6.17 Why copper matte is put in silica lined converter?

Copper matte contains $C{u}_{2}S$ and FeS. Copper matte is put in a silica-lined converter to remove the remaining FeO and FeS present in the matte as slag ($FeSi{O}_{3}$). Also, some silica is added to the silica-lined converter. Then, a hot air blast is blown. As a result, the remaining FeS and FeO are converted to iron silicate ($FeSi{O}_{3}$) and $C{u}_{2}S$ is converted into metallic copper.