Absorption of water vapour into lithium bromide-based solutions with additives using a simple stagnant pool absorber

Abstract

Absorption of water vapour into the 50 mass % lithium bromide solution with four eight-carbon alcohol additives such as n-octanol, 2-octanol, 3-octanol, and 2-ehtyl-1-hexanol were investigated by using a simple stagnant pool absorber. Four solutions of the 60 mass % lithium bromide + water, 68 mass % lithium bromide + ethylene glycol + water (LiBr/HO(CH 2) 2OH = 4.5 by mass), 60 mass % lithium bromide + lithium iodide + water (LiBr/Lil = 4 by mole), and 70 mass % lithium bromide + zinc chloride + water (LiBr/ZnCl 2 = 1 by mass) containing the 2-ethyl-1-hexanol additive were also considered to examine the additive effect on mass transfer of water vapour into the different types of absorbents. The experimental apparatus could be used with good confidence and accuracy particularly for studying mass transfer enhancement over the effective range of additive concentration which, in this work, is mostly between 10 and 500 ppm. A vigorous interfacial turbulence was observed during absorption process using additives. The water vapour absorption rate remarkably increased with increasing the additive concentrations up to about 200 ppm and then stopped increasing above 200 ppm for all the systems considered. The onset additive concentrations for enhancing mass transfer were located between 5 and 8 ppm for all systems except two systems of the 50 mass % lithium bromide solution with 3-octanol and 70 mass % lithium bromide + zinc chloride solution with 2-ethtyl-1-hexanol for which the corresponding concentrations were 2.5 and 35 ppm, respectively.