Investigating the dynamics of segregation of high jetsam binary batch fluidised bed systems

Batch fluidised bed systems of jetsam concentrations (x) over bar = 0.5 and 0.75 were fluidised over a range of velocities, causing segregation into a jetsam-rich defluidised layer and a flotsam-rich fluidised layer. The dynamics of segregation from an initial fully mixed condition were examined by measuring both the concentration within the fluidised layer and the position of the interface between the two layers over time. It was found that the dynamics of both these characteristics could be approximated by a first order equation approaching an equilibrium with a rate constant. Within the aspect ratio range 0.8-1.2, results showed that provided segregation occurred, the type of distributor plate and the aspect ratio of the bed did not affect the equilibrium concentration within the fluidised layer, although segregation with a perforated plate proceeded at a slower rate than with a porous plate. The relationship between the fluidising velocity and the rate constant was not clear. The interface dynamics were greatly affected by the presence of flotsam trapped within the defluidised layer at low fluidising velocities. Where this was not the case, both the equilibrium position of the interface and the rate constant omega(h) showed an inverse linear dependence on the excess gas velocity. (C) 2003 Elsevier B.V. All rights reserved.