Particle-pore scale study of the expansion and minimum fluidization of fine particles

Abstract

A coupled approach combining the Discrete Element Method (DEM) and the Pore Network Model (PNM) is developed to simulate particle-fluid flows at equivalent solving scales, specifically, the particle scale via DEM for capturing solid-phase dynamics, and the pore scale via PNM for characterizing fluid flow. Initially, the DEM-PNM model yields results that are largely consistent with those of the DEM-Lattice Boltzmann Method (DEM-LBM) in simulating a dynamic cell under low Reynolds number conditions. Subsequently, the model is employed to replicate the formation of a stable expanded bed composed of fine particles. By analyzing pore-scale fluid flow, tortuous flow paths, and particle-particle force chains, the results reveal that the development of a stable expanded bed corresponds with microscopic structural evolutions that reduce resistance to gas flow and enhance mechanical stability. Finally, leveraging the micromechanical interactions at the particle and pore scales, a quantitative correlation is derived to predict the minimum bubbling velocity of fine cohesive particles. This correlation explicitly incorporates particle-scale properties, including the Hamaker constant, as well as pore structure characteristics within the particle assembly. Overall, the study demonstrates that the DEM-PNM approach, operating at an equivalent particle-pore scale, holds significant promise for advancing the understanding of particle-fluid flow micromechanics.