Study on the Carbochlorination Process of Mixed Rare Earth Ores with Alumina Synergistic Effect

Abstract

In response to the prominent environmental risks associated with traditional smelting processes for bastnaesite-monazite mixed rare earth ores, this study proposes a carbochlorination synergistic metallurgy technology based on alumina-based fluorine fixation, systematically elucidating the phase transformation mechanism of mixed rare earth ores. Thermodynamic calculations confirmed the feasibility of the reactions. Experimental results demonstrated that under conditions of 10% Al2O3 addition, chlorination temperature of 800°C, chlorine flow rate of 10 L/min, and reaction time of 60 min, the chlorination rates of rare earths, Ca, Ba, and Fe reached 94%, 99%, 96%, and 99%, respectively, with a fluorine fixation efficiency of 75.72%. Combined XRD and in-situ SEM-EDS analysis revealed that Al2O3 reacts with fluorine in the mineral lattice to form AlF3, effectively blocking the generation path of hydrogen fluoride while simultaneously promoting the conversion of rare earth oxides to rare earth chlorides. Based on the shrinking core model, a two-stage interfacial chemical reaction-controlled kinetic equation with activation energies of 27.48 KJ/mol and 14.83 KJ/mol was established, revealing the stepwise mechanism of the carbochlorination process.