Conceptual design and evaluation of membrane gas separation-based CO2 recovery unit for CO2 electrolyzers employing anion exchange membranes

Abstract

Anion exchange membrane (AEM)-based electrolysis for CO₂ reduction reaction (CO₂RR) has garnered attention as a promising carbon dioxide utilization technology due to its superior energy efficiency at high current densities. The major drawback of AEM-based electrolysis for CO₂RR is CO₂ crossover, which leads to the loss of introduced CO₂ feedstock and thus detrimentally affects the process's overall economic and environmental viability. We design a 3-stage membrane-based CO₂ recovery unit to capture CO₂ from the mixture of CO₂ and O₂ discharged from the anode side of AEM-based CO₂ electrolyzers. The membrane area is optimized via a hybrid of genetic algorithm and ‘fmincon’ in MATLAB. The estimated CO₂ capture cost ranges from 43.3 to 109.3 USD/tCO₂, which is economically comparable to piperazine-based amine scrubbing units when recovering CO₂ at a purity of up to 99.5 mol.% under a CO₂/O₂ molar ratio of 1.5∼2. The carbon footprint of the designed process ranges from −0.936 to −0.838 tCO₂eq/tCO₂-captured, indicating superior environmental performance compared to those of the piperazine-based amine scrubbing units.