What is the principle behind the blast furnace in iron extraction?

The principle behind the blast furnace in iron extraction is the reduction of iron oxides to produce pure iron.

The blast furnace is a large structure used for iron extraction from iron ore. The iron ore, usually haematite (Fe2O3), is first heated in the furnace where it reacts with carbon to form carbon dioxide and iron. This process is known as reduction. The principle of reduction is based on the fact that iron has a higher affinity for oxygen than carbon. Therefore, when both are heated together, the oxygen atoms in the iron ore bond with the carbon to form carbon dioxide, leaving behind pure iron.

The furnace is also filled with coke, a form of carbon, and limestone. The coke serves as the reducing agent, providing the carbon needed for the reduction process. The limestone, on the other hand, acts as a flux, removing impurities such as silica present in the iron ore. These impurities combine with the limestone to form slag, a waste product that can be easily removed.

The temperature inside the blast furnace is carefully controlled. The top of the furnace is cooler, allowing the iron ore, coke and limestone to be continuously added. As these materials descend, they encounter increasingly higher temperatures, reaching up to 2000°C at the bottom. This high temperature is necessary to facilitate the reduction process.

In summary, the principle behind the blast furnace in iron extraction is the reduction of iron oxides using carbon as a reducing agent. This process, coupled with the removal of impurities through the use of limestone, allows for the production of pure iron.