阅读说明：本技术 一种物料粉碎粒度控制系统及其控制方法和应用 (Material crushing granularity control system and control method and application thereof ) 是由 蒋文平 唐志强 袁小波 于 2021-07-02 设计创作，主要内容包括：本发明提供一种物料粉碎粒度控制系统及其控制方法和应用,以解决锂电池正极材料粉碎过程易导致粒度不均匀的问题。一种物料粉碎粒度控制系统包括：操作界面单元,用于输入粉碎物料粒度的设定参数；检测单元,用于进行周期取样获取粒度测量值以及记录粒度数据条数与取样次数的实际参数；控制单元,用于将实际参数与设定参数进行计算判断,根据判断结果控制执行单元和检测单元工作；执行单元,用于执行物料粉碎和粉碎过程中的粒度调节机制。通过对粉碎工作中粒度实时监控,发现粒度异常情况自动控制调节机制,将动态取样周期与多档位粒度调节配合,使得以最快速度判断粒度异常的具体情况,在短时间内完成异常调节；提高了效率保证了粒度一致性。(The invention provides a material crushing granularity control system, a control method and application thereof, and aims to solve the problem that the granularity is uneven easily caused in the crushing process of a lithium battery anode material. A material crushing granularity control system comprises: the operation interface unit is used for inputting set parameters of the granularity of the crushed materials; the detection unit is used for carrying out periodic sampling to obtain a granularity measurement value and recording the number of granularity data and actual parameters of sampling times; the control unit is used for calculating and judging the actual parameters and the set parameters and controlling the execution unit and the detection unit to work according to the judgment result; and the execution unit is used for executing the granularity regulation mechanism in the material crushing and crushing process. The granularity in the crushing work is monitored in real time, an automatic control and adjustment mechanism is found for the abnormal granularity condition, and the dynamic sampling period is matched with the multi-gear granularity adjustment, so that the specific condition of the abnormal granularity is judged at the highest speed, and the abnormal adjustment is completed in a short time; the efficiency is improved and the granularity consistency is ensured.)

1. A material crushing granularity control system is characterized by comprising:

the operation interface unit is used for inputting set parameters related to the granularity of the crushed materials, and the set parameters comprise: the granularity target value, the granularity allowable error, the sampling period, the granularity continuous standard exceeding allowable times and the granularity continuous normal setting times;

the detection unit is used for carrying out periodic sampling, acquiring a granularity measurement value and recording actual parameters of the number of granularity data and the sampling times;

the control unit is electrically connected with the operation interface unit and the detection unit and is used for intelligently calculating and judging the actual parameters and the set parameters and controlling the execution unit and the detection unit to work according to the calculation and judgment result;

the execution unit is used for executing a granularity adjusting mechanism in the material crushing and crushing process and comprises a grinding machine, a particle catcher and an induced draft fan, a grading wheel and a crusher for granularity adjustment are arranged in a grinding cavity of the grinding machine, the particle catcher is connected with a discharge hole of the grinding cavity, the induced draft fan is connected with the top of the particle catcher, and the input end of the execution unit is electrically connected with the output end of the control unit; and the execution unit increases or decreases the working frequency of the induced draft fan, the grading wheel and the pulverizer according to the instruction sent by the control unit, so that the material crushing granularity is adjusted to be within the granularity allowable error range.

2. The material crushing size control system according to claim 1, wherein the sampling period is divided into a normal sampling period and an abnormal sampling period.

3. The material crushing size control system according to claim 2, wherein the interval time of the abnormal sampling period is shorter than the normal sampling period; the abnormal sampling period is a plurality of gears, and the lower the gear is, the longer the interval time of the sampling period is; the higher the gear, the shorter the sampling period interval.

4. The material crushing granularity control system as claimed in claim 1, wherein the detecting unit is a granularity meter, a sampling port is arranged on a pipeline connected with the discharge port of the particle catcher, and the position of the granularity meter corresponds to the sampling port.

5. A method for controlling the granularity of material crushing is characterized by comprising the following steps:

step 1: starting a material crushing granularity control system;

step 2: sampling at intervals at the output end of the crushed material according to the set parameters of the normal sampling period;

and step 3: detecting the granularity of the sample material obtained in the step 2, and comparing the granularity measured value with the granularity target value; if the difference value of the two is smaller than the granularity allowable error, the granularity is judged to be normal; if the difference value of the two is larger than the granularity allowable error, judging that the granularity exceeds the standard;

and 4, step 4: returning to the step 2 when the granularity is judged to be normal; when the granularity exceeds the standard, adding 1 to a counting system of 'granularity continuous exceeding times';

and 5: comparing the counting system value of the number of times that the granularity continuously exceeds the standard with the set value of the number of times that the granularity continuously exceeds the standard; if the counting system value of the granularity continuous exceeding times is larger than the set value of the granularity continuous exceeding allowable times, entering the step 6; otherwise, returning to the step 2;

step 6: starting a granularity adjusting mechanism of a material crushing granularity control system, and sampling at intervals according to an abnormal sampling period;

and 7: detecting the granularity of the sample material obtained in the step 6, and comparing the granularity measured value with the granularity target value; if the difference value of the two is smaller than the granularity allowable error, the granularity is judged to be normal; if the difference value of the two is larger than the granularity allowable error, judging that the granularity exceeds the standard;

and 8: returning to the step 6 when the granularity is judged to exceed the standard; when the granularity is judged to be normal, adding 1 to a counting system of 'granularity continuous normal times';

and step 9: comparing the counting system value of the continuous normal times of the granularity with the set value of the continuous normal set times of the granularity; if the counting system value of the continuous normal times of the granularity is larger than the set value of the continuous normal set times of the granularity, closing a granularity adjusting mechanism of a material crushing granularity control system, and then returning to the step 2; otherwise, returning to the step 6;

step 10: and closing the material crushing granularity control system after the material crushing work is finished.

6. The control method according to claim 5, characterized in that: the normal sampling period is a static value, and the abnormal sampling period is a dynamic value; the larger the absolute value of the difference between the granularity measured value and the granularity target value is, the higher the gear of the abnormal sampling period is, and the shorter the interval time of the sampling period is.

7. The control method according to claim 5, characterized in that: the granularity adjusting mechanism is provided with a plurality of levels of gears, and each level of gears corresponds to the working frequency of the one-level crusher, the grading wheel and the induced draft fan.

8. The control method according to claim 7, characterized in that: the gear of the granularity adjusting mechanism automatically selects a gear according to the magnitude relation of the difference between the granularity measured value and the granularity target value;

when the particle size measured value has deviation with the particle size target value but the deviation is larger, the automatically selected gear can enable the working frequency of the pulverizer, the grading wheel and the induced draft fan to change more; when the deviation between the particle size measured value and the particle size target value is small, the automatically selected gear can ensure that the working frequency of the pulverizer, the grading wheel and the induced draft fan changes less;

when the deviation between the granularity measured value and the granularity target value is positive deviation, increasing the working frequency of the pulverizer and the grading wheel, and reducing the working frequency of the induced draft fan; when the granularity measured value and the granularity target value are negative deviation, the working frequency of the pulverizer and the grading wheel is reduced, and the working frequency of the induced draft fan is increased.

9. The control method according to claim 5, characterized in that: the sampling times in the steps 2 and 6 are recorded in a detection unit as the sampling times, and the granularity detection times in the steps 3 and 7 are recorded in a detection unit as the granularity data strip number; when the number of the granularity data is equal to the sampling times, the granularity sampling data is proved to be not lost, and the control unit normally sends out a command for controlling the operation of the execution unit and the detection unit; otherwise, the control unit stops sending the working commands of the execution unit and the detection unit and gives an alarm.

10. Use of the material crushing size control system according to any one of claims 1 to 4 in material crushing size control work of a positive electrode material for a lithium battery.

Technical Field

The invention belongs to the technical field of preparation of lithium battery anode materials, and particularly relates to a material crushing granularity control system and a control method and application thereof.

Background

The lithium ion battery is widely applied to various aspects such as wireless communication, transportation, aerospace and the like, and mainly comprises a positive electrode material, a lithium-embedded transition metal oxide, a negative electrode material such as highly graphitized carbon, a diaphragm such as a polyolefin microporous membrane, an electrolyte material and the like. The lithium ion anode material is a crucial factor for restricting the performance of the lithium ion battery in all aspects.

The performance of the lithium ion battery anode material, which is one of the key materials in the lithium ion battery, directly influences the performance of the whole lithium ion battery. Therefore, researchers have focused on the properties and characteristics of the positive electrode material of the lithium ion battery to solve the problems occurring in the use of the lithium ion battery or to improve the properties of the lithium ion battery. One method for ensuring the performance of the cathode material is to require that the particle size of the raw material monomer is uniform and the particle size meets the requirement when the cathode material is prepared. Because the electrochemical performance of the cathode material is easily reduced due to the excessive material particle size or the uneven size distribution of the raw material monomer. For example, the invention patent CN201811112306.0 discloses a method for preparing a lithium battery anode material NCM811 with uniform particle size; the main idea is to control the synthetic particle size of the lithium battery anode material by a chemical method.

However, after the lithium battery cathode material with a suitable particle size is synthesized by the chemical method, the situation of material hardening is difficult to avoid. Therefore, the prior art generally needs to perform crushing treatment on the chemically synthesized lithium battery cathode material so as to achieve the optimal effect of the material granularity. In the crushing process of the lithium battery anode material, the concrete hardening degree of the material fed in each time period in the crushing system is different, so that the crushed particle size is inevitably uneven if the material is crushed according to a uniform crushing line. Therefore, the rational regulation and control of the crushing process of the lithium battery anode material becomes a problem to be solved urgently.

Disclosure of Invention

The invention provides a material crushing granularity control system, a control method and application thereof for solving the technical problems, and aims to solve the problem that uniform crushing lines in the crushing process of lithium battery anode materials are easy to cause uneven granularity of crushed materials.

The technical scheme adopted by the invention for solving the technical problems is as follows:

a material crushing size control system comprising:

the operation interface unit is used for inputting set parameters related to the granularity of the crushed materials, and the set parameters comprise: the granularity target value, the granularity allowable error, the sampling period, the granularity continuous standard exceeding allowable times and the granularity continuous normal setting times;

the detection unit is used for carrying out periodic sampling, acquiring a granularity measurement value and recording actual parameters of the number of granularity data and the sampling times;

the control unit is electrically connected with the operation interface unit and the detection unit and is used for intelligently calculating and judging the actual parameters and the set parameters and controlling the execution unit and the detection unit to work according to the calculation and judgment result;

the execution unit is used for executing a granularity adjusting mechanism in the material crushing and crushing process and comprises a grinding machine, a particle catcher and an induced draft fan, a grading wheel and a crusher for granularity adjustment are arranged in a grinding cavity of the grinding machine, the particle catcher is connected with a discharge hole of the grinding cavity, the induced draft fan is connected with the top of the particle catcher, and the input end of the execution unit is electrically connected with the output end of the control unit; and the execution unit increases or decreases the working frequency of the induced draft fan, the grading wheel and the pulverizer according to the instruction sent by the control unit, so that the material crushing granularity is adjusted to be within the granularity allowable error range.

More preferably, the sampling period is divided into a normal sampling period and an abnormal sampling period.

More preferably, the interval time of the abnormal sampling period is shorter than the normal sampling period; the abnormal sampling period is a plurality of gears, and the lower the gear is, the longer the interval time of the sampling period is; the higher the gear, the shorter the sampling period interval.

Preferably, the detection unit is a particle size analyzer, a sampling port is arranged on a pipeline connected with a discharge port of the grinder, and the particle catcher is positioned corresponding to the sampling port.

A control method of the material crushing granularity control system comprises the following steps:

step 1: starting a material crushing granularity control system;

step 2: sampling at intervals at the output end of the crushed material according to the set parameters of the normal sampling period;

and step 3: detecting the granularity of the sample material obtained in the step 2, and comparing the granularity measured value with the granularity target value; if the difference value of the two is smaller than the granularity allowable error, the granularity is judged to be normal; if the difference value of the two is larger than the granularity allowable error, judging that the granularity exceeds the standard;

and 4, step 4: returning to the step 2 when the granularity is judged to be normal; when the granularity exceeds the standard, adding 1 to a counting system of 'granularity continuous exceeding times';

and 5: comparing the counting system value of the number of times that the granularity continuously exceeds the standard with the set value of the number of times that the granularity continuously exceeds the standard; if the counting system value of the granularity continuous exceeding times is larger than the set value of the granularity continuous exceeding allowable times, entering the step 6; otherwise, returning to the step 2;

step 6: starting a granularity adjusting mechanism of a material crushing granularity control system, and sampling at intervals according to an abnormal sampling period;

and 7: detecting the granularity of the sample material obtained in the step 6, and comparing the granularity measured value with the granularity target value; if the difference value of the two is smaller than the granularity allowable error, the granularity is judged to be normal; if the difference value of the two is larger than the granularity allowable error, judging that the granularity exceeds the standard;

and 8: returning to the step 6 when the granularity is judged to exceed the standard; when the granularity is judged to be normal, adding 1 to a counting system of 'granularity continuous normal times';

and step 9: comparing the counting system value of the continuous normal times of the granularity with the set value of the continuous normal set times of the granularity; if the counting system value of the continuous normal times of the granularity is larger than the set value of the continuous normal set times of the granularity, closing a granularity adjusting mechanism of a material crushing granularity control system, and then returning to the step 2; otherwise, returning to the step 6;

step 10: and closing the material crushing granularity control system after the material crushing work is finished.

Preferably, the normal sampling period is a static value, and the abnormal sampling period is a dynamic value; the larger the absolute value of the difference between the granularity measured value and the granularity target value is, the higher the gear of the abnormal sampling period is, and the shorter the interval time of the sampling period is.

Further preferably, the particle size adjusting mechanism is provided with a plurality of levels of gears, and each level of gears corresponds to the working frequency of the primary crusher, the grading wheel and the induced draft fan.

Further preferably, the gear of the granularity adjusting mechanism automatically selects the gear according to the size relationship of the difference between the granularity measured value and the granularity target value; when the particle size measured value has deviation with the particle size target value but the deviation is larger, the automatically selected gear can enable the working frequency of the pulverizer, the grading wheel and the induced draft fan to change more; when the deviation between the particle size measured value and the particle size target value is small, the automatically selected gear can ensure that the working frequency of the pulverizer, the grading wheel and the induced draft fan changes less; when the deviation between the granularity measured value and the granularity target value is positive deviation, increasing the working frequency of the pulverizer and the grading wheel, and reducing the working frequency of the induced draft fan; when the granularity measured value and the granularity target value are negative deviation, the working frequency of the pulverizer and the grading wheel is reduced, and the working frequency of the induced draft fan is increased.

Further preferably, the sampling times in the above steps 2 and 6 are recorded in the detection unit as "sampling times", and the particle size detection times in the above steps 3 and 7 are recorded in the detection unit as "number of pieces of particle size data"; when the number of the granularity data is equal to the sampling times, the granularity sampling data is proved to be not lost, and the control unit normally sends out a command for controlling the operation of the execution unit and the detection unit; otherwise, the control unit stops sending the working commands of the execution unit and the detection unit and gives an alarm.

The application of the material crushing granularity control system in the production of the lithium battery positive electrode material.

Compared with the prior art, the invention has the technical advantages that:

the material crushing granularity control system and the control method thereof realize real-time monitoring of the granularity of the material in the crushing work, can find the abnormal condition of the crushing granularity in time and automatically control and start the crushing granularity adjusting mechanism. By setting a multi-period sampling detection mode, the granularity consistency of the crushed materials in the same batch is better ensured.

Through the mode of dynamic cycle sample, under the prerequisite of guaranteeing the sample detection degree of accuracy, the reasonable sampling operation number of times that has reduced for the influence of sample detection process to crushing work process is minimum, has guaranteed the continuity of crushing work.

By setting a multi-gear granularity adjusting mechanism, the adjusting work when the granularity is abnormal is more pertinent, and the condition that the working equipment cannot be adjusted at the optimal working frequency under the condition of larger granularity abnormality is avoided; so that the granularity adjustment work can be completed more quickly.

The dynamic sampling period is matched with a multi-gear granularity adjusting mechanism to work, so that the crushing system can judge the specific condition of granularity abnormity at the highest speed, an optimal adjusting mode is selected, and the abnormity adjustment is completed in a short time; the efficiency of crushing process has greatly been improved.

Drawings

FIG. 1 is a schematic view of a process flow of a material crushing particle size control system according to embodiment 1 of the present invention;

fig. 2 is a schematic diagram illustrating information transfer relationships among units of the material crushing particle size control system according to embodiment 1 of the present invention;

fig. 3 is a logic diagram of a control method of the material crushing particle size control system according to embodiment 2 of the present invention.

Illustration of the drawings:

1. a storage bin; 2. a feeding star valve; 3. feeding a screw; 4. a grinder; 5. a pulverizer; 6. a grading wheel; 7. a particle trap; 8. a discharge butterfly valve; 9. a discharge star valve; 10. a particle size analyzer; 11. an induced draft fan.

Detailed Description

The technical solutions of the present invention will be described clearly and completely with reference to the accompanying drawings, and it should be understood that the described embodiments are some, but not all embodiments of the present invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention. In the description of the present invention, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc., indicate orientations or positional relationships based on the orientations or positional relationships shown in the drawings, and are only for convenience of description and simplicity of description, but do not indicate or imply that the device or element being referred to must have a particular orientation, be constructed and operated in a particular orientation, and thus, should not be construed as limiting the present invention.

Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance. In the description of the present invention, it should be noted that, unless otherwise explicitly specified or limited, the terms "mounted," "connected," and "connected" are to be construed broadly, e.g., as meaning either a fixed connection, a removable connection, or an integral connection; can be mechanically or electrically connected; they may be connected directly or indirectly through intervening media, or they may be interconnected between two elements. The specific meanings of the above terms in the present invention can be understood in specific cases to those skilled in the art.

Example 1:

a material crushing size control system, as shown in fig. 2, comprising:

the operation interface unit is used for inputting set parameters related to the granularity of the crushed materials, and the set parameters comprise: the granularity target value, the granularity allowable error, the sampling period, the granularity continuous standard exceeding allowable times and the granularity continuous normal setting times;

the detection unit is used for carrying out periodic sampling, acquiring a granularity measurement value and recording actual parameters of the number of granularity data and the sampling times;

the control unit is electrically connected with the operation interface unit and the detection unit and is used for intelligently calculating and judging the actual parameters and the set parameters and controlling the execution unit and the detection unit to work according to the calculation and judgment result;

the execution unit is used for executing a granularity adjusting mechanism in the material crushing and crushing process and comprises a grinding machine 4, a particle catcher 7 and an induced draft fan 11, a grading wheel 6 and a crushing machine 5 for granularity adjustment are arranged in a grinding cavity of the grinding machine 4, the particle catcher 7 is connected with a discharge hole of the grinding cavity, the induced draft fan 11 is connected with the top of the particle catcher 7, and the input end of the execution unit is electrically connected with the output end of the control unit; and the execution unit increases or decreases the working frequency of the induced draft fan 11, the grading wheel 6 and the pulverizer 5 according to the instruction sent by the control unit, so that the material crushing granularity is adjusted to be within the granularity allowable error range.

In the present embodiment, the sampling period is divided into a normal sampling period and an abnormal sampling period. The interval time of the abnormal sampling period is shorter than that of the normal sampling period; the abnormal sampling period is a plurality of gears, and the lower the gear is, the longer the interval time of the sampling period is; the higher the gear, the shorter the sampling period interval.

In this embodiment, the detecting unit is a particle analyzer, a sampling port is arranged on a pipeline connected with the discharge port of the grinder, and the particle catcher is positioned corresponding to the sampling port.

In this embodiment, the process flow of the material crushing size control system is shown in FIG. 1,

the material to be crushed falls into the feeding screw 3 from the stock bin 1 through the feeding star valve 2, and then is converted into a grinding cavity which is transversely conveyed into the grinding machine 4 through the feeding screw 3, the grinding machine 5 in the grinding cavity drives the grinding disc of the grinding cavity to rotate so as to crush the material, the grading wheel 6 in the grinding cavity can directly adjust the particle size of the material, the material with small particle size can leave the grinding cavity through the grading wheel 6, the material with large particle size is blocked by the grading wheel 6 and then continuously ground by the grinding disc, the crushed material output from the grinding cavity of the grinding machine 4 is collected through the particle catcher 7 to obtain a crushed material product, and the crushed material product sequentially passes through the discharging butterfly valve 8 and the discharging star valve 9 and is output to the outside of a crushing route. The particle analyzer 10 samples and detects the crushed material product at the output end of the discharge star valve 9. The induced draft fan 11 is connected with the particle catcher 7 and the grinder 4; the draught fan 11 provides power for the material flow in the grinding cavity of the grinding machine 4, the ground material can be sucked to the outside of the grinding cavity by the draught fan 11, and meanwhile, the draught fan 11 conveys return air to the grinding cavity through the air inlet of the grinding cavity.

Example 2:

an operation method for controlling the crushed particle size of the lithium battery positive electrode material in the application of the material crushed particle size control system in the production of the lithium battery positive electrode material is provided in embodiment 1.

The method for inputting the setting parameters in the operation interface unit of the material crushing granularity control system comprises the following steps: the number of times of allowed standard exceeding of continuous granularity is 3, the number of times of normally setting continuous granularity is 3, the target value of granularity is 15 microns, the allowable error of granularity is 1 micron, the normal sampling period is 5 minutes/time, the abnormal sampling period (the abnormal sampling period is two gears, the sampling period of one gear is 3 minutes/time, the sampling period of the second gear is 1 minute/time), and the working frequency parameters of an induced draft fan, a grading wheel and a pulverizer. Then, as shown in fig. 3, the execution unit of the material crushing granularity control system is started to start the following steps:

step 1: starting a material crushing granularity control system;

step 2: sampling at intervals at the output end of the crushed material according to the set parameters of the normal sampling period;

and step 3: detecting the granularity of the sample material obtained in the step 2, and comparing the granularity measured value with the granularity target value; if the difference value of the two is smaller than the granularity allowable error, the granularity is judged to be normal; if the difference value of the two is larger than the granularity allowable error, judging that the granularity exceeds the standard;

and 4, step 4: returning to the step 2 when the granularity is judged to be normal; when the granularity exceeds the standard, adding 1 to a counting system of 'granularity continuous exceeding times';

and 5: comparing the counting system value of the number of times that the granularity continuously exceeds the standard with the set value of the number of times that the granularity continuously exceeds the standard; if the counting system value of the granularity continuous exceeding times is larger than the set value of the granularity continuous exceeding allowable times, entering the step 6; otherwise, returning to the step 2;

step 6: starting a granularity adjusting mechanism of a material crushing granularity control system, and sampling at intervals according to an abnormal sampling period;

and 7: detecting the granularity of the sample material obtained in the step 6, and comparing the granularity measured value with the granularity target value; if the difference value of the two is smaller than the granularity allowable error, the granularity is judged to be normal; if the difference value of the two is larger than the granularity allowable error, judging that the granularity exceeds the standard;

and 8: returning to the step 6 when the granularity is judged to exceed the standard; when the granularity is judged to be normal, adding 1 to a counting system of 'granularity continuous normal times';

and step 9: comparing the counting system value of the continuous normal times of the granularity with the set value of the continuous normal set times of the granularity; if the counting system value of the continuous normal times of the granularity is larger than the set value of the continuous normal set times of the granularity, closing a granularity adjusting mechanism of a material crushing granularity control system, and then returning to the step 2; otherwise, returning to the step 6;

step 10: and closing the material crushing granularity control system after the material crushing work is finished.

In this embodiment, the normal sampling period is a static value, and the abnormal sampling period is a dynamic value; the larger the absolute value of the difference between the granularity measured value and the granularity target value is, the higher the gear of the abnormal sampling period is, and the shorter the interval time of the sampling period is.

In this embodiment, above-mentioned granularity adjustment mechanism is equipped with the level four gear, and the operating frequency of one-level rubbing crusher, gradation wheel and draught fan is corresponded to every level gear. The working frequency corresponding to the first-level gear is 35Hz of the crusher, 20Hz of the grading wheel and 30Hz of the induced draft fan; the working frequency corresponding to the second-level gear is 32Hz of the crusher, 15Hz of the grading wheel and 32Hz of the draught fan; the working frequency corresponding to the three-level gear is 38Hz of the crusher, 25Hz of the grading wheel and 28Hz of the induced draft fan; the working frequency corresponding to the four-stage gear is 40Hz of the crusher, 30Hz of the grading wheel and 26Hz of the induced draft fan.

In this embodiment, when the particle size of the pulverized material in the control system is within the normal range, the operating frequency of each device is as follows: the pulverizer 36Hz, the grading wheel 22Hz and the induced draft fan 29 Hz; when the material crushing granularity in the control system is in an abnormal range, the gear of the granularity adjusting mechanism automatically selects the gear according to the difference value between the granularity measured value and the granularity target value; when the granularity measured value is smaller than the granularity target value, if the difference range is 1-2 μm, selecting a first-level gear, and if the difference range exceeds 2 μm, selecting a second-level gear; when the granularity measured value is larger than the granularity target value, a three-level gear is selected when the difference range is 1-2 mu m, and a four-level gear is selected when the difference range exceeds 2 mu m.

In the present embodiment, the sampling times in the above steps 2 and 6 are recorded in the detection unit as "sampling times", and the particle size detection times in the above steps 3 and 7 are recorded in the detection unit as "number of pieces of particle size data"; when the number of the granularity data is equal to the sampling times, the granularity sampling data is proved to be not lost, and the control unit normally sends out a command for controlling the operation of the execution unit and the detection unit; otherwise, the control unit stops sending the working commands of the execution unit and the detection unit and gives an alarm.