Abstract
Carbon dioxide (CO2) hydrogenation is a promising route for energy storage and carbon recycling, but its strongly exothermic nature leads to hotspot formation in multi-tube reactors. In this study, computational fluid dynamics simulations with conjugate heat transfer were used to investigate CO2 methanation over a commercial 10% Ru/γ-Al2O3 catalyst in multi-tube reactors. Both packed-bed and coated configurations were examined and extended to an industrial-scale reactor. Packed reactors exhibit severe hotspot formation, whereas coated reactors improve temperature control due to enhanced heat transfer. However, the wall-coated configuration can lead to bypass-like flow and reduced effective gas-catalyst contact, thereby limiting methane yield. This limitation can be mitigated by increasing catalyst length, which enhances methane production. Scale-up results show that coated reactors maintain favorable thermal behavior under industrial conditions. In addition, using the reactant mixture as the cooling medium enables simultaneous temperature control and heat recovery through feed preheating, improving overall energy efficiency.
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•Developed a CFD model coupling kinetics and heat transfer for CO2 hydrogenation.•Revealed heat and mass transfer mechanisms in coated and packed-bed reactors.•Proposed cooling strategies for hotspot control and energy integration.