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.

污泥焚烧被广泛认为是一种极具应用前景的能源回收途径。然而，该燃烧过程会产生大量污染物，而其释放特性与作用机理目前仍未得到充分阐释。本研究通过实验构建污泥燃烧模型，并提出了一套包含75种组分与463个自由基反应的详细反应机理。采用误差传播导向关系图（Directed Relation Graph with Error Propagation，DRGEP）与路径通量分析导向关系图（Directed Relation Graph with Path Flux Analysis，DRGPFA）对该机理进行简化，最终得到包含36种组分与208个自由基反应的简化机理。基于该简化机理，本研究针对不同温度、过量空气系数与停留时间条件下的C、N、Cl等污染物排放特性开展分析。研究结果表明，实验数据与简化机理的模拟值具有良好的一致性。进一步分析显示，当停留时间为4秒、过量空气系数为1.38时，温度对污染物排放具有显著影响。在800℃~1000℃的温度区间内，CO浓度降低了3115 mg/m³，N₂O浓度降低了47.5 mg/m³，而NO与HCl浓度分别升高了46.07 mg/m³与55.37 mg/m³。此外，在恒温与固定停留时间条件下，过量空气系数的提升会促进NO的生成。