Research on absorption-desorption performance of low-water absorbents for energy-efficient CO₂ capture

The chemical absorption based on aqueous alkanolamine solutions is a leading technology for CO₂ capture. However, its widespread application is still constrained by the high energy penalty associated with solvent regeneration, due to the high latent heat of water evaporation. To mitigate this, we formulated a water-lean absorbent with a mass ratio of amine∶physical solvent∶water of 30∶60∶10. Based on salting-out effect, polyethylene glycol dimethyl ether (NHD) was selected as the favorable physical solvent to formulate water-lean phase change absorbent, aiming to reduce both the sensible heat required for heating and the latent heat of evaporation. Furthermore, inspired by the concept of blended amines that synergistically combine the advantages of different amines, the N-methyldiethanolamine (MDEA), known for its low reaction heat, was blended with primary/secondary amines to develop water-lean phase change absorbent. This approach significantly reduced the reaction heat during desorption process and the overall regeneration energy consumption. Notably, the optimized absorbent with a mass ratio of 2-(ethylamino)ethanol (EAE)∶MDEA∶NHD∶H₂O of 10∶20∶60∶10 exhibited a remarkably low regeneration energy of 1.92 GJ·t⁻¹ (measure by CO₂), which is significantly lower than that of the benchmark 30% (mass fraction) monoethanolamine (MEA) aqueous solution (~4 GJ·t⁻¹).