JPH0631193A - Method for controlling closed-circuit crushing system - Google Patents

Abstract

PURPOSE:To crush a material with the highest energy efficiency at all times by easily detecting the optimum crushing condition and controlling a closed-circuit crushing system according to the condition. CONSTITUTION:A closed-circuit crushing system 1 is provided with a crusher 4 and a classifier 6. The amt. (p) of product powder and the grain size distribution P are obtained for each amt. (f) of the crushed powder in each crusher according to the given product grain size specification SP from a crushing model formula and a classification model formula. The amt. (f) in which the amt. (p) of product powder is the highest is taken as the optimum value, and the amt. fN of a fresh feed is controlled to maintain the optimum value.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for controlling a closed circuit grinding system for refining various powders such as cement.

In a conventional closed-circuit crushing system for cement or the like, the optimum state, that is, the state where the energy efficiency is maximized,
In order to achieve this, the performance of the crusher and classifier must be maximized and the closed-circuit crushing system must be in an optimal state. For that purpose, it is necessary that the total amount of the newly charged substance into the crusher and the classified coarse powder from the classifier, that is, the amount of the crushed material passing through the crusher becomes an optimum value.

Generally, when the passing amount increases, the pulverizing efficiency of the pulverizer increases, but the classification efficiency of the classifier decreases. Therefore, in the closed circuit grinding system, the optimum value of the passing amount exists in the form in which the grinding efficiency and the classification efficiency are combined.

In a conventional closed circuit crushing system for cement or the like, the following control method is used. (1) A method of determining the optimum value of the load of the powder transporter at the crusher outlet, which is determined by the amount of powder transported, through field experiments, and controlling the amount of newly charged substances so that the optimum value can be maintained. (2) A method in which the optimum value of the sound pressure level in the crusher, which is determined by the amount of crushed material passing through the crusher, is determined by field experiments and the amount of newly charged substances is controlled so that the optimum value can be maintained.

[0005]

In the methods (1) and (2) described above, the optimum values of load and sound pressure level do not have absolute values, but the crushability of the crushed material, the crushing in the crusher, and the like. It varies depending on the medium conditions such as the size and amount of the medium and the particle size specification of the product powder.

In the conventional example, the optimum value is confirmed by an experiment each time, but this experiment is naturally performed in the actual operation. However, this experiment requires labor costs and the loss of crushing energy during the experiment cannot be ignored. In addition, since it is an experiment during actual operation, an experimental error occurs and an optimum value cannot be obtained. Therefore, even though it is not the optimum value, it is judged to be the optimum value and the operation is continued, which often causes a large energy loss.

In view of the above circumstances, the present invention is directed to a closed circuit crushing system in which the hardness of the crushed material, that is, the crushability, the condition of the crushing medium, that is, the size and amount of the medium, and the particle size specification of the product powder are changed. The objective is to always find the optimum grinding conditions and control the closed-circuit grinding system accordingly, so that grinding can always be carried out with maximum energy efficiency.

[0008]

Means for Solving the Problems In the large continuous closed circuit crushing system for cement, the present inventor established a well-known Aryavdin-Midaka-jou formula (hereinafter referred to as crushing model formula) and used it for the crushing model formula. It was confirmed by an experiment that the two crushing speed parameters k and n that are provided correspond to each other.

An analytical solution for conventional closed-circuit crushing cannot be obtained mathematically from this crushing model formula and a modified formula (hereinafter referred to as classification model formula) of the known partial classification efficiency curve Mollerus formula (Molerus). However, the inventor of the present invention has known the Locked-Cycle method (Lock).
It has been found that the closed circuit crushing simulation in which the classification efficiency is also taken into consideration can be very easily applied by applying the ed-cycle).

The present invention has been made based on the above findings. The crushing phenomenon in the crusher is modeled in an extremely simple form, and the optimum "amount of crushed material passing through the crusher" is calculated by also using the classification model. It is controlled by the following. It is configured as follows.

In a closed-circuit crushing system equipped with a crusher and a classifier, the product powder amount and the particle size distribution are determined by the crushing model formula and the classification model formula for each given product particle size specification for each crusher passing amount in each crusher. The control of the closed circuit crushing system is characterized in that the amount of pulverized material passing through the crusher having the highest amount of the product powder is determined as the optimum value, and the amount of newly charged substances is controlled so that the optimum value can be maintained. Method

[0012]

By giving model constants k, n, β and s suitable for the crushing system to the crushing model formula and the classification model formula, the product powder for each crusher passing amount in each crusher for a given product particle size specification. Determine the quantity and particle size distribution. Then, the amount of crushed material passing through the pulverizer having the highest amount of the product powder is determined as the optimum value, and the amount of newly charged substance is controlled so that the optimum value can be maintained.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described with reference to the accompanying drawings. First, a closed circuit grinding system will be briefly described.
As shown in FIG. 1, in a large continuous closed circuit crushing system 1 for cement, a new charge substance 2 such as a cement clinker is sent to a tube mill 4 by a feeder 3 and crushed therein.
Then, the powder is conveyed from the mill 4 through the bucket elevator 5 to the classifier 6, where it is classified into fine powder (product) 7 and coarse powder 8. The fine powder 7 is sent to the bag filter 10, and the coarse powder 8 is sent to the tube mill 4 together with the newly charged substance 2 and is ground again. The crushing is repeated in the same manner thereafter.

Next, a method of controlling the system 1 will be described. A crushing model equation is used as the crushing phenomenon, and a classification model equation is used as the classification phenomenon. The computer 11 simulates closed circuit crushing.

Alyavdin-V.V.U.S.S.R Cypro known as a crushing model formula
cement (1933), Nakajo "Chemical engineering and chemical machinery" 7, 1 (19
See 49)). This equation is represented by R (X, t) / R (X, 0) = exp (-ktX n). In this formula, R (X, 0) is the particle size of the pulverized material at the pulverizer inlet, that is, the particle weight ratio of X μm or more at the time t = 0, and R (X, t) is the pulverizer. The particle size of the crushed material at the outlet, that is, the particle weight ratio of X μm or more at the time t = t.

K and n are crushing speed parameters determined by the conditions of the crusher, that is, the kind of the object to be crushed and the size and amount of the crushing medium. In the crushing model formula, the left side R
(X, t) / R (X, 0) and t and X on the right side were substituted with the measured values between the inlet and the outlet of the tube mill 4, and k and n were obtained using the least squares method. As shown in 2, it became one curve. Therefore, if either k or n is obtained, the other is also obtained. In FIG. 2, k = 0.
It becomes 0392 × 28.6 ⁻ⁿ , and the phenomenon of crushing can be predicted by using the crushing model formula by previously determining the value according to the kind of the object to be crushed and the size and amount of the crushing medium.

The values of the crushing speed parameters k and n are always the same unless the kind of the crushing material and the condition of the crushing medium, that is, the size and the amount thereof are changed. When these changes occur, new model parameters k and n can be easily obtained without conducting a large-scale experiment by examining the particle size distribution at the inlet and outlet of the crusher by using the model formula.

The classification model can be illustrated as shown in FIG. 3, and its model formula is divided into Mollerus formulas β
The following equation is used in consideration of (Molerus et al .: Chem.
Ing.Tech., 41 (5/6), 340 (1969), Onuma, E .: J. Chem. Eng.
See Japan, 6,527 (1973)). Φ (X) = (1-β) (Xc / X) ² exp [s {1- (X / Xc) ² }] / [1+ (Xc / X) ² exp [s {1- (X / Xc) ² }]] In this formula, X represents a particle size (μm) and Xc represents a classification point.

Β and s are classification characteristic values of the classifier, but β
Indicates division, that is, the amount of coarse powder unconditionally, and s indicates the standing condition (sharpness). The division β and the standing condition s differ depending on the type of classifier, but in this embodiment, they are obtained from the following equation. β = 1-exp (−0.036 × Qf / Qa) s = 7 × (0.8exp (−0.094 × Qf / Q
a)) ^{-3.6 In} this formula, Qf is the amount of crushed material at the classifier inlet (kg /
h) and Qa represent the amount of air (m ³ / h) at the inlet of the classifier.

An example of the division β and the standing condition s in this embodiment is shown in FIG. 7 in this figure
p is a fine powder, that is, the product side, 8p is a coarse powder side, A is an ideal classification line, B is an actual partial classification efficiency curve, and C is an actual partial classification efficiency curve corrected by division β.

Next, a locked-cycle (Locked-cycle) is applied to the crushing model formula and the classification model formula.
e) method [Gumtz, G .; D. and D.D. W. Fue
rstenau: Trans. Aime, 247, 330 (197
[See 0)] is applied, and closed circuit crushing simulation is performed in consideration of classification efficiency. This locked-cycle (Lo
The cked-cycle) method will be described with reference to FIG.

First procedure G1: The amount f of crushed material passing through the crusher and its particle size distribution F _N are set. This passing amount is, for example, 5
The particle size distribution is set to 00t / h. Second procedure G2: Assuming that all the crushed material at the entrance of the crusher is a newly charged material, the amount is f, and the particle size distribution is Fo. Third procedure G3: Calculate the crushing amount f and the particle size distribution F at the crusher outlet according to the crushing model formula.

Fourth procedure G4: Fine powder after classification using a classification model formula for the powder quantity f and the particle size distribution F at the crusher outlet,
The amounts p, r and the particle size distributions P, R of each coarse powder are calculated. At this time, the classification characteristic value of the assumed classifier, that is, the division β and the standing condition s are respectively substituted into the classification model formula, but in the present embodiment, the formulas β and s are used. or,
The classification point Xc of the classification model formula is an arbitrary initial value, for example, 5
0 μ is substituted.

Fifth procedure G5: Product particle size distribution P after classification
Determines whether or not the product particle size distribution specification SP given in advance is satisfied. If the spec SP is satisfied (YES), the process proceeds to the next sixth procedure G6. Also,
If it is not satisfied (NO), the classification point Xc of the classification model formula is changed to, for example, Xc = 30 μ,
Returning to the fourth procedure G4, this is repeated until the spec SP is satisfied.

Sixth procedure G6: If the amount p of the product after classification is equal to the amount f _N of the newly charged substance, this calculation is ended, and the amount of the product powder and the particle size distribution become p and P at that time. If P is not equal to f _N , the seventh procedure G7 is carried out, the procedure returns to the third procedure G3, and the sixth procedure G6 is performed until P is equal to f _N.
Repeat each procedure up to. The calculation in the above procedure is performed by the computer 11.

Seventh procedure G7: The amount f _N of newly charged substance is defined as the difference between the amount f of crushed material passing through the crusher and the amount r of coarse powder after classification, that is,
f _N = f−r was changed, the amount of coarse powder returned from the classifier was set to r, and the total particle size distribution was calculated.
And Of course, the total amount of powder is f. In this state, the procedure returns to the third procedure G3, and f and F at the crusher outlet are calculated by the crushing model formula.

As shown in FIG. 5, a calibration curve of the load current value of the bucket elevator 5 which is a powder transporter and the amount of crushed material passing through the crusher is obtained in advance, and the data is used as the above-mentioned computer.
Input it into the data 11. Then, the load current value corresponding to the optimum value of the passage amount f is automatically set. For example, when f = 500 t / h, the load current value of 90 A is selected as the optimum value.

During operation of the system 1, the load current value of the bucket elevator 5 is constantly measured by the ammeter 20 and the measured value is input to the computer 11. When the measured load current value is different from the set value, a control signal is sent from the computer 11 to the feeder 3,
The passing amount f is always kept constant.

The sound pressure gauge 30 provided in the tube mill 4 measures the sound pressure in the tube mill 4 and sends the measured value to the computer 11. A sound pressure upper limit level and a lower limit level are set in the computer 11, and when the passing amount f temporarily exceeds the allowable amount of the crusher due to various disturbances, etc., a control signal is given. Is sent to the computer 11 and the passing amount f is adjusted.
That is, the control by the load current value of the bucket elevator 5 is temporarily suspended until the sound pressure level is restored,
It is configured to restart.

[0030]

EFFECTS OF THE INVENTION Since the present invention is configured as described above, unlike the conventional example, it is possible to easily and accurately obtain the optimum value of the amount of pulverized material passing through the crusher without conducting an experiment during actual operation. It is possible to carry out pulverization while always maintaining the optimum value. Therefore, the closed-circuit grinding system can always be operated with the highest energy efficiency.

Incidentally, a comparative test between the present invention and the conventional example yielded the following results. In the conventional example, when A: product particle size specification is 30 μm and the residue is 19%, the product powder amount is 101 t
/ H Electric power consumption rate 35.6kWh / t B: Product particle size specification 30μm In case of 21% residue, product powder amount 103t
/ H The power consumption rate was 35.0 kWh / t. On the other hand, in the present invention, the above B: product grain size specification 30 μ
When the residual amount is 21%, the product powder amount is 105.5 t / h
The power consumption rate was 34.1 kWh / t.

[Brief description of drawings]

FIG. 1 is a flow chart showing an embodiment of the present invention.

FIG. 2 is a diagram showing a relationship between grinding speed parameters k and n.

FIG. 3 is a diagram showing a partial classification efficiency curve.

FIG. 4 is a diagram showing a locked-cycle method.

FIG. 5 is a diagram showing a calibration curve of a powder transport machine.

[Explanation of symbols]

 1 Closed circuit crushing system 4 Tube mill 5 Bucket elevator 6 Classifier 20 Ammeter 30 Sound pressure meter

Claims (2)

[Claims] 1. In a closed circuit crushing system equipped with a crusher and a classifier, the product powder amount for each crusher passing amount in each crusher is given to a given product particle size specification by a crushing model formula and a classification model formula. A closed circuit crushing system characterized in that the particle size distribution is obtained, the amount of crushed powder passing through the crusher with the highest amount of the product powder is determined as an optimum value, and the amount of newly charged substance is controlled so that the optimum value can be maintained. Control method 2. The control method for a closed circuit crushing system according to claim 1, wherein the crusher is provided with a sound pressure measuring means.