Effect of system composition on mixing in binary fluidised beds

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 (/DK30%)
of Group D particles, the system’s mixing dynamics are only weakly affected by variations in /D . 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.