Question

Compare the process of calcination and roasting.

Answer 1

Comparison of calcination and roasting :

Calcination	Roasting
It is the process of heating the ore  to a high temperature in the  absence of air, or where air does not take part in the reaction.	The process of heating the concentrated ore in the presence of air to a high temperature so as not to melt it is called roasting.
Usually carbonate ores or ores containing water are calcined.	Usually sulphide ores are roasted.
Organic matter, if present in the ore, gets expelled and the ore becomes porous.	The impirirties of P, As and S are removed as their oxides which being volatile, escape as gases.
It is done in reverbratory furnace The holes of the furnace are kept closed.	It is also done in reverbratory furnace but the holes of the furnace are kept open to allow the entry of air in to the furnace.