What are the differences between calcination and roasting?

Chapter No. 8: Metallurgy,

What are the differences between calcination and roasting?

Ans.

Calcination
Roasting
This method is preferred for carbonate ores.
This method is preferred for sulphide ores.
In this method, ores are heated in limited supply of air.
In this method, ores are heated in excess of air.
During calcination, generally carbon dioxide gas is evolved.
During roasting, generally sulphur dioxide gas is evolved.
In this method, carbonate ores decompose to form metal oxide.
E.g.
ZnCO3 → ZnO + CO2
In this method, sulphide ores are oxidized to form metal oxides.
E.g.
2ZnS + 3O2 → 2ZnO + 2SO2