Mass transfer experiments were conducted in a 7.62-cm-ID cocurrent three-phase fluidized bed using an aqueous sodium sulfite/air/glass bead system. Absorbed oxygen reacting with the sulfite ion resulted in an oxygen-free liquid phase, so that mass transfer was independent of liquid axial dispersion. A discontinuous-phase sampling system was developed to enable gas-phase analysis along the bed. These concentration data were used to calculate mass transfer coefficients within the two- and three-phase regions of the column. Bead diameters of 3.2, 4.6, and 6.2 mm were used at superficial gas velocities of 4.3 to 12.9 cm/s and liquid velocities of 1.28 to 11.2 cm/s. The three-phase mass-transfer coefficient (K/sub L/a) was found to decrease with increasing gas velocity at very high and very low gas velocities; a direct proportionality was found for intermediate velocities. K/sub L/a) first decreased, then increased with increasing liquid velocity. Increasing the bead diameter caused an increase in the mass transfer coefficient at low gas velocities and a decrease at higher gas velocities. The existence of three regions (bubble coalescence, bubble disintegration, and slugging) are postulated to account for this behavior. Dispersion coefficients, E/sub L/, were calculated using experimentally determined K/sub L/a's and liquid-phase concentration data from earlier studies. The values obtained are nearly zero, suggesting the liquid phase is also in plug flow. Further mass transfer experiments over a wider range of U/sub L//U/sub MF/ and U/sub G/ are recommended. (ERA citation 04:043619)
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