What it is

Natural gas is a fossil fuel like oil and coal. It is a mixture of hydrocarbons, mostly methane, and other gaseous substances such as carbon dioxide, nitrogen, hydrogen sulphide and, in some cases, helium, radon and krypton. The mixtures that are mainly composed of methane are called dry mixtures, whereas those mainly containing hydrocarbons such as propane, and butane are called wet mixtures.
Before being distributed for use, natural gas is treated to eliminate carbon dioxide and nitrogen, which make it less flammable, and hydrogen sulphide, a corrosive and toxic gas. The result is mainly methane. Methane is the simplest gaseous hydrocarbon and is characterised by the smallest molecule, including one carbon atom and four hydrogen atoms (CH4). It is lighter than the air (at a 15°C temperature and 1013.25 millibar pressure its specific weight is 0.678 kg/m3), it is colourless and odourless and not toxic.
It was very common in the primordial atmosphere of the Earth and probably contributed to the synthesis of the first amino acids and the creation of life on our planet. Mixed with the air, methane becomes flammable only if its concentration ranges between 5 and 15%. Below 5% the quantity of natural gas is insufficient to start the combustion, whereas above 15% the oxygen is insufficient. At temperature of 15°C and atmospheric pressure 1 cubic metre of methane produces over 8 thousand calories. In those conditions one cubic metre of methane has an energy content equivalent to 1.2 kg of coal and 0.83 kg of oil.
Methane becomes liquid at a critical temperature of –83°C and a pressure of 45 bars. The transformation into the liquid state can take place by decreasing temperature or increasing pressure. For example, at –161°C methane becomes liquid at room pressure.
The critical temperature of wet natural gases such as propane and butane, including 3 and 4 carbon atoms respectively, is higher than room temperature, therefore they become liquid simply by increasing pressure.

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    The melting of the ice cells, not only brings about the release of methane gas, but it also produces another…

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    In order to improve supply security, and therefore the diversification of sources to produce electric energy...

  • Cracking operations

    At the end of the fractional distillation, long hydrocarbon molecules can be transformed into lighter molecules by means of more…

    Where does energy come from?

    Every day the Earth receives enough solar energy to satisfy the global energy need...

  • Electricity and electrons

    In all electric plants, excluding photovoltaic solar plants, mechanic energy is transformed into electric energy through the same basic procedure...

    Peat and peat-bogs

    The age of coal starts towards the mid 1600s, stimulated by the need for finding an alternative energy source to…

  • 14 June 2011

    Some curiosities about methane hydrates

    The melting of the ice cells, not only brings about the release of methane gas, but it also produces another…

  • 2 March 2011

    Orimulsion

    In order to improve supply security, and therefore the diversification of sources to produce electric energy...

  • Cracking operations

    At the end of the fractional distillation, long hydrocarbon molecules can be transformed into lighter molecules by means of more…