Why are carbonate ores are calcined while sulphide ores are roasted?

Asked by pb_ckt | 20th Mar, 2019, 01:29: PM

Expert Answer:

Roasting: It is the process in which a sulphide ore is strongly heated in the presence of air to convert it into a metal oxide.

This is done in case of sulphide ores so as to remove sulphur in the form of SO2 and to obtained corresponding metal oxide.

 
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But, in the case of carbonate ores, we need to eliminate the carbonate and moisture. this is done by calcination.
 
 
Calcination: It is the process in which a carbonate ore is heated strongly in the absence of air to convert it into a metal oxide.
 
When zinc carbonate is heated strongly in the absence of air, it decomposes to form zinc oxide and carbon dioxide
 
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So, roasting is not done for carbonate ores, moreover, calcination is more difficult than roasting.

It is easier to obtain metals from their oxides (by reduction) than from carbonates or sulphides. 

So before reduction can be done, the ore is converted into metal oxide.

Answered by Ramandeep | 20th Mar, 2019, 02:52: PM