Aggregation kinetics of small particles in agitated vessels

Rapid coagulation by turbulence in stirred tanks was studied for particles and aggregates smaller than the Kolmogorov microscale. The coagulation kinetics are determined by the floc structure and by the hydrodynamic and colloidal interactions between the colliding particles. The collision efficiency...

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Bibliographic Details
Published in:	Chemical engineering science Vol. 52; no. 1; pp. 107 - 121
Main Authors:	Kusters, Karl A., Wijers, Johan G., Thoenes, Dirk
Format:	Journal Article
Language:	English
Published:	Oxford Elsevier Ltd 1997 Elsevier
Subjects:	Chemistry collision efficiency Colloidal state and disperse state Exact sciences and technology fractal aggregates General and physical chemistry Physical and chemical studies. Granulometry. Electrokinetic phenomena stirred tank Turbulent coagulation Turbulent coagulation collision efficiency stirred tank fractal aggregates Stirred vessel Particle size Turbulence Coagulation Agglomeration Particle suspension Experimental study Grain size distribution Fractal Morphology Particle collection Styrene polymer Models Kinetics Aqueous solution Sodium Chlorides
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Summary:	Rapid coagulation by turbulence in stirred tanks was studied for particles and aggregates smaller than the Kolmogorov microscale. The coagulation kinetics are determined by the floc structure and by the hydrodynamic and colloidal interactions between the colliding particles. The collision efficiency for doublet formation in the heterogeneous shear field of a stirred tank follows from particle trajectory analysis of solid particles in simple shear flow, provided the simple shear rate is made to correspond to the residence time weighted turbulent shear rate. Experimentally, the resulting aggregates proved to be fractal-like with their porosity increasing with aggregate size. Porosity within the aggregates results in penetration of the floc surface by the fluid flow, giving rise to enhanced collision efficiencies compared to solid particles. The collision efficiencies between porous flocs may be estimated by a model that pictures a porous floc as consisting of an impermeable core and a completely permeable shell. With the collision efficiencies from this shell-core model the aggregate growth could be described adequately.
ISSN:	0009-2509 1873-4405
DOI:	10.1016/S0009-2509(96)00375-2