The application of short-distance distillation is to obtain high vacuum, or very low operating pressure (minimum absolute operating pressure can reach 0.001mbar) in the distillation system, so that the separation of high boiling point materials or heat sensitive materials becomes possible. However, the materials before the short-distance distillation generally contain a small amount of low-boiling components, such as water or solvents. If these low boiling point components are not removed before entering the short path evaporator, it will seriously affect the operating pressure in the short path evaporator. For example,
According to the Ideal Gas Law
A certain mass of gas at a constant temperature
P (pressure) × V (volume) = const. (Constant)
For 1 kg of water
Its liquid is: 1 liter
Its vapor state at a pressure of 1 bar is: 1 m³
At 1 mbar: 1,000 m³
At 10-3 mbar: 1,000,000 m³
It is hard to imagine that even if your raw material contains only 1 gram of water, its volume can reach 1000 cubic meters under a pressure of 0.001mbar!
Therefore, under extremely low operating pressure, the volume of low-boiling components is very large, and the pumping capacity of the vacuum pump often cannot meet the requirements. It is bound to increase the absolute pressure in the system, which will affect the separation effect.
Therefore, in general, a degassing section needs to be added before the short-path distillation equipment.
The working principle of the degassing section is to heat the raw materials to a predetermined temperature and enter the pre-evacuated flash tank. The low-boiling light components that have been heated in the flash tank will evaporate under vacuum conditions. The external condenser condenses and realizes the evaporation and separation of low-boiling components.