(4c) Influence of Droplet Size on Particle-Particle Adhesion of Colliding Particles through Droplet: Directnumerical Simulation Study

Authors: 
Nakamura, H., Osaka Prefecture University
Kan, H., Osaka Prefecture University
Ohsaki, S., Osaka Prefecture University
Watano, S., Osaka Prefecture University
In a spray wet granulation, a particle-particle adhesion by a liquid bridge, which shows dynamic motion due to
moving particles, is the most fundamental phenomenon at the primary particle scale. Therefore, understanding
of the particle-particle adhesion by such a dynamic liquid bridge is very important to elucidate mechanisms of
particle agglomeration phenomenon in the wet granulation. In this study, the particle-particle adhesion
phenomenon at the individual particle scale was analyzed using a direct numerical simulation. Collision of two
particles mediated by binder droplets on a particle surface was simulated. In particular, the effect of droplet size
under constant total liquid volume on adhesiveness of two colliding particles was investigated. In the present
simulation, multiple liquid bridges were simultaneously formed, and these liquid bridges coalesced into single
liquid bridge. The simulation results exhibited that the adhesiveness of particles increased with a decrease in
the droplet diameter under a constant total liquid volume. In an initial stage of the particle growth in a fluidized
bed spray granulation, the tendency of the calculations was consistent with experimental results. We revealed
that the capillary pressure force and shapes of the liquid bridge are key factors for particle-particle adhesion at
different droplet sizes under constant total liquid volume.