Helium coarse purification system and method with high recovery rate and low energy consumption

Abstract

The system comprises a multi-channel heat exchanger, four temperature returning pipelines and a cooling pipeline, the four temperature returning pipelines and the cooling pipeline are connected to the multi-channel heat exchanger, and the cooling pipeline exchanges heat with the four temperature returning pipelines through the multi-channel heat exchanger. One ends of the cooling pipeline and the four temperature return pipelines are correspondingly connected with the feed gas inlet pipeline, the gas outlet pipeline, the helium recovery pipeline, the emptying pipeline and the emptying pipeline in sequence respectively. According to the invention, the recoverer is arranged at the rear end of the separator, the separator pressure regulating valve is used for regulating the internal pressure of the separator to be maintained in the first set pressure interval, and the recoverer pressure regulating valve can control the internal pressure of the recoverer to be in the second set pressure interval lower than the pressure in the first set pressure interval; the recovery rate of the whole system can be improved, nitrogen and energy of other streams are evaporated through the multi-channel heat exchanger and the Dewar, public engineering consumption can be greatly reduced, and high economical efficiency is achieved during operation.

Description

Technical Field

[0001] The present invention relates to the technical fields of gas separation and petrochemical industry, and more specifically to a helium rough purification system and method with high recovery rate and low energy consumption. Background Art

[0002] Helium belongs to rare gases. It was first discovered in the sun in 1868 and on the earth in 1895. It has unique physical and chemical properties. Helium was first used to provide buoyancy for balloons and airships, and currently plays an important role in high-tech manufacturing fields such as aerospace, medical treatment, national defense, and superconductivity. It is an indispensable strategic resource in the development of national defense military industry and high-tech industries.

[0003] Generally, the steps of helium process purification are pretreatment, rough extraction, and refining. Pretreatment mainly includes processes such as decarbonization and dehydration. Through pretreatment, impurities with relatively high freezing points such as CO2 and H2O can be removed to prevent blockage and corrosion of pipelines, valves, and other equipment due to solidification at low temperatures, thus deteriorating the process conditions and resulting in operation failure; the main methods for rough extraction of helium include cryogenic condensation method, membrane separation method, adsorption method, absorption method, diffusion method, etc. After rough extraction of helium, the purity of helium can reach about 50%; refining means further purifying the helium after rough extraction through cryogenic adsorption to obtain high-purity helium of 99.999%.

[0004] In the whole process of producing high-purity helium, the process of rough extraction of helium generally selects the corresponding method according to the inlet gas components. Among them, the cryogenic condensation method is currently the main method for rough extraction of helium from mixed gases in industry. The principle is to utilize the extremely low liquefaction temperature of helium to separate it from other gas components with higher boiling points, and it is required that there is no fraction with a boiling point above ethane in the components. The cooling capacity required for condensation is supplied by normal-pressure liquid nitrogen or negative-pressure liquid nitrogen. Summary of the Invention

[0005] The technical problem to be solved by the present invention is how to improve the recovery rate of the helium rough purification system and reduce energy consumption.

[0006] The present invention realizes the solution to the above technical problems through the following technical means: A helium rough purification system with high recovery rate and low energy consumption, including a multi-channel heat exchanger and four temperature-rising pipelines and a temperature-lowering pipeline connected to the multi-channel heat exchanger. The temperature-lowering pipeline exchanges heat with the four temperature-rising pipelines through the multi-channel heat exchanger. One ends of the temperature-lowering pipeline and the four temperature-rising pipelines are respectively connected in sequence to a raw gas inlet pipeline, an outlet pipeline, a helium recovery pipeline, a vent pipeline, and a vent pipeline. The other ends of the temperature-lowering pipeline and the four temperature-rising pipelines all extend into a liquid nitrogen dewar and are respectively connected to a subcooling heat exchanger I, a separator, a subcooling heat exchanger II, a recovery device, and the liquid nitrogen dewar in the liquid nitrogen dewar. The subcooling heat exchanger I, the separator, the subcooling heat exchanger II, and the recovery device are connected in sequence. A separator pressure regulating valve is provided on the temperature-rising pipeline connected to the separator, and the separator pressure regulating valve can adjust the internal pressure of the separator to maintain it within a first set pressure range. A recovery device pressure regulating valve is provided on the temperature-rising pipeline connected to the recovery device, and the recovery device pressure regulating valve can control the internal pressure of the recovery device to a second set pressure range lower than the pressure in the first set pressure range.

[0007] As a preferred technical solution, it further includes a negative pressure liquid nitrogen system connected to the liquid nitrogen dewar. The negative pressure liquid nitrogen system includes a vent pipeline, a vacuum pump, and a dewar pressure regulating valve. The temperature-rising pipeline connected to the liquid nitrogen dewar is connected to the vent pipeline through an evacuation pipeline, and a vacuum pump and a dewar pressure regulating valve are provided on the vent pipeline.

[0008] As a preferred technical solution, the negative pressure liquid nitrogen system further includes a reheater, a circulating water pipeline, a water bath heater sewage discharge pipeline. The input and output ends of the reheater are respectively connected to the circulating water pipeline and the water bath heater sewage discharge pipeline, and a reheater water filling valve and a reheater water discharge valve are respectively provided on the circulating water pipeline and the water bath heater sewage discharge pipeline.

[0009] As a preferred technical solution, the separator is connected to the subcooling heat exchanger II through a connecting pipeline, and a cryogenic throttle valve is provided on the connecting pipeline.

[0010] As a preferred technical solution, the temperature-lowering pipeline is the first pipeline, and the four temperature-rising pipelines are respectively the second pipeline, the third pipeline, the fourth pipeline, and the fifth pipeline. One end of the first pipeline is connected to the raw gas inlet pipeline and the nitrogen pipeline, and the other end is connected to the subcooling heat exchanger I. The outlet pipeline includes a qualified gas pipeline and an unqualified gas pipeline. One end of the second pipeline is connected to the qualified gas pipeline and the unqualified gas pipeline, and the other end is connected to the top of the separator. One end of the third pipeline is connected to the helium recovery pipeline, and the other end is connected to the top of the recovery device. One end of the fourth pipeline is connected to the vent pipeline, and the other end is connected to the bottom of the recovery device.

[0011] As a preferred technical solution, a raw material gas inlet valve and a nitrogen inlet valve are respectively provided on the raw material gas inlet pipeline and the nitrogen pipeline, and a product gas outlet valve and a non-conforming product gas outlet valve are respectively provided on the qualified gas pipeline and the non-conforming gas pipeline.

[0012] As a preferred technical solution, a recovery pressure regulating valve is provided on the helium recovery pipeline, and a recovery liquid level regulating valve is provided on the vent pipeline.

[0013] As a preferred technical solution, a liquid nitrogen input pipeline and a liquid nitrogen output pipeline are connected to the liquid nitrogen dewar, and a dewar liquid level regulating valve and a liquid nitrogen discharge valve are respectively provided on the liquid nitrogen input pipeline and the liquid nitrogen output pipeline.

[0014] As a preferred technical solution, a gas component analyzer is provided on the second pipeline, and the gas component analyzer is located upstream of the connection between the qualified gas pipeline and the non-conforming gas pipeline and the second pipeline.

[0015] The present invention also provides a method for a helium rough purification system with high recovery rate and low energy consumption. The raw material gas passing through the cooling pipeline exchanges heat with four warming pipelines through a multi-channel heat exchanger. The pressure regulating valve of the separator is used to control the internal pressure of the separator to be maintained at medium pressure, so that the helium content in the gas at the upper part of the separator reaches more than 95%. It is necessary to control the internal pressure of the recovery device to be maintained at a low pressure through the pressure regulating valve of the recovery device, so that part of the helium gas dissolved in the mixed liquid at the bottom of the separator at a higher pressure at the front end will flash out and gather in the upper section of the recovery device in gaseous form, and enter a warming channel of the multi-channel heat exchanger through the upper outlet of the recovery device. After being reheated by the multi-channel heat exchanger, it enters the helium recovery pipeline through the pressure regulating valve of the recovery device.

[0016] The beneficial effects of the present invention are as follows:

[0017] (1) In the present invention, the internal pressure of the separator is regulated by the pressure regulating valve of the separator to be maintained in the first set pressure range, so as to obtain a product gas with higher purity. By setting a recovery device at the rear end of the separator, the pressure regulating valve of the recovery device can control the internal pressure of the recovery device to the second set pressure range lower than the pressure in the first set pressure range, so as to improve the recovery rate of the whole system; through the multi-channel heat exchanger, the energy of the evaporated nitrogen of the dewar and other various fluid streams can be utilized, which can greatly reduce the consumption of public works. It has strong economy during operation. By setting the multi-channel heat exchanger, the use of cryogenic valves can be minimized, the project input cost can be greatly reduced during the actual project construction process, and the equipment stability can be greatly improved.

[0018] (2) In the present invention, through the setting of the negative pressure liquid nitrogen system, it can be ensured that the lowest temperature under the negative pressure of liquid nitrogen can be effectively reduced compared with the normal pressure, so as to improve the separation and purification effect. Description of the Drawings

[0019] Figure 1 Schematic diagram of the overall structure provided by the embodiment of the present invention;

[0020] Reference numerals: XV01, raw gas inlet valve; XV02, product gas outlet valve; XV03, unqualified product gas outlet valve; XV04, nitrogen inlet valve; XV05, instrument air inlet valve; XV06, liquid nitrogen discharge valve; PV01, cryogenic throttle valve; PV02, recovery liquid level regulating valve; PV03, Dewar pressure regulating valve; PV04, recovery pressure regulating valve; PV05, Dewar liquid level regulating valve; PV06, separator pressure regulating valve; HV01, reheater water filling valve; HV02, reheater drain valve; P01, vacuum pump; 10, reheater; 20, multi-channel heat exchanger; 30, subcooling heat exchanger I; 40, separator; 50, subcooling heat exchanger II; 60, recovery unit; 70, liquid nitrogen Dewar; 81, first pipeline; 82, second pipeline; 821, qualified gas pipeline; 822, unqualified gas pipeline; 83, third pipeline; 84, fourth pipeline; 85, fifth pipeline; 86, circulating water pipeline; 87, sewage discharge pipeline of water bath heater; 88, nitrogen pipeline; 89, liquid nitrogen input pipeline; 810, liquid nitrogen output pipeline; 811, instrument air inlet pipeline; 812, helium recovery pipeline; 813, vent pipeline; 814, raw gas inlet pipeline; 815, connecting pipeline; 816, evacuation pipeline. Detailed implementation manners

[0021] To make the objectives, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are some, but not all, of the embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0022] Refer to Figure 1, A crude helium purification system with high recovery rate and low energy consumption, including four warming pipelines and one heating pipeline. The four warming pipelines are respectively the second pipeline 82, the third pipeline 83, the fourth pipeline 84, and the fifth pipeline 85. The heating pipeline is the first pipeline 81. The first pipeline 81 exchanges heat with the second pipeline 82, the third pipeline 83, the fourth pipeline 84, and the fifth pipeline 85 through a multi-channel heat exchanger 20, reducing the utility consumption of the overall system to the greatest extent. In the prior art, cryogenic valves are costly and have a higher failure rate than normal-temperature valves. Since this system is provided with a multi-channel heat exchanger 20, the use of cryogenic valves can be minimized, and the project investment cost can be significantly reduced during the actual project construction process, and the equipment stability can be greatly improved. One end of the second pipeline 82, the third pipeline 83, the fourth pipeline 84, and the fifth pipeline 85 all extends into the liquid nitrogen dewar 70; an undercooled heat exchanger I 30, a separator 40, an undercooled heat exchanger II 50, and a recovery device 60 are arranged in the liquid nitrogen dewar 70.

[0023] Among them, one end of the first pipeline 81 is connected to a nitrogen gas pipeline 88 and a raw gas inlet pipeline 814. The nitrogen gas in the nitrogen gas pipeline 88 comes from the nitrogen gas network, and the crude helium in the raw gas inlet pipeline 814 comes from the upstream. A nitrogen gas inlet valve XV04 and a raw gas inlet valve XV01 are respectively arranged on the nitrogen gas pipeline 88 and the raw gas inlet pipeline 814. The other end is connected to the undercooled heat exchanger I 30. The undercooled heat exchanger I 30 is communicated with the separator 40. The top of the separator 40 is connected to one end of the second pipeline 82. The other end of the second pipeline 82 is connected to a qualified gas pipeline 821 and an unqualified gas pipeline 822. The qualified gas pipeline 821 and the unqualified gas pipeline 822 form an outlet gas pipeline. A gas component analyzer is arranged on the second pipeline 82. The gas component analyzer is located upstream of the connection between the qualified gas pipeline 821 and the unqualified gas pipeline 822 and the second pipeline 82. A product gas outlet valve XV02 and an unqualified product gas outlet valve XV03 are respectively arranged on the qualified gas pipeline 821 and the unqualified gas pipeline 822. A separator pressure regulating valve PV06 is arranged on the second pipeline 82. The separator pressure regulating valve PV06 can adjust the internal pressure of the separator to maintain it within the first set pressure range. In this embodiment, the first set pressure range is about 2 Mpa. The qualified gas output from the qualified gas pipeline 821 goes to pressure swing adsorption, and the unqualified gas output from the unqualified gas pipeline 822 returns to the airbag.

[0024] All valves are supplied with gas through an instrument air inlet pipeline 811 to ensure the normal operation of all valves. An instrument air inlet valve XV05 is arranged on the instrument air inlet pipeline 811.

[0025] The bottom of the separator 40 is connected to the subcooled heat exchanger II 50 through a connecting pipeline 815. A low-temperature throttle valve PV01 is provided on the connecting pipeline 815. The subcooled heat exchanger II 50 is connected to the recovery device 60. The top of the recovery device 60 is connected to one end of a third pipeline 83, and the other end of the third pipeline 83 is connected to a helium recovery pipeline 812. A recovery pressure regulating valve PV04 is provided on the helium recovery pipeline 812. The recovery pressure regulating valve PV04 can control the internal pressure of the recovery device 60 to a second set pressure range lower than the pressure in the first set pressure range. In this embodiment, the second set pressure range is about 0.1 Mpa. The bottom of the recovery device 60 is connected to one end of a fourth pipeline 84, and the other end of the fourth pipeline 84 is connected to a vent pipeline 813. A recovery liquid level regulating valve PV02 is provided on the vent pipeline 813. One end of a fifth pipeline 85 is connected to the liquid nitrogen dewar 70, and the other end of the fifth pipeline 85 is connected to the vent pipeline 813 through a evacuation pipeline 816. A vacuum pump P01 is provided on the evacuation pipeline 816. A reheater 10 is also connected to the fifth pipeline 85. The reheater 10 is connected to a circulating water pipeline 86 and a sewage discharge pipeline 87 of a water bath heater. A reheater water filling valve HV01 and a reheater drain valve HV02 are respectively provided on the circulating water pipeline 86 and the sewage discharge pipeline 87 of the water bath heater. The circulating water in the circulating water pipeline 86 comes from the circulating water network. The liquid nitrogen dewar 70 is connected to a liquid nitrogen input pipeline 89 and a liquid nitrogen output pipeline 810. A dewar liquid level regulating valve PV05 and a liquid nitrogen discharge valve XV06 are respectively provided on the liquid nitrogen input pipeline 89 and the liquid nitrogen output pipeline 810. The liquid nitrogen output pipeline 810 is connected to the liquid nitrogen dewar 70 through a part of the pipeline of the liquid nitrogen input pipeline 89.

[0026] Working principle:

[0027] The pre-treated feed gas enters the first pipeline 81 of the multi-channel heat exchanger 20 from the feed gas inlet pipeline 814 through the feed gas inlet valve XV01. This pipeline is the only cooling pipeline of the multi-channel heat exchanger 20. The feed gas passing through the first pipeline 81 undergoes a significant temperature reduction for the first time through heat exchange within the multi-channel heat exchanger 20. The cooled gas flow then enters the sub-cooler 1 30 within the liquid nitrogen dewar 70 for further cooling. After passing through the sub-cooler 1 30, the gas flow temperature is reduced to the temperature within the liquid nitrogen dewar 70. At this time, impurities such as nitrogen and oxygen with higher boiling points liquefy to form liquids at this temperature, and most of the helium gas with a lower boiling point still exists in the gas phase within the stream. The stream enters the separator 40 within the liquid nitrogen dewar 70 in a gas-liquid mixed state. In the separator 40, the gas-liquid mixed stream undergoes gas-liquid separation due to gravity. The liquid impurities such as liquid nitrogen and liquid oxygen with higher boiling points enter the bottom of the separator 40, and the gas components such as unliquefied helium gas with lower boiling points are located in the upper part of the separator 40. At this time, in order to achieve a better gas separation effect within the separator 40 and a higher helium content in the gas in the upper part of the separator 40, it is necessary to control the internal pressure of the separator 40 to be maintained at a medium pressure of approximately 2 Mpa through the separator pressure regulating valve PV06. At this pressure, the helium content in the gas in the upper part of the separator 40 is approximately 95% or more. The purity of the product gas is analyzed by a gas component analyzer (not shown in the figure). The qualified product gas enters the second pipeline 82 of the multi-channel heat exchanger 20 through the top outlet of the separator 40 and exchanges heat with the gas in the first pipeline 81 to be reheated to around room temperature, and then enters the next unit through the product gas outlet valve XV02 on the qualified gas pipeline 821. The unqualified product gas enters the second pipeline 82 of the multi-channel heat exchanger 20 through the top outlet of the separator 40 and exchanges heat with the gas in the first pipeline 81 to be reheated to around room temperature, and then enters the unqualified product unit through the unqualified product gas outlet valve XV03 on the unqualified gas pipeline 822; the cryogenic throttle valve PV01 is used to control the liquid accumulation level of the mixed liquid such as liquid nitrogen and liquid oxygen at the bottom of the separator 40. The liquid at the bottom of the separator 40 undergoes throttling through the cryogenic throttle valve PV01. When the stream enters the cryogenic throttle valve PV01, the stream will leave the liquid nitrogen environment. Due to the heat leakage inside the liquid nitrogen dewar 70, part of the liquid nitrogen and liquid oxygen will vaporize to form gas. In order to reduce the temperature of the stream entering the recovery unit 60 to the liquid nitrogen temperature again, the stream flowing out of the cryogenic throttle valve PV01 will enter the sub-cooler 2 50 for cooling before entering the recovery unit 40, that is, the stream in the connecting pipeline 815; in order to ensure the purity of the product gas produced at the top of the front separator 40, the pressure of the front separator 40 is maintained at a relatively high level. In this embodiment, it is approximately 2 Mpa. However, at this pressure, part of the helium gas will dissolve in the liquid mixture at the bottom of the separator 40 and will enter the rear recovery unit 60 along with the liquid stream. In order to improve the product gas recovery rate of the entire device, it is necessary to control the internal pressure of the recovery unit 60 to be maintained at a low pressure of approximately 0.At about 1 Mpa, under this pressure, some of the helium gas dissolved in the bottom mixed liquid in the separator 40 at a higher pressure at the front end will flash out and accumulate in the upper section of the recovery device 60 in gaseous form, enter the third pipeline 83 of the multi-channel heat exchanger 20 through the upper outlet of the recovery device 60, and enter the airbag recovery after being reheated by the multi-channel heat exchanger 20 through the helium recovery pipeline 812 and the pressure regulating valve PV04 of the recovery device, thereby improving the overall recovery rate.

[0028] The bottom of the recovery device 60 is a liquid mixture of impurities such as liquid oxygen and liquid nitrogen. The liquid level height at the bottom of the recovery device 60 is controlled by the recovery liquid level regulating valve PV02. When the liquid level needs to be lowered, the bottom liquid mixture will enter the fourth pipeline 84 of the multi-channel heat exchanger 20 from the bottom outlet of the recovery device 60. The liquid will be reheated and vaporized in the fourth pipeline 84 of the multi-channel heat exchanger 20 and discharged to the high point for venting through the vent pipeline 813 and the recovery liquid level regulating valve PV02;

[0029] When the process operates normally, the streams passing through the subcooling heat exchanger 1 30 and the subcooling heat exchanger 2 50 need to be cooled down. This part of the cold energy is provided by the liquid nitrogen in the liquid nitrogen dewar 70. Therefore, it is necessary to fill the liquid nitrogen dewar 70 with liquid nitrogen to a certain height and maintain the liquid nitrogen level at a certain height. The liquid nitrogen is added to the liquid nitrogen dewar 70 from the liquid nitrogen storage tank through the liquid nitrogen input pipeline 89 and by controlling the opening of the dewar liquid level regulating valve PV05. During normal operation, the height of the liquid level in the dewar is adjusted by the dewar liquid level regulating valve PV05; when the entire process stops operating, all the liquid nitrogen in the liquid nitrogen dewar 70 needs to be discharged. At this time, the liquid nitrogen is discharged from the bottom liquid inlet and outlet of the liquid nitrogen dewar 70 to the liquid nitrogen recovery device or the pit through the liquid nitrogen discharge valve XV06 on the liquid nitrogen output pipeline 810;

[0030] The lowest temperature of liquid nitrogen under negative pressure can be effectively reduced compared to that under normal pressure. To improve the separation and purification effect, a negative-pressure liquid nitrogen sub-system is set up in this system. The negative-pressure liquid nitrogen system includes a recuperator 10, a vacuum pump P01, a Dewar pressure regulating valve PV03, a recuperator water filling valve HV01, and a recuperator drain valve HV02. The vacuum pump P01 is used to evacuate the liquid nitrogen Dewar 70 to a negative-pressure environment. The nitrogen gas generated by the evaporation of liquid nitrogen due to heat exchange in the liquid nitrogen Dewar 70 is first reheated through the fifth pipeline 85 of the multi-channel heat exchanger 20 under the action of the vacuum pump P01. After leaving the multi-channel heat exchanger 20, the evaporated nitrogen gas enters the recuperator 10. The recuperator 10 is used to further heat the nitrogen gas evaporated in the liquid nitrogen Dewar 70 entering the vacuum pump P01 to room temperature. Before putting the negative-pressure liquid nitrogen system into operation, water needs to be filled into the recuperator 10 through the circulating water pipeline 86 and by keeping the recuperator water filling valve HV01 open. Water is the heat transfer medium of the recuperator 10. When the negative-pressure liquid nitrogen system is out of use, the water medium in the recuperator 10 needs to be emptied through the water bath heater sewage discharge pipeline 87 and by keeping the recuperator drain valve HV02 open. When the system is operating normally, the vacuum degree in the liquid nitrogen Dewar 70 is controlled by the Dewar pressure regulating valve PV03. When the negative-pressure system is not in use and the normal-pressure liquid nitrogen temperature zone is used, the Dewar pressure regulating valve PV03 needs to be opened to avoid overpressure in the Dewar.

[0031] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements on some of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A crude helium purification system with high recovery rate and low energy consumption, characterized in that, It includes a multi-channel heat exchanger and four rewarming pipelines and cooling pipelines connected to the multi-channel heat exchanger. The cooling pipeline exchanges heat with the four rewarming pipelines through the multi-channel heat exchanger. One ends of the cooling pipeline and the four rewarming pipelines are respectively and sequentially connected to a raw gas inlet pipeline, an outlet pipeline, a helium recovery pipeline, a vent pipeline, and a vent pipeline. The other ends of the cooling pipeline and the four rewarming pipelines all extend into a liquid nitrogen dewar and are respectively connected to a subcooling heat exchanger I, a separator, a subcooling heat exchanger II, a recovery device, and the liquid nitrogen dewar in the liquid nitrogen dewar. The subcooling heat exchanger I, the separator, the subcooling heat exchanger II, and the recovery device are connected in sequence. A separator pressure regulating valve is provided on the rewarming pipeline connected to the separator, and the separator pressure regulating valve can adjust the internal pressure of the separator to maintain it within a first set pressure range. A recovery device pressure regulating valve is provided on the rewarming pipeline connected to the recovery device, and the recovery device pressure regulating valve can control the internal pressure of the recovery device to a second set pressure range lower than the pressure in the first set pressure range.

2. The helium rough purification system with high recovery rate and low energy consumption according to claim 1, characterized in that, It also includes a negative pressure liquid nitrogen system connected to the liquid nitrogen dewar. The negative pressure liquid nitrogen system includes a vent pipeline, a vacuum pump, and a dewar pressure regulating valve. The rewarming pipeline connected to the liquid nitrogen dewar is connected to the vent pipeline through an evacuation pipeline, and the vent pipeline is provided with a vacuum pump and a dewar pressure regulating valve.

3. A helium rough purification system with high recovery rate and low energy consumption according to claim 2, characterized in that, The negative pressure liquid nitrogen system also includes a reheater, a circulating water pipeline, and a sewage discharge pipeline for a water bath heater. The input and output ends of the reheater are respectively connected to the circulating water pipeline and the sewage discharge pipeline for the water bath heater, and a reheater water filling valve and a reheater water drainage valve are respectively provided on the circulating water pipeline and the sewage discharge pipeline for the water bath heater.

4. A helium rough purification system with high recovery rate and low energy consumption according to claim 1, characterized in that, The separator is connected to the subcooling heat exchanger II through a connecting pipeline, and a cryogenic throttle valve is provided on the connecting pipeline.

5. A helium rough purification system with high recovery rate and low energy consumption according to claim 1, characterized in that The cooling pipeline is the first pipeline, and the four warming pipelines are respectively the second pipeline, the third pipeline, the fourth pipeline, and the fifth pipeline. One end of the first pipeline is connected to the raw gas inlet pipeline and the nitrogen pipeline, and the other end is connected to the subcooling heat exchanger I. The outlet pipeline includes a qualified gas pipeline and an unqualified gas pipeline. One end of the second pipeline is connected to the qualified gas pipeline and the unqualified gas pipeline, and the other end is connected to the top of the separator. One end of the third pipeline is connected to the helium recovery pipeline, and the other end is connected to the top of the recovery device. One end of the fourth pipeline is connected to the vent pipeline, and the other end is connected to the bottom of the recovery device.

6. The helium gas rough purification system with high recovery rate and low energy consumption according to claim 5, characterized in that, A raw gas inlet valve and a nitrogen inlet valve are respectively provided on the raw gas inlet pipeline and the nitrogen pipeline, and a product gas outlet valve and an unqualified product gas outlet valve are respectively provided on the qualified gas pipeline and the unqualified gas pipeline.

7. A helium rough purification system with high recovery rate and low energy consumption according to claim 5, characterized in that, A recovery pressure regulating valve is provided on the helium recovery pipeline, and a recovery liquid level regulating valve is provided on the vent pipeline.

8. A helium rough purification system with high recovery rate and low energy consumption according to claim 1, characterized in that, A liquid nitrogen input pipeline and a liquid nitrogen output pipeline are connected to the liquid nitrogen dewar, and a dewar liquid level regulating valve and a liquid nitrogen discharge valve are respectively provided on the liquid nitrogen input pipeline and the liquid nitrogen output pipeline.

9. A helium rough purification system with high recovery rate and low energy consumption according to claim 1, characterized in that, A gas component analyzer is provided on the second pipeline, and the gas component analyzer is located upstream of the connection between the qualified gas pipeline and the unqualified gas pipeline and the second pipeline.

10. A method using the helium rough purification system with high recovery rate and low energy consumption as described in any one of claims 1-9, characterized in that, The raw gas passing through the cooling pipeline exchanges heat with four rewarming pipelines through a multi-channel heat exchanger. The internal pressure of the separator is controlled by a separator pressure regulating valve to maintain a medium pressure, causing the helium content in the gas at the upper part of the separator to reach over 95%. It is necessary to control the internal pressure of the recovery device by a recovery device pressure regulating valve to maintain a low pressure, so that part of the helium gas dissolved in the mixed liquid at the bottom of the separator at a relatively high pressure at the front end will flash out and accumulate in the upper section of the recovery device in a gaseous form, enter a rewarming channel of the multi-channel heat exchanger through the upper outlet of the recovery device, and enter the helium gas recovery pipeline through the recovery device pressure regulating valve after being reheated by the multi-channel heat exchanger.

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