Fenomeni sudara kapi u procesu oblaganja Wurster tehnologijom

master's thesis

• Title (english): Droplet impact phenomena in coating process with a Wurster insert
• Author: Tanja Havaić
• Mentor: Krunoslav Žižek (mentor)
• Committee member: Krunoslav Žižek (predsjednik povjerenstva)
• Committee member: Gordana Matijašić (član povjerenstva)
• Committee member: Igor Dejanović (član povjerenstva)
• Granter: University of Zagreb; Faculty of Chemical Engineering and Technology; Zagreb
• Defense date and country: 2016-04-29, Croatia
• Scientific / art field, discipline and subdiscipline: TECHNICAL SCIENCES; Chemical Engineering; Mechanical, Thermal and Separation Processes

Abstract

Ovo se istraživanje bavi mehanizmima sudara između kapljica i krutih čestica tijekom oblaganja tableta u laboratorijskoj izvedbi uređaja za oblaganje s Wursterovom cijevi. Žarište istraživanja su fenomeni koji se preferirano pojavljuju tijekom sudara kapljice otopine za oblaganje i površine tablete. Na ishode sudara pojedine kapljice s površinom tablete moguće je utjecati promjenom određenih procesnih uvjeta (tlak zraka, brzina strujanja otopine, temperatura i položaj Wursterove cijevi). Metodom pokušaja i pogrešaka su dobivene obloge širokog raspona kvalitete. Rezultati su pokazali kako i najmanja promjena pojedine varijable povlači za sobom značajne promjene u ponašanju kapljice nakon sudara, što dovodi do velikih razlika u izgledu konačnog proizvoda, kao i u primjeni istog. Povoljni procesni uvjeti odabrani su nakon prilagodbe procesa temeljene na analizi faktora djelotvornog oblaganja: učinkovitosti oblaganja, ujednačenosti filma na jednoj tableti (intra-tablet uniformity) i ujednačenosti oblaganja u kolektivu među pojedinim tabletama (inter-tablet uniformity). Također je ispitan utjecaj brzine kapljice na njeno razlijevanje (širenje). Rezultati su u skladu s literaturnim podacima i potvrđuju da veća brzina udarca značajno povećava najveći promjer razlijevanja, zbog veće energije sudara kapljice. Naposljetku, konstruiran je dijagram režima sudara na temelju Weberovih i Ohnesorgeovih bezdimenzijskih značajki. Zaključeno je kako određena kombinacija procesnih svojstava i svojstava otopine povećava učestalost pojave upravo željenog mehanizma prianjanja.

Abstract (english)

This study deals with mechanisms involved in numerous droplet-particle collisions during tablet coating in a lab-scale fluid-bed environment with a Wurster tube. The study focuses on phenomena which preferentially occur during the impact of droplet of coating formulation on tablet surface. Impacts of single droplet on tablet surface were affected through variations of certain process properties (air pressure, fluid velocity, temperature and position of the Wurster tube). The method of trial and error results in a wide range of coating quality. Results showed that even the slightest change of single variable drags along considerable changes in a droplet behaviour after impact, leading towards considerable diversity in final product appearance as well as its utility. Favourable process conditions were detected after adaptations based on the analysis of coating efficiency criteria: coating efficiency, intra- and inter-tablet coating variability. The effect of droplet velocity on its spreading was also investigated. Results correspond to literature data and confirm that higher impact speed considerably increases the maximum extent of spreading due to the higher impact energy of droplet. Finally, an impact regime diagram based on Weber and Ohnesorge dimensionless numbers was established. It is shown that the process and formulation properties will synergically result in a preferential occurrence of deposition mechanism.

• Keywords: proces oblaganja; Wursterova cijev; učinkovitost oblaganja; varijabilnost oblaganja; faktor širenja; režim sudara; prianjanje
• Keywords (english): coating process; Wurster tube; coating efficiency; coating variability; spreading factor; impact regime; deposition
• Language: croatian
• URN:NBN: urn:nbn:hr:149:861095
• Study programme: Title: Chemical Engineering - Graduate study; Study programme type: university; Study level: graduate; Academic / professional title: magistar/magistra inženjer/inženjerka kemijskog inženjerstva (magistar/magistra inženjer/inženjerka kemijskog inženjerstva)
• Type of resource: Text
• File origin: Born digital
• Access conditions: Open access
• Repository: Repository of Faculty of Chemical Engineering and Technology University of Zagreb
• Created on: 2017-03-24 13:32:27