JP7696785B2 - Liquefied Gas Transfer System - Google Patents

Description

The present invention relates to a liquefied gas transfer system for transferring liquefied gas, such as liquefied natural gas (LNG) or liquefied hydrogen, stored in a storage tank, and in particular to a liquefied gas transfer system including a pump device for pressurizing the liquefied gas and boil-off gas.

Natural gas is widely used for thermal power generation and as a chemical raw material. Hydrogen is also expected to be an energy source that does not generate carbon dioxide, a cause of global warming. Uses of hydrogen as an energy source include fuel cells and turbine power generation. Natural gas and hydrogen are in a gaseous state at room temperature, so they are cooled and liquefied in order to be stored and transported. Liquefied gases such as liquefied natural gas (LNG) and liquid hydrogen are transported by truck to power plants, hydrogen stations, etc.

There are two types of hydrogen stations: those 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, then vaporize it and supply hydrogen to fuel cell vehicles, etc. The latter can boost the pressure of larger amounts of hydrogen than the former, so the entire hydrogen station requires less equipment.

Figure 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. A pump device 201 sends the liquid hydrogen in the storage tank 200 to an evaporator 202, which turns the liquid hydrogen into hydrogen gas. The hydrogen gas is sent to a pressure accumulator 203, and the high-pressure hydrogen gas is held in the pressure accumulator 203. The hydrogen gas is then sent to a dispenser 204, from which it is supplied to a fuel cell vehicle or the like.

JP 2008-196590 A

However, at hydrogen stations, vaporized hydrogen (boil-off gas: BOG) is generated due to heat input from the outside to the piping and storage tank 200, and heat input due to the operation of the pump device 201. Because the boil-off gas is at almost atmospheric pressure, it is difficult to reuse it within the hydrogen station, and it is usually discarded into the air. Methods for reusing the generated boil-off gas include recovering it in a fuel cell, and compressing the boil-off gas with a compressor and storing it in the system, but both of these methods require expensive capital investment and require a large installation area for the system, which is problematic. Such problems can occur not only with liquid hydrogen, but also with other types of liquefied gas, such as liquefied natural gas.

Therefore, the present invention provides a liquefied gas transfer system that can effectively utilize the boil-off gas generated from liquefied gas with a simple configuration.

In one aspect, a liquefied gas transfer system for transferring liquefied gas in a storage tank is provided, the liquefied gas transfer system comprising a reciprocating pump device for pressurizing the liquefied gas and boil-off gas in the storage tank, the reciprocating pump device comprising a cylinder having a gas pressurization chamber and a liquid pressurization chamber therein, a piston disposed in the cylinder, and an actuator connected to the piston for reciprocating the piston, the piston being positioned between the gas pressurization chamber and the liquid pressurization chamber, and the piston having a gas pressurization surface facing the gas pressurization chamber and a liquid pressurization surface facing the liquid pressurization chamber.

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, and the reciprocating pump device further includes a connecting member that connects the gas pressurizing piston and the liquid pressurizing piston and causes the gas pressurizing piston and the liquid pressurizing piston to reciprocate together, and an intermediate chamber that is located between the gas pressurizing piston and the liquid pressurizing piston and is located within the cylinder.
In one aspect, the reciprocating pump device further includes a communication passage that connects the intermediate chamber and the gas pressurization chamber, and a check valve disposed in the communication passage, the check valve being configured to allow a one-way flow from the intermediate chamber to the gas pressurization chamber.
In one embodiment, the cylinder has a boil-off gas inlet port communicating with the intermediate chamber.
In one embodiment, the communication passage extends through the gas pressurizing piston.
In one embodiment, the communication passage is disposed outside the cylinder.
In one embodiment, the cylinder has a boil-off gas inlet that communicates with the gas pressurizing chamber.
In one aspect, at least a portion of the actuator is disposed within the cylinder.
In one aspect, the location where the actuator is coupled to the piston is within the cylinder.
In one embodiment, the reciprocating pump device further includes a relief valve communicating with the intermediate chamber.

In one aspect, the liquefied gas transfer system further includes a first discharge line connected to the gas pressurization chamber, a second discharge line connected to the liquid pressurization chamber, and a cooling device connected to the first discharge line.
In one aspect, the cooling device is a heat exchanger having adjacent heating and cooling passages, the heating passage being connected to the first discharge line and the cooling passage being connected to the second discharge line.
In one aspect, the liquefied gas transfer system further comprises 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 comprises a return line extending from the pressure reducing device to the storage tank.

According to the present invention, the piston arranged 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 it. 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.

FIG. 1 is a schematic diagram illustrating one embodiment of a liquefied gas transfer system. FIG. 2 is a Mollier diagram showing the state of hydrogen circulating in a liquefied gas transport system. FIG. 1 is a schematic diagram showing another embodiment of a liquefied gas transfer system. FIG. 13 is a schematic diagram showing yet another embodiment of a liquefied gas transfer system. FIG. 11 is a schematic diagram showing another embodiment of the reciprocating pump device. FIG. 13 is a schematic diagram showing still another embodiment of the reciprocating pump device. FIG. 13 is a schematic diagram showing still another embodiment of the reciprocating pump device. FIG. 13 is a schematic diagram showing still another embodiment of the reciprocating pump device. FIG. 13 is a schematic diagram showing still another embodiment of the reciprocating pump device. FIG. 1 is a schematic diagram showing an example of a hydrogen station.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a schematic diagram showing one embodiment of a liquefied gas transfer system. The liquefied gas transfer system of the embodiment shown in FIG. 1 is a system for transferring liquefied hydrogen as an example of liquefied gas. The present invention is not limited to a transfer system for liquefied hydrogen, but can also be applied to transfer systems for other types of liquefied gas, 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 liquid, but a small amount of heat from the surrounding atmosphere is transferred 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, liquefied gas (liquid hydrogen) and boil-off gas (hydrogen gas) exist in the storage tank 1.

The liquefied gas transfer system includes a reciprocating pump device 3 configured to suck in both boil-off gas and 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 to 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 attached to the gas transfer line 5 and the liquid transfer line 6, respectively. These check valves 7 and 8 are configured to allow only one-way flow from the storage tank 1 to the reciprocating pump device 3.

The reciprocating pump device 3 includes a cylinder 14 having a gas pressure chamber 10 and a liquid pressure chamber 11 therein, a piston 17 disposed in the cylinder 14, and an actuator 18 connected to the piston 17 for reciprocating the piston 17 within the cylinder 14. The piston 17 is located between the gas pressure chamber 10 and the liquid pressure chamber 11. The entire actuator 18 is disposed within the cylinder 14. Therefore, no piston rod is provided extending from the piston 17 to the outside of the cylinder 14. The actuator 18 in this embodiment is a linear motor equipped with a permanent magnet 18A and a coil 18B, but the specific configuration of the actuator 18 is not limited to this embodiment. For example, the actuator 18 may be a hydraulic cylinder, or a combination of a crank mechanism and an electric motor.

The cylinder 14 is a sealed container and is configured to not allow leakage of hydrogen introduced inside. The entire piston 17 is located inside the cylinder 14. The piston 17 has a gas pressurizing surface 21 facing the gas pressurizing chamber 10 and a liquid pressurizing surface 22 facing the liquid pressurizing chamber 11. More specifically, the piston 17 has a gas pressurizing piston 24 having the gas pressurizing surface 21, and a liquid pressurizing piston 25 having the liquid pressurizing surface 22. The gas pressurizing piston 24 and the liquid pressurizing piston 25 are connected by a connecting member 30, and the gas pressurizing piston 24 and the liquid pressurizing piston 25 reciprocate together.

The reciprocating pump device 3 is equipped with a seal attached to the side of the piston 17. More specifically, a first seal 26 is attached to the side of the gas pressurizing piston 24, and a second seal 27 is attached to the side of the liquid pressurizing piston 25. The first seal 26 has the function of sealing the gap between the side of the gas pressurizing piston 24 and the inner surface of the cylinder 14, and the second seal 27 has the function of sealing the gap between the side of the liquid pressurizing piston 25 and the inner surface of the cylinder 14.

The reciprocating pump device 3 has an intermediate chamber 32 located in the cylinder 14. This intermediate chamber 32 is located between the gas pressurizing piston 24 and the liquid pressurizing piston 25, and reciprocates together 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 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 top 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.

The actuator 18 is entirely disposed within the cylinder 14. More specifically, the actuator 18 is entirely disposed within the intermediate chamber 32. The permanent magnet 18A of the actuator 18 is fixed to a connecting member 30 in the intermediate chamber 32, and the permanent magnet 18A moves back and forth together with the connecting member 30 and the piston 17. The coil 18B of the actuator 18 is fixed inside the cylinder 14.

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 passage 35 that communicates between the intermediate chamber 32 and the gas pressurizing chamber 10, and a check valve 36 arranged in the communication flow passage 35. In this embodiment, the communication flow passage 35 is formed in the gas pressurizing piston 24 and extends through the gas pressurizing piston 24. One end of the communication flow passage 35 communicates with the intermediate chamber 32, and the other end of the communication flow passage 35 communicates with the gas pressurizing chamber 10. The check valve 36 is arranged in the gas pressurizing piston 24. The communication flow passage 35 and the check valve 36 reciprocate together with the gas pressurizing piston 24. The check valve 36 is configured to allow only one-way flow from the intermediate chamber 32 to the gas pressurizing chamber 10.

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, and the other end of the liquid transfer line 6 is connected to the cylinder 14 and communicates with the liquid pressure chamber 11.

The liquefied gas transfer system further includes a first discharge line 41 connected to the gas pressurization chamber 10, a second discharge line 42 connected to the liquid pressurization 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 flow in the direction out of the reciprocating pump device 3.

The operation of the reciprocating pump device 3 will be described below. When the piston 17, which includes the gas pressurizing piston 24 and the liquid pressurizing piston 25, moves within 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 pressurizing 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, negative pressure is formed in the gas pressurizing chamber 10, and the fluid in the intermediate chamber 32 moves to the gas pressurizing chamber 10 through the communicating 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.

1, the liquid hydrogen in the storage tank 1 is introduced into the liquid pressurization 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 pressurization chamber 10 through the communication passage 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 pressurization chamber 11 is pressurized by the liquid pressurization piston 25. Furthermore, when the piston 17 moves upward in FIG. 1, the boil-off gas in the gas pressurization chamber 10 is pressurized by the gas pressurization piston 24, while the liquid hydrogen in the storage tank 1 is introduced into the liquid pressurization chamber 11 through the liquid transfer line 6.

In this way, as the piston 17 reciprocates, the boil-off gas and liquid hydrogen are alternately pressurized by the piston 17 and alternately discharged from the cylinder 14. The pressure in the gas pressurization chamber 10 fluctuates greatly as the piston 17 reciprocates, 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, which is connected to the intermediate chamber 32, can be adjusted.

When the liquid pressurizing piston 25 pressurizes the liquid hydrogen in the liquid pressurizing chamber 11, a portion 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 communicating flow passage 35. In this way, the boil-off gas generated in the cylinder 14 does not leak from the cylinder 14 to the outside, and the boil-off gas can be recovered.

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. Therefore, a piston rod that passes through the cylinder 14 is not required, and a seal that seals the gap between the piston rod and the cylinder 14 is also not required. Furthermore, boil-off gas does not leak from the gap between the piston rod and the cylinder 14.

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. In 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, and 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) or the like.

In this embodiment, a heat exchanger 50 is provided as a cooling device for cooling the pressurized boil-off gas, but the type of cooling device is not particularly limited as long as it can cool the pressurized boil-off gas. For example, a refrigerator in which a refrigerant circulates inside may be used as the cooling device.

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 disposed downstream of the heat exchanger 50 serving 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 serving as a cooling device to atmospheric pressure, and its specific configuration is not particularly limited as long as it can perform its intended function. For example, examples of the pressure reducing device 55 include an expander and a Joule-Thomson valve.

The liquefied gas transfer system further includes a return line 60 extending from the pressure reducing device 55 to the top 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.

In this way, a portion 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 in the storage tank 1. According to this embodiment, a portion of the boil-off gas that was discarded into the atmosphere in conventional systems can be recycled into liquefied gas. In addition, 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.

Figure 2 is a Mollier diagram showing the state of hydrogen circulating within the liquefied gas transport system shown in Figure 1. The vertical axis represents hydrogen pressure, and the horizontal axis represents hydrogen specific enthalpy. The process from point A to point B in Figure 2 is the process of compressing 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 a supercritical state. Hereinafter, boil-off gas in a supercritical state will be referred to as a supercritical fluid.

The process from point B to point C in FIG. 2 is a process of cooling the supercritical fluid using a 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 using a pressure reducing device 55. As a result of this pressure reducing 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 lengths L2 and L1 shown in FIG. 2.

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 it. Furthermore, the cooled supercritical fluid can be reduced in pressure to turn it into a gas-liquid mixture, from which liquefied gas can be recovered.

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

Figure 5 is a schematic diagram showing another embodiment of the reciprocating pump device 3. The configuration and operation of this embodiment, which are not particularly described, are the same as those of the embodiment described with reference to Figure 1, so duplicated descriptions will be omitted. In the embodiment shown in Figure 5, the communication flow path 35 is arranged outside the cylinder 14. The check valve 36 is also arranged outside the cylinder 14. One end of the communication flow path 35 is connected to the wall of the cylinder 14 that forms the intermediate chamber 32, and the other end of the communication flow path 35 is connected to the wall of the cylinder 14 that forms the gas pressurizing chamber 10. As in the embodiment described with reference to Figure 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.

Figure 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 Figure 1, so the overlapping description will be omitted. In the embodiment shown in Figure 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 together with the piston 17 and the connecting member 30. The coil 18B is located outside the permanent magnet 18A.

Even 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 penetrating the cylinder 14 is not required, and a seal for sealing the gap between the piston rod and the cylinder 14 is also not required. Furthermore, boil-off gas does not leak from the gap between the piston rod and the cylinder 14.

Figure 7 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 Figure 1, so duplicated descriptions will be omitted. In the embodiment shown in Figure 7, the cylinder 14 has a boil-off gas inlet 33 that communicates with the gas pressurization chamber 10. The boil-off gas inlet 33 is formed in the wall of the cylinder 14 that forms the gas pressurization 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 pressurization chamber 10 through the gas transfer line 5.

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 boil-off gas is otherwise the same as in the embodiment shown in FIG. 1. The communicating passage 35 and the check valve 36 are also provided in the embodiment shown in FIG. 7. This is to guide the hydrogen gas leaking from the liquid pressurization chamber 11 to the gas pressurization chamber 10 through the communicating passage 35.

Figure 8 is a schematic diagram showing yet another embodiment of the reciprocating pump device 3. The configuration and operation of this embodiment that are not specifically described are the same as those of the embodiment described with reference to Figure 7, and therefore redundant description will be omitted. In the embodiment shown in Figure 8, the reciprocating pump device includes a relief valve 61 that communicates with the intermediate chamber 32. In this embodiment, the communication flow path 35 and the check valve 36 are not provided.

Liquid hydrogen leaking from the liquid pressure chamber 11 through the second seal 27 into the intermediate chamber 32 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.

Figure 9 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 Figure 1, and therefore the overlapping description will be omitted. In the embodiment shown in Figure 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 passes through the cylinder 14. The reciprocating pump device 3 is provided with a seal 64 that seals the gap between the piston rod and the cylinder 14.

The reciprocating pump device 3 of this embodiment is applicable when a small amount of boil-off gas leakage from the cylinder 14 is acceptable.

The embodiments described with reference to Figures 1 to 9 can be combined as appropriate. For example, any of the embodiments described with reference to Figures 5 to 9 may be applied to the embodiment described with reference to Figure 3 or Figure 4.

The above-described embodiments have been 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-described embodiments would naturally be possible for a person skilled in the art, and the technical ideas of the present invention may also be applied to other embodiments. Therefore, the present invention is not limited to the described embodiments, but is to be interpreted in the broadest scope in accordance with the technical ideas defined by the scope of the claims.

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 pressurization chamber 11 Liquid pressurization chamber 14 Cylinder 17 Piston 18 Actuator 18A Permanent magnet 18B Coil 21 Gas pressurization surface 22 Liquid pressurization surface 24 Gas pressurization piston 25 Liquid pressurization 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 pump device 202 evaporator 203 pressure accumulator 204 dispenser

Claims (14)

A liquefied gas transfer system for transferring liquefied gas in a storage tank, comprising:
a reciprocating pump device for pressurizing the liquefied gas and the 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 within the cylinder;
an actuator coupled 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 piston includes 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 that connects the gas pressurizing piston and the liquid pressurizing piston and allows the gas pressurizing piston and the liquid pressurizing piston to reciprocate together;
2. The liquefied gas transfer system of claim 1, further comprising an intermediate chamber located between said gas pressurizing piston and said liquid pressurizing piston and within said cylinder. The reciprocating pump device includes:
a communication flow passage that communicates the intermediate chamber with the gas pressurizing chamber;
The communication passage further includes a check valve disposed therein,
3. The liquefied gas transfer system of claim 2, wherein the check valve is configured to allow unidirectional flow from the intermediate chamber to the gas pressurization chamber. The liquefied gas transfer system according to claim 3, wherein the cylinder has a boil-off gas inlet that communicates with the intermediate chamber. The liquefied gas transfer system according to claim 3, wherein the communication passage extends through the gas pressurizing piston. The liquefied gas transfer system according to claim 3, wherein the communication passage is disposed outside the cylinder. The liquefied gas transfer system according to any one of claims 1 to 3, wherein the cylinder has a boil-off gas inlet that communicates with the gas pressurization chamber. The liquefied gas transfer system according to any one of claims 1 to 7, wherein at least a portion of the actuator is disposed within the cylinder. The liquefied gas transfer system according to claim 8, wherein the actuator is connected to the piston at a position within the cylinder. The liquefied gas transfer system according to claim 2, wherein the reciprocating pump device further includes a relief valve communicating with the intermediate chamber. A first discharge line connected to the gas pressurizing chamber;
a second discharge line connected to the liquid pressurizing chamber;
11. A liquefied gas transfer system as claimed in any one of claims 1 to 10, further comprising a cooling device connected to the first discharge line. The cooling device is a heat exchanger having a heating passage and a cooling passage adjacent to each other,
12. The liquefied gas transfer system of claim 11, wherein the heating passage is connected to the first discharge line and the cooling passage is connected to the second discharge line. The liquefied gas transfer system of claim 11, further comprising a pressure reducing device connected to the first discharge line and disposed downstream of the cooling device. The liquefied gas transfer system of claim 13, further comprising a return line extending from the pressure reducing device to the storage tank.

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