Absorption and Desorption Behaviors of Ammonia on Calcium Chloride Based Ammonia Absorbents

A new ammonia separation method for the Haber–Bosch process, which is absorption separation, requires ammonia absorbents that are applicable at high temperatures. This study investigated the ammonia absorption/desorption behaviors of CaCl2-based absorbents (CaCl2-LiCl, CaCl2-LiBr, and CaCl2-NaCl) at 473 K using pressure-swing absorption (0.1–0.5 MPa). CaCl2 containing small amounts of lithium compounds (LiCl or LiBr) exhibited higher ammonia absorption and desorption rates than the CaCl2 single salt. Particularly, the ammonia absorption and desorption rates of CC100LC1 (with a molar ratio of CaCl2 : LiCl = 100 : 1) were 23% and 11% higher than those of the CaCl2 single salt, respectively. The ammonia absorption capacity of CC100LC1 was higher than those of conventional ammonia absorbents such as Na-Y zeolite and comparable to that of the CaCl2 single salt. The CaCl2-LiCl mixture is a promising ammonia absorbent for absorption separation because it can easily absorb/desorb ammonia at high temperatures.