Medium-speed coal mill capable of increasing capacity and efficiency and capacity increasing and efficiency increasing method thereof
By optimizing the design of key components of the medium-speed coal mill, the problems of insufficient output, poor adaptability to various coal types, and difficult maintenance of traditional medium-speed coal mills have been solved, thereby increasing the capacity and efficiency of the coal mill and ensuring the safe and stable operation of thermal power plants.
Patent Information
- Application Number
- CN202511709377.9
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-11-20
- Publication Date
- 2025-12-26
AI Technical Summary
Traditional medium-speed coal mills have problems such as complex coal sources, low calorific value and high ash content of coal used in boilers, coal mill output not meeting design requirements, poor adaptability to different coal types, high stone coal emission rate, weak and easily damaged primary air ring structure, and the need for multiple coal mills to operate under high load, making regular maintenance impossible.
The grinding rollers, grinding bowls, impeller assembly, external spring adjustment device, and separator were optimized. The width and diameter of the grinding rollers were increased, a modular design was adopted, the impeller flow field was optimized, an axial self-sealing method was used, the separator rotor structure was improved, and wear-resistant materials and a split design were used to extend service life and improve coal powder separation efficiency.
It improved the grinding output and coal powder separation efficiency of the coal mill, reduced the emission rate of stone coal, extended the service life of key components, ensured the stable operation of the unit under high load, and reduced maintenance time.
Smart Images
Figure CN121198409A_ABST
Abstract
Description
TECHNICAL FIELD
[0001] The present application relates to the technical field of coal mills, in particular to a medium-speed coal mill capable of increasing capacity and efficiency and a method for increasing capacity and efficiency of the medium-speed coal mill. BACKGROUND
[0002] In the power generation process of thermal power plants, the coal mill is one of the most important equipment, and the medium-speed coal mill has been widely used in thermal power plants due to its many advantages. The medium-speed coal mill mainly crushes and grinds raw coal into coal powder through the relative movement of the grinding roller on the grinding disc. Raw coal enters the grinding disc from the center of the coal mill through the coal drop pipe and moves to the edge of the grinding disc under the action of centrifugal force. At the same time, the grinding roller is pressed and ground under the action of the hydraulic device. The ground coal powder is blown from the edge of the grinding disc by hot air and enters the separator for separation. The coal powder meeting the fineness requirement is sent to the boiler for combustion, and the coal powder not meeting the requirement is returned to the grinding disc for further grinding.
[0003] The space of thermal power plants is usually limited, and the medium-speed coal mill has a compact structure and a relatively small footprint, which makes it more flexible in the layout of thermal power plants and can better adapt to different site conditions. Compared with traditional low-speed coal mills, the medium-speed coal mill does not require a large foundation and plant, saving a large amount of construction cost and space resources. The medium-speed coal mill adopts advanced grinding technology and can grind raw coal into coal powder with the required fineness in a short time. The relative movement of the grinding roller and the grinding disc makes the raw coal receive uniform pressure and shear force, thereby improving the grinding efficiency. In addition, the separator of the medium-speed coal mill can accurately control the fineness of the coal powder according to different combustion requirements, ensuring the stability and efficiency of combustion.
[0004] However, the traditional medium-speed coal mill has the following disadvantages:
[0005] (1) The traditional medium-speed coal mill has complex coal sources. The boiler burns coal with lower calorific value, higher ash content, and more gangue than the designed coal, which makes the output of the coal mill not meet the design requirement (67t / h). According to statistics, the maximum output of the coal mill is less than 60t / h within 1000 hours of operation; the maximum output is less than 57t / h after 1000-3000 hours of operation; and the maximum output is less than 54t / h after more than 3000 hours of operation;
[0006] (2) The coal mill has poor adaptability to coal. When grinding individual coal, the stone coal discharge rate is as high as 28%;
[0007] (3) The primary air ring structure is simple and weak, often damaged within the service life of the grinding roller, and the primary air ring efficiency is not high;
[0008] (4) Because the heat value of coal is low, the coal quantity of high load of the unit is large, currently, 6 coal mills need to run to meet the requirement when the load of the unit is more than 85%, there is no standby mill group, and the coal mill cannot be regularly maintained and repaired under the long-term medium and high load during the power supply, which is not conducive to the safe and stable operation of the unit SUMMARY
[0009] The present application aims to provide a medium-speed coal mill capable of increasing capacity and efficiency and a method for increasing capacity and efficiency thereof, so as to solve the problems of the conventional medium-speed coal mill in the background art, i.e., the coal source is complex, the heat value of the coal used in the boiler is low compared with the designed coal, the ash content is large, and the quantity of gangue in the coal is large, etc., which makes the output of the coal mill not reach the designed output (67t / h), according to the statistics, the maximum output of the coal mill is less than 60t / h within 1000 hours of operation, the maximum output of the coal mill is less than 57t / h after 1000-3000 hours of operation, the maximum output of the coal mill is less than 54t / h after more than 3000 hours of operation, the capacity of the coal mill for the coal is poor, the discharge rate of stone coal is as high as 28% when grinding individual coal, the structure of the primary air wind ring is simple and weak, and the primary air wind ring is often damaged within the service life of the grinding roller, the efficiency of the primary air wind ring is not high, the heat value of the coal is low, the coal quantity of high load of the unit is large, currently, 6 coal mills need to run to meet the requirement when the load of the unit is more than 85%, there is no standby mill group, and the coal mill cannot be regularly maintained and repaired under the long-term medium and high load during the power supply, which is not conducive to the safe and stable operation of the unit.
[0010] To achieve the above-mentioned purpose, the present application provides the following technical scheme: a medium-speed coal mill capable of increasing capacity and efficiency, comprising a lower bin shell, a middle bin shell fixedly installed at the top end of the lower bin shell, an upper bin shell fixedly installed at the top end of the middle bin shell, a discharge cone tower fixedly installed at the top end of the upper bin shell, a separator fixedly installed at the top end of the inner wall of the upper bin shell, a grinding roller rotatably connected to one side of the bottom end of the inner wall of the middle bin shell, a grinding bowl fixedly installed below the grinding roller on the middle bin shell, a grinding bowl lining plate laid on the surface of the grinding bowl, two symmetrical bin partition type grinding rings fixedly installed at the other side of the bottom end of the inner wall of the middle bin shell, and an impeller device fixedly installed at the middle of the bottom end of the lower bin shell.
[0011] As a preferred technical scheme of the present application, a primary air inlet is fixedly communicated with the top end of one side of the lower bin shell, and a stone coal hopper is fixedly communicated with the middle of one side of the lower bin shell.
[0012] As a preferred technical scheme of the present application, external spring adjusting devices are fixedly installed at the bottom end of both sides of the lower bin shell, and a gear transmission device connected with the impeller device is fixedly installed at the middle of the bottom end of the lower bin shell.
[0013] As a preferred technical scheme of the present application, the middle part of one side of the intermediate shell is fixedly communicated with a sealed air pipe.
[0014] As a preferred technical scheme of the present application, the top end of the discharge cone tower is fixedly communicated with a plurality of branch pipes, and each of the middle parts of the branch pipes is fixedly installed with a rotary valve.
[0015] As a preferred technical scheme of the present application, the middle part of the top end of the discharge cone tower is fixedly communicated with a central coal feeding pipe, the middle part of the inner wall of the intermediate shell is fixedly installed with a loading frame, the inside of the loading frame is fixedly installed with a plurality of multistage springs, and the middle part of the loading frame is fixedly communicated with the bottom end of the central coal feeding pipe.
[0016] The present application is a method for increasing capacity and efficiency of a medium-speed coal mill, which comprises the following steps:
[0017] Step one, increasing efficiency of grinding output of the coal mill: optimizing the grinding roller and the grinding bowl liner respectively;
[0018] Step two, increasing efficiency of the internal flow field of the coal mill: optimizing the impeller device;
[0019] Step three, optimizing and reforming the spring loading device: optimizing the design of the external spring adjusting device to increase the loading force of the grinding roller and ensure that the coal mill cannot appear violent vibration, and the loading bolt sealing bearing of the external spring adjusting device is made of copper plus graphite material;
[0020] Step four, reforming the rotor body of the dynamic separator: optimizing the separator.
[0021] As a preferred technical scheme of the present application, the optimization of the grinding roller in step one is specifically increasing the width and diameter of the grinding roller to increase the grinding area of the grinding roller, ensure the grinding output of the coal mill, adopt modular design for the grinding roller to facilitate disassembly and assembly work and shorten the maintenance time, adopt cast steel base material plus wear-resistant alloy welding wire build-up welding for the grinding roller, the build-up welding thickness is not less than 40 mm to achieve the purpose of prolonging the service life, the surface hardness of the grinding roller is not less than HRC≥60, the service life of the grinding roller is not less than 10000 hours, the wear amount of the grinding roller of the coal mill is not greater than 40 mm within the service life, and the stone coal discharge amount is less than 0.5% after the coal mill runs for 7000 hours; the optimization of the grinding bowl liner in step one is specifically enlarging the diameter of the grinding bowl to enhance the service life of the grinding bowl liner and ensure the later-stage output of the coal mill, the length of the grinding bowl liner is matched with the grinding roller, the length of the grinding bowl liner is not less than the length of the existing grinding bowl liner to ensure that the grinding area of the grinding roller falls on the grinding bowl liner, and the grinding bowl liner is made of cast steel base material plus wear-resistant alloy welding wire build-up welding, the build-up welding thickness is not less than 30 mm to achieve the purpose of prolonging the service life.
[0022] As a preferred technical scheme of the present application, the optimization of the impeller device in step two is specifically an axial self-sealing mode between the impeller device and the separator liner, without setting an adjustable cover or welding a sealing ring on the separator body, to ensure smooth ventilation and to achieve the effect of reducing stone coal.
[0023] As a preferred technical scheme of the present application, the optimization of the separator in step four is specifically that the dynamic separator rotor body is an important part of the internal flow field of the coal mill, which is related to the coal powder selection efficiency. The separator rotor body is optimized and designed to improve the efficiency of coal powder separation. The separator rotor body is of a split type to facilitate the disassembly and installation of the split rotor body, optimize the maintenance process, and shorten the maintenance time. The separator rotor body is not disassembled when installed on site, and each blade of the rotor body can be disassembled for convenient replacement. The split rotor body is made of high-grade wear-resistant material to prolong the service life. The separator rotor body needs to be dynamically balanced, and the counterweight is added to the bottom plate with a mass imbalance of less than 400g.
[0024] Compared with the prior art, the present application has the following advantages:
[0025] 1. The mill roller, mill bowl, mill bowl liner, impeller device, external spring adjustment device, and separator are optimized respectively, so that the coal mill can realize capacity increase under the existing coal quality conditions, and the output of the modified coal mill is improved.
[0026] 2. The impeller device is optimized and designed, and an axial self-sealing mode is adopted between the impeller device and the separator liner without setting an adjustable cover or welding a sealing ring on the separator body, to ensure smooth ventilation and to achieve the effect of reducing stone coal.
[0027] 3. The separator rotor body is optimized and designed to improve the efficiency of coal powder separation. The separator rotor body is of a split type to facilitate the disassembly and installation of the split rotor body, optimize the maintenance process, and shorten the maintenance time. The separator rotor body is not disassembled when installed on site, and each blade of the rotor body can be disassembled for convenient replacement.
[0028] 4. The width and diameter of the mill roller are increased to increase the mill roller grinding area and ensure the grinding output of the coal mill. The mill roller is designed in a modular manner to facilitate disassembly and installation and to shorten the maintenance time. BRIEF DESCRIPTION OF DRAWINGS
[0029] Figure 1 is a side view of the present application;
[0030] Figure 2 The flow chart of the present application;
[0031] Figure 3 The enlarged schematic diagram of A in the present application;
[0032] Figure 4 The enlarged schematic diagram of B in the present application;
[0033] Figure 5 The schematic diagram of the internal flow field of the coal mill in the present application.
[0034] In the figure: 1, discharge cone tower; 2, branch pipe; 3, central coal feeding pipe; 4, rotary valve; 5, sealing air pipe; 6, separator; 7, grinding roller; 8, grinding bowl lining plate; 9, impeller device; 10, upper housing; 11, loading frame; 12, multi-stage spring; 13, intermediate housing; 14, stone coal hopper; 15, warehouse partition type grinding ring; 16, primary air inlet; 17, lower housing; 18, external spring adjustment device; 19, gear transmission device. DETAILED DESCRIPTION
[0035] The technical solutions in the embodiments of the present application will be clearly and completely described below in conjunction with the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application.
[0036] Please refer to Figures 1-5 The present application provides a medium-speed coal mill capable of increasing capacity and efficiency, which comprises a lower housing 17, a top end of the lower housing 17 is fixedly installed with an intermediate housing 13, a top end of the intermediate housing 13 is fixedly installed with an upper housing 10, a top end of the upper housing 10 is fixedly installed with a discharge cone tower 1, a top end of an inner wall of the upper housing 10 is fixedly installed with a separator 6, a bottom end of an inner wall of the intermediate housing 13 is rotatably connected with a grinding roller 7 on one side, the intermediate housing 13 is fixedly installed with a grinding bowl below the grinding roller 7, a surface of the grinding bowl is paved with a grinding bowl lining plate 8, two symmetrically arranged warehouse partition type grinding rings 15 are fixedly installed on the other side of the bottom end of the inner wall of the intermediate housing 13, and the lower housing 17 is fixedly installed with an impeller device 9 in the middle of the bottom end.
[0037] A primary air inlet 16 is fixedly communicated with the top end of one side of the lower housing 17, and a stone coal hopper 14 is fixedly communicated with the middle of one side of the lower housing 17.
[0038] The bottom end of the lower housing 17 is fixedly installed with external spring adjustment devices 18 on both sides, and the middle of the bottom end of the lower housing 17 is fixedly installed with a gear transmission device 19 connected with the impeller device 9.
[0039] The middle part of the intermediate shell 13 is fixedly communicated with a sealing air pipe 5.
[0040] The top end of the discharge cone tower 1 is fixedly communicated with a plurality of branch pipes 2, and the middle part of each of the plurality of branch pipes 2 is fixedly installed with a rotary valve 4.
[0041] The middle part of the top end of the discharge cone tower 1 is fixedly communicated with a central coal feeding pipe 3, the middle part of the inner wall of the intermediate shell 13 is fixedly installed with a loading rack 11, and the inside of the loading rack 11 is fixedly installed with a plurality of multi-stage springs 12.
[0042] The method for increasing capacity and improving efficiency of a medium-speed coal mill, which comprises the following steps:
[0043] Step one, improving the grinding output of the coal mill: optimizing the grinding roller 7 and the grinding bowl lining plate 8 respectively;
[0044] Step two, improving the internal flow field of the coal mill: optimizing the impeller device 9;
[0045] Step three, optimizing and reforming the spring loading device: optimizing the design of the external spring adjusting device 18 to improve the loading force of the grinding roller 7 and ensure that the coal mill cannot vibrate violently, and the loading bolt sealing bearing of the external spring adjusting device 18 is made of copper plus graphite material;
[0046] Step four, reforming the rotor body of the dynamic separator: optimizing the separator 6.
[0047] In step one, the optimization of the grinding roller 7 specifically includes increasing the width and diameter of the grinding roller 7 to increase the grinding area of the grinding roller 7 and ensure the grinding output of the coal mill, the grinding roller 7 is designed in a modular manner to facilitate disassembly and assembly work and shorten the maintenance time, the grinding roller 7 is made of a cast steel base material plus wear-resistant alloy welding wire build-up welding, the build-up welding thickness is not less than 40 mm to achieve the purpose of prolonging the service life, the surface hardness of the grinding roller 7 is not less than HRC≥60, the service life of the grinding roller 7 is not less than 10,000 hours, the wear of the grinding roller 7 is not greater than 40 mm within the service life, and the stone coal discharge amount is less than 0.5% after the coal mill runs for 7,000 hours.
[0048] The optimization of the impeller device 9 in step two is specifically an axial self-sealing mode between the separator 6 lining plate, without setting an adjustable cover or welding a sealing ring on the separator 6 body, to ensure smooth ventilation flow, so as to reduce the amount of stone coal; the wear parts of the impeller device 9, such as the rectifier plate and the flow guide plate, are made of wear-resistant welding wire surfacing steel plate material, so as to prolong the service life; the flow field of the impeller device 9 is optimized, the flow area of the impeller is redesigned according to the actual working condition, and the air throttling ring is no longer installed on site to reduce the amount of stone coal, and the upper and lower resistance of the mill bowl is increased by not more than 500 Pa.
[0049] The optimization of the separator 6 in step four is specifically that the dynamic separator 6 rotor body is an important part of the internal flow field of the coal mill, which is related to the coal powder selection efficiency. The separator 6 rotor body is optimized and designed to improve the efficiency of coal powder separation. The separator 6 rotor body is of a split type to facilitate the disassembly and installation of the split rotor body, optimize the maintenance process, and shorten the maintenance time. The separator 6 rotor body is not disassembled when installed on site, each blade of the rotor body can be disassembled, and the split rotor body is made of high-grade wear-resistant material to prolong the service life. The separator 6 rotor body needs to be dynamically balanced, and the counterweight is added to the bottom plate, with the mass imbalance controlled within 400 g.
[0050] In the application, the width and diameter of the grinding roller 7 are increased to increase the grinding area of the grinding roller 7, ensure the grinding output of the coal mill, the grinding roller 7 adopts a modular design, which facilitates disassembly and assembly work, shortens the maintenance time, the grinding roller 7 is made of cast steel base material plus wear-resistant alloy welding wire build-up, the build-up thickness is not less than 40 mm, so as to achieve the purpose of prolonging the service life, the surface hardness of the grinding roller 7 is not less than HRC≥60, the service life is not less than 10000 hours, the wear of the grinding roller 7 of the coal mill is not more than 40 mm within the service life, the stone coal discharge amount of the coal mill is less than 0.5% after 7000 hours of operation; the optimization of the grinding bowl liner plate 8 in step one is specifically enlarging the diameter of the grinding bowl, enhancing the service life of the grinding bowl liner plate 8, and ensuring the later-stage output guarantee of the coal mill, the length of the grinding bowl liner plate 8 is matched with the grinding roller 7, the length of the grinding bowl liner plate 8 is not less than the length of the existing grinding bowl liner plate 8, so as to ensure that the grinding area of the grinding roller 7 falls on the grinding bowl liner plate 8, the grinding bowl liner plate 8 is made of cast steel base material plus wear-resistant alloy welding wire build-up, the build-up thickness is not less than 30 mm, so as to achieve the purpose of prolonging the service life, the axial self-sealing mode is adopted between the separator 6 liner plate, no adjustable cover is additionally arranged or a sealing ring is welded on the separator 6 body, so as to ensure smooth ventilation and achieve the effect of reducing stone coal; the wear parts of the impeller device 9, such as the rectifier plate and the flow guide plate, are made of wear-resistant welding wire build-up steel plate material, so as to achieve the purpose of prolonging the service life; the flow field of the impeller device 9 is optimized, the impeller flow area is redesigned according to the actual working condition, the air throttling ring is no longer installed on site to reduce the amount of stone coal, the increase of the upper and lower resistance of the grinding bowl is not more than 500 Pa, the dynamic separator 6 rotor body is an important part of the internal flow field of the coal mill, which is related to the coal powder separation efficiency, the separator 6 rotor body is optimized and designed to improve the efficiency of coal powder separation, the separator 6 rotor body adopts a split type to facilitate the disassembly and assembly of the split rotor body, optimize the maintenance process, shorten the maintenance time, the separator 6 rotor body is not disassembled when installed on site, each blade of the rotor body can be disassembled, which is convenient for replacement, the split rotor body is made of high-grade wear-resistant material, so as to achieve the purpose of prolonging the service life, the separator 6 rotor body needs to be dynamically balanced, the counterweight is added to the bottom plate, and the mass imbalance is controlled within 400 g.
[0051] Although the application has been described in detail with reference to the foregoing embodiments, those skilled in the art can modify the technical solutions recorded in the foregoing embodiments or make equivalent replacements to some technical features within the spirit and principles of the application, and any modification, equivalent replacement, improvement, etc. made within the protection scope of the application shall be included in the protection scope of the application.
Claims
1. A medium-speed coal mill capable of increasing capacity and improving efficiency, comprising a lower hopper shell (17), characterized in that: The lower chamber shell (17) is fixedly installed with an intermediate chamber shell (13) at its top end. The intermediate chamber shell (13) is fixedly installed with an upper chamber shell (10) at its top end. The upper chamber shell (10) is fixedly installed with a discharge cone tower (1) at its top end. The upper chamber shell (10) is fixedly installed with a separator (6) at its top end. A grinding roller (7) is rotatably connected to one side of the bottom end of the intermediate chamber shell (13). A grinding bowl located below the grinding roller (7) is fixedly installed on the intermediate chamber shell (13). A grinding bowl liner (8) is laid on the surface of the grinding bowl. Two symmetrically arranged chamber-type grinding rings (15) are fixedly installed on the other side of the bottom end of the intermediate chamber shell (13). An impeller device (9) is fixedly installed in the middle of the bottom end of the lower chamber shell (17).
2. A medium-speed coal mill capable of increasing capacity and improving efficiency according to claim 1, characterized in that: The top of one side of the lower silo (17) is fixedly connected to a primary air inlet (16), and the middle of one side of the lower silo (17) is fixedly connected to a stone and coal hopper (14).
3. A medium-speed coal mill capable of increasing capacity and improving efficiency according to claim 1, characterized in that: External spring adjustment devices (18) are fixedly installed on both sides of the bottom end of the lower chamber (17), and a gear transmission device (19) connected to the impeller device (9) is fixedly installed in the middle of the bottom end of the lower chamber (17).
4. A medium-speed coal mill capable of increasing capacity and improving efficiency according to claim 1, characterized in that: A sealed air duct (5) is fixedly connected to the middle of one side of the intermediate compartment shell (13).
5. A medium-speed coal mill capable of increasing capacity and improving efficiency according to claim 1, characterized in that: The top of the discharge cone tower (1) is fixedly connected to several branch pipes (2), and a rotary valve (4) is fixedly installed in the middle of each of the branch pipes (2).
6. A medium-speed coal mill capable of increasing capacity and improving efficiency according to claim 1, characterized in that: The top of the discharge cone tower (1) is fixedly connected to the central coal feeding pipe (3), and the middle of the inner wall of the intermediate silo shell (13) is fixedly installed with a loading frame (11). Several multi-stage springs (12) are fixedly installed inside the loading frame (11), and the middle of the loading frame (11) is fixedly connected to the bottom of the central coal feeding pipe (3).
7. A method for increasing the capacity and efficiency of a medium-speed coal mill according to any one of claims 1-6, characterized in that, Includes the following steps: Step 1: Improve the grinding output of the coal mill: Optimize the grinding roller (7) and the grinding bowl liner (8) respectively; Step 2: Improve the internal flow field of the coal mill: Optimize the impeller device (9); Step 3, optimization and modification of the spring loading device: the external spring adjustment device (18) is optimized to improve the loading force of the grinding roller (7) and ensure that the coal mill does not vibrate violently. The sealing bearing of the loading bolt of the external spring adjustment device (18) is made of copper and graphite. Step 4: Modification of the dynamic separator rotor: Optimize the separator (6).
8. The method for increasing the capacity and efficiency of a medium-speed coal mill according to claim 7, characterized in that: The optimization of the grinding roller (7) in step one specifically involves increasing the width and diameter of the grinding roller (7) to increase the grinding area of the grinding roller (7) and ensure the grinding output of the coal mill. The grinding roller (7) adopts a modular design to facilitate disassembly and assembly, thereby shortening maintenance time. The grinding roller (7) is made of cast steel substrate with wear-resistant alloy welding wire, and the welding thickness is not less than 40mm to extend its service life. The surface hardness of the grinding roller (7) is not less than HRC≥60, and its service life is not less than 10,000 hours. Within its service life, the wear of the coal mill grinding roller (7) is not greater than 40mm. After the coal mill has been running for 7000 hours, the amount of stone coal discharged is less than 0.5%; the optimization of the grinding bowl liner (8) in step one is as follows: increase the diameter of the grinding bowl, enhance the service life of the grinding bowl liner (8), ensure the output of the coal mill in the later stage, match the length of the grinding bowl liner (8) with the grinding roller (7), and ensure that the grinding area of the grinding roller (7) falls on the grinding bowl liner (8). The grinding bowl liner (8) is made of cast steel substrate with wear-resistant alloy welding wire, and the welding thickness is not less than 30mm, so as to extend the service life.
9. The method for increasing the capacity and efficiency of a medium-speed coal mill according to claim 7, characterized in that: In step two, the optimization of the impeller device (9) is specifically achieved by adopting an axial self-sealing method between it and the separator (6) liner, without setting an adjustable cover or welding a sealing ring on the separator (6) body to ensure smooth ventilation and reduce the amount of stone coal; the wear parts such as the rectifier plate and guide plate of the impeller device (9) are made of wear-resistant welding wire welded steel plate material to extend the service life; the flow field of the impeller device (9) is optimized, and the impeller flow area is redesigned according to the actual working conditions, and the air throttling ring is no longer installed on site to reduce the amount of stone coal, and the increase in the upper and lower resistance of the grinding bowl does not exceed 500Pa.
10. The method for increasing the capacity and efficiency of a medium-speed coal mill according to claim 7, characterized in that: The optimization of the separator (6) in step four is as follows: The rotor of the dynamic separator (6) is an important part of the internal flow field of the coal mill, which is related to the coal powder selection efficiency. The rotor of the separator (6) is optimized to improve the coal powder separation efficiency. The rotor of the separator (6) adopts a split type to facilitate the disassembly and installation of the split rotor, optimize the maintenance process, and shorten the maintenance time. When the rotor of the separator (6) is installed on site, the top cover of the separator is not removed. Each blade of the rotor can be disassembled for easy replacement. The split rotor is made of high-grade wear-resistant material to extend its service life. The rotor of the separator (6) needs to be dynamic balanced. The counterweight is added to the base plate, and the mass imbalance is controlled within 400g.