In this study, two connected drop tube furnaces (DTFs) were used to clarify the NO emission characteristics during the high-temperature preheating-combustion process. The most important factors, including preheating temperatures, residence times, and excess air ratios (EAR), were studied systematically. Experimental results showed that both increasing the preheating temperature and prolonging the residence time in the preheating zone promoted the release of coal-N as volatile-N, the reduction of volatile-N, and the interaction between char-N and nitrogen-containing gases, and therefore enhanced NO reduction. With the EAR increased in the preheating zone, the NO emission first decreased and then increased. There was an optimal EAR for NO reduction, which was 0.4 in this work. Meanwhile, the lowest NO emission was 223 mg·m⁻³, corresponding conversion ratio of coal-N to NO was 12.6% and NO removal efficiency was 60.38%. Moreover, kinetic modeling confirmed the experimental results, and rate of production (ROP) analysis indicated that the main radicals for NO destruction were NH₂, hydrocarbon (C_iH_j), HCCO, NCO and HCO. In addition, the NO reduction by C_iH_j was stronger than other nitrogen-containing compounds, except NH₂, which contributed nearly 30% of overall NO destruction.

在这项研究中，使用了两个相连的下降管式炉（DTF）来阐明高温预热燃烧过程中的NO排放特征。系统地研究了最重要的因素，包括预热温度，停留时间和过量空气比（EAR）。实验结果表明，提高预热温度和延长在预热区的停留时间均促进了煤-N挥发物-N的释放，挥发物-N的减少以及焦炭-N与含氮气体之间的相互作用，因此增加了NO的减少。随着在预热区中EAR的增加，NO排放量先减少然后增加。对于减少NO，有一个最佳的EAR，在这项工作中为0.4。同时，最低NO排放为223 mg·m ^-3，相应的煤氮转化为NO的比例为12.6％，NO去除效率为60.38％。此外，动力学建模证实了实验结果，并且产率（ROP）分析表明，破坏NO的主要自由基是NH ₂，烃（C _i H _j），HCCO，NCO和HCO。另外，NO还原为C_我ħ _Ĵ比其它的含氮化合物更强，除NH ₂，其贡献了近30％的总NO破坏。