Effect of S02 and NO on the Conversion of Fuel Nitrogen to N20 and NO in Single Particle Combustion of Coal

The effects S0 2 and NO concentrations on the emissions of N 2 0 and NO from a single particle of coal burning in a fluidized bed combustor is reported. The experiments were carried out in a laboratory scale quartz glass fluidized bed reactor in the temperature range 1023-1123 K. Since the combustion processes for the volatiles and char are consecutive, the effects of added NO and SO 2 occurring during the volatiles combustion can be distinguished from those occurring during the subsequent char combustion. During the combustion of the volatiles, addition of NO (250 ppm) results in an increased formation of N 2 0, whereas the net NO formation decreases. This effect is enhanced when both NO (250 ppm) and SO 2 (900 ppm) are included in the fluidizing gas mixture. The effect of NO can be explained by the generally accepted gas phase mechanism of NO and N 2 O formation and destruction. The role of SO 2 is less clear, but is likely to involve its impact on the radical concentrations. During the char combustion stage, similar effects are seen, i.e., the N 2 O formation increases in the presence of NO, and is further increased in the presence of both NO and SO 2 0ver the temperature range investigated, the addition of NO, resulted in an increased emission of N 2 O: whereas the effect of SO 2 decreased with increasing temperature.