The smelting of iron in a blast furnace involves the following processes :

The smelting of iron in a blast furnace involves the following processes:

1. Combustion:

The air blown into the bottom of the furnace is heated using the hot waste gases from the top. The coke (essentially impure carbon) burns in the blast of hot air to form carbon dioxide - a strongly exothermic reaction. 

2. Reduction:

At the high temperature at the bottom of the furnace, carbon dioxide reacts with carbon to produce carbon monoxide.the carbon monoxide which is the main reducing agent in the furnace. Which converts iron oxide into iron. 

3. Slag formation:

The limestone is added to convert rocky material into slag which melts and runs to the bottom. The heat of the furnace decomposes the limestone to give calcium oxide.