System and method for purifying helium and applications

Abstract

The present application relates to helium purification technical field, disclose a kind of system and method and application for purifying helium.The system includes: sequentially connected first gas-liquid separation device, first helium extraction column (11), second gas-liquid separation device, second helium extraction column (27) and nitrogen removal column (33), the first gas-liquid separation device is used to carry out first processing to the helium-containing natural gas (1) and is changed into first gas phase and first liquid phase;The first helium extraction column (11) is used to carry out first rectification to the first gas phase and first liquid phase, obtain second gas phase and second liquid phase;The second gas-liquid separation device is used to carry out second processing to the second gas phase and is changed into third gas phase and third liquid phase;The second helium extraction column (27) is used to carry out second rectification to the third gas phase and third liquid phase, obtain crude helium and fourth liquid phase;The nitrogen removal column (33) is used to carry out nitrogen removal processing to the fourth liquid phase.The system and method provided by the present application have broad application prospect.

Description

Technical Field

[0001] This invention relates to the field of helium purification technology, specifically to a system, method, and application for purifying helium. Background Technology

[0002] Helium is a colorless and odorless rare inert gas with wide applications in high-tech fields such as clinical medicine, national defense, aerospace, nuclear industry, deep-sea diving, cryogenic superconductivity, and high-precision welding. It is a crucial and scarce strategic resource related to national security and the development of high-tech industries. Helium is a monatomic gas and cannot be synthesized through chemical reactions; separating and purifying helium from helium-containing natural gas is currently the only source for industrial helium production. However, my country is short of helium resources and relies heavily on imports. Therefore, developing suitable technologies for extracting helium from natural gas is of significant strategic importance for ensuring national helium security. It is particularly important for the comprehensive and efficient utilization of natural gas resources and improving the economic benefits of gas field development.

[0003] Cryogenic methods are the most widely used and mature separation technology in the field of natural gas helium extraction. They typically consist of natural gas pretreatment and purification, cryogenic distillation to extract crude helium, and helium refining.

[0004] The existing natural gas helium extraction process has the following main defects: (1) The natural gas helium component recovery adopts a deep cryogenic process, which requires deep removal of carbon dioxide to ensure that dry ice does not form under low temperature conditions and freeze and block the cold box and other equipment, resulting in secondary dehydration, high investment and high operating energy consumption, making it difficult to achieve economic efficiency. (2) Multi-stage combined refrigeration is required, which has a long process, high investment, high operating costs, and complex operation, making it impossible to achieve economic efficiency.

[0005] Therefore, finding an economical and efficient process for purifying helium remains a problem that urgently needs to be solved. Summary of the Invention

[0006] The purpose of this invention is to overcome the technical problems existing in the prior art and to provide a system, method and application for purifying helium.

[0007] To achieve the above objectives, a first aspect of the present invention provides a system for purifying helium, the system comprising: a first gas-liquid separation device, a primary helium extraction tower, a second gas-liquid separation device, a secondary helium extraction tower, and a denitrification tower connected in sequence.

[0008] The first gas-liquid separation device is used to process helium-containing natural gas into a first gas phase and a first liquid phase.

[0009] The first-stage helium extraction tower is used to perform a first distillation on the first gas phase and the first liquid phase to obtain a second gas phase and a second liquid phase.

[0010] The second gas-liquid separation device is used to perform a second treatment on the second gas phase to convert it into a third gas phase and a third liquid phase;

[0011] The secondary helium extraction tower is used to perform a second distillation on the third gas phase and the third liquid phase to obtain crude helium product and a fourth liquid phase;

[0012] The denitrification tower is used to denitrify the fourth liquid phase to obtain nitrogen and LNG products.

[0013] A second aspect of the present invention provides a method for purifying helium, the method comprising the following steps:

[0014] (1) The helium-containing natural gas is subjected to a first process to become a first gas phase and a first liquid phase;

[0015] (2) The first gas phase and the first liquid phase are subjected to a first distillation to obtain a second gas phase and a second liquid phase;

[0016] (3) The second gas phase is subjected to a second process to become a third gas phase and a third liquid phase;

[0017] (4) The third gas phase and the third liquid phase are subjected to a second distillation to obtain crude helium product and a fourth liquid phase;

[0018] (5) The fourth liquid phase is subjected to denitrification treatment to obtain nitrogen and LNG products.

[0019] The third aspect of the present invention provides an application of the system described in the first aspect or the method described in the second aspect above in the extraction of helium from natural gas.

[0020] Through the above technical solution, the helium purification system of the present invention is equipped with a coupling device of a primary helium extraction tower, a secondary helium extraction tower, and a denitrification tower, which greatly reduces the refrigerant refrigeration power, significantly reduces investment, and saves operating costs. Specifically, the primary helium extraction tower achieves cryogenic carbon dioxide removal (hereinafter referred to as carbon) and preliminary helium concentration; the secondary helium extraction tower achieves cryogenic denitrification and secondary helium concentration; and the denitrification tower can produce cryogenic nitrogen refrigerant, providing a cryogenic nitrogen cooling source at the top of the secondary helium extraction tower. Without the need for a conventional nitrogen cycle refrigeration system, highly efficient helium extraction is achieved, with a helium recovery rate exceeding 99%. Simultaneously, the LNG byproduct produced at the top of the denitrification tower significantly improves the overall economic efficiency of the process. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of the system for purifying helium according to a specific embodiment of the present invention.

[0022] Explanation of reference numerals in the attached figures

[0023] 1. Helium-containing natural gas; 2. Medium-pressure lean natural gas; 3. Low-pressure lean natural gas.

[0024] 4. External nitrogen supply; 5. First-stage cold box; 6. First-stage cryogenic separator.

[0025] 7. First-stage reboiler at the bottom of the column; 8. First flow regulating valve; 9. First liquid level regulating valve.

[0026] 10. Second liquid level regulating valve; 11. First-stage helium stripping tower; 12. First-stage helium stripping tower top condenser.

[0027] 13. First-stage helium stripping tower reflux tank; 14. First-stage reflux pump; 15. First-stage helium stripping tower top temperature control valve.

[0028] 16. Temperature control valve at the bottom of the denitrification tower; 17. Third liquid level regulating valve; 18. High-pressure refrigerant.

[0029] 19. Low-pressure vapor refrigerant; 20. Crude helium product; 21. First pressure regulating valve.

[0030] 22. Secondary cold box; 23. Fourth liquid level regulating valve; 24. Secondary cryogenic separator

[0031] 25. Fifth liquid level regulating valve; 26. Secondary helium stripping tower top condenser; 27. Secondary helium stripping tower.

[0032] 28. Second pressure regulating valve; 29. ​​Secondary reboiler at the bottom of the column; 30. Second pressure regulating valve.

[0033] 31. Sixth liquid level regulating valve; 32. Top condenser of the denitrification tower; 33. Denitrification tower.

[0034] 34. Reboiler at the bottom of the denitrification tower; 35. LNG product; 36. JT valve for refrigerant. Detailed Implementation

[0035] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0036] like Figure 1 The first aspect of the present invention provides a system for purifying helium, the system comprising: a first gas-liquid separation device, a primary helium extraction tower 11, a second gas-liquid separation device, a secondary helium extraction tower 27, and a denitrification tower 33, connected in sequence.

[0037] The first gas-liquid separation device is used to process the helium-containing natural gas 1 into a first gas phase and a first liquid phase.

[0038] The first-stage helium extraction tower 11 is used to perform a first distillation on the first gas phase and the first liquid phase to obtain a second gas phase and a second liquid phase.

[0039] The second gas-liquid separation device is used to perform a second treatment on the second gas phase to convert it into a third gas phase and a third liquid phase;

[0040] The secondary helium extraction tower 27 is used to perform a second distillation on the third gas phase and the third liquid phase to obtain crude helium product and a fourth liquid phase;

[0041] The denitrification tower 33 is used to denitrify the fourth liquid phase to obtain nitrogen (exported nitrogen) and LNG products (liquefied natural gas).

[0042] According to some embodiments of the present invention, the first gas phase separation device includes: at least one primary cold box 5 and at least one primary cryogenic separator 6.

[0043] According to a preferred embodiment of the present invention, the first gas phase separation device includes: a primary cold box 5 and a primary cryogenic separator 6 connected in sequence.

[0044] According to some embodiments of the present invention, the primary cold box 5 is used to pre-cool the helium-containing natural gas 1 to obtain cryogenic helium-containing natural gas. The primary cryogenic separator 6 is used to perform a first cryogenic separation on the cryogenic helium-containing natural gas to obtain a first gas phase and a first liquid phase.

[0045] According to some embodiments of the present invention, at least one first-stage reboiler 7 is also provided between the first-stage cold box 5 and the first-stage cryogenic separator 6, for cooling the cryogenic helium-containing natural gas before sending it into the first-stage cryogenic separator 6. This arrangement allows some CO2 to condense and precipitate and the first liquid phase to enter the middle and lower part of the first-stage enrichment tower at a higher temperature, which can effectively suppress the probability of CO2 dry ice blockage. At the same time, it provides its own heat to the first-stage enrichment tower as a reboiler heat source while cooling down.

[0046] In this invention, there are no particular restrictions on the relative positions of the inlets and outlets used for communication between the various devices, as long as they meet the requirements of this invention. For example, the gas phase outlet of the first-stage cryogenic separator 6 can be connected to the middle part of the first-stage helium extraction tower 11, and the liquid phase outlet of the first-stage cryogenic separator 6 can be connected to the lower middle part of the first-stage helium extraction tower 11.

[0047] In this invention, one or more (there is no limit to the number) flow regulating valves, level regulating valves, temperature control valves, and pressure regulating valves can be installed between various devices.

[0048] Preferably, the first-stage helium extraction tower 11 is connected to the first-stage reboiler 7 at the bottom of the tower, and is used to exchange heat in the first-stage reboiler 7 before sending the reboiled liquid at the bottom of the first-stage helium extraction tower 11 into the gas phase space at the bottom of the first-stage helium extraction tower 11 to provide heat for the first-stage helium extraction tower 11.

[0049] In this invention, the various devices can be connected by pipelines. For example, the primary cold box 5, the primary reboiler 7, the primary cryogenic separator 6, the first flow regulating valve 8, the first liquid level regulating valve 9, and the primary helium extraction tower 11 are connected by pipelines.

[0050] According to some embodiments of the present invention, the second gas-liquid separation device includes: at least one primary helium extraction tower reflux tank 13 and at least one secondary cryogenic separator 24.

[0051] According to some embodiments of the present invention, the second gas-liquid separation device includes a primary helium extraction tower reflux tank 13 and a secondary cryogenic separator 24 connected in sequence.

[0052] According to some embodiments of the present invention, the primary helium extraction tower reflux tank 13 is used to separate the second gas phase to obtain a gaseous stream and a liquid stream. The secondary cryogenic separator 24 is used to perform a second cryogenic separation on the gaseous stream to obtain a third gaseous phase and a third liquid phase.

[0053] According to some embodiments of the present invention, at least one primary helium extraction tower top condenser 12 (located outside the primary helium extraction tower) is further provided between the primary helium extraction tower 11 and the primary helium extraction tower reflux tank 13, for condensing the second gas phase and then sending it into the primary helium extraction tower reflux tank 13.

[0054] According to some embodiments of the present invention, at least one secondary reboiler 29 is provided between the primary helium extraction tower reflux tank 13 and the secondary cryogenic separator 24, for cooling the gaseous stream before sending it into the secondary cryogenic separator 24.

[0055] According to some embodiments of the present invention, the gas phase outlet of the secondary cryogenic separator 24 is connected to the middle part of the secondary helium extraction tower 27, and the liquid phase outlet of the secondary cryogenic separator 24 is connected to the lower middle part of the secondary helium extraction tower 27.

[0056] In this invention, a fifth liquid level regulating valve 25 may also be provided between the secondary cryogenic separator 24 and the secondary helium extraction tower 27 to control the flow rate into the secondary helium extraction tower 27 and keep it stable.

[0057] According to some embodiments of the present invention, at least one secondary cold box 22 is further provided between the secondary cryogenic separator 24 and the secondary helium extraction tower 27, for subcooling the third gas phase before sending it into the secondary helium extraction tower 27.

[0058] In this invention, a second pressure regulating valve 28 may be provided between the secondary cold box 22 and the secondary helium extraction tower 27 to control the pressure entering the secondary helium extraction tower 27 to a stable state.

[0059] According to some embodiments of the present invention, the gas phase outlet of the secondary helium extraction tower 27 is connected to the secondary cold box 22 for heat exchange of the gas phase discharged from the top of the secondary helium extraction tower 27 through the secondary cold box 22 to obtain crude helium product.

[0060] In this invention, a first pressure regulating valve 21 may also be provided at the outlet of the secondary cold box 22 to control the output pressure of the crude helium product.

[0061] According to some embodiments of the present invention, the secondary helium extraction tower 27 is connected to the secondary tower bottom reboiler 29, which is used to exchange heat in the secondary tower bottom reboiler 29 and then send the reboiled liquid at the bottom of the secondary helium extraction tower 27 into the gas phase space at the bottom of the secondary helium extraction tower 27 to provide heat for the secondary helium extraction tower 27.

[0062] According to some embodiments of the present invention, a denitrification tower top condenser 32 is provided in the upper part of the denitrification tower 33 (that is, it is provided inside the denitrification tower).

[0063] According to some embodiments of the present invention, the top condenser 32 of the denitrification tower is connected to the secondary cold box 22, and is used to cool and liquefy the high-pressure refrigerant 18 in the secondary cold box 22, and then send it to the top condenser 32 of the denitrification tower to provide cooling capacity for the denitrification tower 33 before returning it to the secondary cold box 22 to obtain low-pressure gaseous refrigerant 19.

[0064] In this invention, the upper part of the secondary helium extraction tower 27 is provided with a secondary helium extraction tower top condenser 26 (that is, it is set inside the secondary helium extraction tower), which is used to exchange heat with the gas phase (nitrogen) at the top of the denitrification tower 33 in the secondary helium extraction tower top condenser 26 and provide cooling capacity to the secondary helium extraction tower top condenser 26. Then, the low-temperature cooling capacity is recovered by the secondary cold box 22, and then reheated by the primary cold box 5, and used as an external nitrogen discharge device.

[0065] According to some embodiments of the present invention, the liquid phase outlet at the bottom of the denitrification tower 33 is connected to the secondary cold box 22, which is used to subcool the liquid phase at the bottom of the denitrification tower 33 through the secondary cold box 22 to obtain LNG product.

[0066] According to some embodiments of the present invention, a denitrification tower bottom reboiler 34 is provided in the lower part of the denitrification tower 33 (that is, it is provided inside the denitrification tower).

[0067] According to some embodiments of the present invention, the bottom reboiler 34 of the denitrification tower is connected to the first-stage helium extraction tower 11 and the top condenser 12 of the first-stage helium extraction tower. It is used to transfer a portion of the second liquid phase from the first-stage helium extraction tower 11 to the denitrification tower 33 via heat exchange in the bottom reboiler 34, and then to the top condenser 12 to provide cooling, thus converting it into crude natural gas. This specific arrangement (the flow direction of the second liquid phase in the first-stage helium extraction tower 11) allows for full coupling and utilization of the energy between the various process streams.

[0068] In this invention, a temperature control valve for the bottom of the denitrification tower can also be provided between the reboiler 34 at the bottom of the denitrification tower and the first-stage helium extraction tower 11 to control the nitrogen content in the LNG product at the bottom of the denitrification tower.

[0069] In this invention, a third liquid level regulating valve 17 may also be provided between the top condenser 12 of the first-stage helium extraction tower and the first-stage helium extraction tower 11 to control the reflux flow rate.

[0070] Preferably, the top condenser 12 of the first-stage helium extraction tower is connected to the first-stage cold box 5, and is used to send the crude natural gas into the first-stage cold box 5 for reheating to obtain low-pressure lean natural gas 3.

[0071] According to some embodiments of the present invention, the liquid phase outlet of the primary helium extraction tower reflux tank 13 is connected to the upper part of the primary helium extraction tower 11, and is used to send the liquid phase material of the primary helium extraction tower reflux tank 13 into the upper part of the primary helium extraction tower 11 as the reflux liquid at the top of the primary helium extraction tower 11.

[0072] In this invention, a primary reflux pump 11 and a primary helium extraction tower top temperature control valve 15 can be installed between the primary helium extraction tower reflux tank 13 and the primary helium extraction tower 11. The primary reflux pump is used to physically pressurize the liquid phase, and then, after the flow rate is regulated by the primary helium extraction tower top temperature control valve 15, it is sent to the upper part of the primary helium extraction tower 11.

[0073] According to some embodiments of the present invention, the bottom of the first-stage helium extraction tower 11 is connected to the first-stage cold box 5 for recovering the remaining portion of the second liquid phase to obtain medium-pressure lean natural gas 2.

[0074] In this invention, a second liquid level regulating valve 10 can be provided between the bottom of the first-stage helium extraction tower 11 and the first-stage cold box 5, for controlling the liquid level of the remaining second liquid phase and then sending it into the first-stage cold box 5 for cold energy recovery.

[0075] A second aspect of the present invention provides a method for purifying helium, the method comprising the following steps:

[0076] (1) The helium-containing natural gas is subjected to a first process to become a first gas phase and a first liquid phase;

[0077] (2) The first gas phase and the first liquid phase are subjected to a first distillation to obtain a second gas phase and a second liquid phase;

[0078] (3) The second gas phase is subjected to a second process to become a third gas phase and a third liquid phase;

[0079] (4) The third gas phase and the third liquid phase are subjected to a second distillation to obtain crude helium product and a fourth liquid phase;

[0080] (5) The fourth liquid phase is subjected to denitrification treatment to obtain nitrogen and LNG products.

[0081] According to some embodiments of the present invention, step (1), the first process includes: precooling the helium-containing natural gas to obtain cryogenic helium-containing natural gas.

[0082] According to some embodiments of the present invention, the first process includes: performing a first cryogenic separation on the helium-containing natural gas and / or the cryogenic helium-containing natural gas to obtain the first gas phase and the first liquid phase.

[0083] According to some embodiments of the present invention, the first process further includes: cooling the helium-containing natural gas and / or cryogenic helium-containing natural gas prior to the first cryogenic separation.

[0084] According to some embodiments of the present invention, in step (2), the conditions for the first distillation may include: a temperature of -95°C to -80°C (such as any value between -95°C, -92°C, -90°C, -88°C, -86°C, -85°C, -82°C, -80°C, or higher), and a pressure of 3.5 MPa to 4.5 MPa (such as any value between 3.5 MPa, 3.8 MPa, 4.0 MPa, 4.2 MPa, 4.4 MPa, 4.5 MPa, or higher). These conditions for the first distillation enable helium to be concentrated more than 30 times; simultaneously achieving low-temperature CO2 removal, controlling the entire column to prevent the generation of dry ice, and controlling the CO2 content in the second gas phase to be below 50 ppm.

[0085] According to some embodiments of the present invention, the method may further include a step of subcooling the first gas phase and the first liquid phase prior to the first distillation.

[0086] According to some embodiments of the present invention, the method further includes a step of heat exchange of the reboiling liquid obtained from the first distillation.

[0087] According to some embodiments of the present invention, in step (3), the second process includes: separating the second gas phase to obtain a gas phase stream and a liquid phase stream.

[0088] According to some embodiments of the present invention, the second process includes: performing a second low-temperature separation on the second gas phase and / or the gas phase stream to obtain a third gas phase and a third liquid phase.

[0089] According to some embodiments of the present invention, the second process further includes condensing the second gas phase prior to the separation.

[0090] According to some embodiments of the present invention, the second process further includes: cooling the second gas phase and / or the gas phase stream prior to the second cryogenic separation.

[0091] According to some embodiments of the present invention, the method further includes returning the separated liquid phase stream to the reflux liquid used in the first distillation.

[0092] According to some embodiments of the present invention, in step (4), the conditions for the second distillation include: a temperature of -185°C to -110°C (such as any value between -185°C, -180°C, -170°C, -160°C, -150°C, -140°C, -130°C, -120°C, -110°C, or higher), and a pressure of 2-3 MPa (such as any value between 2 MPa, 2.1 MPa, 2.2 MPa, 2.3 MPa, 2.4 MPa, 2.5 MPa, 2.7 MPa, 2.8 MPa, 3 MPa, or higher). These conditions for the second distillation can significantly reduce the amount of methane and nitrogen, and further increase the helium concentration.

[0093] According to some embodiments of the present invention, the method further includes: subcooling the third gas phase prior to the second distillation.

[0094] According to some embodiments of the present invention, the method further includes a step of heat exchange of the reboiling liquid obtained by the second distillation.

[0095] According to some embodiments of the present invention, the method further includes the step of heat exchange of the gas phase obtained from the second distillation to obtain crude helium product.

[0096] According to some embodiments of the present invention, in step (5), the conditions for the denitrification treatment include: a temperature of -160 to -110°C (such as any value between -160°C, -150°C, -140°C, -130°C, -120°C, -110°C, or higher), and a pressure of 1.5 MPa to 2.5 MPa (such as any value between 1.5 MPa, 1.6 MPa, 1.7 MPa, 1.8 MPa, 2 MPa, 2.2 MPa, 2.5 MPa, or higher). The denitrification treatment can yield LNG products and by-product nitrogen. The nitrogen produced during denitrification can provide ultra-low temperature cooling capacity of -184°C, avoiding the need for a separate nitrogen cycle refrigeration compressor.

[0097] According to some embodiments of the present invention, the method further includes the step of cooling and liquefying the high-pressure refrigerant to obtain a low-pressure gaseous refrigerant.

[0098] According to some embodiments of the present invention, the method further includes the step of subcooling the liquid phase obtained from the denitrification treatment to obtain LNG products.

[0099] According to some embodiments of the present invention, the method further includes: heat-exchanging a portion of the second liquid phase to convert it into crude natural gas.

[0100] According to some embodiments of the present invention, the method further includes: reheating the crude natural gas to obtain low-pressure lean natural gas.

[0101] According to some embodiments of the present invention, the method further includes: recovering the remaining portion of the second liquid phase by cold energy to obtain medium-pressure lean natural gas.

[0102] In this invention, there are no particular restrictions on the specific conditions of condensation, cooling, heat exchange, separation, low-temperature separation (first low-temperature separation and / or second low-temperature separation), etc., as long as they can meet the requirements of this invention, and can be carried out in accordance with conventional methods in the field.

[0103] The present invention does not impose any particular restrictions on the content of each component in the helium-containing natural gas. For example, by volume fraction, the helium-containing natural gas may contain 98-99% CH4, 0.1-0.5% C2H6, 0.2-0.6% N2, 0.3-0.8% CO2, 0.01-0.1% He and 0.005-0.3% H2.

[0104] According to some embodiments of the present invention, the crude helium product may contain 0.2-0.8% CH4, 6-12% N2, 60-70% He and 15-25% H2 by volume fraction.

[0105] The third aspect of the present invention provides an application of the system described in the first aspect or the method described in the second aspect above in the extraction of helium from natural gas.

[0106] According to a preferred embodiment, combined with Figure 1 The method for purifying helium according to the present invention, when used in the system for purifying helium according to the present invention, specifically includes the following steps:

[0107] (a) The helium-containing natural gas is sent to the first-stage cold box 5 for pre-cooling to obtain low-temperature helium-containing natural gas; then the obtained low-temperature helium-containing natural gas is sent to the first-stage bottom reboiler 7 for cooling and then sent to the first-stage low-temperature separator 6 for the first low-temperature separation to obtain the first gas phase and the first liquid phase.

[0108] (b) The first gas phase and the first liquid phase obtained in step (a) are respectively sent to the first-stage cold box 5 for subcooling and then sent to the first-stage helium stripping tower 11 for first-stage distillation to obtain the second gas phase and the second liquid phase. The first gas phase is sent to the middle part of the first-stage helium stripping tower 11 and the first liquid phase is sent to the lower middle part of the first-stage helium stripping tower 11. After the second liquid phase of the first-stage helium stripping tower 11 is heat-exchanged in the reboiler 34 at the bottom of the denitrification tower to provide heat for the denitrification tower 33, it is sent to the condenser 12 at the top of the first-stage helium stripping tower to provide cooling capacity for the condenser 12 and is converted into crude natural gas. The crude natural gas is then sent to the first-stage cold box 5 for reheating to obtain low-pressure lean natural gas. The remaining part of the second liquid phase is then cooled to obtain medium-pressure lean natural gas. The reboiled liquid at the bottom of the first-stage helium stripping tower 11 is heat-exchanged in the reboiler at the bottom of the first-stage tower and then sent to the gas phase space at the bottom of the first-stage helium stripping tower 11 to provide heat for the first-stage helium stripping tower 11.

[0109] (c) The second gas phase obtained in step (b) is condensed in the top condenser 12 of the first-stage helium extraction tower and then separated in the reflux tank 13 of the first-stage helium extraction tower to obtain a gas stream and a liquid stream. The obtained gas stream is then cooled in the bottom reboiler 29 of the second-stage tower and then sent to the second-stage cryogenic separator 24 for second cryogenic separation to obtain a third gas phase and a third liquid phase. The obtained liquid stream is pressurized by the first-stage reflux pump 14 and its temperature is regulated by the top temperature control valve 15 of the first-stage helium extraction tower before being sent to the upper part of the first-stage helium extraction tower 11 as the reflux liquid at the top of the first-stage helium extraction tower 11.

[0110] (d) The third gas phase obtained in step (c) is sent to the secondary cold box 22 for subcooling and then sent to the middle part of the secondary helium tower 27. The third liquid phase obtained in step (c) is sent to the lower middle part of the secondary helium extraction tower 27. The third gas phase and the third liquid phase are subjected to a second distillation in the secondary helium extraction tower 27. The gas phase obtained at the top of the tower and the liquid phase obtained at the bottom of the tower (the fourth liquid phase) are sent to the secondary cold box 22 for heat exchange to obtain crude helium product. The reboiled liquid at the bottom of the secondary helium extraction tower 27 is sent to the gas phase space at the bottom of the secondary helium extraction tower 27 for heat exchange and then sent to the gas phase space at the bottom of the secondary helium extraction tower 27 to provide heat for the secondary helium extraction tower 27.

[0111] (e) The fourth liquid phase obtained in step (d) is subjected to denitrification treatment, resulting in a gas phase at the top of the column and a liquid phase at the bottom of the column. The gas phase at the top of the column is sent to the top condenser 32 of the secondary helium extraction column for heat exchange and to provide cooling capacity to the top condenser 32 of the secondary helium extraction column. Then, it is sent to the secondary cold box 22 for cryogenic cooling capacity recovery. After that, it is reheated in the primary cold box 5 to obtain nitrogen (as exported nitrogen). The liquid phase at the bottom of the column is sent to the secondary cold box 22 for supercooling to obtain LNG product.

[0112] The present invention will be described in detail below through embodiments.

[0113] The following embodiments will all be combined with Figure 1 The present invention describes a method for purifying helium. Unless otherwise stated, the specific operations of the process are as described above.

[0114] Example 1

[0115] In this implementation, the helium-containing natural gas comprises: 98.5313% CH4, 0.2998% C2H6, 0.4812% N2, 0.6311% CO2, 0.0416% He, and 0.0150% H2.

[0116] (1) The above-mentioned helium-containing natural gas is sent to the first-stage cold box for pre-cooling to obtain low-temperature helium-containing natural gas; then the obtained low-temperature helium-containing natural gas is sent to the first-stage bottom reboiler for cooling and then sent to the first-stage low-temperature separator for first low-temperature separation to obtain the first gas phase and the first liquid phase.

[0117] (2) The first gas phase and the first liquid phase obtained in step (1) are respectively sent to the first-stage cold box for subcooling and then sent to the first-stage helium stripping tower for first-stage distillation to obtain the second gas phase and the second liquid phase. The first gas phase is sent to the middle part of the first-stage helium stripping tower and the second liquid phase is sent to the lower middle part of the first-stage helium stripping tower. The operating conditions for the first distillation are: the temperature at the top of the tower is -94℃, the temperature at the bottom of the tower is -81℃, and the pressure is 4.2MPa. Part of the second liquid phase from the first-stage helium stripping tower is sent to the bottom of the denitrification tower. After heat exchange in the reboiler to provide heat for the denitrification tower, it is then sent to the top condenser of the first-stage helium extraction tower to provide cooling and is converted into crude natural gas. The crude natural gas is then sent to the first-stage cold box for reheating to obtain low-pressure lean natural gas. The remaining second liquid phase is then cooled to obtain medium-pressure lean natural gas. Finally, the reboiled liquid at the bottom of the first-stage helium extraction tower is sent to the gas phase space at the bottom of the first-stage helium extraction tower after heat exchange in the reboiler at the bottom of the first-stage tower to provide heat for the first-stage helium extraction tower.

[0118] (3) The second gas phase obtained in step (2) is sent to the top condenser of the first-stage helium extraction tower for condensation, and then sent to the reflux tank of the first-stage helium extraction tower for separation to obtain gas phase stream and liquid phase stream; the obtained gas phase stream is sent to the bottom reboiler of the second-stage tower for cooling and then sent to the second-stage cryogenic separator for second cryogenic separation to obtain the third gas phase and the third liquid phase; wherein, the obtained liquid phase stream is pressurized by the first-stage reflux pump and the temperature is regulated by the temperature control valve at the top of the first-stage helium extraction tower and then sent to the upper part of the first-stage helium extraction tower as the reflux liquid at the top of the first-stage helium extraction tower;

[0119] (4) The third gas phase obtained in step (3) is sent to the middle part of the secondary helium tower after being subcooled in the secondary cold box. The third liquid phase obtained in step (3) is sent to the lower middle part of the secondary helium tower. The third gas phase and the third liquid phase are subjected to a second distillation in the secondary helium tower. The gas phase obtained at the top of the tower and the liquid phase obtained at the bottom of the tower (the fourth liquid phase) are sent to the secondary cold box for heat exchange to obtain crude helium product. The reboiling liquid at the bottom of the secondary helium tower is sent to the gas phase space at the bottom of the secondary helium tower for heat exchange and then sent to the gas phase space at the bottom of the secondary helium tower to provide heat for the secondary helium tower. The operating conditions for the second distillation are: top temperature -181℃, bottom temperature -110℃, and pressure 2.3MPa.

[0120] (5) The fourth liquid phase obtained in step (4) is subjected to denitrification treatment, and a gas phase is obtained at the top of the tower and a liquid phase is obtained at the bottom of the tower. The gas phase at the top of the tower is sent to the top condenser of the secondary helium extraction tower for heat exchange and to provide cooling capacity to the top condenser of the secondary helium extraction tower. Then, it is sent to the secondary cold box for ultra-low temperature cooling capacity recovery, and then reheated in the primary cold box to obtain nitrogen (as exported nitrogen). The liquid phase at the bottom of the tower is sent to the secondary cold box for subcooling to obtain LNG product. The operating conditions for denitrification treatment include: top temperature -160℃, bottom temperature -110℃, and pressure of 1.6MPa.

[0121] The crude helium product comprises, by volume fraction, 0.6117% CH4, 10.3476% N2, 67.7689% He, and 21.2718% H2. The helium recovery rate is 99%.

[0122] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A system for purifying helium, characterized by, The system comprises, in sequence, a first gas-liquid separation device, a first helium extraction column (11), a second gas-liquid separation device, a second helium extraction column (27) and a nitrogen removal column (33), The first gas-liquid separation device is used for converting the helium-containing natural gas (1) into a first gas phase and a first liquid phase through first processing. The first helium extraction column (11) is used for performing first rectification on the first gas phase and the first liquid phase to obtain a second gas phase and a second liquid phase. The second gas-liquid separation device is used for converting the second gas phase into a third gas phase and a third liquid phase through second processing. The second helium extraction column (27) is used for performing second rectification on the third gas phase and the third liquid phase to obtain a crude helium product and a fourth liquid phase. The nitrogen removal column (33) is used for performing nitrogen removal processing on the fourth liquid phase to obtain nitrogen and an LNG product.

2. The system of claim 1, wherein, The first gas-liquid separation device comprises at least one first cold box (5) and at least one first low-temperature separator (6); The first cold box (5) is used for precooling the helium-containing natural gas (1) to obtain low-temperature helium-containing natural gas, and the first low-temperature separator (6) is used for performing first low-temperature separation on the low-temperature helium-containing natural gas to obtain the first gas phase and the first liquid phase.

3. The system of claim 2, wherein, The first gas-liquid separation device comprises, in sequence, a first cold box (5) and a first low-temperature separator (6); And / or, at least one first column bottom reboiler (7) is further arranged between the first cold box (5) and the first low-temperature separator (6) and is used for cooling the low-temperature helium-containing natural gas before the low-temperature helium-containing natural gas is sent into the first low-temperature separator (6); And / or, a gas phase outlet of the first low-temperature separator (6) is connected with a middle part of the first helium extraction column (11), and a liquid phase outlet of the first low-temperature separator (6) is connected with a middle-lower part of the first helium extraction column (11).

4. The system of claim 3, wherein, The first helium extraction column (11) is connected with the first column bottom reboiler (7) and is used for providing heat for the first helium extraction column (11) by exchanging heat between reboiling liquid at a bottom of the first helium extraction column (11) and the first column bottom reboiler (7) and then sending the reboiling liquid into a gas phase space at the bottom of the first helium extraction column (11).

5. The system of claim 2, wherein, The second gas-liquid separation device comprises at least one first helium extraction column reflux tank (13) and at least one second low-temperature separator (24); The first helium extraction column reflux tank (13) is used for separating the second gas phase to obtain a gas phase stream and a liquid phase stream, and the second low-temperature separator (24) is used for performing second low-temperature separation on the gas phase stream to obtain a third gas phase and a third liquid phase.

6. The system of claim 5, wherein, The second gas-liquid separation device comprises, in sequence, a first helium extraction column reflux tank (13) and a second low-temperature separator (24); And / or, at least one first helium extraction column overhead condenser (12) is further arranged between the first helium extraction column (11) and the first helium extraction column reflux tank (13) and is used for condensing the second gas phase before the second gas phase is sent into the first helium extraction column reflux tank (13); And / or, at least one second bottom reboiler (29) is arranged between the first helium extraction reflux tank (13) and the second low-temperature separator (24) to cool the gas phase stream and then send it into the second low-temperature separator (24); And / or, the gas phase outlet of the second low-temperature separator (24) is connected to the middle part of the second helium extraction column (27), and the liquid phase outlet of the second low-temperature separator (24) is connected to the middle and lower part of the second helium extraction column (27); And / or, at least one second cold box (22) is arranged between the second low-temperature separator (24) and the second helium extraction column (27) to supercool the third gas phase and then send it into the second helium extraction column (27).

7. The system of claim 6, wherein, The gas phase outlet of the second helium extraction column (27) is connected to the second cold box (22) to exchange heat between the gas phase discharged from the top of the second helium extraction column (27) and the second cold box (22) to obtain a crude helium product; And / or, the second helium extraction column (27) is connected to the second bottom reboiler (29) to exchange heat between the reboiling liquid at the bottom of the second helium extraction column (27) and the second bottom reboiler (29) and then send the reboiling liquid into the gas phase space at the bottom of the second helium extraction column (27) to provide heat for the second helium extraction column (27).

8. The system of claim 7, wherein, The upper part of the denitrogenation column (33) is provided with a denitrogenation column top condenser (32); And / or, the liquid phase outlet at the bottom of the denitrogenation column (33) is connected to the second cold box (22) to supercool the liquid phase at the bottom of the denitrogenation column (33) in the second cold box (22) to obtain an LNG product.

9. The system of claim 8, wherein, The denitrogenation column top condenser (32) is connected to the second cold box (22) to cool and liquefy the high-pressure refrigerant (18) in the second cold box (22) and then send it into the denitrogenation column top condenser (32) to provide cold energy for the denitrogenation column (33) and then return to the second cold box (22) to obtain a low-pressure gas phase refrigerant (19).

10. The system of claim 7, wherein, The lower part of the denitrogenation column (33) is provided with a denitrogenation column bottom reboiler (34); And / or, the first helium extraction column top condenser (12) is connected to the first cold box (5) to reheat the crude natural gas in the first cold box (5) to obtain a low-pressure lean natural gas (3).

11. The system of claim 10, wherein, The denitrogenation column bottom reboiler (34) is connected to the first helium extraction column (11) and the first helium extraction column top condenser (12) to exchange heat between part of the second liquid phase in the first helium extraction column (11) and the denitrogenation column bottom reboiler (34) to provide heat for the denitrogenation column (33), then send it into the first helium extraction column top condenser (12) to provide cold energy for the first helium extraction column top condenser (12), and convert it into crude natural gas.

12. The system of claim 7, wherein, The liquid phase outlet of the first helium extraction reflux tank (13) is connected to the upper part of the first helium extraction column (11) to send the liquid phase stream of the first helium extraction reflux tank (13) into the upper part of the first helium extraction column (11) as reflux liquid at the top of the first helium extraction column (11).

13. The system of any of claims 2-12, wherein, The bottom of the primary helium extraction column (11) is connected with the primary cold box (5) for recovering cold energy from the remaining second liquid phase to obtain medium-pressure lean natural gas (2).

14. A method of purifying helium gas, characterized by, The method comprises the following steps: (1) performing first treatment on the helium-containing natural gas to obtain a first gas phase and a first liquid phase; (2) performing first rectification on the first gas phase and the first liquid phase to obtain a second gas phase and a second liquid phase; (3) performing second treatment on the second gas phase to obtain a third gas phase and a third liquid phase; (4) performing second rectification on the third gas phase and the third liquid phase to obtain a crude helium product and a fourth liquid phase; (5) performing denitrogenation treatment on the fourth liquid phase to obtain nitrogen and an LNG product.

15. The method of claim 14, wherein, In step (1), the first treatment comprises: pre-cooling the helium-containing natural gas to obtain low-temperature helium-containing natural gas; And / or, the first treatment comprises: performing first low-temperature separation on the helium-containing natural gas and / or the low-temperature helium-containing natural gas to obtain the first gas phase and the first liquid phase.

16. The method of claim 15, wherein, The first treatment further comprises: cooling the helium-containing natural gas and / or low-temperature helium-containing natural gas before the first low-temperature separation.

17. The method of any of claims 14-16, wherein, In step (2), the first rectification is performed under conditions of a temperature of -95°C to -80°C and a pressure of 3.5 MPa to 4.5 MPa; And / or, the method further comprises a step of supercooling the first gas phase and the first liquid phase before the first rectification; And / or, the method further comprises a step of heat exchanging the reboiler liquid obtained by the first rectification.

18. The method of any one of claims 14-16, wherein, In step (3), the second treatment comprises: separating the second gas phase to obtain a gas phase stream and a liquid phase stream; And / or, the second treatment comprises: performing second low-temperature separation on the second gas phase and / or the gas phase stream to obtain a third gas phase and a third liquid phase.

19. The method of claim 18, wherein, The second treatment further comprises: condensing the second gas phase before the separation; And / or, the second treatment further comprises: cooling the second gas phase and / or the gas phase stream before the second low-temperature separation; And / or, the method further comprises recycling the liquid phase stream obtained by the separation as reflux liquid for the first rectification.

20. The method of any one of claims 14-16, wherein, In step (4), the second rectification is performed under conditions of a temperature of -185°C to -110°C and a pressure of 2 MPa to 3 MPa; And / or, the method further comprises: supercooling the third gas phase before the second rectification; And / or, the method further comprises a step of heat exchanging the reboiler liquid obtained by the second rectification; And / or, the method further comprises a step of heat exchanging the gas phase obtained by the second rectification to obtain the crude helium product.

21. The method of any one of claims 14-16, wherein, In step (5), the denitrogenation treatment is performed under conditions of a temperature of -160 to -110°C and a pressure of 1.5 MPa to 2.5 MPa; And / or, the method further comprises a step of cooling and liquefying high-pressure cold agent to obtain low-pressure gas phase cold agent; And / or, the method further comprises a step of supercooling the liquid phase obtained by the denitrogenation treatment to obtain the LNG product; And / or, the method further comprises: heat exchanging part of the second liquid phase to convert it into crude natural gas; And / or, the method further comprises: recovering cold energy from the remaining part of the second liquid phase to obtain a medium-pressure lean natural gas.

22. The method of claim 21, wherein, The method further comprises: re-heating the crude natural gas to obtain a low-pressure lean natural gas.

23. The method of any one of claims 14-16, wherein, The helium-containing natural gas comprises, in volume fraction, 98-99% of CH4, 0.1-0.5% of C2H6, 0.2-0.6% of N2, 0.3-0.8% of CO2, 0.01-0.1% of He and 0.005-0.3% of H2; And / or, the crude helium comprises, in volume fraction, 0.2-0.8% of CH4, 6-12% of N2, 60-70% of He and 15-25% of H2.

24. Use of the system of any one of claims 1-13 or the method of any one of claims 14-23 in helium extraction from natural gas.

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