Multi-stage heat exchange device

The utility model belongs to the technical field of heat exchange, and particularly relates to a multistage heat exchange device which comprises a shell, and a preheater, an evaporator and a superheater which are communicated are arranged in the shell from bottom to top. A high-temperature heat-transfer medium enters the shell through the heat-transfer medium inlet and exchanges heat in the superheater, the evaporator and the preheater, and the low-temperature heat-transfer medium after heat exchange is discharged through the heat-transfer medium outlet; cold water enters the shell through the cold water inlet and exchanges heat with the heat transfer medium in the preheater to generate hot water, the hot water exchanges heat with the heat transfer medium in the evaporator to generate saturated steam, and the saturated steam exchanges heat with the heat transfer medium in the superheater to generate superheated steam. The pipeline valve is used for controlling the flow direction of the heat transfer medium, t