Producer gas is a fuel gas manufactured by blowing air and steam simultaneously through a coke or coal fire. It mainly consists of carbon monoxide (CO), hydrogen (H2), as well as substantial amounts of nitrogen (N2). The caloric value of the producer gas is low (mainly because of its high nitrogen content), and the technology is obsolete. Improvements over producer gas, also obsolete, include water gas, where the solid fuel is treated intermittently with air and steam, and, far more efficiently, synthesis gas, where the solid fuel is replaced with methane. In the US, producer gas may also be referred to by other names based on the fuel used for production, such as wood gas. Producer gas may also be referred to as suction gas, referring to the way the air was drawn into the gas generator by an internal combustion engine.
Etymology The names for this combustible gas across different European languages reflect either the mechanical apparatus used for its creation or the specific chemical process of its generation.
English: Producer gas The term Producer gas is derived from the industrial equipment used to manufacture it: the "gas producer". In the 19th century, a "producer" referred to a furnace—typically a shaft furnace—designed to "produce" a combustible gas through the incomplete combustion of solid fuel (such as coal or coke). Unlike "coal gas," which was distilled in a retort, this gas was the direct result of a continuous industrial production cycle within the unit.
German: Generatorgas In German-speaking regions, the gas is known as Generatorgas, referencing the generator. This term describes the shaft furnace where air is passed through a deep bed of incandescent fuel. The etymology emphasizes that the gas is "generated" by the chemical reduction of carbon dioxide into carbon monoxide within the unit.
Other European Names The nomenclature across Europe often varies based on the specific patent or chemical additive involved:
French (Gaz de gazogène / Gaz pauvre): In French, the term gaz de gazogène refers to the gazogène (gas producer) apparatus. It is also historically known as gaz pauvre ("poor gas" or "lean gas") because of its low calorific value compared to lighting gas (town gas), due to the high concentration of atmospheric nitrogen. Russian (Генераторный газ): Similar to the German naming convention, the Russian generatornyy gaz literally translates to "generator gas," focusing on the device used for the gasification process. Mond gas: A common European variant of producer gas, named after the chemist Ludwig Mond. This version utilized a steam-air blast to recover ammonia as a byproduct, leading to its identification as a distinct chemical "brand" in late 19th-century industrial centers. Halbwassergas (Semi-water gas): A technical term used in German and English contexts to describe a hybrid gas produced by a "generator" using both air and steam. This name combines the etymologies of air-based "producer gas" and steam-based "water gas".
Production Producer gas is generally made from coke, or other carbonaceous material such as anthracite coal. Air is passed over the red-hot carbonaceous fuel and carbon monoxide is produced. The reaction is exothermic. Formation of producer gas from air and carbon:
C + O2 → CO2, +97,600 calories/mol CO2 + C → 2CO, –38,800 calories/mol (mol of the reaction formula) 2C + O2 → 2CO, +58,800 calories/mol (per mol of O2 i.e. per mol of the reaction formula) Reactions between steam and carbon:
H2O + C → H2 + CO, –28,800 calories/mol (presumably mol of the reaction formula) 2H2O + C → 2H2 + CO2, –18,800 calories/mol (presumably mol of the reaction formula) Reaction between steam and carbon monoxide:
H2O + CO → CO2 + H2, +10,000 calories/mol (presumably mol of the reaction formula) CO2 + H2 → CO + H2O, –10,000 calories/mol (presumably mol of the reaction formula) The average composition of ordinary producer gas according to Latta was: CO2: 5.8%; O2: 1.3%; CO: 19.8%; H2: 15.1%; CH4: 1.3%; N2: 56.7%; B.T.U. gross per cu.ft 136 The concentration of carbon monoxide in the "ideal" producer gas was considered to be 34.7% carbon monoxide (carbonic oxide) and 65.3% nitrogen. After "scrubbing", to remove tar, the gas may be used to power gas turbines (which are well-suited to fuels of low calorific value), spark ignited engines (where 100% petrol fuel replacement is possible) or diesel internal combustion engines (where 15% to 40% of the original diesel fuel requirement is still used to ignite the gas ). During World War II in Britain, plants were built in the form of trailers for towing behind commercial vehicles, especially buses, to supply gas as a replacement for petrol (gasoline) fuel. A range of about 80 miles for every charge of anthracite was achieved. In old movies and stories, when there is a description of suicide by "turning on the gas" and leaving an oven door open without lighting the flame, the reference was to coal gas or town gas. As this gas contained a significant amount of carbon monoxide, it was quite toxic. Most town gas was also odorized, if it did not have its own odor. Modern 'natural gas' used in homes is far less toxic, and has a mercaptan added to it for odor for identifying leaks.
Alternative names Various names are used for producer gas, air gas and water gas generally depending on the fuel source, process or end use including:
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