Hydrogen isotope separation system

Abstract

To provide a hydrogen isotope separation system capable of achieving stabilization of operation.SOLUTION: A hydrogen isotope separation system 10 comprises an electrolyzer 12, a separator 14, a coupler 15, a circulation flow passage 10e, a pump 18, and a control device 21 which controls the pump 18. The electrolyzer 12 performs electrolysis upon water including heavy water. The separator 14 separates a hydrogen isotope which is discharged from the electrolyzer 12. The coupler 15 generates power with light hydrogen which is discharged from the separator 14. The circulation flow passage 10e connects an anode supply path 10a and an anode discharge path 10c which are provided with respect to an anode 15b of the coupler 15 to which the light hydrogen is supplied while detouring the coupler 15. The pump 18 circulates fluid from the anode discharge path 10c toward the anode supply path 10a in the circulation flow passage 10e.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a hydrogen isotope separation system. [Background technology]

[0002] In recent years, research and development into fuel cells has been conducted to contribute to energy efficiency, ensuring that more people have access to affordable, reliable, sustainable and advanced energy. Conventionally, for example, a system has been known in which raw water containing heavy water and tritium components is decomposed using an electrolytic cell having an ion exchange membrane and a catalyst to obtain hydrogen and oxygen with low deuterium and tritium contents, respectively (see, for example, Patent Document 1). This system supplies the hydrogen and oxygen obtained by the electrolytic cell to a fuel cell, thereby extracting heavy water and water with low tritium components (light water). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 11-11903 Summary of the Invention [Problem to be solved by the invention]

[0004] In fuel cell technology, it is desirable to stabilize operations such as power generation. For example, in the case of a fuel cell that generates power using hydrogen obtained by an electrolytic cell as fuel, as in the above-mentioned conventional technology, if the balance between the amount of hydrogen consumed and the amount of hydrogen supplied is disrupted due to an increase in the amount of power generated, problems such as the generation of negative pressure between the electrolytic cell and the fuel cell may occur. For example, an excessive drop in pressure between the electrolytic cell and the fuel cell may cause instability in operations such as separation by the electrolytic cell and power generation by the fuel cell.

[0005] The present invention aims to achieve stabilization of operation in order to solve the above problems, and ultimately contribute to energy efficiency. [Means for solving the problem]

[0006] In order to solve the above problems and achieve the above object, the present invention employs the following aspects. (1): A hydrogen isotope separation system according to one aspect of the present invention (e.g., hydrogen isotope separation system 10 in the embodiments) includes an electrolyzer (e.g., electrolyzer 12 in the embodiments) that electrolyzes water containing heavy water, a separator (e.g., separator 14 in the embodiments) that separates hydrogen isotopes discharged from the electrolyzer, a combiner (e.g., combiner 15 in the embodiments) that generates electricity using hydrogen discharged from the separator, a circulation flow path (e.g., circulation flow path 10e in the embodiments) that connects an anode supply path (e.g., anode supply path 10a in the embodiments) and an anode discharge path (e.g., anode discharge path 10c in the embodiments) that are provided for an anode (e.g., anode 15b in the embodiments) of the combiner to which the hydrogen is supplied, bypassing the combiner, a pump (e.g., pump 18 in the embodiments) that circulates a fluid from the anode discharge path to the anode supply path in the circulation flow path, and a control device (e.g., control device 21 in the embodiments) that controls the pump.

[0007] (2): The hydrogen isotope separation system described in (1) above may include a pressure detection unit (e.g., pressure sensor 19 in the embodiment) that is arranged upstream of the connection point with the circulation flow path (e.g., connection point 10h in the embodiment) in the anode supply path, and the control device may obtain the amount of power generated by the coupler based on the pressure detection value output from the pressure detection unit, and may control the amount of fluid in the circulation flow path by operating the pump based on the pressure detection value or the amount of power generated.

[0008] (3) In the hydrogen isotope separation system described in (2) above, the control device may change the amount of fluid so as to increase in accordance with an increase in the pressure detection value or the amount of power generation.

[0009] (4) In the hydrogen isotope separation system described in (3) above, the control device may set the correspondence relationship between the pressure detection value or the amount of power generation and the amount of fluid to be a proportional relationship. [Effects of the Invention]

[0010] According to the above (1), by providing a pump that circulates the fluid in the circulation flow path from the anode discharge path to the anode supply path, it is possible to prevent the supply of hydrogen from being insufficient compared to the amount of hydrogen consumed by power generation in the combiner. This prevents an excessive decrease in hydrogen pressure between the separator and the combiner, and prevents unstable power generation in the combiner.

[0011] In the case of (2) above, the control device can appropriately prevent a shortage of hydrogen supplied to the coupler by controlling the amount of fluid in the circulation flow path based on the pressure detection value or the amount of power generation corresponding to the pressure detection value.

[0012] In the case of (3) or (4) above, the control device can appropriately prevent a shortage of hydrogen required for power generation in the coupler by increasing the fluid volume as the pressure detection value or power generation amount increases. [Brief explanation of the drawings]

[0013] [Figure 1] FIG. 1 is a configuration diagram of a hydrogen isotope separation system according to an embodiment of the present invention. [Figure 2] FIG. 2 is a diagram showing an example of an isotope exchange equilibrium reaction in a separator of the hydrogen isotope separation system according to the embodiment of the present invention. [Figure 3] FIG. 3 is a diagram showing an example of the correspondence relationship between the pressure detected by the pressure sensor and the generated current of the coupler in the hydrogen isotope separation system according to the embodiment of the present invention. [Figure 4] FIG. 3 is a diagram showing an example of the correspondence between the pressure detected by the pressure sensor or the generated current of the coupler and the rotation speed of the pump in the hydrogen isotope separation system according to the embodiment of the present invention. [Figure 5]3 is a flowchart showing an example of the operation of the hydrogen isotope separation system according to the embodiment of the present invention. [Figure 6] FIG. 10 is a configuration diagram of a portion of a hydrogen isotope separation system according to a modified embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0014] Hereinafter, a hydrogen isotope separation system according to an embodiment of the present invention will be described with reference to the accompanying drawings. FIG. 1 is a configuration diagram of a hydrogen isotope separation system 10 according to an embodiment. As shown in FIG. 1 , a hydrogen isotope separation system 10 of the embodiment includes, for example, an anode supply channel 10a and a cathode supply channel 10b, an anode discharge channel 10c and a cathode discharge channel 10d, a circulation channel 10e, an anode condensate discharge channel 10f and a cathode condensate discharge channel 10g, a heavy water tank 11, an electrolyzer 12, a nitrogen tank 13, a separator 14, a combiner 15, an anode-side condenser 16A and a cathode-side condenser 16B, an anode-side on-off valve 17A and a cathode-side on-off valve 17B, a pump 18, a pressure sensor 19, a power storage device 20, and a control device 21.

[0015] The heavy water tank 11 stores water containing heavy water and light water. The heavy water tank 11 supplies water containing heavy water and light water to the electrolyzer 12. Note that the light water is ( 1 H2 16 O), and heavy water is water that contains at least one of the hydrogen isotopes, such as double hydrogen (deuterium: D) and tritium (tritium: T).

[0016] The electrolyzer 12 includes, for example, an electrolytic bath or electrolytic cell that electrolyzes water containing heavy water supplied from the heavy water tank 11. For example, the electrolyzer 12 is an electrolytic bath. The electrolyzer 12 includes, for example, an anode 12a and a negative electrode 12b to which power is supplied from the power storage device 20 described below. In the electrolyzer 12, for example, an electrolytic reaction shown in the following formula (1) occurs. The electrolytic reaction in the electrolyzer 12 includes an electrolytic reaction obtained by replacing dutium (deuterium: D) in the following formula (1) with tritium (tritium: T). For example, the electrolyzer 12 outputs hydrogen (H), hydrogen deuteride (HD), hydrogen tritide (HT), etc. obtained by the electrolysis reaction to the anode supply channel 10a, and outputs oxygen (O) obtained by the electrolysis reaction to the cathode supply channel 10b.

[0017]

number

[0018] The nitrogen tank 13 stores a gas such as air containing nitrogen (N2), and supplies the gas such as air containing nitrogen (N2) to the separator .

[0019] The separator 14 includes, for example, a catalyst or a fuel cell that separates hydrogen isotopes from hydrogen (H 2 ), hydrogen deuteride (HD), hydrogen tritide (HT), etc. supplied from the electrolyzer 12 by an isotope exchange reaction. For example, the separator 14 is a fuel cell stack including a plurality of stacked fuel cell units. Each fuel cell unit includes, for example, an ion exchange membrane (electrolyte membrane) 14a, an anode 14b and a cathode 14c provided on either side of the ion exchange membrane 14a in the thickness direction, an anode-side flow path 14d, and a cathode-side flow path 14e.

[0020] The ion exchange membrane 14a includes, for example, a proton exchange membrane or an anion exchange membrane, the anode 14b includes, for example, a platinum-based anode catalyst and a gas diffusion layer, and the cathode 14c includes, for example, a platinum-based cathode catalyst and a gas diffusion layer.

[0021] The anode-side flow path 14d is formed between the anode 14b and the electrolyzer 12 by, for example, an anode-side separator or the like. The anode-side flow path 14d is connected to the electrolyzer 12 and an anode-side flow path 15d of the combiner 15, which will be described later, by an anode supply path 10a external to the separator 14. Hydrogen (H), deuterated hydrogen (HD), tritiated hydrogen (HT), and the like humidified with water vapor and liquid water are supplied to the anode-side flow path 14d from the electrolyzer 12 via a humidifier (not shown), for example.

[0022] The cathode-side flow path 14e is formed between the cathode 14c and the cathode 14c by, for example, a cathode-side separator etc. Gas such as air containing nitrogen (N2) humidified with water vapor and liquid water is supplied to the cathode-side flow path 14e from, for example, a nitrogen tank 13 via a humidifier (not shown).

[0023] FIG. 2 is a diagram showing an example of an isotope exchange equilibrium reaction in the separator 14 of the hydrogen isotope separation system 10 according to the embodiment. 2, an isotope exchange reaction between water and hydrogen occurs at the anode 14b and cathode 14c in the separator 14. Hydrogen isotopes such as deuterium (D) and tritium (T) migrate to the oxide side and also migrate from the anode 14b side to the cathode 14c side through the ion exchange membrane 14a. For example, an exchange reaction shown in the following formula (2) occurs at the anode 14b and the cathode 14c. Note that the exchange reaction at the anode 14b and the cathode 14c includes an exchange reaction obtained by replacing deuterium (D) in the following formula (2) with tritium (T). In addition, (g) in the following formula (2) represents the state of gas, vapor, etc.

[0024]

number

[0025] In the separator 14, for example, semi-heavy water (HDO), deuterated hydrogen (HD), tritiated water (HTO), and tritiated hydrogen (HT) move from the anode 14b side to the cathode 14c side through the ion exchange membrane 14a. In the separator 14, for example, water (HO) moves from the cathode 14c side to the anode 14b side through the ion exchange membrane 14a. At the anode 14b of the separator 14, for example, water (H2O), heavy water (HDO), tritiated water (HTO), etc. are discharged to the external anode supply path 10a together with hydrogen (H2). At the cathode 14c of the separator 14, for example, heavy water (HDO), tritiated water (HTO), etc. are discharged to the outside together with water (H2O) carried by nitrogen (N2) gas.

[0026] As shown in FIG. 1, the combiner 15 includes, for example, a fuel cell that generates water (H2O) by recombining hydrogen (H2) supplied from the separator 14 and oxygen (O2) supplied from the electrolyzer 12. For example, the coupler 15 is a fuel cell stack including a plurality of stacked fuel cell units. Each fuel cell unit includes, for example, an ion exchange membrane (electrolyte membrane) 15a, an anode 15b and a cathode 15c provided on either side of the ion exchange membrane 15a in the thickness direction, an anode-side flow path 15d, and a cathode-side flow path 15e.

[0027] The ion exchange membrane 15a includes, for example, a proton exchange membrane or an anion exchange membrane, the anode 15b includes, for example, a platinum-based anode catalyst and a gas diffusion layer, and the cathode 15c includes, for example, a platinum-based cathode catalyst and a gas diffusion layer.

[0028] The anode-side flow path 15d is formed between the anode 15b and the anode 15b by, for example, an anode-side separator, etc. The anode-side flow path 15d communicates with the anode supply path 10a and the anode discharge path 10c outside the combiner 15. The cathode-side flow path 15e is formed between the cathode 15c and the coupler 15 by, for example, a cathode-side separator etc. The cathode-side flow path 15e communicates with the cathode supply path 10b and the cathode discharge path 10d outside the coupler 15. Each fuel cell generates electricity through a catalytic reaction between hydrogen (H2) supplied to the anode 15b and oxygen (O2) supplied to the cathode 15c.

[0029] The anode-side condenser 16A is provided in the anode discharge channel 10c. The cathode-side condenser 16B is provided in the cathode discharge channel 10d. The anode-side condenser 16A and the cathode-side condenser 16B separate the fluid discharged from the anode-side flow channel 15d and the cathode-side flow channel 15e of the combiner 15 into a gas component and a liquid component. The liquid component is, for example, light water and heavy water separated from the fluid by condensation.

[0030] For example, the gas component separated by the anode-side condenser 16A is hydrogen (H), and the liquid components are light water (H2O) and heavy water (HDO, HTO). For example, the gas component separated by the anode-side condenser 16A is discharged to the outside via the anode-side on-off valve 17A. The liquid component is discharged to the anode condensate discharge channel 10f. For example, the gas components separated by the cathode-side condenser 16B are nitrogen (N2) or air, and the liquid components are light water (HO) and heavy water (HDO, HTO). For example, the gas components separated by the cathode-side condenser 16B are discharged to the outside via the cathode-side on-off valve 17B. The liquid components are discharged to the cathode condensate discharge channel 10g.

[0031] The pump 18 is driven by, for example, a rotating electric machine and discharges a fluid at a flow rate corresponding to the rotation speed of the rotating electric machine. The pump 18 is provided in the circulation flow path 10e. The circulation flow path 10e connects the anode supply path 10a and the anode discharge path 10c, bypassing the combiner 15. The pump 18 circulates the fluid through the circulation flow path 10e from the anode discharge path 10c toward the anode supply path 10a. The fluid in the circulation flow path 10e is a gas component and a liquid component discharged from the anode-side flow path 15d of the combiner 15, such as hydrogen (H2) humidified with light water (H2O) and heavy water (HDO, HTO).

[0032] The pressure sensor 19 is disposed, for example, upstream of a connection point 10h with the circulation flow path 10e in the anode supply path 10a between the separator 14 and the combiner 15. The pressure sensor 19 detects the pressure of the fluid supplied through the anode supply path 10a from the separator 14 to the anode-side flow path 15d of the combiner 15. The fluid supplied from the separator 14 is, for example, hydrogen (H) humidified with light water (HO) and heavy water (HDO, HTO).

[0033] The power storage device 20 is connected, for example, to the electrolyzer 12 and the combiner 15. The power storage device 20 receives the power generated by the combiner 15 and supplies the power required for the operation of the electrolyzer 12. The power storage device 20 may be supplied with power from, for example, an external power supply unit.

[0034] The control device 21 comprehensively controls the operation of the hydrogen isotope separation system 10. For example, the control device 21 is a software functional unit that functions when a processor such as a CPU (Central Processing Unit) executes a predetermined program. The software functional unit is an ECU (Electronic Control Unit) that includes a processor such as a CPU, a ROM (Read Only Memory) that stores programs, a RAM (Random Access Memory) that temporarily stores data, and electronic circuits such as a timer. At least a part of the control device 21 may be an integrated circuit such as an LSI (Large Scale Integration).

[0035] The control device 21 acquires the amount of power generated by the coupler 15 based on the pressure detection value output from the pressure sensor 19 . FIG. 3 is a diagram showing an example of the correspondence relationship between the pressure detected by the pressure sensor 19 and the generated current of the coupler 15 in the hydrogen isotope separation system 10 according to the embodiment. 3, the control device 21 acquires the amount of power generated by the coupler 15 corresponding to the pressure detection value output from the pressure sensor 19, based on, for example, pre-stored data on the correspondence relationship between the pressure detected by the pressure sensor 19 and the current generated by the coupler 15. The pressure detected by the pressure sensor 19 and the current generated by the coupler 15 have a proportional relationship, for example, such that the generated current tends to increase as the pressure increases.

[0036] The control device 21 controls the amount of fluid in the circulation flow path 10e by operating the pump 18 based on the pressure detection value of the pressure sensor 19 or the amount of power generated by the coupler 15. FIG. 4 is a diagram showing an example of the correspondence relationship between the pressure detected by the pressure sensor 19 or the generated current of the coupler 15 and the rotation speed of the pump 18 in the hydrogen isotope separation system 10 according to the embodiment. 4, the control device 21 acquires the pressure detection value of the pressure sensor 19 or the rotation speed of the pump 18 corresponding to the amount of power generated by the coupler 15, based on, for example, pre-stored data on the correspondence between the pressure detected by the pressure sensor 19 or the generated current of the coupler 15 and the rotation speed of the pump 18 (pump rotation speed). The pressure detected by the pressure sensor 19 or the generated current of the coupler 15 and the pump rotation speed have a proportional relationship, for example, such that the pump rotation speed tends to increase as the pressure or generated current increases.

[0037] FIG. 5 is a flowchart showing an example of the operation of the hydrogen isotope separation system according to the embodiment. First, in step S01 shown in FIG. 5, the control device 21 acquires the pressure detection value of the pressure sensor 19. Next, in step S02, the control device 21 acquires the generated current of the coupler 15 in accordance with the detected pressure value. Next, in step S03, the control device 21 acquires the pump rotation speed in accordance with the detected pressure value or the generated current. Next, in step S04, the control device 21 operates the pump 18 in accordance with the pump rotation speed. Next, in step S05, the control device 21 causes the coupler 15 to generate power. Then, the control device 21 advances the process to the end.

[0038] As described above, the hydrogen isotope separation system 10 of the embodiment is provided with the pump 18 that circulates a fluid through the circulation flow path 10e that runs from the anode discharge path 10c to the anode supply path 10a, thereby preventing the supply of hydrogen (H2) from being insufficient relative to the amount of hydrogen consumed by the power generation in the combiner 15. This prevents the pressure of hydrogen (H2) from decreasing excessively between the separator 14 and the combiner 15, and prevents the power generation in the combiner 15 from becoming unstable. The control device 21 can appropriately prevent a shortage of hydrogen (H2) supplied to the combiner 15 by controlling the amount of fluid in the circulation flow path 10e based on the pressure detection value or the amount of power generation corresponding to the pressure detection value. The control device 21 can appropriately prevent a shortage of hydrogen (H2) required for power generation in the combiner 15 by changing the fluid volume to an increasing trend as the pressure detection value or the amount of power generation increases.

[0039] (Variation) Modifications of the embodiment will be described below. Note that the same parts as those in the above-described embodiment will be denoted by the same reference numerals, and descriptions thereof will be omitted or simplified. In the above-described embodiments, the separation and enrichment of hydrogen isotopes may be performed, for example, by a plurality of separation systems connected in cascade.

[0040] FIG. 6 is a diagram showing the configuration of a portion of a hydrogen isotope separation system 10A according to a modified embodiment. 6, a modified hydrogen isotope separation system 10A includes, for example, at least two separation systems (a first separation system 30a and a second separation system 30b) connected in multiple stages. Each separation system 30a, 30b has, for example, the same configuration and includes an electrolyzer 12, a nitrogen tank 13, a separator 14, a combiner 15, an anode-side condenser 16A and a cathode-side condenser 16B, an anode-side on-off valve 17A and a cathode-side on-off valve 17B, a pump 18, and a pressure sensor 19. Liquid components discharged from the condensers 16A and 16B of the upstream first separation system 30a are supplied to the electrolyzer 12 of the downstream second separation system 30b.

[0041] The modified hydrogen isotope separation system 10A facilitates the separation and enrichment of hydrogen (H) and other hydrogen isotopes, such as deuterium (D) and tritium (T). In the modified hydrogen isotope separation system 10A, the combiner 15 may be omitted in the second-stage or later separation systems (such as the second separation system 30b). Furthermore, the power generated by the combiner 15 in the first-stage separation system (such as the first separation system 30a) may be supplied to the second-stage or later separation systems (such as the second separation system 30b).

[0042] In the above-described embodiment, the control device 21 controls the operation of the pump 18 based on, for example, the pressure detected by the pressure sensor 19 or the correspondence between the generated current of the coupler 15 and the pump rotation speed, but this is not limited to this. For example, when the pump 18 is operated by a driving source other than a rotating electric machine, the control device 21 may control the operation of the pump 18 based on the correspondence between a state quantity other than the pump rotation speed and the pressure detected by the pressure sensor 19 or the generated current of the coupler 15.

[0043] The embodiments of the present invention are presented as examples and are not intended to limit the scope of the invention. These embodiments can be embodied in various other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their modifications are intended to be included within the scope and spirit of the invention, as well as within the scope of the invention and its equivalents as defined in the claims. [Explanation of symbols]

[0044] 10, 10A...hydrogen isotope separation system, 10a...anode supply channel, 10b...cathode supply channel, 10c...anode discharge channel, 10d...cathode discharge channel, 10e...circulation channel, 11...heavy water tank, 12...electrolyzer, 13...nitrogen tank, 14...separator, 15...combiner, 16A...anode side condenser, 16B...cathode side condenser, 17A...anode side on-off valve, 17B...cathode side on-off valve, 18...pump, 19...pressure sensor (pressure detection unit), 20...electricity storage device, 21...control device.

Claims

1. an electrolyzer for electrolyzing water containing heavy water; a separator for separating hydrogen isotopes discharged from the electrolyzer; a combiner that generates electricity using the hydrogen discharged from the separator; a circulation flow path that connects an anode supply path and an anode discharge path provided for the anode of the combiner to which the proton is supplied, bypassing the combiner; a pump that circulates a fluid through the circulation flow path from the anode discharge channel to the anode supply channel; a control device for controlling the pump; Equipped with Hydrogen isotope separation system.

2. a pressure detection unit that is disposed in the anode supply channel upstream of a connection portion with the circulation channel, The control device The amount of power generated by the coupler is acquired based on the pressure detection value output from the pressure detection unit, and the amount of fluid in the circulation flow path is controlled by operating the pump based on the pressure detection value or the amount of power generated. The hydrogen isotope separation system of claim 1 .

3. The control device The amount of fluid is changed to increase as the detected pressure value or the amount of power generation increases. The hydrogen isotope separation system of claim 2 .

4. The control device The correspondence relationship between the pressure detection value or the amount of power generation and the amount of fluid is a proportional relationship. The hydrogen isotope separation system of claim 3 .

Images