Evaluation of a phase change solvent for CO2 capture: Absorption and desorption tests

Abstract A blend of a tertiary amine (DEEA) and a diamine (MAPA) was studied in a screening apparatus for preliminary absorption tests. Two immiscible liquid phases were formed upon CO 2 loading and the system was shown to have large capacity for CO 2 . The two phases were analyzed individually for both amines and CO 2 . MAPA and water were found concentrated in the heavy CO 2 rich phase whereas the CO 2 lean phase contained mainly of DEEA. Volumetric phase ratio was measured as function of CO 2 loading and together with the individual phase compositions this forms part of a basis for an equilibrium model. The CO 2 rich phase was heated to desorption temperatures and shown to regenerate CO 2 at higher pressures than normally used for 30 wt.% MEA. The data enabled understanding the system behavior as MAPA is first loaded in the heavy phase and subsequently DEEA reacts with CO 2 and dissolves. The data show that the system has potential for significant reduction in regeneration heat through high cyclic capacity, very high CO 2 stripping pressures, and for operating where the heat of reaction lies between primary and tertiary amines. The tests also give good estimates for the absorption rate at higher loadings.