Modeling of Solution Droplet Evaporation and Particle Evolution in Droplet-to-Particle Spray Methods

A mathematical model for the entire process of micro- and nanoparticle formation via one-step, direct conversion of solution droplets to particles with application to spray-drying and pyrolysis techniques is developed. Here we identify three physical stages for drying of solution droplets, including shrinkage, induction, and constant-diameter periods. The characteristics of these periods are studied by considering the drying of a population of solution droplets introduced into a hot wall reactor. The particle evolution and intraparticle phenomena in each period are elucidated. Numerical results show that low reactor wall temperatures, larger droplet number densities, and smaller initial droplet sizes favor the formation of fully filled particles, and the carrier gas flow rate has no effect on particle morphology.