TECHNOLOGY AREAS: Air Platform, Ground/Sea Vehicles

ACQUISITION PROGRAM: PMA-263, Unmanned Aerial Vehicles (UAVs); Joint Strike Fighter; PMA-290

OBJECTIVE: Develop advanced methods for the desulphurization of logistic JP-5 jet fuel to ensure compatibility with the stringent electrical, operational, and environmental requirements of compact fuel cell systems to be utilized in Naval aviation applications.

DESCRIPTION: JP-5 is currently the most widespread aviation fuel used by the Navy. It is a kerosene-type fuel with a complex mixture of hydrocarbons comprised of hundreds of different major hydrocarbon components, numerous hydrocarbon and non-hydrocarbon components in trace concentrations, and additives. The actual composition will vary depending on the crude source, refinery process, and product specifications. To control chemical and physical requirements of this fuel the military maintains MIL-PRF-5624 specification requirements limiting the amounts of various detrimental elements including sulfur.

Sulfur is a naturally occurring element in crude oil that is detrimental to the operational performance of the fuel cell catalyst required for power generation. MIL-PRF-5624 states that sulfur-containing compounds called mercaptans (which are undesirable because of there corrosive nature and their offensive odor) may not exceed 0.002 mass percent and the total amount of sulfur cannot exceed 0.30 mass percent maximum. The level of sulfur in the fuel has a marginal effect on the specific energy of the fuel but does affect various other characteristics. Commercially, the Environmental Protection Agency (EPA) has mandated "that by 2005 the nation�s largest oil refineries must reduce the sulfur content of gasoline by 90%, from an average of 300 parts per million (ppm) to 30 ppm." Further steps are to be taken to reduce these numbers even more for diesel fuels.

Fuel cells are seen as an enabling technology for both legacy and future aircraft platforms with such benefits as reduced maintenance, increased fuel efficiency, and reduced emissions. The ONR and NAVAIR are currently working on a program to develop a compact (micro-scale) fuel cell reformer for naval aviation applications to enable the transition of desulphurized JP-5 jet fuel into a pure hydrogen fuel required for fuel cell power generation. The two primary fuel cell types currently being investigated for Naval aviation applications are Proton Exchange Membrane (PEM) and Solid Oxide Fuel Cell (SOFC). Many more types are currently available and are still in consideration for use. Under this program effort, it was determined that the sulfur content of the JP-5 fuel had a severe detrimental effect on the maintenance and life of the fuel cell by reducing catalyst activity and inhibiting cell life.

The Navy and other DoD agencies are investigating state of the art desulphurization technologies for shipboard, ground, and other applications. Most current efforts are being developed for large-scale process methods for stationary or shipboard applications. Such methods include hydrodesulphurization, catalytic distillation, sulfur adsorbents, and fuel distillation. The requirements for these defense applications, and as a result the requirements for the desulphurization process, differ considerably from Naval aviation requirements. When possible, this effort will leverage the desulphurization technology being developed under other Navy and DoD efforts, however there are specific Naval aviation requirements that will guide the research and innovation.

To address these differences, it is the intent of this topic to focus innovative research on solving the technical challenges associated with reducing sulfur content in logistic JP-5 jet fuel to minimize damage and increase life of the fuel cell system while also meeting the stringent size, weight, electrical, operational, and environmental requirements of Naval aviation applications. The goal is to reach sulfur levels in the low parts per million (ppm) to parts per billion (ppb) region. The desulphurization process must be integrated and operated with the compact 1 KW breadboard fuel processor and fuel cell system that is currently being developed by ONR and NAVAIR for Naval aviation applications. Due to severe size and weight restrictions, Naval aviation applications require very compact fuel cell systems. The desulphurization process and the purity of the hydrogen produced will have a significant impact on the power density of the overall fuel cell system. Operational requirements include cold temperature start (-55C), short start-up times (1-8 minutes), short duty cycles (1-2 hours on and 22-23 hours off per day, operating daily), air supply/intake (not available in purified form), and water management (no storage, water must either be recycled or removed). Electrical requirements include MIL-STD-704 power quality, high load inrush currents, rapid response to load changes, transients, and faults. Environmental requirements include temperature (-55C to 91C), altitude (up to 70,000 ft), shock (20G/11ms operational, 40G/11ms crash), vibration (17G functional, 28G endurance), and EMI (MIL-STD-461). In addition to meeting these requirements, the desulphurization process and overall fuel cell system must prove to be cost-effective including meeting applicable acquisition, maintenance, reliability, and other operations and support goals. Applicable Naval aviation requirements will be further defined throughout the solicitation process. Results of this effort should include the design, development, and testing of new or improved processes for sulfur removal including but not limited to advanced catalysts, adsorbent beds, reforming reactions, hydrodesulphurization, or various other desulphurization concepts. This topic can also be extended to current JP-5 use to minimize pollutants and maintain adherence to current and future military regulations and/or EPA civilian mandates.

PHASE I: Define a technical approach and develop an implementation plan for the desulphurization of JP-5 jet fuel to be compatible with the 1KW breadboard fuel processor and fuel cell system that is currently being developed for Naval aviation applications. The proposed desulphurization process must be compatible with the stringent size, weight, electrical, operational, and environmental requirements of Naval aviation applications. Validate the approach analytically or provide test data or bench top hardware that would validate the approach.

PHASE II: Design, develop, and demonstrate a prototype system for desulphurizing JP-5 jet fuel for Naval aviation applications. Demonstration can include a high-fidelity laboratory environment and/or aircraft ground demonstration.

PHASE III: Package and integrate the desulphurizing system into a complete fuel cell system. Perform a functional evaluation of the reduced-sulfur content JP-5 fuel displaying the improved performance of the overall fuel cell system. Perform a flight evaluation of the fuel cell system.

PRIVATE SECTOR COMMERCIAL POTENTIAL/DUAL-USE APPLICATIONS: The successful implementation of a refining process for minimizing or removing sulfur in JP-5 jet fuel can be widespread and range across various gasoline or diesel sulfur-containing fuels. The commercial aviation industry can utilize the technique and/or process to further reduce there operating costs and adhere to EPA and FAA mandates for reduced environmental emissions. Benefits could also carry into the commercial fuel cell sector with a primary impact on reforming operations.

REFERENCES:
1. An Emissions Mission: Solving the Sulfur Problem; Oak Ridge National Laboratory ReVIEW Magazine http://www.ornl.gov/info/ornlreview/v33_3_00/emissions.htm, Vol. 33, No. 3, 2000.

2. Aviation Fuels Technical Review, Ch. 5, Aviation Turbine Fuel Refining, Chevron Product Corporation http://www.chevron.com/prodserv/fuels/bulletin/aviationfuel/5_at_fuel_refining.shtm, 2004.

3. MIL-PRF-5624, Performance Specification, Turbine Fuel, Aviation, JP-5.

KEYWORDS: desulphurization; reforming; sulfur; JP-5 jet fuel; fuel cell

TPOC: Sean Field
Phone: (301)342-0816
Fax: (301)342-4781
Email: [email protected]
2nd TPOC: Clifford Bedford
Phone: (703)696-0437
Fax: (703)696-4274
Email: [email protected]

** TOPIC AUTHOR (TPOC) **

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