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Question:

Write down the reactions taking place in a blast furnace related to the metallurgy of iron in the temperature range 500-1500K. What is the role of limestone in the metallurgy of iron?

Solution:

The reactions taking place in the lower temperature range (500-1500K) in the blast furnace are:

3Fe₂O₃ + CO → 2Fe₃O₄ + CO₂
Fe₃O₄ + 4CO → 3Fe + 4CO₂
Fe₂O₃ + CO → 2FeO + CO₂

Limestone decomposes in the hot furnace, forming calcium oxide (CaO) which removes silicate impurity of ore as slag.

CaCO₃ → CO₂ + CaO
CaO + SiO₂ (Impurity) → CaSiO₃ (Slag)