Characterization and control of slugging behavior of Geldart's group-D particles in a laboratory scale fluidized bed

Fluidization behavior of Geldart's group D particles was investigated for characterization of slugging and for developing control strategies using the recent developments in the field of nonlinear dynamics and chaos. Results demonstrate that chaotic time series analysis of pressure drop measurements can be used for characterization of slugging behavior. Dynamic features associated with different regimes have been identified. The transition from regular slugging to chaotic behavior at increased gas flow rates was identified as intermittency route to chaos. A feedback control method based on nonlinear sensitivity of chaotic systems to small perturbations was developed and implemented. Control perturbations are made by injecting small pulses of fluidization gas through a nozzle located on the bed wall just above the distributor. A control routine determines the dynamical state of the bed from the pressure signal and introduces the pressure pulse based on an empirically learned rule base. The pressure drop is measured much faster than the slugging frequency, while control perturbations are made at time scales on the order of the bed frequency. The time-averaged gas flow through the injector is typically less than four percent of the total gas flow through the bed. Results demonstrate that selective application of small perturbations to a slugging bed of Geldart's group D particles can greatly change the overall dynamics, permitting stabilization or destabilization of the slugging. Based on the experimental results we conclude that it may be possible to employ similar feedback control strategies in commercial fluidized beds of Group D particles to enhance or reduce slugging.