Environmental benefits
Combined cycle technology is one of the most environmentally friendly
forms of fossil fuel generation available. The station burns low-sulfur
natural gas for fuel. Exhaust gases from the natural gas turbines pass
through an SCR system to remove a majority of NOx, and an oxidation
catalyst removes significant amounts of CO and VOCs.
Water usage
¡¡The
station’s cooling towers use ambient air for steam condenser cooling,
which minimizes intake and discharge impacts to the Yadkin River
¡¡Maximum
flow requirements from the Yadkin River are approximately
5 percent of the water used by Buck’s coal-fired units 3 and 4
¡¡No
heated water is discharged to the Yadkin River
Site facts
¡¡Site
preparation began in 2008
¡¡Site
excavation and backfill required more than 60,000 cubic yards
of dirt
¡¡5.6
miles of underground pipe
¡¡1,961
tons of structural steel
¡¡25,191
¡¡177
¡¡A
cubic yards of concrete
miles of cable
20-inch pipeline supplies natural gas to the site
¡¡Commercial
operation began in November 2011
¡¡At
full load, each gas turbine consumes approximately 76,400 lbs/hour
of natural gas, roughly equivalent to a gas grill-sized tank of natural gas
per second
¡¡The
620-MW station has approximately twice the capacity of Buck
Steam Station’s original 369-MW rating
¡¡Power
augmentation systems:
¡¡HRSG
duct burners – At full load each HRSG duct burner system
consumes approximately 26,800 pounds per hour of natural gas
¡¡Additional
heat input is capable of adding up to 65 MW of additional
generating capacity from the steam turbine generator
¡¡Inlet
air chilling – Two 6,000-ton chiller plants capable of cooling the
inlet air to each gas turbine to 45 degrees Fahrenheit. This allows us
to recover lost MW due to elevated temperatures and humidity during
summer months.
¡¡Employs
Buck Combined Cycle Station
approximately 40 people
©2013 Duke Energy Corporation 130977 10/13
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Located in Rowan County, N.C., Duke Energy’s Buck Combined Cycle Station utilizes
one of the most efficient and flexible fossil generation technologies available. The
620-megawatt (MW) station incorporates two natural gas-fired combustion turbine
generator sets, two heat-recovery steam generators and a steam turbine generator
set to produce electricity.
The major components
1Two General Electric 7FA gas turbine generator sets rated at 170 MW at
18 kV each.
2Two Vogt HRSGs capture exhaust heat from the combustion turbine to heat
water inside a series of tubes, producing steam. Gas burners are used to
increase the steam temperature and pressure.
Buck Combined Cycle Station can go from “cold shutdown” to full capacity in
approximately four hours, ramp up and down based on system demand or run
24 hours a day. This flexibility helps Duke Energy manage its generation fleet
cost-effectively.
3A selective catalytic reduction (SCR) system removes a significant amount of
the nitrogen oxide (NOx) from the combustion process. An oxidation catalyst
removes most of the carbon monoxide (CO) and volatile organic compounds
(VOCs) produced.
Buck Combined Cycle Station shares a strong connection to Duke Energy’s early
history and tradition of utilizing the latest, most efficient technology to meet customer
demand for electricity. Just a few hundred yards away stands the Buck Steam Station,
which generated electricity and served the community for more than 80 years.
4Water vapor leaves the stacks, and continuous emissions monitoring equipment
ensures air quality regulations are met.
5One GE D11 steam turbine generator set produces 280 MWs at 18 kV. This
‘traditional” turbine generator uses steam from the HRSGs to produce electricity,
increasing plant efficiency.
Buck Steam Station
In 1926, Buck Steam Station entered commercial operation with two units, the
first in the South to use pulverized coal. Named after James Buchanan “Buck”
Duke, co-founder of Southern Power Company, the station had four additional units
operating by the 1950s. Units 1 and 2 retired from service in 1979, followed
by units 3 and 4 in 2011 and units 5 and 6 in 2013 as part of Duke Energy’s
continuing efforts to modernize its generating fleet.
6A 10-cell cooling tower uses ambient air to dissipate heat from the condenser
cooling water, avoiding the need to discharge heated water to the Yadkin River.
7Three ABB main step-up transformers take voltage from their respective
generator at 18 kV and step it up to 230 kV prior to being pushed to the
power grid.
Adjacent to the station, Duke Energy established and maintained Dukeville Village as
housing for employees and their families well into the 1950s. Employees paid rent,
and their children attended a school located on Dukeville Road.
How does combined cycle technology work?
A natural gas combined cycle generating facility efficiently combines two energy
production processes – gas combustion turbines and a steam turbine – to
convert natural gas fuel to electricity. First, natural gas is burned in
Combustion
two combustion turbines to heat compressed air. The expanding
Turbine
air turns a turbine with mechanical energy that is converted
to electric power by the generator. For increased
1
efficiency, the hot exhaust gases from the natural
gas combustion process are then routed through
Main Step-up
two 93-foot-tall heat recovery steam generators
(HRSGs), which heat water to produce steam.
Transformers
The steam turns a steam turbine generator to
create additional electricity. Combined cycle
7
plants have high operational flexibility, high
thermal efficiency and significantly
reduced emissions.
Heat Recovery
Steam Generator
2
Selective
Catalytic Reduction
3
Stack
4
Steam
Turbine
5
Cooling
Tower
6
The Buck Combined Cycle Station can
generate 620 MW of electricity.
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