There are different steps involved during the extraction of metals from ores are –
- Crushing and Grinding
- Concentration or Dressing
- Calcination and Roasting
Crushing and Grinding:
The big stones of the ore are first crushed into pieces and then ground into a fine dust-like powder.
Concentration or Dressing:
Ores are generally associated with a large number of impurities like sand. Limestone, quartz, silica, etc. Concentration is a very important process in metallurgy as it consists of removing the impurities from the ore and also at the same time increases the % of metal in the ore concentrate. So, the concentration of dressing of the ore is done before calculation and smelting or reduction in the following way depending upon the nature of the ore.
Calcination and Roasting:
Calcination is a process of heating the concentrated ore in limited supply or in absence of air at a temperature below its melting point.
Roasting is a process of heating the concentrated ore in a free supply of air (O2) below its fusion temperature.