IMPACT OF AIR STAGING ON THE FATE OF NO AND N2O IN A CIRCULATING FLUIDIZED-BED COMBUSTOR

This paper presents an experimental investigation of the influence of combustion-air staging on the formation and reduction of NO and N2O fr om coal combustion, carried out in a 6.2-m-tall and 0.161-m i.d. circu lating fluidized-bed (CFB) combustor. The main operating parameters ex amined were secondary air ratio and air staging position. It was found that NO generated in the primary combustion zone could be effectively reduced in the secondary combustion zone. The effect of combustion-ai r staging on the N2O emissions was found to be relatively small. The a xial concentration profile of N2O along the CFB furnace, however, coul d be significantly influenced by the air staging position. Detailed an alyses were made of the chemistry of NO and N2O formation and reductio n under combustion-air staging conditions. It was revealed that the ax ial distribution of NO and N2O along the CFB furnace could be the comb ined effect of initial distribution of intermediate coal-N, coal combu stion performance and furnace hydrodynamics. Unlike traditional approa ches, in which exhaust gases only are discussed, this paper for the fi rst time introduces analyses of axial profiles of NO and N2O in a CFB furnace under combustion-air staging conditions, which should provide a better understanding of the influence of combustion-air staging on N O and N2O formation and reduction in a CFB furnace.