While ZnS is roasted, the temperature is consistently maintained above
8600C while the influx of air is controlled – True or False?
True
This is to prevent the oxidation of ZnS to ZnSO4 which again converts back into ZnS during the smelting-Carbon Reduction step
Above 8600C and under a controlled blast of air, ZnS + 1.5O2 → ZnO + SO2 ↑
With excess air and temperature lower than 8600C
ZnS + 2O2 → ZnSO4
During smelting,
ZnSO4+ 4C → ZnS + 4CO ↑