Burner and combustion furnace

Abstract

A burner includes: a first nozzle including a main fuel outlet that discharges a fuel-air mixture containing main fuel and primary combustion air and a flame holding plate around the outlet; and a second nozzle located coaxially with the first and including a secondary air outlet that emits secondary combustion air at an outer peripheral side of the main fuel outlet; and auxiliary fuel injection nozzles extending along an outer surface of the first nozzle in parallel with a burner axis. The auxiliary fuel injection nozzles include: auxiliary fuel outlets along an outer peripheral edge of the flame holding plate; or auxiliary fuel outlets inside the outer peripheral edge of the flame holding plate and outside an inner peripheral edge of the flame holding plate. The auxiliary fuel outlets discharge gas fuel as auxiliary fuel toward a boundary between flows of the fuel-air mixture and the secondary combustion air.

1 . A burner comprising:
 a first nozzle having a tubular shape about a burner axis and including
 a main fuel outlet that discharges a fuel-air mixture containing main fuel and primary combustion air and 
 a flame holding plate located around the main fuel outlet; 
   a second nozzle located coaxially with the first nozzle and including a secondary air outlet that emits secondary combustion air at an outer peripheral side of the main fuel outlet; and   auxiliary fuel injection nozzles extending along an outer surface of the first nozzle in parallel with the burner axis, wherein:   the auxiliary fuel injection nozzles include
 auxiliary fuel outlets lined up along an outer peripheral edge of the flame holding plate or 
 auxiliary fuel outlets located inside the outer peripheral edge of the flame holding plate and outside an inner peripheral edge of the flame holding plate; and 
   the auxiliary fuel outlets discharge gas fuel as auxiliary fuel toward a boundary between flow of the fuel-air mixture discharged from the main fuel outlet and flow of the secondary combustion air discharged from the secondary air outlet.   
     
     
         2 . The burner according to  claim 1 , wherein the auxiliary fuel injection nozzles are joined to an outer surface of the first nozzle. 
     
     
         3 . The burner according to  claim 1 , wherein downstream ends of the auxiliary fuel injection nozzles extend through the flame holding plate. 
     
     
         4 . The burner according to  claim 1 , wherein:
 the flame holding plate includes cutouts at an outer peripheral edge thereof; and   downstream ends of the auxiliary fuel injection nozzles extend through the cutouts.   
     
     
         5 . The burner according to  claim 1 , wherein the auxiliary fuel outlets discharge the gas fuel to forward flow of a circulating vortex generated at the boundary between the flow of the fuel-air mixture and the flow of the secondary combustion air, the forward flow flowing toward a downstream side. 
     
     
         6 . The burner according to  claim 5 , wherein:
 the circulating vortex includes
 an outer circulating vortex and 
 an inner circulating vortex located closer to the burner axis than the outer circulating vortex; 
   the auxiliary fuel outlets includes an inner auxiliary fuel outlet and an outer auxiliary fuel outlet which are at a substantially same rotational position about the burner axis;   the inner auxiliary fuel outlet discharges the gas fuel toward forward flow of the inner circulating vortex, the forward flow flowing toward the downstream side; and   the outer auxiliary fuel outlet discharges the gas fuel toward forward flow of the outer circulating vortex, the forward flow flowing toward the downstream side.   
     
     
         7 . The burner according to  claim 1 , wherein the auxiliary fuel outlets are switchable so as to emit combustion air instead of the gas fuel. 
     
     
         8 . The burner according to  claim 1 , wherein the gas fuel is an ammonia gas. 
     
     
         9 . A combustion furnace comprising:
 a high-temperature reduction zone which has a reduction atmosphere and at which at least one burner according to  claim 1  is located; and   a low-temperature oxidation zone which has an oxidizing atmosphere and is lower in temperature than the high-temperature reduction zone and into which a combustion gas generated in the high-temperature reduction zone flows.