Electrochemical hydrogen pressurization system

Abstract

SOLUTION: An electrochemical hydrogen pressurization system includes a single cell comprising an electrolyte membrane, an anode electrode provided on one surface of the electrolyte membrane, and a cathode electrode provided on the other surface of the electrolyte membrane, a hydrogen pressurization stack configured to supply hydrogen gas to the anode electrode and to discharge the hydrogen gas pressurized from the cathode electrode, a power supply device configured to apply a voltage to the hydrogen pressurization stack, a hydrogen supply device configured to supply hydrogen gas to the hydrogen pressurization stack, a storage device configured to store the hydrogen gas discharged from the hydrogen pressurization stack, and a return passage configured to return the hydrogen gas discharged from the hydrogen pressurization stack to the hydrogen supply device, wherein a hydrogen storage tank configured to store the hydrogen gas is provided in the return passage.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure 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, ensuring that more people have access to affordable, reliable, sustainable and advanced energy.

[0003] Patent Document 1 discloses a control method for a hydrogen / oxygen production system and a hydrogen / oxygen production system. This hydrogen / oxygen production system includes a water electrolysis device that electrolyzes liquid water by passing an electric current between an anode and a cathode, and a hydrogen gas booster unit (hydrogen booster stack) downstream of the water electrolysis device that boosts hydrogen by passing an electric current between a booster unit anode and a booster unit cathode. When the hydrogen / oxygen production system is stopped, a first pressure reduction process is performed to prevent the pressure reduction rate of the booster unit cathode of the hydrogen booster stack from exceeding a basic pressure reduction rate, and a second pressure reduction process is performed to prevent the pressure reduction rate of the anode of the water electrolysis device from exceeding the pressure reduction rate of the booster unit cathode. This prevents the booster unit cathode from suddenly depressurizing, and prevents damage to the electrolyte membrane of the hydrogen gas booster unit. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 2022-83098 Summary of the Invention [Problem to be solved by the invention]

[0005] However, in a hydrogen booster stack, hydrogen gas remains on the cathode side when the system is shut down. Because the pressure of this hydrogen gas is not high enough, it is released into the atmosphere. This means that the hydrogen gas is not used effectively, which reduces the hydrogen production efficiency of the electrochemical hydrogen booster system.

[0006] The present invention aims to solve the above-mentioned problems. [Means for solving the problem]

[0007] An aspect of the present disclosure is an electrochemical hydrogen boosting system having a single cell including an electrolyte membrane, an anode electrode provided on one side of the electrolyte membrane, and a cathode electrode provided on the other side of the electrolyte membrane, the system comprising: a hydrogen boosting stack that supplies hydrogen gas to the anode electrode and delivers the pressurized hydrogen gas from the cathode electrode; a power supply device that applies voltage to the hydrogen boosting stack; a hydrogen supply device that supplies the hydrogen gas to the hydrogen boosting stack; a storage device that stores the hydrogen gas delivered by the hydrogen boosting stack; and a return flow path that returns the hydrogen gas delivered by the hydrogen boosting stack to the hydrogen supply device, the return flow path being provided with a hydrogen storage tank that stores the hydrogen gas. [Effects of the Invention]

[0008] According to the above-described embodiment, hydrogen gas is returned to the hydrogen supply device through the return flow path, and the hydrogen gas is stored in a hydrogen storage tank provided in the return flow path. This reduces the amount of hydrogen gas remaining on the cathode side that is released to the outside when the hydrogen booster stack is stopped, thereby preventing a decrease in the hydrogen production efficiency of the electrochemical hydrogen booster system. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a schematic diagram of the electrochemical hydrogen boosting system according to the first embodiment. [Figure 2] FIG. 2 is a flowchart according to the first embodiment. [Figure 3] FIG. 3 is an explanatory diagram relating to pressure changes of hydrogen gas according to the first embodiment. [Figure 4] FIG. 4 is a schematic diagram of the electrochemical hydrogen boosting system according to the second embodiment. [Figure 5] FIG. 5 is a flowchart according to the second embodiment. [Figure 6] FIG. 6 is an explanatory diagram relating to pressure changes of hydrogen gas according to the second embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0010] [First embodiment] 1 is a schematic diagram of an electrochemical hydrogen boosting system 10 according to a first embodiment. The electrochemical hydrogen boosting system 10 includes an electrochemical hydrogen boosting device 12, a hydrogen supply device 14, a gas-liquid separator 18, a condenser 20, a moisture removal device 22, a first hydrogen storage tank 96, a storage device 24, and a control device 30.

[0011] The electrochemical hydrogen booster 12 electrochemically boosts the pressure of hydrogen gas and includes a hydrogen booster stack 16 and a power supply 28 that applies a voltage to the hydrogen booster stack 16.

[0012] The hydrogen boosting stack 16 supplies hydrogen gas to the anode electrode 36 and outputs pressurized hydrogen gas (high-pressure hydrogen gas) from the cathode electrode 40. The pressure of the hydrogen gas boosted at the cathode electrode 40 is higher than the pressure of the hydrogen gas supplied to the anode electrode 36.

[0013] The hydrogen booster stack 16 has a hydrogen inlet PT1, a hydrogen outlet PT2, and a high-pressure hydrogen outlet PT3. The hydrogen inlet PT1 introduces hydrogen gas supplied from the hydrogen supply device 14 into the hydrogen booster stack 16. The introduced hydrogen gas is connected to the anode electrode 36 of each unit cell 32. The hydrogen outlet PT2 discharges unused hydrogen gas. The high-pressure hydrogen outlet PT3 discharges high-pressure hydrogen gas (high-pressure hydrogen gas) generated in each unit cell 32. The high-pressure hydrogen gas is connected to the cathode electrode 40 of each unit cell 32.

[0014] The hydrogen booster stack 16 is configured by stacking a plurality of unit cells 32. All of the unit cells 32 have the same structure. Each unit cell 32 has an electrolyte membrane 34, an anode electrode 36 provided on one side of the electrolyte membrane 34, an anode power supply 37, a cathode electrode 40 provided on the other side of the electrolyte membrane 34, and a cathode power supply 41.

[0015] The electrolyte membrane 34 may be, for example, a solid polymer electrolyte membrane (cation exchange membrane). The anode side of the electrolyte membrane 34 may be reinforced with a protective sheet (not shown) including a fibrous skeleton. This allows the electrolyte membrane 34 to withstand the pressure of high-pressure hydrogen gas applied from the cathode side. A fluorine-based electrolyte may be used for the electrolyte membrane 34. The electrolyte membrane 34 may also be an HC (hydrocarbon)-based electrolyte. The electrolyte membrane 34 is sandwiched between the anode electrode 36 and the cathode electrode 40.

[0016] The anode electrode 36 includes an anode catalyst layer bonded to one side of the electrolyte membrane 34. An anode power supply 37 is laminated on the anode catalyst layer. The anode catalyst layer includes a platinum-based catalyst. An anode flow path through which hydrogen gas flows is formed in the anode power supply 37. The anode power supply 37 may be a conductive porous plate. Hydrogen gas introduced through the hydrogen inlet PT1 flows through the anode flow path and reaches the anode catalyst layer. A porous reinforcing plate may be interposed between the anode catalyst layer and the anode power supply 37. The reinforcing plate can effectively withstand the pressure of high-pressure hydrogen gas applied from the cathode side.

[0017] The cathode electrode 40 includes a cathode catalyst layer bonded to the other surface of the electrolyte membrane 34. A cathode current supply 41 is laminated on the cathode catalyst layer. The cathode catalyst layer includes a platinum-based catalyst. A cathode flow path is formed in the cathode current supply 41, through which pressurized high-pressure hydrogen gas flows. The cathode current supply 41 may also be a conductive porous plate. The high-pressure hydrogen gas generated at the cathode electrode 40 flows through the cathode flow path and is discharged from the high-pressure hydrogen outlet PT3.

[0018] When a voltage is applied between the anode electrode 36 and the cathode electrode 40 from the power supply 28, hydrogen gas supplied to the anode electrode 36 from the hydrogen inlet PT1 is ionized into protons (hydrogen ions) and electrons by a catalytic reaction in the anode catalyst layer. The generated protons permeate the electrolyte membrane 34 and move to the cathode electrode 40. At this time, the protons carry moisture with them to the cathode electrode 40. Therefore, the hydrogen gas supplied to the anode electrode 36 from the hydrogen supply device 14 is humidified and contains moisture. At the cathode electrode 40, high-pressure hydrogen gas is generated by an electrochemical reaction in which the protons that have permeated the electrolyte membrane 34 combine with the electrons. Unused hydrogen gas that is not ionized at the anode electrode 36 is discharged from the hydrogen outlet PT2. The pressure of the high-pressure hydrogen gas flowing through the cathode flow path is higher than the pressure of the hydrogen gas flowing through the anode flow path.

[0019] The power supply 28 applies a DC voltage to the hydrogen booster stack 16, causing a current to flow through the hydrogen booster stack 16. The hydrogen booster stack 16 includes a stack of multiple unit cells 32, with an anode connection terminal and a cathode connection terminal disposed at each end of the stack. The positive electrode of the power supply 28 is connected to the anode connection terminal via a connection cable, and the negative electrode of the power supply 28 is connected to the cathode connection terminal via a connection cable. As a result, a positive voltage is applied to the anode electrode 36 of each unit cell 32 via the anode power supply 37, and a negative voltage is applied to the cathode electrode 40 of each unit cell 32 via the cathode power supply 41.

[0020] The power supply device 28 can adjust the magnitude of the voltage applied to the hydrogen booster stack 16 in response to a control command from the control device 30. The voltage applied to the hydrogen booster stack 16 is applied evenly to each unit cell 32. The higher the voltage supplied to the hydrogen booster stack 16, the greater the current flowing from the anode electrode 36 to the cathode electrode 40, and the greater the amount of high-pressure hydrogen gas generated in the hydrogen booster stack 16.

[0021] The hydrogen supply device 14 includes a sealed container 44 in which liquid water is stored downward in the direction of gravity. Raw hydrogen is supplied into the liquid water in the sealed container 44 via a raw hydrogen supply path 50. An on-off valve 52 is provided on the raw hydrogen supply path 50. When the on-off valve 52 is open, it allows the raw hydrogen to flow, and when it is closed, it stops the flow of the raw hydrogen.

[0022] The raw material hydrogen has a predetermined gas pressure, and this gas pressure is the pressure of the raw material hydrogen.

[0023] The raw hydrogen supply path 50 extends in the direction of gravity inside the sealed container 44 and has an opening at its downstream end. This opening is open in the liquid water in the sealed container 44, and the raw hydrogen flows out from the opening as hydrogen gas, turns into bubbles in the liquid water, and rises to the top of the sealed container 44 (bubbling). At this time, the liquid droplets contained in the raw hydrogen are taken into the liquid water. Furthermore, the hydrogen gas that rises to the top of the liquid water is humidified by the liquid water. The sealed container 44 functions both as a gas-liquid separator and a humidifier.

[0024] The feed hydrogen need only contain hydrogen gas and can be produced, for example, by electrolysis of water. Alternatively, feed hydrogen can be produced by a reforming reaction from a feed containing hydrocarbons. The feed hydrogen may contain conductive components such as potassium hydroxide contained in the electrolyte when water is electrolyzed, and impurities other than the hydrogen gas produced during the reforming reaction. These impurities are removed in the hydrogen booster stack 16 and are not contained in the high-pressure hydrogen gas produced.

[0025] A gas chamber 45 is formed above the liquid water stored in the sealed container 44, in which hydrogen gas that has passed through the liquid water and been humidified is collected. The hydrogen gas contained inside the gas chamber 45 is pressurized to a predetermined pressure. This is because pressurized source hydrogen is supplied. A pressure sensor P3 is provided in the sealed container 44, communicating with the gas chamber 45 and measuring the pressure of the hydrogen gas contained in the gas chamber 45. In addition, a hydrogen outlet 46 is provided above the sealed container 44, communicating with the gas chamber 45 and for discharging hydrogen gas. The hydrogen gas pressurized to the predetermined pressure is smoothly discharged from the hydrogen outlet 46.

[0026] The hydrogen outlet 46 communicates with a hydrogen inlet PT1 of the hydrogen booster stack 16 via a hydrogen supply passage 60. The hydrogen outlet PT2 of the hydrogen booster stack 16 communicates with a hydrogen circulation port 67 of the sealed container 44 via a hydrogen circulation passage 62. The hydrogen circulation port 67 communicates with the liquid water in the sealed container 44. Unused hydrogen gas in the hydrogen booster stack 16 is circulated inside the sealed container 44. A circulation pump 66 for circulating the hydrogen gas is provided in the hydrogen circulation passage 62.

[0027] The high-pressure hydrogen outlet PT3 of the hydrogen booster stack 16 is connected to the moisture remover 22 via a high-pressure hydrogen supply passage 70. The high-pressure hydrogen supply passage 70 is provided with a gas-liquid separator 18, a condenser 20, and a check valve 72, in that order from the upstream side. The condenser 20 may be provided depending on the specifications required for the high-pressure hydrogen gas, or may not be provided at all.

[0028] The check valve 72 allows high-pressure hydrogen gas to flow from the condenser 20 to the moisture removal device 22, and prevents high-pressure hydrogen gas from flowing back from the moisture removal device 22 to the condenser 20. This makes it possible to shorten the pressure rise time at the next startup without reducing the internal pressure of the moisture removal device 22.

[0029] The gas-liquid separator 18 separates the high-pressure hydrogen gas into liquid components (liquid droplets) and gas components, and removes the liquid components as liquid water. The high-pressure hydrogen gas from which the liquid water has been removed is then supplied to the moisture removal device 22 via the condenser 20 provided downstream. The gas-liquid separator 18 is composed of a sealed container. A level switch 77 is provided inside the gas-liquid separator 18 to measure the amount of liquid water stored therein. The level switch 77 measures the height of the liquid level (upper surface of the liquid water) stored inside the gas-liquid separator 18.

[0030] A drain flow path 78 that discharges separated liquid water to the outside is connected to the lower side of the gas-liquid separator 18 in the direction of gravity. A throttle valve 75 and an on-off valve 79 are provided in the drain flow path 78, in that order from upstream to downstream. The throttle valve 75 adjusts the flow rate of liquid water flowing through the drain flow path 78. The on-off valve 79 discharges liquid water from the drain flow path 78 by opening it, and stops discharging liquid water by closing it. When the control device 30 detects, based on a signal from the level switch 77, that the amount of liquid water accumulated inside the gas-liquid separator 18 exceeds an upper limit, the control device 30 opens the on-off valve 79 and discharges the liquid water, the flow rate of which has been adjusted, to the outside via the throttle valve 75.

[0031] The gas inlet of the gas-liquid separator 18 communicates with the high-pressure hydrogen outlet PT3 of the hydrogen booster stack 16 via the high-pressure hydrogen supply passage 70. The gas outlet of the gas-liquid separator 18 communicates with the gas inlet of the condenser 20.

[0032] The condenser 20 is provided in the high-pressure hydrogen supply passage 70 between the gas-liquid separator 18 and the moisture remover 22. The condenser 20 cools the high-pressure hydrogen gas by exchanging heat with the flowing high-pressure hydrogen gas. This condenses water vapor, which is the moisture contained in the high-pressure hydrogen gas, and reduces the humidity of the high-pressure hydrogen gas. In other words, the dew point of the high-pressure hydrogen gas is lowered.

[0033] The moisture removal device 22 may be, for example, a PSA (Pressure Swing Adsorption) device. The PSA device includes multiple adsorption towers, each of which is filled with a porous adsorbent such as activated carbon, zeolite, alumina, or silica. The multiple adsorption towers are alternately switched to adsorb moisture contained in the introduced hydrogen gas using the adsorbent, and dry hydrogen gas is output. When the amount of moisture adsorbed by the adsorbent reaches an upper limit, dry hydrogen gas is passed through the adsorption tower to release the adsorbed moisture, thereby regenerating the adsorption tower.

[0034] The hydrogen inlet of the moisture removal device 22 communicates with the high-pressure hydrogen outlet PT3 of the hydrogen booster stack 16 via the high-pressure hydrogen supply passage 70. The hydrogen outlet of the moisture removal device 22 communicates with the storage device 24 via the high-pressure hydrogen outlet passage 122. The storage device 24 includes, for example, a hydrogen tank 25 that stores high-pressure hydrogen gas. The storage device 24 may be any device that is capable of storing high-pressure hydrogen gas, and may be a high-pressure container containing a hydrogen storage alloy therein.

[0035] In the high-pressure hydrogen discharge flow path 122, a back pressure valve 124, a check valve 125, and an on-off valve 126 are provided, in that order from the upstream side. The back pressure valve 124 adjusts the pressure of the high-pressure hydrogen gas being discharged. The check valve 125 allows the high-pressure hydrogen gas to flow from the moisture removal device 22 to the storage device 24, and prevents the high-pressure hydrogen gas from flowing back from the storage device 24 to the moisture removal device 22. Therefore, after the storage device 24 is filled with high-pressure hydrogen gas, the gas pressure inside the storage device 24 is maintained even if the pressure on the upstream side drops during depressurization.

[0036] An on-off valve 126 provided in the high-pressure hydrogen outlet flow path 122 supplies high-pressure hydrogen gas to the storage device 24 when open, and stops the supply of high-pressure hydrogen gas to the storage device 24 when closed. A dispenser, coupler, or the like that can disconnect the hydrogen tank 25 may be provided between the high-pressure hydrogen outlet flow path 122 and the hydrogen tank 25. The hydrogen tank 25 is installed in a mobile vehicle, industrial equipment, stationary power generation equipment, or the like that is equipped with a fuel cell system. The hydrogen tank 25 may also be installed in a device that uses hydrogen gas but is not equipped with a fuel cell system.

[0037] The storage device 24 has a pressure sensor P1 that measures the pressure of the high-pressure hydrogen gas. The pressure sensor P1 is provided in the piping of the high-pressure hydrogen outlet flow path 122, downstream of the back pressure valve 124. The pressure sensor P1 may also be provided directly inside the hydrogen tank 25.

[0038] A gas chamber 19 through which high-pressure hydrogen gas flows is formed above the gas-liquid separator 18 in the direction of gravity. This gas chamber 19 is connected to the interior of the sealed container 44 provided in the hydrogen supply device 14 via a return flow path 94. A first hydrogen storage tank 96, which is a hydrogen storage tank, is provided in the return flow path 94. The first hydrogen storage tank 96 has a gas inlet and a gas outlet. The gas inlet and gas outlet may be combined into a single gas distribution port. In this case, the gas inlet and gas outlet may be separately provided in a pipe connected to the gas distribution port.

[0039] An on-off valve 95 is provided in the return flow path 94 between the first hydrogen storage tank 96 and the sealed container 44. The on-off valve 95 is provided downstream of the first hydrogen storage tank 96. When the on-off valve 95 is open, it supplies hydrogen gas from the first hydrogen storage tank 96 to the sealed container 44, and when it is closed, it stops the supply of hydrogen gas from the first hydrogen storage tank 96 to the sealed container 44.

[0040] The return flow path 94 is connected to the gas chamber 19 of the gas-liquid separator 18, through which high-pressure hydrogen gas flows. Therefore, when the hydrogen booster stack 16 stops operating, the high-pressure hydrogen gas flows smoothly from the gas chamber 19 to the first hydrogen storage tank 96, and the gas chamber 19 is depressurized, so that the cathode-side flow path of the hydrogen booster stack 16, which is connected to the gas chamber 19, can be quickly depressurized.

[0041] The upstream end of the return flow path 94 may be connected to the high-pressure hydrogen supply flow path 70 or the high-pressure hydrogen discharge flow path 122. The upstream end of the return flow path 94 may also be connected to the condenser 20 or the moisture remover 22. The first hydrogen storage tank 96 is configured as a sealed container 44. The shape of the sealed container 44 is not particularly limited. The first hydrogen storage tank 96 may be formed in a shape such as a cylinder, a sphere, or a rectangular parallelepiped. The first hydrogen storage tank 96 is provided with a pressure sensor P2 that measures the pressure of the hydrogen gas stored therein. The pressure sensor P2 may be disposed in a pipe connected to a gas inlet or gas outlet provided in the first hydrogen storage tank 96.

[0042] The downstream end of the return flow path 94 has a hydrogen release port. The hydrogen release port opens into the gas chamber 45 at the top of the sealed container 44. The hydrogen release port may also open into the liquid water in the sealed container 44, as shown in FIG. 1. This allows the hydrogen gas released from the hydrogen release port to have water droplets removed in the liquid water and to be well humidified before reaching the upper gas chamber 45 and being supplied to the hydrogen pressurization stack 16 via the hydrogen supply flow path 60.

[0043] In the return flow path 94, between the gas-liquid separator 18 and the first hydrogen storage tank 96, a pressure reducing valve 73, a flow rate adjustment valve 74, a check valve 97, and an on-off valve 98 are provided, in that order from upstream. In response to a command from the control device 30, the pressure reducing valve 73 reduces the pressure of the high-pressure hydrogen gas discharged from the gas-liquid separator 18. The reduced-pressure hydrogen gas then flows downstream. In response to a command from the control device 30, the flow rate adjustment valve 74 adjusts the flow rate of the hydrogen gas reduced by the pressure reducing valve 73. The check valve 97 allows hydrogen gas to flow from the gas-liquid separator 18 to the first hydrogen storage tank 96 and prevents backflow of hydrogen gas from the first hydrogen storage tank 96 to the gas-liquid separator 18. During normal operation, the flow rate adjustment valve 74 is closed, and hydrogen gas does not flow downstream of the flow rate adjustment valve 74. Normal operation refers to an operating state in which a predetermined amount of hydrogen gas is continuously supplied from the hydrogen supply device 14 to the hydrogen booster stack 16, and the power supply device 28 continues to apply a predetermined voltage to the hydrogen booster stack 16, thereby continuously producing high-pressure hydrogen gas, and does not include operating states during startup, shutdown, or temporary suspension.

[0044] A waste flow path 82 is connected to a branch point 81 in the return flow path 94, which is located between the flow rate adjustment valve 74 and the on-off valve 98. A waste valve 83, which is an on-off valve, is provided in the waste flow path 82. When the waste valve 83 is open, it releases hydrogen gas to the outside, and when it is closed, it stops the release of hydrogen gas to the outside. The outside may be, for example, the atmosphere, water, or outer space. A check valve 97 is provided in the return flow path 94, and when the waste valve 83 is open, the hydrogen gas stored in the first hydrogen storage tank 96 is not released to the outside.

[0045] When hydrogen gas is being supplied from the first hydrogen storage tank 96 to the sealed container 44 via the return flow path 94, raw hydrogen is not supplied to the sealed container 44. That is, the on-off valve 52 provided on the raw hydrogen supply path 50 is closed. Furthermore, the pressure of the hydrogen gas stored in the first hydrogen storage tank 96 is higher than the pressure of the hydrogen gas contained in the sealed container 44. Therefore, even if raw hydrogen is not supplied to the sealed container 44, hydrogen gas can be effectively supplied from the first hydrogen storage tank 96 to the hydrogen pressurization stack 16 via the sealed container 44. The pressure of the raw hydrogen may be higher than the pressure of the hydrogen gas contained in the first hydrogen storage tank 96.

[0046] The control device 30 is composed of an ECU (Electronic Control Unit). The ECU is composed of a computer having one or more processors (CPUs), memory, input / output interfaces, and electronic circuits. The one or more processors (CPUs) execute programs (computer-executable instructions) (not shown) stored in memory. The control device 30 performs all control related to the electrochemical hydrogen boosting system 10.

[0047] The operation of the electrochemical hydrogen boosting system 10 during normal operation will be described with reference to Fig. 1. The arrows shown in Fig. 1 indicate the direction of flow of hydrogen gas.

[0048] The control device 30 opens the on-off valve 52 provided in the raw hydrogen supply path 50 to supply raw hydrogen to the hydrogen supply device 14. The water content of the raw hydrogen supplied to the sealed container 44 of the hydrogen supply device 14 is adjusted with liquid water, and the raw hydrogen is supplied as hydrogen gas to the hydrogen inlet PT1 of the hydrogen booster stack 16 via the hydrogen outlet 46 and the hydrogen supply path 60. Unused hydrogen gas discharged from the hydrogen outlet PT2 of the hydrogen booster stack 16 is circulated to the hydrogen circulation port 67 of the sealed container 44 via the hydrogen circulation path 62. The control device 30 controls the rotation speed of a circulation pump 66 provided in the hydrogen circulation path 62 to adjust the flow rate of the circulating hydrogen gas.

[0049] The hydrogen gas supplied to the hydrogen booster stack 16 is electrochemically boosted in pressure by a voltage applied to the hydrogen booster stack 16 from the power supply device 28, and becomes high-pressure hydrogen gas, which is then discharged from the high-pressure hydrogen outlet PT3 to the high-pressure hydrogen supply flow path 70. The discharged high-pressure hydrogen gas has liquid water removed by a gas-liquid separator 18 provided in the high-pressure hydrogen supply flow path 70, and then supplied to the condenser 20. The high-pressure hydrogen gas dehumidified in the condenser 20 is supplied to the moisture removal device 22. The high-pressure hydrogen gas is then further dehumidified in the moisture removal device 22, becoming dry high-pressure hydrogen gas, which is then supplied to the hydrogen tank 25 or the like provided in the storage device 24 via the high-pressure hydrogen discharge flow path 122.

[0050] The control device 30 adjusts the pressure of the high-pressure hydrogen gas supplied to the hydrogen tank 25 by controlling the back pressure valve 124 provided in the high-pressure hydrogen outlet flow path 122 .

[0051] When normal operation ends and the hydrogen booster stack 16 stops operating, high-pressure hydrogen gas remains in the flow path that communicates with the cathode electrode 40 of the hydrogen booster stack 16. High-pressure hydrogen gas also remains in the gas-liquid separator 18, condenser 20, and moisture remover 22 that are provided downstream of the hydrogen booster stack 16, and in the high-pressure hydrogen supply flow path 70 that communicates with these. These are collectively referred to as "high-pressure hydrogen gas remaining on the cathode side."

[0052] When the hydrogen booster stack 16 stops operating, the high-pressure hydrogen gas remaining on the cathode side is depressurized at an appropriate rate. This operation is called depressurization, and the process for performing this operation is called the depressurization process. If the high-pressure hydrogen gas remaining on the cathode side is suddenly depressurized, the electrolyte membrane 34 of the hydrogen booster stack 16 will be damaged, so the rate of depressurization is adjusted to prevent a sudden depressurization of the high-pressure hydrogen gas.

[0053] In the first embodiment, in order to reduce the pressure of the high-pressure hydrogen gas remaining on the cathode side, the high-pressure hydrogen gas is supplied from the gas-liquid separator 18 provided in the high-pressure hydrogen supply passage 70 to the first hydrogen storage tank 96 via the return passage 94. At this time, the pressure reducing valve 73 and the flow rate adjusting valve 74 provided in the return passage 94 optimally adjust the pressure and flow rate of the high-pressure hydrogen gas, respectively. This makes it possible to prevent damage to the electrolyte membrane 34 of the hydrogen booster stack 16. Excess hydrogen gas that cannot be stored in the first hydrogen storage tank 96 is released to the outside via the waste passage 82.

[0054] When the hydrogen booster stack 16 starts operating, hydrogen gas is returned from the first hydrogen storage tank 96 to the sealed container 44 of the hydrogen supply device 14 via the return flow path 94. The downstream end of the return flow path 94 has an opening that opens into the liquid water contained in the sealed container 44. As a result, the hydrogen gas turns into bubbles that float upward in the liquid water in the sealed container 44 and are humidified by the liquid water.

[0055] The storage device 24 is provided with a pressure sensor P1 that measures the pressure of high-pressure hydrogen gas. The hydrogen gas pressure measured by this pressure sensor P1 corresponds to the amount of high-pressure hydrogen gas contained in the hydrogen tank 25. The hydrogen tank 25 has a maximum storage pressure (Pmax). This maximum storage pressure corresponds to the maximum amount of hydrogen gas that can be stored in the hydrogen tank 25.

[0056] When the gas pressure in the hydrogen tank 25 measured by the pressure sensor P1 is a predetermined value (Ptmp) that is lower than the maximum storage pressure, the hydrogen gas pressure (fillable gas pressure) corresponding to Pmax-Ptmp=Pemp can be filled into the hydrogen tank 25. Therefore, when depressurizing is performed, if the gas pressure in the hydrogen tank 25 is low and the fillable gas pressure is high, the high-pressure hydrogen gas remaining on the cathode side may be first supplied to the hydrogen tank 25, and then the remaining hydrogen gas may be supplied to the first hydrogen storage tank 96.

[0057] In the first embodiment, the fillable gas pressure is calculated from the pressure of hydrogen gas in the hydrogen tank 25 measured by the pressure sensor P1. Then, when the first hydrogen storage tank 96 is filled with hydrogen gas obtained by subtracting this fillable gas pressure from the pressure of the high-pressure hydrogen gas remaining on the cathode side, the pressure of hydrogen gas that can be stored in the first hydrogen storage tank 96 is estimated. In other words, when depressurization is performed, the pressure of hydrogen gas that can be stored in the first hydrogen storage tank 96 is estimated based on the gas pressure measured by the pressure sensor P1 provided in the hydrogen tank 25.

[0058] In this case, the volume of the hydrogen tank 25, the volume of the first hydrogen storage tank 96, and the volume of the flow path related to depressurization are acquired in advance and stored as parameters. The pressure of hydrogen gas that can be stored in the first hydrogen storage tank 96 can be calculated from these volume parameters and the hydrogen gas pressure measured by the pressure sensor P1 provided in the first hydrogen storage tank 96.

[0059] If the estimated pressure of hydrogen gas that can be stored in the first hydrogen storage tank 96 is lower than the pressure of hydrogen gas contained in the sealed container 44, high-pressure hydrogen gas is not supplied to the first hydrogen storage tank 96. This is because if the estimated pressure of hydrogen gas that can be stored in the first hydrogen storage tank 96 is lower than the pressure of hydrogen gas contained in the sealed container 44, hydrogen gas cannot be effectively supplied from the first hydrogen storage tank 96 to the hydrogen booster stack 16 via the hydrogen supply device 14. The pressure of hydrogen gas contained in the sealed container 44 may be measured by a pressure sensor P3, or may be preset as a minimum predetermined pressure value required to supply hydrogen gas to the hydrogen booster stack 16.

[0060] [Flowchart according to the first embodiment] The operation procedure of the electrochemical hydrogen boosting system 10 according to the first embodiment will be described with reference to the flowchart shown in FIG.

[0061] During normal operation, high-pressure hydrogen gas electrochemically pressurized in the hydrogen booster stack 16 flows through the gas-liquid separator 18, the condenser 20, and the moisture remover 22 provided in the high-pressure hydrogen supply flow path 70, and is then stored in the hydrogen tank 25. In step S1, the control device 30 instructs the hydrogen booster stack 16 to stop boosting (stop operation). Specifically, the control device 30 causes the power supply device 28 to stop applying voltage to the hydrogen booster stack 16. In this case, the control device 30 may gradually reduce the voltage over time and eventually stop applying the voltage. At the same time, the control device 30 closes the on-off valve 52 to stop the supply of raw hydrogen. Therefore, the supply of hydrogen gas from the hydrogen supply device 14 to the hydrogen booster stack 16 is stopped.

[0062] In step S2, the control device 30 starts a depressurization process for depressurizing the electrochemical hydrogen boosting system 10.

[0063] In step S3, the control device 30 opens the flow rate adjustment valve 74 and supplies the hydrogen gas depressurized by the pressure reducing valve 73 to the first hydrogen storage tank 96. The flow rate adjustment valve 74 adjusts the flow rate per unit time of the circulating hydrogen gas to an extent that does not damage the hydrogen pressurization stack 16. In this case, the on-off valve 98 provided upstream of the first hydrogen storage tank 96 is open, and the on-off valve 95 provided downstream of the first hydrogen storage tank 96 is closed.

[0064] In step S4, the control device 30 measures the pressure of the hydrogen gas in the first hydrogen storage tank 96 using the pressure sensor P2 provided in the first hydrogen storage tank 96. When depressurization begins and the high-pressure hydrogen gas remaining on the cathode side of the hydrogen pressurization stack 16 begins to flow into the first hydrogen storage tank 96, the pressure of the hydrogen gas in the first hydrogen storage tank 96 increases over time.

[0065] In step S5, the control device 30 determines whether the pressure in the first hydrogen storage tank 96 measured by the pressure sensor P2 is higher than a first predetermined value (P_high). If the determination result is affirmative (step S5: YES), the control device 30 proceeds to step S6. If the determination result is negative (step S5: NO), the control device 30 returns to step S4. The first predetermined value is a pressure that is lower than the pressure of the hydrogen gas delivered by the hydrogen booster stack 16 and higher than the pressure of the hydrogen gas contained in the sealed container 44.

[0066] In step S6, the control device 30 opens the waste valve 83 provided in the waste flow path 82. The waste valve 83 is then closed after being open for a predetermined period of time. This causes the surplus hydrogen gas stored in the first hydrogen storage tank 96 to be released into the atmosphere. In this case, the check valve 97 prevents the hydrogen gas stored in the first hydrogen storage tank 96 from being released to the outside via the waste flow path 82.

[0067] In step S7, the control device 30 determines that depressurization is complete. In the first embodiment, the completion of depressurization is determined based on the pressure of the hydrogen gas stored in the first hydrogen storage tank 96. However, the relationship between the pressure of the high-pressure hydrogen gas remaining on the cathode side when depressurization starts and a predetermined time until depressurization is complete may be measured in advance, and the completion of depressurization may be determined based on this predetermined time.

[0068] In step S8, the control device 30 closes the on-off valve 98 provided upstream of the first hydrogen storage tank 96. This stops the supply of hydrogen gas to the first hydrogen storage tank 96. This ends the depressurization process.

[0069] After a predetermined time has elapsed since the depressurization step was completed, in step S9, the controller 30 instructs the hydrogen booster stack 16 to start boosting the hydrogen.

[0070] In step S10, the control device 30 opens the on-off valve 95 provided downstream of the first hydrogen storage tank 96. As a result, hydrogen gas is supplied from the first hydrogen storage tank 96 to the sealed container 44 of the hydrogen supply device 14. The hydrogen gas is then humidified by the liquid water stored in the sealed container 44 and supplied to the hydrogen pressurization stack 16.

[0071] In step S11, the control device 30 measures the pressure of the hydrogen gas in the first hydrogen storage tank 96 using the pressure sensor P2 provided in the first hydrogen storage tank 96. As the hydrogen gas stored in the first hydrogen storage tank 96 is supplied to the sealed container 44, the measured pressure of the hydrogen gas decreases.

[0072] In step S12, the control device 30 determines whether the pressure of the first hydrogen storage tank 96 measured by the pressure sensor P2 exceeds a second predetermined value (P_low). If the determination result is affirmative (step S12: YES), the control device 30 returns to step S11. If the determination result is negative (step S12: NO), the control device 30 proceeds to step S13. The second predetermined value (P_low) is a pressure higher than the pressure of the hydrogen gas contained in the sealed container 44. This is because if the pressure of the hydrogen gas supplied from the first hydrogen storage tank 96 to the sealed container 44 is lower than the pressure of the hydrogen gas contained in the sealed container 44, the hydrogen gas will not be supplied properly to the hydrogen booster stack 16. The pressure of the hydrogen gas contained in the sealed container 44 may be measured by the pressure sensor P3 or may be preset as a minimum predetermined pressure value necessary to supply hydrogen gas to the hydrogen booster stack 16. The second predetermined value is a pressure lower than the first predetermined value.

[0073] In step S13, the control device 30 closes the on-off valve 95 provided downstream of the first hydrogen storage tank 96. This stops the supply of hydrogen gas from the first hydrogen storage tank 96 to the sealed container 44.

[0074] In step S14, the control device 30 opens the on-off valve 52 provided in the raw hydrogen supply path 50. As a result, the raw hydrogen is supplied to the sealed container 44. The raw hydrogen is then humidified by the liquid water stored in the sealed container 44 and supplied to the hydrogen pressurization stack 16 as hydrogen gas.

[0075] [Timing chart according to the first embodiment] A timing chart according to the first embodiment will be described with reference to Fig. 3. In this timing chart, the flowchart described in Fig. 2 is explained on the time axis.

[0076] This timing chart shows the time changes in the pressure (PA) of high-pressure hydrogen gas at the high-pressure hydrogen outlet PT3 of the hydrogen booster stack 16, the pressure (PB) of hydrogen gas detected by the pressure sensor P2 provided in the first hydrogen storage tank 96, and the pressure (PC) of the hydrogen gas supplied to the hydrogen booster stack 16, which is the pressure in the gas chamber 45 of the sealed container 44 measured by the pressure sensor P3.

[0077] At time t0, voltage is applied from the power supply 28 to the hydrogen booster stack 16, and hydrogen gas at a predetermined pressure (P_std=PC) is supplied to the hydrogen booster stack 16. This starts operation of the hydrogen booster stack 16. The pressure (PA) of the high-pressure hydrogen gas discharged from the high-pressure hydrogen outlet PT3 gradually increases and reaches the rated pressure (P_rate). Note that while the hydrogen booster stack 16 continues to operate, the control device 30 controls the power supply 28 to maintain the pressure (PA) of the high-pressure hydrogen gas discharged from the high-pressure hydrogen outlet PT3 by the hydrogen booster stack 16 at a constant value, the rated pressure (P_rate).

[0078] At time t1, the control device 30 stops the application of voltage from the power supply 28 to the hydrogen booster stack 16, stopping the operation of the hydrogen booster stack 16 (step S1), and starts the depressurization process of the high-pressure hydrogen gas on the cathode side (step S2). Specifically, depressurization is performed by supplying the high-pressure hydrogen gas on the cathode side to the first hydrogen storage tank 96 via the return flow path 94. As the depressurization begins from time t1, the pressure (PA) of the high-pressure hydrogen gas decreases from the rated pressure (P_rate), and the pressure (PB) of the first hydrogen storage tank 96 increases.

[0079] At time t2, the hydrogen gas pressure (PB) in the first hydrogen storage tank 96 reaches the first predetermined value (P_high) (steps S4 and S5: YES). At this time t2, the high-pressure hydrogen gas pressure (PA) on the cathode side drops to a pressure (Pα) between the rated pressure (P_rate) and the first predetermined value (P_high). Thereafter, by opening the waste valve 83 for a predetermined time, the high-pressure hydrogen gas pressure (PA) further drops from the pressure (Pα) until it becomes equal to the external pressure. After time t2, the hydrogen gas pressure (PB) in the first hydrogen storage tank 96 is maintained at a constant pressure, the first predetermined value (P_high) (step S6). In this way, depressurization is completed at time te (step S7). At the completion of depressurization at time te, the control device 30 closes the on-off valve 98 provided upstream of the first hydrogen storage tank 96 (step S8).

[0080] Thereafter, at time t3, in order to start the pressurization operation of the hydrogen pressurization stack 16, the control device 30 opens the on-off valve 95 provided downstream of the first hydrogen storage tank 96. As a result, hydrogen gas is supplied from the first hydrogen storage tank 96 to the hydrogen pressurization stack 16 via the hydrogen supply device 14, and the pressurization operation of the hydrogen pressurization stack 16 starts (steps S9 and S10). After time t3, the pressure (PA) of the high-pressure hydrogen gas discharged from the high-pressure hydrogen outlet PT3 gradually increases, and the pressure (PB) of the first hydrogen storage tank 96 gradually decreases.

[0081] From time t3, the amount of hydrogen gas stored in the first hydrogen storage tank 96 decreases, and at time t4, the pressure of the hydrogen gas (PB) drops to a second predetermined value (P_low) (steps S11 and S12: NO). At this time t4, the control device 30 closes the on-off valve 95 provided downstream of the first hydrogen storage tank 96 (step S13) and opens the on-off valve 52 provided in the raw hydrogen supply path 50. As a result, the supply of hydrogen gas from the first hydrogen storage tank 96 stops, and raw hydrogen (hydrogen gas) is supplied to the sealed container 44 via the raw hydrogen supply path 50, so that the pressure of the high-pressure hydrogen gas (PA) discharged from the high-pressure hydrogen outlet PT3 continues to increase from time t4 onwards.

[0082] After time t4, the pressure (PA) of the high-pressure hydrogen gas discharged from the high-pressure hydrogen outlet PT3 gradually increases, and at time t5 it again reaches the rated pressure (P_rate). The subsequent timing charts are repetitive and will be omitted.

[0083] [Second embodiment] Fig. 4 is a schematic diagram showing the configuration of an electrochemical hydrogen boosting system 100 according to the second embodiment. In Fig. 4, the same components as those described in the first embodiment are assigned the same reference numerals. Note that in the second embodiment, explanations that overlap with those in the first embodiment will be omitted.

[0084] As shown in FIG. 4, the electrochemical hydrogen boosting system 100 includes a first hydrogen storage tank (hydrogen storage tank) 96 and a second hydrogen storage tank (hydrogen storage tank) 106. The second hydrogen storage tank 106 is installed in parallel with the first hydrogen storage tank 96 with respect to the return flow path 94. The pressure of the hydrogen gas stored in the second hydrogen storage tank 106 is higher than the pressure of the hydrogen gas stored in the first hydrogen storage tank 96. In other words, the first hydrogen storage tank 96 is a low-pressure tank, and the second hydrogen storage tank 106 is a high-pressure tank. The number of hydrogen storage tanks (96, 106) installed in parallel with the return flow path 94 needs to be at least two, and may be three or more. In this case, the pressures of the hydrogen gas stored in each hydrogen storage tank (96, 106) are different from each other.

[0085] A branch point 101 is provided in the return flow path 94 between the gas-liquid separator 18 and the pressure reducing valve 73. A connecting flow path 102 is connected to the branch point 101. A second hydrogen storage tank 106 communicates with the return flow path 94 via the connecting flow path 102 and the branch point 101. The second hydrogen storage tank 106 has a gas circulation port. High-pressure hydrogen gas flows into and out of the second hydrogen storage tank 106 via this gas circulation port.

[0086] An on-off valve 103 and a flow rate control valve 104 are provided in the connecting flow path 102 from the branch point 101 toward the second hydrogen storage tank 106. When the on-off valve 103 is opened, high-pressure hydrogen gas flows, and when it is closed, the flow of high-pressure hydrogen gas stops. The control device 30 adjusts the flow rate of the flowing hydrogen gas using the flow rate control valve 104. When the operation of the hydrogen booster stack 16 is stopped, if the high-pressure hydrogen gas remaining on the cathode side is suddenly reduced in pressure, the electrolyte membrane 34 of the hydrogen booster stack 16 will be damaged. Therefore, the flow rate control valve 104 adjusts the pressure reduction rate to prevent a sudden reduction in the high-pressure hydrogen gas. During normal operation, the on-off valve 103 is closed, and the flow of high-pressure hydrogen gas between the return flow path 94 and the second hydrogen storage tank 106 is stopped. The second hydrogen storage tank 106 is provided with a pressure sensor P4 that measures the pressure of the hydrogen gas stored therein. The pressure sensor P4 may be disposed in a pipe connected to a gas flow port provided in the second hydrogen storage tank .

[0087] [Flowchart according to the second embodiment] The operation procedure of the electrochemical hydrogen boosting system 100 according to the second embodiment will be described with reference to the flowchart shown in Fig. 5. In the description of Fig. 5, steps similar to those described in the first embodiment are given the same reference numerals. Note that in the second embodiment, explanations that overlap with those in the first embodiment will be omitted.

[0088] During normal operation, high-pressure hydrogen gas electrochemically pressurized in the hydrogen booster stack 16 flows through the gas-liquid separator 18, the condenser 20, and the moisture remover 22 provided in the high-pressure hydrogen supply flow path 70, and is then stored in the hydrogen tank 25. In step S101, the control device 30 instructs the hydrogen booster stack 16 to stop boosting. Specifically, the control device 30 causes the power supply device 28 to stop applying voltage to the hydrogen booster stack 16. In this case, the control device 30 may gradually reduce the voltage over time and eventually stop applying the voltage. At the same time, the control device 30 closes the on-off valve 52 to stop the supply of hydrogen gas from the hydrogen supply device 14 to the hydrogen booster stack 16.

[0089] In step S102, the control device 30 starts a depressurization process for depressurizing the electrochemical hydrogen boosting system 100.

[0090] In step S103, the control device 30 opens the on-off valve 103 to supply high-pressure hydrogen gas to the second hydrogen storage tank 106. The flow rate control valve 104 adjusts the flow rate per unit time of the hydrogen gas flowing to an extent that does not damage the hydrogen booster stack 16. In this case, the on-off valve 98 provided upstream of the first hydrogen storage tank 96 is closed, and the on-off valve 95 provided downstream of the first hydrogen storage tank 96 is also closed. Therefore, high-pressure hydrogen gas is not supplied to the first hydrogen storage tank 96.

[0091] In step S104, the control device 30 measures the pressure of the hydrogen gas in the second hydrogen storage tank 106 using the pressure sensor P4 provided in the second hydrogen storage tank 106. When depressurization begins and the high-pressure hydrogen gas remaining on the cathode side of the hydrogen pressurization stack 16 begins to flow into the second hydrogen storage tank 106, the pressure of the hydrogen gas in the second hydrogen storage tank 106 increases over time.

[0092] In step S105, the control device 30 determines whether the pressure in the second hydrogen storage tank 106 measured by the pressure sensor P4 is higher than a third predetermined value (P_upper). If the determination result is affirmative (step S105: YES), the control device 30 proceeds to step S106. If the determination result is negative (step S105: NO), the control device 30 returns to step S104.

[0093] In step S106, the control device 30 closes the on-off valve 103. This stops the supply of high-pressure hydrogen gas to the second hydrogen storage tank 106. The second hydrogen storage tank 106 is then maintained filled with hydrogen gas at a third predetermined value (P_upper). In the second embodiment, the on-off valve 103 is closed based on the pressure of the hydrogen gas stored in the second hydrogen storage tank 106. However, it is also possible to measure in advance the relationship between the pressure of the high-pressure hydrogen gas remaining on the cathode side when depressurization is started and the predetermined time until depressurization is completed, and close the on-off valve 103 based on this predetermined time.

[0094] Steps S3 to S14 following step S106 are the same as those described in the first embodiment, and therefore will not be described here.

[0095] [Timing chart according to the second embodiment] A timing chart according to the second embodiment will be described with reference to Fig. 6. In this timing chart, the flowchart described in Fig. 5 is explained on the time axis.

[0096] This timing chart shows the time changes in the pressure (PA) of high-pressure hydrogen gas at the high-pressure hydrogen outlet PT3 of the hydrogen booster stack 16, the pressure (PB1) (PB1=PB) of hydrogen gas measured by the pressure sensor P2 provided in the first hydrogen storage tank 96, the pressure (PB2) of hydrogen gas detected by the pressure sensor P4 provided in the second hydrogen storage tank 106, and the pressure (PC) of the hydrogen gas supplied to the hydrogen booster stack 16, which is the pressure in the gas chamber 45 of the sealed container 44 measured by the pressure sensor P3.

[0097] At time t10, voltage is applied from the power supply 28 to the hydrogen booster stack 16, and hydrogen gas at a predetermined pressure (P_std=PC) is supplied to the hydrogen booster stack 16. This causes the hydrogen booster stack 16 to begin operation. The pressure (PA) of the high-pressure hydrogen gas discharged from the high-pressure hydrogen outlet PT3 gradually increases and reaches the rated pressure (P_rate). Note that while the hydrogen booster stack 16 continues to operate, the control device 30 controls the power supply 28 to maintain the pressure (PA) of the high-pressure hydrogen gas discharged from the high-pressure hydrogen outlet PT3 by the hydrogen booster stack 16 at a constant value, the rated pressure (P_rate).

[0098] At time t11, the control device 30 stops the application of voltage from the power supply 28 to the hydrogen booster stack 16, stopping the operation of the hydrogen booster stack 16 (step S101), and starts the depressurization process of the high-pressure hydrogen gas on the cathode side (step S102). Specifically, depressurization is performed by supplying the high-pressure hydrogen gas on the cathode side to the second hydrogen storage tank 106 via the return flow path 94 and the connecting flow path 102. As the depressurization begins from time t11, the pressure (PA) of the high-pressure hydrogen gas decreases from the rated pressure (P_rate), and the pressure (PB2) of the second hydrogen storage tank 106 increases.

[0099] At time t12, the pressure (PB2) of the high-pressure hydrogen gas stored in the second hydrogen storage tank 106 reaches the third predetermined value (P_upper) (steps S104 and S105: YES). At this time t12, the pressure (PA) of the high-pressure hydrogen gas on the cathode side drops to a pressure (Pβ) between the rated pressure (P_rate) and the third predetermined value (P_upper). After time t12, the pressure (PB2) of the hydrogen gas in the second hydrogen storage tank 106 is maintained at a constant pressure, the third predetermined value (P_upper), by closing the on-off valve 103 provided in the connecting flow path 102.

[0100] Furthermore, at time t12, the high-pressure hydrogen gas at the pressure (PA) flows through the pressure reducing valve 73, the flow rate adjusting valve 74, and the open on-off valve 98, and is introduced into the first hydrogen storage tank 96 (step S3). As a result, the pressure (PA) of the high-pressure hydrogen gas further decreases from time t12, and the pressure (PB1) of the hydrogen gas stored in the first hydrogen storage tank 96 increases.

[0101] At time t13, the pressure (PB1) of the hydrogen gas in the first hydrogen storage tank 96 reaches the first predetermined value (P_high) (steps S4 and S5: YES). Also, at time t13, the pressure (PA) of the high-pressure hydrogen gas on the cathode side drops to a pressure (Pγ) between the third predetermined value (P_upper) and the first predetermined value (P_high). Note that the first predetermined value (P_high) is a pressure lower than the third predetermined value (P_upper).

[0102] After time t13, the control device 30 opens the waste valve 83 for a predetermined time, thereby further reducing the pressure (PA) of the high-pressure hydrogen gas from the pressure (Pγ) until it becomes equal to the external pressure, and maintaining the hydrogen gas pressure (PB1) in the first hydrogen storage tank 96 at a constant first predetermined value (P_high) (step S6). At time te' when the high-pressure hydrogen gas pressure (PA) becomes equal to the external pressure, depressurization is completed (step S7). At depressurization completion time te', the control device 30 closes the on-off valve 98 provided upstream of the first hydrogen storage tank 96 (step S8).

[0103] Thereafter, at time t14, in order to start the pressurization operation of the hydrogen pressurization stack 16, the control device 30 opens the on-off valve 95 provided downstream of the first hydrogen storage tank 96. As a result, hydrogen gas is supplied from the first hydrogen storage tank 96 to the hydrogen pressurization stack 16 via the hydrogen supply device 14, and the pressurization operation of the hydrogen pressurization stack 16 is started (steps S9 and S10). After time t14, the pressure (PA) of the high-pressure hydrogen gas discharged from the high-pressure hydrogen outlet PT3 gradually increases, and the pressure (PB1) of the first hydrogen storage tank 96 gradually decreases.

[0104] Furthermore, at time t15, the control device 30 opens the on-off valve 103 provided in the connecting flow path 102. The high-pressure hydrogen gas stored in the second hydrogen storage tank 106 is supplied to the cathode side of the hydrogen booster stack 16 via the gas-liquid separator 18. This causes the pressure (PA) of the high-pressure hydrogen gas on the cathode side of the hydrogen booster stack 16 to rise quickly. Note that the high-pressure hydrogen gas stored in the second hydrogen storage tank 106 may also be supplied directly to the cathode side of the hydrogen booster stack 16 without passing through the gas-liquid separator 18.

[0105] At time t16, the pressure (PB1) in the first hydrogen storage tank 96 drops to a second predetermined value (P_low) (steps S11 and S12: NO). At time t17, the controller 30 closes the on-off valve 95 provided downstream of the first hydrogen storage tank 96 (step S13) and opens the on-off valve 52 provided in the raw hydrogen supply path 50. After time t17, the supply of hydrogen gas from the first hydrogen storage tank 96 stops, and raw hydrogen, which is hydrogen gas, is supplied to the sealed container 44 via the raw hydrogen supply path 50.

[0106] At time t17, the pressure (PB2) of the high-pressure hydrogen gas in the second hydrogen storage tank 106 becomes the same as the pressure (PA) of the high-pressure hydrogen gas output from the high-pressure hydrogen outlet PT3 of the hydrogen booster stack 16. Therefore, at time t17, the control device 30 closes the on-off valve 103 provided in the connecting flow path 102. This stops the supply of high-pressure hydrogen gas from the second hydrogen storage tank 106.

[0107] After time t17, the pressure (PA) of the high-pressure hydrogen gas discharged from the high-pressure hydrogen outlet PT3 continues to rise gradually, and reaches the rated pressure (P_rate) again at time t18. The timing chart from this point on is repetitive and will not be repeated.

[0108] The following additional notes are further disclosed regarding the above embodiment.

[0109] (Appendix 1) The electrochemical hydrogen boosting systems 10, 100 of the present disclosure have a single cell 32 including an electrolyte membrane 34, an anode electrode 36 provided on one side of the electrolyte membrane 34, and a cathode electrode 40 provided on the other side of the electrolyte membrane 34, and are equipped with a hydrogen boosting stack 16 that supplies hydrogen gas to the anode electrode 36 and discharges the pressurized hydrogen gas from the cathode electrode 40, a power supply device 28 that applies voltage to the hydrogen boosting stack 16, a hydrogen supply device 14 that supplies the hydrogen gas to the hydrogen boosting stack 16, a storage device 24 that stores the hydrogen gas discharged by the hydrogen boosting stack 16, and a return flow path 94 that returns the hydrogen gas discharged by the hydrogen boosting stack 16 to the hydrogen supply device 14, and a hydrogen storage tank 96, 106 that stores the hydrogen gas is provided in the return flow path 94.

[0110] This allows the hydrogen gas remaining on the cathode side of the hydrogen booster stack to be stored in the hydrogen storage tank via the return flow path when the hydrogen booster stack stops operating and is depressurized. Then, when starting operation, the hydrogen gas stored in the hydrogen storage tank can be supplied to the hydrogen booster stack, allowing the hydrogen gas to be circulated and reused within the electrochemical hydrogen booster system, thereby reducing the amount of hydrogen gas released to the outside. This increases the efficiency of hydrogen gas utilization and prevents a decrease in the hydrogen production efficiency of the electrochemical hydrogen booster system. Furthermore, because the amount of hydrogen gas released to the outside is reduced, the configuration of the electrochemical hydrogen booster system associated with the release of hydrogen gas becomes simpler and more economical.

[0111] (Appendix 2) In the electrochemical hydrogen boosting system 10, 100 described in Appendix 1, the hydrogen supply device has a sealed container 44 containing the hydrogen gas, and the pressure of the hydrogen gas stored in the hydrogen storage tank may be higher than the pressure of the hydrogen gas contained in the sealed container.

[0112] This allows the hydrogen gas stored in the hydrogen storage tank to be effectively supplied to the hydrogen booster stack instead of raw hydrogen.

[0113] (Appendix 3) In the electrochemical hydrogen boosting system 10, 100 described in Appendix 2, when the hydrogen gas is supplied from the hydrogen storage tank to the hydrogen supply device, the hydrogen storage tank may continue to supply the hydrogen gas to the hydrogen supply device until the pressure of the stored hydrogen gas drops to a predetermined value.

[0114] This allows for effective utilization of most of the hydrogen gas stored in the hydrogen storage tank, improving hydrogen production efficiency. In addition, because the amount of hydrogen gas stored in the hydrogen storage tank is reduced, the hydrogen gas remaining on the cathode side of the hydrogen booster stack can be introduced.

[0115] (Appendix 4) In the electrochemical hydrogen boosting system 10, 100 described in Appendix 3, raw hydrogen is supplied to the hydrogen supply device via a raw hydrogen supply path 50, and an on-off valve 52 is provided on the raw hydrogen supply path, and when the hydrogen gas is being supplied from the hydrogen storage tank to the hydrogen supply device, the on-off valve may close to stop the supply of raw hydrogen to the hydrogen supply device.

[0116] This makes it possible to reduce the amount of raw hydrogen supplied to the hydrogen boosting stack, thereby improving the efficiency of hydrogen production.

[0117] (Appendix 5) In the electrochemical hydrogen boosting system 10, 100 described in Appendix 1, the storage device has a hydrogen tank 25 for storing the hydrogen gas, and the hydrogen tank is provided with a pressure sensor P1 for measuring the pressure of the stored hydrogen gas, and when depressurizing is performed when the hydrogen boosting stack is stopped, the control device 30 may estimate the pressure of the hydrogen gas that can be stored in the hydrogen storage tank based on the pressure of the hydrogen gas detected by the pressure sensor P1.

[0118] This makes it possible to obtain the pressure of hydrogen gas that can be stored in the hydrogen storage tank, and the hydrogen gas remaining on the cathode side can be used effectively without waste, thereby improving the efficiency of hydrogen production.

[0119] (Appendix 6) In the electrochemical hydrogen boosting system 10, 100 described in Appendix 5, the hydrogen supply device has a sealed container 44 containing the hydrogen gas, and if the estimated pressure of the hydrogen gas that can be stored in the hydrogen storage tank is lower than the pressure of the hydrogen gas contained in the sealed container, the hydrogen gas does not need to be supplied from the hydrogen boosting stack to the hydrogen storage tank.

[0120] This allows the hydrogen gas remaining on the cathode side to be stored directly in the hydrogen tank when depressurizing, without being circulated to the hydrogen pressurization stack, thereby enabling the pressurized high-pressure hydrogen gas to be used efficiently.

[0121] (Appendix 7) In the electrochemical hydrogen boosting system 100 described in Appendix 1, the hydrogen storage tank includes a first hydrogen storage tank 96 and a second hydrogen storage tank 106 installed in parallel to the return flow path, and the pressure of the hydrogen gas stored in the second hydrogen storage tank may be higher than the pressure of the hydrogen gas stored in the first hydrogen storage tank.

[0122] This allows hydrogen gas to be stored in at least two hydrogen storage tanks with different pressures, so that the depressurization speed can be set in stages when depressurizing, making it possible to set an optimal depressurization speed.

[0123] (Appendix 8) In the electrochemical hydrogen boosting system 100 described in Appendix 7, when depressurizing the hydrogen boosting stack, the supply of hydrogen gas to the first hydrogen storage tank may be started when the pressure of the hydrogen gas stored in the second hydrogen storage tank exceeds a predetermined value.

[0124] This allows hydrogen gas to be stored in at least two hydrogen storage tanks in turn when depressurizing is performed, so that the optimum amount and optimum pressure of hydrogen gas can be stored in each hydrogen storage tank.

[0125] (Appendix 9) In the electrochemical hydrogen boosting system 10, 100 described in Appendix 8, when the pressure of the hydrogen gas stored in the first hydrogen storage tank falls below a predetermined value, a waste valve 83 provided in a waste flow path 82 branching off from the return flow path may be opened to release the hydrogen gas remaining in the return flow path to the outside.

[0126] This makes it possible to further reduce the pressure of the hydrogen gas remaining on the cathode side, and effectively prevent the electrolyte membrane from being damaged by the remaining hydrogen gas.

[0127] (Appendix 10) In the electrochemical hydrogen boosting system 100 described in Supplementary Note 7, when the hydrogen boosting stack starts operation, the hydrogen gas may be supplied from the second hydrogen storage tank to the cathode electrode of the hydrogen boosting stack.

[0128] This increases the gas pressure on the cathode side of the hydrogen booster stack, accelerating startup and allowing the hydrogen booster stack to begin operation promptly.

[0129] Although the present disclosure has been described in detail, the present disclosure is not limited to the individual embodiments described above. Various additions, substitutions, modifications, partial deletions, etc. are possible in these embodiments without departing from the gist of the present disclosure or the spirit of the present disclosure derived from the content of the claims and their equivalents. Furthermore, these embodiments can also be implemented in combination. For example, in the above-described embodiments, the order of each operation and the order of each process are shown as examples and are not limited to these. [Explanation of symbols]

[0130] 10...Electrochemical hydrogen boosting system 12...Electrochemical hydrogen boosting device 14...Hydrogen supply device 16...Hydrogen booster stack 18...Gas-liquid separator 20...Condenser 22...Moisture removal device 24...Storage device 28...power supply unit 30...control unit 32...Single cell 34...Electrolyte membrane 36...Anode electrode 40...Cathode electrode 44...sealed container 50...raw material hydrogen supply path 60...hydrogen supply passage 70...high-pressure hydrogen supply passage 94...Return flow path 96...First hydrogen storage tank 106...Second hydrogen storage tank

Claims

1. a hydrogen pressurization stack having a unit cell including an electrolyte membrane, an anode electrode provided on one side of the electrolyte membrane, and a cathode electrode provided on the other side of the electrolyte membrane, the hydrogen pressurization stack supplying hydrogen gas to the anode electrode and discharging pressurized hydrogen gas from the cathode electrode; a power supply device that applies a voltage to the hydrogen boosting stack; a hydrogen supply device for supplying the hydrogen gas to the hydrogen boosting stack; a storage device that stores the hydrogen gas delivered from the hydrogen boosting stack; a return flow path for returning the hydrogen gas output from the hydrogen boosting stack to the hydrogen supply device; Equipped with The return flow path is provided with a hydrogen storage tank for storing the hydrogen gas. Electrochemical hydrogen boosting system.

2. 2. The electrochemical hydrogen boosting system according to claim 1, the hydrogen supply device has a sealed container containing the hydrogen gas, and the pressure of the hydrogen gas stored in the hydrogen storage tank is higher than the pressure of the hydrogen gas contained in the sealed container; Electrochemical hydrogen boosting system.

3. 3. The electrochemical hydrogen boosting system according to claim 2, When the hydrogen gas is supplied from the hydrogen storage tank to the hydrogen supply device, the hydrogen storage tank continues to supply the hydrogen gas to the hydrogen supply device until the pressure of the stored hydrogen gas decreases to a predetermined value. Electrochemical hydrogen boosting system.

4. 4. The electrochemical hydrogen boosting system according to claim 3, raw hydrogen is supplied to the hydrogen supply device through a raw hydrogen supply line; an on-off valve is provided in the raw hydrogen supply path, and when the hydrogen gas is being supplied from the hydrogen storage tank to the hydrogen supply device, the on-off valve closes to stop the supply of the raw hydrogen to the hydrogen supply device; Electrochemical hydrogen boosting system.

5. 2. The electrochemical hydrogen boosting system according to claim 1, The storage device is a hydrogen tank for storing the hydrogen gas, the hydrogen tank being provided with a pressure sensor for measuring the pressure of the stored hydrogen gas, and when depressurizing is performed during shutdown of the hydrogen pressurization stack, a control device estimates the pressure of the hydrogen gas that can be stored in the hydrogen storage tank based on the pressure of the hydrogen gas detected by the pressure sensor; Electrochemical hydrogen boosting system.

6. 6. The electrochemical hydrogen boosting system according to claim 5, the hydrogen supply device has a sealed container containing the hydrogen gas, If the estimated pressure of the hydrogen gas that can be stored in the hydrogen storage tank is lower than the pressure of the hydrogen gas contained in the sealed container, the hydrogen gas is not supplied from the hydrogen pressurization stack to the hydrogen storage tank. Electrochemical hydrogen boosting system.

7. 2. The electrochemical hydrogen boosting system according to claim 1, the hydrogen storage tank includes a first hydrogen storage tank and a second hydrogen storage tank installed in parallel with the return flow path, and the pressure of the hydrogen gas stored in the second hydrogen storage tank is higher than the pressure of the hydrogen gas stored in the first hydrogen storage tank; Electrochemical hydrogen boosting system.

8. 8. The electrochemical hydrogen boosting system according to claim 7, When depressurizing the hydrogen boosting stack, when the pressure of the hydrogen gas stored in the second hydrogen storage tank exceeds a predetermined value, supply of the hydrogen gas to the first hydrogen storage tank is started. Electrochemical hydrogen boosting system.

9. 9. The electrochemical hydrogen boosting system according to claim 8, When the pressure of the hydrogen gas stored in the first hydrogen storage tank falls below a predetermined value, a waste valve provided in a waste flow path branched from the return flow path is opened to release the hydrogen gas remaining in the return flow path to the outside. Electrochemical hydrogen boosting system.

10. 8. The electrochemical hydrogen boosting system according to claim 7, When the hydrogen boosting stack starts operation, the hydrogen gas is supplied from the second hydrogen storage tank to the cathode electrode of the hydrogen boosting stack. Electrochemical hydrogen boosting system.

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