【11.19-25 Weekly Question】+1 to Wealth, +5~20 to Wealth if correct
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Short answer: What is the relationship between the flash point of oils and fuels, their distillation composition, hydrocarbon composition, and pressure? Answer: The lower the boiling point range, the lower the flash point as well. The flash point of olefins is lower than that of alkanes, cycloalkanes, and aromatics. The flash point of oils increases as pressure rises, because higher pressure elevates the boiling range of the oils, making it less likely for them to evaporate, and thus raising their flash point as well.
The lower the boiling point range, the lower the flash point as well. The flash point of olefins is lower than that of alkanes, cycloalkanes, and aromatics. The flash point of oils increases as pressure rises, because higher pressure elevates the boiling range of the oils, making it less likely for them to evaporate, and thus raising their flash point as well.
The heavier the fraction, the higher its flash point; in a hydrocarbon mixture, as the relative molecular mass increases, the flash point rises, while a higher vapor pressure results in a lower flash point.
The flash point of a fuel is related to its vapor pressure as well as its distillation composition; the higher the boiling point of the fuel, the heavier its fractions, and the greater its relative molecular mass, the higher its flash point. Conversely, the lower the boiling point of the oil, the lighter the fraction, the smaller its relative molecular mass, and the easier it is to evaporate; as a result, its flash point and ignition point are lower. The flash point and ignition point of oils depend on the content of low-boiling hydrocarbons; alkanes have higher flash points than the corresponding alkenes. The flash point of a fuel depends on the content of the hydrocarbons with the lowest boiling point in that fuel. When a very small amount of light oil is mixed into high-boiling-point oils, it can cause a significant decrease in the flash point.
As the boiling range of the oil increases, its flash point and ignition point rise, while its autoignition point decreases. Oils with a high content of alkanes have a low auto-ignition point and a high flash point. Within the same family of hydrocarbons, those with a lower molecular weight have a higher autoignition temperature, but lower flash points and ignition temperatures. For hydrocarbons with the same number of carbon atoms, the order of their autoignition points is: alkanes, aromatics. The flash point is measured under certain conditions; I think it is related to the partial pressure occupied by the fuel after it vaporizes. Of course, the level of flash point is essentially related to the molecular composition of the oil. The higher the pressure, the higher the flash point. Quantitative relationships may exist, but for complex mixtures like oils, such relationships are not only difficult to identify but also lack universality; the compositions of different oils vary greatly, so at best only a rough relationship can be established.
What is the relationship between the flash point of oils and fuels, their distillation composition, hydrocarbon composition, and pressure? Under specified conditions, the oil is heated; as the temperature of the oil rises, the concentration of oil vapor in the air (above the liquid surface) increases as well. When the temperature reaches a certain level, if a flame is brought near this mixture, it will ignite. The lowest temperature at which this phenomenon occurs is known as the flash point of the petroleum product. Flash point detectors are available in closed and open types. The flash point measured using a closed-cup flash point tester is called the closed-cup flash point ； It is mainly used for determining the flash point of light oils. The flash point measured using an open-cup flash point tester is called the open-cup flash point, and it is primarily used for determining the flash point of lubricants and heavy oils. The flash point of petroleum products is an indicator that indicates the degree of risk of fire and explosion; it is determined using standard open-cup or closed-cup flash point testers, and serves as a metric for assessing the safety of petroleum products. The flash point is the lowest temperature at which a mixture of vapors from a flammable liquid and air will ignite momentarily when exposed to a flame. A flash fire is a minor explosion, indicating that at this temperature, the oil vapor generated by the evaporation of the oil has reached a concentration in the air sufficient to cause an explosion. Only when the volume fraction of flammable gases in the mixture reaches a certain value will it explode upon exposure to fire. Neither too low nor too high a concentration will cause an explosion; this range of concentrations is known as the explosion limit. Within the explosion limit, the lowest volume fraction of combustible gas in the mixture is referred to as the lower explosion limit, while the highest volume fraction is known as the upper explosion limit. The flash point of a fuel refers to the temperature at which, under normal pressure, the vapor of the fuel mixed with air reaches the lower or upper limit for ignition. Generally, the flash point of high-boiling-point oils is the temperature of the oil at its lower explosion limit. At this temperature, the liquid oil already has a sufficient saturated vapor pressure, causing its concentration in the air to reach exactly the lower limit for ignition. As a result, explosion and combustion occur immediately upon exposure to an open flame. Since very little oil is used under experimental conditions, the combustible mixture is burned out instantly after ignition; as a result, all that is seen is a brief flash of flame. As for low-boiling-point oils, such as gasoline and volatile liquid petroleum products, the vapor concentration at room temperature has **already exceeded their lower explosion limit; their flash point is actually the oil temperature corresponding to their upper explosion limit. If cooling is used to reduce the vapor pressure of gasoline, the flash temperature corresponding to the lower explosion limit can also be measured. Since the flash point is an indicator of the safety level of oils during storage, transportation, and use, it is not practical to determine the temperature at which low-boiling-point oils will explode. 1. It is related to the chemical composition: Generally, alkanes are more easily oxidized than aromatics; therefore, oils with a high content of alkanes have a lower auto-ignition point. However, their flash point is higher than that of oils with the same viscosity but a higher content of naphthenes and aromatics. Among hydrocarbons of the same type, as the relative molecular mass increases, the flash point rises. For hydrocarbons with the same number of carbon atoms, the order of flash points is: alkanes > cycloalkanes, alkenes > aromatics. 2. It is related to the composition of the fractions: the higher the boiling point of the oil, the heavier the fractions, and the greater the relative molecular mass, the higher its flash point will be. Conversely, the lower the boiling point of the oil, the lighter the fraction, the smaller its relative molecular mass, the easier it is to vaporize, and the lower its flash point. The flash point of oils depends on the content of hydrocarbons with low boiling points; alkanes have a higher flash point than the corresponding alkenes. The flash point of a fuel depends on the content of the hydrocarbons with the lowest boiling point in that fuel. When a very small amount of light oil is mixed into high-boiling-point oils, it can cause a significant decrease in the flash point. For example, adding 1% gasoline to a certain lubricant can reduce its flash point from 200°C to 170°C. It is for this reason that crude oil has a very low flash point, and it is classified as a flammable substance along with other oils with low flash points. 3. Relationship with pressure: The flash point of oils is related to their vapor pressure, which increases as pressure rises.
The flash point of oils is related to their distillation composition, chemical composition, and pressure. The lower the boiling point range of a petroleum product, the lower its flash point. The greater the vaporization tendency of a fuel, the lower its flash point. The flash point of oils increases as pressure rises.
Generally, the flash point of high-boiling-point oils is the temperature of the oil at its lower explosion limit. At this temperature, the liquid oil already has a sufficient saturated vapor pressure, causing its concentration in the air to reach exactly the lower limit for ignition. As a result, explosion and combustion occur immediately upon exposure to an open flame. Since very little oil is used under experimental conditions, the combustible mixture is burned out instantly after ignition; as a result, all that is seen is a brief flash of flame. As for low-boiling-point oils, such as gasoline and volatile liquid petroleum products, the vapor concentration at room temperature has **already exceeded their lower explosion limit; their flash point is actually the oil temperature corresponding to their upper explosion limit. If cooling is used to reduce the vapor pressure of gasoline, the flash temperature corresponding to the lower explosion limit can also be measured. Since the flash point is an indicator of the safety level of oils during storage, transportation, and use, it is not practical to determine the temperature at which low-boiling-point oils will explode.
1. Under normal circumstances, alkanes are more easily oxidized than aromatics; therefore, oils with a high content of alkanes have a lower auto-ignition point. However, their flash point is higher than that of oils with the same viscosity but a higher content of naphthenes and aromatics. Among similar hydrocarbons, as the relative molecular mass increases, the autoignition temperature decreases, while the flash point and ignition temperature increase. 2. The flash point of oils is related to their vapor pressure as well as to their distillation fractions. The higher the boiling point of a petroleum product, the heavier its fractions and the greater its relative molecular mass, resulting in a higher flash point. The flash point and ignition point of oils depend on the content of low-boiling hydrocarbons. Alkanes have a higher flash point than the corresponding alkenes. The flash point of a fuel depends on the content of the hydrocarbons with the lowest boiling point in that fuel.
The lower the molecular weight of hydrocarbon molecules, the lighter the fraction and the lower its flash point; as for pressure, it seems to have no relation to the flash point.
What is the relationship between the flash point of oils and fuels, their distillation composition, hydrocarbon composition, and pressure? The flash point of oils is related to their distillation composition, chemical composition, and pressure. The lower the boiling point range of a liquid, the lower its flash point. For example, the flash point of gasoline is between -50 and 30°C, that of kerosene is between 28 and 60°C, and that of lubricating oils is between 130 and 325°C. The greater the volatility of a liquid, the lower its flash point.