Copper matte consists of $\mathrm{Cu}_2\mathrm{S}$ and FeS . When a blast of hot air ispassed through molten matte taken in a silica lined converter, FeS presentin matte is oxidised to FeO which combines with silica $(\mathrm{SiO}_2)$ to form$\mathrm{FeSiO}_3$ (slag). $2\mathrm{FeS} + 3\mathrm{O}_2 \rightarrow 2\mathrm{FeO} + 2\mathrm{SO}_2$ $\mathrm{FeO} + \mathrm{SiO}_2 \rightarrow \mathrm{FeSiO}_3$ $\begin{array}{cc} \text{Silica} & \text{slag} \end{array}$ When complete iron has been removed as slag, some of the $\mathrm{Cu}_2\mathrm{S}$ undergoesoxidation to form $\mathrm{Cu}_2\mathrm{O}$ which then reacts with more $\mathrm{Cu}_2\mathrm{S}$ to form coppermetal. $2\mathrm{Cu}_2\mathrm{S} + 3\mathrm{O}_2 \rightarrow 2\mathrm{Cu}_2\mathrm{O} + 2\mathrm{SO}_2$$2\mathrm{Cu}_2\mathrm{O} + \mathrm{Cu}_2\mathrm{S} \rightarrow 6\mathrm{Cu} + \mathrm{SO}_2$Thus, copper matte is heated in silica lined converter to remove FeSpresent in matte as $\mathrm{FeSiO}_3$ (slag).