Patent Publication Number: US-9427702-B2

Title: Electric reagent launcher for reduction of nitrogen

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     The present application is a Continuation of U.S. patent application Ser. No. 13/963,223, entitled “CHARGE-INDUCED SELECTIVE REDUCTION OF NITROGEN”, filed Aug. 9, 2013, now pending; which application claims priority benefit under 35 USC §119(e) to U.S. Provisional Application Ser. No. 61/683,177; entitled “CHARGE-INDUCED SELECTIVE NON-CATALYTIC REDUCTION (SNCR) OF NITROGEN”, filed Aug. 14, 2012; each of which, to the extent not inconsistent with the disclosure herein, is incorporated herein by reference. 
    
    
     BACKGROUND 
     Oxides of nitrogen (NOx) are undesirable byproducts of combustion of a fuel in air. Some fuels, such as coal and biomass provide additional nitrogen and can be more problematic. Unfortunately, combustion of inexpensive fuels such as coal, biomass, and waste may tend to produce the most NOx. Regulations and general concerns for air quality have caused manufacturers and operators of combustion systems to seek ways to decrease emissions of NOx from combustion processes. 
     One approach to decrease the output of thermal NOx is to decrease peak-combustion reaction temperature. Another approach to decrease the output of NOx is to convert NOx present in post-combustion gases into molecular nitrogen, N 2 . Since NOx is an oxidized form of nitrogen, conversion of NOx to N 2  is referred to as nitrogen reduction. Selective nitrogen reduction processes including selective catalytic reduction (SCR) and selective non-catalytic reduction (SNCR) are used to chemically reduce oxides of nitrogen (NOx) to molecular nitrogen, N 2 . 
     NOx typically includes NO and NO 2 , but at high temperatures is usually dominated by NO. In SNCR, a nitrogen compound such as ammonia (NH 3 ), urea (NH 2 CONH 2 ), or another reagent is injected into hot (but not too hot) combustion fluids, such as in a firebox or boiler. If urea is injected, it reacts to form ammonia according to reaction (1):
 
NH 2 CONH 2 +½O 2 →2 NH 3 +CO 2   (1)
 
     The nitrogen reduction reaction may be expressed as:
 
4NO+4NH 3 +O 2 →4N 2 +6H 2 O  (2)
 
     The mechanism for reaction (2) involves the formation of intermediate .NH 2  radicals that react with NO to form the reaction products N 2  and H 2 O. 
     One complication with the chemistries described above relates to temperature. At temperatures above 1093° C., ammonia decomposes to form NO according to reaction (3):
 
4NH 3 +5O 2 →4NO+6H 2 O  (3)
 
     Other complications to operation of SCR/SNCR systems relate to non-uniform NOx distribution in a combustion volume or flue gas and delivery of an appropriate amount of reducing agent to the NOx distribution. Since central regions of fireboxes and furnaces tend to be hotter than regions near firebox and furnace walls, more NO tends to be formed near the center. Thus, uniform distribution of NH 3  across a combustion volume will not result in uniform reduction in NOx. Moreover, it can be difficult to distribute NH 3  to areas where it is needed. 
     Generally, existing SCR/SNCR systems suffer from ammonia slip (passage of unreacted ammonia out a flue) and lower than theoretical efficiency (equilibrium) with respect to removal of NOx. 
     What is needed is a technology that can improve performance and/or reduce costs of SCR and SNCR systems. 
     SUMMARY 
     According to an embodiment, a charge-induced selective catalytic reduction (SCR) or selective non-catalytic nitrogen oxide (NOx) reduction (SNCR) system is provided. The charge-induced SCR or SNCR system includes a reagent charging apparatus configured to apply electrical charges to a reagent or a fluid carrying the reagent to produce a charged reagent. The reagent can include molecules, an aerosol, droplets, or particles, for example. The SCR or SNCR system includes a reagent launcher operatively coupled to the reagent charging apparatus. The reagent launcher is configured to launch the charged reagent proximate to a combustion reaction or flue gas produced by the combustion reaction. Opposite polarity charges carried by the combustion reaction or flue gas can attract the charged reagent toward a reaction zone. Alternatively, a counter-electrode carrying a voltage opposite in polarity from the reagent charge can attract the charged reagent toward the reaction zone. 
     According to an embodiment, a method for operating a nitrogen oxide (NOx) control system is provided. The method includes applying first electrical charges to an SCR or SNCR reagent and contacting the charged reagent with a combustion reaction or a flue gas from a combustion reaction. The first electrical charges are selected to enhance mixing of the SCR or SCNR reagent with NOx-carrying fluids and/or to enhance reactivity of the reagent with NOx. For example, the first electrical charges can be opposite in polarity to charges carried by the combustion reaction or flue gas. Additionally or alternatively, the first electrical charges can be opposite in polarity to a voltage carried by a counter-electrode positioned to draw the reagent across the combustion reaction or flue gas. Additionally or alternatively, the first electrical charges can be the same polarity as a voltage carried by a launching electrode positioned to repel the reagent across the combustion reaction or flue gas. The reagent reduces the NOx to molecular nitrogen (N 2 ). 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a block diagram depicting a charge-induced selective non-catalytic reduction (SNCR) system for reducing nitrogen oxides (NOx) to molecular nitrogen (N 2 ), according to an embodiment. 
         FIG. 2  is a block diagram depicting a charge-induced selective catalytic reduction (SCR) system for reducing nitrogen oxides (NOx) to molecular nitrogen (N 2 ), according to an embodiment. 
         FIG. 3  is a block diagram of an embodiment of a reagent launcher configured to vaporize and charge the reagent. 
         FIG. 4  is a block diagram of an embodiment of a reagent launcher configured to entrain the reagent in the dielectric gas to form a gas-entrained reagent. 
         FIG. 5  is a block diagram of an embodiment of a reagent launcher configured to eject a stream, a pulse, or a spray of the reagent carrying a voltage or charge. 
         FIG. 6  is a block diagram of an embodiment of a reagent launcher configured to output the reagent in the form of a gas phase reagent. 
         FIG. 7  is a flow diagram that outlines a method for operating a nitrogen oxide (NOx) control system, according to an embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     In the following detailed description, reference is made to the accompanying drawings, which form a part hereof. In the drawings, similar symbols typically identify similar components, unless context dictates otherwise. Other embodiments may be used and/or other changes may be made without departing from the spirit or scope of the disclosure. 
       FIG. 1  is a block diagram depicting a selective catalytic nitrogen oxide (NOx) reduction (SCR) system or a selective non-catalytic nitrogen oxide (NOx) reduction (SNCR) system  101 , according to an embodiment.  FIG. 2  is a block diagram depicting a charge-induced selective catalytic reduction (SCR) system  201  for reducing nitrogen oxides (NOx) to molecular nitrogen (N 2 ), according to an embodiment. 
     With reference to  FIGS. 1 and 2 , The SCR/SNCR systems  101 ,  201  include a reagent charging apparatus  102  configured to apply electrical charges to molecules, an aerosol, droplets, or particles of a reagent or a fluid carrying the reagent to produce a charged reagent  106 . A reagent launcher  104  is operatively coupled to the reagent charging apparatus  102 . The reagent launcher  104  is configured to launch the charged reagent  106  into a flue gas  110  produced by the combustion reaction  108 . Typical reagents can include urea, cyanuric acid, aqueous ammonia, anhydrous ammonia, or coordinated ammonia reactants. Such reagents can be referred to as ammoniacal reagents. The reagent can optionally include a charge carrier mixed with the reactant. Optionally, the particular reagent can be selected to accept a particular polarity of charge. For example, a cyano group can be relatively efficient at accepting and holding a positive charge. In another example, an amine group can be relatively efficient at accepting and holding a negative charge. 
     The primary difference between a SCR system  201  and a SNCR  101  system is the respective presence or absence of a catalyst  204 , which in turn affects a temperature window within which chemical reduction of nitrogen oxide will occur. In an SNCR embodiment, a charged reagent is injected above the combustion reaction  108  in the flue gas  110  at a location where the temperature is between about 1600° F. and 1800° F. (for an ammonia reagent) or between about 1800° F. and 2100° F. (for a urea reagent). Below the temperature window, NOx reduction may substantially not occur. At temperatures above the temperature window, the charged reagent can itself be converted to additional NOx. 
     In a SCR embodiment, a catalyst  204  lowers the NOx reduction temperature. The catalyst bed  204  is typically held in a reduction chamber  202 . Catalysts can include ceramic carrier with an oxide of a base metal such as vanadium, molybdenum, or tungsten; or a precious metal. As depicted schematically in  FIG. 2 , a charge-induced SCR system  201  including the charged reagent launcher  104  is typically positioned farther away from the combustion reaction  108  such that the temperature of the flue gas  110  is further reduced compared to a charged reagent launcher  104  used in a charged-induced SNCR system  101 . Other than positioning, the charge-induced SCR  201  and SNCR  101  systems can operate similarly. 
     According to an embodiment, the charged-induced SNCR charged reagent launcher  104  is positioned between the combustion reaction and a superheater (not shown). According to another embodiment, the charged-induced SNCR charged reagent launcher  104  is positioned downstream from the superheater and upstream from a convective boiler stage (not shown). According to an embodiment, a charged-induced SCR charged reagent launcher  104  is positioned downstream from a superheater (not shown) and upstream from a convective boiler stage (not shown). According to another embodiment, the charged-induced SNCR charged reagent launcher  104  is positioned downstream from a convective boiler stage (not shown) and either upstream or downstream from an economizer (not shown)  203 . Positioning of a charge-induced selective nitrogen reduction system, whether SCR or SNCR, can be adjusted according to operating temperatures of the burner system  203 ,  103 . 
     A counter charge, counter voltage, and/or ground electrode is used to attract the charged reagent. Referring to  FIG. 1 , in the SNCR embodiment  101 , a counter charge is shown as being provided by charging the combustion reaction  108 . If surfaces between the combustion reaction  108  and the reagent launcher  104  are insulated or galvanically isolated, combustion reaction charging may similarly be used in SCR embodiment. Referring to  FIG. 2 , in the SCR embodiment  201 , a counter voltage is shown as being provided by a counter electrode  206 . The counter electrode  206  can similarly be used in a SNCR embodiment. In a SCR embodiment (not shown) the catalyst bed  204  can be used as a counter electrode. For example, a porous electrode structure (not shown) such as a screen can be embedded in the catalyst bed  204  or placed on a surface of the catalyst bed  204 . In applications where the catalyst is conductive (as in a precious metal catalyst), the catalyst surface itself can operate as a counter electrode. Some catalysts operate by providing a free electron to an ammoniacal group. In such cases, applying a positive charge to the reagent and a negative voltage to the catalyst bed can aid in the electron-providing mechanism associated with the catalyst surface. 
     Referring again to  FIGS. 1 and 2 , the reagent launcher  104  and the reagent charging apparatus  102  can together form a portion of a furnace, process heater or a boiler system  103 . The reagent launcher  104  and the reagent charging apparatus  102  cooperate to cause a reduction in an amount of nitrogen oxide (NOx) species output by the furnace, process heater or the boiler system  103 . 
     The furnace, process heater or a boiler system  103 , in addition to the SCR/SNCR system  101 , includes a burner  112  configured to support the combustion reaction  108 . A fuel and oxidant (e.g., air containing oxygen) is provided to the burner  112 . 
     In an embodiment, the reagent charging apparatus  102  forms a portion of the reagent launcher  104 . In another embodiment, the reagent launcher  104  forms a portion of the reagent charging apparatus  102 . 
     The SCR/SNCR system  101  includes a power supply  114  operatively coupled to the reagent charging apparatus  102 . The power supply  114  is configured to apply electrical power as a high voltage to the reagent charging apparatus  102 . High voltage is defined as a (positive or negative) voltage of 1000 volts or more. 
     The SCR/SNCR system  101  can include a reagent controller  116  operatively coupled to the reagent launcher  104 . Optionally, the reagent controller can be one or more user-adjustable controls. In another embodiment, the reagent controller includes an electronic controller (e.g., a microcontroller, PID controller, networked controller, etc.) configured to select or control reagent control parameters. 
     Various reagent control parameters can be selected or controlled. For example, the reagent controller  116  can be configured to control a periodicity of reagent launching and/or a flow rate of reagent launched. The reagent controller  116  can be operatively coupled to the power supply  114 . The reagent controller  116  can be configured to control the power and/or voltage supplied by the power supply  114  to the reagent charging apparatus  102 , a counter electrode, and/or the combustion reaction. 
     The SCR/SNCR system  101  can include one or more sensors  118  operatively coupled to the reagent controller  116  and/or to the furnace, process heater or boiler system  103 . For example, the sensor  118  can measure a parameter that is related to operation of the SCR/SNCR system  101 . Examples of such sensors  118  can include a nitric oxide (NO) sensor, a nitrogen dioxide (NO 2 ) sensor, an ammonia (NH 3 ) sensor, an oxygen (O 2 ) sensor, a fuel flow rate sensor, a combustion reaction temperature sensor, a flue gas temperature sensor, a combustion reaction radiation sensor, a voltage sensor, an electric field sensor, and/or a current sensor. In some embodiments, multiple sensor types or sensor positions are used to provide feedback to the reagent controller  116 . 
     For example, a NOx sensor  118  can provide data to the reagent controller indicative of higher-than-desired NOx concentration in the flue gas. The reagent controller  116  can responsively increase the reagent charge density (e.g., by increasing the power supply voltage), increase the reagent flow rate, and/or decrease time between reagent injections. In another example, a temperature sensor  118  can sense temperature of a flue gas or combustion reaction at a reagent injection location. The reagent controller  116  can determine if the temperature exceeds a temperature window for the NOx reduction reaction. If the temperature is too high, the reagent controller can turn off the reagent launcher or reagent flow to the reagent launcher to avoid increasing NOx further. 
     Alternatively, the reagent controller  116  can change a reagent launch location or trajectory to a cooler location. Other control approaches fall within the scope of this application and will be apparent to one skilled in the art. 
     In some examples, the reagent charging apparatus  102  and the reagent launcher  104  are configured to cooperate to reduce the amount of NOx output compared to application of an uncharged reagent. In several examples, the reagent charging apparatus  102  and the reagent launcher  104  can be configured to cooperate to reduce an amount of reagent used to reach an amount of NOx reduction compared to application of an uncharged reagent. 
     According to an embodiment, the reagent charging apparatus  102  is configured to at least intermittently apply positive electrical charge to the reagent. The positive electrical charges applied to the reagent may be selected to form a higher equilibrium concentration of ammonium ions (NH 4   + ) in the charged reagent compared to an equilibrium concentration of ammonium ions in the uncharged reagent. The higher concentration of ammonium ions may be selected to cooperate with species in the combustion reaction to increase a rate of mass transport of an ammonium or an ammonia species across at least a portion of the combustion reaction  108  compared to a rate of mass transport of an uncharged ammonium or ammonia species. The higher concentration of ammonium ions may be selected to cooperate with NOx molecules to increase a diffusion rate for pairing ammonium ions with NOx molecules compared to an equilibrium concentration of ammonium ions in the uncharged reagent. 
     According to an embodiment, the reagent charging apparatus  102  is configured to at least intermittently apply negative electrical charges to the reagent. The negative electrical charges applied by the reagent charging apparatus  102  can be selected to induce radicalization of ammonia or urea to form aminyl radicals (.NH 2 ). Aminyl radicals may be considered NOx reduction reaction intermediates. Accordingly, the reagent charging apparatus  102  may be configured to cause an increase in concentration of a SCR/SNCR reaction intermediate compared to an uncharged reagent. 
     In some examples, the electrical charges applied by the reagent charging apparatus  102  can be configured to increase reactivity of the reagent with NOx molecules in the flue gas  110  compared to an uncharged reagent. In several examples, the electrical charges applied by the reagent charging apparatus  102  can be selected to increase mixing of the reagent with the flue gas  110  compared to an uncharged reagent. In multiple examples, the increased mixing can reduce ammonia slip, reduce NOx output, or reduce both ammonia slip and NOx output compared to application of an uncharged reagent. 
     In many examples, the SCR/SNCR system  101  can include a combustion reaction charging apparatus  120  configured to apply a voltage or charge to the combustion reaction  108 . For example, the charging apparatus  120  can include an electrode supported in contact with the combustion reaction  108 . In some examples, the charging apparatus is at least partially coextensive with a fuel nozzle configured to support the combustion reaction  108 . 
     The combustion reaction charging apparatus  120  may be configured to apply to the combustion reaction  108  a voltage or a majority charge having an instantaneous sign opposite of an instantaneous polarity of electrical charges applied by the reagent charging apparatus  102 . In some examples, the reagent charging apparatus  102  can be configured to apply a substantially constant charge concentration and polarity to the molecules, aerosol, droplets, or particles of the reagent or the fluid carrying the reagent. In several examples, the reagent charging apparatus  102  may be configured to apply a time-varying charge concentration, a time-varying polarity, or a time-varying charge concentration and polarity to the molecules, aerosol, droplets, or particles of the reagent or the fluid carrying the reagent. When the reagent charging apparatus  102  applies a time varying polarity to the reagent, the combustion reaction charging apparatus  120  can be driven in opposition to the reagent charging apparatus such that the polarity of the combustion reaction and the polarity of the charged reagent are opposite of one another. 
     The reagent launcher  104  can include a reagent control valve (not shown) configured to control a flow rate of the reagent from a reagent source to a reagent mixer (not shown) or a reagent injector. A reagent mixer may include a Venturi or a length of tube (e.g., a constant cross-section tube) with an orifice configured to meter the nitrogenous compounds into a carrier gas or to mix the reagent with charge carrier particles. 
       FIG. 3  is a block diagram of an embodiment  301  of a reagent launcher  104 . In various examples, the apparatus  301  may be configured to vaporize and apply a charge to the reagent or a liquid carrying the reagent. In some examples, the reagent launcher  104  can include a body  302  defining a vaporization or atomization chamber  304 . The apparatus  301  can include a pair of electrodes  306   a  and  306   b  configured to apply a voltage-biased high voltage pulse to the reagent, the reagent-containing droplet, or the liquid carrying the reagent. The apparatus  301  can include a reagent delivery passage  310  configured to deliver the reagent or the liquid carrying the reagent from a reagent source  212  to the vaporization chamber  304 . In some examples, the power supply  114  can be configured to apply the voltage-biased high voltage pulse to the pair of electrodes  306   a  and  306   b  to cause the reagent or fluid carrying the reagent to vaporize and be ejected as a reagent vapor or aerosol  312  carrying the charged reagent  106 . 
     The apparatus  301  can include a reagent controller  116  operatively coupled to the power supply  114 . The apparatus  301  can include a reagent control valve  309  operatively coupled to the reagent source  212 , the reagent delivery passage  310 , and the reagent controller  116 . In some examples, the reagent controller  116  is configured to drive the reagent control valve  309  to admit a quantity of reagent to the vaporization chamber  304  via the reagent delivery passage  310 . The reagent controller  116  (if present) is configured to cause the power supply  114  to apply the voltage-biased high voltage pulse to the electrodes  306   a  and  306   b.    
     The application of a high voltage pulse to a liquid causes the liquid to vaporize, in some examples without any substantial corresponding increase in liquid temperature. By biasing the high voltage pulse positive or negative, a corresponding charge may be placed on the vaporized liquid. For example, positive bias voltage can be caused by applying a positive voltage on one electrode  306   a  and holding the other electrode  306   b  at ground. Alternatively, a positive bias voltage can be caused by applying a relatively large positive voltage on one electrode  306   a  and applying a negative voltage of lower magnitude on the other electrode  306   b.  The positive bias voltage can cause the reagent vapor or aerosol  312  to carry a net positive charge. The positive charge may tend to be carried by nitrogenous compounds in the reagent. 
     In some examples, negative bias voltage can be caused by applying a negative voltage on one electrode  306   a  and holding the other electrode  306   b  at ground. Alternatively, a negative bias voltage may be caused by applying a relatively large negative voltage on one electrode  306   a  and applying a positive voltage of lower magnitude on the other electrode  306   b.  The negative bias voltage causes the reagent vapor or aerosol  312  to carry a net negative charge. The negative charge may tend to be carried by the reagent. 
     The electrodes optionally can be configured to carry reversed combinations of positive, negative, and ground pulses, as applicable. The reagent source  212  may hold a pressurized liquid such as a water solution of dissolved ammonia. Alternatively, the reagent source  212  may be configured to hold the reagent in the form of a solid dispersed in a liquid, for example, a urea slurry. Alternatively, the reagent source  212  may be configured to hold anhydrous ammonia. 
       FIG. 4  is a block diagram of an embodiment  401  of a reagent launcher  104 . The apparatus  401  is configured to meter the reagent into a dielectric gas. The apparatus  401  is configured to entrain the reagent in the dielectric gas to form a gas-entrained reagent  403 . The apparatus  401  is configured to eject a charge into the dielectric gas. The apparatus  401  may be configured to deposit the charge from the dielectric gas onto the gas-entrained reagent  403 . 
     The apparatus  401  may be configured to eject a stream, a pulse, or a cloud of the gas-entrained reagent  403 . In some examples, the reagent launcher  104  can include a body  402  defining a gas flow passage  404  in communication with a gas source and a region proximate to the flue gas  110  produced by the combustion reaction  108 . The apparatus  401  includes a reagent meter  410  configured to meter the reagent into a gas  408  passing through the gas flow passage  404  to form the gas-entrained reagent composition  403 . The reagent charging apparatus can include at least one corona electrode  414  configured to create a charge concentration in the gas  408  passing through the gas flow passage  404  for depositing the charge on the metered reagent entrained in the gas passing through the gas flow passage. The charges ejected by the corona electrode  414  may be deposited substantially completely on the reagent. Alternatively, charge carrier particles can be combined with the reagent, and the charges may be deposited on the charge carrier particles. 
     The reagent launcher  104  includes a reagent control valve  412  configured to control the supply of the reagent to the reagent meter  410 . The reagent controller  116  may be operatively coupled to and configured to control the operation of the reagent control valve  412 . A power supply  114  is operatively coupled to the corona electrode  414 . 
       FIG. 5  is a block diagram of another embodiment  501  of a reagent launcher  104 . The apparatus  501  is configured to eject a stream, a pulse, or spray of a liquid  503  carrying a voltage or a charge and the reagent. In some examples, the apparatus  501  can be configured to eject the stream, the pulse, or the spray of liquid  503  carrying the charged reagent  106 . The reagent launcher  104  includes a nozzle  502  configured to eject the stream, the pulse, or the spray including the reagent  106 . The reagent charging apparatus  102  can be substantially coextensive with the nozzle  502  or the reagent charging apparatus  102  can be operatively coupled to the nozzle  502 . A power supply  114  is operatively coupled to the reagent charging apparatus  102  and configured to cause the reagent charging apparatus  102  to apply the charge to the reagent. 
     In numerous examples of the apparatus  501 , the power supply  114  can be operatively coupled to a combustion reaction charging apparatus  120  and/or to an attraction electrode (see, e.g.,  FIG. 2, 206 ). In various examples, the apparatus  501  includes a reagent control valve  504  operatively coupled to the nozzle  502 . The reagent control valve  504  can be configured to control the flow of the reagent. In some examples, the apparatus  501  includes a reagent controller  116  operatively coupled to the reagent control valve  504 . The reagent controller  116  can be configured to cause the reagent control valve  504  to control the flow of the reagent. 
     In many examples, the apparatus  501  includes a reagent supply subsystem  506 . The reagent supply subsystem  506  can include a reagent tank  508  operatively coupled to the nozzle  502 . The reagent tank  508  can be configured to hold a liquid vehicle for carrying the reagent or a liquid reagent  510 . In some examples, one or more electrical isolators  512  can be operatively coupled to the reagent tank  508 . The electrical isolators  512  can be configured to maintain the reagent tank and the liquid vehicle for carrying the reagent or a liquid reagent  510  in electrical isolation from voltages or ground other than voltages or ground conveyed from a voltage source  114 . The apparatus  501  can further include a dielectric gap  514  formed between a reagent source  516  and the liquid vehicle for carrying the reagent or the liquid reagent  510 . In some examples, the apparatus  501  can further include at least a portion of the reagent source  516 . 
     In addition to or in alternative to galvanic isolation of the liquid reagent tank  508 , the liquid can be selected or treated to have low electrical conductivity. Galvanic isolation of such a liquid can include a relatively long non-conductive pipe having a length selected to limit or eliminate conduction through the liquid. 
       FIG. 6  is a block diagram of another embodiment  601  of a reagent launcher  104  configured to output a gaseous reagent or a gas carrying the reagent. The reagent launcher  104  includes a gas nozzle  604  configured to output the gaseous reagent into the flue gas  110 . The reagent charging apparatus  102  (shown in  FIG. 1 ) may further include an ionizer  606  configured to cause charge ejection into the gaseous reagent. A gaseous reagent supply  602  can be operatively coupled to the gas nozzle  604  and the ionizer  606 . The apparatus  601  can include reagent supply valve  608  operatively coupled to the reagent supply  602  and the gas nozzle  604 . 
     A reagent controller  116  can be operatively coupled to the reagent supply valve  608  and configured to cause the reagent supply valve  608  to control a flow rate of, or a periodicity of providing, the gaseous reagent from the reagent supply  602  to the gas nozzle  604 . A power supply  114  is operatively coupled to at least the ionizer  606  and can be configured to cooperate with the ionizer  606  to eject the charges into the gaseous reagent. 
     The system  103 ,  203  can be configured to output heat from the combustion reaction. A subsystem (not shown) configured to receive heat from the combustion reaction can include an industrial process, a gas turbine, a process material, a boiler, a furnace, a process heater, a prime mover, a power generation system, a commercial heating system, a commercial cooking system, or a commercial or residential hot water system, for example. 
       FIG. 7  is a flow chart that shows a method  701  for operating a nitrogen oxide (NOx) control system, according to an embodiment. In various examples, the method  701  includes an operation  702  of applying first electrical charges to a SCR/SNCR reagent. The method  701  can include an operation  704  of contacting the charged reagent into a combustion reaction or a combustion gas from a combustion reaction. The method  701  can include an operation  706  wherein the electrical charge can be selected to enhance mixing of the SCNR reagent with NOx or to enhance NOx reactivity of the reagent with NOx. The method  701  can include an operation  708  to reduce the NOx to molecular nitrogen (N 2 ). 
     In some examples of the operation  702 , applying first electrical charges to the SCR/SNCR reagent can include applying first electrical charges to urea, ammonia, a solution including urea, or a solution including ammonia. In further examples of the method  701 , operation  702  can include applying first electrical charges to the SCR/SNCR reagent composition by operating a reagent charging apparatus. In multiple examples, operation  702  can include operating a power supply to apply electricity to the reagent charging apparatus. 
     In various examples of the method  701 , the operation  704  for injecting the charged reagent into a combustion reaction or a combustion gas from the combustion reaction includes include operating a reagent launcher. In some examples, the method  701  can include (not shown) operating a reagent controller to control a periodicity or a rate of reagent injected into the combustion reaction or the combustion gas from the combustion reaction. 
     In several examples, the method  701  includes include (not shown) operating at least one sensor. In many examples, the method  701  may include operating the reagent controller responsive to a signal from the at least one sensor. In numerous examples, operating the at least one sensor includes operating a NO sensor. In various examples, operating the at least one sensor includes operating a NO 2  sensor. In some examples, operating the at least one sensor includes operating an ammonia sensor. In several examples, operating the at least one sensor includes operating an oxygen sensor. In many examples, operating the at least one sensor includes operating a combustion fluid flow rate sensor. In multiple examples, operating the at least one sensor includes operating a combustion reaction temperature sensor. In numerous examples, operating the at least one sensor includes operating a combustion reaction radiation sensor. In further examples, operating the at least one sensor includes operating a voltage sensor. In various examples, operating the at least one sensor includes operating an electric field sensor. In some examples, operating the at least one sensor includes operating a current sensor. 
     Referring to  FIG. 7  and to  FIG. 3 , operating the reagent launcher  104  can include operating the apparatus  301  configured to vaporize and apply a charge to the reagent or a liquid carrying the reagent. Referring to  FIG. 7  and to  FIG. 4 , operating the reagent launcher  104  can include operating the apparatus  401  configured to meter the reagent into a dielectric gas. In many examples, operating the reagent launcher  104  can include entraining the reagent in the dielectric gas. Operating the reagent launcher  104  can include ejecting a charge into the dielectric gas. In further examples, operating the reagent launcher  104  can include depositing the charge from the dielectric gas onto the entrained reagent. Referring to  FIG. 7  and to  FIG. 5 , operating the reagent launcher  104  can include operating an apparatus  501  configured eject a stream, a pulse, or a spray of a liquid  503  carrying a voltage or a charge and including the reagent. Referring to  FIG. 7  and to  FIG. 6 , operating the reagent launcher can include operating an apparatus  601  configured to output a gaseous reagent or a gas carrying the reagent. 
     Referring to  FIG. 7 , the operation  702  for applying the first electrical charges to the SCR/SNCR reagent and the operation  704  for injecting the charged reagent into a combustion reaction or a combustion gas from a combustion reaction can include operating a reagent charging apparatus and a reagent launcher that are at least partially coextensive. 
     In multiple examples, applying the first electrical charges to the SCR/SNCR reagent includes applying a voltage include applying electricity to the reagent. In some examples, applying the first electrical charges to the SCR/SNCR reagent can include applying a time-varying charge to the reagent. In further examples, applying a time-varying charge to the SCR/SNCR reagent can include applying a sequence of positive and negative charges to the reagent. In other examples, applying a time-varying charge to the SCR/SNCR reagent can include applying a pulsed charge of a single sign to the reagent. In some examples, applying a charge to the SCR/SNCR reagent can include applying a charge of a single polarity to the reagent. In several examples, charging the SCR/SNCR reagent can include applying a positive voltage to the reagent. 
     In some examples, charging the SCR/SNCR reagent includes applying a negative charge to the SCNR regent. Where the SCNR reagent composition includes ammonia or urea, the method  701  can include forming amide (NH 2 —) ions from the ammonia or the urea. In further examples, the method  701  can include decomposing the amide ions to aminyl radicals (.NH 2 ) after injecting the charged reagent. In several examples, the operation  708  for reducing the NOx to molecular nitrogen includes reacting the aminyl radicals with nitric oxide to produce molecular nitrogen and water. 
     In several examples, operation  706  for enhancing reactivity of the reagent with NOx to operation  708  for reducing the NOx to molecular nitrogen can include causing reagent charging selected to increase a rate of reaction. 
     In many examples, operation  706  for enhancing reactivity of the reagent with NOx and operation  708  for reducing the NOx to molecular nitrogen can include causing reagent charging selected to decrease an average distance between the charged reagent molecules and NOx molecules. 
     In many examples, operation  706  for enhancing reactivity of the reagent with NOx to operation  708  for reducing the NOx to molecular nitrogen can include causing the reagent to adopt an activated form selected to increase attraction between the activated form of the reagent and NO. 
     In embodiments, the method  701  includes operation  712  of supporting the combustion reaction. The method  701  can include operation  710  for providing a fuel to support the combustion reaction. The operation of providing a fuel may include providing a hydrocarbon gas, a hydrocarbon liquid, or powdered coal, for example. 
     In some examples, the method  701  includes an operation  714  of applying second electrical charges or a second voltage to the combustion reaction. The second electrical charges or voltage are opposite in polarity from the first electrical charges. Applying a second voltage to the combustion reaction can include operating the combustion reaction charging apparatus such as a charge electrode. The charge electrode may be at least partially coextensive with a burner configured to support the combustion reaction. The second voltage is opposite in sign from the first electrical charges. Alternatively, the operation  714  can include applying a second voltage and/or a ground potential to an attraction electrode. The attraction electrode can be positioned to draw the charged reagent across a flue or to a SCR catalyst bed. 
     In an embodiment, applying the first electrical charges to the reagent and applying the second voltage to the combustion reaction or the attraction electrode can include synchronously applying opposite polarity time-varying electrical charges and/or voltages. 
     The method  701  can include decreasing NOx produced by the combustion reaction for a given heat output or decreasing an amount of the SCR/SNCR reagent usage for a given amount of NOx reduction compared to injecting non-charged SCR/SNCR reagent, for a given heat output. 
     The method  701  can include applying heat from the combustion reaction to an industrial process, a gas turbine, a process material, a boiler, a furnace, power generation system, a prime mover, a commercial heating system, or to a commercial or residential hot water system, for example. 
     While various aspects and embodiments have been disclosed herein, other aspects and embodiments are contemplated. The various aspects and embodiments disclosed herein are for purposes of illustration and are not intended to be limiting, with the true scope and spirit being indicated by the following claims.