The reflux of liquid at the top of the tower is necessary for the continuous distillation process.

Without reflux, there would be no distillation operation. Reflux is the basis for ensuring reflux operation. In engineering, the distillation operation is ensured because the reflux operation is called.

If there is no reflux, it is not called distillation. The rectification section does not work, only the extraction section is effective.

The purpose of reflux is to allow the refluxing low-temperature liquid to contact the rising vapor in the tower on the tray plate or the surface of the packing to transfer heat and mass, condense the high-boiling-point substances in the gas, vaporize the low-boiling-point substances in the liquid, and gradually purify the product. Therefore, appropriate reflux must be ensured during operation to control the temperature at the top of the tower to ensure that qualified products are obtained.

right! The reflux effect at the top of the tower is: ①It provides reflux of the liquid phase on the tray, causing full contact between the gas and liquid phases to achieve the purpose of heat transfer and mass transfer. ； ②It takes away the excess heat entering the tower and maintains the heat balance of the entire tower to facilitate product quality control. The temperature at the top of the tower is controlled by the reflux flow rate at the top of the tower. If the temperature at the top of the tower is high and the product is heavy, the quality of reflux flow control should be increased. However, the reflux flow rate should not be too large to prevent overloading of the upper tray and tower top system.

To put it directly and clearly, if there is no reflux and no feeding, it should be the same as evaporation. Of course, the evaporated gas will have a different composition from the liquid at the bottom of the tower due to the different volatilities of the components. The proportion of light components will be high and the proportion of heavy components will be low. Then the gas will be condensed in the condenser at the top of the tower. At this time, it seems that the height of the tower is meaningless. If the feed is fed, in the section from the bottom of the tower to the feed tray, the rising gas will exchange material with the descending feed liquid. As the person above said, the stripping section works, but the tray above the feed does not play a role in separation. Then there is reflux, so that all the trays can play a role in separation. The principle of distillation is that gas and liquid substances can be exchanged on each theoretical tray. After understanding this, you can understand the meaning of minimum reflux ratio and total reflux, so that your understanding of distillation will be improved.

In the distillation operation, the reflux at the top of the tower is one of the necessary conditions. It provides the cooling capacity of the rectification section of the tower and carries out mass and heat transfer with the rising steam. The heavy components in the liquid phase become more and more concentrated, and the light components in the gas phase become more and more. Finally, a thicker light component is obtained at the top of the tower, and a thicker heavy component is obtained in the column still.

The tower with reflux is called a rectification tower or distillation tower. The tower without reflux is called a desorption tower or a stripping tower. In fact, there is a certain difference between rectification and distillation.

Reflux is to provide liquid to ensure that the rising gas can contact the liquid for mass and heat transfer.

If there is no reflux, there will be no gas-liquid two-phase contact, and there will be no mass transfer and heat transfer processes.

Without reflux, that's called evaporation. The reflux ratio is used to adjust the material composition accuracy at the top of the tower. Of course, this accuracy is also limited.

To put it bluntly, the reason why it is called essence lies in its return flow. Reflux makes the medium and light components evaporated more concentrated~~

To put it simply, the purpose of setting up reflux at the top of the distillation tower is to provide cooling capacity for the rising steam to condense the heavy components, while the concentration of the light components is getting higher and higher, thereby achieving the purpose of separation and concentration!

The main purpose of distillation is to achieve heat and mass transfer through full contact between the gas and liquid phases on the tray. If there is no cold reflux, where does the liquid phase on the tray come from? How to achieve the purpose of heat transfer and mass transfer?