Gas natural


August 19, 2022

Natural gas is a fossil energy source that, like coal or oil, is made up of a mixture of hydrocarbons, molecules made up of carbon and hydrogen atoms. Its calorific value varies greatly according to its composition, but the highest are between 8,500 and 10,200 kilocalories per cubic meter of natural gas. Natural gas is a primary energy, or one that can be obtained directly without transformation. The other primary energies are solar energy, coal and oil. It is the cleanest fossil energy in terms of waste and atmospheric emissions, and the most efficient fuel for obtaining electricity in thermal power plants, with a total efficiency of 50.7% compared to 25.7 % of fuel oil, 26.1% of uranium (nuclear power plant) and 26.8% of coal. Its direct use, without having to be previously transformed into electricity, has a much higher efficiency of 91.2%. It is also cheaper and easier to store than coal and petroleum derivatives. For all this, it began to be used from the 60s as a preferred fuel except for transport, where oil continues to predominate. In addition, it is also used as a raw material for numerous chemical products. The construction of gas pipelines and the trade of natural gas have led to major armed conflicts between different countries of the world in the 20th and 21st centuries.


It is a mixture of gases lighter than water, non-toxic, colorless and basically odorless (it is smelled as a safety measure, to detect leaks), in which its main component is methane (CH4), a simple molecule made up of one carbon atom and four hydrogen atoms, although it also contains other light hydrocarbons such as ethane (C2H6), propane (C3H8, the main component of the old city gas), butane ( C4H10, main component of gas cylinders for kitchens) or pentane (C5H12) in a much smaller proportion. Its chemical composition varies significantly according to its geographical and geological origin, and tends to be associated with other molecules or elements such as carbon dioxide (CO₂), nitrogen (N2) or rarely helium (He, for example h' there is in the natural gas of the Texas area) that must be extracted when the natural gas is intended for industrial and domestic uses. In some deposits, for example that of Lacq (France), there may be traces of organic compounds of hydrogen sulphide (H2S) and sulphide organic compounds (so-called bittering gases). To extract the energy contained in the C-H chemical bonds, the combustion process must occur. Combustion is an exothermic oxidation reaction of a combustible body (in this case, natural gas) with another oxidizing body (in this case, air) that acts as an oxidizer. This chemical reaction produces a release of heat and energy, and the phenomenon is usually perceptible by the presence of a flame which is also a light source.


Natural gas, like other fossil fuels, has been formed over millions of years by the anaerobic decomposition (without oxygen) of large amounts of the remains of dead organisms deposited on what was then the bottom of the sea or a lake Over time, the organic matter mixed with mud was buried under heavy layers of sediments, which subjected it to high pressure and temperature, without air, for a long time, which gradually altered it chemically. Gases, especially natural gas, were released from this anaerobic decomposition. Today, natural gas is often found in a gaseous state in pockets that lie underground near pockets of oil, which remains in a liquid state. Both fuels are found in rocks of sedimentary origin, where geological phenomena imprison them, one, the other or both, giving rise to large underground pockets. Natural gas can e