Exergetic assessment of CO2 methanation processes for the chemical storage of renewable energies

Abstract

One option in the power-togas scenario is the methanation (Sabatier) reaction using carbon dioxide from anaerobic digestion as a carbon source and hydrogen obtained by electrolysis. The exergetic efficiencies of four process configurations for the methanation are assessed in this contribution. The specifications of the German natural gas grid are used as product quality requirement for the produced methane. The configurations are analyzed on the system level, including the acquisition of the reactants, the chemical conversion process and finally the energy conversion of methane to electrical energy. The results of the analysis demonstrate that the mixture of methane and carbon dioxide from anaerobic digestion can be directly fed into the methanation. No prior removal of biogenic methane is necessary. This configuration is the most efficient process in terms of exergetic efficiency in this study. The process including the electrolysis, methanation, separation via pressure and temperature swing adsorption, and gas conversion to electricity has an overall energetic efficiency of 23.4%, without the excess heat contribution, covering the complete cycle from electricity over chemical storage back to electricity. The exergetic efficiency is higher, when taking the contribution of excess heat into account. The obtained efficiency for methanation is clearly higher than that reported in literature using methanol for energy storage.

Operation range extensionviahot-spot control for catalytic CO2methanation reactors

“…is currently subject of intensive investigations due to its major role for the utilization of renewable energy for synthetic fuels and platform chemicals production. [56][57][58][59][60][61] Some studies also consider the following side-reactions to account for possible CO formation…”

Recent Status and Prospects on Thermochemical Heat Storage Processes and Applications

“…Figure 4 illustrates the described process. Chemical heat storage offers several advantages over the other two TCHS processes [90][91][92][93][94][95][96][97][98][99][100][101][102][103][104][105][106][107]:…”

Solution and Parameter Identification of a Fixed-Bed Reactor Model for Catalytic CO2 Methanation Using Physics-Informed Neural Networks

“…Among the various reactor types, fixed-bed reactors (FBs) are the most commonly used types for CO 2 methanation. As the CO 2 methanation reaction is thermodynamically favored at low temperatures and high pressures [9], an isothermal fixed-bed reactor (IFB) without a hot spot produces high methane selectivity, exhibits stable operation, and prevents deactivation of catalyst particles through processes such as thermal degradation (i.e., nickel sintering [2]). However, the IFB usually requires high recycling and dilution ratios, and adiabatic reactors to maintain suitable productivity [10][11][12].…”