PITTSBURGH, PA — Proceedings from the 2006 Mercury Control Technology Conference highlighting the advances and successes of mercury-control technologies are now available online. The technologies discussed at the conference, which was hosted by the Department of Energy’s National Energy Technology Laboratory (NETL), are aimed at helping coal-fired power plants meet the U.S. Environmental Protection Agency’s 2005 Clean Air Mercury Rule. The conference proceedings contain the latest information about technology development that could save U.S. rate payers millions of dollars per year.
Coal is the United States’ most abundant energy source and a key player in America’s energy security. Coal-burning power plants are also the largest source of manmade mercury air emissions in the United States, accounting for more than 40 percent of emissions. The Clean Air Mercury Rule will permanently cap and reduce mercury emissions from coal-fired power plants.
One of the challenges of finding mercury-control solutions is developing technologies that can consistently and cost-effectively capture mercury from all of the coal-fired power plants in operation. Many factors influence mercury emissions from power plants, including the type of coal being burned, existing air pollution control devices, and the chemical form of mercury released—elemental or oxidized. Currently no single technology can cost-effectively provide add-on mercury control for all power plant configurations or fuel types. Without better technologies, significant costs could be added to the generation of the nation’s electric power to comply with environmental regulations.
The December conference highlighted key accomplishments and furthered communication that should lead to the adoption of new, innovative technologies. This will help coal-burning power plants comply with new regulations, and it ultimately strengthens U.S. energy security by promoting the clean use coal.
At the conference, more than 300 attendees from universities, industry, other research organizations, and the public at large learned about mercury research projects funded by the Energy Department, the U.S. Environmental Protection Agency, Electric Power Research Institute, electric utilities, and other project partners. Presentations were given on groundbreaking technical accomplishments and additional research needs in four areas:
- Sorbent injection—Injecting a sorbent, such as powdered activated carbon, into flue gas is the longest-running and one of the simplest approaches to controlling mercury emissions from coal-fired boilers. The technology is capable of removing up to 90 percent of mercury in flue gas. Based on NETL-funded studies, conference presenters emphasized the need for selecting the right type of sorbent, the right injection point to maximize the time the sorbent has to work, and the right injection system to ensure effective distribution and use of the sorbent. Further research is needed to develop mercury sorbents with increased performance in high-temperature, high acid gas environments because these environments can significantly reduce the success of conventional sorbent injection.
- Mercury in coal utilization byproducts—Mercury captured in coal utilization byproducts, such as fly ash and flue gas desulfurization (FGD) solids, may be re-emitted into the environment during either disposal or utilization. NETL is sponsoring a number of projects that evaluate the potential release of mercury and other trace metals from coal byproducts. The potential thermal release of mercury during the manufacture of wallboard and ways to prevent this release are areas needing additional research.
- Mercury capture with wet FGD systems—By oxidizing elemental mercury, it becomes water-soluble and can be captured in wet FGD systems that are already installed in power plants for control of sulfur dioxide. Depending on site-specific conditions, as much as 90 percent of oxidized mercury can be removed with a wet FGD system. A challenge with oxidation technology is that oxidized mercury can convert back into elemental mercury inside a wet FGD absorber, impeding mercury removal. NETL funds research to mitigate this issue. Additional research on the effect of low-oxidation catalysts on mercury oxidation is needed to better understand the impact of new nitrogen oxide regulations on mercury control.
- Other mercury-control technologies—Notable among these varied technologies, NETL’s onsite researchers developed and patented two new methods for controlling mercury. The first involves extracting partially combusted coal from a boiler and using its unburned carbon as a mercury sorbent. The second method uses ultraviolet light to convert elemental mercury into an oxidized form so that it can be more readily captured by existing air pollution control devices.
Implementation of the Clean Air Mercury Rule is intended to reduce overall U.S. power plant emissions of mercury 70 percent by 2018, but a number of states are implementing more stringent mercury regulations. NETL’s goals are to have mercury-control technology ready for commercial demonstration of 70 percent removal by 2007 and 90 percent removal by 2010.