The basic principle of spray drying is that the material is transported to the atomizer at the top of the spray dryer through the filter by the pump, and the liquid material is dispersed into droplets by using the atomizer, due to the small radius of the droplets, the large specific surface area and surface free energy, and the high degree of dispersion, and the vapor pressure of the moisture on the surface of the droplets is larger than that of the plane of the same conditions of the liquid, so the moisture evaporation is extremely fast, and the products are rapidly dried. Dai life and so on according to the conservation of mass, conservation of energy and Newton's second law deduced a one-dimensional bidirectional static mathematical model of the spray drying process, from the theoretical study of the thermal drying mechanism of spray drying, spray drying to improve the technical level of the spray drying of great significance.

　　Spray granulation dryer is a new type of one-step granulation equipment that organically combines spray drying technology and fluidized bed granulation technology into one, using the induced draft fan negative pressure suction to make the droplets dry, aggregated into granules, and can be adjusted according to the requirements of the particle size, which is more powerful than the general equipment in terms of function.

　　Spray granulation dryer in the working process will be a certain amount of powder material into the fluidized bed as a crystal seed, the liquid material is pumped to the nozzle atomizer, first with the spray with high-temperature air instantly remove part of the water, the residual water in the bottom of the fluidized bed at low temperatures to complete the drying and at the same time into the granule.

　　First of all, the material liquid (solution, suspension, extract, paste) through the atomizer uniformly sprayed to the inert particles in a fluidized state, the inert particles in the distribution plate above, by the distribution plate through the impact of hot air and fluidization. Hot air in the inert particles fluidized at the same time, but also the heat transfer to the particles. When the material sprayed to the particle surface, accept the heat of the particles (from the inside out) and the heat of the hot air (from the outside to the inside) so that the water evaporates quickly, the material on the surface of the particles to form a thin shell. Material from the elastic shrinkage into elastic brittle, due to the violent movement of the particles produce collision and friction, so that the dried material from the particle surface off, and was ground into a fine powder, was dispersed state with the exhaust brought out by the gas-solid separation device collection. The working process can be roughly divided into three stages, that is, the material coated in inert particles on the surface, the moisture by the heat gasification material drying, dry material off.