Numerical simulation of secondary air location effect on waste incineration in a grate boiler

Incineration is an efficient method for solid waste treatment and energy recovery. Secondary air is a critical parameter in the operation of incinerators, yet information on how the position of secondary air affects the incineration of Municipal Solid Waste (MSW) remains poorly understood. Computational Fluid Dynamics (CFD) modeling serves as effective tool for the optimal design and operation of waste incinerators. This study employs ANSYS FLUENT 2021 R1 as the simulation platform to investigate the impact of different secondary air positions on the incineration process in a moving grate incinerator. An optimized incinerator model was developed, featuring three configurations: a baseline case without secondary air and two cases with secondary air inlets at distinct positions. Unlike other secondary air simulations, the solid waste in this study is treated as a porous medium, incorporating chemical reactions related to waste incineration. The results of the FLUENT simulation are visually presented through contour plots, facilitating comparative analysis to determine the optimal configuration for the secondary air inlet. The findings demonstrate that proper secondary air placement significantly reduces soot and pollutant gas concentrations. The CO emissions of pollutant gases was reduced by 92.5%, while the NO concentration was reduced by 95% and 90%, respectively. The model with the secondary air position that yields higher waste calorific value and lower pollutant emissions is identified as the optimal configuration.<i>Implications</i>: This study pioneers a systematic evaluation of how secondary-air port location impacts both combustion performance and emissions in waste-to-energy boilers. The identified optimal air-staging configuration significantly increases waste calorific value while drastically reducing CO and NOx emissions. These results offer concrete engineering guidelines for designing, retrofitting, and operating incineration facilities, enabling immediate technological upgrades globally. Moreover, they provide a scientific basis for stricter emission policies and incentivizing retrofit optimizations, accelerating cleaner waste recovery under carbon‑neutrality goals.