A switchable two-tower helium extraction device and process for natural gas

Abstract

The present invention relates to the technical field of helium recovery from natural gas, and provides a switchable two-tower helium extraction device and process for natural gas, wherein the two-tower helium extraction device comprises a precooling cold box, a primary concentration tower, a secondary concentration tower and a cryogenic cold box; a gas phase outlet is provided at the lower part of the primary concentration tower, and the gas phase outlet is connected to the precooling cold box and then back-connected to an inlet arranged in the middle of the primary concentration tower, and the back-connecting section is connected to a cut-off valve, and the passage where the cut-off valve is located passes through the precooling cold box and outputs natural gas; a gas phase outlet is provided at the top of the primary concentration tower and at least one passage is output to connect to the secondary concentration tower, and at least one passage is output through the cryogenic cold box and outputs helium after the secondary concentration tower performs secondary concentration treatment. The cooperation of the primary concentration tower and the secondary concentration tower realizes the initial extraction and processing of helium and the production of natural gas in the primary concentration tower, and realizes the extraction of crude helium products in the secondary concentration tower, and continues to produce surplus natural gas. The process is simple and the effect is remarkable.

Description

Technical Field

[0001] The present invention relates to the technical field of helium recovery from natural gas, and in particular to a helium extraction device and process capable of switching two natural gas towers. Background Art

[0002] Helium is an inert gas that is usually colorless and odorless. It is the only substance that cannot solidify under standard atmospheric pressure.

[0003] As a rare substance indispensable to the development of engineering technology, helium has important uses due to its stability. It has been widely used in the fields of petrochemical, refrigeration, medical, semiconductor, superconducting experiments, and optoelectronic product production. In the field of nuclear magnetic resonance (low-temperature superconductivity), nuclear magnetic resonance imaging (MRI) uses helium as a cooling medium for low-temperature superconducting magnets; in the field of semiconductors and optical fibers, helium is mainly used as a protective gas for growing germanium and silicon crystals in the semiconductor industry, as well as a cooling and protective atmosphere gas in the production of optical fiber preforms and optical fiber drawing processes; in the field of cryogenic engineering, helium is usually used as a working medium for closed-cycle cryogenic refrigerators; in addition, helium is also widely used in the fields of household appliance refrigeration and automobile manufacturing.

[0004] At present, helium is mainly produced from natural gas. The existing low-temperature helium extraction process of the primary concentration tower system requires natural gas self-expansion to provide cooling capacity, and it is not suitable for the gas quality conditions where the raw gas components are relatively rich. When the natural gas needs to be purified, it is impossible to freely control the production of helium while exporting qualified natural gas. Summary of the invention

[0005] In order to overcome the defects of the prior art mentioned above, the present invention provides a switchable two-tower helium extraction device for natural gas, which is used to produce helium from natural gas, and can freely choose to control the production of helium while achieving natural gas purification. A set of devices can integrate the natural gas purification process and the helium preparation process, and the device operation is simpler and more convenient, and the resource consumption is also less.

[0006] In order to achieve the above object, the technical solution adopted by the present invention is:

[0007] A switchable two-tower helium extraction device for natural gas comprises a precooling cold box, a primary concentration tower, a secondary concentration tower and a cryogenic cold box which are connected in sequence; a gas phase outlet is arranged at the lower part of the primary concentration tower, the gas phase outlet is connected to the precooling cold box and then is connected back to an inlet arranged in the middle of the primary concentration tower, the return section is connected to a cut-off valve, and the passage where the cut-off valve is located passes through the precooling cold box and outputs natural gas; a gas phase outlet is arranged at the top of the primary concentration tower and at least one passage is output to connect to the secondary concentration tower, and at least one passage is output from the secondary concentration tower after secondary concentration treatment passes through the cryogenic cold box and outputs helium.

[0008] The above disclosed helium extraction device realizes the initial extraction and processing of helium and the production of natural gas in the primary concentration tower through the cooperation of the primary concentration tower and the secondary concentration tower, realizes the extraction of crude helium products in the secondary concentration tower, and continues to produce surplus natural gas. The pre-cooling cold box and the deep cold box provide temperature environments for the processes involved in the primary concentration tower and the processes involved in the secondary concentration tower respectively.

[0009] When controlling the production of helium, the shut-off valve is closed to block the passage, and the passage output from the primary concentration tower and through the pre-cooling cold box can return to the entrance in the middle of the primary concentration tower, and after diversion, a passage is output to the secondary concentration tower to complete the subsequent helium preparation process, and at the same time, the production of natural gas can be realized.

[0010] When controlling the production of natural gas without producing helium, the shut-off valve is opened to connect the passage. According to Newton's third law, the material in the passage output from the primary concentration tower and passing through the pre-cooling cold box will not flow back to the primary concentration tower, but will be directly output to the outside after passing through the pre-cooling cold box.

[0011] According to this setting, the production of helium can be freely controlled without affecting the production of natural gas.

[0012] Furthermore, the primary concentration tower and the secondary concentration tower are connected to the equipment for coordinated operation in the device, and the following specific scheme is cited here: the bottom of the primary concentration tower and the secondary concentration tower are respectively provided with a primary reboiler and a secondary reboiler, and the output passages of the primary reboiler and the secondary reboiler pass through the pre-cooling cold box and the deep cooling cold box, respectively, and then are connected to the primary concentration tower and the secondary concentration tower respectively. With this structure, the primary concentration tower plays a direct role in the production of natural gas when it is working, and can complete the first step of producing helium; when helium needs to be produced, the secondary concentration tower intervenes to complete the production of helium.

[0013] Furthermore, the primary reboiler is integrated at the bottom of the primary concentration tower, and the secondary reboiler is integrated at the bottom of the secondary concentration tower. As an integrated device, the loss of cold can be reduced.

[0014] Furthermore, in order to facilitate the preparation of helium, the material output from the primary concentration tower needs to be concentrated again, so the passage is optimized. Here is a specific scheme as follows: a primary condenser is provided in the passage output from the top of the primary concentration tower and connected to the secondary concentration tower, the output end of the primary condenser is connected to the primary reflux tank, the gas phase passage at the top of the primary reflux tank is connected to the secondary concentration tower, and the liquid phase passage at the bottom of the primary reflux tank is connected to the primary purification tower. As one of the multiple feasible options, the significance of such a setting is that the material output from the primary condenser enters the primary reflux tank, and is divided into a gas phase and a liquid phase by reflux, wherein the gas phase contains helium and enters the secondary concentration tower for secondary treatment and concentration to obtain helium; the liquid phase part refluxes to the primary concentration tower as the top reflux liquid.

[0015] Furthermore, the primary condenser and the primary reflux tank are integrated at the top of the primary concentration tower, and the pre-cooling cold box and the integrated primary concentration tower can be integrated as a whole into the interior of a skid, which is convenient for the overall cooling of the equipment and improves the utilization of cold energy during the transportation process.

[0016] Furthermore, part of the concentrated liquid phase material is accumulated at the bottom of the primary concentration tower, and the liquid phase material is processed again to obtain the required natural gas. Here, the structure of the primary concentration tower is optimized, and the following specific scheme is given: the bottom of the primary concentration tower outputs at least two paths, at least one of which passes through the primary condenser and the pre-cooling cold box to output natural gas, and at least one of which passes through the pre-cooling cold box directly to output natural gas. As one of the multiple feasible options, the significance of such a setting is that the path that first passes through the primary condenser can provide a certain amount of cooling for the primary condenser.

[0017] Furthermore, the natural gas produced in the above technical solution needs to be pre-processed to meet the external transmission standards when it is transported to the external natural gas pipeline network. Therefore, the route for exporting natural gas is optimized, and the following specific scheme is given: a compressor and a cooler are provided in the route for exporting natural gas through the pre-cooling cold box. As one of the multiple feasible options, the significance of such a setting is that the natural gas in the route is pressurized and cooled by the compressor and the cooler to reach the pressure required by the external natural gas pipeline network, and then transported to the outside.

[0018] Furthermore, when the secondary concentration treatment is carried out, the secondary concentration tower and the cryogenic cold box are coordinated. Specifically, the secondary concentration tower outputs at least one passage from the top to connect to the cryogenic cold box, and the passage is provided with a secondary condenser and a secondary reflux tank that are connected in sequence, the gas phase passage output from the top of the secondary reflux tank is connected to the cryogenic cold box, and the liquid phase passage output from the bottom of the secondary reflux tank is connected to the secondary concentration tower. As one of the multiple feasible options, the significance of such a setting is that the cryogenic cold box can obtain a crude helium product after removing hydrocarbon substances such as methane from the gas phase material of the secondary reflux tank, thereby realizing the production of helium; the liquid phase material of the secondary reflux tank can be used as the top reflux liquid by refluxing to the secondary concentration tower.

[0019] Furthermore, similar to the primary concentration tower, the secondary condenser and the secondary reflux tank are integrated into the top of the secondary concentration tower. The integrated secondary concentration tower and the deep cold box are integrated into a skid as a whole, which can reduce the loss of cold during transportation and improve the utilization of cold energy.

[0020] When transportation conditions permit, the primary concentration tower, pre-cooling cold box, secondary concentration tower and deep cooling cold box can be integrated into one skid, which can further reduce the loss of cold energy and improve the utilization rate of cold energy during transportation.

[0021] Furthermore, the liquid phase material in the secondary concentration tower is stored at the bottom of the tower, and the liquid phase material can be reprocessed to extract the required materials such as natural gas. Specifically, at least one passage of the secondary concentration tower bottom output passes through a deep cooling box and is connected to the passage output from the top of the primary concentration tower to the pre-cooling box. As one of the multiple feasible options, the significance of such a setting is that the liquid phase is converted into a gas phase material after being reheated by the deep cooling box, and then mixed with the meteorological material output from the primary concentration tower, and can be output as natural gas after being reheated in the pre-cooling box.

[0022] Furthermore, the cryogenic cold box provides a cold temperature environment during operation. The cryogenic cold box can achieve this effect in a variety of ways. Here, the cold source of the cryogenic cold box is optimized, and the following specific scheme is given: the cryogenic cold box is provided with a nitrogen circulation refrigeration device, and the nitrogen circulation refrigeration device includes a circulation passage through the cryogenic cold box, and the circulation passage is provided with a nitrogen inlet, a nitrogen compressor and a compressor unit cooler; the circulation passage includes at least one circulation branch passing through the secondary condenser, and the circulation branch is provided with a co-produced liquid nitrogen outlet. As one of the multiple feasible options, the significance of such a setting is that using nitrogen as a refrigerant gas is very stable and safe, and non-polluting. After passing through the circulation passage, the gaseous nitrogen can take away the heat in the cryogenic cold box and the heat of the secondary condenser, while providing cold for the two. At the same time, the co-produced liquid nitrogen outlet on the circulation branch can extract part of the liquid nitrogen for industrial practicality, and the production of liquid nitrogen can be realized.

[0023] Specifically, the nitrogen gas reheated in the cryogenic cold box and the supplemented high-purity nitrogen enter the nitrogen compressor and the compressor unit cooler, and after being pressurized and cooled to 1.6-2.0MPa.g, 40-50°C, a small part (about 15-40%) enters the cryogenic cold box and condenses into a liquid phase (-170°C), which can be throttled to 0.2MPa.g by the nitrogen refrigerant throttle valve and then enter the nitrogen compressor. The remaining high-pressure and room-temperature nitrogen gas enters the cryogenic cold box and condenses to -170°C, and then enters the nitrogen refrigerant throttle valve and throttles to 0.2MPa.g, and then enters the secondary condenser to provide cooling capacity for it. At the same time, part of the liquid can be extracted from the co-production liquid nitrogen outlet as the factory's liquid nitrogen product. The gas phase reheated in the secondary condenser enters the cryogenic cold box and then enters the nitrogen compressor after reheating, thus completing the nitrogen refrigeration cycle.

[0024] Furthermore, the entire device purifies the natural gas before producing natural gas and helium from the raw gas. Since there are a large number of heavy hydrocarbon substances in the raw gas, the purification part of the device is optimized, and the following specific scheme is cited: the two-tower helium extraction device also includes a heavy hydrocarbon removal device, and the heavy hydrocarbon removal device includes a heavy hydrocarbon washing tower, and the gas phase output path of the heavy hydrocarbon washing tower is connected to the heavy hydrocarbon reflux tank after passing through a pre-cooling cold box; the heavy hydrocarbon reflux tank at least outputs one path connected to the primary concentration tower, at least outputs one path through the pre-cooling cold box and then passes to the primary concentration tower, and also outputs at least one liquid phase path provided with a reflux pump to reflux to the heavy hydrocarbon washing tower. As one of many feasible options, the significance of such an arrangement is that the heavy hydrocarbon washing tower is arranged at the pre-cooling cold box, and the raw gas enters the heavy hydrocarbon washing tower after passing through the pre-cooling cold box, and can be separated to obtain stable light hydrocarbon products and helium-containing gas phase substances. After the helium-containing gas phase substances pass through the pre-cooling cold box environment and the heavy hydrocarbon reflux tank, the gas phase substances and residual liquid phase substances that can be transported to the primary concentration tower are separated, wherein the gas phase substances are connected to the primary concentration tower through two gas phase passages output from the heavy hydrocarbon reflux tank, and the residual liquid phase substances are refluxed to the heavy hydrocarbon washing tower through the liquid phase passage as the top washing liquid.

[0025] The above content discloses a switchable two-tower helium extraction device for natural gas, which can realize the purification of raw gas, produce natural gas from raw gas, and freely control the production and production of helium. The present invention also discloses a two-tower helium extraction process, which uses the above disclosed two-tower helium extraction device to realize natural gas production and helium production, and can be freely selected according to needs during the process. The process is now described.

[0026] A switchable two-tower natural gas helium extraction process, using the above disclosed helium extraction device, comprises:

[0027] Raw gas pre-cooling and decontamination treatment;

[0028] When only natural gas is produced, a primary concentration process including reboiling and condensation is performed to obtain a treated natural gas product;

[0029] When producing natural gas and simultaneously producing helium, a primary concentration treatment including reboiling and condensation is performed to obtain a treated natural gas product, and crude helium is obtained after reflux treatment; and a secondary concentration treatment including reboiling, condensation and reflux is performed to obtain a helium product;

[0030] The liquid products obtained from the primary concentration treatment and the secondary concentration treatment are subjected to environmental treatment in a pre-cooling cold box or a deep-cooling cold box to obtain natural gas for external transmission.

[0031] By using the two-tower helium extraction device disclosed above, the precooling and decontamination treatment of the raw gas is mainly completed in the precooling cold box and the preceding connected equipment. When heavy hydrocarbon substances are used, a heavy hydrocarbon removal device is used as the preceding connected equipment. When other substances need to be removed and purified, appropriate preceding connected equipment can be selected in a targeted manner.

[0032] When switching between the two production modes of producing only natural gas and producing natural gas and simultaneously producing helium, it is achieved through a shut-off valve. When the shut-off valve is in a closed and blocked state, natural gas can be produced and helium can be produced simultaneously. When the shut-off valve is in an open and connected state, only natural gas is produced.

[0033] Compared with the prior art, the present invention has the following beneficial effects:

[0034] The two-tower helium extraction device provided by the present invention switches the production output of natural gas and helium by controlling the primary concentration tower and the secondary concentration tower to participate in the production process; the device can be applied to raw gas with various component ratios, and can separate the components in the raw gas more thoroughly, with a simple process and significant effect. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for use in the embodiments are briefly introduced below. It should be understood that the following drawings only represent some embodiments of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without creative work.

[0036] Figure 1 This is a process step diagram of the double tower helium extraction process;

[0037] Figure 2 This is a schematic diagram of the composition of the double-tower helium extraction equipment.

[0038] In the above drawings, the meanings of the various marks are: 1. pre-cooling cold box; 2. heavy hydrocarbon washing tower; 3. bottom throttle valve; 4. heavy hydrocarbon reflux tank; 5. reflux pump; 6. pressure balance valve; 7. throttle valve; 8. primary concentration tower; 9. primary reboiler; 10. primary condenser; 11. primary reflux tank; 12. compressor; 13. cooler; 14. shut-off valve; 15. nitrogen compressor; 16. compressor unit cooler; 17. secondary reflux tank; 18. deep cold box; 19. secondary concentration tower; 20. secondary reboiler; 21. secondary condenser. DETAILED DESCRIPTION

[0039] The present invention will be further explained below in conjunction with the accompanying drawings and specific embodiments.

[0040] It should be noted that the description of these embodiments is used to help understand the present invention, but does not constitute a limitation of the present invention. The specific structures and functional details disclosed herein are only used to describe the exemplary embodiments of the present invention. However, the present invention can be embodied in many alternative forms, and it should not be understood that the present invention is limited to the embodiments set forth herein.

[0041] Example 1

[0042] like Figure 1 As shown, this embodiment discloses a switchable two-tower natural gas helium extraction process, which can process helium-containing raw gas to ultimately produce natural gas or simultaneously produce helium. The process includes:

[0043] S01: Raw gas pre-cooling and decontamination treatment;

[0044] S02a: When only natural gas is produced, a primary concentration treatment including reboiling and condensation is performed to obtain a treated natural gas product;

[0045] S02b: When producing natural gas and simultaneously producing helium, a primary concentration treatment including reboiling and condensation is performed to obtain a treated natural gas product, and crude helium is obtained after reflux treatment; and a secondary concentration treatment including reboiling, condensation and reflux is performed to obtain a helium product;

[0046] S03: The liquid products obtained from the primary concentration treatment and the secondary concentration treatment are subjected to environmental treatment in the pre-cooling cold box 1 or the deep cooling cold box 18 to obtain natural gas for external transmission.

[0047] By using the two-tower helium extraction device disclosed above, the precooling and decontamination treatment of the raw gas is mainly completed in the precooling cold box 1 and the preceding connected equipment. When heavy hydrocarbon substances are used, a heavy hydrocarbon removal device is used as the preceding connected equipment. When other substances need to be removed and purified, appropriate preceding connected equipment can be selected in a targeted manner.

[0048] When switching between the two production modes of producing only natural gas and producing natural gas and simultaneously producing helium, it is achieved through the shut-off valve 14. When the shut-off valve 14 is in a closed and blocked state, natural gas can be produced and helium can be produced simultaneously. When the shut-off valve 14 is in an open and connected state, only natural gas is produced.

[0049] In the process of producing helium, nitrogen is passed into a nitrogen circulation refrigeration device, and the gaseous nitrogen is converted into liquid nitrogen by heat exchange in the circulation path and output as a production product.

[0050] Example 2

[0051] Based on the preparation process disclosed in Example 1, this example provides a two-tower helium extraction device for processing helium-containing raw gas, and at the same time discloses the details of the process in Example 1 in conjunction with the device.

[0052] The helium-containing raw gas to be treated is 3.0-6.0 MPa.g, and is treated by the following disclosed device:

[0053] like Figure 2 As shown, this embodiment discloses a switchable two-tower helium extraction device for natural gas, comprising a precooling cold box 1, a primary concentration tower 8, a secondary concentration tower 19 and a cryogenic cold box 18 connected in sequence; a gas phase outlet is provided at the lower part of the primary concentration tower 8, and the gas phase outlet is connected to the precooling cold box 1 and then back-connected to an inlet arranged in the middle of the primary concentration tower 8, and the back-connecting section is connected to a cut-off valve 14 by a bypass, and the passage where the cut-off valve 14 is located passes through the precooling cold box 1 and outputs natural gas; a gas phase outlet is provided at the top of the primary concentration tower 8 and at least one passage is output to connect to the secondary concentration tower 19, and after the secondary concentration tower 19 performs secondary concentration treatment, at least one passage is output through the cryogenic cold box 18 and outputs helium.

[0054] The above disclosed helium extraction device realizes the initial extraction and processing of helium and the production of natural gas in the primary concentration tower 8 through the cooperation of the primary concentration tower 8 and the secondary concentration tower 19, realizes the extraction of the crude product of helium in the secondary concentration tower 19, and continues to produce the surplus natural gas. The pre-cooling cold box 1 and the deep cold box 18 provide temperature environments for the processes involved in the primary concentration tower 8 and the processes involved in the secondary concentration tower 19, respectively.

[0055] Generally, after the raw gas enters the pre-cooling cold box 1, it is pre-cooled to -40℃~-75℃, and then undergoes preliminary purification treatment to a temperature of -55℃~-90℃, and a pressure adjustment of 2.92~5.92MPa.g, from which it can enter the primary concentration tower 8 for a primary concentration operation.

[0056] When controlling the production of helium, the shut-off valve 14 is closed to block the passage, and the passage output from the primary concentration tower 8 and through the pre-cooling cold box 1 can return to the entrance in the middle of the primary concentration tower 8, and after diversion, a passage is output to the secondary concentration tower 19 to complete the subsequent helium preparation process, and at the same time, the production of natural gas can be realized.

[0057] When controlling the production of natural gas without producing helium, the shut-off valve 14 is opened to connect the passage. According to Newton's third law, the material in the passage output from the primary concentration tower 8 and passing through the pre-cooling cold box 1 will not flow back to the primary concentration tower 8, but will be directly output to the outside after passing through the pre-cooling cold box 1.

[0058] According to the arrangement of this embodiment, the production mode can be selected by controlling the on-off of the cut-off valve 14 without affecting the production of natural gas, and the production of helium can be freely selected and controlled.

[0059] The primary concentration tower 8 and the secondary concentration tower 19 are connected to the equipment for coordinated operation in the device, and the following specific scheme is cited here: the bottom of the primary concentration tower 8 and the secondary concentration tower 19 are respectively provided with a primary reboiler 9 and a secondary reboiler 20, and the output passages of the primary reboiler 9 and the secondary reboiler 20 pass through the precooling cold box 1 and the deep cooling cold box 18, respectively, and then are respectively connected to the primary concentration tower 8 and the secondary concentration tower 19. With this structure, the primary concentration tower 8 plays a direct role in the production of natural gas when it is working, and can complete the first step of producing helium; when helium needs to be produced, the secondary concentration tower 19 intervenes to complete the production of helium.

[0060] The material enters the primary concentration tower 8, and the primary reboiler 9 performs heat exchange on the material, wherein the material releases heat at the primary reboiler 9 and provides heat for the primary concentration tower 8. The temperature range of the material after the primary reboiler 9 changes to -62°C ~ -97°C, and the material enters the pre-cooling cold box 1 again. After passing through the temperature environment of the pre-cooling cold box 1, the temperature reaches -90°C ~ -120°C and is completely condensed into a liquid phase; the condensed material is adjusted to a pressure of 2 ~ 3.5MPa.g after throttling treatment and enters the middle inlet of the primary concentration tower 8 for concentration treatment.

[0061] The primary reboiler 9 is integrated at the bottom of the primary concentration tower 8, and the secondary reboiler 20 is integrated at the bottom of the secondary concentration tower 19. As an integrated device, the loss of cold can be reduced.

[0062] In order to prepare helium, the material output from the primary concentration tower 8 needs to be concentrated again, so the passage is optimized. Here is a specific scheme: a primary condenser 10 is provided in the passage output from the top of the primary concentration tower 8 and connected to the secondary concentration tower 19. The output end of the primary condenser 10 is connected to the primary reflux tank 11. The gas phase passage at the top of the primary reflux tank 11 is connected to the secondary concentration tower 19, and the liquid phase passage at the bottom of the primary reflux tank 11 is connected to the primary purification tower. As one of the multiple feasible options, the significance of such a setting is that a part of the material output from the primary condenser 10 enters the primary reflux tank 11, and is divided into a gas phase and a liquid phase by reflux, wherein the gas phase part contains helium and enters the secondary concentration tower 19 for secondary treatment and concentration to obtain helium; the liquid phase part refluxes to the primary concentration tower 8 as the top reflux liquid.

[0063] The primary condenser 10 and the primary reflux tank 11 are integrated at the top of the primary concentration tower 8. The precooling cold box 1 and the integrated primary concentration tower can be integrated into a skid block to facilitate the overall cooling of the equipment and improve the utilization of cold energy during transportation.

[0064] The gaseous material output from the top of the primary concentration tower 8 has a pressure and temperature of 1.8 to 3.3 MPa.g and -100°C to -130°C, respectively. After passing through the primary condenser 10, the pressure and temperature change to 1.75 to 3.25 MPa.g and -120°C to -145°C, and then enters the primary reflux tank 11. The output of the primary reflux tank 11 is transported to the secondary concentration tower 19 through the passage, and temperature exchange is carried out in the secondary reboiler 20 at the bottom of the secondary concentration tower 19.

[0065] Part of the concentrated liquid phase material is accumulated at the bottom of the primary concentration tower 8, and the liquid phase material is processed again to obtain the required natural gas. Here, the structure of the primary concentration tower 8 is optimized, and the following specific scheme is given: the bottom of the primary concentration tower 8 outputs at least two passages, at least one of which passes through the primary condenser 10 and the pre-cooling cold box 1 to output natural gas, and at least one passage directly passes through the pre-cooling cold box 1 to output natural gas. As one of the multiple feasible options, the significance of such a setting is that the passage that first passes through the primary condenser 10 can provide a certain amount of cooling for the primary condenser 10.

[0066] The natural gas produced in the above technical solution needs to be pre-processed to reach the external transmission standard when it is transported to the external natural gas pipeline network. Therefore, the path for outputting the natural gas is optimized, and the following specific solution is given: the path for outputting the natural gas through the pre-cooling cold box 1 is provided with a compressor 12 and a cooler 13. As one of the multiple feasible options, the significance of such a setting is that the compressor 12 and the cooler 13 are used to pressurize and cool the natural gas in the path to reach the pressure required by the external natural gas pipeline network, and then transport it to the outside.

[0067] In this embodiment, the liquid phase material at the bottom of the primary concentration tower 8 is LNG (Liquefied Natural Gas), which enters the pre-cooling cold box 1 after the pressure is controlled at a certain value by the throttle valve 7, and is reheated to 15°C to 40°C to form a gas phase and enters the compressor 12 and the cooler 13 to finally reach the pressure of the external natural gas pipeline network before being exported for use. The gas exported is mainly methane. A small part of the LNG at the bottom of the primary concentration tower 8 is controlled to a pressure of 0.35 to 1.3 MPa.g by the throttle valve 7, and then passes through the primary condenser 10 to provide cooling capacity for it, and then enters the pre-cooling cold box 1 after gasification, and is reheated to 15°C to 40°C to form a gas phase, and then passes through the compressor 12 and the cooler 13 to reach the pressure of the external natural gas pipeline network before being exported for use. The external gas is low-pressure gas.

[0068] When the secondary concentration treatment is carried out, the secondary concentration tower 19 and the cryogenic cold box 18 cooperate. Specifically, the secondary concentration tower 19 outputs at least one passage from the top to connect to the cryogenic cold box 18, and the passage is provided with a secondary condenser 21 and a secondary reflux tank 17 that are connected in sequence. The gas phase passage output from the top of the secondary reflux tank 17 is connected to the cryogenic cold box 18, and the liquid phase passage output from the bottom of the secondary reflux tank 17 is connected to the secondary concentration tower 19. As one of the multiple feasible options, the significance of such a setting is that the cryogenic cold box 18 removes methane and other hydrocarbon substances from the gas phase of the secondary reflux tank 17 to obtain a crude helium product, thereby realizing the production of helium; the liquid phase of the secondary reflux tank 17 can be used as a tower top reflux liquid by refluxing to the secondary concentration tower 19.

[0069] Similar to the primary concentration tower, the secondary condenser 21 and the secondary reflux tank 17 are integrated into the top of the secondary concentration tower 19. The integrated secondary concentration tower and the deep cold box 18 are integrated into a skid as a whole, which can reduce the loss of cold during transportation and improve the utilization of cold energy.

[0070] When transportation conditions permit, the primary concentration tower 8, pre-cooling cold box 1, secondary concentration tower 19 and deep cooling cold box 18 can be integrated into one skid, which can further reduce the loss of cold energy and improve the utilization rate of cold energy during transportation.

[0071] The material entering the secondary concentration tower 19 is the gas phase from the primary reflux tank 11, and its pressure and temperature ranges are 1.75 to 3.25 MPa.g and -120°C to -145°C, respectively. A secondary reboiler 20 is provided at the bottom of the secondary concentration tower 19, and the secondary reboiler 20 performs heat exchange on the material, wherein the material releases heat at the outlet of the secondary reboiler 20 and provides heat for the secondary concentration tower 19. The temperature range of the material after passing through the secondary reboiler 20 changes to -133°C to -155°C, and the material then enters the cryogenic cold box 18. After passing through the temperature environment of the cryogenic cold box 18, the temperature reaches -165°C to -175°C and is completely condensed into a liquid phase; the condensed material enters the middle entrance of the secondary concentration tower 19 for concentration treatment.

[0072] After the secondary concentration treatment, the material output from the top of the secondary concentration tower 19 is in the gas phase, and the temperature range is -155°C to -170°C. After condensation in the secondary condenser 21, the temperature changes to -180°C, and then enters the secondary reflux tank 17. The secondary reflux tank 17 outputs the gas phase and the liquid phase, which respectively reach the deep cold box 18 to output the crude helium product and the reflux liquid of the secondary concentration tower 19.

[0073] The liquid phase material in the secondary concentration tower 19 is stored at the bottom of the tower. The liquid phase material can be reprocessed and the required materials such as natural gas can be extracted. Specifically, at least one passage is output from the bottom of the secondary concentration tower 19 through the deep cooling box 18, and is connected to the passage output from the top of the primary concentration tower 8 to the pre-cooling box 1. As one of the multiple feasible options, the significance of such a setting is that the liquid phase is converted into gas phase material after being reheated by the deep cooling box 18, and then mixed with the meteorological material output from the primary concentration tower 8, and can be output as natural gas after being reheated by the pre-cooling box 1.

[0074] Example 3

[0075] Based on Example 2, this embodiment improves the cold source structure of the cryogenic cold box 18, provides cold capacity for the cryogenic cold box 18 through a nitrogen circulation structure, and can also realize the production of liquid nitrogen.

[0076] The details are as follows: Figure 2As shown, the cryogenic cold box 18 provides a cold temperature environment during operation. The cryogenic cold box 18 can achieve this effect in a variety of ways. Here, the cold source of the cryogenic cold box 18 is optimized, and the following specific scheme is cited: the cryogenic cold box 18 is provided with a nitrogen circulation refrigeration device, and the nitrogen circulation refrigeration device includes a circulation passage through the cryogenic cold box 18, and the circulation passage is provided with a nitrogen inlet, a nitrogen compressor 15 and a compressor unit cooler 16; the circulation passage includes at least one circulation branch through the secondary condenser 21, and the circulation branch is provided with a co-production liquid nitrogen outlet. As one of the multiple feasible options, the significance of such a setting is that nitrogen is very stable and safe as a refrigerant gas, and it is non-polluting. After passing through the circulation passage, the gaseous nitrogen can take away the heat in the cryogenic cold box 18 and the heat of the secondary condenser 21, providing cold for both, and realizing the production of liquid nitrogen.

[0077] In this embodiment, the nitrogen gas reheated by the cryogenic cold box 18 and the supplemented high-purity nitrogen enter the nitrogen compressor 15 and the compressor unit cooler 16, and after being pressurized and cooled to 1.6-2.0 MPa.g, 40-50°C, a small part (about 15-40%) enters the cryogenic cold box 18 and condenses into a liquid phase (-170°C), which can be throttled to 0.2 MPa.g by the nitrogen refrigerant throttle valve and then enter the nitrogen compressor 15, and the remaining high-pressure and room-temperature nitrogen gas enters the cryogenic cold box 18 and condenses to -170°C, and then enters the nitrogen refrigerant throttle valve and throttles to 0.2 MPa.g, and then enters the secondary condenser 21 to provide cooling capacity for it, and at the same time, part of the liquid phase can be extracted from the co-production liquid nitrogen outlet as the liquid nitrogen product of the factory. The gas phase reheated by the secondary condenser 21 enters the cryogenic cold box 18 and then enters the nitrogen compressor 15 after reheating, thus completing the nitrogen refrigeration cycle.

[0078] The structures of other parts in this embodiment are the same as those in Embodiment 2 and will not be described in detail here.

[0079] Example 4

[0080] This embodiment improves the purification and decontamination structure of the raw gas on the basis of the embodiment 2. In particular, the heavy hydrocarbon substances are separated and processed separately.

[0081] The details are as follows: Figure 2As shown, the whole device purifies the natural gas before producing natural gas and helium from the raw gas. Since there are a lot of heavy hydrocarbon substances in the raw gas, the purification part of the device is optimized, and the following specific scheme is cited: the two-tower helium extraction device also includes a heavy hydrocarbon removal device, and the heavy hydrocarbon removal device includes a heavy hydrocarbon washing tower 2, and the gas phase output path of the heavy hydrocarbon washing tower 2 passes through a pre-cooling cold box 1 and then passes to a heavy hydrocarbon reflux tank 4; the heavy hydrocarbon reflux tank 4 at least outputs a path connected to a primary concentration tower 8, at least outputs a path through the pre-cooling cold box 1 and then passes to the primary concentration tower 8, and also outputs at least a liquid phase path provided with a reflux pump 5 to reflux to the heavy hydrocarbon washing tower 2.

[0082] The passage from the heavy hydrocarbon reflux tank 4 through the pre-cooling cold box 1 to the primary concentration tower 8 is provided with a pressure balancing valve 6. When the heat demanded by the primary reboiler 9 is greater than the heat provided by the raw gas, part of the raw gas directly enters the pre-cooling cold box 1 through the pressure balancing valve 6.

[0083] The present embodiment can adopt a variety of structures to achieve the treatment of heavy hydrocarbon substances or other pollutants, as one of a variety of feasible options. The significance of the arrangement of the present embodiment is that the heavy hydrocarbon washing tower 2 is arranged at the pre-cooling cold box 1, and the raw gas enters the heavy hydrocarbon washing tower 2 after passing through the pre-cooling cold box 1, and can be separated to obtain stable light hydrocarbon products and helium-containing gas phase substances, wherein the light hydrocarbon products are output to the outside after being restricted and regulated by the throttle valve 3 at the bottom of the tower; the helium-containing gas phase substance passes through the environment of the pre-cooling cold box 1 and the heavy hydrocarbon reflux tank 4, and is separated into gas phase substances and residual liquid phase substances that can be transported to the primary concentration tower 8, wherein the gas phase substances are connected to the primary concentration tower 8 through two gas phase passages output by the heavy hydrocarbon reflux tank 4, and the residual liquid phase substances are refluxed to the heavy hydrocarbon washing tower 2 through the liquid phase passage as the top washing liquid.

[0084] The above are the embodiments of the present invention, but the present invention is not limited to the above optional embodiments. Those skilled in the art can arbitrarily combine the above methods to obtain other various embodiments. Anyone can obtain other various forms of embodiments under the enlightenment of the present invention. The above specific embodiments should not be understood as limiting the scope of protection of the present invention. The scope of protection of the present invention shall be based on the definition in the claims, and the description can be used to interpret the claims.

Claims

1. A switchable two-tower natural gas helium extraction device, characterized in that: The invention comprises a precooling cold box (1), a primary concentration tower (8), a secondary concentration tower (19) and a cryogenic cold box (18) which are connected in sequence; a gas phase outlet is provided at the lower part of the primary concentration tower (8), the gas phase outlet is connected to the precooling cold box (1) and then is connected back to an inlet provided in the middle part of the primary concentration tower (8), the connection section is connected to a cut-off valve (14) and the passage where the cut-off valve (14) is located passes through the precooling cold box (1) and outputs natural gas; a gas phase outlet is provided at the top of the primary concentration tower (8) and at least one passage is connected to the secondary concentration tower (19), and after the secondary concentration tower (19) performs secondary concentration treatment, at least one passage is output through the cryogenic cold box (18) and outputs helium; A primary reboiler (9) and a secondary reboiler (20) are respectively arranged at the bottom of the primary concentration tower (8) and the secondary concentration tower (19); the output passages of the primary reboiler (9) and the secondary reboiler (20) pass through a precooling cold box (1) and a deep cooling cold box (18) respectively, and then are connected to the primary concentration tower (8) and the secondary concentration tower (19) respectively; A primary condenser (10) is provided in the passage output from the top of the primary concentration tower (8) and connected to the secondary concentration tower (19); the output end of the primary condenser (10) is connected to the primary reflux tank (11); the gas phase passage at the top of the primary reflux tank (11) is connected to the secondary concentration tower (19), and the liquid phase passage at the bottom of the primary reflux tank (11) is connected to the primary purification tower; the secondary concentration tower (19) outputs at least one passage from the top connected to the cryogenic cold box (18), and a secondary condenser (21) and a secondary reflux tank (17) are provided in the passage connected in sequence; the gas phase passage output from the top of the secondary reflux tank (17) is connected to the cryogenic cold box (18), and the liquid phase passage output from the bottom of the secondary reflux tank (17) is connected to the secondary concentration tower (19).

2. The switchable two-tower natural gas helium extraction device according to claim 1 is characterized in that: The bottom of the primary concentration tower (8) outputs at least two pathways, wherein at least one pathway outputs natural gas after passing through a primary condenser (10) and a precooling box (1), and at least one pathway outputs natural gas directly after passing through the precooling box (1).

3. The switchable two-tower natural gas helium extraction device according to claim 2 is characterized in that: The passage that passes through the pre-cooling cold box (1) and outputs the natural gas is provided with a compressor (12) and a cooler (13).

4. The switchable two-tower natural gas helium extraction device according to claim 1 is characterized in that: At least one channel is output from the bottom of the secondary concentration tower (19) through a deep cooling box (18) and is connected to a channel output from the top of the primary concentration tower (8) to the pre-cooling box (1).

5. The switchable two-tower natural gas helium extraction device according to claim 1 is characterized in that: The cryogenic cold box (18) is provided with a nitrogen circulation refrigeration device, which includes a circulation passage passing through the cryogenic cold box (18), and the circulation passage is provided with a nitrogen inlet, a nitrogen compressor (15) and a compressor unit cooler (16); the circulation passage includes at least one circulation branch passing through a secondary condenser (21), and the circulation branch is provided with a co-produced liquid nitrogen outlet.

6. The switchable two-tower natural gas helium extraction device according to claim 1 is characterized in that: The invention also comprises a heavy hydrocarbon removal device, wherein the heavy hydrocarbon removal device comprises a heavy hydrocarbon washing tower (2), wherein a gas phase output passage of the heavy hydrocarbon washing tower (2) passes through a pre-cooling cold box (1) and then passes to a heavy hydrocarbon reflux tank (4); the heavy hydrocarbon reflux tank (4) outputs at least one passage connected to a primary concentration tower (8), at least one passage passes through a pre-cooling cold box (1) and then passes to a primary concentration tower (8), and also outputs at least one liquid phase passage provided with a reflux pump (5) to reflux to the heavy hydrocarbon washing tower (2).

7. A switchable two-tower natural gas helium extraction process, using the helium extraction device described in any one of claims 1 to 6, characterized in that: include: Raw gas pre-cooling and decontamination treatment; When only natural gas is produced, a primary concentration process including reboiling and condensation is performed to obtain a treated natural gas product; When producing natural gas and simultaneously producing helium, a primary concentration treatment including reboiling and condensation is performed to obtain a treated natural gas product, and crude helium is obtained after reflux treatment; and a secondary concentration treatment including reboiling, condensation and reflux is performed to obtain a helium product; The liquid products obtained from the primary concentration treatment and the secondary concentration treatment are subjected to environmental treatment in a pre-cooling cold box (1) or a deep cooling cold box (18) to obtain natural gas for external transmission.

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