Gas processing system

Abstract

To provide a gas processing system which discharges electricity according to at least one of an odor intensity of an odorous gas and a concentration of dinitrogen monoxide to enable deodorization according to change of at least one of the odor intensity and the concentration of dinitrogen monoxide.SOLUTION: A gas processing system 1 includes: a plasm processing unit 20 which discharges electricity in an odorous gas including odorous components to generate plasma in the odorous gas; an adsorption unit 30 which is provided at the downstream of the plasma processing unit 20 and adsorbs the odorous components remaining in the odorous gas which contacts with the plasma; and a control unit 43 which controls the number of times of electric discharge of the plasm processing unit 20. The control unit 43 controls the number of times of electric discharge according to an odor intensity of the odorous gas.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a gas processing system. [Background technology]

[0002] 2. Description of the Related Art Conventionally, as a method for treating a gas containing odorous components, a method is known in which plasma is generated by electric discharge and the gas is treated by radicals generated therein.

[0003] Patent Document 1 discloses a deodorizing and sterilizing device in which fluid flow holes are provided at locations corresponding to each electrode for plasma treatment, and an adsorption member that adsorbs airborne bacteria or odorous substances is disposed downstream of the fluid passing through the fluid flow holes. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2012-120768 A Summary of the Invention [Problem to be solved by the invention]

[0005] However, in conventional deodorizing and sterilizing devices, when the odor intensity fluctuates, such as odorous gases generated during sewage treatment, there is a risk that efficient deodorization may not be possible. Furthermore, Patent Document 1 does not disclose the removal of nitrous oxide, which is one of the greenhouse gases.

[0006] The present invention has been made in consideration of the problems associated with the prior art, and an object of the present invention is to provide a gas treatment system capable of treating gas in response to fluctuations in at least one of the odor intensity and nitrous oxide concentration of an odorous gas by discharging in response to at least one of the odor intensity and nitrous oxide concentration of the odorous gas. [Means for solving the problem]

[0007] In order to solve the above problems, the gas treatment system according to the first aspect of the present invention includes a plasma treatment unit that generates plasma in an odorous gas containing odorous components by discharging in the odorous gas, an adsorption unit that is provided downstream of the plasma treatment unit and adsorbs odorous components remaining in the odorous gas that has come into contact with the plasma, and a control unit that controls the number of discharges of the plasma treatment unit. The control unit controls the number of discharges according to the odor intensity of the odorous gas.

[0008] The adsorption unit may include an inorganic adsorbent, and the odor components may be adsorbed by the inorganic adsorbent.

[0009] The odorous gases may be gases produced during sewage treatment.

[0010] The odorous gas may be a gas generated in sewage treatment and may contain nitrous oxide. The plasma treatment unit may remove the nitrous oxide by chemical reaction in the presence of the odorous gas containing hydrocarbons.

[0011] The plasma processing unit may include a first plasma processing section for generating plasma in the odorous gas by discharging in the odorous gas, and a second plasma processing section for generating plasma in a processing gas that is processed in the first plasma processing section and contains a hydrocarbon by discharging in the processing gas.

[0012] A gas processing system according to a second aspect of the present invention includes a plasma processing unit that generates plasma in a nitrous oxide-containing gas containing nitrous oxide and a hydrocarbon by discharging in the nitrous oxide-containing gas, and a control unit that controls the number of discharges of the plasma processing unit according to the nitrous oxide intensity of the nitrous oxide-containing gas. Effect of the Invention

[0013] According to the present invention, a gas treatment system can be provided that can treat gas in response to fluctuations in at least one of the odor intensity and the nitrous oxide concentration of an odorous gas by discharging electricity in response to at least one of the odor intensity and the nitrous oxide concentration. [Brief description of the drawings]

[0014] [Figure 1] 1 is a schematic diagram illustrating an example of a gas processing system according to a first embodiment. [Diagram 2] 1 is a schematic diagram illustrating a plasma processing unit according to an example of a first embodiment. [Diagram 3] FIG. 2 is a schematic diagram showing a reuse mechanism of an adsorbent according to an example of the first embodiment. [Figure 4] FIG. 11 is a schematic diagram illustrating an example of a gas processing system according to a second embodiment. [Diagram 5] FIG. 1 is a schematic diagram showing an example of a hydrocarbon supply unit for supplying biogas. [Figure 6] FIG. 2 is a schematic diagram illustrating another example of a gas processing system. [Figure 7] FIG. 2 is a schematic diagram illustrating another example of a gas processing system. [Figure 8] FIG. 2 is a schematic diagram illustrating another example of a gas processing system. [Figure 9] FIG. 2 is a schematic diagram illustrating another example of a gas processing system. [Figure 10] 1 is a schematic diagram illustrating a gas processing system according to an embodiment. [Figure 11] 11 is a graph showing the relationship between the number of discharges and the hydrogen sulfide concentration at the outlet of the plasma processing unit. [Figure 12] 1 is a graph showing the relationship between the number of discharges and the methyl mercaptan concentration at the outlet of a plasma processing unit. [Figure 13] 13 is a graph showing the relationship between the number of discharges and the methyl sulfide concentration at the outlet of the plasma processing unit. [Figure 14] 1 is a graph showing the relationship between the number of discharges and the methyl disulfide concentration at the outlet of a plasma processing unit. [Figure 15] 1 is a graph showing the relationship between the number of discharges and the hydrogen sulfide removal rate. [Figure 16] 1 is a graph showing the relationship between the number of discharges and the methyl mercaptan removal rate. [Figure 17] 1 is a graph showing the relationship between the number of discharges and the methyl sulfide removal rate. [Figure 18] 1 is a graph showing the relationship between the number of discharges and the methyl disulfide removal rate. [Figure 19] 1 is a graph showing the relationship between frequency and hydrogen sulfide concentration. [Figure 20] 1 is a graph showing the relationship between frequency and methyl mercaptan concentration. [Figure 21] 1 is a graph showing the relationship between frequency and methyl sulfide concentration. [Figure 22] 1 is a graph showing the relationship between frequency and methyl disulfide concentration. [Figure 23] 1 is a graph showing the relationship between the number of discharges and the hydrogen sulfide removal rate. [Figure 24] 1 is a graph showing the relationship between the number of discharges and the methyl mercaptan removal rate. [Diagram 25] 1 is a graph showing the relationship between the number of discharges and the methyl disulfide removal rate. [Figure 26] 1 is a graph showing the relationship between the number of discharges and the concentration of nitrous oxide in the presence or absence of methane. [Figure 27] 1 is a graph showing the relationship between the number of discharges and the concentration of nitrous oxide in the presence of 20 ppm methane. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] Hereinafter, the gas processing system according to the present embodiment will be described in detail with reference to the drawings. Note that the dimensional ratios in the drawings are exaggerated for the convenience of explanation and may differ from the actual ratios.

[0016] [First embodiment] First, a gas treatment system 1 according to the first embodiment will be described with reference to Figs. 1 to 3. As shown in Fig. 1, the gas treatment system 1 according to the present embodiment includes a pretreatment unit 10, a plasma treatment unit 20, an adsorption unit 30, an odor measurement unit 40, and a control unit 43. The pretreatment unit 10, the plasma treatment unit 20, and the adsorption unit 30 are provided in this order in a main flow path L1. The gas treatment system 1 is an apparatus that decomposes odor components in an odorous gas supplied thereinto, thereby discharging clean gas obtained by removing the odorous components from the odorous gas. As will be described later, the odorous gas is a gas that contains odorous components such as hydrogen sulfide, methyl mercaptan, methyl sulfide, and methyl disulfide in the air.

[0017] The pre-treatment unit 10 is disposed upstream of the plasma treatment unit 20. In this embodiment, the pre-treatment unit 10 is a dust removal device that removes foreign matter such as solid matter and water droplets. If foreign matter such as solid matter and water droplets adheres to the discharge portion of the plasma treatment unit 20, the plasma treatment unit 20 may be easily broken down due to abnormal discharge. Therefore, by providing such a pre-treatment unit 10, it is possible to remove the foreign matter and prevent malfunctions of the plasma treatment unit 20. The pre-treatment unit 10 may include, for example, a filter 11, and the filter 11 may collect foreign matter such as solid matter and water droplets.

[0018] An air blowing unit 12 is provided between the pre-treatment unit 10 and the plasma treatment unit 20. The air blowing unit 12 generates an airflow in the main flow path L1 and supplies the odorous gas to the plasma treatment unit 20. In this embodiment, the air blowing unit 12 is disposed between the pre-treatment unit 10 and the plasma treatment unit 20 from the viewpoints of reducing failures due to the inclusion of foreign matter and reducing damage due to radicals. However, the air blowing unit 12 may be disposed at a location other than the above, such as the upstream side of the pre-treatment unit 10.

[0019] The plasma treatment unit 20 generates plasma in the odorous gas by discharging electricity in the odorous gas. By generating plasma, radicals as main products and ozone as a by-product can be generated in the odorous gas. Then, the odorous components are oxidized and decomposed in the plasma treatment unit 20 by the radicals generated in the plasma treatment unit 20, so that the odor in the odorous gas can be reduced.

[0020] FIG. 2 is a schematic diagram showing a plasma processing unit 20 according to an example of this embodiment. As shown in FIG. 2, the plasma processing unit 20 includes a discharge electrode 21, a ground electrode 22, and a power source 23. The discharge electrode 21 and the ground electrode 22 are electrically connected to the power source 23. In addition, the discharge electrode 21 and the ground electrode 22 are arranged with a gap therebetween. With this arrangement, foreign matter is less likely to adhere to the vicinity of the discharge electrode and salt deposition can be reduced, compared to when the discharge electrode is connected to a dielectric. Therefore, it is possible to suppress the occurrence of abnormal discharge, which can prevent damage, and to reduce the frequency of cleaning the electrode.

[0021] The plasma treatment unit 20 can generate discharge by applying a voltage between the discharge electrode 21 and the ground electrode 22 by the power source 23. Then, by the discharge, plasma 24 can be generated in the odorous gas between the discharge electrode 21 and the ground electrode 22. At least a part of the radicals and ozone generated by the generation of the plasma 24 may move to the adsorption unit 30.

[0022] In the plasma treatment unit 20, discharge can be generated by applying a pulse voltage between the discharge electrode 21 and the ground electrode 22. The plasma treatment unit 20 may adjust at least one condition selected from the group consisting of the discharge amount, the number of discharges, and the discharge voltage of the plasma treatment unit 20, and the flow rate of the odorous gas flowing through the plasma treatment unit 20. This makes it possible to control the characteristics of the generated ozone and radicals, thereby making it possible to remove odorous components more effectively.

[0023] In the case of pulse discharge, when the distance (discharge distance) between the discharge electrode 21 and the ground electrode 22 is d cm, the discharge power per pulse injected into the electrode by generating a discharge such as a corona discharge may be (d / 200) J or more and (d / 5) J or less per unit electrode length (unit cm) of the discharge line.

[0024] The discharge rate is, for example, 0.1Wh / m 3 More than 20Wh / m 3 The discharge amount may be 0.3Wh / m or less. 3 The discharge amount may be 5Wh / m or more. 3 may be less than 10Wh / m 3 may be less than 3.5Wh / m 3 may be less than 1Wh / m 3 It may be the following.

[0025] The number of discharges may be, for example, 50 or more. The number of discharges may be 100 or more, 200 or more, or 300 or more. There is no particular upper limit to the number of discharges, but the number of discharges may be, for example, 5000 or less, 4000 or less, 3000 or less, 2000 or less, or 1000 or less. The number of discharges means the number of times that the odorous gas discharges while passing through the plasma treatment unit 20.

[0026] The residence time of the odorous gas in the plasma treatment unit 20 may be 0.1 seconds or more and 10 seconds or less. The residence time of the odorous gas in the plasma treatment unit 20 may be 0.5 seconds or more. The residence time of the odorous gas in the plasma treatment unit 20 may be 2 seconds or less.

[0027] The adsorption unit 30 is provided downstream of the plasma treatment unit 20. The adsorption unit 30 adsorbs odor components remaining in the odorous gas that has come into contact with the plasma. In the plasma treatment unit 20, the odor components are decomposed by contacting them with radicals, etc., but when the odor intensity of the odor components is low, for example, the contact efficiency decreases, and therefore the deodorization efficiency may decrease. However, the adsorption unit 30 can adsorb odor components that have not been completely removed by the plasma treatment unit 20, so that the odor component removal rate in the gas treatment system 1 can be further improved. In addition, by combining the plasma treatment unit 20 and the adsorption unit 30, it is possible to suppress the consumption of more energy than necessary in the plasma treatment unit 20 and improve the deodorization efficiency.

[0028] The adsorption unit 30 may include an adsorbent 31, and the odor components may be adsorbed by the adsorbent 31. When the adsorption unit 30 includes the adsorbent 31, the adsorption of the odor components can be promoted. In addition, the odor components adsorbed to the adsorbent 31 can be decomposed by the radicals and ozone generated in the plasma treatment unit 20, and deodorization of the odorous gas can be promoted. The adsorbent 31 may be in the form of a powder, particle, lump, plate, fiber, fabric, honeycomb, rod, or the like.

[0029] The adsorbent 31 may be, for example, a porous material. By using a porous material for the adsorbent 31, the surface area of ​​the adsorbent 31 is increased, and the adsorption performance of odor components can be improved. In addition, the ozone generated in the plasma treatment unit 20 is a gas, and the ozone gas can reach the odor components adsorbed in the pores of the porous material, so that the odor components in the odorous gas can be effectively oxidized and decomposed.

[0030] The type of adsorbent 31 is not particularly limited, but the adsorbent 31 may contain an inorganic adsorbent, and odor components may be adsorbed by the inorganic adsorbent. Inorganic adsorbents have higher chemical stability than organic adsorbents, and therefore can maintain their adsorption performance for a long period of time. The adsorbent 31 may contain at least one material selected from the group consisting of activated carbon, zeolite, silica, alumina, and silica gel. These materials have a high adsorption effect on odor components, and therefore can effectively remove odor components from odorous gases.

[0031] The adsorbent 31 may contain an adsorbent other than activated carbon. This is because activated carbon may be decomposed by at least one of ozone and radicals generated by plasma, which may shorten the life of the activated carbon, and replacing the activated carbon requires time and cost. The fact that the adsorbent 31 contains an adsorbent other than activated carbon does not mean that the adsorbent 31 does not contain activated carbon, and the adsorbent 31 may contain an adsorbent other than activated carbon and activated carbon. Since activated carbon has high adsorption properties for specific odor components such as methyl mercaptan, the adsorption properties of the specific odor components can be increased and the decomposition of the adsorbent 31 can be suppressed by using activated carbon in combination. The adsorbent 31 may not contain activated carbon and may contain only an adsorbent other than activated carbon.

[0032] The adsorbent 31 may contain at least one of a metal oxide and a metal hydroxide. An example of such an adsorbent 31 is BSR-50 by Guild Associates, Inc., which has been confirmed to remove odorous components several times more than activated carbon. As shown in FIG. 3, at least one of a metal oxide and a metal hydroxide reacts with a sulfur compound such as hydrogen sulfide to generate a metal sulfide. The metal sulfide reacts with water and oxygen contained in the odorous gas to regenerate at least one of the metal oxide and the metal hydroxide. The metal sulfide reacts with a sulfur compound and oxygen contained in the odorous gas to generate a metal subsulfide. The metal subsulfide reacts with hydrogen sulfide to generate a metal oxide, so that it can be used again to adsorb sulfur compounds. In this way, the adsorbent 31 containing at least one of a metal oxide and a metal hydroxide can react with components in the odorous gas even after adsorbing sulfur compounds, thereby self-regenerating the adsorbent 31 containing the metal oxide and the metal hydroxide.

[0033] The odor measuring unit 40 measures the odor intensity of an odorous gas. The odor intensity of an odorous gas may be, for example, the concentration of at least one compound selected from the group consisting of hydrogen sulfide, methyl mercaptan, methyl sulfide, and methyl disulfide. The odor measuring unit 40 may be a hydrogen sulfide concentration meter, a methyl mercaptan concentration meter, a methyl sulfide concentration meter, a methyl disulfide concentration meter, or a combination thereof. The odor measuring unit 40 may also be a measuring device using a gas chromatography method.

[0034] The odor intensity of the odorous gas may be measured by a measuring device that outputs the odor intensity as a level. For example, the odor measuring unit 40 may include an indium oxide hot-wire sintered semiconductor. In such an odor measuring unit 40, odor molecules are adsorbed to the sintered semiconductor, and the electrical resistance value of the sintered semiconductor decreases, so that the odor intensity can be output as a level according to the electrical resistance value. An example of an odor measuring unit 40 that includes a hot-wire sintered semiconductor is the odor sensor XP-329IIIR manufactured by New Cosmos Electric Co., Ltd.

[0035] The odor measuring unit 40 may include a first odor measuring unit 41 and a second odor measuring unit 42. The first odor measuring unit 41 is disposed downstream of the pre-treatment unit 10 and upstream of the plasma treatment unit 20. The first odor measuring unit 41 measures the odor intensity of the odor component that passes through the pre-treatment unit 10 and is supplied to the plasma treatment unit 20. The second odor measuring unit 42 is disposed downstream of the plasma treatment unit 20 and upstream of the adsorption unit 30. The second odor measuring unit 42 measures the odor intensity of the odor component that is discharged from the plasma treatment unit 20 and is supplied to the adsorption unit 30. The first odor measuring unit 41 and the second odor measuring unit 42 may be, for example, the same type of device. For example, the first odor measuring unit 41 may be a hydrogen sulfide concentration meter, and the second odor measuring unit 42 may be a measuring device including an indium oxide hot wire sintered semiconductor. In this case, when the gas treatment system 1 is in operation, only one of the first odor measuring unit 41 or the second odor measuring unit 42 may be operated.

[0036] The control unit 43 controls the number of discharges of the plasma treatment unit 20 according to the odor intensity of the odorous gas. By controlling the number of discharges of the plasma treatment unit 20 according to the odor intensity, deodorization can be performed according to the fluctuation of the odor intensity. Specifically, the control unit 43 is electrically connected to the odor measuring unit 40, and controls the number of discharges of the plasma treatment unit 20 according to the odor intensity of the odorous gas measured by the odor measuring unit 40.

[0037] More specifically, the control unit 43 is electrically connected to the first odor measuring unit 41, and may control the number of discharges of the plasma treatment unit 20 in accordance with the odor intensity of the odorous gas measured by the first odor measuring unit 41. By performing such feedforward control, deodorization in accordance with the odor intensity of the odorous gas can be performed with high responsiveness. Moreover, the control unit 43 is electrically connected to the second odor measuring unit 42, and may control the number of discharges of the plasma treatment unit 20 in accordance with the odor intensity of the odorous gas measured by the second odor measuring unit 42. By performing such feedback control, deodorization in accordance with the odor intensity of the odorous gas can be performed stably.

[0038] For example, when the odor intensity of the odorous gas is higher than a predetermined threshold, the control unit 43 may control the plasma treatment unit 20 to increase the number of discharges. Also, for example, when the odor intensity of the odorous gas is lower than a predetermined threshold, the control unit 43 may control the plasma treatment unit 20 to decrease the number of discharges. The predetermined threshold can be determined by a preliminary experiment or the like. Also, the predetermined threshold may be determined based on a model constructed using AI or the like from data on the odor intensity of the odorous gas in the past linked with conditions such as date, time, temperature, and treatment process.

[0039] The control unit 43 may control the number of discharges of the plasma treatment unit 20 according to the odor components contained in the odorous gas. For example, when the odorous gas does not contain a specific odor component, the control unit 43 may control the plasma treatment unit 20 to reduce the number of discharges. Note that, although an example in which the control unit 43 controls the number of discharges of the plasma treatment unit 20 according to the odor intensity of the odorous gas has been described, the plasma treatment unit 20 may perform plasma treatment at a constant number of discharges that is determined in advance by a preliminary experiment or the like.

[0040] The odorous gas contains odorous components. The odorous components may be compounds containing elemental sulfur. The odorous components may contain at least one compound selected from the group consisting of hydrogen sulfide, methyl mercaptan, methyl sulfide, and methyl disulfide.

[0041] Hydrogen sulfide is a compound represented by the chemical formula H2S. The concentration of hydrogen sulfide in the odorous gas may be, for example, more than 6 ppm, more than 10 ppm, more than 20 ppm, or more than 25 ppm in molar ratio. The concentration of hydrogen sulfide in the odorous gas may be, for example, less than 200 ppm, less than 100 ppm, less than 50 ppm, or less than 40 ppm in molar ratio.

[0042] Methyl mercaptan is a compound represented by the chemical formula CH3SH. The concentration of methyl mercaptan in the odorous gas may be, for example, more than 0.03 ppm, more than 0.5 ppm, more than 1 ppm, or more than 2 ppm in molar ratio. The concentration of methyl mercaptan in the odorous gas may be, for example, less than 10 ppm, less than 7 ppm, less than 5 ppm, or less than 4 ppm in molar ratio.

[0043] Methyl sulfide is a compound represented by the chemical formula CHS. The concentration of methyl sulfide in the odorous gas may be, for example, more than 0.08 ppm, more than 0.1 ppm, more than 0.2 ppm, or more than 0.3 ppm in molar ratio. The concentration of methyl sulfide in the odorous gas may be, for example, less than 5 ppm, less than 2 ppm, less than 1 ppm, or less than 0.5 ppm in molar ratio.

[0044] Methyl disulfide is a compound represented by the chemical formula C2H6S2. The concentration of methyl disulfide in the odorous gas may be, for example, more than 0.08 ppm, more than 0.1 ppm, more than 0.2 ppm, or more than 0.3 ppm in molar ratio. The concentration of methyl disulfide in the odorous gas may be, for example, less than 5 ppm, less than 2 ppm, less than 1 ppm, or less than 0.5 ppm in molar ratio.

[0045] The odorous gas may be, for example, a gas generated in a place such as a sewage treatment facility, a garbage disposal site, a home, etc. The odor intensity of these odorous gases varies due to, for example, a change in the pollutant load, so that the gas treatment system 1 according to this embodiment can deodorize the gas in accordance with the change in odor intensity.

[0046] The odorous gas may be gas generated during sewage treatment. Gas generated during sewage treatment contains large amounts of hydrogen sulfide, methyl mercaptan, methyl sulfide, and methyl disulfide. Therefore, the gas can be efficiently deodorized by the gas treatment system 1 according to this embodiment. The gas generated during sewage treatment may be gas generated from the sewage itself, or gas generated in facilities such as a grit basin, a primary sedimentation basin, and an aeration tank.

[0047] As described above, the gas treatment system 1 according to this embodiment includes the plasma treatment unit 20 that generates plasma in an odorous gas containing odorous components by discharging in the odorous gas. The gas treatment system 1 includes an adsorption unit 30 that is provided downstream of the plasma treatment unit 20 and adsorbs odorous components remaining in the odorous gas that has come into contact with the plasma, and a control unit 43 that controls the number of discharges of the plasma treatment unit 20. The control unit 43 controls the number of discharges according to the odor intensity of the odorous gas.

[0048] According to the gas processing system 1 of this embodiment, the number of discharges of the plasma processing unit 20 is controlled according to the odor intensity of the odorous gas. Therefore, deodorization can be performed according to the variation in odor intensity. Therefore, since deodorization can be performed according to the variation in odor intensity, efficient deodorization can be performed and the amount of energy used can be reduced. In addition, the gas processing system 1 can be designed according to the odor intensity.

[0049] The gas treatment system 1 according to this embodiment can be used in places such as sewage treatment plants, garbage disposal plants, and homes.

[0050] The gas processing system 1 according to the above embodiment includes a pre-processing unit 10. However, for example, as described above, in the plasma processing unit 20 according to the present embodiment, the discharge electrode 21 and the ground electrode 22 are arranged with a gap therebetween, and the influence of foreign matter is small, so that the pre-processing unit 10 is not essential.

[0051] In the above embodiment, the plasma processing unit 20 in which the discharge electrode 21 and the ground electrode 22 are arranged with a gap therebetween is exemplified, but the present invention is not limited to this form, and the discharge electrode 21 and the ground electrode 22 may be connected via a dielectric. In addition, the plasma discharge method of the plasma processing unit 20 is not limited to pulse discharge, and may be other discharge methods such as barrier discharge and surface discharge.

[0052] In the above embodiment, an example has been described in which the odor measurement unit 40 includes the first odor measurement unit 41 and the second odor measurement unit 42. However, the odor measurement unit 40 may include at least one of the first odor measurement unit 41 and the second odor measurement unit 42, as long as it includes either one of them.

[0053] [Second embodiment] Next, the gas processing system 1 according to the second embodiment will be described with reference to FIG. 4. As shown in FIG. 4, the gas processing system 1 according to this embodiment includes a pretreatment unit 10, a plasma processing unit 20, an adsorption unit 30, a control unit 43, and a hydrocarbon supply unit 50. The gas processing system 1 may also include at least one of an odor measurement unit 40 and an N2O measurement unit 45. The gas processing system 1 according to the second embodiment is different from the gas processing system 1 according to the first embodiment in that it includes a hydrocarbon supply unit 50. The gas processing system 1 according to the second embodiment may also include an N2O measurement unit 45, compared to the gas processing system 1 according to the first embodiment. Other points are the same as those of the gas processing system 1 according to the first embodiment, and therefore description thereof will be omitted.

[0054] The plasma treatment unit 20 removes nitrous oxide through chemical reactions in the presence of odorous gases containing hydrocarbons. In this embodiment, the odorous gas is a gas produced during sewage treatment and contains nitrous oxide. Nitrous oxide is one of the greenhouse gases that cause global warming, and has a greenhouse effect approximately 300 times greater than that of carbon dioxide. Therefore, by efficiently removing nitrous oxide, it is possible to suppress the emission of greenhouse gases into the air.

[0055] The hydrocarbon supply unit 50 supplies a hydrocarbon-containing gas containing a hydrocarbon to the plasma processing unit 20. The hydrocarbon supply unit 50 includes, for example, a tank for storing the hydrocarbon-containing gas, and can supply the hydrocarbon-containing gas from the tank. The hydrocarbons contained in the hydrocarbon-containing gas may include at least one selected from the group consisting of methane, ethane, propane, and butane. The hydrocarbon-containing gas may include city gas and biogas. City gas is a gas containing methane as a main component, and contains, for example, 80% or more of methane in molar ratio. The biogas may include methane generated by digestion of sludge. The biogas can be generated by methane fermentation using methanogens. For example, as shown in FIG. 5, the hydrocarbon supply unit 50 may include a sewage treatment unit 51 that treats sewage from a sewage treatment plant or the like, a digestion tank 52 that generates biogas containing methane by methane fermentation, and a tank 53 that stores the biogas. The mechanism by which nitrous oxide can be removed by plasma treatment is not clear, but it is thought that by treating nitrous oxide with plasma in the presence of a hydrocarbon, nitric oxide is reduced to nitrogen gas and removed.

[0056] The hydrocarbon supply unit 50 may supply the hydrocarbon-containing gas to the odorous gas so that the hydrocarbon concentration is 0.1 to 10 times the nitrous oxide concentration. In this way, the efficiency of removing nitrous oxide can be improved. For example, when the nitrous oxide concentration in the odorous gas is 10 ppm to 30 ppm, methane may be supplied to the odorous gas so that the methane concentration is 20 ppm. The hydrocarbon concentration relative to the nitrous oxide concentration may be 0.5 or more, or may be 1 or more. The hydrocarbon concentration relative to the nitrous oxide concentration may be 5 or less, or may be 2 or less.

[0057] The hydrocarbon supply unit 50 may supply the hydrocarbon-containing gas to the odorous gas so that the concentration of the hydrocarbons in the odorous gas is 0.1 ppm or more and 30 ppm or less in molar ratio. The concentration of the hydrocarbons in the odorous gas may be 1 ppm or more, or 2 ppm or more. The concentration of the hydrocarbons in the odorous gas may be 20 ppm or less, 10 ppm or less, or 4 ppm or less. In addition, when the hydrocarbon is methane, it is preferable not to leave methane in the gas after the plasma treatment because methane is a greenhouse gas.

[0058] The number of discharges of the plasma processing unit 20 may be, for example, 50 or more and 250 or less. By setting the number of discharges within the above range, the removal rate of nitrous oxide can be improved. The number of discharges may be 100 or more, or 200 or more.

[0059] The N2O measuring unit 45 may measure the concentration of nitrous oxide contained in the odorous gas. Specifically, the first N2O measuring unit 46 may measure the concentration of nitrous oxide that passes through the pretreatment unit 10 and is supplied to the plasma treatment unit 20. The second N2O measuring unit 47 may measure the concentration of nitrous oxide that is discharged from the plasma treatment unit 20 and is supplied to the adsorption unit 30.

[0060] The control unit 43 may control the number of discharges of the plasma processing unit 20 according to the concentration of nitrous oxide contained in the odorous gas. By controlling the number of discharges of the plasma processing unit 20 according to the concentration of nitrous oxide, it is possible to remove nitrous oxide by chemical reaction according to the fluctuation of the concentration of nitrous oxide. Specifically, the control unit 43 may control the number of discharges of the plasma processing unit 20 according to the concentration of nitrous oxide measured by at least one of the first NO measuring unit 46 and the second NO measuring unit 47, as in the first embodiment.

[0061] The control unit 43 may adjust the amount of the hydrocarbon-containing gas supplied from the hydrocarbon supply unit 50 based on the concentration of nitrous oxide measured by the NO measuring unit 45. With such a configuration, the hydrocarbon supply unit 50 can supply the amount of hydrocarbons according to the amount of nitrous oxide in the odorous gas. Therefore, the hydrocarbon supply unit 50 can supply an appropriate amount of hydrocarbons to the odorous gas, and can suppress the hydrocarbons from remaining in the gas after the plasma treatment.

[0062] In the present embodiment, an example has been described in which the hydrocarbon supply unit 50 is connected to the upstream side of the pretreatment unit 10, and the hydrocarbon-containing gas is supplied to the upstream side of the pretreatment unit 10. However, as shown in FIG. 6, the hydrocarbon supply unit 50 may be connected to the plasma treatment unit 20, and the hydrocarbon-containing gas may be directly supplied to the plasma treatment unit 20. The position to which the hydrocarbon-containing gas is supplied in the plasma treatment unit 20 is not particularly limited. For example, odor components may be mainly removed upstream of the plasma treatment unit 20, and nitrous oxide may be mainly removed by supplying a hydrocarbon-containing gas downstream of the plasma treatment unit 20. With this configuration, it is possible to suppress an increase in the concentration of nitrous oxide due to plasma treatment, and to efficiently remove odor components and nitrous oxide. In this case, the upstream side of the plasma treatment unit 20 may be a first plasma treatment unit, and the downstream side of the plasma treatment unit 20 may be a second plasma treatment unit.

[0063] For example, the plasma processing unit 20 may include multiple sets of electrodes including a discharge electrode 21 and a ground electrode 22, and when the first set of electrodes arranged on the upstream side is defined as the first electrode, the second set of electrodes arranged downstream of the first electrode may be defined as the second electrode. The first plasma processing unit may include the first electrode, and the second plasma processing unit may include the second electrode. The hydrocarbon supply unit 50 may be connected to the second plasma processing unit, and a hydrocarbon-containing gas may be supplied to the second plasma processing unit.

[0064] As shown in FIG. 7, the plasma processing unit 20 may include a first plasma processing unit 20A and a second plasma processing unit 20B. The first plasma processing unit 20A generates plasma in the odorous gas by discharging in the odorous gas. The second plasma processing unit 20B generates plasma in the processing gas by discharging in the processing gas containing hydrocarbons that is processed in the first plasma processing unit 20A. The second plasma processing unit 20B is connected to the downstream side of the first plasma processing unit 20A via a pipe. The hydrocarbon supply unit 50 may be connected to the second plasma processing unit 20B, and a hydrocarbon-containing gas may be supplied from the hydrocarbon supply unit 50 to the second plasma processing unit 20B. This structure also allows the hydrocarbons to be supplied to the rear stage of the plasma processing unit 20. Therefore, the odorous components can be removed by the first plasma processing unit 20A arranged upstream of the plasma processing unit 20, and the nitrous oxide can be efficiently removed by the second plasma processing unit 20B arranged downstream of the plasma processing unit 20.

[0065] As shown in Fig. 8, the first odor measuring unit 41 may be disposed downstream of the pre-treatment unit 10 and upstream of the first plasma treatment unit 20A. The first odor measuring unit 41 can measure the odor intensity of the odor components that pass through the pre-treatment unit 10 and are supplied to the first plasma treatment unit 20A. The second odor measuring unit 42 may be disposed downstream of the first plasma treatment unit 20A and upstream of the second plasma treatment unit 20B. The second odor measuring unit 42 can measure the odor intensity of the odor components that are discharged from the first plasma treatment unit 20A and are supplied to the second plasma treatment unit 20B.

[0066] As shown in FIG. 8, the N2O measuring unit 45 may include a first N2O measuring unit 46 and a second N2O measuring unit 47. The first N2O measuring unit 46 may be disposed downstream of the first plasma processing unit 20A and upstream of the second plasma processing unit 20B. The first N2O measuring unit 46 can measure the concentration of nitrous oxide in the odorous gas that passes through the first plasma processing unit 20A and is supplied to the second plasma processing unit 20B. The second N2O measuring unit 47 may be disposed downstream of the second plasma processing unit 20B and upstream of the adsorption unit 30. The second N2O measuring unit 47 can measure the concentration of nitrous oxide in the odorous gas that is discharged from the second plasma processing unit 20B and is supplied to the adsorption unit 30.

[0067] As shown in FIG. 8, the gas treatment system 1 may include a reflux flow path L2 that refluxes the odor gas treated in the first plasma treatment unit 20A to the first plasma treatment unit 20A. In this embodiment, the reflux flow path L2 is connected to the main flow path L1 downstream of the second odor measuring unit 42 and upstream of the second plasma treatment unit 20B. The main flow path L1 and the reflux flow path L2 are connected via an electric valve V1 such as a three-way valve. The reflux flow path L2 is connected between the first odor measuring unit 41 and the first plasma treatment unit 20A in the main flow path L1. The control unit 43 may determine whether or not to supply the odor gas treated in the first plasma treatment unit 20A to the first plasma treatment unit 20A again via the reflux flow path L2 based on the odor intensity measured by the second odor measuring unit 42. The control unit 43 may control the opening and closing of the motor-operated valve V1 to supply the odor gas treated in the first plasma processing unit 20A to the first plasma processing unit 20A again when the odor intensity is equal to or greater than the threshold, and to flow the odor gas treated in the first plasma processing unit 20A to the second plasma processing unit 20B through the main flow path L1 when the odor intensity is less than the threshold. With this configuration, even if the odor components are not sufficiently treated, the odor gas is plasma-treated again in the first plasma processing unit 20A, improving the removal rate of the odor components.

[0068] As shown in FIG. 8, the gas treatment system 1 may include a reflux flow path L3 that refluxes the odorous gas treated in the second plasma treatment unit 20B to the second plasma treatment unit 20B. In this embodiment, the reflux flow path L3 is connected to the main flow path L1 downstream of the second N2O measurement unit 47 and upstream of the adsorption unit 30. The main flow path L1 and the reflux flow path L3 are connected via an electric valve V2 such as a three-way valve. The reflux flow path L3 is also connected between the first N2O measurement unit 46 and the second plasma treatment unit 20B in the main flow path L1. The control unit 43 may determine whether or not to supply the odorous gas treated in the second plasma treatment unit 20B to the second plasma treatment unit 20B again via the reflux flow path L3 based on the concentration of nitrous oxide measured by the second N2O measurement unit 47. The control unit 43 may control the opening and closing of the motor-operated valve V2 to supply the odorous gas treated in the second plasma processing unit 20B again to the second plasma processing unit 20B when the concentration of nitrous oxide is equal to or higher than the threshold, and to cause the odorous gas treated in the second plasma processing unit 20B to flow through the main flow path L1 to the adsorption unit 30 when the concentration of nitrous oxide is less than the threshold. With this configuration, even if the nitrous oxide is not sufficiently treated, the gas is plasma-treated again in the second plasma processing unit 20B, so that the removal rate of nitrous oxide can be improved.

[0069] Furthermore, the control unit 43 may control the number of discharges of the second plasma treatment unit 20B based on the odor intensity measured by the second odor measuring unit 42, and the odor components in the odorous gas remaining after being treated by the first plasma treatment unit 20A may be treated by the second plasma treatment unit 20B. This configuration also improves the removal rate of the odor components.

[0070] The control unit 43 may also determine whether or not to supply the odor gas treated in the second plasma treatment unit 20B again to the second plasma treatment unit 20B through the return flow path L3 based on the odor intensity measured by the second odor measurement unit 42. The control unit 43 may then control the opening and closing of the motor-operated valve V2 to supply the odor gas treated in the second plasma treatment unit 20B again to the second plasma treatment unit 20B when the odor intensity is equal to or greater than a threshold value, and to control the odor gas treated in the second plasma treatment unit 20B to flow through the main flow path L1 to the adsorption unit 30 when the odor intensity is less than the threshold value. With this configuration, odor components that could not be completely treated in the first plasma treatment unit 20A can be treated in the second plasma treatment unit 20B. The control unit 43 may control the number of discharges of the second plasma processing unit 20B based on the concentration of nitrous oxide measured by the second NO measuring unit 47, and remove the nitrous oxide in the odorous gas by a chemical reaction, for the odorous gas supplied to the second plasma processing unit 20B via the return flow path L3. Note that while the gas treated in the second plasma processing unit 20B is being returned via the return flow path L3, the control unit 43 may control the motor-operated valve V1 so that the odorous gas treated in the first plasma processing unit 20A does not flow to the second plasma processing unit 20B.

[0071] As shown in FIG. 9, the N2O measuring unit 45 may include a third N2O measuring unit 48 disposed downstream of the pretreatment unit 10 and upstream of the first plasma treatment unit 20A. The third N2O measuring unit 48 can measure the concentration of nitrous oxide in the odorous gas that passes through the pretreatment unit 10 and is supplied to the first plasma treatment unit 20A. The third N2O measuring unit 48 may be provided downstream of the connection portion between the main flow path L1 and the return flow path L2. With this configuration, the concentration of nitrous oxide in the odorous gas that is treated in the first plasma treatment unit 20A and returned through the return flow path L2 can be measured. The control unit 43 may control the number of discharges of at least one of the first plasma treatment unit 20A and the second plasma treatment unit 20B based on the concentration of nitrous oxide measured by the third N2O measuring unit 48. With this configuration, the concentration of nitrous oxide in the odorous gas can be further reduced.

[0072] In the second embodiment, an example has been described in which the hydrocarbon supply unit 50 supplies a hydrocarbon-containing gas to the plasma processing unit 20. However, when the odorous gas contains hydrocarbons, nitrous oxide can be reduced and removed without supplying a hydrocarbon-containing gas by the hydrocarbon supply unit 50. Therefore, in such a case, the gas processing system 1 does not need to be provided with the hydrocarbon supply unit 50.

[0073] In the first and second embodiments, the gas processing system 1 has been described which removes odor components in an odorous gas by using the plasma processing unit 20 and the adsorption unit 30 for deodorization. However, the gas processing system 1 may remove only nitrous oxide without removing odor components. In this case, the gas processing system 1 may not be equipped with the adsorption unit 30. The odorous gas in the first and second embodiments may be read as a nitrous oxide-containing gas containing nitrous oxide.

[0074] That is, the gas processing system 1 may include a plasma processing unit 20 that generates plasma in the nitrous oxide-containing gas by discharging in the nitrous oxide-containing gas containing nitrous oxide and hydrocarbon. The gas processing system 1 may include a control unit 43 that controls the number of discharges of the plasma processing unit 20. The control unit 43 may control the number of discharges according to the nitrous oxide intensity of the nitrous oxide-containing gas. According to such a gas processing system 1, by discharging according to the nitrous oxide intensity in the nitrous oxide-containing gas, it is possible to process the gas according to the fluctuation of the nitrous oxide intensity. EXAMPLES

[0075] The present embodiment will be described in further detail below, but the present embodiment is not limited to such examples.

[0076] [Test Example 1] An evaluation device for the gas processing system 100 as shown in FIG. 10 was assembled, and the deodorizing effect of the gas processing system 100 was evaluated.

[0077] An odorous gas was supplied from a gas cylinder 101 to a static mixer 104. The flow rate of the odorous gas was adjusted by a mass flow meter 102. In addition, air was supplied to the static mixer 104 at a flow rate of 50 L / min by a blower 103. The odorous gas and the air were mixed in the static mixer 104 and supplied to a plasma treatment unit 120 including an electrode 121. The odorous gas that had come into contact with plasma in the plasma treatment unit 120 was passed through an adsorption unit 130 including a zeolite adsorbent 131 and then discharged. The flow rate of the exhaust gas discharged from the adsorption unit 130 was measured by a flow meter 140.

[0078] The odorous gas contains the odor components hydrogen sulfide (H2S), methyl mercaptan (CH3SH), methyl sulfide (CH3SCH3), and methyl disulfide (CH3S-SCH3), and the mass flow meter 102 was adjusted to set the concentrations shown in Table 1. For reference, the target concentration and target removal rate of each component in the gas after deodorization are shown in Table 1.

[0079] [Table 1]

[0080] The plasma processing unit 120 discharged under the conditions shown in Table 2. The number of discharge tubes in the plasma processing unit 120 was 12, as shown in FIG. 10. The distance (discharge distance) between the discharge electrode and the ground electrode in each discharge tube of the plasma processing unit 120 was 2 cm. The flow rate of the gas passing through the plasma processing unit 120 was 150 L / min, and the gas passed through the plasma processing unit 120 in approximately 1.87 seconds. The plasma processing unit 120 performed plasma processing only on the positive side of 1 Hz. Therefore, the number of plasma discharges is the value obtained by multiplying the frequency by approximately 1.87.

[0081] [Table 2]

[0082] In addition, the gas discharged from the outlet of the plasma processing unit 120 was collected, and the concentrations of hydrogen sulfide, methyl mercaptan, methyl sulfide, and methyl disulfide in the gas were measured using a gas chromatography method. Specifically, each component was separated using the following packed column, and then detected by an FPD (flame photometric detector). Manufacturer: GL Sciences Inc. Product name: β,β'-ODPN(β,β'-Oxydipropionitrile) Impregnation amount: 25% Support: UniportHP Mesh:60 / 80 Column size: Φ3.2mm×3.1m

[0083] Fig. 11 is a graph showing the relationship between the number of discharges and the hydrogen sulfide concentration at the outlet of the plasma processing unit 120. Fig. 12 is a graph showing the relationship between the number of discharges and the methyl mercaptan concentration at the outlet of the plasma processing unit 120. Fig. 13 is a graph showing the relationship between the number of discharges and the methyl sulfide concentration at the outlet of the plasma processing unit 120. Fig. 14 is a graph showing the relationship between the number of discharges and the methyl disulfide concentration at the outlet of the plasma processing unit 120.

[0084] In addition, the removal rate of each component was calculated by dividing the concentration of each component at each discharge count at the outlet of the plasma processing unit 120 by the concentration of each component at 0 discharge count. Fig. 15 is a graph showing the relationship between the number of discharges and the hydrogen sulfide removal rate. Fig. 16 is a graph showing the relationship between the number of discharges and the methyl mercaptan removal rate. Fig. 17 is a graph showing the relationship between the number of discharges and the methyl sulfide removal rate. Fig. 18 is a graph showing the relationship between the number of discharges and the methyl disulfide removal rate.

[0085] 11 to 18, it was confirmed that the concentrations of hydrogen sulfide, methyl mercaptan, methyl sulfide, and methyl disulfide all decreased when the number of discharges (frequency) was increased, and it was possible to achieve the target concentrations and target removal rates shown in Table 1. This shows that each odor component can be effectively removed by increasing the number of contacts between each odor component and plasma and radical species.

[0086] [Test Example 2] As shown in Table 3, plasma treatment was performed under a plurality of conditions with different discharge amounts, frequencies, discharge voltages, and discharge counts, and the number of discharge tubes in the plasma treatment unit 120 was reduced from 12 to 4, and the odorous gas concentration was measured. Except for this, evaluation was performed in the same manner as in Test Example 1. Note that, as shown in Test Example 1, if the frequency is increased, the odorous components are decomposed, making it difficult to confirm the effect of the discharge amount, so the frequency was reduced compared to Test Example 1 for evaluation.

[0087] [Table 3]

[0088] 19 to 22, it was found that hydrogen sulfide, methyl mercaptan, and methyl disulfide are more affected by the number of discharges (frequency) than the amount of discharge. From this, it can be understood that odor components can be effectively removed by controlling the number of discharges of the plasma treatment unit 120 according to the odor intensity of the odorous gas.

[0089] [Test Example 3] Except for the fact that the discharge amount was 0.2 J / pulse and 0.3 J / pulse, the evaluation was performed in the same manner as in Test Example 1. The results are shown in Figures 23 to 25. As shown in Figures 23 to 25, it was confirmed that the removal rates of hydrogen sulfide, methyl mercaptan, and methyl disulfide increased with the number of discharges, and that the target values ​​could be achieved at, for example, about 500 discharges or more.

[0090] [Test Example 4] We investigated the change in nitrous oxide concentration depending on the number of plasma treatments in the plasma treatment unit when methane was not added to 13 ppm nitrous oxide gas (methane 0 ppm) and when methane was added (methane 16 ppm). The plasma discharge amount was 4.5 to 17.2 W / m 3 The pulse width was 0.2 J / pulse, the air volume was 100 L / min, and the frequency was 254 to 967 Hz. The results are shown in Figure 26. As shown in Figure 26, the concentration of nitrous oxide did not decrease when methane was not added, but the concentration of carbon monoxide decreased when methane was added, confirming that nitrous oxide could be removed.

[0091] As shown in Figure 26, the concentration of nitrous oxide was about 2 ppm when the number of discharges was 250, but even if the number of discharges was increased beyond that, the concentration of nitrous oxide did not decrease, and there was a tendency for the concentration of nitrous oxide to increase. On the other hand, as shown in Figure 27, when methane was added to 150 ppm nitrous oxide gas to make it 20 ppm and plasma treatment was performed, it was confirmed that nitrous oxide gas could be removed even with about 100 discharges.

[0092] Although the present embodiment has been described above, the present embodiment is not limited to this, and various modifications are possible within the scope of the gist of the present embodiment. [Explanation of symbols]

[0093] 1 Gas Processing System 20 Plasma Processing Unit 20A First plasma processing section 20B Second plasma processing section 30 suction units 31 Adsorbents 43 Control Unit

Claims

1. a plasma treatment unit for generating plasma in an odorous gas containing an odor component by discharging in the odorous gas; an adsorption unit provided downstream of the plasma treatment unit for adsorbing the odor components remaining in the odorous gas that has come into contact with the plasma; a control unit for controlling the number of discharges of the plasma processing unit; Equipped with A gas treatment system, wherein the control unit controls the number of discharges depending on the odor intensity of the odorous gas.

2. The gas treatment system according to claim 1 , wherein the adsorption unit includes an inorganic adsorbent, and the odor components are adsorbed by the inorganic adsorbent.

3. 3. The gas treatment system according to claim 1, wherein the odorous gas is a gas produced in sewage treatment.

4. The odorous gas is a gas generated during sewage treatment and contains nitrous oxide; 3. The gas processing system according to claim 1, wherein the plasma processing unit removes nitrous oxide by chemical reaction in the presence of the odorous gas containing hydrocarbon.

5. 3. The gas processing system according to claim 1, wherein the plasma processing unit includes a first plasma processing section that generates plasma in the odorous gas by discharging in the odorous gas, and a second plasma processing section that generates plasma in the processing gas by discharging in a processing gas that is processed in the first plasma processing section and contains a hydrocarbon.

6. a plasma processing unit for generating plasma in a nitrous oxide-containing gas containing nitrous oxide and a hydrocarbon by discharging the gas in the nitrous oxide-containing gas; a control unit for controlling the number of discharges of the plasma processing unit; Equipped with The control unit controls the number of discharges according to the nitrous oxide intensity of the nitrous oxide-containing gas.

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