Effect of system composition on mixing in binary fluidised beds

Abstract

The influence of bed composition – that is, the relative proportions of different components – on the mixing of fluidised beds containing mixtures of Geldart group B and D particles is of considerable importance to a variety of contemporary industrial processes, such as plastic recycling and biomass gasification. In this study, we use Positron Emission Particle Tracking (PEPT) to analyse the detailed, three-dimensional flow dynamics of such a system and, from these measurements, determine the rate of mixing as a function of bed composition. Our results show that for comparatively small fractions (ϕD≲30%) of Group D particles, the system’s mixing dynamics are only weakly affected by variations in ϕD. For higher concentrations, however, the mixing effectiveness of the system is observed to decrease sharply, and marked changes in the system’s flow patterns are observed, with a previously undocumented meta-stable state recorded for the highest concentrations of group D particles.