WO2024069967A1 - Liquid hydrogen tank and method for operating same - Google Patents

Abstract

This liquid hydrogen tank comprises: an inner tank in which liquid hydrogen is stored; an outer tank surrounding the inner tank; and a heat-insulating layer disposed in an inter-tank region between the inner tank and the outer tank, the heat-insulating layer covering the outer wall of the inner tank. In the liquid hydrogen tank, during storage when the inter-tank region is filled with hydrogen gas and liquid hydrogen is stored in the inner tank, an inter-tank pressure, which is the pressure in the inter-tank region, is lower than the saturated vapor pressure of hydrogen at a prescribed temperature.

Description

Liquid hydrogen tank and its operating method

This disclosure relates to a liquid hydrogen tank that contains liquid hydrogen.

Conventionally, double-shell tanks have been known as liquefied gas tanks for storing low-temperature liquefied gas, and are equipped with an inner tank and an outer tank surrounding the inner tank, with the inter-tank area between the inner and outer tanks filled with gas. For example, Patent Document 1 discloses a double-shell tank having an inner and outer tank, in which the space between the inner and outer tanks is filled with boil-off gas discharged from the inner tank. In addition, the space between the tanks is packed with insulating material.

International Publication No. 2020/202578

The gas filled between the tanks may condense and liquefy due to pressure fluctuations in the area between the tanks. If the gas between the tanks liquefies, the tank components may fall below their allowable lower limit temperature and be damaged, the insulation material placed between the tanks may deteriorate, or the heat input may increase due to the heat pipe effect.

This disclosure has been made in consideration of the above circumstances, and its purpose is to suppress liquefaction of the gas in the inter-tank region in a liquid hydrogen tank having an inner tank containing liquid hydrogen, an outer tank surrounding the inner tank, and the inter-tank region between the inner tank and the outer tank filled with vaporized liquid hydrogen gas.

In order to solve the above problems, a liquid hydrogen tank according to one aspect of the present disclosure comprises:
an inner tank for accommodating liquid hydrogen;
An outer tank surrounding the inner tank;
a thermal barrier layer disposed in an inter-tank region between the inner tank and the outer tank and covering an outer wall of the inner tank,
During storage, when the inter-cell region is filled with hydrogen gas and the inner tank contains liquid hydrogen, the inter-cell pressure, which is the pressure in the inter-cell region, is lower than the saturated vapor pressure of hydrogen at a specified temperature.

Further, a method for operating a liquid hydrogen tank according to one aspect of the present disclosure is a method for operating a liquid hydrogen tank comprising an inner tank for accommodating liquid hydrogen, an outer tank surrounding the inner tank, and a thermal barrier layer disposed in an inter-tank region between the inner tank and the outer tank and covering an outer wall of the inner tank, the method comprising the steps of:
During storage, when the inter-cell region is filled with hydrogen gas and the inner tank contains liquid hydrogen, the inter-cell pressure, which is the pressure in the inter-cell region, is maintained lower than the saturated vapor pressure of hydrogen at a specified temperature.

According to the present disclosure, in a liquid hydrogen tank having an inner tank containing liquid hydrogen, an outer tank surrounding the inner tank, and the space between the inner and outer tanks filled with vaporized liquid hydrogen gas, liquefaction of the gas in the space between the tanks can be suppressed.

FIG. 1 is a vertical cross-sectional view showing a schematic configuration of a liquid hydrogen tank according to one embodiment of the present disclosure. FIG. 2 is a vertical sectional view showing a schematic configuration of a liquid hydrogen tank according to a modified example.

Next, an embodiment of the present disclosure will be described with reference to the drawings. Fig. 1 is a vertical cross-sectional view showing the schematic configuration of a liquid hydrogen tank 1 according to one embodiment of the present disclosure. The liquid hydrogen tank 1 shown in Fig. 1 is a container that contains cryogenic liquid hydrogen. The liquid hydrogen tank 1 may be a cargo tank that stores liquid hydrogen as cargo, or a fuel tank that stores liquid hydrogen as fuel. The liquid hydrogen tank 1 may be mounted on a ship or a floating structure, or may be installed on land.

The liquid hydrogen tank 1 comprises an inner tank 21 that contains liquid hydrogen L, and an outer tank 22 that surrounds the inner tank 21. However, the liquid hydrogen tank 1 is not limited to being a double-shelled tank, and may be a triple or more multi-shelled tank that comprises at least one tank that surrounds the outer tank 22. Furthermore, if the liquid hydrogen tank 1 is mounted on a ship's hull, the ship's hull may function as the outer tank 22.

The inner tank 21 and the outer tank 22 are spaced apart in the radial direction of the liquid hydrogen tank 1, and an intertank region 23 is provided between the inner tank 21 and the outer tank 22. A thermal barrier layer 24 is disposed in the intertank region 23. The thermal barrier layer 24 covers the outer wall of the inner tank 21 in the intertank region 23. The thermal barrier layer 24 is made of a heat insulating material, and examples of the heat insulating material include a heat insulating panel, a heat insulating sheet, and a fibrous heat insulating material. In this specification, the region between the outer wall of the inner tank 21 and the thermal barrier layer 24 in the intertank region 23 is referred to as the "annular region 25", and the region between the thermal barrier layer 24 and the inner wall of the outer tank 22 is referred to as the thermal barrier outer peripheral region 26. Here, the annular region 25 may be formed by a gap provided between the outer wall of the inner tank 21 and the thermal barrier layer 24, or the annular region 25 may be formed by gaps or holes formed on the surface of the thermal barrier layer 24 facing the outer wall of the inner tank 21.

The inter-tank region 23 is filled with the same type of gas as the vaporized gas of the liquid hydrogen L contained in the inner tank 21, i.e., hydrogen gas G. The hydrogen gas G may be a vaporized gas produced by vaporizing the liquid hydrogen L inside the inner tank 21, or it may be a gas supplied from outside the liquid hydrogen tank 1. When the liquid hydrogen tank 1 is stored with the liquid hydrogen L contained in the inner tank 21, the pressure in the inter-tank region 23 is adjusted so that the hydrogen gas G in the inter-tank region 23 does not liquefy due to condensation.

The interior of the inner tank 21 and the intertank region 23 are independent spaces. On the other hand, the intertank region 23 may be (i) connected to the annular region 25 and the outer periphery region 26 of the thermal insulation layer, or (ii) independent spaces between the annular region 25 and the outer periphery region 26 of the thermal insulation layer. If the thermal insulation layer 24 is an airtight layer, the annular region 25 and the outer periphery region 26 of the thermal insulation layer will be independent spaces between each other. Therefore, the following describes a method of adjusting the pressure in the intertank region 23 of the liquid hydrogen tank 1 during storage in both cases (i) and (ii).

(i) When the annular region 25 and the thermal insulation layer outer peripheral region 26 are in communication, the pressure inside the inner tank 21 is referred to as the "inner tank pressure P1," and the pressure in the inter-tank region 23 is referred to as the "inter-tank pressure P3." Since the annular region 25 and the thermal insulation layer outer peripheral region 26 are in communication, the pressures in these regions are both the inter-tank pressure P3.

At the initial setting when liquid hydrogen L is stored in the liquid hydrogen tank 1, the inner tank 21 is filled with liquid hydrogen L and the inter-tank region 23 is filled with hydrogen gas G so that the inner tank pressure P1 is a predetermined inner tank standard pressure and the inter-tank pressure P3 is a predetermined inter-tank standard pressure.

The liquid hydrogen tank 1 is provided with an inner tank pressure sensor 31 and an inner tank safety valve 32. The inner tank pressure sensor 31 detects the pressure of the gas phase portion of the inner tank 21, i.e., the inner tank pressure P1. The inner tank safety valve 32 is configured to open when the inner tank pressure P1 exceeds a specified inner tank allowable pressure to release the vaporized gas in the inner tank 21 to the outside, so that the inner tank pressure P1 does not exceed a specified inner tank design pressure. The inner tank allowable pressure is equal to or lower than the inner tank design pressure and is sufficiently higher than the inner tank standard pressure.

The liquid hydrogen tank 1 is equipped with a pressure regulating device 3 that adjusts the pressure in the inter-tank region 23. The pressure regulating device 3 adjusts the inter-tank pressure P3 in the liquid hydrogen tank 1 during storage to be lower than the inner tank pressure P1 and lower than the saturated vapor pressure of hydrogen at a specified temperature. The pressure regulating device 3 in this embodiment includes an inter-tank safety valve 33, a connecting pipe 36, and a differential pressure safety valve 35.

The inter-tank safety valve 33 is provided in the outer tank 22 or in a pipe connected to the inter-tank region 23. The inter-tank safety valve 33 is normally closed and opens when the inter-tank pressure P3 exceeds the inter-tank allowable pressure, and corresponds to the first valve in the claims. The inter-tank safety valve 33 is a self-acting automatic valve that operates using the force generated by the fluid pressure, pilot pressure, spring pressure, etc. However, the inter-tank safety valve 33 is not limited to a self-acting automatic valve, and a control valve (i.e., a passive automatic valve) that opens when the inter-tank allowable pressure is exceeded by an actuator controlled by a control device, or a manual valve may be used. When the inter-tank safety valve 33 is opened, the hydrogen gas G in the inter-tank region 23 is released to the outside of the liquid hydrogen tank 1 via the forced exhaust system, and the inter-tank pressure P3 drops to or below the inter-tank allowable pressure. The forced exhaust system may include a compressor that forcibly exhausts hydrogen gas G, a release tower that safely releases hydrogen gas G into the atmosphere, and a hydrogen fuel consuming device that consumes hydrogen gas G as fuel, etc.

The inter-vessel allowable pressure is lower than the inner vessel standard pressure and lower than the saturated vapor pressure of hydrogen at a predetermined temperature. Here, the predetermined temperature is the temperature of the liquid hydrogen contained in the inner vessel 21, the temperature of the inner surface of the inner vessel 21, the outer surface of the inner vessel 21, or the temperature of the hydrogen gas G filled in the inter-vessel region 23, and is not limited to the actually measured temperature, and may be an estimated or set temperature between -259°C and -240°C. The inter-vessel allowable pressure may be set to the expected minimum value of the inner vessel pressure P1. If the inner vessel pressure P1 falls below 0 KPaG, the inter-vessel pressure P3 becomes a negative pressure less than 0 KPaG, so the minimum value of the inner vessel pressure P1 is higher than 0 KPaG, preferably higher than 5 KPaG. In this way, liquefaction due to condensation of the hydrogen gas G in the inter-vessel region 23 is prevented by adjusting the inter-vessel pressure P3 not to exceed the predetermined inter-vessel allowable pressure.

In the above, as shown in FIG. 2, the pressure regulating device 3 may be provided with an on-off valve 37 provided in a pipe or the like connected to the intertank region 23, in addition to the intertank safety valve 33. As a result, the liquid hydrogen tank 1 has two discharge flow paths, a first discharge flow path which is a discharge flow path of hydrogen gas G from the intertank region 23 through the on-off valve 37, and a second discharge flow path which is a discharge flow path of hydrogen gas G from the intertank region 23 through the intertank safety valve 33. The first discharge flow path and the second discharge flow path are preferably independent of each other, and although these flow paths may merge on the way, it is preferable that they are independent of each other at least at the outlet from the intertank region 23. The on-off valve 37 is closed in a normal state, and when it is opened, the hydrogen gas G in the intertank region 23 is released to the outside of the liquid hydrogen tank 1 through the first discharge flow path. The on-off valve 37 may be a manual valve operated by an operator, or a control valve whose opening and closing is controlled by a control device.

When the liquid hydrogen tank 1 has two discharge flow paths from the intertank region 23 as described above, two levels of intertank allowable pressure are provided: a first intertank allowable pressure and a second intertank allowable pressure higher than the first intertank allowable pressure. Both the first intertank allowable pressure and the second intertank allowable pressure are lower than the saturated vapor pressure of hydrogen at a predetermined temperature. The on-off valve 37 is set to open when the intertank pressure P3 exceeds the first allowable pressure, and the intertank safety valve 33 is set to open when the intertank pressure P3 exceeds the second intertank allowable pressure. When the intertank pressure P3 exceeds the first intertank allowable pressure, the on-off valve 37 is first opened and the hydrogen gas G in the intertank region 23 is released to the outside through the first discharge flow path. An intertank pressure sensor 38 for detecting the intertank pressure P3 is provided in the liquid hydrogen tank 1, and an alarm may be issued to notify the pressure detected by the intertank pressure sensor 38 of the first intertank allowable pressure. When the opening of the on-off valve 37 does not cause the inter-tank pressure P3 to fall below the first inter-tank allowable pressure, but the inter-tank safety valve 33 opens if the inter-tank pressure P3 exceeds the second inter-tank allowable pressure. By opening the on-off valve 37 and the inter-tank safety valve 33, hydrogen gas G is released to the outside through the first release flow path and the second release flow path, and the inter-tank pressure P3 falls to below the first inter-tank allowable pressure.

Returning to FIG. 1, the connecting pipe 36 is a pipe that connects the gas phase in the inner tank 21 to the intertank region 23. The differential pressure safety valve 35 is a valve that opens and closes the flow path in the connecting pipe 36, and corresponds to the first valve in the claims. The differential pressure safety valve 35 maintains the differential pressure between the inner tank pressure P1 and the intertank pressure P3 greater than 0 and equal to or less than the differential pressure set value by introducing the vaporized gas of the inner tank 21 into the intertank region 23. For example, the differential pressure safety valve 35 is configured to open while the differential pressure between the inner tank pressure P1 and the intertank pressure P3 exceeds the differential pressure set value, thereby communicating the inner tank 21 and the intertank region 23 via the connecting pipe 36, and introducing the vaporized gas of the inner tank 21 into the intertank region 23. The differential pressure set value is an arbitrary value that suppresses condensation of hydrogen gas G in the intertank region 23. The differential pressure safety valve 35 maintains the pressure difference between the inner tank pressure P1 and the inter-tank pressure P3, thereby keeping the pressure difference between the inter-tank area 23 and the inner tank 21 within an appropriate range and preventing excessive load from being placed on the components of the liquid hydrogen tank 1. Note that the differential pressure safety valve 35 is a self-acting automatic valve that operates based on the pressure difference between the inner tank pressure P1 and the inter-tank pressure P3, but it may also be a control valve that opens when the pressure difference between the inner tank pressure P1 and the inter-tank pressure P3 exceeds a set pressure difference value using an actuator controlled by a control device.

(ii) In the case where the annular region 25 and the thermal barrier outer peripheral region 26 are independent spaces, similarly to the above, the liquid hydrogen tank 1 includes an inner tank pressure sensor 31, an inner tank safety valve 32, and a pressure regulating device 3. The pressure regulating device 3 includes an inter-tank safety valve 33, a connecting pipe 36, and a differential pressure safety valve 35.

In the intertank region 23, the annular region 25 is spatially independent from other regions of the intertank region 23 (i.e., the outer peripheral region 26 of the thermal insulation layer). Here, the pressure in the annular region 25 of the intertank region 23 is referred to as the annular pressure P2, and the pressure in the region of the intertank region 23 other than the annular region 25 (i.e., the outer peripheral region 26 of the thermal insulation layer) is referred to as the intertank pressure P3.

When liquid hydrogen L is not contained in the inner tank 21 or during initial setup, the annular region 25 is filled with hydrogen gas G in advance to achieve the annular standard pressure. The annular pressure P2 becomes lower than the annular standard pressure due to the cold heat of the liquid hydrogen L contained in the inner tank 21 when loaded, but never becomes higher than the annular standard pressure. The annular standard pressure is lower than the saturated vapor pressure of hydrogen at the temperature of the liquid hydrogen contained in the inner tank 21. Here, the temperature of the liquid hydrogen contained in the inner tank 21 is not limited to the actually measured temperature, and may be an estimated or set temperature between -259°C and -240°C. In this way, liquefaction due to condensation of hydrogen gas G in the annular region 25 is prevented by setting the annular standard pressure.

If the inter-tank pressure P3 becomes lower than the annular pressure P2, there is a risk that the thermal insulation layer 24 supported by the inner tank 21 may float up or the support portion may be damaged, so the inter-tank pressure P3 is adjusted to be equal to or higher than the annular pressure P2. As described above, the annular pressure P2 is equal to or lower than the standard annular pressure, so the inter-tank pressure P3 may be adjusted to be equal to or higher than the standard annular pressure. For example, the standard inter-tank pressure is set to a value equal to or higher than the standard annular pressure, and the differential pressure setting value of the differential pressure safety valve 35 is set so that the inter-tank pressure P3 is equal to or higher than the standard annular pressure.

[Summary]
The liquid hydrogen tank 1 according to the first aspect of the present disclosure comprises:
An inner tank 21 in which liquid hydrogen L is contained;
An outer tank 22 surrounding the inner tank 21;
a heat insulating layer 24 disposed in an inter-tank region 23 between the inner tank 21 and the outer tank 22 and covering an outer wall of the inner tank 21;
When the inter-tank region 23 is filled with hydrogen gas G and the inner tank 21 contains liquid hydrogen L during storage, the inter-tank pressure P3, which is the pressure in the inter-tank region 23, is lower than the saturated vapor pressure of hydrogen at a specified temperature.

In the liquid hydrogen tank 1 configured as above, the hydrogen gas G filled in the inter-chamber region 23 can drop to substantially the same temperature as the liquid hydrogen L contained in the inner tank 21. Therefore, if the inter-chamber pressure P3 becomes lower than the saturated vapor pressure at the temperature of the liquid hydrogen L stored in the inner tank 21, the hydrogen gas G in the inter-chamber region 23 may condense. In the liquid hydrogen tank 1 configured as above, the inter-chamber pressure P3 is maintained at a value lower than the saturated vapor pressure of hydrogen at a predetermined temperature so that the hydrogen gas G does not condense and liquefy even if the temperature of the hydrogen gas G in the inter-chamber region 23 drops. Therefore, damage to the tank components caused by liquefaction of the hydrogen gas G in the inter-chamber region 23, deterioration of the thermal insulation layer 24 arranged in the inter-chamber region 23, and an increase in the amount of heat input due to the heat pipe effect can be suppressed.

The liquid hydrogen tank 1 according to the second item is the liquid hydrogen tank 1 according to the first item, in which during storage, the inter-tank pressure P3 is lower than the inner tank pressure P1, which is the pressure of the gas phase portion inside the inner tank 21.

The temperature of the liquid hydrogen L in the inner tank 21 converges to a temperature according to the inner tank pressure P1 (i.e., the saturation temperature of pressure P1). If the inter-tank pressure P3 is equal to or higher than the inner tank pressure P1, the saturation temperature of the hydrogen gas G in the inter-tank region 23 will be equal to or higher than the temperature of the liquid hydrogen L (= the temperature of the inner tank 21), and liquefaction of the hydrogen gas G will occur on the outer surface of the inner tank 21 in the inter-tank region 23. In contrast, in the liquid hydrogen tank 1 according to the present disclosure, by maintaining the inter-tank pressure P3 at a value lower than the inner tank pressure P1, the inter-tank pressure P3 is maintained at a value lower than the saturated vapor pressure at the temperature of the liquid hydrogen L contained in the inner tank 21. Therefore, with the liquid hydrogen tank 1 configured as described above, even if the temperature of the hydrogen gas G in the inter-tank region 23 drops, liquefaction due to condensation of the hydrogen gas G in the inter-tank region 23 is suppressed. This makes it possible to suppress damage to tank components caused by liquefaction of hydrogen gas G in the inter-tank region 23, deterioration of the thermal insulation layer 24 arranged in the inter-tank region 23, and an increase in the amount of heat input due to the heat pipe effect.

The liquid hydrogen tank 1 pertaining to the third item is the liquid hydrogen tank 1 pertaining to the first or second item, in which the predetermined temperature is the temperature of the liquid hydrogen contained in the inner tank 21, the temperature of the inner surface of the inner tank 21, or the temperature of the outer surface of the inner tank 21.

With the liquid hydrogen tank 1 configured as described above, the inter-vessel pressure P3 is maintained at a value lower than the saturated vapor pressure of hydrogen at the temperature of the liquid hydrogen L contained in the inner vessel 21, so that liquefaction due to condensation of the hydrogen gas G can be prevented even if the temperature of the hydrogen gas G filled in the inter-vessel region 23 drops.

The liquid hydrogen tank 1 according to the fourth item is a liquid hydrogen tank 1 according to any one of the first to third items, and is equipped with a pressure adjustment device 3 that adjusts the inter-tank pressure P3.

The liquid hydrogen tank 1 according to the fifth item is the liquid hydrogen tank 1 according to the fourth item, in which the pressure adjustment device 3 has a first valve that releases hydrogen gas G in the inter-tank region 23 to the outside when the inter-tank pressure P3 exceeds a predetermined inter-tank allowable pressure that is lower than the saturated vapor pressure of hydrogen at the temperature of the liquid hydrogen L contained in the inner tank 21.

The liquid hydrogen tank 1 according to the fourth and fifth items can prevent liquefaction of hydrogen gas G in the inter-tank region 23 without relying on the operator's operation. The first valve corresponds to the inter-tank safety valve 33 in the above embodiment.

The liquid hydrogen tank 1 according to the sixth item is a liquid hydrogen tank 1 according to any one of the first to fifth items, in which the inter-tank region 23 includes an airtight annular region 25 filled with hydrogen gas G between the inner tank 21 and the thermal insulation layer 24, and during storage, the pressure P2 of the annular region 25 is lower than the inner tank pressure P1.

As a result, even if the temperature of the hydrogen gas G filled in the annular region 25 drops, the hydrogen gas G can be prevented from condensing and becoming liquefied.

The liquid hydrogen tank 1 according to the seventh item is the liquid hydrogen tank 1 according to the sixth item, in which the pressure P2 in the annular region 25 is lower than the pressure P3 in the inter-vessel region 23 excluding the annular region 25.

This prevents damage to the heat insulating layer 24 and its supporting members, and prevents the heat insulating layer 24 from floating up.

The liquid hydrogen tank 1 according to the eighth item is the liquid hydrogen tank 1 according to the fourth item, in which the pressure adjustment device 3 maintains the differential pressure between the inner tank pressure P1 and the inter-tank pressure P3 at or below a predetermined differential pressure setting value.

In this way, the pressure difference between the inside of the inner tank 21 and the intertank region 23 is managed within the set pressure difference value, thereby preventing damage to the tank components caused by the pressure difference becoming excessive.

The liquid hydrogen tank 1 according to the ninth item is the liquid hydrogen tank 1 according to the eighth item, in which the pressure adjustment device 3 has a connecting pipe 36 that connects the gas phase of the inner tank 21 to the inter-tank region 23, and a second valve that introduces vaporized gas from the gas phase of the inner tank 21 into the inter-tank region 23 through the connecting pipe 36 when the pressure difference between the inner tank pressure P1 and the inter-tank pressure P3 exceeds the set pressure difference value. The second valve corresponds to the differential pressure safety valve 35 in the above embodiment.

In the liquid hydrogen tank 1 configured as described above, the pressure difference between the inside of the inner tank 21 and the inter-tank region 23 is managed without relying on the operation of an operator. In addition, the inter-tank pressure P3 can be adjusted based on the relative relationship between the inner tank pressure P1 and the inter-tank pressure P3 without measuring the pressure of the inter-tank pressure P3.

A method for operating a liquid hydrogen tank 1 according to a tenth aspect of the present disclosure is a method for operating a liquid hydrogen tank 1 comprising an inner tank 21 for accommodating liquid hydrogen L, an outer tank 22 surrounding the inner tank 21, and a thermal barrier layer 24 disposed in an inter-tank region 23 between the inner tank 21 and the outer tank 22 and covering an outer wall of the inner tank 21, comprising:
During storage, when the inter-tank region 23 is filled with hydrogen gas G and the inner tank 21 contains liquid hydrogen L, the inter-tank pressure P3, which is the pressure in the inter-tank region 23, is maintained lower than the saturated vapor pressure of hydrogen at a specified temperature.

The operating method of the liquid hydrogen tank 1 according to the eleventh item is the operating method of the liquid hydrogen tank 1 according to the tenth item, in which, during storage, when the inter-tank pressure P3 exceeds a predetermined inter-tank allowable pressure that is lower than the saturated vapor pressure of hydrogen at a predetermined temperature, hydrogen gas G is released from the inter-tank region 23 to reduce the inter-tank pressure P3 to below the inter-tank allowable pressure.

According to the operating method of the liquid hydrogen tank 1 relating to the tenth and eleventh items, the inter-tank pressure P3 is maintained at a value lower than the saturated vapor pressure of hydrogen at a predetermined temperature, so that liquefaction due to condensation of the hydrogen gas G is suppressed even if the temperature of the hydrogen gas G in the inter-tank region 23 drops. This makes it possible to suppress damage to the tank components caused by liquefaction of the hydrogen gas G in the inter-tank region 23, deterioration of the thermal insulation layer 24 arranged in the inter-tank region 23, and an increase in the amount of heat input due to the heat pipe effect.

The operating method of the liquid hydrogen tank 1 according to the twelfth item is the operating method of the liquid hydrogen tank 1 according to the tenth item, in which, during storage, when the inter-tank pressure P3 exceeds a predetermined first inter-tank allowable pressure that is lower than the saturated vapor pressure of hydrogen at a predetermined temperature, hydrogen gas G is released from the inter-tank region 23 through the first release flow path, and when the inter-tank pressure P3 exceeds a second inter-tank allowable pressure that is lower than the saturated vapor pressure of hydrogen at a predetermined temperature and higher than the first inter-tank allowable pressure, hydrogen gas G is released from the inter-tank region 23 through the first and second release flow paths, thereby lowering the inter-tank pressure P3 to below the first inter-tank allowable pressure. The first release flow path corresponds to the release flow path that releases hydrogen gas G from the inter-tank region 23 through the on-off valve 37 in the above embodiment. The second release flow path corresponds to the release flow path that releases hydrogen gas G from the inter-tank region 23 through the inter-tank safety valve 33 in the above embodiment.

According to the above-mentioned operating method of the liquid hydrogen tank 1, hydrogen gas G can be released from the inter-tank region 23 of the liquid hydrogen tank 1 in two stages: a first stage using the first release flow path, and a second stage using the first and second release flow paths.

The functions performed by the control device described herein may be implemented in a circuitry or processing circuit, including general purpose processors, application specific processors, integrated circuits, ASICs (Application Specific Integrated Circuits), CPUs (Central Processing Units), conventional circuits, and/or combinations thereof, programmed to perform the described functions. Processors include transistors and other circuits and are considered to be circuitry or processing circuitry. A processor may be a programmed processor that executes a program stored in a memory. In this specification, a circuitry, unit, or means is hardware that is programmed to perform or executes the described functions. The hardware may be any hardware disclosed in this specification or any hardware that is programmed to perform or is known to perform the described functions. If the hardware is a processor, which is considered to be a type of circuitry, the circuitry, means, or unit is a combination of hardware and software used to configure the hardware and/or processor.

The foregoing discussion of the present disclosure has been presented for purposes of illustration and description, and is not intended to limit the present disclosure to the form disclosed herein. For example, in the foregoing detailed description, various features of the present disclosure are grouped together in a single embodiment for purposes of streamlining the disclosure, but some of the features may be combined. Additionally, the features included in the present disclosure may be combined into alternative embodiments, configurations, or aspects other than those discussed above.

Claims (12)

an inner tank for accommodating liquid hydrogen;
An outer tank surrounding the inner tank;
a thermal barrier layer disposed in an inter-tank region between the inner tank and the outer tank and covering an outer wall of the inner tank,
during storage in which the inter-chamber region is filled with hydrogen gas and the inner chamber contains liquid hydrogen, an inter-chamber pressure, which is the pressure in the inter-chamber region, is lower than a saturated vapor pressure of hydrogen at a predetermined temperature;
Liquid hydrogen tank. During the storage, the inter-tank pressure is lower than an inner tank pressure which is a pressure of a gas phase portion in the inner tank.
2. The liquid hydrogen tank according to claim 1. the predetermined temperature is a temperature of the liquid hydrogen contained in the inner tank, a temperature of the inner surface of the inner tank, or a temperature of the outer surface of the inner tank;
3. A liquid hydrogen tank according to claim 1 or 2. A pressure adjusting device for adjusting the inter-tank pressure is provided.
A liquid hydrogen tank according to any one of claims 1 to 3. the pressure regulating device has a first valve that releases the hydrogen gas in the inter-cell region to the outside when the inter-cell pressure exceeds a predetermined inter-cell allowable pressure that is lower than a saturated vapor pressure of hydrogen at the predetermined temperature.
5. The liquid hydrogen tank according to claim 4. The inter-vessel region includes an airtight annular region filled with the hydrogen gas between the inner vessel and the thermal barrier layer,
During the storage, the pressure in the annular region is lower than the pressure in the inner vessel.
A liquid hydrogen tank according to any one of claims 1 to 5. During the storage, the pressure in the annular region is lower than the pressure in the inter-vessel region excluding the annular region;
7. The liquid hydrogen tank according to claim 6. The pressure regulating device maintains a pressure difference between the pressure in the inner tank and the pressure between the tanks at a predetermined pressure difference set value or less.
5. The liquid hydrogen tank according to claim 4. the pressure regulating device includes a connecting pipe connecting the gas phase part of the inner tank and the inter-tank region, and a second valve introducing vaporized gas from the gas phase part of the inner tank through the connecting pipe into the inter-tank region when a pressure difference between the inner tank pressure and the inter-tank pressure exceeds the differential pressure setting value.
9. The liquid hydrogen tank according to claim 8. 1. A method for operating a liquid hydrogen tank comprising: an inner tank for accommodating liquid hydrogen; an outer tank surrounding the inner tank; and a thermal barrier layer disposed in an inter-tank region between the inner tank and the outer tank and covering an outer wall of the inner tank, comprising:
During storage in which the inter-chamber region is filled with hydrogen gas and the inner chamber contains liquid hydrogen, an inter-chamber pressure, which is the pressure in the inter-chamber region, is maintained lower than a saturated vapor pressure of hydrogen at a predetermined temperature.
How to operate a liquid hydrogen tank. during the storage, when the inter-cell pressure exceeds a predetermined inter-cell allowable pressure which is lower than the saturated vapor pressure of hydrogen at the predetermined temperature, the hydrogen gas is released from the inter-cell region to reduce the inter-cell pressure to below the inter-cell allowable pressure;
A method for operating a liquid hydrogen tank according to claim 10. during the storage, when the inter-cell pressure exceeds a predetermined first inter-cell allowable pressure that is lower than the saturated vapor pressure of hydrogen at the predetermined temperature, the hydrogen gas is released from the inter-cell region through a first release flow path, and when the inter-cell pressure exceeds a second inter-cell allowable pressure that is lower than the saturated vapor pressure of hydrogen at the predetermined temperature and higher than the first inter-cell allowable pressure, the hydrogen gas is released from the inter-cell region through the first release flow path and the second release flow path, thereby reducing the inter-cell pressure to less than the first inter-cell allowable pressure;
A method for operating a liquid hydrogen tank according to claim 10.

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