JPH0243544B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for controlling a closed-circuit grinding system for grinding materials such as cement and clinker, and more specifically, a method for controlling a grinder and a classifier under optimal operating conditions. The present invention relates to a method of controlling a grinding system so that a product having a predetermined fineness can be efficiently produced in a stable state by operating the grinding system.

Conventionally, as a method of controlling a closed-circuit crushing system, the transfer rate of a transport device such as a bucket elevator installed at the outlet of the crusher is controlled to a constant level, thereby constantly controlling the amount of crushed product passing through the crusher. A so-called circulation amount constant maintenance control method is adopted in which the circulation amount is maintained constant. However, the following problems have been pointed out regarding this conventional control method.

When the particle size or pulverizability of the crushed material supplied to the crusher changes due to some factor, in conventional control methods, after the crushed material is discharged from the crusher and classified into a predetermined particle size range by a classifier, The above change is detected only when the coarse powder is sent back to the crusher, subjected to re-pulverization, and discharged again. Therefore, since the response of the entire grinding system to the above-mentioned changes is slow, the timing of the adjustment operation is delayed, and the control result often suffers from hunting. In order to prevent such a hunting phenomenon, it has been proposed to provide a large time constant to the control operation, but it has been revealed that this method has the drawback of increasing dispersion in the particle size distribution of the product.

Furthermore, another problem with the conventional method is that when the pulverizability of the crushed material supplied to the pulverizer becomes very good, the pulverized material is pulverized more finely than necessary in the pulverizer, resulting in fine particles colliding with each other. A state of over-grinding occurs in which the particles agglomerate together. This means that grinding energy was consumed unnecessarily.

In order to solve the above-mentioned problems, a method of measuring the amount of coarse powder after pulverization and classification has been proposed and put into practical use, but good control results have not always been obtained.

On the other hand, there is a close correlation between the fineness of cement and the strength of cement, and management of fineness has traditionally been emphasized, and as mentioned above, the fineness of fine powder discharged from a classification device is measured. However, a method is usually used to control the operating conditions of the classifier (rotation speed, damper opening, etc.) based on the measurement results, but the conventional control method is Since the classification device is controlled only after measuring the fineness, as mentioned above, the response of the control operation to the grinding system is slow.
It has been revealed that the entire system is prone to hunting, resulting in a large variation in the fineness of the fine powder.

In the case of cement, the value of specific surface area is usually used to measure fineness, but although specific surface area is a characteristic value that indicates the fineness of the entire cement powder, It is not a scale that displays the distribution by diameter. In order to express the strength of cement, particle size distribution is considered important as a measure of the fineness of cement, and the amount of particle size groups of 2 to 40 microns is considered important for cement products. It is said that the amount of fine particles of 15μ or less contributes to the initial strength, and the amount of particles in the intermediate range of 15 to 40μ contributes to the long-term strength.

Generally, the particle size distribution of cement changes depending on the structure of the classifier and crusher, the operating conditions of the crushing process, etc. Therefore, in order to obtain the optimum particle size distribution to develop the strength of cement and to prevent a decrease in the strength of cement due to poor particle size distribution, it is necessary to increase the value of the specific surface area. There are times when it is necessary. However, measuring the specific surface area requires that measurement atmospheric conditions such as temperature and humidity be kept constant, and while offline measurements can satisfy these conditions,
It is difficult to satisfy these conditions with online measurements. Therefore, high measurement accuracy cannot be expected when the measurement value is online because it is easily influenced by the measurement atmosphere conditions such as temperature and humidity.

The present invention is intended to overcome the problems associated with conventional control methods for closed-circuit grinding systems as described above, and its purpose is to determine the yield value measured at the grinder outlet and the internal By adjusting the operating conditions of the classifier based on the flow rate detected at the appropriate point in the classifier, and at the same time appropriately adjusting the operating conditions of the raw material supply device based on the above-mentioned measured yield value, the system can be closed with high classification efficiency. Improves the responsiveness of the circuit crushing system to reduce the frequency of control operations of the classifier and reduce the amount of adjustment, while also preventing over-grinding in the crusher and minimizing loss of crushing energy. An object of the present invention is to provide a method for controlling a closed-circuit grinding system.

Another object of the present invention, in addition to the above-mentioned adjustment operation, is to sample the fine powder as a product from the crushed product classified by the classifier in the middle of the passage to carry it out from the crushing system, and to ,
By measuring the yield with a yield measuring device and adjusting the operating conditions of the classifier based on the deviation of the measured yield value from the target yield value, it is possible to reduce the variation in the powderiness of the product. An object of the present invention is to provide a control method for a circuit crushing system.

In order to achieve the above object, the present invention samples the crushed product discharged from a crusher, measures the collected sample using a yield measuring device, and calculates the target yield value from the measured yield value. At the same time, the flow rate of the crushed product is detected at an appropriate location within the crushing system, and a calculator calculates the particle size of the crushed product contained in the predetermined particle size range based on the above yield and the flow rate of the crushed product. Find the total amount. On the other hand, based on a correlation formula set in advance between the total amount of particles in a predetermined particle size range and the control amount of the classifier, the control amount of the classifier is calculated by a calculator,
The determined control amount is sent to the classifier to change the operating conditions of the classifier (rotation speed, damper opening, etc.), and the yield value of the product discharged from the classifier becomes the target yield value. At the same time, the control amount of the raw material supply device is calculated by a calculator based on a correlation formula set in advance between the deviation of the measured yield value from the target yield value and the raw material supply amount, The determined control amount is sent to the raw material supply device to change the operating conditions of the raw material supply device (rotation speed of the driving roller of the belt conveyor, opening degree of the hopper, etc.), and the crushed product is discharged from the above-mentioned crusher. The method is characterized in that the yield value is controlled so that it becomes a target yield value.

According to a preferred embodiment of the present invention, in addition to the above-mentioned control operation, the yield is measured by sampling fine powder as a product from the crushed product classified by the classifier, and the measured yield value is set to the target value. When the yield value deviates from the value, it is effective to control the operating conditions of the classifier based on a preset correlation between the yield and the control amount of the classifier. The latter control operation is performed after a predetermined period of time has elapsed after the former control operation was performed.

DESCRIPTION OF THE PREFERRED EMBODIMENTS A control method according to the present invention applied to a closed-circuit crushing system for cement clinker will be described in detail below with reference to the accompanying drawings.

In FIG. 1, cement clinker supplied from a feeder 1, such as a belt feeder, is pulverized in a pulverizer 2. The crushed product discharged from the crusher 2 is sent to a classifier 4, such as an air classifier, by a transport device 3, such as a bucket elevator. Among the crushed products classified by this classifier 4, the fine powder finer than the required fineness passes through the passage 5 and is discharged as a product from the closed circuit crushing system, while the crushed product coarser than the predetermined fineness passes through the passage 5. 6 and sent back to the crusher 2 for re-pulverization.

In order to apply the control method according to the present invention to the cement closed-circuit crushing system configured as described above, a yield measuring device 7 is provided at the outlet of the crusher 2.
The yield of the sample taken from the crushed product discharged from the crusher 2 is measured by the device 7, and the load current of the motor 8 of the transportation device 3 is adjusted to measure the flow rate of the crushed product. Measure. Here, the above-mentioned yield measuring device samples a part of the crushed product crushed by the crusher at the crusher outlet, classifies the collected sample using a classifier as a yield measuring device, and samples the sample. This device measures the percentage of particles within a predetermined particle size range as the yield. For cement, this predetermined particle size range is usually between 2 and 40 microns, preferably between 2 and 14 microns.

The yield value measured by the yield measuring device 7 is input to the calculator 9, and the value of the load current of the motor 8 that drives the transportation device 3 is input to the calculator as a measure for displaying the flow rate of the crushed product. 9 is input. Thereafter, the calculator 9 calculates the amount of particles within a predetermined particle size range contained in the crushed product based on the measured yield value and the flow rate of the crushed product. On the other hand, the correlation between this amount and the rotational speed of the motor 21 of the classification device is set in advance in the form of a correlation formula, and based on this correlation formula, the motor 21 is adjusted to achieve the desired proportion of fine powder in the product. The control amount is calculated by the calculator 9, and this value is sent to the classifier 4 as a control command.
will be sent to. The rotation speed of the motor 21 of the classification device 4 is controlled based on the command from the computing unit 9.

In the control method according to the present invention, simultaneously with the control operation of the classifier 4, the yield measuring device 7
The measured results are input to a separate circuit in the calculator 9, and it is determined whether or not there is a deviation from the target yield value stored in advance in the measured yield value, and if there is a deviation, the yield value is A control value for the raw material supply device is calculated based on a preset correlation between the amount of the raw material supply device 1 and the supply amount of the pulverized material, and a control command is issued to the raw material supply device 1.
Based on this control command, the operating conditions of the raw material supply device 1, such as the rotation speed of the drive roller of the conveyor belt, the opening degree of the hopper outlet, etc., are adjusted.
Control is performed to cause the measured yield value to converge to the target yield value.

Next, the configuration and function of the yield measuring device, which is an essential component for carrying out the control method according to the present invention, will be briefly explained with reference to FIG.

The sample taken at the outlet of the crusher 2 in FIG. Sorting feeder 13
is supplied to The classification feeder 13 is the receiving tank 1
3' and a screw feeder 13'', and the sample is supplied to a classifier 14 as a yield measuring device through the screw feeder 13''. 1
5 is a weighing scale, which measures the amount of sample supplied.

In the case of a cement crushing system, the classifier 14 can be of any structural type as long as it can accurately classify crushed products with a particle size distribution of usually 2 to 40μ, preferably 2 to 14μ. However, it is effective to use, for example, a powder classifier disclosed in JP-A-53-76466.

Among the particles classified by the classifier 14, coarse powder is discharged to a hopper 16. Since this hopper 16 is also provided with a weight scale 17, the proportion of coarse powder in the classified sample can be determined. On the other hand, the fine powder discharged from the classifier 14 is collected by a collection device 18 such as a bag filter. The weight scales 15 and 17 are each
Since it is connected to the calculator 9 in Fig. 1, the yield (measured yield value) is calculated based on the weight of the supplied sample and the weight of the coarse powder among the classified ones, and the target yield is The deviation from the value is determined. The above-described control can then be performed based on this deviation.

The above-mentioned yield measuring device shown in FIG. 2 is disclosed in Japanese Patent Application No. 56-123612, and is used to carry out the control method according to the present invention. This is merely an example, and the application of the method of the present invention is not limited to that shown in FIG. 2. If so, there is no question of its structural type.

Next, the configuration of the classifier which is the object to be controlled by the control method according to the present invention will be briefly explained with reference to FIG.

FIG. 3 conceptually illustrates the configuration of a cyclone separator commonly used for classifying cement. The cement pulverized by the pulverizer is fed into the raw material input port 20 via a transport device. The injected cement is uniformly dispersed in the radial direction by the dispersion plate 26 rotating at high speed, and after being classified by the blade 22 rotating at high speed, it is transported to a plurality of second stage cyclones 25 where it is The product is separated from the air and transported from the grinding system as a product through the passage 5 shown in FIG. 1 from the outlet at the lower end of the cyclone 25. On the other hand, for coarse powder, blade 2
After receiving the classification action in step 2, the first stage cyclone 24
is carried back to the crusher 2 through a passage 6 shown in FIG.

The cyclone separator shown in Fig. 3 is merely an illustration of one typical example of a classification device, and the application of the method of the present invention is not limited to this classification device, as long as it has the required classification performance. Needless to say, any configuration may be used.

FIG. 1 shows that a control command calculated and determined by the calculator 9 is transmitted to the motor 21 to control the rotation speed of the motor 21.

Specific results of adopting the method of the present invention, which simultaneously performs the two control operations described above, include: (1) The number of times the rotation speed of the motor of the classification device must be controlled can be reduced by approximately 30% compared to conventional control methods. At the same time, it was possible to reduce the variation in particle size distribution of fine powder of 2 to 40 microns, which is a cement product, from 7% to 3%, expressed as a daily coefficient of variation within January.

(2) Cement strength (JIS compressive strength on day 28)
We were able to reduce the dispersion of 5.0% to 3.0%, expressed as the daily coefficient of variation within January.

(3) Production output per hour can be increased by 5%,
Moreover, we were able to reduce the variation in production, expressed as the daily coefficient of variation within January, from 5% to 2.5%.

Furthermore, in the control method according to the present invention, variations in cement powderiness can be reduced by using the following control operations in combination. That is, the second step samples the fine powder (product) discharged from the classifier 4 in the middle of the passage 5 where it is carried out from the crushing system, and measures the yield of the collected sample in the particle size range of 2 to 40μ. A yield measuring device 30 is provided, and a measured yield value, which is a measurement result, is input to a second computing unit 31. Second
The calculator 31 calculates the deviation of the measured yield value from the target yield value or the reference yield value, and calculates the rotation speed based on a preset correlation formula between the deviation and the rotation speed of the motor 21. The amount of adjustment is determined, a control command is sent to the motor 21, and the motor 21 is controlled and operated.

Usually, the yield value measured by the first yield measuring device 7 provided at the outlet of the crusher 2 and the transport device 3
After the above-mentioned control operation of the classification device 4 determined by the first computing unit 9 based on the flow rate of the crushed material obtained from the load current of the motor 8, a predetermined period of time (usually 2 to 3 minutes) After the elapsed time, the second yield measuring device 30 and the calculator 31 are operated to obtain the measured yield value, and if there is a difference between the target yield value or the reference yield value, a control signal is sent. The signal is sent to the motor 21.

As a concrete example of the results of using the above-mentioned supplementary control operations in combination, the frequency of operating the rotation speed of the classification device can be reduced by 40% compared to conventional control methods, and the variation in particle size distribution of products between 2 and 40 μ was able to be reduced from 7% to 2%, expressed as a daily coefficient of variation for one month.

In the embodiment shown in FIG. 1, a first yield measuring device 7, a second yield measuring device 30 and a first
The computing unit 9 and the second computing unit 31 are installed separately, but after the use of the first yield measuring device 7 and the computing unit 9 is finished, a switching operation allows both to be used as they are for the second yield. It may be used as a measuring device and a computing unit.

As mentioned above, the present invention has been described with respect to a cement crushing system, but it is understood that the control method according to the present invention is not only applicable to cement crushing systems, but can be used to control all closed circuit crushing systems. Of course.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram illustrating a cement closed circuit crushing system to which the control method according to the present invention is applied. FIG. 2 is a schematic diagram conceptually illustrating the configuration of a yield measuring device necessary for carrying out the method of the present invention. FIG. 3 is a schematic cross-sectional diagram conceptually illustrating the configuration of a cyclone separator. 1... Raw material supply device, 2... Pulverizer, 3... Transport device, 4... Classifier, 8... Motor, 9...
...First computing unit, 10...Damper, 11...Sample transportation device, 12...Sampling gate, 13...Classification feeder, 14...Classifier,
15, 17... Weight scale, 16... Hopper, 18
...Fine powder collection device, 20...Raw material input port, 21...
...Motor, 22...Blade, 23...Blower, 24, 25...Cyclone, 30...Second yield measuring device, 31...Second computing unit.

Claims (1)

[Scope of Claims] 1. The raw material supply device supplies the crushed material to the crusher and crushes it, the crushed material is transferred to the classification device by the transportation device, and the classification device divides the crushed material into fine powder with the required degree of fineness. In a method for controlling a closed-circuit grinding system in which the fine powder is discharged as a product from the grinding system, and the coarse powder is sent back to the grinder for re-grinding, the grinding A part of the crushed product discharged from the crusher is collected near the outlet of the crusher, the yield of the collected sample is measured using a yield measuring device, and the measured yield value and target yield value are measured. A computing unit calculates the deviation from the above deviation, and the computing unit calculates a control amount for the amount of crushed material supplied according to the deviation, and then transmits this controlled amount from the computing unit to the raw material supply device to supply the crushed material. By changing the supply amount of Detect at a suitable location, use a calculator to determine the total amount of particles within a predetermined particle size range contained in the crushed product from the measured yield value and the flow rate of the crushed product; A control amount for the classification capacity is calculated according to the total amount of materials in the range, and then this control amount is transmitted from the computing unit to the classification device to change the classification capacity, and the product discharged from the classification device is collected. A method for controlling a closed-circuit grinding system, characterized by controlling a rate value to a target yield value. 2. The method according to claim 1, wherein the flow rate of the crushed product is detected by the load current of a drive device of a transportation device. 3. The raw material supply device supplies the crushed material to the crusher and crushes it, the crushed material is transferred to the classification device by the transport device, and the classification device separates the fine powder of the required degree of powder and the other coarse powder. A method for controlling a closed-circuit grinding system in which the fine powder is discharged as a product from the grinding system, and the coarse powder is sent back to the grinder for re-pulverization. A portion of the product is collected near the outlet of the crusher, the yield of the collected sample is measured using a first yield measuring device, and the deviation between the measured yield value and the target yield value is determined. is determined by a first computing unit, and the first computing unit computes a control amount for the amount of crushed material supplied according to the deviation, and then this controlled quantity is sent from the first computing unit to the raw material supply device. It transmits a signal to change the supply amount of crushed material so that the yield value of the crushed product discharged from the crusher becomes the target yield value, and also controls the passage of the crushed product discharged from the crusher. Detecting the flow rate at a suitable location in the system, and calculating the total amount of particles within a predetermined particle size range contained in the crushed product from the measured yield value and the flow rate through which the crushed product passes, using the first computing unit, Then, the first computing unit calculates a first control amount of the classification ability according to the total amount of particles in the predetermined particle size range, and then this first control amount is used by the first computing unit to calculate the classification capacity. A signal is sent to the device to change the classification capacity, and a part of the product discharged from the classification device is collected, and the yield of the collected sample is measured using a second yield measuring device. A second computing unit calculates the deviation between the measured yield value and the target yield measurement value, and the second computing unit computes a second control amount of the classification ability according to the deviation, and then, This second control amount is sent from the second computing unit to the classification device to change the classification capacity, and control is performed so that the yield value of the product discharged from the classification device becomes the target yield value. A method for controlling a closed-circuit grinding system characterized by the following. 4 After performing the control operation based on the first control amount calculated by the first calculation unit, after a predetermined period of time has elapsed, perform the control operation based on the second control amount calculated by the second calculation unit. The method according to claim 3, characterized in that: 5. After performing a control operation based on the first control amount, the first yield measuring device and computing unit are used as the second yield measuring device and computing unit by a switching operation. The method described in item 3 of the scope. 6. The method according to claim 3, characterized in that the flow rate of the crushed material is detected by the load current of the drive device of the transportation device.