question_answer 11)

Write the chemical reactions which take place in different zones in the blast furnace during the extraction of iron.

Answer:

Reactions taking place in the blast furnace are: (a) Zone of reduction or top zone (823 K). Ferric oxide is reduced to spongy iron by carbon monoxide coming from the lower portion of the furnace. Fe2O3 + 3CO  2Fe + 3CO2 (b)Zone of slag formation (1123 K): Lime stone gets decomposed into lime, CaO (flux) which forms a fusible slag with sand (impurity). Slag is lighter and has lower melting point metal point than the metal. (c)Zone of fusion (1423 ? 1673 K). CO2 + C   2CO; H = +163 kJ (d) Zone of combustion (2170 K): Carbon combines with oxygen to form carbon dioxide :              C + O2  CO2 = ? 393.5 kJ Iron thus formed is called cast iron or pig iron.