Method for in-furnace reduction and control of sulfur trioxide

Abstract

A method for controlling SO 3 in a combustion process of a sulfur-containing fuel, the method steps including partially combusting the fuel to create a reducing environment; maintaining the reducing environment for a sufficient period such that SO 3 is reduced to SO 2 to achieve a desirable level of SO 3 ; and combusting the remainder of the fuel in an oxidizing environment; thereby reducing the conversion of levels of SO 3 in the flue gases.

1 . A method for reducing SO 3  in a combustion process of a sulfur-containing fuel, the method steps comprising: 
 a) partially combusting the fuel in a first stage to create a reducing environment;    b) maintaining the reducing environment for a sufficient time period such that SO 3  is reduced to SO 2  to achieve a desirable level of SO 3 ;    c) combusting the remainder of the fuel and combustion intermediates in a second stage with oxidizing environment;    thereby reducing the levels of SO 3  in the flue gases.    
     
     
         2 . The method of  claim 1 , further including the step of micro-staging the first stage fuel combustion.  
     
     
         3 . The method of  claim 2 , wherein the micro-staging is provided through the use of low-NOx burners.  
     
     
         4 . The method of  claim 1 , further including the step of macro-staging the first stage of fuel combustion.  
     
     
         5 . The method of  claim 4 , wherein the macro-staging is provided through the use of over-fired air.  
     
     
         6 . The method of  claim 1 , further including a combination of micro-staging and macro-staging.  
     
     
         7 . The method of  claim 6 , wherein the micro-staging is provided by low-NOx burners and the macro-staging is provided by over-fired air.  
     
     
         8 . The method of  claim 1 , wherein the fuel is coal.  
     
     
         9 . A combustion furnace operated with a method for controlling SO 3  in a combustion process of a sulfur-containing fuel, the method steps comprising: 
 a) partially combusting the fuel to create a reducing environment;    b) maintaining the reducing environment for a sufficient period such that SO 3  is reduced to SO 2  to achieve a desirable level of SO 3 ;    c) combusting the remainder of the fuel in an oxidizing environment;    thereby reducing the conversion of levels of SO 3  in the flue gases.    
     
     
         10 . The method of  claim 9 , further including the step of micro-staging the first stage fuel combustion.  
     
     
         11 . The method of  claim 10 , wherein the micro-staging is provided through the use of low-NOx burners.  
     
     
         12 . The method of  claim 9 , further including the step of macro-staging the first stage of fuel combustion.  
     
     
         13 . The method of  claim 12 , wherein the macro-staging is provided through the use of over-fired air.  
     
     
         14 . The method of  claim 9 , further including a combination of micro-staging and macro-staging.  
     
     
         15 . The method of  claim 14 , wherein the micro-staging is provided by low-NOx burners and the macro-staging is provided by over-fired air.  
     
     
         16 . The method of  claim 9 , wherein the fuel is coal  
     
     
         17 . A method for controlling SO 3  concentrations in a combustion process of a sulfur-containing fuel, the method steps comprising: 
 a) partially combusting the fuel in a first stage to create a reducing environment;    b) adjusting the reducing environment time period such that SO 3  is preferentially reduced to SO 2  to achieve a desirable level of SO 3 ;    c) combusting the remainder of the fuel and combustion intermediates in a second stage with oxidizing environment;    thereby controlling the levels of SO 3  in the flue gases.    
     
     
         18 . The method of  claim 17 , further including the step of micro-staging the first stage fuel combustion.  
     
     
         19 . The method of  claim 18 , wherein the micro-staging is provided through the use of low-NOx burners.  
     
     
         20 . The method of  claim 17 , further including the step of macro-staging the first stage of fuel combustion.  
     
     
         21 . The method of  claim 20 , wherein the macro-staging is provided through the use of over-fired air.  
     
     
         22 . The method of  claim 17 , further including a combination of micro-staging and macro-staging.  
     
     
         23 . The method of  claim 22 , wherein the micro-staging is provided by low-NOx burners and the macro-staging is provided by over-fired air.  
     
     
         24 . The method of  claim 17 , wherein the fuel is coal.