Petrol (gasoline) and diesel are two types of solutions used as fuel. Both are derived from crude oil and are classified as refined products. The basis of these two fuels is the hydrocarbons in oil; However, there are differences. The fractional distillation method is used to obtain both gasoline and diesel. Each, of course, separates at different stages due to differences in boiling temperature.
Diesel (French: Gasoil) or petroleum gas or diesel fuel (French: Diésel) is not used as fuel for diesel engines and thermal installations. Its hydrocarbon range is between C14-C20 and even C25 with a boiling point range of 385-250 degrees Celsius. Petroleum gas mainly consists of three groups of paraffinic, naphthenic and aromatic, has a minimum flash point of 54 ° C and a maximum pour point of 0 ° C. Its density at 15.6 ° C is equal to 820-860 kg / m3. The most important feature is the number of cylinders, which must be more than 50 for the engine to run smoothly and quietly.
Diesel
Diesel or gas oil is one of the relatively heavy products of crude oil and is obtained after kerosene in the distillation tower. Diesel is one of the cuts that is produced in both atmospheric distillation tower and vacuum distillation tower. Also, many refinery units, such as cracking, hydrocracking and coking units, produce diesel in addition to gasoline by changing the structure of heavy oil cuts.
Diesel is a colorless liquid, and in order to identify it and distinguish it from other liquids and products, they change its color to a brownish color. Diesel is a mixture of different hydrocarbons that have between 14 and 20 (even up to 25) carbon atoms in their molecular structure. The most important use of diesel is as fuel for diesel engines, thermal installations and fuel of some factories.
The compression ratio of diesel engines is much higher than gasoline engines. Therefore, more power can be obtained from a diesel engine, and these engines are used for heavy vehicles.
What is diesel fuel?
Diesel fuel is any liquid fuel used in diesel engines. This fuel is mostly obtained by a special distillation method other than diesel oil, but there are other methods for processing diesel fuel without the use of oil, such as Biodiesel, liquefied biomass (BTL) and liquefied petroleum gas (GTL) were mentioned, and their global use is increasing rapidly. To dispel the ambiguity between oil-derived species and other species, the oil species is called diesel or petrodiesel. Very Low Sulfur Diesel is the standard definition of diesel that has very low sulfur. According to 2007 statistics, almost all diesel fuel used in the United States and Europe is of a very low sulfur content.
Kian Group International Company is the largest supplier and exporter of petroleum products in Turkey, which with the cooperation of its representative in Iran, Kian Petroleum Company, is able to supply various oil, mineral and steel products directly from the doors of Iranian factories.
Diesel specifications
Density
Diesel has a relatively higher weight compared to other conventional fuels and its density is approximately between 0.8kg / lit to 0.87kg / lit. The higher the amount of petroleum and aromatic hydrocarbons in diesel, the higher its density.
Distillation
The initial point of distillation of diesel is 180 ° C and the final point of distillation is about 370 ° C. According to ASTM standard, the percentage of diesel distillation at different temperatures is as follows:
- Less than 65% at 250 ° C
- More than 85% at 350 ° C
- More than 95% at 370 ° C
viscosity
Diesel has a relatively high viscosity and viscosity. If the viscosity of the diesel is too high, the diesel flow inside the pipes and pumps and the fuel injection injector will drop. Then the transfer and operation of fuel will be difficult. Also, if the diesel has a low viscosity, the fuel quality will decrease and it will not perform well in the diesel engine. The standard allowable value of diesel viscosity should be between 12 and 40 cm.
The point of falling and the point of becoming cloudy
The cloud point is the first temperature at which solid crystals form when the fluid cools. Also, after the fluid freezes and when it is heated, the first temperature that motion is created in the fluid is called the drop point. Diesel and in general a suitable fuel must be highly resistant to cold and retain its fluidity at low temperatures and not crystallize.
The suitable range for cloud and fall points in diesel is 0 to -10˚ and -15 to -30˚, respectively. The more petroleum and aromatic substances in the diesel, the better the pour point and the cloud point.
The amount of sulfur in diesel
The presence of sulfur and sulfur compounds in diesel causes problems such as corrosion of the diesel engine cover and air pollution. The permissible amount of sulfur in diesel according to international standards is less than 50 ppm, and to reduce sulfur compounds, diesel must be completely refined in the refinery.
Stan number and aniline point
Cetane Number is a measure of the quality of diesel and diesel fuels. The higher the cetane number, the faster the combustion operation inside the cylinder and the higher the quality of the diesel.
Aniline point is the lowest temperature at which equal volumes of aniline fuel and material become single-phase. High aniline point in diesel means high diesel index and better fuel quality.
To determine the aniline point, a specific volume of an oil product such as diesel is poured into a container. In equal amounts, a substance called aniline is added. Next, raise the temperature of the mixture and stir it with a mixer. The temperature at which two materials become a homogeneous solution is considered the aniline point of the fuel.
Petrol
This fuel is a mixture of alkanes and cycloalkanes obtained from the distillation of crude oil. The carbon chain length of each gasoline molecule varies from 5 to 12. Gasoline is commonly used in “internal combustion engines” to increase speed. This fuel is lighter than diesel and produces better pollution.
Gasoline
The composition of this fuel includes alkanes and carbon chains in general. Each carbon chain molecule contains 12 carbon atoms. Diesel is a relatively heavier fuel, less volatile and more viscous than gasoline. This fuel is commonly used in “Compression-Ignition Motors”.
Differences between diesel and gasoline
The two fuels are different in terms of different aspects, which we intend to address in more detail below.
The chemical composition of gasoline is basically made from a combination of hydrocarbons of length 7 (heptane) or 8 (trimethylpentane); Diesel, on the other hand, contains a combination of petroleum hydrocarbons in the range of 8 (octane) to 21 (undecode). The chemical formula of gasoline is C8H18 and the chemical formula of diesel is C12H23.
CO2 emissions Because gasoline has a higher percentage of carbon atoms per molecule, it produces approximately 13% more gasoline, CO2, or carbon dioxide.
The energy content of diesel is higher in terms of energy content than gasoline. The energy content of gasoline is 33.7 megajoules per kilogram and diesel is 36.7 megajoules per kilogram; As a result, diesel fuel is 16% ahead of its competitor in this area.
Gasoline has a lower viscosity than diesel. Of course, as the temperature decreases, the viscosity of diesel increases, but such behavior does not occur in gasoline at limited temperature changes.
Ferrarium Due to the lighter nature of gasoline molecules and the presence of some additives, this fuel is more volatile than diesel; This means that at a constant temperature, more gasoline molecules evaporate than diesel. As a result, gasoline ignites faster.
Welding interval First of all, it should be noted that due to the combined nature of these two fuels, it is not possible to use the term boiling point as a pure substance (eg water); In the sense that the two boil in the same temperature range. This range is 20 to 150 degrees Celsius for gasoline and 37 to 450 degrees Celsius for diesel.
In this respect, gasoline consumption is ahead of its competitor; That is, less gasoline is consumed per 100 kilometers than diesel.
Diesel is more powerful than gasoline. The energy production capacity of this fuel is equal to 38.6 megajoules per liter. Another point is that gasoline engines generally produce higher engine speeds. Diesel engines, of course, need more torque.
Diesel combustion in diesel engines
The working process of a diesel engine is completely different from a gasoline engine. In a diesel engine, unlike a gasoline engine, where combustion occurs simultaneously with the injection of fuel into the cylinder, there is a distance between the fuel injection and the combustion, which is called the combustion delay period. The delay period depends on the type of fuel, engine design and combustion conditions.
In a diesel engine, pure air is sucked in during the first stage. During the second stage, the air is compressed and the temperature is raised until fuel is injected into the cylinder. After reaching combustion conditions, the fuel burns spontaneously due to high pressure and temperature without igniting the spark plug, and expands in the third stage of the cylinder. Finally, in the fourth stage, the combustion gases are released through the exhaust through the chamber.
Given the above, the chemical structure of diesel as a diesel engine fuel and diesel engine conditions should be such as to facilitate spontaneous combustion inside the combustion chamber.
Conclusion
Diesel, as a fuel used in diesel engines, is one of the most important petroleum products. Diesel is used not only as a fuel for vehicles but also as a fuel for some heating equipment, power plants, furnaces and factories.
Quality diesel must have a high cetane number and meet the latest Euro emission standards. In the presence of pollutants in diesel, the resulting smoke is spread in the environment and endangers human health and the environment.
Diesel distribution stations have their own equipment, which is sometimes different from the gas station. Also, the location of diesel stations should be chosen on the outskirts of the city and areas where heavy vehicles can travel easily.
Since diesel is a product with a relatively high density and viscosity, special arrangements must be made during the transfer, distribution and operation stages so that the fuel used is of the required quality and its transfer and distribution processes are well performed.