How to understand how steam stripping reduces the partial pressure of oil and gas

1. Dalton’s law of partial pressures – In crude oil distillation units, according to Dalton’s law of partial pressures, the total pressure of the system is equal to the sum of the partial pressures of its various components. When superheated steam is injected at the bottom of the tower, at constant total pressure, the steam occupies some space, thereby increasing the \"share\" of the gas phase. - For example, suppose that initially there is only oil vapor inside the tower; the total pressure is P, and the partial pressure of the oil vapor is P_oil. After steam is injected, the total pressure remains at P. However, at this point, the partial pressure of oil vapor becomes P_oil', while the partial pressure of steam is P_steam. Since P = P_oil' + P_steam, it follows that P_oil' < P_oil; in other words, the partial pressure of oil vapor has decreased. 2. Lowering the boiling point and increasing the vaporization rate – For oils, their boiling point is closely related to pressure; as pressure decreases, the boiling point also decreases. When the partial pressure of hydrocarbons decreases, and the temperature at the bottom of the tower remains unchanged, some of the heavier components that could not vaporize at that temperature before can now do so due to the lower boiling point. - More components vaporizing means that more light oil components can move from the liquid phase to the gas phase, thereby increasing the yield of light oil. 3. Stripping – The injected superheated steam also serves a stripping function. Steam comes into full contact with the oil at the bottom of the tower; as it rises, it is able to \"carry away\" some of the lighter components in the oil, further promoting the separation and vaporization of these light oil components and thereby increasing the yield of light oil. Summary – Injecting superheated steam at the bottom of the tower effectively increases the yield of light oil through mechanisms such as reducing the partial pressure of oil and gas, lowering the boiling point, and promoting vaporization and stripping. This is an important operation in the crude oil distillation process, as it helps to improve product quality and economic efficiency. Your understanding has captured the key principles and is correct; further understanding these principles helps to gain a deeper grasp of the crude oil distillation process.

Your understanding is basically correct. During crude oil distillation, superheated steam is indeed injected to reduce the vapor pressure of the oil, thereby increasing the yield of light oils. Here, the relevant physical principles can be further explained: 1. **The concept of partial pressure**: In a mixed gas, the partial pressure of each gas refers to the pressure that gas would have if it occupied the entire system on its own. According to Dalton’s law of partial pressures, the total pressure of a mixture of gases is equal to the sum of the partial pressures of each component gas. 2. **Steam injection**: When superheated steam is injected at the bottom of the tower, it increases the total amount of gas in the system, but the total pressure of the system remains unchanged. Therefore, the partial pressure of the existing oil and gas will decrease due to the addition of steam. 3. **Decrease in boiling point**: The boiling point of oil is related to its vapor pressure. As the partial pressure of the oil decreases, its boiling point also decreases. This means that the oil can begin to vaporize at lower temperatures, allowing more light components (such as gasoline, diesel, etc.) to be separated from the crude oil. 4. **Increase the yield of light oil**: As the boiling point of the oil decreases, more light components can evaporate at lower temperatures, thereby increasing the yield of light oil. This is very beneficial for improving refining efficiency and product quality. In general, the method of injecting steam to reduce the vapor pressure of oil and gas enables more light components to evaporate at lower temperatures by altering the physical boiling point of the oil, thereby effectively improving the yield and quality of light oil. It is a common and effective technical method in the petroleum refining industry. .

Expressed simply and clearly; thanks for sharing!