Electrochemical hydrogen booster 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 Art

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

[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 through an anode and a cathode, and a hydrogen gas boosting unit (hydrogen boosting stack) that boosts hydrogen by passing an electric current through a boosting unit anode and a boosting unit cathode downstream of the water electrolysis device. When the hydrogen / oxygen production system is stopped, a first pressure reduction process is performed so that the pressure reduction rate of the boosting unit cathode of the hydrogen boosting stack does not exceed a basic pressure reduction rate, and a second pressure reduction process is performed so that the pressure reduction rate of the anode of the water electrolysis device does not exceed the pressure reduction rate of the boosting unit cathode. Thereby, it is said that rapid pressure reduction of the boosting unit cathode can be suppressed, and damage to the electrolyte membrane of the hydrogen gas boosting unit can be suppressed.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] Incidentally, in hydrogen booster stacks, hydrogen gas remains on the cathode side when the system is shut down. Because the pressure of this hydrogen gas is not sufficiently high, it was previously released into the atmosphere. However, this resulted in the hydrogen gas not being effectively utilized, leading to a problem of reduced hydrogen production efficiency in the electrochemical hydrogen booster system.

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

[0007] An aspect of the present disclosure is an electrochemical hydrogen booster system comprising: 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; a hydrogen booster stack that supplies hydrogen gas to the anode electrode and discharges the pressurized hydrogen gas from the cathode electrode; a power supply device that applies a voltage to the hydrogen booster stack; a hydrogen supply device that supplies the hydrogen gas to the hydrogen booster stack; a storage device that stores the hydrogen gas discharged by the hydrogen booster stack; and a return channel that returns the hydrogen gas discharged by the hydrogen booster stack to the hydrogen supply device, wherein the return channel is provided with a hydrogen storage tank for storing the hydrogen gas. [Effects of the Invention]

[0008] According to the above embodiment, hydrogen gas is returned to the hydrogen supply device through the return channel, and moreover, the hydrogen gas is stored in a hydrogen storage tank provided in the return channel. As a result, the amount of hydrogen gas released to the outside from the hydrogen gas remaining on the cathode side when the hydrogen booster stack is stopped is reduced. Therefore, the decrease in the hydrogen production efficiency of the electrochemical hydrogen booster system can be suppressed. [Brief explanation of the drawing]

[0009] [Figure 1] Figure 1 is a schematic diagram of the electrochemical hydrogen booster system according to the first embodiment. [Figure 2] Figure 2 is a flowchart according to the first embodiment. [Figure 3] Figure 3 is an explanatory diagram relating to the pressure change of hydrogen gas according to the first embodiment. [Figure 4] Figure 4 is a schematic diagram of the electrochemical hydrogen booster system according to the second embodiment. [Figure 5] Figure 5 is a flowchart illustrating the second embodiment. [Figure 6] Figure 6 is an explanatory diagram relating to the pressure change of hydrogen gas according to the second embodiment. [Modes for carrying out the invention]

[0010] [First Embodiment] Figure 1 is a schematic diagram of the electrochemical hydrogen blast system 10 according to the first embodiment. The electrochemical hydrogen blast system 10 comprises an electrochemical hydrogen blast device 12, a hydrogen supply device 14, a gas-liquid separator 18, a condenser 20, a water 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 increases the pressure of hydrogen gas. The electrochemical hydrogen booster 12 comprises a hydrogen booster stack 16 and a power supply 28 that applies voltage to the hydrogen booster stack 16.

[0012] The hydrogen boost stack 16 supplies hydrogen gas to the anode electrode 36 and discharges the boosted 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 communicates with the anode electrode 36 of each individual cell 32. The hydrogen outlet PT2 discharges unused hydrogen gas. The high-pressure hydrogen outlet PT3 discharges the high-pressure hydrogen gas (high-pressure hydrogen gas) generated in each individual cell 32. The high-pressure hydrogen gas communicates with the cathode electrode 40 of each individual cell 32.

[0014] The hydrogen boost stack 16 is constructed by stacking multiple single cells 32. Each of the multiple single cells 32 has the same structure. Each single cell 32 includes 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] As the electrolyte membrane 34, for example, a solid polymer electrolyte membrane (cation exchange membrane) is used. The anode side of the electrolyte membrane 34 may be reinforced with a protective sheet (not shown) containing a fibrous skeleton. This allows it to withstand the pressure of the high-pressure hydrogen gas applied from the cathode side well. In addition, a fluorine-based electrolyte can 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 contains a platinum-based catalyst. An anode channel is formed in the anode power supply 37 through which hydrogen gas flows. The anode power supply 37 may be a conductive porous plate. Hydrogen gas introduced from the hydrogen inlet PT1 flows through the anode channel 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 the high-pressure hydrogen gas supplied from the cathode side.

[0017] The cathode electrode 40 includes a cathode catalyst layer joined to the other surface of the electrolyte membrane 34. A cathode current collector 41 is laminated on the cathode catalyst layer. The cathode catalyst layer contains a platinum-based catalyst. A cathode flow path through which the boosted high-pressure hydrogen gas flows is formed in the cathode current collector 41. Note that the cathode current collector 41 may be a porous plate having conductivity. The high-pressure hydrogen gas generated at the cathode electrode 40 flows through the cathode flow path and is led out from the high-pressure hydrogen gas outlet PT3.

[0018] When a voltage is applied between the anode electrode 36 and the cathode electrode 40 from the power supply device 28, the hydrogen gas supplied to the anode electrode 36 from the hydrogen inlet PT1 ionizes into protons (hydrogen ions) and electrons by a catalytic reaction in the anode catalyst layer. The generated protons permeate through the electrolyte membrane 34 and move to the cathode electrode 40. At this time, the protons accompany moisture 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 through the electrolyte membrane 34 and the electrons combine. The unused hydrogen gas that did not ionize at the anode electrode 36 is led out from the hydrogen gas 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 device 28 applies a DC voltage to the hydrogen boosting stack 16. As a result, a current flows through the hydrogen boosting stack 16. The hydrogen boosting stack 16 includes a laminate in which a plurality of single cells 32 are laminated, and anode connection terminals and cathode connection terminals are respectively arranged at both ends of the laminate. The positive electrode of the power supply device 28 is connected to the anode connection terminal via a connection cable, and the negative electrode of the power supply device 28 is connected to the cathode connection terminal via a connection cable. Thereby, a positive voltage is applied to the anode electrode 36 of each single cell 32 via the anode current collector 37, and a negative voltage is applied to the cathode electrode 40 of each single cell 32 via the cathode current collector 41.

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

[0021] The hydrogen supply device 14 includes a sealed container 44 in which liquid water is stored downward in the gravitational direction. The raw material hydrogen is supplied into the liquid water of the sealed container 44 through the raw material hydrogen supply path 50. An on-off valve 52 is provided in the raw material hydrogen supply path 50. The on-off valve 52 allows the raw material hydrogen to flow through by opening the valve and stops the flow of the raw material hydrogen by closing the valve.

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

[0023] The raw material hydrogen supply path 50 extends in the gravitational direction inside the sealed container 44, and the downstream end has an opening. This opening opens in the liquid water of the sealed container 44, and the raw material hydrogen flows out from the opening as hydrogen gas and floats upward in the sealed container 44 as bubbles in the liquid water (bubbling). At this time, the liquid droplets contained in the raw material hydrogen are taken into the liquid water. Also, the hydrogen gas floating above the liquid water is humidified by the liquid water. The sealed container 44 has both the function as a gas-liquid separator and the function as a humidifier.

[0024] The raw material hydrogen only needs to contain hydrogen gas, and for example, it can be generated by electrolysis of water. Alternatively, the raw material hydrogen may be generated by a reforming reaction from a raw material containing hydrocarbons. The raw material hydrogen may contain conductive components such as potassium hydroxide contained in the electrolyte when electrolyzing water, or impurities other than the hydrogen gas generated during the reforming reaction. These impurities are removed by the hydrogen boosting stack 16 and are not contained in the generated high-pressure hydrogen gas.

[0025] Above the liquid water stored in the sealed container 44, a gas chamber 45 is formed where 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 raw hydrogen is supplied. The sealed container 44 is equipped with a pressure sensor P3 that communicates with the gas chamber 45 and measures the pressure of the hydrogen gas contained in the gas chamber 45. In addition, a hydrogen outlet 46 that communicates with the gas chamber 45 and discharges the hydrogen gas is provided above the sealed container 44. The hydrogen gas, pressurized to a predetermined pressure, is smoothly discharged from the hydrogen outlet 46.

[0026] The hydrogen outlet 46 communicates with the hydrogen inlet PT1 of the hydrogen booster stack 16 via the hydrogen supply channel 60. The hydrogen outlet PT2 of the hydrogen booster stack 16 communicates with the hydrogen circulation port 67 of the sealed container 44 via the hydrogen circulation channel 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 hydrogen gas is provided in the hydrogen circulation channel 62.

[0027] The high-pressure hydrogen outlet PT3 of the hydrogen booster stack 16 is connected to the moisture removal device 22 via the high-pressure hydrogen supply channel 70. The high-pressure hydrogen supply channel 70 is equipped 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 or omitted depending on the specifications required for the high-pressure hydrogen gas.

[0028] The check valve 72 allows high-pressure hydrogen gas to flow from the condenser 20 to the moisture removal device 22, while preventing high-pressure hydrogen gas from flowing back from the moisture removal device 22 to the condenser 20. This shortens the pressurization time during the next startup without reducing the internal pressure of the moisture removal device 22.

[0029] The gas-liquid separator 18 separates the liquid component (liquid droplets) and gaseous component contained in the high-pressure hydrogen gas, and removes the liquid component as liquid water. The high-pressure hydrogen gas from which the liquid water has been removed is then supplied to the water removal device 22 via the condenser 20 located downstream. The gas-liquid separator 18 is made up of a sealed container. Inside the gas-liquid separator 18, there is a level switch 77 that measures the amount of liquid water stored. The level switch 77 measures the height of the liquid level (top surface of the liquid water) stored inside the gas-liquid separator 18.

[0030] A drain channel 78 for discharging separated liquid water to the outside is connected to the lower side of the gas-liquid separator 18 in the direction of gravity. The drain channel 78 is equipped with a throttle valve 75 and an on-off valve 79, in order from the upstream side. The throttle valve 75 adjusts the flow rate of liquid water flowing through the drain channel 78. The on-off valve 79 discharges liquid water from the drain channel 78 when opened and stops the discharge of liquid water when closed. When the control device 30 detects from a signal from the level switch 77 that the amount of liquid water stored inside the gas-liquid separator 18 exceeds the upper limit, it opens the on-off valve 79 and discharges the liquid water with the adjusted flow rate to the outside through the throttle valve 75.

[0031] The gas inlet of the gas-liquid separator 18 is connected to the high-pressure hydrogen outlet PT3 of the hydrogen booster stack 16 via the high-pressure hydrogen supply channel 70. The gas outlet of the gas-liquid separator 18 is connected to the gas inlet of the condenser 20.

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

[0033] As the moisture removal device 22, for example, a PSA (Pressure Swing Adsorption) device is used. The PSA device is equipped with multiple adsorption towers, and the inside of each adsorption tower is filled with a porous adsorbent such as activated carbon, zeolite, alumina, or silica. The multiple adsorption towers are switched alternately to adsorb moisture contained in the introduced hydrogen gas using the adsorbent and discharge dry hydrogen gas. When the amount of moisture adsorbed by the adsorbent reaches the upper limit, dry hydrogen gas is circulated through the adsorption tower to release the adsorbed moisture and regenerate it.

[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 channel 70. The hydrogen outlet of the moisture removal device 22 communicates with the storage device 24 via the high-pressure hydrogen outlet channel 122. The storage device 24 includes, for example, a hydrogen tank 25 for storing high-pressure hydrogen gas. The storage device 24 only needs to be capable of storing high-pressure hydrogen gas, and may be a high-pressure vessel containing a hydrogen storage alloy inside.

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

[0036] An on-off valve 126 provided in the high-pressure hydrogen outlet channel 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, etc. that can disconnect from the hydrogen tank 25 may be provided between the high-pressure hydrogen outlet channel 122 and the hydrogen tank 25. The hydrogen tank 25 is installed in a mobile vehicle equipped with a fuel cell system, industrial equipment, a stationary power generation device, etc. However, the hydrogen tank 25 may also be installed in a device that uses hydrogen gas but does not have a fuel cell system.

[0037] The storage device 24 has a pressure sensor P1 for measuring the pressure of the high-pressure hydrogen gas. The pressure sensor P1 is installed in the piping downstream of the back pressure valve 124 in the high-pressure hydrogen outlet channel 122. Alternatively, the pressure sensor P1 may be installed 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 communicates with the inside of a sealed container 44 provided in the hydrogen supply device 14 via a return channel 94. A first hydrogen storage tank 96, which is a hydrogen storage tank, is provided in the return channel 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 flow port. In that case, the gas inlet and gas outlet may be separately arranged in the piping connected to the gas flow port.

[0039] In the return flow path 94, an on-off valve 95 is provided between the first hydrogen storage tank 96 and the sealed container 44. The on-off valve 95 is located 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 channel 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, 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 the cathode-side channel of the hydrogen booster stack 16 that is connected to the gas chamber 19 can be quickly depressurized.

[0041] The upstream end of the return channel 94 may be connected to the high-pressure hydrogen supply channel 70 or the high-pressure hydrogen outlet channel 122. The upstream end of the return channel 94 may also be connected to the condenser 20 or the moisture removal device 22. The first hydrogen storage tank 96 is a sealed container. Vessels and It is composed of a sealed container. VesselsThe shape is not particularly limited. The first hydrogen storage tank 96 may be formed in the shape of a cylinder, a sphere, a rectangular parallelepiped, or the like. The first hydrogen storage tank 96 is equipped with a pressure sensor P2 for measuring the pressure of the stored hydrogen gas. The pressure sensor P2 may be installed in piping connected to the gas inlet or gas outlet of the first hydrogen storage tank 96.

[0042] The downstream end of the return channel 94 has a hydrogen outlet. The hydrogen outlet opens into the gas chamber 45 at the top of the sealed container 44. Alternatively, the hydrogen outlet may open into the liquid water in the sealed container 44, as shown in Figure 1. In this way, the hydrogen gas released from the hydrogen outlet has its water droplets removed and is well humidified in the liquid water before reaching the upper gas chamber 45 and being supplied to the hydrogen booster stack 16 via the hydrogen supply channel 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 control valve 74, a check valve 97, and an on-off valve 98 are provided in order from the upstream side. Upon 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. Upon command from the control device 30, the flow control 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 control valve 74 is closed, and hydrogen gas does not flow downstream of the flow control 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 boost stack 16, and the power supply device 28 continues to apply a predetermined voltage to the hydrogen boost stack 16, thereby continuously generating high-pressure hydrogen gas. This does not include the operating states during startup, shutdown, or temporary pause.

[0044] In the return channel 94, a waste channel 82 is connected to a branching point 81 located between the flow control valve 74 and the on-off valve 98. The waste channel 82 is equipped with a waste valve 83, which is an on-off valve. 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 can be, for example, the atmosphere, water, or outer space. The return channel 94 is equipped with a check valve 97, so that 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 supplied from the first hydrogen storage tank 96 to the sealed container 44 via the return channel 94, raw material hydrogen is not supplied to the sealed container 44. That is, the on-off valve 52 provided in the raw material hydrogen supply channel 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 material hydrogen is not supplied to the sealed container 44, hydrogen gas can be supplied smoothly from the first hydrogen storage tank 96 to the hydrogen booster stack 16 via the sealed container 44. Note that the pressure of the raw material 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 comprised of an ECU (Electronic Control Unit). The ECU is comprised of a computer having one or more processors (CPUs), memory, input / output interfaces, and electronic circuits. One or more processors (CPUs) execute programs (computer-executable commands) stored in memory (not shown). The control device 30 performs all control related to the electrochemical hydrogen booster system 10.

[0047] The operation of the electrochemical hydrogen pressurization system 10 during normal operation will be explained based on Figure 1. The arrows shown in Figure 1 indicate the direction of hydrogen gas flow.

[0048] The control device 30 opens the on-off valve 52 provided in the raw hydrogen supply passage 50 to supply raw hydrogen to the hydrogen supply device 14. The raw hydrogen supplied to the sealed container 44 of the hydrogen supply device 14 has its water content adjusted with liquid water and 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 passage 60. The 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 passage 62. The control device 30 controls the rotation speed of the circulation pump 66 provided in the hydrogen circulation passage 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 by the voltage applied to the hydrogen booster stack 16 from the power supply unit 28 to become high-pressure hydrogen gas, which is then discharged from the high-pressure hydrogen outlet PT3 into the high-pressure hydrogen supply channel 70. After the liquid water is removed from the discharged high-pressure hydrogen gas in the gas-liquid separator 18 installed in the high-pressure hydrogen supply channel 70, it is supplied to the condenser 20. The high-pressure hydrogen gas dehumidified in the condenser 20 is supplied to the moisture removal device 22. After further dehumidification in the moisture removal device 22, it becomes dry high-pressure hydrogen gas and is supplied to the hydrogen tank 25 and other components of the storage device 24 via the high-pressure hydrogen discharge channel 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 channel 122.

[0051] When normal operation ends and the hydrogen booster stack 16 stops operating, high-pressure hydrogen gas remains in the flow path communicating 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, moisture removal device 22, and the high-pressure hydrogen supply flow path 70 connecting them, which are located downstream of the hydrogen booster stack 16. These are collectively referred to as "high-pressure hydrogen gas remaining on the cathode side."

[0052] When the hydrogen booster stack 16 is shut down, the high-pressure hydrogen gas remaining on the cathode side is depressurized at an appropriate rate. This operation is called depressurization, and the process of performing this operation is called the depressurization process. Rapid depressurization of the high-pressure hydrogen gas remaining on the cathode side can damage the electrolyte membrane 34 of the hydrogen booster stack 16, so the rate of depressurization is adjusted to suppress a rapid 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, high-pressure hydrogen gas is supplied from a gas-liquid separator 18 installed in the high-pressure hydrogen supply channel 70 to the first hydrogen storage tank 96 via a return channel 94. At this time, the pressure and flow rate of the high-pressure hydrogen gas are optimally adjusted by a pressure reducing valve 73 and a flow rate control valve 74 installed in the return channel 94, respectively. This prevents damage to the electrolyte membrane 34 of the hydrogen booster stack 16. Any excess hydrogen gas that cannot be stored in the first hydrogen storage tank 96 is released to the outside via a waste channel 82.

[0054] When the hydrogen booster stack 16 starts operation, 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 channel 94. The downstream end of the return channel 94 has an opening, which opens into the liquid water contained in the sealed container 44. As a result, the hydrogen gas floats upward in the liquid water of the sealed container 44 as bubbles and is humidified by the liquid water.

[0055] The storage device 24 is equipped with a pressure sensor P1 for measuring the pressure of high-pressure hydrogen gas. The pressure of the hydrogen gas 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 of the hydrogen tank 25 measured by the pressure sensor P1 is below a predetermined value (Ptmp) that is below 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, if the gas pressure of 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 supplied to the hydrogen tank 25 first, 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 hydrogen gas pressure in the hydrogen tank 25 measured by the pressure sensor P1. Then, the pressure of the hydrogen gas that can be stored in the first hydrogen storage tank 96 is estimated when the hydrogen gas obtained by subtracting this fillable gas pressure from the pressure of the high-pressure hydrogen gas remaining on the cathode side is filled into the first hydrogen storage tank 96. In other words, when depressurization is performed, the pressure of the 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 installed 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. From these volume parameters and the pressure of the hydrogen gas measured by the pressure sensor P1 installed in the first hydrogen storage tank 96, the pressure of the hydrogen gas that can be stored in the first hydrogen storage tank 96 can be calculated.

[0059] Furthermore, 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 will not be 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 properly 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 the pressure sensor P3, or it may be set in advance as the minimum predetermined pressure value necessary to supply hydrogen gas to the hydrogen booster stack 16.

[0060] [Flowchart of the first embodiment] The operation procedure of the electrochemical hydrogen booster system 10 according to the first embodiment will be explained based on the flowchart shown in Figure 2.

[0061] During normal operation, the high-pressure hydrogen gas electrochemically pressurized in the hydrogen booster stack 16 flows through the gas-liquid separator 18, condenser 20, and water removal device 22 located in the high-pressure hydrogen supply channel 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 pressurizing (stop operation). Specifically, the control device 30 instructs 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 initiates a depressurization process to depressurize the electrochemical hydrogen booster system 10.

[0063] In step S3, the control device 30 opens the flow control valve 74 and supplies the hydrogen gas, which has been depressurized by the pressure reducing valve 73, to the first hydrogen storage tank 96. The flow control valve 74 adjusts the flow rate of the hydrogen gas per unit time to such an extent that the hydrogen booster stack 16 is not damaged. In this case, the on-off valve 98 located upstream of the first hydrogen storage tank 96 is open, and the on-off valve 95 located 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 installed in the first hydrogen storage tank 96. When depressurization is started and the high-pressure hydrogen gas remaining on the cathode side of the hydrogen booster 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, as measured by the pressure sensor P2, is higher than a first predetermined value (P_high). If the determination result is positive (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 output 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 located in the waste passage 82. The waste valve 83 is then closed after being open for a predetermined time. This releases any excess hydrogen gas stored in the first hydrogen storage tank 96 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 passage 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 is started 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 located upstream of the first hydrogen storage tank 96. This stops the supply of hydrogen gas to the first hydrogen storage tank 96. This completes the depressurization process.

[0069] After the depressurization process is completed and a predetermined time has elapsed, in step S9, the control device 30 instructs the hydrogen boost stack 16 to start boosting the pressure.

[0070] In step S10, the control device 30 opens the on-off valve 95 located downstream of the first hydrogen storage tank 96. This supplies hydrogen gas 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 booster 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 installed 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 in the first hydrogen storage tank 96, as measured by the pressure sensor P2, exceeds a second predetermined value (P_low). If the determination result is positive (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 it may be pre-set as the minimum predetermined pressure value required 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 located 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 installed in the raw hydrogen supply passage 50. As a result, 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 as hydrogen gas to the hydrogen booster stack 16.

[0075] [Timing chart according to the first embodiment] The timing chart according to the first embodiment will be explained with reference to Figure 3. This timing chart illustrates the flowchart described in Figure 2 along a time axis.

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

[0077] At time t0, a voltage is applied from the power supply unit 28 to the hydrogen boost stack 16, and hydrogen gas at a predetermined pressure (P_std=PC) is supplied to the hydrogen boost stack 16. This starts the operation of the hydrogen boost 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). While the hydrogen boost stack 16 is in operation, the control device 30 controls the power supply unit 28 to maintain the pressure (PA) of the high-pressure hydrogen gas discharged from the high-pressure hydrogen outlet PT3 by the hydrogen boost 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 boost stack 16, thereby stopping the operation of the hydrogen boost stack 16 (step S1), and the depressurization process of the high-pressure hydrogen gas on the cathode side is started (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 channel 94. As depressurization occurs from time t1, the pressure of the high-pressure hydrogen gas (PA) decreases from the rated pressure (P_rate), and the pressure in the first hydrogen storage tank 96 (PB) increases.

[0079] At time t2, the hydrogen gas pressure (PB) in the first hydrogen storage tank 96 reaches a first predetermined value (P_high) (Step S4, Step S5: YES). At this time t2, the pressure of the high-pressure hydrogen gas on the cathode side (PA) decreases to a pressure (Pα) between the rated pressure (P_rate) and the first predetermined value (P_high). Subsequently, by opening the discharge valve 83 for a predetermined time, the pressure of the high-pressure hydrogen gas (PA) decreases further from pressure (Pα) to the same level as the external pressure. From time t2 onward, 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), and at the time te when depressurization is complete, the control device 30 closes the on-off valve 98 located upstream of the first hydrogen storage tank 96 (Step S8).

[0080] Subsequently, 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 located 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). From time t3 onward, the pressure (PA) of the high-pressure hydrogen gas discharged from the high-pressure hydrogen outlet PT3 gradually increases, while 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 hydrogen gas pressure (PB) drops to the second predetermined value (P_low) (steps S11, S12: NO). At this time t4, the control device 30 closes the on-off valve 95 located downstream of the first hydrogen storage tank 96 (step S13) and opens the on-off valve 52 located in the raw hydrogen supply passage 50. As a result, the supply of hydrogen gas from the first hydrogen storage tank 96 is stopped, and raw hydrogen gas is supplied to the sealed container 44 via the raw hydrogen supply passage 50. Therefore, from time t4 onward, the pressure (PA) of the high-pressure hydrogen gas discharged from the high-pressure hydrogen outlet PT3 continues to rise.

[0082] Even after time point t4, the pressure (PA) of the high-pressure hydrogen gas discharged from the high-pressure hydrogen outlet PT3 gradually increases, reaching the rated pressure (P_rate) again at time point t5. The subsequent timing chart is repeated and therefore omitted.

[0083] [Second Embodiment] Figure 4 is a schematic diagram showing the electrochemical hydrogen booster system 100 according to the second embodiment. In Figure 4, components similar to those described in the first embodiment are given the same reference numerals. In the second embodiment, explanations that overlap with those of the first embodiment are omitted.

[0084] As shown in Figure 4, the electrochemical hydrogen booster system 100 includes a second hydrogen storage tank 106 in addition to the first hydrogen storage tank 96. 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. That is, 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 respect to the return flow path 94 can be at least two, or three or more. In this case, the pressure of the hydrogen gas stored in each hydrogen storage tank (96, 106) is different from that of the other.

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

[0086] The connecting flow path 102 is equipped with an on-off valve 103 and a flow control valve 104, extending from the branching point 101 towards the second hydrogen storage tank 106. When the on-off valve 103 is open, high-pressure hydrogen gas flows through it, and when it is closed, the flow of high-pressure hydrogen gas stops. The control device 30 adjusts the flow rate of the hydrogen gas flowing through it using the flow control valve 104. When the operation of the hydrogen booster stack 16 is stopped, rapidly reducing the pressure of the high-pressure hydrogen gas remaining on the cathode side would damage the electrolyte membrane 34 of the hydrogen booster stack 16. Therefore, the flow control valve 104 adjusts the rate of pressure reduction to suppress a rapid reduction in the pressure of 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 equipped with a pressure sensor P4 for measuring the pressure of the stored hydrogen gas. The pressure sensor P4 may be installed in the piping connected to the gas flow port provided in the second hydrogen storage tank 106.

[0087] [Flowchart of the second embodiment] The operation procedure of the electrochemical hydrogen booster system 100 according to the second embodiment will be described based on the flowchart shown in Figure 5. In the description of Figure 5, the same reference numerals are used for steps that are the same as those described in the first embodiment. In the second embodiment, explanations that overlap with those of the first embodiment will be omitted.

[0088] During normal operation, the high-pressure hydrogen gas electrochemically pressurized in the hydrogen booster stack 16 flows through the gas-liquid separator 18, condenser 20, and water removal device 22 located in the high-pressure hydrogen supply channel 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 pressurizing. Specifically, the control device 30 instructs 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, stopping 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 initiates a depressurization process to depressurize the electrochemical hydrogen booster system 100.

[0090] In step S103, the control device 30 opens the shut-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 of hydrogen gas per unit time so as not to damage the hydrogen booster stack 16. In this case, the shut-off valve 98 located upstream of the first hydrogen storage tank 96 is closed, and the shut-off valve 95 located 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 installed in the second hydrogen storage tank 106. When depressurization begins and the high-pressure hydrogen gas remaining on the cathode side of the hydrogen booster 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, as measured by the pressure sensor P4, is higher than the third predetermined value (P_upper). If the determination result is positive (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 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, the relationship between the pressure of the high-pressure hydrogen gas remaining on the cathode side when depressurization begins and the predetermined time until depressurization is completed may be measured in advance, and the on-off valve 103 may be closed based on this predetermined time.

[0094] Steps S3 to S14, which follow step S106, are the same as those described in the first embodiment, so their explanation will be omitted.

[0095] [Timing chart according to the second embodiment] The timing chart according to the second embodiment will be explained with reference to Figure 6. This timing chart illustrates the flowchart described in Figure 5 along a time axis.

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

[0097] At time t10, a voltage is applied from the power supply unit 28 to the hydrogen boost stack 16, and hydrogen gas at a predetermined pressure (P_std=PC) is supplied to the hydrogen boost stack 16. This causes the hydrogen boost stack 16 to start 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). While the hydrogen boost stack 16 is in operation, the control device 30 controls the power supply unit 28 to maintain the pressure (PA) of the high-pressure hydrogen gas discharged from the high-pressure hydrogen outlet PT3 by the hydrogen boost 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 boost stack 16, thereby stopping the operation of the hydrogen boost stack 16 (step S101), and the depressurization process of the high-pressure hydrogen gas on the cathode side begins (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 depressurization begins from time t11, the pressure of the high-pressure hydrogen gas (PA) decreases from the rated pressure (P_rate), and the pressure in the second hydrogen storage tank 106 (PB2) increases.

[0099] At time t12, the pressure (PB2) of the high-pressure hydrogen gas stored in the second hydrogen storage tank 106 reaches a 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 decreases to a pressure (Pβ) between the rated pressure (P_rate) and the third predetermined value (P_upper). From time t12 onward, 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 pressure (PA) is introduced into the first hydrogen storage tank 96 by flowing through the pressure reducing valve 73, the flow control valve 74, and the open on / off valve 98 (step S3). As a result, the pressure (PA) of the high-pressure hydrogen gas decreases further 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 hydrogen gas pressure (PB1) in the first hydrogen storage tank 96 reaches the first predetermined value (P_high) (Step S4, Step S5: YES). Also at time t13, the pressure (PA) of the high-pressure hydrogen gas on the cathode side decreases 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 lower pressure than the third predetermined value (P_upper).

[0102] From time t13 onward, the control device 30 opens the waste valve 83 for a predetermined time, causing the pressure (PA) of the high-pressure hydrogen gas to decrease further from the pressure (Pγ) to become equal to the external pressure, and the pressure (PB1) of the hydrogen gas in the first hydrogen storage tank 96 to be maintained at a constant pressure, a first predetermined value (P_high) (step S6). Depressurization is completed at time te' when the pressure (PA) of the high-pressure hydrogen gas becomes equal to the external pressure (step S7). At time te' when depressurization is complete, the control device 30 closes the on-off valve 98 located upstream of the first hydrogen storage tank 96 (step S8).

[0103] Subsequently, 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 located 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). From time t14 onward, the pressure (PA) of the high-pressure hydrogen gas discharged from the high-pressure hydrogen outlet PT3 gradually increases, while 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 passage 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. As a result, the pressure (PA) of the high-pressure hydrogen gas on the cathode side of the hydrogen booster stack 16 rises rapidly. Alternatively, the high-pressure hydrogen gas stored in the second hydrogen storage tank 106 may be supplied directly to the cathode side of the hydrogen booster stack 16 without going through the gas-liquid separator 18.

[0105] At time t16, the pressure (PB1) in the first hydrogen storage tank 96 decreases to the second predetermined value (P_low) (steps S11, S12: NO). At time t17, the control device 30 closes the on-off valve 95 located downstream of the first hydrogen storage tank 96 (step S13) and opens the on-off valve 52 located in the raw hydrogen supply passage 50. From time t17 onward, the supply of hydrogen gas from the first hydrogen storage tank 96 is stopped, and raw hydrogen gas is supplied to the sealed container 44 via the raw hydrogen supply passage 50.

[0106] At time t17, the pressure of the high-pressure hydrogen gas in the second hydrogen storage tank 106 (PB2) becomes the same as the pressure of the high-pressure hydrogen gas output from the high-pressure hydrogen outlet PT3 of the hydrogen booster stack 16 (PA). 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] Even after time point t17, the pressure (PA) of the high-pressure hydrogen gas discharged from the high-pressure hydrogen outlet PT3 gradually increases, reaching the rated pressure (P_rate) again at time point t18. The subsequent timing chart is repeated and therefore omitted.

[0108] The following additional information is disclosed regarding the above embodiments.

[0109] (Note 1) The electrochemical hydrogen booster systems 10 and 100 of this disclosure include a single cell 32 having 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, a hydrogen booster stack 16 that supplies hydrogen gas to the anode electrode 36 and discharges the boosted hydrogen gas from the cathode electrode 40, a power supply device 28 that applies a voltage to the hydrogen booster stack 16, a hydrogen supply device 14 that supplies the hydrogen gas to the hydrogen booster stack 16, a storage device 24 that stores the hydrogen gas discharged by the hydrogen booster stack 16, and a return channel 94 that returns the hydrogen gas discharged by the hydrogen booster stack 16 to the hydrogen supply device 14, wherein the return channel 94 is provided with hydrogen storage tanks 96 and 106 for storing the hydrogen gas.

[0110] This allows the hydrogen gas remaining on the cathode side of the hydrogen booster stack to be stored in a hydrogen storage tank via a return channel when the hydrogen booster stack stops operating and depressurizes. Then, when operation starts, the hydrogen gas stored in the hydrogen storage tank is supplied to the hydrogen booster stack, allowing the hydrogen gas to be circulated and reused within the electrochemical hydrogen booster system, thus reducing the amount of hydrogen gas released to the outside. Consequently, the utilization efficiency of hydrogen gas is high, and the decrease in the hydrogen production efficiency of the electrochemical hydrogen booster system can be suppressed. In addition, since the amount of hydrogen gas released to the outside is reduced, the configuration of the electrochemical hydrogen booster system related to hydrogen gas release becomes simpler and more economical.

[0111] (Note 2) In the electrochemical hydrogen booster systems 10 and 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 hydrogen gas stored in a hydrogen storage tank to be supplied to the hydrogen booster stack efficiently, instead of raw hydrogen.

[0113] (Note 3) In the electrochemical hydrogen booster systems 10 and 100 described in Appendix 2, when supplying hydrogen gas from the hydrogen storage tank to the hydrogen supply device, the hydrogen storage tank may continue supplying 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 the effective utilization of most of the hydrogen gas stored in the hydrogen storage tank, improving hydrogen production efficiency. Furthermore, because the amount of hydrogen gas stored in the tank is reduced, the hydrogen gas remaining on the cathode side of the hydrogen booster stack can be introduced.

[0115] (Note 4) In the electrochemical hydrogen booster systems 10 and 100 described in Appendix 3, raw hydrogen is supplied to the hydrogen supply device via a raw hydrogen supply passage 50, and an on-off valve 52 is provided in the raw hydrogen supply passage. When hydrogen gas is supplied from the hydrogen storage tank to the hydrogen supply device, the on-off valve may be closed to stop the supply of raw hydrogen to the hydrogen supply device.

[0116] This reduces the amount of raw hydrogen supplied to the hydrogen booster stack, thereby improving hydrogen production efficiency.

[0117] (Note 5) In the electrochemical hydrogen pressurization systems 10 and 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. When depressurization is performed when the hydrogen pressurization 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 allows the hydrogen storage tank to obtain the pressure of the hydrogen gas it can store, and enables efficient use of the hydrogen gas remaining on the cathode side without waste. Consequently, hydrogen production efficiency is improved.

[0119] (Note 6) In the electrochemical hydrogen booster systems 10 and 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 booster stack to the hydrogen storage tank.

[0120] This allows the hydrogen gas remaining on the cathode side during depressurization to be stored directly in the hydrogen tank without being recirculated to the hydrogen booster stack, thus enabling efficient use of the boosted high-pressure hydrogen gas.

[0121] (Note 7) In the electrochemical hydrogen booster 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 with 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, enabling the rate of depressurization to be set in stages during depressurization, thus allowing for the setting of an optimal depressurization rate.

[0123] (Note 8) In the electrochemical hydrogen booster system 100 described in Appendix 7, when depressurizing the hydrogen booster 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 sequentially in at least two hydrogen storage tanks during depressurization, ensuring that each hydrogen storage tank has the optimal amount and pressure of hydrogen gas.

[0125] (Note 9) In the electrochemical hydrogen booster systems 10 and 100 described in Appendix 8, when the pressure of the hydrogen gas stored in the first hydrogen storage tank reaches a predetermined value Exceeded Occasionally, the waste valve 83 provided in the waste channel 82 branched from the return channel may be opened to release the hydrogen gas remaining in the return channel to the outside.

[0126] This further reduces the pressure of hydrogen gas remaining on the cathode side, effectively suppressing damage to the electrolyte membrane caused by the residual hydrogen gas.

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

[0128] This increases the gas pressure on the cathode side of the hydrogen booster stack, which accelerates the start-up process and allows the hydrogen booster stack to begin operation quickly.

[0129] While this disclosure has been described in detail, it is not limited to the individual embodiments described above. These embodiments can be added, replaced, modified, partially deleted, etc., in any way that does not depart from the gist of this disclosure or from the spirit of this disclosure derived from the claims and their equivalents. These embodiments can also be implemented in combination. For example, the order of operations and processes in the embodiments described above are given as examples only and are not limited thereto. [Explanation of Symbols]

[0130] 10... Electrochemical hydrogen blast system 12... Electrochemical hydrogen blast 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...Hydrogen raw material supply channel 60...Hydrogen supply channel 70...High-pressure hydrogen supply channel 94...Return channel 96...First hydrogen storage tank 106... Second hydrogen storage tank

Claims

1. A hydrogen boost stack comprising 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, which supplies hydrogen gas to the anode electrode and discharges the pressurized hydrogen gas from the cathode electrode, A power supply device that applies voltage to the hydrogen boost stack, A hydrogen supply device that supplies the hydrogen gas to the hydrogen boost stack, A storage device for storing the hydrogen gas discharged by the hydrogen booster stack, A return channel for returning the hydrogen gas discharged from the hydrogen boost stack to the hydrogen supply device, Equipped with, The storage device includes a hydrogen tank, Upstream of the hydrogen tank, the hydrogen gas discharged by the hydrogen booster stack flows into the return channel. The return channel is provided with a hydrogen storage tank for storing the hydrogen gas. Electrochemical hydrogen booster system.

2. In the electrochemical hydrogen pressurization 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 booster system.

3. In the electrochemical hydrogen booster system according to claim 2, When supplying hydrogen gas 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 drops to a predetermined value. Electrochemical hydrogen booster system.

4. In the electrochemical hydrogen pressurization system according to claim 3, The hydrogen supply device is supplied with raw hydrogen via a raw hydrogen supply path. The raw hydrogen supply path is provided with an on / off valve, and when hydrogen gas is being supplied from the hydrogen storage tank to the hydrogen supply device, the on / off valve closes, stopping the supply of raw hydrogen to the hydrogen supply device. Electrochemical hydrogen booster system.

5. In the electrochemical hydrogen pressurization system according to claim 1, The hydrogen tank is equipped with a pressure sensor for measuring the pressure of the stored hydrogen gas, and when depressurizing is performed when the hydrogen booster stack is stopped, the 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 booster system.

6. In the electrochemical hydrogen pressurization 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 will not be supplied from the hydrogen booster stack to the hydrogen storage tank. Electrochemical hydrogen booster system.

7. In the electrochemical hydrogen pressurization 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 respect to the return flow path, wherein 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 booster system.

8. In the electrochemical hydrogen pressurization system according to claim 7, When depressurizing the hydrogen booster stack, if the pressure of the hydrogen gas stored in the second hydrogen storage tank exceeds a predetermined value, the supply of the hydrogen gas to the first hydrogen storage tank is initiated. Electrochemical hydrogen booster system.

9. In the electrochemical hydrogen pressurization system according to claim 8, When the pressure of the hydrogen gas stored in the first hydrogen storage tank exceeds a predetermined value, a waste valve provided in a waste channel branched from the return channel is opened, and the hydrogen gas remaining in the return channel is released to the outside. Electrochemical hydrogen booster system.

10. In the electrochemical hydrogen pressurization system according to claim 7, When the hydrogen boost stack starts operation, the hydrogen gas is supplied from the second hydrogen storage tank to the cathode electrode of the hydrogen boost stack. Electrochemical hydrogen booster system.

Images