PEPT study of particle cycle and residence time distributions in a Wurster fluid bed

Research output: Contribution to journalArticlepeer-review


  • Liang Li
  • Anders Rasmuson
  • Mats Johansson
  • Johan Remmelgas
  • Christian von Corswant
  • Staffan Folestad

Colleges, School and Institutes

External organisations

  • AstraZeneca
  • Chalmers Tekniska Hogskola


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.


Original languageEnglish
Pages (from-to)756-768
Number of pages13
JournalAIChE Journal
Issue number3
Early online date18 Nov 2014
Publication statusPublished - Mar 2015


  • Coating, Cycle time, Fluid bed, Positron emission particle tracking, Residence time distribution