Numerical modelling of a sorption-enhanced methanation system

Synthetic natural gas production from CO2 and green hydrogen provides a promising route to renewable energy storage. Reactants maximum conversion degree, limited by CO2 methanation strong exothermicity, can be enhanced by in situ water removal. In this work, reaction/adsorption step of a sorption-enhanced methanation process was modelled using a two-dimensional, heterogeneous, and dynamical model of an externally cooled fixed bed reactor. A bifunctional pellet (Ni on 13X zeolite) was considered. Internal/external catalyst mass and heat transfer resistances were assessed. Effect of variations in gas space velocity (GHSV) and operating pressure on produced methane purity and effective operational time length have been evaluated through a sensitivity analysis. Results show that a pure and dry methane flow was produced until a reactant's breakthrough occurs. At any given operating pressure, there is a non-linear negative correlation between GHSV and breakthrough times. Conversely, for any given GHSV, an increase in operating pressure increases breakthrough time.

Automated summary

Synthetic natural gas production from CO2 and green hydrogen offers a promising solution for renewable energy storage, and in situ water removal can enhance the conversion efficiency. This study developed a 2D, heterogeneous, and dynamic model of an externally cooled fixed bed reactor to simulate the reaction/adsorption step in a sorption-enhanced methanation process. The effects of gas space velocity (GHSV) and operating pressure on methane purity and breakthrough time were analyzed. The results showed that a pure and dry methane flow could be obtained until reactant breakthrough occurred. The breakthrough time was inversely correlated with GHSV and positively correlated with operating pressure.