Collect. Czech. Chem. Commun. 1996, 61, 681-690

Surface Aeration Threshold in Agitated Vessels

Kamil Wichterlea and Tomáš Svěrákb

a Institute of Chemical Process Fundamentals, Academy of Sciences of the Czech Republic, 165 02 Prague 6-Suchdol, Czech Republic
b Research Institute for Macromolecular Chemistry, 656 49 Brno, Czech Republic


Violent agitation of liquids in mixing vessels may result in the regime of surface aeration being attained when the bubbles formed at the liquid surface enter the impeller region. Analysis of data on surface aeration for different liquids in a set of geometrically similar agitated vessels is presented. Data on the just aerated state as observed visually in transparent liquids, and data for the efficient aeration as determined from the break on the power number curve are considered. A simple model is developed for correlation of the data which enables the threshold of aeration to be predicted from the value of the recirculation number Nc = Nd (ρ/σg)1/4. The possibility of interpreting various literature data for the aeration threshold and for the power input with use of Nc is demonstrated. Similar modelling rules hold also for the correlation of beginning of the efficient liquid-liquid dispersion.

Keywords: Agitation; Gas-liquid; Bubbles.