A method for obtaining the hydrodynamic shear of solid particles in a gas-liquid-solid three-phase flow reaction system of a suspension bed

Abstract

The present invention provides a method for obtaining the hydrodynamic shear of solid particles in a gas-liquid-solid three-phase flow reaction system of a suspension bed, including computational fluid dynamics simulation, hydrodynamic parameter derivation, and calculation and result output of the hydrodynamic shear value of solid particles. The computational fluid dynamics simulation simulates the flow field of the three-phase flow reactor of the suspension bed through fluid dynamics software and records various hydrodynamic characteristics. The hydrodynamic parameter derivation uses image recognition technology to derive various hydrodynamic parameter information including turbulent dissipation and solid volume fraction distribution in matrix form. The calculation and result output of the hydrodynamic shear value of solid particles calculate the turbulent dissipation matrix of solid particles based on the turbulent dissipation and solid volume fraction matrix, combine the conversion formula of turbulent dissipation and hydrodynamic shear, calculate the hydrodynamic shear value received by the solid particles, and output the result in matrix form. This method has the characteristics of high calculation accuracy and strong feasibility for calculating and analyzing the hydrodynamic shear value of solid particles in a complex gas-liquid-solid three-phase flow reaction system of a suspension bed.

Description

Technical Field

[0001] The present invention relates to the field of hydraulic shear value calculation, and particularly to a method for obtaining the hydraulic shear of solid particles in a gas-liquid-solid three-phase flow reaction system of a suspension bed. Background Art

[0002] In sewage treatment, the biological fluidized bed treatment technology is an efficient biological treatment technology that uses gas-liquid phase fluids to fluidize solid particles or carriers with microorganisms growing on their surfaces, while degrading organic pollutants. The gas-liquid-solid three-phase biological fluidized bed of the suspension bed is a type of biological fluidized bed, in which the solid phase is suspended in the upward gas-liquid phase flow to form a fluidized state of three-phase coexistence. The hydraulic shear action generated by turbulent fluctuations is an important hydraulic parameter in the gas-liquid-solid three-phase flow reactor. A suitable hydraulic shear action can promote the formation of a stable structure of the biofilm in the three-phase flow reactor and enhance the mass transfer efficiency between phases. In the suspension bed three-phase flow reactor, the hydraulic shear action received by the solid phase fluidization state can be divided into the shear action between the gas-solid phases, the shear action between the liquid-solid phases, and the shear action generated by collision and friction between the solid phases. Among them, the hydraulic shear action generated between the liquid-solid phases is an important part of the three-phase flow reactor. Therefore, the movement law of the solid phase and its flow field characteristics in the suspension bed three-phase flow are the key to the system fluidization performance.

[0003] Common stress calculation methods include empirical formula theoretical analysis, experimental measurement, and fluid mechanics simulation calculation, etc. Among them, empirical formula theoretical analysis directly calculates the stress through the reactor configuration parameters and operating parameters, experimental measurement uses experimental instruments to obtain calculation information, and fluid mechanics simulation calculation obtains the flow velocity and volume fraction of each phase for stress calculation by setting reasonable boundary conditions and grid division. However, empirical formula theoretical analysis is limited by non-linear dynamics, and experimental measurement is limited by flow interference and measurement accuracy. Therefore, fluid mechanics simulation calculation is widely used because of its easy parameter modification and high visualization degree.

[0004] However, in the reaction system of the gas-liquid-solid three-phase flow of the suspension bed, the flow field environment is complex, and the three-phase flow system has the characteristics of non-linearity and multi-scale, which requires high requirements for simulation calculation. It is very difficult to quantitatively describe the hydraulic shear action received by the solid phase. At present, most simulation calculations are based on simplified single-phase flow or two-phase flow. However, the diameter of solid particles or carriers in the suspension bed three-phase flow is relatively large, and it is difficult to use simplified methods. Therefore, there are few simulation calculations for the movement of the gas-liquid-solid three-phase fluid in the suspension bed, and it is still relatively difficult to calculate the hydraulic shear value of solid particles under different hydraulic conditions in the suspension bed three-phase flow reactor. Summary of the Invention

[0005] The present invention provides a method for obtaining the hydrodynamic shear of solid particles in a suspended bed gas-liquid-solid three-phase flow reaction system, aiming to solve the technical problems such as the lack of calculation methods for the hydrodynamic shear value of solid particles under different hydrodynamic conditions in a suspended bed three-phase flow reactor, the complexity of the calculation process, and the low calculation accuracy. Through the present invention, relevant data on the hydrodynamic shear of solid particles in the suspended bed gas-liquid-solid three-phase flow reaction system can be obtained, including the hydrodynamic shear value matrix of solid particles, the hydrodynamic shear diagram, etc., so as to realize the hydrodynamic shear analysis of solid particles in a complex suspended bed three-phase flow.

[0006] The technical solution of the present invention is as follows:

[0007] The present invention provides a method for obtaining the hydrodynamic shear of solid particles in a suspended bed gas-liquid-solid three-phase flow reaction system, which includes the following steps:

[0008] S1: Use the RNG k-ε turbulence model to simulate and analyze the hydrodynamic characteristics in the reactor, and construct a reactor hydrodynamic model;

[0009] S2: After modeling, layer by layer output the two-dimensional turbulent dissipation diagrams and two-dimensional solid holdup distribution diagrams at each layer in the axial direction of the reactor, and use image scanning to identify the turbulent dissipation diagrams and solid holdup distribution diagrams to obtain the turbulent dissipation value matrix and solid holdup distribution matrix at each layer on this axis;

[0010] S3: Based on the turbulent dissipation value matrix and solid holdup distribution matrix at each layer, calculate the turbulent dissipation value matrix of solid particles, and combine the conversion formula between turbulent dissipation and hydrodynamic shear to convert the turbulent dissipation matrix of solid particles at each layer on this axis into a two-dimensional hydrodynamic shear matrix, and then obtain the overall hydrodynamic shear value matrix of solid particles in the reactor.

[0011] According to the preferred scheme of the present invention, the establishment and simulation process of the RNG k-ε turbulence model in S1 specifically includes the following steps:

[0012] Use fluid mechanics software to establish a reactor model for the suspended bed gas-liquid-solid three-phase flow reaction system;

[0013] Set the boundary conditions and initial conditions of the reactor model;

[0014] Set corresponding operating parameters according to different configurations, aeration intensities, and sizes of aeration heads of the reactor.

[0015] According to the preferred scheme of the present invention, in S2, denote the axial direction as the Z direction, and the two directions perpendicular to the axial direction as the X direction and the Y direction, and the X direction and the Y direction are perpendicular to each other; output the two-dimensional turbulent dissipation diagrams and two-dimensional solid holdup distribution diagrams at different heights in the axial direction of the reactor, that is, layer by layer output the X-Y two-dimensional turbulent dissipation diagrams and X-Y two-dimensional solid holdup distribution diagrams at different positions on the Z axis in the reactor.

[0016] More preferably, in S2, the image is scanned to recognize the turbulent dissipation map, and the turbulent dissipation value matrix of each layer in the axial direction is obtained, specifically including:

[0017] Read the XY coordinates and RGB values in the turbulent dissipation maps at different positions on the Z-axis in sequence, and output the corresponding RGB value matrix; after converting the RGB values in the matrix to hexadecimal HEX, convert them to decimal again and output to obtain the RGB value matrix in decimal form; read the highest and lowest turbulent dissipation values and record their corresponding RGB values, and then solve the corresponding function between the turbulent dissipation value and the RGB value; through the RGB value matrix, combined with the corresponding function between the turbulent dissipation value and the RGB value, convert the RGB value matrix at different positions on the Z-axis into the turbulent dissipation value matrix.

[0018] According to the preferred embodiment of the present invention, in S2, the image is scanned to recognize the solid holdup distribution map, and the solid holdup distribution matrix of each layer in the axial direction is obtained, specifically including:

[0019] Read the XY coordinates where the particles are located in the solid holdup distribution maps at different positions on the Z-axis in sequence, assign 1 to the corresponding coordinates, and assign 0 to other positions without particles, so as to form the solid holdup distribution matrix.

[0020] According to the preferred embodiment of the present invention, in S3, the acquisition of the turbulent dissipation value matrix of the solid-phase particles specifically includes:

[0021] Multiply the turbulent dissipation value matrix of the Z1 section in the reactor by the solid holdup matrix to obtain the turbulent dissipation value matrix of the solid-phase particles, and calculate layer by layer to obtain the turbulent dissipation value matrix of the solid-phase particles from Z1 to Z n of.

[0022] According to the preferred embodiment of the present invention, in S3, the following calculation formula is used to convert the output turbulent dissipation value into the hydraulic shear value received by the solid-phase particles:

[0023]

[0024] In the formula: γ—hydraulic shear value, s -1 ;

[0025] ε—turbulent dissipation rate, cm 2 ·s -3 ;

[0026] ν—kinematic viscosity, cm 2 ·s -1 .

[0027] According to the preferred embodiment of the present invention, in S3, the two-dimensional hydraulic shear value matrix of the solid-phase particles in the axial direction of the reactor is exported layer by layer, that is, the two-dimensional hydraulic shear value matrix of each layer from Z1 to Z n is output.

[0028] The present invention provides a method for obtaining the hydrodynamic shear of solid particles in a suspended bed gas-liquid-solid three-phase flow reaction system, including computational fluid dynamics simulation, hydrodynamic parameter derivation, and calculation and result output of the hydrodynamic shear value of solid particles. The computational fluid dynamics simulation uses fluid dynamics software to simulate the flow field of the suspended bed three-phase flow reactor and records various hydrodynamic characteristics. The hydrodynamic parameter derivation uses image recognition technology to derive various hydrodynamic parameter information including turbulent dissipation and solid holdup distribution in matrix form. The calculation and result output of the hydrodynamic shear value of solid particles calculates the turbulent dissipation value matrix of solid particles based on the turbulent dissipation and solid holdup matrix, combines the turbulent dissipation and hydrodynamic shear conversion formula, calculates the hydrodynamic shear value received by the solid particles, and outputs the result in matrix form. This calculation method can quantitatively describe the hydrodynamic shear value received by solid particles in the suspended bed three-phase flow reaction system, and has advantages such as high calculation accuracy and strong feasibility for calculating and analyzing the hydrodynamic shear value of solid particles in complex suspended bed three-phase flows. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 It is a schematic diagram of the model established in the embodiment of the present invention. The volume of the reactor is 6.0 L, and the height-to-diameter ratio (H / D) is 3;

[0030] Figure 2 It is the 2D (X-Y) turbulent dissipation diagram simulated and output when the aeration intensity (Q) is 5.0 L·min in the embodiment of the present invention; -1

[0031] Figure 3 It is the 2D (X-Y) solid holdup distribution diagram simulated and output when the aeration intensity (Q) is 5.0 L·min in the embodiment of the present invention; -1

[0032] Figure 4 It is the turbulent dissipation matrix diagram of solid particles in the Z 50 cross-section in the embodiment of the present invention;

[0033] Figure 5 It is the hydrodynamic shear matrix diagram of solid particles in the Z 50 cross-section in the embodiment of the present invention;

[0034] Figure 6 It is the hydrodynamic shear diagram received by solid particles in the central cross-section of the reaction system when the aeration intensity (Q) is 5.0 L·min in the embodiment of the present invention; -1 DETAILED DESCRIPTION OF THE EMBODIMENTS

[0035] The present invention will be further described and explained below in conjunction with the specific embodiments. The embodiments are only demonstrations of the present disclosure content and do not delimit the scope of limitation. Without conflict, the technical features of each embodiment in the present invention can be combined accordingly.

[0036] Taking an aerobic granular sludge reactor as an example, the method for obtaining the relevant data of the hydraulic shear of solid-phase particles in the suspended-bed gas-liquid-solid three-phase flow reaction system described in the present invention includes:

[0037] The first step is to perform numerical simulation on the suspended-bed gas-liquid-solid three-phase flow reaction system to construct a reactor hydraulics model as Figure 1 shown. The specific process includes:

[0038] 1.1 Reactor model establishment.

[0039] Specifically, the Flow-3D software is used to simulate the movement characteristics of solid-phase particles in the reactor. The simulation initial step size and minimum step size are both default values, and the total running duration is set to 100 s. The gravity direction is set to -Z, and the gravitational acceleration g = -981 cm·s -2 . In the simulation, it is a single fluid, and an incompressible fluid at 20 °C is used as the fluid material. Then the model is calculated using an implicit solver. The solid-phase particles are solid particles (Mass particles), the particle size is set to 0.03 cm, and the density is 1.01 g·cm -3 . The gas-phase bubbles are gas particles (Gas particles), the particle size is set to 0.3 cm, and the density is 0.0013 g·cm -3 .

[0040] 1.2 Mesh generation.

[0041] Specifically, after the physical model is established, the geometric structure of the model can be established according to the radius and height of the reactor. The grid is generated by discretizing the simulated flow calculation domain, and the established geometric model is embedded into the computational grid for mesh generation. The size of a single grid is set to 0.4 cm.

[0042] 1.3 Determination of boundary conditions and initial conditions.

[0043] Specifically, the top of the reactor is set as a pressure (Specified pressure) boundary, and the fluid fraction is set to 0, indicating that it is completely air. The bottom and side walls are set as wall (Wall) boundaries. Then the distribution characteristics of solid particles in the initial state are set to Total, and the total number of solid particles is set to 15000. The aeration head in the reactor is simplified to a cube with a side length of 4 cm, and it is used as the bubble emission source. Then, according to the required aeration intensity (Q), the number of bubbles generated per second is set to 5894 (Q = 5.0 L·min -1 ).

[0044] 1.4 Setting of reactor operating parameters.

[0045] Specifically, corresponding operating parameters are set according to different configurations of the reactor, aeration intensity, size of the aeration head, etc., for analyzing the effects of different operating conditions on solid particles. In the simulation implementation, the height-diameter ratio (H / D) of the reactor is set to 3, and the aeration intensity (Q) is 5.0 L·min -1 , and the size of the aeration head (d) is 4 cm.

[0046] Second step, output the turbulent dissipation map (two-dimensional) and solid holdup distribution map (two-dimensional) of each layer in a certain axial direction in the reactor. Taking the Z-axis as an example, that is, layer by layer output the two-dimensional (X-Y) turbulent dissipation map and two-dimensional (X-Y) solid holdup distribution map at different positions on the Z-axis in the reactor.

[0047] Specifically, select the time point of the graph to be output. In this embodiment, the selected time point is the 90th second, set the threshold of turbulent dissipation to 700 (this threshold can be reasonably set according to the actual situation), and layer by layer output the two-dimensional (X-Y) turbulent dissipation map at different positions on the Z-axis in the reactor, as Figure 2 shown. Select the same time point as the turbulent dissipation map, select the automatic threshold, and layer by layer output the two-dimensional (X-Y) solid holdup distribution map at different positions on the Z-axis in the reactor, as Figure 3 shown.

[0048] Third step, identify the turbulent dissipation map and solid holdup distribution map through image scanning technology, and export the turbulent dissipation value matrix and solid holdup distribution matrix of each layer on the axis. The specific process includes:

[0049] 3.1 Image cutting.

[0050] Specifically, intercept the image through the Crop function. The variable box is a quadruple, which defines the pixel coordinates of the left, upper, right, and lower, and is used to represent the position coordinates intercepted in the original image.

[0051] 3.2 Format conversion.

[0052] Specifically, use Python to convert the information read from the image into the form of an array.

[0053] 3.3 Export the turbulent dissipation value matrix.

[0054] Specifically, use Python to sequentially read the XY coordinates and RGB values in the turbulent dissipation diagrams at different positions on the Z-axis, and output the corresponding RGB value matrix. After converting the RGB values in the matrix to hexadecimal HEX, convert them to decimal again for output to obtain the RGB value matrix (in decimal form). Read the maximum and minimum values of turbulent dissipation and record their corresponding RGB values (in decimal form), and then solve the corresponding function between the turbulent dissipation value and the RGB value (in decimal form). Through the RGB value matrix (in decimal form), combined with the corresponding function between the turbulent dissipation value and the RGB value (in decimal form), convert the RGB value matrix (in decimal form) at different positions on the Z-axis into a turbulent dissipation value matrix.

[0055] 3.4 Derive the solid holdup distribution matrix.

[0056] Specifically, use Python to sequentially read the XY coordinates where the particles are located in the solid holdup distribution diagrams at different positions on the Z-axis, assign 1 to the corresponding coordinates, and assign 0 to other positions without particles, thus forming a solid holdup distribution matrix.

[0057] Fourth step, calculate the turbulent dissipation value matrix of solid-phase particles based on the turbulent dissipation and solid holdup distribution matrices.

[0058] Specifically, divide each cross-section in the Z-axis direction in the reactor into 40*40 cells. Multiply the turbulent dissipation value matrix of the Z1 cross-section in the reactor by the solid holdup distribution matrix to obtain the turbulent dissipation value matrix of solid-phase particles, and calculate layer by layer to obtain the turbulent dissipation value matrix of solid-phase particles from Z1 to Z n For example, the turbulent dissipation value matrix of the cross-section solid-phase particles is as 50 shown. Figure 4

[0059] Fifth step, calculate the hydrodynamic shear value acting on the solid-phase particles.

[0060] Specifically, use the calculation formula to convert the output turbulent dissipation value of the solid-phase particles into the hydrodynamic shear value acting on the solid-phase particles.

[0061] The calculation formula is as follows:

[0062]

[0063] In the formula: γ—hydrodynamic shear, s -1 ;

[0064] ε—turbulent dissipation rate, cm 2 ·s -3 ;

[0065] ν—kinematic viscosity, cm 2 ·s -1 . ​

[0066] Step 6: Output the hydraulic shear value matrix of the solid-phase particles and the hydraulic shear diagram of the solid-phase particles in the reactor.

[0067] Specifically, layer by layer, export the two-dimensional hydraulic shear value matrix of the solid-phase particles in a certain axial direction in the reactor. Taking the Z-axis as an example, that is, output the two-dimensional hydraulic shear value matrices of each layer from Z1-Z n For example, the two-dimensional hydraulic shear value matrices of each layer of the solid-phase particles. Taking Z 50 as an example, the hydraulic shear matrix of the cross-section solid-phase particles is as Figure 5 shown. After layer-by-layer output, obtain the hydraulic shear matrices of all particles in the reactor, and after processing, obtain the hydraulic shear diagram of the solid-phase particles in the reactor, as Figure 6 shown. From the above processes and results, it can be seen that the present invention can quantitatively describe the hydraulic shear received by the solid-phase particles in the three-phase flow reaction system of the suspension bed, can calculate and analyze the hydraulic shear of the solid-phase particles in the complex three-phase flow of the suspension bed, and has high calculation accuracy and strong feasibility.

[0068] The above-described embodiments merely represent several implementation manners of the present invention, and the description thereof is relatively specific and detailed, but it should not be construed as a limitation to the scope of the patent of the present invention. For those of ordinary skill in the art, without departing from the concept of the present invention, several modifications and improvements can still be made, and these all belong to the protection scope of the present invention.

Claims

1. A method for obtaining the hydrodynamic shear of solid particles in a gas-liquid-solid three-phase flow reaction system of a suspension bed, characterized in that, It includes the following steps: S1: Use the RNG k-ε turbulence model to simulate and analyze the hydrodynamic characteristics in the reactor, and construct a reactor hydrodynamic model; S2: After modeling, layer by layer output the two-dimensional turbulent dissipation diagrams and two-dimensional solid holdup distribution diagrams at each layer in the axial direction of the reactor, and use image scanning to identify the turbulent dissipation diagrams and solid holdup distribution diagrams to obtain the turbulent dissipation value matrix and solid holdup distribution matrix at each layer on this axis; S3: Based on the turbulent dissipation value matrix and solid holdup distribution matrix at each layer, calculate the turbulent dissipation value matrix of solid-phase particles, and combine the conversion formula between turbulent dissipation and hydrodynamic shear to convert the turbulent dissipation matrix of solid-phase particles at each layer in this axial direction into a two-dimensional hydrodynamic shear matrix, and then obtain the overall hydrodynamic shear value matrix of solid-phase particles in the reactor.

2. The method for obtaining the hydraulic shear of solid particles in the gas-liquid-solid three-phase flow reaction system of the suspension bed according to claim 1, wherein The establishment and simulation process of the RNG k-ε turbulence model described in S1 specifically includes the following steps: Use fluid mechanics software to establish a reactor model for the gas-liquid-solid three-phase flow reaction system in the suspension bed; Set the boundary conditions and initial conditions of the reactor model; Set corresponding operating parameters according to different configurations, aeration intensities, and sizes of aeration heads of the reactor.

3. The method for obtaining the hydrodynamic shear of solid particles in the gas-liquid-solid three-phase flow reaction system of the suspension bed according to claim 1, wherein In S2, Denote the axial direction as the Z direction, and the two directions perpendicular to the axial direction as the X direction and the Y direction, and the X direction and the Y direction are perpendicular to each other; output the two-dimensional turbulent dissipation diagrams and two-dimensional solid holdup distribution diagrams at different heights in the axial direction of the reactor, that is, layer by layer output the X-Y two-dimensional turbulent dissipation diagrams and X-Y two-dimensional solid holdup distribution diagrams at different positions on the Z axis in the reactor.

4. The method for obtaining the hydraulic shear of solid particles in the gas-liquid-solid three-phase flow reaction system of the suspension bed according to claim 3, wherein, In S2, the image scanning to identify the turbulent dissipation diagram and obtain the turbulent dissipation value matrix at each layer on this axis specifically includes: Read the XY coordinates and RGB values in the turbulent dissipation diagrams at different positions on the Z axis in sequence, and output the corresponding RGB value matrix; after converting the RGB values in the matrix to hexadecimal HEX and then converting them to decimal for output, obtain the RGB value matrix in decimal form; read the highest and lowest values of turbulent dissipation and record their corresponding RGB values, and then solve the corresponding function between turbulent dissipation value and RGB value; through the RGB value matrix, combine the corresponding function between turbulent dissipation value and RGB value to convert the RGB value matrix at different positions on the Z axis into a turbulent dissipation value matrix.

5. The method for obtaining the hydraulic shear of solid particles in the gas-liquid-solid three-phase flow reaction system of the suspension bed according to claim 3, wherein In S2, the image scanning to identify the solid holdup distribution diagram and obtain the solid holdup distribution matrix at each layer on this axis specifically includes: Read the XY coordinates where the particles are located in the solid holdup distribution diagrams at different positions on the Z axis in sequence, assign 1 to the corresponding coordinates, and assign 0 to other positions without particles, so as to form a solid holdup distribution matrix.

6. The method for obtaining the hydrodynamic shear of solid particles in the suspension bed gas-liquid-solid three-phase flow reaction system according to claim 1, characterized in that In S3, the obtaining of the turbulent dissipation value matrix of solid-phase particles specifically includes: The turbulent dissipation value matrix of the solid-phase particles is obtained by dot-multiplying the turbulent dissipation value matrix of the Z1 section in the reactor with the solid holdup matrix, and the turbulent dissipation value matrix of the solid-phase particles from Z1 to Z can be obtained by layer-by-layer calculation. n The turbulent dissipation value matrix of the solid-phase particles is obtained by dot-multiplying the turbulent dissipation value matrix of the Z1 section in the reactor with the solid holdup matrix, and the turbulent dissipation value matrix of the solid-phase particles from Z1 to Z can be obtained by layer-by-layer calculation.

7. The method for obtaining the hydraulic shear of solid particles in the gas-liquid-solid three-phase flow reaction system of the suspension bed according to claim 1, wherein, In S3, use the following calculation formula to convert the output turbulent dissipation value into the hydrodynamic shear value received by the solid-phase particles: Where: γ—hydraulic shear value, s -1 ; ε—Turbulent dissipation rate, cm 2 ·s -3 ; ν - kinematic viscosity, cm 2 ·s -1 。 8. The method for obtaining the hydraulic shear of solid particles in the gas-liquid-solid three-phase flow reaction system of the suspension bed according to claim 1, characterized in that, In S3, the two-dimensional solid-phase particle hydrodynamic shear value matrix in the axial direction inside the reactor is exported layer by layer, that is, the two-dimensional solid-phase particle hydrodynamic shear value matrices of each layer from Z1 to Z n are output.

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