Once the ring formation of rotary kiln, it hinders the smooth flow of air. The kiln head has a positive pressure phenomenon. Most of the high-temperature air flow in the kiln is blocked in the front of the ring body, so that the air flow in the kiln can not be evenly distributed. The materials behind the ring body can not fully absorb heat. The material in the kiln is affected by powder dust, and its movement mode changes from rolling state to sliding state. The material can not be evenly heated The quality of calcination can not be guaranteed