Techno-economic study of integrated high-temperature direct air capture with hydrogen-based calcination and Fischer–Tropsch synthesis for jet fuel production

This work provides a comprehensive techno-economic assessment of high-temperature direct air capture (HTDAC) integrated with Fischer–Tropsch synthesis (FTS) for producing renewable jet fuel on a scale of approximately 25 t/h. Specifically, the HTDAC is based on calcium looping employing calcination in a hydrogen-based atmosphere to enable simultaneous RWGS reaction. A detailed description of the Aspen Plus model for HTDAC, alkaline and solid oxide electrolysis systems, RWGS reactor and the FTS is provided for future reference. Five system configurations are analysed, comparing the energy efficiency effects of hydrogen oxy-fuel combustion and electric calcination in a hydrogen-based atmosphere. In this regard, the potential omission of the RWGS reactor is examined, considering that 62 to 78 % of the CO is already converted into CO in the calciner, with the highest conversion rates achieved through electric calcination. Moreover, the study investigates the impact of alkaline electrolysis and solid oxide electrolysis on the system's energy efficiency. Overall carbon efficiencies of more than 50 % in the jet fuel are achieved, with system energy efficiencies ranging from 30.6 to 39.0 % corresponding to fuel-specific energy consumption in the range of 122 to 156 MJ/kg. Net present value (NPV) analysis reveals a projected minimum fuel selling price (MFSP) in the range of 4.45 to 6.32 €/L, which is significantly higher than previous literature estimates based on more optimistic cost assumptions. Uncertainties in cost parameters are addressed through a Monte Carlo analysis which shows the potential of a significant decrease in the MFSP provided that some of the cost estimates will be cheaper than the conservative initial estimate. Conclusively, this study highlights the significance of developing a financially feasible electrically heated calciner that can effectively handle high-temperature hydrogen. Furthermore, maximising the yield of jet fuel emerges as a critical factor for unlocking the future potential of the process, as it substantially reduces the cost of fuel production. Lastly, the reduction of hydrogen production costs is identified as the most crucial aspect in enhancing the economic viability of the process, as it serves as the biggest contributor to the high minimum fuel selling price.