Nitrogen oxide control using internally recirculated flue gas

Claim 1

An improved burner assembly for a furnace having a combustion zone in which internally recirculating flue gas is created by a combustion flame therein, the furnace having a wall portion and a furnace floor with an inlet port for intake of a combustion supporting fluid, the burner assembly comprising: burner means for combusting a fuel with the combustion supporting fluid to produce the combustion flame, the burner means comprising: a primary fuel nozzle disposed at the inlet port; a burner tile supported by the furnace floor and surrounding the primary fuel nozzle; and a plurality of secondary fuel nozzles extending from the furnace floor and peripherally disposed about the burner tile; means for directing internally recirculating flue gas in the furnace into reaction contact with the combustion flame so that the collected internally recirculating flue gas is reacted with the combustion flame so that the NO x content of the flue gas exhausted from the furnace is substantially diminished while maintaining stability of the combustion flame, the means for directing internally recirculating flue gas comprising: eductor means for driving internal flue gas into the combustion flame when passing a pressurized fluid, the eductor means having at least one eductor pump with an inlet end thereof in communication with internal flue gas and an outlet end directed towards the combustion flame zone; and flue gas gathering means for collecting and directing internal flue gas to the eductor means so that the inlet of each eductor pump is supplied internal flue gas, the flue gas gathering means comprising: a barrier 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 of the furnace, the fluid gas tunnel having fluid communication with the inlet of each eductor pump, the secondary fuel nozzles and the flue gas tunnel cooperating to aspirate a portion of the collected flue gas into the combustion flame.