Rotary flash dryer and system capable of adjusting product particle size

The utility model discloses a rotary flash evaporation dryer and system capable of adjusting product particle size, the rotary flash evaporation dryer comprises a feeder, a scattering crusher, a hot air inlet, a drying cylinder, a grading cone, a base and a discharge port, the drying cylinder is vertically arranged on the base, the feeder is arranged on the outer side of the bottom of the drying cylinder, and the grading cone is arranged on the discharge port. The scattering and crushing device is arranged at the bottom of the drying barrel, is lower than the feeding hole of the feeder, and is used for scattering and crushing materials; the hot air inlet is formed below the scattering crusher, the grading cone is rotatably arranged at the top of the drying cylinder, and the discharge port is formed above the grading cone. The grading cone comprises an upper ring face, a lower disc face, a transmission rod and a plurality of grading grids, the lower disc face is disc-shaped, the diameter of the lower disc face