Calcination is a very simple chemical process, where the solid material or the substance undergoes heating in a control environment.
In the process the temperature is also in regulation. Calcination results in a change in the substance both physically and chemically.
During calcination, the solid substances are in subjection to heat at a very high temperature, this helps in removing volatile substances, water or oxidize the substance.
Hence the process is also a purification process. The word Calcination is a derivative from the Latin word Calcinare which translates as “to burn lime”.
In Calcination separation of carbonate or hydrated oxide ores takes place. Calcination usually takes place in retorts, furnaces and kilns , the materials often undergoes racking or stirring to make the product homogeneous.
However the common equipment useful in calcination is the reverberatory furnace.
The construction of the reverberatory furnace is different.
However in most cases the flames and hot gases from the fire come in direct contact with the material that undergoes calcination, but the fuel separates from them.
In the above figure, the fire burns at the grate present at G, the flames that pass over the bridge present at point E are deflects downward by the low lying sloping roof of the furnace and passes directly over the surface of the charge or the material under subjection to calcination that is presenting the platform B.
Through the throat F of the chimney the fumes and the hot gases escape, then a thin layer of evenly distribution of charge formations occurs.
A carbonate ore produces carbon dioxide under heat exposure
ZnCO3———> ZnO + CO2
The hydrated oxide ore releases water under heat exposure.
The change that takes place during calcination with reactions are: ∙
Moisture and water from hydrated ores, volatile impurities and organic matter are remove. ∙ Ore becomes porous. ∙ Carbonates decompose to oxides
This method is also applicable in the thermal treatment in absence or limited supply of air or oxygen is applied to the ores and other solid material, bringing about thermal decomposition.
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