Why copper matte is put in silica lined converter?

Explanation

Copper matte chiefly consists of `Cu_(2)S` and some unchanged `FeS`. On passing a blast of hot air through molten matte in a converter lined with silica, `FeS` is oxidised to `FeO`, which combines with silica to form `FeSiO_(3)("slag")`
On removing entire iron as slag, some `Cu_(2)S` oxidises to `Cu_(2)O`, which further reacts with more `Cu_(2)S` to form `Cu`.
`2Cu_(2)S+3O_(2)rarr 2Cu_(2)O+2SO_(2)uarr`,
`2Cu_(2)O+Cu_(2)S rarr 6Cu+SO_(2)uarr`
Hence, copper matte is heated in a silica lined converter to remove `FeS`, which is present in matte as `FeSiO_(3)` slag.