(397a) Modeling of CO2 Absorption In and Stripping From Aqueous Amine, Amino Acid and Carbonate Blends

An approximate analytical
method based on steady-state Film Theory has been demonstrated to enable
accurate, computationally efficient prediction of carbon dioxide
absorption and desorption rates in packed columns. The method is based on a
particular scheme for linearizing the coupled
differential equations that govern steady-state diffusion with multiple reversible
reactions. Interphase transport rates calculated based on Film Theory agree
closely with those obtained via exact numerical methods. Notably, the same
accuracy is observed whether the reactions are fast or slow; when their
characteristic times differ by orders of magnitude; and irrespective of the
magnitudes of transport and reaction driving forces. The method was recently
applied [Meldon and Morales-Cabrera, Chem. Eng. J., 2011, 171, 753] to the
analysis of carbon dioxide absorption in and desorption from aqueous solutions
of monoethanolamine, prior modeling of which had
relied for accuracy on numerical methods of analysis. It is extended here to carbon
dioxide capture with aqueous solutions of blends of amines, amino acids and
alkali. The relative merits of candidate scrubbing solutions, for purposes of flue
gas CO₂ capture at coal-fired power plants, are evaluated based on interphase
transfer rates, rich and lean loadings, and stripper reboiler
duties.