Write down the reactions taking place in different zones in the blast furnace during the extraction of iron.

Explanation

The different zones of the blast furnace are as shown in the figure :

The following reactions occur in the blast furnace :
i) Zone of combustion : It is the lower part of the furnace and temperature is around 217 K. In this zone coke bums to form carbon dioxide.
`C + O_2 to CO_2`
ii) Zone of fusion : It is lower part of the furnace and temperature is between 1423-1673 K. The coke present reduces `CO_2` to CO.
`CO_2 + C to 2CO`
iii) Zone of slag formation (Role of `CaCO_3`) :
It is the middle part of the furnace and temperature is around 1123K. In this zone, limestone decomposes to calcium oxide, which acts as flux. This flux combines with silica to form slag.
`CaCO_3(s) to CaO(s) + CO_2(g)`
`CaO(s) + SiO_2 to underset("Calcium silicode (slag)")(CaSiO_3)`
iv) Zone of reduction :It is the upper part of the furnace and temperature is around 323 K. Here ore is reduced to FeO by CO, which on further reduction gives Fe.
`Fe_2O_3 + CO to 2FeO + CO_2 : FeO + CO to Fe + CO_2`
The molten metal and molten slag is collected here. Since, slag is lighter than metal and hence it float on the molten metal. At last, both liquids are periodically tapped off.