The extraction of Chinese medicine liquid should be based on the nature and concentration requirements of Chinese medicine

　　The property of Chinese medicine extract is complex, so the appropriate concentration method and equipment should be selected according to its property and concentration degree.

　　1. Atmospheric concentration

　　It is evaporation and concentration under one atmospheric pressure, which takes a long time and easily leads to the destruction of some components. It is suitable for the concentration of heat stable liquid medicine. The commonly used equipment is the open dumping type sandwich steam boiler. During the concentration process, the stirring should be strengthened to avoid the conjunctiva on the surface. If the extract contains ethanol or other organic solvents, it can be recovered by atmospheric distillation unit.

　　2. Vacuum concentration

　　Evaporation concentration when the pressure in the evaporator is lower than 1 atmospheric pressure. The characteristics are: 1) the boiling point of the solution is reduced; ② The temperature difference of heat transfer is increased and the evaporation efficiency is improved; ③ The solvent vapor can be continuously removed to ensure the smooth evaporation; ④ Low pressure steam or waste gas is used as heating source to reduce boiling point; ⑤ Because of the decrease of vacuum and boiling point, the increase of viscosity and the decrease of heat transfer coefficient, the energy consumption increases. It is suitable for concentration of liquid medicine containing heat sensitive components; It can also be used to recover solvents, but attention should be paid to the loss of organic solvents such as ethanol.

　　3. Membrane concentration

　　It refers to the concentration method of forming a thin film when the liquid flows through the heating surface rapidly and producing a large number of bubbles due to intense boiling, which can increase the evaporation area and significantly increase the evaporation efficiency. It has the following characteristics: 1. It can concentrate the extract quickly and has a short heating time; ② Hydrostatic pressure and overheating can not affect it, and will not damage the composition; ③ It can be operated continuously under normal pressure or reduced pressure; ④ The solvent can be recycled.