JP7449161B2 - Liquefied hydrogen storage method and liquefied hydrogen storage system - Google Patents

Description

The present invention relates to a liquefied hydrogen storage method and a liquefied hydrogen storage system for storing liquefied hydrogen in a liquefied hydrogen tank.

When introducing liquefied hydrogen into a liquefied hydrogen tank, it is first necessary to remove oxygen and moisture from the liquefied hydrogen tank. This process involves lowering the oxygen concentration in the liquefied hydrogen tank sufficiently below the combustion conditions for flammable liquefied hydrogen, and when the temperature inside the liquefied hydrogen tank becomes low due to the introduction of liquefied hydrogen. The purpose is to sufficiently lower the dew point inside the liquefied hydrogen tank to prevent residual water vapor from condensing on the various valves or instruments installed in the liquefied hydrogen tank, causing malfunctions.

Conventionally, liquefied hydrogen is introduced into a liquefied hydrogen tank after the process of removing oxygen and moisture, but since the inside of the liquefied hydrogen tank is at room temperature when introducing liquefied hydrogen, it is not necessary to directly introduce liquefied hydrogen into the liquefied hydrogen tank at room temperature. When liquefied hydrogen is introduced, cracks or deformation may occur in the liquefied hydrogen tank due to local thermal contraction during storage of liquefied hydrogen. Regarding such problems such as cracks or deformation of low-temperature tanks, for example, Patent Document 1 below describes a method for cooling down low-temperature tanks that includes a step of cooling the low-temperature tank with the heat of vaporization of liquefied gas and discharging the vaporized gas. It is disclosed to provide.

Japanese Unexamined Patent Publication No. 54-40327

However, even if the method described above is applied to the introduction of liquefied hydrogen into the liquefied hydrogen tank, even after the introduction of liquefied hydrogen has started, the liquefied hydrogen cannot be kept in the liquefied hydrogen tank until the liquefied hydrogen tank is sufficiently cooled. It cannot be stored and is discharged outside and consumed.

In particular, when attempting to increase the capacity of the liquefied hydrogen tank, the amount of liquefied hydrogen consumed for cooling within the liquefied hydrogen tank increases. Since liquefied hydrogen has a small distribution volume and a high unit price, the conventional method of cooling a liquefied hydrogen tank with liquefied hydrogen cannot reduce costs. Furthermore, since such liquefied hydrogen is flammable, it is desirable to suppress the amount released into the atmosphere.

Therefore, the present invention provides a liquefied hydrogen storage method and a liquefied hydrogen storage system that can reduce the amount of liquefied hydrogen consumed by vaporization when cooling the inside of a liquefied hydrogen tank to a temperature at which liquefied hydrogen is stored. The purpose is to

A liquefied hydrogen storage method according to one embodiment of the present invention is a liquefied hydrogen storage method for storing liquefied hydrogen in a liquefied hydrogen tank, and includes an oxygen removal step of removing oxygen in the liquefied hydrogen tank using nitrogen. , a liquefied hydrogen introduction step of introducing the liquefied hydrogen into the liquefied hydrogen tank from which oxygen has been removed, and before introducing the liquefied hydrogen into the liquefied hydrogen tank, the inside of the liquefied hydrogen tank is cooled in advance.

According to the above method, the inside of the liquefied hydrogen tank is cooled in advance before introducing the liquefied hydrogen into the liquefied hydrogen tank. Therefore, when introducing liquefied hydrogen into the liquefied hydrogen tank, the amount of liquefied hydrogen consumed to cool the liquefied hydrogen tank is reduced. Therefore, when cooling the inside of the liquefied hydrogen tank to a temperature at which liquefied hydrogen is stored, the amount of liquefied hydrogen consumed by vaporization can be reduced.

A liquefied hydrogen storage system according to another aspect of the present invention is a liquefied hydrogen storage system for storing liquefied hydrogen in a liquefied hydrogen tank, and in which oxygen in the liquefied hydrogen tank is removed. a liquefied nitrogen introduction section that introduces liquefied nitrogen into the liquefied hydrogen tank; and a low-temperature gas introduction section that introduces a low-temperature gas obtained by vaporizing the liquefied hydrogen into the liquefied hydrogen tank to remove the liquefied nitrogen introduced into the liquefied hydrogen tank. and a liquefied hydrogen introduction section for introducing the liquefied hydrogen.

According to the above configuration, liquefied nitrogen is introduced to remove oxygen in the liquefied hydrogen tank, thereby removing oxygen in the liquefied hydrogen tank while cooling the inside of the liquefied hydrogen tank with liquefied nitrogen. Therefore, since the inside of the liquefied hydrogen tank is cooled in advance before introducing liquefied hydrogen, consumption of liquefied hydrogen due to vaporization is suppressed when introducing liquefied hydrogen. Further, after oxygen is removed by introducing liquefied nitrogen, and before introducing liquefied hydrogen, nitrogen vaporized during oxygen removal is removed with low-temperature gas. This eliminates the need to use liquefied hydrogen to remove nitrogen, so consumption of liquefied hydrogen can be suppressed. Therefore, when cooling the inside of the liquefied hydrogen tank to a temperature at which liquefied hydrogen is stored, the amount of liquefied hydrogen consumed by vaporization can be reduced.

According to the present invention, it is possible to provide a liquefied hydrogen storage method and a liquefied hydrogen storage system that can appropriately introduce liquefied hydrogen into a liquefied hydrogen tank while suppressing consumption of liquefied hydrogen.

FIG. 1 is a diagram showing a schematic configuration of a liquefied hydrogen storage system according to an embodiment of the present invention. FIG. 2 is a flowchart showing a method for introducing liquefied hydrogen into the system of FIG. FIG. 3 is a diagram showing the flow of the refrigerant introduced into the liquefied hydrogen tank and the gas discharged from the liquefied hydrogen tank according to the flowchart of FIG. 2.

Hereinafter, one embodiment will be described with reference to the drawings. It should be noted that throughout all the figures, the same or corresponding elements are given the same reference numerals and redundant detailed explanations will be omitted.

FIG. 1 is a diagram showing a schematic configuration of a liquefied hydrogen storage system according to an embodiment of the present invention. As shown in FIG. 1, a liquefied hydrogen storage system (hereinafter referred to as a storage system) 100 is a system that stores liquefied hydrogen (hereinafter sometimes referred to as LH ₂ ) in an internal space 13 of a liquefied hydrogen tank 1. . The storage system 100 has a function of removing oxygen and moisture present in the internal space 13 of the liquefied hydrogen tank 1 and cooling the internal space 13 before filling the internal space 13 with liquefied hydrogen.

The liquefied hydrogen tank 1 has a double shell structure to improve heat insulation. The liquefied hydrogen tank 1 has an outer tank 11 and an inner tank 12 that is accommodated in the outer tank 11 and forms an internal space 13 . As an example, the liquefied hydrogen tank 1 (outer tank 11) is formed in a spherical shape, and the inner tank 12 is also formed in a spherical shape. An inter-tank space 14 is formed between the inner surface of the outer tank 11 and the outer surface of the inner tank 12. The inter-tank space 14 is maintained in a vacuum state, and the internal space 13 is vacuum-insulated from the outside of the liquefied hydrogen tank 1 .

Both the outer tank 11 and the inner tank 12 are constructed of pressure walls. For example, the outer tank 11 is configured to have higher pressure resistance than the inner tank 12 in order to withstand the pressure difference between atmospheric pressure and the pressure in the inter-tank space 14 . However, the inner tank 12 may be configured to have higher pressure resistance than the outer tank 11. The inter-tank space 14 may be provided with a plurality of rods (not shown) extending between the inner surface of the outer tank 11 and the outer surface of the inner tank 12 .

The storage system 100 includes a liquefied hydrogen introduction section 2 that introduces liquefied hydrogen (LH ₂ ) into a liquefied hydrogen tank 1 . The liquefied hydrogen introduction section 2 includes a first intake port 21 that draws liquefied hydrogen from the outside, a first discharge port 22 that discharges the drawn liquefied hydrogen in the liquefied hydrogen tank 1, and a liquefied hydrogen introduction pipe 23 that connects them. We are prepared. The first discharge port 22 is provided above the internal space 13 of the liquefied hydrogen tank 1 . The liquefied hydrogen introduction pipe 23 is provided with a first on-off valve 24 that switches between flowing and blocking the flow of liquefied hydrogen.

Furthermore, the storage system 100 includes a low-temperature gas introduction section 3 that introduces low-temperature gas (low-temperature hydrogen gas, hereinafter sometimes referred to as GH ₂ ) obtained by vaporizing liquefied hydrogen into the liquefied hydrogen tank 1. The low-temperature gas introduction section 3 includes a vaporizer 25 that vaporizes liquefied hydrogen drawn through the first intake port 21 . In this embodiment, the low temperature gas generated by the vaporizer 25 is discharged into the liquefied hydrogen tank 1 from the first discharge port 22 . Instead of this, a discharge port exclusively for low temperature gas may be provided. The vaporizer 25 and the first discharge port 22 are connected by a low temperature gas introduction pipe 26. The low-temperature gas introduction pipe 26 is provided with a second on-off valve 27 that switches between flowing and blocking the flow of the low-temperature gas.

Furthermore, the storage system 100 includes a liquefied nitrogen introduction section 4 that introduces liquefied nitrogen (hereinafter sometimes referred to as LN ₂ ) into the liquefied hydrogen tank 1. The liquefied nitrogen introduction section 4 includes a second intake port 28 that draws in liquefied nitrogen from the outside, a second discharge port 29 that discharges the drawn liquefied nitrogen in the liquefied hydrogen tank 1, and a liquefied nitrogen introduction pipe 30 that connects them. It is equipped with The second discharge port 29 is provided at the lower part of the internal space 13 of the liquefied hydrogen tank 1 . The liquefied nitrogen introduction pipe 30 is provided with a third on-off valve 31 that switches between flowing and blocking the flow of liquefied nitrogen.

Furthermore, the storage system 100 includes a first discharge pipe 32 for discharging (exhausting) oxygen and nitrogen gas (GN ₂ ) from the liquefied hydrogen tank 1 in an oxygen removal process to be described later. The first discharge pipe 32 is arranged such that one end is located above the internal space 13 of the liquefied hydrogen tank 1 and the other end is located outside. The first exhaust pipe 32 is provided with a first measuring device (O ₂ sensor) 33 that measures the oxygen concentration within the first exhaust pipe 32 .

Furthermore, the storage system 100 includes a second discharge pipe 34 for discharging (exhausting) nitrogen gas (GN ₂ ) from the liquefied hydrogen tank 1 in a low-temperature gas introduction process to be described later. The second discharge pipe 34 is arranged such that one end is located below the internal space 13 of the liquefied hydrogen tank 1 and the other end is located outside. The second discharge pipe 34 is provided with a second measuring device (H ₂ sensor) 35 that measures the hydrogen gas concentration within the second discharge pipe 34 .

Furthermore, the storage system 100 includes a third discharge pipe 36 for discharging (exhausting) hydrogen gas (GH ₂ ) from the liquefied hydrogen tank 1 in the liquefied hydrogen introduction process described later. The third discharge pipe 36 is arranged such that one end is located below the internal space 13 of the liquefied hydrogen tank 1 and the other end is located outside. Although not shown, each of the discharge pipes 32, 34, and 36 is also provided with an on-off valve. Further, the second discharge pipe 34 and the third discharge pipe 36 may have a piping structure in which a part of the route is a common route, or may be a pipe that is common to each other.

Furthermore, the storage system 100 includes a controller 5. The controller 5 acquires the measurement results from each measuring device 33, 35, and controls the opening/closing of each on-off valve 24, 27, 31 (and each on-off valve of each discharge pipe 32, 34, 36) based on the result. I do. The controller 5 is configured as a processing circuit including a processor, volatile memory, nonvolatile memory, I/O interface, and the like.

FIG. 2 is a flowchart showing a method for introducing liquefied hydrogen into the system of FIG. Moreover, FIG. 3 is a diagram showing the flow of the refrigerant introduced into the liquefied hydrogen tank and the gas discharged from the liquefied hydrogen tank according to the flowchart of FIG. 2. In FIG. 3, of the configurations of the storage system 100 shown in FIG. 1, configurations other than the locations where refrigerant and exhaust gas are introduced in each process (steps S1, S3, and S5, which will be described later) are not shown. There is.

At the start of the liquefied hydrogen storage method in this embodiment, the internal space 13 of the liquefied hydrogen tank 1 is at room temperature and contains air (oxygen, nitrogen, water vapor, etc.). Moreover, the pressure of the internal space 13 is adjusted in advance so that the dew point temperature of the internal space 13 becomes a predetermined value.

First, an oxygen removal process is performed in which oxygen in the liquefied hydrogen tank 1 is removed using nitrogen (step S1). In the oxygen removal process, liquefied nitrogen (LN ₂ ) is introduced from the liquefied nitrogen introducing section 4 to remove (purge) oxygen (O ₂ ) and moisture in the liquefied hydrogen tank 1 . The controller 5 opens the third on-off valve 31 with the first on-off valve 24 and the second on-off valve 27 closed, and supplies liquefied nitrogen from the liquefied nitrogen introduction pipe 30 to the internal space 13 of the liquefied hydrogen tank 1. will be introduced.

By introducing liquefied nitrogen in the oxygen removal step, oxygen in the internal space 13 of the liquefied hydrogen tank 1 is removed while cooling the internal space 13 of the liquefied hydrogen tank 1 with the liquefied nitrogen. The liquefied nitrogen introduced from the lower part of the internal space 13 and the low-temperature nitrogen gas vaporized by cooling the internal space 13 have a higher specific gravity than the residual air (oxygen and nitrogen at room temperature) in the internal space 13, so the internal space It collects from the bottom of 13 and pushes the remaining air upwards. Therefore, residual air is exhausted from the first exhaust pipe 32 provided at the upper part of the internal space 13, and oxygen is efficiently removed.

When the removal of oxygen is completed (the oxygen concentration is less than a predetermined first reference value), the introduced liquefied nitrogen is vaporized by heat exchange (cooling) with the inner space 13. This results in a low-temperature nitrogen gas (GN ₂ ) atmosphere. At this time, the temperature of the internal space 13 becomes the first precooling temperature (for example, about -180° C.) which is higher than the boiling point of nitrogen to some extent.

The controller 5 determines whether the oxygen concentration (O ₂ concentration) measured by the first measuring device 33 has become less than the first reference value (step S2). The first reference value is set to a value when the oxygen concentration in the internal space 13 is sufficiently lower than the combustion conditions for liquefied hydrogen. Note that the combustion conditions for setting the first reference value are determined according to the dew point temperature set in advance in the internal space 13.

If the oxygen concentration measured by the first measuring device 33 is less than the first reference value (Yes in step S2), the process moves to the next step. The next step is a nitrogen removal step in which low-temperature nitrogen gas in the internal space 13 of the liquefied hydrogen tank 1 is removed. In the nitrogen removal process, a low temperature gas (low temperature hydrogen gas: GH _{2 ) obtained by vaporizing liquefied hydrogen (LH 2 )} is introduced into the liquefied hydrogen tank 1 from the low temperature gas introduction part 3 , so that the temperature of the liquefied hydrogen tank 1 is reduced. Nitrogen gas (GN ₂ ) in the internal space 13 is removed (purged) (step S3).

The controller 5 closes the third on-off valve 31 from the state in the oxygen removal process, while opening the second on-off valve 27 to supply low-temperature gas from the low-temperature gas introduction pipe 26 to the internal space 13 of the liquefied hydrogen tank 1. Introduce. The vaporizer 25 vaporizes liquefied hydrogen (LH ₂ ) introduced from the first intake port 21 to generate low-temperature gas (GH ₂ ) at a predetermined temperature.

The temperature of the low-temperature gas is within a predetermined range including the temperature at the end of the oxygen removal step (-180° C. in this embodiment). For example, the temperature of the low temperature gas is set to -180±10°C. As a result, the difference between the temperature during oxygen removal and the temperature during subsequent nitrogen removal becomes small, so that liquefaction or solidification of nitrogen can be prevented while maintaining the cooling state in the liquefied hydrogen tank 1.

The low temperature gas is sprayed from the first discharge port 22 provided at the upper part of the internal space 13 . The low temperature gas (GH ₂ ) introduced from the upper part of the internal space 13 has a lower specific gravity than the residual nitrogen (GN ₂ ) in the internal space 13, so it accumulates in the upper part of the internal space 13 and pushes the residual nitrogen downward. . Therefore, residual nitrogen is discharged from the second discharge pipe 34 provided at the lower part of the internal space 13, and efficient nitrogen removal is performed.

In a state in which nitrogen removal is completed (in a state in which the hydrogen concentration is higher than a predetermined second reference value), the internal space 13 becomes an atmosphere of low-temperature gas (GH ₂ ) introduced into the internal space 13 . At this time, the temperature of the internal space 13 becomes a second precooling temperature (for example, approximately -180°C to -160°C) that is equivalent to or somewhat higher than the temperature at which the low-temperature gas is introduced.

The controller 5 determines whether the hydrogen concentration (H ₂ concentration) measured by the second measuring device 35 has become higher than the second reference value (step S4). The second reference value is set to a value when the nitrogen concentration in the internal space 13 is sufficiently low.

When the hydrogen concentration measured by the second measuring device 35 becomes higher than the second reference value (Yes in step S4), the process moves to the next step. The next step is a liquefied hydrogen introduction step in which liquefied hydrogen (LH ₂ ) is introduced into the internal space 13 of the liquefied hydrogen tank 1 from which oxygen and nitrogen have been removed. In the liquefied hydrogen introduction process, liquefied hydrogen (liquefied hydrogen: LH ₂ ) is introduced into the liquefied hydrogen tank 1 from the liquefied hydrogen introduction part 2, thereby reducing the low temperature gas (GH ₂ ) in the internal space 13 of the liquefied hydrogen tank 1. While removing liquefied hydrogen, liquefied hydrogen is stored in the internal space 13 (step S5).

The controller 5 closes the second on-off valve 27 and opens the first on-off valve 24 from the state in the nitrogen removal process, and supplies liquefied hydrogen ( LH ₂ ) is introduced.

Liquefied hydrogen is sprayed from the first discharge port 22 provided at the upper part of the internal space 13 . The liquefied hydrogen (LH ₂ ) introduced from the upper part of the internal space 13 moves inside the internal space 13 to a temperature near the temperature at which liquefied hydrogen can be stored (the temperature of the boiling point of liquefied hydrogen, i.e. -252.6°C). Further cooling to storage temperature. The residual gas (GH ₂ ) from the previous process is discharged from the third discharge pipe 36 .

By cooling the internal space 13 to a temperature close to the temperature at which liquefied hydrogen can be stored, the liquefied hydrogen is stored in the internal space 13 without being vaporized.

According to the above method, before introducing liquefied hydrogen into the liquefied hydrogen tank 1, the inside of the liquefied hydrogen tank 1 is cooled in advance. Therefore, when introducing liquefied hydrogen into the liquefied hydrogen tank 1, the amount of liquefied hydrogen consumed to cool the liquefied hydrogen tank 1 is reduced. Therefore, when cooling the inside of the liquefied hydrogen tank 1 to a temperature at which liquefied hydrogen is stored, the amount of liquefied hydrogen consumed by vaporization can be reduced. Further, according to the above method, the inside of the liquefied hydrogen tank 1 is cooled in stages, so that local thermal contraction of the liquefied hydrogen tank 1 can be made more difficult to occur.

Furthermore, according to the above method, the inside of the liquefied hydrogen tank 1 is cooled in advance by liquefied nitrogen in the oxygen removal process, so that when liquefied hydrogen is introduced, consumption of liquefied hydrogen by vaporization is suppressed. When using liquefied nitrogen to cool the inside of the liquefied hydrogen tank 1 from room temperature to the first precooling temperature close to the boiling point of liquefied nitrogen, use liquefied hydrogen or low-temperature gas for cooling from room temperature to the first precooling temperature. The cooling efficiency (including the manufacturing cost of the refrigerant) can be made higher than that of the conventional method.

Furthermore, according to the above method, after liquefied nitrogen is introduced in the oxygen removal step, nitrogen vaporized during oxygen removal is further removed using low-temperature gas. Since low-temperature gas obtained by vaporizing liquefied hydrogen is introduced before introducing liquefied hydrogen, a separate step of removing the coolant in the liquefied hydrogen tank 1 after cooling with the low-temperature gas becomes unnecessary. Furthermore, by introducing a low-temperature gas, nitrogen used to remove oxygen in the oxygen removal step can be removed by the low-temperature gas. This eliminates the need to use liquefied hydrogen to remove nitrogen, so consumption of liquefied hydrogen can be suppressed.

Furthermore, when nitrogen is introduced at room temperature to remove oxygen in the liquefied hydrogen tank 1, and then liquefied hydrogen is introduced to remove the nitrogen, as in the conventional case, the liquefied hydrogen tank 1 is filled with nitrogen. There is a risk that some of the nitrogen present may cool rapidly, causing the nitrogen to locally solidify or liquefy. When nitrogen solidifies or liquefies within the liquefied hydrogen tank 1, local thermal contraction of the liquefied hydrogen tank 1 tends to occur at locations where the solidified or liquefied nitrogen occurs. On the other hand, according to the above method, since liquid nitrogen is introduced to remove oxygen in the liquefied hydrogen tank 1, the liquefied hydrogen tank 1 is filled with low-temperature nitrogen gas at the stage where low-temperature gas is introduced. That means you are doing it. Therefore, rapid cooling of nitrogen due to introduction of low-temperature gas can be suppressed, and local solidification or liquefaction of nitrogen can be prevented.

When using liquefied hydrogen (LH ₂ ) to cool the internal space 13 of the liquefied hydrogen tank 1 from room temperature as in the conventional method, the amount of liquefied hydrogen required to cool the internal space 13 to the liquefied hydrogen storage temperature is It increases as the volume of 13 increases. On the other hand, according to the present embodiment, it is thought that the amount of liquefied hydrogen required to cool down to the liquefied hydrogen storage temperature can be suppressed to, for example, about 1/5 of that of the conventional method.

In addition, in this embodiment, the required amount of nitrogen is increased compared to the conventional method, but compared to the production cost and maintenance management cost of liquefied hydrogen (LH ₂ ), the cost of introducing nitrogen (especially liquefied nitrogen) is lower. This makes it possible to reduce the cost of the entire system.

Furthermore, as the liquefied hydrogen tank 1 becomes larger, the amount of liquefied hydrogen (GH ₂ ) released into the atmosphere increases and cannot be ignored using the conventional method. Furthermore, as the liquefied hydrogen tank 1 becomes larger, the above-mentioned problem of solidification or liquefaction of nitrogen becomes more apparent in the conventional method. On the other hand, with the introduction mode of this embodiment, even if the liquefied hydrogen tank 1 becomes large, it is possible to effectively suppress the increase in the amount of hydrogen released into the atmosphere, and also prevent the solidification or liquefaction of nitrogen. can do. Therefore, even if the liquefied hydrogen tank 1 is made larger, an increase in the amount of liquefied hydrogen consumed can be suppressed, and the inside of the liquefied hydrogen tank 1 can be appropriately cooled.

Although the embodiments of the present invention have been described above, the present invention is not limited to the above embodiments, and various improvements, changes, and modifications can be made without departing from the spirit thereof.

For example, in the above embodiment, the liquefied nitrogen introduction pipe 30, the second discharge pipe 34, and the third discharge pipe 36 are provided separately, but it is also possible to share at least two of them. good.

Further, in the above embodiment, the low temperature gas (GH ₂ ) introduced in the nitrogen removal process is generated by vaporizing liquefied hydrogen (LH ₂ ) in the vaporizer 25, but the present invention is not limited to this. For example, when liquefied hydrogen is used as a refrigerant in another facility, the low-temperature gas generated by heat exchange between the liquefied hydrogen and the object to be cooled in that facility is transferred from the low-temperature gas introduction pipe 26 to the internal space 13 of the liquefied hydrogen tank 1. May be introduced.

Further, in the above embodiment, the first measuring device 33 for measuring the oxygen concentration is provided in the first discharge pipe 32, but the first measuring device 33 may be provided in the internal space 13. . Similarly, in the above embodiment, the second measuring device 35 for measuring the hydrogen gas concentration is provided in the second discharge pipe 34, but the second measuring device 35 is not provided in the internal space 13. Good too.

Furthermore, in the above embodiment, liquefied nitrogen (LN ₂ ) is introduced in the oxygen removal step, and low-temperature gas (GH ₂ ) is introduced in the nitrogen removal step (before the liquefied hydrogen introduction step). Although an embodiment has been exemplified in which both of these are implemented, it is also possible to implement only either the introduction of liquefied nitrogen or the introduction of low-temperature gas.

Further, in the above embodiment, a spherical liquefied hydrogen tank 1 is illustrated, but the shape of the liquefied hydrogen tank 1 is not particularly limited, and may be cylindrical, prismatic, or the like. Further, the type of the liquefied hydrogen tank 1 is not particularly limited, and may be, for example, a membrane type, a self-supporting sphere type, or the like.

The present invention is useful for reducing the amount of liquefied hydrogen consumed by vaporization when cooling the inside of a liquefied hydrogen tank to a temperature at which liquefied hydrogen is stored.

1 Liquefied hydrogen tank 2 Liquefied hydrogen introduction section 3 Low temperature gas introduction section 4 Liquefied nitrogen introduction section 100 Liquefied hydrogen storage system

Claims (5)

A liquefied hydrogen storage method for storing liquefied hydrogen in a liquefied hydrogen tank,
an oxygen removal step of introducing liquefied nitrogen into the liquefied hydrogen tank, cooling the inside of the liquefied hydrogen tank in advance, and removing oxygen in the liquefied hydrogen tank;
A liquefied hydrogen storage method comprising : introducing the liquefied hydrogen into the liquefied hydrogen tank from which oxygen has been removed. The liquefied hydrogen storage method according to claim 1, wherein in the liquefied hydrogen introduction step, before introducing the liquefied hydrogen, a low-temperature gas obtained by vaporizing the liquefied hydrogen is introduced. The liquefied hydrogen storage method according to claim 2 , wherein the temperature of the low-temperature gas is within a predetermined range including the temperature at the end of the oxygen removal step. The liquefied hydrogen storage method according to any one of claims 1 to 3 , wherein the liquefied nitrogen is introduced from a lower part of the liquefied hydrogen tank. A liquefied hydrogen storage system for storing liquefied hydrogen in a liquefied hydrogen tank,
a liquefied nitrogen introduction section that cools the inside of the liquefied hydrogen tank in advance and introduces liquefied nitrogen into the liquefied hydrogen tank in order to remove oxygen in the liquefied hydrogen tank;
a low-temperature gas introduction part that introduces low-temperature gas obtained by vaporizing the liquefied hydrogen into the liquefied hydrogen tank in order to remove the liquefied nitrogen introduced into the liquefied hydrogen tank;
A liquefied hydrogen storage system, comprising: a liquefied hydrogen introduction section that introduces the liquefied hydrogen.

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