Role of bubbling behaviour in segregation and mixing of binary gas-solids flow of particles with different density

Abstract

Dynamics of segregation and mixing phenomena of binary gas-solids flow in fluidized beds is predominantly influenced by the bubbling behaviour. In the present work, we have investigated experimentally the effect of the local bubbling behaviour on the segregation and mixing phenomena of binary gas-solids flow with particles differing in density (of the same size) in a pseudo–2D rectangular fluidized bed. The bubbling characteristics were controlled using two different modes of air injection: uniform distributor and two-jet distributor under the same superficial gas velocity (UG). The local individual phase area fraction fluctuations of all the three phases were measured using the high-speed imaging. These measurements were further used to quantify the effects of bed composition, mode of air injection, and UG on the bubbling characteristics and eventually on the segregation/mixing behaviour. The present study shows that the use of the two-jet distributor led to an increase in the amplitude of the local gas-phase area fraction fluctuations in comparison to that of the uniform distributor and thus enhanced the mixing of the particles. Also, with an increase in the flotsam component in the mixture, due to increase in the bubble size and frequency, the bubble-induced mixing of the particles was enhanced further. The results reported here provide the understanding of the effect of local bubbling characteristics on the dynamics of segregation and mixing phenomena of binary mixtures with particles differing in density and also provide the much-needed database for validation of CFD-DEM and Eulerian multi-fluid CFD models.