Why copper matte is put in silica lined converter?

Explanation

Copper mattel chiefly coinsists of `Cu_ 2 S ` 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 + 3 O _ 2 to 2 FeO + 2 SO _ 2 uparrow , FeO + underset ("Silica")(SiO_ 2 ) to underset ("Slag")(FeSiO_ 3 ) `
When whole of iron has been removed as slag, some of the ` Cu_ 2 S ` undergoes oxidation to form ` Cu_ 2 O ` which then reacts with more ` Cu_2 S ` to form copper metal.
` 2 Cu_ 2 S + 3 O _ 2 to 2 Cu_ 2 O + 2 SO _ 2 uparrow , 2 Cu_ 2 O + Cu_ 2 S to 6 Cu + SO_2 uparrow `
Thus, copper matte is heated in silica lined converter to remove FeS present in matte as ` FeSiO_ 3 ` slag.