Diesel fuel, also called diesel oil, heavy oil (historically) 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 without a spark as a result of compression of the inlet air and then injection of fuel. 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 (BTL) or gas to liquid (GTL) diesel are increasingly being developed and adopted. To distinguish these types, petroleum-derived diesel is sometimes called petrodiesel in some academic circles.
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 (ULSD) 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 . 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 . Diesel is often used in . 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[The Macquarie Dictionary 3rd ed, The Macquarie Library 1997] (not to be confused with "distillate" in an older sense referring to a different motor fuel), and in
Indonesia (as well in
Israel), 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 (French:
gazole) 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.
[: "Alle Brennmaterialien in allen Aggregatzuständen sind für Durchführung des Verfahrens brauchbar."] The first diesel engine prototype and the first functional Diesel engine were only designed for liquid fuels.
[Rudolf Diesel: Die Entstehung des Dieselmotors, Springer, Berlin/Heidelberg 1913, p. 125]
At first, Diesel tested crude oil from Pechelbronn, but soon replaced it with petrol and kerosene, because crude oil proved to be too viscous,[Rudolf Diesel: Die Entstehung des Dieselmotors, Springer, Berlin/Heidelberg 1913, p. 107] with the main testing fuel for the Diesel engine being kerosene (Mineral oil).[Rudolf Diesel: Die Entstehung des Dieselmotors, Springer, Berlin/Heidelberg 1913, p. 108] 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,[Rudolf Diesel: Die Entstehung des Dieselmotors, Springer, Berlin/Heidelberg 1913, p. 110] paraffin oil, crude oil, gasoline and fuel oil, which eventually worked as well.[Rudolf Diesel: Die Entstehung des Dieselmotors, Springer, Berlin/Heidelberg 1913, p. 111] In Scotland and France, shale oil was used as fuel for the first 1898 production Diesel engines because other fuels were too expensive.[Rudolf Diesel: Die Entstehung des Dieselmotors, Springer, Berlin/Heidelberg 1913, p. 114] In 1900, the French Otto society built a Diesel engine for the use with crude oil, which was exhibited at the 1900 Paris Exposition[Rudolf Diesel: Die Entstehung des Dieselmotors, Springer, Berlin/Heidelberg 1913, p. 115] and the 1911 World's Fair in Paris.
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.[Rudolf Diesel: Die Entstehung des Dieselmotors, Springer, Berlin/Heidelberg 1913, p. 116] 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.[Rudolf Diesel: Die Entstehung des Dieselmotors, Springer, Berlin/Heidelberg 1913, p. 126] Only in December 1899, did Diesel test a coal-dust prototype, which used external mixture formation and liquid fuel pilot injection.[Rudolf Diesel: Die Entstehung des Dieselmotors, Springer, Berlin/Heidelberg 1913, p. 127] This engine proved to be functional, but suffered from piston ring failure after a few minutes due to coal dust deposition.[Friedrich Sass: Geschichte des deutschen Verbrennungsmotorenbaues von 1860 bis 1918, Springer, Berlin/Heidelberg 1962, p. 499]
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.
[Hans Christian Graf von Seherr-Thoß (auth.): Die Technik des MAN Nutzfahrzeugbaus. In: MAN Nutzfahrzeuge AG (ed.): Leistung und Weg: Zur Geschichte des MAN Nutzfahrzeugbaus. Springer, Berlin/Heidelberg 1991. . p. 436] 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.
[Hans Christian Graf von Seherr-Thoß (auth.): Die Technik des MAN Nutzfahrzeugbaus. In: MAN Nutzfahrzeuge AG (ed.): Leistung und Weg: Zur Geschichte des MAN Nutzfahrzeugbaus. Springer, Berlin/Heidelberg 1991. . p. 437] 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 (often called
Bunker C) can be used in diesel-powered and steam-powered vessels.
[Günter Mau: Handbuch Dieselmotoren im Kraftwerks- und Schiffsbetrieb, Springer-Vieweg, Braunschweig/Wiesbaden 1984, . p. 13]
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 per
molecule.
[ITRC (Interstate Technology & Regulatory Council). 2014. Petroleum Vapor Intrusion: Fundamentals of Screening, Investigation, and Management. PVI-1. Washington, D.C.: Interstate Technology & Regulatory Council, Petroleum Vapor Intrusion Team. [1] ] 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 visbreaker 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.[Werner Dabelstein, Arno Reglitzky, Andrea Schütze and Klaus Reders "Automotive Fuels" in Ullmann's Encyclopedia of Industrial Chemistry 2007, Wiley-VCH, Weinheim. ]
Synthetic diesel
Synthetic diesel can be produced from many carbonaceous precursors but natural gas is most important. Raw materials are converted to
syngas 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
Biodiesel is obtained from
vegetable oil or animal fats (bio
) which are mainly fatty acid methyl esters (FAME), and transesterified with
methanol. It can be produced from many types of oils, the most common being
rapeseed oil (rapeseed methyl ester, RME) in Europe and
soybean oil (soy methyl ester, SME) 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 (B100) 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.
[Bosch Automotive Handbook, 6th edition, pp. 327–328]
FAME used as fuel is specified in DIN EN 14214
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
gasoline (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 (EVA) 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" (salicylaldimines) 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 (European Union)
-
ASTM D975 (United States)
-
GOST R 52368 (Russia; equivalent to EN 590)
-
NATO F 54 (NATO; equivalent to EN 590)
-
DIN 51601 (West Germany; obsolete)
Biodiesel fuel
-
EN 14214 (European Union)
-
ASTM D6751 (United States)
-
CAN/CGSB-3.524 (Canada)
Measurements and pricing
Cetane number
The principal measure of diesel fuel quality is its
cetane number. A cetane number is a measure of the delay of ignition of a diesel fuel.
A higher cetane number indicates that the fuel ignites more readily when sprayed into hot compressed air.
European (EN 590 standard) road diesel has a minimum cetane number of 51. Fuels with higher cetane numbers, normally "premium" diesel fuels with additional cleaning agents and some synthetic content, are available in some markets.
Fuel value and price
About 86.1% of diesel fuel mass is carbon, and when burned, it offers a net heating value of 43.1 MJ/kg as opposed to 43.2 MJ/kg for gasoline. Due to the higher density, diesel fuel offers a higher volumetric energy density: the density of EN 590 diesel fuel is defined as at , about 9.0-13.9% more than EN 228 gasoline (petrol)'s at 15 °C, which should be put into consideration when comparing volumetric fuel prices. The emissions from diesel are 73.25 g/MJ, just slightly lower than for gasoline at 73.38 g/MJ.
Diesel fuel is generally simpler to refine from petroleum than gasoline. Additional refining is required to remove sulfur, which contributes to a sometimes higher cost. In many parts of the United States and throughout the United Kingdom and Australia,[[2]] This fuel is slightly more expensive to produce than regular ULSD. In Germany, the fuel tax on diesel fuel is about 28% lower than the petrol fuel tax.
Taxation
Diesel fuel is similar to
heating oil, which is used in
central heating. In Europe, the United States, and Canada,
on diesel fuel are higher than on heating oil due to the
fuel tax, and in those areas, heating oil is marked with
fuel dyes and trace chemicals to prevent and detect
tax fraud. "Untaxed" diesel (sometimes called "off-road diesel" or "red diesel" due to its red dye) is available in some countries for use primarily in agricultural applications, such as fuel for tractors, recreational and utility vehicles or other
non-commercial vehicles that do not use
. This fuel may have sulfur levels that exceed the limits for road use in some countries (e.g. US).
This untaxed diesel is dyed red for identification,[ Cited as 26 CFR 48.4082-1. This regulation implements .] and using this untaxed diesel fuel for a typically taxed purpose (such as driving use), the user can be fined (e.g. US$10,000 in the US). In the United Kingdom, Belgium and the Netherlands, it is known as red diesel (or gas oil), and is also used in agricultural vehicles, home heating tanks, refrigeration units on vans/trucks which contain perishable items such as food and medicine and for marine craft. Diesel fuel, or marked gas oil is dyed green in the Republic of Ireland and Norway. The term "diesel-engined road vehicle" (DERV) is used in the UK as a synonym for unmarked road diesel fuel. In India, taxes on diesel fuel are lower than on petrol, as the majority of the transportation for grain and other essential commodities across the country runs on diesel.
Taxes on biodiesel in the US vary between states. Some states (Texas, for example) have no tax on biodiesel and a reduced tax on biodiesel blends equivalent to the amount of biodiesel in the blend, so that B20 fuel is taxed 20% less than pure petrodiesel.
Uses
Diesel fuel is mostly used in high-speed diesel engines, especially motor-vehicle (e.g. car, lorry) diesel engines, but not all diesel engines run on diesel fuel. For example, large two-stroke watercraft engines typically use heavy fuel oils instead of diesel fuel,
and certain types of diesel engines, such as MAN
M-System engines, are designed to run on petrol with knock resistances of up to 86 RON.
[Hans Christian Graf von Seherr-Thoß (auth.): Die Technik des MAN Nutzfahrzeugbaus. In: MAN Nutzfahrzeuge AG (ed.): Leistung und Weg: Zur Geschichte des MAN Nutzfahrzeugbaus. Springer, Berlin/Heidelberg 1991. . p. 438] On the other hand,
gas turbine and some other types of internal combustion engines, and external combustion engines, can also be designed to take diesel fuel.
The viscosity requirement of diesel fuel is usually specified at 40 °C.
On-road vehicles
and
, which were often otto-powered in the 1920s through 1950s, are now almost exclusively diesel-powered. Due to its ignition characteristics, diesel fuel is thus widely used in these vehicles. Since diesel fuel is not well-suited for otto engines, passenger cars, which often use otto or otto-derived engines, typically run on petrol instead of diesel fuel. However, especially in Europe and India, many passenger cars have, due to better engine efficiency,
diesel engines, and thus run on regular diesel fuel.
Railroad
Diesel displaced coal and fuel oil for steam-powered vehicles in the latter half of the 20th century, and is now used almost exclusively for the combustion engines of self-powered rail vehicles (locomotives and railcars).
Aircraft
In general, diesel engines are not well-suited for planes and helicopters. This is because of the diesel engine's comparatively low power-to-mass ratio, meaning that diesel engines are typically rather heavy, which is a disadvantage in aircraft. Therefore, there is little need for using diesel fuel in aircraft, and diesel fuel is not commercially used as aviation fuel. Instead, petrol (
Avgas), and
jet fuel (e. g. Jet A-1) are used. However, especially in the 1920s and 1930s, numerous series-production aircraft diesel engines that ran on fuel oils were made, because they had several advantages: their fuel consumption was low, they were reliable, not prone to catching fire, and required minimal maintenance. The introduction of petrol direct injection in the 1930s outweighed these advantages, and aircraft diesel engines quickly fell out of use.
[Konrad Reif: Dieselmotor-Management – Systeme, Komponenten, Steuerung und Regelung, 5th edition, Springer, Wiesbaden 2012, , p. 103] With improvements in power-to-mass ratios of diesel engines, several on-road diesel engines have been converted to and certified for aircraft use since the early 21st century. These engines typically run on Jet A-1 aircraft fuel (but can also run on diesel fuel). Jet A-1 has ignition characteristics similar to diesel fuel, and is thus suited for certain (but not all) diesel engines.
[Cord-Christian Rossow, Klaus Wolf, Peter Horst: Handbuch der Luftfahrzeugtechnik, Carl Hanser Verlag, 2014, , p. 519]
Military vehicles
Until World War II, several military vehicles, especially those that required high engine performance (armored fighting vehicles, for example the M26 Pershing or
Panther tank tanks), used conventional otto engines and ran on petrol. Ever since World War II, several military vehicles with diesel engines have been made, capable of running on diesel fuel. This is because diesel engines are more fuel efficient, and diesel fuel is less prone to catching fire.
Some of these diesel-powered vehicles (such as the Leopard 1 or MAN 630) still ran on petrol, and some military vehicles were still made with otto engines (e. g. Ural-375 or Unimog 404), incapable of running on diesel fuel.
Tractors and heavy equipment
Today's
and
heavy equipment are mostly diesel-powered. Among tractors, only the smaller classes may also offer gasoline-fuelled engines. The
dieselization of tractors and heavy equipment began in Germany before World War II but was unusual in the United States until after that war. During the 1950s and 1960s, it progressed in the US as well. Diesel fuel is commonly used in oil and gas extracting equipment, although some locales use electric or natural gas powered equipment.
Tractors and heavy equipment were often multifuel in the 1920s through 1940s, running either spark-ignition and low-compression engines, akroyd engines, or diesel engines. Thus many farm tractors of the era could burn gasoline, ethanol fuel, kerosene, and any light grade of fuel oil such as heating oil, or tractor vaporising oil, according to whichever was most affordable in a region at any given time. On US farms during this era, the name "distillate" often referred to any of the aforementioned light fuel oils. Spark ignition engines did not start as well on distillate, so typically a small auxiliary gasoline tank was used for cold starting, and the fuel valves were adjusted several minutes later, after warm-up, to transition to distillate. Engine accessories such as vaporizers and radiator shrouds were also used, both with the aim of capturing heat, because when such an engine was run on distillate, it ran better when both it and the air it inhaled were warmer rather than at ambient temperature. Dieselization with dedicated diesel engines (high-compression with mechanical fuel injection and compression ignition) replaced such systems and made more efficient use of the diesel fuel being burned.
Other uses
Poor quality diesel fuel has been used as an extraction agent for liquid–liquid extraction of
palladium from
nitric acid mixtures.
Such use has been proposed as a means of separating the
fission product palladium from
PUREX raffinate which comes from used
nuclear fuel.
In this system of solvent extraction, the
of the diesel act as the
diluent while the di
alkyl act as the extractant.
This extraction operates by a
solvation mechanism.
So far, neither a
pilot plant nor full scale plant has been constructed to recover palladium,
rhodium or
ruthenium from
created by the use of
nuclear fuel.
[Torgov, V.G.; Tatarchuk, V.V.; Druzhinina, I.A.; Korda, T.M. et al., Atomic Energy, 1994, 76(6), 442–448. (Translated from Atomnaya Energiya; 76: No. 6, 478–485 (June 1994))]
Diesel fuel is often used as the main ingredient in oil-base mud drilling fluid.
During development of rocket engines in Germany during World War II J-2 Diesel fuel was used as the fuel component in several engines including the BMW 109-718.
Chemical analysis
Chemical composition
In the United States, petroleum-derived diesel is composed of about 75% saturated hydrocarbons (primarily
Alkane including
n,
iso, and
Cycloalkane), and 25% aromatic hydrocarbons (including
and
alkylbenzenes).
[Agency for Toxic Substances and Disease Registry (ATSDR). 1995. Toxicological profile for fuel oils. Atlanta, GA: U.S. Department of Health and Human Services, Public Health Service] The average chemical formula for common diesel fuel is C
12H
23, ranging approximately from C
10H
20 to C
15H
28.
Chemical properties
Most diesel fuels freeze at common winter temperatures, while the temperatures greatly vary.
Petrodiesel typically freezes around temperatures of , whereas biodiesel freezes between temperatures of .
The viscosity of diesel noticeably increases as the temperature decreases, changing it into a gel at temperatures of , that cannot flow in fuel systems. Conventional diesel fuels vaporise at temperatures between 149 °C and 371 °C.
Conventional diesel vary between 52 and 96 °C, which makes it safer than petrol and unsuitable for spark-ignition engines.
Carbon dioxide formation
As a good approximation the chemical formula of diesel is . Diesel is a mixture of different molecules. As carbon has a molar mass of 12 g/mol and hydrogen has a molar mass of about 1 g/mol, so the fraction by weight of carbon in EN 590 diesel fuel is roughly 12/14.
The reaction of diesel combustion is given by:
2 + 3n 2n + 2n
Carbon dioxide has a molar mass of 44g/mol as it consists of 2 atoms of oxygen (16 g/mol) and 1 atom of carbon (12 g/mol). So 12 g of carbon yield 44 g of Carbon dioxide.
Diesel has a density of 838 g per liter.
Putting everything together the mass of carbon dioxide that is produced by burning 1 liter of diesel fuel can be calculated as:
The figure obtained with this estimation is close to the values found in the literature.
For gasoline, with a density of 0.75 kg/L and a ratio of carbon to hydrogen atoms of about 6 to 14, the estimated value of carbon emission if 1 liter of gasoline is burnt gives:
Hazards
Environment hazards of sulfur
In the past, diesel fuel contained higher quantities of
sulfur. European emission standards and preferential taxation have forced
oil refinery to dramatically reduce the level of sulfur in diesel fuels. In the European Union, the sulfur content has dramatically reduced during the last 20 years. Automotive diesel fuel is covered in the European Union by standard EN 590. In the 1990s specifications allowed a content of 2000 ppm max of sulfur, reduced to a limit of 350 ppm by the beginning of the 21st century with the introduction of Euro 3 specifications. The limit was lowered with the introduction of Euro 4 by 2006 to 50 ppm (
ULSD, Ultra Low Sulfur Diesel). The standard for diesel fuel in force in Europe as of 2009 is the Euro 5, with a maximum content of 10 ppm.
|
| N/a | 1 January 1994 | max. 2000 ppm | min. 49 |
| Euro 2 | 1 January 1996 | max. 500 ppm | min. 49 |
| Euro 3 | 1 January 2001 | max. 350 ppm | min. 51 |
| Euro 4 | 1 January 2006 | max. 50 ppm | min. 51 |
| Euro 5 | 1 January 2009 | max. 10 ppm | min. 51 |
|
In the United States, more stringent emission standards have been adopted with the transition to ULSD starting in 2006, and becoming mandatory on June 1, 2010 (see also diesel exhaust).
Algae, microbes, and water contamination
There has been much discussion and misunderstanding of
algae in diesel fuel. Algae need light to live and grow. As there is no sunlight in a closed fuel tank, no algae can survive, but some
microbes can survive and feed on the diesel fuel.
These microbes form a colony that lives at the interface of fuel and water. They grow quite fast in warmer temperatures. They can even grow in cold weather when fuel tank heaters are installed. Parts of the colony can break off and clog the fuel lines and fuel filters.
Water in fuel can damage a fuel injection pump. Some diesel also trap water. Water contamination in diesel fuel can lead to freezing while in the fuel tank. The freezing water that saturates the fuel will sometimes clog the fuel injector pump.
Road hazard
Diesel is less flammable than
Gasoline. However, because it evaporates slowly, any spills on a roadway can pose a slip hazard to vehicles.
After the light fractions have evaporated, a greasy slick is left on the road which reduces
tire grip and traction, and can cause vehicles to skid. The loss of traction is similar to that encountered on
black ice, resulting in especially dangerous situations for two-wheeled vehicles, such as
and
, in
.
See also
External links
