SUSTAINABLE AVIATION FUEL CANDIDATE DISTILLATION OPTIMIZATION

Zhibin Yang

doi:10.7273/000007110

With the increasing focus on transitioning to sustainable energy and reducing humanity's environmental carbon footprint, methods to replace conventional fuel with sustainable fuels are of considerable interest. The Sustainable Aviation Fuel (SAF) Grand Challenge has set ambitious targets: producing 3 billion gallons of SAF by 2030 and reaching 35 billion gallons by 2050 to meet 100% projected aviation fuel demand in the U.S. However, aviation remains one of the most challenging sectors for decarbonation. While competing technologies like battery electrification, hydrogen fuel cells, and hydrogen combustion are in development, they are not yet ready for widespread adoption, particularly for medium and long-haul flights that contribute 73% of aviation CO2 emissions. SAF emerges as a promising mid-term solution. It is a “drop-in” liquid hydrocarbon jet fuel produced from renewable or waste resource, achieving at least a 50% reduction in life cycle greenhouse gas emissions compared to conventional fuel. Crucially, SAF is compatible with existing aircraft and engines, making it a practical choice for immediate impact. However, the qualification process for SAF, as outlined in ASTM D4054 standards, is rigorous and time-consuming, leading to only a limited number of approved SAF variants so far. To expedite this process, prescreening of novel SAF candidates is proposed to identify promising technologies early on and align them for ASTM D4054 evaluation. This thesis introduces a methodology focused on maximizing SAF yield and determining the optimal blend ratio with petroleum-derived fuels by adjusting distillation cut points. These cut points, specific to each feedstock and conversion technology combination, are pivotal variables in fuel finishing. By exploring various cut point combinations, a Pareto front is established, delineating the trade-off between yield and blend ratio limits while ensuring operability within specification. Computational simulations and experimental validations illustrate this methodology's efficacy. In computational models, eight bulk properties are analyzed to predict the competition between distillation yield and blend limits, with experimental verification along the Pareto front. An experimental optimization case study demonstrates a 37% increase in renewable carbon in the SAF fraction compared to conventional distillation recommendations, with enhanced property specification margins. Included in Appendix A of this thesis is the culmination of years of work in our lab—the SAF prescreening procedure, which I take immense pride in. Appendix B in this thesis includes additional work conducted during the preparation of this thesis, namely dielectric constant measurement for sustainable aviation fuels.

SUSTAINABLE AVIATION FUEL CANDIDATE DISTILLATION OPTIMIZATION

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