Distillation in a disc column: the effect of fluid properties

An experimental study was carried out into the effect of fluid properties upon mass transfer coefficients in packed distillation columns. A column consisting of 19 stainless steel discs supported in a vertical row, with each disc at right angles to its neighbour, was used for this purpose. This assembly was contained in a 1 in. diameter glass tube which allowed observation of the liquid running over the discs. Distillation runs were made with the systems ethanol/water, isopropanol/water, ethanol/benzene and benzene/n-heptane. With surface tension negative mixtures, sprays of droplets were emmitted from the liquid as it ran over the junctions between the discs. The phenomenon was filmed using high speed cine photography. In order to eliminate hydrodynamic effects in droplet formation the surface of a stationary sessile drop supported on a horizontal disc under total reflux conditions was also observed. Small droplets were seen to be ejected from the surface of the sessile drop with surface tension negative conditions, and again filmed using high speed cine photography. The additional interfacial area caused by droplet formation in the disc column was shown to be negligible. Experimental rashl ts, in the disc column wi th systems in which the vapour phase controls the mass transfer rate were used to establish correlations for the vapour side mass transfer coefficient (...continues).