Aggregation in Shear Environments

In a later development, Somasundaran et al. ]57] developed a PBM for aggregation by polymers in shear environments. The D LVO theory was extended for this case, as discussed in the previous section, by using the modifled expression for van der Waals attraction for particles covered with polymers and the expression for bridging attraction or steric repulsion derived from the scaling theory [25]. Their model was tested qualitatively with experimental data for the flocculation of colloidal alumina suspensions in the presence of PAA and was found to reproduce the observed experimental trends [60] reasonably well. 

Instead of assigning different shear rates, he employed different breakage rate expressions for the two zones. The problem of coupling population balance models with fluid flow models has received some attention recently and coupled PB-CFD models have been developed for a wide variety of processes such as fluidization [70], gas-liquid reactions in bubble columns [71] and nanoparticle synthesis in flame aerosol reactors [72]. Complete description of aggregation in turbulent environments requires simultaneous solution of basic balance equations for mass, momentum, energy and concentration of species present along with population balances for particles/aggregates of different size classes. 

Selomulya C, Bushel G, Amal R, Waite TD (2002) Aggregation mechanisms of latex of different particle sizes in a controlled shear environment. Langmuir 18 1974... 

Serra, T. and Logan, B. E. (1999). Collision frequencies of fractal bacterial aggregates with small particles in a sheared fluid. Environ. Set Technol., 33, 2247-2251. 

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