Release Date: August 5, 2003
|Innovative Mercury Removal Technique Shows Early
Photochemical Process Developed in Federal Lab Removes Mercury from Flue Gas
MORGANTOWN, WV - A promising technology to remove mercury from coal-fired power plants -- dubbed the "GP-254 Process" -- has been developed and is currently being tested at the Department of Energy's National Energy Technology Laboratory (NETL). Newly patented, the GP-254 Process enhances mercury removal using ultraviolet light to induce various components of power plant stack gas to react with the mercury, and changes the composition of the mercury into a form that can be removed easily and economically.
"Coal is one of our most plentiful energy sources in the United States and provides a strong measure of our energy security, so we must improve our ability to make use of this resource in a manner that is both environmentally sound and economically feasible," Secretary of Energy Spencer Abraham said. "The GP-254 Process is an exciting technology that could provide an elegantly simple solution to a complex problem. Using equipment similar to that used in water treatment plants to kill microbes, we may be able to dramatically reduce the amount of mercury entering the air from power plants - and it would be inexpensive, benefiting the consumer and our economy."
When power plant flue gases are exposed to the ultraviolet light in the GP-254 Process, the elemental mercury becomes "excited," making it more likely to react with other compounds in the gas. In laboratory experiments with simulated flue gas, the excited mercury reacted with oxygen and sulfur dioxide to form mercurous sulfate and mercuric oxide, both of which were readily removed.
The process is designed to work with existing pollution-control devices. Depending on where the ultraviolet light is applied, it could enhance mercury removal in the particulate collector or a wet scrubber of a coal-fired plant. The process could be especially attractive to power plants that burn "low rank" coals -- softer coals with lower energy content such as sub-bituminous coals and lignite. Not only do low rank coals release more mercury per unit of energy than higher rank coals, but more of the mercury in low rank coals is harder-to-remove.
"A preliminary cost analysis, based on our small-scale lab tests, indicates that operating costs for the GP-254 Process will be lower than those for other methods," said Secretary Abraham. "Our next step will be to test and optimize the process at pilot scale using emissions from NETL's onsite combustor."
Mercury is a naturally occurring element that is present throughout the environment. Most mercury is locked up in ores and it rarely occurs free in nature. Human activities, including municipal waste combustion, medical waste incineration, and coal combustion, release some of that mercury. The result is higher amounts of mercury cycling in our air, soil, and water.
The threat to the environment comes from an organic form of mercury called methyl mercury. Even when mercury is released in an inorganic or elemental form, biological processes can covert it to methyl mercury. Methyl mercury bioaccumulates through the food chain; small organisms and plants take up the mercury as they feed, small animals take in the mercury when they eat the small organisms and plants, and larger animals take it in when they eat the small animals. Humans are exposed mainly from eating fish with high levels of mercury. Forty-three states have advisories warning about high mercury levels in fish.
Citing a "plausible link" between emissions of mercury from fossil fuel-fired power plants and methyl mercury in fish, the U.S. Environmental Protection Agency (EPA) announced in December 2000 that it would regulate emissions from coal-and oil-fired power plants. EPA is developing a "maximum achievable control technology" standard that may require as much as 90 percent mercury control. The final regulation is to be issued by December 2004, with expected compliance by December 2007.
President Bush called for reductions in mercury emissions in his Clear Skies Initiative, announced on February 14, 2002. The initiative calls for phased-in reductions in mercury emissions from power plants beginning in 2010, and proposes a cap-and-trade approach that rewards innovation, reduces cost, and guarantees results. The Clear Skies Act of 2003, supporting the President's initiative, was introduced in the House and Senate in late February 2003. Several other legislative bills that include regulation of coal-fired power plant mercury emissions have been introduced in the 108th session of Congress as well.
Regardless of what form the final regulations take, the Department of Energy (DOE) is helping to arm the utility industry with a number of low-cost mercury-control technologies. DOE's Office of Fossil Energy has conducted a comprehensive, integrated mercury research and development program since the early 1990s.
Implemented by NETL, the current Mercury Control Technology Research and Development Program is conducting full-scale field testing of mercury-control technologies, and continuing bench- and pilot-scale development of a number of novel control concepts, including the GP-254 Process. The program's plans include developing technologies that are ready for commercial demonstration by 2005 and that reduce emissions 50 percent to 70 percent and by 2010 to reduce emissions by 90 percent -- all at costs 25 percent to 50 percent less than current estimates.
In his State of the Union Address, President Bush said that in this century, the greatest environmental progress will come through technology and innovation. "I believe this is an excellent example of what he meant," Secretary Abraham said.
|Contact: David Anna, DOE/NETL, 412-386-4646|