Jet fuel

The title of this article is ambiguous. For rocket propellants designated as kerosene, see RP-1.

Kerosene (ancient Greek κηρός kerós, German 'wax', a light petroleum; in Switzerland called aviation petroleum) is aviation fuel of various specifications used primarily as fuel for the gas turbine engines of jet and turboprop aircraft and helicopters (jet fuel). With the development of special diesel engines suitable for aviation, such as the Thielert Centurion 1.7, it has also been possible since the beginning of the 21st century to run small aircraft equipped in this way on kerosene.

Kerosene is a narrow fractionation cut from the light middle distillate of petroleum refining, with additive packages to achieve the respective specification. The boiling curve of kerosene is quite flat compared to other fuels. The designation according to ADR is KEROSINE, it falls under packing group III.

History

The name kerosene goes back to the physician and geologist Abraham Gesner (1797-1864), who in 1846 in Nova Scotia (Canada) extracted an easily flammable liquid from coal, which corresponds to the German petroleum. A resulting waxy intermediate product, which played an important role in the process, is the reason that he called the liquid kerosene (pronounced: kerrosene or also kerosene), derived from Greek κηρός (keros), Engl. wax. The intermediate product was similar to paraffin, which is why in British English the liquid follow-up product is still called paraffin (oil) today. After improved methods of extracting kerosene from coal were discovered in the early 1850s, and Ignacy Łukasiewicz and Jan Zeh also discovered their distillation from petroleum (patent of December 2, 1853), and the first North American petroleum was found in Ohio in 1858, Gesner's method was no longer profitable, and his company with its rights and licenses was taken over by Standard Oil. However, the brand or the name Kerosene became established almost worldwide.

Linguistic delimitation

Gesner registered both the invention of the product for a US patent and the word kerosene as a trademark. To circumvent the protected trademark rights, other names were also introduced by other manufacturers using different processes, often alluding to the terms wax (kerosene), stone (-charcoal) and oil: Steinöl (German) or Petroleum (Greek-Latin), Cherosene (Italian) or Queroseno (Spanish). This variety of names and additional terms based on gasolene (referring to the distillation of petroleum) lead to the fact that similar-sounding names in different languages designate completely different petroleum raffinates and can lead to dangerous misunderstandings.

In German, kerosene always refers to the jet fuel described in this article, except in the jargon of the German petroleum industry, where it is used as a Germanization for kerosene. This causes irritation with the False Friends in other languages, which almost always refer to what is petroleum in German: kerosene in American English, Spanish queroseno, Dutch kerosine, or cherosene in Italian. Exceptions include kerozin (Croatian) or occasionally kérosène (French), where it can also denote jet fuel. In British English, and thus in many Commonwealth countries, the term kerosene is well known but rather uncommon, and usually also means petroleum.

The jet fuel described herein is referred to in most (European) languages by a word containing the element "jet": e.g. Jet Fuel, Jet-Un or Jet-A.

Manufacture

Kerosene is produced in oil refineries mainly by distillation from crude oil. The crude oil is first desalinated and heated to about 400 °C in tube furnaces. It is then fed to an atmospheric distillation column. A temperature profile is established in this column. The liquid and gas exchange and the temperature profile result in a material separation or an enrichment of components in certain zones of the column. Kerosene, which consists mainly of molecules with about 9 to 13 carbon atoms per hydrocarbon molecule (boiling temperature 150 and 250 °C), and diesel are recovered in the middle distillate fraction. At the bottom of the column are heavy oils and the residue. Depending on the crude oil used, the residue can account for 40-60 % of the crude oil used and is therefore reprocessed in a variety of further processes using conversion plants. In this process, the higher-molecular compounds are broken down by various cracking processes. This again produces streams of the fractions gases, naphtha, middle distillates, heavy oils, wax and finally coke. All refineries still have vacuum distillation at pressures between 10 and 30 mbar in common. This allows material flows to be fractionated that have boiling temperatures above 400 °C at ambient pressure, and in some cases up to 600 °C. The material flows from the various processes are distilled in a vacuum. The material streams from the various processes still contain aliphatic and aromatic sulfur compounds, which must be selectively removed in a hydrogenation reactor if necessary. The specification of kerosene allows a mass fraction of 3000 ppmw sulfur. A crude cut of kerosene contains a maximum of about 1600 ppmw sulfur, while kerosene on the market contains between 100 and 700 ppmw sulfur. The different material streams are blended together in the refinery to produce a fuel that meets the specification requirements. The maximum allowable sulfur contents remain in the same range with values between 1000 ppmw (JP-7), 3000 ppmw (Jet A-1) and 4000 ppm (JP-4). Jet fuels differ from kerosene fractions in the refinery by the addition of numerous additives, such as antioxidants, metal deactivators, antistatic additives, corrosion inhibitors and others.

The narrow fractionation cut means that there are few light and few heavy hydrocarbon compounds in the fuel, which is why it does not ignite too early and burns almost residue-free. Most molecules ignite at the same temperature. Information about this is provided by a boiling analysis, which in the case of kerosene shows a widely stretched, flat boiling line in the middle boiling range. See graph with boiling curves at the top. This lies between heavy gasoline and diesel fuel.

Work is being done on processes that are not based on petroleum as a raw material. In addition to biokerosene, for example, sun-to-liquid technology is under development. The system separates carbon dioxide and water from the air and converts it into hydrogen and carbon monoxide in a multi-step thermochemical process chain. This syngas can then be used to produce kerosene. Researchers at Empa and the Paul Scherrer Institute (PSI) launched the "SynFuels" initiative in 2021.

Approximately 5.2 million tonnes of jet fuel (heavy) were produced in Germany in 2015.