EVALUATION OF GRINDING PARAMETERS AND MICROWAVE PRE-TREATMENT ON THE BREAKAGE BEHAVIOR AND ENERGY EFFICIENCY OF COLEMANITE ORE

Abstract

This research systematically examined the grindability behavior of colemanite ore by analyzing how variations in mill rotation speed and the geometry of grinding media influence the specific breakage rate. The ore, sourced from the Emet Colemanite Mine, was separated into narrow particle size fractions and subjected to grinding tests at speeds between 65% and 90% of the mill’s critical velocity. Findings indicated that higher rotational speeds resulted in increased specific breakage rates and finer particle size distributions. Moreover, cylindrical media consistently delivered better grinding performance than spherical media across all particle size intervals tested. A predictive model was developed to estimate the specific breakage rate based on particle size, rotation speed, and media shape, and was further validated under various operational conditions. Furthermore, the study examined the impact of microwave pre-treatment on colemanite grindability and energy consumption. Microwave irradiation was applied at 180 W for 5 minutes, resulting in internal thermal stress and microcracking that facilitated improved breakage, particularly in coarser fractions. Bond Work Index (BWI) values decreased by approximately 3–4% following microwave treatment—for instance, from 9.02 kWh/ton to 8.72 kWh/ton for the +3350 µm size fraction. However, the π breakage parameter remained virtually unchanged, at approximately 0.53 for both treated and untreated samples, indicating that the fundamental breakage characteristics of the material were not significantly altered. Although microwave pre-treatment enhanced grindability in specific cases, the total energy requirement for comminution—including both microwave exposure and subsequent grinding— did not demonstrate a substantial reduction. These findings suggest that the energy benefits of microwave-assisted grinding are marginal unless the microwave process itself is optimized for energy efficiency.