How does Short-Path Distillation Work？

lanphan

5 years ago

In the industrial and chemical fields, people always need to extract some solvents or purify some substances. There are several ways to achieve those purposes and the short path distillation is one of commonly used methods. The short path distillation is a technique that removes solvents from mixtures through evaporation, which is mainly used for liquid-liquid separation.

Working Principle of Short Path Distillation

As a type of thermodynamic separation technology, the short path distillation can evaporate components with low boiling points by utilizing that the boiling point of each component in the mixed liquid or liquid-solid mixture is different, and then condense the material to separate the whole components. It is the combination of evaporation and condensation unit operations as well as a kind of liquid-liquid separation technology. Compared to other separation methods, such as extraction, filtration and crystallization, it has the advantage that no other solvents than system components are required, thus ensuring that no new impurities are introduced.

Working Process of Short Path Distillation

　　1. Molecules diffuse from the liquid phase to the evaporation surface:

The beginning of the short path distillation’s working is from evaporation flask. Sample will be placed in the evaporation flask and be heated by the heating mantle. The temperature that heating mantle provides can be adjusted according to the boiling points of different solvents.

　　2. Free evaporation of molecules on the liquid surface:

The evaporation speed of solvents can be changed by the heating temperature. Besides, the stability of sample solvents is also an important factor influencing the evaporation speed.

　　3. Molecules fly from the evaporation to the condensation surface:

The extracted gas-phase solvents will be transferred along a short distance, and be condensed along this distance. During this process, gas-phase solvents will be cooled down by the condensing part and turned into liquid-phase solvents.

　　4. Solvents will be collected in the receiving flask:

After gas-phase solvents being turned into liquid-phase solvents, it will be transferred into receiving flask and be collected efficiently. Collecting extracted solvents in the receiving flask is very convenient for users to get.

In the whole working process of short path distillation, there are always vacuum pump providing vacuum and condensing part turning gas-phase solvents into liquid-phase solvents.

Precautions for Using a Short Path Distillation

Check whether the inlet and outlet valves of the refrigeration equipment are normally opened and whether the pressure is in the normal range.
Check whether the power supply of each device is turned on.
With the electric heating, the surface temperature of the external heating body is relatively high. Don’t touch it with your hands to avoid burns.
Check whether the ethanol in the low and constant temperature tank is enough.
Check whether the liquid nitrogen in the tank is sufficient.
Check if the connection between the cold trap and the equipment is greatly sealed.

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