A brief introduction to the process flow of distillation
Release time:
2026-06-04
The actual operation of distillation is carried out in an upright circular distillation tower. The tower is equipped with several layers of trays or filled with a certain height of packing. The gas-liquid two-phase mass transfer can be differential contact or stepwise contact, and the mass transfer equipment is universal for absorption and distillation processes.
The actual operation of distillation is carried out in an upright circular distillation tower. The tower is equipped with several layers of trays or filled with a certain height of packing. The gas-liquid two-phase mass transfer can be differential contact or stepwise contact, and the mass transfer equipment is universal for absorption and distillation processes.
1. Distillation process flow
① After preheating, the raw material liquid is sent into the distillation tower.
② After merging with the reflux liquid descending from the upper part of the tower on the feed plate, it overflows plate by plate and flows into the bottom reboiler of the tower.
③ On each layer, the refluxing liquid comes into contact with the rising vapor for heat and mass transfer.
④ In practical operation, a portion of the liquid is continuously taken out from the reboiler as the bottom product (kettle residue), and some of the liquid vaporizes, causing rising vapor to pass through each layer of the tray.
⑤ The vapor at the top of the tower enters the condenser and is completely condensed. Part of the condensed liquid is sent to the top of the tower as reflux liquid by gravity (or can be pumped), and a part is sent out as the top product (distillate) after passing through the cooler.
2. Distillation and extraction sections
Above the feed plate is called the distillation section - the volatile components in the refined gas phase.
The section below the feed plate (including the feed plate) is called the distillation section - extracting the non-volatile components in the concentrated liquid phase.
The product at the top of the tower is called distillate, which is rich in volatile components.
The bottom product of the tower is called kettle liquid - rich in non-volatile components.
Distillation section: The tower section above the feeding plate. The heavy components in the rising gas phase are transferred to the liquid phase, and the light components in the liquid phase are transferred to the gas phase, completing the refinement of the rising vapor light components.
Distillation section: the tower section below the feeding plate. The light components in the descending liquid are transferred to the gas phase, and the heavy components in the gas phase are transferred to the liquid phase, completing the concentration of heavy components in the descending liquid.
The function of the tower top condenser is to obtain tower top products and ensure appropriate liquid phase reflux.
The function of a reboiler is to provide a certain amount of upward steam flow.
3. The function of reflux:
Increase the concentration of products at the top of the tower;
Supplement volatile components to maintain a certain liquid layer on each board.
Reflux includes liquid phase reflux at the top of the tower and gas phase reflux caused by partial vaporization at the bottom of the tower.
Reflux is a necessary condition for the continuous operation of the distillation process due to the contact mass transfer between gas and liquid phases.
If there is no liquid reflux at the top of the tower, or if there is no reboiler at the bottom of the tower causing vapor reflux, the gas-liquid mass transfer on the tray will lack one side of the interaction, and the separation function of the tray will be lost.
Therefore, the gradual decrease of reflux liquid and the gradual increase of vapor are necessary conditions for achieving distillation.
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