Coal gas

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.

Coal gas contains a variety of calorific gases including hydrogen, carbon monoxide, methane, ethylene 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—virtually all gas for fuel and lighting was manufactured from coal. Town gas was supplied to households via municipally owned piped distribution systems.

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 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.

The discovery of large reserves of natural gas in the North Sea off the English coast in 1965 [1][2] led to the expensive conversion or replacement of most of the UK's gas cookers and gas heaters, except in Northern Ireland, from the late 1960s onwards.

The production process is distinct, both physically and chemically,[clarification needed] from that used to create a range of gaseous fuels known variously as manufactured gas, syngas, hygas, Dowson gas, and producer gas. These gases are made by partial combustion of a wide variety of feed stocks in some mixture of air, oxygen, or steam, to reduce the latter to hydrogen and carbon dioxide although some destructive distillation may also occur.

Manufacturing processes [ edit ]

Gas Works Park, Seattle, preserves most of the equipment for making coal gas. This is the only such plant surviving in the United States.


The first process used was the carbonization and partial pyrolysis of coal. The off gases liberated in the high-temperature carbonization (coking) of coal in coke ovens were collected, scrubbed and used as fuel. Depending on the goal of the plant, the desired product was either a high quality coke for metallurgical use, with the gas being a side product, or the production of a high quality gas, with coke being the side product. Coke plants are typically associated with metallurgical facilities such as smelters or blast furnaces, while gas works typically served urban areas.

A facility used to manufacture coal gas, carburetted water gas (CWG), and oil gas is today generally referred to as a manufactured gas plant (MGP).

In the early years of MGP operations, the goal of a utility gas works was to produce the greatest amount of illuminating gas. The illuminating power of a gas was related to amount of soot-forming hydrocarbons ("illuminants") dissolved in it. These hydrocarbons gave the gas flame its characteristic bright yellow color. Gas works would typically use oily bituminous coals as feedstock. These coals would give off large amounts of volatile hydrocarbons into the coal gas, but would leave behind a crumbly, low-quality coke not suitable for metallurgical processes. Coal or coke oven gas typically had a calorific value between 10 and 20 megajoules per cubic metre (270 and 540 Btu/cu ft); with values around 20 MJ/m3 (540 Btu/cu ft) being typical.


Gas for industrial use [ edit ]

An illustration of typical polycyclic aromatic hydrocarbons. Source: NASA

Fuel gas for industrial use was made using producer gas technology. Producer gas is made by blowing air through an incandescent fuel bed (commonly coke or coal) in a gas producer. The reaction of fuel with insufficient air for total combustion produces carbon monoxide (CO); this reaction is exothermic and self-sustaining. It was discovered that adding steam to the input air of a gas producer would increase the calorific value of the fuel gas by enriching it with CO and hydrogen (H2) produced by water gas reactions. Producer gas has a very low calorific value of 3.7 to 5.6 MJ/m3 (99 to 150 Btu/cu ft); because the calorific gases CO/H2 are diluted with lots of inert nitrogen (from air) and carbon dioxide (CO2) (from combustion)

2C (s) + O2 → 2 CO (exothermic producer gas reaction)
C (s) + H2O (g) → CO + H2 (endothermic water gas reaction)
C + 2 H2O → CO2 + 2 H2 (endothermic)
CO + H2O → CO2 + H2 (exothermic water gas shift reaction)


Blue water gas lacked illuminants; it would not burn with a luminous flame in a simple fishtail gas jet as existed prior to the invention of the Welsbach mantle in the 1890s. Various attempts were made to enrich BWG with illuminants from gas oil in the 1860s. Gas oil (an early form of gasoline) was the flammable waste product from kerosene refining, made from the lightest and most volatile fractions (tops) of crude oil. In 1875 Thaddeus S. C. Lowe invented the carburetted water gas process. This process revolutionized the manufactured gas industry and was the standard technology until the end of manufactured gas era.[5] A CWG generating set consisted of three elements; a producer (generator), carburettor and a super heater connected in series with gas pipes and valves.[6]


Gas in post-war Britain [ edit ]

Mantles in their unused flat-packed form

New manufacturing processes [ edit ]

Following the Second World War the slow recovery of the British coal mining industry led to shortages of coal and high prices.[8]

UK Coal Production
Year Production, million tons Production cost, £/ton
1947 197 2.00
1950 216 2.40
1953 223 3.05
1956 222 3.85
1959 206 4.15
1961 191 4.55
1965 187 4.60
1967 172 4.95

The decline of coal as a feedstock for town gas production using carbonisation is demonstrated in this graph.[9]

Coal-based town gas production, millions of therms

New technologies for manufacturing coal gas using oil, refinery tail gases, and light distillates were developed. Processes included the Lurgi Process, catalytic reforming, the catalytic rich gas process, steam reforming of rich gas, and the gas recycle hydrogenator process.[10] The catalytic rich gas process used natural gas as a feedstock to manufacture town gas. These facilities utilised the chemical reaction processes described above.

The rise of oil as a feedstock to manufacture town gas is shown on the graph below. The peak usage in 1968/9 and subsequent decline coincides with the availability of North Sea gas which, over the next few years, displaced town gas as a primary fuel and led to the decline of oil as a feedstock for gas making, as shown.[9]

Oil-based town gas production, millions of therms

Domestic heating [ edit ]



Natural gas as feedstock [ edit ]

In 1959 the Gas Council in Great Britain demonstrated that liquid natural gas (LNG) could be transported safely, efficiently and economically over long distances by sea. The Methane Pioneer shipped a consignment of LNG from Lake Charles, Louisiana, USA, to a new LNG terminal on Canvey Island, in the Thames estuary in Essex, England. A 212-mile (341 km) long high-pressure trunk pipeline was built from Canvey Island to Bradford.[11] The pipeline and its branches provided Area Gas Boards with natural gas for use in reforming processes to make town gas. A large-scale LNG reception plant was commissioned on Canvey in 1964, this received LNG from Algeria in two dedicated tankers each of 12,000 tonnes.[12]

Conversion to natural gas [ edit ]

The slow decline of the town gas industry in the UK was signalled by the discovery of natural gas by the drilling rig Sea Gem, on 17 September 1965, some forty miles off Grimsby, over 8,000 feet (2,400 m) below the seabed. Subsequently, the North Sea was found to have many substantial gas fields on both sides of the median line defining which nations should have rights over the reserves.

In a pilot scheme customers on Canvey Island were converted from town gas to natural gas supplied from the LNG plant on Canvey.[8][13]


The growth in availability of natural gas is shown in the graph below.[9] Until 1968 this was from supplies of LNG from Algeria, until North Sea gas was available from 1968.

Natural gas available, millions of therms

The exploitation of the North Sea gas reserves, entailing landing gas at Easington, Bacton and St Fergus made viable the building of a national distribution grid, of over 3,000 miles (4,800 km), consisting of two parallel and interconnected pipelines running the length of the country, this became the National Transmission System. All gas equipment in Great Britain (but not Northern Ireland) was converted (by the fitting of different-sized burner jets to give the correct gas/air mixture) from burning town gas to burn natural gas (mainly methane) over the period from 1967 to 1977 at a cost of about £100 million including the writing off of redundant town gas manufacturing plants. All the gas-using equipment of almost thirteen million domestic, four hundred thousand commercial, and sixty thousand industrial customers were converted. Many dangerous appliances were discovered in this exercise and were taken out of service. The UK town gas industry died in 1987 when operations ceased at the last town gas manufacturing plants in Northern Ireland (Belfast, Portadown and Carrickfergus; Carrickfergus gas works is now a restored gasworks museum).[14] The Portadown site has been cleared and is now the subject of a long-term experiment into the use of bacteria for the purpose of cleaning up contaminated industrial land. As well as requiring little processing before use, natural gas is non-toxic; the carbon monoxide (CO) in town gas made it extremely poisonous, accidental poisoning and suicide by gas being commonplace. Poisoning from natural gas appliances is only due to incomplete combustion, which creates CO, and flue leaks to living accommodation. As with town gas, a small amount of foul-smelling substance (mercaptan) is added to the gas to indicate to the user that there is a leak or an unlit burner, the gas having no odour of its own.

The organisation of the British gas industry adapted to these changes, first, by the Gas Act 1965 by empowering the Gas Council to acquire and supply gas to the twelve area boards. Then, the Gas Act 1972 formed the British Gas Corporation as a single commercial entity, embracing all the twelve area gas boards, allowing them to acquire, distribute and market gas and gas appliances to industrial commercial and domestic customers throughout the UK. In 1986, British Gas was privatised and dismembered and the Government no longer has any direct control over it.

During the era of North Sea gas, many of the original cast iron gas pipes installed in towns and cities for town gas were replaced by plastic.

As reported in the DTI Energy Review 'Our Energy Challenge' January 2006 North Sea gas resources have been depleted at a faster rate than had been anticipated and gas supplies for the UK are being sought from remote sources, a strategy made possible by developments in the technologies of pipelaying that enable the transmission of gas over land and under sea across and between continents. Natural gas is now a world commodity. Such sources of supply are exposed to all the risks of any import. There are still substantial coal reserves in the UK and this fact prompts the thought that at some time in the future, coal gas may once again be used as a reliable indigenous source of energy.

In popular culture [ edit ]

Monty Python parodied the conversion from coal to North Sea gas, and the jumping through hoops some encountered, in their "New Cooker Sketch," as part of the episode that began its second series in 1970.

It was used to power several historic balloon ascents in the 19th Century. See The Aeronauts (film).

Gas production in Germany [ edit ]

In many ways, Germany took the lead in coal gas research and carbon chemistry. With the labours of August Wilhelm von Hofmann, the whole German chemical industry emerged. Using the coal gas waste as feedstock, researchers developed new processes and synthesized natural organic compounds such as Vitamin C and aspirin.


Development of Pacific coast oil gas process [ edit ]

The Pacific coast process has significant problems with lampblack. 20 to 30 lb/1000 ft3 (300 to 500 g/m3) of oily soot can be created during combustion. Major pollution problems led to the passage of early state-level environmental legislation.

Layout of a typical gas plant [ edit ]

  • 1880s Coal gasification plant.
  • 1910 CWG plant
Coke oven at smokeless fuel plant, South Wales

Issues in gas processing [ edit ]

WWI-interwar era developments [ edit ]

  • Loss of high-quality gas oil (used as motor fuel) and feed coke (diverted for steelmaking) leads to massive tar problems. CWG (carburetted water gas) tar is less valuable than coal gasification tar as a feed stock. Tar-water emulsions are uneconomical to process due to unsellable water and lower quality by products.
CWG tar is full of lighter polycyclic aromatic hydrocarbons, good for making pitch, but poor in chemical precursors.
  • Various "back-run" procedures for CWG generation lower fuel consumption and help deal with issues from the use of bituminous coal in CWG sets.
  • Electric lighting replaces gaslight. MG industry peak is sometime in the mid-1920s.
Ruins of the German synthetic petrol plant (Hydrierwerke Pölitz – Aktiengeselschaft) in Police, Poland

Post WWII: the decline of manufactured gas [ edit ]

  • Development of natural gas industry. Natural gas has an energy content of 37 MJ/m3, compared to the 10-20 MJ/m3 of town gas.
  • Decline in creosote use for wood preserving.
  • Cast iron & steel are replaced with aluminum and plastics.
  • Phthalic anhydride production shifts from catalytic oxidation of naphthalene to the o-xylol process.

Post WWII positive developments [ edit ]

  • Mobil M-gas process for making gasoline from methanol
  • SASOL coal process plant in South Africa.
  • Direct hydrogenation of coal into liquid and gaseous fuels
  • Dankuni Coal Complex is the only Plant India that is producing Coal Gas / Town Gas in Kolkata using the Continuous Vertical Retort Technology of Babcock-Woodall Duckham (UK), constructed on the recommendation of GoI's Fuel Policy Committee of 1974 after the crippling 1973 Oil Crisis. The Plant uses a modified Low Temperature Carbonisation to produce the Town Gas and Soft Coke. The Plant in 1990s produced various chemical like xylenol, cresol and phenol.[15][16]

Terminology in the UK [ edit ]

In British usage, coal gas specifically means gas made by the destructive distillation of coal. It was more commonly known as town gas. Coal gas is not applied to other coal-derived gases, such as water gas, producer gas and syngas. United States usage may be different.


Manufacture [ edit ]


Composition [ edit ]



By-products [ edit ]

The by-products of coal gas manufacture included coke, coal tar, sulfur and ammonia and these were all useful products. Dyes, medicines such as sulfa drugs, saccharine, and dozens of organic compounds are made from coal tar.[citation needed]

Coke [ edit ]


Coal tar [ edit ]


Sulfur [ edit ]

Used in the manufacture of sulfuric acid

Ammonia [ edit ]

Used in the manufacture of fertilisers

Structure of the industry [ edit ]

Coal gas was initially manufactured by independent companies but in the United Kingdom many of these later became municipal services. In 1948 there was a total of 1,062 gas undertakings. Both the private companies, about two-thirds of the total, and the municipal gas undertakings, about one-third, were nationalised under the Gas Act 1948. Further re-structuring took place under the Gas Act 1972. For further details see British Gas plc.

Apart from in the steel industry's coke oven's by products plants, coal gas is no longer made in the UK. It was replaced first by gas made from oil and later by natural gas from the North Sea.

See also [ edit ]

References [ edit ]

Notes [ edit ]

  1. ^ National Gas Museum: Gas industry timeline
  2. ^ West Sole Gas Fields
  3. ^ Beychok, M.R., Process and environmentals technology for producing SNG and liquid fuels, U.S, EPA report EPA-660/2-2-75-011, May 1975
  4. ^ Beychok, M.R., Coal gasification and the phenolsolvan process, American Chemical Society 168th National Meeting, Atlantic City, September 1974
  5. ^ "The Introduction of Water Gas in the United States"(Google Books excerpt). The Baltimore Gas and Electric News. Consolidated Gas, Electric Light, and Power Company of Baltimore. 5 (6): 383. 1916.
  6. ^ Proceedings of the American Gas Light Association ... By American Gas Light Association, 1881 p.117
  7. ^ Power: devoted to the generation and transmission of power, Volume 26 1906 p.686
  8. ^ a b Williams, Trevor I (1981). A History of the British Gas Industry. Oxford: Oxford University Press. pp. 182–89, 290. ISBN 0198581572.
  9. ^ a b c British Gas (1980). Gas Chronology: the development of the British gas industry. London: British Gas. pp. Appendix 1.
  10. ^ Scott Wilson, D. (1969). The Modern Gas Industry. London: Edward Arnold. pp. 11–34.
  11. ^ Copp, A. D. L., R. G. Hildrew and L. S. Cooper (May 1966). "The Design, Commissioning and Operation of the United Kingdom Gas Industry's Methane Pipeline". Institution of Gas Engineers. Communication 708: 1–18.
  12. ^ Murray, Stephen (2017). "A history of the oil, gas and petrochemical industries on Canvey Island". Essex Archaeology and History. 8: 214–127.
  13. ^ Falkus, Malcolm (1988). Always under Pressure - A History of North Thames Gas since 1949. London: Macmillan. pp. 89–122. ISBN 0333468198.
  14. ^ "Flame Gasworks".
  15. ^ History of Coal India Limited, 1979-80,,
  16. ^ LTC Coke and By-Products,

Sources [ edit ]

  • Everard, Stirling (1949). The History of the Gas Light and Coke Company 1812–1949. London: Ernest Benn Limited. (Reprinted 1992, London: A&C Black (Publishers) Limited for the London Gas Museum. ISBN 0-7136-3664-5.)

Further reading [ edit ]

  • Barty-King, H. (1985). New Flame: How Gas changed the commercial, domestic and industrial life in Britain from 1783 to 1984. Tavistock: Graphmitre. ISBN 0-948051-00-0.
  • Peebles, Malcolm W. H. (1980). Evolution of the Gas Industry. London and Basingstoke: Macmillan. ISBN 0-333-27971-9.
  • Fressoz, J. B. (2007). "The gas lighting controversy, technological risk, expertise and regulation in Paris and London, 1815-1850". Journal of Urban History. 33 (5): 729–755. doi:10.1177/0096144207301418.
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