Effect of Dehydration Conditions on Secondary Reaction Suppression in Calcium Chloride Ammonia Absorbers

Calcium chloride is a promising ammonia absorber for mild-condition separation processes; however, its strong hygroscopicity requires careful dehydration to avoid secondary reactions. In this study, we investigate the effect of dehydration pretreatment on the stability of ammonia absorption in calcium chloride. Dehydration at 220 °C for 1 h resulted in the generation of CaClOH and NH4Cl during subsequent NH3 absorption/desorption cycles, indicating incomplete removal of hydrates. In contrast, extended dehydration at 220 °C for 5 h effectively suppressed these by-products and enabled stable ammonia cycling. These results demonstrate that dehydration duration (e.g., 5 h at 220 °C), rather than temperature alone, critically determines the operational stability of calcium chloride ammonia absorbers.