Dehumidification of Air by Aqueous Lithium Chloride in a Packed Column

A packed bed absorber-stripper system has been designed to dehumidify moist air by contact with aqueous solutions of lithium chloride. The packing material used in the study is 1.6 cm (5/8 inch) polypropylene Flexi rings, which have a surface to volume ratio of 342 m 2 /m 3 (104 ft 2 /ft 3 ). The absorber is capable of handling air face velocities from 3362.4 to 6746.4 kg/m 2 h and liquid flow rates from 2534.1 to 54648 kg/m 2 h. Solutions of 30% and 40% lithium chloride in water were employed as the dehumidifying agent. The minimum liquid flow rate calculated from the equilibrium data would be too low to wet the packing surface completely, and could not be used in the actual operating system. Therefore, liquid flow rates greater than the minimum wetting rate for the packing were used. Measured flooding conditions corresponded closely with exiting empirical correlations. Mass transfer coefficients ranged from 0.062 kmol/m 3 s at 40% flooding to 0.166 kmol/m 3 s at 80% flooding for the 40% lithium chloride solution. The height of a transfer unit calculated from the experimental data ranged from 0.340 m at a column efficiency of 71.6% to 0.617 m at a column efficiency of 50%.