Model-based Optimal Sabatier Reactor Design for Power-to-Gas Applications

The existing infrastructure for natural gas storage and transport made the Sabatier process an attractive step within the power-to-gas process chain for intermittent renewable energy storage. A model-based optimal design for the methanation of carbon dioxide with hydrogen to methane under process-wide constraints is presented. After inclusion of the downstream units into the analysis, the product methane fulfils the specifications for the natural gas grid. The optimization goal was to maximize the space-time yield by applying the systematic flux-oriented elementary process function methodol-ogy. The optimum temperature and concentration profiles along the reaction coordinate were first determined, after which they were approximated using two reaction configurations: 1) a hydrophilic membrane reactor and 2) a cascade of polytropic reactors with interstage condensation. The results show that an optimized cascade of three polytropic fixed bed reactors (e.g., optimum temperature profile) and two intermediate condensation steps is the best technical approximation for maximizing the space-time yield.