CO2 absorption in aqueous NH3 solutions: Novel dynamic modeling of experimental outcomes

It is well known that CO2 capture and re-use is one of the main challenges to be pursued in order to tackle global warming issues. Aqueous ammonia solutions are among the most promising sorbents for post-combustion CO2 capture and could represent a valid and potentially economical alternative to the use of conventional alkanolamines, due to their higher absorption capacity, lower energy requirements for sorbent regeneration and greater resistance to oxidative and thermal degradation. Despite its apparent simplicity and convenience, the dynamic evolution of CO2 − NH3 system needs to be further investigated through proper mathematical models that permit to design, optimize, and control the capture process. In this work, the chemical absorption of carbon dioxide contained in a simulated flue gas (N2+CO2; CO2 15%v/v) by means of aqueous NH3 solutions was investigated both experimentally and theoretically. In particular, a rigorous mathematical model, capable to quantify the CO2 capture efficiency dynamics and the sorbent chemical composition during the process, is proposed for the first time. The model is validated by comparing modeling results with experimental data obtained under different operating conditions. The effect of both operating temperature and sorbent concentration are investigated. The good agreement between model results and experimental data confirms the effectiveness and the reliability of the developed tool that turns out to be able to quantify the dynamics of capture efficiency during the variation of the operating conditions. Therefore, it may be exploited to properly design, optimize and control the capture process and the absorbent regeneration section whose energy requirements also depend on the species concentration into the absorbent solution.