Why copper matte is put in silica lined converter?

Explanation

Copper matte chiefly consists of `Cu_2S` along with some unchanged FeS. When a blast of hot air is passed through molten matte taken in a silica lined converter, FeS present in matte is oxidised to FeO which combines with silica `(SiO_2)` to form `FeSiO_3` slag.
`2FeS+3O_2to2FeO+2SO_2uarr`
`FeO+SiO_2toFeSiO_3`
When whole of iron has been removed as slag, some of the `Cu_2S` undergoes oxidation to form `Cu_2O` which then reacts with more `Cu_2S` to form copper metal.
`2Cu_2S+3O_2to2Cu_2O+2SO_2uarr`
`2Cu_2O+Cu_2Sto6Cu+SO_2uarr`
Thus copper matte is heated in silica lined converter to remove FeS present in matte as `FeSiO_3` slag.