Performance simulation of membrane-based carbon capture systems

This thesis addressed the challenge of rising CO2 emissions from industrial sources by evaluating membrane separation as a sustainable alternative for post-combustion carbon capture. Conventional capture technologies suffer from high energy demand, large footprints, and solvent-related drawbacks, while membranes offer modularity and efficiency but are limited by the trade-off between permeability and selectivity. A custom simulation code based on a Continuous Stirred Tank Reactor (CSTR) model was developed to assess polymeric membranes using literature data. Materials studied included PDMS, Polymers of Intrinsic Microporosity (PIMs), PEO-based copolymers, Polyimides, Polaris™, and PolyActive™. The model quantified membrane areas, permeate and retentate flows, and separation factors for CO2 recovery targets of 60–90%. Results showed a strong inverse relationship between CO2 permeability and required membrane area. High-permeability polymers such as PIM-TMN-Trip (52,800 Barrer) and PDMS (3) (3,195 Barrer) were most efficient, requiring as little as 685 m² to achieve 60% recovery. Polyimides and Polaris™ also performed competitively, while PEO-based copolymers and PolyActive™ generally required much larger areas. The permeability-selectivity trade-off was evident: highly permeable membranes minimized footprint but yielded moderate purity, whereas more selective polymers improved separation at the expense of area. Robeson plot analysis for CO2/N2 and O2/N2 confirmed these trends and showed that PIMs, Polyimides, and PolyActive™ surpass the empirical upper bound, highlighting their potential for advanced separations. This study demonstrates the utility of Robeson plots as a benchmark for identifying promising membranes and emphasizes the need for holistic evaluations, accounting for stability, mixed-gas behavior, and economics, to enable practical deployment of membrane-based CO₂ capture.