Method for recovering BOG helium extraction drying adsorption vent gas

Abstract

The invention belongs to the technical field of waste gas recovery and utilization, and particularly relates to a BOG helium extraction drying adsorption vent gas recovery method, after vent gas in a drying adsorber is pressurized, helium and other gases in the vent gas are subjected to primary separation by a membrane separation method according to different rates of the helium, nitrogen and carbon dioxide passing through a hollow fiber membrane, and then the gas in the vent gas is subjected to secondary separation by the membrane separation method; primary separation permeation gas containing a large amount of helium and primary separation tail gas containing other gases are obtained, and the discharged gas is subjected to primary separation in a primary separation tank; according to the invention, helium recovery is carried out on vented air during recovery of a drying adsorber in a BOG helium extraction process through a membrane separation method, the utilization rate of helium is improved, the waste of helium is reduced, and through series connection of the primary separation tank and the secondary separation tank, the recovery rate of helium in the vented air is improved, the waste of helium is reduced, and the production cost is reduced. And through the parallel connection of the primary separation tank and the secondary separation tank, the helium recovery efficiency is improved.

Description

Technical Field

[0001] The invention belongs to the technical field of waste gas recovery and utilization, and in particular relates to a method for BOG helium extraction, drying, adsorption and air recovery. Background Art

[0002] Helium is a rare gas that is abundant in the universe but rare on Earth. It mainly exists in the atmosphere, rocks and natural gas. Helium is usually a colorless and odorless gas. It is the only substance that cannot solidify under standard atmospheric pressure. Its special physical properties determine the special uses of helium. As a scarce strategic resource for the development of national defense and high-tech industries, helium is widely used in military industry, scientific research, petrochemicals, refrigeration, medical treatment, semiconductors, pipeline leak detection, superconducting experiments, metal manufacturing, deep-sea diving, high-precision welding, optoelectronic product production and other fields, which is of great significance to scientific research.

[0003] The disclosure discloses a system and method for extracting high-purity helium from liquefied natural gas (BOG) flash gas with announcement number CN114674115B. The disclosure adopts cryogenic distillation, cyclic oxygenation and dehydrogenation, cryogenic crude extraction and cryogenic adsorption extraction processes to extract high-purity helium from BOG flash gas. In the cyclic oxygenation and dehydrogenation process, the crude helium after dehydrogenation enters a dryer for drying. The dryer comprises adsorber 1 and adsorber 2. Both adsorber 1 and adsorber 2 are equipped with molecular sieves, alumina and activated carbon. Alumina is used to adsorb water, molecular sieves are used to adsorb CO2, and activated carbon is used to adsorb nitrogen. Adsorbers 1 and 2 are switched for use. When adsorber 1 is adsorbing, adsorber 2 is regenerated for standby use. When adsorber 1 is saturated with adsorption, adsorber 2 is switched to adsorber 2 for adsorption, and then adsorber 1 is regenerated, and the cycle repeats.

[0004] When regenerating the adsorber, it is first necessary to discharge the gas in the adsorber and perform a pressure relief operation on the adsorber. In the prior art, the vented air of the adsorber is directly vented, but the helium content in the vented air is relatively high. If it is directly vented, helium will be wasted. However, the CO2 and water contents in this part of the vented air are relatively high, and it cannot be returned to the BOG raw gas to continue to participate in the helium extraction process. Summary of the invention

[0005] The purpose of the present invention is to provide a method for recovering BOG helium by drying, adsorbing and releasing air, so as to solve the technical problems existing in the existing methods for extracting high-purity helium.

[0006] In order to achieve the above technical purpose, the technical solution of the present invention is: A method for recovering BOG helium-extracting, drying and adsorbing vented air comprises the following steps: after the vented air in a drying adsorber is pressurized, the helium and other gases in the vented air are separated once by a membrane separation method by utilizing the different rates at which helium, nitrogen and carbon dioxide pass through a hollow fiber membrane, so as to obtain a primary separation permeate gas containing a large amount of helium and a primary separation tail gas containing other gases, and the vented air is separated once in a primary separation tank.

[0007] As a further improvement, the inlet of the primary separation tank is connected to the first air inlet pipe, and the pressurized exhaust air enters the primary separation tank through the first air inlet pipe. The primary separation tank is provided with an exhaust gas outlet and a permeate gas outlet. The exhaust gas outlet of the primary separation tank is connected to the secondary separation tank through a series pipe. A stop valve is provided at one end of the series pipe close to the secondary separation tank. The secondary separation tank is also provided with an exhaust gas outlet and a permeate gas outlet. The exhaust gas outlet of the secondary separation tank is connected to the exhaust gas emission pipe.

[0008] As a further improvement, an exhaust gas parallel pipe is connected to one end of the series pipe close to the primary separation tank, a stop valve 2 is arranged on the exhaust gas parallel pipe, the outlet of the exhaust gas parallel pipe is connected to the exhaust gas emission pipe, a second intake pipe is connected to the first intake pipe, the outlet of the second intake pipe is connected to the inlet of the secondary separation tank, and a stop valve 3 is arranged on the second intake pipe.

[0009] As a further improvement, the permeate gas outlets of the primary separation tank and the secondary separation tank are connected to the same permeate gas pipeline through output pipelines.

[0010] As a further improvement, stop valve 2 and stop valve 3 are closed, and stop valve 1 is opened. The tail gas separated in the primary separation tank enters the secondary separation tank through the series pipeline. After secondary separation in the secondary separation tank, the secondary separation tail gas is discharged, and the secondary separation permeate gas obtained in the secondary separation tank enters the output pipeline and is mixed with the primary separation permeate gas obtained in the primary separation tank to obtain industrial helium, which is then compressed and filled into the container.

[0011] As a further improvement, the stop valve 2 and the stop valve 3 are opened, the stop valve 1 is closed, and the air is vented and pressurized and enters the primary separation tank and the secondary separation tank respectively through the first air inlet pipe and the second air inlet pipe, and a separation is performed simultaneously in the primary separation tank and the secondary separation tank, the primary permeate gas obtained in the primary separation tank and the secondary permeate gas obtained in the secondary separation tank enter the permeate gas pipeline through the output pipeline, and the recovered helium is obtained after mixing in the permeate gas pipeline, the primary separation tail gas obtained in the primary separation tank enters the tail gas emission pipeline through the tail gas parallel pipeline, the secondary separation tail gas obtained in the secondary separation tank enters the tail gas emission pipeline, and the primary separation tail gas and the secondary separation tail gas are mixed in the tail gas emission pipeline and then discharged.

[0012] As a further improvement, the membrane separation method uses a carbon molecular sieve hollow fiber membrane.

[0013] Due to the adoption of the above technical solution, the beneficial effects of the present invention are: The method for recovering vented air during BOG helium extraction drying and adsorption provided by the present invention recovers helium from the vented air during the recovery of the drying adsorber in the BOG helium extraction process by a membrane separation method, thereby improving the utilization rate of helium and reducing the waste of helium.

[0014] Close stop valve three, stop valve two and stop valve five, open stop valve one, stop valve four and stop valve six, the primary separation tank and the secondary separation tank are in series, the tail gas obtained from the primary separation tank continues to enter the secondary separation tank for secondary separation, the permeate gas obtained from the primary separation tank and the secondary separation tank can be mixed to fill the container to obtain industrial helium. By connecting the primary separation tank and the secondary separation tank in series, more helium in the vented air can be recovered to reduce the waste of helium.

[0015] When the container does not need to be filled, open stop valve 3, stop valve 2 and stop valve 5, close stop valve 1, stop valve 4 and stop valve 6, the primary separation tank and the secondary separation tank are in parallel state, the primary separation tank and the secondary separation tank separate the venting air at the same time, the obtained permeate gas is mixed and returned to the BOG helium extraction system, the primary separation tank and the secondary separation tank separate the venting air at the same time, and the helium recovery efficiency is improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 This is a process flow chart when the primary separation tank and the secondary separation tank are connected in series in the present invention; Figure 2 This is a process flow chart when the primary separation tank and the secondary separation tank are connected in parallel in the present invention; Figure 3 This is a flow chart of the equipment of the BOG extraction high-purity helium system of the present invention; Among them, 1-drying adsorber, 2-air venting pipeline, 3-air bag, 4-first compressor, 5-primary separation tank, 6-secondary separation tank, 7-first air intake pipeline, 8-second air intake pipeline, 9-series pipeline, 10-exhaust emission pipeline, 11-output pipeline, 12-permeate pipeline, 13-buffer tank, 14-second compressor, 15-container, 16-exhaust parallel pipeline, 17-return pipeline. DETAILED DESCRIPTION

[0017] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0018] like Figure 1-3 As shown, this embodiment provides a BOG helium extraction drying adsorption venting air recovery device, including a dry adsorber 1, an outlet of the dry adsorber 1 is provided with a venting air pipeline 2, the other end of the venting air pipeline 2 is connected to an air bag 3, the outlet of the air bag 3 is connected to a first compressor 4, the outlet of the first compressor 4 is connected to a membrane separation device, and the outlet of the membrane separation device is connected to a tail gas discharge pipeline 10 and a permeate gas pipeline 12.

[0019] When the dry adsorber 1 needs to be regenerated, the vented air in the dry adsorber 1 enters the air bag 3 through the vented air pipeline 2, and then the vented air in the air bag 3 is pressurized by the first compressor 4 and enters the membrane separation device. The membrane separation device adopts a carbon molecular sieve hollow fiber membrane. The membrane separation device utilizes the different rates at which helium, nitrogen and carbon dioxide pass through the fiber membrane to separate the helium and other gases in the vented air. The helium passing through the membrane separation device enters the permeate gas pipeline 12, and the other gases enter the exhaust gas exhaust pipeline 10 for discharge.

[0020] In this embodiment, the membrane separation device includes a primary separation tank 5 and a secondary separation tank 6. The primary separation tank 5 and the secondary separation tank 6 are both provided with an inlet, an exhaust gas outlet and a permeate gas outlet. The inlet of the primary separation tank 5 is connected to the outlet of the first compressor 4 through a first air intake pipe 7, the exhaust gas outlet of the primary separation tank 5 is connected to the inlet of the secondary separation tank 6 through a series pipe 9, the exhaust gas outlet of the secondary separation tank 6 is connected to the exhaust gas discharge pipe 10, and the permeate gas outlets of the primary separation tank 5 and the secondary separation tank 6 are both connected to the permeate gas pipe 12 through an output pipe 11.

[0021] The outlet of the permeate gas pipeline 12 is connected to a buffer tank 13 , the outlet of the buffer tank 13 is connected to a second compressor 14 , and the outlet of the second compressor 14 is provided with a filling port of a container 15 .

[0022] The vented air outputted from the outlet of the first compressor 4 enters the primary separation tank 5 through the first air inlet pipe 7. After separation in the primary separation tank 5, the obtained permeate gas enters the output pipe 11 through the permeate gas outlet of the primary separation tank 5. The tail gas obtained from the tail gas outlet of the primary separation tank 5 enters the secondary separation tank 6 through the series pipe 9. Secondary separation is performed in the secondary separation tank 6. The permeate gas obtained from the permeate gas outlet of the secondary separation tank 6 and the permeate gas obtained from the primary separation tank 5 enter the permeate gas pipe 12 together. The gas in the permeate gas pipe 12 enters the buffer tank 13, and then is compressed by the second compressor 14 and filled into the container 15 through the filling port of the container 15 to obtain industrial helium.

[0023] In this embodiment, the first air intake pipe 7 is also connected to a second air intake pipe 8, the outlet of the second air intake pipe 8 is connected to the inlet of the secondary separation tank 6, and the end of the series pipe 9 close to the exhaust gas outlet of the primary separation tank 5 is also connected to an exhaust gas parallel pipe 16, and the other end of the exhaust gas parallel pipe 16 is connected to the exhaust gas emission pipe 10.

[0024] A stop valve 1 is provided at one end of the series pipe 9 close to the secondary separation tank 6 , a stop valve 2 is provided on the tail gas parallel pipe 16 , a stop valve 3 is provided on the second air intake pipe 8 , and a stop valve 4 is provided at the inlet of the buffer tank 13 .

[0025] The delivery pipeline is also connected to a return pipeline 17 , the permeate gas pipeline 12 is also provided with a carbon dioxide detection device, and the return pipeline 17 is provided with a stop valve 5 .

[0026] The outlet of the buffer tank 13 is provided with a stop valve 6.

[0027] In this embodiment, the membrane separation device uses a carbon molecular sieve hollow fiber membrane.

[0028] The present embodiment also provides a method for recovering BOG helium extraction, drying and adsorption vented air, which uses the above-mentioned BOG helium extraction, drying and adsorption vented air recovery equipment to realize the recovery of BOG helium extraction, drying and adsorption vented air, and comprises the following steps: the vented air in the dry adsorber is pressurized and then enters the primary separation tank 5, and the helium and other gases in the vented air are separated once by a membrane separation method by utilizing the different rates at which helium, nitrogen and carbon dioxide pass through the hollow fiber membrane, so as to obtain a primary separation permeate gas containing a large amount of helium and a primary separation tail gas containing other gases. In actual work, the primary separation permeate gas obtained after the primary separation meets the standards of industrial helium and can be used as industrial helium to be filled into a container, and by detecting that the carbon dioxide content in the primary separation permeate gas is less than 1ppm, the primary separation permeate gas obtained can also be fed back to the BOG extraction high-purity helium process and mixed with the BOG gas to perform the helium extraction process again.

[0029] The inlet of the primary separation tank is connected to the first air inlet pipe, and the pressurized exhaust air enters the primary separation tank through the first air inlet pipe. The primary separation tank is provided with an exhaust gas outlet and a permeate gas outlet. The exhaust gas outlet of the primary separation tank is connected to the secondary separation tank through a series pipeline. A stop valve is arranged at one end of the series pipeline close to the secondary separation tank. The secondary separation tank is also provided with an exhaust gas outlet and a permeate gas outlet. The exhaust gas outlet of the secondary separation tank is connected to the exhaust gas discharge pipeline.

[0030] An exhaust gas parallel pipeline is connected to one end of the series pipeline close to the primary separation tank, a shut-off valve 2 is arranged on the exhaust gas parallel pipeline, the outlet of the exhaust gas parallel pipeline is connected to the exhaust gas emission pipeline, a second intake pipe is connected to the first intake pipe, the outlet of the second intake pipe is connected to the inlet of the secondary separation tank, and a shut-off valve 3 is arranged on the second intake pipe.

[0031] The permeate gas outlets of the primary separation tank and the secondary separation tank are connected to the same permeate gas pipeline through output pipelines.

[0032] Close stop valve 2 and stop valve 3, open stop valve 1, and the tail gas separated in the primary separation tank enters the secondary separation tank through the series pipeline. After secondary separation in the secondary separation tank, the secondary separation tail gas is discharged, and the secondary separation permeate gas obtained in the secondary separation tank enters the output pipeline and is mixed with the primary separation permeate gas obtained in the primary separation tank to obtain industrial helium, which is then compressed and filled into the container.

[0033] Specifically, the industrial helium obtained by mixing the secondary separation permeate gas and the primary separation permeate gas in the output pipeline enters the buffer tank through the permeate gas pipeline, and then is compressed by the second compressor and filled into the container.

[0034] When it is necessary to fill the container, the primary separation tank and the secondary separation tank are arranged in series, and the primary separation tail gas obtained after the primary separation continues to enter the secondary separation tank for secondary separation, and the primary separation permeate gas and the secondary separation permeate gas obtained by the two separations are mixed and filled into the container as industrial helium. By setting up the secondary separation tank, the primary separation tail gas is further separated, so that more helium in the venting air can be recovered and the waste of helium is reduced. In this process, the helium content in the secondary separation tail gas obtained can reach less than 1%.

[0035] In this embodiment, stop valve two and stop valve three are opened, and stop valve one is closed. After the air is vented and pressurized, it enters the primary separation tank and the secondary separation tank respectively through the first air inlet pipe and the second air inlet pipe, and a separation is performed simultaneously in the primary separation tank and the secondary separation tank. The primary permeate gas obtained in the primary separation tank and the secondary permeate gas obtained in the secondary separation tank enter the permeate gas pipeline through the output pipeline, and the recovered helium is obtained after mixing in the permeate gas pipeline. The primary separated tail gas obtained in the primary separation tank enters the tail gas exhaust pipeline through the tail gas parallel pipeline, and the secondary separated tail gas obtained in the secondary separation tank enters the tail gas exhaust pipeline. The primary separated tail gas and the secondary separated tail gas are mixed in the tail gas exhaust pipeline and then discharged.

[0036] When the container filling is not required, the primary separation tank and the secondary separation tank are arranged in parallel. When the primary separation tank and the secondary separation tank are changed from series connection to parallel connection, the recovered helium in the permeate gas pipeline first enters the buffer tank 13, and the recovered helium in the permeate gas pipeline is detected by the carbon dioxide detection device. When the carbon dioxide content in the recovered helium is detected to be less than 1ppm, the recovered helium in the permeate gas pipeline is returned to the BOG extraction high-purity helium process through the return pipeline. The primary separation tank and the secondary separation tank recover helium at the same time, and the recovery efficiency is higher.

[0037] The present invention recovers helium from the vented air during the recovery of the dry adsorber in the BOG helium extraction process by a membrane separation method, thereby improving the utilization rate of helium and reducing the waste of helium. The primary separation tank and the secondary separation tank are connected in series to improve the recovery rate of helium in the vented air and reduce the waste of helium. The primary separation tank and the secondary separation tank are connected in parallel to improve the recovery efficiency of helium.

[0038] The specific implementation of the present invention described above does not constitute a limitation on the protection scope 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 protection scope of the claims of the present invention.

Claims

1. A method for BOG helium extraction, drying, adsorption and air recovery, characterized in that: The following steps are involved: After the vent air in the dry adsorber is pressurized, the helium and other gases in the vent air are separated once by a membrane separation method, utilizing the different rates at which helium, nitrogen and carbon dioxide pass through the hollow fiber membrane, thereby obtaining a primary separation permeate gas containing a large amount of helium and a primary separation tail gas containing other gases. The vent air is separated once in a primary separation tank.

2. The method for recovering BOG by helium extraction, drying, adsorption and degassing according to claim 1, characterized in that: The inlet of the primary separation tank is connected to the first air inlet pipe, and the pressurized exhaust air enters the primary separation tank through the first air inlet pipe. The primary separation tank is provided with an exhaust gas outlet and a permeate gas outlet. The exhaust gas outlet of the primary separation tank is connected to the secondary separation tank through a series pipeline. A stop valve is arranged at one end of the series pipeline close to the secondary separation tank. The secondary separation tank is also provided with an exhaust gas outlet and a permeate gas outlet. The exhaust gas outlet of the secondary separation tank is connected to the exhaust gas discharge pipeline.

3. The method for BOG helium extraction, drying, adsorption and air recovery according to claim 2, characterized in that: An exhaust gas parallel pipeline is connected to one end of the series pipeline close to the primary separation tank, a shut-off valve 2 is arranged on the exhaust gas parallel pipeline, the outlet of the exhaust gas parallel pipeline is connected to the exhaust gas emission pipeline, a second intake pipe is connected to the first intake pipe, the outlet of the second intake pipe is connected to the inlet of the secondary separation tank, and a shut-off valve 3 is arranged on the second intake pipe.

4. The method for recovering BOG by helium extraction, drying, adsorption and degassing according to claim 3 is characterized in that: The permeate gas outlets of the primary separation tank and the secondary separation tank are connected to the same permeate gas pipeline through output pipelines.

5. The method for BOG helium extraction, drying, adsorption and air recovery according to claim 4, characterized in that: Close stop valve 2 and stop valve 3, open stop valve 1, and the tail gas separated in the primary separation tank enters the secondary separation tank through the series pipeline. After secondary separation in the secondary separation tank, the secondary separation tail gas is discharged, and the secondary separation permeate gas obtained in the secondary separation tank enters the output pipeline and is mixed with the primary separation permeate gas obtained in the primary separation tank to obtain industrial helium, which is then compressed and filled into the container.

6. The method for BOG helium extraction, drying, adsorption and air recovery according to claim 4, characterized in that: Open stop valve two and stop valve three, close stop valve one, release and pressurize the air, and then enter the primary separation tank and the secondary separation tank through the first air inlet pipe and the second air inlet pipe respectively, and perform a separation in the primary separation tank and the secondary separation tank at the same time, the primary permeate gas obtained in the primary separation tank and the secondary permeate gas obtained in the secondary separation tank enter the permeate gas pipeline through the output pipeline, and the recovered helium is obtained after mixing in the permeate gas pipeline, the primary separation tail gas obtained in the primary separation tank enters the tail gas emission pipeline through the tail gas parallel pipeline, the secondary separation tail gas obtained in the secondary separation tank enters the tail gas emission pipeline, and the primary separation tail gas and the secondary separation tail gas are mixed in the tail gas emission pipeline and then discharged.

7. The method for recovering BOG by helium extraction, drying, adsorption and degassing according to any one of claims 1 to 6, characterized in that: The membrane separation method adopts a carbon molecular sieve hollow fiber membrane.

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