PEPT Study of Particle Cycle and Residence Time Distributions in a Wurster Fluid Bed
Artikel i vetenskaplig tidskrift, 2015

Particle cycle and residence time distributions are critical factors in determining the coating quality in the Wurster process. Positron emission particle tracking experiments are performed to determine the cycle and residence times of particles in different regions of a Wurster fluid bed. The results show that particles tend to recirculate in and sneak out below from the Wurster tube. The experiments also show that a larger batch size leads to a shorter cycle time and a narrower cycle time distribution (CTD). It is possible to avoid recirculations and obtain a shorter cycle time and a narrower CTD by selecting the operating conditions appropriately or via equipment design. Experiments using binary mixtures of particles with a diameter ratio of 1.5 show that large particles have a longer cycle time than small particles and that the cycle time is shorter for mixtures with approximately equal amounts of small and large particles.

residence time distribution

cycle time

positron emission particle tracking

fluid bed



Liang Li

Chalmers, Kemi och kemiteknik, Kemiteknik

Anders Rasmuson

Chalmers, Kemi och kemiteknik, Kemiteknik

A. Ingram

University of Birmingham

M. Johansson

AstraZeneca AB

Johan Remmelgas

AstraZeneca AB

Christian von Corswant

AstraZeneca AB

S. Folestad

AstraZeneca AB

AICHE Journal

0001-1541 (ISSN) 1547-5905 (eISSN)

Vol. 61 3 756-768





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