The Threat of an Idling Engine
December 2011 / January 2012
Volume 9 Number 6
Many of us have observed tractor trailers idling away at a rest area and probably regarded it as a waste of fuel, not to mention the negative impacts that engine idling has on the environment. The reality of the situation is that professional truck drivers are mandated by the Department of Transportation to rest for 10 hours after every 11 hours of driving. During this rest period, they must leave their engines running to provide HVAC to the cabin where they sleep and to power other electrical devices onboard the truck.
The 2.2 million diesel trucks that haul goods across the United States every day produce an enormous amount of emissions including an estimated 11 million tons of carbon dioxide, 200,000 tons of nitric oxide and 5,000 tons of particulate matter while wasting over 1 billion gallons of fuel annually. This situation has prompted the adoption of anti-idling regulations, which have created the necessity and perfect commercial opportunity for deploying diesel “auxiliary power units” (APUs) based on solid oxide fuel cells (SOFCs).
SOFCs are electrochemical devices that convert chemical energy from fuel oxidation into electrical energy. Advantages of SOFCs include fuel flexibility coupled with high efficiency, long-term stability and low emissions. SOFC-based power units would allow the truck driver to turn the engine off and obtain power from a cleaner, more efficient power source—a fuel cell. If the efficacy of APUs based on SOFCs can be demonstrated in the niche market of trucking, then the doors will be open for their use in large-scale commercial power plants.
Research conducted at the National Energy Technology Laboratory has focused on addressing this problem. Methods for generating synthesis gas from simple hydrocarbons such as methane (a process known as “reforming”) have been available for many years. These processes routinely involve the use of a catalyst—a material that speeds up the reaction but is not consumed—to make the process economically feasible. The high sulfur and aromatic content of fuels such as diesel poses a major technical challenge, since these components can deactivate conventional metal-based reforming catalysts. Unfortunately, no economically feasible reforming catalyst is available for converting heavy hydrocarbons, such as diesel and coal-based fuels, into hydrogen-rich synthesis gas necessary for use in SOFCs.
To minimize catalyst poisoning while still maintaining high activity, NETL researchers developed the novel idea of incorporating active metals into the crystal structure of a thermally stable material, in this case, pyrochlore. The unique crystalline structure of pyrochlore allows for chemical modifications tailored to reforming properties for specific fuels and reaction conditions. Properties such as activity, selectivity and thermal stability can be effectively altered with various metal substitutions into the pyrochlore lattice. This approach minimizes the poisoning effects that compromise traditional catalyst designs. Development of this technology has resulted in two patent-pending inventions, one for utilization of pyrochlore catalysts in hydrocarbon reforming processes and the other for a method of optimizing the performance of pyrochlore catalysts for a particular application or specific operating condition. Together these inventions help overcome the limitations of current catalysts by efficiently reforming diesel fuel while maintaining thermal stability and resistance to sulfur, aromatics, and carbon formation.
Pyrochlore catalysts are less expensive and longer-lasting compared to currently available heavy hydrocarbon reforming catalysts. Additionally, converting liquid fuels to hydrogen by using air as an oxidant rather than water (as do most commercially available catalysts) will benefit mobile fuel cells by decreasing weight, reducing operating size, and reducing system cost and complexity while maintaining high efficiency. Alternatively, the pyrochlore catalyst also has the ability to use both air and water in varying proportions, making them extremely flexible to system design and consumer requirements.The commercial potential of these inventions has recently been recognized through the execution of an exclusive licensing agreement with the newly formed Pyrochem Catalyst Corporation. This agreement marks the first time that an NETL-licensed technology has been used as a basis for the creation of a startup company. Pyrochem was established with financial support from Pittsburgh-based Innovation Works, an organization that invests in promising new business opportunities throughout the state of Pennsylvania. The successful commercialization of pyrochlore-type catalysts for reforming hydrocarbon fuels may lead to the creation of high-technology jobs in the region. Strengthened by a recently initiated cooperative research and development agreement, NETL will continue to collaborate with Pyrochem Catalyst to further develop pyrochlore catalysts for use in fuel cell APUs to provide non-propulsion power for vehicles, including long-haul truck transport, and to supply power in several military power applications. The technology will also be developed for use in distributed or onsite electricity generation, which is inherently efficient since the electricity is generated near the point of use, reducing energy loss during transmission.
Developing stable catalysts to convert diesel fuel to pure hydrogen is an important advancement in the implementation of fuel cells in areas such as stationary power generation and transportation. The ability to produce hydrogen at the diesel source point will allow for more efficient and economical generation of hydrogen and lead to greater adoption of fuel cell technology. The use of pyrochlore catalysts in conjunction with hydrogen-based fuel cell APUs will reduce the economic and environmental costs of diesel engine idling. Significant monetary savings will be realized through decreased fuel consumption and extended engine life. Environmentally, reduced diesel usage will result in lower emissions of oxides and particulate matter, which has now become more important with the advent of new anti-idling regulations.
Paul J. Battista is a technical writer with Performance Results Corporation, a contractor for the National Energy Technology Laboratory.
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