JPS5816941B2 - grinding system - Google Patents

Description

[Detailed description of the invention] The present invention relates to a grinding system for a grinder.

Fig. 1 shows a general closed circuit crushing system. 1 is a crusher, 2 is a packet elevator, 13 is a pneumatic classifier,
4 is a dust collector, and 5 is a weighing machine for newly charged material, which consists of a clinker weighing machine and a plaster weighing machine.

6 is a spout feeder, 7 and 8 are the first transporters from the mill, 9 is a chute for transporting powder back from the classifier to the crusher, 1
0 is the refined powder of the classifier and the powder collected by the dust collector (i.e. product)
11 is a crusher exhaust pipe, 12 is a classifier exhaust transport pipe, and 13 is an exhaust windmill.

The newly charged material is weighed by a weighing machine 5, and the returned powder from the classifier 3 is supplied to the crusher 1 from a chute 9 via a spout feeder 6.

The powder material pulverized in the pulverizer 1 enters the packet elevator 2 via a transporter 7, and then enters the pneumatic classifier 3 via a transporter 8.

Of the substances classified by the wind sieving action in the classifier 3, the coarse powder, that is, the returned powder, passes through the chute 9 and returns to the crusher 1.
The fine powder, that is, the fine powder, becomes the product of this pulverization system.

The exhaust gas from the crusher 1 and the pneumatic classifier 3 is guided by a windmill to the dust collector 4 through pipes 11 and 12, where a large amount of fine powder contained in the exhaust gas is collected and transferred to the dust collector 4. Together with the powder, it becomes a product and is taken out of the system by a transporter 10.

Note that the exhaust gas, from which fine powder has been removed and which has become clean, is discharged into the atmosphere through the wind turbine 13.

In such a grinding system, the ratio of returned powder to fine powder is usually 300 to 600%, which is characterized by a very large amount of returned powder.

In addition, energy efficiency is extremely poor, and the energy required for crushing is the crusher 1, classifier 3, transporter 7,
It is less than one factor of the total input energy, about 0.4 to 0.6% at most, and most of it is dissipated as sound and heat.

Various ideas have been made with the intention of improving the current situation to some extent, and they can be roughly divided into two types.

One is to aim for stable operation and improve efficiency by controlling the sum of the amount of material supplied to the crusher 1, that is, the amount of newly charged material and the amount of returned powder from the classifier 3, to a fixed value. One approach is to improve energy efficiency by adding a small amount of a substance called a grinding aid, which prevents the coating from adhering to the grinding media and lining of the grinder, and reduces the surface energy of the material to be ground. It is something.

The following three methods are currently being implemented in the former category.

(1) Acoustic control of the crusher This is achieved by installing a sound collector at an appropriate location near the body of the crusher 1, effectively extracting the sound, amplifying it, and then making use of the sound spectrum. This is a method of extracting and measuring a frequency band, feeding it back to the weighing machine 5, and controlling the amount of newly charged material so that the sound in the effective frequency band becomes a constant value.

This method has disadvantages such as high noise, impossibility of highly accurate control, large impact on the sound of grinding media wear, and large impact on the sound of crushed objects, and can only improve efficiency by 1 to 2 stages at most. only expected.

(2) Packet elevator current or power control This detects the power consumption or current of the packet elevator 2, feeds it back to the weighing machine 5, and maintains this power or current, that is, the transportation amount in the packet elevator 2, at a fixed value. This is a method of controlling the amount of new material charged so that

In this method, if the grinding is done well in the crusher 1, the fluidity of the powder will improve and the amount entering the packet elevator will increase, so the action of reducing the amount of newly charged material will be taken.As a result, The amount of crushed material held in the crusher will temporarily decrease.

As can be seen in this example, there is a large follow-up delay in the control, and the pulverization state inside the pulverizer is constantly cycled, so there is very little improvement in pulverization efficiency, if any.

(3) Ventilation differential pressure control This method applies the principle that when the flow rate of air flowing through a flow path is constant per unit time, the pressure loss in that flow path is inversely proportional to the square of the cross-sectional area of the flow path. Then, the differential pressure between the static pressure at the supply end and the discharge end of the crusher 1 is measured, and this is used as a control variable to increase or decrease the speed of the metering machine 5 for the newly charged material in response to the change, thereby adjusting the level inside the crusher. This is a control method that keeps the temperature constant.

With this control method, the grinding efficiency improves by about 5 factors under normal conditions, but long-term stable operation may occur due to blockage of the pressure detection pipe, blockage of the slits in the perforated plate in the grinder, and blockage of the draft inside the grinder due to clogging of the back of the dust collector 4. is not possible.

As mentioned above, each of the currently known methods has drawbacks.

The purpose of the present invention is to eliminate such drawbacks and provide a grinding system that can always determine and control the optimum amount of new material to be charged by simply detecting the flow rate of returned powder. This is because, in a closed-circuit grinding system, the flow rate of the return powder from the classifier (6) and the energy per unit amount required for the return powder to turn into powder inside the mill are determined by the flow rate (6). The value (Br) multiplied by the new charge material amount button) and the characteristic value (Bf) corresponding to the energy per unit amount required for the new charge material to become powder inside the crusher. ) multiplied by the sum (
E) is a constant value, the formula % formula % (however, C1 and C2 are constants, 2E=F-Bf
Br +R-Br=constant, F=----R, BfBf
If the fluctuations of Bf and Br can be ignored compared to the fluctuations of H, then E
E3r is derived from considering that Koni C1, positive = 02.

), the grinding system is characterized in that the amount of the newly charged material is controlled.

The present invention will be described below with reference to embodiments shown in the drawings and the like.

Generally, in a crushing system, if the total amount of work required for the material to be crushed in the crusher is E, then E=F1Bf1
+F2Bf2+...+RBr-constant ・=”・(1)
holds true.

In other words, once the type, capacity and circumferential speed of the crusher are determined,
The work energy that the crusher imparts to the material to be crushed remains constant.

Therefore, as the amount of newly charged material and the amount of returned powder increase, the energy per unit amount received by the material to be crushed decreases, and the fineness (Blaine value) decreases.

Furthermore, as the amount of new material charged and the amount of returned powder decrease, the amount of energy applied to the material to be crushed per unit amount increases, and the fineness (Blaine value) increases.

Thus, the above equation (1) is established. However, Fl, F
2... is the amount of new material charged per unit time (t/h),
Bfl, Bf2... are the energy per unit amount required for the amount of newly charged material to become powder in the crusher,
R is the amount of returned powder (t/h), and Br is the energy per unit amount required for the returned powder to become powder in the pulverizer.

Generally, when the chemical components required for the pulverized product are constant, the proportions of the above F, F2, etc. are determined by themselves, so the new charged material can be considered to be one type.

In other words, it can be regarded as F, ten F2, . . . two F.

Therefore, equation (1) can be considered to be E=FBf+RBr-=constant.

In the case of cement grinding, the ratio of plaster to clinker is 3
~4% is added, and this ratio is automatically determined from the quality standard, so the new charged material can be approximately considered to be one type.

Therefore, from equation (1), Br E=F B f +RB r = constant...-(2)
, F = ---RBf Bf .

Considering that the fluctuations of Bf and Br can be ignored compared to the fluctuations of H, can -2- be regarded as a constant?
Bf, E Br L:) 100-01, 1 line-02, then F=C-CR・・・・・・・・・・・・・・・・・・(
3) It becomes 2.

Therefore, in order to operate the grinding system efficiently, R
F can be controlled by detecting .

However, if the above equation (g) is taken as the actual amount of energy consumed as described above, accurate detection and measurement in an actual grinding system is difficult and impractical.

Therefore, in this example, in the above equation (1), the net amount of work (t) required for the material to be crushed in the crusher is a value that can be actually detected, and the actual total physical work (t) ), which is a characteristic value that indicates the amount of crushed material passing through the mill (t/h), and a characteristic value that indicates the specific surface area at the beginning of the mill, such as the Blaine value (CI?L/g). Detect this value by considering it as a product of high.

In addition, Bf and Br in the above equation (1) are also difficult to detect if each unit energy amount remains unchanged, as is the case with E above. In this example, the above-mentioned characteristic values can be used as indicators that can correspond to the unit energy required within the crusher, and can also correspond to the above-mentioned total required work E (t/h・i/L). A Blaine value (cyitl g ) that should be increased until each new powder and recombinant powder reach a predetermined fineness after crushing is adopted and this value is detected.

In the actual control stage, as described above, according to equation (2), first the constant 01. By setting C2 in advance from experimental values, etc., and detecting the amount of returned powder (6) at a certain point in time according to equation (3), the amount of newly charged material (F
′) can be automatically determined.

The following procedure is used to obtain the constants 01 and C2 of the above optimal conditions.

First, the amount of newly charged material (F') under certain specific conditions is measured, and the Blaine value (B1) of the newly charged material is also measured.

Next, the Blaine value (B2) at the beginning of the mill under the above conditions
and the increasing height of the Blaine value for the new charge material (
Bf=B2-B1) is determined.

Similarly, the amount (R) of the returned powder and its Blaine value (Br) are measured under the above conditions, and the increase in the Blaine value for the returned powder (Br=B2-Br) is determined.

Next, E under the conditions is calculated using the above equation (2).

Based on each calculated value above, E
Br -C1- and C2 faces are determined.

Bf In this way, the amount of newly charged material CF) and its Blaine value (B1), as well as the amount of returned powder (6) and its Blaine value (Br) are varied, and the initial amount from the crusher is If the constants 01 and C2 are calculated under the conditions when the Blaine value is optimal, and the constants 01 and C2 are adopted and substituted into the above equation (3), the return powder can be calculated by the equation (3). amount(
By measuring only 6), it is possible to automatically set the new amount of charged material (g) that can obtain the optimum condition E.

FIG. 2 shows an example of an accurate and simple device for detecting the amount of returned powder in this embodiment. This device is a known device and is installed in the chute 9 of the returned powder.

Reference numeral 14 denotes a rectifier for rectifying the flow of the returned powder, and the returned powder passes through the rectifier 14 and falls onto the impact plate 15 with a constant head difference.

The impact plate 15 detects only the horizontal force proportional to the flow rate of the returned powder, and the converter 16 converts this mechanical energy into an electrical signal.

FIG. 3 is a block diagram of the control system according to the present embodiment applied to a cement crushing closed circuit in its simplest form.

In the figure, 17 is the new material, 5' is the operating section, 1' is the controlled object, 18 is the product 19, which is the returned powder, 20.21 is the detection section,
22 is a calculation section, 23 is a setting section, and 24 is a comparison adjustment section.

The new materials 17 are clinker and plaster.

The operation section measures the newly charged material 17.

Controlled object 1' includes up to grade machine 3, where product 1
Divided into 8 and 19.

The returned powder 19 returns to the controlled object 1' and forms one circuit.

The computing device 22 computes the value detected by the detecting section 20 of the newly charged material 17 in the controlled object 1' and the detected value of the amount of powder 19.

The comparator 24 compares the optimality value previously set in the setting device 23 with the value calculated by the calculator 22, and gives an appropriate command to the operating section 5' to set the amount of new charge material 17 to the optimal value. Example 1 Using a closed-circuit grinding system equipped with a two-chamber mill with a diameter of 2.44 m and a length of 10.69 m, the cement was sampled several times at regular intervals without grinding the cement. and obtained the following optimal value.

(1) New charge amount (F')...22t/h Breakdown: Gypsum (Brain value 3000CIit/g)...
0.7 t/h Clinker (Blaine value 50 Cit/g)...21.3 t/1 (2) Return powder (6)...99 t/h (Blaine value 900 days N31(3) ) Product...22t/h (
Blaine value: 3190 cit/&) Using the above numerical values, constants C1 and C2 were determined as follows.

E=FBf+RBr=22(1316-144)+99
(1316-900)=66968(a/ji,
-〇・・・・・・ (4) E 66968 ”-Bf-1□7°-5714 Br 66968 C2 One place-1□72-0・35 [However, in the above formula (4), Bfl-(1316 -1
44)=1172, and Br=(1316-900)=
416 was determined by the following calculation.

Blaine value at the beginning of milling: 3] 90crVgX22t/h+900a', 9X
99t/h-22t/h+99t/h 1316cri't/g Blaine value of new charge material: 0.7t/h x 3000i/,? +21.3t
/h
72 cit/g.

Br=1316i/, 9-900C9-900CrV becomes 'I.

] Substitute the above C1 and C2 into formula (3), F = 57.14 + 0.35 R...
...(5) was obtained.

Based on the above equation (5), F was controlled without measuring R.

The results of the experiment conducted over a period of one month are shown in the table below. However, t: weight, h: time, C: fluctuation rate, and the powderiness was measured using a Blaine specific surface area measuring device.

The fluctuation rate CV (%) of the amount passing through the pulverizer was calculated by measuring the flow rate at the outlet of the pulverizer at the beginning of mill exit at regular intervals for one month, and based on the measurement results.

Further, the variation rate CV (%) of the powderiness of the product was calculated by measuring the powderiness of the final product obtained from the classifier and dust collector at regular intervals for one month, and based on the measurement results.

As is clear from the above table, the operation of the grinding system in which this example was implemented was quite stable, the fluctuation in the amount of crushed material passing through the grinder was reduced to about 1/4, and the variation in the powderiness of the product was also reduced to about 1/4. 3, and the grinding height, that is, the efficiency of the grinding system, improved by 15%.

In this example, the Blaine value (cIit/, 9) was used as a characteristic value that indicates the increase in specific surface area. good.

In the present invention configured as described above, by simply detecting the flow rate of the returned powder from the classifier in the closed circuit crushing system,
The amount of newly charged material under optimal conditions can be automatically controlled, eliminating the waste seen in conventional methods and allowing extremely efficient pulverization.

[Brief explanation of the drawing]

Figure 1 is a conceptual diagram of a closed-circuit crushing system to which the present invention is applied, Figure 2 is a conceptual diagram of a device for measuring the amount of returned powder from a classifier, and Figure 3 is a conceptual diagram of a device that achieves the present invention. FIG. 1 is a block diagram of an embodiment of a control system for controlling the computer. 1...Crusher, 1'...Controlled object, 2
...Packet elevator-13 ... Classifier, 5 ... Weighing machine, 5' ... Operation section, 9 ... Return powder transportation Chute, 15...
・Impact plate, 16...Converter, 17...
New charge material, 18...Product, 19...Return powder, 20.21...Detection section, 22...Calculation section, 23...・Setting section, )24... Comparison adjustment section.

Claims (1)

[Claims] 1. In a closed-circuit grinding system, the flow rate of the returned powder from the classifier (
The value obtained by multiplying this by the characteristic value (Br) corresponding to the energy per unit amount required for the returned powder to become powder inside the crusher, the amount of newly charged material (T), and this The characteristic value (Bf
), so that the sum (g) of the product multiplied by
Br −1−R−Br=constant, F=---R, BfB
If the fluctuations in f Bf and Br can be ignored compared to the fluctuations in R, then E
Br It is derived from considering that 〒=C1, 7=C2. ), a grinding system characterized in that the amount of the new charge is controlled according to the above.