(520d) Coupled Level-Set Volume of Fluid (CLS-VOF) Computational Fluid Dynamics (CFD) of Methane Pyrolysis in Molten-Metal Bubble Column Reactors with Different Alloys

Molten-metal bubble column reactors (MMBCRs) are employed in hydrocarbon pyrolysis to produce low-CO₂ hydrogen and separatable solid carbon. Designing an efficient MMBCR necessitates a comprehensive understanding of hydrodynamics, bubble characteristics, heat and mass transfer, and chemical reaction kinetics. This study investigates the hydrodynamics, heat transfer, and chemical reaction kinetics of methane pyrolysis in three molten-metals alloys—Ni₂₇Bi₇₃, Ni₂₇Bi₇₂Se₁, Ni_2.3Mo_1.3Bi_96.4—at 900 ^oC, using coupled level-set volume-of-fluid (LSVOF) computational fluid dynamics (CFD) model. The reaction kinetics accounts for non-catalytic reaction within the bubble volume and catalytic reaction at the bubble surface. While the non-catalytic reaction depends solely on temperature, the catalytic reaction is influenced by alloy-specific kinetic parameters and interfacial area, which is tied to the molten metal physical properties. The heat transfer between gas and liquid phase is rapid for all alloys, facilitating effective chemical reactions. The Ni_2.3Mo_1.3Bi_96.4 alloy exhibited the highest methane conversion rate. Despite the compositional similarity between Ni₂₇Bi₇₃ and Ni₂₇Bi₇₂Se₁, differences in surface tension and reaction kinetics resulted in notable differences in methane conversion. This approach enables a detailed analysis of hydrodynamics and reaction kinetics in MMBCRs for methane pyrolysis, enhancing reactor design and optimization.