Coal gas

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Coal gas is a flammable gaseous fuel made from coal and supplied to the user via a piped distribution system. It is produced when coal is heated strongly in the absence of air. Town gas is a more general term referring to manufactured gaseous fuels produced for sale to consumers and municipalities.^[1]

The original coal gas was produced by the coal gasification reaction,^[2] and the burnable component consisted of a mixture of carbon monoxide and hydrogen in roughly equal quantities by volume. Thus, coal gas is highly toxic.^[3] Other compositions contain additional calorific gases such as methane,^[4] produced by the Fischer–Tropsch process, and volatile hydrocarbons together with small quantities of non-calorific gases such as carbon dioxide and nitrogen.

Prior to the development of natural gas supply and transmission—during the 1940s and 1950s in the United States and during the late 1960s and 1970s in the United Kingdom and Australia—almost all gas for fuel and lighting was manufactured from coal. Town gas was supplied to households via municipally owned piped distribution systems. Sometimes, this was called syn gas, in contrast to natural gas.^[5] At the time, a popular method of committing suicide was the inhalation of gas from an unlit oven. With the head and upper body placed inside the appliance, the concentrated carbon monoxide would kill quickly.^[6][7] Sylvia Plath famously ended her life with this method.

Originally created as a by-product of the coking process, its use developed during the 19th and early 20th centuries tracking the industrial revolution and urbanization. By-products from the production process included coal tars and ammonia, which were important raw materials (or "chemical feedstock") for the dye and chemical industry with a wide range of artificial dyes being made from coal gas and coal tar. Facilities where the gas was produced were often known as a manufactured gas plant (MGP) or a gasworks.

In the United Kingdom the discovery of large reserves of natural gas, or sea gas as it was known colloquially, in the Southern North Sea off the coasts of Norfolk and Yorkshire in 1965^[8][9] led to the expensive conversion or replacement of most of Britain's gas cookers and gas heaters, from the late 1960s onwards, the process being completed by the late 1970s. Any residual gas lighting found in homes being converted was either capped off at the meter or, more usually, removed altogether. As of 2023, some gas street lighting still remains, mainly in central London and the Royal Parks.

The production process differs from other methods used to generate gaseous fuels known variously as manufactured gas, syngas, Dowson gas, and producer gas. These gases are made by partial combustion of a wide variety of feedstocks in some mixture of air, oxygen, or steam, to reduce the latter to hydrogen and carbon monoxide although some destructive distillation may also occur.