Tuesday, August 8, 2006 10:49 PM CDT
Geology key to site selection for power plant
By HERB MEEKER, Staff Writer
hmeeker@jg-tc.com
What’s under the surface really matters in the FutureGen bid.
Geologic data, not politics, have placed the site northwest of Mattoon, as well as the site west of Tuscola, on the final four list with the FutureGen Alliance. The location of the new power plant will be announced sometime in late 2007.
Underground characteristics are vital to FutureGen officials because they need a safe site for storing millions of tons of carbon dioxide emissions for many years. The plant is expected to go into operation in 2012 and produce power and energy byproducts for at least 30 years.
The new FutureGen power plant will use a heating and pressure process to turn all types of coal, from low- to high-sulfur content, into a synthetic gas, known as syngas. Impurities and sulfur, which will be sold, are removed from syngas in preparation for separating carbon dioxide and hydrogen. The final syngas product will be used to power turbines for generating electricity.
The carbon dioxide will be turned into liquid form for injection into underground saline formations. The hydrogen can be transferred to chemical plants for eventual production of fuel cells for motor vehicles.
Coal gasification is not new technology. It was used by the Germans in World War II to produce synthetic fuel for huge gas-guzzling tanks and new-generation jet warplanes like the Messerschmitt 262. The Germans had no choice as Allied forces cut off or destroyed their captured oil facilities in Europe and Africa. But Germany had plenty of coal.
Ironically, the tipping of the balance on oil reserves over coal reserves for the United States and other oil-dependent nations helped produce the FutureGen project. In addition, concerns with pollution are another reason for developing new, cleaner energy production technology with coal.
The novel element to FutureGen is perfecting technology for injecting liquid carbon dioxide more than a mile underground. Keeping the emissions underground is essential.
That goal made the saline formations under Mattoon and Tuscola an asset compared to other proposed sites. Experts believe there will be enough capstone -- layers of shale rock -- hundreds of feet thick to help prevent seepage of the carbon dioxide to the surface. Some of the geologic formations in Illinois date back to hundreds of millions of years ago when a sea covered sections of today’s Midwest.
“You want enough rock between the carbon dioxide and the surface. The deeper you go, the higher your pressure,” said Kathy Bower, an instructor with the Eastern Illinois University Geology Department. “Otherwise, it will break its way out again.”
With shale, fluids or other materials do not move through it, Bower said.
“Compare it to a stack of marbles and a stack of bricks. The shale is like the bricks. The sandstone is like the marbles. It is going to be much harder for anything to seep through the bricks,” she said.
Sandstone is also part of the underground geology equation for the Illinois FutureGen sites. The saline formations are actually saltwater mixed with sandstone called Mount Simon layers, explained Robert Finley, a geologist with the Illinois State Geological Survey, who has served as that agency’s liaison on the FutureGen project.
“The saltwater in the Mount Simon sandstone is three times as salty as you find in the ocean. It has no economical use. This sandstone layer is 1,000 to 1,200 feet thick and the liquid carbon dioxide will be injected into it,” Finley said.
Experts say the carbon dioxide will remain in liquid form due to the intense pressures at depths of 7,500 to 8,000 feet. The pressure there is 3,700 pounds per square inch, which is more than three times the pressure point for converting carbon dioxide into its liquid form.
With the capstone layers of shale, there is less chance of seepage to the surface, Finley said. There are concerns with faults or cracks in the rock formations, but monitoring of the subsurface will be conducted by seismic devices that send vibrations into the ground to detect cracks. The injection wells might also be used for monitoring the nature of the carbon dioxide in storage.
“If some did come up to the surface, in my judgment it would be a small amount,” said Finley, adding the carbon dioxide would return to its gaseous state if it seeped up to ground level. “There is evidence the capstones have very effective seals.”
Some of the technology for drilling the injection wells and underground monitoring has been developed over the years through the oil industry.
“In many ways, this is like drilling for oil in reverse. Instead of taking fluid out of the earth, we’re putting it underground. This project is benefiting from oil production experience,” Finley said.
The plan is to inject one million tons of carbon dioxide per year underground, Finley said. An 18-wheeler tanker truck can haul about 20 tons of liquid fuel, for example, so the FutureGen plant will be injecting enough carbon dioxide to fill 50,000 tanker trucks over a year’s time.
“But just remember this carbon dioxide isn’t going down there in trucks,” Finley said.
It will travel along “express lane” wells for about a mile and a half straight down. Then it will be in storage for decades.
Contact Herb Meeker at hmeeker@jg-tc.com or 238-6869.
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Stephen wrote on Jul 17, 2006 8:22 AM: