The reduction of rock particles into an optimal particle size for mining of minerals is an important component in current mining operations. But comminution as it is known has been characterized by lack of efficiency. The current trend of having difficult ores to mine and expensive electricity has necessitated a move to optimal circuits in mining.
Energy savings are highest when old equipment is substituted by newer equipment that uses particle physics principles more efficiently. High-Pressure Grinding Rolls (HPGR) have become the better choice compared to other tertiary crushing equipment such as SAG mills.
In contrast to impact crushing, HPGR relies on particle compression to produce micro-fissures at the grain level. The so-called “particle-weakening” phenomenon leads to substantial energy savings during grinding processes. According to recent research conducted on full-scale production, the HPGR-stirred mill circuit consumes energy up to 45% less than conventional SABC (SAG-Ball Mill-Crusher) circuits (Wei et al., 2025).
Energy is frequently wasted on “overgrinding,” where particles already at the target size remain in the mill. This often stems from inefficiencies in hydrocyclones, which may inadvertently return fine, high-density minerals back to the grinding chamber (Kawatra et al., 2001).
To counter this problem, engineers have resorted to the application of two-stage classification and closed circuits. The evacuation of the materials immediately after they attain their liberation sizes within the circuit leads to a dramatic reduction in energy usage per ton (kWh/t).
The digital revolution within the mill floor is responsible for introducing Advanced Process Control (APC), which is more effective than conventional PID control systems. Although conventional systems rely mainly on providing safety during operations, APC employs data analysis in stabilizing parameters such as pulp density and hydrocyclone feed pressure. By ensuring the circuit operates in a fixed mathematical optimum, APC maximizes production efficiency while minimizing the “cost” associated with processing each tonne of material (Costa et al., 2025).
The optimization will also require the processing of the feed before it is introduced into the mill. Among the modern methods are heat treatment and precise blasting, which cause fractures on the ore, making it “softer” (Chimwani, 2023). In addition, proper ore mixing helps maintain the consistency of hardness of the feed, thereby preventing any spikes in energy due to harder mineral seams.
However, improving comminution circuits is never about one thing but about a whole process of synchronizing technology, classification, and computer control. With the move to use less grinding equipment and more efficient grinding systems such as HPGRs and APCs, mining operations will be able to reduce both their carbon emissions and production costs.
References
Chimwani, N. (2023). Editorial for Special Issue “Comminution and Comminution Circuits Optimisation.” Minerals, 13(1). https://doi.org/10.3390/min13010081
Costa, P. K., Vaz, P. N., Calixto, M. F., Torga, D. S., Bergerman, M. G., & Homero Delboni, J. (2025). Performance Assessments of an Advanced Control System in an Iron Ore Industrial Grinding Circuit. Minerals, 15(11). https://doi.org/10.3390/min15111172
Kawatra, S. K., Eisele, T. C., Walqui, H. J., National Energy Technology Lab., P., & National Energy Technology Lab., M. (2001). Optimization of comminution circuit throughput and product size distribution by simulation and control (FC–26-01NT41062-01). National Energy Technology Lab., Pittsburgh, PA (United States). https://inis.iaea.org/records/wpk2h-efx22
Wei, B., Yuan, Z., Feng, Q., Zhang, Q., Xu, X., Meng, Q., Klein, B., & Li, L. (2025). Optimization of High-Pressure Grinding Roll (HPGR) Performance in an Industrial-Scale HPGR/Tower Mill Comminution Circuit. Minerals, 15(10). https://doi.org/10.3390/min15101065
