A stain-resistant perfluoropolymer composite membrane, method of making and use thereof

Abstract

The application discloses a kind of pollution-resistant perfluoropolymer composite membrane, preparation method and application, belong to gas separation membrane technical field.The perfluoropolymer composite membrane of the application is prepared by dissolving perfluoropolymer in perfluorinated solvent to prepare separation layer solution, after defoaming, coating to bottom film, after drying, heating at 40~120 DEG C for 5~240min, obtain the perfluoropolymer composite membrane with defect;Again, it is placed in 20~50 DEG C, perfluorinated solvent vapor accounts for 10~80% of perfluorinated solvent vapor and inert gas mixed gas treatment 10~60min, finally, it is sequentially dried at 40~59, 60~79, 80~99 DEG C respectively for 5~30min, obtain perfluoropolymer composite membrane.The application overcomes the problem of separation layer defect when preparing perfluoropolymer composite membrane in traditional, can obtain perfluoropolymer composite membrane with high gas permeability and high selectivity simultaneously, can be used in hydrogen-containing mixed gas to recover hydrogen, removal of acid gas and nitrogen in natural gas and biogas, extraction of helium in natural gas, with wide application prospect.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of gas separation membrane, and particularly relates to a pollution-resistant perfluoropolymer composite membrane, a preparation method and application thereof. BACKGROUND

[0002] The gas mixture involved in the gas membrane separation industry often has various types of pollutants, which have strong destructive effect on the membrane performance or service life. For example, the condensable hydrocarbons in the petrochemical industry and natural gas, the small amount of NH3 in the synthetic ammonia purge gas and biogas, and H2S in many industries. Taking natural gas as an example, although the hydrocarbons in natural gas are mainly methane, there are also ethane, propane, butane, pentane, and a small amount of hexane and above hydrocarbons. Sometimes, there are even a small amount of naphthenes and aromatics (benzene, toluene, xylene, etc.). Similarly, the composition of refinery gas (refers to various gases produced in the crude oil processing and auxiliary processing of oil refineries) in the petrochemical industry is complex, and the compositions of refinery gas from different sources are different, but mainly hydrogen and C1-C4 alkanes / alkenes, a small amount of C 5+ hydrocarbons (mainly pentane and hexane).

[0003] The pollution caused by impurity gas is an important reason for the performance decline of the gas separation membrane. Even if its content is very low, the aromatic hydrocarbons can be dissolved in the membrane under certain temperature, pressure and feed gas conditions, and distributed around the polymer chain segment. Their presence causes the movement of the polymer chain segment to be hindered, and the movement frequency to be reduced, which means that the channel of the gas through the membrane is reduced, and the diffusion of the gas in the membrane is hindered, thereby causing the membrane flux to be significantly reduced, and the gas treatment capacity to be greatly reduced. Especially when the operating temperature of the membrane module is not strictly controlled, the hydrocarbons may even condense on the membrane surface and directly cause irreversible damage to the membrane module, causing great economic losses to the production enterprises. For example, NH3 can cause the mechanical properties of the polyimide membrane to decrease, and has a fatal damage to the service life of the membrane, which is a major obstacle to the application of gas separation membranes in the biogas purification and synthetic ammonia industries.

[0004] The existing membrane treatment device reduces the influence of impurity gas by strict pretreatment. For example, in the natural gas membrane treatment with higher heavy hydrocarbon content, a regenerative adsorption process (TSA, temperature swing adsorption) is usually used to remove heavy hydrocarbons and water contained in the natural gas, which is generally arranged at the rear end of the gas-liquid separator and in front of the membrane. The problem of heavy hydrocarbon damage to the membrane can be solved, and the service life of the membrane is prolonged (Natural Gas Desulfurization and Treatment Manual, Maurice Stewart, Ken Arnold, Zhao Zhangming, Wang Zhanxu, Tang Hai, Petroleum Industry Press). Increasing the temperature of the feed gas is also a common method, and the main goal is to prevent hydrocarbons from condensing and liquefying on the membrane surface. Any liquid hydrocarbon will cause damage to the membrane. In refinery hydrogen recovery, the operating temperature should be over 35℃ higher than the temperature of the raw material gas. In summary, although pretreatment can partially eliminate membrane pollution, this treatment method increases equipment investment, system operation complexity and energy consumption, causing great waste of fixed investment and operating costs, and cannot fundamentally solve the problem of membrane pollution.

[0005] Different from most traditional gas separation membranes, the high bond energy of C-F bond makes the full fluoropolymer membrane have much stronger resistance to pollution than common membrane materials, and thus is very suitable for the separation field of raw gas containing polluting impurities. For example, helium extraction from natural gas, acid gas removal from natural gas or biogas, nitrogen, hydrogen recovery from hydrogen-containing mixed gas and the like. Compared with the polyimide, polysulfone and cellulose acetate membranes commonly used in the industry, the cyclic structure of the full fluoropolymer material leads to higher gas permeability itself, which means a significant reduction in membrane area. However, since the full fluoropolymer is a glassy material, the stress during the drying to form the separation layer in the coating process is much higher than that of the rubbery material, and defects are easily generated, resulting in a decrease in the separation performance of the final membrane. SUMMARY

[0006] In view of the problem of defects in the existing full fluoropolymer composite membrane due to too fast drying during the manufacturing process, the present application provides a pollution-resistant full fluoropolymer composite membrane, a preparation method and application thereof. The preparation method can avoid the generation of defects, and the obtained full fluoropolymer composite membrane has excellent gas permeability and selectivity.

[0007] The present application provides the following technical solutions:

[0008] A preparation method of a pollution-resistant full fluoropolymer composite membrane mainly comprises the following steps:

[0009] S1: Separation layer solution preparation: Dissolve the particles of the full fluoropolymer in a full fluorine solvent to prepare a separation layer solution with a concentration of 0.1wt.%-3wt.%, and then stand for defoaming;

[0010] S2: composite film preparation: coating the solution obtained in step S1 on a base film, and drying at room temperature for 2-60 min; heating at 40-120°C for 5-240 min to obtain a defective perfluoropolymer composite film;

[0011] S3: defect repairing of the composite film: placing the defective perfluoropolymer composite film obtained in step S2 in an atmosphere of a mixed gas of perfluorosolvent vapor and inert gas at 20-50°C, with the perfluorosolvent vapor accounting for 10-80%, and treating for 10-60 min;

[0012] S4: gradient drying of the composite film: drying the composite film obtained in step S3 at 40-59, 60-79, and 80-99°C for 5-30 min, 5-30 min, and 5-30 min, respectively, to obtain a perfluoropolymer composite film.

[0013] Based on the above technical solution, further, in step S1, the perfluoropolymer is a homopolymer of perfluoro-m-dioxole, perfluoro-m-dioxin, or a cycloalkyl ether, or a copolymer of two or more thereof, or a copolymer with tetrafluoroethylene or chlorotrifluoroethylene.

[0014] Based on the above technical solution, further, in step S1, the perfluoropolymer is a homopolymer of perfluoro-m-dioxole, perfluoro-m-dioxin, or a cycloalkyl ether, or a copolymer of two or more thereof, or a copolymer with tetrafluoroethylene or chlorotrifluoroethylene. AF series of Solvay, AD series of Solvay, and

[0015] Based on the above technical solution, further, in step S1, the perfluorosolvent refers to an alkane, ether, or amine in which the hydrogen atoms on carbon atoms are completely replaced by fluorine atoms.

[0016] Based on the above technical solution, further, in step S1, the concentration of the separation layer solution is 0.1-1 wt.%, and the defoaming time is 1-4 h.

[0017] Based on the above technical solution, further, in step S2, the base film is a flat plate ultrafiltration membrane, a flat plate microfiltration membrane, a hollow fiber ultrafiltration membrane, or a hollow fiber microfiltration membrane.

[0018] Based on the above technical solution, further, in step S2, the base film is made of one or a combination of two or more of polysulfone, polyethersulfone, polyacrylonitrile, polyetherimide, polyvinylidene fluoride, polyimide and polycarbonate, ceramic, or glass.

[0019] Based on the above technical solution, further, in step S2, the thickness of the separation layer on the defective perfluoropolymer composite film obtained is 0.05-3 μm.

[0020] Based on the above technical solution, further, in step S2, the product is air-dried at room temperature for 5-30 minutes and then heated at 50-90°C for 5-40 minutes.

[0021] Based on the above technical solution, further, in step S3, the inert gas is one or a mixture of two or more of nitrogen, argon, and helium.

[0022] Based on the above technical solution, further, in step S4, the composite film obtained in step S3 is dried sequentially at 45-55, 65-75, and 85-95°C for 5-20 min, 5-20 min, and 5-20 min, respectively.

[0023] In another aspect, the present invention provides a pollution-resistant perfluoropolymer composite membrane prepared by the above-described preparation method.

[0024] Another aspect of the present invention provides a fouling-resistant gas separation membrane system, including a membrane separator, wherein the fouling-resistant perfluoropolymer composite membrane is used in the membrane separator.

[0025] Based on the above technical solution, the pollution-resistant gas separation membrane system further includes a gas-liquid separator and a precision filter, wherein the outlet of the gas-liquid separator is connected to the inlet of the precision filter, and the outlet of the precision filter is connected to the inlet of the membrane separator.

[0026] Alternatively, the pollution-resistant gas separation membrane system may further include a precision filter and a heater, wherein the outlet of the precision filter is connected to the inlet of the heater, and the outlet of the heater is connected to the inlet of the membrane separator.

[0027] The present invention also provides the application of the above-described fouling-resistant gas separation membrane system in gas separation and recovery.

[0028] Based on the above technical solution, the application is further described as separating and recovering hydrogen from a hydrogen-containing gas mixture.

[0029] Based on the above technical solution, the hydrogen-containing mixed gas further includes high-pressure exhaust gas from refineries (residue oil hydrotreating (RDS), wax oil hydrotreating and hydrocracking circulating vent gas), low-pressure vent gas (hydrorefining, gasoline / diesel / kerosene hydrocracking and low-part gas such as wax oil), FCC dry gas, methanol vent gas, synthetic ammonia vent gas and vent gas from coal-to-oil processes (high-pressure circulating gas in the direct coal liquefaction process and low-part gas and oil wash dry gas from the hydrocracking unit in the indirect liquefaction process).

[0030] Based on the above technical solution, the application is further specifically the removal of acidic gases and nitrogen from natural gas and biogas.

[0031] Based on the above technical scheme, further, the application is specifically extracting helium from natural gas.

[0032] The beneficial effects of the present application are:

[0033] 1. The present application overcomes the problem of defects in the separation layer when preparing perfluoropolymer composite membrane by traditional method, and can obtain perfluoropolymer composite membrane with high gas permeability and high selectivity;

[0034] 2. The preparation method of the perfluoropolymer composite membrane of the present application is simple and easy to control, and can be used in gas separation process, and has wide application prospect.

[0035] 3. The perfluoropolymer composite membrane of the present application can simplify the pretreatment process in the processes of recovering hydrogen from hydrogen-containing mixed gas, removing acid gas and nitrogen from natural gas and biogas, extracting helium from natural gas, etc., reduce the complexity and land area of equipment, significantly reduce the membrane use area, reduce the fixed investment and operating cost, and prolong the service life of the membrane treatment system. BRIEF DESCRIPTION OF DRAWINGS

[0036] In order to more clearly illustrate the embodiments of the present application, the drawings involved in the embodiments will be briefly introduced below.

[0037] Figure 1 is a schematic diagram of the defects in the separation layer of the perfluoropolymer membrane repaired by the mixed gas of perfluorosolvent vapor and nitrogen.

[0038] Figure 2 is a schematic diagram of the membrane separation system in Comparative Example 3.

[0039] Figure 3 is a schematic diagram of the membrane separation system in Example 5.

[0040] Figure 4 is a schematic diagram of the membrane separation system in Comparative Example 4 and Examples 6-10.

[0041] Figure 5 is a schematic diagram of the membrane separation system in Comparative Example 5. DETAILED DESCRIPTION

[0042] The present application will be described in detail below in combination with the embodiments, but the implementation of the present application is not limited thereto, and obviously, the embodiments described below are only part of the embodiments of the present application, and for those skilled in the art, other similar embodiments obtained without creative labor fall within the protection scope of the present application.

[0043] The raw material information involved in the following examples is as follows:

[0044] Polysulfone substrate membrane: from Sepro, kept wet before coating, coating operation was carried out after wiping off the surface droplets; AD60 and Galden HT70, Solvay.

[0045] Comparative Example 1

[0046] A perfluoropolymer composite membrane disclosed in this comparative example was prepared by the following steps:

[0047] (1) Preparation of separation layer solution: AD60 was dissolved in Galden HT70 to prepare a separation layer solution with a concentration of 1 wt.%, and then left to stand for 2 h to remove bubbles; AD60 was dissolved in Galden HT70 to prepare a separation layer solution with a concentration of 1 wt.%, and then left to stand for 2 h to remove bubbles;

[0048] (2) The solution obtained in step (1) was coated on the polysulfone substrate membrane, and then dried at room temperature for 10 min; and then heated at 70°C for 10 min to obtain a perfluoropolymer composite membrane.

[0049] The permeation properties and separation properties of the perfluoropolymer composite membrane for pure O2 and N2 were tested, and the test results were as follows: J N2 = 70.3 GPU, J O2 = 161.7 GPU, α O2 / N2 = 2.3. The surface of this composite membrane had defects, and the selectivity was poor.

[0050] Comparative Example 2

[0051] A perfluoropolymer composite membrane disclosed in this comparative example was prepared by the following steps:

[0052] (1) Preparation of separation layer solution: AD60 was dissolved in Galden HT70 to prepare a separation layer solution with a concentration of 1 wt.%, and then left to stand for 2 h to remove bubbles; AD60 was dissolved in Galden HT70 to prepare a separation layer solution with a concentration of 1 wt.%, and then left to stand for 2 h to remove bubbles;

[0053] (2) The solution obtained in step (1) was coated on the polysulfone substrate membrane, and then dried at room temperature for 10 min; and then heated at 70°C for 10 min to obtain a perfluoropolymer composite membrane.

[0054] The permeation properties and separation properties of the perfluoropolymer composite membrane for pure O2 and N2 were tested, and the test results were as follows: J N2 = 58.8 GPU, J O2 = 147.0 GPU, α O2 / N2 = 2.5. The use of temperature gradient drying helped to improve the mobility of the polymer chain segments, and the surface defects of the composite membrane were improved compared to Comparative Example 1, but there were still defects, which led to an improvement in selectivity compared to Comparative Example 1, but still not the best result.

[0055] Example 1

[0056] The perfluoropolymer composite membrane disclosed in the embodiment is prepared by the following steps:

[0057] (1) Preparation of separation layer solution: AD60 is dissolved in Galden HT70 to prepare a separation layer solution with a concentration of 1 wt.%, and then left to stand for 2 h to remove bubbles; AD60 is dissolved in Galden HT70 to prepare a separation layer solution with a concentration of 1 wt.%, and then left to stand for 2 h to remove bubbles;

[0058] (2) The solution obtained in step (1) is coated on a polysulfone base film, and then left to stand at room temperature for 10 min to dry; and then heated at 70°C for 10 min to obtain a defective perfluoropolymer composite membrane;

[0059] (3) The defective perfluoropolymer composite membrane obtained in step (2) is placed in an atmosphere of Galden HT70 vapor and nitrogen mixed gas (Galden HT70 vapor accounts for 60%) at 30°C for 20 min;

[0060] (4) Gradient drying of the composite membrane: the composite membrane obtained in step (3) is sequentially dried at 50, 70 and 90°C for 10 min respectively to obtain the perfluoropolymer composite membrane of the present application.

[0061] As shown in the following table, the step (3) can repair the defects on the surface of the perfluorocomposite membrane. Figure 1 The test results of the perfluoropolymer composite membrane on the permeability of pure O2 and N2 and the separation performance are as follows: J N2 = 44.3 GPU, J O2 = 150.6 GPU, and a O2 / N2 = 3.4. The composite membrane has no defects on the surface and has a relatively high selectivity.

[0062] Example 2

[0063] The perfluoropolymer composite membrane disclosed in the embodiment is prepared by the following steps:

[0064] (1) Preparation of separation layer solution: AD60 is dissolved in Galden HT70 to prepare a separation layer solution with a concentration of 1 wt.%, and then left to stand for 2 h to remove bubbles; AD60 is dissolved in Galden HT70 to prepare a separation layer solution with a concentration of 1 wt.%, and then left to stand for 2 h to remove bubbles;

[0065] (2) The solution obtained in step (1) is coated on a polysulfone base film, and then left to stand at room temperature for 10 min to dry; and then heated at 70°C for 10 min to obtain a defective perfluoropolymer composite membrane;

[0066] (3) The defective perfluoropolymer composite membrane obtained in step (2) is placed in an atmosphere of Galden HT70 vapor and nitrogen mixed gas (Galden HT70 vapor accounts for 60%) at 30°C for 20 min;

[0067] (4) Gradient drying of the composite membrane: the composite membrane obtained in step (3) is sequentially dried at 50, 70, 90°C for 10 min respectively to obtain the perfluoropolymer composite membrane of the present application.

[0068] The perfluoropolymer composite membrane is tested for permeability and separation performance for pure O2and N2, and the test results are: J N2 = 51.7 GPU, J O2 = 170.6 GPU, a O2 / N2 = 3.3. Compared with Example 1, a lower concentration of perfluoropolymer solution is used to prepare the composite membrane, and the gas permeability is higher.

[0069] Example 3

[0070] The perfluoropolymer composite membrane disclosed in this example is prepared by the following steps:

[0071] (1) Preparation of the separation layer solution: 0.5 wt.% of is dissolved in Galden HT70 to prepare the separation layer solution, and then left to stand for 2 h to remove bubbles;

[0072] (2) The solution obtained in step (1) is coated on the polysulfone base membrane, and left to stand at room temperature for 10 min; and heated at 70°C for 10 min to obtain a defective perfluoropolymer composite membrane;

[0073] (3) The defective perfluoropolymer composite membrane obtained in step (2) is treated in an atmosphere of Galden HT70 vapor and nitrogen mixed gas (Galden HT70 vapor accounts for 60%) at 30°C for 20 min;

[0074] (4) Gradient drying of the composite membrane: the composite membrane obtained in step (3) is sequentially dried at 50, 70, 90°C for 10 min respectively to obtain the perfluoropolymer composite membrane of the present application.

[0075] The perfluoropolymer composite membrane is tested for permeability and separation performance for pure O2and N2, and the test results are: J N2 = 31.1 GPU, J O2 = 118.2 GPU, a O2 / N2 = 3.8. Compared with Example 1, a material with poor gas permeability and high selectivity is used to prepare the perfluoropolymer composite membrane, which is suitable for application scenarios with higher selectivity requirements.

[0076] Example 4

[0077] The perfluoropolymer composite membrane disclosed in this example is prepared by the following steps:

[0078] ​(1) Separation layer solution preparation: 0.5wt.% of the solution was prepared by dissolving the above-mentioned components in Galden HT70 and then standing for 2h to remove bubbles;

[0079] (2) The solution obtained in step (1) was coated on a polysulfone base film, and then dried at room temperature for 10min and heated at 70℃ for 10min to obtain a defective perfluoropolymer composite film;

[0080] (3) The defective perfluoropolymer composite film obtained in step (2) was treated in a Galden HT70 vapor and nitrogen mixed gas (Galden HT70 vapor accounted for 30%) atmosphere at 30℃ for 20min;

[0081] (4) Composite film gradient drying: the composite film obtained in step (3) was dried at 50, 70 and 90℃ in sequence for 10min to obtain the perfluoropolymer composite film of the application.

[0082] The perfluoropolymer composite film was tested for permeation properties and separation properties of pure O2 and N2, and the test results were: J N2 = 35.4 GPU, J O2 = 130.4 GPU, α O2 / N2 = 3.7. Compared with Example 3, the solvent content was low, and the effect of repairing defects was slightly worse, but still had very high selectivity.

[0083] Comparative Example 3

[0084] In the refining process of residue hydroprocessing (RDS), wax oil hydroprocessing and hydrocracking devices, the continuous consumption of hydrogen and the generation of low-carbon hydrocarbons accompanying it make the hydrocarbons in the hydrogen recycle gas accumulate more and more, affecting the hydrogen partial pressure in the reactor and reducing the reaction rate and space-time yield. In order to maintain sufficient hydrogen partial pressure in the reactor, the generated low-carbon hydrocarbons need to be continuously discharged, and a lot of hydrogen will also be discharged. Generally, the H2 concentration in the discharged gas is 75-90% (mol), and membrane separation technology can be used to recover H2 with a purity of more than 95%, and the recovered hydrogen product can be directly returned to the inlet of the new hydrogen compressor or the diesel hydroprocessing device.

[0085] This comparative example discloses a method for recovering hydrogen from high-pressure hydrogen-rich gas discharged from a residue hydroprocessing device in a certain refinery by using gas membrane separation. In this comparative example, a commonly used polyimide membrane in the industry is used.

[0086] As Figure 2 ​As shown, the high-pressure hydrogen-rich gas (feed gas, 55℃, 16.5MPaG) emitted from the residue hydrotreating unit is cooled to 40℃ by the feed gas cooler (a). At this point, most of the condensable components entrained in the gas will condense into liquid. Then, it passes through a gas-liquid separator (b) to separate most of the liquid, and then through a coalescing filter (c) to further remove entrained droplets. The feed gas after liquid removal enters the pre-membrane heater (d) and is heated to approximately 80℃, away from the gas dew point. It then enters the membrane separator (e) for hydrogen enrichment. The membrane separator is filled with polyimide membrane products. Under the influence of the partial pressure difference across the membrane and the membrane itself, hydrogen in the vent gas preferentially permeates through the membrane, while gases such as Cl are retained on the original side. Thus, the exhaust gas from the residue hydrotreating unit forms two outlet gas streams after membrane separation: one is a hydrogen-rich permeate gas containing 98.75% hydrogen, and the other is a hydrogen-lean tail gas containing 35.78% hydrogen. A 5000m³ membrane is required. 2 The hydrogen recovery rate is 93.35%.

[0087] Table 1 Material Balance of Residue Oil Hydrotreating Emission Membrane Separation System

[0088]

[0089]

[0090] Example 5

[0091] This embodiment discloses a method for separating and recovering hydrogen from high-pressure hydrogen-rich gas emitted from a refinery's residue hydrotreating unit using a pollution-resistant perfluoropolymer composite membrane prepared in Example 3. The conditions of the feed gas are exactly the same as those in Comparative Example 3.

[0092] like Figure 3 As shown, the high-pressure hydrogen-rich gas (feed gas 1, 55℃, 16.5MPaG) emitted from the residue hydrotreating unit is mostly separated into liquid by a gas-liquid separator (a), and then further filtered by a coalescing filter (b) to remove entrained droplets. It then enters a membrane separator (c) for hydrogen enrichment. The membrane separator is filled with a perfluoropolymer composite membrane. After passing through the membrane separator, the hydrogen is enriched at a relatively high rate and is called product hydrogen (3) with a purity of 98.77%. The other gas is called tail gas or permeate gas (4), which requires a 700m³ membrane. 2 The hydrogen recovery rate was 93.42%.

[0093] Table 2 Material Balance of Residue Oil Hydrotreating Emission Membrane Separation System

[0094]

[0095] Compared with the comparative example, the membrane separation system of this invention, while maintaining similar product hydrogen concentration and hydrogen recovery rate, reduces the membrane area from 5000 m².2 Reduced to 700m 2 At the same time, no heating or cooling operations are required (which reduces the requirements for pretreatment; it is only necessary to control the operating temperature to be no lower than the dew point of the system), saving a lot of energy.

[0096] Comparative Example 4

[0097] Low-pressure exhaust gas refers to the low-pressure vent air from units such as hydrorefining, gasoline / diesel / kerosene hydrocracking, and wax oil processing. It contains approximately 60-70% H2 at a pressure of ~2.0 MPaG. After membrane separation, the H2 purity can be increased to 90-95%. After pressurization, it can be directly fed into the low-purity hydrogen pipeline network or further purified by the existing PSA system. Similar to high-pressure exhaust gas, the heavy hydrocarbons in low-pressure exhaust gas cause a significant deterioration in membrane performance, requiring strict pretreatment to remove droplets and increase the temperature before entering the membrane. The temperature must be raised to 35 degrees Celsius above the dew point.

[0098] This comparative example discloses a method for recovering hydrogen from low-pressure vent gas in a refinery. In this embodiment, a commonly used polyimide membrane is employed. The low-pressure vent gas has a pressure of 21.7 barG, a temperature of 30–40°C, and a flow rate of 11976 Nm³ / hr, with the following composition:

[0099] Table 3 Gas composition of low-volume gas

[0100] Name [H2] CH4 C2 C3 iC4 nC4 C5 C5+ H2O Composition Percent (%) 77.82 11 4.32 2.83 0.73 1.23 1.8 0.07 0.19

[0101] like Figure 4 As shown, the low-splitting gas enters a coalescing filter (a) to remove any entrained droplets and impurities, and then enters a heater (b) to be heated to 80°C. This ensures that the gas entering the membrane separator is far from the dew point, preventing droplet condensation on the membrane surface. The heated gas then enters a membrane separator (c) for hydrogen enrichment. The membrane separator is filled with a polyimide membrane. After passing through the membrane separator, the hydrogen is enriched at a relatively high rate and is called product hydrogen (3). The purity of the product hydrogen is 92.35%, the hydrogen yield is 91.2%, and the pressure is 10 barG. The other gas is called tail gas or permeate gas (4), which can be used as fuel gas in the fuel gas pipeline network.

[0102] Table 4 Material Balance of Membrane Separation and Recovery System for Hydrogen Recovery from Low-Syllable Gas

[0103]

[0104] Example 6

[0105] This embodiment discloses a method for recovering hydrogen from low-grade gas in a refinery. The method used in this embodiment is the fouling-resistant perfluoropolymer composite membrane prepared in Example 2. The composition, flow rate, temperature, and pressure of this low-grade gas are exactly the same as those in Comparative Example 4.

[0106] like Figure 4 As shown, the low-splitting gas enters a coalescing filter (a) to remove any entrained droplets and impurities, and then enters a heater (b) to be heated to 60°C. This ensures that the gas temperature entering the membrane separator is higher than the dew point (53°C) to prevent droplet condensation on the membrane surface. The heated gas then enters the membrane separator (c) for hydrogen enrichment. The membrane separator is filled with a perfluoropolymer composite membrane. After passing through the membrane separator, the hydrogen is enriched at a relatively high rate and is called product hydrogen (3). The purity of the product hydrogen is 93.14%, the hydrogen yield is 90.4%, and the pressure is not lower than 10 barG. The other gas is called tail gas or permeate gas (4), which can be used as fuel gas in the fuel gas pipeline network.

[0107] Table 5 Material Balance of Membrane Separation and Recovery System for Hydrogen Recovery from Low-Fragment Gas

[0108]

[0109] Compared with the comparative example, using the membrane separation system of this invention, while ensuring similar product hydrogen concentration and hydrogen recovery rate, the composite membrane area is increased from 5600 m². 2 Reduced to 2200m 2 Meanwhile, the heating temperature is relatively low (80°C in the comparative example, 60°C in this example), which saves a lot of energy.

[0110] Example 7

[0111] In the ammonia synthesis process, hydrogen and nitrogen are the raw materials. Hydrogen and nitrogen react to form ammonia under high pressure, temperature, and with the aid of a catalyst. Due to chemical equilibrium limitations, the reactants cannot be completely converted. Unreacted nitrogen and hydrogen are mixed with fresh gas via a circulating compressor before entering the synthesis tower for the ammonia synthesis reaction. Since both nitrogen and hydrogen, as raw materials, contain certain amounts of inert components, such as argon and methane, these components accumulate during the circulation process. This not only consumes circulating compression work but also reduces the effective volume of the synthesis tower, thus affecting the normal ammonia synthesis reaction. Therefore, a portion of the mixed gas in the synthesis tower must be discharged to control the concentration of inert components argon and methane within the tower. This discharged gas is called ammonia purge gas. The discharge volume is approximately ~300 Nm³. 3 / ton of ammonia, the typical composition of this gas is: H2 50-70% (V), NH3 1-8%, N2 18-25%, and the remainder is methane and argon.

[0112] Currently, membrane separation technology is mostly used to recover hydrogen and ammonia from the purge gas of synthetic ammonia. Because the current membrane material has very poor resistance to ammonia, the high-pressure purge gas must be pretreated to remove ammonia before entering the membrane separator. Generally, high-pressure water washing is used in the ammonia absorption tower to remove ammonia, and the volume content of ammonia in the gas phase is controlled to be less than 0.02%, and then the purge gas enters the membrane separator to recover hydrogen therefrom. The permeated gas of the membrane is enriched hydrogen, which is returned to the synthesis system, and the non-permeated gas of the membrane is mainly methane, nitrogen, argon and a small amount of hydrogen, which is used as fuel. The above method has very strict requirements for the operation of the ammonia absorption tower. The ammonia concentration in the gas phase cannot exceed the standard, and the phenomena of mist entrainment and liquid overflow must be absolutely avoided, otherwise it will cause irreversible damage to the downstream separation membrane. In actual application, there are many examples of membrane separator damage caused by problems in the operation of the ammonia absorption tower.

[0113] The prepared perfluoropolymer composite membrane can tolerate ammonia for a long time, and the recovery of hydrogen and liquid ammonia products therefrom can greatly reduce the requirements for pretreatment.

[0114] The embodiment discloses a method for recovering H2 from the purge gas of synthetic ammonia by gas membrane separation. In the example, the prepared pollution-resistant perfluoropolymer composite membrane of embodiment 3 is used. Figure 4 As shown in the flow, the purge gas 1 discharged from the synthetic ammonia system has a discharge pressure of 12.3 MPa, a temperature of 25℃, and a gas amount of 8000 Nm 3 / hr, and the composition is as follows:

[0115] Table 6 Composition of the purge gas discharged from the synthetic ammonia system

[0116] Component [H2] [N2] CH4 Ar [CAT] Composition Percent (%) 63.00 21.84 8.10 3.55 3.50

[0117] The purge gas first enters the filter a to remove the solid particles and liquid droplets that may be entrained in the gas stream. The impurities filtered out are discharged from the bottom of the filter a. The filtered gas passes through the heat exchanger b, and the temperature of the gas is increased to 40℃ after heat exchange. The gas reaching the membrane temperature enters the membrane separator c. The membrane used in the membrane separator is a perfluoropolymer composite membrane. After membrane separation, the permeated gas has a pressure of 2.6 MPa, a temperature of 41℃, and a gas amount of 4887 Nm 3 / hr, and the composition is as follows:

[0118] Table 7 Composition of the permeated gas

[0119] Component [H2] [N2] CH4 Ar [CAT] Composition Percent (%) 87.87 5.09 0.81 1.48 4.75

[0120] The retained gas after membrane separation has a pressure of 12.2 MPa, a temperature of 41℃, and a gas amount of 3113 Nm 3 / hr, and the composition is as shown in Table 8:

[0121] Table 8 Composition of the retained gas after membrane separation

[0122] Component [H2] [N2] CH4 Ar [CAT] Composition Percent (%) 23.97 48.16 19.54 6.79 1.54

[0123] Comparative Example 5

[0124] This comparative example discloses a method for removing CO2 from natural gas using gas membrane separation. The method used in this comparative example employs a commonly used polyimide membrane. Figure 5 As shown, most of the condensable components entrained in the natural gas 1 (raw material gas, 35.2℃, 67.7 barG) are condensed liquids and particles. After being removed by the filter (a), the gas enters the regenerable temperature-switching adsorption unit (b) for further removal of heavy hydrocarbons, mercury vapor, and water. Then, it enters the pre-membrane heater (c) and is heated to about 60℃, far from the gas dew point (the temperature of the natural gas decreases due to the scorch effect when it passes through the membrane filter). Finally, it passes through a primary filter (d) to remove any adsorbent particles that may be entrained in the gas, and then enters the membrane separator (e) for CO2 removal. The membrane separator is filled with polyimide membrane products. After passing through the membrane separator, CO2 and N2 are enriched and discharged from the system (4) at a relatively fast rate. CH4 and other components in the other gas remain on the high-pressure side, becoming the product gas (5), which can enter the absorption unit for further removal of CO2 and other components.

[0125] Table 9 Material Balance Sheet for Gas Membrane Separation System for Removing CO2 from Natural Gas

[0126]

[0127] Example 8

[0128] This embodiment discloses a method for removing CO2 from natural gas using gas membrane separation. The method used in this embodiment is the fouling-resistant perfluoropolymer composite membrane prepared in Example 3. Figure 4 As shown, most of the condensable components entrained in the natural gas 1 to be treated (raw material gas, 35.2°C, 67.7 barG) condense into liquid and particles, which are removed by the filter (a) and then enter the pre-membrane heater (b), where they are heated to about 40°C, slightly higher than the gas dew point. Then they enter the membrane separator (c) for CO2 removal. The membrane separator is filled with the perfluoropolymer composite membrane of the present invention. After passing through the membrane separator, CO2 and N2 are enriched and discharged from the system (3) at a relatively fast rate. CH4 and other components in the other gas remain on the high-pressure side and become the product gas (4) of this process, which can enter the absorption unit for further removal of CO2 and other components.

[0129] Table 10 Material Balance Sheet of the Membrane Separation System for Removing CO2 from Natural Gas in this Embodiment

[0130]

[0131] Compared to the comparative example, this treatment process did not employ temperature-switching adsorption for pretreatment; the feed gas heating temperature was reduced from 60°C to 40°C; and the membrane area was increased from 560 m². 2 Reduced to 40m 2 This saves on the complexity of preprocessing and a significant amount of fixed asset investment and operating costs.

[0132] Example 9

[0133] This embodiment discloses a method for extracting He from natural gas using gas membrane separation, employing the fouling-resistant perfluoropolymer composite membrane prepared in Example 3. Figure 4 As shown, most of the condensable components entrained in the natural gas 1 (raw material gas, 30.0℃, 50.0 barG) are condensable liquids and particles. After being removed by the filter (a), the gas enters the pre-membrane heater (b), which heats it to about 60℃, slightly above the gas dew point, and then enters the membrane separator (c). The membrane separator is filled with perfluorinated membrane products. After passing through the membrane separator, He passes through the membrane at a relatively fast rate and is enriched to obtain product gas (3). (3) enters the PSA or cryogenic treatment unit to further improve the purity of He. CH4 and other components in the other gas remain on the high-pressure side (4) and can enter other processing processes to obtain other product gases, etc.

[0134] Table 11 Material Balance Table for the Separation and Extraction of He from Natural Gas in this Embodiment

[0135] Fluid Position 1 3 4 Flow (Nm 3 / hr)]]> 1450000 151803.9 1298196.1 Temperature (°C) 35 33.1 33.1 Pressure (bar G) 51 1.7 50 Total Molar Comp. Percent H2O 0.085 0.706 0.012 [H2] 0.002 0.016 0.000 CH4 86.885 58.286 90.230 [C2H6] 0.344 0.119 0.371 [C3H8] 0.033 0.009 0.036 IBUTANE 0.079 0.021 0.086 [C4H 10 ]]> 0.007 0.002 0.008 [C5H 12 ]]> 0.006 0.002 0.007 [N2] 9.051 20.661 7.694 HEXANE 0.001 0.0002 0.002 HEPTANE 0.001 0.0001 0.001 HELIUM 0.129 1.114 0.013 CO2 3.377 19.064 1.542 Dew Point (°C) 30.29 9.78 -0.06 Bulk stream Ideal GHV (MJ / m 3 )]]> 34.94 23.30 36.31 Bulk stream Ideal LHV(MJ / m 3 )]]> 31.47 20.98 32.70

[0136] Example 10

[0137] Biogas contains impurities such as water vapor, ammonia, and H2S, which significantly affect membrane performance. Traditional polyimide membranes require rigorous pretreatment to control their negative impact. These pretreatment processes, including dehydration, desulfurization, and deammoniation, are very complex. However, these impurities have no effect on the perfluoropolymer composite membrane of this invention. The pretreatment requirements can be much more lenient.

[0138] This embodiment discloses a method for removing CO2 from biogas using gas membrane separation. The method used in this embodiment is the fouling-resistant perfluoropolymer composite membrane prepared in Example 3. Application Figure 4The process shown, the majority of condensable components entrained in the biogas 1 (raw gas, 35.2°C, 11.0 barG) to be treated are condensed into liquid and particles, which are removed via filter (a) and then enter the membrane pre-heater (b) to be heated to about 45°C, far from the gas dew point. Then enter the membrane separator (c) for CO2 removal. The membrane separator is filled with a perfluoropolymer composite membrane product. After passing through the membrane separator, CO2 and the like are enriched at a faster rate through the membrane and discharged from the system (3), and the other gas, CH4 and the like, remains on the high-pressure side, becoming the product gas (4) of the process.

[0139] Table 12 Material balance table in the process of removing CO2 from biogas in the present embodiment

[0140]

[0141]

[0142] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, and are not limited thereto; although the present application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that the technical solutions recorded in the foregoing embodiments can still be modified, or some or all of the technical features can be replaced by equivalents; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present application.

Claims

1. A method for producing a pollution-resistant perfluoropolymer composite film, characterized by, The method comprises the following steps: S1: Separation layer solution preparation: dissolving particles of a perfluoropolymer in a perfluorinated solvent to prepare a separation layer solution with a concentration of 0.1wt.%-3wt.%, and then standing to remove bubbles; S2: Composite membrane preparation: coating the solution obtained in step S1 on a base membrane, and drying at room temperature for 2-60 min; heating at 40-120°C for 5-240 min to obtain a defective perfluoropolymer composite membrane; S3: Defect repairing of the composite membrane: placing the defective perfluoropolymer composite membrane obtained in step S2 in an atmosphere of a mixed gas of a perfluorinated solvent vapor and an inert gas at 20-50°C, with the perfluorinated solvent vapor accounting for 10-80%, and treating for 10-60 min; S4: Gradient drying of the composite membrane: sequentially drying the composite membrane obtained in step S3 at 40-59, 60-79 and 80-99°C for 5-30 min, 5-30 min and 5-30 min, respectively, to obtain a perfluoropolymer composite membrane.

2. The production method according to claim 1, characterized by, In step S1, the perfluoropolymer is a homopolymer or copolymer of perfluoro-dioxole or perfluoro-dioxolane, or a copolymer of perfluoro-dioxole and perfluoro-dioxolane with tetrafluoroethylene or chlorotrifluoroethylene.

3. The preparation method according to claim 1, characterized in that, In step S2, the base membrane is a flat ultrafiltration membrane, a flat microfiltration membrane, a hollow fiber ultrafiltration membrane or a hollow fiber microfiltration membrane; the base membrane is made of one or more than two of the following materials: polysulfone, polyethersulfone, polyacrylonitrile, polyetherimide, polyvinylidene fluoride, polyimide, polycarbonate, ceramic or glass.

4. The method of claim 1, wherein, In step S3, the inert gas is one or more than two of the following: nitrogen, argon and helium.

5. The pollution-resistant perfluoropolymer composite membrane prepared by the method of any one of claims 1-4.

6. A fouling resistant gas separation membrane system characterized by, A membrane separator using the pollution-resistant perfluoropolymer composite membrane of claim 5.

7. The foul-resistant gas separation membrane system of claim 6, wherein, The pollution-resistant gas separation membrane system further comprises a gas-liquid separator and a precision filter, the outlet of the gas-liquid separator is connected to the inlet of the precision filter, and the outlet of the precision filter is connected to the inlet of the membrane separator. Alternatively, the pollution-resistant gas separation membrane system further comprises a precision filter and a heater, the outlet of the precision filter is connected to the inlet of the heater, and the outlet of the heater is connected to the inlet of the membrane separator.

8. The pollution-resistant gas separation membrane system of claim 6 or 7 for use in gas separation and recovery.

9. Use according to claim 8, characterized in that, The use is specifically for separating and recovering hydrogen from a hydrogen-containing mixed gas, removing acid gas and nitrogen from natural gas and biogas, or extracting helium from natural gas.

10. Use according to claim 9, characterized in that, The hydrogen-containing mixed gas includes high-pressure discharge gas, low-pressure vent gas, FCC dry gas, methanol vent gas, synthetic ammonia vent gas and vent gas in coal-to-oil process.

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