Mathematical Modeling of High-Temperature Multiphase Solid/Molten Carbonate Membranes for CO2 Capture

Abstract

High-temperature solid/molten-carbonate composite represent an emerging class of CO2 transport membranes to capture CO2 from flue gas with advantages in flux density and selectivity over conventional solvent/sorbent- and polymer-based counterparts. While significant technical progress in these membranes has been made in the past years, a deeper fundamental understanding of CO2 transport mechanisms is still limited. Aimed to bridge this gap, we here report a theoretical study on flux performances of four types of solid/molten-carbonate CO2 transport membranes by analytical and numerical modeling. We found that analytical and numerical results are virtually identical for solids with single charge carrier. However, for mixed conducting solids, numerical methods are preferred since analytical methods cannot solve the nonlinear local concentrations of charge carriers. Application of numerical method to a new three-phase membrane containing a mixed conducting solid, a pure electron conducting solid and molten-carbonate reveals a ∼90% increase in CO2 flux compared to the two-phase (mixed conducting solid and molten-carbonate) counterpart. The models presented here are expected to provide better fundamental insights and guidance for designing next-generation high-performance CO2 transport membranes.