Homogeneous and Heterogeneous Distillation of Ethanol-Benzene Water System by Packed Column with Structured Packing

摘要

An experimental study is made on mass transfer in a packed distillation column with the structured packing covering homogeneous and heterogeneous liquid regions for an ethanol-benzene-water system under total reflux conditions. The vapor phase diffusion fluxes obtained in the homogeneous liquid region agree well with the correlation derived from an acetone-ethanol system by Olano et al. (1995). On the other hand, the observed diffusion fluxes in the heterogeneous liquid region exhibit wide scattering, which may be due to the neglect of the liquid phase resistance and the assumption of three-phase equilibrium at the vapor-liquid interface in this experimental analysis. In order to examine the effect of liquid phase resistance on the separation performance in the packed distillation column, its simulation is also carried out by considering or neglecting the liquid phase resistance. The liquid phase resistance has much influence on the vapor phase concentration driving force, and then the diffusion and convective mass flux in the heterogeneous liquid region. The top concentrations and reflux flow rates predicted by considering the liquid phase resistance agree reasonably well with the experimental data in the heterogeneous liquid region. On the contrary, the effect of the liquid phase resistance on the separation performance in the homogeneous liquid region is very small as generally accepted.