Destructive distillation of coal is the process by which coal is heated in the absence of air (or in a limited supply of air) to produce a number of useful products such as coal gas, coal tar, ammoniacal liquor, and coke. This process breaks down complex carbon compounds in coal into simpler substances through heat.

Coal is a black or brownish-black sedimentary rock formed from the remains of plants that lived and died about 300 million years ago. These remains were buried under layers of soil and rock where they were subjected to heat and pressure over millions of years.

Major sources of coal include: China, the United States, India, Russia, South Africa, Australia, and Nigeria (especially in Enugu, Benue, and Kogi States).

The process is carried out in a special furnace known as a retort or coke oven. The coal is heated to about 1000°C in the absence of air. As it heats up, it decomposes and releases various volatile substances that are collected and condensed into useful products.

Step-by-step explanation:

1. Step 1: Finely crushed coal is placed in an air-tight retort and heated strongly.
2. Step 2: The volatile components escape as gases and vapours, leaving behind a solid residue called coke.
3. Step 3: The vapours are condensed to form coal tar and ammoniacal liquor.
4. Step 4: The uncondensed gases are collected as coal gas.

1. Coke: A hard, porous, black solid mainly composed of carbon.
   • Uses: Used as a fuel, in the manufacture of iron and steel (as a reducing agent), and in domestic heating.
2. Coal Gas: A mixture of gases such as hydrogen, methane, carbon monoxide, and small quantities of other gases.
   • Uses: Used as a fuel for heating and lighting; also as a reducing agent in chemical industries.
3. Coal Tar: A thick, black viscous liquid (semi solid at room temperature) containing aromatic compounds such as benzene, toluene, naphthalene, and phenol.
   • Uses: Used in the manufacture of dyes, explosives, drugs, perfumes, plastics, paints, and disinfectants.
4. Ammoniacal Liquor: A water solution containing ammonia and other nitrogen compounds.
   • Uses: Used in the manufacture of fertilizers such as ammonium sulphate and ammonium nitrate.

Note: Ammoniacal liquor is liquid at room temperature, while coal tar is a semi-solid. Hence, ammoniacal liquor is the only liquid fraction from the distillation of coal

Coal occurs in several grades or types depending on the carbon content and heating value

1. Peat: The lowest grade of coal; brownish in color with high moisture and low carbon content.
2. Lignite (Brown Coal): Slightly better than peat; burns with a smoky flame and has moderate carbon content.
3. Bituminous Coal: A dense, black coal with high carbon and calorific value; commonly used for coke production.
4. Anthracite: The hardest and purest form of coal; has the highest carbon content and burns with a clean, smokeless flame.

• As a fuel for domestic and industrial heating.
• As a source of coke for steel production.
• Coal tar for making chemicals, dyes, and pharmaceuticals.
• Ammoniacal liquor for fertilizer manufacture.
• Coal gas for heating and lighting.
• Raw material for obtaining important organic compounds like benzene and phenol.