Three-Dimensional Numerical Modeling of a Low-Temperature Sabatier Reactor for a Tandem System of CO2 Methanation and Polymer Electrolyte Membrane Water Electrolysis

Abstract

The Sabatier reaction, which converts CO2 and H2 into CH4 and H2O (methanation), is an attractive way to produce a hydrogen carrier for renewable energy and CO2 recycling. Also, for air revitalization in space missions, water electrolysis provides not only O2, but also H2, which can hydrogenate metabolic CO2 from human respiration using the Sabatier reaction, producing H2O for O2 regeneration with the electrolysis. In this study, we have developed a three-dimensional finite element model of a test tandem cell combining a low-temperature Sabatier reactor working at around 220 °C with a proton exchange membrane water electrolyzer at around 120 °C. The model with our developed Sabatier reaction catalyst demonstrated that appropriate heat balance between the reactor and electrolyzer establishes a CO2 conversion above 90 % and thermal self-sustainability. An appropriate thermal insulator between the reactor and electrolyzer maintains them at predetermined temperatures. The thermal analysis also shows thermal self-sustainability for a plurality of the tandem cells, simulating a cell in a stack. Exergy loss ascribed to the entropy production rate with the temperature drop between the Sabatier reactor and electrolyzer is also evaluated.

Keywords

• co2 hydrogenation
• polymer electrolyte electrolysis cell
• hydrogen carrier
• closed-loop air revitalization