Fluidised Beds

Abstract

Gas-fluidised beds have been extensively studied in academia and widely used in industry. When examined at the macro-scale, fluidised beds may appear to behave like a solid, a liquid or a gas, depending on the magnitude of the applied superficial gas velocity. One of the attractions of DEM is that it can model all three different phases. To account for the interstitial gas, a combined Lagrangian-Eulerian approach is used by combining the use of DEM for the particle phase with CFD modelling of the gas phase. In this chapter, following an initial outline of the theoretical background to the methodology, results of 2D and 3D simulations of fluidized beds are presented. Using 2D simulations, we examine the different types of behaviour as the gas velocity is increased to cover the complete range from fixed bed to homogeneous expansion, bubbling, turbulent and fast fluidisation. we also examine how the transition from fixed bed to bubbling bed, i.e. the so-called homogeneous expansion regime, is affected when surface energy is attributed to the particles. Then, using 3D simulations, we examine and provide visualisations of bubble formation, bubble rise and bubble splitting.

In this chapter the results of simulations of fluidised beds are presented. This is restricted to the author’s own work that was motivated by the need to re-examine historical issues that had not been completely resolved. For more general applications of fluidised bed simulations the reader is referred to papers published by Prof. Tsuji’s group in Osaka, Prof. Yu’s group at Monash (previously UNSW) and the group of Prof. Kuipers at Eindhoven (previously Twente).