Coal-based Jet Fuel in the Pipeline
E COLLEGE, Pa. -- With coal getting more attention as crude oil and natural gas prices climb, Penn State scientists believe the fuel can help the nation's military jet fighters fly.
Scientists are blending coal with refined petroleum to create a jet fuel that won't break down in military planes' extremely hot engines. And they say they can produce this new fuel by retrofitting an existing refinery, instead of building a new one, in a process that can be less expensive than refining crude.
"This looks eminently doable," said Harold Schobert, a professor of fuel science and the director of Penn State's Energy Institute.
But whenever coal is raised as a possible alternative energy source, so are questions about its tendency to pollute the air.
Clean-energy advocates question whether the jet fuel is environmentally sound, and competing researchers say they are developing a different coal-to-fuel technology that would be cleaner, but require the construction of refineries.
Without real production or engine tests, it is too early to say whether Penn State's fuel can succeed in the marketplace and satisfy all engine specifications, Air Force and refinery consultants on the project say.
Penn State scientists "are doing things that have never been done before," said Bill Harrison, an Air Force fuels expert at Wright Patterson Air Force Base in Dayton, Ohio. "It's a novel way of using coal with petroleum to make fuel, [but] we always look to see whether this can be commercially viable."
Still, the scientists say they have come a long way since the early 1990s, when they first sat down to figure out why jet fuels broke down into solids under the high heat of jet engines. After simulating refinery and engine combustion processes in their laboratory, researchers believe they could be a year away from running a large-scale production test, and perhaps two years away from trying it out in a jet.
Although the initiative and money for the project have come from the Air Force, the Penn State scientists want to develop fuel formulas that could power both the country's military and commercial aircraft.
"The principal application is for fighter jets, but we're trying to make it as similar to existing jet fuel as we possibly can," Schobert said.
A problem for the military is that although its engines have advanced in the past 30 years, propelling its jets ever faster, fuel technology has remained largely the same, Harrison said.
In a jet engine, fuel also serves as a coolant. When it breaks down, it forms what Harrison described as "gums and varnishes," plugging engine valves or fuel injectors and creating a constant maintenance problem.
Currently, the military uses fuels that, with additives, can remain stable up to 400 or 425 degrees, Harrison said. The intriguing element of the coal-blended fuel is its ability to remain fluid in temperatures reaching 900 degrees.
Coal has molecules that more readily share hydrogen atoms under intense heat, keeping the fuel fluid and shutting down the chemical reactions that result in the formation of solids, Schobert said.
For the Penn State scientists, hurdles remain.
To test the fuel, they'll need more than the $2.5 million a year they have been getting from the Air Force. And although the coal-blended fuel improves upon sulfur emissions from conventional jet fuel, they'll need to significantly reduce its soot emissions.
Clean-energy advocates note that creating a fuel that is both economically and environmentally viable is difficult, and they cautioned that using coal could result in a bigger problem for air quality.
Meanwhile, at the University of Kentucky, federally funded research on technology to gassify coal and blend it with oil is continuing, and would result in a much cleaner fuel, said Gerald Huffman, a professor of chemical engineering at the school.
Although this process would require the construction of a multibillion-dollar refinery, tightening federal air-quality standards could make Penn State's project impractical, Huffman said.
That aside, taking any coal-to-fuel project to completion is going to take more support from the federal government, Huffman said.
"What it's going to take," he said, "is for someone in the federal government to wake up and say . . . $150 billion of our trade deficit is because of all this oil we're importing."
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