DTB type evaporative crystallizer, which is also a type of crystal slurry circulating crystallizer, is a type of evaporative crystallizer with a flow tube and a baffle plate. The lower part of the device is connected with a elutriating column, and the device is provided with a flow guide cylinder and a barrel-shaped baffle plate. During operation, the hot saturated material liquid is continuously added to the lower part of the circulation pipe, and mixed with the mother liquid containing small crystals in the circulation pipe, and then pumped to the heater. The heated solution flows into the crystallizer near the bottom of the deflector and is sent to the liquid surface along the deflector by a slowly rotating propeller. The solution evaporates and cools at the liquid surface, reaching a supersaturated state, in which part of the solute is deposited on the surface of the suspended particles, making the crystals grow. There is also a settling zone outside the ring baffle.