Electrolysis device and electrolysis method

Abstract

This determination method determines whether or not an object molecule containing elemental hydrogen is an electrolyzed hydrogen-containing molecule which contains a hydrogen molecule that is produced by water electrolysis or a molecule that is produced using a hydrogen molecule as a starting material. This determination method determines that the object molecule is an electrolyzed hydrogen-containing molecule if the deuterium abundance ratio relative to light hydrogen in the object molecule is equal to or lower than a predetermined threshold value that is lower than the deuterium abundance ratio relative to light hydrogen in nature.

Description

Technical Field

[0001] The present disclosure relates to a determination method, a quality assurance method, an electrolysis device, and an electrolysis method.

Background Art

[0002] Carbon dioxide is regarded as a cause of global warming, and globally, efforts to suppress carbon dioxide emissions are intensifying. Hydrogen is attracting attention as a fuel alternative to fossil fuels because it does not emit carbon dioxide during use and can also be obtained by electrolyzing water with renewable energy. As a method for electrolyzing water to produce hydrogen, an alkaline water electrolysis device disclosed in Patent Document 1 is known.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] Conventionally, hydrogen has been industrially produced by steam reforming fossil fuels such as natural gas. However, there is no method for confirming that hydrogen has been produced by water electrolysis. In addition, ammonia is expected as a next-generation fuel, and hydrocarbons are used as raw materials for various chemical products. These molecules can be produced using hydrogen as a raw material, but like hydrogen, there is no method for confirming that they have been produced by water electrolysis. If it is possible to confirm whether these molecules have been produced via water electrolysis, the quality of these molecules can be guaranteed.

[0005] Therefore, an object of the present disclosure is to provide a determination method and a quality assurance method capable of confirming whether a target molecule is hydrogen generated by water electrolysis or a molecule generated using the hydrogen as a raw material. Another object of the present disclosure is to provide an electrolysis apparatus and an electrolysis method capable of easily realizing these methods.

Means for Solving the Problems

[0006] The determination method according to the present disclosure is a determination method for determining whether a target molecule containing a hydrogen element is a hydrogen molecule generated by water electrolysis or an electrolytic hydrogen-containing molecule containing a molecule generated using the hydrogen molecule as a raw material. In the determination method, when the deuterium-to-protium abundance ratio of the target molecule is equal to or less than a predetermined threshold that is smaller than the natural deuterium-to-protium abundance ratio, it is determined that the target molecule is an electrolytic hydrogen-containing molecule.

[0007] The target molecule may be a hydrogen molecule, ammonia, or a hydrocarbon.

[0008] The quality assurance method according to the present disclosure is a quality assurance method for ensuring that a target molecule containing a hydrogen element is a hydrogen molecule generated by water electrolysis or an electrolytic hydrogen-containing molecule containing a molecule generated using the hydrogen molecule as a raw material. In the quality assurance method, when the deuterium-to-protium abundance ratio of the target molecule is equal to or less than a predetermined threshold that is smaller than the natural deuterium-to-protium abundance ratio, it is ensured that the target molecule is an electrolytic hydrogen-containing molecule.

[0009] The electrolysis apparatus according to the present disclosure includes an electrolytic cell that electrolyzes water, a circulation flow path through which the water electrolyzed in the electrolytic cell circulates, a water supply flow path that supplies pure water to the circulation flow path, and a drainage flow path that drains a part or all of the water in the circulation flow path downstream of the electrolytic cell and upstream of the water supply via the water supply flow path. In the electrolysis apparatus, the deuterium-to-protium abundance ratio of the hydrogen molecule generated by the water electrolysis in the electrolytic cell is smaller than the natural deuterium-to-protium abundance ratio.

[0010] A flow rate adjustment device for adjusting the drainage volume of the water in the circulation flow path may be provided in the drainage flow path.

[0011] The water supplied to the electrolytic cell may be alkaline water, and the electrolysis device may further include a membrane separation device provided in the drainage channel and including a permeable membrane that selectively permeates water among the alkaline water.

[0012] The electrolysis method according to the present disclosure includes an electrolysis step of electrolyzing water in an electrolytic cell, a water supply step of supplying pure water to a circulation channel that circulates the water electrolyzed in the electrolytic cell, and a drainage step of draining a part or all of the water in the circulation channel downstream of the electrolytic cell and upstream of the water supply in the water supply step. In the electrolysis method, the deuterium-to-light hydrogen abundance ratio of the hydrogen molecules generated by the water electrolysis in the electrolytic cell is smaller than the natural deuterium-to-light hydrogen abundance ratio.

[0013] At least one selected from the group consisting of the ratio of the amount of water consumed by electrolysis in the electrolytic cell to the amount of water supplied to the electrolytic cell, the ratio of the deuterium-to-light hydrogen abundance ratio of the water supplied to the electrolytic cell to the deuterium-to-light hydrogen abundance ratio of the hydrogen molecules generated in the electrolytic cell, and the ratio of the flow rate of the water drained in the drainage step to the flow rate of the water discharged from the electrolytic cell may be controlled.

[0014] The determination device includes a determination unit that determines whether a target molecule containing a hydrogen element is an electrolytic hydrogen-containing molecule containing hydrogen molecules generated by water electrolysis or molecules generated using hydrogen molecules as a raw material. The determination unit determines that the target molecule is an electrolytic hydrogen-containing molecule when the deuterium-to-light hydrogen abundance ratio of the target molecule is equal to or less than a predetermined threshold that is smaller than the natural deuterium-to-light hydrogen abundance ratio.

[0015] The determination device includes a measurement unit that measures the deuterium-to-light hydrogen abundance ratio of the target molecule. The determination device includes a determination unit that determines that the target molecule is an electrolytic hydrogen-containing molecule when the deuterium-to-light hydrogen abundance ratio of the target molecule obtained by the measurement unit is equal to or less than a predetermined threshold that is smaller than the natural deuterium-to-light hydrogen abundance ratio. The determination device includes an output unit that outputs the determination result determined by the determination unit.

Advantages of the Invention

[0016] According to the present disclosure, it is possible to provide a determination method and a quality assurance method capable of confirming whether a target molecule is hydrogen generated by water electrolysis or a molecule generated using the hydrogen as a raw material. Further, according to the present disclosure, it is possible to provide an electrolysis apparatus and an electrolysis method capable of easily realizing these methods.

Brief Description of the Drawings

[0017]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Embodiments for Carrying Out the Invention

[0018] Hereinafter, several exemplary embodiments will be described with reference to the drawings. Note that the dimensional ratios in the drawings are exaggerated for the convenience of explanation and may be different from the actual ratios.

[0019] The determination method according to this embodiment determines whether the target molecule is an electrolytic hydrogen-containing molecule. The electrolytic hydrogen-containing molecule includes hydrogen molecules generated by water electrolysis or molecules generated using the above hydrogen molecules as raw materials. Water electrolysis can be carried out using renewable energy. When the target molecule is an electrolytic hydrogen-containing molecule and is water electrolyzed using renewable energy, it can be determined whether the target molecule is derived from renewable energy.

[0020] The target molecule is a molecule containing hydrogen element. The target molecule may be a hydrogen molecule, ammonia, or hydrocarbon. Similarly, the electrolytic hydrogen-containing molecule may be a hydrogen molecule, ammonia, or hydrocarbon. Hydrogen and ammonia can be used as fuels that do not contain carbon. Therefore, instead of fossil fuels, hydrogen and ammonia can be used as fuels derived from renewable energy. In addition, hydrocarbons can be produced using carbon dioxide as a raw material. Therefore, carbon dioxide contained in the exhaust gas of a factory can be recovered, and the recovered carbon dioxide can be effectively utilized as a raw material for chemical products.

[0021] Hydrogen molecules can be generated by water electrolysis. Water electrolysis can be carried out by an electrolysis device described later. The hydrogen molecule may be hydrogen gas. Molecules such as ammonia and hydrocarbon can be generated using hydrogen molecules generated by water electrolysis as raw materials. Ammonia can be generated, for example, by the Haber-Bosch method using hydrogen molecules as raw materials. The hydrocarbon may contain at least one of methane and olefin. Methane can be generated by a methanation reaction using hydrogen molecules as raw materials. Olefin (alkene) can be generated by a Fischer-Tropsch reaction using hydrogen molecules as raw materials.

[0022] In the hydrogen element existing in nature, there is light hydrogen ( 1 H or H), deuterium ( 2 H or D), and tritium: 3It is known that there are three isotopes of hydrogen (H, D, or T). Light hydrogen is the most abundant isotope of the hydrogen element in nature. Heavy hydrogen is a stable isotope of the hydrogen element. Tritium is a radioactive isotope, and the amount present in nature is extremely small.

[0023] In the determination method according to this embodiment, when the deuterium abundance ratio of the light hydrogen in the target molecule is equal to or less than a predetermined threshold that is smaller than the natural deuterium abundance ratio of the light hydrogen, it is determined that the target molecule is an electrolytic hydrogen-containing molecule. The electrolytic hydrogen-containing molecule generated by the method described later has a smaller deuterium abundance ratio. Therefore, when the deuterium abundance ratio of the target molecule is smaller than the natural deuterium abundance ratio, it can be determined that the target molecule is an electrolytic hydrogen-containing molecule.

[0024] Specifically, in the determination method according to this embodiment, deuterium, which is a stable isotope of the hydrogen element, is used as a tracer to determine whether the target molecule is an electrolytic hydrogen-containing molecule. Although the details will be described later, deuterium molecules such as HD and D2 have a slower reaction rate than light hydrogen molecules such as H2. Therefore, by utilizing this reaction rate difference, the deuterium abundance ratio of the hydrogen molecules obtained by water electrolysis with respect to light hydrogen is smaller than the HDO and D2O abundance ratios with respect to H2O in the electrolytic cell feed water. Accordingly, when the deuterium abundance ratio of the light hydrogen in the target molecule is equal to or less than a predetermined threshold that is smaller than the natural deuterium abundance ratio of the light hydrogen, it can be determined that the target molecule is an electrolytic hydrogen-containing molecule.

[0025] The deuterium-to-hydrogen abundance ratio of hydrogen molecules obtained by water electrolysis as described above is lower than the deuterium-to-hydrogen abundance ratio in nature. Therefore, hydrogen-containing molecules such as ammonia or hydrocarbons produced using hydrogen molecules generated by water electrolysis as a raw material also have the same deuterium-to-hydrogen abundance ratio as the hydrogen molecules. On the other hand, the deuterium-to-hydrogen abundance ratio of hydrogen obtained by steam reforming of fossil fuels such as natural gas is equivalent to the deuterium-to-hydrogen abundance ratio in nature. Therefore, the deuterium-to-hydrogen abundance ratio of hydrogen-containing molecules such as ammonia or hydrocarbons produced using hydrogen molecules with a deuterium-to-hydrogen abundance ratio lower than that of hydrogen in nature is also lower than the deuterium-to-hydrogen abundance ratio in nature.

[0026] The deuterium-to-hydrogen abundance ratio of the target molecule can be obtained by calculating the molar ratio of deuterium to hydrogen contained in the target molecule. Specifically, the deuterium-to-hydrogen abundance ratio of the target molecule is the molar ratio of the molecules containing at least one deuterium atom to the molecules consisting only of hydrogen atoms among the molecules contained in the target molecule. The deuterium-to-hydrogen abundance ratio can be obtained using a mass spectrometer. The deuterium-to-hydrogen abundance ratio may be obtained using a combination of a mass spectrometer and a separation device such as a gas chromatograph. Also, the deuterium-to-hydrogen abundance ratio can be obtained using a combination of a gas chromatograph and a detector such as a TCD (Thermal Conductivity Detector).

[0027] The deuterium-to-hydrogen abundance ratio in nature is said to be 184 ppm or less. Therefore, the deuterium-to-hydrogen abundance ratio in nature may be, for example, 184 ppm or less. Also, the deuterium-to-hydrogen abundance ratio in nature may be the deuterium-to-hydrogen abundance ratio of Vienna Standard Mean Ocean Water (VSMOW). The deuterium-to-hydrogen abundance ratio of Vienna Standard Mean Ocean Water is approximately 155 ppm.

[0028] The above threshold value only needs to be smaller than the deuterium-to-protium abundance ratio in nature. The threshold value may be, for example, 120 ppm, 100 ppm, 80 ppm, 60 ppm, 40 ppm, 20 ppm, or 10 ppm. When the deuterium abundance ratio is small, it is possible to easily determine whether the target molecule is an electrolytic hydrogen-containing molecule. Note that the threshold value may exceed 0 ppm.

[0029] As described above, the determination method according to the present embodiment is a determination method for determining whether a target molecule containing a hydrogen element is a hydrogen molecule generated by water electrolysis or an electrolytic hydrogen-containing molecule containing a molecule generated using the above hydrogen molecule as a raw material. And this determination method determines that the target molecule is an electrolytic hydrogen-containing molecule when the deuterium-to-protium abundance ratio of the target molecule is equal to or less than a predetermined threshold value that is smaller than the deuterium-to-protium abundance ratio in nature.

[0030] As described above, the deuterium abundance ratio of the hydrogen molecule obtained by water electrolysis or the molecule generated using the above hydrogen molecule as a raw material becomes small by utilizing the reaction rate difference. Therefore, when the deuterium abundance ratio of the target molecule is smaller than the deuterium abundance ratio in nature, it can be determined that the target molecule is an electrolytic hydrogen-containing molecule. Therefore, according to the determination method according to the present embodiment, it is possible to confirm whether the target molecule is hydrogen generated by water electrolysis or a molecule generated using the above hydrogen as a raw material.

[0031] In addition, since water electrolysis can be carried out using renewable energy, according to the determination method according to the present embodiment, it can be determined that the target molecule is a molecule generated by renewable energy. That is, by measuring the deuterium-to-protium abundance ratio of the target molecule, it becomes possible to construct the traceability of the molecule generated by renewable energy. The method according to the present embodiment is particularly useful as a sampling inspection at the time of receiving the load. Since the method according to the present embodiment is useful as a sampling inspection, quality assurance can be achieved by attaching the analysis result of the manufactured electrolytic hydrogen-containing molecule to the product as a quality record.

[0032] That is, the method according to this embodiment may be a quality assurance method that ensures that the target molecule containing hydrogen element is an electrolytic hydrogen-containing molecule containing hydrogen molecules generated by water electrolysis or molecules generated using hydrogen molecules as raw materials. The quality assurance method may guarantee that the target molecule is an electrolytic hydrogen-containing molecule when the deuterium abundance ratio of the target molecule to protium is equal to or less than a predetermined threshold that is smaller than the natural deuterium abundance ratio to protium.

[0033] According to the quality assurance method of this embodiment, when accepting the target molecule, the quality of the target molecule can be confirmed by analyzing the deuterium abundance ratio of the target molecule to protium. Also, according to the quality assurance method of this embodiment, before shipping the target molecule, the quality of the target molecule to be shipped can be guaranteed by analyzing the deuterium abundance ratio of the target molecule to protium. The quality of the target molecule may be attached to the product as a certificate or label.

[0034] Note that the determination method may be determined by a determination device including a determination unit. Also, the determination device may include, for example, a measurement unit, a determination unit, and an output unit. The measurement unit may include a device that measures the deuterium abundance ratio of the target molecule to protium. The measurement unit may include, for example, a mass spectrometer. Also, the measurement unit may be a combination of a mass spectrometer and a separation device such as a gas chromatograph, and may include a combination of a gas chromatograph and a detector.

[0035] The determination unit determines whether the target molecule containing a hydrogen element is an electrolytic hydrogen-containing molecule containing a hydrogen molecule generated by water electrolysis or a molecule generated using a hydrogen molecule as a raw material. When the deuterium abundance ratio of the target molecule with respect to light hydrogen is equal to or less than a predetermined threshold that is smaller than the natural deuterium abundance ratio with respect to light hydrogen, the determination unit determines that the target molecule is an electrolytic hydrogen-containing molecule. The determination unit may determine that the target molecule is an electrolytic hydrogen-containing molecule when the deuterium abundance ratio of the target molecule acquired by the measurement unit is equal to or less than a predetermined threshold that is smaller than the natural deuterium abundance ratio with respect to light hydrogen. The signal of the deuterium abundance ratio data output from the measurement unit is output to the determination unit, and the determination unit may acquire the data output from the measurement unit. The determination unit may be, for example, a computer including a CPU (Central Processing Unit) and a memory. The CPU can read the determination program stored in the memory and determine whether the target molecule is an electrolytic hydrogen-containing molecule based on the deuterium abundance ratio of the target molecule acquired by the measurement unit and the threshold value. The output unit outputs the determination result determined by the determination unit. Examples of the output unit include a monitor and a printer. The output unit can output, for example, a determination result such as "the target molecule is an electrolytic hydrogen-containing molecule" or "the target molecule is not an electrolytic hydrogen-containing molecule" to the output unit.

[0036] (Electrolysis device) Next, the electrolysis device according to the present embodiment will be described. The electrolysis device according to the present embodiment can perform the water electrolysis described in the above embodiment. The electrolysis device according to the present embodiment may be a low-temperature type water electrolysis device or a medium-high temperature steam electrolysis device.

[0037] (Low-temperature type water electrolysis device) First, an example of a low-temperature type water electrolysis device will be described with reference to FIG. 1. As shown in FIG. 1, the electrolysis device 1 according to the present embodiment includes an electrolytic cell 10, a circulation flow path 20, a water supply flow path 30, and a drainage flow path 40.

[0038] The electrolyzer 10 electrolyzes water. Hydrogen and oxygen are generated by the electrolysis of water. The electrolysis method in the electrolyzer 10 may be an alkaline water electrolysis, a polymer electrolyte water electrolysis, or a combination thereof. The electrolysis method in the electrolyzer 10 may also be a PEM (Proton Exchange Membrane) type water electrolysis, an alkaline water electrolysis, an AEM (Anion Exchange Membrane) type water electrolysis, etc.

[0039] The electrolyzer 10 includes a membrane 11, a cathode 12, and an anode 13. The electrolyzer 10 includes a DC power source (not shown) electrically connected to the cathode 12 and the anode 13, and water is electrolyzed by applying a voltage to the cathode 12 and the anode 13.

[0040] In the circulation channel 20, the water electrolyzed in the electrolyzer 10 circulates. Since pure water is usually used for the water supplied to the electrolysis device 1, pure water can be effectively utilized by circulating the water. A water supply channel 30 and a drainage channel 40 are connected to the circulation channel 20. The water supply channel 30 supplies pure water to the circulation channel 20. The pure water may be water having an electrical resistivity of 0.1 Ω·cm or more at 25°C. The electrical resistivity of the pure water may be 20 MΩ·cm or less, 10 MΩ·cm or less, or 1.5 MΩ·cm or less. The drainage channel 40 drains part or all of the water in the circulation channel 20 downstream of the electrolyzer 10 and upstream of the water supply via the water supply channel 30. A flow rate adjusting device 41 for adjusting the drainage volume of the water in the circulation channel 20 may be provided in the drainage channel 40. The flow rate adjusting device 41 can adjust the flow rate of the water flowing in the drainage channel 40, and the amount of water in the circulation channel 20 drained from the drainage channel 40 can be adjusted by the flow rate adjusting device 41. Thereby, the deuterium abundance ratio of the hydrogen molecules generated in the electrolyzer 10 can be adjusted. The flow rate adjusting device 41 may be a flow rate adjusting valve or the like.

[0041] The circulation flow path 20 may include a cathode-side water supply pipe 21, an anode-side water supply pipe 22, a cathode-side drain pipe 23, and an anode-side drain pipe 24. The electrolysis device 1 may include an electrolytic solution water supply tank 50 provided in the circulation flow path 20, a hydrogen gas-liquid separator 60 provided in the circulation flow path 20, and an oxygen gas-liquid separator 65 provided in the circulation flow path 20. A pump 25 is provided in the cathode-side water supply pipe 21. A pump 26 is provided in the anode-side water supply pipe 22. The hydrogen gas-liquid separator 60 is provided in the cathode-side drain pipe 23. The oxygen gas-liquid separator 65 is provided in the anode-side drain pipe 24.

[0042] Make-up water is supplied to the electrolytic solution water supply tank 50 via a water supply flow path 30, and water for electrolysis in the electrolytic cell 10 is stored. The outlet of the electrolytic solution water supply tank 50 is connected to the inlet on the cathode 12 side of the electrolytic cell 10 via the cathode-side water supply pipe 21. Then, by driving the pump 25, water is supplied from the electrolytic solution water supply tank 50 to the cathode 12 side of the electrolytic cell 10. Also, the outlet of the electrolytic solution water supply tank 50 is connected to the inlet on the anode 13 side of the electrolytic cell 10 via the anode-side water supply pipe 22. Then, by driving the pump 26, water is supplied from the electrolytic solution water supply tank 50 to the anode 13 side of the electrolytic cell 10.

[0043] The outlet on the cathode 12 side of the electrolytic cell 10 is connected to the inlet of the electrolytic solution water supply tank 50 via the cathode-side drain pipe 23. The hydrogen gas-liquid separator 60 is provided in the cathode-side drain pipe 23. The outlet on the anode 13 side of the electrolytic cell 10 is connected to the inlet of the electrolytic solution water supply tank 50 via the anode-side drain pipe 24. The oxygen gas-liquid separator 65 is provided in the anode-side drain pipe 24. The water that has passed through the electrolytic cell 10 is supplied to the hydrogen gas-liquid separator 60 together with the hydrogen gas generated at the cathode 12, and is supplied to the oxygen gas-liquid separator 65 together with the oxygen gas generated at the anode 13.

[0044] In the hydrogen gas-liquid separator 60, hydrogen generated by electrolysis at the cathode 12 and water discharged without being electrolyzed in the electrolytic cell 10 are separated. The hydrogen separated by the hydrogen gas-liquid separator 60 is recovered and stored, for example, in a storage tank. On the other hand, the water separated by the hydrogen gas-liquid separator 60 is supplied to the electrolytic solution supply tank 50 through the cathode side drain pipe 23.

[0045] In the oxygen gas-liquid separator 65, oxygen generated by electrolysis at the anode 13 and water discharged without being electrolyzed in the electrolytic cell 10 are separated. The oxygen separated by the oxygen gas-liquid separator 65 is stored, for example, in a storage tank. On the other hand, the water separated by the oxygen gas-liquid separator 65 is supplied to the electrolytic solution supply tank 50 through the anode side drain pipe 24.

[0046] In the electrolytic solution supply tank 50, water discharged from the electrolytic cell 10 without being electrolyzed in the electrolytic cell 10 is stored, and the water circulates between the electrolytic cell 10 and the electrolytic solution supply tank 50.

[0047] The electrolysis device 1 may include a control unit 70. The control unit 70 may be electrically connected to at least any one selected from the group consisting of the electrolytic cell 10, the pump 25, the pump 26, and the flow rate adjustment device 41. The control unit 70 may control at least either the applied voltage or the current density of the electrolytic cell 10. The control unit 70 may control the flow rate of water supplied to the electrolytic cell 10 by operating at least either the pump 25 or the pump 26. The control unit 70 may control the flow rate of water in the circulation flow path 20 drained from the drainage flow path 40 by operating the flow rate adjustment device 41. By these controls, the deuterium abundance ratio of light hydrogen in the hydrogen molecules generated in the electrolytic cell 10 can be adjusted.

[0048] Next, the electrolysis reactions in the PEM type water electrolysis device, the alkaline type water electrolysis device, and the AEM type water electrolysis device will be described in detail.

[0049] (PEM type water electrolysis device) First, an example of a PEM type water electrolysis device will be described with reference to Fig. 2. As shown in Fig. 2, in a PEM type water electrolysis device, water is supplied to the anode 13 through the anode side water supply pipe 22 of the electrolytic cell 10. At the anode 13, oxygen and hydrogen ions (H + ) are generated by electrolysis. The membrane 11 is a PEM, and hydrogen ions (H + ) permeate through the membrane 11 and move from the anode 13 side to the cathode 12 side. At the cathode 12, hydrogen gas is generated from the hydrogen ions that have permeated through the membrane 11. Water may be supplied to the cathode 12 side through the cathode side water supply pipe 21, or water may not be supplied through the cathode side water supply pipe 21.

[0050] The rate at which deuterium ions (D + ) permeate through the membrane 11 is slower than the rate at which light hydrogen ions (H + ) permeate through the membrane 11. Also, at the anode 13, the rate at which D + is generated from HDO and D2O is slower than the rate at which H + is generated from H2O. Therefore, at the cathode 12, the amount of deuterium gas such as HD gas and D2 gas generated is less than the amount of light hydrogen gas generated. Thus, the deuterium-to-light hydrogen abundance ratio of the hydrogen molecules generated by the PEM type water electrolysis device is smaller than the deuterium-to-light hydrogen abundance ratio of the water supplied to the electrolytic cell 10.

[0051] (Alkaline type water electrolysis device) Next, an example of an alkaline type water electrolysis device will be described with reference to Fig. 3. As shown in Fig. 3, in an alkaline type water electrolysis device, water is supplied to the cathode 12 and the anode 13 of the electrolytic cell 10 through the cathode side water supply pipe 21 and the anode side water supply pipe 22, respectively. At the cathode 12, hydrogen and hydroxide ions (OH - ) are generated by electrolysis. Hydroxide ions (OH - ) permeate through the membrane 11 and move from the cathode 12 side to the anode 13 side. At the anode 13, the hydroxide ions (OH -Oxygen is generated from

[0052] OD is generated from HDO and D2O at the cathode 12 - And the rates of generation of HD gas and D2 gas are slower than the rates of generation of OH - And H2 gas from H2O. Therefore, at the cathode 12, the amount of deuterium gas such as HD gas and D2 gas generated is less than the amount of light hydrogen gas generated. Therefore, the deuterium-to-light hydrogen abundance ratio of the hydrogen molecules generated in the alkaline water electrolysis device is smaller than the deuterium-to-light hydrogen abundance ratio of the water supplied to the electrolytic cell 10.

[0053] (AEM type water electrolysis device) Next, an example of an AEM type water electrolysis device will be described with reference to FIG. 4. As shown in FIG. 4, in the AEM type water electrolysis device, water is supplied to the anode 13 of the electrolytic cell 10 through the anode side water supply pipe 22. The water permeates through the membrane 11 which is an AEM and moves from the anode 13 side to the cathode 12 side. At the cathode 12, hydrogen and hydroxide ions (OH - ) are generated from the water that has permeated through the membrane 11 by electrolysis. The hydroxide ions (OH - ) generated at the cathode 12 permeate through the membrane 11 and move from the cathode 12 side to the anode 13 side. At the anode 13, oxygen and water are generated from the hydroxide ions (OH - ) that have permeated through the membrane 11. Water may be supplied to the cathode 12 side through the cathode side water supply pipe 21, or water may not be supplied through the cathode side water supply pipe 21.

[0054] The rates at which HDO and D2O permeate through membrane 11 are slower than the rate at which H2O permeates through membrane 11. Also, at cathode 12, the rates at which HD gas and D2 gas are generated from HDO and D2O are slower than the rate at which H2 gas is generated from H2O. Therefore, at cathode 12, the amount of deuterium gas such as HD gas and D2 gas generated is less than the amount of light hydrogen gas generated. Thus, the deuterium-to-light hydrogen abundance ratio of the hydrogen molecules generated in the AEM type water electrolysis device is smaller than the deuterium-to-light hydrogen abundance ratio of the water supplied to electrolyzer 10.

[0055] (Medium and high temperature steam electrolysis device) Next, an example of a medium and high temperature steam electrolysis device will be described with reference to FIG. 5. In electrolyzer 1 according to the present embodiment, the electrolysis method in electrolyzer 10 may be SOEC (Solid Oxide Electrolysis Cell) type water electrolysis and PCEC (Protonic Ceramic Electrolysis Cell) type water electrolysis or a combination thereof. As shown in FIG. 5, electrolyzer 1 according to the present embodiment further includes a heat exchanger 80 provided in circulation channel 20. Other than this, since it is the same as the low temperature type water electrolysis device shown in FIG. 1, the description thereof will be omitted.

[0056] Heat exchanger 80 exchanges the heat of the water supplied to electrolyzer 10 with the heat of the water drained from electrolyzer 10. Heat exchanger 80 may include a first heat exchanger provided so as to straddle cathode side water supply pipe 21 and cathode side drain pipe 23, and a second heat exchanger provided so as to straddle anode side water supply pipe 22 and anode side drain pipe 24. The first heat exchanger can exchange the heat of the water supplied to the cathode 12 side of electrolyzer 10 with the heat of the water discharged from the cathode 12 side of electrolyzer 10. The second heat exchanger can exchange the heat of the water supplied to the anode 13 side of electrolyzer 10 with the heat of the water discharged from the anode 13 side of electrolyzer 10. Note that instead of heat exchanger 80, a heater (not shown) for heating the water supplied to electrolyzer 10 may be provided on at least one of cathode side water supply pipe 21 and anode side water supply pipe 22.

[0057] Next, the electrolysis reactions in the SOEC type water electrolysis device and the PCEC type water electrolysis device will be described in detail.

[0058] (SOEC type water electrolysis device) An example of the SOEC type water electrolysis device will be described with reference to FIG. 6. As shown in FIG. 6, in the SOEC type water electrolysis device, water vapor is supplied to the cathode 12 of the electrolytic cell 10 through the cathode side water supply pipe 21. At the cathode 12, hydrogen gas and oxygen ions (O 2- ) are generated from water vapor by electrolysis. The oxygen ions (O 2- ) permeate through the membrane 11 and move from the cathode 12 side to the anode 13 side. At the anode 13, oxygen gas is generated from the oxygen ions (O 2- ) that have permeated through the membrane 11.

[0059] The rate at which HD gas and D2 gas are generated from HDO and D2O at the cathode 12 is slower than the rate at which H2 gas is generated from H2O. Therefore, at the cathode 12, the amount of deuterium gas such as HD gas and D2 gas generated is less than the amount of light hydrogen gas generated. Accordingly, the deuterium-to-light hydrogen abundance ratio of the hydrogen molecules generated by the SOEC type water electrolysis device is smaller than the deuterium-to-light hydrogen abundance ratio of the water supplied to the electrolytic cell 10.

[0060] (PCEC type water electrolysis device) Next, an example of the PCEC type water electrolysis device will be described with reference to FIG. 7. As shown in FIG. 7, in the PCEC type water electrolysis device, water vapor is supplied to the anode 13 through the anode side water supply pipe 22. At the anode 13, oxygen gas and hydrogen ions (H + ) are generated from water vapor by electrolysis. The hydrogen ions (H + ) permeate through the membrane 11 and move from the anode 13 side to the cathode 12 side. At the cathode 12, hydrogen gas is generated from the hydrogen ions (H + ) that have permeated through the membrane 11.

[0061] Deuterium ions (D +) has a slower rate of permeating through the membrane 11 than that of protium ions (H + ). Also, at the anode 13, the rate of generating D + from HDO and D2O is slower than the rate of generating H + from H2O. Therefore, at the cathode 12, the amount of deuterium gas such as HD gas and D2 gas generated is less than the amount of protium gas generated. Thus, the deuterium-to-protium abundance ratio of the hydrogen molecules generated by the PCEC type water electrolysis device becomes smaller than the deuterium-to-protium abundance ratio of the water supplied to the electrolytic cell 10.

[0062] As described above, in any electrolysis method, the deuterium-to-protium abundance ratio of the generated hydrogen molecules becomes smaller than the deuterium-to-protium abundance ratio of the water supplied to the electrolytic cell 10. On the other hand, the deuterium abundance ratio of the water discharged from the electrolytic cell 10 becomes larger than the deuterium abundance ratio of the water supplied to the electrolytic cell 10. In the electrolysis device 1 according to the present embodiment, a part or all of the water in the circulation channel 20 is drained by the drainage channel 40, and pure water is supplied to the circulation channel 20 by the water supply channel 30. Therefore, the deuterium abundance ratio of the water flowing in the circulation channel 20 is diluted and becomes smaller, and the deuterium abundance ratio of the hydrogen molecules generated in the electrolytic cell 10 also becomes smaller. Therefore, the deuterium-to-protium abundance ratio of the hydrogen molecules generated by the water electrolysis in the electrolytic cell 10 is smaller than the deuterium-to-protium abundance ratio in nature.

[0063] As shown in FIG. 8, the water supplied to the electrolytic cell 10 may be alkaline water, and the electrolysis device 1 may further include a membrane separation device 90. The membrane separation device 90 may be provided in the drainage channel 40. The membrane separation device 90 may include a permeation membrane that selectively permeates water in the alkaline water. The semipermeable membrane selectively permeates water in the alkaline water. The semipermeable membrane permeates water in the alkaline water but does not permeate metal ions such as sodium ions and potassium ions. Therefore, it is possible to discharge only water without discharging alkaline water outside the circulation channel 20.

[0064] The semipermeable membrane may include at least one selected from the group consisting of a flat membrane, a hollow fiber membrane, and a spiral membrane. The pore size of the semipermeable membrane may be such that it allows water molecules to pass through but does not allow sodium ions or the like in the water to be treated to pass through. The pore size of the semipermeable membrane may be 0.5 nm or more, and may be 1 nm or more. Further, the pore size of the semipermeable membrane may be 10 nm or less, may be 5 nm or less, and may be 2 nm or less. The semipermeable membrane may be a reverse osmosis membrane (RO membrane). The semipermeable membrane may include at least one selected from the group consisting of cellulose acetate, polyacrylonitrile, polysulfone, polyethersulfone, polyethylene, polypropylene, polyvinylidene fluoride, and ceramic.

[0065] Next, when the electrolysis device shown in FIG. 1 was operated under various conditions, the deuterium-to-hydrogen abundance ratio was evaluated by simulation. The operating conditions are shown in Table 1, and the deuterium-to-hydrogen abundance ratio is shown in Table 2.

[0066]

Table 1

[0067]

Table 2

[0068] In Table 1, the water utilization rate is the volume ratio of the amount of electrolytically consumed water to the amount of water supplied to the electrolytic cell. The water supplied to the electrolytic cell is the water supplied to the electrolytic cell 10 through the cathode-side water supply pipe 21 and the anode-side water supply pipe 22. The electrolytically consumed water is the water consumed by electrolysis in the electrolytic cell 10.

[0069] The separation factor is a value represented by the following mathematical formula.

[0070] α = ([D] L ) / ([D] G )

[0071] In the above mathematical formula, α is the separation factor, [D] Lis the deuterium-to-light hydrogen abundance ratio of the electrolytic cell feed water, and [D] G indicates the deuterium-to-light hydrogen abundance ratio of the hydrogen gas (hydrogen molecules) generated in the electrolytic cell 10.

[0072] The separation factor can be controlled by using the applied voltage and current density, which are the operating conditions of the electrolytic cell 10, as manipulated variables. The smaller the applied voltage, the smaller the deuterium-to-light hydrogen abundance ratio of the generated hydrogen molecules. Also, the smaller the current density, the smaller the deuterium-to-light hydrogen abundance ratio of the generated hydrogen molecules. Furthermore, the separation factor can also be controlled by selecting the metal species of the electrode catalyst. The separation factor tends to increase in the order of Cu > Fe > Ni > Ag > Au > Pt > Sn.

[0073] The blow ratio is the volume ratio of the flow rate of the blow water to the flow rate of the generated water. The generated water is the water discharged from the electrolytic cell 10 without being electrolyzed. The blow water is the water discharged from the drain channel 40. The flow rate is the amount of water per unit time. The hydrogen gas generation amount is the amount of hydrogen gas (hydrogen molecules) generated by electrolysis in the electrolytic cell 10.

[0074] In Table 2, the makeup water is pure water supplied to the circulation channel 20 through the water supply channel 30. The deuterium-to-light hydrogen abundance ratio of the pure water is set at 150 ppm. The electrolytic cell feed water is the water supplied to the electrolytic cell 10 as described above. The electrolytic cell feed water is the mixed water of the water circulating in the circulation channel 20 without the generated water being discharged as blow water and the makeup water. In this example, the deuterium-to-light hydrogen abundance ratio of the electrolytic cell feed water is larger than that of the makeup water.

[0075] As shown in Table 2, it is possible to control the deuterium-to-light hydrogen abundance ratio of the hydrogen gas generated in the electrolytic cell 10 according to the operating conditions of the electrolysis apparatus. Specifically, the lower the water utilization rate, the more the deuterium-to-light hydrogen abundance ratio can be reduced. Also, the larger the separation factor, the more the deuterium-to-light hydrogen abundance ratio can be reduced. Also, the larger the blow ratio, the more the deuterium-to-light hydrogen abundance ratio can be reduced.

[0076] Therefore, at least one selected from the group consisting of water utilization rate, separation factor, and blow ratio may be controlled. The water utilization rate is the ratio of the amount of water consumed by electrolysis in the electrolytic cell 10 to the amount of water supplied to the electrolytic cell. The separation factor is the ratio of the deuterium abundance ratio of the water supplied to the electrolytic cell 10 to the deuterium abundance ratio of the hydrogen molecules generated in the electrolytic cell 10 with respect to light hydrogen. The blow ratio is the ratio of the flow rate of the water discharged from the electrolytic cell 10 to the flow rate of the water discharged in the drainage process. By generating hydrogen molecules with a small deuterium abundance ratio through the above-described operation, it is possible to more easily distinguish them from hydrogen molecules derived from fossil fuels. These controls may be implemented by the control unit 70 by controlling the electrolytic cell 10, the pump 25, the pump 26, and the flow rate adjustment device 41.

[0077] When the deuterium abundance ratio of the target molecule is measured and the deuterium abundance ratio of the hydrogen molecule is such that it is calculated based on the operating conditions in Table 1, it can be easily determined that the target molecule is an electrolytic hydrogen-containing molecule. Also, by comparing with the specification of the deuterium abundance ratio issued by the manufacturer of the fuel or raw material derived from renewable energy, the quality of the target molecule can be guaranteed.

[0078] As described above, the electrolysis apparatus 1 according to the present embodiment includes an electrolytic cell 10 that electrolyzes water, a circulation flow path 20 through which the water electrolyzed in the electrolytic cell 10 circulates, and a water supply flow path 30 that supplies pure water to the circulation flow path 20. The electrolysis apparatus 1 includes a drainage flow path 40 that drains a part or all of the water in the circulation flow path 20 downstream of the electrolytic cell 10 and upstream of the water supply via the water supply flow path 30. The deuterium abundance ratio of the hydrogen molecules generated by the water electrolysis in the electrolytic cell 10 is smaller than the deuterium abundance ratio of light hydrogen in nature.

[0079] The electrolysis method according to this embodiment includes an electrolysis step of electrolyzing water in the electrolyzer 10 and a water supply step of supplying pure water to a circulation flow path 20 that circulates the water electrolyzed in the electrolyzer 10. The electrolysis method includes a drainage step of draining part or all of the water in the circulation flow path 20 downstream of the electrolyzer 10 and upstream of the water supply in the water supply step. The deuterium-to-light hydrogen abundance ratio of the hydrogen molecules generated by the water electrolysis in the electrolyzer 10 is smaller than the natural deuterium-to-light hydrogen abundance ratio.

[0080] In the electrolyzer and the electrolysis method according to this embodiment, water is electrolyzed in the electrolyzer 10. The deuterium-to-light hydrogen abundance ratio of the hydrogen molecules generated in the electrolyzer 10 becomes smaller than the deuterium-to-light hydrogen abundance ratio of the water supplied to the electrolyzer 10. On the other hand, the deuterium abundance ratio of the water discharged from the electrolyzer 10 becomes larger than the deuterium abundance ratio of the water supplied to the electrolyzer 10. In the electrolyzer 1 according to this embodiment, part or all of the water in the circulation flow path 20 is drained by the drainage flow path 40, and pure water is supplied to the circulation flow path 20 by the water supply flow path 30. Therefore, the deuterium abundance ratio of the water flowing in the circulation flow path 20 is diluted and becomes smaller, and the deuterium abundance ratio of the hydrogen molecules generated in the electrolyzer 10 also becomes smaller. Therefore, the deuterium-to-light hydrogen abundance ratio of the hydrogen molecules generated by the water electrolysis in the electrolyzer 10 is smaller than the natural deuterium-to-light hydrogen abundance ratio.

[0081] On the other hand, when the water in the circulation flow path 20 is not drained, since all the water supplied to the electrolyzer 10 is finally electrolyzed, the deuterium-to-light hydrogen abundance ratio of the hydrogen molecules generated in the electrolyzer 10 becomes the same as the natural deuterium-to-light hydrogen abundance ratio. Therefore, in the electrolyzer and the electrolysis method according to this embodiment, the deuterium-to-light hydrogen abundance ratio of the hydrogen molecules can be reduced as compared with the case where the water in the circulation flow path 20 is not drained. Further, by generating molecules such as ammonia and hydrocarbons using hydrogen molecules with a reduced deuterium abundance ratio as a raw material, the deuterium-to-light hydrogen abundance ratio of the generated molecules can be reduced.

[0082] Therefore, according to the electrolysis apparatus and electrolysis method according to the present embodiment, it is possible to easily confirm whether the target molecule is hydrogen generated by water electrolysis or a molecule generated using the hydrogen as a raw material.

[0083] The entire contents of Japanese Patent Application No. 2022-175572 (filing date: November 1, 2022) are incorporated herein by reference.

[0084] Although several embodiments have been described, it is possible to modify or deform the embodiments based on the above disclosure. All the components of the above embodiments and all the features described in the claims may be individually extracted and combined as long as they do not conflict with each other.

[0085] The present disclosure can contribute to, for example, Goal 7 of the Sustainable Development Goals (SDGs) led by the United Nations, "Ensure access to affordable, reliable, and sustainable modern energy for all", Goal 12, "Ensure sustainable production and consumption patterns", and Goal 13, "Take urgent measures to mitigate climate change and its impacts".

Explanation of Reference Numerals

[0086] 1 Electrolysis apparatus 10 Electrolytic cell 20 Circulation flow path 30 Feed water flow path 40 Drainage flow path 90 Membrane separation device

Claims

1. An electrolytic cell for electrolyzing water, A circulation channel through which the water electrolyzed in the electrolytic cell circulates, A water supply channel for supplying pure water to the circulation channel, A drainage channel for draining part or all of the water in the circulation channel downstream of the electrolytic cell and upstream of the water supply through the water supply channel, An electrolysis apparatus comprising: The deuterium-to-hydrogen abundance ratio of the hydrogen molecules generated by the water electrolysis in the electrolytic cell is smaller than the natural deuterium-to-hydrogen abundance ratio, The water supplied to the electrolytic cell is alkaline water, The electrolysis apparatus further comprises a membrane separation apparatus provided in the drainage channel and including a permeation membrane that selectively permeates water among the alkaline water.

2. The electrolysis apparatus according to claim 1, wherein a flow rate adjustment device for adjusting the drainage volume of the water in the circulation channel is provided in the drainage channel.

3. An electrolysis step of electrolyzing water in an electrolytic cell, A water supply step of supplying pure water to a circulation channel through which the water electrolyzed in the electrolytic cell circulates, A drainage step of draining part or all of the water in the circulation channel downstream of the electrolytic cell and upstream of the water supply in the water supply step, Including: The deuterium-to-hydrogen abundance ratio of the hydrogen molecules generated by the water electrolysis in the electrolytic cell is smaller than the natural deuterium-to-hydrogen abundance ratio, At least one selected from the group consisting of the ratio of the amount of water consumed by electrolysis in the electrolytic cell to the amount of water supplied to the electrolytic cell, the ratio of the deuterium-to-hydrogen abundance ratio of the water supplied to the electrolytic cell to the deuterium-to-hydrogen abundance ratio of the hydrogen molecules generated in the electrolytic cell, and the ratio of the flow rate of the water drained in the drainage step to the flow rate of the water discharged from the electrolytic cell is controlled.

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