Quantifying the Effect of Seeds on Gibbsite Crystallization—Mathematical Modelling of Particle Size Distribution

Abstract

A critical step in the Bayer process is the crystallization of gibbsite (γ-Al(OH)3) from the caustic aluminate solution. It is necessary to add small gibbsite crystals as seeds in the crystallization circuit, which act as sites for the crystal growth and as material for agglomeration. Mathematical models are particularly useful in this context because they provide the particle evolution of the crystals as a function of time, together with the mass balances and reaction kinetics of crystallization. This work presents the particle size distribution (PSD) modelling of the Companhia Brasileira de Alumínio (CBA) alumina refinery, developed in order to study seed effects, assisting the optimization and maximization of the process yield and alumina quality.