Gas decomposition method and gas decomposition device

Abstract

The invention provides a gas decomposition method and a gas decomposition device which can efficiently decompose greenhouse effect gas through a simple method or a simple structure. A gas decomposition method for decomposing nitrous oxide and a saturated hydrocarbon by irradiating a gas to be processed containing oxygen, nitrous oxide and the saturated hydrocarbon with first light having a main emission wavelength of 160 nm or more but less than 200 nm. The gas decomposition device is provided with a chamber for supplying a gas to be processed containing oxygen, nitrous oxide, and the saturated hydrocarbon, and a first light source for irradiating the chamber with the first light.

Description

Technical Field

[0001] The invention relates to a gas decomposition method and a gas decomposition device. Background Art

[0002] After the Industrial Revolution, due to the rise in the average temperature of the earth, global warming countermeasures have become an urgent issue. As greenhouse gases that cause global warming, carbon dioxide, methane, nitrous oxide, freon gas, etc. are known. Among these gases, carbon dioxide has the largest emission, followed by methane, and then nitrous oxide. However, it is reported that the global warming coefficient of methane is 25 times that of carbon dioxide, and the global warming coefficient of nitrous oxide is 298 times that of carbon dioxide. In particular, the impact of global warming caused by the emission of nitrous oxide cannot be ignored.

[0003] Nitrous oxide is not only emitted in large quantities through industrial activities such as the manufacture of chemical products and the burning of waste, but is also emitted in large quantities from the treatment of human and livestock excrement and agriculture. Methane is mostly emitted from the same places as nitrous oxide, such as farmland, livestock waste, biomass burning, and sewage treatment. The reason why nitrous oxide and methane are emitted from the same place is that both are mostly produced by microbial sources. Recently, since the concentrations of nitrous oxide and methane tend to increase, suppressing the increase in the concentrations of nitrous oxide and methane or reducing the concentrations is expected as a countermeasure to global warming.

[0004] In the above-mentioned emission scenarios of nitrous oxide and methane, in most cases, the majority of the emitted gas composition is the atmosphere, and nitrous oxide and methane account for a relatively low concentration in the emission gas composition. As methods for decomposing nitrous oxide, high-temperature combustion methods and catalyst methods have been used. However, in the high-temperature combustion method, a large amount of energy is required to burn the gas. If fossil fuels are used to ensure a large amount of energy, the emission of carbon dioxide increases, so it cannot be said to be effective as a countermeasure to global warming. In the catalyst method, it is also necessary to heat the gas to a high temperature. Furthermore, it is necessary to collect ammonia used in the catalyst or reducing agent, and there is also the problem of wastewater treatment after treatment. Therefore, the catalyst method cannot be said to be effective. In addition, as methods for decomposing methane, a high-temperature combustion method and a catalyst method are known, but there are problems such as those mentioned above. In addition, as another decomposition method, there is also a plasma method. However, if the gas to be processed contains both a gas containing nitrogen atoms such as nitrogen or nitrous oxide and a gas containing oxygen atoms such as oxygen, a large amount of NOx and nitrous oxide, which are environmental pollutants, are generated by plasma, so the composition of the gas to be processed is limited.

[0005] As a new method for decomposing nitrous oxide, it is known that there is a method for decomposing nitrous oxide by irradiation of ultraviolet light. For example, in patent documentation 1, an exhaust purification system of an engine that can decompose nitrous oxide is recorded. It is recorded that by this system, hydrocarbons and CO in the exhaust gas of the engine are oxidized, NOx is removed, and after water vapor is removed, nitrous oxide is decomposed and removed by ultraviolet light of 172nm.

[0006] Prior art literature

[0007] Patent Literature

[0008] Patent Document 1: Japanese Patent Application Publication No. 2021-088964 Summary of the invention

[0009] Problems to be solved by the invention

[0010] The nitrous oxide purification method disclosed in Patent Document 1 has a very complicated structure and is not effective. Therefore, the present invention provides a gas decomposition method and a gas decomposition device that can efficiently decompose greenhouse gas by a simpler method or structure.

[0011] Means for solving problems

[0012] The gas decomposition method of the present invention is to irradiate the treated gas containing oxygen, nitrous oxide and saturated hydrocarbons with a first light having a main emission wavelength of 160nm to less than 200nm to decompose the nitrous oxide and the saturated hydrocarbons.

[0013] In this specification, "oxygen" is referred to as "oxygen" when it is abbreviated as "oxygen" refers to "oxygen molecules" (hereinafter, sometimes described as "O2"). The above-mentioned saturated hydrocarbon may be a single hydrocarbon or two or more hydrocarbons. The details are described below, but the first light directly decomposes nitrous oxide (hereinafter, sometimes described as "N2O"), and the excited oxygen atoms (sometimes referred to as "singlet oxygen" or "O( 1 D)". Hereinafter, it may be described as "O( 1 D)”) decomposes N2O. In addition, O ( 1 D) and the ground state oxygen atom (sometimes called "triplet oxygen" or "O( 3 P)". Hereinafter, it may be described as "O( 3P)".) decomposes the hydrocarbons. As a result, the first light can decompose both N2O and the hydrocarbons. The water (H2O) generated by the decomposition reaction of the hydrocarbons promotes the nitration of NOx generated by the decomposition of N2O. Since NOx is a substance that has adverse effects on humans and animals, reducing NOx is preferred from the perspective of environmental maintenance. Furthermore, from the O( 1 D) From the viewpoint of contributing to the decomposition of the above-mentioned hydrocarbons, it is also preferred that the decomposition of hydrocarbons be performed simultaneously with the decomposition of N2O.

[0014] Nitric acid (hereinafter sometimes referred to as "HNO3") can be obtained by nitrification of NOx. Nitric acid is a substance useful in various industrial fields, and therefore is industrially produced while using a huge amount of energy. In contrast, the above-mentioned gas decomposition method can generate nitric acid without requiring a huge amount of energy, so a secondary effect of being able to recover and utilize the generated nitric acid can be obtained.

[0015] The saturated hydrocarbon may be an alkane. The carbon number of the alkane may be 10 or less, 6 or less, or 4 or less.

[0016] The temperature of the processed gas when irradiated with the first light may be higher than the temperature of the processed gas before being collected. That is, the collected processed gas may be heated. As a heating method, there is a method of using at least one thermal energy of the first light source and the second light source described later or the reaction heat in each chemical reaction, and a method of using a heater for heating the processed gas.

[0017] The above-mentioned processed gas may also contain water (H2O). In this specification, water is a concept including water vapor as a gas and water in a mist form as a liquid. The details are described below, but if the above-mentioned processed gas contains water, the water (H2O) is photodecomposed by the above-mentioned first light or the irradiation of the above-mentioned first light to generate hydroxyl radicals (hereinafter sometimes recorded as "OH".). Hydroxyl radicals promote the decomposition of the above-mentioned hydrocarbons. In addition, as mentioned above, water promotes the nitration of NOx generated by the decomposition of N2O.

[0018] The above-mentioned alkanes may also mainly contain methane. As mentioned above, methane is one of the greenhouse gases like N2O. The inventors have found that by irradiating the above-mentioned first light, both nitrous oxide and methane, two greenhouse gases, can be reduced simultaneously. It should be noted that the hydrocarbons mainly containing methane refer to the hydrocarbons of alkanes with a carbon number of 4 or less in which the gas concentration (vol%) of methane is the largest.

[0019] The details are described below, but the combination of nitrous oxide and methane is discharged from sewers, septic tanks, biomass plants or garbage treatment plants, although it is a relatively low concentration. Most of the wastes containing domestic garbage or human and livestock excrement contain hydrocarbons and ammonia. Therefore, corruption occurs through these wastes, and both nitrous oxide from ammonia sources and methane from hydrocarbon sources are generally produced. Therefore, nitrous oxide and methane can be collected at the same location. It should be noted that nitrous oxide and methane can also be collected from different locations.

[0020] The methane may account for more than 20 vol% relative to the nitrous oxide. When methane is relatively abundant relative to nitrous oxide, a large amount of water is generated by hydrogen and oxygen from the methane source. As a result, NOx generated as a byproduct of N2O decomposition can promote nitration, and as a result, the amount of NOx as a harmful substance can be reduced.

[0021] The above-mentioned processed gas may also be irradiated with a second light having a main emission wavelength of 200 nm or more and less than 1180 nm. That is, by irradiating the second light having a longer wavelength than the first light, ozone (hereinafter sometimes referred to as "O3") generated by the irradiation of the first light is generated. 1 D) or O( 3 P). O( 1 D) is used for the decomposition of N2O, the decomposition of the above hydrocarbons and the generation of hydroxyl radicals. 3 P) is utilized for nitration of NOx and decomposition of the above-mentioned hydrocarbons.

[0022] The second light may also be light having a main emission wavelength of 780 nm or more and less than 1180 nm. That is, the second light may also mainly contain infrared rays. The infrared rays assist in raising the temperature of the gas to be processed and promote the decomposition of hydrocarbons.

[0023] Nitric acid can also be generated from the decomposed treated gas.

[0024] The gas decomposition device of the present invention comprises: a chamber to which a gas to be treated containing oxygen, nitrous oxide and saturated hydrocarbon is supplied; and

[0025] The first light source irradiates the cavity with the first light having a main emission wavelength of 160 nm or more and less than 200 nm,

[0026] The above-mentioned nitrous oxide and the above-mentioned saturated hydrocarbon are decomposed.

[0027] The chamber may also include an inner chamber disposed inside the first light source and an outer chamber disposed in a manner of surrounding the first light source. In this specification, when simply indicated as a "chamber" (including the case of being indicated together with a reference symbol), it refers to the outer chamber disposed in a manner of surrounding the first light source. In this specification, when describing the inner chamber disposed inside the first light source, it is explicitly stated that it is recorded as an "inner chamber" or that the chamber is a chamber disposed inside the light source.

[0028] The saturated hydrocarbon may be an alkane. The carbon number of the alkane may be 10 or less, 6 or less, or 4 or less.

[0029] The chamber may also have a connection port connected to a space where there is a gas containing less than 5 vol% of the above-mentioned nitrous oxide and less than 5 vol% of alkanes with a carbon number of 4 or less. "A space where there is a gas containing less than 5 vol% of the above-mentioned nitrous oxide and less than 5 vol% of alkanes with a carbon number of 4 or less" is, for example, a sewer, a septic tank, a drain pipe, a drain tank, an exhaust pipe, and an exhaust tank of a biomass plant or a garbage disposal plant. Even in the case where both nitrous oxide and the above-mentioned alkanes are at a low concentration of less than 1%, the decomposition of nitrous oxide and the above-mentioned alkanes can be performed. It should be noted that in the case where at least one of the concentration of nitrous oxide and the concentration of the above-mentioned alkanes exceeds 5 vol%, the decomposition of nitrous oxide and the above-mentioned alkanes can be performed.

[0030] The chamber may also be an outer chamber surrounding the first light source.

[0031] The processed gas is supplied to the outer chamber.

[0032] The processed gas supplied to the outer chamber may not contact the first light source. A gap between the outer chamber and the first light source may be filled with a gas that is not easily absorbed by the first light (for example, nitrogen as an inert gas).

[0033] A second light source may be provided outside the outer chamber for irradiating the processed gas between the outer chamber and the first light source with light having a main emission wavelength of 200 nm or more and less than 1180 nm.

[0034] The chamber may also be an inner chamber located inside the first light source.

[0035] The processed gas is supplied into the inner chamber.

[0036] The chamber may include an inner chamber located inside the first light source and an outer chamber surrounding the first light source.

[0037] The processed gas is supplied into the inner chamber and between the outer chamber and the first light source respectively.

[0038] The processed gas may also pass through any one of the inner chamber and the outer chamber and the first light source.

[0039] Pass through the other one of the inner chamber and between the outer chamber and the first light source.

[0040] A light guide portion that transmits light reaching the chamber may be provided in the internal space of the chamber. The light guide portion may be columnar or plate-shaped.

[0041] The light guide portion may have a gap between the light guide portion and the first light source. There may also be no gap between the light guide portion and the first light source.

[0042] The first light source may also be an excimer lamp. The main wavelength of the excimer light may also be 172 nm or near 172 nm. The excimer light may be obtained by lighting a xenon excimer lamp having xenon gas sealed in a light-emitting tube. The excimer lamp is a light source that can be stably mass-produced and has a high cost-cutting effect. The power supplied to the excimer lamp may be controlled by a control unit. The control unit controls the lighting and extinguishing of the excimer lamp.

[0043] In this specification, "near 172nm" refers to the area within the range of 172nm±5nm. In this specification, "main wavelength" refers to the wavelength λi in the wavelength range Z(λi) that shows an integrated intensity of 40% or more relative to the total integrated intensity in the luminescence spectrum when a wavelength range Z(λ) of ±10nm relative to a certain wavelength λ is specified on the luminescence spectrum. In a light source that emits light of the "main wavelength" and has an extremely narrow half-value width, such as a xenon excimer lamp, and shows high light intensity only at a specific wavelength, the wavelength (peak wavelength) with the relatively highest light intensity can usually be regarded as the main wavelength.

[0044] Effects of the Invention

[0045] Thus, a gas decomposition method and a gas decomposition device that can efficiently decompose greenhouse gases with a simpler method or structure can be provided. Providing the gas decomposition method and the gas decomposition device greatly contributes to Goal 13 of the Sustainable Development Goals (SDGs) led by the United Nations, "taking urgent measures to mitigate climate change and its impacts." BRIEF DESCRIPTION OF THE DRAWINGS

[0046] Figure 1A It is a diagram showing a first embodiment of the gas decomposition device.

[0047] Figure 1B yes Figure 1A S1-S1 line cross-sectional view.

[0048] Figure 2 This is a diagram showing an example of a treatment method using nitric acid.

[0049] Figure 3 This is a graph showing the relationship between the temperature and the reaction rate constant of methane gas.

[0050] Figure 4A This is a graph showing the relationship between the ratio of CH4 to N2O and the amount of NOx generated.

[0051] Figure 4B This is a graph showing the relationship between the ratio of CH4 to N2O and the amount of NOx generated.

[0052] Figure 5A It is a diagram showing a first modification example of the first embodiment.

[0053] Figure 5B yes Figure 5A S2-S2 line cross-sectional view.

[0054] Fig. 6A It is a diagram showing a second modified example of the first embodiment.

[0055] Figure 6B yes Fig. 6A S3-S3 line cross-sectional view.

[0056] Fig. 7A It is a diagram showing a second modified example of the first embodiment.

[0057] Figure 7B yes Fig. 7A Cross-sectional view along line S4-S4.

[0058] Fig. 8A It is a figure which shows the 2nd embodiment.

[0059] Figure 8B yes Fig. 8A Cross-sectional view along line S5-S5.

[0060] Fig.9A It is a figure which shows the 3rd embodiment.

[0061] Fig. 9B yes Fig.9A Cross-sectional view along line S6-S6.

[0062] Fig.10 It is a diagram showing a first modified example of the third embodiment.

[0063] Fig.11 It is a diagram showing a second modified example of the third embodiment.

[0064] Fig. 12A It is a figure which shows the 4th embodiment.

[0065] Fig. 12B yes Fig. 12A An enlarged view of the main part.

[0066] Fig. 12C This is a top view of the light guide portion.

[0067] Fig.13 is a diagram showing an experimental apparatus. DETAILED DESCRIPTION

[0068] The embodiments will be described with reference to the drawings as appropriate. It should be noted that the drawings other than the diagrams are schematic diagrams, and the dimensional ratios on the drawings are not necessarily consistent with the actual dimensional ratios, and the dimensional ratios between the drawings are not necessarily consistent.

[0069] <First Embodiment>

[0070] [Overview of Gas Decomposition Device]

[0071] Figure 1A It is a diagram showing a first embodiment of the gas decomposition device. Figure 1B yes Figure 1A The gas decomposition device 10 includes a chamber 2 and a first light source 1 disposed in the chamber 2 and emitting a first light L1 having a main emission wavelength of 160 nm or more and less than 200 nm. The chamber 2 includes a gas supply port 3i and a gas exhaust port 3o. The gas supply port 3i and the gas exhaust port 3o are disposed in a manner opposite to each other with the first light source 1 sandwiched therebetween. In this specification, the first light L1 emitted from the first light source 1 is exemplified by a solid arrow from the first light source 1 to the outside.

[0072] The gas G1 is continuously supplied to the chamber 2 from the gas supply port 3i, and the gas G1 as the processed gas is irradiated with the first light L1 emitted from the first light source 1, and the gas G2 after the light irradiation is discharged from the gas discharge port 3o. Thus, the N2O and hydrocarbons in the gas G1 can be continuously decomposed. The first light source 1 is electrically connected to the control unit 5, and the first light source 1 is lit by supplying power from the control unit 5 to the first light source 1.

[0073] In this embodiment, the first light source 1 is a xenon excimer lamp that emits excimer light with a peak wavelength of 172 nm. The xenon excimer lamp of this embodiment is arranged inside the light emitting tube 1i (see Figure 1B) is sealed with xenon gas. The light-emitting tube of this embodiment is cylindrical. However, the shape of the light-emitting tube is not limited to the cylindrical shape. In addition, the first light source 1 is not limited to a xenon excimer lamp, and may be, for example, a low-pressure mercury lamp. The first light source 1 may also be an excimer lamp sealed with a gas other than xenon. The first light source 1 may also be a solid light source such as an LED or LD.

[0074] The first light L1 is easily absorbed by the gas G1, and the first light L1 does not reach far. Therefore, the distance D1 between the surface of the light-emitting tube of the first light source 1 and the inner wall of the chamber 2 (see Figure 1A or Figure 1B ) is relatively narrow. The interval D1 may be, for example, less than 50 mm, preferably less than 30 mm. By setting the interval D1 to an appropriate distance at which light is not excessively attenuated, the gas G1 passing through the chamber 2 without being irradiated by the first light L1 can be reduced.

[0075] [Processed gas]

[0076] The gas to be processed is described below. The gas G1 as the gas to be processed contains oxygen, N2O, and saturated hydrocarbons, particularly alkanes having 10 or less, 6 or less, or 4 or less carbon atoms.

[0077] The oxygen contained in the gas G1 may be oxygen in the air. That is, the gas G1 may contain air. When the gas G1 contains air, it will inevitably contain nitrogen and a trace amount of carbon dioxide. In addition, the gas G1 may contain water.

[0078] In the case of an alkane having 4 or less carbon atoms, examples of the alkane having 4 or less carbon atoms include methane (hereinafter, sometimes referred to as "CH4"), ethane (C2H6), propane (C3H8), butane (C4H 10 ). The "alkanes having a carbon number of 4 or less" may include one hydrocarbon, or may include two or more hydrocarbons. Among these hydrocarbons, CH4 is a greenhouse gas having a higher global warming coefficient than carbon dioxide.

[0079] When the processed gas contains both N 2 O and CH 4 , both greenhouse gases can be reduced at the same time.

[0080] [N2O decomposition mechanism]

[0081] The decomposition mechanism of N2O using ultraviolet light is explained. There are two methods for decomposing N2O: direct decomposition using ultraviolet light and decomposition using O( 1 D) indirect decomposition.

[0082] The direct decomposition of N2O is described below. When N2O is irradiated with ultraviolet light hν (≤340nm) with a wavelength below 340nm, N2O is decomposed to generate N2 and O ( 1D). It is shown in formula (1).

[0083] N2O+hν(≤340nm)→N2+O( 1 D) (1)

[0084] The decomposition reaction of formula (1) is theoretically caused by ultraviolet light with a wavelength of less than 340nm. However, since the absorption cross-sectional area of ​​light with a wavelength of more than 200nm is small relative to that of N2O, it is more effective to promote the decomposition reaction of formula (1) if light with a wavelength of less than 200nm with a relatively large absorption cross-sectional area is used.

[0085] Next, the indirect decomposition of N2O is described. 1 D) is a highly reactive and active substance. If O( 1 D) When it comes into contact with N2O, oxygen molecules and nitrogen molecules are generated according to formula (2) or nitric oxide (hereinafter sometimes referred to as "NO") is generated according to formula (3).

[0086] N2O+O( 1 D)→O2+N2 (2)

[0087] N2O+O( 1 D) → NO + NO (3)

[0088] The O( 1 D) is generated by the following equations (4) and (5) in addition to equation (1). It should be noted that "hν (≤175 nm)" means ultraviolet light of 175 nm or less, and "hν (≤411 nm)" means ultraviolet light of 411 nm or less.

[0089] O2+hν(≤175nm)→O( 3 P)+O( 1 D) (4)

[0090] O3+hν(≤411nm)→O( 1 D)+O2 (5)

[0091] O3 required for the reaction of formula (5) is generated through the reactions of the following formulas (1), (4), (6), (7), and (8) (shown again with formula (1) and formula (4)). Formula (6) indicates that the reaction shown in formula (6) occurs if the ultraviolet light hv is 242nm or less. "M" contained in formulas (7) and (8) indicates a third body.

[0092] N2O+hν(≤340nm)→N2+O( 1 D) (1)

[0093] O2+hν(≤175nm)→O( 3 P)+O( 1 D) (4)

[0094] O2+hν(≤242nm)→O( 3 P)+O( 3 P) (6)

[0095] O( 1 D)+M→O( 3 P)+M (7)

[0096] O2+O( 3 P)+M→O3+M (8)

[0097] The above is a study on the direct decomposition of N2O using ultraviolet light hν and the use of O( 1 D) Indirect decomposition of N2O is described. Generally, both direct decomposition and indirect decomposition are performed. The ratio of direct decomposition and indirect decomposition varies depending on the gas composition of gas G1.

[0098] However, the above series of reactions generate byproducts. NO generated by the reaction of formula (3) exhibits the following reaction in chamber 2. This reaction is shown in the following formulas (9) to (14).

[0099] NO+O( 3 P)→NO2 (9)

[0100] NO+O3+M→NO2+O2+M (10)

[0101] NO2+O( 3 P)+M→NO3+M (11)

[0102] NO2+O3+M→NO3+O2+M (12)

[0103] NO3+NO2→N2O5 (13)

[0104] N2O5+H2O→HNO3+HNO3 (14)

[0105] NO is converted into nitrogen dioxide (hereinafter sometimes referred to as "NO2") by equations (9) and (10). When O3 and H2O are sufficiently present in chamber 2, NO2 is converted into nitric acid (HNO3) via NO3 and N2O5 by equations (11) to (14). When O3 and H2O are insufficient in the chamber, equations (12) and (14) are not sufficiently induced, and nitration does not occur. O3 is consumed by inducing the NOx cycle reaction, and sometimes O3 is insufficient, in which case NOx remains.

[0106] [NOx cycle reaction]

[0107] The NOx cycle reaction is described. In this specification, NOx is a concept including NO and NO2. NO is converted into NO2 by the following formula (9) and formula (10). On the other hand, NO2 reacts with oxygen atoms O to generate NO by the following formula (15). The oxygen atoms O contained in formula (15) include O( 1 D) and O( 3 P) Both.

[0108] NO+O( 3 P)→NO2 (9)

[0109] NO+O3+M→NO2+O2+M (10)

[0110] NO2+O→NO+O2 (15)

[0111] The reaction of generating NO2 from NO, especially the reaction of formula (10) and the reaction of generating NO from NO2, especially the reaction of formula (15), are sometimes repeated. This is called the NOx cycle reaction. In the process of the NOx cycle reaction, the oxygen atoms O and O( 1 D) is required for the generation of O3 (see formula (5)). Therefore, when the NOx cycle reaction occurs, oxygen atoms O and O3 disappear, hindering the decomposition of N2O and hydrocarbons.

[0112] NOx has adverse effects on humans and animals. Therefore, it is preferred to create an environment in which O3 and H2O are sufficiently present in the chamber to promote the reaction of NOx to generate nitric acid (HNO3). In order to make O3 and H2O sufficiently present, O2 and H2O must be present in the light irradiation space. That is, the gas G1 as the treated gas must contain a lot of O2. One method for making H2O sufficiently present is to include hydrocarbons in the gas G1. The details are described below, but the chemical reaction of hydrocarbons with hydroxyl radicals contributes to the generation of H2O. In addition, it is also preferred to include H2O in the gas G1.

[0113] [Processing method of nitric acid]

[0114] Figure 2 An example of a treatment method with nitric acid is shown in FIG. Figure 2 In the process, the gas G2 containing nitric acid generated in the gas decomposition device 10 and discharged from the chamber 2 contacts the water W1 in the container 12 via the discharge pipe 11 connected to the gas discharge port 3o, so that the nitric acid contained in the gas G2 dissolves in the water W1 and becomes an aqueous nitric acid solution, resulting in the capture of nitric acid. Nitric acid is a raw material for ammonium nitrate and is a useful substance in the chemical industry or agricultural fields. Therefore, the aqueous nitric acid solution in the container 12 can also be recovered. In addition, when the concentration of the aqueous nitric acid solution is so dilute that it can be drained, the aqueous nitric acid solution can be discharged into the sewer without being recovered. The nitric acid that flows into the sewer is decomposed by organisms via NO3 - And eventually transformed into N2. Figure 2 , but a method of simply cooling the gas G2 to liquefy the nitric acid and recovering it may also be possible. The boiling point of nitric acid is about 83° C., so if the gas is cooled, the nitric acid is liquefied from the gas.

[0115] [Gas decomposition mechanism of saturated hydrocarbons]

[0116] The decomposition mechanism of saturated hydrocarbons by ultraviolet light will be described below. Hereinafter, the case where the saturated hydrocarbon is CH4 will be described, but the same description will be given below for saturated hydrocarbons other than CH4.

[0117] CH4 is decomposed by the chemical reactions of the following formulas (16) to (19).

[0118] CH4+O( 1 D) → CH3 + OH (16)

[0119] CH4+O( 1 D)→CH2O+H2 (17)

[0120] CH4+O( 3 P)→CH3+OH (18)

[0121] CH4+OH→CH3+H2O (19)

[0122] O( 1 D) and O( 3 P) is generated by the above formula (1), formula (4), formula (5), formula (6) or formula (7). OH used in formula (19) is generated by the above formula (16) and formula (18) as well as by the following formula (20) and formula (21).

[0123] H2O+hν(≤242nm)→H+OH (20)

[0124] H2O+O( 1 D)→OH+OH (21)

[0125] Therefore, CH4 is converted into O( 1 D), O( 3 P) or OH decomposition. O( 1 D) Since it is used for both the decomposition of N2O and the decomposition of CH4, it can perform decomposition treatment simultaneously. Furthermore, as shown in formula (1), in the decomposition of CH4, O( 1 D) One of the advantageous features of the case where CH 4 is mainly contained as saturated hydrocarbon is that CH 4 can be efficiently decomposed by simultaneously performing the decomposition treatment of CH 4 with the decomposition treatment of N 2 O.

[0126] [Temperature dependence of hydrocarbon decomposition reaction]

[0127] The CH4 decomposition reaction shown below in Formula (18) and Formula (19) depends on temperature. Figure 3 This is a graph showing the relationship between the temperature T1 of methane gas and the reaction rate constant k. Figure 3 The R1 curve of formula (19) shows the reaction rate constant k (m 3 / kmols). Figure 3 The R2 curve of formula (18) shows the reaction rate constant k (m 3 / kmols). From the R1 curve and the R2 curve, it is known that the reactivity of the reactions of formula (18) and formula (19) increases as the temperature increases.

[0128] CH4+O( 3 P)→CH3+OH (18)

[0129] CH4+OH→CH3+H2O (19)

[0130] Furthermore, if the temperature rises, O( 3 The increase in the amount of O( 3 P) promotes the CH4 decomposition reaction shown in the following formula (18).

[0131] O( 1 D)+M→O( 3 P)+M (7)

[0132] CH4+O( 3 P)→CH3+OH (18)

[0133] In the present embodiment, a first light source 1 is disposed in the chamber 2. The first light source 1 is turned on to emit ultraviolet light and release heat. Therefore, the first light source 1 heats the gas around the first light source 1, increases the temperature of the gas G1 containing CH4, and promotes the decomposition reaction of CH4 based on the above-mentioned formula (18) and formula (19). Furthermore, formula (2), formula (3), formula (9) and formula (10) are exothermic reactions that increase the temperature of the gas G1. Therefore, by performing the decomposition treatment of CH4 simultaneously with the decomposition treatment of N2O, effective decomposition can be performed. It should be noted that for saturated hydrocarbons other than CH4, the decomposition reaction also has the same temperature dependence as CH4.

[0134] [Mixture ratio of hydrocarbons and nitrous oxide]

[0135] Figure 4A It is the result of calculating the relationship between the ratio of CH4 to N2O and the amount of NOx generated through simulation. The "ratio of CH4 to N2O" is expressed as the percentage (unit: vol%) of the amount of CH4 contained in the processed gas relative to the amount of N2O. "The amount of NOx generated" represents the sum of the amount of NO generated and the amount of NO2 generated. Curves R3 to R5 have different N2O contents. In curve R3, N2O is 10000ppm. In curve R4, N2O is 1000ppm. In curve R5, N2O is 100ppm. In curve R3 to curve R5, the temperature of gas G1 in chamber 2 is uniformly 500K. It should be noted that in Figure 4A In order to improve the visual confirmation of the graph, the overlapping parts of multiple plots or the parts close to each other are omitted. The R3 to R5 curves are simulated at the same scale on the horizontal axis. It is hoped that there is a part of the omitted plot on each curve.

[0136] The less NOx is generated, the better. Figure 4A It was found that the amount of NOx generated decreased as the ratio of CH4 to N2O increased regardless of the amount of N2O. It was also found that NOx was not generated when CH4 was present at 10 vol% or more relative to N2O. This was because sufficient hydrocarbons were supplied, so NOx was nitrated by H2O generated by the decomposition of hydrocarbons.

[0137] Figure 4B The relationship between the ratio of CH4 to N2O and the amount of NOx generated is obtained through simulation. The meanings of "the ratio of CH4 to N2O" and "the amount of NOx generated" are the same as Figure 4AThe R6 to R9 curves make the temperature of the gas G1 in the chamber 2 different. In the R6 curve, the temperature is 350K. In the R7 curve, the temperature is 400K. In the R8 curve, the temperature is 450K. In the R9 curve, the temperature is 500K. In the R6 to R9 curves, the flow rate of N2O is unified to 10000ppm.

[0138] Depend on Figure 4B It was found that as the temperature in the chamber 2 increases, the amount of NOx generated decreases. It was also found that as the ratio of CH4 to N2O increases, the amount of NOx generated decreases. It was also found that when CH4 is present at 20 vol% or more relative to N2O, NOx is not generated even at 350K. This result is due to the fact that sufficient hydrocarbons are supplied by increasing the temperature or the ratio of CH4, and therefore NOx is nitrated by H2O generated by the decomposition of hydrocarbons.

[0139] according to Figure 4A and Figure 4B The ratio of CH4 to N2O is preferably 20 vol% or more. If it is 20 vol% or more, it is easy to reduce the amount of NOx generated. Figure 4A In the simulation, 100ppm to 10000ppm of N2O and the corresponding amount of CH4 were used. Figure 4B In the simulation, 10000 ppm of N2O and a corresponding amount of CH4 were used, but even with a smaller amount of N2O (e.g., less than 100 ppm) and a corresponding amount of CH4, the same effect can be obtained. Even with saturated hydrocarbons other than CH4, the same effect can be obtained.

[0140] [How to use the gas decomposition device]

[0141] The method of using the gas decomposition device 10 is described. Nitrous oxide is discharged through human and animal excrement, farm and livestock fields, and the process of fermenting biomass or domestic garbage by microorganisms. On the other hand, methane is produced by anaerobic methanogens present in the digestive organs of animals, swamps, seabed deposits or the earth's crust. Therefore, both nitrous oxide and methane are present in the drain pipes, drain tanks, exhaust pipes and exhaust tanks of, for example, sewers or septic tanks or biomass plants or garbage treatment plants as described above. Microorganisms also emit carbon dioxide. However, in the case of sewers or septic tanks, aeration is performed with a large amount of air, thereby containing oxygen with a concentration substantially close to the concentration in the air (about 21vol%) and a large amount of water.

[0142] Then, the gas supply port 3i of the gas decomposition device 10 is connected to the drain pipe, drain tank, exhaust pipe and exhaust tank of the sewer or septic tank or biomass plant, garbage disposal plant or chemical plant. Thus, both nitrous oxide and methane can be collected at the same place. Most of the processed gas is air, and the ratio of nitrous oxide to hydrocarbon is mostly below 5vol%. However, the decomposition method of the present invention can decompose the processed gas even if it is a low concentration of 5vol% or less. The processed gas can also be below 1vol%.

[0143] The same applies to hydrocarbons other than methane.

[0144] [First Modification]

[0145] A first modified example of the first embodiment is shown. The following description will focus on matters different from the first embodiment, and description of matters common to the first embodiment will be omitted. The same applies to the modified examples described later and the second embodiment and thereafter.

[0146] Figure 5A A gas decomposition device 15 according to a first modified example is shown. Figure 5B yes Figure 5A The S2-S2 line cross-section diagram. Figure 5A and Figure 5B As shown in FIG. 1 , a first light source 1 is disposed inside a chamber 2 of a gas decomposition device 15. The first light source 1 is covered by an ultraviolet light transmitting tube 6. The ultraviolet light transmitting tube 6 transmits the first light L1 emitted by the first light source 1. When the first light source 1 is not covered by the ultraviolet light transmitting tube 6, by exposing the first light source 1 to the gas G1, solid components (such as carbides) of the gas G1 may adhere to the surface of the light-emitting tube of the first light source 1. When the first light source 1 is covered by the ultraviolet light transmitting tube 6, solid components of the gas G1 do not adhere to the first light source 1. When solid components adhere to the ultraviolet light transmitting tube 6 and there is a concern about a decrease in illumination, the ultraviolet light transmitting tube 6 may be replaced with an ultraviolet light transmitting tube to which solid components are not adhered. The ultraviolet light transmitting tube 6 may also be replaced regularly. In addition, the ultraviolet light transmitting tube 6 may be filled with nitrogen.

[0147] The ultraviolet light transmitting tube 6 may be made of quartz glass, for example. The ultraviolet light transmitting tube 6 may or may not cover the entire first light source 1. The ultraviolet light transmitting tube 6 may be constructed so as to cover at least the light emitting tube of the first light source 1.

[0148] [Second Modification]

[0149] Fig. 6A A gas decomposition device 20 according to a second modified example is shown. Figure 6B yes Fig. 6A The S3-S3 line cross-section diagram. Fig. 6A and Figure 6B As shown in , the gas decomposition device 20 includes a first chamber 2a and a second chamber 2b in which a gas flow path is branched into two. The first light source 1 is arranged outside the first chamber 2a and the second chamber 2b. Since the first light source 1 is outside the chambers (2a, 2b), the solid components of the gas G1 are not attached to the first light source 1, and the first light source 1 can be easily inspected and replaced.

[0150] The gas decomposition device 20 is configured in such a manner that the first light source 1 is clamped between the first chamber 2a and the second chamber 2b. The first light L1 from the first light source 1 can be guided into the first chamber 2a and the second chamber 2b. The cross-sections of the first light source 1, the first chamber 2a, and the second chamber 2b of the present embodiment are all flat rectangular shapes. The distance traveled by the first light L1 emitted from the first light source 1 outside the chamber (2a, 2b) is short. Therefore, the attenuation of the first light L1 is small, and the first light L1 can easily and evenly reach the chambers (2a, 2b).

[0151] It is more preferable if the space between the first light source 1 and the first and second chambers 2a and 2b is filled with a gas, such as nitrogen, which is not easily absorbed by the first light L1 from the first light source 1. The absorption of the first light L1 can be suppressed outside the chambers (2a, 2b).

[0152] In the present embodiment, the chamber (2a, 2b) is composed of a quartz glass tube that transmits the first light L1. However, not all of the frames that constitute the chamber (2a, 2b) may be composed of ultraviolet light transmitting materials. It is preferable that at least the portion that transmits the first light L1 is composed of ultraviolet light transmitting materials such as quartz glass. The gas decomposition device 20 may also include three or more chambers in which the gas flow path is branched into three or more.

[0153] [Third Modification]

[0154] Fig. 7A A gas decomposition device 25 according to a third modified example is shown. Figure 7B yes Fig. 7A The S4-S4 line cross-sectional diagram. Fig. 7A and Figure 7B As shown in FIG. 2 , the gas decomposition device 25 includes a heater 7 wound around a cylindrical chamber 2 in which a first light source 1 is arranged.

[0155] As described above, the higher the temperature of the gas G1, the more effectively the decomposition is performed, and the less NOx is generated. In the first embodiment described above, the gas G1 is heated by the heat radiated by the excimer lamp. Furthermore, a heater 7 for heating the gas G1 may be configured as in the gas decomposition device 25 in this modification. The heater 7 of this embodiment is a sheath heater that converts electrical energy into heat for heating. The electrical energy is preferably renewable energy.

[0156] Since ozone is decomposed by arranging the heater 7, there is a secondary effect of suppressing the emission of ozone into the atmosphere.

[0157] The heater 7 may also be a fluid heater or a heat pipe using a heat medium flow path. The heater 7 may also be arranged on the upstream side of the first light source 1, and may also guide the gas G1 set to a high temperature to the gas supply port 3i. In addition, the heater 7 may also be sunlight or a fluid heated by sunlight.

[0158] <Second Embodiment>

[0159] Fig. 8A A second embodiment is shown. Figure 8B yes Fig. 8A The gas decomposition device 30 of this embodiment includes a plurality of second light sources 8. The plurality of second light sources 8 emit second light L2 toward the chamber 2. In this specification, the second light L2 emitted from the second light source 8 is illustrated by a dotted arrow pointing outward from the second light source 8. The second light source 8 is preferably arranged so that the space irradiated by the second light L2 overlaps the space irradiated by the first light L1.

[0160] The wavelength of the second light L2 emitted from the second light source 8 is different from the wavelength of the first light L1 emitted from the first light source 1, and the second light L2 has a longer wavelength than the first light L1. The second light L2 is generated from O3 as shown in the following equations (21) and (22): 1 D) or O( 3 P).

[0161] O3+hν(≤411nm)→O( 1 D)+O2 (21)

[0162] O3+hν(≤1180nm)→O( 3 P)+O2 (22)

[0163] Formula (21) and Formula (22) indicate that the active states of oxygen atoms generated by the wavelength of the second light L2 are different. When the second light L2 is ultraviolet light with a wavelength lower than 411 nm, highly active O( 1 D). O( 1D) is used for the decomposition of N2O (see equations (2) and (3)), the decomposition of hydrocarbons (see equations (15) and (16)), and the generation of hydroxyl radicals (see equation (20)).

[0164] When the second light L2 is infrared light or visible light with a wavelength lower than 1180 nm, low-activity O( 3 P). The generated O( 3 P) is used for decomposition of hydrocarbons (see equation (17)) and nitration of NOx (see equations (9) and (11)). In this way, by irradiating the gas G1 with the second light L2, decomposition of N2O and CH4 by the first light L1 can be promoted.

[0165] The second light source 8 may also be a solid light source such as an excimer lamp, an LED or a LD, a low-pressure mercury lamp or a fluorescent lamp. The second light source 8 may also be a lamp that emits ultraviolet light, visible light or infrared light. In addition, when the second light source 8 is a lamp that emits infrared light, as described in the third variant of the first embodiment, the decomposition reaction promoting effect by gas heating can also be obtained. In addition, when the heater 7 is configured for the purpose of heating, the O( 3 P) to promote the decomposition reaction.

[0166] like Fig. 8A and Figure 8B As shown in , when one of the first light source 1 and the second light source 8 is arranged inside the chamber 2, it is preferable to arrange the first light source 1 inside the chamber 2. The reason is that the light emitted by the first light source 1 has a shorter wavelength than the light emitted by the second light source 8, so the light emitted by the first light source 1 is less likely to pass through the chamber 2 than the light emitted by the second light source 8. In order to improve the transmittance of the light emitted by the first light source 1, it is required to select a material such as quartz glass that has a high transmittance even for short-wavelength light as the material of the chamber 2. However, if the first light source 1 is arranged inside the chamber 2, the light emitted by the first light source 1 does not need to pass through the chamber 2, so the selection of materials that can be used in the chamber 2 can be expanded.

[0167] <Third Embodiment>

[0168] Fig.9A A gas decomposition device 50 according to a third embodiment is shown. Fig. 9B yes Fig.9A The S6-S6 line cross-sectional diagram. Fig.9A and Fig. 9BAs shown in the figure, the gas decomposition device 50 has a first light source 51 and an inner chamber 52. The inner chamber 52 is located inside the first light source 51. The first light source 51 has a double tube structure in which an inner tube 54 is arranged in an outer tube 53. The first light source 51 is provided with an outer electrode 55 in contact with the outer wall surface of the outer tube 53, and an inner electrode 56 in contact with the inner wall surface of the inner tube 54. A luminescent gas such as xenon is filled and sealed between the outer tube 53 and the inner tube 54. A discharge space 58 of the luminescent gas is formed by applying a voltage between the outer electrode 55 and the inner electrode 56 (refer to Fig. 9B ), radiating the first light L1 (refer to Fig.9A It should be noted that the inner electrode 56 and the outer electrode 55 are preferably in a mesh shape.

[0169] The inner tube 54 is made of a material that allows the luminescent gas to pass through, such as quartz. The luminescent gas passes through the inner tube 54 and reaches the inner chamber 52. The gas decomposition device 50 has a gas supply port 3i at one end of the inner chamber 52 and a gas exhaust port 3o at the other end of the inner chamber 52. The gas G1 is continuously supplied to the inner chamber 52 from the gas supply port 3i, and the first light L1 emitted from the first light source 1 is irradiated to the gas G1 as the treated gas, and the gas G2 after the light irradiation is discharged from the gas exhaust port 3o. In this way, the N2O and hydrocarbons in the gas G1 can be continuously decomposed.

[0170] The outer tube 53 is made of quartz, for example. The gas decomposition device 50 has a reflective film 57 formed on the inner wall surface of the outer tube 53 to reflect the first light L1. The luminous gas can be radiated toward the outside of the outer tube 53. If the reflective film 57 is formed on the inner wall surface of the outer tube 53, the first light L1 that has been set to the outside of the outer tube 53 is returned to the inside, so that the light intensity in the inner chamber 52 increases.

[0171] In the gas decomposition device 50, the outer diameter D1 of the outer tube 53 is preferably 10 mm to 50 mm, more preferably 20 mm to 40 mm. The outer diameter D2 of the inner tube 54 is preferably 2 mm to 20 mm, more preferably 4 mm to 10 mm.

[0172] Fig.10A gas decomposition device 60 of a first modified example of the third embodiment is shown. The gas decomposition device 60 is different from the gas decomposition device 50 of the third embodiment in that the gas decomposition device 60 does not have a reflective film 57 and has an outer chamber 2 outside the outer tube 53. The gas decomposition device 60 also has a gas supply port 4i at one end of the outer chamber 2 and a gas exhaust port 4o at the other end of the outer chamber 2. Gas G1 is supplied to the outer chamber 2 from the gas supply port 4i, and the gas G1, which is a processed gas, is irradiated with the first light L1 emitted from the first light source 1. The gas decomposition device 60 can process the gas G1 with both the inner chamber 52 and the outer chamber 2, so a large amount of gas can be processed, and the utilization efficiency of the first light L1 is improved.

[0173] Fig.11 1 shows a gas decomposition device 70 of a second modified example of the third embodiment. The difference between the gas decomposition device 60 and the gas decomposition device 60 of the modified example of the third embodiment is that the gas outlet 3o of the inner chamber 52 is connected to the gas supply port 4i of the outer chamber 2. The gas G2 processed in the inner chamber 52 is processed again in the outer chamber 2, so that the processed gas can be processed more efficiently, and the utilization efficiency of the first light L1 is improved.

[0174] In the present modification, an embodiment is shown in which the light beam first passes through the inner chamber 52 and then passes through the outer chamber 2 . However, the light beam may first pass through the outer chamber 2 and then pass through the inner chamber 52 .

[0175] <Fourth Embodiment>

[0176] Fig. 12A The fourth embodiment of the gas decomposition device 80 is shown. The gas decomposition device 80 is provided with a light guide 81 that transmits light reaching the outer chamber (2a, 2b) in the internal space of the outer chamber (2a, 2b). Since there is a gap between the outer chamber (2a, 2b) and the first light source 1, the light guide 81 also has a gap between the first light source 1. The light guide 81 is formed in contact with the tube wall of the outer chamber (2a, 2b). In the gap, it is preferable that a gas (for example, nitrogen) that is difficult to absorb the first light L1 is the main component.

[0177] Fig. 12B yes Fig. 12A An enlarged view of the periphery of the light guide portion 81. Fig. 12B The function of the light guide 81 will be described. The light guide 81 guides the first light L1 inside and diffuses the first light L1 on the surface of the light guide 81. As a result, the area where the first light L1 contacts the gas G1 is expanded, and the photoreaction becomes more efficient.

[0178] Fig. 12CIt is a top surface view of the light guide portion 81, specifically, a view of the light guide portion 81 of the first chamber 2a observed in a direction opposite to the direction in which the first light L1 is emitted from the first light source 1. The light guide portion 81 of the present embodiment is cylindrical in shape, and a plurality of light guide portions 81 are arranged in the first chamber 2a. The light guide portion 81 may be arranged regularly or irregularly. The light guide portion 81 may also be a columnar shape other than a cylindrical shape (for example, a polygonal column shape or an elliptical column shape). The light guide portion 81 may also be a plate shape. In addition, the light guide portion 81 may also be arranged in the inner chamber.

[0179] The above has described various embodiments and variations of the gas decomposition method and the gas decomposition device. The above embodiment merely represents an example of the present invention, and the present invention is not limited to the above embodiment in any way. Various changes or improvements may be made to the above embodiment, or the above embodiment or variations may be combined without departing from the gist of the present invention.

[0180] Example

[0181] Constructed Fig.13 The experimental device 100 shown in FIG. The experimental device 100 is equipped with a gas decomposition device 40. The experimental device 100 includes an air supply source 21, an N2O supply source 22, and a CH4 supply source 23. Furthermore, the experimental device 100 includes a mass flow controller (24, 25, 26) for controlling the supply amount of the air supply source 21, the N2O supply source 22, and the CH4 supply source 23, and a mass flow meter 27 for detecting the amount of the treated gas mixed with air, N2O, and CH4. The gas supply port 3i is connected to the air supply source 21, the N2O supply source 22, and the methane supply source 23 via the mass flow meter 27 and the mass flow controller (24, 25, 26).

[0182] The air supply source 21 is an air supply pipe of the factory. The supplied air has a certain amount of moisture. The air contains nitrogen, oxygen, and a small amount of carbon dioxide. The N2O supply source 22 is a gas cylinder filled with N2O, which substantially contains only N2O. The CH4 supply source 23 is a gas cylinder filled with CH4, which substantially contains only CH4.

[0183] Regarding the gas decomposition device 40, the first light source 1 is a cylindrical xenon excimer lamp with a length of 800 mm. The chamber 2 is a cylindrical pipe with an inner diameter of 38 mm in which the first light source 1 can be arranged. Both sides of the pipe are sealed with sealing components with gas inlet or gas outlet. The power line connected to the first light source 1 passes through one of the sealing components, and the first light source 1 is lit and controlled by the control unit 5 located outside the chamber 2 via the sealing component.

[0184] Three types of gases G1 are prepared, and the three types of gases G1 are respectively fed into the gas decomposition device 10 to perform gas decomposition treatment.

[0185] Sample S1 is a gas containing 1000 ppm N2O added to air.

[0186] Sample S2 is a gas obtained by adding 1000 ppm of CH4 to air.

[0187] Sample S3 is a gas obtained by adding 1000 ppm N2O and 1000 ppm CH4 to air.

[0188] Table 1 summarizes the components (excluding air) contained in samples S1 to S3 of the gas G1.

[0189] Table 1

[0190] Sample No. <![CDATA[Content of N2O (ppm)]]> <![CDATA[CH4 content (ppm)]]> S1 1000 0 S2 0 1000 S3 1000 1000

[0191] Table 2 shows the results of measuring the contents of gas components in the gas G2 discharged from the gas discharge port 3o of the gas decomposition device 40. Each gas component was measured by a gas analyzer FT-IR (model: MATRIX-5) manufactured by Bruker.

[0192] Table 2

[0193]

[0194] The following matters were found out from sample S1.

[0195] N2O is decomposed by the gas decomposition device 40, and as a result, N2O is reduced from 1000ppm to 423ppm. The reduced portion of N2O is converted into N2 and O2, as well as NOx (NO and NO2) and HNO3. It is inferred that the content of H2O exists before decomposition. In addition, although O3 should be generated by the first light source 1, O3 is not included in the gas G2. It is believed that this is because O3 is consumed by the NOx cycle reaction.

[0196] The following matters were learned from sample S2.

[0197] All CH4 is oxidized and decomposed by the gas decomposition device 40 to generate CO2, H2O, and O3. It should be noted that regarding the H2O and CO2 contents in each sample, since the air contained in the gas G1 before treatment of each sample S1 to S3 contains H2O and CO2, not all of the H2O and CO2 contents are generated by the decomposition reaction.

[0198] The following matters were learned from sample S3.

[0199] Sample S3 has CH4 added to sample S1. It is believed that the addition of CH4 makes it difficult to cause the NOx cycle reaction that consumes O3, and the NOx remaining in sample S1 is converted into HNO3 by sufficient amounts of O3 and H2O. The added CH4 is oxidized and decomposed to convert into CO2 and H2O, so CH4 is not included in gas G2.

[0200] Explanation of symbols

[0201] 1,51: First light source

[0202] 2: Chamber

[0203] 2a: First chamber

[0204] 2b: Second chamber

[0205] 3i.4i: Gas supply port

[0206] 3o, 4o: Gas outlet

[0207] 5: Control Department

[0208] 6: UV light transmission tube

[0209] 7: Heater

[0210] 8: Second light source

[0211] 11: Discharge pipe

[0212] 12: Container

[0213] 10, 15, 20, 25, 30, 40, 50, 60, 70, 80: Gas decomposition device

[0214] 81: Light guide

[0215] 21: Air supply source

[0216] 22: Nitrous oxide supply source

[0217] 23: CH4 supply source

[0218] 24, 25, 26: Mass flow controller

[0219] 27: Mass flow meter

[0220] 52: Inner chamber

[0221] 53: External pipe

[0222] 54: Inner tube

[0223] 55: External electrode

[0224] 56: Inner electrode

[0225] 57: Reflective film

[0226] 58: Discharge Space

[0227] 81: Light guide

[0228] 100: Experimental equipment

[0229] G1: Gas (before treatment)

[0230] G2: (treated) gas

[0231] L1: First Light

[0232] L2: Second Light

Claims

1. A gas decomposition method, characterized in that: A first light having a main emission wavelength of 160 nm to less than 200 nm is irradiated on a gas to be treated containing oxygen, nitrous oxide and saturated hydrocarbons to decompose the nitrous oxide and the saturated hydrocarbons.

2. The gas decomposition method according to claim 1, characterized in that: The saturated hydrocarbon is an alkane having 4 or less carbon atoms.

3. The gas decomposition method according to claim 1, characterized in that: The temperature of the processed gas when irradiated with the first light is higher than the temperature of the processed gas before being collected.

4. The gas decomposition method according to claim 1, characterized in that: The processed gas contains water.

5. The gas decomposition method according to claim 2, characterized in that: The alkanes mainly comprise methane.

6. The gas decomposition method according to claim 5, characterized in that: The methane accounts for 20 vol% or more of the nitrous oxide.

7. The gas decomposition method according to any one of claims 1 to 6, characterized in that: The processed gas is irradiated with second light having a main emission wavelength of 200 nm or more and less than 1180 nm.

8. The gas decomposition method according to claim 7, characterized in that: The main emission wavelength of the second light is greater than or equal to 780 nm and less than or equal to 1180 nm.

9. The gas decomposition method according to any one of claims 1 to 7, characterized in that: Nitric acid is generated from the decomposed treated gas.

10. A gas decomposition device, characterized in that: A chamber is provided for supplying a treatment gas containing oxygen, nitrous oxide and saturated hydrocarbon, and a first light source is provided for irradiating the chamber with a first light having a main emission wavelength of not less than 160 nm and not more than 200 nm, The nitrous oxide and the saturated hydrocarbon are decomposed.

11. The gas decomposition device according to claim 10, characterized in that: The saturated hydrocarbon is an alkane having 4 or less carbon atoms.

12. The gas decomposition device according to claim 11, characterized in that: The chamber has a connection port connected to a space where a gas containing 5 vol% or less of the nitrous oxide and 5 vol% or less of the alkane exists.

13. The gas decomposition device according to any one of claims 10 to 12, characterized in that: The chamber is an outer chamber surrounding the first light source, The processed gas is supplied to the outer chamber.

14. The gas decomposition device according to claim 13, characterized in that: The processed gas supplied to the outer chamber does not come into contact with the first light source.

15. The gas decomposition device according to claim 13, characterized in that: A second light source is provided outside the outer chamber to irradiate the processed gas located between the outer chamber and the first light source with light having a main emission wavelength of 200 nm to less than 1180 nm.

16. The gas decomposition device according to any one of claims 10 to 12, characterized in that: The chamber is an inner chamber located inside the first light source, The processed gas is supplied into the inner chamber.

17. The gas decomposition device according to any one of claims 10 to 12, characterized in that: The chamber includes an inner chamber located inside the first light source and an outer chamber surrounding the first light source. The processed gas is supplied into the inner chamber and between the outer chamber and the first light source.

18. The gas decomposition device according to claim 17, characterized in that: After the processed gas passes through any one of the inner chamber and between the outer chamber and the first light source, Through the other of within the inner chamber and between the outer chamber and the first light source.

19. The gas decomposition device according to any one of claims 10 to 12, characterized in that: A light guide portion that transmits light reaching the chamber is provided in the internal space of the chamber.

20. The gas decomposition device according to claim 19, characterized in that: The light guide portion has a gap between itself and the first light source.

21. The gas decomposition device according to any one of claims 10 to 20, characterized in that: The first light source is an excimer lamp.

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