Experimental study on the influence of operating parameters on NOx and N2O emissions during co-firing of NH3 and coal in a CFB

Abstract

Co-firing NH3 in a circulating fluidized bed (CFB) boiler holds promise as a technology for reducing CO2 emissions, yet NOx and N2O emissions remain a concern, and they are influenced by operation parameters. This study investigated the effect of NH3 co-firing ratio, operation oxygen concentration, bed temperature, and primary air fraction on NOx and N2O emissions in a CFB combustor. NOx and N2O concentrations along the furnace height were measured. The results indicated that the emissions of NOx and N2O increased when NH3 co-firing ratio increased. Their generation is mainly concentrated in the vicinity of the secondary air inlet. Elevating oxygen concentration facilitated NOx and N2O formation, in which N2O is more sensitive to oxygen. A 5 % operation oxygen concentration proved advantageous for limiting NOx and N2O emissions, as well as promoting NH3 burnout. Temperature exerted a greater influence on promoting NOx formation compared to operation oxygen concentration. As the primary air fraction increased, NOx initially decreased before rising, while N2O exhibited minimal change. A primary air fraction of approximately 0.58 might be a suitable choice for NOx emission control.