초록 ▼

A burner having lower emissions and lower unburned fuel losses by implementing a transition zone in a low NO.sub.x burner. The improved burner includes a pulverized fuel transport nozzle surrounded by the transition zone which shields the central oxygen-lean fuel devolatilization zone from the swirl

A burner having lower emissions and lower unburned fuel losses by implementing a transition zone in a low NO.sub.x burner. The improved burner includes a pulverized fuel transport nozzle surrounded by the transition zone which shields the central oxygen-lean fuel devolatilization zone from the swirling secondary combustion air. The transition zone acts as a buffer between the primary and the secondary air streams to improve the control of near-burner mixing and flame stability by providing limited recirculation regions between primary and secondary air streams. These limited recirculation regions transport evolved NO.sub.x back towards the oxygen-lean fuel pyrolysis zone for reduction to molecular nitrogen. Alternate embodiments include natural gas and fuel oil firing.

대표청구항 ▼

[ We claim:] [1.] A burner with low emissions and low unburned fuel losses, comprising:means for defining a fuel nozzle for passage of a primary fuel with primary air for combustion in a primary zone, the fuel nozzle having an axis and further having an outlet end;means for defining an annular trans

[ We claim:] [1.] A burner with low emissions and low unburned fuel losses, comprising:means for defining a fuel nozzle for passage of a primary fuel with primary air for combustion in a primary zone, the fuel nozzle having an axis and further having an outlet end;means for defining an annular transition zone concentrically surrounding said fuel nozzle defining means, said transition zone defining means being constructed to provide air for near-burner mixing and flame stability;means for defining an inner secondary air zone and an outer secondary air zone, said inner secondary air zone having a wall concentrically surrounding said transition zone defining means, said outer secondary air zone having a wall concentrically surrounding said inner secondary air zone defining means, first means for imparting swirl positioned in said inner secondary air zone, second means for imparting swirl positioned in said outer secondary air zone, said inner and outer secondary air zones each having an outlet end; andmeans for diverting outer secondary air flow away from said fuel nozzle axis, said diverting means being attached to the wall concentrically surrounding said inner secondary air zone. [14.] A method of reducing emissions and reducing unburned fuel losses in a pulverized coal burner having a pulverized coal and primary air nozzle with an outlet end and inner and outer secondary air zones concentrically located around the pulverized coal and primary air nozzle, the method comprising the steps of:providing an annular concentric cylinder surrounding and spaced apart from the pulverized coal and primary air nozzle and positioned between the nozzle and the inner secondary air zone to form a transition zone surrounding a primary zone formed by the nozzle;producing a pulverized coal flame by diverting secondary combustion air away from an oxygen lean devolatilization zone of a primary combustion region near the nozzle outlet;producing a stoichiometry during coal devolatilization for reducing initial nitrogen oxides formation; andproviding limited recirculation regions between primary and secondary air streams for transporting evolved nitrogen oxides back towards the oxygen-lean devolatilization zone for reduction to molecular nitrogen. A method as recited in claim 14, further comprising the step of swirling air passing through an inner and an outer secondary air zone. A method as recited in claim 15, further comprising the step of providing mixing to improve combustion efficiency with fixed and adjustable angle spin vanes positioned within the burner. A burner with low emissions and low unburned fuel losses, comprising:means for defining a fuel nozzle for passage of a primary fuel with primary air for combustion in a primary zone, the fuel nozzle having an axis and further having an outlet end;means for defining an annular transition zone concentrically surrounding said fuel nozzle defining means, said transition zone defining means being constructed to provide air for near-burner mixing and flame stability; andmeans for defining an inner secondary air zone and an outer secondary air zone, said inner secondary air zone having a wall concentrically surrounding said transition zone defining means, said outer secondary air zone having a wall concentrically surrounding said inner secondary air zone, said inner and outer secondary air zones having an outlet end, and at least one flow turning vane near the outlet end, said inner and outer secondary air zones further including outwardly extending cones at the outlet end of said inner and outer secondary air zones and at an outlet end of said transition zone defining means.