System of close coupled rapid mix burner cells

Abstract

A burner system that utilizes a plurality of single stage rapid mix burner cells which are organized into one or more self-stabilizing matrices. The assemblage combines the advantageous operating characteristics of nozzle mix and premixed type burners and achieves extremely low NO x , CO, and hydrocarbon emissions.

1 . In combination with a boiler or furnace having a refractory bound wall opening for receiving one or more burners; a burner system for mounting at said wall opening that combines the advantageous operating characteristics of nozzle mix and premixed type burners and achieves extremely low NOx, CO, and hydrocarbon emissions; said burner system comprising:
 a plurality of rapid mix burner cells which are configured into a self-stabilizing matrix of side-by-side cells; the individual burner cells terminating in a divergent refractory quarl, and being positioned in said matrix so that the centerlines of adjacent cells are no more than 1.6 burner throat diameters apart both vertically and horizontally;   a common refractory section being formed into the front wall of said system and bordering said matrix, and the flame from each cell exiting into said common refractory section, promoting flame to flame self stabilization and increasing the flame residence time in an environment in which the entrainment of cold furnace gases into the flame is limited; and   the total axial spacing resulting from the said refractory quarl of each burner cell plus the said common refractory section, being at least 20″ before the flame is exposed to externally recirculated furnace gases.   
   
   
       2 . A system in accordance with  claim 1 , wherein each burner cell includes means for swirling the air flow from each cell in the same direction; the rotating burner flow bringing combustion products from the outer portion of the flame, that may have mixed with relatively cold furnace gases, into the reacting zone between the flames from each burner cell, thereby causing the gases rotated between the flames to be reheated and further oxidation of unburned fuel to occur. 
   
   
       3 . A device in accordance with  claim 2 , wherein the said matrix includes two or more of said cells arranged in a single row or column. 
   
   
       4 . A device in accordance with  claim 3 , wherein said matrix includes at least one row and one column of said burner cells, the total number of cells being at least four. 
   
   
       5 . A system in accordance with  claim 2 , wherein each cell of the matrix is a single stage rapid mix burner apparatus comprising:
 an outer shell including a windbox and a first hollow cylinder having an outlet, and an inlet which is in fluid communication with said windbox;   a second hollow cylinder mounted in said shell coaxially with and spaced inwardly from said first cylinder;   an annular flow channel being defined between said first and second cylinder, said channel constituting a throat for oxidant gases provided thereto from said windbox, and having a downstream outlet end for said gases;   means for providing a flow of said oxidant gases to said throat from said windbox;   a divergent quarl being adjoined to said outlet end of said throat and defining a combustion zone for said burner;   a plurality of curved axial swirl vanes being mounted in said annular flow channel to impart swirl to said oxidant gases flowing downstream in said throat;   fuel gas injection means being provided in said annular flow channel proximate to said swirl vanes for injecting said gas into the flow of oxidant gases at a point upstream of said outlet end; and   said fuel gas injection means comprising a plurality of spaced gas injectors, each being defined by a gas ejection hole and means to feed the gas thereto; the ratio of the number of gas ejection holes to the transverse cross-sectional area of the annular flow channel which are fed fuel gas by said injector means being at least 200/ft.sup.2.   
   
   
       6 . Apparatus in accordance with  claim 5 ; further including a third hollow cylinder mounted coaxially within and spaced from said second cylinder, the annular space between said second at third cylinder comprising a manifold for said fuel gas, and said fuel injector means being in communication with said manifold. 
   
   
       7 . Apparatus in accordance with  claim 6 , wherein said swirl vanes are mounted with their leading edges parallel to the axial flow of fuel and oxidant gases, and have a constant radius of curvature along the curved portion of the vanes, whereby said curved portion is a section of a cylinder. 
   
   
       8 . Apparatus in accordance with  claim 6 , wherein the product of the swirl number S and the quarl outlet to inlet diameter ratio C/B is in the range of 1.0 to 3.0. 
   
   
       9 . Apparatus in accordance with  claim 6 , in which said gas injectors are located at the leading edges of said swirl vanes, and inject said fuel gas in the direction of the tangential component of the flow imparted by the swirl vanes. 
   
   
       10 . Apparatus in accordance with  claim 6 , in which said gas injectors are located at the trailing edges of said swirl vanes, and inject said fuel gas in the direction of the tangential component of the flow imparted by the swirl vanes.