Stabilization and destabilization of slugging behavior in a laboratory fluidized bed

In this paper, we present a method for feedback control of slugging in fluidized beds. Several recent studies have concluded that some modes of fluidization can be classified as low-dimensional and chaotic, implying a sensitivity to small perturbations that may be useful for control. We demonstrate here that selective application of small perturbations to a slugging bed of Geldart group D particles can greatly change the overall dynamics, permitting stabilization or destabilization of the slugging. We make control perturbations by injecting small pulses of fluidization gas through a nozzle located on the bed wall just above the distributor. Pulse timing and duration are adjusted based on feedback from the bed as indicated by pressure drop. The pressure drop is measured much faster than the slugging frequency, while control perturbations are made at time scales on the order of the dominant bed frequency. The time-averaged gas flow through the injector is typically less than four percent of the total gas flow through the bed. From our 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.