The flash dryer consists of a dry main engine, feeder, heat source device (hot air furnace or steam), air filter, air blower, cyclone separator, bag filter, and induced draft fan. The hot air tangentially enters the bottom of the dryer and is driven by the agitator to form a powerful rotating wind field. The paste material enters the dryer by the screw feeder. Under the strong action of the high-speed rotating stirring paddle, the material is dispersed under the action of impact, friction and shearing force, the block material is rapidly pulverized, and it is fully contacted with hot air and heated, and dry. The dehydrated dry material rises with the hot gas flow, and the classification ring intercepts the large particles. The small particles are discharged from the center of the ring to the outside of the dryer and are recovered by the cyclone separator and the dust collector. The dry material is not dried or the bulk material is subjected to centrifugal force, fell to the bottom and was crushed and dried.