Combustion-based emission reduction method and system

Abstract

In a combustion apparatus having multiple primary fuel inputs and a flue gas exhaust, a method for controlling combustion of a fuel in the combustion chamber in which a concentration of at least one flue gas component indicative of fuel/oxidant ratio in flue gases is measured at a plurality of locations proximate the flue gas exhaust, each location corresponding to one of the primary fuel inputs. An overall average concentration of the at least one flue gas component is then determined, based upon which a delta value, the difference between the overall average and the flue gas component concentration at each location, for the at least one flue gas component at each of the locations is determined. Based upon the delta values obtained, the fuel input rate is adjusted as necessary for each of the primary fuel inputs, such that the delta value is either reduced or increased to zero.

1 . In a combustion apparatus comprising a combustion chamber having a plurality of primary combustion regions and a flue gas exhaust, each of said primary combustion regions having a corresponding fuel input, a method for controlling combustion of a fuel in said combustion chamber comprising the steps of: 
 measuring a concentration of at least one flue gas component indicative of fuel/oxidant ratio in flue gases generated by said combustion at a plurality of locations proximate said flue gas exhaust, resulting in a plurality of measured concentrations, each of said locations corresponding to one of said primary combustion regions;    determining an average concentration of said at least one flue gas component from said plurality of measured concentrations;    determining a delta value for said at least one flue gas component at each of said locations; and    adjusting a fuel input rate as necessary for each of said primary combustion regions, whereby said delta value is one of reduced and increased to zero.    
     
     
         2 . A method in accordance with  claim 1 , wherein said at least one flue gas component is selected from the group consisting of CO, O 2 , NO x , combustibles and mixtures thereof.  
     
     
         3 . A method in accordance with  claim 1 , wherein said combustion apparatus comprises a combustion system selected from the group consisting of grate-fired spreader stokers and multiple burner furnaces.  
     
     
         4 . A method in accordance with  claim 3 , wherein said combustion apparatus is a grate-fired spreader stoker having a plurality of solid fuel feeders.  
     
     
         5 . A method in accordance with  claim 1  further comprising introducing a reburn fuel into a fuel reburn region in said combustion chamber disposed between said plurality of primary combustion regions and said flue gas exhaust.  
     
     
         6 . A method in accordance with  claim 5  further comprising introducing overfire air into an overfire air region in said combustion chamber disposed between said reburn fuel region and said flue gas exhaust.  
     
     
         7 . In a combustion apparatus comprising a combustion chamber having a plurality of primary combustion regions and a flue gas exhaust, each of said primary combustion regions having a corresponding fuel input, the improvement comprising: 
 a combustion control system comprising a plurality of flue gas sensors disposed within said combustion chamber at a plurality of sensor locations proximate said flue gas exhaust, each of said flue gas sensors adapted to measure an amount of at least one flue gas component indicative of fuel/oxidant ratio;    a data processor operably connected to said flue gas sensors and adapted to determine an average amount of said at least one flue gas component measured by said plurality of flue gas sensors, said data processor comprising a plurality of comparator blocks adapted to generate a delta value for said at least one flue gas component for each of said sensor locations; and    at least one fuel input controller operably connected to said processor and a fuel supply to each of said primary combustion regions, said at least one fuel input adapted to control fuel input to each of said primary combustion regions based upon said delta values.    
     
     
         8 . An apparatus in accordance with  claim 7 , wherein said fuel supply comprises a plurality of solid fuel feeders of a grate-fired spreader stoker, each of said solid fuel feeders providing solid fuel to a corresponding said primary combustion region.  
     
     
         9 . An apparatus in accordance with  claim 8 , wherein said fuel input controller comprises a speed controller corresponding to each of said solid fuel feeders and adapted to control a speed of said corresponding solid fuel feeder based upon output signals from said processor.  
     
     
         10 . An apparatus in accordance with  claim 7 , wherein said fuel supply comprises a plurality of fossil fuel burners, each of said fossil fuel burners adapted to deliver fuel to one of said primary combustion regions.  
     
     
         11 . An apparatus in accordance with  claim 10 , wherein said fuel input controller is adapted to independently control each of said fossil fuel burners.  
     
     
         12 . An apparatus in accordance with  claim 10 , wherein said fossil fuel burners are fired with one of a liquid fossil fuel and a gaseous fossil fuel.  
     
     
         13 . An apparatus in accordance with  claim 7 , wherein said at least one flue gas component is selected from the group consisting of CO, O 2 , NO x , combustibles and mixtures thereof.  
     
     
         14 . An apparatus in accordance with  claim 8  further comprising at least one reburn fuel burner adapted to introduce a reburn fuel into said combustion chamber in a fuel reburn region disposed between said primary combustion regions and said flue gas exhaust.  
     
     
         15 . An apparatus in accordance with  claim 14  further comprising at least one overfire air nozzle adapted to introduce overfire air into said combustion chamber in an overfire air region disposed between said fuel reburn region and said flue gas exhaust.