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Nanoparticle fluidization is an efficient technique to disperse and process nanoparticles. Previous studies show that nanoparticles are not fluidized individually, but as agglomerates with hierarchical fractal structures. In this study, an adhesive CFD-DEM (Computational Fluid Dynamics -Discrete Element Modelling) model is developed, in which we use the simple agglomerate as the discrete element, which are the building blocks of the larger complex agglomerates found in a fluidized bed. We show that both the particle contact model and drag force interaction in the conventional CFD-DEM model need modification for properly simulating fluidization of nanoparticle agglomerates. The contact model includes collision mechanisms of elastic-plastic, cohesive and viscoelastic forces, and the drag force is approximately corrected by a scale factor resulting from particle agglomeration. The model is tested for different cases, including the normal impact, response of angle, and fluidization. The simulation results are promising. With increasing particle cohesive force, the fluidized bed goes from a uniform fluid-like regime, to an agglomerate bubbling regime, and finally to defluidization. The current study provides a tool for gaining insights into the characteristics of nanoparticle fluidization.

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