Method for obtaining particle agglomeration effects in a multiphase flow reactor

Abstract

The application provides a method for obtaining particle agglomeration effect in a multiphase flow reactor, which comprises computational fluid dynamics simulation, particle coordinate information derivation, solid phase particle life cycle calculation and result output. The multiphase flow agglomeration refers to the mutual approach of two or more particles in the motion process in a multiphase flow (gas-liquid-solid) reaction system, and then the particles are gathered together to form a relatively stable cluster structure. The study on the agglomeration effect is of great significance to the colloid flocculation in the water treatment process and the biological granulation. After the simulation of the motion of the multiphase flow particles based on the fluid mechanics software, the time sequence coordinates of the particles in the flow field are derived, the particle agglomeration time and the number of agglomerates in the reaction system are calculated by judging the distance between the particles, and then the particle agglomeration effect in the multiphase flow reaction system is determined. The method can effectively calculate the particle agglomeration effect in the multiphase flow reaction system, and has the advantages of high accuracy and strong applicability.

Description

Technical Field

[0001] This invention belongs to the field of hydraulic calculation and relates to a method for obtaining the particle aggregation effect in a multiphase flow reactor. Background Technology

[0002] In multiphase flow systems, it is common for two or more particles to approach each other during motion and subsequently aggregate to form relatively stable agglomerates; this phenomenon is known as particle aggregation. Examples include particle aggregation during water treatment flocculation, where particles agglomerate and grow larger, forming flocs and accelerating sedimentation; and granular sludge formed through microbial self-agglomeration. Various studies have demonstrated that enhancing the aggregation effect in multiphase flow reaction systems and promoting the formation of aggregates within the system is of great significance for treating organic matter in wastewater.

[0003] However, due to the complexity of multiphase flow system calculations, the generally small size of flocs and agglomerates, the rapid aggregation-disintegration rate, and the difficulty in establishing particle motion in three-phase flow, and the fact that aggregation can only be obtained based on a clear understanding of particle motion, the measurement of aggregation behavior is very difficult. Therefore, there are currently few quantitative descriptions of floc aggregation effects. Summary of the Invention

[0004] To address the above problems, this invention proposes a method for obtaining the solid particle agglomeration effect in a multiphase flow reactor.

[0005] The technical solution of the present invention is as follows:

[0006] This invention provides a method for obtaining the particle aggregation effect in a multiphase flow reactor. The specific steps are as follows: S1: Based on the multiphase flow reactor to be simulated and its operating parameters, the RNG k-ε turbulence model is used to construct a reactor hydraulic model to simulate and analyze the fluid dynamic characteristics in the reactor.

[0007] S2: Based on the simulation of S1, output the coordinate position information of each particle at different time points;

[0008] S3: Based on the coordinate position information of each particle at different time points, calculate the number of aggregates formed by the particles and the total time of aggregation, and obtain the life cycle value of the particles by dividing the total time of aggregation by the number of aggregates, so as to characterize the aggregation effect of solid particles in multiphase flow reaction system.

[0009] According to a preferred embodiment of the present invention, the modeling process of the RNG k-ε turbulence model described in S1 specifically includes the following steps:

[0010] Establish a reactor physical model for a multiphase flow reaction system;

[0011] Set the physical field, computational grid type, reactor running time, reactor internal fluid type, boundary conditions and initial conditions of the reactor hydraulic model;

[0012] By setting the size of the aeration head and the aeration intensity, a hydraulic model of the reactor can be obtained.

[0013] According to a preferred embodiment of the present invention, the coordinate position information at different time points mentioned in S2 is the temporal coordinate of the particle.

[0014] This invention proposes a method for obtaining the solid particle aggregation effect in a multiphase flow reaction system. It employs computational fluid dynamics simulation, hydraulic information export, and programming file processing of particle coordinate position information to calculate particle lifetime values, thereby characterizing the aggregation effect. This overcomes the problems of difficulty in quantifying the solid particle aggregation effect in multiphase flow reaction systems, the complexity of the calculation process, and poor accuracy. It enables the quantitative calculation of the aggregation effect value of solid particles in multiphase flow reaction systems. It offers advantages such as high accuracy and strong feasibility for analyzing and calculating the solid particle aggregation effect value in complex multiphase flows.

[0015] This invention employs fluid dynamics simulation combined with computer programming to solve wastewater treatment problems. The simulation data is processed and analyzed using programming software, and the lifecycle value is used to characterize the aggregation effect of solid particles in the reaction system. The lifecycle value is obtained by dividing the total aggregation time of the formed aggregates by the number of aggregates, i.e., the average aggregation time of individual aggregates. From an aggregation perspective, the longer the average aggregation time of individual aggregates, the higher the probability of forming stable aggregate structures. Therefore, the longer the total aggregation time, the greater the total number of aggregates, and the higher the growth rate of the total aggregation time compared to the growth rate of the number of aggregates, i.e., the higher the lifecycle value, the better the aggregation effect is considered. This invention has significant scientific importance and high practical value for wastewater treatment in multiphase flow systems.

[0016] This invention provides a method for obtaining the particle aggregation effect in a multiphase flow reactor, addressing the problems of difficulty in characterizing the particle aggregation effect, complex calculation process, and poor accuracy in multiphase flow reactors. Through this invention, the temporal position coordinates of particles in a multiphase flow reactor can be obtained, and the particle aggregation effect in the multiphase flow reactor can be calculated based on these coordinates. Attached Figure Description

[0017] Figure 1 This is a flowchart illustrating the implementation of this invention;

[0018] Figure 2 This is a schematic diagram of the model established in the implementation of this invention;

[0019] Figure 3 This describes the particle's movement at a specific point in time in this invention.

[0020] Figure 4 This is a table of partial particle temporal position coordinates output;

[0021] Figure 5 This is a table of lifecycle values ​​for different effective liquid volumes. Detailed Implementation

[0022] The present invention will be further described and illustrated below with reference to specific embodiments. The embodiments described are merely examples of the content of this disclosure and do not limit the scope of the invention. The technical features of each embodiment in the present invention can be combined accordingly, provided that there is no mutual conflict.

[0023] Taking an SBR aerobic granular sludge reactor with a height-to-diameter ratio of 5, a reactor volume of approximately 7L, and a liquid volume of approximately 5L as an example. The specific flow chart is shown below. Figure 1 As shown, the method for obtaining data related to the solid-phase particle aggregation effect in the multiphase flow reaction system of the present invention includes:

[0024] The first step is to perform numerical simulation of the multiphase flow reaction system and construct a reactor hydraulic model, such as... Figure 2 As shown, the specific process includes:

[0025] 1. Reactor model establishment,

[0026] Specifically, the motion characteristics of solid particles in the reactor were simulated using Flow-3d software. The initial and minimum step sizes were set to default values, and the total running time was set to 180 seconds. In the physics model, the Gravity and Non-inertial Reference Frame was selected, with the gravity direction set to -Z and the gravitational acceleration g = -981 cm·s⁻¹. -2 The Viscosity and Turbulence model was selected, with the RNG model chosen. The Particles model was selected, with solid particles having a diameter of 0.03 cm and a density of [missing value].

[0027] 1.01 g·cm -3 The diameter of the gas phase bubbles was 0.3 cm, and the density was 0.0013 g·cm³. -3 The simulation uses a single fluid, which is an incompressible fluid at 20°C.

[0028] 2. Mesh generation and boundary condition determination

[0029] Specifically, after establishing the reactor model, the model's geometry is created according to the reactor's specifications. A mesh is generated by discretizing the simulated flow computational domain. The established geometric model is then embedded into the computational mesh, and the mesh size is set to 0.3–0.5 cm. Based on the actual situation, the reactor's perimeter and bottom are designated as wall boundaries, the top as a specified pressure boundary, and the Fluidfraction is set to 0, indicating that the liquid surface is connected to the atmosphere.

[0030] 3. Set initial conditions

[0031] Specifically, after setting a suitable initial liquid level in the Initial stage, the initial particle configuration is defined. At this point, the solid particles are of type Probe from Particles, and the required number of particles is set. The aeration head is set to source from Particles, and the Particles class is set to gas. This simplifies the aeration head in the reactor to a cube with sides of 3*4cm, which serves as the bubble source. Then, based on the required aeration intensity (Q), the bubble rate per second is calculated and set to 2948 (Q = 2.5 L·min). -1 ).

[0032] 4. Simulation calculation

[0033] After setting all the conditions, click "run simulation" to start the calculation.

[0034] The second step is to export the coordinate position information of each particle at different time points using FlowSight. That is, by opening the Flow-3d calculation file with FlowSight, you can observe the particle motion at a specific moment (e.g., ...). Figure 3 Click on "History data," select the coordinate information for all particles in the History data, and save to file. The output file contains the X, Y, and Z coordinates of each particle at different time points (e.g., ...). Figure 4 ).

[0035] The third step involves processing the exported coordinate information of each particle at different time points using Python programming files to calculate the number of aggregates formed by the particles and the total time of aggregation. The life cycle value of the particles is then obtained by dividing the total time of aggregation by the number of aggregates.

[0036] In this embodiment, the third step specifically includes the following five sub-steps:

[0037] 1) Define the set of stationary particles as Q. 静The stationary particles are those whose XYZ axis coordinates do not change with subsequent time and are skipped in the calculation;

[0038] 2) Define the set of aggregates at the previous time step as Q, and the total number of aggregates as Q. 总 Q 总 The initial value is 0; the duration for which particles form aggregates is defined as T. 持 T 持 The initial value is also 0; the new clustered individual is defined as q, and the set of particles constituting the clustered individual is defined as q. 粒 The time of initial formation of aggregates is defined as q. 初 The set of particles that already belong to the aggregate is defined as q. 已 ;

[0039] 3) Start the calculation from the point when the simulated reaction is running stably. At each time point, iterate through all particles and update Q and Q' during each iteration. 总 , q, q 初 q 已 Update Q after each iteration 静 Q, Q 总 , q, q 初 q 已 The time interval is 0.1s.

[0040] In step 3), the procedure for each iteration is as follows:

[0041] (i) If the particle belongs to the set of stationary particles Q 静 Skip it;

[0042] (ii) If the distance between particles i and j is less than the diameter d of the particles, and neither i nor j belongs to q 已 Then a new aggregate q is formed, and this is the initial formation time q of this aggregate. 初 A new cluster q is added to the cluster set Q, and the total number of clusters is Q. 总 +1, then particles i and j are added to q 已 ;

[0043] (iii) If the distance between particles i and j is less than the particle diameter d, but i or j already belongs to q 已 Then it will not belong to q 已 If particles also join in, it means that the particles are captured by the already formed aggregate.

[0044] The procedure after each iteration in step 3) is as follows:

[0045] (a) Individual aggregate q 粒 The particles in the calculation belong to the set of stationary particles after this point in time, and subsequent calculations skip this particle.

[0046] (b) If the number of particles in the final q particles is ≤1, it means that the aggregate has disintegrated. The time point at which the aggregate was initially formed, q_initial, is the increased duration T_hold of the aggregate.

[0047] (c) If the number of particles in a single aggregate q is greater than 1, and the distance between any two particles in the aggregate is greater than d, it also indicates that the aggregate disintegrates. The time point at which the aggregate is initially formed, q_initial, is the increased duration T_hold of the aggregate.

[0048] 4) The final duration T of the aggregate is obtained. 持 The total number of aggregates Q 总 The duration T of the obtained aggregates 持 That is, the total time of the aggregation and the total number of aggregates Q. 总 This refers to the number of aggregates formed by the particles.

[0049] 5) The final calculated duration of the aggregate is the total number of aggregates Q, which is the output particle lifecycle.

[0050] This embodiment uses lifecycle value to characterize the aggregation effect in a multiphase flow reaction system. The SBR aerobic granular sludge reactor has a height-to-diameter ratio of 5, a reactor volume of approximately 7L, and a liquid volume of approximately 5L, with an aeration rate Q = 2.5 L / min. -1 The reunion effect lasts for 1.67 seconds. Figure 5 The table shows the life cycle values ​​for different effective liquid volumes. For the same SBR aerobic granular sludge reactor, with the same particle size and aeration rate Q = 2.5 L·min⁻¹, the reactor with a height-to-diameter ratio of 5 and a liquid volume of 4 L has a smaller effective volume and more obvious agglomeration behavior, while the reactor with a liquid volume of 6 L has a larger effective volume and relatively less obvious agglomeration behavior.

[0051] The above-described embodiments are merely illustrative of several implementations of the present invention, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the present invention. Those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the scope of protection of the present invention.

Claims

1. A method for obtaining particle aggregation effect in a multiphase flow reactor, characterized in that, Includes the following steps: S1: Based on the multiphase flow reactor to be simulated and its operating parameters, the RNG k-ε turbulence model is used to construct a reactor hydraulic model to simulate and analyze the fluid dynamic characteristics in the reactor; S2: Based on the simulation of S1, output the coordinate position information of each particle at different time points; S3: Based on the coordinate position information of each particle at different time points, calculate the number of aggregates formed by the particles and the total time of aggregation, and obtain the life cycle value of the particles by dividing the total time of aggregation by the number of aggregates, so as to characterize the aggregation effect of solid particles in the multiphase flow reaction system. The calculation of the number of particle aggregates and the total aggregation time described in S3 is as follows: 1) Define the set of stationary particles as Q. 静 The stationary particles are those whose XYZ axis coordinates do not change with subsequent time and are skipped in the calculation; 2) Define the set of aggregates at the previous time step as Q, and the total number of aggregates as Q. 总 Q 总 The initial value is 0; the duration for which particles form aggregates is defined as T. 持 T 持 The initial value is also 0; the new clustered individual is defined as q, and the set of particles constituting the clustered individual is defined as q. 粒 The time of initial formation of aggregates is defined as q. 初 The set of particles that already belong to the aggregate is defined as q. 已 ; 3) Start the calculation from the point when the simulated reaction is running stably. At each time point, iterate through all particles and update Q and Q' during each iteration. 总 , q, q 初 q 已 Update Q after each iteration 静 Q, Q 总 , q, q 初 q 已 The time interval is 0.1s. 4) The final duration T of the aggregate is obtained. 持 The total number of aggregates Q 总 The duration T of the obtained aggregates 持 That is, the total time of the aggregation and the total number of aggregates Q. 总 This refers to the number of aggregates formed by the particles.

2. The method for obtaining particle aggregation effect in a multiphase flow reactor as described in claim 1, characterized in that, The modeling process of the RNG k-ε turbulence model described in S1 specifically includes the following steps: Establish a reactor physical model for a multiphase flow reaction system; Set the physical field, computational grid type, reactor running time, reactor internal fluid type, boundary conditions and initial conditions of the reactor hydraulic model; By setting the size of the aeration head and the aeration intensity, a hydraulic model of the reactor can be obtained.

3. The method for obtaining particle aggregation effect in a multiphase flow reactor as described in claim 1, characterized in that, The coordinate position information at different time points mentioned in S2 is the temporal coordinate of the particle.

4. The method for obtaining particle aggregation effect in a multiphase flow reactor as described in claim 1, characterized in that, The procedure for each iteration in step 3) is as follows: (i) If the particle belongs to the set of stationary particles Q 静 Skip it; (ii) If the distance between particles i and j is less than the diameter d of the particles, and neither i nor j belongs to q 已 Then a new aggregate q is formed, and this is the initial formation time q of this aggregate. 初 A new cluster q is added to the cluster set Q, and the total number of clusters is Q. 总 +1, then particles i and j are added to q. 已 ; (iii) If the distance between particles i and j is less than the particle diameter d, but i or j already belongs to q 已 Then it will not belong to q 已 If particles also join in, it means that the particles are captured by the already formed aggregate.

5. The method for obtaining particle aggregation effect in a multiphase flow reactor as described in claim 1, characterized in that, The procedure after each traversal in step 3) is as follows: (a) Individual aggregate q 粒 The particles in the calculation belong to the set of stationary particles after this point in time, and subsequent calculations skip this particle. (b) If the final q 粒 If the number of particles in the aggregate is ≤1, it indicates that the aggregate has disintegrated. This time point is calculated by subtracting the initial formation time q of the aggregate. 初 The duration T of the increased aggregate is... 持 ; (c) If a single aggregate q 粒 If the number of particles in the aggregate is greater than 1, and the distance between any two particles within the aggregate is greater than d, it also indicates that the aggregate has disintegrated. This time point is calculated by subtracting the initial formation time q of the aggregate. 初 The duration T of the increased aggregate. 持 .

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