Perspectives and Mitigation Methods for Underappreciated Amine Escape from CO2 Desorption

Amine-based CO2 capture is increasingly limited by amine escape and aerosol emissions that drive solvent loss and secondary pollution. Research has focused on the absorber, leaving the desorption section─where intensive CO2 release, water-vapor entrainment, and rapid cooling coincide─overlooked as an escape source. Here, we combine molecular dynamics simulations with bench-scale experiments to resolve the mechanism and control of amine escape during CO2 desorption. Counter to absorber-side expectations, a CO2-rich atmosphere suppresses rather than promotes aerosol nucleation: elevated CO2 competitively disrupts the H2O-H2O hydrogen-bond network stabilizing water-centered nuclei, with stable clusters essentially absent at 75 vol % CO2. New aerosol formation is thus favored near the low-CO2 reboiler outlet, while cooling in the upper column grows preexisting aerosols. Measurements revealed an 82% decrease in the total amine concentration along the column, consistent with the descending rich solvent acting as an important amine sink, while preexisting aerosols continued to grow in the upper section. Guided by this mechanism, a combined mitigation strategy is proposed: a low-volatility solvent formulation lowered aerosol by 66% relative to MEA, increasing the rich-solvent CO2 loading offered a favorable trade-off, and upstream scrubbing-condensation captured residual species. Together, these measures reduced amine escape by over 99% (to <1.4 ppm) while increasing CO2 product purity. By reframing the desorber as a key emission unit, these results support strategies for reducing desorber-side amine and aerosol emissions.