Influence of Ore Mineralogy on the Performance of High-Flux Radiation-Assisted Beneficiation of Low-Grade Iron Ores: A Comparative Experimental Study

Abstract New results are reported for the thermally assisted beneficiation of three low-grade iron ores (LGIOs) with varying hematite-to-goethite (HG) ratios (0.1 to 3), using both rapid high-flux radiation heating (10 to 40 °C/s) and slow convective heating via thermogravimetric analysis (TGA, 0.1 °C/s). Experiments were conducted in the 300 °C to 700 °C range to systematically assess for the first time how heating rate and ore mineralogy influence thermal decomposition, phase transformation, and beneficiation performance under novel high-flux radiation-assisted conditions. The LGIOs, initially containing 51.5 to 55 wt pct Fe, showed mineral-dependent behavior under fast heating conditions. At 700 °C, nearly full conversion was found for samples with HG = 0.1 and 1 while high ore conversion (~ 80 pct) was found for HG = 3, regardless of the heating rate, though high-flux radiation method allowed to achieve conversion significantly faster. Under high-flux radiation, decomposition and goethite-to-hematite transformation occurred within minutes, producing highly porous hematite with elevated surface area and limited recrystallization. Nevertheless, the extent of goethite dehydroxylation at a given temperature in the range of 300 °C to 500 °C, found to decrease with an increase in heating rates > 10 °C/s, showed that the chemical conversion time can also be a rate-limiting factor. For samples with HG = 0.1 and 1, the heating rate strongly affected the resulting ore microstructure at 500 °C to 700 °C, with high-flux radiation treatments providing up to 50 pct greater surface area than the slow-heated samples. When coupled with magnetic separation, the high-flux radiation method yielded Fe grades of 58 to 61 wt pct and Fe recoveries of 50 to 90 pct depending on ore type. Overall, the results demonstrated the strong coupling between ore mineralogy and heating rate on both microstructural changes and beneficiation performance.