Question

Extraction of Iron

Answer 1

Ore of iron:

• Ore of iron 

Haematite	Fe2O3
Magnetite	Fe3O4
Siderite	FeCO3
Limonite	Fe2O3 . 3H2O
Iron pyrite	FeS2

• But the main ore of Iron is Haematite(Fe₂O₃).

Oxide Ore is extracted from Haematite Ore. Which is completed in the following steps-

• Step1 : Concentration

 First of all Ore is powdered. Then generally it is concentrated by Gravity Seperation Method.

• Step2 : Roasting

The concentrat”d ore is heated in a blast furnace in a limited amount of air, which liberates moister, S, As, P etc. And we get Ferrous Oxide (FeO). But due to the presence of air it gets oxidised to Ferric Oxide (Fe₂O₃).

• S(s) + O₂(g) → SO₂(g)
• 4As(s) + 5O₂(g) → 2As₂O₅(g)
• 4P(s) + 5O₂(g) → 2P₂O₅(g)

Concentrated

Ore → FeO (Ferrous Oxide)

FeO + O₂(g) → Fe₂O₃ (Ferric Oxide)

• Step3 : Smelting : Finally, when the concentrated Ore (Fe₂O₃) is mixed with coke (c) and lime stone (CaCO₃), it is smelted in a blast furnace. So various / (following) reactions take place inside the Vatya Bhatti.

Combustion zone (2173K)

In this zone coke (c) burns and a lot of heat is produced.

• C + O₂ → CO₂ + Heat

• CO₂ + C → CO + Heat

Reduction Zone(873 K)

In this zone the Fe2O3 molecule is reduced to Fe which is completed in three steps.

• Fe₂O₃ + CO → Fe₃O₄ + CO₂
• Fe₃O₄ + CO → FeO + CO₂
• FeO + CO → Fe + CO₂

Slag Zone(1273K)

In this zone CaCO₃ decomposes and converts SiO₂ into slag (CaSiO₃).

• CaCO₃ → CaO + CO₂
• SiO₂ + CaO → CaSiO₃

Fusion Zone (1573K)

The following reactions take place in this zone

• CO₂ + C → CO
• FeO + CO → Fe + CO₂
• FeO + C → Fe + CO

Molten Iron: Molten Iron is also called Pig iron. In which 4% carbon (C) and some impurities like – P, As, S etc are present.

When pig iron is melted and a strong jet of hot air is blown through it. Then some amount of ccarbon(C) gets oxidised and the iron obtained is called cast iron. In which 3% carbon(C) is present. It is hard and brittle.