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Question

Describe the different steps involved in the extraction of iron from its haematite ore. Write the necessary chemical equations involved.


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Solution

Part:1

  • It’s a long process that begins with Concentration through calcination roasting.
  • Concentration is used to remove the water and other volatile compounds such as Sulphur and Carbonates.
  • This concentrated ore is reacted with Limestone and Coke and then goes into the blast furnace from the top.
  • In the blast furnace where the extraction of Iron happens.
  • The concentrated Iron ore, Coke, and Limestone are goes from the top, and a blast of hot air is blown into the bottom.
  • All the ingredients are crushed into small pieces and mixed.
  • Hot air is blown from the bottom and coke is burned to yield temperatures up to about 2200K.
  • Burning coke gives the maximum of the heat required for this process.
  • At such high temperatures, Coke reacts with the Oxygen in the presence of hot air to give Carbon Monoxide.
  • The Carbon Monoxide and heat now move up.
  • The temperature in the upper section of the Furnace is generally lower compared to the bottom.
  • Hematite and Magnetite are reduced to Ferrous Oxide.
  • The Limestone also decomposes to Calcium oxide which helps to remove the Silicate impurity of the ore in form of Slag.
  • Silicate can be easily separated from molten Iron.
  • The Iron formed in Blast Furnaces contains about 3-4% of Carbon and very little quantities of many other impurities such as Sulphur, Silicon, etc.
  • Which is called Pig Iron. Pig Iron is a hard but brittle metal and the impurities greatly affect its strength.
  • Carbon appears significant role in affecting the brittleness and hardness balance in Iron.
  • To further reduce the Carbon content of pig iron, the pig Iron is melted again with scraps of Iron and Coke.
  • This kind of Iron is called Cast Iron and has a lower Carbon content of 2-3%.
  • Cast Iron is harder than pig iron.

Part 2:

  • Reactions in the Blast furnace at 500-800K, In the upper parts with lower temperatures,
  • 3Fe2O3(s)+CO(g)2Fe3O4(s)+CO2(g)Iron(II)CarbonIron(II,III)OxideMonoxideOxide
  • Fe3O4(s)+4CO(g)3Fe(s)+4CO2Iron(IIIII)IronOxide
  • Fe2O3(s)+CO(g)2FeO(s)+CO2(g)Iron(II)IronOxideOxide
  • At 900-1500K,
  • C(s)+CO2(g)2CO(g)CarbonCarbonMonoxide
  • FeO(s)+CO(g)Fe(s)+CO2(g)IronCarbonIronCarbonOxideMonoxideDioxide

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