During the operation of spray drying tower, the inlet hot air temperature and outlet air temperature is very important. Exhaust air temperature is related to the moisture content so it should be decided by the acceptable moisture content of the product. The higher the hot air temperature is, the higher the efficiency is and the better the economical efficiency is. However, excessive hot air temperature will lead to poor product quality. As a result, hot air temperature must be appropriately raised on the premise of ensuring product quality.

The hot air temperature of spray dryer will have a obvious effect on the bulk density of product. High temperature hot air tends to produce low bulk density, which is due to the rapid drying effect of hot air, which hardens the surface of the particles and causes the residual moisture to expand, and promotes the formation of air-spherical hollow particles. If it requires high bulk density or solid particles, then the design should not make high temperature hot air contact with formative fogdrop. In the drying of chemicals, the hot air temperature is up to 538 ℃ and the product particles are huge. We can find that residual steam has enough pressure blow holes into the outer surface. During the spray drying of food, the hot air temperature usually is not exceeding 177℃ so the initial diameter of the formative hollow particles is not as big as that of chemicals.

The inlet hot air temperature of spray drying machine affects evaporation intensity directly. According to nonthermosensitive materials, high temperature hot air should be used as far as possible to improve the evaporation intensity.