METHOD FOR TREATING METHANE-CONTAINING GAS AND APPARATUS FOR TREATING METHANE-CONTAINING GAS

Abstract

The present invention provides a technology that enables, with a simple method, degradation of a to-be-treated gas containing a treatment target substance at a low concentration in the order of several hundred ppm or less.　The gas treatment method of the present invention comprises; a step (a) for passing, in a housing, a to-be-treated gas containing a target substance that is mixed with air, that is volatile at normal temperature, and that belongs to at least one type in a group consisting of carbon compounds, nitrogen compounds, and sulfur compounds; a step (b) for introducing ozone, at 200°C or less, into a space inside the housing where the to-be-treated gas is passed; and a step (c) for agitating the to-be-treated gas after execution of the step (b); and a step (d) for heating the to-be-treated gas to 300°C or more after execution of the step (c).

Description

[Technical Field]

[0001] The present invention relates to a gas treatment method and a gas treatment device, and more particularly to a method and device for treating a gas to be treated, which is a mixture of air and a target substance that is volatile at room temperature. [Background technology]

[0002] As global warming progresses, greenhouse gases known to cause global warming include carbon dioxide, methane, and chlorofluorocarbons. Carbon dioxide is the most widely emitted, followed by methane. Methane's global warming potential is said to be about 20 to 70 times that of carbon dioxide, making it a major contributor to global warming. Furthermore, methane concentrations have been rising in recent years, and technology to efficiently decompose emitted methane may become necessary when considering the future state of the global environment.

[0003] A conventional technique for decomposing methane is the methane removal system disclosed in Patent Document 1. Figure 14 is a diagram showing a schematic configuration of the methane removal system.

[0004] The methane removal system 100 is a system for decomposing methane contained in a gas to be treated, and includes a gas to be treated pipe 102, a catalyst 104 for oxidizing and removing methane, plasma generating means 105, and control means .

[0005] The treated gas pipe 102 is set inside a treated gas passage 102a for discharging the treated gas Eg from the treated gas emission source 101. The methane oxidation removal catalyst 104 is accommodated in layers in a catalyst accommodation section 104a set inside the treated gas passage 102a, and is arranged to remove the treated gas Eg flowing through the treated gas passage 102a.

[0006] The plasma generating means 105 includes an external electrode 108a, an internal electrode 108b, and a power supply source 107. The external electrode 108a is disposed on the outer circumferential surface of the gas pipe 102 to surround the catalyst containing section 104a and has a cylindrical shape. The internal electrode 108b is disposed in the gas pipe 102a to be treated at a position corresponding to the catalyst containing section 104a. One terminal of the power supply source 107 is electrically connected to the internal electrode 108b. The other terminal of the power supply source 107 and the external electrode 108a are grounded.

[0007] The plasma generating means 105 generates atmospheric pressure plasma at the location of the methane oxidative removal catalyst 104 housed in the catalyst housing unit 104a by supplying power to the internal electrode 108b using the power supply source 107. As a result, the gas to be treated Eg flowing through the gas to be treated 102a is converted into plasma in the catalyst housing unit 104a, and the generated plasma activates the methane oxidative removal catalyst 104. The methane contained in the gas to be treated Eg is then decomposed into carbon dioxide by the synergistic effect of the action of the activated methane oxidative removal catalyst 104 and the action of the generated plasma. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] Japanese Patent Application Publication No. 2019-155242 Summary of the Invention [Problem to be solved by the invention]

[0009] The largest source of methane released into the environment is said to be the farts and burps emitted by livestock. For example, it is said that a single cow emits about 300 liters of methane per day. Meanwhile, the atmospheric concentration of methane emitted by livestock such as cows kept in barns is about 20 ppm.

[0010] Patent Document 1 describes that methane was decomposed by passing gas to be treated with a methane concentration of 3000 ppm through the system. However, it cannot be said that the technology for decomposing methane at low concentrations of several hundred ppm or less has been fully established at present.

[0011] When decomposing methane from a gas to be treated that contains a high concentration of methane (for example, several thousand ppm or more, but less than a few percent), the simplest and most effective method is to simply combust the gas to be treated. However, in such combustion treatment methods, the residual gas often contains methane at several hundred ppm or less, and decomposing methane by combustion treatment of a gas to be treated that contains such a low concentration of methane gas is not a realistic method from the perspective of the amount of methane decomposed relative to the amount of energy input.

[0012] In addition to the viewpoint of global warming, there is also a need to treat air containing substances that cause odors. For example, the livestock barns described above emit odorous gases such as methane, ammonia, hydrogen sulfide, and methyl mercaptan. Therefore, the atmospheric gas in the livestock barn contains low concentrations of these substances. There is also a need to treat air that contains low concentrations of odor-causing substances, even for gases emitted from places other than livestock barns.

[0013] In view of the above-mentioned problems, an object of the present invention is to provide a technique capable of decomposing a gas to be treated containing a substance to be treated at a low concentration of, for example, several hundred ppm or less, by a simple method. [Means for solving the problem]

[0014] The gas processing method according to the present invention comprises: A process (a) of flowing a gas to be treated, which is a mixture of air and a target substance that is volatile at room temperature and belongs to at least one of the group consisting of carbon compounds, nitrogen compounds, and sulfur compounds, into a housing; a step (b) of introducing ozone at 200°C or less into a space in the housing through which the gas to be treated flows; a step (c) of stirring the gas to be treated after the step (b) is performed; The method is characterized by comprising, after the step (c), a step (d) of heating the gas to be treated to 300° C. or higher.

[0015] As will be described in detail later, through extensive research by the inventors, it has been confirmed that by introducing ozone into the gas to be treated at a temperature of 200°C or less, stirring the gas to be treated, and then performing a heat treatment, the decomposition rate of the target substance contained in the gas to be treated at a low concentration of several hundred ppm or less is improved.

[0016] By stirring the gas to be treated after the introduction of ozone, the probability of contact between the gas to be treated and ozone is improved. Then, by performing a heat treatment, the O( 3 P) comes into contact with the gas to be treated, and the decomposition rate of the target substance contained in the gas to be treated is increased.

[0017] The target substance may be one or more substances belonging to the group consisting of methane, acetylene, ethylene, ethane, propane, methylamine, ammonia, hydrogen sulfide, and methyl mercaptan.

[0018] The step (c) may be a step of passing the gas to be treated through a stirring region in which the cross-sectional area of the flow path is changed or in which a wind shield is provided midway through the flow path.

[0019] This allows the treated gas to be stirred while decreasing the flow rate as it flows toward the outlet from which the treated gas is discharged after the ozone is introduced.

[0020] The length of the stirring region may be longer than the length of the region through which the gas to be treated flows when the step (b) is performed, in relation to the direction in which the gas to be treated flows.

[0021] According to the above method, ozone can be more easily brought into contact with the gas to be treated before the heating step (c) is performed. As a result, the O( 3 P) can be easily brought into contact with the gas to be treated.

[0022] The present invention provides a gas treatment apparatus for treating a gas to be treated, which is a mixture of air and a target substance that is volatile at room temperature and belongs to at least one of the group consisting of carbon compounds, nitrogen compounds, and sulfur compounds, and which comprises: The housing and a gas inlet for introducing the gas to be treated into the housing; an ozone introducing unit that introduces ozone into a gas flow passage through which the gas to be treated flows within the housing; a stirring area disposed downstream of the ozone introducing unit and configured to stir the gas to be treated flowing through the gas flow passage; a heating region disposed downstream of the stirring region and configured to heat the gas to be treated flowing through the gas flow passage; and a gas outlet for discharging the processed gas that has passed through the heating region to the outside of the housing.

[0023] According to the gas treatment device, the gas to be treated and the ozone introduced by the ozone introduction unit are highly likely to come into contact with each other when passing through the stirring area, and then are led to the heating area. As a result, the O( 3 P) comes into contact with the gas to be treated with a high probability, and this O( 3 P) decomposes the target substances contained in the gas to be treated. Therefore, the treated gas in which the target substances have been decomposed with high efficiency is discharged from the gas outlet.

[0024] The gas flow path may be such that the length of the stirring region in the flow direction of the gas to be treated is longer than the length in the flow direction of the gas to be treated from the point where ozone is introduced by the ozone introduction unit to the stirring region.

[0025] According to the above configuration, it is possible to bring ozone into contact with the gas to be treated while it is passing through the stirring region with a higher probability.

[0026] The gas flow passage may be configured to have a heated wall, the wall surface of which is heated to 300° C. or higher, within the heating region.

[0027] As a more specific example of the configuration, a configuration in which the entire heating region is installed in a heating furnace can be adopted. Another example is a configuration in which a heat transfer member such as a metal pipe is placed along the inner wall surface of a gas flow path located in the heating region, and this heat transfer member is heated. Yet another example is a configuration in which a heated plate-like member having an opening is installed in the gas flow path, and the gas to be treated flows through the opening.

[0028] The gas flow passage may be bent within the heating region.

[0029] According to the above configuration, when the gas to be treated flows through the heating region, the flow velocity decreases at the bent portion, and as a result, the time for which the gas to be treated flows through the heating region can be extended. This increases the heating time of the gas to be treated containing ozone, and the O( 3 P) and the gas to be treated are in contact with each other, that is, the time 3 P), the reaction time can be extended, which further increases the decomposition rate of the target substance.

[0030] The gas flow passage may be configured so that the cross-sectional area of the passage changes within the stirring region.

[0031] According to the above configuration, when the gas to be treated flows through a portion where the cross-sectional area of the flow path changes, turbulence is likely to occur due to a pressure difference. This turbulence sufficiently agitates and mixes the gas to be treated and ozone, making it easier for the ozone and the gas to be treated to come into contact with each other.

[0032] The gas flow passage may have a wind shield against which the gas to be treated flowing through it collides within the stirring region.

[0033] According to the above configuration, when the gas to be treated collides with the windshield, the direction of the airflow changes, which makes it easier for turbulence to occur at that location. This turbulence sufficiently agitates and mixes the gas to be treated and ozone, making it easier for the ozone and the gas to be treated to come into contact with each other.

[0034] The ozone introduction unit comprises: a light source that is disposed in the gas flow path and emits ultraviolet light having a main peak wavelength of less than 200 nm; The ultraviolet light from the light source may be irradiated onto the gas to be treated, thereby generating ozone from a part of the gas to be treated.

[0035] According to the above configuration, ozone can be generated from the gas to be treated without separately supplying a gas as an ozone generation source. In particular, when the light source is configured with an excimer lamp using Xe as a light emitting gas, the main peak wavelength is around 172 nm (160 nm or more and less than 180 nm), so NO is emitted when ozone is generated. x This also has the secondary effect of not generating

[0036] The ozone introduction unit comprises: an atmospheric pressure plasma generator disposed in the gas flow path, The gas to be treated may be passed through an atmospheric pressure plasma space generated by the atmospheric pressure plasma generating device, thereby generating ozone from a part of the gas to be treated.

[0037] According to the above configuration, ozone can be generated from the gas to be treated without separately supplying a gas as an ozone generation source.

[0038] The ozone introduction unit may include an ozone generator installed in a flow path separate from the gas flow path, and may supply ozone gas generated by the ozone generator into the gas flow path. [Effects of the Invention]

[0039] According to the present invention, a gas to be treated containing a substance to be treated at a low concentration of, for example, several hundred ppm or less can be decomposed by a simple method. [Brief explanation of the drawings]

[0040] [Figure 1] 1 is a cross-sectional view schematically illustrating a configuration of a first embodiment of a gas treatment device. [Figure 2A] FIG. 1 is a side view schematically showing an example of the configuration of an excimer lamp as an ozone introduction unit. [Figure 2B] 2B is a cross-sectional view taken along the line A1-A1 in FIG. 2A. [Figure 3] 1 is a graph showing the spectrum of ultraviolet light emitted from an excimer lamp filled with a light-emitting gas containing Xe and the absorption spectrum of oxygen (O2) superimposed on each other. [Figure 4A] 1 is a diagram schematically illustrating an example of the configuration of a stirring region. [Figure 4B] 10 is a diagram schematically illustrating another configuration example of the stirring region. [Figure 4C] 10 is a diagram schematically illustrating yet another configuration example of the stirring region. [Figure 5] FIG. 3 is a cross-sectional view schematically showing another configuration of the first embodiment of the gas treatment device. [Figure 6] 1 is a graph showing the relationship between the thermal decomposition rate (half-life) of ozone and temperature. [Figure 7] 1 is a graph showing the relationship between the reaction rate and temperature of the following formulas (7) and (9). [Figure 8A] 10 is a diagram schematically illustrating another configuration example of the heating region. [Figure 8B] 10 is a diagram schematically illustrating yet another configuration example of the heating region. [Figure 9A] FIG. 10 is a cross-sectional view schematically showing another example of the configuration of an excimer lamp as an ozone introduction unit. [Figure 9B] FIG. 10 is a plan view schematically showing another example of the configuration of an excimer lamp as an ozone introduction unit. [Figure 9C] 9C is a cross-sectional view taken along line A2-A2 in FIG. 9B. [Figure 10A] FIG. 2 is a cross-sectional view schematically showing the configuration of a second embodiment of a gas treatment device. [Figure 10B] FIG. 2 is another cross-sectional view schematically illustrating the configuration of the second embodiment of the gas treatment device. [Figure 11A] FIG. 1 is a cross-sectional view schematically showing the configuration of an atmospheric pressure plasma generating device as an ozone introducing unit. [Figure 11B] 11B is a cross-sectional view taken along the line A3-A3 in FIG. 11A. [Figure 12] 1 is a diagram schematically illustrating the structure of an experimental system used in Examples. [Figure 13] 1 is a graph showing the relationship between the concentrations of methane and ozone contained in the treated gas obtained in Examples 1 to 5 and the set temperature of the electric furnace. [Figure 14] 1 is a diagram schematically illustrating the configuration of a conventional methane removal system. DETAILED DESCRIPTION OF THE INVENTION

[0041] A gas processing method and a gas processing apparatus according to the present invention will be described with reference to the drawings. Note that the drawings are schematic illustrations, and the dimensional ratios shown in the drawings do not necessarily correspond to the actual dimensional ratios. Furthermore, the dimensional ratios between the drawings do not necessarily correspond to the actual dimensional ratios.

[0042] [First embodiment] Fig. 1 is a cross-sectional view showing a schematic configuration of a first embodiment of a gas treatment device according to the present invention. The gas treatment device 1 treats a gas G1 to be treated, which is a mixture of a substance to be treated and air, and discharges the treated gas G2. In Fig. 1, the flow direction of the gas G1 to be treated is indicated as d1.

[0043] The substance to be treated belongs to at least one of the group consisting of carbon compounds, nitrogen compounds, and sulfur compounds. Examples of the substance to be treated include methane, acetylene, ethylene, ethane, propane, methylamine, ammonia, hydrogen sulfide, methyl mercaptan, and other compounds that are volatile at room temperature and have an odor.

[0044] The gas processing device 1 includes a housing 2, a gas inlet 3a for introducing a gas G1 to be processed into the housing 2, and a gas outlet 3b for discharging a treated gas G2, which is a gas obtained after the gas G1 to be processed has been processed in the housing 2, to the outside of the housing 2. The housing 2 is provided with a gas flow path 5 for passing the gas G1 to be processed (or the treated gas G2).

[0045] The gas G1 to be treated introduced into the housing 2 from the gas inlet 3a is assumed to be at room temperature or below about 100°C, and no matter how high the temperature may be, it will not exceed 200°C. On the other hand, in the heating region 30 described below, the introduced gas G1 to be treated is heated to 300°C or above.

[0046] In this embodiment, the gas processing device 1 has a built-in excimer lamp 11. This excimer lamp 11 constitutes an ozone introduction unit for introducing ozone into the gas flow path 5. In the following description, the region where ozone is introduced from the ozone introduction unit into the gas flow path 5 may be referred to as the "ozone introduction region 10."

[0047] (Ozone introduction unit) 2A and 2B are diagrams that schematically show an example of the configuration of the excimer lamp 11. Fig. 2A corresponds to a side view of the excimer lamp 11, and Fig. 2B corresponds to a cross-sectional view taken along line A1-A1 in Fig. 2A.

[0048] 2A and 2B includes a tube body 13 and a pair of electrodes (14a, 14b). In this embodiment, the tube body 13 has a double-tube structure. More specifically, as shown in FIG. 2B, the tube body 13 includes an outer tube 13a that is cylindrical and located on the outside, and an inner tube 13b that is cylindrical and has an outer diameter smaller than the inner diameter of the outer tube 13a and is arranged coaxially with the outer tube 13a inside the outer tube 13a.

[0049] 2A and 2B show an example in which the tube axis direction of the tube body 13 is arranged along the flow direction d1 of the gas G1 to be treated. However, the tube axis direction of the tube body 13 does not necessarily have to be parallel to the flow direction d1 of the gas G1 to be treated, and this drawing is merely an example. In the following, for convenience, the flow direction d1 of the gas G1 to be treated and the tube axis direction of the tube body 13 are assumed to be parallel, and in order to avoid an increase in the number of symbols, the same symbol "d1" as the flow direction is used for the tube axis direction as well.

[0050] The outer tube 13a and the inner tube 13b are both sealed at their ends in the tube axis direction d1 (not shown), and a light-emitting space having a ring shape (here, a circular ring shape) when viewed from the tube axis direction d1 is formed between them. A light-emitting gas 15G that forms excimer molecules by discharge is sealed in this light-emitting space.

[0051] One electrode 14a is disposed on the outer wall of the outer tube 13a. In this embodiment, this electrode 14a has a mesh or linear shape. A rod-shaped electrode 14b extending along the axial direction of the tube body 13 is inserted into the inner tube 13b.

[0052] The outer tube 13a and the inner tube 13b are made of a dielectric material such as synthetic quartz glass that is transparent to the ultraviolet light L1. The electrodes (14a, 14b) are made of a metal material such as stainless steel, aluminum, copper, tungsten, titanium, or nickel.

[0053] When a high-frequency AC voltage of, for example, about 1 kHz to 5 MHz is applied between the electrodes (14a, 14b) via a power supply (not shown), the voltage is applied to the light-emitting gas 15G via the tube body 13. At this time, a discharge plasma is generated in the discharge space in which the light-emitting gas 15G is sealed, and the atoms of the light-emitting gas 15G are excited to an excimer state, and when these atoms transition to the ground state, excimer light is emitted.

[0054] The material of the light emitting gas 15G determines the wavelength of the ultraviolet light L1 emitted from the tube 13. When a gas containing xenon (Xe) is used as the light emitting gas 15G, the excimer light emission becomes ultraviolet light L1 having a main peak wavelength in the vicinity of 172 nm.

[0055] The wavelength of the ultraviolet light L1 can be changed by changing the substance used as the luminous gas 15G. For example, ArBr (main peak wavelength near 165 nm), ArCl (main peak wavelength near 175 nm), F2 (main peak wavelength near 153 nm), etc. can be used as the luminous gas 15G. Here, a case where the luminous gas 15G is a gas containing Xe will be described.

[0056] As described above, in the excimer lamp 11 of this embodiment, the electrode 14a disposed on the outer wall of the outer tube 13a has a mesh shape. Therefore, gaps exist in the electrode 14a, and ultraviolet light L1 is extracted through these gaps toward the outside of the outer tube 13a. This ultraviolet light L1 is irradiated onto the gas G1 to be treated flowing through the gas flow passage 5.

[0057] 3 is a graph showing the spectrum of ultraviolet light L1 emitted from an excimer lamp 11 filled with a light-emitting gas 15G containing Xe and the absorption spectrum of oxygen (O2) superimposed on each other. In FIG. 3, the horizontal axis represents wavelength, the left vertical axis represents the relative value of the light intensity of ultraviolet light L1, and the right vertical axis represents the absorption coefficient of oxygen (O2).

[0058] When a gas containing Xe is used as the light emitting gas 15G of the excimer lamp 11, as shown in FIG. 3, the ultraviolet light L1 emitted from the excimer lamp 11 has a main peak wavelength of 172 nm and a band within the range of approximately 155 nm to 190 nm.

[0059] As described above, the gas G1 to be treated is a mixture of air and a substance to be treated. Therefore, when the ultraviolet light L1 with wavelength λ emitted from the excimer lamp 11 is irradiated onto the gas G1 to be treated and absorbed by oxygen (O2), the following reaction (1) proceeds. In formula (1), O( 1 D) is an excited state of the O atom and is extremely reactive. O( 3 P) is an O atom in the ground state. The reactions in equations (1) and (2) occur depending on the wavelength component of the ultraviolet light L1. Specifically, equation (1) is the reaction that occurs when the shorter wavelength component of the ultraviolet light L1 is absorbed by oxygen (O2). More specifically, equation (1) is the reaction that occurs when ultraviolet light L1 with a wavelength λ of less than 175 nm is absorbed, and equation (2) is the reaction that occurs when ultraviolet light L1 with a wavelength λ of 175 nm or more but less than 242 nm is absorbed. O2+ hν(λ) → O( 1 D) + O( 3 P) ...(1) O2+ hν(λ) → O( 3 P) + O( 3 P) ...(2)

[0060] Some of the O atoms generated by the formulas (1) and (2) react with oxygen (O2) contained in the gas G1 to generate ozone (O3) according to the following formula (3): In formula (3), M represents a ternary element (the same applies below). O + O2+ M → O3+ M ‥‥(3)

[0061] As a result, ozone is introduced into the gas G1 to be treated, and the gas G1 to be treated is changed into a gas containing ozone. That is, in the gas treatment device 1 of this embodiment, the excimer lamp 11 constitutes an ozone introducing unit.

[0062] From this viewpoint, it is desirable that the wall surface of the gas flow passage 5 through which the gas to be treated G1 flows is made of an ozone-resistant material, for example, stainless steel, glass, etc. When the wall surface of the gas flow passage 5 is made of a part of the housing 2, the housing 2 itself may be made of the above-mentioned material.

[0063] In addition, the O( 1 D) can react with water (H2O) in the air to generate hydroxyl radicals (OH) according to the following equation (4): O( 1 D) + H2O → OH + OH ‥‥(4)

[0064] Furthermore, when the ultraviolet light L1 has a spectrum in a wavelength range of 185 nm or less, the water vapor (H2O) contained in the gas G1 to be processed absorbs the ultraviolet light L1 and generates hydroxyl radicals (OH) according to the following formula (5). H2O + hν(λ) → H + OH ‥‥(5)

[0065] Because these hydroxyl radicals (OH) are extremely reactive, they may react with and decompose some of the target substances contained in the gas G1 to be treated. However, the amount of target substances contained in the gas G1 to be treated that can be decomposed by hydroxyl radicals (OH) alone is extremely limited. As an example, if the target substance to be treated is methane (CH4), the hydroxyl radicals (OH) may cause the reaction shown in formula (6) below, resulting in the decomposition of the methane. CH4 + OH → CH3 + H2O ‥‥(6)

[0066] In addition, atomic oxygen, O( 1 D) and O( 3Although some of O(P) may react with the substance to be treated and decompose, there is a limit to the amount of decomposition. For example, if methane is included in the substance to be treated, the methane may be decomposed by the reaction shown in the following formula (7). In formula (7), O( 1 D) and O( 3 P) are collectively written as O. CH4+ O → CH3+ OH ‥‥(7)

[0067] Although there is a possibility that some decomposition reaction of the target substance by radicals may occur in accordance with the reactions shown in the above formulas (6) and (7), it is difficult to sufficiently decompose the target substance by this reaction alone.

[0068] Therefore, the gas treatment device 1 of this embodiment has a stirring region 20 that stirs the gas G1 to be treated flowing through the gas flow path 5, and a heating region 30 that heats the gas G1 to be treated flowing through the gas flow path 5, downstream of the region (ozone introduction region 10) where ozone from the ozone introduction unit (excimer lamp 11) is introduced into the gas G1 to be treated. Each of these will be described below.

[0069] (Stirring area 20) In the example of the gas treatment device 1 shown in Fig. 1, a plurality of wind shielding plates 21 are arranged at positions spaced apart along the flow direction d1 in the gas flow passage 5, thereby forming a stirring region 20. When the gas G1 to be treated collides with the wind shielding plates 21, the direction of the airflow changes due to the collision. At that time, some of the gas G1 to be treated generates turbulence. As a result, the gas G1 to be treated is stirred.

[0070] The windshield 21 is preferably made of an ozone-resistant material, similar to the wall surface of the gas flow passage 5 through which the gas G1 to be treated flows, and may be made of, for example, stainless steel or glass.

[0071] Various methods can be used to realize the stirring region 20, in addition to providing the wind shield 21 in the gas flow path 5. As an example, as shown in Fig. 4A, the shape of the gas flow path 5 may be set so that the flow path cross-sectional areas (5a, 5b) in the gas flow path 5 differ at positions in the flow direction d1. In this case, too, the direction of the airflow of the gas G1 to be treated changes at the point where the flow path cross-sectional area changes, and the gases G1 to be treated are stirred.

[0072] 4B, a method can be employed in which one or more bent portions 5c are provided in the gas flow passage 5 within the stirring region 20. In this case as well, the direction of the flow of the gas G1 to be treated changes at the locations where the bent portions 5c are formed, and the gas G1 to be treated is stirred.

[0073] 4C, a method can be employed in which the cross-sectional area 5e of the flow path is common within the stirring region 20, but is different in size from the cross-sectional area 5d of the ozone introduction region 10 upstream of the stirring region 20. When the gas G1 to be treated flows from the ozone introduction region 10 into the stirring region 20, the cross-sectional area of the flow path changes, and the direction of the airflow of the gas G1 to be treated changes, causing the gases G1 to be treated to be stirred.

[0074] As described above, the stirring region 20 is provided for the purpose of stirring the gas G1 to be treated after ozone has been introduced by the ozone introduction region 10. That is, the probability of contact between the gas G1 to be treated and ozone increases when the gas passes through the stirring region 20. From the viewpoint of further increasing this probability of contact, it is preferable that the length of the stirring region 20 in the flow direction d1 be longer than that of the ozone introduction region 10.

[0075] Incidentally, a part of the ozone (O3) introduced by the ozone introducing region 10 may cause a decomposition reaction shown in the following formula (8) when flowing through the stirring region 20 together with the gas G1 to be treated. O3→ O( 3 P) + O2 (8)

[0076] When the above reaction occurs, O( 3 P) acts on the gas to be treated and decomposes a part of the substance to be treated. In other words, the gas flowing through the stirring region 20 may be a mixture of the gas to be treated G1 introduced from the gas inlet 3a and the treated gas G2 in which a part of the substance to be treated contained in the gas to be treated G1 has been decomposed. However, the speed of the ozone (O3) decomposition reaction of formula (8) occurring in the stirring region 20 is sufficiently slow compared to the speed at which the gas to be treated G1 flows toward the heating region 30. For this reason, while the gas to be treated G1 flows through the stirring region 20, the O( 3 P) can decompose the substance to be treated to an extremely small extent. From the above viewpoint, in this specification, the gas flowing from the stirring region 20 toward the heating region 30 is referred to as "gas to be treated G1".

[0077] (Heating area 30) 1 is provided with a heating region 30 for heating the gas G1 to be treated at a position downstream of the stirring region 20. Here, a part of the housing 2 constitutes a heating furnace 31, and the gas flow path 5 is located within this heating furnace 31, thereby constituting the heating region 30.

[0078] However, the heating region 30 does not necessarily have to be installed in the same housing as the housing 2 into which the gas G1 to be treated flows. For example, as shown in Fig. 5, a configuration can be adopted in which the housing 2a into which the gas G1 to be treated flows and the heating furnace 31 are connected by a gas flow path 5. In this case, the heating furnace 31 forms one type of housing 2b, and the housings 2a, 2b, and the gas flow path 5 connecting these housings (2a, 2b) can be considered to form one housing 2.

[0079] In other words, in this specification, the term "housing 2" is not limited to a single box-shaped structure, but is a concept that encompasses all structures that are covered to prevent leakage of the gas to be treated G1 or the treated gas G2 between a gas inlet 3a provided at one location and a gas outlet 3b provided at the other location. In other words, the term "housing 2" also includes a structure that includes multiple housings (2a, 2b, ...) that are connected to each other by gas flow paths 5.

[0080] The heating region 30 heats the gas G1 to be treated flowing through the gas flow path 5 to 300°C or higher. It is known that the higher the temperature of ozone (O3), the more the reaction of formula (8) advances due to thermal decomposition. Figure 6 is a graph showing the relationship between the thermal decomposition rate (half-life) of ozone and temperature. Figure 6 shows that the half-life of ozone is approximately 1000 seconds at 100°C, and within 0.1 seconds at 300°C or higher. In other words, when ozone is heated to 300°C or higher, the reaction of formula (7) advances within 0.1 seconds for half of the ozone present, converting it to O( 3 P) is produced.

[0081] On the other hand, the generated O( 3 Since P) is highly reactive, if there is another substance M around it, it may undergo a reaction that changes it back into oxygen (O2) according to the following formula (9). Note that in this formula (9), O( 3 P) is written as O. For convenience of explanation, equation (7) is shown again. O + O + M → O2 + M ‥‥(9) CH4+ O → CH3+ OH ‥‥(7)

[0082] Figure 7 is a graph showing the temperature dependence of the reaction rates of the above equations (7) and (9). As mentioned above, increasing the temperature increases the reaction rate of equation (8), and the amount of atomic oxygen (O) produced increases. However, because atomic oxygen is highly reactive, it does not contribute to the decomposition of the substance to be treated, and instead undergoes a reaction in which it is converted back into oxygen (O2) according to equation (9). This reaction rate gradually decreases as the temperature increases.

[0083] On the other hand, the reaction rate of equation (7), i.e., the reaction of decomposing the target substance with atomic oxygen (O), increases with increasing temperature. When the target substance is methane (CH4), atomic oxygen (O) reacts with the C-H bond to generate methyl radicals (CH3). In other words, it can be seen that the amount of decomposition of methane contained in the target gas G1 increases with increasing temperature of the target gas G1.

[0084] In order to maximize the contribution of the generated atomic oxygen (O) to the decomposition of the target substance, the gas G1 to be treated is preferably heated to 300°C or higher, more preferably 350°C or higher, in the heating region 30. By heating the gas G1 to be treated to 350°C or higher, the reaction rate of equation (7) exceeds the reaction rate of equation (9), thereby further promoting the decomposition of the target substance.

[0085] Generally, solids are heated more efficiently than gases. For this reason, the heating region 30 is configured to heat the inner wall of the gas flow channel 5 present in the heating region 30. That is, in the heating region 30, the gas flow channel 5 has a heated wall. For example, in the examples of FIGS. 1 and 5, the gas flow channel 5 is disposed in a heating furnace 31, whereby heat from the heating furnace 31 is supplied to the gas flow channel 5, thereby increasing the temperature of the wall surface of the gas flow channel 5. Then, the gas G1 to be treated is caused to flow inside the gas flow channel 5 with the wall surface heated in this manner, thereby increasing the temperature of the gas G1 to be treated.

[0086] 7, it is also clear that it is preferable to increase the temperature of the gas G1 to be treated as rapidly as possible. If the temperature increase rate is slow, the reaction of the generated atomic oxygen (O) to oxygen (O2) according to formula (9) is likely to occur while the temperature of the gas G1 to be treated is increasing.

[0087] From this perspective, it is preferable that the gas G1 to be treated be caused to collide multiple times at a certain flow rate against the wall surface of the gas flow channel 5, which has been heated to a high temperature, in the heating region 30. In the examples shown in Figures 1 and 5, the gas flow channel 5 is configured to bend multiple times in the heating region 30. With this configuration, the gas G1 to be treated advances toward the gas outlet 3b while repeatedly and intermittently colliding with the wall surface of the gas flow channel 5, and therefore the gas G1 to be treated can be rapidly heated to 300°C or higher while flowing through the heating region 30.

[0088] From a similar perspective, as shown in FIG. 8A , the heating region 30 may be configured with multiple heating plates 32 arranged in the gas flow passage 5 at intervals in the gas flow direction and so as to obstruct the gas flow direction d1. The heating plates 32 are made of a material that can be heated to high temperatures, such as a metal material (e.g., stainless steel, aluminum, copper, or silver) or ceramic, and are heated to, for example, about 500°C by heat transfer from an external heat source. In this case, the gas G1 to be treated flows through the heating region 30, intermittently colliding with the heating plates 32 while advancing toward the gas outlet 3b, thereby similarly rapidly heating the gas G1 to be treated. The heating plates 32 may have a coating layer of fluorine, ceramic, or the like formed on their surfaces to prevent deterioration and rust due to ozone.

[0089] 8B , the heating region 30 may be configured by arranging a plurality of heating plates 33, each having a plurality of flow holes 34, at positions spaced apart along the flow direction d1. In this case, it is preferable to set the positions of the flow holes 34 so that the flow holes 34 of adjacent heating plates 33 are not aligned along the flow direction d1. In this case, too, the gas G1 to be treated advances toward the gas outlet 3b through the flow holes 34 while intermittently and repeatedly colliding with the heating plates 33 while flowing through the heating region 30, and thus the gas G1 to be treated can be rapidly heated in the same manner.

[0090] (Another example of an excimer lamp configuration) In this embodiment, the excimer lamp 11 provided as the ozone introduction unit is not limited to the structure shown in FIGS. 2A and 2B.

[0091] For example, as shown in Fig. 9A, excimer lamp 11 may have a single tubular body 13. Fig. 9A is a schematic cross-sectional view of excimer lamp 11 illustrated similarly to Fig. 2B. Tube 13 is sealed at its end in the longitudinal direction, i.e., in the tube axis direction d1 (not shown), and luminous gas 15G is sealed in the internal space. A mesh-shaped or linear electrode 14a is disposed on the outer wall surface of tubular body 13, and a rod-shaped electrode 14b is disposed inside (inside) tubular body 13.

[0092] As another example, a configuration can be employed in which both electrodes (14a, 14b) are disposed on the outer wall surface of the tubular body 13 of the excimer lamp 11. Figures 9B and 9C are diagrams schematically illustrating the structure of this alternative excimer lamp 11, with Figure 9B corresponding to a plan view and Figure 9C corresponding to a cross-sectional view taken along line A2-A2 in Figure 9B. The excimer lamp 11 shown in Figures 9B and 9C has one tubular body 13, and both electrodes (14a, 14b) are disposed on the outer wall surface of the tubular body 13 so as to face each other across the tubular body 13. The electrodes (14a, 14b) are both mesh-shaped or linear-shaped so as not to interfere with the extraction of ultraviolet light L1 generated within the tubular body 13 to the outside of the tubular body 13.

[0093] [Second embodiment] A second embodiment of the gas treatment device according to the present invention will be described, focusing on differences from the first embodiment. Elements common to the first embodiment will be denoted by the same reference numerals, and descriptions thereof will be omitted as appropriate.

[0094] The gas treatment device 1 of this embodiment differs from the first embodiment in the configuration of the ozone introduction unit.

[0095] 10A is a cross-sectional view schematically illustrating the configuration of a second embodiment of a gas treatment apparatus according to the present invention, following the configuration of FIG. 1. In this embodiment, a gas inlet 3c for introducing an ozone raw material gas G3 is provided in the housing 2, in addition to a gas inlet 3a for introducing a gas G1 to be treated. The ozone raw material gas G3 may be air that does not contain the substance to be treated.

[0096] According to this configuration, ozone gas G4 is generated from ozone raw material gas G3 by excimer lamp 11 as an ozone introduction unit, and this ozone gas G4 is introduced into gas flow path 5 through which gas G1 to be treated flows. As a result, ozone is introduced into gas G1 to be treated in ozone introduction region 10, and gas G1 to be treated is changed into a gas containing ozone.

[0097] From the above perspective, it can be seen that the method of generating ozone is not limited in the gas treatment device 1 according to the present invention, as long as ozone is introduced into the gas flow path 5 through which the gas G1 to be treated flows in the ozone introduction region 10. For example, as shown in Fig. 10B, an ozone cylinder 18 containing ozone gas G4 may be housed in the housing 2, and the ozone gas G4 supplied from the ozone cylinder 18 may be introduced into the gas flow path 5 through which the gas G1 to be treated flows.

[0098] [Another embodiment] In the above embodiment, the device for generating ozone from air has been described by taking the excimer lamp 11 as an example. However, instead of the excimer lamp 11, an atmospheric pressure plasma generating device can also be used.

[0099] 11A and 11B are drawings showing a schematic structure of an atmospheric pressure plasma generation apparatus, where FIG. 11A corresponds to a side view of the atmospheric pressure plasma generation apparatus 19, and FIG. 11B corresponds to a cross-sectional view taken along line A3-A3 in FIG. 11A.

[0100] Unlike the excimer lamp 11, the atmospheric pressure plasma generation device 19 does not have a light emitting gas 15G sealed in the tubular body 13. In addition, in Fig. 11A, the gas to be processed G1 is caused to flow through the tubular body 13. The other configurations are the same as those of the excimer lamp 11 described above.

[0101] When a voltage is applied between the electrodes (14a, 14b) from a power supply (not shown), a dielectric barrier discharge occurs in the tubular body 13. This causes a dielectric barrier discharge in the gas G1 to be treated flowing through the discharge space S1, turning it into plasma.

[0102] When oxygen (O2) in the air contained in the gas G1 to be processed flows through the atmospheric pressure plasma space, it exhibits the reaction shown in the following formula (10): In the formula (10), AP means that energy is applied by atmospheric pressure plasma. O2 + AP → O + O ‥‥(10)

[0103] Some of the oxygen atoms (atomic oxygen) O generated by formula (10) react with oxygen (O2) contained in the gas G1 to generate ozone (O3) according to formula (3) above. Formula (3) is shown below. O + O2+ M → O3+ M ‥‥(3)

[0104] That is, when the gas G1 to be treated flows through the atmospheric pressure plasma generating device 19, ozone is introduced into the gas G1 to be treated, and the gas G1 to be treated changes into a gas containing ozone.

[0105] 11A and 11B. For example, a structure similar to the structure of the excimer lamp 11 described above with reference to FIGS. 9A to 9C can be employed. In this case, too, the light emitting gas 15G may not be sealed in the tubular body 13, and the gas to be processed G1 may be caused to flow through the tubular body 13.

[0106] Furthermore, unlike the excimer lamp 11, there is no need to extract light outside the tube body 13, so the electrode 14 formed on the outer wall surface of the tube body 13 does not necessarily have to be mesh-shaped or linear.

[0107] Furthermore, instead of the excimer lamp 11 shown in FIG. 10A and explained in the second embodiment, an atmospheric pressure plasma generating device 19 can be adopted.

[0108] However, when generating ozone using the atmospheric pressure plasma generator 19, the energy of the plasma is high, so NO x Therefore, according to this method, some NO components are contained in the treated gas G2. x After treatment, the gas G2 contains NO x If there is a reason to avoid including the component, it is preferable to use an excimer lamp 11 or an ozone bomb 18 as the ozone introduction unit. [Example]

[0109] The present invention will be described below with reference to examples, but the present invention is not limited to these examples.

[0110] [Explanation of experimental conditions] The experimental conditions are explained below.

[0111] (Experimental) An experiment was carried out using an experimental system that simulated the gas treatment device 1 of the first embodiment. Fig. 12 is a diagram that schematically shows the structure of the experimental system.

[0112] As the ozone introduction region 10, a housing 42 containing an excimer lamp 11 shown in FIG. 9A was prepared. The excimer lamp 11 had an outer diameter of 26 mm and an emission length of 200 mm. The housing 42 was a glass cylindrical body with an inner diameter of 45 mm (diameter), a wall thickness of 3 mm, and a length of 350 mm. The excimer lamp 11 was placed inside the housing 42 with the tube axis of the tube body 13 substantially aligned with the central axis of the housing 42. The excimer lamp 11 had a light-emitting gas 15G containing Xe sealed inside the tube body 13, and emitted ultraviolet light L1 with a main peak wavelength of 172 nm by applying a high-frequency voltage of 40 W input power and 8 kVpp applied voltage to each electrode (13a, 13b) from a power supply (not shown).

[0113] A glass tube 43 having a diameter smaller than the inner diameter of the housing 42 was prepared as the stirring region 20. The glass tube 43 had an inner diameter of 6 mm and a length of 1000 mm.

[0114] A heating furnace 31 made of an electric furnace was prepared as the heating region 30. A heat-resistant glass tube 44 inserted into the heating furnace 31 and a glass tube 43 serving as the stirring region 20 were connected upstream of the heating furnace 31. The heat-resistant glass tube 44 had an inner diameter of 6 mm and a length of 500 mm. The length of the heating furnace 31 along the flow direction d1 was 300 mm.

[0115] The heat-resistant glass tube 44 taken out from the outlet of the heating furnace 31 was connected to a cooling glass tube 45. The cooling glass tube 45 had an inner diameter of 6 mm and a length of 1000 mm.

[0116] The cooling glass tube 45 was connected to the sampling bag 46 via a flow tube 52. The flow tube 52 was made of a silicon tube, had an inner diameter of 6 mm, and was 3 m long.

[0117] A gas G1 to be treated, which was a mixture of air and methane (methane concentration: 100 ppm), was introduced from the gas inlet 3a, and the treated gas G2 obtained by passing through the ozone introduction region 10, the stirring region 20, and the heating region 30 in sequence was introduced into a sampling bag 46 (manufactured by GL Sciences Inc.). Then, the treated gas G2 contained in the sampling bag 46 was subjected to component analysis using FTIR (Fourier transform infrared spectroscopy).

[0118] (Gas to be treated G1) The gas G1 to be treated was determined by FTIR analysis to have the components shown in Table 1. Table 1 does not include nitrogen (N2), oxygen (O2), and argon (Ar) contained in the air in the gas G1 to be treated. y " is generally NO x This is a comprehensive notation that includes NO, NO2, and N2O, as well as N2O5, HNO2, and HNO3.

[0119] [Table 1]

[0120] Examples 1 to 5 Examples 1 to 5 were prepared by varying the temperature setting of the electric furnace and keeping the other conditions the same.

[0121] (Comparative Example 1) The electric furnace was turned off and no heat treatment was performed, which was designated Comparative Example 1. That is, Comparative Example 1 corresponds to the case where no heat treatment was performed on the gas G1 to be treated after the introduction of ozone.

[0122] (Comparative Example 2) The set temperature of the electric furnace was the same as in Example 1, and no power was applied to the excimer lamp 11 in Comparative Example 2. That is, Comparative Example 2 corresponds to a case where heat treatment was performed on the gas G1 to be treated without introducing ozone.

[0123] [verification] Table 2 summarizes the experimental conditions for Examples 1 to 5 and Comparative Examples 1 and 2. In Table 2, the "temperature T2 of treated gas G2" is the temperature of treated gas G2 measured at the outlet of the electric furnace. Under the experimental conditions shown in Table 2, treated gas G1 having components according to the conditions shown in Table 1 was passed from gas cylinder 41 through flow pipe 51 into housing 42 at a flow rate of 10 L / min, and the components of treated gas G2 stored in sampling bag 46 were analyzed. The results are shown in Table 3.

[0124] [Table 2]

[0125] [Table 3]

[0126] (Result analysis) Table 3 confirms that in all examples, the methane concentration in the treated gas G2 was reduced compared to the treated gas G1. It was also confirmed that the higher the set temperature of the electric furnace (heating furnace 31), the greater the amount of methane decomposition and the lower the ozone concentration in the treated gas G2. Figure 13 is a graph showing the relationship between the set temperature of the electric furnace and the remaining amounts of methane and ozone in the treated gas G2 based on the results of Examples 1 to 5. In Figure 13, the horizontal axis represents the set temperature of the electric furnace, the left vertical axis represents the concentration of methane in the treated gas G2, and the right vertical axis represents the concentration of ozone in the treated gas G2.

[0127] On the other hand, in the case of Comparative Example 1, in which heat treatment was not performed, the concentration of methane contained in the treated gas G2 was lower than that of the treated gas G1, but remained at a higher concentration compared to Examples 1 to 5. In addition, in the case of Comparative Example 1, the ozone concentration was higher than in Examples 1 to 5, and it was found that the ozone was not thermally decomposed as compared to Examples 1 to 5. In other words, in the case of Comparative Example 1, it is thought that atomic oxygen (O) was not generated sufficiently, and as a result, methane was not sufficiently decomposed.

[0128] Furthermore, in the case of Comparative Example 2 in which the heat treatment was carried out without introducing ozone, it is clear that methane contained in the treated gas G2 was hardly decomposed.

[0129] [Explanation of simulation conditions] Next, a simulation was performed to verify the difference in methane gas decomposition efficiency depending on whether or not there is a stirring area.

[0130] A cylindrical body (inner diameter 50 mm) containing an excimer lamp 11 was set as the ozone introduction region 10. The excimer lamp 11 had an outer diameter of φ10 mm and an emission length of 300 mm. In addition, a heating region 30 with a length of 150 mm was set downstream of the ozone introduction region 10.

[0131] The methane concentration in the treated gas G2 was calculated when a mixed gas of air and methane (methane concentration 100 ppm) as the gas to be treated G1 was passed through the ozone introduction region 10 at a flow rate of 10 LPM. The methane concentration in the treated gas G2 was calculated for both the case where the heating region 30 was provided immediately after the ozone introduction region 10 (condition #1) and the case where the stirring region 20 made of a cylindrical body was provided between the ozone introduction region 10 and the heating region 30 (condition #2). By comparing these results, the effect of the stirring region 20 on the decomposition and production ability of methane can be confirmed.

[0132] Two patterns were set for the heating region 30: one where the ambient temperature was 450° C. and the other where it was 700° C. The heating region 30 simulated a region in an electric furnace where a cylindrical body through which a mixed gas (gas to be treated G1) flows, similar to the ozone introduction region 10.

[0133] Condition #1 was set as follows: In a cylindrical body having an inner diameter of 50 mm, a region having a length of 300 mm in the longitudinal direction (the direction in which the gas G1 to be treated flows) was set as the ozone introduction region 10. In addition, in the cylindrical body having an inner diameter of 50 mm, a region having a length of 150 mm, which was provided immediately after the ozone introduction region 10 in the longitudinal direction, was set as the heating region 30.

[0134] Condition #2 was set as follows: In a cylinder with an inner diameter of 20 mm, a region 300 mm long in the longitudinal direction was designated as the ozone introduction region 10. In addition, in the cylinder with an inner diameter of 20 mm, a region 300 mm long provided immediately after the ozone introduction region 10 in the longitudinal direction was designated as the stirring region 20, and a region 150 mm long provided immediately after the stirring region 20 was designated as the heating region 30.

[0135] As described above, in Condition #1 and Condition #2, in order to standardize the heating conditions, the length of the heating region 30 in the longitudinal direction is set to the same value (150 mm).

[0136] The results of the verification are shown in Table 4.

[0137] [Table 4]

[0138] In Table 4, the "difference in decomposition rate" is a value calculated by dividing the difference in the amount of methane decomposition between the presence and absence of a stirring region by the initial methane concentration (100 ppm).

[0139] Table 4 confirms that, when compared at the same heating temperature, the amount of methane gas decomposed under condition #2 (with stirring zone) is higher than that under condition #1 (without stirring zone).

[0140] The reason for this is presumed to be as follows. Under condition #1, the mixing region 20 was not provided between the ozone introduction region 10 and the heating region 30, and therefore the mixed gas was introduced into the heating region 30 without sufficient mixing of the ozone and methane gas. As a result, a large proportion of the atomic oxygen generated by the thermal decomposition of ozone disappeared before colliding with the methane gas. In contrast, under condition #2, after ozone is introduced into the gas G1 to be treated, the gas passes through the stirring region 20, promoting the stirring of the ozone and methane gas during this time. Then, the mixed gas in a state in which ozone and methane gas have been stirred after passing through the stirring region 20 is introduced into the heating region 30, increasing the probability of collision between atomic oxygen obtained by thermal decomposition of ozone and methane gas.

[0141] Furthermore, according to Table 4, the higher the heating temperature, the greater the difference in methane gas decomposition ability between Condition #2 (with stirring region) and Condition #1 (without stirring region).

[0142] The reason for this is presumed to be as follows. Because the thermal decomposition of ozone is accelerated as the temperature of the mixed gas increases, the amount of atomic oxygen produced by the thermal decomposition of ozone is greater when the heating temperature is 700°C than when it is 450°C. However, as described above, under condition #1, where the stirring region 20 is not provided, the probability that atomic oxygen will disappear without colliding with methane gas is higher than under condition #2, where the stirring region 20 is provided. As a result, when the heating temperature is increased, the amount of atomic oxygen that disappears without colliding with ozone gas increases when the stirring region 20 is not provided.

[0143] In other words, it can be seen that the higher the heating temperature in the heating region 30, the more significantly the decomposition performance of methane gas can be improved by providing the stirring region 20.

[0144] As described above, by introducing ozone and performing heat treatment after stirring, atomic oxygen (O) can be brought into contact with the target substances contained in the gas G1 to be treated with a high probability, thereby increasing the decomposition rate of the target substances. In particular, the above results confirmed that methane, which was present in the air at an extremely low concentration of 100 ppm, can also be decomposed at a high rate.

[0145] It was also confirmed that the effect of providing the stirring region 20 is particularly remarkable in an apparatus configuration that can effectively perform thermal decomposition of ozone. [Explanation of symbols]

[0146] 1: Gas treatment equipment 2: Housing 2a: Housing 2b: Housing 3a: Gas inlet 3b: Gas outlet 3c: Gas inlet 5: Gas flow path 5c: Bent part 5d: Flow path cross-sectional area 5e: Flow path cross-sectional area 5f: flow path cross-sectional area 10: Ozone introduction area 11: Excimer lamp 13: Body 13a:Outer tube 13b: Inner tube 14: Electrode 14a: Electrode 14b: Electrode 15G: Luminous gas 18: Ozone Cylinder 19: Atmospheric pressure plasma generator 20: Mixing area 21: Wind shielding board 30: Heating area 31:Heating furnace 32: Heating plate 33: Heating plate 34: Flow hole 40W: Input power 41: Gas cylinder 42: Housing 43: Glass tube 44: Heat-resistant glass tube 45: Cooling glass tube 46: Sampling bag 51: Flow pipe 52: Flow pipe 100: Methane removal system 101: Source of treated gas 102: Gas pipe to be treated 102a: gas passage to be treated 104: Catalyst for methane oxidation removal 104a: catalyst housing section 105: Plasma generating means 106: Control means 107: Power supply source 108a: External electrode 108b: Internal electrode G1: Gas to be treated G2: Processed gas G3: Ozone source gas G4: Ozone gas L1: Ultraviolet light d1:Flow direction

Claims

1. A process (a) of flowing a gas to be treated, which is volatile at room temperature and contains methane mixed in air at a concentration of several hundred ppm or less, into a housing; a step (b) of introducing ozone at 200° C. or less into a space in the housing through which the gas to be treated flows; a step (c) of stirring the gas to be treated after the step (b) is performed; A method for treating a methane-containing gas, comprising the step (d) of heating the gas to be treated to 300° C. or higher after the step (c).

2. 2. The method for treating a methane-containing gas according to claim 1, wherein the step (c) is a step of passing the gas to be treated through a stirring region in which the cross-sectional area of the flow path changes or a wind shield is provided midway through the flow path.

3. 3. The methane-containing gas treatment method according to claim 2, wherein the stirring region is longer than the region through which the gas to be treated flows when step (b) is performed, in the direction in which the gas to be treated flows.

4. A methane-containing gas treatment apparatus for treating a gas to be treated, which is volatile at room temperature and contains methane mixed in air at a concentration of several hundred ppm or less, The housing and a gas inlet for introducing the gas to be treated into the housing; an ozone introducing unit that introduces ozone into a gas flow passage through which the gas to be treated flows within the housing; a stirring area disposed downstream of the ozone introducing unit and configured to stir the gas to be treated flowing through the gas flow passage; a heating furnace disposed downstream of the stirring region and configured to heat the gas to be treated flowing through the gas flow passage; a gas exhaust port for exhausting the treated gas that has passed through the heating furnace to the outside of the housing, 10. The methane-containing gas treatment apparatus, wherein the heating furnace is configured to heat the gas to be treated flowing through the gas flow passage disposed in the heating furnace.

5. 5. The methane-containing gas treatment device according to claim 4, wherein the length of the stirring region in the gas flow path in the direction of flow of the gas to be treated is longer than the length in the direction of flow of the gas to be treated from a point where ozone is introduced by the ozone introduction unit to the stirring region.

6. 6. The methane-containing gas treatment device according to claim 5, wherein the gas flow passage is configured to have a heated wall, the wall surface of which is heated to 300[deg.] C. or higher, in the heating furnace.

7. 7. The methane-containing gas treatment device according to claim 6, wherein the gas flow passage is bent within the heating furnace.

8. 8. The methane-containing gas treatment device according to claim 4, wherein the gas flow passage is configured so that a flow passage cross-sectional area changes within the stirring region.

9. 8. The methane-containing gas treatment apparatus according to claim 4, wherein the gas flow passage has a wind shield against which the gas to be treated flowing through the gas flow passage collides within the stirring region.

10. The ozone introduction unit comprises: a light source that is disposed in the gas flow passage and emits ultraviolet light having a main peak wavelength of less than 200 nm; 8. The methane-containing gas treatment device according to claim 4, wherein ozone is generated from a part of the gas to be treated by irradiating the gas to be treated with the ultraviolet light from the light source.

11. The ozone introduction unit comprises: an atmospheric pressure plasma generator disposed in the gas flow path, The methane-containing gas treatment apparatus according to any one of claims 4 to 7, characterized in that ozone is generated from a part of the gas to be treated by causing the gas to be treated to flow through an atmospheric pressure plasma space generated by the atmospheric pressure plasma generating device.

12. 8. The methane-containing gas treatment device according to claim 4, wherein the ozone introduction unit includes an ozone generator installed in a flow path separate from the gas flow path, and the ozone gas generated by the ozone generator is supplied into the gas flow path.

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