Iron is extracted from haematite
in a blast furnace
The raw materials
- Iron ore - this contains the iron.
- Coke - this is almost pure carbon. This is to reduce the iron oxide to iron metal by removing the oxygen.
- Limestone - this takes away impurities in the form of slag.
Step 1 - Reducing the iron ore to iron
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
). This is still solid even at 1500 degrees and stays mixed with the iron. That is until the limestone comes along. The limestone
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.