The heating chamber of the rising film evaporator is composed of many vertical long tubes. The diameter of the commonly used heating tube is 25-50mm, and the ratio of tube length to tube diameter is about 100-150. After preheating, the material liquid is introduced from the bottom of the evaporator, boils and vaporizes rapidly in the heating tube, and the generated steam rises at a high speed in the heating tube.
Generally, the suitable outlet steam speed is 20-50m/s when operating under normal pressure, and the pressure is reduced. The steam speed can reach 100 to 160m/s or more during the down operation. The solution is driven by the rising steam, rises in a film-like shape along the pipe wall and continues to evaporate.
The vapor and liquid mixture is separated in the separator 2, the finished liquid is discharged from the bottom of the separator, and the secondary steam is discharged from the top. It should be noted that if the amount of water evaporating from the feed liquid is not much, it will be difficult to achieve the above-mentioned required steam speed, that is, the rising film evaporator is not suitable for the evaporation of thicker solutions; it is very viscous, easy to crystallize or easy to Fouling materials are also not applicable.
