Experimental and modelling studies on the aeration leaching process for metallic iron removal in the manufacture of synthetic rutile

摘要

The aeration leaching process for the removal ofmetallic iron from reduced ilmenite is a crucial step in themanufacture of synthetic rutile by the Becher process. This process,carried out in a mechanically agitated reactor is a multi-phasesystem involving a complex interplay between mass transfer andchemical reactions. Experimental investigations on the kinetics ofthis process exhibit a constant rate period followed by a decreasingrate period. A process model, which takes into account gas-liquidmass transfer, solid-liquid mass transfer, intraparticle diffusion ofdissolved oxygen, surface reaction and homogeneous liquid phasereaction has been developed to interpret this behaviour. The modelalso accounts for the influence of the precipitated iron oxide (inertmicro-particles) on mass transfer rates, as well as on the overall rateof iron removal. The results indicate that the overall iron removalprocess kinetics can be considered as constituted by an externalmass transfer-controlled period followed by an internal diffusion-controlled regime. The sluggish kinetics observed towards the endof the process is due to the intraparticle diffusion-controlledleaching of iron by dissolved oxygen.