(424g) CFD Simulations for Scale up of Wet Milling in High Shear Mixers

Rotor-stator mixers are widely used in the chemical and pharmaceutical process industries for a variety of emulsion and dispersion applications, that must be scaled to geometrically or dynamically different equipment on the pilot and plant scale. When the process fluid dynamics plays a significant role, a reasonable approach is to simulate the bench, pilot scale and plant scale flow field and deformation rate phenomena and match these on all scales to extrapolate bench scale data with respect to the number of mill head passes and shear rate history.

To date, we have been simulating the flow fields in Silversion L4R (bench scale), 450LS (pilot scale) and 600LS (plant scale) in-line mixers. The working fluid is water and the flow is turbulent. We use a RANS formalism with a k - epsilon turbulence model and non-equilibrium wall functions. Due to the importance of the rotor-stator interaction, a sliding mesh CFD technique must be employed.

The velocity fields and turbulence fields inside these mixers will be compared and discussed along with pumping capacity and power number predictions. The deformation rate fields are also analyzed and compared. The implication of the results to scale-up of wet milling of pharmaceuticals will be also discussed by reference to bench scale data for crystal size reduction.