It is absorbed to the evaporator through vacuum, and is sprayed evenly on the heated surface of the inner barrel wall through the rotating generator. Then a thin and even layer of film is distributed by the scraper, and then heat is transmitted from the cover, which will evaporate and condense rapidly. The condensed liquid enters into the receiver from the outlet directly or through the cooler, and the steam is discharged from the pipe. During this process, for the condensation of easily frothed materials, the scraper can effectively break the bubble, making the solvent evaporate easily.