A BOG treatment device for a marine LNG fuel supply system

Abstract

The application discloses a kind of BOG processing equipment of marine LNG fuel supply system, belong to fuel supply technical field.The BOG processing equipment of the marine LNG fuel supply system, including mounting plate, and the storage tank of being installed on the top outer wall of mounting plate, the outer wall of storage tank is provided with the material injection assembly for being injected to boiler, and the hollow chamber is formed between the shell of storage tank and the body of storage tank, and the inside of chamber is provided with liquefaction component.The application can automatically detect the pressure inside storage tank and switch BOG management mode or LNG pump supply mode by manual or automatic mode, the BOG inside storage tank can be compressed and cooled when ship is at anchor, to re-liquefy it, while two heat exchangers alternately heat or cool fuel, without additional equipment, low energy consumption, and can make full use of BOG, improve the utilization of LNG, heat exchanger simple structure, without additional maintenance, cheap, small footprint, one use one spare, high reliability.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of fuel supply, in particular to a BOG treatment equipment of a marine LNG fuel supply system. BACKGROUND

[0002] Boil-off gas (BOG) is a derivative of liquefied natural gas (LNG), and its existence and emission will not only bring great economic losses to the ship, but also pose a hidden danger to the safety of the ship. After the liquid LNG enters the LNG storage tank, it will inevitably exchange heat with the outside world, causing the temperature of the LNG in the storage tank to rise, so part of the liquid evaporates to produce BOG flash gas. After the formation of BOG, the pressure in the LNG storage tank will increase, and when the pressure reaches a certain pressure, the safety valve will be opened, and the excess natural gas will be discharged into the atmosphere through the vent pipe to relieve the pressure inside the storage tank and avoid the risk of explosion.

[0003] A LNG transport ship BOG treatment system is disclosed in Chinese patent CN112648530B announced on April 26, 2022, which can recover the excess BOG generated when the LNG transport ship is anchored, and make it into relatively stable natural gas hydrate to avoid direct discharge into the atmosphere, causing energy waste and environmental pollution. At the same time, the large amount of cold energy released by LNG and BOG before being used is effectively utilized to prepare low-temperature water, thereby reducing the energy consumption in the synthesis of natural gas hydrate and improving the energy utilization rate. However, the LNG transport ship BOG treatment system is suitable for the case where the LNG storage tank generates a large amount of BOG, and the BOG reliquefaction device has a large investment and complex operation. SUMMARY

[0004] The purpose of the present application is to provide a BOG treatment equipment of a marine LNG fuel supply system to solve the problems raised in the background art.

[0005] In order to achieve the above object, the present application provides the following technical scheme: A BOG processing equipment of a marine LNG fuel supply system, comprising a mounting plate, a storage tank mounted on the top outer wall of the mounting plate, the storage tank comprising a storage tank shell fixedly connected to the top outer wall of the mounting plate, a storage tank body fixedly connected inside the storage tank shell, an injection assembly provided on one end of the outer wall of the storage tank for injecting fuel into the boiler, the injection assembly comprising a separation mechanism for gas-liquid separation of the fuel inside the storage tank, and a control box mounted on the top outer wall of the mounting plate, a control system mounted on the outer wall of the control box, and a heat exchanger mounted on the inner wall of the control box, the separation mechanism being controlled by the control system to select BOG or LNG to be injected into the heat exchanger for heating, a cabin being formed between the storage tank shell and the storage tank body, and a liquefaction assembly being provided inside the cabin, the liquefaction assembly comprising an air pipe for sucking BOG inside the storage tank body into the cabin, and a return pipe for re-injecting liquefied BOG into the storage tank body.

[0006] Further, the separation mechanism comprises a liquid inlet pipe provided on the storage tank shell near the control box side, a second inlet valve mounted on the liquid inlet pipe near the control box side, an injection pipe mounted on one end of the second inlet valve, a water-gas dual-purpose pump mounted on the outer wall of the control box side, a first connecting pipe penetrating the inside of the control box mounted on one end of the water-gas dual-purpose pump, a first check valve mounted on one end of the first connecting pipe extending into the inside of the control box, a feeding pipe mounted on the outer wall of the first check valve side, the feeding pipe being connected to the heat exchanger at one end, a discharge pipe fixedly connected to the outer wall of the heat exchanger side, an electric three-way valve mounted on the outer wall of the discharge pipe side, a second connecting pipe penetrating the outer wall of the control box mounted on the outer wall of the electric three-way valve side, a second check valve mounted on one end of the second connecting pipe extending out of the control box, the second check valve being connected to the return pipe at one end, and an injection pipe for delivering fuel to the boiler mounted on the other end of the second check valve.

[0007] Further, the heat exchanger is provided with two groups inside the control box, the outer wall of the first check valve is provided with two groups of feeding pipes connected to the two groups of control boxes respectively, and the two ends of the discharge pipe on the outer wall of the electric three-way valve are connected to the two groups of control boxes respectively.

[0008] Further, the separation mechanism further comprises a pressure gauge provided on the outer wall of the storage tank shell side, a pressure sensor mounted on the outer wall of the storage tank shell side, an air inlet pipe mounted on the storage tank shell near the control box side, a first inlet valve mounted on the air inlet pipe near the control box side, an air injection pipe provided on one end of the first inlet valve and adapted to the water-gas dual-purpose pump, and one end of the air injection pipe being connected to one end of the air pipe.

[0009] Further, the liquefaction assembly comprises an air inlet opening on the inner wall of the storage tank body, and a plurality of first guide plates and second guide plates arranged along the circumferential direction of the outer peripheral surface of the storage tank body and forming a channel, a gap being present between the first guide plate close to the air vent pipe side and the storage tank shell, a gap being present between the second guide plate close to the air inlet opening side and the storage tank shell, the distance between the first guide plate and the second guide plate decreasing in the direction from point A to point B, and the channel formed by the adjacent closest first guide plate and second guide plate being connected with the air vent pipe.

[0010] Further, the liquefaction assembly further comprises a limiting plate and a limiting rod arranged inside the channel, the limiting plate being provided with a through hole on the surface facing the channel, the limiting rod being arranged at one end of the first guide plate close to the gap and at one end of the second guide plate close to the storage tank shell, a return spring being fixedly connected to the inside of the channel close to the storage tank shell side, a push plate being fixedly connected to the return spring close to the limiting rod side, a connecting rod being slidingly connected to the inner wall of the push plate, a piston plate being fixedly connected to the connecting rod close to the limiting plate side, a connecting spring being arranged on the connecting rod away from the piston plate side, a first air vent hole being provided on the surface of the push plate, a first connecting groove adapted to the limiting rod being arranged at both ends of the push plate, a second air vent hole being provided on the surface of the piston plate, a second connecting groove adapted to the limiting rod being arranged at both ends of the piston plate, and a rubber pad being attached to the inner wall of the second connecting groove.

[0011] The difference from the prior art is that the application has the following beneficial effects:

[0012] The BOG treatment equipment of the ship LNG fuel supply system can automatically detect the internal pressure of the storage tank and switch the BOG management mode or the LNG pump supply mode in a manual or automatic manner, the BOG in the storage tank can be compressed and cooled when the ship is at anchor, so that the BOG is liquefied, two heat exchangers alternately heat or cool the fuel, no additional equipment is needed, the energy consumption is low, the BOG can be fully utilized, the utilization rate of LNG is improved, the heat exchanger structure is simple, no additional maintenance is needed, the price is cheap, the land occupation is small, one is used and one is reserved, and the reliability is high. BRIEF DESCRIPTION OF DRAWINGS

[0013] Figure 1 The figure is a schematic diagram of the three-dimensional structure of the embodiment of the application;

[0014] Figure 2 The figure is a schematic diagram of the mutual cooperation structure of the storage tank shell and the storage tank body of the application;

[0015] Figure 3 The figure is a schematic diagram of the internal structure of the control box of the application;

[0016] Figure 4 Figure 1 is a schematic diagram of the mutual cooperation structure of the air inlet and the guide plate of the application;

[0017] Figure 5 Figure 2 is a schematic diagram of the mutual cooperation structure of the guide plate and the storage tank body of the application;

[0018] Figure 6 Figure 3 is a schematic diagram of the mutual cooperation structure of the return spring and the push plate of the application;

[0019] Figure 7 Figure 4 is a schematic diagram of the mutual cooperation structure of the second connecting groove and the rubber pad of the application.

[0020] In the figure: 1, mounting plate; 2, storage tank; 21, storage tank shell; 22, storage tank body; 3, material injection assembly; 301, pressure gauge; 302, pressure sensor; 303, control box; 304, control system; 305, air inlet pipe; 306, first inlet valve; 307, air injection pipe; 308, water and gas dual-purpose pump; 309, liquid inlet pipe; 310, second inlet valve; 311, liquid injection pipe; 312, first connecting pipe; 313, first check valve; 314, material feeding pipe; 315, heat exchanger; 316, material outlet pipe; 317, electric three-way valve; 318, second connecting pipe; 319, second check valve; 320, material injection pipe; 4, liquefaction assembly; 401, air inlet; 402, first guide plate; 403, air pipe; 404, return pipe; 405, limiting plate; 406, through hole; 407, limiting rod; 408, return spring; 409, push plate; 410, connecting rod; 411, piston plate; 412, connecting spring; 413, first air hole; 414, first connecting groove; 415, second air hole; 416, second connecting groove; 417, rubber pad; 418, second guide plate. DETAILED DESCRIPTION

[0021] The technical solutions in the embodiments of the application will be clearly and completely described below with reference to the drawings in the embodiments of the application. Obviously, the described embodiments are only part of the embodiments of the application, rather than all the embodiments of the application. Based on the embodiments in the application, all other embodiments obtained by those skilled in the art without creative work fall within the protection scope of the application.

[0022] It should be noted that the embodiments in the application and the features in the embodiments can be combined with each other without conflict. The application will be described in detail below with reference to the drawings and in combination with the embodiments.

[0023] Embodiment one

[0024] Please refer to Figures 1-7The application provides a technical scheme: a BOG treatment equipment of a marine LNG fuel supply system, which comprises a mounting plate 1 and a storage tank 2 mounted on the outer wall of the top end of the mounting plate 1. The storage tank 2 comprises a storage tank shell 21 fixedly connected to the outer wall of the top end of the mounting plate 1, and a storage tank body 22 fixedly connected to the inside of the storage tank shell 21. An injection assembly 3 for injecting fuel into a boiler is arranged on the outer wall of one end of the storage tank 2. The injection assembly 3 comprises a separation mechanism for separating gas and liquid of the fuel in the storage tank 2, and a control box 303 mounted on the outer wall of the top end of the mounting plate 1. A control system 304 is mounted on the outer wall of the control box 303, and a heat exchanger 315 is mounted on the inner wall of the control box 303. The separation mechanism is controlled by the control system 304 to select BOG or LNG to be injected into the heat exchanger 315 for heating. A cabin is formed in the hollow space between the storage tank shell 21 and the storage tank body 22, and a liquefaction assembly 4 is arranged in the cabin. The liquefaction assembly 4 comprises an air pipe 403 for sucking the BOG in the storage tank body 22 into the cabin, and a reflux pipe 404 for re-injecting the liquefied BOG into the storage tank body 22.

[0025] When the pressure in the storage tank 2 is greater than 3 Bar, the control system 304 can be manually controlled to enter the BOG management mode and manually exited. When the pressure is less than 2 Bar, the control system 304 will automatically close the BOG management mode and switch to the LNG pump supply mode. When the pressure in the storage tank 2 is greater than 7 Bar, the control system 304 automatically switches to the BOG management mode. If no confirmation is made within 30 seconds, the system will automatically enter the boiler BOG mode. If the “LNG gas supply” of the boiler is manually clicked within 30 seconds, the LNG gas supply will continue. The BOG or LNG in the storage tank body 22 is injected into the heat exchanger 315 in the control box 303 through the separation mechanism for heating, and then transported to the boiler. When the ship is at anchor, the amount of fuel consumed by the boiler is small, and the pressure in the storage tank 2 increases. At this time, the BOG in the storage tank body 22 enters the cabin between the storage tank shell 21 and the storage tank body 22 for extrusion, and then is injected into the inside of the heat exchanger 315 through the air pipe 403 for cooling and condensing into liquid, and finally flows back to the inside of the storage tank body 22 through the reflux pipe 404.

[0026] Please refer to Figure 1 and Figure 3As shown in the figure, the separation mechanism comprises a liquid inlet pipe 309 arranged on the storage tank shell 21 near the side of the control box 303, the liquid inlet pipe 309 is arranged with a second inlet valve 310 near the side of the control box 303, one end of the second inlet valve 310 is arranged with a liquid injection pipe 311, the side wall of the control box 303 is arranged with a water and gas dual-purpose pump 308 matched with the liquid injection pipe 311, one end of the water and gas dual-purpose pump 308 is arranged with a first connecting pipe 312 penetrating the inside of the control box 303, one end of the first connecting pipe 312 penetrating the inside of the control box 303 is arranged with a first check valve 313, the side wall of the first check valve 313 is arranged with a feeding pipe 314, one end of the feeding pipe 314 is connected with a heat exchanger 315, the side wall of the heat exchanger 315 is fixedly connected with a discharging pipe 316, the outer wall of the discharging pipe 316 is arranged with an electric three-way valve 317, the side wall of the electric three-way valve 317 is arranged with a second connecting pipe 318 penetrating the outer wall of the control box 303, one end of the second connecting pipe 318 penetrating the control box 303 is arranged with a second check valve 319, one end of the second check valve 319 is connected with a return pipe 404, and the other end of the second check valve 319 is arranged with a material injection pipe 320 for feeding fuel to the boiler.

[0027] In use, when the pressure inside the storage tank 2 is lower than 2Bar, the control system 304 controls the second inlet valve 310 and the first check valve 313 to open, and at the same time starts the water and gas dual-purpose pump 308 to pump the LNG inside the storage tank body 22 into the inside of the liquid injection pipe 311 through the liquid inlet pipe 309, and then enters the inside of the heat exchanger 315 through the first connecting pipe 312 and the feeding pipe 314, so as to heat the LNG, prevent the case of directly supplying the LNG to the boiler to cause the combustion efficiency to be reduced and the engine to be malfunctioned, and the heated LNG enters the material injection pipe 320 through the discharging pipe 316 and the second connecting pipe 318 and is fed into the boiler, and the first check valve 313 arranged on the surface of the feeding pipe 314 and the second check valve 319 arranged on the surface of the second connecting pipe 318 can avoid the case that the LNG flows back in the case that the pressure of the boiler is too high.

[0028] Please refer to Figure 3 As shown in the figure, the heat exchanger 315 is arranged inside the control box 303, the outer wall of the first check valve 313 is arranged with two groups of feeding pipes 314 connected with two groups of control boxes 303, and the two ends of the discharging pipe 316 on the outer wall of the electric three-way valve 317 are connected with two groups of control boxes 303.

[0029] In use, the first check valve 313 is controlled to inject the fuel in the storage tank body 22 into one of the heat exchangers 315 through the feeding pipe 314 for heating, and then supply the boiler through the discharging pipe 316, and the electric three-way valve 317 on the surface of the discharging pipe 316 can prevent the fuel from flowing back into the other heat exchanger 315, without additional equipment, low energy consumption, and full use of BOG, improving the utilization rate of LNG, the BOG heat exchanger structure is simple, without additional maintenance, low price, small area, one standby, high reliability.

[0030] Please refer to Figure 1 As shown, the separation mechanism further comprises a pressure gauge 301 arranged on one side of the outer wall of the storage tank shell 21, a pressure sensor 302 is installed on one side of the outer wall of the storage tank shell 21, an air inlet pipe 305 is installed on the side of the storage tank shell 21 close to the control box 303, a first inlet valve 306 is installed on the side of the air inlet pipe 305 close to the control box 303, a gas injection pipe 307 adapted to a water-gas dual-purpose pump 308 is arranged at one end of the first inlet valve 306, and one end of the gas injection pipe 307 close to the first inlet valve 306 is connected with one end of the air pipe 403.

[0031] In use, the pressure gauge 301 can monitor the internal pressure of the storage tank body 22 in real time, and transmit the data to the control system 304 through the pressure sensor 302, and when the internal pressure of the storage tank body 22 is too high, the control system 304 will enter the BOG management mode, at this time, the second inlet valve 310 is closed and the first inlet valve 306 is opened, through the pressure in the storage tank body 22, the BOG is automatically injected into the inside of the gas injection pipe 307 through the air inlet pipe 305, then enters the inside of the heat exchanger 315 through the first connecting pipe 312 and the feeding pipe 314 to heat the BOG, and finally enters the injection pipe 320 through the discharging pipe 316 and the second connecting pipe 318 and is transported into the boiler.

[0032] In order to avoid the pressure in the storage tank 2 when the ship is at anchor to keep within a safe range, please refer to Figure 1 、 Figure 4 and Figure 5 As shown, the liquefaction assembly 4 comprises an air inlet 401 opened on the inner wall of the storage tank body 22, and a plurality of first guide plates 402 and second guide plates 418 arranged in the circumferential direction along the outer peripheral surface of the storage tank body 22 and forming channels, there is a gap between the first guide plate 402 close to the side of the air pipe 403 and the storage tank shell 21, there is a gap between the second guide plate 418 close to the side of the air inlet 401 and the storage tank shell 21, the distance between the first guide plate 402 and the second guide plate 418 decreases in the direction from point A to point B, and the channels formed by the adjacent closest first guide plate 402 and second guide plate 418 are connected with the air pipe 403.

[0033] When the pressure inside the storage tank 2 is too high during the docking process, the water-gas dual-purpose pump 308 is started to pump the gas inside the cabin between the storage tank shell 21 and the storage tank body 22 into the interior of the gas injection pipe 307 through the air pipe 403, thereby reducing the air pressure inside the cabin. At this time, the BOG inside the storage tank body 22 can enter the interior of the cabin through the gas inlet 401, and the BOG entering the interior of the cabin can be guided by the multiple sets of first guide plates 402 and second guide plates 418, so that the BOG inside the cabin can only move along the channels formed by the first guide plates 402 and the second guide plates 418, and the BOG entering the interior of the cabin can flow through each corner of the outer wall of the storage tank body 22, and the BOG itself has the characteristics of low temperature, which can insulate the storage tank body 22, thereby reducing the gasification efficiency of the LNG inside the storage tank body 22. The width of the multiple sets of through grooves inside the cabin decreases in turn, so that the BOG is extruded every time it flows into a through groove. When the BOG enters the through groove with the narrowest width, it is sucked into the interior of the gas injection pipe 307 through the air pipe 403, and then enters the interior of the heat exchanger 315 through the first connecting pipe 312 and the feeding pipe 314 for cooling treatment, so that the BOG is reconverted into LNG. Finally, the BOG flows back into the interior of the storage tank body 22 through the discharge pipe 316 and the second connecting pipe 318 and the reflux pipe 404.

[0034] Please refer to Figures 6-7 As shown in the drawings, the liquefaction assembly 4 further comprises a limiting plate 405 and a limiting rod 407 arranged inside the channel. The limiting plate 405 is provided with a through hole 406 on the surface facing the channel. The first guide plate 402 is provided with the limiting rod 407 on the end close to the gap, and the second guide plate 418 is provided with the limiting rod 407 on the end close to the storage tank shell 21. A reset spring 408 is fixedly connected to the inside of the channel close to the storage tank shell 21. The reset spring 408 is fixedly connected to the inside of the channel close to the limiting rod 407. A push plate 409 is fixedly connected to the inside of the channel close to the limiting rod 407. A connecting rod 410 is slidably connected to the inner wall of the push plate 409. A piston plate 411 is fixedly connected to the side of the connecting rod 410 close to the limiting plate 405. A connecting spring 412 is arranged on the side of the connecting rod 410 away from the piston plate 411. A first air hole 413 is arranged on the surface of the push plate 409. A first connecting groove 414 adapted to the limiting rod 407 is arranged on both ends of the push plate 409. A second air hole 415 is arranged on the surface of the piston plate 411. A second connecting groove 416 adapted to the limiting rod 407 is arranged on both ends of the piston plate 411. A rubber pad 417 is attached to the inner wall of the second connecting groove 416.

[0035] When in use, the BOG enters the channel through the gap between the first guide plate 402 and the second guide plate 418 and the outer shell 21 of the storage tank, and then exerts a pushing force on the surface of the push plate 409, so that the push plate 409 and the piston plate 411 slide on the surface of the limiting rod 407 to the direction of the limiting plate 405 and pull the reset spring 408 through the first connecting slot 414 and the second connecting slot 416. At this time, the piston plate 411 will extrude the BOG of the limiting plate 405, so that the BOG between the piston plate 411 and the limiting plate 405 is compressed and enters the other end of the channel through the through hole 406 of the limiting plate 405. When the BOG enters the through hole 406, it will be compressed again, and when the BOG passes through the through hole 406, it will accelerate the flow rate, thereby promoting the liquefaction efficiency of the BOG. After the push plate 409 slides on the surface of the limiting rod 407 for a distance, it will no longer continue to slide under the action of the pulling force of the reset spring 408. At this time, the BOG will enter the inside of the first air hole 413 and push the piston plate 411 to continue to slide on the surface of the limiting rod 407, thereby pulling the connecting rod 410 to slide in the inside of the push plate 409 and extruding the connecting spring 412, so that the push plate 409 and the piston plate 411 are separated and the limiting of the first air hole 413 and the second air hole 415 is released. At this time, the reset spring 408 pulls the push plate 409 back to its original position. Because the inner wall of the second connecting slot 416 is pasted with a rubber pad 417, the friction between the piston plate 411 and the limiting rod 407 is greater than the friction between the push plate 409 and the limiting rod 407, so that the push plate 409 slides backward before the piston plate 411. In this process, the push plate 409 will pull the piston plate 411 to slide synchronously through the connecting rod 410, and the BOG will re-enter between the piston plate 411 and the limiting plate 405 through the first air hole 413 and the second air hole 415. When the push plate 409 is reset, the force exerted on the connecting rod 410 through the connecting spring 412 will pull the piston plate 411 and the push plate 409 to close and re-limit the first air hole 413 and the second air hole 415.

[0036] In the description of the present application, it should be understood that the orientation or positional relationship indicated by terms such as "length", "width", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer" and the like are based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present application and simplifying the description, and are not intended to indicate or imply that the device or element referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as a limitation on the present application.

[0037] In addition, the terms "first", "second", etc. are used only for the purpose of description, and should not be understood as indicating or implying relative importance or an indicated number of technical features. Therefore, the features defined as "first", "second" can explicitly or implicitly include one or more of the features. In the description of the present application, the meaning of "a plurality of" is two or more, unless otherwise specifically limited.

[0038] The above description is merely preferred specific embodiments of the present application, but the protection scope of the present application is not limited thereto, and any person skilled in the art can make equivalent replacements or changes to the technical solutions and the inventive concept of the present application within the technical scope disclosed by the present application, which should be covered within the protection scope of the present application.

Claims

1. A BOG treatment device of a marine LNG fuel supply system, comprising a mounting plate (1) and a storage tank (2) mounted on the outer wall of the top end of the mounting plate (1), wherein the storage tank (2) comprises a storage tank shell (21) fixedly connected to the outer wall of the top end of the mounting plate (1), an inner portion of the storage tank shell (21) is fixedly connected with a storage tank body (22), and an outer wall of one end of the storage tank (2) is provided with a material injection assembly (3) for injecting material into a boiler, characterized in that: The injection assembly (3) comprises a separation mechanism for gas-liquid separation of fuel inside the storage tank (2), and a control box (303) installed on the top outer wall of the mounting plate (1), a control system (304) is installed on the outer wall of the control box (303), a heat exchanger (315) is installed on the inner wall of the control box (303), the separation mechanism is controlled by the control system (304) to select BOG or LNG injection into the heat exchanger (315) for heating, a cabin is formed between the storage tank shell (21) and the storage tank body (22), and a liquefaction assembly (4) is arranged inside the cabin, the liquefaction assembly (4) comprises a breather pipe (403) for sucking BOG inside the storage tank body (22) into the cabin, and a return pipe (404) for re-injecting liquefied BOG into the storage tank body (22); The liquefaction assembly (4) comprises an air inlet (401) opened on the inner wall of the storage tank body (22), and a plurality of first guide plates (402) and second guide plates (418) are arranged along the circumferential direction of the outer peripheral surface of the storage tank body (22) and form channels, the first guide plate (402) has a gap between the storage tank shell (21) in the direction close to the breather pipe (403), the second guide plate (418) has a gap between the storage tank shell (21) in the direction close to the air inlet (401), and the distance between the first guide plate (402) and the second guide plate (418) decreases from the A point to the B point, wherein the highest point of the storage tank shell (21) in the horizontal placement state is the A point, the lowest point of the storage tank shell (21) in the horizontal placement state is the B point, and the breather pipe (403) is connected to the channel formed by the adjacent closest first guide plate (402) and second guide plate (418). The liquefaction assembly (4) further comprises a limiting plate (405) and a limiting rod (407) arranged inside the channel, the limiting plate (405) is provided with a through hole (406) on the surface facing the channel, one end of the first guide plate (402) close to the gap and one end of the second guide plate (418) close to the closed end of the storage tank shell (21) are provided with the limiting rod (407), the inside of the channel is fixedly connected with a return spring (408) in the direction close to the side of the storage tank shell (21), the return spring (408) is fixedly connected with a push plate (409) in the direction close to the limiting rod (407), the inner wall of the push plate (409) is slidably connected with a connecting rod (410), the connecting rod (410) is fixedly connected with a piston plate (411) in the direction close to the limiting plate (405), the connecting rod (410) is provided with a connecting spring (412) matched with the push plate (409) in the direction away from the piston plate (411), the surface of the push plate (409) is provided with a first air hole (413), the two ends of the push plate (409) are provided with a first connecting groove (414) matched with the limiting rod (407), the surface of the piston plate (411) is provided with a second air hole (415), the two ends of the piston plate (411) are provided with a second connecting groove (416) matched with the limiting rod (407), and the inner wall of the second connecting groove (416) is attached with a rubber pad (417).

2. A BOG treatment plant for a marine LNG fuel supply system according to claim 1, characterized in that: The separation mechanism comprises an inlet pipe (309) arranged on the side of the storage tank shell (21) close to the control box (303), a second inlet valve (310) mounted on the side of the inlet pipe (309) close to the control box (303), a liquid injection pipe (311) mounted on one end of the second inlet valve (310), a water and gas dual-purpose pump (308) arranged on the side outer wall of the control box (303) and matched with the liquid injection pipe (311), a first connecting pipe (312) penetrating the inside of the control box (303) and mounted on one end of the water and gas dual-purpose pump (308), a first check valve (313) mounted on the end of the first connecting pipe (312) extending into the inside of the control box (303), a feeding pipe (314) mounted on the side outer wall of the first check valve (313), the feeding pipe (314) connected with a heat exchanger (315) at one end, a discharging pipe (316) fixedly connected with the heat exchanger (315) on the side outer wall, an electric three-way valve (317) mounted on the outer wall of the discharging pipe (316), a second connecting pipe (318) penetrating the outer wall of the control box (303) and mounted on the end of the electric three-way valve (317) extending out of the control box (303), a second check valve (319) mounted on one end of the second connecting pipe (318), and a material injection pipe (320) for delivering fuel to the boiler mounted on the other end of the second check valve (319).

3. A BOG treatment plant for a marine LNG fuel supply system according to claim 2, characterized in that: The heat exchanger (315) is provided with two groups inside the control box (303), the outer wall of the first check valve (313) is provided with two groups of feeding pipes (314) connected with the two groups of control boxes (303) respectively, and the two ends of the discharge pipe (316) on the outer wall of the electric three-way valve (317) are connected with the two groups of control boxes (303) respectively.

4. A BOG treatment apparatus of a marine LNG fuel supply system according to claim 2, characterized in that: The separation mechanism further comprises a pressure gauge (301) arranged on the outer wall of one side of the storage tank shell (21), a pressure sensor (302) mounted on the outer wall of one side of the storage tank shell (21), an air inlet pipe (305) mounted on the side of the storage tank shell (21) close to the control box (303), a first inlet valve (306) mounted on the air inlet pipe (305) close to the control box (303), a gas injection pipe (307) provided with a water-gas dual-purpose pump (308) at one end of the first inlet valve (306), and the end of the gas injection pipe (307) close to the first inlet valve (306) is connected with one end of the air pipe (403).

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