KR101714677B1 - 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 inflator for expanding the remaining natural gas excluding the 'x-flow' (hereinafter referred to as 'y-flow') from the natural gas compressed by the first compressor; A second gas-liquid separator which separates the liquefied natural gas expanded by the first expander and left liquefied natural gas and the natural gas left in a gaseous state; And expansion means for expanding the fluid cooled by the first heat exchanger, wherein the first heat exchanger comprises: liquefied natural gas separated by the second gas-liquid separator; And the gaseous natural gas separated by the second gas-liquid separator are used as a refrigerant to cool the 'x-flow'.

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.

On the other hand, in order to re-liquefy the evaporation gas, a separate liquefaction facility including a plurality of compressors and the like is required. However, the liquefaction facility of a compressor or the like requires a lot of cost and a lot of space in the ship.

In addition, when the amount of evaporation gas generated exceeds the amount required by the engine or the like, the evaporation gas is incinerated. Incineration of the evaporation gas is a waste of the energy and operation cost of the evaporation gas.

It is an object of the present invention to provide a vessel including a storage tank in which evaporation gas is used as a refrigerant for liquefying natural gas without a separate liquefaction facility.

According to an aspect of the present invention, there is provided a ship including a storage tank, 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 inflator for expanding the remaining natural gas excluding the 'x-flow' (hereinafter referred to as 'y-flow') from the natural gas compressed by the first compressor; A second gas-liquid separator which separates the liquefied natural gas expanded by the first expander and left liquefied natural gas and the natural gas left in a gaseous state; And expansion means for expanding the fluid cooled by the first heat exchanger, wherein the first heat exchanger comprises: liquefied natural gas separated by the second gas-liquid separator; And a gaseous natural gas separated by the second gas-liquid separator as a refrigerant to cool the 'x-flow'.
The ship including the storage tank may further include a second inflator for expanding the gaseous natural gas separated by the second gas-liquid separator, wherein the first heat exchanger is separated by the second gas- Liquefied natural gas; And a fluid inflated by the second inflator as a refrigerant, thereby cooling the 'x-flow'.
The liquefied natural gas separated by the second gas-liquid separator may be used as a refrigerant in the first heat exchanger, then expanded by the second expander, and then joined with the fluid used as the refrigerant in the first heat exchanger have.
The gaseous natural gas separated by the second gas-liquid separator may be combined with the evaporated gas discharged from the storage tank and used as a refrigerant in the first heat exchanger.
The vessel including the storage tank may further include a first gas-liquid separator for separating liquefied natural gas that has passed through the expansion means and natural gas remaining in a gaseous state, and the first gas- The natural gas in the gaseous state may be combined with the evaporated gas discharged from the storage tank and used as a refrigerant in the first heat exchanger.
The gaseous natural gas separated by the second gas-liquid separator may be used as a refrigerant in the first heat exchanger and then sent to the front of the first compressor.
The ship including the storage tank may further include a second compressor installed at the rear end of the first heat exchanger, and the gaseous natural gas separated by the second gas-liquid separator is discharged from the first heat exchanger The natural gas compressed and compressed by the second compressor after being used as a refrigerant can be sent to the front side of the first compressor.
The ship including the storage tank may include a third compressor for further compressing the 'x-flow', and the first heat exchanger may include a third compressor for compressing the 'x-flow' And can be cooled by heat exchange.
A ship including the storage tank includes a second heat exchanger using a fluid expanded by the first inflator as a refrigerant; And a fourth compressor for compressing the fluid used as the refrigerant in the second heat exchanger after being expanded by the first expander, and the fluid compressed by the fourth compressor is further subjected to the second heat exchange The refrigerant may be cooled by heat exchange with the refrigerant by the first inflator and then sent to the second gas-liquid separator.
According to another aspect of the present invention, there is provided a fuel cell system comprising: a first compressor for compressing a fuel gas; A refrigerant system for cooling part (hereinafter referred to as 's-1 flow') of the natural gas compressed by the first compressor; (Hereinafter referred to as 's-2 flow') of the natural gas compressed by the first compressor by using the natural gas cooled by the refrigerant system as a refrigerant, except for the 's-1 flow' Liquefaction system for liquefaction; And an evaporation gas supply system for supplying evaporation gas discharged from the storage tank to the liquefaction system, wherein the refrigerant system comprises: a first inflator for expanding the 's-1 flow'; And a second gas-liquid separator for separating liquefied natural gas expanded by the first expander and liquefied natural gas and gaseous natural gas, the liquefaction system comprising: liquefied natural gas separated by the second gas-liquid separator; A natural gas in a gaseous state separated by the second gas-liquid separator; And an evaporation gas supplied from the evaporation gas supply system as a refrigerant to liquefy the 's-2 flow', wherein the refrigerant system is an open loop.
The refrigerant system includes a second heat exchanger using the 's-1 flow' expanded by the first inflator as a refrigerant; And a fourth compressor for compressing the 's-1 flow' used as a refrigerant in the second heat exchanger after being inflated by the first inflator, wherein the fluid compressed by the fourth compressor May be cooled by the second heat exchanger to heat-exchange the fluid expanded by the first expander with the refrigerant, and then be sent to the second gas-liquid separator.
According to another aspect of the present invention to achieve the above object, there is provided a method for separating a natural gas (hereinafter, referred to as "a flow") by bifurcating natural gas into two flows and expanding the natural gas Separating the liquefied natural gas expanded in the step 2) and the natural gas remaining in the gaseous state, expanding the natural gas separated in the step 3), and removing the liquefied natural gas separated in the step 3); And the fluid expanded in the step 4) as a refrigerant and the remaining flow of the natural gas branched in the step 2) (hereinafter referred to as "b flow"), B ' flow is < / RTI > 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 natural gas separated in the step 7) is merged with the evaporated gas discharged from the storage tank, ) The flow merged at the step 8) may be used as a refrigerant to merge with the fluid expanded at the step 4), and to cool the 'b flow' by heat-exchanging at the step 5).
The liquefied natural gas separated in the step 3) may be combined with the fluid used as the refrigerant in the step 5) after being used as the refrigerant in the step 5), and then 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).

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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.

In addition, since the present invention uses evaporative gas as a refrigerant for liquefying natural gas without providing a separate liquefaction facility, it is possible to reduce the installation cost and recover the cold and hot of the evaporative gas.

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. Natural gas passes through each device and can be in a gas, liquid, or gas-liquid mixture depending on 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 inflator (512) for inflating a portion of the natural gas having passed through the first compressor (110) and the first cooler (210); A second inflator (522) for further inflating the fluid that has passed through the first inflator (512); 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 second compressor 511 for compressing the fluid used as the refrigerant in the first heat exchanger 310; A second cooler 230 for cooling the fluid passing through the second compressor 511; And a first valve (20) installed on the line for sending the evaporated gas in the storage tank (10) to the first heat exchanger (310).

The first compressor (110) of this embodiment compresses natural gas. 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 inflator 512 of the present embodiment inflates a portion of the natural gas that has passed through the first compressor 110 and the first cooler 210 and sends it to the second inflator 522.

The second inflator 522 of the present embodiment further inflates the fluid expanded by the first inflator 512 after passing through the first compressor 110 and the first cooler 210 and then flows into the first heat exchanger 310 ).

The first heat exchanger 310 of the present embodiment is a device in which a part of the natural gas that has passed through the first compressor 110 and the first cooler 210 passes through the first inflator 512 and the second inflator 522 And is cooled by self-heat exchange with the fluid and the evaporative gas discharged from the storage tank 10. 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 to be used as the refrigerant in the first heat exchanger 310 is supplied to the first and second inflators 512 and 522 at a temperature sufficiently low to liquefy the natural gas by the first inflator 512 and the second inflator 522, Lt; / RTI >

In addition, the ship including the storage tank of the present embodiment uses the evaporation gas generated in the storage tank 10 as a refrigerant for cooling the natural gas in the first heat exchanger 310, and the evaporated gas generated in the first heat exchanger 310 It is possible to increase the liquefaction efficiency.

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 compressor 511 of the present embodiment includes a fluid used as a refrigerant in the first heat exchanger 310 after passing through the first inflator 512 and the second inflator 522; And evaporation gas used as a refrigerant in the first heat exchanger 310 after being discharged from the storage tank 10.

The second cooler 230 of this embodiment is installed at the downstream end of the second compressor 511 to lower the temperature of the fluid passing through the second compressor 511 as well as the pressure. The fluid having passed through the second compressor 511 and the second cooler 230 is sent to the first compressor 110 together with the natural gas supplied from the outside. The second cooler 230 of this embodiment can cool the fluid by, for example, heat-exchanging fluid with fresh water at about room temperature.

The first valve 20 of the present embodiment is installed on a line for sending the vaporized gas in the storage tank 10 to the first heat exchanger 310 and is supplied from the storage tank 10 to the first heat exchanger 310 Adjust the flow rate and pressure of the vapor to be sent. The first valve 20 is opened when the internal pressure of the storage tank 10 is higher than the set value according to the value sent by the sensor for measuring the pressure inside the storage tank 10, And to be closed if it is lower.

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

The natural gas is compressed by the first compressor (110), cooled by the first cooler (210), and then branched into two flows. One stream is directed to the first heat exchanger 310 and the other stream is directed to the first expander 512 where the first expander 512) is used as the refrigerant.

The natural gas that has passed through the first compressor 110 and the first cooler 210 and then sent to the first inflator 512 is expanded by the first inflator 512 and then sent to the second inflator 522. The fluid once again expanded by the second expander 522 is sent to the first heat exchanger 310.

The cooled fluid passing through the first inflator 512 and the second inflator 522 is heat-exchanged with the natural gas in the first heat exchanger 310 together with the evaporated gas discharged from the storage tank 10, Some or all of which is vaporized, and the partially or fully vaporized fluid is sent to the second compressor 511 and compressed.

The fluid compressed by the second compressor 511 is cooled by the second cooler 230 and then sent back to the first compressor 110 together with the natural gas supplied from the outside so that the above- do.

That is, in this embodiment, the fluid used as the refrigerant is compressed by the second compressor 511 as much as the pressure is lowered by the first inflator 512 and the second inflator 522, and the natural gas is supplied from the outside And then sent to the first compressor (110).

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 the natural gas expanded by the first inflator 512 and the second inflator 522; And the evaporation gas discharged from the storage tank 10, 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.

The evaporated gas generated in the storage tank 10 is passed through the first valve 20 and then sent on a line through which the fluid is sent from the second inflator 522 to the first heat exchanger 310.

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 third compressor 120, the third cooler 240, 1 gas-liquid separator 410, a second valve 710, and a third valve 30, and differences will be mainly described below. 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.

2, the vessel including the storage tank of the present embodiment includes a first compressor 110, a first cooler 210, a first inflator 512, a second inflator 522 A second compressor 511, a second cooler 230, and a first valve 20. The first heat exchanger 310, the expansion unit 600, the second compressor 511, the second cooler 230,

However, the ship including the storage tank of this embodiment is different from the first embodiment in that the third compressor 120 additionally compresses the natural gas firstly compressed by the first compressor 110; A third cooler 240 for lowering the temperature of the natural gas passing through the third 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; A second valve (710) for regulating the flow rate and pressure of the gaseous natural gas separated by the first gas-liquid separator (410); And a third valve 30 for controlling the flow rate and pressure of the liquefied natural gas separated from the first gas-liquid separator 410 and sent to the storage tank 10.

The first compressor 110 of this embodiment compresses natural gas and the first cooler 210 of the present embodiment passes through the first compressor 110 similarly to the first embodiment And lowers the temperature of the natural gas as well as the pressure.

The third 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 third 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, at the front end of the first compressor 110, or after the second compression process, that is, at the rear end of the third cooler 240.

The reason for dividing the natural gas between the first compressor 210 and the third compressor 120 in the present embodiment is that the natural gas, which is branched and sent to the first expander 512 to be used as the refrigerant, Is expanded by the first expansion unit 512 and the second expansion unit 522 and then sent to the first heat exchanger 310. It is inefficient to compress the natural gas to be subjected to the expansion process through the two-stage compression process. 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 third 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 third cooler 240 of the present embodiment lowers the temperature of the natural gas that passes through the third compressor 120 and increases not only in pressure but also in temperature. For example, by exchanging heat between fresh water and natural gas at a room temperature, Natural gas can be cooled.

The first inflator 512 of the present embodiment inflates a part of the natural gas that has passed through the first compressor 110 and the first cooler 210 and sends it to the second inflator 522 as in the first embodiment The second inflator 522 of the present embodiment is configured to further expand the fluid inflated by the first inflator 512 after passing through the first compressor 110 and the first cooler 210 as in the first embodiment And then sent to the first heat exchanger 310.

The first heat exchanger 310 of the present embodiment is a system in which the natural gas that has passed through the first compressor 110, the first cooler 210, the third compressor 120 and the third cooler 240 is introduced into the first inflator 512 and the second inflator 522 and the evaporation gas discharged from the storage tank 10 by the self-heat exchange.

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 passes over the line from the second inflator 522 to the first heat exchanger 310,

The second valve 710 of the present embodiment is installed on a line for sending natural gas from the first gas-liquid separator 410 to the space between the second inflator 522 and the first heat exchanger 310, . In other words, the second valve 710 is connected to the first gas-liquid separator 710 in consideration of the flow rate of the fluid passing through the second inflator 522 to the first heat exchanger 310 and the capacity of the first heat exchanger 310, The amount of natural gas sent from the first inflator 422 to the first inflator 522 and the first heat exchanger 310 and from the second inflator 522 to the first heat exchanger 310, The pressure of the natural gas is adjusted so that the pressure of the natural gas sent from the first gas-liquid separator 410 to the second inflator 522 and the first heat exchanger 310 becomes similar.

The third valve 30 of the present embodiment is installed on a line for sending liquefied natural gas separated from the first gas-liquid separator 410 to the storage tank 10 to regulate the flow rate and pressure of the liquefied natural gas.

The second compressor 511 of the present embodiment is similar to the first embodiment in that the fluid used as the refrigerant in the first heat exchanger 310 after passing through the first inflator 512 and the second inflator 522; And evaporation gas used as a refrigerant in the first heat exchanger 310 after being discharged from the storage tank 10.

The second cooler 230 of the present embodiment is disposed at the downstream end of the second compressor 511 to lower the temperature of the fluid passing through the second compressor 511 as well as the pressure and the temperature, as in the first embodiment. The fluid having passed through the second compressor 511 and the second cooler 230 is sent to the first compressor 110 together with the natural gas supplied from the outside.

The first valve 20 of the present embodiment is provided on the line for sending the vaporized gas in the storage tank 10 to the first heat exchanger 310 and is supplied from the storage tank 10 1 heat exchanger (310).

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

Natural gas, like the first embodiment, is firstly compressed by the first compressor 110, cooled by the first cooler 210, and then branched into two flows. One of them is different from the first embodiment in that it is secondarily compressed by the third compressor 120, cooled by the third cooler 240, and then sent to the first heat exchanger 310, The flow is directed to the first inflator 512, 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 inflator 512 is expanded by the first inflator 512 and then supplied to the second inflator 512, Lt; / RTI > The fluid once again expanded by the second expander 522 is sent to the first heat exchanger 310 as in the first embodiment.

The cooled fluid passing through the first expander 512 and the second expander 522 flows in the first heat exchanger 310 together with the evaporated gas discharged from the storage tank 10 in the same manner as in the first embodiment, Some or all of the fluid is vaporized, and the partially or fully vaporized fluid is sent to the second compression section 511 and compressed.

The fluid compressed by the second compressing unit 511 is cooled by the second 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 repeated again.

The natural gas that has passed through the first compressor 110 and the first cooler 210 and then branched after passing through the third compressor 120 and the third cooler 240 is sent to the first heat exchanger 310, A fluid inflated by the first inflator 512 and the second inflator 522; A natural gas separated by the first gas-liquid separator 410; And the evaporation gas discharged from the storage tank 10, 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 after passing through the third valve 30 and the natural gas separated by the first gas-liquid separator 410 passes through the second valve 710 The evaporation gas discharged from the storage tank 10; And the fluid passing through the second inflator 522 to the first heat exchanger 310 and used again as the refrigerant.

The evaporated gas generated inside the storage tank 10 flows from the second inflator 522 through the first valve 20 and the natural gas separated by the first gas-liquid separator 410, And is sent to a line 310 on which the fluid is sent.

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

The ship including the storage tank of the third embodiment shown in Fig. 3 has the second gas-liquid separator 420 and the fourth valve 720 as compared with the ship including the storage tank of the second embodiment shown in Fig. 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 third compressor 120, a third cooler 240 A first valve 422, a second valve 422, a third valve 423, a third valve 423, a second valve 424, A second compressor 511, a second cooler 230, and a first valve 20.

However, unlike the second embodiment, the vessel including the storage tank of the present embodiment is installed between the first inflator 512 and the second inflator 522, passes through the first inflator 512, A second gas-liquid separator (420) for separating the liquefied natural gas and the natural gas remaining in the gaseous state; And a fourth 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 third 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 second embodiment. The natural gas compressed by the first compressor 110 and the third 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 third cooler 240 of the present embodiment lowers the temperature of the natural gas that has passed through the third compressor 120 and has increased in temperature as well as pressure.

The first inflator 512 of the present embodiment expands a part of the natural gas that has passed through the first compressor 110 and the first cooler 210, as in the second embodiment. However, unlike the second embodiment, the first inflator 512 of the present embodiment inflates a part of the natural gas that has passed through the first compressor 110 and the first cooler 210, 522, but first sends it to the second gas-liquid separator 420.

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 inflator 512, and the liquefied natural gas is introduced into the first heat exchanger 310, To be used as a refrigerant, and the natural gas is sent to the second inflator 522 to be further inflated by the second inflator 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 fourth 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. In other words, the fourth valve 720 is connected to the second gas-liquid separator 720 in consideration of the flow rate of the fluid passing through the second inflator 522 to the first heat exchanger 310 and the capacity of the first heat exchanger 310, The amount of liquefied natural gas sent from the first heat exchanger 310 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, Liquid separator 420 to further expand the liquefied natural gas to be sent to the first heat exchanger 310 so as to increase the liquefaction efficiency in the first gas-liquid separator 420.

The second inflator 522 of the present embodiment inflates the natural gas separated by the second gas-liquid separator 420 and sends it to the first heat exchanger 310.

The first heat exchanger 310 of the present embodiment is similar to the second embodiment in that the first and second heat exchangers 310 and 310 are disposed in the first and second compressors 110 and 210 and the third and fourth compressors 120 and 240, The gas is cooled by self-heat exchange with the fluid that has passed through the first inflator 512 and the second inflator 522 and the evaporated gas discharged from the storage tank 10.

However, unlike the second embodiment, the first heat exchanger 310 of this embodiment uses not only the fluid that has passed both the first inflator 512 and the second inflator 522 as a refrigerant, Liquid separator 420 after being passed through the second gas-liquid separator 512 and 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 Separates the natural gas remaining in the gaseous state with the liquefied natural gas, and sends the natural gas onto the line from which the fluid is sent from the second inflator 522 to the first heat exchanger 310.

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

The third valve 30 of this embodiment is installed on a line for sending liquefied natural gas separated from the first gas-liquid separator 410 to the storage tank 10 as in the second embodiment so that the flow rate of liquefied natural gas And pressure.

The second compressor 511 of the present embodiment compresses the fluid used as the refrigerant in the first heat exchanger 310, as in the second embodiment.

Like the second embodiment, the second cooler 230 of the present embodiment is disposed at the downstream end of the second compressor 511 to lower the temperature of the fluid passing through the second compressor 511 as well as the pressure. The fluid having passed through the second compressor 511 and the second cooler 230 is sent to the first compressor 110 together with the natural gas supplied from the outside.

The first valve 20 of the present embodiment is provided on the line for sending the vaporized gas in the storage tank 10 to the first heat exchanger 310 and is supplied from the storage tank 10 1 heat exchanger (310).

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 third compressor 120, cooled by the third cooler 240, and then sent to the first heat exchanger 310, as in the second embodiment, Is sent to the first inflator 512, as in the second embodiment.

Unlike the second embodiment, the natural gas that has passed through the first compressor 110 and the first cooler 210 and then sent to the first inflator 512 is expanded by the first inflator 512, Liquid separator 420 is not sent directly to the expander 522 but to the second gas-liquid separator 420 first. The fluid that has passed through the first expander 512 and then sent to the second gas-liquid separator 420 is separated from the liquefied natural gas and the natural gas.

The liquefied natural gas separated by the second gas-liquid separator 420 passes through the fourth valve 720 and is sent to the first heat exchanger 310 and used as a refrigerant. The liquefied natural gas used as the refrigerant in the first heat exchanger 310 after passing through the fourth valve 720 is partially or wholly vaporized and sent to the first heat exchanger 310 from the second inflator 522 The fluid passes through the first heat exchanger 310 and then is sent on the line to be sent to the second compressor 511.

The natural gas separated by the second gas-liquid separator (420) is sent to the second expander (522). The fluid once expanded by the second inflator 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 expander 522, and then sent to the first heat exchanger 310 is supplied to the first heat exchanger 310 through the first heat exchanger 310, Fluid partially or fully vaporized and partially or fully vaporized after the heat exchange is transferred from the second gas-liquid separator 420 to the first heat exchanger 310 and integrated with the fluid used as the refrigerant, 511).

The fluid compressed by the second compressor 511 is cooled by the second 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 repeated again.

The natural gas that has passed through the first compressor 110 and the first cooler 210 and then branched after passing through the third compressor 120 and the third cooler 240 is sent to the first heat exchanger 310, A liquefied natural gas that is expanded by the first expander 512 and then separated by the second gas-liquid separator 420; A fluid inflated by the first inflator 512 and separated by the second gas-liquid separator 420 and then once again inflated by the second inflator 522; A natural gas separated by the first gas-liquid separator 410; And the evaporation gas discharged from the storage tank 10, and then expanded by the expansion means 600. [

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 10 after passing through the third valve 30 as in the second embodiment and is supplied to the first gas-liquid separator 410 The natural gas separated by the natural gas is passed through the second valve 710 and then passed through the second inflator 522, as in the second embodiment. And the evaporation gas discharged from the storage tank 10 to the first heat exchanger 310 and used again as a refrigerant.

The evaporated gas generated in the storage tank 10 passes through the first valve 20 and then flows into the second expander 40 together with the natural gas separated by the first gas-liquid separator 410, (522) to the first heat exchanger (310).

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 fourth compressor 130, There is a difference in that it further includes the fourth 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.

Referring to FIG. 4, the ship including the storage tank of the present embodiment includes a first compressor 110, a first cooler 210, a third compressor 120, a third cooler 240 A second gas-liquid separator 420, a fourth valve 720, a second inflator 522, a first heat exchanger 310, an expansion means 600, a first gas-liquid separator (not shown) 410, a second valve 710, a third valve 30, a second compressor 511, a second cooler 230, and a first valve 20.

However, unlike the third embodiment, the vessel including the storage tank of the present embodiment is installed between the first inflator 512 and the second gas-liquid separator 420, and the natural gas which has passed through the first inflator 512 A second heat exchanger (320) for self-heat-exchanging gas to liquefy the gas; A fourth compressor 130 for compressing the fluid that has passed through the second heat exchanger 320 first; And a fourth cooler (250) for lowering the temperature of the fluid passing through the fourth 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 third 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 third 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 third cooler 240 of the present embodiment lowers the temperature of the natural gas that has passed through the third compressor 120 and has increased in temperature as well as pressure.

The first inflator 512 of the present embodiment expands a part of the natural gas that has passed through the first compressor 110 and the first cooler 210 as in the third embodiment. However, unlike the third embodiment, the first inflator 512 of the present embodiment inflates a part of the natural gas that has passed through the first compressor 110 and the first cooler 210, To the second heat exchanger (320), not to the second heat exchanger (420).

The second heat exchanger 320 of this embodiment is configured to pass the fluid that has passed through the first expander 512 and the fourth compressor 130 and the fourth cooler 250 after passing through the second heat exchanger 320 Heat exchange one fluid. That is, the second heat exchanger 320 uses the fluid that has passed through the first inflator 512 as a refrigerant, passes through the fourth compressor 130 and the fourth 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 inflator 512 and the second heat exchanger 320 is compressed by the fourth compressor 130 and then sent to the second heat exchanger 320 so that the first inflator 512, The fluid whose pressure is increased by the fourth compressor 130 is cooled and a part of the fluid can be liquefied.

When the liquefied natural gas is not generated in an amount sufficient for use as a refrigerant in the first heat exchanger 310 only by the expansion by the first expander 512 and the second expander 522, The heat exchanger 320 and the fourth compressor 130 to increase the liquefaction amount of the natural gas used as the refrigerant.

The fourth compressor 130 of the present embodiment increases the pressure of the fluid heat-exchanged as a first refrigerant in the second heat exchanger 320 after passing through the first inflator 512.

The fourth cooler 250 of the present embodiment lowers the temperature of the fluid passing through the fourth compressor 130 as well as the pressure. The fourth cooler 250 can cool the fluid by, for example, heat-exchanging the 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, To the first heat exchanger 310 so that it can be used as a refrigerant and the natural gas is sent to the second inflator 522 to be further inflated by the second inflator 522.

The fourth 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.

The second inflator 522 of the present embodiment inflates the natural gas separated by the second gas-liquid separator 420 and sends it to the first heat exchanger 310 as in the third embodiment.

The first heat exchanger 310 of the present embodiment is configured such that the first compressor 110, the first cooler 210, the third compressor 120, and the third cooler 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 inflator 512, the second heat exchanger 320, the fourth compressor 130 and the fourth cooler 250, The liquefied natural gas liquefied in the second heat exchanger 320 and separated by the second gas-liquid separator 420; Liquid separator 420 can not be liquefied in the second heat exchanger 320 after passing through the first expander 512, the second heat exchanger 320, the fourth compressor 130 and the fourth cooler 250, Fluid after passing through the second inflator 522; A natural gas separated by the first gas-liquid separator 410; And evaporation gas discharged from the storage tank 10 are 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 Separates the natural gas remaining in the gaseous state with the liquefied natural gas, and sends the natural gas onto the line from which the fluid is sent from the second inflator 522 to the first heat exchanger 310.

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

The third valve 30 of this embodiment is installed on a line for sending liquefied natural gas separated from the first gas-liquid separator 410 to the storage tank 10 as in the third embodiment so that the flow rate of liquefied natural gas And pressure.

The second compressor 511 of the present embodiment compresses the fluid used as the refrigerant in the first heat exchanger 310 as in the third embodiment.

The second cooler 230 of the present embodiment is installed at the rear end of the second compressor 511 of the first inflator 512 and passes through the second compressor 511 and not only the pressure but also the temperature Lowering the temperature of the raised fluid. The fluid having passed through the second compressor 511 and the second cooler 230 is sent to the first compressor 110 together with the natural gas supplied from the outside.

The first valve 20 of the present embodiment is installed on a line for sending the vaporized gas in the storage tank 10 to the first heat exchanger 310 as in the third embodiment, 1 heat exchanger (310).

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 the flows is compressed by the third compressor 120, cooled by the third cooler 240, and then sent to the first heat exchanger 310, as in the third embodiment, Is sent to the first inflator 512, as in the third embodiment.

Unlike the third embodiment, the natural gas, which has passed through the first compressor 110 and the first cooler 210 and then sent to the first inflator 512, is expanded by the first inflator 512, 2 gas-liquid separator 420, but is sent to the second heat exchanger 320 first. The fluid that has passed through the first expander 512 and then sent to the second heat exchanger 320 is heat exchanged in the second heat exchanger 320 as the first refrigerant and then flows into the fourth compressor 130 and the fourth cooler 250 And then again exchanges heat with the fluid sent from the first inflator 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 fourth compressor (130) and the fourth 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, Similarly, after passing through the fourth 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 is sent to the second The refrigerant is sent to the expander 522, expanded once 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 fourth valve 720 and the first heat exchanger 310 is partially or completely vaporized as in the third embodiment, The fluid sent from the expander 522 to the first heat exchanger 310 is sent to the second compressor 511 after passing through the first heat exchanger 310.

The fluid separated by the second gas-liquid separator 420, passed through the second expander 522, and then sent to the first heat exchanger 310 is supplied to the first heat exchanger 310 through the first heat exchanger 310, A part or all of the vaporized and partially vaporized fluid is sent from the second gas-liquid separator 420 to the first heat exchanger 310 to be separated from the fluid used as the refrigerant, And is sent to the second compressor 511.

The fluid compressed by the second compressor 511 is cooled by the second cooler 230 and then sent to the first compressor 110 together with the natural gas supplied from the outside as in the third embodiment, We go through a series of steps again.

The natural gas that has passed through the first compressor 110 and the first cooler 210 and then branched and has passed through the third compressor 120 and the third cooler 240 is subjected to the first heat exchange Liquid natural gas separated by the second gas-liquid separator 420; A fluid inflated by the second inflator 522; A natural gas separated by the first gas-liquid separator 410; And the evaporation gas discharged from the storage tank 10, 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 second valve (710), is sent to the first heat exchanger (310) together with the fluid that has passed through the second inflator (522), and is used again as the refrigerant.

The evaporated gas generated in the storage tank 10 passes through the first valve 20 and then flows into the second expander 40 together with the natural gas separated by the first gas-liquid separator 410, (522) to the first heat exchanger (310).

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, 511: compressors 210, 230, 240, 250:
310, 320: heat exchanger 410, 420: gas-liquid separator
512, 522: inflator 600: expansion means
20, 30, 710, 720: valve

Claims (15)

delete delete delete delete delete delete delete delete delete delete delete 1) branching natural gas into two streams;
2) expanding one flow (hereinafter referred to as a flow) of the natural gas branched in the step 1);
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 cooling the remaining fluid (hereinafter, referred to as 'b flow') of the natural gas branched in the step 1) by heat exchange with the refrigerant as the refrigerant and the fluid expanded in the step 4);
6) expanding the 'b-flow' cooled in step 5);
7) separating the liquefied natural gas that has expanded and liquefied in the step 6) and the natural gas remaining in the gaseous state;
8) joining the natural gas separated in the step 7) with the evaporated gas discharged from the storage tank; And
9) joining the flow merged in the step 8) with the fluid expanded in the step 4), and using the 'b-flow' as a refrigerant to cool by heat-exchanging in the step 5);
/ RTI > delete The method of claim 12,
Wherein the liquefied natural gas separated in the step (3) is used as a refrigerant in the step (5), and is then merged with the fluid used as the refrigerant in the step (5) after being expanded in the step (4). The method according to claim 12 or 14,
2-1) the 'a flow' expanded in the step 2) is used as a refrigerant in the second heat exchanger;
2-2) compressing the 'a flow' used as a refrigerant in the step 2-1);
2-3) The 'a flow' compressed in the step 2-2) is cooled by heat exchange with the 'a flow' expanded in the step 2) as refrigerant by the second heat exchanger; And
2-4) separating the liquefied natural gas and the natural gas remaining in a gaseous state in the step 3), wherein the 'a flow' is cooled and heat-exchanged in the step 2-3).
/ RTI >

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