Extraction of Iron from Hematite
The Blast Furnace: Iron is extracted from its ore, hematite (Fe₂O₃), using a large structure
called a blast furnace.
Modern blast furnaces are capable of producing approximately 10,000 tonnes of iron per
day, making them highly efficient for large-scale production. Process Overview:
The main purpose of the blast furnace is to reduce iron oxide (hematite) into iron by
removing the oxygen. The furnace operates continuously, and it is fed with three main raw
materials: Iron Ore (Hematite) - This is the source of iron. Coke - A form of carbon that acts
as a reducing agent and fuel. Limestone (Calcium Carbonate) - This helps remove impurities
by forming slag. Reactions in the Blast Furnace: Combustion Reaction: At the base of the
furnace, hot air is blown in, causing the coke (carbon) to burn:
C (s) + O 2 (g) → CO 2 (g) C (s) + O 2 (g) → CO 2 (g) This reaction produces carbon dioxide
and a lot of heat, raising the temperature in the furnace. Formation of Carbon Monoxide:
Higher up in the furnace, the carbon dioxide reacts with more coke to form carbon
monoxide: CO 2 (g) + C (s) → 2CO (g) CO 2 (g) + C (s) → 2CO (g) Carbon monoxide is
crucial as it acts as the main reducing agent for the iron ore. Reduction of Iron Ore: The
carbon monoxide then reacts with the hematite (iron oxide) to reduce it and produce iron:
Fe 2 O 3 (s) + 3CO (g) → 2Fe (l) + 3CO 2 (g) Fe 2 O 3 (s) + 3CO (g) → 2Fe (l) + 3CO 2 (g) In
this step, the iron oxide loses oxygen and turns into molten iron, which collects at the
bottom of the furnace. Role of Limestone: Limestone is added to remove impurities like
silica (sand) present in the ore. When the limestone (calcium carbonate) is heated, it
decomposes: CaCO 3 (s) → CaO (s) + CO 2 (g) CaCO 3 (s) → CaO (s) + CO 2 (g) The
calcium oxide (CaO) produced then reacts with the impurities to form slag (calcium silicate):
CaO (s) + SiO 2 (s) → CaSiO 3 (l) CaO (s) + SiO 2 (s) → CaSiO 3 (l) The slag is less dense
than molten iron, so it floats on top and can be removed separately. Final Products: The
molten iron collects at the bottom of the blast furnace and is periodically tapped off. The
slag, which forms from the reaction of calcium oxide and silica, also accumulates and is
removed separately. This slag is used in construction or road-building. Summary: The
extraction of iron in a blast furnace involves heating hematite with coke and limestone. The
carbon in coke reduces the iron oxide to iron, while limestone helps remove impurities. The
result is molten iron and slag, with the iron being collected and processed further.