Question

The following reactions take place in the blast furanace in the preparation of impure iron. Identify the reaction pertaining to the formation of the slag.

Answer 1

In extraction of iron from its oxide ore, hot air in blown from bottom of blast furnace so that coke is burnt to give high temperature upto 2200 K at lower portion of furnace only.
Then, CO and heat moves to upper part of furnace.
The temperature is lower in upper part where the iron oxide get reduce in different temperature.

At 500-800 K, iron oxide get reduced only by CO.
\(3Fe_2O_3 + CO \rightarrow 2Fe_3O_4 + CO_2\)
\(Fe_3O_4 + 4CO \rightarrow 3Fe + 4CO_2\)
\(Fe_2O_3 + CO \rightarrow 2FeO + CO_2\)

At 900-1500 K, iron oxide is reduced by both C and CO.
\(C + CO_2 \rightarrow 2CO\)
\(FeO + CO \rightarrow Fe + 2CO\)

Limestone is added to the furnance to remove the \(SiO_2\) as slag \((CaSiO_3)\).
\(CaCO_3 \rightarrow CaO + CO_2\)
\(CaO + SiO_2 \rightarrow CaSiO_3\)