Bubble dynamics in a binary Gas-Solid fluidization system of Geldart B and Geldart D particles

Abstract

In order to gain a more fundamental understanding of binary particle systems, a two-dimensional (2D) fluidized bed was used to study the bubble dynamics and dense phase composition. Digital image analysis (DIA) was employed to measure bubble diameter, bubble rise velocity, bed expansion, and the distribution of the two types of particles in the bed. Magnetite and sand particles as the single components and binary mixtures were used as the bed materials. The bubble diameter and bubble rise velocity both increased with the distance above the gas distributor and the excess gas velocity. The bubble rise velocity also increased while bubbles ascending in the bed due to an increase in bubble size and buoyancy. Both mono particle systems had higher average bubble sizes than that of the system with nearly identical particle composition, which had the smallest bubble size and the lowest bubble rise velocity. The bubble coalescence and splitting processes were also imaged and the total bubble volume was found to increase after coalescence and decrease after splitting due to some uncaptured smaller bubbles. In addition, a preliminary experiment was carried out to trace dense the phase composition and the overall bed density was estimated based on the dense phase composition and bed expansion.