KR102203743B1 - Boil-Off Gas Treatment System and Method for Ship - Google Patents

Abstract

A ship's boil-off gas treatment system and method are provided. In the ship's boil-off gas treatment system of the present invention, in a ship equipped with a main engine and a power generation engine receiving fuel at a lower pressure than the main engine, the main engine is supplied with the boil-off gas generated from the liquefied gas stored in the storage tank of the ship. A compressor that compresses at the fuel supply pressure of the engine; A heat exchanger for receiving part of the compressed gas compressed by the compressor and cooling it by heat exchange with the uncompressed boil-off gas to be supplied to the compressor from the storage tank; A post cooler for receiving the compressed gas cooled by the heat exchanger and further cooling it; And a re-liquefaction unit for re-liquefying the compressed gas cooled through the heat exchanger and the post-cooler, wherein a part of the compressed gas further cooled in the post-cooler is branched, depressurized, and then supplied to the power generation engine through the heat exchanger. And a flash gas generated from the gas reliquefied through the aftercooler and the reliquefaction unit is supplied as a refrigerant to the aftercooler.

Description

Boil-Off Gas Treatment System and Method for Ship}

The present invention relates to a boil-off gas treatment system and method for re-liquefying boil-off gas (BOG) generated from liquefied gas stored in a ship with cold heat of the boil-off gas itself.

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 storing liquefied natural gas is insulated, but external heat is continuously transmitted to the storage tank. -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 DFDE, X-DF engine, and ME-GI engine are used as engines that can use natural gas as fuel.

DFDE is composed of four strokes, and adopts an Otto Cycle in which natural gas with a relatively low pressure of 5.5 barg is injected into the inlet of the combustion air, and the piston rises to compress it.

The X-DF engine consists of two strokes, uses 16 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-described problem, in a ship provided with a main engine and a power generation engine receiving fuel at a lower pressure than the main engine,

A compressor that receives boil-off gas generated from the liquefied gas stored in the storage tank of the ship and compresses it at the fuel supply pressure of the main engine;

A heat exchanger for receiving part of the compressed gas compressed by the compressor and cooling it by heat exchange with the uncompressed boil-off gas to be supplied to the compressor from the storage tank;

A post cooler for receiving the compressed gas cooled by the heat exchanger and further cooling it; And

Including; a reliquefaction unit for re-liquefying the compressed gas cooled through the heat exchanger and the post-cooler,

Part of the compressed gas further cooled in the aftercooler is branched and supplied to the power generation engine through the heat exchanger after decompression,

There is provided a boil-off gas treatment system for a ship, characterized in that the flash gas generated from the gas reliquefied through the after-cooler and the re-liquefied unit is supplied as a refrigerant to the after-cooler.

Preferably, the reliquefaction unit includes: a decompression device for further cooling by decompressing the compressed gas cooled through the heat exchanger and the post cooler; And a gas-liquid separator for gas-liquid separation by receiving the compressed gas depressurized by the decompression device.

Preferably, the system further includes an expansion device branched from the rear end of the post cooler to depressurize the compressed gas to be supplied to the power generation engine and supply the compressed gas to the heat exchanger, wherein in the heat exchanger, the compressed gas compressed by the compressor. , Three flows of the uncompressed boil-off gas to be supplied to the compressor and the boil-off gas branched from the rear end of the post-cooler and depressurized by the expansion device may be heat-exchanged.

Preferably, the flash gas separated in the gas-liquid separator is introduced into the post cooler and heat-exchanged, and then joined to the uncompressed evaporative gas introduced into the heat exchanger from the storage tank, and the separated liquid is stored in the storage tank. Can be.

According to another aspect of the present invention, in a ship provided with a main engine and a power generation engine receiving fuel at a lower pressure than the main engine,

A boil-off gas supply line connected to the main engine from a storage tank provided on the ship to store liquefied gas;

A compressor provided in the boil-off gas supply line and receiving boil-off gas generated from the liquefied gas and compressing it at a fuel supply pressure of the main engine;

A downstream of the compressor is branched from the boil-off gas supply line and connected to the storage tank, and the boil-off gas supplied as fuel of the main engine is cooled by heat exchange with the uncompressed boil-off gas to be supplied to the compressor and reliquefied. A reliquefaction line for restoring into a storage tank;

A heat exchanger provided in the reliquefaction line and configured to receive compressed gas compressed by the compressor and cool it by heat exchange with uncompressed boil-off gas to be supplied to the compressor from the storage tank;

A post cooler provided in the reliquefaction line and receiving the compressed gas cooled by a heat exchanger for additional cooling; And

A branch line branched from the reliquefaction line at the rear end of the aftercooler and connected to the power generation engine; and

The branch line is connected to the power generation engine through the heat exchanger,

In the aftercooler, there is provided a boil-off gas treatment system for a ship, wherein the compressed gas cooled in the heat exchanger is additionally cooled by using flash gas generated from the reliquefied gas as a refrigerant.

Preferably, the system may further include an expansion device provided in the branch line and branched at a rear end of the post cooler to depressurize the compressed gas to be supplied to the power generation engine and supply it to the heat exchanger.

Preferably, the reliquefaction line includes: a decompression device for further cooling by decompressing the compressed gas cooled through the heat exchanger and the post cooler; And a gas-liquid separator for gas-liquid separation by receiving the compressed gas depressurized by the decompression device.

Preferably, a flash gas line connected from the gas-liquid separator to the front end of the boil-off gas supply line through the after-cooler; further comprising, after the flash gas separated in the gas-liquid separator is heat-exchanged in the post cooler, the It may be joined to the uncompressed boil-off gas introduced from the storage tank to the heat exchanger.

Preferably, in the heat exchanger, the compressed gas compressed by the compressor and branched along the reliquefaction line, the uncompressed boil-off gas to be supplied to the compressor along the boil-off gas supply line, and the branch after depressurization in the expansion device Three flows of boil-off gas to be supplied to the power generation engine are heat-exchanged along a line, and in the post-cooler, the compressed gas of the reliquefaction line cooled in the heat exchanger, and the flash gas of the flash gas line separated by the gas-liquid separator Can be heat exchanged.

Preferably, a fuel heater provided in the branch line to heat the boil-off gas to the fuel supply temperature of the power generation engine; further comprising, the boil-off gas branched to the branch line and reduced pressure is heated by heat exchange in the heat exchanger After being heated, it may be additionally heated in the fuel heater and supplied to the power generation engine.

According to another aspect of the present invention, in a ship provided with a main engine and a power generation engine receiving fuel at a lower pressure than the main engine,

Compressing the boil-off gas generated from the storage tank storing the liquefied gas in the ship with a compressor at the fuel supply pressure of the main engine,

Among the boil-off gas compressed by the compressor, the remaining boil-off gas is supplied to the fuel of the main engine, and the remaining boil-off gas is cooled by heat exchange in a heat exchanger with the uncompressed boil-off gas to be introduced into the compressor, further cooled under reduced pressure, and reliquefied to the storage tank. Save again,

The boil-off gas to be reliquefied is cooled in a heat exchanger and then further cooled by heat exchange in a post cooler using flash gas separated from the reliquefied gas as a refrigerant before decompression,

There is provided a method for treating boil-off gas of a ship, characterized in that a part of the boil-off gas to be reliquefied at a rear end of the after-cooler is branched, decompressed, and supplied to the power generation engine through the heat exchanger.

In the system of the present invention, the boil-off gas to be reliquefied after being cooled in a heat exchanger is further cooled by cold heat of flash gas generated from the re-liquefied gas, thereby enhancing re-liquefaction performance and effectively treating the boil-off gas. . In addition, a part of the evaporated gas to be compressed and cooled to be reliquefied is decompressed and supplied to the power generation engine through a heat exchanger, thereby securing additional refrigerant in the heat exchanger, thereby enhancing the cooling performance of the heat exchanger, thereby increasing the re-liquid performance.

In this way, the gas to be reliquefied can be effectively cooled by using the cold heat of the boil-off gas to be supplied to the power generation engine and the cold heat of the flash gas, while the boil-off gas to be supplied to the power generation engine can be heated, thereby increasing the energy efficiency of the system and It can improve the re-liquefaction performance and secure the safety of the ship by effectively treating the boil-off gas.

1 is a schematic diagram of a conventional boil-off gas treatment system.
2 is a schematic diagram of a boil-off gas treatment system of a ship according to a basic embodiment of the present invention.
3 is a schematic diagram of a system for treating boil-off gas of a ship according to a first 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, liquid hydrogen carriers, and ships with self-propelled capabilities such as LNG Regasification Vessels (RVs), LNG Floating Production Storage Offloading (FPSO), and LNG Floating Storage Regasification Units (FSRU). ), but may also 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 basic embodiment of the present invention, and FIG. 3 schematically shows the boil-off gas treatment system of the ship according to the first embodiment of the present invention.

As shown in FIGS. 2 and 3, the system of the present exemplary embodiment receives the boil-off gas generated from the liquefied gas stored in the storage tank T of the ship and compresses it at the fuel supply pressure of the main engine provided on the ship ( 100), a heat exchanger 200 that receives part of the compressed gas compressed by the compressor and cools it by heat exchange with the uncompressed evaporated gas to be supplied from the storage tank to the compressor, and the compressed gas cooled by the heat exchanger. It is a system including a cooling post-cooler 300, a heat exchanger and a re-liquefaction unit 400 for re-liquefying the compressed gas cooled through the post-cooler.

That is, the system of the present basic embodiment and the first embodiment is configured such that the boil-off gas to be reliquefied is cooled in the heat exchanger 200 and then further cooled in the post cooler 300 and then introduced into the reliquefaction unit.

The boil-off gas generated from the storage tank is introduced into a compressor and compressed. The compressor 100 may be provided as a multi-stage compressor in which a plurality of compressors and intermediate coolers are alternately arranged, and through these in sequence, compressing the boil-off gas to the fuel supply pressure of the main engine.

The compressor compresses the boil-off gas to the fuel supply pressure to the main engine, for example, 5.5 barg if a DF engine is provided, 16 barg if an X-DF engine is provided, and 300 barg if a ME-GI engine is provided. can do. The number of compressors and intermediate coolers constituting the multi-stage compressor can be changed according to the fuel supply pressure of the main 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.

The compressed gas compressed by the compressor 100 is supplied as fuel of the main engine ME, and the remaining boil-off gas after the fuel supply may be reliquefied. The boil-off gas to be re-liquefied is cooled through heat exchange with the uncompressed boil-off gas supplied from the storage tank, and then re-liquefied through a post cooler and a re-liquefied unit and stored in a storage tank.

When a power generation engine GE that receives fuel at a lower pressure than the main engine ME is provided, some compressed gas may be branched from the intermediate stage of the multi-stage compressor 100 and supplied to the power generation engine GE.

The reliquefaction unit 400 includes a decompression device 410 for additionally cooling by decompressing the compressed gas cooled through a heat exchanger and a post-cooler, and a gas-liquid separator 420 for gas-liquid separation by receiving the compressed gas depressurized by the decompression device. Include.

The decompression device 410 may be configured as an expander or an expansion valve such as a Joule-Thomson valve for adiabatic expansion of compressed and cooled evaporated gas to cool it.

The compressed, cooled, and expanded-cooled boil-off gas through a compressor, heat exchanger, post-cooler, and decompression device is completely or partially reliquefied and introduced into a gas-liquid separator.

The gas separated by the gas-liquid separator 420 is introduced into the post-cooler 300 and subjected to heat exchange, and then joined to the uncompressed boil-off gas introduced from the storage tank to the heat exchanger.

In this basic embodiment, the compressed gas cooled in the heat exchanger can be further cooled by using the cooling heat of the gas separated in the gas-liquid separator, that is, the flash gas. The reliquefaction rate can be increased by further cooling the compressed gas to be reliquefied in a post cooler prior to decompression in the decompression device. The flash gas, which is further cooled by the compressed gas in the postcooler, joins the refrigerant flow of the uncompressed evaporated gas introduced from the storage tank to the heat exchanger, thereby increasing the refrigerant flow rate of the heat exchanger.

The first embodiment shown in FIG. 3 is an evaporation to be supplied to the power generation engine GE in a ship equipped with a main engine ME and a power generation engine receiving fuel at a lower pressure than the main engine in addition to the above-described basic embodiment. The cooling heat of the gas is also configured so that the boil-off gas can be used as a refrigerant for reliquefaction.

As shown in Figure 3, the system of the first embodiment is a main engine (ME) from a storage tank (T) for storing liquefied gas provided on the ship in a ship equipped with a main engine and a power generation engine that receives fuel at a lower pressure than the main engine. ) Connected to the boil-off gas supply line (GL), branched from the boil-off gas supply line downstream of the compressor 100, and connected to the storage tank, supplied as fuel of the main engine, and the remaining boil-off gas to be supplied to the compressor uncompressed evaporation From the reliquefaction line (RL) that cools by heat exchange with gas and reliquefies and stores it in a storage tank, a branch line (BL) branched from the reliquefaction line at the rear end of the post cooler 300 and connected to the power generation engine, and from the gas-liquid separator. A flash gas line FL connected to the front end of the heat exchanger of the boil-off gas supply line through the post cooler is provided.

The boil-off gas supply line GL is provided with a compressor 100 that receives boil-off gas generated from the liquefied gas and compresses it with the fuel supply pressure of the main engine, as in the above-described basic embodiment.

For example, the main engine may be a ME-GI engine, and the power generation engine may be a DFGE (Dual Fuel Generator Engine), a TFGE (Triple Fuel Generator Engine), or a medium pressure engine that is supplied with fuel at a lower pressure than a ME-GI engine. In this case, the compressor can compress the boil-off gas at a pressure of approximately 300 barg.

A heat exchanger 200, a heat exchanger that receives compressed gas compressed by the compressor and cools it by heat exchange with uncompressed evaporative gas to be supplied to the compressor from the storage tank to the reliquefaction line (RL) branching from the boil-off gas supply line downstream of the compressor. A reliquefaction unit 400 for depressurizing and re-liquefying the compressed gas cooled through the heat exchanger and the post cooler is provided.

The reliquefaction unit includes a decompression device 410 for further cooling by decompressing the compressed gas cooled through the heat exchanger and the post-cooler, and a gas-liquid separator 420 for gas-liquid separation by receiving the compressed gas reduced by the decompression device.

The pressure reducing device may be composed of an expander or an expansion valve such as a Joule-Thomson valve for adiabatic expansion of compressed and cooled boil-off gas to cool it.

The flash gas separated by the gas-liquid separator is introduced into the post cooler 300 along the flash gas line FL and heat-exchanged, and then introduced into the heat exchanger 200 from the storage tank along the boil-off gas supply line in front of the heat exchanger. It joins the compressed boil-off gas. The flash gas passing through the post-cooler joins the refrigerant flow of the uncompressed boil-off gas introduced from the storage tank to the heat exchanger, thereby increasing the refrigerant flow rate of the heat exchanger.

The liquid separated by the gas-liquid separator is stored in a storage tank along the reliquefaction line RL.

The branch line BL is branched from the reliquefaction line RL at the rear end of the after cooler 300 and is connected to the power generation engine through the heat exchanger 200, and the branch line heat exchange by decompressing the compressed gas to be supplied to the power generation engine. An expansion device 500 is provided to supply energy.

The expansion device of the branch line may be composed of an expansion valve such as an expander or a Joule-Thomson valve that decompresses the compressed evaporated gas, and the evaporated gas cooled through the decompression is cold heat for reliquefaction of the evaporated gas in the heat exchanger. It is supplied as a refrigerant and then supplied as fuel for the power generation engine.

The branch line is provided with a fuel heater 600 that additionally heats the boil-off gas to the fuel supply temperature of the power generation engine, and the boil-off gas branched to the branch line and decompressed is heat-exchanged with the compressed gas to be reliquefied through a heat exchanger. It can be further heated by the heater and supplied to the power generation engine.

The amount of boil-off gas supplied to the power generation engine through the branch line may be about 600 to 1000 kg/h, but this may vary depending on the load of the power generation engine, and may also vary according to the configuration of the compressor.

In the present system, the boil-off gas generated in the storage tank is compressed by a compressor and supplied to fuel such as a main engine, and the boil-off gas remaining after the fuel supply can be reliquefied. The boil-off gas to be reliquefied is branched from the rear end of the compressor to a reliquefaction line, is sequentially cooled through a heat exchanger and a post-cooler, is reliquefied through a decompression device and a gas-liquid separator of the reliquefaction line, and is stored in a storage tank.

At this time, in the system of this embodiment, in the heat exchanger 200, the compressed gas compressed by the compressor and branched along the reliquefaction line, the uncompressed boil-off gas to be supplied to the compressor along the boil-off gas supply line, and the branch line after depressurization in the expansion device. Accordingly, the three flows of the boil-off gas to be supplied to the power generation engine are heat-exchanged, and the compressed gas to be reliquefied is cooled by using the uncompressed boil-off gas of the boil-off gas supply line and the boil-off gas of the branch line as refrigerants.

In addition, in the post cooler 300, the compressed gas of the reliquefaction line cooled in the heat exchanger and the flow of the flash gas in the flash gas line separated from the gas-liquid separator are heat-exchanged, and the compressed gas of the reliquefaction line cooled through the heat exchanger is flashed. It is further cooled using the flash gas of the gas line as a refrigerant.

In this way, the reliquefaction performance can be improved and the boil-off gas can be effectively treated by configuring a post-cooler to further cool the gas to be reliquefied, and to use the boil-off gas to be supplied as fuel of the power generation engine as a refrigerant in the heat exchanger.

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
BL: branch line
FL: flash gas line
100: compressor
200: heat exchanger
300: after cooler
400: reliquefaction unit
410: pressure reducing device
420: gas-liquid separator
500: expansion device
600: fuel heater

Claims (11)

In a ship equipped with a main engine and a power generation engine that receives fuel at a lower pressure than the main engine,
A compressor that receives boil-off gas generated from the liquefied gas stored in the storage tank of the ship and compresses it at the fuel supply pressure of the main engine;
A heat exchanger for receiving part of the compressed gas compressed by the compressor and cooling it by heat exchange with the uncompressed boil-off gas to be supplied to the compressor from the storage tank;
A post cooler for receiving the compressed gas cooled by the heat exchanger and further cooling it;
A reliquefaction unit for reliquefying the compressed gas cooled through the heat exchanger and the post cooler; And
Including; an expansion device for supplying to the heat exchanger by decompressing a part of the compressed gas branched from the rear end of the cooler,
The compressed gas depressurized in the expansion device is supplied to the power generation engine through the heat exchanger,
In the heat exchanger, the three flows of the compressed gas compressed by the compressor, the uncompressed boil-off gas to be supplied to the compressor, and the boil-off gas branched at the rear end of the post cooler and depressurized by the expansion device are heat-exchanged,
The reliquefaction unit may further include a decompression device for decompressing the compressed gas cooled through the heat exchanger and the post cooler to further cool it; And a gas-liquid separator for gas-liquid separation by receiving the compressed gas reduced by the decompression device,
The flash gas separated from the gas-liquid separator is introduced as a refrigerant into the aftercooler, heat-exchanged, and then joined to the uncompressed evaporative gas introduced into the heat exchanger from the storage tank, and the separated liquid is stored in the storage tank. Ship's boil-off gas treatment system. delete delete delete In a ship equipped with a main engine and a power generation engine that receives fuel at a lower pressure than the main engine,
A boil-off gas supply line connected to the main engine from a storage tank provided on the ship to store liquefied gas;
A compressor provided in the boil-off gas supply line and receiving boil-off gas generated from the liquefied gas and compressing it at a fuel supply pressure of the main engine;
A downstream of the compressor is branched from the boil-off gas supply line and connected to the storage tank, and the boil-off gas supplied as fuel of the main engine is cooled by heat exchange with the uncompressed boil-off gas to be supplied to the compressor and reliquefied. A reliquefaction line for restoring into a storage tank;
A heat exchanger provided in the reliquefaction line and configured to receive compressed gas compressed by the compressor and cool it by heat exchange with uncompressed boil-off gas to be supplied to the compressor from the storage tank;
A post-cooler provided in the reliquefaction line and receiving the compressed gas cooled by a heat exchanger for additional cooling;
A branch line branched from the reliquefaction line at a rear end of the after-cooler and connected to the power generation engine; And
An expansion device provided in the branch line and branched at a rear end of the after cooler to depressurize the compressed gas to be supplied to the power generation engine and supply it to the heat exchanger; and
The branch line is connected to the power generation engine through the heat exchanger,
In the reliquefaction line, a pressure reducing device for further cooling by depressurizing the compressed gas cooled through the heat exchanger and the post cooler; And a gas-liquid separator for gas-liquid separation by receiving the compressed gas depressurized by the decompression device,
A flash gas line from the gas-liquid separator to the front end of the boil-off gas supply line through the after-cooler; is connected,
In the heat exchanger, the compressed gas compressed by the compressor and branched along the reliquefaction line, uncompressed boil-off gas to be supplied to the compressor along the boil-off gas supply line, and the branch line after decompression in the expansion device. The three flows of boil-off gas to be supplied to the power generation engine are heat-exchanged,
In the aftercooler, the compressed gas cooled in the heat exchanger is further cooled by using the flash gas of the flash gas line separated from the reliquefied gas as a refrigerant. delete delete The method of claim 5,
The flash gas separated by the gas-liquid separator is heat-exchanged in the post cooler and then joined to the uncompressed boil-off gas introduced from the storage tank to the heat exchanger. The method of claim 8,
A fuel heater provided in the branch line to heat the boil-off gas to a fuel supply temperature of the power generation engine;
The boil-off gas branched to the branch line and decompressed is heated by heat exchange in the heat exchanger and then further heated by the fuel heater and supplied to the power generation engine. In a ship equipped with a main engine and a power generation engine that receives fuel at a lower pressure than the main engine,
Compressing the boil-off gas generated from the storage tank storing the liquefied gas in the ship with a compressor at the fuel supply pressure of the main engine,
Among the boil-off gas compressed by the compressor, the remaining boil-off gas is supplied to the fuel of the main engine, and the remaining boil-off gas is cooled by heat exchange in a heat exchanger with the uncompressed boil-off gas to be introduced into the compressor, further cooled under reduced pressure, and reliquefied to the storage tank. Save again,
The boil-off gas to be reliquefied is cooled in a heat exchanger and then further cooled by heat exchange in a post cooler using flash gas separated from the reliquefied gas as a refrigerant before decompression,
A portion of the boil-off gas to be reliquefied at the rear end of the after-cooler is branched and decompressed, and supplied to the power generation engine through the heat exchanger,
In the heat exchanger, three streams of compressed gas to be compressed and reliquefied in the compressor, uncompressed evaporated gas to be supplied to the compressor, and evaporated gas branched from the rear end of the post cooler and reduced to supply to the power generation engine are heat-exchanged,
In the aftercooler, the compressed gas cooled by the heat exchanger and the flash gas separated from the reliquefied gas are heat-exchanged.
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