Furnace system with internal flue gas recirculation

Abstract

A furnace system 10 including a combustion vessel 12 having an outlet end 19 and at least one aperture 20, 22 extending into an interior area 14 defined by the combustion vessel. The furnace system 10 includes a flue duct 42 coupled to the outlet end 19 and in fluid communication with the interior area. A recirculation duct 55 extends from the flue duct 42 to one or more of the apertures 20, 22 and provides fluid communication between the flue duct 42 and the interior area 14.

1 . A furnace system comprising:
 a combustion vessel having an outlet end and at least one aperture extending into an interior area defined by said combustion vessel;   a flue duct coupled to said outlet end and in fluid communication with said interior area; and   a recirculation duct extending from said flue duct to said at least one aperture and providing fluid communication between said flue duct and said interior area.   
   
   
       2 . The furnace system of  claim 1 , further comprising conveying means disposed at least partially in said recirculation duct for causing flow of at least one fluid through said recirculation duct into said interior area in response to a command issued from a controller. 
   
   
       3 . The furnace system of  claim 2 , wherein said conveying means comprises at least one of a fan and a blower and a compressor. 
   
   
       4 . The furnace system of  claim 2 , wherein said conveying means comprises an eductor having a motive fluid supplied thereto for conveying said at least one fluid and said motive fluid into said interior area. 
   
   
       5 . The furnace system of  claim 4 , wherein said motive fluid is oxygen. 
   
   
       6 . The furnace system of  claim 4 , wherein said motive fluid is steam. 
   
   
       7 . The furnace system of  claim 4 , wherein said motive fluid is flue gas. 
   
   
       8 . The furnace system of  claim 1 , further comprising:
 a pollution control system in communication with said flue duct for processing flue gas discharged from said interior area;   an air preheater in fluid communication with said flue duct; and wherein   said recirculation duct is positioned upstream of at least one of said pollution control system and said air preheater.   
   
   
       9 . The furnace system of  claim 8 , further comprising:
 conveying means disposed at least partially in said recirculation duct for causing flow of at least one fluid through said recirculation duct into said interior area in response to a command issued from a controller;   wherein said conveying means comprises an eductor having a motive fluid supplied thereto for conveying said at least one fluid and said motive fluid into said interior area; and   wherein said flue gas is supplied from said pollution control system.   
   
   
       10 . The furnace system of  claim 2 , wherein said at least one fluid is flue gas. 
   
   
       11 . The furnace system of  claim 1 , wherein said furnace is tangentially-fired for combusting a fuel in the presence of oxygen. 
   
   
       12 . A furnace system comprising:
 a combustion vessel having an outlet end and at least one aperture extending into an interior area defined by said combustion vessel;   a flue duct coupled to said outlet end and in fluid communication with said interior area; a recirculation duct extending from said flue duct to said at least one aperture and providing fluid communication between said flue duct and said interior area; and   an eductor disposed at least partially in said recirculation duct and having oxygen supplied thereto for conveying at least some of said flue gas and said oxygen through said recirculation duct into said interior area.   
   
   
       13 . The furnace system of  claim 12 , wherein at least one lance extends through said at least one aperture and into said interior area, said lance having a passage extending therethrough for conveying a portion of said oxygen through said lance into said interior area. 
   
   
       14 . The furnace system of  claim 12 , wherein at least one nozzle extends through said at least one aperture and into said interior area, said nozzle having a passage extending therethrough for conveying a portion of said oxygen through said nozzle into said interior area. 
   
   
       15 . The furnace system of  claim 12 , further comprising:
 a pollution control system in communication with said flue duct for processing flue gas discharged from said interior area;   an air preheater in fluid communication with said flue duct; and wherein   said recirculation duct is positioned upstream of at least one of said pollution control system and said air preheater.