(535c) CO2 Methanation Via Chemical Conversion in Bubbling Fluidized Bed and Biological Conversion in Stirred Bubble Column: Reactor Design Using CFD

The power-to-gas (PtG) technology has been known as one of the most viable solutions for storing intermittent renewable energy sources such as solar and wind to the existing gas grid. In this study, the chemical CO₂ methanation (CCM) is experimentally and numerically investigated for a bubbling fluidized-bed (BFB) reactor at 350 °C and 5 bar, whereas the biological CO₂ methanation (BCM) is operated in a stirred slurry bubble column (SBC) reactor at 60 °C and 8 bar. In CCM, due to the strong exothermic reactions, heat management is an important factor in improving reactor energy efficiency. In BCM, the mass transfer, which is dependent on the interfacial area between phases, is a crucial parameter for investigating the process performance. A two-fluid Eulerian computational fluid dynamics (CFD) model with an empirical correlation of gas-solid heat transfer and a reaction rate model was proposed for the CCM in BFB. A Eulerian CFD coupled with a population balance model (PBM) was developed for the BCM in SBC. The impeller-influenced regions were considered as moving frame reference zones under a fixed speed of 360 rpm. The reactor performance from CFD results for CCM and BCM such as the gas molar fraction of species, CO₂ conversion, CH₄ yield and producer gas purity along the reactor height was evaluated. By comparing CCM and BCM, the important hydrodynamics parameters of BFB and SSBC were highlighted for the CO₂ methanation reactor design.