title: In situ droplet size and speed determination in a fluid-bed granulator.
abstract: The droplet size affects the final product in fluid-bed granulation and coating. In the present study, spray characteristics of aqueous granulation liquid (purified water) were determined in situ in a fluid-bed granulator. Droplets were produced by a pneumatic nozzle. Diode laser stroboscopy (DLS) was used for droplet detection and particle tracking velocimetry (PTV) was used for determination of droplet size and speed. Increased atomization pressure decreased the droplet size and the effect was most strongly visible in the 90% size fractile. The droplets seemed to undergo coalescence after which only slight evaporation occurred. Furthermore, the droplets were subjected to a strong turbulence at the event of atomization, after which the turbulence reached a minimum value in the lower halve of the chamber. The turbulence increased as speed and droplet size decreased due to the effects of the fluidizing air. The DLS and PTV system used was found to be a useful and rapid tool in determining spray characteristics and in monitoring and predicting nozzle performance.
authors.affiliation: Division of Pharmaceutical Technology, Faculty of Pharmacy, PO Box 56 (Viikinkaari 5 E, FI-00014 University of Helsinki, Finland. henrik.ehlers@helsinki.fi
authors.forename: Henrik
authors.initials: H
authors.lastname: Ehlers
authors.forename: Jussi
authors.initials: J
authors.lastname: Larjo
authors.forename: Osmo
authors.initials: O
authors.lastname: Antikainen
authors.forename: Heikki
authors.initials: H
authors.lastname: Räikkönen
authors.forename: Jyrki
authors.initials: J
authors.lastname: Heinämäki
authors.forename: Jouko
authors.initials: J
authors.lastname: Yliruusi
mesh_terms: D000388:Air; D004339:Drug Compounding / Q000295:instrumentation* / Q000379:methods*; D016503:Drug Delivery Systems / Q000295:instrumentation* / Q000379:methods*; D015233:Models, Statistical; D009330:Nebulizers and Vaporizers / Q000706:statistics & numerical data*; D010316:Particle Size; D011312:Pressure; D012212:Rheology / Q000379:methods; D049489:Stroboscopy / Q000379:methods; D013696:Temperature; D014867:Water
chemical_list: D014867:Water