DTB crystallizers can be divided into two types according to different material process routes: continuous evaporation crystallization and continuous cooling crystallization. According to material properties and energy-saving considerations, it can be divided into multi-stage flash evaporation DTB crystallizers and multi-stage cooling DTB crystallizers. The DTB cooling crystallizer adopts an external tube heat exchanger for cooling, which removes the heat from the clarified mother liquor with the coolant, and then sends it to the bottom of the crystallizer through a circulation pump, forming an external circulation channel. This device can achieve continuous operation, high production intensity, and high efficiency; Good mixing effect inside the device, uniform distribution of supersaturation, and less prone to crystallization scars; The crystal products have good quality, coarse particles, and uniform particle size distribution. They can produce large crystalline products with particle sizes up to 500-2000 μ m, which can fully meet the requirements of users for different particle size distributions of product crystallization. The DTB cooling crystallizer is suitable for the crystallization of products such as barium chloride, ferrous sulfate, potassium chloride, magnesium sulfate, potassium sulfate, sodium carbonate, sodium dihydrogen phosphate, disodium hydrogen phosphate, trisodium phosphate, potassium dihydrogen phosphate, ammonium dihydrogen phosphate, urea phosphate, and sodium hypophosphite.