Extraction of Iron (WJEC GCSE Chemistry: Combined Science)

• 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

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