A review on nitrogen migration mechanism during the pyrolysis of organic solid waste: DFT, ReaxFF MD and experimental study

Pyrolysis is an important stage of combustion. During this process, the nitrogen element in organic solid waste (OSW) is converted into NOx precursors (HCN, NH3, and HNCO). These precursors react with free radicals such as H, OH, and O during the subsequent combustion process to generate nitrogen oxides. Therefore, clarifying the mechanism of nitrogen migration during pyrolysis is of great significance for realizing the clean utilization of OSW. This paper firstly summarized the occurrence forms of nitrogen elements in different types of OSW. Subsequently, based on the nitrogen-containing intermediates during the pyrolysis process, the migration and transformation mechanism of nitrogen of OSW were also reviewed. This paper focused on the pyrolysis process of protein-N and DKPs, namely, to calculate the formation path and energy barrier of NOx precursor using molecular simulation (i.e. Density Functional Theory and Reactive Force Field). At the same time, the detailed interaction process between the catalyst and OSW reactants, as well as the influence of process parameters, were analyzed. Finally, the synergistic effects of nitrogen-containing model compounds and other substances (such as cellulose, hemicellulose, glucose, etc) as well as the development direction of new supported catalysts, were prospected.