Nitrogen oxide control using internally recirculated flue gas

Claim 1

In combination with a burner assembly disposed to provide a combination flame in the combustion zone of a furnace in which internally recirculating flue gas is created, the furnace having a wall portion and a furnace floor portion which supports the burner assembly, the burner assembly having a burner tile surrounding a primary fuel nozzle disposed centrally to an inlet port for intake of a combustion supporting fluid, and the burner assembly having a plurality of secondary fuel nozzles peripherally disposed about the burner tile, the improvement comprising: flue gas recirculating means disposed in the furnace for collecting and directing internally recirculating flue gas into the vicinity of the secondary fuel nozzles so that the collected internal flue gas is aspirated into reaction contact with the combustion flame so that the collected internally recirculating flue gas is reacted with the combustion flame to substantially diminish the NO x content of the flue gas exhausted from the furnace, the flue gas recirculating means comprising: a barrier member disposed in proximity to the furnace floor portion and cooperating therewith to form a flue gas tunnel, the flue gas tunnel having an opening to collect internally recirculating flue gas from near the wall portion of the furnace, the barrier member having a central opening disposed about the wall portion of the burner tile to form a flue gas discharge gap therebetween; and the secondary fuel nozzles supported in near proximity to the flue gas discharge gap so that a portion of the internally recirculating flue gas collected in the flue gas tunnel is aspirated into reaction contact with the combustion flame when fuel is dispensed by the secondary fuel nozzles.