Multiple effect falling film evaporator:
Evaporation is the process of heating the lower boiling point solution in the solution with different boiling points to a vaporized state to concentrate it. In most cases, the evaporator uses water vapor as the heating medium (usually called heating steam, primary steam or raw steam).
Falling film evaporation is to let the liquid enter from the upper feed port of the falling film evaporator effect, and evenly distribute it to each heat exchange tube through the liquid distribution and film forming device. Under the action of vacuum, it flows from top to bottom in a uniform film. During the flow process, it is heated and vaporized with the shell side heating medium. The first effect is directly heated by raw steam, and the generated steam and liquid phase enter the separator of the evaporator together. After the vapor and liquid are fully separated, the secondary steam enters the next effect to provide it with a heat source. The secondary steam generated by the last effect enters the condenser for condensation and then discharged.
The entire evaporation process is completed under negative pressure, which is provided by the condenser and the vacuum pump.
Falling film evaporator can be divided into double-effect evaporator, triple-effect evaporator, quadruple-effect evaporator and five-effect evaporator according to production capacity and material characteristics.
Falling film evaporator features:
1) The liquid in the falling film evaporator is added from the top of the evaporator, and falls along the tube wall in a film shape under the action of gravity, and evaporates and concentrates in the process, and a concentrated liquid is obtained at the bottom. The falling film evaporator can evaporate materials with high concentration and high viscosity.
2) Since the solution flows in a film-like manner in the single-pass evaporator, the heat transfer coefficient is high.
3) The residence time is short, which is not easy to cause material deterioration and is suitable for processing heat-sensitive materials.
4) The liquid hold-up is small, and the falling film evaporator can operate quickly according to the changes in energy supply, vacuum, feed amount, concentration, etc. Nearly constant,
5) Since the process fluid flows only under the action of gravity rather than being propelled by a high temperature difference, low temperature differential evaporation can be used.
6) Falling film evaporator is suitable for evaporation and concentration of foaming materials. Since the feed liquid evaporates in the form of a film in the heating tube, vapor-liquid separation is formed. At the same time, most of the feed liquid is pumped away at the bottom of the effect body, and only a small part of the feed liquid and all the secondary steam enter the separator for enhanced separation. The whole process of the feed liquid does not form too much impact, avoiding the formation of foam.
7) Use PLC visual process automatic control to reduce equipment abnormalities caused by human operating errors.
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Scope of application: Falling film evaporator is widely used infoodIt is used for evaporation and concentration of water or organic solvent solutions in industries such as medicine, chemical industry, and light industry, and can be widely used for waste liquid treatment in the above industries. It has high evaporation capacity, energy saving and consumption reduction, low operating cost, and can ensure that the material does not change during the evaporation process.
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