Influence of operating parameters on NOx and N2O axial profiles in a circulating fluidized bed combustor

Abstract This paper reports an experimental investigation of the influence of operating parameters on the formation and reduction of NO x and N 2 O from coal combustion, carried out in a circulating fluidized bed combustor 6.2 m high and 0.161 m i.d. The main operating parameters studied were temperature, excess air factor, secondary/total air ratio, limestone addition and coal particle size. It was found that the NO x emission increased whereas the N 2 O emission decreased when the temperature increased, but the effect of the temperature depended on the excess air factor. Both the NO x and the N 2 O emissions increased with increasing excess air factor and decreased with increasing secondary/total air ratio. Moreover, the NO x emission increased and the N 2 O emission decreased with limestone addition and with increasing coal particle size. Unlike previous studies in which only the exhaust gases were the focus, here an attempt was made to analyse the NO x and N 2 O axial profiles to improve understanding of the formation and destruction of these pollutants. Analyses of the NO x and N 2 O concentration profiles along the riser height suggested that the NO x formed in the bottom was gradually reduced along the height of the combustion chamber and that the N 2 O concentration increased from the bottom to the top of the combustion chamber for all the operating conditions.

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