Pulverized Coal Boiler

Abstract

The present invention provides a highly reliable pulverized coal boiler that ensures suppression of a rise in flame temperature caused during the combustion of an unburnt gas in a furnace when combustion air is supplied from after-air ports so as to reduce the concentration of thermal NOx generated during the combustion. A pulverized coal boiler ( 100 ) according to the present invention comprising a furnace ( 1 ), burners ( 2 ) provided on the wall of the furnace for supplying pulverized coal to the inside of the furnace and burning the pulverized coal, and an after-air port ( 3 or 61 ) provided on the wall of the furnace at a position downstream of the burner for supplying combustion air to the inside of the furnace, the pulverized coal boiler further comprising: a spray nozzle ( 6 ) disposed near a jet port ( 3 or 60 ) of the after-air port for supplying water, steam, or two fluids including water and steam to the inside of the furnace; whereby the water, the steam, or the two fluids including water and steam are sprayed from the spray nozzle are supplied to the inside of the furnace together with the combustion air supplied from the after-air port.

1 . A pulverized coal boiler comprising a furnace, a burner provided on a wall of the furnace for supplying pulverized coal to the inside of the furnace and burning the pulverized coal, and an after-air port provided on the wall of the furnace at a position downstream of the burner for supplying combustion air to the inside of the furnace,
 the pulverized coal boiler further comprising:   a spray nozzle disposed near a jet port of the after-air port for supplying water, steam, or two fluids including water and steam to the inside of the furnace; whereby the water, the steam, or the two fluids including water and steam sprayed from the spray nozzle are supplied to the inside of the furnace together with the combustion air supplied from the after-air port.   
   
   
       2 . The pulverized coal boiler according to  claim 1 , wherein a plurality of after-air ports are disposed in the furnace in a combustion gas flow direction; and
 at least one of the plurality of after-air ports disposed upstream in the combustion gas flow direction in the furnace supplies the water, the steam, or the two fluids including water and steam to the inside of the furnace.   
   
   
       3 . The pulverized coal boiler according to  claim 2 , wherein at least one of the plurality of after-air ports disposed upstream in the combustion gas flow direction in the furnace supplies combustion air less than that of combustion air supplied from the after-air ports disposed downstream in the combustion gas flow direction. 
   
   
       4 . The pulverized coal boiler according to  claim 2 , wherein each of the after-air ports for supplying the water, the steam, or the two fluids including water and steam is provided with a straight flow path for jetting the combustion air as a straight flow, and a swirl flow path formed around an outer circumference of the straight flow path for jetting the combustion air as a swirl flow, internally; and the water, the steam, or the two fluids including water and steam are jetted from the swirl flow path. 
   
   
       5 . The pulverized coal boiler according to  claim 1 , further comprising:
 a NOx detector for detecting a NOx concentration of an exhaust gas exhausted from the pulverized coal boiler; and   a controller for controlling a flow rate of the water, the steam, or the two fluids including water and steam, which are supplied from the spray nozzle to the inside of the furnace, based on the NOx concentration detected by the NOx detector.   
   
   
       6 . The pulverized coal boiler according to  claim 1 , further comprising a controller for controlling a flow rate of the water, the steam, or the two fluids including water and steam, which are supplied from the spray nozzle to the inside of the furnace, based on a load of the pulverized coal boiler. 
   
   
       7 . The pulverized coal boiler according to  claim 1 , wherein a jet port of the spray nozzle for supplying the water, the steam, or the two fluids including water and steam into the inside of the furnace is disposed upstream in a jet flow of combustion air jetted from the jet port of the after-air port. 
   
   
       8 . A pulverized coal boiler comprising a furnace, a burner provided on a wall of the furnace for supplying pulverized coal to the inside of the furnace and burning the pulverized coal, an after-air port provided on the wall of the furnace at a position downstream of the burner for supplying combustion air to the inside of the furnace, a wind box for supplying the combustion air into the after-air port, and a duct pipe for externally supplying the combustion air into the wind box,
 the pulverized coal boiler further comprising:   a spray nozzle disposed in the wind box or in the duct pipe for supplying water, steam, or two fluids including water and steam; whereby the water, the steam, or the two fluids including water and steam sprayed from the spray nozzle into the inside of the wind box or the duct pipe are supplied to the inside of the furnace together with the combustion air supplied from a jet port of the after-air port.   
   
   
       9 . The pulverized coal boiler according to  claim 8 , further comprising:
 a NOx detector for detecting a NOx concentration of an exhaust gas exhausted from the pulverized coal boiler; and   a controller for controlling a flow rate of the water, the steam, or the two fluids including water and steam, which are supplied from the spray nozzle to the inside of the furnace, based on the NOx concentration detected by the NOx detector.   
   
   
       10 . The pulverized coal boiler according to  claim 8 , further comprising a controller for controlling a flow rate of the water, the steam, or the two fluids including water and steam, which are supplied from the spray nozzle to the inside of the furnace, based on a load of the pulverized coal boiler.