Issued on: June 22, 1999
New Clean Coal Technology Report Showcases Advances in Flue Gas Cleaning Technologies
Report Profiles Milliken, Pure Air, and CT-121 Projects; Now Available on DOE's Fossil Energy Web Sites
Three advanced technologies demonstrated in the U.S. Department of Energy's Clean Coal Technology Program have pushed a new generation of technologies for "scrubbing" unwanted pollutants from the flue gas of coal combustion into the 21st century.
To profile the projects, the Energy Department has released a new 27-page topical report entitled Advanced Technologies for the Control of Sulfur Dioxide Emissions from Coal-Fired Boilers. The report describes the federal government's partnership demonstration projects with Pure Air on the Lake, L.P., Southern Company Services, and New York State Electric & Gas Corporation (NYSEG), each of which tested a new improvement in flue gas desulfurization technology.
"Results from the three demonstration projects have expanded the number of options available to utilities for reducing sulfur dioxide emissions while also reducing costs," said Robert Gee, the Energy Department's Assistant Secretary for Fossil Energy. "These technologies will benefit the public not only by helping to clean the air but also by reducing future costs for environmental compliance."
Pure Air on the Lake, L.P.
The first of the three flue gas desulfurization projects to complete its demonstration, Pure Air on the Lake, L.P., ran from 1992 to 1995. Pure Air is a partnership between Air Products and Chemicals, Inc. and Mitsubishi Heavy Industries America, Inc. The Bailly Generating Station of Northern Indiana Public Service Company hosted the Pure Air demonstration at its plant on Lake Michigan, 12 miles northeast of Gary, Indiana.
During the three year demonstration a uniquely designed scrubber treated the combined flue gases from two boilers. Pure Air installed a scrubber with a cocurrent flow of gas and liquid, an air rotary sparger located within the base of the absorber and a novel wastewater evaporation system.
The Pure Air Advanced Flue Gas Desulfurization demonstration removed sulfur dioxide in one absorber which prequenched the flue gas, absorbed the SO2, and oxidized the resulting calcium sulfite to wallboard-grade gypsum. The Pure Air process averaged a 94% SO2 removal rate, with a maximum of over 98%.
During the demonstration United States Gypsum Company has taken Pure Air's entire byproduct gypsum production, an amount exceeding 210,000 tons. U.S. Gypsum's East Chicago plant is the first facility to produce all of its wallboard from FGD gypsum.
In 1992 the Pure Air project received an Outstanding Engineering Achievement Award from the National Society of Professional Engineers and in 1993 it received Power magazine's Powerplant Award.
Southern Company Service's CT-121
Southern Company Service began its Chiyoda CT-121 flue gas desulfurization demonstration in April 1990 at its Georgia Power Company Plant Yates in Newnan, Georgia. A major innovative feature of the CT-121 process was the use of a single absorber vessel - Chiyoda's patented Jet Bubbling ReactorŽ made of fiberglass-reinforced plastic - in place of the spray tower/reaction tank/thickener arrangement used in conventional scrubber systesms. The fiberglass-reinforced plastic design is to avoid the corrosion damage associated with traditional closed-loop flue gas desulfurization systems.
The result was that when Georgia Power burned high-sulfur coal at Plant Yates the CT-121 scrubber achieved a maximum SO2 removal rate of 98% when burning 2.2% sulfur coal, and about 95% with 3.5% coal.
The CT-121 project -- which is now complete except for the final report -- also produced a low-quality gypsum which was tested for agricultural use. In 1996, Georgia Power received a Plant Food Permit from the State of Georgia that allows the unrestricted sale of ash-free gypsum from the Yates project for agricultural purposes. This market exceeds 1 million tons per year in Georgia alone.
The project received Power magazine's 1994 Powerplant Award, the Society of Plastic Industries' 1995 Design Award, and environmental awards from the Air & Waste Management Association and the Georgia Chamber of Commerce.
Milliken Station
Selected during Round IV of the Clean Coal Technology Program, the New York State Electric & Gas Corporation operated its Milliken Station SO2 removal technology, the Saarberg-Holter-Umwelttechnik (S-H-U) flue gas desulfurization process from 1995 to the conclusion of performance testing in 1998. NYSEG completed its final report this spring. On May 14, 1999, NGE Generation, an affiliate of NYSEG, completed the sale of its coal-fired power plants in New York State, including Milliken Station, to The AES Corporation.
In the S-H-U process flue gas is scrubbed with a limestone slurry in a space-saving cocurrent/countercurrent absorber vessel. The process is designed specifically to take advantage of the benefits of organic acid enhanced absorption by using a low concentration of formic acid additive in the scrubbing liquid.
Formic acid acts as a buffer in the absorber. Formic acid addition improves both the rate of limestone dissolution and the solubility of calcium in the scrubbing liquid, thereby enhancing SO2 absorption efficiency, reducing limestone consumption, improving energy efficiency, improving by-product gypsum quality, and reducing waste-water production.
As a result of the performance tests SO2 removal efficiency at Milliken Station was as high as 98%. These tests also demonstrated the benefits of formic acid enhanced operation. In one series of tests, SO2 removal efficiency increased from 83% without formic acid to 95% with formic acid. At the same removal efficiency, using formic acid results in a 75% reduction in energy required for circulating the sorbent slurry.
For more details on all three projects please see the new Topical Report Number 13 now available on the Energy Department's Federal Energy Technology Center Web Site.
- End of TechLine -
For more information, contact:
Hattie Wolfe, DOE Office of Fossil Energy, (202) 586-6503, e-mail: hattie.wolfe@hq.doe.gov
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