Composition and properties

Natural gas is a hydrocarbon consisting mainly of methane, although it usually also contains a variable percentage of nitrogen, ethane, CO2, H2O, butane, propane, mercaptans and traces of heavier hydrocarbons. Methane is one carbon atom joined to four hydrogen atoms (CH4) and can constitute up to 97% of natural gas.

Physical propertiesChemical properties
Molecular formulaCH4
Mixed molecular weight18,2
Boiling temperature at 1 atmosphere-160,0 °C
Melting temperature-180,0 °C
Density of the vapors (Air = 1) at 15.50,61
Density of the liquid (Water = 1) at 0 ° / 4 ° C0,554
Expansion Ratio1 liter of liquid becomes 600 liters of gas
Solubility in water at 20 ° CSlightly soluble (from 0.1 to 1.0%)

Characteristics

  • Natural gas is consumed in the state in which it is found in nature. From extraction at site to its arrival at homes and points of consumption, natural gas does not undergo any transformation process.
  • The simpler molecular structure of natural gas enables a clean burn, so its combustion does not produce solid particles or sulphur.
  • Natural gas is one of the cleanest fossil fuel energy sources, as it emits less pollutant gas (SO2, CO2, NOx and CH4) per unit of energy produced.

Carbon emissions (g CO₂/usable kWh generated)

*The carbon dioxide emissions associated with electricity consumption according to electricity mix data for 2010 from the IDAEA

Source: Fundación Gas Natural – Technical energy and environmental guides.18. The contribution of natural gas to emissions reduction in Spain. (2009)

Emission factor (g/usable kWh generated)

  • NOx
  • SOx
  • Volatile
  • Particles
  • CO

Source: Fundación Gas Natural – Technical energy and environmental guides.18. The contribution of natural gas to emissions reduction in Spain. (2009)

 

In its natural state, natural gas is odourless, colourless and tasteless, but in order to warn of its presence in case of leaks, an aroma compound (mercaptan) is added, giving it its characteristic smell of rotten eggs.

  • It needs ignition for combustion
  • Its relative density makes it lighter than air, so that leaks or emissions quickly dissipate into the upper layers of the atmosphere, making it less likely to form explosive mixtures in the air.
  • It is efficient and abundant
  • It is non-corrosive