Agglomeration of yttrium oxalate particles produced by reaction precipitation in semi-batch reactor

The yttrium oxalate reaction, with precipitation and agglomeration in a sem i-batch reactor, was investigated. It was assumed that aggregates were form ed by particle adhesion following collision and then converted to the agglo merate by the molecular growth, Since the agglomerate was strong enough to resist against the breakage of turbulent shear and collision. Thus, the siz e-reduction of the agglomerate was mainly caused by the breakage of the agg regate. Both the aggregation and breakage depended simultaneously on the tu rbulent mixing. When the particle aggregation was dominantly promoted by th e turbulent mixing, the mean particle (agglomerate) size in the product sus pension increased with increasing the turbulent mixing intensity. When, how ever, the breakage became more sensitive to the turbulent mixing than the a ggregation, the mean particle (agglomerate) size in the product suspension was reduced by increasing the turbulent mixing intensity. The trend of the total particle population with the turbulent mixing intensity was opposite to that of the mean particle size in the product suspension. This mechanism of the particle agglomeration was tested at various feed concentrations an d with gelatin additive and was approximated by a simple model of aggregati on and breakage equations depending on the turbulent mixing intensity. (C) 2000 Elsevier Science Ltd. All rights reserved.