Gravity grading prediction and evaluation method for Raymond machine

Abstract

The invention discloses a gravity grading prediction and evaluation method for a Raymond mill, and belongs to the technical field of mechanical engineering. According to the gravity grading prediction evaluation method, a steady-state solving method is adopted to determine and obtain a grading machine shell radius index on the premise of ensuring a uniform flow field and a small whole machine pressure loss amount, and then a main machine primary model is constructed; an inlet and outlet wind speed index is determined by analyzing a gravity grading outlet wind speed change rule and a whole machine pressure loss value by adopting a transient solving method, and secondary construction is performed on a Raymond machine main machine primary model by utilizing the inlet wind speed index to form a main machine intermediate model; combining an inlet wind speed index with a particle size segmentation mode to obtain a cutting particle size index and a particle settling velocity index, and constructing the host intermediate model according to the cutting particle size index and the particle settling velocity index to form a host ultimate model; and completing a prediction process of related data of the unestablished Raymond mill or an evaluation process of related performance data of the established Raymond mill through the host ultimate model.

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] In the important industries of mining, construction, metallurgy, environmental protection, electricity, chemistry and aerospace, large and complex particle-fluid system equipment such as grinding mills play a vital role. This type of equipment has obvious characteristics: high value, complex design structure, multi-point monitoring and long product life cycle. During the working process of these particle and fluid coupling systems, the internal fluid will exert drag, lift or pressure on the particles, causing the particles to move. This process not only involves collisions between particles and between particles and solid walls, but also the movement of particles will in turn affect the flow of fluids. This complex interaction makes it more complicated and difficult to fully and accurately understand the physical processes such as the movement, distribution and collision characteristics of particle groups in fluid systems. Accurately grasping the fluid-solid two-phase flow state in the powder system is of great significance to improving the transportation efficiency of equipment, reducing equipment surface wear and optimizing the utilization of resources.

[0003] Large Raymond mills integrate multiple functions such as crushing, grinding, screening and transmission. The entire workflow is a complex process involving the coupling of multiple physical fields such as fluid dynamics, particle dynamics and grinding. Raymond mills, also known as pendulum mills, use the main motor to drive the central shaft with a plum blossom frame to rotate. The grinding rollers are connected to the plum blossom frame through horizontal hinges, forming the support point for its swing. Driven by the plum blossom frame, the grinding rollers begin to rotate, and under the action of centrifugal force, they tightly press the grinding rings, and realize their own rotation through friction, thereby crushing the materials. The scraper at the bottom of the plum blossom frame is responsible for lifting the materials. During operation, the grinding rollers and scrapers rotate together, throwing the materials upward and filling them between the grinding rollers and the grinding rings to form a material layer. This material layer is crushed under the outward centrifugal force generated by the revolution of the grinding rollers. At the same time, the airflow 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 product is 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 it is difficult to cater to the trend of my country's fine powder industry to develop towards high-end;

[0006] 2. The machinery fails frequently and emits a lot of pollutants;

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

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

[0009] The limestone raw material is transported to the Raymond Mill through the feed port and ground under the rotation of the grinding roller and grinding ring. The material that reaches the specified fineness will be selected after two classification processes. First, the first classification is carried out by gravity between the main outlet of the Raymond Mill and the bottom of the classifier shell. This stage is mainly based on the difference in gravity of particles of different particle sizes to preliminarily screen the particles, which is called pre-selection or gravity classification. This process has an important influence on the particle size distribution of particles in the centrifugal classification area, which in turn affects the circulation load and classification efficiency of the classifier, and ultimately affects the output and fineness of the product. At present, there is no systematic method that can accurately quantify the gravity classification of the Raymond Mill, nor has it been possible to comprehensively analyze the crux of the collection efficiency and energy consumption reduction of the Raymond Mill, and there is no relevant quantitative evaluation method for the collection efficiency and energy consumption reduction of the Raymond Mill. Summary of the invention

[0010] There is no systematic method in the prior art that can accurately and quantitatively analyze the gravity classification of the Raymond Mill, nor is there a comprehensive analysis of the key issues 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 whole machine pressure loss, and then constructs a host primary model. A transient solution method is used to analyze the gravity classification outlet wind speed change law and the whole machine 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 a segmentation particle size method to obtain a cutting particle size index and a 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 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 a preferred solution: the process of determining the radius index of the classifier shell by using the steady-state solution method under the premise of ensuring a uniform flow field and a small pressure loss of the whole machine is as follows:

[0013] After the material is put into the feeding port 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 wind blown in by the air inlet box to complete the first classification. According to the flow velocity and arbitrary cross-sectional area theory, 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 main machine shell area is uniform. The particles will be sent to the gravity classification area at a speed of 0 to 30 m / 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 main machine 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 is too large, resulting in coarseness; when the system air volume is too small, the qualified particle diameter cannot be selected in time after passing through the classification area, and a material layer is formed after accumulation, resulting in over-grinding, which affects the output; according to the determination process of the radius index of the classifier shell, the plum blossom frame, grinding roller and scraper area in the primary model of the host machine are applied with sliding grids, and transient solution is adopted. The four grinding roller surfaces are used as the particle emission surfaces, and five groups of particles are put in by the uniformity method. The particle diameters are 75, 125, 180, 270 and 380μm respectively, and the system air volume is 42000m 3 / h、45500m3 / h、49200m 3 / h、53000m 3 / h and 56500m 3 / h, where the wind speed and wind 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 with different particle sizes were put into 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 input in Fluent and the simulation was completed. The calculation method of the gravity classification particle pass rate P was as follows: after the Fluent transient simulation calculation was completed, the statistics of the particle information captured at the outlet of the whole machine were completed 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 mass flow rates of 200, 115 and 80 mesh were collected as 0.0237, 0.0239 and 0.0229kg / s respectively. The incident time interval was 0.01s, and there were ten incidents in total. The total incident time was 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 primary model of the host is supplemented and constructed using three-dimensional software to form an intermediate model of the host.

[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] The formula for free settling of particles in a fluid is:

[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 spherical particles and the free sedimentation applicable to the transition zone are 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 can be calculated.

[0027] As a preferred solution: the host intermediate model is supplemented for the second time according to 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 calculated again.

[0028] As a preferred solution: the host intermediate model is supplemented for the second time according to 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] 1. The present invention obtains comprehensive indicators that affect the collection efficiency and energy consumption reduction of the Raymond mill through analysis, which are the classifier shell radius indicator, inlet wind speed indicator, cutting particle size indicator and particle settling speed indicator, and combines relevant methods to form a process of gradually improving step-by-step models until the ultimate model is formed. Not only can the prediction process of the unestablished Raymond mill related data be evaluated through the data corresponding to the ultimate model, but the evaluation process of the established Raymond mill related performance data can also be completed through the data corresponding to the ultimate model.

[0031] Second, the present invention is conducive to analyzing the flow field law, and finally analyzing and collating the test data, reducing the internal pressure loss of the host, improving the efficiency of gravity classification and centrifugal classification, finding measures to jointly improve the classification efficiency, and reducing energy consumption. The present invention is conducive to studying the relationship between flow parameters and pressure loss, flow rate and classification efficiency, ensuring that the material can be effectively transmitted to the outlet of the classifier. It is conducive to improving the fineness of the product and the separation efficiency of the finished powder, while reducing the failure rate of the machinery. 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 the total flow;

[0034] Figure 3 It is a 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 position of the dimensions when the radius of the classifier shell is 1240mm;

[0037] Figure 6-1 It is a schematic diagram of the simulation of the internal flow field velocity of the Raymond mill according to 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 It is a schematic diagram of the simulation of the internal flow field velocity of the Raymond mill according to 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 It is a schematic diagram of the simulation of the internal flow field velocity of the Raymond mill according to 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 It is a schematic diagram of the simulation of the internal flow field velocity of the Raymond mill according to 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 surface in Test 5. In the figure, the velocity file of the gravity graded outlet surface is exported in Fluent and imported into Tecplot software for post-processing of the gravity graded outlet surface. Since the velocity is symmetrically distributed, only one-quarter of the cross section is 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 surface in Test 6. In the figure, the velocity file of the gravity graded outlet surface is exported in Fluent and imported into Tecplot software for post-processing of the gravity graded outlet surface. Since the velocity is symmetrically distributed, only one-quarter of the cross section is taken for comparative analysis with other tests.

[0047] Figure 10-3 This is a simulated wind speed diagram of the gravity graded outlet surface in Test 7. In the figure, the velocity file of the gravity graded outlet surface is exported in Fluent and imported into Tecplot software for post-processing of the gravity graded outlet surface. Since the velocity is symmetrically distributed, only one quarter of the cross section is taken for comparative analysis with other tests.

[0048] Figure 10-4 This is a simulated wind speed diagram of the gravity graded outlet surface in Test 8. In the figure, the velocity file of the gravity graded outlet surface is exported in Fluent and imported into Tecplot software for post-processing of the gravity graded outlet surface. Since the velocity is symmetrically distributed, only one quarter of the cross section is 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 surface in Test 9. In the figure, the velocity file of the gravity graded outlet surface is exported in Fluent and imported into Tecplot software for post-processing of the gravity graded outlet surface. Since the velocity is symmetrically distributed, only one-quarter of the cross section is taken for comparative analysis with other tests.

[0050] Fig.11 It is a schematic diagram of the location of the acquisition line and the outlet surface;

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

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

[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 The second response surface diagram of the interaction of various factors shows the interaction between the spindle speed and the outlet pressure of the whole machine;

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

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

[0057] Figure 16-1 This is a schematic diagram of the wind field trajectory of the wind field speed at 1.2s in the Raymond machine;

[0058] Figure 16-2 This is a schematic diagram of the wind field trajectory of the wind field speed at 1.3s in the Raymond machine;

[0059] Figure 16-3 This is a schematic diagram of the wind field trajectory of the wind field speed at 1.4s in the Raymond machine;

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

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

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

[0063] Fig.17 It 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] In order to make the purpose, technical scheme and advantages of the present invention clearer, the present invention is described below by the specific embodiments shown in the accompanying drawings. However, it should be understood that these descriptions are only exemplary and are not intended to limit the scope of the present invention. In addition, in the following description, the description of well-known structures and technologies is omitted to avoid unnecessary confusion of the concept of the present invention.

[0065] Specific implementation method 1: Combination Figures 1 to 17The present embodiment is described. The gravity grading prediction and evaluation method in the present embodiment is to use a steady-state solution method to determine the radius index of the classifier shell under the premise of ensuring a uniform flow field and a small pressure loss of the whole machine, and then construct a primary model of the host machine. The transient solution method is used to analyze the change law of the gravity grading outlet wind speed and the pressure loss value of the whole machine 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 an intermediate model of the host. 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 intermediate model of the host is constructed according to the cutting particle size index and the particle settling velocity index to form the ultimate model of the host. The prediction process of the unestablished Raymond mill related data or the evaluation process of the established Raymond mill related performance data is completed through the ultimate model of the host.

[0066] The gravity classification prediction and evaluation method in this embodiment is used in the gravity classification area of ​​the host. Through various analyses, the classifier shell radius index, inlet wind speed index, cutting particle size index and particle settling speed index are determined, and the four indicators are used to form a process of gradually establishing and improving the ultimate model of the host. The four indicators can comprehensively evaluate the collection efficiency and energy consumption reduction in the gravity classification area of ​​the host.

[0067] Combination 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 speed u of the particle relative to the fluid can be expressed as the difference between the fluid speed and the particle speed. 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 speed of the particle relative to the fluid is the sum of the two speeds, 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 effect 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 particles 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 falling particles 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 force is weak and cannot completely offset the residual gravity of the particles. This causes the particles to sink downward under the action of gravity, and in addition to overcoming the friction force, there is an additional force that pushes the particles down with a positive acceleration. As the velocity increases, the friction force gradually increases until it reaches equilibrium with the residual gravity of the particles.

[0077] When the fluid velocity is high, the initial friction force is sufficient to overcome the residual gravity of the particles, causing the particles to move with the fluid. As time goes by, the friction force gradually decreases until it is balanced with the residual gravity 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, they will always reach a balance after a period of time. u-u0. Substituting the second relation into Formula 3, we get Formula 6:

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

[0080] In the above formula, u f is the fluid rising speed 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 that flows vertically, they will initially fall faster due to gravity. However, as time goes by, 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 uniform speed. In this state, the particle's velocity u relative to the fluid becomes a fixed value, which is equivalent to the particle's settling velocity in a static state of the same fluid. The absolute velocity of the particle u p , and its direction of movement, is determined by the particle settling velocity and the fluid velocity u fThe difference determines .

[0082] When the fluid velocity u f When it is equal to the stable settling 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 time is called the suspension velocity of particles of this size, which is numerically equivalent to the sedimentation velocity of particles in a stationary fluid.

[0083] When the fluid velocity u f When it is greater than the stable settling 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 is smaller than the stable settling velocity u0 of the particle, that is, u p >0, the particles will continue to settle. In summary, the absolute speed and movement direction of particles in the fluid depend on the relationship between their settling velocity and the fluid velocity.

[0084] Specific implementation method 2: This implementation method is a further limitation of the specific implementation method 1. This implementation method uses a steady-state solution method to determine the process of obtaining the classifier shell radius index under the premise of ensuring a uniform flow field and a small pressure loss of the whole machine:

[0085] After the material is put into the feeding port 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 wind blown in by the air inlet box to complete the first classification. According to the flow velocity and arbitrary cross-sectional area theory, 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 main machine shell area is uniform. The particles will be sent to the gravity classification area at a speed of 0 to 30 m / 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 main machine is constructed using 3D software.

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

[0087] Combination 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 wind 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 velocity and arbitrary cross-sectional area, it is very meaningful to improve the radius of the gravity classification outlet cross-sectional area, that is, the radius of the classifier shell. In order to study the influence of the shell shape of the classifier on the Raymond mill flow field and classification and screening performance, based on the original model of a large Raymond mill with a shell radius of 1240mm, its cross-sectional shape is as follows Figure 5 Four different radii of the classifier shell are designed. Tests 1, 2, 3 and 4 represent the classifier shell radii of 1170, 1240, 1500 and 1720 mm respectively. The other dimensions remain unchanged. Among them, the original model corresponds to a dimension of 1240 mm.

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

[0089] Combination Figure 6-1 , 6-2 , 7-1, 7-2, 8-1, 8-2, 9-1, 9-2 to Fig.12 As shown in Figure 2, according to the four designed classifier shell radii, four groups of single-factor simulation experiments were designed. According to the Fluent simulation results, the internal flow field velocity and wind field trajectory of the Raymond mill were 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 indicates 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 occurs in the local area, indicating that the wind field is unevenly distributed. 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] In the formula, 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, which belongs to the transition zone, and the drag coefficient is

[0097]

[0098] The formula for the free settling of particles in the fluid is: the buoyancy and self-gravity do not increase with the increase of the gas flow rate. According to 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 of spherical particles and applicable to the transition zone is the 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, the law of change of fluid along the flow direction in the total flow is studied, 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 of the flow space between the two end surfaces, which reflects the different density on different sections:

[0104] A1V1=A2V2 (11)

[0105] According to the above theory, the flow velocity and the arbitrary cross-sectional area have the following relationship:

[0106] u0A0=u1A1 (12)

[0107]

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

[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 is too large, resulting in coarseness; when the system air volume is too small, the qualified particle diameter cannot be selected in time after passing through the classification area, and a material layer is formed after accumulation, resulting in over-grinding, which affects the output; according to the determination process of the radius index of the classifier shell, the plum blossom frame, grinding roller and scraper area in the primary model of the host machine are applied with sliding grids, and transient solution is adopted. The four grinding roller surfaces are used as the particle emission surfaces, and five groups of particles are put in by the uniformity method. The particle diameters are 75, 125, 180, 270 and 380μm 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:

[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 with different particle sizes were put into 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 input in Fluent and the simulation was completed. The calculation method of the gravity classification particle pass rate P was as follows: after the Fluent transient simulation calculation was completed, the statistics of the particle information captured at the outlet of the whole machine were completed 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 mass flow rates of 200, 115 and 80 mesh were collected as 0.0237, 0.0239 and 0.0229kg / s respectively. The incident time interval was 0.01s, and there were ten incidents in total. The total incident time was 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 primary model of the main engine is supplemented and constructed using 3D software to form an intermediate model of the main engine.

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

[0116] Specific implementation method 4: This implementation method is a further limitation of specific implementation methods 1, 2 or 3. This implementation method 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] The formula for free settling of particles in a fluid is:

[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 spherical particles and the free sedimentation applicable to the transition zone are 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 can be calculated.

[0122] Specific implementation method five: This implementation method is a further limitation of specific implementation methods one, two, three or four. This implementation method 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 calculated again.

[0123] Specific implementation method six: This implementation method is a further limitation of specific implementation methods one, two, three, four or five. This implementation method 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 implementation method 7: This implementation method is a further limitation of specific implementation methods 1, 2, 3, 4 or 5. The present invention also involves a process of constructing a sliding grid model for a rotating area in a gravity classification area, specifically:

[0125] The sliding mesh model is used to express the dynamic changes that allow relative sliding between adjacent meshes, so that the mesh faces do not need to be completely aligned on the interface. By applying this physical model, the flow through each mesh interface area can be accurately simulated while ensuring computational efficiency, especially the accurate flow calculation in the non-uniform interface area. This is crucial for solving fluid flow problems in engineering applications.

[0126] In the analysis of interfacial flow, as time goes by and the interface moves relative to each other, internal and periodic regions will be generated at the interface. If these wall regions are not completely fitted, appropriate boundary conditions must be used to handle them.

[0127] The focus is on handling overlapping and non-overlapping interface regions, combining Figure 3 As shown in Figure 1, overlapping interface regions generate internal regions, which requires 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 usually correspond to periodic regions, which are characterized by the number of faces in the interface region changing with the relative movement.

[0128] The challenge of sliding mesh technology is to deal with these dynamically changing interfaces to ensure the accuracy and efficiency of flow calculation. Through reasonable design, the sliding mesh model can effectively simulate complex phenomena such as rotating machinery and the interaction between fluid and solid structure, and is one of the important tools in the field of computational fluid dynamics (CFD). The successful application of this technology depends on accurate mesh division, reasonable boundary condition setting and efficient numerical calculation methods to ensure the accuracy and reliability of the analysis results.

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

[0130] The specific process of establishing the sliding grid 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, the sliding grid problem can be calculated using Formula 14.

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

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

[0143] Table 2 Pressure loss in gravity classification area

[0144]

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

[0146] In this embodiment, the influence process of flow field parameters on the flow field and particle screening of the Raymond Mill 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 when the radius of the classifier shell is 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 implementation 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 is too large, and some particle sizes that do not meet the requirements are selected, resulting in coarse particles. When the system air volume is too small, the qualified particle diameter cannot be selected in time after passing through the classification area, and a material layer is formed after accumulation, 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 carried out.

[0154] In this embodiment, the influence of the system air volume on the flow field of the Raymond mill is:

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

[0156] Combination Figure 10-1 to Figure 10-5 , Fig.11 and Fig.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. Export the velocity file of the gravity classification outlet in Fluent and import it into Tecplot software to post-process the gravity classification outlet. 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 speed only appears in a local position, while the maximum wind speed of 15m / s in Figure 10-2 is evenly distributed on the gravity classification outlet surface. The even speed distribution is conducive to the transportation of particles from the outlet surface to the centrifugal classification area. In order to better observe the change in the value of the outlet edge speed, a data acquisition line line1 is established at the gravity classification outlet, where the starting and ending coordinates of line1 are (0.95775, 3.87454, 1.14141) and (0, 3.87454, 0), respectively. Five sets of test speed magnitude change data with X-axis displacement are exported from Fluent and imported into Origin for data processing. After the airflow passes through the scraper roller area, it continues to move upward, and the speed gradually increases from the center of the gravity classification surface to the edge speed. In test 5, the maximum speed reaches 14.92m / s, and in test 9, the maximum speed reaches 20.5m / s. By observing the change of 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 process of analyzing 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 gravitational acceleration, m / s2; z represents spatial position, m;

[0161] According to 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] The difference between P2 and P1 in the above formula is the pressure loss of the Raymond mill.

[0164] When the fluid flows through the wall structure of the mill, the pressure is inevitably reduced 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 finished products, the kinetic energy change caused by the speed change should remain stable, and the potential energy change should be consistent with the equipment height; therefore, the increase in pressure loss will lead to 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 Fig.15As shown in the figure, when the outlet pressure of the whole machine remains unchanged, with the increase of inlet wind speed and the continuous decrease of spindle speed, the pressure loss of the main engine also increases continuously. When the inlet wind speed is 46m / s and the spindle speed is 100r / min, the pressure loss of the main engine reaches a maximum value of 1660Pa. When the spindle speed remains unchanged, with the continuous increase of inlet wind speed and the continuous decrease of main engine outlet pressure, the pressure loss of the main engine also increases continuously, with a maximum value of about 1320Pa. When the inlet wind speed remains unchanged, with the continuous decrease of spindle speed and main engine outlet pressure, the pressure loss of the main engine increases slowly, with a maximum value of about 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 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 roller when y=1.954m, and the outlet plane is extracted in Fluent, and the pressure data of each surface under different inlet wind speeds are calculated to obtain the scraper area and the whole machine pressure loss and its change curve. The data formed by each curve is as shown in Table 3 below:

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

[0168]

[0169] Depend on Fig.14 and Fig.15 It can be seen that when the spindle speed remains unchanged, as the inlet wind speed increases, the pressure loss in the scraper area and the grinding roller area also increases. The particles are emitted from the grinding roller surface and transported upward under the action of the airflow. In this process, the particles constantly collide with the scraper and the grinding roller, so the pressure loss in these two places is relatively large. The pressure loss of the Raymond mill is approximately equal to the sum of the wear in the scraper area and the wear in the grinding roller area. When the inlet wind speed increases to 31m / s, the pressure loss is 1050Pa, which is almost twice that when the inlet wind speed is 23m / s. Therefore, the higher the wind speed, the greater the energy loss.

[0170] Combination Figures 16-1 to 16-6 As shown, the transient flow field and particle position analysis process of the Raymond Mill 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 status 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. Since the continuous phase wind field and discrete phase particles are bidirectionally coupled and transient solution is used, 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 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 discharge, and the wind field traces gradually become denser. The wind field traces become more numerous and more uniform. This uniform wind field distribution helps to ensure that the particles can be effectively transported to the outlet and can improve the collection efficiency and stability of the Raymond Mill.

[0172] Combination Figure 16-4 to Figure 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 intake 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 are easy to gather 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 host, and finally complete the gravity classification.

[0173] The process of gravity classification outlet surface pass rate analysis 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 tests were designed according to the requirements of the enterprise. Five groups of particles with different particle sizes were put into 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 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, it can be seen from Table 4 that the cutting particle size is 45 mesh, that is, 325 microns, and the collection efficiency of coarse products is 49.88%. The particle settling velocity calculated by the Allen formula is

[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 compared with the theoretical calculation data to obtain the calculation 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 also 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 in that: The prediction and evaluation method for gravity classification is to use a steady-state solution method to determine the radius index of the classifier shell under the premise of ensuring a uniform flow field and a small pressure loss of the whole machine, and then build a primary model of the host. The transient solution method is used 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 inlet wind speed index is used to reconstruct the primary model of the Raymond mill host to form an intermediate model of the host. The inlet wind speed index is combined with the segmentation particle size method to obtain the cutting particle size index and the particle settling velocity index. The intermediate model of the host is constructed according to the cutting particle size index and the particle settling velocity index to form the ultimate model of the host. The ultimate model of the host 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.

2. A method for predicting and evaluating gravity classification of a Raymond mill according to claim 1, characterized in that: The process of determining the radius index of the classifier shell by using the steady-state solution method while ensuring a uniform flow field and a small pressure loss of the entire machine is as follows: After the material is put into the feeding port 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 wind blown in by the air inlet box to complete the first classification. According to the flow velocity and arbitrary cross-sectional area theory, 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 main machine shell area is uniform. The particles will be sent to the gravity classification area at a speed of 0 to 30 m / 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 main machine is constructed using 3D software.

3. A method for predicting and evaluating gravity classification of a Raymond mill according to claim 1 or 2, characterized in that: The process of determining the inlet wind speed index by 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 is as follows: 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 is too large, resulting in coarseness; when the system air volume is too small, the qualified particle diameter cannot be selected in time after passing through the classification area, and a material layer is formed after accumulation, resulting in over-grinding, which affects the output; according to the determination process of the radius index of the classifier shell, the plum blossom frame, grinding roller and scraper area in the primary model of the host machine are applied with sliding grids, and transient solution is adopted. The four grinding roller surfaces are used as the particle emission surfaces, and five groups of particles are put in by the uniformity method. The particle diameters are 75, 125, 180, 270 and 380μm 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 wind volume conversion method is L = 3600 × F × V (1) 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; 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: Five groups of particles with 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 input in Fluent and the simulation was completed. The calculation method of the particle passing rate P of gravity classification 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 then 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 meshes collected are 0.0237, 0.0239 and 0.0229kg / s respectively, the time interval of incidence is 0.01s, there are ten incidences in total, and the total incidence time is 0.1s. The inlet wind speed corresponding to the highest value of the gravity classification finished product passing rate P 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.

4. The method for predicting and evaluating gravity classification of a Raymond mill according to claim 3 is characterized in that: 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, which are as follows: 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: The formula for free settling of particles in a fluid is: 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 spherical particles and the free sedimentation applicable to the transition zone are the Allen formula, which is: 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 can be calculated.

5. The method for predicting and evaluating gravity classification of a Raymond mill according to claim 4, characterized in that: According to the cutting particle size index and the particle settling velocity index, the host intermediate model is supplemented for the second time 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 calculated again.

6. The method for predicting and evaluating gravity classification of a Raymond mill according to claim 4, characterized in that: According to the cutting particle size index and the particle settling velocity index, the host intermediate model is supplemented 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.

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