Method of reducing NOx emissions using a fluid-cooled injector

Abstract

A method for reducing emissions of oxides of nitrogen from a combustion process using a temperature sensitive liquid reagent injected into a stream of exhaust gases from the combustion process and passing the exhaust gases and the reagent through a catalytic reactor which reduces the oxides of nitrogen in the presence of the reagent is disclosed. The steps of the method include providing an injector having an orifice for atomizing the liquid reagent; positioning a portion of the injector having the orifice within the stream of exhaust gases; cooling the injector by continuously circulating the reagent therethrough, thereby keeping both the injector and the reagent within the injector below a critical temperature at which the reagent will solidify; and injecting a portion of the reagent into the exhaust stream upstream of the reactor.

What is claimed is:  
     
         1 . A method of reducing emissions of oxides of nitrogen from a combustion process using a temperature sensitive liquid reagent injected into a stream of exhaust gases from said combustion process and passing said exhaust gases and said reagent through a catalytic reactor which reduces the oxides of nitrogen in the presence of the reagent, said method comprising the steps of: 
 providing an injector having an orifice for atomizing said liquid reagent;    positioning a portion of said injector having said orifice within said stream of exhaust gases;    cooling said injector by continuously circulating said reagent therethrough, thereby keeping both said injector and said reagent within said injector below a critical temperature at which said reagent will solidify; and    injecting a portion of said reagent into said exhaust stream upstream of said reactor.    
     
     
         2 . A method according to  claim 1 , wherein said reagent is an aqueous urea solution.  
     
     
         3 . A method according to  claim 2 , wherein said urea has a concentration between about 25% and about 35%.  
     
     
         4 . A method according to  claim 1 , further comprising the steps of providing a surface facing said orifice within said exhaust gas stream, and further atomizing said reagent injected into said exhaust gas stream by impinging said reagent onto said surface.  
     
     
         5 . A method according to  claim 1 , wherein said combustion process occurs within an internal combustion engine.  
     
     
         6 . A method according to  claim 5 , wherein said engine is a diesel engine.  
     
     
         7 . A method according to  claim 6 , wherein said reagent is injected into said stream of exhaust gases in proportion to selected engine operating parameters.  
     
     
         8 . A method of reducing emissions of oxides of nitrogen from a combustion process using a liquid reagent injected through an injector into a stream of exhaust gases from said combustion process, wherein at least a portion of said injector being positioned within said stream of exhaust gases, said method comprising the steps of: 
 (1) continuously circulating said reagent through said injector to keep both said injector and said reagent within said injector below a critical temperature;    (2) injecting at least a portion of said reagent through said injector into said exhaust stream; and    (3) passing said exhaust gases and said reagent injected therein through a catalytic reactor to reduce the oxides of nitrogen.    
     
     
         9 . A method according to  claim 8 , wherein said reagent is an aqueous urea solution.  
     
     
         10 . A method according to  claim 8 , wherein said urea has a concentration between about 25% and about 35%.  
     
     
         11 . A method according to  claim 8 , wherein said injector has an orifice for atomizing said liquid reagent, and further comprising the steps of providing a surface facing said orifice within said exhaust gas stream, and further atomizing said reagent injected into said exhaust gas stream by impinging said reagent onto said surface.  
     
     
         12 . A method according to  claim 8 , wherein said combustion process occurs within an internal combustion engine.  
     
     
         13 . A method according to  claim 8 , wherein said engine is a diesel engine.  
     
     
         14 . A method according to  claim 8 , wherein said reagent is injected into said stream of exhaust gases in proportion to selected engine operating parameters.  
     
     
         15 . A method according to  claim 9 , wherein said critical temperature is between about 95° C. and about 140° C.