KR20200135595A - Boil-Off Gas Treatment System And Method for Ship - Google Patents

Abstract

Disclosed are a boil-off gas treatment system and a method thereof. The boil-off gas treatment system of the present invention includes: a boil-off gas supply line provided in a vessel to be connected from a storage tank storing liquefied gas to a main engine of the vessel; a compressor provided on the boil-off gas supply line and receiving boil-off gas produced from the liquefied gas to compress the gas with fuel supply pressure from the main engine; a re-liquefication line branched from the boil-off gas supply line in the downstream of the compressor to be connected to the storage tank, and re-storing compressed gas, which is remaining after being supplied as fuel for the main engine, by cooling and re-liquefying the gas through a heat exchange with non-compressed boil-off gas to be supplied to the compressor; a heat exchanger provided on the re-liquefication line and cooling the compressed gas through a heat exchange with the non-compressed boil-off gas to be supplied from the storage tank to the compressor along the boil-off gas supply line; a gas combustion part combusting and treating boil-off gas which is not used for vessel fuel supply and re-liquefication for the vessel; and a gas combustion line branched from the front end of the compressor to the boil-off gas supply line to be connected to the gas combustion part. Therefore, the boil-off gas to be combusted can be supplied to the gas combustion part through the gas combustion line after cold and heat recovery via the heat exchanger.

Description

Boil-Off Gas Treatment System and Method for Ship}

The present invention relates to a system and method for treating boil-off gas of a ship, and more particularly, supplying boil-off gas generated in a storage tank as fuel of an onboard engine, and re-liquefying the remaining boil-off gas after fuel supply and storing it in a storage tank. It relates to a ship's boil-off gas treatment system and method.

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 -163°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 ℃ at normal pressure, the 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 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.

As shown in FIG. 1, in the conventional boil-off gas treatment system, 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 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 in 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.

When the vessel is moored or operates at low speed, the amount of boil-off gas required by the engine is small, and even if the amount of boil-off gas to be reliquefied cannot be treated all the boil-off gas generated from the storage tank, maintain the pressure of the storage tank. To burn the boil-off gas, it is sent to the Gas Combustion Unit (GCU).

In the conventional system, the boil-off gas supplied from the storage tank to the gas combustion device is branched from the vapor main at the outlet of the storage tank from the boil-off gas to be fueled and reliquefied, and the heater 50 and the boosting blower 60 do not pass through a heat exchanger or compressor. ) Was supplied to the gas combustion system.

However, in this case, since the boil-off gas supplied to the gas combustion device and to be burned does not pass through the heat exchanger 20, there is a problem in that the cold heat of the boil-off gas to be burned cannot be recovered. An object of the present invention is to solve this problem and propose a system capable of increasing the reliquefaction efficiency by recovering the cold heat of the boil-off gas to be burned.

According to an aspect of the present invention for solving the above-described problem, a boil-off gas supply line connected to the main engine of the ship from a storage tank provided on a 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 compressed 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 re-liquefied. A reliquefaction line for restoring into a storage tank;

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

A gas combustion unit that burns and processes boil-off gas that is not used for fuel supply and reliquefaction in the ship; And

Including; a gas combustion line branched from the boil-off gas supply line at the front end of the compressor and connected to the gas combustion unit,

There is provided a boil-off gas treatment system for a ship, characterized in that the boil-off gas to be burned can be supplied to the gas combustion unit through the gas combustion line after recovery of cold heat through the heat exchanger.

Preferably, the system includes: a blower provided in the gas combustion line and supplying the boil-off gas to the gas combustion unit; And a bypass line connected from the storage tank to the front end of the blower of the gas combustion line; further comprising, the amount of boil-off gas generated in the storage tank is large, or supply of fuel in a ship, such as when the ship is anchored or operated at low speed. And when the boil-off gas that is not used for reliquefaction is removed by combustion, the boil-off gas to be burned is supplied to the blower through the heat exchanger, and the amount of boil-off gas generated in the storage tank is small, and thus through the reliquefaction line. When all or part of the boil-off gas is to be processed by the gas combustion unit without re-liquefying the boil-off gas, the boil-off gas to be burned may be supplied to the blower through the bypass line.

Preferably, the system may further include a heater provided in the bypass line to heat the boil-off gas to be supplied to the blower.

Preferably, the reliquefaction line includes: a pressure reducing device receiving the compressed gas cooled in the heat exchanger and reducing the pressure to cool it; And a gas-liquid separator for gas-liquid separation by receiving the compressed gas depressurized by the decompression device.

Preferably, in the system, the compressor is a multistage compressor that compresses the boil-off gas to the fuel supply pressure of the main engine through a plurality of compressors in sequence, and is provided at a rear end of the compressor to remove oil contained in the compressed gas. An oil separator; further comprising, the boil-off gas compressed through some of the multi-stage compressors may be supplied to a power generation engine receiving fuel having a lower pressure than the main engine.

Preferably, the system comprises: a liquefied gas supply line connected from the storage tank to the main engine to supply the liquefied gas as fuel of the main engine; An HP pump provided in the liquefied gas supply line to compress the liquefied gas to the fuel supply pressure of the main engine; And an HP vaporizer that heats the liquefied gas compressed by the HP pump and supplies it to the main engine.

According to another aspect of the present invention, boil-off gas generated from a storage tank provided on a ship to store liquefied gas is compressed to the fuel supply pressure of the main engine through a compressor,

Among the compressed boil-off gas, the remaining boil-off gas supplied to the fuel of the main engine is cooled by heat exchange in a heat exchanger with the uncompressed boil-off gas to be introduced from the storage tank to the compressor, and re-liquefied and stored in the storage tank,

In the above vessel, boil-off gas that is not used for fuel supply and reliquefaction in the vessel is burned in the gas combustion unit to be treated,

The boil-off gas to be burned is provided with a method for treating boil-off gas of a ship, wherein the boil-off gas to be burned is supplied to the gas combustion unit by branching from the front end of the compressor after recovering the cold heat through the heat exchanger.

Preferably, the boil-off gas to be burned by branching from the front end of the compressor is supplied to the gas combustion unit through a blower, and the amount of boil-off gas generated in the storage tank is large, such as when a ship is anchored or operated at low speed. When the remaining boil-off gas remaining after supplying fuel and reliquefaction on board is burned and removed, the boil-off gas to be burned is supplied to the blower through the heat exchanger, and the amount of boil-off gas generated in the storage tank is small, so that the boil-off gas is recycled. When all or part of the boil-off gas is to be processed by the gas combustion unit without being liquefied, the boil-off gas to be burned may bypass the heat exchanger and be heated by a heater and then supplied to the blower.

Preferably, the boil-off gas cooled in the heat exchanger is depressurized and further cooled through a decompression device, and the boil-off gas further cooled by depressurization is separated by gas-liquid separation, and liquid is supplied to the storage tank, and gas is stored in the storage tank. It may be joined to the uncompressed boil-off gas introduced from the tank to the heat exchanger.

Preferably, when the amount of boil-off gas generated in the storage tank is small, the boil-off gas is supplied to the main engine through the compressor, or supplied to the onboard power generation engine through a part of the compressor, and reliquefied through the heat exchanger. You can handle it.

In the system of the present invention, the re-liquefaction performance can be improved when the boil-off gas is re-liquefied by recovering the cold heat of the boil-off gas to be burned in the gas combustion unit.

In addition, the boil-off gas is recovered through a heat exchanger, or when the reliquefaction system is not operated, the boil-off gas treatment system can be flexibly operated according to the operating conditions of the ship by supplying it to the gas combustion unit through a blower without passing through the heat exchanger. have.

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, 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 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.

As shown in FIGS. 2 and 3, the system of the first and second embodiments includes a boil-off gas supply line GL connected to the main engine of the ship from a storage tank T provided on a ship and storing liquefied gas. , A compressor 100 that is provided in the boil-off gas supply line and receives boil-off gas generated from the liquefied gas and compresses it with the fuel supply pressure of the main engine (ME), and is branched from the boil-off gas supply line at the downstream of the compressor to a storage tank. A reliquefaction line (RL) that cools the remaining compressed gas supplied as fuel of the main engine by heat exchange with uncompressed evaporation gas to be supplied to the compressor, reliquefies and stores it in a storage tank, and is provided in the reliquefaction line and compressed. A heat exchanger 200 that cools the gas from the storage tank by heat exchange with the uncompressed boil-off gas to be supplied to the compressor along the boil-off gas supply line, and the boil-off gas that is not used for fuel supply and reliquefaction in the ship. It includes a gas combustion unit (GCU) and a gas combustion line EL that is branched from the boil-off gas supply line at the front end of the compressor and is connected to the gas combustion unit.

In the present embodiments, the boil-off gas to be burned in the gas combustion unit may be supplied to the gas combustion unit GCU through the gas combustion line EL after recovery of cold heat through a heat exchanger.

When the amount of boil-off gas generated from the storage tank is large, or when the fuel consumption of the main engine is low, such as when the ship is anchored or operated at low speed, the boil-off gas that is not used for fuel supply and reliquefaction in the ship is combusted in the gas combustion section. Can be removed. In this embodiment, when the boil-off gas to be burned and removed is also configured to be supplied to the heat exchanger 200 to recover cold heat and supplied to the gas combustion unit through the gas combustion line EL, when the reliquefaction device is driven. In the heat exchanger, boil-off gas to be supplied as fuel such as a main engine, boil-off gas to be reliquefied, and boil-off gas to be burned in the gas combustion unit may all be used as refrigerants. Accordingly, the flow rate of the refrigerant supplied to the heat exchanger is increased and even the cold heat of the boil-off gas to be burned can be used, so that the boil-off gas to be reliquefied can be more effectively cooled and the re-liquefaction performance can be improved.

The gas combustion line EL is provided with a blower 500 for supplying the boil-off gas to the gas combustion unit. In order to prevent malfunction of the blower and the gas combustion unit, the low-temperature boil-off gas generated in the storage tank must be heated before being supplied to the blower.In these embodiments, the boil-off gas to be burned is heated through heat exchange with compressed gas while passing through a heat exchanger. It can reduce the use of additional heat sources to heat the system and increase the energy efficiency of the system.

On the other hand, in the reliquefaction line RL, a decompression device 300 for receiving compressed gas cooled by a heat exchanger and reducing pressure to cool it, and a gas-liquid separator 400 for gas-liquid separation by receiving the compressed gas depressurized by the decompression device. Can be provided.

The pressure reducing device 300 may be configured as an expander or an expansion valve such as a Joule-Thomson valve that adiabaticly expands and cools the compressed and cooled evaporated gas.

The boil-off gas compressed, cooled, and expanded-cooled through a compressor, a heat exchanger, and a decompression device is completely or partially reliquefied and introduced into a gas-liquid separator. Without configuring a gas-liquid separator, it is decompressed in a decompression device, and the additionally cooled evaporation gas can be sent directly to the storage tank and dissolved in the liquefied natural gas stored in the storage tank.

The liquid separated in the gas-liquid separator 400 is supplied to and stored in a storage tank along the reliquefaction line RL, and the separated gas is combined into the boil-off gas supply line GL and uncompressed evaporation introduced from the storage tank to the heat exchanger. It may be supplied as a refrigerant to the heat exchanger 200 together with the gas.

Meanwhile, the compressor 100 may be provided as a multi-stage compressor in which a plurality of compressors and an intermediate cooler are alternately disposed and sequentially pass through them to compress 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.

An oil separator 600 may be provided at the rear end of the compressor to remove oil such as lubricating oil mixed in the boil-off gas while passing through the compressor. The compressed gas is supplied to the reliquefaction line after oil removal and undergoes a reliquefaction process, and a filter 700 that filters oil vapors not removed from the oil separator from the compressed gas branched after compression is located upstream of the heat exchanger of the reliquefaction line. It can be provided additionally.

When a power generation engine (GE) that receives fuel at a lower pressure than the main engine is provided on board, the compressed boil-off gas can be branched through some of the multi-stage compressors and supplied to a power generation engine that receives fuel at a lower pressure than the main engine. . For example, if a ME-GI engine as the main engine and DFGE as a power generation engine are provided, the compressor supplies fuel to the main engine by compressing the boil-off gas to around 300 barg, and partially extracts the boil-off gas compressed in the middle stage of the multi-stage compressor. It can be branched and supplied as DFGE.

The system of the second embodiment shown in FIG. 3 includes a bypass line BL connected from the storage tank T to the front end of the blower 500 of the gas combustion line EL, and the storage tank. A liquefied gas supply line (LL) is additionally provided, which is connected to the main engine and supplies liquefied gas as fuel of the main engine.

Since the boil-off gas supplied to the blower and the gas combustion unit through the bypass line BL does not pass through the heat exchanger and does not receive a heat source from the compressed gas, a heater 550 for heating the boil-off gas to be supplied to the blower is added to the bypass line. Can be provided.

In the system of the second embodiment, when the amount of boil-off gas generated in the storage tank is large, or when the remaining boil-off gas remaining after fuel supply and reliquefaction in the ship is burned and removed, such as during anchorage or low-speed operation of a ship, The boil-off gas is supplied to the blower along the gas combustion line through a heat exchanger.

When the amount of boil-off gas generated from the storage tank is small, the boil-off gas is supplied to the main engine and power generation engine through all or part of the compressor, and may be reliquefied through a re-liquefaction system through a heat exchanger. It may not work.

In this way, when the amount of boil-off gas generated in the storage tank is small, and the gas combustion unit has to process all or part of the boil-off gas without re-liquefying the boil-off gas through the re-liquefaction line, the boil-off gas to be burned is the storage tank (T ) Can be supplied to the blower without passing through the heat exchanger through the bypass line BL from the vapor main VM.

The liquefied gas supply line LL is provided with an HP pump 800 that compresses liquefied gas to the fuel supply pressure of the main engine, and an HP vaporizer 850 that heats the liquefied gas compressed by the HP pump and supplies it to the main engine. I can.

The liquefied gas pumped from the storage tank by a stripping pump (not shown) is compressed and vaporized through the liquefied gas supply line LL and supplied to the main engine.

Liquefied gas can also be supplied to the power generation engine through a supply line branched from the liquefied gas supply line, and a fuel heater 900 for supplying the liquefied gas branched from the downstream of the HP carburetor in accordance with the fuel supply conditions of the power generation engine. ) And the like may be provided. By configuring the supply line to branch upstream of the HP pump, an LP pump (not shown) that compresses the liquefied gas according to the fuel supply pressure of the power generation engine may be additionally provided, separate from the liquefied gas to be supplied to the main engine.

In the system of the second embodiment, when the reliquefaction system is operated, the reliquefaction performance can be improved by increasing the amount of refrigerant in the heat exchanger by allowing boil-off gas to be supplied to the gas combustion unit to be supplied to the gas combustion unit through the heat exchanger. When not in operation, the boil-off gas to be burned in the gas combustion unit is supplied to the blower through the heater through the bypass line, so that the system can be operated more flexibly according to the conditions of the ship.

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
GCU: gas combustion section
GL: Boil-off gas supply line
RL: Reliquefaction line
LL: Liquefied gas supply line
EL: gas combustion line
BL: Bypass line
100: compressor
200: heat exchanger
300: pressure reducing device
400: gas-liquid separator
500: blower
550: heater
600: oil separator
700: filter
800: HP pump
850: HP Carburetor
900: fuel heater

Claims (10)

A boil-off gas supply line connected to the main engine of the ship 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 compressed 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 re-liquefied. A reliquefaction line for restoring into a storage tank;
A heat exchanger provided in the re-liquefaction line and cooling the compressed gas through heat exchange with the uncompressed boil-off gas to be supplied to the compressor from the storage tank along the boil-off gas supply line;
A gas combustion unit that burns and processes boil-off gas that is not used for fuel supply and reliquefaction in the ship; And
Including; a gas combustion line branched from the boil-off gas supply line at the front end of the compressor and connected to the gas combustion unit,
The boil-off gas treatment system of a ship, characterized in that the boil-off gas to be burned can be supplied to the gas combustion unit through the gas combustion line after recovery of cold heat through the heat exchanger. The method of claim 1,
A blower provided in the gas combustion line and supplying the boil-off gas to the gas combustion unit; And
A bypass line connected from the storage tank to a front end of the blower of the gas combustion line; further comprising,
When the amount of boil-off gas generated in the storage tank is large, or when boil-off gas that is not used for fuel supply and reliquefaction in a ship is removed by combustion, such as at anchoring or low-speed operation of a ship, the boil-off gas to be burned is the heat exchanger It is supplied to the blower through the machine,
When the amount of boil-off gas generated in the storage tank is small and the gas combustion unit has to process all or part of the boil-off gas without re-liquefying the boil-off gas through the re-liquefaction line, the boil-off gas to be burned is Boil-off gas treatment system of a ship, characterized in that supplied to the blower through a bypass line. The method of claim 2,
A heater for heating the boil-off gas to be supplied to the blower provided on the bypass line. The method of claim 2, wherein in the reliquefaction line,
A decompression device for receiving the compressed gas cooled by the heat exchanger and reducing the pressure to cool it; And
A gas-liquid separator for receiving the compressed gas depressurized by the decompression device and separating the gas-liquid; a boil-off gas treatment system of a ship, characterized in that it is provided. The method of claim 2,
The compressor is a multistage compressor that compresses the boil-off gas to the fuel supply pressure of the main engine through a plurality of compressors in sequence,
An oil separator provided at the rear end of the compressor to remove oil contained in the compressed gas; further comprising,
The boil-off gas compressed through some of the multi-stage compressors can be supplied to a power generation engine receiving fuel having a lower pressure than the main engine. The method of claim 5,
A liquefied gas supply line connected from the storage tank to the main engine to supply the liquefied gas as fuel of the main engine;
An HP pump provided in the liquefied gas supply line to compress the liquefied gas to the fuel supply pressure of the main engine; And
An HP vaporizer that heats the liquefied gas compressed by the HP pump and supplies it to the main engine. The boil-off gas generated from the storage tank provided on the ship to store the liquefied gas is compressed to the fuel supply pressure of the main engine through a compressor,
Among the compressed boil-off gas, the remaining boil-off gas supplied to the fuel of the main engine is cooled by heat exchange in a heat exchanger with the uncompressed boil-off gas to be introduced from the storage tank to the compressor, and re-liquefied and stored in the storage tank,
In the above vessel, boil-off gas that is not used for fuel supply and reliquefaction in the vessel is burned in the gas combustion unit to be treated,
The boil-off gas to be burned is a boil-off gas treatment method of a ship, characterized in that after recovering the cold heat through the heat exchanger, branching from the front end of the compressor and supplying it to the gas combustion unit. The method of claim 7,
The boil-off gas to be burned by branching from the front end of the compressor is supplied to the gas combustion unit through a blower,
When the amount of boil-off gas generated from the storage tank is large, or when the remaining boil-off gas remaining after fuel supply and reliquefaction is removed, such as when the ship is anchored or operated at a low speed, the boil-off gas to be burned is the heat exchanger. And supplied to the blower through
When the amount of boil-off gas generated in the storage tank is small, or when all or part of the boil-off gas is to be processed by the gas combustion unit without reliquefying the boil-off gas, the boil-off gas to be burned bypasses the heat exchanger. Boil-off gas treatment method of a ship, characterized in that it can be supplied to the blower after being heated by a heater. The method of claim 8,
The boil-off gas cooled in the heat exchanger is depressurized through a decompression device and further cooled,
The boil-off gas further cooled by reduced pressure is separated from gas-liquid, and the liquid is supplied to the storage tank, and the gas is joined to the uncompressed boil-off gas introduced from the storage tank to the heat exchanger. . The method of claim 8,
When the amount of boil-off gas generated in the storage tank is small, the boil-off gas is supplied to the main engine through the compressor, or supplied to the onboard power generation engine through a part of the compressor, and reliquefied through the heat exchanger to be processed. Boil-off gas treatment method of a ship, characterized in that it can.

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