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

抄録

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.