KR101525686B1 - A Treatment System of Liquefied Gas - Google Patents

Abstract

A liquefied gas processing system according to an embodiment of the present invention includes: an evaporative gas line connected to a liquefied gas storage tank; A plurality of evaporative gas compressors provided on the evaporative gas line for pressurizing the evaporative gas generated in the liquefied gas storage tank in multiple stages; A condenser provided on the evaporation gas line for heat-exchanging the evaporated gas pressurized by the evaporation gas compressor using a refrigerant; A refrigerant line through which the refrigerant is circulated via the condenser; A refrigerant compressor provided on the refrigerant line to pressurize the refrigerant in multiple stages; A refrigerant inflator provided in the refrigerant line for expanding a refrigerant that is pressurized by the refrigerant compressor and heat-exchanged in the condenser; A bypass line branching from the refrigerant line to bypass the refrigerant supplied from the refrigerant inflator; A liquid recovery line connected to the evaporation gas line for recovering at least a part of the evaporated gas discharged from the condenser to the liquefied gas storage tank; And an auxiliary heat exchanger provided on the liquid recovery line for exchanging heat between the evaporation gas supplied from the gas-liquid separator and the refrigerant supplied from the refrigerant inflator via the bypass line.
The liquefied gas processing system according to the present invention is characterized in that the liquefied gas is subcooled by further utilizing the cold heat of the low refrigerant at a temperature of -165 DEG C to -196 DEG C in the refrigerant cycle through the refrigerant line, The generation of the evaporation gas can be suppressed by making the temperature sufficiently lower than the boiling point of -161.5 DEG C of the liquefied gas.

Description

Description of the Related Art A Treatment System of Liquefied Gas

The present invention relates to a liquefied gas processing system.

Liquefied natural gas (Liquefied natural gas), Liquefied petroleum gas (Liquefied petroleum gas) and other liquefied gas are widely used in place of gasoline or diesel in recent technology development.

Liquefied natural gas is a liquefied natural gas obtained by refining natural gas collected from a gas field. It is a colorless and transparent liquid with almost no pollutants and high calorific value. It is an excellent fuel. On the other hand, liquefied petroleum gas is a liquid fuel made by compressing gas containing propane (C3H8) and butane (C4H10), which come from oil in oil field, at room temperature. Liquefied petroleum gas, like liquefied natural gas, is colorless and odorless and is widely used as fuel for household, business, industrial, and automotive use.

Such liquefied gas is stored in a liquefied gas storage tank installed on the ground or stored in a liquefied gas storage tank provided in a ship which is a means of transporting the ocean. The liquefied natural gas is liquefied to a volume of 1/600 The liquefaction of liquefied petroleum gas has the advantage of reducing the volume of propane to 1/260 and the content of butane to 1/230, resulting in high storage efficiency.

These liquefied gases are supplied to various customers and used. Recently, LNG carrier that uses LNG as fuel for LNG carriers that transport liquefied natural gas has been developed. The method used is applied to ships other than LNG carriers.

However, the temperature and pressure of the liquefied gas required by the customer such as the engine may be different from the state of the liquefied gas stored in the liquefied gas storage tank. Therefore, recently, research and development have been conducted on technologies for controlling the temperature and pressure of the liquefied gas stored in a liquid state to supply it to a customer.

It is an object of the present invention to provide a liquefied gas processing system capable of subcooling an evaporating gas to be liquefied to reduce the generation of evaporation gas.

A liquefied gas processing system according to an embodiment of the present invention includes: an evaporative gas line connected to a liquefied gas storage tank; A plurality of evaporative gas compressors provided on the evaporative gas line for pressurizing the evaporative gas generated in the liquefied gas storage tank in multiple stages; A condenser provided on the evaporation gas line for heat-exchanging the evaporated gas pressurized by the evaporation gas compressor using a refrigerant; A refrigerant line through which the refrigerant is circulated via the condenser; A refrigerant compressor provided on the refrigerant line to pressurize the refrigerant in multiple stages; A refrigerant inflator provided in the refrigerant line for expanding a refrigerant that is pressurized by the refrigerant compressor and heat-exchanged in the condenser; A bypass line branching from the refrigerant line to bypass the refrigerant supplied from the refrigerant inflator; A liquid recovery line connected to the evaporation gas line for recovering at least a part of the evaporated gas discharged from the condenser to the liquefied gas storage tank; And an auxiliary heat exchanger provided on the liquid recovery line for exchanging heat between the evaporation gas supplied from the gas-liquid separator and the refrigerant supplied from the refrigerant inflator via the bypass line.

Here, the present invention further includes a gas-liquid separator provided on the evaporation gas line for separating the evaporation gas into gas and liquid, and the liquid recovery line is connected from the gas-liquid separator to the liquefied gas storage tank, And recovering the separated liquid vapor gas into the liquefied gas storage tank, wherein the auxiliary heat exchanger subcools the evaporated gas.

The bypass line is branched downstream of the refrigerant inflator in the refrigerant line so as to be joined to the upstream side of the condenser so that the refrigerant is heat-exchanged with the evaporation gas in the auxiliary heat exchanger and then supplied to the condenser, And the joining point is downstream of a point where the bypass line is branched.

The bypass line is branched downstream of the refrigerant inflator and merged upstream of the refrigerant compressor so that the refrigerant is heat-exchanged with the evaporation gas in the auxiliary heat exchanger and then supplied to the refrigerant compressor. do.

The present invention further includes a gas recovery line connected to the vapor-liquid separator and upstream of the evaporative gas compressor to supply the flash gas to the evaporative gas compressor.

Further, the present invention is characterized by further comprising an evaporative gas pressure reducing device provided upstream of the gas-liquid separator on the branch line, for reducing the pressure of the evaporating gas.

The liquefied gas processing system according to the present invention is characterized in that the liquefied gas is subcooled by further utilizing the cold heat of the low refrigerant at a temperature of -165 DEG C to -196 DEG C in the refrigerant cycle through the refrigerant line, The generation of the evaporation gas can be suppressed by making the temperature sufficiently lower than the boiling point of -161.5 DEG C of the liquefied gas.

1 is a conceptual diagram of a conventional liquefied gas processing system.
2 is a conceptual diagram of a liquefied gas processing system according to an embodiment of the present invention.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

1 is a conceptual diagram of a conventional liquefied gas processing system.

1, a conventional liquefied gas processing system 1 includes a liquefied gas storage tank 10, a customer 20, an evaporative gas compressor 50, a re-liquefier 60, an evaporative gas decompressor 90), and a gas-liquid separator (100). The evaporation gas compressor 50 can be connected to the evaporation gas supply line 16 from the liquefied gas storage tank 10 to the customer 20 and the evaporation gas compressor 50 can be connected to the refueling compressor 60, The decompression device 90 and the gas-liquid separator 100 may be connected to the branch line 17 and the evaporation gas supply line 16 and the branch line 17 may be referred to as evaporation gas lines.

Hereinafter, the liquefied gas may be used to encompass all gaseous fuels generally stored in a liquid state, such as LNG or LPG, ethylene, ammonia, etc. In the case where the gas is not in a liquid state by heating or pressurization, . This also applies to the evaporative gas. In addition, LNG can be used to mean not only NG (Natural Gas) in liquid state but also NG in supercritical state for convenience, and evaporation gas can be used to include not only gaseous evaporation gas but also liquefied evaporation gas have.

The conventional liquefied gas processing system 1 is operated by supplying the evaporated gas generated and discharged from the liquefied gas storage tank 10 by the evaporation gas compressor 50 to the refueling device 60 or the demand place 20 .

At this time, the evaporated gas supplied to the re-liquefier 60 is heat-exchanged with the evaporated gas supplied from the liquefied gas storage tank 10 in the re-liquefier 60, and thereafter, decompressed in the evaporated gas decompressor 90, The evaporation gas at the time is cooled.

The evaporated gas decompressed in the evaporation gas decompressor 90 is supplied to a gas-liquid separator 100 and is separated into a liquid and a gas in the gas-liquid separator 100 so that the liquid is melted in the liquid recovery line 103, Is supplied to the tank 10, and the gas may be discarded as a flash gas or recovered upstream of the evaporative gas compressor 50.

On the other hand, in the conventional liquefied gas processing system 1, liquefied evaporation gas can be recovered to prevent waste of evaporation gas, but since it is in a saturated state, generation of flash gas may increase, and improvement is required.

2 is a conceptual diagram of a liquefied gas processing system according to an embodiment of the present invention.

2, a liquefied gas processing system 2 according to an embodiment of the present invention includes a liquefied gas storage tank 10, a customer 20, an evaporative gas compressor 50, a condenser 70, A refrigerant compressor 81, a refrigerant inflator 82, an evaporation gas decompressor 90, a gas-liquid separator 100, and an auxiliary heat exchanger 110. In the embodiment of the present invention, the liquefied gas storage tank 10, the customer 20 and the like are denoted by the same reference numerals for convenience and convenience in the conventional liquefied gas processing system 1, no.

The liquefied gas storage tank (10) stores liquefied gas to be supplied to the customer (20). The liquefied gas storage tank 10 must store the liquefied gas in a liquid state, wherein the liquefied gas storage tank 10 may have the form of a pressure tank.

The liquefied gas storage tank 10 includes an outer tank (not shown), an inner tank (not shown), and a heat insulating portion (not shown). The outer tank may be formed of steel, and the inner tank may be made of stainless steel and designed to withstand a pressure of 5 bar to 10 bar (for example 6 bar). . The heat insulating portion is provided between the inner tank and the outer tank, and can prevent the external heat energy from being transmitted to the inner tank.

In this embodiment, the evaporation gas generated in the liquefied gas storage tank 10 is supplied to the evaporation gas compressor 50, and the evaporation gas is pressurized and utilized as the fuel of the customer 20, so that the evaporation gas can be efficiently used have.

Here, a forcing vaporizer (not shown) may be provided downstream of the liquefied gas storage tank 10, and the forced vaporizer is operated when the flow rate of the evaporation gas is insufficient, Can be increased. That is, the forced vaporizer is provided on the evaporation gas supply line 16 upstream of the evaporative gas compressor 50 to vaporize the liquefied gas in the liquefied gas storage tank 10 and supply the liquefied gas in the gaseous state to the evaporated gas compressor 50 Can supply.

In addition, a mixer (not shown) may be provided between the forced vaporizer and the evaporative gas compressor 50, and the mixer is provided upstream of the evaporative gas compressor 50 on the evaporative gas supply line 16, Liquid separator 100 and the flash gas recovered in the gas-liquid separator 100 may be introduced. Such a mixer may be in the form of a pressure tank in which a space for storing the evaporating gas and the flash gas is formed. Although not shown in the drawing, the gas recovery line 101 may be connected from the gas-liquid separator 100 to the mixer so that the flash gas may be mixed with the evaporated gas in the mixer and supplied to the evaporated gas compressor 50.

The customer 20 is driven through evaporative gas supplied from the liquefied gas storage tank 10 and flash gas to generate power. At this time, the customer 20 is a high-pressure engine and may be a MEGI engine.

As the piston 20 (not shown) in the cylinder (not shown) reciprocates by the combustion of the liquefied gas, the consumer 20 rotates the crankshaft (not shown) connected to the piston and is connected to the crankshaft A shaft (not shown) can be rotated. Therefore, as the propeller (not shown) connected to the shaft rotates when the consumer 20 is driven, the hull can move forward or backward.

Of course, in this embodiment, the customer 20 may be an engine for driving the propeller, but it may be an engine for generating power or an engine for generating other power. In other words, the present embodiment does not particularly limit the kind of the consumer 20. However, the customer 20 may be an internal combustion engine that generates a driving force by the combustion of the evaporative gas and the flash gas.

The consumer 20 is supplied with the evaporated gas and the flash gas pressurized by the evaporative gas compressor 50 and can obtain the driving force. The state of the evaporative gas and the flash gas supplied to the consumer 20 may vary depending on the state required by the consumer 20.

Or the customer 20 may be a dual fuel engine in which a mixture of the evaporation gas and the oil is not supplied and the evaporation gas or oil is selectively supplied. The dual fuel engine is selectively supplied with the evaporation gas or oil in order to prevent the mixing of the two materials having different combustion temperatures to prevent the efficiency of the consumer 20 from deteriorating.

A vaporizing gas supply line 16 for transferring vaporizing gas may be installed between the liquefied gas storage tank 10 and the customer 20 and a forced vaporizer, And the like, so that the evaporation gas can be supplied to the customer 20. At this time, a fuel supply valve (not shown) is provided in the evaporation gas supply line 16 so that the supply amount of the evaporation gas can be adjusted according to the adjustment of the opening degree of the fuel supply valve.

The evaporative gas compressor (50) pressurizes the evaporative gas generated in the liquefied gas storage tank (10). The evaporation gas compressor 50 can pressurize the evaporation gas generated and discharged from the liquefied gas storage tank 10 and supply it to the condenser 70 or the customer 20.

The plurality of evaporation gas compressors (50) can pressurize the evaporation gas at multiple stages. For example, five evaporative gas compressors 50 are shown (three in the figure, but two evaporative gas compressors may be provided upstream of the condenser on the branch line or upstream of the consumer on the evaporative gas supply line) So that the evaporation gas can be pressurized in five stages. For example, the evaporated gas pressurized to the third or lower stage may be supplied to the customer 20, and the vaporized pressurized gas at the fifth-stage may be pressurized to 200 bar to 400 bar and supplied to the condenser 70.

Here, the branch line 17 that branches off from the evaporation gas supply line 16 may be provided downstream of any of the evaporative gas compressors 50, and the branch line 17 is connected to the gas- (100). At this time, a valve (not shown) may be provided on the evaporation gas supply line 16 at the branching point of the branch line 17 in the evaporation gas supply line 16, The flow rate of the gas or the flow rate of the evaporation gas supplied to the gas-liquid separator 100 through the condenser 70 can be controlled, and can be a three-way valve.

Between the plurality of evaporative gas compressors 50, an evaporative gas cooler (not shown) may be provided. When the evaporation gas is pressurized by the evaporation gas compressor 50, since the temperature may also rise with the pressure increase, this embodiment can lower the temperature of the evaporation gas again by using the evaporation gas cooler. The evaporative gas cooler may be installed in the same number as the evaporative gas compressor 50, and each evaporative gas cooler may be provided downstream of each evaporative gas compressor 50.

As the evaporation gas compressor 50 pressurizes the evaporation gas, the evaporation gas can be in a state where the pressure rises and the boiling point rises and can be liquefied even at a relatively high temperature. Therefore, this embodiment can increase the pressure of the evaporation gas to the evaporation gas compressor 50, so that the evaporation gas can be easily liquefied.

The condenser 70 is provided on the branch line 17 and is provided upstream of the gas-liquid separator 100. The condenser 70 exchanges heat with the pressurized evaporative gas using a refrigerant and then supplies it to the gas-liquid separator 100 ). Here, the refrigerant may be nitrogen (N ₂ ).

The refrigerant passing through the condenser 70 can be circulated through the refrigerant line 71 through the refrigerant compressor 81, the condenser 70, the expander 82, the condenser 70 and the refrigerant compressor 81. Here, the refrigerant line 71 may be a closed circulation line, and the refrigerant compressor 81, the condenser 70, and the expander 82 may be provided in series so that the refrigerant, which is heat-exchanged with the evaporative gas passing through the condenser 70, Can be circulated.

At this time, the condenser 70 has three flow paths, and the refrigerant flowing along the two flow paths except the flow path through which the evaporation gas flows can mutually exchange heat. That is, the refrigerant flowing into the refrigerant compressor (81) and the refrigerant discharged from the refrigerant compressor (81) flow through different channels in the refrigerant compressor (70) 81). ≪ / RTI >

The refrigerant compressor (81) is provided on the refrigerant line (71) in plural and can pressurize the refrigerant in multiple stages. For example, three refrigerant compressors 81 may be provided to pressurize the refrigerant three-steps. The three-stage pressurized refrigerant may be supplied to the condenser 70 and the expander 82 via the refrigerant line 71.

A refrigerant cooler (not shown) may be provided between the plurality of refrigerant compressors 81. When the refrigerant is pressurized by the refrigerant compressor (81), the temperature can be raised according to the pressure increase. Therefore, the present embodiment can lower the temperature of the refrigerant again by using the refrigerant cooler. The coolant cooler may be provided between the plurality of coolant compressors 81 and may be installed in the same number as the coolant compressors 81, and each coolant cooler may be provided downstream of the respective coolant compressors 81.

Here, the bypass lines 72, 111 and 112 are branched from the refrigerant line 71 downstream of the refrigerant inflator 82, and the bypass lines 72, 111 and 112 bypass the refrigerant supplied from the refrigerant inflator 82. A valve (which may be, for example, a three-way valve) is provided at a point where the bypass lines 72, 111 and 112 are branched in the refrigerant line 71 to supply the flow rate of the refrigerant supplied to the condenser 70 to the bypass lines 72, The flow rate of the refrigerant can be adjusted. In the present embodiment, the auxiliary heat exchanger 110 described later is provided on the bypass lines 72, 111, and 112, and the refrigerant can pass through the bypass heat exchanger 110 through the bypass lines 72, 111, and 112. The bypass lines (72, 111, 112) of this embodiment can join the refrigerant line (71) via the auxiliary heat exchanger (110), which will be described later. Alternatively, the refrigerant passing through the bypass lines (72, 111, 112) can be discarded, and the bypass lines (72, 111, 112) can communicate with the outside.

The inflator 82 inflates the refrigerant to lower the pressure of the refrigerant whose pressure has risen in the refrigerant compressor 81, so that the temperature of the refrigerant is lowered to -165 ° C. to -196 ° C. and the cooled refrigerant is supplied to the condenser 70 The liquefaction efficiency of the evaporation gas can be improved.

The evaporative gas decompressor 90 is provided downstream of the condenser 70 on the branch line 17 and is pressurized in the evaporative gas compressor 50 to reduce the evaporated gas heat exchanged in the condenser 70. For example, the evaporation gas decompressor 90 can reduce the pressure of the evaporation gas to 1 to 10 bar, and the evaporation gas can be liquefied and reduced to 1 bar when it is transferred to the liquefied gas storage tank 10, The cooling effect can be achieved.

Here, the evaporated gas pressurized in the evaporative gas compressor (50) is cooled by heat exchange with the refrigerant in the condenser (70), but the pressure can maintain the discharge pressure discharged from the evaporative gas compressor (50). In the present embodiment, the evaporation gas is decompressed by using the evaporation gas decompressor 90 so that the evaporation gas is cooled, and the evaporation gas can be liquefied. At this time, the larger the pressure range to be depressurized, the greater the cooling effect of the evaporative gas.

The evaporative gas decompressor 90 may be a line Thompson valve. Alternatively, the evaporative gas decompressor 90 may comprise an expander. In the case of the Row Thompson valve, depressurization can effectively cool the evaporated gas so that at least some of the evaporated gas is liquefied.

On the other hand, the inflator can be driven without using any extra power, and in particular, the efficiency of the liquefied gas processing system 2 can be improved by utilizing the generated power as electric power for driving the evaporative gas compressor 50. The power transmission may be accomplished by, for example, a gear connection or an electric conversion and the like.

The gas-liquid separator 100 is provided on the branch line 17 downstream of the evaporation gas decompressor 90 to separate the gas from the decompressed evaporation gas in the evaporation gas decompressor 90. In the gas-liquid separator 100, the evaporated gas is separated into a liquid and a gas so that the liquid is supplied to the liquefied gas storage tank 10, and the gas can be recovered as flash gas upstream of the evaporative gas compressor 50.

Here, the evaporation gas supplied to the gas-liquid separator 100 may be decompressed and cooled in the evaporation gas decompressor 90. For example, in the evaporative gas compressor (50), the evaporated gas is multi-stage pressurized, and after the temperature is raised, recovered to the condenser (70), heat-exchanged with the refrigerant and supplied to the evaporative gas decompressor (90).

In this embodiment, the liquefied evaporated gas is recovered into the liquefied gas storage tank 10, the flash gas generated in the gas-liquid separator 100 is recovered without discarding, and the evaporated gas and the flash gas are introduced into the evaporative gas compressor 50, And then supplied to the customer 20.

Liquid separator 100 separates the evaporated gas into a liquid and a gas and the liquefied evaporated gas and the flash gas are respectively supplied to the liquefied gas storage tank 10 and the evaporation gas storage tank 10 through the liquid recovery line 103 and the gas recovery line 101, Can be recovered by the gas compressor (50).

The liquid recovery line 103 is connected from the gas-liquid separator 100 to the liquefied gas storage tank 10 to recover the vaporized liquid state to the liquefied gas storage tank 10 and the gas recovery line 101 is connected to the gas- 100 to the upstream of the evaporative gas compressor 50 to recover the flash gas upstream of the evaporative gas compressor 50 to prevent the flash gas from being thrown away and wasted.

The auxiliary heat exchanger 110 is provided on the liquid recovery line 103 downstream of the gas-liquid separator 100 and is connected to the evaporator gas supplied from the gas-liquid separator 100 via the bypass lines 72, 111 and 112 and the refrigerant inflator 82 The refrigerant supplied can be heat-exchanged.

The auxiliary heat exchanger 110 can heat-exchange the evaporated gas supplied from the gas-liquid separator 100 with the refrigerant whose temperature is lowered in the refrigerant inflator 82, thereby subcooling the evaporated gas. For example, after the evaporation gas is depressurized to 3 bar and a temperature of -160 ° C. is established in the evaporation gas decompressor 90, the refrigerant is heat-exchanged with the refrigerant in the auxiliary heat exchanger 110 via the gas-liquid separator 100, Becomes -165 占 폚, so that the temperature becomes sufficiently lower than -161.5 占 폚, at which the evaporation gas is liquefied. That is, in the present embodiment, the evaporation gas can be sub-cooled by further lowering the temperature of the evaporation gas by further utilizing the cold of the refrigerant. At this time, the liquefied gas in the liquefied gas storage tank 10 can also be sub-cooled by returning to the liquefied gas storage tank 10, thereby suppressing the generation of the evaporated gas.

Here, one of the two flow paths provided in the auxiliary heat exchanger 110 is composed of the bypass lines 72, 111 and 112 so that the refrigerant in the refrigerant line 71 flows to the auxiliary heat exchanger 110.

In this embodiment, the bypass lines 72, 111 and 112 can join the refrigerant line 71 via the auxiliary heat exchanger 110. When the refrigerant supplied from the auxiliary heat exchanger 110 maintains a sufficiently low temperature, (In the range of -165 ° C to -196 ° C, which is the temperature of the refrigerant expanded in the refrigerant inflator 82) -173 ° C to -196 ° C, which is the temperature adjacent to -196 ° C, the bypass line 111 The refrigerant is joined to the downstream side of the refrigerant inflator 82 in the refrigerant line 71 so that the refrigerant is heat-exchanged with the evaporation gas in the auxiliary heat exchanger 110 and then directly supplied to the condenser 70 to heat- 111 may be joined downstream of the branching point.

Even when the cold heat of the refrigerant supplied from the auxiliary heat exchanger 110 is higher than the temperature of the refrigerant expanded in the refrigerant inflator 82 and the cold is insufficient (for example, -160 캜 to -170 캜), the bypass lines 72, Can join the refrigerant line (71) via the auxiliary heat exchanger (110). The bypass line 112 may be joined upstream of the refrigerant compressor 81 in the refrigerant line 71 so that the refrigerant is heat-exchanged with the evaporation gas in the auxiliary heat exchanger 110 and then supplied to the refrigerant compressor 81 .

As described above, in this embodiment, the liquefied evaporated gas is supercooled by further utilizing the cold heat of the low refrigerant at the temperature of -165 DEG C to -196 DEG C in the refrigerant cycle through the refrigerant line 71, 10) is sufficiently lower than the boiling point of the liquefied gas at -161.5 DEG C, generation of evaporation gas can be suppressed.

1,2: liquefied gas processing system 10: liquefied gas storage tank
16: Evaporative gas supply line 17: Branch line
20: Demand source 50: Evaporative gas compressor
60: Evaporative gas heat exchanger 70: Condenser
71: Refrigerant line 72, 111, 112: Bypass line
81: Refrigerant compressor 82: Refrigerant expander
90: Evaporative gas decompressor 100: Gas-liquid separator
101: gas recovery line 103: liquid recovery line
110: auxiliary heat exchanger

Claims (6)

An evaporative gas line connected to the liquefied gas storage tank;
A plurality of evaporative gas compressors provided on the evaporative gas line for pressurizing the evaporative gas generated in the liquefied gas storage tank in multiple stages;
A condenser provided on the evaporation gas line for heat-exchanging the evaporated gas pressurized by the evaporation gas compressor using a refrigerant;
A refrigerant line through which the refrigerant is circulated via the condenser;
A refrigerant compressor provided on the refrigerant line to pressurize the refrigerant in multiple stages;
A refrigerant inflator provided in the refrigerant line for expanding a refrigerant that is pressurized by the refrigerant compressor and heat-exchanged in the condenser;
A bypass line branching from the refrigerant line to bypass the refrigerant supplied from the refrigerant inflator;
A liquid recovery line connected to the evaporation gas line for recovering at least a part of the evaporated gas discharged from the condenser to the liquefied gas storage tank; And
And an auxiliary heat exchanger provided on the liquid recovery line for exchanging heat between the evaporated gas recovered to the liquefied gas storage tank and the refrigerant supplied from the refrigerant inflator via the bypass line. The method according to claim 1,
And a gas-liquid separator provided on the evaporation gas line for separating the evaporation gas into a gas and a liquid,
The liquid recovery line is connected from the gas-liquid separator to the liquefied gas storage tank and recovers the liquid-state evaporative gas separated from the gas-liquid separator to the liquefied gas storage tank,
Wherein the auxiliary heat exchanger subcools the evaporated gas. 3. The apparatus according to claim 2,
The refrigerant is branched at the downstream side of the refrigerant inflator in the refrigerant line and joined to the upstream of the condenser so that the refrigerant is heat-exchanged with the evaporation gas in the auxiliary heat exchanger and then supplied to the condenser, Is downstream of a point where the branching point is branched. 3. The apparatus according to claim 2,
Wherein the refrigerant is branched downstream of the refrigerant inflator in the refrigerant line so as to be joined to the upstream side of the refrigerant compressor so that the refrigerant is heat-exchanged with the evaporation gas in the auxiliary heat exchanger and then supplied to the refrigerant compressor. 3. The method of claim 2,
Further comprising a gas recovery line connected from the gas-liquid separator to an upstream side of the evaporative gas compressor to supply a flash gas separated by the gas-liquid separator to the evaporative gas compressor. 3. The method of claim 2,
Further comprising an evaporation gas decompressor provided upstream of the gas-liquid separator on the evaporation gas line for decompressing the evaporation gas.

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