KR20200142619A - Boil-Off Gas Treatment System and Method for Ship - Google Patents

Abstract

Disclosed are a system and a method for processing boil-off gas of a ship. The system for processing boil-off gas of a ship comprises: a compressor for receiving and compressing boil-off gas generated from liquefied gas stored in a storage tank of a ship; a heat exchanger supplied with all or a part of the boil-off gas compressed by the compressor to cool the same with uncompressed boil-off gas to be supplied to the compressor by heat exchange; a decompression device for decompressing the boil-off gas cooled in the heat exchanger to additionally cool the same; a first gas-liquid separator for receiving the boil-off gas decompressed by the decompression device, and performing gas-liquid separation therefor; and a second gas-liquid separator for receiving the liquefied gas separated by the first gas-liquid separator, and performing gas-liquid separation therefor. The second gas-liquid separator has an internal pressure lower than that of the first gas-liquid separator, separates flash gas generated by supplying the liquefied gas separated by the first gas-liquid separator to the second gas-liquid separator, and supplies the same to the flow of the uncompressed boil-off gas introduced into the heat exchanger. Accordingly, cooling performance of the heat exchanger can be enhanced.

Description

Boil-Off Gas Treatment System and Method for Ship}

The present invention relates to a boil-off gas treatment system and method of a ship, and more particularly, to a boil-off gas treatment system and method of a ship capable of re-liquefying the boil-off gas generated in a storage tank by cooling heat of the boil-off gas itself. will be.

In recent years, the consumption of liquefied natural gas (LNG) and other liquefied gases is increasing rapidly around the world. The liquefied gas obtained by liquefying the gas at a low temperature has an advantage of increasing storage and transfer efficiency because the volume is very small compared to the gas. In addition, liquefied gases, including liquefied natural gas, can remove or reduce air pollutants during the liquefaction process, and thus can be regarded as eco-friendly fuels with little emission of air pollutants during combustion.

Liquefied natural gas is a colorless and transparent liquid obtained by liquefying natural gas containing methane as its main component by cooling it to about -162°C, and has a volume of about 1/600 compared to natural gas. Therefore, when the natural gas is liquefied and transported, it can be transported very efficiently.

However, since the liquefaction temperature of natural gas is a cryogenic temperature of -162°C at normal pressure, liquefied natural gas is sensitive to temperature changes and is easily evaporated. For this reason, the storage tank that stores liquefied natural gas is insulated, but external heat is continuously transferred to the storage tank. Therefore, during the transportation of liquefied natural gas, the liquefied natural gas is continuously evaporated in the storage tank and boiled gas (Boil). -Off Gas, BOG) occurs.

Boil-off gas is a kind of loss and is an important problem in transport efficiency. In addition, if the boil-off gas accumulates in the storage tank, the internal pressure of the tank may increase excessively, and in severe cases, there is a risk of damage to the tank. Therefore, 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, and the boil-off gas as fuel such as a ship's engine. The method of using it as an energy source of the customer is being used.

As a method for re-liquefying the boil-off gas, a method of reliquefying the boil-off gas by heat exchange with the refrigerant by providing a refrigeration cycle using a separate refrigerant, a method of re-liquefying the boil-off gas itself as a refrigerant without a separate refrigerant, etc. There is this.

Meanwhile, among engines generally used in ships, gas-fueled engines such as DF engines, X-DF engines, and ME-GI engines are used as engines that can use natural gas as fuel.

DF engine (DFDE, DFGE) consists of 4 strokes, and adopts the Otto Cycle, which injects natural gas with a relatively low pressure of 5.5 barg into the inlet of the combustion air and compresses it while the piston rises. Are doing.

The X-DF engine consists of two strokes, uses 15 barg of natural gas as fuel, and adopts an auto cycle.

The ME-GI engine is composed of two strokes, and adopts a diesel cycle in which high-pressure natural gas near 300 barg is injected directly into the combustion chamber near the top dead center of the piston.

1 schematically shows a conventional boil-off gas treatment system for ships.

In the conventional boil-off gas treatment system for ships as shown in FIG. 1, when the main engine ME and the power generation engine GE are provided, the boil-off gas discharged from the storage tank T is compressed by the compressor 10 It is supplied as fuel of the main engine, and when the fuel supply pressure of the power generation engine is lower than that of the main engine, the boil-off gas that has undergone a partial compression process of the compressor 10 is branched from the middle and supplied as fuel of the power generation engine GE.

Among the boil-off gas supplied to the compressor 10, the remaining boil-off gas is supplied as fuel for the main engine and power generation engine, and the remaining boil-off gas is supplied to the heat exchanger 20, and is cooled through heat exchange with the boil-off gas discharged from the storage tank T. .

The boil-off gas cooled in the heat exchanger 20 is depressurized by the decompression device 30 and partially re-liquefied, and the re-liquefied liquefied gas and the boil-off gas remaining in a gaseous state are supplied to the gas-liquid separator 40 and phase separated. .

The liquefied gas separated by the gas-liquid separator 40 is supplied to the storage tank T and stored again, and the gaseous evaporative gas separated by the gas-liquid separator 40 joins the boil-off gas discharged from the storage tank T. It is introduced into the heat exchanger 20 as a refrigerant.

In this way, the boil-off gas is reliquefied by using the boil-off gas itself as a refrigerant without a separate refrigerant. The boil-off gas compressed by the compressor is heat-exchanged with the boil-off gas before being compressed by the compressor to cool it, and then expand it by a JT valve. The present applicant named a system for re-liquefying a part of the boil-off gas by making it a PRS (Partial Re-liquefaction System).

The present invention further improves the PRS to more effectively cool the boil-off gas to increase the reliquefaction performance and to propose a system capable of treating the boil-off gas.

According to an aspect of the present invention for solving the above problems, a compressor for receiving and compressing the boil-off gas generated from the liquefied gas stored in the storage tank of the ship;

A heat exchanger that receives all or part of the boil-off gas compressed by the compressor and cools it by heat exchange with the uncompressed boil-off gas to be supplied to the compressor;

A decompression device for further cooling by decompressing the boil-off gas cooled in the heat exchanger;

A first gas-liquid separator for gas-liquid separation by receiving the boil-off gas reduced by the decompression device;

Including; a second gas-liquid separator for gas-liquid separation by receiving the liquefied gas separated by the first gas-liquid separator,

The second gas-liquid separator has an internal pressure lower than that of the first gas-liquid separator, and the liquefied gas separated in the first gas-liquid separator is supplied to the second gas-liquid separator to separate the flash gas generated and introduced into the heat exchanger. There is provided a boil-off gas treatment system of a ship, characterized in that supplying the compressed boil-off gas flow.

Preferably, the flash gas separated in the first gas-liquid separator is supplied to the flow of the uncompressed evaporative gas introduced into the heat exchanger, and a first for decompressing the flash gas separated in the first gas-liquid separator to be introduced into the heat exchanger. Expansion means; may further include.

Preferably, the second expansion means for decompressing the flash gas separated from the second gas-liquid separator to be introduced into the heat exchanger; further comprising, the liquefied gas separated in the second gas-liquid separator to be restored to the storage tank. I can.

Preferably, the first and second expansion means may be an expander or a Joule Thompson valve that depressurizes and cools the flash gas.

Preferably, in the compressor, the boil-off gas is compressed at a fuel supply pressure of a main engine on board, the boil-off gas compressed by the compressor is supplied to the main engine, and the boil-off gas compressed through a part of the compressor is It may be supplied to a power generation engine that receives lower pressure fuel than the main engine.

Preferably, the internal pressure of the first gas-liquid separator may be 5 to 10 barg, and the internal pressure of the second gas-liquid separator may be 2 to 5 barg.

According to another aspect of the present invention, boil-off gas generated from a storage tank in which liquefied gas is stored in a ship is compressed with a compressor,

All or part of the boil-off gas compressed by the compressor is cooled by heat exchange in a heat exchanger with the uncompressed boil-off gas to be introduced into the compressor, and further cooled by reduced pressure,

Gas-liquid separation of the depressurized boil-off gas in a first gas-liquid separator,

The uncompressed evaporation introduced into the heat exchanger by supplying the liquefied gas separated in the first gas-liquid separator to a second gas-liquid separator having an internal pressure lower than that of the first gas-liquid separator, separating the flash gas generated from the liquefied gas and introducing it to the heat exchanger There is provided a method for treating boil-off gas of a ship, characterized in that supplying with a gas flow.

Preferably, the flash gas separated in the first gas-liquid separator is decompressed and supplied to the uncompressed evaporative gas flow introduced into the heat exchanger.

Preferably, the flash gas separated in the second gas-liquid separator is decompressed and supplied to the uncompressed evaporative gas flow to be introduced into the heat exchanger, and the liquefied gas separated in the second gas-liquid separator is restored to the storage tank. Can be.

Preferably, the flash gas separated by the first and second gas-liquid separators may be depressurized and cooled by an expander or a Joule Thompson valve, and then supplied as an uncompressed evaporative gas flow to be introduced into the heat exchanger.

Preferably, in the compressor, the boil-off gas is compressed at a fuel supply pressure of a main engine on board, the boil-off gas compressed by the compressor is supplied to the main engine, and the boil-off gas compressed through a part of the compressor is It may be supplied to a power generation engine that receives lower pressure fuel than the main engine.

In the system of the present invention, the first and second gas-liquid separators are configured, and the flash gas separated from the gas-liquid separators is supplied to the uncompressed evaporative gas flow introduced into the heat exchanger, thereby lowering the temperature of the refrigerant introduced into the heat exchanger and reducing the refrigerant flow rate. It can increase the cooling performance of the heat exchanger.

In this way, the reliquefaction performance can be improved by effectively cooling the gas to be reliquefied, and the safety of the ship can be secured by effectively treating the boil-off gas.

1 is a schematic diagram of a conventional boil-off gas treatment system.
Figure 2 is a schematic diagram of the boil-off gas treatment system of the ship according to the first embodiment of the present invention.
3 is a schematic diagram of a system for treating boil-off gas for 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 object achieved by the implementation of the present invention, reference should be made to the accompanying drawings illustrating preferred embodiments of the present invention and the contents described in the accompanying drawings.

Hereinafter, the configuration and operation of a preferred embodiment of the present invention will be described in detail with reference to the accompanying drawings. Here, in adding reference numerals to elements of each drawing, it should be noted that only the same elements are marked with the same numerals as possible, even if they are indicated on different drawings.

Hereinafter, the ship in the present invention is all types of engines that can use liquefied gas and boil-off gas generated from liquefied gas as fuel for propulsion or power generation engines, or use liquefied gas or boil-off gas as fuel for onboard engines. These ships include LNG carriers, liquefied petroleum gas carriers, and ships with self-propelled capabilities such as LNG RV (Regasification Vessel), LNG Floating Production Storage Offloading (FPSO), and LNG Floating Storage Regasification (FSRU). It does not have propulsion capability like the unit), but may include offshore structures that are floating on the sea.

In addition, in the present invention, the liquefied gas may be transported by liquefying the gas at a low temperature, generating boil-off gas in a stored state, and may include all kinds of liquefied gas that can be used as fuel such as an engine. These liquefied gases are, for example, liquefied petrochemicals such as LNG (Liquefied Natural Gas), LEG (Liquefied Ethane Gas), LPG (Liquefied Petroleum Gas), Liquefied Ethylene Gas, and Liquefied Propylene Gas. It can be gas. However, in the embodiments to be described later, LPG, which is one of the representative liquefied gases, is applied as an example.

Meanwhile, the fluid flowing through each line of the present embodiments may be in any one of a liquid state, a gas-liquid mixture state, a gas state, and a supercritical fluid state, depending on the operating conditions of the system.

Fig. 2 schematically shows the boil-off gas treatment system of the ship according to the first embodiment of the present invention, and Fig. 3 schematically shows the boil-off gas treatment system of the ship according to the second embodiment of the present invention.

The boil-off gas treatment system of the first and second embodiments of the present invention shown in FIGS. 2 and 3 is a compressor 100 that receives and compresses boil-off gas generated from liquefied gas stored in a storage tank T of a ship, A heat exchanger 200 for receiving all or part of the boil-off gas compressed by the compressor and cooling it by heat exchange with the uncompressed boil-off gas to be supplied to the compressor, and a decompression device for additionally cooling the boil-off gas cooled by the heat exchanger ( 300), a first gas-liquid separator 400 receiving the boil-off gas decompressed by a decompression device to separate gas-liquid, and a second gas-liquid separator 500 receiving the liquefied gas separated from the first gas-liquid separator to separate gas-liquid. .

In the system of the present embodiments, as shown in Figs. 2 and 3, a boil-off gas supply line GL is provided from the storage tank T to the main engine ME of the ship, and the boil-off gas supply line is at the rear end of the compressor. The reliquefaction line RL branches from and is connected to the storage tank. A compressor 100 is provided in the boil-off gas supply line GL to compress the boil-off gas, and a heat exchanger 200, a decompression device 300, the first and second gas-liquid separators 400 along the reliquefaction line RL. 500) is provided to re-liquefy the evaporated gas that is not supplied as fuel such as the main engine and store it in a storage tank.

In particular, the first and second gas-liquid separators 400 and 500 separate gas, that is, flash gas from the reliquefied liquefied gas and supply it to the flow of uncompressed evaporated gas in front of the heat exchanger. And increase the reliquefaction performance.

To this end, from the first gas-liquid separator 400 to the front end of the heat exchanger 200 of the boil-off gas supply line GL, the first flash gas line FL1, the second gas-liquid separator 500 to the front end of the heat exchanger of the boil-off gas supply line As a result, the second flash gas lines FL2 are respectively connected.

In addition, the second gas-liquid separator 500 maintains a lower internal pressure than the first gas-liquid separator 400, and the liquefied gas separated in the first gas-liquid separator has a lower internal pressure than the first gas-liquid separator. While being supplied to the separator, the flash gas generated from the liquefied gas is separated again and supplied as a flow of uncompressed evaporation gas to be introduced into the heat exchanger.

However, even after passing through each gas-liquid separator, the flash gas as a gas and the liquefied gas as a liquid may not be 100% phase-separated, and thus the separated liquefied gas may contain an unseparated flash gas.

For example, the internal pressure of the first gas-liquid separator 400 is maintained at 5 to 10 barg, more preferably around 7 barg, and the internal pressure of the second gas-liquid separator 500 is 2 to 5 barg, more preferably Can be maintained at around 3 barg. In this way, when the pressure of the second gas-liquid separator is lower, flash gas may be generated from the liquefied gas as it is introduced from the first gas-liquid separator with a higher pressure to the second gas-liquid separator, and the second gas-liquid separator separates it and creates a second flash. It is supplied to the refrigerant flow of the heat exchanger through a gas line.

The flash gas separated in the first gas-liquid separator is also supplied as an uncompressed boil-off gas flow introduced into the heat exchanger through the first flash gas line.

The first flash gas line FL1 is provided with a first expansion means 450 for decompressing the flash gas separated from the first gas-liquid separator 400 and introduced into the heat exchanger. The first expansion means may be an expander or a Joule Thompson valve for decompressing the flash gas, and the flash gas is cooled through the depressurization and supplied to the front end of the heat exchanger.

By supplying the flash gas separated in the first and second gas-liquid separators to the front end of the heat exchanger of the boil-off gas supply line, the flow rate of the uncompressed boil-off gas flow (Cold BOG) introduced to the heat exchanger can be increased, and the first expansion By supplying the decompressed and cooled flash gas through the means to the flow of uncompressed evaporated gas to be introduced from the storage tank to the heat exchanger, the temperature of the cold BOG can also be lowered, thereby increasing the cooling performance of the heat exchanger and enhancing the reliquefaction performance.

Looking at the boil-off gas treatment method in the present embodiments as a whole, the boil-off gas generated in the storage tank T is introduced into the compressor 100 and compressed. In the compressor, the boil-off gas is compressed by the fuel supply pressure of the ship's main engine (ME), and the boil-off gas compressed by the compressor is supplied to the main engine.

The compressor 100 compresses the boil-off gas and uses the fuel supply pressure to the main engine, for example, 5.5 barg when a DF engine is provided, 15 barg when an X-DF engine is provided, and 300 when a ME-GI engine is provided. Can be compressed in barg. The compressor 100 may be provided as a multi-stage compressor in which a plurality of compressors and intermediate coolers are alternately arranged and compresses the boil-off gas to the fuel supply pressure of the main engine through these sequentially. Can be changed according to the fuel supply pressure of the main engine.

The boil-off gas compressed through a part of the compressor may be supplied to a power generation engine (GE) that receives low-pressure fuel than the main engine.

For example, the main engine is a ME-GI engine, and the power generation engine that receives lower pressure fuel is DFGE (Dual Fuel Generator Engine) or TFGE (Triple Fuel Generator Engine), and a medium-pressure engine that receives fuel with lower pressure than ME-GI engine. It can be composed of.

The boil-off gas compressed through some stages of the compressor may be additionally heated by the heater 600 in accordance with the fuel supply condition of the power generation engine and supplied to the power generation engine.

According to ship regulations, the compressor that supplies fuel to the engine must be designed with redundancy in case of an emergency. Redundancy design means that when one cannot be used for reasons such as failure or maintenance, the other is replaced. It means designing to be usable. To this end, although only one set of compressors is shown in the drawings of the present embodiments, a plurality of compressors may be provided.

In the downstream of the compressor 100, the reliquefaction line RL is branched from the boil-off gas supply line GL and is connected to the storage tank T, and the boil-off gas not supplied as fuel of the main engine is branched to the reliquefaction line. After reliquefaction, it is re-stored in a storage tank.

The reliquefaction line RL is provided with a heat exchanger 200 for cooling the compressed boil-off gas by heat exchange with the uncompressed boil-off gas of the boil-off gas supply line, and a decompression device 300 for decompressing the boil-off gas cooled through the heat exchanger. .

The pressure reducing device 300 may be configured as an expander or an expansion valve such as a Joule-Thomson valve for reducing the compressed evaporated gas. Through decompression, the boil-off gas is adiabatically expanded and further cooled.

The additionally cooled boil-off gas through the decompression device is introduced into the first gas-liquid separator 400, and the liquid separated in the first gas-liquid separator is introduced into the second gas-liquid separator 500 along the reliquefaction line RL, and separated. The resulting gas, that is, the flash gas, is joined to the uncompressed boil-off gas flow of the boil-off gas supply line along the first flash gas line FL1 through the first expansion means 450, and is introduced into the refrigerant of the heat exchanger.

The liquid separated in the first gas-liquid separator may be partially changed into a gaseous state while being introduced into the second gas-liquid separator 500 having a lower internal pressure. In the second gas-liquid separator, the flash gas phase-changed into a gaseous state is separated and supplied to the uncompressed boil-off gas flow of the boil-off gas supply line along the second flash gas line FL2. The liquefied gas separated by the second gas-liquid separator may be supplied to a storage tank along a reliquefaction line and stored again.

Like the system of the second embodiment, the flash gas separated in the first gas-liquid separator is decompressed and supplied to the boil-off gas supply line, and the flash gas is depressurized in the second gas-liquid separator and supplied to the boil-off gas supply line, which is introduced into the heat exchanger. By lowering the temperature of the Cold BOG and increasing the refrigerant flow rate, it was confirmed that the reliquefaction performance can be improved by about 13% compared to the existing system as a result of simulation.

The system of the second embodiment illustrated in FIG. 3 is provided with a second expansion means 550 for decompressing the flash gas separated from the second gas-liquid separator and introduced into the heat exchanger. That is, as in the system of the first embodiment described above, the first expansion means 450 is disposed in the first flash gas line FL1, and the second flash gas is further connected from the second gas-liquid separator to the boil-off gas supply line. The second expansion means 550 is also provided in the line FL2 so that the flash gas separated by the second gas-liquid separator is also cooled under reduced pressure and introduced into the heat exchanger.

The second expansion means 550 may be an expander or a Joule Thompson valve that decompresses and cools the flash gas.

The temperature of the cold BOG introduced into the heat exchanger by depressurizing and cooling the plasma gas separated in the first and second gas-liquid separators, respectively, through the first and second expansion means, and supplying it to the front end of the heat exchanger of the boil-off gas supply line. It can be further lowered, the refrigerant flow rate can be increased, and in the case of this embodiment, it was confirmed that the reliquefaction performance can be improved by about 14% compared to the existing system as a result of the simulation test.

As shown in FIG. 3, since the other configuration is similar to that of the first embodiment described above, a redundant description will be omitted.

As described above, in the present embodiments, the boil-off gas generated from the storage tank in which the liquefied gas is stored in the ship is supplied to the compressor, compressed at the fuel supply pressure of the main engine in the ship, and supplied as fuel among the boil-off gas compressed by the compressor. The uncompressed evaporated gas to be introduced into the compressor is cooled by heat exchange in a heat exchanger, further cooled under reduced pressure, and gas-liquid is separated and reliquefied.

In particular, by configuring the first and second gas-liquid separators, while maintaining the internal pressure of the second gas-liquid separator lower than that of the first gas-liquid separator, the uncompressed evaporation gas introduced into the heat exchanger by separating the flash gas from the first and second gas-liquid separators By supplying it as a flow, the temperature of the refrigerant introduced into the heat exchanger can be lowered and the flow rate of the refrigerant can be increased.

As described above, the gas-liquid separator is configured in two stages, and the separated flash gas is decompressed and supplied, thereby increasing the amount of flash gas supplied to the uncompressed evaporation gas flow and lowering the temperature, thereby improving the cooling effect of the heat exchanger.

Through this, the gas to be reliquefied in the heat exchanger can be effectively cooled, and reliquefaction performance can be improved.

It is obvious to those of ordinary skill in the art that the present invention is not limited to the above embodiments, and can be implemented with various modifications or variations within the scope of the technical gist of the present invention. I did it.

T: storage tank
ME: main engine
GE: Power generation engine
GL: Boil-off gas supply line
RL: Reliquefaction line
FL1: first flash gas line
FL2: second flash gas line
100: compressor
200: heat exchanger
300: pressure reducing device
400: first gas-liquid separator
450: first expansion means
500: second gas-liquid separator
550: second expansion means
600: heater

Claims (11)

Compressor for receiving and compressing the boil-off gas generated from the liquefied gas stored in the storage tank of the ship;
A heat exchanger that receives all or part of the boil-off gas compressed by the compressor and cools it by heat exchange with the uncompressed boil-off gas to be supplied to the compressor;
A decompression device for further cooling by decompressing the boil-off gas cooled in the heat exchanger;
A first gas-liquid separator for gas-liquid separation by receiving the boil-off gas reduced by the decompression device;
Including; a second gas-liquid separator for gas-liquid separation by receiving the liquefied gas separated by the first gas-liquid separator,
The second gas-liquid separator has an internal pressure lower than that of the first gas-liquid separator, and the liquefied gas separated by the first gas-liquid separator is supplied to the second gas-liquid separator to separate the flash gas generated and introduced into the heat exchanger. Boil-off gas treatment system of a ship, characterized in that supplying the compressed boil-off gas flow. The method of claim 1,
The flash gas separated by the first gas-liquid separator is supplied to the uncompressed evaporative gas flow introduced into the heat exchanger,
A system for treating boil-off gas of a ship further comprising a; first expansion means for decompressing the flash gas separated by the first gas-liquid separator and introduced into the heat exchanger. The method of claim 2,
A second expansion means for decompressing the flash gas separated by the second gas-liquid separator and introduced into the heat exchanger; further comprising,
The liquefied gas separated by the second gas-liquid separator is restored to the storage tank. The method of claim 3,
The first and second expansion means are an expander or a Joule Thompson valve that depressurizes and cools the flash gas. The method of claim 3,
In the compressor, the boil-off gas is compressed at the fuel supply pressure of the main engine on board,
The boil-off gas compressed by the compressor is supplied to the main engine, and the boil-off gas compressed through a part of the compressor is supplied to a power generation engine receiving a lower pressure fuel than the main engine. Processing system. The method of claim 5,
The internal pressure of the first gas-liquid separator is 5 to 10 barg, and the internal pressure of the second gas-liquid separator is 2 to 5 barg. Compressing the boil-off gas generated from the storage tank in which the liquefied gas is stored on the ship with a compressor,
All or part of the boil-off gas compressed by the compressor is cooled by heat exchange in a heat exchanger with the uncompressed boil-off gas to be introduced into the compressor, and further cooled by reduced pressure,
Gas-liquid separation of the depressurized boil-off gas in a first gas-liquid separator,
The uncompressed evaporation introduced into the heat exchanger by supplying the liquefied gas separated in the first gas-liquid separator to a second gas-liquid separator having an internal pressure lower than that of the first gas-liquid separator, separating the flash gas generated from the liquefied gas and introducing it to the heat exchanger Boil-off gas treatment method of a ship, characterized in that the supply by gas flow. The method of claim 7,
The flash gas separated by the first gas-liquid separator is decompressed and supplied to the uncompressed boil-off gas flow introduced into the heat exchanger. The method of claim 8,
The flash gas separated in the second gas-liquid separator is decompressed and supplied to the uncompressed evaporative gas flow to be introduced into the heat exchanger,
The liquefied gas separated by the second gas-liquid separator is restored to the storage tank. The method of claim 9,
The flash gas separated by the first and second gas-liquid separators is depressurized by an expander or a Joule Thompson valve, cooled, and supplied as an uncompressed boil-off gas flow to be introduced into the heat exchanger. Way. The method of claim 10,
In the compressor, the boil-off gas is compressed at the fuel supply pressure of the main engine on board,
The boil-off gas compressed by the compressor is supplied to the main engine, and the boil-off gas compressed through a part of the compressor is supplied to a power generation engine receiving a lower pressure fuel than the main engine. Processing method.

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