In a small manufacturing plant on the edge of an icy pond just off the Rappahannock River, Atlantic Research Corp. is making coal pure'e, a new entry into the energy market.

The company is betting that its ARC-COAL fuel slurry--a glossy, viscous mixture that is 70 percent coal, 29 percent water and 1 percent additives--can replace fuel oil used industrially at a cost approximately 30 to 40 percent lower.

Atlantic Research is one of four companies that have a patent on similar coal-water mixtures, but it is the only one, so far, to go into commercial production. Production is 600 barrels a day. That is enough, the company hopes, to give it experience in manufacturing and to supply the needs of customers who want to test it.

"They're beginning to line up now," said Charles Henderson, senior vice president for research and technology. "The people who might use this stuff want to see the plant to make sure it's real."

The mixture is not coal slurry. In coal slurry, the water is there only for the ride, helping carry the coal to its ultimate destination through a pipeline. At the end of the pipeline, the water is removed.

Fuel slurry is a mixture of tiny coal particles, water and additives that help the particles repel each other and keep the mixture from settling. The slurry looks like thin chocolate icing and feels like talcum powder. But when you dip your fingers into the slurry, the water quickly runs off, leaving behind a dry, powdery residue of coal dust.

The particles vary in size, allowing a heavier concentration of coal than would particles of the same size. It is the mix of particles and the additives, which keep the mixture from settling for three months, that makes Atlantic Research's slurry workable, according to Richard Passman, director of the ARC-COAL operations.

The coal arrives at the company's plant in railroad cars, is fed into a crushing device, then into a vat for preliminary blending. It emerges looking like rough concrete and is put through a ball mill (a tank full of metal balls that pulverize the coal) for a finer grind. From there, it goes into tanks to await shipment. ow fast the fuel slurry market develops hinges, in large part, on where oil prices go. "One can't be sure when the window of opportunity opens fully," said Jerry Karaganis, vice president for economics and statistics for the National Coal Association.

First, customers must make a commitment to using the product, said Karaganis. "Then the question is how rapidly it will expand, and I would say by the late 1980s, it would begin expanding rapidly."

"I think it's got some super implications for quality coal use," he said.

So far, Atlantic Research Corp.'s only customer is the Department of Energy, which has bought some of the mixture for testing in a laboratory in Philadelphia. Atlantic Research officials also say that a major chemical company is close to signing a contract for enough ARC-COAL to burn in an industrial boiler for a month. That test would be conducted in cooperation with the Electric Power Research Institute (EPRI), which joined with DOE in providing some of the funding for Atlantic Research's early work.

"Going from something that is do-able to commercial is a very hard thing, because no one wants to be first," said Passman.

The company hopes that, by the end of the year, a utility company will be sufficiently interested to contract for a commercial-sized plant to produce fuel slurry for its needs. The earliest such a plant could be built would be 1986, Passman said.

The coal used to produce the mixture is a low-sulfur, low-ash coal selected to meet the air quality standards for new energy sources for utility companies.

Atlantic Research built the Virginia plant on leased land south of Fredericksburg because of its access to a river and rails and because it was reasonably close to the company's Alexandria headquarters. Atlantic Research also manufactures solid-propellant rockets and commercial and military electronics.

So far the company has spent nearly $6 million on its development of ARC-COAL, including $2.5 million invested in the plant. The project began in 1976, when Atlantic Research began manufacturing small quantities in Alexandria. Then, two years ago, the company built a facility in Alexandria that could produce a barrel an hour. Last year, production was boosted to three barrels an hour.

In the small laboratory at the plant, technicians use a Waring blender and a Kitchenaid mixer to make up new recipes combining the right additives with new varieties of coal. As simple as the product sounds, manufacturing it is not, said Henderson.

"It's not that easy to do. If you just grind up coal and put it in water, it looks like wet sand."

EPRI began testing the water-and-coal fuel slurry after tests with a coal-oil mixture proved economically disappointing. Subsequent tests indicate that the fuel slurry is promising, said Manfred Rolf, EPRI project manager for alternate fuels.

"The underlying question, of course, is what will happen to the future price of oil," he said. Rolf added that the coal-water mixture has other benefits in addition to the economic arguments in its favor. "If it is put into use, it makes us less dependent on oil," he said. "Economics are important, but availability of fuel is important also."