Abstract
We have investigated a possibility to perform comparative evaluation of the effectiveness of grinding process in a tumbling mill under conventional steady and self-excited auto-oscillatory flow modes of the intrachamber fill. A mathematical model for the parameters of impact influence of the milling fill on the ground material has been constructed. We applied an analytical-experimental method to visually analyze flow patterns in the cross-section of a rotating chamber. Numerically, by using approximate procedures, we have established a dynamic effect of increasing mean sums of vertical components in impact pulses and mean sums of power of such components at self-excitation of auto-oscillations. The technological effect has been experimentally established of a significant decrease in energy intensity and a certain increase in productivity of the identified self-oscillatory grinding process, compared with the characteristics of conventional steady-state process. This involved a sieve analysis of the ground product, as well as measuring the fill flow turnover and the power of a drum rotation drive. The example considered was the process of grinding cement clinker at a degree of filling the chamber with a fill of 0.45, at a relative size of ball grinding elements of 0.026, while the gaps between grinding bodies were completely filled with the ground material. It was established that at auto-oscillation self-excitation the grinding energy intensity reduces by 27.2 %, while performance increases by 6.7 %. The effects established in this work make it possible to predict the rational parameters for aself-oscillatory process of grinding in a tumbling mill
Highlights
Study [16] provides an overview of numerical algorithms, based on discrete elements method (DEM) method, to determine the impact action of fill at ball mills and self-grinding mills and its effect on the drum’s chamber lining wear
Paper [24] studied the effect of impact action on the process of grinding in tumbling mills using a numerical simulation by DEM method and an experiment that employed laboratory models
We have approximately nume rically estimated the magnitude of impact pulse and its power based on values for average sums of the vertical components
Summary
Drum-type mills are widely used in many industries for fine grinding of granular materials. Study [16] provides an overview of numerical algorithms, based on DEM method, to determine the impact action of fill at ball mills and self-grinding mills and its effect on the drum’s chamber lining wear. Paper [24] studied the effect of impact action on the process of grinding in tumbling mills using a numerical simulation by DEM method and an experiment that employed laboratory models. There are no generalized models for deter mining the impact action of a granular fill in the rotating drum that account for the wide-range variations in system parameters The lack of such models is evident for the case of self-excitation of auto-oscillations in the intrachamber fill at drum-type mills and the influence of the chamber fill pulsations’ impact action on a grinding process. In this case, grinding is due to the impact action only
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