JP7626642B2 - Hydrogen pressure control method for hydrogen stations and hydrogen stations - Google Patents

Description

The present invention relates to a hydrogen pressure control method for a hydrogen station and the hydrogen station, and in particular to a method for controlling an abnormal increase in hydrogen pressure that occurs within the hydrogen station and the hydrogen station.

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 reformer inside the station to reform methane and other fuels to generate hydrogen gas, which is then supplied to fuel cell vehicles (FCVs) and the like.
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.

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 it 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.

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 blowing pressure of the safety valve, and when an abnormal pressure rise occurs, the pressure is reduced so that it does not reach the blowing pressure of the safety valve (see page 255 of Non-Patent Document 1).

For example, Patent Document 1 discloses a hydrogen station that has a safety valve and a release valve 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).

Patent Document 2 also discloses a technology in which, in a hydrogen distribution unit, if an abnormal pressure rise 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.

JP 2019-178771 A Patent No. 6189981

High Pressure Gas Safety Act: Commentary on the Technical Standards for Compressed Hydrogen Stations, 2nd Edition (March 2017, High Pressure Gas Safety Institute of Japan)

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.

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

In addition, 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, thereby lowering 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 to hydrogen loss at all. Furthermore, there is no mention of the effects of temperature rise after depressurization.

The technology in 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 needs to be switched or multiple valves controlled in the complex piping connections between the accumulator and the dispenser.

In addition, multiple pipes are connected in a complex manner between the accumulator and the dispenser, so 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.

The present invention was developed to solve the problems of the past, and its purpose is to provide a hydrogen pressure control method for a hydrogen station and a hydrogen station that can reduce the pressure to a safe level using a release valve before the safety valve operates, and can safely control the hydrogen pressure even if a temperature rise occurs after depressurization.

In order to achieve the above object, the invention according to 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 from the pressure accumulator into a fuel cell vehicle by 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 blow-out pressure according to the pressure in the flow path and closes at a predetermined blow-out pressure, and a release valve that can be controlled manually or automatically to switch between the open and closed states, and the hydrogen pressure control method for the hydrogen station is set so that the predetermined conditions for switching between the open and closed states of the release 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.

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.)

The invention according to claim 3 is a method for controlling hydrogen pressure at a hydrogen station, in which the condition for closing the release valve is that the pressure after depressurization (Px) satisfies the above-mentioned relational expression (1) and is higher than the blow-off pressure of the safety valve.

The invention according to claim 4 is a hydrogen pressure control method that controls depressurization at a depressurization rate 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 in which the pressure in the flow path would continue to rise if the pressure is not released.

The invention of claim 5 is a hydrogen station which has 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 connected by this piping, and when an abnormal increase in pressure occurs in the flow path connected by 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 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.)

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

The invention according to 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 was not released.

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.

According to the invention of claim 2, the pressure when the release valve is closed is set within a range that satisfies a predetermined relational expression, so that even if an abnormal increase in hydrogen pressure occurs in the flow path, the safety valve does not operate and the release valve can reliably release the pressure, controlling the abnormal increase in hydrogen pressure and making it easier to maintain a safe pressure.

According to the invention of claim 3, the pressure at the condition for closing the release valve is set higher than the blow-off pressure of the safety valve, so the release valve is closed only after depressurization has reached a state where safety can be sufficiently ensured, and the amount of hydrogen released outside the hydrogen station system is reduced, thereby minimizing hydrogen loss.

According to the invention of claim 4, when the pressure in the flow path exceeds a predetermined set pressure and the release valve is in an open state, even under external conditions where the pressure in the flow path would continue to rise if the pressure was not released, the release can be controlled at a release speed that can reduce the pressure in the flow path. For example, when the 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 release by the release valve has begun, the release valve can release pressure faster than the pressure increase due to the rate of temperature rise in the flow path. This makes it possible to control the release at a release speed that can reliably release pressure in the flow path as a release valve, even under conditions where the pressure in the flow path rises suddenly, and the release by the release valve can maintain a safe pressure in the flow path.

According to the invention of claim 5, in a hydrogen station, a pressure accumulator for storing hydrogen gas is arranged in the flow path between the compressor and the 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 the 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 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.

According to the invention of claim 6, when a pressure rise occurs due to a temperature rise or the like in a hydrogen station, in a location in the system where a pressure rise is likely to occur, the release valve can safely release the pressure before it reaches the blow-off pressure of the safety valve, making it easier to maintain a safe pressure in the flow path where abnormal pressure rise is likely to occur in the hydrogen station.

According to the invention of claim 7, 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 not relieved, relief control can be performed at a relief speed capable of lowering the pressure inside the flow path. Therefore, even under conditions where the pressure inside the flow path rises suddenly, relief control can be performed at a relief speed capable of reliably relieving the pressure inside the flow path, and a safe pressure can be maintained inside the flow path by relief using the relief valve.

1 is a diagram illustrating a schematic configuration of a hydrogen station according to the present invention. 2 is a diagram for explaining a schematic configuration of a package unit of the hydrogen station of FIG. 1 . FIG. 2 is an explanatory diagram of a hydrogen pressure control method for a hydrogen station according to the present invention.

Below, a hydrogen pressure control method for a hydrogen station and a hydrogen station according to one embodiment of the present invention will be described in detail with reference to the drawings.

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 we will explain 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.

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 for 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, a purge _N2 unit 15, and a refrigerator unit 16.

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 a trailer or a cart carrying large cylinders, and supplies it to the hydrogen station package unit 13.

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.

The dispenser unit 14 supplies high-pressure hydrogen supplied from the accumulator unit 19 in the hydrogen station package unit 13 to a fuel cell vehicle (FCV) 60 via a filling nozzle (not shown) while controlling the flow rate with 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 because the temperature rises due to adiabatic compression when hydrogen gas is rapidly filled into the tank of a fuel cell vehicle, so the hydrogen is cooled sufficiently in advance to prevent the tank temperature from rising too high.

The _N2 purge unit 15 stores nitrogen ( _N2 ) gas for purging, which removes 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.

The refrigerator unit 16 circulates refrigerant to the precooler of the dispenser unit 14, cooling the hydrogen to be supplied to the fuel cell vehicle 60 to a predetermined temperature.

Next, the configuration of the hydrogen station package unit 13 will be described with reference to Figure 2. As shown in Figure 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.

The compressor unit 18 includes a compressor 25, automatic ball valves 26 and 27 functioning as shutoff valves, and a check valve 28, and boosts (compresses) the hydrogen supplied from the H ₂ receiving unit 12 and fills the accumulator unit 19 through the filling flow path 21. The compressor 25 can be a high-pressure hydrogen compressor with a discharge pressure of more than 80 MPa, and can be any suitable type of compressor such as a reciprocating compressor or a diaphragm compressor. However, in order to make the hydrogen station package unit 13 compact, it is preferable to select a small compressor that corresponds to the hydrogen supply capacity of the hydrogen station. In addition, a booster type compressor is preferable from the viewpoint of reducing costs.

Although not shown in FIG. 2, when the hydrogen gas is compressed by the compressor 25, the temperature of the hydrogen gas rises due to adiabatic compression, so it is preferable to provide a cooler in the compressor unit 18 to cool the hydrogen gas after compression. For example, the refrigerator unit 16 may be used to cool this cooler.

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

In a differential pressure hydrogen station 1 that uses a high-pressure accumulator to supply hydrogen gas to a 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 pressure accumulators 30a, 30b, and 30c all have the same capacity, but pressure accumulators of different sizes may be combined as necessary.

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

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

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

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 the tributary flow path 22a is connected to a hydrogen gas inlet/outlet 35a, the tributary flow path 22b is connected to a hydrogen gas inlet/outlet 35b, and the tributary flow path 22c is connected to a hydrogen gas inlet/outlet 35c. The tributary flow paths 22a, 22b, and 22c are gathered together in the valve unit 20 to form the supply flow path 22.

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

In this way, the valve unit 20 has multiple parallel flow paths that branch off before the pressure accumulator unit 19 and converge after the pressure accumulator unit 19.

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 the first valves that open and close the supply of hydrogen gas from the compressor unit 18 to the accumulator unit 19. This controls the supply of hydrogen gas from the compressor unit 18 to the accumulator unit 19 and prevents backflow of hydrogen gas.

In addition, an automatic ball valve 39a and a check valve 40a are provided in tributary flow path 22a, an automatic ball valve 39b and a check valve 40b are provided in tributary flow path 22b, and an automatic ball valve 39c and a check valve 40c are provided in tributary 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 accumulator unit 19 to the hydrogen gas outlet 34. This controls the supply of hydrogen gas from the accumulator unit 19 to the hydrogen gas outlet 34 and prevents backflow of hydrogen gas.

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 converge, to prevent backflow of hydrogen gas and to control the supply of hydrogen gas to the dispenser unit 14.

Furthermore, a valve 46a is provided in the flow path 45a branched from the flow path 31a, a valve 46b is provided in the flow path 45b branched from the flow path 31b, and a valve 46c is provided in the flow path 45c branched from the 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.

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.

In addition, 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 the compressor 25 is stored in the pressure accumulators 30a, 30b, 30c, and 30d, and also monitor the pressure in the flow paths 31a, 31b, and 31c. When the hydrogen pressure in the flow paths exceeds a predetermined pressure, the hydrogen gas is released outside the system by the above-mentioned release valve, thereby reducing the pressure in the flow paths.

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 for forcibly releasing 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 is a device that 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 when a trouble such as a power loss occurs and the hydrogen station becomes 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.

Because the pressure inside the hydrogen station when the safety valve operates is close to a dangerous pressure, in the event of an abnormal pressure rise, it is preferable to reduce the hydrogen pressure using the release valve before the safety valve operates. Therefore, in the event of an emergency such as when the release valve breaks down, it is preferable to install 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.

At hydrogen stations, for example, when hydrogen is filled into a pressure vessel from a hydrogen supply source (hydrogen source) called a cardle, or when hydrogen gas is pressurized and stored in a pressure vessel and then supplied to a dispenser, the temperature in the piping rises as the hydrogen gas is compressed, which can cause an increase in pressure inside the piping. The piping at hydrogen stations is designed to withstand safe pressure, taking into account factors that could cause a pressure rise during operation, so pressure rises under normal operating conditions are not a problem.

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.

Hydrogen pressure control in the event of an abnormal pressure rise at a hydrogen station is carried out as follows.

- A pressure rise occurs in the piping flow path of the hydrogen station, and it is determined whether the pressure value exceeds a predetermined value. - If the pressure rise exceeds the predetermined value and it is determined to be abnormal, the release valve is controlled to an open state, and hydrogen gas is released outside the system. - If the pressure after depressurization meets a predetermined condition, the release valve is controlled to a closed state. - Control of the release valve is terminated.

In the hydrogen station of this embodiment shown in FIG. 2, for example, when the pressure value of pressure gauge 61a in flow path 31a exceeds a preset pressure value, it is determined that an abnormal pressure increase has occurred, and release valve 46a is activated. The pressure value criteria for determining that an abnormal pressure increase has occurred are 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 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.

When it is determined that an abnormal pressure increase has occurred, the release valve 46a is controlled to an open state 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.

When the pressure is released by the relief valve, if the pressure after relief satisfies a predetermined condition, the relief valve is controlled to close.

Here, when setting the condition for 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, "inside 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, it refers to the flow path from the compressor 25 to the dispenser unit 14. If pressure control is possible individually for multiple banks, each bank can be considered 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 necessary pressure in the system after depressurization is preset, and 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 that pressure.

As mentioned above, when the set pressure is reached at which the release valve is opened, the pressure after depressurization may be preset based on the temperature and pressure conditions at that time, but the pressure within the hydrogen station system may change due to various factors even while depressurization is being performed by the release valve. For example, when the release valve opens, hydrogen within the system is released to the outside of the system, which causes the volume of the hydrogen to expand, causing the temperature of the system to drop. 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.

If the post-depressurization pressure is set based solely 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.

In order to prevent this, when setting the pressure after depressurization, it is preferable to take into consideration 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 consideration in advance, the temperature and pressure in the system during depressurization may be measured in real time, and the release valve may be closed after confirming that the temperature and pressure in the system reliably satisfy the conditions of the later-described relational formula (1).
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.

When the release valve is closed, the pressure Px after depressurization is preferably 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 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.

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.

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.)

This relational expression (1) is derived from the Boyle-Charles relational expression. Here, the volume V of the target flow path depressurized by the relief valve can be considered to be always constant because the influence of expansion, etc. is slight. If the pressure in the flow path at the highest temperature Tm is equal to the blow-off pressure Pm of the safety valve, the pressure Px after depressurization and the temperatures Tx, Tm, and Pm after depressurization satisfy the following relational expression (2).

Px×V/Tx = Pm×V/Tm (2)

Therefore, from this relational expression (2), Px can be calculated 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.

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 operating pressure of the safety valve (blow-off pressure Pm), the blow-off pressure of the safety valve, and the operating pressure of the diffusion valve (Pd). These pressure values are preset, fixed values. The horizontal axis represents temperature (units are Kelvin (K)), and shows the maximum temperature (Tm) expected to be reached in the flow path of the hydrogen station 1. This value is also a preset, fixed value.
When the temperature in the flow passage of the hydrogen station 1 is Tx, if some factor causes an abnormal pressure rise in the flow passage and the pressure reaches the operating pressure Pd of the relief valve (point _P0 in the graph), the relief valve operates to open and the pressure in the flow passage is released, causing the pressure in the flow passage to drop as shown by the white arrow in the graph. This prevents the pressure in the flow passage from reaching the operating pressure of the safety valve.

Here, let us assume that the release valve is closed when the pressure is only slightly released from that state (point _P1 in the graph). If the temperature in the flow path is maintained below Tx, it will be kept below the release valve operating pressure. However, for example, if the cause of the abnormal pressure rise is a sudden temperature rise, the pressure in the flow path will rise again if the temperature continues to rise even after the release valve has released the pressure (dash line indicated by _L0 in the graph). If this happens, the pressure will again exceed Pd and the release valve will need to be opened and closed again. In addition, if the repeated opening and closing of the release valve cannot keep up with the pressure rise, the pressure in the flow path may reach the safety 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) which 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 shown by the solid line L1 in the graph, the pressure when the maximum attained 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.

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.

When the condition satisfies the above relational expression (1), the release valve is closed and release of pressure 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 be activated.

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 maintained 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.

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 situation is such that 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 that is approximately 10% lower than that.

The operating pressure (blowing pressure) and the closing pressure of the safety valve can be set arbitrarily, so 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 standards.

As an example of the range in which the release valve is controlled, if the safety valve outlet pressure is set at 95 MPa, the outlet pressure is set at 84 MPa, the allowable pressure of the pressure accumulator is set at 85 MPa, and the pressure at the maximum temperature reached in the flow path in the hydrogen station is set at 90 MPa, the condition pressure when the release valve is in the open state can be set at 89 MPa, and the condition pressure when the release valve is in the closed state can be set at 85 MPa.

In this way, by controlling the release valve as described above before the safety valve operates, it becomes easier to maintain a safe pressure in flow paths where abnormal pressure increases are 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.).

Furthermore, the pressure inside the hydrogen station system can increase abnormally when, for example, the outside air temperature is high, causing the temperature of the hydrogen station to rise and the pressure inside the hydrogen station system to increase. In such cases, the temperature can rise suddenly, causing a sudden increase in pressure inside the hydrogen station system. If the pressure inside the hydrogen station system exceeds the set pressure of the release valve, causing the release valve to open and releasing hydrogen from the system to the outside, but the rate at which the hydrogen is released is slower than the rate at which the pressure inside the system is rising, the pressure inside the system will continue to rise, and as long as the release valve is open, it may become necessary to activate the safety valve.

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.

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.

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

In addition, in this embodiment, the operation of each unit and the opening and closing of the valves are controlled by a programmable logic controller (PLC) (not shown) that receives signals from other sensors, such as pressure gauges (not shown).

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 eliminate the abnormal pressure rise that occurs within the hydrogen station.

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.

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, the first valve group consisting of valves 37a, 37b, 37c which open and close the supply of hydrogen gas from the compressor unit 18 to the accumulator unit 19, the second valve group consisting of valves 39a, 39b, 39c which open and close the supply of hydrogen gas from the accumulator unit 19 to the hydrogen gas outlet 34, the third valve group consisting of valves 46a, 46b, 46c which open and close the vent for hydrogen gas in the flow path, and the 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.

As a result, 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. In other words, during manufacturing, valves of the same type can be attached to support members, etc. at the same time within a specified area, improving manufacturability. In addition, when inspecting and maintaining the hydrogen station package unit, valves of the same type can be inspected and maintained at the same time, improving maintainability.

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 composed of multiple banks, a bypass pipe or the like may be provided between the banks so that hydrogen gas in the flow path that has abnormally increased in pressure can flow into a bank that has room to be fully filled, thereby eliminating the abnormal increase in pressure.

In the above embodiment, the hydrogen station 1 is composed of multiple banks, each of which can be individually pressure controlled, and there are cases where abnormal pressure rise occurs only in some of the multiple banks. In the case of three banks, banks 1 to 3, as in the above embodiment, if an abnormal pressure rise occurs in the piping flow path 31c of bank 3, for example, if all banks are in a full pressure state, the only way to release pressure is to open the release valve 46c of bank 3 and release hydrogen to the atmosphere. 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.

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. However, it is necessary for the pressurized bank 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 the opening and closing of the diffusion valve and the opening and closing so as to satisfy the conditions of each bank. When abnormal pressure rise can be eliminated without opening the diffusion 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.

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 depressurizes 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) and the abnormal pressure rise can be eliminated. 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.

The hydrogen pressure control method for a hydrogen station and the hydrogen station of the present invention have been described above using an example of an off-site hydrogen station, but the present invention is not limited to off-site hydrogen stations and can also be used in on-site hydrogen stations and in hydrogen stations other than package units.

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, release valves may be provided at regular intervals, and the release valves may be sequentially opened and closed under specified conditions to control the hydrogen pressure.

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 Accumulator 46 46a 46b 46c Discharge valve 51 51a 51b 51c Safety valve 60 Fuel cell vehicle (FCV)

Claims (7)

A method of controlling hydrogen pressure at a hydrogen station, which is a differential pressure type hydrogen station that pressurizes hydrogen from a hydrogen source using a compressor and stores it in a pressure accumulator, and fills a fuel cell vehicle with hydrogen from the pressure accumulator using a differential pressure, and which is equipped with a safety valve in the flow path of the hydrogen station 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 release valve that can be manually or automatically controlled to switch between the open and closed states, and which is characterized in that the predetermined conditions for switching between the open and closed states of the release 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-off pressure of the safety valve even when the maximum temperature expected for the flow path is reached. 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.) 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 after depressurization (Px) satisfies the relational expression (1) and is higher than the blow-off pressure of the safety valve. The hydrogen pressure control method for a hydrogen station according to any one of claims 1 to 3, wherein when the pressure in the flow path exceeds the predetermined 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 in which the pressure in the flow path would continue to rise if the pressure was not released. 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.) 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. The hydrogen station according to claim 5 or 6, in which when the pressure in the flow path exceeds the predetermined set pressure and the release valve is in an open state, depressurization is controlled at a depressurization speed 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 was not released.

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