TRACER EXPERIMENTS IN FIXED-BEDS - EFFECTS OF FLOW MALDISTRIBUTION ONTHE ESTIMATION OF TRANSPORT KINETIC-PARAMETERS

A systematic study of liquid phase axial dispersion was conducted in g lass columns (inner diameters, 1 cm and 1.6 cm), packed randomly with granular sand, by varying the fluid flow rate, particle size and bed h eight. Pulse and step response techniques, with KCl as an inert tracer , were used. The resultant data, covering the Reynolds number range fr om 1 to 50, are presented as plots of the Peclet number based on parti cle diameter against Reynolds number. Inert tracer experiments were al so carried out in a column (inner diameter, 1.6 cm) packed with activa ted carbon granules, using different particle sizes, fluid flow rates and bed heights, in order to estimate the effective intraparticle diff usivity. We show that flow maldistribution produces pulse response cur ves with sharp, narrow peaks which, when compared with theoretical cur ves, result in small intraparticle diffusivities. We illustrate how th e outer-phase transfer function can be obtained from the overall trans fer function of the activated carbon bed and we compare it with the tr ansfer function obtained directly using impermeable particles similar to the activated carbon granules.