Emissions Reduction Technologies
by mike rhodes
NRG Energy’s El Segundo Energy Center, designed for intermediate to continuous
duty and capable of daily cycling, is the second Siemens Flex-Plant combinedcycle power plant to open in California, U.S.A.
Flexing By The Sea
Siemens Flex-Plant 10 provides power for NRG plant upgrade; emissions control, efficiency, lowered
environmental impact key aspects
NRG Energy Inc. and Siemens Energy Inc. have completed a repowering and modernization project at
the 13-hectare El Segundo Energy
Center located on the Pacific Coast
near Los Angeles, California, U.S.A.
The natural gas-fueled, combinedcycle Siemens Flex-Plant 10 power
islands have entered commercial
operation and added an installed
capacity of 550 MW — enough to
supply electricity to approximately
450 000 California homes — to
bring the facility’s total output to
just under 1000 MW.
NRG’s El Segundo Energy Center is the second Siemens Flex-Plant
combined-cycle power plant to open
in California — after the Lodi Flex-
Plant 30 Energy Center in northern
California that went into commercial
operation last year. Siemens said that
both plants are designed for intermediate to continuous duty and capable
of daily cycling.
In 2011 and 2012, more than 1.8
GW of renewable energy was added
to the California grid, three times
as much as the state’s added fossil
power. Complementing California’s
growth of intermittent renewable
energy sources and contributing significant environmental benefits to the
existing site — improving air quality,
reducing noise emissions, and lowering the impact on marine life and local communities — were a major part
of NRG’s modernization efforts.
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“We support the state’s renewable
portfolio standard and maintain our
tradition of being a good neighbor to
the surrounding coastal communities,” said John Chillemi, president of
NRG Energy’s West Region. “We have
worked with the community to improve the visual aesthetics of the site
by incorporating native landscaping,
installing a new sea wall, improving
the bike path along the pristine beach
strand, maintaining coastal views
with a lower plant profile, and the removal of two large oil tanks.”
The most significant environmental
benefit was the removal of two 175
MW steam boilers — constructed in
1953 — and the shutdown of one of
the 335 MW steam boiler units —
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Siemens delivered two Siemens SCC6-5000F 1x1 Flex-Plant 10 combined-cycle power plants. The main components are an SGT6-5000F gas turbine; an SST-800 steam turbine; an SGen6-1000A generator; an SGen6-100A-2P generator; a small-footprint, air-cooled heat exchanger; and two
NEM DrumPlus heat recovery steam generators (HRSGs).
constructed in 1964 — that relied on
ocean water for cooling.
“One of the key benefits of this
project is that it retired approximately 1.5 billion L/day of oncethrough cooling,” said George Piantka,
director of Environmental Business
at NRG Energy Inc.
Piantka said the new Energy Center now uses first pass reverse osmosis
(RO) reclaimed water from the West
Basin Municipal Water District in its
operations, requiring 90% less water
than traditional ramping solutions and
meeting the standards of the oncethrough cooling initiative in California.
“The facility’s emissions meet or
are below federal, state and the South
Coast Air Quality Management District’s (AQMD) air quality standards,
and will use 30% less natural gas per
MW than the original steam boilers,”
Piantka said.
“The El Segundo upgrade became
essential because the available regional electrical resources have proved to
be insufficient to meet the current
and expected growth in the region,”
Chillemi said.
“With the recent closure of the San
Onofre Nuclear Generating Station
(SONGS) and the need to integrate
the grid’s rapid increase of renewables and replace aging steam boiler
generation — consistent with California’s 316(b) policy — the El Segundo
project adds critically needed generation and reliability for the region.”
For the El Segundo Energy Center,
Siemens delivered the first two Siemens SCC6-5000F 1x1 Flex-Plant 10
combined-cycle power plants in commercial operation in the U.S.A. The
main components feature an SGT65000F gas turbine; an SST-800 steam
turbine; an SGen6-1000A generator;
an SGen6-100A-2P generator; a smallfootprint, air-cooled heat exchanger;
and two NEM DrumPlus heat recovery
steam generators (HRSGs).
Siemens also supplied the complete
electrical equipment, engineering services and commissioning of the plant,
and its SPPA-T3000 power plant in-
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strumentation and control system.
From first concept through construction, effective system integration is a
big part of every project, and Siemens
said the SPPA-T3000 provides an
easy-to-use control platform for the
entire combined-cycle plant, including grid connection, water plant and
gas compression.
The main drivers of the two FlexPlant 10 plants are the SGT6-5000F
gas turbines, which are integrated
with a single-pressure, non-reheat
bottoming cycle. Siemens said the
new plants will provide high power
density while requiring a relatively
small plant footprint of 2 hectares
each, an especially important feature
for NRG because the El Segundo site
is nestled between a cliff and the Pacific Ocean and the new plants were
erected while the existing facility was
being operated.
Together, the two units can generate 300 MW — more than half their
combined output — in less than 10
minutes and the balance in less than
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Siemens’ SGT6-5000F gas turbines, which are integrated with a single-pressure, non-reheat bottoming cycle, are the main drivers of the two
Flex-Plant 10 plants.
an hour. Waste heat from each combustion turbine will be used to produce steam, which will generate an
additional 70 MWs of energy per train.
The small-footprint, air-cooled heat
exchanger condenses the steam coming out of the cycle back into the liquid water so it can be recycled and
used again to power the steam turbine. Hot steam travels through finned
tubes while the cooling air flows across
the outer surface to remove the heat,
Siemens said. The Flex-Plant 10 provides a net efficiency of nearly 49%,
making it much higher in efficiency
than conventional peaking solutions,
the company said.
This allows the plant to balance
fluctuating renewable power generation such as wind and solar power and
maintain a consistent and reliable supply of power to the grid, Siemens said.
The site is one of the first to incorporate the Siemens’ Clean-Ramp
Technology, reducing transient emis-
sions as the gas turbines ramp up and
down to meet electricity demands.
“We have advantages as an OEM,”
said Richard Loose, director of Marketing, Energy Solutions, Americas,
Siemens Energy Inc. “We can integrate the start-up sequence at a
whole new level. We began by plotting the events and critical paths
that make up a start-up — how
can we eliminate this one? How
can we overcome that one with an
integrated solution?
“We started putting in things like
final-stage attemperators, steam pipe
warming approaches, steam turbine stress controllers, and the NEM
DrumPlus heat HRSGs. All of these
are integrated through the SPPAT3000 DCS and have reduced startup times and emissions.”
NEM said the design of its DrumPlus boilers ensures that no hold
points are imposed on the gas turbine during start-up. Whereas con-
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ventional drum-type HRSGs run a
high risk of severely reduced lifetime
due to cycling stresses, NEM said its
DrumPlus technology experiences
significantly less peak stress because
of its smaller drum wall thickness,
which is allowed by the external location of the water/steam separators
and other mechanical features.
The company said that fast starting power plants have two significant
advantages compared to cycling baseload plants — NOx emissions during
start-ups are reduced because the gas
turbine is able to reach low NOx operating loads more quickly; and the
plants are able to respond rapidly to
fluctuating power demand and market pricing conditions. These benefits
lead to higher efficiencies and increased kWh for commercial use during the first hour, NEM said.
The company said this can result in
89% less CO emissions per start —
more than 181 tonnes/yr when com-
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pared to traditional F-class combinedcycle plants — and 95% less NOx.
DrumPlus technology is available
for single-, two- and three-pressure
HRSGs. Like any HRSG boiler, NEM
said the DrumPlus needs no special
feedwater equipment, such as a condensate polishing plant, and can use
water that meets ASME requirements.
The output of NEM’s HRSGs is 78 kg/s
with a temperature of 502°C at a
pressure level of 99.5 bar.
“California has some of the most stringent environmental requirements in the
world, so it’s a good thing the HRSGs
and Siemens’ Flex-Plant 10 are capable
of controlling the emissions,” said Hans
Vanderweiden, manager of Operations,
NEM USA Corp. “The communities demand it, and they deserve it. The technology is there, and so load changes
can be anticipated proactively instead
of followed, which allows us even more
emissions control.
“The partnerships developed dur-
ing this project have been vital to its
success. If our technology helps NEM
succeed, then sharing it with Siemens
and NRG increases the effectiveness of
our collective efforts, especially with
these high-demand applications.”
For the repowering project, NRG
delivered the engineering, procurement and construction (EPC), while
Orange County, California, U.S.A.based ARB carried out the building of
the facility. The modules that make up
the facility — gas and steam turbines,
HRGSs, and components of the aircooled heat exchanger — were built
off-site and brought through the Port
of Long Beach and by rail, the company said. Approximately 20 heavyhaul loads were brought through the
city on designated routes, NRG said.
“We certainly could not have
achieved this without close support
and coordination with the cities of
Manhattan Beach, El Segundo and
Los Angeles,” Piantka said.
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Through a 10-year power purchase
agreement, Southern California Edison will obtain the entire output of
the facility, which now produces almost 1000 MW.
“The El Segundo Energy Center
and our Flex-Plant 10 power plants
are a collection of different technologies that have been tested and proven, but may not have been grouped
quite like this,” said Martin Tartibi,
head of Gas Turbine Power Plant Solutions Americas – Power Generation
Division, Siemens Energy.
“Techniques are constantly evolving and there are always lessons
learned as we look ahead to the next
phase. We’re adaptable to the needs
of California and as a company we’re
looking at the dynamic future of energy in a different way. We’d like to
see even more efficient, cleaner, environmentally friendly and cost effective technology that can serve as the
backbone to support renewables.” A
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