Parameter optimization selection method of flexible particle material winnowing separation equipment

Abstract

The invention provides a parameter optimization selection method of flexible particle material winnowing separation equipment. The parameter optimization selection method comprises the following steps that a numerical model of the flexible particle material winnowing separation equipment and a numerical model of the horizontal transportation winnowing separation equipment are built; performing numerical simulation on the flowing and separating process of the flexible particles in the horizontal transportation winnowing separation equipment through a coupling discrete element method and a computational fluid mechanics method; carrying out quantitative characterization on the separation effect by calculating the separation index, the impurity rate and the loss rate; in numerical simulation, working parameters and geometric parameters of winnowing separation equipment are adjusted, and particle flow and separation results under different working conditions are obtained; and through the separation effect and flow field analysis in the separation process, the optimal combination of the working parameters and the geometric parameters of the winnowing separation equipment under the optimal separation effect is determined. According to the method, optimal selection of the equipment parameters can be well achieved, the working parameters and geometric parameters of the equipment are optimized, and the winnowing efficiency and the separation effect of the equipment can be improved.

Description

Technical Field

[0001] The invention belongs to the technical field of tobacco manufacturing, and in particular relates to a parameter optimization selection method for flexible particle material air separation equipment. Background Art

[0002] Under vibration, flow and fluidization conditions, the particle mixture will separate, that is, particles with the same or similar properties (such as density, size and shape) gather together, thereby achieving the separation of particles with different properties. This separation phenomenon is widely present in nature or industrial production, such as the formation of different sand layers in riverbeds, the sorting of coarse coal slime in the coal industry, the removal of impurities in grains in agriculture, and the removal of stems in tobacco processing. At present, the air separation process of flexible biomass particles in industry is still in a black box. People lack an understanding of the influence of key operating parameters, impurity concentrations and equipment geometric characteristics on the separation process and results, and cannot achieve the optimization of parameters in the air separation equipment. Therefore, how to design a parameter optimization selection method for flexible particle material air separation equipment to achieve the optimization selection of parameters for horizontally transported flexible particle material air separation equipment has become a technical problem that technicians in this field urgently need to solve. Summary of the invention

[0003] The purpose of the present invention is to provide a method for optimizing the selection of parameters of a flexible particulate material air separation device to solve the above-mentioned technical problems in the prior art.

[0004] To achieve the above object, the present invention provides the following technical solutions:

[0005] A method for optimizing parameters of a flexible particle material air separation device comprises the following steps:

[0006] Construct numerical models of wind separation equipment with flexible particles and horizontal transport;

[0007] The flow and separation process of flexible particles in horizontally transported wind separation equipment is numerically simulated by coupling discrete element method and computational fluid dynamics method; the separation effect is quantitatively characterized by calculating separation index, impurity content and loss rate;

[0008] In the numerical simulation, the working parameters and geometric parameters of the air separation equipment are adjusted to obtain the particle flow and separation results under different working conditions; through the separation effect and flow field analysis during the separation process, the optimal combination of the working parameters and geometric parameters of the air separation equipment for the best separation effect is determined.

[0009] Preferably, the specific contents of constructing the numerical model of flexible particles are:

[0010] A spherical bond model is constructed in which a deformable and flexible bond connecting unit balls is constructed, in which: the particle size of the unit ball determines the diameter of the flexible particle, characterizing the thickness of the particle; the aspect ratio of the particle characterizes the shape of the particle; the flexibility of the flexible bond is characterized by the elasticity and shear modulus of the bond, reflecting the ability of the particle to deform in tension, compression, shear, bending and torsion.

[0011] Preferably, the specific contents of constructing the numerical model of the horizontal transport wind separation equipment are:

[0012] A particle mixture feeding area, an impurity particle collection area, a fluidized separation area and a clean particle collection area are constructed; the bottom and left and right sides of the fluidized separation area are non-slip solid walls, wherein an opening at a certain height on the right wall is connected to the particle mixture feeding port, and an opening at the left and right ends of the bottom is respectively connected to the clean particle collection port and the impurity particle collection port; the top left part of the area is the airflow outlet; the particle mixture and the airflow enter the equipment from the feed port at the same rate; the equipment wall is the non-slip solid wall boundary of the airflow.

[0013] Preferably, the specific steps of numerically simulating the flow and separation process of flexible particles in a horizontally transported air separation device by coupling discrete element method and computational fluid dynamics method are as follows:

[0014] The fluid dynamics equations are used to simulate air flow, and the particle dynamics equations are used to describe particle motion; the interaction force equations are derived by coupling the flow field dynamics equations and the particle dynamics equations;

[0015] Set the computational boundary conditions for the interaction force equations;

[0016] Initialize the flow field, set the particle properties to be flexible, perform particle separation simulation, collect particle distribution data within a certain time range, and obtain the particle separation effect.

[0017] Preferably, the fluid dynamics equations include the continuity equation and the momentum conservation equation, wherein:

[0018] The continuity equation is:

[0019]

[0020] The momentum conservation equation is:

[0021]

[0022] In the formula, , , and represent the density, pressure, velocity and viscous stress of the gas respectively, is the acceleration due to gravity, is the porosity;

[0023]

[0024] in: Represents the interaction force between gas and solid phases per unit volume;

[0025] Represents the flow field force on all particle unit balls in the i-th fluid grid;

[0026] represents the fluid grid volume;

[0027] is the number of unit balls in a fluid grid unit.

[0028] Preferably, the particle dynamics equations include flexible particle motion control equations and flexible particle deformation control equations, wherein:

[0029] The control equation of flexible particle motion is:

[0030]

[0031]

[0032] in: is the displacement vector of the unit sphere inside the particle;

[0033] is the angular velocity vector of the unit sphere inside the particle;

[0034] For quality The moment of inertia of the unit ball, ;

[0035] is the contact force between particles, is the bonding force, is the contact force damping term, is the bond force damping term;

[0036] is the contact torque, is the bonding torque, is the contact torque damping term, is the bond moment damping term;

[0037] The deformation control equation of flexible particles is:

[0038]

[0039]

[0040]

[0041]

[0042] in: , , ,and They are the normal force, tangential force, torsional moment, and bending moment increment of the virtual key;

[0043] , , They are the normal deformation, tangential deformation, torsion angle deformation, and bending angle deformation increments of the key respectively;

[0044] , , are the normal stiffness, tangential stiffness, torsional stiffness and bending stiffness of the key respectively; the length is =π ; The radius of the cylindrical key is ,

[0045] and are Young's modulus and shear modulus of the bond, respectively;

[0046] , , are the normal deformation velocity, tangential deformation velocity, torsional deformation angular velocity and bending deformation angular velocity of the bond, is the time step.

[0047] Preferably, the interaction force equation is:

[0048]

[0049]

[0050]

[0051]

[0052]

[0053] in: is the volume of the unit sphere in the particle, is the aerodynamic drag acting on the unit sphere, is the unit ball diameter,

[0054] represents the relative speed between the local airflow and the unit sphere, is the drag coefficient, For particle Renault.

[0055] Preferably,

[0056] The calculation formula of the separation index is:

[0057]

[0058] in,

[0059]

[0060]

[0061]

[0062] The computational domain is divided into 10 subdomains of equal size in the x and y directions, and N is the total number of subdomains. is the average concentration of impurity particles in the system, is the average concentration of impurity particles in each subdomain, and n is the average number of particles in each subdomain;

[0063] The calculation formula of impurity content is:

[0064]

[0065] The loss rate is calculated as:

[0066]

[0067] in, is the volume of clean particles collected in the clean particle collection area, is the volume of impurity particles collected in the clean particle collection area, is the volume of clean particles collected in the impurity particle collection area, The volume of foreign particles collected in the foreign particle collection area.

[0068] Preferably, the optimal separation effect refers to:

[0069] Under the condition of specified impurity particle concentration, the impurity content is the smallest and the loss rate is within the permitted range; for conditions with different impurity particle concentrations, the separation index is the largest and both the impurity content and the loss rate are within the permitted range.

[0070] Preferably, the specific contents of adjusting the working parameters and geometric parameters of the air separation equipment are:

[0071] The air inlet velocity, feed velocity, height of the fluidized separation area, width of the impurity particle collection area and impurity particle concentration are adjusted within a certain range; the separation index, impurity content and loss rate under various working conditions are obtained.

[0072] The beneficial effects of the present invention are:

[0073] The parameter optimization selection method of the flexible particle material air separation equipment of the present invention is based on the flexible particle air separation process in actual industrial production, numerically simulates the separation process of the horizontally transported flexible particle material in the air separation equipment, analyzes the influence of key working parameters and equipment geometric parameters on the separation effect, and can better realize the optimization selection of parameter combinations. At the same time, the present invention can optimize the working parameters of the air separation equipment for horizontal transportation of flexible particles, improve the geometric parameters of the equipment, thereby improving the air selection efficiency and separation effect of the equipment. BRIEF DESCRIPTION OF THE DRAWINGS

[0074] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the following will briefly introduce the drawings required for use in the embodiments, and further describe the specific embodiments of the present invention in detail in conjunction with the drawings, wherein

[0075] Figure 1 It is a flow chart of a parameter optimization selection method for a flexible particulate material air separation device provided in an embodiment of the present invention;

[0076] Figure 2 Schematic diagram of a model of a horizontal transport air separation device used in an embodiment of the present invention;

[0077] Figure 3 is a schematic diagram of a flexible particle model used in an embodiment of the present invention;

[0078] Figure 4 is a diagram of physical parameters of flexible particle mixing used in an embodiment of the present invention;

[0079] Figure 5 The impurity concentration is 10%, standard size, , When , the flexible particle distribution visualization image in the calculation area is obtained;

[0080] Figure 6 The impurity concentration is 10%, standard size, , When the movement trajectory images of tobacco shreds and stem particles in the area at different times are calculated;

[0081] Figure 7 The impurity concentration is 10%, standard size, , When the average velocity of tobacco and stem particles in the area changes with time, the change is calculated;

[0082] Figure 8 The impurity concentration is 10%, standard size, The change of impurity content in the tobacco collection area with time at different air intake speeds;

[0083] Fig. 9 The impurity concentration is 10%, standard size, The variation of the loss rate in the stem collection area with time at different air inlet speeds;

[0084] Fig.10 The impurity concentration is 10%, standard size, The motion trajectory images of tobacco shreds and stem particles at different times in the calculation area under different intake velocities;

[0085] Fig.11 The impurity concentration is 10%, standard size, The change of impurity content in the tobacco collection area with time at different feeding speeds;

[0086] Fig.12 The impurity concentration is 10%, standard size, Changes of the loss rate in the stem collection area with time at different feeding speeds;

[0087] Fig.13 The impurity concentration is 10%, the standard stem collection area width (0.084m), , The change of impurity content in the tobacco collection area with time at different fluidization separation area heights;

[0088] Fig.14 The impurity concentration is 10%, the standard stem collection area width (0.084m), , The change of the loss rate in the stem collection area with time at different fluidized separation area heights;

[0089] Fig.15 The impurity concentration is 10%, the standard stem collection area width (0.084m), , The streamline and airflow velocity distribution in the calculation area at different fluidization separation area heights;

[0090] Fig.16 The impurity concentration is 10%, the standard fluidized separation area height (0.192m), , The change of impurity content in the tobacco collection area with time under different stem collection area widths;

[0091] Fig.17 The impurity concentration is 10%, the standard fluidized separation area height (0.192m), , When the width of the stem collection area is different, the change of the loss rate in the stem collection area over time;

[0092] Fig.18 The impurity concentration is 10%, the standard fluidized separation area height (0.192m), , Visualization image of the distribution of flexible particles in the calculation area under different stem collection area widths;

[0093] Fig.19 It is a standard size. , When , the change of separation index in the region with time is calculated;

[0094] Fig. 20 It is a standard size. , The change of impurity content in the tobacco collection area over time;

[0095] Fig.21 It is a standard size. , The loss rate in the collection area changes over time. DETAILED DESCRIPTION

[0096] Various exemplary embodiments of the present invention will now be described in detail with reference to the accompanying drawings. It should be noted that the relative arrangement of components and steps, numerical expressions and numerical values ​​set forth in these embodiments do not limit the scope of the present invention unless otherwise specifically stated.

[0097] The following description of at least one exemplary embodiment is merely illustrative in nature and is in no way intended to limit the invention, its application, or uses.

[0098] Technologies, methods, and equipment known to ordinary technicians in the relevant art may not be discussed in detail, but where appropriate, the technologies, methods, and equipment should be considered as part of the specification.

[0099] In all examples shown and discussed herein, any specific values ​​should be interpreted as merely exemplary and not limiting. Therefore, other examples of the exemplary embodiments may have different values.

[0100] like Figure 1 As shown, an embodiment of the present invention provides a method for optimizing parameters of a flexible particulate material air separation device, which includes the following steps:

[0101] Construct numerical models of wind separation equipment with flexible particles and horizontal transport;

[0102] The flow and separation process of flexible particles in horizontally transported wind separation equipment is numerically simulated by coupling discrete element method and computational fluid dynamics method (i.e. DEM-CFD method); the separation effect is quantitatively characterized by calculating separation index, impurity content and loss rate;

[0103] In the numerical simulation, the working parameters and geometric parameters of the air separation equipment are adjusted to obtain the particle flow and separation results under different working conditions; through the separation effect and flow field analysis during the separation process, the optimal combination of the working parameters and geometric parameters of the air separation equipment for the best separation effect is determined.

[0104] The parameter optimization selection method for the flexible particle material air separation equipment provided by the embodiment of the present invention is based on the flexible particle air separation process in actual industrial production, numerically simulates the separation process of the horizontally transported flexible particle material in the air separation equipment, analyzes the influence of key operating parameters and equipment geometric parameters on the separation effect, and can better achieve the optimization selection of parameter combinations that are beneficial to the particle separation process and separation effect. At the same time, the present invention can optimize the working parameters of the air separation equipment for horizontal transportation of flexible particles, improve the geometric parameters of the equipment, and thus improve the air selection efficiency and separation effect of the equipment.

[0105] Furthermore, the specific contents of constructing the numerical model of flexible particles are as follows:

[0106] A spherical bond model is constructed in which a deformable and flexible bond connects unit balls, wherein: the particle size of the unit ball determines the diameter of the flexible particle, characterizing the thickness of the flexible particle; the aspect ratio of the flexible particle characterizes the shape of the particle; the flexibility of the flexible bond is characterized by the elasticity and shear modulus of the bond, reflecting the ability of the flexible particle to be stretched, compressed, sheared, bent, and torsionally deformed. In other words, a spherical bond model is constructed in which a flexible bond with flexibility connects unit balls, wherein: the particle size controls the diameter of the unit ball, characterizing the thickness of the flexible particle; the flexibility controls the shear modulus of the flexible bond, characterizing the bending deformation ability of the flexible particle; the aspect ratio of the particle controls the number of unit balls connected by the flexible bond, characterizing the length of the flexible particle.

[0107] Specifically, the specific contents of constructing the numerical model of the horizontal transport wind separation equipment are as follows:

[0108] Construct a particle mixture feeding area, an impurity particle collection area, a fluidized separation area, and a clean particle collection area; the bottom and left and right sides of the fluidized separation area are non-slip solid walls, wherein an opening at a certain height on the right wall is connected to the particle mixture feeding port, and an opening at the left and right ends of the bottom is connected to the clean particle collection port and the impurity particle collection port respectively; the top left part of the area is the airflow outlet; the particle mixture and the airflow enter the device from the feed port at the same rate; the device wall is the non-slip solid wall boundary of the airflow. It can be understood that the constructed model can be a first-stage air separation device model.

[0109] like Figure 2 As shown, taking the air separation of tobacco shreds and stems as an example, a particle mixture feeding area at A, a stem collection area at B, i.e., an impurity particle collection area, a fluidized separation area at C, and a tobacco collection area at D, i.e., a clean particle collection area, are constructed; the bottom and left and right sides of the fluidized separation area are non-slip solid walls, wherein an opening at a certain height on the right wall is connected to the particle mixture feeding port, and an opening at the left and right ends of the bottom is connected to the tobacco collection port and the stem collection port respectively; the top is the outlet of the airflow, and the front and back are set as periodic boundaries; the particle mixture feeding area is connected to the right side of the particle mixture feeding port of the fluidized separation area; the right side of the particle mixture feeding area is the gas inlet flowing in at the particle mixture feeding speed, wherein the upper and lower sides are non-slip solid walls, and the front and back are set as periodic boundaries. The tobacco collection area is connected to the bottom of the tobacco collection port of the fluidized separation area, and the bottom, left and right sides of the tobacco collection area are non-slip solid walls, and the front and back are set as periodic boundaries. The stalk collection area is connected to the bottom of the stalk collection port of the fluidized separation area. The bottom of the stalk collection area is a gas inlet with a specified speed, wherein the left and right sides are both non-slip solid walls, and the front and back are both set as periodic boundaries.

[0110] Furthermore, the specific steps of numerically simulating the flow and separation process of flexible particles in a horizontally transported air separation device by coupling the discrete element method and the computational fluid dynamics method are as follows:

[0111] The fluid dynamics equations are used to simulate air flow, and the particle dynamics equations are used to describe the movement of flexible particles. The interaction force equations are derived by coupling the flow field dynamics equations and the particle dynamics equations, that is, the two-way coupling of airflow-particle interaction is achieved through the drag model of flexible and deformable particles.

[0112] Set the computational boundary conditions for the interaction force equations;

[0113] Initialize the flow field, set the particle properties to be flexible, perform particle separation simulation, collect particle distribution data within a certain time range, and obtain the particle separation effect.

[0114] Specifically, the fluid dynamics equations include the continuity equation and the momentum conservation equation, where

[0115] The continuity equation is:

[0116]

[0117] The momentum conservation equation is:

[0118]

[0119] In the formula, , , and represent the density, pressure, velocity and viscous stress of the gas respectively, is the acceleration due to gravity, is the porosity;

[0120]

[0121] in: Represents the interaction force between gas and solid phases per unit volume;

[0122] Represents the flow field force on all particle unit balls in the i-th fluid grid;

[0123] represents the fluid grid volume;

[0124] is the number of unit balls in a fluid grid unit.

[0125] Furthermore, the particle dynamics equations include flexible particle motion control equations and flexible particle deformation control equations, where:

[0126] The control equation of flexible particle motion is:

[0127]

[0128]

[0129] in: is the displacement vector of the unit sphere inside the particle;

[0130] is the angular velocity vector of the unit sphere inside the particle;

[0131] For quality The moment of inertia of the unit ball, ;

[0132] is the contact force between particles, is the bonding force, is the contact force damping term, is the bond force damping term;

[0133] is the contact torque, is the bonding torque, is the contact torque damping term, is the bond moment damping term;

[0134] The deformation control equation of flexible particles is:

[0135]

[0136]

[0137]

[0138]

[0139] in: , , ,and They are the normal force, tangential force, torsional moment, and bending moment increment of the virtual key;

[0140] , , They are the normal deformation, tangential deformation, torsion angle deformation, and bending angle deformation increments of the key respectively;

[0141] , , are the normal stiffness, tangential stiffness, torsional stiffness and bending stiffness of the key respectively; the length is =π ; The radius of the cylindrical key is ,

[0142] and are Young's modulus and shear modulus of the bond, respectively;

[0143] , , are the normal deformation velocity, tangential deformation velocity, torsional deformation angular velocity and bending deformation angular velocity of the bond, is the time step.

[0144] Furthermore, the interaction force equation is:

[0145]

[0146]

[0147]

[0148]

[0149]

[0150] in: is the volume of the unit sphere in the particle, is the aerodynamic drag acting on the unit sphere, is the unit ball diameter,

[0151] represents the relative speed between the local airflow and the unit sphere, is the drag coefficient, For particle Renault.

[0152] Specifically, the calculation formula of the separation index is:

[0153]

[0154] in,

[0155]

[0156]

[0157]

[0158] The computational domain is divided into 10 subdomains of equal size in the x and y directions, and N is the total number of subdomains. is the average concentration of impurity particles in the system, is the average concentration of impurity particles in each subdomain, and n is the average number of particles in each subdomain. The value range is between 0 and 1. The larger the value of , the greater the separation.

[0159] Furthermore, the calculation formula of impurity rate is:

[0160]

[0161] The loss rate is calculated as:

[0162]

[0163] in, is the volume of clean particles collected in the clean particle collection area, is the volume of impurity particles collected in the clean particle collection area, is the volume of clean particles collected in the impurity particle collection area, The volume of foreign particles collected in the foreign particle collection area.

[0164] Specifically, the optimal separation effect refers to:

[0165] Under the condition of specified impurity particle concentration, the impurity content is the smallest and the loss rate is within the permitted range; for conditions with different impurity particle concentrations, the separation index is the largest and both the impurity content and the loss rate are within the permitted range.

[0166] Furthermore, the specific method for adjusting the working parameters and geometric parameters of the air separation equipment is:

[0167] Adjust the air intake speed, feed speed, fluidized separation area height, impurity particle collection area width and impurity particle concentration within a certain range; statistically analyze the separation index, impurity content and loss rate under various working conditions.

[0168] In a specific embodiment, the separation of a mixture of shredded tobacco and stem particles is taken as an example. Figure 2 The air separation equipment model shown in FIG. 1 is used to numerically simulate the fluidized separation process of flexible tobacco shreds and stem particles in the air separation equipment by using the DEM-CFD method; the flexible particles adopt a key-connected ball model, such as Figure 3 As shown in the figure, during the simulation, a uniform mixture of tobacco shreds and stem particles is generated in the horizontal channel in the feed area, and its physical parameters are as follows: Figure 4 As shown; the mixture is fed at a specified rate The air enters the fluidized separation area at a constant speed. At the same time, the air passes through the inlet at the bottom of the stem collection area to specify the air inlet speed. It flows into the stem collection area and flows out from the top outlet of the equipment; the tobacco and stem particles of different sizes and densities are affected differently by the airflow driving force in the fluidized separation area, resulting in different movement trajectories and achieving separation.

[0169] Specifically, adjust the intake speed Adjust the feed rate between the respective suspension gas velocities of the flexible particle mixture In the range of 0.2m / s~0.4m / s; adjust the height of the fluidized separation area to be near the standard height of 0.192m, ranging from 0.132m~0.252m; adjust the width of the stem collection area to be near the standard width of 0.084m, ranging from 0.066m~0.102m; adjust the impurity concentration to be within the range of 6.25%~18.75%, calculated according to the volume fraction.

[0170] When the particle mixture is fluidized and transported to the tobacco collection area or the stem collection area, the volume content of tobacco and stems in each area is counted. When enough particles are collected, the content of particle components in each area (i.e., the particle separation level) tends to be stable, so that quantitative parameters such as separation index, loss rate, and impurity content under different working conditions can be compared and analyzed to measure the quality of separation effect. The best separation effect means: under the condition of specified impurity particle concentration, the impurity content is Minimum, while loss rate Within the permitted range; for different impurity particle concentrations, the separation index Maximum, while impurity rate and loss rate All are within the permitted range.

[0171] Example 1

[0172] In the standard geometry of the air separation equipment, the mixture consists of 10% by volume of stem particles and 90% by volume of cut tobacco particles. The feed rate , intake speed Under the condition of , the visualization results of the separation process at different times are as follows Figure 5 As shown in Figure 2, the movement trajectories of tobacco and stem particles are as follows: Figure 6 As shown in Figure 2, the average velocity of tobacco and stem particles during separation changes as Figure 7 As shown;

[0173] When the mixed particles enter the fluidized separation zone, the particles are mainly affected by gravity and aerodynamic forces. The aerodynamic force has a significant effect on the tobacco particles, causing them to move upward, while the effect on the stem particles is relatively small, causing them to move downward under the action of gravity, such as Figure 5 and Figure 6 As shown in Figure 1. The separation of the particle mixture is mainly due to density differences, which cause them to have different trajectories in the fluidized separation zone. The suspension velocity of the tobacco particles is lower than that of the stem particles. The suspension velocity is the air velocity at which the particles can just be suspended under the combined action of aerodynamic force and gravity. When the bottom inlet air velocity is between the suspension velocities of these two particles, the tobacco particles move upwards, while the stem particles move downwards. Due to these different movements, the average velocity of the tobacco particles is higher than that of the stem particles (such as Figure 7 This difference in average velocity causes differences in the motion trajectories of different particles, leading to the final separation.

[0174] Example 2

[0175] The results of the simulation by DEM-CFD method are as follows Figure 8 and Fig. 9 As shown in Figure 2, the movement trajectories of tobacco shreds and stem particles are as follows: Fig.10As shown, in the standard geometric dimensions of the air separation equipment, the impurity concentration is 10%, and the feed rate Under the condition of The impurity rate and loss rate of different intake velocities are obtained at 2 m / s, 3 m / s, 3.8 m / s, 4.3 m / s and 4.8 m / s respectively;

[0176] At the bottom air intake speed of 2m / s and 3.0m / s, the initially evenly mixed tobacco and stem particles were slowly transported to the fluidized separation area. The particles moved in different trajectories driven by aerodynamic force to achieve separation, but some tobacco particles were found to be brought into the stem collection area along with the stem particles, indicating the loss of product materials. When the bottom air intake speed was increased to 3.8m / s, complete separation was observed, and all particles were effectively collected in the designated collection area. When the bottom air intake speed was further increased to 4.3m / s, at 4.8m / s, more stem particles were observed to enter the tobacco collection area, and the volume fraction of stem particles in the tobacco collection area increased, resulting in a decrease in the purity of the tobacco.

[0177] Example 3

[0178] The results of the simulation by DEM-CFD method are as follows Fig.11 and Fig.12 As shown, in the standard geometric dimensions of the air separation equipment, the impurity concentration is 10%, and the feed rate Under these conditions, the feed rate was adjusted in the numerical simulation. The impurity rate and loss rate at different feed speeds are 0.2 m / s, 0.3 m / s and 0.4 m / s respectively;

[0179] At a feed rate of 0.2 m / s, the impurity content is close to zero; increasing the feed rate to 0.3 m / s and 0.4 m / s, the volume fraction of stem particles in the tobacco collection area gradually increases with the increase in feed rate, indicating that the lower feed rate of 0.2 m / s is more conducive to particle separation. In addition, it is worth noting that at all considered feed rates, the volume fraction of tobacco particles in the stem collection area is close to zero, indicating that the loss of product material is negligible.

[0180] Example 4

[0181] The results of the simulation by DEM-CFD method are as follows Fig.13 and Fig.14 As shown, the streamlines and airflow velocity distribution in the computational domain are as follows: Fig.15 As shown, at the standard width of the air separation equipment (0.084m), the impurity concentration is 10%, and the air intake speed is , feed rate Under these conditions, the height of the fluidized separation area of ​​the air separation equipment was adjusted to 0.132m, 0.192m (standard height) and 0.252m in the numerical simulation, and the impurity content and loss rate at different heights were obtained;

[0182] like Fig.15 As shown in the figure, a smaller separation zone height causes a larger deflection of the air flow path, which will reduce the air flow velocity. If the separation zone height is large, the flow path length increases, resulting in a greater attenuation of the air flow velocity. Therefore, compared with the standard height, both increasing and decreasing the separation zone height will result in a decrease in air flow velocity. The reduction in air flow velocity reduces the content of stem particles in the tobacco collection area, improving the purity of the tobacco product, such as Fig.13 It is worth noting that for all considered separation zone heights, the loss of tobacco particles is negligible, as shown in Fig.14 shown.

[0183] Example 5

[0184] The results of the simulation by DEM-CFD method are as follows Fig.16 and Fig.17 As shown, the computational domain visualization results are as follows Fig.18 As shown, at the standard height (0.192m) of the fluidized separation area of ​​the air separation equipment, the impurity concentration is 10%, and the air intake speed is , feed rate Under these conditions, the width W of the stem collection area was adjusted to 0.066m, 0.084m (standard width) and 0.102m in the numerical simulation, and the impurity content and loss rate under different widths were obtained;

[0185] When W=0.066m, the tobacco particles keep moving forward to the tobacco particle collection area, and the stem particles are also perfectly collected in the stem collection area, achieving a good separation effect. Increasing the width to 0.084m and 0.102m, the bottom wind speed inlet width increases, resulting in an increase in the air flow in the equipment and an increase in the overall average flow rate, causing more stem particles to flow to the tobacco particle collection area, reducing the purity of the tobacco product, and ultimately reducing the separation effect.

[0186] Example 6

[0187] The results of the simulation by DEM-CFD method are as follows Fig.19 , Fig. 20 and Fig.21 As shown, in the standard size of the air separation equipment, the air intake speed , feed rate Under these conditions, the volume fraction of stem impurities was adjusted to 6.25%, 12.50% and 18.75% in the numerical simulation, and the separation index, impurity content and loss rate under different impurity concentrations were obtained;

[0188] In the separation zone, the concentration of stem particles has no significant effect on the overall separation index C. The volume fraction of tobacco particles in the stem collection zone is always close to zero, indicating that the loss of tobacco products is very small. The volume fraction of stem particles in the tobacco collection zone increases with the increase of stem concentration, indicating that the purity of the tobacco products after separation is significantly dependent on the stem content in the raw material mixture. If the stem content in the raw material mixture is high, it is difficult to achieve the purity requirements through a single air separation, and it is necessary to perform multi-stage separation operations to gradually reduce the stem content in the product.

[0189] The present invention constructs a flexible particle model and a horizontally transported air separation equipment model; numerically simulates the separation process of flexible particles through the horizontally transported air separation equipment model by coupling discrete element method (DEM) and computational fluid dynamics (CFD) methods; detects the separation effect of the current air separation equipment under the current working conditions according to the separation index, loss rate and impurity content in the separation process, adjusts the air intake speed and feed speed of the standard air separation equipment model, and simulates the optimal separation effect of the air separation equipment under the current working conditions; adjusts the impurity concentration, adjusts the geometric parameters of the air separation equipment that affect the separation effect, simulates the optimal separation effect under a certain air intake speed and feed speed (such as the values ​​of the air intake speed and feed speed obtained after the above adjustment), and summarizes the basis for optimizing the selection of the working parameters and geometric parameters of the equipment under the optimal separation effect through flow field analysis and separation effect in the separation process, and obtains the combination of working parameters and geometric parameters that enable the equipment to have the best separation effect. For the horizontally transported flexible particle air separation, the present invention provides new insights into the mechanical mechanism of controlling particle separation and proposes a parameter optimization selection method that can effectively improve the separation effect.

[0190] Although some specific embodiments of the present invention have been described in detail by way of example, it will be appreciated by those skilled in the art that the above examples are for illustration only and are not intended to limit the scope of the present invention. It will be appreciated by those skilled in the art that the above embodiments may be modified without departing from the scope and spirit of the present invention. The scope of the present invention is defined by the appended claims.

Claims

1. A method for optimizing the parameters of a flexible particulate material air separation device, characterized in that: It includes the following steps: Construct numerical models of wind separation equipment with flexible particles and horizontal transport; The flow and separation process of flexible particles in horizontally transported wind separation equipment is numerically simulated by coupling discrete element method and computational fluid dynamics method; the separation effect is quantitatively characterized by calculating separation index, impurity content and loss rate; In the numerical simulation, the working parameters and geometric parameters of the air separation equipment are adjusted to obtain the particle flow and separation results under different working conditions; Through the analysis of separation effect and flow field during separation process, the optimal combination of working parameters and geometric parameters of air separation equipment under the best separation effect is determined.

2. The parameter optimization selection method for the flexible granular material air separation equipment according to claim 1 is characterized in that: The specific contents of constructing the numerical model of flexible particles are: A spherical bond model is constructed in which a deformable and flexible bond connecting unit balls is constructed, in which: the particle size of the unit ball determines the diameter of the flexible particle, characterizing the thickness of the particle; the aspect ratio of the particle characterizes the shape of the particle; the flexibility of the flexible bond is characterized by the elasticity and shear modulus of the bond, reflecting the ability of the particle to deform in tension, compression, shear, bending and torsion.

3. The parameter optimization selection method for the flexible granular material air separation equipment according to claim 1 is characterized in that: The specific contents of constructing the numerical model of horizontal transport air separation equipment are as follows: A particle mixture feeding area, an impurity particle collection area, a fluidized separation area and a clean particle collection area are constructed; the bottom and left and right sides of the fluidized separation area are non-slip solid walls, wherein an opening at a certain height on the right wall is connected to the particle mixture feeding port, and an opening at the left and right ends of the bottom is respectively connected to the clean particle collection port and the impurity particle collection port; the top left part of the area is the airflow outlet; the particle mixture and the airflow enter the equipment from the feed port at the same rate; the equipment wall is the non-slip solid wall boundary of the airflow.

4. The parameter optimization selection method for the flexible granular material air separation equipment according to claim 1 is characterized in that: The specific steps of numerically simulating the flow and separation process of flexible particles in a horizontally transported air separation device by coupling discrete element method and computational fluid dynamics method are as follows: The fluid dynamics equations are used to simulate air flow, and the particle dynamics equations are used to describe particle motion; the interaction force equations are derived by coupling the flow field dynamics equations and the particle dynamics equations; Set the computational boundary conditions for the interaction force equations; Initialize the flow field, set the particle properties to be flexible, perform particle separation simulation, collect particle distribution data within a certain time range, and obtain the particle separation effect.

5. The parameter optimization selection method for the flexible granular material air separation equipment according to claim 4 is characterized in that: The fluid dynamics equations include the continuity equation and the momentum conservation equation, where The continuity equation is: The momentum conservation equation is: In the formula, , , and represent the density, pressure, velocity and viscous stress of the gas respectively, is the acceleration due to gravity, is the porosity; in: Represents the interaction force between gas and solid phases per unit volume; Represents the flow field force on all particle unit balls in the i-th fluid grid; represents the fluid grid volume; is the number of unit balls in a fluid grid unit.

6. The parameter optimization selection method for the flexible granular material air separation equipment according to claim 4 is characterized in that: The particle dynamics equations include flexible particle motion control equations and flexible particle deformation control equations, where: The control equation of flexible particle motion is: in: is the displacement vector of the unit sphere inside the particle; is the angular velocity vector of the unit sphere inside the particle; For quality The moment of inertia of the unit ball, ; is the contact force between particles, is the bonding force, is the contact force damping term, is the bond force damping term; is the contact torque, is the bonding torque, is the contact torque damping term, is the bond moment damping term; The deformation control equation of flexible particles is: in: , , ,and They are the normal force, tangential force, torsional moment, and bending moment increment of the virtual key; , , They are the normal deformation, tangential deformation, torsion angle deformation, and bending angle deformation increments of the key respectively; , , are the normal stiffness, tangential stiffness, torsional stiffness and bending stiffness of the key respectively; the length is =π ; The radius of the cylindrical key is , and are Young's modulus and shear modulus of the bond, respectively; , , are the normal deformation velocity, tangential deformation velocity, torsional deformation angular velocity and bending deformation angular velocity of the bond, is the time step.

7. The parameter optimization selection method for the flexible granular material air separation equipment according to claim 6 is characterized in that: The interaction force equation is: in: is the volume of the unit sphere in the particle, is the aerodynamic drag acting on the unit sphere, is the unit ball diameter, represents the relative speed between the local airflow and the unit sphere, is the drag coefficient, For particle Renault.

8. The parameter optimization selection method for the flexible granular material air separation equipment according to claim 1 is characterized in that: The calculation formula of the separation index is: in, The computational domain is divided into 10 subdomains of equal size in the x and y directions, and N is the total number of subdomains. is the average concentration of impurity particles in the system, is the average concentration of impurity particles in each subdomain, and n is the average number of particles in each subdomain; The calculation formula of impurity content is: The loss rate is calculated as: in, is the volume of clean particles collected in the clean particle collection area, is the volume of impurity particles collected in the clean particle collection area, is the volume of clean particles collected in the impurity particle collection area, The volume of foreign particles collected in the foreign particle collection area.

9. The parameter optimization selection method for the flexible granular material air separation equipment according to claim 1 is characterized in that: The best separation effect refers to: Under the condition of specified impurity particle concentration, the impurity content is the smallest and the loss rate is within the permitted range; for conditions with different impurity particle concentrations, the separation index is the largest and both the impurity content and the loss rate are within the permitted range.

10. The parameter optimization selection method for the flexible granular material air separation equipment according to any one of claims 1 to 9, characterized in that: The specific contents of adjusting the working parameters and geometric parameters of the air separation equipment are as follows: The air inlet velocity, feed velocity, height of the fluidized separation area, width of the impurity particle collection area and impurity particle concentration are adjusted within a certain range; the separation index, impurity content and loss rate under various working conditions are obtained.

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