In the rising film evaporator, the liquid enters the tube for heating and flows into the separator; the liquid and steam are separated and then return to the evaporator through the circulation tube to form a closed circulation. This evaporator is also known as the external circulation evaporator. When it comes to the evaporator selection, if a larger evaporation volume is demanded, the multi-effect device can be adopted to achieve the purpose of saving steam and reducing energy consumption.

The heating system is composed of heat exchanging tubes. After it is preheated to reach the boiling point, the liquid is introduced from the bottom of the heating chamber and is driven by the flash steam rising at a high speed. It will be evaporated while it flows along the interior wall of the heat exchanging tube. The remaining liquid will be discharged from the bottom of the separation chamber. The flash steam produced will become the heat source of the next effect after the foam, water drop and impurities are removed at the upper separation board. This evaporator is suitable for disposing thin solutions of higher evaporation, heat sensitive solutions or solutions easy to produce foam. 

This evaporator needs elaborate design and operation, that is, the flash steam in the heating tube shall have higher speed and higher heat transfer coefficient to make the material liquid reach the preset concentration requirement when it passes through the heating tube only once.

The rising film evaporator is suitable for disposing solutions of higher evaporation, heat sensitive solutions of low viscosity and solutions easy to produce foam, but not suitable for solutions of high viscosity, solutions having crystalline precipitation and solutions easy to agglomerate. It is widely used for petrochemical industry, chemical industry, pharmacy fertilizer, paper making, aluminum industry, MSG, brewage, sugar production, etc.