Scraper type evaporator structure: There is a heating steam jacket in the shell, and a rotatable blade, that is, a scraper is installed in the jacket. There are two types of scraper: fixed type and rotor type. The gap between the former and the inner wall of the casing 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 material liquid is added from the upper part of the evaporator along the tangential direction (there is also added to the screed plate coaxial with the scraper).
Due to the effects of gravity, centrifugal force, and the rotating scraper scraping belt, the solution forms a rotating film on the inner wall of the device, and is evaporated and concentrated in the process, and the completed liquid is discharged at the bottom.
This type of evaporator is a single-pass type evaporator that uses external power to form a film. Its outstanding advantages are strong adaptability to materials and short residence time, usually several seconds or tens of seconds, so it can adapt to high viscosity ( (Such as tannin, honey, etc.) and easy to crystallize, scale, heat sensitive materials.
However, its structure is complicated and the power consumption is large. The heat transfer surface per square meter needs about 1.5 ~ 3kW.
In addition, its throughput is small and manufacturing and installation requirements are high.