Organic hydride production apparatus and method for reusing associated water

Abstract

An organic hydride production apparatus 1 comprises: an electrolysis tank 2 having an anode electrode 14 for oxidizing water in an anolyte La to generate protons, a cathode electrode 18 for hydrating a substance α to be hydrated in the cathode liquid Lc with protons to generate an organic hydride β, and a diaphragm 22 positioned between the anode electrode 14 and the cathode electrode 18, the diaphragm 22 moving protons together with produced water W from the anode electrode side 14 to the cathode electrode side 18; an anolyte supply part 6 for supplying the anolyte La to the anode electrode 14; a water separation unit 12 for separating the produced water W from a catholyte Lc sent from the cathode electrode 18; and a water return unit 56 for sending the produced water W separated by the water separation unit 12 to the anolyte supply part 6.

Description

[Technical Field]

[0001] The present invention relates to an organic hydride production apparatus and a method for reusing accompanying water. [Background Art]

[0002] Conventionally, there has been known an organic hydride production apparatus including an electrolytic cell having an anode electrode that generates protons from water, a cathode electrode that hydrogenates an organic compound having an unsaturated bond (hydrogen acceptor), and a diaphragm that separates the anode electrode and the cathode electrode (see, for example, Patent Document 1). In this organic hydride production apparatus, protons are generated by oxidation of water at the anode electrode, the protons move to the cathode electrode side through the diaphragm, and the hydrogen acceptor is hydrogenated by the protons at the cathode electrode, thereby producing an organic hydride. [Prior Art Literature] [Patent Literature]

[0003] [Patent Document 1] International Publication No. 2012 / 091128 [Summary of the Invention] [Problem to be Solved by the Invention]

[0004] According to the above organic hydride production apparatus, generation of protons and hydrogenation of the hydrogen acceptor can be performed in a one-step process. Therefore, compared with the case of producing an organic hydride through a two-step process of producing hydrogen by water electrolysis or the like and chemically hydrogenating the hydrogen acceptor in a reactor such as a plant, the production process of the organic hydride can be simplified. Alternatively, the production efficiency of the organic hydride can be improved. In addition, since the high-pressure container for hydrogen storage, which is required when producing hydrogen by water electrolysis or the like, can be omitted, a significant reduction in equipment cost is expected.

[0005] The inventors of this invention have conducted extensive research on conventional organic hydride manufacturing equipment and have found that there is room to improve the operating efficiency of conventional organic hydride manufacturing equipment.

[0006] This invention was made in view of these circumstances, and one of its objectives is to provide a technology for improving the operating efficiency of an organic hydride production apparatus. [Means for solving the problem]

[0007] One aspect of the present invention is an organic hydride production apparatus. This apparatus comprises an anode electrode that oxidizes water in an anode solution to generate protons, a cathode electrode that hydrogenates a hydride in a cathode solution with protons to generate an organic hydride, and an electrolytic cell having a diaphragm positioned between the anode electrode and the cathode electrode to move protons together with associated water from the anode electrode side to the cathode electrode side, an anode solution supply unit that supplies the anode solution to the anode electrode, a water separation unit that separates associated water from the cathode solution discharged from the cathode electrode, and a water return unit that sends the associated water separated by the water separation unit to the anode solution supply unit.

[0008] Another aspect of the present invention is a method for reusing associated water. This method involves separating associated water from the cathode solution discharged from the cathode electrode and reusing the separated associated water in an electrolytic cell having an anode electrode that oxidizes water in the anode solution to generate protons, a cathode electrode that hydrogenates a hydride in the cathode solution with protons to generate an organic hydride, and a diaphragm placed between the anode electrode and the cathode electrode to move protons together with the associated water from the anode electrode side to the cathode electrode side.

[0009] Any combination of the above components, as well as any conversion of the expressions of this disclosure between methods, apparatus, systems, etc., are also valid forms of this disclosure. [Effects of the Invention]

[0010] According to the present invention, the operating efficiency of an organic hydride production apparatus can be improved. [Brief explanation of the drawing]

[0011] [Figure 1] This is a schematic diagram of an organic hydride manufacturing apparatus according to an embodiment. [Figure 2] This is a schematic diagram of a part of an organic hydride manufacturing apparatus related to a modified example. [Modes for carrying out the invention]

[0012] The present invention will be described below with reference to the drawings, based on preferred embodiments. The embodiments are illustrative and not limiting, and not all features or combinations thereof described in the embodiments are necessarily essential to the invention. The same or equivalent components, members, and processes shown in each drawing are denoted by the same reference numerals, and redundant explanations are omitted as appropriate. Furthermore, the scale and shape of each part shown in each drawing are set for convenience to facilitate explanation and are not to be interpreted restrictively unless otherwise specified. In addition, when terms such as "first," "second," etc. are used in this specification or claims, these terms do not indicate any order or importance, but are used to distinguish one configuration from another. Furthermore, some components that are not important for explaining the embodiments are omitted in each drawing.

[0013] Figure 1 is a schematic diagram of an organic hydride production apparatus 1 according to an embodiment. The organic hydride production apparatus 1 comprises an electrolytic cell 2, a power supply 4, an anode liquid supply unit 6, a cathode liquid supply unit 8, a control unit 10, a water separation unit 12, and a water return unit 56.

[0014] The electrolytic cell 2 hydrogenates the hydride α by an electrochemical reduction reaction to produce an organic hydride β. The electrolytic cell 2 has an anode electrode 14, an anode chamber 16, a cathode electrode 18, a cathode chamber 20, and a diaphragm 22.

[0015] The anode electrode 14 (anode) generates protons by oxidizing water in the anode solution La. The anode electrode 14 is positioned in contact with one main surface of the diaphragm 22. The anode electrode 14 has a metal such as iridium (Ir), ruthenium (Ru), or platinum (Pt), or an oxide thereof, as an anode catalyst. In one example of an anode electrode 14, the anode catalyst is dispersed and supported or coated on an electronically conductive substrate. The substrate is made of a material mainly composed of metals such as titanium (Ti) or stainless steel (SUS). Examples of substrate forms include woven or nonwoven sheets, meshes, porous sintered bodies, foamed molded bodies (foams), and expanded metals. The anode catalyst may also be coated onto the substrate to form a catalyst layer. Alternatively, the anode electrode 14 may be obtained by directly coating the main surface of the diaphragm 22 with the anode catalyst.

[0016] The anode electrode 14 is housed in the anode chamber 16. The space in the anode chamber 16 excluding the anode electrode 14 constitutes a channel for the anode solution La and the oxygen produced in the electrode reaction.

[0017] The cathode electrode 18 (cathode) hydrogenates the hydride α in the cathode liquid Lc with protons to produce an organic hydride β. The cathode electrode 18 is positioned in contact with the other main surface of the diaphragm 22 (the main surface opposite to the anode electrode 14). The cathode electrode 18 has a catalyst layer 18a and a diffusion layer 18b.

[0018] The catalyst layer 18a is positioned in contact with the diaphragm 22. The catalyst layer 18a has, for example, platinum or ruthenium as a cathode catalyst. The catalyst layer 18a also has a catalyst support that holds the cathode catalyst. The catalyst support is composed of an electronically conductive material such as porous carbon, porous metal, or porous metal oxide.

[0019] The diffusion layer 18b is disposed so as to be in contact with the surface of the catalyst layer 18a opposite to the diaphragm 22. The diffusion layer 18b uniformly diffuses liquid hydride α supplied from the outside into the catalyst layer 18a. Further, the organic hydride β produced in the catalyst layer 18a is discharged from the catalyst layer 18a through the diffusion layer 18b. The diffusion layer 18b is made of a conductive material such as carbon or metal. Further, the diffusion layer 18b is a porous body such as a sintered body of fibers or particles, or a foamed molded product. Specific examples of the material constituting the diffusion layer 18b include carbon woven fabric (carbon cloth), carbon non-woven fabric, and carbon paper.

[0020] The cathode electrode 18 is accommodated in the cathode chamber 20. The space in the cathode chamber 20 excluding the cathode electrode 18 constitutes a flow path for the hydride α and the organic hydride β generated by the electrode reaction.

[0021] The anode chamber 16 and the cathode chamber 20 are partitioned by the diaphragm 22. The diaphragm 22 is disposed between the anode electrode 14 and the cathode electrode 18. The diaphragm 22 according to one example is composed of a solid polymer electrolyte membrane having proton conductivity. The solid polymer electrolyte membrane is not particularly limited as long as it is a material that conducts protons, and examples thereof include a fluorine-based ion exchange membrane having a sulfonic acid group such as Nafion (registered trademark). The diaphragm 22 allows protons to move while carrying water from the anode electrode 14 side to the cathode electrode 18 side. Hereinafter, the water that moves together with protons is referred to as accompanying water W.

[0022] In the electrolytic cell 2, the reaction that occurs when toluene (TL) is used as an example of the hydride α is as follows. When toluene is used as the hydride α, the obtained organic hydride β is methylcyclohexane (MCH). <Electrode reaction at anode electrode> 3H2O→3 / 2O2+6H + +6e - <Electrode reaction at cathode electrode> TL+6H + +6e - →MCH

[0023] Specifically, at the anode electrode 14, water is electrolyzed, producing oxygen gas, protons, and electrons. The protons travel across the membrane 22 towards the cathode electrode 18. The electrons flow into the positive electrode of the power supply 4. The oxygen gas is discharged to the outside through the anode chamber 16. At the cathode electrode 18, methylcyclohexane is produced by the reaction of toluene, electrons supplied from the negative electrode of the power supply 4, and protons that have arrived via the membrane 22. Therefore, according to the organic hydride production apparatus 1 of this embodiment, the electrolysis of water and the hydrogenation reaction of the hydride α can be performed in one step.

[0024] Power supply 4 is a DC power supply that supplies power to the electrolytic cell 2. The power supplied from power supply 4 applies a predetermined electrolytic voltage between the anode electrode 14 and the cathode electrode 18 of the electrolytic cell 2. Power supply 4 receives power from the power supply unit 24 and supplies power to the electrolytic cell 2. As an example, the power supply unit 24 can be composed of renewable energy power generation equipment such as a wind power generator 26 or a solar power generator 28. The power supply unit 24 may also include power generation equipment that utilizes renewable energy other than wind and solar power, such as geothermal power generators, wave power generators, thermoelectric power generators, and biomass power generators. Furthermore, the power supply unit 24 is not limited to power generation equipment that utilizes renewable energy.

[0025] The anode solution supply unit 6 supplies anode solution La containing water to the anode electrode 14. The anode solution supply unit 6 includes an anode solution tank 30, an anode solution circulation path 32, an anode solution transfer device 34, and an anode solution gas-liquid separation unit 36. The anode solution tank 30 stores the anode solution La supplied to the anode electrode 14. Examples of anode solution La include solutions with a predetermined ionic conductivity such as aqueous sulfuric acid solution, aqueous nitric acid solution, aqueous hydrochloric acid solution, pure water, and deionized water.

[0026] The anode liquid tank 30 and the anode chamber 16 are connected by an anode liquid circulation path 32. The anode liquid circulation path 32 includes an anode inlet pipe 32a that supplies the anode liquid La from the anode liquid tank 30 to the anode electrode 14, and an anode outlet pipe 32b that returns the anode liquid La discharged from the anode electrode 14 back to the anode liquid tank 30.

[0027] The anode fluid transfer device 34 is installed, for example, in the middle of the anode inlet piping 32a. When the anode fluid transfer device 34 is driven, the anode fluid La flows through the anode fluid circulation path 32 and circulates between the anode fluid tank 30 and the anode electrode 14. As the anode fluid transfer device 34, various pumps such as gear pumps and cylinder pumps, or gravity-fed devices can be used.

[0028] The anode liquid-gas-liquid separation unit 36 ​​is located in the middle of the anode outlet piping 32b. Oxygen is generated at the anode electrode 14 by the electrode reaction. Therefore, the anode liquid La recovered from the anode electrode 14 contains gaseous oxygen and dissolved oxygen in addition to unreacted water. The gaseous oxygen is separated from the anode liquid La in the anode liquid-gas-liquid separation unit 36 ​​and removed from the system. The anode liquid La from which the oxygen has been separated is recovered in the anode liquid tank 30.

[0029] In one example, the anode liquid supply unit 6, the anode inlet pipe 32a is connected to the lower vertical part of the anode chamber 16, and the anode outlet pipe 32b is connected to the upper vertical part of the anode chamber 16. The anode liquid La in the anode liquid tank 30 is pumped up by the anode liquid transfer device 34 and enters the anode chamber 16. The anode liquid La in the anode chamber 16 is pushed out to the anode outlet pipe 32b by the flow of anode liquid La entering the anode chamber 16, and flows down to the anode liquid gas-liquid separation unit 36 ​​by gravity. The anode liquid La is placed under atmospheric pressure in the anode liquid gas-liquid separation unit 36. The anode liquid La in the anode liquid gas-liquid separation unit 36 ​​flows into the anode liquid tank 30 by gravity as the liquid level in the anode liquid tank 30 decreases. Alternatively, the anode inlet pipe 32a may be connected to the upper vertical part of the anode chamber 16, so that the anode liquid La enters the anode chamber 16 from the upper vertical part.

[0030] The cathode liquid supply unit 8 supplies cathode liquid Lc containing the hydride α to the cathode electrode 18. The cathode liquid supply unit 8 includes a cathode liquid tank 38, a cathode liquid circulation path 40, a cathode liquid transfer device 42, and a cathode liquid gas-liquid separation unit 44. The cathode liquid tank 38 stores the cathode liquid Lc supplied to the cathode electrode 18. The cathode liquid Lc stored in the cathode liquid tank 38 contains the hydride α at least before the start of operation of the organic hydride production apparatus 1. The hydride α is a compound that is hydrogenated by the electrochemical reduction reaction in the electrolytic cell 2 to become organic hydride β, that is, a dehydrogenated form of organic hydride β. The hydride α and organic hydride β are preferably liquid at 20°C and 1 atm.

[0031] Hydrogenated substance α and organic hydride β are organic compounds that can have hydrogen added to or removed from them by reversibly undergoing hydrogenation / dehydrogenation reactions. Furthermore, hydrogenated substance α and organic hydride β have a lower specific gravity than water. In addition, hydrogenated substance α and organic hydride β have low miscibility with water and form an interface IF with the associated water W.

[0032] If the detection unit 52, described later, is composed of a sensor that detects the interface IF based on the difference in buoyancy (specific gravity) applied to the float, then a hydride α and an organic hydride β are selected that have a difference in specific gravity with respect to the associated water W to a degree that can be detected by this sensor. In this case, the hydride α may be, for example, a liquid with a specific gravity of 0.6 to 0.9 g / cm³. 3 Examples of aromatic compounds are provided. Furthermore, if the detection unit 52 is composed of a sensor that detects the interface IF based on the difference in capacitance (relative permittivity), then a hydride α and an organic hydride β are selected that have a relative permittivity difference with respect to the associated water W to a degree that can be detected by this sensor. In this case, examples of hydride α include aromatic compounds with a relative permittivity of 1 to 50. Specific examples of hydride α include alkylbenzenes such as benzene and toluene, and nitrogen-containing aromatic compounds such as pyridine and pyrazine.

[0033] The cathode liquid tank 38 and the cathode chamber 20 are connected by a cathode liquid circulation path 40. The cathode liquid circulation path 40 includes a cathode inlet pipe 40a that supplies cathode liquid Lc from the cathode liquid tank 38 to the cathode electrode 18, and a cathode outlet pipe 40b that returns the cathode liquid Lc discharged from the cathode electrode 18 back to the cathode liquid tank 38. As the operating time of the organic hydride production apparatus 1 progresses, in other words, as the number of circulations increases, the concentration of the hydride α decreases and the concentration of the organic hydride β increases in the cathode liquid Lc flowing through the cathode liquid circulation path 40.

[0034] The cathode fluid transfer device 42 is installed, for example, in the middle of the cathode inlet piping 40a. When the cathode fluid transfer device 42 is driven, the cathode fluid Lc flows through the cathode fluid circulation path 40 and circulates between the cathode fluid tank 38 and the cathode electrode 18. As the cathode fluid transfer device 42, various pumps such as gear pumps and cylinder pumps, or gravity-fed devices can be used.

[0035] The cathode liquid-gas-liquid separation unit 44 is located in the middle of the cathode outlet piping 40b. Hydrogen is produced at the cathode electrode 18 by a side reaction. This side reaction is more likely to occur as the supply of hydride α to the cathode electrode 18 becomes insufficient. Therefore, the cathode liquid Lc recovered from the cathode electrode 18 contains gaseous hydrogen and dissolved hydrogen, in addition to the unreacted hydride α and the generated organic hydride β. The gaseous hydrogen is separated from the cathode liquid Lc at the cathode liquid-gas-liquid separation unit 44 and removed from the system. The cathode liquid Lc from which hydrogen has been separated is recovered in the cathode liquid tank 38.

[0036] In one example of a cathode liquid supply unit 8, the cathode inlet pipe 40a is connected to the lower vertical part of the cathode chamber 20, and the cathode outlet pipe 40b is connected to the upper vertical part of the cathode chamber 20. The cathode liquid Lc in the cathode liquid tank 38 is pumped up by the cathode liquid transfer device 42 and enters the cathode chamber 20. The cathode liquid Lc in the cathode chamber 20 is pushed out to the cathode outlet pipe 40b by the flow of cathode liquid Lc entering the cathode chamber 20, and flows down to the cathode liquid gas-liquid separation unit 44 by gravity. The cathode liquid Lc is placed under atmospheric pressure in the cathode liquid gas-liquid separation unit 44. The cathode liquid Lc in the cathode liquid gas-liquid separation unit 44 flows into the cathode liquid tank 38 by gravity as the liquid level in the cathode liquid tank 38 decreases. Alternatively, the cathode inlet pipe 40a may be connected to the upper vertical part of the cathode chamber 20, so that the cathode fluid Lc enters the cathode chamber 20 from the upper vertical part.

[0037] The control unit 10 controls the operation of the organic hydride manufacturing apparatus 1. The control unit 10 is implemented as a hardware component consisting of a computer's CPU, memory, and other elements and circuits, and as a software component consisting of a computer program, etc. However, in Figure 1, it is depicted as a functional block realized through the coordination of these components. It will be obvious to those skilled in the art that this functional block can be realized in various ways through combinations of hardware and software.

[0038] The control unit 10 receives at least one signal from a sensor 46 provided in the electrolytic cell 2: a signal indicating the voltage of the electrolytic cell 2, a signal indicating the potential of the anode electrode 14, and a signal indicating the potential of the cathode electrode 18. The sensor 46 can detect the potential of each electrode and the voltage of the electrolytic cell 2 using known methods. One example of the sensor 46 is a known voltmeter or the like. The sensor 46 may also include a current detection unit that detects the current flowing between the anode electrode 14 and the cathode electrode 18. Based on the detection results of the sensor 46, the control unit 10 controls the power supply 4, the anode liquid transfer device 34, the cathode liquid transfer device 42, etc.

[0039] The water separation unit 12 separates the associated water W from the cathode liquid Lc. As described above, the associated water W moves from the anode electrode 14 side to the cathode electrode 18 side. Therefore, the cathode liquid Lc sent out from the cathode electrode 18 contains not only the hydride α and organic hydride β but also the associated water W. The water separation unit 12 separates this associated water W from the cathode liquid Lc.

[0040] The water separation unit 12 includes a container 48, a drain pipe 50, a detection unit 52, and a switching unit 54. The container 48 stores the cathode liquid Lc sent from the cathode electrode 18. In this embodiment, the container 48 is located in the middle of the cathode outlet piping 40b and also serves as the cathode liquid gas-liquid separation unit 44. Therefore, an exhaust port 48a for discharging hydrogen from the cathode liquid Lc is provided at the upper vertical part of the container 48. The hydride α and organic hydride β have a lower specific gravity than the associated water W and are incompatible with the associated water W. For this reason, the cathode liquid Lc is divided in the container 48 into a lower layer (water layer) containing the associated water W and an upper layer (oil layer) containing the hydride α and organic hydride β.

[0041] The drain pipe 50 is connected to the container 48 to discharge the associated water W accumulated in the container 48. One end of the drain pipe 50 and one end of the cathode outlet pipe 40b are connected to the container 48. The other end of the cathode outlet pipe 40b is connected to the cathode liquid tank 38. The connection position C1 of the drain pipe 50 to the container 48 (cathode liquid gas-liquid separation unit 44) is positioned vertically lower than the connection position C2 of the cathode outlet pipe 40b to the container 48.

[0042] The detection unit 52 detects when a predetermined amount of associated water W has accumulated in the container 48. The "determined amount" can be set appropriately based on experiments or simulations. The detection unit 52 in this embodiment is composed of an interface sensor that detects the interface IF between the layer containing the hydride α and organic hydride β in the cathode liquid Lc and the layer containing the associated water W. Known interface sensors such as float-type interface sensors, capacitance-type interface sensors, and conductivity-type interface sensors can be used in the detection unit 52. Furthermore, those skilled in the art can appropriately select the combination of the types of hydride α and organic hydride β and the detection method of the interface sensor.

[0043] The detection position of the interface IF by the detection unit 52 is set vertically below the connection position C2 of the cathode outlet pipe 40b. The detection position of the interface IF is set vertically above the connection position C1 of the drain pipe 50. The detection unit 52 is located, for example, inside the container 48. However, if the container 48 does not obstruct the detection of the interface IF (for example, if the container 48 is made of a material that allows the capacitance inside the container to be detected from the outside), the detection unit 52 may be located outside the container 48. By detecting the interface IF, the detection unit 52 can detect that a predetermined amount of associated water W has accumulated in the container 48. When the detection unit 52 detects the interface IF, it transmits a control signal to the switching unit 54.

[0044] The switching unit 54 is provided in the drain pipe 50. The switching unit 54 has a mechanism that can switch between a restricting state that restricts drainage from the drain pipe 50 and an execution state that allows drainage from the drain pipe 50. In this embodiment, the switching unit 54 is composed of a valve. As the valve that constitutes the switching unit 54, for example, a known solenoid valve or an air-driven valve can be used. Preferably, the valve that constitutes the switching unit 54 is a normally closed type valve that closes when not energized and opens when energized. When the switching unit 54 is closed, the discharge of accompanying water W from the drain pipe 50 is restricted. When the switching unit 54 is opened, the discharge of accompanying water W from the drain pipe 50 is permitted and drainage is performed.

[0045] The switching unit 54 opens based on the detection result of the detection unit 52. In other words, when the water level of the accompanying water W (interface IF) rises to the detection position of the detection unit 52, the switching unit 54 receives a control signal from the detection unit 52, becomes energized, opens, and the accompanying water W is automatically discharged from the container 48. The amount of accompanying water W that accumulates in the container 48 before the switching unit 54 opens is determined according to the size of the container 48 and the detection position of the interface IF.

[0046] Furthermore, the switching unit 54 closes after a predetermined time has elapsed since opening, thereby restricting drainage. For example, the opening time of the switching unit 54 is adjusted so that it closes before the interface IF reaches the connection position C1 of the drain pipe 50. The opening time can be set in advance based on the amount of associated water W accumulated in the container 48 when the switching unit 54 is open, the drainage rate from the drain pipe 50, etc. This makes it possible to suppress the discharge of the hydride α and organic hydride β from the drain pipe 50. Closing the switching unit 54 (switching to the restricted state) may be achieved by the control of the detection unit 52, or by a timer that stops the power supply to the switching unit 54 after a predetermined time has elapsed.

[0047] The opening and closing of the switching unit 54 may also be controlled as follows. That is, the detection unit 52 has two interface sensors, with one interface sensor positioned lower than the other interface sensor. The detection position of the interface IF by the upper interface sensor is set to be below the connection position C2, and the detection position of the interface IF by the lower interface sensor is set to be above the connection position C1. As the associated water W gradually accumulates and the interface IF rises, the interface IF is detected by the upper interface sensor. As a result, the switching unit 54 opens, the associated water W is discharged, and the interface IF descends. Then, when the interface IF is detected by the lower interface sensor, the switching unit 54 closes. This control also helps to prevent the hydrogenated substance α and organic hydride β from being discharged from the drain pipe 50.

[0048] The switching unit 54 can also be configured as a pump. In this case, the switching unit 54 is driven upon receiving a control signal from the detection unit 52 to perform drainage. The switching unit 54 also stops driving and restricts drainage when a predetermined time has elapsed since the start of drainage.

[0049] The water return section 56 sends the associated water W separated by the water separation section 12 to the anode liquid supply section 6. In this embodiment, the water return section 56 includes a water return pipe 58, an oil separation section 60, an oil return section 62, and an associated water transfer device 64. One end of the water return pipe 58 is connected to the drain pipe 50, and the other end is connected to the anode liquid supply section 6. For example, the other end of the water return pipe 58 is connected to the anode liquid tank 30. An associated water transfer device 64 is provided in the middle of the water return pipe 58. In Figure 1, the associated water transfer device 64 is installed between the water separation section 12 and the oil separation section 60. However, it is not limited to this, and the associated water transfer device 64 may be placed between the oil separation section 60 and the anode liquid supply section 6. As the associated water transfer device 64, various pumps such as gear pumps and cylinder pumps, or gravity-fed devices can be used. The drive of the associated water transfer device 64 is controlled by the control unit 10. For example, the accompanying water transfer device 64 is driven in conjunction with the opening of the valve of the switching unit 54. As a result, the accompanying water W discharged from the drain pipe 50 flows into the anode liquid tank 30 through the water return pipe 58.

[0050] The oil separation section 60 is installed in the middle of the water return pipe 58. Hydrogenated substances α and organic hydrides β are dissolved in the associated water W. Therefore, the associated water W is hydrogenated Thing α The oil contains at least one of the organic hydride β as an oil component. The oil separation unit 60 separates the oil component contained in the associated water W from the associated water W. As an example, the oil separation unit 60 has a filter that separates the oil component from the associated water W by selectively adsorbing the oil component. This makes it possible to separate the oil component from the associated water W physically or chemically. Examples of filters include activated carbon filters, ceramic membrane filters, and PTFE hollow fiber membrane modules.

[0051] Another example is the oil separation unit 60, which cools or heats the associated water W and separates the oil from the associated water W based on the boiling point difference between the water and the oil. For example, if the hydride α is toluene, the oil separation unit 60 can extract toluene and methylcyclohexane as oil from the associated water W by heating and distilling the associated water W. For example, if the organic hydride production apparatus 1 is adjacent to a power plant or an oil refinery, and the heat generated by the various devices in the plant can be utilized, this heat can be used for distillation.

[0052] Another example is the oil separation unit 60, which includes a coalescer. The coalescer coagulates and coarses the oil in the associated water W. This allows the oil to be separated from the associated water W based on the difference in specific gravity between the water and the oil.

[0053] The oil return section 62 sends the oil separated by the oil separation section 60 to the cathode liquid supply section 8. In this embodiment, the oil return section 62 consists of piping connected to the oil separation section 60 and the cathode liquid tank 38. The piping constituting the oil return section 62 may be equipped with an oil transfer device such as a pump as needed. If the oil separation section 60 is equipped with a filter and this filter is regenerative by heating, the oil adsorbed on the filter can be removed by heating the filter with the heat generated in each device of the power plant or petroleum refining plant. Note that the installation of the oil return section 62 is optional. For example, if it is difficult to remove oil from the filter, or if replacing the filter is more efficient than performing oil return, the oil return section 62 may not be provided.

[0054] In the above description, the cathode liquid Lc circulates between the cathode liquid tank 38 and the cathode chamber 20. However, the cathode liquid Lc discharged from the cathode chamber 20 does not necessarily have to be returned to the cathode liquid tank 38. In this case, the cathode liquid Lc discharged from the cathode chamber 20 may be stored in an organic hydride tank (not shown) after passing through the cathode liquid gas-liquid separation unit 44. Also, in the above description, the cathode liquid Lc discharged from the cathode chamber 20 contains unreacted hydride α. However, the cathode liquid Lc discharged from the cathode chamber 20 may not contain hydride α, as all of the hydride α supplied to the cathode chamber 20 may be converted to organic hydride β.

[0055] Furthermore, although only one electrolytic cell 2 is shown in Figure 1, the organic hydride manufacturing apparatus 1 may have multiple electrolytic cells 2. In this case, each electrolytic cell 2 is oriented so that the anode chamber 16 and cathode chamber 20 are aligned in the same direction, and is stacked with a conductive plate in between adjacent electrolytic cells 2. This connects each electrolytic cell 2 electrically in series. The conductive plate is made of a conductive material such as metal. Note that each electrolytic cell 2 may be connected in parallel, or a combination of series and parallel connections may be used.

[0056] As described above, the organic hydride production apparatus 1 according to this embodiment comprises an electrolytic cell 2, an anode liquid supply unit 6, a water separation unit 12, and a water return unit 56. The electrolytic cell 2 has an anode electrode 14 that oxidizes water in the anode liquid La to generate protons, a cathode electrode 18 that hydrogenates the hydride α in the cathode liquid Lc with protons to generate organic hydride β, and a diaphragm 22 that is positioned between the anode electrode 14 and the cathode electrode 18 and moves protons together with the associated water W from the anode electrode 14 side to the cathode electrode 18 side. The anode liquid supply unit 6 supplies the anode liquid La to the anode electrode 14. The water separation unit 12 separates the associated water W from the cathode liquid Lc sent from the cathode electrode 18. The water return unit 56 sends the associated water W separated by the water separation unit 12 to the anode liquid supply unit 6.

[0057] As described above, in organic hydride production using electrolytic cell 2, protons and associated water W move from the anode electrode 14 side to the cathode electrode 18 side. The associated water W that has moved to the cathode electrode 18 side is sent out of electrolytic cell 2 together with the cathode liquid Lc and may accumulate at the bottom of the cathode liquid gas-liquid separation unit 44 located downstream of electrolytic cell 2. In addition, if a circulation channel is provided between the cathode liquid tank 38 and electrolytic cell 2, associated water W may also accumulate at the bottom of the cathode liquid tank 38. If the amount of stagnant associated water W increases, there is a risk that the hydride α and organic hydride β may overflow from the cathode liquid gas-liquid separation unit 44, etc.

[0058] In response to this, it is conceivable to suppress the overflow of the hydride α and organic hydride β by increasing the volume of the cathode liquid-gas-liquid separation unit 44, etc., taking into account the increase in associated water W. However, increasing the volume of the cathode liquid-gas-liquid separation unit 44, etc., would lead to an increase in the size of the organic hydride production apparatus. Therefore, it is desirable to discharge the associated water W that has moved to the cathode side from the system. In addition, the associated water W in the cathode electrode 18 may inhibit the reduction reaction of the hydride α at the cathode electrode 18. Therefore, it is also desirable to discharge the associated water W for this reason as well.

[0059] When discharging produced water W, it is necessary to temporarily store the produced water W in a tank and to transport it. Furthermore, produced water W contains dissolved hydrides α and organic hydrides β. Therefore, from the perspective of reducing environmental impact, it is required to reduce the dissolved substances in produced water W when discharging it. As a result, the treatment of produced water W requires considerable effort and cost. In the actual operation of an organic hydride manufacturing plant, the amount of produced water W generated in a single operation is enormous, and the effort and cost required to treat the produced water W are far greater than imagined. Therefore, the treatment of produced water W reduces the operating efficiency of the organic hydride manufacturing plant and has become a serious problem in actual manufacturing management.

[0060] On the other hand, at the anode, water is consumed by the electrode reaction at the anode electrode 14. Also, water moves across the membrane 22. Therefore, the amount of water in the anode solution La gradually decreases. Consequently, as the electrolytic reduction reaction progresses, it is necessary to replenish the water at the anode. Replenishing the water at the anode requires equipment such as tanks to store the replenishment water, as well as water transportation work, which is labor-intensive and costly.

[0061] In other words, conventional organic hydride production involves the contradictory processes of removing water on the cathode side and replenishing water on the anode side, which is highly inefficient in terms of operation. In contrast, the organic hydride production apparatus 1 according to this embodiment reuses the associated water W by having the water separation unit 12 separate the associated water W from the cathode liquid Lc and having the water return unit 56 return this associated water W to the anode liquid supply unit 6. This reduces the labor and cost associated with the discharge of the associated water W, and also reduces the amount of water that needs to be replenished on the anode side. Therefore, the operating efficiency of the organic hydride production apparatus 1 can be improved.

[0062] In particular, power plants utilizing renewable energy are sometimes installed in areas where water procurement is difficult. When an organic hydride production device 1 is incorporated into such a power plant, securing water to replenish the anode becomes a major challenge. Therefore, reusing the associated water W is extremely effective in improving the operating efficiency of the organic hydride production device 1.

[0063] Furthermore, the water return section 56 of this embodiment has an oil separation section 60 that separates oil (at least one of the hydrogenated substance α and the organic hydride β) contained in the associated water W from the associated water W. One example of the oil separation section 60 has a filter that adsorbs the oil. Another example of the oil separation section 60 cools or heats the associated water W and separates the oil from the associated water W based on the boiling point difference between the water and the oil. Yet another example of the oil separation section 60 has a coalescer that coagulates the oil in the associated water W and separates it from the associated water W. This makes it possible to suppress the disruption of the electrode reaction at the anode electrode 14 or the deterioration of the anode electrode 14 due to the movement of oil to the anode side.

[0064] Furthermore, the organic hydride production apparatus 1 of this embodiment includes a cathode liquid supply unit 8 that supplies cathode liquid Lc to the cathode electrode 18. In addition, as an example, the water return unit 56 has an oil return unit 62 that sends the oil separated by the oil separation unit 60 to the cathode liquid supply unit 8. This allows for the reuse of the hydride α in the associated water W. Moreover, the yield of organic hydride β can be increased by reusing the hydride α and recovering the organic hydride β. Thus, the operating efficiency of the organic hydride production apparatus 1 can be further improved.

[0065] Furthermore, the water separation unit 12 of this embodiment includes a container 48 for storing cathode liquid Lc sent from the cathode electrode 18, a drain pipe 50 connected to the container 48 for discharging the associated water W, a detection unit 52 for detecting when a predetermined amount of associated water W has accumulated in the container 48, and a switching unit 54 provided in the drain pipe 50 that can switch between a restricting state that restricts drainage from the drain pipe 50 and an execution state that performs drainage, and switches from the restricting state to the execution state based on the detection result of the detection unit 52.

[0066] This makes it possible to suppress the overflow of organic hydride β and hydride α from the cathode liquid-gas-liquid separation unit 44, etc., located downstream of the cathode chamber 20, due to an increase in associated water W. In addition, the required size of the cathode liquid-gas-liquid separation unit 44, etc. can be reduced. Thus, the size of the organic hydride production apparatus 1 can be suppressed. Furthermore, according to the water separation unit 12 of this embodiment, the associated water W can be automatically discharged. Therefore, it becomes unnecessary to visually check for the accumulation of associated water W in the cathode liquid-gas-liquid separation unit 44, etc., or to periodically discharge the associated water W, thereby improving the operating efficiency of the organic hydride production apparatus 1.

[0067] The embodiments of the present invention have been described in detail above. The embodiments described above are merely examples of how to implement the present invention. The content of the embodiments does not limit the technical scope of the present invention, and many design changes, such as changes, additions, and deletions of components, are possible as long as they do not depart from the spirit of the invention as defined in the claims. The new embodiments to which design changes have been made combine the effects of the respective embodiments and modifications. In the embodiments described above, the content in which such design changes are possible is emphasized with notations such as "in this embodiment" or "in this embodiment," but design changes are also permitted even if there are no such notations. Any combination of the above components is also valid as an embodiment of the present invention.

[0068] (modified version) This modified example has a configuration common to the embodiment, except for the arrangement of the water separation unit 12. Below, this modified example will be described focusing on the configurations that differ from the embodiment, and the common configurations will not be described. Figure 2 is a schematic diagram of a part of the organic hydride manufacturing apparatus 1 according to the modified example. In this modified example, the electrolytic cell 2, power supply 4, anode liquid supply unit 6, control unit 10, power supply unit 24, and water return unit 56 have the same configuration as in the embodiment.

[0069] The cathode liquid supply unit 8 includes a cathode liquid tank 38, a cathode liquid circulation path 40, a cathode liquid transfer device 42, and a cathode liquid gas-liquid separation unit 44. In the embodiment, a water separation unit 12 is provided in the cathode liquid gas-liquid separation unit 44, but in this modified example, the water separation unit 12 is provided in the cathode liquid tank 38. Except for this point, the configurations of the cathode liquid supply unit 8 are the same as in the embodiment. The water separation unit 12 includes a container 48, a drain pipe 50, a detection unit 52, and a switching unit 54. In this modified example, the container 48 also serves as the cathode liquid tank 38. The cathode liquid Lc stored in the container 48 contains a hydride α, an organic hydride β, and associated water W. The cathode liquid Lc is divided in the container 48 into a lower layer containing associated water W and an upper layer containing the hydride α and organic hydride β.

[0070] One end of the drain pipe 50 is connected to the container 48. Another end of the cathode inlet pipe 40a is connected to the container 48. The other end of the cathode inlet pipe 40a is connected to the cathode chamber 20. The connection position C1 of the drain pipe 50 to the container 48 (cathode liquid tank 38) is located vertically below the connection position C3 of the cathode inlet pipe 40a to the container 48. Naturally, the connection position C1 is also located vertically below the connection position of the cathode outlet pipe 40b to the container 48.

[0071] The detection unit 52 detects when a predetermined amount of associated water W has accumulated in the container 48. As an example, the detection unit 52 is composed of an interface sensor. The detection position of the interface IF by the detection unit 52 is set vertically below the connection position C3 of the cathode inlet pipe 40a. Also, the detection position of the interface IF is set vertically above the connection position C1 of the drain pipe 50.

[0072] The switching unit 54 is provided in the drain pipe 50. In this modified example, the switching unit 54 is composed of a valve, similar to the embodiment, and opens based on the detection result of the detection unit 52. That is, when the water level of the accompanying water W rises to the detection position of the detection unit 52, the switching unit 54 receives a control signal from the detection unit 52, becomes energized, and opens, and the accompanying water W is automatically discharged from the container 48. In another example, the switching unit 54 closes after a predetermined time has elapsed since opening. In addition, as in the embodiment, opening and closing control of the switching unit 54 using two interface sensors can also be employed. Furthermore, the switching unit 54 can also be composed of a pump.

[0073] The organic hydride production apparatus 1 according to this modified example can also obtain the same effects as the organic hydride production apparatus 1 according to the embodiment. Furthermore, an exhaust port 48a may be provided in the container 48 constituting the cathode liquid tank 38, so that the container 48 of the water separation unit 12 also serves as the cathode liquid tank 38 and the cathode liquid gas-liquid separation unit 44. Similarly, the anode liquid supply unit 6 may have the anode liquid gas-liquid separation unit 36 ​​and the anode liquid tank 30 integrated into a single unit.

[0074] The embodiments may be specified by the items described below. [Item 1] An electrolytic cell (2) having an anode electrode (14) that oxidizes water in the anode solution (La) to generate protons, a cathode electrode (18) that hydrogenates the hydride (α) in the cathode solution (Lc) with protons to generate an organic hydride (β), and a diaphragm (22) positioned between the anode electrode (14) and the cathode electrode (18) to move protons together with associated water (W) from the anode electrode (14) side to the cathode electrode (18) side, An anode solution supply unit (6) that supplies anode solution (La) to the anode electrode (14), A water separation unit (12) separates associated water (W) from the cathode liquid (Lc) discharged from the cathode electrode (18), The system includes a water return section (56) that sends the associated water (W) separated by the water separation section (12) to the anode liquid supply section (6), Organic hydride production apparatus (1).

[0075] [Item 2] In an electrolytic cell (2) having an anode electrode (14) that oxidizes water in the anode solution (La) to generate protons, a cathode electrode (18) that hydrogenates the hydrogenated substance (α) in the cathode solution (Lc) with protons to generate an organic hydride (β), and a diaphragm (22) that separates the anode electrode (14) and the cathode electrode (18) and moves protons together with associated water (W) from the anode electrode (14) side to the cathode electrode (18) side, the associated water (W) is separated from the cathode solution (Lc) discharged from the cathode electrode (18), This includes reusing the separated associated water (W) at the anode electrode (14). Methods for reusing associated water (W). [Industrial applicability]

[0076] This invention can be used in organic hydride production apparatus and methods for reusing associated water. [Explanation of Symbols]

[0077] 1 Organic hydride manufacturing apparatus, 2 Electrolytic cell, 6 Anode liquid supply unit, 8 Cathode liquid supply unit, 12 Water separation unit, 14 Anode electrode, 18 Cathode electrode, 22 Diaphragm, 48 Container, 50 Drain pipe, 52 Detection unit, 54 Switching unit, 56 Water return unit, 60 Oil separation unit, 62 Oil return unit.

Claims

1. An electrolytic cell comprising an anode electrode that oxidizes water in the anode solution to generate protons, a cathode electrode that hydrogenates a hydride in the cathode solution with the protons to generate an organic hydride, and a diaphragm disposed between the anode electrode and the cathode electrode to move the protons together with the associated water from the anode electrode side to the cathode electrode side, an anode solution supply unit that supplies the anode solution to the anode electrode, A water separation unit for separating the associated water from the cathode liquid discharged from the cathode electrode, A water return unit that sends the associated water separated by the water separation unit to the anode liquid supply unit, The system includes a cathode liquid supply unit that supplies the cathode liquid to the cathode electrode, The water separation unit comprises a container, a drain pipe, a detection unit, and a switching unit. The container stores the cathode liquid discharged from the cathode electrode, and the cathode liquid is divided within the container into a lower layer containing the associated water and an upper layer containing the hydride and the organic hydride. The drain pipe is connected to the container and discharges the associated water accumulated in the container. The detection unit detects that a predetermined amount of the associated water has accumulated in the container, The switching unit is provided in the drain pipe and includes a mechanism that, upon receiving a control signal from the detection unit, can switch from a restricting state that restricts drainage from the drain pipe to an execution state that allows drainage from the drain pipe. The cathode liquid supply unit is connected to the container and has a cathode liquid tank for storing the cathode liquid supplied to the cathode electrode, and the cathode liquid in the container flows into the cathode liquid tank as the liquid level in the cathode liquid tank decreases. Organic hydride manufacturing equipment.

2. The associated water contains at least one of the hydrogenated substance and the organic hydride as an oil component. The water return section has an oil separation section that separates the oil from the associated water. The apparatus for producing organic hydride according to claim 1.

3. The oil separation unit has a filter for separating the oil from the associated water. The organic hydride production apparatus according to claim 2.

4. The oil separation unit cools or heats the associated water and separates the oil from the associated water based on the difference in boiling points between the water and the oil. The organic hydride production apparatus according to claim 2.

5. The oil separation unit has a coalescer that coagulates the oil in the associated water and separates it from the associated water. The organic hydride production apparatus according to claim 2.

6. The water return section has an oil return section that sends the oil separated by the oil separation section to the cathode liquid supply section. The organic hydride production apparatus according to any one of claims 2 to 5.

7. An electrolytic cell having an anode electrode that oxidizes water in the anode solution to generate protons, a cathode electrode that hydrogenates a hydride in the cathode solution with the protons to generate an organic hydride, and a diaphragm disposed between the anode electrode and the cathode electrode to move the protons together with the associated water from the anode electrode side to the cathode electrode side, wherein the associated water is separated from the cathode solution discharged from the cathode electrode in a water separation unit, This includes reusing the separated associated water at the anode electrode, The water separation unit comprises a container, a drain pipe, a detection unit, and a switching unit. The container stores the cathode liquid discharged from the cathode electrode, and the cathode liquid is divided within the container into a lower layer containing the associated water and an upper layer containing the hydride and the organic hydride. The drain pipe is connected to the container and discharges the associated water accumulated in the container. The detection unit detects that a predetermined amount of the associated water has accumulated in the container, The switching unit is provided in the drain pipe and includes a mechanism that, upon receiving a control signal from the detection unit, can switch from a restricting state that restricts drainage from the drain pipe to an execution state that allows drainage from the drain pipe. The cathode liquid is supplied to the cathode electrode by the cathode liquid supply unit. The cathode liquid supply unit is connected to the container and has a cathode liquid tank for storing the cathode liquid supplied to the cathode electrode, and the cathode liquid in the container flows into the cathode liquid tank as the liquid level in the cathode liquid tank decreases. Methods for reusing associated water.

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