how is destructive distillation of coal carried out?

 When coal is heated without air, it does not burn but produces many by-products.  This process of heating coal in the absence of air is called destructive distillation of coal.

The main products are-

1.Coke

2.Coal Tar

3.Amino acid liquor

4. Coal Gas

Finely powdered coal taken in a test tube is heated. As the coal breaks down coke, coal tar, ammonia and coal gas are produced. Coal tar collects at the bottom of the second test tube and coal gas escapes out through the side tube. The ammonia produced is absorbed in the water forming ammoniacal liquor (ammonium hydroxide). The black residue left in the 1st tube is called coke.Coke is a fuel in its own right which can be used in homes and factories. But it is largely used as a reducing agent in the extraction of metals from their ores. It is also used in making fuel gases like water gas which is a mixture of carbon monoxide and hydrogen.Another by product namely coal tar which is a mixture of different carbon compounds can be used to make soap, fats, dyes plastics perfumes, drugs, pesticides, explosives etc.The other by product, ammonia is used for making fertilizers such as ammonium sulphate, ammonium superphosphate etc.The coal gas, also called as a town gas is a mixture of hydrogen, methane and carbon monoxide which are combustible making the coal gas an excellent fuel having high calorific values.

 The destructive distillation of coal is carried out by heating coal to a high temperature abot 1000 degree in the absence of oxygen.From this we get many organic and inorganic products like coke, coal gas, coal tar and ammonium compounds.

Destructive distillation is the chemical process involving the decomposition of feedstock by heating to a high temperature; the term generally applies to processing of organic material in the absence of air or in the presence of limited amounts of oxygen or otherreagents, catalysts, or solvents, such as steam or phenols, it is an application of pyrolysis. The process breaks up or 'cracks' large molecules. Coke, coal gas, gas carbon, coal tar and ammonia liquor are examples of commercial products of the destructive distillation of coal. 

Currently the major industrial application of destructive distillation is to coal.