Cargo stripping function for vessel for LNG and liquefied nitrogen or for dual purpose extreme low temperature tank on floating storage unit

Abstract

To provide a transportation vessel for storing and transporting extreme low temperature liquid.SOLUTION: A device and a method are provided for storing and transporting extreme low temperature liquid having liquefaction temperature in a dual-purpose extreme low temperature storage tank. A first pump empties a first portion of the extreme low temperature liquid and thus leaves a second portion of the extreme low temperature liquid in the extreme low temperature storage tank. The second portion of the extreme low temperature liquid is concentrated in a place above a bottom unit of the extreme low temperature storage tank. The extreme low temperature storage tank has a second portion of the extreme low temperature liquid emptied by means of the second pump located in the place, and due to that, a residual portion of the extreme low temperature liquid remains there. Since the temperature of the remaining portion is raised higher than the liquefaction temperature and thereby all of the remaining portion is vaporized, heat can be fed to that place by making use of concentrated heating structure.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] 〔Cross - Reference to Related Applications〕 This application claims the benefit of priority of U.S. Provisional Patent Application No. 62 / 904,966, filed on September 24, 2019, entitled "CARGO STRIPPING FEATURES FOR DUAL - PURPOSE CRYOGENIC TANKS ON SHIPS OR FLOTAING STORAGE UNITS FOR LNG AND LIQUID NITROGEN".

[0002] The disclosure of the present invention generally relates to the field of natural gas liquefaction to form liquefied natural gas (LNG). More specifically, the disclosure of the present invention relates to the transportation and storage of LNG and liquid nitrogen (LIN) in dual - purpose tanks.

Background Art

[0003] This section is intended to introduce various aspects of the art relevant to the disclosure of the present invention. This discussion is intended to provide a framework that facilitates a better understanding of specific aspects of the disclosure of the present invention. Therefore, it should be understood that this section is to be read from this perspective and not necessarily as an admission of prior art.

[0004] LNG is a rapidly growing means of supplying natural gas from locations with abundant natural gas supply to remote locations with strong demand for natural gas. The conventional LNG cycle includes: a) initial treatment of natural gas resources to remove contaminants such as water, sulfur compounds, and carbon dioxide; b) separation of some heavier hydrocarbon gases such as propane, butane, and pentane by various possible methods including self-refrigeration, external refrigeration, and lean oil; c) refrigeration of natural gas by substantially external refrigeration to form liquefied natural gas at atmospheric pressure or near it and at about -160 °C; d) transportation of the LNG product in a ship or tanker designed for transportation purposes to an import terminal associated with the market location; and e) recompression and regasification of the LNG in a regasification plant to pressurized natural gas that can be distributed to natural gas consumers.

[0005] One method of natural gas liquefaction uses liquefied nitrogen (LIN) as a refrigerant. Since the nitrogen liquefaction temperature (-196 °C) is lower than the methane liquefaction temperature (-161 °C), LIN can be advantageously used to produce LNG. The challenge in using LIN for LNG production is transporting it to the liquefaction site. It has been proposed to use an empty LNG carrier to transport the LIN there. Figure 1 shows an example of a method of transporting LNG and LIN on the same carrier as disclosed in U.S. Patent Application Publication No. 2017 / 0167787, which is hereby incorporated by reference in its entirety. The LNG cargo ship 100a, also called an LNG carrier, includes one or more dual-purpose tanks 101 designed to transport LNG and LIN inside it at different times. The LNG cargo ship 100a transports LNG from a liquefaction facility to an import terminal 104 where the LNG can be regasified. The liquefaction facility is shown as a floating LNG production (FLNG) facility 102 where natural gas is liquefied and stored, but it could instead be an onshore LNG production facility or even a floating production unit (FPU) that pre-treats natural gas for liquefaction on the LNG cargo ship. After the LNG has been unloaded, the dual-purpose tank 101 is warmed to vaporize any remaining LNG. The tank is then cooled, and the LIN is loaded into the tank.

[0006] Now, the LNG carrier 100b loaded with LIN moves to the FLNG facility 102. LIN is used to cool and liquefy natural gas to produce LNG. The dual-purpose tank 101 empties the LIN and optionally warms it to vaporize any remaining LIN therein. Next, the LNG can be loaded into the dual-purpose tank 101.

Prior Art Documents

Patent Documents

[0007]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0008] One problem when using the dual-purpose tank 101 is that the process of transitioning between LNG and LIN at the import terminal 104 requires removing virtually all of the liquefied or gaseous natural gas from the tank before LIN can be loaded there. Inevitably, there is a small amount of LNG remaining in the tank that is inaccessible to the inlet of the line for the normal loading / unloading pump. A smaller line, called a stripping line, may be used to remove even more LNG, but even the stripping line does not remove all of the LNG from the tank. What remains must be heated and vaporized so that it can be removed in the gaseous state. Since there is a significant amount of LNG remaining in the tank, generally the heating process needs to heat all or most of the tank above the LNG liquefaction temperature (-161 °C) in order to vaporize all of the remaining LNG. However, the more the tank is heated above the LNG liquefaction temperature, the longer it takes to cool the tank to a temperature suitable for LIN transport, i.e., below the LIN liquefaction temperature (-196 °C). Known methods of LNG vaporization and tank cooling can take between 20 and 30 hours. Any method of shortening this time is thought to increase the time that the LNG carrier is actually transporting LNG or LIN, thereby enhancing the profitability of the LNG transport process. What is needed is a method of shortening the time required to transition the dual-purpose tank from LNG storage to LIN storage.

Means for Solving the Problem

[0009] The disclosure of the present invention provides a carrier for storing and transporting cryogenic liquids. The tank stores and transports cryogenic liquids. A first pump fills the tank with cryogenic liquid and empties a first portion of the cryogenic liquid from the tank, thereby leaving a second portion of the cryogenic liquid in the tank. The tank structure concentrates the second portion of the cryogenic liquid in a location above the bottom of the tank. A second pump is positioned at that location and empties the second portion of the cryogenic liquid from the tank such that the remaining portion of the cryogenic liquid is left there. A concentrated heating structure delivers heat to that location. The heat raises the temperature of the remaining portion above the liquefaction temperature of the cryogenic liquid, thereby vaporizing all of the remaining portion.

[0010] The disclosure of the present invention provides a method for transporting liquefied cryogenic liquids by a carrier. The cryogenic liquid is stored and transported in a dual-purpose cryogenic storage tank. A first pump is used to empty a first portion of the cryogenic liquid from the cryogenic storage tank, thereby leaving a second portion of the cryogenic liquid in the cryogenic storage tank. The second portion of the cryogenic liquid is concentrated in a location above the bottom of the cryogenic storage tank. A second pump positioned at that location empties the second portion of the cryogenic liquid from the cryogenic storage tank, thereby leaving the remaining portion of the cryogenic liquid there. A concentrated heating structure delivers heat only to that location and not to other portions of the cryogenic storage tank. The delivered heat raises the temperature of the remaining portion above the liquefaction temperature of the cryogenic liquid, thereby vaporizing all of the remaining portion.

[0011] The above is a general overview of the features of the disclosure of the present invention so that the following detailed description can be better understood. Additional features are also described below in this specification.

[0012] These and other features, aspects, and advantages of the disclosure of the present invention will become apparent from the following description, the appended claims, and the accompanying drawings briefly described below.

Brief Description of the Drawings

[0013]

Figure 1

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Figure 3E

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Figure 3G

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Figure 3J

Figure 3K

Figure 4A

Figure 4B

Figure 5

[0014] Note that the figures are merely illustrative and are not intended to impose any limitation on the scope of the disclosure of the present invention. Further, the figures are generally not drawn to scale but are drawn for the convenience and clarity in illustrating various aspects of the disclosure of the present invention.

Mode for Carrying Out the Invention

[0015] To facilitate the understanding of the principles of the disclosure of the present invention, reference is made here to the features shown in the drawings and they are described using specific language. Nevertheless, it will be understood that no limitation of the scope of the disclosure of the present invention is thereby intended. Any change and yet another modification of the principles of the disclosure of the present invention described herein, as well as any yet another application, are considered to be those that would normally occur to those skilled in the art to which the disclosure of the present invention pertains. For the sake of clarity, some features not relevant to the disclosure of the present invention may not be shown in the drawings.

[0016] First, for ease of reference, a certain set of terms used in this application and their meanings as used in this context are listed. To the extent that the terms used herein are not defined below, the broadest definition given to such terms by those skilled in the art as reflected in at least one published document or issued patent should be given. Further, the technology of the present invention is not limited by the use of the terms shown below, and all equivalents, synonyms, newly developed, and terms or technologies that serve the same or similar purposes are considered to be within the scope of the claims of the present invention.

[0017] As will be recognized by those skilled in the art, different individuals may refer to the same feature or component by different names. This specification is not intended to distinguish components or features that differ only in name. Similarly, the figures are not necessarily to scale. In this specification, certain features and components may be exaggerated in scale or shown schematically, and the details of conventional elements may not be shown for the sake of clarity and brevity. When referring to the figures described in this specification, the same reference numerals may be used in multiple figures for the purpose of simplification. In the following description and claims, the terms "including" and "comprising" are used in an open-ended manner and thus must be construed to mean "including but not limited to".

[0018] The articles "the", "a", and "an" are not necessarily limited to meaning only one, but rather are inclusive and open-ended so as to optionally include a plurality of such elements.

[0019] As used herein, the terms "approximately", "about", "substantially", and similar terms are intended to have a broad meaning consistent with the ordinary and accepted usage by those skilled in the art to which the disclosed subject matter of the invention pertains. Those skilled in the art considering the disclosure of the invention should understand that these terms are intended to enable the description and claim of particular features without restricting the scope of the features being described to an exact numerical range. Accordingly, these terms must be construed to indicate that minor or insignificant modifications or variations of the subject matter being described are considered to be within the scope of the disclosure of the invention.

[0020] Figure 2 is a top view of a cargo ship or carrier 200 having one or more dual-purpose storage tanks 202 according to the disclosed embodiment. The storage tanks are designed to carry both LNG and liquid nitrogen (LIN). Cryogenic loading / unloading line 204 is used to fill and empty the storage tanks 202. The cryogenic loading / unloading line is connected to piping (not shown) for loading and unloading LNG and LIN. Stripping line 206, which is smaller than the loading / unloading line, is used to remove LNG or LIN from the storage tank that cannot be removed by the loading / unloading line. LNG extracted from the storage tank 202 using the stripping line 206 may be landed from an LNG cargo ship or may be recovered onto an individual deck tank for use as fuel. LIN extracted from the storage tank using the stripping line 206 may be stored and used as an inert gas for purging the storage tank.

[0021] Figures 3A - 3K show the cross - section of the storage tank 202 and its details according to an aspect of the disclosure of the present invention. In each of the aspects disclosed in Figures 3A - 3K, the storage tank and / or the waste liquid system is designed to allow for the complete removal of cryogenic liquids such as LNG or LIN. In Figure 3A, raised, corrugated, and perforated baffles 310 are arranged on both sides of the center line of the storage tank 202. The baffles have a gentle concave camber. The stripping pump 312 is located between the baffles 310 and is connected to the stripping line 206. The loading / unloading pump 314 is arranged outside the baffles 310 and is connected to the loading / unloading line 204. Alternatively, the stripping pump 312 and / or the loading / unloading pump 314 are arranged outside the storage tank 202. During the discharge operation, the cargo ship naturally tilts so that the liquid in the storage tank flows towards the loading / unloading pump and the stripping pump. The loading / unloading pump removes most of the cryogenic liquid from the storage tank 202 through the loading / unloading line 204. Next, the stripping pump 312 discharges the residual cryogenic liquid through the stripping line 206. The baffles 310 concentrate the residual cryogenic liquid within the baffles where the stripping pump can easily access the residual liquid. Using the baffles, more residual liquid can be discharged by the stripping pump than with known cryogenic tank designs that do not use baffles. Since the amount of cryogenic residual liquid remaining in the storage tank is small, the storage tank can be heated over a shorter period, and the vaporization / cooling part of the tank discharge process can be significantly shortened.

[0022] Figure 3B shows the tank 202 according to another aspect of the disclosure of the present invention, where a perforated upper part 318 is arranged on the baffle 310 to form a box - like structure around the stripping pump 312. The box - like structure further enhances the performance of the stripping pump 312 by further concentrating the residual cryogenic liquid around the stripping pump.

[0023] Instead of using a baffle to concentrate the residual cryogenic liquid adjacent to the stripping pump, the shape of the storage tank itself can be modified to achieve a similar effect. FIG. 3C shows a storage tank 320 in which the tank bottom 322 slopes downward toward the stripping pump 312. The stripping pump is positioned at the lowest part 324 of the tank bottom. The residual cryogenic liquid naturally accumulates adjacent to the stripping pump, thereby facilitating the process of removing the residual cryogenic liquid. However, the downward-sloping tank bottom 322 may prevent the loading / unloading pump 314 from being positioned at a low location within the storage tank as in the previously disclosed embodiment. FIG. 3D shows a tank 202 according to another aspect of the disclosure of the present invention, in which a pump gutter or pump well 330 is formed at the bottom of the storage tank. The stripping pump 312 is disposed within the pump well 330 to remove as much of the residual cryogenic liquid as possible. The loading / unloading pump 314 is positioned as close as possible to the bottom of the storage tank to minimize the amount of residual cryogenic liquid within the storage tank. FIG. 3E shows a tank 202 having a modification of FIG. 3D in which a perforated top 332 is disposed on the pump well 330 to create a box-like structure that further concentrates the residual cryogenic liquid around the stripping pump 312 as in the top 318 of FIG. 3B.

[0024] Aspects of the disclosure of the present invention as described above concentrate the residual cryogenic liquid in a specific location adjacent to the stripping pump on the floor of the cryogenic storage tank. This not only enables more residual cryogenic liquid to be discharged from the tank using the stripping pump, but also the residual liquid that cannot be discharged by the stripping pump or the loading / unloading pump remains concentrated adjacent to the stripping pump. This liquid, referred to herein as "residual liquid," can only be removed by vaporization, but because it is locally concentrated, only a very small part of the storage tank needs to be heated to vaporize it. FIGS. 3F and 3G show a tank 202 configured similarly to FIGS. 3D and 3E respectively, with an insulated warm gas injection line 340 added that has an outlet within the pump well 330 and adjacent to the stripping pump 312. A warm gas such as nitrogen can be pumped into the pump well 330 at a temperature higher than the liquefaction temperature of the cryogenic liquid being discharged from the storage tank after the operation of the stripping pump 312. The residual liquid concentrated entirely within the pump well 330 is vaporized and can then be removed from the storage tank 202. It can be seen that only the pump well 330 and the portion of the storage tank directly adjacent to it are heated by the warm gas injected therein. As a result, the temperature of the storage tank is not warmed as much, and thus the time required to cool the storage tank for use with other cryogenic liquids such as LIN is significantly reduced compared to known storage tank designs. The aspects depicted in FIGS. 3F and 3G can also be implemented using the baffle structure disclosed in FIGS. 3A and 3B or the inclined floor disclosed in FIG. 3C.

[0025] Other methods of local storage tank heating can be implemented. FIGS. 3H and 3I show tank 202 according to another aspect of the disclosure of the present invention where a warm gas injection line 350 is inserted into one or more of the loading / unloading lines 204 and extends to an outlet 352 adjacent to the stripping pump 312. The warm gas, such as nitrogen, is pumped from the outlet 352 only when the liquid is not being discharged from the storage tank 202 or is not being discharged into the storage tank 202, preferably only after the stripping pump 312 has removed as much of the residual cryogenic liquid as possible.

[0026] FIGS. 3J and 3K show tank 202 according to another aspect of the disclosure of the present invention where a heating system 360 is installed in or under the bottom floor 362 of the storage tank instead of inserting a heating medium through the top of the storage tank. Specifically, the heating system 360 can be localized or positioned directly below the location where the residual liquid, which includes the pump well 330 in FIGS. 3J and 3K, is collected. The heating system 360 may include an electric heating element or, alternatively, may include a series of pipes incorporated into the bottom floor 362 through which a heating fluid can be induced. The heating fluid can include a gas such as ambient air or nitrogen gas, or can include a liquid such as water or glycol. The heating system provides sufficient heat to vaporize the residual liquid. By heating only the pump well 330 and optionally only the adjacent portion of the storage tank, the temperature rise within the tank during the vaporization procedure can be minimized. The embodiments depicted in FIGS. 3J and 3K can also be implemented using the baffle structure disclosed in FIGS. 3A and 3B or the inclined floor disclosed in FIG. 3C.

[0027] FIG. 4A is a top view of a cargo ship or carrier 400 having one or more storage tanks 402 according to another aspect of the disclosure of the present invention. Compared to the storage tank 202 described above, the storage tank 402 has a significant longitudinal dimension parallel to the length of the cargo ship 400. The storage tank is designed to carry both LNG and liquid nitrogen (LIN). The cryogenic loading / unloading line 404 is used to fill and empty the storage tank 402. The cryogenic loading / unloading line is connected to piping (not shown) for loading and discharging LNG and LIN. The stripping line 406, which is smaller than the loading / unloading line, is used to remove LNG or LIN from the storage tank that cannot be removed by the loading / unloading line. The LNG extracted from the storage tank 402 using the stripping line 406 may be discharged from the LNG cargo ship or recovered onto an individual deck tank for use as fuel. The LIN extracted from the storage tank using the stripping line 406 can be stored and used as an inert gas for purging the storage tank. As shown in FIG. 4B, both sides 422 of the bottom of each tank slope towards the central portion 424 of the tank bottom. The stripping pump 412 connected to the stripping line 406 is positioned adjacent to the central portion 424. The loading / unloading pump 414 is connected to the loading / unloading line 404. During the discharging process, the loading / unloading pump 414 discharges most of the cryogenic liquid, and the stripping pump 412 discharges the residual liquid that the loading / unloading pump cannot discharge. In this or other aspects, the times when the loading / unloading pump and the stripping pump are active may overlap. The disclosed method can be used to heat and vaporize the residual liquid, i.e., the liquid that the loading / unloading pump cannot discharge.

[0028] FIG. 5 is a flowchart of a method 500 for transporting liquefied cryogenic liquid by a carrier according to the disclosed embodiment. In block 502, the cryogenic liquid is stored and transported in a dual-purpose cryogenic storage tank. In block 504, a first pump is used to empty the cryogenic storage tank of a first portion of the cryogenic liquid, thereby leaving a second portion of the cryogenic liquid in the cryogenic storage tank. In block 506, the second portion of the cryogenic liquid is concentrated at a location at the bottom of the cryogenic storage tank. In block 508, a second pump disposed at that location empties the cryogenic storage tank of the second portion of the cryogenic liquid, thereby leaving a residual portion of the cryogenic liquid therein. In block 510, a concentrated heating structure delivers heat only at that location and not at other parts of the cryogenic storage tank. The heat delivered raises the temperature of the residual portion above the liquefaction temperature of the cryogenic liquid such that all of the residual portion is vaporized in block 512.

[0029] The steps depicted in FIG. 5 are provided for illustrative purposes only, and certain steps may not be necessary to perform the disclosed method. Further, FIG. 5 may not show all steps that can be performed. Only the claims and the scope of the claims define the disclosed system and method.

[0030] The embodiments described herein have several advantages over known technologies. As discussed above, using baffles, box-like structures, pump wells, or sloped tank bottoms to direct residual cryogenic liquids towards the stripper pump results in more residual liquid being discharged using the stripper pump. As a result, the amount of residual liquid to be heated and vaporized is reduced, and the time taken for the vaporization process is shorter than in known technologies. In addition, since the residual liquid is concentrated or focused in one location (between baffles, within a pump well, etc.), the means for heating and vaporizing the residual liquid (heating gas injection lines, heating elements) can be concentrated at that location rather than throughout the storage tank as is done in known storage tanks. The concentrated heating can lower the temperature of the entire storage tank after vaporization is complete, thereby shortening the time required to cool the storage tank for the next cryogenic liquid loading. Combined, the disclosed methods for concentrating residual liquids and for concentrated heating can substantially shorten the time required to prepare, for example, a storage tank emptied of LNG to be filled with, for example, LIN. Such time savings can be on the order of 30%, or 40%, or 50%, or even more than 50% of the preparation time required by known technologies.

[0031] It should be understood that numerous changes, modifications, and alternatives to the foregoing disclosure can be made without departing from the scope of the disclosure of the present invention. The foregoing description is, therefore, not meant to limit the scope of the disclosure of the present invention. Rather, the scope of the disclosure of the present invention is to be determined solely by the appended claims and their equivalents. The structures and features in the embodiments of the present invention are also contemplated to be able to be changed, rearranged, substituted, deleted, replicated, combined, or added to each other.

Description of Reference Numerals

[0032] 100a, 100b LNG carrier 101 Dual-purpose tank 102 Floating LNG production (FLNG) facility 104 Import terminal

Claims

1. A carrier ship for storing and transporting cryogenic liquids, comprising: a tank configured to store and transport cryogenic liquids having a liquefaction temperature; a first pump configured to fill the tank with the cryogenic liquid and empty a first portion of the cryogenic liquid from the tank, thereby leaving a second portion of the cryogenic liquid in the tank; a tank structure configured to concentrate the second portion of the cryogenic liquid at a location on the bottom of the tank; a second pump positioned at the location and configured to empty the second portion of the cryogenic liquid from the tank, thereby leaving a residual portion of the cryogenic liquid therein; The carrier ship including the above components.

2. The carrier ship according to claim 1, wherein the tank structure includes a baffle surrounding the second pump, and the baffle is attached to the bottom of the tank.

3. The carrier ship according to claim 2, further including an upper baffle enclosing the second pump within the baffle, above the baffle, and within the bottom of the tank.

4. The carrier ship according to claim 1, wherein the tank structure includes a pump well in the bottom of the tank, the pump well includes a recessed portion of the bottom of the tank, and the second pump is positioned within the recessed portion.

5. The carrier ship according to claim 4, further including an upper pump well covering the pump well and enclosing the second pump within the pump well.

6. The carrier ship according to claim 1, wherein the tank structure includes an inclined tank bottom that slopes downward from both sides of the tank.

7. A concentrated heating structure configured to deliver heat to the location, the heat being configured to raise the temperature of the residual portion above the liquefaction temperature, thereby vaporizing all of the residual portion; The carrier ship according to any one of claims 1 to 6, further including the above concentrated heating structure.

8. The carrier ship according to claim 7, wherein the concentrated heating structure includes a gas injection line having an outlet adjacent to the second pump, the gas injection line being configured to introduce gas at the location at the bottom of the tank, and the gas having a temperature higher than the liquefaction temperature.

9. A first pump line connected to the first pump 5 and configured to convey the cryogenic liquid into or from the tank, the first pump line further including the gas injection line disposed within the first pump line, the carrier ship according to claim 8.

10. The centralized heating structure includes a heating element disposed below the location on the bottom of the tank, The heating element is configured to heat the remaining portion of the cryogenic liquid above the liquefaction temperature, The carrier ship according to claim 7.

11. The cryogenic liquid is one of liquefied natural gas and liquid nitrogen, the carrier ship according to any one of claims 1 to 10.

12. A method for transporting a liquefied cryogenic liquid by a carrier ship, Storing and transporting a cryogenic liquid having a liquefaction temperature in a dual-purpose cryogenic storage tank, Emptying the cryogenic storage tank of a first portion of the cryogenic liquid using a first pump, thereby leaving a second portion of the cryogenic liquid in the cryogenic storage tank, Concentrating the second portion of the cryogenic liquid at a location on the bottom of the cryogenic storage tank, Emptying the cryogenic storage tank of the second portion of the cryogenic liquid using a second pump positioned at the location, thereby leaving a remaining portion of the cryogenic liquid therein, A method comprising.

13. The second portion of the cryogenic liquid is concentrated using a baffle surrounding the second pump, the baffle being attached to the bottom of the cryogenic storage tank, the method according to claim 12.

14. The method according to claim 13, further including a baffle upper portion enclosing the second pump between the baffle and the baffle upper portion and the bottom of the cryogenic storage tank.

15. The second portion of the cryogenic liquid is concentrated using a pump well at the bottom of the cryogenic storage tank, the pump well including a recessed portion of the bottom of the cryogenic storage tank in which the second pump is positioned, the method according to claim 12.

16. The method according to claim 15, further including a pump well upper portion covering the pump well and enclosing the second pump in the pump well.

17. The method according to claim 12, wherein the second portion of the cryogenic liquid is concentrated using an inclined tank bottom that slopes downward from both sides of the cryogenic storage tank.

18. Delivering heat only to the location using a focused heating structure; Raising the temperature of the remaining portion above the liquefaction temperature using the focused heating structure, thereby vaporizing all of the remaining portion; The method according to any one of claims 12 to 17, further comprising:

19. The focused heating structure includes a gas injection line having an outlet adjacent to the second pump, The method comprising: Introducing, using the gas injection line, a gas having a temperature higher than the liquefaction temperature into the location at the bottom of the cryogenic storage tank; further comprising: The method according to claim 18.

20. Conveying the cryogenic liquid into or out of the cryogenic storage tank using a first pump line connected to the first pump; Disposing the gas injection line within the first pump line; The method according to claim 19, further comprising:

21. The focused heating structure includes a heating element disposed below the location on the bottom of the tank, The method comprising: Heating the remaining portion of the cryogenic liquid above the liquefaction temperature using the heating element; further comprising: The method according to claim 18.

22. The cryogenic liquid is a first cryogenic liquid, After the remaining portion has been vaporized, cooling the cryogenic storage tank to a temperature at or below the liquefaction temperature of a second cryogenic liquid, wherein the composition of the second cryogenic liquid is different from the composition of the first cryogenic liquid; Filling the cryogenic storage tank with the second cryogenic liquid; The method according to claim 18, further comprising:

23. The method according to any one of claims 11 to 22, wherein the cryogenic liquid is one of liquefied natural gas and liquid nitrogen.

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