| Manufactured gas | Feedstock | Manufacture | Composition | Heat yield at STP (BTU/ft3) | Light yield at STP (std candle/ft3) | Notes |
|---|---|---|---|---|---|---|
| Coal gas | Primarily bituminous or cannel coal. Lignite occasionally used. | Carbonization (pyrolysis) of the coal feedstock (the heating of the coal feedstock in the absence of oxygen.) The gas produced by the hot coal is the gas distributed. | As distributed, contains a moderate proportion of marsh gas (methane, CH4), hydrogen (H2), carbonic oxide (carbon monoxide, CO), and simple hydrocarbon "illuminants", including oliefant gas (ethylene, C2H4) and acetylene gas (C2H2). In addition, prior to treatment, contains coal tars (complex aliphatic and aromatic hydrocarbons), ammoniacal liquor (gaseous ammonia, NH3, and aqueous ammonia, NH4OH), the sulfuret of hydrogen (H2S), and the sulfuret of carbon (CS2). | 500–650 | 10–18 | The oldest type, introduced in 1798 by Murdoch, et al.; when the term "manufactured gas" or "town gas" is used without qualifiers, it generally refers to coal gas. Substantially greater illuminant yield with use of special "cannel coal", which may be modern oil shale, richer in hydrocarbons than most regular gas coal (bituminous coal). |
| Wood gas | Timber resources. | Carbonization (pyrolysis) of the timber feedstock (the heating of the timber feedstock in the absence of oxygen.) The volatiles evolved from the heated wood is the gas distributed. | Resulting products unknown. Probably marsh gas, hydrogen, and carbonic oxide, along with some hydrocarbons and organics, like turpentine. | ? | < 10 | Wood was used as a feedstock during the early days (1820s - 1850s) of manufactured gas in certain areas of the United States, due to lack of development of coal resources. Wood was carbonized in a manner similar to coal; however, the gas evolved was markedly inferior to that of coal in lighting and heating qualities. Still very useful for lighting. This wood gas produced solely through pyrolysis should not be confused with wood gas as used today; the modern wood gas generator produces its synthesis gas through the complete gasification process, as described below. |
| Oil pyrolytic gas. | Petroleum oil. | Carbonization (pyrolysis) of petroleum (the heating of the petroleum feedstock in the absence of oxygen.) The gas produced by the heated & decomposed oil is the gas distributed. | As distributed, contains an extremely high proportion of simple hydrocarbon "illuminants", including oliefant gas (ethylene, C2H4) and acetylene gas (C2H2), as well as propane gas (C3H8), marsh gas (methane, CH4), hydrogen (H2), and a small amount of carbonic oxide (carbon monoxide, CO). | 1000–1500 | 40–60 | Initial experiments in 1817–1825, which were failures; began to be used widely in 1860s. Simpler, much less labor intensive manufacturing process. Oil very expensive feedstock compared to coal; prices (and illuminous efficacy per ft3) double to triple that of regular coal gas. |
| Oil catalytic semi-water gas. (Improved Jones Process) | Petroleum oil. | Staged partial reaction of petroleum oil using steam at high temperature in catalytic environment. The gas produced by the partially reacted and partially cracked oil is the gas distributed. | As distributed, contains 35 – 40% hydrogen (H2), 45% – 50% marsh gas (methane, CH4), and the balance of higher hydrocarbons and carbonic oxide (carbon monoxide, CO). | 500–700 | 10–18 | E.C. Jones, chief gas engineer of the San Francisco Gas Light Company (later the PG&E) developed this ingenious process to turn oil into a gas very similar to that produced by the pyrolysis of coal using a catalytic backflush of already produced gas and steam to provide a hydrogen atmosphere to stimulate disassociation of the oil with the minimal production of lampblack. Singlehandedly revolutionized gasmaking on the Pacific Coast, as oil was plentiful compared to coal, and could be turned into a gas capable of drop-in replacement for coal gas, eliminating the need for coal to be shipped by water transport from Australia and the Far East to Pacific ports at high expense. The Improved Jones Process and evolutions of that process continued to be used on the Pacific Coast until the end of the manufactured gas age. |
| Producer gas | Anthracite coal, coke, bituminous coal dust and waste, lignite, or biomass. | Manufactured by the incomplete combustion of varying carboniferous feedstocks in an extremely hot (>= 1100°C), limited-oxygen atmosphere aided by the injection of a small, stochiometric flow of steam. | Contains a high proportion of nitrogen (N2) and carbonic oxide (carbon monoxide, CO), limited amounts of hydrogen (H2), and a very small quantity of swamp gas (methane, CH4). | 100–170 | nil | Produced in early days of coal gasification; however, only became common after invention of Otto cycle internal combustion engine for which it was an ideal fuel, as well as small-sized, reliable gas producers, which allowed the easy generation of producer gas nearly anywhere a supply of anthracite or coke was available. Gas generally not distributed past the walls of the production site, but used on location, due to low energy content and that it was mostly composed of deadly carbonic oxide. Used for standard domestic gas needs within institutions large enough to justify a hired man for the upkeep of the producer; these institutions often included work-houses, alms-houses, reformatories, orphanages, houses of correction, lunatic asylums, lyceums, industrial schools, and penitentiaries. Bulk heating, electric generation, and engine-running uses; also for welding purposes, as it possesses a "reducing flame" and a high temperature. N.B. One variant of producer gas was Mond gas, known for both its consistent yield and that ammonia could be obtained as a byproduct. Slight modifications of producer necessary. |
| Water gas | Coke or anthracite coal and steam. | Manufactured by the reaction of extremely hot feedstock and steam in a superheated non-oxygen atmosphere. | Contains high proportions of carbonic oxide (carbon monoxide, CO) and hydrogen (H2), and very low proportions of other gasses. | ~ 300 | nil | Manufacture known since late 1830s. However, not optimized for profitable generation until approximately 1865–70. Produced using an intermittent process; first, the exothermic "blow", where the feedstock was heated by blowing air through it, followed by an endothermic "run", where the air was cut off, and steam passed through the now superhot feedstock, leading to the decomposition of the steam and scavenging of carbon from the feedstock. Generally mixed with coal gas, valued for being able to be produced "just in time" with 1 hour's notice, unlike coal gas, which would require 4+ days to bring online from idle. Low labor and capital costs, however, high, inefficient use of anthracite/coke feedstock. |
| Carburetted water gas | Water gas and petroleum or coal tar. | Manufactured by passing just-produced, super-hot water gas through a superheated "carburettor" in to which petroleum or coal tar oil is sprayed, accomplishing the "cracking" of the oil into the gas. | Contains high proportions of carbonic oxide (carbon monoxide, CO) and hydrogen (H2), and moderate proportions of marsh gas (methane, CH4) and mixed hydrocarbon illuminant gasses. | 400–700 | 10–25 | Introduced in 1876. Became a common process during the heady days of gas-lighting from the 1870s to the first decade of the 20th century, especially useful for mixing with coal gas. Process had similar positives and negatives as straight water gas, but also had illuminant value, as well as higher cost, due to oil/tar use. Variable illuminant yield, depending on amount/quality of oil spray. As gas steadily lost ground as an illuminant, extensive carburetting reduced to low values or carburetting omitted entirely, representing a return to water gas. |
| Complete gasification gas | Gas-evolving coal or other organics. | Manufactured by a complex, staged process where as coal travelled down the vertical axis of an upright, semi-cylindrical reaction chamber, it would be subject to different chemical reactions based on what was being fed into that area of the reaction chamber. | Mix of carbonic oxide (carbon monoxide, CO), marsh gas (methane, CH4), hydrogen (H2), a small quantity of simple hydrocarbon illuminants, along with small quantities of nitrogen and carbon dioxide. | 330–400 | > 8 | Earliest processes from 1895, came into industrial-scale use by 1918 (Meade, p. 766–769). Numerous processes developed, many in Germany, Austria, and other Continental nations. Potential of retaining over 75% energy of feedstock in gas with heat recovery from raw gas (Meade, p. 762), as compared to ~55% feedstock energy retention of other gasification processes. |
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