JPH0243542B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for controlling a closed-circuit crushing system for crushing materials such as cement and clinker, and more specifically, by constantly maintaining the crushing operation in the crusher in an optimal state. The present invention relates to a method of controlling a grinding system to stably and efficiently produce products with a predetermined fineness.

Conventionally, as a method of controlling a closed-circuit crushing system, the transfer amount of a transport device such as a bucket elevator installed at the outlet of the crusher is controlled to a constant level, thereby ensuring that the amount of crushed material passing through the crusher is always constant. A so-called constant circulation rate control method is adopted. 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, the crushed material is discharged from the crusher and classified into a predetermined particle size range by a classifier. The above change is then 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 give a large time constant to the control operation, but it has been revealed that if this proposal is implemented, the dispersion in the particle size distribution of the product will increase.

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

In order to solve the above-mentioned problems, a method has been proposed and put into practical use that detects changes in the fineness of the crushed material after it has been crushed and classified, and estimates and controls the amount of returned powder. However, good control results have not always been obtained.

The purpose of the present invention is to solve the problems associated with the conventional control methods as described above. Based on the deviation of the yield value from the target yield value and the correlation formula set in advance between the yield and the raw material supply amount, a calculator is used to determine the change control amount for the supplied crushed material, and this change is The gist of the invention is to control a raw material supply device according to a controlled amount. According to the control method according to the present invention, the crushing system quickly responds to changes in the crushing characteristics of the crusher and the pulverizability of the crushed material, and the particle size distribution of the crushed product is always kept stably and accurately within a predetermined range. In addition, it is possible to prevent excessive grinding in the grinder and suppress the loss of grinding energy to a minimum level.

The present invention will now be described in detail with reference to the accompanying drawings, which illustrate the control method according to the present invention applied to a cement clinker grinding system.

For example, cement clinker sent from a raw material supply device 1 such as a belt feeder is crushed in a crusher 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 classification device 4, the fine powders finer than a predetermined fineness are conveyed out of the crushing system as products through a passage 5, while the crushed products coarser than the predetermined fineness are passed through a passage 6. It is then sent back to the crusher 2 and subjected to re-pulverization.

In order to implement the control method according to the present invention, a yield measuring device 7 is provided at the outlet of the crusher 2 in the cement crushing system as described above. Here, this yield measuring device is a device that samples a part of the crushed product crushed by the crusher 2 at the crusher outlet and measures the percentage of the sample that falls within a predetermined particle size range as the yield. It is. For cement, this predetermined particle size range is 2-40μ, preferably 2
~14μ. The data measured by the yield measuring device 7 is sent to a computing unit 8. This calculator 8 calculates the deviation of the actually measured yield value from the target yield value, and calculates the deviation of the cement/clinker supply amount based on the correlation formula set in advance between the yield and the supply amount of the crushed material. A change control value is calculated for the change control value, and a command is issued to the raw material supply device 1. The operating conditions of the raw material supply device 1, such as the rotation speed of the belt drive roller, the opening degree of the hopper outlet, etc., are adjusted based on the commands from the calculator 8, and the actual yield value of the crushed product discharged from the crusher 2 is determined. Control is performed so that the yield approaches the target yield value.

Next, the configuration of the yield measuring device 7, which is an essential component for carrying out the control method according to the present invention, will be briefly explained with reference to FIG. 2.

The sample extracted at the outlet of the crusher 2 in FIG. It is then supplied to the classification feeder 13. The classification feeder 13 has a receiving tank 13'.
and a screw feeder 13'', through which the sample is fed to a classifier 14 for measuring the yield. 15
is a weighing scale and measures the amount of sample supplied.

In the case of a cement pulverization system, the classifier 14 for measuring the yield is one that can accurately classify crushed products with a particle size distribution of usually 2 to 40μ, preferably 2 to 14μ. Any structure or model may be used, but for example,
It is effective to use the 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 weighing 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 8 in Fig. 1, the weight ratio of the classified particles in a predetermined particle size range to the weight of the supplied sample, that is, the yield, is calculated, and the deviation from the target yield value is calculated. is required. The above-described control can then be carried out 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 present invention is not limited to what is shown in FIG. It does not inquire about its configuration, model, etc.

Furthermore, it goes without saying that the method of the present invention is not only applicable to cement grinding systems, but can also be used to control all closed-circuit grinding systems.

As described above, according to the control method of the present invention, the pulverization state can be detected by sampling immediately after pulverization, so when the particle size or pulverizability of the pulverized material fluctuates, and as a result, the pulverization state changes. However, since it is possible to immediately initiate an adjustment operation in response to this change, the crushed material is always kept in a stable state without the hunting phenomenon that is often seen when implementing conventional control methods. Grinding can be carried out.

As a concrete result of adopting the method of the present invention,
The production output per hour increased by 3%, and the variation in production output, expressed as the daily coefficient of variation within January, was reduced from 5% to 3%, and moreover, stable operation could be continued. .

[Brief explanation of drawings]

FIG. 1 is a schematic diagram illustrating a closed circuit crushing system for cement to which the control method according to the present invention is applied. Second
The figure is a schematic diagram conceptually illustrating the configuration of a yield measuring device necessary for carrying out the method of the present invention. 1... Raw material supply device, 2... Pulverizer, 3... Transportation device, 4... Classification device, 5, 6... Passage, 7...
... Yield measurement device, 8 ... Arithmetic unit, 11 ... Sample transporter, 12 ... Sampling gate, 13
...Classification feeder, 13'...Receiver tank, 13''...
Screw feeder, 14... Classifier, 15...
...Weight scale, 16...Hopper, 17...Weight scale,
18... Collection device.

Claims (1)

[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 separates fine powder of the required degree of powder and 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 yield measuring device, and the deviation between the measured yield value and the target yield value is calculated using a calculator. At the same time, the calculation unit calculates a control amount of the amount of crushed material supplied according to the deviation, and then this control amount is transmitted from the calculation unit to the raw material supply device to supply the crushed material to the crusher. A control method for a closed-circuit pulverization system, characterized in that the amount is changed so that the yield value of the crushed product discharged from the pulverizer becomes a target yield value.