Transforming iron ore processing – Simplifying the comminution and replacing reverse flotation with magnetic and gravity separation

Much of the remaining iron ore resources in Brazil consist of low-grade itabirite ores. Accordingly, a typical beneficiation circuit includes a four-staged crushing/screening plant, followed by grinding in a closed-circuit ball mill, desliming in hydrocyclones and final ore mineral concentration via multistage reverse flotation and thickening of the final product. With the need for decarbonisation in the iron and steelmaking industry, there is a growing demand for high grade iron ore concentrate at more than 67% Fe. In the context of declining ore grades, there is an increasing need for a more effective circuit for beneficiating the itabirite ore. A proposed flowsheet consisting of a primary crushing stage, SAG mill, primary concentration using a VPHGMS magnetic separator, and a final concentration stage using the Reflux Classifier was investigated. The work demonstrated the significant reduction in energy consumption, and the potential for achieving high Fe grade of more than 67%, with high recovery, and in turn considerable process simplification. The new circuit would eliminate secondary to tertiary crushing, desliming stages, complex flotation circuits, product thickening and the flotation reagent plant. Further project assessments indicated an 8% smaller footprint, and 5% CAPEX and 42% OPEX reductions compared with the conventional circuit. These improvements would lead to a 50% higher Net Present Value.