Carbon dioxide removal by alkanolamines in aqueous organic solvents: A method for enhancing the desorption process

Process concepts of using alkanolamines in aqueous organic solvents have been evaluated by experimental work and process simulations using the Procede Process Simulator. N-methyldiethanolamine (MDEA), methanol, and ethanol were chosen as the respective alkanolamine and organic compounds in the current work. In previous work, the dissociation constants of protonated MDEA at infinite dilution in methanol-water and ethanol-water solvents and the initial mass transfer rates of CO₂ in 3 kmol m^-3 MDEA in methanol-water and ethanol-water solvents were determined. In the current work, experimental values of the CO₂ vapor liquid equilibria in 3 kmol m^-3 MDEA have been determined in methanol-water and ethanol-water solvents. The experimentally determined results have been implemented into the Procede Process Simulator, which has been used to simulate a CO₂ removal plant with 90% CO₂ removal based on the specification of the flue gas of an 827 MWe pulverized coal fired power plant. A solvent of 3 kmol m^-3 MDEA in aqueous methanol solution was considered for conceptual purposes. The results indicatively show a maximum decrease in the reboiler duty of the desorber of about 7.5% at methanol fractions of about 0.06 compared to purely aqueous solutions and a reboiler temperature decrease with increasing methanol fractions. Further experimental results are, however, necessary in order to more precisely simulate CO₂ removal processes by alkanolamines in aqueous organic solvents.