Integrated low NO.sub.x tangential firing system

An integrated low NO.sub.x tangential firing system for a pulverized solid fuel-fired furnace having a plurality of walls embodying therewithin a burner region containing a multiplicity of combustion zones of differing stoichiometries comprising:

• a. a pulverized solid fuel supply means for supplying pulverized solid fuel of a predetermined fineness;
• b. a windbox mounted within the burner region of the pulverized solid fuel-fired furnace;
• c. a plurality of pulverized solid fuel compartments mounted within said windbox;
• d. a flame attachment pulverized solid fuel nozzle tip supported in mounted relation within each of said plurality of pulverized solid fuel compartments, each of said plurality of flame attachment pulverized solid fuel nozzle tips, being connected to said pulverized solid fuel supply means for receiving therefrom pulverized solid fuel of a predetermined fineness, said flame attachment pulverized solid fuel nozzle tips being operative to effect the injection therethrough into the burner region of the pulverized solid fuel-fired furnace of the pulverized solid fuel of a predetermined fineness received thereby from said pulverized solid fuel supply means in such a manner that the ignition point of the injected pulverized solid fuel of a predetermined fineness is located less than two feet from said flame attachment pulverized solid fuel nozzle tips;
• e. a plurality of combustion supporting air compartments mounted within said windbox, said plurality of combustion supporting air compartments being operative to inject therethrough into the burner region of the pulverized solid fuel-fired furnace a sufficient quantity of combustion supporting air such that the stoichiometry is between 0.4 and 0.75 in a first combustion zone of the burner region of the pulverized solid fuel-fired furnace;
• f. at least one close coupled overfire air compartment mounted in said windbox, said at least one close coupled overfire air compartment being operative to inject therethrough into the burner region of the pulverized solid fuel-fired furnace a sufficient quantity of close coupled overfire air such that the stoichiometry is between 0.7 and 0.9 in a second combustion zone of the burner region of the pulverized solid fuel-fired furnace;
• g. a low level of separated overfire air located in spaced relation to said windbox within the burner region of the pulverized solid fuel-fired furnace, said low level of separated overfire air being operative to inject into the burner region of the pulverized solid fuel-fired furnace a sufficient quantity of separated overfire air such that the stoichiometry is between 0.9 and 1.02 in a third combustion zone of the burner region of the pulverized solid fuel-fired furnace;
• and
• h. a high level of separated overfire air located in spaced relation to both said low level of separated overfire air and said windbox such that the time that it takes for the gases generated from the combustion of the injected pulverized solid fuel to travel from the top of said windbox to the top of said high level of separated overfire air exceeds 0.3 seconds, said high level of separated overfire air being operative to inject into the burner region of the pulverized solid fuel-fired furnace a sufficient quantity of separated overfire air such that the stoichiometry exceeds 1.07 in a fourth combustion zone of the burner region of the pulverized solid fuel-fired furnace.