(569ds) Multiscale Modelling to Estimate Methane Cracking Conversion in Molten Media

The use of molten catalytic media is becoming a growing trend as a suitable means for simultaneously achieving solid carbon product separation and hydrocarbon cracking, hence avoiding catalyst regeneration. Reactor performance can be predicted using a multiscale approach that integrates the evolution of the reaction inside single bubbles with the macroscopic dynamics of two-phase flow under conditions relevant to industrial production. Here, we propose both an analytically solvable thermodynamically-consistent model to predict the effective reaction rate resulting from the interaction of surface reactions at the gas/liquid interface and diffusive transport inside the bubbles and a two phase CFD model to evaluate the average bubble residence time in the liquid. The analytical solution is derived from a spectral (eigenvalue/eigenfunction) expansion of the concentration profiles. We demonstrate how the dominant eigenvalue of the diffusion-reaction problem can be directly used to predict the effective characteristic time of the reaction under practically accessible conditions. Based on the limiting solution of the spectral model, we develop a simplified model which explicitly yields the dependence of methane conversion on equilibrium, kinetics, and transport parameters. This model is then combined with the average residence time predicted by the CFD model in order to estimate the overall reaction yields for a given reactor geometry.