Numerical study of particle segregation during spray drying of binary suspension droplets
Numerical study of particle segregation during spray drying of binary suspension droplets
Spray drying is a widely used industrial process to convert liquid feedstock into dry powders by rapidly evaporating the solvent using a hot gas stream. It finds critical applications in pharmaceuticals, food processing, ceramics, and nanotechnology. In particular, the drying behavior of binary suspension droplets—droplets containing two different types of particles—has drawn considerable attention due to the complexity of particle interactions and segregation phenomena during the drying process.
In this study, we present a numerical investigation into the particle segregation behavior during the spray drying of binary suspension droplets. The goal is to understand how different physical parameters influence the final spatial distribution of particles inside the dried droplet (or particle). Particle segregation can significantly impact the microstructure, functional properties, and performance of the resulting powder, making it crucial for optimizing formulations and controlling product quality.
We use Computational Fluid Dynamics (CFD) coupled with Discrete Element Method (DEM) to simulate the drying process of droplets containing two particle types with differing physical properties—typically size, density, and surface energy. The numerical framework solves mass, momentum, and energy conservation equations while tracking the movement and interaction of individual particles inside the evaporating droplet.
As the solvent evaporates from the surface, the particle concentration increases, leading to capillary-driven flow, Marangoni convection, and Brownian motion, all of which contribute to the radial or axial redistribution of particles. We observe that particles with higher mobility (typically smaller or less dense) tend to migrate toward the droplet surface, while larger or denser particles often remain at the center. This results in a core-shell structure or layered morphology, depending on initial conditions and drying rate.
The model incorporates evaporation kinetics, particle–particle interactions, and temperature-dependent diffusivity, making it robust and adaptable to a wide range of systems. Our simulation results align well with existing experimental observations in the literature, validating the reliability of the model.
Global Particle Physics Excellence Awards
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