Cleaning Up at Duke Power

Duke and Fluor Daniel complete $450 million emissions project at Belews Creek

By Debra Wood

Duke Power has finished installing a four-layer, $450 million selective catalytic reduction system at its Belews Creek Steam Station in Stokes County, N.C., which will decrease nitrogen oxide emissions by about 80 percent at the energy plant.

"We knew the overall plan had to reduce nitrogen oxide emissions for the system, so Duke made a commitment at Belews Creek and at Cliffside to install the SCR (selective catalytic reduction)," said Jay Huntley, energy manager for the Belews plant.

The 30-year-old, coal-fired Belews plant generates about 2,300 MW and serves two million homes. The plant burns about 5.5 million tons of coal annually. Huntley said that, historically, it has been one of the most efficient coal plants in the nation.

"The sheer size of the station made this project very challenging from the beginning," he added.

The SCR project consists of two 30-story steel structures built directly behind the existing plant. The steel frames house honeycombed ceramic equipment, similar to an auto's catalytic converter, which changes nitrogen oxide into harmless water and nitrogen. The new structure's footprint is approximately 100 by 150 ft.

It represented one of the largest construction jobs in North Carolina during the past decade and one of the largest SCR projects in the country. The construction workforce peaked at 2,000, with some crews working to modify and upgrade other equipment. Every worker passed through security checkpoints at multiple entrances to the congested jobsite, and Duke hired staff just to manage the logistics of accommodating so many additional people.

"We were successful at maintaining the facility," Huntley said. "I'm proud of the people at the plant and the way we worked through the issues."

Design work began in fall 2000 by Duke Power; Duke/Fluor Daniel, a joint-venture partnership of Duke and the Fluor Corp. of Aliso Viejo, Calif.; and Babcock Power Inc. of Boston. They completed structural monitoring on a computer to test the new and existing structures' abilities to withstand winds.

Fluor Corp. provides global engineering, procurement, construction, operations, maintenance and project management services. Babcock Power, through its subsidiaries such as Babcock Borsig Power Inc., supplies technology, equipment and services to the power generation industry. It has worked with Duke on other projects. Babcock Borsig Power has experience designing, installing and commissioning selective catalytic reduction systems.

Huntley said it was an engineering feat to mesh the new technology with the existing. "I compare it to a puzzle," he said. "You have all these pieces and at the end of the day, you have to get the pieces to fit together correctly."

Each boiler connects to its own SCR. The air passes down through an ammonia injection grid and four catalyst layers.

Construction began in fall 2001, when crews began core drilling the foundation. The plant sits on solid rock. Crews excavated 15-ft.-sq. cubes and then drilled steel rock anchors an additional 8 to 10 ft. into the bedrock, grouted them and filled them with concrete. Anchor bolts were tied to the rock anchors.

"The foundation not only had to carry the weight of the structural steel and SCR, it ties the thing down so it doesn't blow over," said Ray Hollins, general manager for plant betterment with Duke/Flour Daniel. "Not only does it hold it up, it holds it down."

Before starting work on the SCR, structural steel within the power plant required additions and modifications. Some of the siding was removed to access existing steel in the 13-story plant. Cladding and reinforcements were added to the existing structural steel, and instruments and electrical panels had to be temporarily removed before crews could complete the work.

The plant continued operating during construction.

"We had a process set up to do an operational review of the equipment attached to the column," Huntley said. "It took a tremendous amount of teamwork between the station and our contractors to pull that off."

The plant remained operating except during two 4.5-month tie-in periods. During that time, crews tore out some of the existing duct route, installed new ducts and replaced the air preheaters.

The project went 1.5 million work hours without a recordable injury and experienced no major incidents. Nets were installed to protect the operating equipment under construction areas.

A $6 million, 450-ft. Manitowoc 21000 crane was used to lift the structural steel and the expansive duct elements of the SCR devices. Each of the dual structures contains 6,900 tons of steel.

Fourteen-in. wide, 742-lb.-per-ft. rolled structural steel was imported from Luxemburg to provide extra strength. In addition, crews covered the columns with 2-in.-thick steel plates to further stiffen them.

The crane was brought from the World Trade Center site in New York on 60 flatbed trailers. It rests on four corner crawler treads. During lifts, its counterweight rolled on a separate radio-controlled trailer.

"You had to do so much planning," Hollins said. "You couldn't move that crane overnight. We had to decide where that crane was going to set and where to put it to maximize the number of lifts before moving it again."

The balance of the $1.5 billion Duke plans to spend on pollution control will include installation of sulfur dioxide scrubbers, which inject a mixture of limestone and water into the emissions, and selective noncatalytic reductions, which inject urea into the furnaces and are less effective than SCRs but more appropriate for some plants.

"You have to look at the way the plant operates and overall strategies," Huntley said. "It's just another tool in the toolbox."

Duke broke ground in February on a scrubber at its Marshall Steam Station, built in 1965. By 2007, Duke Power's nitrogen oxide emissions will be reduced more than 33 percent and by more than 70 percent by 2013. The Belews completion was a major step forward.

"We were able to work through the largest construction project not just in the Piedmont Triad but one of the largest SCR installations in the United States," Huntley said. "That gives you a sense of pride in what we have been able to accomplish."

Useful sources:
Selective Catalytic Reduction
Duke Power
http://www.duke-energy.com/environment/air-quality/selective-catalytic-reduction.asp