One‐dimensional kinetic model with novel bubble size equation in molten‐metal bubble column reactors for CH₄ pyrolysis

Non‐oxidative methane pyrolysis produces hydrogen and solid carbon without CO 2 in molten‐metal bubble column reactors (MMBCRs). One‐dimensional MMBCR models, which involve bubble hydrodynamics, reactions, heat transfer, and axial dispersion, have been developed for reactor design; however, empirical equations of the mean bubble size derived from bench‐scale experiments have also been used for industrial‐scale MMBCRs. In this study, a novel bubble size equation based on dimensionless numbers was proposed for the bubbling, transient, and slugging flow regimes, which is applicable to both bench‐ and industrial‐scale reactors. Using the MMBCR model coupled with the new bubble size, reaction kinetic parameters were identified for four bench‐scale MMBCRs with Te‐based alloys in the bubbling flow regime. In four industrial‐scale MMBCRs at 980°C, belonging to the transient flow regime for an H 2 production of 10,000 Nm 3 /h, the bubble size and methane conversion were approximately 40 mm and under 35%, respectively.