KR20210059829A - Boil-Off Gas Treatment System and Method for Ship - Google Patents

Abstract

Disclosed are a boil-off gas treatment system and a method for a ship. According to the present invention, the boil-off gas treatment system for the ship comprises: a compressor which receives boil-off gas generated from liquefied gas stored in a storage tank in the ship and compresses the boil-off gas; a heat exchanger which receives all or part of the compressed gas compressed by the compressor, and cools the compressed gas by making the compressed gas exchange heat with uncompressed boil-off gas which is going to be supplied to the compressor; a reliquefaction unit which receives, additionally cools, and reliquefies the compressed gas cooled in the heat exchanger; a first fuel supply line which separates flash gas including gas in the reliquefaction unit, and supplies the flash gas as fuel to a power generator engine of the ship; and a branch line which is placed between the heat exchanger and the reliquefaction unit to branch the compressed gas and supplies the branched compressed gas to the power generator engine. The branch line joins the first fuel supply line on a front end of the heat exchanger. The fuel which is going to be supplied to the power generator engine along the first fuel supply line passes through the heat exchanger and exchanges heat in the heat exchanger, and then is supplied to the power generator engine. The present invention aims to provide a boil-off gas treatment system and method for the ship, which are able to increase the cooling performance of the heat exchanger, and to improve the reliquefaction performance.

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 gas 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 transport 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 easily evaporated because it is sensitive to temperature changes. For this reason, the storage tank storing liquefied natural gas is insulated, but external heat is continuously transferred to the storage tank. -Off Gas, BOG) occurs.

Boil-off gas is a kind of loss and is an important problem in transportation efficiency. In addition, if the boil-off gas accumulates in the storage tank, the internal pressure of the tank may increase excessively, and in extreme 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 to fuel the engine of a ship, etc. 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 re-liquefying 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 consists of four strokes, and adopts an Otto Cycle in which natural gas with a relatively low pressure of about 5.5 barg is injected into the inlet of the combustion air and compressed while the piston is raised.

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 employs 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 a ship.

In the conventional boil-off gas treatment system for ships as shown in Figure 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 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 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 for phase separation. .

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 re-liquefied 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, cooled, and then expanded 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 improve 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, a compressor for receiving and compressing boil-off gas generated from liquefied gas stored in a storage tank of a ship;

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

A reliquefaction unit receiving the compressed gas cooled by the heat exchanger and further cooling it to reliquefy;

A first fuel supply line for separating flash gas including unliquefied gas in the reliquefaction unit and supplying it as fuel of an onboard power generation engine; And

A branch line for branching the compressed gas between the heat exchanger and the reliquefaction unit and supplying the compressed gas to the power generation engine; and

The branch line is joined to the first fuel supply line at a front end of the heat exchanger, and the fuel to be supplied to the power generation engine along the first fuel supply line is supplied to the power generation engine after heat exchange through the heat exchanger. The ship's boil-off gas treatment system is provided.

Preferably, the reliquefaction unit includes: a first decompression means for receiving the compressed gas cooled from the heat exchanger and further cooling it under reduced pressure; And a gas-liquid separator for receiving the vaporized gas depressurized by the first decompression means and separating the gas-liquid, wherein the liquid separated by the gas-liquid separator is restored to the storage tank, and the gas-liquid separator may have a variable operating pressure. have.

Preferably, a second pressure reducing means provided in the branch line and receiving the compressed gas branched to the branch line after cooling from the heat exchanger and reducing the pressure to the fuel supply pressure of the power generation engine; may further include.

Preferably, a boil-off gas supply line connected from the storage tank to the main engine on board; further includes, wherein the main engine is supplied with fuel having a higher pressure than the power generation engine, and the compressor is provided in the boil-off gas supply line and the evaporation The gas can be compressed at the fuel supply pressure of the main engine.

Preferably, the compressor is provided with a multi-stage compressor including a plurality of compressors, and a second fuel supply line for supplying boil-off gas compressed through some stages of the multi-stage compressor to the power generation engine; may further include.

Preferably, a first valve provided upstream of a junction point of the branch line in the first fuel supply line; And a second valve provided in the second fuel supply line.

Preferably, according to the nitrogen concentration of the flash gas separated from the gas-liquid separator and supplied to the first fuel supply line, the second valve is opened to transfer the boil-off gas compressed through a partial stage of the multistage compressor to the flash gas. It can be mixed and supplied to the power generation engine.

Preferably, a flash gas line for joining the flash gas separated in the gas-liquid separator into the flow of uncompressed boil-off gas at the front end of the heat exchanger; A pressure control valve provided in the flash gas line; A liquid line connected from the gas-liquid separator to a storage tank; And a level control valve provided in the liquid line.

Preferably, a spray nozzle line branched from the liquid line and provided to spray the liquid separated by the gas-liquid separator above the storage tank may be further included.

According to another aspect of the present invention, the boil-off gas generated from the storage tank in which the liquefied gas is stored 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 re-liquefied to separate gas and liquid in a gas-liquid separator, and the separated liquid is restored to the storage tank. And, the flash gas separated by the gas-liquid separator is supplied to the onboard power generation engine,

When the amount of the flash gas is less than the required amount of fuel of the power generation engine, a part of the compressed gas cooled in a heat exchanger after compression is branched to join the flash gas and supplied as fuel of the power generation engine,

After the flash gas and the compressed gas are merged, there is provided a method of supplying boil-off gas for a ship, characterized in that they are supplied to the power generation engine through the heat exchanger.

Preferably, the compressed gas to be reliquefied by being cooled in the heat exchanger is further cooled by reduced pressure before being introduced into the gas-liquid separator, the gas-liquid separator has a variable operating pressure, and the compressed gas branched to be supplied to the power generation engine is the After depressurizing by the fuel supply pressure of the power generation engine, the flash gas may be joined.

Preferably, the compressed gas compressed by the compressor is supplied to an onboard main engine receiving fuel at a higher pressure than the power generation engine, and the compressor may compress the boil-off gas to the fuel supply pressure of the main engine.

Preferably, the compressor is provided with a multi-stage compressor including a plurality of compressors, and the boil-off gas compressed through some stages of the multi-stage compressor according to the nitrogen concentration of the flash gas separated from the gas-liquid separator and supplied to the power generation engine May be mixed with the flash gas and supplied to the power generation engine.

Preferably, when there is no boil-off gas to be reliquefied among the boil-off gas generated in the storage tank, the boil-off gas compressed through some stages of the multi-stage compressor may be supplied to the power generation engine.

In the system of the present invention, by supplying the flash gas with increased nitrogen content separated by the gas-liquid separator to the power generation engine through the heat exchanger, additional refrigerant in the heat exchanger can be secured to increase the cooling performance of the heat exchanger, and remain in the reliquefaction system. Re-liquefaction performance can be improved by reducing the nitrogen content.

In addition, the flash gas separated by the gas-liquid separator may be supplied as a flow of uncompressed evaporated gas introduced into the heat exchanger to increase the flow rate of refrigerant introduced into the heat exchanger, thereby improving the cooling performance of the heat exchanger.

In this way, the present invention can secure the safety of the ship by effectively treating the boil-off gas generated in the storage tank.

1 is a schematic diagram of a conventional boil-off gas treatment system.
Figure 2 schematically shows the boil-off gas treatment system of the ship according to an 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 equipped with an engine capable of using liquefied gas and boil-off gas generated from liquefied gas as fuel for propulsion or power generation engines, or all types of liquefied gas or boil-off gas as fuel for the ship's engine. LNG carriers, liquefied petroleum gas carriers, LNG RV (Regasification Vessels), including ships with self-propelled capabilities, 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, it will be described by taking as an example that LNG, which is one of the representative liquefied gases, is applied.

Meanwhile, the fluid flowing through each line of the present exemplary 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.

Figure 2 schematically shows the boil-off gas treatment system of the ship according to an embodiment of the present invention.

As shown in Figure 2, the boil-off gas treatment system of the ship according to the present embodiment, in a ship provided with a main engine (ME) and a power generation engine (GE) that receives a lower pressure fuel than the main engine, the storage tank of the ship (T ), a compressor 100 that receives boil-off gas generated from the liquefied gas stored in and compresses it at the fuel supply pressure of the main engine, and receives boil-off gas not supplied to the main engine among the boil-off gas compressed by the compressor, and is supplied to the compressor. It includes a heat exchanger 200 for cooling by heat exchange with uncompressed evaporation gas.

For fuel supply and re-liquefaction, a boil-off gas supply line GL connected from the storage tank T to the main engine ME is provided, and a re-liquefaction line branching from the boil-off gas supply line GL at the rear end of the compressor ( RL) is provided, and a heat exchanger 200 and a reliquefaction unit 300 are provided along the reliquefaction line.

The boil-off gas generated in the storage tank T is introduced into the compressor 100 and compressed. The compressor 100 may be provided as a multi-stage compressor in which a plurality of compressors and an intermediate cooler are alternately arranged, and through these in sequence, compressing the boil-off gas to the fuel supply pressure of 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 compressor compresses the boil-off gas to the fuel supply pressure to the main engine, e.g. 5.5 barg if a DF engine is provided, 15 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. In redundancy design, when one cannot be used due to failure or maintenance, the other is used instead. It means designing to be able to do it. To this end, only one set of compressors is shown in the drawings of the embodiments, but may be provided in plural.

The uncompressed boil-off gas to be supplied to the compressor while passing through the re-liquefaction line (RL) and re-liquefied after cooling through heat exchange in a heat exchanger are re-stored in the storage tank (T). do.

The heat exchanger 200 may be provided with a printed circuit heat exchanger (PCHE) or a direct contact type heat exchanger (DCHE). The boil-off gas to be introduced into the heat exchanger may be introduced into the heat exchanger after removing the lubricating oil mixed in the compression process through an oil filter (not shown).

The boil-off gas cooled in the heat exchanger is introduced into the reliquefaction unit 300, further cooled by reduced pressure in the first decompression means 310, and separated by gas-liquid in the gas-liquid separator 320, and the condensate is connected to the storage tank. It is supplied to the storage tank through

The first pressure reducing means may be provided with, for example, a J-T valve or an expander, and the compressed gas may be further cooled through adiabatic expansion or isoentropy expansion in the first pressure reducing means.

Meanwhile, the gas separated by the gas-liquid separator 320 of the reliquefaction unit 300 and the flash gas including the unliquefied gas may be supplied as fuel of the onboard power generation engine GE along the first fuel supply line SLa. .

A branch line BL is provided between the heat exchanger 200 and the first decompression means 310 of the reliquefaction unit to supply the compressed gas to the power generation engine, and the branch line supplies the first fuel at the front end of the heat exchanger. It is joined by line SLa.

The fuel to be supplied to the power generation engine GE along the first fuel supply line SLa is supplied to the power generation engine after heat exchange through the heat exchanger 200.

The gas-liquid separator 320 has a variable operating pressure, and in particular, the flash gas separated by the gas-liquid separator can be supplied as fuel for the power generation engine by allowing it to be operated even at the fuel supply pressure of the power generation engine. For example, the gas-liquid separator has an operating pressure range of 3 to 8 barg, and can be operated at 5 to 8 barg when fuel is supplied to the power generation engine.

In the flash gas generated in the gas-liquid separator, nitrogen, which is highly volatile compared to methane and hydrocarbon components, is first volatilized and separated in the gas-liquid separator, so the nitrogen content remaining in the reliquefaction loop is reduced by supplying the flash gas as fuel for the power generation engine. Reduced, the process can be stabilized and the reliquefaction performance can be improved.

In other words, when the flash gas containing a large amount of nitrogen is combined with the flow of uncompressed evaporated gas at the front of the heat exchanger or sent to the storage tank, a large amount of nitrogen is contained in the evaporated gas and introduced into the compressor. Since energy is consumed, energy loss occurs as much as the nitrogen content in the capacity of the compressor.Through this embodiment, by reducing the nitrogen content in the reliquefaction loop, methane (C1) achieves a thermodynamically stabilized equilibrium, and the energy of the compressor You can reduce the loss.

When the amount of flash gas separated from the gas-liquid separator is less than the required amount of fuel of the power generation engine, a part of the high-pressure and low-temperature compressed gas that has passed through the heat exchanger 200 is branched to the branch line BL to join the flash gas to the power generation engine. Can supply. The branch line BL is provided with a second decompression means 400 for reducing the compressed gas branched to the branch line to the fuel supply pressure of the power generation engine after cooling from the heat exchanger. The second pressure reducing means may be provided with, for example, a J-T valve or an expander, and the compressed gas may be further cooled while being reduced by the fuel supply pressure of the power generation engine in the second pressure reducing means.

The flash gas separated by the gas-liquid separator 320 and the compressed gas decompressed after branching to the branch line BL are supplied to the power generation engine by passing through the heat exchanger 200 again through the first fuel supply line SLa.

Accordingly, in the heat exchanger 200, the boil-off gas of the reliquefaction line RL compressed by the compressor, the uncompressed boil-off gas of the boil-off gas supply line GL to be introduced into the compressor, the flash gas separated from the gas-liquid separator, and the branch line are used. The three flows of the fuel gas of the first fuel supply line SLa to which the branched and depressurized boil-off gas are joined are exchanged.

Through such a configuration, cold heat of the boil-off gas to be supplied as fuel of the power generation engine can also be used in the heat exchanger, so that the gas to be reliquefied can be more effectively cooled and the reliquefaction performance can be improved. In addition, the boil-off gas to be supplied to the power generation engine is heated through a heat exchanger, thereby effectively utilizing the thermal energy of the system.

On the other hand, when the nitrogen concentration in the flash gas separated from the gas-liquid separator and supplied to the power generation engine is high, the heat of the fuel is low, or when it is necessary to adjust the processing capacity of the compressor, the compressed boil-off gas through some stages of the compressor is transferred to the flash gas. It can also be mixed and supplied to the power generation engine.

To this end, a second fuel supply line SLb for supplying the boil-off gas compressed through some stages of the multistage compressor to the power generation engine is provided, and a first valve ( V1) is provided with a second valve V2 in the second fuel supply line, respectively.

When the amount of boil-off gas supplied to the main engine is large and there is no or small amount of gas to be reliquefied, such as during high-speed navigation of a ship, when the re-liquefaction system does not need to be operated, the compressed boil-off gas through some stages of the compressor 100 May be supplied to the power generation engine through the second fuel supply line SLb.

A flash gas line FL for joining the flash gas separated by the gas-liquid separator 320 into a flow of uncompressed boil-off gas at the front end of the heat exchanger is provided, and a pressure control valve FV is provided in the flash gas line. The internal pressure of the gas-liquid separator can be adjusted through the pressure control valve.

A liquid line (LL) is connected from the gas-liquid separator to the bottom of the storage tank to send the condensate separated in the gas-liquid separator to the bottom of the storage tank. A level control valve (LV) is provided in the liquid line, and the liquid level inside the gas-liquid separator can be adjusted by opening and closing the level control valve.

A spray nozzle line Lla may be provided to diverge from the liquid line and spray the liquid and condensate separated by the gas-liquid separator to the top of the storage tank. By spraying the low-temperature condensate separated by the gas-liquid separator to the top of the storage tank, the boil-off gas on the top of the storage tank can be cooled.

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 not departing from 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
SLa: first fuel supply line
SLb: second fuel supply line
BL: branch line
FL: flash gas line
LL: liquid line
V1: first valve
V2: second valve
FV: pressure control valve
LV: level control valve
100: compressor
200: heat exchanger
300: reliquefaction unit
310: first depressurization means
320: gas-liquid separator
400: second decompression means

Claims (14)

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 compressed gas compressed by the compressor and cools it by heat exchange with the uncompressed boil-off gas to be supplied to the compressor;
A reliquefaction unit receiving the compressed gas cooled by the heat exchanger and further cooling it to reliquefy;
A first fuel supply line for separating flash gas including unliquefied gas in the reliquefaction unit and supplying it as fuel for an onboard power generation engine; And
A branch line for branching the compressed gas between the heat exchanger and the reliquefaction unit and supplying the compressed gas to the power generation engine; and
The branch line is joined to the first fuel supply line at a front end of the heat exchanger, and the fuel to be supplied to the power generation engine along the first fuel supply line is supplied to the power generation engine after heat exchange through the heat exchanger. Ship's boil-off gas treatment system. The method of claim 1, wherein the reliquefaction unit
A first decompression means for receiving the compressed gas cooled from the heat exchanger and further cooling it under reduced pressure; And
Includes; a gas-liquid separator for gas-liquid separation by receiving the boil-off gas reduced by the first pressure reducing means
The liquid separated by the gas-liquid separator is restored to the storage tank, and the gas-liquid separator has a variable operating pressure. The method of claim 2,
A second decompression means provided in the branch line and receiving the compressed gas branched to the branch line after cooling from the heat exchanger and reducing the pressure to the fuel supply pressure of the power generation engine. The method of claim 3,
It further includes; boil-off gas supply line connected from the storage tank to the main engine on board,
The main engine is supplied with fuel having a higher pressure than the power generation engine, and the compressor is provided in the boil-off gas supply line to compress the boil-off gas to the fuel supply pressure of the main engine. The method of claim 4,
The compressor is provided as a multistage compressor including a plurality of compressors,
A second fuel supply line for supplying the boil-off gas compressed through some stages of the multi-stage compressor to the power generation engine. The method of claim 5,
A first valve provided upstream of a junction point of the branch line in the first fuel supply line; And
A system for treating boil-off gas of a ship further comprising a second valve provided in the second fuel supply line. The method of claim 5,
According to the nitrogen concentration of the flash gas separated from the gas-liquid separator and supplied to the first fuel supply line, the second valve is opened and the boil-off gas compressed through a partial stage of the multistage compressor is mixed with the flash gas to generate the power generation. Boil-off gas treatment system of a ship, characterized in that it can be supplied to the engine. The method of claim 6,
A flash gas line for joining the flash gas separated by the gas-liquid separator into a flow of uncompressed boil-off gas at the front end of the heat exchanger;
A pressure control valve provided in the flash gas line;
A liquid line connected from the gas-liquid separator to a lower portion of the storage tank; And
A level control valve provided in the liquid line; the boil-off gas treatment system of the ship further comprising. The method of claim 8,
A spray nozzle line branched from the liquid line and provided to spray the liquid separated by the gas-liquid separator above the storage tank. Compressing the boil-off gas generated from the storage tank in which the liquefied gas is stored 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 re-liquefied to separate gas and liquid in a gas-liquid separator, and the separated liquid is restored to the storage tank. And, the flash gas separated by the gas-liquid separator is supplied to the onboard power generation engine,
When the amount of the flash gas is less than the required amount of fuel of the power generation engine, a part of the compressed gas cooled in a heat exchanger after compression is branched to join the flash gas and supplied as fuel of the power generation engine,
After the flash gas and the compressed gas are joined, the boil-off gas supply method of a ship, characterized in that supplied to the power generation engine through the heat exchanger. The method of claim 10,
The compressed gas to be cooled and reliquefied in the heat exchanger is further cooled under reduced pressure before being introduced into the gas-liquid separator, and the gas-liquid separator has a variable operating pressure,
The boil-off gas supply method of a ship, characterized in that the compressed gas branched to be supplied to the power generation engine is reduced to the fuel supply pressure of the power generation engine and then merges with the flash gas. The method of claim 11,
The compressed gas compressed by the compressor is supplied to the main engine on board receiving fuel at a higher pressure than the power generation engine,
The compressor compresses the boil-off gas to the fuel supply pressure of the main engine. The method of claim 12,
The compressor is provided as a multistage compressor including a plurality of compressors,
According to the nitrogen concentration of the flash gas separated from the gas-liquid separator and supplied to the power generation engine, boil-off gas compressed through some stages of the multistage compressor may be mixed with the flash gas and supplied to the power generation engine. How to treat boil-off gas on a ship. The method of claim 13,
When there is no boil-off gas to be reliquefied among the boil-off gas generated in the storage tank, the boil-off gas compressed through some stages of the multi-stage compressor can be supplied to the power generation engine.

Images