Hydrogen pressure control method for hydrogen stations and hydrogen stations

Abstract

To provide a method for controlling hydrogen pressure at a hydrogen station and the hydrogen station capable of reducing hydrogen pressure to a safety level with a diffusion valve before a safety valve is actuated and safely controlling the hydrogen pressure even when a hydrogen temperature is increased after depressurization.SOLUTION: A differential pressure type hydrogen station 1 comprises, in a flow channel thereof: a safety valve 51 which is put into an open state when pressure inside the flow channel becomes predetermined blow-starting pressure and put into a closed state when the same becomes predetermined blow-stopping pressure; and a diffusion valve 46 which is arbitrarily controlled manually or automatically so as to be switched between an open state and a closed state. In a method for controlling hydrogen pressure at the hydrogen station, as predetermined conditions to switch the diffusion valve 46 between the open state and the closed state, predetermined set pressure lower than the blow-starting pressure of the safety valve 51 is used as the predetermined condition to put the diffusion valve 46 into the open state and the pressure is less than the blow-starting pressure of the safety valve 51 even when a hydrogen temperature reaches a maximum temperature expected in the flow passage is used as the predetermined condition to put the diffusion valve 46 into the closed state.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present invention relates to a hydrogen pressure control method for a hydrogen station and the hydrogen station, and more particularly to a method for controlling an abnormal increase in hydrogen pressure that occurs within the hydrogen station and the hydrogen station. [Background technology]

[0002] Conventionally, there are known hydrogen stations, which are classified as on-site hydrogen stations and off-site hydrogen stations. An on-site hydrogen station is a type of compressed hydrogen station that uses a reforming device to reform methane and other fuels within the station to generate hydrogen gas, which is then supplied to fuel cell vehicles (FCVs) and other vehicles. An off-site hydrogen station is a type of compressed hydrogen station where hydrogen gas produced at a location other than the station is transported in containers such as hydrogen trailers or hydrogen cartridges, and hydrogen is supplied from outside the compressed hydrogen station.

[0003] Hydrogen stations are required to be equipped with safety valves. In the event of an abnormal increase in pressure within the flow path, the safety valve releases hydrogen gas to the outside, reducing the pressure within the hydrogen station and preventing the pressure from exceeding the design pressure limit of the hydrogen station equipment. A safety valve is a safety device that mechanically opens and forcibly releases the pressure to the atmosphere when a certain pressure is exceeded. Generally, the pressure (blowing pressure) at which the safety valve operates is set to a pressure close to the design pressure limit of the hydrogen station equipment.

[0004] For this reason, a release valve (pressure relief valve) is installed to eliminate the abnormal pressure rise before the safety valve operates. The pressure (set pressure) at which the release valve operates is set to a pressure lower than the blow-off pressure of the safety valve, so that when an abnormal pressure rise occurs, the pressure is reduced so that it does not reach the blow-off pressure of the safety valve (see page 255 of Non-Patent Document 1).

[0005] For example, Patent Document 1 discloses a hydrogen station in which a safety valve and a release valve are provided in a flow path connected by piping between a pressure accumulator that stores pressurized hydrogen and a dispenser that supplies the stored hydrogen to a fuel cell vehicle (FCV).

[0006] Furthermore, Patent Document 2 discloses a technology in which, in a hydrogen distribution unit, if an abnormal pressure increase occurs in a conduit when hydrogen distribution is completed, a block valve is opened to transport the hydrogen to another conduit, and a bleed valve installed in the conduit to which the hydrogen is transported is opened to reduce the hydrogen pressure in the conduit. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] JP 2019-178771 A [Patent Document 2] Patent No. 6189981 [Non-patent literature]

[0008] [Non-Patent Document 1] High Pressure Gas Safety Act: Commentary on the Technical Standards for Compressed Hydrogen Stations, 2nd Edition (March 2017, High Pressure Gas Safety Association) Summary of the Invention [Problem to be solved by the invention]

[0009] Incidentally, the hydrogen gas discharged to the outside of the system to eliminate the abnormal pressure increase is discharged to the outside world unused, and therefore from an economical point of view it is preferable to discharge as little hydrogen gas as possible. In addition, there are cases where the temperature inside the flow passages rises after depressurization due to the effects of direct sunlight or radiant heat, causing the hydrogen pressure to rise and leading to an abnormal increase in pressure. For this reason, there is a demand for technology that can safely control abnormal increases in hydrogen pressure while minimizing hydrogen gas loss.

[0010] However, Patent Document 1 does not disclose any specific method for controlling the hydrogen pressure when an abnormal pressure increase occurs.

[0011] Furthermore, in Patent Document 2, when a specified pressure is reached, the block valve and bleed valve are controlled to release hydrogen gas in the conduit and reduce the pressure in the flow path before the safety valve is activated. However, more hydrogen gas than necessary is released, and no consideration is given at all to hydrogen loss. Furthermore, there is no mention of the effects of temperature rise after depressurization.

[0012] Furthermore, the technology of Patent Document 2 is a technology that reduces pressure to a safe level when an abnormal pressure rise occurs in a hydrogen gas distribution unit (dispenser) after hydrogen gas is supplied to an FCV. Therefore, when an abnormal pressure rise occurs in piping such as a hydrogen gas storage facility (pressure accumulator) at a hydrogen station upstream of the dispenser, control becomes complicated if the piping to be connected to distribute the pressure is switched or multiple valves are controlled in the complex piping connections between the accumulator and the dispenser.

[0013] Furthermore, since multiple pipes are connected in a complex manner between the accumulator and the dispenser, installing separate pipes and parts for depressurization would not only increase costs, but would also increase the number of pipes and valves, making maintenance more difficult.

[0014] Therefore, the present invention has been developed to solve the problems associated with the prior art, and its purpose is to provide a hydrogen pressure control method for a hydrogen station, and a hydrogen station that can reduce the hydrogen pressure to a safe level using a release valve before the safety valve operates, and that can safely control the hydrogen pressure even if a temperature rise occurs after depressurization. [Means for solving the problem]

[0015] In order to achieve the above-mentioned object, the invention of claim 1 is a differential pressure type hydrogen station in which hydrogen from a hydrogen source is pressurized by a compressor and stored in a pressure accumulator, and hydrogen is filled into a fuel cell vehicle from the pressure accumulator by the differential pressure, and a flow path of this hydrogen station is provided with a safety valve that opens at a predetermined blow-out pressure depending on the pressure in the flow path and closes at a predetermined blow-off pressure, and a diffusion valve that can be controlled manually or automatically to switch between the open and closed states, and a hydrogen pressure control method for a hydrogen station in which the predetermined conditions for switching between the open and closed states of this diffusion valve are a predetermined set pressure that is lower than the blow-out pressure of the safety valve, and a pressure that is lower than the blow-out pressure of the safety valve even when the maximum temperature expected in the flow path is reached.

[0016] The invention according to claim 2 is a hydrogen pressure control method for a hydrogen station, in which the condition for closing the release valve is that the post-depressurization pressure (Px) satisfies the following relational expression (1). Px <Pm×Tx / Tm (1) (In the relational expression (1), Px is the pressure after depressurization, Pm is the blowing pressure of the safety valve, Tx is the temperature in the flow path after depressurization, and Tm is the maximum temperature expected to be reached in the flow path.)

[0017] The invention of claim 3 is a hydrogen pressure control method at a hydrogen station, in which the condition for closing the release valve is that the pressure after depressurization (Px) satisfies the above relational equation (1) and is higher than the blow-off pressure of the safety valve.

[0018] The invention of claim 4 is a hydrogen pressure control method in which, when the pressure in the flow path exceeds a predetermined set pressure and the release valve is opened, depressurization is controlled at a depressurization rate that can reduce the pressure in the flow path, even under external conditions in which the pressure in the flow path would continue to rise if the pressure is not depressurized.

[0019] The invention of claim 5 is a hydrogen station which comprises a compressor, a pressure accumulator which stores hydrogen pressurized by the compressor, and a dispenser which supplies hydrogen from the pressure accumulator to a fuel cell vehicle, all connected by piping, and a safety valve and a release valve disposed in the flow path of the piping, wherein when an abnormal increase in pressure occurs in the flow path of the piping, the release valve is opened to release pressure, and after release of pressure, the release valve is controlled manually or automatically so as to be closed, the condition for opening the release valve is a predetermined set pressure which is set lower than the blowing pressure of the safety valve, and the condition for closing the release valve is such that the pressure after depressurization (Px) satisfies the following relational expression (1). Px <Pm×Tx / Tm (1) (In the relational expression (1), Px is the pressure after depressurization, Pm is the blowing pressure of the safety valve, Tx is the temperature in the flow path after depressurization, and Tm is the maximum temperature expected to be reached in the flow path.)

[0020] The invention according to claim 6 is a hydrogen station in which a safety valve and a release valve are disposed in a flow path between a compressor and a dispenser, and hydrogen in this flow path is released to the outside of the system.

[0021] The invention of claim 7 is a hydrogen station that controls depressurization at a depressurization speed that can reduce the pressure in the flow path when the pressure in the flow path exceeds a predetermined set pressure and the release valve is opened, even under external conditions where the pressure in the flow path would continue to rise if the pressure is not released. Effect of the Invention

[0022] According to the invention of claim 1, when an abnormal increase in pressure occurs in the flow path within the piping of a hydrogen station, the release valve is opened before the safety valve is activated, thereby making it possible to reduce the pressure before it reaches a dangerous pressure that would activate the safety valve. In addition, the condition for closing the release valve is set to a pressure that is lower than the blowing pressure of the safety valve even if the expected maximum temperature in the flow path is reached, so that, for example, the temperature will not rise further after depressurization, causing the pressure in the flow path to rise again, preventing the release valve from being able to depressurize in time and causing the safety valve to operate. Furthermore, by controlling the release valve to be closed under a predetermined condition that is a safe pressure, hydrogen loss can be reduced. Therefore, the pressure can be safely released by the release valve before the safety valve operates, and even if the pressure increases after depressurization due to a rise in temperature, etc., it will not reach the blowing pressure of the safety valve, so that abnormal increases in hydrogen pressure can be controlled without rising to the operating pressure of the safety valve.

[0023] According to the invention of claim 2, the pressure when the condition for closing the release valve is set within a range that satisfies a predetermined relational expression. Therefore, even if an abnormal increase in hydrogen pressure occurs in the flow path, the safety valve will not operate, and the pressure can be reliably released by the release valve, controlling the abnormal increase in hydrogen pressure and making it easier to maintain a safe pressure.

[0024] According to the invention of claim 3, the pressure under the condition for closing the release valve is set higher than the shutoff pressure of the safety valve. Therefore, the release valve is closed only after depressurization has reached a state where safety can be sufficiently ensured, thereby reducing the amount of hydrogen released outside the hydrogen station system and minimizing hydrogen loss.

[0025] According to the invention of claim 4, when the pressure inside the flow path exceeds a predetermined set pressure and the relief valve is in an open state, even under external conditions where the pressure inside the flow path would continue to rise if the pressure was not released, the relief valve can control the relief at a relief speed capable of lowering the pressure inside the flow path.Therefore, for example, when the pressure inside the flow path increases as the temperature of the flow path rises due to a hydrogen station being exposed to unexpectedly high temperatures, causing an abnormal pressure increase inside the flow path, even after relief by the relief valve has started, the relief valve can release the pressure faster than the pressure increase due to the rate of temperature rise in the flow path.As a result, even under conditions where the pressure in the flow path suddenly rises, the relief valve can control the relief at a relief speed that can reliably release the pressure inside the flow path, and the relief valve can maintain a safe pressure inside the flow path by releasing the pressure.

[0026] According to the invention of claim 5, in a hydrogen station, a pressure accumulator for storing hydrogen gas is arranged in a flow path between a compressor and a dispenser, and when a pressure rise occurs in this flow path due to a temperature rise or the like, the pressure can be safely released by a release valve before the pressure reaches the blow-off pressure of the safety valve. In particular, since a large amount of hydrogen gas is stored at high pressure in the accumulator, the flow path including the accumulator experiences a significant increase in pressure due to a temperature rise compared to a portion that is normally cut off from the accumulator (such as the piping inside the dispenser when hydrogen is not being supplied to the FCV). However, according to the present invention, it is easy to maintain a safe pressure in the flow path including such a pressure accumulator. Therefore, it is possible to provide an economical hydrogen station that reduces hydrogen loss more than before.

[0027] According to the invention of claim 6, when a pressure increase occurs due to a temperature rise or the like at a hydrogen station, in places in the system where a pressure increase is likely to occur, the pressure can be safely released by the relief valve before the pressure reaches the blow-off pressure of the safety valve. This makes it easier to maintain a safe pressure in places in the flow path where abnormal pressure increases are likely to occur at the hydrogen station.

[0028] According to the invention of claim 7, when the pressure inside the flow path exceeds a predetermined set pressure and the relief valve is opened, even under external conditions where the pressure inside the flow path would continue to rise if the pressure was not released, the relief valve can control the relief at a relief speed that can reduce the pressure inside the flow path, so even under conditions where the pressure inside the flow path rises suddenly, the relief valve can control the relief at a relief speed that can reliably relieve pressure inside the flow path, and the relief valve can maintain a safe pressure inside the flow path by releasing pressure. [Brief description of the drawings]

[0029] [Figure 1] 1 is a diagram illustrating a schematic configuration of a hydrogen station according to the present invention. [Diagram 2] 2 is a diagram for explaining a schematic configuration of a package unit of the hydrogen station in FIG. 1. [Diagram 3] FIG. 2 is an explanatory diagram of a hydrogen pressure control method for a hydrogen station according to the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0030] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A hydrogen pressure control method for a hydrogen station and a hydrogen station according to an embodiment of the present invention will be described below in detail with reference to the drawings.

[0031] The hydrogen pressure control method for a hydrogen station according to the present invention can be applied to both on-site and off-site hydrogen stations, but an embodiment in which the hydrogen pressure control method for a hydrogen station according to the present invention is applied to an off-site hydrogen station will be described.

[0032] The hydrogen station in the present invention is a differential pressure type hydrogen station that fills a fuel cell vehicle (FCV) with hydrogen from a pressure accumulator by differential pressure. Fig. 1 is a diagram explaining the schematic configuration of the hydrogen station in the present invention. As shown in Fig. 1, the hydrogen station 1 is an off-site simplified hydrogen station 1 that uses a hydrogen station package unit, and is composed of an H2 receiving unit 12, a hydrogen station package unit 13, a dispenser unit 14 with a built-in precooler that cools hydrogen gas, an N2 unit 15 for purging, and a refrigerator unit 16.

[0033] The H2 receiving unit 12 (hydrogen source) receives hydrogen gas (hereinafter sometimes referred to as "hydrogen") that has been produced on a large scale at an existing industrial plant or the like and transported to a hydrogen station by trailer or cart with large cylinders bundled together, and supplies it to the hydrogen station packaging unit 13.

[0034] The hydrogen station package unit 13 packages a compressor unit 18, a pressure accumulator unit 19, and a valve unit 20 in a housing 17. The compressor unit 18 and the pressure accumulator unit 19 are connected by a filling flow path 21 via the valve unit 20, and the pressure accumulator unit 19 and the dispenser unit 14 are connected by a supply flow path 22 via the valve unit 20.

[0035] The dispenser unit 14 supplies hydrogen to a fuel cell vehicle (FCV) 60 via a filling nozzle (not shown) while controlling the flow rate of the high-pressure hydrogen supplied from the pressure accumulator unit 19 in the hydrogen station package unit 13 using a flow control valve (not shown). The dispenser unit 14 also includes a pre-cooler (heat exchanger) that cools the hydrogen to be supplied to the fuel cell vehicle 60 to a predetermined temperature (e.g., -40°C). This is to cool the hydrogen sufficiently in advance to prevent the tank temperature from rising too high, since the temperature rises due to adiabatic compression when hydrogen gas is rapidly filled into the tank of the fuel cell vehicle.

[0036] The N2 purge unit 15 stores nitrogen (N2) gas for purging to remove impurities such as air, as well as hydrogen remaining in the flow paths and valves of the hydrogen station package unit 13, and supplies nitrogen to the hydrogen station package unit 13 via the H2 receiving unit 12 as necessary to purge hydrogen gas and other impurities remaining in the flow paths.

[0037] The refrigerator unit 16 circulates and supplies a refrigerant to the precooler of the dispenser unit 14, and cools the hydrogen to be supplied to the fuel cell vehicle 60 to a predetermined temperature.

[0038] Next, the configuration of the hydrogen station package unit 13 will be described with reference to Fig. 2. As shown in Fig. 2, the hydrogen station package unit 13 packages a compressor unit 18, a pressure accumulator unit 19, and a valve unit 20 within a housing 17.

[0039] The compressor unit 18 includes a compressor 25, automatic ball valves 26 and 27 that function as shutoff valves, and a check valve 28, and pressurizes (compresses) the hydrogen supplied from the H2 receiving unit 12 and fills it into the pressure accumulator unit 19 via the filling flow path 21. The compressor 25 can be any suitable type of compressor, such as a reciprocating compressor or a diaphragm type compressor, as long as it is a high-pressure hydrogen compressor with a discharge pressure of more than 80 MPa. However, in order to configure the hydrogen station package unit 13 in a compact size, it is preferable to select a small compressor that corresponds to the hydrogen supply capacity of the hydrogen station. Also, a booster type compressor is preferable from the viewpoint of reducing costs.

[0040] 2, since the temperature of the hydrogen gas rises due to adiabatic compression when the hydrogen gas is compressed by the compressor 25, it is preferable to provide a cooler in the compressor unit 18 for cooling the hydrogen gas after compression. For example, the refrigerator unit 16 may be used in combination with this cooler for cooling.

[0041] The pressure accumulator unit 19 has a function of storing high-pressure (over 80 MPa) hydrogen gas pressurized by the compressor unit 18, and includes four pressure accumulators 30a, 30b, 30c, and 30d in the form of long tanks with a capacity of 300 L.

[0042] In the differential pressure hydrogen station 1 that uses a high-pressure accumulator to supply hydrogen gas to the fuel cell vehicle 60, it is considered that bank switching by combining a low-pressure bank, a medium-pressure bank, and a high-pressure bank is efficient. Therefore, in this embodiment, the low-pressure bank 1 is composed of two accumulators 30a and 30b, the medium-pressure bank 2 is composed of the accumulator 30c, and the high-pressure bank 3 is composed of the accumulator 30d, and the high-pressure hydrogen gas stored in the accumulators is supplied to the fuel cell vehicle 60 in the order of the low-pressure bank 1, the medium-pressure bank 2, and the high-pressure bank 3. Since the low-pressure bank 1 has the largest supply of hydrogen gas when supplying hydrogen gas to the fuel cell vehicle 60, two accumulators 30a and 30b are used to ensure the supply amount. However, the number of accumulators can be increased or decreased as appropriate depending on the hydrogen supply capacity required for the simplified hydrogen station 1. In this embodiment, the accumulators 30a, 30b, and 30c are all the same capacity, but accumulators of different sizes may be combined as necessary.

[0043] In order to fill and remove hydrogen gas from the pressure accumulators, a flow path 31a is connected to bank 1, a flow path 31b is connected to bank 2, and a flow path 31c is connected to bank 3. Since bank 1 is composed of two pressure accumulators 30a and 30b, the flow path 31a branches immediately before the pressure accumulators 30a and 30b and is connected to each of the pressure accumulators 30a and 30b.

[0044] The valve unit 20 controls the filling of the hydrogen gas pressurized by the compressor unit 18 into the pressure accumulators 30a, 30b, 30c, and 30d in the pressure accumulator unit 19, and the removal of the hydrogen gas stored in the pressure accumulators 30a, 30b, 30c, and 30d. For this purpose, the valve unit 20 is provided with a hydrogen gas inlet 33 to which the branch flow path 21 can be detached, and a hydrogen gas outlet 34 to which the supply flow path 22 can be detached, as well as hydrogen gas inlets 35a, 35b, and 35c to which the three flow paths 31a, 31b, and 31c of the pressure accumulator unit 19 can be detached.

[0045] The filling flow path 21 branches into branch flow path 21a that supplies hydrogen gas to bank 1 within the valve unit 20, branch flow path 21b that supplies hydrogen gas to bank 2, and branch flow path 21c that supplies hydrogen gas to bank 3, with branch flow path 21a being connected to a hydrogen gas inlet / outlet 35a, branch flow path 21b being connected to a hydrogen gas inlet / outlet 35b, and branch flow path 21c being connected to a hydrogen gas inlet / outlet 35c.

[0046] In addition, in order to supply hydrogen gas from the accumulators 30a, 30b, 30c, and 30d in the accumulator unit 19 to the dispenser unit 14, a tributary flow path 22a for extracting hydrogen gas from bank 1, a tributary flow path 22b for extracting hydrogen gas from bank 2, and a tributary flow path 22c for extracting hydrogen gas from bank 3 are provided, and tributary flow path 22a is connected to a hydrogen gas inlet / outlet 35a, tributary flow path 22b is connected to a hydrogen gas inlet / outlet 35b, and tributary flow path 22c is connected to a hydrogen gas inlet / outlet 35c. The tributary flow paths 22a, 22b, and 22c are gathered together within the valve unit 20 to form the supply flow path 22.

[0047] As shown in FIG. 2, branch flow path 21a and tributary flow path 22a, branch flow path 21b and tributary flow path 22b, and branch flow path 21c and tributary flow path 22c share part of the flow path just before hydrogen gas inlets and outlets 35a, 35b, and 35c, but the branch flow paths and tributary flow paths may be connected to the hydrogen gas inlets and outlets individually.

[0048] In this way, the valve unit 20 has a plurality of parallel flow paths that branch off before the pressure accumulator unit 19 and gather after the pressure accumulator unit 19.

[0049] An automatic ball valve 37a and a check valve 38a are provided in the branch flow path 21a, an automatic ball valve 37b and a check valve 38b are provided in the branch flow path 21b, and an automatic ball valve 37c and a check valve 38c are provided in the branch flow path 21c. These automatic ball valves 37a, 37b, and 37c are first valves that open and close the supply of hydrogen gas from the compressor unit 18 to the pressure accumulator unit 19. This controls the supply of hydrogen gas from the compressor unit 18 to the pressure accumulator unit 19 and prevents backflow of hydrogen gas.

[0050] In addition, an automatic ball valve 39a and a check valve 40a are provided in the branch flow path 22a, an automatic ball valve 39b and a check valve 40b are provided in the branch flow path 22b, and an automatic ball valve 39c and a check valve 40c are provided in the branch flow path 22c. These automatic ball valves 39a, 39b, and 39c are second valves that open and close the supply of hydrogen gas from the pressure accumulator unit 19 to the hydrogen gas outlet 34. This controls the supply of hydrogen gas from the pressure accumulator unit 19 to the hydrogen gas outlet 34 and prevents backflow of hydrogen gas.

[0051] A check valve 43 and an automatic ball valve 44 are provided in the supply flow path 22 where the branch flow paths 22a, 22b, and 22c join together to prevent backflow of hydrogen gas and to control the supply of hydrogen gas to the dispenser unit 14.

[0052] Furthermore, a valve 46a is provided in flow path 45a branched from flow path 31a, a valve 46b is provided in flow path 45b branched from flow path 31b, and a valve 46c is provided in flow path 45c branched from flow path 31c. These valves 46a, 46b, and 46c are vent valves (hereinafter referred to as "diffusion valves") that open and close the vents for hydrogen gas in the flow paths. The diffusion valves 46 (46a, 46b, and 46c) are connected to a diffusion pipe (not shown) and release hydrogen gas from the diffusion pipe to the outside of the hydrogen station system. The release valve not only vents hydrogen gas or nitrogen gas in the flow path during maintenance, but also releases hydrogen gas to the outside of the system to reduce the abnormal pressure in the flow path piping in the system by a hydrogen pressure control method described later when an abnormal pressure rise occurs in the flow path. The release valve is controlled by a control unit (not shown) or the like to switch from a closed state to an open state before the pressure reaches the pressure at which the safety valve operates, and the release valve releases hydrogen gas to the outside of the system to reduce the pressure in the flow path, thereby controlling the hydrogen pressure so that the pressure in the flow path does not exceed the set pressure limit of the equipment. The release valve may be a known manual or automatic valve (such as a ball valve), but an automatic ball valve is preferred since high-pressure gas is released when the pressure is released.

[0053] In addition, the diffusion pipe connected to the diffusion valve may be connected to the piping flow path of the bank so that, in the event of an abnormal pressure rise, the hydrogen gas in the piping flow path where the abnormal pressure rise has occurred may be transferred to the bank, which is in a safe pressure state, where it may be accumulated, thereby eliminating the abnormal pressure. Furthermore, a storage container for storing hydrogen gas may be connected to the diffusion pipe connected to the diffusion valve before the hydrogen gas is released to the outside of the hydrogen station system.

[0054] Furthermore, a pressure gauge 61a is provided in flow path 31a, a pressure gauge 61b in flow path 31b, and a pressure gauge 61c in flow path 31c. The pressure gauges 61a, 61b, and 61c monitor the pressure when the hydrogen gas pressurized by compressor 25 is stored in pressure accumulators 30a, 30b, 30c, and 30d, and also monitor the pressure in flow paths 31a, 31b, and 31c. When the hydrogen pressure in a flow path reaches or exceeds a predetermined pressure, the hydrogen gas is released to the outside of the system by the above-mentioned release valve, thereby reducing the pressure in the flow path.

[0055] Further, a safety valve 51a is provided in the branch flow path 22a, a safety valve 51b is provided in the branch flow path 22b, and a safety valve 51c is provided in the branch flow path 22c. The safety valve 51 (51a, 51b, 51c) is a safety device that forcibly releases hydrogen gas outside the system when an abnormal pressure rise occurs in the piping in the hydrogen station so that the pressure in the piping does not exceed the set pressure limit of the hydrogen station equipment. The safety valve opens to reduce the pressure when the pressure reaches a predetermined pressure (blow pressure), and closes to forcibly release the pressure when the pressure drops to the predetermined pressure (recess pressure). The pressure at which the safety valve operates (blow pressure) and the pressure at which the safety valve stops operating (recess pressure) can be freely set by the user within the range of the product standard of the safety valve. Since the safety valve is a device that forcibly releases pressure, it is installed as a final safety device in the event of a trouble such as a power loss that makes the hydrogen station uncontrollable. Therefore, the operating pressure (blow pressure) of the safety valve is generally set to a pressure in the piping that is very close to the set pressure limit of the hydrogen station equipment.

[0056] For this reason, since the pressure inside the hydrogen station when the safety valve operates is close to a dangerous pressure, it is preferable to reduce the hydrogen pressure by the release valve before the safety valve operates in the event of an abnormal pressure increase. Therefore, in the event of an emergency such as when the release valve breaks down, it is preferable to provide the safety valve downstream of the release valve so that the safety valve can be operated to reliably release pressure. There are no particular limitations on the type of safety valve, but a spring-type safety valve is preferable.

[0057] Incidentally, at hydrogen stations, for example, when hydrogen is filled into a pressure accumulator from a hydrogen supply source (hydrogen source), or when hydrogen gas is pressurized and stored in a pressure accumulator and supplied to a dispenser, the temperature in the piping rises due to the compression of the hydrogen gas, and the pressure in the piping may increase. The piping at hydrogen stations is designed to have a safe pressure resistance in consideration of factors that cause pressure increases during operation, so pressure increases under normal operating conditions do not pose a problem.

[0058] However, external factors such as direct sunlight or radiant heat, or equipment failure can cause an abnormal increase in hydrogen pressure. Therefore, the hydrogen pressure control method for a hydrogen station of the present invention is characterized by controlling the opening and closing of the diffusion valve to release hydrogen gas and reduce the pressure to a safe level before the pressure reaches the pressure at which the safety valve operates, while minimizing hydrogen loss due to depressurization.

[0059] Hydrogen pressure control in the event of an abnormal pressure rise at a hydrogen station is carried out as follows. - Determine whether pressure rise occurs in the piping of a hydrogen station and whether the pressure value exceeds a specified value. If the pressure rise exceeds a certain value and is determined to be abnormal, the release valve is opened to release hydrogen gas outside the system. When the pressure after decompression reaches a specified condition, the release valve is controlled to close. Ending control of the release valve

[0060] In the hydrogen station of this embodiment shown in Fig. 2, when the pressure value of the pressure gauge 61a in the flow path 31a exceeds a preset pressure value, it is determined that an abnormal pressure increase has occurred, and the release valve 46a is activated. The pressure value standard for determining that an abnormal pressure increase has occurred is not particularly limited, but may be, for example, a value exceeding the pressure that can be safely stored in a high-pressure hydrogen gas accumulator (bank), a value exceeding the maximum pressure in the flow path expected during normal operation, or the maximum pressure value that the piping, etc. can withstand. In addition, this pressure value is set to be less than the pressure (blowing pressure) at which the safety valve operates.

[0061] When it is determined that an abnormal pressure rise has occurred, the release valve 46a is controlled to be open by a control unit (not shown) or the like. When the release valve 46a is open, the hydrogen gas in the flow path 31a passes through the flow path 45a, and is released from the release valve 46a via a release pipe to the outside of the hydrogen station system, causing the hydrogen pressure in the flow path 31a to decrease.

[0062] When the pressure is released by the release valve, if the pressure after release satisfies a predetermined condition, the release valve is controlled so as to be in a closed state.

[0063] Here, when setting the condition of the predetermined pressure after depressurization, it can be set, for example, as follows. First, when the pressure in the hydrogen station system reaches the pressure set as the operating condition of the release valve in the event of abnormal pressure increase, the temperature and pressure in the hydrogen station system at that time are measured. In addition, "in the hydrogen station system" refers to the flow path in the hydrogen station 1 from the compressor 25 until the high-pressure hydrogen gas pressurized by the compressor 25 is supplied to the FCV 60, and in this embodiment, refers to the flow path from the compressor 25 to the dispenser unit 14. When pressure control is possible individually in multiple banks, each bank can be regarded as a separate system. Then, based on the temperature and pressure in the hydrogen station system (in each bank system) measured in this way, the pressure in the system after the necessary depressurization is preset, the release valve is opened until the pressure drops to the predetermined pressure, and the release valve is closed when the pressure is reduced to the pressure.

[0064] As described above, the pressure after depressurization may be preset based on the temperature and pressure conditions at the time when the set pressure at which the release valve is opened is reached, but the pressure in the hydrogen station system may change due to various factors even during depressurization by the release valve. For example, when the release valve opens, hydrogen in the system is released to the outside of the system, which causes the volume of hydrogen to expand, lowering the temperature of the system. Therefore, compared to depressurization while maintaining the same temperature, the amount of hydrogen released is less even when the pressure is lowered to the same level.

[0065] If the pressure after depressurization is set in advance based only on the temperature and pressure in the system at the time the release valve is opened, in some cases the amount of hydrogen released may be insufficient, and after the release valve is closed, the pressure may rise again and exceed the set pressure or even reach the blow-off pressure of the safety valve.

[0066] To prevent this, when setting the pressure after depressurization, it is preferable to consider not only the temperature and pressure conditions in the system, but also the temperature drop due to depressurization and other external factors that affect the pressure in the system. Alternatively, if it is difficult to take such effects into account in advance, the temperature and pressure in the system during depressurization may be measured in real time, and the release valve may be closed only after it is confirmed that the temperature and pressure in the system reliably satisfy the conditions of the relational expression (1) described below. In addition, it is more preferable to set the conditions for closing the release valve so that the depressurization speed within the flow path when the release valve is in the open state is such that the depressurization speed within the flow path can be depressurized even in a case where the pressure within the flow path increases due to influences outside the system while the release valve is in the open state to release pressure.

[0067] When the release valve is closed, the pressure Px after depressurization is set to a pressure that is lower than the discharge pressure (Pm) of the safety valve even when the maximum temperature Tm expected to be reached in the flow path in the hydrogen station is reached, and is preferably set to a pressure that is lower than the operating pressure (Pd) of the release valve even when Tm is reached. If Px is a pressure that is lower than Pm even when Tm is reached, it is possible to avoid a situation in which the safety valve is activated even if a sudden temperature rise occurs after depressurization. In particular, it is more preferable if Px is lower than the operating pressure (Pd) of the release valve even when Tm is reached, as this avoids a situation in which the release valve is activated again due to a temperature rise after depressurization.

[0068] Here, the "maximum temperature expected to be reached in the flow path" refers to the maximum temperature that is predefined and can be tolerated by the hydrogen station when a temperature rise occurs in the hydrogen station. There are no particular limitations on the standard for setting this maximum temperature, but it may be, for example, the temperature at which water sprinkling begins in the hydrogen station. The water sprinkling start temperature is the maximum allowable safety temperature set to prevent fires when the temperature rises abnormally, so this temperature may be used as the standard. For example, the water sprinkling start temperature in a hydrogen station may be set to 40°C. Alternatively, the temperature of the hydrogen gas at the pressure (blow-off pressure) at which the safety valve is activated may be used as the standard.

[0069] When the following relational expression (1) is satisfied, the release valve is controlled to a closed state. Px <Pm×Tx / Tm (1) (In the relational expression (1), Px is the pressure after depressurization, Pm is the blowing pressure of the safety valve, Tx is the temperature in the flow path after depressurization, and Tm is the maximum temperature expected to be reached in the flow path.)

[0070] This relational expression (1) is derived from the Boyle-Charles relational expression. Here, the volume V of the target flow path where the relief valve releases pressure can be considered to be constant because the effects of expansion, etc. are negligible. If the pressure in the flow path at the highest temperature Tm is equal to the relief valve's blow-off pressure Pm, then the pressure Px after release and the temperatures Tx, Tm, and Pm after release will satisfy the following relational expression (2). Px × V / Tx = Pm × V / Tm (2) Therefore, from this relational expression (2), it is possible to find Px when the pressure in the flow path at Tm becomes Pm. In this embodiment, depressurization is performed so that the pressure at Tm is smaller than Pm, so that the above relational expression (1) is derived regarding Px after depressurization.

[0071] Here, the relationship between the temperature and pressure in the flow passage of the hydrogen station 1 when the diffusion valve is operated in this embodiment will be described with reference to the temperature-pressure graph of FIG. In the graph of Figure 3, the vertical axis represents pressure (units are arbitrary pressure units), and shows the safety valve operating pressure (blow-off pressure Pm), the safety valve shut-off pressure, and the release valve operating pressure (Pd). These pressure values ​​are fixed values ​​that are set by configuration. The horizontal axis represents temperature (units are Kelvin (K)), and shows the maximum temperature (Tm) expected to be reached within the flow path of hydrogen station 1. This value is also a fixed value that is set by configuration. When the temperature in the flow passage of hydrogen station 1 is Tx, if some factor causes an abnormal pressure rise in the flow passage and the pressure reaches the release valve operating pressure Pd (point P0 in the graph), the release valve operates and opens, depressurizing the flow passage and causing the pressure in the flow passage to drop as indicated by the white arrow in the graph. This prevents the flow passage from reaching the operating pressure of the safety valve.

[0072] Now, let us suppose that the relief valve is closed when the pressure has been slightly relieved from that state (point P1 on the graph). If the temperature inside the flow path is maintained below Tx, it will be kept below the relief valve operating pressure. However, if the abnormal pressure rise is caused by a sudden rise in temperature, for example, even if the relief valve has relieved the pressure, if the temperature continues to rise, the pressure inside the flow path will rise again (dotted line indicated by L0 on the graph). If this happens, the pressure will again exceed Pd, requiring the relief valve to open and close again. Furthermore, if the repeated opening and closing of the relief valve cannot keep up with the pressure rise, the pressure inside the flow path may reach the relief valve operating pressure. In contrast, in this embodiment, once the pressure in the flow path reaches the relief valve operating pressure Pd (point P0 in the graph), the relief valve is opened to release pressure in the flow path until the pressure reaches Px (point P2 in the graph) that satisfies the above-mentioned relational expression (1). If pressure is released in this manner, even if the temperature rises after pressure release and a pressure increase occurs as indicated by the solid line L1 in the graph, the pressure when the maximum temperature Tm is reached (point P3 in the graph) will be lower than the relief valve operating pressure Pm, so the relief valve will not be activated.

[0073] In this way, the safety valve is controlled to be in the closed state when the relational expression (1) is satisfied in order to prevent the safety valve from operating even if the temperature in the flow path after the relief valve is depressurized rises for some reason. For example, if the temperature rises further after depressurization, the pressure in the flow path may rise again, and the relief valve may not be able to depressurize in time and may activate the relief valve. Therefore, even if pressure increases due to a rise in temperature after depressurization, the relief valve is closed only after sufficient depressurization has been achieved to a safe pressure that will not activate the relief valve.

[0074] When the condition satisfies the above relational expression (1), the release valve is closed and depressurization is terminated once the pressure Px after depressurization by the release valve becomes sufficiently safe, so that the release valve can control an abnormal increase in hydrogen pressure without reaching a pressure at which the safety valve would activate.

[0075] The pressure (Px) that closes the release valve is set so that the pressure in the flow path when the maximum temperature (Tm) is reached is less than the safety valve's blow-off pressure (Pm). As shown in Figure 3, if the pressure at Tm is set to be less than Pm, the pressure in the flow path will always be kept lower than Pm as far as temperature fluctuations are concerned, so it will never reach Pm. The pressure in the flow path at Tm is lower than Pm, but it is preferable to set it to a value lower than the release valve's operating pressure Pd, as this can prevent the release valve from operating again due to a rise in temperature after depressurization.

[0076] On the other hand, the lower limit of the pressure (Px) at which the release valve is closed can be made higher than the blow-off pressure of the safety valve to reduce hydrogen loss due to depressurization of the release valve. That is, the smaller Px is made within the range satisfying the relational expression (1), the lower the hydrogen pressure in the flow path, so safety is improved, but hydrogen loss also increases. In order to reduce hydrogen loss, it is preferable not to make Px smaller than necessary, and for example, as a standard, it is preferable that Px is higher than the blow-off pressure of the safety valve (solid line indicated by L4 in the graph of FIG. 3). This makes it possible to reduce hydrogen loss compared to the case where the safety valve is activated. In this case, in the graph shown in FIG. 3, Px is preferably a pressure lower than the two-dot chain line indicated by L2 and higher than the solid line indicated by L4, and more preferably a pressure lower than the solid line indicated by L3 and higher than the solid line indicated by L4. If the release valve can be operated, it is possible to control the pressure in the flow path and safety can be easily maintained. Therefore, from the viewpoint of minimizing hydrogen loss, it is preferable that Px be set to the pressure at which the pressure in the flow path when Tm is reached becomes the release valve operating pressure Pd (the pressure indicated by the solid line L3 in the graph), and even if greater safety is taken into consideration, it is preferable to set Px within a pressure range approximately 10% lower than that.

[0077] In addition, since the operating pressure (blow-off pressure) and the receding pressure of the safety valve can be set arbitrarily, the operating pressure of the relief valve and the pressure at which the relief valve is closed can be set arbitrarily based on the above-mentioned relational expressions and criteria.

[0078] As an example of the range in which the release valve is controlled, if the safety valve's outlet pressure is set at 95 MPa, the outlet pressure is set at 84 MPa, the accumulator's allowable pressure is set at 85 MPa, and the pressure at the maximum temperature reached in the flow path within the hydrogen station is set at 90 MPa, the condition pressure for opening the release valve can be 89 MPa, and the condition pressure for closing the release valve can be set at 85 MPa.

[0079] In this way, by controlling the relief valve as described above before the safety valve is activated, it becomes easier to maintain a safe pressure in flow paths where abnormal pressure rise is likely to occur (for example, the flow path between the compressor and the pressure accumulator, the flow path between the pressure accumulator and the dispenser, etc.).

[0080] Furthermore, the pressure in the hydrogen station system may increase abnormally when, for example, the outside air temperature is high, causing the temperature of the hydrogen station to rise and the pressure in the hydrogen station system to increase. In such a case, the temperature may rise suddenly, causing the pressure in the hydrogen station system to rise rapidly. If the pressure in the hydrogen station system exceeds the set pressure of the release valve, the release valve opens, and hydrogen in the system is released to the outside of the system, but if the release speed is slower than the pressure rise speed in the system, the pressure in the system will continue to rise, and as long as the release valve is open, the only option may be to activate the safety valve.

[0081] Therefore, it is preferable that the relief valve not only be able to simply release pressure within the hydrogen station system, but also be able to exert a depressurization speed that exceeds the rate of pressure increase over time that is likely to occur when an abnormal pressure increase occurs. For example, in order to ensure safety when hydrogen is released into the atmosphere, hydrogen stations are required to meet certain hydrogen release conditions that maintain the hydrogen concentration around the station at a certain level or lower, and an orifice or the like is provided in the release flow path to meet these conditions. Therefore, it is preferable for the release valve to be one that is within a range that satisfies such an upper limit and can achieve a depressurization speed that is greater than the pressurization speed within the hydrogen station system.

[0082] In addition, the depressurization speed at which pressure is released within a hydrogen station system is affected by the flow rate of the relief valve and the flow rate of the orifice, and in the present invention, the influence of the orifice is taken into consideration so that when the pressure within the flow path exceeds a predetermined set pressure and the relief valve is opened, depressurization can be controlled at a depressurization speed that can reduce the pressure within the flow path even under external conditions where the pressure within the flow path would continue to rise if depressurization was not performed. Therefore, for example, when a hydrogen station is exposed to unexpectedly high temperatures and the pressure in the flow path increases as the temperature of the flow path rises, causing an abnormal increase in pressure in the flow path, even after depressurization by the depressurization valve has begun, the depressurization can be controlled by the depressurization valve at a depressurization speed that can reliably depressurize the flow path, even under conditions where the pressure in the flow path rises suddenly, so that a safe pressure can be maintained in the flow path by depressurization by the depressurization valve.

[0083] In the hydrogen pressure control method for a hydrogen station described above, it is preferable to use a ball valve as the release valve. When using a ball valve as the release valve, compared to a needle valve, a ball valve is capable of flowing a large amount of fluid at a high speed (large flow rate), and therefore is more preferable as the release valve because it can achieve a high depressurization speed. Also, it is more preferable to use a ball valve with a large flow rate. In FIG. 2, one diffusion valve is provided in each of the flow paths 31a, 31b, and 31c, but if two or more diffusion valves are provided in each flow path, a faster depressurization speed can be obtained.

[0084] In this embodiment, the operation of each unit and the opening and closing of the valves are controlled by a PLC (Programmable Logic Controller) (not shown) that receives signals from other sensors such as pressure gauges (not shown).

[0085] The hydrogen station package unit 13 is configured as described above, and when an abnormal pressure rise occurs, the release valve can be controlled to open and close to resolve the abnormal pressure rise that has occurred within the hydrogen station.

[0086] Furthermore, the hydrogen station of this embodiment can pressurize (compress) hydrogen gas supplied from the H2 receiving unit 12 in the compressor unit 18, fill and store the hydrogen gas in the pressure accumulation unit 19, and supply it to the dispenser unit 14 as needed. The filling of hydrogen gas into the pressure accumulation unit 19 and the removal of hydrogen gas from the pressure accumulation unit 19 are controlled by opening and closing a plurality of valves provided in the valve unit 20.

[0087] In addition, in the valve unit 20, various valves for opening and closing the supply of hydrogen gas and for opening and closing the vent for hydrogen gas are mounted in an integrated state. That is, a first valve group consisting of valves 37a, 37b, 37c that open and close the supply of hydrogen gas from the compressor unit 18 to the pressure accumulator unit 19, a second valve group consisting of valves 39a, 39b, 39c that open and close the supply of hydrogen gas from the pressure accumulator unit 19 to the hydrogen gas outlet 34, a third valve group consisting of valves 46a, 46b, 46c that open and close the vent for hydrogen gas in the flow path, and a fourth valve group consisting of safety valves 51a, 51b, 51c are each arranged in an integrated state in different specified areas within the valve unit 20.

[0088] Therefore, in the hydrogen station 1, various units can be efficiently integrated and arranged, taking into consideration the flow of hydrogen gas from the compressor unit to the accumulator, improving compactness while also improving manufacturability and maintainability. That is, during manufacturing, valves of the same type can be attached to support members, etc. at the same time within a specified area, improving manufacturability. Furthermore, during inspection and maintenance of the hydrogen station package unit, valves of the same type can be inspected and maintained at the same time, improving maintainability.

[0089] Here, in the above-described embodiment, a method has been described in which when an abnormal pressure increase occurs in a hydrogen station system, the pressure in the system is reduced by opening the release valve to release hydrogen in the system into the atmosphere, but the method of reducing the pressure in the system is not limited to this. In the accumulator unit 19 consisting of multiple banks, a bypass pipe or the like may be provided between the banks to allow hydrogen gas in the flow path that has abnormally increased pressure to flow into a bank that has room to be fully filled, thereby eliminating the abnormal increase in pressure.

[0090] In the above-mentioned embodiment, the hydrogen station 1 is composed of a plurality of banks, and each bank can be individually pressure-controlled, and there are cases where abnormal pressure rise occurs only in some of the plurality of banks. In the case of three banks, banks 1 to 3, as in the above-mentioned embodiment, if an abnormal pressure rise occurs in the piping flow path 31c of bank 3, for example, if all the banks are in a full pressure state, the only way to release the hydrogen is to open the release valve 46c of bank 3 and release the hydrogen to the atmosphere to depressurize. On the other hand, for example, after hydrogen is supplied from this hydrogen station to the FCV, when some of the pressure accumulators (for example, banks 1 and 2) have not recovered to full pressure, it is assumed that only bank 3 will be in an abnormal pressure rise state, and hydrogen can be transferred from the bank in the abnormal pressure rise state (bank 3) to another bank (back 1 or 2) that is not in an abnormal pressure rise state.

[0091] In this case, hydrogen is depressurized in the piping flow passage 31c of bank 3, while the bank 1 or 2 to which the hydrogen has been transferred is pressurized. In the pressurized bank, it is necessary to satisfy a pressure that is less than the blow-off pressure of the safety valve even when the maximum temperature expected for each bank is reached, and it is more preferable to satisfy the above relational expression (1). For example, abnormal pressure rise can be eliminated by providing a flow passage pipe that bypasses the banks and controlling opening and closing by the release valve and by controlling opening and closing so as to satisfy the conditions for each bank. When abnormal pressure rise can be eliminated without opening the release valve, hydrogen gas in the flow passage is stored in the bank where abnormal pressure rise is not occurring, and hydrogen gas is not released outside the system, thereby reducing hydrogen gas loss. Furthermore, when this method is combined with the hydrogen pressure control method of the present invention using the above-mentioned diffusion valve, it is possible to reduce hydrogen gas loss while further increasing the depressurization speed in the piping flow path where abnormal pressure rise has occurred, thereby further improving the safety of the hydrogen station.

[0092] Furthermore, it is also assumed that an abnormal pressure rise may occur while hydrogen is being supplied from the hydrogen station 1 to the FCV 60, and in the hydrogen station 1 of the above-described embodiment, for example, an abnormal pressure rise may occur in bank 2 or 3 while hydrogen is being supplied to the FCV from bank 1. In this case, the abnormal pressure rise in the flow path of the hydrogen station can be eliminated by switching the bank that is supplying hydrogen to the FCV (for example, switching from bank 1 to bank 2 or 3). That is, since the residual pressure in bank 1 has already dropped to a certain extent, abnormal pressure rise is unlikely to occur, and since supplying hydrogen to the FCV means depressurizing the hydrogen in the bank that is supplying that hydrogen, supplying hydrogen to the FCV from the bank where abnormal pressure rise is occurring (e.g., bank 2 or 3) also depressurizes that bank (e.g., bank 2 or 3), thereby eliminating the abnormal pressure rise. In this way, abnormal pressure rise in the flow path of the hydrogen station can be eliminated by switching the bank that is supplying hydrogen to the FCV to another bank without using a release valve.

[0093] The above describes the hydrogen pressure control method for a hydrogen station and the hydrogen station of the present invention, taking as an example when used in an off-site hydrogen station. However, the present invention is not limited to off-site hydrogen stations and can also be used in on-site hydrogen stations, and can also be used in hydrogen stations other than package units.

[0094] In addition, although the control of hydrogen pressure in the piping flow path between the accumulator and the dispenser has been described, it can also be used to control hydrogen pressure in the piping flow path between the dispenser and the FCV. There is no particular limit to the number of release valves and safety valves arranged in the flow path, and the number may be increased as desired. For example, the release valves may be provided at regular intervals, and the release valves may be sequentially opened and closed under predetermined conditions to control the hydrogen pressure. [Explanation of symbols]

[0095] 1. Hydrogen station (simple hydrogen station) 12 Hydrogen source (H2 receiving unit) 14 Dispenser (dispenser unit) 18 Compressor unit 19 Accumulator Unit 25 Compressor 30a 30b 30c 30d Pressure accumulator 46 46a 46b 46c Discharge valve 51 51a 51b 51c Safety valve 60 Fuel cell vehicle (FCV)

Claims

1. A hydrogen station is a differential pressure type hydrogen station where hydrogen from a hydrogen source is pressurized by a compressor and stored in a pressure accumulator, and hydrogen is filled into a fuel cell vehicle from the pressure accumulator using the differential pressure, and the hydrogen station is provided in a flow path of the hydrogen station with a safety valve that opens at a predetermined outlet pressure depending on the pressure in the flow path and closes at a predetermined stop pressure, and a diffusion valve that can be manually or automatically controlled to switch between the open and closed states, and the hydrogen pressure control method for a hydrogen station is characterized in that the predetermined conditions for switching between the open and closed states of the diffusion valve are a predetermined set pressure that is lower than the outlet pressure of the safety valve, and a pressure that is lower than the outlet pressure of the safety valve even when the maximum temperature expected in the flow path is reached.

2. 2. The hydrogen pressure control method for a hydrogen station according to claim 1, wherein the condition for closing the release valve is that the pressure (Px) after depressurization satisfies the following relational expression (1): Px<Pm×Tx / Tm (1) (In the relational expression (1), Px is the pressure after depressurization, Pm is the blowing pressure of the safety valve, Tx is the temperature in the flow path after depressurization, and Tm is the maximum temperature expected to be reached in the flow path.)

3. 3. The hydrogen pressure control method for a hydrogen station according to claim 2, wherein the condition for closing the release valve is that the pressure (Px) after depressurization satisfies the relational expression (1) and is higher than the blow-off pressure of the safety valve.

4. A hydrogen pressure control method for a hydrogen station as described in any one of claims 1 to 3, wherein when the pressure in the flow path exceeds the specified set pressure and the release valve is opened, depressurization is controlled at a depressurization speed that can reduce the pressure in the flow path, even under external conditions where the pressure in the flow path would continue to rise if not depressurized.

5. 1. A hydrogen station comprising: a compressor, a pressure accumulator that stores hydrogen pressurized by the compressor, and a dispenser that supplies hydrogen from the pressure accumulator to a fuel cell vehicle, connected by piping; a safety valve and a release valve disposed in a flow path connected by piping; wherein, when an abnormal increase in pressure occurs in the flow path connected by piping, the release valve is opened to release pressure, and after release of pressure, the release valve is closed, and the condition for opening the release valve is a predetermined set pressure that is set lower than the blowing pressure of the safety valve; and the condition for closing the release valve is such that the pressure after release (Px) satisfies the following relational expression (1). Px<Pm×Tx / Tm (1) (In the relational expression (1), Px is the pressure after depressurization, Pm is the blowing pressure of the safety valve, Tx is the temperature in the flow path after depressurization, and Tm is the maximum temperature expected to be reached in the flow path.)

6. 6. The hydrogen station according to claim 5, wherein the safety valve and the release valve are disposed in a flow path between the compressor and the dispenser, and release hydrogen in this flow path to the outside of the system.

7. A hydrogen station as described in claim 5 or claim 6, wherein when the pressure in the flow path exceeds the specified set pressure and the release valve is opened, depressurization is controlled at a depressurization speed that can reduce the pressure in the flow path, even under external conditions where the pressure in the flow path would continue to rise if the pressure was not released.

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