BOG liquefaction recovery device of LNG storage tank

Abstract

The utility model discloses a BOG liquefaction recovery device of an LNG storage tank. The LNG storage tank is provided with a gas phase opening and a liquid phase opening, and the gas phase opening is formed in the top of the LNG storage tank; the BOG liquefaction recovery device comprises a refrigerating machine, an LNG buffer tank and an LNG pump, the LNG pump is installed in the LNG buffer tank, a liquid phase inlet is formed in the bottom of the LNG buffer tank, the refrigerating machine is provided with a gas phase inlet and a liquid phase outlet, a gas phase opening of the LNG storage tank is connected with the gas phase inlet of the refrigerating machine through a first gas phase pipeline, a first valve is installed on the first gas phase pipeline, and a second valve is installed on the second gas phase pipeline. A liquid phase outlet of the refrigerating machine is connected with a liquid phase inlet of the LNG buffer tank through a first liquid phase pipeline, a second valve is installed on the first liquid phase pipeline, a liquid outlet of the LNG pump is connected with a liquid phase opening of the LNG storage tank through a second liquid phase pipeline, and a third valve is installed on the second liquid phase pipeline. The BOG in the LNG storage tank can be liquefied and recycled, and therefore emission of the BOG in the LNG storage tank is effectively reduced.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of BOG recovery of LNG storage tank, in particular to a BOG liquefaction recovery device of LNG storage tank. BACKGROUND

[0002] At present, LNG (Liquefied Natural Gas) stations (including LNG filling stations, L-CNG filling stations, LNG gasification stations and LNG storage stations) are all provided with LNG storage tanks as storage devices. The temperature of LNG is extremely low, which can be as low as-162℃. During the storage process, LNG will continuously absorb heat from the environment and evaporate BOG (Boil Off Gas) to be stored in the LNG storage tank. At the same time, BOG produced by the absorption of heat in other equipment and pipelines of the LNG station will eventually return to the LNG storage tank. The pressure in the LNG storage tank will gradually increase with the increase of BOG. Once the maximum working pressure of the LNG storage tank is reached, if there is no BOG recovery equipment, it will be discharged.

[0003] At present, most LNG stations do not have BOG recovery equipment. The discharge amount of some stations with small gas filling amount can even reach 50%. However, the LNG stations with BOG recovery equipment mostly use the BOG after heating and pressure regulation as the boiler and kitchen on the station. However, due to the small amount of gas used by the boiler and kitchen on the station, the BOG of the LNG storage tank is still difficult to be fully utilized, and most of the BOG will be discharged. SUMMARY

[0004] To solve the above technical problems, the present application provides a BOG liquefaction recovery device of LNG storage tank, which can liquefy and recover the BOG in the LNG storage tank, thereby effectively reducing the discharge of BOG in the LNG storage tank.

[0005] The purpose of the present application is to provide a BOG liquefaction recovery device of LNG storage tank which can recover the BOG in the LNG storage tank.

[0006] The above application purpose of the present application is achieved by the following technical scheme:

[0007] A BOG liquefaction recovery device of LNG storage tank, the LNG storage tank is provided with a gas phase port and a liquid phase port, the gas phase port is arranged at the top of the LNG storage tank, the BOG liquefaction recovery device comprises a refrigeration machine, an LNG buffer tank and an LNG pump, the LNG pump is installed in the LNG buffer tank, the bottom of the LNG buffer tank is provided with a liquid phase inlet, the refrigeration machine is provided with a gas phase inlet and a liquid phase outlet,

[0008] The gas phase port of the LNG storage tank is connected with the gas phase inlet of the refrigerator through a first gas phase pipeline, a first valve is installed on the first gas phase pipeline, the liquid phase outlet of the refrigerator is connected with the liquid phase inlet of the LNG buffer tank through a first liquid phase pipeline, a second valve is installed on the first liquid phase pipeline, the liquid outlet of the LNG pump is connected with the liquid phase port of the LNG storage tank through a second liquid phase pipeline, and a third valve is installed on the second liquid phase pipeline.

[0009] Preferably, the liquid phase port of the LNG storage tank comprises a top liquid inlet arranged at the top of the LNG storage tank, the second liquid phase pipeline comprises a liquid phase main pipeline and a first liquid phase branch pipeline, one end of the liquid phase main pipeline is connected with the liquid outlet of the LNG pump, the other end of the liquid phase main pipeline is connected with one end of the first liquid phase branch pipeline, the other end of the first liquid phase branch pipeline is connected with the top liquid inlet of the LNG storage tank, and the third valve is installed on the liquid phase main pipeline.

[0010] Preferably, the liquid phase port of the LNG storage tank comprises a bottom liquid phase port arranged at the bottom of the LNG storage tank, the second liquid phase pipeline comprises a liquid phase main pipeline and a second liquid phase branch pipeline, one end of the liquid phase main pipeline is connected with the liquid outlet of the LNG pump, the other end of the liquid phase main pipeline is connected with one end of the second liquid phase branch pipeline, the other end of the second liquid phase branch pipeline is connected with the bottom liquid phase port of the LNG storage tank, and the third valve is installed on the liquid phase main pipeline.

[0011] Preferably, the liquid phase port of the LNG storage tank further comprises a bottom liquid phase port arranged at the bottom of the LNG storage tank, and the second liquid phase pipeline further comprises a second liquid phase branch pipeline, one end of the second liquid phase branch pipeline is connected with the end of the liquid phase main pipeline away from the LNG pump, and the other end of the second liquid phase branch pipeline is connected with the bottom liquid phase port of the LNG storage tank.

[0012] Preferably, the BOG liquefaction and recovery device of the LNG storage tank further comprises a second gas phase pipeline, a third liquid phase pipeline, a fourth valve and a fifth valve, the LNG buffer tank is provided with a gas phase outlet at the top, wherein,

[0013] One end of the second gas phase pipeline is connected with the gas phase outlet of the LNG buffer tank, the other end of the second gas phase pipeline is connected with the end of the first gas phase pipeline close to the LNG storage tank, and the fourth valve is installed on the second gas phase pipeline.

[0014] One end of the third liquid phase pipeline is connected with the end of the liquid phase main pipeline close to the LNG pump, the other end of the third liquid phase pipeline is connected with the end of the first liquid phase pipeline close to the LNG buffer tank, and the fifth valve is installed on the third liquid phase pipeline.

[0015] Preferably, the first valve, the second valve, the third valve, the fourth valve and the fifth valve are electrically controlled valves,

[0016] The BOG liquefaction recovery device of the LNG storage tank further comprises a controller, first, second, third, fourth, fifth and sixth control terminals of the controller are connected with the first valve, the second valve, the third valve, the fourth valve, the fifth valve and the LNG pump respectively.

[0017] Preferably, the BOG liquefaction recovery device of the LNG storage tank further comprises a liquid level instrument, the liquid level instrument is installed in the LNG buffer tank, and a signal output terminal of the liquid level instrument is connected with a first signal input terminal of the controller,

[0018] The liquid level instrument is used for detecting a liquid level signal of the LNG buffer tank.

[0019] Preferably, the BOG liquefaction recovery device of the LNG storage tank further comprises a first pressure transmitter, the first pressure transmitter is installed on the LNG buffer tank, and a signal output terminal of the first pressure transmitter is connected with a second signal input terminal of the controller,

[0020] The first pressure transmitter is used for detecting a pressure signal of the LNG buffer tank.

[0021] Preferably, control valves are arranged at the gas phase port and the liquid phase port of the LNG storage tank.

[0022] Preferably, the BOG liquefaction recovery device of the LNG storage tank further comprises a second pressure transmitter, the second pressure transmitter is installed on the LNG storage tank, and the second pressure transmitter is used for detecting a pressure signal of the LNG storage tank.

[0023] The BOG liquefaction recovery device of the LNG storage tank has the following beneficial effects:

[0024] The BOG liquefaction recovery device of the LNG storage tank of the application is provided with a refrigerator, an LNG buffer tank and an LNG pump, the LNG pump is installed in the LNG buffer tank, the LNG storage tank is provided with a gas phase port and a liquid phase port, the gas phase port of the LNG storage tank is connected with a gas phase inlet of the refrigerator through a first gas phase pipeline, a first valve is installed on the first gas phase pipeline, a liquid phase outlet of the refrigerator is connected with a liquid phase inlet of the LNG buffer tank through a first liquid phase pipeline, a second valve is installed on the first liquid phase pipeline, a liquid outlet of the LNG pump is connected with the liquid phase port of the LNG storage tank through a second liquid phase pipeline, and a third valve is installed on the second liquid phase pipeline, so that when it is necessary to recover the BOG in the LNG storage tank, the BOG delivered by the LNG storage tank is cooled and liquefied by the refrigerator and then returned to the LNG storage tank, the recovery of the BOG gas in the LNG storage tank is realized, the pressure of the LNG storage tank is reduced, and the emission of the BOG in the LNG storage tank due to the excessively high pressure in the LNG storage tank is avoided, the whole device has a simple structure, and the BOG in the LNG storage tank can be liquefied and recovered, so that the emission of the BOG in the LNG storage tank is effectively reduced. BRIEF DESCRIPTION OF DRAWINGS

[0025] In order to more clearly illustrate the technical solutions in the embodiments of the application or the prior art, the drawings needed to be used in the embodiments or the prior art description will be briefly introduced. Obviously, the drawings in the following description are only some embodiments described in the application, and other drawings can be obtained by those skilled in the art without creative effort.

[0026] Figure 1 FIG. 1 is a structural schematic diagram of a BOG liquefaction recovery device of an LNG storage tank according to an embodiment of the application;

[0027] Figure 2 FIG. 2 is a structural schematic diagram of a BOG liquefaction recovery device of an LNG storage tank according to another embodiment of the application;

[0028] Figure 3 FIG. 3 is a structural schematic diagram of a BOG liquefaction recovery device of an LNG storage tank according to still another embodiment of the application;

[0029] Figure 4 FIG. 4 is a control principle block diagram of the BOG liquefaction recovery device of the LNG storage tank shown in the embodiment. Figure 3 DETAILED DESCRIPTION

[0030] ​In order to enable a person skilled in the art to better understand the technical solutions in the present application, the technical solutions in the embodiments of the present application will be clearly and completely described below. Obviously, the described embodiments are only some of the embodiments of the present application, but not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by a person skilled in the art without creative work fall within the scope of protection of the present application.

[0031] In the embodiments provided in the present application, it should be understood that the disclosed methods and systems can be implemented in other ways. The system embodiments described below are only illustrative. For example, the division of units and modules is only a logical function division. In actual implementation, there can be another division manner. For example, a plurality of units or modules can be combined, or integrated into another system, or some features can be ignored or not executed. In addition, the coupling or direct coupling or communication connection between the various components shown or discussed can be indirect coupling or communication connection through some interfaces, devices or modules, which can be electrical, mechanical or other forms.

[0032] In addition, each functional unit in each embodiment of the present application can be integrated into one processor, or each unit can be a separate device, or two or more units can be integrated into one device. Each functional unit in each embodiment of the present application can be realized in the form of hardware or hardware plus software functional unit.

[0033] A person skilled in the art can understand that all or part of the steps of the following method embodiments can be completed by program instructions and related hardware. The aforementioned program instructions can be stored in a computer readable storage medium. When the program instructions are executed, the steps of the method embodiments are executed. The aforementioned storage medium includes mobile storage devices, read-only memories (ROM), magnetic discs or optical discs, and various media that can store program codes.

[0034] In addition, the terms "first", "second" are used only for descriptive purposes, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of indicated technical features. Therefore, the features defined with "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" or "several" is two or more, unless otherwise explicitly specified.

[0035] The present application provides a BOG liquefaction recovery device of an LNG storage tank, as shown in Figures 1-4As shown, the LNG storage tank 100 is provided with a gas phase port and a liquid phase port, the gas phase port is arranged at the top of the LNG storage tank 100, the BOG liquefaction recovery device comprises a refrigerator 1, an LNG buffer tank 2 and an LNG pump 3, the LNG pump 3 is installed in the LNG buffer tank 2, the bottom of the LNG buffer tank 2 is provided with a liquid phase inlet, the refrigerator 1 is provided with a gas phase inlet and a liquid phase outlet,

[0036] The gas phase port of the LNG storage tank 100 is connected with the gas phase inlet of the refrigerator 1 through a first gas phase pipeline 4, the first gas phase pipeline 4 is provided with a first valve 5, the liquid phase outlet of the refrigerator 1 is connected with the liquid phase inlet of the LNG buffer tank 2 through a first liquid phase pipeline 6, the first liquid phase pipeline 6 is provided with a second valve 7, the liquid outlet of the LNG pump 3 is connected with the liquid phase port of the LNG storage tank 100 through a second liquid phase pipeline 8, and the second liquid phase pipeline 8 is provided with a third valve 9.

[0037] The working principle of the BOG liquefaction recovery device of the LNG storage tank in the embodiment of the present application is as follows:

[0038] When it is necessary to recover the BOG in the LNG storage tank 100, the refrigerator 1 is started, the BOG in the LNG storage tank 100 enters the LNG storage tank BOG liquefaction recovery device through the gas phase port of the LNG storage tank 100, enters the refrigerator 1 through the gas phase inlet of the refrigerator 1 after the first valve 5, is cooled and liquefied into LNG after the BOG is cooled, and then enters the LNG buffer tank 2 through the liquid phase inlet of the LNG buffer tank 2 through the second valve 7 of the liquid phase outlet of the refrigerator 1, the LNG in the LNG buffer tank 2 is pumped out by starting the LNG pump 3, and is recovered into the LNG storage tank 100 through the liquid phase port of the LNG storage tank 100 through the third valve 9.

[0039] The BOG liquefaction recovery device of the LNG storage tank in the embodiment of the application comprises a refrigerator 1, an LNG buffer tank 2 and an LNG pump 3. The LNG pump 3 is installed in the LNG buffer tank 2. The LNG storage tank 100 is provided with a gas phase port and a liquid phase port. The gas phase port of the LNG storage tank 100 is connected with a gas phase inlet of the refrigerator 1 through a first gas phase pipeline 4. A first valve 5 is installed on the first gas phase pipeline 4. A liquid phase outlet of the refrigerator 1 is connected with a liquid phase inlet of the LNG buffer tank 2 through a first liquid phase pipeline 6. A second valve 7 is installed on the first liquid phase pipeline 6. A liquid outlet of the LNG pump 3 is connected with the liquid phase port of the LNG storage tank 100 through a second liquid phase pipeline 8. A third valve 9 is installed on the second liquid phase pipeline 8. When it is necessary to recover the BOG in the LNG storage tank 100, the BOG delivered from the LNG storage tank 100 is cooled and liquefied by the refrigerator 1 and then returned to the LNG storage tank 100, so that the BOG gas in the LNG storage tank 100 is recovered and the pressure of the LNG storage tank 100 is reduced. The emission of the BOG in the LNG storage tank 100 is avoided. The whole device has a simple structure and can liquefy and recover the BOG in the LNG storage tank 100, so that the emission of the BOG in the LNG storage tank 100 is effectively reduced.

[0040] As shown in Figure 1 , Figure 3 In one embodiment, the liquid phase port of the LNG storage tank 100 comprises a top liquid inlet arranged at the top of the LNG storage tank 100. The second liquid phase pipeline 8 comprises a liquid phase main pipeline 801 and a first liquid phase branch pipeline 802. One end of the liquid phase main pipeline 801 is connected with the liquid outlet of the LNG pump 3. The other end of the liquid phase main pipeline 801 is connected with one end of the first liquid phase branch pipeline 802. The other end of the first liquid phase branch pipeline 802 is connected with the top liquid inlet of the LNG storage tank 100. The third valve 9 is installed on the liquid phase main pipeline 801.

[0041] In the embodiment, when it is necessary to recover the BOG in the LNG storage tank 100, the LNG cooled and liquefied can enter the LNG storage tank 100 through the top liquid inlet arranged at the top of the LNG storage tank 100. The recovered LNG enters the LNG storage tank 100 from the top of the LNG storage tank 100, so that part of the BOG in the space at the top of the LNG storage tank 100 is cooled and liquefied to further reduce the pressure of the LNG storage tank 100, thereby better reducing the emission of the BOG in the LNG storage tank 100.

[0042] As shown in Figure 3As shown, based on the previous embodiment, in one embodiment, the liquid phase port of the LNG storage tank 100 also includes a bottom liquid phase port arranged at the bottom of the LNG storage tank 100, and the second liquid phase pipeline 8 also includes a second liquid phase branch pipe 803, one end of the second liquid phase branch pipe 803 is connected to the end of the liquid phase main pipe 801 away from the LNG pump 3, and the other end of the second liquid phase branch pipe 803 is connected to the bottom liquid phase port of the LNG storage tank 100.

[0043] In this embodiment, by setting a bottom liquid phase port at the bottom of the LNG storage tank 100, when the BOG in the LNG storage tank 100 needs to be recovered, the LNG that enters the LNG buffer tank 2 after cooling and liquefaction can also enter the LNG storage tank 100 through the bottom liquid inlet at the bottom of the LNG storage tank 100. The recovered LNG enters the LNG storage tank 100 from the bottom of the LNG storage tank 100, which can cool the LNG in the LNG storage tank 100, and then reduce the pressure of the LNG storage tank 100, thereby better reducing the emission of BOG in the LNG storage tank 100.

[0044] like Figure 3 As shown, based on the previous embodiment, in one embodiment, the BOG liquefaction recovery device of the LNG storage tank further includes a second gas phase pipeline 10, a third liquid phase pipeline 11, a fourth valve 12 and a fifth valve 13, and a gas phase outlet is provided on the top of the LNG buffer tank 2, wherein,

[0045] One end of the second gas phase pipeline 10 is connected to the gas phase outlet of the LNG buffer tank 2, and the other end of the second gas phase pipeline 10 is connected to the end of the first gas phase pipeline 4 close to the LNG storage tank 100. The fourth valve 12 is installed on the second gas phase pipeline 10;

[0046] One end of the third liquid phase pipeline 11 is connected to the end of the liquid phase main pipe 801 close to the LNG pump 3, and the other end of the third liquid phase pipeline 11 is connected to the end of the first liquid phase pipeline 6 close to the LNG buffer tank 2. The fifth valve 13 is installed on the third liquid phase pipeline 11.

[0047] In this embodiment, by providing a second gas phase pipeline 10, a third liquid phase pipeline 11, a fourth valve 12 and a fifth valve 13, and providing a gas phase outlet at the top of the LNG buffer tank 2,

[0048] On the one hand, before starting the refrigerator 1 to cool and liquefy the BOG in the LNG storage tank 100 for recovery, the LNG buffer tank 2 and pipelines can be pre-cooled. This can ensure that the liquid in the LNG buffer tank 2 can submerge the LNG pump 3 when the refrigerator 1 is started, meeting the liquid level required for the LNG pump 3 to work, and can also prevent the LNG from being vaporized in large quantities due to the high temperature of the LNG buffer tank 2 in the initial stage of the refrigerator 1 startup, thereby causing cavitation to the LNG pump 3. The pre-cooling process is as follows:

[0049] Before the operation of the refrigerator 1, the third valve 9, the fourth valve 12 and the fifth valve 13 are opened, and the LNG in the LNG storage tank 100 flows out from the bottom liquid phase port under the action of gravity, enters the LNG buffer tank 2 through the third valve 9 and the fifth valve 13, and the BOG generated in the LNG tank during the precooling process enters the LNG storage tank 100 from the gas phase port at the top of the LNG storage tank 100 through the fourth valve 12 and the gas phase outlet at the top of the LNG buffer tank 2, so as to realize the precooling of the LNG storage tank 100 and part of the pipeline.

[0050] On the other hand, during the operation of the refrigerator 1, when the pressure of the LNG buffer tank 2 rises, the fourth valve 12 is opened, and the BOG in the LNG buffer tank 2 enters the LNG storage tank 100 from the gas phase port of the LNG storage tank 100 through the fourth valve 12 and the gas phase outlet of the LNG buffer tank 2, so as to realize the pressure reduction of the LNG buffer tank 2.

[0051] As shown in Figure 3 , Figure 4 , on the basis of the previous embodiment, in an embodiment, the first valve 5, the second valve 7, the third valve 9, the fourth valve 12 and the fifth valve 13 are electrically controlled valves,

[0052] The BOG liquefaction recovery device further comprises a controller 14, and the first control end, the second control end, the third control end, the fourth control end, the fifth control end, the sixth control end and the seventh control end of the controller 14 are connected with the first valve 5, the second valve 7, the third valve 9, the fourth valve 12, the fifth valve 13, the LNG pump 3 and the refrigerator 1 respectively.

[0053] In this embodiment, by setting each valve as an electrically controlled valve and setting the controller 14 to uniformly control each valve, the automation degree of the BOG liquefaction recovery device is effectively improved, and remote automatic control of the liquefaction recovery of the BOG in the LNG storage tank 100 is realized.

[0054] Specifically, in this embodiment, the controller 14 can adopt PLC.

[0055] As shown in Figure 3 , Figure 4 , on the basis of the previous embodiment, in an embodiment, the BOG liquefaction recovery device of the LNG storage tank further comprises a liquid level instrument 15, the liquid level instrument 15 is installed in the LNG buffer tank 2, and the signal output end of the liquid level instrument 15 is connected with the first signal input end of the controller 14,

[0056] The liquid level instrument 15 is used for detecting the liquid level signal of the LNG buffer tank 2.

[0057] In this embodiment, a liquid level meter 15 is provided to detect the liquid level signal of the LNG buffer tank 2. When it is detected that the liquid level of the LNG buffer tank 2 reaches a preset high liquid level threshold, the controller 14 starts the LNG pump 3 in an interlocked manner, and the pumped LNG enters the top liquid inlet or the bottom liquid inlet of the LNG storage tank 100 through the valve. When it is detected that the liquid level of the LNG buffer tank 2 reaches a preset low liquid level threshold, the controller 14 shuts down the LNG pump 3 in an interlocked manner, thereby realizing automatic control of the start and stop of the LNG pump 3 and improving the degree of automation of the BOG liquefaction recovery device.

[0058] like Figure 3 、 Figure 4 As shown, based on the previous embodiment, in one embodiment, the BOG liquefaction recovery device of the LNG storage tank further includes a first pressure transmitter 16, which is installed on the LNG buffer tank 2, and the signal output end of the first pressure transmitter 16 is connected to the second signal input end of the controller 14.

[0059] The first pressure transmitter 16 is used to detect the pressure signal of the LNG buffer tank 2 .

[0060] In this embodiment, a first pressure transmitter 16 is provided on the LNG buffer tank 2 to detect the pressure signal of the LNG buffer tank 2. When it is detected that the pressure of the LNG buffer tank 2 reaches a preset high pressure threshold, the controller 14 opens the fourth valve 12 in an interlocking manner. The BOG in the LNG buffer tank 2 enters the LNG storage tank 100 from the gas phase outlet of the LNG buffer tank 2 through the fourth valve 12 and the gas phase port of the LNG storage tank 100, thereby realizing automatic control of the pressure reduction of the LNG buffer tank 2.

[0061] like Figure 3 、 Figure 4 As shown, in one embodiment, the BOG liquefaction recovery device of the LNG storage tank further includes a second pressure transmitter 17 . The second pressure transmitter 17 is installed on the LNG storage tank 100 and is used to detect the pressure signal of the LNG storage tank 100 .

[0062] In this embodiment, a second pressure transmitter 17 is installed on the LNG storage tank 100 to detect the pressure signal of the LNG storage tank 100. When it is detected that the pressure of the LNG storage tank 100 reaches a preset maximum working pressure threshold of the tank, the controller 14 starts the refrigerator 1 in an interlocked manner to liquefy and recover the BOG in the LNG storage tank 100, thereby realizing automatic control of the liquefaction and recovery of the BOG in the LNG storage tank 100.

[0063] like Figures 1-3As shown, in one embodiment, control valves are provided at both the gas and liquid ports of the LNG storage tank 100. This facilitates controlling the opening and closing of the liquid and gas ports of the LNG storage tank 100 as needed. It is understood that the control valves at the gas and liquid ports of the LNG storage tank 100 can be either electrically controlled or manually operated.

[0064] like Figure 2 As shown, in one embodiment, the liquid phase port of the LNG storage tank 100 includes a bottom liquid phase port arranged at the bottom of the LNG storage tank 100, the second liquid phase pipeline 8 includes a liquid phase main pipe 801 and a second liquid phase branch pipe 803, one end of the liquid phase main pipe 801 is connected to the liquid outlet of the LNG pump 3, the other end of the liquid phase main pipe 801 is connected to one end of the second liquid phase branch pipe 803, the other end of the second liquid phase branch pipe 803 is connected to the bottom liquid phase port of the LNG storage tank 100, and the third valve 9 is installed on the liquid phase main pipe 801.

[0065] In this embodiment, a bottom liquid phase port is provided at the bottom of the LNG storage tank 100. When BOG within the LNG storage tank 100 needs to be recovered, the LNG that has been cooled and liquefied and entered the LNG buffer tank 2 can enter the LNG storage tank 100 through the bottom liquid phase port at the bottom of the LNG storage tank 100. The recovered LNG enters the LNG storage tank 100 from the bottom of the LNG storage tank 100, thereby cooling the LNG within the LNG storage tank 100 and reducing the pressure within the LNG storage tank 100, thereby further reducing the discharge of BOG within the LNG storage tank 100.

[0066] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. Reference can be made to the common and similar parts between the various embodiments. For the devices disclosed in the embodiments, since they correspond to the methods disclosed in the embodiments, the description is relatively simple, and the relevant parts can be referred to the method description.

[0067] Professionals may further appreciate that the units and algorithm steps of each example described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, computer software, or a combination of the two. In order to clearly illustrate the interchangeability of hardware and software, the above description has generally described the components and steps of each example according to their functions. Whether these functions are performed in hardware or software depends on the specific application and design constraints of the technical solution. Professionals and technicians may use different methods to implement the described functions for each specific application, but such implementation should not be considered beyond the scope of this application.

[0068] The steps of a method or algorithm described in connection with the embodiments disclosed herein can be embodied directly in hardware, in a software module executed by a processor, or in a combination of the two. A software module can reside in Random Access Memory (RAM), non-volatile memory (ROM), erasable programmable ROM (EPROM), electrically erasable programmable ROM (EEPROM), registers, hard disk, a removable disk, a CD-ROM, or any other form of storage medium known in the art

[0069] The above description of disclosed embodiments is intended to be illustrative and not restrictive. Many embodiments of the application will be apparent to those of skill in the art upon reviewing the above description. The scope of the application should, therefore, be determined not with reference to the above description, but instead should be given with reference to the appended claims, along with their full scope of equivalents.

Claims

1. A BOG liquefaction recovery device for an LNG storage tank, characterized in that: The LNG storage tank is provided with a gas phase port and a liquid phase port, wherein the gas phase port is provided at the top of the LNG storage tank. The BOG liquefaction recovery device includes a refrigerator, an LNG buffer tank and an LNG pump. The LNG pump is installed in the LNG buffer tank. A liquid phase inlet is provided at the bottom of the LNG buffer tank. The refrigerator is provided with a gas phase inlet and a liquid phase outlet. in, The gas phase port of the LNG storage tank is connected to the gas phase inlet of the refrigerator through a first gas phase pipeline, and a first valve is installed on the first gas phase pipeline. The liquid phase outlet of the refrigerator is connected to the liquid phase inlet of the LNG buffer tank through a first liquid phase pipeline, and a second valve is installed on the first liquid phase pipeline. The liquid outlet of the LNG pump is connected to the liquid phase port of the LNG storage tank through a second liquid phase pipeline, and a third valve is installed on the second liquid phase pipeline.

2. The BOG liquefaction recovery device for an LNG storage tank according to claim 1, characterized in that: The liquid phase port of the LNG storage tank includes a top liquid inlet arranged at the top of the LNG storage tank, the second liquid phase pipeline includes a liquid phase main pipe and a first liquid phase branch pipe, one end of the liquid phase main pipe is connected to the liquid outlet of the LNG pump, the other end of the liquid phase main pipe is connected to one end of the first liquid phase branch pipe, the other end of the first liquid phase branch pipe is connected to the top liquid inlet of the LNG storage tank, and the third valve is installed on the liquid phase main pipe.

3. The BOG liquefaction recovery device for an LNG storage tank according to claim 1, characterized in that: The liquid phase port of the LNG storage tank includes a bottom liquid phase port arranged at the bottom of the LNG storage tank, the second liquid phase pipeline includes a liquid phase main pipe and a second liquid phase branch pipe, one end of the liquid phase main pipe is connected to the liquid outlet of the LNG pump, the other end of the liquid phase main pipe is connected to one end of the second liquid phase branch pipe, the other end of the second liquid phase branch pipe is connected to the bottom liquid phase port of the LNG storage tank, and the third valve is installed on the liquid phase main pipe.

4. The BOG liquefaction recovery device for an LNG storage tank according to claim 2, characterized in that: The liquid phase port of the LNG storage tank also includes a bottom liquid phase port arranged at the bottom of the LNG storage tank, and the second liquid phase pipeline also includes a second liquid phase branch pipe, one end of the second liquid phase branch pipe is connected to the end of the liquid phase main pipe away from the LNG pump, and the other end of the second liquid phase branch pipe is connected to the bottom liquid phase port of the LNG storage tank.

5. The BOG liquefaction recovery device for an LNG storage tank according to claim 4, characterized in that: It also includes a second gas phase pipeline, a third liquid phase pipeline, a fourth valve and a fifth valve. The top of the LNG buffer tank is provided with a gas phase outlet, wherein, One end of the second gas phase pipeline is connected to the gas phase outlet of the LNG buffer tank, the other end of the second gas phase pipeline is connected to the end of the first gas phase pipeline close to the LNG storage tank, and the fourth valve is installed on the second gas phase pipeline; One end of the third liquid phase pipeline is connected to an end of the liquid phase main pipe close to the LNG pump, the other end of the third liquid phase pipeline is connected to an end of the first liquid phase pipeline close to the LNG buffer tank, and the fifth valve is installed on the third liquid phase pipeline.

6. The BOG liquefaction recovery device for an LNG storage tank according to claim 5, characterized in that: The first valve, the second valve, the third valve, the fourth valve and the fifth valve are all electrically controlled valves. The BOG liquefaction recovery device also includes a controller, wherein a first control end, a second control end, a third control end, a fourth control end, a fifth control end, a sixth control end, and a seventh control end of the controller are respectively connected to the first valve, the second valve, the third valve, the fourth valve, the fifth valve, the LNG pump, and the refrigerator.

7. The BOG liquefaction recovery device for an LNG storage tank according to claim 6, characterized in that: It also includes a liquid level meter, which is installed in the LNG buffer tank, and the signal output end of the liquid level meter is connected to the first signal input end of the controller. The liquid level meter is used to detect the liquid level signal of the LNG buffer tank.

8. The BOG liquefaction recovery device for an LNG storage tank according to claim 6, characterized in that: The controller further includes a first pressure transmitter, which is installed on the LNG buffer tank, and a signal output terminal of the first pressure transmitter is connected to a second signal input terminal of the controller. The first pressure transmitter is used to detect the pressure signal of the LNG buffer tank.

9. The BOG liquefaction recovery device for an LNG storage tank according to claim 1, characterized in that: The gas phase port and the liquid phase port of the LNG storage tank are both provided with control valves.

10. The BOG liquefaction recovery device for an LNG storage tank according to any one of claims 1 to 9, characterized in that: It also includes a second pressure transmitter, which is installed on the LNG storage tank and is used to detect the pressure signal of the LNG storage tank.

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