Reducing NOx emissions from a circulating fluid bed combustor

This paper describes improvement in a circulating fluidized bed combustion zone wherein a carbon and nitrogen-containing fuel is burned at an elevated temperature by contact with oxygen-containing as in a generally vertical combustor comprising a fast fluidized bed of particulates wherein at least a majority of the particulate matter in the fast fluidized bed has a particle diameter in excess of .100 microns, to generate a flue gas/particulate stream which is discharged from the top of the combustor, the flue gas comprising excess oxygen, nitrogen oxides (NOx), fines having a particle diameter less than about 100 microns, and circulating particles having an average particle size of about 100--500 microns, which flue gas passes through a separation means to recover from the flue gas at least a majority of the 100-500 micron particles which are recycled to the circulating fluidized bed combustion zone. The improvement comprises burning the fuel in the presence of a catalytically effective amount of a DeNOx catalyst which reduces the amount of NOx present in the flue gas relative to operation without addition of a DENOx catalyst