According to the structural characteristics of the flash dryer, the working process is divided into four stages: crushing, gas-solid contact, drying and classification. The working principle is: the pulverization of the slurry and the airflow is carried out immediately after the material enters the flash dryer to increase the dispersion of the material and the surface area of ​​the wet material per unit volume. Since the agitator pulverizes the material and produces a dispersion effect, the hot air entering the drying chamber is also in a state of high turbulence, and the gas-solid mixing is quickly achieved, so that the bulk material is in a good fluidized state and surrounded by the hot air. During the drying process of mass transfer heat transfer between the material and the hot air, most of the water evaporates at this stage. After the material is crushed and the water evaporates, the buoyancy is greater than gravity, and the material moves upwards and enters the classifier. The material spirals up under the entrainment of the gas. Under the action of centrifugal force, the particle size of the material is small in the inner ring, and the larger and drier is in the outer ring. The small particles are taken out from the center of the drying chamber when the moisture reaches the requirement, and the larger wet particles continue to be pulverized and dried, thereby ensuring uniformity of water content and particle size of the product. The flash dryer is a vertical fluidized bed drying device with a rotary pulverizing device, mainly used for drying paste materials. The main body is a cylindrical drying chamber, which is composed of a pulverizing fluidized section at the bottom, a middle drying section and a top grading section, and can simultaneously perform operations such as pulverization, drying and grading of materials. The flash dryer has the following structural features: (1) The bottom of the drying chamber of the flash dryer is an inverted tapered structure equipped with a stirrer. The inverted tapered structure expands the hot air circulation cross section from bottom to top, and the bottom gas velocity is high, and the upper gas velocity is low, so that the lower large particles and the upper small particles can be in a good fluidized state. The inverted tapered structure also shortens the length of the agitator shaft cantilever and increases operational reliability. (2) A stepping ring is arranged on the upper part of the drying chamber of the flash dryer. The function of the classification ring is mainly to make the particles larger, or the materials that have not been dried are separated from the qualified products, and the unqualified products are blocked in the drying room, which can effectively ensure the particle size and moisture requirements of the products. (3) The flash dryer drying system is closed. The drying process is continuously operated, and the feeding amount, hot air temperature and product particle size can be controlled within a certain range, thereby ensuring various indexes of the dried product. (4) Set crushing, drying and grading into one. The flash dryer has optimized functions, compact structure and small footprint. The flash dryer is an optimized combination of fluidization technology, swirling technology, spray technology and convection heat transfer technology, which greatly simplifies the production process and saves equipment investment and operating costs.