Methane purification system

Abstract

It promotes the reaction between methane and ozone on the catalyst. [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, a catalyst structure 31 located downstream of the ozone supply unit 20 in the pipeline 10 and purifying methane by reacting ozone with methane, and a heater 35 located in contact with the catalyst structure 31 in the pipeline 10 and heating the catalyst structure 31.

Description

Technical Field

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

Background Art

[0002] Patent Document 1 below discloses a technique for supplying a gas containing methane and ozone to a catalyst and reacting methane and ozone 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] The water generated by the reaction of methane and ozone adheres to the catalyst. When water adheres to the catalyst, it becomes difficult for methane and ozone to come into contact with the catalyst, thus inhibiting the reaction between methane and ozone.

[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 on the catalyst.

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, a catalyst structure provided downstream of the ozone supply unit in the pipeline and that reacts the ozone and the methane to purify the methane, and a heater that is in contact with the catalyst structure in the pipeline and heats the catalyst structure.

[0007] Furthermore, the catalyst structure may have a honeycomb-structured support for the catalyst, and the heater may be in contact with the side surface of the support.

[0008] Alternatively, the catalyst structure may be divided into a first catalyst structure and a second catalyst structure, and the heater may be sandwiched between the first catalyst structure and the second catalyst structure.

[0009] Furthermore, the heater may be flat in shape and positioned in the center of the pipeline along the axial direction of the pipeline.

[0010] Furthermore, the first side surface of the first catalyst structure may face the second side surface of the second catalyst structure with the heater in between, and the heater may be in contact with both the first and second side surfaces.

[0011] Furthermore, the heater may be fixed to the first catalyst structure and the second catalyst structure with a thermally conductive adhesive.

[0012] Furthermore, the catalyst structure may have a rectangular parallelepiped shape, and the heater may be in contact with each of the two opposing outer surfaces of the catalyst structure.

[0013] Furthermore, the catalyst may include any of zeolite, iron ion exchange zeolite, and cobalt ion exchange zeolite. [Effects of the Invention]

[0014] According to the present invention, the reaction between methane and ozone on the catalyst can be promoted. [Brief explanation of the drawing]

[0015] [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 methane decomposition unit 30. [Figure 3]It is a schematic diagram showing the decomposition of the methane decomposition unit 30. [Figure 4] It is a schematic diagram for explaining a modification.

Embodiments for Carrying Out the Invention

[0016] <Configuration of Methane Purification Device> FIG. 1 is a schematic diagram showing the configuration of a methane purification device 1 according to an embodiment. The methane purification device 1 is a device for purifying a gas to be purified which is a gas containing methane. Here, the gas to be purified is air containing methane. The methane purification device 1 can be installed in a factory, a house, or the like. The methane purification device 1 includes a pipeline 10, a filter 11, a fan 12, an ozone supply unit 20, a methane decomposition unit 30, a temperature sensor 40, a storage unit 50, and a control unit 60.

[0017] The pipeline 10 forms a flow path through which the gas to be purified containing methane flows. The pipeline 10 is, for example, a pipe having a rectangular cross-section. Inside the pipeline 10, a filter 11, a fan 12, an ozone supply unit 20, a methane decomposition unit 30, and a temperature sensor 40 are provided.

[0018] The filter 11 removes dust and specific components (components that inhibit the reaction between methane and ozone, and for example, hydrocarbons) in the gas to be purified. The filter 11 is provided in the pipeline 10 near the inlet of the gas to be purified. Note that the filter 11 may not be provided.

[0019] The fan 12 sucks in the gas to be purified containing methane in the pipeline 10. The gas to be purified sucked in by the fan 12 flows toward the methane decomposition unit 30 on the downstream side of the fan 12. Although the fan 12 is provided inside the pipeline 10, it is not limited thereto, and the fan 12 may be provided outside the pipeline 10.

[0020] 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.

[0021] 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).

[0022] 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 structure 31 for decomposing methane, and decomposes methane into water and carbon dioxide by reacting ozone and methane on the catalyst.

[0023] By the way, the water generated when methane reacts with ozone adheres to the catalyst of the catalyst structure 31. When water adheres to the catalyst, it becomes difficult for methane and ozone to come into contact with the catalyst, so the reaction between methane and ozone is inhibited. As a result, the purification of methane in the methane decomposition unit 30 decreases.

[0024] Therefore, in this embodiment, the methane decomposition unit 30 has a heater 35 that heats the catalyst structure 31, and the heater 35 is in contact with the catalyst structure 31. In this case, the heater 35 directly heats the catalyst structure 31, and the temperature of the catalyst in the catalyst structure 31 increases. As a result, moisture adhering to the catalyst is evaporated and removed from the catalyst. As a result, methane and ozone can come into proper contact with the catalyst, and the reaction between methane and ozone on the catalyst is promoted.

[0025] Figure 2 is a schematic diagram showing an example of the configuration of the methane decomposition unit 30. Figure 3 is a schematic diagram of the methane decomposition unit 30 disassembled. In Figure 2, the direction in which the gas to be purified and ozone flow to the methane decomposition unit 30 is indicated by arrows. The catalyst structure 31 of the methane decomposition unit 30 is divided into two parts here. As shown in Figure 3, the methane decomposition unit 30 has a first catalyst structure 32A, a second catalyst structure 32B, and a heater 35.

[0026] The first catalyst structure 32A is located downstream of the ozone supply unit 20 in the pipeline 10 and purifies the methane by reacting ozone with methane in the gas to be purified. The methane decomposition unit 30 has a rectangular parallelepiped shape. However, it is not limited to this, and the methane decomposition unit 30 may also have a cylindrical shape.

[0027] The first catalyst structure 32A is located above the heater 35 and is in contact with the heater 35. Specifically, the lower surface 33a (Figure 3) of the first catalyst structure 32A is in contact with the upper surface 35a (Figure 3) of the heater 35. The first catalyst structure 32A is located in the upper half of the pipeline 10 as seen from the heater 35. The lower surface 33a, which is the first side surface of the first catalyst structure 32A, is opposite the upper surface 34a, which is the second side surface of the second catalyst structure 32B, with the heater 35 in between.

[0028] The first catalyst structure 32A has a first support 33 that supports the catalyst. The first support 33 is a honeycomb structure in this case. However, it is not limited to this, and the first support 33 may have a corrugated structure, a mesh structure or a porous structure, for example. The material of the first support 33 may be cordierite, silicon carbide, aluminum titanate, stainless steel, iron-chromium-aluminum alloy, glass wool, glass fiber or titanium. By using a thermally conductive support, the heat from the heater 35 is more easily transferred to the entire first catalyst structure 32A, thereby facilitating the reaction between ozone and methane on the catalyst of the first catalyst structure 32A.

[0029] A catalyst layer is formed on the surface of the first support 33, with the catalyst attached to it. The catalyst here includes one of zeolite, iron ion exchange zeolite, and cobalt ion exchange zeolite. The catalyst layer is formed over the entire surface of the first support 33. However, it is not limited to this, and there may be areas on the surface of the first support 33 where the catalyst layer is not formed.

[0030] The second catalyst structure 32B, like the first catalyst structure 32A, is located downstream of the ozone supply unit 20 and purifies methane by reacting ozone with methane. The second catalyst structure 32B, like the first catalyst structure 32A, has a rectangular parallelepiped shape. The second catalyst structure 32B is located below the heater 35 and is in contact with the heater 35. Specifically, the upper surface 34a (Figure 3) of the second catalyst structure 32B is in contact with the lower surface 34b (Figure 3) of the heater 35. The second catalyst structure 32B is located in the lower half of the pipeline 10 as seen from the heater 35.

[0031] The second catalyst structure 32B, like the first catalyst structure 32A, has a second support 34 that supports the catalyst. Furthermore, a catalyst layer is formed on the surface of the second support 34, with the catalyst adhering to it. The configuration of the second support 34 and the catalyst layer of the second catalyst structure 32B is the same as that of the first support 33 and the catalyst layer of the first catalyst structure 32A. This facilitates the reaction between ozone and methane on the catalyst of the second catalyst structure 32B.

[0032] The heater 35 is sandwiched between the first catalyst structure 32A and the second support 34 within the pipeline 10, and heats the first catalyst structure 32A and the second catalyst structure 32B. Specifically, the heater 35 is in contact with both the first support 33 of the first catalyst structure 32A and the second support 34 of the second catalyst structure 32B, and heats the first support 33 and the second support 34. The heater 35 has a heating element that generates heat when electricity is supplied to it. The heating element includes, for example, an electric heating wire that converts electrical energy into thermal energy.

[0033] The heater 35 heats the first support 33 and the second support 34, increasing the temperature of the catalysts in the first support 33 and the second support 34. In particular, when the first support 33 and the second support 34 have a honeycomb structure, the heat from the heater 35 is more easily transferred to the first support 33 and the second support 34, causing the catalyst temperature to rise more easily. As a result, any moisture adhering to the catalyst is evaporated and removed from the catalyst. Consequently, methane and ozone can come into proper contact with the catalyst, thus promoting the reaction between methane and ozone on the catalyst.

[0034] The heater 35 is flat and located in the center of the pipeline 10, along the axial direction of the pipeline 10 (see Figure 1). The thickness of the heater 35 should be as small as possible so as not to obstruct the gas flow in the pipeline 10, for example, about 1 / 10 the thickness of the first catalyst structure 32A.

[0035] The heater 35 is in contact with both the first side surface of the first support 33 of the first catalyst structure 32A and the second side surface of the second support 34 of the second catalyst structure 32B. Specifically, the upper surface 35a of the heater 35 is in contact with the lower surface 33a of the first support 33, and the lower surface 35b of the heater 35 is in contact with the upper surface 34a of the second support 34. This allows the first support 33 and the second support 34 to be heated efficiently by a single heater 35. In particular, because the heater 35 is located in the center of the pipeline 10, it is easier to heat the first support 33 and the second support 34 located above and below the heater 35 uniformly, and moisture adhering to the catalyst can be efficiently removed.

[0036] The heater 35 may be fixed to the first catalyst structure 32A and the second catalyst structure 32B with a thermally conductive adhesive. Specifically, the heater 35 is fixed to the lower surface 33a of the first support 33 and the upper surface 34a of the second support 34 with a thermally conductive adhesive. The thermally conductive adhesive can be made of any material that is thermally conductive. This ensures that the heat generated by the heater 35 is properly transferred to the first support and the second support 34.

[0037] It may be considered to place the heater 35 upstream of the methane decomposition unit 30. However, if the heater 35 is located upstream of the methane decomposition unit 30, there is a risk that the ozone will come into contact with the heater 35 before it comes into contact with the catalyst in the methane decomposition unit 30. Since the ozone reacts with the heater 35, it will be converted into oxygen. In this case, the amount of ozone that reacts with methane will decrease. In contrast, by arranging the heater 35 between the first catalyst structure 32A and the second catalyst structure 32B, as in this embodiment, contact between ozone and the heater 35 can be suppressed, and as a result, the reduction of ozone can be suppressed.

[0038] 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 pipeline 10 and is a sensor for detecting the temperature around the methane decomposition unit 30. 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 thermocouple and is installed in this case within the methane decomposition unit 30 (specifically, the catalyst structure 31). However, it is not limited to this, and the temperature sensor 40 may be installed downstream of the catalyst structure 31.

[0039] 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.

[0040] The control unit 60 includes a processor such as a CPU (Central Processing Unit). The control unit 60 heats the first catalyst structure 32A and the second catalyst structure 32B by supplying electricity to the heater 35. As a result, methane and ozone react on the catalyst whose temperature has risen. 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 a detection unit 62 and a heater control unit 64 by executing a program stored in the storage unit 50.

[0041] The detection unit 62 detects the temperature of the catalyst in the methane decomposition unit 30. The detection unit 62 detects the temperature of the catalyst in the methane decomposition unit 30 (specifically, the catalyst structure 31) by acquiring the temperature detected by the temperature sensor 40, for example. 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.

[0042] The heater control unit 64 controls the operation of the heater 35. For example, when the ozone supply unit 20 starts supplying ozone to the gas to be purified, the heater control unit 64 activates the heater 35 to heat the catalyst structure 31 (specifically, the first support 33 and the second support 34). The heater control unit 64 also controls the operation of the heater 35 based on the temperature detected by the detection unit 62.

[0043] It is known that ozone decomposes within a few seconds when it exceeds a predetermined first temperature (for example, 300°C). When ozone decomposes, the amount of ozone that reacts with methane decreases. Therefore, the heater control unit 64 operates the heater 35 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 heater 35 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 heater 35 is operated.

[0044] Furthermore, in order to suppress the condition in which water adheres to the catalyst, the heater control unit 64 may operate the heater 35 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.

[0045] (modified version) In the above description, the heater 35 is assumed to be sandwiched above and below by the first catalyst structure 32A and the second catalyst structure 32B, but this is not limited to this configuration. For example, the heater 35 may be sandwiched between the first catalyst structure 32A and the second catalyst structure 32B from the left and right. Furthermore, although the above assumes that the catalyst structure 31 is divided into a first catalyst structure 32A and a second catalyst structure 32B, and that the heater 35 is positioned between the first catalyst structure 32A and the second catalyst structure 32B, the invention is not limited to this configuration. For example, the catalyst structure 31 may be a single unit, and the heater 35 may be positioned as shown in Figure 4.

[0046] Figure 4 is a schematic diagram illustrating a modified example. In this modified example, two heaters 35 are in contact with each of the outer surfaces of a catalyst structure 31. Specifically, one heater 35 is in contact with the left side surface 36a of the support 36 of the catalyst structure 31, and the other heater 35 is in contact with the right side surface 36b of the support 36. In this case, the catalyst structure 31 is heated by the two heaters 35, which raises the temperature of the catalyst in the catalyst structure 31. As a result, moisture adhering to the catalyst is evaporated and removed from the catalyst.

[0047] In the modified example, the two heaters 35 are positioned on the left and right sides of the catalyst structure 31, but this is not the only option. For example, the heaters 35 may be arranged so as to wrap around the outer surface of the catalyst structure 31. Also, in the above example, the heaters 35 are assumed to be in contact with the outer surface of the catalyst structure 31, but this is not the only option. For example, the heaters 35 may be arranged in a rod shape inside the catalyst structure 31.

[0048] 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.

[0049] <Effects of this embodiment> The methane purification apparatus 1 of the above-described embodiment includes a catalyst structure 31 located downstream of the ozone supply unit 20 in the pipeline 10, which purifies methane by reacting ozone with methane, and a heater 35 located in the pipeline 10 in contact with the catalyst structure 31, which heats the catalyst structure 31. The heater 35 directly heats the catalyst structure 31, raising the temperature of the catalyst. As a result, moisture adhering to the catalyst evaporates and is removed from the catalyst. Consequently, methane and ozone can come into proper contact with the catalyst, thus promoting the reaction between methane and ozone on the catalyst.

[0050] 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]

[0051] 1. Methane purification system 10 conduit 20 Ozone Supply Department 31 Catalyst structure 32A First catalyst structure 32B Second catalyst structure 33 First carrier 34 Second carrier 35 Heater

Claims

1. A pipeline through which a gas containing methane flows, An ozone supply unit that supplies ozone to the aforementioned gas, A catalyst structure is provided downstream of the ozone supply unit in the pipeline, which reacts the ozone with the methane to purify the methane, A heater is in contact with the catalyst structure in the aforementioned pipeline and heats the catalyst structure, A methane purification system equipped with the following features.

2. The catalyst structure has a honeycomb structure carrier that supports the catalyst, The heater is in contact with the side surface of the carrier. The methane purification apparatus according to claim 1.

3. The catalyst structure is divided into a first catalyst structure and a second catalyst structure. The heater is sandwiched between the first catalyst structure and the second catalyst structure. The methane purification apparatus according to claim 1.

4. The heater is flat in shape and is located in the center of the conduit along the axial direction of the conduit. The methane purification apparatus according to claim 3.

5. The first side surface of the first catalyst structure faces the second side surface of the second catalyst structure with the heater in between. The heater is in contact with both the first and second sides. The methane purification apparatus according to claim 4.

6. The heater is fixed to the first catalyst structure and the second catalyst structure with a thermally conductive adhesive. The methane purification apparatus according to claim 3.

7. The catalyst structure has a rectangular parallelepiped shape. The heater is in contact with each of the two opposing outer surfaces of the catalyst structure. The methane purification apparatus according to claim 1.

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

Images