Hydrogen gas production system and hydrogen gas production method

Abstract

To provide a hydrogen gas production system that can produce a hydrogen gas having a content ratio of deuterium D equal to or greater than that of raw water with high collection rate.SOLUTION: A hydrogen gas production system 100 comprises: a first tank 10 for storing raw water including heavy water; an electrolysis apparatus 30 in which a hydrogen gas is generated by electrolyzing raw water; a storage device 50 for storing the hydrogen gas; a liquid delivery device 20 for delivering the raw water from the first tank 10 to the electrolysis apparatus 30; and a gas delivery device 40 for delivering the hydrogen gas generated in the electrolysis apparatus 30 to the storage device 50. The liquid delivery device 20 is controlled to replenish raw water from the first tank 10 to the electrolysis apparatus 30 with the decrease of the raw water remaining in the electrolysis apparatus 30. The gas delivery device 40 is controlled to supply the hydrogen gas generated in the electrolysis apparatus 30 to the storage device 50 continuously before and after the replenishment. The storage device 50 stores the hydrogen gas generated in the electrolysis apparatus 30 before and after the replenishment.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a hydrogen gas production system and a hydrogen gas production method for producing hydrogen gas by electrolyzing water. [Background technology]

[0002] A stable isotope of hydrogen that exists naturally in water and hydrogen gas, etc., has a mass number of 1 (the nucleus is made up of only one proton). 1 H (hereafter also written as H) and deuterium, which has a mass number of 2 (the atomic nucleus consists of one proton and one neutron). 2 H (hereafter also written as D) and tritium, which has a mass number of 3 (the atomic nucleus consists of one proton and two neutrons). 3 There is H (hereinafter also referred to as T), and the content ratio of D or T is overwhelmingly smaller than that of H. In the fields of semiconductor manufacturing and nuclear power, there are known applications in which D is particularly effective. For this reason, there is a demand for low-cost production of water and hydrogen gas with a high D content.

[0003] Incidentally, as a general method for producing hydrogen gas, an electrolysis method is often used in which water is electrolyzed to generate oxygen gas and hydrogen gas. It is known that in the electrolysis method, it is possible to produce deuterium-enriched hydrogen gas (hydrogen gas having a higher content of deuterium D than normal hydrogen gas) by using deuterium-enriched water (water having a higher content of deuterium D than normal pure water) as raw water. Patent Document 1 proposes a technology for generating deuterium-enriched hydrogen gas using a batch-type electrolysis device. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 8-323154 Summary of the Invention [Problem to be solved by the invention]

[0005] However, when deuterium-enriched water as raw water is electrolyzed to obtain deuterium-enriched hydrogen gas, the light water (H2O) contained in the raw water is decomposed first due to the isotope effect. Therefore, the content ratio of D in the total hydrogen atoms in the obtained hydrogen gas changes over time, being low immediately after the start of electrolysis and gradually increasing. Conventionally, when producing deuterium-enriched hydrogen gas, the hydrogen gas generated before the desired content ratio of D was reached was discarded, which resulted in a low hydrogen gas recovery rate and high production costs.

[0006] In theory, if the entire amount of D contained in the deuterium-enriched water (raw water) once fed into the electrolysis device can be converted into hydrogen gas, the content ratio of D in the total hydrogen atoms in the finally obtained hydrogen gas will be equal to the content ratio of D in the total hydrogen atoms in the raw water. However, in the actual operation of the electrolysis device, in the case of a batch-type electrolysis device as described in Patent Document 1, the electrodes need to be immersed in the raw water, and in the case of a flow-type electrolysis device, a minimum amount of liquid needs to be secured to drive the liquid delivery pump, so that it is unavoidable that raw water remains in the electrolysis device. Therefore, it is impossible to electrolyze the entire amount of the fed raw water, and in consideration of the phenomenon of the above-mentioned change over time, the conventional hydrogen gas production method has a problem that the content ratio of D in the total hydrogen atoms in the obtained hydrogen gas is lower than the content ratio of D in the total hydrogen atoms in the raw water.

[0007] In view of the above problems, the present invention aims to provide a hydrogen gas production system and a hydrogen gas production method capable of producing hydrogen gas having a content ratio of deuterium D equal to or greater than the content ratio of deuterium D in all hydrogen atoms in raw water at a high recovery rate. [Means for solving the problem]

[0008] The present inventors have made extensive research to solve the above problems, and have found the following. By storing hydrogen gas obtained from an electrolyzer in a reservoir, the content ratio of D in all hydrogen atoms in the hydrogen gas can be averaged over time. In addition, due to the operation of the electrolyzer, the content ratio of D in all hydrogen atoms in the raw water remaining in the device is higher than before the start of electrolysis. Therefore, as the amount of raw water in the electrolyzer decreases, hydrogen gas with a higher content ratio of D can be continuously generated by replenishing the electrolyzer with deuterium-enriched water (raw water). By combining these, hydrogen gas having a content ratio of D equal to or higher than the content ratio of D in all hydrogen atoms in the raw water can be produced without discarding the generated hydrogen gas.

[0009] That is, the gist and configuration of the present invention are as follows.

[0010] [1] A first tank containing raw water including heavy water; an electrolysis device that electrolyzes the raw water to generate hydrogen gas; A reservoir for storing the hydrogen gas; a liquid delivery device that delivers the raw water from the first tank to the electrolysis device; A gas supply device that supplies the hydrogen gas generated in the electrolysis device to the reservoir; having the liquid delivery device is controlled to replenish the raw water from the first tank to the electrolyzer as the amount of the raw water remaining in the electrolyzer decreases; A hydrogen gas production system characterized in that the gas supply device is controlled to continuously supply the hydrogen gas generated in the electrolyzer to the storage container before and after the replenishment, and the storage container stores the hydrogen gas generated in the electrolyzer before and after the replenishment.

[0011] [2] The electrolysis apparatus, an electrolysis cell in which an anode chamber containing an anode and a cathode chamber containing a cathode are adjacent to each other via an ion exchange membrane; A second tank that accommodates the raw water supplied from the first tank; a liquid supply pipe connecting the second tank and the anode chamber and supplying the raw water from the second tank to the anode chamber; a return pipe connecting the anode chamber and the second tank and for returning the raw water from the anode chamber to the second tank; a circulation device that circulates the raw water between the second tank and the anode chamber via the liquid delivery pipe and the return pipe; The hydrogen gas production system according to [1] above,

[0012] [3] storing raw water containing heavy water in a first tank; sending the raw water from the first tank to an electrolysis device; an electrolysis step of electrolyzing the raw water in the electrolysis device to generate hydrogen gas; Sending the hydrogen gas generated in the electrolysis device to a reservoir; having replenish the electrolyzer with the raw water from the first tank as the amount of the raw water remaining in the electrolyzer decreases; A method for producing hydrogen gas, comprising continuously supplying the hydrogen gas generated in the electrolysis device to the storage tank before and after the replenishment, and storing the hydrogen gas generated in the electrolysis device in the storage tank before and after the replenishment.

[0013] [4] The electrolysis device includes an electrolysis cell in which an anode chamber accommodating an anode and a cathode chamber accommodating a cathode are adjacent to each other via an ion exchange membrane, and a second tank accommodating the raw water supplied from the first tank; The hydrogen gas production method described in [3] above, in which, in the electrolysis step, the raw water is supplied from the second tank to the anode chamber via a liquid supply piping connecting the second tank and the anode chamber, while the raw water is returned from the anode chamber to the second tank via a return piping connecting the anode chamber and the second tank, thereby circulating the raw water between the second tank and the anode chamber via the liquid supply piping and the return piping. Effect of the Invention

[0014] According to the hydrogen gas production system and method of the present invention, it is possible to produce hydrogen gas having a content ratio of deuterium D equal to or greater than the content ratio of deuterium D in all hydrogen atoms in the raw water with a high recovery rate. [Brief description of the drawings]

[0015] [Figure 1] 1 is a schematic diagram showing the device configuration of a hydrogen gas production system according to one embodiment of the present invention. [Diagram 2] 1 is a schematic diagram showing the device configuration of a hydrogen gas production system having a flow-type electrolyzer in one embodiment of the present invention. FIG. [Diagram 3] FIG. 1 is a schematic diagram showing the device configuration of a hydrogen gas production system having a batch-type electrolyzer in one embodiment of the present invention. [Figure 4] 1 is a graph showing the content ratio of D to all hydrogen atoms in hydrogen gas obtained versus the operating time of an electrolyzer in a comparative example. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0016] Hereinafter, an embodiment of a hydrogen gas production system and a hydrogen gas production method according to the present invention will be described. Note that the embodiment described below is an example of the present invention, and the configuration of the present invention is not limited to this specific example.

[0017] [Hydrogen gas production system and hydrogen gas production method] 1 shows the configuration of a hydrogen gas production system 100 according to an embodiment of the present invention. The hydrogen gas production system 100 includes a first tank 10 for storing raw water containing heavy water, an electrolyzer 30 for generating hydrogen gas by electrolyzing the raw water, a reservoir 50 for storing hydrogen gas, a liquid delivery device 20 for delivering raw water from the first tank 10 to the electrolyzer 30, and an air delivery device 40 for delivering hydrogen gas generated in the electrolyzer 30 to the reservoir 50. The hydrogen gas production system 100 is further characterized in that the liquid delivery device 20 is controlled to replenish raw water from the first tank 10 to the electrolyzer 30 as the amount of raw water remaining in the electrolyzer 30 decreases, the air delivery device 40 is controlled to continuously deliver hydrogen gas generated in the electrolyzer 30 to the reservoir 50 before and after the replenishment, and the reservoir 50 stores the hydrogen gas generated in the electrolyzer 30 before and after the replenishment of raw water.

[0018] In Fig. 1, piping 60 connects the first tank 10 and the liquid delivery device 20, and defines a flow path through which raw water is delivered. Pipe 62 connects the liquid delivery device 20 and the electrolyzer 30, and defines a flow path through which raw water is delivered. Pipe 64 connects the electrolyzer 30 and the gas delivery device 40, and defines a flow path through which hydrogen gas is delivered. Pipe 66 connects the gas delivery device 40 and the reservoir 50, and defines a flow path through which hydrogen gas is delivered.

[0019] A hydrogen gas production method according to an embodiment of the present invention can be suitably carried out using a hydrogen gas production system 100, and includes the steps of storing raw water containing heavy water in a first tank 10, sending the raw water from the first tank 10 to an electrolyzer 30, an electrolysis step of electrolyzing the raw water in the electrolyzer 30 to generate hydrogen gas, and sending the hydrogen gas generated in the electrolyzer 30 to a reservoir 50. The hydrogen gas production method is further characterized in that, as the amount of raw water remaining in the electrolyzer 30 decreases, the raw water is replenished from the first tank 10 to the electrolyzer 30, and the hydrogen gas generated in the electrolyzer 30 is continuously sent to the reservoir 50 before and after the replenishment, and the reservoir 50 stores the hydrogen gas generated in the electrolyzer 30 before and after the replenishment.

[0020] (raw water) The raw water is water containing heavy water (D2O). If the content ratio of D in the total hydrogen atoms in the raw water (deuterium enriched water) is 90 [atom%D] or more, hydrogen gas in which D is sufficiently concentrated can be obtained, which is preferable. The upper limit of the content ratio of D in the total hydrogen atoms in the raw water (deuterium enriched water) is not particularly limited, but from an industrial point of view, the content ratio of D in the total hydrogen atoms in the raw water (deuterium enriched water) is approximately 99.98 [atom%D] or less. The raw water may contain a portion of half-heavy water (HDO), and the D contained in the half-heavy water is also included in the above content ratio. In addition, the raw water may contain a supporting salt such as potassium hydroxide or hypochlorite depending on the electrolysis device used.

[0021] The content ratio of D to all hydrogen atoms in the raw water can be determined by subjecting the raw water to analysis using a nuclear magnetic resonance spectrometer (e.g., manufactured by JEOL Ltd.), measuring the areas of H atoms and D atoms, and calculating the ratio of the area of ​​D atoms to the total area of ​​H atoms and D atoms.

[0022] (First Tank) The first tank 10 is a device that stores raw water, and is connected to the liquid delivery device 20 via piping 60. The material of the first tank 10 is not particularly limited, but it is preferable to use a material that is easily permeable to air components, such as resin, which may allow moisture in the air to pass through and thereby reduce the content ratio of D in the total hydrogen atoms in the raw water in the first tank 10. Therefore, it is preferable to use a material such as stainless steel or glass that is not permeable to air components.

[0023] (Liquid delivery device and liquid delivery process) The liquid delivery device 20 is a device that delivers raw water from the first tank 10 to the electrolyzer 30, and is connected to the first tank 10 via a pipe 60 and to the electrolyzer 30 via a pipe 62. The liquid delivery device 20 may be, for example, a liquid delivery pump. The liquid delivery step is a step of delivering raw water from the first tank 10 to the electrolyzer 30 using the liquid delivery device 20. By delivering raw water, the amount of water in the electrolyzer 30 is increased so that the electrolyzer 30 can operate. The amount of liquid to be delivered is preferably the upper limit amount that the electrolyzer 30 can accommodate.

[0024] The liquid delivery device 20 is controlled to replenish raw water from the first tank 10 to the electrolyzer 30 as the amount of raw water remaining in the electrolyzer 30 decreases during the process of electrolysis of raw water by the electrolyzer 30. The control for replenishing raw water is not limited, but the following embodiment is preferable. The electrolyzer 30 is preferably provided with a liquid level sensor. The liquid level sensor detects the liquid level of the raw water in the electrolyzer 30 (i.e., the amount of raw water remaining), and outputs a signal when the liquid level falls to a predetermined threshold value. The output signal of the liquid level sensor is sent to a control unit (CPU, etc.), and the control unit operates the liquid delivery device 20 upon receiving an input of the signal from the liquid level sensor, and replenishing raw water to the electrolyzer 30. Alternatively, the output signal of the liquid level sensor may be in the form of light, sound, etc., or an operator may recognize the output signal of the liquid level sensor and operate the liquid delivery device 20 to replenishing raw water to the electrolyzer 30.

[0025] When the above-mentioned liquid level sensor is installed in the electrolyzer 30, the timing for replenishing the raw water is preferably when the liquid level falls to a predetermined threshold value. Here, the threshold value of the liquid level may be the liquid level at the operating limit of the electrolyzer 30 described later, or may be set to a value higher than the operating limit so that the raw water can be replenished before the operating limit is reached. When the liquid level sensor is not installed in the electrolyzer 30, an operator may periodically check the liquid level, and when it is determined that the liquid level has decreased, the liquid delivery device 20 may be operated to replenish the raw water. Since the consumption rate of the raw water can be determined based on the capacity of the electrolyzer 30 and the electrolysis conditions, the consumption amount of the raw water may be calculated in advance, and after performing electrolysis for a certain period of time, the liquid delivery device 20 may be operated automatically by the control unit or by the operator to replenish the raw water. The timing for replenishing the raw water is not particularly limited, and the raw water may be constantly replenished during electrolysis.

[0026] When the electrolyzer 30 generates hydrogen gas, light water (H2O) contained in the raw water is decomposed first due to the isotope effect. Therefore, the content ratio of D in all hydrogen atoms in the raw water remaining in the electrolyzer 30 increases over time. During the process of electrolyzing the raw water by the electrolyzer 30, by replenishing the raw water to the electrolyzer 30 by the liquid delivery device 20, the electrolyzer 30 can electrolyze raw water having a higher content ratio of D, and as a result, hydrogen gas having a higher content ratio of D is obtained than the hydrogen gas obtained before the replenishing of the raw water.

[0027] (Plumbing) The hydrogen gas production system 100 has a pipe 60 that connects the first tank 10 and the liquid delivery device 20 and defines a flow path through which raw water is delivered from the first tank 10 to the liquid delivery device 20, and a pipe 62 that connects the liquid delivery device 20 and the electrolyzer 30 and defines a flow path through which raw water is delivered from the liquid delivery device 20 to the electrolyzer 30. The material of the pipes 60 and 62 is not particularly limited, but a material that is easily permeable to air components, such as resin, may allow moisture in the air to pass through, which may reduce the content of D in the total hydrogen atoms in the raw water in the pipes 60 and 62, so it is preferable to use a stainless steel or glass material that is not permeable to air components.

[0028] (Electrolysis Apparatus) The electrolyzer 30 is a device that electrolyzes raw water, and is connected to the liquid delivery device 20 via a pipe 62, and to the air delivery device 40 via a pipe 64. The electrolyzer 30 is not particularly limited as long as it is capable of electrolyzing raw water to generate hydrogen gas, and a conventionally known electrolyzer can be used. Generally, two types of electrolyzers 30 are widely used: a flow type and a batch type.

[0029] FIG. 2 shows a schematic diagram of a hydrogen gas production system 102 having a flow-type electrolyzer 30A in one embodiment of the present invention. The configuration other than the electrolyzer 30A is the same as that in FIG. 1. The electrolyzer 30A has an electrolysis cell 80, and the electrolysis cell 80 has a configuration in which an anode chamber 82 that accommodates an anode and a cathode chamber 84 that accommodates a cathode are adjacent to each other via an ion exchange membrane 86. Furthermore, the electrolyzer 30A has a second tank 32 that accommodates raw water supplied from the first tank 10 by the liquid supply device 20, and a circulation device 38 that circulates the raw water between the second tank 32 and the anode chamber 82 via a liquid supply pipe 34 and a return pipe 36. The liquid supply pipe 34 is a pipe that connects the second tank 32 and the anode chamber 82 and supplies raw water from the second tank 32 to the anode chamber 82. The return pipe 36 connects the second tank 32 and the anode chamber 82, and is a pipe for returning the raw water from the anode chamber 82 to the second tank 32. The circulation device 38 may be, for example, a liquid delivery pump. The installation position of the circulation device 38 is not particularly limited, but it is installed, for example, in the liquid delivery pipe 34 as shown in FIG.

[0030] Fig. 3 is a schematic diagram of a hydrogen gas production system 104 having a batch-type electrolyzer 30B in one embodiment of the present invention. The configuration other than that of the electrolyzer 30B is the same as that of Fig. 1. The electrolyzer 30B has an electrolytic cell 90, in which an anode 92 and a cathode 94 are housed, and the anode 92 and the cathode 94 are immersed in raw water 96 also housed in the electrolytic cell 90. A pipe 68 is used when oxygen gas by-produced at the anode 92 of the electrolytic cell 90 is discharged.

[0031] (Electrolysis process) The electrolysis step is a step of generating hydrogen gas using the electrolysis device 30. When using the flow-type electrolysis device 30A shown in Fig. 2, it is preferable to operate the circulation device 38 at all times during electrolysis to circulate the raw water between the second tank 32 and the anode chamber 82.

[0032] When electrolysis is performed using the flow-type electrolyzer 30A shown in FIG. 2, raw water is decomposed into oxygen gas and hydrogen ions in the anode chamber 82 in the electrolysis cell 80 by the oxidation reaction shown in the following formula (1). The hydrogen ions generated in the anode chamber 82 permeate the ion exchange membrane 86 and move to the cathode chamber 84, where they become hydrogen gas by the reduction reaction shown in the following formula (2). The hydrogen gas generated in the cathode chamber 84 is sent to the reservoir 50 via the pipes 64 and 66 by the gas supply device 40. Note that most of the oxygen gas generated in the anode chamber 82 does not permeate the ion exchange membrane 86, but the very small amount of oxygen gas that does permeate reacts with the hydrogen ions under the reducing conditions in the cathode chamber 84 to become water, and is therefore not included in the hydrogen gas generated in the cathode chamber 84. H2O → 1 / 2O2 + 2H + +2e - (1) 2H + +2e - →H2···(2)

[0033] The hydrogen gas obtained by electrolysis of heavy water (D2O) is deuterium gas (D2). If the raw water contains semi-heavy water (HDO), the hydrogen gas obtained by electrolysis of semi-heavy water is semi-deuterium gas (HD). If the raw water is deuterium-enriched water, the hydrogen gas obtained will also be deuterium-enriched hydrogen gas (hydrogen gas with a higher proportion of deuterium D than normal hydrogen gas).

[0034] Similarly, when the batch-type electrolyzer 30B shown in Fig. 3 is used, in the electrolytic cell 90, the oxidation reaction shown in the above formula (1) occurs at the anode 92, and the reduction reaction shown in the above formula (2) occurs at the cathode 94. The electrolytic cell 90 does not have an ion exchange membrane 86, but has spaces above the anode side and the cathode side, as shown in Fig. 3. With this structure, oxygen gas generated at the anode 92 and hydrogen gas generated at the cathode 94 do not mix with each other, and the oxygen gas moves to the space above the anode 92 side, and the hydrogen gas moves to the space above the cathode 94 side. The hydrogen gas is sent to the reservoir 50 by the gas supply device 40 through the pipes 64 and 66.

[0035] When the electrolysis process is started at a stage where the electrolyzer 30 contains raw water up to its upper limit, the raw water in the electrolyzer 30 is decomposed and gradually decreases. Therefore, in the process of electrolysis of raw water by the electrolyzer 30, as the amount of raw water remaining in the electrolyzer 30 decreases, the liquid delivery device 20 replenishes raw water from the first tank 10 to the electrolyzer 30. The replenishment of raw water is performed before the amount of raw water remaining in the electrolyzer 30 reaches the liquid amount of the operating limit of the electrolyzer 30. In the case of the flow-type electrolyzer 30A, the operating limit refers to a state in which the minimum amount of raw water required to drive the circulation device 38 is reached, or in the case of the batch-type electrolyzer 30B, the amount of liquid reaches a state in which the anode 92 or the cathode 94 is above the liquid level of the raw water, etc.

[0036] When hydrogen gas is generated in the electrolysis process, light water (H2O) contained in the raw water is decomposed first due to the isotope effect. Therefore, the content ratio of D in the total hydrogen atoms in the raw water remaining in the electrolysis device 30 increases over time. During the process of electrolysis of raw water by the electrolysis device 30, the electrolysis device 30 is able to electrolyze raw water with a higher content ratio of D by replenishing the raw water to the electrolysis device 30 using the liquid delivery device 20, and as a result, hydrogen gas with a higher content ratio of D is obtained than the hydrogen gas obtained before the replenishing of the raw water.

[0037] (Air supply device) The gas supply device 40 is a device that supplies hydrogen gas from the electrolyzer 30 to the reservoir 50, and is connected to the electrolyzer 30 by a pipe 64, and to the reservoir 50 by a pipe 66. The gas supply device 40 is controlled so as to continuously supply hydrogen gas generated in the electrolyzer 30 to the reservoir 50 before and after the liquid supply device 20 replenishes the electrolyzer 30 with raw water. A booster can be used as the gas supply device 40.

[0038] (Air supply process) The gas supplying step is a step of supplying hydrogen gas generated in the electrolyzer 30 to the reservoir 50 using the gas supplying device 40. The gas supplying to the reservoir 50 is performed continuously before and after the liquid supplying device 20 replenishes the raw water to the electrolyzer 30. As a result, the hydrogen gas stored in the reservoir 50 has an averaged content ratio of D to all hydrogen atoms in the continuously obtained hydrogen gas. The hydrogen gas generated in the electrolyzer 30 generally has a pressure of about 0.3 MPa. Therefore, as an example of the gas supplying step, the inside of the reservoir 50 is reduced in pressure before the operation of the electrolyzer 30, and the hydrogen gas is filled into the reservoir 50 by the self-pressure of the generated hydrogen gas immediately after the operation of the electrolyzer 30, and the hydrogen gas can be further pressurized by the gas supplying device 40 and filled into the reservoir.

[0039] (Plumbing) The hydrogen gas production system 100 has a pipe 64 that connects the electrolyzer 30 and the gas supply device 40 and defines a flow path through which hydrogen gas is supplied from the electrolyzer 30 to the gas supply device 40. The material of the pipe 64 is not particularly limited, but since a material that is easily permeable to air components, such as resin, leads to a decrease in the purity of the obtained hydrogen gas, it is preferable to use a stainless steel or glass material that is not permeable to air components.

[0040] In addition, between the flow paths that send the hydrogen gas generated from the electrolyzer 30 to the reservoir 50, devices for controlling the amount of hydrogen gas sent, such as a mass flow controller or a back pressure valve, a purifier for removing moisture and air components from the generated hydrogen gas, and a compressor for pressurizing the generated hydrogen gas may be appropriately provided.

[0041] (Reservoir) The reservoir 50 is a device for storing hydrogen gas obtained by electrolysis, and is connected to the gas supply device 40 by piping 66. The reservoir 50 stores hydrogen gas generated in the electrolyzer 30 before and after the liquid supply device 20 replenishes raw water to the electrolyzer 30. By continuously storing hydrogen gas in the reservoir 50, the content ratio of D to all hydrogen atoms in the stored hydrogen gas is averaged.

[0042] The material of the reservoir 50 is not particularly limited, but since materials that are easily permeable to air components, such as resin, lead to a decrease in the purity of the resulting hydrogen gas, it is preferable to use stainless steel or glass materials that are not permeable to air components.

[0043] (Plumbing) The hydrogen gas production system 100 has a pipe 66 that connects the gas supply device 40 and the reservoir 50 and defines a flow path through which hydrogen gas is supplied from the gas supply device 40 to the reservoir 50. The material of the pipe 66 is not particularly limited, but since materials that are easily permeable to air components, such as resin, lead to a decrease in the purity of the obtained hydrogen gas, it is preferable to use a stainless steel or glass material that is not permeable to air components.

[0044] (Hydrogen gas) According to the hydrogen gas production system and the hydrogen gas production method of the embodiment of the present invention described above, hydrogen gas having a content ratio of D equal to or higher than the content ratio of deuterium D in all hydrogen atoms in the raw water (deuterium enriched water) can be obtained without discarding the hydrogen gas generated in the initial stage. In particular, if the content ratio of D in all hydrogen atoms in the raw water is 90 [atom%D] or more, hydrogen gas having a content ratio of D in all hydrogen atoms in the hydrogen gas of 90 [atom%D] or more can be obtained, which is preferable. The upper limit of the content ratio of D in all hydrogen atoms in the hydrogen gas is not particularly limited, and the content ratio of D in all hydrogen atoms in the hydrogen gas can be 100.00 [atom%D] or less. As described above, from an industrial point of view, the upper limit of the content ratio of D in all hydrogen atoms in the raw water is 99.98 [atom%D], and in this case, the content ratio of D in all hydrogen atoms in the obtained hydrogen gas can be 99.98 [atom%D] or more. Hydrogen gas may contain a portion of deuterium gas (HD), and the D contained in deuterium gas is also included in the above content ratio. The content ratio of D to all hydrogen atoms in hydrogen gas can be determined in the same manner as for raw water.

[0045] Regarding steps and conditions not described in the present invention, conventional methods can be used. EXAMPLES

[0046] [Example 1] Using an apparatus with the same configuration as in Figure 2, 940 g of raw water (deuterium-enriched water) with a D content of 99.84 atom%D was first put into the electrolyzer, and the first operation of the apparatus was started. Six hours after the start of operation, the D content of the hydrogen gas stored in the reservoir was measured and found to be 99.81 atom%D. At this time, 400 g of raw water remained in the electrolyzer, and the D content of the remaining raw water was 99.92 atom%D.

[0047] Next, 540g of raw water with a D content of 99.84 atom%D was added from the first tank to bring the D content of the raw water in the electrolysis device to 99.87 atom%D, and the second operation of the device was started to generate hydrogen gas. Six hours after the start of operation, the D content of the hydrogen gas stored in the reservoir was measured and found to be 99.83 atom%D. At this time, 400g of raw water remained in the electrolysis device, and the D content of the remaining raw water was 99.95 atom%D.

[0048] Therefore, 540g of raw water with a D content of 99.84 atom%D was similarly added from the first tank to bring the D content of the raw water in the electrolysis device to 99.88 atom%D, and the third operation of the device was started to generate hydrogen gas. Six hours after the start of operation, the D content of the hydrogen gas stored in the reservoir was measured and found to be 99.84 atom%D. At this time, 400g of raw water remained in the electrolysis device, and the D content of the remaining raw water was 99.95 atom%D.

[0049] Similarly, 540 g of raw water with a D content of 99.84 atom% D was added from the first tank to bring the D content of the raw water in the electrolysis device to 99.88 atom% D, and the fourth operation of the device was started to generate hydrogen gas. Six hours after the start of operation, the D content of the hydrogen gas stored in the reservoir was measured and found to be 99.85 atom% D. At this time, 400 g of raw water remained in the electrolysis device, and the D content of the remaining raw water was 99.95 atom% D. Table 1 shows the measurement results.

[0050] The recovery rate of hydrogen gas generated from the electrolysis device, which has a D content equal to or greater than the D content in the total hydrogen atoms in the raw water in the storage tank, was ≥99%. The recovery rate was calculated as follows: Recovery rate [%] = Amount of hydrogen gas recovered in the storage tank [L] / Total amount of hydrogen gas generated by the electrolysis device [L] × 100 [%]

[0051] [Table 1]

[0052] [Example 2] Using an apparatus with the same configuration as in Figure 3, 100 g of raw water (deuterium-enriched water) with a D content of 99.84 atom%D was first put into the electrolyzer, and the first operation of the apparatus was started. One hour after the start of operation, the D content of the hydrogen gas stored in the reservoir was measured and found to be 99.83 atom%D. At this time, 12 g of raw water remained in the electrolyzer, and the D content of the remaining raw water was 99.97 atom%D.

[0053] Next, 88 g of raw water with a D content of 99.84 atom% D was added from the first tank to bring the D content of the raw water in the electrolysis device to 99.85 atom% D, and the second operation of the device was started to generate hydrogen gas. One hour after the start of operation, the D content of the hydrogen gas stored in the reservoir was measured and found to be 99.84 atom% D. At this time, 12 g of raw water remained in the electrolysis device, and the D content of the remaining raw water was 99.97 atom% D.

[0054] Therefore, 88 g of raw water with a D content of 99.84 atom% D was similarly added from the first tank to bring the D content of the raw water in the electrolyzer to 99.85 atom% D, and the third operation of the device was started to generate hydrogen gas. One hour after the start of operation, the D content of the hydrogen gas stored in the reservoir was measured and found to be 99.85 atom% D. At this time, 12 g of raw water remained in the electrolyzer, and the D content of the remaining raw water was 99.97 atom% D. Table 2 shows the measurement results.

[0055] The recovery rate was calculated in the same manner as in Example 1. The recovery rate of hydrogen gas generated from the electrolysis device and having a D content equal to or higher than the D content in all hydrogen atoms in the raw water in the reservoir was ≧99%.

[0056] [Table 2]

[0057] [Comparative Example 1] Of the devices used in Example 1, the electrolysis device was used to electrolyze raw water (deuterium-enriched water) having a content ratio of D of 99.84 atom%D, without using the first tank and the reservoir. The generated hydrogen gas was sampled periodically to measure the content ratio of D. FIG. 4 shows the content ratio of D in the total hydrogen atoms in the obtained hydrogen gas versus the operation time of the electrolysis device. As a result, it took 3.8 hours or more of operation until the content ratio of D in the generated hydrogen gas reached 99.84 atom%D, which is the content ratio of D in the raw water. That is, when the reservoir is not used, in order to obtain hydrogen gas having a content ratio of D of 99.84 atom%D, it is necessary to discard the hydrogen gas for 3.8 hours until the content ratio is reached. Assuming that the hydrogen gas for 3.8 hours was discarded, the recovery rate was calculated in the same manner as in Example 1, and the recovery rate of hydrogen gas having a content ratio of D equal to or greater than the content ratio of D in the total hydrogen atoms in the raw water in the reservoir was 37%. [Explanation of symbols]

[0058] 100 Hydrogen gas production system 102 Hydrogen gas production system with flow-type electrolysis device 104 Hydrogen gas production system with batch electrolysis device 10. First Tank 20 Liquid delivery device 30 Electrolysis Apparatus 30A Flow Electrolyzer 30B Batch Electrolyzer 32 Second Tank 34 Liquid delivery piping 36 Return piping 38 Circulation device 40 Air supply device 50 Reservoir 60 Piping 62 Piping 64 Piping 66 Piping 68 Piping 80 Flow Electrolysis Cell 82 Anode chamber 84 Cathode Chamber 86 Ion Exchange Membrane 90 Batch electrolysis cell 92 Anode 94 Cathode 96 Raw water

Claims

1. a first tank for storing raw water including heavy water; an electrolysis device that electrolyzes the raw water to generate hydrogen gas; A reservoir for storing the hydrogen gas; a liquid delivery device that delivers the raw water from the first tank to the electrolysis device; A gas supply device that supplies the hydrogen gas generated in the electrolysis device to the reservoir; having the liquid delivery device is controlled to replenish the raw water from the first tank to the electrolyzer as the amount of the raw water remaining in the electrolyzer decreases; A hydrogen gas production system characterized in that the gas supply device is controlled to continuously supply the hydrogen gas generated in the electrolyzer to the storage container before and after the replenishment, and the storage container stores the hydrogen gas generated in the electrolyzer before and after the replenishment.

2. The electrolysis device comprises: an electrolysis cell in which an anode chamber containing an anode and a cathode chamber containing a cathode are adjacent to each other via an ion exchange membrane; A second tank that accommodates the raw water supplied from the first tank; a liquid supply pipe connecting the second tank and the anode chamber and supplying the raw water from the second tank to the anode chamber; a return pipe connecting the anode chamber and the second tank and for returning the raw water from the anode chamber to the second tank; a circulation device that circulates the raw water between the second tank and the anode chamber via the liquid supply pipe and the return pipe; The hydrogen gas production system according to claim 1 ,

3. storing raw water containing heavy water in a first tank; sending the raw water from the first tank to an electrolysis device; an electrolysis step of electrolyzing the raw water in the electrolysis device to generate hydrogen gas; Sending the hydrogen gas generated in the electrolysis device to a reservoir; having replenish the electrolyzer with the raw water from the first tank as the amount of the raw water remaining in the electrolyzer decreases; A method for producing hydrogen gas, comprising continuously supplying the hydrogen gas generated in the electrolysis device to the storage tank before and after the replenishment, and storing the hydrogen gas generated in the electrolysis device in the storage tank before and after the replenishment.

4. the electrolysis device includes an electrolysis cell in which an anode chamber accommodating an anode and a cathode chamber accommodating a cathode are adjacent to each other via an ion exchange membrane, and a second tank accommodating the raw water supplied from the first tank, 4. The hydrogen gas production method according to claim 3, wherein in the electrolysis step, the raw water is supplied from the second tank to the anode chamber via a liquid supply piping connecting the second tank and the anode chamber, while the raw water is returned from the anode chamber to the second tank via a return piping connecting the anode chamber and the second tank, thereby circulating the raw water between the second tank and the anode chamber via the liquid supply piping and the return piping.

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