LAUSR

Abstract Air-staging combustion is the widely-used low-nitrogen combustion technology. In this process of NOx reduction, the role played by CO resulted from the air-staged combustion cannot be ignored. In this study, quantum chemistry method is used to investigate the effects of the CO on the NOx generation/reduction and on the char surface. Theoretical calculations indicate that CO is involved in nitrogen fixation during the migration and transformation of N. During the oxidation of N-containing char, CO increases the binding energy of N of pyridine with adjacent C atoms, which is not conducive to the N precipitation. During reduction of NOx by char, CO decreases the desorption energy barrier of N2 and promotes NO heterogeneous reduction. On the other hand, CO promotes the re-embedding of N in generated NO into the char to form char-N. XPS experiments are carried out for the coal char samples after the air-staged combustion. The experimental results show that high CO concentration is conducive to retention N. When the excess air coefficient (α) is 0.8, the increase of N-6 content is 7.2% larger than that of α = 0.9. This work discovers the nitrogen fixation of CO, enriches and expands the understanding of the role of CO.