Extraction of Iron from Hematite | Chemistry for Grade 11 (IGCSE) PDF Download

Extraction of Iron from Hematite

• Iron extraction occurs in a specialized structure known as a blast furnace, typically from hematite ore.
• Contemporary blast furnaces have a notable output, yielding around 10,000 tons of iron daily.
• The process of iron extraction involves specific steps, which are outlined and elucidated below:

Diagram showing the carbon extraction of iron

• In the blast furnace, hematite ore, coke, and limestone are introduced from the top.
• Hot air is blown into the bottom of the furnace.
• Coke, an impure carbon variant, undergoes combustion in Zone 1 with the hot air, producing carbon dioxide and releasing heat.
• The generated heat aids in heating the furnace due to the exothermic nature of the reaction.
• In Zone 2, coke reacts further with carbon dioxide at elevated temperatures, yielding carbon monoxide.
• This step involves the reduction of carbon dioxide to carbon monoxide.
• In Zone 3, carbon monoxide acts as a reducing agent for iron(III) oxide in the hematite ore, resulting in the formation of molten iron.
• The molten iron accumulates at the furnace's base and is extracted periodically.
• Limestone is incorporated into the furnace to eliminate ore impurities.
• The thermal decomposition of calcium carbonate from limestone produces calcium oxide and carbon dioxide.
• Calcium oxide then reacts with silicon dioxide, an impurity in the ore, to produce calcium silicate.
• The resulting calcium silicate forms a molten slag that floats atop the molten iron, allowing for separate removal.

Equations for Extraction of Iron from Hematite

• Introduction: In the extraction of iron from hematite, several stages are involved, each with specific reactions.
• Zone 1 - Burning of Carbon: This stage involves the burning of carbon (coke) to provide heat and produce carbon dioxide.
  C (s) + O₂ (g) → CO₂ (g)
• Zone 2 - Reduction of Carbon Dioxide: Carbon dioxide is reduced to carbon monoxide in this stage.
  CO₂ (g) + C (s) → 2CO (g)
• Zone 3 - Reduction of Iron(III) Oxide: Iron(III) oxide is reduced by carbon monoxide in this crucial stage.
  Fe₂O₃ (s) + 3CO (g) → 2Fe (l) + 3CO₂ (g)
• When calcium carbonate (limestone) is heated, it undergoes thermal decomposition to produce calcium oxide and carbon dioxide.
  CaCO₃ (s) → CaO (s) + CO₂ (g)
• The Formation of Slag:
  CaO (s) + SiO₂ (s) → CaSiO₃ (l)