Detailed Understanding of the Blending of Wet Powders and the Liquid Distribution Therein

Liquid transfer between wet particles plays an important role in many industrial processes, such as mixing, granulation and coating. Previous studies on liquid transfer mainly focused on the static bridges, or bridge rupture [1,2]. However, few theoretical and experimental studies provide a detailed understanding of the initial bridge formation process, and the subsequent liquid transfer rate. In this work, we provide detailed models to predict liquid transport, and the distribution of liquid in a powder bed by extending our previous work [3, 4, 5].
Specifically, we employ two approaches to study the transfer of liquid: Direct Numerical Simulations (DNS) [3, 4] and the Discrete Element Method (DEM) [5]. The DNS methods allow us to resolves the solid particle motion and the liquid interface, using either (i) the Volume of Fluid (VoF), or (ii) the Immersed Boundary (IBM) method combined with VoF. Based on these simulations, we extract data on the time evolution of the liquid bridge volume between wet particles, and parameterize a recently proposed liquid transfer model [3, 4]. A probabilistic model for predicting wet collisions, as well as a sub-model for roughness effects complements these transfer models.
Finally, the DEM is supplemented with the scale-bridging liquid transfer models, allowing us to perform realistic, yet efficient simulations of liquid transfer associated with each particle-particle contact. Our results lay the foundation for the future development of continuum models that can be used to predict process performance of, e.g., granulation devices, in industrial applications.