Abstract
[Display omitted]
•Segregation of highly porous agglomerated ultrafine nanosilica was investigated.•Bed collapse studies were conducted using pressure transients.•Pronounced agglomerates’ size-based segregation occurred due to initial flow spike.•Modified inlet flow strategy suppressed size-based segregation of agglomerates.
Unlike conventional fluidization of micron-sized particles, the hydrodynamics of ultrafine nanopowders is controlled by their agglomerates, which show strong segregation pattern along the bed height. This aspect was carefully investigated in this study by carrying out collapse experiments in a low-frequency pulsed fluidized bed. Unlike previous studies, the inlet flow was modified with the help of four-way valve configuration to eliminate the inlet flow spike. The region-wise collapse dynamics was monitored by recording pressure transients along the height of the fluidized bed while double drainage deaeration strategy, termed modified dual drainage (MDD), was employed. The size of agglomerates in the different bed regions were evaluated and compared with the conventional single drainage (SD) and dual drainage (DD) deaeration configurations using two-way and three-way solenoid valves. The elimination of the flow spike with MDD helped to suppress the size-based segregation of agglomerates, thereby resulting in faster and smoother bed collapse.