KR20200048092A - Boil-Off Gas Treatment System And Method For Ship - Google Patents

Abstract

Disclosed are a boil-off gas treatment system for a vessel and a method thereof. According to the present invention, the boil-off gas treatment system includes: a multistage compressor receiving boil-off gas (BOG) produced from an LNG storage tank of a vessel, which can make an outboard transfer of regasification gas, to compress the boil-off gas through a plurality of unit compressors; a main engine producing electric power and thrust required for the vessel by receiving LNG or the BOG compressed in the multistage compressor; a shaft generator connected to shafting including a shaft delivering the output of the main engine to a propeller of the vessel to produce electric power with the output of the main engine; a clutch separating the main engine and the shaft generator and the propeller and the shaft; a generator engine producing electric power required for the vessel by receiving the LNG or the BOG compressed through some of the unit compressors of the multistage compressor; and a re-condenser receiving the BOG compressed through some of the unit compressors of the multistage compressor to condense the gas by mixing the LNG supplied from the LNG storage tank. Therefore, the boil-off gas treatment system is capable of reducing costs for operation by using a main engine for producing thrust and electric power.

Description

Boil-off gas treatment system and method for ship

The present invention relates to an evaporation gas treatment system and method of a ship, and more specifically, a plurality of unit compressors receiving BOG (Boil Off Gas) generated in an LNG storage tank of a ship capable of transporting regasification offboard. Compressed and compressed multi-stage compressor, LNG or BOG compressed through all or part of the multi-stage compressor is supplied to the main engine that generates the propulsion and electric power required for the ship, or the generator engine that generates power, and the part of the multi-stage compressor is supplied. The present invention relates to a system and method for treating boil-off gas in a ship that allows compressed BOG to be transported to the outboard.

Natural gas is a fossil fuel that contains methane as a main component and contains a small amount of ethane and propane, and has recently been spotlighted as a low-pollution energy source in various technical fields.

Natural gas is consumed a lot with economical and eco-friendly energy, but it has a large volume and is inefficient in transportation and storage to transport it as a natural gas.

In order to compensate for this, a method of transporting and storing in a liquefied natural gas (LNG) state has been proposed. Liquefied natural gas is a colorless, transparent, cryogenic liquid whose natural gas, mainly composed of methane, is cooled at atmospheric pressure to a cryogenic condition of -162 ° C, reducing its volume to 1/600.

However, since the natural gas liquefaction temperature is extremely low at -162 ° C under normal pressure, LNG is easily sensitive to temperature changes and evaporates easily. Although the LNG storage tank of the LNG carrier is insulated, since external heat is continuously transferred to the LNG storage tank, LNG is continuously vaporized in the LNG storage tank during the LNG transportation process by the LNG carrier, and LNG Boil-off gas (BOG) is generated in the storage tank.

BOG is a kind of LNG loss, which is an important problem in the transportation efficiency of LNG, and when boil-off gas accumulates in the LNG storage tank, the pressure in the LNG storage tank rises excessively, and there is a risk of damage to the tank. A variety of methods for dealing with are being studied.

Recently, for the treatment of BOG, a method of re-liquefying BOG and returning it to a storage tank, a method of using BOG as an energy source of a ship engine, and the like are used. And for the excess BOG, a method of combustion in a gas combustion unit (GCU) is used.

In addition, a dual fuel engine has been developed that can use natural or forced vaporized gas and fuel oil as fuel in propulsion or power generation devices in the LNG carrier itself, and is used as the main engine and generator engine. It is also supplied as fuel on board.

1 schematically shows a vessel provided with an engine that receives fuel from a conventional LNG storage tank.

As shown in FIG. 1, a plurality of engines are provided on a ship, and when a regasification plant is driven in a FSRU (Floating Storage Regasification Unit), a plurality of large engines are provided because power consumption is high. When a 4-stroke Dual Fuel engine is provided, LNG or BOG is supplied from the LNG storage tank (T) to the engine (E) via the fuel supply unit (10), and oil such as HFO, MDO, LSMGO is also supplied.

Electricity produced by driving the engine (E) passes through a switchboard (SWBD), through a transformer 20, a converter 30, a propulsion motor 40, a reduction gear 50, and the like to a fixed pitch propeller (FPP) It is transmitted by power.

These 4-Stroke engines provided in the FSRU can be less efficient than 2-Stroke engines, and the engine output is transmitted to the propellers through the switchboard, transformer, converter, propulsion motor, and reduction gear, so the output is lost through each stage. This can occur, and there is a problem of high maintenance costs.

 In addition, if the gas consumption at the onshore side is low and the regasification gas transfer rate is low or if the gas is not regasified for a long time, a lot of evaporation gas is generated in the storage tank. For this, there is a problem in that it is impossible to efficiently use evaporation gas when it is burned and removed from a gas combustion unit (GCU). In addition, since the GCU also consumes a large amount of power, there is a problem of double energy loss.

The present invention is intended to solve this problem, and to increase the flexibility of evaporation gas management, so as to more effectively manage evaporation gas, and to propose a system of a ship that can increase engine efficiency and reduce maintenance costs.

According to an aspect of the present invention for solving the above-described problem, receiving the BOG (Boil Off Gas) generated in the LNG storage tank of the ship capable of transporting the regasification offboard is compressed through a plurality of unit compressors compressor;

A main engine that receives compressed BOG from LNG or the multi-stage compressor and produces propulsion and electric power required for the ship;

An axial generator connected to an axial system including an axis for transmitting the output of the main engine to the propeller of the ship to produce power with the output of the main engine;

A clutch separating the main engine and the shaft generator from the propeller and shaft;

A generator engine that receives the compressed BOG through LNG or a part of the unit compressor of the multi-stage compressor and produces power required for the ship; And

Provided is a boil-off gas treatment system for a vessel including; a re-condenser that receives compressed BOG through some of the unit compressors of the multi-stage compressor and mixes it with LNG supplied from the LNG storage tank to condense it.

Preferably, the HP pump that receives the compressed LNG from the re-condenser and compresses it at high pressure; An HP carburetor receiving and vaporizing compressed LNG from the HP pump; And a measurement unit for transferring gas vaporized from the HP vaporizer to the outside of the ship.

Preferably, the BOG compressed through a part of the unit compressor of the multi-stage compressor may be transferred to the ship through the measurement unit.

Preferably, the HP carburetor can vaporize the LNG by heat exchange with seawater by an open loop or a closed loop.

Preferably, the main engine is an engine supplied with BOG compressed to 250 to 450 bar, the generator engine is an engine supplied with BOG compressed to 5 to 20 bar, and the multi-stage compressor is composed of four unit compressors. BOG can be compressed to the required pressure of the main engine.

Preferably, a compressor that receives and compresses BOG (Boil Off Gas) generated in the LNG storage tank; FG pump that receives and compresses LNG from the LNG storage tank; And an FG vaporizer that receives and vaporizes the compressed high pressure LNG from the FG pump. When the multistage compressor is not driven, the recondenser and the generator engine receive compressed BOG from the compressor, and the main The engine may be supplied with compressed and vaporized gas via the FG pump and FG vaporizer, and the compressed and vaporized gas via the FG pump and FG vaporizer may be supplied outboard.

Preferably, when the vessel is a floating storage regasification unit (FSRU) that propels itself when it is evacuated, the multistage compressor is not installed, and the recondenser and the generator engine are supplied with compressed BOG from the compressor and the main engine Silver may be supplied with compressed and vaporized gas through the FG pump and the FG vaporizer.

According to another aspect of the present invention, BOG (Boil Off Gas) generated in an LNG storage tank of a ship capable of transporting regasified gas outboard is compressed by a multi-stage compressor including a plurality of unit compressors, and propulsion and electric power required for the ship It is supplied to the main engine to produce, and the BOG compressed through some of the unit compressors of the multi-stage compressor is supplied to the generator engine to produce electric power required for the ship,

A shaft generator capable of producing electric power with the output of the main engine is connected to a shaft system including a shaft that delivers the output of the main engine to a propeller, and a clutch for separating the main engine and shaft generator from the propeller and shaft is provided. The main engine and the shaft generator can generate electric power even when the ship is not in propulsion,

A BOG compressed through some of the unit compressors of the multi-stage compressor is supplied to a re-condenser and mixed with LNG supplied from the LNG storage tank to be condensed.

Preferably, it further includes a compressor that receives and compresses BOG (Boil Off Gas) generated in the LNG storage tank, and when the multi-stage compressor is not driven, the re-condenser and the generator engine are BOG compressed by the compressor. And the main engine receives and supplies LNG as fuel by compressing and vaporizing LNG from the LNG storage tank, and the multi-stage compressor and compressor may constitute redundancy.

Preferably, the BOG compressed through a part of the unit compressor of the multi-stage compressor may be transferred to the outboard.

The present invention can increase the efficiency by applying a 2-stroke engine as the main engine to lower the fuel cost during voyage, and adopt a shaft generator to enable the main engine to be used for power generation, and configure a clutch to propeller and By separating the shaft from the main engine and the shaft generator, it is possible to produce power required for the re-gasification, for example, when not in navigation, using the main engine.

In addition, operation costs can be reduced by using the main engine, which has less equipment failure and lower maintenance cost, than the generator engine for propulsion and power generation.

Multistage compressors and compressors can be used to configure redundancy, and do not require much power generation, perform BOG management through a recondenser, or when the regasification transfer rate to the outboard is low. By using a compressor without driving a multi-stage compressor during abnormalities or maintenance, the flexibility of evaporation gas management is increased, so that evaporation gas can be managed more effectively.

1 schematically shows a vessel provided with an engine that receives fuel from a conventional LNG storage tank.
2 schematically shows a system for treating boil-off gas in a ship according to a first embodiment of the present invention.
3 schematically shows a system for treating boil-off gas in a ship according to a second embodiment of the present invention.

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

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, when adding reference numerals to the components of each drawing, it should be noted that the same components are denoted by the same reference numerals as much as possible even though they are displayed on different drawings.

In the embodiments of the present invention described below, the vessel may be an engine that can use liquefied gas as fuel for a propulsion engine or fuel for a power generation engine, or may be any type of vessel that uses liquefied gas as fuel. Typically, self-propelled ships such as LPG carriers, LNG carriers, liquid hydrogen carriers, and LNG regasification vessels (LVs), LNG floating production storage offloading (FPSO), and LNG floating storage regasification units (FSRUs) As well, offshore structures floating on the sea are included.

In addition, the present embodiments can be applied to a fuel supply system of all types of liquefied gas that can be transported by liquefying at a low temperature, generating evaporation gas in a stored state, and supplying fuel to the engine. Such liquefied gas is, for example, liquefied petrochemicals such as Liquefied Natural Gas (LNG), Liquefied Ethane Gas (LEG), Liquefied Petroleum Gas (LPG), Liquefied Ethylene Gas, Liquefied Propylene Gas, etc. It can be gas.

In embodiments to be described later, an LNG floating vessel regasification unit (FSRU) among ships to which LNG, which is one of typical liquefied gases, is applied, will be described as an example.

2 schematically shows a system for treating boil-off gas in a ship according to a first embodiment of the present invention.

As shown in FIG. 2, the evaporation gas treatment system of the first embodiment receives a BOG (Boil Off Gas) generated in the LNG storage tank (T) of the ship and compresses it through a plurality of unit compressors (100A) ), The main engine (ME) that receives the compressed BOG from the multi-stage compressor to produce the power required for the ship, and the generator engine that produces the electric power required for the ship by receiving the compressed BOG through some of the unit compressors of the multi-stage compressor ( GE), it is configured to include a re-condenser 200 to receive the compressed BOG through a part of the unit compressor of the multi-stage compressor and mix and condense with the LNG supplied from the LNG storage tank.

This ship is an FSRU that regasifies LNG and supplies it to the outboard. In the system, the HP pump 300 that receives condensed LNG from the recondenser and compresses it at high pressure to regasify the LNG and transport it to the outboard is compressed by the HP pump. HP carburetor 400 to vaporize the supplied LNG, and further includes a measurement unit (metering unit, 500), a heat exchanger 600, a manifold 700 to transfer gas vaporized from the HP carburetor to the outside of the ship do.

The main engine ME is a 2-stroke engine supplied with BOG compressed to 250 to 450 bar, and a shaft generator (SG) is employed. A propeller (PP) generating the propulsion of the ship using the output of the main engine is connected to the shaft (S) for transmitting the output of the main engine to the propeller, the shaft generator (SG) is connected to the shaft system including these shafts. In addition, a clutch (C) is provided to separate the main engine and the shaft generator from the propeller and shaft.

The generator engine GE may be composed of a 4-stroke engine supplied with BOG compressed to 5 to 20 bar. For example, the main engine may be a MAN-ES (company) ME-GI engine.

By applying the 2-stroke engine as the main engine in this way, it is possible to increase the efficiency during sailing, and by using the shaft generator, the power required during sailing can be produced as the output of the main engine, and the shaft generator and the main engine are separated from the shaft. By employing the clutch, even when not in the voyage, for example, during regasification, the main engine ME and the shaft generator SG can be used to produce the required power.

This saves fuel costs both on and off the sea, and reduces the frequency of equipment failures and maintenance costs. In addition, the frequency of use of the generator engine GE can be reduced, and the number of units can be reduced.

On the other hand, the multi-stage compressor (100A) is composed of a plurality of, for example, four unit compressors, BOG can be compressed to 250 to 450 bar, which is the required pressure of the main engine, through four unit compressors. The generator engine and the re-condenser are supplied with BOG compressed to 5 to 20 bar, more preferably 7 to 15 bar, through one of the unit compressors of the multi-stage compressor.

It is possible to increase the efficiency in the re-condenser by compressing the pressure of the BOG to 5 to 20 bar, more preferably 7 to 15 bar through a part of the multi-stage compressor and supplying it to the re-condenser 200.

The HP carburetor 400 can vaporize LNG by heat exchange with seawater by an open loop or a closed loop, and the system of FIG. 2 includes seawater with a heat medium such as glycol water. A closed loop system is shown in which heat exchange, heat medium circulates through the closed loop and reheats LNG by transferring heat energy from seawater through heat exchange with LNG in an HP vaporizer. Instead, it can also be configured as a system that directly transfers the heat energy of seawater to LNG through an open loop to regasify it.

In this embodiment, some of the unit compressors of the multi-stage compressor 100A, for example, BOG compressed to 50 to 100 bar through two of the four unit compressors may also be transferred to the ship through the measurement unit 500. BOG compressed through two unit compressors can be pressure-controlled with a pressure reducing valve, etc., and transported out of the board through a measurement unit. These pressure reducing valves can also act as shut down valves.

On the other hand, in the system of the present embodiment, the compressor 100B that receives and compresses BOG (Boil Off Gas) generated in the LNG storage tank, and the FG pump 900 that compresses the LNG from the LNG storage tank and compresses it in the FG pump. FG vaporizer 910 that is vaporized by receiving the high-pressure LNG is further configured.

Without driving the multistage compressor, the recondenser 200 and generator engine GE are supplied with compressed BOG from the compressor 100B, and the main engine ME is compressed through the FG pump 900 and the FG vaporizer 910 And by receiving vaporized gas, multi-stage compressors and compressors can form redundancy.

Compressors can be used without driving multistage compressors, such as when power generation is not required and BOG management is performed through a recondenser or when the regasification transfer rate to the outboard is low.

If necessary, compressed and vaporized gas may be supplied offboard through an FG pump and an FG vaporizer.

The main engine and generator engine fuel or compressed BOG that is supplied to the recondenser after compression can be supplied as fuel such as an auxiliary boiler (Aux. Boiler) or supplied on board to a gas combustion unit (GCU) for processing.

3 schematically shows a system for treating boil-off gas in a ship according to a second embodiment of the present invention.

In the second embodiment system of FIG. 3, when the vessel is a floating storage regasification unit (FSRU) that propels itself when evading, a multi-stage compressor configured in the system of the first embodiment is not installed, thereby reducing system installation cost and power consumption It is to help reduce.

As shown in FIG. 3, the multi-stage compressor is not constituted, only the compressor is configured, the recondenser and generator engine is supplied with compressed BOG from the compressor, and the main engine is compressed from the LNG storage tank through the FG pump and FG vaporizer, and Vaporized gas can be supplied.

If necessary, compressed and vaporized gas may also be supplied to the ship through the pressure regulating valve 940 through the FG pump and the FG vaporizer.

The present invention is not limited to the above embodiments, and can be variously modified or modified within a range not departing from the technical gist of the present invention, which is obvious to those skilled in the art to which the present invention pertains. Did.

T: LNG storage tank
ME: main engine
PP: propeller
S: axis
C: Clutch
SG: axial generator
GE: Generator engine
100A: multistage compressor
100B: compressor
200: recondenser
300: HP pump
400: HP carburetor
GL: glycol water circulation line
500: measuring unit
600: heat exchanger
700: Manifold
800: seawater heat exchanger
900: FG pump
910: FG vaporizer
920, 940: valve
930: FG heater
LC: LNGC
1000: HD compressor

Claims (10)

A multi-stage compressor for receiving boil off gas (BOG) generated in an LNG storage tank of a ship capable of transporting regasification offboard and compressing it through a plurality of unit compressors;
A main engine that receives compressed BOG from LNG or the multi-stage compressor and produces propulsion and electric power required for the ship;
An axial generator connected to an axial system including an axis that delivers the output of the main engine to the propeller of the ship to produce power with the output of the main engine;
A clutch separating the main engine and the shaft generator from the propeller and shaft;
A generator engine that receives the compressed BOG through LNG or a part of the unit compressor of the multi-stage compressor and produces power required for the ship; And
And a condenser that receives compressed BOG through a part of the unit compressor of the multi-stage compressor and mixes it with LNG supplied from the LNG storage tank to condense it. According to claim 1,
An HP pump that receives LNG condensed from the re-condenser and compresses it at high pressure;
An HP carburetor receiving and vaporizing compressed LNG from the HP pump; And
The evaporation gas treatment system of the ship further comprising; a measurement unit for transferring the gas vaporized in the HP vaporizer to the outside of the ship. According to claim 2,
The BOG compressed through a part of the unit compressor of the multi-stage compressor can be transported out of the ship through the measurement unit. According to claim 2,
The HP vaporizer is an open loop (close loop) or closed loop (closed loop) of the ship's evaporation gas treatment system, characterized in that to vaporize the LNG by heat exchange with seawater. According to claim 1,
The main engine is an engine supplied with BOG compressed to 250 to 450 bar, and the generator engine is an engine supplied with BOG compressed to 5 to 20 bar,
The multi-stage compressor is composed of four unit compressors, BOG compression system for the vessel, characterized in that for compressing the required pressure of the main engine. According to claim 1,
A compressor that receives and compresses BOG (Boil Off Gas) generated in the LNG storage tank;
FG pump that receives and compresses LNG from the LNG storage tank; And
Including the FG vaporizer that is vaporized by receiving the compressed high pressure LNG from the FG pump, including,
When the multi-stage compressor is not driven, the re-condenser and the generator engine may receive compressed BOG from the compressor, and the main engine may receive compressed and vaporized gas through the FG pump and FG vaporizer,
Compressed and vaporized gas via the FG pump and FG vaporizer can be supplied to the ship's evaporation gas treatment system, characterized in that. The method of claim 6,
When the ship is a floating storage regasification unit (FSRU) that propels itself when it is evacuated, the multistage compressor is not installed, the recondenser and generator engine are supplied with compressed BOG from the compressor, and the main engine is the FG The evaporation gas treatment system of the vessel, characterized in that the compressed and vaporized gas is supplied through a pump and an FG vaporizer. BOG (Boil Off Gas) generated in the LNG storage tank of a ship capable of transporting regasified gas outboard is compressed by a multi-stage compressor including a plurality of unit compressors and supplied to the main engine that produces the propulsion and electric power required for the ship. , By supplying the BOG compressed through a part of the unit compressor of the multi-stage compressor to the generator engine to produce the power required for the ship,
A shaft generator capable of producing electric power with the output of the main engine is connected to a shaft system including a shaft that delivers the output of the main engine to a propeller, and a clutch for separating the main engine and shaft generator from the propeller and shaft is provided. The main engine and the shaft generator can generate electric power even when the ship is not in propulsion,
The BOG compressed through a part of the unit compressor of the multi-stage compressor is supplied to a re-condenser and can be mixed with LNG supplied from the LNG storage tank and condensed. The method of claim 8,
Further comprising a compressor that receives and compresses BOG (Boil Off Gas) generated in the LNG storage tank,
When the multi-stage compressor is not driven, the re-condenser and the generator engine are supplied with compressed BOG from the compressor, and the main engine is supplied with fuel by compressing and vaporizing LNG from the LNG storage tank, and with the multi-stage compressor. Compressor redundancy treatment method of the vessel, characterized in that constitutes the redundancy. The method of claim 8,
BOG compressed through a part of the unit compressor of the multi-stage compressor is characterized in that it can be transferred to the outboard vessel evaporation gas treatment method.

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