KR20200086965A - Method and system for transferring liquefied gas - Google Patents

Abstract

A method for transferring liquefied gas and a system thereof are disclosed. According to the present invention, the method for transferring liquefied gas comprises: a pressurizing step of increasing the internal pressure of a supply-side storage tank (12); and a transfer step of pressurizing and discharging liquefied gas in the supply-side storage tank (12) by the increased internal pressure. The method transfers the liquefied gas while suppressing an increase in enthalpy of the liquefied gas accommodated in the supply-side storage tank (12). The liquefied gas transferring system comprises a liquefied gas vaporization line (L10) configured to provide a path for pressurizing the liquefied gas stored in the supply-side storage tank (12) by a supply pump (14), heating by a vaporizer (16), and then returning into the supply-side storage tank (12).

Description

METHOD AND SYSTEM FOR TRANSFERRING LIQUEFIED GAS}

The present invention relates to a method and system for transporting liquefied gas, such as LNG or LPG, to a storage tank, and more specifically, flash gas generated inside the storage tank when receiving liquefied gas (flash gas) It relates to a method and system for transporting a liquefied gas to transfer the liquefied gas to a supercooled state while suppressing an increase in the enthalpy of the liquefied gas so as to suppress ).

Natural gas is transported in gaseous form through on-shore or offshore gas piping, or stored in LNG carriers in the form of liquefied liquefied natural gas (LNG) or liquefied petroleum gas (LPG) and transported to remote consumers. Liquefied natural gas is obtained by cooling natural gas to an extremely low temperature (approximately -163°C), and its volume is reduced to approximately 1/600 than that of natural gas in gas, so it is very suitable for long-distance transportation by sea.

A liquefied gas carrier for carrying liquefied gas such as LNG or LPG and operating the sea to unload the liquefied gas shipped from the production site is a storage tank (commonly referred to as a'cargo') that can withstand the cryogenic temperature of liquefied gas. Includes.

In addition to the liquefied gas carrier, the storage tank capable of receiving the liquefied gas may be installed in a floating plant such as LNG FPSO (Floating, Production, Storage and Offloading), LNG FSRU (Floating Storage and Regasification Unit).

In recent years, ships (LNG propulsion vessels) propelled by engines that use clean fuel, LNG, as fuel to suppress environmental pollution are increasing, and in the case of such LNG propulsion vessels, liquefied gas storage tanks capable of storing LNG as fuel are also being used. It is mounted. In addition, as the number of LNG propulsion vessels increased, a fuel bunkering ship (LNG bunkering ship) was developed to supply fuel to the LNG propulsion vessel for refueling, and the liquefied gas storage tank is also installed inside the hull.

As such, LNG carriers, LNG RVs, LNG propulsion vessels, and fuel supply ships that transport or store liquefied gases such as LNG as cargo or store them as fuel, or LNG in floating plants such as LNG FPSO, LNG FSRU, etc. A liquefied gas storage tank for storing liquefied gas in a cryogenic state is installed.

In order to transfer the liquefied gas stored in the terminal or the ship to the storage tank, a liquefied gas transfer system (eg, a bunkering system) is required. 1 is a view schematically showing a liquefied gas transfer system according to the prior art, liquefied gas for transporting liquefied gas from the supply-side storage tank 110 installed in the land terminal to the demand-side storage tank 120 installed in the ship The transfer system is illustrated.

Referring to FIG. 1, a conventional liquefied gas transfer system extends from a supply-side storage tank 1 installed on a land terminal to a demand-side storage tank 4 installed on a ship to supply a liquefied gas loading line L1 for supplying liquefied gas. And, the evaporation gas recovery line extending from the demand-side storage tank (4) to the supply-side storage tank (1) to recover the boil-off gas (flash gas) generated in the demand-side storage tank (4) to the supply-side storage tank (1) L2).

A supply pump 2 is installed inside the supply-side storage tank 1 to supply liquefied gas to the demand-side storage tank 4 through the liquefied gas loading line L1, and liquefied gas from the supply pump 2 The loading line L1 starts.

An evaporation gas compressor 3 is installed in the evaporation gas recovery line L2 to compress the evaporation gas generated in the demand-side storage tank 4 and supply it to the supply-side storage tank 1.

By the way, since such a conventional liquefied gas transfer system is configured to compress the liquefied gas stored in the supply-side storage tank 1 by the supply pump 2 and transfer it to the demand-side storage tank 4, This results in a significant increase in the enthalpy of liquefied gas during the transfer process. Accordingly, there is a problem in that a large amount of flash gas is generated in the storage tank 4 on the demand side receiving liquefied gas.

The present invention is to solve the conventional problems as described above, to increase the internal pressure of the supply-side storage tank during the transfer of liquefied gas, and by this internal pressure to supply liquefied gas from the supply-side storage tank to the supply-side storage tank By doing so, it is possible to suppress the increase in enthalpy of liquefied gas while allowing the liquefied gas to be transported in a supercooled state, thereby providing a method and system for transporting liquefied gas that can suppress the generation of flash gas inside the storage tank on the demand side Is to provide.

According to an aspect of the present invention for achieving the above object, a method for transporting a liquefied gas, the pressing step of increasing the internal pressure of the supply-side storage tank; A transfer step of pressurizing and discharging the liquefied gas in the supply-side storage tank by the increased internal pressure; Including, it is possible to provide a liquefied gas transfer method characterized in that while transporting the liquefied gas while suppressing the increase in the enthalpy of the liquefied gas accommodated in the supply-side storage tank.

In the pressurizing step, the liquefied gas accommodated in the supply-side storage tank is pressurized and discharged, and the liquefied gas is vaporized to generate evaporation gas, and then the generated evaporation gas is supplied into the supply-side storage tank to supply the storage-side storage tank. Can increase the internal pressure.

The pressurizing step may include a fuel supply step of branching a portion of the vaporized evaporation gas and supplying it as fuel to the combustion device.

The transfer step may be performed until the shipment of the liquefied gas to the demand-side storage tank receiving the liquefied gas is completed, or until the liquefied gas in the dischargeable supply-side storage tank disappears.

The transfer step, after being generated inside the demand-side storage tank receiving the liquefied gas, the boil-off gas discharged to the outside of the demand-side storage tank, the boil-off gas to be processed at a liquefied gas supply source including the supply-side storage tank It may include a processing step.

In the evaporation gas processing step, the evaporation gas discharged from the demand-side storage tank may be burned and processed in a combustion apparatus included in the liquefied gas supply source.

The evaporation gas processing step may include an evaporation gas recovery step of supplying at least a portion of the evaporation gas discharged from the demand-side storage tank to the supply-side storage tank.

According to another aspect of the present invention, a system for transporting liquefied gas, comprising: one or more supply-side storage tanks installed at a liquefied gas supply source; A supply pump installed inside the supply-side storage tank and pressurizing liquefied gas to discharge it to the outside of the supply-side storage tank; A vaporizer for vaporizing by heating the liquefied gas discharged from the supply-side storage tank; A liquefied gas vaporization line configured to pressurize the liquefied gas stored in the supply-side storage tank by the supply pump, heat it by the vaporizer, and then provide a path to return to the supply-side storage tank again; Liquefied gas transfer system, characterized in that it can be provided.

The liquefied gas transfer system, when the internal pressure of the supply-side storage tank rises by receiving the pressurized and vaporized evaporation gas through the liquefied gas vaporization line, the liquefied gas stored in the supply-side storage tank using the increased internal pressure It may further include a liquefied gas transfer line configured to provide a path for supplying the storage tank to the demand side.

The starting point of the liquefied gas transfer line may be located below the supply-side storage tank.

The liquefied gas delivery system may further include a fuel supply line configured to provide a path for supplying pressurized and vaporized evaporated gas as fuel to the combustion device while passing through the liquefied gas vaporization line.

The liquefied gas transfer system may further include a liquefied gas connection line configured to provide a path for supplying liquefied gas discharged from the supply-side storage tank to the liquefied gas transfer line through the liquefied gas vaporization line.

The liquefied gas transfer system, when receiving liquefied gas through the liquefied gas transfer line, is configured to provide a path for transporting and processing the evaporated gas generated in the demand-side storage tank and discharged to the liquefied gas supplier An evaporation gas treatment line may be further included.

The liquefied gas delivery system may further include an evaporation gas recovery line configured to provide a path for supplying and recovering at least a portion of the evaporation gas discharged from the demand-side storage tank to the supply-side storage tank.

According to the present invention, a method and system for transferring liquefied gas configured to increase the internal pressure of a supply-side storage tank when transferring liquefied gas and supply liquefied gas from a supply-side storage tank to a supply-side storage tank by the internal pressure Can.

According to the method and system for transporting liquefied gas of the present invention, an increase in enthalpy of liquefied gas to be transported is suppressed, and the liquefied gas can be transported in a supercooled state.

Therefore, the generation of flash gas in the inside of the demand-side storage tank receiving liquefied gas can be suppressed as much as possible.

1 is a view schematically showing a liquefied gas transfer system according to the prior art.
2 is a view schematically showing a liquefied gas delivery system according to an embodiment of the present invention.
3 is a view for explaining a method of transferring a liquefied gas using a liquefied gas transfer system according to an embodiment of the present invention, a view showing a pressing step of raising the internal pressure of the supply-side storage tank.
4 is a view for explaining a method of transferring a liquefied gas using a liquefied gas transfer system according to an embodiment of the present invention, a view showing a transfer step of supplying the liquefied gas to the storage tank on the demand side.
5A and 5B are pressure-enthalpy diagrams for explaining a change in enthalpy of liquefied gas to be transferred when liquefied gas is transferred using a prior art and a liquefied gas transfer system according to an embodiment of the present invention.

Hereinafter, a liquefied gas delivery system according to an embodiment of the present invention will be described in detail with reference to the drawings. 2 is a view schematically showing a liquefied gas transfer system according to an embodiment of the present invention. In addition, FIGS. 3 and 4 are views for explaining a method for transferring liquefied gas using a liquefied gas transfer system according to an embodiment of the present invention. In FIG. 3, a pressing step of raising the internal pressure of the supply-side storage tank A diagram showing is shown, and FIG. 4 is a diagram showing a transfer step in which liquefied gas is supplied to a storage tank on the demand side. 2 to 4, the pipe through which the liquefied gas flows is indicated by a solid line, and the pipe through which the evaporated gas flows is indicated by a dotted line.

2 to 4, an LNG supply ship as an liquefied gas supply source 10, that is, a fuel bunkering vessel (LNG bunkering ship) is exemplified, and a ship propulsed by an engine using LNG as fuel as the liquefied gas demand source 30 Phosphorus LNG propulsion ships are exemplified.

However, in addition to those illustrated in the drawings, the liquefied gas supply source 10 may be an LNG terminal on land or a plant such as LNG FPSO floating on the sea, and the liquefied gas demand source 30 may use liquefied gas such as LNG or LPG. It may be a liquefied gas carrier to be transported or a fuel supply ship to supply fuel to an LNG propulsion vessel. In addition, when the LNG transported through the LNG carrier is unloaded to an on-shore tank installed in an on-shore LNG terminal, the LNG terminal may be a demand for liquefied gas.

As such, the liquefied gas supply source 10 and the liquefied gas demand source 30 may be determined according to whether the liquefied gas is supplied or the liquefied gas is supplied in each situation, and a specific facility or facility is necessarily liquefied gas It is not limited to any one of the supply destination 10 and the liquefied gas demand destination 30.

In addition, the present invention is not limited by the number of tanks or types of tanks installed in the liquefied gas supply source 10 and the liquefied gas demand source 30, but the liquefied gas supply source 10 includes a plurality of liquefied gas storage tanks At least one of the liquefied gas storage tanks installed in the liquefied gas supply source 10 may have a capacity to be completely emptied in one transfer operation.

2 to 4, the liquefied gas delivery system according to an embodiment of the present invention, a liquefied gas supply source 10, for example, one or more supply-side storage tanks 12 installed on a fuel supply line, and this supply-side storage Installed inside the tank (12), the supply pump (14) that pressurizes the liquefied gas and discharges it to the outside of the supply-side storage tank (12), and a vaporizer to heat and vaporize the liquefied gas discharged from the supply-side storage tank (12) ( 16) and the liquefied gas configured to provide a path for pressurizing the liquefied gas stored in the supply-side storage tank 10 by the supply pump 14 and heating it by the vaporizer 16, and then returning it back to the supply-side storage tank 10 again. Gas vaporization line (L10).

The supply-side storage tank 12 may be any type of tank as long as it can accommodate cryogenic liquefied gas, and may be, for example, a membrane-type tank or a stand-alone tank. The supply-side storage tank 12 is configured to withstand the pressure rise due to the returning evaporation gas after being pressurized and heated through the supply pump 14 and the vaporizer 16.

The supply pump 14 may be a submersible pump installed under the supply side storage tank 12. 2 to 4, one supply-side storage tank 12 and one supply pump 14 are shown, but a plurality of supply-side storage tanks 12 may be installed at the liquefied gas supply source 10, and one A plurality of supply pumps 14 may be installed in the supply-side storage tank 12.

The vaporizer 16 may be a heat exchange device capable of forcibly vaporizing the liquefied gas through heat exchange between the liquefied gas and the heat medium.

The liquefied gas vaporization line L10 starts to extend from the supply pump 14 in the supply-side storage tank 12, extends to the outside of the supply-side storage tank 12, passes through the carburetor 16, and then returns to the supply-side storage tank. (12). The vaporized gas vaporized by the vaporizer 16 can be supplied to the upper side of the supply-side storage tank 12, that is, the portion of the naturally occurring vaporized gas in the supply-side storage tank 12 is present by the vaporizer 16. The end of the liquefied gas vaporization line L10 is connected to the upper portion of the supply-side storage tank 12 so that the vaporized boil-off gas can be supplied.

In addition, the liquefied gas transfer system according to an embodiment of the present invention, when the internal pressure of the supply-side storage tank 12 rises by receiving the pressurized and vaporized evaporation gas through the liquefied gas vaporization line (L10), the It may include a liquefied gas transfer line (L14) configured to provide a path for supplying the liquefied gas stored in the supply-side storage tank (12) to the demand-side storage tank (32) using internal pressure.

The starting point of the liquefied gas transfer line L14 is a lower portion of the supply-side storage tank 12 so that the liquefied gas contained in the supply-side storage tank 12 can be pushed out by using the internal pressure of the supply-side storage tank 12. May be located in a portion close to the bottom of the supply-side storage tank (12). The liquefied gas transfer line L14, which starts to extend from the bottom proximal portion of the supply-side storage tank 12 in the supply-side storage tank 12, extends to the outside of the supply-side storage tank 12. The liquefied gas transfer line L14 may extend to the interior of the demand-side storage tank 32.

2 to 4, the liquefied gas transfer line L14 is illustrated as extending from the supply-side storage tank 12 to the demand-side storage tank 32 with one pipe, but the liquefied gas transfer lines L14 are connected to each other. It may consist of multiple sections. For example, the liquefied gas transfer line (L14), the start section installed in the liquefied gas supply source 10, the end section installed in the liquefied gas demand source 30, and the intermediate section connecting these start section and end section to each other It may consist of sections.

In the present specification, the liquefied gas transfer line L14 means to include at least a start section among the start section, middle section, and end section described above. That is, the liquefied gas transfer line L14 may mean the entire pipe extending from the supply-side storage tank 12 of the liquefied gas supply destination 10 to the demand-side storage tank 32 of the liquefied gas demand destination 30, Supply-side storage tank 12 up to another pipe capable of supplying liquefied gas to the shipping piping installed in the liquefied gas demand source 30 so that the liquefied gas can be shipped into the demand-side storage tank 32 It may mean a pipe for transferring liquefied gas from.

In addition, the liquefied gas delivery system according to an embodiment of the present invention, a fuel supply configured to provide a path for supplying the pressurized and vaporized evaporation gas through the liquefied gas vaporization line L10 to the combustion device 24 as fuel Line L12 may be included.

The fuel supply line L12 extends from the liquefied gas vaporization line L10 to the combustion device 24 by branching from the liquefied gas vaporization line L10 on the downstream side of the vaporizer 16. In the fuel supply line (L12), the compressor (20) as a pressure regulating device for regulating the pressure of the evaporated gas at a pressure required by the combustion device (24), and the cooler (22) as a temperature regulating device for regulating the temperature of the evaporated gas Can be installed.

After the liquefied gas vaporization line (L10), the boil-off gas has been pressurized by the compressor (20), cooled by the cooler (22), and can be supplied as fuel to the combustion device (24).

The combustion device 24 may be, for example, various engines, boilers, GCUs, etc. that can use evaporated gas as fuel.

In addition, the liquefied gas transfer system according to an embodiment of the present invention, a path for supplying the liquefied gas discharged from the supply-side storage tank 12 through the liquefied gas vaporization line (L10) to the liquefied gas transfer line (L14) It may include a liquefied gas connection line (L16) configured to provide.

The liquefied gas connection line (L16) is branched from the liquefied gas vaporization line (L10), in detail, on the upstream side of the liquefied gas vaporization line (L10) and extends to the liquefied gas transfer line (L14). Liquefied gas connection line (L16), after pressurizing the liquefied gas by the supply pump 14, can be used to supply the pressurized liquefied gas directly to the storage tank 32 on the demand side.

In addition, the liquefied gas transfer system according to an embodiment of the present invention, when the liquefied gas is supplied through the liquefied gas transfer line (L14) is generated in the storage tank 32 on the demand side, the evaporated gas discharged, liquefied gas It may include a boil-off gas treatment line (L20) configured to provide a path for processing by transferring to the supply source (10).

The evaporation gas treatment line L20 extends from the demand-side storage tank 32 so that the evaporation gas discharged from the demand-side storage tank 32 can be supplied and processed as fuel to the combustion device 24, and the fuel supply line is extended. (L12). More specifically, the boil-off gas treatment line L20 extending from the demand-side storage tank 32 may be connected to the upstream side of the compressor 20 in the fuel supply line L12.

2 to 4, the evaporation gas treatment line (L20) is shown as extending from the demand side storage tank 32 to the fuel supply line (L12) with one pipe, but the evaporation gas treatment line (L20) is connected to each other It may consist of multiple sections. For example, the evaporation gas processing line L20 is an intermediate section connecting the start section installed in the liquefied gas demand source 30, the end section installed in the liquefied gas supply source 10, and these start sections and end sections. It may consist of sections.

In the present specification, the evaporation gas treatment line L20 means that at least a termination section is included among the above-described start section, middle section, and end section. That is, the boil-off gas processing line L20 may mean the entire pipe extending from the demand-side storage tank 32 of the liquefied gas demand source 30 to the supply-side storage tank 12 of the liquefied gas supply destination 10, It may mean a pipe installed in the liquefied gas supply source 10 so that the boil-off gas generated in the demand-side storage tank 32 is received and transmitted to the fuel supply line L12.

In addition, the liquefied gas transfer system according to an embodiment of the present invention, evaporation configured to provide a path for supplying and recovering at least a portion of the evaporation gas discharged from the demand-side storage tank 32 to the supply-side storage tank 12 It may include a gas recovery line.

In the above, the boil-off gas recovery line (L22), the amount of supply of fuel (ie, boil-off gas) supplied to the combustion device 24 through the fuel supply line (L12) is the required amount required by the combustion device (24 Or, when more than the processing capacity (which can be processed by the combustion device 24), or when it is necessary to increase the internal pressure of the supply-side storage tank 12, among the fuel being transferred in the fuel supply line (L12) It is configured to be able to recover by supplying the storage tank (12) by branching a part.

The boil-off gas recovery line (L22), after being discharged from the demand-side storage tank (32), forms a path through which at least a portion of the boil-off gas transferred to the fuel supply line (L12) can be transferred to the supply-side storage tank (12). For this purpose, it is branched from the cooler 22 and the combustion device 24 in the upstream side of the combustion device 24 in the fuel supply line L12, and more specifically, in the fuel supply line L12, to vaporize liquefied gas. In line L10 it can be connected to the downstream side of the vaporizer 16.

Evaporative gas recovery line (L22), instead of being connected to the liquefied gas vaporization line (L10), may be configured to extend directly to the storage tank 12 on the supply side.

The liquefied gas transfer system according to an embodiment of the present invention is configured as described above, and the operation and effects of the liquefied gas transfer system will be described in detail below with reference to FIGS. 3 and 4. 3 and 4, the pipe through which the liquefied gas flows is indicated by a solid line, and the pipe through which the evaporated gas flows is indicated by a dotted line.

The method for transporting liquefied gas using the liquefied gas transfer system according to an embodiment of the present invention includes a pressurizing step of raising the internal pressure of the supply-side storage tank 12 and an increased internal pressure of the supply-side storage tank 12. It includes a transfer step of discharging and transporting the liquefied gas in the supply-side storage tank 12 by using.

As shown in FIG. 3, in the pressurization step of raising the internal pressure of the supply-side storage tank 12, the supply pump 14 is operated to supply the liquefied gas to the vaporizer 16 through the liquefied gas vaporization line L10. Then, while passing through the vaporizer 16, the evaporated gas vaporized is returned to the supply-side storage tank 12 through the liquefied gas vaporization line L10.

Due to the evaporated gas returning after being vaporized while passing through the liquefied gas vaporization line L10, the internal pressure of the supply-side storage tank 12 rises. Until the internal pressure of the supply-side storage tank 12 reaches a pressure value that can transfer the liquefied gas of the supply-side storage tank 12 to the demand-side storage tank 32 only with the internal pressure of the supply-side storage tank 12 , Pressurization step is performed.

The pressurization step may include a fuel supply step of branching a part of the vaporized evaporation gas and supplying it to the combustion device 24 as fuel. The fuel supply step can be performed when the operation of the combustion device 24 is required. The fuel supply step may be performed simultaneously with the pressurization step. Also, the fuel supply step may be started while the pressurization step is being performed, or, conversely, the pressurization step may be started while the fuel supply step is being performed.

The supply pump 14 installed in the supply-side storage tank 12 may be a pump whose driving speed is adjusted or may be a pump whose driving speed is not adjusted. When a pump whose driving speed is not regulated is used as the supply pump 14, in the pressurization step, a larger amount of boil-off gas is generated than is necessary for pressurization of the supply-side storage tank 12, and the amount of boil-off gas remaining in the fuel supply step It can be configured to burn all of the treatment. To this end, the liquefied gas delivery system may include one or more combustion devices 24 or may be configured to increase or decrease the processing capacity of the combustion devices 24.

When pressurization of the supply-side storage tank 12 by the pressurization step is completed, as shown in FIG. 4, the valve installed in the liquefied-gas transfer line L14 is opened to supply the liquefied gas accommodated in the supply-side storage tank 12 to the supply side. After discharging only the internal pressure of the storage tank 12, a transfer step is performed to transfer it to the storage tank 32 on the demand side.

The transfer step is performed until the shipment of the liquefied gas to the storage tank 32 on the demand side is completed, or until the liquefied gas in the supply side storage tank 12 that can be discharged by the liquefied gas transfer line L14 disappears. Can be. Normally, shipment of liquefied gas to the storage tank 32 on the demand side can be considered to be completed when 96 to 99%, or 97 to 98% of the tank storage capacity is filled. In addition, in the present specification, the expression "there is no liquefied gas in the supply-side storage tank 12 that can be discharged" does not mean that all the liquefied gas in the supply-side storage tank 12 is unloaded and the supply-side storage tank 12 is emptied. , As the liquid level of the liquefied gas is lower than the inlet position of the liquefied gas transfer line L14, it means that the liquefied gas is no longer discharged only by the internal pressure of the supply-side storage tank 12.

In the transfer step, as the liquefied gas is supplied to the storage tank 32 on the demand side, the vaporized gas generated inside the storage tank 32 on the demand side and discharged to the outside of the storage tank 32 on the demand side is liquefied gas. It may include an evaporation gas treatment step of processing in the supply source (10).

In the boil-off gas processing step, the boil-off gas discharged from the demand-side storage tank 32 may be supplied to the combustion apparatus 24 through the boil-off gas treatment line L20 and the fuel supply line L12 for processing. The evaporation gas treatment step may be carried out simultaneously with the transfer step. Alternatively, the evaporation gas treatment step may be started while the transfer step is being performed.

The boil-off gas treatment step may include a boil-off gas recovery step of branching a part of the boil-off gas supplied to the combustion device 24 and supplying it to the supply-side storage tank 12.

In the evaporation gas recovery step, the supply amount of fuel (ie, evaporation gas) supplied to the combustion device 24 in the evaporation gas processing step is to be processed in the required amount (or the combustion device 24) required by the combustion device 24. It can be carried out when it is more than the processing capacity), or when it is necessary to increase the internal pressure of the supply-side storage tank 12.

The evaporation gas recovery step may be carried out simultaneously with the evaporation gas treatment step. In addition, the evaporation gas recovery step may be started while the evaporation gas treatment step is being performed.

While the evaporation gas treatment step is being performed, all the evaporation gas that has been transferred to the liquefied gas supply source 10 through the evaporation gas treatment line L20 may be processed in the combustion device 24. To this end, the liquefied gas delivery system may include one or more combustion devices 24 or may be configured to increase or decrease the processing capacity of the combustion devices 24.

Conversely, an evaporation gas recovery step may be performed while the evaporation gas is not being supplied as fuel to the combustion device 24. At this time, all the boil-off gas that has been transferred to the liquefied gas supply source 10 through the boil-off gas treatment line (L20) can be recovered to the supply-side storage tank (12).

FIG. 5A shows a pressure-enthalpy diagram for explaining a change in the enthalpy of the liquefied gas to be transferred when the liquefied gas is transferred using the liquefied gas transfer system according to the prior art as shown in FIG. 1, and FIG. 5B 2 shows a pressure-enthalpy diagram for explaining a change in the enthalpy of the liquefied gas to be transferred when the liquefied gas is transferred using the liquefied gas transfer system according to an embodiment of the present invention as shown in FIG. 2.

Referring to FIG. 5A, the liquefied gas transfer system according to the prior art shown in FIG. 1 pressurizes the liquefied gas stored in the supply-side storage tank 1 by the supply pump 2 and transfers it to the demand-side storage tank 4 This resulted in an increase in the enthalpy of the liquefied gas being transported. In FIG. 5A, P1 represents the state of liquefied gas accommodated in the supply-side storage tank 1, P2 represents the state of liquefied gas pressurized by the supply pump 2, and P3 is the demand-side storage tank 4 On the way to the side, the temperature rises due to the heat inflow through the pipe or the like, and P4 represents the state of liquefied gas after being supplied to the storage tank 4 on the demand side.

The enthalpy values at each point of the liquefied gas in the pressure-enthalpy diagram are indicated by E1, E2, E3, and E4. As can be seen in Figure 5a, when stored in the supply-side storage tank (1), that is, compared to the enthalpy value (E1) of the liquefied gas in P1, after being transferred to the demand-side storage tank (4), that is The enthalpy value (E4) of the liquefied gas at P4 increases. Evaporation gas (for example, flash gas) is generated in the storage tank 4 on the demand side by the increment (Δ1 = E4-E1) of the enthalpy value.

Referring to Figure 5b, the liquefied gas delivery system according to the prior art shown in Figure 2, unlike the liquefied gas delivery system shown in Figure 1, the inside of the supply-side storage tank 12 by the evaporated gas forcibly vaporized After raising the pressure, since the liquefied gas stored in the supply-side storage tank 12 is pressurized and transferred to the demand-side storage tank 4 using only the increased internal pressure, the enthalpy of the transferred liquefied gas does not increase. In FIG. 5B, P1 denotes the state of liquefied gas contained in the supply-side storage tank 12, P2' denotes the state of liquefied gas contained in the supply-side storage tank 12 after the internal pressure rises through the pressing step, and P3' denotes While the liquefied gas is being transferred toward the storage tank 32 on the demand side, the temperature rises due to heat inflow through a pipe or the like, and P4' represents the state of liquefied gas after being supplied to the storage tank 4 on the demand side.

The enthalpy values at each point of the liquefied gas in the pressure-enthalpy diagram are indicated by E1, E2', E3', and E4'. As can be seen in Figure 5b, when stored in the supply-side storage tank 12, that is, compared to the enthalpy value (E1) of the liquefied gas in P1, after being transferred to the demand-side storage tank 32, that is Although the enthalpy value (E4') of the liquefied gas in P4' increases, it increases only by a significantly smaller value compared to FIG. 5A. Evaporation gas (for example, flash gas) is generated in the storage tank 32 on the demand side by the increment (Δ2 = E4'-E1) of the enthalpy value.

5A and 5B, it can be confirmed that the enthalpy increase (Δ2) by the liquefied gas delivery system according to an embodiment of the present invention is smaller than the enthalpy increase (Δ1) by the conventional liquefied gas delivery system, and eventually According to the liquefied gas delivery system according to an embodiment of the present invention, it can be seen that the amount of evaporated gas is reduced.

According to an embodiment of the present invention, a plurality of liquefied gas storage tanks may be installed at the liquefied gas supply source 10. When the internal pressure of the tank in which the liquefied gas is stored increases, the temperature of the liquefied gas increases with time, so it is preferable that the liquefied gas accommodated in the supply-side storage tank 12 having an increased internal pressure be unloaded at once. .

To this end, at least one of the liquefied gas storage tanks installed in the liquefied gas supply source 10 may have a capacity that can be completely emptied in one transfer operation.

When a plurality of liquefied gas storage tanks are installed at the liquefied gas supply source 10, and one of the liquefied gas storage tanks is configured to be used as a supply-side storage tank having a capacity that can be completely emptied in one transfer operation, In order to unload the liquefied gas stored in the plurality of liquefied gas storage tanks, it is possible to pass through the supply-side storage tank. That is, the liquefied gas contained in the liquefied gas storage tank is first transferred to the supply side storage tank only as much as the capacity of the demand side storage tank, and then the liquefied gas transferred to the supply side storage tank is continuously transferred to the demand side storage tank in one transfer operation. By doing so, no liquefied gas remains in the pressurized supply-side storage tank.

On the other hand, when the storage tank 32 on the demand side is made of a pressurized tank in which the internal pressure is maintained higher than the normal pressure, the enthalpy is not reduced even if the liquefied gas is directly pressed by the supply pump 14 and transferred to the storage tank 32 on the demand side. May not increase.

As described above, although specific embodiments have been described in the detailed description of the present invention, various modifications are possible without departing from the scope of the technical spirit of the present invention. Therefore, the scope of the present invention should not be limited to the described embodiments, but should be defined not only by the claims described below, but also by the claims and equivalents.

10: LNG supply ship as liquefied gas supply source, 12: supply side storage tank, 14: supply pump, 16: vaporizer, 20: compressor, 22: cooler, 24: combustion device, 30: LNG propulsion ship as liquefied gas supply source, 32: Storage tank on demand side, L10: liquefied gas vaporization line, L12: fuel supply line, L14: liquefied gas transfer line, L16: liquefied gas connection line, L20: evaporated gas treatment line, L22: evaporated gas recovery line.

Claims (14)

As a method of transporting liquefied gas,
A pressing step of increasing the internal pressure of the supply-side storage tank;
A transfer step of pressurizing and discharging the liquefied gas in the supply-side storage tank by the increased internal pressure;
Including, liquefied gas transfer method characterized in that while transporting the liquefied gas while suppressing the increase in the enthalpy of the liquefied gas contained in the supply-side storage tank. The method according to claim 1,
In the pressurizing step, the liquefied gas accommodated in the supply-side storage tank is pressurized and discharged, and the liquefied gas is vaporized to generate evaporation gas, and then the generated evaporation gas is supplied into the supply-side storage tank to supply the storage-side storage tank. To increase the internal pressure of the liquefied gas. The method according to claim 2,
The pressurizing step includes a fuel supply step of branching a portion of the vaporized evaporation gas and supplying it as fuel to the combustion device. The method according to claim 1,
The transfer step is carried out until the completion of the shipment of liquefied gas to the demand-side storage tank receiving the liquefied gas, or until the liquefied gas in the dischargeable supply-side storage tank disappears. The method according to claim 1,
The transfer step, after being generated inside the demand-side storage tank receiving the liquefied gas, the boil-off gas discharged to the outside of the demand-side storage tank, the boil-off gas to be processed at a liquefied gas supply source including the supply-side storage tank Liquefied gas transfer method comprising a treatment step. The method according to claim 5,
In the boil-off gas processing step, the boil-off gas discharged from the demand-side storage tank is burned and processed in a combustion apparatus included in the liquefied gas supplier, and the liquefied gas is transferred. The method according to claim 5,
The boil-off gas processing step includes a boil-off gas recovery step of supplying at least a portion of the boil-off gas discharged from the demand-side storage tank to the supply-side storage tank. As a system for transporting liquefied gas,
One or more supply-side storage tanks installed at a liquefied gas supply source;
A supply pump installed inside the supply-side storage tank and pressurizing liquefied gas to discharge it to the outside of the supply-side storage tank;
A vaporizer for vaporizing by heating the liquefied gas discharged from the supply-side storage tank;
A liquefied gas vaporization line configured to pressurize the liquefied gas stored in the supply-side storage tank by the supply pump, heat it by the vaporizer, and then provide a path to return to the supply-side storage tank again;
Liquefied gas transfer system comprising a. The method according to claim 8,
When the internal pressure of the supply-side storage tank increases by receiving the pressurized and vaporized evaporation gas through the liquefied gas vaporization line, the liquefied gas stored in the supply-side storage tank is supplied to the demand-side storage tank by using the increased internal pressure. A liquefied gas transfer system further comprising a liquefied gas transfer line configured to provide a path for doing so. The method according to claim 9,
The starting point of the liquefied gas transfer line is located below the supply-side storage tank, liquefied gas transfer system. The method according to claim 8,
A liquefied gas transfer system further comprising a fuel supply line configured to provide a path for supplying pressurized and vaporized boil-off gas as fuel to the combustion device while passing through the liquefied gas vaporization line. The method according to claim 11,
And a liquefied gas connection line configured to provide a path for supplying liquefied gas discharged from the supply-side storage tank to the liquefied gas transfer line through the liquefied gas vaporization line. The method according to claim 9,
When receiving the liquefied gas through the liquefied gas transfer line further comprises an evaporation gas treatment line configured to provide a path for transporting and processing the evaporated gas generated in the demand-side storage tank and discharged to the liquefied gas supplier. The liquefied gas delivery system. The method according to claim 9,
And a vaporization gas recovery line configured to provide a path for supplying and recovering at least a portion of the vaporized gas discharged from the storage tank at the demand side to the storage tank at the supply side.

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