Application of discrete element method simulation for studying fluidization of nanoparticle agglomerates

Abstract

The usefulness of discrete element method simulation for studying fluidization of nanoparticle agglomerates is explored. Nanoparticle agglomerates were simulated by using solid particles of equivalent sizes and densities. Validity of the present simulation was assessed through comparisons of simulation results and experimental observations of bed expansion, characteristic fluidization behaviour, and dense-bed settling. The simulation was then used to investigate initial bed expansion and bed uniformity under particulate fluidization conditions. The role of inter-agglomerate interparticle force in fluidization of nanoparticle agglomerates was examined. A stability analysis originally developed for addressing the transition from particulate to bubbling fluidization for conventional particles was used for predicting the start of bubbling in fluidized beds of nanoparticle agglomerates.On aétudié l'utilité de la simulation par la méthode deséléments discrets pour l'étude de la fluidisation d'agglomérats de nano particules. Les agglomérats de nano particules ontété simulésà l'aide de particules solides de tailles et de masses volumiqueséquivalentes. La validité de la présente simulation aétéévaluée par des comparaisons de résultats de simulations et des observations expérimentales sur l'expansion de lit, le comportement de fluidisation caractéristique et la décantation en lit dense. On a ensuite utilisé cette simulation pourétudier l'expansion de lit initiale et l'uniformité de lit dans des conditions de fluidisation de particules. Le rôle de la force interparticulaire et inter-agglomérats dans la fluidisation des agglomérats de nano particules aété examiné. Une analyse de la stabilité mis au pointà l'origine pour traiter la transition entre la fluidisation particulaire et par bullage pour des particules conventionnelles a servià la prédiction du début du bullage dans les lits fluidisés d'agglomérats de nano particules.

Fluidization of nanopowders: a review

“…In CFD models of the latter type, the gas phase is treated as continuous and the particles are modeled individually by a discrete element model (DEM). In the case of NPs, the discrete elements are the agglomerates rather than the individual NPs (Wang et al 2008 ). The agglomerate motion is calculated by integrating Newton’s law of motion and the fluid is modeled by approximating the Navier−Stokes equations in a finite volume discretized framework.…”

“…In this approach, it is assumed that when the spheres collide, they deform elastically and suffer a repulsive force of strength proportional to the magnitude of the overlap. To prevent excessively large computational times, these simulations are limited to 2D (Wang et al 2008 ) or pseudo 2D (van Ommen et al 2010a ) geometries. These simulations assume a constant agglomerate size (i.e., agglomerate breakage is not considered).…”

“…Wang et al ( 2008 ) showed by simulations that the stability analysis of Foscolo and Gibilaro ( 1987 )—originally developed for conventional particles—is useful for predicting the transition from particulate to bubbling fluidization. van Ommen et al ( 2010a ) studied the high-velocity microjet technique for enhancing nanopowder fluidization.…”

An adhesive CFD‐DEM model for simulating nanoparticle agglomerate fluidization

“…In literature, there are a few studies trying to model nanoparticle fluidization by assuming complex agglomerates as particle (Bahramian et al, 2013;Wang et al, 2008). By treating the simple agglomerate as the DEM particle, one advantage is that we do not need to model particle fragmentation.…”

Experimental investigation on the microstructure of fluidized nanoparticle agglomerates by TEM image analysis

“…[ 6 ] The complex structure of FNPAs can strongly affect the hydrodynamics and their group behaviours during fluidization. [ 7,8 ] Nevertheless, the solid and pore structures inside FNPAs have not been fully resolved due to their fragile nature. The aspects mentioned show that a fundamental and detailed characterization of their morphology and internal structure is of vital importance.…”