Investigation of the Ball Size Distribution Fineness Effect on Dry Size Reduction Performance of a Low-Grade Chromite Ore in a Standard Bond Ball Mill

Abstract Dry batch ball mill grinding tests were performed on a low-grade chromite ore to evaluate ball size distribution fineness effect on size reduction performance by using a mill feed with full size distribution (-3.35 mm material) instead of using narrow size ranges as used in conventional batch dry grinding kinetic tests mentioned in the literature. Ball mill feed material was also prepared by jaw crushing and dry rod milling. High chromium casted iron multi-size ball distributions with weighted average ball sizes of 36.70 mm, 25.45 mm and 21.18 mm were used to evaluate the effect of ball size distribution fineness on dry size reduction performance. Industrial scale conditions were simulated with the laboratory scale conditions in terms of ball mill feed size distribution and multi-size ball charge distributions. 80% and 50% cumulative passing sizes of mill feed and products were determined to characterize size reduction ratios. Bond’s energy equation was used to calculate and evaluate specific comminution energy consumption (kWh/t) in batch tests. Variations in size reduction performance and comminution energy consumption were evaluated as a function of time. Findings indicated that by using 17 mm and 15 mm ball sizes in the charge distributions, size reduction performance could be increased at finer size ranges. Ball charge distribution with a weighted average ball size of 25.45 mm was determined to be the optimum ball distribution. The ball charge distribution fineness effects could have been reflected on the size reduction performance successfully with the applied test methodology. Research results provided some useful insights into the industrial scale operations.