Abstract: To assess the co-firing adaptability of the oversize fraction of aged landfill waste (AG) in a mechanical-grate municipal solid waste incinerator, a coupled FLIC-Fluent model was developed for an 850 t/d unit, with AG blending ratios ranging from 0 to 70%. Combustion stability was compared for co-firing AG with high-calorific-value municipal solid waste (MSW-A) and conventional municipal solid waste (MSW-B). Using MSW-A as the representative base waste, NOx formation and selective non-catalytic reduction (SNCR), fly-ash erosion, and high-temperature chlorine corrosion were further investigated. The results showed that with the increase of AG blending ratio, the lower heating value of the mixed waste reduced, the ignition position delayed, the furnace temperature and high-temperature gas residence time decreased, and local low-temperature zones enlarged. Optimizing the secondary-air injection angle improved local gas mixing and temperature-field uniformity. For MSW-A, the increase in NOx concentration with AG blending was consistent with the enhanced influence of fuel-nitrogen input, but the contributions of individual NOx formation pathways were not quantitatively separated. After selecting the appropriate injection level for each case according to the 850-1 050 ℃ temperature window, SNCR using 15% aqueous ammonia resulted in model-predicted NOx concentrations below 200 mg/m3, with predicted removal efficiencies ranging from 31.5% to 58.0%. These differences were jointly affected by the temperature field, injection level, and gas-mixing conditions rather than directly caused by AG blending. Severe fly-ash erosion was mainly located at the contraction of the second flue and the rear wall of the third flue. Although AG blending increased the HCl concentration, the accompanying decrease in furnace temperature reduced the predicted corrosion rate on some heating surfaces, while Wall 3 exhibited the highest corrosion risk. Considering combustion stability, NOx control, fly-ash erosion, and high-temperature chlorine corrosion, the recommended AG blending ratio for MSW-A was no more than 30% under the investigated furnace and fuel conditions. For MSW-B, which was evaluated only in terms of combustion stability and high-temperature combustion conditions, the AG blending ratio should be limited to 20%. The results are intended for relative trend analysis and engineering risk screening under the investigated conditions.

Key words: co-combustion of aged stockpiled MSW, SNCR denitrification, fly ash abrasion, high-temperature acid corrosion