Boil-off gas storage system

Abstract

This invention provides a boil-off gas storage system that can reliquefy boil-off gas as needed and store it as liquefied hydrogen. [Solution] The boil-off gas storage system comprises: a boil-off gas storage section connected to a liquefied hydrogen dispenser by a recovery line, which stores boil-off gas, which is hydrogen gas sent from the liquefied hydrogen dispenser through the recovery line; a liquefied hydrogen storage section connected to the boil-off gas storage section by a liquefaction line equipped with a hydrogen liquefaction unit that cools the hydrogen gas to produce liquefied hydrogen, which stores the liquefied hydrogen produced by the hydrogen liquefaction unit; and a supply line connecting the liquefied hydrogen storage section to the liquefied hydrogen dispenser. The boil-off gas storage section has a hydrogen storage material capable of storing the boil-off gas.

Description

Technical Field

[0001] The present disclosure relates to a boil-off gas storage system.

Background Art

[0002] Patent Document 1 describes a conventional boil-off gas storage system (in Patent Document 1, a boil-off gas treatment device). The boil-off gas treatment device described in Patent Document 1 includes a storage tank for storing liquefied gas and a treatment tank for recovering boil-off gas generated by heat input to the storage tank. The treatment tank can store boil-off gas until the maximum filling pressure is reached. The treatment tank can send the stored boil-off gas to equipment operating as fuel.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, the boil-off gas treatment device described in Patent Document 1 sends boil-off gas to equipment operating with hydrogen gas as fuel and does not re-liquefy boil-off gas. Therefore, one of the objects of the present disclosure is to provide a boil-off gas storage system that can re-liquefy boil-off gas as needed and store it as liquefied hydrogen.

Means for Solving the Problems

[0005] A boil-off gas storage system according to this disclosure comprises: a boil-off gas storage unit connected to a liquefied hydrogen dispenser by a recovery line for storing boil-off gas, which is hydrogen gas, sent from the liquefied hydrogen dispenser through the recovery line; a liquefied hydrogen storage unit connected to the boil-off gas storage unit by a liquefaction line equipped with a hydrogen liquefaction unit that cools the hydrogen gas to convert it into liquefied hydrogen, for storing the liquefied hydrogen liquefied by the hydrogen liquefaction unit; and a supply line connecting the liquefied hydrogen storage unit to the liquefied hydrogen dispenser, wherein the boil-off gas storage unit has a hydrogen storage material capable of storing the boil-off gas. [Effects of the Invention]

[0006] The above boil-off gas storage system provides a boil-off gas storage system that can reliquefy boil-off gas as needed and store it as liquefied hydrogen. [Brief explanation of the drawing]

[0007] [Figure 1] Figure 1 is a schematic diagram showing the piping system of a boil-off gas storage system according to one embodiment of the present disclosure. [Figure 2] Figure 2 is a schematic cross-sectional view of the boil-off gas storage unit according to the above embodiment. [Figure 3] Figure 3 is a schematic cross-sectional view of a modified boil-off gas storage section. [Modes for carrying out the invention]

[0008] [Description of Embodiments in this Disclosure] Embodiments of the present disclosure will be listed and described first. A boil-off gas storage system according to the present disclosure comprises: a boil-off gas storage unit connected to a liquefied hydrogen dispenser by a recovery line and storing boil-off gas, which is hydrogen gas, sent from the liquefied hydrogen dispenser through the recovery line; a liquefied hydrogen storage unit connected to the boil-off gas storage unit by a liquefaction line equipped with a hydrogen liquefaction unit that cools the hydrogen gas to liquefy hydrogen, and stores the liquefied hydrogen liquefied by the hydrogen liquefaction unit; and a supply line connecting the liquefied hydrogen storage unit to the liquefied hydrogen dispenser. The boil-off gas storage unit has a hydrogen storage material capable of storing the boil-off gas.

[0009] In the boil-off gas storage system of this disclosure, boil-off gas can be stored in a hydrogen storage material, reliquefied by a hydrogen liquefaction device as needed, and stored in a liquefied hydrogen storage unit.

[0010] In the boil-off gas storage system described above, an intermediate tank for pressurizing liquefied hydrogen may be provided in the supply line. In the boil-off gas storage system of this disclosure, pressurizing the liquefied hydrogen in the intermediate tank makes it possible to obtain supercooled liquefied hydrogen, thereby reducing the boil-off gas generated when supplying liquefied hydrogen from a liquefied hydrogen dispenser. Furthermore, by providing an intermediate tank for pressurizing liquefied hydrogen, the operating pressure in the liquefied hydrogen storage section can be reduced, thereby reducing the boil-off gas generated in the liquefied hydrogen storage section.

[0011] In the boil-off gas storage system described above, a storage material cooler may be further provided for cooling the hydrogen storage material to a temperature below the hydrogen inversion temperature. In the boil-off gas storage system of this disclosure, there is no need to cool the boil-off gas to below the inversion temperature separately when reliquefying it, so it can be reliquefied efficiently.

[0012] In the boil-off gas storage system described above, the hydrogen storage material may be a metal-organic structure or a carbon material capable of adsorbing hydrogen gas. The boil-off gas storage system of this disclosure makes it easier to store boil-off gas at low temperatures.

[0013] In the boil-off gas storage system described above, a first supply channel may be further provided connecting the liquefied hydrogen storage unit to the storage material cooler, wherein the storage material cooler may be configured to cool the hydrogen storage material using liquefied hydrogen supplied from the liquefied hydrogen storage unit via the first supply channel. In the boil-off gas storage system of this disclosure, the hydrogen storage material can be cooled using the liquefied hydrogen stored in the liquefied hydrogen storage unit. By cooling the hydrogen storage material, the boil-off gas can be stored at a low temperature, and the boil-off gas can be efficiently reliquefied.

[0014] The boil-off gas storage system further comprises an intermediate tank provided in the supply line for storing pressurized liquefied hydrogen, and a first recovery path connecting the storage material cooler to the intermediate tank, wherein the first recovery path may send hydrogen gas vaporized from the liquefied hydrogen by cooling the hydrogen storage material in the storage material cooler to the intermediate tank. In the boil-off gas storage system of this disclosure, the hydrogen gas generated from the liquefied hydrogen used to cool the hydrogen storage material can be used to pressurize the intermediate tank.

[0015] In the boil-off gas storage system described above, a second supply channel may be further provided connecting the liquefied hydrogen storage unit to the hydrogen liquefier, and the hydrogen liquefier may be configured to cool the hydrogen gas flowing through the liquefaction line using liquefied hydrogen supplied from the liquefied hydrogen storage unit via the second supply channel. In the boil-off gas storage system of this disclosure, the liquefied hydrogen stored in the liquefied hydrogen storage unit is used to liquefy the hydrogen gas, thereby enabling efficient reliquefaction of the boil-off gas.

[0016] In the boil-off gas storage system, an intermediate tank provided in the supply line for storing pressurized liquefied hydrogen, and a second recovery path connecting the hydrogen liquefier to the intermediate tank are further provided. The second recovery path may send the hydrogen gas vaporized from the liquefied hydrogen sent from the liquefied hydrogen storage section to the intermediate tank by cooling the hydrogen gas flowing through the liquefaction line in the hydrogen liquefier. In the boil-off gas storage system of the present disclosure, the hydrogen gas generated from the liquefied hydrogen used in the hydrogen liquefier can be used for pressurizing the intermediate tank.

[0017] In the boil-off gas storage system, the recovery line may have a heat-insulating pipe connecting the liquefied hydrogen dispenser and the boil-off gas storage section. In the boil-off gas storage system of the present disclosure, the boil-off gas flowing from the liquefied hydrogen dispenser to the boil-off gas storage section can be sent to the boil-off gas storage section while maintaining a low temperature, and the boil-off gas can be stored at a low temperature with respect to the hydrogen storage material.

[0018] [Details of Embodiments of the Present Invention] Next, an embodiment of a boil-off gas storage system (hereinafter referred to as BOG storage system 1) according to the present disclosure will be described below with reference to the drawings. In the following drawings, the same or corresponding parts are denoted by the same reference numerals and their descriptions will not be repeated.

[0019] (Outline of the Structure of BOG Storage System 1) FIG. 1 is a diagram schematically showing the piping system of the BOG storage system 1 according to the present embodiment. Referring to FIG. 1, the BOG storage system 1 according to the present embodiment is used by being connected to a liquefied hydrogen dispenser 8, and can recover the boil-off gas generated when supplying liquefied hydrogen to the moving body M1. Further, the BOG storage system 1 according to the present embodiment can reliquefy the recovered boil-off gas and store the reliquefied liquefied hydrogen. In the present disclosure, "liquefied hydrogen" means liquefied hydrogen and is synonymous with "liquid hydrogen".

[0020] Referring to FIG. 1, the BOG storage system 1 according to this embodiment includes a boil-off gas storage section (hereinafter sometimes referred to as the BOG storage section 2), a hydrogen liquefier 4, a liquefied hydrogen storage section 5, a pressurizing device 7, and an intermediate tank 6. The BOG storage section 2 is connected to a liquefied hydrogen dispenser 8 by a recovery line (hereinafter sometimes referred to as the first recovery line LN1). The BOG storage section 2 and the liquefied hydrogen storage section 5 are connected by a liquefaction line LN3. The hydrogen liquefier 4 is provided in the liquefaction line LN3. The liquefied hydrogen storage section 5 is connected to the liquefied hydrogen dispenser 8 by a supply line LN4. The pressurizing device 7 and the intermediate tank 6 are provided in the supply line LN4.

[0021] The moving body M1 moves using liquefied hydrogen as a driving source. The moving body M1 according to this embodiment is a vehicle. Examples of the vehicle include a fuel cell vehicle (FCV; Fuel Cell Vehicle). Examples of the fuel cell vehicle include a passenger car, a truck, a bus, a motorcycle, a tricycle, an agricultural tractor, etc. Further, the moving body M1 is not limited to a vehicle, and may be, for example, a flying body such as a drone or an aircraft, or a ship.

[0022] (Liquefied Hydrogen Dispenser 8) The liquefied hydrogen dispenser 8 is a device that supplies liquefied hydrogen to the moving body M1. Referring to FIG. 1, the liquefied hydrogen dispenser 8 includes a dispenser body 81, a hose 82, and a plug portion 83.

[0023] The liquefied hydrogen sent from the supply line LN4 enters the dispenser body 81 and then is sent to the hose 82. A plug portion 83 is attached to the hose 82. The plug portion 83 is removably connected to the liquefied hydrogen supply port M11 of the moving body M1. When the plug portion 83 is connected to the liquefied hydrogen supply port M11, the liquefied hydrogen is supplied from the dispenser body 81 through the hose 82 and the plug portion 83 to the fuel tank of the moving body M1. By supplying the liquefied hydrogen in a supercooled state in the intermediate tank into the fuel tank, reliquefaction of the gas phase portion in the fuel tank can be expected.

[0024] When supplying fuel to the fuel tank of the mobile unit M1, heat may enter the dispenser body 81, hose 82, plug section 83, the flow path from the liquefied hydrogen supply port M11 to the fuel tank, and at least a portion of the fuel tank, causing some of the liquefied hydrogen to vaporize. Hydrogen gas vaporized by external heat input to liquefied hydrogen is called "boil-off gas." In the liquefied hydrogen dispenser 8, filling it with supercooled liquefied hydrogen produced in the intermediate tank can reduce the generation of boil-off gas during supply, but it cannot be completely eliminated. The generated boil-off gas flows through the liquefied hydrogen dispenser 8 and the first recovery line LN1 to the BOG storage unit 2.

[0025] (Collection line) The recovery line supplies boil-off gas to the BOG storage unit 2. As described above, the recovery line includes a first recovery line LN1 connecting the liquefied hydrogen dispenser 8 and the BOG storage unit 2, and a second recovery line LN2 connecting the liquefied hydrogen storage unit 5 and the BOG storage unit 2.

[0026] The first recovery line LN1 has insulated piping connecting the liquefied hydrogen dispenser 8 and the BOG storage unit 2. The insulated piping is provided along the entire length from the liquefied hydrogen dispenser 8 to the BOG storage unit 2. This suppresses the temperature rise of the boil-off gas between the liquefied hydrogen dispenser 8 and the BOG storage unit 2.

[0027] The second recovery line LN2 sends the boil-off gas generated by the heat input to the liquefied hydrogen storage unit 5 to the BOG storage unit 2. The second recovery line LN2 has piping connecting the liquefied hydrogen storage unit 5 and the BOG storage unit 2. It is preferable that this piping be made of insulated piping, similar to the first recovery line LN1. This suppresses the temperature rise of the boil-off gas between the liquefied hydrogen storage unit 5 and the BOG storage unit 2.

[0028] The insulated piping only needs to suppress the heat input to the boil-off gas flowing through the recovery lines LN1 and LN2; it does not need to provide complete heat shielding. There are no particular restrictions on the insulated piping; for example, it can have an inner pipe through which the boil-off gas flows, an outer pipe concentric with the inner pipe, and an insulating layer provided between the inner and outer pipes. The insulating layer may be formed from a vacuum or from an insulating material such as glass wool. Alternatively, the insulated piping may simply consist of insulating material wrapped around the outer surface of the pipe.

[0029] (BOG Storage Unit 2) The BOG storage unit 2 is equipment for recovering and storing boil-off gas. The BOG storage unit 2 is connected to the liquefied hydrogen dispenser 8 by a first recovery line LN1. As a result, boil-off gas generated in the dispenser body 81, hose 82, plug 83, the flow path from the liquefied hydrogen supply port M11 to the fuel tank, and the fuel tank is collected and recovered in the BOG storage unit 2 via the first recovery line LN1.

[0030] The BOG storage unit 2 is connected to the liquefied hydrogen storage unit 5 by a second recovery line LN2. The boil-off gas generated in the liquefied hydrogen storage unit 5 is collected and recovered in the BOG storage unit 2 via the second recovery line LN2.

[0031] Figure 2 is a schematic cross-sectional view illustrating the specific configuration of the BOG storage unit 2 according to this embodiment. Referring to Figure 2, the BOG storage unit 2 comprises a recovery tank 21 and a hydrogen storage material 22 housed within the recovery tank 21. The recovery tank 21 has an outer tank 212 and an inner tank 211, and an insulating layer 213 located between the outer tank 212 and the inner tank 211. The outer tank 212 and the inner tank 211 are sealed containers. The inner tank 211 is connected to a recovery line (first recovery line LN1, second recovery line LN2), and the boil-off gas flowing through the recovery line flows into the interior of the inner tank 211. The hydrogen storage material 22 is arranged inside the inner tank 211. The insulating layer 213 reduces the conduction of heat from the outside to the inner tank 211. The thermal insulation layer 213 according to this embodiment is a layer consisting of a super-insulation structure that combines a heat shield that reduces the conduction of radiant heat and a vacuum layer, but it is not limited to this, and may be composed of thermal insulation materials such as fibrous thermal insulation materials (glass wool, rock wool, etc.), foamed resin thermal insulation materials (polyurethane resin, phenolic resin, etc.), a vacuum layer, etc.

[0032] The inner tank 211 and outer tank 212 in this embodiment are formed in a horizontal cylindrical shape, but they may also be vertical cylindrical or spherical. The recovery tank 21 does not necessarily have to be a double-walled structure consisting of an inner tank 211 and an outer tank 212.

[0033] The hydrogen storage material 22 is made of a material capable of storing hydrogen gas. The hydrogen storage material 22 according to this embodiment can store hydrogen gas at the temperature supplied from the recovery lines LN1 and LN2. The hydrogen storage material 22 according to this embodiment is placed inside the inner tank 211. When hydrogen gas that flows into the inner tank 211 comes into contact with the hydrogen storage material 22, it is adsorbed onto the hydrogen storage material 22. As a result, the hydrogen gas is stored in the hydrogen storage material 22.

[0034] The amount of hydrogen gas stored (adsorbed) in the hydrogen storage material 22 can be increased by cooling the hydrogen storage material 22. The BOG storage system 1 according to this embodiment includes a storage material cooler 3 for cooling the hydrogen storage material 22. Referring to Figure 2, the storage material cooler 3 has a supply port 31, a discharge port 32, and a cooling pipe 33 connecting the supply port 31 and the discharge port 32. The supply port 31 is connected to a first supply passage 91 which leads to a liquefied hydrogen storage section 5. The discharge port 32 is connected to a first recovery passage 92 which leads to an intermediate tank 6. The cooling pipe 33 is arranged along the inner tank 211. In this embodiment, the cooling pipe 33 is wound along the outer surface of the inner tank 211. The liquefied hydrogen supplied to the supply port 31 cools the hydrogen storage material 22 by passing through the cooling pipe 33 and exchanging heat with the hydrogen storage material 22. At this time, the liquefied hydrogen vaporizes due to the heat received and becomes hydrogen gas, which exits from the discharge port 32, passes through the first recovery path 92, and flows into the intermediate tank 6. In this way, the BOG storage system 1 according to this embodiment can increase the amount of hydrogen gas stored by cooling the hydrogen storage material 22 using the storage material cooler 3 as needed.

[0035] In the BOG storage system 1 according to this embodiment, since the hydrogen gas released from the BOG storage unit 2 is liquefied by the liquefaction line LN3, it is preferable to cool the hydrogen gas to below the hydrogen inversion temperature when storing it. In this embodiment, by keeping the hydrogen storage material 22 in the BOG storage unit 2 below the hydrogen inversion temperature, the hydrogen gas to be stored can be cooled to below the hydrogen inversion temperature. The hydrogen inversion temperature is, for example, -80 degrees Celsius in a 1.0 MPa environment. As a result, when the hydrogen gas is liquefied using the expansion valve 42 in the hydrogen liquefaction unit 4 described later, it can be liquefied by expanding due to the Joule-Thomson effect of the expansion valve, and liquefaction of liquefied hydrogen can be efficiently produced.

[0036] Furthermore, the amount of hydrogen gas stored in the hydrogen storage material 22 can also be increased by increasing the pressure in the inner tank 211. The BOG storage system 1 may have a pressurizer that pressurizes the inside of the inner tank 211. By driving the pressurizer as needed and pressurizing the inside of the inner tank 211, the amount of hydrogen gas stored in the hydrogen storage material 22 can be increased. However, from the viewpoint of handling hydrogen gas, the pressure inside the inner tank 211 may be kept below 1.0 MPa. Based on this, when increasing the amount of hydrogen gas stored in the hydrogen storage material 22, the pressure inside the inner layer should be set to the highest possible pressure within the range of less than 1.0 MPa.

[0037] The hydrogen gas stored in the hydrogen storage material 22 can be released as needed. For example, by opening the on / off valve provided in the liquefaction line LN3 and reducing the pressure in the inner tank 211, the hydrogen gas stored in the hydrogen storage material 22 can be released. This allows the hydrogen gas released from the BOG storage section 2 to flow into the liquefaction line LN3.

[0038] To increase the release rate of hydrogen gas stored in the hydrogen storage material 22, in addition to opening the on / off valve, the temperature of the hydrogen storage material 22 may also be increased. That is, the BOG storage system 1 may have a heater to heat the hydrogen storage material 22. This allows the release rate of hydrogen gas stored in the hydrogen storage material 22 to be increased as needed.

[0039] Preferably, the hydrogen storage material 22 is a material that can adsorb hydrogen gas at a low temperature without raising the hydrogen gas to room temperature. There are no particular restrictions on the hydrogen storage material 22, but examples include carbon materials such as carbon nanotubes and metal-organic frameworks (MOFs). By using carbon materials or metal-organic frameworks as the hydrogen storage material 22, boil-off gas can be stored at a low temperature, and the temperature of the adsorbed boil-off gas can be kept low. Furthermore, when releasing the adsorbed boil-off gas, the boil-off gas can also be kept at a low temperature. Therefore, the energy required for liquefaction can be reduced. The temperature of boil-off gas immediately after generation is around -200°C, but if it flows through piping that does not have an insulating structure, the temperature of the boil-off gas will rise to around room temperature. However, in the BOG storage system 1 according to this embodiment, since insulating piping is used in the recovery line, the temperature rise of the boil-off gas can be reduced, and as a result, the hydrogen storage material 22 can store the boil-off gas at a low temperature. In this disclosure, "low-temperature boil-off gas" means boil-off gas below the hydrogen inversion temperature, and specifically means boil-off gas at -80°C or below.

[0040] (Hydrogen liquefaction unit 4) Referring to Figure 1, the hydrogen liquefier 4 is installed in the liquefaction line LN3 and can cool hydrogen gas to produce liquid hydrogen. The hydrogen liquefier 4 according to this embodiment includes a heat exchanger 41 and an expansion valve 42. It is preferable that insulated piping is used for the piping forming the liquefaction line LN3. This allows for efficient liquefaction of hydrogen gas and reduces the generation of boil-off gas from the liquefied liquid hydrogen.

[0041] The heat exchanger 41 performs heat exchange between hydrogen gas flowing through the liquefaction line LN3 and a fluid flowing from a heat source. The heat exchanger 41 comprises a primary side flow path 411 connected to the heat source and a secondary side flow path 412 connected to the liquefaction line LN3. In this embodiment, the primary side flow path 411 is connected between a second supply path 93 connected to the liquefied hydrogen storage unit 5 and a second recovery path 94 connected to the intermediate tank 6, and uses liquefied hydrogen stored in the liquefied hydrogen storage unit 5 as the heat source. When liquefied hydrogen is supplied to the primary side flow path 411 from the liquefied hydrogen storage unit 5 through the second supply path 93, heat exchange occurs between the liquefied hydrogen flowing through the primary side flow path 411 and the hydrogen gas flowing through the secondary side flow path 412, and the hydrogen gas flowing through the secondary side flow path 412 is cooled. In the primary side flow path 411, the liquefied hydrogen that has received heat partially or completely vaporizes and is sent to the intermediate tank 6 through the second recovery path 94.

[0042] The hydrogen gas cooled in the secondary flow path 412 flows into the expansion valve 42. The expansion valve 42 expands the hydrogen gas exiting the secondary flow path 412 using the Joule-Thomson effect, lowering its temperature and allowing it to liquefy. The liquefied hydrogen liquefied by the expansion valve 42 flows along the liquefaction line LN3 and is sent to the liquefied hydrogen storage unit 5.

[0043] In the hydrogen liquefier 4, if cooling by the heat exchanger 41 is insufficient, the hydrogen gas may be returned to the front of the heat exchanger 41 and cooled again before entering the expansion valve 42. In order to increase the liquefaction rate by the expansion valve 42, a cooling mechanism may be used in addition to the heat exchanger 41. Examples of cooling mechanisms include expansion turbines and magnetic refrigerators. Alternatively, a magnetic refrigerator may be used instead of the expansion valve 42.

[0044] (Liquefied hydrogen storage section 5) The liquefied hydrogen storage unit 5 is equipment capable of storing liquefied hydrogen. The liquefied hydrogen storage unit 5 has at least one liquefied hydrogen tank 51. The liquefied hydrogen tank 51 is a sealed container capable of storing liquefied hydrogen. The liquefied hydrogen storage unit 5 may have a pressure regulating device capable of adjusting the pressure inside the liquefied hydrogen tank 51.

[0045] As described above, the liquefied hydrogen storage unit 5 is connected to the BOG storage unit 2 by a liquefaction line LN3, and is also connected separately to the liquefaction line LN3 by a second recovery line LN2. The liquefied hydrogen storage unit 5 is connected to the heat exchanger 41 by a second supply line 93, and to the storage material cooler 3 by a first supply line 91. Furthermore, the liquefied hydrogen storage unit 5 is connected to the liquefied hydrogen dispenser 8 by a supply line LN4. In the BOG storage system 1 according to this embodiment, as shown in Figure 1, a part of the supply line LN4, a part of the first supply line 91, and a part of the second supply line 93 are shared and branched as appropriate, but each may be piped independently.

[0046] The liquefied hydrogen storage unit 5 can independently supply liquefied hydrogen to the supply line LN4, the first supply channel 91, and the second supply channel 93. The liquefied hydrogen storage unit 5 can supply liquefied hydrogen using the pressure inside the liquefied hydrogen tank 51. The liquefied hydrogen storage unit 5 may supply liquefied hydrogen using only the hydrostatic pressure of the liquefied hydrogen, but if the pressure is insufficient, the inside of the liquefied hydrogen tank 51 may be pressurized using a pressure regulating device.

[0047] There are no particular restrictions on the shape of the liquefied hydrogen tank 51; for example, it can be a horizontal cylindrical shape, a vertical cylindrical shape, a spherical shape, etc.

[0048] (Pressurizing device 7, intermediate tank 6) The supply line LN4 is equipped with a pressurizer 7 and an intermediate tank 6. The intermediate tank 6 temporarily stores liquefied hydrogen when it is supplied to the mobile body M1 by the liquefied hydrogen dispenser 8, and the pressurizer 7 can pressurize the liquefied hydrogen in the intermediate tank 6. By keeping the pressure in the intermediate tank 6 higher than the pressure in the fuel tank of the mobile body M1, liquefied hydrogen can be supplied to the fuel tank of the mobile body M1 from the liquefied hydrogen dispenser 8. In addition, by pressurizing the liquefied hydrogen in the intermediate tank 6, a supercooled state of liquefied hydrogen can be produced. Here, when liquefied hydrogen is pressurized and a certain amount of time has passed, the liquefied hydrogen reaches its saturation temperature, so the temperature of the liquid hydrogen rises. However, it takes time to reach the saturation temperature. Therefore, after pressurizing the liquefied hydrogen, before it reaches the saturation temperature, it is at a temperature lower than the saturation temperature corresponding to that pressure, and becomes supercooled liquefied hydrogen. The pressure in the intermediate tank 6 may be, for example, 1.0 MPa to 3.0 MPa or 1.5 MPa to 2.0 MPa.

[0049] Hydrogen gas flows into the intermediate tank 6 from the first recovery channel 92 and the second recovery channel 94. A third recovery channel 95 is also provided, connecting the BOG storage unit 2 and the intermediate tank 6. Hydrogen gas stored in the hydrogen storage material 22 can be supplied to the intermediate tank 6 via the third recovery channel 95 as needed. Furthermore, hydrogen gas supplied from the pressurizing device 7 flows into the intermediate tank 6. This allows the pressure inside the intermediate tank 6 to be maintained at a high level.

[0050] Pressurization through the first recovery path 92, the second recovery path 94, or the third recovery path 95 (sometimes referred to as first pressurization) can be performed with priority over pressurization using the pressurizing device 7 (sometimes referred to as second pressurization). This allows the system to operate while keeping the pressure in the liquefied hydrogen tank 51 and the recovery tank 21 as low as possible.

[0051] The pressurizing device 7 vaporizes and compresses the liquefied hydrogen flowing through the supply line LN4, and then puts it into the intermediate tank 6, thereby increasing the pressure inside the intermediate tank 6. The pressurizing device 7 is provided in a flow path branched from the supply line LN4 and includes a vaporizer that vaporizes the liquefied hydrogen, and a compressor that pressurizes the hydrogen gas vaporized by the vaporizer. The pressurizing device 7 is configured, for example, to pressurize the pressure inside the intermediate tank 6 to a set pressure by feedback control. However, the compressor is not required.

[0052] As described above, the BOG storage system 1 according to this embodiment can store a large amount of boil-off gas using the hydrogen storage material 22, and can liquefy the stored boil-off gas as needed. Furthermore, the liquefied liquefied hydrogen can be stored in the liquefied hydrogen storage unit 5 and supplied using the liquefied hydrogen dispenser 8 as needed.

[0053] Furthermore, the BOG storage system 1 according to this embodiment can store boil-off gas at a low temperature using the hydrogen storage material 22. Because the boil-off gas stored in the hydrogen storage material 22 is at a low temperature, it can be efficiently liquefied by the hydrogen liquefaction unit 4. The boil-off gas immediately after generation is at about -200°C, and its temperature may rise due to heat input during transport, so the temperature of the boil-off gas during storage is, for example, between -200°C and -80°C.

[0054] Furthermore, in the BOG storage unit 2 according to this embodiment, the storage material cooler 3 can cool the boil-off gas during storage to below the hydrogen inversion temperature. Because the storage material cooler 3 allows the boil-off gas to be stored at a low temperature, re-liquefaction can be performed more efficiently when liquefaction is carried out by the expansion valve 42 in the hydrogen liquefaction unit 4.

[0055] The recovery line has insulated piping connecting the liquefied hydrogen dispenser 8 and the BOG storage unit 2, allowing the boil-off gas to be sent to the BOG storage unit 2 while maintaining its temperature immediately after generation, thus enabling the boil-off gas to be stored at a low temperature. As a result, liquefaction can be performed efficiently when the hydrogen liquefier 4 is used.

[0056] In this embodiment, the BOG storage system 1 is configured such that the storage material cooler 3 and the hydrogen liquefier 4 are cooled using liquefied hydrogen supplied from the liquefied hydrogen storage unit 5. Therefore, the boil-off gas can be efficiently reliquefied.

[0057] The BOG storage system 1 according to this embodiment is configured to send hydrogen gas generated when cooling the storage material cooler 3 and the hydrogen liquefaction unit 4 to the intermediate tank 6. Therefore, the hydrogen gas generated when cooling the storage material cooler 3 and the hydrogen liquefaction unit 4 can be used to pressurize the intermediate tank 6, and supercooled liquefied hydrogen can be supplied by the liquefied hydrogen dispenser 8.

[0058] (modified version) In the above embodiment, the storage material cooler 3 was installed such that the cooling pipe 33 wound around the outer circumference of the inner tank 211. However, as shown in Figure 3, the cooling pipe 33 may be placed inside the inner tank 211. The cooling pipe 33 can directly cool the hydrogen storage material 22 inside the inner tank 211.

[0059] The hydrogen storage material 22 according to the above embodiment is formed from a metal-organic structure or a carbon material, as a material that can adsorb hydrogen gas at low temperatures without raising the hydrogen gas to room temperature. However, the hydrogen storage material 22 according to the present invention may be a hydrogen storage alloy capable of adsorbing boil-off gas at room temperature. Examples of hydrogen storage alloys include magnesium (Mg), titanium (Ti), vanadium (Mg), and lanthanum (La). The boil-off gas recovered by the hydrogen storage alloy may be reliquefied using the liquefied hydrogen stored in the liquefied hydrogen storage section 5, as in the above embodiment. When storing hydrogen gas at room temperature using a hydrogen storage alloy, the hydrogen liquefaction unit 4 may include a compressor for compressing the hydrogen gas, a cooler for cooling the compressed hydrogen gas, and an expansion valve for adiabatically expanding the cooled hydrogen gas.

[0060] The hydrogen liquefaction 4 may also be equipped with a compressor for compressing hydrogen gas and an expansion valve for adiabatically expanding the compressed hydrogen gas, instead of the heat exchanger 41 and expansion valve 42.

[0061] In the BOG storage system 1 according to the above embodiment, insulated piping is used in the recovery line to maintain the temperature of the boil-off gas immediately after its generation to some extent while sending it to the BOG storage section 2, and the boil-off gas is stored in the BOG storage section 2 at a low temperature. However, ordinary piping can also be used in the recovery line instead of insulated piping. In this case, after storing the boil-off gas in the BOG storage section 2, it may be cooled by the storage material cooler 3 and stored as low-temperature boil-off gas.

[0062] In the BOG storage system 1 according to the above embodiment, a pressurizing device 7 and an intermediate tank 6 are provided in the supply line LN4, but a liquid transfer pump may be provided instead of the pressurizing device 7 and intermediate tank 6.

[0063] As methods for pressurizing the intermediate tank 6, we have mentioned a first pressurization through the first recovery path 92, the second recovery path 94, or the third recovery path 95, and a second pressurization by the pressurizing device 7, but pressurization by either one of these methods may be used. In addition, the timing for filling the mobile body M1 with liquefied hydrogen may be predicted by AI based on statistical analysis of past data, and the system may be controlled to switch between the first and second pressurization based on this prediction.

[0064] In the above embodiment, the BOG storage system 1 was described assuming that each element, such as the recovery tank 21, the liquefied hydrogen tank 51, and the intermediate tank 6, is a single unit. However, it may be composed of multiple recovery tanks 21, multiple liquefied hydrogen tanks 51, and multiple intermediate tanks 6.

[0065] The embodiments disclosed herein should be understood to be illustrative in all respects and not restrictive in any way. The scope of the invention is defined by the claims and not by the foregoing description, and all modifications within the meaning and scope of the claims are intended to be included. [Explanation of Symbols]

[0066] 1 BOG storage system, 2 BOG storage section, 21 Recovery tank, 211 Inner tank, 212 Outer tank, 213 Insulation layer, 22 Hydrogen storage material, 3 Storage material cooler, 31 Supply port, 32 Discharge port, 33 Cooling pipe, 4 Hydrogen liquefaction unit, 41 Heat exchanger, 411 Primary flow path, 412 Secondary flow path, 42 Expansion valve, 5 Liquefied hydrogen storage section, 51 Liquefied hydrogen tank, 6 Intermediate tank, 7 Pressurization device, LN1 First recovery line, LN2 Second recovery line, LN3 Liquefaction line, LN4 Supply line, 91 First supply path, 92 First recovery path, 93 Second supply path, 94 Second recovery path, 95 Third recovery path, M1 Mobile unit, M11 Liquefied hydrogen supply port, 8 Liquefied hydrogen dispenser, 81 Dispenser body, 82 Hose, 83 Plug section.

Claims

1. A boil-off gas storage unit is connected to a liquefied hydrogen dispenser by a recovery line and stores boil-off gas, which is hydrogen gas sent from the liquefied hydrogen dispenser through the recovery line. The boil-off gas storage section is connected by a liquefaction line equipped with a hydrogen liquefaction unit that cools hydrogen gas to produce liquid hydrogen, and the liquid hydrogen storage section stores the liquid hydrogen liquefied by the hydrogen liquefaction unit. A supply line connecting the liquefied hydrogen storage unit to the liquefied hydrogen dispenser, Equipped with, The boil-off gas storage unit has a hydrogen storage material capable of storing the boil-off gas. Boil-off gas storage system.

2. The supply line further includes an intermediate tank for pressurizing liquefied hydrogen, The boil-off gas storage system according to claim 1.

3. The system further includes a storage material cooler for cooling the hydrogen storage material to a temperature below the hydrogen inversion temperature. The boil-off gas storage system according to claim 1.

4. The hydrogen storage material is a metal-organic structure or carbon material capable of adsorbing hydrogen gas. The boil-off gas storage system according to claim 3.

5. The system further includes a first supply channel connecting the liquefied hydrogen storage unit to the storage material cooler, The storage material cooler is configured to cool the hydrogen storage material using liquefied hydrogen supplied from the liquefied hydrogen storage unit through the first supply passage. A boil-off gas storage system according to claim 3 or claim 4.

6. An intermediate tank provided in the supply line for containing pressurized liquefied hydrogen, The system further comprises a first recovery path connecting the storage material cooler to the intermediate tank, The first recovery path sends hydrogen gas vaporized from the liquefied hydrogen by cooling the hydrogen storage material in the storage material cooler to the intermediate tank. The boil-off gas storage system according to claim 5.

7. The system further includes a second supply channel connecting the liquefied hydrogen storage unit to the hydrogen liquefaction unit. The hydrogen liquefier is configured to cool the hydrogen gas flowing through the liquefaction line using liquefied hydrogen supplied from the liquefied hydrogen storage unit via the second supply channel. The boil-off gas storage system according to claim 1.

8. An intermediate tank provided in the supply line for containing pressurized liquefied hydrogen, The system further comprises a second recovery path connecting the hydrogen liquefaction unit to the intermediate tank, The second recovery path cools the hydrogen gas flowing through the liquefaction line in the hydrogen liquefier, thereby sending the vaporized hydrogen gas from the liquefied hydrogen storage unit to the intermediate tank. The boil-off gas storage system according to claim 7.

9. The recovery line has insulated piping connecting the liquefied hydrogen dispenser and the boil-off gas storage unit. The boil-off gas storage system according to claim 1.

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