Manufacture of Pig Iron

Three stages are involved in the manufacture of pig iron, viz.,

1. Dressing
2. Calcination and roasting and
3. Smelting

Dressing is the process in which the iron ores obtained from mines are crushed into pieces of about 25 cm diameter sizes by rock crushers. If the ores contain impurities like clay, loam and other earthy materials they are removed by washing the ores.

After dressing, the ores are calcinated and roasted. Calcination is the process where the ores are heated in the presence of air to oxidise them. By this action carbon dioxide and water are removed. Roasting the ores enables the dissipation of the volatile parts such as sulphur.

Smelting is the process of melting so as to separate metal from the ore. It is carried out in a special furnace called the blast furnace. The blast furnaces of the old type had a capacity of producing 15,000 KN of pig iron per day, whereas the more modern types have a capacity of 25,000 KN.