Liquid hydrogen transfer system

Abstract

Provided is a technology that makes it possible to more easily prevent boil-off gas from being generated due to transfer of liquid hydrogen. A liquid hydrogen transfer system 1 according to one embodiment of the present invention comprises: a liquid hydrogen storage tank 10 that stores liquid hydrogen; a liquid hydrogen storage tank 20 that stores liquid hydrogen; transfer pipes 30, 40 that connect the liquid hydrogen storage tank 10 and the liquid hydrogen storage tank 20; liquid hydrogen flow paths 31, 41 that are provided inside the transfer pipes 30, 40, and through which the liquid hydrogen can be transferred between the liquid hydrogen storage tank 10 and the liquid hydrogen storage tank 20; and BOG flow paths 32, 42, 43 that are provided inside the transfer pipes 30, 40, and through which boil-off gas, which is the liquid hydrogen in a vaporized form, is discharged to the outside from at least one of the liquid hydrogen storage tank 10 and the liquid hydrogen storage tank 20.

Description

Liquid Hydrogen Transfer System

[0001] The present disclosure relates to a liquid hydrogen transfer system.

[0002] BACKGROUND ART A transfer system for transferring liquid hydrogen between a first storage unit and a second storage unit has been known (see Patent Document 1).

[0003] JP 2014-108759 A

[0004] For example, in the liquid hydrogen transfer flow path connecting the first storage unit and the second storage unit, external heat input can vaporize the liquid hydrogen, generating boil-off gas (BOG). Furthermore, for example, if the temperature of the pipe section corresponding to the transfer flow path is relatively high at the start of transfer, cold energy transfers from the liquid hydrogen to the pipe section during transfer until the temperature of the pipe section is cooled by the liquid hydrogen, generating boil-off gas due to pre-cooling of the pipe section. Furthermore, for example, if the transfer of liquid hydrogen begins when the temperature of the transfer destination, either the first storage unit or the second storage unit, is relatively high, boil-off gas will be generated due to pre-cooling of the transfer destination, just as when the temperature of the pipe section corresponding to the transfer flow path is relatively high. Therefore, for example, if the destination of liquid hydrogen does not have equipment that can use boil-off gas as fuel, it becomes necessary to release boil-off gas to the atmosphere as the pressure at the transfer destination increases. Therefore, it is desirable to suppress the generation of boil-off gas during the transfer of liquid hydrogen.

[0005] On the other hand, it is possible to suppress the generation of boil-off gas by adopting a structure that allows the liquid hydrogen transport flow path and the storage unit to which the liquid hydrogen is transported to be cooled with liquid nitrogen, etc., but this may result in the equipment becoming more complex and increasing costs.

[0006] In view of the above problems, an object of the present invention is to provide a technology that can more easily suppress the generation of boil-off gas that accompanies the transport of liquid hydrogen.

[0007] In order to achieve the above object, one embodiment of the present disclosure provides a liquid hydrogen transfer system comprising: a first storage section for storing liquid hydrogen; a second storage section for storing liquid hydrogen; a pipe section connecting the first storage section and the second storage section; a first flow path provided inside the pipe section and capable of transferring liquid hydrogen between the first storage section and the second storage section; and a second flow path provided inside the pipe section and outputting boil-off gas, which is vaporized liquid hydrogen, from at least one of the first storage section and the second storage section to the outside.

[0008] According to the above-described embodiment, it is possible to more easily suppress the generation of boil-off gas that accompanies the transfer of liquid hydrogen.

[0009] It is a diagram showing an example of a liquid hydrogen transfer system. It is a cross-sectional view showing an example of the structure of a transfer pipe. It is a cross-sectional view showing an example of the structure of a transfer pipe. It is a diagram showing an example of the configuration of a re-liquefaction device.

[0010] Hereinafter, an embodiment will be described with reference to the drawings.

[0011] [Configuration of Liquid Hydrogen Transfer System] A liquid hydrogen transfer system 1 according to this embodiment will be described with reference to FIG.

[0012] FIG. 1 is a diagram showing an example of a liquid hydrogen transfer system 1.

[0013] The liquid hydrogen transfer system 1 includes liquid hydrogen storage tanks 10 and 20 , transfer pipes 30 and 40 , an insulated valve box 50 , and a re-liquefaction device 60 .

[0014] The liquid hydrogen storage tank 10 stores liquid hydrogen. For example, the liquid hydrogen storage tank 10 is installed in a facility for storing liquid hydrogen on the ground L adjacent to the quay Q.

[0015] The liquid hydrogen storage tank 20 stores liquid hydrogen. For example, the liquid hydrogen storage tank 20 is mounted on a ship SP that is docked at a quay Q.

[0016] The transfer pipes 30, 40 are pipes that transfer liquid hydrogen between the liquid hydrogen storage tank 10 and the liquid hydrogen storage tank 20. The transfer pipes 30, 40 have a thermally insulated structure, as will be described later. Thermal insulation not only refers to a state in which no heat is transferred in or out of the pipe, but also includes a state in which the transfer of heat is suppressed more than in pipes with a normal structure, and will be used in the same sense hereinafter.

[0017] The transfer pipe 30 is used to transfer liquid hydrogen from the liquid hydrogen storage tank 10 to the liquid hydrogen storage tank 20. For example, the transfer pipe 30 is used when the ship SP stores liquid hydrogen in the liquid hydrogen storage tank 20 and transports it to the outside.

[0018] One end of the transfer pipe 30 is connected to the liquid hydrogen storage tank 20, and the other end branches into transfer pipes 30-1 and 30-2.

[0019] The tip of the transfer pipe 30-1 is connected to the liquid hydrogen storage tank 10.

[0020] The tip of the transfer pipe 30-2 is connected to an insulating valve box 50.

[0021] The transfer pipe 30 includes a liquid hydrogen flow path 31 and a BOG flow path 32 .

[0022] The liquid hydrogen flow path 31 has one end connected to the liquid hydrogen storage tank 20 and the other end connected to the bottom of the liquid hydrogen storage tank 10 by being enclosed within the transfer pipe 30-1, and transfers liquid hydrogen from the liquid hydrogen storage tank 10 to the liquid hydrogen storage tank 20.

[0023] One end of BOG flow path 32 is connected to liquid hydrogen storage tank 20, and the other end is connected to insulated valve box 50 in a manner that it is enclosed within transfer pipe 30-2, and transfers boil-off gas (BOG) from liquid hydrogen storage tank 20 to reliquefaction device 60 via insulated valve box 50. This makes it possible to suppress the amount of heat entering the liquid hydrogen in liquid hydrogen flow path 31 from the outside by a heat shield effect that utilizes the sensible heat of the cryogenic boil-off gas that flows through BOG flow path 32, which is arranged along liquid hydrogen flow path 31. As a result, the amount of liquid hydrogen gasified can be reduced, and energy loss can be suppressed.

[0024] The boil-off gas in the liquid hydrogen storage tank 20 includes boil-off gas generated during the transfer of liquid hydrogen through the liquid hydrogen flow path 31 and boil-off gas generated inside the liquid hydrogen storage tank 20. The boil-off gas generated during the transfer of liquid hydrogen includes gas generated by flashing due to heat input from the outside and gas generated by flashing due to a pressure difference. The gas generated by flashing due to a pressure difference includes gas generated by flashing due to pressure loss in the liquid hydrogen flow path 31, flashing due to a valve passed through during transfer, and flashing due to expansion when the liquid hydrogen flows from the liquid hydrogen flow path 31 into the liquid hydrogen storage tank 20. The boil-off gas generated inside the liquid hydrogen storage tank 20 includes all evaporated gases, including evaporated gases generated by the heat of transition associated with the conversion of ortho-hydrogen, a nuclear spin isomer of hydrogen, to para-hydrogen (ortho-para equilibrium conversion).

[0025] The transfer pipe 40 is used to transfer liquid hydrogen from the liquid hydrogen storage tank 20 to the liquid hydrogen storage tank 10. For example, the transfer pipe 40 is used when the ship SP comes alongside the quay Q with liquid hydrogen stored in the liquid hydrogen storage tank 20.

[0026] One end of the transfer pipe 40 is connected to the bottom of the liquid hydrogen storage tank 20 and the other end is connected to the heat-insulating valve box 50 .

[0027] The transfer pipe 40 includes a liquid hydrogen flow path 41 and BOG flow paths 42 and 43 .

[0028] The liquid hydrogen flow path 41 has one end connected to the bottom of the liquid hydrogen storage tank 20 and the other end connected to the liquid hydrogen storage tank 10 via the inside of the insulated valve box 50, and transfers liquid hydrogen from the liquid hydrogen storage tank 20 to the liquid hydrogen storage tank 10.

[0029] One end of the BOG flow path 42 is connected to the liquid hydrogen storage tank 20 and the other end is connected to the insulated valve box 50, and the boil-off gas is transported from the liquid hydrogen storage tank 20 to the reliquefaction device 60 via the insulated valve box 50. This makes it possible to suppress the amount of heat entering the liquid hydrogen in the liquid hydrogen flow path 41 from the outside by a heat shield effect that utilizes the sensible heat of the cryogenic boil-off gas that flows through the BOG flow path 42 arranged along the liquid hydrogen flow path 41. As a result, the amount of liquid hydrogen gasified can be reduced, and energy loss can be suppressed.

[0030] The BOG flow path 42 is provided with a valve 42V.

[0031] The valve 42V can open and close the BOG flow path 42 .

[0032] One end of the BOG flow path 43 is connected to the middle of the BOG flow path 42, and the other end is connected to the liquid hydrogen storage tank 10 via the insulated valve box 50, and transfers boil-off gas from the liquid hydrogen storage tank 10 to the BOG flow path 42 and joins the BOG flow path 42. This makes it possible to suppress the amount of heat entering the liquid hydrogen in the liquid hydrogen flow path 41 through a heat shield effect that utilizes the sensible heat of the cryogenic boil-off gas that flows through the BOG flow path 43 arranged along the liquid hydrogen flow path 41. As a result, the amount of liquid hydrogen gasified can be reduced, and energy loss can be suppressed.

[0033] Furthermore, BOG flow path 43 is connected to BOG flow path 42 on the insulated valve box 50 (reliquefaction device 60) side of valve 42V of BOG flow path 42. As a result, when valve 42V is closed, only boil-off gas from liquid hydrogen storage tank 10 flows through BOG flow paths 42, 43, thereby suppressing the amount of heat entering the liquid hydrogen in liquid hydrogen flow path 41 from the outside. As a result, the amount of liquid hydrogen gasified can be reduced, and energy loss can be suppressed.

[0034] The transfer pipe 30 may also be provided with a BOG flow path that merges the boil-off gas from the liquid hydrogen storage tank 10 with the BOG flow path 32, similar to the transfer pipe 40. The boil-off gas from the liquid hydrogen storage tank 10 includes boil-off gas generated during the transfer of liquid hydrogen through the liquid hydrogen flow path 41 and boil-off gas generated inside the liquid hydrogen storage tank 10. The boil-off gas generated during the transfer of liquid hydrogen includes gas generated by flashing due to heat input from the outside and gas generated by flashing due to a pressure difference. The gas generated by flashing due to a pressure difference includes gas generated by flashing due to pressure loss in the liquid hydrogen flow path 41, flashing due to a valve passing through during transfer, and flashing due to expansion when the liquid hydrogen flows from the liquid hydrogen flow path 41 into the interior of the liquid hydrogen storage tank 10. The boil-off gas generated inside the liquid hydrogen storage tank 10 includes all evaporated gases, including evaporated gases generated by the heat of transition associated with the conversion of ortho-hydrogen, a nuclear spin isomer of hydrogen, to para-hydrogen (ortho-para equilibrium conversion).

[0035] The insulated valve box 50 is installed in a facility for storing liquid hydrogen on the ground L, and inputs the boil-off gas transferred through the BOG flow paths 32, 42 into the reliquefaction device 60. The insulated valve box 50 is installed, for example, above the liquid hydrogen storage tank 20. The insulated valve box 50 has a thermal insulating structure, and can suppress the penetration of heat from the outside into the liquid hydrogen and boil-off gas in each flow path passing through the inside of the insulated valve box 50.

[0036] For example, the insulated valve box 50 selectively inputs the boil-off gas transferred from the BOG flow paths 32 and 42 into one of a plurality of input paths of the reliquefaction device 60. Specifically, the insulated valve box includes a plurality of flow paths connected to the plurality of input paths, and a group of valves for selectively injecting the boil-off gas into one of the plurality of flow paths.

[0037] Reliquefaction device 60 is installed in a facility for storing liquid hydrogen on ground L, and reliquefies boil-off gas from liquid hydrogen storage tank 10 and liquid hydrogen storage tank 20. Liquid hydrogen output from reliquefaction device 60 is returned to liquid hydrogen storage tank 10.

[0038] The insulated valve box 50 and the reliquefaction device 60 may be omitted. In this case, the boil-off gas in the BOG passages 32, 42 is used to suppress the amount of heat entering the liquid hydrogen in the liquid hydrogen passages 31, 41 from the outside, and is then released to the atmosphere. Also, instead of or in addition to the reliquefaction device 60, equipment may be provided that can directly consume the boil-off gas in its gaseous state as fuel, etc.

[0039] [Structure of Transfer Pipe] Next, the structure of the transfer pipes 30 and 40 will be described with reference to FIGS.

[0040] 2 and 3 are cross-sectional views showing an example of the transfer pipe 30. Specifically, Fig. 2 and Fig. 3 are cross-sectional views of different portions of the example of the transfer pipe 30.

[0041] Since the structures of the transfer pipes 30 and 40 are substantially the same, the following description will focus on the structure of the transfer pipe 30, and illustrations and descriptions of the structure of the transfer pipe 40 will be simplified.

[0042] As shown in FIGS. 2 and 3, the transfer pipe 30 includes an outer pipe 30A, a shielded inner pipe 30B, and transfer pipes 30C and 30D.

[0043] The outer tube 30A corresponds to the outer shape of the transfer tube 30 and has, for example, a circular cross section.

[0044] The shielded inner pipe 30B is provided inside the outer pipe 30A so that radiant heat input from the outer pipe 30A is not directly transmitted to the transfer pipe 30C. For example, the shielded inner pipe 30B has an outer diameter smaller than that of the outer pipe 30A and a circular cross section that is approximately concentric with the outer pipe 30A. The word "approximately" is intended to allow for, for example, manufacturing errors and limitations, and will be used in the same sense hereinafter.

[0045] Spacers 30F are provided between the outer pipe 30A and the shielded inner pipe 30B at predetermined intervals in the extension direction of the transfer pipe 30. This allows the position of the shielded inner pipe 30B to be maintained within the vacuum insulation layer inside the outer pipe 30A.

[0046] The space SP1 between the outer pipe 30A and the shielded inner pipe 30B is, for example, in a substantially vacuum state. This suppresses heat input from the outer pipe 30A to the shielded inner pipe 30B, and reduces the amount of heat that penetrates into the liquid hydrogen and boil-off gas transferred through the transfer pipes 30C and 30D. This suppresses energy loss due to gasification of liquid hydrogen.

[0047] The transfer pipe 30C is provided inside the shielded inner pipe 30B so as to prevent direct transmission of radiant heat from the outer pipe 30A and the shielded inner pipe 30B. For example, the transfer pipe 30C has an outer diameter smaller than that of the shielded inner pipe 30B and a circular cross section that is approximately concentric with the outer pipe 30A and the shielded inner pipe 30B. The interior of the transfer pipe 30C corresponds to the liquid hydrogen flow path 31, through which liquid hydrogen flows.

[0048] Spacers 30G are provided between the shielded inner pipe 30B and the transfer pipe 30C at predetermined intervals in the extension direction of the transfer pipe 30. This allows the position of the transfer pipe 30C to be maintained within the vacuum insulation layer inside the shielded inner pipe 30B.

[0049] The space SP2 between the shield inner tube 30B and the transfer tube 30C is, for example, in a substantially vacuum state. This suppresses heat input from the outer tube 30A and the shield inner tube 30B to the transfer tube 30C, thereby suppressing the amount of heat entering the liquid hydrogen being transferred through the transfer tube 30C. This reduces the amount of liquid hydrogen that is gasified, thereby suppressing energy loss.

[0050] The transfer pipe 30D is disposed in thermal contact with the shield inner pipe 30B. For example, the transfer pipe 30D has a circular cross section with an outer diameter smaller than that of the shield inner pipe 30B. The inside of the transfer pipe 30D corresponds to the BOG flow path 32 and has a cross-sectional inner diameter sufficient to allow the boil-off gas to flow therethrough.

[0051] The transfer pipe 30D is attached to, for example, the shield inner pipe 30B. Specifically, a portion of the shield inner pipe 30B may be cut out in the circumferential direction, and the transfer pipe 30D may be fitted into the cutout portion and fixed therein. This allows the shield inner pipe 30B to be maintained at an effective radiation shielding temperature by the action of the transfer pipe 30D, through which the cryogenic boil-off gas flows. As a result, the amount of heat entering the liquid hydrogen in the transfer pipe 30C inside the shield inner pipe 30B can be further suppressed. This further reduces the amount of gasification of liquid hydrogen, thereby further suppressing energy loss.

[0052] Furthermore, for example, multiple transfer pipes 30D (two in this example) are provided. The circumferential positions of the multiple transfer pipes 30D are optimally determined depending on the temperature level of the boil-off gas flowing through each of them. In this example (FIGS. 2 and 3), two transfer pipes 30D are arranged circumferentially at 180-degree intervals. This further reduces the amount of heat entering the liquid hydrogen in the transfer pipe 30C. As a result, the amount of gasification of liquid hydrogen can be further reduced, and energy loss can be further suppressed.

[0053] Furthermore, spacers 30H are provided between the outer pipe 30A and the transfer pipe 30D at predetermined intervals in the extension direction of the transfer pipe 30. This allows the shielded inner pipe 30B to be held in a vacuum insulation layer within the outer pipe 30A via the transfer pipe 30.

[0054] In the case of transfer pipe 40, the interior of a pipe similar to transfer pipe 30D (hereinafter referred to as "transfer pipe 40D" for convenience) corresponds to either of BOG flow paths 42 and 43. Therefore, in the case of transfer pipe 40, some of the multiple transfer pipes 40D may be configured to correspond to BOG flow path 42, and the remaining some of the transfer pipes 40D may be configured to correspond to BOG flow path 43.

[0055] In this way, in this example, the shield inner pipe 30B can provide double vacuum insulation for the transfer pipe 30C, and the boil-off gas in the transfer pipe 30D can maintain the shield inner pipe 30B at an effective radiation shielding temperature. This makes it possible to suppress the amount of heat entering the liquid hydrogen flowing through the transfer pipe 30C inside the shield inner pipe 30B, thereby reducing the amount of gasification of the liquid hydrogen and suppressing energy loss.

[0056] [Configuration of Reliquefaction Device] Next, with reference to FIG. 4, an outline of the configuration of the reliquefaction device 60 will be described.

[0057] Fig. 4 is a diagram showing a schematic configuration example of a reliquefaction device. Specifically, Fig. 4 shows a Claude cycle as an example of a process with relatively high liquefaction efficiency.

[0058] 4, in practice, reliquefaction unit 60 will require components such as a low-temperature catalyst tank for accelerating the conversion of ortho-hydrogen to para-hydrogen during the liquefaction of hydrogen gas. Reliquefaction unit 60 may employ any of a variety of systems, including a system incorporating another liquefied gas (e.g., liquid helium) as an auxiliary refrigerant, or a separated Bryton system in which the turbine circuit and the liquefaction circuit are completely separated.

[0059] The reliquefaction device 60 includes paths L1 to L3, a compressor CP, heat exchangers HX1 to HX6, a supercritical expansion turbine EP, a Joule-Thomson valve JT, an expansion turbine EP3, low-pressure returns IN1 and IN2, and a liquefaction path OUT.

[0060] The path L1 sends the liquefied circulating gas and boil-off gas (hydrogen gas) input through the low-pressure return gases IN1 and IN2 to the suction side of the compressor CP.

[0061] Path L1 passes through heat exchanger HX6, heat exchanger HX5, heat exchanger HX4, heat exchanger HX3, heat exchanger HX2, and heat exchanger HX1 in that order from the cryogenic side (upstream side), and is connected to compressor CP.

[0062] In path L2, hydrogen gas mechanically compressed by compressor CP using external energy is cooled by heat exchangers HX1 to HX6 with hydrogen gas (low-pressure return gas) in path L1, and finally, the hydrogen gas is circulated to be liquefied partially by adiabatic expansion using a Joule-Thomson valve JT or the like.

[0063] Path L2 passes through, in order from the high temperature side (upstream side), heat exchanger HX1, heat exchanger HX2, heat exchanger HX3, heat exchanger HX4, heat exchanger HX5, a supercritical expansion turbine, heat exchanger HX6, and Joule-Thomson valve JT.

[0064] Path L3 branches off hydrogen gas from a point between heat exchangers HX2 and HX3 on path L2, and merges it with a point between heat exchangers HX6 and HX5 on path L1 so that the hydrogen gas, which has been adiabatically expanded and cooled by expansion turbine EP3, can be used for refrigeration.

[0065] The compressor CP adiabatically compresses the hydrogen gas supplied from the path L1 and discharges it to the path L2.

[0066] The heat exchanger HX1 exchanges heat between the relatively low-temperature hydrogen gas upstream of the path L1 and the liquid nitrogen supplied from the outside, and the relatively high-temperature hydrogen gas immediately after being mechanically compressed by the compressor CP in the path L2, thereby sequentially cooling the hydrogen gas in the path L2.

[0067] The heat exchanger HX2 exchanges heat between the relatively low-temperature hydrogen gas in the path L1 and the relatively high-temperature hydrogen gas in the path L2, thereby further cooling the hydrogen gas in the path L2 after passing through the heat exchanger HX1.

[0068] The heat exchanger HX3 exchanges heat between the relatively low-temperature hydrogen gas in the path L1 and the relatively high-temperature hydrogen gas in the path L2, thereby further cooling the hydrogen gas in the path L2 after passing through the heat exchanger HX2.

[0069] The heat exchanger HX4 exchanges heat between the relatively low-temperature hydrogen gas in the path L1, the relatively low-temperature hydrogen gas in the path L3 that has been adiabatically expanded by the expansion turbine EP31, and the relatively high-temperature hydrogen gas upstream of the path L2, thereby further cooling the hydrogen gas in the path L2 that has passed through the heat exchanger HX3.

[0070] The heat exchanger HX5 exchanges heat between the relatively low-temperature hydrogen gas in the path L1 and the relatively high-temperature hydrogen gas upstream of the path L2, thereby further cooling the hydrogen gas in the path L2 after passing through the heat exchanger HX4.

[0071] The heat exchanger HX6 exchanges heat between the relatively low-temperature hydrogen gas in the path L1 and the relatively high-temperature hydrogen gas in the path L2, thereby further cooling the hydrogen gas adiabatically expanded in the supercritical expansion turbine EP.

[0072] The supercritical expansion turbine EP is provided between the heat exchangers HX5 and HX6 on the path L2, and reduces the temperature of the hydrogen gas that has passed through the heat exchanger HX5 by adiabatic expansion, and supplies the hydrogen gas to the heat exchanger HX6.

[0073] The Joule-Thomson valve JT isenthalpic-expands the hydrogen gas output from the heat exchanger HX6 through path L2. Because the temperature of the hydrogen gas supplied to the Joule-Thomson valve JT is below the inversion temperature, the isenthalpic expansion causes a temperature drop. As a result, the Joule-Thomson valve JT liquefies a portion of the hydrogen gas and outputs it to the liquefaction path OUT, allowing the liquid hydrogen to be returned to the liquid hydrogen storage tank 10.

[0074] As described above, the expansion turbine EP3 is provided on the path L3. The expansion turbine EP3 includes expansion turbines EP31 and EP32. The expansion turbine EP3 adiabatically expands the hydrogen gas in the path L3 and returns it to the path L1. This makes it possible to generate the amount of refrigeration required for the path L1, which is the low-temperature side of the heat exchangers HX1 to HX5.

[0075] The expansion turbine EP31 adiabatically expands the hydrogen gas at the most upstream position of the path L3, thereby further lowering the temperature of the hydrogen gas that has passed through the heat exchanger HX2 in the path L2, and enabling the hydrogen gas to be supplied to the downstream side of the path L3 (the heat exchanger HX4).

[0076] The expansion turbine EP32 adiabatically expands the hydrogen gas output from the heat exchanger HX4 on the path L3. This further reduces the temperature of the hydrogen gas, allowing the relatively low-temperature hydrogen gas to be returned to the path L1. This ensures that the required amount of refrigeration is available on the low-temperature side (path L1) of the heat exchangers HX1 to HX5.

[0077] The low-pressure return IN1 is used to introduce boil-off gas (hydrogen gas) from the liquid hydrogen storage tank 10 into the re-liquefaction device 60 (path L1).

[0078] The low-pressure return IN2 is used to inject the boil-off gas from the liquid hydrogen storage tank 20, which is transferred through the BOG flow paths 32, 42, into the low-temperature side (path L1) of the reliquefaction device 60.

[0079] The low pressure return IN2 includes low pressure returns IN21 to IN23.

[0080] The low-pressure return IN21 is used to inject boil-off gas from the liquid hydrogen storage tank 20, which is transferred through the BOG flow paths 32, 42, into the upstream side of the heat exchanger HX6, which has the lowest temperature (the most upstream) in the path L1.

[0081] The low-pressure return IN 22 is used to inject boil-off gas from the liquid hydrogen storage tank 20, which is transferred through the BOG flow paths 32, 42, into the path L1 between the heat exchanger HX6 and the heat exchanger HX5.

[0082] The low-pressure return IN 23 is used to inject boil-off gas from the liquid hydrogen storage tank 20, which is transferred through the BOG flow paths 32, 42, into the path L1 between the heat exchanger HX2 and the heat exchanger HX1.

[0083] As described above, which of the low-pressure return IN21 to IN23 introduction paths is used can be switched by appropriately controlling the open / close states of the valve group housed in the insulated valve box 50. The control device that controls the valve group in the insulated valve box 50 may be installed in any location. For example, the control device may be installed in the reliquefaction device 60, the insulated valve box 50, or a liquid hydrogen storage facility on the ground L.

[0084] For example, the control device controls the valve group depending on the temperature state of the boil-off gas transferred through the BOG flow paths 32, 42, and selectively uses one of the low-pressure return INs 21 to 23. The temperature state of the boil-off gas transferred through the BOG flow paths 32, 42 is measured, for example, by a temperature sensor provided in the insulated valve box 50, and the measurement result is input to the control device. Specifically, the temperature range of the boil-off gas may be divided into first to third ranges, from lowest to highest. The control device may then use the low-pressure return IN 21 when the temperature of the boil-off gas is in the first range, the low-pressure return IN 22 when the temperature of the boil-off gas is in the second range, and the low-pressure return IN 23 when the temperature of the boil-off gas is in the third range. This allows the control device to appropriately select the input path of the boil-off gas into path L1 in accordance with the temperature of the hydrogen gas, which increases downstream along path L1.

[0085] The control device may also selectively use any one of the low-pressure return gases IN21 to IN23, taking into further consideration the temperature state of the boil-off gas from the liquid hydrogen storage tank 10 that is introduced into path L1 via the low-pressure return gas IN1. The temperature state of the boil-off gas from the liquid hydrogen storage tank 10 is measured, for example, by a temperature sensor installed in the liquid hydrogen storage tank 10, and the measurement result is input into the control device. For example, the temperature ranges (first to third ranges) of the boil-off gas are varied depending on the temperature state of the boil-off gas from the liquid hydrogen storage tank 10. This allows the control device to appropriately select the introduction path of the boil-off gas into path L1 in accordance with the temperature state of the boil-off gas from the liquid hydrogen storage tank, which is dominant over the temperature state of path L1.

[0086] The low-pressure return IN2 may include only one or two input paths through which the boil-off gas from the liquid hydrogen storage tank 20 can be input, or may include four or more input paths.

[0087] The liquefaction path OUT outputs the liquid hydrogen output from the Joule-Thomson valve JT toward the liquid hydrogen storage tank 10.

[0088] Thus, in this example, the re-liquefaction device 60 represents an example of a circuit that can re-liquefy the boil-off gas in the liquid hydrogen storage tanks 10 and 20 and return it to the liquid hydrogen storage tank 10 .

[0089] Furthermore, in this example, the reliquefaction device 60 changes the position at which the boil-off gas from the liquid hydrogen storage tank 20 is merged with the hydrogen gas before adiabatic compression, which is used to cool the hydrogen gas after adiabatic compression, in accordance with the temperature state of the boil-off gas transferred from the liquid hydrogen storage tank 20. This makes it possible to select an operation that always optimizes the efficiency of liquefaction.

[0090] [Operation] Next, the operation of the liquid hydrogen transfer system 1 according to this embodiment will be described.

[0091] For example, in a liquid hydrogen transfer flow path connecting the first storage unit and the second storage unit, the liquid hydrogen may be vaporized by heat input from the outside, generating boil-off gas.

[0092] Furthermore, if the liquefied hydrogen is not in an equilibrium state between ortho-hydrogen and para-hydrogen in the liquid hydrogen transport flow path or in the storage area to which it is transported, the ortho-para equilibrium conversion may proceed, and the heat of the conversion may further accelerate the gasification of the liquid hydrogen.

[0093] Furthermore, if the temperature of the pipe section corresponding to the transfer flow path is relatively high at the start of transfer, cold energy will be transferred from the liquid hydrogen being transferred to the pipe section until the temperature of the pipe section is cooled by the liquid hydrogen, and a large amount of boil-off gas will be generated due to pre-cooling of the pipe section.

[0094] Furthermore, for example, when the transfer of liquid hydrogen begins when the temperature of the storage section at the transfer destination is relatively high, a large amount of boil-off gas is generated due to pre-cooling of the transfer destination, just as when the temperature of the pipe section corresponding to the transfer flow path is relatively high.

[0095] Therefore, for example, if the destination of liquefied hydrogen does not have any facilities that can use the boil-off gas as fuel, it will be necessary to release the boil-off gas into the atmosphere as the pressure at the destination increases. Therefore, it is desirable to suppress the generation of boil-off gas during the transport of liquefied hydrogen.

[0096] On the other hand, it is possible to suppress the generation of boil-off gas by adopting a structure that allows the liquid hydrogen transport flow path and the storage unit to which the liquid hydrogen is transported to be cooled with liquid nitrogen, etc., but this may result in the equipment becoming more complex and increasing costs.

[0097] In contrast, in this embodiment, the liquid hydrogen transfer system 1 includes a first storage unit, a second storage unit, a pipe unit, a first flow path, and a second flow path. The first storage unit is, for example, liquid hydrogen storage tank 10. The second storage unit is, for example, liquid hydrogen storage tank 20. The pipe unit is, for example, transfer pipe 30 or 40. The first flow path is, for example, liquid hydrogen flow path 31 or 41. The second flow path is, for example, BOG flow path 32 or BOG flow paths 42, 43. Specifically, the first storage unit stores liquid hydrogen. The second storage unit stores liquid hydrogen. The pipe unit connects the first storage unit and the second storage unit. The first flow path is provided inside the pipe unit and is configured to be able to transfer liquid hydrogen between the first storage unit and the second storage unit. The second flow path is provided inside the tube portion and outputs boil-off gas, which is vaporized liquid hydrogen, from at least one of the first storage portion and the second storage portion to the outside.

[0098] As a result, the cryogenic boil-off gas in the second flow path inside the pipe section can suppress a temperature rise of the liquid hydrogen in the first flow path inside the pipe section. Therefore, the liquid hydrogen transfer system 1 can suppress the generation of boil-off gas accompanying the transfer of liquid hydrogen between the first storage section and the second storage section by utilizing the boil-off gas in the first storage section and the second storage section. Furthermore, the first storage section and the second storage section may contain boil-off gas resulting from unavoidable flash gas generated by a pressure difference during the transfer of liquid hydrogen. Therefore, by utilizing the boil-off gas, which cannot be reduced to zero, the generation of boil-off gas accompanying the transfer of liquid hydrogen between the first storage section and the second storage section can be stably suppressed.

[0099] In this embodiment, the tubular portion may include a first tubular portion corresponding to the outer shape and a second tubular portion disposed inside the first tubular portion. The first tubular portion may be, for example, the outer tubular portion 30A. The second tubular portion may be, for example, the shielded inner tubular portion 30B. The first flow path may be provided inside the second tubular portion, and the second flow path may be attached along the second tubular portion.

[0100] As a result, the liquid hydrogen transfer system 1 can cool the second pipe section using the boil-off gas in the second flow path, thereby suppressing the temperature rise of the liquid hydrogen in the first flow path arranged inside the second pipe section.

[0101] In this embodiment, the liquid hydrogen transfer system 1 may further include a liquefaction unit that liquefies the boil-off gas transferred through the second flow path. The liquefaction unit is, for example, a re-liquefaction device 60.

[0102] As a result, the liquid hydrogen transport system 1 can re-liquefy the boil-off gas and use it as liquid hydrogen without discharging it into the atmosphere.

[0103] Although the embodiments have been described in detail above, the present disclosure is not limited to such specific embodiments, and various modifications and changes are possible within the scope of the gist described in the claims.

[0104] Finally, this application claims priority based on Japanese Patent Application No. 2022-078401, filed on May 11, 2022, the entire contents of which are incorporated herein by reference.

[0105] DESCRIPTION OF SYMBOLS 1 Liquid hydrogen transfer system 10 Liquid hydrogen storage tank (first storage section) 20 Liquid hydrogen storage tank (second storage section) 30, 30-1, 30-2 Transfer pipe (pipe section) 30A Outer pipe (first pipe section) 30B Shielded inner pipe (second pipe section) 30C Transfer pipe 30D Transfer pipe 30F Spacer 30G Spacer 30H Spacer 31 Liquid hydrogen flow path (first flow path) 32 BOG flow path (second flow path) 40 Transfer pipe (pipe section) 41 Liquid hydrogen flow path (first flow path) 42 BOG flow path (second flow path) 42V Valve 43 BOG flow path (second flow path) 50 Insulated valve box 60 Reliquefaction device (liquefaction section) CP Compressor EP Supercritical expansion turbine EP3, EP31, EP32 Expansion turbine HX1 to HX6 Heat exchanger IN1 Low pressure return IN2, IN21 to IN23 Low pressure return JT Joule-Thomson valve L1 to L3 Path OUT Liquefaction path

Claims

1. a first storage section for storing liquid hydrogen; a second storage section for storing liquid hydrogen; A pipe portion connecting the first storage portion and the second storage portion; a first flow path provided inside the pipe portion and capable of transporting liquid hydrogen between the first storage portion and the second storage portion; a second flow passage provided inside the tube portion and configured to output boil-off gas produced by vaporization of liquid hydrogen from at least one of the first storage portion and the second storage portion to the outside; The pipe portion includes a first pipe portion corresponding to an outer shape and a second pipe portion disposed inside the first pipe portion, The first flow path and the second flow path are provided inside the second pipe portion. Liquid hydrogen transfer system.

2. the pipe portion includes the first pipe portion, the second pipe portion, and a third pipe portion that is disposed inside the second pipe portion and has an interior that corresponds to the first flow path, the first tube portion, the second tube portion, and the third tube portion have concentric circular cross sections.

2. The liquid hydrogen transfer system of claim 1.

3. The pipe portion includes the first pipe portion, the second pipe portion, and a fourth pipe portion whose interior corresponds to the second flow path, The second pipe portion has a circumferential portion cut out, The fourth tube portion is fitted into the cut-out portion of the second tube portion.

3. The liquid hydrogen transport system according to claim 1 or 2.