How much do you know about diesel quality standard?Issuing time:2022-03-08 14:56 Diesel oil is extracted from petroleum in the temperature range of 260 ~ 350℃, which is mainly composed of carbon, hydrogen and partial oxygen. There are two kinds of diesel oil, heavy diesel oil and light diesel oil, according to the fractions. Among them, heavy diesel oil is suitable for medium and low speed diesel engines below 1000r/min, while light diesel oil is suitable for high speed engines above 1000r/min. The fundamental difference is that the sulfur content is different, the sulfur content of light diesel oil is not more than 0.2%, and that of vehicle diesel oil is not more than 0.035%. At present, the diesel oil quality standard in the market mainly adopts the national standard GB 19147-2016. 1. Specifications and uses Light diesel oil can be divided into 7 brands such as 10#, 5#, 0#, -10#, -20#, -35# and -50# according to the freezing point. According to the requirements of GB 252 and GB 19147 standards, the selection of diesel oil brands should follow the following principles: (1) No.10 light diesel oil is suitable for diesel engines with preheating equipment; (2) No.5 light diesel oil is suitable for use in areas with a risk rate of 10% and a temperature above 8℃. (3) No.0 light diesel oil is suitable for use in areas with a risk rate of 10% * * * * * where the temperature is above 4℃; (4)-No.10 light diesel oil is suitable for use in areas with a risk rate of 10% and a temperature above -5℃. (5)-No.20 light diesel oil is suitable for use in areas with a risk rate of 10% and a temperature above -14℃. 2. Performance indicators and requirements The main indexes of diesel oil are: combustibility, evaporation, fluidity, stability and corrosiveness, etc. (1) combustibility (ignitability): The combustibility of diesel directly affects the work of diesel engine. Cetane number is an important index to indicate the ignition and combustion performance of diesel oil in engine. The cetane number of diesel oil directly affects the combustion process of fuel in diesel engine. Diesel oil has high cetane number and low self-ignition point, which makes it easy to spontaneously ignite in the cylinder of diesel engine and makes the engine work smoothly. For more information about oil products, please pay attention to WeChat WeChat official account Oil Products Circle. If the cetane number of diesel oil is too low, it will be difficult for the fuel to ignite, which will cause abnormal combustion and reduce the power of the engine. However, the cetane number of diesel oil should not be too high. If it is too high, diesel oil will not burn completely and the oil consumption will increase. Cetane number of diesel oil is related to its chemical composition. The cetane number of n-alkanes is * * * * *, followed by naphthenes, and the cetane number of polycyclic aromatic hydrocarbons is * * * * *. Usually, the cetane number of vehicle diesel should be in the range of 45 ~ 60. (2) Evaporation: In order to make the engine start and work normally, diesel oil is required to have good evaporability. However, the evaporation should not be too strong, because the evaporation speed is too fast, and a large amount of diesel oil will accumulate during combustion, which will make the engine unstable. At the same time, the evaporation is strong, that is, the fraction is light and the viscosity is necessarily small, which will not only increase the wear of the fuel injection pump, but also reduce the spray quality and worsen the combustion process. That is to say, the evaporation of diesel oil is too strong or too poor, that is, the fraction is too light or too heavy. The evaporability of diesel oil is mainly evaluated by distillation range and closed flash point. ① Distillation range 50% recovery temperature: the lower the temperature, the more light components in diesel oil, the better the evaporation, which makes diesel oil easy to start. The standard stipulates that the 50% recovery temperature is not higher than 300℃. 90% recovery temperature and 95% recovery temperature: The lower the temperature, the less heavy components in diesel oil, which can improve the combustion performance and power performance of diesel engine, reduce oil consumption and mechanical wear. According to the standard, 90% recovery temperature and 95% recovery temperature are not higher than 355℃ and 365℃ respectively. ② Flash point The flash point of diesel oil is not only a project to control the evaporation of diesel oil, but also a project to ensure the stability of diesel oil. Generally, it is considered that the flash point of light fuel higher than 35℃ is safe during storage and transportation. The standard stipulates that the flash point of No.0 diesel oil is not less than 55℃. (3) Liquidity: The fluidity of diesel oil is mainly represented by viscosity, freezing point and cold filter point. ① Viscosity is an important performance item of diesel oil, which is closely related to the amount of diesel oil, atomization, combustibility and lubricity. When a high-speed diesel engine is running, the fuel injection time is only 0.001 ~ 0.002 seconds each time. In such a short time, the injected diesel oil should be gasified and spontaneously ignited, and the droplet diameter should not exceed 0.025mm, so as to ensure complete combustion. Atomization depends on viscosity. If the viscosity is too high, the droplets will be large, and the mixture with air will be uneven, resulting in incomplete combustion to form carbon deposit. If the viscosity is too small, the atomization is good, but the injection angle is large and close, and it can't be completely mixed with air. At the same time, the lubrication performance of parts such as the fuel injector will become worse and the wear will increase. According to the standard, the kinematic viscosity of No.0 light diesel oil at 20℃ is 3.0 ~ 8.0 mm2/s. Only in this range can diesel oil have good lubricity to the engine fuel supply system, good atomization performance and supply amount, and thus good combustion performance of diesel oil. ② Solidification point and cold filter point are the two main indexes to evaluate the low-temperature fluidity of diesel oil. In China, diesel oil is graded according to solidification point, which is the temperature at which diesel oil can't flow. However, in actual use, wax crystals are precipitated before the diesel oil is completely solidified, and when the crystals reach a certain size, the filter screen of the filter may be blocked, so that the diesel oil cannot be used before it reaches the freezing point. Under specified conditions, the temperature at which diesel oil can't pass through the filter screen is called the cold filter point of diesel oil. There is a good correspondence between the cold filter point and the service performance of diesel oil, and the actual service temperature range of each brand of diesel oil is divided according to the cold filter point. (4) Stability: The stability of diesel oil has the same effect on the engine as that of gasoline. Diesel oil has poor stability, easy oxidation and deterioration, dark color, increased sediment and colloid, blocked filter, and easily formed a large amount of carbon deposit in combustion chamber. Diesel injection system forms paint film and makes piston ring stick and increase wear, which has great influence on the storage and use of diesel oil. The stability index of diesel oil is mainly expressed by 10% steam residue carbon residue and total insoluble matter. At the same time, the size and change of chroma can also reflect the stability of diesel oil. (5) Corrosiveness: The corrosivity of diesel oil is basically the same as that of gasoline, which is controlled by three indexes: sulfur content, acidity and copper corrosion. (1) Acidity Acid value and acidity represent the sum of acidic substances in petroleum products. Generally, diesel oil is expressed by acidity. The diesel oil with high acidity not only corrodes the parts, but also increases the coking and fouling of the fuel injector and combustion chamber. The national standard stipulates that the acidity of diesel oil is not more than 7㎎KOH/100ml. ② Corrosion test Corrosion test is a qualitative test to evaluate the corrosion effect of oil on one or several metals. The purpose is to check whether the oil contains mercaptan, active sulfur or free sulfur, acidic substances, alkaline substances, water and other substances which have corrosion effect on metals. The national standard stipulates that the corrosion of copper sheet is not greater than Grade 1. (3) Sulfur content sulfur content refers to the content of sulfur and its derivatives in oil products, which is an index to ensure that oil-using machinery is not corroded, operators are not harmed to health and environmental pollution is prevented. When the sulfur content in fuel is high, active sulfur can corrode oil storage and transportation equipment and mechanical oil supply system; SO2 and SO3 are formed after combustion of non-active sulfur, sulfurous acid and sulfuric acid are formed when meeting water, which corrodes machinery, and SO2 and SO3 discharged into the atmosphere will cause pollution. According to the standard, the sulfur content of diesel oil is not more than 0.2%, and that of vehicle diesel oil is not more than 0.05%. (6) Density: The density of diesel oil increases with the increase of carbon, oxygen and sulfur in its composition. As the density decreases with the increase of temperature, China generally uses the density measured at 20℃, which is called the standard density. The standard density of diesel oil is generally 0.81 ~ 0.86g/ml. Apparent density refers to the density at the test temperature (ambient temperature), and the density measured by general customers in oil products is the apparent density. If the density of diesel oil is too low, the engine will knock and the fuel consumption will increase. If the density is too high, the diesel oil will not be fully burned, and carbon deposits will be generated in the cylinder and nozzle, which will cause the cylinder to wear and block the oil circuit, and increase the oil consumption. (7) Moisture and mechanical impurities: And moisture and mechanical impurities are important quality indexes of most petroleum products. Water and mechanical impurities may be mixed in the process of oil storage and transportation for various reasons, which is harmful to the use of oil products. It will block the pipelines and filters of the oil supply system and increase the wear and tear of the oil-using machinery and equipment. When diesel oil contains water, it will not only increase the corrosion and reduce the efficiency of the equipment, but also worsen the fuel process. At low temperature, the moisture in the fuel will freeze and block the engine oil circuit, which will affect the oil supply. (8) Chroma: Chromaticity is an indicator of diesel oil color, and the national standard stipulates that the chromaticity of light diesel oil is not more than 3.5. The chromaticity of diesel oil is related to the quality of crude oil, refining technology and refining degree. The color of diesel oil produced by different refineries will be quite different. Nonstandard diesel oil 1. Source of non-standard diesel oil Non-standard diesel oil is generally produced by simple distillation of imported No.180 fuel oil, and then some additives are added to improve some quality indexes. At the initial stage, all the quality indexes of this kind of non-standard diesel oil meet the current national standards, including cetane number with high difficulty requirements. One of the serious defects of this kind of oil is that the storage period is only about 20 days, after which it will oxidize rapidly and turn black; Secondly, the sulfur content exceeds the standard. Because No.180 fuel oil is easy to import, low in price and easy to refine, some small refineries generally use straight-run method to produce non-standard diesel oil and oil residue, which is one of the main sources of non-standard diesel oil in the market. The second method is to mix smuggled red oil with white oil. Some refineries will sell a kind of white oil, which is cheaper than smuggled red oil. White oil and smuggled red oil are blended into non-standard diesel oil according to a certain proportion. This kind of oil is of poor quality and relatively high cost. Almost all social individual gas stations like this light oil, which is abundant in the surrounding areas of Shenzhen. The third is to use naphtha (light oil) or odorless lamp oil, solvent oil and other blended fuel oil (heavy diesel oil), and the blended oil is sold as light diesel oil, mainly to factories, ships and so on. 2. Harm of non-standard diesel oil The hazards of non-standard diesel oil to automobiles are as follows: (1) diesel vehicles knock, causing strong mechanical wear and tear, while cold start is difficult, fuel consumption is high, and exhaust smoke is black. Sediment and colloid are formed, which will block the automobile filter, form a large amount of carbon deposit in the combustion chamber, and make the piston stick and increase wear. (2) Excessive sulfur content will not only lead to engine system corrosion and wear, but also generate acid rain in the atmosphere. Significantly increase the particulate matter (PM) emissions, and reduce the efficiency of diesel engine emission treatment system, poisoning, or even failure. Main reasons for quality change of diesel oil during storage and transportation 1. Oxidation It is a chemical change, which will produce colloid. For more information about oil products, please pay attention to WeChat WeChat official account oil circle for oil blending technology. Diesel oil is shown in the test items of oxidation stability. For more information about oil products, please pay attention to WeChat WeChat official account Oil Products Circle. Adding additives to some oil products will also accelerate the oxidation of oil products after photodegradation. 2. Impurity pollution Interrupt the oil supply, increase the wear of parts, and block the filter and oil circuit. Most of the impurities are mixed in during transportation and storage. Storage and management of oil products based on 1. Keep oil storage containers such as oil tanks clean. Coating anticorrosive coating on the inner wall of oil storage tanks can reduce rust falling into oil. 2. Ensure that the oil tank is sealed without leakage. Avoid open-air loading and unloading operations in rainy days or when there is a lot of dust in the air, and prevent water intrusion. 3. Regularly measure the oil tank water level. Spot check the oil samples at the bottom of the tank frequently, and if there is any water impurity, pump it out by hand pump in time. 4. Clean the oil tank regularly. Clean the light oil tank every 3 years. Serious pollution should shorten the tank cleaning cycle. |