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Non‐oxidative methane pyrolysis produces hydrogen and solid carbon without CO2 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 H2 production of 10,000 Nm3/h, the bubble size and methane conversion were approximately 40 mm and under 35%, respectively. [ABSTRACT FROM AUTHOR]

A one-dimensional (1D) molten-metal-based bubble-column reactor (MMBCR) model coupled with heat transfer and axial dispersion was developed for non-oxidative CH 4 pyrolysis to produce low-carbon H 2. The MMBCR model included mass, momentum, and energy balances, accounting for catalytic and non-catalytic reaction kinetics, and hydrodynamic parameters such as the gas holdup (α G), gas velocity (u G), bubble size (d b), and specific interfacial surface area of bubbles (a s). The 1D MMBCR model was compared with other 1D reactor models and bench-scale experimental data for CH 4 conversion (X M). The MMBCR model agreed well with the experimental data. When heat transfer and axial dispersion were considered for an industrial-scale MMBCR to produce 10,000 Nm3/h, the reactor length increased to 2.4 times higher than that estimated by the model without axial dispersion to meet 80% X M. The MMBCR model has the potential to design industrial-scale MMBCRs and optimize operating conditions. [Display omitted] • One-dimensional molten metal-based bubble column reactor (MMBCR) model was developed. • MMBCR model for CH 4 pyrolysis was coupled with heat transfer and axial dispersion. • Heat transfer and axial dispersion slightly affect bench-scale MMBCRs CH 4 conversion. • Axial dispersion lowered the CH 4 conversion of an industrial-scale MMBCR by 17%. • The MMBCR model is useful to design the reactors and optimize operating conditions. [ABSTRACT FROM AUTHOR]