Boilers

Clean Coal Research and the “Future”

Issue 4 and Volume 115.

By Brian Wheeler, Associate Editor

Fossil fuels are expected to continue to be a source of power generation in the United States for years to come. However, the U.S. Department of Energy and Environmental Protection Agency both remain firm on their goals of reducing carbon dioxide emissions. Carbon capture and storage (CCS) technology is being pursued to meet future energy and environmental needs. Currently, nine projects have been launched by DOE to demonstrate at- scale CCS technology. One of those projects is the FutureGen 2.0 project in Illinois. The DOE has committed $1 billion in funding to demonstrate one technology to capture and store CO2.

In September 2010, Ameren Energy Resource Co. (AER) signed a cooperative agreement with the DOE to repower the 200 MW oil-fired Unit 4 at its Meredosia Power Plant in Illinois. The plan is to repower Unit 4 into a full scale, oxy-combustion coal-fired unit. Ameren and its partners, the Babcock & Wilcox Co. (B&W), URS and Air Liquide Process and Construction (ALPC), are in initial engineering and economic analysis for the project.

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The Meredosia plant in Morgan County, Ill. Photo courtesy Ameren Corp.

“This project is the only U.S. oxy-combustion project, and is therefore quite significant,” said Don Langley, vice president and Chief Technology Officer for B&W. “More importantly, the FutureGen 2.0 project would be a fully integrated, long-term test of CCS technology because it embodies capture, transportation and geologic storage.”

The Unit 4 project is one part of FutureGen 2.0, which calls for transporting the captured CO2 over a new regional pipeline to an injection storage facility that will be developed by the FutureGen Industrial Alliance.

Last summer, DOE restructured FutureGen to be two pieces instead of one. Before then, FutureGen had envisioned developing a 200 MW IGCC project co-located with a storage facility in Mattoon, Ill. Due to rising project costs, that project was canceled.

FutureGen 2.0 has a utility (Ameren) that will own and operate the CCS technology. The Meredosia repowering calls for B&W to construct a purpose-built boiler for oxy-combustion and air quality control systems. The boiler will match the steam conditions that the current Unit 4 turbine has. The boiler design is based on a 30 MWth pilot plant in Ohio that B&W has been testing.

“This project represents that final step of demonstrating the technology at scale and, when successful, will position us to offer a commercial embodiment of the technology,” said Langley.

B&W and ALPC would design, fabricate and erect the new equipment needed for the repowering. AER would handle all condition assessments and equipment modifications to the existing turbine island and balance of plant.

B&W is working with ALPC on the oxy-combustion repowering portion of the project.

In typical combustion both air and coal is used. Air is roughly 78 percent nitrogen which leads to flue gas products having CO2 concentration in the range of 16 to 18 percent, depending on the coal. “When you try to capture that CO2, it is very diluted,” said Langley.

The oxy-combustion process uses oxygen mixed with recycled flue gas to replace the boiler’s normal combustion air. So as coal is burned, the resulting flue gas consists primarily of CO2.

ALPC will provide an air separation unit that will produce a CO2 concentration coming out of the boiler in excess of 80 percent by removing the nitrogen before the air enters the boiler. The air separation unit will provide the plant with 95 percent oxygen. A compression and purification unit, also provided by ALPC, will perform the final purification, including capturing mercury, and compress the CO2 to liquid form to be sent out into the pipeline. This process could lead to capturing 90 percent of the plant’s CO2, or 1.3 million tons a year for the Meredosia facility.

“This technology (oxy-combustion) offers the opportunity for a very economical solution to near zero emissions,” said Jim Wood, deputy assistant secretary for Clean Coal in the Office of Fossil Energy. With oxy-combustion “we have a major opportunity to see whether or not this type of repowering project will put a plant in the clean coal portfolio at scale and allow power companies to look at coal again as a source of power.” 

Storage 

The second piece of the FutureGen 2.0 puzzle is storing the captured CO2. The FutureGen Industrial Alliance, which also signed a cooperative agreement with DOE, is in charge of constructing the pipeline network from Meredosia to a suitable site.

In late February, the FutureGen Alliance selected a site in Morgan County, Ill. not far from the Meredosia plant as its preferred storage location.

With help from the Illinois State Geological Society and the use of geophysical surveys, the Alliance has discovered geologic structures that may have the ability to safely store the captured CO2, such as Mt. Simon Sandstone in the Illinois Basin.

“It is a formation that has been tested in other locations and one where there was a lot of data taken,” said Wood.

At the Morgan County site, an area the Alliance has studied for the past five years, the Mt. Simon formation is about 850 feet deep. Ken Humphreys, FutureGen Alliance CEO, said the Eau Claire Shale, which is several hundred feet thick, will serve as the cap rock.

“The deep saline formations are the necessary geology if a widespread carbon capture and storage industry is to ultimately come about,” he said.

The FutureGen Alliance must also select a pipe design to transport the captured CO2. In total, the pipeline will be 32 miles long and four feet underground with a greater depth under roads and waterways. The Alliance is currently assessing capital costs and right-of-way issues that may exist in the process of installing the pipeline. DOE expects that the final estimate and some engineering will be known in late summer or early fall this year.

The next step will be for the project to move into the front-end engineer and design (FEED) stage to keep the capture and storage projects on parallel tracks. This summer may mark the beginning of construction on characterization wells. Heavy construction could start in 2013.

After two years of construction, start-up and operating data could be available in 2015 and establish how the capture and storage projects will integrate with one another. There are still a number of challenges that must be addressed, such as permitting and ongoing cost analysis. Perhaps the biggest challenge of them all is developing the public confidence that storing CO2 is safe and secure.

“I think there are a lot of advantages in doing this and we will just have to wait until 2015 to see if they all play out the way people think they will,” said Wood. 

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