JPS62160149A - Crushing control of closed circuit tube mill - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a method for controlling a closed-circuit grinding system, and more particularly to a method for controlling a closed-circuit tube mill used in the cement industry.

[Prior Art] FIG. 2 is a schematic diagram of a typical closed circuit tube mill. The raw material to be pulverized supplied by the raw material supply device 1 is sent to the mill 2 together with the pulverized material having a large particle size (return powder) that has been classified by the air separator 4 . The material to be crushed discharged from the mill 2 is transported by a packet elevator 3 to an air separator 4, where it is classified into fine powder to be taken out of the system and coarse powder (return powder) to be fed into the mill 2 again. Ru. The controlled variables used to control this grinding system include the power consumption of the packet elevator 3, the amount of returned powder, the circulating load (=the amount of returned powder/the amount of raw material supplied to be crushed), and the vibrations and sounds generated by the mill 2. It is used. Conventional control methods have been constant value control in which the feed rate of the raw material to be crushed is controlled by using any of these variables alone or in combination to keep the signal obtained therefrom constant.

In addition, water is sprinkled into Mill 2 when the temperature of the milled powder increases due to an increase in the temperature of the supplied cement clinker, etc., but the amount of water sprinkled is controlled in order to maintain the quality of the cement product within the specified value. For the purpose of control, this is performed automatically or manually in a separate loop from the aforementioned control of the supply amount of the raw material to be crushed.

[Problems to be solved by the invention] Controlled variables with excellent characteristics in terms of responsiveness and controllability among the aforementioned packet elevator power consumption, amount of returned powder, circulating load, vibration, and sound. can be said to be vibration. Therefore, there is a tendency for the controlled variable to shift from the power consumption of packet elevators, which have been widely used up until now, to vibration or sound. This vibration as a controlled variable is
This shows the state of coarse grinding in one chamber. As the amount of charge in one chamber increases, the vibration becomes smaller, and as the amount of charge decreases, the vibration increases.

From the perspective of grinding efficiency and controllability, vibration can be controlled and varied.

In the control method that uses the amount of raw material to be crushed as the operational variable, it is possible to control only the coarse crushing area in one chamber, and the fine crushing area in the second chamber cannot be controlled. If a disturbance occurs in the fine pulverization state in the second chamber due to a change in the pulverization properties of Therefore, when performing fixed price control of vibration in a multi-chamber mill, especially a two-chamber mill, some measure must be taken against fluctuations in the two chambers, that is, fluctuations in fine grindability. One solution to this problem is to use a weighted average of vibration and packet elevator power consumption as the controlled variable instead of vibration.Packet elevator power consumption is the amount of material to be crushed passing through the mill. It can be said to reflect the crushing state of the entire mill, including the case where the powder is transported directly to the packet elevator by the ventilation inside the mill.One variable that can be created from the combination of vibration and this packet elevator power consumption is , it is possible to say that the pulverization state of the two chambers is a controlled variable that expresses it to some extent, but vibration and packet elevator power consumption are variables that exhibit similar behavior, although there are considerable differences in terms of responsiveness. By taking a weighted average of these, the number of variables can be reduced from 1 to 2.
This is not desirable because it reduces the amount of information.

As mentioned above, the first problem with conventional control methods is that
In a one-man power, one-output control system with one controlled variable (variables such as vibration, packet elevator power consumption, or a combination thereof) and one manipulated variable (supply of raw material to be crushed), the information obtained from the crushing system is controlled by one room. This is related to the grinding state of the grinding system alone or of the whole grinding system, and the grinding states of the first chamber and the second chamber cannot be taken into the control system as one piece of information.

The second problem is that the temperature-water sprinkling amount control loop and the above-mentioned vibration-pulverization raw material supply amount control loop are independent and independent loops.

The amount of water sprinkled is controlled to keep the temperature of the material to be crushed at the mill outlet constant, but just as the temperature of the material to be ground changes depending on the amount of water sprinkled, the temperature of the material to be ground changes depending on the amount of raw material supplied. do. In other words, both the water sprinkling amount and the supply amount of the raw material to be ground can be manipulated variables to keep the temperature of the material to be ground at the mill outlet constant. In addition, water sprinkling has an auxiliary effect that improves grindability, such as reducing the amount of returned powder when the amount is increased.

This is largely related to the grinding capacity of the mill, and when the circulating load is small, the vibration, which is a controlled variable in the control system for the amount of raw material to be ground, tends to change due to water sprinkling, as shown in Figure 3. This has been confirmed in our experiments. Furthermore, when the supplied raw material to be crushed and the amount of water sprinkled are constant, there is a difference between the vibration and the temperature of the crushed object, as shown in Figure 4 (A), when the vibration increases, the temperature of the crushed object increases as shown in Figure 4 (B). ) to rise like this. On the other hand, it has been confirmed that when the temperature of the material to be crushed increases as shown in FIG. 5(A), the vibration increases as shown in FIG. 5(CB). In this way, the above two
The operating variables of each control system (supply amount of raw material to be crushed,
The amount of water sprinkled) is closely related to the controlled variables of the other control system (vibration, temperature of the material to be crushed), and conventional control methods completely ignore the effects of these variables on each other. .

[Means for Solving the Problems] Earlier, it was stated that the first four problems of the conventional control method are that the grinding state of the two chambers cannot be taken into consideration, and there is little information representing the grinding state. As a result of our research on actual mills, we found that when the temperature of the material to be ground at the mill exit is high, the pulverization performance in the second chamber decreases and the amount of returned powder increases; It has been found that the temperature of the material to be crushed at the mill outlet indicates a finely pulverized state, that is, a good pulverized state in the two chambers, due to the phenomenon that the pulverization property is improved and the amount of returned powder is reduced. Therefore, the controlled variables of the control system are:
Vibration is a variable that represents the state of coarse pulverization in the first chamber, and temperature of the material to be crushed at the mill outlet is a variable that represents the state of the pulverized material in the second chamber.
Variables are the best.

It is desirable to combine this with two operating variables, the amount of water sprinkling and the amount of raw material supplied, to make the control method a multi-input, multi-output, multivariable control.

If vibration and the temperature of the material to be ground at the mill outlet are used as controlled variables in a multivariable control system, the two possible operating variables are the amount of raw material supplied and the amount of water sprinkled, which are the operating variables for each controlled variable. It will be done. At this time, the amount of water sprinkled does not only contribute to the quality control of the product, but is also closely related to the temperature of the material to be crushed at the mill outlet, which reflects the pulverization properties in the two chambers mentioned earlier. It will also make a large contribution to the system. If multivariable control is performed using these four variables, the two control loops in a conventional control system can be reduced to one.
Since it is possible to perform control that takes into account the influence of variables on each other, the second problem mentioned above is also solved.

Therefore, in the present invention, these four variables are incorporated into a multivariable control system, and the amount of raw material to be crushed and the amount of water sprinkled are controlled by vibration (or vibration and the power consumption of the transportation device, each multiplied by a predetermined load). The temperature of the material to be crushed and the temperature of the material to be crushed are controlled comprehensively as operating variables.

[Function] Therefore, during mill operation, the signal from the vibration meter attached to the bearing metal at the mill inlet, the signal from the product temperature meter at the mill outlet, and the signal from the weighing machine installed in the raw material supply system transport machine are transmitted every moment. signals, as well as water flowmeters,
Based on the four pieces of information, the appropriate raw material supply amount and water sprinkling amount at that point in time are calculated using pre-given calculation formulas, and commands are issued to the raw material supply device and water sprinkling control valve, and this process is repeated. .

[Example] A case in which the control method according to the present invention is applied to cement tarinka crushing is shown in FIG. 1, and its details will be described.

Cement clinker and gypsum, which are raw materials to be crushed, are sent to the mill 2 by a raw material supply device 1.

The material to be crushed discharged from the mill 2 is sent to the packet elevator 3.
Then, it is transported to the air separator 4. In this air separator 4, the fine powder is classified into fine powder smaller than a predetermined particle size and other coarse powder, and the fine powder is taken out of the grinding system through a path 5 as a product. On the other hand, the coarse powder is returned to the mill 2 via path 6 and is ground again. In such a grinding system, in order to carry out the control method of the present invention, a vibration meter 8 is installed at the mill inlet bearing metal 7, and a thermometer 9 is installed at the mill 2 outlet.

A metering device 10 is installed in the raw material supply device 1, and a flow meter 12 is installed in the water sprinkler device 11, respectively.

The signal detected by the vibration meter 8 attached to the mill inlet bearing metal passes through a filter 13 to remove unnecessary frequency components and is sent to a controller 14. Similarly, the signal from the thermometer 9 and the signal from the measuring device 10,
The signals of the amount of water detected from the flowmeter 12 are also sent to the controller 14 through filters 15, 16, 17, respectively. In the controller 14, the operating amounts of the supply amount of the raw material to be crushed and the water sprinkling amount are calculated based on these four variables, and the raw material supply device 1 and the water sprinkling amount regulating valve 18 are controlled according to these operating amounts.

In other words, the vibration (or the vibration and the power consumption of the transportation device multiplied by a predetermined load) and the temperature of the pulverized material are the controlled variables, and the amount of raw material supplied and the amount of water sprinkled in the mill are controlled. If the controlled variable becomes large, the manipulated variable is increased accordingly.

The purpose is to reduce the above-mentioned controlled variable and restore the original stable state. Similarly, when the controlled variable becomes small, it goes without saying that the reverse operation can be performed, such as reducing the manipulated variable to return to the original stable state.

[effect] The control method according to the present invention has the following features.

(a) By incorporating the vibration generated from the mill, which reflects the grinding state in one chamber, and the temperature of the material to be ground at the mill outlet, which reflects the grinding state in two chambers, as one controlled variable, into a multivariable control system, It is possible to maintain a constant state of coarse and fine pulverization in the mill.

(b) The four variables of supply amount of raw material to be crushed, amount of water sprinkling, vibration, and temperature of crushed material at the mill outlet influence each other, but since it is a multivariable control system, control is performed taking these influences into consideration. be able to.

(c) Due to the reasons (a) and (b) above, a very stable control system can be obtained. The variation in the fine powder particle size becomes so small that it becomes unnecessary to adjust the fine powder particle size by, for example, changing the rotational speed of the air separator.

By implementing this control, the entire grinding system is stabilized, and as a result, it becomes easy to optimize the grinding efficiency, resulting in a power saving effect.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram showing one embodiment of an apparatus for carrying out the method of the present invention, FIG. 2 is a flowchart diagram representing a conventional general closed circuit tube mill grinding system, and FIGS.
FIG. 5 is an explanatory diagram showing the relationship between controlled variables and manipulated variables based on changes over time. 1... Raw material supply device, 2... Mill, 3...
Packet elevator, 4... air separator. 5...Route (powder), ・6...Route (returning powder)
, 7... Mill inlet bearing metal, 8... Vibration meter, 9...
...Thermometer, lO...Measuring device, 11...
・Water sprinkler, 12...flow meter, 13...filter, 14...controller, 15...
・Filter, 16...Filter, 17...
・Filter, 18...Flow control valve. Patent applicant: Ube Industries, Ltd. Figure 1 Figure 3 Time Time Figure 4 Time Figure 5 Time Fin

Claims (2)

[Claims] (1) A raw material supply device supplies the material to be crushed to a mill, and the crushed material is transferred to an air separator by a transportation device, and in this air separator, a predetermined particle size is taken out of the grinding system. In the closed-circuit grinding system, which separates fine powder into fine powder and coarse powder, which is fed into the mill again, and returns the coarse powder to the mill for re-grinding, vibrations generated from the mill and crushed particles discharged from the mill are generated. The temperature of the object is the controlled variable, and the amount of raw material to be crushed and the amount of water sprinkled into the mill are the manipulated variables, and when the temperature of the object to be crushed increases, the vibration increases with a slight delay. However, conversely, when the vibration increases, the temperature of the crushed material rises with a slight delay. Considering the influence between the temperature of the crushed material and vibration, the controlled variable consisting of the vibration and the temperature of the crushed material was increased. When the raw material to be crushed A grinding control method for a closed circuit tube mill, characterized in that the supply amount and the water sprinkling amount are comprehensively controlled as operating variables for vibration and the temperature of the material to be ground, respectively. (2) The raw material to be crushed is supplied to the mill by the raw material supply device and pulverized, the pulverized material to be crushed is transferred to the air separator by the transportation device, and in this air separator, the predetermined particle size is taken out from the crushing system. In the closed-circuit grinding system, which separates fine powder into fine powder and coarse powder, which is fed into the mill again, and returns the coarse powder to the mill for re-grinding, vibrations generated from the mill and the ground material discharged from the mill are generated. The two variables to be controlled are the power consumption of the transportation device that transfers the raw material to the air separator, multiplied by a predetermined load, and the temperature of the crushed material discharged from the mill, and the supplied amount of the raw material to be crushed. and the amount of water sprinkled into the mill were used as the manipulated variables, and when the temperature of the material to be crushed increased, the vibration increased with a slight delay, and conversely, when the vibration increased, the temperature of the material to be crushed increased with a slight delay. , when a controlled variable consisting of the vibration and the power consumption multiplied by a predetermined load and the temperature of the object to be crushed increases, taking into account the influence between the temperature of the object to be crushed and the vibration; The above four variables are incorporated into a multivariable control system by increasing the operating variables consisting of the feed rate of the raw material to be crushed and the amount of water sprinkled in the mill and decreasing the controlled variables. A grinding control method for a closed circuit tube mill, characterized in that the amount of water sprinkled is comprehensively controlled as an operating variable for vibration and the temperature of the object to be ground, respectively.