Destructive distillation of coal is carried out by heating coal strongly to 1000°C in the absence of air. When coal is heated without air, it does not burn but breaks down to produce following by-products:
(a) Coke: It is used in industries for manufacturing of steel and extraction of many metals. It is used as a domestic fuel for cooking and heating.
(b) Coal tar: It can be used to make soap, fats, dyes, plastics perfumes, drugs, pesticides, explosives etc.
(c) Coal gas: It is used as fuel in coal processing plants and in various other industrial units situated near coal processing plants.
(d) Ammonia: It is used for making nitrogenous fertilisers.