Energy-efficient solvent regeneration in enzymatic reactive absorption for carbon dioxide capture

Although recent studies on the application of enzyme-catalyzed reactive absorption of carbon dioxide (CO2) with thermodynamically favorable solvents such as tertiary amine N-methyldiethanolamine (MDEA) have demonstrated competitiveness with kinetically favorable solvents such as primary amine monoethanolamine (MEA), experimental data on the desorption of CO2 in MDEA are scarce. However, these data are necessary to validate the energetic benefit expected from an enzyme-catalyzed reactive absorption process with an aqueous MDEA solvent. To bridge this gap, the current work presents the experimental results of aqueous MDEA solvent regeneration at the pilot scale with consideration of different solvent flow rates, CO2 loadings and applied reboiler duties. Furthermore, a process model that accurately describes the experimental data was developed to evaluate the energy requirements in a closed-loop absorption-desorption process. For this purpose, the desorption process model was extended using a previously validated enzymatic reactive absorption model to determine the energy efficiency of the overall enzymatic reactive absorption-desorption process. Although the MEA benchmark process requires a specific reboiler duty of approximately 3.8MJ·kgCO2-1, it was found that this value could be reduced by more than 40% to 2.13MJ·kgCO2-1 with use of the enzymatic reactive absorption process based on aqueous MDEA solvent.