Many experimental studies reveal that suspended solids considerably alter the coalescence behaviour and hydrodynamic functions of two-phase flow. But no systematic efforts have yet been undertaken to separate the effects of different particle properties on local gas hold-up, bubble size and interfacial area gasiliquid. The aim of this paper is to present the local values of these parameters in three-phase fluidized beds of different solids, using miniaturized optical fibre and conductivity needle probes. It is shown that particle concentration, size and, in particular, density are decisive for the change in coalescence behaviour. Ranges of normal (e, > eL) and inverse fluidization (e, < eL) must be distinguished and the flow regime also exerts a strong influence on the interactions between the dispersed phases, the transition point itself being a function of particle properties. For certain combinations of solid parameters, even increased interfacial areas gaslliquid can be observed. This effect is evaluated for different column diameters, between 0.1 and 0.3 m.

In den letzten Jahren haben sich Dreiphasen-Blasensaulen einen schnell wachsenden Anwendungsbereich in der Biotechnologie erschlossen [l]