An adhesive CFD‐DEM model for simulating nanoparticle fluidization Daoyin Liu 1,2 , Berend G. M. van Wachem 3 , Robert F. Mudde 2 , Xiaoping Chen 1 , J. Ruud van Ommen 2 * * Corresponding author. Telephone: +31 15 278 2133. E‐mail address: j.r.vanommen@tudelft.nl 1 Key Laboratory of Energy Thermal Conversion and Control of Ministry of Education, School of Energy and Environment, Southeast University, Nanjing 210096, Jiangsu, China 2 Department of Chemical Engineering, Faculty of Applied Sciences, Delft University of Technology, Julianalaan 136, 2628 BL Delft, The Netherlands 3 Thermofluids Division, Department of Mechanical Engineering, Imperial College London, London, United Kingdom Abstract 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. Keywords: Nanoparticle Fluidization, Agglomerate, Discrete Element Model; Adhesion 1. Introduction Nanoparticle fluidization has attracted increasing attention in the past decade, as a promising technique to disperse and process nanoparticles (van Ommen et al., 2012). The structure of nanoparticle agglomerates formed during fluidization have been studied extensively. It is known that nanoparticles are not fluidized individually but as agglomerates: very dilute clusters of around a few hundreds of micrometres (de Martín et al., 2014a; Hakim et al., 2005; Valverde and Castellanos, 2008; Wang et al., 2002). The macroscopic behavior of nanoparticle fluidized bed can have two different appearances: the bed expands highly and homogeneously without obvious bubbles (APF type), or the bed expands slightly with significant bubbles (ABF type). Especially ABF type beds often require an assistance method to obtain proper fluidization; examples of such methods are electric fields, vibration, micro‐jets, and sound waves. (Lepek et al., 2010; Matsuda et al., 2004; Quevedo et al., 2010; Zhu et al., 2004). Studies of nanoparticle fluidization are often limited to macroscopic properties (Huang et al., 2008; Tamadondar et