Boil-off gas liquefaction system

Abstract

This invention provides a boil-off gas liquefaction system that can reliquefy boil-off gas sent from a liquefied hydrogen dispenser and supply it to the liquefied hydrogen dispenser as liquefied hydrogen when the dispenser is in use. [Solution] The boil-off gas liquefaction system is used in a liquefied hydrogen supply device in which an intermediate tank is provided in the supply line connecting a liquefied hydrogen storage unit that stores liquefied hydrogen to a liquefied hydrogen dispenser that supplies liquefied hydrogen to a recipient, and comprises: a compressor connected to the liquefied hydrogen dispenser by a first line and compressing boil-off gas, which is hydrogen gas sent from the liquefied hydrogen dispenser through the first line; a cooler provided in a second line connecting the compressor and the intermediate tank and cooling the hydrogen gas compressed by the compressor; and an expansion valve provided in the second line on the intermediate tank side of the cooler and liquefying the hydrogen gas cooled by the cooler.

Description

Technical Field

[0001] The present invention relates to a boil-off gas liquefaction system.

Background Art

[0002] Patent Document 1 describes a conventional boil-off gas liquefaction 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. In the treatment tank, boil-off gas can be stored until the maximum filling pressure is reached. The treatment tank can send the stored boil-off gas to facilities operating with 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 facilities operating with hydrogen gas as fuel and cannot be used for devices using liquefied hydrogen as fuel. Therefore, an object of the present disclosure is to provide a boil-off gas liquefaction system that can reliquefy boil-off gas sent from a liquefied hydrogen dispenser and supply it to the liquefied hydrogen dispenser as liquefied hydrogen when using the liquefied hydrogen dispenser.

Means for Solving the Problems

[0005] A boil-off gas liquefaction system according to the present disclosure is a boil-off gas liquefaction system used in a liquefied hydrogen supply device in which an intermediate tank is provided in a supply line connecting a liquefied hydrogen storage unit that stores liquefied hydrogen to a liquefied hydrogen dispenser that supplies liquefied hydrogen to a recipient, and comprises: a compressor connected to the liquefied hydrogen dispenser by a first line for compressing boil-off gas, which is hydrogen gas sent from the liquefied hydrogen dispenser through the first line; a cooler provided in a second line connecting the compressor and the intermediate tank for cooling the hydrogen gas compressed by the compressor; and an expansion valve provided in the second line on the intermediate tank side of the cooler for liquefying the hydrogen gas cooled by the cooler. [Effects of the Invention]

[0006] The above boil-off gas liquefaction system provides a boil-off gas liquefaction system that, when using a liquefied hydrogen dispenser, can reliquefy the boil-off gas sent from the liquefied hydrogen dispenser and supply it to the liquefied hydrogen dispenser 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 liquefaction system according to the first embodiment. [Figure 2] Figure 2 is a schematic cross-sectional view of the intermediate tank according to the above embodiment. [Figure 3] Figure 3 is a schematic diagram showing the piping system of a boil-off gas liquefaction system according to the second embodiment. [Modes for carrying out the invention]

[0008] [Description of Embodiments in this Disclosure] The embodiments of the present disclosure will be listed and described first. The boil-off gas liquefaction system of the present disclosure is a boil-off gas liquefaction system used in a liquefied hydrogen supply device in which an intermediate tank is provided in the supply line connecting a liquefied hydrogen storage unit that stores liquefied hydrogen to a liquefied hydrogen dispenser that supplies liquefied hydrogen to a supply recipient. The boil-off gas liquefaction system comprises: a compressor connected to the liquefied hydrogen dispenser by a first line for compressing boil-off gas, which is hydrogen gas sent from the liquefied hydrogen dispenser through the first line; a cooler provided in a second line connecting the compressor and the intermediate tank for cooling the hydrogen gas compressed by the compressor; and an expansion valve provided in the second line on the intermediate tank side of the cooler for liquefying the hydrogen gas cooled by the cooler.

[0009] In the boil-off gas liquefaction system of this disclosure, boil-off gas sent from a liquefied hydrogen dispenser is liquefied, and the liquefied hydrogen can be stored in an intermediate tank. Therefore, the liquefied hydrogen obtained by liquefying boil-off gas can be supplied to the recipient by the liquefied hydrogen dispenser.

[0010] The boil-off gas liquefaction system described above may further include a recovery tank connected to a recovery path branched from the first line, and a return path that returns the boil-off gas recovered by the recovery tank back to the first line. This configuration allows boil-off gas that cannot be liquefied to be temporarily stored in the recovery tank.

[0011] In the boil-off gas liquefaction system described above, the boil-off gas recovery unit may have a stainless steel container for storing the boil-off gas. With this configuration, there is no need to perform the exothermic reaction of ortho-para conversion when liquefying the boil-off gas, making it easier to achieve efficient hydrogen gas liquefaction. Consequently, the liquefaction rate of the boil-off gas is improved, and the amount of liquefied hydrogen produced per unit time tends to increase. As a result, the amount of electricity required per unit amount of liquefied hydrogen produced (electricity consumption per unit) tends to be reduced.

[0012] In the boil-off gas liquefaction system described above, the cooler has at least one heat exchanger connected to the second line and the first line, and at least one of the heat exchangers may cool the hydrogen gas sent from the compressor using the boil-off gas passing through the first line. With this configuration, the cold energy of the boil-off gas can be used to reliquefy the boil-off gas, improving the liquefaction rate of the boil-off gas and making it easier to increase the amount of liquefied hydrogen produced per unit time. As a result, it is easier to reduce the amount of electricity consumed per unit amount of liquefied hydrogen produced (electricity consumption per unit).

[0013] In the boil-off gas liquefaction system described above, the cooler may further include a branch line in the second line that branches off from the downstream side of at least one of the heat exchangers and is connected to the upstream side of a flow path leading to at least one of the heat exchangers, and a cooling device that lowers the temperature of the hydrogen gas passing through the branch line. This configuration allows the cooler to cool the hydrogen gas supplied from the compressor more effectively.

[0014] In the boil-off gas liquefaction system described above, the discharge section of the second line may be located within the liquid phase of the intermediate tank. This configuration allows for bubbling of the liquid phase in the intermediate tank, making it easier to liquefy the hydrogen gas. Furthermore, because the discharge section of the second line is located within the liquid phase, the liquefaction of hydrogen gas is less affected by the temperature of the gas phase in the intermediate tank. As a result, the boil-off gas liquefaction system makes it easier to improve the liquefaction rate of the boil-off gas and reduce the power consumption per unit area.

[0015] In the boil-off gas liquefaction system described above, the cooler has at least one heat exchanger connected to the second line, and the heat exchanger is connected to a liquefied hydrogen flow path that connects the liquefied hydrogen storage unit to the intermediate tank, and the hydrogen gas passing through the second line may be cooled by the liquefied hydrogen passing through the liquefied hydrogen flow path. With this configuration, the boil-off gas can be reliquefied using the liquefied hydrogen storage unit, while the intermediate tank can be pressurized.

[0016] [Details of Embodiments of the Present Invention] (First Embodiment) Next, a first embodiment of a boil-off gas liquefaction system according to the present disclosure (hereinafter referred to as the BOG liquefaction system 10) 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 description will not be repeated.

[0017] (Outline of BOG Liquefaction System 10) FIG. 1 is a diagram schematically showing the piping system of the BOG liquefaction system 10 according to the present embodiment. Referring to FIG. 1, the BOG liquefaction system 10 according to the present embodiment is used in addition to the liquefied hydrogen supply device 9, so that the boil-off gas generated when supplying liquefied hydrogen to the supply target can be liquefied during the supply of liquefied hydrogen to the supply target and the liquefied liquefied hydrogen can be returned to the liquefied hydrogen supply device 9 again. In the present disclosure, "liquefied hydrogen" means liquefied hydrogen and is synonymous with "liquid hydrogen".

[0018] (Liquefied Hydrogen Supply Device 9) The liquefied hydrogen supply device 9 is a device for supplying liquefied hydrogen to a supply target. Referring to FIG. 1, the liquefied hydrogen supply device 9 includes a liquefied hydrogen storage unit 91, a liquefied hydrogen dispenser 94, an intermediate tank 92, and a liquid transfer device 93.

[0019] The supply target is an object to which liquefied hydrogen is supplied by the liquefied hydrogen dispenser 94. Examples of the supply target include a moving body, a stationary tank, and a portable container. In the present embodiment, as an example of the supply target, the moving body M1 will be described.

[0020] The moving body M1 moves using liquefied hydrogen as a drive source. The moving body M1 according to the present 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 two-wheeled vehicle, a three-wheeled vehicle, an agricultural tractor, and the like. 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.

[0021] The liquefied hydrogen storage unit 91 is a facility capable of storing liquefied hydrogen. The liquefied hydrogen storage unit 91 has at least one liquefied hydrogen tank 911. The liquefied hydrogen tank 911 is a sealed container and can store liquefied hydrogen. The liquefied hydrogen storage unit 91 may have a pressure adjustment device capable of adjusting the pressure inside the liquefied hydrogen tank 911.

[0022] The liquefied hydrogen storage unit 91 is connected to the liquefied hydrogen dispenser 94 by a supply line LN3, and liquefied hydrogen can be sent along the supply line LN3. The liquefied hydrogen storage unit 91 can send liquefied hydrogen to the intermediate tank 92 by utilizing the pressure inside the liquefied hydrogen tank 911. The liquefied hydrogen storage unit 91 may send liquefied hydrogen only by the head pressure of the liquefied hydrogen stored in the liquefied hydrogen tank 911, but when the pressure is insufficient, the inside of the liquefied hydrogen tank 911 may be pressurized by a pressure adjustment device.

[0023] The liquefied hydrogen dispenser 94 supplies liquefied hydrogen to the moving body M1. The liquefied hydrogen dispenser 94 includes a dispenser main body 941, a hose 942, and a plug portion 943. The liquefied hydrogen sent from the supply line LN3 is supplied to the dispenser main body 941 and then sent to the hose 942. A plug portion 943 is attached to the hose 942. The plug portion 943 is removably connected to the liquefied hydrogen supply port M11 of the moving body M1. When the plug portion 943 is connected to the liquefied hydrogen supply port M11, the liquefied hydrogen is supplied from the dispenser main body 941 through the hose 942 and the plug portion 943 to the fuel tank of the moving body M1.

[0024] The intermediate tank 92 can pressurize the liquefied hydrogen supplied from the liquefied hydrogen storage unit 91 and send the pressurized liquefied hydrogen to the liquefied hydrogen dispenser 94. Pressurizing the liquefied hydrogen in the intermediate tank 92 makes it easier to raise the saturation temperature and make it easier to supercool the liquefied hydrogen. By sending the supercooled liquefied hydrogen (sometimes called supercooled liquefied hydrogen) to the liquefied hydrogen dispenser 94, the supercooled liquefied hydrogen being supplied from the liquefied hydrogen dispenser 94 to the mobile unit M1 makes it easier to liquefy the gas phase portion in the fuel tank of the mobile unit M1. By supplying supercooled liquefied hydrogen to the liquefied hydrogen dispenser 94, the amount of liquefied hydrogen being supplied to the recipient can be improved.

[0025] In the intermediate tank 92, when liquefied hydrogen is pressurized and a certain amount of time has passed, the temperature of the liquid hydrogen rises as it reaches its saturation temperature. At this time, it takes a considerable amount of time to reach the saturation temperature. Therefore, after pressurizing the liquefied hydrogen, before it reaches the saturation temperature, it becomes a state where the temperature is lower than the saturation temperature corresponding to that pressure, that is, it is supercooled liquefied hydrogen. The intermediate tank 92 can supply this supercooled liquefied hydrogen to the liquefied hydrogen dispenser 94.

[0026] The intermediate tank 92 can be pressurized by supplying vaporized hydrogen gas through the heat exchangers 3, 4, and 5 in the BOG liquefaction system 10. The pressure in the intermediate tank 92 may be, for example, between 0.1 MPa and 3.0 MPa, or between 0.3 MPa and 1.5 MPa. For example, if the liquid delivery device 93 is a pressurizing pump, the pressure in the intermediate tank 92 may be between 0.3 MPa and 0.6 MPa. If the liquid delivery device 93 is a vacuum pipe, the pressure in the intermediate tank 92 may be 1.0 MPa or higher. The structure of the intermediate tank 92 will be described in detail later.

[0027] The liquid transfer device 93 is installed in the supply line LN3 between the intermediate tank 92 and the liquefied hydrogen dispenser 94. The liquid transfer device 93 can transfer the liquefied hydrogen in the intermediate tank 92 to the liquefied hydrogen dispenser 94. The liquid transfer device 93 may include, for example, a pressure pump (e.g., a vacuum pump) and vacuum piping.

[0028] When the liquefied hydrogen dispenser 94 supplies liquefied hydrogen to the fuel tank of the mobile unit M1, heat may enter the dispenser body 941, hose 942, plug section 943, 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. The hydrogen gas vaporized by external heat input to the liquefied hydrogen is called "boil-off gas." By generating supercooled liquefied hydrogen in the intermediate tank 92, the generation of boil-off gas during supply by the liquefied hydrogen dispenser 94 can be reduced, but it cannot be completely eliminated. The generated boil-off gas flows from the liquefied hydrogen dispenser 94 to the BOG liquefaction system 10.

[0029] (BOG liquefaction system 10) The BOG liquefaction system 10 comprises a compressor 2, a cooler R1, an expansion valve 71, and a boil-off gas recovery unit (hereinafter referred to as the BOG recovery unit 1). The compressor 2 is connected to the liquefied hydrogen dispenser 94 by a first line LN1 and to the intermediate tank 92 by a second line LN2. Hydrogen gas supplied through the first line LN1 is converted into high-temperature, high-pressure hydrogen gas by the compressor 2. The compressor 2 according to this embodiment is a boil-off gas compressor, which can input low-temperature boil-off gas while maintaining its low temperature and compress it to a desired pressure. There are no particular limitations on the compressor 2, and examples include a reciprocating compressor (reciprocating air compressor), a turbo compressor, and an oil-free compressor.

[0030] (Cooler R1) A cooler R1 is provided in the second line LN2. The cooler R1 can cool the high-temperature, high-pressure hydrogen gas flowing through the second line LN2. The cooler R1 in this embodiment comprises a plurality of heat exchangers 3, 4, and 5, and an expansion turbine 70.

[0031] The cooler R1 according to this embodiment includes a plurality of heat exchangers 3, 4, and 5, namely a first heat exchanger 3, a second heat exchanger 4, and a third heat exchanger 5. The first heat exchanger 3, the second heat exchanger 4, and the third heat exchanger 5 are arranged in this order along the second line LN2. Each of the plurality of heat exchangers 3, 4, and 5 has a primary side flow path on the heat source side that supplies cold energy, and a secondary side flow path that is cooled by the cold energy. At least one of the primary side flow paths in the plurality of heat exchangers 3, 4, and 5 is connected to the first line LN1 and can pass boil-off gas. The secondary side flow paths in the plurality of heat exchangers 3, 4, and 5 are connected to the second line LN2 and can pass hydrogen gas sent from the compressor 2.

[0032] (1st heat exchanger 3) The first heat exchanger 3 comprises a first heat exchanger first channel 31, a first heat exchanger second channel 32, and a first heat exchanger third channel 33. The first heat exchanger first channel 31 and the first heat exchanger third channel 33 are primary channels, and the first heat exchanger second channel 32 is a secondary channel. The first heat exchanger first channel 31 is connected to the first line LN1. The first heat exchanger second channel 32 is connected to the second line LN2. The first heat exchanger third channel 33 is connected to a liquefied hydrogen channel 84 that connects the liquefied hydrogen storage section 91 to the intermediate tank 92. With this configuration, the first heat exchanger 3 can cool the hydrogen gas sent from the compressor 2 using the cold energy of liquefied hydrogen and boil-off gas.

[0033] The entry temperature T13 of the third flow path 33 of the first heat exchanger is lower than the entry temperature T12 of the second flow path 32 of the first heat exchanger. The entry temperature T13 of the third flow path 33 of the first heat exchanger may be less than or equal to the entry temperature T11 of the first flow path 31 of the first heat exchanger, or it may be less than or equal to (temperature T12 + temperature T33) / 2. In this disclosure, "entry temperature" means the temperature of the fluid immediately before it enters a flow path connected to equipment such as a heat exchanger.

[0034] (Second heat exchanger 4) The second heat exchanger 4 comprises a second heat exchanger first channel 41, a second heat exchanger second channel 42, a second heat exchanger third channel 43, and a second heat exchanger fourth channel 44. The second heat exchanger first channel 41, second heat exchanger second channel 42, and second heat exchanger fourth channel 44 are primary side channels, and the second heat exchanger third channel 43 is a secondary side channel. The second heat exchanger first channel 41 is connected to the recovery path 12 (referred to as the first recovery path 121) in the BOG recovery unit 1. The second heat exchanger second channel 42 is connected to the first line LN1. The second heat exchanger third channel 43 is connected to the second line LN2. The second heat exchanger fourth channel 44 is connected to the liquefied hydrogen channel 84. With this configuration, the second heat exchanger 4 can cool the hydrogen gas sent from the compressor 2 using the cold energy of liquefied hydrogen and boil-off gas.

[0035] In this embodiment, a flow control valve 123 is provided in the first recovery path 121. The flow control valve 123 is located upstream of the second heat exchanger 4 in the first recovery path 121. In the first recovery path 121, the temperature of the boil-off gas after passing through the flow control valve 123 tends to be lower than the temperature of the boil-off gas before entering the flow control valve 123. Therefore, the second heat exchanger 4 can more effectively cool the hydrogen gas passing through the second line LN2.

[0036] Furthermore, in the first line LN1, a branch line 8 is connected between the third heat exchanger 5 and the second heat exchanger 4. Some of the hydrogen gas whose temperature has been lowered by the expansion turbine 70 (described later) flows in through the branch line 8. As a result, the temperature of the hydrogen gas entering the second flow path 42 of the second heat exchanger tends to be lower. Therefore, the second heat exchanger 4 can more effectively cool the hydrogen gas passing through the second line LN2.

[0037] The entry temperature T23 of the third flow path 43 of the second heat exchanger is higher than the entry temperature T21 of the first flow path 41 of the second heat exchanger, the entry temperature T22 of the second flow path 42 of the second heat exchanger, and the entry temperature T24 of the fourth flow path 44 of the second heat exchanger. Temperature T24 may be lower than each of temperatures T21 and T22, but it may be higher than each of temperatures T21 and T22 as long as it is lower than temperature T23.

[0038] (Third heat exchanger 5) The third heat exchanger 5 comprises a third heat exchanger first channel 51, a third heat exchanger second channel 52, and a third heat exchanger third channel 53. The third heat exchanger first channel 51 and the third heat exchanger third channel 53 are primary channels, and the third heat exchanger second channel 52 is a secondary channel. The third heat exchanger first channel 51 is connected to the first line LN1. The third heat exchanger second channel 52 is connected to the second line LN2. The third heat exchanger third channel 53 is connected to the liquefied hydrogen channel 84 and is configured to allow liquefied hydrogen to pass through. With this configuration, the third heat exchanger 5 can cool the hydrogen gas sent from the compressor 2 using the cold energy of liquefied hydrogen and boil-off gas.

[0039] In this embodiment, a pressure reducing valve 81 is provided between the first flow path 51 of the third heat exchanger and the liquefied hydrogen dispenser 94 in the first line LN1. The boil-off gas supplied from the liquefied hydrogen dispenser 94 is approximately -160°C, which is below the hydrogen inversion temperature. Therefore, the temperature of the boil-off gas passing through the first line LN1 is reduced by the pressure reducing valve 81. Consequently, the third heat exchanger 5 can more effectively cool the hydrogen gas passing through the second line LN2.

[0040] The entry temperature T32 of the second flow path 52 of the third heat exchanger is higher than the entry temperature T31 of the first flow path 51 of the third heat exchanger and the entry temperature T33 of the third flow path 53 of the third heat exchanger. Temperature T33 may be less than or equal to temperature T31, or less than or equal to (temperature T31 + temperature T32) / 2.

[0041] (Expansion Turbine 70) The expansion turbine 70 is located in the second line LN2, between the second heat exchanger 4 and the third heat exchanger 5. The hydrogen gas cooled by the second heat exchanger 4 is further cooled by adiabatic expansion in the expansion turbine 70, making it more likely to become supercritical hydrogen gas. However, the hydrogen gas that has passed through the expansion turbine 70 does not necessarily have to be in a supercritical state.

[0042] The hydrogen gas that has passed through the expansion turbine 70 returns to the first line LN1 through a branching channel 8, and another portion enters the third heat exchanger 5 along the second line LN2. A cooling device 82 is provided in the branching channel 8. The branching channel 8 branches off from between the second heat exchanger 4 and the third heat exchanger 5 in the second line LN2 and connects between the third heat exchanger 5 and the second heat exchanger 4 in the first line LN1.

[0043] The cooling device 82 reduces the temperature of the hydrogen gas passing through the branch line 8. Examples of the cooling device 82 include a pressure reducing valve and an expansion turbine. In this embodiment, the cooling device 82 is located immediately after the expansion turbine 70, and since the inlet temperature to the cooling device 82 is below the hydrogen reversal temperature, a pressure reducing valve is used.

[0044] The hydrogen gas that enters the first line LN1 via the branching path 8 mixes with the boil-off gas passing through the first line LN1, lowering its temperature. As a result, the hydrogen gas supplied from the compressor 2 can be cooled more effectively in the second heat exchanger 4 and the first heat exchanger 3, making it easier to miniaturize the second heat exchanger 4 and the first heat exchanger 3. Furthermore, because the hydrogen gas supplied from the compressor 2 can be cooled effectively, the input temperature of the expansion turbine 70 in the second line LN2 can be lowered compared to when the branching path 8 is not provided. As a result, the hydrogen gas that has passed through the expansion turbine 70 is more likely to reach a supercritical state. Consequently, the BOG liquefaction system 10 according to this embodiment makes it easier to improve the liquefaction rate of the boil-off gas and reduce the power consumption per unit (energy consumption).

[0045] (Expansion valve 71) In the second line LN2, the hydrogen gas, which has undergone adiabatic expansion by the expansion turbine 70 and then cooled by the third heat exchanger 5, enters the expansion valve 71. The expansion valve 71 lowers the temperature of the hydrogen gas by expanding it using the Joule-Thomson effect, allowing it to be liquefied in the intermediate tank 92. The liquefied hydrogen is stored in the intermediate tank 92. Some of the hydrogen gas that was not liquefied by the expansion valve 71 is returned to the first line LN1 via the BOG liquefaction return path 921 after passing through the gas phase in the intermediate tank 92.

[0046] (BOG recovery unit 1) The BOG recovery unit 1 temporarily recovers boil-off gas from the first line LN1 that exceeds the amount of boil-off gas that can be liquefied. The BOG recovery unit 1 includes a plurality of recovery paths 12, including the first recovery path 121 described above, a recovery tank 11, and a return path 13.

[0047] Multiple recovery paths 12 connect the first line LN1 and the recovery tank 11. The BOG recovery unit 1 includes the first recovery path 121 and the second recovery path 122 as multiple recovery paths 12. The first recovery path 121 branches off from the first line LN1 and is connected to the recovery tank 11 via the second heat exchanger first flow path 41 of the second heat exchanger 4. The second recovery path 122 branches off from the first line LN1 and is connected to the recovery tank 11.

[0048] The first recovery channel 121 is not connected to the primary side flow path of the third heat exchanger 5. From the viewpoint of liquefaction, it is preferable for the hydrogen gas exiting the secondary side flow path of the third heat exchanger 5 (third heat exchanger second flow path 52) to cool to a supercooled temperature, but the boil-off gas passing through the first recovery channel 121 is at a temperature higher than the supercooled state. Therefore, by not connecting the first recovery channel 121 to the primary side flow path of the third heat exchanger 5, the liquefaction rate can be increased.

[0049] Furthermore, the first recovery channel 121 is not connected to the primary flow path of the first heat exchanger 3. If the first recovery channel 121 were connected to the primary flow path of the first heat exchanger 3, the boil-off gas entering the first heat exchanger 3 would exchange heat with the high-temperature, high-pressure hydrogen gas flowing through the second line LN2 in the first heat exchanger 3, and with its temperature raised to approximately room temperature, it would flow from the first recovery channel 121 into the recovery tank 11. Therefore, by not connecting the first recovery channel 121 to the primary flow path of the first heat exchanger 3, the reduction in the amount of boil-off gas recovered in the recovery tank 11 can be mitigated.

[0050] A flow control valve 123 is provided in the first recovery channel 121 upstream of the second heat exchanger 4. The flow control valve 123 can adjust the flow rate of the boil-off gas flowing through the first recovery channel 121 by adjusting the throttling amount. In addition to lowering the temperature of the boil-off gas, the flow control valve 123 can also adjust the amount of boil-off gas liquefied and the amount of hydrogen gas recovered in the recovery tank 11.

[0051] Each of the first recovery path 121 and the second recovery path 122 is provided with an on-off valve 124. The on-off valve 124 can switch between closing and allowing the flow of boil-off gas in each of the first recovery path 121 and the second recovery path 122. The on-off valve 124 is, for example, a solenoid valve. The on-off valve 124 can, as needed, switch between recovering boil-off gas from the recovery tank 11 through the flow control valve 123 or recovering boil-off gas without passing it through the flow control valve 123.

[0052] The recovery tank 11 stores the boil-off gas. Examples of recovery tanks 11 include a hollow stainless steel container and a container containing a hydrogen storage material (e.g., hydrogen storage alloy, MOF, carbon nanotube). By using a container containing a hydrogen storage material as the recovery tank 11, the amount of boil-off gas that can be stored can be increased. However, when a container containing a hydrogen storage material is used, the boil-off gas undergoes para-orthoconversion during storage and is converted to normal hydrogen. When reliquefying normal hydrogen, ortho-paraconversion is necessary, but since ortho-paraconversion is an exothermic reaction, the efficiency of reliquefaction decreases. Therefore, if it is desired to improve the efficiency of boil-off gas reliquefaction, a hollow stainless steel container (i.e., a stainless steel container without a hydrogen storage material) may be used as the recovery tank 11.

[0053] The boil-off gas recovered by the recovery tank 11 is returned to the first line LN1 via the return path 13. The return path 13 is equipped with an on / off valve 124. By switching the on / off valve 124 open or closed as needed, a desired amount of hydrogen gas can be returned to the first line LN1 from the boil-off gas recovered in the recovery tank 11.

[0054] (Details of the structure of the intermediate tank 92) Next, the structure of the intermediate tank 92 will be described. Figure 2 is a schematic cross-sectional view illustrating the internal structure of the intermediate tank 92. Referring to Figure 2, the discharge section 841 formed at the downstream end of the liquefied hydrogen flow path 84 is located inside the lower part of the intermediate tank 92. As a result, the discharge section 841 of the liquefied hydrogen flow path 84 is located within the liquid phase of the intermediate tank 92. In this disclosure, "lower part of the intermediate tank 92" means the area below the vertical center of the intermediate tank 92, and "upper part of the intermediate tank 92" means the area above the vertical center of the intermediate tank 92. The liquefied hydrogen flowing through the liquefied hydrogen flow path 84 vaporizes and changes into hydrogen gas as it passes through the third heat exchanger 5, the second heat exchanger 4, and the first heat exchanger 3. Therefore, by discharging hydrogen gas into the liquid phase from the discharge section 841 of the liquefied hydrogen flow path 84, the liquefied hydrogen in the intermediate tank 92 can be bubbled and the inside of the intermediate tank 92 can be pressurized. This makes it easier to maintain a saturated state in the gas phase within the intermediate tank 92.

[0055] A pressurizing pipe 87 is connected to the intermediate tank 92. The pressurizing pipe 87 supplies hydrogen gas into the intermediate tank 92 to pressurize it. In this embodiment, the pressurizing pipe 87 is connected to the top of the intermediate tank 92 (in this case, the top surface). As a result, the discharge portion 871 of the pressurizing pipe 87 is located in the gas phase. The pressurizing pipe 87 is not limited to the top surface; it may also be connected to the side wall of the intermediate tank 92.

[0056] The pressurized pipe 87 may be connected to a vaporizer that vaporizes liquefied hydrogen, or it may be branched off from the liquefied hydrogen flow path 84. The vaporizer may be configured to take liquefied hydrogen stored in the intermediate tank 92 and vaporize it, or it may be configured to take liquefied hydrogen from the liquefied hydrogen tank 911 and vaporize it.

[0057] The intermediate tank 92 is connected to two liquid transfer pipes 931 and 932, which form part of the supply line LN3 connecting the liquefied hydrogen storage unit 91 to the liquefied hydrogen dispenser 94. Liquid transfer pipe 931, which is connected to the liquefied hydrogen tank 911, is connected to the lower part of the intermediate tank 92. Liquid transfer pipe 932, which is connected to the liquefied hydrogen dispenser 94, is also connected to the lower part of the intermediate tank 92. This allows liquefied hydrogen to be stored in the intermediate tank 92 and to be sent to the liquefied hydrogen dispenser 94.

[0058] A supply pipe 86 is connected to the intermediate tank 92. The supply pipe 86 is a pipe that supplies liquefied hydrogen. A sprinkler 861 is connected to the discharge port of the supply pipe 86. The liquefied hydrogen discharged from the supply pipe 86 is sprayed into the gas phase by the sprinkler 861. The supply pipe 86 may be branched from the supply line LN3 or connected to the liquefied hydrogen storage unit 91. This makes it easier to maintain a saturated state in the gas phase of the intermediate tank 92. The sprinkler 861 can spray liquefied hydrogen over the entire surface of the gas phase of the intermediate tank 92 and the inner surface of the intermediate tank 92 facing the gas phase.

[0059] The discharge section 83 of the second line LN2 is located inside the intermediate tank 92. The discharge section 83 of the second line LN2 is located in the liquid phase. The discharge section 83 protrudes from the lower end of a vertical pipe 832 that extends vertically from the expansion valve 71 and penetrates the upper part (here, the top surface) of the intermediate tank 92, in a direction intersecting the vertical direction. Multiple discharge ports 831 are formed in the discharge section 83. The diameter of each discharge port 831 is, for example, 0.5 mm to 10 mm, or 1.0 mm to 5.0 mm. This allows the liquid phase of the intermediate tank 92 to be bubbled with fine bubbles, making it easier to liquefy the hydrogen gas. In addition, because the discharge section 83 of the second line LN2 is located in the liquid phase, the liquefaction of hydrogen gas is less affected by the temperature of the gas phase in the intermediate tank 92. As a result, the liquefaction rate of the boil-off gas is easily improved, and the power consumption per unit is easily reduced.

[0060] The intermediate tank 92 is connected to a BOG liquefaction return passage 921 whose inlet is located in the gas phase. The BOG liquefaction return passage 921 is connected to the first line LN1. As described above, some of the hydrogen gas that passes through the expansion valve 71 is liquefied, while other parts remain as hydrogen gas without liquefaction. The unliquefied hydrogen gas is used to pressurize the intermediate tank 92, but when the pressure in the intermediate tank 92 exceeds a certain pressure, it is returned to the first line LN1 via the BOG liquefaction return passage 921. This allows the boil-off gas to be circulated and improves the liquefaction rate.

[0061] The intermediate tank 92 is provided with a vent section 922. The vent section 922 is used to depressurize the intermediate tank 92 after supplying liquefied hydrogen to the mobile body M1. After depressurizing the intermediate tank 92, liquefied hydrogen is supplied through the liquefied hydrogen flow path 84 in preparation for the next filling of the mobile body M1. The vent section 922 may be connected to the BOG liquefaction return path 921, or it may be connected directly to the first line LN1.

[0062] (Second Embodiment) Next, a second embodiment of the BOG liquefaction system 10 according to this disclosure will be described with reference to Figure 3. Since this embodiment is largely the same as the first embodiment described above, the same reference numerals will be used for identical or corresponding parts, and their descriptions will not be repeated.

[0063] Figure 3 is a schematic diagram showing the piping system of the BOG liquefaction system 10 according to this embodiment. Referring to Figure 3, the BOG liquefaction system 10 according to this embodiment, like the first embodiment, is used in addition to the liquefied hydrogen supply device 9 to liquefy the boil-off gas generated when supplying liquefied hydrogen to the supply recipient (e.g., mobile body M1) during the supply of liquefied hydrogen, and then return the liquefied liquefied hydrogen to the liquefied hydrogen supply device 9. The liquefied hydrogen supply device 9 comprises a liquefied hydrogen storage unit 91, a liquefied hydrogen dispenser 94, an intermediate tank 92, and a liquid transfer device 93. The liquefied hydrogen supply device 9 can adopt the same configuration as the first embodiment.

[0064] Referring to Figure 3, the BOG liquefaction system 10 according to this embodiment comprises a compressor 2, a cooler R1, an expansion valve 71, and a BOG recovery unit 1. The compressor 2 is the same as in the first embodiment in that it is connected to the liquefied hydrogen dispenser 94 by a first line LN1 and to the intermediate tank 92 by a second line LN2. In this embodiment, the configuration of the cooler R1 is the main difference from the first embodiment.

[0065] A cooler R1 is provided in the second line LN2. The cooler R1 according to this embodiment comprises a plurality of heat exchangers 3, 4, 5, 61, 62 and an expansion turbine 70. Similar to the first embodiment, the cooler R1 according to this embodiment comprises a first heat exchanger 3, a second heat exchanger 4 and a third heat exchanger 5, but in addition to these, it also comprises a fourth heat exchanger 61 and a fifth heat exchanger 62. The first heat exchanger 3, the second heat exchanger 4, the fourth heat exchanger 61, the fifth heat exchanger 62 and the third heat exchanger 5 are arranged in this order along the second line LN2. The secondary flow paths of the plurality of heat exchangers 3, 4, 5, 61, 62 are connected to the second line LN2 and can cool the hydrogen gas sent from the compressor 2.

[0066] (1st heat exchanger 3) The first heat exchanger 3 comprises a first heat exchanger second flow path 32 and a first heat exchanger third flow path 33. Unlike the first embodiment, the first heat exchanger 3 according to this embodiment does not have a first heat exchanger first flow path 31, which is a primary flow path connected to the first line LN1. The first heat exchanger third flow path 33 is a primary flow path, and the first heat exchanger second flow path 32 is a secondary flow path. The first heat exchanger second flow path 32 is connected to the second line LN2. The first heat exchanger third flow path 33 is connected to the liquefied hydrogen flow path 84. With this configuration, the first heat exchanger 3 can cool the hydrogen gas sent from the compressor 2 using the cold energy of the hydrogen gas.

[0067] The inlet temperature T13 of the third flow path 33 of the first heat exchanger is lower than the inlet temperature T12 of the second flow path 32 of the first heat exchanger. For example, in design, temperature T12 is 25°C and temperature T13 is -238°C. In this case, the temperature difference between the outlet temperature T131 of the third flow path 33 of the first heat exchanger and temperature T12 may be 2°C or less, or 1°C or less. The outlet temperature T131 of the third flow path 33 of the first heat exchanger is, for example, 24.0°C. In this specification, "outlet temperature" means the temperature of the fluid immediately after it leaves a flow path connected to equipment such as a heat exchanger.

[0068] (Second heat exchanger 4) The second heat exchanger 4 comprises a second heat exchanger second flow path 42 and a second heat exchanger third flow path 43. Unlike the first embodiment, the second heat exchanger 4 according to this embodiment does not have a second heat exchanger first flow path 41, which is a primary side flow path connected to the first recovery path 121, and a second heat exchanger fourth flow path 44, which is connected to the liquefied hydrogen flow path 84. The second heat exchanger second flow path 42 is a primary side flow path, and the second heat exchanger third flow path 43 is a secondary side flow path. The second heat exchanger second flow path 42 is connected to the first line LN1 and the BOG liquefaction return path 921. The second heat exchanger third flow path 43 is connected to the second line LN2. With this configuration, the second heat exchanger 4 can cool the hydrogen gas sent from the compressor 2 using the cold energy of liquefied hydrogen and boil-off gas.

[0069] The connection point of the first line LN1 to the second flow path 42 of the second heat exchanger may be upstream of the inlet of the second flow path 42 of the second heat exchanger. However, when the hydrogen gas flowing through the BOG liquefaction return path 921 is mixed with the boil-off gas flowing through the first line LN1, the temperature of the hydrogen gas may rise. In this case, the connection point of the first line LN1 to the second flow path 42 of the second heat exchanger may be changed depending on the temperature after mixing the hydrogen gas flowing through the BOG liquefaction return path 921 with the boil-off gas flowing through the first line LN1. In the second flow path 42 of the second heat exchanger, the temperature of the hydrogen gas increases as it moves upstream. For example, the first line LN1 may be connected to a point where the temperature of the hydrogen gas in the second flow path 42 of the second heat exchanger is equal to or greater than the temperature of the boil-off gas flowing through the first line LN1, and the temperature difference between the hydrogen gas in the second flow path 42 of the second heat exchanger and the hydrogen gas in the third flow path 43 of the second heat exchanger is 1°C or less.

[0070] In the second heat exchanger 4, the inlet temperature T22 of the second flow path 42 of the second heat exchanger is lower than the inlet temperature T23 of the third flow path 43 of the second heat exchanger. In the second heat exchanger 4, the inlet temperature T21 of the first line LN1 to the second flow path 42 of the second heat exchanger is lower than the inlet temperature T23 of the third flow path 43 of the second heat exchanger. As an example in design, the temperature T23 is -15.1°C, the temperature T22 is -224°C, and the temperature T21 is -178.4°C. In this case, the outlet temperature of the second flow path 42 of the second heat exchanger is assumed to be -78.1°C.

[0071] (4th heat exchanger 61) The fourth heat exchanger 61 comprises a fourth heat exchanger first channel 611, a fourth heat exchanger second channel 612, and a fourth heat exchanger third channel 613. The fourth heat exchanger first channel 611 and the fourth heat exchanger second channel 612 are primary side channels, and the fourth heat exchanger third channel 613 is a secondary side channel. The fourth heat exchanger first channel 611 is connected to the first line LN1. The fourth heat exchanger second channel 612 is connected to the BOG liquefaction return path 921. The fourth heat exchanger third channel 613 is connected to the second line LN2. With this configuration, the fourth heat exchanger 61 can cool the hydrogen gas supplied from the compressor 2 using the cold energy of the boil-off gas and hydrogen gas.

[0072] In the fourth heat exchanger 61, the entry temperature T41 of the first flow path 611 of the fourth heat exchanger is lower than the entry temperature T43 of the third flow path 613 of the fourth heat exchanger. In the fourth heat exchanger 61, temperature T43 is lower than the entry temperature T42 of the second flow path 612 of the fourth heat exchanger. Temperature T41 may be less than or equal to temperature T42, or less than or equal to (temperature T43 + temperature T42) / 2. As an example of the design, temperature T41 is -172°C, temperature T42 is -240°C, and temperature T43 is -224.1°C.

[0073] (5th heat exchanger 62) The fifth heat exchanger 62 comprises a fifth heat exchanger first flow path 621, a fifth heat exchanger second flow path 622, and a fifth heat exchanger third flow path 623. The fifth heat exchanger first flow path 621 and the fifth heat exchanger third flow path 623 are primary flow paths, and the fifth heat exchanger second flow path 622 is a secondary flow path. The fifth heat exchanger first flow path 621 is connected to the BOG liquefaction return path 921. The fifth heat exchanger second flow path 622 is connected to the second line LN2. The fifth heat exchanger third flow path 623 is connected to the liquefied hydrogen flow path 84. With this configuration, the fifth heat exchanger 62 can cool the hydrogen gas sent from the compressor 2 using the cold energy of liquefied hydrogen and hydrogen gas.

[0074] In the fifth heat exchanger 62, the inlet temperature T51 of the first flow path 621 of the fifth heat exchanger is lower than the inlet temperature T52 of the second flow path 622 of the fifth heat exchanger. In the fifth heat exchanger 62, temperature T52 is lower than the inlet temperature T53 of the third flow path 623 of the fifth heat exchanger. Temperature T53 may be less than or equal to temperature T51, or less than or equal to (temperature T51 + temperature T52) / 2. As an example in the design, temperature T51 is -241.2°C, temperature T52 is -227.5°C, and temperature T53 is -241.2°C. The outlet temperature of the first flow path 621 of the fifth heat exchanger is assumed to be -238.5°C, but because it mixes with hydrogen gas whose temperature has decreased after passing through the cooling device 82 in the branch path 8, temperature T42 is expected to be about 1.5°C lower than the outlet temperature of the fifth heat exchanger 62.

[0075] (Third heat exchanger 5) The third heat exchanger 5 comprises a third heat exchanger first flow path 51, a third heat exchanger second flow path 52, and a third heat exchanger third flow path 53. The third heat exchanger first flow path 51 and the third heat exchanger third flow path 53 are primary flow paths, and the third heat exchanger second flow path 52 is a secondary flow path, as in the first embodiment. However, the third heat exchanger first flow path 51 is connected to the BOG liquefaction return path 921 instead of the first line LN1. With this configuration, the third heat exchanger 5 can cool the hydrogen gas sent from the compressor 2 using the cold energy of liquefied hydrogen and hydrogen gas.

[0076] The connection point between the third heat exchanger's third channel 53 and the liquefied hydrogen channel 84 is preferably such that the temperature of the liquefied hydrogen flowing through the liquefied hydrogen channel 84 is lower than or equal to the temperature of the hydrogen gas flowing through the third heat exchanger's second channel 52. In the third heat exchanger's third channel 53, the temperature of the hydrogen gas increases as it moves upstream. This allows for more efficient cooling of the hydrogen gas flowing through the second line LN2.

[0077] In the third heat exchanger 5, the inlet temperature T31 of the first passage 51 of the third heat exchanger is lower than the inlet temperature T32 of the second passage 52 of the third heat exchanger. In the third heat exchanger 5, the inlet temperature T33 of the third passage 53 of the third heat exchanger is lower than the inlet temperature T32 of the second passage 52 of the third heat exchanger. Temperature T33 may be less than or equal to temperature T31, or less than or equal to (temperature T31 + temperature T32) / 2. As an example in the design, temperature T31 is -246°C, temperature T32 is -240.2°C, and temperature T33 is -244.1°C. The outlet temperature of the second passage 622 of the fifth heat exchanger is assumed to be -238.3°C, but the hydrogen gas that exits the second passage 622 of the fifth heat exchanger is expected to experience a temperature drop of about 1.9°C after passing through the expansion turbine 70.

[0078] (Fork in the road 8) The branch line 8 branches off in the second line LN2 from between the second heat exchanger 4 and the third heat exchanger 5. More specifically, the branch line 8 branches off in the second line LN2 from between the second heat exchanger 4 and the fourth heat exchanger 61. The branch line 8 is connected in the BOG liquefaction return line 921 from between the fourth heat exchanger 61 and the fifth heat exchanger 62. A cooling device 82 is provided in the branch line 8. In this embodiment, the cooling device 82 is an expansion turbine. If the hydrogen gas passing through the branch line 8 is below the reversal temperature, a pressure reducing valve may be used instead of the expansion turbine as the cooling device 82.

[0079] In this embodiment, the upstream end of the branch line 8 branches off from between the second heat exchanger 4 and the fourth heat exchanger 61 in the second line LN2, but it may also branch off from between the fourth heat exchanger 61 and the fifth heat exchanger 62 in the second line LN2. Also, in this embodiment, the downstream end of the branch line 8 is connected to the BOG liquefaction return line 921, but it may also be connected to the first line LN1, or any other flow path that leads to a heat exchanger. This allows the heat exchanger downstream of the flow path to which the branch line 8 is connected to cool the hydrogen gas sent from the compressor more effectively.

[0080] (BOG recovery unit 1) The BOG recovery unit 1 comprises a recovery path 12 branched from the first line LN1, a recovery tank 11, and a return path 13. Unlike the first embodiment, the recovery path 12 is not connected to a heat exchanger. In the first embodiment, the return path 13 was connected to the upstream side of the third heat exchanger 5 in the first line LN1, but in this embodiment, it is connected between the second heat exchanger 4 and the compressor 2 in the first line LN1. A pressure reducing valve 81 is provided in the return path 13.

[0081] (modified version) In the first and second embodiments, the piping constituting the first line LN1, the second line LN2, the liquefied hydrogen flow path 84, the recovery path 12, and the return path 13 may be insulated piping. Insulated piping only needs to suppress heat input to the flow path; it does not need to provide heat shielding. There are no particular restrictions on the insulated piping, and examples include a configuration having an inner pipe through which the fluid 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, from an inert gas, or from an insulating material such as glass wool. In the insulated piping, the portion located inside the intermediate tank 92 may consist of only a single inner pipe.

[0082] In the first and second embodiments, the intermediate tank 92 may be an insulated tank. The insulated tank comprises, for example, an inner tank, an outer tank, and an insulating layer disposed between the inner and outer tanks. The insulating layer may be formed from a vacuum, from an inert gas, or from an insulating material such as glass wool. This further improves the efficiency of hydrogen gas liquefaction in the intermediate tank 92.

[0083] In the second line LN2 of the first and second embodiments, a flow control valve may be placed upstream of the expansion turbine 70. Alternatively, as a cooling device 82 provided in the branch line 8, a flow control valve may be placed upstream of the pressure reducing valve, or an expansion turbine may be used instead of the pressure reducing valve.

[0084] In the first and second embodiments, a pressure gauge and a thermometer may be provided upstream of the pressure reducing valve and the flow control valve, respectively. This allows the throttling by the pressure reducing valve to be reduced if the temperature of the hydrogen gas before it enters the pressure reducing valve exceeds the hydrogen reversal temperature. Similarly, if the temperature of the hydrogen gas before it enters the flow control valve exceeds the hydrogen reversal temperature, the opening of the flow control valve can be reduced. This facilitates efficient liquefaction of the BOG liquefaction system 10.

[0085] In the first and second embodiments, the rotational power of the expansion turbine 70 and the expansion turbine as a cooling device 82 may be recovered as electricity. This makes it easier to achieve a reduction in power consumption per unit.

[0086] In the first and second embodiments, a submerged pump may be used as the pressure regulating device provided in the liquefied hydrogen tank 911 included in the liquefied hydrogen storage unit 91. By using a submerged pump, the liquefied hydrogen tank 911 in the liquefied hydrogen storage unit 91 can be operated at a lower pressure. This allows the hydrogen gas passing through the third flow path 33 of the first heat exchanger to be at a relatively low temperature, improving the liquefaction rate of the hydrogen gas in the intermediate tank 92. Furthermore, by lowering the pressure inside the liquefied hydrogen tank 911, the amount of boil-off gas generated inside the liquefied hydrogen tank 911 can be reduced.

[0087] In the BOG liquefaction system 10 according to the first and second embodiments, the BOG recovery unit 1 may be omitted. Instead of the BOG recovery unit 1, it may be connected to a hydrogen station for supplying hydrogen gas, and the boil-off gas that could not be liquefied may be used at the hydrogen station.

[0088] In the first and second embodiments, the BOG liquefaction system 10 was described by assuming that each element, such as the recovery tank 11, the liquefied hydrogen tank 911, and the intermediate tank 92, is a single unit. However, it may be composed of multiple recovery tanks 11, multiple liquefied hydrogen tanks 911, and multiple intermediate tanks 92.

[0089] In the first and second embodiments, the discharge section 83 of the second line LN2 is located in the liquid phase of the intermediate tank 92, but it may also be located in the gas phase.

[0090] 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]

[0091] 10 BOG liquefaction system, 1 BOG recovery unit, 11 recovery tank, 12 recovery path, 121 first recovery path, 122 second recovery path, 123 flow control valve, 124 on / off valve, 13 return path, 2 compressor, 3 first heat exchanger, 31 first heat exchanger first path, 32 first heat exchanger second path, 33 first heat exchanger third path, 4 second heat exchanger, 41 second heat exchanger first path, 42 second heat exchanger second path, 43 second heat exchanger third path, 44 second heat exchanger fourth path, 5 third heat exchanger, 51 third heat exchanger first path, 52 third heat exchanger second path, 53 third heat exchanger third path, 61 fourth heat exchanger, 611 fourth heat exchanger first path, 612 fourth heat exchanger second path, 613 624 Heat Exchanger No. 4 No. 3 channel, 625 Heat Exchanger No. 5 No. 5 No. 1 channel, 6225 Heat Exchanger No. 5 No. 2 channel, 6235 Heat Exchanger No. 5 No. 3 channel, 705 Expansion Turbine, 715 Expansion Valve, 88 Branch Channel, 815 Pressure Reducing Valve, 825 Cooling Device, 835 Discharge Section, 831 Outlet, 845 Liquefied Hydrogen Channel, 841 Discharge Section, 855 Hydrogen Gas Supply Channel, 865 Supply Pipe, 8615 Sprinkler, 875 Pressure Pipe, 871 Discharge Section, 9615 Liquefied Hydrogen Supply Device, 915 Liquefied Hydrogen Storage Section, 9115 Liquefied Hydrogen Tank, 925 Intermediate Tank, 9215 Return Channel for BOG Liquefaction, 9225 Vent Section, 935 Liquid Transfer Device, 9315 Liquid Transfer Pipe, 9325 Liquid Transfer Pipe, 945 Liquefied Hydrogen Dispenser, 9415 Dispenser Body, 9425 Hose, 943 plug section, M1 mobile unit, M11 supply port, R1 cooler, LN1 first line, LN2 second line, LN3 supply line.

Claims

1. A boil-off gas liquefaction system used in a liquefied hydrogen supply device, wherein an intermediate tank is provided in the supply line connecting a liquefied hydrogen storage unit that stores liquefied hydrogen to a liquefied hydrogen dispenser that supplies liquefied hydrogen to a recipient, A compressor connected to the liquefied hydrogen dispenser by a first line, which compresses the boil-off gas, which is hydrogen gas, sent from the liquefied hydrogen dispenser through the first line, A cooler is provided in the second line connecting the compressor and the intermediate tank, and cools the hydrogen gas compressed by the compressor. An expansion valve is provided in the second line on the intermediate tank side of the cooler, which liquefies the hydrogen gas cooled by the cooler, Equipped with, Boil-off gas liquefaction system.

2. A recovery tank connected to a recovery path branched off from the first line, A return path for returning the boil-off gas recovered by the recovery tank back to the first line, It also has, The boil-off gas liquefaction system according to claim 1.

3. The boil-off gas recovery unit has a stainless steel container for storing the boil-off gas. The boil-off gas liquefaction system according to claim 2.

4. The cooling unit has at least one heat exchanger connected to the second line and the first line, At least one of the heat exchangers cools the hydrogen gas supplied from the compressor using boil-off gas passing through the first line. The boil-off gas liquefaction system according to claim 1.

5. The aforementioned cooling device is In the second line, a branch path is provided that branches off from the downstream side of at least one of the heat exchangers and is connected to the upstream side of a flow path that leads to at least one of the heat exchangers, A cooling device to lower the temperature of the hydrogen gas passing through the aforementioned branching path, It further has, The boil-off gas liquefaction system according to claim 4.

6. The discharge section of the second line is located within the liquid phase of the intermediate tank. The boil-off gas liquefaction system according to claim 1.

7. The cooling unit has at least one heat exchanger connected to the second line, The heat exchanger is connected to a liquefied hydrogen flow path that connects the liquefied hydrogen storage section to the intermediate tank, and cools the hydrogen gas passing through the second line with the liquefied hydrogen passing through the liquefied hydrogen flow path. The boil-off gas liquefaction system according to claim 1.

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