A Gravity Grading Prediction and Evaluation Method for Raymond Mill

Abstract

A gravity classification prediction and evaluation method for a Raymond mill belongs to the field of mechanical engineering technology. The gravity classification prediction and evaluation method uses a steady-state solution method to determine the classifier shell radius index under the premise of ensuring a uniform flow field and a small overall pressure loss, and then constructs a host primary model. A transient solution method is used to analyze the change pattern of the gravity classification outlet wind speed and the overall pressure loss value to determine the inlet wind speed index. The inlet wind speed index is used to reconstruct the primary model of the Raymond mill host to form a host intermediate model. The inlet wind speed index is combined with the particle size segmentation method to obtain the cutting particle size index and the particle settling velocity index. The host intermediate model is constructed based on the cutting particle size index and the particle settling velocity index to form the host ultimate model. The host ultimate model is used to complete the prediction process of unestablished Raymond mill related data or the evaluation process of established Raymond mill related performance data.

Description

Technical Field

[0001] The invention belongs to the technical field of mechanical engineering, and in particular relates to a gravity classification prediction and evaluation method for a Raymond mill. Background Art

[0002] Large, complex particle-fluid systems, such as grinding mills, play a vital role in key industries such as mining, construction, metallurgy, environmental protection, electricity, chemicals, and aerospace. These devices are characterized by high cost, complex design and structure, the need for multi-point monitoring, and a long product lifecycle. During the operation of these coupled particle-fluid systems, the internal fluid exerts drag, lift, or pressure on the particles, causing them to move. This process involves not only collisions between particles and with solid walls, but also particle motion that in turn affects the flow of the fluid. This complex interaction complicates and challenges a comprehensive and accurate understanding of the physical processes involved in the movement, distribution, and collision characteristics of particle populations within fluid systems. Accurately understanding the fluid-solid two-phase flow state within powder systems is crucial for improving equipment conveying efficiency, reducing surface wear, and optimizing resource utilization.

[0003] Large-scale Raymond mills integrate multiple functions, including crushing, grinding, screening, and conveying. The entire process is a complex multi-physics coupling involving fluid dynamics, particle dynamics, and the grinding action. Raymond mills, also known as pendulum mills, utilize a main motor to drive a central shaft with a quincunx frame. The grinding rollers are connected to the quincunx frame via horizontal hinges, forming the support point for their swing. Driven by the quincunx frame, the grinding rollers begin to rotate. Centrifugal force presses them tightly against the grinding rings, causing friction to propel them and pulverize the material. A scraper located at the bottom of the quincunx frame lifts the material. During operation, the grinding rollers and scraper rotate together, throwing the material upward and filling it between the rollers and the grinding rings, forming a material layer. This material layer is pulverized by the outward centrifugal force generated by the revolution of the grinding rollers. At the same time, the air flow blown in from the air inlet of the Raymond Mill is increased in speed after passing through the main air duct volute and blade structure, and an internal wind field is formed in the whole machine. The fine particles produced by the grinding of the roller and ring areas are coupled with the wind field and transported upward. Under the screening action of the classifier, the finished products are finally selected from the outlet of the whole machine.

[0004] During the operation of the Raymond Mill, a large-scale particle flow system is formed. Due to the complexity of the internal spatial structure of the equipment, its internal flow field usually presents a complex fluid-particle multiphase flow state, covering the vortex flow generated between the grinding roller and the grinding ring, the contraction flow phenomenon in the gravity classification area, and the strong vortex flow in the centrifugal separation area. In these complex system equipment, the interaction mechanism between the flow patterns of the gas-solid mixture is still unclear, and the current calculation models and methods are difficult to accurately describe the above coupling relationship. The specific main problems are:

[0005] 1. The fineness is insufficient, which can only meet the needs of the basic powder industry and is difficult to cater to the trend of my country's fine powder industry to develop towards high-end;

[0006] 2. The frequency of mechanical failure is high and the emission of pollutants is high;

[0007] 3. The recovery and separation effects of finished powder did not meet expectations, resulting in energy waste.

[0008] The existing Raymond Mill has problems of low grade efficiency and high energy consumption of the whole machine. There is a lack of unified and standardized evaluation method for the relevant data of the Raymond Mill under design.

[0009] Limestone raw material is fed into the Raymond Mill through the feed port and ground by the rotating grinding rollers and rings. Material that reaches the specified fineness undergoes two classification processes before being selected. First, gravity classification occurs between the Raymond Mill's main outlet and the bottom of the classifier housing. This stage primarily involves preliminary screening of particles based on their gravity differences, known as pre-selection or gravity classification. This process significantly influences the particle size distribution within the centrifugal classification zone, which in turn affects the classifier's circulating load and classification efficiency, ultimately affecting product yield and fineness. Currently, there is no systematic method for accurately and quantitatively analyzing gravity classification in a Raymond Mill. Nor has a comprehensive analysis been conducted to identify the key issues affecting the Raymond Mill's collection efficiency and energy consumption reduction. There is also no quantitative evaluation method for these issues. Summary of the Invention

[0010] There is no systematic method in the existing technology that can accurately and quantitatively analyze the gravity classification of the Raymond Mill, nor is there a comprehensive analysis to find out the crux of the problem affecting the collection efficiency and energy consumption reduction of the Raymond Mill. There is no relevant quantitative evaluation method for the collection efficiency and energy consumption reduction of the Raymond Mill.

[0011] A gravity classification prediction and evaluation method for a Raymond mill is disclosed. The gravity classification prediction and evaluation method uses a steady-state solution method to determine the classifier shell radius index under the premise of ensuring a uniform flow field and a small overall pressure loss, and then constructs a host primary model. A transient solution method is used to determine the inlet wind speed index by analyzing the change law of the gravity classification outlet wind speed and the overall pressure loss value. The inlet wind speed index is used to reconstruct the Raymond mill host primary model to form a host intermediate model. The inlet wind speed index is combined with a particle size segmentation method to obtain a cutting particle size index and a particle settling velocity index. The host intermediate model is constructed based on the cutting particle size index and the particle settling velocity index to form a host ultimate model. The host ultimate model is used to complete the prediction process of unestablished Raymond mill related data or the evaluation process of established Raymond mill related performance data.

[0012] As the preferred solution, the process of determining the classifier shell radius index using the steady-state solution method while ensuring a uniform flow field and a small pressure loss of the entire machine is as follows:

[0013] After the material is fed into the Raymond mill inlet, it is ground by the grinding roller and grinding ring. The powder that reaches a certain fineness is sent to the gravity classification area by the air blown in by the air inlet box to complete the first classification. According to the theory of flow velocity and arbitrary cross-sectional area, the improved gravity classification outlet cross-sectional radius is the classifier shell radius. According to the Fluent simulation results, the internal flow field velocity and wind field trajectory of the Raymond mill are compared. The speed distribution in the grinding roller and host shell area is uniform. The particles will be sent to the gravity classification area at a speed of 0-30m / s. The corresponding classifier shell radius is used as the classifier shell radius index. The wind track line corresponding to the classifier shell radius index spirals upward evenly and has a clear boundary in the gravity classification area. After determining the classifier shell radius index, the primary model of the host is constructed using 3D software.

[0014] As a preferred solution: the process of using the transient solution method to analyze the change law of the gravity classification outlet wind speed and the pressure loss value of the whole machine to determine the inlet wind speed index is as follows:

[0015] The air volume of the Raymond mill system is the driving force in the process of conveying materials of a certain fineness to the gravity classification area and the centrifugal classification area. When the system air volume is too large, the air flow velocity entering the two classification areas will be too large, resulting in coarse particles. When the system air volume is too small, the qualified particles cannot be selected in time after passing through the classification area, and the material layer will be formed after accumulation, resulting in over-grinding and affecting the output. According to the process of determining the radius index of the classifier shell, the plum blossom frame, grinding roller and scraper area in the primary model of the host are applied with sliding grids, and transient solution is adopted. The four grinding roller surfaces are used as the particle emission surfaces. Five groups of particles are input using the uniformity method. The particle diameters are 75, 125, 180, 270 and 380 μm respectively, and the system air volume is 42000 m 3 / h、45500m3 / h、49200m 3 / h、53000m 3 / h and 56500m 3 / h, where the wind speed and air volume conversion method is:

[0016] L=3600×F×V (1)

[0017] In the above formula, L is the inlet air volume, m 3 / h; F is the ventilation area of the air outlet, m 2 ; V is the average velocity at the air outlet, m / s;

[0018] According to formula 1, experiments 5, 6, 7, 8 and 9 represent inlet wind speeds of 23m / s, 25m / s, 27m / s, 29m / s and 31m / s, respectively. The mass flow rate of each group of particles is 3.333kg / s, the incident time is 0.1s, and there are ten incidents in total. The other working conditions remain unchanged. Five groups of simulation tests are carried out, specifically:

[0019] Five groups of particles of different particle sizes were used in each test, including three finished particles and two coarse particles. The sliding grid was used to simulate the rotation of the scraper, grinding roller, main shaft and plum blossom rack. The boundary conditions were entered in Fluent and the simulation was completed. The calculation method for the gravity classification particle pass rate P was as follows: after the Fluent transient simulation calculation was completed, the particle information captured at the outlet of the whole machine was statistically analyzed in the Sample of Discrete Phase under Reports, and the mass flow rate of particles of each mesh size was obtained. When the inlet wind speed was 23m / s, the collected mass flow rates of 200, 115 and 80 mesh were 0.0237, 0.0239 and 0.0229kg / s respectively. The incident time interval was 0.01s, and there were ten incidents with a total incident time of 0.1s. The inlet wind speed corresponding to the highest value of the gravity classification finished product pass rate P was used as the inlet wind speed index.

[0020] After determining the inlet wind speed index, the host primary model is supplemented and constructed using three-dimensional software to form a host intermediate model.

[0021] As a preferred solution, the inlet wind speed index is combined with the segmentation particle size method to obtain the cut particle size index and the particle settling velocity index, specifically:

[0022] The cut particle size index is obtained according to the inlet wind speed index. The process of calculating the particle settling velocity by combining the inlet wind speed index and the cut particle size index with the Allen formula is as follows:

[0023] Formula for free sedimentation of particles in fluid:

[0024] The buoyancy and self-gravity do not increase with the increase of gas flow rate. According to the balance of the three forces, the calculation formula of the theoretical gravity classification zone cutting particle size is obtained. Since the particle Reynolds number belongs to the transition zone, the free sedimentation of spherical particles and the transition zone is applicable to the Allen formula, which is:

[0025]

[0026] In the above formula, g is the acceleration due to gravity, m / s 2 ; ρ is the medium density, kg / m 3 ; Thus the particle settling velocity is calculated.

[0027] As a preferred solution: the host intermediate model is supplemented and constructed for the second time based on the cutting particle size index and the particle settling velocity index to form the host ultimate model, and the simulation data corresponding to the host ultimate model is compared with the unestablished Raymond mill related data. When the error between the simulation data corresponding to the host ultimate model and the unestablished Raymond mill related data is less than 5%, it means that the unestablished Raymond mill related data is reliable and can be put into use; when the error between the simulation data corresponding to the host ultimate model and the unestablished Raymond mill related data is greater than 5%, it means that the unestablished Raymond mill related data needs to be recalculated.

[0028] As a preferred solution: the host intermediate model is supplemented and constructed for the second time based on the cutting particle size index and the particle settling velocity index to form the host ultimate model, and the simulation data corresponding to the host ultimate model is compared with the established Raymond mill related performance data. When the error between the simulation data corresponding to the host ultimate model and the established Raymond mill related performance data is less than 10%, it means that the established Raymond mill related performance is good; when the error between the simulation data corresponding to the host ultimate model and the established Raymond mill related performance data is greater than 10%, it means that the established Raymond mill needs to improve its basic performance.

[0029] Compared with the prior art, the present invention has the following beneficial effects:

[0030] First, the present invention analyzes and derives comprehensive indicators that influence the collection efficiency and energy consumption of a Raymond Mill blower, namely the classifier housing radius, inlet air velocity, cut particle size, and particle settling velocity. This is then combined with relevant methods to gradually refine the model step by step until the ultimate model is achieved. This method not only uses the data corresponding to the ultimate model to evaluate the prediction process for unestablished Raymond Mill blower data, but also uses the data corresponding to the ultimate model to complete the evaluation process for established Raymond Mill blower performance data.

[0031] Second, the present invention facilitates analysis of flow field patterns, ultimately analyzing and organizing test data to reduce internal pressure loss within the main machine, improve the efficiency of gravity and centrifugal classification, identify measures to jointly improve classification efficiency, and reduce energy consumption. The present invention facilitates studying the relationship between flow parameters and pressure loss, flow rate, and classification efficiency, ensuring that materials are effectively transported to the classifier outlet. This helps improve product fineness and the separation efficiency of finished powders, while also reducing mechanical failure rates. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 This is a schematic diagram of the force analysis of particles in the gravity classification area;

[0033] Figure 2 Schematic diagram of the mass conservation principle of total flow;

[0034] Figure 3 Schematic diagram of the intersection area of the non-periodic interface;

[0035] Figure 4 It is a schematic diagram of the two-dimensional grid interface;

[0036] Figure 5 This is a schematic diagram of the corresponding dimensions when the radius of the classifier shell is 1240mm;

[0037] Figure 6-1 The figure is a schematic diagram of the simulation of the internal flow field velocity of the Raymond mill based on the Fluent simulation results in Experiment 1;

[0038] Figure 6-2 This is a schematic diagram of the simulation of the wind field trajectory inside the Raymond Mill according to the Fluent simulation results in Test 1;

[0039] Figure 7-1 The figure is a schematic diagram of the simulation of the internal flow field velocity of the Raymond mill based on the Fluent simulation results in Experiment 2;

[0040] Figure 7-2 This is a schematic diagram of the simulation of the wind field trajectory inside the Raymond Mill according to the Fluent simulation results in Test 2;

[0041] Figure 8-1 The figure is a schematic diagram of the simulation of the internal flow field velocity of the Raymond mill based on the Fluent simulation results in Experiment 3;

[0042] Figure 8-2 This is a schematic diagram of the simulation of the wind field trajectory inside the Raymond Mill according to the Fluent simulation results in Test 3;

[0043] Figure 9-1 The figure is a schematic diagram of the simulation of the internal flow field velocity of the Raymond mill based on the Fluent simulation results in Experiment 4;

[0044] Figure 9-2 This is a schematic diagram of the simulation of the wind field trajectory inside the Raymond Mill according to the Fluent simulation results in Test 4;

[0045] Figure 10-1 This is a simulated diagram of the wind speed at the gravity-graded outlet in Test 5. The velocity file of the gravity-graded outlet was exported in Fluent and imported into Tecplot software for post-processing of the gravity-graded outlet. Due to the symmetrical distribution of the velocity, only one-quarter of the cross section was taken for comparative analysis with other tests.

[0046] Figure 10-2 This is a simulated diagram of the wind speed at the gravity-graded outlet in Test 6. The velocity file of the gravity-graded outlet was exported in Fluent and imported into Tecplot software for post-processing of the gravity-graded outlet. Due to the symmetrical distribution of the velocity, only one-quarter of the cross section was taken for comparative analysis with other tests.

[0047] Figure 10-3 This is a simulated diagram of the wind speed at the gravity-graded outlet in Test 7. The velocity file of the gravity-graded outlet was exported in Fluent and imported into Tecplot software for post-processing of the gravity-graded outlet. Due to the symmetrical distribution of the velocity, only one-quarter of the cross section was taken for comparative analysis with other tests.

[0048] Figure 10-4 This is a simulated diagram of the wind speed at the gravity-graded outlet surface in Test 8. The velocity file of the gravity-graded outlet surface was exported in Fluent and imported into Tecplot software for post-processing of the gravity-graded outlet surface. Due to the symmetrical distribution of the velocity, only one-quarter of the cross section was taken for comparative analysis with other tests.

[0049] Figure 10-5 This is a simulated diagram of the wind speed at the gravity-graded outlet in Test 9. The velocity file of the gravity-graded outlet was exported in Fluent and imported into Tecplot software for post-processing of the gravity-graded outlet. Due to the symmetrical distribution of the velocity, only one-quarter of the cross section was taken for comparative analysis with other tests.

[0050] Figure 11 Schematic diagram of the acquisition line and outlet surface location;

[0051] Figure 12 This is a schematic diagram comparing the speed of line 1 in different system air volumes;

[0052] Figure 13-1 This is a schematic diagram of the first response surface of the interaction of various factors, which shows the interaction between inlet wind speed and main shaft speed;

[0053] Figure 13-2The second response surface diagram of the interaction of various factors shows the interaction between the inlet wind speed and the outlet pressure of the whole machine;

[0054] Figure 13-3 This is the second response surface diagram of the interaction of various factors, which shows the interaction between the spindle speed and the outlet pressure of the whole machine;

[0055] Figure 14 This is a schematic diagram comparing the pressure loss in the scraper area, the grinding roller area, and the main engine;

[0056] Figure 15 This is a schematic diagram of the position structure between the pressure loss in the scraper area, the pressure loss in the grinding roller area and the whole machine area;

[0057] Figure 16-1 The wind field trajectory diagram of the wind field speed at 1.2s in the Raymond mill;

[0058] Figure 16-2 The wind field trajectory diagram of the wind field speed at 1.3s in the Raymond mill;

[0059] Figure 16-3 The wind field trajectory diagram of the wind field speed at 1.4s in the Raymond mill;

[0060] Figure 16-4 Schematic diagram of particle position distribution in the Raymond Mill at 1.2s;

[0061] Figure 16-5 Schematic diagram of particle position distribution in the Raymond Mill at 1.3s;

[0062] Figure 16-6 Schematic diagram of particle position distribution in the Raymond Mill at 1.4s;

[0063] Figure 17 This is a comparison chart of the finished product collection efficiency in the gravity classification area and the coarse product collection efficiency in the gravity classification area. DETAILED DESCRIPTION

[0064] To make the objectives, technical solutions, and advantages of the present invention more clearly apparent, the present invention is described below using specific embodiments shown in the accompanying drawings. However, it should be understood that these descriptions are merely illustrative and are not intended to limit the scope of the present invention. In addition, in the following description, descriptions of well-known structures and technologies are omitted to avoid unnecessary confusion of the concepts of the present invention.

[0065] Specific implementation method 1: Combination Figures 1 to 17This embodiment is described. The gravity grading prediction and evaluation method in this embodiment is to use a steady-state solution method to determine the classifier shell radius index under the premise of ensuring a uniform flow field and a small overall pressure loss, and then construct a host primary model. A transient solution method is used to determine the inlet wind speed index by analyzing the gravity grading outlet wind speed change law and the overall pressure loss value. The inlet wind speed index is used to reconstruct the primary model of the Raymond mill host to form a host intermediate model. The inlet wind speed index is combined with the particle size segmentation method to obtain the cutting particle size index and the particle settling velocity index. The host intermediate model is constructed according to the cutting particle size index and the particle settling velocity index to form the host ultimate model. The host ultimate model is used to complete the prediction process of the unestablished Raymond mill related data or the evaluation process of the established Raymond mill related performance data.

[0066] The gravity classification prediction and assessment method in this embodiment is applied to the gravity classification zone of the mainframe. Through various analyses, the classifier housing radius, inlet air velocity, cut particle size, and particle settling velocity are determined. These four indicators form a process for gradually building and refining the ultimate mainframe model. These four indicators enable a comprehensive assessment of the collection efficiency and energy consumption reduction within the mainframe's gravity classification zone.

[0067] Combine Figure 1 As shown, in this embodiment, the particles in the gravity classification zone are mainly subjected to the gas drag force F d Buoyancy F b and gravity G. Under the interaction of the three forces, coarse particles will settle downwards and fine particles will spiral up to the centrifugal classification area.

[0068] The movement of particles in a vertically flowing fluid is as follows: when the fluid moves at a uniform speed u f The particle moves upward, and under the action of gravity, it moves at a speed u relative to the fixed space. p When moving downward, the relative velocity u of the particle relative to the fluid can be expressed as the difference between the fluid velocity and the particle velocity. Since the upward movement of the fluid and the downward movement of the particle under the action of gravity are in opposite directions, the relative velocity of the particle relative to the fluid is the sum of the two velocities, that is,

[0069] u=u p +u f (3)

[0070] Since the relative motion between particles and fluid produces resistance, the particles move under the combined action of residual gravity and fluid resistance. Assuming the particles are spherical, then

[0071]

[0072] In the above formula, u0 is the sedimentation velocity of the particle in the same static fluid; the residual gravity is the particle gravity minus the buoyancy.

[0073] Since u=u p +u f , and u f is a constant, so du=du p , so the formula is rewritten as

[0074]

[0075] In the above formula It is equivalent to the initial acceleration of particles falling when the fluid is stationary. It is only related to the density of the particles and the fluid, but has nothing to do with the particle size and is a constant.

[0076] When the fluid velocity is low, the initial friction is weak and cannot completely offset the residual weight of the particles. This causes the particles to sink downward under the influence of gravity. At the same time, in addition to overcoming friction, an additional force pushes the particles downward with positive acceleration. As the velocity increases, the friction force gradually increases until it reaches equilibrium with the residual weight of the particles.

[0077] When the fluid velocity is high, the initial friction force is sufficient to overcome the residual weight of the particles, causing the particles to move with the fluid. Over time, the friction force gradually decreases until it is balanced with the residual weight of the particles.

[0078] It can be seen that particles are affected by gravity and friction in the vertically flowing fluid. Regardless of whether the two forces are balanced at the beginning, after a period of time, the two forces will always reach equilibrium. u-u0. Substituting this relationship into Formula 3, we get Formula 6:

[0079] u p =u0-u f (6)

[0080] In the above formula, u f is the rising velocity of the fluid in a fixed space, u p is the velocity of the particle under the action of gravity, that is, the absolute velocity, and u0 is the sedimentation velocity when it is stationary in the same fluid.

[0081] When particles move in a fluid flowing vertically, they initially fall faster due to gravity. However, over time, the resistance of the fluid to the particles gradually increases until it is balanced with the effective gravity of the particles. The effective gravity is the difference between gravity and buoyancy. At this point, the particles reach a stable settling velocity and then move at a constant speed. In this state, the particle's velocity u relative to the fluid becomes a fixed value, which is equivalent to the particle's sedimentation velocity in the same fluid at rest. The absolute velocity of the particle u is p , and its direction of movement is determined by the particle settling velocity and fluid velocity u fThe difference is determined by .

[0082] When the fluid velocity u f When it is equal to the stable sedimentation velocity u0 of the particles, that is, u p = 0, then the velocity u of the particle relative to the fixed space p The velocity of the fluid at this point is called the suspension velocity of particles of that size, which is numerically equivalent to the settling velocity of particles in a stationary fluid.

[0083] When the fluid velocity u f When it is greater than the stable sedimentation velocity u0 of the particles, that is, u p <0, the particles will move upward with the fluid. On the contrary, if the fluid velocity u f Less than the stable sedimentation velocity u0 of the particle, that is, u p >0, the particles will continue to settle. In summary, the absolute velocity and direction of movement of particles in a fluid depend on the relationship between their settling velocity and the fluid velocity.

[0084] Specific embodiment 2: This embodiment is a further limitation of specific embodiment 1. This embodiment adopts a steady-state solution method to determine the classifier housing radius index under the premise of ensuring a uniform flow field and a small pressure loss of the entire machine. The process is as follows:

[0085] After the material is fed into the Raymond mill inlet, it is ground by the grinding roller and grinding ring. The powder that reaches a certain fineness is sent to the gravity classification area by the air blown in by the air inlet box to complete the first classification. According to the theory of flow velocity and arbitrary cross-sectional area, the improved gravity classification outlet cross-sectional radius is the classifier shell radius. According to the Fluent simulation results, the internal flow field velocity and wind field trajectory of the Raymond mill are compared. The speed distribution in the grinding roller and host shell area is uniform. The particles will be sent to the gravity classification area at a speed of 0-30m / s. The corresponding classifier shell radius is used as the classifier shell radius index. The wind track line corresponding to the classifier shell radius index spirals upward evenly and has a clear boundary in the gravity classification area. After determining the classifier shell radius index, the primary model of the host is constructed using 3D software.

[0086] The specific selection process of the classifier shell radius index in this embodiment is as follows:

[0087] Combine Figure 5The figure shows the cross-sectional shape of a large Raymond mill. After the material is fed into the inlet of the Raymond mill, it is ground by the grinding roller and grinding ring. The powder that reaches a certain fineness is sent to the gravity classification area by the air blown in by the air inlet box to complete the first classification. In order to improve the screening efficiency of the gravity classification area, according to the theory of flow rate and arbitrary cross-sectional area, it is very meaningful to improve the cross-sectional radius of the gravity classification outlet, that is, the radius of the classifier shell. In order to study the influence of the shape of the classifier shell on the Raymond mill and the flow field and the classification and screening performance, based on the original model of a large Raymond mill with a classifier shell radius of 1240mm, its cross-sectional shape is as follows Figure 5 Four different radii of the classifier housing are designed. Tests 1, 2, 3, and 4 represent classifier housing radii of 1170, 1240, 1500, and 1720 mm, respectively. The other dimensions remain unchanged. The original model corresponds to a dimension of 1240 mm.

[0088] The velocity field analysis process of the Raymond mill is as follows:

[0089] Combine Figure 6-1 、 6-2 , 7-1, 7-2, 8-1, 8-2, 9-1, 9-2 to Figure 12 As shown in the figure, according to the four designed classifier shell radii, four groups of single factor simulation experiments are designed. According to the Fluent simulation results, the internal flow field velocity and wind field trajectory of the Raymond mill are compared. Figure 6-1 、 6-2 7-1 and 7-2 show that there are fewer wind tracks at the edge of the classifier shell, and the particles are less distributed in this area. This shows that when the radius of the classifier shell is 1170 and 1240 mm, the gravity classification area is not well utilized. Figure 4 -9 shows that when the radius of the classifier shell is 1720mm, there are many chaotic and high-speed wind limits inside the classifier shell. Due to the high speed, they may also hover inside the shell, which will cause the particles in this area to hit the classifier shell at a high speed. Figure 8-1 、 8-2 It can be seen that when the radius of the classifier shell is 1500 mm, the wind track spirals upward more evenly and has an obvious distribution in the gravity classification area.

[0090] Depend on Figure 6-1 、 6-2 , 7-1, and 7-2 show that there is a velocity gradient in the wireframe area, and the wind field is unstable, which is not conducive to the transportation of particles. Figure 9-1 and Figure 9-2 It can be seen that when the radius of the classifier shell is 1720mm, there is a zero wind speed area in the classifier shell, and a relatively high wind speed in the local area, indicating that the wind field distribution is uneven. Figure 8-1 and Figure 8-2It can be seen that when the radius of the classifier shell is 1500mm, the speed distribution in the grinding roller and main machine shell area is uniform, and the particles will be quickly sent to the gravity classification area at a higher speed, which is more conducive to the rapid completion of particle collection.

[0091] Specific implementation method three: This implementation method is a further limitation of specific implementation method one or two. This implementation method uses a transient solution method to analyze the change law of the gravity classification outlet wind speed and the pressure loss value of the whole machine to determine the inlet wind speed index. The process is as follows: First, the particle Reynolds number is calculated: According to the Fluent transient calculation results, the particle velocity and flow field velocity of different particle diameters are used to calculate the particle Reynolds number. The relative velocity of the particle is the difference between the particle velocity and the wind speed. The air viscosity μ is 1.79E-5Pa·s, and the air density is 1.29kg / m3. The Reynolds number for particles with a diameter of 7.50E-5m is

[0092]

[0093] Where R ep is the Reynolds number; d p is the cutting diameter of spherical particles, m; u0 is the relative motion speed of particles in the fluid, m / s; ρ p is the fluid density, kg / m3; ξ is the drag coefficient; μ is the air viscosity, Pa·s;

[0094] Table 1 Reynolds numbers corresponding to different particle diameters

[0095]

[0096] According to the calculation in Table 1 above, the particle Reynolds number is between 0 and 1000, belonging to the transition zone, and the drag coefficient is

[0097]

[0098] The formula for the free settling of particles in a fluid is: buoyancy and self-gravity do not increase with the increase of gas flow rate. Based on the balance of the three forces, the calculation formula for the theoretical gravity classification zone cut-off particle size can be obtained. Since the particle Reynolds number belongs to the transition zone, the free settling formula for spherical particles and applicable to the transition zone is Allen formula:

[0099]

[0100] In the above formula, g is the acceleration due to gravity, m / s 2 ; ρ is the medium density, kg / m 3 ;

[0101] The theory and calculation process of flow velocity and arbitrary cross-sectional area are as follows: starting from the law of conservation of mass, study the changing law of fluid along the flow direction in the total flow, such as Figure 2As shown, when the mass of the flow space between the two sections is conserved, it is assumed that the average velocities of the fluid passing through the two sections with areas A1 and A2 are V1 and V2 respectively. According to the law of conservation of mass, the mass flowing into a system must be equal to the mass flowing out of the system. Assuming that the fluid density is constant throughout the flow process, the mass m1 flowing into section A1 within the time interval dt can be expressed as: m1 = ρ1A1V1dt. The mass flowing out of section A2 can be expressed as: m2 = ρ1A2V2dt. Under ideal conditions, there is no mass loss or gain, and we have m1 = m2, from which we can get

[0102] A1V1dt=A2V2dt (10)

[0103] Eliminating dt, we can obtain the continuity equation for mass conservation in the flow space between the two end surfaces, which reflects the different densities at different sections:

[0104] A1V1=A2V2 (11)

[0105] According to the above theory, the relationship between flow velocity and arbitrary cross-sectional area is as follows:

[0106] u0A0=u1A1 (12)

[0107]

[0108] In the above formula, u0 and u1 are the average velocities through the cross-sectional areas A0 and A1, respectively, in m / s; u0 and u1 are the sedimentation velocities, u1 is the average velocity at the gravity classification outlet, in m / s; A0 and A1 are the gravity classification outlet cross-sectional areas and the main engine outlet cross-sectional areas, respectively, in m 2 ; r0 and r1 are the radius of the gravity classification outlet section and the main engine outlet section, respectively, in meters;

[0109] The air volume of the Raymond mill system is the driving force in the process of conveying materials of a certain fineness to the gravity classification area and the centrifugal classification area. When the system air volume is too large, the air flow velocity entering the two classification areas will be too large, resulting in coarse particles. When the system air volume is too small, the qualified particles cannot be selected in time after passing through the classification area, and the material layer will be formed after accumulation, resulting in over-grinding and affecting the output. According to the process of determining the radius index of the classifier shell, the plum blossom frame, grinding roller and scraper area in the primary model of the host are applied with sliding grids, and transient solution is adopted. The four grinding roller surfaces are used as the particle emission surfaces. Five groups of particles are input using the uniformity method. The particle diameters are 75, 125, 180, 270 and 380 μm respectively, and the system air volume is 42000 m 3 / h、45500m 3 / h、49200m 3 / h、53000m 3 / h and 56500m 3 / h, where the wind speed and air volume conversion method is:

[0110] L=3600×F×V (1)

[0111] In the above formula, L is the inlet air volume, m 3 / h; F is the ventilation area of the air outlet, m 2 ; V is the average velocity at the air outlet, m / s;

[0112] According to formula 1, experiments 5, 6, 7, 8 and 9 represent inlet wind speeds of 23m / s, 25m / s, 27m / s, 29m / s and 31m / s, respectively. The mass flow rate of each group of particles is 3.333kg / s, the incident time is 0.1s, and there are ten incidents in total. The other working conditions remain unchanged. Five groups of simulation tests are carried out, specifically:

[0113] Five groups of particles of different particle sizes were used in each test, including three finished particles and two coarse particles. The sliding grid was used to simulate the rotation of the scraper, grinding roller, main shaft and plum blossom rack. The boundary conditions were entered in Fluent and the simulation was completed. The calculation method for the gravity classification particle pass rate P was as follows: after the Fluent transient simulation calculation was completed, the particle information captured at the outlet of the whole machine was statistically analyzed in the Sample of Discrete Phase under Reports, and the mass flow rate of particles of each mesh size was obtained. When the inlet wind speed was 23m / s, the collected mass flow rates of 200, 115 and 80 mesh were 0.0237, 0.0239 and 0.0229kg / s respectively. The incident time interval was 0.01s, and there were ten incidents with a total incident time of 0.1s. The inlet wind speed corresponding to the highest value of the gravity classification finished product pass rate P was used as the inlet wind speed index.

[0114] After determining the inlet wind speed index, the host primary model is supplemented and constructed using 3D software to form a host intermediate model.

[0115] The model component method is the same as the existing model component method, and can be supplemented and constructed using existing modeling software.

[0116] Specific embodiment 4: This embodiment is a further limitation of specific embodiments 1, 2 or 3. This embodiment combines the inlet wind speed index with the segmentation particle size method to obtain the cut particle size index and the particle settling velocity index, specifically:

[0117] The cut particle size index is obtained according to the inlet wind speed index. The process of calculating the particle settling velocity by combining the inlet wind speed index and the cut particle size index with the Allen formula is as follows:

[0118] Formula for free sedimentation of particles in fluid:

[0119] The buoyancy and self-gravity do not increase with the increase of gas flow rate. According to the balance of the three forces, the calculation formula of the theoretical gravity classification zone cutting particle size is obtained. Since the particle Reynolds number belongs to the transition zone, the free sedimentation of spherical particles and the transition zone is applicable to the Allen formula, which is:

[0120]

[0121] In the above formula, g is the acceleration due to gravity, m / s 2 ; ρ is the medium density, kg / m 3 ; Thus the particle settling velocity is calculated.

[0122] Specific embodiment five: This embodiment is a further limitation of specific embodiments one, two, three or four. This embodiment performs secondary supplementation on the host intermediate model based on the cutting particle size index and the particle settling velocity index to form the host ultimate model, and compares the simulation data corresponding to the host ultimate model with the unestablished Raymond mill related data. When the error between the simulation data corresponding to the host ultimate model and the unestablished Raymond mill related data is less than 5%, it means that the unestablished Raymond mill related data is reliable and can be put into use; when the error between the simulation data corresponding to the host ultimate model and the unestablished Raymond mill related data is greater than 5%, it means that the unestablished Raymond mill related data needs to be recalculated.

[0123] Specific embodiment six: This embodiment is a further limitation of specific embodiments one, two, three, four or five. This embodiment performs secondary supplementation on the host intermediate model based on the cutting particle size index and the particle settling velocity index to form the host ultimate model, and compares the simulation data corresponding to the host ultimate model with the established Raymond mill related performance data. When the error between the simulation data corresponding to the host ultimate model and the established Raymond mill related performance data is less than 10%, it means that the established Raymond mill related performance is good; when the error between the simulation data corresponding to the host ultimate model and the established Raymond mill related performance data is greater than 10%, it means that the established Raymond mill needs to improve basic performance.

[0124] Specific embodiment seven: This embodiment is a further limitation of specific embodiments one, two, three, four or five. The present invention also involves the process of constructing a sliding grid model for the rotating area in the gravity classification area, specifically:

[0125] The sliding mesh model is used to express dynamic changes that allow for relative sliding between adjacent meshes, eliminating the need for perfect mesh alignment at interfaces. By applying this physical model, flow through each mesh interface can be accurately simulated while maintaining computational efficiency. This is particularly important for accurately calculating flow in regions with non-uniform interfaces. This is crucial for solving fluid flow problems in engineering applications.

[0126] In interfacial flow analysis, as time passes and the interface moves relative to each other, internal and periodic regions are generated at the interface. If these wall regions do not conform perfectly, appropriate boundary conditions must be used to address them.

[0127] The focus is on handling overlapping and non-overlapping interface regions, combining Figure 3 As shown in Figure 1, overlapping interface regions create internal regions, requiring flow calculations to be performed on the new faces generated by the intersection of the interfaces, rather than simply based on the area of the original interfaces. Overlapping interface regions often correspond to periodic regions, characterized by the number of faces within the interface region changing with relative motion.

[0128] The challenge of sliding mesh technology lies in handling these dynamically changing interfaces and ensuring accurate and efficient flow calculations. Properly designed, sliding mesh models can effectively simulate complex phenomena such as rotating machinery and the interaction between fluids and solid structures, making them a key tool in computational fluid dynamics (CFD). The successful application of this technology relies on precise meshing, appropriate boundary condition settings, and efficient numerical calculation methods to ensure accurate and reliable analysis results.

[0129] Combine Figure 3 and Figure 4 As shown, the interface region is composed of multiple surfaces, such as AB and BC, as well as DE and EF, which form the boundaries for fluid flow. At the intersections of these surfaces, such as the ad, db, and be surfaces, a complex interface structure is formed. At the overlap of two unit regions, the db, be, and ec surfaces together form an internal region, which is a key area for fluid flow and exchange. The remaining ad and cf surfaces, due to symmetry or periodic boundary conditions, form periodic regions in pairs, which are very useful for simulating flows with periodic characteristics.

[0130] The specific process of establishing the sliding mesh control equation is as follows:

[0131] The general governing equations for a sliding mesh are similar to those for a moving mesh. In any control volume V, whose boundary is in motion, the general formula of the conservation equation is:

[0132]

[0133] In the above formula, ρ is the density of the liquid; u s is the deformation velocity of the moving mesh; u is the velocity vector of the liquid; ∈ is the diffusion coefficient; is the source term of the flux Represents the boundary of the control volume V.

[0134] In the above formula, the first term can be expressed in differential form as

[0135]

[0136] In the above formula, n and n+1 represent the values of the current and next time steps.

[0137] Since the mesh motion of the sliding mesh is rigid and the mesh does not deform, it can be simplified to

[0138] V n+1 =V n (16)

[0139]

[0140] After applying the simplified formula above, Equation 14 can be used to calculate the sliding grid problem.

[0141] The pressure field analysis process of the Raymond Mill machine in this embodiment is as follows:

[0142] The pressure loss in the gravity classification area is the difference between the main unit outlet and the average pressure of the entire machine outlet. The main unit pressure loss is the difference between the average pressure of the air inlet and the main unit outlet. The pressure loss value directly reflects the amount of energy loss. Four groups of tests were designed based on different classifier shell radii. The pressure loss in the gravity classification area is shown in Table 2 below:

[0143] Table 2 Pressure loss in gravity classification areas

[0144]

[0145] It can be seen from the above table that when the radius of the classifier shell is 1170 and 1720 mm, the maximum and minimum pressure losses in the gravity classification area are 1371 and 1977 Pa respectively, and the maximum and minimum pressure losses in the main engine area are 1344 and 904 Pa respectively. With the increase of the radius of the classifier shell, the pressure loss in the gravity classification area shows a trend of first increasing, then decreasing, and then increasing again, while the pressure loss of the main engine has been increasing. When the radius of the classifier shell is 1500 mm, the pressure loss is 1466 Pa, and the total pressure loss is the minimum 2617 Pa. This shows that when the diameter of the classifier shell is 1500 mm, the smaller the flow energy loss of the whole machine is, the lower the energy consumption of the mill is.

[0146] The influence of flow field parameters on the flow field and particle screening of the Raymond Mill in this embodiment is as follows:

[0147] The inlet wind speed is an important factor affecting the efficiency of gravity classification. The velocity field, structural field and pressure field distribution are optimal according to the classifier shell radius of 1500mm. According to the standards given by the enterprise, the target particle size of the gravity classification area is 45 mesh. Therefore, the structure with a classifier shell radius of 1500mm is selected as the research object, and particles mixed with finished products and coarse products are input. The other boundary conditions remain unchanged and the inlet wind speed is optimized.

[0148] The system air volume selection process in this embodiment is as follows:

[0149] The air volume of the Raymond mill system is an important flow field parameter. Its main function is to transport materials of a certain fineness to the gravity classification area and the centrifugal classification area. When the system air volume is too large, the air flow velocity entering the two classification areas will be too high, and some particles that do not meet the requirements will be selected, resulting in coarse particles. When the system air volume is too small, the qualified particles cannot be selected in time after passing through the classification area, and they will accumulate to form a material layer, resulting in over-grinding and greatly reducing the output.

[0150] In order to better simulate the movement of particles during the classification process, based on the analysis of the influence of the radius of the classifier shell on the flow field of the Raymond mill, the plum blossom frame, grinding roller and scraper area are used with sliding grids and transient solutions. The transient solution has advantages in simulating the dynamic process, nonlinear phenomena and time dependence in the fluid system, and can provide more accurate and comprehensive simulation results. In order to simulate the existence of particles of different fineness during the operation of the Raymond mill, this study uses the four grinding roller surfaces as the particle emission surfaces, and uses the uniformity method to inject five groups of particles, with particle diameters of 75, 125, 180, 270 and 380 μm, respectively, and the system air volume is 42000m 3 / h、45500m 3 / h、49200m 3 / h、53000m 3 / h and 56500m 3 / h, where the wind speed and air volume conversion method is:

[0151] L=3600×F×V (1)

[0152] In the above formula, L is the inlet air volume, m 3 / h; F is the ventilation area of the air outlet, m 2 ; V is the average velocity at the air outlet, m / s;

[0153] According to formula 8, experiments 5, 6, 7, 8 and 9 represent inlet wind speeds of 23 m / s, 25 m / s, 27 m / s, 29 m / s and 31 m / s, respectively. The mass flow rate of each group of particles is 3.333 kg / s, the incident time is 0.1 s, and there are ten incidents in total. The other working conditions remain unchanged, and five groups of simulation tests are performed.

[0154] The influence of the system air volume on the flow field of the Raymond mill in this embodiment is as follows:

[0155] Part 1: Comparative analysis process of wind speed at the outlet of gravity classification:

[0156] Combine Figures 10-1 to 10-5 、 Figure 11 and Figure 12 As shown in the figure, the wind speed at the gravity classification outlet directly affects the efficiency of gravity classification screening, so it is very necessary to observe the wind speed at the gravity classification outlet. The velocity file of the gravity classification outlet is exported in Fluent and imported into Tecplot software for post-processing of the gravity classification outlet surface. Since the velocity is symmetrically distributed, only one-quarter of the cross section is taken for comparative analysis. In order to compare the velocity changes, the velocity color bar scale range is selected to be the largest. Figure 4-1 0 It can be seen that as the inlet wind speed increases, the speed at the outlet edge also increases, and the particles gain more kinetic energy at the edge, causing large diameter particles to fly out of this plane. Figure 10-5 It can be observed that the maximum velocity occurs only in local locations, while the maximum wind speed of 15 m / s in Figure 10-2 is relatively evenly distributed at the gravity classification outlet surface. The uniform velocity distribution is conducive to the transportation of particles from the outlet surface to the centrifugal classification area. In order to better observe the numerical changes in the outlet edge velocity, a data acquisition line line 1 is established at the gravity classification outlet, where the starting and ending coordinates of line 1 are (0.95775, 3.87454, 1.14141) and (0, 3.87454, 0) respectively. Five sets of test velocity magnitude versus X-axis displacement data are exported from Fluent and imported into Origin for data processing. After passing through the scraper grinding roller area, the airflow continues to move upward, and the velocity gradually increases from the center of the gravity classification surface to the edge. In test 5, the maximum velocity reaches 14.92 m / s, and in test 9, the maximum velocity reaches 20.5 m / s. By observing the changes in velocity with X-axis displacement at each air volume, it can be seen that the curve change trends are roughly the same, indicating that the system air volume only changes the value of the velocity on the gravity classification outlet surface, and has no substantial effect on the flow field distribution on this surface.

[0157] Part 2: The analysis process of the internal pressure loss of the Raymond Mill is as follows:

[0158] The internal pressure difference of the Raymond mill is an important parameter for studying the flow field of the mill. The pressure difference of the mill is of great significance for reducing energy consumption. The energy equation for steady flow with energy input is described as:

[0159]

[0160] In the above formula, W shaft，net in is the unit mass shaft work input to the fluid; is the flow energy per unit mass; is the kinetic energy per unit mass; gz is the potential energy per unit mass of the fluid; e is the internal energy; q net in is the unit mass heat transferred to the fluid; intermolecular collisions are not considered in this paper, so the internal energy and the heat transferred to the fluid (u2-u1-q net in ) is negligible; P is absolute pressure, Pa; ρ is density, kg / m3; V is velocity, m / s; g is acceleration due to gravity, m / s2; z represents spatial position, m;

[0161] Based on the above analysis, formula 18 is reorganized and the change law of the flow energy of gas at the inlet and outlet of the mill main engine is as follows:

[0162]

[0163] In the above formula, the difference between P2 and P1 is the pressure loss of the Raymond mill.

[0164] When the fluid flows through the wall structure of the mill, the pressure inevitably decreases due to the generation of structural resistance and the dissipation of flow energy by vortices. Combined with Formula 19, it can be seen that the flow energy of the pressure component is a component of the energy balance equation. The greater the pressure loss, the greater the flow energy loss of the mill. For the collection of completed products, the change in kinetic energy caused by speed changes should remain stable, and the change in potential energy should be consistent with the height of the equipment; therefore, an increase in pressure loss will result in the need for greater shaft power input to maintain energy conservation, that is, to ensure a greater input of motor energy for the main engine air intake, spindle speed, and classifier speed. Therefore, pressure loss is an important component that can reflect the energy consumption of the mill.

[0165] Response surface of Box-Behnken test results Figure 13-1 、 13-2 , 13-3, 14 and Figure 15As shown in the figure, when the outlet pressure of the whole machine remains unchanged, the main engine pressure loss increases with the increase of inlet wind speed and the continuous decrease of main shaft speed. When the inlet wind speed is 46m / s and the main shaft speed is 100r / min, the main engine pressure loss reaches a maximum of 1660Pa. When the main shaft speed remains unchanged, as the inlet wind speed continues to increase and the main engine outlet pressure continues to decrease, the main engine pressure loss also continues to increase, with a maximum value of approximately 1320Pa. When the inlet wind speed remains unchanged, as the main shaft speed and main engine outlet pressure continue to decrease, the main engine pressure loss increases more slowly, with a maximum value of approximately 1260Pa.

[0166] In addition to affecting the wind speed at the gravity classification outlet, the inlet wind speed also affects the internal pressure loss of the Raymond Mill. As the inlet wind speed increases, the pressure loss of the wind field through the scraper and grinding roller increases. At the same time, as the inlet wind speed increases, more particles will move upward with the wind field. In order to better explore the internal pressure changes of the Raymond Mill, the average pressure of the four pressure values at the inlet, the scraper when y=0.57m, the grinding roller when y=1.954m, and the outlet plane was extracted in Fluent. The pressure data of each surface under different inlet wind speeds were calculated to obtain the pressure loss curves of the scraper area and the whole machine, as well as their change curves. The data formed by each curve are shown in Table 3 below:

[0167] Table 3 Pressure on each plane under different system air volumes

[0168]

[0169] Depend on Figure 14 and Figure 15 It can be seen that, with the spindle speed remaining constant, as the inlet wind speed increases, the pressure loss in the blade area and the grinding roller area also increases. Particles are ejected from the grinding roller surface and transported upward by the airflow. During this process, the particles continuously collide with the blade and grinding roller, resulting in greater pressure loss in these two areas. The pressure loss of the Raymond mill is approximately equal to the sum of the wear in the blade area and the grinding roller area. When the inlet wind speed increases to 31m / s, the pressure loss is 1050Pa, almost double that at an inlet wind speed of 23m / s. Therefore, the higher the wind speed, the greater the energy loss.

[0170] Combine Figures 16-1 to 16-6 As shown, the transient flow field and particle position analysis process of the Raymond Mill machine in this embodiment is as follows:

[0171] When studying the effect of inlet wind speed on gravity classification, transient solution is used to consider time factors and the changes of system state over time. According to the simulation results, the changes of wind field traces and cross-section speed over time are analyzed, and the changes of particle positions of different particle sizes at different times are analyzed. Due to the bidirectional coupling between the continuous phase wind field and the discrete phase particles and the transient solution, when the material is just launched, due to the large number of particles at the beginning, the particles have an obstructive effect on the wind field, so in Figures 16-1 to 16-3It can be seen that the wind field traces are relatively sparse. As time goes by, some particles are transported to the outlet for removal, and the wind field traces gradually become denser. The wind field traces also become more numerous and more uniform. This uniform wind field distribution helps ensure that the particles can be effectively transported to the outlet and can improve the collection efficiency and stability of the Raymond Mill blower.

[0172] Combine Figures 16-4 to 16-6 It can be seen that after the particles are ground by the grinding roller and grinding ring, they are transported to the outlet of the whole machine by the system air volume input by the air inlet box. In the Fluent simulation, particles of different particle sizes are emitted from the four grinding roller surfaces and spiral upward under the action of the wind field. After 0.1s, the particles move to Figure 16-4 At the position shown, as the system continues to input air volume, coarse and fine particles gradually separate in the process of spiral rise. Due to the greater gravity of coarse particles, they tend to aggregate during the transportation process, and some particles fall along the wall. After another 0.1s, according to Figure 16-6 It can be seen that the finished particles are transported to the gravity classification area before the coarse particles, and then transported to the centrifugal classification area. The coarse particles reach the gravity classification area later, or remain in the Raymond mill main unit and finally complete the gravity classification.

[0173] The process of analyzing the pass rate of the gravity classification outlet surface in this embodiment is as follows:

[0174] In order to explore the influence of different inlet wind speeds on the pass rate of gravity classification, five groups of experiments were designed. According to the requirements of the enterprise, five groups of particles with different particle sizes were put into each group of experiments, including three finished particles and two coarse particles. The sliding grid was used to simulate the rotation of the scraper, grinding roller, main shaft and plum blossom frame. The boundary conditions were input in Fluent and the simulation was completed. The calculation method of the gravity classification particle pass rate P is as follows: After the Fluent transient simulation calculation is completed, the statistics of the particle information captured at the outlet of the whole machine are completed in the Sample of Discrete Phase under Reports, and the mass flow rate of particles of each mesh size is obtained. For example, when the inlet wind speed is 23m / s, the mass flow rates of 200, 115 and 80 mesh collected are 0.0237, 0.0239 and 0.0229kg / s respectively. The incident time interval is 0.01s, a total of ten incidents, and the total incident time is 0.1s. The gravity classification finished product pass rate P is

[0175]

[0176] According to the above calculation method, the particle mass collected at the gravity classification outlet plane is shown in Table 4:

[0177] Table 4 Particle passing rate of different sizes under different system air volumes

[0178]

[0179]

[0180] The present invention also carries out the gravity classification outlet surface wind speed and theoretical verification process, specifically:

[0181] As the inlet wind speed increases, the collection efficiency of finished products and coarse products at the gravity classification outlet plane also increases. This is because the greater the wind speed, the more particles will be blown out of the outlet and collected. However, when the inlet wind speed is 25m / s, as shown in Table 4, the cutting particle size is 45 mesh, that is, 325 microns, and the coarse product collection efficiency is 49.88%. Using the Allen formula, the particle settling velocity is calculated to be

[0182]

[0183] The average Y-direction velocity of the test 6 outlet collected in Fluent is 1.82m / s. In order to better describe the error between the Fluent simulation results and the theoretical calculation, the difference between the simulation data and the theoretical calculation data is calculated by comparing the difference with the theoretical calculation data to obtain the calculated error:

[0184]

[0185] According to the above research, the calculation error is 3.4%. In subsequent research, the system air volume can be selected with a wind speed of 25m / s, and the optimal value of the classifier shell radius is 1500mm.

[0186] The present invention may have many other embodiments. Without departing from the spirit and essence of the present invention, those skilled in the art may make various corresponding changes and modifications based on the present invention, but these corresponding changes and modifications should all fall within the scope of protection of the claims attached to the present invention.

Claims

1. A method for predicting and evaluating gravity classification of a Raymond Mill, characterized by: The gravity classification prediction and evaluation method is to use a steady-state solution method to determine the classifier shell radius index under the premise of ensuring a uniform flow field and a small overall pressure loss, and then build a host primary model. The transient solution method is used to analyze the change law of the gravity classification outlet wind speed and the overall pressure loss value to determine the inlet wind speed index. The inlet wind speed index is used to reconstruct the Raymond mill host primary model to form a host intermediate model. The inlet wind speed index is combined with the particle size segmentation method to obtain the cutting particle size index and the particle settling velocity index. The host intermediate model is constructed based on the cutting particle size index and the particle settling velocity index to form the host ultimate model. The host ultimate model is used to complete the prediction process of the unestablished Raymond mill related data or the evaluation process of the established Raymond mill related performance data. The process of obtaining the index of the radius of the classifier shell is as follows: After the material is fed into the Raymond mill inlet, it is ground by the grinding roller and grinding ring. The powder that reaches a certain fineness is sent to the gravity classification area by the air blown in by the air inlet box to complete the first classification. According to the theory of flow velocity and arbitrary cross-sectional area, the improved gravity classification outlet cross-sectional radius is the classifier shell radius. According to the Fluent simulation results, the internal flow field velocity and wind field trajectory of the Raymond mill are compared. The velocity distribution in the grinding roller and host shell area is uniform. The particles will be sent to the gravity classification area at a speed of 0~30m / s. The corresponding classifier shell radius is used as the classifier shell radius index. The wind track line corresponding to the classifier shell radius index spirals upward evenly and has a clear boundary in the gravity classification area. After determining the classifier shell radius index, the primary model of the host is constructed using 3D software. The process of deriving the inlet wind speed index is: The air volume of the Raymond mill system is the driving force in the process of transporting materials of a certain fineness to the gravity classification area and the centrifugal classification area. When the system air volume is too large, the air velocity entering the two classification areas will be too high, resulting in coarse particles. When the system air volume is too small, the qualified particles cannot be selected in time after passing through the classification area, and the material layer will be accumulated, resulting in over-grinding and affecting the output. According to the process of determining the radius index of the classifier shell, the plum blossom frame, grinding roller and scraper area in the primary model of the host are applied with sliding grids, and transient solution is adopted. The four grinding roller surfaces are used as the particle emission surfaces. Five groups of particles are injected using the uniformity method, and the particle diameters are 75, 125, 180, 270 and 380 respectively. , the system air volume is 42000 、45500 、49200 , 53000 and 56500 , where the wind speed and wind volume conversion method is （1） In the above formula, is the inlet air volume, ; is the ventilation area of the vent, ; is the average velocity at the air outlet, m / s.

2. The method for predicting and evaluating gravity classification of a Raymond mill according to claim 1, wherein: According to formula (1), the inlet wind speeds of the five tests are 23m / s, 25m / s, 27m / s, 29m / s and 31m / s, the mass flow rate of each group of particles is 3.333kg / s, the incident time is 0.1s, and there are ten incidents in total. The other working conditions remain unchanged. Five groups of simulation tests are carried out, specifically: Each test involved five groups of particles of varying sizes, including three finished products and two coarse products. A sliding mesh was used to simulate the rotation of the scraper, roller, spindle, and mill frame. Boundary conditions were entered in Fluent, and the simulation was completed. The passing rate of gravity classification particles The calculation method is as follows: After the Fluent transient simulation is completed, the statistics of the particle information captured at the outlet of the whole machine are completed in the Sample of Discrete Phase under Reports, and the mass flow rate of particles of each mesh size is obtained. When the inlet wind speed is 23m / s, the mass flow rates of 200, 115 and 80 mesh collected are 0.0237, 0.0239 and 0.0229kg / s respectively. The injection time interval is 0.01s, and there are ten injections in total, with a total injection time of 0.1s. The pass rate of the finished product of gravity classification is: The inlet wind speed corresponding to the highest value is used as the inlet wind speed index; After determining the inlet wind speed index, the host primary model is supplemented and constructed using three-dimensional software to form a host intermediate model.

3. The method for predicting and evaluating gravity classification of a Raymond mill according to claim 2, wherein: The inlet wind speed index is combined with the segmentation particle size method to obtain the cut particle size index and the particle settling velocity index, specifically: The cut particle size index is obtained according to the inlet wind speed index. The process of calculating the particle settling velocity by combining the inlet wind speed index and the cut particle size index with the Allen formula is as follows: Formula for free sedimentation of particles in fluid: The buoyancy and self-gravity do not increase with the increase of gas flow rate. According to the balance of the three forces, the calculation formula of the theoretical gravity classification zone cutting particle size is obtained. Since the particle Reynolds number belongs to the transition zone, the free sedimentation of spherical particles and the transition zone is applicable to the Allen formula, which is: （2） In the above formula, is the acceleration due to gravity, m / s 2 ; is the medium density, kg / m 3 ; Thus the particle settling velocity is calculated.

4. The method for predicting and evaluating gravity classification of a Raymond mill according to claim 3, wherein: According to the cutting particle size index and the particle settling velocity index, the host intermediate model is supplemented and constructed to form the host ultimate model. The simulation data corresponding to the host ultimate model is compared with the unestablished Raymond mill related data. When the error between the simulation data corresponding to the host ultimate model and the unestablished Raymond mill related data is less than 5%, it means that the unestablished Raymond mill related data is reliable and can be put into use; when the error between the simulation data corresponding to the host ultimate model and the unestablished Raymond mill related data is greater than 5%, it means that the unestablished Raymond mill related data needs to be recalculated.

5. The method for predicting and evaluating gravity classification of a Raymond mill according to claim 3, wherein: The host intermediate model is supplemented and constructed based on the cutting particle size index and the particle settling velocity index to form the host ultimate model. The simulation data corresponding to the host ultimate model is compared with the established Raymond mill related performance data. When the error between the simulation data corresponding to the host ultimate model and the established Raymond mill related performance data is less than 10%, it means that the established Raymond mill related performance is good. When the error between the simulation data corresponding to the ultimate model of the host and the relevant performance data of the established Raymond mill is greater than 10%, it means that the basic performance of the established Raymond mill needs to be improved.

Images