A membrane separation oxygen and nitrogen production system based on multi-cycle coupling

Abstract

This invention belongs to the field of gas separation technology, specifically a membrane separation oxygen and nitrogen generation system based on multi-cycle coupling. The system consists of two-stage membrane separation cycle systems coupled organically. The first-stage membrane separation cycle system includes two membrane separators connected in series and a compression device, capable of obtaining nitrogen-rich gas with a purity of over 95%. The second-stage membrane separation cycle system includes two membrane separators connected in series and a compression device, capable of obtaining oxygen with a concentration of over 95%. The organic coupling of the first and second membrane separation cycles includes the compression device, used to compress the mixed gas on the permeate side of the first-stage membrane separator to a higher pressure, so as to mix it with the stagnation side gas of the second-stage membrane separator, serving as the feed gas for the second-stage membrane separator, thus forming a cycle separation. This invention is particularly suitable for industrial applications requiring both high-pressure, high-purity oxygen and nitrogen.

Description

Technical Field

[0001] This invention belongs to the field of gas separation technology, specifically relating to a system for simultaneously producing high-purity oxygen and nitrogen directly from the air using a membrane separation process based on multi-cycle coupling. Background Technology

[0002] Oxygen and nitrogen, as the most important industrial gases, are widely used in steel metallurgy, chemical synthesis, electronics manufacturing, healthcare, food preservation, and aerospace. With the rapid development of high-end manufacturing, the demand for on-site gas production is growing rapidly, and the market's need for small- to medium-scale, flexible, efficient production technologies that can directly provide high-purity oxygen and nitrogen gases at medium to high pressures is becoming increasingly urgent. Traditional air separation methods mainly rely on cryogenic distillation and pressure swing adsorption (PSA). While these technologies are mature, they have inherent limitations in addressing these emerging demands.

[0003] Currently, most industrial applications requiring both high-purity oxygen (95% or even 99.5%) and high-purity nitrogen (95% or even 99.99%) utilize cryogenic air separation technology to extract these gases from the air. This involves liquefying the air and then distilling it using the boiling point difference to produce ultra-high-purity oxygen, nitrogen, and argon products on a large scale. However, cryogenic air separation technology is energy-intensive, requiring approval for construction. It also involves safety issues related to liquid air and even liquid oxygen, necessitating safety assessments, environmental impact assessments, and energy assessments. The equipment is large, requires significant land area, involves high investment, and has a long construction period. Furthermore, the cryogenic air separation process is complex, with slow start-up and load adjustment (taking several hours), demanding high levels of technical expertise in operation, use, and maintenance. It lacks flexibility in switching between start-up and shutdown, making it unsuitable for rapid deployment of temporary, distributed gas usage in industrial settings, thus severely limiting its application.

[0004] Other processes, such as Pressure Swing Adsorption (PSA), utilize the preferential adsorption properties of zeolite molecular sieves for nitrogen to produce oxygen-enriched air (typically 93% purity) or carbon molecular sieves to produce nitrogen. Although PSA equipment is relatively compact and starts up quickly, there is a trade-off between product purity and recovery rate. Producing high-purity oxygen (above 99.5%) is extremely difficult and energy consumption increases dramatically. Product pressure is limited by the adsorption / desorption cycle, typically at atmospheric or low pressure, requiring subsequent pressurization. Furthermore, there are issues such as frequent valve switching, molecular sieve pulverization, and noise from exhaust emissions.

[0005] Membrane separation technology, as an emerging gas separation technology, utilizes the difference in permeation rate (permeability coefficient) of gas passing through a polymer membrane to separate oxygen and nitrogen. Since its emergence in the 1980s, it has been widely used in the field of air separation. This technology can easily achieve the separation of oxygen and nitrogen in air by utilizing the different permeation characteristics of oxygen and nitrogen in the membrane separation material. It has a series of advantages such as simple equipment, no moving parts, instant start-up, quiet operation, low energy consumption, and simple operation. However, traditional single-stage membrane separation processes are limited by the separation factor (α, O2 / N2) and permeability (P, O2). Single-stage membrane separation processes are difficult to obtain oxygen with a purity of over 50% and nitrogen with a purity of over 99.9% or even over 99.99%, and even more difficult to obtain oxygen with a purity of over 95% or even 99.5%. Membrane separation is usually mainly used to produce oxygen-enriched air (25%-45% O2) or medium-low purity nitrogen (95%-99% N2). To improve purity, multiple stages are often required in series or the feed pressure is significantly increased / the production capacity is reduced, leading to deterioration in energy consumption and economic efficiency. In particular, the gas exiting from the permeate side of the membrane separation process is close to atmospheric pressure and cannot be used directly, making it impossible to obtain high-pressure products directly. The addition of an extra booster obviously increases equipment costs and especially reduces the reliability of the system.

[0006] Therefore, in order to meet the needs of industrial applications that require both high-purity oxygen and nitrogen, there is an urgent need for a separation process that is simple, inexpensive, and energy efficient. Summary of the Invention

[0007] In view of the shortcomings of the existing technology, the present invention aims to overcome the technical and performance bottlenecks of a single membrane separation process and provide a system for directly and simultaneously producing high-purity oxygen and nitrogen from the air based on a multi-cycle coupling membrane separation process.

[0008] This invention constructs a highly integrated and optimized coupled multi-cycle (multi-stage) membrane separation system, which precisely couples the material flow and energy flow of membrane separation units (cycles) with different functional positions, and matches them with corresponding compression, reflux and control strategies, so as to achieve the simultaneous production of multiple high-purity gases in a membrane separation process based on multi-cycle coupling.

[0009] This invention can directly produce oxygen with a purity of 95% or even 99.5% or higher from the air and output it at a high pressure. It can also simultaneously produce nitrogen with a purity of 95% or even 99.99% or higher and output it at a high pressure. This solves the problems of purity limitation, high energy consumption and system complexity in existing membrane separation oxygen and nitrogen production technologies.

[0010] The multi-cycle coupled membrane separation oxygen and nitrogen generation system provided by this invention mainly consists of a two-stage membrane separation cycle system organically coupled together, wherein:

[0011] The first-stage membrane separation cycle system consists of at least two membrane separators connected in series. All the gas on the sluggish side of the first-stage membrane separator is used as the feed gas for the second-stage membrane separator and fed sequentially.

[0012] The membrane separation cycle system is equipped with at least one set of feed gas compression equipment to receive feed air and at least a portion of the permeate gas from the downstream separator in the membrane separation cycle system. The gas is also drawn in before the compressor through a pipeline and used as feed gas. Since the aforementioned air and the permeate gas from the downstream membrane separator are drawn in through the front end of the compressor and mixed to form the feed gas of the cycle system, the first membrane separation cycle is formed. At least a portion of the permeate gas from the downstream separator in the membrane separation cycle system is used as the purge carrier gas on the permeate side of the upstream separator in the second membrane separation cycle.

[0013] In this stage of membrane separation cycle separation system, all the gas on the stagnation side of the downstream membrane separator is used as the high-purity nitrogen output. Since this gas only needs to overcome the resistance of the upstream and downstream membrane separators in this stage of membrane separation cycle system, it still has a high pressure. Therefore, the nitrogen output from this outlet is high-pressure, high-purity nitrogen (95% or even 99.99% or more nitrogen-rich gas).

[0014] All the permeate gas from the pre-membrane separator in this stage of the membrane separation cycle system is used as the output of nitrogen- and argon-poor oxygen-enriched gas and as the feed gas for the second-stage membrane separation cycle system.

[0015] Furthermore, in this stage of membrane separation cycle separation system, both the upstream and downstream membrane separators connected in series use membrane separation materials with a separation coefficient α (O2 / N2) ≥ 6. Typically, membrane separation materials such as polyimide and polysulfone are used, which are mainly used to remove most of the nitrogen and some of the argon. In the upstream membrane separator, a nitrogen-poor and argon-poor oxygen-rich gas with an oxygen concentration of 30-75% can be obtained on the permeate side, while a nitrogen-rich gas with a concentration of 95% or even 99.99% or more can be obtained on the stagnation side of the downstream membrane separator.

[0016] The second-stage membrane separation cycle system consists of at least two membrane separators connected in series. The high-pressure side of the first-stage membrane separator serves as the feed end, receiving all the permeate gas from the permeate side of the first-stage membrane separator and the sludge gas from the subsequent membrane separator. The permeate gas from the first and second-stage membrane separators is connected by a compressor and then compressed before entering the feed end of the subsequent membrane separator for further purification to the required oxygen concentration.

[0017] The membrane separation cycle system also includes at least one feed gas compression device, which is used to sequentially receive at least a portion of the permeate gas from the downstream separator in the first-stage membrane separation cycle system. Before the permeate gas from the upstream and downstream separators is introduced into the compressor through a pipeline, at least a portion of the compressed gas is recycled back to the feed gas side of the downstream membrane separator in the first-stage membrane separation cycle system as feed gas. All the gas on the stagnation side of the downstream membrane separator is mixed with the permeate gas from the upstream membrane separator in the first-stage membrane separation cycle system and used as the feed gas for the upstream membrane separator in this stage (second-stage membrane separation cycle system), thus forming the second-stage membrane separation cycle.

[0018] In this membrane separation cycle system, at least a portion of the permeate gas from the downstream separator in the first-stage membrane separation cycle system, as well as all the permeate gas from the upstream and downstream separators in this membrane separation cycle system, is introduced into the compressor through a pipeline. At least a portion of the compressed gas is output as a high-pressure, high-purity oxygen product (oxygen concentration of 95% or even 99.5% or higher).

[0019] The stagnant gas after separation by the upstream membrane separator in this stage membrane separation cycle system can also be used as the feed gas for the first stage membrane separation cycle system (after being introduced into the compressor of the first stage membrane separation cycle system through the coupling separation system).

[0020] Furthermore, in this stage of membrane separation cycle separation system, both the pre- and post-stage membrane separators connected in series use membrane separation materials with separation coefficients α(O2 / N2) ≥ 6 and α(O2 / Ar) ≥ 3.5, and more preferably, α(O2 / Ar) ≥ 10. Typically, membrane separation materials such as polyimide and polysulfone are used. For example, polysulfone is used as a porous support layer and coated with a high-permeability polymer (PTMSP) or a membrane material with oxygen-promoting transport (such as a polymer membrane containing cobalt porphyrin complex) can be used to effectively further remove nitrogen and argon, and obtain oxygen concentrations of 95% or even 99.5% or higher on the permeate side of the membrane in the post-stage membrane separator of the second cycle separation system.

[0021] Organic coupling of the first / second membrane separation cycle

[0022] To achieve the organic coupling of the first / second membrane separation cycle, at least one compression device is provided to compress the nitrogen- and argon-deficient oxygen-enriched gas on the permeate side of the pre-membrane separator of the first cycle separation system to a higher pressure, so as to mix with the stagnation side gas of the post-membrane separator of the second cycle separation system, and can be used as the feed gas for the pre-membrane separator of the second cycle separation system to form a cycle separation.

[0023] Furthermore, the nitrogen- and argon-poor oxygen-rich gas on the permeate side of the pre-membrane separator of the first cycle separation system, and the stagnation gas from the post-membrane separator of the second cycle separation system, after overcoming the resistance of the pre-membrane separator of the second cycle separation system, should also meet the pressure conditions of the compressor in the first cycle membrane separation system, so that the gas can be recycled back to the first cycle membrane separation system as feed gas.

[0024] Furthermore, in this invention, when the nitrogen- and argon-poor oxygen-rich gas from the permeate side of the downstream membrane separator of the first circulating separation system is drawn in by the compressor and mixed with the gas from the stagnation side of the upstream membrane separator of the second circulating separation system, measures such as designing and matching the membrane area of ​​each stage, adjusting the permeate flow rate of each stage membrane separator, and adjusting the compression and circulating gas flow rate should be taken to ensure that the oxygen concentration of the two gases is close to equilibrium, preferably within a difference of ≤1%.

[0025] This constitutes an organic coupling between the first and second membrane separation cycles.

[0026] In this invention, after being compressed to the membrane separation working pressure by a compressor, typically 4 to 20 atm (gauge pressure), the compressed air can pass through a pretreatment system consisting of a filter (including an activated carbon oil remover or filter), a freeze dryer, or an adsorption dryer, as known in the art, to remove moisture, solid particulate impurities, and oil from the compressed air before entering the membrane separator. The filter can be multi-stage or combined, and the adsorption dryer and freeze dryer can be used in combination or individually. According to the usual design requirements, those skilled in the art can flexibly grasp the components and design requirements included in the pretreatment system.

[0027] Furthermore:

[0028] In the first-stage membrane separation cycle system:

[0029] All the gas on the stagnation side of the pre-stage membrane separator is used as the feed gas for the subsequent membrane separator and fed sequentially.

[0030] This also includes necessary control valves and their connecting pipelines;

[0031] The compression equipment is used to receive raw material air, as well as a portion of the permeate gas from the downstream separator in this stage of the membrane separation cycle system, which is also drawn in as raw material gas and introduced into the compressor through a pipeline. The compressed air then passes through a pretreatment system composed of filters such as activated carbon oil removers or filters, freeze dryers or adsorption dryers, etc., in order to remove moisture, solid particulate impurities and oil from the compressed air before entering the membrane separator. The filters can be multi-stage or combined, and the adsorption dryers and freeze dryers can be combined or used separately. According to the usual design requirements, the technical personnel in this field can flexibly grasp the components and design requirements included in the pretreatment system.

[0032] This also includes necessary control valves and their connecting pipelines;

[0033] All the gas on the stagnation side of the downstream membrane separator is used as the output of high-purity nitrogen.

[0034] This includes installing necessary control valves and their connecting pipelines;

[0035] All the gas on the permeate side of the pre-membrane separator is used as the output of nitrogen- and argon-poor oxygen-enriched gas and as the feed gas for the second-stage membrane separation cycle system.

[0036] This includes the necessary control valves and their connecting pipelines;

[0037] In the second-stage membrane separation cycle system:

[0038] The high-pressure side of the pre-stage membrane separator serves as the feed end, which is used to receive all the permeate gas from the pre-stage membrane separator of the first-stage membrane separation cycle system and the stagnation gas from the downstream membrane separator. The permeate gas pipelines of the pre-stage and downstream membrane separators are connected and compressed by a compressor before entering the feed end of the downstream membrane separator for further purification to the required oxygen concentration for output.

[0039] The compression device is used to sequentially receive all the permeate gas from the pre- and post-stage separators in the current membrane separation cycle system and introduce it into the compressor through a pipeline. Before this gas is introduced into the compressor, at least a portion of the compressed gas is recycled back to the feed gas side of the post-stage membrane separator in the current membrane separation cycle system as feed gas. All the gas on the stagnation side of the post-stage membrane separator is mixed with the permeate gas from the pre-stage membrane separator in the first-stage membrane separation cycle system and used as the feed gas for the pre-stage membrane separator in this stage (second-stage membrane separation cycle system), thereby constituting the second-stage membrane separation cycle.

[0040] This includes the necessary control valves and their connecting pipelines;

[0041] In this membrane separation cycle system, all the permeate gas from the pre- and post-separators is introduced into the compressor through pipelines. At least a portion of the compressed gas is output as a high-pressure, high-purity oxygen product (oxygen concentration of 95% or even 99.5% or higher).

[0042] This includes the necessary control valves and their connecting pipelines;

[0043] The stagnant gas after separation by the upstream membrane separator in this stage membrane separation cycle system can also be used as the feed gas for the first stage membrane separation cycle system (after being introduced into the compressor of the first stage membrane separation cycle system through the coupling separation system).

[0044] This includes the necessary control valves and their connecting pipelines;

[0045] In the organic coupling of the first / second membrane separation cycle

[0046] The compression device is used to compress the nitrogen- and argon-poor oxygen-rich gas on the permeate side of the pre-membrane separator of the first cycle separation system to a higher pressure, and mix it with the stagnation side gas of the post-membrane separator of the second cycle separation system, so as to serve as the feed gas for the pre-membrane separator of the second cycle separation system, thus forming a cycle separation.

[0047] This includes the necessary control valves and their connecting pipelines.

[0048] Furthermore, the nitrogen- and argon-poor oxygen-rich gas on the permeate side of the pre-membrane separator of the first cycle separation system, and the stagnation gas from the post-membrane separator of the second cycle separation system, after overcoming the resistance of the pre-membrane separator of the second cycle separation system, should also meet the pressure conditions of the compressor in the first cycle membrane separation system, so that the gas can be recycled back to the first cycle membrane separation system as feed gas.

[0049] This includes the necessary control valves and their connecting pipelines;

[0050] Furthermore, when the nitrogen- and argon-poor oxygen-rich gas from the permeate side of the downstream membrane separator of the first cycle separation system is drawn in by the compressor and mixed with the gas from the stagnation side of the upstream membrane separator of the second cycle separation system, measures such as matching the membrane area of ​​each stage, adjusting the permeate flow rate of each stage membrane separator, and adjusting the compression and circulation gas flow rate should be taken to ensure that the oxygen concentration of the two gases is close to equilibrium. Preferably, the difference should be within ≤1%. In addition, necessary sensors and analyzers for monitoring oxygen concentration should be provided.

[0051] This includes the necessary control valves and their connecting pipelines.

[0052] Furthermore, when the nitrogen- and argon-poor oxygen-rich gas from the permeate side of the first-stage membrane separator of the first-cycle separation system is drawn in by the compressor and mixed with the gas from the stagnation side of the second-stage membrane separator of the second-cycle separation system, measures such as matching the membrane area of ​​each stage, adjusting the permeate flow rate of each stage membrane separator, and adjusting the compression and circulation gas flow rate should be taken to ensure that the oxygen concentration of the two gases is close to equilibrium. Preferably, the difference should be within ≤1%. In addition, necessary sensors and analyzers for monitoring oxygen concentration should be provided.

[0053] This includes the necessary control valves and their connecting pipelines.

[0054] This constitutes an organic coupling between the first and second membrane separation cycles.

[0055] The present invention is also equipped with at least one complete control component to analyze and monitor the oxygen purity of the product flow, waste flow, and circulating gas, so as to perform necessary operation control on the valves in the circuit as described above, and to perform necessary operation on the compression equipment.

[0056] The membrane separator of this invention has at least one feed gas inlet and one retained gas outlet, the former referred to as the membrane separator head and the latter as the membrane separator tail; it also has at least one permeate outlet. Furthermore, the membrane separator has a high-pressure side and a low-pressure side. One end of the high-pressure side is connected to the feed gas inlet, i.e., the membrane separator head, to receive the feed gas, and the other end is connected to the retained gas outlet, i.e., the membrane separator tail, to remove gases that are difficult to pass through the membrane separation material. The low-pressure side is connected to the permeate outlet to remove gases that are easier to pass through the membrane separation material.

[0057] The pressure mentioned in this invention is gauge pressure.

[0058] This invention creatively integrates, optimizes, and reconstructs existing known technical elements (specific membrane separation materials, membrane separation coupled cycle steps, online detection and control), specifically:

[0059] (1) Innovation of multi-cycle coupling process: The present invention adopts a two-stage multi-cycle coupling membrane separation process. The first stage mainly removes nitrogen and some argon. The second stage adopts a multi-cycle system to further remove argon and residual nitrogen. Through precise circulation flow control and pressure matching, the oxygen purity is increased from the upper limit of conventional membrane method (~45%) to 95% or even 99.5% or more through two-stage deep purification cycle, realizing the production of high-purity oxygen. Through multi-stage circulation recovery, low-concentration permeate gas is effectively recovered and reprocessed, effectively recovering gas components and compression energy, significantly improving the overall utilization rate of raw material air and product recovery rate, reducing interstage mixing loss, improving separation efficiency, and thus reducing energy consumption.

[0060] (2) Innovative Dual-Product Synergistic Production and Direct High-Pressure Output: Through system integration design, this invention can simultaneously and with a focus on producing two products: high-purity oxygen and / or high-purity nitrogen, overcoming the limitation of traditional membrane separation technology that can only produce oxygen or nitrogen individually. Furthermore, through reasonable process design and parameter optimization, the synergistic production of the two high-purity gases can be achieved, facilitating orientation adjustment when oxygen or nitrogen is required, thus improving equipment utilization and economic efficiency. Moreover, by retaining the high-purity product gas on the non-permeable side (high-pressure side) of the membrane module and using a circulating compressor to maintain system pressure, medium-to-high-pressure oxygen and nitrogen are directly produced, eliminating or simplifying the external pressurization process for the product gas.

[0061] (3) Innovation in membrane material selection and configuration: The present invention uses membrane materials with different properties in different levels of membrane separators. The first stage uses a general membrane material with a separation coefficient α(O2 / N2)≥6. The second stage uses a high-selectivity membrane material with a separation coefficient α(O2 / N2)≥6 and α(O2 / Ar)≥3.5. More preferably, α(O2 / Ar)≥10. Through graded separation and material optimization, the production of high-purity gas is achieved.

[0062] (4) Pressure and Concentration Monitoring, Control, and Energy Consumption Optimization Innovation: This invention maintains a low energy consumption level while producing high-purity gas through precise pressure and concentration monitoring, control, and energy consumption optimization design. By collecting pressure and concentration data in real time, the working pressure can be automatically adjusted according to product requirements, optimizing energy consumption allocation. According to test data, the unit energy consumption of this invention can be reduced by 15-25% compared to traditional multi-stage membrane separation systems.

[0063] (5) System Integration Innovation: This invention adopts a modular integrated design, integrating oxygen and nitrogen generation functions into one system. By sharing the pretreatment system and some membrane separation components, it reduces equipment investment and floor space, making the layout more flexible and the response speed faster. The system adopts PLC automatic control, enabling intelligent operation and remote monitoring.

[0064] The multi-cycle coupled membrane separation oxygen and nitrogen generation system provided by the present invention can simultaneously produce oxygen with a purity of 95% or even 99.5% or higher, and nitrogen with a purity of 95% or even 99.99% or higher, directly from the air and output them at a high pressure.

[0065] The system provided by this invention has broad application prospects in fields such as oxygen-enriched combustion, chemical oxidation processes, clinical medicine, high-end medical and health care, diffused oxygen supply in high-altitude areas, oxygen for cutting, wastewater treatment, and bio-fermentation. Attached Figure Description

[0066] Figure 1This is a schematic diagram of the structure of the multi-cycle coupled membrane separation oxygen and nitrogen generation system invented by Sinen.

[0067] In the diagram, the following labels are used: M101, M102, and M201 are 3-port membrane separators; M202A is a 4-port membrane separator; V100, V101, V102, and V103 are control valves; QTV100, QTV101, QTV102, and QTV103 are automatic control valves with flow control and regulation capabilities; AB01 is a pressure boosting device.

[0068] 1 is air input; 2 is the mixing point of M102 permeate side and air; 3 is the mixing point of M201 stagnation gas and M102 permeate side and air; 4 is M101 permeate side (nitrogen- and argon-poor, oxygen-rich); 5 is M102 permeate side (nitrogen- and argon-poor, oxygen-rich mixed gas); 6 is M102 stagnation side (high-pressure, high-purity nitrogen output); 7 is the mixing point of M101 permeate side and M202 stagnation side; 8 is M201 stagnation gas side; 9A is M102 permeate gas side; 9B is M102 and M201 permeate gas; 10 is M102 and M201 permeate gas; 11 is M201 and M201 permeate gas; 12 is M201 and M201 permeate gas; 13 is M201 and M201 permeate gas; 14 is high-pressure oxygen. Detailed Implementation

[0069] The present invention will be further illustrated below with reference to the embodiments and accompanying drawings.

[0070] The membrane separation oxygen and nitrogen generation system based on multi-cycle coupling provided by this invention mainly consists of a two-stage membrane separation cycle system organically coupled together, as shown in the attached figure. Figure 1 As shown. Wherein:

[0071] The first-stage membrane separation system consists of membrane separators M101 and M102, and compressor AB01 connected by pipelines. The feed gas inlet A0 of membrane separator M101 is connected to compressor AB01 via pipeline, and compressor AB01 is connected to the feed gas inlet via pipeline. Control valves V100 and QTV100 are sequentially installed on this connecting pipeline. The stagnant gas outlet A2 of membrane separator M101 is connected to the feed gas inlet A0 of membrane separator M102 via pipeline. The stagnation gas outlet A2 of membrane separator M102 outputs high-pressure, high-purity nitrogen gas, and its output pipeline is equipped with valve QTV101 and control valve V101 in sequence; the permeate gas outlet A1 of membrane separator M102 is connected to the inlet pipeline of compressor AB01; valve QTV102A is installed on this connecting pipeline; at the same time, the permeate gas outlet A1 of membrane separator M102 is connected to port A132 below membrane separator M201, and valve QTV102B is installed on this connecting pipeline;

[0072] The second-stage membrane separation system consists of membrane separators M201 and M202, and compressor AB02 connected by pipelines. The permeate outlet A1 of membrane separator M201 is connected to port A142 below membrane separator M202 via pipeline. The sludge outlet A2 above membrane separator M202 outputs a nitrogen- and argon-poor oxygen-enriched mixed gas, and its output pipeline is equipped with valve QTV103 and control valve V103 in sequence. The permeate outlet A1 of membrane separator M202 is connected to the output pipeline of the nitrogen- and argon-poor oxygen-enriched mixed gas from the sludge outlet A2 above membrane separator M202 via pipeline, and compressor AB02 is installed on this connecting pipeline.

[0073] The first and second stage membrane separation cycles are coupled; compressor AB03, control valve V102, and valve QTV102 are used; compressor AB03 is installed on the connecting pipeline between the permeate outlet A1 of membrane separator M101 and the stagnant gas outlet A2 above membrane separator M201; control valve V102 and valve QTV102 are sequentially installed on the connecting pipeline between the feed gas inlet A0 of membrane separator M201 and the feed gas inlet A0 of membrane separator M101, with connection point 3, on the connecting pipeline between the feed gas inlet A0 of membrane separator M101 and compressor AB01;

[0074] in:

[0075] Membrane separators M101 and M102 are three-port membrane separators. Each membrane separator is divided into a high-pressure side and a low-pressure side by a membrane separation material. One end of the high-pressure side is connected to a feed gas inlet, i.e., the head of the membrane separator, to receive feed gas, and the other end is connected to a sludge gas outlet, i.e., the tail of the membrane separator, to remove gases that are more difficult to pass through the membrane separation material. The low-pressure side is connected to a permeate gas outlet to remove gases that are more easily passed through the membrane separation material. This membrane separator has the function of separating oxygen from nitrogen and argon. Oxygen passes through more easily, while nitrogen and argon pass through more difficultly.

[0076] Membrane separators M201 and M202 are four-port membrane separators, divided into a high-pressure side and a low-pressure side by a membrane separation material. One end of the high-pressure side is connected to a feed gas inlet, i.e., the head of the membrane separator, to receive feed gas, and the other end is connected to a sludge outlet, i.e., the tail of the membrane separator, to remove gases that are more difficult to pass through the membrane separation material. The low-pressure side is connected to two permeate outlets to remove gases that are more easily passed through the membrane separation material. One permeate outlet is close to the feed gas inlet side, or the head of the membrane separator, and the other permeate outlet is close to the sludge outlet side, or the tail of the membrane separator. This membrane separator has the function of separating oxygen from nitrogen and argon, with oxygen passing through more easily while nitrogen and argon are more difficult to pass through.

[0077] V represents a control valve, such as V100, V101, V102, V103, etc., which are all control valves that can be opened, closed, and adjusted as needed;

[0078] QTV stands for automatic control valve with flow control and regulation capabilities, such as QTV100, QTV101, QTV102, QTV103, etc. These valves can be manually, pneumatically controlled, or electrically and hydraulically controlled automatic valves.

[0079] AB01 represents pressure boosting equipment, such as compressors and vacuum pumps.

[0080] The workflow involves setting control conditions and parameters such as speed, temperature, and pressure to prepare oxygen with a concentration of over 99.5% and nitrogen with a purity of over 99.99%. The specific workflow is as follows:

[0081] First-stage membrane separation cycle

[0082] This membrane separation cycle separation system consists of at least two membrane separators M101 and M102 connected in series. All the gas on the stagnation side of the first membrane separator M101 is used as the feed gas for the second membrane separator M102, and is fed sequentially from the compression device AB01 and the pretreatment device (not shown) after the feed.

[0083] The membrane separation cycle system has at least one set of feed gas compression equipment AB01, which is used to receive feed air from 1 and input it through regulating valves V100 and QTV100. It is used as feed gas along with a portion of the permeate gas from the downstream separator M102 in this membrane separation cycle system, which is introduced into the compressor through pipeline 5 and then drawn in from 2. Since the aforementioned air and the permeate gas from the downstream membrane separator M102 are drawn in through the front end of the compressor AB01 and mixed, they are used as part of the feed gas of this cycle system. The outlet pressure of AB01 is controlled at 0.7~1.2 MPa (gauge pressure), and the outlet temperature is ≤60℃, thus constituting the first-stage membrane separation cycle.

[0084] All the gas from the stagnation side of the downstream membrane separator M102 in this membrane separation cycle system is used as the high-purity nitrogen output. It is output from point 6 via regulating valves V101 and QTV101. Since this gas only needs to overcome the resistance of the membrane separators M101 and M102 in this membrane separation cycle system, it still has a high pressure. Therefore, the nitrogen output from this outlet is high-pressure, high-purity nitrogen (pressure 0.6-1.1 MPa, nitrogen-rich gas with 95% or even 99.99% purity or higher).

[0085] All the permeate gas from the pre-membrane separator M101 of this membrane separation cycle system is output as nitrogen- and argon-poor oxygen-rich gas at the output end 4, with an oxygen concentration of 45-75%, and is used as the feed gas for the second-stage membrane separation cycle system.

[0086] Furthermore, in this stage of membrane separation cycle separation system, the membrane separators M101 and M102 connected in series in the front and back stages both use membrane separation materials with a separation coefficient α (O2 / N2) ≥ 6. Typically, membrane separation materials such as polyimide and polysulfone are used, which are mainly used to remove most of the nitrogen and some of the argon. On the permeate side 4 of the front membrane separator M101, a nitrogen-poor and argon-poor oxygen-rich gas with an oxygen concentration of 30-75% can be obtained, while on the retention side 6 of the back membrane separator M102, a nitrogen-rich gas output of 95% or even 99.99% or more can be obtained. The operating temperature is controlled at 45-55℃.

[0087] Second-stage membrane separation cycle

[0088] This membrane separation cycle system consists of at least two membrane separators M201 and M202 connected in series. The high-pressure side 7 between the two membrane separators serves as the feed end, i.e., the intermediate feed, where the oxygen concentration of the mixed gas is controlled at 60-80%.

[0089] The membrane separation cycle system of this stage is equipped with at least one set of feed gas compression equipment AB02, which is used to sequentially receive the permeate gas from the pre-stage separator M201 and the post-stage separator M202 in this stage membrane separation cycle system. Before all the permeate gas is introduced into the compressor through pipeline 11 from 9 to 10 to 11, at least a portion of the compressed gas is recycled back to the feed gas side of the post-stage membrane separator M202 in this stage membrane separation cycle system as feed gas through 12 to 13. The outlet pressure of compressor AB02 is 0.5 to 0.8 MPa. All the gas on the sludge side of the post-stage membrane separator M202 is mixed with the permeate gas from the pre-stage membrane separator M101 of the first stage membrane separation cycle system and introduced through 7 as the feed gas of the pre-stage membrane separator M201 of this stage (second stage membrane separation cycle system). The oxygen concentration of the sludge gas in M202 before mixing is 85 to 95%, thus forming the second stage membrane separation cycle.

[0090] In this membrane separation cycle system, the permeate gas from the pre- and post-separators M201 and M202 passes through 9 to 10 to 11, and is then introduced into the compressor via pipeline 11. At least a portion of the compressed gas is then output from 14 via 12, regulating valve V103, and QTV103 as a high-pressure, high-purity oxygen product (oxygen concentration of 95% or even 99.5% or higher, pressure 0.5–0.8 MPa).

[0091] The sludge gas separated by the pre-membrane separator M201 in this stage membrane separation cycle system is introduced from 8 via regulating valves V102 and QTV102 as the feed gas for the first stage membrane separation cycle system (it is introduced into the compressor AB01 of the first stage membrane separation cycle system via the coupling separation system and then sent in). The oxygen concentration of this sludge gas is 85-95%.

[0092] Furthermore, in this stage of membrane separation cycle separation system, the membrane separators M201 and M202 connected in series in the front and back stages adopt separation coefficients α(O2 / N2)≥6 and α(O2 / Ar)≥3.5, respectively. More preferably, membrane separation materials with α(O2 / Ar)≥10 are used. Typically, membrane separation materials such as polyimide and polysulfone are used. For example, polysulfone is used as a porous support layer and coated with a high-permeability polymer (PTMSP) or a membrane material with oxygen-promoting transport (such as a polymer membrane containing cobalt porphyrin complex) can be used to effectively remove nitrogen and argon. Oxygen with an oxygen concentration of 95% or even 99.5% or higher is obtained on the permeate side 11 of the back stage membrane separator M202 in the second cycle separation system and output as product gas through 12 to 14. The operating temperature of M201 / M202 is controlled at 40-50℃.

[0093] Organic coupling of the first / second membrane separation cycle

[0094] To achieve the organic coupling of the first / second membrane separation cycle, at least one compression device AB03 is provided. This device introduces the nitrogen- and argon-poor oxygen-rich gas from the permeate side of the pre-membrane separator M101 of the first cycle separation system into the compressor AB03 and compresses it to a higher pressure. The outlet pressure of AB03 is 1.0 to 1.5 MPa, which is sufficient to mix with the stagnation side gas of the post-membrane separator M202 of the second cycle separation system. It can also be used as the feed gas for the pre-membrane separator M201 of the second cycle separation system to form a cycle separation.

[0095] Furthermore, the nitrogen- and argon-deficient, oxygen-enriched gas from the permeate side 4 of the pre-membrane separator M101 of the first cycle separation system, and the stagnation side gas from the post-membrane separator M202 of the second cycle separation system are mixed at 7. The stagnation gas 8, after overcoming the resistance of the pre-membrane separator M201 of the second cycle separation system, is separated. Its pressure should also meet the pressure conditions of the compressor AB01 supplied to the membrane separation system of the first cycle, so that the gas can be recycled back to the membrane separation system of the first cycle as feed gas. The circulating gas volume can be adjusted within the range of 10% to 30% of the product oxygen content.

[0096] Furthermore, when the nitrogen- and argon-deficient, oxygen-enriched gas from the permeate side of the downstream membrane separator M102 of the first cycle separation system is drawn in by the compressor AB01 and mixed with the gas from the stagnation side of the upstream membrane separator M201 of the second cycle separation system, the oxygen concentration of the two gases should be close to equilibrium by designing and matching the membrane area of ​​each stage, adjusting the permeate flow rate of each stage membrane separator, and adjusting the compression and circulation gas flow rate. Preferably, the oxygen concentration at the mixing point 3 should be within a difference of ≤1%, and the target oxygen concentration should be 25-35%.

[0097] Furthermore, when the nitrogen- and argon-deficient, oxygen-enriched gas from the permeate side of the first-stage membrane separator M101 in the first-cycle separation system is drawn in by the compressor at point 4 and mixed with the gas from the stagnation side of the second-stage membrane separator M202 in the second-cycle separation system at point 7, measures such as matching the membrane area of ​​each stage, adjusting the permeate flow rate of each stage membrane separator, and adjusting the compression and circulation gas flow rate should be taken to ensure that the oxygen concentration of the two gases is close to equilibrium. Preferably, the oxygen concentration at the mixing point 7 should be within a difference of ≤1%, and the target oxygen concentration should be 60-80%.

[0098] Thus, the above constitutes an organic coupling of the first and second membrane separation cycles. Through the above separation steps, oxygen with a purity of 95% or even 99.5% or higher and nitrogen with a purity of 95% or even 99.99% or higher can be directly produced from the air and output at a high pressure.

[0099] As described above in the separation steps, the booster equipment is designed to overcome system resistance, achieve the required process pressure and flow rate for circulation, and maintain purity. It can be designed according to known technologies, including matching appropriate membrane separation materials.

[0100] The implementation methods described above only illustrate some important features of the present invention. Those skilled in the art should understand that although the present invention has been partially described in conjunction with the accompanying drawings, this is merely an application example or method of the present invention. All methods, apparatuses, or improvements in combination with the present invention that do not depart from the essence of the present invention, as well as implementation schemes that can be adopted in the practice of the present invention, including various modifications that do not deviate from the scope of the present invention, should be included within the scope of the appended claims. Furthermore, all technologies implemented based on the above content of the present invention fall within the scope of the invention.

Claims

1. A membrane separation oxygen and nitrogen generation system based on multi-cycle coupling, characterized in that, It consists of a two-stage membrane separation cycle system that is organically coupled, wherein: The first-stage membrane separation cycle system consists of at least two membrane separators connected in series. All the gas on the sluggish side of the first-stage membrane separator is used as the feed gas for the second-stage membrane separator and fed sequentially. The membrane separation cycle system also includes at least one feed gas compression device for receiving feed air and at least a portion of the permeate gas from the downstream separator in the membrane separation cycle system. The gas is also drawn in before the compressor via a pipeline and used as feed gas. Since the aforementioned air and the permeate gas from the downstream membrane separator are drawn in through the front end of the compressor and mixed to form the feed gas of the cycle system, the first membrane separation cycle is formed. At least a portion of the permeate gas from the downstream separator in the membrane separation cycle system is used as the purge carrier gas on the permeate side of the upstream separator in the second membrane separation cycle. All the gas on the stagnation side of the downstream membrane separator in this membrane separation cycle system is used as the high-purity nitrogen output. Since this gas only needs to overcome the resistance of the upstream and downstream membrane separators in this membrane separation cycle system, it has a high pressure. Therefore, the nitrogen output from this outlet is high-pressure, high-purity nitrogen with a purity of 95% or even 99.99% or higher. All the permeate gas from the pre-membrane separator in this stage of the membrane separation cycle system is used as the output of nitrogen- and argon-poor oxygen-enriched gas and as the feed gas for the second-stage membrane separation cycle system. The second-stage membrane separation cycle system consists of at least two membrane separators connected in series. The high-pressure side of the first-stage membrane separator serves as the feed end, receiving all the permeate gas from the permeate side of the first-stage membrane separator and the sludge gas from the second-stage membrane separator. The permeate gas pipelines of the first and second-stage membrane separators are connected and compressed by a compressor before entering the feed end of the second-stage membrane separator for further purification to the required oxygen concentration for output. The membrane separation cycle system also includes at least one feed gas compression device, which is used to sequentially receive at least a portion of the permeate gas from the downstream separator in the first-stage membrane separation cycle system. Before the permeate gas from the upstream and downstream separators is introduced into the compressor through a pipeline, at least a portion of the compressed gas is recycled back to the feed gas side of the downstream membrane separator in the first-stage membrane separation cycle system as feed gas. All the gas on the stagnation side of the downstream membrane separator is mixed with the permeate gas from the upstream membrane separator in the first-stage membrane separation cycle system and used as the feed gas for the upstream membrane separator in this stage, thus forming the second-stage membrane separation cycle. In this membrane separation cycle system, at least a portion of the permeate gas from the downstream separator in the first-stage membrane separation cycle system, as well as all the permeate gas from the upstream and downstream separators in this membrane separation cycle system, is introduced into the compressor through a pipeline. At least a portion of the compressed gas is output as a high-pressure, high-purity oxygen product with an oxygen concentration of 95% or even 99.5% or higher. The stagnant gas after separation by the upstream membrane separator in this stage membrane separation cycle system is used as the feed gas for the first stage membrane separation cycle system. It is introduced into the compressor of the first stage membrane separation cycle system through the coupling separation system and then sent in. Organic coupling of the first / second membrane separation cycle; At least one compression device is provided to compress the nitrogen- and argon-deficient oxygen-enriched gas on the permeate side of the pre-membrane separator of the first cycle separation system to a higher pressure so as to mix with the gas on the stagnation side of the post-membrane separator of the second cycle separation system, and can be used as the feed gas for the pre-membrane separator of the second cycle separation system to form a cycle separation. Furthermore, the nitrogen- and argon-poor oxygen-rich gas on the permeate side of the pre-membrane separator of the first cycle separation system, and the stagnation gas from the post-membrane separator of the second cycle separation system, after being separated by overcoming the resistance of the pre-membrane separator of the second cycle separation system, should also meet the pressure requirements of the compressor in the first cycle membrane separation system, so that the gas can be recycled back to the first cycle membrane separation system as feed gas.

2. The multi-cycle coupled membrane separation oxygen and nitrogen generation system according to claim 1, characterized in that, In the first-stage membrane separation cycle system, both the pre- and post-stage membrane separators connected in series use membrane separation materials with a separation coefficient α (O2 / N2) ≥ 6 to remove most of the nitrogen and some of the argon, so that a nitrogen-poor, argon-poor, and oxygen-rich gas with an oxygen concentration of 30-75% is obtained on the permeate side of the pre-stage membrane separator, while a nitrogen-rich gas with a concentration of 95% or even 99.99% or more is obtained on the retention side of the post-stage membrane separator.

3. The multi-cycle coupled membrane separation oxygen and nitrogen generation system according to claim 1, characterized in that, In the second-stage membrane separation cycle system, both the pre- and post-stage membrane separators connected in series use membrane separation materials with separation coefficients α(O2 / N2)≥6 and α(O2 / Ar)≥3.5 to effectively remove nitrogen and argon, and obtain oxygen-enriched gas with an oxygen concentration of 95% or even 99.5% or higher on the permeate side of the membrane in the post-stage membrane separator of the second cycle separation system.

4. The multi-cycle coupled membrane separation oxygen and nitrogen generation system according to claim 1, characterized in that: When the nitrogen- and argon-poor oxygen-rich gas from the permeate side of the downstream membrane separator in the first cycle separation system is drawn in by the compressor and mixed with the gas from the stagnation side of the upstream membrane separator in the second cycle separation system, the oxygen concentration of the two gases is brought close to equilibrium by designing and matching the membrane area of ​​each stage, adjusting the permeate flow rate of each stage membrane separator, and compressing and circulating gas flow rate.

5. The multi-cycle coupled membrane separation oxygen and nitrogen generation system according to claim 1, characterized in that, The compressed air is compressed to a working pressure of 4–20 atm (gauge pressure) by a compressor; a pretreatment system consisting of a filter, a freeze dryer or an adsorption dryer is installed to remove moisture, solid particulate impurities and oil from the compressed air before it enters the membrane separator.

6. The multi-cycle coupled membrane separation oxygen and nitrogen generation system according to claim 1, characterized in that: In the first-stage membrane separation cycle system: All the gas on the stagnation side of the pre-stage membrane separator is used as the feed gas for the subsequent membrane separator and fed sequentially. The compression device is used to receive raw material air, as well as a portion of the permeate gas from the downstream separator in this stage of the membrane separation cycle system, which is also drawn in as raw material gas before being introduced into the compressor via a pipeline; All the gas on the stagnation side of the downstream membrane separator is used as the output of high-purity nitrogen. All the gas on the permeate side of the pre-membrane separator is used as the output of nitrogen- and argon-poor oxygen-enriched gas and as the feed gas for the second-stage membrane separation cycle system. In the second-stage membrane separation cycle system: The high-pressure side of the pre-stage membrane separator serves as the feed end, which is used to receive all the permeate gas from the pre-stage membrane separator of the first-stage membrane separation cycle system and the stagnation gas from the downstream membrane separator. The permeate gas pipelines of the pre-stage and downstream membrane separators are connected and compressed by a compressor before entering the feed end of the downstream membrane separator for further purification to the required oxygen concentration for output. The compression device is used to sequentially receive all the permeate gas from the pre- and post-stage separators in the current membrane separation cycle system and introduce it into the compressor through a pipeline. Before the compressed gas is introduced into the compressor, at least a portion of the gas is recycled back to the feed gas side of the post-stage membrane separator in the current membrane separation cycle system as feed gas. All the gas on the stagnation side of the post-stage membrane separator is mixed with the permeate gas from the pre-stage membrane separator in the first-stage membrane separation cycle system and used as the feed gas of the pre-stage membrane separator in this stage, thereby forming the second-stage membrane separation cycle. In this membrane separation cycle system, all the permeate gas from the pre- and post-separators is introduced into the compressor through pipelines. At least a portion of the compressed gas is output as a high-pressure, high-purity oxygen product with an oxygen concentration of 95% or even 99.5% or higher. The stagnant gas after separation by the upstream membrane separator in this stage membrane separation cycle system is used as the feed gas for the first stage membrane separation cycle system. It is introduced into the compressor of the first stage membrane separation cycle system through the coupling separation system and then sent in. In the organic coupling of the first / second membrane separation cycle: The compression device is used to compress the nitrogen- and argon-poor oxygen-rich gas on the permeate side of the pre-membrane separator of the first cycle separation system to a higher pressure, and mix it with the stagnation side gas of the post-membrane separator of the second cycle separation system, so as to serve as the feed gas for the pre-membrane separator of the second cycle separation system, thus forming a cycle separation. Furthermore, the nitrogen- and argon-poor oxygen-rich gas on the permeate side of the pre-membrane separator of the first cycle separation system, and the stagnation gas from the post-membrane separator of the second cycle separation system, after overcoming the resistance of the pre-membrane separator of the second cycle separation system, should also meet the pressure conditions of the compressor in the first cycle membrane separation system, so that the gas can be recycled back to the first cycle membrane separation system as feed gas. Furthermore, when the nitrogen- and argon-poor oxygen-rich gas from the permeate side of the downstream membrane separator of the first cycle separation system is drawn in by the compressor and mixed with the gas from the stagnation side of the upstream membrane separator of the second cycle separation system, the oxygen concentration of the two gases should be nearly balanced by designing and matching the membrane area of ​​each stage, adjusting the permeate flow rate of each stage membrane separator, and compressing and circulating gas flow rate. Furthermore, when the nitrogen- and argon-poor oxygen-rich gas from the permeate side of the first-stage membrane separator of the first-cycle separation system is drawn in by the compressor and mixed with the gas from the stagnation side of the second-stage membrane separator of the second-cycle separation system, the oxygen concentration of the two gases is brought close to equilibrium by designing and matching the membrane area of ​​each stage, adjusting the permeate flow rate of each stage membrane separator, and compressing and circulating gas flow rate.

7. The multi-cycle coupled membrane separation oxygen and nitrogen generation system according to claim 1, characterized in that, It is also equipped with at least one set of control components to analyze and monitor the oxygen purity of the product flow, waste flow, and circulating gas, and to control the operation of valves and compression equipment in the circuit. The membrane separator has at least one feed gas inlet and one sludge outlet, the former being called the membrane separator head and the latter the membrane separator tail; it also has at least one permeate outlet; and the membrane separator has a high-pressure side and a low-pressure side, wherein one end of the high-pressure side is connected to the feed gas inlet, i.e., the membrane separator head, to receive the feed gas, and the other end is connected to the sludge outlet, i.e., the membrane separator tail, to remove gases that are difficult to pass through the membrane separation material, while the low-pressure side is connected to the permeate outlet to remove gases that are easier to pass through the membrane separation material.

8. The multi-cycle coupled membrane separation oxygen and nitrogen generation system according to claim 1, characterized in that: The first-stage membrane separation system consists of membrane separators M101 and M102, and compressor AB01 connected by pipelines. The feed gas inlet A0 of membrane separator M101 is connected to compressor AB01 via pipeline, and compressor AB01 is connected to the feed gas inlet via pipeline. Control valves V100 and QTV100 are sequentially installed on this connecting pipeline. The stagnant gas outlet A2 of membrane separator M101 is connected to the feed gas inlet A0 of membrane separator M102 via pipeline. The stagnation gas outlet A2 of membrane separator M102 outputs high-pressure, high-purity nitrogen gas, and its output pipeline is equipped with valve QTV101 and control valve V101 in sequence; the permeate gas outlet A1 of membrane separator M102 is connected to the inlet pipeline of compressor AB01; valve QTV102A is installed on this connecting pipeline; at the same time, the permeate gas outlet A1 of membrane separator M102 is connected to port A132 below membrane separator M201, and valve QTV102B is installed on this connecting pipeline; The second-stage membrane separation system consists of membrane separators M201 and M202, and compressor AB02 connected by pipelines. The permeate outlet A1 of membrane separator M201 is connected to port A142 below membrane separator M202 via pipeline. The sludge outlet A2 above membrane separator M202 outputs a nitrogen- and argon-poor oxygen-enriched mixed gas, and its output pipeline is equipped with valve QTV103 and control valve V103 in sequence. The permeate outlet A1 of membrane separator M202 is connected to the output pipeline of the nitrogen- and argon-poor oxygen-enriched mixed gas from the sludge outlet A2 above membrane separator M202 via pipeline, and compressor AB02 is installed on this connecting pipeline. The first and second stage membrane separation cycles are coupled; compressor AB03, control valve V102, and valve QTV102 are used; compressor AB03 is installed on the connecting pipeline between the permeate outlet A1 of membrane separator M101 and the stagnant gas outlet A2 above membrane separator M201; control valve V102 and valve QTV102 are sequentially installed on the connecting pipeline between the feed gas inlet A0 of membrane separator M201 and the feed gas inlet A0 of membrane separator M101, with connection point 3, on the connecting pipeline between the feed gas inlet A0 of membrane separator M101 and compressor AB01.

9. The multi-cycle coupled membrane separation oxygen and nitrogen generation system according to claim 8, characterized in that: Membrane separators M101 and M102 are three-port membrane separators. Each membrane separator is divided into a high-pressure side and a low-pressure side by membrane separation material. One end of the high-pressure side is connected to a feed gas inlet, which is the head of the membrane separator, to receive the feed gas, and the other end is connected to a sludge gas outlet, which is the tail of the membrane separator, to remove gases that are more difficult to pass through the membrane separation material. The low-pressure side is connected to a permeate gas outlet to remove gases that are more easily passed through the membrane separation material. This membrane separator has the function of separating oxygen from nitrogen and argon. Oxygen passes through more easily, while nitrogen and argon pass through more difficultly. Membrane separators M201 and M202 are four-port membrane separators, divided into a high-pressure side and a low-pressure side by a membrane separation material. One end of the high-pressure side is connected to a feed gas inlet, i.e., the head of the membrane separator, to receive feed gas, and the other end is connected to a sludge outlet, i.e., the tail of the membrane separator, to remove gases that are more difficult to pass through the membrane separation material. The low-pressure side is connected to two permeate outlets to remove gases that are more easily passed through the membrane separation material. One permeate outlet is close to the feed gas inlet side, or the head of the membrane separator, and the other permeate outlet is close to the sludge outlet side, or the tail of the membrane separator. This membrane separator has the function of separating oxygen from nitrogen and argon, with oxygen passing through more easily while nitrogen and argon are more difficult to pass through.

10. The multi-cycle coupled membrane separation oxygen and nitrogen generation system according to claim 9, characterized in that, Its workflow is as follows: First-stage membrane separation cycle: All the gas on the stagnation side of the pre-membrane separator M101 is used as the feed gas for the subsequent membrane separator M102, and is fed sequentially from the compressor AB01 and the pretreatment equipment. The compressor AB01 receives raw material air from point 1 and inputs it through regulating valves V100 and QTV100. It is also used as raw material gas along with a portion of the permeate gas from the downstream separator M102 in this stage of the membrane separation cycle system, which is introduced into the compressor through point 2 via point 5 and pipeline. The aforementioned air and the permeate gas from the downstream membrane separator M102 are drawn into the front end of the compressor AB01 and mixed to form part of the raw material gas for this stage of the cycle separation system. The outlet pressure of AB01 is controlled at 0.7 to 1.2 MPa (gauge pressure), and the outlet temperature is ≤60℃, thus constituting the first stage membrane separation cycle. All the gas from the stagnation side of the downstream membrane separator M102 in this membrane separation cycle system is used as the high-purity nitrogen output. It is output from point 6 via regulating valves V101 and QTV101. Since this gas only needs to overcome the resistance of the membrane separators M101 and M102 in this membrane separation cycle system, it still has a high pressure. Therefore, the nitrogen-rich gas with a pressure of 0.6 to 1.1 MPa and a purity of over 99.99% is output from this outlet. All the permeate gas from the pre-membrane separator M101 of this membrane separation cycle system is output as nitrogen- and argon-poor oxygen-rich gas at the output end 4, with an oxygen concentration of 45-75%, and is used as the feed gas for the second-stage membrane separation cycle system. Furthermore, in this membrane separation cycle system, the membrane separators M101 and M102 connected in series in the front and back stages both use membrane separation materials with a separation coefficient α (O2 / N2) ≥ 6. On the permeate side 4 of the front membrane separator M101, oxygen-poor nitrogen and argon-poor oxygen gas with an oxygen concentration of 30-75% is obtained, while on the retention side 6 of the back membrane separator M102, nitrogen-rich gas with a concentration of over 99.99% is obtained. The operating temperature is controlled at 45-55℃. Second-stage membrane separation cycle: The high-pressure side 7 between the two-stage membrane separators M201 and M202 connected in series serves as the feed end, i.e., intermediate feed, where the oxygen concentration of the mixed gas is controlled at 60-80%. The feed gas compression device AB02 is used to sequentially receive the permeate gas from the pre-separator M201 and the post-separator M202 in this stage membrane separation cycle system. Before all the permeate gas is introduced into the compressor through pipeline 11 from 9 to 10 to 11, at least a portion of the compressed gas is circulated back to the feed gas side of the post-separator M202 in this stage membrane separation cycle system via 12 to 13 as feed gas. The outlet pressure of the compressor AB02 is controlled at 0.5 to 0.8 MPa. All the gas on the sludge side of the post-separator M202 is mixed with the permeate gas from the pre-separator M101 of the first stage membrane separation cycle system and introduced into the pre-separator M201 as feed gas. The oxygen concentration of the sludge gas in M202 before mixing is 85 to 95%, thus forming the second stage membrane separation cycle. In this membrane separation cycle system, the permeate gas from the pre- and post-separators M201 and M202 passes through 9 to 10 to 11, and all the permeate gas is introduced into the compressor through pipeline 11. At least a portion of the compressed gas is output from 14 through 12, regulating valve V103, and QTV103 as a high-pressure, high-purity oxygen product with an output concentration of over 99.5% and a pressure of 0.5 to 0.8 MPa. The sludge gas after separation by the pre-membrane separator M201 in this stage membrane separation cycle system is introduced from 8 via regulating valves V102 and QTV102 as the feed gas for the first stage membrane separation cycle system. It is then introduced into the compressor AB01 of the first stage membrane separation cycle system via the coupling separation system and sent in. The oxygen concentration of this sludge gas is 85-95%. Furthermore, in this stage of membrane separation cycle separation system, the membrane separators M201 and M202 connected in series in the front and back stages adopt membrane separation materials with separation coefficients α(O2 / N2)≥6 and α(O2 / Ar)≥3.5, respectively. Oxygen with an oxygen concentration of 99.5% or higher is obtained on the permeate side 11 of the back stage membrane separator M202 in the second cycle separation system and output as product gas via 12 to 14. The operating temperature of M201 / M202 is controlled at 40~50℃. Coupling of the first / second membrane separation cycle: The nitrogen- and argon-poor oxygen-rich gas on the permeate side of the pre-membrane separator M101 in the first cycle separation system is introduced into the compressor AB03 via 4 for compression. The outlet pressure of AB03 is controlled at 1.0 to 1.5 MPa to ensure that it is mixed with the stagnation side gas of the post-membrane separator M202 in the second cycle separation system. It can also be used as the feed gas for the pre-membrane separator M201 in the second cycle separation system to form a cycle separation. Furthermore, the nitrogen- and argon-deficient, oxygen-enriched gas from the permeate side 4 of the pre-membrane separator M101 of the first cycle separation system, and the stagnation side gas from the post-membrane separator M202 of the second cycle separation system are mixed at 7. The stagnation gas 8, after overcoming the resistance of the pre-membrane separator M201 of the second cycle separation system, is separated. Its pressure should also meet the pressure conditions of the compressor AB01 supplied to the membrane separation system of the first cycle, so that the gas can be recycled back to the membrane separation system of the first cycle as feed gas. The circulating gas volume can be adjusted within the range of 10% to 30% of the product oxygen content. Furthermore, when the nitrogen- and argon-deficient, oxygen-enriched gas from the permeate side of the downstream membrane separator M102 of the first cycle separation system is drawn in by the compressor AB01 and mixed with the gas from the stagnation side of the upstream membrane separator M201 of the second cycle separation system, the oxygen concentration of the two gases should be nearly balanced by designing and matching the membrane area of ​​each stage, adjusting the permeate flow rate of each stage membrane separator, and adjusting the compression and circulation gas flow rate. The target oxygen concentration at the mixing point 3 is 25-35%. Furthermore, the nitrogen- and argon-deficient, oxygen-enriched gas from the permeate side of the first-stage membrane separator M101 in the first-cycle separation system, after being drawn in by the compressor at point 4, mixes with the gas from the stagnation side of the second-stage membrane separator M202 at point 7. Through design matching of membrane areas at each stage, adjustment of the permeate flow rate of each membrane separator, compression, and circulation gas flow rate, the oxygen concentration of the two gases is brought close to equilibrium, with a target oxygen concentration of 60-80% at mixing point 7. Thus, the above process forms an organic coupling between the first and second membrane separation cycles. Through the above separation steps, oxygen with a purity of over 99.5% and nitrogen with a purity of over 99.99% can be directly and simultaneously produced from the air and output at a high pressure.

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