Methane purification system

Abstract

The reaction between methane and ozone is carried out while suppressing the adhesion of water to the catalyst. [Solution] The methane purification device 1 includes a gas cooling unit 20 that cools the first gas by exchanging heat between the first gas and the refrigerant, an ozone supply unit 22 that supplies ozone to the first gas cooled by the gas cooling unit 20, a gas heating unit 23 that heats the second gas by exchanging heat between the first gas, a second gas containing ozone, and the refrigerant, a circulation path 26 that connects the gas cooling unit 20 and the gas heating unit 23 and through which the refrigerant circulates between the gas cooling unit 20 and the gas heating unit 23, a refrigerant cooling unit 28 provided upstream of the gas cooling unit 20 and downstream of the gas heating unit 23 in the circulation direction of the circulation path 26 to lower the temperature of the refrigerant, a refrigerant heating unit 27 provided downstream of the gas cooling unit 20 and upstream of the gas heating unit 23 in the circulation direction of the circulation path 26 to raise the temperature of the refrigerant, and a catalyst 25 that decomposes the methane contained in the second gas.

Description

Technical Field

[0001] The present invention relates to a methane purification device.

Background Art

[0002] The pollutant treatment method of Patent Document 1 includes methane and ozone, and by bringing a gas whose temperature is within a predetermined range into contact with a catalyst, the methane contained in the gas is oxidized and removed by ozone.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] Methane is more likely to react on the catalyst as the temperature increases, but ozone is more likely to decompose itself as the temperature increases, making it difficult for methane to be oxidized. Therefore, a strategy of raising the temperature to a temperature at which ozone is difficult to decompose and reacting methane with ozone can be considered. However, in this case, the water condensed from the water vapor contained in the gas adheres to the catalyst, making it difficult for methane and ozone to react on the catalyst.

[0005] Therefore, the present invention has been made in view of these points, and an object thereof is to react methane with ozone while suppressing the adhesion of water to the catalyst.

Means for Solving the Problems

[0006] A methane purification apparatus according to an aspect of the present invention comprises: a pipeline through which a first gas containing methane flows; a gas cooling unit that cools the first gas by exchanging heat between the first gas flowing through the pipeline and a refrigerant; an ozone supply unit that supplies ozone to the first gas cooled by the gas cooling unit; a gas heating unit provided downstream of the gas cooling unit in the pipeline and that heats the second gas by exchanging heat between the first gas flowing through the pipeline, the ozone supplied by the ozone supply unit and the refrigerant; and the gas cooling unit The system comprises a circulation path connecting the gas cooling section and the gas heating section, through which the refrigerant circulates between the gas cooling section and the gas heating section; a refrigerant cooling section provided upstream of the gas cooling section and downstream of the gas heating section in the circulation direction of the circulation path, which lowers the temperature of the refrigerant; a refrigerant heating section provided downstream of the gas cooling section and upstream of the gas heating section in the circulation direction of the circulation path, which raises the temperature of the refrigerant; and a catalyst provided downstream of the gas heating section in the pipeline, which decomposes the methane contained in the second gas.

[0007] The system may further include a detection unit for detecting the temperature of the catalyst, and a temperature control unit for causing the refrigerant heating unit to heat the refrigerant so that the temperature detected by the detection unit falls within a temperature range indicating a temperature at which the amount of methane decomposed by the catalyst in the second gas exceeds a predetermined proportion.

[0008] The system may further include a storage unit that stores a methane decomposition rate map showing the methane decomposition rate corresponding to the temperature of the catalyst for each type of catalyst, and the temperature control unit may specify the temperature range by referring to the methane decomposition rate map.

[0009] The system further includes a methane decomposition section containing the catalyst, and the temperature control section may obtain catalyst identification information for identifying the catalyst from the methane decomposition section and specify the temperature range for the type of catalyst corresponding to the catalyst identification information.

[0010] The catalyst may include zeolite, iron ion exchange zeolite, or cobalt ion exchange zeolite.

[0011] The pipeline may further include a detection unit that detects the temperature and humidity of the first gas at the inlet of the pipeline, and a temperature control unit that identifies a target temperature for removing water vapor contained in the first gas based on the temperature and humidity, and causes the refrigerant cooling unit to cool the refrigerant so that the temperature of the first gas reaches the target temperature.

[0012] The system may further include a water tank for storing water generated by cooling the first gas in the gas cooling unit, a warning light indicating whether the water tank is full, and a purification control unit that stops the gas cooling unit, the gas heating unit, the refrigerant cooling unit, and the refrigerant heating unit, and illuminates the warning light when the amount of water stored in the water tank exceeds a predetermined amount. [Effects of the Invention]

[0013] According to the present invention, the effect of reacting methane and ozone while suppressing the adhesion of water to the catalyst is achieved. [Brief explanation of the drawing]

[0014] [Figure 1] This diagram shows an overview of the methane purification device 1 according to this embodiment. [Figure 2] This figure shows an example of a methane decomposition rate map. [Figure 3] This figure shows an example of the processing sequence in methane purification device 1. [Modes for carrying out the invention]

[0015] <Overview of Methane Purification System 1> Figure 1 is a diagram showing an overview of the methane purification device 1 according to this embodiment. The methane purification device 1 shown in Figure 1 comprises a pipeline 10, an intake section 11, a gas cooling section 20, a water tank 21, an ozone supply section 22, a gas heating section 23, a methane decomposition section 24, a circulation path 26, a refrigerant heating section 27, a refrigerant cooling section 28, a temperature sensor 31, a temperature sensor 33, a humidity sensor 34, a water level sensor 35, a warning section 36, a memory section 41, and a control section 42. The methane purification device 1 is a device that has the function of decomposing methane contained in the air to produce water and carbon dioxide.

[0016] The conduit 10 is a conduit through which methane-containing air (hereinafter referred to as "first gas") flows. The intake section 11 is, for example, an intake fan that draws the first gas into the conduit 10.

[0017] The gas cooling unit 20 is located downstream of the intake unit 11 and upstream of the ozone supply unit 22 in the pipeline 10, and cools the first gas by exchanging heat between the first gas flowing through the pipeline 10 and the refrigerant. The gas cooling unit 20 has, for example, stacked fins and heat transfer tubes that penetrate the fins, and cools the first gas by exchanging heat between the first gas flowing between the stacked fins and the refrigerant, which is a low-temperature, low-pressure liquid flowing through the heat transfer tubes, thereby changing the refrigerant into vapor. The gas cooling unit 20 then generates water from the water vapor contained in the first gas by cooling the first gas and removes the water vapor. The ends of the heat transfer tubes of the gas cooling unit 20 are connected to the circulation path 26. The water tank 21 is a tank for storing the water generated by cooling the first gas in the gas cooling unit 20.

[0018] The ozone supply unit 22 is provided downstream of the gas cooling unit 20 and upstream of the gas heating unit 23 in the pipeline 10, and supplies ozone to the first gas cooled by the gas cooling unit 20. The ozone supply unit 22 has, for example, an AC power supply 22a and an electrode 22b coated with a dielectric such as glass, and supplies ozone by performing a process of generating ozone (so-called silent discharge method) by applying an AC voltage from the AC power supply 22a to the electrode 22b. The ozone supply unit 22 may generate ozone by performing a process of discharging on the surface of the dielectric covering the electrode (so-called surface discharge method), a process of electrolyzing water (so-called electrolysis method), or a process of irradiating ultraviolet rays to the first gas (so-called ultraviolet lamp method). The ozone supply unit 22 generates a second gas containing the first gas and ozone by supplying the generated ozone to the first gas.

[0019] The gas heating unit 23 is provided downstream of the gas cooling unit 20 in the pipeline 10, and heats the second gas containing the first gas flowing through the pipeline 10 and the ozone supplied by the ozone supply unit 22 by heat-exchanging with a refrigerant. In FIG. 1, the gas heating unit 23 is provided further downstream of the ozone supply unit 22 provided downstream of the gas cooling unit 20 in the pipeline 10 and upstream of the methane decomposition unit 24. The gas heating unit 23 has, for example, laminated fins and a heat transfer tube penetrating the fins, and heat-exchanges the second gas flowing between the laminated fins and the refrigerant which is high-temperature and high-pressure steam flowing through the heat transfer tube, thereby changing the refrigerant into a liquid and heating the second gas. The end of the heat transfer tube of the gas heating unit 23 is connected to the circulation path 26.

[0020] The methane decomposition unit 24 is provided downstream of the gas heating unit 23 in the pipeline 10 and houses a catalyst 25. The methane decomposition unit 24 decomposes methane to generate water and carbon dioxide by reacting ozone and methane contained in the second gas heated by the gas heating unit 23 on the catalyst 25.

[0021] The catalyst 25 is provided downstream of the gas heating section 23 in the pipeline 10 and decomposes methane contained in the second gas. The catalyst 25 has a carrier with a predetermined structure and a coating layer supported on the surface of the carrier. The predetermined structure is, for example, a honeycomb structure, a corrugated structure, a mesh structure or a porous structure. The material of the carrier is, for example, cordierite, silicon carbide, aluminum titanate, stainless steel, an iron-chromium-aluminum alloy, glass wool, glass fiber or titanium. The coating layer contains, for example, zeolite, iron ion-exchanged zeolite or cobalt ion-exchanged zeolite. Note that the surface area of the carrier may include a region that does not support the coating layer.

[0022] The circulation path 26 connects the gas cooling section 20 and the gas heating section 23, and the refrigerant circulates between the gas cooling section 20 and the gas heating section 23. The refrigerant heating section 27 is provided downstream of the gas cooling section 20 and upstream of the gas heating section 23 in the circulation direction D of the circulation path 26 and raises the temperature of the refrigerant. The refrigerant heating section 27 has, for example, a compressor, and changes the refrigerant, which is a low-temperature and low-pressure vapor flowing from the gas cooling section 20 into the circulation path 26, into a high-temperature and high-pressure vapor by compressing it, and outputs it to the gas heating section 23 via the circulation path 26.

[0023] The refrigerant cooling section 28 is provided upstream of the gas cooling section 20 and downstream of the gas heating section 23 in the circulation direction D of the circulation path 26 and lowers the temperature of the refrigerant. The refrigerant cooling section 28 has, for example, an expansion valve, and changes the refrigerant, which is a high-temperature and high-pressure liquid flowing from the gas heating section 23 into the circulation path 26, into a low-temperature and low-pressure liquid by decompressing it, and outputs it to the gas cooling section 20 via the circulation path 26.

[0024] The temperature sensor 31 is a sensor provided on the inner wall surface of the methane decomposition section 24 for detecting the temperature of the second gas flowing through the methane decomposition section 24, and is, for example, a thermistor or a thermocouple. The temperature sensor 33 is a sensor provided upstream of the intake section 11 in the pipeline 10 for detecting the temperature of the first gas, and is, for example, a thermistor or a thermocouple. The humidity sensor 34 is a sensor provided upstream of the intake section 11 in the pipeline 10 for detecting the humidity of the first gas, and includes, for example, a hygrometer sandwiched between electrodes. The temperature sensor 33 and the humidity sensor 34 may be provided downstream of the intake section 11 and upstream of the gas cooling section 20 in the pipeline 10.

[0025] The water level sensor 35 is a sensor for detecting the distance (height) from the bottom of the water tank 21 to the water surface of the water stored in the water tank 21. For example, the water level sensor 35 detects the distance from the bottom to the water surface based on the position of a float suspended inside the water tank 21 when it floats on the water surface of the water stored in the water tank 21. The warning unit 36 ​​has, for example, a warning light that indicates whether the water tank 21 is full or not. For example, the warning unit 36 ​​turns on the warning light if it indicates that the water tank 21 is full, and turns off the warning light if the water tank 21 is not full. For example, the warning unit 36 ​​obtains instruction information from the control unit 42 indicating an instruction to turn on or off the warning light, and executes the instruction (turn on or turn off) corresponding to the instruction information.

[0026] The memory unit 41 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 41 stores the program executed by the control unit 42 and various information for decomposing the methane containing the second gas.

[0027] The control unit 42 includes a processor such as a CPU (Central Processing Unit). The control unit 42 cools the refrigerant in the refrigerant cooling unit 28, causing the gas cooling unit 20 to exchange heat between the first gas and the refrigerant to cool the first gas and remove water vapor contained in the first gas. The control unit 42 heats the refrigerant in the refrigerant heating unit 27, causing the gas heating unit 23 to exchange heat between the second gas and the refrigerant to heat the second gas, causing the methane and ozone contained in the second gas to react on the catalyst 25. The control unit 42 may consist of one processor, or it may consist of multiple processors or a combination of one or more processors and electronic circuits.

[0028] As described above, the control unit 42 operates in such a way that the methane purification device 1 can decompose the methane contained in the second gas by supplying ozone to the first gas from which water vapor has been removed and reacting the second gas, generated by this ozone reaction, on the catalyst 25. As a result, the amount of water vapor in the first gas decreases, and the control unit 42 can prevent the water vapor condensed in the second gas from adhering to the catalyst 25 and blocking the areas on the catalyst 25 where methane and ozone come into contact and react (so-called reaction sites), thereby suppressing the difficulty of the reaction between methane and ozone on the catalyst 25. The configuration and operation of the control unit 42 will be described in detail below.

[0029] <Configuration of control unit 42> As shown in Figure 1, the control unit 42 includes a detection unit 421, a temperature control unit 423, and a purification control unit 424. The control unit 42 functions as the detection unit 421, temperature control unit 423, and purification control unit 424 by executing a program stored in the storage unit 41.

[0030] The detection unit 421 detects the temperature of the catalyst 25. For example, the detection unit 421 acquires the temperature of the second gas flowing through the methane decomposition unit 24, as detected by the temperature sensor 31, as the temperature of the catalyst 25. The detection unit 421 detects the temperature and humidity of the first gas at the inlet of the pipeline 10. For example, the detection unit 421 acquires the temperature detected by the temperature sensor 33 as the temperature of the first gas at the inlet of the pipeline 10, and acquires the humidity detected by the humidity sensor 34 as the humidity of the first gas at the inlet of the pipeline 10.

[0031] The temperature control unit 423 cools the refrigerant in the refrigerant cooling unit 28, thereby causing the gas cooling unit 20 to exchange heat between the refrigerant cooled by the refrigerant cooling unit 28 and the first gas, and to cool the first gas. The temperature control unit 423 determines a target cooling temperature for removing water vapor contained in the first gas based on, for example, the temperature and humidity of the inlet of the pipeline 10, and causes the refrigerant cooling unit 28 to cool the refrigerant so that the temperature of the first gas reaches the target temperature.

[0032] The temperature control unit 423 identifies the target cooling temperature corresponding to the temperature detected by the temperature sensor 33 and the humidity detected by the humidity sensor 34, acquired by the detection unit 421, by referring to a temperature map stored in the memory unit 41 that shows the target cooling temperature corresponding to the temperature and humidity. The temperature map shows, for example, a target cooling temperature lower than the temperature at the inlet of the pipeline 10 the higher the humidity at the inlet of the pipeline 10. The temperature control unit 423 then adjusts the valve opening of the expansion valve of the refrigerant cooling unit 28 so that the temperature difference between the temperature detected by the temperature sensor 33 and the target cooling temperature becomes smaller. The temperature control unit 423 increases the valve opening as the temperature difference increases.

[0033] By operating as described above, the temperature control unit 423 can cause the refrigerant flowing into the gas cooling unit 20 to be cooled by the refrigerant cooling unit 28. The gas cooling unit 20 can then exchange heat with the first gas using the refrigerant cooled by the refrigerant cooling unit 28, thereby generating water by condensing the water vapor contained in the first gas. As a result, the temperature control unit 423 can reduce the amount of water vapor contained in the first gas.

[0034] The temperature control unit 423 causes the refrigerant heating unit 27 to heat the refrigerant, thereby causing the gas heating unit 23 to exchange heat between the refrigerant heated by the refrigerant heating unit 27 and the second gas, and to heat the second gas. The temperature control unit 423 causes the refrigerant heating unit 27 to heat the refrigerant so that, for example, the temperature of the second gas detected by the detection unit 421 falls within a target temperature range that indicates the temperature at which the amount of methane decomposed by the catalyst 25 out of the amount of methane contained in the second gas is equal to or greater than a predetermined ratio. The target temperature range is within a temperature range in which ozone contained in the second gas is less likely to undergo thermal decomposition, for example, 50°C or more and less than 150°C.

[0035] The temperature control unit 423 has, for example, a feedback controller that sets a target heating temperature (target value) to a temperature within the target temperature range, and adjusts the rotation speed of the compressor motor of the refrigerant heating unit 27 to reduce the temperature difference between the temperature of the second gas and the target heating temperature. For example, if the temperature of the second gas is lower than the target heating temperature, the temperature control unit 423 increases the rotation speed of the motor as the temperature difference increases, and if the temperature of the second gas is equal to or greater than the target heating temperature, the temperature control unit 423 decreases the rotation speed of the motor as the temperature difference increases.

[0036] As described above, the temperature control unit 423 can cause the refrigerant flowing into the gas heating unit 23 to be heated in the refrigerant heating unit 27. The gas heating unit 23 then heats the second gas to a temperature within the target temperature range by exchanging heat with the refrigerant heated in the refrigerant heating unit 27. As a result, the temperature control unit 423 can react the methane contained in the second gas with ozone on the catalyst 25 at a temperature at which methane can be easily decomposed. Furthermore, since the temperature control unit 423 can heat the second gas, which contains the first gas from which water vapor has been removed, in the gas heating unit 23 and react it on the catalyst 25, it is possible to suppress the blockage of reaction sites by water condensed from the water vapor contained in the second gas.

[0037] The temperature of the refrigerant cooled by the refrigerant cooling unit 28 to remove water vapor from the first gas should be higher than the freezing point of the refrigerant and close to the freezing point (for example, if the refrigerant is water, it should be higher than 0°C and close to 0°C). However, the lower the temperature of the cooled refrigerant, the more difficult it becomes for the refrigerant heating unit 27 to raise the temperature of the refrigerant to the target heating temperature.

[0038] Therefore, the temperature control unit 423 may lower the target heating temperature of the refrigerant heated by the refrigerant heating unit 27 as the target cooling temperature of the refrigerant cooled by the refrigerant cooling unit 28 decreases. For example, the temperature control unit 423 sets a lower target heating temperature within the target temperature range and reduces the rotation speed of the compressor motor of the refrigerant heating unit 27 as the valve opening of the expansion valve of the refrigerant cooling unit 28 increases. By operating in this manner, the temperature control unit 423 can lower the temperature of the first gas to a temperature at which water vapor contained in the first gas can be easily removed, and raise the temperature of the second gas to a temperature at which methane and ozone can easily react.

[0039] The methane decomposition rate corresponding to the temperature of the second gas (the ratio of the amount of methane decomposed by the catalyst 25 to the amount of methane contained in the second gas flowing into the methane decomposition unit 24) differs depending on the type of coating layer of the catalyst 25. Therefore, the temperature control unit 423 may specify the target temperature range by referring to the methane decomposition rate map stored in the memory unit 41. The methane decomposition rate map is a map that shows the methane decomposition rate corresponding to the temperature of the catalyst 25 for each type of coating layer of the catalyst 25.

[0040] Figure 2 shows an example of a methane decomposition rate map. The horizontal axis of Figure 2 represents the temperature of catalyst 25 (temperature of the second gas), and the vertical axis represents the methane decomposition rate. In Figure 2, catalysts M1, M2, and M3 are shown as types of catalyst 25. The coating layer of catalyst M1 is cobalt ion exchange zeolite (Co-BEA), in which cobalt is supported on a β-type skeletal structure zeolite. The coating layer of catalyst M2 is iron ion exchange zeolite (Fe-BEA), in which iron is supported on a β-type skeletal structure zeolite. The coating layer of catalyst M3 is β-type skeletal structure zeolite (BEA).

[0041] For example, if the coating layer of catalyst 25 is cobalt ion exchange zeolite, the temperature control unit 423 refers to the methane decomposition rate map shown in Figure 2 to identify a target temperature range "temperature T10°C or higher and temperature T less than T20°C" where the methane decomposition rate of catalyst M1 is greater than or equal to decomposition rate C. For example, if the coating layer of catalyst 25 is iron ion exchange zeolite, the temperature control unit 423 refers to the methane decomposition rate map shown in Figure 2 to identify a target temperature range "temperature T30°C or higher and temperature T less than T40°C" where the methane decomposition rate of catalyst M2 is greater than or equal to decomposition rate C. By operating in this manner, the temperature control unit 423 can identify the optimal target temperature range according to the type of coating layer of catalyst 25.

[0042] The temperature control unit 423 obtains catalyst identification information (hereinafter referred to as "catalyst ID") for identifying the catalyst 25 corresponding to the catalyst 25 housed in the methane decomposition unit 24 from the methane decomposition unit 24 or the storage unit 41, and identifies the type of coating layer of the catalyst 25 corresponding to the catalyst ID. The temperature control unit 423 identifies the type of coating layer of the catalyst 25 corresponding to the obtained catalyst ID by, for example, referring to a coating layer table stored in the storage unit 41 that shows the types of coating layers of the catalyst 25 corresponding to the catalyst ID.

[0043] The temperature control unit 423 then identifies the target temperature range for the type of coating layer of the identified catalyst 25 by, for example, referring to the methane decomposition rate map stored in the memory unit 41. By operating as described above, the temperature control unit 423 can identify the target temperature range corresponding to the type of catalyst 25 housed in the methane decomposition unit 24. Furthermore, even if the user of the methane purification device 1 replaces the catalyst 25 with a different type of catalyst 25 than the one being replaced, the optimal target temperature range for the new catalyst 25 can be identified.

[0044] The purification control unit 424 turns on or off the warning light on the warning unit 36 ​​based on the water level (distance from the bottom to the water surface) of the water tank 21 detected by the water level sensor 35. For example, if the amount of water stored in the water tank 21 is greater than or equal to a predetermined amount, the purification control unit 424 stops the gas cooling unit 20, the gas heating unit 23, the refrigerant cooling unit 28, and the refrigerant heating unit 27, and turns on the warning light on the warning unit 36. The predetermined amount is, for example, a predetermined percentage (for example, 80%) of the amount of water that the water tank 21 can store, and is stored in the memory unit 41. If the amount of water stored in the water tank 21 is greater than or equal to a predetermined amount, the purification control unit 424 may further stop the intake unit 11 and the ozone supply unit 22.

[0045] The purification control unit 424, for example, turns off the warning light on the warning unit 36 ​​if the amount of water stored in the water tank 21 is less than a predetermined amount. By operating in this manner, the purification control unit 424 notifies the user of the methane purification device 1 that the amount of water stored in the water tank 21 is above a predetermined amount (i.e., full), and prevents the water stored in the water tank 21 from overflowing.

[0046] <Processing sequence in methane purification device 1> Figure 3 shows an example of a processing sequence in the methane purification device 1. The processing sequence shown in Figure 3 is a processing sequence in which the temperature control unit 423 controls the refrigerant heating unit 27 and the refrigerant cooling unit 28 so that the temperature of the catalyst 25 (i.e., the temperature of the second gas) reaches a temperature included in the target temperature range R, and the temperature of the first gas reaches the target cooling temperature T3.

[0047] The temperature control unit 423 identifies the type of coating layer of the catalyst 25 corresponding to the catalyst ID obtained from the methane decomposition unit 24 by referring to the coating layer table stored in the memory unit 41 (step S11). The temperature control unit 423 identifies a target temperature range R, which indicates the temperature at which the methane decomposition rate becomes equal to or greater than the decomposition rate C for the identified type of coating layer of the catalyst 25, by referring to the methane purification rate map stored in the memory unit 41 (step S12).

[0048] The detection unit 421 detects the temperature T1 of the catalyst 25 (i.e., the temperature T1 of the second gas) by acquiring the temperature from the temperature sensor 31 (step S13). If the temperature T1 is not within the target temperature range R (YES in step S14), the temperature control unit 423 raises the temperature of the refrigerant flowing to the gas heating unit 23 by having the refrigerant heating unit 27 heat the refrigerant (step S15). If the temperature T1 is within the target temperature range R (NO in step S14), the temperature control unit 423 does not perform the process of heating the refrigerant in the refrigerant heating unit 27.

[0049] The detection unit 421 detects the temperature T2 of the first gas by acquiring the temperature from the temperature sensor 33 and detects the humidity M of the first gas by acquiring the humidity from the humidity sensor 34 (step S16). The temperature control unit 423 identifies the target cooling temperature T3 corresponding to the temperature T2 and humidity M by referring to the temperature map stored in the storage unit 41 (step S17).

[0050] If the temperature T2 is greater than the target cooling temperature T3 (YES in step S18), the temperature control unit 423 causes the refrigerant cooling unit 28 to cool the refrigerant, thereby lowering the temperature of the refrigerant flowing to the gas cooling unit 20 (step S19). If the temperature T2 is less than or equal to the target cooling temperature T3 (NO in step S18), the temperature control unit 423 does not perform the process of cooling the refrigerant in the refrigerant cooling unit 28.

[0051] If the methane purification device 1 does not accept the operation to terminate the process (NO in step S20), the methane purification device 1 repeats the process from step S13 to step S19. If the methane purification device 1 accepts the operation to terminate the process (YES in step S20), the methane purification device 1 terminates the process.

[0052] <First variation> In the above description, the operation of the methane purification device 1 in which it decomposes methane contained in air has been illustrated, but it is not limited to this. The methane purification device 1 may also decompose methane contained in exhaust gas emitted by equipment or vehicles installed in the plant. For example, the methane purification device 1 may be installed in the exhaust passage downstream of the engine of a vehicle and decompose methane contained in the engine's exhaust gas.

[0053] <Second variation> In the above description, an example configuration was given in which the water generated by the cooling of the first gas by the gas cooling unit 20 is stored in the water tank 21, but the system is not limited to this configuration. The methane purification device 1 may have a drain hose (not shown) instead of the water tank 21, and the generated water may be drained through the drain hose. With this configuration, if the methane purification device 1 is installed in a location where drainage facilities are provided, the water can be drained using those facilities. Furthermore, the methane purification device 1 can be configured without a water tank 21, a water level sensor 35, a warning unit 36, and a purification control unit 424.

[0054] <Effects of Methane Purification Device 1> As described above, the methane purification device 1 comprises a pipeline 10 through which a first gas containing methane flows, a gas cooling unit 20 that cools the first gas by exchanging heat between the first gas flowing through the pipeline 10 and a refrigerant, an ozone supply unit 22 that supplies ozone to the first gas cooled by the gas cooling unit 20, a gas heating unit 23 located downstream of the gas cooling unit 20 in the pipeline 10 that heats the second gas by exchanging heat between the first gas flowing through the pipeline 10, a second gas containing ozone supplied by the ozone supply unit 22, and a refrigerant, and the gas cooling unit 20 The gas cooling section 20 and the gas heating section 23 are connected, and the system includes a circulation path 26 through which the refrigerant circulates between the gas cooling section 20 and the gas heating section 23, a refrigerant cooling section 28 located upstream of the gas cooling section 20 and downstream of the gas heating section 23 in the circulation direction of the circulation path 26 to lower the temperature of the refrigerant, a refrigerant heating section 27 located downstream of the gas cooling section 20 and upstream of the gas heating section 23 in the circulation direction of the circulation path 26 to raise the temperature of the refrigerant, and a catalyst 25 located downstream of the gas heating section 23 in the pipeline 10 to decompose methane contained in the second gas.

[0055] With the methane purification device 1 configured in this way, the methane purification device 1 can heat the second gas, which contains the first gas from which water vapor has been removed by the gas cooling unit 20 and the ozone supplied by the ozone supply unit 22, in the gas heating unit 23. As a result, the methane purification device 1 can react the methane and ozone contained in the second gas while suppressing the blockage of reaction sites on the catalyst 25 by the adhesion of water condensed from the water vapor contained in the second gas to the catalyst 25. Furthermore, by heating the second gas, which contains the first gas cooled by the gas cooling unit 20, in the gas heating unit 23, the methane purification device 1 can decompose methane at a temperature at which methane and ozone are likely to react.

[0056] 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]

[0057] 1. Methane purification system 10 conduit 11 Intake section 20 Gas Cooling Section 21 Water Tanks 22 Ozone Supply Department 22a AC power supply 22b electrode 23 Gas heating section 24 Methane decomposition section 25 Catalyst 26 Circulation path 27 Refrigerant heating section 28 Refrigerant Cooling Unit 31 Temperature sensor 33 Temperature Sensor 34 Humidity Sensor 35 Water level sensor 36 Warning section 41 Storage section 42 Control Unit 421 Detection Unit 423 Temperature Control Unit 424 Purification Control Unit

Claims

1. A pipeline through which the first gas containing methane flows, A gas cooling unit that cools the first gas by exchanging heat between the first gas and the refrigerant flowing through the pipeline, The gas cooling unit supplies ozone to the first gas that has been cooled by the gas cooling unit, A gas heating unit is provided downstream of the gas cooling unit in the pipeline and heats the second gas by exchanging heat between the first gas flowing through the pipeline, the second gas containing the ozone supplied by the ozone supply unit, and the refrigerant. The gas cooling section and the gas heating section are connected, and a circulation path is provided between the gas cooling section and the gas heating section through which the refrigerant circulates. A refrigerant cooling unit is provided upstream of the gas cooling unit and downstream of the gas heating unit in the circulation direction of the circulation path, and lowers the temperature of the refrigerant. A refrigerant heating unit is provided downstream of the gas cooling unit and upstream of the gas heating unit in the circulation direction of the circulation path, and raises the temperature of the refrigerant. A catalyst is provided downstream of the gas heating section in the aforementioned pipeline for decomposing the methane contained in the second gas, A methane purification device having the following features.

2. A detection unit for detecting the temperature of the catalyst, The system further includes a temperature control unit that causes the refrigerant heating unit to heat the refrigerant so that the temperature detected by the detection unit falls within a temperature range indicating a temperature at which the amount of methane decomposed by the catalyst in the second gas exceeds a predetermined proportion. The methane purification apparatus according to claim 1.

3. The system further includes a storage unit that stores a methane decomposition rate map showing the methane decomposition rate corresponding to the temperature of the catalyst for each type of catalyst. The temperature control unit determines the temperature range by referring to the methane decomposition rate map. The methane purification apparatus according to claim 2.

4. The system further comprises a methane decomposition section containing the catalyst, The temperature control unit obtains catalyst identification information for identifying the catalyst from the methane decomposition unit and identifies the temperature range for the type of catalyst corresponding to the catalyst identification information. The methane purification apparatus according to claim 3.

5. The catalyst includes zeolite, iron ion exchange zeolite, or cobalt ion exchange zeolite. The methane purification apparatus according to claim 1.

6. A detection unit for detecting the temperature and humidity of the first gas at the inlet of the pipeline, The system further includes a temperature control unit that identifies a target temperature for removing water vapor contained in the first gas based on the temperature and humidity, and causes the refrigerant cooling unit to cool the refrigerant so that the temperature of the first gas reaches the target temperature. The methane purification apparatus according to claim 1.

7. A water tank for storing water generated by cooling the first gas in the gas cooling unit, A warning light indicating whether the water tank is full or not, The system further includes a purification control unit that, when the amount of water stored in the water tank exceeds a predetermined amount, stops the gas cooling unit, the gas heating unit, the refrigerant cooling unit, and the refrigerant heating unit, and illuminates the warning light. The methane purification apparatus according to claim 1.

Images