STUDY OF N2O FORMATION CHARACTERISTICS IN CHAR COMBUSTION

Formation/destruction characteristics of nitrous oxide (N2O) in bubbling fluidized - bed coal combustion, especially in char combustion, were experimentally studied, using a fixed-bed reactor in which char particles were packed in a single layer. In the combustion experiment, such combustion parameters as bed temperature, supplied oxygen concentration and char type were varied. The change of gas species concentration and compositions in the burning char were analyzed during the char combustion process. In the initial stage of char combustion NO was produced rapidly, but N2O concentration increased slowly. This result is caused by N2O destruction due to H radical, which is produced from the oxidation of CO. In the latter half of combustion, however, N2O concentration increased faster since the formation rate of H radical decreased. The N2O concentration increased with decreasing bed temperature and with increasing supplied O2 concentration. This tendency is similar to that in the volatile combustion. From chemical and physical analyses of the burning char particles, the evolution behavior of N-component is influenced by the difference in surface and internal structures (network or balloon type) during the char combustion.