Hematite and magnetite, the two predominant iron ores, require different processing routes. High-grade hematite direct shipping ores (DSOs) generally only require crushing and screening to meet the size requirements of lump (typically between 6 and 30mm) and fines (typically less than 6mm) products. Low-grade hematite ores require additional beneficiation to achieve the desired iron content, but the comminution of these ores still generally only involves crushing and screening, which is not particularly energy-intensive. Conversely, fine-grained magnetite ores require fine grinding, often to below 30m, to liberate the magnetite from the silica matrix, incurring greater costs and energy consumption. The comminution energy consumption could be over 30kWh/t, an order of magnitude higher than for hematite ores. However, with the depletion of high-grade deposits and strong demand for steel, a greater number of low-grade deposits are being developed.
To operate viably and sustainably, there is a need to reduce costs and energy consumption, particularly of the energy-intensive grinding required for low-grade magnetite deposits. This chapter reviews current iron ore comminution and classification technologies and presents some examples of flowsheets from existing operations. New trends and advances in comminution technologies are presented and discussed, particularly with regard to the impact on energy, operating, and capital costs.