May 22-27, 2016
Nanoparticles can be fluidized as agglomerates, but for some materials this is cumbersome due to the cohesive nature. Micro-jets are shown to be effective for improving the fluidization in such cases (1). In this study, the mechanisms of micro-jet assistance are investigated by using an adhesive CFD-DEM (Computational Fluid Dynamics – Discrete Element Modelling) model. In previous studies, the complex agglomerates found in a fluidized bed are treated as the discrete elements (2). Here we use the simple agglomerates as the discrete elements, which are the building blocks of the larger complex agglomerates. The collision of the simple agglomerates are modeled by including collision mechanisms of elastic-plastic, cohesive and viscoelastic forces.
Particles with =40 and =250 are used to represent the simple agglomerates. The cohesive force is expressed by the non-dimensional parameter , definded by the ratio of der Waals force over the particle gravity. A fluidized bed with dimension of 3 mm × 0.4 mm × 12 mm containing ~120,000 particles is simulated. At different cases, a micro-jet with horizontal cross-section size of 20 x 20 pointing downwards is turned ON or OFF (36 m/s) while the gas velocity to the bed is set as 2.8 cm/s or 4 cm/s, respectively. The schematic of the microjet in the bed is shown in Figure 1. In this way, like in our previous study, we keep the total amount of gas provided to the bed equal (2).
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Daoyin Liu, Berend G. M. van Wachem, J. Ruud van Ommen, Robert F. Mudde, and Xiaoping Chen, "CFD-DEM simulation of nanoparticle agglomerates fluidization with a micro- jet" in "Fluidization XV", Jamal Chaouki, Ecole Polytechnique de Montreal, Canada Franco Berruti, Wewstern University, Canada Xiaotao Bi, UBC, Canada Ray Cocco, PSRI Inc. USA Eds, ECI Symposium Series, (2016). http://dc.engconfintl.org/fluidization_xv/142