Design Optimization and Techno-Economic Analysis of a Molten Metal Bubble Column Reactor for Catalytic Methane Decomposition

Catalytic methane decomposition using molten metal bubble column reactors (MMBCRs) represents an emerging technology for hydrogen production that avoids high carbon dioxide emissions. This study optimizes the geometric dimensions, operational conditions and molten medium type of the MMBCR by developing a numerical model and conducts a techno-economic analysis. The one-dimensional model established demonstrates strong agreement with experimental data across different temperatures, exhibiting a normalized root-mean-square error (NRMSE) of 3.18% and providing detailed profiles of hydrodynamic and reaction kinetic parameter variations along the melt height. Parameter sensitivity analysis identifies temperature as the most influential operational parameter affecting methane conversion rate, while melt height and diameter become significant at elevated feed rates. Catalyst screening reveals that molten alloys exhibit higher catalytic performance than most pure metals. Multiobjective optimization results indicate that using pure Cu at a hydrogen production rate of 600 N m³·h^–1 is the optimal solution, yielding a minimal levelized cost of hydrogen (LCOH) of $3.34 per kilogram. The LCOH is $0.25 lower than that of conventional steam methane reforming (SMR) with carbon capture and storage (CCS). Furthermore, the LCOH becomes competitive with coal to hydrogen (CTH) when the recovery rate of carbon byproduct (carbon black) reaches 25%. Techno-economic analysis reveals that methane and heating costs collectively constitute over 84% of the annual costs, with electric heating being the most economical heating method. Among these costs, methane cost is the most significant factor influencing the LCOH across the scenarios.