Dispersion Characteristics and Mass Transfer in a Pilot‐Scale Gas‐Liquid Oscillatory‐Plate Column

Abstract

Mass transfer and hydrodynamic characteristics of an oscillatory-plate column (OPC) and their relation to energy dissipation were investigated using a 0.1-m diameter pilot-scale unit. The column is characterized by having plates with a small hole diameter (1.6-3.2 mm) oscillating at 180°out of phase at higher frequencies (0-30 Hz) and small amplitudes (0-3.2 mm). Using this design, it was possible to achieve gas holdup and specific interfacial areas as high as ∼0.8 and 400 m -1 , respectively. The maximum gas superficial velocity achieved reaches as high as 1.7 m/s, while the axial dispersion coefficient ranged from ∼10 -4 to over ∼3 × 10 -3 m 2 s -1 , which is almost one order of magnitude lower than that in bubble columns under similar flow rates. The value of gas velocity of ∼0.1 m s -1 seems to mark a transition beyond which interfacial area, holdup, and axial mixing become practically unchanged. Keeping in view its performance characteristics, the column can satisfactorily meet many of the demands posed by intensified wastewater treatment processes, namely high rates of oxygen transfer, multistage operational mode, uniform distribution of small-scale turbulence structure, and the ability to handle sludge with relatively high concentrations of suspended solids.

CO2 Dissolution and Design Aspects of a Multiorifice Oscillatory Baffled Column

“…At such values of U G the mass transfer enhancement is usually challenging because of the very limiting interfacial area in a gas−liquid or multiphase system. Consequently, the K L a values obtained were somewhat smaller than the maximum K L a values reported by some authors for CO 2 and other gases 6,19,33 at much higher U G values. Compared to the very few studies carried out at a similar range of U G mean gas velocities used in this study (U G = 0.12−0.81 mm s −1 ) significant improvements could be observed in respect to K L a values.…”

“…Al-Abduly et al 34 and Hewgill et al 13 obtained a relationship very close to the linearity. Gomaa et al 33 …”

“…Al-Abduly et al 34 and Hewgill et al 13 obtained a relationship very close to the linearity. Gomaa et al 33 compiled a set of eight correlations commonly used for K L a estimation of the type K L a α U G b , where b has a value in the range of 0.14−1.55. For one of those correlations b is close to unity, as it happens with the MOBC.…”