KR102584509B1 - Fuel gas re-liquefaction system - Google Patents

Abstract

A fuel gas re-liquefaction system is disclosed that can improve re-liquefaction performance and efficiency of fuel gas even when the temperature of boil-off gas compressed and pressurized by a compressor is relatively high. A fuel gas re-liquefaction system according to an embodiment of the present invention includes a storage tank for storing liquefied gas; A compressor that compresses the evaporation gas generated in the storage tank to generate fuel gas; a re-liquefaction device including a heat exchanger that re-liquefies at least a portion of the boil-off gas pressurized by the compressor; and an expander installed between the rear end of the compressor and the reliquefaction machine based on the flow of the boil-off gas. The expander is configured to expand and cool the pressurized boil-off gas and then supply it to the heat exchanger.

Description

Fuel gas re-liquefaction system

The present invention relates to a fuel gas re-liquefaction system, and more specifically, to a fuel gas re-liquefaction system that can increase the re-liquefaction performance and efficiency of fuel gas even when the temperature of the boil-off gas compressed and pressurized by a compressor is relatively high. It's about.

The fuel gas re-liquefaction system of liquefied natural gas (LNG) carriers is designed to be used for fuel demand such as high-pressure gas injection engines, generator engines, and gas combustion devices. Boil-Off Gas (BOG) is used. The boil-off gas generated in the storage tank is pressurized by a compressor to the pressure required by the fuel consumer and is sent out as fuel gas. If the amount of boil-off gas (fuel gas) discharged from the compressor is greater than the amount of fuel gas required by the fuel consumer, part of the fuel gas is re-liquefied by a re-liquefaction machine and returned to the storage tank. In order to ensure normal reliquefaction performance, the temperature of the boil-off gas must be low. However, in the case of ballast voyage, etc., the temperature of the boil-off gas is high, so the re-liquefaction performance may be reduced.

The present invention is intended to provide a fuel gas re-liquefaction system that can improve fuel gas re-liquefaction performance and efficiency even when the temperature of the boil-off gas compressed and pressurized by a compressor is relatively high.

In addition, the present invention is intended to provide a fuel gas re-liquefaction system that does not require a cooler for precooling the boil-off gas for re-liquefaction, thereby reducing the equipment cost of the re-liquefaction device and increasing re-liquefaction efficiency.

In addition, the present invention is intended to provide a fuel gas reliquefaction system that can reliquefy boil-off gas using a mixed refrigerant and efficiently cool and circulate the mixed refrigerant without using a complicated mixed refrigerant cycle or cooler.

The problem to be solved by the present invention is not limited to the problems mentioned above. Other technical problems not mentioned will be clearly understood by those skilled in the art from the following description.

A fuel gas re-liquefaction system according to an embodiment of the present invention includes a storage tank for storing liquefied gas; A compressor that compresses the evaporation gas generated in the storage tank to generate fuel gas; a re-liquefaction device including a heat exchanger that re-liquefies at least a portion of the boil-off gas pressurized by the compressor; and an expander installed between the rear end of the compressor and the reliquefaction machine based on the flow of the boil-off gas. The expander is configured to expand and cool the pressurized boil-off gas and then supply it to the heat exchanger.

The re-liquefaction unit may be configured to re-liquefy the boil-off gas cooled by the expander by heat-exchanging a mixed refrigerant containing two or more different components of the refrigerant with the boil-off gas.

In one embodiment of the present invention, the re-liquefaction unit includes a heat exchanger that re-liquefies the boil-off gas cooled by the expander by exchanging heat with the mixed refrigerant; a mixed refrigerant compressor that receives mixed refrigerant from an expansion tank that stores the mixed refrigerant discharged from the heat exchanger and pressurizes it; A mixed refrigerant expander that cools the mixed refrigerant pressurized by the mixed refrigerant compressor by depressurizing and expanding it; And it may include a mixed refrigerant gas-liquid separator that separates gas and liquid from the mixed refrigerant cooled by the mixed refrigerant expander.

The mixed refrigerant compressor and the mixed refrigerant expander may be composed of a compander.

The reliquefaction unit includes a gaseous mixed refrigerant transfer line that transfers the gaseous mixed refrigerant separated by the mixed refrigerant gas-liquid separator to a first heat exchange line in the heat exchanger; a mixed refrigerant line that introduces the mixed refrigerant discharged from the first heat exchange line into a second heat exchange line in the heat exchanger; And it may further include a liquid mixed refrigerant transfer line that introduces the liquid mixed refrigerant separated by the mixed refrigerant gas-liquid separator into a second heat exchange line.

In another embodiment of the present invention, the reliquefaction device includes a first heat exchanger that cools the boil-off gas by exchanging heat with the mixed refrigerant and the boil-off gas cooled by the expander; a second heat exchanger for re-liquefying the boil-off gas discharged from the first heat exchanger by heat-exchanging the boil-off gas with the mixed refrigerant; a mixed refrigerant compressor that receives mixed refrigerant from an expansion tank that stores the mixed refrigerant discharged from the first heat exchanger and pressurizes it; a mixed refrigerant line delivering the mixed refrigerant pressurized by the mixed refrigerant compressor to a first heat exchanger line in the first heat exchanger; a first mixed refrigerant delivery line that transfers the mixed refrigerant heat-exchanged with the boil-off gas in the first heat exchanger line to a second heat exchanger line in the second heat exchanger; a first discharge line that discharges the mixed refrigerant heat-exchanged with the boil-off gas from the second heat exchanger line and flows it into a third heat exchange line within the second heat exchanger; A pressure reducing valve installed in the first discharge line and cooling the mixed refrigerant by reducing the pressure; a mixed refrigerant gas-liquid separator that separates gas and liquid from the mixed refrigerant discharged from the third heat exchange line through the second discharge line; And it may include a mixed refrigerant expander that is installed in the vapor line after the mixed refrigerant gas-liquid separator and cools the gaseous mixed refrigerant by depressurizing and expanding it.

The reliquefaction unit includes a second mixed refrigerant delivery line that introduces the mixed refrigerant expanded and cooled by the mixed refrigerant expander into a fourth heat exchanger line in the first heat exchanger; And it may further include a liquid line that introduces the liquid mixed refrigerant separated by the mixed refrigerant gas-liquid separator into the second mixed refrigerant delivery line.

According to an embodiment of the present invention, a fuel gas reliquefaction system is provided that can improve fuel gas reliquefaction performance and efficiency even when the temperature of boil-off gas compressed and pressurized by a compressor is relatively high.

In addition, according to an embodiment of the present invention, a cooler for precooling the boil-off gas is not required for reliquefaction, thereby reducing the equipment cost of the fuel gas reliquefaction system and increasing reliquefaction efficiency.

In addition, according to an embodiment of the present invention, the boil-off gas can be re-liquefied using a mixed refrigerant, and the boil-off gas can be re-liquefied by efficiently cooling and circulating the mixed refrigerant without using a complicated mixed refrigerant cycle or a cooler.

The effects of the present invention are not limited to the effects described above. Effects not mentioned can be clearly understood by those skilled in the art from this specification and the attached drawings.

1 is a configuration diagram of a fuel gas reliquefaction system according to an embodiment of the present invention.
Figure 2 is a configuration diagram of a fuel gas reliquefaction system according to another embodiment of the present invention.

Other advantages and features of the present invention and methods for achieving them will become clear by referring to the embodiments described in detail below along with the accompanying drawings. However, the present invention is not limited to the embodiments disclosed below, and the present invention is only defined by the scope of the claims. Even if not defined, all terms (including technical or scientific terms) used herein have the same meaning as generally accepted by the general art in the prior art to which this invention belongs. General descriptions of known configurations may be omitted so as not to obscure the gist of the present invention. In the drawings of the present invention, the same reference numerals are used as much as possible for identical or corresponding components. To facilitate understanding of the present invention, some components in the drawings may be shown somewhat exaggerated or reduced.

The terms used in this application are only used to describe specific embodiments and are not intended to limit the invention. Singular expressions include plural expressions unless the context clearly dictates otherwise. In this application, terms such as “comprise,” “have,” or “equipped with” are intended to designate the presence of features, numbers, steps, operations, components, parts, or combinations thereof described in the specification. It should be understood that it does not exclude in advance the presence or addition of other features, numbers, steps, operations, components, parts, or combinations thereof.

1 is a configuration diagram of a fuel gas reliquefaction system according to an embodiment of the present invention. The fuel gas re-liquefaction system according to an embodiment of the present invention can be provided to ships such as liquefied gas carriers or marine structures. Referring to Figure 1, the fuel gas re-liquefaction system 100 according to an embodiment of the present invention includes a storage tank 110, a compressor 120, an expander 140, a re-liquefaction device 150, and a gas-liquid separator 160. It can be included.

The storage tank 110 can store liquefied gas. The storage tank 110 may be provided in the hull. For example, the storage tank 110 stores liquefied gas such as liquefied natural gas (LNG) and liquefied petroleum gas (LPG) at a cryogenic temperature (for example, about -160°C in the case of LNG). below) can be saved. The storage tank 110 may be provided as an insulated tank.

In order to supply fuel gas to the fuel demand source 130, boil-off gas (BOG; Boil-Off Gas) naturally vaporized or forcibly vaporized within the storage tank 110 is supplied to a compressor through the boil-off gas supply line (L1). Can be supplied as (120). The compressor 120 can compress the boil-off gas supplied through the boil-off gas supply line L1 to the pressure required by the fuel demand source 130. The boil-off gas (fuel gas) pressurized by the compressor 120 is supplied to the main engine 132, generator 134, gas combustion device (not shown), etc. through the fuel gas supply line (L2). It can be supplied to the fuel demand source 130.

In an embodiment, the compressor 120 may be provided as a single compressor consisting of one compression device, or as a multi-stage compressor in which several compression devices are connected in a multi-stage structure. Fuel gas may be supplied to the fuel demand source 130 from the last end of the compressor 120, or in the case of a multi-stage compressor, may be supplied to the fuel demand source 130 from the last end or an intermediate stage between compression devices.

Some of the boil-off gas pressurized by the compressor 120 is supplied to the fuel consumer 130, and the remaining boil-off gas is supplied to the expander through the boil-off gas branch line (L3) branched from the fuel gas supply line (L2) for re-liquefaction. It can be supplied as (Expander) 140. The expander 140 may be provided between the rear end of the compressor 120 and the reliquefaction device 150 based on the flow of boil-off gas.

The expander 140 can cool the boil-off gas by expanding the pressurized boil-off gas supplied through the boil-off gas branch line (L3) after being compressed by the compressor 120. The warm boil-off gas pressurized by the compressor 120 can be cooled through the expander 140 and then transferred to the re-liquefaction device 150 through the boil-off gas transfer line (L4). Therefore, by utilizing the cold heat of the boil-off gas by the expander 140, the cooling efficiency of the reliquefaction device 150 can be increased. In addition, since it does not require a cooler to precool the evaporation gas and does not require additional refrigerant to cool the mixed refrigerant, the equipment cost of the fuel gas reliquefaction system can be reduced and reliquefaction efficiency can be increased.

The reliquefaction unit 150 can reliquefy the boil-off gas by heat-exchanging a mixed refrigerant containing two or more different components of the refrigerant with the boil-off gas. The mixed refrigerant may include, but is not limited to, two or more different components selected from hydrocarbon refrigerants such as nitrogen refrigerants, methane, ethane, propane, butane, methylene, and ethylene.

The boil-off gas can be re-liquefied into a liquefied gas by heat exchange with the mixed refrigerant in the re-liquefaction device 150. The re-liquefied liquefied gas can be supplied to the gas-liquid separator 160 through the liquefied gas discharge line (L5). The gas-liquid separator 160 can separate gas and liquid from the liquefied gas supplied through the liquefied gas discharge line (L5).

The liquefied gas in a liquid state separated in the gas-liquid separator 160 can be recovered to the storage tank 110 through the liquefied gas recovery line (L6). The gaseous boil-off gas separated by the gas-liquid separator 160 may be supplied to the boil-off gas supply line (L1) through the boil-off gas line (L7) and supplied to the compressor (120). Valves (V1, V2, V3) are installed in the liquefied gas discharge line (L5), liquefied gas recovery line (L6), and boil-off gas line (L7), respectively, to control the flow rate of liquefied gas or boil-off gas.

The reliquefaction unit 150 may include a heat exchanger 151, an expansion tank 152, a mixed refrigerant compressor 153, a mixed refrigerant expander 154, and a mixed refrigerant gas-liquid separator 155. The heat exchanger 151 can re-liquefy the boil-off gas by exchanging heat with the mixed refrigerant for the cooled boil-off gas expanded by the expander 140. The mixed refrigerant, which is heated during heat exchange with the boil-off gas in the heat exchanger 151, may be supplied to the expansion tank 152 through the mixed refrigerant discharge line (L8).

The mixed refrigerant stored in the expansion tank 152 may be supplied to the mixed refrigerant compressor 153 through the mixed refrigerant supply line (L9). The mixed refrigerant compressor 153 can pressurize the mixed refrigerant to a pressure of about 10 bar or more. The mixed refrigerant pressurized by the mixed refrigerant compressor 153 may be supplied to the mixed refrigerant expander 154 through the mixed refrigerant transfer line (L10). The mixed refrigerant expander 154 can cool the mixed refrigerant by depressurizing and expanding the pressurized mixed refrigerant to a pressure of about 3 to 50 bar. The mixed refrigerant compressor 153 and the mixed refrigerant expander 154 may be configured as a compander, in which case power efficiency can be increased.

The mixed refrigerant expanded and cooled by the mixed refrigerant expander 154 may be supplied to the mixed refrigerant gas-liquid separator 155 through the mixed refrigerant delivery line (L11). The mixed refrigerant gas-liquid separator 155 can separate the gas-liquid mixed refrigerant expanded and cooled by the mixed refrigerant expander 154. By the mixed refrigerant gas-liquid separator 155, the liquid mixed refrigerant can be discharged to the liquid mixed refrigerant transfer line (L12), and the gaseous mixed refrigerant can be discharged to the gas mixed refrigerant transfer line (L13).

The gaseous mixed refrigerant is transferred to the first heat exchange line (L14) in the heat exchanger 151 through the gaseous mixed refrigerant transfer line (L13), and flows along the first heat exchange line (L14) to exchange heat with the boil-off gas to produce boil-off gas. can be cooled. The mixed refrigerant discharged from the first heat exchange line (L14) may flow into the second heat exchange line (L17) in the heat exchanger 151 through the mixed refrigerant lines (L15 and L16). A valve (V5) may be installed in the mixed refrigerant lines (L15, L16) to cool the mixed refrigerant by decompression/expansion. As an example, the valve V5 may be provided as a pressure reducing valve such as a Joule thomson valve.

A valve (V4) may be installed in the liquid mixed refrigerant transfer line (L12) for controlling the flow rate of the mixed refrigerant or for cooling by decompression/expansion. As an example, the valve V4 may be provided as a pressure reducing valve such as a Joule thomson valve. The mixed refrigerant discharged in liquid form from the mixed refrigerant gas-liquid separator 155 joins the second heat exchange line (L17) in the heat exchanger 151 through the liquid mixed refrigerant transfer line (L12) and flows from the second heat exchange line (L17). The boil-off gas can be re-liquefied by heat exchange with the boil-off gas. The mixed refrigerant that has exchanged heat with the boil-off gas in the second heat exchange line (L17) is supplied back to the expansion tank (152) through the mixed refrigerant discharge line (L8) and circulated.

According to an embodiment of the present invention, the boil-off gas pressurized by the compressor 120 is expanded by the expander 140 for primary cooling and then supplied to the heat exchanger 151 of the reliquefaction device 150 to increase the boil-off gas cooling efficiency. and re-liquefaction efficiency can be increased. In addition, it does not require a cooler to precool the evaporation gas and does not require additional refrigerant to cool the mixed refrigerant, thereby reducing the equipment cost of the fuel gas reliquefaction system and increasing reliquefaction efficiency. Additionally, by adding a mixed refrigerant expander 154 at the rear of the mixed refrigerant compressor 153, the mixed refrigerant can be efficiently cooled without using a complicated mixed refrigerant cycle or cooler.

Figure 2 is a configuration diagram of a fuel gas reliquefaction system according to another embodiment of the present invention. In describing the embodiment of FIG. 2, overlapping descriptions of components that are the same as or correspond to the embodiment of FIG. 1 may be omitted. In the fuel gas reliquefaction system 100 according to the embodiment of FIG. 2, the reliquefaction unit 170 includes a first heat exchanger 171, a second heat exchanger 172, an expansion tank 173, and a mixed refrigerant compressor 174. , It includes a mixed refrigerant gas-liquid separator 175 and a mixed refrigerant expander 176, and the mixed refrigerant expander 176 is installed in the vapor line (L25) at the rear of the mixed refrigerant gas-liquid separator 175, similar to the embodiment described above. There is a difference.

The boil-off gas supplied to the reliquefaction device 170 in a cooled state by the expander 140 is heat-exchanged with the mixed refrigerant in the first heat exchanger 171 and the second heat exchanger 172 of the reliquefaction device 170 to produce liquefied gas. It can be reliquefied. The re-liquefied liquefied gas may be supplied to the gas-liquid separator 160 through the liquefied gas discharge line (L5) connected to the second heat exchanger 172.

The first heat exchanger 171 can re-liquefy the boil-off gas expanded and cooled by the expander 140 by exchanging heat with the mixed refrigerant. The mixed refrigerant whose temperature is raised during heat exchange with the boil-off gas in the first heat exchanger 171 may be supplied to the expansion tank 173 through the mixed refrigerant discharge line (L8).

The mixed refrigerant stored in the expansion tank 173 may be supplied to the mixed refrigerant compressor 174 through the mixed refrigerant supply line (L9). The mixed refrigerant compressor 174 can pressurize the mixed refrigerant to a pressure of about 10 bar or more. The mixed refrigerant pressurized by the mixed refrigerant compressor 174 may be delivered to the first heat exchanger line (L19) in the first heat exchanger 171 through the mixed refrigerant line (L18).

The mixed refrigerant that has exchanged heat with the boil-off gas in the first heat exchanger line (L19) may be transferred to the second heat exchanger line (L21) in the second heat exchanger (172) through the mixed refrigerant transfer line (L20). The mixed refrigerant that has exchanged heat with the boil-off gas in the second heat exchanger line (L21) is discharged to the first discharge line (L22), and is decompressed, expanded, and cooled by the valve (V6) installed in the heat exchanger discharge line (L22). It can be supplied again to the third heat exchanger line (L23) in the second heat exchanger (172).

In the third heat exchanger line (L23), the mixed refrigerant exchanges heat with the boil-off gas to cool the boil-off gas, and then is discharged through the second discharge line (L24) and supplied to the mixed refrigerant gas-liquid separator (175). The mixed refrigerant gas-liquid separator 175 can separate the mixed refrigerant gas and liquid discharged from the second heat exchanger 172 and supplied through the second discharge line (L24). By the mixed refrigerant gas-liquid separator 175, the gaseous mixed refrigerant is discharged to the vapor line (L25) and supplied to the mixed refrigerant expander 176, and the liquid mixed refrigerant can be discharged to the liquid line (L28).

The mixed refrigerant expander 176 is installed at the rear of the mixed refrigerant gas-liquid separator 175 based on the flow of the mixed refrigerant, and can cool the mixed refrigerant by depressurizing and expanding the mixed refrigerant to a pressure of about 50 bar or less. The mixed refrigerant compressor 174 and the mixed refrigerant expander 176 may be configured as a compander, in which case power efficiency can be increased. The mixed refrigerant expanded and cooled by the mixed refrigerant expander 176 flows into the fourth heat exchanger line (L27) in the first heat exchanger 171 through the mixed refrigerant transfer line (L26) and undergoes heat exchange with the evaporation gas. Evaporative gas can be cooled. The liquid mixed refrigerant discharged from the mixed refrigerant gas-liquid separator 175 through the liquid line (L28) is decompressed, expanded, and cooled by a valve (V7) such as an expansion valve (pressure reducing valve), and then cooled through the mixed refrigerant transfer line (L26). ) and may flow into the first heat exchanger (171).

According to an embodiment of the present invention, the boil-off gas pressurized by the compressor 120 is expanded by the expander 140, cooled first, and then supplied to the first heat exchanger 171 of the reliquefaction device 170 to produce boil-off gas. Cooling efficiency and reliquefaction efficiency can be improved. In addition, it does not require a cooler to precool the evaporation gas and does not require additional refrigerant to cool the mixed refrigerant, thereby reducing the equipment cost of the fuel gas reliquefaction system and increasing reliquefaction efficiency. In addition, by adding a mixed refrigerant expander 176 to the vapor line L25 at the rear of the mixed refrigerant gas-liquid separator 175, the mixed refrigerant can be efficiently cooled without using a complicated mixed refrigerant cycle or cooler.

It should be understood that the above embodiments are provided to aid understanding of the present invention, and do not limit the scope of the present invention, and that various modifications possible thereto also fall within the scope of the present invention. The scope of protection of the present invention should be determined by the technical spirit of the claims, and the scope of protection of the present invention is not limited to the literal description of the claims themselves, but actually extends to inventions of equal technical value. You must understand that it is.

100: Fuel gas reliquefaction system 110: Storage tank
120: Compressor 130: Fuel demand source
140: expander 150: reliquefaction device
151: heat exchanger 152: expansion tank
153: mixed refrigerant compressor 154: mixed refrigerant expander
155: Mixed refrigerant gas-liquid separator 160: Gas-liquid separator
170: Reliquefaction 171: First heat exchanger
172: second heat exchanger 173: expansion tank
174: Mixed refrigerant compressor 175: Mixed refrigerant gas-liquid separator
176: Mixed refrigerant expander

Claims (5)

A storage tank for storing liquefied gas;
A compressor that compresses the evaporation gas generated in the storage tank to generate fuel gas;
a re-liquefaction device including a heat exchanger that re-liquefies at least a portion of the boil-off gas pressurized by the compressor; and
An expander installed between the rear end of the compressor and the reliquefaction machine based on the flow of the boil-off gas,
The expander is configured to expand and cool the pressurized boil-off gas and then supply it to the heat exchanger;
The reliquefaction machine,
a heat exchanger that re-liquefies the boil-off gas cooled by the expander by exchanging heat with a mixed refrigerant;
a mixed refrigerant compressor that receives mixed refrigerant from an expansion tank that stores the mixed refrigerant discharged from the heat exchanger and pressurizes it;
A mixed refrigerant expander that cools the mixed refrigerant pressurized by the mixed refrigerant compressor by depressurizing and expanding it; and
A fuel gas reliquefaction system comprising a mixed refrigerant gas-liquid separator that separates gas and liquid from the mixed refrigerant cooled by the mixed refrigerant expander. delete According to paragraph 1,
The reliquefaction machine,
a gaseous mixed refrigerant transfer line that transfers the gaseous mixed refrigerant separated by the mixed refrigerant gas-liquid separator to a first heat exchange line in the heat exchanger;
a mixed refrigerant line that introduces the mixed refrigerant discharged from the first heat exchange line into a second heat exchange line in the heat exchanger; and
A fuel gas reliquefaction system further comprising a liquid mixed refrigerant transfer line that introduces the liquid mixed refrigerant separated by the mixed refrigerant gas-liquid separator into a second heat exchange line. A storage tank for storing liquefied gas;
A compressor that compresses the evaporation gas generated in the storage tank to generate fuel gas;
a re-liquefaction device including a heat exchanger that re-liquefies at least a portion of the boil-off gas pressurized by the compressor; and
An expander installed between the rear end of the compressor and the reliquefaction machine based on the flow of the boil-off gas,
The expander is configured to expand and cool the pressurized boil-off gas and then supply it to the heat exchanger;
The reliquefaction machine,
a first heat exchanger that cools the boil-off gas cooled by the expander by exchanging heat with a mixed refrigerant;
a second heat exchanger that re-liquefies the boil-off gas discharged from the first heat exchanger by heat-exchanging the boil-off gas with a mixed refrigerant;
a mixed refrigerant compressor that receives mixed refrigerant from an expansion tank that stores the mixed refrigerant discharged from the first heat exchanger and pressurizes it;
a mixed refrigerant line delivering the mixed refrigerant pressurized by the mixed refrigerant compressor to a first heat exchanger line in the first heat exchanger;
a first mixed refrigerant delivery line that transfers the mixed refrigerant heat-exchanged with the boil-off gas in the first heat exchanger line to a second heat exchanger line in the second heat exchanger;
a first discharge line that discharges the mixed refrigerant heat-exchanged with the boil-off gas from the second heat exchanger line and flows it into a third heat exchange line within the second heat exchanger;
A pressure reducing valve installed in the first discharge line and cooling the mixed refrigerant by reducing the pressure;
a mixed refrigerant gas-liquid separator that separates gas and liquid from the mixed refrigerant discharged from the third heat exchange line through the second discharge line; and
A fuel gas reliquefaction system including a mixed refrigerant expander installed in the vapor line after the mixed refrigerant gas-liquid separator and cooling the gaseous mixed refrigerant by decompressing and expanding it. According to paragraph 4,
The reliquefaction machine,
a second mixed refrigerant delivery line that introduces the mixed refrigerant expanded and cooled by the mixed refrigerant expander into a fourth heat exchanger line in the first heat exchanger; and
A fuel gas reliquefaction system further comprising a liquid line that introduces the liquid mixed refrigerant separated by the mixed refrigerant gas-liquid separator into the second mixed refrigerant delivery line.

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