Question

How does calcination different from roasting.

Answer 1

The difference between roasting and calcination are,

Calcination	Roasting
In this process, heating of ore is done in presence of limited air.	In this process, heating of ore is done in presence of excess air.
In this process, a Carbonate ore is converted into Oxide ore.	In this process, a Sulphide ore is converted into Oxide ore.
For example, $$\begin{gathered} {\mathrm{ZnCO}}_3\left(\mathrm{s}\right)\stackrel{∆}{\to }\mathrm{ZnO}\left(\mathrm{s}\right)+{\mathrm{CO}}_2\left(\mathrm{g}\right) \\ \mathrm{Zinc}\mathrm{Zinc}\mathrm{oxide}\mathrm{Carbon} \\ \mathrm{Carbonate}\mathrm{dioxide} \\ (\mathrm{Calamine}\mathrm{ore}) \end{gathered}$$	For example, $$\begin{gathered} 2\mathrm{ZnS}\left(\mathrm{s}\right)+3{\mathrm{O}}_2\left(\mathrm{g}\right)\to 2\mathrm{ZnO}\left(\mathrm{s}\right)+2{\mathrm{SO}}_2\left(\mathrm{g}\right) \\ \mathrm{Zinc}\mathrm{Oxygen}\mathrm{Zinc}\mathrm{oxide}\mathrm{Sulphur} \\ \mathrm{sulphide}\mathrm{dioxide} \\ (\mathrm{Zinc}\mathrm{blende}) \end{gathered}$$