JP2012154241A - On-board ammonia production device and method for producing ammonia on-board - Google Patents

Abstract

Ammonia supplied as a NOx reducing agent to a selective catalytic reduction catalyst is continuously generated, whereby ammonia is continuously supplied to the selective catalytic reduction catalyst.
SOLUTION: Ammonia to be supplied to a selective catalytic reduction catalyst 13 mounted on a vehicle is manufactured using an in-vehicle ammonia manufacturing apparatus 14 mounted on the vehicle. A mixed gas obtained by mixing the air supplied from the air supply source 17 and the fuel 15 supplied from the fuel supply source 18 is heated by the heating means 19, and the mixed gas heated by the heating means 19 is converted into the reforming catalyst 21. It is configured to be reformed to generate at least hydrogen. The NOx generation means 22 generates NOx from nitrogen in the air supplied from the air supply source 17 or generates NOx in the exhaust gas by combustion of fuel in the vehicle engine, and the ammonia generation catalyst 23 is used for the hydrogen and the above. It is configured to generate ammonia by reaction with NOx.
[Selection] Figure 1

Description

  The present invention relates to an ammonia production apparatus mounted on a vehicle for producing ammonia to be supplied to a selective reduction catalyst mounted on the vehicle, and to produce ammonia on the vehicle for supply to the selective reduction catalyst. It is about how to do.

  Conventionally, a lean NOx trap absorbs and holds NOx from the exhaust gas of a diesel engine under a lean exhaust condition, and reduces and releases the retained NOx under a fuel (HC) rich exhaust condition. The ammonia-SCR catalyst receiving the gas released from the catalyst reacts with ammonia capable of reducing NOx under the condition of lean exhaust gas to act as a catalyst, and further, an additional catalyst placed between the lean NOx trap and the ammonia-SCR catalyst However, there is disclosed an exhaust aftertreatment system for a diesel engine configured to reduce the concentration of hydrocarbons in exhaust gas under fuel (HC) rich exhaust conditions (see, for example, Patent Document 1). In this exhaust aftertreatment system, the lean NOx trap absorbs and holds NOx from the exhaust gas of the diesel engine under lean exhaust conditions, and in the reducing environment formed in the exhaust for regeneration (denitration) of the lean NOx trap Thus, the absorbed NOx is reduced and removed. The lean NOx trap is configured to be able to generate ammonia during denitration (during regeneration of the lean NOx trap).

  In the exhaust aftertreatment system for a diesel engine configured as described above, the lean NOx trap absorbs and holds NOx under a lean exhaust condition, and reduces NOx under a fuel (HC) rich exhaust condition. Releases and produces ammonia. After the ammonia-SCR catalyst absorbs almost all of the ammonia produced by the lean NOx trap, the absorbed ammonia reacts with NOx to act as a catalyst, thereby reducing NOx that has passed through the lean NOx trap. It has become.

JP-T 2009-540189 (Claim 1, paragraphs [0008], [0009], [0024])

  However, in the exhaust aftertreatment system for a diesel engine shown in the above-mentioned conventional patent document 1, the lean NOx trap absorbs and stores NOx under the lean exhaust condition, and the exhaust condition of fuel (HC) rich NOx is reduced and released at the same time as ammonia is generated, so that ammonia cannot be generated under lean exhaust conditions. For this reason, the exhaust aftertreatment system disclosed in Patent Document 1 has a problem that ammonia cannot be continuously generated and ammonia cannot be continuously supplied to the ammonia-SCR catalyst. Further, in the exhaust aftertreatment system disclosed in the above-mentioned conventional patent document 1, ammonia is generated by a lean NOx trap using NOx of exhaust gas from a diesel engine as a raw material. Therefore, NOx is reduced by an ammonia-SCR catalyst. There was also a problem that the optimum amount of ammonia required could not be generated.

  An object of the present invention is to provide an on-vehicle ammonia production apparatus and a vehicle that can continuously generate ammonia supplied as a reducing agent for NOx to a selective catalytic reduction catalyst, thereby continuously supplying ammonia to the selective catalytic reduction catalyst. The object is to provide a method for producing ammonia. Another object of the present invention is to adjust the generation amount of ammonia supplied to the selective reduction catalyst as a NOx reducing agent, thereby selectively reducing the optimum amount of ammonia required for NOx reduction in the selective reduction catalyst. An object is to provide an in-vehicle ammonia production apparatus and a method for producing ammonia on a vehicle, which can be supplied to a catalyst.

  As shown in FIG. 1, a first aspect of the present invention is an in-vehicle ammonia production apparatus mounted on a vehicle for producing ammonia to be supplied to a selective catalytic reduction catalyst 13 mounted on the vehicle. Heating means 19 for heating a mixed gas obtained by mixing the air supplied from the source 17 and the fuel 15 supplied from the fuel supply source 18, and reforming the mixed gas heated by the heating means 19 to generate at least hydrogen A reforming catalyst 21 for generating NOx from nitrogen in the air supplied from the air supply source 17 or NOx generating means 22 for generating NOx in exhaust gas by combustion of fuel in a vehicle engine, and the hydrogen And an ammonia generation catalyst 23 that generates ammonia by the reaction of NOx with the NOx.

  The second aspect of the present invention is an invention based on the first aspect, wherein the reforming catalyst generates hydrogen and carbon monoxide, and the ammonia generating catalyst generates ammonia by the reaction of hydrogen and NOx. The ammonia is produced by the reaction between hydrogen produced from carbon monoxide and NOx.

  A third aspect of the present invention is an invention based on the first aspect, and is characterized in that the heating means 19 is a heater or a burner as shown in FIG.

  The fourth aspect of the present invention is an invention based on the first aspect, and further, as shown in FIG. 1, the NOx generating means 22 uses the plasma generated by the plasma generator 28 to use the air supply source 17. It is characterized by generating NOx from nitrogen in the air supplied from the factory.

  A fifth aspect of the present invention is an invention based on the first or second aspect, and as shown in FIG. 1, the reforming catalyst 21 is an alumina catalyst in which platinum and rhodium are supported on alumina, or palladium. And an alumina catalyst in which rhodium is supported on alumina.

  A sixth aspect of the present invention is an invention based on the first or second aspect, and further, as shown in FIG. 1, the ammonia generating catalyst 23 is an oxidation catalyst having platinum supported on alumina. To do.

  As shown in FIG. 1, the seventh aspect of the present invention is a method for producing ammonia on a vehicle to be supplied to a selective catalytic reduction catalyst 13 mounted on the vehicle, which is supplied from an air supply source 17. A heating step of heating the mixed gas obtained by mixing the heated air and the fuel 15 supplied from the fuel supply source 18, a reforming step of reforming the heated mixed gas to generate at least hydrogen, and an air supply source NOx is generated from nitrogen in the air supplied from 17, or NOx is generated in exhaust gas by combustion of fuel in a vehicle engine, and ammonia is generated by reaction of the hydrogen and NOx. And an ammonia production step.

  The eighth aspect of the present invention is an invention based on the seventh aspect, further generating hydrogen and carbon monoxide in the reforming step, and generating ammonia by reaction of hydrogen and NOx in the ammonia generating step. In addition, it is characterized in that ammonia is generated by a reaction between hydrogen generated by reacting carbon monoxide with water generated by combustion of the fuel 15 and NOx.

  The ninth aspect of the present invention is an invention based on the seventh aspect, and is characterized in that a heater 29 or a burner is used to heat the mixed gas in the heating step as shown in FIG. To do.

  A tenth aspect of the present invention is an invention based on the seventh aspect, and further generates NOx from nitrogen in the air supplied from the air supply source 17 in the NOx generation step as shown in FIG. Furthermore, the plasma generated by the plasma generator 28 is used.

  An eleventh aspect of the present invention is an invention based on the seventh or eighth aspect, and further, as shown in FIG. 1, platinum and rhodium are used to reform the mixed gas heated in the reforming step. An alumina catalyst 21 in which is supported on alumina or an alumina catalyst in which palladium and rhodium are supported on alumina is used.

  A twelfth aspect of the present invention is an invention based on the seventh or eighth aspect, and as shown in FIG. 1, an oxidation catalyst in which platinum is supported on alumina to produce ammonia in the ammonia production step. 23 is used.

  In the apparatus according to the first aspect of the present invention, the heating unit heats the mixed gas obtained by mixing the air supplied from the air supply source and the fuel supplied from the fuel supply source, and the mixed gas heated by the heating unit. The reforming catalyst reforms to generate at least hydrogen, and the NOx generating means generates NOx from nitrogen in the air supplied from the air supply source, or NOx in the exhaust gas by combustion of fuel in the vehicle engine Furthermore, the ammonia generation catalyst generates ammonia by the reaction of the hydrogen with the NOx, so that the ammonia supplied as the NOx reducing agent to the selective reduction catalyst can be continuously generated and the generation of the ammonia. The amount can be adjusted. As a result, ammonia can be continuously supplied to the selective catalytic reduction catalyst, and an optimum amount of ammonia necessary for NOx reduction in the selective catalytic reduction catalyst can be supplied to the selective catalytic reduction catalyst.

  In the apparatus according to the second aspect of the present invention, the reforming catalyst generates hydrogen and carbon monoxide, the ammonia generating catalyst generates ammonia by the reaction of hydrogen and NOx, and the hydrogen generated from carbon monoxide and Since ammonia is generated by the reaction with NOx, similarly to the apparatus of the first aspect of the present invention, ammonia supplied as a reducing agent for NOx to the selective reduction catalyst can be continuously generated, and the generation of the ammonia The amount can be adjusted. As a result, ammonia can be continuously supplied to the selective catalytic reduction catalyst, and an optimum amount of ammonia necessary for NOx reduction in the selective catalytic reduction catalyst can be supplied to the selective catalytic reduction catalyst. The apparatus according to the second aspect of the present invention can generate more ammonia than the apparatus according to the first aspect of the present invention.

  In the method according to the seventh aspect of the present invention, a mixed gas obtained by mixing air supplied from an air supply source and fuel supplied from a fuel supply source is heated, and the heated mixed gas is reformed to at least Hydrogen is generated, NOx is generated from nitrogen in the air supplied from an air supply source, or NOx is generated in exhaust gas by combustion of fuel in a vehicle engine, and further, the reaction between the hydrogen and the NOx is performed. In addition, ammonia is produced by the reaction of the hydrogen produced by reacting the carbon monoxide with the water produced by the combustion of the fuel and the NOx, so that, similarly to the above, NOx is added to the selective catalytic reduction catalyst. Ammonia supplied as a reducing agent can be continuously produced, and the amount of ammonia produced can be adjusted. As a result, ammonia can be continuously supplied to the selective catalytic reduction catalyst, and an optimum amount of ammonia necessary for NOx reduction in the selective catalytic reduction catalyst can be supplied to the selective catalytic reduction catalyst.

  In the method according to the eighth aspect of the present invention, hydrogen and carbon monoxide are generated in the reforming step, ammonia is generated by the reaction of hydrogen and NOx in the ammonia generating step, and carbon monoxide is used for combustion of the fuel 15. Since ammonia is produced by the reaction of hydrogen produced by reacting with the produced water and NOx, the ammonia supplied as the NOx reducing agent to the selective catalytic reduction catalyst is reduced as in the method of the seventh aspect. It can be produced continuously and the amount of ammonia produced can be adjusted. As a result, ammonia can be continuously supplied to the selective catalytic reduction catalyst, and an optimum amount of ammonia necessary for NOx reduction in the selective catalytic reduction catalyst can be supplied to the selective catalytic reduction catalyst. The method according to the eighth aspect of the present invention can generate more ammonia than the method according to the seventh aspect of the present invention.

It is a block diagram which shows the intake system and exhaust system of a diesel engine containing the vehicle-mounted ammonia manufacturing apparatus of this invention embodiment. It is a figure which respectively shows ammonia concentration (Example 1) when the high frequency power supply of a plasma generator is turned on, and ammonia concentration (Comparative example 1) when a high frequency power supply of a plasma generator is turned off.

Next, an embodiment for carrying out the present invention will be described with reference to the drawings. As shown in FIG. 1, the vehicle includes a diesel engine 11 that is a drive source of the vehicle, a selective reduction catalyst 13 provided in an exhaust pipe 12 that guides exhaust gas discharged from the engine 11 to the atmosphere, An ammonia production device 14 for producing ammonia supplied as a NOx reducing agent to the selective catalytic reduction catalyst 13 is mounted. The selective catalytic reduction catalyst 13 is provided in the exhaust pipe 12 and is accommodated in a case 16 having a larger diameter than the exhaust pipe 12. The selective catalytic reduction catalyst 13 has a function of reacting ammonia with NO and NO ₂ in the exhaust gas and reducing NO and NO ₂ to N ₂ . Further, the selective catalytic reduction catalyst 13 is a monolithic catalyst in form, and although not shown, a cordierite cylindrical honeycomb having both ends opened and formed with a plurality of cells (through holes) extending in the exhaust gas flow direction. The support is coated with copper ion exchanged zeolite (Cu-ZSM-5) or the like, or is formed of a stainless steel cylindrical shape in which a plurality of cells (through holes) that are open at both ends and extend in the flow direction of exhaust gas are formed. It is formed by coating a metal carrier with copper ion exchanged zeolite (Cu-ZSM-5) or the like. The copper ion exchange zeolite catalyst is a substance obtained by ion exchange of Na ions of Na type ZSM-5 zeolite with Cu ions. Instead of copper ion exchanged zeolite, iron ion exchanged zeolite, zeolite, titanium oxide, vanadium oxide, cerium oxide, zirconium oxide, or tungsten oxide may be coated.

  On the other hand, the ammonia production apparatus 14 is heated by the heating means 19 for heating the mixed gas obtained by mixing the air supplied from the air supply source 17 and the fuel 15 supplied from the fuel supply source 18, and the heating means 19. A reforming catalyst 21 that reforms the mixed gas to generate hydrogen, NOx generating means 22 that generates NOx from nitrogen in the air supplied from the air supply source 17, and ammonia by a reaction between the hydrogen and the NOx. And an ammonia generation catalyst 23 for generating. In this embodiment, the air supply source 17 is an air tank that is mounted on a vehicle and stores compressed air, and the fuel supply source 18 is a fuel that is mounted on the vehicle and stores fuel (light oil) 15 supplied to the diesel engine 11. It is a tank and the heating means 19 is an electric heater. The heater 19 includes a heater body 19a housed in a cylindrical first housing 41, and a heater power source 19b that supplies electric power to the heater body 19a. The air tank 17 and one end surface of the first housing 41 are connected by an air supply pipe 24 and a first air branch supply pipe 31, and the fuel tank 18 and one end face of the first housing 41 are connected by a fuel supply pipe 26. . The first housing 41 accommodates the heater body 19a and the reforming catalyst 21 in order from one end surface to the other end surface of the housing 41. The heater body 19a is accommodated in a heater pipe 19c formed in a spiral shape with a diameter gradually decreasing from one end to the other end of the first housing 41, and insulated by an insulating powder such as MgO in the heater pipe 19c. Nichrome wire (not shown). When the heater power supply 19b is turned on, the nichrome wire is heated, and this heat is transferred to the heater pipe 19c via the insulating powder, and the mixed gas of air and fuel 15 (including fine particles of the fuel 15) flowing into the first housing 41. Is configured to be in contact with the outer peripheral surface of the heater pipe 19c and heated to a predetermined temperature. A mixer (not shown) that mixes the fuel 15 and air is provided on one end face side of the heater body 19a in the first housing 41. Further, reference numeral 27 in FIG. 1 denotes a fuel return pipe that returns excess fuel 15 out of the fuel 15 supplied by a fuel pump 34 described later to the fuel tank 18.

  In this embodiment, a heater having a spiral heater body housed in the first housing and gradually decreasing in diameter and a heater power source for supplying electric power to the heater body is described as the heating means. One heater may be a heater having a spiral heater main body formed with a small diameter and wound on the outer peripheral surface thereof, and a heater power supply for supplying electric power to the heater main body, or air and fuel A burner that burns and heats a part of the mixed gas may be used.

  The reforming catalyst 21 is a monolith catalyst in form, and is an alumina catalyst in which platinum and rhodium are supported on alumina, or an alumina catalyst in which palladium and rhodium are supported on alumina. Specifically, an alumina catalyst in which platinum and rhodium are supported on alumina is formed by coating a honeycomb carrier made of cordierite with a slurry containing alumina powder in which platinum and rhodium are supported. An alumina catalyst in which palladium and rhodium are supported on alumina is formed by coating a honeycomb carrier made of cordierite with a slurry containing alumina powder in which palladium and rhodium are supported.

  On the other hand, the NOx generating means 22 is configured to generate NOx from nitrogen in the air supplied from the air supply source 17 using the plasma generated by the plasma generator 28. Specifically, the NOx generating means 22 includes the air tank 17 in which compressed air is stored, and a cylindrical second housing having one end surface connected to the air tank 17 by an air supply pipe 24 and a second air branch supply pipe 32. 42 and the plasma generator 28 for generating plasma for generating NOx from nitrogen in the air supplied to the second housing 42. The plasma generator 28 includes two disk-shaped first and second punching metal plates 28a and 28b, which are housed in a second housing 42 and formed of stainless steel and coated on both sides with a dielectric, and punching thereof. A high-frequency power source 28c that applies a high-frequency AC voltage of about 25 kHz between the metal plates 28a and 28b. The first and second punching metal plates 28a and 28b are accommodated in a cylindrical second housing 42 so as to partition the inside of the second housing 42 into two left and right chambers. When the high-frequency power supply 28c is turned on, a high-frequency AC voltage of about 25 kHz is applied to the discharge gap between the first and second punching metal plates 28a and 28b, and plasma is generated between the peripheral edges of the first and second punching metal plates 28a and 28b. Is supposed to occur.

  The ammonia generation catalyst 23 is accommodated in the third housing 43. The ammonia generation catalyst 23 is a monolith catalyst in form, and is an oxidation catalyst in which platinum is supported on alumina. Specifically, the ammonia generation catalyst 23 is configured by coating a honeycomb carrier made of cordierite with a slurry containing alumina powder supporting platinum. One end face of the third housing 43 is connected to the other end face of the first housing 41 by the first communication pipe 51 and the joining communication pipe 29, and the second communication pipe 52 and the joining communication pipe are connected to the other end face of the second housing 42. 29 is connected. One end of the ammonia supply pipe 30 is connected to the other end surface of the third housing 43, and the other end of the ammonia supply pipe 30 is connected to the ammonia injection nozzle 33. The ammonia injection nozzle 33 is provided in the exhaust pipe 12 on the exhaust gas upstream side of the selective catalytic reduction catalyst 13 and is configured to inject gaseous ammonia toward the selective catalytic reduction catalyst 13.

  On the other hand, the fuel supply pipe 26 is provided with a fuel pump 34 for supplying the fuel 15 in the fuel tank 18 to the first housing 41, and the fuel supply pipe 26 between the fuel pump 34 and the first housing 41 is provided in the fuel supply pipe 26. Is provided with a fuel flow rate adjusting valve 36 for adjusting the flow rate of the fuel 15 supplied to the first housing 41. The first air branch supply pipe 31 is provided with a first air flow rate adjustment valve 61 that adjusts the flow rate of the air that supplies compressed air in the air tank 17 to the first housing 41, and the second air branch supply pipe 31 has an air tank. A second air flow rate adjustment valve 62 that adjusts the flow rate of the air that supplies the compressed air in 17 to the second housing 42 is provided. The ammonia supply pipe 30 is provided with an ammonia flow rate adjustment valve 37 for adjusting the flow rate of ammonia flowing through the ammonia supply pipe 30 in order to adjust the injection amount of ammonia injected from the ammonia injection nozzle 33. A first temperature sensor 71 for detecting the temperature of hydrogen and carbon monoxide generated by the reforming catalyst 21 is provided on the other end side of the reforming catalyst 21 in the first housing 41. A second temperature sensor 72 for detecting the temperature of NOx generated by the plasma generator 28 is provided on the other end surface side of the second punching metal plate 28b.

  On the other hand, an intake pipe 39 is connected to an intake port of the diesel engine 11 via an intake manifold 38, and the exhaust pipe 12 is connected to an exhaust port via an exhaust manifold 44. The intake pipe 39 is provided with a compressor housing 46 a of the turbocharger 46 and an intercooler 47 that cools the intake air compressed by the turbocharger 46, and the exhaust pipe 12 is provided with a turbine of the turbocharger 46. A housing 46b is provided. Compressor rotor blades (not shown) are rotatably accommodated in the compressor housing 46a, and turbine rotor blades (not shown) are rotatably accommodated in the turbine housing 46b. The compressor rotor blades and the turbine rotor blades are connected by a shaft (not shown), and the compressor rotor blades are rotated via the turbine rotor blades and the shaft by the energy of the exhaust gas discharged from the engine 11, and the compressor rotor blades are rotated. Thus, the intake air in the intake pipe is compressed. Further, the exhaust manifold 44 and the intake pipe 39 are connected to each other by bypassing the engine 11 by an EGR pipe 48. That is, the EGR pipe 48 branches from the exhaust manifold 44 and joins the intake pipe 39 on the downstream side of the intake air from the intercooler 47. The EGR pipe 48 is provided with an EGR valve 49 for adjusting the flow rate of exhaust gas (EGR gas) recirculated from the EGR pipe 48 to the intake pipe 39. Further, the rotation speed of the engine 11 is detected by the rotation sensor 53, and the load of the engine 11 is detected by the load sensor 54. 1 is an EGR cooler that cools the exhaust gas (EGR gas) that passes through the EGR pipe 48, and reference numeral 57 is an exhaust gas temperature sensor that detects the exhaust gas temperature immediately before flowing into the selective catalytic reduction catalyst 13.

  The detection outputs of the first temperature sensor 71, the second temperature sensor 72, the rotation sensor 53, the load sensor 54, and the exhaust gas temperature sensor 57 are connected to the control input to the controller 58. The control output of the controller 58 is the heater power supply 19b, the high frequency power supply. 28c, a fuel pump 34, a fuel flow rate adjustment valve 36, a first air flow rate adjustment valve 31, a second air flow rate adjustment valve 32, an ammonia flow rate adjustment valve 37, and an EGR valve 49, respectively. A memory 59 is connected to the controller 58. In this memory 59, the temperature of hydrogen and carbon monoxide generated by the reforming catalyst 21 in the first housing 41, the temperature of NOx generated by the NOx generating means 22 in the second housing 42, the engine speed, The heater power source 19b, the high frequency power source 28c, and the fuel pump 34 are turned on / off according to the engine load, the exhaust gas temperature just before flowing into the selective reduction catalyst 13, and the like, the fuel flow rate adjusting valve 36, the first air flow rate adjusting valve 31, 2 Openings of the air flow rate adjustment valve 32, the ammonia flow rate adjustment valve 37, and the EGR valve 49 are stored in advance.

  A method for producing ammonia on a vehicle using the on-vehicle ammonia production apparatus 14 configured as described above will be described. Immediately after the engine 11 is started, when the engine 11 is in a low load operation (when the exhaust gas temperature is extremely low as less than 150 ° C.) or when the engine 11 shifts from a low load operation to a medium load operation (exhaust gas temperature is 150˜ Since the exhaust gas temperature on the inlet side of the selective catalytic reduction catalyst 13 is too low and almost no NOx can be reduced by the selective catalytic reduction catalyst 13, the controller 58 includes an exhaust gas temperature sensor 57, a rotation sensor. Based on the respective detection outputs of 53 and load sensor 54, EGR valve 49 is controlled to open EGR pipe 48 at a predetermined opening, and exhaust gas is recirculated to intake air at a predetermined flow rate. As a result, EGR gas that is a part of the exhaust gas of the engine 11 is recirculated to the engine 11 through the EGR pipe 48, the EGR cooler 56, the intake pipe 39, and the intake manifold 38, so that the combustion temperature of the fuel 15 in the engine 11 decreases. And generation | occurrence | production of NOx can be suppressed. At this time, since the reduction activity of NOx in the selective catalytic reduction catalyst 13 is low, the heater power source 19b, the high frequency power source 28c and the fuel pump 34 are kept off, and the fuel flow rate adjustment valve 36 and the first air flow rate adjustment valve 31 are left. The second air flow rate adjustment valve 32 and the ammonia flow rate adjustment valve 37 are closed to keep ammonia (gas) from being injected from the ammonia injection nozzle 33.

When the engine 11 shifts from the medium load operation to the high load operation, that is, when the exhaust gas temperature changes from 200 to 400 ° C. and from the medium low temperature region to the medium high temperature region, the exhaust gas temperature on the inlet side of the selective catalytic reduction catalyst 13 increases. The NOx reduction activity by the type catalyst 13 is increased. At this time, the controller 58 keeps the EGR pipe 48 open at a predetermined opening based on the detection outputs of the exhaust gas temperature sensor 57, the rotation sensor 53, and the load sensor 54, as well as the heater power source 19b, the high frequency power source 28c, Each of the fuel pumps 34 is turned on, and the fuel flow rate adjustment valve 36, the first air flow rate adjustment valve 31, the second air flow rate adjustment valve 32, and the ammonia flow rate adjustment valve 37 are each opened at a predetermined opening degree. As a result, the fuel 15 in the fuel tank 18 flows into the first housing 41, and the compressed air in the air tank 17 flows into the first housing 41. The fuel 15 and air flowing into the first housing 41 are mixed by the mixer, and then heated to a predetermined temperature (for example, 600 ° C.) by the heater 19. The heated mixed gas flows into the reforming catalyst 21, and the reformed catalyst 21 reforms the mixed gas (including hydrocarbons) to generate hydrogen. On the other hand, the compressed air in the air tank 17 flows into the second housing 42, a high frequency AC voltage of about 25 kHz is applied to the discharge gap between the first and second punching metal plates 28a, 28b, and the first and second punching metals. Plasma is generated between the peripheries of the plates 28a and 28b. This plasma generates NOx (NO and NO ₂ ) from nitrogen (N ₂ ) and oxygen (O ₂ ) in the air flowing into the second housing 42. The reaction formulas are shown in the following formulas (1) to (5).

N ₂ → 2N ^* (1)
O ₂ → 2O ^* (2)
N ^* + O ^* → NO ...... (3)
NO + O ^* → NO ₂ …… (4)
nNO + mO ₃ → NO ₂ (5)
In the above formulas (1) to (4), N ^* represents activated nitrogen, and O ^* represents activated oxygen. The hydrogen generated by the reforming catalyst 21 flows into the merging communication pipe 29 through the first communication pipe 51, and the NOx generated by the NOx generating means 22 passes through the second communication pipe 52 and joins the communication pipe 29. Flow into. Then, hydrogen and NOx are mixed in the joining communication pipe 29 and flow into the second housing 42. The hydrogen and NOx flowing into the second housing 42 react with the ammonia generation catalyst 23 to generate ammonia. The reaction formula is shown in the following formula (6).

2NO ₂ + 7H ₂ → 2NH ₃ + 4H ₂ O (6)
Ammonia produced by the ammonia production catalyst 23 is injected from an ammonia injection nozzle 33 through an ammonia supply pipe 30. Ammonia injected from the injection nozzle 33 is introduced into the selective catalytic reduction catalyst 13 together with the exhaust gas. The catalyst 13 reacts with the ammonia and NOx (NO, NO _2, etc.) in the exhaust gas, and NOx (NO or NO). NO ₂ etc.) is reduced to N ₂ . The reaction formulas are shown in the following formulas (7) to (9).

NO + NO ₂ + 2NH ₃ → 2N ₂ + 3H ₂ O (7)
4NO + O ₂ + 4NH ₃ → 4N ₂ + 6H ₂ O (8)
6NO ₂ + 8NH ₃ → 7N ₂ + 12H ₂ O (9)
As a result, NOx in the exhaust gas can be efficiently reduced in a wide temperature range from the middle load operation region to the high load operation region of the engine 11, that is, from the low intermediate temperature region to the intermediate high temperature region of the exhaust gas. In addition, ammonia supplied as a reducing agent for NOx to the selective reduction catalyst 13 can be continuously generated, and the amount of ammonia produced can be adjusted, so that ammonia can be continuously supplied to the selective reduction catalyst 13 and selected. The optimum amount of ammonia necessary for the reduction of NOx in the reduction catalyst 13 can be supplied to the selective reduction catalyst 13.

  In the above embodiment, hydrogen is generated by the reforming catalyst, NOx is generated by the NOx generating means, and ammonia is generated by reacting the hydrogen and NOx with the ammonia generating catalyst. And carbon monoxide, NOx is produced by the NOx production means, ammonia is produced by the reaction of the hydrogen and NOx with an ammonia production catalyst, and the carbon monoxide is produced with water produced by the combustion of fuel. Ammonia may be generated by a reaction between hydrogen generated by the reaction and the NOx. Thereby, more ammonia can be produced than in the above embodiment. In the above embodiment, the NOx generator is configured to generate NOx from nitrogen in the air supplied from the air supply source. However, the NOx generator is generated in the exhaust gas by the combustion of fuel in the vehicle engine. You may comprise so that NOx may be produced | generated.

Next, examples of the present invention will be described in detail together with comparative examples.
<Example 1>
As shown in FIG. 1, ammonia was produced using an ammonia production apparatus 14. The ammonia production apparatus 14 includes a heater 19 that heats a mixed gas obtained by mixing the air supplied from the air tank 17 and the fuel 15 supplied from the fuel tank 18 in the first housing 41, and is heated by the heater 19. A reforming catalyst 21 that reforms the mixed gas in the first housing 41 to generate hydrogen, a NOx generating means 22 that generates NOx from nitrogen in the air supplied from the air tank 17 to the second housing 42, hydrogen And an ammonia generating catalyst 23 for generating ammonia by reacting NOx with the NOx in the third housing 43.

  As the reforming catalyst 21, an alumina catalyst having platinum and rhodium supported on alumina was used. Further, the NOx generating means 22 is configured to generate NOx from nitrogen in the air supplied from the air tank 17 using the plasma generated by the plasma generator 28. As the plasma generator 28, two disc-shaped first and second punching metal plates 28a, 28b, which are housed in a second housing 42 and formed of stainless steel and further coated on both sides with a dielectric, and these A device comprising a high frequency power source 28c for applying a high frequency AC voltage of about 25 kHz between the punching metal plates 28a and 28b was used. The thickness, the hole diameter, and the hole area ratio of the first and second punching metal plates 28a and 28b were respectively set to 0.5 mm, 1 mm, and 30%. The discharge gap length between the first and second punching metal plates 28a and 28b was set to 10 to 30 μm depending on the thickness and unevenness of the coated dielectric film. An inverter type neon transformer was used as the high frequency power supply 28c. Further, as the ammonia generation catalyst 23, an oxidation catalyst having platinum supported on alumina was used. Fuel 15 and air are supplied into the first housing 41 at a flow rate of 2.5 g / min and 10 liter / min, respectively, air is supplied into the second housing 42 at a flow rate of 10 liter / min, and a heater power supply 19b. And the high frequency power supply 28c of the plasma generator 28 was turned on.

<Comparative Example 1>
Using the ammonia production apparatus of Example 1, fuel and air are supplied into the first housing at a flow rate of 2.5 g / min and 10 liter / min, respectively, and air is supplied into the second housing at 10 liter / min. Although the heater power supply was turned on while supplying at a flow rate, the high frequency power supply of the plasma generator was not turned on.

<Comparative test 1 and evaluation>
In Example 1 and Comparative Example 1, the concentration of ammonia gas discharged from the third housing was measured. The result is shown in FIG. As apparent from FIG. 2, no ammonia gas was generated in Comparative Example 1, whereas about 900 ppm of ammonia gas was generated in Example 1.

13 Selective Reduction Catalyst 14 Ammonia Production Equipment 15 Fuel 17 Air Tank (Air Supply Source)
18 Fuel tank (fuel supply source)
19 Heater (heating means)
DESCRIPTION OF SYMBOLS 21 Reforming catalyst 22 NOx production | generation means 23 Ammonia production | generation catalyst 28 Plasma generator

Claims (12)

An on-vehicle ammonia production apparatus mounted on the vehicle for producing ammonia to be supplied to the selective catalytic reduction catalyst (13) mounted on the vehicle,
Heating means (19) for heating a mixed gas obtained by mixing the air supplied from the air supply source (17) and the fuel (15) supplied from the fuel supply source (18);
A reforming catalyst (21) for reforming the mixed gas heated by the heating means (19) to generate at least hydrogen;
NOx generating means (22) for generating NOx from nitrogen in the air supplied from the air supply source (17) or generating NOx in exhaust gas by combustion of fuel in the engine of the vehicle;
An on-vehicle ammonia production apparatus comprising: an ammonia production catalyst (23) that produces ammonia by a reaction between the hydrogen and the NOx.   The reforming catalyst generates the hydrogen and carbon monoxide, the ammonia generating catalyst generates ammonia by the reaction of the hydrogen and NOx, and the reaction of the hydrogen generated from the carbon monoxide and the NOx. The on-vehicle ammonia production apparatus according to claim 1, wherein the ammonia production apparatus is configured to generate ammonia.   The in-vehicle ammonia production apparatus according to claim 1, wherein the heating means (19) is a heater or a burner.   The NOx generating means (22) is configured to generate the NOx from nitrogen in the air supplied from the air supply source (17) using plasma generated by a plasma generator (28). The in-vehicle ammonia production apparatus according to Item 1.   The in-vehicle ammonia production apparatus according to claim 1 or 2, wherein the reforming catalyst (21) is an alumina catalyst in which platinum and rhodium are supported on alumina, or an alumina catalyst in which palladium and rhodium are supported on alumina.   The in-vehicle ammonia production apparatus according to claim 1 or 2, wherein the ammonia generation catalyst (23) is an oxidation catalyst in which platinum is supported on alumina. A method for producing on the vehicle ammonia for supplying to the selective catalytic reduction catalyst (13) mounted on the vehicle,
A heating step of heating a mixed gas obtained by mixing the air supplied from the air supply source (17) and the fuel (15) supplied from the fuel supply source (18);
A reforming step of reforming the heated mixed gas to generate at least hydrogen;
NOx generation step of generating NOx from nitrogen in the air supplied from the air supply source (17) or generating NOx in exhaust gas by combustion of fuel in the engine of the vehicle;
A method for producing ammonia on a vehicle, comprising: an ammonia production step for producing ammonia by a reaction between the hydrogen and the NOx.   The reforming step generates the hydrogen and carbon monoxide, the ammonia generation step generates ammonia by the reaction of the hydrogen and the NOx, and the carbon monoxide is generated by combustion of the fuel (15). The method for producing ammonia on a vehicle according to claim 7, wherein ammonia is produced by reaction of hydrogen produced by reacting with the produced water and the NOx.   The method for producing ammonia on a vehicle according to claim 7, wherein a heater (19) or a burner is used to heat the mixed gas in the heating step.   The vehicle according to claim 7, wherein the plasma generated by the plasma generator (28) is used to generate the NOx from nitrogen in the air supplied from the air supply source (17) in the NOx generation step. A method for producing ammonia.   An alumina catalyst (21) in which platinum and rhodium are supported on alumina or an alumina catalyst in which palladium and rhodium are supported on alumina is used to modify the heated mixed gas in the reforming step. A method for producing ammonia on a vehicle according to claim 8.   The method for producing ammonia on a vehicle according to claim 7 or 8, wherein an oxidation catalyst (23) supporting platinum on alumina is used to produce the ammonia in the ammonia production step.

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