Modeling-Aided Scale-Up of High-Shear Rotor–Stator Wet Milling for Pharmaceutical Applications

Abstract

This work describes a modeling-aided approach to scale-up high-shear rotor−stator wet milling processes for pharmaceutical applications. A population balance equation was used that applies known breakage distribution functions and specific breakage rate to provide valuable insight into the significance of different scale-up factors to predict milling performance as well as the importance of accounting for flow-induced breakage in recirculation configurations. Case studies involved the size reduction of platelike and rodlike organic crystalline compounds.

Modelling geometrical and fluid-dynamic aspects of a continuous fluidized bed crystallizer for separation of enantiomers

“…More detailed models with a larger validity range have been proposed e.g. by Luciani et al (2015), but are outside the scope of this work. Assuming perfect mixing in the disperser, the population balance equation for the number size density n M (L, t) in the disperser reads…”

Designs of continuous-flow pharmaceutical crystallizers: developments and practice

“…Generally speaking, the larger the energy output (e.g., normalization through an energy factor and a probability factor), or the finer the tooth geometry (e.g., fine vs. coarse), the smaller the particle size. 57,126,127 For a defined mill head (tooth) geometry, larger tip (rotational) speed leads to larger recycling flow rate (and cycle number, or turnover number per residence time), and usually more secondary nucleation and crystal breakage (smaller average crystal size). 55,126 Besides high shear wet milling, wet media milling (using milling beads) has also been used in continuous recirculation mode for reducing drug particle size in suspensions to nanoparticle scale (details described elsewhere 128,129 ).…”

Scalability and Predictability of Polymorph Transformations Under High Shear

“…The application of high-shear wet milling in industry has been studied for a number of operations, such as liquid–liquid emulsification , and particle size reduction. ,− Specific to particle size reduction, a topic of debate is the approach to scale-up, where performance across scales can be estimated by selecting the proper descriptor parameter (e.g., tip speed, shear frequency, etc. ). ,, These methods rely on maintaining the selected parameter constant across scales. A more recent approach developed by Engstrom et al, however, relies on quantifying the energy input experienced by the slurry crystals, E *, due to collisions with the mill .…”