Screening and Performance Evaluation of Triethylenetetramine Nonaqueous Solutions for CO2 Capture with Microwave Regeneration

While CO2 capture with nonaqueous solutions is a promising approach, regeneration of the solutions often requires high energy consumption. This energy consumption can be potentially reduced by microwave regeneration, the performance of which is strongly affected by the selection of solvent. Therefore, we investigated the characteristics of microwave regeneration for nine triethylenetetramine (TETA) solutions. The results show that the heating rate of a solution in the microwave was primarily affected by its viscosity, dielectric constant, and heat capacity. The desorption energy consumption of CO2-loaded solutions had a strong linear correlation with the dielectric constant of the solvents over a certain solvent viscosity range (1.4–88.8 mPa·s, 20 °C). A comparison of microwave heating and conductive heating shows that the former performs better when considering regeneration temperature, CO2 recovery, and energy requirement. Under the condition of 800 W, the energy consumption using microwave regeneration for 30 wt % TETA/BDO and TETA/PEG200 solutions decreased by 69% and 76%, while CO2 recovery increased by 2.6 and 2.7 times, respectively, compared to a 30 wt % monoethanolamine aqueous solution regenerated by conductive heating. Therefore, TETA with microwave regeneration represents a promising approach for CO2 capture and recovery.