Rotary dryer is the most commonly used drying equipment. It has the advantages of simple structure, reliable operation, high efficiency, strong adaptability. It is applicable to dry large particles, high specific gravity material in chemical industry, mining, metallurgy and other industries . Such as: ore, blast furnace slag, coal, metal powder, phosphate, ammonium sulfate. and powder, granular materials with special requirements, such as: foam, lees residue, precipitated calcium carbonate, activated clay, magnetic powder, graphite, dregs. Rotary dryer structure features: Dryer consists of wet material belt machine, a combustion chamber, rotary drying machine body, dry material belt machine, cyclone dust collector, precipitator, exhaust fan, a chimney, spiral conveyer. Rotary dryer is the subject of a rotating cylinder with certain slope body, angle of inclination of 3°-- 6°rotation speed of 2-8 r/min. Cylinder is equipped with a tire and the ring gear and supported by the tire on the wheel. On one side of the tire of the drive is fitted with gear wheel, to limit the cylinder traverse along the tilt direction . Under the action of the driving device , cylinder rotates through the ring gear. Rotary dryer working principle: The wet material is added from the feeder to drum body. Cylinder has a certain inclination and rotates continuously, which makes the material under the action of gravity move from high to low. Materials and high-temperature flue gas as a drying medium enter into the dryer cylinder body under the action of the suction of the exhaust device . Material in the process of gradually moving exchanges heat with high-temperature flue gas in the way of convection, radiation, conduction. The material is heated, the water evaporation to dryness medium, and the water contained in the material is taken away, which is the mass transfer process. After drying, the material is discharged from the low-end, the material residence time in the dryer about 20 to 40 min. Exhaust gas also flows from low pressure site to high pressure site. Material is unloaded from the dryer after drying and the exhaust gas is discharged to the atmosphere by the dust collector.