Purification system

Abstract

Reduce the energy consumption when purifying methane. [Solution] The purification system S comprises a flow channel 101 through which a gas to be purified containing methane flows, a supply unit 110 provided in the flow channel 101 for supplying ozone to the gas to be purified, and a radiator 120 provided downstream of the supply unit 110 in the flow channel 101 for heat exchange between a heat transfer medium that cools a heat source 130 and the gas to be purified, wherein the radiator 120 has a catalyst that purifies methane in the gas under an ozone atmosphere.

Description

Technical Field

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[0001] The present invention relates to a purification system for purifying methane.

Background Art

[0002] A catalyst for decomposing methane, which is an air pollutant, in an ozone atmosphere is known. Patent Document 1 discloses a technique for purifying methane by heating a gas containing methane and ozone in a heating unit to 100° C. or higher and then bringing it into contact with a catalyst in which iron is supported on silica, zeolite, or the like.

Prior Art Documents

Patent Documents

[0007] The radiator may have the catalyst on at least one of the surfaces of the heat dissipation fins of the radiator and the surfaces of the pipelines through which the heat transfer medium flows.

[0008] The catalyst may also contain a cobalt ion exchange zeolite.

[0009] The supply unit supplies the ozone to the gas when the temperature of the heat transfer medium is above a predetermined temperature, and does not need to supply the ozone to the gas when the temperature is below the predetermined temperature.

[0010] The supply unit may supply ozone to the gas if the concentration of methane in the gas is above a threshold, and may not supply ozone to the gas if the concentration is below the threshold.

[0011] The supply unit may increase the amount of ozone supplied to the gas as the concentration of methane in the gas increases.

[0012] The supply unit may start supplying ozone to the gas when the temperature of the heat medium reaches a predetermined temperature or higher after the engine, which is the heat source, starts operating, and may continue supplying ozone to the gas when the temperature of the heat medium falls below the predetermined temperature after the engine stops operating. [Effects of the Invention]

[0013] According to the present invention, the energy consumption during methane purification can be reduced. [Brief explanation of the drawing]

[0014] [Figure 1] This is a diagram illustrating the configuration of the purification system. [Figure 2] This is a schematic diagram of a radiator. [Figure 3] This is a schematic diagram showing a magnified portion of a radiator. [Figure 4] This is a diagram to explain the methane purification rate. [Figure 5] This is a flowchart illustrating an example of a methane purification process. [Modes for carrying out the invention]

[0015] <Configuration of the purification system S> Figure 1 is a diagram illustrating the configuration of the purification system S. The purification system S is installed in vehicles and ships equipped with a heat source 130, such as an engine. The purification system S includes a flow path section 101, a methane sensor 102, an intake section 103, a supply section 110, a radiator 120, a heat source 130, a heat transfer medium circuit 131, a temperature sensor 132, and a supply control device 200. The purification system S adds ozone to a gas containing methane and reacts the ozone and methane on a catalyst to decompose the methane and produce water and nitrogen dioxide. In the following description, the decomposition of methane to produce water and nitrogen dioxide is sometimes referred to as "purifying methane."

[0016] The flow path 101 is through which the gas to be purified, which contains methane, flows. The gas to be purified is, for example, the atmosphere. When the purification system S is installed in a vehicle, the flow path 101 is surrounded by other devices installed in the engine compartment. In other words, the flow path 101 is a gap created by other devices installed in the engine compartment.

[0017] The methane sensor 102 is installed in the flow path section 101 and detects the amount of methane in the gas to be purified. The methane sensor 102 detects, for example, the methane concentration in the gas to be purified as the amount of methane. The methane sensor 102 outputs the detected methane concentration to the supply control device 200.

[0018] The intake section 103 is, for example, an intake fan provided within the flow path section 101. The intake section 103 draws the gas to be purified into the flow path section 101. The intake section 103 is located downstream of the methane sensor 102 in the flow path section 101. In Figure 1, the intake section 103 draws in the gas to be purified so that it flows through the flow path section 101 from left to right in the z-direction.

[0019] The supply unit 110 is provided between the methane sensor 102 and the intake unit 103. The supply unit 110 supplies ozone to the gas to be purified. The supply unit 110 has, for example, an AC power source 111 and an electrode 112 coated with a dielectric such as glass. The supply unit 110 performs a process of generating ozone (so-called silent discharge method) by applying an AC voltage from the AC power source 111 to the electrode 112. The supply unit 110 may generate ozone by performing a process of discharging on the surface of the dielectric covering the electrode 112 (so-called surface discharge method), 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 radiator 120 is provided downstream of the supply unit 110 in the flow path unit 101. The radiator 120 is provided between the supply unit 110 and the intake unit 103. The radiator 120 is provided downstream of the heat source 130 in a heat medium circuit 131 through which a heat medium for cooling the heat source 130 flows. The radiator 120 cools the heat source 130 by exchanging heat between the heat medium and the gas to be purified. The heat medium is, for example, water or ethylene glycol, but is not limited thereto.

[0021] [[ID=,10]]FIG. 2 is a schematic diagram of the radiator 120. The radiator 120 has a plurality of pipes 121 and a plurality of heat radiation fins 122. The pipe 121 is a pipe through which the heat medium flows. The pipe 121 is connected to the heat medium circuit 131 at connection points 133 and 134. Specifically, the pipe 121 is connected to the heat medium circuit 131 downstream of the heat source 130 at the connection point 133 and to the heat medium circuit 131 upstream of the heat source 130 at the connection point 134.

[0022] The pipes 121 are arranged so that the heat transfer medium flows in both the horizontal (x-direction) and vertical (y-direction). The heat transfer medium discharged from the heat source 130 enters the pipes 121 at connection point 133 and flows horizontally (x-direction) into multiple pipes 121. The heat transfer medium flows from top to bottom in the y-direction within each pipe 121. In this embodiment, there are five pipes 121 through which the heat transfer medium flows from top to bottom in the y-direction, but there may be six or more, or four or fewer. The heat transfer medium exits the pipes 121 at connection point 134, passes through the heat transfer medium circuit 131, and enters the heat source 130.

[0023] Each of the multiple heat dissipation fins 122 is connected to a pipe 121. Each heat dissipation fin 122 is positioned to connect two pipes 121. Each heat dissipation fin 122 is positioned so that the gas to be purified can pass between them. A gap is provided between each heat dissipation fin 122 and a pipe 121. The gap is the region enclosed by the heat dissipation fin 122 and the pipe 121. As the heat transfer medium flows through the pipe 121, the heat from the heat transfer medium is transferred to the heat dissipation fin 122, and heat exchange occurs between the gas to be purified flowing through the gap and the heat dissipation fin 122. The radiator 120 is a so-called corrugated type radiator, but other types of radiators may also be used.

[0024] The heat source 130 is, for example, an engine. An engine generates power by burning and expanding a mixture of fuel and intake air. The engine is, for example, a diesel engine installed in an automobile, but it may also be a gasoline engine. However, the heat source 130 is not limited to an engine as long as it is a device that requires cooling. The heat source 130 may be, for example, a motor, a fuel cell, or a storage battery, and it may be a device that is cooled using the radiator 120.

[0025] The temperature sensor 132 is a sensor that detects the temperature of the heat transfer medium. The tip of the temperature sensor 132 is inserted into the heat transfer medium circuit 131 and detects the temperature of the heat transfer medium flowing through the heat transfer medium circuit 131. The temperature sensor 132 outputs the detected temperature of the heat transfer medium to the supply control device 200.

[0026] The catalyst 150 is provided on the radiator 120. The catalyst 150 is provided, for example, on at least one of the surfaces of the pipe 121 and the heat dissipation fins 122 of the radiator 120. Figure 3 is a schematic diagram of a magnified portion of the radiator 120. In Figure 3, the catalyst 150 is shown in dark gray. The catalyst 150 is provided on the surface of the heat dissipation fins 122. Specifically, the catalyst 150 is provided on both sides of the heat dissipation fins 122 so as to cover the surface of the heat dissipation fins 122. Note that there may be areas of the catalyst 150 that do not cover the surface of the heat dissipation fins 122.

[0027] Catalyst 150 purifies methane in the gas to be purified under an ozone atmosphere. Catalyst 150 purifies methane by reacting ozone with methane on its surface, thereby decomposing the methane to produce water and carbon dioxide. Catalyst 150 includes, for example, at least one of zeolite, iron ion exchange zeolite, and cobalt ion exchange zeolite. Catalyst 150 is not limited to these, and any catalyst capable of purifying methane under an ozone atmosphere is acceptable.

[0028] The methane purification rate of catalyst 150 changes with temperature. Figure 4 is a diagram illustrating the methane purification rate. The horizontal axis of Figure 4 shows the temperature of catalyst 150 (corresponding to the temperature of the heat transfer medium), and the vertical axis shows the methane purification rate. In Figure 4, catalysts M1, M2, and M3 are shown as types of catalyst 150. Catalyst M1 is a cobalt ion exchange zeolite (Co-BEA) in which cobalt is supported on a β-type skeleton structure zeolite. Catalyst M2 is an iron ion exchange zeolite (Fe-BEA) in which iron is supported on a β-type skeleton structure zeolite. Catalyst M3 is a β-type skeleton structure zeolite (BEA). As shown in Figure 4, regardless of whether catalyst 150 is catalyst M1, catalyst M2, or catalyst M3, when the temperature is below 150°C, the methane purification rate increases with increasing temperature.

[0029] Since the catalyst 150 is installed in the radiator 120, it is heated by the heat of the radiator 120. In other words, the purification system S can heat the catalyst 150 to the same temperature as the heat transfer medium by the heat transferred from the heat source 130 to the radiator 120 via the heat transfer medium. As a result, the purification system S can heat the catalyst 150 using the heat from the heat source 130 without using a heater or the like to heat the catalyst 150. Consequently, the purification system S can reduce the energy consumption when purifying methane compared to when the catalyst 150 is heated using a heater or the like.

[0030] As shown in Figure 4, the purification rate of catalyst 150 decreases if the temperature becomes too high. However, when the heat transfer medium is water or ethylene glycol, the temperature of the heat transfer medium does not exceed 120°C. Therefore, the purification rate of catalyst 150 does not decrease due to the catalyst temperature becoming too high.

[0031] Incidentally, if the amount of methane in the gas to be purified is high, more ozone needs to be supplied. Also, if the gas to be purified does not contain methane, supplying ozone will waste energy.

[0032] Therefore, the supply control device 200 controls the amount of ozone supplied to the gas to be purified according to the amount of methane contained in the gas to be purified. The configuration of the supply control device 200 will be described below. The supply control device 200 has a storage unit 210 and a control unit 220. The storage unit 210 is a storage medium including ROM (Read Only Memory), RAM (Random Access Memory), and hard disk. The storage unit 210 stores the program to be executed by the control unit 220.

[0033] The control unit 220 is a computing resource that includes a processor, such as a CPU (Central Processing Unit). The control unit 220 performs the functions of the acquisition unit 221 and the supply control unit 222 by executing a program stored in the storage unit 210.

[0034] The acquisition unit 221 acquires the methane concentration detected by the methane sensor 102. The acquisition unit 221 also acquires the temperature of the catalyst 150. Since the temperature of the catalyst 150 is approximately equal to the temperature of the heat transfer medium, the acquisition unit 221 may acquire the temperature of the heat transfer medium detected by the temperature sensor 132 as the temperature of the catalyst 150. The acquisition unit 221 outputs the acquired methane concentration and the temperature of the heat transfer medium to the supply control unit 222.

[0035] The supply control unit 222 controls the amount of ozone supplied to the gas to be purified. When the supply unit 110 supplies ozone to the gas to be purified by discharge, the supply control unit 222 increases the amount of ozone supplied to the gas to be purified by increasing at least one of the voltage and frequency of the AC voltage applied by the AC power supply 111 to the electrode 112 of the supply unit 110.

[0036] The supply control unit 222 supplies ozone to the gas to be purified when the temperature of the heat transfer medium, acquired by the acquisition unit 221 as the temperature of the catalyst 150, is above a predetermined temperature. The predetermined temperature is the temperature at which the methane purification rate, which indicates the amount of methane that the catalyst 150 can purify, becomes above a predetermined value. The predetermined value is, for example, 50%, and preferably 80%. When the catalyst is cobalt ion exchange zeolite (see M1 in Figure 4), the temperature at which the methane purification rate becomes 50% is 60°C, and the temperature at which the methane purification rate becomes 80% is 75°C. As a result, the supply control unit 222 can supply ozone when the catalyst 150 is able to sufficiently purify methane.

[0037] The supply control unit 222 does not supply ozone to the gas to be purified if the temperature of the heat transfer medium is below a predetermined temperature. In other words, the supply control unit 222 does not supply ozone to the gas to be purified if the temperature of the heat transfer medium is low and the catalyst 150 is not heated, resulting in the methane purification rate of the catalyst 150 falling below a predetermined value. As a result, the supply control unit 222 does not supply ozone when the methane purification rate of the catalyst 150 is low, thus suppressing energy waste.

[0038] The supply control unit 222 supplies ozone to the gas to be purified when the methane concentration of the gas to be purified is above a threshold. The threshold is, for example, the lower limit at which the methane sensor 102 can detect methane. When the methane concentration is above the threshold, the supply control unit 222 increases the amount of ozone supplied to the gas to be purified as the methane concentration increases. Specifically, the supply control unit 222 increases at least one of the frequency and voltage value of the AC voltage applied to the electrode 112 of the supply unit 110 as the methane concentration increases. In this way, the supply control unit 222 can supply more ozone to the gas to be purified as the amount of methane in the gas to be purified increases. As a result, the reaction between ozone and methane on the catalyst 150 becomes easier, and the methane purification rate improves.

[0039] The supply control unit 222 does not supply ozone to the gas to be purified if the methane concentration is below a threshold. As a result, if the amount of methane in the gas to be purified is so low that it cannot be detected by the methane sensor 102, the supply control unit 222 does not supply ozone to the gas to be purified, thereby suppressing energy waste.

[0040] The supply control unit 222 may supply ozone to the gas to be purified depending on the operating state of the heat source 130. For example, the supply control unit 222 may start supplying ozone after the engine, which is the heat source 130, has started operating. Specifically, after the engine has started operating, the supply control unit 222 does not supply ozone to the gas to be purified while the temperature of the heat transfer medium is below a predetermined temperature, and starts supplying ozone to the gas to be purified when the temperature of the heat transfer medium reaches or exceeds the predetermined temperature. As a result, the supply control unit 222 can supply ozone to the gas to be purified when the catalyst 150 has been heated and is in a state where it can sufficiently purify methane. Consequently, the supply control unit 222 can efficiently use energy for methane purification.

[0041] Incidentally, even after the engine, which is the heat source 130, stops operating, the engine, heat transfer medium, and catalyst 150 remain at high temperatures for a while. Therefore, the supply control unit 222 continues to supply ozone to the gas to be purified until the temperature of the heat transfer medium falls below a predetermined temperature after the engine stops operating. In this case, the intake unit 103 continues to draw in the gas to be purified. In this way, the catalyst 150 can purify methane even after the engine has stopped operating.

[0042] The supply control unit 222 stops supplying ozone to the gas to be purified if the temperature of the heat transfer medium falls below a predetermined temperature after the engine has stopped operating. This allows the supply control unit 222 to suppress the supply of ozone when the temperature of the catalyst 150 drops and the methane purification rate decreases, thereby reducing energy waste.

[0043] [Process to purify methane] Figure 5 is a flowchart illustrating an example of a methane purification process. For example, the methane purification process is performed after the engine, which is the heat source 130, starts operating.

[0044] The acquisition unit 221 acquires the temperature of the heat transfer medium (step S1). Specifically, the acquisition unit 221 acquires the temperature of the heat transfer medium detected by the temperature sensor 132. The supply control unit 222 determines whether the temperature of the heat transfer medium is above a predetermined temperature (step S2). If the temperature of the heat transfer medium is below the predetermined temperature (No in step S2), the supply control unit 222 returns to step S1 and waits until the temperature of the heat transfer medium reaches or exceeds the predetermined temperature.

[0045] The acquisition unit 221 acquires the methane concentration (step S3) if the temperature of the heat transfer medium is above a predetermined temperature (Yes in step S2). Specifically, the acquisition unit 221 acquires the methane concentration detected by the methane sensor 102.

[0046] The supply control unit 222 determines whether the methane concentration is above or below the threshold (step S4). If the methane concentration is below the threshold (No in step S4), the supply control unit 222 returns to step S3 and waits until the methane concentration becomes above or below the threshold.

[0047] The supply control unit 222 supplies ozone to the gas to be purified (step S5) if the methane concentration is above a threshold (Yes in step S4). For example, the supply control unit 222 supplies a larger amount of ozone to the gas to be purified the higher the methane concentration. The supply control unit 222 repeats the process from step S1 to step S5 until the engine stops, and the supply control device 200 repeats the process from step S1 to step S5 until the engine stops.

[0048] The supply control unit 222 supplies ozone to the gas to be purified until the temperature of the heat transfer medium falls below a predetermined temperature when the engine stops operating. When the temperature of the heat transfer medium falls below the predetermined temperature, the supply control unit 222 stops supplying ozone to the gas to be purified.

[0049] [Effects of the Purification System S] As described above, the purification system S includes a flow channel 101 through which a gas to be purified containing methane flows, a supply unit 110 provided in the flow channel 101 for supplying ozone to the gas to be purified, and a radiator 120 provided downstream of the supply unit 110 in the flow channel 101 for heat exchange between a heat transfer medium that cools the heat source 130 and the gas to be purified. The radiator 120 has a catalyst 150 that purifies methane in the gas to be purified under an ozone atmosphere.

[0050] In the purification system S, when the temperature of the radiator 120 rises due to the heat from the heat source 130, the catalyst 150 is heated and its temperature rises. In this way, the purification system S can heat the catalyst 150 without using a heater or other means to heat the catalyst 150. As the temperature of the catalyst 150 rises, the methane purification rate improves, so the purification system S can purify methane more efficiently. Furthermore, since the purification system S heats the catalyst 150 using the heat from the heat source 130, it can reduce the energy consumption when purifying methane from the atmosphere compared to when a heater is used to heat the catalyst 150.

[0051] 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]

[0052] S Purification System 101 Flow channel section 102 Methane Sensor 103 Intake section 110 Supply section 120 Radiator 121 pipe 122 heat dissipation fins 130 Heat source 131 Heat carrier circuit 132 Temperature Sensor 150 catalysts 200 Supply control device 210 Storage section 220 Control Unit 221 Acquisition Department 222 Supply Control Unit

Claims

1. A channel through which a gas containing methane flows, A supply unit provided in the flow path section for supplying ozone to the gas, A radiator is provided in the flow path section downstream of the supply section and exchanges heat between a heat transfer medium for cooling the heat source and the gas, It has, The radiator has a catalyst for purifying the methane in the gas under an ozone atmosphere. Purification system.

2. The radiator has the catalyst on at least one of the surfaces of the heat dissipation fins of the radiator and the surfaces of the pipes through which the heat transfer medium flows. The purification system according to claim 1.

3. The catalyst includes a cobalt ion exchange zeolite. The purification system according to claim 1 or 2.

4. The supply unit supplies the ozone to the gas when the temperature of the heat transfer medium is above a predetermined temperature, and does not supply the ozone to the gas when the temperature is below the predetermined temperature. The purification system according to claim 1 or 2.

5. The supply unit supplies ozone to the gas when the concentration of methane in the gas is above a threshold, and does not supply ozone to the gas when the concentration is below the threshold. The purification system according to claim 1 or 2.

6. The supply unit increases the amount of ozone supplied to the gas as the concentration of methane in the gas increases. The purification system according to claim 1 or 2.

7. The aforementioned supply unit is After the engine, which is the heat source, starts operating, the supply of ozone to the gas is started when the temperature of the heat transfer medium reaches a predetermined temperature or higher. After the engine stops operating, the supply of ozone to the gas continues until the temperature of the heat transfer medium falls below the predetermined temperature. The purification system according to claim 1 or 2.

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