CO2 absorption in NaOH-Na2CO3 solutions: Combined CFD and thermodynamics-based, experimentally validated analysis

• A novel computational approach is presented for CO 2 absorption in NaOH-Na 2 CO 3. • The developed approach combines thermodynamic and CFD modelling. • A good agreement between predictions and experimental measurements is obtained. • The models reveal key mechanisms and phenomena that dictate process dynamics. • The interplay between transport and chemical reactions is studied in detail. Carbonation processes find numerous applications; however, the complex nature of their underlying mechanisms has hindered their detailed understanding. The fluid dynamics occurring within stirred tanks, the multiphase CO 2 bubble flow, as well as the interphase mass transfer and chemical reactions, are all simultaneously affecting the carbonation process. Furthermore, the interplay between all those mechanisms and phenomena deems the in-depth mechanistic understanding of the process dynamics via experimental studies a rather challenging task. In this work, a novel combined computational approach, consisting of a thermodynamic and a three-dimensional CFD model, is developed for the CO 2 absorption in NaOH-Na 2 CO 3 liquid solutions. Information on the equilibrium conditions is provided by the thermodynamic to the CFD model, which calculates the dynamics of CO 2 absorption in the solution. These results are fed back to the thermodynamic model, enabling the simulation of the chemical reactions, in conditions closer to the actual experiments. The results are validated using experimental measurements for the CO 2 flow and the pH within the solution, achieving good agreement. This approach enables the integration of insights from both methodologies, revealing the relationship between the different phenomena and mechanisms that constitute the carbonation process, which might be challenging to define solely experimental results. Specifically, it elucidates the process dynamics which unravels key mechanisms during the carbonation process. The combined computational approach can assist the knowledge-based process and reactor design, while it can also pave the way for the optimized scale-up of carbonation-precipitation processes.