The role of reflux

Function of reflux: 1. Provide cold reflux on the tray to remove excess heat from within the tower, thereby maintaining thermal balance in it； 2. A cold fluid is supplied to the tray, where the gas and liquid phases come into contact in opposite directions. The heavier components in the rising gas condense, while the lighter components in the descending liquid absorb heat and vaporize. This repeated process of condensation and vaporization further improves the precision of product separation. Impact of reflux on product quality: As reflux increases, the top temperature of the tower decreases, the cutting point for the product at the top of the tower drops, and the product becomes lighter; conversely ； Backflow decreases, the top temperature rises, and the product at the top becomes heavier.

Function of reflux: 1. Provide liquid-phase reflux on the tray to remove excess heat from within the tower, thereby maintaining thermal balance in it； 2. High-temperature reflow can also recover some thermal energy ； 3. Adjust product quality ； 4. The catalytic fractionator bottom slurry reflux also serves to remove superheat and the catalyst powder from the washed gas oil ；

Take a look at the principles of chemical engineering. Hehe, on one hand, it removes heat from within the tower to maintain its thermal balance; on the other hand, it improves the separation accuracy of the tower

The purpose of reflux is mass transfer. The others are important, but not the goal; therefore, as backflow increases, the theoretical number of plates decreases ； Other factors have no causal relationship with it. He is an independent variable.

When the cold reflux flow increases, the purity of the product obtained at the top of the tower is higher. In a diesel and gasoline distillation tower, an increased amount of cold reflux will lead to an increase in the yield of diesel at the bottom of the tower, but the flash point of the diesel will decrease. So our strategy at the factory is to produce as much diesel as possible when its price is favorable, while ensuring quality.

Apart from the few well-known methods, reflux is a means of maintaining the gas-liquid equilibrium within the tower, and it cannot be simply regarded as a temperature control method.

This post was last edited by Catalytic additive on 2009-6-10 00:22. 1. Theoretically, the purpose of reflux is to provide a liquid phase for mass and heat transfer. 2. Top reflux is intended to ensure that there is liquid-phase reflux throughout the entire tower, thereby guaranteeing sufficient contact between the vapor and liquid phases at each tray in the tower. Vaporize part of the liquid phase and liquefy part of the vapor phase. To achieve the purpose of distillation. 3. In practical operation, reflux at each section is employed to ensure vapor-liquid equilibrium, pressure equilibrium, and thermal equilibrium throughout the entire tower. Generally, controlling the temperature (thermal equilibrium) is the main focus. To ensure that all products are qualified. 4. From a practical perspective, the backflow rate is not extremely high or excellent. An excessively large liquid phase, first, increases energy consumption; second, it can lead to local flooding of the tower. In our catalytic unit’s fractionation tower, we experienced excessive mid-stage reflux, which led to diesel of substandard quality.

The explanation on the 5th floor was very concise and clear; thank you.

Distillation is multi-stage distillation; and since it is distillation, there must be gas and liquid phases. What would happen if there is no backflow? That means the feed undergoes one flash on the feed plate; then the gas goes as gas and the liquid goes as liquid, which is what constitutes normal flashing. So what is the backflow effect? Multi-stage distillation requires multi-stage gas-liquid equilibrium; there must be a gas-liquid phase equilibrium on each theoretical plate, from the top of the tower to the bottom. According to Raoult’s law, if a high concentration of the light component is desired in the gas phase, it must also be high in the liquid phase. Just like in stock trading, if you want to make more money, you need to invest more. Moreover, the theoretical calculations for distillation are based on three assumptions, one of which is constant molar flow. It is assuming that the molar flow rates of the gas and liquid phases are constant. It’s impossible to calculate without countercurrent distillation.