CN110277141B - CFD-based heavy metal wastewater vulcanization precipitation reactor optimization method - Google Patents
CFD-based heavy metal wastewater vulcanization precipitation reactor optimization method Download PDFInfo
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- 238000001556 precipitation Methods 0.000 title claims abstract description 54
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- 229910001385 heavy metal Inorganic materials 0.000 title claims abstract description 41
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- UCKMPCXJQFINFW-UHFFFAOYSA-N Sulphide Chemical compound [S-2] UCKMPCXJQFINFW-UHFFFAOYSA-N 0.000 claims description 17
- 229910052979 sodium sulfide Inorganic materials 0.000 claims description 17
- GRVFOGOEDUUMBP-UHFFFAOYSA-N sodium sulfide (anhydrous) Chemical compound [Na+].[Na+].[S-2] GRVFOGOEDUUMBP-UHFFFAOYSA-N 0.000 claims description 17
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- JPVYNHNXODAKFH-UHFFFAOYSA-N Cu2+ Chemical compound [Cu+2] JPVYNHNXODAKFH-UHFFFAOYSA-N 0.000 description 7
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- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 description 1
- RWSOTUBLDIXVET-UHFFFAOYSA-N Dihydrogen sulfide Chemical compound S RWSOTUBLDIXVET-UHFFFAOYSA-N 0.000 description 1
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Abstract
The invention discloses a CFD-based heavy metal wastewater vulcanization precipitation reactor optimization method, which comprises the following steps: establishing a fluid computational domain geometric model of a vulcanization precipitation reactor; determining a control equation and defining boundary conditions and initial values of the model according to the established geometric model and the actual situation and the design thought; carrying out grid division on a geometric model of the vulcanization precipitation reactor, and solving the flow field of the model, the concentration distribution of reaction substances and the like by utilizing multi-physical field coupling; and (3) repeating the above processes by modifying the related parameters, performing numerical simulation calculation for multiple times, and comparing and analyzing the calculation results under different geometric structures and process parameters to obtain the optimal reactor structure and process parameters. The invention can perform simulation calculation on the vulcanization precipitation process under different reactor structures and process parameters to obtain the results of the water inlet and outlet concentration of the reactor, the internal flow field distribution characteristics of the reactor, the concentration distribution of various substances and the like so as to evaluate the performance of the reactor under different conditions.
Description
Technical Field
The invention belongs to the technical field of heavy metal wastewater treatment simulation, and particularly relates to a CFD-based heavy metal wastewater vulcanization precipitation reactor optimization method.
Background
Mineral resource development, metal processing and smelting, chemical production, fertilizer industry and the like have been proved to be main sources of heavy metal pollution, and heavy metal wastewater generated in large quantities is a difficult problem to be solved urgently. In recent years, with the increase of environmental protection requirements, higher requirements are put on the discharge of heavy metal sewage, and correspondingly, more efficient treatment processes and devices are required to be further developed.
For the treatment of heavy metal industrial wastewater, the sulfide precipitation method has been greatly developed in application in recent decades by virtue of its applicability in a wide pH range and the advantages of low solubility, high stability and easy dehydration of most metal sulfides. However, the conventional vulcanization method for treating heavy metal wastewater is usually carried out in a stirred tank reactor, the continuous operation process is complex, the reaction time is long, and meanwhile, the reactor needs excessive vulcanizing agents, and a large amount of hydrogen sulfide gas easily causes secondary pollution, so that the novel structure of the vulcanization precipitation reactor needs to be developed and designed, and the operation parameters of the reactor need to be optimized so as to meet higher economic and environmental requirements.
The design and optimization of the sulfurization-precipitation reactor at present usually adopt the following methods: firstly, manufacturing small experimental equipment according to a design thought, then carrying out small-scale experimental verification, secondly, modifying the structure and the technological parameters of the reactor according to experimental results and phenomena, and finally, repeating the process until the optimal structure and technological parameters are found. The method can cause the technical problems of great waste of materials and time and the like, and can not meet the analysis requirement on the design optimization of the reactor.
Disclosure of Invention
The present application is directed to solving at least one of the problems in the prior art. Therefore, the invention aims to provide a CFD-based heavy metal wastewater sulfurization precipitation reactor optimization method. The method is beneficial to improving the development efficiency of the novel vulcanization precipitation reactor and effectively reducing the research and development investment, and the method can effectively research the influence of the structure and the process parameters of the reactor on the efficiency of the vulcanization precipitation process and provide a theoretical basis for further optimization of the structure and the process parameters.
In order to solve the problems, the invention adopts the following technical scheme:
a CFD-based heavy metal wastewater vulcanization precipitation reactor optimization method comprises the following steps:
1) Establishing a geometric model of a fluid calculation domain of the sulfidation precipitation reactor according to basic size parameters of the sulfidation precipitation reactor;
2) Determining a control equation of the model, and calculating a flow field by adopting a k-epsilon turbulence model;
3) Defining boundary conditions and initial values of the model;
4) Carrying out mesh division on the model;
5) Carrying out numerical simulation calculation, and solving the flow field and the concentration distribution of reaction substances of the model by utilizing multi-physical field coupling to obtain a flow field velocity vector diagram, a concentration distribution diagram of each substance, a streamline distribution diagram and time-varying data of the ion concentration in the effluent under a set condition;
6) And (3) according to the simulation result obtained in the step 5), performing reactor characteristic analysis, and optimizing by changing the basic size parameters in the step 1) and/or the boundary conditions and initial values in the step 3), and repeating the steps 1) to 6) until an optimal design scheme of the vulcanization precipitation reactor is obtained.
The optimal design scheme of the vulcanization precipitation reactor is the scheme corresponding to the situation that in the step, when simulation calculation is carried out under different reactor structures and boundary condition settings, the calculation results of the concentration of the heavy metal ions and the concentration of the sulfides in the effluent of the reactor are the lowest.
Further, the setting of the boundary condition and the initial value in step 3) includes:
setting boundary conditions and initial values of an inlet flow field: including the position of the boundary of the inlet and the outlet, the inflow speed, the outflow speed, the pressure and the gravity condition;
setting of boundary conditions and initial values of chemical reaction fields: the method comprises the steps of setting the concentration of substances in the whole area of a reactor, setting the diffusion coefficient of each substance, setting the concentration of the substances flowing into the reactor and setting a custom function of the chemical reaction rate of heavy metal ions and sulfide.
Further, the parameters changed in step 5) include: the basic shape and size, the position of an inlet and an outlet, the size of the inlet and the outlet, the shape of the inlet and the outlet, the initial concentration and inflow speed of the heavy metal wastewater and the initial concentration and inflow speed of the sodium sulfide solution of the vulcanization precipitation reactor.
Further, in step 2), a control equation is selected according to a chemical transfer field and a flow field, in order to simulate the influence of the reactor structure on the mass transfer effect, chemical reaction dynamics, mass transfer and fluid flow are coupled in a model, a speed field and concentration distribution are solved, the flow characteristics in the reactor are calculated into turbulence through a Reynolds number, and a main control equation set of the heavy metal sulfide precipitation reactor model is determined by combining a mass transfer equation as follows:
the material flux vector equation is expressed as:
in the formula D i Is the diffusion coefficient (m) 2 /s)，c i Is the concentration (mol/m) of the substance 3 ) U is the velocity vector (m/s) in the fluid flow field;
the equilibrium equation of the materials is as follows:
wherein,
is the Laplace operator, R i Represents the reaction rate (mol/m) of a substance 3 S) in the process of the sulfide precipitation of the heavy metal wastewater, the sulfide precipitation reaction of the heavy metal ions is the reaction process mainly considered by the method, and the reaction rate R i Described by formula (3):
in the formula k 1 As a reaction rate constant (determined by experiment),
is the metal ion concentration (mol/m) 3 ),/>
As the sulfide concentration (mol/m) 3 )
In the model, the fluid in the reactor is regarded as incompressible Newtonian fluid, and the continuity equation and the momentum equation of the turbulent flow are respectively expressed by equation (4) and equation (5):
where ρ is the density of the mixed fluid, μ is the dynamic viscosity, u is the velocity vector of the fluid, p is the pressure, I is the unit tensor, F is the unit volume force acting on the fluid, μ T Is the turbulent viscosity, and k is the turbulent kinetic energy;
for turbulent flow in a reactor, a k-epsilon turbulent flow model is selected for simulation, and two dependent variables are introduced into the model: turbulent kinetic energy k and turbulent dissipation factor ε, turbulent viscosity μ in equation (5) T In the k-epsilon turbulence model, the kinetic energy and the dissipation rate of turbulence are determined (equation (6)):
the turbulence kinetic energy k and the turbulence dissipation factor epsilon in the k-epsilon turbulence model are controlled by the equations (7) and (8), respectively:
in the formula sigma k ,σ ε ,C μ ,C ε1 And C and ε2 are model constants having values of 1.0,1.3,0.09, and 1.44, respectively, the term of formation P of turbulent energy k Is defined by formula (9);
furthermore, the grid division adopts tetrahedral grid division, and the grid independence test is carried out.
According to the invention, by utilizing the multi-physical-field numerical simulation method, simulation calculation can be carried out on the vulcanization precipitation process under different reactor structures and process parameters, and the results of the inlet and outlet water concentration of the reactor, the internal flow field distribution characteristics of the reactor, the concentration distribution of various substances and the like are obtained to evaluate the performance of the reactor under different conditions, so that an efficient, economic and rapid way is provided for realizing the design and optimization of the heavy metal wastewater vulcanization precipitation reactor.
The invention adopts a multi-physical-field simulation means combining Computational Fluid Dynamics (CFD) with a chemical reaction field and a mass transfer field, adopts a high-efficiency, convenient and efficient method to predict the performance of the vulcanization precipitation reactor, can obtain a reactor performance prediction result with higher precision, saves a large amount of time, manpower and financial resources, greatly shortens the development period of the reactor and reduces the development cost.
Drawings
FIG. 1 is a diagram of a geometric model of a reactor;
FIG. 2 is a reactor model grid section;
fig. 3 is a distribution diagram of ion concentration distribution and flow field distribution of each ion when t =35s in the reactor;
wherein: (a) Copper ion concentration (mol/m) 3 ) Distribution and flow field distribution; (b) The sulfur ion concentration (mol/m) 3 ) And streamline distribution; (c) Reaction Rate distribution (mol/(m) 3 ·s))；
FIGS. 4 (a) - (b) are the copper ion concentration and the sulfur ion concentration (mol/m) in the effluent of the reactor at different wastewater inflow rates (0.25 m/s,0.5m/s,0.75m/s,1.5 m/s) 3 ) A graph of changes over time;
FIGS. 5 (a) - (b) are the concentrations of copper ions and sulfur ions (mol/m) in the effluent of the reactor at different inlet positions for sodium sulfide solution (20mm, 50mm,75mm,100mm, 125mm) 3 ) Graph over time.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
A method for designing and optimizing a heavy metal wastewater vulcanization precipitation reactor based on CFD technology mainly comprises the following steps:
determining a physical model of a vulcanization precipitation reactor according to actual conditions and design thoughts, namely establishing a geometric model of a fluid calculation domain of the vulcanization precipitation reactor;
determining the main structure of the reactor and the positions of the inlets and the outlets, parameterizing the basic size of the vulcanization precipitation reactor and the positions of the inlets and the outlets, and constructing a geometric model;
determining a model control equation, considering the problem that the incompressible liquid flows in the reactor, calculating and determining the flow type to be turbulent flow according to the actual condition and Reynolds number, and calculating the flow field by adopting a k-epsilon turbulent flow model; in order to simulate the influence of the reactor structure on the mass transfer effect;
and step three, defining the boundary condition and the initial value of the model established in the step one according to the actual situation and the design idea, and parameterizing the related definition data. Specifically, the method comprises setting boundary conditions and initial values of an inflow field (including setting of boundary positions of an inlet and an outlet, inflow speed, outflow speed, pressure and gravity conditions), setting boundary conditions and initial values of a chemical reaction field (including setting of substance concentration of the whole region of a reactor, setting of diffusion coefficients of various substances, setting of substance concentration of the inflow reactor and setting of a custom function of chemical reaction rate of heavy metal ions and sulfides);
step four, carrying out mesh division on the geometric model, carrying out mesh independence inspection and optimization, and adopting tetrahedral mesh division for the three-dimensional model;
fifthly, carrying out numerical simulation calculation to obtain a flow field velocity vector diagram, a concentration distribution diagram of each substance, a streamline distribution diagram and time-varying data of effluent concentration of the vulcanization precipitation reactor under set conditions;
and step six, according to the simulation result obtained in the step five, performing reactor characteristic analysis, changing one or more parameters defined in the step one and the step three on the basis, specifically comprising the basic shape and size, the inlet and outlet positions, the inlet and outlet sizes, the inlet and outlet shapes, the initial concentration and inflow speed of the heavy metal wastewater and the initial concentration and inflow speed of the sodium sulfide solution of the vulcanization precipitation reactor, repeating the steps one to six, and comparing the simulation graphic data obtained under different conditions until the results of optimization of the vulcanization precipitation reactor structure and process parameter design are obtained.
Examples
1) And (2) establishing a geometric model of the reactor, and establishing a geometric structure of the reactor as shown in a figure I according to a design idea, wherein 1 is a heavy metal wastewater inlet, 2 is a sodium sulfide solution inlet, and 3 is a reactor outlet. The total height of the reactor is 20cm, the diameter of the reactor is 4cm, heavy metal wastewater and sodium sulfide solution enter the reactor through transverse convection at the position 18cm higher than the reactor, the diameters of an inlet and an outlet are both 6mm, namely the axis of the heavy metal wastewater inlet is in the x direction, and the coordinates are y =0m and z =0.180m. The axis of the water outlet is in the z direction with coordinates x =0m and y =0m, and the axis of the sodium sulfide solution inlet is in the x direction with coordinates y =0m and z =0.180m.
2) Determining a control equation of the model, selecting the control equation according to the chemical transfer field and the flow field, coupling chemical reaction dynamics, mass transfer and fluid flow in the model, and solving a velocity field and concentration distribution in order to simulate the influence of the reactor structure on the mass transfer effect. The flow characteristics in the reactor are calculated as turbulence through Reynolds number, and the main control equation set for determining the heavy metal sulfide precipitation reactor model by combining with a mass transfer equation is as follows:
the process of the heavy metal wastewater vulcanization and precipitation has no electric field effect, the mass transfer only depends on free diffusion and convection, and the material flux vector equation is expressed as follows:
in the formula, D i Is the diffusion coefficient (m) 2 /s)，c i Is the concentration of a substance: (mol/m 3 ) U is the velocity vector (m/s) in the fluid flow field;
the equilibrium equation of the materials is as follows:
wherein,
is the Laplace operator, R i Represents the reaction rate (mol/m) of a substance 3 S) in the process of the sulfide precipitation of the heavy metal wastewater, the sulfide precipitation reaction of the heavy metal ions is the reaction process mainly considered by the method, and the reaction rate R i Described by formula (3):
in the formula k 1 As a reaction rate constant (determined by experiment),
is the metal ion concentration (mol/m) 3 ),/>
As sulfide concentration (mol/m) 3 )
In the model, the fluid in the reactor is regarded as incompressible Newtonian fluid, and the continuity equation and the momentum equation of the turbulent flow are respectively expressed by equation (4) and equation (5):
where ρ is the density of the mixed fluid, μ is the dynamic viscosity, and u is the velocity vector of the fluidP is pressure, I is unit tensor, F is unit volume force acting on the fluid, μ T Is the turbulent viscosity, and k is the turbulent kinetic energy;
for turbulent flow in a reactor, a k-epsilon turbulent flow model is selected for simulation, and two dependent variables are introduced into the model: turbulent kinetic energy k and turbulent dissipation factor ε, turbulent viscosity μ in equation (5) T In the k-epsilon turbulence model, the kinetic energy and the dissipation rate of turbulence are determined (equation (6)):
the turbulence kinetic energy k and the turbulence dissipation factor epsilon in the k-epsilon turbulence model are controlled by the equations (7) and (8), respectively:
in the formula sigma C ,σ ε ,C μ ,C ε1 And C and ε2 are model constants having values of 1.0,1.3,0.09, and 1.44, respectively, the term of formation P of turbulent energy k Is defined by formula (9);
3) The boundary conditions and initial values of the model are defined.
In this example, 10g/L Cu was contained 2+ (0.1575 mol/L) simulated heavy metal wastewater flows in from the position of the No. 1 opening of the reactor at the speed of 0.5m/S and simultaneously contains 16g/L S 2+ (0.5 mol/L) sodium sulfide simulant sodium sulfide solution flowed into the reactor at 0.1575m/s from position 2, i.e., when the metal ions and sulfide entered the reactor at an equimolar ratio. The reactor was initially set to be filled with 10g/L Cu 2+ Shape ofState; the outlet position of port No. 3 of the reactor was set to a prescribed outflow velocity of 0.6575m/s in accordance with the conservation of mass. The other boundaries than the 1, 2, 3 boundaries for the mass transfer field are set to no flux and the boundaries are set to wall function boundary conditions for the flow field. Taking into account both the pressure inside the reaction and the gravitational force.
4) And (5) dividing the model mesh. In this example, the model region of the reactor is discretized into tetrahedral mesh cells, as shown in fig. 2. After the grid independence test was completed, the complete grid of the model consisted of 728294 domain cells, 29980 boundary cells, and 949 edge cells.
The maximum cell size, minimum cell size and maximum cell growth rate of the domain grid cells in the model were 0.00212m,0.0004m and 1.13, respectively. Triangular border elements form a structured layer on the surface borders and these finer border element layers are integrated with the existing tetrahedral field mesh elements in the model, forming three layers of border element layers along all surface borders, the first layer being 0.0012 μm thick and the border layer stretch coefficient being 1.2, which means that the thickness of the border layer increases 20% layer by layer from 0.0012 μm. The triangular boundary elements had a maximum cell size of 0.00148 μm, a minimum cell size of 0.00016 μm, and a maximum cell growth rate of 1.1. The edges of the model geometry are discretized into edge cells.
5) Model calculation and data result arrangement. After the steps 1) to 4) above, obtaining the data of the flow field velocity vector diagram, the concentration distribution diagram of each substance, the streamline distribution diagram and the outlet water concentration changing with time of the vulcanization precipitation reactor under the set conditions, as shown in fig. 3 (a) - (c).
6) And (4) analyzing data and further optimizing the structure and parameters. In this example, preliminary numerical simulations of the sulfidation precipitation reactor based on CFD techniques yielded the results described in step (5). It can be seen that under the constraint of step (3), there is a large relative movement speed between the wastewater and the sodium sulfide solution, but because the wastewater has a much larger flow speed than the sodium sulfide solution, the sodium sulfide solution cannot continue to flow transversely after entering the reactor and then flows reversely to the inner wall near the inlet under the impact of the transverse wastewater flow. In such a case, the reactionThe flow field distribution within the reactor may also be characterized by three zones, a top vortex zone and a middle turbulent zone spaced at the upper middle portion of the reactor by the inlet location, and a tubular laminar zone at the lower middle portion of the reactor. Wherein the vortex region at the top and the turbulent region at the middle are the main reaction regions due to the extremely fast reaction rate of the copper ion sulfurization precipitation reaction and the wastewater and Na 2 The S solution is well mixed and most of the copper and sulfur ions are reacted away in both regions. The combined flow of the reaction then becomes a downward tube laminar flow in the lower portion of the reactor and flows out of the reactor.
On the basis, further optimization of the reactor structure and parameters is carried out. Specifically, the positions of a wastewater inlet and a sodium sulfide solution inlet are changed to optimize the structure of the reactor; further, calculations were performed at different inflow rates to optimize the process parameters. The detailed boundary condition settings are shown in table 1.
The effluent concentrations over time at different reactor inflow rates are shown in FIG. 4. It was found that the wastewater flow and Na were present due to the manner of transverse convection and the smaller diameter of the reactor (4 cm) 2 The convection between the S solutions is strong even at a small inflow velocity (0.25 m/S), with flow field distributions similar to those at 0.5m/S and 0.75 m/S. But when the inflow velocity is increased to 1.5m/s, the upper vortex zone streamlines in the reactor become more chaotic. At the same time, the concentration of sulfur ions in the top vortex region becomes higher as the inflow velocity increases, since Na 2 The increase in the flow rate of the S solution allows more sulfur ions to enter the reactor while transferring more sulfur ions to the top zone than copper ions. As the inflow rate decreases, the copper ion and sulfur ion concentrations in the effluent become lower. Higher sulfide precipitation performance can be achieved at lower inflow velocities because direct lateral convection between the wastewater and the Na2S solution causes them to mix well. However, since the residence time of the wastewater and the Na2S solution in the reactor is short, the reaction is insufficient when the treatment load is increased.
The water concentration was varied with time for different reactor configurations as shown in FIG. 5. It was found that as the inlet position moves downward, the turbulence area at the top of the reactor increases and the turbulence area in the lower part of the reactor becomes smaller, resulting in a smaller bottom tube laminar flow area. When the inlet is in the lower position (z =120mm, z =140mm, z = 160mm), the flow field distribution characteristics inside the reactor are the same as when z =180 mm. But when the inlets for wastewater and Na2S solution were located at z =195mm, the fluid flow distribution inside the reactor was completely different from the fluid distribution at z =180 mm. Meanwhile, when the inlet is arranged at different positions, the main reaction zone in the reactor is positioned near the inlet of the Na2S solution, and the concentration of copper ions and the concentration of sulfur ions in the effluent are reduced along with the upward movement of the position of the inlet.
In summary, in the case of a continuous flow sulfidation precipitation reactor with cross-flow convection, the inlet should be located as close to the upper part of the reactor as possible, and a better mixing effect and treatment efficiency can be obtained at a lower inflow velocity. The method provided by the invention can provide good guidance for the design and optimization of the sulfurization precipitation reactor.
TABLE 1 boundary condition setting table for structure and parameter optimization
The above examples are merely illustrative for clearly illustrating the present invention and are not intended to limit the embodiments. Other variations and modifications will be apparent to persons skilled in the art in light of the above description. Nor is it intended to be exhaustive of all embodiments. And obvious variations or modifications of the invention may be made without departing from the scope of the invention.
Claims (5)
1. A CFD-based heavy metal wastewater vulcanization precipitation reactor optimization method is characterized by comprising the following steps:
1) Establishing a geometric model of a fluid calculation domain of the sulfidation precipitation reactor according to basic size parameters of the sulfidation precipitation reactor;
2) Determining a control equation of the model, and selecting a k-epsilon turbulence model to simulate and calculate the flow field distribution in the reactor after comprehensively considering the model precision and the calculation cost;
3) Defining boundary conditions and initial values of the geometric model;
4) Carrying out mesh division on the geometric model;
5) Carrying out numerical simulation calculation, solving the flow field and reaction substance concentration distribution of the model by utilizing multi-physical field coupling to obtain a flow field velocity vector diagram, each substance concentration distribution diagram, a streamline distribution diagram and time-varying data of the ion concentration in the effluent under a set condition;
6) And (3) analyzing the characteristics of the reactor according to the simulation result obtained in the step 5), optimizing by changing the basic size parameters in the step 1) and/or the boundary conditions and initial values in the step 3), and repeating the steps 1) to 6) until an optimal design scheme of the vulcanization precipitation reactor is obtained, wherein the optimal design scheme is a scheme corresponding to the lowest calculation results of the concentrations of the heavy metal ions and the sulfides in the effluent of the reactor when simulation calculation is carried out under different reactor structures and boundary conditions in the steps.
2. The CFD-based heavy metal wastewater sulfidation precipitation reactor optimization method according to claim 1, wherein the setting of the boundary conditions and the initial values in the step 3) comprises:
setting flow field boundary conditions and initial values: inlet and outlet boundary positions, inflow speed, outflow speed, pressure and gravity conditions;
setting of boundary conditions and initial values of chemical reaction fields: the method comprises the steps of setting the concentration of substances in the whole area of a reactor, setting the diffusion coefficient of each substance, setting the concentration of the substances flowing into the reactor and setting a custom function of the chemical reaction rate of heavy metal ions and sulfide.
3. The CFD-based heavy metal wastewater sulfidation precipitation reactor optimization method of claim 2, wherein: the parameters changed in the step 5) comprise: the basic shape and size, the position of an inlet and an outlet, the size of the inlet and the outlet, the shape of the inlet and the outlet, the initial concentration and inflow speed of the heavy metal wastewater and the initial concentration and inflow speed of the sodium sulfide solution of the vulcanization precipitation reactor.
4. The CFD-based heavy metal wastewater sulfidation precipitation reactor optimization method of claim 1, wherein the meshing is tetrahedral meshing and a mesh independence test is performed.
5. The CFD-based heavy metal wastewater sulfidation precipitation reactor optimization method according to any one of claims 1-4, wherein: in step 2), selecting a control equation according to a chemical transfer field and a flow field, coupling chemical reaction dynamics, mass transfer and fluid flow in a model in order to simulate the influence of a reactor structure on a mass transfer effect, solving a speed field and concentration distribution, calculating the flow characteristics in the reactor into turbulent flow through Reynolds number, and determining a main control equation set of the heavy metal sulfide precipitation reactor model by combining a mass transfer equation as follows:
the material flux vector equation is expressed as:
in the formula, D i Is the diffusion coefficient (m) 2 /s)，c i Is the concentration of the substance (mol/m) 3 ) U is the velocity vector (m/s) in the fluid flow field;
the equilibrium equation of the materials is as follows:
wherein,
is Laplace operator, R i Represents the reaction rate (mol/m) of a substance 3 S) in the process of the sulfide precipitation of the heavy metal wastewater, the sulfide precipitation reaction of the heavy metal ions is the reaction process mainly considered by the method, and the reaction rate R i Described by formula (3):
in the formula k 1 As a reaction rate constant, as measured by experiments,
is the metal ion concentration (mol/m) 3 ),
As the sulfide concentration (mol/m) 3 )
In the model, the fluid in the reactor is regarded as incompressible Newtonian fluid, and the continuity equation and the momentum equation of the turbulent flow are respectively expressed by equation (4) and equation (5):
where ρ is the density of the mixed fluid, μ is the dynamic viscosity, u is the velocity vector of the fluid, p is the pressure, + is the unit tensor, F is the unit volume force acting on the fluid, μ T Is the turbulent viscosity, and k is the turbulent kinetic energy;
for turbulent flow in a reactor, a k-epsilon turbulent flow model is selected for simulation, and two dependent variables are introduced into the model: turbulent kinetic energy k and turbulent dissipation factor ε, turbulent viscosity μ in equation (5) T In the k-epsilon turbulence model there areTurbulent kinetic energy and turbulent dissipation ratio (equation (6)):
the turbulence kinetic energy k and the turbulence dissipation factor epsilon in the k-epsilon turbulence model are controlled by the equations (7) and (8), respectively:
in the formula sigma C ,σ ε ,C μ ,C ε1 And C and ε2 are model constants having values of 1.0,1.3,0.09, and 1.44, respectively, the generation term P of the turbulent energy k Is defined by formula (9);
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