An experimental insight of the hydrodynamics of microjet assisted fluidized bed of ultrafine particles

Strong interparticle forces (IPFs) in ultrafine powders lead to agglomeration and poor fluidization quality posing a major challenge in many industrial processes. This study investigates the use of a high-energy microjet to improve the fluidization of nanosilica. A 200 μm nozzle was used to inject a secondary flow at a sonic velocity of 312 m/s, creating intense, localized turbulence. Analysis of local pressure drop transients confirmed that this energy input effectively de-agglomerated the powder, particularly in the lower bed. The combination of the microjet with a primary inlet gas flow produced a substantial improvement in fluidization, achieving a maximum bed expansion of approximately ten times the initial height. Furthermore, by conducting successive runs, we demonstrated a significant persistence effect. The bed retained its improved hydrodynamic characteristics, responding more rapidly in subsequent runs, implying an irreversible microjet-induced change in the powder's agglomerate structure.