IMPROVING THE PERFORMANCE OF THE BALL MILL AS A CONTROLLED OBJECT IN THE ORE DRESSING PROCESS

Abstract

Due to insufficient mixing of the material in the initial part of the ball mill drum, the grinding media loses efficiency, resulting in a waste of electrical energy, balls and liner. This process has been investigated by a number of authors in Ukraine and abroad since the mid-1970s. Research models, mixing criterion in the form of probability coefficient, which can vary within 0...1, have been proposed. However, at present the problems of material mixing in ball mills have not been fully solved. There is no general assessment of material pulsation in the drum, the condition of the material in the initial section has not been evaluated and no approaches for improvement have been suggested. It is clear that the way out of this situation can be found in improving the ball mill by improving its performance. The research was carried out as part of the implementation of the topic «Optimisation of ball mill productivity for ore and finished product with minimum energy and material overruns», which is part of the scientific theme of the Central-Ukrainian National Technical University. From this point of view the topic of the article is actual. The aim of this work is to reduce the overuse of energy, balls and liners in the raw material grinding process by improving the performance of the ball mill by improving the loading of ore, spiral classifier sands and water, based on the assessment of material pulsation in the initial section of the drum. In the process of research, methods of comparison, analysis, ball mill theory, automatic control theory, probability theory, mathematical statistics, and random process theory were used. By means of computer processing of the data array using a special programme, areas of variation of the vibrational parameters at the ball mill inlet for solids and water, at which the relative mass deviations of the material in the unit do not exceed ±3.0%, are obtained, which guarantees the normal course of the technological process. It has been found that for both solids and water, oscillations with too low a frequency and large amplitudes are the most dangerous. The problem of mixing the material in the initial part of the ball mill drum is important, because here the efficiency of averaging is low. The most sensible way is to improve the mixing conditions by eliminating the existing disadvantages. Firstly, before the ore enters the mill it should be wetted with part of the water flow, and the sands before entering the coil feeder should be thinned as much as possible with a second part of the water flow. A third of the water flow into the mill has to be sprayed over a wide area where the ore enters the process unit. Such operations ensure efficient mixing and grinding of the material already in the initial section of the mill drum. Exciting influences along the ore flow do not disturb the process flow of the ball mill.