Electrochemical hydrogen boosting system

Abstract

To provide an electrochemical type hydrogen booster system that can prevent occurrence of a chemical reaction, which could otherwise be caused by oxygen gas generated by electrolysis and mixed in hydrogen gas being supplied.SOLUTION: An electrochemical type hydrogen booster system 10 comprises: a supply route 46 communicating with an anode side of a unit cell 28; a discharge route 72 communicating with a cathode side of the unit cell 28; a hydrogen return route 76 directing hydrogen to the supply route 46 from a downstream side of a gas-liquid separator 20 present on the discharge route 72; and a controller 22. The controller 22 opens a hydrogen return valve 78 attached to the hydrogen return route 76 when a voltage or an electric value representing resistance exceeds a predetermined threshold when a current of a hydrogen booster stack 24 is at a predetermined value.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to an electrochemical hydrogen boosting system. [Background technology]

[0002] In recent years, research and development has been conducted on electrochemical hydrogen boosting systems that contribute to energy efficiency in order to ensure that more people have access to affordable, reliable, sustainable and advanced energy.

[0003] The electrochemical hydrogen boosting system of Patent Document 1 includes an electrochemical hydrogen boosting device that boosts hydrogen. The electrochemical hydrogen boosting device includes a hydrogen boosting stack (hydrogen boosting section) and a power supply (power source). The hydrogen boosting stack includes unit cells including an electrolyte membrane, an anode power supply, and a cathode power supply. The power supply supplies current to the hydrogen boosting stack, causing the hydrogen boosting stack to generate high-pressure hydrogen gas at a higher pressure than the hydrogen gas supplied to the hydrogen boosting stack.

[0004] Patent Document 1 discloses that, based on information regarding the wetness state of the electrolyte membrane, the outlet of the hydrogen boosting stack through which unreacted hydrogen gas is discharged is regulated, and water vapor is retained in the unit cell to maintain the electrolyte membrane in a good wet state. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2022-94891 A Summary of the Invention [Problem to be solved by the invention]

[0006] However, if a large amount of moisture remains in the unit cell when current is supplied to the hydrogen boosting stack, the moisture tends to electrolyze. If the oxygen gas produced by electrolysis mixes with the hydrogen gas supplied to the hydrogen boosting stack, a chemical reaction may occur depending on the concentration of the oxygen gas.

[0007] The present invention aims to solve the above-mentioned problems. [Means for solving the problem]

[0008] An aspect of the present invention is an electrochemical hydrogen boosting system comprising a hydrogen boosting stack including a unit cell including an electrolyte membrane, an anode electrode, and a cathode electrode, a power supply device that supplies an electric current to the unit cell to generate high-pressure hydrogen gas at a higher pressure on the cathode side of the unit cell than the hydrogen gas supplied to the anode side of the unit cell, and a hydrogen supply source that supplies the hydrogen gas to the hydrogen boosting stack via a supply path, the hydrogen boosting system comprising: a gas-liquid separator that is provided in an exhaust path that communicates with the cathode side of the unit cell and separates moisture from the high-pressure hydrogen gas; and a gas-liquid separator that is provided in an exhaust path that communicates with the cathode side of the unit cell and separates moisture from the high-pressure hydrogen gas, the high-pressure hydrogen gas from which the moisture has been separated, and a dry high-pressure hydrogen gas that is ... the hydrogen boost stack is provided with a hydrogen return path that leads from a downstream side of the gas-liquid separator in the hydrogen boost stack to the supply path that communicates with the anode side of the unit cell, a hydrogen return valve provided in the hydrogen return path, a detector that detects an electrical value that indicates the voltage or resistance of the hydrogen boost stack, and a control device that controls the hydrogen return valve and the power supply device, wherein the control device closes the hydrogen return valve if the electrical value when the current is a predetermined value does not exceed a predetermined threshold, and opens the hydrogen return valve if the electrical value when the current is a predetermined value exceeds the threshold, thereby supplying the dry high-pressure hydrogen gas to the hydrogen boost stack via the supply path. Effect of the Invention

[0009] According to the above aspect, the amount of water remaining in the unit cells when current is supplied to the hydrogen booster stack can be reduced. This reduces the amount of oxygen gas generated by electrolysis of water remaining in the unit cells that is mixed into the hydrogen gas supplied to the hydrogen booster stack. As a result, the occurrence of a chemical reaction between oxygen gas and hydrogen gas can be suppressed. [Brief description of the drawings]

[0010] [Figure 1] FIG. 1 is a schematic diagram showing an electrochemical hydrogen boosting system. [Diagram 2] FIG. 2 is a flowchart showing the procedure of the water retention suppression process. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] 1 is a schematic diagram showing an electrochemical hydrogen boosting system 10. The electrochemical hydrogen boosting system 10 includes an electrochemical hydrogen boosting device 12, a hydrogen supply source 14, a humidifier 16, a high-pressure hydrogen storage device 18, a gas-liquid separator 20, and a control device 22.

[0012] The electrochemical hydrogen booster 12 is a device that electrochemically boosts the pressure of hydrogen gas. The electrochemical hydrogen booster 12 includes a hydrogen booster stack 24 and a power supply 26.

[0013] The hydrogen booster stack 24 has an inlet port PT1, an outlet port PT2, and a high-pressure hydrogen port PT3. The inlet port PT1 is a port for introducing hydrogen gas and is connected to the anode side of each unit cell 28. The outlet port PT2 is a port for discharging unreacted hydrogen gas and is connected to the anode side of each unit cell 28. The high-pressure hydrogen port PT3 is a port for discharging high-pressure hydrogen gas generated in the unit cell 28 and is connected to the cathode side of each unit cell 28.

[0014] The plurality of unit cells 28 each have the same configuration. Each unit cell 28 has an electrolyte membrane 30, an anode electrode 32 provided on one surface of the electrolyte membrane 30, and a cathode electrode 34 provided on the other surface of the electrolyte membrane 30.

[0015] The electrolyte membrane 30 is, for example, a solid polymer electrolyte membrane (cation exchange membrane). The electrolyte membrane 30 may be reinforced on the anode side with a protective sheet (not shown) including a fibrous skeleton. The electrolyte membrane 30 may use a fluorine-based electrolyte or an HC (hydrocarbon)-based electrolyte. The electrolyte membrane 30 is sandwiched between an anode electrode 32 and a cathode electrode 34.

[0016] The anode electrode 32 includes an anode catalyst layer bonded to one surface of the electrolyte membrane 30, and an anode power supply laminated on the anode catalyst layer. The cathode electrode 34 includes a cathode catalyst layer bonded to the other surface of the electrolyte membrane 30, and a cathode power supply laminated on the cathode catalyst layer. The anode power supply and the cathode power supply are formed into a structure that allows hydrogen gas to flow through them.

[0017] When a current is supplied between the anode electrode 32 and the cathode electrode 34, a part of the hydrogen gas supplied to the anode electrode 32 from the inlet port PT1 is converted into protons (H + The protons are converted into protons (protons) through the electrolyte membrane 30 and transported to the cathode electrode 34. At the cathode electrode 34, an electrochemical reaction using the transported protons occurs, generating high-pressure hydrogen gas. The high-pressure hydrogen gas flows out from the high-pressure hydrogen port PT3. Hydrogen gas that has not reacted at the anode electrode 32 flows out from the exhaust port PT2.

[0018] The hydrogen gas flowing out from the exhaust port PT2 is supplied into the sealed container 38 via the low-pressure exhaust path 36, or is exhausted via a vent path 40 branching off from the low-pressure exhaust path 36. A discharge valve 42 and a pump 44 are provided in the low-pressure exhaust path 36. A vent valve 45 is provided in the vent path 40. The discharge valve 42 and the vent valve 45 each open or close under the control of the control device 22. The pump 44 is driven under the control of the control device 22, and applies a flow force from the upstream side to the downstream side to the hydrogen gas.

[0019] The power supply device 26 supplies an electric current to the hydrogen booster stack 24. This causes the hydrogen booster stack 24 to generate high-pressure hydrogen gas at a pressure higher than the pressure of the supplied hydrogen gas.

[0020] The power supply device 26 applies a voltage to the anode electrode 32 and the cathode electrode 34 of each unit cell 28, and supplies a current to the unit cell 28. The power supply device 26 is configured to be able to adjust the magnitude of the current supplied to each unit cell 28 in response to control by the control device 22. The larger the current supplied to a unit cell 28, the greater the amount of high-pressure hydrogen gas generated in that unit cell 28.

[0021] The hydrogen supply source 14 is a device capable of supplying hydrogen gas. The hydrogen supply source 14 may be a cylinder in which a plurality of gas cylinders in which hydrogen gas is stored are collected together, or may be a tank in which hydrogen gas is stored. The hydrogen supply source 14 supplies hydrogen gas to the hydrogen booster stack 24 via a supply path 46.

[0022] The supply path 46 is a path that guides hydrogen gas from the hydrogen supply source 14 to the hydrogen booster stack 24. The upstream end of the supply path 46 is connected to an output port (not shown) of the hydrogen supply source 14. The downstream end of the supply path 46 is connected to an inlet port PT1 of the hydrogen booster stack 24. A pressure reducing valve 48, a hydrogen supply valve 50, and a flow rate control valve 52 are provided in this order in the supply path 46 from the upstream side to the downstream side.

[0023] 1, there is one pressure reducing valve 48, but there may be two or more pressure reducing valves 48. The hydrogen supply valve 50 opens or closes under the control of the controller 22. The flow rate control valve 52 adjusts the flow rate of hydrogen gas supplied to the hydrogen booster stack 24 under the control of the controller 22.

[0024] The humidifier 16 is a device that humidifies hydrogen gas. The humidifier 16 has a sealed container 38. The humidifier 16 vaporizes liquid water stored in the sealed container 38. The humidifier 16 supplies water vapor to the supply path 46 via the outlet path 54.

[0025] The outlet path 54 is a path that leads water vapor from the humidifier 16 to the supply path 46. The upstream end of the outlet path 54 is disposed in the gas phase space of the sealed container 38. The downstream end of the outlet path 54 is connected to the supply path 46 between the hydrogen supply valve 50 and the flow rate adjustment valve 52. The outlet path 54 is provided with an outlet valve 56. The outlet valve 56 opens or closes under the control of the control device 22.

[0026] The humidifier 16 may be a bubbler type humidifier. FIG. 1 shows an example in which the humidifier 16 is a bubbler type humidifier. In this case, the humidifier 16 has a bubble generator 58. In this embodiment, the bubble generator 58 is disposed in the liquid water in the sealed container 38. The bubble generator 58 releases hydrogen gas supplied from the supply path 46 via an introduction path 60 into the liquid water as bubbles. In this case, the hydrogen gas contains moisture (water vapor). The hydrogen gas containing the moisture is supplied to the supply path 46 via an outlet path 54.

[0027] The introduction path 60 is a path that guides a portion of the hydrogen gas flowing through the supply path 46 from the supply path 46 to the bubble generator 58. The upstream end of the introduction path 60 is connected to a location on the supply path 46 upstream of the connection location of the downstream end of the outlet path 54. The downstream end of the introduction path 60 is connected to the bubble generator 58. An introduction valve 62 is provided in the introduction path 60. The introduction valve 62 opens or closes under the control of the control device 22.

[0028] A temperature adjustment device 64 may be provided to adjust the temperature of the liquid water stored in the sealed container 38. The temperature adjustment device 64 includes a heat exchanger 66, a circulation path 68 that circulates the liquid water between the heat exchanger 66 and the sealed container 38, and a pump 70 provided in the circulation path 68. The temperature adjustment device 64 drives the pump 70 to circulate the liquid water between the heat exchanger 66 and the sealed container 38 via the circulation path 68, and adjusts the liquid water to a set temperature by heat exchange with the heat exchanger 66.

[0029] The high-pressure hydrogen storage device 18 is a device configured to be able to store high-pressure hydrogen gas. The high-pressure hydrogen storage device 18 may be a cylinder consisting of a plurality of gas cylinders in which high-pressure hydrogen gas is stored, or may be a tank in which high-pressure hydrogen gas is stored. The high-pressure hydrogen storage device 18 stores high-pressure hydrogen gas supplied from the hydrogen booster stack 24 via a discharge path 72. The discharge path 72 is a path that guides the high-pressure hydrogen gas discharged from the hydrogen booster stack 24. The upstream end of the discharge path 72 is connected to a high-pressure hydrogen port PT3 of the hydrogen booster stack 24. The downstream end of the discharge path 72 is connected to an input port (not shown) of the high-pressure hydrogen storage device 18. A back pressure valve 74 is provided in the discharge path 72.

[0030] The gas-liquid separator 20 is provided in the discharge path 72 between the back pressure valve 74 and the hydrogen booster stack 24. The gas-liquid separator 20 separates moisture from the high-pressure hydrogen gas. The dry high-pressure hydrogen gas, which is the high-pressure hydrogen gas from which the moisture has been separated, flows downstream of the discharge path 72. The dry high-pressure hydrogen gas is supplied to the high-pressure hydrogen storage device 18 via the discharge path 72, or is supplied to the supply path 46 via a hydrogen return path 76 branching off from the discharge path 72.

[0031] The hydrogen return path 76 is a path that guides dry high-pressure hydrogen gas from the downstream side of the gas-liquid separator 20 in the discharge path 72 to the supply path 46. The upstream end of the hydrogen return path 76 is connected to the discharge path 72. In this embodiment, the upstream end of the hydrogen return path 76 is connected to the discharge path 72 between the gas-liquid separator 20 and the back pressure valve 74. The downstream end of the hydrogen return path 76 is connected to the supply path 46. In this embodiment, the downstream end of the hydrogen return path 76 is connected to the supply path 46 between the flow rate regulating valve 52 and the hydrogen booster stack 24. A hydrogen return valve 78 is provided in the hydrogen return path 76. The hydrogen return valve 78 opens or closes according to the control of the control device 22.

[0032] The moisture separated by the gas-liquid separator 20 is supplied to the humidifier 16 via a water supply path 80. The water supply path 80 is a path that supplies water from the gas-liquid separator 20 to the humidifier 16. The upstream end of the water supply path 80 is connected to a water discharge port of the gas-liquid separator 20 (not shown). The downstream end of the water supply path 80 is connected to a water inlet port (not shown) of the sealed container 38 of the humidifier 16. A water supply valve 82 is provided in the water supply path 80. The water supply valve 82 opens or closes according to the control of the control device 22.

[0033] The control device 22 is a computer that controls the electrochemical hydrogen boosting system 10. The control device 22 includes one or more processors and a storage medium. The storage medium may be composed of a volatile memory and a non-volatile memory. Examples of the processor include a CPU, an MCU, etc. Examples of the volatile memory include a RAM, etc. Examples of the non-volatile memory include a ROM, a flash memory, etc.

[0034] A detector 84 is connected to the control device 22. Using the detector 84, the control device 22 acquires an electrical value of the hydrogen booster stack 24 when the current of the hydrogen booster stack 24 is a predetermined value. The electrical value is a value indicating voltage or resistance. The higher the voltage of the hydrogen booster stack 24 compared to a reference voltage that is a voltage suitable for operation of the hydrogen booster stack 24, the more moisture will remain in the unit cells 28. Similarly, the higher the resistance of the hydrogen booster stack 24 compared to a reference resistance that is a resistance suitable for operation of the hydrogen booster stack 24, the more moisture will remain in the unit cells 28. Therefore, the control device 22 can capture the amount of moisture remaining in the unit cells 28 by acquiring an electrical value when the current of the hydrogen booster stack 24 is a predetermined value.

[0035] The detector 84 is provided in the hydrogen booster stack 24. The detector 84 may be a voltage sensor. In this case, the control device 22 acquires, as an electrical value, a voltage value (detected voltage value) detected by the voltage sensor when the current in the hydrogen booster stack 24 is a predetermined value. The detector 84 may be a resistance sensor. In this case, the control device 22 detects, as an electrical value, a resistance value (detected resistance value) detected by the resistance sensor when the current in the hydrogen booster stack 24 is a predetermined value.

[0036] The voltage or resistance may be calculated using Ohm's law, so the value detected by detector 84 may be used by controller 22 to calculate the detected voltage value or detected resistance value.

[0037] The detected voltage value may be a voltage value applied across both ends of a plurality of unit cells 28 included in the hydrogen boosting stack 24. Alternatively, the detected voltage value may be a voltage value of one unit cell 28 selected from the plurality of unit cells 28. Alternatively, the detected voltage value may be a statistical value of the voltage values ​​of each of the plurality of unit cells 28. Alternatively, the detected voltage value may be a statistical value of the voltage values ​​of two or more unit cells 28 selected from the plurality of unit cells 28. Examples of the statistical value include an average value, a median value, a total value, etc.

[0038] Similarly, the detected resistance value may be a resistance value detected at both ends of a plurality of unit cells 28 included in the hydrogen boosting stack 24. Alternatively, the detected resistance value may be a resistance value of one unit cell 28 selected from the plurality of unit cells 28. Alternatively, the detected resistance value may be a statistical value of the resistance values ​​of each of the plurality of unit cells 28. Alternatively, the detected resistance value may be a statistical value of the resistance values ​​of two or more unit cells 28 selected from the plurality of unit cells 28. Examples of the statistical value include an average value, a median value, a total value, etc.

[0039] Upon receiving the operation command, the controller 22 puts the hydrogen booster stack 24 into operation. In this case, the controller 22 opens the hydrogen supply valve 50 to supply hydrogen gas from the hydrogen supply source 14 to the hydrogen booster stack 24. The controller 22 also controls the power supply device 26 to apply a predetermined voltage to the hydrogen booster stack 24 and supply a current to the hydrogen booster stack 24. In each unit cell 28 of the hydrogen booster stack 24, an electrochemical reaction is carried out based on the hydrogen gas supplied from the hydrogen supply source 14. As a result, high-pressure hydrogen gas is generated on the cathode side of each unit cell 28.

[0040] During operation of the hydrogen booster stack 24, the controller 22 drives the pump 44 and opens the exhaust valve 42 to supply unreacted hydrogen gas in the hydrogen booster stack 24 to the sealed container 38. The controller 22 also opens the vent valve 45 at any timing to exhaust the hydrogen gas.

[0041] During operation of the hydrogen booster stack 24, the controller 22 controls the opening of the flow control valve 52 based on the target generation amount of high-pressure hydrogen gas, thereby adjusting the flow rate of hydrogen gas supplied to the hydrogen booster stack 24.

[0042] During operation of the hydrogen booster stack 24, the control device 22 compares the level of the liquid water stored in the sealed container 38 with a predetermined water level threshold at a predetermined cycle. The level of the liquid water stored in the sealed container 38 is detected by a water level sensor 86 provided in the sealed container 38. When the level of the liquid water exceeds the water level threshold, the control device 22 closes the water supply valve 82. On the other hand, when the level of the liquid water falls below the water level threshold, the control device 22 opens the water supply valve 82. The control device 22 may open the water supply valve 82 until the level of the liquid water exceeds the water level threshold. Alternatively, the control device 22 may open the water supply valve 82 until a predetermined period of time has elapsed since the level of the liquid water falls below the water level threshold.

[0043] During operation of the hydrogen booster stack 24, the controller 22 opens the inlet valve 62 and the outlet valve 56 to introduce water vapor together with hydrogen gas into the supply path 46. In this way, the controller 22 humidifies the hydrogen gas supplied to the hydrogen booster stack 24. In this case, the controller 22 may control at least one of the aperture of the hydrogen supply valve 50 and the aperture of the inlet valve 62 to adjust the flow rate ratio of the hydrogen gas that passes through the humidifier 16 and the hydrogen gas that does not pass through the humidifier 16.

[0044] When the amount of humidification of the hydrogen gas increases, moisture tends to accumulate in the unit cells 28. As the amount of moisture that accumulates in the unit cells 28 increases, the voltage applied to the hydrogen booster stack 24 increases.

[0045] Therefore, in this embodiment, when operation of the hydrogen booster stack 24 begins, the controller 22 closes the hydrogen return valve 78, and then compares the electrical value when the current of the hydrogen booster stack 24 is at a predetermined value with a predetermined threshold value at predetermined cycles. If the electrical value when the current of the hydrogen booster stack 24 is at a predetermined value exceeds the threshold value, the controller 22 executes a process to suppress the retention of water in the unit cell 28 (water retention suppression process).

[0046] The water retention suppression process may be defined by a program. Alternatively, the water retention suppression process may be realized by an integrated circuit such as an ASIC or an FPGA. Alternatively, the water retention suppression process may be realized by an electronic circuit including a discrete device. Fig. 2 is a flowchart showing the procedure of the water retention suppression process.

[0047] In step S1, the controller 22 closes the inlet valve 62 and the outlet valve 56, and then proceeds to step S2. When the inlet valve 62 and the outlet valve 56 are closed, the supply of hydrogen gas containing water vapor to the supply path 46 is stopped. Therefore, the hydrogen gas output from the hydrogen supply source 14 is supplied to the hydrogen booster stack 24 without being humidified by the humidifier 16.

[0048] In step S2, the controller 22 opens the hydrogen return valve 78, and then proceeds to step S3. When the hydrogen return valve 78 opens, the dry high-pressure hydrogen gas, which is the high-pressure hydrogen gas from which water has been separated by the gas-liquid separator 20, is supplied from the discharge path 72 to the supply path 46 due to the pressure difference between the discharge path 72 and the supply path 46. The dry high-pressure hydrogen gas supplied to the supply path 46 is supplied to the hydrogen booster stack 24 together with the hydrogen gas output from the hydrogen supply source 14.

[0049] In step S3, the controller 22 uses the detector 84 to obtain an electrical value when the current in the hydrogen booster stack 24 is at a predetermined value, and compares it with a predetermined threshold. If the electrical value when the current in the hydrogen booster stack 24 is at the predetermined value still exceeds the predetermined threshold, the controller 22 determines that moisture still remains in the hydrogen booster stack 24. In this case, the controller 22 remains in step S3. On the other hand, if the electrical value when the current in the hydrogen booster stack 24 is at the predetermined value is less than the predetermined threshold, the controller 22 determines that there is almost no moisture remaining in the hydrogen booster stack 24. In this case, the controller 22 proceeds to step S4.

[0050] In step S4, the controller 22 closes the hydrogen return valve 78 to stop the supply of dry high-pressure hydrogen gas to the hydrogen booster stack 24. Thereafter, the controller 22 proceeds to step S5.

[0051] In step S5, the controller 22 opens the inlet valve 62 and the outlet valve 56 to resume the supply of hydrogen gas containing water vapor to the supply path 46. Thereafter, the controller 22 ends the water retention suppression process.

[0052] As described above, in this embodiment, the hydrogen return path 76 is provided between the exhaust path 72 communicating with the cathode side of the unit cell 28 and the supply path 46 communicating with the anode side of the unit cell 28. The hydrogen return path 76 guides dry high-pressure hydrogen gas from the exhaust path 72 downstream of the gas-liquid separator 20 to the supply path 46.

[0053] During operation of the hydrogen booster stack 24, if the electrical value when the current of the hydrogen booster stack 24 is at a predetermined value does not exceed a predetermined threshold value, the control device 22 closes the hydrogen return valve 78 provided in the hydrogen return path 76.

[0054] On the other hand, when the electrical value when the current of the hydrogen booster stack 24 is at a predetermined value exceeds a predetermined threshold value, the control device 22 opens the hydrogen return valve 78 and supplies dry high-pressure hydrogen gas from the exhaust path 72 via the supply path 46 to the hydrogen booster stack 24.

[0055] As a result, the discharge path 72 and the supply path 46 are connected to each other, and the cathode side of the unit cell 28 is depressurized. Therefore, the dry high-pressure hydrogen gas can be supplied to the hydrogen booster stack 24 through the supply path 46 due to the pressure difference between the discharge path 72 and the supply path 46. Therefore, the moisture remaining in the unit cell 28 can be moved to the cathode side of the unit cell 28. Furthermore, the moisture remaining in the unit cell 28 can be discharged from the cathode side of the unit cell 28 to the discharge path 72 by the hydrogen gas supplied to the hydrogen booster stack 24 from the hydrogen supply source 14. Furthermore, the dry high-pressure hydrogen gas from which the moisture has been separated by the gas-liquid separator 20 is supplied to the hydrogen booster stack 24, so that the moisture remaining in the unit cell 28 can be discharged early and the hydrogen gas can be used efficiently. Therefore, the amount of oxygen gas generated by the electrolysis of water remaining in the unit cell 28 mixed into the hydrogen gas supplied to the hydrogen booster stack 24 can be reduced. As a result, the occurrence of a chemical reaction between the oxygen gas and the hydrogen gas can be suppressed.

[0056] Furthermore, because the pressure difference between the exhaust line 72 and the supply line 46 allows dry high-pressure hydrogen gas to be supplied to the hydrogen booster stack 24 via the supply line 46, there is no need to install a pump in the hydrogen return line 76, etc. Therefore, the amount of moisture remaining in the unit cell 28 can be reduced while suppressing an increase in the number of parts in the electrochemical hydrogen booster system 10.

[0057] Furthermore, since the moisture in the unit cell 28 discharged from the cathode side of the unit cell 28 to the exhaust path 72 can be separated by the gas-liquid separator 20, the moisture can be prevented from returning again via the hydrogen return path 76.

[0058] In this embodiment, when the electric value when the current of the hydrogen booster stack 24 is at a predetermined value exceeds a predetermined threshold value, the controller 22 closes the inlet valve 62 and the outlet valve 56 to stop the supply of water vapor to the supply path 46. This makes it possible to reduce the amount of water remaining in the unit cell 28 more effectively than in the case where the supply of water vapor to the supply path 46 is not stopped.

[0059] In addition, in this embodiment, a water supply path 80 is provided that guides the moisture separated in the gas-liquid separator 20 from the gas-liquid separator 20 to the sealed container 38 of the humidifier 16. This makes it possible to improve the efficiency of water use.

[0060] Furthermore, in this embodiment, when the level of the liquid water in the sealed container 38 exceeds the water level threshold, the control device 22 closes the water supply valve 82 provided in the water supply path 80. On the other hand, when the level of the liquid water in the sealed container 38 falls below the water level threshold, the control device 22 opens the water supply valve 82. This makes it possible to maintain the amount of water stored in the sealed container 38 at or above a certain level. As a result, it is possible to prevent the hydrogen gas flowing through the supply path 46 from being insufficiently humidified.

[0061] The above embodiment can be modified as follows.

[0062] (Variation 1) The control device 22 may control at least one of the opening degree of the hydrogen return valve 78 and the magnitude of the current supplied to the unit cell 28 to make the supply amount of dry high-pressure hydrogen gas greater than the generation amount of high-pressure hydrogen gas. This can increase the depressurization speed on the cathode side of the unit cell 28. Therefore, compared to a case in which the depressurization speed on the cathode side of the unit cell 28 is not increased, moisture remaining in the unit cell 28 can be discharged from the cathode side of the unit cell 28 to the discharge path 72 at an earlier stage.

[0063] The supply amount of dry high-pressure hydrogen gas is the amount of dry high-pressure hydrogen gas per unit time supplied from the hydrogen return valve 78 to the supply path 46. The generation amount of high-pressure hydrogen gas is the amount of high-pressure hydrogen gas generated per unit time in each unit cell 28 of the hydrogen booster stack 24.

[0064] The larger the opening of the hydrogen return valve 78, the greater the supply amount of dry high-pressure hydrogen gas. Similarly, the larger the magnitude of the current supplied to the unit cell 28, the greater the generation amount of high-pressure hydrogen gas. Therefore, the control device 22 can make the supply amount of dry high-pressure hydrogen gas greater than the generation amount of high-pressure hydrogen gas by making the opening of the hydrogen return valve 78 greater than the current value. Similarly, the control device 22 can make the supply amount of dry high-pressure hydrogen gas greater than the generation amount of high-pressure hydrogen gas by making the magnitude of the current supplied to the unit cell 28 smaller than the current value.

[0065] For example, the control device 22 calculates the amount of high-pressure hydrogen gas generated that corresponds to the magnitude of the current currently being supplied to the unit cell 28. Thereafter, the control device 22 calculates the opening degree of the hydrogen return valve 78 that can supply more dry high-pressure hydrogen gas than the calculated amount of high-pressure hydrogen gas generated, and controls the hydrogen return valve 78.

[0066] Also, for example, the control device 22 calculates the supply amount of dry high-pressure hydrogen gas corresponding to the current opening degree of the hydrogen return valve 78. Thereafter, the control device 22 calculates the magnitude of the current that can generate an amount of high-pressure hydrogen gas that is less than the calculated supply amount of dry high-pressure hydrogen gas, and controls the power supply device 26.

[0067] The control device 22 may store a first table indicating the relationship between the opening degree of the hydrogen return valve 78 and the amount of dry high-pressure hydrogen gas supplied from the hydrogen return valve 78 to the supply path 46 per unit time. The control device 22 may also store a second table indicating the relationship between the magnitude of the current supplied to the unit cell 28 and the amount of high-pressure hydrogen gas generated in the hydrogen booster stack 24 per unit time.

[0068] The degree of opening of the hydrogen return valve 78 that can be controlled by the control device 22 includes the case where it is zero. When the degree of opening of the hydrogen return valve 78 is zero, this means that the hydrogen return valve 78 is closed. Note that the hydrogen return valve 78 provided in the hydrogen return path 76 may be composed of a flow rate adjustment valve and a pressure reducing valve (on-off valve) downstream of the flow rate adjustment valve.

[0069] (Variation 2) When the electrical value when the current of the hydrogen booster stack 24 is a predetermined value exceeds a predetermined threshold, the control device 22 does not have to close the inlet valve 62 and the outlet valve 56. In this case, the control device 22 may control the opening degree of the inlet valve 62 and the outlet valve 56 to reduce the amount of water vapor supplied from the humidifier 16 to the supply path 46. For example, when the electrical value when the current of the hydrogen booster stack 24 is a predetermined value exceeds a predetermined threshold, the control device 22 reduces the amount of water vapor supplied compared to when the electrical value is less than the threshold. This makes it possible to reduce the amount of moisture remaining in the unit cell 28 more effectively compared to when the amount of water vapor supplied is not reduced.

[0070] (Variation 3) The bubble generator 58, the introduction path 60 and the introduction valve 62 may be omitted from the electrochemical hydrogen boosting system 10. The hydrogen gas flowing through the supply path 46 can be humidified even without providing the bubble generator 58, the introduction path 60 and the introduction valve 62. Therefore, the same effects as those of the above embodiment can be obtained even without providing the bubble generator 58, the introduction path 60 and the introduction valve 62.

[0071] (Variation 4) The gas-liquid separator 20 may be provided above the sealed container 38. In this case, water can be easily supplied from the gas-liquid separator 20 to the sealed container 38 without providing a pump in the water supply path 80 or the like.

[0072] (Variation 5) When the opening degree of the hydrogen return valve 78 is not adjusted, the hydrogen return valve 78 may be a three-way valve.

[0073] (Variation 6) If the capacity of the sealed container 38 is large, or if a mechanism for discharging water is provided in the sealed container 38, the water supply valve 82 does not have to be provided. In other words, the water supply valve 82 is not essential.

[0074] The invention and effects that can be understood from the above description will be described below.

[0075] (1) The present invention provides an electrochemical hydrogen boosting system (10) comprising: a hydrogen boosting stack (24) provided with a unit cell (28) including an electrolyte membrane (30), an anode electrode (32), and a cathode electrode (34); a power supply device (26) that supplies current to the unit cell to generate high-pressure hydrogen gas on the cathode side of the unit cell, the high-pressure hydrogen gas having a higher pressure than the hydrogen gas supplied to the anode side of the unit cell; and a hydrogen supply source (14) that supplies the hydrogen gas to the hydrogen boosting stack via a supply path (46). The electrochemical hydrogen boosting system includes a gas-liquid separator (20) provided in a discharge path (72) communicating with the cathode side of the unit cell and separating moisture from the high-pressure hydrogen gas, a hydrogen return path (76) for guiding dry high-pressure hydrogen gas, which is the high-pressure hydrogen gas from which the moisture has been separated, from a downstream side of the gas-liquid separator in the discharge path to the supply path communicating with the anode side of the unit cell, a hydrogen return valve (78) provided in the hydrogen return path, a detector (84) for detecting an electrical value indicating the voltage or resistance of the hydrogen boosting stack, and a control device (22) for controlling the hydrogen return valve and the power supply device. The control device closes the hydrogen return valve when the electrical value when the current is a predetermined value does not exceed a predetermined threshold value, and opens the hydrogen return valve when the electrical value when the current is a predetermined value exceeds the threshold value, thereby supplying the dry high-pressure hydrogen gas to the hydrogen boosting stack via the supply path.

[0076] This allows dry high-pressure hydrogen gas to be supplied to the unit cell from the anode side to the cathode side of the unit cell while reducing the pressure on the cathode side of the unit cell. Therefore, moisture remaining in the unit cell can be discharged from the cathode side of the unit cell to the discharge path. As a result, the amount of moisture remaining in the unit cell when current is being supplied to the hydrogen boosting stack can be reduced.

[0077] (2) The present invention is the electrochemical hydrogen boosting system described in (1) above, wherein the control device may control the opening of the hydrogen return valve to make the supply amount of the dry high-pressure hydrogen gas greater than the generation amount of the high-pressure hydrogen gas. This makes it possible to increase the depressurization speed on the cathode side of the unit cell. Compared to a case in which the depressurization speed on the cathode side of the unit cell is not increased, moisture remaining in the unit cell can be discharged from the cathode side of the unit cell to the discharge path more quickly.

[0078] (3) The present invention is the electrochemical hydrogen boosting system according to (1) or (2) above, wherein the control device may control the magnitude of the current supplied to the unit cell to make the supply amount of the dry high-pressure hydrogen gas greater than the generation amount of the high-pressure hydrogen gas. This makes it possible to increase the depressurization speed on the cathode side of the unit cell. Compared to a case in which the depressurization speed on the cathode side of the unit cell is not increased, moisture remaining in the unit cell can be discharged from the cathode side of the unit cell to the discharge path more quickly.

[0079] (4) The present invention provides an electrochemical hydrogen boosting system as described in (1) above, further comprising a humidifier (16) for supplying water vapor to the supply path via an outlet path (54), and an outlet valve (56) provided in the outlet path and controlled by the control device, wherein the control device may control an aperture of the outlet valve to reduce the amount of water vapor supplied from the humidifier to the supply path when the electrical value when the current is a predetermined value exceeds the threshold value, compared to when the electrical value when the current is a predetermined value is less than the threshold value. This makes it possible to reduce the amount of moisture retained in the unit cell more effectively than when the amount of water vapor supplied is not reduced.

[0080] (5) The present invention provides the electrochemical hydrogen boosting system according to (1) above, further comprising a humidifier for supplying water vapor to the supply path via an outlet path, and an outlet valve provided in the outlet path and controlled by the control device, wherein the control device may close the outlet valve to stop the supply of water vapor to the supply path when the electrical value when the current of the hydrogen boosting stack is a predetermined value exceeds the threshold value. This makes it possible to reduce the amount of moisture remaining in the unit cells more effectively than if the supply of water vapor was not stopped.

[0081] (6) The present invention may be the electrochemical hydrogen boosting system according to (4) or (5) above, further comprising a water supply path (80) for guiding the moisture separated by the gas-liquid separator from the gas-liquid separator to the humidifier, thereby improving water utilization efficiency.

[0082] The present invention is not limited to the above disclosure, and various configurations can be adopted without departing from the gist of the present invention. [Explanation of symbols]

[0083] 10...Electrochemical hydrogen boosting system 12...Electrochemical hydrogen boosting device 14...Hydrogen supply source 16...Humidifier 18...High pressure hydrogen storage device 20...Gas-liquid separator 22...Control device 24...Hydrogen booster stack 26...Power supply unit 28...Unit cell 30...electrolyte membrane 32...anode electrode 34: cathode electrode; 38: sealed container 46…Supply route 54…Extraction route 56: Outlet valve 72: Discharge path 76...Hydrogen return path 78...Hydrogen return valve 80...water supply path 82...water supply valve 84…Detector

Claims

1. a hydrogen boosting stack including a unit cell including an electrolyte membrane, an anode electrode, and a cathode electrode; a power supply device that supplies a current to the unit cell to generate high-pressure hydrogen gas at a cathode side of the unit cell, the high-pressure hydrogen gas having a pressure higher than that of hydrogen gas supplied to an anode side of the unit cell; a hydrogen supply source that supplies the hydrogen gas to the hydrogen boosting stack via a supply path; An electrochemical hydrogen boosting system comprising: a gas-liquid separator provided in an exhaust passage communicating with a cathode side of the unit cell, the gas-liquid separator separating moisture from the high-pressure hydrogen gas; a hydrogen return path that guides the dry high-pressure hydrogen gas, which is the high-pressure hydrogen gas from which the moisture has been separated, from a downstream side of the gas-liquid separator in the discharge path to the supply path that communicates with the anode side of the unit cell; A hydrogen return valve provided in the hydrogen return path; a detector for detecting an electrical value indicative of a voltage or resistance of the hydrogen boosting stack; a control device that controls the hydrogen return valve and the power supply device; Equipped with The control device closes the hydrogen return valve when the electrical value when the current is a predetermined value does not exceed a predetermined threshold, and opens the hydrogen return valve when the electrical value when the current is a predetermined value exceeds the threshold, thereby supplying the dry high-pressure hydrogen gas to the hydrogen boost stack via the supply path.

2. 2. The electrochemical hydrogen boosting system according to claim 1, The control device controls the opening of the hydrogen return valve to make the supply amount of the dry high-pressure hydrogen gas greater than the generation amount of the high-pressure hydrogen gas.

3. 3. The electrochemical hydrogen boosting system according to claim 1 or 2, The control device controls the magnitude of the current supplied to the unit cell to make the supply amount of the dry high-pressure hydrogen gas greater than the generation amount of the high-pressure hydrogen gas.

4. 2. The electrochemical hydrogen boosting system according to claim 1, a humidifier that supplies water vapor to the supply path through an outlet path; an outlet valve provided in the outlet path and controlled by the control device; Further equipped with The control device, when the electrical value when the current is a predetermined value exceeds the threshold value, controls the opening degree of the outlet valve to reduce the amount of water vapor supplied from the humidifier to the supply path compared to when the electrical value when the current is a predetermined value is less than the threshold value.

5. 2. The electrochemical hydrogen boosting system according to claim 1, a humidifier that supplies water vapor to the supply path through an outlet path; an outlet valve provided in the outlet path and controlled by the control device; Further equipped with The control device, when the electrical value when the current is a predetermined value exceeds the threshold value, closes the outlet valve to stop the supply of the water vapor to the supply path.

6. 6. The electrochemical hydrogen boosting system according to claim 4 or 5, The electrochemical hydrogen boosting system further comprises a water supply path that guides the moisture separated in the gas-liquid separator from the gas-liquid separator to the humidifier.

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