Abstract:
A method for operating a combustion system to facilitate reducing emissions from the system is provided. The method includes supplying an aqueous selective reducing agent from an aqueous selective reducing agent source to an atomizer that is directly coupled in flow communication with the aqueous selective reducing agent source. The method also includes atomizing the selective reducing agent in the atomizer, and injecting atomized droplets of the selective reducing agent from the atomizer directly into a transport stream of flue gas flowing within a temperature zone defined within the combustion system.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    This invention relates generally to industrial combustion systems, and more particularly to methods and systems for reducing NO x  in industrial combustion systems. 
         [0002]    During the combustion of natural gas and pulverized coal, nitrogen oxides (“NO x ”) emissions are formed by the oxidation of nitrogen in combustion air that is under high temperatures. At least some known NO x  emission sources include devices such as, but not limited to, industrial boilers and furnaces, larger utility boilers and furnaces, gas turbine engines, steam generators, and other combustion systems. Because of stringent emission control standards, it is desirable to control NO x  emissions by either suppressing NO x  formation and/or by reducing NO x  to molecular nitrogen (“N 2 ”) and water (“H 2 O”). 
         [0003]    At least some known combustion systems attempt to reduce NO x  emissions from a furnace/boiler in at least the following stages: (1) before combustion—using pre-combustion control technologies, (2) during combustion—using combustion modification control technologies that modify the combustion process so that the combustion process produces less NO x , and/or (3) after combustion—using post-combustion control technologies that inject a selective reagent such as, but not limited to, ammonia (“NH 3 ”), urea, and/or similar reducing agents, into the combustion flue gas to facilitate reducing NO x  emissions. 
         [0004]    Before combustion, at least some known pre-combustion control technologies burn low nitrogen fuels to facilitate reducing NO x  emissions. However, generally pre-combustion technologies may be limited in reducing NO x  emissions because air containing N 2  is used to burn the low nitrogen fuel, and as such, oxidation of the N 2  in the air may occur during combustion to form additional NO x  emissions. 
         [0005]    During combustion, at least some known combustion modification control technologies may reduce NO x  by attempting to: (1) lower the temperature in a main combustion zone to suppress formation of NO x , (2) decrease the oxygen concentration in high temperature zones by supplying only enough oxygen to oxidize the fuel, but not enough to form NO x  and carbon monoxide (“CO”) emissions, and/or (3) create conditions under which NO x  can be reduced to N 2  through reacting with hydrocarbon fragments. However, generally combustion modification control technologies include limited NO x  emissions reduction, stringent operating tolerances, and limited residence times to complete combustion. 
         [0006]    After combustion, at least some known post-combustion control technologies such as, but not limited to, Selective Catalytic Reduction (“SCR”) and Selective Non-Catalytic Reduction (“SNCR”) may be used to selectively reduce NO x  emissions. In combustion systems using SCR technology, NO x  is selectively reduced by injecting a nitrogenous reducing agent (“N-agent”) such as, NH 3  or urea, into the furnace/boiler in the presence of at least one catalyst. Although the SCR system significantly reduces NO x  more efficiently than known combustion modification control technologies, known SCR systems require a large catalyst bed, large amounts of catalysts, and catalysts disposal systems, all of which may be more difficult and more expensive to operate than combustion modification systems. 
         [0007]    In combustion systems using SNCR technology, an N-agent is injected into the combustion flue gas at a high temperature. Under a non-catalytic reaction, the NO x  formed during combustion may be reduced to N 2  through a reaction with the N-agent. Although the SNCR system significantly reduces NO x  more efficiently than known combustion modification control technologies, known SNCR systems reduce NO x  less efficiently than the SCR systems. On the other hand, the SNCR system is generally less expensive than the SCR system, but more expensive than combustion modification systems. Moreover, although known SCR and SNCR systems reduce NO x  more efficiently than combustion modification systems, both the SCR and SNCR systems include additional components that increase the overall costs, complexity, “foot print” (space in plant occupied by emissions control systems that could be devoted to production) and maintenance in comparison to known combustion modification control technologies. 
       BRIEF DESCRIPTION OF THE INVENTION 
       [0008]    In one aspect, a method for operating a combustion system to facilitate reducing emissions from the system is provided. The method includes supplying an aqueous selective reducing agent from an aqueous selective reducing agent source to an atomizer that is directly coupled in flow communication with the aqueous selective reducing agent source. The method also includes atomizing the selective reducing agent in the atomizer, and injecting atomized droplets of the selective reducing agent from the atomizer directly into a transport stream of flue gas flowing within a temperature zone defined within the combustion system. 
         [0009]    In another aspect, a combustion system to facilitate reducing emissions is provided. The combustion system includes an aqueous selective reducing agent source for supplying an aqueous selective reducing agent, and an atomizer directly coupled in flow communication with the aqueous selective reducing agent source. The atomizer receives and atomizes the selective reducing agent that is supplied from the aqueous selective reducing agent source. The combustion system also includes a temperature zone defined within the combustion system. The atomizer directly injects atomized droplets of the selective reducing agent into a transport stream of flue gas flowing within the temperature zone. 
         [0010]    In another aspect, a reagent injection system to facilitate reducing emissions from a combustion system is provided. The reagent injection system includes an aqueous selective reducing agent source for supplying an aqueous selective reducing agent, and an atomizer directly coupled in flow communication with the aqueous selective reducing agent source. The atomizer receives and atomizes the selective reducing agent that is supplied from the aqueous selective reducing agent source, and injects atomized droplets of the selective reducing agent from the atomizer directly into a transport stream of flue gas flowing within a temperature zone defined within the combustion system. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0011]      FIG. 1  is a schematic diagram of an exemplary known Selective Non-Catalytic Reduction (SNCR) injection system; 
           [0012]      FIG. 2  is a schematic diagram of an exemplary known Selective Catalytic Reduction (SCR) injection system; 
           [0013]      FIG. 3  is a schematic diagram of an exemplary SNCR injection system; and 
           [0014]      FIG. 4  is a schematic diagram of an exemplary SCR injection system. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0015]    The exemplary methods and systems described herein overcome the structural disadvantages of known Selective Catalytic Reduction (SCR) and Selective Non-Catalytic Reduction (SNCR) systems by reducing the number of components coupled within each respective system. 
         [0016]    It should be appreciated that the term “SCR system” is used throughout this application to refer to a combustion system implementing a Selective Catalytic Reduction (SCR) control technology that injects a reagent to facilitate selectively reducing nitrogen oxides (“NO x ”) emissions. 
         [0017]    It should be appreciated that the term “SNCR system” is used throughout this application to refer to a combustion system implementing a Selective Non-Catalytic Reduction (SNCR) control technology that injects a reagent to facilitate selectively reducing NO x  emissions. 
         [0018]      FIG. 1  illustrates a schematic diagram of a known SNCR system  100 . In the exemplary embodiment, SNCR system  100  includes a furnace/boiler  110 , a reagent injection system  120 , an air preheater  150 , and optionally, other pollution control devices  160 . Furnace/boiler  110  serves as a combustion chamber that includes fuel injection ports  112 , air injection ports  114 , a combustion zone  116 , and a temperature zone  118  which is at an optimum SNCR temperature range of approximately 1500 to 2100° F., more specifically, approximately 1600 to 2000° F., and all subranges therebetween depending on the reagent injected into the flue gas in SNCR system  100 . In the exemplary embodiment, at least one fuel injection port  112  and at least one air injection port  114  are coupled to furnace/boiler  110  to inject fuel and air, respectively, into combustion zone  116 . After combustion of the fuel, a generated combustion exhaust gas, also known as a combustion flue gas, flows in a transport stream into furnace/boiler temperature zone  118 . 
         [0019]    The reagent injection system  120  includes a reagent storage device  122  that is an aqueous selective reducing agent source, a pump  124 , a blower  126 , an air heater  128 , a vaporizer  130 , and a mixer  132 . The reagent storage device  122  stores an aqueous reagent such as, but not limited to, ammonia (“NH 3 ”), urea, and/or similar nitrogenous reducing agents (“N-agents”) that may be pumped out by pump  124  to vaporizer  130 . Blower  126  blows air into air heater  128  to heat air that is used to vaporize the reagent in vaporizer  130 . Subsequently air, reagent, and water vapors are premixed in mixer  132  to form a premixed gas prior to entry into furnace/boiler temperature zone  118 . 
         [0020]    After entering temperature zone  118 , the premixed gas reacts with flue gas to facilitate reducing NO x . Any remaining flue gas then travels through air preheater  150 , which heats secondary air to facilitate heating air supplied to furnace/boiler  110  for combustion. After flowing through air preheater  150 , flue gas may optionally travel through other pollution control devices  160  prior to being discharged to ambient. Such pollution control devices  160  may include devices such as, but are not limited to devices including, sulfur oxides (“SO x ”) control devices, particulate control devices, filtering devices, and/or similar emissions control devices. 
         [0021]      FIG. 2  illustrates a schematic diagram of a known SCR system  200 . In the exemplary embodiment, the SCR system  200  includes a furnace/boiler  210 , a reagent injection system  220 , an SCR reactor  240 , an air preheater  250 , and optionally, other pollution control devices  260 . Furnace/boiler  210  serves as a combustion chamber that includes fuel injection ports  212 , air injection ports  214 , and a combustion zone  216 . In the exemplary embodiment, at least one fuel injection port  212  and at least one air injection port  214  are coupled to furnace/boiler  210  to inject fuel and air, respectively, into combustion zone  216 . After combustion of the fuel, a generated flue gas flows in a transport stream to SCR reactor  240 . SCR reactor  240  includes a temperature zone  248  which is at an optimum SCR temperature range of approximately 450 to 840° F., more specifically, approximately 500 to 750° F., and all subranges therebetween depending on the reagent and the catalyst used in SCR system  200 . 
         [0022]    The reagent injection system  220  includes a reagent storage device  222 , a pump  224 , a blower  226 , an air heater  228 , a vaporizer  230 , and a mixer  232 . Reagent storage device  222  stores an aqueous reagent such as, but not limited to, NH 3 , urea, and/or similar N-agents that may be pumped out by pump  224  to vaporizer  230 . Blower  226  blows air into air heater  228  to heat air that is used to vaporize the reagent in vaporizer  230 . Subsequently air, reagent, and water vapors are premixed in mixer  232  to form a premixed gas. The premixed gas may be injected into the transport stream of flue gas that is located in a duct  234  positioned upstream of SCR reactor  240 . 
         [0023]    In the exemplary embodiment, the SCR reactor  240 , includes a catalyst bank  242  having one or more layers of catalyst for treatment. On the surface of catalyst bank  242 , the premixed gas reacts with flue gas in temperature zone  248  of SCR system  200  to selectively reduce NO x  by forming harmless byproducts such as, nitrogen (“N 2 ”) and water (“H 2 O”). Any remaining flue gas is channeled through air preheater  250  to facilitate heating air supplied to furnace/boiler  210  for combustion. 
         [0024]    Flue gas may optionally travel through other pollution control devices  260  prior to being discharge to ambient. Such pollution control devices  260  may include devices such as, but are not limited to devices including, SO x  control devices, particulate control devices, filtering devices, and similar emissions control devices. 
         [0025]    Known SNCR and SCR systems include additional components such as, but are not limited to components including, an air heater, a vaporizer, and a mixer to introduce a reagent into a combustion flue gas. Such components at least partially define a flow/travel path of the reagent introduced to the system. Because of the length of travel path in such systems, a reaction time for reducing NO x  may be delayed from a time that the reagent is introduced to the system. As a result, a droplet size and timed release of the reagent must be calculated to ensure a chemical reaction occurs between the reagent and the flue gas to facilitate reducing NO x  contained therein. Therefore, such components increase equipment size, materials, complexity, maintenance, and cost of each known system. 
         [0026]      FIG. 3  illustrates a schematic diagram of an exemplary Selective Non-Catalytic Reduction (SNCR) system  300 . SNCR system  300  includes a furnace/boiler  310 , a reagent injection system  320 , an air preheater  350 , and optionally, other pollution control devices  360 . Furnace/boiler  310  serves as a combustion chamber that includes fuel injection ports  312 , air injection ports  314 , a combustion zone  316 , and a temperature zone  318 , which in the exemplary embodiment has an optimum SNCR temperature range of approximately 1500 to 2100° F., more specifically, 1600 to 2000° F., and all subranges therebetween depending on the reagent injected into the flue gas in SNCR system  300 . Specifically, in the exemplary embodiment, such temperature range facilitates optimizing the reaction between the reagent and the flue gas. At least one fuel injection port  312  and at least one air injection port  314  are operatively coupled to furnace/boiler  310  to inject fuel and air, respectively, into combustion zone  316 . After combustion of the fuel, a generated flue gas flows in a transport stream into temperature zone  318 . 
         [0027]    The reagent injection system  320  is different from known reagent injection systems, such as reagent injection system  120  (shown in  FIG. 1 ). Specifically, reagent injection system  320  includes a reagent storage device  322 , an optional blower  326 , and an atomizer  327 . Unlike known SNCR reagent injection systems, such as reagent injection system  120 , reagent injection system  320  does not include an air heater, a vaporizer, or a mixer nor any component which functions to replace such components. 
         [0028]    In the exemplary embodiment, reagent storage device  322  stores an aqueous reagent such as, but not limited to, NH 3 , urea, and/or similar N-agents, and is directly coupled in flow communication to atomizer  327 . Although the reagent has been described as including NH 3 , urea, and/or similar N-agents, it should be appreciated that the reagent may include any aqueous reducing agent, known or later developed, that selectively reduces NO x . Optionally, the reagent may be forced out to atomizer  327  via blower  326 . Although SNCR reagent injection system  320  has been described as including optional blower  326 , it should be appreciated that blower  326  may be optionally replaced with a pump or any other device, known or later developed, which facilitates channeling reagent to furnace/boiler  310  as described herein. Subsequently, atomizer  327  may directly inject particles of a reagent/air mixture into temperature zone  318 . 
         [0029]    After entering temperature zone  318 , the reagent/air mixture reacts with flue gas to facilitate reducing NO x . Any remaining flue gas is forced through air preheater  350  to facilitate heating air supplied to furnace/boiler  310  for combustion. After flowing through air preheater  350 , flue gas may optionally travel through other pollution control devices  360  prior to being discharged to ambient. Such pollution control devices  360  may include devices such as, but are not limited to devices including, SO x  control devices, particulate control devices, filtering devices, and/or similar emissions control devices. 
         [0030]    During operation of SNCR system  300 , in the exemplary embodiment, an aqueous selective reducing agent (“reagent”) may be stored in reagent storage device  322 . The reagent may be channeled through atomizer  327  that is directly coupled in flow communication with reagent storage device  322 . Atomizer  327  atomizes the reagent into fine droplets and injects the droplets into the combustion flue gas in furnace/boiler temperature zone  318 . In the exemplary embodiment, temperature zone  318  has an optimum SNCR temperature range of approximately 1500 to 2100° F., more specifically, approximately 1600 to 2000° F., and all subranges therebetween depending on the reagent injected into the flue gas in SNCR system  300 . 
         [0031]    In the exemplary embodiment, the SNCR reagent injection system  320  includes atomizer  327  directly coupled in flow communication with reagent storage device  322  to introduce a reagent into a combustion flue gas to facilitate reducing NO x . More specifically, in the exemplary embodiment, an air heater, a vaporizer, and a mixer of known SNCR reagent injection systems, such as reagent injection system  120 , are excluded from SNCR system  300 . As such, an overall size of SNCR system  300  is smaller than known SNCR systems, such as SNCR system  100 . More specifically, in SNCR system  300 , a flow/travel path of a reagent introduced to the system is shorter than a flow/travel path of the known SNCR systems. 
         [0032]    Because of the shorter length of the reagent flow/travel path in SNCR system  300 , a reaction time for reducing NO x  is increased compared to the known SNCR systems. As a result, a size reduction of an initial reagent droplet prior to entry in a flue gas in SNCR system  300  is substantially less than a size reduction of an initial reagent droplet prior to entry in a flue gas in known SCR systems. Therefore, in SNCR system  300 , a reagent droplet size upon entry in the flue is substantially similar to an initial droplet size. As such, in SNCR system  300 , less complex calculations are required to determine reagent droplet size upon entry and timed release of the reagent compared to known SNCR systems, such as SNCR system  100 , to ensure a chemical reaction occurs between the reagent and flue gas to facilitate reducing NO x  contained therein. Therefore, the overall SNCR system  300  facilitates reducing equipment size, material, complexity, maintenance, and cost as compared to known SNCR systems. 
         [0033]      FIG. 4  illustrates a schematic diagram of an exemplary Selective Catalytic Reduction (SCR) system  400 . In the exemplary embodiment, SCR system  400  includes a furnace/boiler  410 , a reagent injection system  420 , a SCR reactor  440 , an air preheater  450 , and other pollution control devices  460 . Furnace/boiler  410  serves as a combustion chamber that includes fuel injection ports  412 , air injection ports  414 , and a combustion zone  416  At least one fuel injection port  412  and at least one air injection port  414  are coupled to furnace/boiler  410  to inject fuel and air, respectively, into combustion zone  416 . After combustion of the fuel, a generated flue gas flows in a transport stream to a temperature zone  448  which has an optimum SCR temperature range of approximately 450 to 840° F., more specifically, approximately 500 to 750° F., and all subranges therebetween depending on the reagent and the catalyst used in SCR system  400 . 
         [0034]    The reagent injection system  420  is different from known reagent injection system, such as reagent injection system  220  (shown in  FIG. 2 ). Specifically, in the exemplary embodiment, reagent injection system  420  includes a reagent storage device  422 , an optional blower  426 , and an atomizer  427 . Unlike known SCR reagent injection systems, such as reagent injection system  220 , reagent injection system  420  does not include an air heater, a vaporizer, or a mixer. 
         [0035]    In the exemplary embodiment, the reagent storage device  422  stores an aqueous reagent such as, but not limited to, NH 3 , urea, and/or similar N-agents, and is directly coupled in flow communication to the atomizer  427 . Although the reagent has been described as including NH 3 , urea, and/or similar N-agents, it should be appreciated that the reagent may include any aqueous reducing agent, known or later developed, that selectively reduces NO x . Optionally, the reagent may be forced into atomizer  427  via blower  426 . Although the SCR reagent injection system  420  has been described as including optional blower  426 , it should be appreciated that blower  326  may be optionally replaced with a pump or any other device, known or later developed, which facilitates channeling reagent to furnace/boiler  410  as described herein. Subsequently, atomizer  427  may directly inject particles of a reagent/air mixture into the transport stream of flue gas via a duct  434  positioned upstream of SCR reactor  440 . 
         [0036]    In the exemplary embodiment, SCR reactor  440  includes a catalyst bank  442  having one or more layers of catalyst to facilitate treatment. Specifically, in the exemplary embodiment, the reagent/air mixture reacts with flue gas across a surface of catalyst bank  442  in temperature zone  448  of SCR system  400  to selectively reduce NO x  by forming harmless byproducts such as, H 2 O and N 2 . Any remaining flue gas is channeled through air preheater  450  to facilitate heating air supplied to furnace/boiler  410  for combustion. 
         [0037]    After flowing through air preheater  450 , flue gas may optionally travel through other pollution control devices  460  prior to being discharged to ambient. Such pollution control devices  460  include devices such as, but are not limited to devices including, SO x  control devices, particulate control devices, filtering devices, and/or similar emissions control devices. 
         [0038]    During operation of SCR system  400 , in the exemplary embodiment, an aqueous selective reducing agent (“reagent”) may be stored in reagent storage device  422 . The selective reducing agent may be channeled through atomizer  427  that is directly coupled in flow communication with reagent storage device  422 . Atomizer  427  atomizes the reagent into fine droplets and injects the droplets into a transport stream of combustion flue gas. 
         [0039]    In the exemplary embodiment, the reagent is injected upstream of SCR reactor  440 . Specifically, the reagent is injected into furnace/boiler temperature zone  448 . In the exemplary embodiment, temperature zone  448  has an optimum SCR temperature range of approximately 450 to 840° F., more specifically, approximately 500 to 750° F., and all subranges therebetween depending on the reagent injected into the flue gas in SCR system  400 . Although the reagent has been described as being injected into the transport stream of flue gas via a duct  434 , it should be appreciated that the reagent may be injected into any portion of SCR system  400  wherein the transport stream of the flue gas is within the desired SCR temperature range. 
         [0040]    In the exemplary embodiment, the SCR reagent injection system  420  includes atomizer  427  directly coupled in flow communication with reagent storage device  422  to introduce a reagent into a combustion flue gas to facilitate reducing NO x . More specifically, in the exemplary embodiment, an air heater, a vaporizer, and a mixer of known SCR reagent injection systems, such as reagent injection system  220 , are excluded from SCR system  400 . As such, an overall size of SCR system  400  is smaller than known SCR systems, such as SCR system  200 . More specifically, in SCR system  400 , a flow/travel path of a reagent introduced to the system is shorter than a flow/travel path of the known SCR systems. 
         [0041]    Because of the shorter length of the reagent flow/travel path in SCR system  400 , a reaction time for reducing NO x  is increased compared to the known SCR systems. As a result, a size reduction of an initial reagent droplet prior to entry in a flue gas in SCR system  400  is substantially less than a size reduction of an initial reagent droplet prior to entry in a flue gas in known SCR systems. Therefore, in SNCR system  400 , a reagent droplet size upon entry is substantially similar to an initial droplet size. As such, in SCR system  400 , less complex calculation are required to determine reagent droplet size and timed release of the reagent compared to known SCR systems, such as SCR system  200 , to ensure a chemical reaction occurs between the reagent and flue gas to facilitate reducing NO x  contained therein. Therefore, the overall SCR system  400  facilitates reducing equipment size, material, complexity, maintenance, and cost as compared to known SCR systems. 
         [0042]    For both SNCR system  300  and SCR system  400 , the effectiveness of NO x  reduction depends on an optimal temperature at an area of injection of reagent into a transport stream of flue gas in each respective system  300  and  400 . For example, if the reagent is injected into the transport stream where the temperature is too low, then ammonia slip emissions may occur. In contrast, if reagent is injected into the transport stream where the temperature is too high, then oxidation of nitrogen in the reagent may occur to produce additional NO x . Therefore, in SNCR system  300  and SCR system  400 , reagent is injected into respective temperature zones  318  and  448  each having optimum temperature ranges to facilitate reducing No x . 
         [0043]    The effectiveness of NO x  reduction also depends on the size of droplets of reagent injected into the transport stream of the flue gas. For example, if the droplet size of the reagent is too large when the droplet enters into the transport stream, the reagent may not fully react with NO x  in the flue gas. Moreover, if the droplets are larger in size, the larger droplets generally take longer to evaporate to a smaller droplet size that facilitates a chemical reaction with the NO x  contained in the flue gas. Further, the size of the droplets is selected depending on the application. For example, larger droplet may be less suitable for injection into a smaller industrial furnace/boiler that utilizes a smaller resonance time for the droplet to travel as compared to a larger utility furnace/boiler that utilizes a larger resonance time for the droplet to travel. 
         [0044]    In contrast, for example, if the droplets are smaller in size, the smaller droplets generally take less time to evaporate. Moreover, if the droplet size of the reagent is too small when the droplet enters into the transport stream, the reagent may not fully react with NO x  in the flue gas. For example, such droplet size may be inadequate to facilitate a chemical reaction with the NO x  contained in the flue gas due to a substantial evaporation of the droplet. Further, as discussed above, the size of the droplets is selected depending on the application. For example, a substantially smaller initially injected N-agent droplet may be less suitable for injection into smaller industrial furnaces/boilers that utilizes a smaller resonance time for the droplet to travel as compared a larger industrial furnace/boiler that utilizes a larger resonance time for the droplet to travel. 
         [0045]    In the exemplary SNCR and SCR systems  300  and  400 , reagent droplets are injected with air into the respective temperature zones  318  and  448 . Compared to larger utility furnaces/boilers, the smaller industrial SNCR and SCR systems  300  and  400  act to release fine reagent droplets closely coupled to a reagent injection port so that the droplets may react sooner with the flue gas to reduce NO x . Therefore, the air heater, the vaporizer, and the mixer of the known SCR and SNCR systems, such as SNCR and SCR systems  100  and  200  (shown in  FIGS. 1 and 2 ), may be eliminated in the exemplary SNCR and SCR systems of the present application. As a result, the exemplary SNCR and SCR systems of the present application streamline SNCR and SCR systems design and facilitate more cost-effective systems by reducing capital and utility costs for smaller industrial combustion systems. 
         [0046]    In the exemplary SNCR and SCR systems of the present application, the above-described systems each include a reagent injection system having an atomizer directly coupled in flow communication with a reagent storage device to facilitate reducing NO x . As a result, each reagent injection system facilitates reducing a number of system components, such as an air heater, a vaporizer, and a mixer. Moreover, a flow/travel path of a reagent introduced to each system is shorter than a flow/travel path of known SNCR and SCR systems. Therefore, the reduced number of system components and reduce flow/travel path length facilitate reducing equipment size, material, complexity, maintenance, and cost. 
         [0047]    Exemplary embodiments of reagent injection systems are describe in detail above. The reagent injection systems are not limited to use with the specific SNCR and SCR systems described herein, but rather, the reagent injection systems can be utilized independently and separately from other system components described herein. Moreover, the invention is not limited to the embodiments of the reagent injection systems described above in detail. Rather, other variations of the reagent injection systems may be utilized within the spirit and scope of the claims. 
         [0048]    While the invention has been described in terms of various specific embodiments, those skilled in the art will recognize that the invention can be practiced with modification within the spirit and scope of the claims.