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A blast furnace is a special type of furnace for smelting iron from ore. Blast furnaces are very large. They can be up to 60 metres (200 ft) tall and 15 metres (49 ft) in diameter. The blast furnace is the biggest chemical reactor. Blast furnaces are also called high ovens.
A blast furnace is usually built with a steel case and bricks made of magnesium oxide or other refractory material inside the case. The hot furnace cannot melt these bricks. The furnace is cooled with water running inside part of the case and bricks.
The process of making iron is simple. Iron ore is basically iron oxide. Iron is made by removing the oxygen. This leaves crude iron called pig iron. This process of removing oxygen is called smelting. Carbon is used in the reduction process, with the ore heated to a high temperature. Carbon easily takes the oxygen off the ore in high temperatures.
1. Hot blast ("wind") from Cowper stoves
2. Melting zone (bosh)
3. Reduction zone of ferrous oxide (barrel)
4. Reduction zone of ferric oxide (stack)
5. Pre-heating zone (throat)
6. Feed of ore, limestone, and coke
7. Exhaust gases
8. Column of ore, coke and limestone
9. Removal of slag
10. Tapping of molten pig iron
11. Collection of waste gases