Phase Transformations and Microstructure Evolution of Soda-Ash Roasted Boron-Containing Iron Concentrate: A Comparative Investigation of Varying Roasting Atmospheres

In the utilization of boron-containing iron concentrate(BIC),its complex mineralogical composition and finely disseminated mineralparticles restrict its large-scale exploitation. Soda-ash roastingproves to be a practical approach for boron activation and extraction,wherein reactions among magnetite, silicates, and soda ash are involved,which affect the consumption of soda ash and the subsequent recoveryof iron. This study investigates and compares the phase transformations,microstructure evolution, and magnetism changes of soda-ash roastedBIC under different roasting atmospheres. Results indicate that neutral(100 vol % N-2) and weakly reductive atmospheres (50 vol% N-2 + 5 vol % CO + 45 vol % CO2) regulatedthe iron species into the Fe3O4 and Mg x Fe3-x O4 phases with strong magnetism, respectively. In contrast, the ironspecies presented as interwoven Fe2O3 and MgFe2O4 under an oxidative atmosphere (79 vol % N-2 + 21 vol % O-2). When the roasting atmosphere wasintensely reductive (100 vol % CO), the roasted ore consisted of spongeiron and Mg y Fe1-y O.