SU1230686A1 - Automatic control system for monitoring the wear of balls in the mill - Google Patents

Description

This invention relates to an automatic control of a dry grinding process and can be used in the metallurgical, cement and mining industries.

The purpose of the invention is to improve the accuracy of control.

The drawing shows the scheme of the proposed system.

The ball wear monitoring system consists of an acoustic sensor 1, a noise-sensing mill, an amplifier 2, an amplifying signal of an acoustic sensor, a frequency meter 3, an absolute magnitude detector 4, a reference element 5, a divider 6 two signals, a band-pass filter 7, a discriminator 8, a low-pass filter 9, the controller 10, the integrator 11, the Converter 12, the measuring device 13.

The principle of operation of the system is as follows.

The amplitude and frequency components of the noise spectrum emitted by the mill depend on the time of the collision of the balls with the lining and between themselves. The impact time is determined by both the mass and geometrical parameters of the impinging bodies, as well as the elasticity of the impact, which depends on the amount and physicomechanical properties of the material to be ground between the colliding surfaces. A decrease in the amount or size of the material between the colliding surfaces leads to an increase in the frequency and amplitude of the noise emitted by the mill, and a decrease in the mass of the grinding bodies leads to an increase in the frequency and decrease / amplitude components of the spectrum. In this case, the amplitude and frequency of the maximum peak of the low-frequency part of the spectrum are characterized mainly by the largest components of the ball load, the amplitude and frequency of Rais of the whole spectrum are measured, which more fully take into account both large and smaller balls. For a given state of ball loading, the collision time and, accordingly, the amplitude and frequency are entirely dependent on the parameters of the material being milled. Thus, to obtain a signal proportional to the mass of the ball and invariant to the quantity and quality of the material being milled, the ratio of the amplitude of the acoustic spectrum to the Rais frequency of the mill noise spectrum is chosen, which eliminates the components of the signals characterizing the collision time. In the amplitude and frequency signals, there are constant components of the signals in a given state of ball loading, which depend on the type of static characteristics of the noise-load channel and on the position of the operating points on them. In addition, both measured parameters carry low frequency interference signals (with a mean frequency of 0.01-1 Hz), which is of a random nature, therefore in the generated parameter at the output of the divider

the division error with the characteristics of a random process, the standard deviation of which is of an extreme nature and depends on the value of. Therefore, forming 00 as a control action by searching for the minimum multiplicative component of the low-frequency interference ratio and subtracting it from the amplitude component of the signal, we obtain as a result of dividing the signal proportional to the current average mass of the ball.

The system works as follows. Acoustic signal taken from sensor 1 through the amplifier 2 is fed to a frequency meter 3 connected in parallel and a detector

5 4 absolute values, the signal proportional to the frequency is fed to the first input of the divider 6, and the signal proportional to the amplitude of the spectrum from the detector output goes to the first input of the comparison element 5, the second input of which receives the signal

in the output of the integrator 11, the signal proportional to (A-in) is fed to the second input of the divider, at the first output of which we receive a signal proportional to Mm with the interference signal present in it, which is extracted by the filter 7 and through the serially connected discriminator 8, low-frequency filter 9 and extreme regulator 10 are fed to the integrator input. The splitter signal generated in this way, proportional to the mass of the shara, is fed through the transducer 12 to the measuring device 13, the scale of which is calibrated in units of the mass of grinding media. Thus, the control system allows us to estimate the average mass of the ball by the formula

35

Msh K

A - In

fR

where Mn is the average mass of the ball;

K - coefficient of proportionality; And the amplitude of the acoustic spectrum

signal;

In - constant component, formed by minimizing the multiplicative component of the ratio of low-frequency interference present in the amplitude and

frequency signals; n - the frequency of Rais.

Experiments conducted in a laboratory mill with filling ratios f = 0.2–0.1, diameters of Osh balls 25–15 mm and using silica sand as a grinding material showed that the relative error in measuring wear is less than 4% and determined by the change in the fill factor of the mill

tsy balls.

The system provides more reliable and accurate information on the wear of the balls and allows, on this basis, with greater

efficiency and accuracy of production is close to optimal, with this, sodon their loading into the mill in the process of ball loading, in a timely manner

its operation. This allows support-to-complete replacement of worn out unit performance at a level, even load.

Claims (1)

AUTOMATIC BALL WEAR CONTROL SYSTEM IN THE MILL, including an acoustic sensor, an amplifier, a bandpass filter, an extreme regulator, a transducer, a comparison element and a recording device, characterized in that, in order to increase the control accuracy, it is equipped with a frequency meter, an absolute signal detector, a signal divider , a discriminator, a low-pass filter and an integrator, the acoustic sensor through an amplifier connected to the inputs of the frequency meter and the detector of the absolute value of the signal, the output frequency An era is connected to the first input of the divider, and the output of the detector of the absolute value of the signal is connected to one of the inputs of the comparison element, the second input of which is connected to the output of the integrator, the output of the comparison element is connected to the second input of the divider, the first output of which is connected through a series-pass filter, discriminator, low-frequency the filter and the extreme controller are connected to the input of the integrator, and the second output of the divider through the converter is connected to the input of the recording device. SU, 1230686