Process intensification and emissions reduction in co-incineration of municipal solid waste and sewage sludge: A full-scale modeling study.

The co-incineration of municipal solid waste (MSW) with sewage sludge (SS) is pivotal for urban waste-to-energy strategies, yet its operational instability poses significant challenges for environmental management, leading to incomplete combustion and elevated pollutant emissions. This study investigates how to minimize its environmental footprint by optimizing key operational parameters. A validated three-dimensional full-scale unsteady-state model of a 500 t/d mechanical grate incinerator was developed to simulate the real incineration process. It systematically quantified the impact of fuel heterogeneity on combustion stability and pollutant generation under different sewage sludge blending ratios, sewage sludge moisture content, and primary air distribution ratio. Results demonstrate that exceeding a sewage sludge blending ratios of 7 % induces calorific value dilution and stratified combustion, shifting the drying zone outward by 0.2-0.6 m and increasing the risk of incomplete combustion. Similarly, sewage sludge moisture content above 40 % extends the main combustion zone by 0.8-2.5 m, substantially raising CO emissions. Critically, this study proposes and validates an optimized primary air distribution ratio scheme (1.2:1.5:2.5:2.5:1.2:1.1) as a process intensification strategy. This management lever effectively enhances fuel drying and reactor environment, achieving a carbon burnout rate of 99.4 % and reducing CO emissions to 0.006 % in the MSW/SS co-incineration process. This work translates complex combustion mechanisms into actionable operational thresholds and control strategies, providing a robust simulation-driven framework for plant managers and policymakers to optimize co-incineration performance, minimize environmental footprint, and advance sustainable waste management.