Abstract: A damper box for an orifice air injector, the damper box comprising front and rear faces with respective front and rear openings therein, a pair of sides, a top and a bottom; and a pair of gates pivotally mounted within the damper box and actuatable between open and closed positions.

Abstract: A damper box for an orifice air injector, the damper box comprising front and rear faces with respective front and rear openings therein, a pair of sides, a top and a bottom; and a pair of gates pivotally mounted within the damper box and actuatable between open and closed positions.

Abstract: A low NO.sub.x burner system for a furnace having spaced apart front and rear walls, comprises a double row of cell burners on each of the front and rear walls. Each cell burner is either of the inverted type with a secondary air nozzle spaced vertically below a coal nozzle, or the non-inverted type where the coal nozzle is below the secondary air port. The inverted and non-inverted cells alternate or are provided in other specified patterns at least in the lower row of cells. A small percentage of the total air can be also provided through the hopper or hopper throat forming the bottom of the furnace, or through the boiler hopper side walls. A shallow angle impeller design also advances the purpose of the invention which is to reduce CO and H.sub.2 S admissions while maintaining low NO.sub.x generation.