Comminution – crushing of solid materials to reduce their particle size – is the most energy-consuming process in mineral processing. The modern development of the industry makes it important to improve the efficiency of energy consumption to crush hard and abrasive ores. In this context, the challenge relates to comparing the conventional ball mill – that is using the grinding mechanism based on tumbling of media for rock breakage – with high-pressure grinding rolls (HPGR) that use compressive force to create fracturing of rock beds. Thus, it is necessary to compare the mechanical nature of these technologies.
The conventional ball milling uses the processes of impact and attrition due to tumbling of steel balls in a cylinder. The disadvantage of this process is low efficiency for hard abrasive ores. A lot of energy is consumed for heating, mechanical losses and noise production instead of grinding. Due to the energy balance of surface energy of powder and kinetic energy of the media, there is grinding inhibition because more energy results in less efficiency of particle size reduction (Martelli & Di Nunzio, 2024).
In comparison, the HPGR process is based on inter-particle comminution. The ore bed is placed between counter-rotating rollers that create high hydraulic pressure for fracturing. It means that instead of impacts of grinding media on the particles due to falling from the cylinder, the ore particles are forced to compress each other with the help of the rollers. Thus, the energy is used in order to create micro-fractures with the help of compressive shear force of the rollers.
This efficiency gap is highly evident when using hard ores in industrial application. The major benefit of using HPGR is low energy consumption. Reported savings in energy used in comminution range between 10% and 50% in harder raw materials (Saramak & Saramak, 2024). As hard ores need exponential amounts of energy to break under impact, the compression force provided by HPGR avoids the point at which ball mill loses energy and cuts down the specific energy consumption.
HPGR’s effect on energy savings affects the rest of the process flow greatly. The micro cracks that form due to pressure in HPGR weaken the abrasive ore structure; this process is not common in ball milling. If further fine grinding is required, the weakening process greatly helps to decrease the amount of energy needed to liberate the ores. Not only does this help the process of ore processing; the lack of consumable steel media required in ball milling, but should be replaced all the time, saves energy as well (Saramak & Saramak, 2024).
In summary, there is an evident difference between energy consumption of HPGR and ball milling. In spite of the fact that ball milling is required for the final stage of grinding of hard rocks, its use is inefficient because of the random impact on ores. HPGR helps to avoid the energy losses that occur due to tumbling media.
References
Martelli, S., & Di Nunzio, P. E. (2024). Powder ball milling: An energy balance approach to particle size reduction. Journal of Materials Research. https://doi.org/10.1557/s43578-024-01502-6
Saramak, D., & Saramak, A. (2024). Review of High-Pressure Technology in Terms of Technological and Economic Benefits Achieved in Raw Materials Processing. Mineral Processing and Extractive Metallurgy Review, 45, 991–1004. https://doi.org/10.1080/08827508.2024.2410288
