Burner, fuel combustion method and boiler retrofit method

Abstract

In a burner of construction having a primary nozzle, a secondary nozzle and a tertiary nozzle, a partition wall partitioning the secondary nozzle and the tertiary nozzle and having a flow path change member provided thereon, the partition wall is formed so as to be movable in parallel to the burner axis to control jetting speeds and flow rates of secondary air and tertiary air, whereby it is possible to cool the burner constituent members while reducing NOx. The partition wall is composed of a fixed wall and a movable wall. The burner comprises a bypass passage through which tertiary air in the tertiary nozzle bypasses the tertiary nozzle to flow into the secondary nozzle or the primary nozzle.

1 . A fuel combustion burner comprising a primary nozzle for supplying fuel and primary air, a secondary nozzle for supplying secondary air, provided outside said primary nozzle, and a tertiary nozzle for supplying tertiary air, provided outside said secondary nozzle so as to contact with the outside of said secondary nozzle, said secondary nozzle and said tertiary nozzle being partitioned by a partition wall, wherein 
 said partition wall has thereon a flow path change member for changing a flow of tertiary air from a flow along an axis of the burner to an outward flow and jetting the tertiary air, and said partition wall is movable in the burner axial direction.    
   
   
       2 . A fuel combustion burner according to  claim 1 , wherein said partition wall has a guide sleeve as said flow path change member at an end thereof.  
   
   
       3 . A fuel combustion burner according to  claim 1 , wherein said primary nozzle is a nozzle constituted so as to pneumatically transfer fuel with a primary air.  
   
   
       4 . A fuel combustion burner according to  claim 1 , wherein said partition wall is provided thereon with a bypass mechanism for allowing a part of the tertiary air to bypass said tertiary nozzle into one of said primary nozzle and said secondary nozzle when said partition wall is moved to a predetermined position.  
   
   
       5 . A fuel combustion burner according to  claim 1 , wherein said partition wall is composed of a fixed wall and a movable wall, said flow path change member is provided on said movable wall.  
   
   
       6 . A fuel combustion burner according to  claim 5 , wherein holes for allowing tertiary air to bypass are formed in said fixed wall and said movable wall, respectively.  
   
   
       7 . A fuel combustion burner according to  claim 6 , wherein said primary nozzle has a hole formed in an outer wall thereof, and a bypass pipe is provided between said hole formed in said fixed wall and said hole formed in said outer wall of said primary nozzle so that tertiary air passed through said holes formed in said fixed wall and said movable wall flows into said primary nozzle.  
   
   
       8 . A fuel combustion burner according to  claim 7 , wherein said bypass pipe has a jet outlet formed so that the tertiary air flowed into said primary nozzle flows along an inner wall of said primary nozzle.  
   
   
       9 . A fuel combustion burner according to  claim 7 , wherein said primary nozzle is a nozzle for supplying pulverized coal, said primary nozzle has a pulverized coal concentrator provided inside for narrowing a cross-sectional area of a flow path and concentrating the pulverized coal, and said bypass pipe is extended to said pulverized coal concentrator so that the tertiary air flowed into said primary nozzle flows along the surface of said pulverized coal concentrator.  
   
   
       10 . A fuel combustion burner according to  claim 1 , wherein fins for cooling said flow path change member an d said partition wall in the vicinity of said flow path change member are provided on said flow path change member and said partition wall in the vicinity of said flow path change member.  
   
   
       11 . A fuel combustion burner according to  claim 5 , wherein said partition wall is constituted so that said movable wall slides on said fixed wall, and guide rollers for guiding said movable wall are provided on said fixed wall.  
   
   
       12 . A fuel combustion burner according to  claim 5 , wherein a stopper for stopping said movable wall is provided on at lease one of said fixed wall and said movable wall.  
   
   
       13 . A fuel combustion burner according to  claim 1 , wherein a wind box for supplying secondary air and tertiary air is provided, and a mechanism for moving said partition wall is arranged outside said wind box.  
   
   
       14 . A fuel combustion method by a burner comprising a primary nozzle for supplying fuel and primary air, a secondary nozzle for supplying secondary air, provided outside said primary nozzle, a tertiary nozzle for supplying tertiary air, provided outside said secondary nozzle so as to contact with the outside of said secondary nozzle, said secondary nozzle and said tertiary nozzle being partitioned by a partition wall, and a flow path change member provided on said partition wall for changing a flow of the tertiary air from a flow along the burner axis to an outward flow, said partition wall being constituted to be movable in the burner axis direction, wherein 
 said partition wall is moved in dependence with any condition or conditions of a load change, a temperature at burner axis end portion, properties of fuel, the concentration of nitrogen oxides, the concentration of unburned fuel, and fuel supply stoppage, and adjusts a flow rate of the tertiary air supplied from said tertiary nozzle.    
   
   
       15 . A fuel combustion method according to  claim 14 , wherein at the time of stoppage of fuel supply to said burner, said partition wall is moved so that the cross-sectional area of a tertiary air jetting outlet of said tertiary nozzle becomes small, thereby to increase a flow rate of the secondary air from said secondary air nozzle.  
   
   
       16 . A fuel combustion method according to  claim 14 , wherein said method further comprises step of moving said partition wall so that the cross-sectional area for jetting tertiary air of said tertiary nozzle decreases when a temperature of said flow path change member becomes higher than a set temperature during combustion of fuel by the burner, and increasing a flow speed of the tertiary air.  
   
   
       17 . A fuel combustion method according to  claim 14 , wherein a part of the tertiary air supplied to said tertiary nozzle is caused to bypass a flow path of said tertiary nozzle into said secondary nozzle during stoppage of fuel supply to said the burner.  
   
   
       18 . A fuel combustion method according to  claim 14 , wherein a part of the tertiary air supplied to said tertiary nozzle is caused to bypass a flow path of said tertiary nozzle to flow along an inner wall of said primary nozzle during stoppage of fuel supply to said the burner.  
   
   
       19 . A method of retrofitting a boiler having a burner which is provided on a furnace wall and comprises a primary nozzle for supplying fuel and primary air, a tubular secondary nozzle for supplying secondary air, provided outside said primary nozzle so as to enclose said primary nozzle, a tubular tertiary nozzle for supplying tertiary air, provided outside said secondary nozzle, a tubular partition wall fixed between said secondary nozzle and said tertiary nozzle, wherein said method comprises: 
 removing at least an end portion of said partition wall; and    providing, around the position of the removed portion of said partition wall, a tubular partition wall with a flow path change member for changing a flow of tertiary air from a flow along the burner axis to an outward flow so as to be movable in the burner axial direction.