Method for extracting helium by coupling membrane separation technology with methanation dehydrogenation and application of method

Abstract

The invention relates to the field of refining, and discloses a method for extracting helium by coupling a membrane separation technology with methanation dehydrogenation and application of the method. The method comprises the following steps: (1) raw material gas passes through a front membrane separation unit to obtain permeable gas subjected to membrane separation and retentate gas not subjected to membrane separation, the permeable gas contains H2, He and CO2, and the retentate gas contains CO, CO2 and methane; (2) mixing the permeate gas and the retentate gas for methanation reaction to remove most of hydrogen, and controlling the hydrogen-carbon ratio in the methanation reaction to meet the condition that H2 / (4CO2 + 3CO) is greater than or equal to 1; and (3) carrying out oxidative dehydrogenation on the mixed gas obtained in the step (2) to further remove hydrogen and generate water vapor, and carrying out dehydration and a rear membrane separation unit to obtain helium. According to the method, efficient separation of hydrogen and helium can be achieved, and high-purity helium is recycled; and methane generated by the methanation reaction is recovered and treated.

Description

Technical Field

[0001] The present invention relates to the field of refining, and in particular to the technical field of extracting helium from industrial tail gas, and in particular to a method and application of extracting helium by coupling membrane separation technology with methanogenic dehydrogenation. Background Art

[0002] Helium, as a strategic resource, mainly exists in natural gas. Natural gas can not only be used as fuel gas and liquefied natural gas, but also as an important raw material in the chemical industry, and has a very high demand. In particular, the inert helium contained in natural gas does not participate in any reaction and can eventually be enriched in BOG gas from LNG plants and vent gas from chemical plants.

[0003] It can be seen that helium is widely present in industrial tail gas with natural gas as raw material, but due to the different helium content and composition and properties of impurity gases in various tail gases, it is still very difficult to extract helium from some tail gases. The most common problem is the large amount of hydrogen in the system. Conventional physical separation technologies including adsorption, absorption, membrane separation, cryogenic separation, etc. and chemical technologies including catalytic combustion oxidative dehydrogenation are not applicable.

[0004] The specific reasons include the following:

[0005] (1) Hydrogen, carbon monoxide and methane all have extremely low boiling points. The application of cryogenic separation technology will cause a large amount of energy consumption and is not economical.

[0006] (2) Hydrogen and helium have the smallest and similar kinetic diameters, while carbon dioxide has a smaller kinetic diameter. It is basically impossible to achieve effective separation using organic polymer membranes with a large flux. Metal membranes such as palladium membranes have a low flux and high cost, and are easily contaminated and poisoned, making it difficult to achieve efficient removal of hydrogen. Alloy adsorption is expensive and has a low yield.

[0007] (3) Other impurities will be introduced during the catalytic combustion reaction.

[0008] (4) A large amount of hydrogen will cause the temperature of the oxidative dehydrogenation reaction to be too high.

[0009] (5) The composition of factory exhaust gas is usually unstable and fluctuates.

[0010] In summary, for helium-containing tail gas such as chemical plant exhaust gas, purely from the perspective of helium production and concentration, this type of helium-containing tail gas has a very high extraction value. However, from the perspective of technology and overall economy, conventional means cannot achieve efficient separation of hydrogen and helium, resulting in poor economic efficiency of purification. This is also the main reason restricting the development of related technologies and processes in this field at home and abroad.

[0011] Therefore, it is of great significance to study and develop a method to extract helium from industrial tail gas. Summary of the invention

[0012] The purpose of the present invention is to overcome the defect problem that conventional means cannot achieve efficient separation of hydrogen and helium in the prior art, and to provide a method and application of extracting helium by coupling membrane separation technology with methanogenic dehydrogenation. The purpose of the present invention is to efficiently remove hydrogen from helium-rich tail gas to recover and purify helium to obtain high-purity helium, and at the same time indirectly convert the hydrogen in the tail gas into usable resources and reduce carbon emissions. It is aimed at tail gas that contains H2, CO2, and CO at the same time and the hydrogen content in the methanogenic reaction gas directly used is insufficient to react CO2 and CO. The method uses membrane separation technology with membrane separation as the core to separate enriched hydrogen and helium, and at the same time uses CO and CO2-rich permeate gas to adjust the methanogenic hydrogen-carbon ratio for methanogenic dehydrogenation, and then deeply removes hydrogen through oxidation reaction, and finally realizes deep dehydrogenation treatment of a gas system containing hydrogen, helium, carbon monoxide and methane, realizes efficient separation of hydrogen and helium, and recovers high-purity helium therefrom; and recovers methane produced by the methanogenic reaction.

[0013] In order to achieve the above object, the first aspect of the present invention provides a method for extracting helium by coupling membrane separation technology with methanogenic dehydrogenation, wherein the method comprises:

[0014] (1) passing the feed gas through a pre-membrane separation unit to obtain a permeate gas that has passed through membrane separation and a retentate gas that has not passed through membrane separation, wherein the permeate gas contains H2, He and CO2, and the retentate gas contains CO, CO2 and methane;

[0015] (2) mixing the permeate gas and the retentate gas to perform a methanation reaction to remove most of the hydrogen, wherein the hydrogen-to-carbon ratio in the methanation reaction is controlled to meet the following conditions: H2 / (4CO2+3CO)≥1;

[0016] (3) The mixed gas obtained in step (2) is subjected to oxidative dehydrogenation to further remove hydrogen and generate water vapor, and then subjected to dehydration and a post-membrane separation unit to obtain helium.

[0017] A second aspect of the present invention provides an application of the aforementioned method in extracting helium from industrial tail gas.

[0018] Through the above technical solution, the technical solution of the present invention has the following beneficial effects:

[0019] (1) The present invention innovatively develops a helium extraction process for chemical off-gas, which can simultaneously remove hydrogen from chemical tail gas containing hydrogen, helium, methane, carbon monoxide and carbon dioxide and purify high-purity helium, while recovering methane;

[0020] (2) The high-purity helium concentration purified by the present invention can reach 99.999%, the yield is greater than 90%, and the methane concentration can reach >85%, which brings considerable economic benefits to the chemical plant.

[0021] (3) In addition, the method provided by the present invention solves the problems of waste of helium resources and high energy consumption of hydrogen-helium separation, and can substantially reduce carbon emissions. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 It is a schematic flow diagram of a method for extracting helium by coupling the membrane separation technology provided by the present invention with methanogenic dehydrogenation.

[0023] Description of Reference Numerals

[0024] S1-raw gas;

[0025] S2-permeate gas separated by the membrane in the front membrane separation unit;

[0026] S3-the retentate gas that has not been separated by the membrane in the front membrane separation unit;

[0027] S4 - gas distribution for methanation reaction from gas storage unit;

[0028] S0-residual gas in the gas tank unit;

[0029] S5-mixed gas obtained after methanation reaction in the methanation reaction unit;

[0030] S6-mixed gas obtained after oxidative dehydrogenation reaction in the oxidative dehydrogenation unit;

[0031] S7-mixed gas obtained after dehydration by the dehydration unit;

[0032] S8-the retentate gas that has not passed through the membrane separation in the post-membrane separation unit (recycling);

[0033] S9-high purity helium separated by membrane in the post-membrane separation unit;

[0034] S10-gas rich in methane, exits the system. DETAILED DESCRIPTION

[0035] The endpoints and any values ​​of the ranges disclosed in this article are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of each range, the endpoint values ​​of each range and the individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed in this article.

[0036] As mentioned above, the first aspect of the present invention provides a method for extracting helium by coupling membrane separation technology with methanogenic dehydrogenation, wherein the method comprises:

[0037] (1) passing the feed gas through a pre-membrane separation unit to obtain a permeate gas that has passed through membrane separation and a retentate gas that has not passed through membrane separation, wherein the permeate gas contains H2, He and CO2, and the retentate gas contains CO, CO2 and methane;

[0038] (2) mixing the permeate gas and the retentate gas to perform a methanation reaction to remove most of the hydrogen, wherein the hydrogen-to-carbon ratio in the methanation reaction is controlled to meet the following conditions: H2 / (4CO2+3CO)≥1;

[0039] (3) The mixed gas obtained in step (2) is subjected to oxidative dehydrogenation to further remove hydrogen and generate water vapor, and then subjected to dehydration and a post-membrane separation unit to obtain helium.

[0040] The inventors of the present invention have found that: (1) Efficient separation of hydrogen and helium is a common problem in the industry. (2) In order to remove hydrogen to the ppm level, it is not easy to achieve this using oxidation technology alone in terms of the existing composition, and it will also cause a huge waste of resources. (3) As an efficient separation method, membrane technology can better separate small molecules such as H2 and He from "large molecules" such as methane and N2. (4) Methanation technology can simultaneously react and remove H2, CO, and CO2, and convert them into methane at the same time, but the hydrogen-to-carbon ratio is an important condition affecting the methanation reaction. Insufficient H2 will reduce the conversion rate and introduce more by-products, such as carbon deposition. It is not easy to adjust the hydrogen-to-carbon ratio without introducing additional materials. (5) This purpose can be achieved by coupling membrane separation technology with methanation, so that the reactants of the methanation reaction can be matched. (6) In addition, this technology can not only be used for dehydrogenation to extract high-purity helium, but also make new attempts and provide new ideas compared to traditional methanation technology.

[0041] According to the present invention, the main reactions of methanation are: CO+3H2→CH4+H2O; CO2+4H2→CH4+2H2O; it can be seen that 1 mol CO requires 3 mol H2, and 1 mol CO2 requires 4 mol H2, so in order to fully carry out the reaction, the ratio of H2 to CO and CO2 must be ≥1 for methanation. In the intake composition specified by the present invention, since the concentrations of CO and CO2 in the intake are much greater than the concentration that can be reacted by the intake H2, it will cause insufficient reaction, side reactions, and easy formation of carbon deposits. Therefore, for the intake of this component, the present invention first enriches hydrogen using a hydrogen separation membrane, and then uses a storage tank to perform the optimal ratio for the methanation reaction, so that H2 can be reacted to the greatest extent. In order to reduce the side reaction rate of the reaction, the proportion of hydrogen is appropriately increased, and the remaining unreacted hydrogen is further reduced to the ppm level through subsequent oxidative dehydrogenation.

[0042] According to the present invention, preferably, 1.25≥H2 / (4CO2+3CO)≥1; more preferably, the hydrogen-carbon ratio satisfies: H2 / (4CO2+3CO)=1.1. In the present invention, it should be noted that the hydrogen-carbon ratio H2 / (4CO2+3CO) refers to the ratio of hydrogen to carbon monoxide and carbon dioxide; if the hydrogen-carbon ratio is too high, it will cause excessive hydrogen to affect subsequent treatment, and ultimately result in poor overall dehydrogenation effect; if the hydrogen-carbon ratio is too low, it will lead to insufficient reaction, while increasing the risk of carbon deposition and causing catalyst deactivation.

[0043] According to the present invention, the device used in the method comprises a front membrane separation unit, a gas storage tank unit, a methanation reaction unit, an oxidative dehydrogenation unit, a dehydration unit and a rear separation membrane unit.

[0044] According to the present invention, the separation membranes provided in the front membrane separation unit and the rear membrane separation unit are the same or different, and the materials of the separation membranes are respectively one or more of polysulfone, polyethersulfone, polyimide, polypropylene, polyethylene, synthetic resin, polyvinylidene fluoride, polytetrafluoroethylene, polyetheretherketone, polybenzimidazole (PBI), block copolymer, cellulose acetate membrane, polycarbonate membrane, polymethyl methacrylate membrane, silica membrane, zeolite molecular sieve membrane, carbon molecular sieve membrane and metal organic framework material (MOFs).

[0045] According to the present invention, preferably, the separation membrane is a polyimide hollow fiber membrane; more preferably, the polyimide hollow fiber membrane is a hollow fiber membrane disclosed in CN115501758B.

[0046] In a further preferred case, in the present invention, the polyimide hollow fiber membrane is a PI hydrogen-helium hollow fiber separation membrane (referred to as Beijing Chemical Research Institute PI separation membrane) prepared by (BHY_SINO) Sinopec (Beijing) Chemical Research Institute Co., Ltd. (formerly known as: Beijing Chemical Research Institute of China Petrochemical Corporation).

[0047] According to the present invention, the separation membrane may be one or more of a spiral membrane, a hollow fiber membrane, a flat membrane and a tubular membrane.

[0048] According to the present invention, the separation membrane may be one or more of a homogeneous membrane, a heterogeneous membrane and a composite membrane.

[0049] According to the present invention, the separation membrane may be a primary membrane and / or a multi-stage membrane. In the present invention, if the separation membrane is a combination of a primary membrane and a multi-stage membrane, it is a multi-stage membrane.

[0050] According to the present invention, in step (1), after the raw gas is separated by the front membrane separation unit, the total concentration of H2 and He in the permeate gas separated by the membrane is greater than 90%; and the total yield of H2 and He in the permeate gas is greater than 85%.

[0051] According to the present invention, the membrane separation conditions include: membrane separation temperature of 0-120°C, transmembrane pressure of 0.1-10MPa; preferably, membrane separation temperature of 10-80°C, transmembrane pressure of 2-5MPa. In addition, in the present invention, it should be noted that the membrane separation conditions refer to the "front membrane separation unit" and / or the "rear membrane separation unit".

[0052] According to the present invention, in step (2), after the methanation reaction, the conversion rate of hydrogen is greater than 99%, and the removal rates of carbon monoxide and carbon dioxide are greater than 99.9%.

[0053] According to the present invention, in step (2), the conditions for the methanation reaction include: a temperature of 500-700°C, within which the reaction activity can be ensured while preventing the CO disproportionation reaction from inhibiting carbon deposition; in addition, the inlet gas temperature is greater than 300°C; it should be noted that the inlet gas refers to the mixed gas in step (2), that is, the mixed gas temperature is greater than 300°C.

[0054] According to the present invention, the methanation reaction can adopt one or more of an adiabatic fixed bed process, an isothermal fixed bed (tube-in-tube) process, a slurry bed process and a fluidized bed process, and can be a cyclic and / or non-cyclic type.

[0055] According to the present invention, preferably, the methanation reaction is a cyclic multi-stage fixed bed process.

[0056] According to the present invention, the catalyst used in the methanation reaction may be a high-temperature catalyst, which includes a Davy-GRC catalyst and / or an MCR-2X catalyst, wherein the nickel content in the high-temperature catalyst is greater than 30% and is resistant to high temperatures above 600°C.

[0057] According to the present invention, the Davy-GRC catalyst includes a GRC-S2S type catalyst.

[0058] According to the present invention, preferably, the catalyst used in the methanation reaction is a GRC-S2S catalyst, which has a shape of a 3.4 mm × 3.5 mm black cylinder and a bulk density of 1450 kg / m 3 The catalyst has a wide application temperature range and has good catalytic activity between 320-670℃. It has a wide applicable pressure range and can maintain structural stability between 3-6MPa. The catalyst life is more than 2 years, with high cost performance.

[0059] In the present invention, the process used for the methanation reaction can be at least one of the new non-circulating VESTA coal-to-natural gas process developed by Denmark's Topsoe, Britain's Davy, Lurgi, Foster Wheeler and Clariant in the United States, and the new non-circulating methanation technology (NRMT) developed by Beijing Huafu, Dalian Ruike, and China Coal Longhua.

[0060] According to the present invention, the raw gas is a gas system containing hydrogen, helium, carbon monoxide and methane, for example, it can be a chemical plant purge gas. In the present invention, chemical plant purge gas is relatively broad. In the present invention, chemical plant purge gas is just an example. The most important thing is that this type of gas must contain hydrogen, carbon monoxide and carbon dioxide at the same time. Secondly, the hydrogen content in the intake composition is lower than that of carbon monoxide and carbon dioxide, resulting in the inability to directly treat it with methanation. Specifically, hydrogen is more than 3 times the mole or volume fraction of CO and 4 times the mole of CO2. The raw gas allows H2 fluctuations, but most of the time it is insufficient, so this set of process adjustment is required.

[0061] According to the present invention, preferably, the raw gas contains one or more of methane, hydrogen, helium, nitrogen, carbon monoxide and carbon dioxide.

[0062] According to the present invention, preferably, the content of hydrogen is 20-30 volume % based on the total volume of the raw gas.

[0063] According to the present invention, in a more preferred case, based on the total volume of the raw gas, the content of hydrogen is 20-30% by volume, the content of methane is 20-50% by volume, the content of helium is 10-20% by volume, the content of nitrogen is 0-10% by volume, the content of carbon monoxide is 5-10% by volume, and the content of carbon dioxide is 1-5% by volume.

[0064] According to the present invention, the total content of carbon monoxide and carbon dioxide is less than 10% by volume.

[0065] According to the present invention, in step (3), the catalyst used in the oxidative dehydrogenation is a metal oxide; preferably, the metal oxide is selected from one or more of copper oxide, iron oxide, chromium oxide, zinc oxide and magnesium oxide; more preferably, the metal oxide is copper oxide.

[0066] According to the present invention, in step (3), the conditions for the oxidative dehydrogenation include: a temperature of 200-500°C, a space velocity of 1 m / s 3 / m 3 ·h-1000m 3 / m 3 ·h; preferably, the temperature is 300-400°C, the air speed is 100m 3 / m 3 ·h-300m 3 / m 3 ·h.

[0067] According to the present invention, in step (3), the dehydration is carried out by adsorption dehydration by a dehydration unit, which is achieved by molecular sieve pressure swing adsorption technology; the adsorbent can be selected from one or more of 3A, 4A and 13X molecular sieves, the adsorption pressure is 0.01-10Mpa, and the air velocity is 1m 3 / m 3 ·h-100m 3 / m 3 ·h. 13X molecular sieve is preferred as adsorbent, adsorption pressure is 2-5Mpa, space velocity is 3m 3 / m 3 ·h-20m 3 / m 3 ·h.

[0068] According to a particularly preferred embodiment of the present invention, Figure 1 As shown, the present invention provides a method for extracting helium by coupling membrane separation technology with methanogenic dehydrogenation, wherein the method comprises:

[0069] (1) The raw gas S1 passes through the front membrane separation unit to obtain the permeate gas S2 that passes through the membrane separation and the retentate gas S3 that does not pass through the membrane separation;

[0070] The raw material gas S1 contains hydrogen, helium, carbon monoxide, methane, nitrogen and carbon dioxide.

[0071] The permeate gas S2 mainly contains H2, He and CO2, and also contains methane, nitrogen and carbon monoxide;

[0072] The retentate gas S3 mainly contains CO, CO2 and methane, and also contains helium, nitrogen and hydrogen;

[0073] (2) The permeate gas S2 enters the methanation reaction unit, and the retentate gas S3 enters the gas storage tank unit. The hydrogen-carbon ratio in the methanation reaction is controlled to meet the following conditions: 1.25≥H2 / (3CO+4CO2)≥1, that is, the methanation reaction unit is gasified S4 by monitoring the hydrogen concentration, so that the hydrogen is basically completely reacted without generating carbon deposits. In the methanation reaction unit, hydrogen and helium are enriched in this process. S2 enters the methanation reactor after heat exchange and is mixed with the gas storage tank gasification S4 to perform a methanation reaction of hydrogen, carbon monoxide and carbon dioxide, so that most of the hydrogen is consumed in this process and forms a mixed gas S5 of water, methane and hydrogen and helium;

[0074] (3) The mixed gas S5 obtained in step (2) is passed through an oxidative dehydrogenation reaction unit (reactor), in which hydrogen and an oxidant react fully to be removed and generate water vapor, forming a mixed gas S6 containing a certain amount of water vapor, methane and a large amount of helium. The waste heat of S6 is recovered to be used as medium-pressure steam or to preheat S2. After heat exchange, S6 enters the dehydration section to completely remove water vapor and then enters the post-membrane separation unit. After separation, a retentate gas S8 containing a large amount of methane is formed. S8 is mixed with S0 to form a methane-rich S10 for reuse or deep-cold liquefaction. High-purity helium S9 is formed on the permeate side.

[0075] A second aspect of the present invention provides an application of the aforementioned method in extracting helium from industrial tail gas.

[0076] The present invention will be described in detail below through examples.

[0077] In the following examples and comparative examples:

[0078] The gas composition (volume fraction) parameters were measured by gas chromatography detection method;

[0079] Copper oxide: MINSTRONG, chemically synthesized highly active copper oxide catalyst, MC-F series, granular.

[0080] 13X molecular sieve: Zibo Henghuan Aluminum Co., Ltd., synthetic zeolite sodium X (13X), 13XAGP molecular sieve HHMM-304.

[0081] Example 1

[0082] This embodiment is intended to illustrate the extraction of helium using the method of the present invention.

[0083] A certain helium-containing chemical tail gas S1 includes 19% helium, 44% methane, 3% nitrogen, 2.83% carbon dioxide, 23% hydrogen and 6% carbon monoxide; the intake flow rate of the tail gas composition is normalized.

[0084] according to Figure 1 The membrane separation technology provided by the present invention is coupled with a methanogenic dehydrogenation method for extracting helium to extract helium, which specifically includes the following steps:

[0085] (1) The raw gas S1 passes through the front membrane separation unit to obtain the permeate gas S2 that passes through the membrane separation and the retentate gas S3 that does not pass through the membrane separation;

[0086] The front membrane separation unit uses the PI separation membrane of Beijing Institute of Chemical Industry (polyimide-based hollow fiber membrane prepared in Example 1 of CN115501758B), the temperature is 25°C, and the operating pressure is 3.5MPa;

[0087] (2) The permeate gas S2 enters the methanation reaction unit, and the retentate gas S3 enters the gas storage tank unit. The hydrogen-carbon ratio in the methanation reaction is controlled to meet the following conditions: H2 / (3CO+4CO2)=1.1, that is, the methanation reaction unit is gasified S4 by monitoring the hydrogen concentration, so that the hydrogen is basically completely reacted without generating carbon deposits. In the methanation reaction unit, hydrogen and helium are enriched in this process. S2 enters the methanation reactor after heat exchange and is mixed with the gas storage tank gasification S4 to perform a methanation reaction of hydrogen, carbon monoxide and carbon dioxide, so that most of the hydrogen is consumed in this process and forms a mixed gas S5 of water, methane and hydrogen and helium;

[0088] Among them, the methanation process uses a circulating multi-stage fixed bed process, and the methanation temperature is controlled at 600°C;

[0089] (3) The mixed gas S5 obtained in step (2) is passed through an oxidative dehydrogenation reaction unit (reactor), in which hydrogen and an oxidant react fully to be removed and generate water vapor, forming a mixed gas S6 containing a certain amount of water vapor, methane and a large amount of helium. The waste heat of S6 is recovered to be used as medium-pressure steam or to preheat S2. After heat exchange, S6 enters the dehydration section to completely remove water vapor and then enters the post-membrane separation unit. After separation, a retentate gas S8 containing a large amount of methane is formed. S8 is mixed with S0 to form a methane-rich S10 for reuse or deep-cold liquefaction. High-purity helium S9 is formed on the permeate side.

[0090] Among them, copper oxide is used as the oxidant for chemical dehydrogenation, and the air velocity is 100m 3 / m 3 h, temperature 400℃;

[0091] PSA molecular sieve pressure swing adsorption is used for dehydration and decarbonization, 13X molecular sieve is used as adsorbent, adsorption pressure is 5Mpa, space velocity is m 3 / m 3 ·h;

[0092] The post-membrane separation unit selected the PI separation membrane of Beijing Institute of Chemical Industry (polyimide-based hollow fiber membrane prepared in Example 1 of CN115501758B), the temperature was 25°C, and the operating pressure was 3.5 MPa.

[0093] The treatment results are shown in Table 1-1 and Table 1-2. It should be noted that S0 has no utilization value for the time being and is directly discharged from the system; among them, the helium concentration is >99.9999%, the yield is >90%, the methane-rich concentration is >90%, and at the same time >84% of CO2 is converted into methane and collected for reuse to reduce carbon emissions.

[0094] Table 1-1

[0095]

[0096]

[0097] Table 1-2

[0098]

[0099] Note: H2 / (4CO2+3CO) represents the hydrogen-carbon ratio, which can also be expressed as H2-CO2 / (3CO+4CO2), that is, the amount of hydrogen is several times that of CO and CO2, which expresses whether the reaction can be carried out completely. The above two formulas express the same formula.

[0100] Example 2

[0101] This embodiment is intended to illustrate the extraction of helium using the method of the present invention.

[0102] Helium is extracted in the same manner as in Example 1, except that:

[0103] A certain helium-containing chemical tail gas S1 includes 19% helium, 48% methane, 4% nitrogen, 1% carbon dioxide, 20% hydrogen and 6% carbon monoxide; wherein, the intake flow rate of the tail gas composition is normalized.

[0104] according to Figure 1 Schematic diagram of the process of extracting helium by coupling membrane separation technology with methanogenic dehydrogenation. The difference is that:

[0105] Among them, H2 / (4CO2+3CO) in the mixed gas = 1.1.

[0106] The front membrane separation unit uses the PI separation membrane of Beijing Institute of Chemical Industry (polyimide-based hollow fiber membrane prepared in Example 1 of CN115501758B), the temperature is 10°C, and the operating pressure is 1.5MPa;

[0107] The methanation process uses a circulating multi-stage fixed bed process, and the methanation temperature is controlled at 610°C;

[0108] Chemical dehydrogenation uses copper oxide as the oxidant, with an air velocity of 180m 3 / m 3 h, temperature, 305°C;

[0109] PSA molecular sieve pressure swing adsorption is used for dehydration and decarbonization, 13X molecular sieve is used as adsorbent, adsorption pressure is 4.2Mpa, space velocity is 12m 3 / m 3 ·h;

[0110] The post-membrane separation unit selected the PI separation membrane of Beijing Institute of Chemical Industry (polyimide-based hollow fiber membrane prepared in Example 1 of CN115501758B), with a temperature of 80°C and an operating pressure of 4 MPa.

[0111] The treatment results are shown in Table 2-1 and Table 2-2, wherein the helium concentration is >99.999%, the yield is >90%, the methane-rich concentration is >90%, and at the same time >77% of CO2 is converted into methane and collected for reuse to reduce carbon emissions.

[0112] Table 2-1

[0113] Logistics / composition% Helium Methane Nitrogen <![CDATA[CO2]]> hydrogen water CO total flow 0.19 0.48 0.04 0.01 0.20 0.00 0.07 1.00 Raw gas S1 19.28 48.15 4.09 1.43 20.10 0.00 6.96 100.00 flow 0.17 0.00 0.00 0.00 0.17 0.00 0.00 0.36 Front membrane permeate gas S2 48.79 1.22 0.16 1.09 48.31 0.00 0.44 100.00 flow 0.02 0.48 0.04 0.01 0.03 0.00 0.07 0.64 Front membrane retentate gas S3 2.99 74.05 6.26 1.62 4.52 0.00 10.56 100.00 flow 0.01 0.36 0.03 0.01 0.03 0.00 0.04 0.48 Gas tank outlet S4 3.03 74.92 6.33 1.49 5.21 0.00 9.01 100.00 flow 0.19 0.37 0.03 0.01 0.20 0.00 0.04 0.84 After mixing S2+S4 22.47 43.61 3.71 1.32 23.53 0.00 5.37 100.00 flow 0.19 0.42 0.03 0.00 0.02 0.07 0.00 0.73 Methanation S5 25.94 58.06 4.28 0.00 2.48 9.24 0.00 100.00 flow 0.19 0.42 0.03 0.00 0.00 0.09 0.00 0.73 Chemical dehydrogenation S6 25.94 58.06 4.28 0.00 0.00 11.72 0.00 100.00 flow 0.19 0.42 0.03 0.00 0.00 0.00 0.00 0.64 Dehydration S7 29.38 65.77 4.85 0.00 0.00 0.00 0.00 100.00 flow 0.18 0.00 0.00 0.00 0.00 0.00 0.00 0.18 Post-membrane penetration S9 99.99989 0.00003 0.00002 0.00000 0.00005 0.00001 0.00000 100.00 flow 0.01 0.42 0.03 0.00 0.00 0.00 0.00 0.46 Post-membrane retentate S8 2.04 91.23 6.72 0.00 0.00 0.00 0.01 100.00

[0114] Table 2-2

[0115]

[0116] Example 3

[0117] This embodiment is intended to illustrate the extraction of helium using the method of the present invention.

[0118] Helium is extracted in the same manner as in Example 1, except that:

[0119] A certain helium-containing chemical tail gas S1 includes 15% helium, 44% methane, 8% nitrogen, 4% carbon dioxide, 22% hydrogen and 5% carbon monoxide; wherein, the intake flow rate of the tail gas composition is normalized.

[0120] according to Figure 1 Schematic diagram of the process of extracting helium by coupling membrane separation technology with methanogenic dehydrogenation. The difference is that:

[0121] Among them, H2 / (4CO2+3CO) in the mixed gas = 1.1.

[0122] The front membrane separation unit uses the PI separation membrane of Beijing Institute of Chemical Industry (polyimide-based hollow fiber membrane prepared in Example 1 of CN115501758B), the temperature is 45°C, and the operating pressure is 3MPa;

[0123] The methanation process uses a circulating multi-stage fixed bed process, and the methanation temperature is controlled at 510°C;

[0124] Chemical dehydrogenation uses copper oxide as the oxidant, with an air velocity of 300m 3 / m 3 h, temperature 360℃;

[0125] PSA molecular sieve pressure swing adsorption is used for dehydration and decarbonization, 13X molecular sieve is used as adsorbent, adsorption pressure is 5Mpa, and air velocity is 20m 3 / m 3 ·h;

[0126] The post-membrane separation unit selected the PI separation membrane of Beijing Institute of Chemical Industry (polyimide-based hollow fiber membrane prepared in Example 1 of CN115501758B), the temperature was 25°C, and the operating pressure was 3.5 MPa.

[0127] The treatment results are shown in Table 3-1 and Table 3-2, where the helium concentration is >99.999%, the yield is >90%, the methane-rich concentration is >85%, and at the same time >65% of CO2 is converted into methane and collected for reuse to reduce carbon emissions.

[0128] Table 3-1

[0129] No.\Composition% Helium Methane Nitrogen <![CDATA[CO2]]> hydrogen water CO total flow 0.15 0.45 0.08 0.04 0.22 0.00 0.05 1.00 Raw gas S1 15.21 44.70 8.25 4.40 22.24 0.00 5.20 100.00 flow 0.14 0.00 0.00 0.01 0.19 0.00 0.00 0.35 Front membrane permeate gas S2 39.66 1.17 0.32 3.44 55.08 0.00 0.34 100.00 flow 0.02 0.44 0.08 0.03 0.03 0.00 0.05 0.65 Front membrane retentate gas S3 2.32 67.66 12.43 4.90 4.93 0.00 7.76 100.00 flow 0.01 0.22 0.04 0.02 0.02 0.00 0.02 0.33 Gas tank outlet S4 2.31 67.23 12.35 5.21 5.71 0.00 7.18 100.00 flow 0.14 0.22 0.04 0.03 0.21 0.00 0.02 0.67 After mixing S2+S4 21.47 33.33 6.18 4.30 31.04 0.00 3.67 100.00 flow 0.14 0.28 0.04 0.00 0.02 0.08 0.00 0.57 Methanation S5 25.54 49.13 7.35 0.00 3.37 14.59 0.00 100.00 flow 0.14 0.28 0.04 0.00 0.00 0.10 0.00 0.57 Chemical dehydrogenation S6 25.54 49.13 7.35 0.00 0.00 17.97 0.00 100.00 flow 0.14 0.28 0.04 0.00 0.00 0.00 0.00 0.46 Dehydration S7 31.14 59.89 8.96 0.00 0.00 0.00 0.00 100.00 flow 0.14 0.00 0.00 0.00 0.00 0.00 0.00 0.14 Post-membrane penetration S9 99.99987 0.00002 0.00003 0.00000 0.00007 0.00001 0.00000 100.00 flow 0.01 0.28 0.04 0.00 0.00 0.00 0.00 0.33 Post-membrane retentate S8 2.21 85.06 12.73 0.00 0.00 0.00 0.00 100.00

[0130] Table 3-2

[0131]

[0132] Example 4

[0133] This embodiment is intended to illustrate the extraction of helium using the method of the present invention.

[0134] Helium is extracted in the same manner as in Example 1, except that:

[0135] Among them, H2 / (4CO2+3CO) in the mixed gas = 1.25.

[0136] The treatment results are shown in Table 4-1 and Table 4-2, where the helium concentration is >99.999%, the yield is >91%, the methane-rich concentration is >90%, and at the same time >58% of CO2 is converted into methane and collected for reuse to reduce carbon emissions.

[0137] Table 4-1

[0138] Logistics / composition% Helium Methane Nitrogen <![CDATA[CO2]]> hydrogen water CO total flow 0.19 0.45 0.03 0.03 0.24 0.00 0.06 1.00 Raw gas S1 19.21 44.80 3.33 2.83 23.80 0.00 6.02 100.00 flow 0.17 0.00 0.00 0.01 0.20 0.00 0.00 0.39 Front membrane permeate gas S2 44.34 1.03 0.12 1.96 52.20 0.00 0.35 100.00 flow 0.02 0.44 0.03 0.02 0.03 0.00 0.06 0.61 Front membrane retentate gas S3 3.15 72.77 5.39 3.39 5.66 0.00 9.65 100.00 flow 0.01 0.27 0.02 0.01 0.02 0.00 0.03 0.37 Gas tank outlet S4 3.17 73.37 5.44 3.23 5.94 0.00 8.84 100.00 flow 0.18 0.27 0.02 0.02 0.23 0.00 0.03 0.76 After mixing S2+S4 24.31 36.22 2.70 2.58 29.70 0.00 4.48 100.00 flow 0.18 0.32 0.02 0.00 0.07 0.06 0.00 0.66 Methanation S5 27.77 48.48 3.09 0.44 10.09 9.61 0.51 100.00 flow 0.18 0.32 0.02 0.00 0.00 0.13 0.00 0.66 Chemical dehydrogenation S6 27.77 48.48 3.09 0.44 0.00 19.70 0.51 100.00 flow 0.18 0.32 0.02 0.00 0.00 0.00 0.00 0.53 Dehydration S7 34.78 60.71 3.87 0.00 0.00 0.00 0.64 100.00 flow 0.18 0.00 0.00 0.00 0.00 0.00 0.00 0.18 Post-membrane penetration S9 99.99982 0.00002 0.00001 0.00002 0.00009 0.00001 0.00003 100.00 flow 0.01 0.32 0.02 0.00 0.00 0.00 0.00 0.36 Post-membrane retentate S8 2.60 90.67 5.78 0.03 0.00 0.00 0.96 100.00

[0139] Table 4-2

[0140]

[0141] Example 5

[0142] This embodiment is intended to illustrate the extraction of helium using the method of the present invention.

[0143] Helium is extracted in the same manner as in Example 1, except that:

[0144] Among them, H2 / (4CO2+3CO)=1 in the mixed gas.

[0145] The treatment results are shown in Table 5-1 and Table 5-2, where the helium concentration is >99.999%, the yield is >93%, the methane-rich concentration is >90%, and at the same time >80% of CO2 is converted into methane and collected for reuse to reduce carbon emissions.

[0146] Table 5-1

[0147]

[0148]

[0149] Table 5-2

[0150]

[0151] Comparative Example 1

[0152] Helium is extracted in the same manner as in Example 1, except that:

[0153] Among them, H2 / (4CO2+3CO) in the mixed gas = 1.3.

[0154] The treatment results are shown in Table 6-1 and Table 6-2, among which the hydrogen content obviously exceeds the standard, the helium concentration is lower than that in Example 1, and the yield, methane-rich concentration, and CO2 recovery rate are all lower than those in Example 1. Excessive hydrogen will increase the separation burden and dehydrogenation burden of the rear membrane unit, resulting in poor results.

[0155] Table 6-1

[0156]

[0157]

[0158] Table 6-2

[0159]

[0160] Comparative Example 2

[0161] Helium is extracted in the same manner as in Example 1, except that:

[0162] This process does not include a pre-membrane unit, i.e., direct methanation reaction.

[0163] The treatment results are shown in Table 7-1 and Table 7-2, among which the hydrogen content exceeds the standard, the helium concentration cannot reach the high-purity level and is lower than that in Example 1, the methanation reaction rate is low, and the CO2 recovery rate is much lower than that in Example 1. The front membrane unit and the gas storage tank play the role of adjusting the hydrogen-carbon ratio of the methanation reaction, so that the reaction can be carried out under the optimal atmosphere, thereby improving the reaction efficiency. Obviously, the direct methanation effect is poor, and the components cannot be fully reacted.

[0164] Table 7-1

[0165]

[0166]

[0167] Table 7-2

[0168]

[0169] Comparative Example 3

[0170] Helium is extracted in the same manner as in Example 1, except that:

[0171] The chemical tail gas S1 components include 5% helium, 63% methane, 8% nitrogen, 4% carbon dioxide, 14% hydrogen and 3% carbon monoxide; among them, the intake flow rate of the tail gas composition is normalized.

[0172] The treatment results are shown in Table 8-1 and Table 8-2, among which, methane exceeds the standard, the helium concentration cannot reach the high purity level, the methane-rich concentration is reduced, and the CO2 recovery rate is much lower than that in Example 1. Due to the low hydrogen concentration and the increased gas mixing volume in the gas storage tank, the methanation effect is poor.

[0173] Table 8-1

[0174]

[0175]

[0176] Table 8-2

[0177]

[0178] Comparative Example 4

[0179] Helium is extracted in the same manner as in Example 1, except that:

[0180] No methanogenic dehydrogenation unit is provided.

[0181] The treatment results are shown in Table 9-1 and Table 9-2. Since the dehydrogenation burden of the oxidation unit alone is too heavy and the reaction temperature is too high, the dehydrogenation effect is poor. In the end, the hydrogen, water, and CO2 exceed the standard, the helium concentration cannot reach the 5N level, CO cannot be converted into methane, the CO2 emission reduction is 0, and the methane-rich concentration is only 27.61%, which cannot meet the use standard.

[0182] Table 9-1

[0183] Logistics / composition% Helium Methane Nitrogen <![CDATA[CO2]]> hydrogen water CO total flow 0.19 0.45 0.03 0.03 0.24 0.00 0.06 1.00 Raw gas S1 19.21 44.80 3.33 2.83 23.80 0.00 6.02 100.00 flow 0.17 0.00 0.00 0.01 0.20 0.00 0.00 0.39 Front membrane permeate gas S2 44.34 1.03 0.12 1.96 52.20 0.00 0.35 100.00 flow 0.02 0.44 0.03 0.02 0.03 0.00 0.06 0.61 Front membrane retentate gas S3 3.15 72.77 5.39 3.39 5.66 0.00 9.65 100.00 flow 0.17 0.00 0.00 0.01 0.00 0.20 0.00 0.39 Chemical dehydrogenation S6 44.34 1.03 0.12 1.96 0.00 52.20 0.35 100.00 flow 0.17 0.00 0.00 0.00 0.00 0.00 0.00 0.18 Dehydration S7 96.66 2.25 0.25 0.00 0.01 0.06 0.76 100.00 flow 0.16 0.00 0.00 0.00 0.00 0.00 0.00 0.16 Post-membrane permeation S10 99.9965 0.0000 0.0000 0.0001 0.0032 0.0002 0.0000 100.00 flow 0.01 0.00 0.00 0.00 0.00 0.00 0.00 0.01 Post-membrane retentate S8 59.18 27.61 3.08 0.04 0.03 0.77 9.28 100.00

[0184] Table 9-2

[0185]

[0186] In summary, the concentration of high-purity helium purified by the present invention can reach 99.999%, the helium yield is greater than 90%, and the methane concentration can reach >85%, thereby increasing considerable economic benefits for chemical plants.

[0187] The preferred embodiments of the present invention are described in detail above, but the present invention is not limited thereto. Within the technical concept of the present invention, the technical solution of the present invention can be subjected to a variety of simple modifications, including the combination of various technical features in any other suitable manner, and these simple modifications and combinations should also be regarded as the contents disclosed by the present invention and belong to the protection scope of the present invention.

Claims

1. A method for extracting helium by coupling membrane separation technology with methanogenic dehydrogenation, characterized in that: The method includes: (1) passing the feed gas through a pre-membrane separation unit to obtain a permeate gas that has passed through membrane separation and a retentate gas that has not passed through membrane separation, wherein the permeate gas contains H2, He and CO2, and the retentate gas contains CO, CO2 and methane; (2) mixing the permeate gas and the retentate gas to perform a methanation reaction to remove most of the hydrogen, wherein the hydrogen-to-carbon ratio in the methanation reaction is controlled to meet the following conditions: H2 / (4CO2+3CO)≥1; (3) The mixed gas obtained in step (2) is subjected to oxidative dehydrogenation to further remove hydrogen and generate water vapor, and then subjected to dehydration and a post-membrane separation unit to obtain helium.

2. The method according to claim 1, wherein: 1.25≥H2 / (4CO2+3CO)≥1.

3. The method according to claim 1 or 2, wherein: The separation membranes provided in the front membrane separation unit and the rear membrane separation unit are the same or different, and the materials of the separation membranes are respectively one or more of polysulfone, polyethersulfone, polyimide, polypropylene, polyethylene, synthetic resin, polyvinylidene fluoride, polytetrafluoroethylene, polyetheretherketone, polybenzimidazole, block copolymer, cellulose acetate membrane, polycarbonate membrane, polymethyl methacrylate membrane, silicon dioxide membrane, zeolite molecular sieve membrane, carbon molecular sieve membrane and metal organic framework material; And / or, the separation membrane is one or more of a rolled membrane, a hollow fiber membrane, a flat membrane and a tubular membrane.

4. The method according to claim 3, wherein: The separation membrane is a polyimide hollow fiber membrane.

5. The method according to any one of claims 1 to 4, wherein: The total concentration of H2 and He in the permeate gas is greater than 90%; And / or, the total yield of H2 and He in the permeate gas is greater than 85%.

6. The method according to any one of claims 1 to 5, wherein: After the methanation reaction, the conversion rate of hydrogen is greater than 99%, and the removal rates of carbon monoxide and carbon dioxide are greater than 99.9%.

7. The method according to any one of claims 1 to 6, wherein: The raw gas is the off-gas from a chemical plant; Preferably, the feed gas contains one or more of methane, hydrogen, helium, nitrogen, carbon monoxide and carbon dioxide; Preferably, based on the total volume of the raw gas, the content of hydrogen is 20-30 volume %; More preferably, based on the total volume of the raw gas, the content of hydrogen is 20-30% by volume, the content of methane is 20-50% by volume, the content of helium is 10-20% by volume, the content of nitrogen is 0-10% by volume, the content of carbon monoxide is 5-10% by volume, and the content of carbon dioxide is 1-5% by volume; More preferably, the total volume content of carbon monoxide and carbon dioxide is less than 10 volume %.

8. The method according to claim 1, wherein: The membrane separation conditions include: membrane separation temperature of 0-120°C, membrane pressure of 0.1-10MPa; Preferably, the membrane separation temperature is 25-80°C and the transmembrane pressure is 2-5 MPa.

9. The method according to claim 1, wherein: The conditions of the methanation reaction include: a temperature of 500-700°C; And / or, in step (2), the mixed gas temperature is greater than 300°C.

10. The method according to claim 1, wherein: The catalyst used in the oxidative dehydrogenation is a metal oxide; Preferably, the metal oxide is selected from one or more of copper oxide, iron oxide, chromium oxide, zinc oxide and magnesium oxide; Preferably, the conditions for the oxidative dehydrogenation include: a temperature of 200-500°C, a space velocity of 1 m / s 3 / m 3 ·h-1000m 3 / m 3 ·h.

11. The method according to claim 1, wherein: The dehydration is achieved by adsorption dehydration in a dehydration unit through molecular sieve pressure swing adsorption technology; and / or, the adsorbent is selected from one or more of 3A, 4A and 13X molecular sieves; And / or, adsorption pressure is 0.01-10Mpa, air velocity is 1m 3 / m 3 ·h-1000m 3 / m 3 ·h; Preferably, the adsorbent is 13X molecular sieve; Preferably, the adsorption pressure is 2-5Mpa, and the air velocity is 3m 3 / m 3 ·h-20m 3 / m 3 ·h.

12. Use of the method according to any one of claims 1 to 11 in extracting helium from industrial tail gas.

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