Nitric Oxide Emission From Fluidized Bed and Circulating Fluidized Bed Coal Combustors

　Systematic measurements were made on the nitric oxide (NOx) emission levels from different types of experimental fluidized bed coal combustors; three bubbling bed combustors (FBC) and a circulating bed combustor (CFBC). Among the FBC types, the lowest emission level was observed in the case of a dual-bed mode with staging air supply. The emission level from the CFBC combustion was as low as that from the dual-bed combustion when silica sand particles were used as a circulating solid. However, a remarkably higher emission level was observed when fresh limestone particles were employed. This difference in the emission levels dependent on the circulating solid could qualitatively be explained by the reaction model previously proposed by the authors.