Separation and residence times of larger particles in a spout-fluid bed

Optimum conditions for the separation of added large particles from a spout-fluid bed of Geldart Type B powder have been determined. A shallow bed, 100 mm in diameter, with porous conical distributor was used. Mean and distributions of residence time of the large particles depend on the two gas flow rates, especially that to the distributor, and on spout inlet diameter and large particle size. Bed regimes studied were mainly spouting with aeration and spout-fluidization. In the latter regime an optimum range of fluidizing gas flow rates that minimised mean and spread of residence times was identified. RTD data were correlated by a model incorporating a minimum time supplemented by a distributor for an ideally mixed system.