Combustion system

Abstract

A combustion system capable of decreasing nitrogen oxide discharged from exhaust gas is provided. The combustion system includes: a combustion furnace ( 2 ) having a burner unit ( 2 a ) for supplying fuel and combustion oxygen to the inside of the furnace, a reduction zone formed on a downstream side of the burner unit ( 2 a ) for combusting the fuel, and a combustion oxygen supply port ( 2 b ) for supplying combustion oxygen ( 21 ) so that unburned fuel which has passed the reduction zone completely combusts; and a smoke removal device ( 9 ) for removing smoke in the exhaust gas discharged from the combustion furnace ( 2 ). Part of exhaust gas ( 22 ) diverging from between the combustion furnace ( 2 ) and the smoke removal device ( 9 ) is introduced to the burner unit ( 2 a ), while part of exhaust gas ( 23 ) diverging from a downstream side of the smoke removal device ( 9 ) is introduced to the combustion oxygen supply port ( 2 b ).

1 . A combustion system, comprising:
 a combustion furnace having:
 a burner unit for supplying fuel and combustion oxygen to an inside of the furnace; 
 a reduction zone formed on a downstream side of the burner unit for combusting the fuel; and 
 a combustion oxygen supply port for supplying combustion oxygen so that unburned fuel which has passed the reduced zone completely combusts; and 
   a smoke removal device for removing smoke in the exhaust gas discharged from the combustion furnace, wherein   part of exhaust gas diverging from between the combustion furnace and the smoke removal device is introduced to the burner unit, while part of exhaust gas diverging from a downstream side of the smoke removal device is introduced to the combustion oxygen supply port.   
     
     
         2 . The combustion system according to  claim 1 , wherein
 the smoke removal device includes:
 a denitration unit for removing nitrogen oxide; 
 a heat exchange unit for conducting heat exchange between exhaust gas which has passed the denitration unit and exhaust gas which is introduced to the combustion oxygen supply port; 
 a dust removal unit for removing dust in exhaust gas which has passed the heat exchange unit; 
 a desulfurization unit for removing sulfur oxide in exhaust gas which has passed the dust removal unit; and 
 a cooling unit for cooling exhaust gas which has passed the desulfurization unit, wherein 
   part of exhaust gas diverging from between the desulfurization unit and the cooling unit is introduced to the combustion oxygen supply port.   
     
     
         3 . The combustion system according to  claim 2 , wherein
 part of exhaust gas diverging from between the dust removal unit and the desulfurization unit is introduced to the combustion oxygen supply port.   
     
     
         4 . The combustion system according to  claim 2 , wherein
 part of exhaust gas diverging from between the denitration unit and the dust removal unit is introduced to the combustion oxygen supply port.   
     
     
         5 . The combustion system according to  claim 2 , wherein
 the denitration unit includes:
 an ammonia supply unit for supplying ammonia into exhaust gas; and 
 a catalyst unit for allowing exhaust gas supplied by the ammonia supply unit to pass therethrough.