Control device for organic compound production system, control method for organic compound production system, and organic compound production system

Abstract

To improve the faradaic efficiency of an organic hydride production system. [Solution] The organic hydride production system (1) comprises an electrolytic cell (2) having a cathode chamber (18), a first cathode opening (30) and a second cathode opening (32), with the first cathode opening (30) positioned lower than the second cathode opening (32); a cathode fluid supply device (8) that can switch between supplying cathode fluid from the first cathode opening (30) to the cathode chamber (18) and supplying cathode fluid from the second cathode opening (32) to the cathode chamber (18); and a control device (10) that controls the cathode fluid supply device (8) to form an upflow of cathode fluid in the cathode chamber (18) under steady state conditions and to form a downflow of cathode fluid in the cathode chamber (18) under specified conditions.

Description

[Technical Field]

[0001] The present invention relates to an organic hydride production system, a control device for the organic hydride production system, and a control method for the organic hydride production system. [Background technology]

[0002] In recent years, the use of renewable energy sources such as solar, wind, hydroelectric, and geothermal power has been expected to reduce carbon dioxide emissions during the energy generation process. One example is a system that generates hydrogen by electrolyzing water using electricity derived from renewable energy. Organic hydride systems have also attracted attention as an energy carrier for the large-scale transport and storage of hydrogen derived from renewable energy.

[0003] Regarding organic hydride production technology, a conventional organic hydride production system is known that includes an electrolytic cell having an oxidizing electrode that generates protons from water and a reducing electrode that hydrogenates an organic compound having an unsaturated bond (substance to be hydrogenated) (see, for example, Patent Document 1). In this organic hydride production system, water is supplied to the oxidizing electrode, and the substance to be hydrogenated is supplied to the reducing electrode while a current is passed between the oxidizing electrode and the reducing electrode, whereby hydrogen is added to the substance to be hydrogenated, thereby obtaining an organic hydride. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] International Publication No. 2012 / 091128 Summary of the Invention [Problem to be solved by the invention]

[0005] As a result of extensive research into the above-mentioned organic hydride production technology, the inventors have come to realize that there is room for improvement in the faradic efficiency (current efficiency) of organic hydride production systems in conventional technology.

[0006] The present invention has been made in view of the above circumstances, and one of its objects is to provide a technique for improving the faradic efficiency of an organic hydride production system. [Means for solving the problem]

[0007] One aspect of the present invention is an organic hydride production system that includes: a cathode chamber that houses a cathode electrode that hydrogenates a substance to be hydrided in a cathode fluid with protons to produce an organic hydride; an electrolytic cell that has a first cathode opening and a second cathode opening that communicate between the inside and outside of the cathode chamber, with the first cathode opening being located below the second cathode opening; a cathode fluid supply device that can switch between supplying the cathode fluid from the first cathode opening to the cathode chamber and supplying the cathode fluid from the second cathode opening to the cathode chamber; and a control device that controls the cathode fluid supply device so that, under steady state conditions, the cathode fluid is supplied from the first cathode opening to the cathode chamber to form an upflow of the cathode fluid in the cathode chamber, and the cathode fluid is supplied from the second cathode opening to the cathode chamber to form a downflow of the cathode fluid in the cathode chamber under predetermined conditions.

[0008] Another aspect of the present invention is a control device for an organic hydride production system including an electrolytic cell and a cathode fluid supply device. The electrolytic cell has a cathode chamber that houses a cathode electrode that hydrogenates a substance to be hydrided in the cathode fluid with protons to produce an organic hydride, and a first cathode opening and a second cathode opening that communicate between the inside and outside of the cathode chamber, with the first cathode opening being located below the second cathode opening. The cathode fluid supply device is capable of switching between supplying the cathode fluid from the first cathode opening to the cathode chamber and supplying the cathode fluid from the second cathode opening to the cathode chamber. The control device controls the cathode fluid supply device so that, during steady state operation, the cathode fluid is supplied from the first cathode opening to the cathode chamber to form an upflow of the cathode fluid in the cathode chamber, and under predetermined conditions the cathode fluid is supplied from the second cathode opening to the cathode chamber to form a downflow of the cathode fluid in the cathode chamber.

[0009] Another aspect of the present invention is a method for controlling an organic hydride production system including an electrolytic cell having a cathode chamber accommodating a cathode electrode for producing an organic hydride by hydrogenating a substance to be hydrided in a cathode fluid with protons, the method comprising forming an upflow of the cathode fluid in the cathode chamber during steady state operation and forming a downflow of the cathode fluid in the cathode chamber under predetermined conditions.

[0010] Any combination of the above components, and conversion of the expression of the present disclosure into a method, device, system, etc., are also valid aspects of the present disclosure. [Effects of the Invention]

[0011] According to the present invention, the faradaic efficiency of an organic hydride production system can be improved. [Brief explanation of the drawings]

[0012] [Figure 1] 1 is a schematic diagram showing an organic hydride manufacturing system and a first path of a catholyte according to an embodiment. [Figure 2] FIG. 4 is a schematic diagram showing a second path of the catholyte. [Figure 3] FIG. 10 is a schematic diagram showing a third path of the catholyte. [Figure 4] FIG. 1 is a graph showing the relationship between the current density of an electrolytic cell and the concentration of the substance to be hydrided from which hydrogen gas is generated. [Figure 5] 10 is a flowchart showing an example of selection control of a catholyte path. DETAILED DESCRIPTION OF THE INVENTION

[0013] The present invention will be described below with reference to the drawings based on preferred embodiments. The embodiments are illustrative and do not limit the invention, and all features and combinations thereof described in the embodiments are not necessarily essential to the invention. The same or equivalent components, parts, and processes shown in the drawings are designated by the same reference numerals, and redundant descriptions will be omitted where appropriate. The scale and shape of each part shown in the drawings are set for convenience to facilitate explanation and should not be interpreted as limiting unless otherwise specified. Furthermore, when terms such as "first" and "second" are used in this specification or claims, these terms do not indicate any order or importance, but are intended to distinguish one configuration from another. Furthermore, some components that are not important for explaining the embodiments are omitted from the drawings.

[0014] 1 is a schematic diagram showing an organic hydride production system 1 and a first path for the cathode fluid according to an embodiment. The organic hydride production system 1 mainly comprises an electrolytic cell 2, a power source 4, an anode fluid supply device 6, a cathode fluid supply device 8, and a control device 10.

[0015] The electrolytic cell 2 hydrogenates the material to be hydrogenated, which is a dehydrogenated form of an organic hydride, by an electrochemical reduction reaction to produce the organic hydride. The electrolytic cell 2 has an anode electrode 12, a cathode electrode 14, an anode chamber 16, a cathode chamber 18, and a diaphragm 20.

[0016] The anode electrode 12 (anode) oxidizes water in the anolyte to generate protons. The anode electrode 12 contains an anode catalyst, such as a metal such as iridium (Ir), ruthenium (Ru), or platinum (Pt), or an oxide of these metals. The anode catalyst may be dispersed and supported on or coated on an electronically conductive substrate. The substrate is made of a material whose main component is a metal such as titanium (Ti) or stainless steel (SUS). Examples of the substrate form include woven or nonwoven sheets, mesh, porous sintered bodies, foamed molded bodies, and expanded metals.

[0017] The cathode electrode 14 (negative electrode) hydrogenates the substance to be hydrogenated in the cathode solution with protons to produce an organic hydride. The cathode electrode 14 of this embodiment has a catalyst layer 14a and a diffusion layer 14b. The catalyst layer 14a is disposed closer to the membrane 20 than the diffusion layer 14b. The catalyst layer 14a of this embodiment is in contact with the main surface of the membrane 20. The catalyst layer 14a contains, for example, platinum or ruthenium as a cathode catalyst that hydrogenates the substance to be hydrogenated. Preferably, the catalyst layer 14a also contains a porous catalyst carrier that supports the cathode catalyst. The catalyst carrier is made of an electron-conductive material such as porous carbon, porous metal, or porous metal oxide.

[0018] The cathode catalyst is coated with an ionomer (cation exchange type ionomer). For example, a catalyst carrier supporting the cathode catalyst is coated with the ionomer. Examples of the ionomer include perfluorosulfonic acid polymers such as Nafion (registered trademark) and Flemion (registered trademark). It is preferable that the ionomer partially coats the cathode catalyst. This allows the three elements (substances to be hydrogenated, protons, and electrons) required for the electrochemical reaction in the catalyst layer 14a to be efficiently supplied to the reaction field.

[0019] The diffusion layer 14b uniformly diffuses the liquid material to be hydrogenated, which is supplied from the outside, into the catalyst layer 14a. The organic hydride produced in the catalyst layer 14a is discharged to the outside of the catalyst layer 14a through the diffusion layer 14b. The diffusion layer 14b in this embodiment is in contact with the main surface of the catalyst layer 14a opposite the diaphragm 20. The diffusion layer 14b is made of a conductive material such as carbon or metal. The diffusion layer 14b is a porous body such as a sintered body of fibers or particles, or a foam molded body. Specific examples of materials that can be used to form the diffusion layer 14b include woven carbon fabric (carbon cloth), nonwoven carbon fabric, and carbon paper.

[0020] The anode electrode 12 is housed in the anode chamber 16. The anode chamber 16 is defined by, for example, a diaphragm 20, an end plate 22a, and a spacer 24a. The end plate 22a is a plate made of a metal such as stainless steel or titanium, and is installed on the opposite side of the anode electrode 12 from the diaphragm 20. As an example, the end plate 22a has a groove-shaped flow path on its main surface facing the anode electrode 12. The anolyte supplied to the anode chamber 16 passes through this flow path to the anode electrode 12 and is then discharged from the anode chamber 16 through this flow path. The spacer 24a is a frame-shaped sealing material disposed between the diaphragm 20 and the end plate 22a. The space in the anode chamber 16 excluding the anode electrode 12 constitutes the flow path for the anolyte.

[0021] The end plate 22a is also provided with a first anode opening 26 and a second anode opening 28 that communicate between the inside and outside of the anode chamber 16. The first anode opening 26 is disposed lower than the second anode opening 28. In this embodiment, the first anode opening 26 is provided on the bottom surface of the anode chamber 16, and the second anode opening 28 is provided on the top surface of the anode chamber 16. The first anode opening 26 and the second anode opening 28 may or may not overlap when viewed vertically.

[0022] The cathode electrode 14 is housed in the cathode chamber 18. The cathode chamber 18 is defined by, for example, a diaphragm 20, an end plate 22b, and a spacer 24b. The end plate 22b is a plate made of a metal such as stainless steel or titanium, and is installed on the opposite side of the cathode electrode 14 from the diaphragm 20. As an example, the end plate 22b has a groove-shaped flow path on its main surface facing the cathode electrode 14. The catholyte supplied to the cathode chamber 18 passes through this flow path to the cathode electrode 14 and is discharged from the cathode chamber 18 through this flow path. The spacer 24b is a frame-shaped sealing material disposed between the diaphragm 20 and the end plate 22b. The space in the cathode chamber 18 excluding the cathode electrode 14 constitutes the flow path for the catholyte. Therefore, the shape of the flow path for the catholyte within the cathode chamber 18 is not limited.

[0023] The end plate 22b is also provided with a first cathode opening 30 and a second cathode opening 32 that communicate between the inside and outside of the cathode chamber 18. The first cathode opening 30 is disposed lower than the second cathode opening 32. In this embodiment, the first cathode opening 30 is provided on the bottom surface of the cathode chamber 18, and the second cathode opening 32 is provided on the top surface of the cathode chamber 18. The first cathode opening 30 and the second cathode opening 32 may or may not overlap when viewed vertically. For example, the first cathode opening 30 and the second cathode opening 32 may be provided on the side surface of the cathode chamber 18.

[0024] In the present disclosure, the position of each cathode opening is defined by the position of its inner end, i.e., the position of an opening provided in the inner wall surface of the cathode chamber 18. Therefore, "the first cathode opening 30 is located lower than the second cathode opening 32" means that the inner end of the first cathode opening 30 is located lower than the inner end of the second cathode opening 32. In this embodiment, the cathode chamber 18 is defined by the diaphragm 20, the end plate 22b, and the spacer 24b. The first cathode opening 30 and the second cathode opening 32 are provided in the end plate 22b. In this case, the position of the opening formed in the inner wall surface of the end plate 22b by each cathode opening is the position of each cathode opening.

[0025] 1 to 3, each cathode opening extends linearly. Therefore, the outer end of the first cathode opening 30, i.e., the opening connected to the outside of the electrolytic cell 2, is also located lower than the outer end of the second cathode opening 32. However, the position of the outer end of each cathode opening is not particularly limited. For example, the second cathode opening 32 may be routed downward outside the cathode chamber 18 (for example, inside the plate material that constitutes the end plate 22b), so that the outer end of the second cathode opening 32 is at the same height as the outer end of the first cathode opening 30.

[0026] The anode chamber 16 and the cathode chamber 18 are separated by a diaphragm 20. The diaphragm 20 is sandwiched between the anode electrode 12 and the cathode electrode 14. In this embodiment, the diaphragm 20 is made of a proton-conductive solid polymer electrolyte membrane, and allows protons to move from the anode chamber 16 to the cathode chamber 18. The solid polymer electrolyte membrane is not particularly limited as long as it is made of a proton-conductive material, and examples thereof include fluorine-based ion exchange membranes having sulfonic acid groups.

[0027] An anolyte is supplied to the anode chamber 16 by an anolyte supply device 6. The anolyte contains water to be supplied to the anode electrode 12. Examples of the anolyte include an aqueous sulfuric acid solution, an aqueous nitric acid solution, an aqueous hydrochloric acid solution, pure water, and ion-exchanged water.

[0028] A cathode fluid is supplied to the cathode chamber 18 by the cathode fluid supply device 8. The cathode fluid contains an organic hydride raw material (material to be hydrogenated) to be supplied to the cathode electrode 14. As an example, the cathode fluid does not contain any organic hydride before the organic hydride production system 1 starts operating, and after the start of operation, the cathode fluid is mixed with organic hydride produced by electrolysis, thereby becoming a mixed liquid of the material to be hydrogenated and the organic hydride. The material to be hydrogenated and the organic hydride are preferably liquids at 20°C and 1 atmosphere.

[0029] The material to be hydrogenated and the organic hydride used in this embodiment are not particularly limited as long as they are organic compounds that can add / desorb hydrogen by reversibly causing a hydrogenation reaction / dehydrogenation reaction, and a wide range of compounds can be used, such as acetone-isopropanol, benzoquinone-hydroquinone, aromatic hydrocarbons, etc. Among these, aromatic hydrocarbons are preferred from the viewpoint of transportability during energy transportation, etc.

[0030] The aromatic hydrocarbon compound used as the substance to be hydrogenated is a compound containing at least one aromatic ring, and examples thereof include benzene, alkylbenzene, naphthalene, alkylnaphthalene, anthracene, diphenylethane, etc. Alkylbenzenes include compounds in which 1 to 4 hydrogen atoms of the aromatic ring are substituted with a linear or branched alkyl group having 1 to 6 carbon atoms. Examples of such compounds include toluene, xylene, mesitylene, ethylbenzene, diethylbenzene, etc. Alkylnaphthalenes include compounds in which 1 to 4 hydrogen atoms of the aromatic ring are substituted with a linear or branched alkyl group having 1 to 6 carbon atoms. Examples of such compounds include methylnaphthalene, etc. These may be used alone or in combination.

[0031] The substance to be hydrogenated is preferably at least one of toluene and benzene. Nitrogen-containing heterocyclic aromatic compounds such as pyridine, pyrimidine, pyrazine, quinoline, isoquinoline, N-alkylpyrrole, N-alkylindole, and N-alkyldibenzopyrrole can also be used as the substance to be hydrogenated. Organic hydrides are the hydrogenated versions of the above-mentioned substances to be hydrogenated, and examples thereof include cyclohexane, methylcyclohexane, dimethylcyclohexane, and piperidine.

[0032] Although only one electrolytic cell 2 is shown in FIG. 1, the organic hydride production system 1 may have multiple electrolytic cells 2. In this case, the electrolytic cells 2 are aligned, for example, so that the anode chambers 16 and cathode chambers 18 are aligned in the same direction, and are stacked with a current-carrying plate sandwiched between adjacent electrolytic cells 2. This electrically connects the electrolytic cells 2 in series. The current-carrying plate is made of a conductive material such as metal. The electrolytic cells 2 may be connected in parallel, or a combination of series and parallel connections may be used.

[0033] The reaction that occurs in the electrolytic cell 2 when toluene (TL) is used as an example of the substance to be hydrogenated is as follows: When toluene is used as the substance to be hydrogenated, the resulting organic hydride is methylcyclohexane (MCH). <Electrode reaction at the anode electrode> 3H2O → 3 / 2O2 + 6H + +6e - <Electrode reaction at the cathode electrode> TL+6H + +6e - →MCH

[0034] That is, the electrode reaction at the anode electrode 12 and the electrode reaction at the cathode electrode 14 proceed in parallel. Protons produced by the electrolysis of water at the anode electrode 12 are supplied to the cathode electrode 14 via the diaphragm 20. Electrons produced by the electrolysis of water are supplied to the cathode electrode 14 via the end plate 22a, the external circuit, and the end plate 22b. The protons and electrons supplied to the cathode electrode 14 are used to hydrogenate toluene at the cathode electrode 14. As a result, methylcyclohexane is produced.

[0035] Therefore, according to the organic hydride producing system 1 of this embodiment, the electrolysis of water and the hydrogenation reaction of the material to be hydrogenated can be carried out in one step. This makes it possible to improve the efficiency of organic hydride production compared to conventional techniques that produce organic hydrides through a two-stage process consisting of a process of producing hydrogen by water electrolysis or the like and a process of chemically hydrogenating the material to be hydrogenated in a reactor of a plant or the like. Furthermore, since there is no need for a reactor for chemical hydrogenation or a high-pressure vessel for storing hydrogen produced by water electrolysis or the like, it is possible to significantly reduce equipment costs.

[0036] At the cathode electrode 14, in addition to the main reaction of hydrogenation of the material to be hydrogenated, the side reaction of hydrogen gas generation described below may occur. As the amount of material to be hydrogenated supplied to the catalyst layer 14a becomes insufficient, this side reaction becomes more likely to occur. <Possible side reactions at the cathode electrode> 2H + +2e - →H2

[0037] Furthermore, the protons move along with water molecules when they move from the anode chamber 16 side to the cathode chamber 18 side through the diaphragm 20. Therefore, as the electrolytic reduction reaction progresses, water accumulates in the catalyst layer 14a.

[0038] The power supply 4 is a DC power supply that supplies power to the electrolytic cell 2. When power is supplied from the power supply 4 to the electrolytic cell 2, a predetermined electrolysis voltage is applied between the anode electrode 12 and the cathode electrode 14 of the electrolytic cell 2, causing an electrolysis current to flow. The power supply 4 receives power from a power supply device 34 and supplies power to the electrolytic cell 2. The power supply device 34 can be configured as a power generation device that generates power using renewable energy, such as a wind power generation device or a solar power generation device. The power supply device 34 is not limited to a power generation device that uses renewable energy, and may be a system power supply, or a power storage device that stores power from a renewable energy power generation device or a system power supply. Alternatively, it may be a combination of two or more of these.

[0039] The anode fluid supply device 6 supplies the anode fluid to the anode chamber 16. The anode fluid supply device 6 has an anode fluid tank 36, a gas-liquid separation unit 38, a first anode pipe 40, a second anode pipe 42, a third anode pipe 44, a first anode pump 46, and a second anode pump 48. The gas-liquid separation unit 38 can be configured with a known gas-liquid separation tank. The first anode pump 46 and the second anode pump 48 can be configured with known pumps such as gear pumps or cylinder pumps. The anode fluid supply device 6 may circulate the anode fluid using a fluid delivery device other than a pump.

[0040] The anolyte tank 36 stores the anolyte to be supplied to the anode chamber 16. The anolyte tank 36 is connected to the anode chamber 16 by a first anode pipe 40. One end of the first anode pipe 40 is connected to the anolyte tank 36, and the other end is connected to the first anode opening 26. A first anode pump 46 is provided in the middle of the first anode pipe 40. The gas-liquid separation unit 38 is connected to the anode chamber 16 by a second anode pipe 42. One end of the second anode pipe 42 is connected to the second anode opening 28, and the other end is connected to the gas-liquid separation unit 38. The gas-liquid separation unit 38 is connected to the anolyte tank 36 by a third anode pipe 44. A second anode pump 48 is provided in the middle of the third anode pipe 44.

[0041] The anolyte in the anolyte tank 36 flows into the anode chamber 16 from the first anode opening 26 via the first anode piping 40 by driving the first anode pump 46. The anolyte is supplied to the anode chamber 16 by upflow and is used for the electrode reaction at the anode electrode 12. The anolyte in the anode chamber 16 flows into the gas-liquid separator 38 via the second anode piping 42. Oxygen gas is generated by the electrode reaction at the anode electrode 12. As a result, the anolyte discharged from the anode chamber 16 contains oxygen gas. The gas-liquid separator 38 separates the oxygen gas from the anolyte and discharges it outside the system. The anolyte from which the oxygen gas has been separated is returned to the anolyte tank 36 via the third anode piping 44 by driving the second anode pump 48.

[0042] The cathode fluid supply device 8 supplies cathode fluid to the cathode chamber 18. The cathode fluid supply device 8 includes a cathode fluid tank 50, a gas-liquid separation unit 52, an oil-water separation unit 54, a gas tank 56, a first cathode pipe 58 to an eighth cathode pipe 72, a first cathode pump 74 to a fifth cathode pump 82, and a first on-off valve 84 to a sixth on-off valve 94. The gas-liquid separation unit 52 may be configured as a known gas-liquid separation tank. The oil-water separation unit 54 may be configured as a known oil-water separation tank. The first cathode pump 74 to the fifth cathode pump 82 may be configured as known pumps such as gear pumps or cylinder pumps. The cathode fluid supply device 8 may also circulate the cathode fluid using a fluid delivery device other than a pump. The first on-off valve 84 to the sixth on-off valve 94 may be configured as known valves such as solenoid valves or air-driven valves.

[0043] The cathode fluid tank 50 stores the cathode fluid to be supplied to the cathode chamber 18. The cathode fluid tank 50 is connected to the cathode chamber 18 by a first cathode piping 58. One end of the first cathode piping 58 is connected to the cathode fluid tank 50, and the other end is connected to the first cathode opening 30. A first cathode pump 74 and a first on-off valve 84 are provided in the first cathode piping 58. The first cathode pump 74 is disposed closer to the cathode chamber 18 than the first on-off valve 84. The gas-liquid separation unit 52 is connected to the cathode chamber 18 by a second cathode piping 60. One end of the second cathode piping 60 is connected to the second cathode opening 32, and the other end is connected to the gas-liquid separation unit 52. A second on-off valve 86 is provided in the second cathode piping 60.

[0044] The oil-water separation unit 54 is connected to the gas-liquid separation unit 52 by a third cathode pipe 62. A second cathode pump 76 and a third on-off valve 88 are provided in the third cathode pipe 62. The second cathode pump 76 is disposed closer to the gas-liquid separation unit 52 than the third on-off valve 88. The oil-water separation unit 54 is connected to the cathode fluid tank 50 by a fourth cathode pipe 64. A third cathode pump 78 is provided in the fourth cathode pipe 64. A fifth cathode pipe 66 is connected to the oil-water separation unit 54. One end of the fifth cathode pipe 66 is connected to the oil-water separation unit 54, and the other end is connected to, for example, a drainage tank (not shown). A fourth cathode pump 80 and a water volume sensor 96 are provided in the fifth cathode pipe 66. The water volume sensor 96 detects the flow rate of water flowing through the fifth cathode pipe 66. The water volume sensor 96 can be configured as a known flow meter.

[0045] The cathode fluid tank 50 is also connected to the cathode chamber 18 by a sixth cathode pipe 68. One end of the sixth cathode pipe 68 is connected to the cathode fluid tank 50, and the other end is connected to the second cathode opening 32 via the second cathode pipe 60. A fifth cathode pump 82 and a fourth on-off valve 90 are provided along the sixth cathode pipe 68. The fifth cathode pump 82 is disposed closer to the cathode chamber 18 than the fourth on-off valve 90. In this embodiment, the other end of the sixth cathode pipe 68 is connected to a region of the second cathode pipe 60 closer to the cathode chamber 18 than the second on-off valve 86, and is thereby connected to the second cathode opening 32 via the second cathode pipe 60. However, this configuration is not limited thereto, and the sixth cathode pipe 68 may be directly connected to the second cathode opening 32.

[0046] The oil-water separation unit 54 is connected to the cathode chamber 18 by a seventh cathode pipe 70. One end of the seventh cathode pipe 70 is connected to the first cathode opening 30 via the first cathode pipe 58, and the other end is connected to the oil-water separation unit 54 via the third cathode pipe 62. A fifth on-off valve 92 is provided midway along the seventh cathode pipe 70. In this embodiment, one end of the seventh cathode pipe 70 is connected to a region of the first cathode pipe 58 that is closer to the cathode chamber 18 than the first on-off valve 84, and is thereby connected to the first cathode opening 30 via the first cathode pipe 58. However, this configuration is not limited to this, and the seventh cathode pipe 70 may be connected directly to the first cathode opening 30. Furthermore, the other end of the seventh cathode pipe 70 is connected to a region of the third cathode pipe 62 that is closer to the oil-water separation section 54 than the third on-off valve 88, and is thereby connected to the oil-water separation section 54 via the third cathode pipe 62. However, this configuration is not limited thereto, and the seventh cathode pipe 70 may be directly connected to the oil-water separation section 54.

[0047] The gas tank 56 is connected to the cathode chamber 18 by an eighth cathode pipe 72. One end of the eighth cathode pipe 72 is connected to the gas tank 56, and the other end is connected to the second cathode opening 32 via the second cathode pipe 60. A sixth on-off valve 94 is provided midway along the eighth cathode pipe 72. In this embodiment, the other end of the eighth cathode pipe 72 is connected to a region of the second cathode pipe 60 that is closer to the cathode chamber 18 than the second on-off valve 86, and is thereby connected to the second cathode opening 32 via the second cathode pipe 60. However, the present invention is not limited to this configuration, and the eighth cathode pipe 72 may be connected directly to the second cathode opening 32.

[0048] 1 , the cathode fluid supply device 8 can form a first path for the cathode fluid by using the cathode fluid tank 50, first cathode pipe 58, cathode chamber 18, second cathode pipe 60, gas-liquid separation unit 52, third cathode pipe 62, oil-water separation unit 54, and fourth cathode pipe 64. In the first path, an upflow of the cathode fluid is formed within the cathode chamber 18. In this disclosure, the "upflow" of the cathode fluid refers to the flow of the cathode fluid into the cathode chamber 18 from the first cathode opening 30 located below and the discharge of the cathode fluid from the second cathode opening 32 located above.

[0049] Specifically, when the first cathode pump 74 is driven, the cathode fluid in the cathode fluid tank 50 flows through the first cathode piping 58 and into the cathode chamber 18 from the first cathode opening 30. The first on-off valve 84 is open, allowing the cathode fluid to flow from the cathode fluid tank 50 to the first cathode opening 30. The fifth on-off valve 92 is closed, blocking the flow of the cathode fluid from the cathode fluid tank 50 to the oil-water separation unit 54. The cathode fluid is supplied to the cathode chamber 18 by an upflow.

[0050] The cathode fluid in the cathode chamber 18 flows into the gas-liquid separation unit 52 via the second cathode piping 60. The second on-off valve 86 is open, allowing the cathode fluid to flow from the second cathode opening 32 to the gas-liquid separation unit 52. The fourth on-off valve 90 is closed, blocking the flow of the cathode fluid from the second cathode opening 32 to the cathode fluid tank 50. The sixth on-off valve 94 is closed, blocking the flow of the cathode fluid from the second cathode opening 32 to the gas tank 56. As described above, hydrogen gas is generated by a side reaction at the cathode electrode 14. Therefore, hydrogen gas is mixed into the cathode fluid discharged from the cathode chamber 18. The gas-liquid separation unit 52 separates the hydrogen gas in the cathode fluid from the cathode fluid and discharges it to the outside of the system.

[0051] The cathode fluid from which hydrogen gas has been separated flows into the oil-water separation unit 54 via the third cathode piping 62 by driving the second cathode pump 76. The third on-off valve 88 is open, allowing the cathode fluid to flow from the gas-liquid separation unit 52 to the oil-water separation unit 54. The fifth on-off valve 92 is closed, blocking the flow of the cathode fluid from the gas-liquid separation unit 52 to the cathode fluid tank 50 and the cathode chamber 18.

[0052] As described above, water moves from the anode electrode 12 to the cathode electrode 14 along with protons. Therefore, water is mixed in the cathode fluid discharged from the cathode chamber 18. The oil-water separator 54 separates the water in the cathode fluid from the cathode fluid. The separated water is discharged to the drain tank via the fifth cathode piping 66 by driving the fourth cathode pump 80. The amount of water separated from the cathode fluid by the oil-water separator 54, in other words, the amount of water discharged from the cathode chamber 18, is detected by the water volume sensor 96. The cathode fluid from which the water has been separated is returned to the cathode fluid tank 50 via the fourth cathode piping 64 by driving the third cathode pump 78.

[0053] 2 is a schematic diagram showing the second cathode fluid path. As shown in FIG. 2, the cathode fluid supply device 8 can form the second cathode fluid path by the cathode fluid tank 50, the sixth cathode pipe 68, the second cathode pipe 60, the cathode chamber 18, the first cathode pipe 58, the seventh cathode pipe 70, the third cathode pipe 62, the oil-water separator 54, and the fourth cathode pipe 64. In the second path, a downflow of the cathode fluid is formed within the cathode chamber 18. In this disclosure, the "downflow" of the cathode fluid refers to the flow of the cathode fluid into the cathode chamber 18 from the second cathode opening 32 located above and the discharge of the cathode fluid from the first cathode opening 30 located below.

[0054] Specifically, by driving the fifth cathode pump 82, the cathode fluid in the cathode fluid tank 50 flows through the sixth cathode piping 68 and the second cathode piping 60 and into the cathode chamber 18 from the second cathode opening 32. The fourth on-off valve 90 is open, allowing the cathode fluid to flow from the cathode fluid tank 50 to the second cathode opening 32. The second on-off valve 86 is closed, blocking the flow of cathode fluid from the cathode fluid tank 50 to the gas-liquid separation unit 52. The sixth on-off valve 94 is closed, blocking the flow of cathode fluid from the cathode fluid tank 50 to the gas tank 56. The cathode fluid is supplied to the cathode chamber 18 by downflow.

[0055] The cathode fluid in the cathode chamber 18 flows into the oil-water separation section 54 via the first cathode piping 58, the seventh cathode piping 70, and the third cathode piping 62. The fifth on-off valve 92 is open, allowing the cathode fluid to flow from the first cathode opening 30 to the oil-water separation section 54. The first on-off valve 84 is closed, blocking the flow of cathode fluid from the first cathode opening 30 to the cathode fluid tank 50. The third on-off valve 88 is closed, blocking the flow of cathode fluid from the first cathode opening 30 to the gas-liquid separation section 52.

[0056] The oil-water separator 54 separates the water in the cathode fluid from the cathode fluid. The separated water is discharged to a drain tank via the fifth cathode piping 66 by driving the fourth cathode pump 80. The amount of separated water is detected by a water volume sensor 96. The cathode fluid from which the water has been separated is returned to the cathode fluid tank 50 via the fourth cathode piping 64 by driving the third cathode pump 78. Note that the cathode fluid tank 50 may also have the function of the oil-water separator 54.

[0057] 3 is a schematic diagram showing the third path of the cathode fluid. As shown in FIG. 3, the cathode fluid supply device 8 can form the third path of the cathode fluid by the gas tank 56, the eighth cathode pipe 72, the second cathode pipe 60, the cathode chamber 18, the first cathode pipe 58, the seventh cathode pipe 70, the third cathode pipe 62, the oil-water separator 54, the fourth cathode pipe 64, and the cathode fluid tank 50.

[0058] Specifically, when the sixth on-off valve 94 is open, a predetermined gas stored in the gas tank 56 flows into the cathode chamber 18 from the second cathode opening 32 via the eighth cathode pipe 72 and the second cathode pipe 60. The second on-off valve 86 is closed, blocking the flow of gas from the gas tank 56 to the gas-liquid separation unit 52. Examples of gases stored in the gas tank 56 include inert gases such as nitrogen gas and hydrogen gas. For example, the gas tank 56 is filled with gas at high pressure. Therefore, when the sixth on-off valve 94 is opened, the gas stored in the gas tank 56 automatically flows into the cathode chamber 18. The gas filling pressure in the gas tank 56 need only be a pressure that is not negative relative to the pressure outside the gas tank 56. For example, if the gas tank 56 is disposed above the cathode chamber 18, the oil-water separation unit 54, and the cathode fluid tank 50 are disposed below the gas tank 56, the gas may be filled in the gas tank 56 at normal pressure.

[0059] When gas flows into the cathode chamber 18, the cathode fluid in the cathode chamber 18 is pushed out of the cathode chamber 18 and flows into the oil-water separation section 54 via the first cathode piping 58, the seventh cathode piping 70, and the third cathode piping 62. The fifth on-off valve 92 is open, allowing the cathode fluid to flow from the first cathode opening 30 to the oil-water separation section 54. The first on-off valve 84 is closed, blocking the flow of cathode fluid from the first cathode opening 30 to the cathode fluid tank 50. The third on-off valve 88 is closed, blocking the flow of cathode fluid from the first cathode opening 30 to the gas-liquid separation section 52.

[0060] The oil-water separator 54 separates the water in the cathode fluid from the cathode fluid. The separated water is discharged to the drain tank via the fifth cathode piping 66 by driving the fourth cathode pump 80. The amount of separated water is detected by a water volume sensor 96. The cathode fluid from which the water has been separated is returned to the cathode fluid tank 50 via the fourth cathode piping 64 by driving the third cathode pump 78.

[0061] The first cathode pipe 58 corresponds to the first pipe connecting the cathode fluid tank 50 and the cathode chamber 18 in this disclosure. The second cathode pipe 60 and the sixth cathode pipe 68 correspond to the second pipe connecting the cathode fluid tank 50 and the cathode chamber 18 in this disclosure. The first cathode pump 74 corresponds to the supply device in this disclosure that supplies cathode fluid from the cathode fluid tank 50 to the cathode chamber 18 via the first cathode pipe 58, which is the first pipe. The fifth cathode pump 82 corresponds to the supply device that supplies cathode fluid from the cathode fluid tank 50 to the cathode chamber 18 via the sixth cathode pipe 68 and the second cathode pipe 60, which are the second pipes. The gas tank 56 and the sixth on-off valve 94 correspond to the gas supply mechanism in this disclosure that supplies a predetermined gas to the cathode chamber 18.

[0062] The control device 10 controls the supply of power from the power source 4 to the electrolytic cell 2. The potentials of the anode electrode 12 and the cathode electrode 14 are controlled by the control device 10. The control device 10 is realized as a hardware configuration by elements and circuits such as a computer CPU and memory, and as a software configuration by a computer program, etc., but in Figures 1 to 3 it is depicted as a functional block realized by the cooperation of these. It will be naturally understood by those skilled in the art that these functional blocks can be realized in various ways by combining hardware and software.

[0063] At least one of a signal indicating the voltage of the electrolytic cell 2, a signal indicating the potential of the anode electrode 12, and a signal indicating the potential of the cathode electrode 14 is input to the control device 10 from a detection unit 98 provided in the electrolytic cell 2. The detection unit 98 can detect the potential of each electrode and the voltage of the electrolytic cell 2 using a known method. The detection unit 98 has, for example, a known voltmeter.

[0064] When the detection unit 98 detects the potential of the anode electrode 12 or the cathode electrode 14, a reference electrode is provided on the diaphragm 20. The reference electrode is maintained at a reference electrode potential. For example, the reference electrode is a reversible hydrogen electrode (RHE). One terminal of the detection unit 98 is connected to the reference electrode, and the other terminal is connected to the electrode to be detected, thereby detecting the potential of the electrode relative to the reference electrode. When the detection unit 98 detects the voltage of the electrolytic cell 2, one terminal of the detection unit 98 is connected to the anode electrode 12, and the other terminal is connected to the cathode electrode 14, thereby detecting the potential difference between the two electrodes, i.e., the voltage. The detection unit 98 transmits a signal indicating the detection result to the control device 10.

[0065] The detection unit 98 also includes a current detection unit that detects the current flowing between the anode electrode 12 and the cathode electrode 14. The current detection unit is configured, for example, with a known ammeter. The current value detected by the current detection unit is input to the control device 10. The control device 10 may previously store information on the current-voltage characteristics (IV characteristics) of the electrolytic cell 2. If the control device 10 stores information on the IV characteristics, this information may be updateable as desired. The IV characteristics of the electrolytic cell 2 are determined depending on the catalyst composition of each electrode, the type of diffusion layer and substrate, the type of diaphragm 20, the flow path structure of the anolyte and catholyte in the electrolytic cell 2, the dimensions of each component, and other factors, and can be measured and determined in advance. In this case, the control device 10 receives a signal indicating the amount of power supplied from the power supply device 34 to determine the amount of power that can be supplied to the electrolytic cell 2 from the power source 4, and calculates the voltage to be applied to the electrolytic cell 2 from the IV characteristics, i.e., controls the value of the current flowing through the electrolytic cell 2.

[0066] The control device 10 also controls the anode fluid supply device 6 and the cathode fluid supply device 8. Specifically, the control device 10 controls the driving of the first anode pump 46, the second anode pump 48, and the first cathode pump 74 to the fifth cathode pump 82. The control device 10 also controls the opening and closing of the first on-off valve 84 to the sixth on-off valve 94. The control device 10 also receives a signal from the water volume sensor 96 indicating the detection result.

[0067] As described above, the hydrogenation reaction of the material to be hydrogenated occurs as a main reaction at the cathode electrode 14, and a hydrogen generation reaction may occur as a side reaction. The occurrence of a side reaction leads to a decrease in the faradaic efficiency of the organic hydride production system 1. Furthermore, as protons migrate from the anode electrode 12 side to the cathode electrode 14 side, accompanied by water, water accumulates in the cathode chamber 18. Water inhibits the flow of the material to be hydrogenated. Therefore, if a large amount of water accumulates in the cathode chamber 18, the amount of material to be hydrogenated supplied to the reaction site of the catalyst layer 14a decreases, making the side reaction more likely to proceed. Furthermore, hydrogen gas generated in the side reaction also inhibits the flow of the material to be hydrogenated. Therefore, the hydrogen gas generated in the side reaction further facilitates the side reaction. Therefore, it is desirable to discharge the hydrogen gas and water remaining in the cathode chamber 18 from the cathode chamber 18.

[0068] Hydrogen gas has a lower specific gravity than the material to be hydrogenated and organic hydrides. On the other hand, water has a higher specific gravity than the material to be hydrogenated and organic hydrides. Therefore, when an upflow of the cathode fluid is formed in the cathode chamber 18, hydrogen gas is easily discharged from the cathode chamber 18, but water is difficult to discharge from the cathode chamber 18, and accumulates at the bottom of the cathode chamber 18. Conversely, when a downflow is formed in the cathode chamber 18, water is easily discharged from the cathode chamber 18, but hydrogen gas is difficult to discharge from the cathode chamber 18, and accumulates at the top of the cathode chamber 18.

[0069] If hydrogen gas accumulates in the cathode chamber 18, it becomes difficult for the cathode fluid to be distributed uniformly over the entire surface of the cathode electrode 14. Furthermore, the internal pressure of the cathode chamber 18 increases, which may cause leakage of the cathode fluid. For this reason, conventional organic hydride production systems have focused on exhausting hydrogen gas and have always supplied the cathode fluid to the cathode chamber 18 by upflow. However, no adequate measures have been taken to deal with water that accumulates in the cathode chamber 18.

[0070] However, in order to improve the faradic efficiency of an organic hydride production system, water accumulation in the cathode chamber 18 is an issue that cannot be ignored. In response to this, the control device 10 of the present embodiment controls the cathode fluid supply device 8 so as to supply cathode fluid from the first cathode opening 30 to the cathode chamber 18 during steady state operation, thereby forming an upflow of cathode fluid within the cathode chamber 18. The control device 10 also controls the cathode fluid supply device 8 so as to supply cathode fluid from the second cathode opening 32 to the cathode chamber 18 under predetermined conditions, thereby forming a downflow of cathode fluid within the cathode chamber 18.

[0071] That is, the control device 10 controls the cathode pumps and on-off valves to form a first path for the cathode fluid during steady state operation. In the first path, the first cathode opening 30 serves as the inlet for the cathode fluid, and the second cathode opening 32 serves as the outlet for the cathode fluid, forming an upflow of the cathode fluid into the cathode chamber 18. This promotes the discharge of hydrogen gas accumulated in the upper part of the cathode chamber 18, thereby suppressing the occurrence of side reactions. It also prevents the internal pressure of the cathode chamber 18 from becoming excessive.

[0072] The control device 10 then controls the cathode pumps and on-off valves to temporarily form a second path for the cathode fluid. In the second path, the second cathode opening 32 serves as an inlet for the cathode fluid, and the first cathode opening 30 serves as an outlet for the cathode fluid, forming a downflow of the cathode fluid in the cathode chamber 18. This facilitates the discharge of water accumulated at the bottom of the cathode chamber 18, and can suppress the occurrence of side reactions.

[0073] In particular, the lower the solubility of the substance to be hydrogenated and the organic hydride in water, the more effective the water discharge by forming a downflow. For example, when the solubility of at least one of the substance to be hydrogenated and the organic hydride in water is preferably 3 g / 100 mL or less, more preferably 2 g / 100 mL or less, the water discharge by a downflow is more effective. Examples of substances to be hydrogenated and organic hydrides that can be expected to be discharged by a downflow include benzene (0.18 g / 100 mL HO) and cyclohexane (0.36 g / 100 mL HO), toluene (0.05 g / 100 mL HO) and methylcyclohexane (1.6 g / 100 mL HO), naphthalene (0.003 g / 100 mL HO) and decahydronaphthalene (0.001 g / 100 mL HO), etc.

[0074] In this embodiment, steady state refers to a state in which the electrolytic cell 2 is not in a state that satisfies the predetermined conditions described below. As an example, steady state refers to a state in which the organic hydride production system 1 is in operation. Operation refers to a state in which a positive current that causes electrolysis in the electrolytic cell 2, i.e., an electrolytic current, flows. During operation of the organic hydride production system 1, side reactions may occur due to changes in the concentration of the substance to be hydrided in the cathode fluid or the magnitude of the electrolytic current flowing in the electrolytic cell 2. For this reason, an upflow of the cathode fluid is formed in the cathode chamber 18 during steady state.

[0075] On the other hand, when the possibility of side reactions occurring is lower than in steady state, it is possible to prioritize the discharge of water over the discharge of hydrogen gas. Therefore, in this embodiment, a state in which the possibility of side reactions occurring is lower than in steady state is set as a predetermined condition, and when this predetermined condition is met, the upflow of the cathode fluid is switched to a downflow. This makes it possible to suppress the occurrence of side reactions caused by water while avoiding an increase in the internal pressure of the cathode chamber 18.

[0076] In this embodiment, the predetermined condition includes the shutdown of the electrolytic cell 2. "Shutdown" refers to a state in which no electrolytic current flows through the electrolytic cell 2. When the electrolytic cell 2 is shut down, the possibility of hydrogen gas being generated is naturally lower than when the electrolytic cell 2 is in operation. The control device 10 can determine whether the electrolytic cell 2 is in operation, in other words, whether an electrolytic current is flowing through the electrolytic cell 2, based on a signal sent from the detection unit 98 or the power source 4. When the control device 10 detects that the electrolytic cell 2 has stopped operating, it considers that the predetermined condition has been met and switches from the first pathway to the second pathway.

[0077] The predetermined condition also includes a state in which the amount of hydrogen gas generated during operation of the electrolytic cell 2 is equal to or less than a predetermined value, which is derived from the relationship between the current (e.g., current density) flowing through the electrolytic cell 2 and the concentration of the substance to be hydrided in the cathode fluid. Fig. 4 is a diagram showing the relationship between the current density of the electrolytic cell 2 and the concentration of the substance to be hydrided at which hydrogen gas is generated.

[0078] At a certain current density, when the concentration of the substance to be hydrided in the catholyte is sufficiently high, hydrogenation of the substance to be hydrided occurs primarily, and the generation of hydrogen gas is suppressed. On the other hand, even at the same current density, when the concentration of the substance to be hydrided falls to a certain value, the substance to be hydrided becomes insufficient, side reactions occur, and hydrogen gas begins to be generated. Also, at a certain concentration of the substance to be hydrided, if the electrolysis current in the electrolytic cell 2 is small, the electrode reaction does not proceed easily, and the consumption of the substance to be hydrided decreases. As a result, there is no shortage of the substance to be hydrided, and the generation of hydrogen gas is suppressed. On the other hand, at the same concentration of the substance to be hydrided, when the current density is high, the electrolytic reaction proceeds easily, and the consumption of the substance to be hydrided increases. As a result, the substance to be hydrided becomes insufficient, and side reactions occur, and hydrogen gas begins to be generated.

[0079] Therefore, even when the electrolytic cell 2 is in operation, when the current density is below a predetermined value and the concentration of the substance to be hydrided is above a predetermined value, the control device 10 assumes that the amount or possibility of hydrogen gas generation is lower than in steady state, and switches from the first path to the second path, assuming that the predetermined condition is satisfied. Regarding the range of current density and concentration of the substance to be hydrided that satisfies the condition, measurement line A shown in Figure 4 was obtained from the concentration (measurement point) of the substance to be hydrided at each current density when the substance to be hydrided is toluene. For example, when the current density is 0.7 A / cm 2 When the concentration of the substance to be hydrided in the catholyte is 27 mol %, hydrogen gas begins to be generated.

[0080] Measurement line A can be obtained, for example, by the following test: Using a predetermined electrolytic bath, 2 Constant current electrolysis (preliminary run) is carried out for 10 minutes at a current density of 0.7 A / cm. The entire electrolytic cell is maintained at 60°C during electrolysis. A 1M aqueous sulfuric acid solution is passed through the anode chamber at a flow rate of 20 mL / min. The cathode chamber is passed through the reservoir at a flow rate of 20 mL / min. The cathode solution is 0.5 mol of 100 mol% toluene. After the preliminary run, the current density is increased to 0.7 A / cm. 2 The conditions are the same as those for the preliminary run except for the current density. After electrolysis starts, when bubbles (hydrogen gas generated by a side reaction) are confirmed at the outlet of the electrolytic cell, the current density is increased to 0.05 A / cm 2 Just lower it to 0.65A / cm 2 As the current density is adjusted, the cathode solution is sampled and the concentrations of toluene and methylcyclohexane are measured by gas chromatography. The toluene concentration at which bubbles are visually observed is the concentration at which hydrogen gas is generated at that current density. A current density of 0.65 A / cm 2 Continue constant current electrolysis at 0.05 A / cm. When bubbles are observed at the outlet of the electrolytic cell, reduce the current density to 0.05 A / cm. 2 The catholyte is sampled and the concentrations of toluene and methylcyclohexane are measured. This measurement is carried out at a current density of 0.2 A / cm. 2Repeating this process until bubbles are detected gives measurement line A. In Figure 4, the maximum current density is 0.7 A / cm 2 However, this is due to the limitations of the evaluation equipment, and the upper limit of the current density is set to 0.7 A / cm 2 It is not intended to be limited to.

[0081] Therefore, in FIG. 4 , in the first range B where the concentration of the substance to be hydrided is above the measurement line A, theoretically, hydrogen gas is not generated. In other words, this is a state in which the amount of hydrogen gas generated is equal to or less than a predetermined value. In this embodiment, the predetermined value is 0, but is not limited to this and can be set appropriately based on experiments or simulations. The relationship between the current density and the concentration of the substance to be hydrided that generates hydrogen gas shown in FIG. 4 , i.e., information regarding the first range B, is determined depending on the catalyst composition of each electrode, the type of diffusion layer and substrate, the type of diaphragm 20, the flow path structure of the anolyte and catholyte in the electrolytic cell 2, the dimensions of each part, and the like, and can be measured and known in advance. In the measurement, the start of hydrogen gas generation can be confirmed, for example, visually or by automatic detection using an optical analysis device that utilizes the difference in refractive index between liquid and gas.

[0082] The upper limit of the current density and the lower limit of the concentration of the substance to be hydrided in the first range B can be set as appropriate based on experiments or simulations, as long as they are not equal to or lower than the measurement line A. In addition, the path switching condition may be set to a second range C, which has an even narrower allowable range for the current density and the concentration of the substance to be hydrided than the first range B. The upper limit of the current density and the lower limit of the concentration of the substance to be hydrided in the second range C can also be set as appropriate based on experiments or simulations.

[0083] The control device 10 can determine the concentration of the substance to be hydrided in the cathode solution by receiving a signal from a known concentration sensor 100 provided in, for example, the cathode solution tank 50. The control device 10 can also calculate the amount of organic hydride produced from the total amount of power supplied to the electrolytic cell 2 and calculate the concentration of the substance to be hydrided from the result. In this case, the concentration sensor 100 can be omitted. The control device 10 can also determine the current density based on signals received from the detection unit 98, the power source 4, and the power supply device 34. When the control device 10 detects that the current density in the electrolytic cell 2 and the concentration of the substance to be hydrided in the cathode solution are within the first range B or the second range C, the control device 10 switches from the first path to the second path, assuming that a predetermined condition is satisfied.

[0084] The above-mentioned state in which the amount of hydrogen gas generated is equal to or less than the predetermined value occurs while the electrolytic cell 2 is in operation. In other words, "during operation" of the electrolytic cell 2 includes a state that falls within the first range B or the second range C (hereinafter referred to as a low-load operating state as appropriate) and a state that does not fall within the first range B or the second range C (hereinafter referred to as a high-load operating state as appropriate). When the predetermined condition includes a low-load operating state, "steady state" refers to a time when the electrolytic cell 2 is in a high-load operating state.

[0085] When the power supply device 34 is a power generation device that generates electricity using renewable energy, the amount of power generated varies significantly depending on weather conditions. For example, in the case of a solar power generation device, the amount of power generated decreases on cloudy days or after sunset. This causes the current density in the electrolytic cell 2 to decrease, and the amount of hydrogen gas generated tends to fall below a predetermined value. By switching from upflow to downflow in such a state, the water accumulated in the cathode chamber 18 can be efficiently discharged and the faradic efficiency can be improved while suppressing a decrease in the operating rate of the organic hydride production system 1.

[0086] The predetermined conditions under which the control device 10 switches the flow of the cathode fluid to downflow may include when the internal pressure of the cathode chamber 18 is below a predetermined value or when a sudden increase in internal pressure is not expected. The predetermined conditions may also include when a tendency for the Faraday efficiency to decrease is detected. For example, a tendency for the Faraday efficiency to decrease may occur when the Faraday efficiency that the electrolytic cell 2 would normally achieve is not being achieved during current operation. The Faraday efficiency that would normally be achieved is derived, for example, based on statistical information on the Faraday efficiency during past operation. Furthermore, the predetermined conditions may include information such as the time, weather forecast, and past power generation data, as well as information on predicted power generation amounts based on the information.

[0087] As another example, the control device 10 stops the downflow after a predetermined time has elapsed since switching to downflow. The control device 10 has a built-in timer and can detect when a preset predetermined time has elapsed. The predetermined time can be set appropriately based on experiments or simulations. For example, the predetermined time is the time it is estimated that the water in the cathode chamber 18 will have completely discharged, and is determined based on the volume of the cathode chamber 18, the flow rate of the cathode fluid, etc.

[0088] As another example, the control device 10 stops the downflow when it detects that the amount of water discharged from the cathode chamber 18 by the downflow has fallen below a predetermined value, based on a signal received from the water volume sensor 96. The predetermined value can be set appropriately based on experiments or simulations, and is, for example, 0.

[0089] If electrolytic cell 2 is in operation when the downflow is stopped, controller 10 switches the flow of the catholyte to an upflow. Also, if electrolytic cell 2 is not in operation when the downflow is stopped, controller 10 stops the flow of the catholyte.

[0090] Furthermore, when the control device 10 of this embodiment detects a stop of operation of the electrolytic cell 2 and switches the flow of the cathode fluid to downflow, it controls the sixth on-off valve 94, which serves as a gas supply mechanism, to supply the gas in the gas tank 56 to the cathode chamber 18 after the downflow has stopped. That is, the control device 10 switches the path of the cathode fluid to the third path and performs a gas purge process for the cathode chamber 18. This fills the cathode chamber 18 with gas. By filling the cathode chamber 18 with gas, water in the cathode chamber 18 can be more reliably discharged. For example, the control device 10 closes the sixth on-off valve 94 to stop the release of gas from the gas tank 56 after a predetermined time has elapsed since the start of gas supply. The predetermined time can be set appropriately based on experiments or simulations. Note that the flow may be switched from the first path to the third path without going through the second path, i.e., switched from upflow to performing a gas purge process. An example of switching from the first route to the third route is when a high load operating state directly leads to an operation shutdown.

[0091] The selection control of the cathode fluid path will be described below. Fig. 5 is a flowchart showing an example of the selection control of the cathode fluid path. This control flow is repeatedly executed at a predetermined timing by the control device 10. Note that Fig. 5 illustrates an example in which the downflow is stopped after a predetermined time has elapsed.

[0092] First, the control device 10 determines whether the electrolysis state of the electrolytic cell 2 is in a steady state (high-load operating state) based on signals received from the detection unit 98, the power source 4, the power supply device 34, the concentration sensor 100, etc. (S101). If the electrolysis state is in a steady state (Y in S101), the control device 10 controls each cathode pump and each on-off valve to form a first path (upflow) of the cathode fluid or to maintain the first path (S102), and then ends this routine.

[0093] If the electrolytic cell 2 is not in a steady state (N in S101), the controller 10 determines whether the electrolytic cell 2 is in an operation-stopped state (S103). If the electrolytic cell 2 is in an operation-stopped state (Y in S103), the controller 10 controls the cathode pumps and the on-off valves to form a second path (downflow) for the cathode fluid (S104). The controller 10 then determines whether a predetermined time has elapsed since the second path was formed (S105). If the predetermined time has not elapsed (N in S105), the controller 10 repeats the determination in step S105. If the predetermined time has elapsed (Y in S105), the controller 10 controls the cathode pumps and the on-off valves to form a third path (gas purge) for the cathode fluid (S106). The controller 10 then determines whether a predetermined time has elapsed since the third path was formed (S107). If the predetermined time has not elapsed (N in S107), the control device 10 repeats the determination in step S107. If the predetermined time has elapsed (Y in S107), the control device 10 ends this routine.

[0094] If the electrolytic cell 2 is not in a stopped state (N in S103), the controller 10 determines whether the electrolytic cell 2 is in a low-load operating state (S108). If the electrolytic cell 2 is not in a low-load operating state (N in S108), the controller 10 ends this routine. If the electrolytic cell 2 is in a low-load operating state (Y in S108), the controller 10 controls the cathode pumps and on-off valves to form a second path (downflow) for the cathode fluid (S109). Then, the controller 10 determines whether a predetermined time has elapsed since the second path was formed (S110). If the predetermined time has not elapsed (N in S110), the controller 10 repeats the determination in step S110. If the predetermined time has elapsed (Y in S110), the controller 10 controls the cathode pumps and on-off valves to form a first path for the cathode fluid (S111), and ends this routine.

[0095] As described above, the organic hydride producing system 1 according to this embodiment includes the electrolytic cell 2, the cathode fluid supply device 8, and the control device 10. The electrolytic cell 2 includes an anode electrode 12 that oxidizes water in the anolyte to produce protons, a cathode electrode 14 that hydrogenates a substance to be hydrogenated in the catholyte with the protons to produce an organic hydride, an anode chamber 16 that houses the anode electrode 12, a cathode chamber 18 that houses the cathode electrode 14, and a diaphragm 20 that separates the anode chamber 16 from the cathode chamber 18 and allows protons to move from the anode chamber 16 side to the cathode chamber 18 side.

[0096] The cathode fluid supply device 8 has a cathode fluid tank 50 that stores the cathode fluid to be supplied to the cathode chamber 18, a first cathode pipe 58 (first pipe) that connects the cathode fluid tank 50 and the cathode chamber 18, and a second cathode pipe 60 and a sixth cathode pipe 68 (second pipe) that connect the cathode fluid tank 50 and the cathode chamber 18. The cathode fluid supply device 8 can switch between supplying the cathode fluid from the cathode fluid tank 50 to the cathode chamber via the first cathode pipe 58 and supplying the cathode fluid via the second cathode pipe 60 and the sixth cathode pipe 68. The control device 10 controls the cathode fluid supply device 8.

[0097] The electrolytic cell 2 has a first cathode opening 30 and a second cathode opening 32 that communicate between the inside and outside of the cathode chamber 18. The first cathode opening 30 is located lower than the second cathode opening 32. The first cathode piping 58 is connected to the first cathode opening 30, and the second cathode piping 60 is connected to the second cathode opening 32. The sixth cathode piping 68 is connected to the second cathode piping 60 and the cathode fluid tank 50. Therefore, the cathode fluid supply device 8 can switch between supplying the cathode fluid from the first cathode opening 30 to the cathode chamber 18 and supplying the cathode fluid from the second cathode opening 32 to the cathode chamber 18. The control device 10 controls the cathode fluid supply device 8 so that, during steady state, the cathode fluid is supplied from the first cathode opening 30 to the cathode chamber 18 to form an upflow of the cathode fluid within the cathode chamber 18, and under predetermined conditions the cathode fluid is supplied from the second cathode opening 32 to the cathode chamber 18 to form a downflow of the cathode fluid within the cathode chamber.

[0098] In this way, by flowing the cathode solution into the cathode chamber 18 in an upflow manner during normal operation of the electrolytic cell 2, the hydrogen gas generated at the cathode electrode 14 can be efficiently discharged from the cathode chamber 18. This prevents the flow of the material to be hydrogenated from being obstructed by the hydrogen gas. This also prevents an increase in the internal pressure of the cathode chamber 18. By flowing the cathode solution into the cathode chamber 18 in a downflow manner under predetermined conditions, the water accumulated in the cathode chamber 18 can be efficiently discharged from the cathode chamber 18. This prevents the flow of the material to be hydrogenated from being obstructed by the water remaining in the cathode chamber 18. As described above, according to the organic hydride manufacturing system 1 of this embodiment, the occurrence of side reactions at the cathode electrode 14 can be suppressed, thereby improving the faradaic efficiency.

[0099] Furthermore, the predetermined condition in this embodiment includes the shutdown of the electrolytic cell 2. When the operation of the electrolytic cell 2 is stopped, no side reactions occur at the cathode electrode 14, and therefore no hydrogen gas is generated. Therefore, when or while the operation of the electrolytic cell 2 is stopped, by flowing the cathode solution downflow into the cathode chamber 18, it is possible to discharge the water in the cathode chamber 18 while suppressing an increase in the internal pressure of the cathode chamber 18 due to hydrogen gas.

[0100] Furthermore, the predetermined condition in this embodiment includes a state in which the amount of hydrogen gas generated during operation of the electrolytic cell 2 is equal to or less than a predetermined value, which is derived from the relationship between the current flowing through the electrolytic cell 2 and the concentration of the hydride in the cathode fluid. Even when the electrolytic cell 2 is in operation, if the amount of hydrogen gas generated is equal to or less than the predetermined value, hydrogen gas is unlikely to accumulate in the cathode chamber 18 even if the cathode fluid is flowed downflow into the cathode chamber 18. Therefore, when the electrolytic cell 2 is in a state in which the amount of hydrogen gas generated is equal to or less than the predetermined value, by flowing the cathode fluid downflow into the cathode chamber 18, it is possible to discharge the water in the cathode chamber 18 while suppressing an increase in the internal pressure of the cathode chamber 18 due to hydrogen gas.

[0101] Furthermore, the control device 10 of this embodiment stops the downflow after a predetermined time has elapsed since switching to the downflow. This prevents the downflow from continuing unnecessarily and increasing the power consumption of the organic hydride manufacturing system 1. The organic hydride manufacturing system 1 of this embodiment also includes a water volume sensor 96 that detects the amount of water discharged from the cathode chamber 18 by the downflow. In this case, the control device 10 may stop the downflow when the water volume sensor 96 detects that the amount of water has fallen below a predetermined value.

[0102] The organic hydride manufacturing system 1 of this embodiment also includes a gas tank 56 and a sixth on-off valve 94 as a gas supply mechanism that supplies a predetermined gas to the cathode chamber 18. The control device 10 controls the gas supply mechanism so that the cathode solution flows downflow into the cathode chamber 18 when the electrolytic cell 2 is out of operation, and supplies gas to the cathode chamber 18 after the downflow stops. This makes it possible to more reliably discharge water from the cathode chamber 18. The gas supply mechanism may also be omitted.

[0103] The embodiments of the present invention have been described in detail above. The above-described embodiments merely illustrate specific examples of implementing the present invention. The content of the embodiments does not limit the technical scope of the present invention, and many design modifications, such as changing, adding, or deleting components, are possible within the scope of the inventive concept defined in the claims. A new embodiment with design modifications will combine the effects of the combined embodiments and modifications. In the above-described embodiments, content that allows such design modifications is emphasized by using notations such as "in this embodiment" or "in this embodiment," but design modifications are also permitted even in content without such notation. Any combination of the above-described components is also valid as an aspect of the present invention.

[0104] The embodiments may be specified by the following items. [Item 1] an electrolytic cell (2) having a cathode chamber (18) accommodating a cathode electrode (14) that hydrogenates a substance to be hydrogenated in a cathode solution with protons to produce an organic hydride, and a first cathode opening (30) and a second cathode opening (32) that communicate between the inside and outside of the cathode chamber (18), with the first cathode opening (30) being located below the second cathode opening (32); a cathode fluid supply device (8) capable of switching between supplying the cathode fluid from the first cathode opening (30) to the cathode chamber (18) and supplying the cathode fluid from the second cathode opening (32) to the cathode chamber (18); a control device (10) that controls the cathode fluid supply device (8) so that, during steady state, cathode fluid is supplied to the cathode chamber (18) from the first cathode opening (30) to form an upflow of cathode fluid in the cathode chamber (18), and cathode fluid is supplied to the cathode chamber (18) from the second cathode opening (32) under predetermined conditions to form a downflow of cathode fluid in the cathode chamber (18). Organic hydride production system (1). [Item 2] The predetermined condition includes stopping the operation of the electrolytic cell (2). Item 1 Organic hydride production system (1). [Item 3] At the cathode electrode (14), a side reaction occurs in which hydrogen gas is generated. the predetermined condition includes a state in which the amount of hydrogen gas generated during operation of the electrolytic cell (2) is equal to or less than a predetermined value, which is derived from the relationship between the current flowing through the electrolytic cell (2) and the concentration of the substance to be hydrided in the cathode solution; An organic hydride production system according to item 1 or 2 (1). [Item 4] The control device (10) stops the downflow after a predetermined time has elapsed since the downflow was switched on. 4. The organic hydride production system (1) according to any one of Items 1 to 3. [Item 5] The electrolytic cell (2) has an anode chamber (16) that houses an anode electrode (12) that oxidizes water in the anolyte to produce protons; The protons move together with the water from the anode chamber (16) to the cathode chamber (18), The organic hydride production system (1) includes a water amount sensor (96) that detects the amount of water discharged from the cathode chamber (18) by downflow, The control device (10) stops the downflow when the water volume sensor (96) detects that the amount of water has fallen below a predetermined value. 4. The organic hydride production system (1) according to any one of Items 1 to 3. [Item 6] The organic hydride production system (1) includes a gas supply mechanism (56, 94) that supplies a predetermined gas to the cathode chamber (18), The predetermined condition is that the electrolytic cell (2) is stopped from operating. the control device (10) controls the gas supply mechanism (56, 94) to supply gas to the cathode chamber (18) after the downflow has stopped; Item 4 or 5 organic hydride production system (1).

[0105] [Item 7] A control device (10) for an organic hydride production system (1) including an electrolytic cell (2) and a cathode liquid supply device (8), the electrolytic cell (2) has a cathode chamber (18) containing a cathode electrode (14) that hydrogenates a substance to be hydrogenated in a cathode solution with protons to produce an organic hydride, and a first cathode opening (30) and a second cathode opening (32) that communicate between the inside and outside of the cathode chamber (18), the first cathode opening (30) being located below the second cathode opening (32); the cathode fluid supply device (8) is capable of switching between supplying the cathode fluid from the first cathode opening (30) to the cathode chamber (18) and supplying the cathode fluid from the second cathode opening (32) to the cathode chamber (18); The control device (10) controls the cathode fluid supply device (8) so that, in a steady state, the cathode fluid is supplied from the first cathode opening (30) to the cathode chamber (18) to form an upflow of the cathode fluid in the cathode chamber (18), and the cathode fluid is supplied from the second cathode opening (32) to the cathode chamber (18) under predetermined conditions to form a downflow of the cathode fluid in the cathode chamber (18). A control device (10) for an organic hydride production system (1).

[0106] [Item 8] A method for controlling an organic hydride production system (1) including an electrolytic cell (2) having a cathode chamber (18) containing a cathode electrode (14) that hydrogenates a substance to be hydrided in a cathode solution with protons to produce an organic hydride, the method comprising: forming an upflow of catholyte in the cathode chamber (18) during steady state operation, and forming a downflow of catholyte in the cathode chamber (18) under predetermined conditions; A method for controlling an organic hydride production system (1). [Industrial Applicability]

[0107] The present invention can be used in an organic hydride production system, a control device for an organic hydride production system, and a control method for an organic hydride production system. [Explanation of symbols]

[0108] 1 organic hydride production system, 2 electrolytic cell, 4 power supply, 8 cathode liquid supply device, 10 control device, 12 anode electrode, 14 cathode electrode, 16 anode chamber, 18 cathode chamber, 20 diaphragm, 30 first cathode opening, 32 second cathode opening, 50 cathode liquid tank, 58 first cathode piping, 60 second cathode piping, 68 sixth cathode piping, 96 water volume sensor.

Claims

1. A control device for an organic hydride production system including an electrolytic cell and a catholyte supply device, the electrolytic cell has a cathode chamber accommodating a cathode electrode that hydrogenates a substance to be hydrogenated in a cathode solution with protons to produce an organic hydride, and a first cathode opening and a second cathode opening that communicate between the inside and outside of the cathode chamber, the first cathode opening being located below the second cathode opening; the cathode fluid supply device is capable of switching between supplying the cathode fluid from the first cathode opening to the cathode chamber and supplying the cathode fluid from the second cathode opening to the cathode chamber; the control device controls the cathode fluid supply device so that, in a steady state, the cathode fluid is supplied from the first cathode opening to the cathode chamber to form an upflow of the cathode fluid in the cathode chamber, and under a predetermined condition, the cathode fluid is supplied from the second cathode opening to the cathode chamber to form a downflow of the cathode fluid in the cathode chamber. Control device for organic hydride production system.

2. 1. A control method for an organic hydride production system including an electrolytic cell having a cathode chamber accommodating a cathode electrode that hydrogenates a substance to be hydrided in a cathode solution with protons to produce an organic hydride, the method comprising: forming an upflow of the cathode fluid in the cathode chamber during steady state and forming a downflow of the cathode fluid in the cathode chamber under predetermined conditions; A method for controlling an organic hydride production system.

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