Permit litigation, steel price increases, first-of-a-kind materials and a tight labor market are among the challenges facing a Wisconsin utility one year into a supercritical pulverized-coal powerplant project, one of only two in progress in the U.S. So far, the materials and labor challenges have not adversely affected the projects schedule and budget, but a state court decision could seriously delay it if the utility loses.
The Sierra Club contends the permit for Wisconsin Public Service Corp.s 500-MW Weston powerplant unit 4 does not comply with the Clean Air Act. The dry scrubber allowed in the permit is "not best-available control technology under the Clean Air Act," argues Bruce Nilles, a Sierra Club attorney. The court decision is due the first week in January, he says.
An adverse decision "could delay the project a year to two years," says Kelly Zagrzebski, WPSC community-relations coordinator, adding that the Green Bay-based utility probably would not appeal if that happens.
Construction began in October 2004 on the supercritical Weston unit in Marathon County, Wis. Labor availability is the main challenge, says Matt Kurian, B&W project manager. In the drought of coal-plant construction after 1980, construction skills were lost through attrition. Now, with several coal-fired plants under construction in Wisconsin, labor is tight, says Kurian.
The plant will burn low-sulfur coal from Wyomings Powder River Basin. The utility selected a supercritical system for its efficiency and because supercriticals "availability has proven equivalent to subcritical," says Dan Yagodinski, WPSC engineering manager. Supercritical systems operate at very high temperatures and pressures, and provide more complete combustion while using less fuel
The $752-million Weston 4 will use a spiral-wound universal-pressure boiler. The system will deliver a maximum of 3.641 million lb per hour of steam at 3,775 psig pressure. Steam will be superheated to 1,085°F and reheated to 1,085°F at 630 psig.
"This is the first application of P92 [a high-chromium alloy] in the U.S. for main steam and hot reheat," says Stephen Pieschl, Black & Veatch project director. B&V is project engineer for design, permitting support, procurement, startup and training.
The use of new materials has required some training for craft workers, but it has not been an issue. "From a materials standpoint, this is basic powerplant construction like it was done 20 years ago," says Charles Meyer, project construction manager for Washington Group International, the construction manager at-risk.
In supercritical systems, "the feedwater heaters are heavier," Pieschl notes. Weston 4s feedwater heater weighs 80 tons. "It was set with a crane instead of jackup and rolling into place," Meyer says.
The units air-pollution-control equipment includes a dry scrubber to conform with the plants permit. But the Sierra Club wants the permit to require a wet scrubber, more commonly used at plants that burn high-sulfur eastern coal and which removes more sulfur. It also wants 90% control efficiency in the units selective catalytic reduction system, to reduce NOx emissions.
There have been a few surprises, including higher steel prices a year ago, says Meyer. But at 21% completion, the plant is on schedule for June 2008 commercial operation and the budget is still holding at $752 million, he says.
Another supercritical unit began construction in September 2003 at MidAmerican Energy Co.s Council Bluffs Energy Center in Council Bluffs, Iowa. A 790-MW Babcock-Hitachi supercritical sliding-pressure-operation Benson boiler designed for 5.5 million lb per hour at 3,690 psi will be Council Bluffs Unit 4. It will have main steam temperature of 1,050°F and reheat of 1,100°F. Hitachi America Ltd., Tarrytown, N.Y., is contractor for engineering, procurement and construction. The $1.2-billion project is on schedule for commercial operation in 2007.
LG&E Powergens Trimble County Unit 2 in Kentucky could be next. The $1-billion, 750-MW unit received its permit from the state and is negotiating an EPC contract with Bechtel Power Corp. Scott Straight, LG&E director of project engineering, says he expects to complete the contract next year. The plant is scheduled for commercial operation in spring of 2010.
"Ninety percent of all new boilers from this point will be supercritical," Straight says.