University researchers have successfully powered a helicopter jet engine with fuel derived from at least 50 percent bituminous coal, a percentage that could go half again as high.
"We have shown in tests that the mix can go to at least 75 percent coal," said Harold H. Schobert, professor of fuel science and director of Penn State's Energy Institute.
The fuel, provisionally named JP900, is produced in one of two processes under investigation by Schobert. Both processes use light cycle oil, a petroleum by-product and coal derived refined chemical oil a by-product of the coke industry. The researchers mix those two components and then add hydrogen. When distilled, jet fuel seeps off as a distillate.
Schobert's coal-based fuel provides several advantages over existing military and commercial jet fuel.
"Combustion tests show that JP900 meets or exceeds almost all specification for JP8 and Jet-A," Schobert said. Schobert presented his results at the March meeting of the American Chemical Society in Atlanta.
These tests showed that JP900 has a flash point higher than required for JP8, a lower viscosity and freezing point and a higher smoke point. The coal based fuel is also lower in aromatics compounds such as benzene and toluene, than conventional jet fuels and is almost sulfur free.
From an energy point of view, JP900 produces almost exactly the same BTU as JP8.
Coal-based fuels could also reduce dependence on imported petroleum for jet fuel purposes by about one half, a benefit looking all the more attractive now that the price of oil has soared to all-time highs.
A Military Secret
Schobert's project began originally to develop jet fuel for the next generation of high performance military aircraft that would require thermally stable fuels. The U.S. Air Force Office of Scientific Research is funding this work, with help from the Department of Energy.
"Initially, the goal of this research was to develop a fuel that could also be used as a heat sink on board aircraft, in addition to the obvious role of providing the propulsion energy," Schobert said.
Such a fuel would be useful for the F-22, Joint Strike Fighter and F-35. However, according to Schobert, in the recent past, the Air Force has suggested that the focus be shifted to the development of a "drop in" coal based replacement for current JP 8.
While the JP900 fuel was created for and funded by the military, it could eventually find its way into wing tanks of commercial jetliners.
Tailoring this fuel to meet JP-8 specifications basically means that it would also be equivalent to Jet-A or Jet A-1. Therefore, it could be used, in principle at least, as a replacement for those current commercial fuels.
Schobert said commercialization depends on two factors. The first is being able to 'qualify' the fuel for use and the second, economics.
"We do not yet have a solid economic evaluation of this fuel," he said. One of the refiners in the private sector has said they would want to make 50,000 barrels of fuel, equivalent to running 5,000 barrels per day for ten days, to get reliable engineering data on which to base an economic analysis.
That much production is beyond the present scope of the project.
So far, Schobert has produced only 500 gallons of a prototype fuel, and that was shipped to the Air Force Research Laboratory, Wright Patterson Air Force Base, for testing. The results of that work included the successful operation of a T-63 turboshaft engine.
"I can tell you that two major U.S. airlines have expressed some interest in this fuel and I have briefed some fairly high level managers from one of them," Schobert said. Schobert declined to name the airlines, but said they are national or international carriers.
A coal-based jet fuel intrigues some aviation experts.
"If JP900 is found to be a proper replacement for Jet-A (which is kerosene based), it is conceivable that the jet fleet could eventually switch over to the new fuel after FAA certification," said Will Alibrandi, an Aero Gas Turbine Analyst for the aviation market analysis firm, Forecast International. Alibrandi said the big obstacle will be the cost to produce this fuel compared to the petro-based jet fuels currently being used.
Schobert said the process that creates JP900 can be carried out in existing refineries with some retrofitting and small amounts of the leftover components will feed into various portions of the petroleum stream. The lighter portions will go to the pool of chemicals that make gasoline and the heavier ones go to the diesel or fuel oil streams.
"The advantages of JP900 would have to be weighed against the cost and environmental considerations, although the applications for such a fuel could be wide ranging," Alibrandi said.
This is not the first time coal has been used to produce fuel. In the late 1930s, one of the ways Hitler's National Socialist Party sought economic self sufficiency for Germany was to replace imported oil with an alternative fuel derived from domestic coal.
When the Allies bombed German oil refineries, the Germans were forced to put the technology into operation. By the end of World War II, they were producing millions of barrels of coal-based fuels. "It is amazing that we are only now considering replicating technology that existed in production format 60 or more years ago," said military technology expert Ned Barnett. Barnett said as long as petroleum was relatively cheap and plentiful, there was no incentive to confront the entrenched oil industry with alternative technologies.
"After the second OPEC oil embargo, we flirted with many alternate technologies during the Carter years, but once OPEC's back was broken as an effective price fixing force, those initiatives died away, even when they worked and made sense," he said.
Since cheap, plentiful oil is a thing of the past, one solution may lie in coal-based fuels. "We clearly have more coal than oil," Barnett said.
Change Takes Time
The switch to coal-based fuels, if it ever comes, will require a monumental paradigm shift in the energy industry.
Barnett doesn't think a switch to coal based fuels will happen commercially until the country is faced with a stable price of five dollars per gallon gas and then only if coal gas could provide the same BTU power at a stable price of about three dollars a gallon.
"It would take that kind of cost differential to drive infrastructure, and regulatory reform," he said.
The bigger issue pertains to the infrastructure—getting coal based fuel into a parallel distribution with petro fuels, assuming the oil-based and coal-based fuels couldn't be mixed for technological or regulatory reasons.
"This will be hugely expensive, at least at first and the government will likely have to fund that," Barnett said.
Any transition to coal-based fuel may in fact be led by Asian or European nations, who have less indigenous oil, more available coal, and a huge, growing demand for fuels of all kinds. One thing is certain. Aviation is not likely to be the leader.
"The aviation industry, whose major focus is on safety, is remarkably cautious," Barnett said.