Optimization of Anode and Cathode Frames for Compact Hydroxide Exchange Membrane Carbon Capture

• Kenneth King, Chemical Engineering, University of Delaware

• Anil Bika, Mechanical Engineering, University of Delaware

Airborne carbon dioxide (CO₂) must be carefully controlled in submarines because elevated concentrations can impair cognitive performance and contribute to hypercapnia. Although conventional liquid-amine scrubbers remove CO₂ effectively, they require substantial space because the amine must be thermally regenerated; therefore, multiple units are needed to maintain near-continuous operation. As a compact alternative, hydroxide exchange membrane carbon capture (HEMCC) was investigated as a continuously operating system. This project focuses on reducing the volume contribution of the anode and cathode frames while preserving channels capable of resisting deformation under stack-assembly compression. The previous frame design provided 100 cm² of active area and measured 196 mm × 126 mm, with thicknesses of 4.72 mm for the cathode and 6.71 mm for the anode. In comparison, the optimized frames measured 340.6 mm × 90.0 mm × 3.5 mm and increased the active area to 200.5 cm², representing approximately 26% and 48% reductions in cathode and anode thickness, respectively. To achieve this improvement, three-dimensional models were created in Autodesk Fusion, and the channel geometry was optimized to maximize active membrane area, reduce frame volume, and limit cathode-side airflow resistance. Because thinner channel supports increase the risk of collapse, structural integrity was treated as a primary design constraint. Consequently, a static finite element analysis applied four 2,500 N remote loads representing compression from the stack-assembly screws. The model produced a minimum safety factor of 2.595, a maximum von Mises stress of 18.879 MPa, and a maximum displacement of 0.037 mm. Furthermore, the 3D-printed frames retained their channel geometry without visible collapse. Overall, these results demonstrate that active area can be doubled while reducing frame thickness without compromising structural performance, supporting future testing of a six-person prototype before scale-up to a 125-person system.