An investigation of Bayer desilication product agglomeration mechanisms by kernel function population balance modelling

The mechanism of Bayer desilication product (DSP) size enlargement has not been fully investigated to date. Experimental data has shown that agglomeration plays an important role in DSP size enlargement. In this work, a population balance model was developed to quantify the agglomeration mechanisms during precipitation of DSP in caustic aluminate solutions. Precipitation conditions were selected where both the nucleation rate was negligible and the growth rate was minimal, to isolate and investigate agglomeration. In order to identify the most suitable kernel function for this system, particle size distribution (PSD) curves were measured by AccuSizer particle counting, at different time intervals under batch operating conditions. The data was then fit to eight agglomeration kernels. It was shown that DSP agglomeration cannot be successfully modelled by a size independent agglomeration kernel. A size dependent two variable agglomeration kernel function gave the best PSD shape matching and resulted in the best fit to experimental data