Modelling the bed characteristics in fluidised-beds for top-spray coating processes--颗粒学报PARTICUOLOGY

Vanderroost, M., Ronsse, F., Dewettinck, K., & Pieters, J. G. (2012). Modelling the bed characteristics in fluidised-beds for top-spray coating processes. Particuology, 10(6), 649–662. https://doi.org/10.1016/j.partic.2012.02.004

Modelling the bed characteristics in fluidised-beds for top-spray coating processes

Mike Vanderroost ^a, Frederik Ronsse ^a, Koen Dewettinck ^b, Jan G. Pieters ^a *

a Department of Biosystems Engineering, Ghent University, Coupure links 653, 9000 Ghent, Belgium
b Laboratory of Food Technology and Engineering, Ghent University, Coupure links 653, 9000 Ghent, Belgium

10.1016/j.partic.2012.02.004

Volume 10, Issue 6, December 2012, Pages 649-662

Received 4 November 2011, Revised 4 January 2012, Accepted 20 February 2012, Available online 24 April 2012.

E-mail: Jan.Pieters@UGent.be

Highlights

► A particle sub-model, describing the bed characteristics in terms of bed heights and particle distribution, is presented.

► Grey-box model is based on theoretical and empirical data from the literature and complemented with abstractions.

► Additional assumptions because information and data in the literature are sparse or non-existent.

► The model was capable of predicting the bed characteristics with good accuracy in less than 5 min calculation on a regular desktop PC.

Abstract

A particle sub-model describing the bed characteristics of a bubbling fluidised bed is presented. Atomisation air, applied at high pressures via a nozzle positioned above the bed for spray formation, is incorporated in the model since its presence has a profound influence on the bed characteristics, though the spray itself is not yet considered. A particle sub-model is developed using well-known empirical relations for particle drag force, bubble growth and velocity and particle distribution above the fluidised-bed surface. Simple but effective assumptions and abstractions were made concerning bubble distribution, particle ejection at the bed surface and the behaviour of atomisation air flow upon impacting the surface of a bubbling fluidised bed. The model was shown to be capable of predicting the fluidised bed characteristics in terms of bed heights, voidage distributions and solids volume fractions with good accuracy in less than 5 min of calculation time on a regular desktop PC. It is therefore suitable for incorporation into general process control models aimed at dynamic control for process efficiency and product quality in top-spray fluidised bed coating processes.

Graphical abstract

Keywords

Fluidised bed; Modelling; Voidage distribution; Fluidised bed characteristics; Multiphase flow; Coating process

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