(231b) Particle Formation from the Drying of Liquid Droplets Containing Insoluble Material

Spray-drying is a manufacturing process utilized by a wide range of industries such as food, agriculture, and pharmaceutical for converting a liquid feed containing insoluble solid particles into particulate form. By removing the moisture, it is intended to achieve a final product with desired chemical composition, morphology (e.g., hollow particles, solid cores, agglomerates, etc.), and particle size distribution. There are many variables that affect the drying process, and due to its complexity, traditional trial-and-error methods have been the primary technique in achieving the desired product. The drying conditions and dynamics affect the internal flow patterns within a droplet. The flow patterns are dominated by surface tension and evaporative effects which ultimately disperse the suspended particles in the droplet and finally determine the final product morphology. In the presented work, the drying and internal transport of insoluble particles within a droplet were simulated using a volume of fluid method, where the particle and liquid phases are tightly coupled. In our model, the motions of individual particles are tracked within the droplet, and the impact of particles on the internal flow field is assessed. The model is used to simulate crust formation near the surface of the droplet, where the solid volume fraction increases as droplet evaporates. Simulations are performed at different drying conditions, where temperature, air velocity, and initial droplet diameter are varied to determine their effect of crust formation.