Revisiting film theory to consider approaches for enhanced solvent-process design for carbon capture

Abstract

Application of carbon capture at the gigaton-scale necessary for significant reduction in atmospheric CO₂ requires a portfolio of technologies for applications that may span point-source capture to more dilute systems such as CO₂ removal from the atmosphere. We argue that for absorption separation processes there is a strong coupling between the solvent and process properties, which are uniquely dependent upon the starting concentration of CO₂. We revisit Whitman's film theory and consider mass-transfer correlations to determine the most critical solvent and process parameters that influence the flux of CO₂ from the gas to the liquid phase, within which it is ultimately captured. Finally, results of this work indicate, for instance, that increasing the kinetics of a reacting solvent with CO₂ has a greater impact on direct air capture (DAC) systems, than natural gas- or coal-fired power plant emissions. In addition, the solvent kinetics is a more influential parameter than the Henry's law solubility coefficient for DAC systems, while the reverse may be found for more concentrated CO₂ gas mixtures.