System and method for firing a biofuel

Abstract

A method of firing a biofuel is provided. The method includes: introducing the biofuel into a combustion chamber having a first stage and a second stage; combusting the biofuel in a suspended state while flowing from the first stage to the second stage; and introducing a first air stream and a second air stream into the combustion chamber at the first stage and at the second stage, respectively, to facilitate combustion of the biofuel.

What is claimed is: 
     
         1 . A method of firing a biofuel a comprising:
 introducing the biofuel into a combustion chamber having a first stage and a second stage;   combusting the biofuel in a suspended state while flowing from the first stage to the second stage; and   introducing a first air stream and a second air stream into the combustion chamber at the first stage and at the second stage, respectively, to facilitate combustion of the biofuel.   
     
     
         2 . The method of  claim 1 , wherein introducing the biofuel into a combustion chamber further comprises:
 tangentially firing at least some of the biofuel at the first stage.   
     
     
         3 . The method of  claim 1 , wherein the biofuel has a maximum particle size less than or equal to about 2 mm. 
     
     
         4 . The method of  claim 1 , wherein the first air stream provides a greater than or equal amount of the air consumed by combustion of the biofuel than the second air stream. 
     
     
         5 . The method of  claim 4 , wherein the first air stream provides about 50-70% of the air consumed by combustion of the biofuel. 
     
     
         6 . The method of  claim 1 , wherein combusting the biofuel produces less than or equal to about 0.08 lb/MBtu of NOx. 
     
     
         7 . The method of  claim 1 , wherein the biofuel is at least one of bagasse, wood, peat, straw, and grass. 
     
     
         8 . A system for firing a biofuel comprising:
 a combustion chamber having a first stage and a second stage and operative to provide for combustion of the biofuel in a suspended state while flowing from the first stage to the second stage; and   wherein the combustion chamber further has a first injector and a second injector operative to introduce a first air stream and a second air stream into the combustion chamber at the first stage and at the second stage, respectively, to facilitate combustion of the biofuel.   
     
     
         9 . The system of  claim 8 , wherein the first injector is operative to introduce at least some of the biofuel into the combustion chamber at the first stage via tangential firing. 
     
     
         10 . The system of  claim 8  further comprising:
 a mill operative to provide the biofuel to the combustion chamber at a maximum particle size less than or equal to about 2 mm. 
 
     
     
         11 . The system of  claim 8 , wherein the first air stream provides a greater than or equal amount of the air consumed by combustion of the biofuel than the second air stream. 
     
     
         12 . The system of  claim 11 , wherein the first air stream provides about 50-70% of the air consumed by combustion of the biofuel. 
     
     
         13 . The system of  claim 8  further comprising:
 a selective catalytic reducer that is operative to limit NOx emissions resulting from combustion of the biofuel to less than or equal to about 0.01 lb/MBtu. 
 
     
     
         14 . The system of  claim 8 , wherein the biofuel is at least one of bagasse, wood, peat, straw, and grass. 
     
     
         15 . A non-transitory computer readable medium storing instructions configured to adapt a controller to:
 introduce a biofuel into a combustion chamber having a first stage and a second stage;   combust the biofuel in a suspended state while flowing from the first stage to the second stage; and   introduce a first air stream and a second air stream into the combustion chamber at the first stage and at the second stage, respectively, to facilitate combustion of the biofuel.   
     
     
         16 . The non-transitory computer readable medium of  claim 15 , wherein at least some of the biofuel is introduced into the combustion chamber at the first stage via tangential firing. 
     
     
         17 . The non-transitory computer readable medium of  claim 15 , wherein the biofuel has a maximum particle size less than or equal to about 2 mm. 
     
     
         18 . The non-transitory computer readable medium of  claim 15 , wherein the first air stream provides a greater than or equal amount of the air consumed by combustion of the biofuel than the second air stream. 
     
     
         19 . The non-transitory computer readable medium of  claim 18 , wherein the first air stream provides about 50-70% of the air consumed by combustion of the biofuel. 
     
     
         20 . The non-transitory computer readable medium of  claim 15 , wherein combustion of the biofuel produces less than or equal to about 0.08 lb/MBtu of NOx.