Continuum modelling of particle flows in high shear granulation
Doktorsavhandling, 2015

High shear granulation is an important process in the pharmaceutical industry. The aim of the process is to produce granules with specific properties, like size and hardness, from powder mixtures. The properties of the granules are determined by the flow field in the mixer. The most common approach taken to modelling the flow in a mixer includes tracking the forces on each individual particle and resolving each occurring collision. This gives detailed information, but the computational cost restricts this use to small-scale equipment. Continuum modelling of particle flows means that averages are made to form a continuous flow rather than tracking individual entities. The problem that arises in this procedure is correctly describing the transfer rates of mass and momentum in the system. The focus of the research in this thesis is on evaluating previously used continuum models, and finding and developing new approaches. The connection between flow field information and the evolution of particle properties is also studied through the development of a compartment model. Results show that the continuum model currently being used has a promising parameterization for describing the overall effect on a flow field caused by particle property changes that occur during granulation. The model is; however, not capable of adequately resolving the flow field in the important regions close to the walls and the impeller of the vessel where the particle volume fraction is high. A rheology-like model is used to improve the dense granular flow regions, while the theory for the more dilute parts is improved via kinetic theory models modified for inelasticity and improved for its validity in the transition region to dense flows.

parameter study

High shear granulation

continuum modelling

resolution dependence

granular flow

compartment model

kinetic theory of granular flow

HA2
Opponent: Agba Salman

Författare

Per Abrahamsson

Chalmers, Kemi och kemiteknik

On the continuum modeling of dense granular flow in high shear granulation

Powder Technology,; Vol. 268(2014)p. 339-346

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Parameter study of a kinetic-frictional continuum model of a disk impeller high-shear granulator

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On continuum modeling using kinetic-frictional models in high shear granulation

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I denna avhandling så utvärderas och utvecklas modeller för partikel flöden inom omrörd granulering. I denna process finns alla olika partikel-beteenden med i samma enhet: fast, vätska och gas-likt beteende. Processen är ett del-steg i tablett tillverkning för läkemedel och består av att de olika ingredienserna blandas i pulver form i en mixer. En vätska sprayas in under kontrollerade former och den gör att aggregat av pulver-partiklar bildas, så kallade granuler. Egenskaperna hos dessa granuler i form av storlek, hårdhet och sammansättning är av största vikt för läkemedlets funktion. Det kan tillexempel styra lösligheten hos den senare pressade tabletten vilket i sin tur påverkar hur snabbt och vart i kroppen läkemedlet tas upp. Att partikelflödet i en granulator är så komplicerat gör att processen blir svårstyrd och en stor del av de producerade granulerna måste återföras till processen för att nybildas med de önskvärda egenskaperna. De modeller som beskrivs här har utvecklats för att bättre förstå och förutsäga hur flödet i en granulator påverkar granulernas egenskaper vilket kan leda till effektivare produktion och mindre resursförbrukning.

High shear granulation is an important process in the pharmaceutical industry. The aim of the process is to produce granules with specific properties, like size and hardness, from powder mixtures. The properties of the granules are determined by the flow field in the mixer. The most common approach taken to modelling the flow in a mixer includes tracking the forces on each individual particle and resolving each occurring collision. This gives detailed information, but the computational cost restricts this use to small-scale equipment. Continuum modelling of particle flows means that averages are made to form a continuous flow rather than tracking individual entities. The problem that arises in this procedure is correctly describing the transfer rates of mass and momentum in the system. The focus of the research in this thesis is on evaluating previously used continuum models, and finding and developing new approaches. The connection between flow field information and the evolution of particle properties is also studied through the development of a compartment model.

Styrkeområden

Produktion

Ämneskategorier

Kemiteknik

Medicinsk apparatteknik

Strömningsmekanik och akustik

ISBN

978-91-7597-184-1

Doktorsavhandlingar vid Chalmers tekniska högskola. Ny serie

HA2

Opponent: Agba Salman