The special air pressure sealing device and bearing cooling device of the rotary flash dryer of Jiangsu Taian drying equipment manufacturing Co., Ltd. effectively extend the service life of the transmission part. The larger and wetter particles are mechanically broken under the action of the agitator, and the particles with lower moisture content and smaller particle size are entrained and raised by the rotary airflow, and further dried in the rising process. A special cooling device is set at the bottom of the rotary flash dryer to avoid the deterioration of the materials in the high temperature area at the bottom. The inlet pipe enters the mixing and crushing drying chamber from the bottom of the dryer at an appropriate spouting speed, causing strong shear, collision and friction to the materials, which leads to the granulation and enhances the mass and heat transfer.