Quantification and actual measurement method for segregation degree of millstone particles of vertical mill

Abstract

The invention relates to the field of powder engineering and technology, in particular to a vertical mill millstone particle segregation degree quantification and actual measurement method which comprises the steps that a vertical mill simulation model is established according to physical property parameters of a simulation material, and simulation is conducted; uniformly dividing the simulation area into grids in the radial direction and the axial direction; respectively counting the total mass of the particles in each grid, and calculating the average particle size of the grids and the average particle size of all the particles; calculating radial and axial grid weights according to a mass ratio, and calculating a traditional mass segregation index and a traditional particle size segregation index as well as a radial weighted mass segregation index and an axial weighted particle size segregation index; and partitioning the weighted segregation index, and quantifying the segregation degree. By applying the method, the axial segregation measurement precision can be improved, the radial segregation measurement workload can be reduced, and then the segregation degree of millstone particles can be efficiently and accurately evaluated.

Description

Technical Field

[0001] This invention relates to the field of powder engineering and technology, and in particular to a method for quantifying and measuring the degree of particle segregation in a vertical mill grinding disc. Background Technology

[0002] A vertical roller mill is a grinding equipment that grinds materials into fine powder. Due to differences in material properties, feeding methods, and grinding disc structures, material segregation can occur on the grinding disc, resulting in localized over- or under-grinding. In addition, segregation can also lead to the aggregation of large particles on the surface, exacerbating wear on the grinding rollers. By measuring the degree of segregation, operating parameters can be adjusted or the grinding disc structure can be optimized to avoid under-grinding and over-grinding, thereby stabilizing the product particle size within the target range. However, in actual production processes, there are common problems such as difficulty in quantifying and measuring the degree of segregation, as well as low measurement accuracy. At this time, a highly precise and efficient method for segregation quantification is needed to shorten the production cycle.

[0003] Vertical mill grinding discs exhibit both axial and radial segregation of particles, characterized by a significantly smaller axial dimension compared to the radial dimension. Axial segregation is primarily caused by particle size effects, characterized by a thin axial material layer that makes fine meshing difficult, resulting in low measurement accuracy and high complexity. Radial segregation is mainly caused by mill operating parameters and structure, characterized by a larger measurement range. While radial segregation is easier to mesh, increasing the mesh count is necessary to improve measurement accuracy; therefore, fewer meshes result in lower accuracy, while more meshes lead to lower efficiency.

[0004] Currently, there are two main methods for measuring particle segregation: invasive and non-invasive. Although non-invasive methods, such as tomography, spectral analysis, and acoustic emission technology, can visually display the segregation distribution without damaging the particle system, these methods require specialized equipment, have high application costs, and are not applicable due to the harsh internal environment of vertical mills, where some methods are easily affected by external factors.

[0005] For invasive methods, Chinese patent CN111539103A provides a quantitative method for particle segregation in ball mills based on the Lacey method. This method divides the simulation area into several regions along the radial and axial directions during ball mill motion simulation, and statistically analyzes the particle distribution in each region. It uses the nearest neighbor segregation factor and center compensation distance to define the degree of mixing and segregation, characterizing the evolution of particle-particle positional relationships in the particle system. This reflects the degree of mixing and segregation (homogeneity) in space and time, avoiding the inaccurate quantification caused by neglecting local segregation characteristics in traditional methods. It accurately reflects the precise average instantaneous information of particle mixing and segregation in different cross-sections of the ball mill shaft, thus providing a quantitative description of particle segregation at the particle scale distribution, which is helpful for theoretical research on particle system mixing and segregation. However, the weights calculated are based on the proportion of particle number. In actual production, it is almost impossible to calculate the number of particles after grinding and crushing. In addition, the quantitative method based on the lacey method can only be used to measure the mixing degree of particles in a closed volume, and cannot be adapted to conditions such as vertical mill grinding discs where particles are constantly entering and exiting.

[0006] Currently, research on methods for high-precision and efficient quantification and measurement of particle segregation within mills is scarce. Although there are many methods for calculating the segregation index, they are mostly applied to simulation measurements. In actual production, due to the limitation of the number of samples collected (i.e., the influence of the number of grids), most traditional measurement methods have large errors. Image analysis methods can lead to increased costs. Furthermore, these non-invasive methods can only acquire surface information and perform quantitative analysis, and cannot reflect the internal information of the material layer. Therefore, the measurement results cannot guarantee high-precision quantification. Summary of the Invention

[0007] To address the aforementioned technical problems, this invention provides a method for quantifying and measuring the degree of particle segregation in vertical mill grinding discs. The main objective of this invention is to provide a low-cost, simple, and highly accurate method for quantifying the degree of particle segregation in vertical mill grinding disc particle systems, improving the accuracy of axial segregation measurement, reducing the workload of radial segregation measurement, and thus efficiently and accurately assessing the degree of particle segregation in the grinding discs.

[0008] The technical means employed in this invention are as follows: A method for quantifying and measuring the degree of particle segregation on a vertical mill grinding disc, comprising: Based on the physical properties of the simulated materials, a simulation model of the vertical mill was established and simulation was performed. The simulation region is uniformly divided into grids along the radial and axial directions; The total mass of particles in each grid is counted, and the average particle size of the grid and the average particle size of all particles are calculated. Calculate the weights of each grid in the radial and axial directions based on the mass percentage, and calculate the traditional mass segregation index, the traditional particle size segregation index, the radially weighted mass segregation index, and the axially weighted particle size segregation index. The degree of bias is quantified by dividing the weighted bias index into regions.

[0009] Furthermore, the simulation model of the vertical mill is established, specifically including: The physical properties of the simulated material include intrinsic parameters and contact parameters; a model of the vertical mill grinding disc is established, the grinding disc rotation speed and simulation time step parameters are set, and two kinds of particles with equal mass but different particle sizes are generated in the grinding disc, with the initial particle distribution characteristics being completely random; the model of the vertical mill grinding disc is used for simulation, and the grinding disc is rotated until the particles exhibit stable segregation.

[0010] Furthermore, the mesh division follows the principle of equal volume, wherein the axial mesh should contain all particles, and the uppermost layer is allowed to have a mesh with very few particles or an empty mesh. The radial mesh boundary fits the retaining ring and is not allowed to exceed the maximum inner diameter of the grinding disc. The size is determined by the formula of the outer radius of the annulus with the inner ring area proportionally expanded:

[0011] in, n The number of grid cells with equal area; m The sequence number of the ring; R n The radius of the central circle; R n-m The outer radius of the annulus is the area of ​​the inner ring that is proportionally expanded. The axial grid is used to calculate the particle size segregation index to reflect the concentration of hard, large particles in the upper layer of the material layer, and the radial grid is used to calculate the mass segregation index to reflect the distribution of the material layer on the grinding disc.

[0012] Further, the average particle size of the grid and the average particle size of all particles are calculated, specifically including: Calculate the average area mass Mass per unit area of ​​the grid :

[0013]

[0014] in, M The total mass of all grid particles; A This represents the total area of ​​the grid. m i for i The mass of the particles within the grid; A i for i Grid area; calculate i Average mesh size Compared with the average particle size of all particles :

[0015]

[0016] in, i For grid numbering, j For particle size classification, d j For particle size range j Particle diameter of size M The total mass of all grid particles, m i,j for i The particle size range within the grid is j Grade of particle mass, m i This represents the mass of all particles within the grid.

[0017] Further, the conventional segregation index is calculated. and Specifically, it includes: For any given total number of samples n s ,sample i weight k i The calculation formula is:

[0018] Weight k i Conditions met:

[0019] in, m i for i Quality within the mesh, M The total mass of all grid particles; The normalized formulas for calculating the traditional mass segregation index and particle size segregation index are as follows:

[0020]

[0021] in, k i For the sample i The weight, n s The total number of samples, fori Mesh mass per unit area For average area mass, for i Average grain size of the grid The average particle size is denoted as .

[0022] Further, the radially weighted mass segregation index is calculated. With axial weighted particle size segregation index : The formulas for calculating the unbiased estimated and normalized radially weighted mass segregation index and axially weighted particle size segregation index are as follows:

[0023]

[0024] in, k i For the sample i The weight, n s The total number of samples, for i Mesh mass per unit area For average area mass, for i Average grain size of the grid The average particle size is denoted as .

[0025] Furthermore, when quantifying the degree of segregation by dividing the weighted segregation index, a mapping relationship is established for the specified segregation values ​​when the traditional mass segregation index and the traditional particle size segregation index are below 0.4; when the traditional mass segregation index and the traditional particle size segregation index are above 0.4, the mapping relationship is not used, and the weighted segregation index value is directly used as the quantification result. The degree of segregation is defined based on the traditional segregation index to suppress mesh error.

[0026] Furthermore, for any of the traditional quality segregation indices, the specified segregation value for measuring the degree of segregation is... Each has a specified segregation value corresponding to any weighted mass segregation index. :

[0027] in, n s The same number of grids is used for both indices. For the unit area mass of each grid, The average area mass.

[0028] Furthermore, for any of the conventional particle size segregation indices, the specified segregation value for measuring the degree of segregation is... Each has a segregation value specified by the segregation index corresponding to any weighted particle size. :

[0029] in, n s The same number of grids is used for both indices. The average particle size of each grid is calculated based on the particle size test report. The average particle size of all particles calculated based on the particle size test report. Sampling quality for each grid; The sum of the sampling quality for all grids.

[0030] Compared with the prior art, the present invention has the following advantages: The method for quantifying and measuring particle segregation in vertical mill grinding discs provided by this invention eliminates the interference of segregation in non-critical areas on the overall results, making the quantification accuracy and analysis effect of the weighted segregation index superior to that of the traditional segregation index. Simulation results show that the weighted segregation index has different quantification effects under different segregation levels: for particle systems with low segregation levels, i.e., when the traditional segregation index is below 0.4, the weighted segregation index has higher quantification accuracy, and the quantification accuracy of the weighted particle size segregation index is higher than that of the weighted mass segregation index; for particle systems with high segregation levels, i.e., when the traditional segregation index is above 0.4, the weighted segregation index has higher analysis accuracy, and the higher the segregation index, the higher the analysis accuracy.

[0031] The method for quantifying and measuring particle segregation in vertical mill grinding discs in this invention combines actual production with simulation analysis, improving measurement accuracy and efficiency. It also distinguishes between simulation and measured average particle size calculation methods, reducing the difficulty of actual measurement. In mesh generation, simulation and measured meshes are not differentiated, but only one mesh is selected for actual measurement, i.e., the optimal mesh number is chosen based on the simulation (radial meshes are selected based on the radial mass segregation index, and axial meshes are selected based on the axial particle size segregation index). In the particle size calculation method, the methods and formulas are differentiated. Simulation calculates the average particle size based on all statistically analyzed particles, while actual measurement uses the particle size test report of a local sample to calculate the average particle size.

[0032] Based on the above reasons, this invention can be widely promoted in the fields of powder engineering and technology. Attached Figure Description

[0033] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0034] Figure 1 This is a flowchart of the method for quantifying and measuring the degree of particle segregation in the grinding disc of a vertical mill in this invention.

[0035] Figure 2 This describes the segregation characteristics of two particles with different sizes in this invention.

[0036] Figure 3 This describes the specific division method of axial and radial grids in this invention.

[0037] Figure 4 This is a flowchart of the weighted partial index algorithm in this invention.

[0038] Figure 5 This is a comparison chart of the conventional segregation index and the weighted segregation index of radial mass for tetrahedral particles and spherical particles in this invention.

[0039] Figure 6 This is an error curve of the weighted mass segregation index in this invention compared to the traditional mass segregation index.

[0040] Figure 7 The results of particle size segregation quantification for simulated meshes with different axial directions are shown in the embodiments of the present invention.

[0041] Figure 8 This is an error curve of the weighted particle size segregation index relative to the traditional particle size segregation index in an embodiment of the present invention.

[0042] Figure 9 This is a schematic diagram of the radial mass segregation measurement method in this invention.

[0043] Figure 10 This is a schematic diagram of the axial particle size segregation measurement method in this invention. Detailed Implementation

[0044] It should be noted that, unless otherwise specified, the embodiments and features described in the present invention can be combined with each other. The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0045] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The following description of at least one exemplary embodiment is merely illustrative and is in no way intended to limit the present invention or its application or use. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0046] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the scope of exemplary embodiments according to the invention. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0047] Unless otherwise specifically stated, the relative arrangement, numerical expressions, and values ​​of the components and steps described in these embodiments do not limit the scope of the invention. It should also be understood that, for ease of description, the dimensions of the various parts shown in the drawings are not drawn to actual scale. Techniques, methods, and devices known to those skilled in the art may not be discussed in detail, but where appropriate, such techniques, methods, and devices should be considered part of the specification. In all examples shown and discussed herein, any specific values ​​should be interpreted as merely exemplary and not as limitations. Therefore, other examples of exemplary embodiments may have different values. It should be noted that similar reference numerals and letters in the following figures denote similar items; therefore, once an item is defined in one figure, it need not be further discussed in subsequent figures.

[0048] like Figure 1 As shown, this invention provides a method for quantifying and measuring the degree of particle segregation on a vertical mill grinding disc, including: Based on the physical properties of the simulated material, a vertical mill simulation model is established and simulation is performed. Specifically, in a preferred embodiment of this invention, the physical properties of the simulated material include intrinsic parameters and contact parameters. A model of the vertical mill grinding disc is established, and the grinding disc rotation speed and simulation time step parameters are set. Two types of particles with equal mass but different particle sizes are generated in the grinding disc, with the initial particle distribution characteristics being completely random. The vertical mill grinding disc model is used for simulation, rotating the grinding disc until the particles exhibit stable segregation. The segregation characteristics of the two types of particles in steady state are as follows: Figure 2 As shown.

[0049] The simulation area is uniformly divided into grids radially and axially. In a preferred embodiment of the invention, the grid division follows the principle of equal volume, wherein the axial grid should contain all particles, and the uppermost layer is allowed to have a grid with very few particles or an empty grid. The radial grid boundary fits the retaining ring and is not allowed to exceed the maximum inner diameter of the grinding disc. The size is determined by the formula of the outer radius of the ring with the inner area proportionally expanded.

[0050] in, n The number of grid cells with equal area; m The sequence number of the ring;R n The radius of the central circle; R n-m The outer radius of the annulus is the area of ​​the inner circle expanded proportionally.

[0051] The specific methods for dividing the axial and radial meshes are as follows: Figure 3 As shown, the axial grid is used to calculate the particle size segregation index to reflect the concentration of hard, large particles in the upper layer of the material layer, while the radial grid is used to calculate the mass segregation index to reflect the distribution of the material layer on the grinding disc.

[0052] In the simulation, based on the convergence of the radial conventional mass segregation index calculated by the simulation, the maximum number of grids in the radial direction is set to 8. Based on the maximum material layer thickness and maximum particle diameter in the simulation, the maximum number of grids in the axial direction is also set to 8. The minimum number of grids in the radial direction is 2, with meshes refined sequentially at intervals of 1. The minimum number of grids in the axial direction is also 2, with meshes refined sequentially at intervals of 1.

[0053] In actual production, the mesh used for measurement is divided based on simulation results. Radial mesh division should be determined in conjunction with particle flowability. If particle flowability is low, the minimum mesh number required to achieve convergence (mass segregation results) in the simulation is used. If particle flowability is high, the mesh number is based on the mesh number corresponding to the convergence condition of the relative error curves of the conventional and weighted mass segregation indices in the simulation. Axial mesh division is similar to radial mesh division, but it is based on the relative error curves of the conventional and weighted particle size segregation indices in the simulation.

[0054] The total mass of particles in each grid is calculated, and the average particle size of the grid and the average particle size of all particles are also calculated. In a preferred embodiment of this invention, the average area mass is calculated. Mass per unit area of ​​the grid :

[0055]

[0056] in, M The total mass of all grid particles; A This represents the total area of ​​the grid. m i for i The mass of the particles within the grid; A i for i Grid area; calculate i Average mesh size Compared with the average particle size of all particles :

[0057]

[0058] in, i For grid numbering, j For particle size classification, d j For particle size range j Particle diameter of size M The total mass of all grid particles, m i,j for i The particle size range within the grid is j Grade of particle mass, m i This represents the mass of all particles within the grid.

[0059] In actual production, sampling should be performed after the machine is stopped. First, the number of axial meshes to be sampled in actual production should be determined based on the simulation results. Sampling should be performed on different axial meshes, with each mesh sampled twice. Grain size testing should be conducted on each mesh sample separately. Then, the second sample from all meshes should be combined and subjected to grain size testing again. The grain size should be calculated based on the grain size test report. i Average mesh size and the average particle size of all particles .

[0060] If the particle size test report is a volume distribution, assume the volume percentage of each particle size range. The range represents the particle size. Both average particle sizes are calculated using volume-weighted average particle size. d 43 calculate:

[0061] If the particle size test report is a mass distribution, assume the mass percentage of each particle size range. The range represents the particle size. Both average particle sizes are calculated using a mass-weighted average particle size distribution. d 32 calculate: .

[0062] The weights of each grid cell in the radial and axial directions are calculated based on their mass percentage. The traditional mass segregation index and the traditional particle size segregation index, as well as the radially weighted mass segregation index and the axially weighted particle size segregation index, are calculated. In a preferred embodiment of this invention, for any given total number of samples... n s ,sample i weight k i The calculation formula is:

[0063] Weight k i Conditions met:

[0064] in, for i Quality within the mesh, The total mass of all mesh particles; in the simulation, This represents the statistical particle mass within each complete grid cell. This represents the total mass of all complete grid particles; in actual production, This represents the particle mass counted at the sampling location. This represents the total mass of particles at all sampling locations.

[0065] Unnormalized traditional quality segregation index :

[0066] Unnormalized weighted quality bias index pxm w Derivation of the maximum value:

[0067] Make the unnormalized weighted quality segregation index pxm w The maximum value is further increased to reduce the error of low grid numbers, and one of them is... For any and All have :

[0068]

[0069] The normalized formulas for calculating the traditional mass segregation index and particle size segregation index are as follows:

[0070]

[0071] in, k i For the sample i The weight, n s The total number of samples, for i Mesh mass per unit area For average area mass, for i Average grain size of the grid The average particle size is denoted as .

[0072] In a specific implementation, as a preferred embodiment of the present invention, the radial weighted mass segregation index is calculated. With axial weighted particle size segregation index The weighted partial index algorithm process is as follows: Figure 4 As shown, the formulas for calculating the unbiased estimated and normalized radially weighted mass segregation index and the axially weighted particle size segregation index are as follows:

[0073]

[0074] in, k i For the sample i The weight, n s The total number of samples, for i Mesh mass per unit area For average area mass, for i Average grain size of the grid The average particle size is denoted as .

[0075] When assessing the degree of particle segregation on a vertical mill grinding disc, the specified value for measuring the degree of segregation is not absolute; the definition of the degree of segregation varies under different conditions. While traditional segregation index partitioning can often be used empirically to define the degree of segregation, direct partitioning is difficult with weighted segregation indices. Therefore, it is necessary to establish a mapping relationship for the specified segregation values. Partitioning the weighted segregation index quantifies the degree of segregation.

[0076] When quantifying the degree of segregation by dividing the weighted segregation index into zones, a mapping relationship is established for the specified segregation values ​​when the traditional mass segregation index and the traditional particle size segregation index are below 0.4; when the traditional mass segregation index and the traditional particle size segregation index are above 0.4, the mapping relationship is not used, and the weighted segregation index value is directly used as the quantification result. The degree of segregation is defined based on the traditional segregation index to suppress mesh error.

[0077] By comparing the weighted segregation index with the traditional segregation index and mapping the traditional segregation index to the weighted segregation index, the partitions of the weighted mass segregation index and the weighted particle size segregation index can be obtained. When partitioning the weighted mass segregation index, the mapping of the traditional segregation index to the weighted mass segregation index is calculated as follows: In a specific implementation, as a preferred embodiment of the present invention, a specified segregation value for measuring the degree of segregation in any traditional mass segregation index is used. ,like and Two specified values, It is usually 0.1. The standard value is 0.4. Values ​​between 0 and 0.1 indicate no segregation, values ​​between 0.4 and 1.0 indicate severe segregation, and values ​​between 0.1 and 0.4 indicate moderate segregation. Each value has a corresponding predefined segregation value for any weighted mass segregation index. :

[0078] in, n s The same number of grids is used for both indices. For the unit area mass of each grid, The average area mass is 0.4, calculated based on the traditional mass segregation index value at the time corresponding to the intersection of the relative error curves.

[0079] When the degree of mass segregation is not high, the mass per unit area of ​​all grids can be approximated. If they are equal, then the specified value can be estimated: .

[0080] In a specific implementation, as a preferred embodiment of the present invention, the specified segregation value for measuring the degree of segregation in any traditional particle size segregation index is used. Each has a segregation value specified by the segregation index corresponding to any weighted particle size. :

[0081] in, n s The same number of grids is used for both indices. The average particle size of each grid is calculated based on the particle size test report. The average particle size of all particles calculated based on the particle size test report. Sampling quality for each grid; The sum of the sampling quality for all grids.

[0082] When the degree of particle size segregation is not high, the quality of each grid can be considered as good. m i If they are equal, the specified value can be approximately estimated: .

[0083] Example like Figure 5 As shown, this embodiment compares and analyzes the quantitative effects of the traditional segregation index and the weighted segregation index. Figure 5This figure compares the traditional and weighted segregation indices for radial mass of tetrahedral and spherical particles. When the segregation index is low, i.e., in the initial dynamic stage and the exponential evolution stage, the segregation index changes significantly, and the error in the number of grid cells gradually becomes apparent. This is because as the grinding disc rotates, the mixed particles begin to segregate, changing the mass of particles in each grid cell. Some grid cells begin to have low particle mass or empty grids, which interfere with the overall results. This interference is significant in the segregation index results for spherical particles, especially in the exponential evolution stage and the steady-state equilibrium stage. In the figure, n2 to n8 represent the number of grid cells from 2 to 8. At low grid numbers, the error caused by the grid is extremely large. This error is significant in the segregation index results for tetrahedral particles, especially in the exponential evolution stage.

[0084] Tetrahedral particles exhibit mesh count errors, while spherical particles exhibit both mesh count errors and mesh interference errors. This is because the two types of particles have different flowability: tetrahedral particles have low flowability and uniform mesh mass distribution, so their errors are mainly manifested as errors in the number of meshes; spherical particles have high flowability, uneven mesh mass distribution, and high segregation, requiring extremely high mesh resolution and containing many empty meshes, so their errors are manifested as both mesh count errors and mesh interference errors.

[0085] The results for spherical particles in the figure also show that when the number of grids is low and the degree of segregation is high, the traditional segregation index cannot effectively distinguish the degree of segregation, while the weighted segregation index can clearly distinguish the curves corresponding to different grid numbers. That is, the weighted segregation index has higher analytical accuracy for particle systems with a high degree of segregation.

[0086] Figure 6 The figure shows the error curves of the weighted mass segregation index relative to the traditional mass segregation index. For spherical particles, there are significant grid number errors and grid interference errors at low grid numbers, and the traditional segregation index is larger, while the weighted segregation index is always lower than the traditional segregation index. Therefore, the larger the relative error, the more accurate the result of the weighted segregation index. This conclusion also applies to tetrahedral particles. In the first 2 seconds, the relative error is relatively high, indicating that the weighted segregation index has higher quantization accuracy for particle systems with low segregation.

[0087] Figure 7 The figure shows a comparison between the traditional and weighted segregation indices for axial particle size of spherical particles. For the axial particle size segregation index, the error caused by the mesh is similar to that of the mass segregation index. Both the traditional and weighted segregation indices have a lower convergence limit as the mesh count increases, thus the quantization results are generally too large. If relative error is used to represent the quantization effect of the weighted particle size segregation index, the larger the relative error, the closer the weighted particle size segregation index is to the accurate value. The error curves of the weighted particle size segregation index relative to the traditional particle size segregation index are shown below. Figure 8As shown, similar to the tetrahedral particles in the error curve of the weighted mass segregation index relative to the traditional mass segregation index, the relative error increases with the number of grid cells after 2 seconds, and the relative error curve also shows a convergence trend as the number of grid cells increases. Therefore, for particle size segregation indices with low segregation levels, the weighted particle size segregation index has high quantization accuracy, while the higher relative error of particle size segregation indicates that the quantization accuracy of the weighted particle size segregation index is higher than that of the weighted mass segregation index.

[0088] The number of grids used in the actual measurement can be determined based on the mass segregation quantization results of different radial grids and the particle size segregation quantization results of different axial grids in the simulation. Schematic diagrams of the radial mass segregation measurement method and the axial particle size segregation measurement method are shown below. Figure 9 and Figure 10 As shown. When measuring radial mass segregation, only a small angle measurement area needs to be selected. The angle value can be 5~10°, or it can be appropriately widened. Then, use a partition to divide the area according to the optimal grid and count the mass of each area. It is worth noting that the grid should be close to the retaining ring, and the radius parameters of each zone should be calculated according to the radius when they are close together.

[0089] In the actual measurement of axial particle size segregation, a sampling area can be determined along the circumferential or radial direction of the test area after the action of the grinding roller. This will yield the particle size segregation index distribution along the circumferential or radial direction. Alternatively, data from only one sampling area can be used to characterize local particle size segregation. However, for each sampling area, all powder particles should be collected completely. Then, the area should be divided according to the simulated optimal axial grid number, and the quality should be statistically analyzed (the axial material layer structure should remain unchanged before division). For each divided area, two samples should be taken. For sample 1, stratified particle size analysis should be performed, and the number of particle size analysis reports obtained should be equal to the number of grids. For sample 2, mixed particle size analysis should be performed, and one particle size analysis report should be obtained. Finally, the corresponding segregation index is calculated according to the formula.

[0090] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for quantifying and measuring the degree of particle segregation on a vertical mill grinding disc, characterized in that, include: Based on the physical properties of the simulated materials, a simulation model of the vertical mill was established and simulation was performed. The simulation region is uniformly divided into grids along the radial and axial directions; The total mass of particles in each grid is counted, and the average particle size of the grid and the average particle size of all particles are calculated. Calculate the weights of each grid in the radial and axial directions based on the mass percentage, and calculate the traditional mass segregation index, the traditional particle size segregation index, the radially weighted mass segregation index, and the axially weighted particle size segregation index. The degree of bias is quantified by dividing the weighted bias index into regions.

2. The method for quantifying and measuring the degree of particle segregation in a vertical mill grinding disc according to claim 1, characterized in that, The establishment of the vertical mill simulation model specifically includes: The physical properties of the simulated material include intrinsic parameters and contact parameters; a model of the vertical mill grinding disc is established, the grinding disc rotation speed and simulation time step parameters are set, and two kinds of particles with equal mass but different particle sizes are generated in the grinding disc, with the initial particle distribution characteristics being completely random; the model of the vertical mill grinding disc is used for simulation, and the grinding disc is rotated until the particles exhibit stable segregation.

3. The method for quantifying and measuring the degree of particle segregation in a vertical mill grinding disc according to claim 1, characterized in that, The grid division follows the principle of equal volume, wherein the axial grid should contain all particles, and the uppermost layer is allowed to have a grid with very few particles or an empty grid. The radial grid boundary fits the retaining ring and is not allowed to exceed the maximum inner diameter of the grinding disc. The size is determined by the formula of the outer radius of the ring with the inner ring area proportionally expanded: in, The number of grid cells with equal area; The sequence number of the ring; The radius of the central circle; The outer radius of the annulus is the area of ​​the inner ring that is proportionally expanded. The axial grid is used to calculate the particle size segregation index to reflect the concentration of hard, large particles in the upper layer of the material layer, and the radial grid is used to calculate the mass segregation index to reflect the distribution of the material layer on the grinding disc.

4. The method for quantifying and measuring the degree of particle segregation in a vertical mill grinding disc according to claim 1, characterized in that, The calculation of the average particle size of the grid and the average particle size of all particles specifically includes: Calculate the average area mass Mass per unit area of ​​the grid : in, M The total mass of all grid particles; A This represents the total area of ​​the grid. m i for i The mass of the particles within the grid; A i for i Grid area; calculate i Average mesh size Compared with the average particle size of all particles : in, i For grid numbering, j For particle size classification, d j For particle size range j Particle diameter of size M The total mass of all grid particles, m i,j for i The particle size range within the grid is j Grade of particle mass, m i This represents the mass of all particles within the grid.

5. The method for quantifying and measuring the degree of particle segregation in a vertical mill grinding disc according to claim 1, characterized in that, Calculate the traditional segregation index and Specifically, it includes: For any given total number of samples n s ,sample i weight k i The calculation formula is: Weight k i Conditions met: in, m i for i Quality within the mesh, M The total mass of all grid particles; The normalized formulas for calculating the traditional mass segregation index and particle size segregation index are as follows: in, k i For the sample i The weight, n s The total number of samples, for i Mesh mass per unit area For average area mass, for i Average grain size of the grid The average particle size is denoted as .

6. The method for quantifying and measuring the degree of particle segregation in a vertical mill grinding disc according to claim 1, characterized in that, Calculate the radial weighted mass segregation index With axial weighted particle size segregation index : The formulas for calculating the unbiased estimated and normalized radially weighted mass segregation index and axially weighted particle size segregation index are as follows: in, k i For the sample i The weight, n s The total number of samples, for i Mesh mass per unit area For average area mass, for i Average grain size of the grid The average particle size is denoted as .

7. The method for quantifying and measuring the degree of particle segregation in a vertical mill grinding disc according to claim 1, characterized in that, When quantifying the degree of segregation by dividing the weighted segregation index into zones, a mapping relationship is established for the specified segregation values ​​when the traditional mass segregation index and the traditional particle size segregation index are below 0.4; when the traditional mass segregation index and the traditional particle size segregation index are above 0.4, the mapping relationship is not used, and the weighted segregation index value is directly used as the quantification result. The degree of segregation is defined based on the traditional segregation index to suppress mesh error.

8. The method for quantifying and measuring the degree of particle segregation in a vertical mill grinding disc according to claim 7, characterized in that, For any of the conventional mass segregation indices, the specified segregation value for measuring the degree of segregation. Each has a specified segregation value corresponding to any weighted mass segregation index. : in, n s The same number of grids is used for both indices. For the unit area mass of each grid, The average area mass.

9. The method for quantifying and measuring the degree of particle segregation in a vertical mill grinding disc according to claim 7, characterized in that, For any of the conventional particle size segregation indices, the specified segregation value for measuring the degree of segregation. Each has a segregation value specified by the segregation index corresponding to any weighted particle size. : in, n s The same number of grids is used for both indices. The average particle size of each grid is calculated based on the particle size test report. The average particle size of all particles calculated based on the particle size test report. Sampling quality for each grid; The sum of the sampling quality for all grids.

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