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A SECOND ACT FOR ILLINOIS COAL?

Illinois coal is well suited to new, cleaner energy systems on the horizon. Reducing global warming and developing a hydrogen economy may depend on these technologies, which are being researched intensively at SIUC.

by Marilyn Davis

coal is transported into a cleaning plant at the Willow Lake Mine complex

Solar power, wind power, biomass power, hydrogen--all have the potential to reduce our dependence on foreign oil. But any significant reduction in the near term, energy experts seem to agree, will depend on an old standby: coal.

"The general consensus at the national level is that we're going to be using coal for the next 30 to 50 years, and probably until the end of the 21st century," says Paul Chugh, professor of mining and mineral resources engineering at SIUC.

That is even more true for rapidly industrializing Third World nations than for the United States. Coal is significantly less expensive than natural gas or oil. It is energy-rich, producing a lot of power for its volume. And although it is a nonrenewable resource, the United States, and the world, have abundant, well-distributed reserves of it--enough to fuel us through the decades it will take to make renewable energy systems economical enough to be widely adopted.

"The only way for the foreseeable future to keep electricity easily affordable is to burn coal," says Satya Harpalani, professor and chair of mining and mineral resources engineering. "The question is how to do that in an environmentally sound way."

The good news, environmentally, is that the United States and other industrialized nations are already starting to move toward using coal in a different way than coal-burning power plants do now. The future, many experts believe, lies in new twists on an old idea: gasification.

Coal gasification and associated technologies may be the key in moving toward a hydrogen-based economy while reducing emissions of carbon dioxide, one of the so-called "greenhouse gases" that contribute to global warming. And with gasification, the Achilles' heel of Illinois coal--its high sulfur content--is no longer a problem.

"Gasification is very attractive for Illinois coal because the high sulfur content is not a disincentive; it is actually a useful byproduct," says John Mead, director of SIUC's Coal Research Center.

"To increase use of Illinois coal, the challenge is to identify new technologies. Sulfur dioxide control technologies are in limited use in Illinois, and so it's not a matter of providing incremental improvements in scrubbers, say. That's not going to radically increase the use of Illinois coal.

"Commercializing gasification is going to."

A new day for gasification

In the early to mid-1900s, many U.S. cities and towns had their own coal gasification plant. Coal was heated in the presence of steam and a carefully controlled amount of air to produce a moderate-Btu gas that could be burned for heat and light. This so-called water gas was used in residences, businesses, and street lamps. The process produced a lot of waste and pollution, however. More efficient gasification processes were developed in the 1940s; Germany, for example, used gasification to produce gasoline and other liquid fuels during World War II. But the technology gradually gave way in the 1950s and 1960s to the use of natural gas, which was then cheaper than coal.

In recent years the concept of coal gasification has been revived and gasification technology has been improved. Today's gasifiers use high-temperature, high-pressure vessels and oxygen instead of air to produce high-quality syngas (primarily hydrogen and carbon monoxide), which is burned in gas turbines to generate electricity.

Several pilot coal gasification plants are now operating in the United States and other countries, producing both electricity (from syngas) and diesel fuel. The U.S. Department of Energy (DOE) and energy companies are funding research to extend the benefits of gasification, as is SIUC (see Putting Technology into Practice). These benefits are threefold: efficiency, versatility, and pollution control.

In conventional power plants, coal is burned in order to heat water to drive steam turbine-generators. Only about 30 percent of the coal's energy value actually winds up producing electricity; the rest is waste heat. By using what's called a combined cycle to produce electricity, gasification plants can ratchet efficiency up to 50 percent or more. After syngas is burned, the waste heat from the turbines can itself be used to drive conventional steam turbines, generating additional electricity. In industry jargon, such plants are called IGCC systems, which stands for "integrated gasification combined-cycle."

Gearing up for the hydrogen economy

Gasification can be used for much more than making electricity, however.

"Gasification is a pretty nice process--whatever you need, you can make," says Tomasz Wiltowski, an associate professor of mechanical engineering and energy processes who does research in this area. "And it's more environmentally friendly. Gasification is coming back with new materials and new approaches."

an IGCC power plant near Lakeland, Florida

"The real advantage of gasification is that it allows an engineer to design a system where all of the output products can be processed and used," Mead explains. Besides syngas, those products can include methane (natural gas), liquid fuels such as diesel fuel and methanol, chemical feedstocks, and last but not least, hydrogen.

DOE will soon choose a site for a 275-megawatt, near-zero-emissions, IGCC pilot plant that will gasify coal to produce both electricity and surplus hydrogen for uses such as fuel cells. Illinois and a number of other states are lobbying for the billion-dollar project, dubbed FutureGen. But wherever it is sited, it will serve as a major impetus for new clean-coal technologies.

Many hopes have been pinned on hydrogen as the transportation fuel of the future. Hydrogen is a clean fuel: when it is burned, it produces only water as a byproduct. But how do you get large quantities of hydrogen to begin with?

You can make it from methane, or by using electricity to split water molecules apart. Both are expensive options, however. Producing hydrogen by gasifying coal may be the best bet, and it can be done cleanly.

A slice of the prehistoric garden

Even the finest coal starts out dirty, a hodge-podge of organic material and inert minerals.

"Coal is truly a slice of garden back in Pennsylvanian times," says Mead. "It's inherently complex. It's a monster molecule incorporating carbon, hydrogen, oxygen, sulfur, chlorine, and other elements--plus there's mineral matter that is physically bound up with coal as it forms, such as pyrite and silica.

"No matter how coal is processed, there are trace solids as byproducts. But there's a different set of technologies today, and environmental control is at the center of the process."

For years SIUC and other universities have worked with government and industry on improved coal-cleaning methods, combustion systems, and smokestack equipment to reduce sulfur and other pollutants emitted from coal-burning power plants--emissions that cause acid rain and smog.

But many U.S. power plants have chosen to burn low-sulfur western coal to meet Clean Air standards rather than invest in clean-coal technology. That's the case even though they have to burn 25 to 30 percent more western coal to get energy production equivalent to that of eastern coal.

Consequently, some eastern mines have closed while mines in western states have opened. Illinois coal production has dropped almost 50 percent since 1990. In 1999, for the first time, more coal was mined west of the Mississippi than east of it.

Gasification levels the playing field for high-sulfur coal.

"It produces very concentrated gas, liquid, and solid streams that are much easier to handle," Mead says. Instead of being drawbacks, pollutants can be separated out and sold to companies as chemical feedstocks. "Gas cleanup systems developed years ago to clean up natural gas can capture nearly 100 percent of the sulfur," Mead explains, "and elemental sulfur can be used for a lot of things. Gasification also is the best means of chemically capturing trace elements such as mercury and selenium."

Types of coal differ significantly from one geographical region to another, which can slow the adoption of new technology by the coal industry. Fortunately, Illinois coal is highly suitable for gasification--better, actually, than western coal.

"It has some advantages because of its chemical composition, energy content, and moisture content," Mead says. "All of the major new gasification technologies worldwide have been designed and evaluated with coal types that include those in Illinois." In fact, Illinois no. 6 coal, a standard grade often used as a reference, is one of the most-researched types of coal in the world.

One thorny problem remains: carbon dioxide. But gasification offers a way to deal with that, too.

Just as climate change is a global concern, carbon dioxide emissions are a global--and growing--problem. Humans produce 25 billion tons of CO2 every year, mostly from burning fossil fuels in power plants, automobiles, factories, and homes. CO2 makes up 82 percent of the greenhouse gas "load" in the atmosphere and is considered responsible for much of the global temperature rise of 1 degree Fahrenheit over the past century. Warming is expected to accelerate over the next few decades.

"Countries that burn a lot of fossil fuels, like China, India, Ukraine, and Poland, have growing economies; they're very energy-hungry," Harpalani says. "They'll continue to burn coal because it's available and cheap."

In 2003 the European Commission estimated that without corrective measures, CO2 emissions will increase another 50 percent by 2020. Government, environmentalists, and even the energy industry have arrived at the consensus that controlling global warming, and thus putting the brakes on climate change, will require controlling those emissions.

About one-third of the United States' emitted CO2 comes from coal-burning power plants, and removing those emissions at the stack would be very expensive. Because today's coal gasification plants are more efficient than coal-burning plants, they emit less carbon dioxide per ton of coal used, which is a plus. But DOE hopes to go much further.

DOE's plan is for FutureGen to separate out CO2 at the gasification stage and then sequester it--store it underground to keep it out of the atmosphere. And if pure hydrogen is burned for power, the only byproduct is water.

"DOE is trying to implement clean-coal technologies such as IGCC so we can meet air quality standards of the future, not just today," says Paul Chugh. "And that has long-term implications worldwide, because it could open markets in other countries for our technologies."

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