Experiment and numerical analysis of catalytic CO₂ methanation in bubbling fluidized bed reactor

This study experimentally and numerically investigated the hydrodynamics, reaction kinetics, and heat transfer of a bench-scale bubbling fluidized bed (BFB) reactor for CO₂ methanation. A three-dimensional gas–solid Eulerian computational fluid dynamics (CFD) model coupled with a modified Syamlal–O'Brien drag model and reaction kinetics for Ni-based catalysts was developed. The CFD model was validated against experimental data for pressure, temperature, and gas composition at 1 bar and an inlet flow rate of 2 L/min with an inlet N₂ content of 77.5%. The axial pressure drop, solid volume fraction, temperature, gas composition, and bed-to-wall heat transfer coefficient (HTC) were compared for four inlet N₂ contents: 77.5%, 50%, 25%, and 0%. As the inlet N₂ content decreased, the mean bed temperature increased from 340 to 456 °C, the gas volume decreased owing to the reaction, the fluidizing number (u_g/u_mf) decreased from 4.1 to 3.5, and the solid holdup increased. Consequently, the HTC increased from 327 to 386 W/m²/K. This study identified successfully the effects of hydrodynamics and reaction kinetics on HTC in the BFB for CO₂ methanation.