REACTION OF CHAR NITROGEN DURING FLUIDIZED-BED COAL COMBUSTION - INFLUENCE OF NITRIC-OXIDE AND OXYGEN ON NITROUS-OXIDE

The conditions that favor the formation of nitrous oxide from char under fluidized bed combustion conditions are shown to be the oxidation of the char to make the nitrogen bound in the heterocyclic rings accessible so that it can react heterogeneously either with oxygen to form NO or with nitric oxide to form N2O. This was demonstrated by measurement of the gas composition when a batch of coal particles was introduced into a fluidized sand bed electrically heated to 1023 K. Oxygen and nitric oxide were added to the fluidizing helium gas in varying concentrations. N2O was formed in amounts that increased with increasing NO concentration showing the importance of NO for N2O formation. The N2O concentration, however, fell to zero when the O2 supply was interrupted underlying the essential role of oxygen in freeing the organically bound nitrogen so that it can react with NO to form N2O.