Calcination – It is the process of converting an ore into its oxide by heating strongly, below its melting point either in a limited supply or in absence of air. This method is commonly used for converting carbonates and hydroxides to their respective oxides. During calcination, moisture and volatile impurities are also removed.For example: Calcium carbonate is converted into calcium oxide by calcination.CaCO3 → CaO + CO2Roasting – In this process, an ore is converted into its oxide by heating it strongly in excess of air. This method is commonly used for sulphide ores. During roasting, moisture and non metallic impurities\xa0are also removed as volatile gases .For example: Zinc sulphide is converted into zinc oxide by roasting.2ZnS + 3O2 → 2ZnO + 2SO2The difference between roasting and calcination is that roasting is done in excess of air while calcination is done in limited supply or absence of air.\xa0
Calcination requires no oxygen but roasting requires oxygen