PLANT, COMBUSTION APPARATUS, AND METHOD FOR REDUCTION OF NOx EMISSIONS

Abstract

A combustion apparatus includes a combustion chamber having multiple combustion zones. A first wind box is in communication with the first combustion zone to feed the fuel to be fed into the combustion chamber for initial combustion of the fuel within the first combustion zone. A second wind box has a reburner in communication with the second combustion zone. The reburner is configured to feed fuel, a reagent and a first portion of the flue gas to be recycled to the second combustion zone into the second combustion zone to reduce nitrogen oxide emissions of the apparatus. A third wind box is in communication with the third combustion zone to feed air to the third combustion zone to complete the combustion process.

What is claimed is: 
     
         1 . A combustion apparatus, comprising:
 a combustion chamber having multiple combustion zones for combustion of fuel, the combustion zones including a first combustion zone, a second combustion zone, and a third combustion zone wherein the second combustion zone is located between the first and third combustion zones, the combustion chamber having at least one outlet configured to emit flue gas formed from combustion of the fuel in the combustion chamber;   a first wind box in communication with the first combustion zone for feeding of fuel into the combustion chamber for initial combustion within the first combustion zone;   a second wind box in communication with second combustion zone to feed a first gas having oxygen into the second combustion zone;   a third wind box in communication with the third combustion zone to feed a second gas having oxygen into the third combustion zone; and   a conduit in communication with the second combustion zone to feed a reagent into the second combustion zone.   
     
     
         2 . The combustion apparatus of  claim 1 , wherein the second wind box has a reburner in communication with the second combustion zone, the reburner configured to feed fuel into the second combustion zone and also feed the reagent into the second combustion zone. 
     
     
         3 . The combustion apparatus of  claim 2 , wherein the reburner comprises a nozzle that is configured to spray the reagent into the second combustion zone with the fuel fed to the second combustion zone via the second feed conduit. 
     
     
         4 . The combustion apparatus of  claim 1 , wherein the first and second gases are air. 
     
     
         5 . The combustion apparatus of  claim 2 , wherein each of the first, second and third feed conduits comprise at least one wind box. 
     
     
         6 . The combustion apparatus of  claim 5 , wherein the reburner is positioned at an upper compartment of the second wind box or is positioned above the second wind box between the second wind box and the third wind box. 
     
     
         7 . The combustion apparatus of  claim 1 , wherein at least one of the first, second, and third wind boxes are configured to facilitate tangential firing of fuel. 
     
     
         8 . The combustion apparatus of  claim 2 , wherein the reburner is also configured to feed a first portion of the flue gas to be recycled into the second combustion zone. 
     
     
         9 . The combustion apparatus of  claim 1 , wherein the reagent is provided to the second combustion zone at an upper compartment of the second wind box or is positioned above the second wind box between the second wind box and the third wind box. 
     
     
         10 . The combustion apparatus of  claim 1 , wherein the second wind box is configured to feed a first portion of the flue gas to be recycled into the second combustion zone with the reagent to facilitate mixing of the reagent within the second combustion zone. 
     
     
         11 . A method of operating a combustion apparatus having a combustion chamber including a first combustion zone, a second combustion zone, and a third combustion zone wherein the second combustion zone is located between the first and third combustion zones; the method comprising:
 providing a first fuel into the first combustion zone of the combustion chamber;   providing a reagent and a first gas having oxygen to the second combustion zone of the combustion chamber; and   providing a second gas having oxygen to the third combustion zone of the combustion chamber.   
     
     
         12 . The method of  claim 11  further comprising:
 feeding a second fuel to the second combustion zone, wherein the reagent and the second fuel are simultaneously fed to the second combustion zone. 
 
     
     
         13 . The method of  claim 12  further comprising:
 recycling a first portion of flue gas exiting the combustion chamber to the second combustion zone such that the reagent, the second fuel and the first portion of the flue gas are simultaneously fed to the second combustion zone. 
 
     
     
         14 . The method of  claim 13  wherein the first and second gases are air. 
     
     
         15 . The method of  claim 12 , wherein:
 the first fuel is coal and the first fuel is fed into the first combustion zone;   the second fuel is natural gas or oil; and   the reagent is one of aqueous ammonia, aqueous urea, and anhydrous ammonia.   
     
     
         16 . The method of  claim 12 , wherein:
 the first, second, and third combustion zones are each positioned adjacent to a respective wind box; and   the second fuel being fed into the second combustion zone via a sole reburner of the wind box of the second combustion zone, the reburner being positioned at one of:
 an upper compartment of the wind box of the second combustion zone, and 
 above the wind box of the second combustion zone between the wind box of the second combustion zone and the wind box of the third combustion zone. 
   
     
     
         17 . The method of  claim 11 , wherein the feeding of the first fuel into the combustion chamber comprises feeding the first fuel into the first combustion zone, the method also comprising:
 feeding a second fuel to the second combustion zone, the second fuel differing from the first fuel such that the reagent and the second fuel are simultaneously fed to the second combustion zone; and   combusting the first fuel in the combustion chamber via a tangential firing system.   
     
     
         18 . The method of  claim 11 , wherein the reagent is a liquid and is sprayed into the second combustion zone. 
     
     
         19 . The method of  claim 18 , wherein the reagent is fed into the second combustion zone while no fuel is fed into the second combustion zone via a reburner. 
     
     
         20 . The method of  claim 12 , wherein the reagent is provided to the second combustion zone above the location where the gas having oxygen is provided to the second combustion zone.