Methanol production via carbon dioxide hydrogenation for the maritime sector - Techno-economic assessment and social acceptance

Interest in Power-to-X technologies, where X stands for various chemical molecules produced from renewable electricity via water electrolysis, has recently accelerated. Methanol is one of these X molecules, where, in addition to hydrogen, captured carbon dioxide also participates in the synthesis. Methanol is an excellent alternative fuel for the maritime industry due to its high energy density, ease of storage and distribution thanks to its liquid state at ambient conditions, biodegradability, and water miscibility. This research has investigated the utilisation of synthetic methanol and the techno-economics of its production. The techno-economics part has focused on assessing large-scale synthetic methanol plants, while the utilisation part investigated methanol usage as an alternative marine fuel from the social acceptance point of view. Aspen Plus® was utilised for the process modelling environment in the techno-economic part. The developed plants ranged from industrial-scale comparable in output to fossil methanol plants to smaller but still large-scale plants. The energy efficiency of these plants was around 80%, and the differences can be attributed mainly to the varying targets of the heat integration. Furthermore, a new parameter was introduced to the process simulation environment, the implemented kinetic model describing methanol synthesis. The selected three kinetic models were first compared in a simple one-pass reactor and later in full-scale synthetic methanol plants. The most recent model has outperformed the other two in all technical key performance indicators. The most recent kinetic model also predicts the lowest levelised cost of methanol, which was 801 €/tonne, 10% below the worst-performing model. Overall, the levelised cost of methanol was calculated to be around 700-900 €/tonne, which is around 75% higher than the current fossil methanol price at 395 €/tonne. Moreover, a series of sensitivity analyses were also conducted, which found that synthetic methanol's production cost is significantly influenced by the cost of electricity and the potential co-sale of the oxygen by-product from the electrolyser. In this research, the developed one-pass reactor model in Aspen Plus® was also used to verify a mathematical model in computational fluid dynamics describing synthetic methanol synthesis and the process conditions' effect. In the utilisation part of this research, passengers of roll-on/roll-off passenger vessels were questioned about their knowledge and preferences of alternative marine fuels and other emission mitigation tools. The research found that most passengers are willing to accept increased fare prices when the vessel runs on alternative marine fuels. Furthermore, passengers prefer lower-emitting fuels and fuel production technologies; however, they lack the knowledge to decide consciously.