Falling film evaporation is to add the material liquid from the upper tube box of the Falling film evaporator heating chamber, and distribute it evenly into the heat exchange tube through the liquid film forming device. Under the action of gravity, vacuum induction and air flow, it becomes a uniform film. Flow from top to bottom. In the flow process, it is heated and vaporized by the heating medium on the shell side, and the vapor and liquid phase produced enter the separation chamber of the falling film evaporator together. After the vapor and liquid are completely separated, the vapor enters the condenser to condense or enter the next-effect Falling film evaporator as the medium heating to achieve multi-effect operation, and the liquid phase is discharged from the separator.

The operation failure of Falling film evaporator is because the low vacuum is too low to maintain the boiling point of the concentrated liquid, which increases the temperature of the secondary steam, thereby reducing the temperature difference between the heating steam and the concentrated liquid, thereby reducing heat transfer and slowing down the vapor evaporation rate . In addition, the heating temperature of the heating material will affect the preservation of the effective ingredients. Due to the low vacuum, in addition to the influence of mass concentration, the production capacity of Falling film evaporator is also reduced. The reasons for the low vacuum are as follows:

1. Compress all parts of the equipment into air. The penetration of air will increase the burden on the vacuum equipment and may even cause failure.
2. Insufficient cooling water. In addition to pumping equipment, the main reason for insufficient cooling water is that the pipes of the falling film evaporator are blocked, which leads to valve damage. Excessive cooling water will prevent the secondary steam from condensing in time, seriously affecting the operation of the vacuum equipment.
3. The cooling water temperature is too high. If the cooling water temperature is too high, the large amount of secondary steam generated by the central heating will not be able to condense in time. Therefore, the vacuum degree of the falling film evaporator will rapidly decrease.
4. The steam pressure is too high. If the heating steam pressure is too high, the evaporation rate of the Falling film evaporator will increase rapidly. The generation of a large amount of secondary steam increases the load of the cooling equipment, and the degree of vacuum gradually decreases. Reducing the degree of vacuum will also increase the evaporation temperature of the material and affect the quality of the product, thereby reducing the production capacity of the Falling film evaporator.