Chapter No. 8: Metallurgy,
What are the differences between calcination and roasting?
Ans.
Calcination
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Roasting
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This method is preferred for carbonate ores.
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This method is preferred for sulphide ores.
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In this method, ores are heated in limited supply of air.
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In this method, ores are heated in excess of air.
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During calcination, generally carbon dioxide gas is evolved.
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During roasting, generally sulphur dioxide gas is evolved.
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In this method, carbonate ores decompose to form metal oxide.
E.g.
ZnCO3 → ZnO + CO2 ↑
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In this method, sulphide ores are oxidized to form metal oxides.
E.g.
2ZnS + 3O2 → 2ZnO + 2SO2 ↑
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