Ammonia combustion device and ammonia combustion method

Abstract

Provided are an ammonia combustion device and an ammonia combustion method that accelerate combustion of ammonia with a simple method using irradiation with ultraviolet light. An ammonia combustion device according to the present invention comprises: a fuel supply unit that supplies a fuel (F) containing ammonia and an oxidant; a combustion unit that combusts the fuel (F); and an irradiation unit that irradiates ammonia in the fuel (F). The fuel supply unit has a flow path for supplying the fuel (F). The irradiation unit has a light source that emits ultraviolet light. The oxidant contains oxygen.

Description

Ammonia combustion device and ammonia combustion method

[0001] This application claims priority to Japanese Patent Application No. 2024-124842, filed on July 31, 2024, the contents of which are incorporated herein by reference.

[0002] When ammonia is burned, CO ２ Since no ammonia (hereinafter referred to as NH ３ Ammonia (also referred to as ammonia) has been proposed as an alternative fuel to fossil fuels and has emerged as a promising candidate in the transition to a decarbonized energy system. However, ammonia is less reactive with oxygen than fossil fuels and therefore less combustible. Therefore, when using ammonia as a fuel, it is necessary to design a new ammonia combustion device to facilitate ammonia combustion. For example, Patent Document 1 discloses an ammonia internal combustion engine in which ammonia is supplied into a combustion chamber and ignited by an ignition device disposed in the combustion chamber. To facilitate ammonia combustion, it is proposed to use at least one plasma jet spark plug that emits a plasma jet or multiple spark plugs that generate sparks as the ignition device.

[0003] JP 2010-159705 A

[0004] In the above-mentioned Patent Document 1, an attempt is made to solve the problem of ammonia being difficult to burn by improving the ignition device of the ammonia combustion device, but a high amount of energy is still required to burn ammonia, and the improvement in combustibility is insufficient. Furthermore, the plasma jet ignition plug used in these ammonia combustion devices is poor in durability and expensive.

[0005] The present invention has been made in view of the above problems, and aims to provide an ammonia combustion apparatus and an ammonia combustion method in which the combustibility of ammonia is promoted in a simple manner by irradiating ammonia with ultraviolet light.

[0006] In order to solve the above problems, the present invention provides the following means.

[0007] [1] An ammonia combustion apparatus comprising: a fuel supply unit that supplies a fuel (F) containing ammonia and an oxidant; a combustion unit that combusts the fuel (F); and an irradiation unit that irradiates the ammonia contained in the fuel (F), wherein the fuel supply unit has a flow path for supplying the fuel (F), the irradiation unit has a light source that emits ultraviolet light, and the oxidant contains oxygen. [2] The ammonia combustion apparatus according to [1], wherein the wavelength of the ultraviolet light emitted by the light source is 170 nm or more and 300 nm or less. [3] The ammonia combustion apparatus according to [1] or [2], wherein the oxidant is oxygen. [4] The ammonia combustion apparatus according to any of [1] to [3], wherein the irradiation unit is disposed inside or near the combustion unit, and the fuel supplied to the combustion unit is irradiated with the ultraviolet light. [5] The ammonia combustion apparatus according to any of [1] to [4], wherein the fuel supply unit further comprises flow paths for separately supplying ammonia and an oxidant. [6] The ammonia combustion apparatus according to any one of [1] to [5], further comprising an exhaust unit for exhausting combustion gas. [7] The ammonia combustion apparatus according to any one of [1] to [6], wherein the ultraviolet light is generated by the combustion of hydrogen or hydrocarbon. [8] The ammonia combustion apparatus according to any one of [1] to [7], wherein the ultraviolet light is generated by an electrical device including any one of an LED, a lamp, and a laser. [9] The ammonia combustion apparatus according to any one of [1] to [7], wherein the irradiation unit is disposed near the fuel supply unit, and the ammonia in the fuel supply unit is irradiated with the ultraviolet light.

[10] An ammonia combustion method comprising: a fuel supply step of supplying fuel (F) containing ammonia and an oxidizer; a combustion step of burning the fuel (F); and an irradiation step of irradiating the ammonia in the fuel (F) with ultraviolet light, wherein the oxidizer contains oxygen.

[11] The ammonia combustion method according to

[10] , wherein the ammonia in the fuel (F) is photoexcited by the ultraviolet light.

[12] An ammonia combustion method using the ammonia combustion device according to any one of [1] to [9], comprising: a fuel supply step of supplying the fuel (F) containing the ammonia and the oxidant; a combustion step of burning the fuel (F); and an irradiation step of irradiating the ammonia in the fuel (F) with ultraviolet light.

[0008] According to the present invention, it is possible to provide an ammonia combustion apparatus and an ammonia combustion method that promote the combustibility of ammonia in a simple manner.

[0009] 1 is a schematic diagram showing an ammonia combustion apparatus according to one embodiment of the present invention; FIG. 2 is a schematic diagram showing an ammonia combustion apparatus according to another embodiment of the present invention; ３ 1 is a diagram showing simulation results and experimental results of the first absorption band from the ground state to the excited electronic state of OH, the emission spectrum from the excited state of OH (solid line), and the average transmittance of quartz glass (dashed line). FIG. 1 is a schematic diagram of an ammonia combustion apparatus of Example 1. FIG. 2 is a schematic diagram showing a combustion section (quartz tube) and an irradiation section (hydrogen / air burner) in the ammonia combustion apparatus of Example 1. FIG. 3 is a principle diagram showing the photoreaction mechanism of ammonia by ultraviolet light irradiation. FIG. 4 is a schematic diagram showing a combustion section (quartz tube) and a heating section (electric furnace) in an experimental apparatus of Comparative Example 1. FIG. 5 is a diagram showing the temperature profile of the tube wall surface in the combustion section (quartz tube) in the ammonia combustion apparatus of Example 1 and Comparative Example 1. FIG. 6 is a diagram showing the relationship between the amount of residual ammonia contained in the discharged combustion gas and the temperature of the combustion section (quartz tube) in Example 1 and Comparative Example 1.

[0010] The present embodiment will be described in detail below with reference to the accompanying drawings. The drawings used in the following description may show characteristic portions enlarged for the sake of clarity, and the dimensional proportions of each component may differ from the actual proportions. The materials, dimensions, etc. exemplified in the following description are merely examples, and the present invention is not limited thereto. Appropriate modifications may be made within the scope of the present invention.

[0011] (Ammonia Combustion Apparatus) As shown in FIG. 1, an ammonia combustion apparatus 1 according to one embodiment of the present invention includes a fuel supply unit 10 that supplies a fuel (F) containing ammonia and an oxidant, a combustion unit 20 that combusts the fuel (F), and an irradiation unit 30 that irradiates the ammonia in the fuel (F). The fuel supply unit 10 has a flow path (not shown) that supplies the fuel (F). The irradiation unit 30 has a light source (not shown) that emits ultraviolet light. The wavelength of the ultraviolet light emitted by the light source is preferably 170 nm or more and 300 nm or less. The oxidant contains oxygen, and is preferably oxygen. Examples of the oxidant include air and pure oxygen.

[0012] A preferred example of the ammonia combustion apparatus of this embodiment is an ammonia combustion apparatus 100 shown in Fig. 2. The ammonia combustion apparatus 100 includes a fuel supply unit 110 that supplies fuel (F), a combustion unit 120 that combusts the fuel (F), an irradiation unit 130 that irradiates ammonia in the fuel (F), and an exhaust unit 140 that exhausts combustion gas generated by the combustion of the fuel (F). As shown in Fig. 2, the fuel supply unit 110 includes an ammonia supply flow path 112 and an oxidant supply flow path 114.

[0013] [Fuel Supply Unit] The fuel supply unit 110 of the ammonia combustion apparatus 100 shown in Fig. 2 may separately supply ammonia and an oxidant using the ammonia supply passage 112 and the oxidant supply passage 114. Alternatively, the ammonia supply passage 112 and the oxidant supply passage 114 may be directly connected to the combustion unit 120, respectively, so that the ammonia and the oxidant do not need to be mixed before being introduced into the combustion unit 120. As a modification of Fig. 2, a mixing section that mixes the ammonia and the oxidant may be provided between the combustion unit 120 and the fuel supply unit 110. In this case, the ammonia supply passage 112 and the oxidant supply passage 114 are first connected to the mixing section. The ammonia and the oxidant may be supplied to the mixing section, mixed, and then supplied to the combustion unit 120.

[0014] In the fuel supply unit (10, 110) of this embodiment, the ammonia to be supplied may be, for example, liquid ammonia supplied from a liquid ammonia tank. The method for supplying ammonia from the liquid ammonia tank to the fuel supply unit is not particularly limited. For example, the fuel tank may be filled with high-pressure liquid ammonia, preferably at a pressure of 0.2 MPa or more and 10 MPa or less, more preferably at a pressure of 0.8 MPa or more and 1.0 MPa or less, and a fuel supply pump may be disposed in the fuel tank. The ammonia can be supplied from the fuel supply pump via an ammonia supply passage to the combustion unit. The method for supplying ammonia to the combustion unit is not particularly limited, but for example, the ammonia supply passage may be connected to a liquid ammonia injector, and the ammonia can be supplied to the combustion unit via the liquid ammonia injector.

[0015] The ammonia combustion apparatus of this embodiment may supply ammonia gas to the combustion section, for example, depending on the purpose of use. In that case, the ammonia gas can be supplied to the combustion section through an ammonia gas injection valve. When ammonia gas is supplied to the combustion section, a vaporization section that vaporizes liquid ammonia may be provided between the fuel tank and the combustion section. When the vaporization section is installed upstream of the ammonia flow path, ammonia gas may be supplied through the ammonia flow path. Furthermore, when the vaporization section is installed downstream of the ammonia flow path, liquid ammonia can be supplied to the vaporization section through a first ammonia flow path, and the ammonia gas can be supplied to the combustion section from the vaporization section through a second ammonia flow path.

[0016] The oxidant supplied through the oxidant supply passage 114 of the ammonia combustion apparatus 100 shown in FIG. 2 includes oxygen. Examples of the oxidant include air or oxygen. For example, air (compressed air) may be supplied. Depending on the purpose of use, a mixed gas of oxygen and air, oxygen gas, or liquid oxygen may be supplied. Furthermore, for the purpose of recirculating the combustion gas or achieving multi-stage combustion, combustion gas or a mixed gas of combustion gas and air may be used as the oxidant.

[0017] [Combustion Section] As in the ammonia combustion apparatus 1 shown in FIG. 1 , the combustion section 20 according to this embodiment has a space for combusting the fuel (F) supplied from the fuel supply section 10. The ammonia combustion apparatus 1 according to this embodiment may be applied to, for example, an internal combustion engine, an external combustion engine, or an industrial furnace. When the ammonia combustion apparatus 1 according to this embodiment is used in an internal combustion engine, the combustion section 20 may be configured to include a combustion chamber of the internal combustion engine. In the combustion chamber, the fuel (F) containing ammonia is combusted, and the resulting high-temperature gas expands to a large volume, releasing a large amount of pressure and heat. When the ammonia combustion apparatus 1 according to this embodiment is used in an external combustion engine or an industrial furnace, the combustion section 20 may be configured to include a combustion chamber of the external combustion engine or the industrial furnace. In the combustion chamber, the fuel (F) containing ammonia is combusted, and heating is performed by the high-temperature gas generated by the combustion. The combustion section 20 may include an ignition section for starting the combustion of ammonia. A known ignition device used in ammonia combustion apparatuses can be used as the ignition section. For example, the ignition device disclosed in the above-mentioned Patent Document 1 may be used.

[0018] In the ammonia combustion apparatus 1 of this embodiment, it is preferable that an irradiation unit 30, which will be described later, is disposed inside or near the combustion unit 20. In this case, the ammonia in the combustion unit 20 can be irradiated with ultraviolet light from the irradiation unit 30.

[0019] In the combustion section 20, the combustibility of ammonia is promoted in a simple manner by irradiating the ammonia with ultraviolet light. It is presumed that this is due to the promotion effect caused by the irradiation of the ammonia with ultraviolet light, which causes a portion of the ammonia to be photoexcited and then decomposed to generate active radicals. The combustibility of ammonia in the combustion section is promoted compared to when ultraviolet light is not irradiated. The present invention is not limited to this reaction promotion mechanism, as long as the combustibility of ammonia in the combustion section is promoted by irradiating the ammonia with ultraviolet light.

[0020] In the ammonia combustion apparatus 1 of this embodiment, the arrangement of the irradiation unit 30 within the combustion unit 20 is not particularly limited as long as the ultraviolet light irradiation location is located within the combustion unit 20. The irradiation unit 30 does not necessarily have to be located within the combustion unit 20. For example, if the irradiation unit 30 has an optical path such as an optical waveguide or optical fiber, or if the ultraviolet light emission location and the ammonia irradiation location are different, the emission location as part of the irradiation unit 30 may be located outside the combustion unit, and the optical path may extend inside the combustion unit 20 to irradiate ammonia within the combustion unit. In this case, the ammonia in the combustion unit 20 can be irradiated with ultraviolet light from the irradiation unit 30. Furthermore, for example, if the ultraviolet light is generated by the combustion of hydrogen or hydrocarbons, as described below, a flow path for supplying hydrogen or hydrocarbons may be located outside the combustion unit, while the combustion flame of the hydrogen or hydrocarbons may be set to be inside the combustion unit. Furthermore, for example, when the ammonia combustion apparatus 1 of this embodiment is an internal combustion engine, it is preferable to arrange the control part and the like of the irradiation part 30 outside the combustion part 20 from the viewpoint of protecting the irradiation part 30 from high-pressure, high-temperature gas generated by ammonia combustion.

[0021] In the ammonia combustion apparatus 1 of this embodiment, an example of the arrangement of the irradiation unit 30 near the combustion unit 20 is to provide an ultraviolet light transmitting section in the combustion unit 20, to place the irradiation unit 30 near the ultraviolet light transmitting section, and to transmit the ultraviolet light generated from the irradiation unit 30 through the ultraviolet light transmitting section, thereby irradiating the ammonia inside the combustion unit 20 with the ultraviolet light. In the verification example of Example 1 described later, a quartz tube is used as the combustion unit 20, and a H ２ In the verification example of Example 1, ultraviolet light was irradiated onto the entire central portion of the quartz tube, but in the ammonia combustion apparatus of this embodiment, an ultraviolet light transmitting portion that transmits ultraviolet light may be provided from a portion of the wall of the combustion portion to irradiate the ammonia in the combustion portion.

[0022] In the ammonia combustion apparatus 1 of the present embodiment, in addition to the embodiment in which the irradiation unit 30 is arranged inside or near the combustion unit 20, for example, the irradiation unit 30 may be arranged inside or near the fuel supply unit 10, even if the irradiation unit 30 does not irradiate ultraviolet light onto the ammonia in the combustion unit 20. For example, the irradiation unit 30 may be installed at a location in the fuel supply unit 10 close to the combustion unit 20. In the case where the fuel supply unit 110 of the ammonia combustion apparatus 100 in FIG. 2 includes an ammonia supply flow path 112 and a flow path 114 for supplying an oxidant, for example, an ultraviolet light transmitting portion may be provided on a part of the wall of the flow path 112 for supplying the ammonia at a location in the vicinity of the combustion unit 120 of the ammonia supply flow path 112, and the irradiation unit 130 may be arranged near the ultraviolet light transmitting portion. In this case, the ultraviolet light generated by the irradiation unit 130 can be transmitted through the ultraviolet light transmitting portion and irradiate the ammonia in the ammonia supply flow path 112. The ammonia irradiated with the ultraviolet light is then supplied to the combustion section 120, where the combustibility of the ammonia can be promoted. Regarding the promotion effect, by irradiating the ammonia with ultraviolet light, part of the ammonia is photoexcited and decomposed to generate active radicals, and these active radicals are introduced into the combustion section. It is presumed that the combustibility of the ammonia in the combustion section is promoted compared to when the active radicals are not introduced.

[0023] In the ammonia combustion apparatus 1 of this embodiment shown in FIG. 1 , if the fuel supply unit 10 has a mixing unit that mixes ammonia and an oxidizer, the irradiation unit 30 may be disposed inside or near the mixing unit. For example, the irradiation unit 30 may be disposed in a location of the mixing unit close to the combustion unit 20. In this case, ultraviolet light generated by the irradiation unit 30 can be transmitted through an ultraviolet light transmitting unit of the mixing unit to irradiate the ammonia in the mixing unit. The ammonia irradiated with the ultraviolet light is then supplied to the combustion unit 20, where the combustibility of the ammonia can be promoted. Regarding the promotion effect, it is presumed that irradiating the ammonia with ultraviolet light photoexcites and decomposes a portion of the ammonia to generate active radicals, which are then introduced into the combustion unit. This promotes the combustibility of the ammonia in the combustion unit compared to when no active radicals are introduced.

[0024] The ammonia combustion apparatus 1 of this embodiment may further include a photoactive ammonia supply unit that supplies ammonia irradiated with ultraviolet light, in addition to the fuel supply unit 10 and the combustion unit 20. In this case, the irradiation unit 30 may be disposed inside or near the photoactive ammonia supply unit. When the photoactive ammonia supply unit is provided, the amount of ammonia supplied as fuel, the mixing ratio with the oxidizer, and the like are controlled by the fuel supply unit, and the supply of photoactive ammonia can be controlled independently. Furthermore, for example, the temperature and pressure at the location where ammonia is irradiated can be independently optimized, thereby optimizing the amount of photoactive ammonia generated or the amount of generated photoactive ammonia supplied to the combustion unit.

[0025] [Irradiation Unit] As described above, the irradiation unit 30 of the ammonia combustion apparatus 1 of this embodiment shown in FIG. 1 may be disposed inside or near the combustion unit 20, or inside or near the fuel supply unit 10. Furthermore, when the ammonia combustion apparatus 1 of this embodiment further includes the photoactivated ammonia supply unit, the irradiation unit 30 may be disposed inside or near the photoactivated ammonia supply unit. The irradiation unit includes a light source that emits ultraviolet light. To further improve the combustibility of ammonia, the wavelength of the ultraviolet light emitted by the light source is preferably 170 nm or more and 300 nm or less. From the viewpoint of enhancing the effect of improving the combustibility of ammonia, the wavelength of the ultraviolet light emitted by the light source may be 200 nm or more and 250 nm or less. On the other hand, for example, when the pressure of the combustion unit 20 is high, from the viewpoint of reducing attenuation of the ultraviolet light in the combustion unit 20, the wavelength of the ultraviolet light emitted by the light source may be 250 nm or more and 300 nm or less. The optimal wavelength range of the ultraviolet light may be appropriately selected in consideration of the trade-off between improving the combustibility of ammonia and attenuation of the ultraviolet light. The light source is not particularly limited as long as it can generate part of ultraviolet light having a wavelength of 170 nm or more and 300 nm or less. Examples of the light source include a device that generates the ultraviolet light by burning hydrogen or hydrocarbon, and a device that generates the ultraviolet light by an electrical device including any one of an LED, a lamp, and a laser.

[0026] FIG. 3 shows the NH ３ 1 shows the simulation results and experimental results of the first absorption band from the ground state to the excited electronic state of OH, and the emission spectrum (solid line) from the excited state of OH in the hydrogen / air flame of Example 1 described later, and the average transmittance of quartz glass (dashed line). In the hydrogen / air flame of Example 1 described later, the ultraviolet light generated by the combustion of hydrogen in air is mainly derived from excited OH. Among the vibrational bands of the OH emission spectrum, A ２ Σ ＋ →X ２ The Π(0,0) band shows the maximum intensity at a wavelength of 308 nm. As a result of the simulation, the emission coefficient in the range of 195 nm to 230 nm is shown in FIG. 3. In the above wavelength range, A２ Σ ＋ →X ２ In the (6,0), (5,0), and (6,1) bands of Π(v',v"), there are emission bands at corresponding wavelengths of 211.8 nm, 220.7 nm, and 229.1 nm. On the other hand, the absorption bands of ammonia are known to be at 216.35 nm (experimental value) and 218.78 nm (calculated value). The transmittance of the quartz tube of Example 1 is shown in Figure 3 as the transmittance spectrum of quartz glass with a thickness of 1 mm. It was found that the transmittance of quartz glass with a thickness of 1 mm is 80% or more for ultraviolet light in the range from 195 nm to 230 nm. 4 and 5, based on the results of Example 1, when using a hydrogen / air burner (irradiation unit) 230 having a light source that generates ultraviolet light in the range of 190 nm to 230 nm, providing quartz glass windows in the walls of the quartz tube (combustion unit) 220, the fuel supply unit 210, etc. makes it possible to irradiate the ammonia with the ultraviolet light. Also, by using the quartz glass, it is possible to provide a portion of the irradiation unit 230 inside the combustion unit 220, and irradiate the ammonia with ultraviolet light from inside the combustion unit.

[0027] [Study on the photoreaction mechanism of ammonia] The mechanism of promoting the photoreaction of ammonia and ammonia combustibility of the present invention was investigated using NH ３ The photoreaction of NH around 200 nm shown in Figure 3 is presumed to have the following mechanism. ３ In the first absorption band of ３ In this excited state, NH ３ From NH ２ Dissociation into radicals and H atoms occurs (shown in formula (A) below). The generated NH ２ The radicals and H atoms react with the ammonia and oxidizing agent in the ammonia (since the oxidizing agent contains oxygen, for example, as shown in the following formulas (B1) and (B2)), thereby promoting the combustibility of the ammonia. ３ + Ultraviolet light → NH ２ ・+H (A) H+O ２ →O+・OH (B1) NH ３ + OH → NH ２ ・+H ２O (B2) (In formulas (A), (B1), and (B2), NH ２ ・ is NH ２ radical, H represents a hydrogen atom, O represents an oxygen atom, and .OH represents an OH radical.)

[0028] 6 shows the photoreaction mechanism of the irradiation unit 230 consisting of a hydrogen / air burner, the quartz tube 220, and the ammonia inside the tube in the verification example of Example 1 described below. In FIG. 6, the following four steps are included. Step 1: Ultraviolet light is generated from the hydrogen / air burner. Step 2: The ultraviolet light is transmitted through the wall of the quartz tube. Step 3: The transmitted ultraviolet light is used to excite the ammonia inside the quartz tube, photodissociating the ammonia and generating NH ２ Radicals and hydrogen atoms are generated (see formula (A) above). Fourth step: As shown in formulas (B1) and (B2) above, the combustibility of ammonia is promoted.

[0029] (Ammonia Combustion Method) An ammonia combustion method according to one embodiment of the present invention includes a fuel supply step of supplying a fuel (F) containing ammonia and an oxidant, a combustion step of combusting the fuel (F), and an irradiation step of irradiating the ammonia in the fuel (F) with ultraviolet light. The oxidant contains oxygen. Examples of the oxidant include air or oxygen. In the irradiation step, the ammonia in the fuel (F) may be photoexcited or photodissociated by the ultraviolet light. In the supply step, the ammonia and the oxidant may be supplied separately, or the ammonia and the oxidant may be mixed and then supplied as a mixture. The wavelength of the ultraviolet light emitted by the light source is preferably 170 nm or more and 300 nm or less. The ultraviolet light may be generated by the combustion of hydrogen or hydrocarbon, or may be generated by an electrical device including any one of an LED, a lamp, and a laser. The combustion step may be performed after the irradiation step or simultaneously with the irradiation step. That is, in the ammonia combustion apparatus of this embodiment, as explained above regarding the positional relationship between the combustion unit and the irradiation unit, ammonia irradiated with ultraviolet light (photoactivated ammonia) can be supplied to the combustion unit before the combustion step, and the fuel (F) can be burned in the combustion unit. Alternatively, as explained above regarding the positional relationship between the combustion unit and the irradiation unit, the combustion step can be performed in which the fuel (F) is burned while ultraviolet light is irradiated onto the ammonia in the combustion unit.

[0030] The ammonia combustion method of this embodiment preferably uses the ammonia combustion apparatus of this embodiment and its preferred embodiments described above.

[0031] Example 1 A schematic diagram of an experimental apparatus (ammonia combustion apparatus) 200 of Example 1 is shown in Figure 4. A quartz tube (combustion section) 220 with an inner diameter of 2 mm was used as a reactor, and the maximum wall temperature (T ｗ，ｍａｘ) to form a steady temperature distribution. A hydrogen / air burner (irradiation section) 230 was used as the heat source. Figure 5 is a detailed view of the hydrogen / air burner (irradiation section) 230. In the hydrogen / air burner 230, the inner wall temperature of the quartz tube (combustion section) 220 was controlled by changing the equivalence ratio of the hydrogen / air mixture. The hydrogen / air burner 230 heated the quartz tube (combustion section) 220 by thermal convection while irradiating the quartz tube (combustion section) 220 with ultraviolet light generated by hydrogen combustion. In the hydrogen / air burner 230, the hydrogen / air flame 231 was a flat flame, and the flame nozzle diameter was 4 cm. The hydrogen / air flow rate was controlled by mass flow controllers (MQV0050 and MQV0200, manufactured by Azbil Corporation). The maximum wall temperature T along the inner wall of the quartz tube 220 was ｗ，ｍａｘ was changed in the range of 1100 K or more and 1300 K or less with an accuracy of 10 K, including the temperature difference between the top and bottom of the furnace inner surface. In the experimental apparatus (ammonia combustion apparatus) 200 of Example 1, the temperature profile of the reactor (quartz tube 220) was controlled using an MFR (Micro flow reactor with a controlled temperature profile, a temperature distribution controlled micro flow reaction experimental apparatus) shown in Figure 4. For details of the MFR, the explanation in the following Non-Patent Document A is cited.

[0032] [Non-patent document A] K. Tamaoki, Y. Murakami, K. Kanayama, T. Tezuka, M. Izumi, H. Nakamura, Roles of NH ２ reactions in ammonia oxidation at intermediate temperatures: Experiments and chemical kinetic modeling, Combust. Flame (2024) 113177.

[0033] The inner wall temperature was measured using a K-type thermocouple inserted from the outlet of the reactor (quartz tube 220). A stoichiometric ammonia / air mixture was tested using each heating method. The flow rates of ammonia and air were controlled using a mass flow controller (SEC-Z500X, Horiba, Ltd.), and the inlet flow rate was set to 2.0 cm / s at a temperature of 273 K and a pressure of 1 atm. The purity of the gases in the cylinders supplying ammonia and air was 99.999%. Ammonia and air were supplied via the ammonia supply line 212 and the air (oxidant) supply line 214, respectively. The exhaust gas from the reactor was introduced into a mass analyzer QMS (quadrupole mass spectrometer, JMS-Q1500, JEOL, Ltd.). To prevent condensation of water vapor, the stainless steel tube from the reactor outlet to the QMS was heated to 373 ± 5 K using an electric heater. Because ammonia is corrosive, the surface of the stainless steel tube was subjected to a passivation treatment. Ammonia consumption was measured by QMS using 10.8 eV photoionization. The accuracy of the ammonia signal in QMS was ±5%. The reactor pressure was atmospheric.

[0034] 8 is a diagram showing the wall temperature profile of the quartz tube 220 in the combustion section (quartz tube) of the ammonia combustion apparatus of Example 1. The horizontal axis represents the distance from the inlet to the outlet of the quartz tube.

[0035] [Relationship between Ammonia Consumption and Maximum Wall Temperature] In the ammonia combustion apparatus of Example 1, the maximum wall temperature T ｗ，ｍａｘ The ammonia consumption was measured in the range of 1100 K to 1300 K. The ammonia consumption and the maximum wall temperature T ｗ，ｍａｘ The relationship between T and T is shown in FIG. ｗ，ｍａｘ However, at around 1100 K, ammonia was not consumed and almost all of it was discharged without reacting. ｗ，ｍａｘ At around 1300 K, all of the ammonia was consumed (no ammonia was detected in the exhaust). Compared to Comparative Example 1 (not irradiated with ultraviolet light) described later, it was confirmed that the combustibility of ammonia was promoted by irradiation with ultraviolet light.

[0036] Comparative Example 1 The reactor (quartz tube 220) was heated in the same manner as in Example 1, except that an electric furnace 250 was used instead of the hydrogen / air burner (irradiation section) 230 of Example 1, as shown in FIG. 7, and the amount of ammonia discharged was measured in the same manner as in Example 1. In the electric furnace, the reactor was heated by heat rays within the electric furnace and radiant heat from the heated insulation. Note that, since the reactor was located at the center of the electric furnace from the flow direction, the temperature difference on the inner wall surface was negligible. FIG. 8 shows the temperature profile of the quartz tube wall surface in the combustion section (quartz tube) 220 in the experimental apparatus of Comparative Example 1.

[0037] [Relationship between residual ammonia amount and maximum wall temperature] In the experimental apparatus of Comparative Example 1, the maximum wall temperature T ｗ，ｍａｘ The ratio of the amount of remaining ammonia to the amount of supplied ammonia (ammonia residual ratio) was measured in the range of 1100 K to 1400 K. The ammonia residual ratio is a value obtained by normalizing the ammonia mole fraction measured after the reaction by the ammonia mole fraction supplied. This ammonia residual ratio and the maximum wall temperature T ｗ，ｍａｘ The relationship between T and T is shown in FIG. ｗ，ｍａｘ At around 1100 K, the residual ammonia ratio was high, close to 1.0. This means that ammonia was not consumed and was almost entirely discharged. ｗ，ｍａｘ At around 1300K, about 90% of the ammonia remains, and T ｗ，ｍａｘ Approximately 50% of the ammonia remained even at around 1400 K. In other words, in contrast to Example 1 (with ultraviolet light irradiation), no promotion of ammonia combustibility was observed in normal combustion without ultraviolet light irradiation.

[0038] (Discussion) Compared to the oxidation reaction of ammonia and oxygen caused by thermal energy, the photoreaction of ammonia caused by ultraviolet light has a lower activation energy. Furthermore, compared to the oxidation reaction of ammonia and oxygen, the oxidation reaction of ammonia and OH radicals caused by thermal energy also has a lower activation energy. By generating H atoms at low energy through a photoreaction, OH radicals are generated by the reaction of H atoms with oxygen. Furthermore, because the oxidation reaction of ammonia and OH radicals has a low activation energy, the oxidation reaction can promote the combustion reaction of ammonia at low energy. Furthermore, ultraviolet light of 170 nm or more and 300 nm or less has a relatively long wavelength among ultraviolet light, so attenuation within the combustion zone is small and it can be selectively irradiated to any location in the combustion zone. Therefore, the energy required to generate ultraviolet light is also small. Because ultraviolet light has low energy, it is difficult to directly break the covalent bond of ammonia. However, the above-mentioned mechanism can achieve the effect of improving the combustibility of ammonia even with low energy. Furthermore, nitrogen oxides produced by the oxidation of ammonia and NH produced by the photoreaction are easily oxidized. ２ The reaction with radicals is a highly exothermic reaction, which further improves the combustibility of ammonia and is expected to reduce nitrogen oxide emissions.

[0039] 1, 100... Ammonia combustion device 10, 110, 210... Fuel supply section 20, 120... Combustion section 30, 130... Irradiation section 112, 212... NH ３ Supply flow path 114, 214...oxidant supply flow path 140...exhaust section 220...combustion section (quartz tube) 230...irradiation section (hydrogen / air burner) 231...hydrogen / air flame 250...electric furnace QMS...mass spectrometer

Claims

1. An ammonia combustion apparatus comprising: a fuel supply unit that supplies fuel (F) containing ammonia and an oxidant; a combustion unit that combusts the fuel (F); and an irradiation unit that irradiates the ammonia in the fuel (F), wherein the fuel supply unit has a flow path for supplying the fuel (F), the irradiation unit has a light source that emits ultraviolet light, and the oxidant contains oxygen.

2. The ammonia combustion device according to claim 1, wherein the wavelength of the ultraviolet light emitted by the light source is 170 nm or more and 300 nm or less.

3. The ammonia combustion apparatus of claim 1, wherein the oxidant is oxygen.

4. An ammonia combustion apparatus according to claim 1, wherein the irradiation unit is disposed inside or near the combustion unit, and the fuel supplied to the combustion unit is irradiated with the ultraviolet light.

5. The ammonia combustion device according to claim 1, wherein the fuel supply unit further comprises flow paths for separately supplying the ammonia and the oxidizer.

6. The ammonia combustion device according to claim 1, further comprising an exhaust port for exhausting combustion gas.

7. The ammonia combustion device of claim 1, wherein the ultraviolet light is produced by the combustion of hydrogen or a hydrocarbon.

8. The ammonia combustion apparatus of claim 1, wherein the ultraviolet light is generated by an electrical device including one of an LED, a lamp, and a laser.

9. The ammonia combustion device according to claim 1, wherein the irradiation unit is disposed near the fuel supply unit, and the ammonia in the fuel supply unit is irradiated with the ultraviolet light.

10. A method for burning ammonia, comprising: a fuel supply step of supplying a fuel (F) containing ammonia and an oxidant; a combustion step of burning the fuel (F); and an irradiation step of irradiating the ammonia in the fuel (F) with ultraviolet light, wherein the oxidant contains oxygen.

11. The method for burning ammonia according to claim 10, wherein the ammonia in the fuel (F) is photoexcited by the ultraviolet light.

12. A method for burning ammonia using the ammonia combustion device according to any one of claims 1 to 9, comprising: a fuel supply step of supplying the fuel (F) containing the ammonia and the oxidizer; a combustion step of burning the fuel (F); and an irradiation step of irradiating the ammonia in the fuel (F) with the ultraviolet light.

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