The energy content (calorific value) of a hydrocarbon gas mixture such as fuel gases may widely vary. Purchasers of fuel gas are concerned about the energy content of the fuel and, in addition, industrial consumers need detailed information about gas components which affect their plant processes.
The energy content of a hydrocarbon mixture is directly related to the dielectric constant of the gas mixture. However, this well behaved relationship is altered when a non-hydrocarbon gas is present in the hydrocarbon gas mixture and dilutes the mixture.
The present invention is directed to the provision of a method and an apparatus which determines the energy content of hydrocarbon gas mixtures having one or more diluent gases present. The present invention is directed to a method and an apparatus for inferring the energy content of hydrocarbon gas mixtures such as natural gas. The present method and apparatus indirectly measures energy content based upon the relationship between the specific gravity of the gas and the gas dielectric along with the ability to compensate for one or more diluent gases such as nitrogen and carbon dioxide in natural gas.