Mass transfer coefficients in a packed tower: Height, end and solute concentration effects

Abstract

An intermediate sampling technique has been used to investigate the mass transfer of ammonia into water in a packed tower. The technique was of sufficient accuracy to be able to investigate not only the general mass transfer over the tower but also the solute, end and height effects. The general mass transfer correlation which was obtained was useful for prediction purposes only when it was handling an identical situation of system and geometry. No solute effect was found as such but a reduction in mass transfer was noted which was caused by a change in surface tension, altering the effective interfacial area for mass transfer. A definite end effect was noted which was caused by gas absorption proceeding in the region outside the tower under the baseplate. The height effect was caused by the changing liquid distribution in the top 0 - (10 – 12)Z/d region of the tower. As the liquid distribution worsened from the top of the tower downwards, the mass transfer rate fell because of the changing interfacial area until it came to a constant value at about Zld = 10 – 12 where the liquid distribution became constant. The predominant variable which effects the mass transfer as far as these characteristics of the packed tower are concerned is the liquid rate distribution through its influence on the interfacial area of the packing.