BOG helium extraction device

Abstract

The utility model belongs to the technical field of helium extraction, and particularly relates to a BOG (Boil Off Gas) helium extraction device which comprises a low-temperature crude extraction system, a low-temperature rectification system, a circulating oxygenation, hydrogen removal and methane removal system, a low-temperature condensation system, a low-temperature adsorption system and a vacuumizing system, a liquid nitrogen storage tank is arranged outside the two low-temperature adsorbers, liquid nitrogen is contained in the liquid nitrogen storage tank, and the liquid nitrogen storage tank is connected with the vacuumizing system. According to the utility model, the BOG gas is taken as a raw material, helium in the BOG gas is extracted through low-temperature crude extraction, cyclic oxygenation, hydrogen removal and methane removal, low-temperature condensation and low-temperature adsorption, the purity of the obtained high-purity helium reaches 99.999%, the pressure in the liquid nitrogen storage tank is less than 1KPa under the action of the vacuum-pumping system, the vaporization rate of liquid nitrogen is higher, more heat is absorbed, and the purpose of high-purity helium extraction is achieved. The adsorption efficiency of the second adsorber is improved, and the consumption of liquid nitrogen is reduced.

Description

Technical Field

[0001] The utility model belongs to the technical field of helium extraction, and particularly relates to a BOG helium extraction device. Background Art

[0002] Helium is a rare gas found primarily in the atmosphere, rocks, and natural gas. Normally colorless and odorless, helium is the only substance that does not solidify under standard atmospheric pressure. Its unique physical properties dictate its unique applications, including military, scientific research, petrochemicals, refrigeration, healthcare, semiconductors, pipeline leak detection, superconducting experiments, metal manufacturing, deep-sea diving, high-precision welding, and optoelectronics production, making it of great significance to scientific research.

[0003] There are many feasible solutions for extracting helium from BOG at home and abroad, some of which have been industrialized, such as cryogenic method, liquefaction method, pressure swing adsorption method, membrane separation, etc.

[0004] For example, a BOG helium extraction system and method, published in CN114264116A, includes a cryogenic distillation unit and a palladium membrane separation and dehydrogenation unit. The cryogenic distillation unit is used to separate BOG through cryogenic methods to obtain a first-stage crude helium gas containing small amounts of nitrogen, hydrogen, and oxygen. The palladium membrane separation and dehydrogenation unit is used to remove hydrogen from the first-stage crude helium gas through a palladium membrane separation process to obtain a second-stage crude helium gas. Although membrane separation has significant advantages in terms of modularity and energy efficiency, it can only produce helium with a concentration of 99%. Utility Model Content

[0005] The purpose of the present invention is to provide a BOG helium extraction device to solve the problems raised in the above background technology.

[0006] In order to achieve the above technical objectives, the technical solution of the utility model is:

[0007] A BOG helium extraction device comprises a cryogenic crude extraction system, a cryogenic distillation system, a circulating oxygenation, hydrogenation and methane removal system, a cryogenic condensation system, a cryogenic adsorption system and a vacuum system. The cryogenic crude extraction system uses a cryogenic method to separate crude helium from BOG gas. The circulating oxygenation, hydrogenation and methane removal system removes hydrogen and methane from the crude helium to obtain rich helium. The cryogenic condensation system uses a cryogenic method to separate refined helium from the rich helium. The cryogenic adsorption system removes nitrogen and oxygen from the refined helium by cryogenic adsorption to obtain high-purity helium.

[0008] The low-temperature adsorption system includes two low-temperature adsorbers arranged in parallel. Liquid nitrogen storage tanks are provided outside the two low-temperature adsorbers. Liquid nitrogen is contained in the liquid nitrogen storage tanks, and the liquid nitrogen storage tanks are connected to the vacuum pumping system.

[0009] As an improvement, the low-temperature crude extraction system includes a first heat exchanger, in which a BOG gas pipeline and a liquid nitrogen pipeline are provided. The outlet of the BOG gas pipeline is connected to a first separation tank, the top outlet of the first separation tank is connected to the circulating oxygenation, dehydrogenation and demethane removal system, and the bottom outlet of the first separation tank is connected to the low-temperature distillation system.

[0010] As a further improvement, the circulating oxygenation, dehydrogenation and demethane removal system comprises a buffer tank, a mixer, a preheater, a reactor, a cooler and a first adsorber connected in sequence, and the inlet of the buffer tank is connected to the top outlet of the first separation tank;

[0011] The outlet of the first adsorber is connected to a circulating air compressor and a compressor. The inlets of the circulating air compressor and the compressor are both provided with automatic valves. The outlet of the circulating air compressor is connected to the inlet of the buffer tank through a pipeline, and the outlet of the compressor is connected to the low-temperature condensation system.

[0012] As a further improvement, the low-temperature condensation system includes a second heat exchanger, the second heat exchanger includes a helium-rich gas pipeline and a liquid nitrogen pipeline, the inlet of the helium-rich gas pipeline is connected to the compressor outlet, the outlet of the helium-rich gas pipeline is connected to a second separation tank, and the top outlet of the second separation tank is connected to the inlet of the second heat exchanger.

[0013] As a further improvement, the vacuum pumping system includes a third heat exchanger connected to the liquid nitrogen storage tank, and the outlet of the third heat exchanger is connected to a vacuum pump.

[0014] As a further improvement, a methane pipeline and a nitrogen pipeline are further provided in the first heat exchanger, the inlet of the methane pipeline is connected to the bottom outlet of the cryogenic distillation system, and the inlet of the nitrogen pipeline is connected to the top outlet of the cryogenic distillation system.

[0015] As a further improvement, the first adsorber includes two dry adsorbers arranged in parallel, a nitrogen inlet is provided at the bottom of the two dry adsorbers, the nitrogen inlet is connected to an external electric heating furnace, a regeneration gas outlet is provided at the top of the dry adsorber, and the two dry adsorbers are filled with molecular sieves, alumina and activated carbon.

[0016] As a further improvement, a nitrogen and oxygen pipeline is further provided in the second heat exchanger, and the inlet of the nitrogen and oxygen pipeline is connected to the bottom outlet of the second separation tank.

[0017] Due to the adoption of the above technical solution, the beneficial effects of the utility model are:

[0018] The BOG helium extraction device provided by the utility model removes a large amount of methane and nitrogen through a low-temperature crude extraction system, then removes hydrogen and methane through a circulating oxygenation, dehydrogenation and demethane system, then removes nitrogen and a small amount of oxygen through a low-temperature condensation system, and finally removes impurities in the refined helium through a low-temperature adsorption system to obtain high-purity helium. The purity of the high-purity helium reaches 99.999%, which is even higher.

[0019] In the circulating oxygenation, dehydrogenation and methane removal system, the rich helium gas after drying and adsorption is returned to the buffer tank for circulation to add oxygen, dehydrogenate and remove methane. The rich helium gas returned to the buffer tank is mixed with the crude helium gas in the buffer tank, which can dilute the hydrogen content in the crude helium gas in the buffer tank and remove the reaction heat in time.

[0020] The nitrogen vaporized by heat exchange in the liquid nitrogen storage tank is discharged through a vacuum pump, and the pressure in the liquid nitrogen storage tank is reduced to less than 1KPa. The vaporization rate of liquid nitrogen is higher and more heat is absorbed, which improves the adsorption efficiency of the second adsorber and reduces the consumption of liquid nitrogen. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 This is the equipment flow chart of the BOG helium extraction device of the utility model;

[0022] Among them: 1-first heat exchanger, 2-first separation tank, 3-distillation tower, 4-buffer tank, 5-mixer, 6-preheater, 7-reactor, 8-cooler, 9-first adsorber, 10-vacuum pump, 11-circulating air compressor, 12-compressor, 13-second heat exchanger, 14-second separation tank, 15-second adsorber, 16-third heat exchanger, 17-external electric heating furnace, 18-product tank, 19-BOG gas pipeline, 20-liquid nitrogen pipeline, 21-methane pipeline, 22-nitrogen pipeline, 23-enriched helium pipeline, 24-nitrogen and oxygen pipeline, 25-refined helium pipeline, 26-vent pipeline. DETAILED DESCRIPTION

[0023] The present invention is further described below with reference to specific embodiments and accompanying drawings. The accompanying drawings are for illustrative purposes only and are schematic, not actual, representations. They should not be construed as limiting the present invention. To better illustrate the embodiments of the present invention, some components in the accompanying drawings may be omitted, enlarged, or reduced in size, and do not represent the actual dimensions of the product. It is understandable to those skilled in the art that some well-known structures and their descriptions may be omitted from the accompanying drawings.

[0024] The same or similar numbers in the drawings of the embodiments of the present invention correspond to the same or similar parts; in the description of the present invention, it should be understood that if the terms "up", "down", "left", "right", etc. indicate directions or positional relationships, they are based on the directions or positional relationships shown in the drawings. This is only for the convenience of describing the present invention and simplifying the description, and does not indicate or imply that the device or element referred to must have a specific direction, be constructed and operated in a specific direction. Therefore, the terms describing the positional relationship in the drawings are only used for illustrative purposes and cannot be understood as limiting the present application. For ordinary technicians in this field, the specific meanings of the above terms can be understood according to specific circumstances.

[0025] like Figure 1 As shown, a BOG helium extraction device includes a cryogenic crude extraction system, a cryogenic distillation system, a circulating oxygenation, dehydrogenation and methane removal system, a cryogenic condensation system, a cryogenic adsorption system and a vacuum system. BOG gas first enters the cryogenic crude extraction system to remove methane and nitrogen to obtain crude helium gas. The crude helium gas enters the circulating oxygenation, dehydrogenation and methane removal system, where hydrogen and methane in the crude helium gas react with oxygen to generate water and carbon dioxide, respectively. The water and carbon dioxide are then removed by dry adsorption to obtain rich helium gas. The rich helium gas enters the cryogenic condensation system, where nitrogen and oxygen in the rich helium gas are liquefied and separated to obtain refined helium gas. The refined helium gas enters the cryogenic adsorption system, where a small amount of nitrogen, oxygen and other impurities in the refined helium gas are adsorbed at low temperature to obtain high-purity helium gas.

[0026] In this embodiment, the cryogenic crude extraction system includes a first heat exchanger 1 and a first separator 2. A BOG gas pipeline 19 and a liquid nitrogen pipeline 20 are provided within the first heat exchanger 1. BOG gas enters the BOG gas pipeline 19 and undergoes cryogenic heat exchange with liquid nitrogen within the liquid nitrogen pipeline 20, liquefying the methane and nitrogen in the BOG gas. The BOG gas then enters the first separator 2. The crude helium enters the circulating oxygenation, hydrogenation, and methane removal system from the top of the first separator 2, while the methane and nitrogen enter the cryogenic distillation system from the bottom of the first separator 2.

[0027] The cryogenic distillation system includes a distillation tower 3. A methane pipeline 21 and a nitrogen pipeline 22 are also provided in the first heat exchanger 1. In the distillation tower 3, according to the different boiling points of methane and nitrogen, methane enters the methane pipeline 21 of the first heat exchanger 1 from the bottom of the distillation tower 3, and nitrogen enters the nitrogen pipeline 22 of the first heat exchanger 1 from the top of the distillation tower 3. After heat exchange in the first heat exchanger 1, the methane enters the subsequent recovery and utilization process, and the nitrogen is discharged after heat exchange in the first heat exchanger 1. The energy in the methane and nitrogen is recovered through the first heat exchanger 1 to improve the energy utilization rate.

[0028] In this embodiment, the circulating oxygenation, dehydrogenation and demethane removal system includes a buffer tank 4, a mixer 5, a preheater 6, a reactor 7, a cooler 8 and a first adsorber 9. The crude helium enters the buffer tank 4 from the first separation tank 2 and then enters the mixer 5. It is mixed with oxygen in the mixer 5 to form a mixed gas. The mixed gas enters the preheater 6 and is preheated to 60°C in the preheater 6. Then it enters the reactor 7. The reactor includes a hydrogen reactor and a methane reactor. The mixed gas enters the hydrogen reactor. The oxygen and hydrogen in the mixer react. The mixed gas is heated to 72-132°C in the hydrogen reactor and then enters the methane reactor. In the methane reactor, after the mixed gas is heated to 330-440°C, the oxygen and methane in the mixed gas react. The reacted gas enters the cooler 8 and is cooled in the cooler 8 before entering the first adsorber 9. The first adsorber 9 is filled with molecular sieves, alumina and activated carbon. In the first adsorber 9, water and carbon dioxide are adsorbed to obtain rich helium gas, which enters the low-temperature condensation system.

[0029] The first adsorber 9 includes two parallel dry adsorbers. When one dry adsorber is adsorbing, the other dry adsorber is regenerating. Automatic switching valves are provided at the inlets of the two dry adsorbers. In actual use, the system for extracting high-purity helium from BOG also includes a carbon dioxide analyzer. The carbon dioxide analyzer can be provided between the dry adsorber and the low-temperature condensation system. The carbon dioxide content in the refined helium gas is detected by the carbon dioxide analyzer. When the carbon dioxide content in the refined helium gas is detected to be greater than 0.8 ppm, the automatic switching valve automatically switches, so that the dry adsorber originally in the adsorption program undergoes the regeneration program, and the dry adsorber that has completed the regeneration enters the adsorption program. In this way, the two dry adsorbers are automatically switched and used, and the adsorption efficiency is higher.

[0030] The outlet of the cooler 8 is connected to the bottom inlet of the dry adsorber. A regeneration inlet is also provided at the bottom of the dry adsorber, which is connected to the outlet of the external electric heating furnace 17. Nitrogen is introduced into the inlet of the external electric heating furnace 17. After being heated by the external electric heating furnace 17, the nitrogen enters the dry adsorber to regenerate the dry adsorber. A regeneration gas outlet is provided at the top of the dry adsorber, and the regenerated gas after the regeneration of the dry adsorber is discharged from the regeneration gas outlet.

[0031] In this embodiment, the circulating oxygenation, dehydrogenation and methane removal system also includes a circulating air compressor 11 and a compressor 12 connected to the outlet of the first adsorber 9. Automatic valves are provided at the inlets of the circulating air compressor 11 and the compressor 12. The outlet of the circulating air compressor 11 is connected to the inlet of the buffer tank 4, and the outlet of the compressor 12 is connected to the low-temperature condensation system. The helium-rich gas at the outlet of the first adsorber 9 is transported to the buffer tank 4 through the circulating air compressor 11 for further oxygenation, dehydrogenation and methane removal, pushing the gas to circulate in the circulating oxygenation, dehydrogenation and methane removal system to dilute the hydrogen content in the crude helium gas in the buffer tank 4. Part of the rich helium gas enters the low-temperature condensation system through the compressor 12. A methane content detection device is provided at the outlet of the circulating air compressor 11 to detect the methane content in the rich helium gas. Under normal circumstances, the methane content in the rich helium gas meets the process standards. However, if it is detected that the methane content in the rich helium gas does not meet the process standards, it means that there is a problem with the operation of the circulating oxygenation, dehydrogenation and methane removal system and it needs to be adjusted.

[0032] In this embodiment, the low-temperature condensation system includes a second heat exchanger 13 and a second separation tank 14. The second heat exchanger 13 includes a helium-rich gas pipeline 23 and a liquid nitrogen pipeline 20. The helium-rich gas from the compressor 12 enters the helium-rich gas pipeline 23, exchanges heat with the liquid nitrogen in the liquid nitrogen pipeline 20 to cool down, and the nitrogen and oxygen in the helium-rich gas are liquefied, and then the helium-rich gas enters the second separation tank 14.

[0033] A nitrogen and oxygen pipeline 24 is also provided in the second heat exchanger 13. The liquefied nitrogen and oxygen enter the nitrogen and oxygen pipeline 24 of the second heat exchanger 13 from the bottom of the second separation tank 14. The liquefied nitrogen and oxygen exchange heat with the helium-rich gas in the helium-rich gas pipeline 23, and the cold energy of the liquefied nitrogen and oxygen is recovered, and then discharged from the outlet of the liquid nitrogen pipeline 20.

[0034] A refined helium pipeline 25 is further provided in the second heat exchanger 13. The refined helium gas at the top outlet of the second separation tank enters the refined helium pipeline 25 of the second heat exchanger 13, exchanges heat with liquid nitrogen, and then enters the cryogenic adsorption system.

[0035] In this embodiment, the cryogenic adsorption system includes a second adsorber 15, which includes two cryogenic adsorbers. The two cryogenic adsorbers are arranged in parallel. Both cryogenic adsorbers are filled with molecular sieves and activated carbon to adsorb residual oxygen, nitrogen and other impurities in the refined helium gas to obtain high-purity helium. The outlet of the cryogenic adsorber is connected to the product tank 18, and the high-purity helium is pressurized at the outlet of the cryogenic adsorber and transported to the product tank 18.

[0036] In this embodiment, a liquid nitrogen storage tank is provided outside each of the two cryogenic adsorbers. The liquid nitrogen storage tank is filled with liquid nitrogen. The liquid nitrogen serves as a cold source to provide cooling capacity to the cryogenic adsorber for cryogenic adsorption. The liquid nitrogen storage tank is connected to a vacuum pumping system, which includes a third heat exchanger 16 and a vacuum pump 10. During the cryogenic adsorption process, refined helium gas enters the interior of the cryogenic adsorber. A small amount of nitrogen, oxygen, and other impurities in the refined helium gas are adsorbed by the molecular sieve and activated carbon in the cryogenic adsorber. At the same time, the liquid nitrogen in the liquid nitrogen storage tank exchanges heat with the adsorbed nitrogen and oxygen in the cryogenic adsorber, so that the temperature in the cryogenic adsorber is always maintained at a deep cold condition. After the liquid nitrogen in the liquid nitrogen storage tank is vaporized by heat exchange, it enters the third heat exchanger 16 for further heat exchange and is then discharged through the vacuum pump 10. Due to the vacuum pumping action of the vacuum pump 10, the pressure in the liquid nitrogen storage tank is less than 1 kPa, the vaporization rate of the liquid nitrogen is higher, and more heat is absorbed, thereby improving the adsorption efficiency and reducing the consumption of liquid nitrogen.

[0037] A regeneration inlet is provided at the bottom of each of the two cryogenic adsorbers, and the regeneration inlet is connected to an external electric heating furnace 17. A regeneration gas outlet is provided at the top of each of the two cryogenic adsorbers. Automatic switching valves are provided at the inlets of each of the two cryogenic adsorbers. In actual use, a high-purity helium quality detection device is provided at the inlet of the product tank 18 to detect the impurity content in the high-purity helium, and to control the opening and closing of the automatic switching valves at the inlets of the two cryogenic adsorbers. The two cryogenic adsorbers perform the regeneration procedure and the adsorption procedure alternately.

[0038] In this embodiment, a vent line 26 is also included. The vent line 26 is connected to the nitrogen line 22 in the first heat exchanger, the nitrogen oxygen line 24 in the second heat exchanger, the regeneration gas line at the top of the first adsorber, and the regeneration gas line at the top of the second adsorber. The gases in the nitrogen line 22, the nitrogen oxygen line 24, and the regeneration gas line are all discharged through the vent line 26.

[0039] When this embodiment is in use, the BOG gas enters the cryogenic crude extraction system. After deep cooling and heat exchange in the first heat exchanger, the methane and nitrogen in the BOG gas are liquefied and then enter the first separation tank. The crude helium enters the circulating oxygenation, dehydrogenation and methane removal system from the top of the first separation tank. The liquefied methane and oxygen enter the cryogenic distillation system from the bottom of the first separation tank. Methane enters the methane pipeline 21 of the first heat exchanger from the bottom of the distillation tower, and nitrogen enters the nitrogen pipeline 22 of the first heat exchanger from the top of the distillation tower.

[0040] In the circulating oxygenation, dehydrogenation and methane removal system, the crude helium first enters the buffer tank 4, then enters the mixer 5 to be mixed with oxygen, enters the preheater to be preheated to 60°C, and then enters the reactor 7. In the reactor, the oxygen and hydrogen in the mixed gas react and the temperature is raised to 72-132°C. The mixed gas then enters the methane reactor, where the oxygen and methane in the mixed gas react. The reacted gas enters the cooler 8, is cooled in the cooler 8, and then enters the first adsorber 9. In the first adsorber 9, water and carbon dioxide are adsorbed to obtain rich helium gas. Part of the rich helium gas is transported to the buffer tank 4 through the circulating air compressor 11 to continue oxygenation, dehydrogenation and methane removal, thereby diluting the hydrogen content in the crude helium in the buffer tank 4 and reducing the methane content in the rich helium gas. Part of the rich helium gas enters the low-temperature condensation system through the compressor 12;

[0041] The rich helium gas is in the cryogenic condensation system and undergoes deep cooling and heat exchange in the second heat exchanger, where the nitrogen and oxygen in the gas are liquefied. The rich helium gas then enters the second separation tank. The refined helium gas enters the refined helium pipeline 25 of the second heat exchanger from the top of the second separation tank, and the liquefied nitrogen and oxygen enter the nitrogen and oxygen pipeline 24 of the second heat exchanger from the bottom of the second separation tank.

[0042] After the refined helium undergoes cryogenic heat exchange in the second heat exchanger, it enters the cryogenic adsorber of the cryogenic adsorption system. A small amount of impurities in the refined helium are adsorbed to obtain high-purity helium, which enters the product tank. The liquid nitrogen in the liquid nitrogen storage tank exchanges heat with the adsorbed nitrogen and oxygen in the cryogenic adsorber, so that the interior of the cryogenic adsorber is always in a cryogenic condition. After the liquid nitrogen in the liquid nitrogen storage tank is vaporized by heat exchange, it enters the third heat exchanger 16 for further heat exchange and is then discharged through the vacuum pump 10. During actual use, the vacuum pump is always in working condition.

[0043] The utility model uses BOG gas as raw material, extracts helium from the BOG gas through low-temperature crude extraction, cyclic oxygenation to remove hydrogen and methane, low-temperature condensation, and low-temperature adsorption. The purity of the obtained high-purity helium reaches 99.999%. In addition, through the action of the vacuum system, the pressure in the liquid nitrogen storage tank is reduced to less than 1KPa, the vaporization rate of the liquid nitrogen is higher, and more heat is absorbed, thereby improving the adsorption efficiency of the second adsorber and reducing the consumption of liquid nitrogen.

[0044] The specific embodiments of the present invention described above do not limit the scope of protection of the present invention. Any other corresponding changes and modifications made based on the technical concept of the present invention should be included in the scope of protection of the claims of the present invention.

Claims

1. A BOG helium extraction device, characterized in that: It includes a low-temperature crude extraction system, a low-temperature distillation system, a circulating oxygenation, hydrogenation and methane removal system, a low-temperature condensation system, a low-temperature adsorption system and a vacuum system. The low-temperature crude extraction system uses a cryogenic method to separate crude helium from BOG gas, the circulating oxygenation, hydrogenation and methane removal system removes hydrogen and methane from the crude helium to obtain rich helium, the low-temperature condensation system uses a cryogenic method to separate refined helium from the rich helium to obtain refined helium, and the low-temperature adsorption system removes nitrogen and oxygen from the refined helium by low-temperature adsorption to obtain high-purity helium. The low-temperature adsorption system includes two low-temperature adsorbers arranged in parallel. Liquid nitrogen storage tanks are provided outside the two low-temperature adsorbers. Liquid nitrogen is contained in the liquid nitrogen storage tanks, and the liquid nitrogen storage tanks are connected to the vacuum pumping system.

2. The BOG helium extraction device according to claim 1, characterized in that: The low-temperature crude extraction system includes a first heat exchanger, in which a BOG gas pipeline and a liquid nitrogen pipeline are provided. The outlet of the BOG gas pipeline is connected to a first separation tank, the top outlet of the first separation tank is connected to the circulating oxygenation, dehydrogenation and demethane removal system, and the bottom outlet of the first separation tank is connected to the low-temperature distillation system.

3. The BOG helium extraction device according to claim 2, characterized in that: The circulating oxygenation, dehydrogenation and demethane removal system comprises a buffer tank, a mixer, a preheater, a reactor, a cooler and a first adsorber connected in sequence, wherein the inlet of the buffer tank is connected to the top outlet of the first separation tank; The outlet of the first adsorber is connected to a circulating air compressor and a compressor. The inlets of the circulating air compressor and the compressor are both provided with automatic valves. The outlet of the circulating air compressor is connected to the inlet of the buffer tank through a pipeline, and the outlet of the compressor is connected to the low-temperature condensation system.

4. The BOG helium extraction device according to claim 3, characterized in that: The low-temperature condensation system includes a second heat exchanger, which includes a helium-rich gas pipeline and a liquid nitrogen pipeline. The inlet of the helium-rich gas pipeline is connected to the compressor outlet, the outlet of the helium-rich gas pipeline is connected to a second separation tank, and the top outlet of the second separation tank is connected to the inlet of the second heat exchanger.

5. The BOG helium extraction device according to claim 1, characterized in that: The vacuum pumping system includes a third heat exchanger connected to the liquid nitrogen storage tank, and an outlet of the third heat exchanger is connected to a vacuum pump.

6. The BOG helium extraction device according to claim 2, characterized in that: A methane pipeline and a nitrogen pipeline are further provided in the first heat exchanger. The inlet of the methane pipeline is connected to the bottom outlet of the cryogenic distillation system, and the inlet of the nitrogen pipeline is connected to the top outlet of the cryogenic distillation system.

7. The BOG helium extraction device according to claim 3, characterized in that: The first adsorber includes two dry adsorbers arranged in parallel, a nitrogen inlet is provided at the bottom of the two dry adsorbers, the nitrogen inlet is connected to an external electric heating furnace, a regeneration gas outlet is provided at the top of the dry adsorber, and the two dry adsorbers are filled with molecular sieves, alumina and activated carbon.

8. The BOG helium extraction device according to claim 4, characterized in that: A nitrogen and oxygen pipeline is further provided in the second heat exchanger, and an inlet of the nitrogen and oxygen pipeline is connected to the bottom outlet of the second separation tank.

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