Comparative study of the regeneration characteristics of LiCl and a new mixed liquid desiccant solution

Abstract

This study first fabricated a new mixed liquid desiccant solution via the addition of hydroxyethyl urea to lithium chloride solution to reduce its causticity in a metal-based regenerator. The formula of the new solution—25% LiCl, 39% hydroxyethyl urea, and 36% water—was determined according to the vapor pressure measured with the static method. Accordingly, its basic thermal properties (e.g., density, viscosity, and conductivity) were measured and compared with those of a 35% LiCl solution. The corrosion characteristics of the mixed solution and the LiCl solution were analyzed with an electrochemical testing method. The regeneration performances of the solutions were experimentally studied, and the results show that the new solution significantly reduced causticity due to the addition of hydroxyethyl urea and a reduction in LiCl concentration. The regeneration effectiveness showed an average relative increase of 14.1% because of the larger wetting ratio and greater fluctuation of falling film. The wetting ratio increased from 81.5% to 87.8%, and the standard deviation of the film thickness increased from 25.441 μm to 31.672 μm with more rigorous fluctuations. Finally, an empirical equation for regeneration effectiveness was developed with an average absolute relative deviation of 4.01%, which provides a useful guide for the design of regenerators.