Pig iron productions

Introduction :

Pig iron is the intermediate product which is obtained during the smelting of iron ore with coke, in this process limestone is used as flux. Pig iron has maximum carbon content, it is around 3.5–4.5% which improves the brittleness of iron. In olden days, the Chinese Zhou dynasty were making pig iron in Europe. The plant used for the pig iron production is sinter plant.There will be use of two furnaces for the pig iron production. The word pig iron comes from old casting blast furnace iron method into moulds which are arranged on the beds of sand.

Pig iron production:

Blast furnace used for pig iron production:

Pig iron production is done by blast furnace method which involves the smelting of iron ore like hematite, i.e.
Fe₂O₃ + 3CO → 2Fe + 3CO₂

A blast of preheated air is blown through the furnace which reacts with carbon which is in the form of coke to produce carbon monoxide and also a large amount of heat is produced. The produced carbon monoxide reacts with the iron ore to form molten iron and carbon dioxide. Unreacted carbon monoxide, nitrogen which is present in the blown air and hot carbon dioxide are fed into the reaction zone as a fresh feed so that there will be preheating of fresh feed using counter current gases and also there will be the decomposition of limestone to calcium oxide and carbon dioxide and starts to reduce iron oxide in the solid state. So formed calcium oxide reacts with some of the acidic impurities which are present in iron which form a slag called calcium silicate. The reactions involved in the pig iron production are

C + O₂ → CO₂
CO₂ + C → 2CO
CaCO₃ → CaO + CO₂
SiO₂ + CaO → CaSiO₃(slag)

The pig iron obtained by this method has high carbon content so which increases the brittleness by that it has limited commercial applications. If there is a need to reduce the carbon content, pig iron undergoes further processes.

Applications of Pig iron:

• Pig iron sometimes used to produce cast iron and Gray iron which is achieved by smelting the pig iron.
• Pig iron is used to produce steel metal.