Low NO.sub.x burner system

A low NO.sub.x burner system for a furnace having spaced apart front and rear walls connected between spaced apart side walls, the furnace including a lower hopper, the system comprising:

• a plurality of cell burners lying along at least one horizontal row in at least one of the front and rear walls, each cell comprising a coal nozzle for projecting a primary air plus coal mixture into the furnace, and a secondary air port spaced vertically from the coal nozzle for supplying secondary air into the furnace at a vertically spaced yet adjacent location to the primary air plus coal mixture supplied to the furnace;
• means for supplying primary air and coal to the coal nozzle;
• means for supplying primary air and coal to the coal nozzles;
• means for supplying secondary air to the secondary air ports;
• and
• means for supplying from 2 to 10% of the total air through the hopper into the furnace.

A low NO.sub.x burner system for a furnace having spaced apart front and rear walls connected between spaced apart side walls, the furnace including a lower hopper, the system comprising:

• a plurality of cell burners lying along at least one horizontal row in at least one of the front and rear walls, each cell comprising a coal nozzle for projecting a primary air plus coal mixture into the furnace, and a secondary air port spaced vertically from the coal nozzle for supplying secondary air into the furnace at a vertically spaced yet adjacent location to the primary air plus coal mixture supplied to the furnace;
• means for supplying primary air and coal to the coal nozzles;
• means for supplying secondary air to the secondary air ports;
• and
• each coal nozzle including an inner conduit for carrying a primary air plus coal mixture into the furnace, each inner conduit having a front end near the front or rear wall of the furnace, an outer conduit around the inner conduit defining a space for secondary air around the inner conduit and into the furnace, and a shallow angle impeller at the front end of the inner conduit.