13-03-04
The Air Force's search for a jet fuel that doesn't break down under high heat could lead it to a hard, bright black mineral identified with propelling the steamships and locomotives of the industrial revolution, instead of modern aircraft.
After about 15 years of study, scientists at Pennsylvania State University say
they are getting ready to test a fuel, half of which is derived from coal, which
they believe can provide the stability required by the ever-hotter-burning
engines in fighter jets.
Not only that, but Penn State scientists say they have removed a major
obstacle to producing a coal-blended fuel by coming up with a way to make it in
an existing refinery, instead of building a new one. And if they can sell off
some of the by-products, they believe that getting fuel from coal could finally
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.
The progress comes at a good time, when politicians are clamouring to reduce
the country's reliance on foreign oil. For Pennsylvania, which has lost 75 % of
its coal production since 1918, the peak year, there are hopes that the project
could mean more work in depressed areas still marked by piles of black coal slag
and shuttered mines.
Clean-energy advocates question whether the fuel can be environmentally sound,
and competing researchers say they are working on 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 Air Force engine
specifications.
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, who is involved in the project. "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."
Penn State 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.
Now, after simulating refinery and engine combustion processes in their
laboratory, the scientists 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. They say they are realistic about the challenges ahead, and are working
hard to ensure that they satisfy the Air Force, refineries and engine makers.
"It's not like we're a bunch of nut-case professors in their laboratory
dreaming something up," Schobert said.
While the initiative and money for the project have come from the Air Force,
Penn State scientists are looking to develop fuel formulas that could power the
country's military and commercial aircraft, which together consume about 35 bn
gallons of fuel a year, at least during peacetime. Such broad use could mean
eventually replacing up to 1.5 mm barrels of the 9 mm to 10 mm barrels of crude
oil that the United States imports each day, Schobert said.
"The principle application is for fighter jets, but we're trying to make it
as similar to existing jet fuel as we possibly can," Schobert said.
The intriguing element of the coal-blended fuel is its ability to remain
fluid in temperatures reaching 900 degrees. Currently, the Air Force uses fuels
that, with additives, can remain stable up to 400 or 425 degrees, Harrison said.
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.
In a jet engine, fuel also serves as a coolant. When exposed to high enough
heat, fuel can break down into what Harrison described as "gums and
varnishes," creating a constant maintenance problem. The solids gradually
build up and plug engine valves or fuel injectors, "like clogging your
arteries," he said.
Fighter jets are always achieving higher speeds -- and hotter temperatures --
as engine technology advances. But the heat-resistant properties in jet fuels
have not similarly advanced, Harrison said. The result, he said, are engine
designs that must adjust for the heat limitations of existing fuels.
"If you look at commercial aviation fuel 30 years ago vs. today, they're
nearly identical," Harrison said. But "in the military, we've made a
series of improvements over that period" in engines and fuel additives.
For the Penn State scientists, a number of hurdles remain. They need more
than the $ 2.5 mm a year they have been getting from the Air Force to follow
through with tests that could convince the military, commercial refineries and
engine makers that the fuel is viable, Schobert said. About $ 30 mm over four
years would do it, he said, and Pennsylvania's representatives in Congress have
pledged to request the money.
While the coal-blended fuel would improve upon the sulphur emissions from
conventional jet fuel, the scientists say they must significantly reduce its
soot emissions if the fuel is to work in all military engines. And the country's
commercial refineries must be able to produce it at a cost that is competitive
with refined crude.
One refinery executive who has consulted on the project said the long-term
goal is for his refinery to produce the jet fuel, but it is too early to say
whether it is possible. Robert Ennis, the vice president of planning and
engineering for United Refining Co., said he has not seen a final formulation or
production flow chart for the jet fuel.
"Participating in research is one thing," Ennis said. "Making a
statement on economic viability is another thing."
Clean-energy advocates note that creating a fuel that is both economically and
environmentally viable is a tall order that many researchers have failed to
satisfy, and cautioned that using coal could result in a bigger problem for air
quality. The project's goals are "admirable," said Nathan Willcox of
PennEnvironment, but he worried that it was "taking one dirty fuel and
turning it into another dirty fuel."
Federally funded research on technology to gasify coal and blend it with oil
is happening at the University of Kentucky, and would result in a much cleaner
fuel, said Gerald Huffman, a professor of chemical and material engineering at
the school.
While 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, pushing any coal-to-fuel project
across the finish line 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 bn of our trade deficit is
because of all this oil we're importing."
Source: The Associated Press