Analysis of operating conditions for CO₂ capturing process using deep eutectic solvents

Selected types of deep eutectic solvents (DESs) were compared for designing CO₂ capturing process. Specifically, the typical absorption-desorption process is examined. A mathematical model based on Peng-Robinson equation of state was developed to estimate the CO₂ solubility and to determine the VLE conditions in the desorption unit. The comparison of the DES performance is based on the solvent requirement in the absorption unit and the temperature condition in the desorption unit. Ethanol amine based DES has shown the best performance when operating the absorber at 10 bar and the stripper at 1 bar. However, the simulation results indicate that in order to reduce the energy requirements in the regeneration process a large amount of solvent is needed. In fact, for 80% CO₂ recovery the solvent intake rate should be at least 5 times the flue gas flow rate. Finally, we have shown that (i) the desorption energy required with MEA based DESs is much lower compared to the classical MEA process and that (ii) the energy required for compression remains the most important drawback for a such process, especially at low CO₂ concentrations.