May 22-27, 2016
Vibrated fluidized beds are a process intensification technique consisting in introducing vibratory kinetic energy in a fluidized bed (1). In this work we assess experimentally the effect of vibration on the gulf-stream circulation pattern of particles in a fluidized bed that is of triangular shape. The bed has 0.206 m span and 0.01 m thickness. The base of the bed is composed of two inclined walls, each one forming an angle of 45º with the horizontal. Air was injected through the inclined bed walls to fluidize the bed (see Figure 1a). This gas injection, together with vibration, can make the dynamics of this bed different to that found in a spouted fluidized bed (2). The bed is filled with ballotini particles with a mean diameter of 1.15 mm up to the top of the inclined walls. The bed vessel is made of antistatic PMMA to allow optical access with a high-speed camera. The bed was mounted on an electrodynamic shaker which produces the vibration.
A high speed camera is used to record the motion of particles. The particle velocity was obtained via Particle Image Velocimetry (PIV). As a function of vibration amplitude and frequency, we observe several circulation patterns when the fluidization velocity is just below and above the minimum fluidization velocity. Noticeably, for zero gas velocity, particles ascend close to the side walls descend in the center of the bed. By injecting fluidization gas, the circulation pattern of the bed could be reversed (i.e. particles descending near the side walls ascend in the center of the bed) for certain conditions. For example, reversal of the gulf stream circulation of particles appeared in the triangular bed for gas superficial velocities higher than the minimum fluidization velocity and sufficiently high values of the vibration strength. This phenomenon is illustrated in Figure 1b in which, for the same vibrating conditions, the injection of gas superficial velocity through the walls reverses the gulf stream motion of particles in the bed.
- R. Gupta, A.S. Mujumdar, Hydrodynamic of vibrated fluidized bed, Can. J. Chem. Eng., 58:332-338, 1980.
- Vinayak S. Sutkar, Niels G. Deen, J.A.M. Kuipers, Spout fluidized beds: Recent advances in experimental and numerical studies, Chem. Eng. Sci., 86:124:136, 2013.
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E. Cano-Pleite, A. Acosta-Iborra, F. Hernández-Jiménez, and C. R. Müller, "Reversal of gulf stream circulation in a vertically vibrated triangular fluidized bed" 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/157