Extraction of Iron from Hematite (Cambridge (CIE) IGCSE Combined Science): Revision Note

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 

The blast furnace

Diagram showing the carbon extraction of iron

• 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

Zone 1

• Coke burns in the hot air to form carbon dioxide 

• The reaction is exothermic and provides heat for the furnace

carbon + oxygen → carbon dioxide

Zone 2

• At high temperatures, carbon (coke) reacts with carbon dioxide to form carbon monoxide.

• Carbon monoxide is the main reducing agent in the furnace.

carbon + carbon dioxide → carbon monoxide

Zone 3

• Carbon monoxide reduces the iron(III) oxide to iron

  • Iron is extracted by reduction because oxygen is removed from iron(III) oxide

• The molten iron collects at the bottom of the furnace and is tapped off

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

• Limestone (calcium carbonate) is added to the furnace to remove impurities in the ore

  • The calcium carbonate in the limestone thermally decomposes to form calcium oxide

calcium carbonate → calcium oxide + carbon dioxide

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

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

calcium oxide + silicon dioxide →  calcium silicate

Equations for extraction of iron from hematite

Extended tier only

Zone 1

• The burning of carbon (coke) to provide heat and produce carbon dioxide:

C (s)  +  O₂ (g)  →  CO₂ (g)

Zone 2

• The reduction of carbon dioxide to carbon monoxide:

CO₂ (g)  +  C (s)  →  2CO (g)

Zone 3

• The reduction of iron(III) oxide by carbon monoxide:

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

• The thermal decomposition of calcium carbonate (limestone) to produce calcium oxide:

CaCO₃ (s)  →  CaO (s)  +  CO₂ (g)

• The formation of slag:

CaO (s)  +  SiO₂ (s)  →  CaSiO₃ (l)