Thermodynamic analysis of CO2 methanation integrated with carbon capture for energy storage

The conversion of captured carbon dioxide and renewable hydrogen into synthetic methane is a promising pathway for long-term energy storage and carbon dioxide utilization. This work presents a thermodynamic analysis of a CO2 methanation process integrated with amine-based carbon capture and operated under pilot plant conditions at an industrial site of TAURON Wytwarzanie S.A. in Poland. The analysed system combines carbon dioxide separated from flue gas with hydrogen produced by water electrolysis and converts them into synthetic natural gas in a two-stage catalytic reactor with a nominal capacity of 4.5 m3n/h of synthetic natural gas production. The study focuses on the interpretation of experimental process data in terms of material and energy balances, carbon dioxide conversion, methane concentration, hydrogen slip, water formation and the potential use of reaction heat within the integrated capture and utilization system. The analysis also considers the consistency of the available process data and the role of balance-based evaluation in improving the reliability of thermodynamic indicators. Attention is given to the balance structure of the coupled process, because measurement uncertainty, process variability and transient operation may affect the calculated performance of the system. The proposed approach identifies key variables required for consistent process evaluation and provides a methodological basis for further application of advanced data validation and balance reconciliation methods. The results are discussed in the context of power-to-gas energy storage, where the quality of pilot plant data is essential for process modelling, scale-up and the design of integrated carbon capture and utilization technologies. The work supports the development of reliable thermodynamic indicators for CO2-to-methane systems and contributes to future optimization of synthetic natural gas production coupled with industrial carbon capture plants.