Chemistry
Compare roasting and calcination.
Metallurgy
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Answer
| Roasting | Calcination |
|---|---|
| The ore is heated in the excess air. | The ore is heated in the absence of air |
| Generally sulphide ores are roasted and hence sulphur dioxide is given out. | Generally carbonate and hydrated ores are calcinated and hence carbon dioxide and water vapour is given off. |
| 2ZnS + 3O2 ⟶ 2ZnO + 2SO2 | ZnCO3 ⟶ ZnO + CO2[g] |
| Volatile impurities are removed as oxides (SO2, P2O5, As2O3) and the ore becomes porous and more reactive. | Moisture and organic impurities are removed and the ore becomes porous and more reactive. |
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