Q.Why copper matte is put in silica lined converter?

Copper matte (mainly $Cu_2S$ with some FeS) is charged into a converter lined with silica and a mixture of silica and lime, then blasted with air. The residual FeS is oxidised to FeO, which reacts with the silica lining/flux to form fusible iron silicate slag, $FeO + SiO_2 \rightarrow FeSiO_3$, which is poured off, leaving $Cu_2S$ to undergo self-reduction to blister copper. …

Step 1 – Composition of copper matte

Copper matte, obtained from smelting roasted copper pyrites with silica, is a molten mixture consisting mainly of cuprous sulphide ($Cu_2S$) along with some residual iron(II) sulphide (FeS) that was not fully slagged off in the smelting furnace.

Step 2 – Why the converter needs a silica lining

The matte is transferred to a converter — a cylindrical vessel lined with silica (often as a silica/magnesia mixture) — and a blast of air is blown through it. This air blast oxidises the remaining FeS to FeO:

Step 3 – Role of the silica lining

The silica lining itself (and any additional silica flux added) reacts with this freshly formed FeO to form a low-melting, easily removable slag:

This slag is skimmed off, ensuring that essentially all remaining iron impurity is eliminated at this stage, and — importantly — protects the vessel lining and the copper from being lost into a basic slag (silica lining resists attack better than a basic lining would, given the acidic slag being formed).

Step 4 – Final self-reduction

With iron removed, the remaining $Cu_2S$ undergoes self-reduction as more air is blown through:

$2Cu_2S + 3O_2 \rightarrow 2Cu_2O + 2SO_2$ …

Trace what remains in the matte after smelting (residual FeS), what the air blast does to it (oxidises to FeO), and why silica is present specifically to react with THAT FeO (formin …

• Thinking silica reacts with the copper itself — it specifically targets the residual iron oxide, not copper. …