CN117287624B

CN117287624B - Self-circulation BOG condensation coupling type low-temperature storage tank

Info

Publication number: CN117287624B
Application number: CN202311476967.2A
Authority: CN
Inventors: 郭宏新; 姜龙骏; 田朝阳; 王玉珏; 黄张飞
Original assignee: Jiangsu Sunpower Technology Co Ltd
Current assignee: Jiangsu Sunpower Technology Co Ltd
Priority date: 2023-11-08
Filing date: 2023-11-08
Publication date: 2024-06-18
Anticipated expiration: 2043-11-08
Also published as: CN117287624A

Abstract

The invention relates to the technical field of LNG storage tanks, and particularly discloses a self-circulation BOG condensation coupling type low-temperature storage tank which comprises a storage tank, a condensing device and an external transmission pipeline, wherein a liquid space for storing LNG and a gas phase space positioned above the liquid space are arranged in the storage tank, and an LNG circulating liquid return port and an LNG circulating liquid output port which are communicated with the liquid space are arranged on the storage tank; the condensing device comprises an LNG circulating liquid input pipeline, an LNG circulating liquid output pipeline and a heat exchange pipe arranged in the gas phase space, wherein one end of the LNG circulating liquid input pipeline is communicated with an LNG circulating liquid output port, the other end of the LNG circulating liquid input pipeline is communicated with an inlet of the heat exchange pipe, one end of the LNG circulating liquid output pipeline is communicated with an outlet of the heat exchange pipe, and the other end of the LNG circulating liquid output pipeline is communicated with an LNG circulating liquid reflux port; one end of the external transmission pipeline is communicated with the other end of the LNG circulating liquid output pipeline, and the other end of the external transmission pipeline is communicated with other equipment. This self-loopa BOG condensation coupling formula low temperature storage tank can reduce the risk that BOG revealed, can make full use of LNG's cold volume again, and energy utilization efficiency is higher.

Description

Self-circulation BOG condensation coupling type low-temperature storage tank

Technical Field

The invention relates to the technical field of LNG storage tanks, in particular to a self-circulation BOG condensation coupling type low-temperature storage tank.

Background

The LNG tank (liquefied natural gas tank) is a cryogenic tank, and the temperature is below-162 ℃. During the transportation and storage of LNG, a portion of LNG may be vaporized into Boil-Off Gas (BOG) by absorbing heat from the external environment and may be collected in the unfilled portion of the LNG storage chamber to form a BOG Gas phase space. In the process of filling liquid into an LNG storage tank by an LNG carrier, along with the increase of the liquid level in the LNG storage tank, the BOG gas phase space can be extruded to cause the increase of the pressure in the tank, the LNG conveying efficiency is affected, and meanwhile, certain threat can be caused to the safety of the LNG storage tank.

At present, a condensation process is mainly adopted to recycle and treat the BOG, for example, the BOG is led out of an LNG storage tank, is subjected to preliminary compression by a compressor, enters a recooler to be condensed and is then conveyed back into the LNG storage tank, and the BOG is easy to leak due to equipment problems in the processes of outward transportation, compression and condensation, so that the BOG is wasted; or the condensing device is arranged in the BOG gas phase space of the LNG storage tank, and the BOG is condensed by exchanging heat between the externally-conveyed cooling medium and the BOG, but the externally-conveyed cooling medium is required in the mode, so that the energy utilization efficiency is low.

Therefore, it is desirable to provide a self-circulating BOG condensing coupled cryogenic storage tank to solve the above-mentioned problems.

Disclosure of Invention

The invention provides a self-circulation BOG condensation coupling type low-temperature storage tank, which utilizes LNG with low temperature in the storage tank as a heat exchange medium to realize the condensation recovery of BOG, can reduce the risk of BOG leakage, can fully utilize the cold energy of the LNG, and has higher energy utilization efficiency.

In order to achieve the above purpose, the invention adopts the following technical scheme:

A self-circulating BOG condensing coupled cryogenic storage tank comprising:

the LNG storage device comprises a storage tank, wherein a liquid space for storing LNG and a gas phase space positioned above the liquid space are arranged in the storage tank, and an LNG circulating liquid output port and an LNG circulating liquid return port which are communicated with the liquid space are arranged on the storage tank;

The condensing device comprises an LNG circulating liquid input pipeline, an LNG circulating liquid output pipeline and a heat exchange tube arranged in the gas phase space, one end of the LNG circulating liquid input pipeline is communicated with the LNG circulating liquid output port, the other end of the LNG circulating liquid input pipeline is communicated with an inlet of the heat exchange tube, one end of the LNG circulating liquid output pipeline is communicated with an outlet of the heat exchange tube, the other end of the LNG circulating liquid output pipeline is communicated with the LNG circulating liquid reflux port, and LNG in the liquid space can flow in a circulating mode through the LNG circulating liquid input pipeline, the heat exchange tube and the LNG circulating liquid output pipeline;

And one end of the external transmission pipeline is communicated with the other end of the LNG circulating liquid output pipeline, and the other end of the external transmission pipeline is communicated with other equipment.

Optionally, a first flow equalizing unit is arranged below the heat exchange tube, and the first flow equalizing unit is used for disturbing the BOG below the heat exchange tube.

Optionally, the self-circulation BOG condensation coupling type cryogenic storage tank further comprises:

the flow regulating valve is arranged on the LNG circulating liquid input pipeline and is used for regulating the input flow of the LNG;

The temperature sensor is arranged at the outlet of the heat exchange tube and used for detecting the temperature of the LNG after heat exchange;

The gas concentration sensor is arranged in the gas phase space and used for detecting the concentration of BOG;

And the controller is in signal connection with the flow regulating valve, the temperature sensor and the gas concentration sensor, and can control the opening of the flow regulating valve according to the temperature signal transmitted by the temperature sensor and the BOG concentration signal transmitted by the gas concentration sensor.

Optionally, the condensing device further comprises:

the other end of the LNG circulating liquid input pipeline is communicated with the inlet of the input bundling pipe box, and the outlet of the input bundling pipe box is communicated with the inlet of the heat exchange pipe;

the outlet of the heat exchange tube is communicated with the inlet of the output bundling tube box, and the outlet of the output bundling tube box is communicated with one end of the LNG circulating liquid output pipeline;

The heat exchange tubes are arranged in a plurality, and the heat exchange tubes are arranged at intervals along the length direction of the input bundling tube box and the output bundling tube box.

Optionally, the diameters of the heat exchange tubes sequentially decrease from an inlet close to the input cluster tube box to an inlet far from the input cluster tube box along the length direction of the input cluster tube box.

Optionally, a second flow equalizing unit is arranged in the input bundling tube box, and/or a third flow equalizing unit is arranged in the output bundling tube box.

Optionally, the plurality of heat exchange tubes located in the same plane are a group of heat exchange tube groups, the heat exchange tube groups are provided with a plurality of heat exchange tube groups, and the plurality of heat exchange tube groups are arranged at intervals along the height direction of the gas phase space.

Optionally, the heat exchange tube is a fin tube, a corrugated tube or a pitted surface tube.

The suspended ceiling is arranged at the gas phase space in the storage tank and is in sealing connection with the inner wall of the storage tank, and the heat exchange tube is arranged above the suspended ceiling;

the venturi tube penetrates through the suspended ceiling, and the BOG below the suspended ceiling is conveyed to the upper side of the suspended ceiling through the venturi tube to exchange heat with the heat exchange tube;

the feed liquor end of fluid-discharge tube wears to locate the furred ceiling, the play liquid end of fluid-discharge tube inserts in the LNG in liquid space.

Optionally, the liquid discharge pipe is provided with a plurality of liquid discharge pipes.

Optionally, the furred ceiling is the cambered surface structure that the indent was established downwards, the fluid-discharge tube sets up the position minimum of furred ceiling.

The beneficial effects of the invention are as follows:

The invention provides a self-circulation BOG condensation coupling type low-temperature storage tank which comprises a storage tank, a condensing device and an output pipeline. Through setting up condensing equipment's heat exchange tube in the gaseous phase space of storage tank, with the BOG heat transfer in the gaseous phase space, can make BOG condensation backward flow to the liquid space in the storage tank, and then realize the in-tank recovery of BOG, this kind of mode BOG of retrieving BOG need not to be introduced outside the storage tank, has reduced the risk that BOG revealed, and the security is higher. In addition, LNG with lower temperature in the liquid space in the storage tank is used as a heat exchange medium to exchange heat with the BOG, so that the cost for conveying other heat exchange mediums is saved, and the economic benefit is improved. Meanwhile, the LNG after heat exchange can be used as preheated LNG to be continuously output to other equipment, so that the load of the equipment for heating the LNG later can be reduced, the energy utilization efficiency is improved, and the running cost is reduced.

Drawings

FIG. 1 is a schematic diagram of a self-circulation BOG condensation coupling type low-temperature storage tank according to an embodiment of the present invention;

FIG. 2 is a schematic structural diagram of a heat exchange tube according to an embodiment of the present invention;

Fig. 3 is a schematic structural diagram of a self-circulation BOG condensation coupling type low-temperature storage tank according to the second embodiment of the present invention.

In the figure:

100. A storage tank; 101. a main tank body; 102. a secondary tank; 103. a heat insulating layer; 110. a liquid space; 120. a gas phase space; 200. a condensing device; 210. an LNG recycle liquid input line; 211. a pump; 220. an LNG cycle export line; 230. a heat exchange tube; 240. a flow regulating valve; 250. inputting a bundling pipe box; 251. a first current equalizing unit; 260. outputting a bundling pipe box; 261. a second current equalizing unit; 270. a first turbulence unit; 300. an outer conveying pipeline; 400. suspended ceiling; 500. a venturi tube; 600. and a liquid discharge pipe.

Detailed Description

The following description of the embodiments of the present invention will be made apparent and fully in view of the accompanying drawings, in which some, but not all embodiments of the invention are shown. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.

In the description of the present invention, it should be noted that the directions or positional relationships indicated by the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc. are based on the directions or positional relationships shown in the drawings, are merely for convenience of describing the present invention and simplifying the description, and do not indicate or imply that the devices or elements referred to must have a specific orientation, be configured and operated in a specific orientation, and thus should not be construed as limiting the present invention. Furthermore, the terms "first," "second," and the like, are used for descriptive purposes only and are not to be construed as indicating or implying relative importance. Wherein the terms "first location" and "second location" are two distinct locations and wherein the first feature is "above," "over" and "over" the second feature includes the first feature being directly above and obliquely above the second feature, or simply indicates that the first feature is level above the second feature. The first feature being "under", "below" and "beneath" the second feature includes the first feature being directly under and obliquely below the second feature, or simply means that the first feature is less level than the second feature.

In the description of the present invention, it should be noted that, unless explicitly specified and limited otherwise, the terms "mounted," "connected," and "connected" are to be construed broadly, and may be either fixedly connected, detachably connected, or integrally connected, for example; can be mechanically or electrically connected; can be directly connected or indirectly connected through an intermediate medium, and can be communication between two elements. The specific meaning of the above terms in the present invention will be understood in specific cases by those of ordinary skill in the art.

Embodiments of the present invention are described in detail below, examples of which are illustrated in the accompanying drawings, wherein like or similar reference numerals refer to like or similar elements or elements having like or similar functions throughout. The embodiments described below by referring to the drawings are illustrative only and are not to be construed as limiting the invention.

Example 1

The embodiment provides a self-circulation BOG condensation coupling type low-temperature storage tank, which utilizes LNG with low temperature in the storage tank 100 as a heat exchange medium to realize the condensation recovery of BOG, so that the risk of BOG leakage can be reduced, the cold energy of the LNG can be fully utilized, and the energy utilization efficiency is higher.

Specifically, as shown in fig. 1, the self-circulating BOG condensation coupling type cryogenic tank includes a tank 100, a condensing unit 200, and an output pipe 300.

Wherein, a liquid space 110 for storing LNG and a gas phase space 120 positioned above the liquid space 110 are arranged in the storage tank 100, and an LNG circulating liquid return port and an LNG circulating liquid output port which are communicated with the liquid space 110 are arranged on the storage tank 100.

It will be appreciated that LNG is fed into the liquid space 110 of the storage tank 100 through the LNG circulation liquid return port of the storage tank 100, and is externally fed to other equipment from the LNG circulation liquid outlet port of the storage tank 100. When LNG is heated, BOG is formed in the heated portion, and the BOG is light in weight and stored in the gas phase space 120 of the storage tank 100.

It should be noted that the storage tank 100 is a sealed tank, so that the BOG formed after LNG is heated does not leak to the outside of the storage tank 100, but is stored in the gas phase space 120 of the storage tank 100.

The condensing apparatus 200 includes an LNG circulation liquid input pipe 210, an LNG circulation liquid output pipe 220, and a heat exchange pipe 230 disposed in the gas phase space 120, wherein one end of the LNG circulation liquid input pipe 210 is connected to the LNG circulation liquid output port, the other end is connected to the inlet of the heat exchange pipe 230, one end of the LNG circulation liquid output pipe 220 is connected to the outlet of the heat exchange pipe 230, and the other end is connected to the LNG circulation liquid return port. That is, LNG in the liquid space 110 can flow circularly through the LNG circulation liquid inlet pipe 210, the heat exchange pipe 230 and the LNG circulation liquid outlet pipe 220, and in the LNG circulation flow process, LNG in the heat exchange pipe 230 exchanges heat with BOG in the gas phase space 120, so that BOG is cooled and condensed into LNG, and the LNG flows back into the liquid space 110, thereby realizing BOG recovery.

It will be appreciated that to ensure that LNG can circulate at the desired flow rate, a pump 211 may be provided on either LNG feed line 210 or LNG take-off line 220 to power the LNG flow.

One end of the external pipeline 300 is communicated with the other end of the LNG circulating fluid output pipeline 220, and the other end of the external pipeline 300 is communicated with other equipment.

The self-circulation BOG condensation coupling type low-temperature storage tank provided by the embodiment is characterized in that the heat exchange tube 230 of the condensing device 200 is arranged in the gas phase space 120 of the storage tank 100, and the heat exchange is carried out between the BOG and the BOG in the gas phase space 120, so that the BOG can be condensed and flows back to the liquid space 110 in the storage tank 100, further the in-tank recovery of the BOG is realized, the BOG in the BOG recovery mode is not required to be introduced outside the storage tank, the risk of BOG leakage is reduced, and the safety is higher. In addition, by adopting LNG with lower temperature in the liquid space 110 in the storage tank 100 as a heat exchange medium to exchange heat with the BOG, the cost for conveying other heat exchange mediums is saved, and the economic benefit is improved. Meanwhile, the LNG after heat exchange can be used as the preheated LNG to be continuously conveyed to other equipment through the outer conveying pipeline 300, so that the load of the equipment for heating the LNG later can be reduced, the energy utilization efficiency is improved, and the running cost is reduced.

Optionally, the heat exchange tube 230 may be a corrugated tube, a fin tube, a pitted surface tube or other heat exchange tube type with high-efficiency enhanced condensation, and compared with a traditional light tube, the heat exchange efficiency of the BOG outside the heat exchange tube 230 can be improved, so as to ensure the small temperature difference heat exchange effect between the BOG and the LNG, and also reduce the flow of the required low-temperature LNG.

Further, with continued reference to fig. 1, the self-circulation BOG condensation coupling type cryogenic storage tank further includes a flow rate regulating valve 240, a temperature sensor (not shown), a gas concentration sensor (not shown), and a controller (not shown). Wherein, a flow regulating valve 240 is provided on the LNG circulation liquid input pipe 210 for regulating the input flow of LNG. The temperature sensor is disposed at the outlet of the heat exchange pipe 230 for detecting the temperature of the heat exchanged LNG. A gas concentration sensor is provided in the gas phase space 120 for detecting the concentration of BOG. The controller is in signal connection with the flow regulating valve 240, the temperature sensor and the gas concentration sensor, and can control the opening of the flow regulating valve 240 according to the temperature signal transmitted by the temperature sensor and the BOG concentration signal transmitted by the gas concentration sensor.

Specifically, the controller can obtain the BOG concentration in the gas phase space 120 according to the BOG concentration signal transmitted by the gas concentration sensor, when the BOG concentration is low, the flow regulating valve 240 can be controlled to enable the LNG to continuously enter the heat exchange tube 230 at a low flow rate or enable the LNG to intermittently enter the heat exchange tube 230, meanwhile, the controller controls the time for the LNG to intermittently enter the heat exchange tube 230 according to the temperature signal transmitted by the temperature sensor, so as to ensure that the BOG outside the heat exchange tube 230 can be fully condensed, and the LNG in the heat exchange tube 230 cannot be overheated and evaporated.

It should be noted that, although this control manner may make the heat exchange efficiency of LNG relatively low, the BOG concentration outside the heat exchange tube 230 is generally low, and the condensation heat exchange coefficient does not change greatly, so that the condensation effect of BOG outside the heat exchange tube 230 is not affected.

It should be noted that, in this embodiment, the temperature detected by the temperature sensor is ensured to be between-162 ℃ and-190 ℃. Of course, the temperature value is determined according to the design pressure, temperature conditions and the boiling point of LNG under the working conditions.

Further, as shown in fig. 3, a first flow equalizing unit 270 is disposed below the heat exchange tube 230, and the first flow equalizing unit 270 is used for disturbing the BOG below the heat exchange tube 230. By providing the first flow equalizing unit 270, the flow speed of BOG can be increased, so that BOG is condensed more sufficiently.

In this embodiment, the first current equalizing unit 270 may be a spoiler, and the structure of the spoiler is not described in detail because the spoiler is in the prior art.

Further, with continued reference to fig. 2 and 3, the condensing apparatus 200 further includes an input cluster tool box 250 and an output cluster tool box 260.

Specifically, the other end of the LNG circulation liquid input pipe 210 is communicated with the inlet of the input cluster pipe box 250, the outlet of the input cluster pipe box 250 is communicated with the inlet of the heat exchange pipe 230, the connection between the LNG circulation liquid input pipe 210 and the heat exchange pipe 230 is realized through the input cluster pipe box 250, the connection strength is high, and the risk of LNG leakage is low.

In the present embodiment, the input cluster tool box 250 is disposed within the gas phase space 120.

The outlet of the heat exchange tube 230 is communicated with the inlet of the output bundling tube box 260, the outlet of the output bundling tube box 260 is communicated with one end of the LNG circulating liquid output pipeline 220, the output tube is connected with the heat exchange tube 230 through the output bundling tube box 260, the connection strength is high, and the risk of LNG leakage is low.

In the present embodiment, the output cluster tube box 260 is disposed within the gas phase space 120.

The heat exchange tubes 230 are provided in plurality, and the plurality of heat exchange tubes 230 are arranged at intervals along the longitudinal direction of the input bundling tube box 250 and the output bundling tube box 260, and the diameters of the heat exchange tubes 230 are sequentially reduced from the inlet close to the input bundling tube box 250 to the inlet far from the input bundling tube box 250 along the longitudinal direction of the input bundling tube box 250 (the extending direction of the central axis a of fig. 2).

Because the distances of the inlets of the input cluster tube box 250 are different, the flow distribution of the heat exchange tubes 230 at different positions is uneven, so that the diameter of the heat exchange tube 230 close to the inlet of the input cluster tube box 250 is smaller than that of the heat exchange tube 230 far from the inlet of the input cluster tube box 250 in order to enable the BOG to exchange heat sufficiently outside the heat exchange tube 230, the flow of each heat exchange tube 230 can be uniform, and the BOG can be condensed sufficiently.

It should be noted that, in the present embodiment, the storage tank 100 is cylindrical, so the length of the heat exchange tube 230 is also adjusted according to the size of the storage tank 100, that is, the heat exchange tube 230 near the center line of the storage tank 100 is longer, and the heat exchange tube 230 far from the center line of the storage tank 100 is shorter.

Further, in one embodiment, the second flow equalizing unit 251 is disposed in the input bundling tube box 250, and the second flow equalizing unit 251 can increase the turbulence degree of the LNG in the input bundling tube box 250, so as to enhance the heat exchange effect between the heat exchange tube 230 and the BOG. Alternatively, the second current equalizing unit 251 may be a spoiler.

Of course, in another embodiment, the third current equalizing unit 261 may also be disposed in the output cluster tube box 260. In other embodiments, the second current equalizing unit 251 may also be disposed in the input cluster pipe box 250, while the third current equalizing unit 261 may be disposed in the output cluster pipe box 260.

Preferably, the plurality of heat exchange tubes 230 located in the same plane are a group of heat exchange tubes, and the plurality of heat exchange tubes can be arranged in the gas phase space 120 according to the height of the gas phase space 120, and the plurality of heat exchange tubes are arranged at intervals along the height direction of the gas phase space 120, so that BOG in the gas phase space 120 can be fully contacted with the heat exchange tubes 230, and then fully condensed, and the BOG recovery effect is better.

Further, with continued reference to fig. 1 and 3, the storage tank 100 includes a main tank 101 and a sub-tank 102 surrounding the main tank 101, a heat insulating layer 103 is provided between the main tank 101 and the sub-tank 102, and lng is stored in the main tank 101. Through setting up heat insulating layer 103, can play the effect of thermal insulation, reduce the influence of external environment temperature to the LNG in the main tank body 101, and then reduce the LNG heat absorption and form the risk of BOG.

Example two

The present embodiment provides a self-circulation BOG condensation coupling type cryogenic storage tank, which has substantially the same structure as the first embodiment and is modified only on the basis of the first embodiment. Therefore, only the differences between the two are described herein, and the same structure as that of the first embodiment of the present embodiment will not be described herein.

With continued reference to fig. 3, in this embodiment, a ceiling 400 is disposed in the gas phase space 120 of the storage tank 100 and is hermetically connected to the inner wall of the storage tank 100, and the heat exchange tube 230 is disposed above the ceiling 400, i.e., by disposing the ceiling 400, the gas phase space 120 is divided into two completely isolated spaces.

The self-circulating BOG condensation coupled cryogenic tank further includes a venturi 500 and a drain 600.

Wherein, venturi 500 wears to locate furred ceiling 400, and the BOG that is located furred ceiling 400 below carries to the top of furred ceiling 400 and heat exchange tube 230 heat transfer through venturi 500. The liquid inlet end of the liquid discharge pipe 600 is penetrated through the suspended ceiling 400, and the liquid outlet end of the liquid discharge pipe 600 is inserted into the LNG in the liquid space 110.

Specifically, after BOG is generated in the storage tank 100, the gas pressure of the storage tank 100 is increased, and the BOG in the storage tank 100 can be introduced into the space above the suspended ceiling 400 by using the suction and injection effect of the venturi tube 500, and is condensed by heat exchange with the heat exchange tube 230 in the space above the suspended ceiling 400 to form LNG, and the LNG can enter the liquid discharge tube 600 and flow back to the liquid space 110 of the storage tank 100 through the liquid discharge tube 600. After BOG condensation, the gas pressure above the suspended ceiling 400 is reduced, forming a low pressure zone, thereby forming a circulation.

By providing the venturi 500, BOG can be concentrated to exchange heat with the heat exchange tube 230, so that BOG can be sufficiently condensed. By inserting the drain 600 into LNG, a gas-phase seal can be formed, ensuring reliability of the operation of the venturi 500 for pumping BOG, and avoiding large fluctuation of the LNG liquid level when BOG is condensed and falls.

Preferably, a plurality of drain pipes 600 may be provided, and by providing a plurality of drain pipes 600, the reflux efficiency of LNG formed after BOG condensation can be improved. In the present embodiment, two liquid discharge tubes 600 are provided, and two liquid discharge tubes 600 are provided at opposite sides of the ceiling 400.

Further, the suspended ceiling 400 has a cambered surface structure concavely arranged downwards, and the liquid drain pipe 600 is arranged at the lowest position of the suspended ceiling 400. Through setting the furred ceiling 400 to the cambered surface structure that the indent was established downwards, can make the LNG that drips on the furred ceiling 400 converge to the position minimum of furred ceiling 400 to flow back to the liquid space 110 of storage tank 100 through the fluid-discharge tube 600 that is located the minimum of furred ceiling 400. This arrangement can improve the LNG reflux efficiency.

It is to be understood that the above examples of the present invention are provided for clarity of illustration only and are not limiting of the embodiments of the present invention. Other variations or modifications of the above teachings will be apparent to those of ordinary skill in the art. It is not necessary here nor is it exhaustive of all embodiments. Any modification, equivalent replacement, improvement, etc. which come within the spirit and principles of the invention are desired to be protected by the following claims.

Claims

1. Self-circulation BOG condensation coupling formula low temperature storage tank, its characterized in that includes:

The LNG storage device comprises a storage tank (100), wherein a liquid space (110) for storing LNG and a gas phase space (120) positioned above the liquid space (110) are arranged in the storage tank (100), and an LNG circulating liquid outlet and an LNG circulating liquid return port which are communicated with the liquid space (110) are arranged on the storage tank (100);

The condensing device (200) comprises an LNG circulating liquid input pipeline (210), an LNG circulating liquid output pipeline (220) and a heat exchange tube (230) arranged in the gas phase space (120), one end of the LNG circulating liquid input pipeline (210) is communicated with the LNG circulating liquid output port, the other end of the LNG circulating liquid input pipeline is communicated with an inlet of the heat exchange tube (230), one end of the LNG circulating liquid output pipeline (220) is communicated with an outlet of the heat exchange tube (230), the other end of the LNG circulating liquid output pipeline is communicated with the LNG circulating liquid reflux port, and LNG in the liquid space (110) can flow in a circulating mode through the LNG circulating liquid input pipeline (210), the heat exchange tube (230) and the LNG circulating liquid output pipeline (220);

An external pipeline (300), wherein one end of the external pipeline (300) is communicated with the other end of the LNG circulating liquid output pipeline (220), and the other end of the external pipeline (300) is communicated with other equipment;

a flow rate adjustment valve (240) provided in the LNG circulation input pipe (210) for adjusting the LNG input flow rate;

The temperature sensor is arranged at the outlet of the heat exchange tube (230) and is used for detecting the temperature of the LNG after heat exchange;

a gas concentration sensor disposed in the gas phase space (120) for detecting the concentration of BOG;

The controller is in signal connection with the flow regulating valve (240), the temperature sensor and the gas concentration sensor, and can control the opening of the flow regulating valve (240) according to the temperature signal transmitted by the temperature sensor and the BOG concentration signal transmitted by the gas concentration sensor;

A suspended ceiling (400) arranged at the gas phase space (120) in the storage tank (100) and in sealing connection with the inner wall of the storage tank (100), wherein the heat exchange tube (230) is arranged above the suspended ceiling (400);

The venturi tube (500) penetrates through the suspended ceiling (400), and BOG below the suspended ceiling (400) is conveyed to the upper side of the suspended ceiling (400) through the venturi tube (500) to exchange heat with the heat exchange tube (230);

the liquid inlet end of the liquid discharge pipe (600) penetrates through the suspended ceiling (400), and the liquid outlet end of the liquid discharge pipe (600) is inserted into LNG in the liquid space (110).

2. The self-circulating BOG condensing coupled cryogenic storage tank of claim 1, characterized in that a first flow equalizing unit (270) is arranged below the heat exchange tube (230), and the first flow equalizing unit (270) is used for disturbing BOG below the heat exchange tube (230).

3. The self-circulating BOG condensing coupled cryogenic storage tank of claim 1, characterized in that the condensing means (200) further comprises:

The other end of the LNG circulating fluid input pipeline (210) is communicated with the inlet of the input cluster pipe box (250), and the outlet of the input cluster pipe box (250) is communicated with the inlet of the heat exchange pipe (230);

An output bundling tube box (260), wherein the outlet of the heat exchange tube (230) is communicated with the inlet of the output bundling tube box (260), and the outlet of the output bundling tube box (260) is communicated with one end of the LNG circulating liquid output pipeline (220);

the heat exchange tubes (230) are arranged in a plurality, and the heat exchange tubes (230) are arranged at intervals along the length direction of the input bundling tube box (250) and the output bundling tube box (260).

4. A self-circulating BOG condensing coupled cryogenic storage tank according to claim 3, characterized in that the diameter of the heat exchange tubes (230) decreases in sequence from the inlet close to the input cluster tube box (250) to the inlet far from the input cluster tube box (250) along the length of the input cluster tube box (250).

5. A self-circulating BOG condensing coupled cryogenic storage tank according to claim 3, characterized in that a second flow equalizing unit (251) is arranged in the input bundling tube box (250) and/or a third flow equalizing unit (261) is arranged in the output bundling tube box (260).

6. A self-circulating BOG condensing coupled cryogenic storage tank according to claim 3, characterized in that the plurality of heat exchange tubes (230) located in the same plane are a group of heat exchange tube groups, the heat exchange tube groups are provided in plurality, and the plurality of heat exchange tube groups are arranged at intervals along the height direction of the gas phase space (120).

7. The self-circulating BOG condensing coupled cryogenic storage tank of claim 1, characterized in that the drain pipe (600) is provided in plurality.

8. The self-circulating BOG condensation coupling type low-temperature storage tank according to claim 1, wherein the suspended ceiling (400) is of a cambered surface structure concavely arranged downwards, and the liquid discharge pipe (600) is arranged at the lowest position of the suspended ceiling (400).