Study of modes and parameters of mineral raw material grinding process in ball drum mills

Abstract

The paper presents the results of research on the vibration-acceleration signal of the ball mill drum bearing support depending on its load when grinding mineral raw materials. Investigations of vibration sensor readings, installed on the bearing support of the mill drum, and amplitudes of the vibration-acceleration signal from the volumetric filling of the installation drum have been carried out. The dependences of vibro-acceleration signal amplitudes on the frequency spectrum of Fourier series at different volumetric filling of the mill drum in the interval of loads from 0 t/h to 18 t/h are investigated. In research on the interrelation of a signal of vibro-acceleration and consumed power of an electric drive of a drum depending on the degree of its volume filling, their averaged values are established. According to the values of averaged numerical values of amplitudes of vibro-acceleration signal amplitudes, the graphs of their dependence on the frequency spectrum of Fourier series in the range from 0 to 30000 Hz are obtained, the dependences of the consumed power of the ball mill and the amplitude of the vibro-acceleration signal on the volumetric filling of the drum are established, the algorithm of determining the level of filling of the mill drum is developed, the dependences of the vibro-acceleration signal and consumed power on the level of filling of the ball mill in volumetric units are established. It is established that the filling of the mill drum by the consumed power of the electric drive can be controlled up to 0.7 of the volumetric filling of the mill drum. At the same time, the value of volumetric filling of the mill drum, expressed through the signal of vibration velocity of the bearing support, smoothly grows in the whole range of drum filling from 0.0 to 1.0. In this case the reliability of the received information on vibration acceleration of the mill drum support with deviation from the approximating curve, not exceeding 5–6%. Tracking of the level of filling of the mill drum is provided by the signal of the vibration sensor, which allows to maintain of optimal performance, grinding quality, and power consumption. The obtained results give grounds to use the vibration acceleration signal in the system of automatic control of the coal grinding process as a criterion for evaluating the degree of filling of the mill drum during its operation. Keywords: ball drum mill, grinding, vibration acceleration signal amplitudes, coal.