Diesel fuel
Diesel fuel, also called diesel oil, fuel oil, or simply diesel, is any liquid fuel specifically designed for use in a diesel engine, a type of internal combustion engine in which fuel ignition takes place as a result of compression of the inlet air and then injection of fuel without a spark. Therefore, diesel fuel needs good compression ignition characteristics.
The most common type of diesel fuel is a specific fractional distillate of petroleum fuel oil, but alternatives that are not derived from petroleum, such as biodiesel, biomass to liquid or gas to liquid diesel are increasingly being developed and adopted. To distinguish these types, petroleum-derived diesel is sometimes called petrodiesel in some academic circles. Diesel is a high-volume product of oil refineries.
In many countries, diesel fuel is standardized. For example, in the European Union, the standard for diesel fuel is EN 590. Ultra-low-sulfur diesel is a diesel fuel with substantially lowered sulfur contents. As of 2016, almost all of the petroleum-based diesel fuel available in the United Kingdom, mainland Europe, and North America is of a ULSD type. Before diesel fuel had been standardized, the majority of diesel engines typically ran on cheap fuel oils. These fuel oils are still used in watercraft diesel engines. Despite being specifically designed for diesel engines, diesel fuel can also be used as fuel for several non-diesel engines, for example the Akroyd engine, the Stirling engine, or boilers for steam engines. Diesel is often used in heavy trucks. However, diesel exhaust, especially from older engines, can cause health damage.
Names
Diesel fuel has many colloquial names; most commonly, it is simply referred to as diesel. In the United Kingdom, diesel fuel for road use is commonly called diesel or sometimes white diesel if required to differentiate it from a reduced-tax agricultural-only product containing an identifying coloured dye known as red diesel. The official term for white diesel is DERV, standing for diesel-engine road vehicle. In Australia, diesel fuel is also known as distillate, and in Indonesia and most of the Middle East, it is known as Solar, a trademarked name from the country's national petroleum company Pertamina. The term gas oil is sometimes also used to refer to diesel fuel.History
Origins
Diesel fuel originated from experiments conducted by German scientist and inventor Rudolf Diesel for his compression-ignition engine, which he invented around 1892. Originally, Diesel did not consider using any specific type of fuel. Instead, he claimed that the operating principle of his rational heat motor would work with any kind of fuel in any state of matter. The first diesel engine prototype and the first functional Diesel engine were only designed for liquid fuels.At first, Diesel tested crude oil from Pechelbronn, but soon replaced it with petrol and kerosene, because crude oil proved to be too viscous, with the main testing fuel for the Diesel engine being kerosene. Diesel experimented with types of lamp oil from various sources, as well as types of petrol and ligroin, which all worked well as Diesel engine fuels. Later, Diesel tested coal tar creosote, paraffin oil, crude oil, petrol and fuel oil, which eventually worked as well. In Scotland and France, shale oil was used as fuel for the first 1898 production Diesel engines because other fuels were too expensive. In 1900, the French Otto society built a Diesel engine for use with crude oil, which was exhibited at the 1900 Paris Exposition and the 1911 World's Fair in Paris. The engine actually ran on peanut oil instead of crude oil, and no modifications were necessary for peanut oil operation.
During his first Diesel engine tests, Diesel also used illuminating gas as fuel, and managed to build functional designs, both with and without pilot injection. According to Diesel, neither was a coal-dust–producing industry existent, nor was fine, high-quality coal-dust commercially available in the late 1890s. This is the reason why the Diesel engine was never designed or planned as a coal-dust engine. Only in December 1899, did Diesel test a coal-dust prototype, which used external mixture formation and liquid fuel pilot injection. This engine proved to be functional, but suffered from piston ring failure after a few minutes due to coal dust deposition.
Since the 20th century
Before diesel fuel was standardised, diesel engines typically ran on cheap fuel oils. In the United States, these were distilled from petroleum, whereas in Europe, coal-tar creosote oil was used. Some diesel engines were fuelled with mixtures of fuels, such as petrol, kerosene, rapeseed oil, or lubricating oil, which were cheaper because, at the time, they were not being taxed. The introduction of motor-vehicle diesel engines, such as the Mercedes-Benz OM 138, in the 1930s meant that higher-quality fuels with proper ignition characteristics were needed. At first no improvements were made to motor-vehicle diesel fuel quality. After World War II, the first modern high-quality diesel fuels were standardised. These standards were, for instance, the DIN 51601, VTL 9140–001, and NATO F 54 standards. In 1993, the DIN 51601 was rendered obsolete by the new EN 590 standard, which has been used in the European Union ever since. In sea-going watercraft, where diesel propulsion had gained prevalence by the late 1970s due to increasing fuel costs caused by the 1970s energy crisis, cheap heavy fuel oils are still used instead of conventional motor-vehicle diesel fuel. These heavy fuel oils can be used in diesel-powered and steam-powered vessels.Types
Diesel fuel is produced from various sources, the most common being petroleum. Other sources include biomass, animal fat, biogas, natural gas, and coal liquefaction.Petroleum diesel
Petroleum diesel is the most common type of diesel fuel. It is produced by the fractional distillation of crude oil between at atmospheric pressure, resulting in a mixture of carbon chains that typically contain between 9 and 25 carbon atoms per molecule. This fraction is subjected to hydrodesulfurization.Usually such "straight-run" diesel is insufficient in supply and quality, so other sources of diesel fuels are blended in. One major source of additional diesel fuel is obtained by cracking heavier fractions, using visbreaking and coking. This technology converts less useful fractions but the product contains olefins which require hydrogenation to give the saturated hydrocarbons as desired. Another refinery stream that contributes to diesel fuel is hydrocracking. Finally, kerosene is added to modify its viscosity.
Synthetic diesel
Synthetic diesel can be produced from many carbonaceous precursors but natural gas is most important. Raw materials are converted to synthesis gas which by the Fischer–Tropsch process is converted to a synthetic diesel. Synthetic diesel produced in this way generally is mainly paraffins with low sulfur and aromatics content. This material is blended often into the above mentions petroleum derived diesel.Biodiesel
is obtained from vegetable oil or animal fats which are mainly transesterified with methanol to form fatty acid methyl esters. It can be produced from many types of oils, the most common being rapeseed oil in Europe and soybean oil in the US. Methanol can also be replaced with ethanol for the transesterification process, which results in the production of ethyl esters. The transesterification processes use catalysts, such as sodium or potassium hydroxide, to convert vegetable oil and methanol into biodiesel and the undesirable byproducts glycerine and water, which will need to be removed from the fuel along with methanol traces. Biodiesel can be used pure in engines where the manufacturer approves such use, but it is more often used as a mix with diesel, BXX where XX is the biodiesel content in percent.FAME used as fuel is specified in DIN EN 14214 and ASTM D6751 standards.
Storage and additives
In the US, diesel is recommended to be stored in a yellow container to differentiate it from kerosene, which is typically kept in blue containers, and petrol, which is typically kept in red containers. In the UK, diesel is normally stored in a black container to differentiate it from unleaded or leaded petrol, which are stored in green and red containers, respectively.Ethylene-vinyl acetate is added to diesel as a "cold flow improver". 50–500 ppm of EVA inhibits crystallization of waxes, which can block fuel filters. Antifoaming agents, antioxidants, and metal deactivating agents are other additives. Their use is dictated by the particular composition of and storage plans for diesel fuels. Each is added at the 5–50 ppm level.
Standards
The diesel engine is a multifuel engine and can run on a huge variety of fuels. However, development of high-performance, high-speed diesel engines for cars and lorries in the 1930s meant that a proper fuel specifically designed for such engines was needed: diesel fuel. In order to ensure consistent quality, diesel fuel is standardised; the first standards were introduced after World War II. Typically, a standard defines certain properties of the fuel, such as cetane number, density, flash point, sulphur content, or biodiesel content. Diesel fuel standards include:Diesel fuel
- EN 590
- ASTM D975
- GOST R 52368
- NATO F 54
- DIN 51601
- EN 14214
- ASTM D6751
- CAN/CGSB-3.524
Measurements and pricing