Refrigerant charging system for ship reliquefaction systems

Abstract

A refrigerant charging system for a marine reliquefaction system is disclosed. The refrigerant filling system of the ship reliquefaction system of the present invention compresses evaporated gas generated in a storage tank in which liquefied gas is stored, and reliquefies the compressed evaporated gas by heat exchange with a refrigerant circulating in a refrigerant circulation line in a heat exchanger, and includes a utility N that is supplied to the ship. 2 A buffer tank that stores the utility water N supplied from the buffer tank 2 The boost compressor compresses the refrigerant and supplies it to the refrigerant circulation line, and the utility N 2 and a first load-up line that supplies the refrigerant to the refrigerant circulation line by bypassing the boost compressor. When the refrigerant circulation line is initially charged with refrigerant while the reliquefaction system is stopped, the pressure difference between the refrigerant circulation line and the buffer tank is utilized to supply the utility N 2 is supplied to the refrigerant circulation line through a first load-up line, thereby filling the refrigerant.

Description

[Technical Field]

[0001] The present invention relates to a refrigerant charging system for a reliquefaction system for a ship, and more particularly to a refrigerant charging system for charging a refrigerant circulating in a reliquefaction system that reliquefies evaporated gas generated on a ship. [Background technology]

[0002] Natural gas, primarily composed of methane, emits almost no environmental pollutants when burned, and is therefore gaining attention as an environmentally friendly fuel. Liquefied natural gas (LNG) is obtained by liquefying natural gas by cooling it to approximately -163°C at atmospheric pressure. Since liquefied natural gas has a volume that is approximately 1 / 600 of that of gaseous natural gas, it is highly suitable for long-distance transportation via sea routes. For this reason, natural gas is primarily stored and transported in the liquefied natural gas state, which is advantageous for storage and transportation.

[0003] Because the liquefaction point of natural gas is an extremely low temperature of approximately -163°C at atmospheric pressure, LNG storage tanks are usually insulated to maintain the LNG in a liquid state, but even with insulation, there is a limit to how well the LNG can be blocked from external heat.As a result, external heat is continuously transferred to the LNG storage tank, causing the LNG inside the LNG storage tank to naturally vaporize during the LNG transportation process, generating boil-off gas (BOG).

[0004] The continued generation of evaporative gases in LNG storage tanks causes the pressure inside the tank to rise. If the internal pressure inside the LNG storage tank exceeds the set safety pressure, there is a risk of an emergency such as tank rupture, so it is necessary to use a safety valve to release the evaporative gases outside the storage tank. However, since evaporative gases are one type of LNG loss and are a significant issue in terms of LNG transportation efficiency and fuel efficiency, various methods are used to deal with evaporative gases generated in storage tanks.

[0005] In recent years, methods have been developed and are being used that involve using evaporated gas at fuel demand sources such as ship engines, re-liquefying evaporated gas and recovering it in storage tanks, or combining these two methods. Summary of the Invention [Problem to be solved by the invention]

[0006] When using a reliquefaction cycle to reliquefy evaporated gas on a ship, two typical reliquefaction methods are known, for example, the SMR cycle and the C3MR cycle. The C3MR cycle (Propane-precooled Mixed Refrigerant Cycle) is a method in which natural gas is cooled using a single refrigerant, propane, and then liquefied by cooling it with a mixed refrigerant. The SMR cycle (Single Mixed Refrigerant Cycle) is a method in which natural gas is liquefied using a mixed refrigerant composed of multiple components.

[0007] Since these SMR and C3MR cycles use a mixed refrigerant, refrigerant leakage occurs as the liquefaction process progresses, causing the composition ratio of the mixed refrigerant to change and resulting in a decrease in liquefaction efficiency. For this reason, it is necessary to continuously measure the composition ratio of the mixed refrigerant and to maintain the refrigerant composition ratio by filling in any missing refrigerant components.

[0008] As another re-liquefaction cycle method for re-liquefying evaporated gas, a single-cycle liquefaction method using nitrogen refrigerant is known.

[0009] While nitrogen refrigerants have a lower cooling efficiency than refrigeration cycles that use mixed refrigerants, they have the advantage of being safe because nitrogen is an inert substance and does not undergo phase changes, making them easy to apply to ships. Furthermore, nitrogen refrigerants also tend to leak as the liquefaction process progresses, so refrigerant refilling is required.

[0010] FIG. 1 is a schematic diagram of a refrigerant charging system for a conventional reliquefaction system using nitrogen refrigerant.

[0011] A ship equipped with storage tanks for storing LNG is usually provided with a nitrogen generator to supply nitrogen to the insulation space of the storage tank as well as utility N2 to be supplied on board the ship. As shown in FIG. 1, nitrogen is supplied from an air compressor 10 and generated by a nitrogen generator 20, and stored in a buffer tank 30. The nitrogen in the buffer tank 30 is supplied on board as utility N2. The nitrogen in the buffer tank 30 is also supplied to a refrigerant charging system and charged into a reliquefaction system RS.

[0012] The refrigerant charging system is composed of a drying and filtering section 40 that receives utility N2 and lowers the dew point of the supplied utility N2, a boost compressor 50 that compresses the utility N2, and an inventory tank 60 that receives and stores the utility N2 compressed by the boost compressor 50.

[0013] Focusing on the operation process in which refrigerant is charged into the refrigerant circulation line until the re-liquefaction cycle, which is in a stopped state, returns to a normal operating state, while the re-liquefaction cycle is in a stopped state, in the refrigerant charging system, utility N2 in the buffer tank 30 is supplied to the drying and filtering section 40, compressed by the boost compressor 50, and then charged into the inventory tank 60.

[0014] When the re-liquefaction cycle begins operation, the refrigerant in the inventory tank 60 is supplied to the refrigerant circulation line of the re-liquefaction system RS to continuously charge the refrigerant, and the load on the re-liquefaction cycle is gradually increased (Load-up) until the re-liquefaction cycle reaches normal operating condition.

[0015] When the reliquefaction cycle reaches a normal operating state, the reliquefaction system RS charges refrigerant into the inventory tank 60 or discharges refrigerant from the inventory tank 60 depending on the load of the reliquefaction cycle, and the load of the reliquefaction cycle is adjusted. Charging or discharging of refrigerant is performed between the inventory tank 60 and the refrigerant circulation line, and depending on the status of the inventory tank 60, the pressure in the inventory tank 60 is adjusted by either charging additional nitrogen refrigerant from the buffer tank 30 via the drying and filtering section 40 and the boost compressor 50 into the inventory tank 60 or discharging part of the nitrogen in the inventory tank 60 to the atmosphere.

[0016] When the load on the reliquefaction system RS is reduced (load-down), nitrogen refrigerant is supplied to the inventory tank 60 by utilizing the pressure difference between the pressure in the refrigerant circulation line and the pressure in the inventory tank 60. Also, when the load on the reliquefaction system RS falls below a predetermined value and it becomes difficult to supply nitrogen refrigerant due to the pressure difference between the pressure in the refrigerant circulation line and the pressure in the inventory tank 60, nitrogen is supplied upstream of the boost compressor 50, compressed by the boost compressor 50, and then supplied to the inventory tank 60. Furthermore, a supply pipe is provided to periodically replenish the reliquefaction system RS with nitrogen consumed by the compander and other devices in the reliquefaction cycle, and a vent line is provided to rapidly extract the nitrogen refrigerant from the reliquefaction system RS in an emergency.

[0017] Here, the present invention proposes a method for reducing the number of devices installed in a refrigerant charging system, realizing a refrigerant charging system with a compact and simple structure, and smoothly charging or discharging the nitrogen refrigerant required for the reliquefaction system. [Means for solving the problem]

[0018] In order to solve the above-mentioned problems, the present invention provides a refrigerant charging system for a ship reliquefaction system, which is provided on a ship and compresses evaporated gas generated in a storage tank that stores liquefied gas, and reliquefies the compressed evaporated gas by heat exchange with a refrigerant circulating in a refrigerant circulation line using a heat exchanger; a buffer tank that stores utility N2 to be supplied on board the ship; a boost compressor that compresses the utility N2 supplied from the buffer tank and supplies it to the refrigerant circulation line; and a first load-up line that supplies the utility N2 in the buffer tank to the refrigerant circulation line, bypassing the boost compressor, wherein, when the refrigerant circulation line is initially charged with refrigerant while the reliquefaction system is stopped, the utility N2 in the buffer tank is supplied to the refrigerant circulation line via the first load-up line using the pressure difference between the refrigerant circulation line and the buffer tank, thereby charging the refrigerant into the refrigerant circulation line.

[0019] Furthermore, in the present invention, it is preferable that a second load-up line be provided that supplies the utility N2 in the buffer tank to the boost compressor and then to the refrigerant circulation line, and when refrigerant is charged into the refrigerant circulation line to increase the load of the reliquefaction system and the pressure in the refrigerant circulation line becomes equal to or higher than the pressure in the buffer tank, the utility N2 in the buffer tank is supplied to the boost compressor via the second load-up line, compressed by the boost compressor, and supplied to the refrigerant circulation line.

[0020] Furthermore, in the present invention, it is preferable that the system further includes a first load-down line connecting the refrigerant circulation line and the buffer tank and discharging the refrigerant in the refrigerant circulation line, and a second load-down line connecting the refrigerant circulation line and the buffer tank via the boost compressor, wherein when the load on the reliquefaction system is reduced, the refrigerant in the refrigerant circulation line is discharged through the first load-down line by utilizing the pressure difference between the refrigerant circulation line and the pressure in the buffer tank, and when the pressure in the buffer tank becomes equal to or higher than the pressure in the refrigerant circulation line, the refrigerant in the refrigerant circulation line is supplied through the second load-down line to the boost compressor, compressed, and recovered in the buffer tank.

[0021] In addition, in the present invention, the refrigerant circulation line includes a refrigerant compressor that compresses the refrigerant discharged from the heat exchanger after cooling the evaporated gas in the heat exchanger, and an expander that expands the refrigerant compressed by the refrigerant compressor and cooled in the heat exchanger, and when the refrigerant expanded and cooled in the expander is supplied to the heat exchanger and the refrigerant is filled from the buffer tank into the refrigerant circulation line, it is preferable that utility N2 is supplied upstream of the refrigerant compressor, and when the load on the reliquefaction system is reduced, the refrigerant is discharged from the refrigerant circulation line downstream of the refrigerant compressor into the buffer tank.

[0022] In the present invention, the buffer tank is preferably provided in a nitrogen generator that generates utility N2 to be supplied as an insulating layer for the storage tank, as a seal gas for an onboard compressor, or as a refrigerant for the reliquefaction system.

[0023] In addition, in the present invention, it is preferable that the nitrogen generation device further includes a nitrogen generator that generates the utility N2 from compressed air and supplies it to the buffer tank, and an air compressor that compresses air and supplies it to the nitrogen generator.

[0024] In addition, in the present invention, it is preferable to provide a dryer downstream of the nitrogen generator to lower the dew point of the utility N2, or to adjust the moisture content of the utility N2 generated by the nitrogen generator so that the utility N2 supplied from the buffer tank is supplied to the refrigerant circulation line without additional drying. [Effects of the Invention]

[0025] The present invention eliminates the need for devices such as dryers and inventory tanks that are installed in conventional refrigerant charging systems, thereby reducing the initial installation costs for installing a reliquefaction system and contributing to the conservation of space on board the ship.

[0026] In addition, by reducing the equipment configuration, a refrigerant charging system with a compact and simple structure can be realized, and the load of the reliquefaction system can be smoothly adjusted by effectively operating already installed equipment and charging or discharging the refrigerant in the reliquefaction system. [Brief explanation of the drawings]

[0027] [Figure 1] 1 shows a schematic diagram of a refrigerant charging system for a conventional reliquefaction system using nitrogen refrigerant. [Figure 2] 1 is a schematic diagram illustrating a refrigerant charging system of a marine reliquefaction system according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0028] The operational advantages of the present invention and the objects achieved by the embodiments of the present invention will now be described by way of example with reference to the drawings and the contents depicted in the drawings.

[0029] The configuration and operation of the embodiment of the present invention will be described below with reference to the drawings. Note that, with respect to the reference numerals given to components in each drawing, the same reference numerals are used to designate the same components in other drawings as far as possible.

[0030] The vessels of the embodiments of the present invention described below may be any type of vessel equipped with storage tanks for storing liquefied gas. Typical examples include self-propelled vessels such as LNG carriers, liquid hydrogen carriers, and LNG regasification vessels (RVs), as well as floating offshore structures without propulsion capabilities, such as LNG floating production storage offloading systems (FPSOs) and LNG floating storage regasification units (FSRUs).

[0031] Furthermore, this embodiment can liquefy gas at low temperatures for transportation and can be applied to the re-liquefaction cycle of all types of liquefied gases that generate evaporated gas during storage. Examples of such liquefied gases include liquefied natural gas (LNG), liquefied ethanol gas (LEG), liquefied petroleum gas (LPG), liquefied ethylene gas, and liquefied propylene gas. Note that in the embodiments described below, LNG, one of the representative liquefied gases, will be used as an example.

[0032] FIG. 2 is a schematic diagram illustrating a refrigerant charging system of a marine reliquefaction system according to an embodiment of the present invention.

[0033] The refrigerant charging system of this embodiment is intended to efficiently charge the reliquefaction cycle of a ship's reliquefaction system, i.e., the refrigerant cycle, with refrigerant, and to efficiently replenish or discharge nitrogen refrigerant in accordance with load fluctuations in the reliquefaction cycle.

[0034] The reliquefaction system RS compresses and cools the evaporated gas generated from the liquefied gas stored in the ship's storage tank, re-liquefies it, and returns it to the storage tank. The reliquefaction system RS includes a compressor (not shown) that compresses the evaporated gas, a heat exchanger (not shown) that cools the compressed evaporated gas, and a gas-liquid separator (not shown) that separates the evaporated gas cooled and re-liquefied by the heat exchanger into gas and liquid.

[0035] The refrigerant cycle (not shown) includes a refrigerant circulation line (not shown) that circulates the refrigerant supplied to the heat exchanger, a refrigerant compressor (not shown) that is provided in the refrigerant circulation line and compresses the refrigerant discharged from the heat exchanger after cooling the evaporative gas in the heat exchanger, and an expander (not shown) that expands and further cools the refrigerant compressed by the refrigerant compressor and then supplied to the heat exchanger, and the refrigerant cooled by expansion is supplied to the heat exchanger as refrigerant. Note that the refrigerant compressor and expander may be connected via a common shaft to form a compander that compresses the refrigerant using the expansion energy of the refrigerant.

[0036] The refrigerant that is circulated through the refrigerant circulation line and supplied to the heat exchanger is, for example, nitrogen (N2).

[0037] The refrigerant charging system of this embodiment is intended to supply the nitrogen refrigerant circulating through such a refrigerant circulation line to the refrigerant cycle of the reliquefaction system RS or to discharge the nitrogen refrigerant from the refrigerant cycle.

[0038] 2, the refrigerant charging system of this embodiment includes a buffer tank 110 that stores utility N2 to be supplied onboard the ship, and a boost compressor 200 that compresses the utility N2 supplied from the buffer tank 110. The nitrogen compressed by the boost compressor 200 is supplied to a refrigerant circulation line. The system also includes a first load-up line UL1 that supplies the utility N2 in the buffer tank 110 to a refrigerant circulation line provided in the refrigerant cycle, bypassing the boost compressor 200, and a second load-up line UL2 that supplies the utility N2 in the buffer tank 110 to the boost compressor 200 and then to the refrigerant circulation line.

[0039] The buffer tank 110 is provided in a nitrogen generator 100 that generates utility N2 to be supplied onboard the ship. The nitrogen generator 100 includes a nitrogen generator 120 that generates utility N2 from compressed air, and an air compressor 130 that compresses the air supplied to the nitrogen generator 120. The utility N2 generated by the nitrogen generator 120 is supplied to the buffer tank 110. The nitrogen generated by the nitrogen generator 100 is also supplied as an insulating layer for storage tanks that store LNG, as seal gas for onboard compressors, and as a refrigerant for the reliquefaction system RS.

[0040] In addition, a dryer that lowers the dew point of the utility N2 may be further installed downstream of the nitrogen generator 120 of the nitrogen generating device 100, or the moisture content of the utility N2 generated by the nitrogen generator 120 may be adjusted (to lower the moisture content) so that the utility N2 stored in the buffer tank 110 can be supplied to the refrigerant circulation line without additional drying.

[0041] When the amount of evaporated gas discharged from the storage tank to be reliquefied changes, the amount of cold energy (required cold energy) required by the reliquefaction system RS changes accordingly. In this case, without adjusting the expander's VGN (Variable Geometry Nozzle), the compression ratio / expansion ratio of the refrigerant compressor and expander is maintained at a fixed value, and the amount of cold energy in the refrigerant cycle is adjusted by either replenishing nitrogen refrigerant in the refrigerant cycle or discharging some of the nitrogen refrigerant in the refrigerant cycle to change the mass flow rate of the nitrogen refrigerant, thereby adjusting the load of the reliquefaction system RS.

[0042] For this reason, a first load-up line UL1 and a second load-up line UL2, which fill the refrigerant circulation line with nitrogen refrigerant from the buffer tank 110, are connected to the low-pressure section of the refrigerant circulation line, i.e., upstream of the refrigerant compressor (not shown), to fill the refrigerant circulation line with nitrogen refrigerant.

[0043] In addition, a first load-down line DL1 is provided which connects the refrigerant circulation line and the buffer tank 110 and discharges the nitrogen refrigerant in the refrigerant circulation line, and a second load-down line DL2 which connects the refrigerant circulation line and the buffer tank 110 via the boost compressor 200. These first and second load-down lines DL1 and DL2 are connected to the buffer tank 110 from the high-pressure section of the refrigerant circulation line, i.e., downstream of the refrigerant compressor, and discharge the nitrogen refrigerant in the refrigerant circulation line into the buffer tank 110.

[0044] The process of charging the refrigerant circulation line with nitrogen refrigerant using the refrigerant charging system of this embodiment will be described in more detail below. First, when initially charging the refrigerant circulation line with nitrogen refrigerant while the reliquefaction system RS is stopped, the utility N2 in the buffer tank 110 is charged into the refrigerant circulation line of the reliquefaction system RS through the first load-up line UL1 by utilizing the pressure difference between the pressure in the refrigerant circulation line and the pressure in the buffer tank 110, and nitrogen refrigerant is supplied to the refrigerant cycle.

[0045] When the refrigerant circulation line is filled with nitrogen refrigerant, the pressure in the refrigerant circulation line becomes equal to the pressure in the buffer tank 110, or the pressure difference between them is reversed. Therefore, when it is not possible to supply nitrogen refrigerant to the refrigerant circulation line by utilizing the pressure difference between the pressure in the refrigerant circulation line and the pressure in the buffer tank 110, the utility N2 in the buffer tank 110 is supplied to the boost compressor 200 via the second load-up line UL2, compressed by the boost compressor 200, and then supplied to the refrigerant circulation line.

[0046] When the amount of cold energy required by the reliquefaction system RS increases and refrigerant is charged into the refrigerant circulation line to increase the load on the reliquefaction system RS (load-up), if the pressure of the nitrogen refrigerant in the refrigerant circulation line exceeds the operating pressure of the buffer tank 110, the utility N2 in the buffer tank 110 is supplied to the boost compressor 200 via the second load-up line UL2, compressed by the boost compressor 200, and then supplied to the refrigerant circulation line to replenish the nitrogen refrigerant.

[0047] On the other hand, when the amount of cold energy required by the reliquefaction system RS decreases and the load on the reliquefaction system RS is reduced (load-down), the pressure difference between the pressure in the refrigerant circulation line and the pressure in the buffer tank 110 is utilized to discharge part of the nitrogen refrigerant in the refrigerant circulation line from downstream of the refrigerant compressor to the buffer tank 110 via the first load-down line DL1, thereby reducing the mass flow rate of the nitrogen refrigerant. Once the pressure in the refrigerant circulation line and the pressure in the buffer tank 110 become equal due to the discharge of the nitrogen refrigerant, the nitrogen refrigerant in the refrigerant circulation line is supplied via the second load-down line DL2 to the upstream of the boost compressor 200, where it is compressed by the boost compressor 200 and then recovered in the buffer tank 110.

[0048] Furthermore, since nitrogen refrigerant is consumed by the refrigerant compressor and other components during operation of the refrigerant cycle, a supply pipe RSL is provided to periodically supply utility N2 from the buffer tank 110 to the refrigerant circulation line. Additionally, an N2 vent line VL is connected to the refrigerant circulation line of the refrigerant cycle to rapidly extract the nitrogen refrigerant from the reliquefaction system RS in an emergency.

[0049] As described above, the refrigerant charging system of this embodiment eliminates the need for devices such as a dryer or inventory tank that are separately installed for the refrigerant cycle, thereby reducing initial installation costs and contributing to the preservation of space on board the ship. Furthermore, by utilizing the pressure difference between the already installed devices and each device, nitrogen refrigerant can be charged or discharged from the reliquefaction system RS, allowing for smooth adjustment of the load on the reliquefaction system RS.

[0050] The present invention is not limited to the above-described embodiments, and it will be obvious to those skilled in the art to which the present invention pertains that various changes or modifications can be made without departing from the technical gist of the present invention.

Claims

1. a re-liquefaction system that is provided on the ship and compresses evaporated gas generated in a storage tank in which liquefied gas is stored, and re-liquefies the compressed evaporated gas by heat exchange with a refrigerant circulating in a refrigerant circulation line in a heat exchanger; and Utilities N supplied on board the ship ２ a buffer tank for storing the Utility N supplied from the buffer tank ２ a boost compressor for compressing the refrigerant and supplying it to the refrigerant circulation line; and Utility N in the buffer tank ２ a first load-up line that bypasses the boost compressor and supplies the refrigerant to the refrigerant circulation line; When the refrigerant circulation line is initially charged with refrigerant while the reliquefaction system is stopped, the pressure difference between the refrigerant circulation line and the buffer tank is used to charge the utility N in the buffer tank. ２ to the refrigerant circulation line through the first load-up line to fill the refrigerant in the refrigerant circulation line; The amount of cold energy in the refrigerant circulation line is adjusted by replenishing the refrigerant in the refrigerant circulation line or by partially discharging the refrigerant in the refrigerant circulation line, thereby adjusting the load of the reliquefaction system. Refrigerant charging system for marine reliquefaction systems.

2. Utility N in the buffer tank ２ a second load-up line that supplies the boost compressor with the refrigerant, and then supplies the refrigerant to the refrigerant circulation line; When the refrigerant circulation line is filled with refrigerant to increase the load of the reliquefaction system, and the pressure in the refrigerant circulation line becomes equal to or higher than the pressure in the buffer tank, the utility N ２ is supplied to the boost compressor through the second load-up line, compressed in the boost compressor, and supplied to the refrigerant circulation line. The refrigerant charging system for a marine reliquefaction system according to claim 1.

3. a first load-down line connecting the refrigerant circulation line and the buffer tank to discharge the refrigerant in the refrigerant circulation line; and a second load-down line connecting the refrigerant circulation line and the buffer tank via the boost compressor; When the load on the reliquefaction system is to be reduced, the refrigerant in the refrigerant circulation line is discharged through the first load-down line by utilizing a pressure difference between the pressure in the refrigerant circulation line and the pressure in the buffer tank, and when the pressure in the buffer tank becomes equal to or higher than the pressure in the refrigerant circulation line, the refrigerant in the refrigerant circulation line is supplied through the second load-down line to the boost compressor, compressed, and recovered in the buffer tank. The refrigerant charging system for a marine reliquefaction system according to claim 2.

4. the refrigerant circulation line includes a refrigerant compressor that compresses the refrigerant discharged from the heat exchanger after cooling the evaporated gas in the heat exchanger, and an expander that expands the refrigerant compressed by the refrigerant compressor and cooled by the heat exchanger, and the refrigerant expanded and cooled by the expander is supplied to the heat exchanger, When charging the refrigerant from the buffer tank into the refrigerant circulation line, a utility N is provided upstream of the refrigerant compressor. ２ and when the load on the reliquefaction system is reduced, the refrigerant is discharged from the refrigerant circulation line downstream of the refrigerant compressor into the buffer tank. The refrigerant charging system for a marine reliquefaction system according to claim 3.

5. The buffer tank may be used as a heat insulating layer for the storage tank, as a seal gas for the onboard compressor, or as a refrigerant for the reliquefaction system. ２ The nitrogen generating apparatus is characterized in that it is provided in The refrigerant charging system for a marine reliquefaction system according to any one of claims 1 to 4.

6. The nitrogen generator is Compressed air to the utility N ２ a nitrogen generator that generates and supplies the nitrogen to the buffer tank; an air compressor that compresses air and supplies it to the nitrogen generator; 6. A refrigerant charging system for a marine reliquefaction system according to claim 5.

7. A utility N ２ or a dryer for lowering the dew point of the utility nitrogen generated by the nitrogen generator. ２ Adjust the moisture content of Utility N supplied from the buffer tank ２ is supplied to the refrigerant circulation line without additional drying. The refrigerant charging system for a marine reliquefaction system according to claim 6.

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