Bessemerisation is a method in which the air is blown into the molten copper mat that is deposited in a Bessemer converter. In the final stage of smelting, the other products that remain, including FeS, are oxidized and removed as slag(FeSiO3).
Cu2S (Copper sulfide) is partially converted into Cu2O (copper oxide) by the air blast, that reacts to the remaining molten copper. The chemical equation can be expressed as
2Cu2S + 3O2 → 2Cu2O + 2SO2
2Cu2O + Cu2S → 6Cu + SO2