Modeling of an High-Concentration Solar Reactor for Dry Methane Reforming

Abstract

Direct solar-powered reforming of methane has the potential to lower the CO₂ footprint of reforming and to harvest solar energy with high-efficiency [1]. Combined with bio-sourced feedstock and recycled CO₂ to perform dry methane reforming (DMR), this approach can highly decrease methane reforming environmental impact [2]. Using high solar concentration solar towers or parabolic dishes to provide the highly endothermal reaction heat required for DMR, it is possible to reach the temperatures of conventional reformers, ranging from 800°C up to 900°C. At this temperature, radiation losses are such that high solar concentrations approaching 1000x are required to reach high thermal efficiency, making heat flux management highly challenging. Previous work from Université de Sherbrooke experimentally shown the potential for such reactors to operate under high heat flux [3],[4]. The current work presents the modeling approach used to design these reactors and increase the heat flux within the absorption surface, while maintaining reasonable temperature drop within the reactor. Dimensional analysis if first assess that no diffusion limitation occurs within the reactor and the system can be simulated as a plug flow reactor with porous catalyst. Using DMR and RWGS kinetics from literature with 2D modeling in COMSOL Multiphysics, temperature and reaction rates along the reactor are evaluated showing consistency with experimental values. Parametrical analysis shows that optimal catalyst channels width appears to be equal or under 0.5 mm. Finally, it is demonstrated that optimal conversion occurs when around 1/3 of the catalytic bed is covered with metallic conductive fins. Over this value, increased conductivity gains are overpassed by the lowering of catalyst volume within the conduction chamber.