Optimization design method of internal circulation ozone contact reaction tower

Abstract

The invention discloses an optimal design method of an internal circulation ozone contact reaction tower. The method comprises the following steps: S1, designing a reaction tower structure; s2, designing parameters of a reaction tower; according to the invention, the internal structure of the reaction tower is optimally designed, the internal circulation assembly is added, and the model is adopted to simulate a gas-liquid flow field in the internal circulation ozone contact reaction tower, so that the structure and the size of the reaction tower are optimized, and the ozone utilization rate and the organic matter removal effect are remarkably improved.

Description

Technical Field

[0001] The invention relates to the technical field of water treatment, and in particular to an optimization design method for an internal circulation ozone contact reaction tower. Background Art

[0002] In recent years, many closed chemical companies have left behind soil and groundwater pollution problems. When treating these contaminated soils, multiphase extraction methods are used. Multiphase extraction (MPE) technology is an in-situ remediation technology with high remediation efficiency, large treatment area, and can be applied to high-concentration contaminated land. Through vacuum extraction, soil gas, groundwater and floating oil layers in underground contaminated areas are extracted to the ground for phase separation and treatment to achieve the purpose of site remediation. Multiphase extraction will obtain a large amount of multiphase extracts, which also contain low-concentration dissolved organic matter, with complex components, large concentration fluctuations, variable flow rates, and many difficult-to-degrade organic matter. They need to be treated before they can be reused or directly discharged into surface water.

[0003] In the process of water treatment of multiphase extracts, advanced oxidation processes are usually used; advanced oxidation processes can produce free radicals with strong oxidizing properties. These free radicals are non-selective to organic matter and can treat toxic and harmful wastewater. Advanced oxidation processes include Fenton process, photochemical oxidation process, electrochemical oxidation process, catalytic ozonation process, etc. Among them, catalytic ozonation process has the characteristics of high oxidation ability, short treatment time, low selectivity to organic matter, and the catalyst can form different oxidation mechanisms, has strong adaptability to wastewater, and is a potential process for treating multiphase extracts.

[0004] At present, in the catalytic ozonation process, due to the poor ozone mass transfer effect and low ozone utilization rate in the traditional packed tower, the ozone dosage in actual application is large, and the energy consumption of the ozone preparation process is high, resulting in high cost of ozone technology. According to the results of literature calculations, the ozone transfer efficiency in the empty tower is less than 25%. In actual application, the ozone mass transfer effect is generally improved by increasing the height of the reactor to control the cost of ozone technology. Since ozone can produce hydroxyl radicals through self-decomposition reaction, as the height increases, the residence time of ozone in the reactor is prolonged, which is conducive to the decomposition of more hydroxyl radicals to participate in the reaction, thereby improving the utilization rate of ozone. However, in order to make the treated wastewater meet the standards, some designed reactors are far beyond the range that can be accommodated by the wastewater treatment site. At the same time, the excessive height of the reactor will increase the operating pressure of the water pump and the aeration equipment, which is not conducive to saving energy. Therefore, it is necessary to develop an ozone-liquid contact reactor that can extend the gas-liquid contact time without increasing the height, has strong shock load resistance, and has low energy consumption, which is conducive to reducing the operation and investment costs of ozonation technology and providing technical support for its further development and wide application. Summary of the invention

[0005] In order to solve the above problems, the present invention provides an optimization design method for an internal circulation ozone contact reaction tower.

[0006] An optimization design method for an internal circulation ozone contact reaction tower comprises the following steps:

[0007] S1. Design the reaction tower structure;

[0008] The reaction tower comprises a tower body and a central tube located at the center of the tower body and fixed to the tower body, wherein the central tube is provided with a first air inlet pipe for conveying water to a lifting pipe in the central tube; the lifting pipe is used to convey water to the inside of the tower body outside the central tube;

[0009] A plurality of filling pads for ozone oxidation of water are arranged in the tower body outside the central tube, the filling pads are in annular shape, and the inner ring of the filling pads is sleeved on the outer wall of the central tube, and a catalyst is arranged on each layer of the filling pads; a second air inlet pipe is arranged in the tower body for transporting part of the ozone-oxidized water back to the central tube for circulation treatment;

[0010] S2. Design reaction tower parameters;

[0011] Constructing the internal circulation ozone contact reaction tower model, wherein the input of the internal circulation ozone contact reaction tower model is the reaction tower parameter, and the output of the internal circulation ozone contact reaction tower model is the gas holdup;

[0012] Determining the optimal values ​​of the reaction tower parameters with the goal of maximizing the gas holdup;

[0013] Among them, the reaction tower parameters include: the aspect ratio of the tower body, the ratio of the diameter of the central tube to the diameter of the tower body, the ratio of the height of the central tube to the height of the tower body, the number of filling cushions, the ratio of the tower body height to the catalyst layer spacing, the diameter of the first air inlet pipe, the diameter of the riser, the spacing between the bottom surface of the tower body and the bottom of the central tube, and the material of the filling cushion.

[0014] Description: The above method can be used to optimize the reaction tower of water treatment, make the internal circulation effect better, extend the ozone residence time, improve the utilization rate of ozone and the gas content at the bottom of the central tube, and through the reflux setting, the water body can be treated multiple times, thereby improving the effect of water treatment.

[0015] Furthermore, through the internal circulation ozone contact reaction tower model, the optimal values ​​of the reaction tower parameters are obtained as follows: the height-to-diameter ratio of the tower body is 6, the ratio of the diameter of the central tube to the diameter of the tower body is 0.9, the ratio of the height of the central tube to the height of the tower body is 0.88-0.92, the number of filling cushions is 2, the ratio of the height of the reaction tower to the spacing between the catalyst layers is 6, the first air inlet pipe is 7-9 mm, the diameter of the riser is 3-5 mm, the spacing between the inner bottom surface of the tower body and the bottom of the central tube is 35-50 mm, and the filling cushion is made of porous titanium plate.

[0016] Note: Through the above-mentioned design of height-to-diameter ratio, the utilization rate of ozone can be increased by more than 20%, affecting the gas vector flow rate. Increasing the gap spacing at the bottom of the reaction tower increases the gas holdup in the middle of the outer tube. Adjusting the ratio of the inner wall height to the outer wall height of the center tube increases the gas holdup at the bottom of the center tube. The smaller the inner diameter of the center tube, the greater the gas holdup in the descending area at the bottom of the outer tube, which weakens the fluid driving force in the ascending area inside the guide tube, and the ozone residence time is extended by 44.5%. The catalyst layer will capture part of the ozone gas and block the upward process of the gas. When the spacing between the catalyst layers is relatively small, the resistance is too large, causing the gas to deposit at the bottom. The higher the catalyst layer, the slower the gas flow rate, and the amount of water reacted on the upper part of the catalyst will decrease, which is not conducive to the mixing effect of ozone and water. The ratio of the reactor height to the spacing between the catalyst layers is 6, which is the best effect, and the flow rate is increased by more than 20%. The increase in the diameter of the inlet pipe and the riser increases the volume of the ozonated gas per unit time, which will increase the gas holdup in the reaction tower. When the reflux window is too low, the upper gas will be reduced. When the reflux window is too high, the gas reflux power on the lower side of the outer cylinder will be insufficient. When the ratio of the reflux window height to the reactor height is 80%, the interphase fluidization effect inside the reaction tower is optimal, and the circulation flow rate is increased by more than 7%.

[0017] Furthermore, the second air inlet pipe is arranged at the bottom of the tower body, and a microporous diffuser is provided on the second air inlet pipe.

[0018] Note: By setting the position of the air inlet pipe and the microporous diffuser, relatively uniform aeration can be achieved: the microporous diffuser can produce a large number of tiny bubbles, which are in full contact with the water during the rising process in the water, which helps to evenly distribute the gas and improve the aeration efficiency.

[0019] Furthermore, the interior of the tower body outside the central tube is connected to the interior of the central tube through a reflux window arranged on the central tube, and the reflux window is located on the central tube above the filling cushion layer.

[0020] Note: The reflux window arranged above can facilitate the reflux of treated water.

[0021] Furthermore, the filling cushion layer is in the shape of a circular column, and the filling cushion layer is fixedly sleeved on the inner wall of the central tube, and the lifting pipe passes through the filling cushion layer.

[0022] Description: The above arrangement enables the water flow to sequentially pass through the filling cushion layer and the catalyst located thereon, achieving a better ozone oxidation catalytic effect, thereby achieving the treatment of polluted water bodies.

[0023] Furthermore, the internal circulation ozone contact reaction tower model includes a simulation module and a calculation module;

[0024] The simulation module includes a geometric simulation module for simulating the reaction tower structure and a material simulation module for simulating the reactant state; the reactant state includes the flow rate of the continuous phase fluid and the flow rate of the dispersed phase particles; the calculation module is used to calculate the simulation parameters of the simulation module to obtain the gas holdup, ozone residence time and circulation flow rate.

[0025] Note: The above model construction can simulate the water treatment process inside the reaction tower; by building geometric models and material modules, the structure of the reaction tower and the state of the reactants can be accurately simulated, so as to more accurately predict the gas holdup and reaction efficiency. The design of the reaction tower, including size, shape, material and internal structure, can be optimized to improve the gas holdup and reaction efficiency.

[0026] Furthermore, the method for constructing the geometric simulation module includes:

[0027] First, a three-dimensional model of the reaction tower is built;

[0028] Then meshing the three-dimensional model;

[0029] Finally, the boundary conditions are set, and the geometric simulation module is constructed;

[0030] Wherein, the boundary conditions include the reaction tower inlet velocity, the reaction tower outlet velocity, and the wall conditions; the reaction tower inlet includes an air inlet and a water inlet, and the reaction tower outlet includes an air outlet and a water outlet.

[0031] Note: The above method can establish a geometric model and use the geometric model to realize the setting of the reaction tower, central tube, etc. The above key positions include the air inlet, catalyst and filling cushion, gas-liquid contact area, air outlet and liquid discharge port.

[0032] Furthermore, the grid division method is:

[0033] The tower body, the central tube and the filling layer are divided by using quadrilateral grids;

[0034] The aeration pipe, the connection between the aeration pipe and the tower body, the connection between the aeration pipe and the central tube, the connection between the first air inlet pipe and the tower body, the connection between the first air inlet pipe and the tower body, the connection between the second air inlet pipe and the central tube, and the connection between the second air inlet pipe and the tower body are all divided using hexahedral grids;

[0035] The first air intake pipe, the second air intake pipe and the riser are divided using tetrahedral grids.

[0036] Note: During the model building process, there are usually some tiny geometric features, such as slits, tangent angles, protrusions, micropores, etc. Although these geometric features have very little effect on the flow, when generating the mesh, in order to ensure the quality of the mesh, a smaller mesh size is required to describe these geometric features, which will cause a significant increase in the number of meshes, thereby increasing the calculation time. Therefore, for these geometric features that have very little effect on the flow, it is necessary to simplify them appropriately before generating the mesh; that is, to establish the model in the above way, it can save the amount of calculation and achieve a higher simulation accuracy.

[0037] Furthermore, the method for constructing the material simulation module includes:

[0038] First, the properties of the continuous phase fluid and the dispersed phase particles are defined; the properties include density and viscosity;

[0039] Then, the initial conditions of the continuous phase fluid and the dispersed phase particles are set, wherein the initial conditions include an initial flow rate and an initial concentration;

[0040] Selecting a flow model and determining a fluid conservation equation, the construction of the material simulation module is completed;

[0041] The operation method of the computing module includes:

[0042] Firstly, based on mesh division, multiple key interfaces of the reaction tower are determined;

[0043] Then, based on the initial conditions and boundary conditions, the fluid conservation equation is used to calculate and iteratively update the flux on each of the key interfaces; the flux includes mass flux, momentum flux and energy flux;

[0044] Converting the flux on each of the key interfaces to obtain gas holdup, ozone residence time and circulation flow rate;

[0045] The key interfaces include: air inlet, catalyst and filling cushion, water distributor, gas-liquid contact area, air outlet and liquid discharge port.

[0046] Note: The above method can accurately predict the flow behavior of fluid in a specific geometric model, including flow rate, pressure, temperature and turbulence parameters, through numerical calculation and finite volume method. Based on the simulation results, the geometric design of the equipment or system can be optimized to improve efficiency, reduce energy consumption or meet specific performance requirements; it can save time and cost. The above key positions include the air inlet, catalyst and packing pad, gas-liquid contact area, air outlet and liquid outlet.

[0047] Further, the method for determining the optimal value of the reaction tower parameter with the goal of maximizing the gas holdup comprises:

[0048] Define an objective function of the gas holdup φ at the key position; Where V g is the gas volume, V l is the volume of the liquid, V g 、V l Obtained by the calculation module;

[0049] Determine multiple groups of reaction tower parameters; based on the reaction tower parameters and boundary conditions, calculate the reaction tower parameter values ​​with the maximum gas holdup φ, and use the values ​​as the optimal values ​​of the reaction tower parameters.

[0050] Note: The above method can be used to optimize the operating parameters of the reaction tower based on boundary conditions.

[0051] The beneficial effects of the present invention are:

[0052] The method of the present invention can be used to optimize the reaction tower of water treatment, so that the effect of internal circulation is better, the ozone residence time is extended, the utilization rate of ozone and the gas content at the bottom of the central tube are improved, and the water body can be treated multiple times by setting the reflux, thereby improving the effect of water body treatment; the model construction of the present invention can realize the simulation process of water treatment inside the reaction tower; by constructing a geometric model and a material module, the structure and reactant state of the reaction tower can be accurately simulated, so as to more accurately predict the gas content and reaction efficiency. The design of the reaction tower is optimized, including the size, shape, material and internal structure, so as to improve the gas content and reaction efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0053] Figure 1 This is a schematic diagram of the structure of an internal circulation ozone reaction tower in an embodiment of the present invention;

[0054] Wherein: 1-tower body, 2-center tube, 3-water inlet pipe, 4-first air inlet pipe, 5-lift pipe, 6-top cover of center tube, 7-bottom plate of center tube, 8-inner wall of center tube, 9-microporous diffuser, 10-second air inlet pipe, 11-catalyst layer, 12-cushion, 13-reflux window, 14-total water outlet pipe of reaction tower, 15-ozone air guide pipe, 16-check valve, 17-drain pipe, 18-air guide pipe;

[0055] Figure 2 It is a schematic diagram of the assembly of the model in the embodiment of the present invention;

[0056] Figure 3 1 is a comparison of the gas holdup distribution cloud diagrams of the embodiments of the present invention (a is an internal circulation reactor; b is a common reactor);

[0057] Figure 4 This is a comparison of the ozone utilization effect of the embodiments of the present invention;

[0058] Figure 5 The effect of the height-to-diameter ratio on the removal effect of COD and TOC in the embodiment of the present invention (a: COD; b: TOC);

[0059] Figure 6 The effect of the catalyst layer spacing on the COD and TOC removal effects of the embodiments of the present invention (a: COD; b: TOC);

[0060] Figure 7 The effect of the number of catalyst layers on the removal effect of COD and TOC in the embodiment of the present invention (a: COD; b: TOC);

[0061] Figure 8 The effect of aeration pore size on COD and TOC removal in the embodiment of the present invention (a: COD; b: TOC);

[0062] Fig. 9 The effect of the reflux window height on the removal effect of COD and TOC in the embodiment of the present invention (a: COD; b: TOC);

[0063] Fig.10 The effect of the diameters of the air pipe and the riser pipe on the removal effect of COD and TOC in the embodiment of the present invention (a: COD; b: TOC);

[0064] Fig.11 The effect of the inner cylinder height on the COD and TOC removal effects in the embodiment of the present invention (a: COD; b: TOC);

[0065] Fig.12 The effect of the inner cylinder diameter on the COD and TOC removal effects of the embodiment of the present invention (a: COD; b: TOC);

[0066] Fig.13The effect of the bottom gap distance on the removal effect of COD and TOC in the embodiment of the present invention (a: COD; b: TOC);

[0067] Fig.14 It is the internal circulation ozone contact reaction tower model and grid division according to the embodiment of the present invention. DETAILED DESCRIPTION

[0068] In order to further illustrate the method adopted by the present invention and the effect achieved, the technical solution of the present invention will be clearly and completely described in combination with experiments below.

[0069] Embodiment 1: A method for optimizing the design of an internal circulation ozone contact reaction tower comprises the following steps:

[0070] S1. Design the reaction tower structure;

[0071] like Figure 1 As shown, the reaction tower comprises a tower body 1 and a central tube 2 located at the center of the tower body 1 and fixed to the tower body 1. The central tube 2 is provided with a first air inlet pipe 4 for conveying water to a lifting pipe 5 in the central tube 2; the lifting pipe 5 is used to convey water to the inside of the tower body 1 outside the central tube 2;

[0072] A plurality of filling pads 12 for ozone oxidation of water are arranged in the tower body 1 outside the central tube 2. The filling pads 12 are annular in shape, and the annular inner ring of the filling pads 12 is sleeved on the outer wall of the central tube 2. A catalyst is arranged on each layer of the filling pads 12. A second air inlet pipe 10 is arranged in the tower body 1 for transporting part of the ozone-oxidized water back to the central tube 2 for circulation treatment.

[0073] S2. Design reaction tower parameters;

[0074] Constructing the internal circulation ozone contact reaction tower model, wherein the input of the internal circulation ozone contact reaction tower model is the reaction tower parameter, and the output of the internal circulation ozone contact reaction tower model is the gas holdup;

[0075] Determining the optimal values ​​of the reaction tower parameters with the goal of maximizing the gas holdup;

[0076] Among them, the reaction tower parameters include: the height-to-diameter ratio of the tower body 1, the ratio of the diameter of the central tube 2 to the diameter of the tower body 1, the ratio of the height of the central tube 2 to the height of the tower body 1, the number of filling cushions 12, the ratio of the height of the tower body 1 to the spacing between the catalyst layers, the diameter of the first air inlet pipe 4, the diameter of the riser 5, the spacing between the inner bottom surface of the tower body 1 and the bottom of the central tube 2, and the material of the filling cushion 12.

[0077] The simulation results show that the height-to-diameter ratio of the tower body is 6, the ratio of the diameter of the central tube to the diameter of the tower body is 0.9, the ratio of the outer wall height of the central tube to the inner wall height of the central tube is 0.88-0.92, the number of the filling cushions is 2, the ratio of the height of the reaction tower to the spacing between the catalyst layers is 6, the first air inlet pipe is 7-9 mm, the diameter of the riser is 3-5 mm, the spacing between the bottom surface of the tower body and the bottom of the central tube is 35-50 mm, and the filling cushion is made of porous titanium plate;

[0078] The second air inlet pipe 10 is arranged at the bottom of the tower body 1, and a microporous diffuser 9 is provided on the second air inlet pipe 10; the interior of the tower body 1 outside the central tube 2 is connected with the interior of the central tube 2 through a reflux window 13 arranged on the central tube 2, and the reflux window 13 is located on the central tube 2 above the filling cushion layer 12; the filling cushion layer 12 is in the shape of a circular column, and the filling cushion layer 12 is fixedly sleeved on the inner wall of the central tube 2, and the lifting pipe 5 passes through the filling cushion layer 12.

[0079] In the embodiment of the present invention, the internal circulation ozone contact reaction tower model includes a simulation module and a calculation module;

[0080] The simulation module includes a geometric simulation module for simulating the reaction tower structure and a material simulation module for simulating the reactant state; the reactant state includes the flow rate of the continuous phase fluid, the turbulence parameters of the continuous phase fluid, the flow rate of the dispersed phase particles, and the turbulence parameters of the dispersed phase particles; the calculation module is used to calculate the simulation results of the simulation module to obtain the gas holdup, ozone residence time and circulation flow rate.

[0081] The construction method of the geometric simulation module includes:

[0082] The first step is to establish a three-dimensional model of the reaction tower; define the geometric size and structure of the reaction tower; use the geometric modeling tool in the CFD software to create a three-dimensional model of the reaction tower;

[0083] The second step is to mesh the three-dimensional model;

[0084] The grid division method is:

[0085] The tower body 1, the central tube 2 and the filling layer are divided into quadrilateral grids;

[0086] The aeration pipe, the connection between the aeration pipe and the tower body 1, the connection between the aeration pipe and the central tube 2, the connection between the first air inlet pipe 4 and the tower body 1, the connection between the first air inlet pipe 4 and the tower body 1, the connection between the second air inlet pipe and the central tube 2, and the connection between the second air inlet pipe 10 and the tower body 1 are all divided using hexahedral grids;

[0087] The first air intake pipe 4, the second air intake pipe 10 and the riser pipe 5 are divided by using a tetrahedral grid;

[0088] Specifically, Fig.14 As shown; in order to obtain high-quality meshes, quadrilateral meshes are mainly used for division, and different types are selected according to whether the polygon shape is regular, so as to obtain high-quality meshes. The cross-sectional areas of aeration pipes and other parts are divided by hexahedral meshes in the Cooper method, while the connection between the air pipe and the riser is divided by tetrahedral meshes due to the complex geometry; the reason is that in 3D models, there are usually some small geometric features, such as slits, tangent angles, protrusions, micropores, etc. Although these geometric features have very little effect on the flow, when generating the mesh, in order to ensure the quality of the mesh, a smaller mesh size is required to describe these geometric features, which will cause a significant increase in the number of meshes, thereby increasing the calculation time. Therefore, for these geometric features that have very little effect on the flow, it is necessary to simplify them appropriately before generating the mesh. The software Gambit is used to establish the model and divide the mesh.

[0089] Since this experimental model is an axisymmetric figure, half of it can be simulated in Fluent simulation, and then symmetric processing can be performed. Therefore, in order to save calculation time, only half of it is meshed and calculated. When dividing the mesh, the cross-sectional area of ​​the aeration pipe and so on adopts the Cooper method of hexahedral mesh division, while the connection area between the air pipe and the riser is more complicated due to the complex geometry. The final number of mesh units is about 55w;

[0090] The third step is to set the boundary conditions, that is, the geometric simulation module is built;

[0091] Wherein, the boundary conditions include the reaction tower inlet velocity, the reaction tower outlet velocity, and the wall conditions. The reaction tower inlet includes an air inlet and a water inlet, and the reaction tower outlet includes an air outlet and a water outlet. For example, the reaction tower mass flow inlet velocity is 0.7 m / s, and the reaction tower mass flow water distributor velocity is 0.04 m / s. The wall of the reactor is set as a no-slip wall boundary.

[0092] Steps to establish the material simulation module:

[0093] First, define the properties of the continuous phase fluid (such as water) and the dispersed phase particles (such as bubbles); the properties include density, viscosity, diffusion coefficient and reaction rate; the density of water is 1000 kg / m 3 , viscosity is 0.001Pa·s; the diffusion coefficient of ozone bubbles in water is 2.0×10 -5 cm 2 / s, the reaction rate of ozone bubbles in water is 107 mol / L·s.

[0094] Then, initial conditions of the continuous phase fluid and the dispersed phase particles are set, wherein the initial conditions include initial flow rate, initial pressure and initial concentration;

[0095] The flow model is selected and the fluid conservation equation is determined, and the construction of the material simulation module is completed.

[0096] The flow model includes a multiphase flow model;

[0097] Ⅰ. Through the following fluid conservation equations, the mass flux, momentum flux and energy flux values ​​on the key interface can be calculated in real time;

[0098] The mass conservation equation for multiphase flow is: Where ρ is the fluid density, Yi is the mass fraction of gas phase component i, v is the fluid velocity vector, and Ri is the velocity of gas phase component i;

[0099] The momentum conservation equation is:

[0100] Where p is the pressure, μ is the dynamic viscosity, and f is the volume force;

[0101] The energy conservation equation is:

[0102] Where h is enthalpy, k is thermal conductivity, T is temperature, and φ is the internal heat source;

[0103] The above fluid conservation equation is discretized by the finite volume method, and then the discretized fluid conservation equation is solved by the iterative method based on the boundary conditions and initial conditions;

[0104] Ⅱ. Based on the above conservation equation, we can conclude that:

[0105] The mass flux at the critical interface is m = ρ·v·n, where ρ is the fluid density, v is the fluid velocity vector, and n is the normal vector of the interface.

[0106] The momentum flux at the critical interface is equal to ρv 2 ; Where ρ is the fluid density and v is the fluid velocity vector;

[0107] The energy flux at the critical interface is equal to ρ is the fluid density, v is the fluid velocity vector, h is the enthalpy, k is the thermal conductivity, and T is the temperature;

[0108] Among them, the velocity v is corrected by the Ke turbulence model; the Ke turbulence model affects the distribution of velocity by providing turbulent viscosity;

[0109] III. Calculation method of gas holdup: Calculate the gas volume flow rate based on the above mass flux and fluid density; Divide the gas volume flow rate by the total volume flow rate to obtain the gas holdup;

[0110] Calculation method of circulation flow: Calculate the circulation flow by mass flux and fluid density;

[0111] The calculation method of ozone residence time is: the volume of the reaction tower divided by the circulation flow rate to obtain the residence time.

[0112] Model selection: As a general fluid mechanics solving software, Fluent provides a variety of physical models to simulate different flow problems, such as multiphase flow model (Multiphase Model), radiation model (Radiation Model), component model (Species Model), discrete phase model (Discrete Phase Model) and noise model (AcousticModel) and other models.

[0113] Fluent provides two physical models to simulate multiphase flow: multiphase flow model and discrete phase model. The multiphase flow model is based on the Euler-Euler method, and the discrete phase model is based on the Euler-Lagrange method. The multiphase flow involved in this embodiment is more suitable for simulation using the Euler-Euler method, so Fluent's multiphase flow model is used to simulate the reaction tower. According to the strength of the interaction between the phases, Fluent's multiphase flow model is divided into VOF (Volume of Fluid) model, Mixture model and Euler model.

[0114] ①VOF model: The VOF model is a surface tracking method under a fixed Euler grid. This model can be used when it is necessary to obtain the interface between one or more immiscible fluids. In the VOF model, different fluid components share a set of momentum equations. During calculation, the volume ratio occupied by each fluid component is recorded in each calculation unit of the entire flow field. Application examples of the VOF model include stratified flow, free surface flow, injection, sloshing, flow of large bubbles in liquid, water flow when a dam breaks, and prediction of surface tension of jet failure.

[0115] ②Mixture model: The mixture model can be used for two-phase flow or multiphase flow (fluid or particle). Because in the Euler model, each phase is treated as an interpenetrating continuum, the mixture model solves the momentum equation of the mixture and describes the discrete phases by relative velocity. Applications of the mixture model include low-load particle-loaded flow, bubble flow, sedimentation, and cyclone separators. The mixture model can also be used for uniform multiphase flow without relative velocity of discrete phases.

[0116] ③Eulerian model: The Euler model is the most complex multiphase flow model in CFD. It establishes momentum equations and continuity equations to solve each phase. The pressure term and the interface exchange coefficients are coupled together, and the coupling method depends on the conditions of the phases involved. The treatment of granular flow (fluid-solid) is different from that of non-granular flow (flow-flow). Through CFD user-defined functions (UDF, user-defined functions), researchers can customize the calculation method of momentum exchange. Applications of the Euler model include bubble columns, flotation, particle suspension, and fluidized beds.

[0117] The multiphase flow model in the embodiment of the present invention adopts the Euler model, and the turbulence model adopts the ke two-equation model; the multiphase flow model and turbulence can be used to solve the multiphase flow fluid operation, and after the initial conditions and boundary conditions are given, the solution is performed to obtain the final gas holdup, circulation flow rate and ozone residence time, etc. The Euler model based on the Euler-Euler method simulates the internal circulation ozone contact reaction tower. The Euler model can not only obtain accurate phase interface information, but also consider the interaction between each phase. Therefore, this model can be used to predict the ozone mass transfer effect in the reactor. The above-mentioned finite volume method is a numerical algorithm widely used in the field of computational fluid dynamics. It divides the calculation area into a series of non-overlapping control volumes and integrates the conservation equations on each control volume to obtain a set of discrete equations; the core of this method is to ensure the conservation of physical quantities in the entire calculation domain, so that it has significant advantages in dealing with complex geometric shapes and boundary conditions.

[0118] The operation method of the computing module includes:

[0119] Firstly, based on mesh division, multiple key interfaces of the reaction tower are determined;

[0120] Then, based on the initial conditions and boundary conditions, the fluid conservation equation and the turbulence equation are used to calculate and iteratively update the flux on each of the key interfaces; the flux includes mass flux, momentum flux and energy flux;

[0121] The flux on each of the key interfaces is converted to obtain gas holdup, ozone residence time and circulation flow rate; (see the calculation method above)

[0122] The key interfaces include: air inlet, catalyst and filling cushion, water distributor, gas-liquid contact area, air outlet and liquid discharge port.

[0123] The operation of the above calculation module is completed through the solver in the CFD software (such as ANSYS Fluent, OpenFOAM, and the solver uses a double-precision pressure-based solver); the continuous fluid dynamics equations (such as the Navier-Stokes equations) are discretized to make them applicable to each control volume. This usually involves integrating the flux on the interface of each control volume. It is solved iteratively using numerical methods (such as the SIMPLE algorithm, the SIMPLER algorithm, or the SIMPLEC algorithm).

[0124] Specifically, in the process of establishing the model, calculations are performed according to the following principles:

[0125] 1) The lateral movement of bubbles in the central tube is negligible;

[0126] 2) Liquid enters evenly from the top of the central tube and flows out evenly from the bottom. Ignoring the interaction between gas and liquid phases, the bubble group can be balanced according to the law of conservation of momentum.

[0127] 3) The gas phase contains only oxygen and ozone, without other impurities, and the effects of convection, absorption, and ozone self-decomposition on the aeration process are not considered;

[0128] 4) The gas phase satisfies the group equilibrium model in the central tube, and no other factors affect the total volume of the gas.

[0129] 5) Using the symmetry assumption, gravity is vertically downward, ignoring the influence of temperature, and the density of air and water remains unchanged.

[0130] The internal structure of the reactor was simulated using two-dimensional and three-dimensional models. First, the reactor height-to-diameter ratio, diameter ratio, bottom gap height, catalyst layer, air pipe and riser diameter, and aeration equipment were optimized using the two-dimensional model. Since this experimental model is an axisymmetric figure, half of it can be simulated in the Fluent simulation, and then symmetric processing can be performed.

[0131] The CFD software Fluent is used to simulate the flow field in the reactor. The flow in the reactor includes the flow of liquid and gas, and the two affect each other, which is a typical multiphase flow. There are currently two types of processing methods for simulating multiphase flow: Euler-Lagrangian method and Euler-Euler method. The Euler-Lagrangian method is to divide the fluid into a continuous phase and a discrete phase, in which the continuous phase is solved by the NS equation, and the discrete phase is tracked by the Lagrangian method. The influence of the discrete phase on the continuous phase is reflected by the momentum source term. The Euler-Euler method regards the multiphase flow as a continuous phase and solves the NS equation based on the multiphase flow. This method is suitable for situations where the concentration difference between the phases is not particularly large.

[0132] According to the flow characteristics in the reaction tower, this embodiment uses the Euler model based on the Euler-Euler method to simulate the internal circulation ozone contact reaction tower. The Euler model can not only obtain accurate phase interface information, but also consider the interaction between the phases. Therefore, this model can be used to well predict the ozone mass transfer effect in the reaction tower, thereby theoretically confirming the existence of oxidation and reduction reactions. The solution uses a double-precision pressure-based solver, the multiphase flow model uses the Euler model, the turbulence model uses the ke turbulence model, the difference format uses the first-order upwind format, the relaxation factor uses the default value, and the convergence standard is set to 0.001.

[0133] Taking the maximization of the gas holdup as the goal, a method for determining a set of the reaction tower parameters is as follows:

[0134] First, based on the parameters of the key position in the reaction tower (the filling cushion where the catalyst is located) obtained through the above simulation process, the objective function of the gas holdup φ is defined. Where V g is the gas volume, V l is the liquid volume (volume parameters are obtained through simulation);

[0135] Then determine the reaction tower parameters;

[0136] Then set the boundary conditions (such as the velocity size is set to 0.7m / s. The water distributor is set as the velocity inlet boundary, the velocity size is set to 0.04m / s, the gas outlet is set as the pressure outlet; the wall of the reaction tower is set as the no-slip wall boundary), and the boundary conditions also include the energy consumption limit E (i.e. not more than twice the value calculated by the above formula 5) and the pressure drop not exceeding 10kPa;

[0137] Finally, the optimization algorithm (particle swarm optimization PSO) is used to iterate, update the reaction tower parameters in each iteration, and calculate the objective function value to find the optimal solution that maximizes the gas holdup φ.

[0138] By the above-mentioned implementation method, corresponding simulation results (such as the content of Experimental Example 1 below) can be obtained.

[0139] Experimental Example 1:

[0140] The test was conducted using a reaction tower made of transparent acrylic plates, the valves used organic plastics, the aeration device used titanium aeration plates and annular aeration stones, the air pipes and lifting pipes used rubber tubes, and the air intake device was equipped with a diverter, part of the air entered the air pipe as a power to lift the water body, and part of the air entered the bottom for aeration.

[0141] The working principle of the reactor is as follows:

[0142] First, the water in the central tube 2 enters the lifting pipe 5 under the aeration lifting action of the first air inlet pipe 4, and then comes out from the opening at the upper end of the lifting pipe 5 and enters the central tube water inlet pipe 8 together with the water inlet of the reaction tower main water inlet pipe 3, and flows into the reaction tower from top to bottom. The ozonated air is released by the microporous diffuser 9 below the inner wall 8 of the central tube, and makes a preliminary countercurrent contact with the inlet water from bottom to top; then the inlet water flows out from the inner wall 8 of the central tube, flows to the tower body 1 through the perforated water distribution wall, and the ozonated air comes in from the second air inlet pipe 10 and passes through the microporous diffuser 9. Release, water vapor flows upward through the cushion layer 12 and catalyst layer 11 in the outer tube 1, and the high rising flow rate can form a good turbulent state, the ozonated air can be fully dissolved, and the water vapor can fully contact and react; after flowing through the cushion layer 12 and the catalyst layer 11, part of the water enters the central tube 2 from the reflux window 13 on the central tube 2, and then forms an internal circulation through air lifting, and the remaining water flows out of the reaction tower from the total water outlet pipe 14 of the reaction tower, and the remaining ozone is discharged into the atmosphere through the air guide pipe 18, thus completing a cycle of operation. When the concentration of influent pollutants is high, the internal circulation volume can be increased by increasing the air volume to reduce the impact load on the reaction tower, prolong the reaction time, and ensure the quality of the effluent water. An air distribution device for flushing the filler and a water distribution device for flushing the filler are provided below and in the middle of the filler cushion layer 12, which can flush the filler to avoid clogging of the filler area and affect the mixing efficiency. During flushing, the one-way valve 16 in the water inlet pipe 3 can prevent water vapor from entering and affecting the flushing effect. The drain pipe is closed during flushing, and the flushing water is discharged from the drain pipe 17.

[0143] It is understandable that the ozone mass transfer efficiency is the core of the catalytic ozone process, and the performance of the ozone reaction tower is the core factor affecting the catalytic ozonation process. The design of the internal structure of the reaction tower has a direct impact on the ozone mass transfer efficiency, and is directly related to the core elements such as gas residence time, circulation flow rate and gas-liquid flow rate. The residence time of the gas determines the time of gas-liquid mass transfer contact. The longer the contact time, the longer the material transfer process between the gas and the liquid will last, and the more the amount of material transferred from the gas phase to the liquid phase. The ozone residence time in the traditional packed tower is short, the ozone mass transfer effect is poor, and the ozone utilization rate is low, resulting in a large amount of ozone added in practical applications, which in turn causes the cost of ozonation technology to remain high. In order to improve the ozone utilization rate and reduce the ozone addition amount, the present embodiment is optimized from the aspects of the height-to-diameter ratio of the reaction tower, the diameter of the inner cylinder, the height of the inner cylinder, the number of catalyst layers, the spacing between the catalyst layers, the diameter of the riser and the air pipe, the bottom gap height, and the aeration device, and is divided into two parts without a catalyst layer and with a catalyst layer for experiment, and verified according to the removal effect of COD and TOC.

[0144] This study uses two-dimensional (2D) and three-dimensional (3D) models to simulate the internal structure of the reactor. First, the 2D model is used to optimize the reactor's height-to-diameter ratio, diameter ratio, bottom gap height, catalyst layer, air pipe and riser diameter, and aeration equipment.

[0145] 1. Simulation results;

[0146] 1-1. Study on the influence of height-to-diameter ratio;

[0147] With the same reactor volume, different bottom gap distances are selected, and the bottom gap distances are 20mm, 35mm, and 50mm. From the obtained gas content distribution cloud results, it can be seen that the gas content at the bottom of the outer tube decreases with the increase of the height-to-diameter ratio. Through comparative analysis, it can be concluded that the increase in the height of the reaction tower will also increase the gas leakage phenomenon, which will lead to an increase in the gas content outside the guide tube. The external gas content of the reaction tower with a low height-to-diameter ratio is low, and increasing the height-to-diameter ratio will significantly increase the gas content outside the guide tube. This is because increasing the height-to-diameter ratio of the straight tube will also increase the gravitational potential energy required for fluidization of the packing inside the straight tube, affecting the fluidization state of the particles at the upper end of the guide tube, resulting in excessive accumulation of gas-solid media at the bottom of the inner tube, and the gas flows from the bottom gap space of the inner tube to the side wall of the outer tube, which ultimately affects the fluidization state of the solid particles.

[0148] 1-2. Study on the influence of the number of catalyst layers;

[0149] With the same reactor volume, different catalyst layers are selected, the number of catalyst layers is 1, 2, and 3. From the obtained gas content distribution cloud results, it can be seen that the gas content of the outer cylinder side wall increases with the increase of the number of catalyst layers. Since the catalyst layer will capture a part of the ozone gas, the consumption of gas near the catalyst layer will increase, and since the gas is blocked, the ozone gas will be more likely to stay inside the reactor to participate in the reaction. In this ozone reaction tower simulation, when the number of catalyst layers in the reaction tower is 2, the interphase fluidization effect inside the reaction tower is the best.

[0150] 1-3. Study on the influence of catalyst layer spacing;

[0151] With the same reactor volume, different catalyst layer spacings were selected, and the ratios of reactor height to catalyst layer spacing were 4, 6, and 12, respectively. From the obtained gas holdup distribution cloud results, it can be seen that the gas holdup of the outer cylinder side wall increases first and then decreases with the increase of catalyst layer spacing. Since the catalyst layer will block the ozone gas, when the catalyst layer spacing is relatively small, the resistance is too large, causing the gas to deposit at the bottom. When the catalyst layer spacing is too large, the amount of water reacted by the catalyst and the upper catalyst layer will decrease, which is not conducive to the mixing effect of ozone and water. According to the experimental results, with the increase of catalyst spacing, the circulation flow rate increases first and then decreases. When the ratio of reactor height to catalyst layer spacing is 6, the circulation flow rate of the reaction tower is 4.465×10 -6 m 3 / s, which is higher than 4.193×10 -6 m 3 / s, which is higher than the 4.175×10-6 m 3 / s,; the gas residence time shows a trend of first increasing and then decreasing with the increase of the catalyst layer spacing. When the ratio of reactor height to catalyst layer spacing is 6, the residence time of the reaction tower is 18.31s, which is higher than 15.7s when the ratio is 4, and higher than 14.4s when the ratio is 12. In the ozone reaction tower simulation, when the ratio of reactor height to catalyst layer spacing is 6, the interphase fluidization effect inside the reaction tower is the best.

[0152] 1-4. Study on the influence of air pipe and riser pipe diameter;

[0153] With the same reactor volume, different diameters of air pipes and riser pipes are selected. The diameters of air pipes and riser pipes are group A: air pipe inner diameter 2mm outer diameter 4mm, riser inner diameter 6mm outer diameter 8mm, group B: air pipe inner diameter 3mm outer diameter 5mm, riser inner diameter 7mm outer diameter 9mm, group C: air pipe inner diameter 4mm outer diameter 6mm, riser inner diameter 8mm outer diameter 10mm. From the obtained gas holdup distribution cloud results, it can be seen that the gas holdup of the outer cylinder side wall shows an increasing trend with the increase of the diameters of the air pipe and riser pipe. The increase in the diameters of the air pipe and riser pipe increases the volume of the ozonated gas per unit time, which will increase the gas holdup in the reaction tower. According to the experimental results, with the increase of the catalyst spacing, the circulation flow rate shows a decreasing trend. When the inner diameter of the reactor air pipe is 3mm and the outer diameter is 5mm, and the inner diameter of the riser is 7mm and the outer diameter is 9mm, the circulation flow rate of the reaction tower is 4.465×10 -6 m 3 / s, which is lower than 4.911×10 when the air pipe has an inner diameter of 2 mm and an outer diameter of 4 mm and the lifting pipe has an inner diameter of 6 mm and an outer diameter of 8 mm. -6 m 3 / s, which is higher than the 3.518×10 of the air pipe with an inner diameter of 4mm and an outer diameter of 6mm and the riser with an inner diameter of 8mm and an outer diameter of 10mm. -6 m 3 / s,; The gas residence time shows a trend of increasing first and then decreasing with the increase of the catalyst layer spacing. When the inner diameter of the reactor air tube is 3mm and the outer diameter is 5mm, and the inner diameter of the riser is 7mm and the outer diameter is 9mm, the residence time of the reaction tower is 18.31s, which is higher than the 15.25s when the inner diameter of the air tube is 2mm and the outer diameter is 4mm, and the inner diameter of the riser is 6mm and the outer diameter is 8mm, and higher than the 16.78s when the inner diameter of the air tube is 4mm and the outer diameter is 6mm, and the inner diameter of the riser is 8mm and the outer diameter is 10mm. In summary, in the ozone reaction tower simulation, when the inner diameter of the reaction tower air tube is 3mm and the outer diameter is 5mm, and the inner diameter of the riser is 7mm and the outer diameter is 9mm, the interphase fluidization effect inside the reaction tower is the best.

[0154] 1-5. Study on the influence of reflow window height;

[0155] With the same reactor volume, different reflux window heights are selected, and the ratio of the reflux window height to the reactor height is 75%, 80%, and 85%. From the obtained gas holdup distribution cloud results, it can be seen that the ratio of the window height to the reactor is 75%; the ratio of the reflux window height to the reactor is 85%); the gas holdup distribution cloud shows that the gas holdup of the outer cylinder side wall shows a trend of first increasing and then decreasing with the increase of the reflux window height. Since the reflux window is too low, the upper gas will decrease, resulting in a decrease in the overall gas holdup. When the reflux window is too high, the gas reflux power on the lower side of the outer cylinder is insufficient, resulting in a decrease in the gas holdup in the lower part. According to the experimental results, with the increase of the reflux window height, the circulation flow rate shows a trend of first increasing and then decreasing. When the ratio of the reflux window height to the reactor height is 80%, the circulation flow rate of the reaction tower is 4.465×10 -6 m 3 / s, which is higher than 4.193×10 when the ratio is 75%. -6 m 3 / s, which is higher than 4.292×10 -6 m 3 / s; the gas residence time shows a trend of first increasing and then decreasing with the increase of the catalyst layer spacing. When the ratio of the reflux window height to the reactor height is 80%, the residence time of the reaction tower is 18.31s, which is higher than 13.28s when the ratio is 75%, and higher than 12.3s when the ratio is 85%. In summary, in the ozone reaction tower simulation, when the ratio of the reflux window height to the reactor height is 80%, the interphase fluidization effect inside the reaction tower is the best. Figure 4 It is known that under the condition of adding catalyst, the internal circulation ozone reaction tower has a significantly improved ozone utilization rate compared with the ordinary ozone reaction tower. After 10 minutes of treatment, the ozone dosage is 200 mg / (L·h), and the ozone utilization rates of wastewater treatment are 85.35% and 62.02%, respectively, which is an increase of 23.33%. Under the condition of empty tower, the treatment is 10 minutes, the ozone dosage is 400 mg / (L·h), and the ozone utilization rates of ICR and OR for wastewater treatment are 83.11% and 56.65%, respectively, which is an increase of 26.46%. Under the condition of empty tower, the treatment is 10 minutes, the ozone dosage is 600 mg / (L·h), and the ozone utilization rates of ICR and OR for wastewater treatment are 76.58% and 55.22%, respectively, which is an increase of 21.36%.

[0156] exist Figure 4 From the gas holdup distribution cloud diagram, we can see that the gas holdup on the side wall of the internal circulation ozone tower is higher than that of the ordinary reaction tower due to the internal circulation. In addition, since the internal circulation provides greater power, the gas holdup at the bottom of the reaction tower is also higher. During the process of passing through the catalyst layer, the internal circulation ozone reaction tower has a better gas-liquid mixing effect because it is divided into inner and outer cylinders.

[0157] In summary, the internal phase fluidization effect of the internal circulation ozone reaction tower is much better than that of the ordinary ozone reaction tower.

[0158] Analysis of the mechanism of promoting ozone oxidation by optimizing the structure of the internal circulation ozone contact reaction tower: The ozone mass transfer effect in the internal circulation ozone reaction tower is directly related to the ozone residence time, gas vector flow rate, circulation flow rate, gas volume fraction and gas streamline distribution. The increase in the height of the reaction tower will also increase the gas leakage phenomenon, which will lead to an increase in the gas content outside the guide tube. While increasing the height-to-diameter ratio of the straight tube, it will also increase the gravitational potential energy required for the fluidization of the packing inside the straight tube, affecting the fluidization state of the particles at the upper end of the guide tube, resulting in excessive accumulation of gas-solid medium at the bottom of the inner tube. The gas flows from the bottom space of the inner tube to the side wall of the outer tube, which ultimately affects the fluidization state of the solid phase particles. The catalyst layer will capture part of the ozone, so the gas consumption near the catalyst layer will increase, and because the gas is blocked, the ozone gas will be more likely to stay inside the reactor to participate in the reaction. The catalyst layer will block the upward process of the gas, so the higher the catalyst layer, the slower the gas flow rate. When the distance between the catalyst layers is relatively small, the resistance is too large, causing the gas to settle at the bottom. When the distance between the catalyst layers is relatively large, the amount of water reacting on the upper part of the catalyst layer will decrease, which is not conducive to the mixing effect of ozone and water. The shorter the distance between the catalysts, the greater the resistance of the gas and the slower the gas flow rate. The increase in the diameter of the air pipe and the riser will increase the volume of the ozonated gas per unit time, which will increase the gas holdup in the reaction tower. After the diameter increases, the gas flow per unit volume will decrease, and the flow rate will also decrease. If the reflux window is too low, the gas in the upper part will decrease, resulting in a decrease in the overall gas holdup. When the reflux window is too high, the gas reflux power on the lower side of the outer tube is insufficient, resulting in a decrease in the gas holdup in the lower part. If the reflux window is too high, the reflux power will be weakened, which will affect the gas flow rate.

[0159] The fluid mechanics performance (gas phase flow rate, liquid phase flow rate, gas volume fraction, circulation flow rate) of the internal circulation ozone contact reaction tower and the ordinary ozone reaction tower was systematically studied using CFD technology, and the parameters obtained from the experiment in Chapter 3 were verified. The multiphase flow involved in this paper is more suitable for simulation using the Euler-Euler method, so the multiphase flow model of Fluent is used to simulate the reaction tower. The internal structure of the internal circulation ozone contact reaction tower was simulated, and then an internal circulation ozone contact reaction tower with good hydraulic performance and high ozone utilization rate was developed, and compared with the ordinary ozone reaction tower. The specific conclusions are as follows: Increasing the height-to-diameter ratio prolongs the ozone residence time and affects the gas vector flow rate. Properly increasing the bottom gap height increases the gas holdup in the middle of the outer cylinder. Properly increasing the inner cylinder height increases the gas holdup at the bottom of the outer cylinder. This is because the too low inner cylinder height will reduce the bottom gas reflux, which is not conducive to fluidization between gas, liquid and solid phases, and is easy to cause short flow and form a circulation dead corner. The smaller the diameter, the greater the gas holdup in the descending area at the bottom of the outer cylinder, which weakens the fluid driving force in the ascending area inside the guide cylinder. The catalyst layer will capture a portion of the ozone gas, so the gas consumption near the catalyst layer will increase, and because the gas is blocked, the ozone gas will more easily stay inside the reactor to participate in the reaction. The catalyst layer will block the gas upward process, so the higher the catalyst layer, the slower the gas flow rate. When the distance between the catalyst layers is relatively small, the resistance is too large, causing the gas to settle at the bottom. When the distance between the catalyst layers is relatively large, the amount of water in the reaction on the upper part of the catalyst will decrease, which is not conducive to the mixing effect of ozone and water. The increase in the diameter of the air pipe and the riser will increase the volume of the ozonated gas per unit time, which will increase the gas holdup in the reaction tower. If the reflux window is too low, the upper gas will decrease, resulting in a decrease in the overall gas holdup. When the reflux window is too high, the gas reflux power on the lower side of the outer tube is insufficient, resulting in a decrease in the gas holdup at the lower part, which in turn affects the gas flow rate.

[0160] 2. Experimental verification;

[0161] By using the reaction tower structure in Experimental Example 1 to conduct the following experiment, we obtained:

[0162] Catalytic ozonation experiment: 4000 mL of the liquid to be treated and 800 g of spherical aluminum-based catalyst were placed in a 4.7 L reactor, and then an aeration flow rate of 600 mL / min was introduced into the reactor with a concentration of 22.5 g / m 3 O3, ozone dosage 200mg / (L·h), treatment for 60 minutes; an aeration flow rate of 600mL / min was introduced into the reactor with a concentration of 45g / m 3 O3, ozone dosage 400mg / (L·h), treatment for 60 minutes; an aeration flow rate of 900mL / min was introduced into the reactor with a concentration of 45g / m 3O3, ozone dosage 600mg / (L·h), treatment for 60 minutes. Samples were taken at 0, 10, 20, 30, 40, 50, and 60 minutes of reaction, nitrogen was passed through the samples to blow out the ozone, and the samples were tested for TOC or COD on the same day. After the reaction was completed, an appropriate amount of potassium iodide with a mass fraction of 20% was added to consume the residual ozone in the remaining solution.

[0163] 2-1. Research on height-to-diameter ratio optimization;

[0164] With the same reactor volume, different ratios of height to diameter were selected. Under the conditions of height-to-diameter ratios of 3, 6, and 9, 800 g of catalyst was added to investigate the effect of height-to-diameter ratio on TOC and COD removal. Figure 5 shown by Figure 5 It is known that the height-to-diameter ratio of the internal circulation ozone reaction tower has a significant effect on the removal efficiency of COD and TOC. When the height-to-diameter ratio is 6 and the tower is empty, the removal rate of TOC and COD in the reaction tower is significantly better than that of the height-to-diameter ratio of 3 and the height-to-diameter ratio of 9. When the catalyst is added, the treatment lasts for 60 minutes. The ozone dosage is 200mg / (L·h), 400mg / (L·h), and 600mg / (L·h). When the height-to-diameter ratio is 6, the COD degradation amount is 232mg / L, 424mg / L, and 496mg / L respectively, and the TOC degradation amount is 61mg / L, 86mg / L, and 94mg / L respectively. When the ozone dosage is low, the COD removal rate of the reaction tower with a height-to-diameter ratio of 6 is increased by more than 50% compared with the height-to-diameter ratio of 3, and the TOC removal rate is increased by more than 60%. The COD removal rate of the reaction tower with a height-to-diameter ratio of 6 is increased by more than 35% compared with the height-to-diameter ratio of 9, and the TOC removal rate is increased by more than 45%. When the ozone dosage is high, the COD removal rate of the reaction tower with a height-to-diameter ratio of 6 is more than 40% higher than that of the height-to-diameter ratio of 3, and the TOC removal rate is more than 50%. The COD removal rate of the reaction tower with a height-to-diameter ratio of 6 is more than 30% higher than that of the height-to-diameter ratio of 9, and the TOC removal rate is more than 35%. Fan Jingfu et al. used a two-fluid model to describe the gas-liquid two-phase flow process. By changing the height-to-diameter ratio, they obtained that as the height-to-diameter ratio increases, the reactor circulation liquid velocity increases, but when it exceeds a certain range, it is not conducive to improving the reactor efficiency. There is an optimal height-to-diameter ratio. It can be seen that under the same conditions, the internal circulation ozone reaction tower with a height-to-diameter ratio of 6 is more conducive to improving the COD and TOC removal efficiency.

[0165] 2-2. Research on optimization of catalyst interlayer spacing;

[0166] With the same reactor volume, different catalyst layer spacings were selected. When the ratio of reactor height to catalyst layer spacing was 4, 6, and 12, 800 g of catalyst was added to investigate the effect of height-to-diameter ratio on TOC and COD removal. Figure 6 As shown. Figure 6It is known that under the condition of adding catalyst, the catalyst layer spacing of the internal circulation ozone reaction tower has a significant effect on the removal efficiency of COD and TOC. When the ratio of reactor height to catalyst layer spacing is 6, the removal rate of TOC and COD of the reaction tower is better than that of the ratio of reactor height to catalyst layer spacing is 4 and 12. Under the condition of adding catalyst, the treatment is 60min. The ozone dosage is 200mg / (L·h), and the ratio of reactor height to catalyst layer spacing is 4, 6, and 12. The COD removal rate is 57.02%, 61.86%, and 50.42% respectively, and the TOC degradation amount is 54.15%, 57.97%, and 51.53% respectively. The COD removal rate of the reaction tower with a ratio of reactor height to catalyst layer spacing of 6 is 4.84% and 11.44% higher than that of the reaction tower with a ratio of reactor height to catalyst layer spacing of 4 and 12, and the TOC removal rate is 3.82% and 6.44% higher. The design of the catalyst layer spacing will affect the use effect of the catalyst. Reasonable selection of the catalyst layer spacing can maximize the catalytic effect of the catalyst and will also affect the ozone flow state, which is of great significance to improving the performance of the reactor. It can be seen that under the same conditions, the internal circulation ozone reaction tower with a ratio of reactor height to catalyst layer spacing of 6 is more conducive to improving the COD and TOC removal efficiency.

[0167] 2-3. Research on optimization of catalyst layers;

[0168] With the same reactor volume, different catalyst layers were selected. Under the conditions of 1, 2, and 3 catalyst layers, 800g of catalyst was added to investigate the effect of height-to-diameter ratio on TOC and COD removal. Figure 7 shown by Figure 7 It is known that when adding catalyst, the number of catalyst layers of the internal circulation ozone reaction tower has a significant effect on the removal efficiency of COD and TOC. When the number of catalyst layers is 2, the removal rate of TOC and COD of the reaction tower is better than that of catalyst layers 1 and 3. When adding catalyst, the treatment lasts for 60 minutes. The ozone dosage is 400 mg / (L·h), and the number of catalyst layers is 1, 2, and 3. The COD removal rates are 57.72%, 61.86%, and 52.94%, respectively, and the TOC degradation amounts are 53.73%, 57.97%, and 52.03%, respectively. The COD removal rate of the reaction tower with 2 catalyst layers is 4.14% and 8.92% higher than that of the reaction tower with 1 and 3 catalyst layers, and the TOC removal rate is 4.24% and 5.94%. Different catalyst layers will affect the amount of water contacted by the catalyst in different sections, and will affect the fluidization state of ozone gas inside the reaction tower, and affect the gas-liquid-solid three-phase mixing effect. It can be seen that under the same conditions, the internal circulation ozone reaction tower with 2 catalyst layers is more conducive to improving the gas-liquid mass transfer effect.

[0169] 2-4. Study on optimization of aeration aperture;

[0170] With the same reactor volume, different aeration apertures were selected. The aeration device was an annular aeration stone with an aperture of 8-10 mm and a titanium aeration plate with an aperture of 2-3 mm. 800 g of catalyst was added to investigate the effect of aeration aperture on the removal of TOC and COD. Figure 8 shown by Figure 8 It is known that when a catalyst is added, the aeration aperture of the internal circulation ozone reaction tower has a significant effect on the removal efficiency of COD and TOC. The aeration device is a titanium aeration plate, and the removal rate of TOC and COD by the reaction tower is better than that of the annular aeration stone.

[0171] When the catalyst is added, the treatment is 60 minutes. The ozone dosage is 200mg / (L·h), 400mg / (L·h), 600mg / (L·h), and the height-diameter ratio is 6. The COD degradation amounts are 236.5mg / L, 428.5mg / L, and 503mg / L, respectively, and the TOC degradation amounts are 64.5mg / L, 91mg / L, and 98mg / L, respectively. When the ozone dosage is low, the COD removal rate of the reaction tower with titanium aeration plates as the aeration device is more than 60% higher than that of the reaction tower with annular aeration stones, and the TOC removal rate is more than 65%. When the ozone dosage is high, the COD removal rate of the reaction tower with titanium aeration plates as the aeration device is more than 40% higher than that of the reaction tower with annular aeration stones, and the TOC removal rate is more than 35%. Although the aeration disk with a smaller aperture has a better cutting effect on the gas, it is more conducive to increasing the gas-liquid contact area. It can be seen that under the same conditions, the internal circulation ozone reaction tower with titanium aeration plates as the aeration device is more conducive to improving the COD and TOC removal efficiency.

[0172] 2-5. Research on optimization of reflux window height;

[0173] With the same reactor volume, different reflux window heights were selected. When the ratio of the reflux window height to the reactor height was 75%, 80%, and 85%, 800g of catalyst was added to investigate the effect of the reflux window height on the removal of TOC and COD. Fig. 9 As shown. Fig. 9It is known that when adding catalyst, the reflux window height of the internal circulation ozone reaction tower has a significant effect on the removal efficiency of COD and TOC. The ratio of the reflux window height to the outer tube height is 80%, and the removal rate of the reaction tower for TOC and COD is better than the ratio of the reflux window height to the outer tube height of 75% and 85%. When adding catalyst, the treatment is 60min. The ozone dosage is 200mg / (L·h), 400mg / (L·h), 600mg / (L·h), and the height-to-diameter ratio is 6. The COD degradation amount is 243mg / L, 437.5mg / L, 515.5mg / L respectively, and the TOC degradation amount is 71.5mg / L, 90mg / L, 99.5mg / L respectively. When the ozone dosage is low, the COD removal rate of the reaction tower with a ratio of reflux window height to outer tube height of 80% is increased by more than 80% compared with the reaction towers with 70% and 85%, and the TOC removal rate is increased by more than 75%. When the ozone dosage is high, the COD removal rate of the reaction tower with a ratio of the inner tube height to the outer tube height of 90% is more than 30% higher than that of the reaction tower with a ratio of 85% and 95%, and the TOC removal rate is more than 40%. The appropriate reflux window height provides better power for the circulation flow and maximizes the circulation flow, which is conducive to increasing the opportunity for gas-liquid contact. It can be seen that under the same conditions, the internal circulation ozone reaction tower with a ratio of the reflux window height to the outer tube height of 80% is more conducive to improving the COD and TOC removal efficiency.

[0174] 2-6. Study on optimization of air pipe and riser;

[0175] With the same reactor volume, different air pipe and riser diameters were selected. The air pipe and riser diameters were 2mm inner diameter and 4mm outer diameter, 6mm inner diameter and 8mm outer diameter, 3mm inner diameter and 5mm outer diameter, 7mm inner diameter and 9mm outer diameter, 4mm inner diameter and 6mm outer diameter, and 8mm inner diameter and 10mm outer diameter. 800g of catalyst was added to investigate the effect of air pipe and riser diameter on TOC and COD removal. Fig.10It is known that the diameter of the air pipe and the riser of the internal circulation ozone reaction tower has a significant effect on the removal efficiency of COD and TOC. The air pipe has an inner diameter of 3mm and an outer diameter of 5mm, and the riser has an inner diameter of 7mm and an outer diameter of 9mm. The removal rate of TOC and COD of the reaction tower is better than that of the air pipe with an inner diameter of 2mm and an outer diameter of 4mm, the riser has an inner diameter of 6mm and an outer diameter of 8mm, and the air pipe with an inner diameter of 4mm and an outer diameter of 6mm, and the riser has an inner diameter of 8mm and an outer diameter of 10mm. When the catalyst is added, the treatment lasts for 60 minutes. The ozone dosage is 200mg / (L·h), 400mg / (L·h), and 600mg / (L·h). The COD degradation of A treated wastewater is 231.5mg / L, 428.5mg / L, and 495.5mg / L, respectively, and the TOC degradation is 66.5mg / L, 80mg / L, and 90.5mg / L, respectively. When the ozone dosage is low, the COD removal rate of A is more than 23% higher than that of B and C, and the TOC removal rate is more than 13%. When the ozone dosage is high, the COD removal rate of A is more than 25% higher than that of B and C, and the TOC removal rate is more than 12%. The appropriate diameter of the air pipe riser provides a suitable negative pressure for the internal circulation of the reaction tower, ensures the realization of the internal circulation function, and increases the circulation flow. It can be seen that under the same conditions, the internal circulation ozone reaction tower with an air pipe inner diameter of 3mm and an outer diameter of 5mm, and a riser inner diameter of 7mm and an outer diameter of 9mm is more conducive to the improvement of COD and TOC removal efficiency.

[0176] 2-7. Research on optimization of inner tube height;

[0177] With the same reactor volume, different inner tube heights were selected. When the ratio of the inner tube height to the reactor height was 85%, 90%, and 95%, 800g of catalyst was added to investigate the effect of the inner tube height on the TOC and COD removal effects.

[0178] Depend on Fig.11 It is known that when a catalyst is added, the inner cylinder height of the internal circulation ozone reaction tower has a significant effect on the removal efficiency of COD and TOC. The ratio of the inner cylinder height to the outer cylinder height is 90%. The removal rate of TOC and COD by the reaction tower is better than the ratio of the inner cylinder height to the outer cylinder height of 85% and 95%.

[0179] When the catalyst is added, the treatment lasts for 60 minutes. The ozone dosage is 200mg / (L·h), 400mg / (L·h), and 600mg / (L·h). The ratio of the inner cylinder height to the outer cylinder height is 90%. The COD degradation amounts are 239mg / L, 435.5mg / L, and 502mg / L, respectively, and the TOC degradation amounts are 67mg / L, 88.5mg / L, and 96.5mg / L, respectively. When the ozone dosage is low, the COD removal rate of the reaction tower with a ratio of the inner cylinder height to the outer cylinder height of 90% is more than 70% higher than that of the reaction tower with a ratio of 85% and 95%, and the TOC removal rate is more than 65%. When the ozone dosage is high, the COD removal rate of the reaction tower with a ratio of the inner cylinder height to the outer cylinder height of 90% is more than 25% higher than that of the reaction tower with a ratio of 85% and 95%, and the TOC removal rate is more than 40%. Li Hanbo and others changed the path of the rising airflow to form a swirl between the inner and outer cylinders. The appropriate height of the inner cylinder can strengthen the contact between the gas and liquid phases, form a more complete swirl, effectively strengthen the mixing, extend the residence time of the gas, and improve the mass transfer effect. It can be seen that under the same conditions, the internal circulation ozone reaction tower with a ratio of 80% of the reflux window height to the outer cylinder height is more conducive to improving the COD and TOC removal efficiency.

[0180] 2-8. Research on optimization of inner cylinder diameter;

[0181] With the same reactor volume, different inner cylinder diameters were selected. When the ratio of the inner cylinder diameter to the reactor outer cylinder diameter was 40%, 50%, and 60%, 800g of catalyst was added to investigate the effect of the inner cylinder diameter on the removal of TOC and COD. Fig.12It is known that when adding catalyst, the inner diameter of the inner circulation ozone reaction tower has a significant effect on the removal efficiency of COD and TOC. When the ratio of the inner diameter to the outer diameter is 50%, the removal rate of the reaction tower for TOC and COD is better than the ratio of the inner diameter to the outer diameter of 40% and 60%. When adding catalyst, the treatment lasts for 60 minutes. The ozone dosage is 200mg / (L·h), 400mg / (L·h), 600mg / (L·h), and the ratio of the inner tube height to the outer tube height is 90%. The COD degradation amount is 243.5mg / L, 445.5mg / L, 498mg / L respectively, and the TOC degradation amount is 65.5mg / L, 90mg / L, 98mg / L respectively. When the ozone dosage is low, the COD removal rate of the reaction tower with a ratio of the inner diameter to the outer diameter of 50% is increased by more than 90% compared with the reaction towers with a ratio of 40% and 60%, and the TOC removal rate is increased by more than 80%. When the ozone dosage is high, the COD removal rate of the reaction tower with a ratio of 50% of the inner cylinder diameter to the outer cylinder diameter is more than 40% higher than that of the reaction tower with a ratio of 85% and 95%, and the TOC removal rate is more than 50%. Some scholars have used numerical simulation methods to study the influence of diameter ratio on reactor performance parameters and found that when the ratio of the inner cylinder diameter to the outer cylinder diameter is 50%, the liquid circulation flow is the largest and the reactor has the optimal fluidization state. It can be seen that under the same conditions, the internal circulation ozone reaction tower with a ratio of 50% of the inner cylinder diameter to the outer cylinder diameter is more conducive to improving the COD and TOC removal efficiency.

[0182] 2-9. Research on optimization of the bottom gap distance (the distance between the bottom surface of the tower body and the bottom of the central tube);

[0183] With the same reactor volume, different bottom gap distances were selected. Under the conditions of bottom gap distances of 20mm, 35mm, and 50mm, 800g of catalyst was added to investigate the effect of bottom gap distance on TOC and COD removal. Fig.13As we know, when adding catalyst, the bottom gap distance of the internal circulation ozone reaction tower has a significant effect on the removal efficiency of COD and TOC. When the bottom gap distance is 50mm, the removal rate of TOC and COD of the reaction tower is better than that of the bottom gap distance of 20mm and 35mm. Treatment for 60min. The ozone dosage is 200mg / (L·h), 400mg / (L·h), 600mg / (L·h), and the height-diameter ratio is 6. The COD degradation amount is 226.5mg / L, 418.5mg / L, 491.5mg / L respectively, and the TOC degradation amount is 59mg / L, 80.5mg / L, 91.5mg / L respectively. When the ozone dosage is low, the COD removal rate of the reaction tower with a bottom gap distance of 50mm is more than 35% higher than that of the reaction tower with a bottom gap distance of 20mm and 35mm, and the TOC removal rate is more than 50%. When the ozone dosage is high, the COD removal rate of the reaction tower with a bottom gap distance of 50mm is more than 19% higher than that of the reaction towers with 20mm and 35mm, and the TOC removal rate is more than 25%. Zhu Jialiang et al. used the Euler-Euler model to construct a CFD model and found that the bottom gap height has a great influence on the liquid circulation speed in the reactor, and also determines the flow state of the flow field. By optimizing the bottom gap spacing, the dead zone can be effectively reduced, the gas-liquid flow can be improved, and the mass transfer and heat transfer efficiency can be improved. It can be seen that under the same conditions, the internal circulation ozone reaction tower with a bottom gap distance of 50mm is more conducive to the improvement of COD and TOC removal efficiency.

[0184] 3. Comparative Study on Simulation Effect Verification

[0185] First, determine the effect of the optimization parameters obtained from the simulation:

[0186] The optimal design of the internal circulation ozone reaction tower was determined according to the experimental research of Experimental Example 2, and compared with the simulation in Experimental Example 1, it was found that the simulation results of Experimental Example 1 were the same as the test results in Experimental Example 2, both of which had a high oxidation catalytic degradation rate in the water treatment process; therefore, it was shown that the simulation method used for simulation had a high accuracy; (i.e., a height-to-diameter ratio of 6, a ratio of the inner cylinder height to the outer cylinder height of 90%, a ratio of the inner cylinder diameter to the outer cylinder diameter of 50%, a bottom gap height of 5mm, 2 catalyst layers, a ratio of the catalyst layer spacing to the outer cylinder height of 1:6, an aeration device was a titanium aeration plate, an air pipe with an inner diameter of 3mm and an outer diameter of 5mm, a riser pipe with an inner diameter of 7mm and an outer diameter of 9mm, and a ratio of the reflux window height to the outer cylinder height of 80%).

[0187] Second, determine whether the reaction tower parameters are optimal;

[0188] Compared with the common reaction tower (ozone reaction tower without circulation reflux setting), the circulation flow rate, residence time, velocity vector, gas holdup and other indicators are compared. The internal circulation ozone contact reaction tower in the embodiment of the present invention (and the optimized design of its parameters) will have a higher COD and TOC removal effect, higher ozone utilization efficiency, less influence on the flow state of the liquid after passing through the catalyst layer, smaller gas resistance, smoother ozone flow, more uniform ozone distribution, higher ozone utilization rate compared with the common reaction tower, ozone utilization rate increased by more than 30%, and COD removal rate increased by more than 35%.

Claims

1. An optimization design method for an internal circulation ozone contact reaction tower, characterized in that: The following steps are involved: S1. Design the reaction tower structure; The reaction tower comprises a tower body (1) and a central tube (2) located at the center of the tower body (1) and fixed to the tower body (1); the central tube (2) is provided with a first air inlet pipe (4) for conveying water to a lifting pipe (5) in the central tube (2); the lifting pipe (5) is used to convey water to the inside of the tower body (1) outside the central tube (2); A plurality of filling cushion layers (12) for oxidizing water bodies with ozone are arranged in the tower body (1) outside the central tube (2); the filling cushion layer (12) is annular in shape, and the annular inner ring of the filling cushion layer (12) is sleeved on the outer wall of the central tube (2); and a catalyst is arranged on each layer of the filling cushion layer (12); a second air inlet pipe (10) is arranged in the tower body (1) for conveying part of the water bodies after oxidizing with ozone back to the central tube (2) for circulation treatment; S2. Design reaction tower parameters; Constructing the internal circulation ozone contact reaction tower model, wherein the input of the internal circulation ozone contact reaction tower model is the reaction tower parameter, and the output of the internal circulation ozone contact reaction tower model is the gas holdup; Determining the optimal values ​​of the reaction tower parameters with the goal of maximizing the gas holdup; The reaction tower parameters include: the height-to-diameter ratio of the tower body (1), the ratio of the diameter of the central tube (2) to the diameter of the tower body (1), the ratio of the height of the central tube (2) to the height of the tower body (1), the number of filling cushions (12), the ratio of the height of the tower body (1) to the spacing between catalyst layers, the diameter of the first air inlet pipe (4), the diameter of the riser (5), the spacing between the inner bottom surface of the tower body (1) and the bottom of the central tube (2), and the material of the filling cushion (12).

2. The optimization design method of an internal circulation ozone contact reaction tower according to claim 1, characterized in that: The second air inlet pipe (10) is arranged at the bottom of the tower body (1), and a microporous diffuser (9) is provided on the second air inlet pipe (10).

3. The optimization design method of an internal circulation ozone contact reaction tower according to claim 1, characterized in that: The interior of the tower body (1) outside the central tube (2) is connected to the interior of the central tube (2) via a reflux window (13) arranged on the central tube (2); the reflux window (13) is located on the central tube (2) above the filling cushion layer (12).

4. The optimization design method of an internal circulation ozone contact reaction tower according to claim 1, characterized in that: The filling cushion layer (12) is in the shape of a circular column, and the filling cushion layer (12) is fixedly sleeved on the inner wall of the central tube (2), and the lifting pipe (5) passes through the filling cushion layer (12).

5. The optimization design method of an internal circulation ozone contact reaction tower according to claim 1, characterized in that: The internal circulation ozone contact reaction tower model includes a simulation module and a calculation module; The simulation module includes a geometric simulation module for simulating the reaction tower structure and a material simulation module for simulating the state of reactants; the state of reactants includes the flow rate of the continuous phase fluid and the flow rate of the dispersed phase particles; The calculation module is used to calculate the simulation parameters of the simulation module to obtain the gas holdup, ozone residence time and circulation flow rate.

6. The optimization design method of an internal circulation ozone contact reaction tower according to claim 5, characterized in that: The construction method of the geometric simulation module includes: First, a three-dimensional model of the reaction tower is built; Then meshing the three-dimensional model; Finally, the boundary conditions are set, and the geometric simulation module is constructed; Wherein, the boundary conditions include the reaction tower inlet velocity, the reaction tower outlet velocity, and the wall conditions; the reaction tower inlet includes an air inlet and a water inlet, and the reaction tower outlet includes an air outlet and a water outlet.

7. The optimization design method of an internal circulation ozone contact reaction tower according to claim 6, characterized in that: The grid division method is: The tower body (1), the central tube (2) and the filling layer are divided into quadrilateral grids; The aeration pipe, the connection between the aeration pipe and the tower body (1), the connection between the aeration pipe and the central tube (2), the connection between the first air inlet pipe (4) and the tower body (1), the connection between the first air inlet pipe (4) and the tower body (1), the connection between the second air inlet pipe and the central tube (2), and the connection between the second air inlet pipe (10) and the tower body (1) are all divided using hexahedral grids; The first air intake pipe (4), the second air intake pipe (10) and the riser pipe (5) are divided using tetrahedral grids.

8. The optimization design method of an internal circulation ozone contact reaction tower according to claim 6, characterized in that: The method for constructing the material simulation module includes: First, the properties of the continuous phase fluid and the dispersed phase particles are defined; the properties include density and viscosity; Then, the initial conditions of the continuous phase fluid and the dispersed phase particles are set, wherein the initial conditions include an initial flow rate and an initial concentration; Selecting a flow model and determining a fluid conservation equation, the construction of the material simulation module is completed; The operation method of the computing module includes: Firstly, based on mesh division, multiple key interfaces of the reaction tower are determined; Then, based on the initial conditions and boundary conditions, the fluid conservation equation is used to calculate and iteratively update the flux on each of the key interfaces; the flux includes mass flux, momentum flux and energy flux; Calculating gas holdup, ozone residence time and circulation flow rate according to the flux on the key interface; The key interfaces include: air inlet, catalyst and filling cushion, water distributor, gas-liquid contact area, air outlet and liquid discharge port.

9. The optimization design method of an internal circulation ozone contact reaction tower according to claim 8, characterized in that: The method for determining the optimal value of the reaction tower parameter with the goal of maximizing the gas holdup comprises: Define an objective function of the gas holdup φ at the key position; Where V g is the gas volume, V l is the volume of the liquid, V g 、V l Obtained by the calculation module; Determine multiple groups of reaction tower parameters; based on the reaction tower parameters and boundary conditions, calculate the reaction tower parameter values ​​with the maximum gas holdup φ, and use the values ​​as the optimal values ​​of the reaction tower parameters.

10. The optimization design method of an internal circulation ozone contact reaction tower according to claim 9, characterized in that: The optimal values ​​of the reaction tower parameters are: the height-to-diameter ratio of the tower body (1) is 6, the ratio of the diameter of the central tube (2) to the diameter of the tower body (1) is 0.9, the ratio of the outer wall height of the central tube (2) to the inner wall height of the central tube (2) is 0.88-0.92, the number of filling cushion layers (12) is 2, the ratio of the height of the reaction tower to the spacing between the catalyst layers is 6, the first air inlet pipe (4) is 7-9 mm, the diameter of the riser (5) is 3-5 mm, the spacing between the inner bottom surface of the tower body (1) and the bottom of the central tube (2) is 35-50 mm, and the filling cushion layer (12) is made of a porous titanium plate.

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