Explain the extraction of iron from haematite.

Extraction of Iron From Haemetite: The haemetite is also known as cast iron which is actually an oxide of iron.The extraction of iron is done by common metallurgy as follow:

Step 1: Concentration:- The ore is at first crushed and then concentrated by gravity separation method followed by washing in a stream of water so that the lighter sand and clay particles are washed away and heavier ore particles settle down.

Step 2: Calcination:-  Now the concentrated ore is heated or roasted strongly in limited air in a reverberatory furnace so that the moisture is removed and impurities of S, P, and As escape as they are volatile.As for ex.:  S₈ + 8O₂ = 8SO₂ 

_{Ferrous oxides are oxidised to ferric oxide prevebting loss of iron as slag.}  4FeO + O₂--> 2Fe₂O₃

_{Now the ore becomes porous and is suitable for reduction to metallic state by smelting process.}

Step 3: Smelting or Reduction: The ore is now smelted in the blast furnace where it is reduced by Carbon. In blast furnace the following action takes place.

1. At zone of combustion: At the bottom, small pipes called tuyers , provides hot air and coke burns to form CO₂ as ; C+ O₂ --> CO₂

_{2. At zone of heat absorption; in the middle part of furnace temp. is arround 1300K now the CO2 produce moves up and mixes with the coke layer and produces carbon monoxide by rduction as;}  CO₂ + C -->2CO

3, At zone of reduction; in the upper part with temp. 700-900K the ferric oxide mixes with CO and reduces to spongy iron as;  Fe₂O₃ + 3CO -->2Fe + 3CO₂  

FeO + CO --> Fe + CO₂

_{4.At zone of slag formation; when spongy iron and lime stone reaches the middle part, lime stone decomposes to give lime and carbon dioxide. Now lime combines with silica to form a fusible slag. as;}

CaCO₃ --> CaO +CO₂

CaO + SiO₂ --> CaSiO₃

5. At the zone of fusion; in this bottom part the the iron falling down melts and  the two separate layer formed in which slag is above as it is lighter and the molten metal setteles down.

Now the molten matal is tapped off from the furnace and and solidified in the form of blocks called "pig" and so it is called as pig or cast iron.