1. uneven feeding and excessive fluctuation; 2. There is aggregate or crust in the preheater; 3. Improper coordination of system feed air (small air consumption); 4. Preheater flap valve is inflexible; 5. Excessive fuel fluctuation; 6. Improper spreading device; 7. The air leakage of the preheater system is large. Will cause the phenomenon of rotary kiln flushing.