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Sulfur Tolerant JP-8 Reformer


OBJECTIVE: Develop a highly sulfur-tolerant fuel reformer for JP-8 and highway diesel fuel, for use with a sulfur-tolerant Solid Oxide Fuel Cell (SOFC) in a compact, 20-kilowatt (kW) net output system. DESCRIPTION: In order for Fuel Cell based Auxiliary Power Units (APUs) to meet the increasing power demands in the limited space claims available on combat and tactical vehicles, further development of sulfur-tolerant components is essential. TARDEC has developed and will be testing 7-10kW fuel cell based APUs that operate on JP-8 fuel, the U.S. single battlefield fuel. These APUs allocate up to 30% of their volume to hardware that removes sulfur-bearing molecules from JP-8 before it is reacted in the fuel reformer. Without desulfurized JP-8, the reformer and the fuel cell downstream would be poisoned. A sulfur-tolerant reformer would eliminate the need for JP-8 desulfurization, but would convert sulfur in the JP-8 into hydrogen sulfide (H2S) gas, a fuel cell poison, in the reformate (fuel gas). To deal with H2S, it can be absorbed with a compact, effective zinc oxide filter, a sulfur-tolerant fuel cell can be used, or a combination of the two approaches. This proposal is to develop a sulfur tolerant reformer capable of supporting a 20kW APU. Developing a reformer that does not require sulfur to be removed from the fuel is one of two essential pieces needed in a sulfur tolerant APU design, the other being the fuel cell stack. TARDEC is currently developing a Sulfur Tolerant Solid Oxide Fuel Cell stack through an Army SBIR that has successfully completed Phase 1. Aligning the sulfur tolerant reformer program to integrate with the sulfur tolerant stack program has the potential to deliver the high power density fuel cell APU system that is quiet, efficient and has reduced system complexity compared to other fuel cell APU systems and especially conventional engine based APUs. This technology has support from both the Office of Naval Research (ONR) and Air Force Research Laboratory (AFRL), making it a multi-service program. PHASE I: The contractor shall design a reformer to provide sufficient flow of reformate gas for a 20kW SOFC, assumed to operate at 40% efficiency at rated power. The reformate gas delivered to the fuel cell must have a sulfur content not exceeding 50 parts per million volume (ppmv) when processing JP-8 with a sulfur content of 3000 parts per million by weight (ppmw), and it is assumed that gas-phase sulfur removal will be used to limit sulfur levels in the reformate. Further, the reformate must contain less than 40 ppmv of two-carbon or higher-carbon reforming by-products to deter coke formation in the fuel cell system. PHASE II: The contractor shall build the reformer designed in Phase I, with automatic controls, and operate it for 2000 hours to demonstrate capability to operate on ultra-low sulfur diesel (ULSD) fuel and on JP-8 at typical sulfur levels (about 600 ppm) and maximum sulfur levels while delivering the required reformate quality. The contractor shall demonstrate through packaging studies how the reformer would be packaged with a sulfur-resistant SOFC. PHASE III: Military uses of the design are the Abrams tank ECP 2 and other future combat vehicles; power for medium Unmanned Ground Vehicles (UGVs) and for special operations all-terrain vehicles. The intended commercial applications are as a power source for refrigerated semi-trailers, and as a quiet substitute for mobile diesel generators. The core sulfur-resistant reforming technology can be adapted to SOFC power systems ranging from a few kilowatt to hundreds of kilowatts with diverse applications in aircraft APUs, recreation vehicles, marine craft and ships, that variously use jet fuels, commercial highway diesel fuel, compressed natural gas and propane.
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