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

Explanation

In blast furnace , reducing of iron oxides takes place in different temperature ranges. The lower part of the blast furnace has high temperature of the order of 2200 K (called combustion zone) and the top of the furnace has low temperature of the order of 500-800 K (called reduction zone.) The reduction occuring in the lower temperature range (upper part) is by carbon and in the higher temperature range (lower part) is by carbon monoxide.
At lower temperature range (500-800 K) in upper part of furnace the reactions occuring are :
`3Fe_2O_3 + CO to 2Fe_3 O_4 + CO_2`
`Fe_3 O_4 + 4CO to 3Fe + 4CO_2`
`Fe_2O_3 + CO to 2FeO + CO_2`
At higher temperature range (900-1500K) in lower part of furnace the reactions occuring are :
`C + CO_2 to 2CO`
`FeO + CO to Fe + CO_2`
In the middle portion (at point 1270 K), limestone decomposes to give lime (CaO) and `CO_2` . Lime acts as a flux and combines with silicate impurity to form slag.
`CaCO_3 to CaO + CO_2`
`underset("Lime")(CaO) + underset("Impurity")(SiO_2) to underset("Calcium silicate (slag)")(CaSiO_3)`
Slag is in the molten state adn separates out from iron.