Finite element simulation-based hollow fiber membrane mechanical property optimization method

Abstract

The invention discloses a hollow fiber membrane mechanical property optimization method based on finite element simulation, and relates to a hollow fiber membrane mechanical property optimization method. The invention aims to solve the problem that the mechanical property of a membrane material directly affects the stability and efficiency of a membrane under an operation condition. The method comprises the following steps: step 1, preparing a hollow fiber membrane sample, and carrying out mechanical property test on the sample according to a preset standard; step 2, constructing a finite element numerical simulation model of the hollow fiber membrane based on the test result and the physical attribute of the membrane material; 3, setting boundary conditions and loading conditions, and performing finite element simulation analysis on the model; and 4, proposing an optimization scheme according to the simulation structure. The invention belongs to the technical field of gas-liquid membrane separation.

Description

Technical Field

[0001] The present invention relates to a method for optimizing the mechanical properties of hollow fiber membranes, belonging to the technical field of gas-liquid membrane separation. Background Art

[0002] Given the increasingly severe environmental problems and the demand for energy-saving technologies, efficient and sustainable industrial gas separation processes have become more urgent than ever. Gas-liquid membrane separation technology, with its characteristics of high efficiency and energy conservation, has been widely used in the field of industrial gas separation, such as biogas upgrading, carbon dioxide capture, and industrial waste gas purification. This technology can effectively separate different components in gas mixtures and improve the purity of target gases, which is of great significance for environmental protection and resource recovery. During the biogas upgrading process, membrane separation technology can effectively separate methane and carbon dioxide from the gas generated by biomass fermentation, thereby increasing the energy density of biogas and making it a cleaner energy source. In terms of carbon dioxide capture, membrane separation technology helps reduce carbon emissions in industrial processes and contributes to addressing global climate change. In addition, membrane separation technology also shows unique advantages in many fields such as natural gas purification and hydrogen purification. However, the success of this technology depends to a large extent on the mechanical strength of the membrane materials used, especially under harsh industrial operating conditions. In the field of membrane materials, hollow fiber membranes have attracted much attention due to their high specific surface area, which is beneficial for efficient gas-liquid interaction. The mechanical properties of these membranes, including strength and stiffness, are crucial for ensuring the stability and efficiency of the separation process. It is worth noting that the performance of these membranes under operating conditions is directly related to their ability to withstand internal pressure without compromising their structural integrity.

[0003] A gas-liquid membrane contactor is an efficient separation technology that uses a membrane material as the interface between gas and liquid to facilitate mass transfer between the two phases. Its operating mechanism is to create a negative pressure environment inside the hollow fiber membrane filaments through vacuum pumping or gas purging, while the liquid flows on the outer surface of these filaments. The filaments are hydrophobic-treated and have micropores on the surface, allowing gas molecules to pass through while preventing water molecules from permeating. Under the influence of negative pressure, the gas dissolved in the liquid migrates through these micropores into the interior of the membrane filaments and is then carried away by the gas pumped or purged, thus achieving gas-liquid separation. The gas-liquid membrane contactor provides a fixed and well-defined interface that enables mass transfer between gas and liquid without mutual mixing, improving separation efficiency and selectivity. This technology has a wide range of applications in fields such as carbon dioxide capture, water deoxygenation, air humidity control, and ethylene / ethane separation. The core component of the gas-liquid membrane contactor is the hollow fiber membrane material, usually made of polymers, which has high gas permeability and hydrophobicity. This membrane material provides a large contact area, thus improving the mass transfer efficiency. Researchers prepared hollow fiber membranes blended with porous polyvinylidene fluoride (PVDF) and multi-walled carbon nanotubes (MWCNT) for carbon dioxide absorption in gas-liquid membrane contactors. The design of the hollow fiber membrane features a hollow fiber, providing a significantly larger surface area per unit volume of the device, contributing to the compactness and modularity of the separation device. In addition, the spiral design of the hollow fiber membrane can prevent liquid condensation and accumulation on the membrane surface, ensuring the optimal mass transfer performance and stable operation of the device.

[0004] Mechanical properties, as a key attribute of membrane materials, are crucial for the successful implementation of these applications because they are directly related to the stability and efficiency of the membrane under actual operating conditions. During the membrane separation process, the membrane material must possess sufficient strength to withstand various pressures encountered during the separation process. These pressures may come from the gas mixture itself or the external environment, such as temperature changes. Researchers proposed a new composite additive system for preparing porous silicon carbide ceramic membranes to control the mechanical properties and pore structure of porous silicon carbide ceramics through temperature regulation. The strength of the membrane material is the basis for ensuring that it does not rupture under these conditions. The membrane material needs to maintain shape stability under pressure differences or temperature changes. A membrane material with poor resistance to deformation may cause changes in the pore structure of the membrane, thereby affecting separation efficiency and selectivity. Therefore, the membrane requires good structural stiffness to maintain its shape under high-pressure operation, thus maintaining the reliability and efficiency of the separation process. Membrane materials with excellent mechanical properties can operate at higher absorbent flow rates, which not only improves separation efficiency but also reduces energy consumption. For example, hollow fiber composite membranes, due to their high strength and stiffness, remain stable in high-speed fluid flow and can achieve more efficient gas separation.

[0005] Therefore, improving the mechanical properties of the membrane is crucial for ensuring the efficient and stable operation of membrane separation technology in the field of industrial gas separation. Researchers doped different amounts of TiO2 into a blend membrane composed of polyetherimide (PEI) and polyvinyl acetate (PVAc), and found that the blend membrane containing TiO2 exhibited excellent mechanical and thermal properties, especially in terms of hardness. At the same time, the test results of the separation performance of two groups of gases (CO2 / CH4 and CO2 / N2) showed that the membrane containing TiO2 had better separation ability. This enables the membrane material to maintain structural stability under various pressures and environmental changes, improve separation efficiency and selectivity, reduce energy consumption, and extend service life. Therefore, it plays an important role in environmental protection and resource recovery. Summary of the Invention

[0006] In order to solve the problem that the mechanical properties of the membrane material directly affect the stability and efficiency of the membrane under operating conditions, the present invention further provides an optimization method for the mechanical properties of hollow fiber membranes based on finite element simulation.

[0007] The technical solutions adopted by the present invention to solve the above problems are as follows: The steps of the present invention include:

[0008] Step 1: Prepare hollow fiber membrane samples and conduct mechanical property tests on the samples according to preset standards;

[0009] Step 2: Construct a finite element numerical simulation model of the hollow fiber membrane based on the test results and the physical properties of the membrane material;

[0010] Step 3: Set boundary conditions and loading conditions, and conduct finite element simulation analysis on the model;

[0011] Step 4: Propose an optimization plan according to the simulation results.

[0012] Further, Step 1 specifically includes:

[0013] Step 101: Conduct mechanical property tests on the hollow fiber membrane samples using an Instron 6800 instrument according to the ASTM D638 standard;

[0014] Step 102: Prepare the hollow fiber membrane samples into dumbbell shapes, with a length of 165 mm, a width of 13 mm, and a gauge length of 50 mm;

[0015] Step 103: Use rubber-faced clamps that do not damage the thin film samples, and apply adjustable inlet pressure to ensure that the samples are firmly clamped throughout the test.

[0016] Further, Step 2 specifically includes:

[0017] Step 201: Based on the physical properties of PVDF and SiO2 / PVDF composite membrane materials, establish a finite element numerical simulation model of the hollow fiber membrane;

[0018] Step 202: Use advanced finite element simulation software to mesh the model and set boundary conditions and loading conditions;

[0019] The boundary conditions include fixing all translational and rotational degrees of freedom at both ends of the membrane to simulate the case where the internal pressure is 1 bar.

[0020] Furthermore, step 3 specifically includes:

[0021] Step 301: Use finite element simulation technology to analyze the strength and stiffness of PVDF and SiO2 / PVDF composite hollow fiber membranes;

[0022] Step 302: Evaluate its mechanical properties by simulating the deformation and stress distribution of the membrane structure under internal pressure;

[0023] Step 303: Use nominal strain to report the elongation after yielding, and use the post-processing function of the finite element simulation software to extract and analyze the simulation results.

[0024] Furthermore, step 4 specifically includes:

[0025] Step 401: According to the simulation analysis results, compare the mechanical properties of PVDF and SiO2 / PVDF composite membranes, and propose specific solutions to optimize the mechanical properties of the hollow fiber membrane;

[0026] Step 402: Analyze the mechanical properties of PVDF membranes and SiO2 / PVDF composite membranes with different wall thicknesses to determine the optimal wall thickness to improve the stiffness and strength of the membrane.

[0027] Furthermore, the finite element numerical simulation model includes PVDF membranes and SiO2 / PVDF composite membranes.

[0028] Furthermore, the boundary conditions include fixing all translational and rotational degrees of freedom at both ends of the membrane to simulate the case where the internal pressure is a preset value.

[0029] Furthermore, the optimization solution refers to adjusting the composition, structure, and wall thickness of the membrane material.

[0030] The beneficial effects of the present invention are:

[0031] 1. Improve accuracy and efficiency: By combining experimental tests and finite element simulations, the present invention can more accurately evaluate and optimize the mechanical properties of hollow fiber membranes, improving the accuracy and efficiency of analysis;

[0032] 2. Optimize the structural design: Through finite element simulation analysis, the deformation and stress distribution of the membrane structure can be visually observed, providing strong support for optimizing the structural design of the membrane.

[0033] 3. Reduce costs: The optimization scheme proposed in the present invention can reduce the weight of the membrane material, thereby potentially reducing the reactor operation cost and equipment transportation cost.

[0034] 4. Enhance application performance: The SiO2 / PVDF composite membrane shows significantly improved loading capacity and shear resistance, enabling the membrane separation technology to operate efficiently under high-pressure conditions. Description of the Drawings

[0035] Figure 1 is a schematic diagram of boundary conditions and loads in the present invention;

[0036] Figure 2 is a schematic diagram of the structural deformation of PVDF hollow fiber membranes with different thicknesses;

[0037] Figure 2 The thickness of the PVDF hollow fiber membrane in a is 0.1 mm, Figure 2 The thickness of the PVDF hollow fiber membrane in b is 0.2 mm, Figure 2 The thickness of the PVDF hollow fiber membrane in c is 0.4 mm, Figure 2 The thickness of the PVDF hollow fiber membrane in d is 0.6 mm;

[0038] Figure 3 is a schematic diagram of the structural stress of PVDF fiber membranes with different thicknesses; Figure 3 The thickness of the PVDF fiber membrane in a is 0.1 mm, Figure 3 The thickness of the PVDF fiber membrane in b is 0.2 mm, Figure 3 The thickness of the PVDF fiber membrane in c is 0.4 mm, Figure 3 The thickness of the PVDF fiber membrane in d is 0.6 mm. Detailed Embodiments

[0039] Detailed Embodiment 1: As Figures 1 to 3 shown, a method for optimizing the mechanical properties of hollow fiber membranes based on finite element simulation, the specific steps include:

[0040] Step 1. Prepare hollow fiber membrane samples and conduct mechanical property tests on the samples according to preset standards; specifically including:

[0041] Step 101. Conduct mechanical property tests on the hollow fiber membrane samples using an Instron 6800 instrument according to the ASTM D638 standard.

[0042] Step 102: Prepare the hollow fiber membrane sample into a dumbbell shape with a length of 165 mm, a width of 13 mm, and a gauge length of 50 mm;

[0043] Step 103: Use rubber-faced clamps that do not damage the thin film sample and apply an adjustable inlet pressure to ensure that the sample is firmly clamped throughout the test;

[0044] Step 2: Based on the test results and the physical properties of the membrane material, construct a finite element numerical simulation model of the hollow fiber membrane; specifically including:

[0045] Step 201: Based on the physical properties of PVDF and SiO2 / PVDF composite membrane materials, establish a finite element numerical simulation model of the hollow fiber membrane;

[0046] Step 202: Use advanced finite element simulation software to mesh the model and set boundary conditions and loading conditions;

[0047] Step 203: The boundary conditions include fixing all translational and rotational degrees of freedom at both ends of the membrane, simulating the case where the internal pressure is 1 bar;

[0048] Step 3: Set boundary conditions and loading conditions and perform finite element simulation analysis on the model; specifically including:

[0049] Step 301: Use finite element simulation technology to analyze the strength and stiffness of PVDF and SiO2 / PVDF composite hollow fiber membranes;

[0050] Step 302: By simulating the deformation and stress distribution of the membrane structure under internal pressure, evaluate its mechanical properties;

[0051] Step 303: Use nominal strain to report the elongation after yielding and use the post-processing function of finite element simulation software to extract and analyze the simulation results;

[0052] Step 4: Propose an optimization plan based on the simulation results; specifically including:

[0053] Step 401: According to the simulation analysis results, compare the mechanical properties of PVDF and SiO2 / PVDF composite membranes and propose specific plans to optimize the mechanical properties of the hollow fiber membrane;

[0054] Step 402: Analyze the mechanical properties of PVDF membranes and SiO2 / PVDF composite membranes with different wall thicknesses to determine the optimal wall thickness to improve the stiffness and strength of the membrane.

[0055] Among them, the finite element numerical simulation model includes PVDF membranes and SiO2 / PVDF composite membranes;

[0056] The boundary conditions include all translational and rotational degrees of freedom at both ends of the fixed film, simulating the case where the internal pressure is a preset value;

[0057] The optimization scheme refers to adjusting the composition, structure and wall thickness of the film material.

[0058] The above are only the preferred embodiments of the present invention, and do not impose any formal limitations on the present invention. Although the present invention has been disclosed above with preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some changes or modifications to equivalent embodiments by using the disclosed technical content within the scope of the technical solution of the present invention. However, as long as it does not depart from the content of the technical solution of the present invention, any simple modification, equivalent replacement and improvement made to the above embodiments according to the technical essence of the present invention within the spirit and principle of the present invention still fall within the protection scope of the technical solution of the present invention.

Claims

1. A method for optimizing the mechanical properties of hollow fiber membranes based on finite element simulation, characterized in that: The specific steps include: Step 1, preparing hollow fiber membrane samples, and testing the mechanical properties of the samples according to preset standards; Step 2: construct a finite element numerical simulation model of the hollow fiber membrane based on the test results and the physical properties of the membrane material; Step 3: Set boundary conditions and loading conditions, and perform finite element simulation analysis on the model; Step 4: Propose an optimization plan based on the simulation structure.

2. The method for optimizing the mechanical properties of hollow fiber membranes based on finite element simulation according to claim 1, characterized in that: Step 1 specifically includes: Step 101, according to ASTM D638 standard, use Instron 6800 instrument to test the mechanical properties of the hollow fiber membrane sample; Step 102, prepare a hollow fiber membrane sample in a dumbbell shape with a length of 165 mm, a width of 13 mm, and a gauge length of 50 mm; Step 103, using a rubber surface clamp that does not damage the film sample, and applying an adjustable inlet pressure to ensure that the sample is firmly clamped during the entire test process.

3. The method for optimizing the mechanical properties of hollow fiber membranes based on finite element simulation according to claim 1, characterized in that: Step 2 specifically includes: Step 201, based on the physical properties of PVDF and SiO2 / PVDF composite membrane materials, a finite element numerical simulation model of the hollow fiber membrane is established; Step 202: using advanced finite element simulation software to mesh the model and set boundary conditions and loading conditions; Step 203, the boundary conditions include all translational and rotational degrees of freedom at both ends of the fixed membrane, simulating the case where the internal pressure is 1 bar.

4. The method for optimizing the mechanical properties of hollow fiber membranes based on finite element simulation according to claim 1, characterized in that: Step 3 specifically includes: Step 301: Analyze the strength and stiffness of PVDF and SiO2 / PVDF composite hollow fiber membranes using finite element simulation technology; Step 302, evaluating the mechanical properties of the membrane structure by simulating the deformation and stress distribution of the membrane structure under the internal pressure; Step 303: Use nominal strain to report the elongation after yielding, and use the post-processing function of the finite element simulation software to extract and analyze the simulation results.

5. The method for optimizing the mechanical properties of hollow fiber membranes based on finite element simulation according to claim 1, characterized in that: Step 4 specifically includes: Step 401: According to the simulation analysis results, the mechanical properties of PVDF and SiO2 / PVDF composite membranes are compared, and a specific scheme for optimizing the mechanical properties of hollow fiber membranes is proposed; Step 402: Analyze the mechanical properties of PVDF membranes and SiO2 / PVDF composite membranes with different wall thicknesses to determine the optimal wall thickness to improve the rigidity and strength of the membrane.

6. The method for optimizing the mechanical properties of hollow fiber membranes based on finite element simulation according to claim 1, characterized in that: The finite element numerical simulation model includes a PVDF membrane and a SiO2 / PVDF composite membrane.

7. The method for optimizing the mechanical properties of hollow fiber membranes based on finite element simulation according to claim 1, characterized in that: The boundary conditions include all translational and rotational degrees of freedom at both ends of the fixed membrane, simulating the situation where the internal pressure is a preset value.

8. The method for optimizing the mechanical properties of hollow fiber membranes based on finite element simulation according to claim 1, characterized in that: The optimization scheme refers to adjusting the composition, structure and wall thickness of the membrane material.

Images