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Ind. Eng. Chem. Res. 2009, 48, 302–309
Improved Drying in a Pulsation-Assisted Fluidized Bed Ali Akhavan,† J. Ruud van Ommen,‡ John Nijenhuis,‡ Xiao S. Wang,† Marc-Olivier Coppens,*,‡,§ and Martin J. Rhodes† Department of Chemical Engineering, Monash UniVersity, P.O. Box 36, Clayton 3800, Victoria, Australia, DelftChemTech, Delft UniVersity of Technology, Julianalaan 136, 2628 BL Delft, The Netherlands, and Howard P. Isermann Department of Chemical and Biological Engineering, Rensselaer Polytechnic Institute, Troy, New York 12180, U.S.A.
Gas flow pulsation was employed to improve the drying of porous pharmaceutical granules in a cylindrical fluidized bed. In our approach, a fraction of the total flow was oscillating intermittently and periodically, typically at 3 Hz during 2 min and remaining constant during the other 2 min of each 4 min cycle. It was found that such pulsationassisted fluidization not only shortened the total drying time but also enhanced homogeneity. A transition in fluidization behavior, reflected by a distinct transition in the bed dominant frequencies, was observed. 1. Introduction Drying often represents an essential stage in food, pharmaceutical, agricultural, and many other chemical processes. There are advantages to fluidized bed dryers compared to other types of dryers, such as tumble dryers and tray dryers. Fluidized beds are favorable for drying applications due to the high heat- and mass-transfer coefficients and the large exchange area between the solid and the gas. As a result, the drying rates are normally higher in fluidized bed dryers than in other types of dryers. In fluidized bed dryers, it is possible to decrease the moisture content to a very low level (
