First, the pulverized coal was too late to burn and was swept away by the strong wind. The induced wind of rotary kiln is too large, and the temperature in the kiln is not high, which leads to the flame being blown out by too strong wind, and the discharged gas is mixed with pulverized coal that is not burned in time, resulting in black smoke.

Second, insufficient combustion of pulverized coal. This reason specifically includes the following situations. ① If the coal quality of rotary kiln is not good and the ventilation effect of rotary kiln is not good, it is easy to emit black smoke; (2) Excessive moisture and coarse particles in rotary kiln coal will cause insufficient fuel combustion and lead to black smoke; ③ Serious ring formation in rotary kiln will lead to poor ventilation effect and insufficient fuel combustion, which will lead to black smoke; (4) The coal under the rotary kiln is not smooth, and when there is a flowing medium phenomenon, it is often accompanied by black smoke emission.