Working principle of three-effect evaporator for high-salt wastewater

The three-effect evaporator is a kind of extraction and concentration equipment, which is widely used in the evaporation and concentration process of liquid materials such as pharmaceuticals, chemicals, food, and light industry. The physical heating time is short, the evaporation speed is fast, the concentration ratio is large, and the original effect of the material is effectively maintained, and the energy saving effect is significant.

At present, the main job of the three-effect evaporator is to treat high-salinity wastewater in the production process, and the suitable wastewater content is 3.5% to 25%. The author has learned that the three-effect evaporator is mainly composed of three sets of evaporators, condensers, salt separators and auxiliary equipment connected in series.


Regarding the treatment of high-salt wastewater, some experts said that high-salinity wastewater will first enter a forced circulation crystallization evaporator. The crystallization evaporator is equipped with a circulating pump to pump the wastewater into the evaporation heat exchange chamber. In the evaporation heat exchange chamber, The external steam liquefaction generates latent heat of vaporization to heat the wastewater. However, due to the high pressure in the evaporation heat exchange chamber, the waste water is heated to overheat at a pressure higher than the normal liquid boiling point in the evaporation heat exchange chamber.

After the heated liquid enters the crystallization and evaporation chamber, the pressure of the waste water drops rapidly, causing part of the waste water to flash or boil quickly. The steam after evaporation of wastewater enters the two-effect forced circulation evaporator as the power steam to heat the two-effect evaporator, and the unevaporated wastewater and salt are temporarily stored in the crystallization evaporation chamber.

The one-effect, two-effect, and three-effect forced circulation evaporators are connected through a balance pipe. Under the action of negative pressure, the high-salinity wastewater flows from the first effect to the second effect and the third effect in sequence. The salt concentration is getting higher and higher. When the salt in the wastewater exceeds the saturation state, the salt in the water will continuously precipitate and enter the salt collection chamber at the lower part of the evaporation crystallization chamber.

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Post time: Sep-18-2020