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Fluid Dynamics and Granular Growth in High Shear Wet Granulation

Experiments and Mechanistic Modelling

Anders Darelius (Institutionen för kemi- och bioteknik, Kemisk apparatteknik)
Göteborg : Chalmers University of Technology, 2007. ISBN: 978-91-7291-907-5.- 94 s.
[Doktorsavhandling]

High shear wet granulation is a key step in the manufacturing of tablets in the pharmaceutical industry. From the pharmaceutical industry’s point of view, there is a desire for predictive quantitative process models to be able to make in-silico process and scale-up simulations, which would shorten and reduce the cost of technology transfer from laboratory scale to manufacturing scale in drug development. The primary objective of the thesis is to develop mathematical models for describing the high shear granulation process. Population balance models are found to describe granule coalescence and growth well and in this study, both one-dimensional and multi-dimensional population balances have been implemented. However, the applicability of the population balances is limited if the particle flow in the granulator is not known in detail. Thus, the secondary objective of the thesis focuses on Experimental Fluid Dynamics (EFD), i.e. to develop experimental techniques for measuring the powder flow pattern, and to model the flow using Computational Fluid Dynamics (CFD). In the one-dimensional population balance, the granule size distribution alone is modelled. By dividing the coalescence kernel into two factors, collision frequency and collision efficiency, respectively, it is found that the collision frequency expression derived from the assumption of equipartition of translational momentum between the colliding granules best describes the granulation process. In the multi-dimensional case, liquid saturation and porosity distributions for the granules are modelled as well. By generalizing the existing model, the temporal evolution of the distributions of particle size, liquid saturation and porosity can all be well modelled. Experimentally, a high speed camera is successfully used to obtain velocity data on the powder flow at the granulator wall and by using Laser Doppler Anemometry (LDA), the velocity field from the wall and up to 4 mm into the dense rotating powder mix can be measured. In the CFD flow simulations, the Kinetic Theory of Granular Flow combined with frictional stress models, is found to roughly describe the flow, and the experimentally found velocities act as validation of the flow model.

Nyckelord: High shear granulation, Population balances, Multi-dimensional, Coalescence kernel, High speed imaging, Laser Doppler Anemometry, EFD, CFD, Multiphase flows, Frictional Stress Models


Additional lncluded work under the authors previous name Anders Jansson:
Empirical to mechanistic modelling in high shear granulation
Author(s): Ingela Niklasson Björn (External/Unspec); Anders Jansson (Department of Chemical and Biological Engineering, Chemical Engineering Design); Magnus Karlsson (External/Unspec); Staffan Folestad (External/Unspec); Anders Rasmuson (Department of Chemical and Biological Engineering, Chemical Engineering Design)
Published in: Chemical Engineering Science, 60 p. 3795-3803
CPL Record number: 10804



Denna post skapades 2007-05-02. Senast ändrad 2013-09-25.
CPL Pubid: 41094

 

Institutioner (Chalmers)

Institutionen för kemi- och bioteknik, Kemisk apparatteknik (2005-2014)

Ämnesområden

Kemiska processer

Chalmers infrastruktur

Relaterade publikationer

Inkluderade delarbeten:


High shear wet granulation modelling - a mechanistic approach using population balances


A Volume-Based Multi-Dimensional Population Balance Approach for Modelling High Shear Granulation


Measurement of the velocity field and frictional properties of wet masses in a high shear mixer


Examination

Datum: 2007-05-25
Tid: 10:00
Lokal: HC3
Opponent: Prof. Jonathan Seville

Ingår i serie

Doktorsavhandlingar vid Chalmers tekniska högskola. Ny serie 2588