The blast furnace process is the most widely used method for extracting iron from iron ores.

It is a continuous process used in large-scale iron production.

Definition

Blast Furnace

A blast furnace is a tall vertical furnace used to extract molten iron from iron ore by reduction using coke and limestone at high temperature.

Raw Materials Used in Blast Furnace

Three main raw materials are charged into the furnace:

Main Parts of a Blast Furnace

Important components include:

• Charging hopper

• Stack

• Bosh

• Hearth

• Tuyeres (air inlet pipes)

• Tap hole (molten iron outlet)

Working of Blast Furnace

The blast furnace operates at temperatures around 1500–2000°C.

Step 1: Charging

Iron ore, coke, and limestone are charged from the top of the furnace.

Step 2: Combustion of Coke

Hot air is blown through the tuyeres.

Coke burns to form carbon dioxide.

$$C + O_2 \rightarrow CO_2$$

Step 3: Formation of Carbon Monoxide

Carbon dioxide reacts with coke to produce carbon monoxide, which acts as a reducing agent.

$$CO_2 + C \rightarrow 2CO$$

Step 4: Reduction of Iron Ore

Carbon monoxide reduces iron oxide to iron.

$$Fe_2O_3 + 3CO \rightarrow 2Fe + 3CO_2$$

Step 5: Formation of Slag

Limestone decomposes to form calcium oxide.

$$CaCO_3 \rightarrow CaO + CO_2$$

Calcium oxide reacts with silica impurities.

$$CaO + SiO_2 \rightarrow CaSiO_3$$

This molten product is called slag.

Products of Blast Furnace

The blast furnace produces two main outputs:

Slag is removed separately and used in cement and road construction.

Exam-Focused Points

Key points for competitive exams:

• Coke acts as fuel and reducing agent

• Limestone acts as flux

• Slag removes impurities

• Molten iron collects in hearth