Dependence of mine gas calorific value on methane concentration
|Methane concentration in mine gas (%)||30||40||50||0||70||80||90|
Calorific value (MJ/kg)||10.5||14.3||17.8||21.3||24.7||28.5||32.1|
In most cases, methane concentration in mine gas ranges within 35–40% vol. For use as a fuel, gas shall have the lower calorific value of at least 16.0 MJ/m³ which corresponds to the CH4 content of 46% vol.
A similar situation (impossibility of direct gas use as a fuel due to its extremely low calorific value) exists with regard to associated petroleum gas (APG) showing high nitrogen content (in some cases up to 90% vol.).
Grasys membrane plants allow treating mine gas as well as associated petroleum gas with high nitrogen content for further use as a fuel at gas-fired reciprocating plants and gas turbine power plants, boiler houses.