Reactor Design for a Greener Future: Comparing isothermal and adiabatic CO 2 methanation reactors under renewable energy fluctuations

Integrating renewable energy into chemical processes is critical to Shell’s ambition of producing net zero emissions by 2050, and, given the global commercial importance of liquefied natural gas (LNG), finding ways to enhance the efficiency of the methanation process. A key factor is the performance of the methanation reactor under dynamic conditions. This study explores the dynamic behavior of adiabatic and isothermal fixed-bed reactors for carbon dioxide $\left(\mathrm{CO}_{2}\right)$ methanation - a key power-to-gas ($\mathrm{P2G}$) pathway that converts renewable (green) hydrogen and captured CO<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> into synthetic methane. All simulations used the computational fluid dynamics (CFD) software COMSOL Multiphysics to build and validate detailed fixed-bed reactor models. These findings offer direct business value by supporting the development of flexible methanation systems that can be directly coupled to intermittent renewable sources. This reduces the capital and operating costs required for storage while enhancing system responsiveness. This study demonstrates the value of multiscale modeling in optimizing methanation reactor performance under dynamic conditions. Both reactor configurations, adiabatic and isothermal, showed good performance under variable load. The time necessary to stabilize for both was under 5 s.