Make use of the difference of the volatile capacity of each component in the mixture, through the reflux of liquid and gas, make the gas and liquid two reverse multi-stage contact, under the constraint of the relationship of thermal energy driving and phase equilibrium, it makes volatile components (light components) transfer continuously from the liquid phase to the gas phase, while the volatile components migrate from the gas phase to the liquid phase, which makes the mixture separate continuously. This process is called rectification. In this process, the process of heat transfer and mass transfer is carried out at the same time, which belongs to the control of mass transfer process. Raw materials enter the tower from the appropriate position in the middle of the tower, and divide the tower into two sections. The upper section is the distillation section without feed, and the lower section contains feed plate as the retention section. The condenser provides liquid reflux from the top of the tower, the reheater provides gas flow from the bottom of the tower. Gas and liquid reflux is an important feature of rectification.
In the distillation section, during the rising process of the gas phase, the light components of the gas phase are constantly refined, and the concentration is constantly increased in the gas phase, obtaining the light component products at the top of the tower.
In the distillation section, during the process of the liquid phase falling, its light components are continuously extracted and distilled, which makes the recombinant components constantly concentrated in the liquid phase and obtain the product of recombinant components at the bottom of the tower.
The biggest difference between the rectification process and other distillation processes is to provide liquid and gas flow with high purity at both ends of the tower, which provides the necessary conditions for mass transfer for the rectification process. Provide high-purity recirculation, so that under the condition of the same theoretical plate, when achieving high-purity separation for rectification, a certain mass transfer driving force can always be guaranteed. Therefore, as long as there are enough theoretical plates and the recirculation is large enough, light component products with high purity may be obtained at the top of the tower, while heavy component products with high purity may be obtained at the bottom of the tower
