Method and system for recovering hydrogen in mixed gas by using pressure swing adsorption and membrane separation method

Abstract

The invention relates to a method and a system for recovering hydrogen in mixed gas by using a pressure swing adsorption and membrane separation method. The method comprises the following steps: S1, preliminary impurity removal: carrying out multi-layer adsorption impurity removal on mixed gas containing silane, disilane and hydrogen, and cooling to 22-28 DEG C; s2, pressure swing adsorption: feeding the mixed gas subjected to primary impurity removal into a pressure swing adsorption device, wherein an adsorbent in the adsorption device is modified activated carbon which is activated at high temperature and is loaded with 3-5% of copper oxide on the surface; s3, membrane separation and adsorption: the mixed gas passing through the pressure swing adsorption device enters a filter and a dryer, and finally passes through a membrane separation device, silane and disilane are collected on the enrichment side of the membrane separation device for further purification, and hydrogen is collected on the permeation side of the membrane separation device for further purification. According to the invention, a process of combining pressure swing adsorption and a membrane separation method is adopted, the advantages of the two technologies are fully exerted, and efficient separation of silane, disilane and hydrogen is realized.

Description

Technical Field

[0001] This application relates to the field of gas separation and purification technology, specifically to a method and system for recovering hydrogen from a mixed gas using pressure swing adsorption and membrane separation. Background Technology

[0002] In cutting-edge technology fields such as semiconductor manufacturing, photovoltaic material production, and specialty gas preparation, silane (SiH4) and disilane (Si2H6), as important silicon source gases, are commonly used in key processes such as chemical vapor deposition (CVD) and epitaxial growth. Their usage is growing exponentially with the rapid development of the new energy and electronics industries. At the same time, the production process inevitably generates a large amount of mixed gas containing silane, disilane, and hydrogen (H2). Hydrogen is not only the core carrier of the hydrogen energy economy but also an indispensable reducing gas in chemical synthesis, metal smelting, and electronic device manufacturing. Silane and disilane can be recycled and reused in production, significantly reducing raw material costs for enterprises. Therefore, the efficient separation and recovery of the components in this type of mixed gas not only conforms to the concept of a circular economy but also effectively alleviates my country's dependence on imported high-purity gases, which is of great strategic significance for promoting the green and high-quality development of related industries.

[0003] Currently, industrial methods for separating hydrogen from gas mixtures mainly include pressure swing adsorption (PSA), membrane separation, cryogenic separation, and metal hydride adsorption. While PSA offers flexibility and low energy consumption, traditional adsorbents have limited selective adsorption capacity for silanes and disilanes, making hydrogen recovery rates susceptible to issues in the presence of high concentrations of these substances. Membrane separation relies on highly selective membrane materials; existing polysulfone and polyimide-based membranes are prone to rapid flux decay due to impurities clogging the membrane pores when processing complex gas mixtures, and their separation accuracy is insufficient to meet the production requirements of electronic-grade hydrogen (purity ≥99.999%). Cryogenic separation requires cooling the gas mixture to extremely low temperatures, resulting in significant equipment investment and high energy consumption, making it unsuitable for small-scale gas processing. While metal hydride adsorption can achieve high-purity hydrogen separation, its long adsorption-desorption cycle time and high metal material cost limit its industrial application.

[0004] In actual production, the composition and operating conditions of the gas mixture exhibit significant fluctuations. For example, in the exhaust gas treatment stage of photovoltaic cell production, the silane content may fluctuate between 15% and 30%, and the ethylsilane content may fluctuate between 8% and 18%, influenced by adjustments to process parameters. In the etching process of semiconductor chip manufacturing, exhaust gas pressure and temperature can change drastically depending on the equipment's operating status. When the gas mixture composition approaches its limits, or when operating parameters are at boundary conditions, the limitations of existing separation technologies become more pronounced. Traditional pressure swing adsorption (PSA) processes may experience a sharp drop in hydrogen purity due to adsorbent overload; membrane separation systems may suffer from membrane damage and separation performance failure due to insufficient thermal stability of the membrane material or pressure shocks. Furthermore, equipment failure rates increase significantly under extreme operating conditions, leading to substantial increases in maintenance costs, making it difficult for existing technologies to meet the demands of continuous and stable production.

[0005] Therefore, developing a new process that can adapt to complex working conditions and achieve efficient hydrogen separation and recovery, while solving the technical bottlenecks of existing technologies under extreme conditions, has become a key problem that urgently needs to be solved in this field. Summary of the Invention

[0006] To address the problems of existing industrial production methods being unable to adapt to complex operating conditions, having low separation efficiency, and high production costs, this application proposes a novel process that can adapt to complex operating conditions and achieve efficient hydrogen separation and recovery. Simultaneously, it overcomes the technical bottlenecks of existing technologies under extreme conditions. The technical solution of this application is as follows:

[0007] On the one hand, this application provides a method for recovering hydrogen from a mixed gas using pressure swing adsorption and membrane separation, comprising the following steps:

[0008] Step S1. Preliminary impurity removal: The mixed gas containing 20%–25% silane, 10%–15% silane, and 60%–70% hydrogen is subjected to multilayer adsorption for impurity removal and then cooled to 22–28°C;

[0009] Step S2. Pressure Swing Adsorption: The mixed gas after preliminary impurity removal enters the pressure swing adsorption device. The adsorbent in the adsorption device is modified activated carbon that has been activated at high temperature and has a surface loading of 3% to 5% copper oxide.

[0010] Step S3. Membrane separation adsorption: The mixed gas after passing through the pressure swing adsorption device then enters the filter and dryer, and finally passes through the membrane separation device. Silane and silane are collected on the enrichment side of the membrane separation device for further purification, and hydrogen is collected on the permeate side of the membrane separation device.

[0011] Preferably, in step S1, the multilayer adsorption includes a first coarse filtration layer and a second fine filtration layer, wherein the filtration accuracy of the first coarse filtration layer is 1 μm and the accuracy of the second fine filtration layer is 0.05 μm.

[0012] Preferably, in step S2, the high-temperature activation process is as follows: Activated carbon is placed in a high-temperature furnace under inert gas or nitrogen protection and heated to 820-900°C at a heating rate of 5-10°C / min, and held at that temperature for 2-3 hours; copper oxide is loaded using an equal-volume impregnation method, where copper nitrate solution is uniformly impregnated onto the activated activated carbon, dried at 80-100°C for 12-16 hours, and then calcined at 320-400°C for 3.2-4 hours to obtain a modified activated carbon adsorbent with a specific surface area of ​​1500 m². 2 The pore size is above / g and concentrated in the range of 0.8 to 1.5 nm.

[0013] Preferably, in step S2, the flow rate of the mixed gas is controlled at 10-20 L / min, while the composition of the mixed gas is monitored in real time to ensure that the proportion of each component fluctuates within ±0.5%; the pressure swing adsorption is controlled at 0.6-0.8 MPa, and the pressure rise rate is maintained at 0.06-0.08 MPa / min; the desorption pressure is 0.05-0.1 MPa, and the pressure fall rate is 0.12-0.15 MPa / min.

[0014] Preferably, in step S2, during the pressure swing adsorption process, the purity of hydrogen output from the pressure swing adsorption device is monitored in real time. If the purity is lower than 99%, the system automatically fine-tunes the adsorption time by 1 to 3 minutes, with an adsorption time of 5 to 15 minutes and a desorption time of 3 to 10 minutes.

[0015] Preferably, in step S3, the filter is a filter with an accuracy of 0.1 to 1 μm; the dryer is filled with molecular sieve desiccant, and the dew point temperature of the gas after drying is below -40°C.

[0016] Preferably, in step S3, the membrane separation device is equipped with a modified polyimide-ceramic composite membrane, the pressure difference is 0.3 to 0.8 MPa, the thickness of the modified polyimide-ceramic composite membrane is 10 to 50 μm, and the porosity is 30% to 60%.

[0017] Preferably, the modified layer of the modified polyimide-ceramic composite film is coated with a fluorinated silane coupling agent, and the coating thickness is 0.1-0.5 μm.

[0018] On the other hand, this application provides a system for recovering a mixed gas using pressure swing adsorption and membrane separation, comprising a mixed gas cylinder, a pretreatment unit, a pressure swing adsorption unit, and a membrane separation unit connected in sequence. The pretreatment unit includes a first filter and a second filter connected in series, with coolers provided outside the first and second filters. The pressure swing adsorption unit includes at least three adsorption towers connected in parallel. The membrane separation unit includes a third filter, a dryer, and a membrane separation device connected in series. The enrichment side of the membrane separation device is connected to a distillation column for silane and diethylsilane, and the permeate side of the membrane separation device is connected to a hydrogen collection unit. The hydrogen collection unit includes a primary buffer tank and a secondary buffer tank connected in series, and the secondary buffer tank is connected to a hydrogen storage device.

[0019] The beneficial effects of this application are as follows:

[0020] 1. High-efficiency separation: The process combines pressure swing adsorption and membrane separation, giving full play to the advantages of both technologies, and achieves high-efficiency separation of silane, silane and hydrogen. Compared with traditional methods, it significantly improves the recovery rate and purity of hydrogen, with hydrogen purity reaching over 99.7% and recovery rate reaching up to 97%.

[0021] 2. Adsorbent Advantages: The specially modified activated carbon adsorbent, through high-temperature activation and copper oxide loading, optimizes the physicochemical properties of the adsorbent. Its high specific surface area and specific pore size distribution, as well as the interaction between copper oxide and silane and disilane, greatly enhance the adsorption capacity for silane and disilane. At the same time, precise control of pressure swing adsorption parameters further improves the adsorption and desorption efficiency.

[0022] 3. Membrane separation characteristics: The modified polyimide-ceramic composite membrane selected has high selective permeability to hydrogen. Under suitable pressure difference conditions, it can efficiently separate hydrogen from silane and silane. Moreover, the membrane separation process has mild operating conditions and low energy consumption, which helps to reduce production costs.

[0023] 4. High economic benefits: The method proposed in this application can not only recover high-purity hydrogen to meet the demand for high-quality hydrogen in industrial production, but also effectively enrich silane and ethylsilane, realize the full utilization of resources, reduce raw material waste, and improve the economic and environmental benefits of industrial production, and has broad application prospects. Attached Figure Description

[0024] Appendix Figure 1 This is a process flow diagram of the recovery of hydrogen from a mixed gas using pressure swing adsorption and membrane separation in this application.

[0025] Appendix Figure 2 This is a system diagram of the recovery of hydrogen from a mixed gas using pressure swing adsorption and membrane separation methods as described in this application.

[0026] Figure labels: 1. Mixed gas cylinder; 2. Pretreatment unit; 21. First filter; 22. Second filter; 23. Cooler; 3. Flow meter; 4. Online analyzer; 5. Pressure swing adsorption unit; 51. Adsorption tower; 6. Membrane separation unit; 7. Hydrogen collection unit; 71. Primary buffer tank; 72. Secondary buffer tank; 8. Hydrogen storage device. Detailed Implementation

[0027] To further illustrate the technical means and effects adopted by this application in order to achieve the intended purpose of the invention, the following detailed description of the specific implementation methods, structures, features and effects of this application is provided in conjunction with the accompanying drawings and preferred embodiments.

[0028] Device Examples

[0029] This embodiment provides a device utilizing pressure swing adsorption and membrane separation to participate in... Figure 2 Specifically, it includes a mixed gas cylinder 1, a pretreatment unit 2, a pressure swing adsorption unit 5, and a membrane separation unit 6 connected in sequence. The pretreatment unit 2 includes a first filter 21 and a second filter 22 connected in series. The first filter 21 and the second filter 22 are equipped with a cooler 23 on their exterior. The pressure swing adsorption unit 5 includes at least three adsorption towers 51 connected in parallel. The membrane separation unit 6 includes a third filter, a dryer, and a membrane separation device connected in series. The enrichment side of the membrane separation device is connected to a distillation tower for silane and diethylsilane. The permeate side of the membrane separation device is connected to a hydrogen collection unit 7. The hydrogen collection unit 7 includes a primary buffer tank 71 and a secondary buffer tank 72 connected in series. The secondary buffer tank 72 is connected to a hydrogen storage device 8.

[0030] The operating principle of the device is as follows:

[0031] Step S1. A mixed gas containing 20%–25% silane, 10%–15% silane, and 60%–70% hydrogen is introduced into the pretreatment unit 2. The pretreatment unit 2 is equipped with a first filter 21 and a second filter 22. The first filter 21 contains a first coarse filter layer, and the second filter 22 contains two fine filter layers. The filtration accuracy of the first coarse filter layer is 1 μm, and the filtration accuracy of the second fine filter layer is 0.05 μm. Simultaneously, a cooler 23 is used to cool the mixed gas. The cooler 23 is an air-cooled cooling system. Cooler 23 maintains the temperature of the mixed gas at 22-28℃. Cooler 23 is equipped with a temperature adaptive control system that automatically adjusts the flow and temperature of the cooling medium according to the real-time temperature and flow of the mixed gas to ensure the cooling effect of the mixed gas. Cooler 23 is made of corrosion-resistant aluminum alloy and the surface is treated with anti-corrosion coating to extend the service life of the equipment. Pretreatment unit 2 is equipped with an automatic impurity backflushing system. When the pressure difference before and after the filter reaches the set threshold, the backflushing program is automatically started to remove impurities from the filter element using compressed nitrogen to ensure stable filtration performance.

[0032] Step S2. The mixed gas is then introduced into the pressure swing adsorption (PSA) unit 5. Using a high-precision gas mass flow meter 3, the flow rate of the mixed gas is stably controlled at 10–20 L / min. Simultaneously, the composition of the mixed gas is monitored in real time to ensure that the proportions of each component fluctuate within ±0.5%. The PSA unit 5 includes at least three parallel adsorption towers 51, connected by an automatic valve group. Based on the mixed gas flow rate, composition changes, and adsorbent saturation, the automatic control system dynamically adjusts the switching time of the adsorption towers 51, with a precision range of 1.5–4 minutes, ensuring continuous and efficient operation of the device. Each adsorption tower 51 utilizes a built-in rotary gas stirrer. The stirring rate is dynamically adjusted according to the mixed gas flow rate and the pressure within the adsorption tower 51, ranging from 60–90 r / min. The stirrer blades feature a curved surface design to enhance gas mixing, promote full contact between the mixed gas and the adsorbent, and improve adsorption efficiency. The adsorption tower 51 is made of high-strength 316L stainless steel, with its inner wall electrolytically polished to a roughness as low as Ra0.5 μm.

[0033] Step S3. The pre-purified mixed gas is first passed through a filter to remove impurity particles, then through a molecular sieve desiccant in a dryer to remove moisture, and then passed into a membrane separation device equipped with a modified polyimide-ceramic composite membrane. Under the action of pressure difference, hydrogen permeates and is enriched on the permeate side. The permeate side of the membrane separation device is connected to a hydrogen collection unit 7. The hydrogen collection unit 7 includes a primary buffer tank 71 and a secondary buffer tank 72 connected in series. The primary buffer tank 71 has a volume of 60L, and the secondary buffer tank 72 has a volume of 80L. It is equipped with a pressure regulating valve to stabilize the output hydrogen pressure at 0.5-0.6MPa. At the same time, the purity of hydrogen is detected by an online hydrogen analyzer 4. The gas that does not permeate through the membrane is enriched with silane and ethylsilane on the retrieval side.

[0034] The embodiments are based on the devices provided in the device embodiments, and the specific operations are as follows:

[0035] Example 1

[0036] Step S1. Preliminary impurity removal: The mixed gas containing 20% ​​silane, 10% silane and 70% hydrogen is subjected to multi-layer adsorption for impurity removal and cooled to 25°C; wherein, the first coarse filter layer and the second fine filter layer have a filtration accuracy of 1μm and an accuracy of 0.05μm respectively.

[0037] Step S2. Preliminary purification by pressure swing adsorption: A mixed gas containing 20% ​​silane, 10% silane, and 70% hydrogen is introduced into the pressure swing adsorption (PSA) unit. The flow rate of the mixed gas is controlled at 15 L / min, and the composition of the mixed gas is monitored in real time to ensure that the proportion of each component fluctuates within ±0.5%. The adsorption time is 5 min, and the desorption time is 3 min. During the PSA process, the purity of the hydrogen output from the PSA unit is monitored in real time. If the purity is lower than 99%, the system automatically fine-tunes the adsorption time.

[0038] The adsorbent in the pressure swing adsorption unit is modified activated carbon that has been activated at high temperature and has a surface loading of 3% copper oxide, with a specific surface area of ​​1550 m². 2 / g, with pore sizes concentrated between 0.8 and 1.2 nm; the high-temperature activation process is as follows: activated carbon is placed in a high-temperature furnace under nitrogen protection and heated to 850°C at a heating rate of 6°C / min, and held at that temperature for 2.5 hours; copper oxide is loaded using an equal-volume impregnation method, where a calculated copper nitrate solution (mass fraction of 8%) is uniformly impregnated onto the activated carbon, dried at 90°C for 14 hours, and then calcined at 350°C for 3.5 hours. The adsorption pressure is controlled at 0.6 MPa, with a pressure rise rate of 0.06 MPa / min; the desorption pressure is controlled at 0.05 MPa, with a pressure fall rate of 0.12 MPa / min. The mixed gas is then treated to obtain preliminarily purified hydrogen.

[0039] Step S3. Further purification via membrane separation: The pre-purified mixed gas is first passed through a particle filter with a precision of 0.3 μm to remove impurities, and then through a molecular sieve desiccant to remove moisture. The molecular sieve is regenerated at 250℃ for 5 hours. Then, it is passed through a membrane separation device equipped with a modified polyimide-ceramic composite membrane (the modified layer is coated with perfluorodecyltriethoxysilane, with a coating thickness of 0.3 μm). Under a pressure difference of 0.3 MPa, hydrogen permeates through the polyimide membrane and is enriched on the permeate side, while the gas that does not permeate is enriched with silane and diethylsilane on the retrieval side. The final hydrogen purity reaches 99.9%, and the hydrogen recovery rate is 96%.

[0040] Example 2

[0041] Step S1. Preliminary impurity removal: The mixed gas containing 22% silane, 10% silane and 68% hydrogen is subjected to multi-layer adsorption for impurity removal and cooled to 26°C; wherein, the first coarse filter layer and the second fine filter layer have a filtration accuracy of 1μm and an accuracy of 0.05μm respectively.

[0042] Step S2. The mixed gas, after preliminary impurity removal, enters the pressure swing adsorption (PSA) device. The flow rate of the mixed gas is controlled at 18 L / min, and the composition of the mixed gas is monitored in real time to ensure that the proportion of each component fluctuates within ±0.5%. The adsorption time is 7 min and the desorption time is 5 min. During the PSA process, the purity of the hydrogen output from the PSA device is monitored in real time. If the purity is lower than 99%, the system automatically fine-tunes the adsorption time.

[0043] The adsorbent in the pressure swing adsorption unit is modified activated carbon that has been activated at high temperature and has a surface loading of 4% copper oxide, with a specific surface area of ​​1600 m². 2 / g, pore size concentrated in the range of 0.9–1.3 nm; for high-temperature activation, activated carbon was heated to 880 °C at a heating rate of 8 °C / min under argon protection and held at that temperature for 2.8 hours; for copper oxide loading, copper nitrate solution (mass fraction 8%) was impregnated, dried at 95 °C for 15 hours, and calcined at 400 °C for 4 hours. The adsorption pressure was controlled at 0.7 MPa, with a pressure rise rate of 0.07 MPa / min; the desorption pressure was controlled at 0.07 MPa, with a pressure fall rate of 0.13 MPa / min, to achieve adsorption and desorption of silane and disilane, and to preliminarily purify hydrogen.

[0044] Step S3. Further purification via membrane separation: The preliminarily purified mixed gas is subjected to particle filtration and drying. A 0.2 μm filter cartridge is used for particle filtration. The molecular sieve regeneration temperature during drying is 220℃, and the regeneration time is 4.5 hours. Then, the mixture is passed through a membrane separation device equipped with a modified polyimide-ceramic composite membrane (the modified layer is coated with perfluorodecyltriethoxysilane, with a coating thickness of 0.1 μm). Under a pressure difference of 0.5 MPa, hydrogen is enriched on the permeate side, while silane and diethylsilane are enriched on the retrieval side, ultimately yielding hydrogen with a purity of 99.8% and a hydrogen recovery rate of 95%.

[0045] Example 3

[0046] Step S1. Preliminary impurity removal: The mixed gas containing 25% silane, 15% silane and 60% hydrogen is subjected to multi-layer adsorption for impurity removal and cooled to 22°C; wherein, the first coarse filter layer and the second fine filter layer have a filtration accuracy of 1μm and an accuracy of 0.05μm respectively.

[0047] Step S2. The mixed gas, after preliminary impurity removal, enters the pressure swing adsorption (PSA) device. The flow rate of the mixed gas is controlled at 10 L / min, and the composition of the mixed gas is monitored in real time to ensure that the proportion of each component fluctuates within ±0.5%. The adsorption time is 10 min, and the desorption time is 7 min. During the PSA process, the purity of the hydrogen output from the PSA device is monitored in real time. If the purity is lower than 99%, the system automatically fine-tunes the adsorption time.

[0048] The adsorbent in the pressure swing adsorption unit is modified activated carbon that has been activated at high temperature and has a surface loading of 5% copper oxide, with a specific surface area of ​​1580 m². 2 / g, with pore sizes concentrated between 1.0 and 1.5 nm; high-temperature activation involved heating the activated carbon to 860 °C at a rate of 7 °C / min under helium protection and holding for 2.2 hours; in the copper oxide loading process, the activated carbon was impregnated and then dried at 85 °C for 13 hours and calcined at 380 °C for 3.8 hours. The adsorption pressure was controlled at 0.8 MPa with a pressure rise rate of 0.08 MPa / min; the desorption pressure was controlled at 0.1 MPa with a pressure fall rate of 0.15 MPa / min, completing the pressure swing adsorption process and initially purifying hydrogen.

[0049] Step S3. Further purification via membrane separation: The pre-purified mixed gas is purified to remove impurities and moisture. The particle filtration accuracy is 0.4 μm, the molecular sieve regeneration temperature is 280℃, and the regeneration time is 5.5 hours. Then, it is passed through a membrane separation device equipped with a modified polyimide-ceramic composite membrane (the modified layer is coated with perfluorodecyltriethoxysilane, with a coating thickness of 0.4 μm). Under a pressure difference of 0.8 MPa, hydrogen permeates through the membrane and accumulates on the permeate side, ultimately achieving a hydrogen purity of 99.95% and a hydrogen recovery rate of 94%.

[0050] Example 4

[0051] Step S1. Preliminary impurity removal: The mixed gas containing 21% silane, 11% silane and 68% hydrogen is subjected to multi-layer adsorption for impurity removal and cooled to 28°C; wherein, the first coarse filter layer and the second fine filter layer have a filtration accuracy of 1μm and an accuracy of 0.05μm respectively.

[0052] Step S2. Preliminary purification by pressure swing adsorption: The mixed gas, after preliminary purification, enters the pressure swing adsorption device. The flow rate of the mixed gas is controlled at 20 L / min, and the composition of the mixed gas is monitored in real time to ensure that the proportion of each component fluctuates within ±0.5%. The adsorption time is 12 min, and the desorption time is 9 min. During the pressure swing adsorption process, the purity of the hydrogen output from the pressure swing adsorption device is monitored in real time. If the purity is lower than 99%, the system automatically fine-tunes the adsorption time.

[0053] The adsorbent in the pressure swing adsorption unit is modified activated carbon that has been activated at high temperature and has a surface loading of 3.5% copper oxide, with a specific surface area of ​​1560 m². 2 / g, pore size concentrated in the range of 0.8–1.3 nm; for high-temperature activation, activated carbon was heated to 820 °C at a heating rate of 5 °C / min under nitrogen protection and held for 3 hours; copper oxide was loaded using an equal-volume impregnation method, impregnating the carbon with a copper nitrate solution (mass fraction of 8%), drying at 80 °C for 16 hours, and calcining at 320 °C for 3.2 hours. The adsorption pressure was controlled at 0.65 MPa, with a pressure rise rate of 0.065 MPa / min; the desorption pressure was controlled at 0.06 MPa, with a pressure fall rate of 0.13 MPa / min. The mixed gas was then treated to obtain preliminarily purified hydrogen.

[0054] Step S3. Further purification via membrane separation: The pre-purified mixed gas is first passed through a particle filter with a precision of 0.1 μm to remove impurities, and then through a molecular sieve desiccant to remove moisture. The molecular sieve is regenerated at 200℃ for 6 hours. Then, it is passed through a membrane separation device equipped with a modified polyimide-ceramic composite membrane (the modified layer is coated with perfluorodecyltriethoxysilane, with a coating thickness of 0.5 μm). Under a pressure difference of 0.4 MPa, hydrogen permeates through the composite membrane and is enriched on the permeate side, while the gas that does not permeate is enriched with silane and diethylsilane on the retain side. The final hydrogen purity reaches 99.92%, and the hydrogen recovery rate is 94%.

[0055] Example 5

[0056] Step S1. Preliminary impurity removal: The mixed gas containing 24% silane, 14% silane and 62% hydrogen is subjected to multi-layer adsorption for impurity removal and cooled to 27°C; wherein, the first coarse filter layer and the second fine filter layer have a filtration accuracy of 1μm and an accuracy of 0.05μm respectively.

[0057] Step S2. Preliminary purification by pressure swing adsorption: The mixed gas, after preliminary impurity removal, enters the pressure swing adsorption device. The flow rate of the mixed gas is controlled at 19 L / min, and the composition of the mixed gas is monitored in real time to ensure that the proportion of each component fluctuates within ±0.5%. The adsorption time is 15 min, and the desorption time is 10 min. During the pressure swing adsorption process, the purity of the hydrogen output from the pressure swing adsorption device is monitored in real time. If the purity is lower than 99%, the system automatically fine-tunes the adsorption time.

[0058] The adsorbent in the pressure swing adsorption unit is modified activated carbon that has been activated at high temperature and has a surface loading of 4.5% copper oxide, with a specific surface area of ​​1590 m². 2 / g, pore size concentrated in the range of 0.9–1.4 nm; the high-temperature activation process involves heating activated carbon to 900 °C at a heating rate of 10 °C / min under argon protection and holding at that temperature for 2 hours; for copper oxide loading, the carbon is impregnated with copper nitrate solution (mass fraction of 8%), dried at 100 °C for 12 hours, and calcined at 360 °C for 3.6 hours. The adsorption pressure is controlled at 0.75 MPa with a pressure rise rate of 0.075 MPa / min; the desorption pressure is controlled at 0.08 MPa with a pressure fall rate of 0.14 MPa / min, achieving adsorption and desorption of silanes and disilanes, and initially purifying hydrogen.

[0059] Step S3. Further purification via membrane separation: The preliminarily purified mixed gas is subjected to particle filtration and drying. A 0.5 μm filter cartridge is used for particle filtration. The molecular sieve regeneration temperature during drying is 300℃, and the regeneration time is 4 hours. Then, the mixture is passed through a membrane separation device equipped with a modified polyimide-ceramic composite membrane (the modified layer is coated with perfluorodecyltriethoxysilane, with a coating thickness of 0.3 μm). Under a pressure difference of 0.6 MPa, hydrogen is enriched on the permeate side, while silane and diethylsilane are enriched on the retrieval side. The final hydrogen purity is 99.88%, and the hydrogen recovery rate is 96%.

[0060] Example 6 (Extreme Mixture Composition Condition)

[0061] Step S1. Preliminary impurity removal: The mixed gas containing 25% silane, 15% silane, and 60% hydrogen (the hydrogen content in the mixed gas is at the lower limit) is subjected to multi-layer adsorption impurity removal and cooled to 22-28℃; wherein, the first coarse filter layer and the second fine filter layer have a filtration accuracy of 1μm and an accuracy of 0.05μm respectively.

[0062] Step S2. Preliminary purification by pressure swing adsorption: The mixed gas, after preliminary impurity removal, enters the pressure swing adsorption unit. The flow rate of the mixed gas is controlled at 14 L / min, and the composition of the mixed gas is monitored in real time to ensure that the proportion of each component fluctuates within ±0.5%. The adsorption time is 10 min, and the desorption time is 5 min. During the pressure swing adsorption process, the purity of the hydrogen output from the pressure swing adsorption unit is monitored in real time. If the purity is lower than 99%, the system automatically fine-tunes the adsorption time.

[0063] The adsorbent in the pressure swing adsorption unit is modified activated carbon that has been activated at high temperature and has a surface loading of 5% copper oxide, with a specific surface area of ​​1580 m². 2 / g, pore size concentrated in the range of 1.0–1.5 nm; high-temperature activation involves heating the activated carbon to 860 °C at a heating rate of 7 °C / min under helium protection and holding at that temperature for 2.2 hours; in the copper oxide loading process, after impregnation, the carbon is dried at 85 °C for 13 hours and calcined at 380 °C for 3.8 hours. The adsorption pressure is controlled at 0.8 MPa (upper limit), and the pressure rise rate is 0.08 MPa / min (upper limit); the desorption pressure is controlled at 0.05 MPa (lower limit), and the pressure fall rate is 0.15 MPa / min (upper limit), thus completing the pressure swing adsorption process and initially purifying hydrogen.

[0064] Step S3. Further purification via membrane separation: The pre-purified mixed gas is purified to remove impurities and moisture. The particle filtration accuracy is 0.1 μm (upper limit), the molecular sieve regeneration temperature is 300℃ (upper limit), and the regeneration time is 4 hours (lower limit). Then, it is passed through a membrane separation device equipped with a modified polyimide-ceramic composite membrane (the modified layer is coated with perfluorodecyltriethoxysilane, with a coating thickness of 0.3 μm). Under a pressure difference of 0.8 MPa (upper limit), hydrogen permeates through the membrane and accumulates on the permeate side, ultimately achieving a hydrogen purity of 99.9% and a hydrogen recovery rate of 92%.

[0065] Example 7 (Extreme Pressure Swing Adsorption Parameter Conditions)

[0066] Step S1. Preliminary impurity removal: The mixed gas containing 20% ​​silane, 10% silane and 70% hydrogen is subjected to multi-layer adsorption for impurity removal and cooled to 26°C; wherein, the first coarse filter layer and the second fine filter layer have a filtration accuracy of 1μm and an accuracy of 0.05μm respectively.

[0067] Step S2. Preliminary purification by pressure swing adsorption: The mixed gas, after preliminary purification, enters the pressure swing adsorption device. The flow rate of the mixed gas is controlled at 17 L / min, and the composition of the mixed gas is monitored in real time to ensure that the proportion of each component fluctuates within ±0.5%. The adsorption time is 8 min, and the desorption time is 9 min. During the pressure swing adsorption process, the purity of the hydrogen output from the pressure swing adsorption device is monitored in real time. If the purity is lower than 99%, the system automatically fine-tunes the adsorption time.

[0068] The adsorbent in the pressure swing adsorption unit is modified activated carbon that has been activated at high temperature and has a surface loading of 3% copper oxide, with a specific surface area of ​​1550 m². 2 / g, pore size concentrated in the range of 0.8–1.2 nm; the high-temperature activation process is as follows: the activated carbon is placed in a high-temperature furnace under nitrogen protection and heated to 900℃ (upper limit) at a heating rate of 10℃ / min (upper limit), and held at that temperature for 2 hours (lower limit); copper oxide is loaded using an equal-volume impregnation method, where a calculated copper nitrate solution (mass fraction of 8%) is uniformly impregnated onto the activated carbon, dried at 100℃ for 12 hours (lower limit), and then calcined at 400℃ for 3 hours (lower limit). The adsorption pressure is controlled at 0.6 MPa, the pressure rise rate is 0.08 MPa / min (upper limit); the desorption pressure is controlled at 0.1 MPa (upper limit), the pressure fall rate is 0.12 MPa / min (lower limit), and the mixed gas is treated to obtain preliminarily purified hydrogen.

[0069] Step S3. Further purification via membrane separation: The pre-purified mixed gas is first passed through a particle filter with a precision of 0.3 μm to remove impurities, and then through a molecular sieve desiccant to remove moisture. The molecular sieve is regenerated at 250℃ for 5 hours. Then, it is passed through a membrane separation device equipped with a modified polyimide-ceramic composite membrane (the modified layer is coated with perfluorodecyltriethoxysilane, with a coating thickness of 0.3 μm). Under a pressure difference of 0.5 MPa, hydrogen permeates through the polyimide membrane and is enriched on the permeate side, while the gas that does not permeate is enriched with silane and diethylsilane on the retrieval side. The final hydrogen purity reaches 99.85%, and the hydrogen recovery rate is 95%.

[0070] Example 8 (Extreme Membrane Separation Parameter Conditions)

[0071] Step S1. Preliminary impurity removal: The mixed gas containing 23% silane, 13% silane and 64% hydrogen is subjected to multi-layer adsorption for impurity removal and cooled to 23°C; wherein, the first coarse filter layer and the second fine filter layer have a filtration accuracy of 1μm and an accuracy of 0.05μm respectively.

[0072] Step S2. Preliminary purification by pressure swing adsorption: The mixed gas, after preliminary purification, enters the pressure swing adsorption device. The flow rate of the mixed gas is controlled at 12 L / min, and the composition of the mixed gas is monitored in real time to ensure that the proportion of each component fluctuates within ±0.5%. The adsorption time is 7 min, and the desorption time is 10 min. During the pressure swing adsorption process, the purity of the hydrogen output from the pressure swing adsorption device is monitored in real time. If the purity is lower than 99%, the system automatically fine-tunes the adsorption time.

[0073] The adsorbent in the pressure swing adsorption unit is modified activated carbon that has been activated at high temperature and has a surface loading of 4% copper oxide, with a specific surface area of ​​1600 m². 2 / g, pore size concentrated in the range of 0.9–1.3 nm; for high-temperature activation, activated carbon was heated to 880 °C at a heating rate of 8 °C / min under argon protection and held at that temperature for 2.8 hours; for copper oxide loading, copper nitrate solution (mass fraction 8%) was impregnated, dried at 95 °C for 15 hours, and calcined at 400 °C for 4 hours. The adsorption pressure was controlled at 0.7 MPa, with a pressure rise rate of 0.07 MPa / min; the desorption pressure was controlled at 0.07 MPa, with a pressure fall rate of 0.13 MPa / min, to achieve adsorption and desorption of silane and disilane, and to preliminarily purify hydrogen.

[0074] Step S3. Further purification via membrane separation: The preliminarily purified mixed gas is subjected to particle filtration and drying. The particle filtration uses a filter element with a precision of 0.5 μm (upper limit). The molecular sieve regeneration temperature during drying is 200℃ (lower limit), and the regeneration time is 6 hours (upper limit). Then, the mixture is passed through a membrane separation device equipped with a modified polyimide-ceramic composite membrane (the modified layer is coated with perfluorodecyltriethoxysilane, with a coating thickness of 0.3 μm). Under a pressure difference of 0.3 MPa (lower limit), hydrogen is enriched on the permeate side, while silane and diethylsilane are enriched on the retrieval side, ultimately yielding hydrogen with a purity of 99.7% and a hydrogen recovery rate of 96%.

[0075] Comparative analysis of examples:

[0076] Example Mixture composition Adsorption pressure Pressure difference hydrogen purity Hydrogen recovery rate Example 1 70% H2 0.6MPa 0.3MPa 99.9％ 96％ Example 2 64% H2 0.7MPa 0.5MPa 99.8％ 95％ Example 3 60% H2 0.8MPa 0.8MPa 99.95％ 94％ Example 4 68% H2 0.65MPa 0.4MPa 99.92％ 94％ Example 5 62% H2 0.75MPa 0.6MPa 99.88％ 96％ Example 6 <![CDATA[60% H2 (lower limit)]]> 0.8MPa (upper limit) 0.8MPa (upper limit) 99.9％ 92％ Example 7 <![CDATA[70%H2]]> 0.6MPa 0.5MPa 99.85％ 95％ Example 8 <![CDATA[64%H2]]> 0.7MPa 0.3 MPa (lower limit) 99.7％ 96％

[0077] As can be seen from the above embodiments, even under extreme operating conditions (Examples 6 to 8), the method of this application can still maintain high hydrogen purity and recovery rate, verifying the stability and adaptability of the purification method of this application. In particular, under the condition of the lowest hydrogen content (Example 6), by adjusting the upper limit of the parameters of pressure swing adsorption and membrane separation, high-purity hydrogen of 99.9% can still be obtained; while under the condition of the lowest membrane separation pressure difference (Example 8), the hydrogen recovery rate reached 96%, demonstrating the advantages of the process of this application under different operating conditions.

[0078] The above description is merely a preferred embodiment of this application and is not intended to limit this application in any way. Although this application has been disclosed above with reference to preferred embodiments, it is not intended to limit this application. Any person skilled in the art can make some modifications or alterations to the above-disclosed technical content to create equivalent embodiments without departing from the scope of the technical solution of this application. Any simple modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of this application without departing from the scope of the technical solution of this application shall still fall within the scope of the technical solution of this application.

Claims

1. A method for recovering hydrogen from a mixture of gases by pressure swing adsorption and membrane separation, characterized in that, It comprises the following steps: Step S1. Preliminary impurity removal: the mixed gas containing 20%-25% silane, 10%-15% disilane and 60-70% hydrogen is subjected to multi-layer adsorption impurity removal and is cooled to 22-28℃; Step S2. Pressure swing adsorption: the mixed gas subjected to preliminary impurity removal enters a pressure swing adsorption device, and the adsorbent in the adsorption device is modified activated carbon with high-temperature activation and surface loading of 3%-5% copper oxide; Step S3. Membrane separation adsorption: the mixed gas subjected to the pressure swing adsorption device is then subjected to filtration and drying, and finally is subjected to membrane separation, and the silane and disilane are collected on the enrichment side of the membrane separation device for further purification, and the hydrogen is collected on the permeation side of the membrane separation device.

2. The method for recovering hydrogen from a mixture according to claim 1, wherein, In the step S1, the multi-layer adsorption comprises a first rough filtration layer and a second fine filtration layer, the filtration precision of the first rough filtration layer is 1 μm, and the precision of the second fine filtration layer is 0.05 μm.

3. The method of claim 1, wherein the method further comprises: In the step S2, the high-temperature activation process is: placing the activated carbon in an inert gas or nitrogen-protected high-temperature furnace, heating to 820-900℃ at a heating rate of 5-10℃ / min, and keeping the temperature for 2-3 hours; the copper oxide loading is carried out by an equal-volume impregnation method, uniformly impregnating a copper nitrate solution on the activated activated carbon, drying at 80-100℃ for 12-16 hours, and then calcining at 320-400℃ for 3.2-4 hours to obtain the modified activated carbon adsorbent, the specific surface area of the modified activated carbon adsorbent reaches 1500m 2 / g or more, and the pore size is concentrated in the range of 0.8-1.5nm.

4. The method for recovering hydrogen from a mixture according to claim 1, wherein, In the step S2, the flow rate of the mixed gas is controlled to be 10-20 L / min, and the composition of the mixed gas is monitored in real time to ensure that the proportion of each component fluctuates within ±0.5%; the adsorption pressure of the pressure swing adsorption is controlled to be 0.6-0.8 MPa, and the pressure rise rate is maintained at 0.06-0.08 MPa / min; the desorption pressure is 0.05-0.1 MPa, and the pressure drop rate is 0.12-0.15 MPa / min.

5. The method of claim 1, wherein the method further comprises: In the step S2, during the pressure swing adsorption process, the purity of the hydrogen output from the pressure swing adsorption device is monitored in real time, and when the purity is lower than 99%, the system automatically adjusts the adsorption time by 1-3 minutes, the adsorption time is 5-15 minutes, and the desorption time is 3-10 minutes.

6. The method of claim 1, wherein the method further comprises: In the step S3, the filter adopts a filter with a precision of 0.1-1 μm; the dryer is filled with molecular sieve drying agent, and the dew point temperature of the dried gas is lower than -40℃.

7. The method of claim 1, wherein the method further comprises: In the step S3, the membrane separation device is provided with a modified polyimide-ceramic composite membrane, and the pressure difference is 0.3-0.8 MPa; the thickness of the modified polyimide-ceramic composite membrane is 10-50 μm, and the porosity is 30%-60%.

8. The method of claim 7, wherein the method further comprises: The modified layer of the modified polyimide-ceramic composite membrane is coated with a fluorosilane coupling agent, and the coating thickness is 0.1-0.5 μm.

9. A system for recovering hydrogen from a mixture of gases by pressure swing adsorption and membrane separation according to any one of claims 1 to 8, characterized in that, It comprises a mixed gas cylinder, a pretreatment unit (2), a pressure swing adsorption unit (5) and a membrane separation unit (6) connected in sequence, the pretreatment unit (2) comprises a first filter (21) and a second filter (22) connected in series, and the first filter (21) and the second filter (22) are provided with a cooler (23) outside; the pressure swing adsorption unit (5) comprises at least three adsorption towers (51) arranged in parallel; the membrane separation unit (6) comprises a third filter, a dryer and a membrane separation device connected in series, the enrichment side of the membrane separation device is connected with a rectification tower for collecting silane and disilane, the permeation side of the membrane separation device is connected with a hydrogen collection unit (7), the hydrogen collection unit (7) comprises a first-stage buffer tank (71) and a second-stage buffer tank (72) connected in series, and the second-stage buffer tank (72) is connected with a hydrogen storage device (8).

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