Combustion optimization and low-NOx control in a waste-to-energy incinerator: The effect of primary and secondary air distribution

To reveal the coupling influence of the mechanism of air distribution within the furnace on combustion and NOx generation, the influence of different primary air ratios and primary-to-secondary air ratios on waste combustion and NOx generation characteristics was numerically studied using the fluid dynamic incinerator code (FLIC) and Fluent software. The findings show that under different primary air distribution ratios, reducing the ratio of primary air in air chamber 1 and increasing it in Chambers 2 and 3 can optimize the combustion efficiency and center the furnace flame. Adjusting the primary–secondary air ratio can enhance turbulence and create a broader vortex zone. When the air distribution ratio between air chamber 1 and air chamber 2 is 0.25:0.45, the NOx concentration at the flue outlet is significantly reduced to 164.1 mg/m3, which represents a 20.8% decrease compared to the 0.40:0.30 air distribution ratio, and moderately increasing the secondary air ratio to 0.31 can further reduce the NO concentration to 142.6 mg/m3. Comprehensive analysis indicates that the optimal air distribution configuration has a primary-to-secondary air ratio of 0.73:0.27, with primary air ratios across chambers of 0.25:0.45:0.15:0.15. These findings can provide a valuable reference for NOx control in grate-type municipal solid waste incinerators.