Reheat boiler and gas temperature controlling method of reheat boiler

Abstract

A reheat boiler according to the present invention includes a main boiler configured to make combustion gas originating from combustion in a burner flow from a furnace ( 102 ) and pass through a super heater and an evaporation tube bank, a reheat furnace ( 108 ) including a reheat burner ( 107 ) provided downstream of the evaporation tube bank, and a reheater ( 109 ) provided on the upper side of the reheat furnace ( 108 ), and also includes a combustion air supply portion ( 12 ) that is provided at a position opposite to the reheat burner ( 107 ) in the reheat furnace ( 108 ) to supply a part of the combustion air as combustion air ( 11 b ). By making combustion gas ( 107 a ) and the combustion air ( 11 b ) collide head-on to facilitate mixing of the combustion gas ( 107 a ) with the combustion air ( 11 b ), the flow patterns of the combustion gas are changed, whereby temperature unevenness of the combustion gas ( 107 a ) at the outlet of the reheat furnace ( 108 ) is reduced.

1 . A reheat boiler that includes a main boiler in which combustion gas produced by combustion in a burner flows through a super heater and an evaporation tube bank from a furnace, a reheat furnace with a reheat burner provided downstream of the evaporation tube bank, and a reheater provided on an upper side of the reheat furnace, the reheat boiler comprising:
 a combustion air supply portion that is provided at a position opposite to the reheat burner in the reheat furnace to supply a part of combustion air.   
     
     
         2 . The reheat boiler according to  claim 1 , wherein
 at least two stages of such combustion air supply portions are provided in a height direction of the reheat furnace.   
     
     
         3 . The reheat boiler according to  claim 1 , wherein
 a part of the combustion air is supplied to the combustion air supply portion by a rate of 50% or less.   
     
     
         4 . The reheat boiler according to  claim 1 , wherein
 at least two stages of such combustion air supply portions are provided in a height direction of the reheat furnace, and each stage of the combustion air supply portions supplies a different volume of the combustion air.   
     
     
         5 . A gas temperature controlling method of the reheat boiler according to  claim 1 , the method comprising:
 supplying a part of the combustion air into the reheat furnace from a position opposite to the reheat burner to reduce temperature unevenness of the combustion gas on an outlet side of the reheat furnace.