Apparatus and method for separating carbon dioxide and nitrogen by inorganic membrane

Abstract

This invention discloses an apparatus and method for separating carbon dioxide and nitrogen using an inorganic membrane. The apparatus includes at least: a metal outer shell with a mixed gas inlet, a permeate-side outlet, and a residual gas outlet; multiple membrane tubes arranged laterally within the outer shell, sealed and fixed within the shell by a tube sheet to form a shell side and a tube side; the membrane tubes are a structure combining a support and a separation membrane, the separation membrane being a molecular sieve membrane; and multiple baffles arranged radially and alternately along the membrane tubes to form a baffled gas channel. This invention, by using a microporous inorganic molecular sieve membrane as the separation medium and incorporating baffles outside the membrane tubes within the outer shell, effectively increases the separation efficiency of carbon dioxide and nitrogen, thereby significantly improving the performance of membrane separation in capturing carbon dioxide from flue gas.

Description

Technical Field

[0001] This invention relates to the field of petrochemical gas separation technology, and in particular to an apparatus and method for separating carbon dioxide and nitrogen using inorganic membranes. Background Technology

[0002] Carbon dioxide capture has become a key global concern. Currently, methods for carbon dioxide capture mainly include chemical absorption, physical adsorption, cryogenic separation, and membrane separation. Among these, membrane separation utilizes the pressure difference across a membrane as the driving force, achieving separation based on the different permeation rates of carbon dioxide and other components within the membrane. It features high efficiency, low energy consumption, and easy equipment integration. In recent years, with the continuous development of membrane fabrication technology, more and more scholars have focused their research on membrane separation methods.

[0003] Existing technologies include solutions that use transfer-promoting membranes as separation membrane materials. For example, Chinese patent application CN109423344A discloses a process system for removing carbon dioxide from syngas. This system uses a transfer-promoting membrane as the membrane material for gas separation. The syngas is dehumidified, humidified, and dust-removed. Foam carried by the gas is removed by a demister at the top of a water washing tower. The gas exiting the tower passes through a gas-liquid separator and a buffer tank before entering a primary membrane separator. The gas retained in the primary membrane separator is purified gas with carbon dioxide removed. The permeate gas is compressed and heat-exchanged before entering a secondary membrane separator. The permeate gas in the secondary membrane separator is carbon dioxide gas. Because this type of solution uses a transfer-promoting membrane as the separation membrane material, the separation efficiency of the transfer-promoting membrane is relatively low. Furthermore, the separation requires water to wet the membrane surface. If the moisture content in the transfer-promoting membrane decreases, the separation performance will also decrease, making it difficult to achieve stable separation over a long period.

[0004] In addition, Chinese patent application CN112752603A discloses a gas separation device that uses an inorganic zeolite membrane attached to a support. The support allows gas to pass through a porous component. The connection between the two ends of the support and the interior is sealed to form an outer cylinder and an inner cylinder. The outer cylinder is cooled so that the temperature difference between the gas on the front and back sides of the membrane before and after separation is more than 10°C. Carbon dioxide can pass through the separation membrane and be separated from the mixed gas. Although this type of solution uses a membrane separation device, it does not consider the influence of flow field factors on the membrane separation efficiency.

[0005] Therefore, there is an urgent need for an inorganic membrane separation device and method for carbon dioxide and nitrogen. Considering that the molecular diameters of the two gases are relatively similar, when using a microporous molecular sieve membrane as the separation medium, the gas flow field is disturbed to increase the separation effect of carbon dioxide and nitrogen, thereby improving the performance of current membrane separation methods for capturing carbon dioxide in flue gas.

[0006] The information disclosed in this background section is intended only to enhance the understanding of the overall background of the invention and should not be construed as an admission or in any way implying that the information constitutes prior art known to those skilled in the art. Summary of the Invention

[0007] The purpose of this invention is to provide an apparatus and method for separating carbon dioxide and nitrogen using an inorganic membrane. By employing a microporous molecular sieve membrane as the separation medium and setting a turbulence-inducing component outside the membrane tube inside the apparatus housing, the separation effect of carbon dioxide and nitrogen can be effectively increased, thereby improving the performance of the membrane separation method for capturing carbon dioxide in flue gas.

[0008] To achieve the above objectives, according to a first aspect of the present invention, an apparatus for separating carbon dioxide and nitrogen using an inorganic membrane is provided, comprising at least: a shell, which is made of metal and has a mixed gas inlet, a permeate-side outlet, and a residual gas outlet; multiple membrane tubes arranged laterally within the shell, the membrane tubes being sealed and fixed within the shell by a tube sheet to form a shell side and a tube side; the membrane tubes having a structure combining a support and a separation membrane, the separation membrane being a molecular sieve membrane; and multiple baffles arranged vertically and vertically along the radial direction of the membrane tubes to form a gas channel in a baffled state.

[0009] Furthermore, in the above technical solution, the baffles are preferably arranged at non-uniform intervals, and the spacing between the baffles gradually decreases along the mainstream gas flow direction, with the decrease being consistent with the decrease in inlet and outlet pressure of the device casing.

[0010] Furthermore, in the above technical solution, the spacing of the baffles is preferably 20%-60% of the inner diameter of the outer shell.

[0011] Furthermore, in the above technical solution, the baffle plate can be provided with venturi-structured baffle holes to disturb the gas at the closed end of the baffle plate and / or to create airflow turbulence on the leeward side of the membrane tube.

[0012] Furthermore, in the above technical solution, the number of openings on different baffles can be gradually reduced along the mainstream gas flow direction. Preferably, the number of openings is reduced by 1-5% in each step.

[0013] Furthermore, in the above technical solution, the inner diameter of the turbulence hole can be 1 / 10 to 1 / 20 of the diameter of the membrane tube.

[0014] Furthermore, in the above technical solution, the molecular sieve membrane can be coated on the support and preferably has pores of 0.36 nm, allowing only CO2 molecules to pass through, so that CO2 permeates into the tube side as a permeate gas, while N2 molecules are trapped, so that N2 remains in the shell side as a permeate gas.

[0015] Furthermore, in the above technical solution, the support body can be made of porous ceramic, porous glass, porous stainless steel plate or MOF material.

[0016] According to a second aspect of the present invention, the present invention provides a method for separating carbon dioxide and nitrogen using an inorganic membrane, employing the aforementioned apparatus, comprising at least the following steps: A. Under preset pressure and gas flow rate conditions, a mixed gas containing carbon dioxide and nitrogen is radially introduced into the outer shell of the apparatus along the membrane tube; B. Under the action of the molecular sieve membrane in the membrane tube, CO2 permeates into the tube side, while N2 is retained in the shell side, and the gas in the shell side is subjected to the action of spaced baffles, resulting in a baffled flow pattern in the main flow of the gas; C. The gas in the shell side is disturbed at the baffle holes opened on the baffles, forming local turbulence at the closed end of the baffles and / or local turbulence on the leeward side of the membrane tube; D. Under the condition of disturbed gas flow, CO2 molecules farther from the molecular sieve membrane can quickly reach the membrane surface, forming continuous permeation and eliminating concentration polarization.

[0017] Furthermore, in the above technical solution, the turbulent airflow can be constructed to create an airflow state that first accelerates and then decelerates through the turbulence holes of the Venturi structure.

[0018] Furthermore, in the above technical solution, the local turbulence and local disturbance in step C can be formed by the superposition of the radial flow formed by the deflector and the axial flow passing through the turbulence hole.

[0019] Furthermore, in the above technical solution, the CO2 content on the permeation side after continuous permeation and elimination of concentration polarization can reach more than 60%.

[0020] Compared with the prior art, the present invention has the following beneficial effects:

[0021] 1) This invention uses a molecular sieve membrane with pores between the diameters of CO2 and N2 molecules. Theoretically, only CO2 molecules can pass through, but a small amount of N2 molecules will also pass through. The inventors have found that, under the condition of using the molecular sieve membrane of this invention, by adding staggered baffles at different positions in the radial direction of the membrane tube, the main direction of the airflow can be guided into a deflection state, which can effectively extend the running path of the mixed gas in the limited shell side space. The mixed gas can have more opportunities to contact the membrane tube multiple times, resulting in a larger contact area. Moreover, the "radial flow" generated by the deflection is more conducive to the permeation of CO2 gas into the membrane tube.

[0022] 2) The baffle plate in this invention can disturb the flow field in the shell side, allowing CO2 molecules farther from the membrane to quickly reach the membrane surface. This causes the local gas flow on both sides of the membrane to be cross-flow relative to the membrane, while the overall flow remains parallel or counter-flow. Experiments have shown that this invention, using a molecular sieve membrane as the separation membrane and combining it with the baffle plate design, has a synergistic effect, achieving optimal separation performance.

[0023] 3) The "gradual densification" setting of the baffle plate along the main flow direction of the airflow in this invention can further extend the running path of the mixed gas, so that the mixed gas has more opportunities to contact the membrane tube compared with the baffle plate set in "uniform interval", thereby further increasing the number of membrane passes and further improving the permeation separation efficiency.

[0024] 4) This invention incorporates turbulence holes on a baffle plate. These holes, positioned at different locations, serve different functions: the first turbulence hole agitates the gas at the closed end of the baffle plate, preventing "dead zones" in the airflow; the second turbulence hole is arranged in the intervals between membrane tubes, primarily in the leeward area of ​​each tube. Existing membrane tubes often suffer from poor airflow coverage in the leeward area, resulting in wasted tube area. However, the arrangement of the second turbulence hole in this invention creates airflow turbulence on the leeward side of the membrane tube. This turbulent airflow is formed by the superposition of axial flow passing through the turbulence hole and radial flow generated by the deflection. This arrangement not only creates airflow turbulence on the leeward side of the membrane tube, allowing for better airflow coverage of all parts of the tube and thus increasing the permeation area, but also mitigates localized concentration polarization to some extent. Because the pore diameter of the inorganic molecular sieve membrane used in this invention is between that of CO2 molecules and N2 molecules, CO2 gas in the mixed gas on the membrane surface can quickly permeate into the membrane tube. At this time, the local CO2 gas concentration on the membrane surface decreases rapidly, while the N2 concentration increases rapidly. The turbulence of the airflow can more effectively bring CO2 gas from a distance to the membrane surface at this location, thereby improving the permeation efficiency.

[0025] 5) The Venturi structure used in the turbulence holes of this invention can accelerate and then decelerate the airflow, thereby further enhancing the turbulence effect of the shell-side airflow at the closed end of the turbulence plate and at the membrane tube interval (especially at the leeward side of the membrane tube) in the local area.

[0026] The above description is merely an overview of the technical solution of the present invention. In order to better understand the technical means of the present invention and to implement it according to the contents of the specification, and to make the above and other objects, technical features and advantages of the present invention easier to understand, one or more preferred embodiments are listed below and described in detail with reference to the accompanying drawings. Attached Figure Description

[0027] Figure 1 This is an internal cross-sectional schematic diagram of the inorganic membrane separation device for carbon dioxide and nitrogen of the present invention.

[0028] Figure 2 is a front view schematic diagram of the spoiler of the present invention (wherein, Figure 2-A This is a front view schematic diagram of the first spoiler; Figure 2-B This is a front view schematic diagram of the second spoiler; Figure 2-C This is a front view schematic diagram of the third spoiler; Figure 2-D (This is a front view schematic of the fourth spoiler).

[0029] Figure 3 This is a schematic cross-sectional view of the internal flow-disrupting hole of the present invention.

[0030] Explanation of key figure labels:

[0031] 1-Outer shell, 11-Mixed gas inlet, 12-Permeate outlet, 13-Residual permeate outlet, 2-Membrane tube, 20-Tube sheet, 21-Sealing ring, 3-Baffle plate, 3A-First baffle plate, 3B-Second baffle plate, 3C-Third baffle plate, 3D-Fourth baffle plate, 30-Baffle hole, 30a-First baffle hole, 30b-Second baffle hole, 301-Baffle hole contraction section, 302-Baffle hole throat section, 303-Baffle hole expansion section, 31-Airflow channel, 31A-First channel, 31B-Second channel, 31C-Third channel, 31D-Fourth channel, 32-Baffle plate mounting hole. Detailed Implementation

[0032] The specific embodiments of the present invention will now be described in detail with reference to the accompanying drawings, but it should be understood that the scope of protection of the present invention is not limited to the specific embodiments.

[0033] Unless otherwise expressly stated, throughout the specification and claims, the term "comprising" or its variations such as "including" or "comprises" shall be understood to include the stated elements or components without excluding other elements or other components.

[0034] In this document, for ease of description, spatial relative terms such as “below,” “under,” “down,” “above,” “above,” “upper,” etc., are used to describe the relationship of one element or feature to another element or feature in the accompanying drawings. It should be understood that spatial relative terms are intended to encompass different orientations of an object in use or operation, in addition to those depicted in the figures. For example, if an object in the figure is flipped, an element described as “below” or “under” another element or feature would be oriented “above” that element or feature. Thus, the exemplary term “below” can encompass both the downward and upward orientations. An object may also have other orientations (rotated 90 degrees or other orientations), and the spatial relative terms used herein should be interpreted accordingly.

[0035] In this document, the terms "first," "second," etc., are used to distinguish two different elements or parts, and are not used to define specific positions or relative relationships. In other words, in some embodiments, the terms "first," "second," etc., can also be used interchangeably.

[0036] This invention, from the perspective of fluid mechanics and engineering applications, addresses the problem of low gas separation efficiency caused by pressure drop and concentration polarization near the membrane during the flow of gas within the membrane module in inorganic membrane separation methods for capturing carbon dioxide. It provides a multi-membrane tube inorganic membrane enhanced separation device. The inventors discovered that nitrogen and carbon dioxide are the most difficult to separate during carbon dioxide capture and separation because their molecular diameters are similar (CO2 molecule diameter is 0.33 nm, N2 molecule diameter is 0.364 nm). Furthermore, pressure drop and concentration polarization also affect the separation efficiency of both gases when using inorganic membrane separation methods. Based on this, this invention uses a microporous molecular sieve membrane coated on a support as the inorganic membrane of the membrane tube. The molecular sieve membrane has channels with diameters between those of CO2 and N2 molecules. Simultaneously, internal components are added in the shell side to increase gas turbulence and change the concentration of carbon dioxide in the gas at the membrane surface. The synergistic effect of these two methods enhances the separation effect and improves the performance of current membrane separation methods for capturing carbon dioxide in flue gas.

[0037] like Figures 1 to 3 As shown, the present invention provides an inorganic membrane separation device for carbon dioxide and nitrogen, comprising at least a shell 1, a membrane tube 2, and a baffle plate 3. The shell 1 is made of metal and has a mixed gas inlet 11 and a permeate-side outlet 12 (i.e.,...). Figure 1 The CO2 gas outlet collected on the right end of the middle membrane tube 2) and the permeate outlet 13 (i.e. Figure 1 The outer casing 1 is preferably a horizontal cylindrical structure with end caps at both ends, and the mixed gas inlet 11 is located at... Figure 1 The permeate outlet 13 is located on the lower left side of the middle. Figure 1 The permeate outlet 12 is located at the upper right side of the right end cap. Multiple membrane tubes 2 are arranged laterally within the outer shell 1. The membrane tubes 2 are sealed and fixed within the outer shell 1 by a tube sheet 20, forming a shell side and a tube side. Specifically, the number of membrane tubes is ≥3. The membrane tube joints are sealed and fixed to the tube sheet 20 at both ends using sealing rings 21. The tube sheet 20 is then connected to the outer shell 1 and the end cap using gaskets and flanges, forming two relatively isolated cavities: the shell side and the tube side. The membrane tube 2 of this invention is a structure combining a support and a separation membrane. The separation membrane is an inorganic molecular sieve membrane. The support is preferably made of porous ceramic, porous glass, porous stainless steel plate, or MOF material. The inorganic molecular sieve membrane of this invention is coated on the support and preferably has channels of 0.36 nm (i.e., the molecular sieve membrane has channels between the diameters of CO2 and N2 molecules), allowing only CO2 molecules to pass through, so that CO2 permeates into the tube side as permeate gas, while N2 molecules are retained, so that N2 remains in the shell side as residual permeate gas. The number of baffles 3 is multiple and they are arranged alternately up and down along the radial direction of the membrane tube 2 to form a gas channel in a deflection state.

[0038] In the above-described technical solution of this invention, a molecular sieve membrane with pores between the diameters of CO2 and N2 molecules is used. Theoretically, only CO2 molecules can pass through, but a small amount of N2 molecules will also permeate. The inventors have discovered that, when using the inorganic molecular sieve membrane of this invention, adding staggered baffles at different radial positions of the membrane tube can not only guide the main direction of the airflow into a deflected state, effectively extending the path of the mixed gas within the limited shell-side space, allowing the mixed gas to have more opportunities to contact the membrane tube multiple times, resulting in a larger contact area, but the "radial flow" generated by the deflection also facilitates the permeation of CO2 gas into the membrane tube. Furthermore, the baffles can disturb the flow field in the shell-side, allowing CO2 molecules farther from the membrane to quickly reach the membrane surface, causing local gas flow on both sides of the membrane to be cross-flow relative to the membrane, while the overall flow remains parallel or counter-flow. Experiments have shown that the inorganic molecular sieve membrane used in this invention, combined with the design of the baffles, has a synergistic effect, achieving optimal separation performance.

[0039] Further as Figure 1 As shown, the baffles 3 are preferably arranged with non-uniform spacing. The spacing of the baffles gradually decreases along the main gas flow direction, and the decrease is consistent with the decrease in inlet and outlet pressure of the device shell. As the mixed gas continues to run in the shell side, the pressure of the mixed gas gradually decreases because CO2 gas in the mixed gas permeates into the membrane tube 2. Therefore, the "gradual densification" arrangement of the baffles along the main gas flow direction can further extend the running path of the mixed gas, allowing the mixed gas to have more opportunities to contact the membrane tube 2, thereby increasing the number of membrane passes and further improving the permeation separation efficiency. The spacing of the baffles 3 can fluctuate between 20% and 60% of the inner diameter of the shell, preferably 24% to 50%.

[0040] Further as Figure 1 As shown in Figure 2, the baffles 3 at different positions are arranged radially at intervals along the membrane tube 2 in the shell side, and are fixed to the outer shell 1 by the connecting support through the baffle mounting holes 32. The structure of the first baffle 3A closest to the gas mixture inlet 11 is as follows: Figure 2-A As shown, the upper circular opening is the first airflow channel 31A, and second spoilers 3B are arranged sequentially at intervals along the main airflow direction (reference). Figure 2-B The lower circular section is the second airflow channel 31B, and the third spoiler 3C (see reference). Figure 2-C The upper circular section is the third airflow channel 31C) and the fourth spoiler 3D (see reference). Figure 2-DThe lower circular notch is the fourth airflow channel 31D, etc. Figure 2 only shows the structure of four spoilers; the other spoilers are similar and will not be described in detail here. Each spoiler may be provided with venturi-structured turbulence holes 30. The structures of the turbulence holes 30 are the same, but the functions of the turbulence holes at different positions are different. The turbulence-disrupting holes 30 of the present invention include a first turbulence-disrupting hole 30a and a second turbulence-disrupting hole 30b. The first turbulence-disrupting hole 30a is disposed on the opposite side of the airflow channel (i.e., the closed end of the turbulence-disrupting plate), as shown in Figure 2. For example, the first turbulence-disrupting holes 30a on the first turbulence-disrupting plate 3A are arranged opposite the first channel 31A (4 holes); the first turbulence-disrupting holes 30a on the second turbulence-disrupting plate 3B are arranged opposite the second channel 31B (3 holes); the first turbulence-disrupting holes 30a on the third turbulence-disrupting plate 3C are arranged opposite the third channel 31C (2 holes); and the first turbulence-disrupting hole 30a on the fourth turbulence-disrupting plate 3D is arranged opposite the fourth channel 31D (1 hole). With this arrangement, the first turbulence-disrupting hole 30a can be used to disturb the gas at the closed end of the turbulence-disrupting plate, avoiding a "dead airflow zone." The second turbulence-disrupting holes 30b are arranged in the interval area of ​​the membrane tubes 2 (refer to Figure 2), with a focus on the leeward area of ​​each membrane tube (refer to Figure 2). Figure 1 The existing membrane tubes do not easily cover the leeward area with airflow, resulting in wasted membrane tube area. However, by adopting the arrangement of the second turbulence hole 30b in this invention, airflow turbulence can be formed on the leeward side of the membrane tube 2. This turbulent airflow can be... Figure 1 The axial flow passing through the turbulence holes and the radial flow generated by the deflection are superimposed. This arrangement not only creates airflow turbulence on the leeward side of the membrane tube, allowing the airflow to better cover all parts of the membrane tube and thus increase the permeation area, but also eliminates local concentration polarization to some extent. That is, since the pore diameter of the molecular sieve membrane used in this invention is between the diameters of CO2 and N2 molecules, CO2 gas in the mixed gas on the membrane surface can quickly permeate into the membrane tube. At this time, the local CO2 gas concentration on the membrane surface decreases rapidly, while the N2 concentration increases rapidly. The airflow turbulence can more effectively bring CO2 gas from a distance to the membrane surface at this location, thereby improving the permeation efficiency.

[0041] Further as Figure 1 As shown in Figure 2, preferably but not limitingly, the number of openings (including the first and second turbulence holes 30a and 30b) on different turbulence plates gradually decreases along the main gas flow direction. Preferably, the number of openings decreases by 1-5% in each step, and most preferably by 0.5-3%. The inner diameter of the turbulence hole 30 is preferably 1 / 10-1 / 20 of the membrane tube diameter (reference). Figure 3 ). Further as Figure 3As shown, the turbulence hole 30 of the present invention can be configured as a Venturi structure, that is, including a contraction section 301, a throat section 302 and an expansion section 303. Such a channel design can make the passing airflow accelerate first and then decelerate, thereby locally enhancing the disturbance effect of the shell-side airflow at the closed end of the turbulence plate and the turbulence effect at the membrane tube interval (especially at the leeward side of the membrane tube).

[0042] refer to Figures 1 to 3 The present invention also provides a method for separating carbon dioxide and nitrogen using an inorganic membrane, employing the aforementioned apparatus, and comprising at least the following steps:

[0043] Step S101: Under preset pressure and gas flow rate conditions, a mixed gas containing carbon dioxide and nitrogen is radially introduced into the device housing 1 along the membrane tube 2.

[0044] In step S102, under the action of the molecular sieve membrane (preferably with pores of 0.36 nm, the pore diameter being between the diameters of CO2 molecules and N2 molecules) in the membrane tube 2, CO2 permeates into the tube side, while N2 is trapped in the shell side. Under the action of the spaced baffles 3, the main flow of the gas in the shell side is in a baffled state.

[0045] In step S103, the gas in the shell side is disturbed at the turbulence holes 30 on the baffle 3, forming local turbulence at the closed end of the baffle and / or local turbulence on the leeward side of the membrane tube. Preferably, but not limitingly, the disturbed airflow can be constructed into an airflow state of first acceleration and then deceleration through the venturi-structured turbulence holes 30. The local turbulence and local turbulence in this step are formed by the superposition of radial flow formed by the deflection and axial flow passing through the turbulence holes.

[0046] In step S104, under turbulent airflow conditions, CO2 molecules farther from the molecular sieve membrane rapidly reach the membrane surface, forming continuous permeation and eliminating concentration polarization. Experiments have shown that, through the synergistic effect of the inorganic molecular sieve membrane coated on the membrane tube 2 of this invention and the spaced-apart baffles, the CO2 content on the permeate side after continuous permeation and elimination of concentration polarization can reach over 60%.

[0047] Example 1

[0048] refer to Figure 1 As shown in Figure 2, seven 500mm long membrane tubes 2 are inserted into the metal casing 1 of the device of the present invention. The membrane tubes are sealed to the metal cavity with rubber rings, and the bottom end of the sealed membrane tubes (i.e., Figure 1 At the middle left end, a baffle plate 3 with baffle holes 30 is fixed between the gas inlet and outlet with a screw, and the top of the membrane tube (i.e., Figure 1 The middle right end is connected to the CO2 collection bag. The metal shell 1 is equipped with a mixed gas inlet 11 and a nitrogen outlet 13, which are respectively connected to the gas source and the outlet pressure gauge and regulating valve.

[0049] When N2 with a CO2 content of 15% is introduced into the mixed gas inlet 11 of the device, under the conditions of pressure 0.6 MPa and flow rate 300 L / h, the CO2 content on the permeate side is measured to be 60%.

[0050] Comparative example

[0051] refer to Figure 1 As shown in Figure 2, seven 500mm long membrane tubes 2 are inserted into the metal casing 1 of the device of the present invention. The membrane tubes are sealed to the metal cavity with rubber rings, and the bottom end of the sealed membrane tubes (i.e., Figure 1 At the middle left end, a baffle plate 3 without baffle holes 30 is fixed between the gas inlet and outlet with a screw, and the top of the membrane tube (i.e., Figure 1 The middle right end is connected to the CO2 collection bag. The metal shell 1 is equipped with a mixed gas inlet 11 and a nitrogen outlet 13, which are respectively connected to the gas source and the outlet pressure gauge and regulating valve.

[0052] When N2 with a CO2 content of 15% is introduced into the mixed gas inlet 11 of the device, under the conditions of pressure 0.6 MPa and flow rate 300 L / h, the CO2 content on the permeation side is measured to be 55%.

[0053] The foregoing description of specific exemplary embodiments of the present invention is for illustrative and explanatory purposes. These descriptions are not intended to limit the invention to the precise forms disclosed, and it will be apparent that many changes and variations can be made in accordance with the foregoing teachings. The exemplary embodiments were chosen and described in order to explain the specific principles of the invention and its practical application, thereby enabling those skilled in the art to implement and utilize various different exemplary embodiments of the invention, as well as various different choices and variations. Any simple modifications, equivalent changes, and alterations made to the foregoing exemplary embodiments should fall within the scope of protection of the present invention.

Claims

1. An apparatus for separating carbon dioxide and nitrogen using an inorganic membrane, characterized in that, include: The outer casing is made of metal and has a mixed gas inlet, a permeate-side outlet, and a residual gas outlet. Multiple membrane tubes are arranged laterally within the outer shell. The membrane tubes are sealed and fixed within the outer shell by a tube sheet, forming a shell side and a tube side. The membrane tubes are a combination of a support and a separation membrane, and the separation membrane is an inorganic molecular sieve membrane. Multiple baffles are arranged alternately up and down along the radial direction of the membrane tube to form a gas channel in a deflection state.

2. The apparatus for separating carbon dioxide and nitrogen using an inorganic membrane according to claim 1, characterized in that, The baffles are arranged at non-uniform intervals, and the spacing between the baffles gradually decreases along the main gas flow direction. The decrease in spacing is consistent with the decrease in inlet and outlet pressure of the device casing.

3. The apparatus for separating carbon dioxide and nitrogen using an inorganic membrane according to claim 2, characterized in that, The spacing between the baffles is 20%-60% of the inner diameter of the outer casing.

4. The apparatus for separating carbon dioxide and nitrogen using an inorganic membrane according to claim 2, characterized in that, The baffle plate is provided with venturi-structured baffle holes to agitate the gas at the closed end of the baffle plate and / or to create airflow turbulence on the leeward side of the membrane tube.

5. The apparatus for separating carbon dioxide and nitrogen using an inorganic membrane according to claim 4, characterized in that, The number of openings on different baffle plates gradually decreases along the main gas flow direction.

6. The apparatus for separating carbon dioxide and nitrogen using an inorganic membrane according to claim 5, characterized in that, The number of openings is reduced by 1-5% at each stage.

7. The apparatus for separating carbon dioxide and nitrogen using an inorganic membrane according to claim 4, characterized in that, The inner diameter of the turbulence hole is 1 / 10 to 1 / 20 of the diameter of the membrane tube.

8. The apparatus for separating carbon dioxide and nitrogen using an inorganic membrane according to claim 1, characterized in that, The molecular sieve membrane is coated on the support and has 0.36 nm pores, allowing only CO2 molecules to pass through, so that CO2 permeates into the tube side as a permeate gas, while N2 molecules are trapped, so that N2 remains in the shell side as a permeate gas.

9. The apparatus for separating carbon dioxide and nitrogen using an inorganic membrane according to claim 8, characterized in that, The support is made of porous ceramic, porous glass, porous stainless steel plate or MOF material.

10. A method for separating carbon dioxide and nitrogen using an inorganic membrane, characterized in that, Using the apparatus as described in any one of claims 1 to 9, the method includes the following steps: A. Under preset pressure and gas flow rate conditions, a mixture of carbon dioxide and nitrogen is introduced radially into the device housing along the membrane tube. B. Under the action of the inorganic molecular sieve membrane in the membrane tube, CO2 permeates into the tube side, while N2 is retained in the shell side. The gas in the shell side is in a baffled state due to the baffles set at intervals. C. The gas in the shell side is disturbed at the turbulence holes opened on the turbulence plate, forming local turbulence at the closed end of the turbulence plate and / or local turbulence on the leeward side of the membrane tube. D. Under turbulent airflow conditions, CO2 molecules that are far from the molecular sieve membrane quickly reach the membrane surface, forming continuous permeation and eliminating concentration polarization.

11. The method for separating carbon dioxide and nitrogen using an inorganic membrane according to claim 10, characterized in that, The disturbed airflow creates an airflow state that first accelerates and then decelerates through the turbulence holes of the Venturi structure.

12. The method for separating carbon dioxide and nitrogen using an inorganic membrane according to claim 11, characterized in that, The local turbulence and local disturbance in step C are formed by the superposition of radial flow generated by the deflector and axial flow passing through the turbulence hole.

13. The method for separating carbon dioxide and nitrogen using an inorganic membrane according to claim 10, characterized in that, The CO2 content on the permeate side after continuous permeation and elimination of concentration polarization is above 60%.

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