KR20200012670A - Boil-off gas cooling system and ship having the same - Google Patents

Abstract

The present invention relates to a boil off gas cooling system and a ship. The boil off gas cooling system includes: a cooling device heat-exchanging boil off gas generated in a liquefied gas storage tank with a first refrigerant; a compressor compressing the boil off gas heat-exchanged in the cooling device; a liquefier heat-exchanging the boil off gas compressed in the compressor and the first refrigerant with a second refrigerant; and a refrigerant heat exchanger cooling the first refrigerant or the second refrigerant by using liquefied gas supplied to a demand source from the liquefied gas storage tank.

Description

Boil-off gas cooling system and ship having the same

The present invention relates to a boil-off gas cooling system and a ship.

Liquefied gas carriers that carry liquefied gases, such as Liquefied Natural Gas or Liquefied Petroleum Gas, are those that have a boiling point below room temperature. Is forcibly liquefied and stored in a liquid tank.

Liquefied natural gas is liquefied by cooling methane (CH4) obtained by refining natural gas collected from a gas field. It is a colorless and transparent liquid. Liquefied petroleum gas, on the other hand, is a liquid made of gas containing propane (C3H8) and butane (C4H10), which come with petroleum from oil fields, and is widely used as a fuel for household, business, industrial, and automobiles. Liquefied natural gas is reduced to a volume of 1/600 by liquefaction, liquefied petroleum gas has the advantage of high storage efficiency by reducing the volume of propane is 1/260, butane is 1/230 by liquefaction.

By the way, the storage tank for storing the liquefied gas is implemented a heat insulation function, but can not completely block the vaporization of the liquefied gas. Therefore, in the storage tank, a gaseous evaporation gas generated by the liquefied gas evaporates, and the evaporated gas increases the internal pressure of the storage tank, so it must be discharged from the storage tank for safety.

In order to lower the internal pressure of the storage tank, the evaporated gas discharged from the storage tank is combusted and discarded by a gas combustion unit. By the way, the boil-off gas also corresponds to some of the cargo carried by the ship, the emission of the boil-off gas is a problem because it reduces the reliability of the cargo transportation.

Therefore, in recent years, continuous research and development has been made on a method for effectively treating the boil-off gas generated in the storage tank without discarding it.

The present invention was created to solve the problems of the prior art as described above, an object of the present invention, an evaporation gas cooling system and a vessel comprising the same to reduce the capacity of the reliquefaction configuration by liquefying the evaporated gas into a refrigerant without precooling It is to provide.

It is also an object of the present invention to provide an evaporative gas cooling system and a vessel including the same, which promotes energy consumption while propelling liquefied gas while using evaporated gas as a fuel or reliquefying it.

An evaporative gas treatment system according to an aspect of the present invention includes a cooler configured to heat-exchange an evaporated gas generated in a liquefied gas storage tank with a first refrigerant; A compressor for compressing the boil-off gas exchanged in the cooler; A liquefier for exchanging the boil-off gas and the first refrigerant compressed by the compressor with the second refrigerant; And a refrigerant heat exchanger for cooling the first refrigerant or the second refrigerant by using the liquefied gas supplied from the liquefied gas storage tank to the demand destination.

Specifically, the first refrigerant may be a material in which a phase change occurs by heat exchange with the second refrigerant or the boil-off gas.

Specifically, the cooler may be returned to the liquefied gas storage tank after receiving the evaporated gas heat-exchanged with the second refrigerant in the liquefier again and heat exchanged with the first refrigerant.

Specifically, the refrigerant heat exchanger may cool the first refrigerant before cooling the second refrigerant by using liquefied gas supplied to the demand destination.

Specifically, the first refrigerant circulation line via the cooler and the liquefier; A first refrigerant compressor provided in the first refrigerant circulation line; And a refrigerant gas-liquid separator for gas-liquid separating the first refrigerant heat-exchanged with the second refrigerant, wherein the refrigerant heat exchanger is provided upstream of the liquefier in the first refrigerant circulation line, The boil-off gas may be cooled by the first refrigerant in a liquid state separated from the refrigerant gas-liquid separator.

Specifically, the refrigerant heat exchanger may be provided in the first refrigerant circulation line between the first refrigerant compressor and the liquefier.

Specifically, the refrigerant heat exchanger may be provided in the first refrigerant circulation line between the refrigerant gas-liquid separator and the cooler.

Specifically, the second refrigerant circulation line via the liquefier; And a second refrigerant compressor provided in the second refrigerant circulation line, wherein the refrigerant heat exchanger may be provided in the second refrigerant circulation line between the second refrigerant compressor and the liquefier.

Specifically, a pump for pressurizing the liquefied gas discharged from the liquefied gas storage tank, wherein the refrigerant heat exchanger may be provided downstream of the pump on the basis of the flow of the liquefied gas.

In detail, the liquefied gas which is sequentially heat-exchanged by the liquefier and the cooler may be mixed with the liquefied gas discharged from the liquefied gas storage tank and supplied to the demand destination.

Ship according to one aspect of the invention, characterized in that having the boil-off gas cooling system.

The evaporative gas cooling system and the ship including the same according to the present invention can reduce the capacity of the liquefier by not precooling the evaporated gas before the heat exchange of the refrigerant, and can increase the energy consumption efficiency while returning the liquefied gas or supplying it to the engine for consumption. have.

1 is a conceptual diagram of an evaporative gas cooling system according to a first embodiment of the present invention.
2 is a conceptual diagram of an evaporative gas cooling system according to a second embodiment of the present invention.
3 is a conceptual diagram of an evaporative gas cooling system according to a third embodiment of the present invention.
4 is a conceptual diagram of an evaporative gas cooling system according to a fourth embodiment of the present invention.
5 is a conceptual diagram of an evaporative gas cooling system according to a fifth embodiment of the present invention.
6 is a conceptual diagram of an evaporative gas cooling system according to a sixth embodiment of the present invention.
7 is a conceptual diagram of an evaporative gas cooling system according to a seventh embodiment of the present invention.

The objects, specific advantages and novel features of the present invention will become more apparent from the following detailed description and the preferred embodiments associated with the accompanying drawings. In the present specification, in adding reference numerals to the components of each drawing, it should be noted that the same components as possible, even if displayed on different drawings have the same number as possible. In addition, in describing the present invention, if it is determined that the detailed description of the related known technology may unnecessarily obscure the subject matter of the present invention, the detailed description thereof will be omitted.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. Hereinafter, in the present specification, the gas may be used to encompass all substances vaporized in a gaseous state at room temperature, such as LNG or LPG, ethylene, ethane, ammonia, etc. Hereinafter, in the present specification, liquefied gas includes methane, propane, butane, etc. for convenience. It is assumed that it contains LNG.

In addition, liquefied gas means a gas liquefied for storage, evaporated gas means a natural vaporized gas, and the state of liquefied gas or evaporated gas is not limited to liquid and gas, respectively. For reference, liquefied gas contains heavy carbon such as propane and butane, while natural vaporized evaporated gas has (almost) no heavy carbon and mainly contains methane.

In addition, liquefaction in the following does not mean only the case of completely reliquefaction, but can be used as a meaning encompassing at least some intended liquefaction cooling, it is noted that the high pressure and low pressure is a relative meaning, not an absolute value.

The present invention includes a vessel having an evaporative gas cooling system described below, wherein the vessel encompasses all commercial vessels having no type limitation, such as container ships or bulk carriers, in addition to gas ships carrying liquefied gas. Furthermore, in the present specification, a vessel may be used to encompass a marine plant fixed or floating in the ocean in addition to the general merchant vessel.

1 is a conceptual diagram of an evaporative gas cooling system according to a first embodiment of the present invention.

1, the boil-off gas cooling system 1 according to the first embodiment of the present invention, the liquefied gas storage tank 10, the compressor 20, the liquefier 30, the gas-liquid separator 40, the pump (50).

The liquefied gas storage tank 10 stores liquefied gas. The liquefied gas storage tank 10 is not limited to its type, such as a stand-alone type, a membrane type, a pressure vessel type, and the like, and an installation position in a ship is not particularly limited.

For example, when the vessel is a gas line, the liquefied gas storage tank 10 may be a cargo tank provided in plural in the ship in the longitudinal direction, and when the vessel is another ship type such as a container ship other than a ship that transports liquefied gas, the deck It may be a pressure vessel disposed above the bow or stern.

The liquefied gas storage tank 10 may implement heat insulation to store the liquefied gas in the liquid phase, and / or increase the storage pressure to prevent vaporization of the liquefied gas.

The boil-off gas generated in the liquefied gas storage tank 10 may be discharged to the outside because the internal pressure of the liquefied gas storage tank 10 increases, and the boil-off gas discharged to the outside may be discharged by the liquefier 30 to be described later. It may be cooled / liquefied and returned to the liquefied gas storage tank 10 or consumed at the demand destination E.

For reference, in the present specification, the demand source E for consuming boil-off or liquefied gas may be a propulsion engine for propelling a ship, or a power generation engine generating power required in a ship, and / or a turbine, a boiler, in addition to an engine. The gas combustion device (GCU), the fuel cell and the like are not limited in kind.

The compressor 20 compresses the boil-off gas generated in the liquefied gas storage tank 10. The boil-off gas discharged from the liquefied gas storage tank 10 may be around 1 bar corresponding to the internal pressure of the liquefied gas storage tank 10, and the present specification uses the compressor 20 to increase the boiling point of the boil-off gas. Can be compressed.

The compressor 20 is not limited to the type of centrifugal type, reciprocating type, and the like, and may be provided in one stage or two or more stages in series. In addition, the compressor 20 may be provided with a plurality of compressors 20 in parallel as shown in the figure, in this case it may be possible to back up each other.

In the liquefied gas storage tank 10 through the compressor 20, the liquefier 30 to be described later may be provided with an liquefied gas liquefaction line (L1), the liquefied gas liquefied line (L1) is downstream of the liquefier (30) It can be connected to the gas-liquid separator 40.

In the boil-off gas liquefaction line (L1) downstream of the compressor 20, a boil-off gas branch line (L2) is provided may be connected to the demand destination (E). In this case, the demand source E may mean a power generation engine, a GCU, or the like, and may include all demand sources E having a required pressure corresponding to the discharge pressure of the compressor 20. However, the boil-off gas branch line L2 may be provided to branch in the middle of the multistage compressor 20 according to the specifications of the compressor 20.

As will be described later, the pump 50 may supply the liquefied gas and the boil-off gas to the demand destination E, wherein the demand destination E may be a main engine such as a high pressure engine. However, since there is no pressurization means between the compressor 20 and the pump 50, the pump 50 may be provided as a specification for compressing the evaporated gas by the difference in the required pressure of the power generation engine and the main engine.

The liquefier 30 liquefies the compressed boil-off gas. The liquefier 30 may cool the evaporated gas using various refrigerants, which are not limited. For example, the liquefier 30 may be nitrogen, liquefied gas, mixed refrigerant, or the like.

The boil-off gas liquefied by the liquefier 30 may be returned to the liquefied gas storage tank 10 in the liquid phase. Therefore, even if the boil-off gas is generated in the liquefied gas storage tank 10, as the boil-off gas is returned after discharge and liquefaction, the internal pressure of the liquefied gas storage tank 10 can be maintained at a stable level.

However, the evaporated gas flowing into the liquefier 30 may be in a compressed state to increase the boiling point, and a valve (not shown) to reduce the evaporated gas between the liquefier 30 and the liquefied gas storage tank 10. ) May be provided.

Of course, considering the internal volume of the liquefied gas storage tank 10, even if the evaporated gas is returned without a separate decompression may be naturally reduced in the liquefied gas storage tank 10, the pressure reducing valve may not be provided.

The liquefier 30 may use a mixed refrigerant (Mixed Refrigerant), in which case the liquefier 30 may be via a closed loop refrigerant circulation line (L10). In the refrigerant circulation line L10, the refrigerant changes in the order of compression, cooling, expansion, and heating, and the boil-off gas may be cooled when the refrigerant is heated.

A refrigerant compressor 100 for compressing a refrigerant may be provided in the refrigerant circulation line L10, and a refrigerant cooler 120 for cooling the compressed refrigerant is provided downstream of the refrigerant compressor 100 in the refrigerant circulation line L10. Can be prepared. The refrigerant cooler 120 may use a cold source that is not limited for cooling the refrigerant. However, since the compressed refrigerant may be cooled in the liquefier 30, the refrigerant cooler 120 may be omitted.

The refrigerant compressed by the refrigerant compressor 100 (cooled by the refrigerant cooler 120 after compression) is in a cryogenic state as the refrigerant is decompressed / expanded by the refrigerant pressure reducing valve 110. At this time, the refrigerant in the cryogenic state again flows into the liquefier 30, and heat-exchanges with the boil-off gas introduced into the liquefier 30 along the boil-off gas liquefaction line L1 to cool the boil-off gas.

In addition, the low pressure refrigerant in the cryogenic state may cool the high pressure refrigerant compressed in the refrigerant compressor 100 while cooling the evaporated gas compressed in the liquefier 30. That is, the liquefier 30 may implement heat exchange between the refrigerants while cooling the boil-off gas with the refrigerants.

The refrigerant may be liquefied by a reduced pressure as a mixed refrigerant including propane and the like, and may be vaporized while exchanging heat with the boil-off gas in the liquefier 30. Therefore, the latent heat absorbed when the refrigerant is vaporized can be utilized for cooling the boil-off gas.

As described above, the evaporation gas liquefaction line L1 is connected to the liquefier 30 in the liquefied gas storage tank 10, which is introduced into the liquefier 30 through the evaporation gas liquefaction line L1 in this embodiment. The boil-off gas may be discharged from the liquefied gas storage tank 10 and then introduced into the liquefier 30 without precooling.

When the boil-off gas is pre-cooled with a cooled boil-off gas, the volume of the boil-off gas flowing into the compressor 20 is reduced, so that the load of the compressor 20 can be reduced, but the temperature of the boil-off gas flowing into the liquefier 30 is reduced. As is lowered, the temperature of the refrigerant used to cool the boil-off gas in the liquefier 30 should be further lowered.

In this case, in order to further lower the temperature of the refrigerant, the specifications of the refrigerant compressor 100, the refrigerant cooler 120, and the like described above are inevitably expanded, so that the capacity of the liquefier 30 itself increases. The problem that the installation cost or operating cost of the machine 30 increases.

Therefore, the present invention considers that the effect due to the reduction of the capacity of the liquefier 30 is greater than the effect due to the load reduction of the compressor 20, so that the pre-cooling of the evaporating gas is omitted and the relatively high temperature of the evaporating gas is liquefied. By directly entering the device 30, the temperature required for the refrigerant can be increased to reduce the capacity of the liquefier 30.

However, the present invention omits that the compressor 20 is pre-cooled by liquefied boil-off gas or the like, and when the compressor 20 is provided in multiple stages, the compressor 20 is located between the compressors 20 or downstream of the final compressor 20. Note that it does not mean to omit the intercooler 21 is provided as a set).

In the present embodiment, the liquefier 30 liquefies the evaporated gas compressed by the compressor 20 with the refrigerant, and the liquefied gas (and the liquid evaporated gas) supplied to the demand destination E by the pump 50. It may be provided to recover the cold heat. That is, the liquefier 30 may be provided such that refrigerant before and after the pressure reducing valve flows, the evaporated gas compressed by the compressor 20 flows, and the liquefied gas pressurized by the pump 50 flows.

In this case, the liquefied gas supplied to the demand destination E may be heated while cooling the boiled gas. Therefore, the liquefied gas 30 may be used as a vaporizing means of the liquefied gas while liquefiing the boiled gas.

Alternatively, even if the vaporizer 51 for vaporizing the liquefied gas is provided separately in this embodiment, as long as the liquefied gas is heated in the liquefier 30, the load of the vaporizer 51 can be reduced.

Thus, since the liquefier 30 recovers the cold heat of the liquefied gas supplied to the demand destination E, the present embodiment further liquefies in addition to the capacity reduction of the liquefier 30 due to not precooling the boil-off gas. 30 capacity reduction is possible.

The temperature at which the liquefier 30 cools the evaporated gas may be equal to or lower than the boiling point in consideration of the pressure of the evaporated gas. For example, the evaporated gas discharged from the liquefier 30 when the discharge pressure of the compressor 20 is 5 to 20 bar. The temperature of can be around -120 degrees Celsius. Although described later, the cooling temperature of the liquefier 30 may be such that the cavitation does not occur in the pump 50.

The gas-liquid separator 40 is provided between the liquefier 30 and the pump 50 to be described later, and transfers the liquid vaporized gas out of the boil-off heat exchanged by the liquefier 30 to the pump 50. Even if the liquefier 30 liquefies the boil-off gas using a mixed refrigerant or the like, nitrogen or the like having a very low boiling point included in the boil-off gas may remain in a gaseous state.

At this time, when a gas such as nitrogen is introduced into the pump 50, the pump 50 may have a cavitation phenomenon, and operation efficiency and durability may be reduced. Therefore, the gas-liquid separator 40 may filter the material remaining in the gaseous state of the evaporated gas introduced through the liquefier 30 to transfer the liquid evaporated gas to the pump 50, wherein the gaseous material is the flash gas. (flash gas).

The flash gas contains nitrogen but still has a calorific value, and since it is a low temperature state, recycling is preferable. Therefore, the flash gas may be discharged from the gas-liquid separator 40 and introduced into the compressor 20 upstream, or may be used for heat exchange in the liquefier 30, and may be delivered to a separate consumer and consumed.

Alternatively, this embodiment may re-liquefy nitrogen so that nitrogen can be delivered from gas-liquid separator 40 to pump 50 and supplied to demand E. To this end, the gas-liquid separator 40 may maintain the internal pressure at a high pressure to sufficiently increase the boiling point of nitrogen, and the compressor 20 may also compress the boil-off gas to allow liquefaction of nitrogen in the liquefier 30. .

In this case, nitrogen contained in the boil-off gas can be maintained in the liquid phase in the gas-liquid separator 40, so that the liquid boil-off gas containing nitrogen and the liquefied gas mixed therein are pumped to the demand (E) via the pump (50). Inflow and consumption. Therefore, by supplying nitrogen to the pump 50 in the liquid phase, it is possible to prevent the accumulation of nitrogen in the system, and also to prevent the reduction in engine efficiency due to the accumulation of nitrogen.

Alternatively, the nitrogen gas may be separated into the flash gas in the gas-liquid separator 40 without being reliquefied and then joined downstream of the pump 50 to be supplied to the demand destination E. In this case, the pressure of the flash gas may be supplied to the demand destination E. Of course, it may be provided with a separate compression means to meet the required pressure of).

The boil-off gas liquefaction line (L1) is extended from the liquefied gas storage tank 10 may be connected to the gas-liquid separator 40 through the boil-off gas compressor 20, the liquefier 30, the liquefied gas in the gas-liquid separator 40 The storage tank 10 is provided with a boil-off gas return line (L3). The liquid evaporated gas may be introduced into the liquefied gas storage tank 10 along the evaporated gas return line L3.

The boil-off gas flowing from the liquefier 30 to the gas-liquid separator 40 may be in a supercooled state, and the pressure of the boil-off gas may be 5 to 10 bar (for example, 8 bar), and may be lower than the internal pressure of the liquefied gas storage tank 10. Can be kept high.

Therefore, since the boiling point of the boil-off gas in the gas-liquid separator 40 is higher than the boiling point of the boil-off gas at atmospheric pressure, the boil-off gas in the gas-liquid separator 40 can maintain the liquid phase relatively easily. Therefore, the cold heat consumption of the liquefier 30 can be reduced, and the cavitation of the pump 50 can be suppressed as the evaporation gas is introduced while maintaining the liquid phase in the pump 50 provided downstream of the gas-liquid separator 40. .

When the boil-off gas is returned from the gas-liquid separator 40 to the liquefied gas storage tank 10, the pressure of the boil-off gas decreases due to the internal volume of the liquefied gas storage tank 10, and the boil-off gas is celsius due to the Joule-Thomson effect. The temperature can drop to around -160 degrees. Therefore, the liquid evaporated gas flowing into the liquefied gas storage tank 10 maintains the supercooled state, thereby suppressing the generation of the evaporated gas in the liquefied gas storage tank 10.

The liquefied gas discharged by the transfer pump (not shown) from the liquefied gas storage tank 10 may be introduced into the gas-liquid separator 40. That is, the gas-liquid separator 40 may be a mixing means for mixing the liquefied gas discharged from the liquefied gas storage tank 10 and the boil-off gas liquefied in the liquefier 30.

The liquid evaporated gas + liquefied gas separated from the gas-liquid separator 40 may be delivered to the demand-side E through the liquefied gas supply line L5 connected from the gas-liquid separator 40 to the demand-side E. In this case, the liquefied gas supply line L5 may be directly connected to the demand destination E in the gas-liquid separator 40 or branched off from the boil-off gas return line L3 to be connected to the demand destination E.

Therefore, the boil-off gas introduced into the gas-liquid separator 40 is returned to the liquefied gas storage tank 10 through the boil-off gas return line L3 or through the liquefied gas supply line L5 and the pump 50. ) Can be supplied. That is, in this embodiment, the boil-off gas may be mixed with the liquefied gas and consumed as fuel or liquefied by a refrigerant, and a cooling load (cooling temperature of the evaporated gas) in the liquefier 30 to consume the boil-off gas as fuel. Of course, the control can be reduced.

When all the boil-off gas generated in the liquefied gas storage tank 10 is mixed with the liquefied gas and supplied to the demand destination E, the consumption of the liquefied gas decreases as the amount of the boil-off gas increases, so that energy consumption efficiency can be improved. have.

However, when the amount of boil-off gas is insufficient when using the boil-off gas together with the liquefied gas as fuel, there is a problem that the energy consumption efficiency is not good.

On the other hand, if all the liquefied gas generated from the liquefied gas storage tank 10 is liquefied and only the liquefied gas is supplied to the demand destination E, the energy consumption efficiency is relatively constant regardless of the amount of generated boiled gas.

However, in this case, there is a problem that energy may be wasted a little because the refrigerant must be used for reliquefaction of the boiled gas at all times, and if a large amount of boiled gas is generated, a large amount of refrigerant needs to be cooled, so energy consumption is higher than that of supplying boil-off gas as fuel. The efficiency becomes worse.

In this embodiment, in consideration of the energy consumption efficiency in the case of using the evaporated gas as the total amount of fuel, and the total amount of re-liquefied evaporated gas, it is possible to supply the re-liquefied evaporated gas to the fuel while re-liquefying the evaporated gas. For example, the liquefied gas may be mixed with the boil-off gas supplied as fuel.

In this embodiment, when the amount of generated evaporation gas is less than the demand (E), the liquefied gas is re-liquefied and the liquefied gas is mainly supplied as fuel (mixed supply of liquefied gas and evaporated gas) to increase energy consumption efficiency. On the contrary, if the amount of generated boil-off gas is larger than the demand (E), it is possible to increase the energy consumption efficiency by supplying the boil-off gas mainly as fuel (stopping the supply of the liquefied gas).

At this time, the amount of generated boil-off gas can be measured by a pressure gauge provided in the liquefied gas storage tank 10 or a flow meter provided in the boil-off gas liquefaction line (L1) and the like. Obviously, it can be confirmed through an engine load.

The pump 50 supplies the evaporation gas heat-exchanged by the liquefier 30 to the demand destination E. As shown in FIG. In this case, the demand destination E may be a high-pressure engine such as ME-GI or XDF as the main engine, and the pump 50 may pressurize the boil-off gas in accordance with the required pressure of the high-pressure engine.

Evaporation gas and liquefied gas of the liquid delivered from the gas-liquid separator 40 may be introduced into the pump 50, and as described above, the gas-liquid separator 40 maintains the high pressure such as 8 bar to maintain the evaporated gas in the liquid phase. As such, cavitation of the pump 50 can be sufficiently prevented.

The boil-off gas (and the liquefied gas) supplied to the demand destination E by the pump 50 can flow through the liquefier 30 while flowing along the liquefied gas supply line L5. Therefore, the liquefier 30 may cool the boil-off gas compressed by the compressor 20 with the boil-off gas supplied to the demand destination E, and through this, the heating load and the liquefier of the boil-off gas delivered to the demand destination E ( The capacity of 30) can be reduced as described above.

In other words, the present embodiment can recover the cold heat of the liquefied gas used in the high-pressure engine evenly to a higher temperature, thereby increasing the liquefaction efficiency and the like.

Although not shown in the drawings, a vaporizer (not shown) is provided downstream of the pump 50, and the vaporizer is pressurized by the pump 50 and then heated to the liquefied gas 30 in the liquefied gas 30 to obtain the required temperature of the demand destination E. You can change it accordingly.

As described above, the present embodiment can reduce the capacity of the liquefier 30 by exchanging the evaporated gas with the refrigerant in the liquefier 30 without precooling, and ensure the energy consumption efficiency by appropriately controlling the liquefaction and fuel supply of the evaporated gas. can do.

In addition, in the present embodiment, the cold heat of the liquefied gas (and the liquid evaporated gas) supplied to the demand destination E is sufficiently recovered for the liquefaction of the boiled gas, so that the capacity of the liquefier 30 can be further reduced, thereby improving the overall efficiency of the system. It can be improved.

2 is a conceptual diagram of an evaporative gas cooling system according to a second embodiment of the present invention.

Referring to FIG. 2, in the boil-off gas cooling system 1 according to the second embodiment of the present invention, in comparison with the first embodiment, at least a portion of the boil-off gas between the liquefier 30 and the pump 50 is liquefied. Returning to (30), it is possible to exchange heat with the refrigerant.

Hereinafter, the present embodiment will be described based on the point that the present embodiment is different from the previous embodiment, and the description thereof will be replaced with the above contents. This also applies to the contents of other embodiments described below.

The liquefier 30 of the present embodiment cools the evaporated gas compressed by the compressor 20 with the refrigerant decompressed by the refrigerant pressure reducing valve 110, and at the same time between the liquefier 30 and the pump 50 (liquefier). And between the 30 and the gas-liquid separator 40 can be cooled.

In this case, the liquefied gas storage tank 10 is branched from between the liquefier 30 and the gas-liquid separator 40 to the boil-off gas liquefaction line L1 connected to the gas-liquid separator 40 via the liquefier 30. The boil-off gas return line L3 connected to the liquefied gas storage tank 10 after passing through the liquefier 30 may be provided.

Therefore, the boil-off gas is compressed by the compressor 20 along the boil-off gas liquefaction line L1 and then primarily cooled by the refrigerant in the liquefier 30, at least a part of which is a gas-liquid separator through the boil-off gas liquefaction line L1. 40, the remainder is secondly cooled by the refrigerant in the liquefier 30 through the boil-off gas return line L3 upstream of the gas-liquid separator 40 to be recovered to the liquefied gas storage tank 10. Can be.

Since the present embodiment is capable of two-stage cooling in the liquefier 30 with respect to the boil-off gas, the boil-off gas may not be supercooled at the time of the first cooling in the liquefier 30, the two in the liquefier 30 The evaporation gas may be supercooled during the secondary cooling.

That is, the boil-off gas may be a liquid phase when first cooled in the liquefier 30 through the boil-off gas liquefaction line (L1) and then introduced into the gas-liquid separator 40, and the liquefier through the boil-off gas return line (L3). After the second cooling at 30, the liquefied gas storage tank 10 may be in a subcooled state when introduced.

In this case, since the gas-liquid separator 40 maintains a higher internal pressure than the liquefied gas storage tank 10, the evaporated gas delivered from the gas-liquid separator 40 to the pump 50 is introduced into the liquid phase and the cavitation of the pump 50 is Can be suppressed.

In the present embodiment, the vaporized gas return line L3 may not be provided from the gas-liquid separator 40 to the liquefied gas storage tank 10, and is liquefied in the liquefier 30 and then introduced into the gas-liquid separator 40. The boil-off gas may be mixed with the liquefied gas and supplied to the customer E through the pump 50.

That is, the evaporated gas downstream of the liquefier 30 may be introduced into the gas-liquid separator 40 to be used as fuel, or may be re-introduced into the liquefier 30 to be recovered to the liquefied gas storage tank 10. The flow rate at which the primary cooled boil-off gas is distributed to the gas-liquid separator 40 and the liquefier 30 may be appropriately controlled according to the amount of the boil-off gas generated and the demand of the customer E.

Such control may be achieved by adjusting the opening degree of the flow rate control valve 31 installed near the point where the boil-off gas return line L3 branches in the boil-off gas liquefaction line L1. That is, the flow regulating valve 31 may be two valves, one three-way valve, or the like, and the opening degree may be changed in conjunction with the amount of generated evaporation gas and the required amount of the demand destination E.

However, at least one of the flow control valve 31 provided in the boil-off gas liquefaction line L1 or the boil-off gas return line L3 may be a pressure reducing valve. For example, the flow regulating valve 31 provided in the boil-off gas return line L3 may be a pressure reducing valve, and the pressure reducing valve may reduce / decrease the temperature of the boil-off gas by reducing / expanding the compressed boil-off gas at a pressure for increasing liquefaction efficiency. Can be induced.

The pressure reducing valve may be provided upstream of the liquefier 30 in the boil-off gas return line L3. Therefore, the boil-off gas may be caused to decrease in temperature due to depressurization between primary and secondary cooling in the liquefier 30 and may be placed in a sufficient low temperature state when returned to the liquefied gas storage tank 10.

Of course, the flow control valve 31 provided between the liquefier 30 and the gas-liquid separator 40 in the boil-off gas liquefaction line (L1) can also be used as a pressure reducing valve, in this embodiment, the gas-liquid separator 40 is about 8bar Since it is possible to prevent the cavitation of the pump 50 by maintaining the high pressure, even if a pressure reducing valve is provided in the boil-off gas liquefaction line (L1), the decompression degree of the pressure-reducing valve is less than the pressure reducing valve provided in the boil-off gas return line (L3). Can be.

As such, the present embodiment divides the flow of the liquefied boil-off gas from the liquefier 30 into what is returned after subcooling and is consumed as fuel after being pressurized by the pump 50 to reduce the energy required in the liquefier 30. Since the liquefier 30 capacity can be reduced.

3 is a conceptual diagram of an evaporative gas cooling system according to a third embodiment of the present invention.

Referring to FIG. 3, in the boil-off gas cooling system 1 according to the third embodiment of the present invention, the liquefier 30 may include a first liquefier 30a and a second liquefier 30b. .

The first liquefier 30a cools the boil-off gas compressed by the compressor 20 with the refrigerant decompressed by the refrigerant pressure reducing valve 110. It may be a three-stream structure provided not to use the cold heat of the liquefied gas and to cool the evaporated gas in two stages.

That is, the first liquefier 30a may have a form in which the refrigerant depressurized by the refrigerant pressure reducing valve 110 exchanges heat with the refrigerant compressed by the refrigerant compressor 100 and the evaporated gas compressed by the compressor 20. The cooled boil-off gas may be at least partially liquefied but not subcooled.

The low temperature boil-off gas discharged from the first liquefier 30a flows into the gas-liquid separator 40 along the boil-off gas liquefaction line L1, and the boil-off gas return line L3 branches to the boil-off gas liquefaction line L1. The liquefied gas storage line L1 may be connected to the liquefied gas storage tank 10 via the second liquefier 30b.

The second liquefier 30b is provided between the first liquefier 30a and the liquefied gas storage tank 10 and decompressed by the refrigerant pressure reducing valve 110 before being introduced into the first liquefier 30a. As the refrigerant, the boil-off gas discharged from the first liquefier 30a may be cooled.

That is, the low temperature refrigerant depressurized by the refrigerant pressure reducing valve 110 may liquefy the boil-off gas in the first liquefier 30a after subcooling the boil-off gas in the second liquefier 30b, and conversely, the compressor 20 The compressed boil-off gas may be liquefied in the first liquefier 30a and then subcooled in the second liquefier 30b.

However, the boil-off gas is liquefied in the first liquefier 30a, delivered to the gas-liquid separator 40, mixed with the liquefied gas, and then supplied by the pump 50 to the fuel of the demand E, or the first liquefier 30a In the cooling), the second cooling in the second liquefier (30b) is supercooled and can be delivered to the liquefied gas storage tank (10).

In other words, the present embodiment similarly to the second embodiment, branches the flow of boil-off gas liquefied by the refrigerant into a fuel supply flow and a subcooled flow, except that the present embodiment uses one liquefier 30 instead. The liquefier 30 may be divided into a first liquefier 30a and a second liquefier 30b.

At this time, the branch of the flow, as in the previous embodiment may be implemented by one or more flow control valve 31 is installed at the point where the boil-off gas return line (L3) in the boil-off gas liquefaction line (L1), flow rate control As described above, at least one of the valves 31 installed in the boil-off gas return line L3 may be a pressure reducing valve.

As described above, the present embodiment includes a first liquefier 30a and a second liquefier 30b to liquefy the boil-off gas to be supplied as fuel to the first liquefier 30a to prevent cavitation of the pump 50. In addition, the second liquefier (30b) is to cool the primary liquefied evaporated gas and then return to the liquefied gas storage tank 10 to effectively suppress the generation of evaporated gas in the liquefied gas storage tank 10, The capacity of one liquefier 30a and the energy consumed in the liquefier 30 as a whole can be reduced.

4 is a conceptual diagram of an evaporative gas cooling system according to a fourth embodiment of the present invention.

Referring to FIG. 4, the boil-off gas cooling system 1 according to the fourth embodiment of the present invention, similarly to the first embodiment, cools the liquefied gas supplied to the demand destination E in the liquefier 30. Unlike the first embodiment, the boil-off gas may be returned to the liquefied gas storage tank 10 after liquefaction, and the liquefied gas may be supplied to the demand destination E after cooling the boil-off gas. That is, this embodiment may not supply the liquid evaporated gas as fuel as compared to the previous embodiment.

In this case, the liquefier 30 may be provided in plurality, and the first liquefier 30a cools the compressed refrigerant and the compressed evaporated gas by using the low-temperature refrigerant decompressed / expanded by the refrigerant pressure reducing valve 110. In addition, the second liquefier 30b may cool the compressed boil-off gas by using the low-temperature refrigerant depressurized by the refrigerant pressure reducing valve 110, and transmit the cold heat of the liquefied gas to the boil-off gas.

That is, the first liquefier 30a illustrated in the upper side liquefies the boil-off gas using a refrigerant, and the second liquefier 30b illustrated in the lower side liquefies the boil-off gas using the refrigerant and the liquefied gas. have. In this case, the liquefied boil-off gas in each liquefier 30 may be mixed and returned to the liquefied gas storage tank 10.

In order to have the liquefier 30 in parallel, the boil-off gas liquefaction line L1 may be branched downstream of the compressor 20 and connected to each liquefier 30, but evaporated downstream of each liquefier 30. The gas liquefaction line L1 may be joined. The line after confluence may be referred to as boil-off gas return line L3.

The boil-off gas cooled in the first liquefier 30a using the coolant may have a different temperature from the boil-off gas cooled in the second liquefier 30b using both the coolant and the liquefied gas. It depends on the amount of liquefied gas flowing in (required amount of the demand E) and the amount of generated boil-off gas.

Therefore, in the present embodiment, the flow rate at which the boil-off gas compressed by the compressor 20 branches to the liquefiers 30 is adjusted according to the demand amount E, the boil-off gas generation amount, and the like. It can be recovered enough.

However, if the temperature of the refrigerant compressed by the refrigerant compressor 100 and the temperature of the liquefied gas pressurized by the pump 50 are the same / similar, when the flow rate flowing inside the liquefier 30 is the same, each liquefier 30 The degree to which the boil-off gas is cooled may be the same.

However, unlike the drawing, when the pump 50 is provided downstream of the second liquefier 30b, unlike the first liquefier 30a, the boil-off gas may be supercooled in the second liquefier 30b. In this embodiment, however, the second liquefier 30b is disposed downstream of the pump 50 so that the liquefied gas pressurized by the pump 50 is heated by the boil-off gas in the second liquefier 30b. The load of the vaporizer 51 between the pump 50 and the demand destination E can be reduced.

In other words, the present embodiment uses the cooling heat of the liquefied gas to cool the evaporated gas, but by appropriately controlling the flow rate of the evaporated gas heat exchanged with the liquefied gas in accordance with the amount of the liquefied gas to load the load of the liquefier 30 and the vaporizer 51 Can be saved.

However, unlike the drawings, the present embodiment may have a form in which the first liquefier 30a and the second liquefier 30b are combined into one liquefier 30, in which case the liquefier 30 is a refrigerant. The refrigerant depressurized by the pressure reducing valve 110, the refrigerant compressed by the refrigerant compressor 100, the evaporated gas compressed by the compressor 20, and the liquefied gas pressurized by the pump 50 may have a structure in which heat exchange at a time. . At this time, the boil-off gas compressed by the compressor 20 is liquefied and returned to the liquefied gas storage tank 10, and the pump 50 heated by the boil-off gas is supplied to the demand destination E through the vaporizer 51.

As described above, in the present embodiment, when the evaporated gas is compressed and cooled by the refrigerant, the cold heat of the liquefied gas supplied to the demand destination E can be recovered, thereby allowing the liquefier 30 and the vaporizer 51 for heating the liquefied gas. ) Can be reduced.

5 is a conceptual diagram of an evaporative gas cooling system according to a fifth embodiment of the present invention.

Referring to FIG. 5, the boil-off gas cooling system 1 according to the fifth embodiment of the present invention may cool the boil-off gas by using two refrigerants that are heat-exchanged with each other, unlike the previous embodiments. The embodiment may further include a cooler 60 and a refrigerant heat exchanger 70 in addition to the compressor 20, the liquefier 30, the gas-liquid separator 40, and the pump 50.

The cooler 60 of this embodiment heat-exchanges the boil-off gas generated in the liquefied gas storage tank 10 with the first refrigerant. The cooler 60 may be provided upstream of the compressor 20 in the boil-off gas liquefaction line L1.

For example, the boil-off gas may be discharged from the liquefied gas storage tank 10 and then exchanged with the first refrigerant in the cooler 60 and transferred to the compressor 20, where it may be cooled by the first refrigerant. However, this embodiment does not implement pre-cooling using a material other than a refrigerant such as a liquid evaporation gas before the boil-off gas exchanges heat with the refrigerant as in the previous embodiments.

In addition, the cooler 60 may receive the evaporated gas heat-exchanged with the second refrigerant in the liquefier 30 to be described later, in which case the second evaporated gas introduced into the cooler 60 is firstly cooled by the cooler 60. After cooling (supercooling) while exchanging heat with the refrigerant, the refrigerant may be returned to the liquefied gas storage tank 10 along the boil-off gas return line L3 extending from the cooler 60 to the liquefied gas storage tank 10.

Thus, although the evaporated gas passing through the cooler 60 and the liquefied gas 30 after being discharged from the liquefier 30 before compression can be cooled by the first refrigerant in the cooler 60, the degree of cooling There may be a difference.

However, the cooler 60 cools the boil-off gas introduced into the compressor 20 by using the first refrigerant, and the liquefied boil-off gas in the liquefier 30 does not go through the cooler 60 to the liquid gas storage tank ( Of course, it can be returned to 10).

On the contrary, the evaporated gas discharged from the liquefied gas storage tank 10 and introduced into the compressor 20 does not go through the cooler 60, and the evaporated gas discharged from the liquefier 30 is cooled via the cooler 60. It is also possible to recover to the liquefied gas storage tank (10).

The cooler 60 may be provided with a first refrigerant circulation line L10a, and the first refrigerant circulation line L10a may pass through the cooler 60 and the liquefier 30. The first circulation line is provided with a first refrigerant compressor 100a, a first refrigerant cooler 120a, a first refrigerant pressure reducing valve 110a, a refrigerant gas-liquid separator 130, a refrigerant heat exchanger 70, and the like.

The first refrigerant compressed by the first refrigerant compressor 100a is cooled through the first refrigerant cooler 120a and the refrigerant heat exchanger 70 described later, and then flows into the liquefier 30. In this case, the liquefier 30 may liquefy the boil-off gas using the second refrigerant, while allowing the second refrigerant and the first refrigerant to exchange heat.

The first refrigerant whose temperature is changed (cooled or heated) by the second refrigerant in the liquefier 30 is introduced into the refrigerant gas-liquid separator 130 after at least a part of the phase change between the gas and the liquid. The refrigerant gas-liquid separator 130 may separate the first refrigerant heat-exchanged with the second refrigerant by gas-liquid separation, separate the first refrigerant in the gaseous phase and the first refrigerant in the liquid phase, and then transfer the first refrigerant in the liquid phase to the cooler 60.

The first refrigerant in the gaseous phase delivered to the cooler 60 may be decompressed by the refrigerant decompression valve 110 after heat exchange with the boil-off gas, and may be liquefied at the time of decompression. The first refrigerant depressurized by the refrigerant pressure reducing valve 110 flows back into the cooler 60 to cool the evaporated gas. At this time, the first refrigerant in the liquid phase is depressurized at a certain point in the cooler 60 or upstream of the cooler 60. While mixing with the first refrigerant, the liquid phase first refrigerant may also cool the evaporated gas in the cooler 60.

The first refrigerant discharged from the cooler 60 after being depressurized by the refrigerant pressure reducing valve 110 (and the liquid first refrigerant separated from the refrigerant gas-liquid separator 130 and then joined in the cooler 60) is again the first. The refrigerant may be circulated along the first refrigerant circulation line L10a while being delivered to the refrigerant compressor 100a.

The first refrigerant may include, but is not limited to, propane. However, the first refrigerant may be a material that undergoes a phase change by heat exchange with the second refrigerant or the boil-off gas, and the phase change means that at least part of the first refrigerant is liquefied or vaporized.

For example, after the first refrigerant is introduced into the first refrigerant compressor 100a in a gas state and compressed, the first refrigerant may be liquefied by the second refrigerant, or the first refrigerant in the gas state compressed in the first refrigerant compressor 100a. After liquefying by the refrigerant heat exchanger 70 to be described later may be evaporated by evaporation gas or the like.

The liquefier 30 of the present embodiment may cool the boil-off gas exchanged with the first refrigerant in the cooler 60 and compressed by the compressor 20 with the second refrigerant. In this case, the second refrigerant may be the same / similar material as the first refrigerant, and is provided to exchange heat with the first refrigerant in the liquefier 30.

That is, the liquefier 30 may allow the boil-off gas compressed by the compressor 20 to exchange heat with the first and second refrigerants, and the second refrigerant may be heated while cooling the boil-off gas. However, the temperature change in the liquefier 30 may vary depending on the degree or degree of heat exchange in the refrigerant heat exchanger 70 of the first refrigerant heat exchanged in the liquefier 30.

The liquefier 30 may be passed through a second refrigerant circulation line L10b, and a second refrigerant compressor 100b and a second refrigerant cooler 120b may be provided in the second refrigerant circulation line L10b. . Accordingly, the second refrigerant is liquefied after being compressed in the second refrigerant compressor 100b and cooled in the second refrigerant cooler 120b (which may be decompressed / expanded by a second refrigerant pressure reducing valve (not shown) if necessary). The second refrigerant introduced into the air 30 and heat-exchanged with the boil-off gas and the first refrigerant in the liquefier 30 is transferred back to the second refrigerant compressor 100b.

The refrigerant heat exchanger 70 may cool the first refrigerant or the second refrigerant by using the liquefied gas supplied from the liquefied gas storage tank 10 to the demand destination E via the pump 50. The heat exchanger 70 is provided upstream of the liquefier 30 in the first refrigerant circulation line L10a, and uses the liquefied gas supplied to the demand destination E to cool the first refrigerant before it is heat-exchanged with the second refrigerant. As a result, the cooling efficiency of the boil-off gas in the liquefier 30 can be improved.

Specifically, as shown in FIG. 5, the refrigerant heat exchanger 70 may be provided in the first refrigerant circulation line L10a between the first refrigerant compressor 100a and the liquefier 30. In this case, the refrigerant heat exchanger 70 cools the first refrigerant introduced into the liquefier 30 by using the liquefied gas, thereby realizing a capacity reduction of the liquefier 30, and reduces the cooling burden by the second refrigerant. I can ease it.

The refrigerant heat exchanger 70 may be provided downstream of the pump 50, so that the liquefied gas supplied to the demand destination E may be heated by the refrigerant heat exchanger 70. As a result, the present embodiment may reduce or omit the vaporizer 51.

Since the first embodiment directly cools the first refrigerant using the liquefied gas, the heating load of the liquefied gas can be reduced, and the capacity load in the liquefier 30 can be reduced.

Since the supply amount of the liquefied gas varies depending on the ship speed, when cooling the boil-off gas with the liquefied gas, the temperature of the boil-off gas to be liquefied is not constant, and the liquefaction efficiency varies.

On the other hand, the present invention, by liquefying the gas directly with the refrigerant to be used for cooling the refrigerant, while maintaining the temperature of the liquefied gas to be maintained at a relatively constant level irrespective of the ship speed, the liquefaction efficiency through the cold heat of the liquefied gas It can greatly improve. Or in this case, the composition of the refrigerant | mixture (mixed refrigerant) which the liquefier 30 has optimal efficiency can be kept constant.

As described above, the present embodiment prevents the boil-off gas from being exchanged with the liquefied gas at a variable flow rate, thereby maintaining the temperature of the boil-off gas heat-exchanged with the refrigerant at a relatively constant level, while ensuring liquefaction efficiency and supplying it to the demand destination E. By utilizing the cold heat of the liquefied gas to liquefy the evaporated gas can reduce the capacity of the liquefier (30).

6 is a conceptual diagram of an evaporative gas cooling system according to a sixth embodiment of the present invention.

Referring to FIG. 6, in the boil-off gas cooling system 1 according to the sixth embodiment of the present invention, the position of the refrigerant heat exchanger 70 is changed in comparison with the fifth embodiment.

In the present embodiment, the refrigerant heat exchanger 70 may be provided in the first refrigerant circulation line L10a between the refrigerant gas-liquid separator 130 and the cooler 60. In this case, the refrigerant heat exchanger 70 may cool the liquid first refrigerant that is transferred from the refrigerant gas-liquid separator 130 to the cooler 60 by heat-exchanging with the liquefied gas.

In addition, the present embodiment may include a boil-off gas supply line (L4) is branched from the boil-off gas return line (L3) connected to the liquefied gas supply line (L5). In this case, the boil-off gas that is heat-exchanged in the liquefier 30 and the cooler 60 may be mixed with the liquefied gas discharged from the liquefied gas storage tank 10 and supplied to the demand destination E.

The mixing of the boil-off gas with the liquefied gas and supplying the fuel to the demand destination E may be adjusted according to the generation amount of the boil-off gas and the demand amount of the demand destination E, and the control content described in the first embodiment is equally applied. Detailed descriptions are omitted here.

7 is a conceptual diagram of an evaporative gas cooling system according to a seventh embodiment of the present invention.

Referring to FIG. 7, unlike the fifth and sixth embodiments, in the boil-off gas cooling system 1 according to the seventh embodiment of the present invention, a refrigerant heat exchanger 70 is provided in the second refrigerant circulation line L10b. Can be.

In this case, the refrigerant heat exchanger 70 may be provided in the second refrigerant circulation line L10b between the second refrigerant compressor 100b and the liquefier 30 and the second refrigerant introduced into the liquefier 30. Can be cooled with liquefied gas.

Therefore, in the present embodiment, similarly to the fifth embodiment, the liquefaction efficiency in the liquefier 30 can be increased by cooling the refrigerant flowing into the liquefier 30 with the liquefied gas, and also in the liquefier 30 Capacity can be reduced.

The present invention is not limited to the above-described embodiments, and may include, as another embodiment, a combination of at least two or more of the above embodiments or a combination of at least one of the contents of the embodiments and a known technology. Of course.

The present invention has been described above with reference to the embodiments of the present invention. However, the present invention is only an example, and is not intended to limit the present invention. Those skilled in the art do not depart from the essential technical details of the present embodiment. It will be appreciated that various combinations or modifications and applications that are not exemplified in the embodiments are possible in scope. Therefore, technical matters related to modifications and applications easily derivable from the embodiments of the present invention should be interpreted as being included in the present invention.

1: Evaporative gas cooling system E: demand
10: liquefied gas storage tank 20: compressor
21: intercooler 30: liquefier
30a: first liquefier 30b: second liquefier
31: flow control valve 40: gas-liquid separator
50: pump 51: carburetor
60: cooler 70: refrigerant heat exchanger
100: refrigerant compressor 100a: first refrigerant compressor
100b: second refrigerant compressor 110: refrigerant pressure reducing valve
110a: first refrigerant pressure reducing valve 120: refrigerant cooler
120a: first refrigerant cooler 120b: second refrigerant cooler
130: refrigerant gas liquid separator L1: boil off gas liquefaction line
L2: boil off gas branch line L3: boil off gas return line
L4: Evaporative Gas Supply Line L5: Liquefied Gas Supply Line
L10: refrigerant circulation line L10a: first refrigerant circulation line
L10b: second refrigerant circulation line

Claims (11)

A cooler configured to heat-exchange the boil-off gas generated in the liquefied gas storage tank with the first refrigerant;
A compressor for compressing the evaporated gas heat exchanged in the cooler;
A liquefier for exchanging the boil-off gas and the first refrigerant compressed by the compressor with the second refrigerant; And
And a refrigerant heat exchanger for cooling the first refrigerant or the second refrigerant by using the liquefied gas supplied from the liquefied gas storage tank to the demand destination. The method of claim 1, wherein the first refrigerant,
Evaporating gas cooling system, characterized in that the phase change is made by the heat exchange with the second refrigerant or the boil-off gas. The method of claim 1, wherein the cooler,
The evaporator gas cooling system characterized in that the liquefier receives the evaporated gas heat exchanged with the second refrigerant again and heat exchanged with the first refrigerant to return to the liquefied gas storage tank. The method of claim 1, wherein the refrigerant heat exchanger,
An evaporative gas cooling system characterized by cooling the first refrigerant before cooling the second refrigerant using the liquefied gas supplied to the demand destination. The method of claim 3, wherein
A first refrigerant circulation line passing through the cooler and the liquefier;
A first refrigerant compressor provided in the first refrigerant circulation line; And
Further comprising a refrigerant gas-liquid separator for gas-liquid separation of the first refrigerant heat exchanged with the second refrigerant,
The refrigerant heat exchanger is provided upstream of the liquefier in the first refrigerant circulation line,
The cooler, the evaporation gas cooling system, characterized in that for cooling the evaporated gas with the first refrigerant in the liquid state separated from the refrigerant gas-liquid separator. The method of claim 5, wherein the refrigerant heat exchanger,
Evaporation gas cooling system, characterized in that provided in the first refrigerant circulation line between the first refrigerant compressor and the liquefier. The method of claim 5, wherein the refrigerant heat exchanger,
Evaporative gas cooling system, characterized in that provided in the first refrigerant circulation line between the refrigerant gas-liquid separator and the cooler. The method of claim 1,
A second refrigerant circulation line passing through the liquefier; And
Further comprising a second refrigerant compressor provided in the second refrigerant circulation line,
The refrigerant heat exchanger is provided in the second refrigerant circulation line between the second refrigerant compressor and the liquefier is boil-off gas cooling system, characterized in that. The method of claim 3, wherein
A pump for pressurizing the liquefied gas discharged from the liquefied gas storage tank,
And the refrigerant heat exchanger is provided downstream of the pump based on the flow of the liquefied gas. The method of claim 9,
Evaporative gas cooling system characterized in that the liquefied gas from the liquefied gas storage tank and the liquefied gas which is sequentially heat exchanged in the liquefier and the cooler is mixed with the liquefied gas and supplied to the demand destination. Ship having the boil-off gas cooling system according to any one of claims 1 to 10.

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