A method and device for inorganic membrane multi-stage gas separation

Abstract

The present invention discloses an inorganic membrane multi-stage gas separation method, the steps are: S1, pre-treating the raw gas in a pre-treatment unit. S2, the pre-treated raw gas enters the multi-stage membrane separation component for separation treatment, the permeate gas enters the lower component, and the retentate gas refluxes to continue separation. S3, collecting gas products on the retentate side of the first-stage component and the permeate side of the last-stage component and recycling them. The device includes a pre-treatment module, a single-stage membrane component, an air pump, a mass flow controller and a back pressure valve. After the raw material is pre-treated, it enters the multi-stage membrane component through the mass flow controller, the back pressure valve controls the pressure on the retentate side of the first-stage component, and multiple components are connected in series through pipelines. The permeate gas of each stage enters the next stage as the raw gas, and the retentate gas of the first stage is connected to the back pressure valve to control the top extraction. The retentate gas of each other stage component is returned to the upper component through the air pump to mix with the feed gas, and the gas product on the permeate side of the last stage component is collected under normal pressure.

Description

Technical Field

[0001] The invention relates to a method for multi-stage gas separation using an inorganic membrane, in particular to separation and purification of binary or multi-component mixed gases with low single-stage membrane separation selectivity. Background Art

[0002] As an important basic raw material for modern industry, gas products have a wide range of applications. In addition to the common general industrial gases in industry, special gases play an important role in industries such as electronic information, aerospace, petrochemicals, and medical and environmental protection. For example, ultra-pure nitrogen can be used as a protector for ultra-large-scale integrated circuits, and neon isotopes can be used in military industries such as missile guidance. However, my country's special gas enterprises are small in scale and have few independent research and development results. At present, my country cannot mass-produce gases used in the production of submicron integrated circuits. The research and application of special gas isotope separation are still in the initial stage, and production dependence requires foreign imports. The main methods for separating mixed gases are cryogenic distillation, pressure swing adsorption, and membrane separation. Cryogenic distillation involves phase change separation, high energy consumption, large device scale, and high equipment cost; pressure swing adsorption has a low recovery rate and requires continuous vacuuming and compression of the gas. There are also problems such as high equipment cost and complex operation. The field of special gas separation and purification also involves methods such as precious metal catalysis, thermal diffusion, and molecular sieve purification technology. However, all of the above methods have problems such as high cost, high energy consumption, high equipment cost, and complex operation.

[0003] In the application of membrane gas separation, the patent with patent number CN201310329942.X mentions a biogas decarbonization process that couples two-stage membrane separation with CO2 liquefaction, but the process needs to be coupled with low-temperature liquefaction, and the operation is relatively complicated; the patent with patent number CN201510045066.7 designs a three-stage gas separation membrane unit to separate gas. The device adds an additional mixing container during the reflux process and it is difficult to meet the separation requirements for systems with low membrane separation coefficients, which has great limitations.

[0004] In addition, in a specific membrane separation application field, Summary of the invention

[0005] The purpose of the present invention is to provide a method for multi-stage gas separation using an inorganic membrane to achieve gas separation and purification, and solve the problems of high equipment investment, complex operation, and high energy consumption in traditional methods such as cryogenic distillation and pressure swing adsorption. The series connection of multi-stage membrane components can effectively improve the separation purity of a mixed system with low membrane separation selectivity, achieve the recovery of the target gas, significantly increase production capacity, and improve economic benefits.

[0006] The multi-stage inorganic membrane gas separation method of the present invention can achieve the separation requirements only by the membrane separation process, without coupling with other processes, and the residual gas of each stage can be directly refluxed to the upper stage; the gas system with low single-stage membrane separation selectivity can be separated by multi-stage membrane separation, which greatly improves the separation efficiency and reduces the operating cost. This technology has great application potential in the fields of enrichment of oxygen, nitrogen and rare gases in the air, preparation of high-purity electronic gases, separation and purification of isotope gases, and natural gas denitrification and recovery and separation of hydrocarbon components in the petrochemical industry.

[0007] In one application field, the present invention also realizes the online recycling technology of xenon gas in closed-circuit medical xenon anesthesia using DD3R molecular sieve membrane, which can selectively separate CO2 / Xe. The single-component carbon dioxide permeability is 1.5×10 - 7 mol·m -2 ·s -1 ·Pa -1 , the separation selectivity of carbon dioxide to xenon is 570. The permeation flux is one order of magnitude higher than that of traditional membrane materials. The all-silicon characteristics of DD3R molecular sieve make it hydrophobic, which can effectively weaken the blockage of water vapor on the molecular sieve pores.

[0008] The first aspect of the present invention provides:

[0009] A method for inorganic membrane multi-stage gas separation comprises the following steps:

[0010] Step 1, sending the gas mixture to be separated into a gas separation device for separation;

[0011] The gas separation device is composed of a plurality of membrane modules connected in series. The material obtained from the permeate side of the previous stage is sent to the retentate side of the next stage for further separation; the material obtained from the retentate side of the next stage is refluxed to the retentate side of the previous stage for further separation.

[0012] In step 2, the first gas component is obtained on the permeate side of the last stage, and the second gas component is produced on the retentate side of the first stage.

[0013] In one embodiment, in step 1, the gas mixture to be separated is pretreated by a pretreatment unit.

[0014] In one embodiment, the pretreatment comprises compression, drying, filtering or heating.

[0015] In one embodiment, in step 1, the gas product on the retentate side of the first stage is produced under the control of a back pressure valve.

[0016] In one embodiment, in step 1, the material obtained from the retentate side of the next stage is refluxed to the retentate side of the previous stage or stages.

[0017] In one embodiment, in step 1, the gas mixture to be separated is fed into a membrane module whose gas composition on the retentate side is closest to the gas composition of the gas mixture to be separated.

[0018] In one embodiment, in step 1, the feed pressure range of the gas mixture to be separated is controlled to be 0.1-5 MPa.

[0019] In one embodiment, for a membrane module containing refluxed retentate gas, a reflux ratio needs to be set; wherein the reflux ratio refers to: the amount of gas refluxed from the retentate side of the membrane module of that stage to the amount of gas to be separated entering the gas separation device.

[0020] In one embodiment, the operating temperature of each membrane module is 28K to 973K.

[0021] In one embodiment, the material used in the gas separation membrane installed in the membrane assembly can be one or more inorganic membrane materials such as molecular sieve membrane, ceramic membrane, carbon membrane, etc.; the carrier of the gas separation membrane can be in the form of tubular or hollow fiber.

[0022] In one embodiment, the gas mixture to be separated contains one or a mixture of several of N2, CO2, H2, O2, Kr, Xe, CH4, and He.

[0023] In one embodiment, the gas mixture to be separated is composed of 5% CO2, 30% N2 and 65% Xe mixed gas, and also contains H2O, and the partial pressure of H2O is 2.3 kPa; and the gas separation membrane used is DD3R molecular sieve membrane.

[0024] The second aspect of the present invention provides:

[0025] An inorganic membrane multi-stage gas separation device, comprising:

[0026] A pretreatment unit, used for pretreating the gas mixture to be separated;

[0027] A gas separation device, connected to the pretreatment unit, for separating gas components in a gas mixture to be separated;

[0028] The gas separation device comprises a plurality of membrane modules, which are connected in series; the permeate side gas outlet of the upper membrane module is connected to the retentate side gas inlet of the lower membrane module; the retentate side gas outlet of the lower membrane module is connected to the retentate side gas inlet of the upper membrane module;

[0029] The permeate-side gas outlet of the last-stage membrane assembly is connected to a first gas component receiving pipeline; the retentate-side gas outlet of the first-stage membrane assembly is connected to a second gas component receiving pipeline.

[0030] In one embodiment, the membrane assembly includes a shell and a gas separation membrane installed in the shell; and the retentate side air inlet and the retentate side air outlet are connected to the shell, and the permeate side of the gas separation membrane is connected to the permeate side air outlet.

[0031] In one embodiment, the gas separation membrane is a tubular type or a hollow fiber type.

[0032] In one embodiment, the material of the gas separation membrane is a molecular sieve membrane, a ceramic membrane or a carbon membrane.

[0033] In one embodiment, the retentate-side gas outlet of the next-stage membrane module is connected to the retentate-side gas inlet of the previous-stage or previous-stage membrane modules.

[0034] In one embodiment, the retentate side gas outlet of the next-stage membrane module is connected to the upper-stage membrane module via a trace air pump.

[0035] In one embodiment, the pretreatment unit is connected to the gas separation device via a mass flow controller.

[0036] In one embodiment, the pretreatment unit is connected to the membrane module of any stage.

[0037] In one embodiment, a back pressure valve is connected to the retentate side gas outlet of the first stage membrane module.

[0038] The third aspect of the present invention provides:

[0039] The above-mentioned inorganic membrane multi-stage gas separation device is used in the separation of multi-component gases.

[0040] Beneficial Effects

[0041] The present invention is easy to operate and can achieve gas separation and concentration by only connecting multiple membrane separation components in series. The device has low investment, can achieve gas separation at room temperature, is energy-saving and environmentally friendly, and has significant economic benefits. For a mixed gas system with low single-stage membrane separation selectivity and low purity of the separated product, multi-stage membrane separation can significantly improve the purity of gas separation, especially for the separation and concentration of some special gases, which can generate huge economic benefits. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Figure 1 This is a schematic diagram of the separation process of a multi-stage series membrane separation device.

[0043] Figure 2Schematic diagram of several typical retentate gas (except the first stage) reflux methods.

[0044] Figure 3 Effect of Xe molar composition on the separation performance of CO2 / Xe mixed gas (feed pressure: 3 bar).

[0045] Figure 4 This is the separation performance of DD3R molecular sieve membrane.

[0046] Figure 5 The separation performance of DD3R molecular sieve membrane for CO2 and Xe.

[0047] Among them, 1. pretreatment unit; 2. mass flow controller; 3. membrane assembly; 4. shell; 5. gas separation membrane; 6. retentate side air inlet; 7. retentate side air outlet; 8. head; 9. permeate side air outlet; 10. pipeline; 11. micro air pump; 12. back pressure valve. DETAILED DESCRIPTION

[0048] Figure 1 It is shown that the raw gas is pretreated by the pretreatment unit 1 so that the parameters such as moisture content, pressure and temperature in the raw gas meet the requirements. The pretreatment unit 1 used in the present invention is not particularly limited, and may include a compression device, a drying device, a filtering device or a heating device, and the raw material is pretreated before entering the series membrane separation component to meet the corresponding gas state requirements. The treated raw gas enters the multi-stage membrane separation component at an appropriate feed position through the mass flow controller 2.

[0049] In the present invention, when the membrane modules are connected in series, the module at the most upstream is the first stage, and the one (most downstream) from which the retentate gas is discharged as the final product is the nth stage.

[0050] The single membrane module used in the present invention Figure 1 It is shown that the membrane assembly 3 includes a shell 4 and an internal gas separation membrane 5. The shell 4 is made of stainless steel or nylon. The shell 4 and the gas separation membrane 5 divide the space inside the assembly into a permeate side and a residual side. The figure takes a tubular gas separation membrane 5 as an example. Its configuration is tubular, and the separation layer is selected to be located outside the tubular membrane. There are an air inlet 6 and an air outlet 7 on the shell. The two ends of the shell use threaded caps 8, one end has a permeate side air outlet 9, and the other end is a dead end. The single-stage membrane assembly 3 is connected in series with a pipeline 10. The permeate side air outlet 9 of the upper stage is connected to the air inlet 6 of the shell of the lower stage to complete the series operation of the device; the residual gas outlet 7 of the lower assembly is connected to the shell air inlet 6 of the upper assembly to complete the reflux operation.

[0051] When the above structure is adopted, a major improvement lies in the use of a reflux treatment of the retentate gas to the upper level. When the feed gas to be separated contains two components A and B, when a single-stage membrane assembly is used for separation, it is assumed that component B enters the permeate side, and the retentate gas (assuming it is A) often cannot reach a sufficient purity, so that the retentate gas cannot be effectively reused. When the retentate gas is refluxed to the upper level for further separation, the concentrated gas containing A can be further concentrated again. After the B gas continues to be fed into the series assembly of the next level, the material mainly containing B gas is further separated, and finally a relatively pure A is obtained in the first stage, and a relatively pure B is obtained in the last stage.

[0052] Figure 1 It is shown that the raw gas is separated in the multi-stage series membrane assembly, the permeate gas of each stage assembly enters the next stage assembly for further separation, and the residual gas returns to the previous stage through the air pump 11 to mix with the feed gas.

[0053] Figure 1 The permeate outlet 4 of the last stage assembly collects the separated permeate product. The retentate outlet 7 of the first stage assembly is connected to the back pressure valve 12 to control the gas volume of the retentate gas, and the retentate product is obtained through the back pressure valve 12.

[0054] The retentate gas reflux includes but is not limited to the reflux method of returning to the previous level component. The retentate gas can be adjusted to reflux to the inlet of other membrane components before the current level component to mix with the feed gas. Figure 2 As shown, they can all be refluxed to the previous stage in sequence, or to several previous stages, or multiple membrane modules can be refluxed to the same stage above.

[0055] In addition, in addition to the first-stage retentate outlet, when the system to be separated contains impurities and the impurities are enriched to a high concentration after a certain number of separations, you can choose to add a branch production at the appropriate level of retentate outlet to reduce the impact of high-concentration gas on the membrane separation of the target system.

[0056] During the raw material feeding process of the first-stage membrane assembly, the pressure range is controlled within 0.1-5 MPa.

[0057] The operating temperature range of the gas separation process of each stage of the above components is 28K to 973K.

[0058] During the retentate gas reflux process of each stage of the above-mentioned components, the gas reflux ratio (reflux ratio refers to the ratio of (the amount of gas refluxed from the retentate side of the membrane component of this stage - the amount of gas permeated from the membrane component of this stage) to the amount of gas to be separated entering the gas separation device) through the micro gas pump is controlled in the range of <10. For example: a series device contains 10 membrane components, and the mixed gas feed position is at the 5th stage membrane component. Then for the 4th stage membrane component, it has both the gas refluxed from the 5th stage retentate side and the gas obtained from the 3rd stage permeate side. Then the reflux ratio is: the amount of gas refluxed from the 4th stage retentate side (the amount of gas from the 3rd stage permeate side + the amount of gas refluxed from the 5th stage retentate side - the amount of gas permeated from the 4th stage) / the amount of gas to be separated entering the gas separation device.

[0059] The pore size of the material of the inorganic membrane used in the above separation device is in the range of 2 to 200 nm.

[0060] The inorganic membrane used in the membrane separation device may be made of one or more of a ceramic membrane, a molecular sieve membrane, and a carbon membrane. The carrier may be in the form of a tube or a hollow fiber.

[0061] Example 1

[0062] A mixed gas of 80% N2 and 20% O2 is passed into the pretreatment device to remove moisture and other solid particles in the mixed gas, so that the temperature of the treated gas reaches 25°C and the pressure is increased to 1.5MPa. The pretreated raw gas is passed through the mass flow controller with a certain feed rate through the first-stage air inlet into the separation device. The outlet of the first-stage component on the retentate side is connected to a back pressure valve to control the retentate side pressure to be stable at 3.5-4bar (gauge pressure). The retentate gas of each level of components is returned to the previous level component through an air pump, and the reflux ratio is 0.8. The membrane material in each level of membrane separation components is TiO2-coated alumina hollow fiber membrane with a membrane pore size of 100nm, which has both high mechanical strength and excellent antioxidant properties.

[0063] Under this condition, the last stage permeate gas is produced at normal pressure, and after 45-stage membrane separation, the concentration of N2 in the last stage permeate gas is >99%. The permeate gas discharged from the first stage assembly through the back pressure valve can be directly discharged into the air.

[0064] Example 2

[0065] A mixed gas consisting of 80% Kr and 20% Xe is passed into the pretreatment unit, pressurized to 3MPa and the gas temperature is maintained at about 25°C. The pretreated mixed gas is passed into the air inlet of the 10th membrane component of the series device, the feed amount is controlled by the mass flow controller, and the back pressure valve is adjusted to control the first stage retentate gas outlet. The retentate gas of each level of components is returned to the previous level component through a trace air pump, and the reflux ratio is 1. Inorganic ceramic membrane is used as the membrane separation material, the membrane pore size is 50nm, and it has both high mechanical strength and excellent antioxidant properties. The retentate gas discharged from the first stage component through the back pressure valve is recycled, in which the Xe concentration is about 35%. The last stage permeate gas is extracted as raw material at normal pressure. The number of separation stages required to achieve different theoretical purities is as follows:

[0066]

[0067] Example 3

[0068] The natural gas with N2 content <10% (main component CH4>90%) is introduced into the pretreatment unit to remove moisture and other solid particles in the mixed gas, pressurize the mixed gas to 0.7MPa, and control the temperature of the mixed raw gas at about 25°C. The pretreated mixed gas is introduced into the air inlet of the 10th membrane component of the series device, and the feed amount is controlled by the mass flow controller. The first-stage back pressure valve controls the first-stage residual gas outlet so that the first-stage residual gas side pressure is stabilized at 3.5-4bar (gauge pressure). The residual gas of each level of components is returned to the previous level of components through the air pump, and the reflux ratio is 1.5. The non-polar ceramic membrane is used as the separation material, and the membrane pore size is 100-150nm.

[0069] Under this condition, after 20 stages of separation, the last stage permeate gas is produced at normal pressure, wherein the concentration of CH4 is >99%. The permeate gas is collected as the product, and the first stage component permeate gas is discharged through the back pressure valve for recycling except for reflux.

[0070] Example 4

[0071] A mixed gas composed of 50% He and 50% N2 is introduced into the treatment unit, and the mixed gas is pressurized to 1MPa and the temperature is controlled at room temperature. The pretreated raw material mixer enters the 6-stage series membrane assembly through the air inlet of the 4th stage assembly for separation, and the feed rate is controlled to 1.5L / h by the mass flow controller. The back pressure valve is controlled to regulate the pressure on the first stage retentate side to stabilize at 3-3.5 bar. The retentate gas of the first stage assembly is directly recovered through the back pressure valve, and the reflux ratio of the remaining assemblies is maintained at 0.66, ensuring that the reflux rate of each stage assembly is 1L / h, and the reflux direction returns to the feed of the previous stage assembly, and the permeate volume of each stage and the final bottom production volume are maintained at 0.5L / h. The separation membrane material uses a hollow fiber molecular sieve membrane with a membrane pore size of 2nm and excellent mechanical stability. The last stage permeate gas is produced at normal pressure and collected as a product. Under this condition, the parameters of each stage obtained according to the balance are shown in the following table:

[0072]

[0073] Example 5

[0074] A mixed gas composed of 90% H2 and 10% CO2 is introduced into the pretreatment unit, pressurized to 0.5MPa and the gas temperature is maintained at about 25°C. The pretreated mixed gas is introduced into the gas inlet of the 5th membrane assembly of the series device, the feed amount is controlled by the mass flow controller, and the back pressure valve is adjusted to control the gas outlet of the first-stage retentate gas, so that the pressure on the first-stage retentate side is stabilized at 2-2.4bar (gauge pressure). The retentate gas of each level of assembly is returned to the previous level assembly through an air pump, and the reflux ratio is 0.5. Hollow fiber molecular sieve membrane is used as the separation membrane material.

[0075] Under this condition, after separation of 9-stage components, the concentration of hydrogen in the last-stage permeate gas is >99.9%. The permeate gas is produced as a raw material at normal pressure, and the retentate gas discharged from the first-stage component through the back pressure valve is recycled, wherein the concentration of CO2 is about 30%. In this embodiment, the 5th-stage membrane component is fed, and after separation of this stage, the gas on the retentate side of the 5th stage contains 16.3% CO2 and 84.7% H2. By comparison, it can be seen that by refluxing the retentate side gas of this stage to the previous stage, the CO2 gas is finally further concentrated.

[0076] Example 6

[0077] In this embodiment, DD3R molecular sieve membrane is used for online recycling technology of xenon in closed-circuit medical xenon anesthesia. The single-component carbon dioxide permeability is 1.5×10 -7 mol·m -2 ·s -1 ·Pa -1, the separation selectivity of carbon dioxide to xenon is 570. The permeation flux is one order of magnitude higher than that of traditional membrane materials. The membrane separation performance is mainly determined by the difference in diffusion coefficients of CO2 and Xe molecules in the DD3R molecular sieve. However, the mass transfer rate of CO2 is significantly reduced due to the presence of Xe, which is very different from the previous separation results of eight-membered ring molecular sieve membranes in CO2 / N2 and CO2 / CH4 binary components. The results of molecular dynamics simulation show that Xe molecules adsorbed on the surface of the molecular sieve membrane form surface resistance for CO2 adsorption and diffusion. Under conditions related to medical xenon anesthesia, that is, when the carbon dioxide content is less than 5% and water vapor is present, the CO2 permeability and CO2 / Xe separation selectivity are 2.0×10 -8 mol·m -2 ·s -1 ·Pa -1 and 67. Due to the all-silicon characteristics of the DD3R molecular sieve membrane, the permeability of CO2 is weakly affected by water vapor, which is different from the aluminum-containing molecular sieve membrane whose pores are easily blocked by adsorbed water. High CO2 flux and high CO2 / Xe selectivity, as well as long-term stability, ensure the good prospects of hollow fiber DD3R molecular sieve membrane in the online recycling of medical anesthesia xenon. The preparation process of the DD3R molecular sieve membrane used in this embodiment can refer to the prior art, such as CN110745839A "A process for activating defect-free DD3R molecular sieve membrane".

[0078] First, a separation test of CO2 / Xe mixed gas was conducted. Figure 3 The effect of Xe molar composition on the separation performance of CO2 / Xe mixed gas (feed pressure: 3 bar) is shown. The decrease in CO2 permeability becomes more significant with the increase in Xe composition ( Figure 2 Finally, when the CO2 content dropped to 5%, the CO2 permeability was 0.24×10 -7 mol·m -2 ·s -1 ·Pa -1 ; However, the separation selectivity of CO2 / Xe is always around 43, showing good separation selectivity at low CO2 concentration.

[0079] The CO2 single component permeability of the hollow fiber DD3R molecular sieve membrane reported in this application is 1.5×10 -7 mol·m -2 ·s -1 ·Pa -1 , which is one order of magnitude higher than the results reported in the literature ( Figure 4 At different temperatures, the separation performance of DD3R molecular sieve membrane for single component CO2, binary component CO2 / H2O and ternary component CO2 / H2O / Xe is shown in Figure 2. Figure 4 As shown in area b; Figure 4 The c region is the long-term stability of DD3R molecular sieve membrane for Xe recovery from a mixture of 0.76% H2O, 4.96% CO2, 29.77% N2 and 64.51% Xe at 3 bara. Water vapor is often present in anesthesia exhaled air. Due to the presence of water vapor, the CO2 single component permeability decreases by 37-45% ( Figure 4 b region); however, under the same conditions, the gas permeability of the aluminum-containing 8-membered ring zeolite membrane decreased more significantly. The DD3R zeolite membrane has better hydrophobic properties and can effectively weaken the reduction in CO2 permeability caused by water vapor adsorption. Non-proton template agents and ion-free synthetic solutions were used to prepare more hydrophobic DD3R zeolite membranes for CO2 / Xe separation in a humid environment. The effect of water vapor on CO2 permeability and selectivity was further studied, such as Figure 3 The b area and Figure 5 As shown in area a. In a water vapor environment, the separation selectivity of the membrane is higher than that of a dry gas. Si-OH at the grain boundary of the molecular sieve membrane layer can strongly adsorb water molecules, thereby blocking the diffusion of gas molecules in such pores. Therefore, in a humid environment, the permeability of Xe is lower than that in a dry gas. The permeability of water vapor gradually weakens with increasing temperature, for example, it decreases by 55% at 100°C; 52% at 125°C; and 42% at 150°C. However, whether in wet or dry gas, the permeability of CO2 molecules is mainly contributed by the DD3R molecular sieve.

[0080] During anesthesia, in addition to CO2, human tissues and organs release nitrogen in the initial stage of anesthesia. It is used to recover xenon in a mixture of 5% CO2, 30% N2 and 65% Xe. When 2.3kP water vapor is introduced, the permeability of both CO2 and N2 decreases slightly ( Figure 3 Finally, the carbon dioxide permeability stabilized at 2.0×10 -8 mol·m -2 ·s -1 ·Pa -1 , CO2 / Xe selectivity is 67±12; N2 permeability is 2.4×10 -9 mol·m -2 ·s -1 ·Pa -1 , N2 / Xe selectivity is 8±2.

[0081] The above separation experiment was conducted on the recovery of xenon gas using a single-stage DD3R separation membrane. Next, multi-stage separation was used for deep recovery. When a three-stage series separation process was used, under the same operating conditions, recovered xenon gas containing 99.19% and 99.23% of Xe was obtained in the second and third stages, respectively, indicating that xenon gas with higher purity can be obtained through multi-stage series separation.

Claims

1. An inorganic membrane multi-stage gas separation method, characterized in that: The device used in the inorganic membrane multi-stage gas separation method includes: A pretreatment unit (1), used for pretreating the gas mixture to be separated; A gas separation device is connected to a pretreatment unit (1) and is used to separate gas components in a gas mixture to be separated; the gas separation device comprises a plurality of membrane modules (3), the membrane modules (3) being connected in series with each other; the permeate side gas outlet (9) of the upper membrane module (3) is connected to the retentate side gas inlet (6) of the lower membrane module (3); the retentate side gas outlet (7) of the lower membrane module (3) is connected to the retentate side gas inlet (6) of the upper membrane module (3); The permeate-side gas outlet (9) of the last-stage membrane assembly (3) is connected to a first gas component receiving pipeline; the retentate-side gas outlet (7) of the first-stage membrane assembly (3) is connected to a second gas component receiving pipeline; The membrane assembly (3) comprises a shell (4) and a gas separation membrane (5) installed in the shell (4); the retentate side air inlet (6) and the retentate side air outlet (7) are connected to the shell (4); the permeate side of the gas separation membrane (5) is connected to the permeate side air outlet (9); The inorganic membrane multi-stage gas separation method comprises the following steps: A mixed gas consisting of 90% H2 and 10% CO2 is introduced into a pretreatment unit, pressurized to 0.5MPa and the gas temperature is maintained at 25°C. The pretreated mixed gas is introduced into the air inlet of the 5th membrane component of the series device, the feed amount is controlled by a mass flow controller, and the back pressure valve is adjusted to control the gas outlet of the first-stage retentate gas so that the pressure on the first-stage retentate side is stabilized at a gauge pressure of 2 to 2.4 bar. The retentate gas of each stage of the component is returned to the previous stage component through an air pump, and the reflux ratio is 0.

5. A hollow fiber molecular sieve membrane is used as the separation membrane material. After separation of 9 stages of components, the concentration of hydrogen in the last stage of permeate gas is >99.9%. The permeate gas is produced as a raw material at normal pressure, and the retentate gas discharged from the first stage component through the back pressure valve is recycled, wherein the concentration of CO2 is 30%.

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