Optimization of Fine Grinding for Banded Iron Low-Grade Deposit in a Vertical Stirred Media Mill

With the growing emphasis on decarbonization, minimizing energy in comminution circuits has become a critical focus area in mineral processing flowsheets. The present investigation emphasized a banded iron formation (BIF) deposit from eastern India to grind to finer sizes in an energy-efficient vertical stirred media mill (VSMM), along with supported characterization data. From the characterization, it was found that the BIF deposit is a low-grade ore assaying 36.3% iron with a gangue of 47.8% silica. The mineralogy studies confirmed the presence of hematite as an iron mineral and quartz/jasper as a major gangue mineral. Liberation analysis revealed hematite liberation at 23 μm, while quartz liberated at coarser sizes. The grinding studies were carried out using VSMM based on the design of experiments with Response Surface Methodology-Central Composite Design (RSM-CCD). Further optimization of the process was carried out. Among the grinding parameters studied, stirrer speed and residence time significantly influenced product fineness (P₈₀) and specific energy consumption (E_cs) in the mill. Optimal grinding conditions achieved a product size of 75 μm at 5.5 kWh/t. Pre-concentration efficiently rejected 65% of the feed mass, upgrading iron content to 49.8% with 60% Fe recovery using high-intensity dry magnetic separation. The integration of pre-concentration and stirred media milling not only reduced the grinding load but also offered 12–20% energy savings. This approach, based on dry or semi-dry processing, presents a viable pathway toward the decarbonization of the iron ore industry by reducing both energy and water consumption, thereby aligning with broader sustainability goals.