Enhancing CO2 desorption in MEA solvent using low-frequency ultrasound: A flow-through reactor study

Abstract

This study explores the efficacy of ultrasound (US)-assisted CO₂ desorption in a 30 wt. % monoethanolamine (MEA) solvent using a flow-through reactor. The tests demonstrated that the application of low-frequency (20 kHz) ultrasound accelerates the desorption process and reduces the desorption time required to release the same amount of CO₂ for a given solvent compared to desorption by only heating the sample. This acceleration is attributed to the direct energy input into the solvent as well as the enhancement of heat and mass transfer caused by acoustic streaming and acoustic cavitation. The use of flow-through reactor systems suggests that the results can be scaled up to larger-scale processing. Notable improvements were observed at higher desorption temperatures, with sonication at 80 °C and above reducing CO₂ loading in MEA below its thermodynamic equilibrium by 16 %. This allows CO₂ release at 100 °C, compared to 120 °C with heating alone. The two-peak CO₂ release pattern under sonication — initially from thermolysis and later from enhanced mass transfer — highlights the benefits of acoustic effects such as microstreams, vortices, and rectified diffusion. This method may also mitigate solvent degradation at high temperatures. Compared to conventional heating, applying sonication in a 30 wt. % MEA solvent consumes much less energy (172.65 kJ/mol CO₂ compared to 343.85 kJ/mol CO₂) to release the same amount of CO₂ at similar desorption temperatures. This demonstrates that the application of low-frequency ultrasound can significantly decrease energy consumption during CO₂ desorption. This method may result in decreased operational costs, provided affordable power is accessible for carbon capture facilities, especially via US-assisted desorption.