Insights into the Dielectric-Heating-Enhanced Regeneration of CO₂-Rich Aqueous Amine Solutions

Microwaves (MW) and radio frequency (RF) dielectric heating were used to facilitate the regeneration of CO2-rich amine solutions, and the mechanism of the rate enhancement by dielectric heating was discussed. Dielectric measurements of aqueous solutions of monoethanolamine (primary amine), 2-(ethylamino)ethanol (secondary amine), and N-methyl diethanolamine (tertiary amine) revealed that the formation of carbamate and bicarbonate ions by CO2 absorption improves the dielectric loss tangent. Dielectric heating by MWs (2.45 GHz, 915 MHz) and RF (200 MHz) was compared to facilitate regeneration of the CO2-rich amine solution at a constant power of 40 W. The CO2 release rate was the highest at 2.45 GHz in all aqueous amine solutions, which was 1.47 to 1.74 times that of conventional heating by an oil bath operated at 120 °C. However, the CO2 release rate decreased as the frequency decreased to 915 and 200 MHz. Electromagnetic field simulation suggested that CO2 release was enhanced owing to the generation of a more intense electric field at 2.45 GHz than at lower frequencies.