A research team led by Carlos E. Romero, principal research scientist and associate director of Lehigh's Energy Research Center, has developed a cost-effective system for controlling mercury emissions in coal-fired power plants.
The breakthrough follows years of work by ERC researchers in optimizing boiler operations to control emissions of NOx, CO, particulate and other pollutants.
Coal-fired power plants emit about 40 percent of the estimated 48 tons of mercury that is discharged into the air each year in the United States. Mercury, a neurotoxin, usually affects humans through fish consumption.
U.S. and international environmental agencies have sought for 15 years to reduce mercury emissions. The U.S. Environmental Protection Agency decided in 2000 that regulating mercury emissions from coal-fire power plants was "appropriate and necessary." No rules are yet in place, but utilities in some states expect regulations to be enforced as early as 2007.
The technology developed by Romero's team manipulates operating conditions of different pieces of equipment in a power plant boiler to promote oxidation of mercury in the flue gas and enable it to be absorbed and captured in the fly ash.
The technology was developed by Romero, ERC associate director Nenad Sarunac, ERC research scientist Harun Bilirgen, and Ying Li, a graduate student who recently completed his M.S. degree in mechanical engineering.
Romero's group received a total of $1.2 million in funding from a consortium of utility companies, the Pennsylvania Infrastructure Technology Alliance and the U.S. Department of Energy to develop modeling capabilities, test the feasibility of the concept and perform full-scale mercury testing at three coal-fired boilers.
The ERC researchers collaborated with Western Kentucky University to perform field tests. Their technology achieved a 50- to 75-percent reduction in stack emissions of total mercury in the flue gas with minimal to modest impact on unit thermal performance and fuel cost.
Romero says the ERC technology would result in significant cost savings for utility companies that currently use activated carbon injection for mercury control and emission compliance.
Activated carbon injection is the retrofit technology with the widest potential application for controlling mercury emissions in power plants. But it costs $1 to $3 million a year for a 250-MW unit to reduce mercury emissions by 50 percent.
"We believe this cost would be offset by adopting the modifications to boiler operation indicated by the ERC technology," says Romero.
Romero discussed his group's findings at the 2004 Pittsburgh Coal Conference in Osaka, Japan, where he gave a paper titled "Impact of Boiler Operating Conditions on Mercury Emission in Coal-Fired Utility Boilers."