Techno-economic analysis and optimisation of grey and green methanol synthesis using flowsheet automation and surrogate modelling

Recognizing methanol's versatile role as a chemical precursor and energy carrier, the study addresses its traditional production from fossil fuels and the associated challenges in pivoting to green alternatives due to the cost of green hydrogen. The research focuses on techno-economic analysis and optimization, employing a validated chemical process simulation tool integrated with economic analyses, reflecting CAPEX and OPEX models, and considering heat recovery to promote self-sufficiency. The study compares grey (traditional syngas) and green (biogenic CO$_2$ and green hydrogen) methanol production pathways while also optimizing process factors, such as feed pressure, purge rate, temperature and catalyst volume, to achieve cost-effectiveness. In green methanol production specifically, the paper finds that optimal conditions are slightly milder than for grey methanol, highlighting the importance of process variables like purge rate given the high cost of green hydrogen. Still with current price level of hydrogen from electrolysis the levelised cost of methanol is several times more expensive via direct hydrogenation compared to production from fossil syngas. Results from the simulation-driven optimization underline the delicate balance between various objectives, such as minimizing costs or maximizing output, and demonstrate instances of pareto optimality. This study thus contributes with an integrated assessment of methanol production techniques, utilizing process simulation, economic evaluation, and heat integration for both grey and green methanol, aiming to pave the way for more sustainable chemical processes in the industry.