KR101996283B1 - Boil-Off Gas Proceeding System and Method for Ship - Google Patents

Abstract

The present invention relates to a system and method for treating a boil-off gas of a vessel for compressing the boil-off gas and supplying it as fuel to a ship's engine and re-liquefying the remaining boil-off gas. The present invention relates to a ship's boil-off gas treatment system and method capable of safely treating the re-liquefied boil-off gas containing the oil component.
Evaporation gas treatment system of the ship according to the invention, the high-pressure gas injection engine; One or more liquefied gas storage tanks; A multistage compressor including one or more compression units and compressing the boil-off gas generated in the liquefied gas storage tank to the required fuel pressure of the high-pressure gas injection engine; Reliquefaction means compressed in the multistage compressor and supplied to fuel of the high-pressure gas injection engine to re-liquefy remaining high-pressure evaporated gas; And a reliquefaction gas storage tank for storing the reliquefaction evaporated gas liquefied by the reliquefaction means, wherein the multistage compressor is a refueling compressor, and the high pressure evaporated gas compressed by the multistage compressor flows from the multistage compressor. The oil component is included, and the reliquefied gas storage tank is characterized in that it is provided with a smaller capacity than the liquefied gas storage tank.

Description

Boil-Off Gas Proceeding System and Method for Ship

The present invention relates to a system and method for treating a boil-off gas of a vessel for compressing the boil-off gas and supplying it as fuel to a ship's engine and re-liquefying the remaining boil-off gas, more specifically, incorporating it in the compression process of the boil-off gas. The present invention relates to a ship's boil-off gas treatment system and method capable of safely treating the re-liquefied boil-off gas containing the oil component.

Liquefied Natural Gas (LNG) is obtained by liquefying natural gas containing methane as the main component at about -163 ℃ under normal pressure, and its volume is reduced to about 1/600 than that of gas. Therefore, the LNG carrier (LNG Carrier) that can be very suitable for long distance transport through the sea, which can transport LNG is used as an example.

Although LNG storage tanks of LNG carriers are insulated, there is a limit to blocking external heat, and since the external heat is continuously transferred to LNG storage tanks, LNG is continuously maintained in LNG storage tanks during LNG transportation. Boil-Off Gas (BOG) is generated by natural vaporization.

BOG is a kind of LNG loss, which is an important problem in LNG transportation efficiency, and there is a risk that the tank will be damaged when the internal pressure of the storage tank exceeds the set safety pressure due to the generation of boil-off gas in the LNG storage tank. Therefore, various methods for discharging the boil-off gas to the outside of the storage tank and treating the discharged boil-off gas have been used.

The evaporated gas discharged to the outside of the storage tank is supplied with fuel such as an engine of a ship, or re-liquefied to return to the storage tank.

In the case of applying a dual fuel combustion engine as a main propulsion device in a propulsion system of an LNG carrier, the boil-off gas generated from a storage tank can be used as the fuel of the main propulsion engine to treat the boil-off gas. Marine engines that can be used as fuels include high pressure gas injection engines such as the ME-GI engine (Man Electronic Gas Injection Engine) and low pressure gas injection engines such as the dual fuel diesel electric (DFDE) engine.

The ME-GI engine is composed of two strokes and employs a diesel cycle which injects about 300 bar of high pressure natural gas directly into the combustion chamber near the top dead center of the piston. It is composed of four strokes and adopts the Otto Cycle, which injects low pressure natural gas of about 6.5 bar to 18 bar into the combustion air inlet and compresses the piston as it rises.

In this way, the boil-off gas must be compressed and supplied according to the required pressure required by the engine in order to supply the fuel of the engine. The compressed boil-off gas is supplied to the engine fuel from the boil-off gas compressed in the compressor and the remaining compressed boil-off gas is reliquefied. Partial Re-liquefaction System (PRS) can be applied together with the recovery tank.

In order to liquefy the gas, it is possible to use the Joule-Thomson effect that compresses the gas to a critical pressure and causes a phase change to a liquid or adiabatic expansion of the gas from a high pressure to a low pressure, thereby lowering the temperature of the gas. In order to increase the reliquefaction efficiency, it can be said that it is preferable to compress the boil-off gas to a high pressure.

In order to compress the boil-off gas at high pressure, a multi-stage compressor including a plurality of compression parts and a cooling part may be used to compress the boil-off gas in multiple stages.

In the case of a multistage compressor of three or more stages, for example, a five-stage compressor including five compression units (cylinders) to compress the evaporated gas through five stages of compression, the three front end compression units are oil-free. While the latter two compression units operate in an oil-lubricated manner, which increases the pressure of the fluid toward the rear end, which increases the risk of abrasion of the piston ring of the cylinder. This is to supply lubrication oil to the cylinder.

Therefore, when the compressed boil-off gas is discharged in four or more stages using such a multi-stage compressor, the compressed boil-off gas may include a lubricating oil component and is introduced into the rear stage process with the lubricating oil component included.

In order to re-liquefy the boil-off gas, it can be introduced into a heat-exchange means for cooling the boil-off gas compressed at high pressure and an expansion means for adiabatic expansion. The foreign matter enters the heat-transfer means, the expansion means, and the pipe for transferring the boil-off gas. Can lead to blockage.

Since the high pressure evaporated gas is cooled in the heat exchange means or the expansion means, the lubricating oil component contained in the high pressure evaporated gas also increases in viscosity by cooling, thereby increasing the risk of clogging the pipe. Pipe blockage not only damages the equipment, but also creates the risk of shutting down the reliquefaction system, and also leads to a decrease in reliquefaction efficiency.

To this end, it is considered to install a separation means such as a filter for separating the lubricating oil component contained in the boil-off gas, but the lubricating oil is still in the reliquefied boil-off gas recovered in the storage tank even after passing through the separation means. It is found that this is because the performance of the filter decreases with time, and the phase separation performance in the filter or the like is significantly lowered when the evaporation gas is a high pressure.

If the liquefied liquefied gas is recovered into the storage tank with the lubricating oil component contained therein, not only does the storage tank be damaged by the high viscosity lubricating oil component or the frozen lubricating oil component due to the cold heat of the boil-off gas, but also the storage tank. It degrades the quality by polluting the liquefied natural gas stored in the tank. For this reason, ship owners and shippers do not prefer to recover the reliquefied boil-off gas containing lubricating oil into the storage tank, and it is urgent to develop a system to solve this problem.

Accordingly, an object of the present invention is to solve the problems recognized as described above, that is, the evaporation of a vessel that compresses the boil-off gas and supplies it as fuel to the ship's engine and re-liquefies and processes the remaining boil-off gas. To provide a gas treatment system and method, and in particular, to provide a ship's boil-off gas treatment system and method that can safely process the re-liquefied boil-off gas containing the oil component incorporated in the compression process of the boil-off gas.

According to an aspect of the present invention for achieving the above object, a high-pressure gas injection engine; One or more liquefied gas storage tanks; A multistage compressor including one or more compression units and compressing the boil-off gas generated in the liquefied gas storage tank to the required fuel pressure of the high-pressure gas injection engine; Reliquefaction means compressed in the multistage compressor and supplied to fuel of the high-pressure gas injection engine to re-liquefy remaining high-pressure evaporated gas; And a reliquefaction gas storage tank for storing the reliquefaction evaporated gas liquefied by the reliquefaction means, wherein the multistage compressor is a refueling compressor, and the high-pressure evaporated gas compressed by the multistage compressor flows from the multistage compressor. The liquefied gas storage tank is provided, wherein the reliquefied gas storage tank is provided with a smaller capacity than the liquefied gas storage tank is provided.

Preferably, the multi-stage compressor includes at least four compression units to compress the boil-off gas in at least four stages or more.

Preferably, the high pressure evaporated gas compressed in the multistage compressor may be 100 bar to 400 bar or 150 bar to 300 bar.

Preferably, the reliquefied gas storage tank is provided in the hull and may be provided in the membrane type or C-Type and on the deck of the ship.

Preferably, the reliquefied boil-off gas stored in the reliquefied gas storage tank may be supplied to the fuel of the high-pressure gas injection engine when the level of the liquefied gas stored in the liquefied gas storage tank is lower than or equal to a set value.

Preferably, the rear end of the multi-stage compressor; oil separation means for filtering the oil component mixed in the high-pressure evaporation gas; may be further provided.

Preferably, the reliquefaction means, the heat exchanger for cooling the high-pressure evaporated gas by heat-exchanging the high-pressure evaporated gas and the evaporated gas supplied to the multi-stage compressor; And expansion means for adiabatic expansion of the high-pressure evaporated gas cooled by the heat exchanger, wherein the expansion liquid is connected to the reliquefied gas storage tank, and the liquefied reliquefied evaporated gas passes through the expansion means. Re-liquefied gas transfer line to be transferred to the liquefied gas storage tank; may further include.

Preferably, the reliquefaction means further includes a gas-liquid separator for gas-liquid separation of the gas-liquid mixture generated while passing through the expansion means, wherein the re-liquefaction evaporated gas separated from the gas-liquid separator is the re-liquefaction gas. The gaseous non-reliquefied boil-off gas, which is transferred to the storage tank and separated from the gas-liquid separator, may be joined to the front of the heat exchanger.

According to another aspect of the present invention for achieving the above object, at least one liquefied gas storage tank; A primary compressor including one or more compression units and compressing the boil-off gas generated in the liquefied gas storage tank to the required fuel pressure of the propulsion engine; A secondary compressor for further compressing the compressed boil-off gas compressed in the primary compressor above a critical pressure; Reliquefaction means for reliquefying the high pressure boil-off gas compressed in the secondary compressor; And a reliquefaction gas storage tank for storing the reliquefaction evaporated gas liquefied by the reliquefaction means, wherein the secondary compressor is a lubricated compressor, and the secondary high pressure gas is compressed in the secondary compressor. The oil component introduced from the compressor is included, wherein the reliquefied gas storage tank is provided with a smaller capacity than the liquefied gas storage tank, there is provided a vessel boil-off gas treatment system.

Preferably, the primary compressor may compress the boil-off gas to 6.5 bar to 18 bar.

Preferably, the secondary compressor may compress the boil-off gas to 60 bar or more.

Preferably, the re-liquefied gas storage tank is provided in the hull and provided in the membrane type, or C-Type may be provided on the deck of the ship.

Preferably, the engine receiving the compressed boil-off gas compressed by the primary compressor as a fuel, and the secondary compressor may further compress the remaining compressed boil-off gas supplied to the engine.

Preferably, the reliquefied boil-off gas stored in the reliquefied gas storage tank may be supplied to the fuel of the engine when the level of the liquefied gas stored in the liquefied gas storage tank is lower than or equal to a set value.

Preferably, an oil separation means for filtering the oil component mixed with the high-pressure boil-off gas at the rear end of the secondary compressor may be further provided.

Preferably, the reliquefaction means, the heat exchanger for cooling the high-pressure evaporated gas by heat-exchanging the high-pressure evaporated gas and the evaporated gas supplied to the primary compressor; And expansion means for adiabatic expansion of the high pressure evaporated gas cooled by the heat exchanger, wherein the reliquefied boil-off gas passing through the expansion means is connected to the expansion means and the reliquefied gas storage tank. Re-liquefied gas transfer line to be transferred to the tank; may further include.

Preferably, the gas-liquid separator for gas-liquid separation of the gas-liquid mixture generated while passing through the expansion means, wherein the liquid liquefied evaporated gas separated from the gas-liquid separator is transferred to the re-liquefied gas storage tank, The gaseous non-reliquefied boil-off gas separated in the gas-liquid separator may be joined to the front of the heat exchanger.

In addition, according to another aspect of the present invention for achieving the above object, during full ship operation of the vessel, by compressing the boil-off gas generated in the liquefied gas storage tank to supply the fuel of the engine, the fuel of the engine The remaining compressed boil-off gas is re-liquefied and recovered into a separate tank for storing re-liquefied gas, and when the ballast of the vessel is operated, the re-liquefied boil-off gas stored in the tank for storing the re-liquefied gas is supplied as the fuel of the engine. However, the reliquefied boil-off gas stored in the tank for storing the re-liquefied gas is provided with a fuel supply method of the ship, containing the oil component mixed while compressing the boil-off gas.

Preferably, the vessel is provided with a high-pressure gas injection engine as a propulsion engine, the boil-off gas generated in the liquefied gas storage tank is compressed to 100 bar to 400 bar to supply the fuel of the high-pressure gas injection engine, the high pressure The high-pressure evaporated gas remaining after supplying the fuel of the gas injection engine is re-liquefied to be recovered to the reliquefied gas storage tank, and the evaporated gas may be compressed at least four stages by supplying a lubricating oil to the compressor.

Preferably, the vessel is provided with a low pressure gas injection engine as a propulsion engine, the boil-off gas generated in the liquefied gas storage tank is compressed to 6.5 bar to 18 bar to supply the fuel of the low pressure gas injection engine, the low pressure The remaining compressed boil-off gas supplied as a fuel of the gas injection engine may be further compressed to a high pressure of 60 bar or more, and then re-liquefied to recover the re-liquefied gas storage tank.

Preferably, the reliquefaction of the high pressure evaporated gas comprises heat-exchanging the high pressure evaporated gas containing the oil component and the evaporated gas to be compressed to cool the high pressure evaporated gas, and adiabatic expansion of the cooled high pressure evaporated gas to liquefy. The reliquefied boil-off gas may be recovered to the tank for storing the reliquefied gas.

Preferably, the liquefied boil-off gas may be gas-liquid separated, and the separated gas may be joined to the boil-off gas to be heat exchanged with the high-pressure boil-off gas, and the separated liquid may be recovered to the re-liquefied gas storage tank.

Preferably, the reliquefied gas storage tank is a C-type storage tank provided on the membrane-type storage tank or deck provided in the hull, it can be provided with a smaller capacity than the liquefied gas storage tank. .

The system and method for treating a boil-off gas in accordance with the present invention may compress the boil-off gas generated in a vessel's liquefied gas storage tank and supply it as fuel to a ship's engine and re-liquefy the remaining boil-off gas to recover the engine. It can be applied regardless of the type.

In addition, according to the present invention, it is possible to safely treat the re-liquefied evaporated gas containing the oil component mixed in the compression process of the boil-off gas, it is possible to prevent damage to the storage tank or contamination of the liquefied gas, which is high from the owner or shipper Reliability can be secured.

In addition, by recovering the re-liquefied evaporated gas containing the oil component as the fuel of the engine can not waste the evaporated gas, it is possible to stably supply the liquefied gas fuel to the engine during the ballast voyage (Ballast Voyage) of the vessel.

1 and 2 are views schematically showing the configuration of the boil-off gas treatment system according to a first embodiment of the present invention.
3 and 4 are views schematically showing the configuration of the boil-off gas treatment system according to the second embodiment.

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 which illustrate 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 numerals to the components of each drawing, it should be noted that the same reference numerals are denoted by the same reference numerals as much as possible even if displayed on different drawings.

In the following examples, a case of Liquefied Natural Gas (LNG) will be described as an example, but the present invention can be applied to various Liquefied Gases, and the following Examples can be modified in various other forms. The scope of the present invention is not limited to the following examples.

In the following embodiments, the fluid flowing through each flow path may be in a gaseous state, a gas-liquid mixed state, a liquid state, or a supercritical fluid state, depending on the operating conditions of the system.

In addition, the following embodiments may be applied to a ship or offshore structure, for example, LNG carrier (LNG Carrier) for transporting liquefied natural gas as a cargo, LNG Floating Storage with a storage tank for storing liquefied natural gas A liquefied gas storage tank, such as a Regasification Unit, LNG Floating Production Storage Offloading (FPSO), or LNG Regasification Vessel (RV RV), is available and can be applied to any ship or offshore structure that has an engine supplied with liquefied gas as fuel.

Therefore, the present invention can be applied to any ship that is provided with a propulsion engine supplied with liquefied natural gas as fuel and has a propulsion force by the engine or can generate and use electric power by driving the engine.

Hereinafter, the boil-off gas treatment system according to the present invention will be described by taking an example of being applied to an LNG carrier that carries LNG.

1 and 2 are schematic diagrams illustrating a system for treating boil-off gas in accordance with a first embodiment of the present invention. Hereinafter, a system and method for treating boil-off gas in accordance with a first embodiment of the present invention will be described with reference to FIGS. 1 and 2.

The boil-off gas treatment system according to the first embodiment of the present invention, the high-pressure gas injection engine (ME) provided in the LNG carrier, one or more liquefied gas storage tank 10 for storing LNG, at least one compression unit High-pressure gas among the high-pressure boil-off gas compressed by the multistage compressor 30 and the multistage compressor 30 to compress the boil-off gas generated in the liquefied gas storage tank 10 to high pressure to satisfy the fuel demand pressure of the high-pressure gas injection engine ME. Re-liquefaction means for re-liquefying the remaining high-pressure evaporated gas supplied to the fuel of the injection engine (ME), Re-liquefied gas storage tank (11a, 11b) for storing the re-liquefied re-liquefied evaporated gas in the reliquefaction means Include.

The LNG carrier may be stored as cargo in the liquefied gas storage tank 10 provided with at least one LNG at the production site, transported to the destination, and returned after unloading the LNG from the destination to the demand destination. In addition, the boil-off gas generated from the LNG stored in the liquefied gas storage tank 10 may be supplied as a fuel, such as a propulsion engine of the LNG carrier described later, a power generation engine for generating electric power, or a boiler for producing steam.

The liquefied gas storage tank 10 may be provided in one or more LNG carriers, in this embodiment four liquefied gas storage tank 10 is provided, the liquefied gas storage tank 10 is shown in Figures 1 and 2 As one example, the four will be provided in the hull as a membrane type (Membrane Type) will be described as an example. However, the present invention is not limited thereto, and a storage tank of a suitable type may be provided in an appropriate number according to the type or size of the ship, and the present invention may be applied without being limited thereto.

In this embodiment, the high-pressure gas injection engine (ME) may be a ME-GI engine (MAN Electronic Gas-Injection Engine), the ME-GI engine (ME) is about 100 bar to 400 bar, preferably 150 The high pressure boil-off gas compressed to bar to 300 bar may be supplied as a fuel and driven.

In addition, the multi-stage compressor 30 includes one or more compression units and a cooling unit to compress the boil-off gas into multiple stages, and the cooling units are respectively provided at one or more stages of the one or more compression units to cool the compressed boil-off gas whose temperature has risen by compression. .

The compression unit may be a reciprocating compressor that compresses gas by using the reciprocating motion of the piston in the cylinder, and the cooling unit may cool the compressed boil-off gas by using sea water or fresh water.

In the present embodiment, the multi-stage compressor 30 includes at least four compression units, and compresses the boil-off gas into four or more stages, thereby compressing the high-pressure boil-off gas of about 150 bar to 300 bar, which is the fuel condition of the ME-GI engine (ME). 1 and 2, it may be a five-stage compressor for compressing the evaporation gas five stages including five compression units. However, the number of stages of the multistage compressor 30 is not limited thereto and may vary according to the target pressure of the boil-off gas.

That is, in this embodiment, the boil-off gas generated in the liquefied gas storage tank 10 connects the multi-stage compressor 30 and the ME-GI engine ME from the liquefied gas storage tank 10 and transfers the boil-off gas to the engine. The high pressure compressed in the five-stage compressor 30 to the fuel of the ME-GI engine (ME) can be supplied to the fuel of the ME-GI engine (ME) in the five-stage compressor 30 along the supply line (FL) The boil-off gas may be a supercritical fluid.

The five-stage compressor 30 of this embodiment operates by lubrication lubrication to compress the boil-off gas to a high pressure of 100 bar or more. Preferably, the first to third compression units operate by lubrication-free lubrication, and the fourth compression unit. And the fifth compression unit is operated by lubrication, and lubrication is performed for lubrication and cooling to prevent wear of the cylinder and piston and to prevent overheating.

Therefore, the high-pressure boil-off gas compressed in the five-stage compressor 30 of the present embodiment may be discharged in a state in which the lubricating oil component is mixed.

In this embodiment, the excess high-pressure evaporated gas containing the lubricating oil component remaining after being supplied as fuel of the ME-GI engine (ME) among the high-pressure evaporated gas compressed by the multistage compressor (30) is the fuel at the rear end of the multistage compressor (30). The liquid may be reliquefied in the reliquefaction means along the reliquefaction line RL branched from the supply line FL and may be recovered to the reliquefied gas storage tanks 11a and 11b.

The reliquefied gas storage tank 10 of the present embodiment reliquefies a high-pressure boil-off gas containing a lubricant component, which is supplied as fuel of the ME-GI engine (ME) among the high-pressure boil-off gases compressed by the multi-stage compressor 30. And to store the reliquefaction evaporated gas containing the lubricating oil component. In addition, the reliquefied boil-off gas including the lubricating oil component stored in the reliquefied gas storage tanks 11a and 11b of the present embodiment may be supplied as a fuel of the ME-GI engine ME.

That is, according to the present embodiment, the high-pressure evaporated gas remaining after being compressed by the multi-stage compressor 30 and supplied as fuel of the ME-GI engine ME is burned by a gas combustor (GCU; Gas Combustion Unit (not shown)) or the like. Or by re-liquefying and recovering the re-liquefied evaporated gas containing the lubricating oil component to the liquefied gas storage tank 10 as a fuel in the separate re-liquefied gas storage tank (11a, 11b), thereby incinerating the evaporated gas The quality of the liquefied gas may not be wasted, and the liquefied gas storage tank 10 may be recovered as a cargo to contaminate the liquefied gas storage tank 10 and the liquefied gas, or the liquefied gas storage tank 10 may be deteriorated. It can be used effectively because it can not be.

Re-liquefied gas storage tank (11a, 11b) of this embodiment is provided in the hull, as shown in Figure 1 may be installed as a tank of tank type, as shown in Figure 2, provided on the deck of the ship It can also be installed as a C-type tank, ie a pressure vessel.

However, it is preferable that the reliquefied gas storage tanks 11a and 11b have a capacity smaller than that of one of the liquefied gas storage tanks 10.

For example, when the LNG carrier has a capacity of 170k, 1 to 4 liquefied gas storage tanks 10 may be provided in the LNG carrier, and 170k class LNG carriers may be loaded in one or more liquefied gas storage tanks 10. The total amount of liquefied gas that can be used is about 170,000 m ³ , whereby the reliquefied gas storage tanks 11a and 11b are about 500 m ³ to 3,000 m ³ , preferably about 500 m ³ to 2,000 m ³ , more preferably about 700 m. ³ to it is sufficient provided that the capacity of 1,200m ^3.

That is, the reliquefied gas storage tank (11a, 11b) may be provided with a capacity of about 50 times or more, preferably about 30 times or more, more preferably 10 times or more of the liquefied gas storage tank 10, Therefore, in order to install the reliquefied gas storage tanks 11a and 11b, there is less burden due to the space constraints in securing additional space or arranging the reliquefied gas storage tanks 11a and 11b.

In this embodiment, the reliquefaction means includes a heat exchanger 20 for cooling the high pressure evaporated gas compressed in the multistage compressor 30 and introduced into the reliquefaction line RL, and the high pressure evaporated gas cooled in the heat exchanger 20. It comprises an expansion means (40) for lowering the pressure, preferably, by adiabatic expansion to lower the temperature.

In the heat exchanger 20 of the present embodiment, the high-pressure evaporated gas introduced into the reliquefaction line RL and discharged from the storage tanks 10, 11a and 11b are introduced into the multistage compressor 30 along the fuel supply line FL. The low pressure boil-off gas to be exchanged, and the high pressure boil-off gas is cooled by cold heat of the low pressure boil-off gas.

That is, the low pressure evaporated gas discharged after the heat exchange from the heat exchanger 20 is supplied to the multistage compressor 30 in a state in which the temperature is elevated after the cooling heat is recovered, and the high pressure evaporated gas discharged after the heat exchange is expanded in the cooled state ( 40).

In addition, the high pressure evaporated gas supplied to the heat exchanger 20 may be in a supercritical state.

The expansion means 40 of the present embodiment is a means for lowering the temperature of the high pressure evaporated gas cooled by the heat exchanger 20, preferably by adiabatic expansion to lower the temperature of the high pressure evaporated gas by expansion and liquefying it. Expander) or Joule-Thomson Valve. 1 and 2, the Joule-Thompson valve is provided as the expansion means 40 as an example.

The boil-off gas passing through the expansion means 40 is reliquefied gas storage tanks 11a and 11b through the reliquefied gas transfer line LL connecting the expansion means 40 to the reliquefied gas storage tanks 11a and 11b. In other words, according to the present embodiment, the reliquefied boil-off gas containing oil components such as lubricating oil is recovered to separate reliquefied gas storage tanks 11a and 11b.

The reliquefaction means according to the present embodiment, as shown in Figures 1 and 2, may further include a gas-liquid separator 50 for gas-liquid separation of the evaporated gas passed through the expansion means (40).

The boil-off gas passing through the expansion means 40 may be a gas-liquid mixture at least partially liquefied and may be gas-liquid separated in the gas-liquid separator 50, and the oil may be contained in the liquid reliquefied boil-off gas separated in the gas-liquid separator 50. The components may be included and recovered to the reliquefied gas storage tanks 11a and 11b as described above.

In addition, the non-reliquefied uncondensed boil-off gas in the gas state separated by the gas-liquid separator 50 is connected to the fuel supply line FL from the top of the gas-liquid separator 50 along the fuel supply line GL. FL, more specifically, may be joined to the front end of the heat exchanger 20. That is, the re-liquefied boil-off gas in the gas state separated from the gas-liquid separator 50 may be supplied to the multi-stage compressor 30 after cold heat is recovered from the heat exchanger 20.

In addition, the boil-off gas treatment system according to the present embodiment, the oil separation means (OS) capable of filtering oil components or foreign substances, such as lubricating oil mixed in the high-pressure boil-off gas compressed by the multi-stage compressor (30) is a multi-stage compressor (30) And a fuel supply line FL between the ME-GI engine ME.

The oil separation unit OS may be provided to have a shape capable of removing solids contained in the fluid, such as a filter or a strainer. In this embodiment, the strainer may be provided as shown in FIGS. 1 and 2. It will be described taking as an example an example.

In addition, the oil separation means OS may be provided in the fuel supply line FL and the reliquefaction line RL may be branched after the oil separation means OS, as shown in FIGS. 1 and 2. Or, although not shown in the drawings, the oil separation means OS may be provided on the reliquefaction line RL, and at least one may be provided in each of the fuel supply line FL and the reliquefaction line RL. Of course you can.

That is, the high-pressure boil-off gas compressed in the multi-stage compressor 30 is introduced into the oil separating means (OS) to remove solid foreign substances such as oil components contained in the high-pressure boil-off gas, and then the ME-GI engine (ME) and the reliquefaction line. Supplied as (RL).

However, the oil separation means (OS) such as a strainer or a filter is a means for physically filtering the solid foreign matter, so it is necessary to periodically clean or replace, otherwise the filter is clogged, the resistance is increased and the separation performance is lowered.

In addition, since the oil component contained in the high pressure evaporation gas may affect various devices, it is preferable to separate and remove the oil component before it is introduced into the reliquefaction means. In other words, the separation is not easy because it may be in the form of a fluid having a high viscosity and not a low enough temperature to form a particle.

In addition, the high-pressure evaporated gas discharged from the multi-stage compressor 30 is a high pressure of about 300 bar or more, so that a trip may occur due to high pressure. When the high pressure is higher than the critical pressure, that is, the fluid is in a supercritical state, the solid may be filtered. Separation efficiency is low.

Therefore, even if the oil separating means OS is provided at the rear stage of the multistage compressor 30 operating by lubrication lubrication, it is difficult to completely remove the oil component entrained in the high pressure evaporated gas introduced into the reliquefaction means, and reliquefaction evaporation. In the gas, the oil component is recovered in a mixed state.

According to the present invention, an oil component is mixed in the reliquefied evaporated gas, and the ash containing the oil component is recovered by separate reliquefied gas storage tanks 11a and 11b without being recovered into the liquefied gas storage tank 10. The problem that the liquefied boil-off gas is recovered to the liquefied gas storage tank 10 can be prevented.

The boil-off gas treatment system according to the present embodiment may further include a re-liquefied gas fuel supply line RF for supplying the re-liquefied boil-off gas stored in the re-liquefied gas storage tanks 11a and 11b as a fuel of the engine. .

That is, the reliquefied boil-off gas stored in the reliquefied gas storage tanks 11a and 11b may be supplied as an engine fuel of a ship. Here, the engine receiving the reliquefied evaporated gas as fuel may be a high-pressure gas injection engine (ME), which is the main propulsion engine described above, or may be other engines capable of receiving natural gas such as a power generation engine or a boiler. In this embodiment, it will be described taking as an example to supply the fuel of the propulsion engine (ME).

The reliquefied gas fuel supply line RF may be connected to the fuel supply line FL from the reliquefied gas storage tanks 11a and 11b as illustrated in FIGS. 1 and 2. Or it may be arranged in a separate line, it is preferable to use the multi-stage compressor 30 of the fuel supply line (FL) by supplying to the fuel supply line (FL).

The reliquefied boil-off gas stored in the reliquefied gas storage tanks 11a and 11b may be supplied as a fuel of the engine ME during the ship's collinear operation (ballast operation).

At the time of full-scale operation of the LNG carrier, the amount of generated evaporated gas from the liquefied gas storage tank 10 is sufficient, and if necessary, the liquefied gas stored in the liquefied gas storage tank 10 is converted into a forced vaporizer (not shown) and a high pressure pump (not shown). The compressed and vaporized forced vaporized gas may be supplied as a fuel, but the LNG carrier may be liquefied gas stored in the liquefied gas storage tank 10 after unloading the liquefied gas stored in the destination. The level of the liquefied gas stored in the tank 10 is below a certain level and the amount of generated boil-off gas is little or less than the fuel demand.

Therefore, in the present embodiment, when liquefied gas as well as liquefied gas can not be supplied as fuel from the liquefied gas storage tank 10, such as the ship's collinear operation or the water level of the liquefied gas storage tank 10 is below a certain level, The reliquefied boil-off gas stored in the gas storage tanks 11a and 11b may be supplied as a fuel of the engine ME.

When fuel is supplied from the reliquefied gas storage tanks 11a and 11b to the ME-GI engine ME, the reliquefied gas storage tank 11a as well as the evaporated gas naturally vaporized in the reliquefied gas storage tanks 11a and 11b. , 11b) may be supplied by compressing the forced vaporized gas obtained by forcibly vaporizing the reliquefied vaporized gas.

The boil-off gas naturally vaporized in the reliquefied gas storage tanks 11a and 11b supplies the boil-off gas to the multistage compressor 30 through the reliquefied gas fuel supply line RF and is required by the ME-GI engine ME. It can be supplied by compressing to a pressure, that is, about 100 bar to 400 bar, more preferably 150 bar to 300 bar, and may be branched to the reliquefaction line RL remaining after the fuel supply.

In addition, a forced vaporizer (not shown) for forcibly vaporizing the reliquefied boil-off gas stored in the reliquefied gas storage tank (11a, 11b), the temperature of the forced vaporized gas vaporized in the forced vaporizer to supply fuel to the ME-GI engine (ME) Temperature control means (not shown) for adjusting to the conditions and pressure control means (not shown) for adjusting the pressure may be further provided, and the forced vaporizer for reliquefied boil-off gas stored in the reliquefied gas storage tank (11a, 11b) It can also be supplied as ME-GI engine (ME) propulsion fuel when the ship is in line with the ship.

The pressure regulating means may utilize the multistage compressor 30 as a pressure regulating means by forcibly vaporizing the reliquefied evaporated gas in a forced vaporizer and then supplying and compressing the forced vaporized gas to the multistage compressor 30, or the forced vaporizer. At the front end, a high pressure pump (not shown) for compressing the liquid reliquefied evaporated gas in accordance with the fuel supply conditions of the engine ME may be further provided, and the high pressure pump may be used as a pressure regulating means.

In addition, the forced vaporizer, the pressure regulating means and the temperature regulating means may be provided separately to forcibly vaporize the reliquefied boil-off gas stored in the reliquefied gas storage tank (11a, 11b) to supply to the ME-GI engine (ME) or For example, the liquefied gas stored in the liquefied gas storage tank 10 may be supplied by utilizing the gas provided to forcibly supply the liquefied gas as the fuel of the ME-GI engine ME.

3 and 4 is a schematic view showing a boil-off gas treatment system of a ship according to a second embodiment of the present invention. 3 and 4, an evaporation gas treatment system and method of a ship according to a second embodiment of the present invention will be described.

This embodiment, compared with the first embodiment described above, is applied to the propulsion engine (ME) to be applied, a compressor including at least one compression unit for compressing the boil-off gas, the forced vaporization gas to supply the fuel of the propulsion engine (ME) There are some differences in the means, and the first embodiment described above may be referred to even if the detailed description is omitted for the remaining members.

A boil-off gas treatment system according to a second embodiment of the present invention includes a propulsion engine (ME) of an LNG carrier, one or more liquefied gas storage tanks 10 for storing LNG, and one or more compression units, and a liquefied gas storage tank. The compressed compressor boil-off gas compressed in the primary compressor 31 and the primary compressor 31 to compress the boil-off gas generated in (10) to satisfy the fuel demand pressure of the propulsion engine ME is further than the critical pressure of the boil-off gas. And a secondary compressor 32 to compress.

In this embodiment, the compressed boil-off gas compressed in the primary compressor 31 is supplied as fuel of the propulsion engine ME, and the secondary compressor 32 is supplied as fuel of the propulsion engine ME and the remaining compression evaporation is performed. The gas is further compressed to high pressure.

In addition, the boil-off gas treatment system according to the present embodiment, the re-liquefaction means for re-liquefying the high-pressure boil-off gas compressed by the secondary compressor 32 and the separate liquid for storing the re-liquefied re-liquefaction evaporated gas in the re-liquefaction means Re-liquefied gas storage tank (11a, 11b) is further included.

One or more liquefied gas storage tank 10 may be provided in a ship to which the present embodiment is applied, and in this embodiment, four liquefied gas storage tanks 10 are provided, as shown in FIGS. 3 and 4. It will be described taking an example provided in the hull as a membrane type (Membrane Type). However, it is not limited thereto.

In this embodiment, the propulsion engine (ME) is a DF engine (Dual Fuel Engine), which is a low pressure gas injection engine, and supplies as a fuel the boil-off gas compressed to about 3 bar to 45 bar, preferably about 6.5 bar to 18 bar. It may be a dual fuel diesel electric (DFDE) engine or an eXtra long stroke Duel fuel (X-DF) engine.

The primary compressor 31 and the secondary compressor 32 of this embodiment include one or more compression units and a cooling unit to compress the boil-off gas, and the cooling unit cools the compressed boil-off gas whose temperature rises by compression at the rear end of the compression unit. You can. The compression unit may be a reciprocating compressor that compresses the gas by using the reciprocating motion of the piston in the cylinder, and the cooling unit may cool the compressed boil-off gas by using sea water or fresh water.

The primary compressor 31 may include one or more compression units to compress the boil-off gas in one stage or multiple stages under the fuel condition of the DF engine ME, and may operate with oil-free lubrication. In the present embodiment, the primary compressor 31 may be provided as a two-stage compressor 31 including two compression units, as shown in FIGS. Compression to ME) fuel conditions.

The secondary compressor 32 of the present embodiment connects the liquefied gas storage tank 10, the primary compressor 31, and the DF engine ME, and the boil-off gas is discharged from the liquefied gas storage tank 10 to form a primary pressure. It may be provided on the reliquefaction line RL branched from the fuel supply line FL to be compressed in the compressor 31 and supplied to the DF engine ME, and in the primary compressor 31, the DF engine ME. After compressed to the fuel condition of the DF engine (ME) is supplied to the fuel can be further compressed to the compressed boil-off gas remaining at high pressure.

The secondary compressor 32 may include one or more compression units and a cooling unit, and may be provided as a multistage compressor for compressing the evaporated gas into multiple stages, the compression unit may be provided as a reciprocating compressor, and the cooling unit may include one or more compression units. The compressed boil-off gas, which is provided at the rear end and whose temperature is increased by compression, can be cooled by using sea water or fresh water.

In addition, the secondary compressor 32 may compress the compressed boil-off gas compressed in the fuel condition of the DF engine ME in the primary compressor 31 to a critical pressure or more, and may operate with oil supply lubrication. Lubrication is carried out for the purpose of lubrication and cooling to prevent wear of the cylinder and piston and to prevent overheating. In the present embodiment, the secondary compressor 32 may include three compression units to compress the boil-off gas at high pressure over three stages, as shown in FIGS. 3 and 4, and may be compressed in the secondary compressor 32. The high pressure evaporated gas may be a supercritical fluid.

In the present embodiment, the number of compression units and cooling units of the primary compressor 31 and the secondary compressor 32 is not particularly limited, and the primary compressor 31 may include a DF engine supplied with a low pressure gas fuel ( ME), and the second compressor 32 provides the boil-off gas compressed by the primary compressor 13 at the rear end of the secondary compressor 32. It can be provided with a high pressure enough to be able to re-liquefy in the re-liquefaction means, preferably a stage capable of compressing above the critical pressure of the boil-off gas.

3 and 4, the secondary compressor 32 is illustrated as being provided on the reliquefaction line RL branched from the fuel supply line FL, but is not limited thereto. ) And one or more compression units of the secondary compressor 32 are provided as one compression unit on the fuel supply line FL as in the first embodiment described above, and the reliquefaction line RL is 1. The pressure of the compression unit included in the secondary compressor 31, that is, the boil-off gas discharged from the compression unit may be provided so as to branch at the rear end of the compression unit that satisfies the fuel condition of the DF engine ME. However, the post compression stage (secondary compressor) after branching requires lubricating oil and is operated by lubricating oil.

Therefore, the high pressure boil-off gas compressed by the secondary compressor 32 of the present embodiment may be discharged in a state in which the lubricating oil component is mixed.

In this embodiment, the high-pressure evaporated gas containing the lubricating oil component while being compressed in the secondary compressor 32 is liquefied by the reliquefaction means along the reliquefaction line RL to the reliquefaction gas storage tanks 11a and 11b. Can be recovered. In addition, the reliquefied boil-off gas including the lubricating oil component stored in the reliquefied gas storage tanks 11a and 11b may be supplied as a fuel of the DF engine ME.

Accordingly, the remaining compressed boil-off gas supplied from the primary compressor 31 to the fuel of the DF engine ME among the compressed boil-off gas compressed under the fuel condition of the DF engine ME is branched to the reliquefaction line RL. The high pressure evaporated gas containing the lubricating oil component mixed while being supplied to the secondary compressor 32 operated by lubrication lubrication, compressed to a high pressure above the critical pressure in the secondary compressor 32 and then compressed in the secondary compressor 32 Is supplied to the reliquefaction means for reliquefaction, and the reliquefaction evaporated gas containing the lubricating oil component is stored in the reliquefaction gas storage tanks 11a and 11b and the reliquefaction gas stored in the reliquefaction gas storage tanks 11a and 11b. Can be fueled by a DF engine.

That is, according to the present embodiment, the secondary compressor 32 does not waste the compressed boil-off gas, which is compressed by the primary compressor 31 and supplied as fuel of the DF engine ME, by burning in a gas combustor or the like to be processed. Can be recovered by compressing it to a critical pressure or more in the above, except that the reliquefied boil-off gas in which the lubricating oil is mixed while being compressed in the secondary compressor 32 is not recovered to the liquefied gas storage tank 10. By recovering as a fuel to the gas storage tank (11a, 11b), the reliquefied evaporated gas is recovered as a cargo to the liquefied gas storage tank 10 to contaminate the liquefied gas storage tank (10) and liquefied gas to deteriorate the quality, The liquefied gas evaporation gas can be effectively utilized without damaging the liquefied gas storage tank 10.

The reliquefied gas storage tanks 11a and 11b of this embodiment may be installed in the hull as a membrane type tank, as shown in FIG. 3, and as shown in FIG. 4, a C-Type, that is, a pressure vessel. It may be installed on the deck of the ship. However, the reliquefied gas storage tanks (11a, 11b) is preferably provided to have a smaller capacity than the capacity of one of the liquefied gas storage tank (10), and thus to further installation of the reliquefied gas storage tank (11a, 11b) There is little spatial constraint. Since the reliquefied gas storage tanks 11a and 11b of the present embodiment may be applied in the same manner as the reliquefied gas storage tanks 11a and 11b of the first embodiment, detailed descriptions thereof will be omitted.

In the present embodiment, the reliquefaction means lowers the pressure of the high pressure evaporated gas cooled in the heat exchanger 20 and the heat exchanger 20 to cool the high pressure evaporated gas compressed in the secondary compressor 32, and preferably, Expansion means 40 for thermal expansion to lower the temperature.

In the heat exchanger 20 of the present embodiment, the high-pressure evaporated gas, preferably the supercritical evaporated gas compressed in the secondary compressor 32, and the primary compressor 31 are introduced along the fuel supply line FL. The low pressure boil-off gas is heat exchanged, and the high pressure boil-off gas is cooled by cold heat of the low pressure boil-off gas.

That is, the low pressure evaporated gas discharged after the heat exchange from the heat exchanger 20 is supplied to the primary compressor 31 in a state in which the temperature rises after the cooling heat is recovered, and the high pressure evaporated gas discharged after the heat exchange is expanded in the cooled state. 40 is supplied.

The expansion means 40 is a means for liquefying the boil-off gas by lowering the temperature of the high-pressure boil-off gas cooled by the heat exchanger 20, preferably by adiabatic expansion to lower the temperature of the high-pressure boil-off gas by expansion. It may be a Joule-Thomson valve.

The boil-off gas passing through the expansion means 40 is reliquefied gas storage tanks 11a and 11b through the reliquefied gas transfer line LL connecting the expansion means 40 to the reliquefied gas storage tanks 11a and 11b. In other words, according to the present embodiment, the reliquefied boil-off gas containing oil components such as lubricating oil is recovered to separate reliquefied gas storage tanks 11a and 11b.

The reliquefaction means according to the present embodiment, as shown in Figure 3 and 4, may further include a gas-liquid separator 50 for gas-liquid separation of the evaporated gas passed through the expansion means 40, Since the expansion means 40 and the gas-liquid separator 50 have the same characteristics as those of the expansion means 40 and the gas-liquid separator 50 of the first embodiment described above, the detailed description will be omitted.

The boil-off gas passing through the expansion means 40 may be a gas-liquid mixture at least partially liquefied and may be gas-liquid separated in the gas-liquid separator 50, and the oil may be separated into the liquid re-liquefied boil-off gas separated in the gas-liquid separator 50. The components may be included and recovered to the reliquefied gas storage tanks 11a and 11b as described above.

In addition, the gaseous non-reliquefied boil-off gas separated in the gas-liquid separator 50 is connected to the fuel supply line FL from the top of the gas-liquid separator 50 along the fuel supply line FL. ), More specifically, may be joined to the front end of the heat exchanger 20. That is, the vaporized gas which has not been reliquefied in the gas state separated from the gas-liquid separator 50 may be supplied to the primary compressor 31 after the cold heat is recovered from the heat exchanger 20.

In addition, the boil-off gas treatment system according to the present embodiment, the oil separation means (OS) capable of filtering oil components or foreign substances, such as lubricating oil mixed in the high-pressure boil-off gas compressed in the primary compressor 31 is a secondary compressor ( 32 may be provided on the reliquefaction line RL between the reliquefaction means.

Alternatively, when the primary compressor 31 of the present embodiment is provided with a multistage compressor operating by oil lubrication, the oil separating means OS may be provided at the rear end of the primary compressor 31.

The oil separation unit OS may be provided to have a shape capable of removing solids contained in the fluid such as a filter or a strainer. In the present embodiment, as illustrated in FIGS. 3 and 4. It will be described taking as an example an example.

However, as described in the first embodiment described above, even when the oil separation means OS is provided, it is not easy to completely separate the oil components contained in the supercritical evaporation gas, The oil component may be recovered in a mixed state, but the liquid liquefied boil-off gas containing the oil component may be recovered by the liquefied gas storage tanks 10a and 11b instead of being recovered into the liquefied gas storage tank 10. Problems caused by the recovery to the tank 10 can be prevented.

The boil-off gas treatment system according to the present embodiment further includes a re-liquefied gas fuel supply line RF for supplying the re-liquefied boil-off gas stored in the re-liquefied gas storage tanks 11a and 11b as a fuel of the engine ME. can do.

That is, the reliquefied boil-off gas stored in the reliquefied gas storage tanks 11a and 11b may be supplied to the engine (ME) fuel of the ship. Here, the engine receiving the reliquefied evaporated gas as fuel may be a DF engine (ME), that is, the main propulsion engine described above, that is, a low pressure gas injection engine, and may receive a natural gas such as a power generation engine or a boiler as fuel. Although other engines may be used, the present embodiment will be described by taking the fuel of the propulsion engine ME as an example.

The reliquefied gas fuel supply line RF may be connected to the fuel supply line FL from the reliquefied gas storage tanks 11a and 11b as illustrated in FIGS. 3 and 4. Alternatively, it may be arranged in a separate line, it is preferable to use the heat exchanger 20 and the primary compressor 31 of the fuel supply line (FL) by supplying to the fuel supply line (FL) as shown in FIG. Do.

As described in the first embodiment, the reliquefied gas stored in the reliquefied gas storage tanks 11a and 11b may be stored in a liquefied gas such as a ship collinear operation or a water level of the liquefied gas storage tank 10 is lower than a predetermined level. When the liquefied gas as well as the boil-off gas from the tank 10 cannot be supplied as fuel, the re-liquefied boil-off gas stored in the re-liquefied gas storage tanks 11a and 11b can be supplied as the fuel of the engine ME.

In addition, when fuel is supplied from the reliquefied gas storage tanks 11a and 11b to the DF engine ME, the reliquefied gas storage tank 11a as well as the evaporated gas naturally vaporized in the reliquefied gas storage tanks 11a and 11b. , 11b) may be supplied with a forced vaporized gas fueled by forced vaporization of the reliquefied boil-off gas in the liquid state.

The boil-off gas naturally vaporized in the re-liquefied gas storage tanks 11a and 11b supplies the boil-off gas to the primary compressor 31 through the re-liquefied gas fuel supply line RF and is required by the DF engine ME. It can be compressed and supplied to the pressure, and the remaining boil-off gas supplied by the fuel may be compressed by high pressure in the secondary compressor 32 and then re-liquefied to recover.

In addition, a forced vaporizer (not shown) for forcibly vaporizing the reliquefied boil-off gas stored in the reliquefied gas storage tank (11a, 11b), the temperature control to adjust the temperature of the forced gas in accordance with the fuel supply conditions of the DF engine (ME) A means (not shown) and a pressure regulating means (not shown) for adjusting the pressure are further provided, so that the liquefied boil-off gas stored in the reliquefied gas storage tanks 11a and 11b can be operated in the ship's collinear operation. It can also be supplied as fuel.

The pressure regulating means may utilize the primary compressor 31 as a pressure regulating means by forcibly vaporizing the reliquefied evaporated gas in a forced vaporizer and then supplying and compressing the forced vaporized gas to the primary compressor 31. In front of the forced vaporizer, a pump (not shown) for compressing the liquid reliquefied evaporated gas in accordance with the fuel supply conditions of the engine ME may be further provided, and the pump may be used as a pressure regulating means.

In addition, unlike the ME-GI engine of the first embodiment, the DF engine ME requires a certain level of methane number (MN) for fuel gas conditions, and the methane value of the fuel supplied to the DF engine ME is calculated. If it is not adjusted to the requirements, the heat output of the fuel or the speed of combustion may not be sufficient and the engine output may drop.

Methane is one of the indicators of knocking property and indicates the composition of fuel gas. In addition to methane, natural gas contains hydrocarbon components such as ethane, propane, butane and pentane, and inert gas components such as nitrogen and carbon dioxide. Methane and carbon monoxide are hard to knock, and heavy hydrocarbons such as propane and butane are likely to knock.

Therefore, according to the present embodiment, the methane number adjusting means (not shown) for controlling the methane number of the forced vaporization gas may be further included. The methane number control means may be a drum, and may be a means for controlling the methane number by liquefying and separating the heavy hydrocarbons included in the forced vaporization gas using the fact that the bicarbonate is higher in liquefaction point than the methane.

The forced vaporizer, methane number adjusting means, pressure adjusting means, temperature adjusting means and the like in the present embodiment supply the liquid reliquefied boil-off gas from the reliquefied gas storage tanks 11a and 11b to the fuel of the DF engine ME. In order to provide a separate liquefied gas in the liquid state stored in the liquefied gas storage tank 10 for the fuel of the DF engine (ME) may be utilized.

As described above, according to the present invention, it is possible to safely process the reliquefied evaporated gas containing the oil component mixed in the compression process of the evaporated gas, it is possible to prevent damage to the storage tank or contamination of the liquefied gas, ship owner or shipper It is possible to secure high reliability. In addition, instead of recovering the reliquefied evaporated gas containing the oil component as a liquefied gas cargo, a separate tank may be provided to recover the fuel as the engine's fuel so as not to waste the evaporated gas, and during ballast voyage of the vessel. Edo engine can reliably supply liquefied gas fuel.

The present invention is not limited to the above embodiments, and various modifications or changes may be made without departing from the technical spirit of the present invention, which will be apparent to those of ordinary skill in the art. It is.

ME: propulsion engine
10: liquefied gas storage tank
11a, 11b: Reliquefied gas storage tank
20: heat exchanger
30: multi stage compressor
40: expansion means
50: gas-liquid separator
OS: oil separation means
FL: Fuel Supply Line
RL: Reliquefaction Line
RF: Reliquefied Gas Fuel Supply Line

Claims (26)

High pressure gas injection engine;
One or more liquefied gas storage tanks;
A multistage compressor including one or more compression units and compressing the boil-off gas generated in the liquefied gas storage tank to the required fuel pressure of the high-pressure gas injection engine;
Reliquefaction means compressed in the multistage compressor and supplied to fuel of the high-pressure gas injection engine to re-liquefy remaining high-pressure evaporated gas;
A reliquefaction gas storage tank storing reliquefaction evaporated gas liquefied by the reliquefaction means;
A reliquefaction gas transfer line connecting the reliquefaction means and the reliquefied gas storage tank to transfer the reliquefied evaporated gas in the liquid state liquefied by the reliquefaction means to the reliquefied gas storage tank; And
And a reliquefied gas fuel supply line for supplying a reliquefied boil-off gas stored in the reliquefied gas storage tank to an engine using the liquefied gas as a fuel.
The reliquefaction means,
A heat exchanger in which the high pressure boil-off gas compressed to high pressure by the multi-stage compressor and the low pressure boil-off gas introduced into the multi-stage compressor from the liquefied gas storage tank are heat-exchanged to cool the high-pressure boil-off gas; And
And expansion means for lowering the pressure of the high pressure evaporated gas cooled by the heat exchanger.
The multistage compressor is a lubrication type compressor, the high pressure evaporated gas compressed by the multistage compressor includes an oil component introduced from the multistage compressor,
The reliquefied gas storage tank is provided with a smaller capacity than the liquefied gas storage tank, the boil-off gas treatment system of the ship. The method according to claim 1,
The multistage compressor includes at least four compression units to compress the boil-off gas in at least four stages or more, the vessel's boil-off gas treatment system. The method according to claim 1,
The high pressure boil-off gas compressed in the multi-stage compressor is 100 bar to 400 bar, the boil off gas treatment system. The method according to claim 3,
The high pressure boil-off gas compressed in the multi-stage compressor is 150 bar to 300 bar, the boil off gas treatment system. delete delete delete The method according to claim 1,
The rear end of the multi-stage compressor; oil separation means for filtering the oil component mixed in the high-pressure evaporated gas; further provided, the evaporation gas treatment system of the ship. delete delete One or more liquefied gas storage tanks;
A primary compressor including one or more compression units and compressing the boil-off gas generated in the liquefied gas storage tank to the required fuel pressure of the propulsion engine;
A secondary compressor for further compressing the compressed boil-off gas compressed in the primary compressor above a critical pressure;
Reliquefaction means for reliquefying the high pressure boil-off gas compressed in the secondary compressor;
And a reliquefaction gas storage tank configured to store reliquefaction evaporated gas liquefied by the reliquefaction means.
A reliquefaction gas transfer line connecting the reliquefaction means and the reliquefaction gas storage tank so that the reliquefaction gas in liquid state liquefied by the reliquefaction means is transferred to the reliquefaction gas storage tank; And
And a reliquefied gas fuel supply line for supplying a reliquefied boil-off gas stored in the reliquefied gas storage tank to an engine using the liquefied gas as a fuel.
The reliquefaction means,
A heat exchanger in which the high pressure boil-off gas compressed by the second compressor and the low pressure boil-off gas introduced into the second compressor are heat-exchanged to cool the high-pressure boil-off gas; And
And expansion means for lowering the pressure of the high pressure evaporated gas cooled by the heat exchanger.
The secondary compressor is a lubricated compressor, the high pressure boil-off gas compressed in the secondary compressor includes an oil component introduced from the secondary compressor,
The reliquefied gas storage tank is provided with a smaller capacity than the liquefied gas storage tank, the boil-off gas treatment system of the ship. The method according to claim 11,
Said primary compressor compresses said boil-off gas to 6.5 bar to 18 bar. The method according to claim 11,
Said secondary compressor compresses said boil-off gas to at least 60 bar. The method according to claim 1 or 11,
The re-liquefied gas storage tank is provided in the hull and membrane type, the vessel's boil-off gas treatment system. The method according to claim 1 or 11,
The re-liquefied gas storage tank is provided in a C-Type and provided on the deck of the vessel, the boil-off gas treatment system of the vessel. The method according to claim 11,
And a low pressure gas injection engine supplied with the compressed boil-off gas compressed by the primary compressor as fuel.
And the secondary compressor further compresses the remaining compressed boil-off gas supplied to the low-pressure gas injection engine. The method according to claim 1 or 16,
Re-liquefied boil-off gas stored in the re-liquefied gas storage tank,
The vessel's boil-off gas treatment system is supplied to the fuel of the engine when the level of the liquefied gas stored in the liquefied gas storage tank is below a set value. The method according to claim 11,
An oil separation means for filtering an oil component mixed with the high pressure boil-off gas is provided at the rear end of the secondary compressor. delete The method according to claim 1 or 11,
The reliquefaction means,
And a gas-liquid separator for gas-liquid separation of the gas-liquid mixture generated while passing through the expansion means.
The reliquefied boil-off gas in the liquid state separated from the gas-liquid separator is transferred to the reliquefied gas storage tank,
The gaseous non-reliquefied boil-off gas separated in the gas-liquid separator is joined to the heat exchanger front end, the vessel's boil-off gas treatment system. In full operation of the ship,
Compressing the boil-off gas produced in the liquefied gas storage tank,
Compressed evaporative gas is supplied to the engine fuel,
The remaining compressed boil-off gas supplied as fuel of the engine is cooled by heat-exchange with the boil-off gas before compression,
Re-liquefy by depressurizing the compressed high-pressure compressed boil-off gas,
Reliquefied liquid liquefied evaporated gas is stored in a separate reliquefied gas storage tank,
In the ballast operation of the vessel,
Supply the re-liquefied boil-off gas stored in the re-liquefied gas storage tank as the fuel of the engine,
The re-liquefied boil-off gas stored in the re-liquefied gas storage tank contains an oil component mixed while compressing the boil-off gas. The method according to claim 21,
The vessel is provided with a high-pressure gas injection engine as a propulsion engine,
The boil-off gas generated in the liquefied gas storage tank is compressed to 100 bar to 400 bar and supplied as a fuel of the high-pressure gas injection engine,
Supplying the fuel of the high-pressure gas injection engine and re-liquefied the remaining high-pressure evaporated gas to recover the re-liquefied gas storage tank,
The compressor for compressing the boil-off gas is operated by refueling lubrication. The method according to claim 21,
The vessel is provided with a low pressure gas injection engine as a propulsion engine,
The boil-off gas generated in the liquefied gas storage tank is compressed to 4 bar to 45 bar and supplied as a fuel of the low pressure gas injection engine,
After supplying to the fuel of the low-pressure gas injection engine the remaining compressed evaporated gas is further compressed and re-liquefied to recover the re-liquefied gas storage tank,
The compressed boil-off gas is compressed to a high pressure of 60 bar or more, the fuel supply method of the ship. delete The method according to claim 21,
By gas-liquid separation of the reliquefaction evaporated gas,
The separated gas is joined to the boil-off gas to be heat exchanged with the high-pressure compressed boil-off gas,
The separated liquid is recovered to the reliquefied gas storage tank, the fuel supply method of the ship. The method according to claim 21,
The reliquefied gas storage tank,
C-type storage tank provided on the membrane type storage tank or deck provided in the hull,
A ship fuel supply method provided with a smaller capacity than the liquefied gas storage tank.

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