Hydrodynamics and mass transfer in different zones of a three-phase fluidized bed

Three-phase, gas-liquid-solid (G-L-S) fluidized beds are extensively used in various chemical and biochemical applications and therefore a proper characterization of the hydrodynamics and mass transfer is an important aspect of the reactor design and scale-up. Depending upon the flow regime, one of the key factors influencing the hydrodynamics is the distributor which causes flow non-uniformities making the modeling process extremely difficult.;A study was performed to understand the liquid flow hydrodynamics and solid-liquid mass transfer in the distributor region and the main bed region of a three-phase fluidized bed. Experiments were carried out in both a liquid-solid (L-S) fluidized bed and a G-L-S fluidized bed to understand and compare the influence of the gas phase. Residence Time Distribution (RTD) experiments were carried out to evaluate the dispersion coefficient values as well as the applicability of the Continuous Stirred Tank Reactor (CSTR)-Dispersion model proposed by Asif et al. (1992) to a three-phase fluidized bed (TPFB).;Fluctuations in wall pressure were used to identify the flow regime in a TPFB. Pressure fluctuations in different zones of the bed were measured to study the influence, and to understand the influence of the distributor on different zones for light and heavy particles.;Various experimental techniques for solid-liquid mass transfer in three-phase fluidized beds have been reviewed and their limitations have been discussed here. The dissolution of tethered particles coated with benzoic acid was used to study the mass transfer in different zones. While mass transfer measurements were repeatable in the main bed region, wide variations in the mass transfer coefficients were observed for experiments in the distributor region. Because of this wide variation no difference in the mass transfer rates between the main bed and the distributor region could be observed.