Production of rare earth oxides from raw ore in fluidized bed reactor.

• Fluidized bed is a promising reactor for the calcination of a rare earth bearing ore. • Higher recovery of REE is obtained in the downstream leaching process after calcination of a Geldart's group B ore. • Ore particles undergo cracking during calcination enhancing the mass transfer of produced gases. • Bastnäsite is thermally decomposed by gas-solid reaction at moderate temperature. • Monazite's decomposition depends on its association with carbonate minerals. This study deals with the calcination of a rare earth bearing ore to produce rare earth oxides in a fluidized bed reactor, with the aim of demonstrating the advantage of calcining bigger particles to decompose stable minerals such as monazite by its mineral association within a particle. Rare earth oxides were produced by the decomposition of its bearing minerals, bastnäsite and monazite along with the gangues. During the calcination, bastnäsite decomposed at relatively low temperature while monazite reacted CaO at high temperature. The formation of cracks, revealed by BET and SEM analysis, allowed the particle's degassing while the size remained constant, thus describing a crackling core behavior. The association of monazite to calcite for bigger particles (−60 mesh) allowed its decomposition to produce rare earth oxides with a monazite conversion of 50 %. Also, an extraction process comprised of calcination and mild acid leaching enriched the rare earth oxides in the ore by 3.34 and improved leaching efficiency of the gangues compared to smaller size (enrichment ration of 2.35). Using bigger particle sizes in the upstream process of a mining industry, i.e. comminution, can also reduce the energy consumption. [ABSTRACT FROM AUTHOR]