BELEWS PROJECT Largest SCR job in U.S. required big boom and jib crane.

A North Carolina utility is spending nearly $2 billion to clean its emissions. A federally driven $450-million selective catalytic reduction project, the largest in the U.S., is now nearing completion and another $1.5-billion state-driven sulfur dioxide reduction program is just ramping up.

Duke Power, Charlotte, N.C., has started engineering on a $1.5-billion program designed to reduce nitrogen oxide emissions by 30% and sulfur dioxide emissions by 70% at its seven North Carolina coal-fired powerplants. The effort was driven by state clean air legislation passed last year that also freezes rates for five years. The program will be amortized through existing rates and costs recouped in a flexible manner to keep earnings stable. "We’ll be scrubbing 12 units and likely do selective noncatalytic reductions on 24 units," says Mary Katherine Green, Duke spokesperson.

Persistent smog, acid rain and air quality problems in the western part of the state drove the cleanup. On hot, sunny days NOx combines with organic chemicals in the air to form ground-level ozone, a component of smog. Sulfur dioxide also contributes to smog and acid rain. SCRs channel hot flue gasses and injected anhydrous ammonia through ceramic honeycombed bricks to convert more than 80% NOx into nitrogen and water. SNCRs inject ammonia into the gas stream, converting NOx to a lesser degree, or about 25%. Wet scrubbers bubble flue gas through molten limestone to transform SO2 into gypsum and water. "We used SCRs where the largest emissions were and where we could do the engineering," says Thomas C. Williams, Duke communications manager. "SNCRs are more cost-effective on smaller and older units and scrubbers will be used on all large plants."

Duke will perform SNCR engineering work in-house but Alstom Power, Knoxville, Tenn., will provide the engineering, equipment scoping and site testing for the scrubber work. Plants involved include: the five-unit Allen station, unit number five at the Cliffside station, the four units at the Marshall station and the two units at Belews Creek station. Contracts totaling about $300 million to $400 million will be let in the next six months for the Marshall work. Work at all plants must be completed by 2013.

MARSHALL PLAN Scrubber backfit, to be let soon, could cost uptp $400 million.

Duke is wrapping up about $550 million in federally driven SCR work at two plants. Unit five at Cliffside, a 760-Mw plant, is finished and phase two at Belews Creek, a two-unit, 2,400-Mw plant, is nearing a June 2004 completion. Belews Creek is Duke’s largest coal-burning plant, consuming up to 19,000 tons of coal per day. To comply with federal clean air standards, Duke is reducing NOx emissions by 80% there.

Charlotte, N.C.-based Duke/Fluor Daniel heads the three-year engineer-procure-construct deal at Belews. Because of a tight site, the SCR’s had to be built over existing boiler buildings and precipitators, resulting in 300-ft-tall towers that were structurally integrated into the plant. "The SCR creates a huge sail so we had to drill and grout several hundred rock anchors about 30 ft to 40 ft deep in bedrock," says Harold L. Backman, Duke project director. Over 7,000 tons of structural steel and 44,500 linear ft of piping were used on unit one. It has been operating at full capacity since August.

The 29-year-old plant provides power to more than 2 million homes in the Carolinas. It cost about $357 million to build. Duke also is replacing boiler tubing and controls and completing a precipitator refurbishment. Because of the project size and location of the SCRs, a Manitowoc 21000 crane with a 420-ft boom and jib was needed to lift equipment and ductwork fabricated on the ground. The rig was last used in the cleanup at the World Trade Center.

"This is the largest SCR project in the U.S. owing to the electric output of the station and the tight site and the capacity for four layers of catalysts," says Ray Hollins, general manager of the joint venture. "We upsized the four induced draft and four forced draft fans and motors and added variable frequency drive to the ID fans to better control speed." He notes they also replaced the air heaters to increase boiler efficiency. That required significant interior plant demolition and increased structural steel on the SCR and building to support the heaters. The SCR currently uses only two levels of catalysts but two more levels are available for future management.

Duke/Fluor Daniel also completed the Cliffside work. In July officials announced the venture would disband because of a decline in powerplant construction. The transition could take two years.

Source: Duke Energy