Membrane separation device and method for carbon isotope separation

Abstract

The present invention discloses a membrane separation device and method for carbon isotope separation, including a cylindrical cavity for loading a separation membrane tube, a stainless steel wire mesh reel, and a porous membrane (such as a polyethersulfone resin membrane or a polypropylene membrane), wherein the porous membrane is wrapped around the outer wall of the stainless steel wire mesh reel and completely wrapped around for one week, and liquid glue is used on the side of the reel for adhesion and sealing, and the reel wrapped with the porous membrane is loaded into the cylindrical cavity and sealed at both ends with liquid glue, and the cylindrical cavity loaded with the separation membrane tube has three groups of ports, two of which are at both ends of the axial direction, and one group is on the side wall, the side wall is a light component material flow outlet, one group at the axial end is a feed inlet, and the other group is a heavy component material flow outlet. The advantages of the present invention are: it can achieve a relatively significant carbon isotope separation based on the molecular leakage principle, and the effective proportion of carbon isotopes in the separation medium is high.

Description

Technical Field

[0001] The present invention belongs to the technical field of isotope separation, and in particular relates to a membrane separation device and method for carbon isotope separation. Background Art

[0002] As people pay more attention to health and food safety, the application of stable isotopes in medical diagnosis, food safety and other fields has become more and more extensive and in-depth. At the same time, higher requirements have been put forward for the separation and preparation technology of domestic carbon isotopes. The main application form of carbon isotopes is organic compounds labeled with carbon-13 isotopes. Since carbon is an essential element in organic compounds and carbon-13 isotopes do not have any radioactivity, it has a broad application space. Breath reagents in different compound forms labeled with high-abundance carbon-13 isotopes (>99%) have been used in many clinical applications such as Helicobacter pylori detection, diabetes detection, and liver cirrhosis diagnosis. In addition, various allotropes of carbon show diverse structural characteristics, and experimental research on their isotope effects has been reflected in basic scientific research.

[0003] Carbon has two natural stable isotopes: carbon-12 (98.9%) and carbon-13 (1.1%). Since the natural abundance of carbon-13 isotope is very low, but high-abundance carbon-13 isotope is required in most applications, very high requirements are placed on the separation and preparation technology of carbon isotopes. At present, the industrial production method of carbon isotopes is cryogenic distillation, but the related technology has not yet been domestically produced. In addition, the research on laser method, chemical catalytic exchange method and gas centrifugation method for carbon isotope separation has made progress, but none of them has achieved a certain scale of production.

[0004] Isotope gas diffusion separation technology is mainly used in early uranium enrichment production, and one of its key technologies is the membrane separation device. At present, membrane separation technology mainly uses the selective permeability of the membrane to separate macromolecules or certain particles from the liquid, especially in the fields of water treatment, chemical industry, and medical treatment. With the improvement of chemical production level, the types and performance of separation membranes have also become more diversified, and the economic efficiency of separation membranes has also been continuously improved, laying the foundation for the application and expansion of membrane separation technology. Summary of the invention

[0005] 1. Technical issues to be resolved

[0006] In view of the above problems, the main object of the present invention is to provide a membrane separation device and method for carbon isotope separation so as to solve at least one of the above problems.

[0007] (II) Technical solution

[0008] In order to achieve the above object, as one aspect of the present invention, a membrane separation device for carbon isotope separation is provided, comprising a cylindrical cavity, a stainless steel wire mesh drum and a porous membrane, wherein:

[0009] The porous membrane is wrapped around the outer wall of the stainless steel wire mesh roll and is completely wrapped around it. Liquid glue is used to adhere and seal the side of the stainless steel wire mesh roll. The roll wrapped with the porous membrane is loaded into the cylindrical cavity and sealed at both ends with liquid glue. The cylindrical cavity loaded with the roll has three groups of openings, two of which are at the two axial ends and the other is on the side wall. One group of openings on the side wall is the light component material flow outlet, and one of the two groups of openings at the axial end is the feed inlet and the other is the heavy component material flow outlet.

[0010] In some embodiments, the porous membrane is a polyethersulfone resin membrane or a polypropylene membrane, with a thickness of 0.1±0.05 mm and an average pore size between 30 nm and 100 nm.

[0011] According to another aspect of the present disclosure, a method for separating carbon isotopes using the membrane separation device is provided, comprising:

[0012] Passing the purified gaseous working fluid into the membrane separation device, adjusting the feed inlet pressure and the split ratio; wherein ethylene / carbon monoxide / methane are selected as the gaseous working fluid;

[0013] Liquid nitrogen cold traps are used to collect the materials at the outlets of the light and heavy fractions respectively, and a vacuum pump is used to maintain the air partial pressure of the supply and take-out system within 2Pa;

[0014] After the system runs continuously until the carbon isotope abundance distribution is stable, enriched / depleted carbon isotopes are obtained.

[0015] In some embodiments, the feed inlet pressure, i.e., the pressure before the membrane, is 650-3300 Pa, and the split ratio is 0.45-0.55.

[0016] In some embodiments, the carbon isotope abundance distribution takes more than 10 hours to stabilize, after which sampling is performed and component analysis is performed using a gas mass spectrometer.

[0017] (III) Beneficial effects

[0018] The present invention provides a membrane separation device and method for carbon isotope separation, which can achieve relatively significant carbon isotope separation based on the molecular leakage principle, and the effective proportion of carbon isotopes in the separation medium is high. The device and method are used for the separation and preparation of carbon isotopes, which is technically feasible. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1It is a schematic structural diagram of a membrane separation device for carbon isotope separation according to an embodiment of the present invention.

[0020] Figure 2 4 is a cross-sectional view of a cylindrical cavity according to an embodiment of the present invention.

[0021] Figure 3 It is a schematic diagram of the principle of a membrane separation system of a single separation unit according to an embodiment of the present invention.

[0022]

Description of the accompanying drawings

[0023] 1-feed inlet; 2-heavy component outlet; 3-light component outlet; 4-cylindrical cavity for loading separation membrane tube; 5-stainless steel wire mesh reel; 6-porous membrane;

[0024] 10-membrane separation device; 20-pressure stabilizing container; 30-heavy component receiving bottle; 40-light component receiving bottle; 50-liquid nitrogen cold trap; 60-liquid nitrogen cold trap; 70-vacuum pump; 80-gas mass spectrometer. DETAILED DESCRIPTION

[0025] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with specific embodiments and with reference to the accompanying drawings.

[0026] It should also be noted that the present invention may provide demonstrations of parameters including specific values, but these parameters do not need to be exactly equal to the corresponding values, but can be approximated to the corresponding values ​​within an acceptable error tolerance or design constraint. Directional terms mentioned in the embodiments, such as "upper", "lower", "front", "back", "left", "right", etc., are only referenced to the directions of the drawings and are not intended to limit the scope of protection of the present invention.

[0027] It should be noted that throughout the accompanying drawings, the same elements are represented by the same or similar reference numerals. In the following description, some specific embodiments are only used for descriptive purposes and should not be understood as any limitation to the present invention, but are only examples of embodiments of the present invention. Conventional structures or configurations will be omitted when they may cause confusion in understanding the present invention. It should be noted that the shapes and sizes of the components in the figures do not reflect the actual size and proportion, but only illustrate the contents of the embodiments of the present invention.

[0028] Furthermore, "comprising" does not exclude the presence of elements or steps not listed in a claim. The word "a" or "an" preceding an element does not exclude the presence of a plurality of such elements.

[0029] The ordinal numbers used in the specification and claims, such as "first", "second", "third", etc., to modify the corresponding elements, do not themselves mean that the elements have any ordinal numbers, nor do they represent the order of one element and another element, or the order in the manufacturing method. The use of these ordinal numbers is only used to clearly distinguish a component with a certain name from another component with the same name.

[0030] In one embodiment, if Figure 1-2 As shown, the present invention provides a membrane separation device for carbon isotope separation, which includes a cylindrical cavity 4 for loading a separation membrane tube, a stainless steel wire mesh roll 5, and a porous membrane 6 (such as a polyethersulfone resin membrane or a polypropylene membrane), the porous membrane is wrapped around the outer wall of the stainless steel wire mesh roll, and is completely wrapped around, and liquid glue is used on the side of the roll for adhesion and sealing, 7 rolls wrapped with the same porous membrane are loaded into the cylindrical cavity, and liquid glue is used at both ends to seal (seal the gap between the roll wrapped with the porous membrane and the cylindrical cavity at both ends). The cylindrical cavity loaded with the separation membrane tube (the separation membrane tube is the roll wrapped with the porous membrane) has three groups of ports, two of which are at the axial ends, one group is on the side wall, the side wall is the light component material flow outlet 3, the axial end is a feed inlet 1, and the other group is the heavy component material flow outlet 2.

[0031] Of course, although this embodiment is described by taking 7 reels as an example, the present invention does not limit the number of reels.

[0032] The thickness of the porous membrane is 0.1±0.05 mm, and the average pore size is between 30 nm and 100 nm.

[0033] In another embodiment, if Figure 3 As shown, the membrane separation system for carbon isotope separation includes the membrane separation device 10 for carbon isotope separation, and further includes:

[0034] A pressure stabilizing container 20, connected to the feed inlet 1 of the membrane separation device 10, for providing a stable feed flow;

[0035] A heavy component receiving bottle 30 is connected to the heavy component outflow port 2 of the membrane separation device 10 and is used to receive the heavy component;

[0036] A light component material receiving bottle 40 is connected to the light component material outflow outlet 3 of the membrane separation device 10 and is used to receive the light component material;

[0037] Liquid nitrogen cold traps 50, 60, the heavy component receiving bottle and the light component receiving bottle are respectively located in the liquid nitrogen cold traps 50, 60;

[0038] A vacuum pump 70, connected to the heavy component receiving bottle and the light component receiving bottle, for maintaining the vacuum degree of the system; and

[0039] The gas mass spectrometer 80 is used to analyze the components flowing out of the heavy component flow outlet and the light component flow outlet.

[0040] It should be noted that the membrane separation system may include one membrane separation device or multiple membrane separation devices.

[0041] In another embodiment, the present invention provides a method for carbon isotope separation using the membrane separation device / system. In this embodiment, ethylene / carbon monoxide / methane can be selected as the working medium, the purified gaseous working medium is passed into the membrane separation device, the feed inlet pressure (pressure before the membrane) and the split ratio are adjusted, and liquid nitrogen cold traps are used to collect the materials at the light and heavy fraction flow ends, and a vacuum pump is used to maintain the air partial pressure of the feed and take-off system within 2Pa; after the system is continuously operated until the carbon isotope abundance distribution is stable, concentrated / depleted carbon isotopes are obtained.

[0042] The present invention can realize relatively significant carbon isotope separation based on the molecular leakage principle, and the effective proportion of carbon isotopes in the separation medium is high.

[0043] In the present invention, the porous membrane structure used in the membrane separation method is quite complex, and the channels of the internal pores are interlaced and uneven in width. In order to facilitate research and design, the complex porous membrane is often simplified into a capillary model, which can better analyze the situation when the gas passes through the membrane in practical applications. The porous membrane in the capillary model has a large number of cylindrical holes with a length of l and a diameter of d.

[0044] The interaction between gas and membrane pores when passing through a porous membrane is closely related to the mean free path λ of the gas. When λ>>d and l>>d, the collision between gas molecules is far less than the collision between gas and capillary wall. At this time, the gas will form molecular leakage when passing through the capillary membrane. In the case of molecular leakage, the gas flow rate mainly depends on the mass of the gas molecules themselves. Therefore, in order to achieve the separation effect of gas when passing through the capillary, it should be ensured that the gas passes through the membrane in the form of molecular leakage. In actual production practice, the separation effect of the membrane will vary depending on the type of membrane, the type of gas, etc.

[0045] A porous membrane (such as polyethersulfone resin membrane or polypropylene membrane) is selected as the separation membrane of carbon isotopes, and ethylene / carbon monoxide / methane is selected as the working medium. Combined with the required working parameters, the thickness of the selected porous membrane is 0.1±0.05mm, and the average pore size is between 30nm and 100nm.

[0046] Adjust the pipeline connection of the supply and withdrawal system so that the connection of the system is in normal working condition. Supply the purified working fluid into the above-mentioned membrane separation device, adjust the feed orifice plate so that the feed inlet pressure (pressure before the membrane) is 650~3300Pa. In order to ensure the stability of the feed flow rate, a larger pressure-stabilizing container is connected in parallel to the feed inlet. Adjust the valve of the supply and withdrawal system so that the split ratio is within the range of 0.45~0.55. At the same time, liquid nitrogen cold traps are used to collect materials at the refined and lean ends, and a vacuum pump is used to maintain the vacuum degree of the supply and withdrawal system within 2Pa. After all fluid parameters are adjusted, the system is allowed to run continuously and stably for at least 10 hours. Liquid nitrogen cold traps are used to take materials at the refined and lean ends. At this time, a sample with stable carbon isotope abundance can be obtained.

[0047] The membrane separation system of the present invention is further described in detail below with reference to examples.

[0048] Select ethylene as the working medium, adjust the pipeline connection of the supply and withdrawal system, so that the connection of the system is in normal working condition. Supply the purified ethylene into the above-mentioned membrane separation device, adjust the feed orifice plate so that the feed inlet pressure (pressure before the membrane) is 2660Pa, and in order to ensure the stability of the feed flow rate, a larger pressure-stabilizing container is connected in parallel to the feed inlet. Adjust the valve of the supply and withdrawal system so that the split ratio is 0.5, and use liquid nitrogen cold traps at the refined and lean ends to collect the material, and use a vacuum pump to maintain the vacuum degree of the supply and withdrawal system within 2Pa. After all the fluid parameters have been adjusted, the system is allowed to run continuously and stably for at least 10 hours, and liquid nitrogen cold traps are used to take materials at the refined and lean ends. At this time, a sample with stable carbon isotope abundance can be obtained.

[0049] Before taking the material for analysis, the isotopic composition of natural ethylene is analyzed first. 12 C and 13 There are two stable isotopes of C, with natural abundances of 98.9% and 1.1% respectively. Natural hydrogen has two stable isotopes of H and D, with natural abundances of 99.985% and 0.015% respectively. Hydrogen can be approximately regarded as a monoisotopic element. The isotopic composition and natural abundance of ethylene molecules are shown in Table 1. According to the above analysis assumptions, there are three isotopic components of the separation medium C2H4, but because the content of the component with a relative molecular mass of 30 is extremely low, the membrane separation of ethylene can be further approximated as binary separation.

[0050] Table 1 Isotopic composition of natural ethylene

[0051] Molecular composition Molecular weight <![CDATA[Content in natural C2H4]]> <![CDATA[ 12 C 12 CH4]]> 28 97.73％ <![CDATA[ 13 C 12 CH4]]> 29 2.25％ <![CDATA[ 13 C 13 CH4]]> 30 0.01％

[0052] By using binary separation theory and processing the mass spectrometry analysis results of ethylene, it can be obtained that the single-stage separation coefficient of ethylene by membrane separation is 1.010, which illustrates the feasibility of using the above membrane separation device for carbon isotope separation.

[0053] In summary, the present invention can achieve relatively significant carbon isotope separation based on the molecular leakage principle, and the effective proportion of carbon isotopes in the separation medium is high. It is technically feasible to use the membrane separation device for the separation and preparation of carbon isotopes.

[0054] The specific embodiments described above further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for separating carbon isotopes using a membrane separation device, characterized in that: include: Passing the purified gaseous working medium into the membrane separation device, adjusting the feed inlet pressure and the split ratio; wherein ethylene / carbon monoxide / methane are selected as the gaseous working medium, the feed inlet pressure, i.e. the pressure before the membrane, is 650-3300 Pa, and the split ratio is 0.45-0.55; Liquid nitrogen cold traps are used to collect the materials at the outlets of the light and heavy fractions, respectively, and a vacuum pump is used to maintain the air partial pressure of the supply and take-out system within 2 Pa; After the system is continuously operated until the carbon isotope abundance distribution is stable, the enriched / depleted carbon isotope is obtained; Among them, a membrane separation device for carbon isotope separation includes a cylindrical cavity, a stainless steel wire mesh roll and a porous membrane; The porous membrane is wrapped around the outer wall of the stainless steel wire mesh drum and is completely wrapped around. Liquid glue is used to adhere and seal the side of the stainless steel wire mesh drum. The drum wrapped with the porous membrane is loaded into the cylindrical cavity and sealed at both ends with liquid glue. The cylindrical cavity loaded with the drum has three groups of openings, two of which are at the two ends of the axial direction and the other is on the side wall. One group of openings on the side wall is the light component material flow outlet, and one of the two groups of openings at the axial end is the feed inlet and the other is the heavy component material flow outlet. Wherein, the porous membrane is a polyethersulfone resin membrane or a polypropylene membrane, with a thickness of 0.1±0.05 mm, an average pore size between 30 nm and 100 nm, and the porous membrane satisfies the following conditions: the average free path λ of the gas passing through the porous membrane is >> d and l>>d, so that the gas forms a molecular leakage when passing through the porous membrane, wherein d is the diameter of the cylindrical pore in the capillary model when the porous membrane is simplified to a capillary model, and l is the length of the cylindrical pore.

2. The method according to claim 1, characterized in that: The carbon isotope abundance distribution takes more than 10 hours to stabilize, after which sampling is performed and component analysis is performed using a gas mass spectrometer.

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