Study of the performance, simplification and characteristics of SNCR de-NOx in large-scale cyclone separator

•The optimized mechanism of the SNCR reaction was presented verified.•The optimized mechanism and CFD software were combined to simulate the process of SNCR de-NOx.•CFD software was used to study gas–solid characteristics. CHMKIN software was used to optimize the mechanism of SNCR reaction. Then the optimized 18-element mechanism and CFD software were combined to simulate the process of SNCR de-NOx and meanwhile the gas–solid characteristics in a cyclone separator of a supercritical CFB boiler were studied. The gas–solid characteristics and SNCR characteristics of the large-scale cyclone separator were obtained. The total pressure difference of the cyclone separator increases with the inlet velocity, and the rate of increase increases gradually. When the inlet velocity is 20m/s, the total pressure difference is 1987.6Pa. The classification efficiency of the cyclone separator increases with the inlet velocity, but the rate of increase decreases gradually. When the inlet velocity is 20m/s, the classification efficiency is 66.74%. The window of the reaction temperature for the SNCR process is in the range of 1123–1323K. The de-NOx efficiency first increases and then decreases with the increase of temperature, reaching a peak at 1223K. At low temperature, improving the NSR has little effect on the de-NOx efficiency. When the reaction temperature is in the temperature window, improving the NSR can effectively enhance the de-NOx efficiency. But after increasing the NSR to a certain extent, the de-NOx efficiency increase will slow down. Setting NSR=1.5 is suitable.