KR20230040429A - Fuel Supplying System For Liquefied Gas Carrier - Google Patents

Abstract

Disclosed is a fuel supplying system for a liquefied gas carrier. The fuel supplying system for a liquefied gas carrier comprises: a composite tank provided on a ship to store liquefied gas transported as cargo and liquefied fuel supplied as fuel for the engine of the ship; a fuel supply tank receiving the liquefied fuel from the composite tank and supplying the same to the engine; and a fuel supply pump pumping the liquefied fuel from the composite tank and transferring the same to the fuel supply tank. The composite tank is spatially divided into: a cargo tank storing the liquefied gas transported as the cargo; the fuel storage tank storing the liquefied fuel; and a cofferdam provided between the cargo tank and the fuel storage tank, by a plurality of bulkheads disposed therein. Therefore, the fuel supplying system can efficiently store the liquefied gas to be transported as the cargo and the liquefied fuel to be supplied as the fuel for the engine in the ship through the composite tank spatially divided by the bulkheads.

Description

Fuel supply system of liquefied gas carrier {Fuel Supplying System For Liquefied Gas Carrier}

The present invention relates to a fuel supply system for a liquefied gas carrier, and more particularly, while supplying liquefied fuel containing ammonia as fuel to an engine in a ship carrying liquefied gas such as ammonia or LPG as a cargo, It relates to a fuel supply system for a liquefied gas carrier capable of re-liquefying and treating boil-off gas without discharging it into the atmosphere.

Efforts are being made to reduce greenhouse gas emissions worldwide as the global warming phenomenon intensifies, and as the Kyoto Protocol in 1997, which contained the obligations of developed countries to reduce greenhouse gases, expired in 2020, the conference was held in Paris, France in December 2015. According to the Paris Climate Change Accord, which was adopted in the 21st United Nations Framework Convention on Climate Change and entered into force in November 2016, the 195 Parties participating in the agreement are making various efforts to reduce greenhouse gases.

Along with this global trend, interest in renewable energy (or renewable energy) such as wind power, solar power, solar heat, bioenergy, tidal power, and geothermal heat has increased and various technologies have been developed as pollution-free energy that can replace fossil fuels and nuclear power. are losing

Although LNG is evaluated as an eco-friendly fuel compared to other fossil fuels, it still generates carbon dioxide when burned, and ships that use it as fuel emit carbon dioxide during operation.

Several studies have been conducted on eco-friendly fuels capable of reducing carbon dioxide emissions during ship operation, and recently, a technology for a ship engine capable of using ammonia as a fuel has been developed.

Ammonia (NH ₃ ) is a substance in which three hydrogens are bonded to one nitrogen, and it is easy to liquefy because it can form a strong hydrogen bond between molecules, and has a boiling point of -33.34 ° C and a melting point of -77.73 ° C under normal pressure.

In the case of applying an eco-friendly fuel such as ammonia as a fuel for a ship engine, the present invention increases the utilization of space inside the ship to store cargo and fuel, while preventing the emission of boil-off gas and vent gas into the atmosphere due to toxicity and corrosiveness. In consideration of this, we would like to propose a fuel supply system that can effectively process fuel in a ship.

According to one aspect of the present invention for solving the above problems, a composite tank provided on a ship and storing liquefied fuel supplied as fuel for liquefied gas and inboard engines transported as cargo;

a fuel supply tank receiving the liquefied fuel from the complex tank and supplying the liquefied fuel to the engine; and

A fuel supply pump for pumping the liquefied fuel from the combined tank and transferring it to the fuel supply tank;

The composite tank is provided between a cargo tank for storing liquefied gas transported as cargo, a fuel storage tank for storing liquefied fuel, and the cargo tank and the fuel storage tank by a plurality of bulkheads disposed therein A fuel supply system for a liquefied gas carrier, characterized in that space is separated by a cofferdam, is provided.

Preferably, a bulkhead valve provided on the bulkhead between the cargo tank and the cofferdam further includes, and the cofferdam is filled with an inert gas, and the liquefied gas of the cargo tank and the liquefied fuel of the fuel storage tank are the same. At this time, the bulkhead valve can be opened to fill the liquefied gas into the cofferdam.

Preferably, it is provided in the fuel storage tank and further comprises an eductor for receiving a portion of the liquefied fuel pumped by the fuel supply pump and discharging it into the tank to stir the liquefied fuel in the fuel storage tank. can

Preferably, a re-liquefaction line for transferring boil-off gas generated from the liquefied fuel stored in the complex tank to the fuel supply tank; and a re-liquefaction unit receiving the boil-off gas from the fuel supply tank and re-liquefying it, wherein the internal pressure of the fuel supply tank may be maintained lower than the internal pressure of the combined tank.

Preferably, the re-liquefaction unit includes a compression unit for receiving and compressing boil-off gas from the fuel supply tank; and a condensing unit for receiving and cooling the boil-off gas compressed by the compression unit.

Preferably, the re-liquefaction unit includes a phase separation tank for receiving the evaporation gas cooled in the condensation unit and performing gas-liquid separation; and a pressure reducing valve for reducing the pressure of the liquid separated from the phase separation tank, wherein the liquid separated from the phase separation tank is transferred to the fuel supply tank via the pressure reducing valve, and the gas separated from the phase separation tank is depressurized. It may be transferred to the fuel supply tank.

Preferably, a transfer pump for transferring liquefied fuel from the fuel supply tank to the engine; a compression pump for compressing the liquefied fuel transferred from the transfer pump to a pressure required by the engine; and a fuel heater provided at a rear end of the compression pump and heating the compressed liquefied fuel to a temperature required by the engine.

Preferably, a heat medium circulation line through which the heat medium supplied to the fuel heater for heating the liquefied fuel is circulated; and a heat medium supply unit provided in the heat medium circulation line to heat the heat medium, wherein the fuel heater heats the liquefied fuel and the cooled heat medium is returned to the heat medium supply unit through the condensation unit of the re-liquefaction unit.

Preferably, a return line for recovering liquefied fuel not consumed by the engine and liquefied fuel remaining in the engine when the engine is stopped to a front end of the compression pump further includes, and vent gas discharged from the engine is supplied to the fuel supply It can be returned to the tank.

Preferably, an emergency discharge line connected from the return line to the fuel supply tank; And a decompression unit provided in the emergency discharge line to depressurize the liquefied fuel to be recovered to the fuel supply tank; and discharged to the fuel supply tank.

Preferably, the liquefied fuel may contain ammonia.

In the present invention, the liquefied gas to be transported as cargo and the liquefied fuel to be supplied as fuel of the ship's engine can be efficiently stored through the complex tank spaced apart by the bulkhead.

In particular, the evaporation gas generated from the liquefied fuel is transferred to the fuel supply tank to which the liquefied fuel to be supplied as fuel for the onboard engine is transferred, and the fuel supply tank is used as a suction drum of the evaporation gas re-liquefaction system to increase the utilization of the device and to increase the evaporation When re-liquefying gas, it is possible to increase energy efficiency while effectively re-liquefying and processing boil-off gas by using cold heat from fuel to be supplied to the ship's engine.

In addition, the vent gas discharged from the ship's engine is also configured to be transported to the fuel supply tank, so that even when using liquefied fuel such as ammonia, it can be treated on board without air emission.

1 schematically shows a fuel supply system for 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 a preferred embodiment of the present invention will be described in detail with reference to the accompanying drawings. In adding reference numerals to the components of each drawing, it should be noted that the same components are marked with the same numerals as much as possible, even if they are displayed on different drawings.

In an embodiment of the present invention described later, a ship is a ship that transports liquefied gas that can be liquefied at a low temperature and transported as a cargo, and such liquefied gas is, for example, LNG (Liquefied Natural Gas), LEG (Liquefied Ethane Gas), It may be liquefied petrochemical gas such as LPG (Liquefied Petroleum Gas), liquefied ethylene gas (Liquefied Ethylene Gas), liquefied propylene gas (Liquefied Propylene Gas), and ammonia. Representative examples of such ships include LPG carriers, LNG carriers, liquid hydrogen carriers, and ammonia carriers.

In addition, the ship of the present invention is a ship that can use liquefied fuel as a fuel for a ship engine such as for propulsion or power generation. A ship to which an engine used as fuel alone or together with other liquefied gas such as LPG will be described as an example.

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

As shown in FIG. 1, the fuel supply system of this embodiment is provided in a ship and stores liquefied gas transported as cargo and liquefied fuel supplied as fuel for an onboard engine (MT1, MT2), liquefied from the composite tank. It includes a fuel supply tank (FST) that receives fuel and supplies it to the engine.

As shown in FIG. 1, the composite tanks MT1 and MT2 have a plurality of bulkheads (BH) disposed therein, for example, a cargo tank (CT1) for storing liquefied gas transported as cargo by two bulkheads. , CT2), fuel storage tanks (FT1, FT2) for storing liquefied fuel, and cofferdams (CD1, CD2) provided between the cargo tank and the fuel storage tank.

The cargo tanks (CT1, CT2) of the complex tank are loaded with liquefied gas to be transported as cargo, and the fuel storage tanks (FT1, FT2) are loaded with liquefied fuel to be supplied as fuel for the ship's engine, and the inside of the cofferdam (CD1, CD2) Filled with inert gas, it is possible to completely separate the cargo tank and the fuel storage tank. However, through the composite tank, the cargo tank and the fuel storage tank share a tank dome (not shown), thereby saving space in the ship.

On the other hand, in addition to the composite tank, general cargo tanks (CT3, CT4) for accommodating liquefied gas to be transported as cargo are also provided in the ship.

A bulkhead valve (BV) is provided on the bulkhead (BH) between the cargo tank and the cofferdam, and when the liquefied gas in the cargo tank and the liquefied fuel in the fuel storage tank are the same, that is, for example, the same liquefied gas in the cargo tank and the fuel storage tank. When loading the cofferdam, there is no need to separate the cargo tank and the fuel storage tank by filling the cofferdam with inert gas, so by opening the bulkhead valve (BV) and filling the cofferdam with liquefied gas, the amount of transported cargo is increased, and the entire complex tank cargo hold can be operated with liquefied gas, eg ammonia tanks.

Fuel supply pumps FP1 and FP2 are disposed in the combined tanks MT1 and MT2 to pump liquefied fuel from the fuel storage tank of the combined tank and transfer it to the fuel supply tank.

The fuel storage tank of the combined tank may be provided with eductors (ED1, ED2) that receive a portion of the liquefied fuel pumped from the fuel supply pump and discharge it into the tank to stir the liquefied fuel inside the fuel storage tank. .

The fuel supply tank (FST) may be provided on the upper or lower deck, and the fuel supply line (FL) is connected from the fuel storage tanks (FT1, FT2) to the engine (E) via the fuel supply tank (FST).

In addition, a re-liquefaction line (RL) is connected to transfer boil-off gas generated from the liquefied fuel stored in the complex tank to the fuel supply tank, and the boil-off gas is supplied from the re-liquefaction unit along the re-liquefaction line from the fuel supply tank to re-liquefy. . Therefore, the fuel supply tank (FST) serves as an intermediate tank for supplying liquefied fuel to the engine, as well as a re-liquefaction unit that re-liquefies the evaporation gas generated from liquefied fuel, that is, a suction drum of the re-liquefaction system. carry out

To this end, the internal pressure of the fuel supply tank (FST) is maintained lower than the internal pressure of the composite tanks (MT1, MT2) so that the boil-off gas can be transferred from the composite tanks (MT1, MT2) to the fuel supply tank (FST). . For example, when a complex tank is provided as a membrane type tank and SLNG (Sealing LNG) is applied, the internal pressure can be maintained up to 1.5 atm (gauge pressure), and is maintained at 0.7 bar or less in normal cases, and the fuel supply tank The internal pressure can be kept the same or lower, from 0 to 0.24 bar.

The re-liquefaction unit includes a compression unit 100 that receives and compresses the boil-off gas from the fuel supply tank, a condensation unit 110 that receives and cools the boil-off gas compressed from the compression unit, and receives the cooled boil-off gas from the condenser to gas-liquid. It includes a phase separation tank 120 for separation and a pressure reducing valve 130 for reducing the liquid separated in the phase separation tank. The phase separation tank 120 is provided with a level sensor 125 for detecting the liquid level inside the tank, and the pressure reducing valve 130 is controlled according to the liquid level detected by the level sensor to discharge liquefied fuel from the phase separation tank.

The compression unit 100 may be provided as a multi-stage compressor including a plurality of compressors 100a and 100b as needed, or may be composed of a single compressor, and the pressure of the fuel supply tank is reduced by re-liquefying boil-off gas. You can drive intermittently to keep up. The evaporation gas compressed in the compression unit 100 is condensed while being cooled by a heat medium in the condensation unit 110 and moved to the phase separation tank 120 . In the phase separation tank 120, the condensed compressed gas is gas-liquid separated, and the separated liquid is transferred to the fuel supply tank FST via the pressure reducing valve 130. The condensate, that is, liquefied fuel transferred to the fuel supply tank may be supplied to the engine E along the fuel supply line FL, or may be transferred to the fuel storage tanks FT1 and FT2 of the combined tank. If necessary, the separated liquefied fuel may be recovered after condensation directly from the phase separation tank to the fuel storage tank without going through the fuel supply tank.

The gas separated in the phase separation tank is also transferred to the fuel supply tank after depressurization (VV) through the gas line (VL) without being discharged to the atmosphere.

On the other hand, in the fuel supply line FL, a transfer pump 200 for transferring liquefied fuel from the fuel supply tank to the engine so that liquefied fuel can be supplied according to the pressure and temperature conditions required by the engine, and the liquefied fuel transferred from the transfer pump A compression pump 210 for compressing fuel to a pressure required by the engine, and a fuel heater 220 provided at a rear end of the compression pump and heating the compressed liquefied fuel to a temperature required by the engine are provided.

An engine supplied with liquefied fuel may be, for example, a MAN Diesel & Turbo ME-LGIP engine. In addition to LPG, methanol and ethanol, the ME-LGIP engine can be supplied with liquefied gas such as ammonia as fuel. , the engine is operated by spraying it to the nozzle at a pressure of 600 to 700 bar with hydraulic pressure from the engine. In the case of ammonia, it can be supplied to the engine at around 50 to 85 bar and 24 to 45 ° C through a compression pump and a fuel heater.

The fuel heater 220 is provided with a heating medium circulation line (HL) through which a heating medium supplied to heat the liquefied fuel circulates, and a heating medium supply unit 300 for heating the heating medium is provided in the heating medium circulation line.

The heat medium supplied from the heat medium supply unit 300 to the fuel heater 220 along the heat medium circulation line HL heats the compressed liquefied fuel and supplies it to the engine E, and heats the liquefied fuel and cools the heat medium to the re-liquefaction unit. It is returned to the heat medium supply unit 300 through the condensation unit 110 of the By the heat medium supplied from the fuel heater to the condensing unit, the evaporation gas compressed in the compression unit receives cooling heat from the heating medium and is condensed. The heat medium of the heat medium circulation line (HL) may be, for example, glycol, and this glycol is supplied to the fuel heater 220 at around 36 ° C from the heat medium supply unit 300 to heat the liquefied fuel and cool to around 12 ° C. It is supplied to the condensing unit 110 of the re-liquefaction unit, and the boil-off gas is introduced into the condensing unit 110 at around 6.5 bar and 16 ° C through the compression unit 100, cooled by a heat medium, and condensed.

On the other hand, when an incompressible fluid with little or no change in volume even when pressure is applied, liquid LPG and ammonia are supplied as engine fuel, excess liquefied fuel is supplied to the engine to respond to engine load fluctuations and prevent cavitation. . Among the liquefied fuel supplied to the engine, the remaining liquefied fuel consumed as fuel and the liquefied fuel remaining in the engine when the engine is stopped are recovered to the front end of the compression pump 210. To this end, a return line (RTL) is connected from the engine to the front end of the compression pump, that is, between the compression pump and the transfer pump. In the case of ammonia, it can be recovered and recycled from the engine to the front end of the compression pump 210 through the return line (RTL) at around 30 bar and 60 ° C.

In addition, an emergency discharge line (RLa) is connected from the return line to the fuel supply tank, and a pressure reducing unit (RV) for reducing the liquefied fuel is provided in the emergency discharge line. The liquefied fuel recovered to the front end of the compression pump through the return line and recirculated to the engine can be decompressed and discharged to the fuel supply tank in an emergency through the emergency discharge line. The pressure reducing unit (RV) may be provided with, for example, a pressure reducing valve or a knockout drum.

Vent gas including ammonia discharged from the engine is not emitted to the atmosphere but is collected in the knockout drum inside the engine, and can be discharged from the engine and recovered to the fuel supply tank in emergency situations such as fuel change or purging in the engine.

As described above, in this embodiment, the boil-off gas generated from the liquefied fuel and the vent gas discharged from the engine are not released into the atmosphere, but are sent to the fuel supply tank to be re-liquefied or circulated as fuel, thereby reducing toxicity and corrosiveness such as ammonia. When eco-friendly fuel, which is difficult to discharge to the outside through a vent mast, is applied as a ship engine fuel, boil-off gas and vent gas can be effectively treated inside the ship.

The present invention is not limited to the above embodiments, and it can be practiced with various modifications or variations within a range that does not deviate from the technical gist of the present invention to those skilled in the art to which the present invention belongs. It is self-evident.

E: engine
MT1, MT2: Combined Tank
BH: Bulkhead
CT1, CT2, CT3, CT4: Cargo Tank
FT1, FT2: fuel storage tank
CD1, CD2: cofferdam
FST: fuel supply tank
FL: fuel supply line
RL: reliquefaction line
HL: heat medium circulation line
100: compression unit
110: condensation unit
120: phase separation tank
130: pressure reducing valve
200: transfer pump
210: compression pump
220: fuel heater
300: heat medium supply unit

Claims (11)

A composite tank provided on a ship and storing liquefied gas transported as cargo and liquefied fuel supplied as fuel for an onboard engine;
a fuel supply tank receiving the liquefied fuel from the complex tank and supplying the liquefied fuel to the engine; and
A fuel supply pump for pumping the liquefied fuel from the combined tank and transferring it to the fuel supply tank;
The composite tank is provided between a cargo tank for storing liquefied gas transported as cargo, a fuel storage tank for storing liquefied fuel, and the cargo tank and the fuel storage tank by a plurality of bulkheads disposed therein A fuel supply system for a liquefied gas carrier, characterized in that space is separated by a cofferdam. According to claim 1,
Further comprising: a bulkhead valve provided on the bulkhead between the cargo tank and the cofferdam,
The cofferdam is filled with an inert gas,
When the liquefied gas in the cargo tank and the liquefied fuel in the fuel storage tank are the same, the fuel supply system of the liquefied gas carrier, characterized in that the liquefied gas can be filled with the cofferdam by opening the bulkhead valve. According to claim 1,
It is provided in the fuel storage tank and receives a portion of the liquefied fuel pumped from the fuel supply pump and discharges it into the tank to stir the liquefied fuel inside the fuel storage tank. fuel supply system. According to claim 1,
a re-liquefaction line for transporting boil-off gas generated from the liquefied fuel stored in the complex tank to the fuel supply tank; and
Further comprising a re-liquefaction unit for re-liquefying by receiving the boil-off gas from the fuel supply tank,
The fuel supply system of the liquefied gas carrier, characterized in that the internal pressure of the fuel supply tank is maintained lower than the internal pressure of the combined tank. The method of claim 4, wherein the re-liquefying unit
a compression unit for receiving and compressing the boil-off gas from the fuel supply tank; and
A fuel supply system for a liquefied gas carrier comprising: a condensing unit for receiving and cooling the boil-off gas compressed in the compression unit. The method of claim 5, wherein the re-liquefying unit
a phase separation tank receiving the evaporation gas cooled in the condensing unit and performing gas-liquid separation thereon; and
Further comprising a pressure reducing valve for reducing the liquid separated in the phase separation tank,
The liquid separated from the phase separation tank is transferred to the fuel supply tank through the pressure reducing valve, and the gas separated from the phase separation tank is transferred to the fuel supply tank after decompression. A fuel supply system for a liquefied gas carrier. According to claim 5,
a transfer pump transferring liquefied fuel from the fuel supply tank to the engine;
a compression pump for compressing the liquefied fuel transferred from the transfer pump to a pressure required by the engine; and
A fuel supply system for a liquefied gas carrier further comprising a fuel heater provided at a rear end of the compression pump and heating the compressed liquefied fuel to a temperature required by the engine. According to claim 7,
a heat medium circulation line through which a heat medium supplied to the fuel heater for heating the liquefied fuel is circulated; and
Further comprising: a heat medium supply unit provided in the heat medium circulation line to heat the heat medium,
The fuel supply system of a liquefied gas carrier, characterized in that the heat medium cooled by heating the liquefied fuel in the fuel heater is recovered to the heat medium supply unit through the condensation unit of the re-liquefaction unit. According to claim 7,
A return line for recovering the liquefied fuel not consumed by the engine and the liquefied fuel remaining in the engine when the engine is stopped to a front end of the compression pump;
The fuel supply system of the liquefied gas carrier, characterized in that the vent gas discharged from the engine is recovered to the fuel supply tank. According to claim 9,
an emergency discharge line connected from the return line to the fuel supply tank; and
Further comprising: a decompression unit provided in the emergency discharge line to depressurize the liquefied fuel to be recovered to the fuel supply tank,
The fuel supply system of a liquefied gas carrier, characterized in that the liquefied fuel recovered to the front end of the compression pump through the return line is depressurized through the emergency discharge line in an emergency and discharged to the fuel supply tank. According to any one of claims 1 to 10,
The liquefied fuel is a fuel supply system for a liquefied gas carrier, characterized in that it contains ammonia.

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