Experimental study of divalent metal ion effects on ammonia escape and carbon dioxide desorption in regeneration process of ammonia decarbonization

Ammonia is a promising CO2 capture solvent, but the volatile characteristics limit its large-scale application. In this study, the CO2 desorption features from ammonia rich solution are analyzed theoretically and experimentally, with the metal ions as additives to reduce ammonia emission. The influences of suction temperature, ion adding and CO2 loading rate on the CO2 desorption and ammonia escape are investigated. The results show that the rates of CO2 desorption and ammonia escape increase greatly as the rising of the temperature to a certain extent. The addition of divalent metal ions (Ni, Cu and Zn) can promote the CO2 desorption process and inhibit the ammonia escape during the regeneration, with the ammonia emission reduced by 26.2%, 9.7% and 9.6%, respectively. Ni(II) presents the excellent inhibitory effect on ammonia escape and the strong effect on carbon dioxide desorption enhancement owing to the greater complexation between metal ions and free ammonia than Cu(II) and Zn (II). The additives of divalent metal ions are recommended during the regeneration process of ammonia decarbonization to enhance the CO2 desorption and inhibit the ammonia escape at the cost of less energy consumption.