Low partial pressure CO2 capture in packed tower by EHA+Diglyme water-lean absorbent

The results of beaker experiments (Fu et al., 2021, 2022) showed that water-lean 2-ethylhexan-1-amine (EHA) + diglyme absorbent has more advantages than the commercial water-based ethanolamine (MEA) absorbent in terms of characteristics of carbon dioxide (CO2) absorption and desorption. Verifying CO2 capture characteristics in a tower facility is essential to absorbents development. In this work, a pilot packed tower was set up and the Dg16 type polypropylene step ring was taken as packing to test the capture efficiency and mass transfer performance of EHA + diglyme water-lean absorbent for low partial pressure CO2, and then the effects of gas-liquid ratio, CO2 partial pressure and packing height on the capture performance were clarified. The results showed that the absorption of CO2 by EHA + diglyme water-lean absorbent was dominated by liquid-phase mass transfer in the packed tower. Compared with aqueous 30 wt%MEA, the water-lean EHA + diglyme achieved much higher CO2 capture efficiency and overall volumetric mass transfer coefficient. This work demonstrated the transition from water-free absorption to water-lean absorption under the existence of water vapor in flue gas. It can provide basic data for the design of the CO2 capture process based on water-lean absorption in packed towers.