Water balance challenge in humid flue gas CO2 capture: A 700-h bench-scale demonstration of a water-lean monophasic solvent

Nonaqueous amine-based absorbents offer advantages over aqueous monoethanolamine (MEA), but they inevitably evolve into water-lean systems when treating humid flue gas, presenting a challenge for long-term performance stability. In this work, a formulated water-lean absorbent, 50B-40BE-10 W, was evaluated for CO 2 capture from simulated humid flue gas in an upgraded lab-scale continuous plant over 720 h, benchmarking it against 30 mass% MEA. Key operational parameters and water balance behavior were systematically investigated to inform rational process design. Under a framework of absorbent-tailored regeneration strategy coupled with dynamic water-balance control, the 50B-40BE-10 W solvent achieved a remarkably low desorber heat duty, about 50–65% reduction compared to MEA. Critically, a dynamic water-management strategy was proposed and demonstrated, involving controlled discharge of desorber overhead condensate following a membrane dehydration process. This approach successfully maintained stable water content of ∼10 wt% in the solvent over a 100-h period, effectively addressing the challenge of water accumulation in water-lean systems. Furthermore, NMR analysis of the absorbent after ∼1700 h of operation, even under high‑oxygen exposure, indicated no catastrophic degradation. The compelling performance and stability demonstrated at the bench-scale pave a solid pathway for further development of this advanced water-lean capture technology.