CN111821818A - Method and device for multistage gas separation by inorganic membrane - Google Patents

Abstract

The invention discloses an inorganic membrane multi-stage gas separation method. The steps are: S1, pre-processing the raw gas in the pre-processing unit. S2. The pretreated raw material gas enters the multi-stage membrane separation module for separation treatment, the permeate gas enters the lower-level module, and the retentate gas flows back to complete the separation. S3. Collect gas products on the retentate side of the first-stage module and the permeate side of the last-stage module and recycle them. The device includes a pretreatment module, a single-stage membrane module, an air pump, a mass flow controller and a back pressure valve. After the raw material is pretreated, it enters the multi-stage membrane module through the mass flow controller. The back pressure valve controls the pressure on the retentate side of the first-stage module. Multiple modules are connected in series through the pipeline. The retentate gas of the first stage is connected to the back pressure valve to control the top production, and the retentate gas of the other components of each stage is returned to the upper-level component through the air pump to be mixed with the feed gas, and the gas product on the permeate side of the last-stage component is collected under normal pressure.

Description

Method and device for multistage gas separation by inorganic membrane

technical field

The invention relates to a method for multi-stage gas separation by inorganic membranes, in particular to the separation and purification of binary or multi-component mixed gases with low selectivity of single-stage membrane separation.

Background technique

As an important basic raw material for modern industry, gas products have a wide range of applications. In addition to general industrial gases common in industry, special gases play an important role in electronic information, aerospace, petrochemical, medical and environmental protection industries. For example, ultra-pure nitrogen can be used as a protector for very large-scale integrated circuits, and neon isotopes can be used in military industries such as missile guidance. However, the scale of special gas enterprises in my country is relatively small, and there are few achievements in independent research and development. At present, my country cannot produce gases used in the production of sub-micron integrated circuits on a large scale. The research and application of isotope separation of special gases is still in its infancy, and production depends on foreign imports. . The separation methods of mixed gas mainly include cryogenic rectification, pressure swing adsorption and membrane separation. Cryogenic rectification involves phase change separation, high energy consumption, large device scale, and high equipment cost; pressure swing adsorption method has a low recovery rate, requires continuous vacuuming and compression of the gas, and also has high equipment costs and complex operations. And other issues. The field of special gas separation and purification also involves precious metal catalysis, thermal diffusion and molecular sieve purification technology. However, the above methods all have problems such as high cost, high energy consumption, high equipment cost and complicated operation.

In the application of membrane separation of gas, the patent No. CN201310329942.X mentioned a biogas decarbonization process with two-stage membrane separation coupled with CO ₂ liquefaction, but this process needs to be coupled with low-temperature liquefaction, and the operation is relatively complicated; The patent No. CN201510045066.7 designed a device for separating gas with a three-stage gas separation membrane unit. The reflux process of the device adds an additional mixing container, and it is difficult to meet the separation requirements for a system with a low membrane separation coefficient, and the limitations are relatively large.

In addition, in a specific membrane separation application field,

SUMMARY OF THE INVENTION

The purpose of the present invention is to provide a method for multi-stage gas separation by inorganic membranes to realize the separation and purification of gas, and to solve the problems of high equipment investment, complicated operation and high energy consumption of traditional cryogenic rectification, pressure swing adsorption and other methods. The series connection of multi-stage membrane modules can effectively improve the separation purity of the mixed system with low membrane separation selectivity, and realize the recovery of target gas, which can significantly increase the production capacity and improve the economic benefits.

The multi-stage inorganic membrane gas separation method in the present invention only needs the membrane separation process to meet the separation requirements, and does not need to be coupled with other processes, and the retentate gas of each stage can be directly returned to the upper stage; single-stage membrane separation can be achieved through multi-stage membrane separation The separation of the gas system with lower selectivity greatly improves the separation efficiency and reduces the operating cost. The technology has great application potential in the enrichment of oxygen, nitrogen and rare gases in the air, the preparation of high-purity electronic gases, the separation and purification of isotopic gases, the removal of nitrogen from natural gas, and the recovery and separation of hydrocarbon components in the petrochemical industry. .

In one application field, the present invention also realizes the on-line recycling technology of xenon gas in the closed-circuit medical xenon gas anesthesia process using DD3R molecular sieve membrane, which can selectively separate CO ₂ /Xe. The single-component carbon dioxide permeability is 1.5×10 ^-7 mol·m ^-2 ·s ^-1 ·Pa ^-1 , and the separation selectivity of carbon dioxide to xenon is 570. The permeation flux is an order of magnitude higher than that of traditional membrane materials. The all-silicon feature of DD3R molecular sieve makes it have a certain degree of hydrophobicity, which can effectively reduce the blockage of molecular sieve channels by water vapor.

A first aspect of the present invention provides:

A method for inorganic membrane multistage gas separation, comprising the following steps:

The first step is to send the gas mixture to be separated into a gas separation device for separation;

The gas separation equipment 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 returned to The retentate side of the upper stage continues to separate;

In the second step, 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.

In one embodiment, in the first step, the gas mixture to be separated is pretreated by a pretreatment unit.

In one embodiment, the pretreatment includes compression, drying, filtration or heating.

In one embodiment, in the first step, the gas product on the retentate side of the first stage is connected to a back pressure valve to control the production.

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.

In one embodiment, in the first step, the gas mixture to be separated is sent to the membrane module whose gas composition is the closest to the gas composition of the gas mixture to be separated on the retentate side.

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

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 on the retentate side of the membrane module at this stage and the gas to be separated entering the gas separation equipment quantity.

In one embodiment, the working temperature of each stage membrane module is 28K-973K.

In one embodiment, the material used in the gas separation membrane installed in the membrane module may be one or more of inorganic membrane materials such as molecular sieve membrane, ceramic membrane, carbon membrane, etc.; the carrier of the gas separation membrane may be tubular or form of hollow fibers.

In one embodiment, the gas mixture to be separated contains one or a mixture of N ₂ , CO ₂ , H ₂ , O 2 , Kr, Xe, CH ₄ , and He.

In one embodiment, the composition of the gas mixture to be separated is a mixture of 5% CO ₂ , 30% N ₂ and 65% Xe, and also contains H ₂ O, and the partial pressure of H ₂ O is 2.3 kPa; And the gas separation membrane used is DD3R molecular sieve membrane.

A second aspect of the present invention provides:

An inorganic membrane multistage gas separation device, comprising:

a pretreatment unit for pretreatment of the gas mixture to be separated;

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

The gas separation equipment includes a plurality of membrane modules, and the membrane modules are connected in series with each other; the gas outlet on the permeate side of the membrane module in the upper stage is connected to the gas inlet on the retentate side of the membrane module in the lower stage; The retentate side air outlet of the first-stage membrane module is connected to the retentate-side air inlet of the upper-stage membrane module;

A first gas component receiving pipeline is connected to the permeate side gas outlet of the last stage membrane module; a second gas component receiving pipeline is connected to the retentate side gas outlet of the first stage membrane module.

In one embodiment, the membrane module includes a casing and a gas separation membrane installed in the casing; and the retentate-side gas inlet and the retentate-side gas outlet are connected to the casing, and the gas separation membrane The permeate side is connected to the permeate side outlet.

In one embodiment, the gas separation membrane is of tubular type or hollow fiber type.

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

In one embodiment, the retentate-side gas outlet of the membrane module of the next stage is connected to the retentate-side gas inlet of the membrane module of the previous stage or several stages above.

In one embodiment, the air outlet on the retentate side of the membrane module of the next stage is connected to the membrane module of the upper stage through a micro air pump.

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

In one embodiment, the pretreatment unit is connected to any stage of membrane modules.

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

A third aspect of the present invention provides:

Application of the above-mentioned inorganic membrane multistage gas separation device in multicomponent gas separation.

beneficial effect

The invention is simple and convenient to operate, and the separation and concentration of the gas can be realized only by connecting the multi-stage membrane separation components in series. The device investment is low, the gas separation can be realized at normal temperature, energy saving and environmental protection, and the economic benefit is remarkable. For mixed gas systems with low selectivity of single-stage membrane separation and low purity of separated products, multi-stage membrane separation can significantly improve the purity of gas separation, especially for the separation and concentration of some special gases, which can produce huge economic benefits.

Description of drawings

FIG. 1 is a schematic diagram of the separation process of a multi-stage serial membrane separation device.

Figure 2 is a schematic diagram of several typical retentate gas (except the first stage) recirculation mode.

Figure 3 shows the effect of Xe molar composition on the separation performance of CO ₂ /Xe mixture (feed pressure: 3 bar).

Figure 4 shows the separation performance of the DD3R molecular sieve membrane.

Figure 5 shows the separation performance of DD3R molecular sieve membrane for _CO and Xe.

Among them, 1, pretreatment unit; 2, mass flow controller; 3, membrane module; 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 ways

Figure 1 shows 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 materials are pretreated before entering the series membrane separation module to achieve the corresponding gas state Require. The treated raw gas enters the multi-stage membrane separation module through the mass flow controller 2 at an appropriate feeding position.

In the present invention, when the membrane modules are connected in series, the most upstream module is the first stage, and the (most downstream) stage where the retentate gas is discharged as the final product (the most downstream) is the nth stage.

Figure 1 shows a single membrane module used in the present invention, the membrane module 3 includes a shell 4 and an internal gas separation membrane 5, the shell 4 is made of stainless steel or nylon, and the shell 4 and the gas separation membrane 5 divide the inner space of the module. For the permeation measurement and retentate side, the figure takes the 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 casing, and both ends of the casing are provided with threaded heads 8, one end has a permeation side air outlet 9, and the other end is a dead end. The single-stage membrane modules 3 are connected in series with pipelines 10, and the permeate side air outlet 9 of the upper stage is connected to the lower-stage shell air inlet 6 to complete the series operation of the device; the retentate gas outlet 7 of the lower-stage module is connected to The housing air inlet 6 of the upper-level assembly is connected to complete the recirculation operation.

When the above structure is adopted, a major improvement is that the retentate gas is used for the upstream reflux treatment. When the feed gas to be separated contains two components, A and B, the single-stage membrane is used. When the components are separated, it is assumed that component B is allowed to enter the permeate side, and the retentate gas (assumed to be A) often cannot reach sufficient purity, so that the retentate gas cannot be effectively reused, and the retentate gas will continue to be refluxed to the upper stage. During separation, the concentrated gas containing A can be further enriched to A again, and after the B gas continues to be fed to the next-level series component, the material mainly containing the B gas is further separated, and finally This results in a purer A in the first stage and a purer B in the last stage.

Figure 1 shows that the raw gas is separated in the multi-stage series membrane module, the permeate gas of each stage module enters the next stage module for further separation, and the retentate gas is returned to the previous stage through the air pump 11 to be mixed with the feed gas.

Figure 1 shows that the permeate outlet 4 of the last stage module collects the separated permeate product. The gas outlet 7 on the retentate side of the first-stage component is connected to the back pressure valve 12 to control the gas output of the retentate gas, and the retentate product is produced through the back pressure valve 12 .

The retentate gas return includes, but is not limited to, the return method of returning to the previous stage module. The retentate gas can be adjusted to be mixed with the feed gas before the retentate gas is returned to the other membrane modules before the current stage module. For the recirculation of the gas on the retentate side, as shown in Fig. 2, both can be recirculated to the upper stage in sequence, or can be recirculated to several upper stages, or multiple membrane modules can be recirculated to the same stage above.

In addition, in addition to the first-stage retentate gas outlet, when the system to be separated contains impurities and the impurities are enriched to a high concentration after a certain number of stages of separation, the retentate gas outlet of an appropriate stage can be selected. Increase branch production to reduce the impact of high-concentration gas on the membrane separation of the target system.

In the above-mentioned first-stage membrane module raw material feeding process, the pressure range is controlled within 0.1-5MPa.

The operating temperature range of the gas separation process of the above-mentioned components of each stage ranges from 28K to 973K.

During the retentate gas backflow process of the above-mentioned modules of each stage, the gas backflow ratio (return ratio refers to: (the amount of gas flowing back from the retentate side of the membrane module of this stage - the amount of gas permeated by the membrane module of this stage) through the micro air pump is separated from the incoming gas. The ratio of the amount of gas to be separated in the equipment) is controlled in the range of <10. For example: a series equipment contains 10 membrane modules, and the mixed gas feed position is in the fifth-stage membrane module, then for the fourth-stage membrane module, it also has the gas flowing back from the fifth-stage retentate side, and also contains The gas obtained from the third stage permeate side, then the reflux ratio is: the amount of reflux gas on the fourth stage retentate side (the third stage permeate side gas volume + the fifth stage retentate side reflux volume - the fourth stage gas permeation volume) / enter The amount of gas to be separated in the gas separation plant.

The pore diameter of the material of the inorganic membrane used in the above separation device is in the range of 2 to 200 nm.

The inorganic membrane material used in the above membrane separation device can be one or more of ceramic membrane, molecular sieve membrane and carbon membrane. The support may be in the form of tubular or hollow fibers, among others.

Example 1

The mixed gas of 80% N ₂ and 20% O ₂ was passed into the pretreatment device to remove the moisture and other solid particles in the mixed gas, so that the temperature of the treated gas reached 25°C, and the pressure was increased to 1.5MPa. The pretreated raw gas enters the separation device through the first-stage air inlet with a certain amount of feed through the mass flow controller, and the retentate side air outlet of the first-stage component is connected to the back pressure valve to control the retentate side pressure to be stable at 3.5～4bar (gauge pressure). The retentate gas of each component is returned to the previous component through the air pump, and the reflux ratio is 0.8. The membrane material in each membrane separation module is _TiO2 -coated alumina hollow fiber membrane with a pore size of 100nm, which has both high mechanical strength and excellent anti-oxidation performance.

Under this condition, the last-stage permeate gas is produced at normal pressure, and after 45-stage membrane separation, the _N2 concentration in the last-stage permeate gas is >99%. The permeate exhausted from the back pressure valve in the first stage assembly can be exhausted directly to air.

Example 2

The mixed gas with the composition of 80% Kr and 20% Xe was passed into the pretreatment unit, and the pressure was increased to 3MPa and the gas temperature was kept at about 25°C. The pretreated mixed gas is passed into the air inlet of the 10th-stage membrane module of the series device, the feed amount is controlled by the mass flow controller, and the outflow amount of the first-stage retentate gas is controlled by regulating the back pressure valve. The retentate gas of each component is returned to the previous component through the micro air pump, and the reflux ratio is 1. Inorganic ceramic membrane is used as the membrane separation material, the membrane pore size is 50nm, which has both high mechanical strength and excellent anti-oxidation performance. The retentate gas discharged from the first-stage assembly through the back pressure valve is recycled, and the concentration of Xe is about 35%. The last stage of permeate gas is extracted under normal pressure as the raw material, and the separation stages required to achieve different theoretical purities are as follows:

Example 3

The natural gas with N ₂ content <10% (the main component CH ₄ >90%) is passed into the pretreatment unit to remove the moisture and other solid particles in the mixed gas, the mixed gas is pressurized to 0.7MPa, and the mixed raw material gas temperature Controlled at around 25°C. Pass the pretreated mixed gas into the air inlet of the 10th-stage membrane module of the series device, control the feeding amount through the mass flow controller, and control the first-stage retentate gas output by the first-stage regulating back pressure valve so that the first-stage The pressure on the retentate side is stable at 3.5 to 4 bar (gauge pressure). The retentate gas of each component is returned to the previous component through the air pump, and the reflux ratio is 1.5. The electrodeless ceramic membrane is used as the separation material, and the pore size of the membrane is 100-150 nm.

Under this condition, after 20 stages of separation, the last stage permeate gas is produced at atmospheric pressure, where the concentration of _CH4 is >99%, this permeate gas is collected as a product, and the first stage module retentate gas except for reflux It is recycled after being discharged through the back pressure valve.

Example 4

A mixed gas with a composition of 50% He and 50% N was introduced into the treatment unit, the mixed gas was pressurized to ₁ MPa, and the temperature was controlled at room temperature. The pre-treated raw material mixer is fed into the 6-stage serial membrane module through the air inlet of the 4-stage module for separation, and the feed rate is controlled by a mass flow controller to be 1.5L/h. Control the back pressure valve to regulate the pressure on the first-stage retentate side to stabilize at 3 to 3.5 bar. The retentate gas of the first-stage components is directly recovered through the back pressure valve, and the return ratio of the other components is kept at 0.66, ensuring that the return flow of each level component is 1L/h, and the return direction is returned to the upper level component feed, and each level The infiltration volume and the final bottom recovery volume were maintained at 0.5L/h. The separation membrane material is a hollow fiber molecular sieve membrane with a pore size of 2nm and excellent mechanical stability. The last stage permeate is produced at atmospheric pressure and collected as product. Under this condition, according to the balance calculation, the parameters of each level are shown in the following table:

Example 5

A mixed gas composed of 90% _H2 and 10% _CO2 was passed into the pretreatment unit, pressurized to 0.5 MPa and the gas temperature was maintained at about 25 °C. Pass the pretreated mixed gas into the air inlet of the fifth-stage membrane module of the series device, control the feed amount through the mass flow controller, and adjust the back pressure valve to control the outflow of the first-stage retentate gas, so that the first-stage retentate gas can be controlled. The side pressure is stable at 2 ~ 2.4bar (gauge pressure). The retentate gas of each component is returned to the previous component through the air pump, and the reflux ratio is 0.5. A hollow fiber molecular sieve membrane was used as the separation membrane material.

Under this condition, after the separation of the 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 under normal pressure, and the retentate gas discharged from the first-stage components through the back pressure valve Recycling, in which the concentration of CO ₂ is about 30%. In this embodiment, it is the feed to the fifth-stage membrane module. After this stage of separation, the gas on the retentate side of the fifth stage contains 16.3% CO. ₂ and 84.7% H ₂ , it can be seen from the comparison that the further enrichment of CO ₂ gas is finally achieved by refluxing the gas from the retentate side of this stage to the previous stage.

Example 6

In this embodiment, the DD3R molecular sieve membrane is used for the on-line recycling technology of xenon gas in the closed-circuit medical xenon gas anesthesia process. The single-component carbon dioxide permeability is 1.5×10 ^-7 mol·m ^-2 ·s ^-1 ·Pa ^-1 , and the separation selectivity of carbon dioxide to xenon is 570. The permeate flux is an order of magnitude higher than conventional membrane materials. The membrane separation performance is mainly determined by the difference in the diffusion coefficients of _CO2 and Xe molecules in DD3R molecular sieves. However, the mass transfer rate of CO ₂ is significantly reduced by the presence of Xe, which is very different from the previous results of the separation of CO ₂ /N ₂ and CO ₂ /CH ₄ binary components by eight-membered ring zeolite membranes. The molecular dynamics simulation results show that the adsorption of Xe molecules on the surface of the molecular sieve membrane forms the surface resistance for _CO adsorption and diffusion. The CO ₂ permeability and CO ₂ /Xe separation selectivity were 2.0 × 10 ^-8 mol·m ^-2 ·s ^-1 under conditions relevant to medical xenon anesthesia, i.e. carbon dioxide content below 5% and the presence of water vapour, respectively · Pa ^-1 and 67. Due to the all-silicon properties of the DD3R molecular sieve membrane, the permeability of CO ₂ is weakly affected by water vapor, which is different from the fact that the pores of the aluminum-containing molecular sieve membrane are easily blocked by adsorbed water. High CO ₂ flux and high CO ₂ /Xe selectivity, as well as long-term stability, ensure a good prospect of the hollow fiber DD3R molecular sieve membrane in the on-line reuse of medical anesthesia xenon gas. For the preparation process of the DD3R molecular sieve membrane used in this embodiment, reference may be made to the prior art, for example, CN110745839A "An Activation Process of a Defect-Free DD3R Molecular Sieve Membrane".

First, the separation test of CO ₂ /Xe mixed gas was carried out. Figure 3 shows the effect of Xe molar composition on the separation performance of CO ₂ /Xe mixed gas (feed pressure: 3 bar). The CO ₂ permeability decreased with the increase of Xe This is even more pronounced as the composition increases (panel c in Figure 2). Finally, when the _CO content was reduced to 5%, the _CO permeability was 0.24×10 ^-7 mol·m ^-2 ·s ^-1 ·Pa ^-1 ; however, the separation selectivity of CO ₂ /Xe was always around 43 , showing good separation selectivity at low _CO2 concentrations.

The CO ₂ 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 current literature (Fig. 4a area). At different temperatures, the separation performance of DD3R molecular sieve membrane for CO ₂ single component, CO ₂ /H ₂ O binary component and CO ₂ /H ₂ O/Xe ternary component is shown in the b area of Fig. 4; Fig. 4 The c region is the long-term stability of the DD3R molecular sieve membrane at 3 bara for the recovery of Xe in a mixture consisting of 0.76% H ₂ O, 4.96% CO ₂ , 29.77% N ₂ and 64.51% Xe. Water vapor is often present in anesthetized exhaled breath. Due to the presence of water vapor, the _CO2 single-component permeability decreased by 37-45% (region b of Fig. 4); however, under the same conditions, the gas permeability of the aluminum-containing 8-membered ring molecular sieve membrane decreased more significantly, The DD3R molecular sieve membrane has better hydrophobic properties, which can effectively weaken the _CO2 permeability reduction caused by water vapor adsorption. The use of aprotic template agent and non-ionic synthesis solution was used to prepare a more hydrophobic DD3R molecular sieve membrane for the separation of CO ₂ /Xe in a humid environment. The effect of water vapor on _CO permeability and selectivity was further investigated, as shown in area b of Fig. 3 and area a of Fig. 5. In the water vapor environment, the separation selectivity of the membrane is higher than that of the dry gas. The Si-OH at the grain boundaries of the molecular sieve film 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 in a dry gas. The permeation of water vapor gradually weakened with increasing temperature, for example, it decreased by 55% at 100°C; by 52% at 125°C; and by 42% at 150°C. However, in both wet and dry gases, the permeability of _CO2 molecules is mainly contributed by DD3R molecular sieves.

During the anesthesia process, except for CO ₂ , the impurities in the exhaled anesthetic gas, the human tissues and organs will release nitrogen gas in the initial stage of anesthesia. It was used to recover xenon in a mixture of 5% CO ₂ , 30% N ₂ and 65% Xe. When 2.3kP water vapor was introduced, the permeability of both _CO2 and _N2 decreased slightly (Fig. 3). Finally, the permeability of CO2 stabilized at 2.0× ^10-8 mol·m ^-2 ·s ^-1 ·Pa ^-1 , the CO ₂ /Xe selectivity is 67±12; the N ₂ permeability is 2.4×10 ^-9 mol·m ^-2 ·s ^-1 ·Pa ^-1 , and the N ₂ /Xe selectivity is 8±2.

The separation experiment of recovering xenon gas using one-stage DD3R separation membrane was carried out above. Next, multi-stage separation was used for deep recovery. When using the 3-stage series separation process, according to the same operating conditions, the recovered xenon containing 99.19% and 99.23% Xe was obtained in the second and third stages in turn, indicating that higher purity can be obtained through multi-stage series separation. Xenon.

Claims (10)

1. A method for inorganic membrane multistage gas separation, comprising the steps of:

step 1, sending a gas mixture to be separated into gas separation equipment for separation;

the gas separation equipment is formed by connecting a plurality of membrane modules in series, and materials obtained from the permeation side of the previous stage are sent to the permeation side of the next stage for continuous separation; the obtained material on the retentate side of the next stage flows back to the retentate side of the upper stage for continuous separation;

and 2, obtaining a first gas component on the permeation side of the last stage, and obtaining a second gas component on the retentate side of the first stage.

2. The inorganic membrane multistage gas separation method of claim 1, wherein in step 1, the gas mixture to be separated is pretreated by a pretreatment unit for the mixed gas;

in one embodiment, the pretreatment comprises compression, drying, filtration, or heating.

3. The inorganic membrane multi-stage gas separation process of claim 1 wherein in step 1, the gas product on the retentate side of the first stage is withdrawn under a back pressure valve control;

in one embodiment, in step 1, the resulting material from the retentate side of the next stage is refluxed to the retentate side of the previous stage or stages;

in one embodiment, in step 1, the gas mixture to be separated is fed to the membrane module whose gas composition on the retentate side is closest to the gas composition of the gas mixture to be separated;

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

4. The method for multistage inorganic membrane gas separation according to claim 1, wherein a reflux ratio is required to be set for the membrane module containing the refluxed retentate gas; wherein the reflux ratio is as follows: the return gas quantity of the retentate side of the membrane module and the gas quantity to be separated entering the gas separation equipment;

in one embodiment, the working temperature of each stage of membrane module is 28K-973K;

in one embodiment, the material used in the gas separation membrane installed in the membrane module may be one or more of inorganic membrane materials such as a molecular sieve membrane, a ceramic membrane, and a carbon membrane; the carrier of the gas separation membrane may be in the form of a tube or hollow fiber, etc.

5. The method of inorganic membrane multi-stage gas separation of claim 1, wherein in one embodiment, the gas mixture to be separated contains N₂、CO₂、H₂、O2、Kr、Xe、CH₄And one or more of He;

in one embodiment, the composition of the gas mixture to be separated is 5% CO₂, 30% N₂And 65% Xe gas mixture, and further contains H₂O， H₂The partial pressure of O was 2.3 kPa; and the gas separation membrane used was a DD3R molecular sieve membrane.

6. An apparatus for inorganic membrane multistage gas separation, comprising:

a pre-treatment unit (1) for pre-treating a gas mixture to be separated;

the gas separation equipment is connected with the pretreatment unit (1) and is used for separating gas components in a gas mixture to be separated;

the gas separation equipment comprises a plurality of membrane modules (3), and the membrane modules (3) are connected in series; the permeation side air outlet (9) of the upper stage membrane component (3) is connected with the residual side air inlet (6) of the lower stage membrane component (3); a surplus side air outlet (7) of the membrane module (3) at the next stage is connected with a surplus side air inlet (6) of the membrane module (3) at the upper stage;

an air outlet (9) at the permeation side of the membrane component (3) at the last stage is connected with a first gas component receiving pipeline; a second gas component receiving pipeline is connected with a gas outlet (7) at the retentate side of the membrane component (3) of the first stage.

7. The inorganic membrane multistage gas separation device according to claim 6, wherein in one embodiment, the membrane module (3) comprises a shell (4) and a gas separation membrane (5) installed in the shell (4); the residual side gas inlet (6) and the residual side gas outlet (7) are connected to the shell (4), and the permeation side of the gas separation membrane (5) is connected to the permeation side gas outlet (9);

in one embodiment, the gas separation membrane (5) is of tubular or hollow fiber type;

in one embodiment, the material of the gas separation membrane (5) is a molecular sieve membrane, a ceramic membrane or a carbon membrane.

8. The inorganic membrane multistage gas separation apparatus according to claim 6, wherein in one embodiment, the retentate side gas outlet (7) of the membrane module (3) of the next stage is connected to the retentate side gas inlet (6) of the membrane module (3) of the previous stage or stages;

in one embodiment, the retentate side air outlet (7) of the membrane module (3) at the next stage is connected with the membrane module (3) at the upper stage by a micro air pump (11).

9. The apparatus for inorganic membrane multistage gas separation according to claim 6, characterized in that in one embodiment the pretreatment unit (1) is connected to the gas separation device by means of a mass flow controller (2);

in one embodiment, the pretreatment unit (1) is connected to the membrane module (3) of any stage;

in one embodiment, a back pressure valve (12) is connected to the retentate side gas outlet (7) of the first stage membrane module (3).

10. Use of the apparatus for inorganic membrane multistage gas separation of claim 6 for multi-component gas separation.

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