Activated carbon for mercury emissions control earns R&D 100 Award

Palo Alto, Calif., Oct. 16, 2003 — A technology for controlling mercury emissions from coal-fired power plants by injecting activated carbon into a plant’s flue gas has earned a 2003 R&D 100 Award for the Electric Power Research Institute (EPRI) and 10 other project partners.

A key partner was the U.S. Department of Energy’s National Energy Technology Laboratory (DOE/NETL), which provided the majority of the funding for these pioneering tests of mercury controls on power plants. The award is given by R&D Magazine for this year’s most outstanding technology developments with commercial potential.

The award was for full-scale tests to evaluate the performance of carbon injection for mercury control upstream of electrostatic precipitators (ESPs) or in a smaller fabric filter added after the ESP in an EPRI-patented process known as TOXECONà¢â€ž-. Testing host plants included units burning Powder River Basin and low-sulfur bituminous coals and sites with high and low natural mercury removal.

“These projects, the industry’s first-ever, full-scale tests of mercury emissions controls on operating power plants, were a critical step in determining the effectiveness of activated carbon injection for reducing mercury emissions,” says Ramsay Chang, manager for air emission controls in EPRI’s Generation Department. “After further development, we expect the technology to be one of the leading candidates for a number of existing coal-fired boilers when they are required to meet mercury emission limits. It can be a relatively low capital-cost solution, can be retrofit with little or no operating downtime, and is applicable to a wide range of coals and operating conditions.”

When coal is burned, mercury is released in a gaseous form as elemental mercury and oxidized mercury. Elemental mercury does not dissolve in water, and as a result cannot be retained in wet scrubbers for flue gas desulfurization. Oxidized mercury, on the other hand, dissolves in water and can be collected in wet scrubbers, but the accumulation is sometimes incomplete. Plants that do not have a wet scrubber, or that need to reduce mercury emissions below that achieved by their wet scrubber, can inject powdered activated carbon into the flue gas, where it acts as a sorbent, capturing the gaseous mercury on its surface. The composite material is then collected by the plant particulate control and recycled for other applications or discarded.

EPRI was one of the first organizations to undertake research on this topic. The early laboratory studies were followed by pilot-scale testing, often in collaboration with DOE/NETL. These efforts led to the full-scale tests at four utility power plant sites that were the basis for the R&D 100 Award.

EPRI shares the award with DOE/NETL as co-sponsor, ADA Environmental Solutions (ADA-ES) as lead contractor, and the following industrial partners: FirstEnergy, Ontario Power Generation, PG&E NEG (host sites), Southern Company (host site), Tennessee Valley Authority, We Energies (host site), as well as Kennecott Energy and Arch Coal. Based upon the success of this program, DOE selected TOXECON for a Clean Coal Power Initiative award at the We Energies’ Presque Isle power plant. This will be the first commercial demonstration of mercury control technology for coal-fired power plants.

EPRI, headquartered in Palo Alto, Calif., was established in 1973 as a non-profit center for public interest energy and environmental research. EPRI’s collaborative science and technology development program now spans nearly every area of power generation, delivery and use. More than 1,000 energy organizations and public institutions in 40 countries draw on EPRI’s global network of technical and business expertise.

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The Clarion Energy Content Team is made up of editors from various publications, including POWERGRID International, Power Engineering, Renewable Energy World, Hydro Review, Smart Energy International, and Power Engineering International. Contact the content lead for this publication at

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