Techno-economic analysis of a CCU process based on CO2 capture by PSA and its conversion to synthetic methane using renewable hydrogen

Nowadays, climate change due to global warming has a significant impact on the human activities.. The major greenhouse gas (GHG) is the carbon dioxide, CO₂, and its rising concentration in the atmosphere leads to an increase of average global temperature of the Earth. Over the last decade, considerable research has been conducted to explore the utilization of CO₂ together with H₂ in order to produce synthetic natural gas (CH₄) and water (H₂O), but the process is still not feasible for large-scale applications. The use of renewable energy sources (RES) is an alternative way to produce energy than the fossil fuels with the aim of reducing carbon emissions. They include bioenergy, hydropower, geothermal energy, solar energy and wind energy and are considered clean sources of energy. This work investigates the feasibility of integrating a carbon capture process as the Pressure Swing Adsorption (PSA) with a RES-fed alkaline water electrolyser (AWE) in order to produce synthetic natural gas(CH4) via CO2 hydrogenation with the possibility to inject the natural gas in the distribution grid within a Power-to-X path. A PSA system model was developed in MATLAB, while the alkaline electrolyzer and the methanation reactor were modelled using Aspen Plus. The PSA model consists of a code that simulates a 2-bed capture system with solid sorbents for the biogas upgrading to obtain a product stream with a high amount of carbon dioxide. Subsequently, the captured CO2 stream is mixed with the hydrogen produced from the electrolyzer and sent to a reactor for methanation process. The study evaluated the performance metrics of PSA system and AWE focusing on their operational efficiency. In addition, the overall system efficiency was analysed, highlighting its potential as sustainable solution for decarbonization process. An economic analysis is also performed to investigate the cost of the synthetic methane produced.