Extraction of Iron (WJEC GCSE Chemistry: Combined Science)

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Philippa

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Philippa

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Extraction of Iron from Hematite

  • Iron is extracted in a large container called a blast furnace from its ore, hematite 
  • Modern blast furnaces produce approximately 10,000 tonnes of iron per day 
  • This is a continuous process with new raw materials added and products removed all the time due to the time and cost associated with getting the furnace up to temperature

The Blast Furnace

The blast furnace

There are three main zones in the blast furnace

  • The raw materials: iron ore (hematite), coke (an impure form of carbon), and limestone are added into the top of the blast furnace
  • Hot air is blown into the bottom

Table of raw materials and their uses

Raw material Formula Use
 Iron ore (heamatite)  Fe2O3  Source of iron
 Coke  C  To provide carbon
 Limestone  CaCO3  To neutralise acidic impurities

Zone 1

  • Coke burns in the hot air forming carbon dioxide 
  • The reaction is exothermic so it gives off heat, heating the furnace

carbon + oxygen → carbon dioxide

C (s)  +  O2 (g)  →  CO2 (g)

Zone 2

  • At the high temperatures in the furnace, more coke reacts with carbon dioxide forming carbon monoxide
  • Carbon dioxide has been reduced to carbon monoxide

carbon + carbon dioxide → carbon monoxide

CO2 (g)  +  C (s)  →  2CO (g)

Zone 3

  • Carbon monoxide reduces the iron(III) oxide in the iron ore to form iron 
  • This will melt and collect at the bottom of the furnace, where it is tapped off:

iron(III) oxide + carbon monoxide  →  iron + carbon dioxide

Fe2O3 (s)  +  3CO (g)  →  2Fe (I)  +  3CO2 (g)

Removal of impurities 

  • Limestone (calcium carbonate) is added to the furnace to remove acidic impurities in the ore
    • The calcium carbonate in the limestone thermally decomposes to form calcium oxide

calcium carbonate → calcium oxide + carbon dioxide

CaCO3 (s)  →  CaO (s)  +  CO2 (g)

  • The calcium oxide formed reacts with the silicon dioxide, which is an impurity in the iron ore, to form calcium silicate by neutralisation

calcium oxide + silicon dioxide →  calcium silicate

CaO (s)  +  SiO2 (s)  →  CaSiO3 (l)

  • This melts and collects as a molten slag floating on top of the molten iron, which is tapped off separately

Worked example

a) Balance the symbol equation for the following reaction that occurs in the blast furnace.

Fe2O3 +   ____ CO →   ____ Fe +  ____ CO2

b) Give the name of the substance that is oxidised in the reaction.

Answer

a) The balanced equation is

  • Fe2O3 +  CO →   Fe +  CO2
  • Balance the oxygen atoms
    • Fe2O33CO →   Fe +  3CO2
  • The carbon atoms are now also balanced
  • Balance the iron atoms
    • Fe2O33CO →   2Fe +  3CO2

b) The species oxidised is:

  • Carbon monoxide
  • This is because the carbon monoxide has gained oxygen to form carbon dioxide

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Philippa

Author: Philippa

Expertise: Chemistry

Philippa has worked as a GCSE and A level chemistry teacher and tutor for over thirteen years. She studied chemistry and sport science at Loughborough University graduating in 2007 having also completed her PGCE in science. Throughout her time as a teacher she was incharge of a boarding house for five years and coached many teams in a variety of sports. When not producing resources with the chemistry team, Philippa enjoys being active outside with her young family and is a very keen gardener.