Binary collisions of drying maltodextrin droplets and glass beads

Abstract

Spray drying is often used in combination with agglomeration to produce powders with good functional properties, yet the mechanistic understanding of this agglomeration is limited. This research is a fundamental study into the binary collision dynamics underlying agglomeration, identifying specific collision outcome regimes. A sessile single drying droplet was subjected to collisions with glass beads. For maltodextrins with a dextrose equivalent of 6, 21 and 38, collisions were performed at different time points in the drying process. A shift in the collision outcome was observed during drying. The transition from merging as sole collision outcome to a regime where also sticking and bouncing were observed was linked to the locking point of the drying droplet. The sticking regime was observed from 0.75 to 1.5 tcollision/tlock. This indicates that precise timing of the collisions between drying droplets and dry fines is needed to optimize the agglomeration within a spray dryer.