Assessment of combustion properties of non-hydroprocessed Fischer-Tropsch fuels for aviation

A demonstrative Fischer-Tropsch fuel without any cost intensive post-processing treatment has been investigated for its application potential as a synthetic blending component with conventional petroleum-derived aviation fuels. As a first step, the focus of the analysis was purely on combustion related properties. The Fischer-Tropsch fuel was obtained via a specific Power-to-Liquid Fischer-Tropsch process, developed by Ineratec. Whereas the already approved Fischer-Tropsch-SPK process (ASTM D7566 Annex A1) utilizes hydrotreatment and is applied in large-scale plants, the herein presented plant features a unique and compact container-scale set-up, with no further downstream hydrotreatment, which allows for a significant reduction of production time and costs. Main objective of this paper is to provide the fuel producer with fast feedback to find the minimum complexity of fuel processing technology to achieve a synthetic blending component for aviation fuels directly from a container plant. As a first step in the ongoing process, the combustion properties of the non-hydroprocessed Fischer-Tropsch fuels are assessed regarding their suitability for aviation purposes. Fuel characterization was carried out regarding the physiochemical properties of the fuels and their chemical composition to monitor selected fit-for-purpose properties for aviation with regard to combustion properties. Additional combustion experiments were conducted in a high-temperature flow-reactor with coupled molecular beam mass spectrometer (MBMS) for two stoichiometries to map lean and rich combustion (Phi = 0.8 and 1.2), allowing quantitative access to the chemical reaction species formed within the combustion. The general combustion chemistry and reaction temperature regime was found similar to Jet A-1 and pure n-alkane decane. This indicates the dominant species for the observed combustion process are aliphatic hydrocarbons. The detailed evaluation of relevant intermediates allows for an observation on typical soot precursors (e.g. benzene, naphthalene) in the combustion process and enables the estimation on the pollutant reduction potential of the Fischer-Tropsch fuel when used as blending component to Jet A-1. Blending analysis has been performed utilizing the data from the CRC world fuel survey to evaluate the range of blending ratios of the Fischer-Tropsch fuel with conventional jet fuels determined by identified limiting factors. The presented evaluations demonstrate the potential of the Fischer-Tropsch fuel as a blending component with conventional jet fuels considering the combustion behavior only.