Liquefied gas transfer system

Abstract

To provide a liquefied gas transfer system capable of making effective use of boil-off gas generated from liquefied gas in a simple construction.SOLUTION: The liquefied gas transfer system includes a reciprocating pump device 3 for pressurizing liquefied gas and boil-off gas in a storage tank 1, the reciprocating pump device 3 including a cylinder 14 having a gas pressurizing chamber 10 and a liquid pressurizing chamber 11 inside, a piston 17 arranged in the cylinder 14, and an actuator 18 connected to the piston 17 for applying reciprocating motion to the piston 17, the piston 17 being located between the gas pressurizing chamber 10 and the liquid pressurizing chamber 11, the piston 17 having a gas pressurizing face 21 facing the gas pressurizing chamber 10, and a liquid pressurizing face 22 facing the liquid pressurizing chamber 11.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a liquefied gas transfer system for transferring liquefied gases such as liquefied natural gas (LNG) and liquid hydrogen stored in a storage tank, and more particularly to a liquefied gas transfer system including a pump device for pumping liquefied gas and boil-off gas.

Background Art

[0002] Natural gas is widely used as a fuel for thermal power generation and as a chemical raw material. Hydrogen is expected as an energy source that does not generate carbon dioxide, which causes global warming. Applications of hydrogen as an energy source include fuel cells and turbine power generation. Since natural gas and hydrogen are in a gaseous state at normal temperature, they are cooled and liquefied for storage and transportation. Liquefied gases such as liquefied natural gas (LNG) and liquid hydrogen are transferred to power plants and hydrogen stations by transport vehicles.

[0003] There are hydrogen stations that vaporize stored liquid hydrogen, pressurize it with a compressor, and supply hydrogen to fuel cell vehicles, etc., and those that pressurize stored liquid hydrogen with a pump and then vaporize it to supply hydrogen to fuel cell vehicles, etc. The latter can boost a larger amount of hydrogen than the former, so the equipment configuration throughout the hydrogen station can be reduced.

[0004] FIG. 10 is a schematic diagram showing an example of a hydrogen station. Liquid hydrogen is transported to the hydrogen station by a transport vehicle (not shown) and stored in a storage tank 200. The pump device 201 sends the liquid hydrogen in the storage tank 200 to the evaporator 202, and the liquid hydrogen is converted into hydrogen gas by the evaporator 202. The hydrogen gas is sent to the accumulator 203, and the high-pressure hydrogen gas is held in the accumulator 203. Further, the hydrogen gas is sent to the dispenser 204 and supplied from the dispenser 204 to a fuel cell vehicle or the like.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] However, in a hydrogen station, boil-off gas (BOG) is generated due to heat input from outside to pipes and the storage tank 200, and heat input associated with the operation of the pump device 201. Since the boil-off gas is at approximately atmospheric pressure, it is difficult to reuse it again within the hydrogen station and it is usually discarded into the air. As methods for reusing the generated boil-off gas, there are a method of recovering and using it in a fuel cell and a method of compressing the boil-off gas with a compressor and accumulating pressure within the system. However, both methods require a high-cost equipment investment and have a problem that the installation area of the system increases. Such problems can occur not only with liquid hydrogen but also with other types of liquefied gas such as liquefied natural gas.

[0007] Therefore, the present invention provides a liquefied gas transfer system capable of effectively using boil-off gas generated from liquefied gas with a simple configuration.

Means for Solving the Problems

[0008] In one aspect, there is provided a liquefied gas transfer system for transferring liquefied gas in a storage tank, comprising a reciprocating pump device for pressurizing the liquefied gas and boil-off gas in the storage tank. The reciprocating pump device includes a cylinder having a gas pressurizing chamber and a liquid pressurizing chamber inside, a piston disposed within the cylinder, and an actuator connected to the piston for reciprocating the piston. The piston is positioned between the gas pressurizing chamber and the liquid pressurizing chamber, and the piston has a gas pressurizing surface facing the gas pressurizing chamber and a liquid pressurizing surface facing the liquid pressurizing chamber.

[0009] In one aspect, the piston has a gas pressurizing piston having the gas pressurizing surface and a liquid pressurizing piston having the liquid pressurizing surface, the reciprocating pump device connects the gas pressurizing piston and the liquid pressurizing piston, and has a connecting member for integrally reciprocating the gas pressurizing piston and the liquid pressurizing piston, and further includes an intermediate chamber located between the gas pressurizing piston and the liquid pressurizing piston and located in the cylinder. In one aspect, the reciprocating pump device further includes a communication flow path for communicating the intermediate chamber and the gas pressurizing chamber, and a check valve disposed in the communication flow path, and the check valve is configured to allow a one-way flow from the intermediate chamber to the gas pressurizing chamber. In one aspect, the cylinder has a boil-off gas inlet communicating with the intermediate chamber. In one aspect, the communication flow path extends through the gas pressurizing piston. In one aspect, the communication flow path is disposed outside the cylinder. In one aspect, the cylinder has a boil-off gas inlet communicating with the gas pressurizing chamber. In one aspect, at least a part of the actuator is disposed in the cylinder. In one aspect, the position where the actuator is connected to the piston is within the cylinder. In one aspect, the reciprocating pump device further includes a relief valve communicating with the intermediate chamber.

[0010] In one aspect, the liquefied gas transfer system further includes a first discharge line connected to the gas pressurizing chamber, a second discharge line connected to the liquid pressurizing chamber, and a cooling device connected to the first discharge line. In one aspect, the cooling device is a heat exchanger having a heating flow path and a cooling flow path adjacent to each other, the heating flow path is connected to the first discharge line, and the cooling flow path is connected to the second discharge line. In one aspect, the liquefied gas transfer system further includes a pressure reducing device connected to the first discharge line and disposed downstream of the cooling device. In one aspect, the liquefied gas transfer system further includes a return line extending from the pressure reducing device to the storage tank.

Advantages of the Invention

[0011] According to the present invention, the piston disposed in the cylinder can alternately pressurize the liquefied gas and the boil-off gas. Therefore, there is no need to provide a dedicated compressor for pressurizing the boil-off gas, and the installation area does not increase. The boil-off gas is pressurized by the piston to become a supercritical fluid. The supercritical fluid can be reused by cooling. Furthermore, by depressurizing the cooled supercritical fluid, the supercritical fluid can be made into a gas-liquid mixed fluid, and the liquefied gas can be recovered from the gas-liquid mixed fluid.

Brief Description of the Drawings

[0012]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Embodiments for Carrying Out the Invention

[0013] Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a schematic diagram showing an embodiment of a liquefied gas transfer system. The liquefied gas transfer system of the embodiment shown in FIG. 1 is a system for transferring liquid hydrogen as an example of liquefied gas. The present invention is not limited to a transfer system for liquid hydrogen, and can also be applied to transfer systems for other types of liquefied gases such as liquefied natural gas (LNG), liquefied ammonia, liquid nitrogen, liquefied ethylene gas, and liquefied petroleum gas. Liquid hydrogen is stored in a storage tank 1. Most of the hydrogen in the storage tank 1 is in a liquid state, but the heat of the surrounding atmosphere is slightly transmitted to the liquid hydrogen through the wall of the storage tank 1. As a result, a part of the liquid hydrogen is gasified to form boil-off gas (BOG). Therefore, as shown in FIG. 1, in the storage tank 1, there are liquefied gas (liquid hydrogen) and boil-off gas (hydrogen gas).

[0014] The liquefied gas transfer system includes a reciprocating pump device 3 configured to suck both the boil-off gas and the liquid hydrogen present in the storage tank 1 and pressurize them separately, and a gas transfer line 5 and a liquid transfer line 6 that connect the reciprocating pump device 3 and the storage tank 1. The boil-off gas (BOG) in the storage tank 1 is transferred to the reciprocating pump device 3 through the gas transfer line 5, and the liquid hydrogen in the storage tank 1 is transferred to the reciprocating pump device 3 through the liquid transfer line 6. A gas check valve 7 and a liquid check valve 8 are respectively attached to the gas transfer line 5 and the liquid transfer line 6. These check valves 7 and 8 are configured to allow only a one-way flow from the storage tank 1 to the reciprocating pump device 3.

[0015] The reciprocating pump device 3 includes a cylinder 14 having a gas pressurization chamber 10 and a liquid pressurization chamber 11 inside, a piston 17 disposed inside the cylinder 14, and an actuator 18 connected to the piston 17 for reciprocatingly moving the piston 17 within the cylinder 14. The piston 17 is positioned between the gas pressurization chamber 10 and the liquid pressurization chamber 11. The entire actuator 18 is disposed inside the cylinder 14. Therefore, a piston rod extending from the piston 17 to the outside of the cylinder 14 is not provided. The actuator 18 of the present embodiment is a linear motor including a permanent magnet 18A and a coil 18B, but the specific configuration of the actuator 18 is not limited to the present embodiment. For example, the actuator 18 may be a hydraulic cylinder, a combination of a crank mechanism and an electric motor, or the like.

[0016] The cylinder 14 is a sealed container and has a configuration that does not allow leakage of hydrogen introduced therein. The entire piston 17 is positioned inside the cylinder 14. The piston 17 has a gas pressurization surface 21 facing the gas pressurization chamber 10 and a liquid pressurization surface 22 facing the liquid pressurization chamber 11. More specifically, the piston 17 has a gas pressurization piston 24 having the gas pressurization surface 21 and a liquid pressurization piston 25 having the liquid pressurization surface 22. The gas pressurization piston 24 and the liquid pressurization piston 25 are connected by a connecting member 30, and the gas pressurization piston 24 and the liquid pressurization piston 25 reciprocate integrally.

[0017] The reciprocating pump device 3 includes a seal attached to the side surface of the piston 17. More specifically, a first seal 26 is attached to the side surface of the gas pressurization piston 24, and a second seal 27 is attached to the side surface of the liquid pressurization piston 25. The first seal 26 functions to block the gap between the side surface of the gas pressurization piston 24 and the inner surface of the cylinder 14, and the second seal 27 functions to block the gap between the side surface of the liquid pressurization piston 25 and the inner surface of the cylinder 14.

[0018] The reciprocating pump device 3 has an intermediate chamber 32 located within the cylinder 14. This intermediate chamber 32 is positioned between the gas pressurizing piston 24 and the liquid pressurizing piston 25, and reciprocates integrally with the gas pressurizing piston 24 and the liquid pressurizing piston 25. The intermediate chamber 32 is located between the gas pressurizing chamber 10 and the liquid pressurizing chamber 11. The cylinder 14 has a boil-off gas inlet 33 that communicates with the intermediate chamber 32. The boil-off gas inlet 33 is formed in the wall portion of the cylinder 14 that forms the intermediate chamber 32. The gas transfer line 5 communicates with the intermediate chamber 32 through the boil-off gas inlet 33. That is, one end of the gas transfer line 5 is connected to the upper part of the storage tank 1, and the other end of the gas transfer line 5 is connected to the boil-off gas inlet 33 of the cylinder 14 and communicates with the intermediate chamber 32.

[0019] The entire actuator 18 is disposed within the cylinder 14. More specifically, the entire actuator 18 is disposed within the intermediate chamber 32. The permanent magnet 18A of the actuator 18 is fixed to a connecting member 30 within the intermediate chamber 32, and the permanent magnet 18A reciprocates integrally with the connecting member 30 and the piston 17. The coil 18B of the actuator 18 is fixed inside the cylinder 14.

[0020] The intermediate chamber 32 is located between the gas pressurizing chamber 10 and the liquid pressurizing chamber 11. The reciprocating pump device 3 further includes a communication flow path 35 that communicates the intermediate chamber 32 and the gas pressurizing chamber 10, and a check valve 36 disposed in the communication flow path 35. In the present embodiment, the communication flow path 35 is formed within the gas pressurizing piston 24 and extends through the gas pressurizing piston 24. One end of the communication flow path 35 communicates with the intermediate chamber 32, and the other end of the communication flow path 35 communicates with the gas pressurizing chamber 10. The check valve 36 is disposed within the gas pressurizing piston 24. The communication flow path 35 and the check valve 36 reciprocate integrally with the gas pressurizing piston 24. The check valve 36 is configured to allow only a one-way flow from the intermediate chamber 32 to the gas pressurizing chamber 10.

[0021] The cylinder 14 has a liquefied gas inlet 38 that communicates with the liquid pressure chamber 11. The liquefied gas inlet 38 is formed in the wall of the cylinder 14 that forms the liquid pressure chamber 11. The liquid transfer line 6 communicates with the liquid pressure chamber 11 through the liquefied gas inlet 38. That is, one end of the liquid transfer line 6 is connected to the lower part of the storage tank 1, the other end of the liquid transfer line 6 is connected to the cylinder 14, and communicates with the liquid pressure chamber 11.

[0022] The liquefied gas transfer system further includes a first discharge line 41 connected to the gas pressure chamber 10, a second discharge line 42 connected to the liquid pressure chamber 11, a first discharge-side check valve 44 attached to the first discharge line 41, and a second discharge-side check valve 45 attached to the second discharge line 42. The boil-off gas (hydrogen gas) and liquid hydrogen pressurized by the reciprocating pump device 3 are discharged through the first discharge line 41 and the second discharge line 42. The first discharge-side check valve 44 and the second discharge-side check valve 45 are configured to allow only the flow in the direction flowing out from the reciprocating pump device 3.

[0023] The operation of the reciprocating pump device 3 will be described below. When the piston 17 including the gas pressure piston 24 and the liquid pressure piston 25 moves in the cylinder 14, the boil-off gas (hydrogen gas) and liquid hydrogen in the storage tank 1 are introduced into the intermediate chamber 32 and the liquid pressure chamber 11 through the gas transfer line 5 and the liquid transfer line 6, respectively. More specifically, when the piston 17 moves downward in FIG. 1, a negative pressure is formed in the gas pressure chamber 10, and the fluid in the intermediate chamber 32 moves to the gas pressure chamber 10 through the communication flow path 35. As a result, the boil-off gas in the storage tank 1 is introduced into the intermediate chamber 32 through the gas transfer line 5.

[0024] When the piston 17 moves upward in FIG. 1, the liquid hydrogen in the storage tank 1 is introduced into the liquid pressurizing chamber 11 through the liquid transfer line 6. Then, when the piston 17 moves downward in FIG. 1, the boil-off gas in the intermediate chamber 32 moves to the gas pressurizing chamber 10 through the communication flow path 35, and the boil-off gas in the storage tank 1 is introduced into the intermediate chamber 32 through the gas transfer line 5. At the same time, the liquid hydrogen in the liquid pressurizing chamber 11 is pressurized by the liquid pressurizing piston 25. Further, when the piston 17 moves upward in FIG. 1, the boil-off gas in the gas pressurizing chamber 10 is pressurized by the gas pressurizing piston 24, while the liquid hydrogen in the storage tank 1 is introduced into the liquid pressurizing chamber 11 through the liquid transfer line 6.

[0025] In this way, with the reciprocating movement of the piston 17, the boil-off gas and the liquid hydrogen are alternately pressurized by the piston 17 and alternately discharged from the cylinder 14. The pressure in the gas pressurizing chamber 10 varies greatly with the reciprocating movement of the piston 17, but the pressure in the intermediate chamber 32 is maintained by the set pressure of the check valve 36. As a result, the pressure in the storage tank 1 communicating with the intermediate chamber 32 can be adjusted.

[0026] When the liquid pressurizing piston 25 pressurizes the liquid hydrogen in the liquid pressurizing chamber 11, a part of the liquid hydrogen in contact with the second seal 27 is gasified to become boil-off gas, and the boil-off gas flows into the intermediate chamber 32. This boil-off gas is mixed with the boil-off gas introduced from the storage tank 1 in the intermediate chamber 32 and flows into the gas pressurizing chamber 10 through the communication flow path 35. In this way, the boil-off gas generated in the cylinder 14 does not leak to the outside of the cylinder 14, and the boil-off gas can be recovered.

[0027] In particular, the entire actuator 18 is disposed within the cylinder 14, and the position where the actuator 18 is connected to the piston 17 is within the cylinder 14. Accordingly, a piston rod passing through the cylinder 14 is unnecessary, and a seal for sealing the gap between the piston rod and the cylinder 14 is also unnecessary. Further, boil-off gas does not leak from the gap between the piston rod and the cylinder 14.

[0028] The liquefied gas transfer system further includes a heat exchanger 50 as a cooling device connected to the first discharge line 41 and the second discharge line 42. The boil-off gas and liquid hydrogen pressurized by the reciprocating pump device 3 are sent to the heat exchanger 50 through the first discharge line 41 and the second discharge line 42. The heat exchanger 50 has a heating flow path 51 and a cooling flow path 52 adjacent to each other. The heating flow path 51 is connected to the first discharge line 41, and the cooling flow path 52 is connected to the second discharge line 42. Within the heat exchanger 50, the pressurized boil-off gas flows through the heating flow path 51, and the pressurized liquid hydrogen flows through the cooling flow path 52. Heat exchange is performed between the pressurized boil-off gas in the heating flow path 51 and the pressurized liquid hydrogen in the cooling flow path 52. As a result, the pressurized boil-off gas is cooled, and the liquid hydrogen is heated. The heated liquid hydrogen is sent to an evaporator (for example, the evaporator 202 shown in FIG. 10).

[0029] In the present embodiment, the heat exchanger 50 is provided as a cooling device for cooling the pressurized boil-off gas. However, as long as the pressurized boil-off gas can be cooled, the type of the cooling device is not particularly limited. For example, a refrigerator in which a refrigerant circulates inside may be used as the cooling device.

[0030] The liquefied gas transfer system further includes a pressure reducing device 55 connected to the first discharge line 41. The pressure reducing device 55 is arranged on the downstream side of the heat exchanger 50 as a cooling device. The pressure reducing device 55 is a device for reducing the pressure of the pressurized and cooled boil-off gas that has passed through the heat exchanger 50 as a cooling device to atmospheric pressure, and its specific configuration is not particularly limited as long as its intended function can be exerted. For example, examples of the pressure reducing device 55 include an expander and a Joule-Thomson valve.

[0031] The liquefied gas transfer system further includes a return line 60 extending from the pressure reducing device 55 to the upper part of the storage tank 1. When the pressure of the pressurized and cooled boil-off gas is reduced to atmospheric pressure by the pressure reducing device 55, the boil-off gas becomes a gas-liquid mixed fluid. This gas-liquid mixed fluid is returned to the storage tank 1 through the return line 60. The liquid hydrogen (liquefied gas) contained in the gas-liquid mixed fluid is mixed with the liquid hydrogen held in the storage tank 1. The hydrogen gas contained in the gas-liquid mixed fluid is mixed with the boil-off gas (hydrogen gas) held in the storage tank 1.

[0032] In this way, a part of the boil-off gas sent from the storage tank 1 to the reciprocating pump device 3 forms liquid hydrogen (liquefied gas) and is recovered into the storage tank 1. According to the present embodiment, a part of the boil-off gas that was discarded into the atmosphere in the conventional system can be regenerated into liquefied gas. Also, the piston 17 arranged in the single cylinder 14 can alternately pressurize the liquefied gas and the boil-off gas. Therefore, there is no need to provide a dedicated compressor for pressurizing the boil-off gas, and the installation area does not increase.

[0033] Figure 2 is a Mollier diagram showing the state of hydrogen circulating in the liquefied gas transfer system shown in Figure 1. The vertical axis represents the pressure of hydrogen, and the horizontal axis represents the specific enthalpy of hydrogen. The process from point A to point B in Figure 2 is the process of compressing the boil-off gas (hydrogen gas) by the reciprocating pump device 3. As a result of this compression process, the boil-off gas transitions from the gas phase to the supercritical state. Hereinafter, the boil-off gas in the supercritical state is referred to as a supercritical fluid.

[0034] The process from point B to point C in FIG. 2 is a process of cooling the supercritical fluid by the heat exchanger 50 as a cooling device. As a result of this cooling process, the temperature of the supercritical fluid decreases while the pressure of the supercritical fluid is maintained. The process from point C to point D in FIG. 2 is a process of reducing the pressure of the supercritical fluid by the pressure reducing device 55. As a result of this pressure reduction process, the supercritical fluid becomes a gas-liquid mixed fluid. The mass ratio of liquid hydrogen (liquefied gas) to hydrogen gas (boil-off gas) in the gas-liquid mixed fluid corresponds to the ratio of the lengths L2 and L1 shown in FIG. 2.

[0035] As described above, the boil-off gas is pressurized by the piston 17 to become a supercritical fluid. The supercritical fluid can be reused by cooling. Furthermore, by reducing the pressure of the cooled supercritical fluid, the supercritical fluid can be made into a gas-liquid mixed fluid, and the liquefied gas can be recovered from the gas-liquid mixed fluid.

[0036] As shown in FIGS. 3 and 4, the pressure reducing device 55 may be omitted. In the embodiment shown in FIG. 3, the boil-off gas (supercritical fluid) pressurized and cooled by the heat exchanger 50 as a cooling device is returned into the storage tank 1 through the return line 60, contributing to maintaining the pressure in the storage tank 1. In the embodiment shown in FIG. 4, the boil-off gas (supercritical fluid) pressurized and cooled by the heat exchanger 50 as a cooling device is sent to a dispenser or accumulator (for example, the dispenser 204 or accumulator 203 shown in FIG. 10) of a hydrogen station, and supplied to a fuel cell vehicle or the like through the dispenser.

[0037] FIG. 5 is a schematic diagram showing another embodiment of the reciprocating pump device 3. The configuration and operation of this embodiment not specifically described are the same as those of the embodiment described with reference to FIG. 1, so redundant explanations thereof are omitted. In the embodiment shown in FIG. 5, the communication flow path 35 is disposed outside the cylinder 14. The check valve 36 is also disposed outside the cylinder 14. One end of the communication flow path 35 is connected to the wall portion of the cylinder 14 forming the intermediate chamber 32, and the other end of the communication flow path 35 is connected to the wall portion of the cylinder 14 forming the gas pressurizing chamber 10. Similar to the embodiment described with reference to FIG. 1, the boil-off gas in the storage tank 1 is introduced into the intermediate chamber 32 as the piston 17 reciprocates, flows through the communication flow path 35, and flows into the gas pressurizing chamber 10.

[0038] FIG. 6 is a schematic diagram showing yet another embodiment of the reciprocating pump device 3. The configuration and operation of this embodiment not specifically described are the same as those of the embodiment described with reference to FIG. 1, so redundant explanations thereof are omitted. In the embodiment shown in FIG. 6, a part of the actuator 18 is disposed inside the cylinder 14, and the other part is disposed outside the cylinder 14. Specifically, the actuator 18 includes a permanent magnet 18A fixed to a connecting member 30 that connects the gas pressurizing piston 24 and the liquid pressurizing piston 25, and a coil 18B disposed outside the cylinder 14. The permanent magnet 18A is disposed in the intermediate chamber 32 of the cylinder 14 and reciprocates integrally with the piston 17 and the connecting member 30. The coil 18B is located outside the permanent magnet 18A.

[0039] Also in the embodiment shown in FIG. 6, the position where the actuator 18 is connected to the piston 17 is inside the cylinder 14. Therefore, a piston rod passing through the cylinder 14 is unnecessary, and a seal for sealing the gap between the piston rod and the cylinder 14 is also unnecessary. Furthermore, boil-off gas does not leak from the gap between the piston rod and the cylinder 14.

[0040] FIG. 7 is a schematic diagram showing still another embodiment of the reciprocating pump device 3. The configuration and operation of this embodiment not particularly described are the same as those of the embodiment described with reference to FIG. 1, and thus the overlapping description thereof will be omitted. In the embodiment shown in FIG. 7, the cylinder 14 has a boil-off gas inlet 33 communicating with the gas pressurizing chamber 10. The boil-off gas inlet 33 is formed in the wall portion of the cylinder 14 that forms the gas pressurizing chamber 10. The gas transfer line 5 is connected to the boil-off gas inlet 33. Therefore, the boil-off gas in the storage tank 1 is directly introduced into the gas pressurizing chamber 10 through the gas transfer line 5.

[0041] In the embodiment shown in FIG. 7, the boil-off gas in the storage tank 1 is not introduced into the intermediate chamber 32, but the flow of the other boil-off gas is the same as that of the embodiment shown in FIG. 1. The communication flow path 35 and the check valve 36 are provided in the same manner also in the embodiment shown in FIG. 7. This is to guide the hydrogen gas leaked from the liquid pressurizing chamber 11 to the gas pressurizing chamber 10 through the communication flow path 35.

[0042] FIG. 8 is a schematic diagram showing still another embodiment of the reciprocating pump device 3. The configuration and operation of this embodiment not particularly described are the same as those of the embodiment described with reference to FIG. 7, and thus the overlapping description thereof will be omitted. In the embodiment shown in FIG. 8, the reciprocating pump device includes a relief valve 61 communicating with the intermediate chamber 32. In this embodiment, the communication flow path 35 and the check valve 36 are not provided.

[0043] The liquid hydrogen leaked from the liquid pressurizing chamber 11 into the intermediate chamber 32 through the second seal 27 becomes hydrogen gas, and the pressure in the intermediate chamber 32 rises. The relief valve 61 is configured to open when the pressure in the intermediate chamber 32 exceeds a set value and release the hydrogen gas in the intermediate chamber 32 to the outside of the cylinder 14.

[0044] FIG. 9 is a schematic diagram showing still another embodiment of the reciprocating pump device 3. The configuration and operation of this embodiment that are not particularly described are the same as those of the embodiment described with reference to FIG. 1, and thus the overlapping description thereof will be omitted. In the embodiment shown in FIG. 9, the actuator 18 is disposed outside the cylinder 14. The piston 17 is connected to the actuator 18 by a piston rod 63 that penetrates the cylinder 14. The reciprocating pump device 3 includes a seal 64 that seals the gap between the piston rod and the cylinder 14.

[0045] The reciprocating pump device 3 of this embodiment is applicable when a slight leakage of boil-off gas from the cylinder 14 is allowed.

[0046] The embodiments described with reference to FIGS. 1 to 9 can be combined as appropriate. For example, any of the embodiments described with reference to FIGS. 5 to 9 may be applied to the embodiment described with reference to FIG. 3 or FIG. 4.

[0047] The above-described embodiments are described for the purpose of enabling a person having ordinary knowledge in the technical field to which the present invention pertains to practice the present invention. Various modifications of the above embodiments can be naturally made by those skilled in the art, and the technical idea of the present invention can also be applied to other embodiments. Therefore, the present invention is not limited to the described embodiments, but is to be construed in the broadest scope in accordance with the technical idea defined by the claims.

Explanation of Reference Numerals

[0048] 1 Storage tank 3 Reciprocating pump device 5 Gas transfer line 6 Liquid transfer line 7 Gas check valve 8 Liquid check valve 10 Gas pressurizing chamber 11 Liquid pressurizing chamber 14 Cylinder 17 Piston 18 Actuator 18A Permanent Magnet 18B Coil 21 Gas Pressurized Surface 22 Liquid Pressurized Surface 24 Gas Pressurizing Piston 25 Liquid Pressurizing Piston 26 First Seal 27 Second Seal 30 Connecting Member 32 Intermediate Chamber 33 Boil-off Gas Inlet 35 Communication Flow Path 36 Check Valve 38 Liquefied Gas Inlet 41 First Discharge Line 42 Second Discharge Line 44 First Discharge Side Check Valve 45 Second Discharge Side Check Valve 50 Heat Exchanger (Cooling Device) 51 Heating Flow Path 52 Cooling Flow Path 55 Pressure Reducing Device 60 Return Line 61 Relief Valve 63 Piston Rod 64 Seal 200 Storage Tank 201 Pumping Device 202 Evaporator 203 Accumulator 204 Dispenser

Claims

1. A liquefied gas transfer system for transferring liquefied gas in a storage tank, comprising: A reciprocating pump device for pressurizing the liquefied gas and boil-off gas in the storage tank; The reciprocating pump device includes: A cylinder having a gas pressurizing chamber and a liquid pressurizing chamber therein; A piston disposed in the cylinder; An actuator connected to the piston for reciprocating the piston; The piston is located between the gas pressurizing chamber and the liquid pressurizing chamber; The piston has a gas pressurizing surface facing the gas pressurizing chamber and a liquid pressurizing surface facing the liquid pressurizing chamber, the liquefied gas transfer system.

2. The piston has a gas pressurizing piston having the gas pressurizing surface and a liquid pressurizing piston having the liquid pressurizing surface; The reciprocating pump device includes: A connecting member connecting the gas pressurizing piston and the liquid pressurizing piston and reciprocating the gas pressurizing piston and the liquid pressurizing piston integrally; The liquefied gas transfer system according to claim 1, further comprising an intermediate chamber located between the gas pressurizing piston and the liquid pressurizing piston and located in the cylinder.

3. The reciprocating pump device includes: A communication flow path communicating the intermediate chamber and the gas pressurizing chamber; The reciprocating pump device further includes a check valve disposed in the communication flow path; The check valve is configured to allow a one-way flow from the intermediate chamber to the gas pressurizing chamber, the liquefied gas transfer system according to claim 2.

4. The cylinder has a boil-off gas inlet communicating with the intermediate chamber, the liquefied gas transfer system according to claim 3.

5. The liquefied gas transfer system according to claim 3, wherein the communication flow path extends through the gas pressurizing piston.

6. The liquefied gas transfer system according to claim 3, wherein the communication flow path is disposed outside the cylinder.

7. The liquefied gas transfer system according to any one of claims 1 to 3, wherein the cylinder has a boil-off gas inlet communicating with the gas pressurizing chamber.

8. The liquefied gas transfer system according to any one of claims 1 to 7, wherein at least a part of the actuator is disposed within the cylinder.

9. The liquefied gas transfer system according to claim 8, wherein the position where the actuator is connected to the piston is within the cylinder.

10. The liquefied gas transfer system according to claim 2, wherein the reciprocating pump device further includes a relief valve communicating with the intermediate chamber.

11. A first discharge line connected to the gas pressurizing chamber, A second discharge line connected to the liquid pressurizing chamber, The liquefied gas transfer system according to any one of claims 1 to 10, further comprising a cooling device connected to the first discharge line.

12. The cooling device is a heat exchanger having a heating flow path and a cooling flow path adjacent to each other, The liquefied gas transfer system according to claim 11, wherein the heating flow path is connected to the first discharge line, and the cooling flow path is connected to the second discharge line.

13. The liquefied gas transfer system according to claim 11, further comprising a pressure reducing device connected to the first discharge line and disposed downstream of the cooling device.

14. The liquefied gas transfer system according to claim 13, further comprising a return line extending from the pressure reducing device to the storage tank.

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