Determination of ammonium salt/ion speciation in the CO2 absorption process using ammonia solution: Modeling and experimental approaches

Abstract

Abstract Ammonia solution has received special attention as an effective absorbent in CO 2 capture process because of its higher CO 2 absorption capacity and lower chemical cost rather than amine solution such as monoethanolamine. In ammonia based CO 2 capture process, various ammonium salts/ions would be formed reacting with ammonia and CO 2 . The ammonium speciation in the liquid phase greatly affected the overall process efficiency, the energy requirement of ammonia regeneration or CO 2 recovery process. In this study, we examined the ammonium speciation in ammonia solution during the CO 2 absorption reaction using a 13 C-NMR (nuclear magnetic resonance) spectrometry and identified bicarbonate (HCO 3 − ), carbonate (CO 3 2− ) and carbamate (NH 2 COO − ) ions. Moreover VLE (vapor-liquid equilibrium) model which is thermodynamic model in vapor-liquid phase was also applied to simulate ammonium speciation. The simulation results for the ammonium speciation were generally well-agreed with the experimental results, even though some discrepancies were observed as the absorbed amount of CO 2 increased. In conclusion, a combined approach utilizing both ( 13 C-NMR analysis and VLE model) can help to understand the reactions between ammonia and CO 2 and optimize the CO 2 capture process using ammonia solution.