Spray drier uses hot air to dry misty products. The hot air for drying enters the drying tower from the tower mouth, and the exhaust gas after drying is exhausted by the induced draft fan. During the operation of spray drying equipment, it is very important to control the hot air temperature and exhaust air temperature when the hot air for drying enters the tower, which determines the quality of products and drying bulk density, so it needs to be strictly controlled.

In spray drier operation, the exhaust air temperature is related to the moisture content of the product and should be determined according to the allowable moisture content of the product. The higher the hot air temperature, the higher the thermal efficiency and the better the economic benefit. However, the high hot air temperature will cause the product quality to deteriorate, and its hot air temperature will affect the bulk density of the product.

High temperature hot air has a change of low bulk density, which is due to the drying effect of hot air, which hardens the particle surface and expands the residual moisture, thus forming balloon-shaped hollow particles. If high bulk density (low specific volume) is required, or solid particles are required, high-temperature hot air should not be used in the design to contact with newly formed droplets.

In the drying of chemicals, the hot air temperature can reach 538℃, and the product particles are large. It can be found that the residual steam has enough pressure to blow the outer surface into a cavity. In food spray drying, the temperature of hot air generally does not exceed 177℃, so the initial diameter of hollow particles is not as large as that of chemicals.

In order to prevent wall sticking in spray drier, a drying tower with a wall should be selected and cooled by air to ensure that the wall temperature is always below 50 degrees Celsius. The secondary air introduced by the rotating air sheet on the tower wall is directly tangentially cooled in the tower wall.

A row of air brooms composed of nozzles can be installed in the tower near the wall, and it can be ensured to rotate slowly along the tower wall; Increase the air hammer on the tower wall, and use the air hammer to knock, forcing the materials sticking to the wall to separate; Improving the machining accuracy of the equipment and polishing the inner wall of the tower can actually reduce the wall sticking phenomenon.