According to operating pressure, the evaporator is divided into 3 kinds, pressure and decompression. According to the solution in the evaporator in the movement of the status of: ① circulation type. Boiling solution in the heating chamber several times through the heating of the surface, such as central circulation tube type, suspended basket type, outside heat type, Levin type and forced circulation type. ② one-way type. Boiling solution in the heating chamber at one time through the heating surface, do not make the circulation flow, the discharge of concentrated liquid, such as rising film type, falling film type, stirring film type and centrifugal film type. ③ direct contact type. Heating medium and solution direct contact Heat transfer, such as submerged combustion evaporator. Evaporation device in the operation process, to consume a large number of heating steam, in order to save heating steam, can use a multiple-effect evaporation device and steam-compression evaporator. Evaporator is widely used in chemical industry, light industry and other departments.