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Clean liquid fuel from coal possible, but it'll cost

Monday, December 23, 2002

By Byron Spice, Post-Gazette Science Editor

Researchers from five universities, including the University of Pittsburgh, are developing a process to turn dirty-but-abundant coal into a liquid fuel so clear "you'd swear it was water."

"It's crystal clear," said the University of Kentucky's Gerald Huffman, director of the Consortium for Fossil Fuel Science. Whether formulated as gasoline, diesel or aviation fuel, it burns with little smoke.

The only problem is, it costs 30 percent to 40 percent more than fuels made from petroleum.

Driving down the cost of the process is a major goal of the consortium, which has signed a three-year, $5.7 million contract with the U.S. Department of Energy's National Energy Technology Laboratory.

At the heart of the process is something called C1 chemistry, which involves breaking down carbon-containing materials like coal and natural gas into carbon monoxide and hydrogen gas, which together are known as synthesis gas.

"Once you have this synthesis gas, you can make any petroleum product," said Irving Wender, professor of chemical and petroleum engineering at Pitt.

It's a process different from coal liquefaction, a technology explored following the 1970s energy crisis but eventually discarded as impractical.

Instead, coal is "gasified" by heating it to 1,800 degrees and blasting it with steam. Carbon monoxide and hydrogen are released, leaving a residue that can be used for road paving, Wender said. In what is called the Fischer-Tropsch process, iron or cobalt catalysts are then used to drive reactions between carbon monoxide and hydrogen to produce various fuels.

It takes a ton of coal to produce three or four barrels of Fischer-Tropsch fuel, Huffman said.

The process, named for the pair of German coal researchers who invented it in 1923, was used by Germany to make fuel during World War II, Wender noted. But the Germans lacked a good way to remove sulfur from the fuel, which limited its use.

Researchers in South Africa subsequently solved the sulfur problem and the process is used at a number of plants there. U.S. companies have opened 14 pilot plants that use the Fischer-Tropsch process, Wender said, but all use natural gas as a feedstock, not more abundant coal.

Huffman said the military might be one of the first customers for the synthesized diesel and jet fuel because it may be willing to pay a premium for fuel supplies that are not subject to foreign disruption. Fischer-Tropsch diesel fuel already is being imported to California for use as an ultraclean additive to standard diesel.

In the meantime, the consortium is working to increase the efficiency of the process. At Pitt, Wender and his colleagues are trying to improve the iron and cobalt catalysts and gain a better understanding of exactly what is happening in the Fischer-Tropsch process.

Huffman said consortium scientists also are looking at novel processes that increase the oxygen content of the fuels, allowing them to burn even cleaner. And Kentucky researchers in particular are focusing on ways of maximizing the production of hydrogen from coal and natural gas; hydrogen is the fuel most favored for use in fuel cells, which convert fuel directly into electrical power without combustion.

Byron Spice can be reached at bspice@post-gazette.com or 412-263-1578.

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