Construction of the attainable region candidates for ball milling operations under downstream size constraints

Abstract

This study investigated the influence of the attainable region technique to ball milling as applied in reactor technology. Flow rate, ball filling, mill speed, ball size and mill density were varied. When each was varied, the rest of the parameters were kept constant in-order to determine the influence of each parameter on the process of milling. Selection function and breakage function parameters were selected for the mill model. These were kept constant for all four circuit configurations: open milling circuit, normal closed circuit, reverse closed circuit, and combined closed circuit. Flow rate was varied from 10 tph to 150 tph. It was observed that in all circuit configurations the optimum results were obtained from 90 tph upwards. When ball filling was varied, the optimum results were obtained between 30 % and 40 % of ball filling. At this range the mill is neither experiencing under-filling nor over-filling. When the mill speed was varied, at 60 – 80 % of critical speed the product specification was achieved and for grinding balls, sizes of between 60 mm and 90 mm yielded the optimum results. Varying the mill density resulted in insignificant changes. From the results, the combined closed circuit produced more of the product specification.