Chapter Two - Fluid dynamics aspects and reactor scale simulations of chemical reactors for turquoise hydrogen production

The thermo- or thermo-catalytic decomposition of methane, resulting in the concomitant production of CO2-neutral turquoise hydrogen and solid carbon is gaining importance as a technology capable of fostering the decarbonization of the chemical and energy industries. Methane pyrolysis is an intrinsically multiscale and multiphase process where the gas phase cracking is accompanied by the interactions with the carbon fragments and/or the catalyst surface. To achieve a fundamental understanding, it is required to develop modeling techniques capable of accounting for the complex fluid dynamics behavior and the mass/heat transfer along with the description of the homogeneous and heterogeneous chemistry. Such modeling approaches contribute to the interpretation of the experiments and provide in-depth insights into the reactor behavior, resulting in the rational design of the reactors during process development. This chapter provides an in-depth and up-to-date review of the different modeling approaches that have been adopted to couple the transport phenomena with reaction kinetics in the methane cracking reactors for the production of turquoise hydrogen. Different modeling strategies with growing levels of complexity (1D, 2D, homogeneous, heterogeneous, multiphase, CFD) are analyzed in the context of non-catalytic (tubular, stirred, plasma, molten media) and catalytic (chemical vapor deposition, fluidized bed, catalytic molten media) reactor configurations. The key features of the modeling approaches together with their assumptions, prediction capabilities and possible disadvantages are critically discussed.