestone and mill scale, but with a limited yield.Magnetic separation, which was used as an auxiliary technique, effectively retrieved most occluded metallic particles, even at 1473K.