Declining ore grades are increasing the amount of material that mining companies must process to produce the same quantity of metal, placing greater emphasis on crushing and grinding efficiency. The challenge is making each tonne of ore require less energy to process. As a result, comminution has become an increasingly important area for mining technology and equipment suppliers.
Weir targets energy reductions through integrated circuits
Weir is promoting flowsheets that combine high-pressure grinding rolls (HPGR), large-format screening, stirred milling and coarse-particle flotation. The company has cited potential energy reductions of up to approximately 40% from HPGR technology and around 38% from stirred milling in suitable applications.
Metso is addressing the same processing challenge through HPGR, fine-grinding and vertical-roller-mill technologies. Its Loesche-based dry-grinding systems have been presented as capable of reducing energy requirements by as much as approximately 40% for appropriate ore types. The actual reductions vary significantly according to the deposit and processing flowsheet, while the scale of potential savings reflects the amount of electricity consumed by comminution.
Lower-grade ores increase processing requirements
Grinding is among the largest electricity consumers at hard-rock mines. In low-grade copper operations, maintaining or increasing production can require substantial increases in material movement and milling volumes. Improving the efficiency of the processing circuit can therefore affect both operating expenditure and infrastructure requirements. Lower electricity consumption can also reduce the amount of new power generation, transmission infrastructure and backup capacity required by a project. This can influence development schedules and capital requirements.
Equipment selection shifts toward energy performance
The changing economics are also affecting equipment procurement, with mining companies increasingly evaluating mills and crushers according to energy consumption per tonne, wear rates, maintenance requirements and downstream recovery, rather than throughput alone.
Equipment suppliers capable of improving several of these performance measures simultaneously can therefore play a larger role in mine processing strategies. The underlying challenge is the increasing difficulty of producing metal from lower-grade and more complex material. As ore quality declines, mining companies must process more material to maintain metal output, placing greater emphasis on efficient comminution within mine development and processing plans.
