Extraction of Iron from Haematite

Iron

Symbol: Fe

Latin name: Ferrum

Atomic Number: 126

Atomic Mass: 55

Valency: 2 and 3

Electronic Configuration: 1s2, 2s2, 2s6, 3s2, 3p6 , 3d6, 4s2

Occurrence: Iron is the fourth must abundant metal in this universe. Due to its high reactivity, it rarely occurs in free state. The main ores of iron are:

  •  Oxide Ores: Haematite (Fe2O3), Magnetite Fe33O4
  •  Carbonate ores: FeCO3 (Clay iron stone)
Note: Iron is mined and smelted extensively in different parts of Nepal since 200 years before, but at present but none of the mine is in operation at present.

Extraction of Iron:

Iron is extracted from its chief ore Haematite Fe2O3. The various steps involved in the process are as follows:

1. Crushing: The ores are crushed in jaw crusher and powdered in ball mills.

2. Concentration: The crushed ore is washed with steam or cold water to remove clay and sand. The washed ore is then concentrated by electromagnetic separation process.

3. Calcination: The concentrated ore is then heated strongly in presence of air. This process is called calcination. During calcination:

  • Moisture is driven out.
  •  Sulphur, arsenic and phosphorous impurities are expelled out as their volatile oxides.
    $$\ce{S + O2->SO2 ^}$$
    $$\ce{4As + 5O2->2As2O5 ^}$$
    $$\ce{4P + 5O2->2P2O5 ^}$$
  • Carbonate ore changes into oxide ore.
    $$\ce{FeCO3->FeO + CO2}$$
  • Ferric oxide changes into ferric oxide.
    $$\ce{4FeO + O2->2Fe2O3}$$

4. Smelting: The calcinated ore is now reduced in the metallic iron chamber called blast furnace. This process is called smelting. Blast furnace is a cylindrical tall tower like structure made up of iron sheet. The systematic diagram of blast furnace and different zones are described below.

Blast Furnace

  • Combustion Zone (Lower Zone):
    In this zone, carbon burns in presence of hot air. The reaction is exothermic and hence temprature rises to 1500o C.
    $$\ce{C + O2->[\Delta]CO2}$$
    Here, Carbon Dioxide rises upwards and mixed with red hot coke. It is reduced to carbon monoxide. The reaction is endothermic and the temperature drops to 1200oC.
    $$\ce{CO2 + C->2CO}$$
  • Reduction zone: At the temperature of 500-7000oC, the oxide ore is reduced to spongy ion in this zone.
    $$\ce{FeO + CO->Fe + CO2}$$
  • Slag formation zone: As the temperature ranges 800-1000oC, the limestone present in the charge decomposes into calcium oxide and carbon dioxide.
    $$\ce{CaCO3 ->CaO +  CO2}$$ This lime acts as a flux as it combines with silica.
    $$\ce{CaO + SiO2->CaSiO3}$$
Note: Silicates, phosphates and Manganates are reduced to Si, P and Mn here.
  • Zone of Fusion:
    The molten slag being lighter floats on the top. The slag and molten metals are removed from the respective holes. The molten iron tapped off from the furnace is solidified into blocks known as pig. This forms an iron called pig iron or cast iron which is called pig iron or cast iron.

The iron thus obtained contains 93% iron, 5% carbon and 2% of other impurities. This iron is further purified as per needed.

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2 Responses to “Extraction of Iron from Haematite”

  1. Mayank

    Atomic no. of Fe is wrong

    • B.Ndulute

      Atomic No.=55.9~56