The general principle of distillation process is that the feed liquid is added from the middle of the tower, and the tower section above the feed inlet further enriches the volatile components in the rising steam, which is called distillation section; The tower section below the feed inlet extracts volatile components from the falling liquid, which is called stripping section.

As for why there must be reflux, it is because the steam from the top of the distillation column is condensed, and part of the condensate returns to the distillation column from the top as reflux liquid, and the remaining distillate is the top product. The liquid from the bottom of the tower is partially gasified by the reboiler, the vapor rises along the tower, and the remaining liquid is used as the bottom product. The ratio of the amount of liquid flowing back into the tower at the top of the tower to the amount of products at the top of the tower is called reflux ratio, which will affect the separation effect and energy consumption of distillation operation.

Distillation is a separation process, which uses the different volatilities of the components in the mixture to separate the components. Commonly used equipment are plate distillation column and packed distillation column. The principle and equipment flow of precision distillation are the same as those of ordinary distillation, but the relative volatility between components in the system to be separated is small (

Isomers usually coexist in natural essential oil, which is the raw material for producing isolated spices. For example, citronellol and rosanol coexisting in natural essential oils such as geranium oil, rose oil and rose grass oil are optical isomers. The boiling point difference of these isomers is relatively small, so it is difficult to achieve effective separation of this kind of separated perfume by general distillation process, so precision distillation is widely used in the production of separated perfume.

Efficient packing used in precision distillation column includes bulk packing such as Q-ring packing, McMahon packing and structured packing such as Seiler packing. These packings have large specific surface area, good wettability and low liquid holdup and fluid resistance, but the diameter of bulk packed tower should not be too large, otherwise the mass transfer and separation efficiency will drop sharply, which is the "amplification effect" of packed tower. The amplification effect of structured packing is small, so the application of wire mesh corrugated structured packing is more and more extensive.

reference data

Baidu encyclopedia-distillation