Iron is extracted from iron ore in a huge container called a blast furnace. Iron ores such as haematite contain iron(III) oxide, Fe2O3. The oxygen must be removed from the iron(III) oxide in order to leave the iron behind. Reactions in which oxygen is removed are called reduction reactions.
|Iron ore (haematite)||Iron(III) oxide (Fe2O3)||A compound that the iron is extracted from|
|Coke||Carbon (C)||Used as a fuel and reacts to form carbon monoxide (needed to reduce the iron(III) oxide)|
|Limestone||Calcium carbonate (CaCO3)||Helps to remove acidic impurities from the iron by reacting with them to form molten slag|
|Air||Oxygen (O2)||Provides oxygen to allow the coke to burn, and so produces heat|
Step 1 – Hot air (oxygen) reacts with the coke (carbon) to produce carbon dioxide and heat energy to heat up the furnace.
C(s) + O2(g) → CO2(g)
Step 2 – More coke is added to the furnace and reduces the carbon dioxide into carbon monoxide, a good reducing agent.
CO2(g) + C(s) → 2CO(g)
Step 3 – iron(III) oxide is reduced.
iron(III) oxide + carbon → iron + carbon dioxide
2Fe2O3(s) + 3C(s) → 4Fe(l) + 3CO2(g)
In the blast furnace, it is so hot that carbon monoxide can be used, in place of carbon, to reduce the iron(III) oxide:
iron(III) oxide + carbon monoxide → iron + carbon dioxide
Fe2O3(s) + 3CO(g) → 2Fe(l) + 3CO2(g)
calcium carbonate → calcium oxide + carbon dioxide
CaCO3(s) → CaO(s) + CO2(g)
The calcium oxide then reacts with silica (sand) impurities in the haematite, to produce slag – which is calcium silicate. This is separated from the iron and used to make road surfaces.
calcium oxide + silica → calcium silicate
CaO(s) + SiO2(s) → CaSiO3(l)
There are a number of important factors to consider when choosing the site of a blast furnace. A blast furnace should be:
Port Talbot, in south Wales, is a good example of a suitable site for a blast furnace.