Water electrolysis-integrated methanation cell, and electrolysis methanation device using the same

Abstract

To provide a water electrolysis-integrated methanation cell that enables water electrolysis and methanation, allowing for relatively easy temperature management, while also achieving an excellent methanation reaction rate.SOLUTION: A water electrolysis-integrated methanation cell includes: a water electrolytic part consisting of an anode part that electrolyzes water or water vapor to produce oxygen and hydrogen ions, a cathode part that reduces hydrogen ions to produce hydrogen, and a bipolar plate; and a methanation part that reduces carbon dioxide to produce a carbon compound. The bipolar plate is disposed between the anode part and the cathode part and has channels on both surfaces. The methanation part has a first channel for flowing cooling water to cool the heat generated by the methanation reaction and a second channel for supplying the water vapor generated from the cooling water due to the heat generation to the water electrolytic part.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present disclosure relates to an integrated water electrolysis methanation cell and an electrolytic methanation device using the same. [Background technology]

[0002] In recent years, the need for methane fermentation processing has increased as an effort to reduce carbon dioxide emissions in the waste treatment field. In addition, as a method of reducing carbon dioxide, attempts are being made to separate and collect carbon dioxide from other gases, and store and inject it deep underground, such as "CCS (Carbon dioxide Capture and Storage)". In the future, there will also be a demand for "CCUS (Carbon dioxide Capture Utilization and Storage)", that is, to utilize the separated and stored carbon dioxide.

[0003] On the other hand, from the perspective of carbon neutrality, there is also a demand to replace part of the gas supply with e-methane, and consideration is being given to the introduction of e-methane gas into the gas supply.

[0004] To date, there have been reports of renewable energy utilization systems that include a water electrolysis device that produces hydrogen and oxygen using surplus electricity from a renewable energy power generation device, and a methanation facility that synthesizes the hydrogen produced in the water electrolysis device with carbon dioxide generated within the system to produce hydrocarbon fuels such as methane (Patent Document 1). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2020-45430 A Summary of the Invention [Problem to be solved by the invention]

[0006] In the technology described in Patent Document 1, water electrolysis and methanation are performed in separate devices (facilities), which requires large-scale facilities. Therefore, the present inventors have investigated performing water electrolysis and methanation in a single device rather than in separate devices.

[0007] One issue to be addressed in this regard is that if overvoltage occurs during the methanation reaction or water electrolysis, both of these reactions will become exothermic, making temperature control difficult.

[0008] Therefore, a main object of the present disclosure is to provide a water electrolysis integrated methanation cell that can perform water electrolysis and methanation, has relatively easy temperature control, and is excellent in methanation reaction rate. [Means for solving the problem]

[0009] One aspect of the present disclosure is to provide a method for producing a water electrolysis unit including an anode section that electrolyzes water or water vapor to generate oxygen and hydrogen ions, a cathode section that reduces the hydrogen ions to generate hydrogen, and a bipolar plate; A methanation unit that reduces carbon dioxide to generate carbon compounds, The bipolar plate is provided between the anode portion and the cathode portion and has flow paths on both sides. The methanation unit relates to a water electrolysis integrated methanation cell, the methanation unit having a first flow path through which cooling water for cooling heat generated by a methanation reaction flows, and a second flow path through which water vapor generated from the cooling water by the heat generation is supplied to the water electrolysis unit.

[0010] An electrolytic methanation device according to yet another aspect of the present disclosure includes the above-described integrated water electrolysis methanation cell, and a power source that applies a current between the anode portion and the cathode portion. Effect of the Invention

[0011] According to the present disclosure, it is possible to provide an integrated water electrolysis methanation cell that is capable of performing water electrolysis and methanation, that allows relatively easy temperature control and has an excellent methanation reaction rate, and to provide a stacked methanation cell and an electrolytic methanation device using the same. [Brief description of the drawings]

[0012] [Figure 1] FIG. 1 is a schematic diagram showing an example of a water electrolysis integrated methanation cell according to the present embodiment. [Diagram 2] FIG. 2 is a schematic diagram showing an example of a bipolar plate that can be used in the integrated water electrolysis methanation cell of this embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] Hereinafter, embodiments of the present disclosure will be specifically described with reference to the drawings, but the present disclosure is not limited thereto. In addition, all drawings used in this specification are schematic diagrams (schematic diagrams).

[0014] [Water electrolysis integrated methanation cell] The methanation cell integrated with water electrolysis of this embodiment is a methanation cell that is used in a methanation device and integrates water electrolysis and methanation. The methanation cell integrated with water electrolysis of this embodiment can perform water electrolysis and methanation using carbon dioxide and water (or water vapor) as raw materials to obtain a desired carbon compound. The carbon compound obtained by the methanation cell of this embodiment is methane (CH 4 ), carbon monoxide (CO), and methanol.

[0015] 1 is a schematic diagram showing an example of the configuration of a water electrolysis integrated methanation cell (hereinafter also simply referred to as a "methanation cell") according to a first embodiment of the present disclosure. The water electrolysis integrated methanation cell 1 of this embodiment includes a water electrolysis unit 10 including an anode unit 11, a cathode unit 12, and a bipolar plate 13, and a methanation unit 20. The bipolar plate 13 is provided between the anode unit 11 and the cathode unit 12, and has flow paths on both sides. The methanation unit 20 includes a first flow path 23 through which cooling water flows for cooling heat generated by a methanation reaction, and a second flow path 24 through which water vapor generated from the cooling water by the heat generation is supplied to the water electrolysis unit.

[0016] With this configuration, first, water electrolysis and methanation can be performed in one facility. In other words, the gases that need to be supplied are carbon dioxide and water (water vapor), so there is an advantage that hydrogen gas does not leave the system and handling is simplified. Furthermore, the integrated water electrolysis methanation cell of the present disclosure is relatively easy to control the temperature and has an excellent methanation reaction rate.

[0017] The methanation cell 1 is not particularly limited, but may be fixed by a pair of support plates (not shown) or may be covered by a housing (not shown). The support plates and housing are preferably made of a material with low chemical reactivity and high conductivity. Examples of such materials include metal materials such as SUS, or carbon. The shape of the methanation cell 1 is not particularly limited, and may be a box shape or a cylindrical shape.

[0018] As long as the methanation cell 1 includes the water electrolysis unit 10 and the methanation unit 20 as described above, other configurations are not particularly limited. As shown in FIG. 1 , an insulating layer 30 may be provided between the water electrolysis unit 10 and the methanation unit 20 to prevent physical contact between the water electrolysis unit 10 and the methanation unit 20 and suppress electrical short-circuiting.

[0019] An insulating plate or a gas layer such as air can be used as the insulating layer 30. Specifically, for example, a separator made of a cellulose film, a polymer, a ceramic, a composite material of a polymer and a ceramic, or the like can be used.

[0020] The water electrolysis unit 10 includes an anode unit 11 that electrolyzes water or water vapor to produce oxygen and hydrogen ions, and a cathode unit 12 that reduces the hydrogen ions produced in the anode unit 11 to produce hydrogen.

[0021] The anode section 11 typically includes an anode, a flow path for supplying water or water vapor to the anode, and an electrolyte having hydrogen ion conductivity. 2 O) oxidation reaction occurs, and oxygen (O 2 ) and hydrogen ions (H + ) is an electrode (oxidation electrode).

[0022] The anode is preferably made of a catalyst material (anode catalyst material) capable of electrolyzing water or water vapor to generate oxygen and hydrogen ions. Specific examples of the catalyst material include metals such as platinum (Pt), palladium (Pd), and nickel (Ni), alloys and intermetallic compounds containing these metals, binary metal oxides such as manganese oxide (Mn-O), iridium oxide (Ir-O), nickel oxide (Ni-O), cobalt oxide (Co-O), iron oxide (Fe-O), tin oxide (Sn-O), indium oxide (In-O), ruthenium oxide (Ru-O), lithium oxide (Li-O), and lanthanum oxide (La-O), ternary metal oxides such as Ni-Co-O, Ni-Fe-O, La-Co-O, Ni-La-O, and Sr-Fe-O, quaternary metal oxides such as Pb-Ru-Ir-O and La-Sr-Co-O, and metal complexes such as Ru complexes and Fe complexes. Among these, it is preferable to use Pt or iridium oxide, etc., from the viewpoint of reducing the overvoltage.

[0023] The anode may be composed of only the above-mentioned anode catalyst material, but may further include a substrate. As the substrate for the anode, a substrate having a structure capable of diffusing water and generated oxygen, such as a porous structure such as a mesh material, a punching material, a porous body, or a sintered metal fiber body, is suitable. In addition, the substrate is preferably composed of a metal material such as titanium (Ti), nickel (Ni), iron (Fe), or an alloy containing at least one of these metals (e.g., SUS).

[0024] When an oxide as described above is used as the anode catalyst material of the anode, it is preferable to form the anode by adhering or laminating the anode catalyst material on the surface of a substrate made of the above-mentioned metal material.

[0025] The anode section 11 is provided with a flow path for supplying water or steam to the anode. In the methanation cell 1, a second flow path 24, which will be described later, is used as the flow path for supplying water or steam to the anode. The water supplied to the anode may be used as is, or may be in the form of steam. In this regard, the water supplied from the second flow path 24 is steam generated in the methanation section 20, so that the electrolysis reaction can be carried out efficiently.

[0026] The anode section 11 may also be provided with an outlet for discharging unused excess water (water vapor) and oxygen generated together with hydrogen ions in the electrolysis reaction. This outlet may be the outlet of the second flow path 24.

[0027] An electrolyte is usually provided between the anode and the cathode described later. The electrolyte to be used is not particularly limited as long as it has hydrogen ion conductivity, and polymer electrolytes such as polyvinylidene fluoride, polyacrylic acid, polyethylene oxide, polyacrylonitrile, and polymethyl methacrylate, as well as cesium hydrogen phosphate, an aqueous potassium chloride solution, and an aqueous sodium chloride solution can be used. The form of the electrolyte is also not particularly limited, and for example, the electrolyte may be a sheet-like membrane type, in which case an electrolyte membrane may be provided.

[0028] Next, the cathode section 12 in the water electrolysis section 10 will be described.

[0029] The cathode section 12 has a cathode that reduces hydrogen ions to generate hydrogen. A hydrogen ion reduction reaction mainly takes place in the cathode. The cathode is preferably composed of a catalyst material (cathode catalyst material) capable of the reduction reaction. Specific examples of the catalyst material include palladium-silver, platinum, iridium, platinum-coated titanium, platinum-supported carbon, palladium-supported carbon, cobalt glyoxime, and nickel glyoxime. An ionomer may be mixed into the cathode catalyst material.

[0030] The cathode may be composed of only the above-mentioned cathode catalyst material, or may further include a substrate such as carbon paper, carbon cloth, carbon nonwoven fabric, or titanium nonwoven fabric.

[0031] The cathode can be obtained, for example, by applying a mixture of the above-mentioned cathode catalyst material and an ionomer to the above-mentioned substrate.

[0032] The anode and the cathode can be connected to a power source, for example, by using a terminal board, etc. An electric current can be supplied between the anode and the cathode from the power source, and an electrolytic reaction can be carried out in the water electrolysis unit 10.

[0033] The hydrogen thus generated in the water electrolysis unit 10 is supplied to the methanation unit 20, which will be described later, through a flow path (third flow path 14). The third flow path 14 is not particularly limited, but is preferably made of a material that has low chemical reactivity and high conductivity. Examples of such materials include metal materials such as SUS, and carbon. Furthermore, the third flow path 14 may be provided with a flow controller that adjusts the amount of hydrogen supplied to the methanation unit 20, a measuring device that measures the amount of hydrogen, and the like.

[0034] The water electrolysis unit 10 of this embodiment further includes a bipolar plate 13 between the anode unit 11 and the cathode unit 12. The bipolar plate 13 blocks various supply gases and generated gases between the anode unit 11 and the cathode unit 12, and has flow paths for carrying water (water vapor) supplied to the anode and hydrogen generated at the cathode.

[0035] By providing such a bipolar plate 13, it is possible to reduce the number of members and parts used in the methanation cell 1. This is because the bipolar plate 13 can be used as a substitute for the anode section 11 and the cathode section 12. As a result, the device can be made more compact.

[0036] 2 shows an example of the bipolar plate 13. A bipolar plate used in technical fields such as fuel cells can be used as the bipolar plate 13. The material may be metal or carbon, but metal is preferable from the viewpoint of low electrical resistance.

[0037] As described above, the bipolar plate 13 has flow paths on both sides, and while flow path A is shown on one side in FIG. 2, a similar flow path B is also formed on the other side. By connecting flow path A of the bipolar plate 13 to the second flow path 24, the water vapor generated in the methanation section 20 can be transported to the anode. In addition, by connecting flow path B of the bipolar plate 13 to the third flow path 14, the hydrogen generated at the cathode can be transported to the methanation section 20.

[0038] The bipolar plate 13 may be a single piece, but as shown in Fig. 1, two or more bipolar plates can be stacked between the anode section 11 and the cathode section 12. By stacking a plurality of bipolar plates 13 in this way, the anode section 11 and the cathode section 12 can be stacked, which has the advantage of making the device more compact than if they were separate devices.

[0039] Next, the methanation unit 20 included in the methanation cell 1 of this embodiment will be described. In the methanation unit 20, the methanation reaction and water vapor generation take place. Since the methanation reaction is an exothermic reaction, when the methanation reaction is cooled with cooling water, the cooling water turns into water vapor due to the heat generated by methanation. The obtained water vapor is supplied to the water electrolysis unit 10 described above and used for the charge reaction. In this manner, in this embodiment, the cooling of the methanation reaction and the generation of water vapor can be performed simultaneously, which has the advantages of facilitating temperature management and improving reaction efficiency.

[0040] The methanation unit 20 uses hydrogen generated at the cathode and supplied from the third flow path 14 to produce carbon dioxide (CO 2 In the methanation section 20, carbon dioxide (CO 2 ) to methane (CH 4 ), carbon monoxide (CO), methanol, and other carbon compounds are produced (methanation reaction).

[0041] In order to carry out the methanation reaction, the methanation section 20 is typically equipped with a fourth flow path 25 that supplies carbon dioxide to the methanation section 20, a catalyst 21 that reduces the carbon dioxide to produce carbon compounds, and an outlet 26 that discharges the produced carbon compounds.

[0042] The fourth flow path 25 that supplies carbon dioxide is connected to a carbon dioxide supply unit (not shown), and is preferably made of a material with low chemical reactivity, although there is no limitation as long as it can supply carbon dioxide to the methanation unit 20. Examples of such materials include metal materials such as SUS, and carbon. Furthermore, the fourth flow path 25 may be provided with a flow controller that adjusts the amount of carbon dioxide supplied to the methanation unit 20, a measuring device that measures the amount of carbon dioxide, and the like.

[0043] The catalyst 21 is made of a catalyst material. Specific examples of catalyst materials that can be used in this embodiment include metals such as zirconium (Zr), gold (Au), silver (Ag), copper (Cu), platinum (Pt), palladium (Pd), nickel (Ni), cobalt (Co), iron (Fe), manganese (Mn), titanium (Ti), cadmium (Cd), zinc (Zn), indium (In), gallium (Ga), lead (Pb), and tin (Sn), metal materials such as alloys and intermetallic compounds containing at least one of the above metals, oxides of the above metals, carbon materials such as carbon (C), graphene, CNT (carbon nanotube), fullerene, and Ketjen Black, and metal complexes such as Ru complexes and Re complexes.

[0044] The shape of the catalyst in the methanation section 20 is not particularly limited, and various shapes such as powder, plate, mesh, wire, particle, porous, thin film, and island shapes can be used.

[0045] Carbon dioxide is supplied to the methanation unit 20 from the fourth flow path 25. Specifically, for example, a gas containing carbon dioxide is introduced by a flow controller (not shown). The fourth flow path 25 may merge with the third flow path 14 that carries the hydrogen generated at the cathode, in which case a mixed gas of hydrogen and carbon dioxide is supplied to the methanation unit 20. The introduced carbon dioxide is reduced by contacting with the catalyst 21 of the methanation unit 20, and carbon compounds such as methane are generated. The generated gas containing carbon compounds (e.g., methane gas) is discharged from an outlet 26. This outlet 26 may be the outlet of the third flow path 14.

[0046] The methanation unit 20 in this embodiment has a first flow path 23 through which cooling water for cooling the methanation heat flows, and a second flow path 24 through which water vapor generated from the cooling water by the methanation heat is supplied to the water electrolysis unit 10. With this configuration, in the methanation unit 20, water vapor is generated from the cooling water for cooling the methanation heat. That is, the methanation cell 1 of this embodiment can use the water vapor generated from the water used for cooling for the electrolysis reaction in the water electrolysis unit 10 while cooling the heat generated from the methanation reaction. As a result, the temperature management of the equipment can be facilitated, and the methanation reaction rate can be improved. The first flow path 23 and the second flow path 24 are preferably made of a material with low chemical reactivity. Furthermore, it is preferable to use a material with high thermal conductivity for the first flow path 23. Examples of such materials include metal materials such as SUS, carbon, and the like. Furthermore, the first flow path 23 may be provided with a thermometer for measuring the temperature of the methanation unit 20, a flow rate controller for adjusting the flow rate of the cooling water supplied according to the temperature, and the like. The second flow path 24 may also be provided with a flow rate controller that adjusts the amount of water or water vapor supplied to the water electrolysis unit 10, a measuring device that measures the amount of water or water vapor, and the like.

[0047] In order to obtain a better effect from the cooling water in the methanation section 20, it is preferable that the inlet of the first flow path 23 and the outlet of the second flow path 24 are as far away from each other as possible. In other words, it is preferable that the inlet of the first flow path 23 and the outlet of the second flow path 24 are provided above and below the methanation section 20, respectively. There is no particular limitation as to which is the above and which is the below.

[0048] 1, cooling water is supplied from a first flow path 23 provided above the methanation unit 20, and flows through the cooling unit 22 to cool the heat generated by the methanation reaction in the adjacent catalyst 21. As the cooling water comes into contact with the heat generated by the methanation reaction and flows downward in the methanation unit 22, it becomes water vapor due to the heat generated by methanation from the adjacent catalyst 21, and the water vapor is transported from the second flow path 24 below to the water electrolysis unit 10. The longer the distance that the cooling water flows through the cooling unit 22, the more improved the cooling efficiency and the rate of water vapor production.

[0049] [Stacked methanation cell] In the methanation section 20 of the methanation cell, the catalyst 21 and the cooling section 22 may be a single layer, or as shown in Figure 1, a structure in which a plurality of catalysts 21 and cooling sections 22 are stacked can be used. By forming the methanation section 20 into a stacked structure in this way, a stacked methanation cell can be obtained, which allows electrolytic methanation to be performed on a larger scale than a single-layer methanation cell.

[0050] In addition, in the water electrolysis unit 10, the anode unit 11 and the cathode unit 12 may be a single layer, or as shown in Fig. 1, a structure in which a plurality of anode units 11 and cathode units 12 are stacked using bipolar plates 13 is also possible. This has the advantage that the device can be made more compact than if they were installed separately.

[0051] [Electrolytic methanation device] Next, an electrolytic methanation device including the above-mentioned integrated water electrolysis methanation cell will be described.

[0052] The electrolytic methanation device of the present embodiment is an electrolytic methanation device including the above-mentioned integrated water electrolysis methanation cell and a power source that supplies current between the anode portion and the cathode portion.

[0053] Examples of power sources that can be used in the present embodiment include, but are not limited to, ordinary commercially available power sources, batteries, etc. In addition, a device that can supply renewable energy such as a solar cell as power can be used as the power source.

[0054] The electrolytic methanation device of the present embodiment is not particularly limited in other configuration as long as it is an electrolytic device including the above-mentioned integrated water electrolysis methanation cell and a power source. The configuration of a known carbon dioxide electrolysis device or the like can be appropriately adopted as necessary.

[0055] The electrolytic methanation device of the present embodiment can produce carbon compounds from carbon dioxide, but as a specific example, the synthesis of methane will be described.

[0056] First, in the water electrolysis integrated methanation cell, a current is supplied from a power source between the anode and cathode, and water vapor (H 2 O) is supplied, H 2 At the anode in contact with O, H 2 O oxidation occurs. Specifically, H 2 O is oxidized to oxygen (O 2 ) and hydrogen ions (H + ) is produced. Hydrogen ions (H + The second flow path passes through the anode and electrolyte and travels toward the cathode in the cathode section. The oxygen-containing gas produced at the anode is discharged from the outlet of the second flow path.

[0057] Hydrogen is generated in the cathode section by electrons derived from the current supplied from the power source to the cathode and hydrogen ions that have moved from the anode to the cathode. The hydrogen is transported to the methanation section through the third flow path, where carbon dioxide supplied from the fourth flow path is reduced by the catalyst in the methanation section. This reduction reaction synthesizes methane and water from carbon dioxide and hydrogen.

[0058] That is, in the case of methane synthesis, the following oxidation reaction and reduction reaction occur in the electrolytic methanation device of this embodiment. Anode section: H 2 O→2H + +1 / 2O 2 +2e- Cathode: CO 2 +4H 2 →CH 4 +2H 2 O 2H + +2e - →H 2

[0059] In the electrolytic methanation device of this embodiment, water electrolysis and methanation reactions can be carried out in one device. In other words, the gases that need to be supplied are carbon dioxide and water (water vapor), so there is an advantage that hydrogen gas does not leave the device, making handling easier.

[0060] Furthermore, in the electrolytic methanation device of this embodiment, the methanation unit is provided with a first flow path for flowing cooling water and a second flow path for supplying the generated water vapor to the electrolysis unit. Therefore, cooling of the methanation reaction and generation of water vapor are performed in the methanation unit, so that heat generation (temperature rise) due to the methanation reaction can be controlled, facilitating temperature management of the device and improving reaction efficiency.

[0061] As described above, this specification discloses various aspects of the technology, the main technologies of which are summarized below.

[0062] The integrated water electrolysis methanation cell in a first aspect includes an anode part that electrolyzes water or water vapor to produce oxygen and hydrogen ions, a cathode part that reduces the hydrogen ions to produce hydrogen, and a water electrolysis part including a bipolar plate, and a methanation part that reduces carbon dioxide to produce carbon compounds. The bipolar plate is provided between the anode part and the cathode part, and has flow paths on both sides. The methanation part has a first flow path through which cooling water flows to cool heat generated by the methanation reaction, and a second flow path through which water vapor generated from the cooling water by the heat generation is supplied to the water electrolysis part.

[0063] With such a configuration, it is possible to provide a water electrolysis integrated methanation cell that can perform water electrolysis and methanation, and that is relatively easy to control temperature and has an excellent methanation reaction rate.

[0064] The water electrolysis integrated methanation cell in the second aspect is the methanation cell in the first aspect, characterized in that the water electrolysis unit has two or more bipolar plates between the anode unit and the cathode unit. It is believed that such a configuration can further improve the reaction efficiency and make the cell thinner. In addition, the number of parts used in the cell can be reduced.

[0065] An electrolytic methanation device in a third aspect includes the integrated water electrolysis methanation cell in the first or second aspect, and a power source that applies a current between the anode portion and the cathode portion. [Explanation of symbols]

[0066] 1. Water electrolysis integrated methanation cell 10 Water electrolysis section 11 Anode part 12 Cathode section 13 Bipolar Plate 14 Third flow path 20 Methanation Department 21 Catalyst 22 Cooling section 23 First Channel 24 Second flow path 25 Fourth flow path 26 Exhaust port

Claims

1. a water electrolysis unit including an anode section that electrolyzes water or water vapor to generate oxygen and hydrogen ions, a cathode section that reduces the hydrogen ions to generate hydrogen, and a bipolar plate; A methanation unit that reduces carbon dioxide to generate carbon compounds, The bipolar plate is provided between the anode portion and the cathode portion and has flow paths on both sides. The methanation unit has a first flow path through which cooling water flows for cooling heat generated by a methanation reaction, and a second flow path through which water vapor generated from the cooling water by the heat generation is supplied to the water electrolysis unit. Water electrolysis integrated methanation cell.

2. 2. The integrated water electrolysis methanation cell according to claim 1, wherein the water electrolysis section has two or more bipolar plates between the anode section and the cathode section.

3. 3. An electrolytic methanation device comprising: the water electrolysis integrated methanation cell according to claim 1 or 2; and a power source that applies a current between the anode portion and the cathode portion.

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