Thermally Assisted Beneficiation of a Low-Grade Iron Ore Powder in a Pilot-Scale Drop Tube Reactor: Effects on Ore Upgrading, Mineralogy and Chemical-Physical Characteristics

Abstract This study presents an in-depth analysis of thermally assisted beneficiation of a low-grade iron ore (goethite/hematite, 54.8 wt pct Fe) powder sourced from the Pilbara region in Western Australia. It was calcined in an electrically heated pilot-scale drop tube reactor (DTR) at relatively low temperatures (300 °C, 400 °C, and 500 °C), coupled with wet high-intensity magnetic separation to determine iron upgrade and recovery, and impurities removal. Various characterization techniques, including thermogravimetric analysis (TGA), X-ray diffraction, nitrogen adsorption, scanning electron microscope with energy dispersive X-ray spectroscopy, and X-ray fluorescence, were used to study the impact of flash heating on ore conversion, changes in ore mineralogy, and chemical-physical characteristics. It was found that the degree of conversion (calcination via goethite dehydroxylation) and mineralogy are strongly influenced by both heating rate ( HR ) and particle residence time ( τ ); samples heated under conditions relevant to flash heating in the DTR ( HR of 30 to 50 °C/s; τ in the order of minutes) exhibited different thermal decomposition behaviors to samples heated slowly in a TGA ( HR of 5 to 40 °C/min; τ in the order of hours). The analysis also shows that the proposed thermally assisted beneficiation method produces a hematite-rich concentrate with an iron upgrade and recovery of up to 60 wt pct and 94 pct Fe, respectively, and a high specific surface area (fivefold increase). Graphical abstract