High temperature (up to 1873K) oxy-fuel combustion experiments were conducted on a fixed-bed reactor. Two combustion modes were designed: coupled combustion (volatile combustion and char combustion are simultaneous) and separated combustion (volatile combustion and char combustion are separated and individual). Bases on it, effect of alkali and alkali earth metals (AAEMs) and transition metals (TMs) in coal ash on the fuel-NO release characteristics was studied. Results show that in the coupled combustion, AAEMs accelerate the fuel-NO release rate. Besides, AAEMs decreased fuel-NO release amount by around 10% at different temperatures. This inhibition effect is related to activity of metal elements. The effect of TMs is sensitive to temperature. Mn promotes the oxidation of fuel-N intensively at lower temperature, while Fe and Cu can improve the fuel-NO reduction efficiency at higher temperature. Coal ash is beneficial to NO reduction and the reduction efficiency is higher than 50% at 1873K. In the separated combustion, Mg, Ca and Mn have almost no effect on volatile-NO and char-NO release. Na and K can decrease the volatile-NO and char-NO release amount below 1573K. Both volatile-NO and char-NO reduction efficiency of K and Na decreases from 20% to 0% as temperature rises. Fe and Cu can suppress the release of volatile-NO and char-NO. The volatile-NO reduction efficiency of Fe and Cu increases but the char-NO reduction efficiency decreases with temperature increasing. Coal ash can improve the proportion of volatile-NO in fuel-NO, about 25% at 1573K. At last, the potential catalytic mechanisms in coupled and separated combustion were proposed.

在固定床反应器上进行了高温（最高1873K）的含氧燃料燃烧实验。设计了两种燃烧模式：耦合燃烧（挥发性燃烧和焦炭燃烧是同时发生的）和分离燃烧（挥发性燃烧和焦炭燃烧是分离且单独的）。在此基础上，研究了煤灰中碱金属和碱土金属（AAEMs）及过渡金属（TMs）对燃料NO排放特性的影响。结果表明，在耦合燃烧中，AAEMs加快了NO的释放速度。此外，AAEMs在不同温度下将燃料NO释放量降低了约10％。这种抑制作用与金属元素的活性有关。TM的作用对温度敏感。Mn在较低温度下强烈促进燃料N的氧化，Fe和Cu可以提高高温下的NO还原效率。煤灰有利于NO的还原，在1873K时还原效率高于50％。在分离的燃烧中，Mg，Ca和Mn对挥发性NO和char-NO的释放几乎没有影响。Na和K可以将挥发性NO和char NO释放量降低到1573K以下。随着温度的升高，K和Na的挥发性NO和char-NO还原效率均从20％降低至0％。Fe和Cu可以抑制挥发性NO和char-NO的释放。Fe和Cu的挥发性NO还原效率增加，但char-NO还原效率随温度升高而降低。粉煤灰可以提高挥发性NO在燃料NO中的比例，在1573K时约为25％。最后，提出了耦合燃烧和分离燃烧的潜在催化机理。