Help needed with basic knowledge.
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This post was last edited by zls1457 on 2016-3-18 at 13:58. The lighter the oil, the smoother it is (). Please explain, can you clarify? Thank you.
The lighter the oil, the lower its flash point. Spontaneous combustion occurs when a combustible material can ignite and continue to burn on its own, without the presence of any external spark or flame. The lowest temperature at which automatic ignition can occur is called the autoignition point. Flash point and auto-ignition temperature of various oils and crude oil in air: Oil type, Flash point (°C), Auto-ignition temperature (°C). Gasoline: < 28, 510–530; Kerosene: 28–45, 380–425; Light diesel: 45–120, 350–380; Heavy diesel: > 120, 300–330; Paraffin oil: > 120, 300–320; Tar: > 120, 230–240; Crude oil (Daqing): 28
Oil is light, more volatile, and tends to form flammable vapors. However, light oil generally has a low calorific value; to maintain combustion relying on the heat generated by its own burning, more steam and a higher temperature are required.
The lighter the oil, the higher its autoignition temperature. Lighter oils vaporize more easily when heated, and vaporization requires heat absorption, which lowers the temperature of the liquid phase; as a result, it is harder for such oils to reach the temperature at which they can ignite spontaneously, so their autoignition temperature is higher.
The lighter the oil, the higher its flash point. Oil is light, more volatile, and tends to form flammable vapors. However, light oil generally has a low calorific value; to maintain combustion relying on the heat generated by its own burning, more steam and a higher temperature are required.
The lighter the oil, the lower its flash point.
The lighter the oil, the higher its flash point. The lower the boiling point of a petroleum product, the lighter its fractions are, and its relative molecular mass is smaller; as a result, it is more volatile, with lower flash points and ignition points ； Contrary to the ignition point, the lower the boiling point of a petroleum product, the lighter its fractions are, and the less likely it is to catch fire on its own; consequently, its autoignition point is higher.
The ease of burning of oils is closely related to three parameters of petroleum products: flash point, ignition point, and autoignition point. The lighter the oil, the lower its flash point, and the greater the risk of ignition. However, the autoignition temperature of light oils is higher than that of heavy oils, so light oils do not ignite spontaneously. For heavy oils, although their flash point is high, their autoignition point is low, resulting in a high risk of ignition; this is why leaks of high-temperature heavy oils are prone to catching fire.
High: When both light oil and heavy oil are heated to the same temperature, light oil first reduces the accumulation of heat within it by evaporating its lighter components, which means that a higher temperature is required before spontaneous combustion occurs. Heavy oil is different; it does not volatilize easily when heated, and heat accumulates within it. The amount of heat carried away by vaporization is less than the amount of heat that accumulates, and once enough heat has accumulated, spontaneous combustion occurs. Light oil loses heat through vaporization and is less prone to spontaneous ignition, while heavy oil loses less heat through vaporization and is also less likely to catch fire spontaneously: