Enhanced hydrogen-based reduction of hematite by bastnaesite: Kinetics and microstructural evolution mechanisms

Abstract

To investigate the hydrogen-based reduction mechanism of the polymetallic Bayan Obo hematite, this study utilized pure hematite and bastnaesite minerals to conduct fundamental kinetic research on the hydrogen reduction process of hematite influenced by bastnaesite, Isothermal reduction experiments were conducted under controlled hydrogen atmospheres, followed by kinetic modeling to elucidate reaction parameters, while phase and microstructural evolution were revealed through XRD, SEM, and BET analyses. Kinetic models were applied to compare the hydrogen reduction kinetics of pure Bayan Obo hematite and its mixture with bastnaesite, highlighting the promoting effect of bastnaesite on the reaction rate. Results show that bastnaesite accelerates the reduction process and reduces the apparent activation energy (E_α). X-ray diffraction (XRD), scanning electron microscopy (SEM), and Brunauer-Emmett-Teller (BET) surface area analysis were employed to examine phase transformation and microstructural evolution process. XRD revealed that bastnaesite promotes the efficient conversion phenomenon of hematite to magnetite. SEM images showed that bastnaesite enhances crack and pore formation and development in hematite particles. BET analysis confirmed that bastnaesite increases the surface area of the reduction products. These results not only reveal the promoting effect of bastnaesite on the hydrogen-based reduction of hematite, but also suggest its potential application in low-carbon metallurgical processes involving rare earth minerals. With hydrogen-based reduction technologies advancing, rare earth minerals are expected to play a key role in efficient, cleaner steel production, contributing to the green transformation of metallurgy.