(331c) Particles, Bubbles and Electrostatics in Gas-Solids Fluidized Beds

This presentation will  discuss recent advances in several important areas of fluidization which Derek Geldart pioneered or contributed. First, the transition velocity Uc for group A powders will be discussed based on a simple mechanics pressure fluctuation model by assuming that the bubble reaches a maximum stable size as predicted by the Geldart equation, the comparison between the predicted and measured Uc values will be presented. Secondly, the fluidization behaviour of sawdust particles as observed in a vibrating fluidized bed will be discussed based on the measured angle of repose and Geldart powder classifications. Thirdly, the effect of particle charging and charge distribution on bubble and particle movements, a phenomenon first explored by Geldart in early 1970s, will be discussed based on our recent simulation and measurement using both collision and induction electrostatic probes. The reconstructed charge distribution around gas bubbles will be compared with early observations of Boland and Geldart (1971/1972).