Extraction of iron

Iron is extracted from its ore, haematite (Fe₂O₃), in a blast furnace. This large industrial process involves several chemical reactions to produce molten iron and a waste material called slag. The process relies on the use of carbon (in the form of coke) and limestone to reduce iron(III) oxide to iron while removing impurities.

Key steps in the extraction process

1. Burning Carbon to Provide Heat

   • Reaction: Carbon (coke) reacts with oxygen to produce carbon dioxide. This is an exothermic reaction that generates the heat needed to maintain the furnace's high temperature (~2000°C).

     • Symbol Equation: C + O2 → CO2

2. Reduction of Carbon Dioxide to Carbon Monoxide

   • Carbon dioxide reacts with more carbon at high temperatures to produce carbon monoxide.

     • Symbol Equation: C + CO2 → 2CO

   • Carbon monoxide acts as a reducing agent in subsequent reactions.

3. Reduction of Iron(III) Oxide by Carbon Monoxide

   • The main chemical reaction occurs when carbon monoxide reduces iron(III) oxide (Fe2O3) to molten iron. The iron collects at the base of the furnace.

     • Symbol Equation: Fe2O3 + 3CO → 2Fe + 3CO2​

4. Thermal Decomposition of Limestone

   • Limestone (CaCO3) is added to the furnace to remove impurities such as silica (SiO2). The limestone decomposes into calcium oxide and carbon dioxide at high temperatures.

     • Symbol Equation: CaCO3 → CaO + CO2

5. Formation of Slag

   • The calcium oxide reacts with silica impurities to form slag (CaSiO3). Slag is molten and floats on top of the molten iron, where it can be removed.

     • Symbol Equation: CaO + SiO2 → CaSiO3

Key outputs from the blast furnace

1. Molten Iron:

   • Collects at the base of the furnace and is tapped off.

   • Used in the production of steel and other alloys.

2. Slag:

   • A by-product used in construction (e.g., road-building materials).

Application and context