KR102333072B1 - Fuel Supplying System And Method For Liquefied Gas Carrier - Google Patents

Abstract

Disclosed are a fuel supplying system and a method for a liquefied gas carrier. The fuel supplying system for a liquefied gas carrier according to the present invention comprises: a fuel supply line for supplying liquefied gas to an engine of a ship from a fuel supply tank arranged on a deck of the ship; a compression pump arranged on the fuel supply line and compressing the liquefied gas to be supplied to the engine of the ship with pressure necessary for the engine; a separator arranged on the fuel supply line and receiving the liquefied gas from the fuel supply tank to transport the same to the compression pump; a return line for recirculating liquefied gas not consumed by the engine among the liquefied gas to the upstream of the engine; and a depressurization part arranged on the return line and depressurizing the recirculated liquefied gas, wherein the liquefied gas depressurized by the depressurization part is introduced into the separator and the separator receives the liquefied gas supplied from the fuel supply tank and the liquefied gas recirculated through the return line to transport the same to the compression pump. Therefore, provided is a system for effectively treating LPG recovered from an engine.

Description

Fuel Supplying System And Method For Liquefied Gas Carrier

The present invention relates to a fuel supply system and method for a liquefied gas carrier, and more particularly, to a fuel supply for a liquefied gas carrier that recovers and recirculates the remaining LPG from a ship using a liquefied gas such as LPG as fuel, which is excessively supplied to an engine. It relates to systems and methods.

The consumption of liquefied gas such as LNG (Liquefied Natural Gas) or LPG (Liquefied Petroleum Gas) is rapidly increasing worldwide. Liquefied gas is transported in a gaseous state through a gas pipeline on land or sea, or stored in a liquefied gas carrier in a liquefied state and transported to a remote consumer. Liquefied gas such as LNG or LPG is obtained by cooling natural gas or petroleum gas to cryogenic temperatures (approximately -163°C in the case of LNG).

The liquefaction temperature of petroleum gas is a low temperature of about -42°C under normal pressure, and can be stored in a liquid state up to a temperature of about 45°C at 18 bar and 20°C at 7 bar. Since LPG evaporates when the atmospheric pressure is higher than -42℃, the LPG storage tank of the ship is insulated. However, since external heat is continuously transferred to the LPG, the LPG is continuously vaporized in the LPG storage tank during the LPG transportation process, thereby generating boil-off gas in the LPG storage tank.

In LPG carriers, when BOG accumulates in the LPG storage tank, the pressure in the LPG storage tank rises excessively. do.

On the other hand, conventional LPG carriers employ a fuel supply system using heavy oil such as bunker C oil, which is relatively inexpensive as a propulsion fuel for ships. Due to the strengthening of regulations, it was necessary to separately install a heavy oil fuel tank (LSHFO tank) with low sulfur content, and the demand for an eco-friendly fuel supply system that meets international environmental regulations has grown.

Recently, the application of fuel supply systems that use LPG or LNG and boil-off gas generated therefrom as propulsion fuel is increasing in LPG or LNG carriers. The number of ships used as propulsion fuel is increasing.

In particular, LPG is easier to store than LNG, which is liquefied at cryogenic temperatures, and does not significantly fall in SPECIFIC ENERGY and ENERGY DENSITY compared to conventional HFO, and has excellent effects in reducing SOX, NOX, CO2, PM, etc. compared to conventional HFO.

An example of a fuel supply system from a ship using LPG as a fuel to a conventional engine is schematically shown in FIG. 1 .

As shown in FIG. 1 , LPG to be supplied as fuel to the engine E is supplied from the fuel supply tank according to the fuel supply conditions of the engine while passing through a fuel supply system including a compression pump and a heater. It is supplied to the engine of the ship via line L1.

LPG, which is an incompressible fluid, can be supplied in excess of the fuel required by the engine to respond immediately to changes in engine load. It is withdrawn from the engine upstream of the engine via line L2.

However, since LPG recovered through the recovery line is compressed and heated according to the fuel supply condition of the engine and is in a high temperature and high pressure state, there is a problem in that the pressure and temperature in the tank increase when it is sent to the fuel supply tank, and the sealing oil introduced from the engine ), there is a risk of LPG contamination. On the other hand, there is a problem of wasting fuel if the recovered LPG is discharged and burned as it is.

The present invention is to solve this problem, to provide a system capable of effectively processing LPG recovered from the engine.

According to one aspect of the present invention for solving the above problems, a fuel supply line through which liquefied gas is supplied from a fuel supply tank provided on a deck of a ship to an in-board engine;

a compression pump provided in the fuel supply line and compressing the liquefied gas to be supplied to the onboard engine to a pressure required for the engine;

a separator provided in the fuel supply line and supplied with the liquefied gas from the fuel supply tank and transferred to the compression pump;

a return line for recirculating the liquefied gas not consumed by the engine among the liquefied gas to an upstream of the engine; and

and a decompression unit provided in the return line for decompressing the recirculated liquefied gas;

The liquefied gas decompressed in the decompression unit is introduced into the separator, and the separator receives the liquefied gas supplied from the fuel supply tank and the liquefied gas recirculated through the return line and transfers it to the compression pump. A fuel supply system for a liquefied gas carrier is provided.

Preferably, a fuel tank provided in the ship to store the liquefied gas to be supplied to the onboard engine and supply the liquefied gas to the fuel supply tank; a cargo tank provided on the ship and storing liquefied gas to be transported; a first vapor line connected from the separator to at least one of the fuel tank and the cargo tank for transferring the gas separated from the separator; and a pressure control valve provided in the first vapor line to control the transferred gas.

Preferably, a first pressure sensing unit provided in the fuel supply tank to sense the internal pressure of the fuel supply tank; and a second pressure sensing unit provided in the separator to sense the pressure of the separator, wherein the pressure control valve is controlled according to the pressures sensed by the first pressure sensing unit and the second pressure sensing unit to control the pressure control valve. By controlling the amount of gas discharged from the separator and maintaining the pressure of the separator lower than the pressure of the fuel supply tank, the liquefied gas may be transferred from the fuel supply tank to the separator.

Preferably, a second vapor line for transferring the gas separated from the separator to the fuel supply tank; and a fuel heater provided at the rear end of the compression unit in the fuel supply line and heating the compressed liquefied gas to a temperature required by the engine.

Preferably, the return line includes: a first return line connected from the engine to the separator; and a second return line connected to the separator from a fuel supply line between the compression pump and the fuel heater.

Preferably, the pressure reducing unit includes: a first pressure reducing device provided in the first return line; and a second pressure reducing device provided on the second return line.

Preferably, the re-liquefaction unit for receiving the boil-off gas generated from the cargo tank for storing the liquefied gas to be transported provided on the ship and re-liquefied; and a cooling line connected to the cargo tank from the reliquefaction unit through the fuel supply tank, wherein the liquefied gas reliquefied in the reliquefaction unit cools the fuel supply tank along the cooling line and the cargo tank can be transferred to

Preferably, the liquefied gas may be transferred from the fuel tank to the fuel supply tank to cool the fuel supply tank.

According to another aspect of the present invention, liquefied gas is transferred from a fuel supply tank provided on the deck of a ship to a separator along a fuel supply line, compressed by a compression pump, and supplied as fuel to an onboard engine,

A decompression unit is provided in a return line for recirculating liquefied gas not consumed in the engine among the liquefied gas compressed by the compression pump to the upstream of the engine to decompress the liquefied gas to be recirculated, and the recirculated liquefied gas cooled by the reduced pressure is transferred to a separator. introduced,

In the separator, there is provided a fuel supply method for a liquefied gas carrier, characterized in that the liquefied gas supplied from the fuel supply tank and the liquefied gas recirculated through the return line are supplied and transferred to the compression pump.

Preferably, the gas separated from the separator is one of the fuel tank for storing liquefied gas to be supplied to the onboard engine and supplying the liquefied gas to the fuel supply tank and the cargo tank for storing the liquefied gas to be transported to the ship. The fuel is transferred to at least one, but by sensing the pressure of the fuel supply tank and the pressure of the separator, adjusting the amount of gas transferred from the separator, and maintaining the pressure of the separator lower than the pressure of the fuel supply tank, The liquefied gas may be transferred from the supply tank to the separator.

Preferably, the boil-off gas generated from the cargo tank is re-liquefied in the re-liquefaction unit, and the liquefied gas re-liquefied in the re-liquefaction unit cools the fuel supply tank through the fuel supply tank and can be transferred to the cargo tank. have.

In the present invention, a separator is provided in the fuel supply line to which fuel is supplied to the engine, and liquefied gas not consumed as fuel among the boil-off gas compressed for fuel supply is reduced in pressure and supplied to the separator, so that the separator is supplied from the fuel supply tank. It was configured to receive liquefied gas and recirculated liquefied gas through a return line and transfer it to a compression pump.

As such, the recirculated liquefied gas and the liquefied gas from the fuel supply tank are transferred to the compression pump through a single separator and supplied to the engine, thereby simplifying the control logic and at the suction of the compression pump. The risk of vapor generation can be eliminated.

In addition, it is possible to transfer liquefied gas from the fuel supply tank to the separator without configuring a separate pump for transferring the liquefied gas by adjusting the amount of gas discharged from the separator while recirculating the remaining liquefied gas that is consumed as fuel by being excessively supplied to the engine. can

Furthermore, by re-liquefying the boil-off gas generated in the cargo tank and transferring it to the cargo tank through the fuel supply tank through the cooling line, the fuel supply tank is cooled through the reliquefied liquefied gas to safely maintain the pressure and temperature of the tank. .

1 schematically shows a fuel supply system from a ship equipped with an engine using LPG as a fuel to a conventional engine.
Figure 2 schematically shows a fuel supply system of a liquefied gas carrier according to an embodiment of the present invention.

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

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

In an embodiment of the present invention to be described later, the vessel may be any type of vessel in which an engine capable of using liquefied petroleum gas as a fuel for a propulsion engine or a fuel for a power generation engine is installed. Typical examples include ships with self-propelled capabilities such as LPG carriers, LNG carriers, liquid hydrogen carriers, and LNG RVs (Regasification Vessels), as well as LNG FPSO (Floating Production Storage Offloading) and LNG FSRU (Floating Storage Regasification Unit). It may also include offshore structures that do not have propulsion capabilities, but are floating in the sea.

In addition, this embodiment can be transported by being liquefied at a low temperature, and BOG is generated in a stored state and can be applied to a fuel supply system of all kinds of liquefied gas that can be supplied as fuel of an engine. Such liquefied gas is, for example, liquefied petrochemicals such as LNG (Liquefied Natural Gas), LEG (Liquefied Ethane Gas), LPG (Liquefied Petroleum Gas), Liquefied Ethylene Gas, Liquefied Propylene Gas, etc. gas and ammonia, and the like. However, in the embodiments to be described later, an example in which LPG, which is one of representative liquefied gases, is applied will be described.

2 schematically shows a fuel supply system for a liquefied gas carrier according to an embodiment of the present invention.

As shown in Fig. 2, the fuel supply system of this embodiment is a fuel supply line (SL) through which liquefied gas is supplied from a fuel supply tank (DT) provided on the deck of the ship to the in-board engine (E), and the fuel supply line. A compression pump 110 that is provided and compresses liquefied gas to be supplied to the onboard engine to a pressure required for the engine, a separator 100 that is provided in the fuel supply line and receives liquefied gas from the fuel supply tank and transfers it to the compression pump, liquefied It includes return lines RL1 and RL2 for recirculating liquefied gas not consumed by the engine among the gases to an upstream of the engine, and decompression units 210 and 220 for decompressing the recirculated liquefied gas provided in the return line.

In this embodiment, the liquefied gas recirculated through the return line is decompressed through the decompression unit and introduced into the separator, so that in the separator 100 , the liquefied gas supplied from the fuel supply tank DT and the liquefied gas recirculated through the return line RL1 are liquefied. It is characterized in that the gas is supplied and transferred to the compression pump (110). That is, in this embodiment, the recirculated liquefied gas and the liquefied gas from the fuel supply tank are transferred to the compression pump through the separator and supplied to the engine.

In this embodiment, the transfer of the liquefied gas from the fuel supply tank to the separator may be performed by adjusting the pressure of the separator.

In the ship, fuel tanks (FT1, FT2) for supplying liquefied gas to be supplied as fuel for the onboard engine to a fuel supply tank disposed on the deck and a cargo tank (not shown) for storing liquefied gas to be transported through the ship are provided. , a first vapor line (VL1) for transferring the gas separated from the separator to at least one of the fuel tank and the cargo tank is connected, and a pressure control valve (CV) for controlling the gas discharged from the separator and transferred to the first vapor line is provided

A first pressure sensing unit PC1 sensing the internal pressure of the fuel supply tank is provided in the fuel supply tank, and a second pressure sensing unit PC2 sensing the internal pressure of the separator is provided in the separator, respectively, the first pressure sensing unit and According to the pressure sensed by the second pressure sensing unit, the pressure control valve (CV) is opened and closed and the opening degree is controlled to adjust the amount of gas discharged from the separator to the fuel tank. In this way, while sensing the pressure of the fuel supply tank and the separator, the gas separated from the separator is discharged to the fuel tank or cargo tank, and the pressure of the separator is maintained lower than the pressure of the fuel supply tank. The liquefied gas can be transferred from the fuel supply tank to the separator without a pump, and the cost of configuring the device can be reduced. For example, the operating pressure range of the fuel supply tank may be 1 to 8 barg, and the pressure of the separator may be maintained at about 1 barg lower than the pressure of the fuel supply tank.

For example, assuming that the operating pressure of the fuel supply tank is 4 barg, the operating pressure of the separator 100 is maintained at about 1 bar lower than that, so that the liquefied gas can be smoothly transferred from the fuel supply tank to the separator.

To this end, the second pressure sensing unit PC2 receives the pressure signal from the first pressure sensing unit PC1, and the second pressure sensing unit PC2 to the pressure control valve CV of the first vapor line VL1. By sending a set value signal and adjusting the opening degree of the pressure control valve, the pressure of the separator is maintained 1 bar lower than the pressure of the fuel supply tank. When the pressure sensed by the first pressure sensing unit PC1 decreases, the second pressure sensing unit PC2 receiving the pressure signal accordingly controls the pressure regulating valve CV to discharge gas from the separator into the fuel tank, thereby separating the separator. can maintain the pressure of 1 bar lower than the pressure of the fuel supply tank.

The gas separated from the separator may be transferred to the fuel supply tank along the second vapor line VL2, but in normal operation, the valve is closed and not transferred to the fuel supply tank.

The compression pump 110 is a high-pressure pump that compresses the fuel supply pressure required by the engine, and may be composed of a diaphragm pump. The provided fuel heater 120 is heated to a temperature required by the engine and supplied to the engine.

The compressed and heated liquefied gas from the fuel supply line SL through the compression pump and the fuel heater is supplied to the engine E through the filter 130 that filters out foreign substances in the fuel and the service valve unit SVT. In the service valve part, while supplying LPG to the engine, when LPG fuel supply is stopped due to engine fuel oil switching, LPG mode stop, trip, etc., each pipe is double blocked through the valve to relieve pressure in the pipe.

An engine receiving such compressed and heated LPG as fuel may be, for example, a ME-LGIP engine of MAN Diesel & Turbo. In this case, LPG is supplied to the engine in a high-pressure liquid state of about 54 bar and 35° C. through a compression pump and a fuel heater, and the engine is operated by being injected into the nozzle at a pressure of 600 to 700 bar hydraulically from the engine.

That is, in the engine of this embodiment, compressed and heated fuel is supplied to the engine in a liquid state, and unlike the engine to which a compressive fluid having a large volume change according to a change in pressure, that is, gas fuel is supplied, the volume change even when pressure is applied. When there is no or little incompressible fluid or liquid LPG as engine fuel, sufficient fuel is supplied to respond immediately to changes in engine load and excess LPG is supplied to the engine to prevent cavitation. Among the LPG supplied to the engine, the remaining LPG consumed as fuel is discharged from the engine through the return line and recirculated. ), and may pose a threat to the safety of the tank and ship by increasing the pressure and temperature in the fuel supply tank.

In this embodiment, in order to solve this problem, the decompression units 210 and 220 for decompressing the liquefied gas are provided in the return line, so that the liquefied gas discharged from the engine can be decompressed and recirculated. The compressed liquefied gas is cooled by the Joule-Thomson effect while undergoing adiabatic expansion or isentropic expansion during the decompression process.

The compressed liquefied gas recirculated from the engine E through the return line RL1 is reduced in pressure through the decompression unit 210 and cooled, introduced into the separator 100 for gas-liquid separation, and the liquid liquefied gas separated from the separator is It is transferred to the compression pump 110 along the fuel supply line and recirculated, and the gas separated from the separator is recovered to the fuel tank FT through the first vapor line VL1.

That is, by introducing the recirculated liquefied gas cooled through reduced pressure into the separator of the fuel supply line, the liquefied gas from the fuel supply tank and the recirculated liquefied gas from the return line are transferred to the compression pump through the separator singly.

In this way, the recirculated liquefied gas and the liquefied gas from the fuel supply tank are transferred to the compression pump through a single separator and supplied to the engine, thereby simplifying the control logic for supplying LPG to the engine, and the compression It can eliminate the risk of vapor generation in the suction part of the pump.

In the decompression unit, the compressed liquefied gas is decompressed and transferred to the separator. When the temperature of the recirculated liquefied gas is high, the fuel heater must have a cooling function as well as a heating function in order to meet the fuel requirements of the engine. The gas in the recirculation liquefied gas is recovered to the fuel tank (FT), and the mass flow of the high-temperature recirculated liquefied gas sucked into the compression pump is reduced, so that fuel at an appropriate temperature can be supplied to the engine without additional cooling. Since the heater only needs to have a heating function, the cost of the device can be reduced and operation is easy.

On the other hand, the return line is the separator 100 from the first return line RL1 connected from the engine E to the separator 100 and the fuel supply line SL between the compression pump 110 and the fuel heater 120 . ) and a second return line RL2 connected to each other. In addition, the decompression unit may include a first decompression device 210 provided in the first return line and a second decompression device 220 provided in the second return line. The first and second pressure reducing devices may include an expander for cooling the compressed liquefied gas by adiabatic or isentropic expansion or an expansion valve such as a Joule-Thomson valve.

A return valve unit (RVT) and a filter 230 are provided upstream of the first pressure reducing device in the first return line, and the liquefied gas discharged from the engine is introduced into the first pressure reducing device through the return valve unit and the filter. The filter can filter lubricating oil mixed in the liquefied gas discharged from the engine.

The first return line and the first pressure reducing device depressurize the liquefied gas discharged from the engine, and the second return line and the second pressure reducing device depressurize the compressed liquefied gas through the compression pump and transfer it to the separator.

Through this, the LPG remaining in the engine and fuel supply line can also be cooled under reduced pressure and transferred to the separator when the LPG fuel supply is stopped, such as when the engine is stopped in LPG mode or when tripping. Since there is no need to recirculate the LPG from the separator to the fuel supply line when the LPG fuel supply is stopped, it can be sent to the fuel supply tank, and for this, a transfer line (not shown) from the separator to the fuel supply tank may be provided.

On the other hand, a third pressure sensing unit PC3 that senses the pressure between the compression pump and the fuel heater and sends a pressure signal, and a fourth pressure that senses the pressure between the filter and the first pressure reducing device in the first return line and sends a pressure signal. A sensing unit PC4 is provided.

The first return line RL1 returning from the engine controls the first pressure reducing device 210 by the fourth pressure sensing unit to maintain the pressure upstream of the first pressure reducing device at 22 barg, and the pressure at the rear end of the first pressure reducing device is Maintain the same pressure as the separator pressure of 3 barg.

When the fuel consumption changes due to a change in the fuel consumption due to a change in the load in the engine and the pressure at the rear end of the compression pump changes, the pressure is sensed by the third pressure sensing unit (PC3). The pump speed is lowered by adjusting, and if the pressure is still increased from 54 barg or more to 55 barg, the second pressure reducing device 220 of the second return line is opened to lower the pressure.

The ship of this embodiment is provided with a cargo tank (not shown) for storing and transporting liquefied gas as a liquefied gas carrier, the boil-off gas generated from the liquefied gas stored in the cargo tank is supplied to the reliquefaction unit (RS) and reliquefied .

Since the fuel supply tank is provided on a deck in the ship, the temperature in the tank may be increased by external air or gas separated from the separator and introduced. In this embodiment, the liquefied gas re-liquefied from the re-liquefaction unit RS A cooling line CL is provided so as to be connected to the cargo tank (not shown) via the fuel supply tank DT, so that the fuel supply tank can be cooled by using the cooling heat of the liquefied gas reliquefied in the reliquefaction unit.

On the other hand, when the re-liquefaction unit is not operated, liquefied gas may be supplied from the fuel tank to the fuel supply tank and the fuel supply tank may be cooled by the low-temperature liquefied gas.

The present invention is not limited to the above embodiments, and it is understood by those of ordinary skill in the art that various modifications or variations can be implemented without departing from the technical gist of the present invention. it is self-evident

E: engine
DT: fuel supply tank
FT1, FT2: fuel tank
SL: fuel supply line
PC1: first pressure sensing unit
PC2: second pressure sensing unit
RL1: first return line
RL2: second return line
VL1: first vapor line
VL2: second vapor line
CV: pressure control valve
SVT: Service valve part
RVT: return valve part
RS: reliquefaction unit
CL: cooling line
100: separator
110: compression pump
120: fuel heater
130, 230: filter
210: first pressure reducing device
220: second pressure reducing device

Claims (11)

a fuel supply line through which liquefied gas is supplied from a fuel supply tank provided on the deck of the ship to the onboard engine;
a compression pump provided in the fuel supply line and compressing the liquefied gas to be supplied to the onboard engine to a pressure required for the engine;
a separator provided in the fuel supply line and supplied with the liquefied gas from the fuel supply tank and transferred to the compression pump;
a return line for recirculating the liquefied gas not consumed by the engine among the liquefied gas to an upstream of the engine; and
and a decompression unit provided in the return line for decompressing the recirculated liquefied gas;
The liquefied gas decompressed in the decompression unit is introduced into the separator, and the liquefied gas of the fuel supply tank is supplied to the engine through the separator,
In the separator, the liquefied gas supplied from the fuel supply tank and the liquefied gas recirculated through the return line are supplied and transferred to the compression pump. The method of claim 1,
a fuel tank provided in the ship to store liquefied gas to be supplied to an onboard engine and supply the liquefied gas to the fuel supply tank;
a cargo tank provided on the ship and storing liquefied gas to be transported;
a first vapor line connected from the separator to at least one of the fuel tank and the cargo tank for transferring the gas separated from the separator; and
A fuel supply system for a liquefied gas carrier further comprising: a pressure regulating valve provided in the first vapor line to control the gas transferred. 3. The method of claim 2,
a first pressure sensing unit provided in the fuel supply tank to sense an internal pressure of the fuel supply tank; and
A second pressure sensing unit provided in the separator to sense the pressure of the separator further comprises:
The pressure control valve is controlled according to the pressures sensed by the first pressure sensing unit and the second pressure sensing unit to adjust the amount of gas discharged from the separator, and the pressure of the separator is higher than the pressure of the fuel supply tank. By keeping it low, the fuel supply system of a liquefied gas carrier, characterized in that the liquefied gas is transferred from the fuel supply tank to the separator. 3. The method of claim 2,
a second vapor line for transferring the gas separated from the separator to the fuel supply tank; and
A fuel supply system for a liquefied gas carrier further comprising: a fuel heater provided at a rear end of the compression pump in the fuel supply line and heating the compressed liquefied gas to a temperature required by the engine. 5. The method of claim 4, wherein the return line comprises:
a first return line connected from the engine to the separator; and
A fuel supply system for a liquefied gas carrier including: a second return line connected to the separator from a fuel supply line between the compression pump and the fuel heater. The method of claim 5, wherein the decompression unit,
a first pressure reducing device provided on the first return line; and
A fuel supply system for a liquefied gas carrier comprising: a second pressure reducing device provided in the second return line. 4. The method of claim 3,
a re-liquefaction unit receiving the boil-off gas generated from the cargo tank and re-liquefying it; and
Further comprising: a cooling line connected to the cargo tank from the reliquefaction unit through the fuel supply tank,
The liquefied gas reliquefied in the reliquefaction unit cools the fuel supply tank along the cooling line and is transferred to the cargo tank. 8. The method of claim 7,
A fuel supply system for a liquefied gas carrier, characterized in that it can cool the fuel supply tank by transferring the liquefied gas from the fuel tank to the fuel supply tank. Liquefied gas is transferred from the fuel supply tank provided on the deck of the ship to the separator along the fuel supply line, compressed by the compression pump, and supplied as fuel to the onboard engine,
A decompression unit is provided in a return line for recirculating liquefied gas not consumed in the engine among the liquefied gas compressed by the compression pump to the upstream of the engine to decompress the liquefied gas to be recirculated, and the recirculated liquefied gas cooled by the reduced pressure is transferred to a separator. introduced,
In the separator, the liquefied gas supplied from the fuel supply tank and the liquefied gas recirculated through the return line are supplied and transferred to the compression pump. 10. The method of claim 9,
The gas separated from the separator is transferred to at least one of the fuel supply tank that stores liquefied gas to be supplied to the onboard engine and supplies the liquefied gas to the fuel supply tank and a cargo tank that stores the liquefied gas to be transported to the ship. but,
By sensing the pressure of the fuel supply tank and the pressure of the separator, the amount of gas transferred from the separator is adjusted, the pressure of the separator is maintained lower than the pressure of the fuel supply tank, and the separator from the fuel supply tank A fuel supply method of a liquefied gas carrier, characterized in that the liquefied gas is transferred to the furnace. 11. The method of claim 10,
Re-liquefying the boil-off gas generated from the cargo tank in the re-liquefaction unit,
The liquefied gas re-liquefied in the re-liquefaction unit cools the fuel supply tank through the fuel supply tank, and the fuel supply method of the liquefied gas carrier, characterized in that it is transferred to the cargo tank.

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