POWER May 2011 - 69

THE FUTURE OF COAL
4. Rising steam. Tracking the steam conditions of supercritical coal-fired plant design by
region shows rapid progress in Japan and China over the past few years. U.S. progress has
been slower. Dotted lines indicate where the market is headed in terms of further improving
USC technology for all countries. Source: www.worldbank.org
Europe
1,292F
/5,076 psi
1,112F
/4,200 psi
1,040F
/3,916 psi
1,004F
/3,625 psi
1,000F
/2,400 psi
1970
1980
Waigaoqiao 2x 900 MW
3,635 psi, 1,000F/1,050F
1990
Year
Table 4. Plant stats. Lünen Plant, a state-of-the-art ultrasupercritical coal-fired plant, is
under construction in Germany and slated for a late 2012 start-up. Here are some of its key
performance and technical features. Source: Navigant
Gross power output
Net efficiency (LHV basis)
Steam generator
Gas cleaning
Steam parameters
Steam turbine
Generator
Feedwater preheating
813 MW (rated output; 50 Hz), single unit
~45.6% (@ design point)
Tower-type once-through boiler with vertical evaporator tubing
Selective catalytic reactor (DeNOx), electrostatic precipitators (particulate
matters), and wet limestone flue gas desulfurization (SOx)
4,060 psi/1,112F/1,130F steam conditions at boiler outlet
SST5-6000 with single reheat and two double-flow LP turbines (4x12.5 m²
exhaust annular area)
SGen5-3000W, water/hydrogen-cooled
Nine stages: 3 high-pressure FWPH (header-type) with one external desuperheater,
5 low-pressure FWPH (plate-type); feedwater heaters A1 & A2 are
located in the condenser neck as a duplex heater
Final feedwater temperature 586F
Feedwater pump concept
Condenser
Flue gas discharge
Distributed control system
2 x 50% electric motor-driven feedwater pumps
Dual-pressure serial condenser operating at 0.88 and 1.32 in. Hg, respectively
Via the natural-draft wet cooling tower
SPPA-T3000 power plant automation system
Japan is clearly leading the way, followed
closely by China and Europe, while the U.S.
clearly is lagging behind. China has made
tremendous investments in advanced supercritical
design in recent years. Two of that
country's more recent projects are identified
in Figure 4.
Further improvements in efficiency are
dependent on the availability of new nickelbased
alloys for the high temperatures and
pressures in ultrasupercritical PC boilers.
Two major development programs currently
under way-the European Commission's
Thermie Project and a U.S. program managed
by the Electric Power Research InMay
2011 | POWER
stitute for the U.S. Department of Energy
and the Ohio Coal Development Office-
aim to achieve steam parameters of 5,439
psi and 1,292F/1,328F and 5,500 psi and
1,346F/1,400F, respectively. (Efficiency increases
approximately 1% for each 36F rise
in superheat and reheat temperature.)
Lünen: State-of-the-Art
Ultrasupercritical Plant
One current example of a state-of-the-art ultrasupercritical
plant is the Lünen plant, located
just outside of Lünen, Germany. It is an
800-MW unit burning international low-sulfur
bituminous coal delivered by river barge.
www.powermag.com
Coal's Future
Coal is sure to play a continuing and vital
role in meeting the world's future electricity
needs. However, increasing global political
pressure to reduce carbon emissions may
severely diminish coal's favored status going
forward. Clean coal technologies, such as
integrated gasification combined-cycle and
CCS, are under development but have yet to
prove their technical or commercial viability.
In the meantime, global electricity demand
is increasing, and so is interest in advanced
coal-fired plant designs, such as the Lünen
USC plant. ■
-Dale Probasco is a managing director
with Navigant's Energy Practice and can
be reached at dprobasco@navigant.com.
Bob Ruhlman is an associate director with
Navigant's Energy Practice and can be
reached at rruhlman@navigant.com.
69
2000
2010
2020
Japan
USA
China
Yuhuan 4 x 1,000 MW
4,000 psi, 1,121F/1,117F
The estimated project cost is €1.4 billion-
equivalent to an installed cost of $2,547/kW
(2009 $). The plant, now under construction,
is expected to enter service late in 2012.
Some of the plant's key technical features are
listed in Table 4.
In order to obtain the desired high efficiency
at a reasonable costs, the Lünen
plant designers focused on four specific areas:
optimizing the combustion processes,
increasing the steam parameters, reducing
the condenser pressure, and improving the
internal efficiency of the steam turbines. The
Lünen plant's USC steam generator combustion
efficiency was also increased by:
■ Optimizing the steam generator heating
surface arrangement.
■ Raising the final feedwater temperature to
586F.
■ Keeping the excess air coefficient in the
firing system at less than 1.2.
■ Controlling the reheater outlet temperature
without water injection.
■ Reducing the exhaust gas temperature
downstream of the air preheater to 248F.
■ Minimizing steam- and gas-side pressure
drops.
Perhaps just as interesting as the plant's
design features is the fact that the plant is
being constructed in the European Union
(EU), where utilities have a legal requirement
to reduce carbon emissions. However,
instead of eliminating coal as a power
generation fuel, the EU (and Japan, too)
replaces older, less-efficient coal plants
with new, high-efficiency coal plants that
produce a net decrease in carbon emissions.
(See " Isogo Thermal Power Station
Unit 2, " October 2010 for a good example
of this replacement process.)
Steam conditions

http://www.worldbank.org http://www.powermag.com

POWER May 2011

Table of Contents for the Digital Edition of POWER May 2011