Model based determination of the optimal reactor concept for Sabatier reaction in small-scale applications over Ru/Al2O3

The CO2 methanation is an exothermic reaction controlled by thermodynamic equilibrium. For this reason, the high CO2 conversion, required by the natural gas grid regulations, can be achieved only with a proper thermal management of the reactor. The model-based optimization of the Sabatier reaction by controlling the heat transfer is developed in this paper. The focus of the study is on small-scale applications, which gives rise to various specific technical limitations for the optimization study. We found that the reactor can be divided into three zones: an initial zone, for reaction activation; a central zone, to remove excess heat; and a final zone, to achieve high conversion reaching the thermodynamic equilibrium curve. The effect of the variation of the heat transfer coefficient along the axial coordinate of the reactor is assessed and the optimal profile is defined. Based on these results, a technical approximation of the optimal reactor is proposed, allowing high CO2 conversion with a simple manufacturing.