Dynamic simulation of the CO2 methanation in a micro-structured fixed-bed reactor

Abstract

The dynamic operation of methanation reactors is under discussion due to the increasing interest in power-to-gas technology. Here, hydrogen is supplied via a water electrolyzer which is powered by fluctuating renewable energy sources. With dynamic process modeling and simulation, the methanation reactor can be designed. Since the methanation reaction proceeds fast in the presence of an active catalyst and releases a large amount of reaction heat, the model has to account for the pellet phase in terms of energy, species mass and reaction. In this work, a dynamic 1D heterogeneous model is presented. The model describes a micro-structured fixed-bed reactor for the methanation of carbon dioxide under industrially relevant operating conditions with periodic oscillations of the inlet feed composition. The simulation shows that the hot spot temperature changes significantly during the periodic operation, both in position and magnitude. For high frequency changes the reactor behavior moves towards a thermally relaxed steady state. The outlet methane concentration in the dynamic operation does not reach the steady-state value. However, the model reveals interesting insights of the dynamic CO2 methanation, which will be accompanied with experiments in the future.