The Effect of Viscosity on Mass Transfer in a Rotating Packed Bed
Date Issued
2004
Date
2004
Author(s)
Chen, Yu-Shao
DOI
zh-TW
Abstract
The application of a rotating packed bed (i.e. Higee) has become one of the most significant developments in the field of process intensification. It is achieved by contacting liquids and vapors in a centrifugal field to intensify mass transfer. Though the characteristics of a rotating packed bed have been widely studied in literatures, the influence of liquid viscosity on mass transfer was not systematically investigated.
In this study, experiments of deoxygenation were performed with viscous Newtonian fluids (glycerol solutions) and non-Newtonian fluids (CMC solutions). Results showed that mass transfer could be enhanced by centrifugal force, and reduced by increasing liquid viscosity. Less influence of liquid viscosity on mass transfer was obtained in a rotating packed bed than in a packed column, indicating that a more significant enhancement on mass transfer could be achieved in a rotating packed bed as liquid viscosity increases. On the other hand, a theoretical analysis based on laminar liquid film flow on a rotating disk with the assumption of the randomly inclined surfaces in a rotating packed bed was developed to predict the film thickness, apparent viscosity and mass transfer coefficient. Besides, the end effects in a rotating packed bed was investigated with various radii of the packed bed. Based on the calculated values of apparent viscosity, a correlation taking end effects into consideration was obtained to predict the liquid-side mass transfer coefficient. Agreement between the predicted values and the experimental values of the liquid- side mass transfer coefficient in this study as well as in literatures was quite good.
Further, the characteristics of gas-side mass transfer coefficients and gas-flow behavior were investigated based on the experiments of absorbing VOCs into water and glycerol solutions. It is found that the gas-flow behavior was similar to that in a packed column, and a correlation for a packed column was applicable to predict the gas-side mass transfer coefficient in a rotating packed bed. In addition, the characteristics of a liquid-liquid micromixing system and liquid-solid adsorption system were investigated. Results showed that, in a rotating packed bed, micromixing efficiency could be enhanced by centrifugal force, and was higher than other mixing devices. The mass transfer resistance may be reduced with increasing micromixing efficiency. Besides, in a liquid-solid adsorption system, the adsorption rate increased with increasing rotational speed. Compared with a packed column, higher rate and amount of oil adsorbed were obtained in a rotating packed bed.
Subjects
旋轉填充床
超重力場
微觀混合
質傳
黏度
higee viscosity
mass transfer
rotating packed bed
Type
thesis
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