In the middle of Georgetown University's pleasant campus squats a windowless brick building, carefully designed to fit in with its surroundings. Nothing gives away its function.

Although the building has no belching smokestack, it is in fact a power plant using new technology to burn high-sulfur coal in an urban area for the first time since the environmental era began a decade ago.

What emerges into the atomsphere above the power plant is just hot air -- with none of the sulfur fumes or ash that the U.S. Environmental Protection Agency and local jurisdictions prohibit under the terms of local laws and the U.S. Clean Air Act of 1970.

"A lot of people on this campus still don't know we're operating a coal plant," said Dennis Shaff, manager of the plant.

The U.S. Department of Energy footed most of the $16 million bill for the project as part of its program to promote new coal technology.

Far more coal is available in the United States than oil or natural gas, although coal supplies only about 20 percent of the nation's energy. Coal is also the dirtiest of the fuels, and high-sulfur coal, the most abundant, is the dirtiest kind of coal.

Energy experts from around the nation and the world regularly visit the Georgetown plant, and the Energy Department is now studying the results of the operations since the plant opened a year ago.

So far, the results are inconclusive although Shaff said the plant has had "more than our (fair) share of debugging" and has been so costly to run that he was "embarrassed" to disclose cost figures.

Shaff and DOE officials said, however, that power plants typically have many problems when they go into operation. They said they expect the Georgetown plant to be operating efficiently at full power in the near future. g

The new coal-burning process is called "fluidized-bed combustion." Crushed limestone is held in swirling suspension -- or "fluidized" -- above the floor of the boiler by air blasted in through thousands of tiny holes in the floor. Crushed coal is spewed in and burns on top of and mixes with the limestone.

The limestone absorbs the sulfur from the coal, becoming calcium sulphate and calcium oxide -- a hard, dry grainy material that is continuously drained out of the boiler as new limestone is added.

Ash that flies out the top of the boiler is captured in a "baghouse," a machine that operates exactly like a giant vacuum cleaner. Thus, the plant spews forth nothing but the hot air.

In contrast, in a standard coal boiler the coal is simply spewed in and burned. And sulfur in the coal goes into the atmosphere in fumes unless it is removed by a "scrubber" -- the only other technology available for removing sulfur from burning coal.

Many utility companies -- although not the ones in the Washington area -- have had to install the big, unreliable, multimillion-dollar scrubbers on their smokestacks to meet clean air requirements.

In the Washington area, the Pototmac Electric Power Co. and Virginia Electric and Power Co. have met clean air requirements by burning low-sulfur coal, which is not as plentiful as the high-sulfur variety in the East and which is somewhat more expensive.

"Scrubbers are expensive and sometimes difficult to operate," said DOE spokesman Robert C. Porter. "They produce a wet sludge that never dries out and is difficult to dispose of."

On the other hand, the dry by-product of the new process may be useful in agriculture and construction, officials said.

Orus L. Benett, a research scientist with the U.S. Department of Agriculture, said the by-product may be used in place of limestone to treat acid agricultural soils.

"You may have to use more than you would of limestone to get the same benefit, but you could probably get this free for hauling it off from a power plant," Benett said "Limestone cost $10 to $15 a ton."

Officials said the material may be useful in road construction and even to make cinderblocks -- but all applications are still in an experimental stage.

Even if the material weren't useful, however, it would still be easier to handle and dispose of than the toothpaste-like sludge disgorged by scrubbers.

While the Georgetown plant appears to be headed for a successful demonstration of the new technology, many problems remain and officials say it may be a decade or more before the nation's big electric utility boilers -- 20 times or more the size of the Georgetown plant -- begin to use the process.

Vepco, for example, is planning to convert 10 power plants from oil to coal before 1984 -- but it has no plans to use either scrubbers or the new process. Instead, the company will try to buy low-sulfur coal.

"The technology hasn't been proven yet for large boilers," said Morris Brehmer, Vepco's manager for environmental services." . . . We just don't know yet (if the new technology is) economical."

Pepco is already burning about 85 percent coal in its system, but has no plans to use the new process soon for much the same reasons that Vepco hasn't.

DOE officials say it is important to perfect the new technology to help the nation decrease its dependence on foreign oil, and they think that in addition the new technology may provide cheaper energy than the old coal-burning technology.

But that contention is based on preliminary data. Terry Lund, a scientist with the Electric Power Research Institute, an electric-utility funded research organization, said that "cost estimates vary" on the new process and it is by no means clear yet that it is cheaper.

For one thing, Lund said, the chemical reaction of the limestone requires so much heat that it can lower boiler efficiency as much as 5 percent from what it would have been had coal alone been burned.

Scientist are working to correct this problem.

"If we can reduce the amount of limestone (needed in the process), then we can reduce the cost sufficiently to show a cost advantage," Lund said.

Lund said a key to getting good limestone performance in the new process is proper reinjection of ash into the furnace. Shaff, the Georgetown project manager, said his ash reinjectors have given him a good deal of trouble.

The Georgetown plant has been out of operation about two-thirds of the time during its first year. Lund said, however, that the plant showed a "good achievement. It operates stably and I know they've removed as much sulfur as required."

Federal energy officials and others said that coal now provides about 20 percent of the nation's total energy supplies, but that that figure may rise to 30 percent in the decades ahead. They said the country has enough coal to last for hundreds of years.

While much of that coal will eventually be squeezed for liquid "synfuels," "the majority of the coal that we use between now and the end of the century will be burned directly," according to DOE spokesman Porter. He said more and more of this coal will be burned in boilers like the one at Georgetown.