(48d) Fischer-Tropsch Fuel for Use by the Us Military as Battlefield Use Fuel of the Future

The United States Department of Defence (DoD) currently uses a single kerosene-type fuel for all its gas turbine and diesel engine applications. Technological changes introduced to the battle space make the single battlefield fuel philosophy of the DoD less prone to the use of crude-oil derived kerosene-type fuel. The DoD initiated a three phase Joint Battlefield Use Fuel of the Future (JBUFF) program to evaluate, demonstrate, certify and implement turbine fuels produced from alternative energy resources such as Fischer-Tropsch (FT) fuels for use in all its gas turbine and diesel engine applications. Sasol Synfuels International (Pty) Ltd, amongst others, was invited to participate in the program with the objective to supply the DoD with a FT BUFF that conforms to fuel volatility and low temperature fluidity requirements. These requirements included a freezing point of -47 °C, viscosity of 8 cSt at -20 °C and a flashpoint of 38 °C for a BUFF conforming to ?Jet Propellant # 8? (JP-8) specifications and a flashpoint of 60 °C for a BUFF conforming to JP-5 specifications for the handling of fuel on aircraft carriers. Technical, economic and strategic challenges related to the introduction of FT fuels into the military fleet include the interchangeability of FT fuels with crude-oil derived kerosene-type fuels; elastomer compatibility of fuel systems already conditioned in crude-oil derived kerosene-type fuels with subsequent exposure to FT fuels containing no aromatics; demand and supply of FT fuels at a price comparable to crude-oil derived kerosene-type fuels; and the modification of existing fuel specifications to allow for general approval of FT kerosene-type fuel. Although the DoD is more interested in Coal-to-Liquid (CTL) technology, fractionator feed from the Gas-to-Liquid (GTL) Products Work-Up Demonstration Unit in Sasolburg, South Africa, was used to evaluate the possibility of producing a BUFF fraction from the Sasol Slurry Phase Distillate^TM (SPD^TM) low temperature FT (LTFT) and Chevron ISOCRACKING® technology. The fractionator feed used to develop a BUFF from the Sasol SPD^TM LTFT process contains only normal and iso-paraffins with virtually no aromatics or naphthenes. Concluded from the study was that the production of a synthetic BUFF is feasible using the Sasol SPD^TM technology alongside the current Chevron ISOCRACKING® technology. Also concluded from the study was that the Sasol SPD^TM LTFT BUFF product yield and the FBP of the product will be restricted by the freezing point requirement due to the low iso to normal paraffin ratio of ~1:1 of the Sasol SPD^TM LTFT BUFF and not by the maximum viscosity requirement like the ?Single Battlefield Fuel? of the Syntroleum Corporation (S-5) which has an iso to normal paraffin ration of ~14:1. One would therefore need to optimize the hydrocracking process conditions to increase the product yield. Sasol recently demonstrated that fully synthetic high temperature FT (HTFT) aviation turbine fuel, produced at Sasol Synfuels in Secunda, South Africa, is fit-for-purpose for commercial use. The fully synthetic HTFT aviation turbine fuel comprises of blends of hydrocracked tar liquid, light distillate refinery streams and iso-paraffinic kerosene. It differs from Sasol SPD^TM LTFT kerosene in that it contains naphthenes and aromatics resulting in a comparable elastomer response with crude-oil derived aviation turbine fuel with similar aromatic content. The fully synthetic HTFT aviation turbine fuel addresses the technical challenges related to the introduction of FT fuels into the military fleet. It further conforms to all JP-5 specifications with properties and characteristics that are typical of conventional, crude-oil derived aviation turbine fuel. Modification of existing fuel specifications is therefore not required for a HTFT BUFF. A comparison between the bulk composition of LTFT and HTFT fuel for use by the US Military as a BUFF will be presented.