Question

Why copper metal is put in silica lined converter?

Answer 1

Copper matte has Cu2S and FeS. Copper matte is put in a silica-lined converter to remove the remaining FeO and FeS present in the matte as slag 

Answer 2

Copper matte is put in a silica-lined converter to remove the remaining FeO and FeS present in the matte as slag (FeSiO3). A hot air blast is blown. That is when the remaining FeS and FeO are converted to iron silicate(FeSiO3) and Cu2S is converted into metallic copper as shown in the reactions below.