Chemical kinetic analysis of multi-pollutant emissions from high temperature combustion of sewage sludge

The incineration of sludge is widely recognized as a promising method for energy recovery. However, the combustion process generates substantial pollutants, and their release characteristics and mechanisms remain inadequately understood. This study aimed to establish a sludge combustion model through experiments and proposed a detailed reaction mechanism involving 75 components and 463 radical reactions. The mechanism was simplified using Directed Relation Graph with Error Propagation (<i>DRGEP</i>) and Directed Relation Graph with Path Flux Analysis (<i>DRGPFA</i>), resulting in a reduced mechanism with 36 components and 208 radical reactions. Using this simplified mechanism, pollutant emissions such as C, N, and Cl were analyzed under varying temperatures, excess air factors, and residence times. The results demonstrated good agreement between the experimental data and the simulated values of the simplified mechanism. Further analysis revealed that at a residence time 4 seconds and an excess air factor of 1.38, temperature had a significant effect on pollutant emissions. Within the temperature range of 800°C-1000°C, CO concentration decreased by 3115 mg/m³, and N₂O concentration decreased by 47.5 mg/m³, while NO and HCl concentrations increased by 46.07 mg/m³ and 55.37 mg/m³, respectively. In addition, under constant temperature and residence time, an increase in the excess air factor promoted NO formation.