Cominuição

Cominuição is the set of processes in mineral processing that reduces rock and ore to smaller sizes through crushing and grinding. Its primary purpose is to liberate valuable minerals from the surrounding rock and to prepare material for subsequent separation techniques such as flotation, magnetic separation, or leaching. Cominuição is typically one of the most energy-intensive steps in mining and often dominates operating costs.

The process is commonly divided into crushing and grinding. Crushing reduces large rocks to manageable fragments using crushers (jaw, gyratory, cone). Grinding further reduces particle size to the target range required for efficient liberation, typically with ball mills, rod mills, autogenous (AG) mills, semi-autogenous (SAG) mills, or increasingly high-pressure grinding rolls (HPGR) for energy efficiency. In many plants, material passes through closed or semi-closed circuits where mill discharge is classified by screens or cyclones, and coarse material is returned for reprocessing.

Key design and performance metrics include P80 and F80 (the particle sizes at which 80% of material passes), specific energy consumption (kWh per tonne), and the Bond Work Index (Wi). Process models, such as population balance approaches, are used to predict throughput and product size distributions and to optimize energy use versus mineral liberation.

In practice, cominuição must contend with ore hardness, moisture, mineralogy, and the trade-off between overgrinding and adequate liberation. Emerging trends focus on energy efficiency and finer control, with developments such as HPGR, stirred mills, pre-concentration, ore sorting, and advanced process automation driving improvements in performance and sustainability.