Method for analyzing distribution of multiple physical fields in photocatalytic device and application thereof

Abstract

The application provides a method for analyzing the distribution law of multiple physical fields in a photocatalytic device and application, a three-dimensional reactor model is constructed by using Taylor-Kuait vortex principle, a carbon dot / bismuth oxychloride photocatalytic degradation rhodamine B process in the reactor is simulated by ANSYS-Fluent, and a comprehensive CFD model containing a light field, a flow field, a discrete phase and a reaction field is established. In combination with experiments, the degradation efficiency under different operating conditions is simulated and predicted by using the comprehensive CFD model. The numerical simulation method used in the application reduces the cost of reactor design, and reveals the relationship between multiple physical fields in the reactor, thereby providing engineering guidance for photocatalysis.

Description

Technical Field

[0001] This invention belongs to the field of photocatalytic reactor design, specifically a method for analyzing the distribution law of multiple physical fields in a photocatalytic device and its application. Background Technology

[0002] Since the concept of photocatalysis was proposed, photocatalysis technology has gained significant recognition in fields such as clean energy and environmental governance. It boasts advantages such as simple and convenient operation, and the semiconductor materials used in photocatalysis are not only inexpensive but also readily available. Despite its immense application value, the industrialization of this technology is hampered by limitations in semiconductor photocatalytic materials and photocatalytic reactors. Semiconductor photocatalytic materials have been extensively studied. Titanium dioxide, as a conventional photocatalyst, only responds to ultraviolet light and has low quantum efficiency. Carbon dot / bismuth oxychloride, also a widely used photocatalytic material, extends its photoresponse region into the visible light range due to its unique layered structure. Therefore, selecting carbon dot / bismuth oxychloride for the photocatalytic degradation of the traditional pollutant Rhodamine B is representative and reduces the impact of studying another factor hindering the development of photocatalysis technology.

[0003] Research on photocatalytic reactors often lacks understanding of the distribution of light fields and photocatalytic materials, making it difficult to improve quantum efficiency and mass transfer efficiency. Traditional photocatalytic reactors, such as immobilized reactors and fluidized bed reactors, cannot simultaneously achieve high photon transmission and mass transfer efficiency, and provide limited reaction contact time between the photocatalytic material and the treated organic pollutants. Therefore, there is an urgent need to develop novel photocatalytic reactors. Reactors designed based on the Taylor-Couette vortex concept have advantages such as low shear stress, low axial backmixing, and large surface contact area of ​​the reaction medium, providing new ideas for the design of photocatalytic reactors. However, the internal conditions of the reactor remain like a "black box," making it impossible to explore. This necessitates the introduction of numerical simulation methods to analyze the flow of pollutants, the distribution of photocatalytic materials, and the distribution of light fields within the reactor. This invention allows for a better and more convenient application of Taylor-Couette photocatalytic reactors to photocatalytic reactions, contributing to the further industrialization of photocatalytic technology. Summary of the Invention

[0004] In view of this, the purpose of this invention is to provide a method for analyzing the distribution law of multiple physical fields in a photocatalytic device, so as to provide a theoretical basis and technical support for the industrialization of the Taylor-Couette reactor in the field of photocatalysis.

[0005] To achieve the above-mentioned objectives, the present invention provides the following technical solution:

[0006] A method for analyzing the distribution of multiphysics fields in a photocatalytic device, employing a combination of experimental and simulation methods for numerical simulation, includes the following steps:

[0007] Step S1: Using Rhodamine B as the treatment target and photocatalytic materials as catalysts, the apparent rate constant and photocatalytic degradation efficiency of Rhodamine B are obtained through photocatalytic degradation experiments.

[0008] Step S2: Determine and simplify the structure and dimensions of the Taylor-Kueit reactor, construct a three-dimensional geometric model in ICEM software and perform structured mesh generation;

[0009] Step S3: Import the divided 3D mesh model into ANSYS-Fluent for simulation and solve, and write and import the UDF program; set the multiphase flow model, turbulence model, radiation model, DPM model, and chemical reaction parameters according to the experimental parameters; use the Coupled algorithm for Pressure-Velocity Coupling, and use Warped-Face GradientCorrection and High-order Term Relaxation to assist in the calculation; perform standard initialization of the model and set boundary conditions; perform transient calculations on the flow field, radiation field, and distribution of photocatalytic materials in the Taylor-Couette reactor under the set rotation speed and light intensity conditions, and the reaction kinetics of the Rhodamine B degradation process to obtain the degradation efficiency of Rhodamine B under the simulated conditions;

[0010] Step S4: In the Result, view the flow field distribution cloud map, radiation field and discrete phase distribution cloud map, and the degradation efficiency of Rhodamine B under simulated conditions.

[0011] Furthermore, in step S1, the remaining concentration C of Rhodamine B at time t is... t (mg / l) was obtained through the standard equation, C t = 9.64AU, where AU is the absorbance at time t, with a standard error of 99.97%, and the apparent rate constant k r Using a pseudo-first-order reaction rate equation, we obtain:

[0012] Furthermore, the degradation efficiency D% of Rhodamine B under the photocatalytic conditions of the photocatalytic material in step S1 is obtained through the equation: We obtain, where C0 is the initial concentration of Rhodamine B.

[0013] Furthermore, the UDF program in step S3 includes the gas phase and liquid phase volume fractions, the reaction rate of the photocatalytic reaction, and the mass fraction of the product.

[0014] Furthermore, the boundary conditions set in step S3 are as follows:

[0015] Radiation boundary type: semi-transparent

[0016] DPM boundary type: reflect

[0017] Boundary material: glass

[0018] Inner cylinder wall surface movement state: Relative to Adjacent Cell Zone Roatational.

[0019] Furthermore, in step S3, the multiphase flow model adopts the Eulerian-Eulerian two-phase flow model, the turbulence model adopts the k-ε model, and the radiation model adopts the DO model, by solving the radiation transfer equation: Where e is the radiative intensity of photocarriers absorbed by the photocatalytic material at time t, and κ λ σ λ and Φ λ λ represents the volume absorption coefficient, volume scattering coefficient, and radiative flux of the photocatalytic material at wavelength λ; r is the vector representing the direction of photocarrier transport; s is the velocity vector of photocarriers at the lamp source; s' is the velocity vector of photocarriers after transporting a certain distance; Ω' is the angle at which photocarriers transport to the solid. DPM model settings:

[0020] Injection type: Surface

[0021] Particle size distribution: uniform.

[0022] Furthermore, the degradation rate r of Rhodamine B in the UDF procedure described in step S3... RhB Through the equation: We obtain K, where K is the adsorption equilibrium constant, M is the molar mass of Rhodamine B, e is the numerical value of photocarrier radiation intensity, and I is the light source intensity.

[0023] Furthermore, the photocatalytic material is carbon dot / bismuth oxychloride.

[0024] The application of the analysis method for the distribution law of multiple physical fields in the photocatalytic device is characterized by guiding the structural design of the photocatalytic device; combining the flow field, radiation field, and discrete phase distribution cloud map to change the rotation speed and light field intensity to obtain the distribution of the flow field, radiation field, and discrete phase of the photocatalytic material and the degradation efficiency of Rhodamine B in the Taylor-Couette reactor under multiple reaction conditions; based on the simulation results and referring to the degradation efficiency of the standard degradation process of Rhodamine B, the structural design of the photocatalytic device is adjusted and guided, and suitable reaction conditions are determined.

[0025] The application of the analytical method for the distribution law of multiple physical fields in the photocatalytic device is characterized by being used to determine the photocatalytic degradation reaction conditions of the photocatalytic device.

[0026] In this invention, the chemical reaction rate of Rhodamine B is simulated by coupling the chemical reaction with the flow field, radiation field, and discrete phase. The interior of the Taylor-Couette reactor is visualized using contour plots, which facilitates the analysis of the impact of different operating conditions on the final degradation efficiency. This invention can provide the internal flow field, radiation field, and discrete phase distribution of the Taylor-Couette reactor under different operating conditions, and also provide the degradation efficiency of the photocatalytic material at different time points. This allows for the selection of more suitable operating conditions according to different needs, reduces trial-and-error costs, accelerates the application of the Taylor-Couette reactor in the field of photocatalysis, and is of great significance to the industrialization of photocatalysis technology. Attached Figure Description

[0027] Figure 1 The diagram shows the structure of the Taylor-Couette photocatalytic reactor used in the example simulation.

[0028] Figure 2 The following are simplified three-dimensional mesh diagrams of the reactor, labeled as follows: (a) Overall mesh structure; (b) Main mesh diagram; (c) Top view mesh diagram.

[0029] Figure 3 The figure shows a comparison between experimental and simulated numerical values ​​(inner cylinder rotation speed is 43 rpm, xenon lamp power is 300W).

[0030] Figure 4 The flow field distribution cloud map is shown at different rotation speeds in the example (xenon lamp power is 300W).

[0031] Figure 5 The radiation field and discrete phase distribution cloud maps at different rotation speeds in the embodiment are shown (xenon lamp power is 300W).

[0032] Figure 6 The radiation field and discrete phase distribution cloud map are shown in the example under different xenon lamp powers (inner cylinder rotation speed is 43 rpm).

[0033] In the diagram: 1-lamp holder, 2-outer cylinder, 3-inner cylinder, 4-xenon lamp, 5-motor, 6-gearbox. Detailed Implementation

[0034] The present invention will be further described below with reference to the accompanying drawings and examples:

[0035] The method for analyzing the distribution of multiple physics fields in a photocatalytic device according to the present invention employs a combination of experimental and simulation methods for numerical simulation, and includes the following steps:

[0036] Step S1: Prepare a 10 mg / L Rhodamine B solution as the treatment target, and prepare 5 ωt% carbon dot / bismuth oxychloride as the photocatalyst material. Obtain the characterization kinetic constants and photocatalytic degradation efficiency of Rhodamine B through photocatalytic degradation experiments; where the remaining concentration C of Rhodamine B at time t is... t (mg / l) via the standard equation: C t =9.64AU, where AU is the absorbance at time t, with a standard error of 99.97%, and the apparent rate constant k. r The rate was obtained using a pseudo-first-order reaction rate equation.

[0037]

[0038] In this embodiment, the photocatalyst material is carbon dot / bismuth oxychloride, and the apparent rate constant k is... r =6.25m 3 / mol. The degradation efficiency D% of Rhodamine B under photocatalysis of carbon dots / bismuth oxychloride is obtained by the equation: The result is that C0 is the initial concentration of Rhodamine B, which is 10 mg / L.

[0039] Step S2: with Figure 1 Taking a ring-shaped photocatalytic reactor as an example, the multiphysics field distribution law is analyzed. First, the structure of the Taylor-Couette reactor is determined, including an inner cylinder with a radius of 45 mm and a height of 424.5 mm, an outer cylinder with a radius of 60 mm and a height of 424.5 mm, a xenon lamp, lamp holder, gearbox, and motor. The motor is connected to the gearbox, controlling the rotation of the inner cylinder, thereby driving the solution in the ring-shaped cavity formed by the inner and outer cylinders to form a Taylor-Couette vortex; (Refer to...) Figure 2 Secondly, the reactor structure was simplified, and a three-dimensional geometric model was constructed in ICEM software. Then, Ogrid Block was used to mesh the computational domain, and finally, the unstructured mesh was converted into a structured mesh.

[0040] Step S3: Import the pre-defined 3D mesh model into ANSYS-Fluent for simulation and solve the problem, and write and import the UDF program; based on the experimentally obtained properties of Rhodamine B and carbon point / bismuth oxychloride, set the multiphase flow model, turbulence model, radiation model, DPM model, and chemical reaction parameters; use the Coupled algorithm for Pressure-Velocity Coupling, and use Warped-Face Gradient Correction and High-order Term Relaxation to assist in the calculation; perform standard initialization of the model and set boundary conditions, perform transient calculations, and perform transient calculations on the flow field, radiation field, and distribution of photocatalytic materials in the Taylor-Couette reactor under the set rotation speed and light intensity conditions, as well as the reaction kinetics of the Rhodamine B degradation process, to obtain the degradation efficiency of Rhodamine B under the simulated conditions.

[0041] The UDF program includes the gas and liquid phase volume fractions, the photocatalytic reaction rate, and the product mass fraction at each time point.

[0042] The multiphase flow model adopts the Euler-Euler two-phase flow model, the turbulence model adopts the k-ε model, and the radiation model adopts the DO model. This is achieved by solving the radiative transfer equation:

[0043] Where e is the radiative intensity of photocarriers absorbed by the photocatalytic material at time t, and κ λ σ λ and Φ λ λ represents the volume absorption coefficient, volume scattering coefficient, and radiative flux of the photocatalytic material at wavelength λ; r is the vector representing the direction of photocarrier transport; s is the velocity vector of photocarriers at the lamp source; s' is the velocity vector of photocarriers after transporting a certain distance; Ω' is the angle at which photocarriers transport to the solid. DPM model settings:

[0044] Injection type: Surface

[0045] Particle size distribution: uniform.

[0046] The boundary conditions set are as follows:

[0047] Radiation boundary type: semi-transparent

[0048] DPM boundary type: reflect

[0049] Boundary material: glass

[0050] Inner cylinder wall surface movement state: Relative to Adjacent Cell Zone Roatational.

[0051] The degradation rate r of Rhodamine B in the UDF program is described. RhB Through the equation: We obtain K, where K is the adsorption equilibrium constant of Rhodamine B, M is the molar mass of Rhodamine B, e is the photocarrier radiation intensity, and I is the light source intensity.

[0052] Step S4: Set the rotation speed of the inner cylinder to 43, 114, and 200 rpm, and the xenon lamp power to 300, 310, and 320 W, respectively. View the flow field distribution cloud map, radiation field, and discrete phase distribution cloud map, as well as the degradation efficiency of Rhodamine B under simulated conditions in the Result file. Compare the degradation efficiency of Rhodamine B under simulated conditions with the photocatalytic degradation efficiency actually measured under the corresponding experimental conditions to observe whether the results are consistent. (Refer to...) Figure 3 The simulation values ​​obtained in this embodiment are basically consistent with the experimental values, proving that the simulation settings are accurate.

[0053] Combination Figure 4 and Figure 5 Analyzing the distribution of flow field, radiation field, and discrete phase within the reactor at different inner cylinder rotation speeds reveals the formation of Taylor vortices within the reactor. These vortices are most abundant at 114 rpm, allowing for better entrainment and dispersion of the photocatalytic material in the solution, resulting in more uniform photon reception and enhanced catalytic activity. Combined with… Figure 6 Analyzing the distribution of radiation field and discrete phase within the reactor under different xenon lamp powers reveals that as the lamp power increases, more photons are distributed within the reactor. However, when the amount of photocatalytic material is fixed, the amount of photons that can be received is limited. In this embodiment, the photocatalytic material's absorption of photons is already close to saturation at 300W, so higher power is not required, thus helping to reduce energy consumption. Therefore, these analyses can help select the most suitable operating conditions.

[0054] Adding Rhodamine B to the chemical reaction rate couples the chemical reaction with the flow field, radiation field, and discrete phase. By using cloud maps to visualize the interior of the Taylor-Couette reactor, it is easier to analyze the impact of different operating conditions on the final degradation efficiency, providing a theoretical basis for the scale-up and application of the Taylor-Couette reactor in the field of photocatalysis.

[0055] The embodiments described above are preferred embodiments of the present invention, but the present invention is not limited to the above embodiments. Any obvious improvements, substitutions or modifications that can be made by those skilled in the art without departing from the essence of the present invention shall fall within the protection scope of the present invention.

Claims

1. A method for analyzing the distribution law of multiple physics fields in a photocatalytic device, characterized in that, The specific steps are as follows: Step S1: Using Rhodamine B as the treatment target and photocatalytic materials as catalysts, the apparent rate constant and photocatalytic degradation efficiency of Rhodamine B are obtained through photocatalytic degradation experiments. Step S2: Determine and simplify the structure and dimensions of the Taylor-Kueit reactor, construct a three-dimensional geometric model in ICEM software and perform structured mesh generation; Step S3: Import the divided 3D mesh model into ANSYS-Fluent for simulation and solve, and write and import the UDF program; set the multiphase flow model, turbulence model, radiation model, DPM model, and chemical reaction parameters according to the experimental parameters; use the Coupled algorithm for Pressure-Velocity Coupling, and use Warped-Face Gradient Correction and High-order Term Relaxation to assist the calculation; perform standard initialization of the model and set boundary conditions; perform transient calculations on the flow field, radiation field, and distribution of photocatalytic materials in the Taylor-Couette reactor under the set rotation speed and light intensity conditions, and the reaction kinetics of the Rhodamine B degradation process to obtain the degradation efficiency of Rhodamine B under the simulated conditions; The multiphase flow model adopts the Euler-Euler two-phase flow model, the turbulence model adopts the k-ε model, and the radiation model adopts the DO model. This is achieved by solving the radiative transfer equation: Where e is the radiative intensity of photocarriers absorbed by the photocatalytic material at time t, and κ λ σ λ and Φ λ Here, λ represents the volume absorption coefficient, volume scattering coefficient, and radiative flux of the photocatalytic material at wavelength λ; r is the vector representing the direction of photocarrier transport; s is the velocity vector of photocarriers at the lamp source; s' is the velocity vector of photocarriers after transporting a certain distance; and Ω' is the angle at which photocarriers transport to the solid. DPM model settings: Injection type: Surface Particle size distribution: uniform; The degradation rate r of Rhodamine B in the UDF program RhB Through the equation: We obtain, where K is the adsorption equilibrium constant of Rhodamine B, M is the molar mass of Rhodamine B, e is the photocarrier radiation intensity, and I is the light source intensity. Step S4: In the Result, view the flow field distribution cloud map, radiation field and discrete phase distribution cloud map, and the degradation efficiency of Rhodamine B under simulated conditions.

2. The method for analyzing the distribution law of multiple physics fields in the photocatalytic device according to claim 1, characterized in that, In step S1, the remaining concentration C of Rhodamine B at time t is... t (mg / l) was obtained through the standard equation, C t =9.64AU, where AU is the absorbance at time t, with a standard error of 99.97%, and the apparent rate constant k r The pseudo-first-order reaction rate equation was used to obtain... .

3. The method for analyzing the distribution law of multiple physics fields in the photocatalytic device according to claim 2, characterized in that, In step S1, the degradation efficiency D% of Rhodamine B under the photocatalytic conditions of the photocatalytic material is determined by the equation: We obtain, where C0 is the initial concentration of Rhodamine B.

4. The method for analyzing the distribution law of multiple physics fields in the photocatalytic device according to claim 1, characterized in that, The UDF program in step S3 includes the gas phase and liquid phase volume fractions, the photocatalytic reaction rate, and the mass fraction of the product.

5. The method for analyzing the distribution law of multiple physics fields in the photocatalytic device according to claim 1, characterized in that, In step S3, boundary conditions are set: Radiation boundary type: semi-transparent DPM boundary type: reflect Boundary material: glass Inner cylinder wall surface movement state: Relative to Adjacent Cell Zone Roatational.

6. The method for analyzing the distribution law of multiple physics fields in the photocatalytic device according to claim 1, characterized in that, The photocatalytic material is carbon dot / bismuth oxychloride.

7. The application of the analytical method for the distribution law of multiphysics fields in the photocatalytic device according to any one of claims 1-6, characterized in that, This method is used to guide the structural design of photocatalytic devices. By combining flow field, radiation field, and discrete phase distribution cloud map, and changing the rotation speed and light field intensity, the flow field, radiation field, and discrete phase distribution of the photocatalytic material, as well as the degradation efficiency of Rhodamine B, are obtained under multiple reaction conditions in the Taylor-Couette reactor. Based on the simulation results and referring to the degradation efficiency of the standard degradation process of Rhodamine B, the structural design of the photocatalytic device is adjusted and appropriate reaction conditions are determined.

8. The application of the analytical method for the distribution law of multiphysics fields in the photocatalytic device according to any one of claims 1-6, characterized in that, Used to determine the photocatalytic degradation reaction conditions of the photocatalytic device.

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