Chemical Composition of Natural Gas

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Chemical Composition of Natural Gas
Natural gas is a naturally occurring gas mixture, consisting mainly of methane. While most of the gas supplied to Union Gas is from western Canada, some gas is supplied from other sources, including the United States and Ontario producers. While the gas from these sources has a similar analysis, it is not entirely the same. The table below outlines the typical components of natural gas on the Union Gas system and the typical ranges for these values (allowing for the different sources). Note that there is no guarantee of the following composition at your location or as an overall system average. Since the different gas supplies enter the Union Gas system at different locations, the exact composition at any site will vary among the different regions. The system average heating value will depend on the mix of gas supplies (which is increasingly controlled by our customers), and therefore can vary from the typical value listed below. ComponentTypical Analysis

(mole %)Range
(mole %)
Methane95.287.0 - 96.0
Ethane2.51.5 - 5.1
Propane0.20.1 - 1.5
iso - Butane0.030.01 - 0.3
normal - Butane0.030.01 - 0.3
iso - Pentane0.01trace - 0.14
normal - Pentane0.01trace - 0.04
Hexanes plus0.01trace - 0.06
Nitrogen1.30.7 - 5.6
Carbon Dioxide0.70.1 - 1.0
Oxygen0.020.01 - 0.1
Hydrogentracetrace - 0.02

Specific Gravity0.580.57 - 0.62
Gross Heating Value (MJ/m3), dry basis *37.836.0 - 40.2

* The gross heating value is the total heat obtained by complete combustion at constant pressure of a unit volume of gas in air, including the heat released by condensing the water vapour in the combustion products (gas, air, and combustion products taken at standard temperature and pressure). Sulphur:

In the Union Gas system, the typical sulphur content is 5.5 mg/m3. This includes the 4.9 mg/m3 of sulphur in the odourant (mercaptan) added to gas for safety reasons. Water:
The water vapour content of natural gas...
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