A method for calculating the grinding capacity of a coal mill from the mill face rate
By introducing the grinding surface distance ratio (GSAR), the grinding output of the coal mill is calculated, which solves the problem of inaccurate output prediction after the retrofit of the existing ZGM coal mill and realizes a high-precision output retrofit design.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- BEIJING KANGSHENGHONGDA TECH CO LTD
- Filing Date
- 2026-03-20
- Publication Date
- 2026-06-19
AI Technical Summary
The existing ZGM coal mill lacks an accurate grinding output prediction model after modification, resulting in blind setting of operating parameters and sluggish adjustment response, making it difficult to balance output improvement and equipment stability.
The concept of grinding surface distance ratio (GSAR) is introduced. By calculating the grinding range angle θ, grinding linear velocity and the arc chord ratio C of the grinding roller profile, and combining the proportional coefficient k, the grinding output of the coal mill is calculated.
It enables accurate prediction of the output of the coal mill after modification, improves the controllability and accuracy of the modification design, and meets the output modification requirements.
Smart Images
Figure CN122242024A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of coal mill technology, and specifically to a method for calculating the grinding output of a coal mill based on the grinding surface distance ratio. Background Technology
[0002] Influenced by the global energy structure transformation, the high proportion of new energy connected to the grid, and the trend of flexible transformation of thermal power plants, and with the advancement of carbon peaking and carbon neutrality goals, the role of thermal power generation in the energy system is shifting from baseload power to peak-shaving power, which puts forward higher requirements for the efficiency, flexibility and intelligence of coal mills.
[0003] To adapt to the variable load operation requirements under peak shaving conditions in thermal power plants, existing coal mill units urgently need to break through their original output limits and achieve a wider range of output regulation capabilities. Upgrading and improving the efficiency of coal mills has become one of the core directions for the technological upgrading of thermal power enterprises.
[0004] Taking the commonly used ZGM type coal mill as an example, the ZGM type medium-speed roller coal mill has become the mainstream pulverizing equipment in domestic thermal power plants due to its advantages such as compact structure, high grinding efficiency, low power consumption, and convenient adjustment of coal powder fineness. It has a large existing stock and concentrated demand for retrofitting. The ZGM type coal mill forms a grinding zone through a grinding disc and grinding rollers, combined with hot air drying, air-coal conveying, and dynamic / static separator classification, to achieve continuous pulverization and output of raw coal. However, due to limitations in original design parameters, coal type adaptability, and equipment aging, the existing ZGM coal mills generally suffer from insufficient rated output.
[0005] For ZGM coal mills, the grinding of raw coal is accomplished by three grinding rollers mounted on a grinding disc. These three rollers are evenly distributed and fixed around their circumference. A loading cylinder drives a pull rod to apply downward pressure, causing the grinding disc to rotate. The coal bed lies between the roller sleeves and the liners. The grinding action of the roller sleeves and liners crushes the raw coal into coal powder. The coal powder, propelled by the centrifugal force of the rotating grinding disc, reaches the nozzle ring and is carried away by the airflow for separation. Therefore, the size of the area between the grinding rollers and liners where the raw coal can be compressed determines the mill's crushing capacity, thus allowing calculation of the mill's final output. Common modification methods for ZGM coal mills include increasing the diameter of the grinding disc and widening the roller sleeves. For example, a power plant modified a ZGM95N coal mill (upgrading it to a ZGM95G model). By replacing the grinding disc, grinding rollers, and other major grinding components, the output increased by more than 10.7%. However, this data is a result of post-construction testing and evaluation. Reliable predictive methods are lacking before modification. The existing ZGM coal mill lacks an accurate grinding output prediction model after modification, resulting in blind setting of operating parameters and sluggish adjustment response, making it difficult to balance output improvement and equipment stability.
[0006] It is evident that the calculation of output for the modification of medium-speed roller mills is currently a blind spot. Most calculations are based on experience, which often results in actual output failing to meet customer requirements or having excessive redundancy due to a lack of rigor. Summary of the Invention
[0007] To alleviate or solve at least one aspect or point of the above-mentioned problems, the present invention is proposed. A method for calculating the grinding output of a coal mill based on the grinding surface distance ratio according to the present invention includes the following steps: Obtain the mill roller thickness B and pitch circle radius of the coal mill. Rated speed n, grinding roller radius Pitch circle radius Grinding roller radius The maximum distance t for grinding; Calculate the grinding range angle θ:
[0008] Calculate the effective area of grinding :
[0009] Calculate the grinding line speed:
[0010] Calculate the arc chord ratio C of the grinding roller profile:
[0011] Calculate the grinding surface moment factor:
[0012] Obtain the proportionality coefficient k; Calculate the grinding output of the coal mill .
[0013] Preferably, the range of values for t is: .
[0014] Preferably, obtaining the proportionality coefficient k includes setting k = 100-110.
[0015] Preferably, obtaining the proportionality coefficient k includes: calculating the GSAR of the coal mill before the modification, and obtaining the grinding output of the coal mill before the modification. .
[0016] Preferably, it is used for calculating the grinding output when modifying a coal mill.
[0017] Preferably, the grinding output of the coal mill is calculated. At that time, GSAR was calculated based on the parameters of the modified coal mill.
[0018] Preferably, if the working medium or operating conditions of the coal mill change, the coal mill output of the original coal mill is obtained based on the new working medium and operating conditions.
[0019] Preferably, the coal mill is a ZGM type coal mill.
[0020] Preferably, the effective grinding area is calculated. Based on the principle that the grinding range angle θ is relatively small, the effective grinding area is calculated through approximate simplification. .
[0021] Preferably, when calculating the grinding linear velocity, the linear velocity at the pitch circle position of the grinding disc is taken as the average value of the linear velocity of the entire grinding area.
[0022] This invention introduces the concept of grinding surface distance ratio (GSAR) and utilizes the proportionality coefficient k to accurately calculate grinding output. This fills a gap in the calculation field for improving coal mill output, elevating the calculation of output improvement design to a controllable stage and providing a reference for coal mill output improvement design.
[0023] In the calculation process, this invention introduces the grinding range angle θ, and based on the principle that the grinding range angle θ is relatively small, the calculation is simplified to obtain the effective grinding area. By introducing the arc-chord ratio C, the grinding curvature of the grinding roller is characterized, and the average linear velocity is introduced to characterize the grinding speed. The product of these three factors can effectively reflect the grinding output of the coal mill. Verification has confirmed that the parameters of this invention can predict the grinding output with extremely high accuracy and can meet the output modification requirements of coal mills. Attached Figure Description
[0024] Figure 1 This is a schematic diagram of the fit between the grinding disc and grinding rollers in an existing ZGM coal mill.
[0025] Figure 2 This is a three-dimensional schematic diagram of the existing ZGM coal mill grinding rollers.
[0026] Figure 3 Calculation of effective grinding area as an exemplary embodiment of the present invention A schematic diagram.
[0027] Figure 4 for Figure 2 A magnified view of the effective area location in the diagram.
[0028] Figure 5 This is a schematic diagram illustrating the calculation of the length of line segment UM, which is an exemplary embodiment of the present invention.
[0029] Figure 6 This is a cross-sectional schematic diagram of a grinding roller as an exemplary embodiment of the present invention.
[0030] Figure 7 This is a schematic diagram illustrating the relationship between the grinding surface distance ratio and the grinding output force, which is an exemplary embodiment of the present invention.
[0031] Figure 8 This is a schematic diagram illustrating the relationship between the calculated force and the actual output force using the method of the present invention, as an exemplary embodiment of the present invention. Detailed Implementation
[0032] The following description of embodiments of the present invention with reference to the accompanying drawings is intended to explain the overall inventive concept of the invention and should not be construed as a limitation thereof. In this invention, the same reference numerals denote the same or similar parts.
[0033] The features described herein may be implemented in different forms and should not be construed as limited to the examples described herein. Rather, the examples described herein are provided only to illustrate some of the many feasible ways of implementing the methods, apparatus, and / or systems described herein, which will become clear upon understanding the disclosure of the invention.
[0034] The terminology used herein is for the purpose of describing various examples only and is not intended to limit disclosure. Unless the context clearly indicates otherwise, the singular form is intended to include the plural form as well. The terms “comprising,” “including,” and “having” indicate the presence of the described features, quantities, operations, components, elements, and / or combinations thereof, but do not preclude the presence or addition of one or more other features, quantities, operations, components, elements, and / or combinations thereof.
[0035] To enable those skilled in the art to utilize the content of this invention, the following exemplary embodiments may be provided in conjunction with specific application scenarios, specific systems, device and component parameters, and specific connection methods. However, these embodiments are merely examples for those skilled in the art, and the general principles defined herein can be applied to other embodiments and application scenarios without departing from the spirit and scope of this invention.
[0036] According to an exemplary embodiment of the present invention: Figure 1 The diagram shown illustrates the fit (cross-sectional view) between the grinding rollers and the grinding disc of the ZGM coal mill. The main parameters include: D G —Grinding roller diameter, Rg—Grinding roller radius, Rm—Pitch circle radius, Dm—Pitch circle diameter, B—Grinding roller thickness, n—Grinding disc rotation speed. It is the angle between the centerline of the grinding roller and the grinding disc or horizontal plane.
[0037] Although Figure 1 The diagram illustrates the diameter D of the grinding roller. GTo characterize the size of the grinding roller, R can obviously also be used. G —represented by the radius of the grinding roller, the radius of the grinding roller R G D is the diameter of the grinding roller. G Half of it. Although Figure 1 The pitch circle radius Rm is used schematically to represent the size of the grinding disc. Obviously, the pitch circle diameter Dm can also be used, which is twice the pitch circle radius. It should be noted that, in this invention, the pitch circle radius Rm and the grinding roller radius R are used in the calculation process as an example. G It is used to calculate the speed difference, but obviously, the pitch circle diameter Dm and the grinding roller diameter D can be used instead. G The above conversion method is obviously equivalent to the present invention and is within the protection scope of the present invention.
[0038] like Figure 1 As shown, in the ZGM coal mill, the grinding of raw coal is accomplished by three grinding rollers located on the grinding disc. The curved surface of the grinding roller sleeves forms tangential contact with the grinding disc liner, achieving power transmission. Because the rotation radius of the grinding rollers and liners in the corresponding grinding areas varies gradually outside the tangential contact point, there is a difference in the linear velocity of the grinding rollers and liners at each grinding point. The resulting shear force and compressive force work together to grind and crush the raw coal particles. Due to the variation in the rotation radius of the grinding rollers and liners outside the tangential contact point, the linear velocity of the grinding rollers and liners at each grinding point is different, thus generating shear force to complete the grinding and crushing of the coal powder particles.
[0039] As shown in the figure, based on this principle, the concept of Grinding Surface Aspect Ratio (GSAR) is introduced, denoted by the symbol GSAR. It represents the effective grinding area. Grinding line speed , Curve ratio of grinding roller profile The product of these three factors is given by the following formula: It is used to characterize the theoretically effective volume of raw coal ground by the grinding rollers per unit time under normal grinding disc rotation conditions. Among them, the effective grinding area... For the direction of movement of the grinding roller, the grinding roller is at an angle The projection of the inner surface onto the grinding wheel. For ease of calculation, such as... Figure 1 As shown, the grinding rollers and the grinding disc are at an angle. , its projection on the millstone.
[0040] like Figure 2-4 The diagram illustrates the projection of the grinding roller onto the grinding disc, where the shaded area represents the effective grinding area. .like Figure 2-4As shown, M is the midpoint of HN, M is the tangent point between the grinding roller and the grinding disk, and the length of EM is the pitch circle radius Rm. N and H are the projections of the tangent arc N1H1 of the grinding roller onto the grinding disk. KM corresponds to the circumferential grinding arc of the grinding roller, U is the projection of point K onto the grinding disk, QN is the tangent line of the outer circle at point N, UM is the tangent line of the pitch circle at point M, FH is the tangent line of the inner circle at point H, and line segment KU is perpendicular to line segment UM, where the angle is... The grinding range angle is denoted by t. t is the maximum grinding distance. The value of t is determined by the maximum size of the coal block supplied to the mill by the coal feeder. Typically, the maximum size of the coal block supplied to the mill by the coal feeder is required to be 50mm. The distance between the circumferential grinding arc KM and the grinding disc ranges from 0 to 50mm, for example. Therefore, t in the figure is taken as 50mm.
[0041] like Figure 4 , 5 As shown, calculate the grinding range angle. To simplify the calculation, since UM is a tangent to LM, it is assumed that the lengths of the line UM and the arc LM are the same, and the length of UM is... Calculate the grinding range angle according to the arc length formula. Among them, the grinding range angle In radians:
[0042] Calculate the effective area of grinding ,like Figure 2-4 As shown, in this invention, the area of the shaded region enclosed by FHJN is used as the effective grinding area. For ease of calculation, JN is considered as a straight line. Therefore, the area of the shaded region is obtained by subtracting the area of triangle JQN from the area of trapezoid FHNQ.
[0043] To calculate the area of trapezoid FHNQ, since FHNQ is a right trapezoid and M is the midpoint of NH, the area of the trapezoid FHNQ = the length of line segment UM. B, due to the grinding range angle Smaller, therefore, the length of line segment UM = Thus, the following can be calculated: Area of trapezoid FHNQ =
[0044] Calculate the area of triangle JQN, such as Figure 2-4 As shown, since the grinding range angle θ is small, JN is considered as a straight line, and the area of triangle JQN = the area of triangle EQN minus the area of sector EJN. Area of triangle JQN =
[0045] Therefore, to obtain : .
[0046] Calculate the grinding line speed, such as Figure 2-4 As shown, the linear velocity at the pitch circle position of the grinding disc is taken as the average value of the linear velocity of the entire grinding area:
[0047] Calculate the arc-chord ratio C of the grinding roller profile, such as Figure 6 As shown, the arc length is the radial grinding arc length H1N1 of the grinding roller, and the chord length is the thickness B of the grinding roller: as Figure 6 As shown, the angle can be calculated first. = ; Arc length H1N1=2 Thus, the arc-chord ratio C is obtained:
[0048] Calculate the grinding surface moment factor: = , Right now for The function.
[0049] According to an exemplary embodiment of the present invention: calculating the K value. Obtaining the proportionality coefficient k includes: calculating the original coal mill's... To obtain the grinding output of the coal mill before the modification. .
[0050] Calculate the predicted output of the modified coal mill .in Based on the thickness B of the grinding rollers and the pitch circle radius of the modified coal mill Rated speed n, grinding roller radius Pitch circle radius Grinding roller radius The maximum grinding distance t is calculated.
[0051] Experimental verification: Table 1
[0052] As shown in Table 1 and Figure 7 As shown in Table 1, ZGM80G, ZGM95N, ZGM113N, ZGM123N, and ZGM133N were selected for verification calculations of this scheme. The k parameter in Table 1 is set to 106, and the error between the calculated output and the standard output is very small. Therefore, for the ZGM type coal mill, k can be taken as a predetermined value, such as 106. Meanwhile, referring to... Figure 7 As shown, it can be seen The specific force is directly proportional to the grinding output. By correcting with k, the calculated specific force is found to be very close to the standard output, which can be used in the design of grinding mills.
[0053] It should be noted that although the header of Table 1 indicates the units for each parameter, other units can obviously also be used; only the modified units are needed. During calculation, compared to before the modification All parameters can be used in the same unit.
[0054] Table 2
[0055] Table 2 and Figure 8 The table shows the calculation results of the Dujiangyan 95N mill renovation project using the method of this invention, and a comparison with the actual measurement results. As can be seen from Table 2, the k-coefficient is related to the specific circumstances of each project. Therefore, optionally, the k-coefficient of the old mill needs to be determined before each renovation, and then the renovation design can be carried out. Multiplying the k-coefficient calculated from the old mill by the grinding surface torque of the renovated coal mill yields the calculated output force. Combined with... Figure 8 It can be seen that the calculated output and the actual output are very close, which can fully meet the requirements of the transformation.
[0056] Preferably, if the operating conditions change during application, the k-coefficient needs to be adjusted. Since the output of a coal mill is also related to the properties of the coal, the actual modification process is designed based on the same conditions, such as the modified coal mill using the same working fluid and operating conditions as the original coal mill. For example, if the working fluid or operating conditions change in this invention, a new working fluid and operating conditions are used to obtain the output of the original coal mill, and the k-value is recalculated, i.e., the k-value is readjusted.
[0057] This invention defines the grinding surface moment factor, which achieves coal particle crushing through the shearing action generated by the difference between the linear velocity of the grinding roller at this point and the linear velocity of the liner at this point. Its advantage lies in the fact that the calculated results closely approximate the actual output B of the modified coal mill. M This changes the previous situation where power output was calculated based on selection.
[0058] This calculation method fills a gap in the field of calculation for improving the output of coal mills, elevates the calculation of output improvement design to a controllable stage, and can provide the best guidance for all coal mill output improvement design.
[0059] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that variations and combinations of elements may be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.
Claims
1. A method for calculating the grinding output of a coal mill based on the grinding surface distance ratio, characterized in that: Includes the following steps: Obtain the mill roller thickness B and pitch circle radius of the coal mill. Rated speed n, grinding roller radius Pitch circle radius Grinding roller radius The maximum distance t for grinding; Calculate the grinding range angle : ; Calculate the effective area of grinding : ； Calculate the grinding line speed: ; Calculate the arc chord ratio C of the grinding roller profile: ; Calculate the grinding surface moment ratio: ; Obtain the proportionality coefficient k; Calculate the grinding output of the coal mill .
2. The method according to claim 1, characterized in that: The range of values for t is .
3. The method according to claim 1, characterized in that: Obtaining the proportional coefficient k involves setting k = the first preset value.
4. The method according to claim 1, characterized in that: Obtaining the proportionality coefficient k includes: calculating the GSAR of the coal mill before the modification, and obtaining the grinding output of the coal mill before the modification. .
5. The method according to claim 1, characterized in that: When used to modify coal mills, it increases grinding output. The calculation.
6. The method according to claim 1, characterized in that: Calculate the grinding output of the coal mill At that time, GSAR was calculated based on the parameters of the modified coal mill.
7. The method according to claim 1, characterized in that: If the working medium or operating conditions of the coal mill change, the original coal mill's grinding output can be obtained based on the new working medium and operating conditions.
8. The method according to claim 1, characterized in that: The coal mill is a ZGM type coal mill.
9. The method according to claim 1, characterized in that: Calculate the effective area of grinding Based on the principle that the grinding range angle θ is relatively small, the effective grinding area is calculated through approximate simplification. .
10. The method according to claim 1, characterized in that: When calculating the grinding linear velocity, the linear velocity at the pitch circle position of the grinding disc is taken as the average value of the linear velocity of the entire grinding area.