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In the smelting of iron ore, the addition of limestone (calcium carbonate) serves which purpose?

Option: 1

Acts as a reducing agent

Option: 2

Increases the melting point of iron

Option: 3

Removes impurities as slag

Option: 4

Facilitates the extraction of carbon monoxide

Answers (1)


In the smelting of iron ore, the addition of limestone (calcium carbonate) serves the purpose of removing impurities as slag.

During the smelting process, iron ore is heated in a blast furnace along with coke (carbon) and limestone. The limestone serves as a flux, which means it helps to remove impurities from the iron ore and forms a slag.

The main impurities in iron ore include silica ( \mathrm{SiO}_2 ), \text{alumina} \left(\mathrm{Al}_2 \mathrm{O}_3\right ), and other minerals. When limestone is added to the furnace, it reacts with the impurities present in the ore, forming a molten slag. The slag is a combination of calcium silicate \left(\mathrm{CaSiO}_3\right) and calcium aluminate ( \mathrm{CaAl}_2 \mathrm{O}_4 ), which are both liquid at the high temperatures in the blast furnace.

The role of the slag is to float on top of the molten iron and act as a protective layer, preventing the contact of the iron with atmospheric oxygen. This protects the iron from being oxidized and helps maintain the high temperatures required for the smelting process.

Furthermore, the slag also helps in the separation of impurities from the molten iron. The impurities present in the ore react with the calcium oxide (CaO) in the limestone, forming various compounds that become part of the slag. This allows for the removal of impurities from the iron, resulting in a purer final product.

Posted by

Suraj Bhandari

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