The Wobbe Index (WI) is the main indicator of the interchangeability of fuel gases such as natural gas LPG and Town Gas and is frequently defined in the specifications of gas supply and transport utilities. It is defined as: Fuel is any material that is capable of releasing energy when its chemical or physical structure is changed or converted. ... Natural gas is a gaseous fossil fuel consisting primarily of methane. ... LPG might be an initialism or abbreviation for: Liquified petroleum gas Laboratoire de Planetologie, Grenoble, France Literary Press Group of Canada Landwirtschaftliche Produktionsgenossenschaft (German, obsolete/historical) Long period grating This page concerning a three-letter acronym or abbreviation is a disambiguation page — a navigational aid which lists other pages that... Town gas is a generic term referring to manufactured gas produced for sale to consumers and municipalities. ...

 Wobbe Index = higher heating value/(square root of gas specific gravity) 

It is used to compare the combustion energy output of different composition fuel gases in an appliance (fire, cooker etc.). If two fuels have identical Wobbe Indices then for a given valve setting the energy output will also be identical. Typically variations of up to 5% are allowed as these would not be noticeable to the consumer. The Wobbe Index is a critical factor to minimise the impact of the changeover when analyzing the use of SNG fuels such as propane-air mixtures. The Higher Heating Value (HHV) of a fuel is defined as the amount of heat released by a specified quantity (initially at 25°C) once it is combusted and the reactants have returned to a temperature of 25°C. The Higher Heating Value takes into account the latent heat of... In mathematics, a square root of a number x is a number whose square (the result of multiplying the number by itself) is x. ... Relative density (also known as specific gravity) is a measure of the density of a material. ... ENG is a broadcasting (usually television) industry acronym which stands for electronic news gathering. ... Propane is a three-carbon alkane, normally a gas, but compressible to a liquid that is transportable in inexpensive containers. ... AIR is a three-letter abbreviation with multiple meanings, as described below: The Annals of Improbable Research, a monthly magazine devoted to scientific humour All India Radio - Indias Government Radio service AIR, a popular electronica band from France. ...

Wobbe Index (kcal per standard cubic meter) of common fuel gases

 Fuel Gas Upper Index Lower Index Hydrogen 11,528 9,715 Methane 12,735 11,452 Ethane 16,298 14,931 Ethylene 15,253 14,344 Natural gas 12,837 11,597 Propane 19,376 17,817 Propylene 18,413 17,180 n-butane 22,066 20,336 Iso-butane 21,980 20,247 Butylene-1 21,142 19,728 LPG 20,755 19,106 Acetylene 14,655 14,141 Carbon monoxide 3,060 3,060 

General Name, Symbol, Number hydrogen, H, 1 Chemical series nonmetals Group, Period, Block 1, 1, s Appearance colorless Atomic mass 1. ... Methane is a significant and plentiful fuel which is the principal component of natural gas. ... Ethane is a chemical compound with chemical formula C2H6. ... Ethylene (or IUPAC name ethene) is the chemical compound with the formula CH2CH2. ... Natural gas is a gaseous fossil fuel consisting primarily of methane. ... Propane is a three-carbon alkane, normally a gas, but compressible to a liquid that is transportable in inexpensive containers. ... Propylene, also known by its IUPAC name propene, is an organic compound having the chemical formula C3H6. ... R-phrases S-phrases , , Flash point −60 °C Autoignition temperature 287 °C Explosive limits 1. ... LPG might be an initialism or abbreviation for: Liquified petroleum gas Laboratoire de Planetologie, Grenoble, France Literary Press Group of Canada Landwirtschaftliche Produktionsgenossenschaft (German, obsolete/historical) Long period grating This page concerning a three-letter acronym or abbreviation is a disambiguation page — a navigational aid which lists other pages that... Acetylene (IUPAC name: ethyne) is the simplest alkyne hydrocarbon, consisting of two hydrogen atoms and two carbon atoms connected by a triple bond. ... Carbon monoxide, with the chemical formula CO, is a colourless, odourless and tasteless gas. ...

Usage

The Wobbe index is commonly expressed in Btu per standard cubic foot or megajoules per standard cubic meter (1000 BTU/scf = 37.3 Mj/Sm3). In the case of natural gas (Mol. Wt. 17), the typical heating value is around 1,050 Btu per cubic foot and the specific gravity is approximately 0.59, giving a typical Wobbe index of 1,367.

There are three ranges or ‘families’ of fuel gasses that have been internationally agreed based on Wobbe Index. Family 1 covers manufactured gases, family 2 covers natural gases (with high and low ranges) and family 3 covers liquefied petroleum gas (LPG). Combustion equipment is typically designed to burn a fuel gas within a a particular family - hydrogen-rich Town Gas, Natural Gas or LPG.

 Family Wobbe Index range (MJ/Sm3) Type of gas 1 22.5 – 30 Town gas / Syn Gas 2 L 39 – 45 Natural H 45.5 – 55 3 73.5 – 87.5 LPG 

Other flame characteristics and composition limits may determine the acceptability of the replacement gas, e.g. flame speed, 'yellow tipping' due to incomplete combustion, sulphur content, oxygen content etc..

External link

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