Process intensification : mass transfer and pressure drop for countercurrent rotating packed beds

Abstract

The mass transfer and the pressure drop characteristics for countercurrent rotating packed bed (RPB) with a continuous gas phase for the removal of ethylene dichloride (EDC) from water using air stripping have been investigated. The aim of this research was to understand the behaviour of the mass transfer performance and the pressure drop behaviour in a centrifugal environment. The mass transfer results showed that the height of a transfer unit (HTU) in a liquid film limited system can be in the range between 30 to 70mm at moderate centrifugal acceleration between 44 to 280g. Three packings of different packing densities ranging from 870 to 2300 m2/m3 were tested. The HTU values were found to vary with the centrifugal acceleration as HTU a g-0.11 to -0.28. It has been shown that the packing density may not have a notable effect on the separation performance of the bed. The pressure drop results indicated that in RPB the pressure drop is relatively higher than its equivalent packed beds operate at 1g. The usual flooding restrictions were relaxed thus high hydraulic capacities can be achieved per unit size of equipment. At the flooding point, experimental findings indicated that a part of the liquid is not accelerated by the bed. A model to predict the pressure drop was developed. The model was verified against experimental data and good agreement was obtained.