Extracting Iron from haematite

Iron is extracted from haematite, Fe₂O₃ by reduction in a blast furnace.

The raw materials

1. Iron ore - this contains the iron.
2. Coke - this is almost pure carbon. This is to reduce the iron oxide to iron metal by removing the oxygen.
3. Limestone - this takes away impurities in the form of slag.

Step 1 - Reducing the iron ore to iron

Hot air is blasted into the furnace, raising the temperature to 1500 degrees. This makes the coke burn very fast. As the coke burns, it produces carbon dioxide -

C + O₂ -> CO₂
Carbon + Oxygen -> Carbon dioxide

This CO₂ then reacts with the unburnt coke to produce carbon monoxide -

CO₂ + C -> 2CO
Carbon dioxide + Carbon -> Carbon Monoxide

Finally, the carbon monoxide reduces the iron ore to iron.

3CO + Fe₂O₃ -> 3CO₂ + 2Fe
Carbon monoxide + Iron(III) Oxide -> Carbon dioxide + Iron

The iron is molten at this temperature and can be tapped off the bottom of the furnace.

Step 2 - Removing the impurities

The main impurity is sand (silicon dioxide). This is still solid even at 1500 degrees and stays mixed with the iron. That is until the limestone comes along. The limestone is decomposed by the heat into calcium oxide and CO₂.

CaCO₃ -> CaO + CO₂
Limestone -> Calcium oxide + Carbon dioxide

The calcium oxide then reacts with the sand to form slag (calcium silicate) which can be tapped off and used as fertiliser.

CaO + SiO₂ -> CaSiO₃
Calcium oxide + Sand -> Slag

And that's how you get iron from ore.