It is called fuels all matter susceptible to violent oxidation reactions that release (exothermic) amounts of heat energy, usually by releasing carbon dioxide (COtwo) and other chemical compounds as waste. For example: wood, kerosene, natural gas. This behavior is known as combustion and responds to the formula:
fuel + oxidising = products + energy
- fuels. They are flammable substances, whose caloric potential is commonly used by man to heat their homes, cook and even generate electricity (as in power plants) or movement (as in internal combustion engines).
- Oxidizing. They are the substances or means capable of promoting this combustion process. They are mostly powerful oxidants.
There are various forms of fuel and different classification criteria. According to their chemical constitution there are:
- Fossil fuels. These are mixtures of hydrocarbons and other compounds of organic origin, which went through a sedimentation process and were subjected to high pressure for millions of years. This type of fuel has a high caloric power. For example: oil and natural gas.
- Biofuels. They are a mixture of organic compounds derived from biomass (organic matter useful as an energy source). They are produced through processes of anaerobic fermentation of organic waste, transesterification of oils and fats and fermentation of sugars. The most advanced are bioethanol (produced from the fermentation of sugar cane, beets and cereals) and biodiesel (produced from vegetable oils).
- mineral fuels. These are metals and compounds obtained from nature and susceptible to combustion under natural conditions or even in specific situations, such as certain metals that produce flame.
- nuclear fuels. These are materials made up of natural or synthetic radioactive elements. The processes to obtain energy using this type of fuel are usually nuclear fission (the division of an atomic nucleus into lighter nuclei and particles such as neutrons, photons, among others) and nuclear fusion (the union of atomic nuclei of similar charges to form a heavier nucleus). Although they are not combustion processes per se, they generate large amounts of usable energy in various processes. The nuclear fuel par excellence for obtaining energy by fission is an isotope of uranium, although energy can also be obtained by fusion using isotopes of hydrogen, such as tritium and deuterium.
- Oil and grease based fuels. These are fats, oils and other substances of living origin whose nature allows ignition under certain conditions and which we often use in the kitchen.
- Density. It is the total mass of the substance according to the volume it occupies and the degree of union between its particles.
- calorific power. It is the heat generation capacity, that is, the amount of heat energy that can be generated with respect to its mass or volume during the combustion reaction.
- ignition temperature. It is the lowest temperature at which a fuel starts to burn at atmospheric pressure (1013 hPa), without the need to add additional heat to perpetuate the flame.
- moisture content. It is the degree of water present in the fuel.
- Viscosity. It is the resistance of a fluid to the displacement of its particles. It is a characteristic mainly of liquid fuels.
Examples of fuels
- Coal. Coal is one of the forms of presentation of carbon in nature, along with graphite and diamonds, agglomerations of atoms of this element but arranged in a very different way, so that some are more resistant than others and have physical properties. and different chemicals. In the case of mineral coal, it is a highly flammable black and sedimentary rock due to its additional content of hydrogen, sulfur and other elements.
- Wood. Composed of cellulose and lignin, substances secreted by the trunk of trees, wood grows year after year in a system of concentric rings. It has been the quintessential fuel for ovens, fireplaces and so on since ancient times, as it burns relatively easily and forms embers (for grilling). This also often causes forest fires capable of consuming large areas of wood and organic matter.
- kerosene. Also known as canfin or kérex, it is a liquid mixture of hydrocarbons, flammable and obtained by distillation of oil, initially used in stoves and lamps and today used as jet fuel (Jet Petrol) and in the manufacture of pesticides and as solvent.
- Gasoline. It is the most refined product of fuel derivatives of petroleum. This mixture of hydrocarbons is obtained by fractional distillation (FCC) and is used to fuel internal combustion engines throughout the world. It has a high energy yield with respect to its mass and is classified according to an index of octane present or octane number. Its combustion, however, releases numerous gases and toxic compounds into the atmosphere.
- alcohols. They are organic substances composed of a hydroxyl group (-OH) covalently bonded to a saturated carbon atom. They are very common substances in nature and are produced as a result of the fermentation of sugars. Their particular chemical properties make them good solvents, fuels and, in the specific case of ethanol, a component of many beverages.
- Natural gas. Natural gas is a fossil fuel product of a light mixture of gaseous hydrocarbons that can be found in underground deposits or accompanying coal or oil deposits in nature. It is widely used to power combustion engines, district heating and power plants.
- Vegetable oil. This organic compound is obtained from the seeds, fruits and stems of the plants in whose tissues it is produced (for example, the sunflower, the olive or the corn). It is made up, like most fatty acids, of triglycerides (three fatty acids and an ester), which is why it is used as food, to make soaps and other products, and even as biofuel in hybrid or adapted vehicles.
- Benzene. This aromatic hydrocarbon with chemical formula C6H6 whose carbon atoms occupy the vertices of a regular hexagon, it is a colorless and highly flammable liquid, carcinogenic and with a sweet aroma. It is perhaps the most produced chemical product in the world, since it is essential to synthesize other hydrocarbons and chemical compounds, as well as being an essential part of numerous vehicle fuels and solvents.
- Magnesium. It is the chemical element with symbol Mg, the seventh in abundance in the earth’s crust and third among those dissolved in sea water. The Mg ion2+ It is an essential ion for all forms of life, although this metal is never found pure in nature. It is highly flammable, especially in the form of chips or powder, producing an intense white light that was often used in the early days of photography. However, once ignited it is difficult to extinguish, given its reactivity with nitrogen and COtwo of the atmosphere.
- Propane. It is a colorless and odorless organic gas with the chemical formula C3H8, whose enormous combustibility and explosiveness make it ideal, along with butane gas (C4H10), to feed ovens, stoves and other domestic equipment since at room temperature it is inert when in contact with many compounds and, therefore, relatively safe. Both are obtained from various stages of oil refining and together they constitute the majority of the flammable gases in common commercial use today (liquefied gas) in cylinders and jugs.