By Steve Blankinship, Associate Editor
The Comanche Station in Pueblo, Colo., has overcome the unique challenge of managing a two-unit baseload coal plant while adding a 750 MW unit and constructing major environmental retrofits. The new supercritical coal-fired unit goes into service in December. Total project cost is $1.3 billion.
Owned and operated by Public Service Co. of Colorado (PSCo), a unit of Xcel Energy, Comanche’s new supercritical coal unit will double the site’s total generating capacity to more than 1,400 MW and make it Xcel’s largest plant in Colorado. Despite doubling the facility’s output, overall plant emissions will fall thanks to additional emission controls being installed on all three Comanche units, combined with the higher operating temperature and related efficiencies of the new supercritical unit.
As a further commitment to the environment, Comanche Unit 3 will use air-cooled condensation, thus reducing water consumption from the Pueblo reservoir. The system will cut water use for Unit 3 by about half. Units 1 and 2 currently use about 9,500 acre feet of water annually with wet cooling only. With the air-cooled system, Unit 3 running at a 90 percent capacity factor will require 4,750 to 5,500 acre feet of water a year.
 Comanche Unit 3 rises next to two existing units. |
Comanche Unit 3’s supercritical boiler is provided by Alstom and the turbine generator is from Mitsubishi. Scrubbers on all three units are provided by Babcock & Wilcox. All three Comanche units use low sulfur Powder River Basin coal delivered from Gillette, Wyo., about 450 miles away. With the addition of Comanche Unit 3, Fred Arellano, director of the Comanche Station, has added 60 employees, bringing the total operational staff to 160 for all three units and the flu gas desulfurization (FGD) scrubbers added to Units 1 and 2 during construction of Unit 3. As a concession to environmental groups during the permitting of Unit 3, scrubbers were added to the units despite the fact that PRB is compliance coal.
Unit 3 has a baghouse and baghouses were retrofitted to Units 1 and 2. Low NOX burners were also added to both existing units. All of the units are also fitted with activated carbon injection systems for mercury control. The end result is that emissions from the entire plant will be lower than when Units 1 and 2 operated alone.
“We achieved an agreement with eight state and national environmental groups that was very beneficial in getting Unit 3 approved,” said Kathy Worthington, PSCo’s area manager for community and local government affairs in southern Colorado. “We had good negotiations and we gave up a lot. They were wise enough to see the global picture and keep our price as low as possible by using coal.”
Due to a combination of employee attrition, the addition of Unit 3 and environmental retrofits for the existing units, Arellano has been adding a steady stream of new employees in recent years, 110 overall. “That’s been the biggest challenge, getting those employees hired and trained,” he said. “At the same time, we’ve been operating two units and focusing on getting the third unit built and commissioned.”
About 1,700 construction employees were on site at the height of construction. As construction winds up and commissioning nears, that number has fallen to about 1,250. Arellano said most of the plant’s senior personnel have chosen to operate the new unit. “We are now commissioning systems, receiving on-the-job training, working with vendors to learn systems and hanging equipment tags as we get things done,” he said.
The transition appears to be going well. Operators who were hired while Unit 3 was being built started learning how to operate Units 1 and 2. Arellano said it’s still too early to tell what operational differences may arise with the new supercritical technology.
PSCo agreed with its union that operations personnel for the new and the old units would be separate through commissioning and probably through the first year of operation. “We didn’t want to be switching people around in the middle of commissioning and operating a new unit and not have anyone who would be highly qualified and trained to operate a new unit,” Arellano said. “After we operate the plant for a year we’ll decide whether to cross-train everyone to operate all three units or if they need to be dedicated to operate the new unit.”
In short, the Comanche Peak project represents the ultimate in power plant operation multi-tasking.