Direct numerical simulations of collision dynamics of wet particles
May 22-27, 2016
Fluidized beds involving liquid injection have a wide industrial application ranging from physical operation, like agglomeration and coating, to chemical processes including catalytic oxidization, fluid catalytic cracking, condensed-mode polyethylene (1). The injection of the liquid results in wet particles, which behave completely different from dry particles and hence lead to much more complicated hydrodynamics of fluidized beds (2). Nevertheless, a fundamental description of the dynamics of wet particles is predominantly missing, which however is crucial for prediction of fluidization behavior effecting on the product quality.
Despite significant investigation, experimental studies of wet collisions under actual fluidization condition (e.g., low particle velocity, thin liquid layer) are virtually impossible to perform and control. Direct numerical simulations can complement experiments by providing quantitative predictions of the micro-mechanical collisional behaviour of one or more particles with well-defined and easy-controlled system parameters. Jain et al. (3) demonstrated that the experimentally observed phenomena of collision between a particle and a wet wall can be reproduced by a hybrid model combining the volume of fluid (VOF) method and the immersed boundary method (IBM). Such simulations will be extended in this work to investigate the effects of liquid layer thickness, impact velocity, particle size and surface tension on the wet restitution coefficient () under normal collisions as well as oblique collisions. The motion of a solid particle is described by the IBM (Figure 1), which enforces a no-slip condition at the particle surface. Whereas, the VOF (Figure 2) describes the motion of the gas-liquid interface by a piece-wise linear reconstruction of the interface.
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Niels G. Deen, Yali Tang, Jochem Scholte, J.A.M. (Hans) Kuipers, Sergiy Antonyuk, Stefan Heinrich, and Britta Crüger, "Direct numerical simulations of collision dynamics of wet particles" 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/92