A gasworks or gas house is fundamentally a scalable (by output quantity) flammable gas producer/generator whose size depends on the scale of the gas distribution system it supports.
Coal-based town gas production was generally displaced by petroleum-based gas and natural gas. However, Great Britain continued her use of coal-based town gas until the North Sea natural gas discoveries in the 1960s and 1970s. Many of these have been made redundant in the developed world by the use of natural gas, though they are still used for storage space.
Type Infrastructure typePrimary feedstockGas typeScale & logicNormal to massive central gasworksBituminous coalTown gasCentralized "production & distribution" Utility using a "topographic reticulation (mesh network)" of pipes for street lighting, metropolitan heating, and heavy industry.Centralized sub-plantCoke + AirProducer gas (Internal)Centralized Utility: Located inside the main gasworks to heat the coal retorts.Coke + steam + oilCWGCentralized utility: integrated into "larger works" to handle "peak shaving" of town gas demand.Niche oil-gas worksNaphtha / shale oilPintsch gasSpecialized distribution of portable "bottled" gas for rail carriages and maritime buoys. Onsite industrial to mini remote gasworksCoke + steam + airSemi-water gas (Halbwassergas)Factories able to generate their own low cost "power gas" without being connected to a city gas main.Micro remote gasworksAnthracite / coke / charcoalProducer gas (external)Standalone units for isolated tasks
Remote uses +Gasworks reliant aspirated engine typeTechnical labelFuel delivery logicStandardConstant volume (Otto cycle)Constant "pushed" gas delivery from a pressurized mainSuctionDemand-variable (suction cycle)Gas is "pulled" from an adjacent micro gasworks TypePrimary feedstockScale & logicPrimary remote usesDowson Gas PlantAnthracite / cokeMini-utility: small plant with a boiler and a pressurized gasholder supporting a remote (Otto cycle) engine.Private estate "mini-grids", remote isolated hotelsRemote gasworksStandalone: engine (suction cycle) "on-demand" fuelRailway signaling, water pumping, rock pulverization (ore), small business and farm mechanizationWaste By-product producerSawdust, rice husks, coconut shellsFeedstock scavenger standalone: waste-to-energy conversionSawmills, plantations
Gasworks for industrial districts and remote locations Gasworks, specifically for Mond gas, made low-quality gas (which was sold at low cost) on a massive scale for industrial districts. They used cheap coal slack and recovered ammonia as a byproduct, then piped the low-quality gas to nearby factories. It was a "centralized" version of a "remote" technology. +Location of gasworks Engine typeConnectionRemoteSuction Connected directly to an adjacent micro gasworksCentralizedStandardConnected to a large iron "town gas" mainIndustrial (centralized)MondOtto cycle gas engine featuring a non-standard, larger-bore cylinder, connected to a Mond gas industrial district main.
Early gasworks
Gasified coal was introduced to Great Britain in the 1790s as an illuminating gas by the Scottish inventor William Murdoch.
Early gasworks were usually located beside a river or canal so that coal could be brought in by barge. Transport was later shifted to railways and many gasworks had internal railway systems with their own locomotives.
Early gasworks were built for factories in the Industrial Revolution from about 1805 as a light source and for industrial processes requiring gas, and for lighting in country houses from about 1845. Country house gas works are extant at Culzean Castle in Scotland and Owlpen in Gloucestershire.
Wood-gas process
1878 European towns lighted by a gaswork using forest timber for gas production:
Oil-gas process
Early 20th century towns lighted by a gaswork using the petroleum industry's undesirable heavy oil for gas production:
Bunker C / No. 6 Fuel Oil (firing steam boilers in power plants and large vehicles)Gasworks heavy oil (feedstock) TypeResidual Fuel Oil (RFO), the heavy non-volatile residue left after fractional distillationResidual Fuel Oil (RFO), often called gas oil or crude oil (if a whole, heavy crude was used)MarketA direct-burn fuel to make steam. Feedstock for cracking into a gaseous fuel (town gas)PriceGenerally the cheapest commercial petroleum product by volume, as it was the byproduct remaining after all other valuable cuts were distilled.Price was determined by its cracking efficiency—a slightly cleaner heavy oil, yielding more town gas, would justify a higher price than lower yielding pure RFO/waste oil. The "blast" (heating) phase: oil and air were injected into the generators and ignited. The "run" (gas-making) phase: the air was shut off, and steam was injected alongside a "gas-making" spray of oil. Scrubbing and washing Purification +Oil-Gas Process: Pre-1915 vs. Post-1915 "Improved" process by E.C. and L.B. Jones Pre-1915Post-1915High-candlepower light (illumination)High-BTU heat (heating & power)Waste product. Large quantities of wet, oily soot that was difficult to manage. A major disposal expense and environmental pollutant.A revenue stream; sold as "Magic Black Briquets" for home heating.
Equipment A gasworks was divided into several sections for the production, purification and storage of gas.
Retort house
This contained the retorts in which coal was heated to generate the gas. The crude gas was siphoned off and passed on to the condenser. The waste product left in the retort was coke. In many cases the coke was then burned to heat the retorts or sold as smokeless fuel.
Condenser This consisted of a bank of air-cooled gas pipes over a water-filled sump. Its purpose was to remove tar from the gas by condensing it out as the gas was cooled. Occasionally the condenser pipes were contained in a water tank similar to a boiler but operated in the same manner as the air-cooled variant. The tar produced was then held in a tar well/tank which was also used to store liquor.
Exhauster An impeller or pump was used to increase the gas pressure before scrubbing. Exhausters were optional components and could be placed anywhere along the purifying process but were most often placed after the condensers and immediately before the gas entered the gas holders.
Scrubber A sealed tank containing water through which the gas was bubbled. This removed ammonia and ammonium compounds. The water often contained dissolved lime to aid the removal of ammonia. The water left behind was known as ammonical liquor. Other versions of the purifier consisted of a tower packed with coke, through which water was trickled.
Purifier Also known as an iron sponge, this removed hydrogen sulfide from the gas by passing it over wooden trays containing moist ferric oxide. The gas then passed on to the gasholder and the iron sulfide was sold to extract the sulfur. Waste from this process often gave rise to blue billy, a ferrocyanide contaminant in the land which causes problems when trying to redevelop an old gasworks site.
Gasholder
The gas holder or gasometer was a tank used for storage of the gas and to maintain even pressure in distribution pipes. The gas holder usually consisted of an upturned steel bell contained within a large frame that guided it as it rose and fell depending on the amount of gas it contained.
Types of gases produced
The following gases were produced in gas plants, among other things: Wood gas, made from wood. Lignite gas, instead of using hard coal (bituminous/coke), brown coal (lignite) was used. Coal gas - retort gas - luminous gas - city gas, coal gas shines bright as an open flame. Oil gas (Pintsch gas, Blau gas), produced by super-heating oil in the absence of air. This gas was bottled to be transportable.Oelgas. In: Luegers Lexikon der gesamten Technik. 2. Auflage. Band 6. Deutsche Verlags-Anstalt, Leipzig / Stuttgart 1908, S. 765–766 Water gas - blue water gas - BWG, a primitive Syngas, produced from hot coke and hot water vapor (300∘C /572∘F steam), that burns blue—unsuitable for lighting until enrichment to CWG. Coal gasification, similar to Syngas, but using air (which contains oxygen and nitrogen) instead of pure steam or oxygen. The practice of gasworks using their red-hot coke byproduct to make Producer Gas, began in the first half of the 19th century. The historical lighting of towns relied heavily on town gas, which was primarily coal gas for much of the 19th century. Water gas (upgraded to CWG) was introduced later.
Benzole plant Benzole: A mixture of aromatic hydrocarbons including benzene, toluene, and xylenes (BTX).
Often only used at large gasworks sites, including those in continental Europe, a benzole plant consisted of a series of vertical tanks containing petroleum oil through which the gas was bubbled. The purpose of a benzole plant was to extract benzole from the gas. The benzole dissolved into the petroleum oil was run through a steam separating plant to be sold separately as a motor fuel and chemical feedstock.
Byproducts and derived hydrocarbons
The by-products of gas-making, such as coke, coal tar, ammonia and sulfur had many uses.
The thermal decomposition of coal and oil at gasworks produced a variety of valuable and often toxic chemical substances in addition to the manufactured Town Gas. The efficient recovery and subsequent sale of these materials—which often became feedstocks for the nascent chemical and dye industries—was crucial to the economic success of the gasworks.
Coal Tar, a complex mixture of organic compounds, was subjected to fractional distillation to extract numerous products, including: Naphthalene: a solid aromatic hydrocarbon that was filtered out from the gas stream. Creosote: a tar-derived oil used primarily as a wood preservative. Phenols and cresols: hydrocarbon derivatives used as disinfectants and raw materials for early plastics. Pitch: The final residue from tar distillation, widely used for roads and roofing.
Non-hydrocarbon and waste products Coke: The solid carbon residue left after heating the coal, sold as a smokeless fuel or used to create water gas. Ammonia: removed by scrubbing the gas with water, resulting in "ammoniacal liquor". It was processed and sold as ammonium sulfate fertilizer.Die Schweizerische Gasindustrie 1850-2020 Sulfur/spent oxide: hydrogen sulfide was removed using moist iron oxide or lime. The resulting iron sulfide ("Spent oxide") was later sold for the manufacture of sulfuric acid. "Blue Billy": A toxic, visible waste created when hydrogen cyanide in the crude gas reacted with iron in the purification material, forming ferrocyanide compounds (Prussian blue).
British gasworks today Coal gas is no longer made in the UK but many gasworks sites are still used for storage and metering of natural gas and some of the old gasometers are still in use. Fakenham gasworks dating from 1846 is the only complete, non-operational gasworks remaining in England. Other examples exist at Biggar in Scotland and Carrickfergus in Northern Ireland.
Gasworks in popular culture Gasworks were noted for their foul smell and generally located in the poorest metropolitan areas. Cultural remnants of gasworks include many streets named Gas Street or Gas Avenue and groups or gangs known as Gas House Gang, such as the 1934 St. Louis Cardinals baseball team. The 1946 film Gas House Kids features children from New York's Gas House District taking on a gang, and spawned two sequels. Ewan McColl's 1968 song "Dirty Old Town" (about his home town of Salford) famously begins "Found my love by the gaswork croft" (in cover versions often "I met my love by the gasworks wall")
Fans of Bristol Rovers F.C. in south west England are known as 'Gas-Heads' due to the proximity of gasometers near to their original ground at Eastville in Bristol. Bristol Rovers F.C. is also known as 'The Gas'.
Railway gasworks