title: Classification of annular bed flow patterns and investigation on their influence on the bottom spray fluid bed coating process.
abstract: OBJECTIVE
  This study aims to classify annular bed flow patterns in the bottom spray fluid bed coating process, study their influence on coat uniformity and investigate the feasibility of developing real-time annular bed flow pattern detection as a PAT tool.
  
  
  METHODS
  High-speed imaging and particle image velocimetry were used to visualize annular bed flow. Color coating and subsequent tristimulus colorimetry were employed to determine influence of annular bed flow pattern on coat uniformity. Feasibility of monitoring annular bed flow pattern through an observation window was tested using miniaturized particle velocity field and time series particle velocity orientation information.
  
  
  RESULTS
  Three types of annular bed flow patterns were identified. Plug flow gave the best coat uniformity followed by global and localized fluidization. Plug flow may be advantageous for high spray-rate conditions, large-scale coating and prevention of particle segregation. Plug flow could be differentiated from the other flow patterns through a simulated observation window.
  
  
  CONCLUSIONS
  Annular bed flow patterns were classified and found to influence particle coat uniformity noticeably. Availability of annular bed flow information for large-scale coaters would enable adjustments for process optimization. This study highlights the potential of monitoring annular bed flow pattern as a PAT tool.
authors.affiliation: GEA-NUS Pharmaceutical Processing Research Laboratory, Department of Pharmacy, National University of Singapore, 18 Science Drive 4, Singapore, 117543, Singapore.
authors.forename: Li Kun
authors.initials: LK
authors.lastname: Wang
authors.forename: Paul Wan Sia
authors.initials: PW
authors.lastname: Heng
authors.forename: Celine Valeria
authors.initials: CV
authors.lastname: Liew
mesh_terms: D000465:Algorithms; D002626:Chemistry, Pharmaceutical / Q000379:methods*; D003116:Color; D003124:Colorimetry; D003692:Delayed-Action Preparations; D007091:Image Processing, Computer-Assisted; D010316:Particle Size; D011336:Probability; D013608:Tablets, Enteric-Coated
chemical_list: D003692:Delayed-Action Preparations; D013608:Tablets, Enteric-Coated