(380aq) Fluidization of Nanopowders: Effects of Vibration and Stirring
Due to strong inter-particle interactions (such as Van der Waals, electrostatic and moisture-induced surface tension forces), fluidization of most nanoparticles is difficult to achieve, which may require the introduction of external forces. In this study, we investigate both mechanical vibration and stirring to enhance the fluidization of nanopowders. Hydrophilic nanosilica is used as the testing nanopowders, which shows strong agglomeration behavior leading to poor fluidization hydrodynamics. Compared to using a stirring blade in previous studies, we use a fishbone structure as the stirring bar. This modification can greatly reduce the possibility that induces flow turbulence in the fluidized bed and particlesâ attaching to the blade surface as a result of using the blade which has a relatively big surface area. Effects of the vibration direction (horizontal or vertical), vibration conditions (amplitude range from 0.5 to 5 mm and frequency from 20 to 100 Hz) and rotational speed of the stirrer (range from 30 to 200 r/min) on the fluidization quality of nanoparticles, the agglomerate formation (structure), pressure drop curve, bed expansion, and the minimum fluidization velocity, have been experimentally investigated.