Extraction of Iron

:- Iron is extracted by hametite are which consist impurity of silica , phosphorus , carbon etc. Extraction of it completed in following steps :-

1. Concentration of Ore :- Such ore is concentration by Hydraulic washing or gravity separation.
2. Calcination :- Concentratrated is strongly heated in limited supply of oxygen then volatile impurity removed as well as impurity removed of non metal also removed in the form of their oxide.

            Fe₂O₃ . 2H₂O  Fe₂O₃

            4P + 5O₂  2P₂O₅

           4As + 3O₂ 2As₂O₃

3. Carbon reduction process :-. Reduction of iron oxide by carbon in presence of strong heat , is called smelting which occurs in blast furnace. Blast furnace :- It is long tower like structure which is conical at the top and border in the middle and again narrow at the bottom. It is made up of fire proof pricks and the inner wall of it is lined by silica. At the bottom of the furnace blast of hot air passed inside furnace. In such furnace these are four different zones which has different temperature and in which has different chemical reactions are taken.

• Zone of combustion
• Zone of fusion
• Zone of slag formation
• Zone of reduction
• 
• Zone of combustion :- It is present at the lowest part of the furnace. The temperature of such zone is 2200k. From the bottom of the furnace blast of hot air passed inside it which react with upcoming coke such reaction is highly exothermic and temperature of such zone become 2200k.

            C+ O₂ → Co₂ + Heat

Zone of fusion :- Such zone is present above zone of combustion. CO₂ formed in zone of combustion rises up and react with upcoming coke and form CO. Such rkⁿ is endothermic in nature so temperature of such zone is decreased and reached up to 1570k.

                        CO₂ + C → 2CO – Heat

In such zone reduced iron coming from zone of reduction get fused in such zone and also some of the from oxide also get reduced into iron.

                 Fe₂O₃ + 3CO → 2Fe + 3Co₂

                 Fe(s) → Fe (l)

Zone of slag formation :- In such zone limestone get dissociated and form calcium oxide along with CO₂. This CaO act as flux which react with impurity of silica and form slag.

          CaCO  CaO + CO₂

          CaO   +  SiO₂ → CaSiO₃ (slag)

  (Impurities)  (Flux) 

Slag form in such zone covered the molten iron and prevent it further oxidation of molten iron.

Zone of reduction :– It is upper zone of the furnace here temperature is lowest i.e 875k with respect to other zone. In such zone iron oxide reduces by CO into another form of iron oxide which further reduces by coke into iron.

Fe₂O₃ + CO → 2FeO + CO₂

FeO + C → Fe + CO

From the bottom of the furnace lets collect molten iron and slag in different container. This molten iron is called Pig iron.

It steel consist impurity more than 5%. This pig iron change into cast iron by heating of it with scrape of iron in presence of blast of hot air. After that it becomes cast iron which is more than pig iron.

Formation of wrought Iron :- Such iron is the purest form of iron. It consist impurity up to only 0.5%. When cast iron is heated in Reverboratery furnace along with hematite are then  wrought  iron is obtained. Impurity present in cast iron get oxides by hematite are which provide oxygen for the oxidation of such impurity.

2Fe₂O₃ + 3C → 4Fe + 3CO₂

2Fe₂O₃ + 3S → 4Fe + 3SO₂

Fe₂O₃ + 3Mn → 2Fe + 3MnO

MnO + SiO₂ → MnSiO₃ (slag)