DISTILLATION PERFORMANCE OF WETTED-WALL COLUMN WITH IMPROVED WETTING CHARACTER-ISTICS IN THE RANGE OF LOW REFLUX RATE UNDER REDUCED PRESSURE

Abstract

To achieve an effective distillation in a wetted-wall column in the range of low liquid reflux flow rate, a swathed glass tube, a ground glass tube and a stainless steel mesh tube were used as the wall surface with improved wetting characteristics. Their efficiency results have shown a serious dependency of wettability and an effect of heat transfer from surroundings to system and between phases. The swathed glass tube has the widest range for effective operation of the three in a surface tension positive system, and also shows an extremely good performance in a negative system in comparison with smooth glass tube. And the other two, which have the same efficiency as that for the swathed tube in a positive system above the minimum wetting rate, are more wettable and effective than the smooth glass in a negative system.
Analytical treatments have been also made by use of a model to consider the effect of vaporization due to heat transfer. The result obtained points out a significant effect of evaporation in the low vapor flow range and accounts for the deviation of the experimental data from theoretical solution in such a range to some extent.