Analysis of Industrial Flue Gas Compositions and Their Impact on Molten Carbonate Fuel Cell Performance for CO 2 Separation

The study examines the influence of diverse flue gas compositions on the operational parameters and efficiency of MCFCs (molten carbonate fuel cells) as CO 2 separation devices to provide foundational knowledge on MCFC operation under various industrial conditions. MCFCs inherently rely on the presence of CO 2 at the cathode, where it combines with oxygen to form carbonate ions that migrate through the electrolyte; thus, CO 2 acts as a carrier species rather than a fuel, enabling simultaneous electricity generation and CO 2 separation. The findings indicate that MCFCs are most effective when operated with CO 2 -rich flue gases, such as those from coal and lignite-fired power plants with CO 2 contents of roughly 12–15 vol.% and O 2 contents of 2–6 vol.%. In these cases, CO 2 reduction rates of up to 80% can be achieved while maintaining favorable cell voltages. Under such conditions, relevant also for the cement industry (CO 2 between 15 and 35 vol.%), the Nernst voltage can reach about 1.18 V. In contrast, flue gases from gas turbines, which typically contain only 4–6 vol.% CO 2 and 11–13 vol.% O 2 , result in lower Nernst voltages (0.6–0.7 V) and a decrease in efficiency. To address this issue, potential modifications to the MCFC electrolyte are suggested to enhance oxygen-ion conductivity and improve performance. By quantifying the operational window and CO 2 -reduction potential for different sectors at 650 °C and 1 atm using a reduced-order model, the paper provides a technology assessment that supports sustainable industrial operation and the design of CCS (carbon capture and sequestration) strategies in line with climate goals.