KR20220036446A - Fuel Supplying System And Method For Liquefied Gas Carrier - Google Patents

Abstract

Disclosed are a fuel supply system and method for a liquefied gas carrier. According to the present invention, the fuel supply method for the liquefied gas carrier is able to compress liquefied gas along a fuel supply line from a fuel supply tank prepared on a deck of the carrier, supply the compressed liquefied gas as fuel to an engine of the carrier, return the unused liquefied gas among the liquefied gas supplied to the engine and the liquefied gas remaining in the engine when the engine stops toward an upstream of the engine through a return line, separate gas and liquid from the liquefied gas returned from the engine through the return line at a separator, return the separated gas to the fuel supply tank, recirculate the liquid to the fuel supply line supplying the liquid as fuel for the engine, detect the pressure of the fuel supply line to which the liquefied gas, which is separated at the separator and is to be recirculated, control the volume of gas returned from the separator to the fuel supply tank in accordance with the detected pressure, and maintain the pressure of the separator higher than the pressure detected at the fuel supply line. The present invention aims to provide a fuel supply system and method for a liquefied gas carrier, which are capable of keeping a safe pressure and temperature in a tank.

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 a fuel to an engine in excess. 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 offshore, 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, a LSHFO tank with low sulfur content had to be installed separately, and the demand for an eco-friendly fuel supply system that meets international environmental regulations has grown.

Recently, the application of a fuel supply system that uses LPG or LNG and boil-off gas generated therefrom as a 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 it does not significantly fall in SPECIFIC ENERGY and ENERGY DENSITY compared to conventional HFO, and has an excellent effect in reducing SOX, NOX, CO2, PM, etc. compared to conventional HFO.

In ships using LPG as fuel, LPG to be supplied to the engine as fuel goes through the fuel supply system including the compression pump and heater from the fuel supply tank, and is supplied to the engine of the ship according to the fuel supply conditions of the engine. is supplied

LPG, an incompressible fluid, can be supplied in excess of the fuel required by the engine to respond immediately to changes in engine load. When the engine is stopped, the LPG remaining in the engine and piping is recovered upstream of the engine.

However, if the recovered LPG is discharged and burned as it is, there is a problem of wasting fuel. In addition, since the recovered LPG 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 of increasing the pressure and temperature in the tank when it is sent to the fuel supply tank.

An object of the present invention is to provide a system capable of efficiently supplying fuel while effectively processing LPG recovered from an engine by solving this problem.

According to one aspect of the present invention for solving the above problems, the liquefied gas is compressed along the fuel supply line from the fuel supply tank provided on the deck of the ship and supplied as fuel to the onboard engine,

Unconsumed liquefied gas among the liquefied gas supplied to the engine and the liquefied gas remaining in the engine when the engine is stopped are recovered upstream of the engine through a return line,

The liquefied gas recovered from the engine through the return line is gas-liquid separated in a separator, the separated gas is recovered to the fuel supply tank, and the liquid is recirculated to the fuel supply line supplied as fuel of the engine,

The pressure of the fuel supply line to which the liquefied gas separated from the separator is supplied and recirculated is sensed, and the amount of gas recovered from the separator to the fuel supply tank is adjusted according to the sensed pressure to adjust the pressure of the separator to the fuel. There is provided a fuel supply method for a liquefied gas carrier, characterized in that it is maintained higher than the pressure sensed in the supply line.

Preferably, the fuel supply line includes a transfer pump for transferring liquefied gas from the fuel supply tank; and a compression pump for pumping the liquefied gas transferred from the transfer pump to increase the pressure to a required pressure in the engine, and the liquefied gas to be separated from the separator and recirculated is supplied to a fuel supply line between the transfer pump and the compression pump. and can be recycled.

Preferably, the pressure of the rear end of the transfer pump is sensed, and the amount of gas recovered from the separator to the fuel supply tank is adjusted according to the sensed pressure, so that the pressure of the separator is 0.5 to greater than the pressure of the rear end of the transfer pump. It can be kept as high as 2 barg.

Preferably, by sensing the pressure at the rear end of the compression pump, when the sensed pressure is higher than the set value, the pump speed of the compression pump is lowered first, and if it is still higher than the set value, a portion of the liquefied gas at the rear end of the compression pump is reduced It is possible to control the pressure at the end of the compression pump by discharging it to the separator.

Preferably, a decompression unit is provided in the return line, and unconsumed liquefied gas among the liquefied gas supplied to the engine and liquefied gas remaining in the engine when the engine is stopped are decompressed through the decompression unit of the return line and then to the separator. It can be introduced into gas-liquid separation.

Preferably, a discharge pipe for separating and discharging the lubricant mixed in the liquefied gas returned to the separator may be provided at the bottom of the separator.

Preferably, the boil-off gas generated from the cargo tank for storing the liquefied gas to be transported provided in the ship is reliquefied in the reliquefaction unit, and the liquefied gas reliquefied in the reliquefaction unit is passed through the fuel supply tank to the cargo tank. It can be transferred to cool the fuel supply tank.

According to another aspect of the present invention, a fuel supply line through which liquefied gas is supplied from the fuel supply tank provided on the deck of the ship to the onboard engine;

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

A separator for gas-liquid separation of the recirculated liquefied gas provided in the return line and recovering the separated gas to the fuel supply tank;

By sensing the pressure of the fuel supply line, adjusting the amount of gas recovered from the separator to the fuel supply tank according to the sensed pressure, and maintaining the pressure of the separator higher than the pressure sensed in the fuel supply line,

There is provided a fuel supply system for a liquefied gas carrier, characterized in that the liquid separated in the separator is recirculated to the fuel supply line.

Preferably, the fuel supply line includes: a transfer pump for transferring liquefied gas from the fuel supply tank; and a compression pump for pumping the liquefied gas transferred from the transfer pump to increase the pressure in the engine to a pressure required by the engine. It can be recirculated to the fuel supply line between and the compression pump.

Preferably, it further comprises a decompression unit provided in the return line for decompression of the liquefied gas recovered through the return line without being consumed by the engine, wherein the liquefied gas recovered along the return line is depressurized through the decompression unit may be introduced into the separator.

Preferably, a discharge pipe provided at the bottom of the separator for separating and discharging the lubricating oil mixed in the liquefied gas returned to the separator; and a re-liquefaction unit for re-liquefying boil-off gas generated from a cargo tank for storing liquefied gas to be transported and provided on the ship, wherein the liquefied gas re-liquefied in the re-liquefaction unit passes through the fuel supply tank to the cargo tank By transport, it is possible to cool the fuel supply tank.

In the present invention, the liquefied gas not consumed in the engine among the liquefied gas compressed for fuel supply to the engine is recirculated through the return line, and a separator is provided in the return line to separate gas-liquid gas recovered through the return line, and a separator Only the liquid liquefied gas from the separator is recirculated to the fuel supply line by adjusting the pressure of the In this way, it is possible to prevent incomplete combustion of the engine and the generation of pollutants in the exhaust by preventing the lubricating oil from being mixed into the fuel while adequately recirculating the remaining liquefied gas after being consumed as fuel by being oversupplied to the engine. It is possible to prevent LPG contamination and crystallization of lubricant in the fuel supply tank due to sealing oil.

In addition, by providing a pressure reducing unit in the return line to cool the recirculated liquefied gas, separate the gas and liquid, and introduce it into the compression pump together with subcooled LPG supplied from the fuel supply tank through the transfer pump, the compression pump suction It is possible to reduce the risk of vapor generation in the pump and prevent malfunction of the pump without installing additional equipment to remove it.

The gas separated from the separator is transferred to the fuel supply tank, and the boil-off gas generated in the cargo tank is reliquefied and transferred to the cargo tank through the fuel supply tank through the cooling line. By cooling, the pressure and temperature of the tank can be safely maintained.

1 schematically shows a fuel supply system for a liquefied gas carrier according to an embodiment of the present invention.
Figure 2 schematically shows the configuration of the discharge unit for discharging the lubricant from the separator in the fuel supply system of the 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, it should be noted that in adding reference signs to the elements of each drawing, the same elements are indicated with the same reference numerals as much as possible even though 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), LNG Floating Production Storage Offloading (FPSO), 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.

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

1, the fuel supply system of this embodiment is a fuel supply line (SL) through which liquefied gas is supplied from the fuel supply tank (DT) provided on the deck of the ship to the in-board engine (E), and the fuel supply line. A transfer pump 110 that is provided and transports liquefied gas to be supplied from the fuel supply tank to the engine, a compression pump 120 that is provided in the fuel supply line and compresses the liquefied gas to the pressure required for the engine, among the liquefied gas that is not consumed by the engine Return lines (RL1, RL2) for recirculating the unrecycled liquefied gas to the upstream of the engine, a separator 210 provided in the return line to receive the recirculated liquefied gas and gas-liquid separation, and a fuel supply line for the liquid liquefied gas separated from the separator It includes a liquid line (LL) for supplying to the rear end of the transfer pump, and a vapor line (VL) for recovering the gas separated from the separator to the fuel supply tank (DT).

A pressure reducing unit for reducing the recirculated liquefied gas is provided upstream of the separator in the return line, and a pressure regulating valve 250 for controlling the gas transferred to the fuel supply tank DT is provided in the vapor line connected from the separator to the fuel supply tank. will be prepared

Detects the pressure at the rear end of the transfer pump of the fuel supply line to which liquefied gas separated from the separator and recirculated through the liquid line is supplied, and the pressure control valve is controlled according to the sensed pressure to measure the amount of gas recovered from the separator to the fuel supply tank. By adjusting, the pressure of the separator is characterized in that it is maintained higher than the pressure sensed in the fuel supply line.

A detailed description of the fuel supply process to the engine in the system of the present embodiment is performed as follows.

The fuel supply from the fuel supply tank to the engine includes a transfer pump 110 that pumps and transfers liquefied gas, and a compression pump 120 that pumps the transferred liquefied gas and boosts the pressure to a required pressure in the engine. made by the pump.

The transfer pump 110 is a low-pressure pump for transferring liquefied gas, for example, a centrifugal pump, and the compression pump 120 is a high-pressure pump that compresses the fuel supply pressure required by the engine, and is a diaphragm pump. ), and the liquefied gas passing through the transfer pump and the compression pump is heated to a temperature required by the engine in the fuel heater 130 provided at the rear end of the compression pump and supplied to the engine.

The compressed and heated liquefied gas from the fuel supply line through the compression pump and fuel heater is supplied to the engine E through the filter 140 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 around 54 bar and 35° C. through the compression unit and the fuel heater, and the engine is operated by being hydraulically injected into the nozzle at a pressure of 600 to 700 bar.

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 compressible fluid having a large volume change according to a change in pressure, that is, gas fuel is supplied, the volume changes 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 is discharged from the engine through the return line and recirculated. If the compressed and heated LPG is recirculated as it is or sent to the fuel supply tank, the ), and may pose a threat to tank and ship safety by increasing the pressure and temperature in the fuel supply tank.

In this embodiment, in order to solve this problem, the decompression units 220 and 230 for decompressing the liquefied gas are provided in the return line, so that the liquefied gas discharged from the engine can be recirculated by decompressing the liquefied gas. The compressed liquefied gas is cooled by the Joule-Thomson effect while undergoing adiabatic 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 220 and cooled, introduced into the separator 210 for gas-liquid separation, and the liquid liquefied gas separated from the separator is It is supplied to the fuel supply line SL between the transfer pump 110 and the compression pump 120 through the liquid line LL and recirculated, and the gas separated from the separator is supplied to the fuel supply tank DT through the vapor line VL. ) is returned.

In this embodiment, the liquefied gas cooled through decompression is introduced into the separator, and the liquid liquefied gas after gas-liquid separation is introduced into the compression pump 120 together with the subcooled LPG supplied from the fuel supply tank through the transfer pump. , it is possible not to configure a separate device for vapor removal by reducing the risk of vapor generation in the suction part of the compression pump.

In addition, 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 decompressed recirculation liquefied gas is recovered to the fuel supply tank, and the mass flow of the high-temperature recirculated liquefied gas sucked into the second pump is reduced, so that fuel at an appropriate temperature can be supplied to the engine without additional cooling. Since the fuel heater only needs to have a heating function, the equipment cost can be reduced and operation is easy.

Meanwhile, the return line includes a first return line RL1 connected from the engine E to the separator 210 , and a separator 210 from the fuel supply line SL between the compression pump 120 and the fuel heater 130 . ) and a second return line RL2 connected to each other. In addition, the pressure reducing unit may include a first pressure reducing device 220 provided in the first return line and a second pressure reducing device 230 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 240 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 decompress the liquefied gas discharged from the engine, and the second return line and the second pressure reducing device decompress the liquefied gas compressed by the fuel supply pressure of the engine from the compression pump from the upstream of the fuel heater to the separator. transport

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 interrupted, such as when the engine is stopped in LPG mode or when tripping. When the LPG fuel supply is stopped, it is not necessary to recirculate the LPG from the separator to the fuel supply line, so 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.

In the present embodiment system, a plurality of pressure sensing units are provided to control the operating pressure. A first pressure sensing unit (PC1) that senses the pressure between the compression pump and the fuel heater and sends a pressure signal, a second pressure sensing unit that senses the pressure between the filter and the first pressure reducing device in the first return line and sends a pressure signal (PC2), a third pressure sensing unit (PC3) sensing the pressure of the rear end of the transfer pump, and a fourth pressure sensing unit (PC4) sensing the pressure of the separator are provided, respectively.

The operating pressure in the system of the present embodiment may be controlled as follows, for example.

The operating pressure range of the fuel supply tank is 1 to 8 barg. Assuming that the operating pressure is 4 barg, the differential pressure of the transfer pump is about 2 bar, and the rear end pressure of the transfer pump is 6 barg. The operating pressure of the separator 210 is maintained at about 0.5 to 2 bar, more preferably 0.5 to 1 bar higher than the pressure at the rear end of the first pump, so that the liquid recirculation gas separated from the separator can be smoothly transferred to the rear end of the transfer pump. there is.

To this end, the fourth pressure sensing unit PC4 receives the pressure signal from the third pressure sensing unit PC3, and the fourth pressure sensing unit PC4 sets the set value to the pressure control valve 250 of the vapor line VL. By sending a signal and adjusting the opening degree of the pressure control valve, the pressure of the separator is maintained at 6.5 to 7 barg.

The liquid separated from the separator is supplied to the front end of the compression pump along the liquid line LL, and is pumped by the compression pump and pressurized to 54 barg.

The separator is provided with a level sensor (LC) that detects the liquid level of the separator, and controls the valve (V1) according to the liquid level of the separator detected by the level sensor to adjust the flow rate of the liquefied gas transferred to the fuel supply line. can

The first return line RL1 returning from the engine controls the first pressure reducing device 220 from the second 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 at 6.5 to 7 barg equal to the separator pressure.

When the pressure at the rear end of the compression pump changes due to a change in fuel consumption due to a change in the load in the engine, the first pressure sensing unit PC1 detects the pressure and, if it is higher than the set value (54 barg) of the first pressure sensing unit, first the VFD of the second pump to lower the pump speed, and if the pressure still rises from 54 barg or more to 55 barg, the second pressure reducing device 230 of the second return line is opened to lower the pressure.

Meanwhile, a discharge pipe DL is provided at the bottom of the separator 210 . Lubricating oil separated from the separator is discharged to a discharge unit including a discharge pipe (DL). Figure 2 schematically shows the configuration of the discharge unit for discharging the lubricant from the separator in the fuel supply system of the liquefied gas carrier according to an embodiment of the present invention.

The liquefied gas recovered from the engine may contain, in addition to liquid LPG, gas such as boil-off gas generated through compression and heating for fuel supply, and sealing oil introduced from the engine. If it is supplied as a fuel for the fuel, it will be incompletely combusted, which may generate air pollutants in the exhaust and adversely affect fuel efficiency. In addition, when lubricating oil flows into the fuel supply tank, there is a risk of crystallization in the tank. In this embodiment, this can be prevented by separating and discharging the lubricant oil mixed in the liquefied gas from the separator through the discharge pipe DL provided at the bottom of the separator.

LPG is mainly composed of propane (C ₃ H ₈ ) and butane (C ₄ H ₁₀ ). Although there is a difference depending on the ratio of propane and butane, the specific gravity is about 0.5, and the specific gravity of lubricating oil is about 0.9. Therefore, in the separator, the gas is separated to the upper part, and the lubricating oil heavier than LPG is layered at the bottom due to the difference in specific gravity. For smoother separation and discharge of lubricating oil, a floating buoyancy body capable of sinking in LNG and floating in lubricating oil may be provided in the separator.

If the pressure of the separator is maintained at 10 barg or less, the separation and discharge of the lubricant due to the difference in viscosity and specific gravity can be easily achieved.

The discharge part includes a discharge pipe (DL) connected from the bottom of the separator 210 and a lubricant discharge tank (SDT) where the discharged lubricant is collected, and a retention pot (retention pot, 300) between the separator and the lubricant discharge tank in the discharge pipe. ) is provided. A magnetic float level gauge 310 is provided in the retention pot to check the liquid level, and between the separator and the retention pot in the discharge pipe, as shown in FIG. 2 , a first discharge valve DV1 And a second discharge valve (DV2) is provided. A third discharge valve (DV3) is provided between the retention pod and the lubricant discharge tank to discharge the separated lubricant to the lubricant discharge tank. During normal discharge mode operation, the first and second discharge valves (DV1, DV2) are opened, the third discharge valve (DV3) is closed, and the retention time in the pipe is increased by the retention pot provided in the discharge pipe to separate the lubricant efficiency can be increased.

A fourth discharge valve that opens and closes the piping branched from the discharge pipe and connected to the lubricant discharge tank in order to relieve the pressure of the discharge pipe between the second discharge valve and the retention pod and to relieve the vacuum state when the lubricant is drained. (DV4) is provided. In addition, the level gauge 320 for measuring the liquid level is provided in the lubricant discharge tank SDT, and a fifth discharge valve DV5 is provided to discharge the lubricant from the lubricant discharge tank, and the discharged lubricant is in the engine room. It can be sent to the oil tank for reuse or disposal.

On the other hand, the ship of this embodiment is provided with a cargo tank (not shown) for storing and transporting liquefied gas as a liquefied gas carrier. In this embodiment, boil-off gas generated from the liquefied gas stored in the cargo tank (not shown) is liquid A cooling line CL is provided so that the liquefied gas re-liquefied by sending it to the re-liquefaction unit RS is connected to the cargo tank (not shown) through the fuel supply tank DT, and the re-liquefaction unit It was configured to cool the fuel supply tank by using the cooling heat of the liquefied gas re-liquefied in the

That is, the fuel supply tank supplies fuel to the onboard engine while storing LPG at a pressure of 8 barg or less. Since it is provided on the deck of the ship, the temperature in the tank increases due to external air or gas introduced from the separator. The pressure may rise, in this embodiment by configuring the cooling line CL to re-liquefy the boil-off gas generated from the liquefied gas cargo stored in the cargo tank and then to return to the cargo tank via the fuel supply tank DT, It is possible to cool the fuel supply tank by using the cooling heat of the reliquefied liquefied gas.

Meanwhile, in the ship, fuel tanks FT1 and FT2 for supplying liquefied gas to be supplied as fuel of the onboard engine to the fuel supply tank DT disposed on the deck are additionally provided. It is also possible to supply liquefied gas from the fuel supply tank to the fuel supply tank to cool the fuel supply tank by the low-temperature liquefied gas.

In this way, the temperature and pressure of the fuel supply tank can be adjusted by re-liquefying the boil-off gas generated from the cargo in the cargo tank and cooling the fuel supply tank with the cooling heat of the re-liquefied gas. By returning and storing, it is possible to prevent mixing of fuel and transported cargo.

The present invention is not limited to the above embodiments, and it is to 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
RL1: first return line
RL2: second return line
SVT: service valve part
RVT: return valve part
RS: reliquefaction unit
CL: cooling line
110: transfer pump
120: compression pump
130: fuel heater
140, 240: filter
210: separator
220: first pressure reducing device
230: second pressure reducing device
250: pressure control valve
PC1, PC2, PC3, PC4: first to fourth pressure sensing units

Claims (11)

The liquefied gas is compressed along the fuel supply line from the fuel supply tank provided on the deck of the ship and supplied as fuel to the onboard engine,
Unconsumed liquefied gas among the liquefied gas supplied to the engine and the liquefied gas remaining in the engine when the engine is stopped are recovered upstream of the engine through a return line,
The liquefied gas recovered from the engine through the return line is gas-liquid separated in a separator, the separated gas is recovered to the fuel supply tank, and the liquid is recirculated to the fuel supply line supplied as fuel of the engine,
By sensing the pressure of the fuel supply line to which the liquefied gas to be separated and recirculated from the separator is supplied, the amount of gas recovered from the separator to the fuel supply tank is adjusted according to the sensed pressure to increase the pressure of the separator to the fuel. A fuel supply method for a liquefied gas carrier, characterized in that it is maintained higher than the pressure sensed in the supply line. The method of claim 1,
a transfer pump for transferring liquefied gas from the fuel supply tank to the fuel supply line; And a compression pump for pumping the liquefied gas transferred from the transfer pump to increase the pressure to the required pressure in the engine: is provided,
The liquefied gas to be separated and recirculated in the separator is supplied to a fuel supply line between the transfer pump and the compression pump and recirculated. 3. The method of claim 2,
By sensing the pressure at the rear end of the transfer pump, and adjusting the amount of gas recovered from the separator to the fuel supply tank according to the sensed pressure, the pressure of the separator is maintained 0.5 to 2 barg higher than the pressure at the end of the transfer pump A fuel supply method of a liquefied gas carrier, characterized in that. 3. The method of claim 2,
By sensing the pressure at the rear end of the compression pump, if the detected pressure is higher than the set value, first lower the pump speed of the compression pump,
If it is still higher than the set value, a fuel supply method for a liquefied gas carrier, characterized in that the pressure at the rear end of the compression pump is controlled by depressurizing a part of the liquefied gas at the rear end of the compression pump and discharging it to the separator. 5. The method according to any one of claims 1 to 4,
The return line is provided with a pressure reducing unit,
Of the liquefied gas supplied to the engine, unconsumed liquefied gas and liquefied gas remaining in the engine when the engine is stopped are decompressed through the decompression unit of the return line and then introduced into the separator for gas-liquid separation. of fuel supply method. 6. The method of claim 5,
A fuel supply method for a liquefied gas carrier, characterized in that a discharge pipe for separating and discharging lubricating oil mixed in the liquefied gas returned to the separator is provided at the bottom of the separator. 6. The method of claim 5,
Re-liquefying boil-off gas generated from a cargo tank for storing liquefied gas to be transported and provided on the ship in a re-liquefaction unit,
The liquefied gas reliquefied in the reliquefaction unit is transferred to the cargo tank through the fuel supply tank to cool the fuel supply tank. a fuel supply line through which liquefied gas is supplied from the fuel supply tank provided on the deck of the ship to the onboard engine;
a compression unit 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 return line for recirculating the liquefied gas not consumed by the engine among the liquefied gas to an upstream of the engine; and
A separator for gas-liquid separation of the recirculated liquefied gas provided in the return line and recovering the separated gas to the fuel supply tank;
By sensing the pressure of the fuel supply line, adjusting the amount of gas recovered from the separator to the fuel supply tank according to the sensed pressure, and maintaining the pressure of the separator higher than the pressure sensed in the fuel supply line,
A fuel supply system for a liquefied gas carrier, characterized in that the liquid separated in the separator is recirculated to the fuel supply line. 9. The method of claim 8,
a transfer pump for transferring liquefied gas from the fuel supply tank to the fuel supply line; And a compression pump for pumping the liquefied gas transferred from the transfer pump to increase the pressure to the required pressure in the engine: is provided,
A fuel supply system for a liquefied gas carrier, characterized in that by sensing the pressure at the rear end of the transfer pump, the liquefied gas to be separated from the separator and recirculated is recirculated to a fuel supply line between the transfer pump and the compression pump. 10. The method of claim 9,
Further comprising: a decompression unit provided in the return line to decompress the liquefied gas recovered through the return line without being consumed by the engine;
The liquefied gas recovered along the return line is introduced into the separator after decompression through the decompression unit. 11. The method of claim 10,
a discharge pipe provided at the bottom of the separator to separate and discharge the lubricating oil mixed in the liquefied gas returned to the separator; and
Further comprising: a re-liquefaction unit for re-liquefying boil-off gas generated from a cargo tank for storing liquefied gas to be transported provided in the ship;
A fuel supply system for a liquefied gas carrier, characterized in that by transferring the liquefied gas reliquefied in the reliquefaction unit to the cargo tank through the fuel supply tank, and cooling the fuel supply tank.

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