Extraction of Iron

Iron is extracted from its main ore, haematite (iron(III) oxide, $\mathrm{Fe_2O_3}$), in a tall, hot tower called a blast furnace. Because iron is below aluminium in the reactivity series, it can be extracted by heating with carbon (from coke) instead of by electrolysis.

Raw materials and their roles

• Haematite ($\mathrm{Fe_2O_3}$) – provides the iron.
• Coke (carbon) – burns to release heat and makes carbon monoxide, the reducing agent.
• Hot air – supplies oxygen so coke can burn.
• Limestone ($\mathrm{CaCO_3}$) – removes sandy impurity (silicon dioxide, $\mathrm{SiO_2}$) by forming slag.

What happens inside the blast furnace

Think of a layered pizza oven: solids go in at the top, hot gases rise from the bottom. The lower part is very hot (about 1500 °C), so reactions happen quickly and the products melt and separate.

Key reactions (symbol equations)

1) Burning of coke to provide heat and $\mathrm{CO_2}$:

$$\mathrm{C + O_2 \rightarrow CO_2}$$

2) Making carbon monoxide (the reducing agent):

$$\mathrm{CO_2 + C \rightarrow 2CO}$$

3) Reduction of iron(III) oxide by carbon monoxide to iron:

$$\mathrm{Fe_2O_3 + 3CO \rightarrow 2Fe + 3CO_2}$$

4) Thermal decomposition of limestone to quicklime:

$$\mathrm{CaCO_3 \rightarrow CaO + CO_2}$$

5) Removal of impurity (sand, $\mathrm{SiO_2}$) by forming slag:

$$\mathrm{CaO + SiO_2 \rightarrow CaSiO_3}$$

Products and separation

• Molten iron – very dense, collects at the bottom and is tapped off.
• Molten slag ($\mathrm{CaSiO_3}$) – less dense, floats on iron and is removed; used in road building.
• Waste gases – mainly $\mathrm{CO_2}$, $\mathrm{CO}$, and $\mathrm{N_2}$ leave from the top.

Common misconceptions

• The main reducing agent is carbon monoxide, not oxygen or limestone.
• Limestone does not make iron; it removes acidic impurities by forming slag.
• Iron from the furnace is not stainless steel; it is usually converted into steel later.