Repeated performance testing at the new 825-MW Cliffside Steam Station Unit 6 demonstrates, said Duke Energy (NYSE: DUK) in an Oct. 2 statement, that the company has delivered on its promise to build one of the cleanest coal units in the nation.
Cliffside Unit 6 in Mooresboro, N.C., which came on-line at the end of 2012, uses the most effective air emissions controls available. This innovative use of proven technologies enables the unit to be classified as a minor source of hazardous air pollutants (HAPs.)
Testing for a variety of air emissions has shown all are well below permit limits under full load conditions. Future test results may vary, but control equipment will assure compliance well below permit limits, Duke noted.
“During the time the company was going through the air permitting process to build Cliffside unit 6, there was significant debate about whether a new coal unit could achieve this level of emissions reductions. We can close that chapter and put those concerns to rest,” said plant manager Rick Roper. “This unit’s air permit is one of the most restrictive in the country, and it’s performing very well.”
State regulators determine what permit limits are required to protect air quality and public health. To be considered a minor source of HAPs, a unit would have to emit less than 10 tons a year of any one HAP or 25 tons a year of all HAPs combined.
Hydrogen chloride (HCl) is the HAP emitted in greatest volume from a coal plant, and Cliffside Unit 6 is emitting less than a quarter of its permitted amount. This is equivalent to less than 2.5 tons of HCl emitted annually or greater than a 99.913% removal rate.
Cliffside Unit 6 removes 99% of SO2, 90% of NOx and 90% of mercury. The performance of Unit 6 shows it is well positioned to demonstrate compliance with the federal mercury rule that will be in effect by April 2015, including the mercury standard of 0.013 lb/GW-hr, Duke said.
At the unit, Duke also handles all coal ash in a dry form and manages it in an engineered, lined landfill.
Cliffside Unit 6 received recognition this fall for its innovation. The October issue of POWER Magazine named the plant as a POWER Top Plant for 2013. It is also a finalist for the “Best Coal Project” in the Projects of the Year Awards sponsored by Power Engineering and Renewable Energy World magazines to be awarded in November.
Cliffside Unit 6 began commercial operation last December. Units 1-4 – a total of 198 MW – were retired in October 2011 as part of a deal with state regulators to get Unit 6 built. There is also Cliffside Unit 5, which remains in operation for the long term. Built in 1972, the 556-MW Unit 5 has since undergone two major upgrades focused on air emissions: in 2002 a selective catalytic reduction system reduced NOx output by about 80%; and in 2010, a new flue gas desulfurization system reduced SO2 emissions by about 99%.
U.S. Energy Information Administration data shows that coal suppliers to Cliffside earlier this year included: B&W Resources out of the Manchester Tipple in eastern Kentucky; Duke Energy itself with coal sourced out of the Cyrus Dock in West Virginia and the Calvert City Terminal in Kentucky; and Alpha Coal out of the Homer III Processing operation in West Virginia and Roxana prep plant in Kentucky.
In addition to Cliffside Unit 6, Duke Energy has built four natural gas combined-cycle plants in North Carolina since 2011, with a fifth expected to begin commercial operation in Wilmington later this year. This new generation allows the company to retire older, less efficient coal plants, and Duke will have retired seven of its 14 coal plants in North Carolina by the end of this year.
All of the remaining coal plants have installed advanced pollution controls that are highly effective in reducing emissions of SO2, NOx and HAPs, including mercury and HCl.
Across the country, Duke Energy is planning to retire nearly 6,300 MW of coal capacity in the coming years, which represents 25% of its coal fleet. By the end of 2013, Duke will have retired more than 3,800 MW of this older coal capacity.