Fischer-Tropsch Fuel for Use by the Us Military as Battlefield Use Fuel ofthe Future

摘要

The United States Department of Defence (DoD) currently uses a single kerosene-type fuel forrnall its gas turbine and diesel engine applications. Technological changes introduced to thernbattle space make the single battlefield fuel philosophy of the DoD less prone to the use ofrncrude-oil derived kerosene-type fuel. The DoD initiated a three phase Joint Battlefield Use Fuelrnof the Future (JBUFF) program to evaluate, demonstrate, certify and implement turbine fuelsrnproduced from alternative energy resources such as Fischer-Tropsch (FT) fuels for use in allrnits gas turbine and diesel engine applications. Sasol Synfuels International (Pty) Ltd, amongstrnothers, was invited to participate in the program with the objective to supply the DoD with a FTrnBUFF that conforms to fuel volatility and low temperature fluidity requirements. Thesernrequirements included a freezing point of -47 °C, viscosity of 8 cSt at -20 °C and a flashpoint ofrn38 °C for a BUFF conforming to "Jet Propellant # 8" (JP-8) specifications and a flashpoint of 60rn°C for a BUFF conforming to JP-5 specifications for the handling of fuel on aircraft carriers.rnTechnical, economic and strategic challenges related to the introduction of FT fuels into thernmilitary fleet include the interchangeability of FT fuels with crude-oil derived kerosene-typernfuels; elastomer compatibility of fuel systems already conditioned in crude-oil derivedrnkerosene-type fuels with subsequent exposure to FT fuels containing no aromatics; demandrnand supply of FT fuels at a price comparable to crude-oil derived kerosene-type fuels; and thernmodification of existing fuel specifications to allow for general approval of FT kerosene-typernfuel. Although the DoD is more interested in Coal-to-Liquid (CTL) technology, fractionator feedrnfrom the Gas-to-Liquid (GTL) Products Work-Up Demonstration Unit in Sasolburg, SouthrnAfrica, was used to evaluate the possibility of producing a BUFF fraction from the Sasol SlurryrnPhase Distillate TM (SPD TM ) low temperature FT (LTFT) and Chevron ISOCRACKING?rntechnology. The fractionator feed used to develop a BUFF from the Sasol SPD TM LTFTrnprocess contains only normal and iso-paraffins with virtually no aromatics or naphthenes.rnConcluded from the study was that the production of a synthetic BUFF is feasible using thernSasol SPD TM technology alongside the current Chevron ISOCRACKING? technology. Alsornconcluded from the study was that the Sasol SPD TM LTFT BUFF product yield and the FBP ofrnthe product will be restricted by the freezing point requirement due to the low iso to normalrnparaffin ratio of ~1:1 of the Sasol SPD TM LTFT BUFF and not by the maximum viscosityrnrequirement like the "Single Battlefield Fuel" of the Syntroleum Corporation (S-5) which has anrniso to normal paraffin ration of ~14:1. One would therefore need to optimize the hydrocrackingrnprocess conditions to increase the product yield. Sasol recently demonstrated that fullyrnsynthetic high temperature FT (HTFT) aviation turbine fuel, produced at Sasol Synfuels inrnSecunda, South Africa, is fit-for-purpose for commercial use. The fully synthetic HTFT aviationrnturbine fuel comprises of blends of hydrocracked tar liquid, light distillate refinery streams andrniso-paraffinic kerosene. It differs from Sasol SPD TM LTFT kerosene in that it containsrnnaphthenes and aromatics resulting in a comparable elastomer response with crude-oilrnderived 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 thernmilitary fleet. It further conforms to all JP-5 specifications with properties and characteristicsrnthat are typical of conventional, crude-oil derived aviation turbine fuel. Modification of existingrnfuel specifications is therefore not required for a HTFT BUFF. A comparison between the bulkrncomposition of LTFT and HTFT fuel for use by the US Military as a BUFF wi