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Industry Tests Show Bio-Derived Synthetic Paraffinic Kerosene Performs as Well as Petroleum Jet Fuel; Aviation Partners Push for Approval for Use

Overview of UOP’s Bio-SPK production process. Click to enlarge.

Boeing and a team from across the aviation industry today released high-level elements of a study that shows that sustainable biofuels analyzed in a series of test flights performed favorably in comparison to petroleum-based fuel.

According to the study, Evaluation of Bio-Derived Synthetic Paraffinic Kerosene (Bio-SPK), a series of laboratory, ground and flight tests conducted between 2006 and 2009 indicated the Bio-SPK test fuels performed as well as or better than typical petroleum-based Jet A. The testing included several commercial airplane engine types using blends of up to 50% petroleum-based Jet A/Jet A-1 fuel and 50% sustainable biofuels.

Other general findings included:

  • Bio-SPK fuel blends used in the test flight program met or exceeded all technical parameters for commercial jet aviation fuel. Those standards include freezing point, flash point, fuel density and viscosity, among others.

  • Bio-SPK fuel blends had no adverse effects on the engines or their components.

  • Bio-SPK blends have greater energy content by mass than typical petroleum-derived jet fuel—which potentially could lower fuel consumption per mile.

“Well-to-wheels” comparison of Bio-SPK from two different feedstocks compared to petroleum-derived jet fuel. Click to enlarge.

Production of Bio-SPK. The Bio-SPK process converts bio-derived oils (triglycerides and free fatty acids) to Bio-SPKs. First, the oils are cleaned using standard oil cleaning procedures. The oils were then converted to the shorter chain diesel-range paraffins using UOP’s Renewable Jet Process (earlier post), which converts the natural oils by removing oxygen molecules from the oil (deoxygenation) and converting any olefins to paraffins by reaction with hydrogen (hydrogenation). The removal of the oxygen atoms raises the heat of combustion of the fuel and the removal of the olefins increases the thermal and oxidative stability of the fuel.

A second reaction then isomerizes and cracks the diesel-range paraffins to paraffins with carbon numbers in the jet range. The end product is a Bio-SPK fuel that contains the same types of molecules that are typically found in conventional petroleum based jet fuel.

The report notes that there are many similarities between the Bio-SPK process and the Sasol Fischer-Tropsch SPK process, which produces a final SPK fuel using a starting material produced by the Fischer-Tropsch process. In both processes the final steps is hydroprocessing followed by separation.

Testing and the report. Test flights involved an ANZ 747-400 powered by Rolls-Royce engines, a CAL 737-800 powered by CFM engines and a JAL 747-300 powered by Pratt & Whitney engines. In addition, GE conducted static testing at its Ohio facility. Virgin Atlantic proved the technical viability of biofuels at high altitude with its test flight in early 2008.

Each of the test flights used a different blend of biofuel sources: The Air New Zealand flight used fuel derived from jatropha; the Continental flight used a blend of jatropha and algae-based fuels; and the JAL flight used a blend of jatropha, algae and camelina-based fuels.

The report is endorsed by Boeing, fuel technology developer UOP, a Honeywell company; engine-makers GE Aviation, CFM International, Pratt & Whitney, Rolls-Royce and Honeywell and airlines Air New Zealand (ANZ), Continental Airlines (CAL), Japan Airlines (JAL) and Virgin Atlantic.

For next steps, Boeing, in cooperation with UOP and the US Air Force Research Laboratory, is preparing a comprehensive research report for submission to the ASTM International Aviation Fuel Committee later this year. The report will support efforts to gain approval to use Bio-SPK fuel at up to a 50% blend in support of industry goals to accelerate availability and use.

To increase the bio-derived fuel component beyond 50% in the end jet fuel would require more than paraffins—the fuel requires aromatics to meet density specs. UOP is developing a process of catalytic stabilization and deoxygenation of pyrolysis oil that could deliver the requisite jet range cyclic hydrocarbons, and that would result in bio-content greater than 50%. Approval for this renewable jet fuel will take longer than approval of the Bio-SPK. (Earlier post.)



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