KR101714672B1 - Vessel Including Storage Tanks - Google Patents

Abstract

A ship comprising a storage tank is disclosed.
The ship including the storage tank includes: a first compressor for compressing natural gas; A first heat exchanger for cooling a part of the natural gas compressed by the first compressor (hereinafter referred to as "x-flow") by heat exchange with the refrigerant; A first expansion unit for expanding the remaining natural gas other than the 'x-flow' (hereinafter referred to as 'y-flow') from the natural gas compressed by the first compressor; A first compression unit disposed downstream of the first heat exchanger; A second gas-liquid separator which separates the liquefied natural gas expanded by the first expansion part and left liquefied natural gas and the natural gas left in a gaseous state; Expansion means for expanding the fluid cooled by said first heat exchanger; And a first gas-liquid separator for separating the liquefied natural gas passed through the expansion means and the natural gas remaining in a gaseous state, wherein the first expansion part and the first compression part constitute a first compander , The first heat exchanger further comprises: liquefied natural gas separated by the second gas-liquid separator; Liquid separator for separating the gaseous natural gas separated by the second gas-liquid separator and the gaseous natural gas separated by the second gas-liquid separator as a refrigerant, cooling the 'x-flow' The flow of the gaseous natural gas separated by the first gas-liquid separator and the gaseous natural gas separated by the second gas-liquid separator is used as a refrigerant in the first heat exchanger, And the natural gas compressed by the first compressor is sent to the front of the first compressor.

Description

[0001] VESSEL Including Storage Tanks [0002]

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a ship including a storage tank, and more particularly, to a ship including a storage tank, To a storage tank, comprising a storage tank.

Recently, the consumption of liquefied gas such as Liquefied Natural Gas (LNG) and Liquefied Petroleum Gas (LPG) has been rapidly increasing worldwide. The liquefied gas obtained by liquefying the gas at a low temperature has an advantage of being able to increase the storage and transport efficiency because the volume becomes very small as compared with the gas. In addition, liquefied natural gas (LNG) and other liquefied gases can be used as eco-friendly fuels that can reduce or eliminate air pollutants during the liquefaction process.

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

However, since the liquefaction temperature of natural gas is a cryogenic temperature of about -162 ° C at normal pressure, liquefied natural gas is easily vaporized due to temperature change sensitivity. However, since the external heat is continuously transferred to the storage tank, the liquefied natural gas is naturally vaporized continuously in the storage tank during the transportation of the liquefied natural gas, and the evaporation gas (BOG; Boil -Off Gas) occurs. This also applies to other low temperature liquefied gases such as ethane.

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

It is an object of the present invention to provide a vessel including a storage tank that liquefies natural gas using liquefied natural gas itself as a refrigerant and returns it to a storage tank without using a separate refrigerant system.

According to an aspect of the present invention, there is provided a compressor for compressing natural gas, comprising: a first compressor for compressing natural gas; A first heat exchanger for cooling a part of the natural gas compressed by the first compressor (hereinafter referred to as "x-flow") by heat exchange with the refrigerant; A first expansion unit for expanding the remaining natural gas other than the 'x-flow' (hereinafter referred to as 'y-flow') from the natural gas compressed by the first compressor; A first compression unit disposed downstream of the first heat exchanger; A second gas-liquid separator which separates the liquefied natural gas expanded by the first expansion part and left liquefied natural gas and the natural gas left in a gaseous state; Expansion means for expanding the fluid cooled by said first heat exchanger; And a first gas-liquid separator for separating the liquefied natural gas passed through the expansion means and the natural gas remaining in a gaseous state, wherein the first expansion part and the first compression part constitute a first compander , The first heat exchanger further comprises: liquefied natural gas separated by the second gas-liquid separator; Liquid separator for separating the gaseous natural gas separated by the second gas-liquid separator and the gaseous natural gas separated by the second gas-liquid separator as a refrigerant, cooling the 'x-flow' The flow of the gaseous natural gas separated by the first gas-liquid separator and the gaseous natural gas separated by the second gas-liquid separator is used as a refrigerant in the first heat exchanger, And the natural gas compressed by the first compressing unit is sent to the front side of the first compressor.
The ship including the storage tank may include a second expander for expanding the natural gas in the gaseous state separated by the second gas-liquid separator; And a second compression unit installed on a line supplied with the fluid discharged from the first heat exchanger to the first compression unit, and the second expansion unit and the second compression unit may further include a second compressor And the first heat exchanger may comprise liquefied natural gas separated by the second gas-liquid separator; And a flow in which gaseous natural gas separated by the first gas-liquid separator and a fluid expanded by the second expansion unit are combined, can be used as a refrigerant to cool the 'x-flow' 1, the flow of the gaseous natural gas separated by the gas-liquid separator and the fluid expanded by the second expansion portion is used as a refrigerant in the first heat exchanger, and then the second compression portion and the first And can be sequentially compressed by the compression unit.
The liquefied natural gas separated by the second gas-liquid separator may be combined with a 'z-flow' after being used as a refrigerant in the first heat exchanger, and the 'z-flow' And may be a fluid used as a refrigerant in the first heat exchanger after the separated gaseous natural gas and the fluid expanded by the second expansion unit are combined.
After being used as a refrigerant in the first heat exchanger, the natural gas sequentially compressed by the second compression unit and the first compression unit can be sent to the front side of the first compressor.
The ship including the storage tank may include a second compressor for further compressing the 'x-flow', and the first heat exchanger may include a compressor for compressing the 'x-flow' And can be cooled by heat exchange.
The ship including the storage tank may include a second heat exchanger using the fluid expanded by the first expansion unit as a refrigerant; And a third compressor that compresses the fluid used as the refrigerant in the second heat exchanger after being expanded by the first expansion part, and the fluid compressed by the third compressor is compressed by the second compressor The fluid expanded by the first expansion portion can be cooled by heat exchange with the refrigerant and then sent to the second gas-liquid separator by the heat exchanger.
According to another aspect of the present invention, there is provided a process for producing natural gas, comprising the steps of: 1) branching natural gas into two streams, and 2) separating one stream of natural gas (hereinafter referred to as a stream) 3) separating the liquefied natural gas that has expanded and liquefied in the step 2) and the natural gas remaining in the gaseous state, 4) expanding the natural gas separated in the step 3), and 5) Liquefied natural gas separated in step; And the fluid expanded in the step 4) is used as a refrigerant, and the remaining flow of the natural gas branched in the step 1) (hereinafter referred to as "b flow") is cooled by heat exchange, and 6) B) expanding the cooled 'b-flow', 7) separating the liquefied natural gas expanded and liquefied in step 6) and the natural gas remaining in the gaseous state, 8) separating the gaseous natural Gas is mixed with the fluid expanded in the step 4), and the refrigerant is used as a refrigerant for cooling by heat-exchanging the 'b flow' in the step 5); 9) the fluid expanded in the step 4) Is used as a refrigerant for cooling the " b-flow " in the step 5), and is then compressed by the energy released when the natural gas is expanded in the step 4) And 10) the natural gas compressed in the step 7) Is further compressed by the energy released when the natural gas is expanded.
The liquefied natural gas separated in the step 3) may be combined with the 'c flow' after being used as a refrigerant to cool by cooling the 'b flow' in the step 5), and the 'c flow' B 'flow in the step 5) after joining the gaseous natural gas separated in the step 7) with the fluid expanded in the step 4).
2-1) The 'a flow' expanded in the step 2) is used as a refrigerant in the second heat exchanger, 2-2) the 'a flow' used as a refrigerant in the 2-1) 2-3) The 'a flow' compressed in the step 2-2) is a refrigerant which is cooled by the heat exchanged by the second heat exchanger and flows through the 'a flow' expanded in the step 2) ) The 'a flow' that has been heat-exchanged and cooled in the step 2-3) may be separated into the liquefied natural gas and the natural gas remaining in a gaseous state in the step 3).

According to the present invention, since a separate refrigerant system is not used, there is an advantage that the system is simple and convenient to operate.

In addition, a system using the liquefied natural gas itself as a refrigerant can be roughly divided into a closed loop and an open loop. Since the present invention uses an open loop, The control of the refrigerant system is simple and the components of the system are simple.

Since the energy obtained by cooling the natural gas in the expander of the compander can be used to compress the natural gas in the compressor connected to the expansion part and the shaft, Can be reduced to a minimum.

1 is a schematic view showing a ship including a storage tank according to a first preferred embodiment of the present invention.
2 is a schematic view showing a ship including a storage tank according to a second preferred embodiment of the present invention.
3 is a schematic view showing a ship including a storage tank according to a third preferred embodiment of the present invention.
4 is a schematic view showing a ship including a storage tank according to a fourth preferred embodiment of the present invention.
5 is a graph schematically illustrating the phase change of methane with temperature and pressure.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. The vessel including the storage tank of the present invention can be applied to various applications on ships equipped with liquefied natural gas storage tanks and onshore. In addition, the following examples can be modified in various forms, and the scope of the present invention is not limited to the following examples.

1 is a schematic view showing a ship including a storage tank according to a first preferred embodiment of the present invention.

The term "fluid" in this embodiment means a natural gas, a liquefied natural gas, or a mixture of natural gas and liquefied natural gas. The gaseous natural gas passes through each device and can be in a gaseous, liquid or gas-liquid mixture depending on the pressure and temperature. Hereinafter, the same applies.

Referring to FIG. 1, a ship including a storage tank of the present embodiment includes a first compressor 110 for compressing natural gas supplied from the outside; A first cooler 210 for cooling the natural gas compressed by the first compressor 110; A first compander 510 and a second compander 520 for expanding or compressing the fluid; A first heat exchanger (310) for cooling the natural gas using the expanded fluid as a refrigerant; Expansion means (600) for expanding the fluid having passed through the first heat exchanger (310); A third cooler 230 for cooling the fluid passing through the first compander 510; And a second cooler (220) for cooling the fluid passing through the second compander (520).

The first compressor (110) of this embodiment compresses the natural gas supplied from the outside. The ship including the storage tank of the present embodiment is for delivering natural gas having passed through the first compressor 110 to the storage tank through the first heat exchanger 310 and the expansion means 600, Compressing by the first compressor 110 before being sent to the first heat exchanger 310 is to increase liquefaction efficiency in the first heat exchanger 310. A more detailed explanation is as follows.

5 is a graph schematically illustrating the phase change of methane with temperature and pressure. Referring to FIG. 5, methane enters a supercritical fluid state at a temperature of approximately -80 DEG C or higher and a pressure of approximately 50 bar or more. That is, in the case of methane, the critical point is about -80 ° C, 50 bar. The supercritical fluid state is a third state different from the liquid state or gas state.

However, in the course of re-liquefaction of the evaporated gas, the natural gas may contain a nitrogen component. Depending on the content of nitrogen, the critical point may be changed.

On the other hand, if the temperature is lower than the critical point at a pressure higher than the critical point, the state of the supercritical fluid may be similar to that of the supercritical fluid, which is different from the general liquid state. , Hereinafter referred to as "high pressure liquid state ".

5, the natural gas in the relatively low pressure state (X in FIG. 5) is passed through the first heat exchanger 310 and the expansion means 600 to lower the temperature and the pressure, (X 'of FIG. 5). However, it can be seen that even if the temperature and pressure are lowered equally after increasing the pressure of the gas (Y in FIG. 5) have. That is, it is known that the liquefaction efficiency increases as the natural gas pressure is increased before the natural gas passes through the first heat exchanger 310, and the liquefaction can be theoretically 100% if the pressure can be sufficiently increased (Z in FIG. 5) (Z 'in Fig. 5).

Accordingly, the ship including the storage tank of the present embodiment includes the first compressor 110 to increase the pressure of the natural gas before sending the natural gas to the first heat exchanger 310, Thereby increasing the liquefaction efficiency. The first compressor 110 of the present embodiment preferably compresses the natural gas at a pressure of about 50 bar or more so that the natural gas can be in a supercritical state.

The first cooler 210 of the present embodiment lowers the temperature of the natural gas that has passed through the first compressor 110 and has increased temperature as well as pressure. The first cooler 210 can cool natural gas by, for example, heat-exchanging natural gas with fresh water at about room temperature.

The first compander 510 of the present embodiment includes a first expansion portion 512 for expanding the fluid and a first compression portion 511 for compressing the fluid. The first expanding part 512 and the first compressing part 511 are connected by an axis so that the first compressing part 511 compresses the fluid by the energy obtained by expanding the fluid by the first expanding part 512 do. Since the ship including the storage tank of this embodiment compresses and expands the fluid by using the compander, the energy released as the fluid expands can be used for compressing the fluid, so that energy can be efficiently used.

The first expansion unit 512 of the first compander 510 expands a portion of the natural gas that has passed through the first compressor 110 and the first compressor 210 and then sends the expanded natural gas to the second compander 520 The first compressing unit 511 compresses the fluid sent from the second compander 520 and sends the compressed fluid to the first compressor 110 again.

The second compander 520 of this embodiment includes a second expanding section 522 for expanding the fluid and a second compressing section 521 for compressing the fluid similarly to the first compander 510. The second expanding portion 522 and the second compressing portion 521 are connected by a shaft like the first expanding portion 512 and the first compressing portion 511 so that the second expanding portion 522 The second compression section 521 compresses the fluid by the energy obtained by expanding the fluid.

The second expanding portion 522 of the second compander 520 is configured to expand the fluid primarily expanded by the first expanding portion 512 of the first compander 510, (310). The fluid expanded by the first expansion portion 512 and the second expansion portion 522 is used as a refrigerant for cooling the natural gas in the first heat exchanger 310. The second compression section 521 of the second compander 520 is used as a refrigerant in the first heat exchanger 310 after passing through the first expansion section 512 and the second expansion section 522 The fluid is compressed and then sent to the first compander 510.

The first heat exchanger 310 of the present embodiment is configured so that a part of the natural gas that has passed through the first compressor 110 and the first cooler 210 is divided into the first expansion portion 512 and the second expansion portion 522 Self-heat exchanges with the passing fluid to cool. Self-cooling means that a part of the natural gas is cooled without using a separate refrigerant, and the natural gas itself is used as a refrigerant for cooling the natural gas.

The ship including the storage tank of the present embodiment liquefies part of the natural gas that has passed through the first compressor 110 and the first cooler 210 by the first heat exchanger 310 and the expansion means 600 The fluid used as the refrigerant in the first heat exchanger 310 is supplied to the first expansion portion 512 and the second expansion portion 522 in a sufficient amount to liquefy the natural gas Lt; / RTI >

The expansion means (600) of this embodiment lowers the pressure of the fluid whose temperature has been lowered by the heat exchange in the first heat exchanger (310). The natural gas is partly or entirely liquefied while passing through the first heat exchanger 310 and the expansion means 600 and the liquefied natural gas is mixed with the natural gas remaining in the gaseous state in a gas-liquid mixed state Liquefied natural gas is sent to a storage tank. The expansion means 600 may be an expansion valve or an expander.

The second cooler 220 of the present embodiment is disposed at the downstream end of the second compressing section 521 of the second compander 520 and passes through the second compressing section 521 and has a temperature . The fluid having passed through the second compressing section 521 and the second cooler 220 is sent to the first compander 510.

The third cooler 230 of the present embodiment is installed at the downstream end of the first compressing section 511 of the first compander 510 so as to allow the temperature of the fluid passing through the first compressing section 511, . The fluid having passed through the first compression unit 511 and the third cooling unit 230 is sent to the first compressor 110 together with the natural gas supplied from the outside.

The second cooler 220 and the third cooler 230 of this embodiment can cool the fluid by, for example, heat-exchanging the fluid with the fresh water at about room temperature.

The flow of the fluid in this embodiment will be described as follows.

The natural gas supplied from the outside is compressed by the first compressor 110, cooled by the first cooler 210, and then branched into two flows. One stream is sent to the first heat exchanger 310 and the other stream is sent to the first compander 510. In order to liquefy the natural gas sent to the first heat exchanger 310, Natural gas sent to the panda 510 is liquefied and used as a refrigerant.

Natural gas that has passed through the first compressor 110 and the first cooler 210 and then sent to the first compander 510 is expanded by the first expansion unit 512 and then introduced into the second compander 520 And is sent to the second bulging portion 522. The fluid once again expanded by the second expansion part (522) is sent to the first heat exchanger (310).

The cooled fluid passing through the first expansion part 512 and the second expansion part 522 is heat-exchanged with the natural gas in the first heat exchanger 310 and then the cold heat is taken up by the natural gas, The partially or fully vaporized fluid is again sent to the second compander 520 and compressed by the second compression section 521.

The fluid compressed by the second compressing unit 521 is cooled by the second cooler 220 and then sent to the first compander 510 and compressed again by the first compressing unit 511 . The fluid compressed by the first compressor 511 is cooled by the third cooler 230 and then sent to the first compressor 110 together with the natural gas supplied from the outside so that the above- .

That is, in the present embodiment, the fluid used as the refrigerant is supplied to the first compression section 511 and the second compression section 521 as much as the pressure is lowered by the first expansion section 512 and the second expansion section 522 And is sent to the first compressor 110 after recovering the pressure when the natural gas is supplied from the outside.

The natural gas that has passed through the first compressor 110 and the first cooler 210 and then sent to the first heat exchanger 310 is supplied to the first expansion portion 512 and the second expansion portion 522, And is then expanded by the expansion means 600. [ The fluid that has passed through the first heat exchanger 310 and the expansion means 600 and partially or fully liquefied is sent to the storage tank.

2 is a schematic view showing a ship including a storage tank according to a second preferred embodiment of the present invention.

The ship including the storage tank of the second embodiment shown in Fig. 2 is different from the ship including the storage tank of the first embodiment shown in Fig. 1 in that the second compressor 120, the fourth cooler 240, 1 gas-liquid separator 410 and a first valve 710. Hereinafter, differences will be mainly described. A detailed description of the same components as those of the ship including the storage tank of the above-described first embodiment will be omitted.

Referring to FIG. 2, a ship including the storage tank of the present embodiment includes a first compressor 110, a first cooler 210, a first compander 510, A second heat exchanger 520, a first heat exchanger 310, an expansion means 600, a second cooler 220, and a third cooler 230.

However, the ship including the storage tank of the present embodiment is different from the first embodiment in that the second compressor 120 additionally compresses the natural gas firstly compressed by the first compressor 110; A fourth cooler 240 for lowering the temperature of the natural gas passing through the second compressor 120; A first gas-liquid separator (410) installed downstream of the expansion means (600) for separating liquefied natural gas from natural gas in a gaseous state; And a first valve (710) for regulating the flow rate and pressure of the gaseous natural gas separated by the first gas-liquid separator (410).

The first compressor (110) of this embodiment compresses the natural gas supplied from the outside in the same manner as the first embodiment, and the first cooler (210) of this embodiment is similar to the first embodiment in that the first compressor 110) to lower the temperature of the natural gas as well as the pressure.

The second compressor 120 of this embodiment further compresses some of the natural gas that has passed through the first compressor 110 and the first cooler 210. As described above, it is advantageous in terms of liquefaction efficiency to increase the pressure of the natural gas before the natural gas passes through the first heat exchanger 310. It is not sufficient to compress the natural gas to a sufficient pressure with only the first compressor 110 In this case, as in the present embodiment, it may further include a compressor. In this embodiment, the natural gas is compressed in two stages. However, a compression process may be added as needed.

In this embodiment, the natural gas is branched between the first compressor 210 and the second compressor 120 before the second compression process after the first compression process. However, The natural gas may be branched before the first compression process, that is, before the first compressor 110, or after the second compression process, that is, after the fourth cooler 240. [

The reason why the natural gas is branched between the first cooler 210 and the second compressor 120 in the present embodiment is that the natural gas which is branched and sent to the first compander 510 to be used as the refrigerant, After being expanded by the expansion unit 512 and the second expansion unit 522, the natural gas is sent to the first heat exchanger 310. Compressing the natural gas to be subjected to the expansion process through the two-stage compression process is inefficient Because. Therefore, the branch point can be determined in consideration of the natural gas to be used as the refrigerant and the required pressure of the natural gas to be liquefied.

The natural gas compressed by the first compressor 110 and the second compressor 120 of the present embodiment preferably has a pressure of about 50 bar or more so as to be in a supercritical state.

The fourth cooler 240 of the present embodiment lowers the temperature of the natural gas that passes through the second compressor 120 and increases not only in pressure but also in temperature. For example, by exchanging heat between natural gas and fresh water at a room temperature, Natural gas can be cooled.

As in the first embodiment, the first compander 510 of the present embodiment includes a first expansion portion 512 for expanding the fluid and a first compression portion 511 for compressing the fluid. The first expanding section 512 and the first compressing section 511 are axially connected to each other by the energy obtained by expanding the fluid by the first expanding section 512, (511) compresses the fluid.

The first expansion portion 512 of the first compander 510 expands a part of the natural gas that has passed through the first compressor 110 and the first cooler 210 as in the first embodiment, And the first compressor 511 compresses the fluid sent from the second compander 520 and sends the compressed fluid to the first compressor 110 as in the first embodiment.

As in the first embodiment, the second compander 520 of the present embodiment includes a second expanding section 522 for expanding the fluid and a second compressing section 521 for compressing the fluid. Similarly to the first embodiment, the second expanding section 522 and the second compressing section 521 are axially connected to each other so that the energy of the second expanding section 522 expanding the fluid causes the second compressing section 521 compress the fluid.

The second expanding portion 522 of the second compander 520 is configured such that the fluid primarily expanded by the first expanding portion 512 of the first compander 510 is once again And then sent to the first heat exchanger 310. The fluid expanded by the first expansion portion 512 and the second expansion portion 522 is used as a refrigerant for cooling the natural gas in the first heat exchanger 310 as in the first embodiment.

The second compressing section 521 of the second compander 520 passes through the first expanding section 512 and the second expanding section 522 and then flows into the first heat exchanger 310, And then sends the compressed fluid to the first compander 510.

The first heat exchanger 310 of the present embodiment is configured to mix the natural gas that has passed through the first compressor 110, the first cooler 210, the second compressor 210 and the fourth cooler 240, Self-heat exchange with the fluid that has passed through the second expansion portion 512 and the second expansion portion 522.

As in the first embodiment, the expansion means 600 of the present embodiment lowers the pressure of the fluid whose temperature has been lowered by the heat exchange in the first heat exchanger 310, and the natural gas is introduced into the first heat exchanger 310 and the expansion means 600, the liquid is partly or entirely liquefied. The expansion means 600 may be an expansion valve or an expander.

The first gas-liquid separator 410 of the present embodiment is disposed at the downstream end of the expansion means 600 and passes through the first heat exchanger 310 and the expansion means 600 and remains in a gaseous state with a part of liquefied natural gas Separates the natural gas and delivers the liquefied natural gas to the storage tank and the natural gas sends it from the second expansion portion 522 to the first heat exchanger 310 on the line through which the fluid is sent.

The first valve 710 of the present embodiment is installed on a line for sending natural gas between the second expansion portion 522 and the first heat exchanger 310 from the first gas-liquid separator 410, Adjust the pressure. In consideration of the flow rate of the fluid passing through the second expansion portion 522 to the first heat exchanger 310 and the capacity of the first heat exchanger 310, The amount of natural gas sent from the separator 410 to the second expansion unit 522 and the first heat exchanger 310 is controlled and is sent to the first heat exchanger 310 through the second expansion unit 522 Controls the pressure of the natural gas so that the pressure of the natural gas sent from the first gas-liquid separator (410) to the second expansion portion (522) and the first heat exchanger (310) becomes similar.

The second cooler 220 of the present embodiment is disposed at the rear end of the second compression section 521 of the second compander 520 and passes through the second compression section 521 and is compressed But the temperature also lowers the temperature of the raised fluid. The fluid having passed through the second compressing section 521 and the second cooler 220 is sent to the first compander 510.

The third cooler 230 of the present embodiment is installed at the rear end of the first compressing section 511 of the first compander 510 so as to pass through the first compressing section 511, But the temperature also lowers the temperature of the raised fluid. The fluid having passed through the first compression unit 511 and the third cooling unit 230 is sent to the first compressor 110 together with the natural gas supplied from the outside.

The flow of the fluid in this embodiment will be described as follows.

The natural gas supplied from the outside is firstly compressed by the first compressor 110, cooled by the first cooler 210, and then branched into two flows, as in the first embodiment. Among them, one stream is compressed secondarily by the second compressor 120, cooled by the fourth cooler 240, and then sent to the first heat exchanger 310, unlike the first embodiment, The flow is sent to the first compander 510 as in the first embodiment.

Natural gas that has passed through the first compressor 110 and the first cooler 210 and then sent to the first compander 510 is expanded by the first expansion unit 512, 2 compander 520. The second expanding portion 522 of the second compander 520 is then moved to the second expanding portion 522 of the second compander 520. The fluid once again expanded by the second expanding section 522 is sent to the first heat exchanger 310 as in the first embodiment.

As in the first embodiment, the cooled fluid passing through the first expansion portion 512 and the second expansion portion 522 is heat-exchanged with the natural gas in the first heat exchanger 310, and some or all of the fluid is vaporized , The partially or fully vaporized fluid is again sent to the second compander 520 and compressed by the second compression section 521.

The fluid compressed by the second compressing unit 521 is cooled by the second cooler 220 and then sent to the first compander 510 so as to be supplied to the first compressing unit 511, Lt; / RTI > The fluid compressed by the first compressing section 511 is cooled by the third cooler 230 and then sent to the first compressor 110 together with the natural gas supplied from the outside as in the first embodiment , The above-mentioned series of steps is again performed.

The natural gas that has passed through the first compressor 110 and the first cooler 210 and then branched and passed through the second compressor 120 and the fourth cooler 240 is sent to the first heat exchanger 310, Exchanged with the fluid expanded by the first expanding portion 512 and the second expanding portion 522, and then expanded by the expansion means 600.

Unlike the first embodiment, the fluid which has passed through the first heat exchanger 310 and the expansion means 600 and partially or completely liquefied is not sent directly to the storage tank in a gas-liquid mixed state, The liquid phase and the gas phase are separated by the separator 410. The liquefied natural gas separated by the first gas-liquid separator 410 is sent to the storage tank, and the natural gas separated by the first gas-liquid separator 410 passes through the first valve 710, Is sent to the first heat exchanger (310) together with the fluid passing through the second heat exchanger (522) and used again as the refrigerant.

3 is a schematic view showing a ship including a storage tank according to a third preferred embodiment of the present invention.

The vessel including the storage tank of the third embodiment shown in Fig. 3 is different from the vessel including the storage tank of the second embodiment shown in Fig. 2 in that the second gas-liquid separator 420 and the second valve 720 There is a difference therebetween. In the following, the difference will be mainly described. A detailed description of the same components as those of the ship including the storage tank of the second embodiment described above will be omitted.

Referring to FIG. 3, the ship including the storage tank of the present embodiment includes a first compressor 110, a first cooler 210, a second compressor 120, a fourth cooler 240 The first compander 510, the second compander 520, the first heat exchanger 310, the expansion means 600, the first gas-liquid separator 410, the first valve 710, (220) and a third cooler (230).

However, unlike the second embodiment, the vessel including the storage tank of the present embodiment is installed between the first expansion portion 512 and the second expansion portion 522, and passes through the first expansion portion 512 A second gas-liquid separator (420) for separating the partially liquefied natural gas and the natural gas remaining in the gaseous state; And a second valve (720) for regulating the flow rate and pressure of the liquefied natural gas separated by the second gas-liquid separator (420) and sent to the first heat exchanger (310).

The first compressor (110) of this embodiment compresses the natural gas supplied from the outside in the same manner as the second embodiment, and the first cooler (210) of the present embodiment is similar to the second embodiment in that the first compressor 110) to lower the temperature of the natural gas as well as the pressure.

The second compressor 120 of this embodiment additionally compresses some of the natural gas that has passed through the first compressor 110 and the first cooler 210 as in the second embodiment. The natural gas compressed by the first compressor 110 and the second compressor 120 of the present embodiment preferably has a pressure of about 50 bar or more so as to be in a supercritical state.

As in the second embodiment, the fourth cooler 240 of the present embodiment lowers the temperature of the natural gas that has passed through the second compressor 120 and has increased in temperature as well as pressure.

As in the second embodiment, the first compander 510 of the present embodiment includes a first expanding section 512 for expanding the fluid and a first compressing section 511 for compressing the fluid. The first expanding section 512 and the first compressing section 511 are connected to each other by an axis in the same manner as in the second embodiment and the first expanding section 512 and the first compressing section 511 are connected to each other by the energy obtained by expanding the fluid by the first expanding section 512, (511) compresses the fluid.

Unlike the second embodiment, the first expansion unit 512 of the first compander 510 inflates a part of the natural gas that has passed through the first compressor 110 and the first cooler 210, Liquid separator 420, not directly to the second compander 520.

The first compressing unit 511 of the first compander 510 compresses the fluid sent from the second compander 520 and sends the compressed fluid to the first compressor 110 in the same manner as in the second embodiment.

The second gas-liquid separator (420) of this embodiment separates the liquefied natural gas and the remaining natural gas from the liquefied natural gas passing through the first expansion portion (512), and the liquefied natural gas is introduced into the first heat exchanger To be used as a refrigerant, and the natural gas is sent to the second compander 520 to be further expanded by the second expansion portion 522.

The vessel including the storage tank of this embodiment allows the liquefied natural gas separated by the second gas-liquid separator 420 including the second gas-liquid separator 420 to be used as the refrigerant in the first heat exchanger 310 The liquefaction efficiency in the first heat exchanger 310 can be higher than in the first and second embodiments.

The second valve 720 of the present embodiment is installed on a line for sending the liquefied natural gas separated by the second gas-liquid separator 420 to the first heat exchanger 310 to control the flow rate and pressure of the liquefied natural gas do. That is, the second valve 720 controls the flow rate of the second vaporizer 720 in consideration of the flow rate of the fluid passing through the second expansion portion 522 and sent to the first heat exchanger 310 and the capacity of the first heat exchanger 310, The amount of liquefied natural gas sent from the separator 420 to the first heat exchanger 310 is controlled and the temperature of the liquefied natural gas used as the refrigerant in the first heat exchanger 310 is further lowered to the first heat exchanger 310 Liquid separator 420 to further expand the liquefied natural gas sent to the first heat exchanger 310 so as to increase the liquefaction efficiency in the first gas-

As in the second embodiment, the second compander 520 of the present embodiment includes a second expanding section 522 for expanding the fluid and a second compressing section 521 for compressing the fluid. Similarly to the second embodiment, the second expanding section 522 and the second compressing section 521 are axially connected to each other by the energy obtained by expanding the fluid by the second expanding section 522, 521 compress the fluid.

The second expansion portion 522 of the second compander 520 is expanded primarily by the first expansion portion 512 of the first compander 510 but can not be liquefied and the second expansion portion 522 of the second gas- To the first heat exchanger (310). The fluid expanded by the first expanding section 512 and the second expanding section 522 is used as a refrigerant for cooling the natural gas in the first heat exchanger 310 as in the second embodiment.

The second compression section 521 of the second compander 520 compresses the fluid used as the refrigerant in the first heat exchanger 310 and sends it to the first compander 510 as in the second embodiment .

The first heat exchanger 310 of the present embodiment is configured such that the first compressor 110, the first compressor 210, the second compressor 210, and the fourth compressor 240, Gas is cooled by self-heat exchange with the fluid that has passed through the first expanding section 512 and the second expanding section 522.

However, unlike the second embodiment, the first heat exchanger 310 of this embodiment uses not only the fluid that has passed both the first expansion portion 512 and the second expansion portion 522 as the refrigerant, 1 liquefied natural gas which has been liquefied after passing through the expansion portion 512 and separated by the second gas-liquid separator 420 is also used as a refrigerant.

As in the second embodiment, the expansion means 600 of the present embodiment lowers the pressure of the fluid whose temperature has been lowered by the heat exchange in the first heat exchanger 310, and the natural gas is introduced into the first heat exchanger 310 and the expansion means 600, the liquid is partly or entirely liquefied. The expansion means 600 may be an expansion valve or an expander.

The first gas-liquid separator 410 of the present embodiment is provided at the downstream end of the expansion means 600 and passes through the first heat exchanger 310 and the expansion means 600 to partially liquefy liquefied natural gas The liquefied natural gas is sent to the storage tank and the natural gas is sent from the second expansion portion 522 to the first heat exchanger 310 on the line through which the fluid is sent.

The first valve 710 of the present embodiment is installed on the line for sending natural gas between the second expansion portion 522 and the first heat exchanger 310 from the first gas-liquid separator 410 as in the second embodiment Thereby controlling the flow rate and pressure of the natural gas.

The second cooler 220 of the present embodiment is installed at the rear end of the second compression section 521 of the second compander 520 and passes through the second compression section 521 and is compressed But the temperature also lowers the temperature of the raised fluid. The fluid having passed through the second compressing section 521 and the second cooler 220 is sent to the first compander 510.

The third cooler 230 of the present embodiment is disposed at the rear end of the first compressing section 511 of the first compander 510 so as to pass through the first compressing section 511, But the temperature also lowers the temperature of the raised fluid. The fluid having passed through the first compression unit 511 and the third cooling unit 230 is sent to the first compressor 110 together with the natural gas supplied from the outside.

The flow of the fluid in this embodiment will be described as follows.

The natural gas supplied from the outside is firstly compressed by the first compressor 110, cooled by the first cooler 210, and then branched into two flows, as in the second embodiment. One of the flows is secondarily compressed by the second compressor 120, cooled by the fourth cooler 240, and then sent to the first heat exchanger 310, as in the second embodiment, Is sent to the first compander 510 as in the second embodiment.

Unlike the second embodiment, the natural gas, which has passed through the first compressor 110 and the first cooler 210 and then sent to the first compander 510, is expanded by the first expansion unit 512 Liquid separator 420 is not sent directly to the second compander 520, but is first sent to the second gas-liquid separator 420. The fluid sent to the second gas-liquid separator (420) after passing through the first expansion portion (512) is separated from the liquefied natural gas and the natural gas.

The liquefied natural gas separated by the second gas-liquid separator 420 is sent to the first heat exchanger 310 after passing through the second valve 720 and used as a refrigerant. The liquefied natural gas used as the refrigerant in the first heat exchanger 310 after passing through the second valve 720 is partially or wholly vaporized and flows from the second expansion portion 522 to the first heat exchanger 310 The sent fluid is sent on a line that is sent to the second compression section 521 after passing through the first heat exchanger 310.

The natural gas separated by the second gas-liquid separator (420) is sent to the second expansion portion (522) of the second compander (520). The fluid once expanded by the second expansion part 522 after being separated by the second gas-liquid separator 420 is sent to the first heat exchanger 310 and used as a refrigerant.

The fluid separated by the second gas-liquid separator 420, passed through the second expansion portion 522, and then sent to the first heat exchanger 310 is returned to the first heat exchanger 310 through the first heat exchanger 310, A part or all of the vaporized and partially vaporized fluid after heat exchange with the gas is sent from the second gas-liquid separator 420 to the first heat exchanger 310 and integrated with the fluid used as the refrigerant, And sent to the second compression section 521 of the panda 520. [

The fluid compressed by the second compressing unit 521 is cooled by the second cooler 220 and then sent to the first compander 510 so as to be supplied to the first compressing unit 511, Lt; / RTI > The fluid compressed by the first compressing unit 511 is cooled by the third cooler 230 and then sent to the first compressor 110 together with the natural gas supplied from the outside as in the second embodiment , The above-mentioned series of steps is again performed.

The natural gas that has passed through the first compressor 110 and the first cooler 210 and then branched and passed through the second compressor 120 and the fourth cooler 240 is sent to the first heat exchanger 310, A liquefied natural gas expanded by the first expansion portion 512 and separated by the second gas-liquid separator 420; And a fluid once expanded by the first expansion portion 512 and separated by the second gas-liquid separator 420 and then once again expanded by the second expansion portion 522, and then introduced into the expansion means 600 Lt; / RTI >

The fluid having passed through the first heat exchanger 310 and the expansion means 600 and partially or completely liquefied is separated from the liquid phase and the gas phase by the first gas-liquid separator 410, as in the second embodiment. The liquefied natural gas separated by the first gas-liquid separator 410 is sent to the storage tank in the same manner as the second embodiment, and the natural gas separated by the first gas-liquid separator 410 is sent to the storage tank , Passes through the first valve (710), is sent to the first heat exchanger (310) together with the fluid that has passed through the second expansion portion (522), and is used again as the refrigerant.

4 is a schematic view showing a ship including a storage tank according to a fourth preferred embodiment of the present invention.

The ship including the storage tank of the fourth embodiment shown in Fig. 4 is different from the ship including the storage tank of the third embodiment shown in Fig. 3 in that the second heat exchanger 320, the third compressor 130, There is a difference in that it further includes the fifth cooler 250, and the difference will be mainly described below. A detailed description of the same components as those of the ship including the storage tank of the third embodiment described above will be omitted.

4, the ship including the storage tank of the present embodiment includes a first compressor 110, a first cooler 210, a second compressor 120, a fourth cooler 240 The first compander 510, the second gas-liquid separator 420, the second valve 720, the second compander 520, the first heat exchanger 310, the expansion means 600, A separator 410, a first valve 710, a second cooler 220, and a third cooler 230.

However, unlike the third embodiment, the vessel including the storage tank of the present embodiment is installed between the first expansion portion 512 and the second gas-liquid separator 420, and passes through the first expansion portion 512 A second heat exchanger 320 for self-heat-exchanging a natural gas to liquefy; A third compressor (130) for compressing the fluid that has passed through the second heat exchanger (320) first; And a fifth cooler 250 for lowering the temperature of the fluid passing through the third compressor 130.

 The first compressor 110 of this embodiment compresses the natural gas supplied from the outside in the same manner as the third embodiment and the first compressor 210 of this embodiment is similar to the compressor of the first embodiment 110) to lower the temperature of the natural gas as well as the pressure.

The second compressor 120 of this embodiment further compresses some of the natural gas that has passed through the first compressor 110 and the first cooler 210 as in the third embodiment. The natural gas compressed by the first compressor 110 and the second compressor 120 of the present embodiment preferably has a pressure of about 50 bar or more so as to be in a supercritical state.

As in the third embodiment, the fourth cooler 240 of the present embodiment lowers the temperature of the natural gas, which has passed through the second compressor 120 and has increased in temperature as well as pressure.

As in the third embodiment, the first compander 510 of the present embodiment includes a first expansion portion 512 for expanding the fluid and a first compression portion 511 for compressing the fluid. The first expanding section 512 and the first compressing section 511 are axially connected to each other in the same manner as in the third embodiment so that by the energy obtained by expanding the fluid by the first expanding section 512, (511) compresses the fluid.

Unlike the third embodiment, the first expander 512 of the first compander 510 inflates a portion of the natural gas that has passed through the first compressor 110 and the first cooler 210, Liquid separator 420, but sends it to the second heat exchanger 320 first.

The first compressor 511 of the first compander 510 compresses the fluid sent from the second compander 520 and sends it to the first compressor 110 as in the third embodiment.

The second heat exchanger 320 of the present embodiment is configured such that the fluid that has passed through the first expansion portion 512 and the third compressor 130 and the fifth cooler 250 after passing through the second heat exchanger 320 Exchanges the fluid that has passed therethrough. That is, the second heat exchanger 320 uses the fluid that has passed through the second inflator as a refrigerant, passes through the third compressor 130 and the fifth cooler 250, and liquefies the fluid having a high pressure.

As shown in FIG. 5, when the pressure is low, even if the temperature of the natural gas is lowered, it may not be liquefied (X in FIG. 5) (Y in Fig. 5).

Accordingly, the fluid that has passed through the first expansion portion 512 and the second heat exchanger 320 is compressed by the third compressor 130 and then sent to the second heat exchanger 320, 512) and self-heat exchanges with the fluid passing through the third compressor 130, the fluid whose pressure has been raised by the third compressor 130 is cooled and a part can be liquefied.

In the case where a sufficient amount of liquefied natural gas is not generated in the first heat exchanger 310 for use as a refrigerant only by expansion by the first expansion portion 512 of the first compander 510, The second heat exchanger 320 and the third compressor 130 to increase the liquefaction amount of the natural gas used as the refrigerant.

The third compressor 130 of the present embodiment increases the pressure of the fluid that has been heat-exchanged as the first refrigerant in the second heat exchanger 320 after passing through the first expansion portion 512.

The fifth cooler 250 of the present embodiment lowers the temperature of the fluid passing through the third compressor 130 as well as the pressure. The fifth cooler 250 can cool the fluid by, for example, heat-exchanging fluid with fresh water at about room temperature.

The second gas-liquid separator (420) of this embodiment separates the partially liquefied natural gas and the natural gas remaining in the gaseous state through the second heat exchanger (320) and, as in the third embodiment, And the natural gas is sent to the second compander 520 so that it can be further expanded by the second expansion part 522.

The second valve 720 of this embodiment is installed on a line for sending the liquefied natural gas separated by the second gas-liquid separator 420 to the first heat exchanger 310 as in the third embodiment, Adjust the flow and pressure of the gas.

As in the third embodiment, the second compander 520 of the present embodiment includes a second expanding section 522 for expanding the fluid and a second compressing section 521 for compressing the fluid. The second expanding section 522 and the second compressing section 521 are coupled by an axis in the same manner as in the third embodiment so that the energy of the second expanding section 522 inflating the fluid causes the second compressing section 521 compress the fluid.

The second expansion portion 522 of the second compander 520 can not be liquefied by the first expansion portion 512 and the second heat exchanger and can return natural gas separated by the second gas- And then sent to the first heat exchanger 310. The fluid expanded by the second expansion portion 522 is used as a refrigerant for cooling the natural gas in the first heat exchanger 310, as in the third embodiment.

The second compression section 521 of the second compander 520 compresses the fluid used as the refrigerant in the first heat exchanger 310 and sends it to the first compander 510 as in the third embodiment .

The first heat exchanger 310 of the present embodiment is configured such that the first compressor 110, the first compressor 210, the second compressor 210, and the fourth compressor 240, The gas is cooled by self-heat exchange with the refrigerant.

The first heat exchanger 310 of the present embodiment is different from the third embodiment in that the first expansion portion 512, the second heat exchanger 320, the third compressor 130, and the fifth cooler 250 ), Liquefied natural gas liquefied in the second heat exchanger (320) and separated by the second gas-liquid separator (420); And after passing through the first expansion portion 512, the second heat exchanger 320, the third compressor 130 and the fifth cooler 250, they can not be liquefied in the second heat exchanger 320, 420 and then passed through the second expansion portion 522. The refrigerant is used as the refrigerant.

As in the third embodiment, the expansion means 600 of the present embodiment lowers the pressure of the fluid whose temperature has been lowered by heat exchange in the first heat exchanger 310, and the natural gas is introduced into the first heat exchanger 310 and the expansion means 600, the liquid is partly or entirely liquefied. The expansion means 600 may be an expansion valve or an expander.

The first gas-liquid separator 410 of the present embodiment is disposed at the downstream end of the expansion means 600 and passes through the first heat exchanger 310 and the expansion means 600 and is partly liquefied natural The liquefied natural gas is sent to the storage tank and the natural gas is sent from the second expansion portion 522 to the first heat exchanger 310 on the line through which the fluid is sent.

The first valve 710 of the present embodiment is installed on the line for sending natural gas between the second expansion portion 522 and the first heat exchanger 310 from the first gas-liquid separator 410 as in the third embodiment Thereby controlling the flow rate and pressure of the natural gas.

The second cooler 220 of the present embodiment is disposed at the rear end of the second compression section 521 of the second compander 520 and passes through the second compression section 521 and has a pressure But the temperature also lowers the temperature of the raised fluid. The fluid having passed through the second compressing section 521 and the second cooler 220 is sent to the first compander 510.

The third cooler 230 of the present embodiment is installed at the rear end of the first compressing section 511 of the first compander 510 so as to pass through the first compressing section 511, But the temperature also lowers the temperature of the raised fluid. The fluid having passed through the first compression unit 511 and the third cooling unit 230 is sent to the first compressor 110 together with the natural gas supplied from the outside.

The flow of the fluid in this embodiment will be described as follows.

The natural gas supplied from the outside is firstly compressed by the first compressor 110, cooled by the first cooler 210, and then branched into two flows, as in the third embodiment. One of them is compressed by the second compressor 120, cooled by the fourth cooler 240, and then sent to the first heat exchanger 310, as in the third embodiment, Is sent to the first compander 510 as in the third embodiment.

Unlike the third embodiment, natural gas that has passed through the first compressor 110 and the first cooler 210 and then sent to the first compander 510 is expanded by the first expansion unit 512 Liquid separator 420, but is sent to the second heat exchanger 320 first. The fluid sent to the second heat exchanger 320 after passing through the first expansion portion 512 is heat-exchanged in the second heat exchanger 320 as a first refrigerant and then flows into the third compressor 130 and the fifth cooler 250 and then again exchanges heat with the fluid sent from the first expansion portion 512 to the second heat exchanger 320. The fluid that has undergone the second heat exchange in the second heat exchanger (320) after passing through the third compressor (130) and the fifth cooler (250) is sent to the second gas-liquid separator (420).

The liquid sent to the second gas-liquid separator 420 is separated from the liquefied natural gas and the natural gas and separated by the second gas-liquid separator 420 in the same manner as in the third embodiment, Likewise, after passing through the second valve 720, it is sent to the first heat exchanger 310 to be used as a refrigerant, and the natural gas separated by the second gas-liquid separator 420, The refrigerant is sent to the second expansion portion 522 of the compander 520 and expanded again, and then sent to the first heat exchanger 310 to be used as a refrigerant.

The liquefied natural gas that has been separated by the second gas-liquid separator 420 and passed through the second valve 720 and the first heat exchanger 310 is partially or wholly vaporized as in the third embodiment, The fluid sent from the expansion portion 522 to the first heat exchanger 310 is sent to the second compression portion 521 after passing through the first heat exchanger 310.

The fluid separated by the second gas-liquid separator 420, passed through the second expansion portion 522, and then sent to the first heat exchanger 310 is returned to the first heat exchanger 310 through the first heat exchanger 310, A fluid partially or wholly vaporized and partially or fully vaporized after heat exchange with the gas is sent from the second gas-liquid separator 420 to the first heat exchanger 310 and is used as a refrigerant And is sent to the second compression unit 521 of the second compander 520.

The fluid compressed by the second compressing unit 521 is cooled by the second cooler 220 and then sent to the first compander 510 so as to be supplied to the first compressing unit 511, Lt; / RTI > The fluid compressed by the first compressing unit 511 is cooled by the third cooler 230 and then sent to the first compressor 110 together with the natural gas supplied from the outside as in the third embodiment , The above-mentioned series of steps is again performed.

The natural gas that has passed through the first compressor 110 and the first cooler 210 and then branched and has passed through the second compressor 120 and the fourth cooler 240 is subjected to the first heat exchange Liquid natural gas separated by the second gas-liquid separator 420; And the fluid expanded by the second expansion portion 522, and then expanded by the expansion means 600.

The liquid, which has passed through the first heat exchanger 310 and the expansion means 600 and partially or completely liquefied, is separated from the liquid phase and the gas phase by the first gas-liquid separator 410 as in the third embodiment. The liquefied natural gas separated by the first gas-liquid separator 410 is sent to the storage tank similarly to the third embodiment, and the natural gas separated by the first gas-liquid separator 410, , Passes through the first valve (710), is sent to the first heat exchanger (310) together with the fluid that has passed through the second expansion portion (522), and is used again as the refrigerant.

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

110, 120, 130: compressors 210, 220, 230, 240, 250:
310, 320: heat exchanger 410, 420: gas-liquid separator
510, 520: Compander 511, 521:
512, 522: expanding part 600: expansion means
710, 720: valve

Claims (23)

A first compressor for compressing natural gas;
A first heat exchanger for cooling a part of the natural gas compressed by the first compressor (hereinafter referred to as "x-flow") by heat exchange with the refrigerant;
A first expansion unit for expanding the remaining natural gas other than the 'x-flow' (hereinafter referred to as 'y-flow') from the natural gas compressed by the first compressor;
A first compression unit for compressing a fluid used as a refrigerant in the first heat exchanger;
A second gas-liquid separator which separates the liquefied natural gas expanded by the first expansion part and left liquefied natural gas and the natural gas left in a gaseous state;
Expansion means for expanding the fluid cooled by said first heat exchanger; And
And a first gas-liquid separator for separating the liquefied natural gas passed through the expansion means and the natural gas remaining in a gaseous state,
Wherein the first expanding portion and the first compressing portion constitute a first compander,
Wherein the first heat exchanger comprises: liquefied natural gas separated by the second gas-liquid separator; Liquid separator for separating the gaseous natural gas separated by the first gas-liquid separator and the gaseous natural gas separated by the second gas-liquid separator as the refrigerant, the 'x-flow'
Wherein a flow of the gaseous natural gas separated by the first gas-liquid separator and the gaseous natural gas separated by the second gas-liquid separator is used as a refrigerant in the first heat exchanger, Lt; / RTI >
Wherein the natural gas compressed by the first compressing unit is sent to the front side of the first compressor. The method according to claim 1,
A second expansion unit for expanding the gaseous natural gas separated by the second gas-liquid separator; And
And a second compression unit installed on a line supplied to the first compression unit after the fluid expanded by the second expansion unit is used as refrigerant in the first heat exchanger,
The second expanding portion and the second compressing portion constitute a second compander,
Wherein the first heat exchanger comprises: liquefied natural gas separated by the second gas-liquid separator; And a flow in which a gaseous natural gas separated by the first gas-liquid separator and a fluid expanded by the second expansion unit are combined, as a refrigerant, to cool the 'x-flow'
Wherein a flow in which gaseous natural gas separated by the first gas-liquid separator and a fluid expanded by the second expansion unit are combined is used as a refrigerant in the first heat exchanger, And is compressed sequentially by the first compression unit. The method of claim 2,
The liquefied natural gas separated by the second gas-liquid separator is used as a refrigerant in the first heat exchanger, then merged with the 'z flow'
The 'z-flow' is a fluid used as a refrigerant in the first heat exchanger after the gaseous natural gas separated by the first gas-liquid separator and the fluid expanded by the second expansion unit are merged. Ships containing tanks. The method of claim 2,
Wherein natural gas sequentially compressed by the second compressing unit and the first compressing unit is sent to the front side of the first compressor after being used as a refrigerant in the first heat exchanger. The method according to claim 1 or 2,
And a second compressor for further compressing said 'x-flow'
Wherein said first heat exchanger comprises a storage tank for cooling said " x-flow " compressed by said second compressor by heat exchange with a refrigerant. The method according to claim 1 or 2,
A second heat exchanger using the fluid expanded by the first expansion portion as a refrigerant; And
And a third compressor for expanding the fluid used as the refrigerant in the second heat exchanger after being expanded by the first expansion part,
And the fluid compressed by the third compressor is cooled by the second heat exchanger, the fluid expanded by the first expansion part is heat-exchanged with the refrigerant, and is then sent to the second gas-liquid separator The ship. 1) diverts natural gas into two streams,
2) expanding one of the natural gas branched in the step 1) (hereinafter referred to as a flow)
3) separating the liquefied natural gas that has expanded and liquefied in the step 2) and the natural gas remaining in the gaseous state,
4) expanding the natural gas separated in the step 3)
5) the liquefied natural gas separated in the step 3); And a fluid expanded in the step 4) as a refrigerant, and cooling the other of the natural gas branched in the step 1) (hereinafter referred to as "b-flow"
6) The 'b-flow' cooled in step 5) is expanded
7) separating the liquefied natural gas expanded and liquefied in the step 6) and the natural gas remaining in the gaseous state,
8) The gaseous natural gas separated in the step 7) is merged with the fluid expanded in the step 4), and the 'b-flow' is used as a refrigerant to be cooled by heat-
9) The combined flow of the fluid expanded in the step 4) and the gaseous natural gas separated in the step 7) is used as a coolant for cooling the 'b-flow' in the step 5) ) Stage is compressed by the energy released when the natural gas is expanded,
10) The natural gas compressed in the step 9) is further compressed by the energy released when the natural gas is expanded in the step 2). The method of claim 7,
The liquefied natural gas separated in the step 3) is used as a refrigerant for cooling by heat-exchanging the 'b-flow' in the step 5), then merged with the 'c-flow'
The 'c-flow' is a refrigerant in which the natural gas separated in the step 7) and the fluid expanded in the step 4) are combined and the refrigerant is cooled by heat-exchanging the 'b- The fluid being used. The method according to claim 7 or 8,
2-1) The 'a flow' expanded in the step 2) is used as a refrigerant in the second heat exchanger,
2-2) The 'a flow' used as the refrigerant in the step 2-1) is compressed,
2-3) The 'a flow' compressed in the step 2-2) is a refrigerant which is cooled by the heat exchanged by the second heat exchanger, the 'a flow' expanded in the step 2)
2-4) The 'a flow', which is heat-exchanged and cooled in step 2-3), is separated into liquefied natural gas and natural gas remaining in the gaseous state in step 3). delete delete delete delete delete delete delete delete delete delete delete delete delete delete

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