Fuel gas is one of a number of

fuel A fuel is any material that can be made to react with other substances so that it releases energy as thermal energy or to be used for work (physics), work. The concept was originally applied solely to those materials capable of releasing chem ...

s that under ordinary conditions are

gas Gas is a state of matter that has neither a fixed volume nor a fixed shape and is a compressible fluid. A ''pure gas'' is made up of individual atoms (e.g. a noble gas like neon) or molecules of either a single type of atom ( elements such as ...

eous. Most fuel gases are composed of

hydrocarbon In organic chemistry, a hydrocarbon is an organic compound consisting entirely of hydrogen and carbon. Hydrocarbons are examples of group 14 hydrides. Hydrocarbons are generally colourless and Hydrophobe, hydrophobic; their odor is usually fain ...

s (such as

methane Methane ( , ) is a chemical compound with the chemical formula (one carbon atom bonded to four hydrogen atoms). It is a group-14 hydride, the simplest alkane, and the main constituent of natural gas. The abundance of methane on Earth makes ...

and

propane Propane () is a three-carbon chain alkane with the molecular formula . It is a gas at standard temperature and pressure, but becomes liquid when compressed for transportation and storage. A by-product of natural gas processing and petroleum ref ...

hydrogen Hydrogen is a chemical element; it has chemical symbol, symbol H and atomic number 1. It is the lightest and abundance of the chemical elements, most abundant chemical element in the universe, constituting about 75% of all baryon, normal matter ...

carbon monoxide Carbon monoxide (chemical formula CO) is a poisonous, flammable gas that is colorless, odorless, tasteless, and slightly less dense than air. Carbon monoxide consists of one carbon atom and one oxygen atom connected by a triple bond. It is the si ...

, or mixtures thereof. Such gases are sources of

energy Energy () is the physical quantity, quantitative physical property, property that is transferred to a physical body, body or to a physical system, recognizable in the performance of Work (thermodynamics), work and in the form of heat and l ...

that can be readily transmitted and distributed through pipes. Fuel gas is contrasted with

liquid fuel Liquid fuels are combustible or energy-generating molecules that can be harnessed to create mechanical energy, usually producing kinetic energy; they also must take the shape of their container. It is the fumes of liquid fuels that are flammable ...

s and

solid fuel Solid fuel refers to various forms of solid material that can be burnt to release energy, providing heat and light through the process of combustion. Solid fuels can be contrasted with liquid fuels and gaseous fuels. Common examples of solid fu ...

s, although some fuel gases are liquefied for storage or transport (for example,

autogas Autogas is liquefied petroleum gas (LPG) used as a fuel in internal combustion engines of vehicles as well as in stationary applications such as generators. It is a mixture of propane and butane. Autogas is widely used as a "green" fuel, ...

and

liquified petroleum gas Liquefied petroleum gas, also referred to as liquid petroleum gas (LPG or LP gas), is a fuel gas which contains a flammable mixture of hydrocarbon gases, specifically propane, ''n''-butane and isobutane. It can also contain some propyl ...

). While their gaseous nature has advantages, avoiding the difficulty of transporting solid fuel and the dangers of spillage inherent in liquid fuels, it also has limitations. It is possible for a fuel gas to be undetected and cause a

gas explosion A gas explosion is the Combustion, ignition of a mixture of air and flammable gas, typically from a gas leak. In household accidents, the principal explosive gases are those used for heating or cooking purposes such as natural gas, methane, propan ...

. For this reason,

odorizer An odorizer is a device that adds an odorant to a gas. The most common type is one that adds a mercaptan liquid into natural gas distribution systems so that leaks can be readily detected. Other types have been used for carbon dioxide fire ex ...

s are added to most fuel gases. The most common type of fuel gas in current use is

natural gas Natural gas (also fossil gas, methane gas, and gas) is a naturally occurring compound of gaseous hydrocarbons, primarily methane (95%), small amounts of higher alkanes, and traces of carbon dioxide and nitrogen, hydrogen sulfide and helium ...

Types of fuel gas

There are two broad classes of fuel gases, based not on their chemical composition, but their source and the way they are produced: those found naturally, and those manufactured from other materials.

Manufactured fuel gas

Manufactured fuel gases are those produced by chemical transformations of solids, liquids, or other gases. When obtained from solids, the conversion is referred to as

gasification Gasification is a process that converts biomass- or fossil fuel-based carbonaceous materials into gases, including as the largest fractions: nitrogen (N2), carbon monoxide (CO), hydrogen (H2), and carbon dioxide (). This is achieved by reacting ...

and the facility is known as a

gasworks A gasworks or gas house is an industrial plant for the production of flammable gas. 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. Early gasworks Coal ...

. Manufactured fuel gases include: *

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 ...

, obtained from pyrolysis of coal *

Water gas Water gas is a kind of fuel gas, a mixture of carbon monoxide and hydrogen. It is produced by "alternately hot blowing a fuel layer okewith air and gasifying it with steam". The caloric yield of the fuel produced by this method is about 10% o ...

, largely obsolete, obtained by passing steam over hot coke *

Producer gas 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 pro ...

, largely obsolete, obtained by passing steam and air over hot coke *

Syngas Syngas, or synthesis gas, is a mixture of hydrogen and carbon monoxide in various ratios. The gas often contains some carbon dioxide and methane. It is principally used for producing ammonia or methanol. Syngas is combustible and can be used as ...

, major current technology, obtained mainly from

Wood gas Wood gas is a fuel gas that can be used for furnaces, stoves, and vehicles. During the production process, biomass or related carbon-containing materials are gasified within the oxygen-limited environment of a wood gas generator to produce a c ...

, obtained mainly from

wood Wood is a structural tissue/material found as xylem in the stems and roots of trees and other woody plants. It is an organic materiala natural composite of cellulosic fibers that are strong in tension and embedded in a matrix of lignin t ...

, once was popular and of relevance to

biofuel Biofuel is a fuel that is produced over a short time span from Biomass (energy), biomass, rather than by the very slow natural processes involved in the formation of fossil fuels such as oil. Biofuel can be produced from plants or from agricu ...

s *

Biogas Biogas is a gaseous renewable energy source produced from raw materials such as agricultural waste, manure, municipal waste, plant material, sewage, green waste, Wastewater treatment, wastewater, and food waste. Biogas is produced by anaerobic ...

, obtained from landfills *

Blast furnace gas Blast furnace gas (BFG) is a by-product of blast furnaces that is generated when the iron ore is redox, reduced with coke (fuel), coke to metallic iron. It has a very low heating value, about 3.5 MJ/m3 (93 BTU/cu.ft), because it consis ...

Hydrogen Hydrogen is a chemical element; it has chemical symbol, symbol H and atomic number 1. It is the lightest and abundance of the chemical elements, most abundant chemical element in the universe, constituting about 75% of all baryon, normal matter ...

from

Electrolysis In chemistry and manufacturing, electrolysis is a technique that uses Direct current, direct electric current (DC) to drive an otherwise non-spontaneous chemical reaction. Electrolysis is commercially important as a stage in the separation of c ...

Steam reforming Steam reforming or steam methane reforming (SMR) is a method for producing syngas (hydrogen and carbon monoxide) by reaction of hydrocarbons with water. Commonly, natural gas is the feedstock. The main purpose of this technology is often hydrogen ...

The coal gas made by the pyrolysis of coal contains impurities such a tar,

ammonia Ammonia is an inorganic chemical compound of nitrogen and hydrogen with the chemical formula, formula . A Binary compounds of hydrogen, stable binary hydride and the simplest pnictogen hydride, ammonia is a colourless gas with a distinctive pu ...

and

hydrogen sulfide Hydrogen sulfide is a chemical compound with the formula . It is a colorless chalcogen-hydride gas, and is toxic, corrosive, and flammable. Trace amounts in ambient atmosphere have a characteristic foul odor of rotten eggs. Swedish chemist ...

. These must be removed and a substantial amount of plant may be required to do this.

Well or mine extracted fuel gases

In the 20th century,

, composed primarily of

, became the dominant source of fuel gas, as instead of having to be manufactured in various processes, it could be extracted from deposits in the earth. Natural gas may be combined with hydrogen to form a mixture known as HCNG. Additional fuel gases obtained from natural gas or

petroleum Petroleum, also known as crude oil or simply oil, is a naturally occurring, yellowish-black liquid chemical mixture found in geological formations, consisting mainly of hydrocarbons. The term ''petroleum'' refers both to naturally occurring un ...

: *

Propane Propane () is a three-carbon chain alkane with the molecular formula . It is a gas at standard temperature and pressure, but becomes liquid when compressed for transportation and storage. A by-product of natural gas processing and petroleum ref ...

Butane Butane () is an alkane with the formula C4H10. Butane exists as two isomers, ''n''-butane with connectivity and iso-butane with the formula . Both isomers are highly flammable, colorless, easily liquefied gases that quickly vaporize at ro ...

* Regasified

liquefied petroleum gas Liquefied petroleum gas, also referred to as liquid petroleum gas (LPG or LP gas), is a fuel gas which contains a flammable mixture of hydrocarbon gases, specifically propane, Butane, ''n''-butane and isobutane. It can also contain some ...

The composition of natural gas varies widely, but the table shows a typical composition. Natural gas is produced with water and gas condensate. These liquids have to be removed before the gas can be used as fuel. Even after treatment the gas will be saturated and liable to condense as liquid in the pipework. This can be reduced by superheating the fuel gas.

Specification

In addition to chemical composition fuel gas may need to comply with parameters such as

calorific value The heating value (or energy value or calorific value) of a substance, usually a fuel or food (see food energy), is the amount of heat released during the combustion of a specified amount of it. The ''calorific value'' is the total energy release ...

, Wobbe index, dewpoint, etc. The following specification is for the British National Transmission System. Incomplete Combustion Factor (ICF) – an empirical index that relates the composition of a gas to its tendency to burn incompletely in a gas appliance. Dutton defined the ICF as: ICF = 0.64 × (W − 50.73 + 0.03 × PN) where W is the Wobbe index, MJ/m³; PN is the volumetric percentage of C₃H₈ plus N₂ in a three-component mixture. Soot Index (SI) – an empirical index that relates the composition of a gas to its tendency to produce soot during combustion in a gas appliance. The calorific value of manufactured gas is around 500 Btu per cubic foot (18,629 kJ/m³). Whereas, the calorific value of natural gas is twice that at around 1000 Btu per cubic foot (37,259 kJ/m³). For a given amount of heat only half the volume of natural gas is required.

Uses of fuel gas

One of the earliest uses was

gas lighting Gas lighting is the production of artificial light from combustion of a fuel gas such as methane, propane, butane, acetylene, ethylene, hydrogen, carbon monoxide, coal gas (town gas) or natural gas. The light is produced either directly by ...

, which enabled the widespread adoption of

streetlamp A street light, light pole, lamp pole, lamppost, streetlamp, light standard, or lamp standard is a raised source of light on the edge of a road or path. Similar lights may be found on a railway platform. When urban electric power distribution b ...

s and the illumination of buildings in towns. Fuel gas was also used in

gas burner A gas burner is a device that produces a non-controlled flame by mixing a fuel gas such as acetylene, natural gas, or propane with an oxidizer such as the ambient air or supplied oxygen, and allowing for wikt:ignition, ignition and combustion. ...

s, in particular the

Bunsen burner A Bunsen burner, named after Robert Bunsen, is a kind of ambient air gas burner used as laboratory equipment; it produces a single open gas flame, and is used for heating, sterilization, and combustion. The gas can be natural gas (which is main ...

used in laboratories. It may also be used gas heaters, camping stoves, and even to power vehicles, as they have a high calorific value. Fuel gas is widely used by industrial, commercial and domestic users. Industry uses fuel gas for heating furnaces, kilns, boilers and ovens and for space heating and drying . The electricity industry uses fuel gas to power gas turbines to generate electricity. The specification of fuel gas for gas turbines may be quite stringent. Fuel gas may also be used as a feedstock for chemical processes. Fuel gas in the commercial sector is used for heating, cooking, baking and drying, and in the domestic sector for heating and cooking. Currently, fuel gases, especially syngas, are used heavily for the production of ammonia for fertilizers and for the preparation of many detergents and specialty chemicals. On an industrial plant fuel gas may be used to purge pipework and vessels to prevent the ingress of air. Any fuel gas surplus to needs may be disposed of by burning in the plant

gas flare A gas flare, alternatively known as a flare stack, flare boom, ground flare, or flare pit, is a gas combustion device used in places such as petroleum refineries, chemical plants and natural gas processing plants, oil or gas extraction sites ha ...

system. For users that burn gas directly fuel gas is supplied at a pressure of about 15 psi (1 barg). Gas turbines need a supply pressure of 250-350 psi (17-24 barg).

References

{{DEFAULTSORT:Fuel Gas Industrial gases Synthetic fuel technologies Combustion