Coal by-products

When coal is heated, or carbonised, several gases and other substances are released and these can all be used as well. The National Coal Board (NCB) had its own carbonisation plants for creating other by-products.

Gases Before the discovery of natural gas in the UK in the 1960s all gas was created from coal and known as 'town gas'. The coal is heated in a retort (like an oven) and the gas that comes off as a result is purified and then piped to the gas user. The retorts could be used continually for up to five years and then shut down for repairs. Other gases produced were benzole, ammonia, sulphuretted hydrogen or sulphuric acid, and fire damp. Benzole could be used to produce many things, such as rubber solvents, waterproof material, lino, weed killer, explosives, paint, polishes, plastics, dyes and medicines. Ammonia was also used in lino, explosives, fertilizers, soap, and was used in refrigeration. Sulphuric acid was used in crop spraying, fertilizers, and batteries. Fire damp was mostly methane and is the natural gas given off by coal. It was not dangerous to breath but it was highly flammable and many accidents in mines were caused by fire damp explosions. Coke As well as creating this gas, the heating process also led to coke, which could be re-used as a smokeless fuel. In the 1950s the NCB had 48 coking plants, which carbonised 10 million tons of coal a year (40% of the coal carbonised in coke plants in Britain). Gasworks often had coking plants as well where coke was produced, especially for use in steel making. Coal tar Coal tar was another by-product given off when coal was heated to produce gas. The tar was extracted from the gas in condensers, which cooled the gas, allowing the tar to turn to liquid and run off into wells or pits. Coal tar and some of its by-products could be used in a variety of ways such as fuel, antiseptics, in plastics, as resins for paint making, in roofing felt, creosote, moth balls (napthalene), pitch for roads, in making drugs, in food flavourings, perfumes and plastics. The NCB also had 80 brickworks (which provided 7½% of the national brick production).

The front of the programme for the official inspection of the Benzole Recovery Plant at Provan Gas Works on 28 August 1936. Courtesy of the National Gas Archive