A BOG reliquefaction device

Abstract

This invention relates to the field of BOG (Bottle-Off Gas) processing technology and discloses a BOG reliquefaction device, including an installation platform. The installation platform is equipped with a control module, a primary compression module, a secondary compression module, a first cooling heat exchange module, a second cooling heat exchange module, a cooling module, and a buffer storage module. The control module controls the movement of the entire device. The primary compression module performs primary compression of the refrigerant, the secondary compression module performs secondary compression of the refrigerant, and the first cooling heat exchange module cools the refrigerant. It can maintain a stable tank pressure of 5-15 kPa under extreme conditions of zero external output and high ambient temperature. The cryogenic device and buffer tank are integrated on a single skid, resulting in high integration, small footprint, compact structure, and low energy consumption. It offers timely response to changing operating conditions, strong site adaptability, avoids direct BOG processing, and provides high safety and reliability. The cryogenic device uses a closed-loop system, resulting in a long maintenance-free period and simple operation and maintenance.

Description

Technical Field

[0001] This invention belongs to the field of BOG processing technology, specifically a BOG reliquefaction device. Background Technology

[0002] Liquefied natural gas (LNG) has a boiling point of approximately -163°C at atmospheric pressure. Although storage tanks employ high-vacuum multi-layer insulation, environmental heat leakage, flash evaporation, and atmospheric pressure changes can still cause LNG to continuously vaporize, generating 0.05%–0.10% / day of low-temperature boil-off gas (BOG). BOG accumulation can cause an increase in tank pressure. Direct venting or flaring would result in economic losses, methane emissions, and safety hazards; therefore, efficient recovery is essential.

[0003] Currently, traditional processing routes include:

[0004] (1) Direct compression for external transmission: BOG needs to be boosted to 30~90 bar, which consumes a lot of energy and depends on the downstream pipeline network, and has poor station adaptability.

[0005] (2) Flare / gas turbine combustion: simple but wasteful of cold energy and materials, with high CO2 and NOx emissions.

[0006] (3) Conventional recondensation: Low-pressure LNG is directly contacted with compressed BOG for heat exchange. The process is simple, but it is greatly affected by the fluctuation of ship-to-shore LNG export volume. Under low export conditions, the cold energy is insufficient, making it difficult to achieve full liquefaction of BOG.

[0007] To overcome the limitations of traditional BOG (Boiled Air Gathering) processing methods due to poor economics and "limited cooling energy," LNG reliquefaction utilizes a closed nitrogen reverse Brayton refrigeration cycle to actively cool BOG from -100℃ to approximately -160℃, causing it to completely condense. The LNG is then reinjected into the storage tank, enabling independent tank pressure control. This method is suitable for load fluctuations of 10% to 100%, with a methane recovery rate of >99%. It can provide a safe, economical, and low-carbon BOG solution for LNG storage and distribution stations, gas stations, and satellite tank farms. Summary of the Invention

[0008] In view of the above situation and to overcome the defects of the prior art, the present invention provides a BOG reliquefaction device that effectively solves the problems mentioned in the background art.

[0009] To achieve the above objectives, the present invention provides the following technical solution: a BOG reliquefaction device, comprising an installation platform, wherein the installation platform is provided with a control module, a primary compression module, a secondary compression module, a first cooling heat exchange module, a second cooling heat exchange module, a cooling module, and a buffer storage module;

[0010] The control module is used to control the movement of the entire device. The primary compression module is used to perform primary compression of the refrigerant. The secondary compression module is used to perform secondary compression of the refrigerant. The first cooling heat exchange module is used to cool the refrigerant to prevent excessive temperature from damaging subsequent electrical equipment and to prevent excessive temperature from affecting the cooling effect when entering the next stage. The second cooling heat exchange module is used to cool the refrigerant to prevent excessive temperature from damaging subsequent electrical equipment and to prevent excessive temperature from affecting the cooling effect when entering the next stage. The cooling module is used to cool and exchange heat with BOG so that BOG liquefies into LNG after heat exchange. The buffer storage module is used to buffer and store LNG.

[0011] Preferably, the primary compression module includes a mounting frame mounted on the mounting platform, a mounting plate mounted on the mounting frame, a mounting stand mounted on the mounting plate, a sliding table slidably connected to the mounting stand, a magnetic levitation compression-expansion integrated machine base fixedly mounted on the top of the sliding table, a magnetic levitation compression-expansion integrated machine mounted on the magnetic levitation compression-expansion integrated machine base, a primary compression input pipe connected to one end of the magnetic levitation compression-expansion integrated machine, a primary compression input pipe protective shell provided on the outer surface of the primary compression input pipe, a primary compression output pipe connected to one end of the magnetic levitation compression-expansion integrated machine, a primary compression circulation pipe connected to one end of the magnetic levitation compression-expansion integrated machine, a primary compression pipeline one connected to one end of the magnetic levitation compression-expansion integrated machine, a primary compression pipeline two connected to one end of the magnetic levitation compression-expansion integrated machine, a primary compression cooling conveying pipe connected to one end of the end wall of the magnetic levitation compression-expansion integrated machine on the same side as the primary compression input pipe, a primary compression cooling conveying pipe protective shell provided on the outer surface of the primary compression cooling conveying pipe, and a primary compression connecting pipe connected to one end of the magnetic levitation compression-expansion integrated machine.

[0012] Preferably, the secondary compression module includes a magnetic levitation secondary compressor base mounted on the mounting plate on one side of the mounting frame, a magnetic levitation secondary compressor mounted on the magnetic levitation secondary compressor base, a secondary compression output pipe connected to one end of the magnetic levitation secondary compressor, a tubular heat exchange conveying pipe connected to one end of the magnetic levitation secondary compressor on the same side as the tubular heat exchange conveying pipe, a circulation pipe connected to one end of the magnetic levitation secondary compressor on the same side as the secondary compression output pipe, a secondary compression connecting pipe connected to one end of the magnetic levitation secondary compressor, a secondary compression pipeline connected to one end of the magnetic levitation secondary compressor, and a secondary compression pipeline connected to one end of the magnetic levitation secondary compressor.

[0013] Preferably, the cooling heat exchange module one includes a tubular heat exchanger one, which is mounted on the mounting platform via a base. A base for a second tubular heat exchanger is mounted on the mounting platform, and a second tubular heat exchanger is mounted on the base. The second tubular heat exchanger is located above the first tubular heat exchanger. One side of the first tubular heat exchanger is connected to a cooling pipe, and the other side is connected to the other end of the secondary compression connecting pipe. The upper part of the first tubular heat exchanger is connected to one end of a heat exchange connecting pipe, and the other end of the heat exchange connecting pipe is connected to the upper part of the second tubular heat exchanger. One lower side of the first tubular heat exchanger is connected to one end of a heat exchange connecting pipe, and the other end of the heat exchange connecting pipe is connected to a water supply pipe. The end of the water supply pipe is connected to the lower part of the second tubular heat exchanger. The other end of the second primary compression pipeline is connected to the water supply pipeline. One side of the second tubular heat exchanger is connected to the other end of the first-stage compression connecting pipe. The other side of the second tubular heat exchanger is connected to one end of the heat exchange output pipeline, which is connected to the first-stage compression output pipe. Two electrically controlled valves are connected to the heat exchange connecting pipe. A cooling water pipeline is connected to the heat exchange connecting pipe between the electrically controlled valves. The other end of the first secondary compression pipeline is connected to the cooling water pipeline. The electrically controlled valve is connected to the first primary compression pipeline. The other end of the second secondary compression pipeline is connected to the water supply pipeline. The other end of the first primary compression pipeline is connected to the water supply pipeline.

[0014] Preferably, the second cooling heat exchange module includes a base for a tubular heat exchanger three and a base for a tubular heat exchanger four mounted on the mounting platform. A tubular heat exchanger three is mounted on the base for the tubular heat exchanger three, and a tubular heat exchanger four is mounted on the base for the tubular heat exchanger four. The tubular heat exchanger four is located above the tubular heat exchanger three. The other end of the tubular heat exchange delivery pipe is connected to the tubular heat exchanger four. A heat exchange connecting pipe is connected to one end of the tubular heat exchanger four. The other end of the water supply pipe is connected to the lower part of the tubular heat exchanger four. A connecting pipe is connected to one end of the water supply pipe, and the other end of the connecting pipe is connected to the lower part of the tubular heat exchanger three. The water supply pipe is provided with an interface to a cooling water return pipe. The interface is located between the connection point of the connecting pipe and the water supply pipe and the connection point of the water supply pipe and the tubular heat exchanger four. A branch pipe is connected to the other end of the cooling water pipe. One end of the branch pipe is connected to the upper part of the tubular heat exchanger four, and the electrically controlled valve is installed on the branch pipe near the tubular heat exchanger four. The other end of the branch pipe is connected to the upper part of the tubular heat exchanger three, and the electrically controlled valve is installed on the branch pipe near the tubular heat exchanger three. A self-cooling water supply pipe is provided in the cooling water pipe near the branch pipe. The other end of the primary compression circulation pipe is connected to the tubular heat exchanger three, and the other end of the secondary compression output pipe is connected to the tubular heat exchanger three.

[0015] Preferably, the cooling module mounting platform has a plate-fin heat exchanger base, with a plate-fin heat exchanger mounted on the upper part of the base. The other end of the primary compression input pipe is connected to the plate-fin heat exchanger, as are the other ends of the heat exchange connecting pipe and the primary compression output pipe. The other end of the primary compression cooling delivery pipe is also connected to the plate-fin heat exchanger. A branch pipe is connected to one end of the plate-fin heat exchanger, and the other end of the branch pipe is connected to the cooling working fluid input pipe. An input regulating valve is connected to the cooling working fluid input pipe. A liquid supply pipe is connected to one end of the branch pipe, and two input regulating valves are installed on the branch pipe, located on either side of the connection between the branch pipe and the liquid supply pipe. A branch connecting pipe is connected to one end of the heat exchange connecting pipe, and the other end of the branch connecting pipe is connected to the primary compression output pipe.

[0016] Preferably, the buffer storage module includes an LNG buffer tank installed on the installation platform. The LNG buffer tank is equipped with a user-side BOG pipeline, and a nitrogen sealing pipeline interface is connected to the user-side BOG pipeline. The LNG buffer tank is connected to a gas venting pipeline to the buffer tank and a gas analysis pipeline. One end of a circulation pipeline is connected to the LNG buffer tank, and a circulation pump is installed at the other end of the circulation pipeline. The electrically controlled valve is installed on the circulation pipeline. A pre-cooled LNG inlet interface is connected to the other end of the supply pipe. A supply connection pipe connects the supply pipe to the LNG buffer tank. A cooling working fluid input pipe is connected to the LNG storage... At one end of the tank pipeline, the cooling working fluid input pipe is connected to the end of one end of the nitrogen purging and evacuation pipeline, and at the other end of the LNG storage tank pipeline, the LNG storage tank pipeline interface is connected. An electrically controlled regulating valve is installed on the nitrogen purging and evacuation pipeline. The connection point between the nitrogen purging and evacuation pipeline and the cooling working fluid input pipe is located above the connection point between the branch pipe and the cooling working fluid input pipe. The connection point between the LNG storage tank pipeline and the cooling working fluid input pipe is located below the connection point between the branch pipe and the cooling working fluid input pipe. A flow rate regulator is installed on the liquid supply pipe.

[0017] Preferably, the control module includes a main power supply cabinet, a PLC cabinet, a frequency converter cabinet one, and a frequency converter cabinet two, which are sequentially installed on the installation platform.

[0018] Compared with the prior art, the beneficial effects of the present invention are:

[0019] 1. This invention provides a BOG reliquefaction device that can maintain a stable tank pressure of 5~15kPa under extreme operating conditions of zero external output and high ambient temperature.

[0020] 2. This invention provides a BOG reliquefaction device that integrates the cryogenic device and the buffer tank onto a single skid, resulting in high integration, small equipment footprint, compact structure, and low energy consumption.

[0021] 3. This invention provides a BOG reliquefaction device that responds promptly to changing operating conditions, has strong adaptability to the site, avoids direct BOG processing, and is highly safe and reliable. The cryogenic device adopts a closed-loop circulation, has a long maintenance-free period, and is simple to operate and maintain. Attached Figure Description

[0022] The accompanying drawings are provided to further illustrate the invention and form part of the specification. They are used together with the embodiments of the invention to explain the invention and do not constitute a limitation thereof.

[0023] In the attached diagram:

[0024] Figure 1 This is a schematic diagram of the first orientation structure of a BOG reliquefaction device according to the present invention;

[0025] Figure 2 This is a schematic diagram of the second orientation structure of a BOG reliquefaction device according to the present invention;

[0026] Figure 3 This is a third-direction structural diagram of a BOG reliquefaction device according to the present invention.

[0027] Figure 4 This is a schematic diagram of the fourth direction structure of a BOG reliquefaction device according to the present invention;

[0028] Figure 5 This is a schematic diagram of the fifth direction structure of a BOG reliquefaction device according to the present invention;

[0029] Figure 6 This is a schematic diagram of the first disassembled structure of a BOG reliquefaction device according to the present invention;

[0030] Figure 7 This is a schematic diagram of the second disassembled structure of a BOG reliquefaction device according to the present invention;

[0031] Figure 8 This is a schematic diagram of the third disassembled structure of a BOG reliquefaction device according to the present invention;

[0032] Figure 9 This is a schematic diagram of the fourth disassembled structure of a BOG reliquefaction device according to the present invention;

[0033] Figure 10 This is a schematic diagram of the fifth disassembled structure of a BOG reliquefaction device according to the present invention;

[0034] Figure 11 This is a schematic diagram of the sixth direction structure of a BOG reliquefaction device according to the present invention.

[0035] In the diagram: 1-Installation platform, 2-LNG buffer tank, 3-Main power supply cabinet, 4-PLC cabinet, 5-Variable frequency drive cabinet one, 6-Variable frequency drive cabinet two, 7-Mounting bracket, 8-Magnetic levitation secondary compressor, 9-Mounting plate, 10-Secondary compression output pipe, 11-Primary compression output pipe, 12-Primary compression circulation pipe, 13-Magnetic levitation compression expander, 14-Primary compression connection pipe, 15-Primary compression input pipe protective shell, 16-Primary compression input pipe, 17-Plate-fin heat exchanger, 18-Tube heat exchanger two, 19-Tube heat exchanger two Heat exchanger 1, 20-Secondary compression connection pipe, 21-Secondary compression pipeline 1, 22-Secondary compression pipeline 2, 23-Magnetic levitation secondary compressor base, 24-Primary compression pipeline 1, 25-Primary compression pipeline 2, 26-Magnetic levitation compression-expander integrated machine base, 27-Tube heat exchanger 3, 28-Tube heat exchanger 4, 29-Heat exchange connection pipe, 30-Primary compression cooling delivery pipe protective shell, 31-Primary compression cooling delivery pipe, 32-Tube heat exchange delivery pipe, 33-Cooling pipeline, 34-Electrically controlled valve, 35-Cooling water Piping, 36-Water supply pipeline, 37-Heat exchange output pipeline, 38-Heat exchange connection pipeline, 39-Branch pipe, 40-Cooling medium input pipe, 41-Input regulating valve, 42-Branch pipe, 43-Nitrogen blanketing pipeline interface, 44-From user-side BOG pipeline, 45-To gas analysis pipeline, 46-Pre-cooled LNG inlet interface, 47-To nitrogen purging and evacuation pipeline interface, 48-To LNG storage tank pipeline interface, 50-Circulation pipeline, 51-Circulation pump, 52-Supply pipe, 53-Flow rate regulator, 55-To LNG storage 56 - Nitrogen purging pipeline, 57 - Cooling water return pipe interface, 58 - Cooling water supply pipe, 59 - Branch connection pipe, 60 - Slide table, 61 - Mounting frame, 62 - Plate-fin heat exchanger base, 63 - Circulation pipe, 64 - Tubular heat exchanger base three, 65 - Connecting pipeline, 66 - Tubular heat exchanger base one, 67 - Tubular heat exchanger base two, 68 - Tubular heat exchanger base four, 69 - Heat exchange connecting pipe, 70 - Gas venting pipeline to buffer tank, 71 - Liquid supply connection pipe, 72 - Electrically controlled regulating valve. Detailed Implementation

[0036] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0037] like Figure 1-11As shown, the present invention provides a BOG reliquefaction device, including an installation platform 1, wherein the installation platform 1 is provided with a control module, a primary compression module, a secondary compression module, a cooling heat exchange module one, a cooling heat exchange module two, a cooling module and a buffer storage module;

[0038] The control module is used to control the movement of the entire device. The primary compression module is used to perform primary compression of the refrigerant. The secondary compression module is used to perform secondary compression of the refrigerant. The first cooling heat exchange module is used to cool the refrigerant to prevent excessive temperature from damaging subsequent electrical equipment and to prevent excessive temperature from affecting the cooling effect when entering the next stage. The second cooling heat exchange module is used to cool the refrigerant to prevent excessive temperature from damaging subsequent electrical equipment and to prevent excessive temperature from affecting the cooling effect when entering the next stage. The cooling module is used to cool and exchange heat with BOG so that BOG liquefies into LNG after heat exchange. The buffer storage module is used to buffer and store LNG.

[0039] The refrigerant consists of nitrogen, helium, and a small amount of methane.

[0040] Advantageously, the primary compression module includes a mounting frame 7 mounted on the mounting platform 1, a mounting plate 9 mounted on the mounting frame 7, a mounting stand 61 mounted on the mounting plate 9, a slide table 60 slidably connected to the mounting stand 61, a magnetic levitation compression-expansion integrated machine base 26 fixedly mounted on the top of the slide table 60, a magnetic levitation compression-expansion integrated machine 13 (for pressurizing and expanding the refrigerant) mounted on the magnetic levitation compression-expansion integrated machine base 26, one end of a primary compression input pipe 16 connected to the magnetic levitation compression-expansion integrated machine 13, and a primary compression input pipe protective shell 15 provided on the outer surface of the primary compression input pipe 16. One end of the first-stage compression output pipe 11 is connected to the magnetic levitation compression and expansion integrated machine 13. One end of the first-stage compression circulation pipe 12 is connected to the magnetic levitation compression and expansion integrated machine 13. One end of the first-stage compression pipeline 24 is connected to the magnetic levitation compression and expansion integrated machine 13. One end of the first-stage compression cooling and conveying pipe 31 is connected to the end wall of the magnetic levitation compression and expansion integrated machine 13 on the same side as the first-stage compression input pipe 16. The outer surface of the first-stage compression cooling and conveying pipe 31 is provided with a first-stage compression cooling and conveying pipe protective shell 30. One end of the first-stage compression connecting pipe 14 is connected to the magnetic levitation compression and expansion integrated machine 13.

[0041] Advantageously, the secondary compression module includes a magnetically levitated secondary compressor base 23 mounted on the mounting plate 9 on one side of the mounting frame 61. A magnetically levitated secondary compressor 8 (for pressurizing the refrigerant) is mounted on the magnetically levitated secondary compressor base 23. One end of the secondary compression output pipe 10 is connected to the magnetically levitated secondary compressor 8. One end of the tubular heat exchange conveying pipe 32 is connected to the magnetically levitated secondary compressor 8 on the same side as the tubular heat exchange conveying pipe 32. One end of the circulation pipe 63 is connected to the other end of the magnetically levitated secondary compressor 8 on the same side as the secondary compression output pipe 10. One end of the secondary compression connecting pipe 20 is connected to the magnetically levitated secondary compressor 8. One end of the first secondary compression pipeline 21 is connected to the magnetically levitated secondary compressor 8. One end of the second secondary compression pipeline 22 is connected to the magnetically levitated secondary compressor 8.

[0042] Advantageously, the first cooling heat exchange module includes a tubular heat exchanger 19 (for cooling the refrigerant). The tubular heat exchanger 19 is mounted on the mounting platform 1 via a tubular heat exchanger base 66. A second tubular heat exchanger base 67 is mounted on the mounting platform 1, and a second tubular heat exchanger 18 (for cooling the refrigerant) is mounted on the second tubular heat exchanger base 67. The second tubular heat exchanger 18 is located above the first tubular heat exchanger 19, and a cooling coil is connected to one side of the first tubular heat exchanger 19. Pipeline 33 connects the other end of the tubular heat exchanger 19 to the other end of the secondary compression connecting pipe 20. One end of heat exchange connecting pipe 38 is connected to the upper part of the tubular heat exchanger 19, and the other end of heat exchange connecting pipe 38 is connected to the upper part of the tubular heat exchanger 18. One end of heat exchange connecting pipe 69 is connected to the lower side of the tubular heat exchanger 19, and the other end of heat exchange connecting pipe 69 is connected to water supply pipe 36. One end of water supply pipe 36 is connected to the tubular heat exchanger 18. 8. The lower part is connected to the secondary compression pipeline 22, with the other end connected to the water supply pipeline 36. One side of the tubular heat exchanger 18 is connected to the other end of the primary compression connecting pipe 14. The other side of the tubular heat exchanger 18 is connected to one end of the heat exchange output pipeline 37, which is connected to the primary compression output pipe 11. Two electrically controlled valves 34 are connected to the heat exchange connecting pipeline 38 between the electrically controlled valves 34. There is a cooling water pipe 35, and the other end of a secondary compression pipe 21 is connected to the cooling water pipe 35. The electronically controlled valve 34 is connected to the secondary compression pipe 21. The other end of a primary compression pipe 25 is connected to the cooling water pipe 35. The electronically controlled valve 34 is connected to the primary compression pipe 25. The other end of a secondary compression pipe 22 is connected to the water supply pipe 36. The other end of a primary compression pipe 24 is connected to the water supply pipe 36.

[0043] Advantageously, the second cooling heat exchange module includes a tubular heat exchanger base 64 and a tubular heat exchanger base 68 mounted on the mounting platform 1. A tubular heat exchanger 27 (for cooling the refrigerant) is mounted on the tubular heat exchanger base 64, and a tubular heat exchanger 28 (for cooling the refrigerant) is mounted on the tubular heat exchanger base 68. The tubular heat exchanger 28 is located above the tubular heat exchanger 27, and the tubular heat exchanger delivery pipe... The other end of the 32 is connected to the tubular heat exchanger 28. A heat exchange connecting pipe 29 is connected to one end of the tubular heat exchanger 28. The other end of the water supply pipe 36 is connected to the lower part of the tubular heat exchanger 28. A connecting pipe 65 is connected to one end of the water supply pipe 36. The other end of the connecting pipe 65 is connected to the lower part of the tubular heat exchanger 27. The water supply pipe 36 is provided with a cooling water return pipe interface 57. The cooling water return pipe interface 57 is located between the connection point of the connecting pipe 65 and the water supply pipe 36 and the connection point of the water supply pipe 36 and the tubular heat exchanger 28. The other end of the cooling water pipe 35 is connected to a branch pipe 39. One end of the branch pipe 39 is connected to the upper part of the tubular heat exchanger 28, and the electrically controlled valve 34 is installed on the branch pipe 39 near the tubular heat exchanger 28. The other end of the branch pipe 39 is connected to the upper part of the tubular heat exchanger 27, and the electrically controlled valve 34 is installed on the branch pipe 39 near the tubular heat exchanger 27. The cooling water pipe 35 is provided with a self-cooling water supply pipe 58 near the branch pipe 39. The other end of the primary compression circulation pipe 12 is connected to the tubular heat exchanger 27, and the other end of the secondary compression output pipe 10 is connected to the tubular heat exchanger 27.

[0044] Advantageously, a plate-fin heat exchanger base 62 is installed on the cooling module mounting platform 1, and a plate-fin heat exchanger 17 (for deep cooling of LNG and reheating of the refrigerant) is installed on the upper part of the plate-fin heat exchanger base 62. The other end of the first-stage compression inlet pipe 16 is connected to the plate-fin heat exchanger 17, the other end of the heat exchange connecting pipe 29 is connected to the plate-fin heat exchanger 17, the other end of the first-stage compression outlet pipe 11 is connected to the plate-fin heat exchanger 17, and the other end of the first-stage compression cooling delivery pipe 31 is connected to the plate-fin heat exchanger 17. A branch pipe 42 is connected to the plate-fin heat exchanger 17. At one end of the branch pipe 42, the other end is connected to the cooling working fluid input pipe 40. One end of the cooling working fluid input pipe 40 is connected to the plate-fin heat exchanger 17. An input regulating valve 41 is connected to the cooling working fluid input pipe 40. One end of the branch pipe 42 is connected to the liquid supply pipe 52. Two input regulating valves 41 are installed on the branch pipe 42, and the input regulating valves 41 are located on both sides of the connection between the branch pipe 42 and the liquid supply pipe 52. One end of the branch connecting pipe 59 is connected to the heat exchange connecting pipe 29. The other end of the branch connecting pipe 59 is connected to the first-stage compression output pipe 11.

[0045] Advantageously, the buffer storage module includes an LNG buffer tank 2 installed on the installation platform 1 for BOG reliquefaction. The LNG buffer tank 2 is equipped with a user-side BOG pipeline 44, which is connected to a nitrogen sealing pipeline interface 43. The LNG buffer tank 2 is connected to a buffer tank gas vent pipeline 70 and a gas analysis pipeline 45. One end of a circulation pipeline 50 is connected to the LNG buffer tank 2, and a circulation pump 51 (for achieving LNG cryogenic circulation) is installed at the other end of the circulation pipeline 50. The electrically controlled valve 34 is installed on the circulation pipeline 50. A pre-cooled LNG inlet interface 46 is connected to the other end of the supply pipe 52. A supply connection pipe 71 connects the supply pipe 52 and the LNG buffer tank 2. The cooling working fluid input pipe 4... The cooling working fluid input pipe 40 is connected to one end of the LNG storage tank pipeline 55. The cooling working fluid input pipe 40 is connected to one end of the nitrogen purging and evacuation pipeline 56. The other end of the LNG storage tank pipeline 55 is connected to the LNG storage tank pipeline interface 48. The other end of the nitrogen purging and evacuation pipeline 56 is connected to the nitrogen purging and evacuation pipeline interface 47. An electrically controlled regulating valve 72 is installed on the nitrogen purging and evacuation pipeline 56. The connection between the nitrogen purging and evacuation pipeline 56 and the cooling working fluid input pipe 40 is located above the connection between the branch pipe 42 and the cooling working fluid input pipe 40. The connection between the LNG storage tank pipeline 55 and the cooling working fluid input pipe 40 is located below the connection between the branch pipe 42 and the cooling working fluid input pipe 40. A flow rate regulator 53 is installed on the liquid supply pipe 52.

[0046] Advantageously, the control module includes a main power supply cabinet 3 (for powering the entire device), a PLC cabinet 4 (as a control terminal for controlling the entire device), a frequency converter cabinet 5 (for controlling the magnetic levitation compression and expansion integrated machine 13), and a frequency converter cabinet 6 (for controlling the magnetic levitation secondary compressor 8) installed sequentially on the installation platform 1.

[0047] The entire process of the unit: The LNG reliquefaction unit consists of three cycles: LNG cycle, refrigerant cycle, and cooling water cycle. The process and methods used are as follows:

[0048] 1) LNG circulation: LNG is drawn from LNG buffer tank 2 by circulation pump 51, pressurized and enters plate-fin heat exchanger 17 through liquid supply pipe 52. Then it exchanges heat with refrigerant to obtain cooling capacity and becomes subcooled LNG. It is then sprayed back to LNG buffer tank 2 from the top of the tank, liquefying the evaporated gas in the upper space and cooling it into liquid phase, while balancing the pressure.

[0049] 2) Refrigerant Circulation: The refrigerant compression is performed in two stages. In the first stage, the refrigerant enters the compression end of the magnetic levitation compressor-expander 13 through the primary compression output pipe 11 to increase its temperature and pressure. It then flows out from the primary compression circulation pipe 12, is collected at the outlet of the compression end, and enters the tubular heat exchanger 27. It is cooled to room temperature through counter-current heat exchange with cooling water. The temperature of the refrigerant gas is about 3K higher than the inlet temperature of the cooling water. In the second stage, the refrigerant enters the magnetic levitation secondary compressor 8 through the secondary compression output pipe 10 for further pressurization, and then enters the tubular heat exchanger 28 through the tubular heat exchange delivery pipe 32 for cooling. After two stages of compression, the refrigerant then enters the plate-fin heat exchanger 17 for regenerative heat exchange, and then enters the expansion end of the magnetic levitation compressor-expander 13 through the primary compression cooling delivery pipe 31 for cooling and depressurization. It then returns to the plate-fin heat exchanger 17 through the primary compression input pipe 16 to provide cooling for the BOG. ​​After cooling is completed, it returns to the compression end inlet of the magnetic levitation compressor-expander 13. In addition, after the refrigerant is compressed in the first stage and cooled by the tubular heat exchanger 27, a branch is drawn from the primary compression circulation pipe 12 to provide cooling gas for the motor of the magnetic levitation secondary compressor 8. After heat exchange, the cooling gas enters the tubular heat exchanger 19 through the secondary compression connecting pipe 20. After heat exchange with the cooling water, it is cooled to room temperature and flows into the cooling pipe 33, which then serves as the motor cooling gas for the magnetic levitation compression-expansion integrated machine 13. After heat exchange, the cooling gas enters the tubular heat exchanger 18 through the primary compression connecting pipe 14. After heat exchange with the cooling water, it is cooled to room temperature and then flows into the primary compression output pipe 11 again.

[0050] 3) Cooling water circulation: The cooling water exchanges heat with the refrigerant at the compressor outlet through tubular heat exchanger 3 27 and tubular heat exchanger 4 28, and exchanges heat with the refrigerant used as motor cooling gas through tubular heat exchanger 1 19 and tubular heat exchanger 2 18 to cool the refrigerant.

[0051] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.

[0052] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A BOG reliquefaction device, characterized in that: The device includes an installation platform (1), which is equipped with a control module, a primary compression module, a secondary compression module, a cooling heat exchange module one, a cooling heat exchange module two, a cooling module, and a buffer storage module. The control module is used to control the movement of the entire device. The primary compression module is used to perform primary compression of the refrigerant. The secondary compression module is used to perform secondary compression of the refrigerant. The cooling heat exchange module one is used to cool the refrigerant to prevent excessive temperature from damaging subsequent electrical equipment and to prevent excessive temperature from affecting the cooling effect when entering the next stage. The cooling heat exchange module two is used to cool the refrigerant to prevent excessive temperature from damaging subsequent electrical equipment and to prevent excessive temperature from affecting the cooling effect when entering the next stage. The cooling module is used to cool and exchange heat with BOG so that BOG liquefies into LNG after heat exchange. The buffer storage module is used to buffer and store LNG. The first-stage compression module includes a mounting frame (7) installed on the mounting platform (1), a mounting plate (9) fixedly installed on the mounting frame (7), a mounting stand (61) mounted on the mounting plate (9), a sliding table (60) slidably connected on the mounting stand (61), a magnetic levitation compression and expansion integrated machine base (26) fixedly installed on the top of the sliding table (60), and a magnetic levitation compression and expansion integrated machine (13) installed on the magnetic levitation compression and expansion integrated machine base (26); the compression end inlet of the magnetic levitation compression and expansion integrated machine (13) is connected to one end of the first-stage compression output pipe (11), and the compression end outlet is connected to one end of the first-stage compression circulation pipe (12). The refrigerant enters the compression end of the magnetic levitation compression and expansion integrated machine (13) through the first-stage compression output pipe (11) to be heated and pressurized, and then flows out from the first-stage compression circulation pipe (12). At the same time, a branch is led out from the first-stage compression circulation pipe (12) to provide cooling gas for the motor of the second-stage compression module. The secondary compression module includes a magnetic levitation secondary compressor base (23) mounted on a mounting plate (9) on one side of the mounting frame (61), and a magnetic levitation secondary compressor (8) is mounted on the magnetic levitation secondary compressor base (23); the inlet of the magnetic levitation secondary compressor (8) is connected to one end of the secondary compression output pipe (10), the outlet is connected to one end of the tubular heat exchange conveying pipe (32), and its motor is connected to the cooling gas branch led out from the primary compression circulation pipe (12) for introducing cooling gas to cool the motor; After the first stage of cooling, the refrigerant enters the magnetic levitation second-stage compressor (8) through the second-stage compression output pipe (10) for further pressurization, and is then sent to the subsequent cooling structure for cooling through the tubular heat exchange delivery pipe (32); The cooling heat exchange module includes a tubular heat exchanger (19), which is mounted on the mounting platform (1) via a tubular heat exchanger base (66). A tubular heat exchanger base (67) is mounted on the mounting platform (1), and a tubular heat exchanger (18) is mounted on the tubular heat exchanger base (67). One side of the tubular heat exchanger (19) is connected to one end of the cooling pipe (33), and the other side is connected to one end of the secondary compression connecting pipe (20). The other end of the secondary compression connecting pipe (20) is connected to the motor cooling gas outlet of the magnetic levitation secondary compressor (8) for introducing the cooled gas after heat exchange. One side of the tubular heat exchanger (18) is connected to one end of the primary compression connecting pipe (14), and the other end of the cooling pipe (33) is connected to the magnetic levitation compressor expansion pipe. The motor cooling gas inlet of the expansion unit (13) is connected, and the other end of the first-stage compression connecting pipe (14) is connected to the motor cooling gas outlet of the magnetic levitation compression expansion unit (13). The cooling gas outlet of the tubular heat exchanger (18) is connected to the first-stage compression output pipe (11) to collect the cooled gas after heat exchange into the first-stage compression output pipe (11). The cooling gas drawn out from the first-stage compression circulation pipe (12) is cooled by the motor of the magnetic levitation second-stage compressor (8), and enters the tubular heat exchanger (19) through the second-stage compression connecting pipe (20) to exchange heat with the cooling water to room temperature. It then enters the cooling pipe (33) as the motor cooling gas of the magnetic levitation compression expansion unit (13). After heat exchange, the cooling gas enters the tubular heat exchanger (18) through the first-stage compression connecting pipe (14) to exchange heat to room temperature, and finally enters the first-stage compression output pipe (11) to re-enter the circulation. The second cooling heat exchange module includes a tubular heat exchanger base (64) and a tubular heat exchanger base (68) installed on the installation platform (1). A tubular heat exchanger (27) is installed on the tubular heat exchanger base (64), and a tubular heat exchanger (28) is installed on the tubular heat exchanger base (68). The tubular heat exchanger (27) is connected to the other end of the first-stage compression circulation pipe (12) and is used to cool the refrigerant after the first-stage compression. That is, the refrigerant flowing out of the first-stage compression circulation pipe (12) enters the tubular heat exchanger (27) and is cooled to room temperature by counter-current heat exchange with cooling water. The tubular heat exchanger (28) is connected to the other end of the tubular heat exchange conveying pipe (32) and is used to cool the refrigerant after the second-stage compression. After cooling, the refrigerant enters the plate-fin heat exchanger (17). The cooling module includes a plate-fin heat exchanger base (62) mounted on the mounting platform (1), and a plate-fin heat exchanger (17) is mounted on the upper part of the plate-fin heat exchanger base (62). The plate-fin heat exchanger (17) is connected to the tubular heat exchanger (28), the primary compression cooling conveying pipe (31), and the primary compression input pipe (16), respectively. The other end of the primary compression cooling conveying pipe (31) is connected to the expansion end inlet of the magnetic levitation compression expansion machine (13), and the other end of the primary compression input pipe (16) is connected to the magnetic levitation compression expansion machine. The expansion end outlet of the integrated unit (13) is connected to realize the refrigerant's heat exchange, cooling and depressurization, and cold energy supply. After two stages of compression and cooling, the refrigerant enters the plate-fin heat exchanger (17) for heat exchange, and then enters the expansion end of the magnetic levitation compression-expansion integrated unit (13) for cooling and depressurization via the first-stage compression cooling delivery pipe (31). Subsequently, it returns to the plate-fin heat exchanger (17) through the first-stage compression input pipe (16) to provide cold energy for the BOG. ​​After the cooling is completed, it returns to the compression end inlet of the magnetic levitation compression-expansion integrated unit (13) to complete the entire refrigerant cycle.

2. The BOG reliquefaction apparatus according to claim 1, characterized in that: The outer surface of the primary compression input pipe (16) is provided with a primary compression input pipe protective shell (15). The magnetic levitation compression expansion machine (13) is connected to one end of the primary compression pipeline (24). The magnetic levitation compression expansion machine (13) is connected to one end of the primary compression pipeline (25). The end of the primary compression cooling conveying pipe (31) is connected to the end wall of the magnetic levitation compression expansion machine (13) on the same side as the primary compression input pipe (16). The outer surface of the primary compression cooling conveying pipe (31) is provided with a primary compression cooling conveying pipe protective shell (30). The end of the primary compression connecting pipe (14) is connected to the magnetic levitation compression expansion machine (13).

3. The BOG reliquefaction apparatus according to claim 2, characterized in that: The magnetic levitation secondary compressor (8) on the same side as the tubular heat exchange conveying pipe (32) is connected to one end of a circulation pipe (63). The other end of the circulation pipe (63) is connected to the magnetic levitation secondary compressor (8) on the same side as the secondary compression output pipe (10). The magnetic levitation secondary compressor (8) is connected to one end of a secondary compression connecting pipe (20). The magnetic levitation secondary compressor (8) is connected to one end of a secondary compression pipeline (21). The magnetic levitation secondary compressor (8) is connected to one end of a secondary compression pipeline (22).

4. The BOG reliquefaction apparatus according to claim 3, characterized in that: The second tubular heat exchanger (18) is located above the first tubular heat exchanger (19). The other side of the first tubular heat exchanger (19) is connected to the other end of the secondary compression connecting pipe (20). The upper part of the first tubular heat exchanger (19) is connected to one end of the heat exchange connecting pipe (38). The other end of the heat exchange connecting pipe (38) is connected to the upper part of the second tubular heat exchanger (18). The lower side of the first tubular heat exchanger (19) is connected to one end of the heat exchange connecting pipe (69). The other end of the heat exchange connecting pipe (69) is connected to the water supply pipe (36). One end of the water supply pipe (36) is connected to the lower part of the second tubular heat exchanger (18). The other end of the second secondary compression pipe (22) is connected to the water supply pipe (36). The other side of the second tubular heat exchanger (18) is connected to the other end of the second tubular heat exchanger (18). The heat exchange output pipeline (37) is connected to one end of the heat exchange output pipeline (37), and the other end of the heat exchange output pipeline (37) is connected to the first-stage compression output pipeline (11). Two electrically controlled valves (34) are connected to the heat exchange connection pipeline (38), and a cooling water pipeline (35) is connected to the heat exchange connection pipeline (38) between the electrically controlled valves (34). The other end of the second-stage compression pipeline (21) is connected to the cooling water pipeline (25), and the electrically controlled valve (34) is connected to the second-stage compression pipeline (21). The other end of the first-stage compression pipeline (25) is connected to the cooling water pipeline (35), and the electrically controlled valve (34) is connected to the second-stage compression pipeline (25). The other end of the first-stage compression pipeline (24) is connected to the water supply pipeline (36).

5. A BOG reliquefaction apparatus according to claim 4, characterized in that: The tubular heat exchanger four (28) is located above the tubular heat exchanger three (27). A heat exchange connecting pipe (29) is connected to one end of the tubular heat exchanger four (28). The other end of the water supply pipe (36) is connected to the lower part of the tubular heat exchanger four (28). A connecting pipe (65) is connected to one end of the water supply pipe (36). The other end of the connecting pipe (65) is connected to the lower part of the tubular heat exchanger three (27). The water supply pipe (36) is provided with a cooling water return pipe interface (57). The cooling water return pipe interface (57) is located between the connection point of the connecting pipe (65) and the water supply pipe (36) and the connection point of the water supply pipe (36) and the tubular heat exchanger four (28). The other end of the cooling water pipe (35)... A diversion pipe (39) is connected to the upper part of the tubular heat exchanger four (28) on one side, and an electrically controlled valve (34) is installed on the diversion pipe (39) near the tubular heat exchanger four (28). The diversion pipe (39) is connected to the upper part of the tubular heat exchanger three (27) on the other side, and an electrically controlled valve (34) is installed on the diversion pipe (39) near the tubular heat exchanger three (27). A cooling water pipeline (35) is provided with a self-cooling water supply pipe (58) near the diversion pipe (39). The other end of the primary compression circulation pipe (12) is connected to the tubular heat exchanger three (27). The other end of the secondary compression output pipe (10) is connected to the tubular heat exchanger three (27).

6. A BOG reliquefaction apparatus according to claim 5, characterized in that: The other end of the primary compression input pipe (16) is connected to the plate-fin heat exchanger (17), the other end of the heat exchange connecting pipe (29) is connected to the plate-fin heat exchanger (17), the other end of the primary compression output pipe (11) is connected to the plate-fin heat exchanger (17), the other end of the primary compression cooling conveying pipe (31) is connected to the plate-fin heat exchanger (17), one end of the plate-fin heat exchanger (17) is connected to a branch pipe (42), the other end of the branch pipe (42) is connected to the cooling working fluid input pipe (40), the cooling working fluid input pipe ( 40) One end is connected to the plate-fin heat exchanger (17). An input regulating valve (41) is connected to the cooling working fluid input pipe (40). One end of the supply pipe (52) is connected to the branch pipe (42). Two input regulating valves (41) are installed on the branch pipe (42). The input regulating valves (41) are located on both sides of the connection between the branch pipe (42) and the supply pipe (52). One end of the branch connecting pipe (59) is connected to the heat exchange connecting pipe (29). The other end of the branch connecting pipe (59) is connected to the first-stage compression output pipe (11).

7. A BOG reliquefaction apparatus according to claim 6, characterized in that: The buffer storage module includes an LNG buffer tank (2) installed on the installation platform (1). A user-side BOG pipeline (44) is installed on the LNG buffer tank (2). A nitrogen sealing pipeline interface (43) is connected to the user-side BOG pipeline (44). A gas venting pipeline (70) to the buffer tank and a gas analysis pipeline (45) to the LNG buffer tank (2) are connected. One end of a circulation pipeline (50) is connected to the LNG buffer tank (2). A circulation pump (51) is installed at the other end of the circulation pipeline (50). The electrically controlled valve (34) is installed on the circulation pipeline (50). A pre-cooled LNG inlet interface (46) is connected to the other end of the liquid supply pipe (52). A liquid supply connection pipe (71) connects the liquid supply pipe (52) and the LNG buffer tank (2). A line to the LNG storage tank is connected to the cooling working fluid input pipe (40). At one end of the pipeline (55), the cooling working fluid input pipe (40) is connected to one end of the nitrogen purging pipeline (56), and at the other end of the pipeline to the LNG storage tank (55), the LNG storage tank pipeline interface (48) is connected. At the other end of the pipeline to the nitrogen purging pipeline (56), the nitrogen purging pipeline interface (47) is connected. An electrically controlled regulating valve (72) is installed on the nitrogen purging pipeline (56). The connection between the nitrogen purging pipeline (56) and the cooling working fluid input pipe (40) is located above the connection between the branch pipe (42) and the cooling working fluid input pipe (40). The connection between the pipeline to the LNG storage tank (55) and the cooling working fluid input pipe (40) is located below the connection between the branch pipe (42) and the cooling working fluid input pipe (40). A flow rate regulator (53) is installed on the liquid supply pipe (52).

8. A BOG reliquefaction apparatus according to claim 7, characterized in that: The control module includes a main power cabinet (3), a PLC cabinet (4), a frequency converter cabinet one (5), and a frequency converter cabinet two (6) installed sequentially on the installation platform (1).

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