Dispersion of powders in liquids in a stirred vessel

The dispersion of powders in liquids can be divided into four steps: wetting, submersing, dispersing and dissolving (if soluble). While the subject of dispersing and suspending particles in liquids in mechanically agitated vessels has been investigated by several authors, the immersion step has remained largely uninvestigated. However, in many cases, the wettability of the powder is of decisive importance for the process of making a dispersion. Experiments in a baffled stirred vessel are presented and compared with results of different laboratory wetting tests to illustrate the importance of wettability for the dispersion process. Further experiments in an unbaffled vessel were conducted to investigate the influence of vortex formation on the powder immersion step. (C) 1999 Elsevier Science S.A. All rights reserved.