KR20180093405A - Method of BOG Reliquefaction - Google Patents

Abstract

Disclosed is a method to supply boil-off gas (BOG) discharged from a storage tank mounted on a vessel to an engine as fuel and reliquefy the excessive BOG not used as the fuel of the engine. According to the method to reliquefy BOG of the present invention, a part or all of the BOG discharged from the storage tank is compressed by first and second compressors, wherein the BOG compressed by the first compressor is supplied as the fuel of the engine and the BOG compressed by the second compressor is circulated through a close-loop refrigerant cycle. The excessive BOG not supplied as the fuel of the engine among the BOG compressed by the first compressor is sent to a first heat exchanger by being additionally compressed in a third compressor or bypassing the third compressor, and the BOG sent to the first heat exchanger additionally compressed by the third compressor or bypassing the third compressor is cooled through heat exchange by using the BOG discharged from the storage tank as a refrigerant. The BOG cooled by the first heat exchanger is additionally cooled in a second heat exchanger by using a fluid circulated in a refrigerant cycle as a refrigerant or bypasses the second heat exchanger to be sent to a first decompressor.

Description

{Method of BOG Reliquefaction}

The present invention relates to a method for re-liquefying a remaining evaporated gas used as fuel for an engine among evaporated gases generated in a storage tank.

In recent years, consumption of liquefied gas such as Liquefied Natural Gas (LNG) has been rapidly increasing worldwide. The liquefied gas obtained by liquefying the gas at a low temperature has an advantage of being able to increase the storage and transport efficiency because the volume becomes very small as compared with the gas. In addition, liquefied natural gas, including liquefied natural gas, can be removed as an eco-friendly fuel with less air pollutant emissions during combustion because air pollutants can be removed or reduced during the liquefaction process.

Liquefied natural gas is a colorless transparent liquid obtained by cooling methane-based natural gas to about -162 ° C and liquefying it, and it has a volume of about 1/600 of that of natural gas. Therefore, when the natural gas is liquefied and transported, it can be transported very efficiently.

However, since the liquefaction temperature of natural gas is a cryogenic temperature of -162 ° C at normal pressure, liquefied natural gas is sensitive to temperature changes and is easily evaporated. As a result, the storage tank storing the liquefied natural gas is subjected to heat insulation, but the external heat is continuously transferred to the storage tank. Therefore, in the transportation of liquefied natural gas, the liquefied natural gas is naturally vaporized continuously in the storage tank, -Off Gas, BOG) occurs. This also applies to other low temperature liquefied gases such as ethane.

Evaporation gas is a kind of loss and is an important issue in transport efficiency. Further, when the evaporation gas accumulates in the storage tank, the internal pressure of the tank may rise excessively, and there is a risk that the tank may be damaged. Accordingly, various methods for treating the evaporative gas generated in the storage tank have been studied. Recently, a method of re-liquefying the evaporated gas and returning it to the storage tank for treating the evaporated gas, a method of returning the evaporated gas to the storage tank And a method of using it as an energy source of a consuming place.

As a method for re-liquefying the evaporation gas, there is a method of re-liquefying the evaporation gas by heat exchange with the refrigerant by providing a refrigeration cycle using a separate refrigerant, and a method of re-liquefying the evaporation gas by using the evaporation gas itself as a refrigerant . Particularly, the system adopting the latter method is called a Partial Re-liquefaction System (PRS).

On the other hand, among the engines used in ships, there are gas-fuel engines such as DF engine, X-DF engine and ME-GI engine which can use natural gas as fuel.

The DF engine adopts the Otto Cycle, which consists of four strokes, and injects natural gas with a relatively low pressure of about 6.5 bar into the combustion air inlet and compresses the piston as it rises.

The X-DF engine is composed of two strokes, using natural gas of about 16 bar as fuel and adopting autocycle.

The ME-GI engine consists of two strokes and employs a diesel cycle in which high pressure natural gas at around 300 bar is injected directly into the combustion chamber at the top of the piston.

An object of the present invention is to provide an efficient evaporation gas re-liquefaction method in various operating conditions of vessels depending on availability of equipment, line speed, amount of generated evaporation gas, and the like.

According to an aspect of the present invention, there is provided a method of supplying evaporative gas discharged from a storage tank mounted on a ship to fuel of an engine and re-liquefying excess evaporative gas not used as fuel of the engine Wherein a part or all of the evaporated gas discharged from the storage tank is compressed by a first compressor and a part or all of the evaporated gas discharged from the storage tank is supplied to a second compressor installed in parallel with the first compressor And the evaporated gas compressed by the first compressor is supplied to the fuel of the engine and the evaporated gas compressed by the second compressor circulates the refrigerant cycle of the closed loop and is compressed by the one compressor The surplus evaporated gas not being supplied to the fuel of the engine among the evaporated gases is further compressed by the third compressor or bypassed by the third compressor, Exchanged by the third compressor, or the evaporated gas which is further compressed by the third compressor or bypassed to the third compressor and sent to the first heat exchanger is cooled by heat exchange with the refrigerant discharged from the storage tank, The evaporating gas cooled by the first heat exchanger is further cooled by the second heat exchanger as the refrigerant circulating the refrigerant cycle or bypassed to the second heat exchanger to send the evaporated gas to the first decompressor / RTI >

Wherein the refrigerant cycle is capable of connecting the second compressor, the second heat exchanger, the second decompressor, the second heat exchanger, the fourth compressor, and again the second compressor, And the fluid expanded by the second pressure reducing device may be used as the refrigerant of the second heat exchanger and then supplied to the fourth compressor.

The evaporated gas compressed by the fourth compressor may be cooled by the cooler and then sent to the second compressor.

The fluid expanded by the first decompression device can be separated by the gas-liquid separator into the liquefied gas re-liquefied and the gaseous gas.

The gaseous gas separated by the gas-liquid separator may be combined with the evaporated gas discharged from the storage tank and used as the refrigerant of the first heat exchanger.

When the required pressure of the engine satisfies the pressure necessary for the re-liquefaction, the evaporated gas compressed by the first compressor can be bypassed to the first heat exchanger by bypassing the third compressor.

When the required pressure of the engine satisfies the pressure required for re-liquefaction, the engine may be an ME-GI engine.

The evaporating gas cooled by the first heat exchanger may be further cooled by the second heat exchanger as the refrigerant circulating the refrigerant cycle when the amount of evaporative gas to be re-liquefied is a predetermined value or more.

If the amount of the evaporative gas to be liquefied is equal to or greater than a predetermined value, the ship may be at a velocity not higher than 15.5 knots or when the ship is anchored.

The evaporating gas cooled by the first heat exchanger may be bypassed to the first decompressor by bypassing the second heat exchanger when the amount of the evaporated gas to be re-liquefied is less than the predetermined value.

When the amount of the evaporative gas to be liquefied is less than the predetermined value, it may be the case that the linear velocity of the ship exceeds 15.5 knots.

If the required pressure of the engine does not satisfy the pressure required for re-liquefaction, the evaporated gas compressed by the first compressor may be further compressed by the third compressor and then sent to the first heat exchanger.

If the required pressure of the engine does not satisfy the pressure required for re-liquefaction, the engine may be an X-DF engine.

The evaporating gas cooled by the first heat exchanger may be further cooled by the second heat exchanger as the refrigerant circulating the refrigerant cycle when the amount of evaporative gas to be re-liquefied is a predetermined value or more.

The evaporating gas cooled by the first heat exchanger may be bypassed to the first decompressor by bypassing the second heat exchanger when the amount of the evaporated gas to be re-liquefied is less than the predetermined value.

Wherein when the at least one of the second compressor, the second heat exchanger, the second decompressor, and the fourth compressor can not be used, the evaporated gas compressed by the second compressor is not supplied to the refrigerant cycle, The evaporated gas cooled by the first heat exchanger can be bypassed to the first decompressor by bypassing the second heat exchanger.

When the third compressor can not be used, the evaporated gas compressed by the first compressor can be bypassed to the first heat exchanger by bypassing the third compressor.

According to another aspect of the present invention, there is provided a method of supplying evaporative gas discharged from a storage tank mounted on a ship to fuel of an engine and re-liquefying excess evaporative gas not used as fuel of the engine Wherein a part or all of the evaporated gas discharged from the storage tank is compressed by a first compressor and a part or all of the evaporated gas discharged from the storage tank is supplied to a second compressor installed in parallel with the first compressor And when the first compressor can be used, the evaporated gas compressed by the first compressor is used as fuel of the engine, and the evaporated gas compressed by the second compressor is compressed by the refrigerant cycle of the closed loop And the excess evaporative gas not supplied to the fuel of the engine among the evaporative gases compressed by the one compressor is circulated by the third compressor The evaporated gas which is compressed horizontally or bypassed the third compressor to the first heat exchanger and further compressed by the third compressor or bypassed the third compressor and sent to the first heat exchanger, Gas is cooled by heat exchange with the refrigerant and the evaporated gas cooled by the first heat exchanger is further cooled by the second heat exchanger as the refrigerant circulating the refrigerant cycle or bypasses the second heat exchanger by the first decompression And supplies the evaporated gas compressed by the second compressor to the fuel of the engine and supplies the evaporated gas compressed by the second compressor to the refrigerant cycle when the first compressor can not be used, A method for re-liquefying an evaporated gas is provided.

When the first compressor can not be used, the surplus evaporated gas not used as the fuel of the engine among the evaporated gases compressed by the second compressor is further compressed by the third compressor or bypassed by the third compressor The evaporation gas sent to the first heat exchanger and further compressed by the third compressor or bypassed to the third compressor is cooled by heat exchange with the refrigerant discharged from the storage tank, The evaporated gas cooled by the first heat exchanger may be sent to the first decompressor by bypassing the second heat exchanger.

According to another aspect of the present invention, there is provided a method of re-liquefying a surplus evaporated gas remaining as fuel for an engine by heat exchange of the evaporated gas itself with a coolant, Is determined depending on the required pressure of the engine and the amount of evaporative gas to be liquefied, the cooled fluid which is heat-exchanged with the refrigerant in the evaporative gas itself, the evaporated gas circulating in the refrigerant cycle as the refrigerant, The amount of the evaporated gas to be re-liquefied is determined according to the amount of the evaporated gas to be resolidified.

According to the present invention, it is possible to determine whether the third compressor is driven or not depending on the required pressure of the engine and the amount of the evaporative gas to be re-liquefied. According to the amount of the evaporative gas to be re-liquefied, It is possible to flexibly cope with the operation status of the ship in consideration of the amount of re-liquefaction and economical factors.

FIG. 1 is a schematic view of a system to which the evaporative gas re-liquefaction method according to a preferred embodiment of the present invention is applied.
Figs. 2 and 3 are graphs showing the re-liquefaction amount of the evaporation gas at a pressure range from 39 bara to 300 bara.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. INDUSTRIAL APPLICABILITY The present invention can be applied to various applications such as a ship equipped with an engine using natural gas as fuel and a ship including a liquefied gas storage tank. In addition, the following examples can be modified in various forms, and the scope of the present invention is not limited to the following examples.

Methods for the treatment of the evaporative gas to be described below of the present invention include all kinds of ships and marine structures equipped with storage tanks capable of storing low temperature liquid cargo or liquefied gas such as LNG Carrier and Liquefied Ethane Gas Carrier) and LNG RV, as well as LNG FPSO, LNG FSRU and other marine structures. However, in the following embodiments, liquefied natural gas, which is a typical low temperature liquid cargo, will be described as an example for convenience of explanation.

The fluid in each line of the present invention may be in any one of a liquid state, a gas-liquid mixed state, a gas state, and a supercritical fluid state, depending on operating conditions of the system.

FIG. 1 is a schematic view of a system to which the evaporative gas re-liquefaction method according to a preferred embodiment of the present invention is applied.

Referring to FIG. 1, a system to which the evaporative gas re-liquefaction method of the present embodiment is applied includes a first heat exchanger 110, a first compressor 210, a second compressor 220, a third compressor 230, 1 pressure reducing device 510, a second heat exchanger 120, a second pressure reducing device 520, and a fourth compressor 240.

The system to which the evaporation gas re-liquefaction method of the present embodiment is applied is a system in which a part or all of the evaporated gas discharged from the storage tank T is used as the fuel for the engines E1 and E2 and the demand amount of the engines E1 and E2 The surplus evaporating gas is branched off and the liquid is re-liquefied.

The evaporation gas passing through the re-liquefaction process is basically compressed by the first compressor 210 and the third compressor 230 and cooled by the first heat exchanger 110 and the second heat exchanger 120 A part of or all of the refrigerant is re-liquefied through the expansion process by the first decompressor 510 and may bypass the third compressor 230 or bypass the second heat exchanger 120 depending on the operational state of the ship. The following is a detailed description.

The first heat exchanger 110 of the present embodiment is configured to use the evaporation gas discharged from the storage tank T as a refrigerant to evaporate the evaporated gas compressed by the third compressor 230 or the second bypass line L2 Thereby cooling the supplied evaporation gas. The evaporated gas used as the refrigerant in the first heat exchanger 110 after being discharged from the storage tank T is diverted into two flows and a part thereof is sent to the first compressor 210, Lt; / RTI >

The evaporation gas discharged from the storage tank T is bypassed to the first heat exchanger 110 along the first bypass line L1 so as to bypass the first compressor V1 210 and the second compressor 220. [

When a surplus evaporated gas that has not been sent to the engines E1 and E2 among the evaporated gases compressed by the first compressor 210 is supplied to the first heat exchanger 110 for a certain period of time after the system is driven, (V1) is closed to allow the evaporated gas discharged from the storage tank (T) to be supplied to the first heat exchanger (110). Hereinafter, after a certain period of time has elapsed since the system is started, the evaporated gas discharged from the storage tank T is used as refrigerant in the first heat exchanger 110, and then one of the first compressor 210 and the second compressor 220 The following describes a case where the above is sent.

The first compressor 210 of this embodiment compresses the evaporated gas used as the refrigerant in the first heat exchanger 110 after being discharged from the storage tank T and supplies it to the engines E1 and E2.

The ship to which the evaporation gas re-liquefaction method of the present embodiment is applied may include a first engine E1 and a second engine E2, wherein the first engine E1 is connected to the second engine E2 at a higher pressure The engine can be an engine requiring the evaporation gas of fuel as fuel. Further, the first engine E1 may be a propulsion engine, and the second engine E2 may be a power generation engine. For example, the first engine E1 may be an ME-GI engine and the second engine E2 may be a DF engine. In another example, the first engine E1 may be an X-DF engine and the second engine E2 may be a DF Engine.

The ship to which the evaporation gas re-liquefaction method of this embodiment is applied includes a first engine E1 and a second engine E2, wherein the first engine E1 is evaporated at a higher pressure than the second engine E2, The first compressor 210 compresses the evaporation gas to the required pressure of the first engine E1 and some of the evaporated gas compressed by the first compressor 210 is compressed to the third It may be reduced to the required pressure of the second engine E2 by the pressure reducing device 530 and then supplied to the second engine E2. The third pressure reducing device 530 may be an expansion valve such as a line-Thomson valve.

The second compressor 220 of the present embodiment is installed in parallel with the first compressor 210 and is discharged from the storage tank T and then discharged from the first compressor 210 of the evaporated gas used as the refrigerant in the first heat exchanger 110. [ It is possible to compress the remaining evaporation gas not sent to the evaporator 210. The evaporated gas compressed by the second compressor 220 circulates through the refrigerant cycle C of the closed loop and is used as the refrigerant in the second heat exchanger 120.

The surplus evaporated gas passing through the re-liquefaction process in this embodiment is not further cooled by the second heat exchanger 120 after being cooled by the first heat exchanger 110 and is cooled along the third bypass line L3 The refrigerant can be directly supplied to the first decompressor 510 bypassing the second heat exchanger 120. When the evaporative gas subjected to the liquefaction process is not further cooled by the second heat exchanger 120, It is not necessary to supply the refrigerant to the heat exchanger 120, so that it is not necessary to cause the evaporation gas to circulate through the refrigerant cycle C in the closed loop.

Therefore, when the evaporated gas passing through the re-liquefaction process is not further cooled by the second heat exchanger 120, the third valve V3 is closed and the evaporation gas is not supplied to the second compressor 220. [

The second compressor 220 of the present embodiment may be used as a redundancy device of the first compressor 210. That is, the second compressor 220 of the present embodiment can serve as the first compressor 210 when the first compressor 210 can not be used.

When the first compressor (210) can not be used due to failure, maintenance, or the like, the second valve (V2) is closed to prevent the evaporator from being supplied to the first compressor (210) The evaporated gas compressed by the second compressor 220 is supplied to the engines E1 and E2 through the sixth valve V6.

Even when the second compressor 220 is used as the fuel for the engine E1 or E2 instead of the first compressor 210, the engine E1 or E2 ) May be sent to the third compressor 230 or the second bypass line L2 for re-liquefaction.

When the second compressor 220 is used as a fuel for the engines E1 and E2 instead of the first compressor 210, the evaporated gas compressed by the second compressor 220 is cooled by the refrigerant of the closed loop The evaporated gas cooled by the first heat exchanger 110 is directly sent to the first decompressor 510 along the third bypass line L3 even when the re-circulation of the excess evaporative gas is not performed , And is not further cooled by the second heat exchanger (120).

The third compressor 230 of the present embodiment further compresses the excess evaporative gas not used as the fuel of the engine E1 or E2 among the evaporated gases compressed by the first compressor 210, 110, and may be installed as many as necessary.

Figs. 2 and 3 are graphs showing the re-liquefaction amount of the evaporation gas at a pressure range from 39 bara to 300 bara.

2 and 3, according to the evaporation gas re-liquefaction method of the present embodiment, the higher the pressure of the evaporation gas supplied to the first heat exchanger 110 is, the higher the re-liquefaction amount is, The amount becomes the maximum. Also, it can be seen that when the pressure of the evaporation gas is between about 150 bara and 300 bara, the change in the amount of resolidification is not significant.

The ship to which the evaporation gas re-liquefaction method of this embodiment is applied includes a first engine E1 and a second engine E2, wherein the first engine E1 is evaporated at a higher pressure than the second engine E2, In the case of an engine requiring gas as fuel, the first compressor 210 compresses the evaporation gas to the required pressure of the first engine E1, and the evaporated gas compressed by the required pressure of the first engine E1 is re- If the pressure is insufficient to pass the process, the evaporated gas may be further compressed by the third compressor 230 and sent to the first heat exchanger 110. When the third compressor 230 further compresses the evaporated gas compressed by the first compressor 210, the fourth valve V4 is kept closed.

However, when the pressure of the evaporated gas compressed by the first compressor E1 to the required pressure of the first engine E1 is sufficient to undergo the re-liquefaction process, the evaporated gas is further supplied by the third compressor 230 The fourth valve V4 is opened so that the evaporated gas compressed by the first compressor 210 bypasses the third compressor 230 and flows along the second bypass line L2 to the first heat exchanger (110).

In one example, when the first engine E1 is an X-DF engine, the X-DF engine uses approximately 16 bara of evaporative gas as the fuel, so that the first compressor 210 compresses the evaporative gas to approximately 16 bara . When the evaporated gas compressed to about 16 bara by the first compressor 210 is directly subjected to the re-liquefaction process, the amount of the re-liquefied gas drastically drops, so that the evaporated gas compressed by the first compressor 210 is supplied to the third compressor 230 And supplies the compressed gas to the first heat exchanger 110. [ The pressure of the evaporation gas, which is further compressed by the third compressor 230, is preferably about 150 bara at which the amount of resolidification becomes the highest.

As another example, when the first engine E1 is an ME-GI engine, the ME-GI engine uses approximately 300 bara of evaporative gas as fuel, so that the first compressor 210 compresses the evaporative gas to approximately 300 bara . Since the evaporation gas compressed by the first compressor 210 to about 300 bara is sufficient to undergo the re-liquefaction process, the evaporated gas compressed by the first compressor 210 flows along the second bypass line L2 To the first heat exchanger (110).

On the other hand, when the amount of liquefied natural gas in the storage tank (T) is large and a large amount of evaporative gas is generated or when the speed of the ship is low and the evaporative gas is used less in the propulsion engine (E1) The evaporation gas quantity to be re-liquefied when the evaporation gas is used in the propulsion engine E1 due to the low evaporation gas or the high speed of the ship due to the small amount of liquefied natural gas in the storage tank T, Even when the pressure of the evaporated gas compressed by the required pressure of the first engine E1 of the present embodiment undergoes the re-liquefaction process and the amount of the surplus evaporative gas to be re-liquefied is not large, 1 compressor 210 can be sent directly to the first heat exchanger 110 along the second bypass line L2 without further compression by the third compressor 230. [

For example, in the case where the first engine E1 of the present embodiment is an X-DF engine, if the evaporation gas compressed by approximately 16 bara by the first compressor 210 is immediately subjected to the re-liquefaction process, If the line speed is 15.5 knots or more, it is not necessary to further compress the evaporated gas compressed by the first compressor 210 by the third compressor 230 because the amount of the evaporated gas to be re-liquefied is small.

According to the present invention, whether or not the third compressor (230) is driven can be determined according to the required pressure of the engine and the amount of evaporative gas to be re-liquefied. Therefore, it is possible to flexibly cope with the operating condition of the ship .

The evaporated gas compressed by the first compressor 210 or the first compressor 210 and the third compressor 230 of the present embodiment is cooled by the first heat exchanger 110 and is cooled by the second heat exchanger 120. [ Cooled by the first heat exchanger 110 and then bypassed the second heat exchanger 120 along the third bypass line L3 after being cooled by the first heat exchanger 110 It may be directly sent to the first decompressor 510.

When the amount of evaporative gas to be liquefied is large, the fluid cooled by the first heat exchanger (110) can be further cooled by the second heat exchanger (120) to increase the amount of liquefaction, When the amount of gas is small, the fluid cooled by the first heat exchanger 110 is directly sent to the first decompressor 510 along the third bypass line L3, and the second heat exchanger 120 and the waste The refrigerant cycle C of the loop is not driven, thereby saving energy and cost.

For example, when the linear velocity is 15.5 knots or less, the fluid cooled by the first heat exchanger 110 is further cooled by the second heat exchanger 120 and then sent to the first decompressor 510, If the flow rate exceeds 15.5 knots, the fluid cooled by the first heat exchanger 110 is directly sent to the first pressure reducing device 510 along the third bypass line L3, and the second heat exchanger 120 and the closed loop The refrigerant cycle C of the refrigerant circuit of FIG.

According to the present invention, whether or not the second heat exchanger (120) and the refrigerant cycle (C) in the closed loop are driven can be determined according to the amount of evaporative gas to be re-liquefied, It can flexibly cope upward.

The first decompression device 510 of the present embodiment is configured to expand the evaporation gas cooled by the first heat exchanger 110 or the evaporation gas cooled by the first heat exchanger 110 and the second heat exchanger 120 . The compression process by the first compressor 210 or the first compressor 210 and the third compressor 230 and the compression process by the first heat exchanger 110 or the first heat exchanger 110 and the second heat exchanger 120 And the evaporation gas that has undergone the expansion process by the first decompressor 510 is partially or totally re-liquefied. The first pressure reducing device 510 of this embodiment may be an expansion valve such as a line-Thomson valve.

The system to which the evaporation gas re-liquefaction method of this embodiment is applied may further include a gas-liquid separator 600 installed at the downstream end of the first decompressor 510 to separate the re-liquefied liquefied gas from the gaseous gas . The gas in the gaseous state separated by the gas-liquid separator 600 may be a fluid in which the evaporation gas left without being re-liquefied and the flash gas generated by being expanded by the first decompressor 510 are mixed.

The liquefied natural gas separated by the gas-liquid separator 600 is returned to the storage tank T and the gaseous gas separated by the gas-liquid separator 600 is combined with the evaporated gas discharged from the storage tank T 1 heat exchanger (110).

On the other hand, the evaporated gas compressed by the second compressor 220 of the present embodiment is cooled by the second heat exchanger 120 and then sent to the second decompressor 520.

The second decompression device 520 of the present embodiment expands the fluid cooled by the second heat exchanger 120 after being compressed by the second compressor 220, and then sends the expanded fluid to the second heat exchanger 120. The fluid expanded by the second decompression device 520, as well as the pressure and temperature, is used as the refrigerant in the second heat exchanger 120.

That is, in the second heat exchanger 120, the fluid expanded by the second decompressor 520 is used as the refrigerant, the fluid primarily cooled by the first heat exchanger 110 and the fluid cooled by the second compressor 220 And then cooled by heat exchange with the evaporation gas sent to the refrigerant cycle (C). The fluid used as the refrigerant in the second heat exchanger 120 after being expanded by the second decompression device 520 is sent to the fourth compressor 240 and the second decompression device 520 of the present embodiment is the expansion device have.

The fourth compressor 240 of the present embodiment compresses the fluid used as the refrigerant in the second heat exchanger 120 after being expanded to the second decompressor 520. [ The fourth compressor 240 serves to maintain the average pressure of the evaporated gas circulating in the refrigerant cycle C of the closed loop by compensating the pressure of the evaporated gas expanded and lowered by the second decompressor 520 . The fourth compressor 240 of the present embodiment can be driven by the power generated by the second decompressor 520 and the second decompressor 520 by expanding the fluid by forming the second decompressor 520 and the compressor.

The system to which the evaporation gas re-liquefaction method of the present embodiment is applied may further include a cooler 400 that is compressed by the fourth compressor 240 and lowers the temperature of the evaporated gas not only in pressure but also in temperature.

The system to which the evaporation gas re-liquefaction method of this embodiment is applied includes the cooler 400. The system to which the evaporation gas re-liquefaction method of this embodiment is applied includes the second compressor 220, the second heat exchanger 120, The refrigerant cycle C of the closed loop connecting the second pressure reducing device 520, the second heat exchanger 120, the fourth compressor 240, the cooler 400 and the second compressor 220 again And the evaporated gas circulating in the refrigerant cycle C is used as the refrigerant of the second heat exchanger 120. [

A method of liquefying a vaporized gas according to a preferred embodiment of the present invention is summarized as follows.

1. All equipment is operating normally.

1) When the required pressure of the engine satisfies the pressure required for re-liquefaction, for example, when the first engine E1 is the ME-GI engine and the first compressor 210 compresses the evaporation gas at a pressure of approximately 300 bar The third compressor 230 is not used. When the required pressure of the engine satisfies the pressure required for re-liquefaction, whether to use the refrigerant cycle (C) and the second heat exchanger (120) is determined according to the amount of evaporative gas to be re-liquefied as follows.

- The refrigerant cycle (C) and the second heat exchanger (120) are used when the amount of evaporative gas to be re-liquefied exceeds a predetermined value, for example, when the linear velocity is 15.5 knots or less or when the ship is anchored. The evaporated gas passing through the re-liquefaction process is compressed by the first compressor 210 and then supplied to the first heat exchanger 110 along the second bypass line L2 and is cooled by the first heat exchanger 110 Is further cooled by the second heat exchanger (120) and then sent to the first decompressor (510).

- If the amount of evaporative gas to be re-liquefied is less than a certain value, for example, if the linear velocity exceeds 15.5 bara, the refrigerant cycle (C) and the second heat exchanger (120) are not used. The evaporated gas passing through the re-liquefaction process is compressed by the first compressor 210 and then supplied to the first heat exchanger 110 along the second bypass line L2 and is cooled by the first heat exchanger 110 Is sent to the first pressure reducing device (510) along the third bypass line (L3).

2) If the required pressure of the engine does not satisfy the pressure required for re-liquefaction, for example, if the first engine E1 is an X-DF engine and the first compressor 210 compresses the evaporation gas at a pressure of approximately 16 bar Occation

The third compressor 230, the refrigerant cycle C, and the second heat exchanger 120, when the evaporation gas amount to be re-liquefied exceeds a predetermined value, for example, when the linear velocity is 15.5 bara or less, use. The evaporated gas passing through the re-liquefaction process is compressed by the first compressor 210 and the third compressor 230 and then supplied to the first heat exchanger 110. The evaporated gas that has been cooled by the first heat exchanger 110 Is further cooled by the second heat exchanger (120) and then sent to the first decompressor (510).

The third compressor 230, the refrigerant cycle C and the second heat exchanger 120 are not used when the evaporation gas amount to be resolidified is less than a predetermined value, for example, when the linear velocity exceeds 15.5 bara. The evaporated gas passing through the re-liquefaction process is compressed by the first compressor 210 and then supplied to the first heat exchanger 110 along the second bypass line L2 and is cooled by the first heat exchanger 110 Is sent to the first pressure reducing device (510) along the third bypass line (L3).

2. If you have unavailable equipment

1) When the first compressor 210 can not be used, the second compressor 220 is used instead of the first compressor 210, and the refrigerant cycle C and the second heat exchanger 120 are not used. The evaporated gas compressed by the second compressor 220 is supplied to the fuel of the engine E1 or E2 through the sixth valve V6 and the evaporated gas which is subjected to the liquefaction process is supplied to the second compressor 220 by the second compressor 220 Compressed and then sent to the first heat exchanger 110 through the third compressor 230 or the second bypass line L2. The fluid cooled by the first heat exchanger (110) is sent to the first decompressor (510) along the third bypass line (L3).

2) If one or more of the second compressor 220, the second heat exchanger 120, the second decompressor 520, and the fourth compressor 240 can not be used, the refrigerant cycle C and the second heat exchange The device 120 is not used. The evaporated gas passing through the re-liquefaction process is compressed by the first compressor 210 and then sent to the first heat exchanger 110 through the third compressor 230 or the second bypass line L2. The fluid cooled by the first heat exchanger (110) is sent to the first decompressor (510) along the third bypass line (L3).

3) When the third compressor 230 can not be used, the evaporator gas compressed by the first compressor 210 is directly supplied to the second bypass line L2 along the second bypass line L2 without using the third compressor 230 1 heat exchanger (110).

It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the spirit and scope of the invention. It is.

T: Storage tank E1, E2: Engine
V1 to V6: valves L1, L2, L3: bypass line
C: refrigerant cycle 110, 120: heat exchanger
210, 220, 230, 240: compressors 510, 520, 530: pressure reducing device
400: cooler 600: gas-liquid separator

Claims (20)

A method for re-liquefying a surplus evaporated gas not used as fuel for an engine, comprising the steps of: supplying evaporated gas discharged from a storage tank mounted on a ship to fuel of an engine,
A part of or all of the evaporated gas discharged from the storage tank is compressed by a first compressor,
Compressing a part or all of the evaporated gas discharged from the storage tank by a second compressor installed in parallel with the first compressor,
The evaporated gas compressed by the first compressor is supplied to the fuel of the engine,
Wherein the evaporated gas compressed by the second compressor circulates the refrigerant cycle of the closed loop,
The excess evaporative gas not supplied to the fuel of the engine among the evaporated gases compressed by the one compressor is further compressed by the third compressor or bypassed to the third compressor and is sent to the first heat exchanger,
The evaporated gas further compressed by the third compressor or bypassed to the third compressor and sent to the first heat exchanger is cooled by heat exchange with the refrigerant discharged from the storage tank,
Wherein the evaporated gas cooled by the first heat exchanger is further cooled by the second heat exchanger as a refrigerant through the refrigerant circulating in the refrigerant cycle or is bypassed to the first heat exchanger by the second heat exchanger, Way. The method according to claim 1,
Wherein the refrigerant cycle connects the second compressor, the second heat exchanger, the second decompressor, the second heat exchanger, the fourth compressor, and the second compressor again,
And the fluid expanded by the second pressure reducing device after being cooled by the second heat exchanger is used as the refrigerant of the second heat exchanger and then supplied to the fourth compressor. The method of claim 2,
Wherein the evaporated gas compressed by the fourth compressor is cooled by a cooler and then sent to the second compressor. The method according to claim 1,
And the fluid expanded by the first decompression device is separated into a liquefied gas and a gaseous gas that have been re-liquefied by the gas-liquid separator. The method of claim 4,
Wherein the gaseous gas separated by the gas-liquid separator is combined with the evaporated gas discharged from the storage tank and used as a refrigerant in the first heat exchanger. The method according to any one of claims 1 to 5,
And when the required pressure of the engine satisfies the pressure necessary for re-liquefaction, the evaporated gas compressed by the first compressor is bypassed to the first heat exchanger by bypassing the third compressor. The method of claim 6,
And when the required pressure of the engine satisfies the pressure required for re-liquefaction, the engine is an ME-GI engine. The method of claim 6,
Wherein the evaporating gas cooled by the first heat exchanger is further cooled by the second heat exchanger with the refrigerant circulating the refrigerant cycle when the amount of evaporative gas to be resuplicated is equal to or greater than a predetermined value, Way. The method of claim 8,
Wherein when the amount of the evaporative gas to be re-liquefied is equal to or greater than a predetermined value, the linear velocity of the ship is 15.5 knots or less, or when the ship is anchored. The method of claim 6,
And the evaporated gas cooled by the first heat exchanger is bypassed to the first decompressor when the amount of the evaporated gas to be re-liquefied is less than the predetermined value. The method of claim 10,
Wherein when the amount of the evaporative gas to be liquefied is less than the predetermined value, the linear velocity of the ship is more than 15.5 knots. The method according to any one of claims 1 to 5,
Wherein the first compressor further compresses the evaporated gas compressed by the first compressor and then sends the compressed gas to the first heat exchanger when the required pressure of the engine does not satisfy the pressure required for re- Way. The method of claim 12,
Wherein the engine is an X-DF engine when the required pressure of the engine does not satisfy the pressure required for re-liquefaction. The method of claim 12,
Wherein the evaporating gas cooled by the first heat exchanger is further cooled by the second heat exchanger with the refrigerant circulating the refrigerant cycle when the amount of evaporative gas to be resuplicated is equal to or greater than a predetermined value, Way. The method of claim 12,
And the evaporated gas cooled by the first heat exchanger is bypassed to the first decompressor when the amount of the evaporated gas to be re-liquefied is less than the predetermined value. The method of claim 2,
When at least one of the second compressor, the second heat exchanger, the second decompressor, and the fourth compressor can not be used,
The refrigerant cycle is not supplied to the refrigerant cycle by the evaporation gas compressed by the second compressor,
Wherein the evaporated gas cooled by the first heat exchanger is bypassed to the first decompressor and bypassed to the second heat exchanger. The method according to any one of claims 1 to 5,
And when the third compressor can not be used, the evaporated gas compressed by the first compressor is bypassed to the third heat exchanger and is sent to the first heat exchanger. A method for re-liquefying a surplus evaporated gas not used as fuel for an engine, comprising the steps of: supplying evaporated gas discharged from a storage tank mounted on a ship to fuel of an engine,
A part of or all of the evaporated gas discharged from the storage tank is compressed by a first compressor,
Compressing a part or all of the evaporated gas discharged from the storage tank by a second compressor installed in parallel with the first compressor,
When the first compressor can be used,
Using the evaporated gas compressed by the first compressor as fuel for the engine,
Wherein the evaporated gas compressed by the second compressor circulates the refrigerant cycle of the closed loop,
The excess evaporative gas not supplied to the fuel of the engine among the evaporated gases compressed by the one compressor is further compressed by the third compressor or bypassed to the third compressor and is sent to the first heat exchanger,
The evaporated gas further compressed by the third compressor or bypassed to the third compressor and sent to the first heat exchanger is cooled by heat exchange with the refrigerant discharged from the storage tank,
The evaporated gas cooled by the first heat exchanger is further cooled by the second heat exchanger as the refrigerant circulating the refrigerant cycle or bypassed to the second heat exchanger to be sent to the first decompressor,
If the first compressor can not be used,
Wherein the evaporative gas compressed by the second compressor is supplied to the fuel of the engine and the evaporated gas compressed by the second compressor is not supplied to the refrigerant cycle. 19. The method of claim 18,
If the first compressor can not be used,
The surplus evaporated gas not used as the fuel of the engine among the evaporated gases compressed by the second compressor is further compressed by the third compressor or is bypassed to the third compressor and is sent to the first heat exchanger,
The evaporated gas further compressed by the third compressor or bypassed to the third compressor and sent to the first heat exchanger is cooled by heat exchange with the refrigerant discharged from the storage tank,
Wherein the evaporated gas cooled by the first heat exchanger is sent to the first decompressor by bypassing the second heat exchanger. A method for re-liquefying excess evaporative gas remaining as fuel for an engine by heat-exchanging the evaporative gas itself with a refrigerant,
Whether or not to further compress the compressed evaporative gas for supply to the engine is determined by the required pressure of the engine and the amount of evaporative gas to be resolidified,
Wherein whether or not the refrigerant cooled by the heat exchange of the evaporated gas itself with the refrigerant and the evaporated gas circulating the refrigerant cycle by the additional heat exchange with the refrigerant is to be cooled is determined according to the amount of the evaporated gas to be re-liquefied.

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