JP2024022455A - Gas decomposition method and gas decomposition device - Google Patents

Abstract

To provide a gas decomposition method and a gas decomposition device which can efficiently decompose greenhouse effect gas with a simple method or structure.SOLUTION: A gas decomposition method irradiates treated gas containing oxygen, dinitrogen monoxide and saturated hydrocarbon with first light having a main light-emission wavelength of 160 nm or more and less than 200 nm, and decomposes the dinitrogen monoxide and the saturated hydrocarbon. A gas decomposition device includes a chamber for supplying treated gas containing oxygen, dinitrogen monoxide and the saturated hydrocarbon, and a first light source for irradiating the chamber with the first light.SELECTED DRAWING: Figure 1A

Description

The present invention relates to a gas decomposition method and a gas decomposition device.

Since the industrial revolution, the average temperature of the earth has been rising, making countermeasures against global warming an urgent issue. Carbon dioxide, methane, dinitrogen monoxide, chlorofluorocarbon gas, and the like are known as greenhouse gases that cause global warming. Among these gases, carbon dioxide has the largest amount of emissions, followed by methane, and then nitrous oxide. However, it has been reported that the global warming potential of methane is 25 times that of carbon dioxide, and that of nitrous oxide is 298 times that of carbon dioxide. In particular, the impact of global warming due to nitrous oxide emissions cannot be ignored.

Dinitrogen monoxide is emitted in large quantities not only from industrial activities such as the manufacture of chemical products and from the combustion of waste, but also from the processing of human and livestock excrement and from agriculture. Methane is often emitted from the same sources as nitrous oxide, such as agricultural land, livestock waste, biomass combustion, and sewage treatment. The reason why dinitrogen monoxide and methane are emitted from the same place is that both are often generated from microorganisms. Recently, the concentrations of dinitrogen monoxide and methane have been on the rise, so suppressing or reducing the concentrations of dinitrogen monoxide and methane is expected to be a countermeasure against global warming.

In the above-mentioned emission situations of dinitrogen monoxide and methane, most of the gas composition exhausted is the atmosphere, and dinitrogen monoxide and methane often occupy a relatively low concentration in the exhaust gas composition. High-temperature combustion and catalytic methods have long been used to decompose dinitrogen monoxide. However, the high-temperature combustion method requires a large amount of energy to combust the gas. Using fossil fuels to secure large amounts of energy increases carbon dioxide emissions, so it cannot be said to be an efficient means of combating global warming. Catalytic systems also require heating the gas to high temperatures. Furthermore, it is necessary to procure ammonia for use in catalysts and reducing agents, and there is also the problem of wastewater treatment after treatment. Therefore, the catalytic method cannot be said to be efficient either. Furthermore, high-temperature combustion methods and catalyst methods are known as methods for decomposing methane, but these methods have the same problems as described above. There is also a plasma method as another decomposition method. However, if the gas to be treated contains both a gas containing nitrogen atoms, such as nitrogen or dinitrogen monoxide, and a gas containing oxygen atoms, such as oxygen, the plasma will generate environmental pollutants such as NOx and dinitrogen monoxide. Since a large amount of nitrogen is generated, the composition of the gas to be treated is limited.

As a new method for decomposing dinitrogen monoxide, a method is known in which dinitrogen monoxide is decomposed by irradiation with ultraviolet light. For example, Patent Document 1 describes an engine exhaust purification system that can decompose dinitrogen monoxide. This system describes that after oxidizing hydrocarbons and CO in engine exhaust gas, removing NOx, and removing water vapor, dinitrogen monoxide is decomposed and removed using 172 nm ultraviolet light.

JP2021-088964A

The method for purifying dinitrogen monoxide disclosed in Patent Document 1 has a very complicated structure and is not efficient. Therefore, the present invention provides a gas decomposition method and a gas decomposition device that can efficiently decompose greenhouse gases using a simpler method or structure.

The gas decomposition method of the present invention irradiates a gas to be treated containing oxygen, dinitrogen monoxide, and saturated hydrocarbons with first light having a main emission wavelength of 160 nm or more and less than 200 nm, and Decompose nitrogen and the saturated hydrocarbons.

In this specification, "oxygen" when simply written as "oxygen" is intended to mean "oxygen molecule" (hereinafter, sometimes written as "O ₂ "). The saturated hydrocarbon may be one type of hydrocarbon or two or more types of hydrocarbon. Although the details will be described later, the first light directly decomposes dinitrogen monoxide (hereinafter sometimes referred to as "N ₂ O"), and at the same time decomposes excited oxygen atoms (" Oxygen (sometimes referred to as "singlet oxygen" or "O( ¹ D)" (hereinafter sometimes referred to as "O( ¹ D)") decomposes N ₂ O. In addition, O( ¹ D) generated by the first light irradiation and oxygen atoms in the ground state (sometimes called "triplet oxygen" or "O( ³ P)". Hereinafter, "O( ³ P)"P)" decomposes the hydrocarbon. As a result, the first light can decompose both N ₂ O and the hydrocarbon. Water (H ₂ O) produced by the hydrocarbon decomposition reaction promotes nitrification of NOx produced by N ₂ O decomposition. Since NOx is a substance that has an adverse effect on the human body and animals, reducing NOx is preferable from the viewpoint of environmental maintenance. Furthermore, since O( ¹ D) generated by N ₂ O decomposition contributes to the decomposition of the hydrocarbons, it is preferable to perform the decomposition simultaneously with the decomposition of N ₂ O.

Nitric acid (hereinafter sometimes referred to as "HNO ₃ ") is obtained by nitric oxidation of NOx. Since nitric acid is a useful substance in various industrial fields, nitric acid is industrially produced using a lot of energy. On the other hand, in the gas decomposition method, nitric acid can be produced without requiring much energy, so a secondary effect is obtained in that the produced nitric acid can be recovered and used.

The saturated hydrocarbon may be an alkane. The number of carbon atoms in the alkane may be 10 or less, 6 or less, or 4 or less.

The temperature of the gas to be treated when the first light is irradiated may be higher than the temperature before the gas to be treated is collected. In other words, the collected gas to be processed may be heated. As heating methods, there are two methods: a method that utilizes thermal energy of at least one of a first light source and a second light source (described later) and reaction heat of each chemical reaction, and a method that utilizes a heater for heating the gas to be processed.

The gas to be treated may contain water (H ₂ O). In this specification, water is a concept that includes water vapor, which is a gas, and mist water, which is a liquid. The details will be described later, but if the gas to be treated contains water, water (H ₂ O) will be photolyzed by the first light or irradiation with the first light, and hydroxyl radicals (hereinafter referred to as "OH ”) is generated. Hydroxy radicals promote the decomposition of the hydrocarbons. Furthermore, as described above, water promotes nitrification of NOx generated by N ₂ O decomposition.

The alkane may mainly contain methane. As mentioned above, methane, like N ₂ O, is one of the greenhouse gases. The present inventor has discovered that two types of greenhouse gases, dinitrogen monoxide and methane, can be reduced simultaneously by irradiation with the first light. Note that hydrocarbons mainly containing methane refer to the case where the gas concentration (vol%) of methane is the highest among the hydrocarbons of alkanes having 4 or less carbon atoms.

As will be discussed in more detail below, the combination of dinitrogen monoxide and methane is discharged from sewers or septic tanks, or from biomass plants or garbage disposals, albeit at relatively low concentrations. Wastes, including food scraps and human and livestock waste, often contain hydrocarbons and ammonia. Therefore, as these wastes decompose, both dinitrogen monoxide derived from ammonia and methane derived from hydrocarbons are generated in general. Therefore, dinitrogen monoxide and methane can be procured from the same location. Note that dinitrogen monoxide and methane may be procured from different locations.

The methane may occupy 20 vol% or more with respect to the dinitrogen monoxide. When methane is relatively abundant compared to nitrogen monoxide, a large amount of water is produced due to hydrogen and oxygen derived from methane. As a result, NOx generated as a byproduct of N ₂ O decomposition can promote nitric oxidation, and as a result, the amount of NOx, which is a harmful substance, can be reduced.

The gas to be treated may be irradiated with second light having a main emission wavelength of 200 nm or more and less than 1180 nm. In other words, by irradiating the second light with a longer wavelength than the first light, _O ( ¹ D) or O( ³ P). O( ¹ D) is used to decompose N ₂ O, decompose the hydrocarbons, and generate hydroxy radicals. O( ³ P) is used for nitric oxidation of NOx and decomposition of the hydrocarbons.

The second light may be light whose main emission wavelength is 780 nm or more and less than 1180 nm. In other words, the second light may mainly include infrared rays. Infrared rays assist in increasing the temperature of the gas to be treated, promoting the decomposition of hydrocarbons.

Nitric acid may be generated from the decomposed gas to be treated.

The gas decomposition apparatus of the present invention includes a chamber that supplies a gas to be treated containing oxygen, dinitrogen monoxide, and saturated hydrocarbons;
a first light source that irradiates the chamber with first light whose main emission wavelength is 160 nm or more and less than 200 nm;
The dinitrogen monoxide and the saturated hydrocarbon are decomposed.

The chamber may include an inner chamber disposed inside the first light source and an outer chamber disposed to surround and cover the first light source. In this specification, when simply referred to as a "chamber" (including when referred to with a reference numeral), it refers to an outer chamber that is arranged to surround and cover the first light source. In this specification, when describing the inner chamber disposed inside the first light source, the term "inner chamber" is used or it is specified that the chamber is a chamber disposed inside the light source.

The saturated hydrocarbon may be an alkane. The number of carbon atoms in the alkane may be 10 or less, 6 or less, or 4 or less.

The chamber may have a connection port connected to a space in which a gas containing 5 vol% or less of the dinitrogen monoxide and 5 vol% or less of an alkane with a carbon number of 4 or less exists. "A space where a gas containing 5 vol% or less of the dinitrogen monoxide and 5 vol% or less of an alkane with a carbon number of 4 or less exists" means, for example, a sewer or a septic tank, or a drain pipe of a biomass factory or a garbage treatment plant, These are a drainage tank, an exhaust pipe, and an exhaust tank. Even when dinitrogen monoxide and the alkane are both at low concentrations of 1% or less, decomposition of dinitrogen monoxide and the alkane is possible. Note that dinitrogen monoxide and the alkane can be decomposed even when at least one of the concentration of dinitrogen monoxide and the concentration of the alkane exceeds 5 vol%.

the chamber is an outer chamber surrounding the first light source;
The gas to be processed may be supplied to the outer chamber.

The processing gas supplied to the outer chamber does not need to come into contact with 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 gas, which is an inert gas).

A second light source is provided outside the outer chamber that irradiates light having a main emission wavelength of 200 nm or more and less than 1180 nm toward the gas to be treated located between the outer chamber and the first light source. I don't mind.

the chamber is an inner chamber located inside the first light source;
The gas to be processed may be supplied into the inner chamber.

The chamber includes both an inner chamber located inside the first light source and an outer chamber surrounding the first light source,
The gas to be processed may be supplied into the inner chamber and between the outer chamber and the first light source.

After the gas to be treated passes through either one of the inner chamber and between the outer chamber and the first light source,
The light may be passed through the inner chamber and the other between the outer chamber and the first light source.

A light guiding portion that transmits light reaching the chamber may be provided in the internal space of the chamber. The light guide portion may have a columnar shape or a plate shape.

The light guide portion may have a gap between it and the first light source. There may be no gap between the light guide and the first light source.

The first light source may be an excimer lamp. The main wavelength of the excimer light may be 172 nm or around 172 nm. Such excimer light is obtained by lighting a xenon excimer lamp whose arc tube is filled with xenon gas. Excimer lamps are light sources that can be stably mass-produced and have a high cost reduction effect. The electric power supplied to the excimer lamp is controlled by the control section. The control unit controls turning on and turning off the excimer lamp.

In this specification, "near 172 nm" refers to a region within the range of 172 nm±5 nm. In this specification, "principal wavelength" means 40% or more of the total integrated intensity within the emission spectrum when a wavelength range Z(λ) of ±10 nm is defined on the emission spectrum for a certain wavelength λ. refers to the wavelength λi in the wavelength range Z(λi) showing the integrated intensity of . When a light source that emits light at a "main wavelength" has an extremely narrow half-width and a high light intensity only at a specific wavelength, such as a xenon excimer lamp, the light intensity is usually relatively low. The highest wavelength (peak wavelength) may be regarded as the main wavelength.

Thereby, it is possible to provide a gas decomposition method and a gas decomposition device that can efficiently decompose greenhouse gases using a simpler method or structure. Providing such gas decomposition methods and gas decomposition equipment will greatly contribute to Goal 13 of the Sustainable Development Goals (SDGs) led by the United Nations: “Take urgent measures to reduce climate change and its impacts.” It is something.

FIG. 1 is a diagram showing a first embodiment of a gas decomposition device. FIG. 1A is a sectional view taken along line S1-S1 in FIG. 1A. It is a figure showing an example of the processing method of nitric acid. It is a graph showing the relationship between the temperature of methane gas and the reaction rate constant. 2 is a graph showing the relationship between the ratio of CH ₄ to N ₂ O and the amount of NOx produced. 2 is a graph showing the relationship between the ratio of CH ₄ to N ₂ O and the amount of NOx produced. It is a figure showing the first modification of the first embodiment. FIG. 5A is a sectional view taken along line S2-S2 in FIG. 5A. It is a figure showing the second modification of the first embodiment. FIG. 6A is a sectional view taken along line S3-S3 in FIG. 6A. It is a figure showing the second modification of the first embodiment. FIG. 7A is a sectional view taken along line S4-S4 in FIG. 7A. It is a figure showing a second embodiment. 8A is a sectional view taken along line S5-S5 of FIG. 8A. FIG. It is a figure showing a third embodiment. FIG. 9A is a sectional view taken along line S6-S6 in FIG. 9A. It is a figure showing the first modification of the third embodiment. It is a figure showing the second modification of the third embodiment. It is a figure showing a fourth embodiment. FIG. 12A is an enlarged view of the main part of FIG. 12A. It is a top view of a light guide part. It is a diagram showing experimental equipment.

Embodiments will be described with reference to the drawings as appropriate. Please note that all drawings, excluding graphs, are schematic illustrations, and the dimensional ratios on the drawings do not necessarily match the actual dimensional ratios, and the dimensional ratios do not necessarily match between drawings. Not yet.

<First embodiment>
[Overview of gas decomposition equipment]
FIG. 1A is a diagram showing a first embodiment of a gas decomposition device. FIG. 1B is a sectional view taken along the line S1-S1 in FIG. 1A. The gas decomposition device 10 includes a chamber 2 and a first light source 1 disposed in the chamber 2 that emits 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 discharge port 3o. The gas supply port 3i and the gas discharge port 3o are arranged to face each other with the first light source 1 in between. In this specification, the first light L1 emitted from the first light source 1 is illustrated by a solid arrow pointing outward from the first light source 1.

Gas G1 is supplied to the chamber 2 from the gas supply port 3i, the gas G1, which is the gas to be treated, is irradiated with the first light L1 emitted from the first light source 1, and the gas G2 after the light irradiation is released from the gas discharge port 3o. Continue to drain. Thereby, N ₂ O and hydrocarbons in the gas G1 can be continuously decomposed. The first light source 1 is electrically connected to the control unit 5, and when power is supplied from the control unit 5 to the first light source 1, the first light source 1 is turned on.

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

The first light L1 is easily absorbed by the gas G1, and the first light L1 does not reach far. Therefore, the distance D1 (see FIG. 1A or FIG. 1B) between the surface of the arc tube of the first light source 1 and the inner wall of the chamber 2 is relatively narrow. The distance D1 may be, for example, 50 mm or less, and preferably 30 mm or less. By setting the interval D1 to an appropriate distance that does not attenuate the light too much, it is possible to reduce the amount of gas G1 that passes through the chamber 2 without being irradiated with the first light L1.

[Gas to be processed]
The gas to be processed will be explained. Gas G1, which is the gas to be treated, contains oxygen, N ₂ O, and saturated hydrocarbons, particularly alkanes having 10 or less carbon atoms, 6 or less carbon atoms, or 4 or less carbon atoms.

The oxygen contained in the gas G1 may be oxygen in the air. That is, the gas G1 may contain air. When gas G1 contains air, it will necessarily contain nitrogen and a trace amount of carbon dioxide. Further, the gas G1 may contain water.

In the case of alkanes with 4 or less carbon atoms, examples of alkanes with 4 or less carbon atoms include methane (hereinafter sometimes referred to as "CH ₄ "), ethane (C ₂ H ₆ ), propane (C ₃ H ₈ ) and butane (C ₄ H ₁₀ ). The "alkane having 4 or less carbon atoms" may contain one type of hydrocarbon, or may contain two or more types of hydrocarbons. Among these hydrocarbons, _CH4 is a greenhouse gas with a higher global warming potential than carbon dioxide. When the gas to be treated contains both N ₂ O and CH ₄ , two types of greenhouse gases can be reduced at the same time.

[N ₂ O decomposition mechanism]
The decomposition mechanism of N ₂ O by ultraviolet light will be explained. Methods for decomposing N ₂ O include direct decomposition using ultraviolet light and indirect decomposition using O( ¹ D) generated by ultraviolet light.

Direct decomposition of N ₂ O will be explained. When N ₂ O is irradiated with ultraviolet light hv (≦340 nm) having a wavelength of 340 nm or less, N ₂ O is decomposed to generate N ₂ and O( ¹ D). This is shown in equation (1).

N ₂ O + hν (≦340 nm) → N ₂ + O ( ¹ D) … (1)

The decomposition reaction of formula (1) is theoretically caused by ultraviolet light having a wavelength of 340 nm or less. However, the absorption cross section of light with a wavelength of 200 nm or more for N ₂ O is small, so in order to promote the decomposition reaction of equation (1), it is necessary to use light with a wavelength of less than 200 nm, which has a relatively large absorption cross section. , more efficient.

Next, indirect decomposition of N ₂ O will be explained. O( ¹ D) is a highly reactive and highly active substance. When O( ^1D ) generated by ultraviolet light comes into contact with _N2O , oxygen molecules and nitrogen molecules are generated according to equation (2), or nitric oxide (hereinafter referred to as "NO") is generated according to equation (3). ") is generated.

_N2O +O( ^1D ) → _O2 + _N2 ...(2)
_N2O +O( ^1D ) → NO+NO…(3)

O( ¹ D) required for the reactions of formulas (2) and (3) is generated not only by formula (1) but also by formulas (4) and (5) below. Note that "hv (≦175 nm)" represents ultraviolet light of 175 nm or less, and "hv (≦411 nm)" represents ultraviolet light of 411 nm or less.

O ₂ + hν (≦175 nm) → O ( ³ P) + O ( ¹ D) … (4)
O ₃ + hν (≦411 nm) → O ( ¹ D) + O ₂ … (5)

O ₃ required for the reaction of formula (5) is produced through the reactions of formulas (1), (4), (6), (7), and (8) below (formula (1) and ( 4) The formula is reproduced). Regarding equation (6), if the ultraviolet light hv is 242 nm or less, it means that the reaction shown in equation (6) occurs. "M" included in formulas (7) and (8) represents a third body.

N ₂ O + hν (≦340 nm) → N ₂ + O ( ¹ D) … (1)
O ₂ + hν (≦175 nm) → O ( ³ P) + O ( ¹ D) … (4)
O ₂ + hν (≦242 nm) → O ( ³ P) + O ( ³ P) … (6)
O( ¹ D)+M → O( ³ P)+M…(7)
O ₂ + O ( ³ P) + M → O ₃ + M … (8)

Above, the direct decomposition of N ₂ O by ultraviolet light hv and the indirect decomposition of N ₂ O by O( ¹ D) generated by ultraviolet light have been explained. Both direct and indirect decomposition are usually performed. The ratio at which direct decomposition and indirect decomposition occur differs depending on the gas composition of gas G1.

By the way, the series of reactions described above generate byproducts. NO generated by the reaction of formula (3) exhibits the following reaction within the chamber 2. This reaction is shown in the following formulas (9) to (14).

NO+O( ^3P ) → _NO2 …(9)
NO+O ₃ +M → NO ₂ +O ₂ +M…(10)
NO ₂ + O ( ³ P) + M → NO ₃ + M … (11)
NO ₂ +O ₃ +M → NO ₃ +O ₂ +M…(12)
_NO3 + _NO2 → _{N2O5 ...} (13)
_N2O5 + _{H2O → HNO3} + _HNO3 ...(14)

According to equations (9) and (10), NO is converted to nitrogen dioxide (hereinafter sometimes referred to as "NO ₂ "). Then, when there are sufficient O ₃ and H ₂ O in the chamber 2, NO ₂ is converted to nitric acid (HNO ₃ ) through NO ₃ and N ₂ O ₅ according to equations (11) to (14). converted. If there is not enough O ₃ and H ₂ O in the chamber, equations (12) and (14) will not occur sufficiently, and nitrification will not occur. O ₃ may be consumed due to the NOx cycle reaction, resulting in a deficiency of O ₃ , and in this case, NOx remains.

[NOx cycle reaction]
The NOx cycle reaction will be explained. In this specification, NOx is a concept that includes NO and _NO2 . NO is converted to NO ₂ using equations (9) and (10), which are reproduced below. On the other hand, NO ₂ reacts with oxygen atom O to generate NO according to the following equation (15). The oxygen atom O included in formula (15) includes both O( ¹ D) and O( ³ P).

NO+O( ^3P ) → _NO2 …(9)
NO+O ₃ +M → NO ₂ +O ₂ +M…(10)
NO ₂ + O → NO + O ₂ … (15)

In particular, the reaction of equation (10) for producing NO ₂ from NO and the reaction of equation (15) for producing NO from NO ₂ may be repeated. This is called a NOx cycle reaction. In the course of the NOx cycle reaction, oxygen atoms O, which are necessary for the decomposition of N ₂ O and hydrocarbons, and O ₃ (see equation (5)), which are necessary for the production of O( ¹ D), continue to be consumed. Therefore, when the NOx cycle reaction occurs, oxygen atoms O and O ₃ disappear, preventing the decomposition of N ₂ O and hydrocarbons.

NOx has a negative impact on humans and animals. Therefore, it is desirable to create an environment with sufficient O ₃ and H ₂ O in the chamber to promote the reaction of producing nitric acid (HNO ₃ ) from NOx. In order to have a sufficient amount of O ₃ and H ₂ O, it is necessary that O ₂ and H ₂ O exist in the light irradiation space. In other words, it is necessary to include a large amount of O ₂ in the gas G1, which is the gas to be processed. A method of making H ₂ O sufficiently present includes a method of including hydrocarbons in the gas G1. Although details will be described later, a chemical reaction between hydrocarbons and hydroxyl radicals contributes to the production of H ₂ O. It is also preferable that the gas G1 contains H ₂ O.

[Nitric acid treatment method]
FIG. 2 shows an example of a nitric acid treatment method. In FIG. 2, gas G2 containing nitric acid produced in the gas decomposition device 10 and discharged from the chamber 2 passes through the discharge pipe 11 connected to the gas discharge port 3o and comes into contact with the water W1 in the container 12. As a result, the nitric acid contained in the gas G2 is dissolved in the water W1 to become a nitric acid aqueous solution, and as a result, the nitric acid can be trapped. Nitric acid is a raw material for ammonium nitrate, and is a substance useful in the chemical industry, agriculture, and the like. Therefore, the nitric acid aqueous solution in the container 12 may be recovered. Furthermore, if the concentration of the nitric acid aqueous solution is low enough to allow drainage, the nitric acid aqueous solution may be flushed into the sewer system without being recovered. Nitric acid discharged into sewers is biodegraded into NO ₃ ^- and finally converted into N ₂ . Although FIG. 2 shows a method of recovering nitric acid by dissolving it in water W1, it is also possible to liquefy nitric acid and recover it by simply cooling gas G2. Since the boiling point of nitric acid is approximately 83°C, when the gas is cooled, nitric acid turns from a gas to a liquid.

[Gas decomposition mechanism of saturated hydrocarbons]
The decomposition mechanism of saturated hydrocarbons by ultraviolet light will be explained. In the following, a case will be described in which the saturated hydrocarbon is CH ₄ , but saturated hydrocarbons other than CH ₄ will also be explained in the same manner as below.

CH ₄ is decomposed by the chemical reactions of formulas (16) to (19) below.

CH ₄ +O( ¹ D) → CH ₃ +OH…(16)
_CH4 +O( ^1D ) → _CH2O + _H2 ...(17)
CH ₄ +O( ^3P ) → CH ₃ +OH…(18)
CH ₄ +OH → CH ₃ +H ₂ O…(19)

O( ¹ D) and O( ³ P) are generated by the above formula (1), formula (4), formula (5), formula (6), or formula (7). OH used in equation (19) is generated not only by equations (16) and (18) above, but also by equations (20) and (21) below.

_H2O +hν(≦242nm) → H+OH…(20)
_H2O +O( ^1D ) → OH+OH...(21)

Therefore, CH ₄ is decomposed by O( ¹ D), O( ³ P), or OH generated by irradiation with ultraviolet light. Since O( ¹ D) generated by irradiation with ultraviolet light is used for both N ₂ O decomposition and CH ₄ decomposition, the decomposition process can proceed at the same time. Furthermore, as shown by formula (1), in the decomposition of CH ₄ , O( ¹ D) obtained by decomposing N ₂ O can be used. One advantageous feature of saturated hydrocarbons that mainly contain CH ₄ is that CH ₄ can be decomposed at the same time as N ₂ O, resulting in more efficient decomposition. be.

[Temperature dependence of hydrocarbon decomposition reaction]
Among the CH ₄ decomposition reactions, the reactions of formulas (18) and (19), which are reproduced below, depend on the temperature. FIG. 3 is a graph showing the relationship between the temperature T1 of methane gas and the reaction rate constant k. The R1 curve in FIG. 3 represents the reaction rate constant k (m ³ /kmol s) with respect to the temperature T1 (° C.) in equation (19). The R2 curve in FIG. 3 represents the reaction rate constant k (m ³ /kmol s) with respect to the temperature T1 (° C.) in equation (18). From the R1 curve and the R2 curve, it can be seen that in both the reactions of formulas (18) and (19), the reactivity increases as the temperature increases.

CH ₄ +O( ^3P ) → CH ₃ +OH…(18)
CH ₄ +OH → CH ₃ +H ₂ O…(19)

Furthermore, as the temperature rises, the amount of O( ³ P) produced increases according to equation (7), which is reproduced below. This increase phenomenon is caused by the decomposition of ozone due to heat. The increased O( ³ P) then promotes the CH ₄ decomposition reaction of formula (18), which is reproduced below.

O( ¹ D)+M → O( ³ P)+M…(7)
CH ₄ +O( ^3P ) → CH ₃ +OH…(18)

In this embodiment, the first light source 1 is placed inside the chamber 2 . The first light source 1 is turned on, emits ultraviolet light, and generates heat. Therefore, the first light source 1 heats the gas around the first light source 1, increases the temperature of the gas G1 containing CH ₄ , and promotes the decomposition reaction of CH ₄ according to equations (18) and (19) above. do. Furthermore, equations (2), (3), (9), and (10) are exothermic reactions, and in order to increase the temperature of gas G1, the decomposition treatment of CH ₄ is performed at the same time as the decomposition treatment of N ₂ O. By doing so, more efficient decomposition becomes possible. Note that for saturated hydrocarbons other than CH ₄ as well, the decomposition reaction is temperature dependent, similar to CH ₄ .

[Mixing ratio of hydrocarbon and dinitrogen monoxide]
FIG. 4A shows the results obtained by simulation of the relationship between the ratio of CH ₄ to N ₂ O and the amount of NOx produced. “Ratio of CH ₄ to N ₂ O” is expressed as a percentage (unit: vol%) of the amount of CH ₄ to the amount of N ₂ O contained in the gas to be treated. The “amount of NOx produced” represents the sum of the amount of NOx produced and the amount of NO ₂ produced. The R3 to R5 curves have different N ₂ O contents. In the R3 curve, N ₂ O is 10,000 ppm. In the R4 curve, N ₂ O is 1000 ppm. In the R5 curve, N ₂ O is 100 ppm. In the R3 curve to R5 curve, the temperature of the gas G1 in the chamber 2 is unified to 500K. Note that in FIG. 4A, in order to improve the visibility of the graph, some plots where multiple plots overlap or are close to each other are omitted. The R3 curve to R5 curve are all simulated at the same rate on the horizontal axis. It should be understood that some omitted plots are present on each curve.

The smaller the amount of NOx produced, the better. From FIG. 4A, it can be seen that the amount of NOx produced decreases as the ratio of CH ₄ to N ₂ O increases, regardless of the amount of N ₂ O. When CH ₄ is present at 10 vol % or more relative to N ₂ O, it means that NOx is not generated. This is because sufficient hydrocarbons were supplied and NOx was nitrated by H ₂ O produced by decomposition of hydrocarbons.

FIG. 4B shows the results obtained by simulation of the relationship between the ratio of CH ₄ to N ₂ O and the amount of NOx produced. The meanings of “ratio of CH ₄ to N ₂ O” and “amount of NOx produced” are the same as in FIG. 4A. The R6 to R9 curves have different temperatures of the gas G1 in the chamber 2. In the R6 curve, the temperature is 350K. In the R7 curve, the temperature is 400K. For the R8 curve, the temperature is 450K. For the R9 curve, the temperature is 500K. In the R6 curve to R9 curve, the flow rate of N ₂ O is unified to 10,000 ppm.

From FIG. 4B, it can be seen that as the temperature inside the chamber 2 increases, the amount of NOx generated decreases. Furthermore, it can be seen that as the ratio of CH ₄ to N ₂ O increases, the amount of NOx produced decreases. Further, when CH ₄ exists at 20 vol % or more with respect to N ₂ O, it means that NOx is not generated even at 350K. This result indicates that sufficient hydrocarbons were supplied by increasing the temperature or by increasing the proportion of _CH4 , so that NOx was nitrified by _H2O produced by decomposition of hydrocarbons. This is because of this.

From FIGS. 4A and 4B, the ratio of CH ₄ to N ₂ O is preferably 20 vol% or more. When it is 20 vol% or more, the amount of NOx generated can be easily reduced. In addition, in FIG. 4A, the simulation was performed with 100 ppm to 10,000 ppm of N ₂ O and the corresponding amount of CH ₄ , and in FIG. 4B, the simulation was performed with 10,000 ppm of N ₂ O and the corresponding amount of CH ₄ . However, similar effects can be obtained with less N ₂ O (eg, less than 100 ppm) and a corresponding amount of CH ₄ . Similar effects can be obtained with saturated hydrocarbons other than CH ₄ .

[How to use gas decomposition equipment]
A method of using the gas decomposition device 10 will be explained. Dinitrogen monoxide is emitted by human and animal waste, agricultural and livestock farms, and the process of microbial fermentation of biomass or food waste. On the other hand, methane is produced by anaerobic methanogens present in the digestive organs of animals, marshes, seafloor sediments, the earth's crust, and the like. Therefore, both dinitrogen monoxide and methane are present, as mentioned above, in drain pipes, sump tanks, exhaust pipes and exhaust tanks, for example in sewers or septic tanks, or in biomass plants or garbage disposal plants. Microorganisms also emit carbon dioxide. However, in the case of a sewer or a septic tank, a large amount of water and oxygen at a concentration close to that in the air (approximately 21 vol%) are contained due to the process of aerating with a large amount of air.

Therefore, the gas supply port 3i of the gas decomposition device 10 is connected to a sewer or a septic tank, or a drain pipe, a drainage tank, an exhaust pipe, an exhaust tank, etc. of a biomass factory, a garbage treatment plant, or a chemical factory. This allows both dinitrogen monoxide and methane to be procured at the same location. Most of the gas to be treated is air, and the proportions of dinitrogen monoxide and hydrocarbons therein are often both 5 vol% or less. However, the decomposition method of the present invention can decompose even the gas to be treated at a low concentration of 5 vol% or less. The gas to be treated may be 1 vol% or less. The same applies to hydrocarbons other than methane.

[First variation]
A first modification of the first embodiment is shown. Below, the explanation will focus on matters that are different from the first embodiment, and descriptions of matters common to the first embodiment will be omitted. The same applies to modifications and second embodiments and subsequent embodiments that will be described later.

FIG. 5A shows a gas decomposition device 15 of a first modification. FIG. 5B is a sectional view taken along the line S2-S2 in FIG. 5A. As shown in FIGS. 5A and 5B, the first light source 1 is arranged inside the chamber 2 of the gas decomposition device 15. The first light source 1 is covered with an ultraviolet light transmitting tube 6. The ultraviolet light transmitting tube 6 transmits the first light L1 emitted from the first light source 1. When the first light source 1 is not covered with the ultraviolet light transmitting tube 6, when the first light source 1 is exposed to the gas G1, solid components (for example, carbide) of the gas G1 are transferred to the arc tube of the first light source 1. There is a risk of it adhering to the surface. When the first light source 1 is covered with the ultraviolet light transmitting tube 6, the 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 that the illuminance will decrease, it is preferable to replace the ultraviolet light transmitting tube 6 with an ultraviolet light transmitting tube to which solid components do not adhere. The ultraviolet light transmitting tube 6 may be replaced periodically. Further, the inside of the ultraviolet light transmitting tube 6 may be filled with nitrogen.

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 configured to cover at least the arc tube of the first light source 1.

[Second modification]
FIG. 6A shows a gas decomposition device 20 of a second modification. FIG. 6B is a sectional view taken along line S3-S3 in FIG. 6A. As shown in FIGS. 6A and 6B, the gas decomposition device 20 includes a first chamber 2a and a second chamber 2b, each of which has a gas flow path 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 located outside the chamber (2a, 2b), the solid components of the gas G1 do not adhere to the first light source 1, and the first light source 1 can be easily maintained, inspected, and replaced.

The gas decomposition device 20 is arranged such that the first chamber 2a and the second chamber 2b sandwich the first light source 1 therebetween. The first light L1 from the first light source 1 can be guided to the first chamber 2a and the second chamber 2b. In this embodiment, the first light source 1, the first chamber 2a, and the second chamber 2b all have a rectangular shape with a flat cross section. The distance that the first light L1 emitted from the first light source 1 travels outside the chamber (2a, 2b) is short. Therefore, the amount of attenuation of the first light L1 is small, and the first light L1 easily reaches the chambers (2a, 2b) evenly.

It is more preferable that the space between the first light source 1 and the first chamber 2a and second chamber 2b is filled with a gas that is difficult to absorb the first light L1 from the first light source 1, such as nitrogen gas. Absorption of the first light L1 can be suppressed outside the chamber (2a, 2b).

In this embodiment, the chambers (2a, 2b) are constructed of quartz glass tubes that transmit the first light L1. However, all the casings that make up the chambers (2a, 2b) do not need to be made of ultraviolet light transmitting material. It is preferable that at least a portion through which the first light L1 is transmitted is made of an ultraviolet light transmitting material such as quartz glass. The gas decomposition device 20 may include three or more chambers in which the gas flow path is branched into three or more.

[Third variation]
FIG. 7A shows a gas decomposition device 25 of a third modification. FIG. 7B is a sectional view taken along line S4-S4 in FIG. 7A. As shown in FIGS. 7A and 7B, the gas decomposition device 25 includes a heater 7 wound around the outside of a cylindrical chamber 2 in which the first light source 1 is disposed.

As described above, the higher the temperature of the gas G1, the more efficiently the decomposition progresses and the less NOx is produced. In the first embodiment described above, the gas G1 is heated by the heat radiated by the excimer lamp. Furthermore, like the gas decomposition device 25 in this modification, a heater 7 that heats the gas G1 may be arranged. The heater 7 of this embodiment is a sheathed heater that heats by converting electrical energy into heat. Preferably, the electrical energy is renewable energy.
Since ozone is decomposed by arranging the heater 7, there is a secondary effect of suppressing the emission of ozone into the atmosphere.

The heater 7 may be a fluid heating device using a heat medium flow path or a heat pipe. The heater 7 may be arranged upstream of the first light source 1, and may guide the heated gas G1 to the gas supply port 3i. Further, the heater 7 may be sunlight or a fluid heated by sunlight.

<Second embodiment>
FIG. 8A shows a second embodiment. FIG. 8B is a sectional view taken along line S5-S5 in 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 broken line arrow pointing outward from the second light source 8. The second light source 8 is preferably arranged such that the space irradiated with the second light L2 overlaps the space irradiated with the first light L1.

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 generates O( ¹ D) or O( ³ P) from O ₃ as shown in the following equations (21) and (22).

O ₃ + hν (≦411 nm) → O ( ¹ D) + O ₂ … (21)
O ₃ + hν (≦1180 nm) → O ( ³ P) + O ₂ … (22)

Equations (21) and (22) represent that the active state of the oxygen atoms generated differs depending on the wavelength of the second light L2. When the second light L2 is ultraviolet light with a wavelength of less than 411 nm, highly active O( ¹ D) is generated. O( ¹ D) generated by the formula (21) is generated by the decomposition of N ₂ O (see formulas (2) and (3)), the decomposition of hydrocarbons (see formulas (15) and (16)), It is used to generate hydroxyl radicals (see formula (20)).

When the second light L2 is infrared or visible light with a wavelength of less than 1180 nm, low activity O( ³ P) is generated. The generated O( ³ P) is used for decomposition of hydrocarbons (see equation (17)) and nitric oxidation of NOx (see equations (9) and (11)). In this way, by irradiating the gas G1 with the second light L2, the decomposition of N ₂ O and CH ₄ by the first light L1 is promoted.

The second light source 8 may be an excimer lamp, a solid light source such as an LED or an LD, a low-pressure mercury lamp, or a fluorescent lamp. The second light source 8 may be a lamp that emits ultraviolet light, visible light, or infrared light. Furthermore, when the second light source 8 is a lamp that emits infrared rays, the effect of promoting the decomposition reaction by gas heating can also be obtained, as explained in the third modification of the first embodiment. Further, even when the heater 7 is arranged for the purpose of heating, the effect of promoting the decomposition reaction due to the generation of O( ³ P) by infrared rays can be obtained by the arranged heater 7.

As shown in FIGS. 8A and 8B, when any one of the first light source 1 and the second light source 8 is disposed inside the chamber 2, the first light source 1 is preferably disposed inside the chamber 2. This is because the light emitted from the first light source 1 has a shorter wavelength than the light emitted from the second light source 8. Difficult to penetrate. In order to increase the transmittance of the light emitted from the first light source 1, it is required to select a material for the chamber 2 that has a high transmittance even for short wavelength light, such as quartz glass. However, when the first light source 1 is placed inside the chamber 2, the emitted light from the first light source 1 does not have to pass through the chamber 2, so that the choices of materials that can be used for the chamber 2 can be expanded.

<Third embodiment>
FIG. 9A shows a gas decomposition device 50 according to a third embodiment. FIG. 9B is a sectional view taken along line S6-S6 in FIG. 9A. As shown in FIGS. 9A and 9B, the gas decomposition device 50 includes a first light source 51 and an inner chamber 52. As shown in FIGS. Inner chamber 52 is located inside first light source 51 . The first light source 51 has a double tube structure in which an inner tube 54 is disposed within an outer tube 53. In the first light source 51, an outer electrode 55 is arranged in contact with the outer wall surface of the outer tube 53, and an inner electrode 56 is arranged in contact with the inner wall surface of the inner tube 54. The space between the outer tube 53 and the inner tube 54 is filled with a luminescent gas such as xenon gas and sealed. By applying a voltage between the outer electrode 55 and the inner electrode 56, a discharge space 58 of luminescent gas is formed (see FIG. 9B), and the first light L1 is emitted (see FIG. 9A). Note that the inner electrode 56 and the outer electrode 55 preferably have a net shape.

The inner tube 54 is made of a material that transmits the luminescent gas, 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 discharge port 3o at the other end of the inner chamber 52. Gas G1 is supplied to the inner chamber 52 from the gas supply port 3i, the gas G1, which is the gas to be processed, is irradiated with the first light L1 emitted from the first light source 1, and the gas G2 after the light irradiation is sent to the gas exhaust port 3o. Continue to drain from. Thereby, N ₂ O and hydrocarbons in the gas G1 can be continuously decomposed.

The outer tube 53 is made of quartz, for example. In the gas decomposition device 50, a reflective film 57 that reflects the first light L1 is formed on the inner wall surface of the outer tube 53. The luminescent gas can be emitted toward the outside of the outer tube 53, but if the reflective film 57 is formed on the inner wall surface of the outer tube 53, the first light L1 that was about to go to the outside of the outer tube 53 will be emitted inside. Due to the folding, the light intensity within the inner chamber 52 increases.

In the gas decomposition device 50, the outer diameter D1 of the outer tube 53 is preferably 10 mm or more and 50 mm or less, more preferably 20 mm or more and 40 mm or less. The outer diameter D2 of the inner tube 54 is preferably 2 mm or more and 20 mm or less, and more preferably 4 mm or more and 10 mm or less.

FIG. 10 shows a gas decomposition device 60 of a first modification of the third embodiment. The gas decomposition device 60 differs 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 discharge port 4o at the other end of the outer chamber 2. Gas G1 is supplied from the gas supply port 4i to the outer chamber 2, and the first light L1 emitted from the first light source 1 is irradiated onto the gas G1, which is the gas to be processed. Since the gas decomposition device 60 can process the gas G1 in both the inner chamber 52 and the outer chamber 2, it can process a large amount of gas and improve the utilization efficiency of the first light L1.

FIG. 11 shows a gas decomposition device 70 of a second modification of the third embodiment. The gas decomposition device 60 differs from the gas decomposition device 60 of the modification of the third embodiment in that the gas exhaust port 3o of the inner chamber 52 is connected to the gas supply port 4i of the outer chamber 2. Since the gas G2 processed in the inner chamber 52 is processed again in the outer chamber 2, the gas to be processed can be processed more effectively, and the utilization efficiency of the first light L1 is improved.

In this modification, an embodiment is shown in which the tube first passes through the inner chamber 52 and then the outer chamber 2, but it is also possible to first pass through the outer chamber 2 and then pass through the inner chamber 52.

<Fourth embodiment>
FIG. 12A shows a gas decomposition device 80 according to a fourth embodiment. The gas decomposition device 80 is provided with a light guide section 81 in the internal space of the outer chambers (2a, 2b) that transmits light that reaches the outer chambers (2a, 2b). Since there is a gap between the outer chamber (2a, 2b) and the first light source 1, the light guide part 81 also has a gap between it and the first light source 1. The light guide portion 81 is formed in contact with the tube wall of the outer chamber (2a, 2b). It is preferable that the main component of the gap is a gas (for example, nitrogen gas) that is difficult to absorb the first light L1.

FIG. 12B is an enlarged view of the vicinity of the light guide section 81 in FIG. 12A. The function of the light guide section 81 will be explained using FIG. 12B. The light guide section 81 guides the first light L1 into its interior, and diffuses the first light L1 on the surface of the light guide section 81. As a result, the area where the first light L1 contacts the gas G1 is expanded, and the photoreaction becomes more effective.

FIG. 12C is a top view of the light guide section 81, specifically, a view of the light guide section 81 of the first chamber 2a viewed in the opposite direction to the direction in which the first light L1 is emitted from the first light source 1. The light guide section 81 of this embodiment has a cylindrical shape, and a plurality of light guide sections 81 are arranged in the first chamber 2a. The light guide portions 81 may be arranged regularly or irregularly. The light guide portion 81 may have a columnar shape other than a cylindrical shape (for example, a polygonal columnar shape or an elliptical columnar shape). The light guide section 81 may have a plate shape. Further, the light guide section 81 may be arranged in the inner chamber.

The gas decomposition method and the embodiments and modifications of the gas decomposition apparatus have been described above. The above-mentioned embodiment shows only an example of the present invention, and the present invention is not limited to the above-described embodiment at all. Various changes or improvements can be made to the above-described embodiments, or the above-described embodiments or modifications can be combined without departing from the spirit of the present invention.

Experimental equipment 100 shown in FIG. 13 was constructed. Experimental equipment 100 incorporates gas decomposition device 40 . The experimental equipment 100 includes an air supply source 21, a N ₂ O supply source 22, and a CH ₄ supply source 23. Furthermore, the experimental equipment 100 includes mass flow controllers (24, 25, 26) for controlling the supply amounts of the air supply source 21, the N ₂ O supply source 22, and _the CH ₄ supply source 23, and ₄ is provided with a mass flow meter 27 for detecting the amount of the mixed gas to be treated. The gas supply port 3i is connected to an air supply source 21, an N ₂ O supply source 22, and a methane supply source 23 via a mass flow meter 27 and a mass flow controller (24, 25, 26).

The air supply source 21 is a factory air supply pipe. The supplied air has a constant moisture content. Air includes nitrogen, oxygen, trace amounts of carbon dioxide, and the like. The N ₂ O source 22 is a gas cylinder filled with N ₂ O, which contains substantially only N ₂ O. The CH ₄ source 23 is a gas cylinder filled with CH ₄ , which contains substantially only CH ₄ .

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 placed. Both sides of the piping are each sealed with a sealing member with a gas inflow path or a gas outflow path. A power line connected to the first light source 1 passes through one of the sealing members, and the first light source 1 is controlled to be turned on by a control unit 5 located outside the chamber 2 via the sealing member.

Three types of gases G1 were prepared, and each of the three types of gases G1 was sent to the gas decomposition device 10 for gas decomposition treatment.
Sample S1 is a gas in which 1000 ppm of N ₂ O is added to air.
Sample S2 is a gas in which 1000 ppm of CH ₄ is added to air.
Sample S3 is a gas in which 1000 ppm of N ₂ O and 1000 ppm of CH ₄ are added to air.

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

Table 2 shows the measurement results of the gas component content of the gas G2 discharged from the gas exhaust port 3o of the gas decomposition device 40. Each gas component was measured using a gas analyzer FT-IR (model: MATRIX-5) manufactured by Bruker.

The following matters can be found from sample S1.
As a result of decomposing N ₂ O by the gas decomposition device 40, N ₂ O decreased from 1000 ppm to 423 ppm. The loss of _N2O was converted to _N2 and _O2 , as well as NOx (NO and NO2) and _HNO3 . It is presumed that the content of H ₂ O was present before decomposition. Further, although O ₃ is supposed to be generated from the first light source 1, O ₃ is not included in the gas G2. This is considered to be because O ₃ was consumed by the NOx cycle reaction.

The following matters can be found from sample S2.
All the CH ₄ was oxidized and decomposed by the gas decomposition device 40 to generate CO ₂ , H ₂ O, and O ₃ . Regarding the H ₂ O and CO ₂ contents in each sample, since the air contained in the gas G1 before processing of each sample S1 to S3 contains H ₂ O and CO ₂ , H ₂ O and CO 2 Not all of the content of ₂ was produced by the decomposition reaction.

The following matters can be found from sample S3.
Sample S3 has CH ₄ added to sample S1. It is considered that the addition of CH ₄ made it difficult for the NOx cycle reaction that consumes O ₃ to occur, and that the NOx remaining in sample S1 was converted to HNO ₃ by a sufficient amount of O ₃ and H ₂ O. Since the added CH ₄ was oxidized and decomposed and converted into CO ₂ and H ₂ O, CH ₄ is not included in the gas G2.

1, 51: first light source 2: chamber 2a: first chamber 2b: second chamber 3i. 4i: Gas supply ports 3o, 4o: Gas discharge ports 5: Control unit 6: Ultraviolet light transmission tube 7: Heater 8: Second light source 11: Discharge tube 12: Containers 10, 15, 20, 25, 30, 40, 50 , 60, 70, 80: Gas decomposition device 81: Light guiding section 21: Air supply source 22: Nitrogen monoxide supply source 23: _CH4 supply source 24, 25, 26: Mass flow controller 27: Mass flow meter 52: Inner chamber 53: Outer tube 54: Inner tube 55: Outer electrode 56: Inner electrode 57: Reflective film 58: Discharge space 81: Light guide section 100: Experimental equipment G1: (Before treatment) Gas G2: (After treatment) Gas L1 :First light L2 :Second light

Claims (21)

A gas to be treated containing oxygen, dinitrogen monoxide, and saturated hydrocarbons is irradiated with first light having a main emission wavelength of 160 nm or more and less than 200 nm to decompose the dinitrogen monoxide and the saturated hydrocarbons. A gas decomposition method characterized by: The gas decomposition method according to claim 1, wherein the saturated hydrocarbon is an alkane having 4 or less carbon atoms. The gas decomposition method according to claim 1, wherein the temperature of the gas to be treated when the first light is irradiated is higher than the temperature before the gas to be treated is collected. The gas decomposition method according to claim 1, wherein the gas to be treated contains water. The gas decomposition method according to claim 2, characterized in that the alkane mainly contains methane. The gas decomposition method according to claim 5, wherein the methane occupies 20 vol% or more with respect to the dinitrogen monoxide. The gas decomposition method according to any one of claims 1 to 6, characterized in that the gas to be treated 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, wherein the second light has a main emission wavelength of 780 nm or more and less than 1180 nm. The gas decomposition method according to any one of claims 1 to 7, characterized in that nitric acid is generated from the decomposed gas to be treated. a chamber for supplying a gas to be treated containing oxygen, dinitrogen monoxide, and saturated hydrocarbon;
a first light source that irradiates the chamber with first light whose main emission wavelength is 160 nm or more and less than 200 nm;
A gas decomposition device characterized in that the dinitrogen monoxide and the saturated hydrocarbon are decomposed. The gas decomposition apparatus according to claim 10, wherein the saturated hydrocarbon is an alkane having 4 or less carbon atoms. The gas decomposition device according to claim 11, wherein the chamber has a connection port connected to a space in which a gas containing 5 vol% or less of the dinitrogen monoxide and 5 vol% or less of the alkane exists. . the chamber is an outer chamber surrounding the first light source;
The gas decomposition apparatus according to claim 10, wherein the gas to be treated is supplied to the outer chamber. 14. The gas decomposition device according to claim 13, wherein the gas to be treated that is supplied to the outer chamber does not come into contact with the first light source. A second light source is provided outside the outer chamber that irradiates light whose main emission wavelength is 200 nm or more and less than 1180 nm toward the gas to be processed located between the outer chamber and the first light source. The gas decomposition device according to claim 13, characterized in that: the chamber is an inner chamber located inside the first light source;
The gas decomposition apparatus according to any one of claims 10 to 12, characterized in that the gas to be treated is supplied into the inner chamber. The chamber includes both an inner chamber located inside the first light source and an outer chamber surrounding the first light source,
The gas decomposition device according to claim 10, wherein the gas to be treated is supplied into the inner chamber and between the outer chamber and the first light source, respectively. . After the gas to be treated passes through either one of the inner chamber and between the outer chamber and the first light source,
18. Gas decomposition device according to claim 17, characterized in that the gas passes through the inner chamber and the other between the outer chamber and the first light source. 13. The gas decomposition apparatus according to claim 10, further comprising a light guide section provided in the interior space of the chamber to transmit light that reaches the chamber. 20. The gas decomposition device according to claim 19, wherein the light guiding section has a gap between it and the first light source. The gas decomposition apparatus according to claim 10, wherein the first light source is an excimer lamp.