Due to the short residence time of ammonia water and flue gas in the calciner, ammonia water in the middle area will be sufficient and excessive, resulting in ammonia gas escaping. A large number of side wall areas are blind areas, which will lead to the failure of denitration reaction of dusty flue gas. The final result is that ammonia water consumption is high, ammonia escape is high, nitrogen oxides can not meet the ultra-low emission requirements, and denitrification efficiency is not high, which is also a common problem in SNCR denitrification operation in domestic cement industry.