The scraper evaporator structure is provided with a heating steam jacket inside the casing, which is provided with a rotatable blade or a scraper. The squeegee has two types: fixed type and rotor type. The gap between the former and the inner wall of the housing is 0.5 to 1.5 mm, and the gap between the latter and the wall varies with the number of revolutions of the rotor.
The feed liquid is fed in the tangential direction from the upper part of the evaporator (also added to the tray that is coaxial with the squeegee).
Due to the action of gravity, centrifugal force and rotating scraper scraping, the solution forms a downwardly swirling film on the inner wall of the vessel, and is concentrated by evaporation during this process, and the finished liquid is discharged at the bottom.
This type of evaporator is a one-pass type evaporator which uses external force to form a film. Its outstanding advantage is that it has strong adaptability to materials and short residence time, generally several seconds or several tens of seconds, so it can be adapted to high viscosity ( Such as silicone, honey, etc.) and materials that are easy to crystallize, scale, and heat sensitive.
However, its structure is complicated, power consumption is large, and the heat transfer surface per square meter needs about 1.5 to 3 kW.
In addition, its handling capacity is small and manufacturing and installation requirements are high.