Methane purification system

Abstract

It accelerates the reaction between methane and ozone. [Solution] The methane purification device 1 comprises a pipeline 10 through which a gas containing methane flows, an ozone supply unit 20 that supplies ozone to the gas, and a non-metallic catalyst heater 32 located downstream of the ozone supply unit 20 in the pipeline 10 and heating the gas and ozone. The catalyst heater 32 supports a catalyst that purifies methane by reacting ozone with methane.

Description

Technical Field

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[0001] The present invention relates to a methane purification device for purifying methane in a gas.

Background Art

[0002] The following Patent Document 1 discloses a technique in which a gas containing methane and ozone are supplied to a catalyst, and methane and ozone are reacted on the catalyst to purify methane. Specifically, methane is purified by reacting with ozone and decomposing into carbon dioxide and water.

Prior Art Document

Patent Document

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] By the way, in the above technique, when the temperature of the catalyst is low, the reaction between methane and ozone on the catalyst hardly proceeds, so methane cannot be efficiently purified.

[0005] Therefore, the present invention has been made in view of these points, and an object thereof is to promote the reaction between methane and ozone.

Means for Solving the Problems

[0006] In one aspect of the present invention, there is provided a methane purification device including a pipeline through which a gas containing methane flows, an ozone supply unit that supplies ozone to the gas, and a non-metallic heater provided downstream of the ozone supply unit in the pipeline and that heats the gas and the ozone, wherein the heater supports a catalyst that reacts the ozone and the methane to purify the methane.

[0007] Furthermore, the heater may have a honeycomb-structured heating element, and the heating element may have the catalyst supported on its surface.

[0008] Furthermore, the heating element may be made of silicon carbide. Furthermore, the heater may have a plurality of flat heating plates arranged at predetermined intervals along the axial direction of the pipeline, and each of the plurality of heating plates may have the catalyst supported on its surface.

[0009] Furthermore, the catalyst may include any of zeolite, iron ion exchange zeolite, and cobalt ion exchange zeolite.

[0010] Furthermore, the system may also include a detection unit for detecting the temperature of the catalyst, and a temperature control unit for operating the heater so that the temperature of the catalyst is below the first temperature at which the ozone decomposes.

[0011] Furthermore, the temperature control unit may operate the heater such that the temperature of the catalyst is lower than the first temperature and at or above the second temperature at which water evaporates.

[0012] Furthermore, the temperature control unit may alternately repeat low-temperature control, which operates the heater to maintain a third temperature lower than the second temperature at which moisture evaporates for a first hour, and high-temperature control, which operates the heater to maintain a temperature between the second and first temperatures for a second hour that is shorter than the first hour. [Effects of the Invention]

[0013] According to the present invention, the reaction between methane and ozone can be accelerated. [Brief explanation of the drawing]

[0014] [Figure 1] This is a schematic diagram showing the configuration of a methane purification device 1 according to one embodiment. [Figure 2]This is a schematic diagram showing an example of the configuration of the catalytic heater 32. [Figure 3] This is a schematic diagram illustrating the first temperature control by the heater control unit 64. [Figure 4] This is a schematic diagram illustrating the second temperature control by the heater control unit 64. [Figure 5] This is a schematic diagram to illustrate a variation. [Modes for carrying out the invention]

[0015] <Configuration of a methane purification system> Figure 1 is a schematic diagram showing the configuration of a methane purification device 1 according to one embodiment. The methane purification device 1 is a device that purifies a gas to be purified, which is a gas containing methane. In this case, the gas to be purified is air containing methane. The methane purification device 1 can be installed in factories, houses, etc. The methane purification device 1 has a pipeline 10, a fan 12, an ozone supply unit 20, a methane decomposition unit 30, a temperature sensor 40, a memory unit 50, and a control unit 60.

[0016] The pipeline 10 forms a flow path through which the gas to be purified, containing methane, flows. The pipeline 10 is, for example, a cylindrical pipe. Inside the pipeline 10, a fan 12, an ozone supply unit 20, a methane decomposition unit 30, and a temperature sensor 40 are installed.

[0017] Fan 12 draws in the gas to be purified, which contains methane, into the pipeline 10. The gas to be purified drawn in by fan 12 flows toward the methane decomposition section 30 downstream of fan 12. Although fan 12 is installed inside the pipeline 10, it is not limited to this, and fan 12 may also be installed outside the pipeline 10.

[0018] The ozone supply unit 20 is provided on the downstream side of the fan 12 in the pipeline 10, and supplies ozone to the gas to be purified sucked by the fan 12. The ozone supply unit 20 generates ozone and supplies the ozone to the gas to be purified containing methane. The ozone flows toward the methane decomposition unit 30 together with the gas to be purified. Specifically, the ozone is mixed with the gas to be purified and flows toward the methane decomposition unit 30.

[0019] The ozone supply unit 20 generates ozone by, for example, a process of performing silent discharge on the gas to be purified (so-called silent discharge method). Specifically, the ozone supply unit 20 generates ozone by applying an alternating voltage from the power supply 23 to the electrode 22 covered with a dielectric such as glass. However, it is not limited to the above, and the ozone supply unit 20 may generate ozone by performing a process of electrolyzing water (so-called electrolysis method) or a process of irradiating the gas to be purified with ultraviolet rays (so-called ultraviolet lamp method).

[0020] The methane decomposition unit 30 is provided downstream of the ozone supply unit 20 in the pipeline 10, and has a function of decomposing methane in the gas to be purified using ozone. The methane decomposition unit 30 has a catalyst for decomposing methane, and decomposes methane into water and carbon dioxide by reacting ozone and methane on the catalyst.

[0021] By the way, methane reacts with ozone on the catalyst and is decomposed. However, if the temperature of the catalyst is low, the reaction between methane and ozone does not proceed, and it is difficult to decompose methane. This is because the catalyst has the property that the reaction between methane and ozone is promoted as the temperature is higher.

[0022] Therefore, in the present embodiment, in order to promote the reaction between methane and ozone on the catalyst, the methane decomposition unit 30 has a catalyst heater 32 having a function as a heater for heating the gas to be purified and ozone. And the catalyst heater 32 supports the catalyst. In this case, since the temperature of the catalyst rises when the gas to be purified and ozone heated by the catalyst heater 32 come into contact with the catalyst, the reaction between methane and ozone on the catalyst is promoted.

[0023] Figure 2 is a schematic diagram showing an example of the configuration of the catalytic heater 32. The catalytic heater 32 is located downstream of the ozone supply unit 20 and heats the gas to be purified that has passed through the ozone supply unit 20 and the ozone generated by the ozone supply unit 20. As shown in Figure 2, the catalytic heater 32 has a honeycomb structured carrier 33. The catalytic heater 32 has a heating element 34 that generates heat when electricity is supplied to the inside of the carrier 33, for example. Therefore, the carrier 33 in this embodiment functions as a heating element.

[0024] The heating element 34 includes, for example, an electric heating element that converts electrical energy into thermal energy. The electric heating element exchanges heat with the gas to be purified and ozone, thereby heating the gas to be purified and ozone and raising their temperatures. The carrier 33 is cylindrical in shape, as shown in Figure 2, and has the heating element 34 in its center. However, it is not limited to the above, and the carrier 33 may be a rectangular parallelepiped.

[0025] The catalytic heater 32 is made of a non-metallic material. Specifically, the support 33 of the catalytic heater 32 is made of silicon carbide. Because silicon carbide is electrically conductive, it generates heat when electricity is supplied. As a result, when the catalytic heater 32 is made of silicon carbide, it is easy to appropriately heat the gas to be purified and ozone in the pipeline 10.

[0026] Unlike this embodiment, if the support 33 of the catalyst heater 32 is made of metal, ozone readily reacts with the metal of the support 33, causing the metal to oxidize and the ozone to change into oxygen. In this case, the amount of ozone that reacts with methane decreases. Therefore, in this embodiment, the catalyst heater 32 is made of a non-metallic material to prevent the reduction of ozone due to oxidation.

[0027] While ceramic heating elements can also be considered for the catalytic heater 32, a silicon carbide catalytic heater 32 heats the gas to be purified and ozone more quickly than a ceramic one. Furthermore, by forming a honeycomb structure with silicon carbide, the surface area of ​​the heating portion of the catalytic heater 32 can be increased, allowing the catalytic heater 32 to heat the gas to be purified and ozone more efficiently.

[0028] The catalytic heater 32 supports a catalyst that purifies methane by reacting ozone with methane. Specifically, the support 33 of the catalytic heater 32 supports the catalyst. In other words, a catalyst layer is formed on the surface of the support 33, with the catalyst attached to it. The catalyst includes one of the following: zeolite, iron ion exchange zeolite, or cobalt ion exchange zeolite. With such a catalyst, the reaction between ozone and methane becomes easier even at low catalyst temperatures.

[0029] Ozone and methane come into contact with the catalyst layer of the catalyst heater 32 and react on the catalyst layer. When the catalyst heater 32 heats the gas to be purified and ozone, the heated gas to be purified and ozone come into contact with the catalyst layer, and the temperature of the catalyst layer rises. As a result, the reaction between ozone and methane on the catalyst layer is accelerated.

[0030] In the above description, the catalyst heater 32 (specifically, the support 33) is assumed to be made of silicon carbide, but it is not limited to this. The catalyst heater 32 may be formed mainly from non-metallic materials, for example, barium titanate. In this case as well, the gas to be purified and the ozone can be appropriately heated while preventing the reduction of ozone. Furthermore, although the above assumes that the support 33 has a honeycomb structure, it is not limited to this. The support 33 may have a corrugated structure or a mesh structure as long as the catalyst can be supported on its surface.

[0031] Returning to Figure 1, we will continue the explanation of the configuration of methane purification device 1. The temperature sensor 40 is installed in the methane decomposition unit 30 and is a sensor for detecting the temperature around the catalyst heater 32. Specifically, the temperature sensor 40 detects the temperature of the gas to be purified and ozone flowing through the methane decomposition unit 30. The temperature sensor 40 is, for example, a thermistor or a thermocouple.

[0032] The memory unit 50 has a storage medium such as ROM (Read Only Memory), RAM (Random Access Memory), HDD (Hard Disk Drive), or SSD (Solid State Drive). The memory unit 50 stores the program executed by the control unit 60 and various information for decomposing methane.

[0033] The control unit 60 includes a processor such as a CPU (Central Processing Unit). The control unit 60 supplies electricity to the catalyst heater 32, thereby heating the gas to be purified and ozone in the catalyst heater 32. As a result, methane and ozone react on the catalyst, which has reached a higher temperature. The control unit 60 may consist of one processor, or it may consist of multiple processors or a combination of one or more processors and electronic circuits. The control unit 60 functions as the detection unit 62 and the heater control unit 64 by executing a program stored in the storage unit 50.

[0034] The detection unit 62 detects the temperature of the catalyst in the catalyst heater 32. The detection unit 62 detects the temperature of the catalyst in the catalyst heater 32 by, for example, acquiring the temperature detected by the temperature sensor 40. For example, the detection unit 62 detects the temperature detected by the temperature sensor 40 as the temperature of the catalyst. However, it is not limited to this, and the detection unit 62 may also detect a value obtained by multiplying the temperature detected by the temperature sensor 40 by a predetermined coefficient as the temperature of the catalyst.

[0035] The heater control unit 64 controls the operation of the catalytic heater 32, which heats the gas to be purified and the ozone. For example, when the ozone supply unit 20 starts supplying ozone to the gas to be purified, the heater control unit 64 activates the catalytic heater 32 to heat the gas to be purified and the ozone. The heater control unit 64 also controls the operation of the catalytic heater 32 based on the temperature detected by the detection unit 62.

[0036] It is known that ozone decomposes thermally when it exceeds a predetermined first temperature (for example, 150°C). When ozone decomposes thermally, the amount of ozone that reacts with methane decreases. Therefore, the heater control unit 64 operates the catalyst heater 32 so that the temperature of the catalyst is below the first temperature at which ozone decomposes. Specifically, the heater control unit 64 controls the supply of electricity to the catalyst heater 32 so that the temperature of the catalyst detected by the detection unit 62 is below the first temperature. This suppresses the thermal decomposition of ozone when the catalyst heater 32 is operated.

[0037] As mentioned earlier, when ozone reacts with methane on a catalyst, carbon dioxide and water are produced, but the water produced can adhere to the catalyst. When water adheres to the catalyst, the surface area in contact with the catalyst by ozone and methane decreases, thus inhibiting the reaction between ozone and methane. Therefore, in this embodiment, in order to suppress the state in which water adheres to the catalyst, the heater control unit 64 operates the catalyst heater 32 so that the temperature of the catalyst detected by the detection unit 62 is lower than the first temperature and is at or above the second temperature (for example, 100°C) at which the water evaporates.

[0038] Figure 3 is a schematic diagram showing the first temperature control by the heater control unit 64. The heater control unit 64 operates the catalyst heater 32 so that the catalyst temperature is lower than the first temperature E1 (150°C) and higher than the second temperature E2 (100°C). In this case, the heater control unit 64 operates the catalyst heater 32 so that the catalyst temperature is maintained at approximately 130°C. In this case, the thermal decomposition of ozone is suppressed while preventing moisture from adhering to the catalyst. This promotes the reaction between ozone and methane, and increases the methane purification rate.

[0039] In the first temperature control described above, the heater control unit 64 operated the catalyst heater 32 to maintain a constant catalyst temperature, but it is not limited to this. For example, the heater control unit 64 may alternately repeat low-temperature control and high-temperature control, as shown in Figure 4.

[0040] Figure 4 is a schematic diagram showing the second temperature control by the heater control unit 64. The heater control unit 64 performs low-temperature control by operating the catalyst heater 32 so that the catalyst temperature detected by the detection unit 62 remains at a third temperature E3 (approximately 60°C), which is lower than the second temperature E2 (100°C), for a first time T1. The heater control unit 64 also performs high-temperature control by operating the catalyst heater 32 so that the catalyst temperature remains between the second temperature E2 and the first temperature E1 (150°C) for a second time T2, which is shorter than the first time T1. The second time T2 is shorter than the first time T1 (for example, 10 minutes), for example, 1 minute. The third temperature E3 is greater than 50°C and less than 100°C.

[0041] The heater control unit 64 then alternately repeats low-temperature control and high-temperature control. Specifically, the heater control unit 64 performs high-temperature control between low-temperature control cycles. The second temperature control is performed when the catalyst in the catalyst heater 32 is a cobalt ion exchange zeolite, because it has the characteristic of promoting the reaction between methane and ozone at the third temperature (low temperature). When the first temperature control is performed, the catalyst is, for example, an iron ion exchange zeolite. By implementing a second temperature control, the reaction between methane and ozone can be promoted through low-temperature control, while the adhesion of moisture to the catalyst can be suppressed through high-temperature control.

[0042] Incidentally, when iron ion exchange zeolite or cobalt ion exchange zeolite is used as a catalyst, if the catalyst temperature exceeds 150°C, ozone may oxidize the metal of the catalyst, potentially leading to a decrease in ozone. In response to this, the heater control unit 64 can suppress the decrease in ozone by keeping the catalyst temperature below 150°C (first temperature) in the first and second temperature control settings.

[0043] (modified version) In the above description, the catalyst heater 32 is assumed to be a honeycomb structure, but it is not limited to this. For example, the catalyst heater 32 may have a structure as shown in Figure 5.

[0044] Figure 5 is a schematic diagram illustrating a modified configuration. In Figure 5, only the configuration of the catalyst heater 32 differs from that in Figure 1; the other configurations are the same as those in Figure 1, so a detailed explanation is omitted. As shown in Figure 5, the modified catalyst heater 32 has a plurality of flat heating plates 36 arranged at predetermined intervals along the axial direction of the pipeline 10. The heating plates 36 are made of non-metallic material (e.g., silicon carbide) and generate heat when electricity is supplied. Multiple through holes are formed in the heating plates 36 at predetermined intervals, and the gas to be purified and ozone pass through these through holes. Each of the plurality of heating plates 36 has a catalyst supported on its surface.

[0045] In the modified example, the temperature of the catalyst rises when the gas to be purified and ozone heated by the heating plate 36 come into contact with the catalyst, thereby promoting the reaction between methane and ozone on the catalyst. Furthermore, because the heating plate 36 is made of a non-metallic material, the reduction of ozone due to reaction with metal can be suppressed.

[0046] In the above description, the methane purification device 1 is assumed to purify methane contained in the air, but it is not limited to this. For example, the methane purification device 1 may purify methane contained in exhaust gas emitted by an internal combustion engine of a vehicle or the like. In this case, the methane purification device 1 is installed in the exhaust passage of the internal combustion engine and purifies the methane in the exhaust gas flowing through the exhaust passage.

[0047] <Effects of this embodiment> The methane purification apparatus 1 of the above-described embodiment is provided downstream of the ozone supply unit 20 in the pipeline 10 through which the gas to be purified containing methane flows, and has a non-metallic catalyst heater 32 that heats the gas to be purified and ozone. The catalyst heater 32 supports a catalyst that purifies methane by reacting ozone with methane. The catalytic heater 32 heats the gas to be purified and the ozone, causing the temperature of the catalyst in the catalytic heater 32 to rise. This promotes the reaction between methane and ozone on the catalyst. Furthermore, because the catalytic heater 32 is made of a non-metallic material, the reduction of ozone due to reaction with metal can be suppressed.

[0048] Although the present invention has been described above using embodiments, the technical scope of the present invention is not limited to the scope described in the above embodiments, and various modifications and changes are possible within the scope of its gist. For example, all or part of the apparatus can be configured by functionally or physically distributing and integrating in any unit. Furthermore, new embodiments resulting from any combination of multiple embodiments are also included in the embodiments of the present invention. The effects of the new embodiments resulting from the combinations are combined with the effects of the original embodiments. [Explanation of Symbols]

[0049] 1. Methane purification system 10 conduit 20 Ozone Supply Department 32 Catalytic converter heater 33 Carrier 36 Heating plate 62 Detection unit 64 Heater control unit

Claims

1. A pipeline through which a gas containing methane flows, An ozone supply unit that supplies ozone to the aforementioned gas, A non-metallic heater is provided downstream of the ozone supply unit in the pipeline and heats the gas and the ozone, Equipped with, The heater supports a catalyst that reacts the ozone with the methane to purify the methane. Methane purification system.

2. The heater has a heating element with a honeycomb structure, The heating element has the catalyst supported on its surface. The methane purification apparatus according to claim 1.

3. The heating element is made of silicon carbide. The methane purification apparatus according to claim 2.

4. The heater has a plurality of flat heating plates arranged at predetermined intervals along the axial direction of the pipeline. Each of the plurality of heating plates has the catalyst supported on its surface. The methane purification apparatus according to claim 1.

5. The catalyst comprises any of zeolite, iron ion exchange zeolite, and cobalt ion exchange zeolite. The methane purification apparatus according to claim 1.

6. A detection unit for detecting the temperature of the catalyst, The system further includes a temperature control unit that operates the heater so that the temperature of the catalyst is below a first temperature at which the ozone decomposes. The methane purification apparatus according to claim 1.

7. The temperature control unit operates the heater such that the temperature of the catalyst is lower than the first temperature and at or above the second temperature at which water evaporates. The methane purification apparatus according to claim 6.

8. The temperature control unit, The process alternately repeats a low-temperature control, in which the heater is operated so that the temperature of the catalyst remains at a third temperature, which is lower than the second temperature at which water evaporates, for a first hour, and a high-temperature control, in which the heater is operated so that the temperature of the catalyst remains between the second temperature and the first temperature for a second hour, which is shorter than the first hour. The methane purification apparatus according to claim 6.

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