Numerical simulation of homogeneous fluidization behaviour of Geldart Group A particles in gas tapered fluidized beds

Abstract

AbstractA two‐dimensional gas–solid tapered fluidized bed at laboratory‐scale in a homogenous fluidization regime is simulated using the computational fluid dynamics (CFD) software COMSOL 5.4. The Eulerian–Eulerian (EE) hydrodynamic model is used to predict the minimum fluidization velocity, minimum bubbling velocity, bed height, and solid volume fraction of alumina particles (in Geldart Group A) in the bed with different tapered angles. The effects of static bed heights on the minimum fluidization velocity of tapered beds are investigated. The highest minimum fluidization velocity is 6 mm/s with a static height of 11 mm and a tapered angle of 12°. The bed height is increased with increasing superficial air velocity. At a given air velocity, the minimum bed height is obtained at a 12° tapered angle. A decrease in solid volume fraction is also observed upon an increase in the superficial air velocity. The CFD results show an almost uniform solid concentration over the bed height. The homogenous or non‐bubbling regime appears in a wider range of critical velocity at a 12° tapered angle. In the case of a 0° tapered angle, the results of this study and the discrete element method computational fluid dynamics (DEM‐CFD) simulation exhibit a good match. In the case of 6° and 12° tapered angles, the proposed model leads to good predictions based on the theory of homogenous fluidization of Geldart Group A. This research introduces a rapid and cost‐effective approach for the better design and operation of a tapered fluidized bed in large scales.