Cleaning up Midwest coal
When it comes to coal, America's West has a clean advantage over the Midwest. The comparatively low sulfur content of Western coal has made it a favorite - even after adding shipping costs - of many electric utilities and industries, which must hew the line on clean air rules.
But Illinois researchers are ow experimenting with a new coal-cleaning method that could bring the heartland's rich reserves of ''dirty,'' high-sulfur coal back into a much more competitive position.
Research under way at the new Illinois Center for Research on Sulfur in Coal aims to get as much as 90 percent of the sulfur out of Midwestern coal before it's burned. The center is a partnership of the University of Illinois, Southern Illinois University, and the Illinois State Geological Survey.
'T-bone instead of hamburger'
One of the projects combines a new discovery with the old and well-tested technology of low-temperature charring used by the Germans to make liquid fuel during World War II. Under that method, coal is heated in a special oven. The process removes about 40 percent of the sulfur and releases hydrocarbons, which can be refined into liquid fuel.
Beyond that, Carl Kruse of the Illinois State Geological Survey and his colleagues have discovered that by chemically treating the coal char that remains, it is possible to get an extra 50 percent of the sulfur out.
Another key center project, this one at Southern Illinois University, focuses on extracting a significant Amounv of sulfur, along with liquid fuels and other valuable byproducts, by mixing coal and grain alcohol under pressure at a high temperature. Sulfur from the remaining solid fuel could be further reduced by the chemical treatment method being tested by Dr. Kruse and his colleagues.
''Both methods have promise if we can clean up the char that's left and keep the price down,'' Kruse says. ''We're trying to remove the valuable components of the coal first. It's better to save the T-bone steaks than grind everything into hamburger. Then what's left is easier to work on. And we think we've discovered that getting the sulfur out of the remaining solid fuel is not as difficult as we had thought.''
Cheaper than 'scrubbing'
One major advantage of both precombustion studies: The clean solid fuel remaining can be burned in existing utilities and boilers after only minor modifications.
Demand for electricity - at least half of which is generated by coal - has been slipping in recent years. And nuclear plant construction has been at a virtual standstill. Yet a further crackdown on sulfur emissions from those concerned about acid-rain pollution is considered a strong possibi ity. Thus the prime challenge is to find an economical way to use the Midwest's high-sulfur coal - which actually has a higher heating value and less moisture than Western coal - without having to build a new plant to do it.
To use this region's coal now, existing plants must install very expensive and not always reliable ''scrubbers,'' which remove much of the sulfur after the coal is burned and before the results hit the air. The other alternative: installation of fluidized bed boilers that burn crushed coal at a low temperature with limestone, which absorbs the sulfur during the combustion process. But bed boilers require a new plant and are considered best for small coal users.
Most coal researchers concede that getting the sulfur out before burning the coal may be the best possible way to tackle the sulfur problem. But they say the case for it has yet to be proved.
''The idea of turning coal into a sulfur-free fuel is very exciting to industry and researchers, but the techniques are highly experimental, the risks are great, and there's a serious question of whether or not the idea is economically viable,'' says John Mead of the Illinois Energy Resources Commission.
Kruse concedes that the question of economic viability is critical. They argue that by selling fuel byproducts to finance further cleaning of the remaining solid fuel and by using more of the potential energy of a given amount of coal, the price of electricity could even be reduced. The Illinois researchers expect to have the answer within five years, if funding from the Illinois Coal Research Board and others continues at the current pace.
''This is a regional problem,'' Kruse concludes.''We've argued that this research approach wasn't being given its fair share of attention - partly because the results wouldn't be broadly applicable to coal across the country. We felt this part of the country should get on the stick and do something about the gap.''