POWER September 2014 - 31

TOP PLANTS
1. Flexible turbine operations. The high-pressure and intermediate-pressure steam
turbines are connected to the low-pressure (LP) condensing turbine via a clutch. When the
steam heating demand is high, the LP clutch allows isolated operation of the HP and IP turbines,
which are on a common shaft. When steam demand is low, the clutch engages the LP condensing
turbine for maximum power production. Courtesy: Beijing Jingqiao Thermal Power Co., Ltd.
turbine secured, CTs at full load) is 592 MWt
at 260C. The CTs are normally operated at
baseload when feeding power into the Beijing
Municipal Power Corp. grid. Under extreme
cold conditions or during an outage of
other steam heating resources, the steam produced
by the HRSGs can completely bypass
the steam turbine, be desuperheated, and then
sent directly to the steam heat system. Under
those conditions, the maximum heating capacity
of the system is 729 MWt.
The design of JPP is to meet most of the
heating demand of southwest Beijing in extreme
cold conditions (very cold weather or
malfunction of other heating resources) and
it is the biggest gas-fired heating center in its
service territory.
bines (CTs) with low-NOx burner technology
were provided by Shanghai Electric Power
Generation Group (SEC PG). Siemens as a
subcontractor of SEC PG provided the core
engines and its SPPA-T3000 control system
for the CTs, the single steam turbine, and coordinated
plant operation. Siemens also provided
an on-site field technical adviser during
CT installation and commissioning.
Wuxi Huaguang Boiler Co., Ltd. supplied
the two triple-pressure heat-recovery steam
generators (HRSGs) designed to operate at
12.5 MPa with 545C superheat and 540C
reheat temperatures. The HRSG is a vertical
type, with five modules. In between the third
and fourth module is the selective catalytic
reduction catalyst. There is no bypass stack
between the CT and HRSG. The steam production
of each HRSG is 512 tons/hr.
NOx production is on par with the best
of the modern generation of gas-fired combined
cycle units now being installed around
the world. During the performance test, CT
emissions were under the 25-ppm guarantee.
The denitrification system placed within the
HRSG further reduced NOx by 85%, thereby
producing HRSG stack NOx emission of approximately
4 ppm (7.3 mg/m3).
The steam turbine was manufactured
by Shanghai Turbine Plant, part of SEC
PG. Shanghai Generator Plant, also part
of SEC PG, supplied the three 300-MW
electric generators.
Two Operating Modes
The arrangement of the condensing cycle is
unique. The high-pressure (HP) and interSeptember
2014 | POWER
mediate-pressure (IP) steam turbines (on a
common shaft) are connected with its lowpressure
(LP) turbine via an overrunning
clutch supplied by SSS Clutch Co., Inc. The
generator is connected at the HP end of the
steam turbine. When operating in full condensing
mode (maximum power) the clutch
is fully engaged and the three steam turbines
operate in unison (Figure 1).
On the steam side, HP steam produced by
the HRSG expands through the HP turbine.
Cold reheat steam mixes with the HRSG's
IP steam and enters the reheater to become
the hot reheat steam, which expands through
the IP and then the LP turbine. LP steam, the
third pressure level steam produced by the
HRSG, is mixed with the IP exit steam as it
enters the LP turbine. Steam exits the LP turbine
and condenses in the condenser at 0.4
MPa via wet cooling towers. A startup boiler
is used to provide heating steam when the
plant is out of service for maintenance.
When heating steam demand rises, the LP
turbine can be disconnected from the driveline
and secured. The steam exhausting from the
HP and IP turbines that would normally go
to the LP turbine is then directed to the steam
heat system. When steam demand drops, the
steam can be redirected to the LP turbine.
When the LP turbine accelerates up to synchronous
speed, the clutch reconnects the LP
turbine to the driveline to produce electricity.
When operating in combined cycle mode
(no steam heating) the plant operates at a
very respectable 59.5% thermal efficiency,
as confirmed during performance tests. The
maximum thermal energy production (LP
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Looks Count
Making the combined heat and power facility
aesthetically pleasing was a high priority for
its designers, as is evident from the photos.
Because the plant is located within the 4th
Ring Road in Beijing (an eight-lane expressway
that circles the city about 8 kilometers
from the center) the view of the plant was
" deindustrialized. " For example, the building
height matches the height of the HRSG
stacks and a noise-reduction wall surrounds
the CT air intake. Also, the steam turbine
building was placed next to an office building
located to the east of the plant as a buffer to
reduce stray equipment noise. The noise level
outside the plant is approximately 45 dB, less
than the noise level found in a typical business
office.
The compact plant site also presented a
significant design challenge because sufficient
land for another 2 x 1 combined heat
and power plant was set aside. The specific
area of the unit is 0.063 m2/kW, compared to
typical U.S. combined cycle plants that often
use 0.5 m2/kW to 1.0 m2/kW or more.
Did you notice the plant substation is
missing in the lead photo? It's actually located
completely underground for aesthetic reasons
and because of the constrained site. The
generator's enclosed bus ducts are located
3 meters underground and connect with the
main transformers located 9 meters underground.
The high-voltage power cables are
connected to the Beijing grid via a channel
located 6 meters beneath the surface. The rest
of the plant is also well hidden from view.
The longest continuous operation of the
plant since entering commercial service was
about 100 days, and that long run was interrupted
by order of the grid dispatcher placing
the plant into standby mode. The plant
equivalent availability factor was an excellent
82.28% in 2013, its first year of operation. ■
-Dr. Robert Peltier, PE is POWER's
consulting editor.
31

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POWER September 2014

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