Experiments on Vacuum Distillation in a Wetted-Wall Column

Abstract

Experiments on vacuum distillation were made in a 2. 2 cm i. d. wetted-wall column 143 cm in length in a range of pressure from 0.05 to 2 mmHg by using three binary systems : ethyl oxalate (E. O.) -methyl salicylate (M. S.), methyl palmitate (M. P.) -di-n-butyl phthalate (D. B. P.) and D. B. P.-di-n-butyl sebacate (D. B. S.). The results obtained show the following facts. 1) The pressure drop data agree with the analytical equation in which a compressibility effect is considered. 2) For E. O.-M. S. and M. P.-D. B. P. systems (Surface tension positive), when reflux rate per wetted perimeter is over 0.0030.007 g/cm·sec the performance of the column is nearly equal to that predicted by the theoretical mass transfer rate in the vapor phase, but when the reflux rate is below that, lower efficiency results. 3) For D. B. P.-D. B. S. system (Surface tension negative), the performance comes down to 1/31/6 of that for the positive systems.