Coupled low NOx control of MSW incineration based on flue gas recirculation and flow field optimization

Reducing NOx emission in flue gas is currently an essential issue in municipal solid waste incineration. Based on an 850 t/d waste incinerator, the denitrification roles of secondary air arrangement, flue gas recirculation (FGR), and SNCR technologies in the waste incineration process were studied using numerical simulation. The impact of different secondary air layouts, secondary air injection angles, and air distribution ratios on the temperature field and NOx emission inside the incinerator were investigated. The denitrification effect of the combined application of these measures was also considered. The findings indicated that the flue gas temperature was lower, and the mixing degree was higher in the double cut-circle layout than in the hedging layout, which enhanced the NOx removal performance of FGR. Appropriately increasing the SA ratio and the FGR injection angle contributed to reducing NOx emission. By increasing the injection angle from 15 degrees to 55 degrees, the NOx concentration at the third flue outlet was decreased by 29.71 mg/Nm3, and the NOx removal effect was improved by 12.2%. When both FGR and SNCR were utilized, the best NOx removal performance (76.21%) was achieved with the optimized secondary air arrangement, demonstrating that combining denitrification technologies based on flow field optimization could achieve lower NOx emission during incineration.