High Shear (Rotor-Stator) Mixers, 25 Years Later

In June 1995 a session was held at MIXING XV in Banff, Alberta on rotor-stator mixers titled “High Shear Mixers – An Introduction and Overview”. The session consisted of four presentations by industrial experts who clearly demonstrated the importance of these poorly understood devices for the production of emulsions and dispersions and called for academic/industrial research to better understand and place them on a common design basis with stirred tanks and other conventional mixers. Now, 25 years later, this challenge has/is being addressed globally by several academic and industrial groups. In this presentation, this class of mixers will be introduced and experts will discuss the state of the art as well as current and future needs.

With respect to application, we will review four subtopics:

1. Hydrodynamics & power draw
2. Liquid-liquid systems & emulsions
3. Solid-liquid systems and dispersions
4. Scale up & process specification

For each topic, examples will be given that illustrate common and/or desperate operating and design principles across device geometry. Emphasis will be placed on rotor-stator mixers but results for related high shear devices such as colloid mills and valve homogenizers will also be presented. The extent to which high shear devices share common ground with other mixing equipment will be discussed and placed in context.

This will be an extended presentation resulting from a collaboration among the authors to bring the current state of knowledge into focus. Several authors will speak based on expertise and availability. The talk will be dedicated to the memory of our recently deceased fellow collaborator Jerzy R. Baldyga of Warsaw Technical University.