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Transient behavior of pulsed particulate fluidized beds
Author(s) -
van der Wielen L. A. M.,
Fa A. W. K. G. Sjauw Koen,
Potters J. J. M.,
Luyben K. Ch. A. M.
Publication year - 1997
Publication title -
aiche journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.958
H-Index - 167
eISSN - 1547-5905
pISSN - 0001-1541
DOI - 10.1002/aic.690430308
Subject(s) - countercurrent exchange , fluidization , mechanics , fluidized bed , inertia , transient (computer programming) , residence time (fluid dynamics) , contactor , overshoot (microwave communication) , slugging , settling , porosity , thermodynamics , flow (mathematics) , materials science , geotechnical engineering , engineering , classical mechanics , physics , power (physics) , electrical engineering , computer science , operating system , composite material
Abstract Transient phenomena in solid–liquid fluidized‐bed systems are important in designing pulsed, countercurrent (multistage) fluidized‐bed contactors of the Cloete‐Streat type at high‐solids flow rate. Of particular interest are the residence times or corresponding velocities of porosity gradients in the bed and the excess or overshoot height of the bed after refluidization. Theory assuming local equilibrium between holdup and velocity of the phases (local‐equilibrium model) for stepwise perturbations in the liquid flow is readily available. It is investigated whether the local‐equilibrium theory can be used for more complex perturbations and whether inertia effects, such as are encountered in countercurrent multistage fluidized‐bed systems, can be ignored. Therefore, the detailed particle‐bed model of Foscolo and Gibilaro, which incorporates inertia effects, was applied to investigate the transient behavior of fluidized‐bed systems. Transient fluidization experiments were performed with a broad range of water‐fluidized particles in a laboratory‐scale multistage fluidized‐bed contactor. The operating conditions corresponded to those for countercurrent contact. Numerical simulations with the particle‐bed model predict satisfactory experimental results. The “overshoot” heights of the fluidized bed were estimated correctly by the particle‐bed model, whereas the local‐equilibrium model only provides a conservative estimate. However, the local‐equilibrium model allows an analytical solution that is more interesting for design, as it avoids tedious calculations. The residence time of the last perturbation before the fluidized bed relaxes to steady state was estimated with similar accuracy by both models.