Coal mill capable of operating at adjustable speed

Abstract

The utility model relates to a coal mill capable of operating at adjustable speed. The coal mill comprises a driving assembly, a transmission assembly, a mill body, a counter-acting force hydraulic variable loading device and a separator, the driving assembly comprises a permanent magnet synchronous motor. The transmission assembly comprises a permanent magnet speed regulator and a planetary reducer. The input end of the planetary reducer is in transmission connection with the output end of the permanent magnet synchronous motor through a permanent magnet speed regulator. The grinder body comprises a shell, a grinding disc and a grinding roller. And the grinding roller and the grinding disc are arranged in the shell. The millstone is in transmission connection with the output end of the planetary reducer. And the reactive force hydraulic variable loading system is arranged outside the shell and is used for loading the grinding roller on the grinding disc and adjusting the pressure between the grinding roller and the grinding disc. The separator comprises a dynamic separator. The dynamic separator is located at the upper end of the shell and used for screening pulverized coal ground by the grinding roller and the grinding disc. The coal mill provided by the utility model has better operation stability and economical efficiency under the working condition of low load when the coal quality is worsened and the deep peak regulation is carried out.

Description

TECHNICAL FIELD

[0001] The utility model relates to the technical field of coal mill, in particular to a coal mill of adjustable speed operation. BACKGROUND

[0002] The pace of clean and low-carbon transformation of China's power system will be further accelerated, and coal power will gradually change from the main power source providing power and electricity to the supporting and regulating power source of power and electricity, and the installed capacity and power generation proportion will decrease, and the flexible regulation capacity and clean and efficient level need to be improved.

[0003] In the prior art, the thermal power unit is changed to a regulating power source, and in recent years, under the impact of high coal prices, fuel costs have occupied an increasingly important position in power plant operation. At present, the thermal power plant uses power coal with lower and lower calorific value, which seriously deviates from the design coal, so there are new requirements and challenges for the coal mill. The stability and economy of the coal mill under low load working condition when the coal quality is poor and deep peak regulation are poor, and improvement is urgently needed. UTILITY MODEL CONTENTS

[0004] In order to improve the stability and economy of the coal mill under low load working condition when the coal quality is poor and deep peak regulation, the application provides a coal mill capable of adjustable speed operation.

[0005] The coal mill provided by the utility model adopts the following technical scheme:

[0006] A coal mill capable of adjustable speed operation, comprising a driving assembly, a transmission assembly, a grinding body, a reaction force hydraulic variable loading system and a separator, wherein the driving assembly comprises a permanent magnet synchronous motor, the transmission assembly comprises a planetary reducer, the input end of the planetary reducer is in transmission connection with the output end of the permanent magnet synchronous motor, the grinding body comprises a shell, a grinding disc and a grinding roller, the grinding roller and the grinding disc are arranged in the shell, the grinding disc is in transmission connection with the output end of the planetary reducer, the reaction force hydraulic variable loading system is arranged outside the shell and connected with the grinding roller, the grinding roller is used for loading the grinding roller on the grinding disc through the reaction force hydraulic variable loading system, and the pressure between the grinding roller and the grinding disc is adjusted, and the separator comprises a dynamic separator, the dynamic separator is located at the upper end of the shell and used for screening the coal powder after being ground by the grinding roller and the grinding disc.

[0007] Optionally, the permanent magnet synchronous motor is of double-shaft type, installed horizontally, the cooling mode is IC611, the protection level is not less than IP54, the power factor is greater than or equal to 0.98, and the motor guaranteed efficiency is greater than or equal to 96%.

[0008] Optionally, the transmission assembly further comprises a permanent magnet speed regulator; the permanent magnet speed regulator is drivingly connected between the output end of the permanent magnet synchronous motor and the input end of the planetary reducer, for adjusting the torque input to the planetary reducer by the permanent magnet synchronous motor without changing the rotation speed of the output end of the permanent magnet synchronous motor.

[0009] Optionally, the permanent magnet speed regulator comprises a disc type permanent magnet speed regulator, a cylinder type permanent magnet speed regulator or a double cylinder type permanent magnet speed regulator.

[0010] Optionally, the output end of the permanent magnet speed regulator is provided with a speed sensor; the speed sensor is used for measuring the rotation speed of the output end of the permanent magnet synchronous motor, and is in communication connection with the DCS system, so that the DCS system can display the rotation speed of the output end of the permanent magnet speed regulator measured by the speed sensor.

[0011] Optionally, the reaction force hydraulic variable loading system is in communication connection with the DCS system, so that the DCS system can display the loading force and the reaction force of the reaction force hydraulic variable loading system.

[0012] Optionally, the loading force and the reaction force of the reaction force hydraulic variable loading system are controlled by a hydraulic pump station.

[0013] Optionally, the dynamic separator is a dynamic and static combined dynamic separator; the transmission mode of the dynamic separator is belt transmission or gear transmission.

[0014] Optionally, the dynamic separator is driven by a frequency converter and a variable frequency motor; the dynamic separator, the frequency converter and the variable frequency motor are all in communication connection with the DCS system, so that the DCS system can automatically and remotely adjust the rotation speed of the variable frequency motor, and then adjust the rotation speed of the dynamic separator.

[0015] As described above, the speed-adjustable coal mill has better stability and economy in the low load working condition of the coal mill when the coal quality is poor and the depth of peak regulation is high, and has the following advantages:

[0016] 1. The speed-adjustable coal mill adopts a permanent magnet synchronous motor, which overcomes the defects of low power factor, low efficiency and large energy consumption of an asynchronous motor, meets the requirements of the heavy load and frequent start of the coal mill, and is more energy-saving.

[0017] 2. The output rotation speed of the planetary reducer can be speed-adjusted between 0-40 rpm under the adjustment of the permanent magnet speed regulator, which can effectively reduce the unit consumption of the permanent magnet synchronous motor in the low load of the coal mill, and improve the economy of the coal mill.

[0018] 3. By installing the permanent magnet speed regulator between the permanent magnet synchronous motor and the planetary reducer, the output rotating speed of the planetary reducer can be reduced at low load, the coal mill power consumption is reduced, the vibration is reduced, the coal mill can be operated stably at below 20% load, and the wear of the grinding parts is reduced; the output rotating speed of the planetary reducer can be increased at full load, the grinding capacity is increased, and the insufficient grinding capacity caused by poor coal quality is compensated.

[0019] 4. The grinding roller adopts the reaction force hydraulic variable loading system, so that part of the weight of the grinding roller can be offset, and the power consumption of the grinding roller at low load is reduced.

[0020] 5. By adopting the dynamic separator, the adaptability of the coal mill to coal variety change is improved, and the boiler can be operated economically and stably. BRIEF DESCRIPTION OF DRAWINGS

[0021] Figure 1 is a schematic diagram of the coal mill with adjustable speed operation according to the present application.

[0022] Figure 2 is a schematic diagram of the working principle of the reaction force variable loading system.

[0023] Reference signs: 1, permanent magnet synchronous motor; 2, permanent magnet speed regulator; 3, planetary reducer; 4, mill body; 5, dynamic separator; 6, reaction force hydraulic variable loading system; 61, oil cylinder; 611, loading cavity; 612, back pressure cavity; 7, grinding disc; 8, grinding roller; 9, overflow valve. DETAILED DESCRIPTION

[0024] The embodiments of the present application are described below through specific examples, and those skilled in the art can easily understand other advantages and effects of the present application from the disclosure of the present specification. The present application can also be implemented or applied through other different embodiments, and each detail in the present specification can be modified or changed based on different viewpoints and applications without departing from the spirit of the present application. It should be noted that the following examples and features in the examples can be combined with each other without conflict. It should also be understood that the terms used in the embodiments of the present application are for describing specific specific embodiments, and are not intended to limit the protection scope of the present application. The test methods not specified in the following examples are usually performed under conventional conditions or under conditions recommended by the manufacturers.

[0025] It is to be understood that the structures, proportions, sizes and the like shown in the drawings attached to the present specification are only used to cooperate with the content disclosed in the specification, so as to be understood and read by those skilled in the art, and do not have technical substantive significance, and any modification of the structure, change of the proportional relationship or adjustment of the size, without affecting the effect and purpose that can be achieved by the present application, should still fall within the scope of the technical content disclosed by the present application. Meanwhile, the terms such as "upper", "lower", "left", "right", "middle" and "one" in the present specification are only for the convenience of clear description, and are not used to limit the scope of the present application, and the change or adjustment of the relative relationship, without substantially changing the technical content, is also regarded as the scope of the present application.

[0026] Please refer to Figure 1 The application discloses a speed-adjustable coal mill, which comprises a driving assembly, a transmission assembly, a grinding body 4, a reaction force hydraulic variable loading system and a separator. The driving assembly comprises a permanent magnet synchronous motor 1. The transmission assembly comprises a planetary reducer 3. The input end of the planetary reducer 3 is in transmission connection with the output end of the permanent magnet synchronous motor 1. The grinding body 4 comprises an outer shell, a grinding disc 7 and a grinding roller 8. The grinding roller 8 and the grinding disc 7 are arranged in the outer shell. The grinding disc 7 is in transmission connection with the output end of the planetary reducer 3. The reaction force hydraulic variable loading system 6 is arranged outside the outer shell and is connected with the grinding roller 8. The grinding roller 8 is used for loading the grinding roller 8 on the grinding disc 7 through the reaction force hydraulic variable loading system, and the pressure between the grinding roller 8 and the grinding disc 7 is adjusted. The separator comprises a dynamic separator 5. The dynamic separator 5 is located at the upper end of the outer shell. After the grinding roller 8 and the grinding disc 7 grind the material into coal powder, air is blown from bottom to top at the bottom of the outer shell, so that the coal powder is blown into the dynamic separator 5. The dynamic separator 5 is used for screening the coal powder ground by the grinding roller 8 and the grinding disc 7.

[0027] Specifically, the speed-adjustable coal mill adopts the permanent magnet synchronous motor 1 as the driving assembly. Compared with the three-phase asynchronous motor used in the existing coal mill, the permanent magnet synchronous motor has a high power factor, a high efficiency and a lower energy consumption. Moreover, the permanent magnet synchronous motor 1 has a high starting torque, and can meet the requirement of the heavy-load frequent starting load of the coal mill.

[0028] More specifically, in the present application, the permanent magnet synchronous motor 1 is of a double-shaft type, is installed horizontally, has an IC611 cooling mode, has a protection level of not less than IP54, has a power factor of not less than 0.98, and has a motor guaranteed efficiency of not less than 96%.

[0029] The load of the coal mill is generally 25% to 100%, and the coal mill is unstable and vibrates greatly when it is in low load operation. When the thermal power plant is in deep peak regulation, the coal mill is in low load operation, the unit consumption of the coal mill is doubled, and the economy of the coal mill is poor. In order to deal with this situation, the input stage of the planetary reducer 3 adopts an input stage spiral bevel gear pair. The input stage spiral bevel gear pair includes an input stage bevel gear shaft and a bevel gear. The bevel gear is installed on the input stage bevel gear shaft and is used for transmission. The bevel gear adopts an extended epitrochoid tooth system and is a hard tooth surface gear, and the tooth surface hardness is HRC58-HRC6, for example, HRC58, HRC60 or HRC62. In this way, while increasing the output rotating speed of the planetary reducer 3, the strength of the bevel gear is ensured, which helps to improve the service life of the planetary reducer 3.

[0030] The transmission assembly further includes a permanent magnet speed regulator 2. The permanent magnet speed regulator 2 is transmissionally connected between the output end of the permanent magnet synchronous motor 1 and the input end of the planetary reducer 3, and is used for adjusting the torque input from the permanent magnet synchronous motor 1 to the planetary reducer 3 without changing the rotating speed of the output end of the permanent magnet synchronous motor 1. The output end of the permanent magnet synchronous motor 1 is connected with the input end of the planetary reducer 3 through the permanent magnet speed regulator 2, so that the permanent magnet speed regulator 2 also has the function of a shaft coupling. The permanent magnet speed regulator 2 can be any one of a disc type permanent magnet speed regulator 2, a cylinder type permanent magnet speed regulator 2 or a double cylinder type permanent magnet speed regulator 2, and can be selected according to the use requirement of the coal mill in actual application.

[0031] The permanent magnet speed regulator 2 transmits torque through the air gap between the conductor rotor and the permanent magnet, adjusts the torque output at the load end by changing the coupling area, and achieves the purpose of speed regulation without changing the rotating speed of the permanent magnet synchronous motor 1. The permanent magnet speed regulator 2 is a pure mechanical non-contact structure without mechanical connection, can isolate vibration, allow impact load, and prolong the service life of each component (bearing, seal, etc.) of the transmission system. It effectively eliminates power harmonic pollution and electromagnetic interference, avoids the transmission of vibration between the permanent magnet synchronous motor 1 and the load. The permanent magnet speed regulator also has the advantages of strong environmental adaptability, and can work normally in humid, dusty, flammable and explosive, serious harmonic, and large power grid fluctuation environments. Under the background of carbon peak and carbon neutral, the thermal power unit is transformed into an adjustable power source, and the speed regulation operation of the coal mill is particularly important. Reducing the output rotating speed of the planetary reducer 3 at low load can reduce the power consumption of the coal mill and reduce vibration, and the coal mill can stably operate at a load of less than 20%, while reducing the wear of the grinding parts. Increasing the output rotating speed of the planetary reducer 3 at full load can improve the grinding output and make up for the insufficient output caused by poor coal quality.

[0032] Further, the output end of the permanent magnet speed regulator 2 is provided with a speed sensor. The speed sensor is used to measure the rotating speed of the output end of the permanent magnet synchronous motor 1, and is in communication connection with the DCS system, so that the DCS system can display the rotating speed of the output end of the permanent magnet speed regulator 2 measured by the speed sensor, and then the rotating speed of the permanent magnet speed regulator 2 is associated with the coal supply amount of the coal mill, and the coal supply amount of the coal mill is associated with the power generation load, so that the rotating speed of the permanent magnet speed regulator 2 is associated with the power generation load, and the automatic operation and maintenance of the permanent magnet synchronous motor 1, the planetary reducer 3 and the permanent magnet speed regulator 2 of the coal mill is realized.

[0033] It should be noted here that the DCS system is a distributed control system. In the coal-fired power plant, the DCS system controls various execution components according to various analog data quantities through the logic of the power plant operation, and is a comprehensive system.

[0034] Please continue to refer to Figure 1 The reason why the adjustable-speed running coal mill of the present application is provided with the reaction force hydraulic variable loading system 6 is that the grinding roller 8 itself has a large self-weight, and when the coal mill is running at a low load, the self-weight of the grinding roller 8 will cause the pressure between the grinding roller 8 and the grinding disc 7 to be too large, increasing the power consumption of the grinding roller 8, so it is necessary to load a reaction force to the grinding roller 8 to offset a part of the self-weight of the grinding roller 8.

[0035] Specifically, the reaction force hydraulic variable loading system 6 can exert forces in the upward and downward directions to the grinding roller 8 to offset a part of the self-weight of the grinding roller 8 when the coal mill is running at a low load. The loading pressure and the reaction pressure of the reaction force hydraulic variable loading system 6 are controlled by proportional overflow valves 9. The proportional overflow valves 9 are adjusted according to the change of the coal supply amount of the coal mill to realize the adjustment of the loading pressure of the reaction force hydraulic variable loading system 6. The proportional overflow valves 9 are in communication connection with the DCS system, and the control signals of the proportional overflow valves 9 can be adjusted online in the DCS system according to the change of the coal supply amount of the coal mill, so as to realize the online real-time adjustment of the reaction force hydraulic variable loading system 6.

[0036] More specifically, please refer to Figure 2 The loading force and the reaction force of the reaction force hydraulic variable loading system 6 are controlled by a hydraulic pump station system. The hydraulic pump station system adopts a method combining the control of a lower computer PLC and the control of an upper computer configuration software to realize automatic control, online control and remote control.

[0037] The hydraulic pump station system supplies oil to the upper and lower chambers of the oil cylinder 61 through a double pump, the loading chamber 611 is high-pressure and small-flow, and the back pressure chamber 612 is low-pressure and large-flow. The pressure of the two oil paths is adjusted by two proportional overflow valves 9, and there are two plug-in check valves in the valve group, which can supply oil to the loading chamber 611 when the grinding roller 8 is descending to ensure the speed of the descending grinding roller 8.

[0038] Please refer toFigure 1 Because the static separator has poor adjustment performance, poor fineness, and insufficient adaptability to coal variety change, which affects the economic and stable operation of the boiler, the coal mill of the application adopts a dynamic separator 5 instead of a static separator. The dynamic separator 5 is a dynamic and static combined dynamic separator 5. Compared with the static separator, the dynamic and static combined dynamic separator 5 has the advantages of convenient adjustment of coal fineness, good uniformity, and low resistance. The transmission mode of the dynamic separator 5 is belt transmission or gear transmission.

[0039] Specifically, the dynamic separator 5 is driven by a frequency converter and a frequency conversion motor. The dynamic separator 5, the frequency converter, and the frequency conversion motor are in communication connection with a DCS system. Through the DCS system, the speed of the rotor of the frequency conversion motor can be automatically and remotely adjusted, thereby adjusting the speed of the dynamic separator 5, changing the fineness of the coal powder at the powder outlet of the dynamic separator 5, so as to meet the needs of users for different coal powder fineness, expand the selection range of coal varieties in power plants, reduce fuel costs, and realize automatic operation and maintenance of the dynamic separator 5.

[0040] In summary, the coal mill with adjustable speed operation of the application has good stability and economy in low load operation of the coal mill under poor coal quality and deep peak shaving, and has the following advantages:

[0041] 1. The coal mill with adjustable speed operation of the application adopts a permanent magnet synchronous motor 1, which overcomes the defects of low power factor, low efficiency, and large energy consumption of an asynchronous motor, meets the requirements of the load of the coal mill under heavy load and frequent starting, and is more energy-saving.

[0042] 2. The output speed of the planetary reducer 3 can be adjusted between 0 and 40 rpm under the adjustment of the permanent magnet speed regulator, which can effectively reduce the unit consumption of the permanent magnet synchronous motor 1 under low load of the coal mill, and improve the economy of the coal mill.

[0043] 3. By installing a permanent magnet speed regulator 2 between the permanent magnet synchronous motor 1 and the planetary reducer 3, the output speed of the planetary reducer 3 can be reduced under low load, the power consumption of the coal mill can be reduced, the vibration can be reduced, the coal mill can be stably operated under 20% load, and the wear of the grinding parts can be reduced; the output speed of the planetary reducer 3 can be increased under full load, the grinding capacity can be improved, and the problem of insufficient capacity due to poor coal quality can be solved.

[0044] 4. The grinding roller 8 adopts a counterforce hydraulic variable loading system 6, so that part of the weight of the grinding roller 8 can be offset, and the power consumption of the grinding roller 8 under low load operation is reduced.

[0045] 5. By adopting the dynamic separator 5, the adaptability of the coal mill to coal variety change is improved, so that the boiler can be economically and stably operated.

[0046] The above embodiments only exemplarily illustrate the principles and effects of the present application, and are not used to limit the present application. Any person skilled in the art can modify or change the above embodiments without departing from the spirit and scope of the present application. Therefore, all equivalent modifications or changes completed by those skilled in the art without departing from the spirit and technical thought disclosed by the present application should be covered by the claims of the present application.

Claims

1. A coal mill operable at variable speeds, characterised in that: It comprises a driving assembly, a transmission assembly, a grinding body (4), a reaction force hydraulic variable loading system (6) and a separator, wherein, The driving assembly comprises a permanent magnet synchronous motor (1); The transmission assembly comprises a planetary reducer (3); the input end of the planetary reducer (3) is in transmission connection with the output end of the permanent magnet synchronous motor (1); The transmission assembly further comprises a permanent magnet speed regulator (2); The permanent magnet speed regulator (2) is in transmission connection between the output end of the permanent magnet synchronous motor (1) and the input end of the planetary reducer (3), and is used for adjusting the torque input by the permanent magnet synchronous motor (1) to the planetary reducer (3) without changing the rotation speed of the output end of the permanent magnet synchronous motor (1); The grinding body (4) comprises an outer shell, a grinding disc (7) and a grinding roller (8); the grinding roller (8) and the grinding disc (7) are both arranged in the outer shell; the grinding disc (7) is in transmission connection with the output end of the planetary reducer (3); The reaction force hydraulic variable loading system (6) is arranged outside the outer shell and is connected with the grinding roller (8); the grinding roller (8) is used for loading the grinding roller (8) on the grinding disc (7) and adjusting the pressure between the grinding roller (8) and the grinding disc (7) through the reaction force hydraulic variable loading system (6); The separator comprises a dynamic separator (5); the dynamic separator (5) is located at the upper end of the outer shell and is used for screening the coal powder after being ground by the grinding roller (8) and the grinding disc (7).

2. A coal pulverizer capable of variable speed operation according to claim 1, characterized in that: The permanent magnet synchronous motor (1) is of a double-shaft type, is horizontally installed, has an IC611 cooling mode, has a protection level not less than IP54, has a power factor greater than or equal to 0.98, and has a motor guaranteed efficiency greater than or equal to 96%.

3. A coal pulverizer capable of variable speed operation according to claim 2, characterized in that: The input stage of the planetary reducer (3) adopts an input stage spiral bevel gear pair; The input stage spiral bevel gear pair comprises an input stage bevel gear shaft and a bevel gear; the bevel gear is installed on the input stage bevel gear shaft and is used for transmission; The bevel gear adopts an extended epicycloid tooth system and is a hard tooth surface gear with a tooth surface hardness of HRC58-HRC62.

4. The adjustable speed operation coal mill as claimed in claim 1, wherein: The permanent magnet speed regulator (2) comprises a disc type permanent magnet speed regulator, a cylinder type permanent magnet speed regulator or a double cylinder type permanent magnet speed regulator.

5. The adjustable speed operation coal mill as claimed in claim 1, wherein, The output end of the permanent magnet speed regulator (2) is provided with a speed sensor; The speed sensor is used for measuring the rotation speed of the output end of the permanent magnet synchronous motor (1) and is in communication connection with a DCS system, so that the DCS system can display the rotation speed of the output end of the permanent magnet speed regulator (2) measured by the speed sensor.

6. The adjustable speed operation coal mill of claim 1, wherein, The reaction force hydraulic variable loading system (6) is in communication connection with the DCS system, so that the DCS system can display the loading force and the reaction force of the reaction force hydraulic variable loading system (6).

7. The adjustable speed operation coal mill as claimed in claim 1, wherein, The loading force and the reaction force of the reaction force hydraulic variable loading system (6) are controlled by a hydraulic pump station.

8. The adjustable speed operation coal mill of claim 1, wherein, The dynamic separator (5) is a dynamic and static combined dynamic separator (5); the transmission mode of the dynamic separator (5) is belt transmission or gear transmission.

9. The adjustable speed operation coal mill as claimed in claim 1, wherein, The dynamic separator (5) is driven by a frequency converter and a variable frequency motor; The dynamic separator (5), the frequency converter and the variable frequency motor are in communication connection with the DCS system, so that the DCS system can automatically and remotely adjust the rotating speed of the variable frequency motor, and then adjust the rotating speed of the dynamic separator (5).

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