KR102105071B1 - Boil-Off Gas Reliquefaction System and Method for Ship - Google Patents

Abstract

Disclosed are a boil-off gas reliquefaction system for a ship and a method thereof which can increase reliquefaction performance. According to the present invention, the boil-off gas reliquefaction system for a ship comprises: a compressor to receive boil-off gas produced from liquefied gas stored in a storage tank arranged in a ship to compress the boil-off gas by a fuel supply pressure of a main engine arranged in the ship; a heat exchanger to receive a portion of boil-off gas compressed by the compressor to cool the boil-off gas by heat exchange with uncompressed boil-off gas to be supplied to the compressor from the storage tank; a reliquefaction unit to receive the compressed gas cooled by the heat exchanger to additionally cool the compressed gas to reliquefy the compressed gas; a compander compressor to receive another portion of the compressed gas compressed by the compressor to additionally compress the compressed gas to introduce the compressed gas to the heat exchanger; and a compander expander to receive the compressed gas cooled through the heat exchanger after additional compression by the compander compressor to expand and cool the compressed gas. The compander compressor is connected to the compander expander to additionally compress the compressed gas by expansion energy of the compressed gas. The compressed gas expanded and cooled by the compander expander merges with a flow of the uncompressed boil-off gas supplied to the heat exchanger from the storage tank to be supplied as a refrigerant of the heat exchanger.

Description

{Boil-Off Gas Reliquefaction System and Method for Ship}

The present invention relates to a reliquefaction system and method for re-liquefying boil-off gas (BOG) generated from liquefied gas by cooling heat of the boil-off gas itself.

In recent years, the consumption of liquefied gas such as liquefied natural gas (Liquefied Natural Gas, LNG) has been increasing worldwide. Liquefied gas liquefied gas at a low temperature has a very small volume compared to gas, and thus has an advantage of increasing storage and transport efficiency. In addition, liquefied gas, including liquefied natural gas, can remove or reduce air pollutants during the liquefaction process, so it can be regarded as an eco-friendly fuel with less emission of air pollutants during combustion.

Liquefied natural gas is a colorless and transparent liquid that can be obtained by liquefying natural gas containing methane as its main component to about -163 ° C, and has a volume of about 1/600 compared to natural gas. Therefore, when natural gas is liquefied and transported, it can be transported very efficiently.

However, since the liquefaction temperature of natural gas is an extremely low temperature of -162 ° C under normal pressure, liquefied natural gas is sensitive to temperature changes and evaporates easily. Due to this, the storage tank for storing the liquefied natural gas is insulated, but since external heat is continuously transferred to the storage tank, the liquefied natural gas is continuously vaporized in the storage tank during the transportation of the liquefied natural gas, and the evaporated gas (Boil) -Off Gas, BOG) is generated.

Evaporation gas is a kind of loss, which is an important problem in transportation efficiency. In addition, when the boil-off gas accumulates in the storage tank, the internal pressure of the tank may rise excessively. Accordingly, various methods for treating the boil-off gas generated in the storage tank have been studied. Recently, for the treatment of the boil-off gas, a method of re-liquefying the boil-off gas and returning it to the storage tank, the boil-off gas is used as fuel for ship engines, etc. A method of using it as an energy source of a consumer is used.

As a method for re-liquefying the evaporated gas, a refrigeration cycle using a separate refrigerant is provided to heat and re-liquefy the evaporated gas with a refrigerant, a method of re-liquefying the evaporated gas as a refrigerant without a separate refrigerant, etc. There is this.

On the other hand, among the engines commonly used in ships, there are gas fuel engines such as DFDE, X-DF engine, and ME-GI engine as engines that can use natural gas as fuel.

DFDE is composed of four strokes, and adopts an Otto Cycle that injects natural gas having a pressure of about 5.5 bar, which is relatively low pressure, into the combustion air inlet and compresses it as the piston rises.

The X-DF engine consists of two strokes, uses natural gas of about 16 bar as fuel, and adopts an auto cycle.

The ME-GI engine is composed of two strokes and adopts a diesel cycle that injects high-pressure natural gas at around 300 bar directly into the combustion chamber near the top dead center of the piston.

The present applicant is a method of re-liquefying the evaporation gas by using the evaporation gas itself as a refrigerant without a separate refrigerant, and cooling the evaporation gas compressed by the compressor by exchanging it with the evaporation gas before being compressed by the compressor, followed by a JT valve or the like. A method of expanding and re-liquefying a part of the evaporation gas has been invented, and such a system is called a PRS (Partial Re-liquefaction System).

When the amount of liquefied gas inside the storage tank is large and the amount of evaporated gas is large, when the vessel is moored or the engine is operated at a low speed and the amount of evaporated gas used in the engine is small. , PRS alone may not satisfy the required reliquefaction amount, and the present applicant has invented a technique in which PRS is improved so that more evaporated gas can be reliquefied.

As a PRS improvement technology, a system that allows the evaporation gas to be further cooled by a refrigerant cycle using the evaporation gas itself as a refrigerant is called a Methane Refrigeration System (MRS).

The present invention is further directed to propose a system capable of enhancing the reliquefaction performance by effectively cooling the evaporation gas to be reliquefied without additionally providing a refrigerant heat exchanger like MRS.

According to an aspect of the present invention for solving the above problems is a compressor for receiving the boil-off gas generated from the liquefied gas stored in the storage tank of the ship to compress the fuel supply pressure of the main engine provided in the ship;

A heat exchanger that receives a portion of compressed gas compressed by the compressor and cools it by heat exchange with uncompressed evaporated gas to be supplied to the compressor from the storage tank;

A re-liquefaction unit receiving the compressed gas cooled in the heat exchanger and further cooling to re-liquefy it;

A compressor compressor receiving another part of the compressed gas compressed by the compressor and further compressing it to introduce the heat exchanger; And

Includes; after the additional compression in the compressor compressor expander to receive the compressed gas cooled through a heat exchanger to expand and cool;

The compander compressor is connected to the compander expander to further compress the compressed gas by the expansion energy of the compressed gas,

The compressed gas expanded and cooled in the expander expander is re-liquefied in the ship's evaporation gas, characterized in that it is joined to the flow of the uncompressed evaporation gas supplied from the storage tank to the heat exchanger and supplied as a refrigerant in the heat exchanger. A system is provided.

Preferably, the re-liquefaction unit, the decompression device for cooling by receiving the compressed gas cooled in the heat exchanger to reduce pressure; It includes; a gas-liquid separator to receive the compressed gas cooled by the decompression device to separate gas-liquid, the liquid separated from the gas-liquid separator is supplied to the storage tank, the separated gas is introduced from the storage tank to the heat exchanger It may be joined to the uncompressed evaporation gas.

Preferably, the system includes a boosting compressor provided between the compressor and the heat exchanger, receiving compressed gas to be reliquefied through the heat exchanger and the reliquefaction unit after compression, and further compressing and introducing the heat exchanger into the heat exchanger; And a cooler provided between the compander compressor and the heat exchanger to cool the compressed gas compressed into the heat exchanger.

The compressor includes a main compressor for compressing the boil-off gas to the fuel supply pressure of the main engine; And a redundancy compressor provided in parallel with the main compressor.

Preferably, in the system, the main compressor and the redundancy compressor may be driven either at the same time or simultaneously.

According to another aspect of the present invention, an evaporation gas supply line provided to the ship and connected to a main engine of the ship from a storage tank for storing liquefied gas;

A compressor which is provided on the boil-off gas supply line and receives boil-off gas generated from the liquefied gas and compresses it to the fuel supply pressure of the main engine;

It is branched from the evaporation gas supply line downstream of the compressor and connected to the storage tank, cooling and re-liquefying the remaining compressed gas supplied as fuel of the main engine by heat exchange with uncompressed evaporation gas to be supplied to the compressor. A reliquefaction line for re-storing to a storage tank;

A heat exchanger provided on the reliquefaction line and cooling the compressed gas by heat exchange with the uncompressed evaporated gas to be supplied to the compressor along the evaporated gas supply line from the storage tank;

A refrigerant replenishing line branched from the boil-off gas supply line downstream of the compressor and connected to the front end of the heat exchanger of the boil-off gas supply line; And

Included in the refrigerant replenishment line is a compressor that is compressed by the compressor and supplied by the compressed gas branched to the refrigerant replenishment line to further compress it and introduce it into the heat exchanger, and expand and cool the compressed gas cooled through the heat exchanger. And

The compander is provided with an evaporation gas reliquefaction system of a vessel, characterized in that the compressed gas is further compressed by the expansion energy of the compressed gas.

Preferably, the compander is compressed by the compressor, receives the compressed gas branched to the refrigerant supplement line, and further compresses the compressor to introduce the compressor into the heat exchanger; And a compander expander that receives and compresses the compressed gas cooled through a heat exchanger after additional compression in the compander compressor, and the compander compressor is connected to the compander expander and the shaft to expand the compressed gas. It can be driven by receiving energy.

Preferably, the re-liquefaction line, receiving the compressed gas cooled by the heat exchanger, a pressure reducing device for cooling by reducing the pressure; It includes; a gas-liquid separator to receive the compressed gas cooled by the pressure reducing device to separate gas-liquid, the liquid separated from the gas-liquid separator is supplied to the storage tank along the re-liquefaction line, the separated gas is from the storage tank It may be joined to the uncompressed boil-off gas introduced into the heat exchanger.

Preferably, the system comprises: a boosting compressor provided upstream of the heat exchanger in the reliquefaction line, receiving the compressed gas to be reliquefied through the heat exchanger after compression, and further compressing it to be introduced into the heat exchanger; And a cooler provided between the compander compressor and the heat exchanger in the refrigerant filling line and cooling the compressed gas compressed into the heat exchanger.

Preferably, the compressor, the main compressor for compressing the boil-off gas to the fuel supply pressure of the main engine; And a redundancy compressor provided in parallel with the main compressor.

Preferably, in the system, the boil-off gas supply line is branched at the front end of the main compressor and the redundancy compressor, then joined at the rear end of the main compressor and redundancy compressor, and the rear end of the main compressor and the redundancy compressor in the boil-off gas supply line. A first valve provided between the confluence points of the; A second valve provided between the rear end of the redundancy compressor and the confluence point in the boil-off gas supply line; It may further include a; a third valve provided upstream of the compressor compressor in the refrigerant filling line.

Preferably, an interlocking line is provided in the system connecting the rear end of the main compressor and the redundancy compressor upstream of the confluence point of the evaporation gas supply line, and is connected from the interlocking line to the rear end of the third valve of the refrigerant filling line. A fourth valve provided between the main compressor and the branch point of the connection line in the connection line; And a fifth valve provided between the redundancy compressor and the branch point of the connection line in the interlocking line.

According to another aspect of the present invention, the evaporation gas generated from the storage tank provided in the vessel to store the liquefied gas is compressed by the compressor to the fuel supply pressure of the main engine,

A part of the compressed gas is branched from the downstream of the compressor, cooled by heat exchange in an uncompressed evaporation gas to be supplied to the compressor, and re-liquefied to be stored again in the storage tank,

A portion of the compressed gas compressed by the compressor is branched and further compressed by a compander to be introduced into the heat exchanger to cool, and the cooled compressed gas is expanded and cooled, so that the uncompressed boil-off gas to be supplied from the storage tank to the compressor Provided is a method of treating boil-off gas in a vessel, characterized in that it is supplied to the refrigerant of the heat exchanger by joining the.

Preferably, the compander may further compress the compressed gas by the expansion energy of the compressed gas.

In the system of the present invention, a part of the compressed boil-off gas may be compressed, cooled, and expanded to be supplied upstream of the heat exchanger to increase the flow rate of the refrigerant introduced into the heat exchanger.

As such, by increasing the flow rate of the refrigerant in the heat exchanger, the evaporation gas to be re-liquefied can be cooled more effectively to increase the re-liquefaction rate.

In addition, by applying a compander so that the expansion energy of the compressed gas can be used for additional compression of the evaporated gas to be replenished with a refrigerant, the use of power consumed to further compress the evaporated gas can be reduced, and the energy efficiency of the ship can be increased. have.

On the other hand, since the boil-off gas to be re-liquefied is further compressed with a boosting compressor, and the boil-off gas to be replenished with the refrigerant is further compressed with the expansion energy of the compressed gas by a compander, the compressor compresses the boil-off gas with the fuel supply pressure of the main engine on board. It can be designed to reduce the motor size and reduce the power required by the compressor.

1 is a schematic diagram of an evaporation gas reliquefaction system of a ship according to a first embodiment of the present invention.
2 is a schematic diagram of a system for re-liquefying evaporation gas of a ship according to a second embodiment of the present invention.

In order to fully understand the operational advantages of the present invention and the objects achieved by the practice of the present invention, reference should be made to the accompanying drawings and the contents described in the accompanying drawings, which illustrate preferred embodiments of the present invention.

Hereinafter, the configuration and operation of the preferred embodiment of the present invention will be described in detail with reference to the accompanying drawings. Here, when adding reference numerals to the components of each drawing, it should be noted that the same components are denoted by the same reference numerals as much as possible even though they are displayed on different drawings.

Hereinafter, in the ship of the present invention, an engine capable of using liquefied gas and boiled gas generated from liquefied gas as fuel for propulsion or power generation engines is installed, or all types using liquefied gas or boiled gas as fuel for ship engines. The vessels are self-propelled, such as LNG carriers, liquid hydrogen carriers, LNG regasification vessels (LVs), LNG floating production storage offloading (FPSO), and LNG floating storage regasification units (FSRUs). ) May also include offshore structures that do not have propulsion capability but are floating on the sea.

In addition, the liquefied gas in the present invention may include all kinds of liquefied gas that can be transported by liquefying the gas at a low temperature, and generates evaporation gas in a stored state and used as fuel for an engine or the like. Such liquefied gas is liquefied petrochemical such as Liquefied Natural Gas (LNG), Liquefied Ethane Gas (LEG), Liquefied Petroleum Gas (LPG), Liquefied Ethylene Gas, Liquefied Propylene Gas, etc. It can be gas. However, in the embodiment described below, LPG, which is one of the representative liquefied gases, is applied as an example.

On the other hand, the fluid flowing through each line of the present embodiments may be any one of a liquid state, a gas-liquid mixing state, a gas state, and a supercritical fluid state, depending on operating conditions of the system.

FIG. 1 schematically shows a system for re-liquefying evaporation gas of a ship according to a first embodiment of the present invention, and FIG. 2 schematically shows a system for re-liquefying evaporation gas of a ship according to a second embodiment of the present invention.

As shown in Figures 1 and 2, the system of the first and second embodiments is provided in the vessel, the evaporation gas supply line (GL) connected to the ship's main engine from a storage tank (T) for storing liquefied gas , Compressor 100 is provided in the boil-off gas supply line and receives boil-off gas generated from liquefied gas and compresses it to the fuel supply pressure of the main engine, and is branched from the boil-off gas supply line downstream of the compressor and connected to a storage tank, It is provided in the reliquefaction line (RL) which cools and reliquefies the remaining compressed gas supplied as the fuel of the main engine and heat exchanges with the uncompressed evaporation gas to be supplied to the compressor and re-liquefies, and the reliquefaction line, and provides compressed gas. , It comprises a heat exchanger 200 for cooling by heat exchange with the uncompressed evaporation gas to be supplied to the compressor along the evaporation gas supply line from the storage tank.

The system of the first and second embodiments is further provided with a refrigerant replenishment line (CL) branched from the evaporation gas supply line downstream of the compressor and connected to the front end of the heat exchanger of the evaporation gas supply line. It is possible to increase the flow rate of the refrigerant introduced into the heat exchanger by constructing a compander 400 that receives compressed gas that is compressed and branched to the refrigerant replenishing line, further compresses it and introduces it into the heat exchanger, and expands and cools the compressed gas cooled through the heat exchanger. It was configured to. In this way, by increasing the flow rate of the refrigerant (cold BOG) of the heat exchanger, the evaporation gas to be reliquefied can be cooled more effectively to increase the reliquefaction rate.

In these embodiments, the compander further compresses the compressed gas by the expansion energy of the compressed gas, thereby reducing power consumption for further compression of the compressed gas.

The comparator 400 is compressed by a compressor, receives compressed gas branched to a refrigerant replenishing line, and further compresses and introduces it into a heat exchanger, and is further compressed by a compander compressor and then cooled through a heat exchanger. It comprises a compander inflator 420 that receives and compresses compressed gas to expand and cool, and the compander compressor is connected to a compander inflator and a shaft so that it can be driven by receiving the expansion energy of the compressed gas.

In the refrigerant replenishment line CL, a cooler 450 is provided between the compander compressor and the heat exchanger to cool the additional compressed compressed gas and introduce it into the heat exchanger 200.

Meanwhile, the heat exchanger may be provided in a PCHE (Printed Circuit Heat Exchanger) type. The evaporated gas to be introduced into the heat exchanger may be introduced into the heat exchanger after removing the lubricating oil mixed through an oil filter (not shown).

On the other hand, the reliquefaction line (RL) is provided with a reliquefaction unit, the reliquefaction unit is supplied with the compressed gas cooled by the heat exchanger to reduce pressure to cool the pressure reducing device (310), and the compressed gas cooled by the pressure reducing device is supplied with gas liquid A gas-liquid separator 320 for separating is provided.

The pressure reducing device 310 may be configured by an expansion valve such as an expander or a Joule-Thomson valve that cools the compressed and cooled boil-off gas by adiabatic expansion.

Compressed, cooled and expanded-cooled evaporated gas through a compressor, a heat exchanger, and a pressure reducing device is partially or partially re-liquefied and introduced into the gas-liquid separator 320. It is decompressed in a decompression device without configuring a gas-liquid separator, and the additional cooled evaporation gas can be sent directly to a storage tank and dissolved in liquefied natural gas stored in the storage tank.

The liquid separated from the gas-liquid separator is supplied to and stored in the storage tank along the reliquefaction line (RL), and the separated gas is combined with the uncompressed evaporation gas that is joined to the evaporation gas supply line (GL) and introduced from the storage tank to the heat exchanger. It may be supplied as a refrigerant to the heat exchanger.

In the re-liquefaction line, a boosting compressor 500 is provided upstream of the heat exchanger to receive compressed gas to be re-liquefied through a heat exchanger after compression, and further compress it and introduce it into the heat exchanger.

In the case of methane, the main component of LNG, the state of about -80 ℃ and 55bar is the critical point. When re-liquefying the boil-off gas generated in LNG, the higher the compression pressure of the boil-off gas, the higher the re-liquefaction rate, and the largest amount of re-liquefaction when compressed within 150 to 170 bar, but there is a significant change in the amount of re-liquefaction between 150 and 300 bar. Found none. Therefore, in order to effectively re-liquefy the boil-off gas, it is preferable to compress to 100 bar or more, preferably 150 bar to 300 bar. However, if the main engine that receives boil-off gas does not need such a high-pressure fuel, compressing all the boil-off gas to high pressure for re-liquefaction consumes a lot of power and wastes energy. It is also expensive. Therefore, in the present invention, the compressor compresses only the fuel supply pressure of the main engine, and the boil-off gas to be re-liquefied and the boil-off gas to be supplemented with the refrigerant can be further compressed by the boosting compressor 500 and the compander compressor 410, respectively. .

Through this, the compressor 100 can be designed to compress the evaporation gas with the fuel supply pressure of the main engine on the ship, thereby reducing the motor size, reducing equipment costs, and reducing the power required by the compressor, thereby reducing operating costs.

For example, if the X-DF engine is used as the main engine, the compressor compresses the boil-off gas by about 16 bar, and the boosting compressor further compresses the compressed gas to 100 bar or more, preferably 150 bar to 170 bar. You can.

The compressor 100 includes a main compressor 100a for compressing boil-off gas to the fuel supply pressure of the main engine, and a redundancy compressor 100b provided in parallel with the main compressor.

Compressors that supply fuel to engines according to ship regulations must be designed for redundancy in case of an emergency. Redundancy design means that when one cannot be used due to failure, maintenance, etc., the other one is substituted. It means designing for use. To this end, in this embodiment, the compressor is designed as a main compressor and a redundancy compressor.

The boil-off gas supply line (GL) is branched in front of the main compressor and the redundancy compressor so as to supply the boil-off gas to the main compressor and the redundancy compressor, and then joins at the rear end of the main compressor and the redundancy compressor.

In the boil-off gas supply line, a first valve (V1) is provided between the rear end of the main compressor and a confluence point with the redundancy compressor, and a second valve (V2) is provided between the rear end of the redundancy compressor and the confluence point, respectively. A third valve V3 is provided upstream of the compander compressor in the line.

The system of the second embodiment shown in FIG. 2 provides an interlocking line (NL) connecting the rear end of the main compressor and the redundancy compressor upstream of the confluence point of the evaporation gas supply line, in addition to the system described above, and the interlocking line The connection line NLa is connected to the rear end of the third valve of the refrigerant filling line.

In the interlocking line, a fourth valve V4 is provided between the main compressor and the branching point of the connection line, and a fifth valve V5 is provided between the redundancy compressor in the interlocking line and the branching point of the connection line.

Thus, the interlocking line and the connecting line are provided, and the main compressor and the redundancy compressor can be used for fuel supply, re-liquefaction of evaporation gas, and replenishment of refrigerant through opening and closing of the first to fifth valves. It can increase elasticity and increase utilization.

For example, when the second, third and fourth valves are closed and the first and fifth valves are opened, the main compressor supplies the boil-off gas for fuel supply and re-liquefaction, and the redundancy compressor can be driven to replenish the refrigerant.

In the event of a failure or maintenance of the main compressor, the first and fourth valves are blocked, and the second, third and fifth valves are opened to supply fuel, re-liquefy evaporation gas, and replenish the refrigerant through a redundancy compressor.

In addition, various valves can be opened and closed according to various system conditions.

The present invention is not limited to the above embodiments, and can be variously modified or modified within a range not departing from the technical gist of the present invention, which is obvious to a person skilled in the art to which the present invention pertains. It is done.

T: Storage tank
GL: Evaporation gas supply line
RL: Reliquefaction line
CL: refrigerant supplement line
NL: Interlocking line
NLa: Connection line
V1, V2, V3, V4, V5: first to fifth valves
100: compressor
100a: main compressor
100b: redundancy compressor
300: reliquefaction unit
310: pressure reducing device
320: gas-liquid separator
400: compander
410: compander compressor
420: compander inflator
450: cooler
500: boosting compressor

Claims (8)

1) compressing boil-off gas generated from a storage tank provided on a ship and storing liquefied gas to a fuel supply pressure of the ship's main engine;
2) branching a portion of the compressed gas downstream of the compressor to cool and re-liquefy the uncompressed boil-off gas to be supplied to the compressor by heat exchange in a heat exchanger; And
3) The other part of the compressed gas compressed by the compressor is branched to cool through the heat exchanger, and the cooled compressed gas is expanded and cooled to join the uncompressed boil-off gas to be supplied to the compressor from the storage tank. Including the step of supplying to the refrigerant of the heat exchanger, including,
Cooling the compressed gas compressed by the compressor in the heat exchanger and expansion cooling to increase the flow rate of the refrigerant introduced into the heat exchanger, the method for increasing the flow rate of the refrigerant for re-liquefaction of the ship. According to claim 1,
The compressed gas branched in step 3) is introduced into the heat exchanger and further compressed in a compander before being cooled,
The compander is characterized in that the compressed gas is further compressed by expansion energy when expanding and cooling the compressed gas, the method of increasing the flow rate of the refrigerant for re-liquefaction of the ship. According to claim 2,
The compressed gas to be re-liquefied in the step 2) is further compressed by a boosting compressor, and then introduced into the heat exchanger and cooled, a method for increasing the flow rate of a refrigerant for re-liquefaction of a ship. According to claim 3,
In step 2), the compressed gas cooled in the heat exchanger is further cooled under reduced pressure, and gas-separated to supply the separated liquid to the storage tank,
The gas separated by gas-liquid separation is characterized in that it is supplied to the refrigerant of the heat exchanger by joining the uncompressed boil-off gas introduced into the heat exchanger from the storage tank, the method of increasing the flow rate of the refrigerant for re-liquefaction of the ship. The method of claim 4,
The compressor includes a main compressor for compressing the boil-off gas to the fuel supply pressure of the main engine; And a redundancy compressor provided in parallel with the main compressor.
The main compressor and the redundancy compressor are either driven or can be driven at the same time, characterized in that the refrigerant flow rate increase method for reliquefaction of a ship. The method of claim 5,
A refrigerant filling line connected to the front end of the heat exchanger is provided to branch the compressed gas downstream of the compressor and cool it in the heat exchanger and expand it to be introduced into the refrigerant of the heat exchanger.
An interlocking line connecting the rear ends of the main compressor and the redundancy compressor; And a connection line connected from the interlocking line to the refrigerant filling line: is provided,
Between the main compressor and the branch point of the connection line in the interlocking line; A redundancy compressor in the interlocking line and a branch point of the connecting line; And a valve provided in the refrigerant filling line upstream of the connection point of the connection line, respectively.
A method of increasing the flow rate of refrigerant for reliquefaction of a ship, characterized in that the main compressor and the redundancy compressor can be resiliently driven to supply fuel, re-liquefy liquefied gas, and replenish refrigerant by opening and closing each valve. According to claim 3,
In the compressor, the evaporation gas is compressed by the fuel supply pressure of the main engine, and the boosting compressor further compresses the compressed gas to be re-liquefied to 55 to 300 bar. The method of claim 7,
The main engine is an X-DF engine,
In the boosting compressor, a method of increasing the flow rate of a refrigerant for re-liquefying a vessel, characterized in that the compressed gas to be re-liquefied is further compressed to 100 to 170 bar.

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