Method of reducing nitrogen oxides in a gas stream with vaporized ammonia

Abstract

The present invention is a method for selective reduction of nitrogen oxides in a gas stream with ammonia wherein the ammonia is vaporized prior to contacting it with the carrying fluid. The present invention also comprises a reducing agent dispersion system for use in substantially uniformly mixing a reducing agent with nitrogen oxides in a flue gas stream comprising a header and a plurality of lances. Further, the present invention comprises a novel reactor design for use in selective reduction of nitrogen oxides in a gas stream.

1 .- 16 . (canceled) 
     
     
         17 . A reactor for use in reducing nitrogen oxides contained in flue gas comprising:
 a) a catalyst holder wherein the catalyst holder comprises a first end, a second end, an interior wall, an exterior wall, and a center, wherein the first end is open, the second end is closed and the center is hollow; and   b) a reactor casing, wherein the reactor casing comprises an inlet, an outlet, an inner wall, and an outer wall, wherein the inlet has an opening to allow a flue gas mixture to enter only or substantially only the center of the catalyst holder and the outlet has an opening to allow the flue gas mixture to exit the reactor;   wherein the reactor casing surrounds the exterior wall of the catalyst holder and surrounds at least a portion of the first end and second end;   wherein a space is present between the exterior wall of the catalyst holder and the inner wall of the reactor casing;   wherein a plurality of catalyst elements form the interior wall and exterior wall of the catalyst holder and wherein at least one catalyst element comprises a plurality of channels; and   wherein the channels are positioned substantially perpendicular to a path for the flue gas mixture.   
     
     
         18 . The reactor of  claim 17  wherein the catalyst elements are a honey-comb structure. 
     
     
         19 . The reactor of  claim 18  wherein the catalyst elements have a hydraulic diameter of between about 0.7 mm and about 4.7 mm. 
     
     
         20 . The reactor of  claim 17  wherein the catalyst elements have a thickness of about 2 to about 24 inches. 
     
     
         21 . The reactor of  claim 17  further comprising the reducing agent dispersion system of claim  10  wherein the reducing agent dispersion system is located in a mixing duct upstream of the catalyst holder. 
     
     
         22 . A reactor for use in reducing nitrogen oxides contained in flue gas comprising:
 a) a catalyst holder wherein the catalyst holder comprises a first end, a second end, an interior wall, an exterior wall, and a center, wherein the first end is closed, the second end is open and the center is hollow; and   b) a reactor casing, wherein the reactor casing comprises an inlet, an outlet, an inner wall, and an outer wall, wherein the inlet has an opening to allow a flue gas mixture to enter a space between the exterior wall of the catalyst holder and the inner wall of the reactor casing and the outlet has an opening to allow the flue gas mixture to exit the reactor;   wherein the reactor casing surrounds the exterior wall of the catalyst holder and surrounds at least a portion of the first end and second end;   wherein a plurality of catalyst elements form the interior wall and exterior wall of the catalyst holder and wherein at least one catalyst element comprises a plurality of channels;   wherein the channels are positioned substantially perpendicular to a path for the flue gas mixture;   wherein the center of the catalyst holder is adapted to receive the flue gas mixture prior to exiting the reactor through the outlet.   
     
     
         23 . A system for reducing nitrogen oxides contained in flue gas comprising:
 A) a reactor, wherein the reactor comprises:
 a catalyst holder wherein the catalyst holder comprises a first end, a second end, an interior wall, an exterior wall, and a center, wherein the first end is open, the second end is closed and the center is hollow; and 
 a reactor casing, wherein the reactor casing comprises an inlet, an outlet, an inner wall, and an outer wall, wherein the inlet has an opening to allow a flue gas mixture to enter only or substantially only the center of the catalyst holder and the outlet has an opening to allow the flue gas mixture to exit the reactor; 
 wherein the reactor casing surrounds the exterior wall of the catalyst holder and surrounds at least a portion of the first end and second end; 
 wherein a plurality of catalyst elements form the interior wall and exterior wall of the catalyst holder and wherein at least one catalyst element comprises a plurality of channels; 
 wherein the channels are positioned substantially perpendicular to a path for the flue gas mixture; and 
   B) a reducing agent dispersion system;   wherein the reducing agent dispersion system comprises a header and a plurality of lances;   wherein the header is coupled to the lances;   wherein the header is adapted to receive a reducing agent and deliver the reducing agent to the lances;   wherein the lances comprise at least one opening in a surface of the lances;   wherein the lances are adapted to receive the reducing agent from the header and distribute the reducing agent through the at least one opening into a path of a carrying fluid;   wherein the reducing agent dispersion system is located in a mixing duct upstream of the catalyst holder of the reactor;   wherein the reducing agent is ammonia, wherein the ammonia is vaporized prior to contacting the vaporized ammonia with the carrying fluid.   
     
     
         24 . The system of  claim 23  further comprising:
 a space is present between the exterior wall of the catalyst holder and the inner wall of the reactor casing.