Optimal integration of post-combustion CO2 capture configurations with PEM electrolysis for methanol production: Energy and exergy assessment

Abstract

Industrial facilities are among the largest sources of CO2 emissions, and converting captured CO2 into useful chemicals is a key lever for decarbonization and for a circular carbon economy. Selecting the most suitable capture technology is difficult, however, because the decision depends on technical, economic, environmental, and social factors that cannot be reduced to a single metric. This thesis first develops a quantitative multi-criteria decision-analysis (MCDA) framework, combining the Analytic Hierarchy Process (AHP) for criterion weighting with the Technique for Order of Preference by Similarity to Ideal Solution (TOPSIS) for ranking, to identify the most suitable post-combustion capture technology for three power-plant categories. It then uses this outcome to evaluate, in detail, an integrated power-to methanol cycle from energy and exergy perspectives. In the first part, the AHP TOPSIS framework was applied to natural-gas combined cycle (NGCC), lignite, and coal power plants over nine criteria spanning technical, economic, environmental, and social dimensions. For NGCC, calcium looping ranked highest due to its high efficiency and technological maturity. For lignite-based systems, chemical absorption with N-methyldiethanolamine (MDEA) was the top option, while the Selexol process performed best for coal. The results highlight the need to balance the cost of avoided CO2 with technology readiness when selecting a capture process. The second part of the thesis focuses on the technical details of producing green methanol from captured CO2 and renewable hydrogen. Using Aspen HYSYS software, five different capture designs were tested to see which worked best with an electrolyzer and a methanol reactor. The "Rich Solvent Recycle" (RSR) design was the most efficient, reaching a total system exergy efficiency of 50.7%. The study also found that the system performs best when using a specific hydrogen-to-CO2 ratio of 3 at a pressure of 50 bar. The main contribution of this work is twofold: (i) it delivers the first nine-criteria MCDA framework that integrates technical, economic, environmental, and social dimensions for ranking CO2 capture technologies across three fuel categories, and (ii) it provides a configuration-level energy and exergy comparison of five MEA-based post-combustion processes coupled to a PEM electrolyzer and methanol synthesis unit, identifying the operating conditions that maximise the overall second-law efficiency. The results establish a transparent, reproducible path for designing efficient integrated systems that convert industrial CO2 into green methanol.

Date	1 Aug 2026
Original language	American English
Awarding Institution	École de technologie supérieure
Supervisor	Adrian Ilinca (Supervisor)