POWER November 2016 - 32

PLANT DESIGN
For Further Reading
The POWER archives contain many profiles
of plants that rely on circulating
fluidized bed technology to combust
opportunity fuels. To see all the articles
covering the technology, enter " circulating
fluidized bed " in the search field at
powermag.com. Included in the results
are plant profiles of these award winners,
among others: Virginia City Hybrid
Energy Center (October 2012), Northside
Generating Station (October 2012), Polaniec
Green Unit (October 2013), and
Spiritwood Station (October 2015).
been effective at reducing erosion and corrosion
damage, particularly in the latest generation
of supercritical and ultrasupercritical
boilers.
CFB Problems and Solutions
Ash produced by combustion must be continuously
removed from the bed material
along with the reacted sorbent. Quantifying
the amount and characteristics of the ash produced
by the fuel is paramount. If a region
of the bed operates near the softening temperature
of the ash or the sorbent, then agglomeration
of ash and bed particles is likely,
which causes an increase in tube fouling-
perhaps the most common problem reported
by CFB users, right behind furnace tube erosion.
Also, ash removed from the bed must be
cooled prior to handling, and the ash coolers
are prone to plugging and erosion.
Hot cyclones, operating at gas path temperatures,
have been a source of frequent outages
in the past. The cyclones were protected
by multiple layers of refractory, although
cracking of the refractory often went undetected,
resulting in heavy damage to the cyclones,
particularly in units that are routinely
thermally cycled. Water- and steam-cooled
cyclones have significantly reduced cyclone
unplanned outages and extended cyclone
maintenance intervals.
Recent improvements in fuel and sorbent
feeders, as well as ash extraction and cooling
systems, have also improved CFB availability.
CFB system availability in the late 1980s
ranged from 50% to 70%, depending on the
data source. Over the past 20 years, availability
has not dropped below 80%, and modern
plants commonly report plant availability of
90% or higher-on par with pulverized coal
units. Multi-fuel CFB units are challenged by
variable ash characteristics, such as the presence
of potassium, chlorine, zinc, and lead in
some waste fuels.
Each fuel has its own ash-forming charac32
3.
Go big or go home. The Korea Southern Power Co. Ltd., part of the KEPCO Group,
is developing the Samcheok Green Power Plant on reclaimed land located on the east coast of
Korea. At 2,200 MW, the plant will become the largest CFB plant in the world when completed,
which is expected to be in early 2017. Courtesy: KEPCO
teristics, and the effect of fouling, slagging,
and fluidization is difficult to predict with
precision.
State-of-the-Art Projects
The first CFB used solely for power generation
was a 90-MW plant constructed in Duisburg,
Germany, in 1985. For the next 25 years,
CFB technology units lagged conventional
coal-fired units in one extremely important
measure: thermal efficiency. In June 2009,
the 460-MW Lagisza Power Plant (LPP),
located in Lagisza, Poland, became the first
supercritical bituminous coal-fired plant to
enter commercial service (Figure 2). LPP,
owed by Poludniowy Koncern Energetyczny,
was supplied by Foster Wheeler Energia and
its Polish subsidiary Foster Wheeler Energia
Polska, and is designed to burn bituminous
coal sourced from 10 different mines.
This first deployment of a supercritical,
once-through steam generator increased
CFB thermal efficiency by approximately
5%, thereby closing the efficiency gap between
conventional coal and CFB plants.
The thermal efficiency of LPP was an advertised
43.3% when commissioned, which
is comparable to that of pulverized coal-fired
technology.
Since the LPP, the market for CFB units
has continued to rapidly expand. Several new
CFB units operating with ultrasupercritical
(USC) and supercritical steam conditions
have been commissioned or are under construction
that build on the success of the LPP.
Over the past decade, CFBs coupled with
www.powermag.com
supercritical steam generators have been installed
in South Korea and China in the 550MW
to 600-MW range, with units up to 800
MW now advertised as commercially available.
Reported thermal efficiency and availability
also continue to steadily rise as the
technology advances.
South Korea. The Korea Electric Power
Corp. (KEPCO) recently invested heavily
in CFB technology for its future baseload
power needs. The KEPCO Research Institute
reported in December 2015 that global USC
and supercritical CFB projects will grow at
an annual rate of 35% with China, Japan, and
Australia leading the way with 56 USC and
supercritical CFB plants in service by 2018.
The Institute predicts Southeast Asia will follow
with 22 units, Europe with 20 units, and
North America with 18.
Perhaps the most interesting KEPCO
project under construction is Korea Southern
Power Co. Ltd.'s Samcheok Green Power
Project (Figure 3). Planning for the plant
began after several nuclear power plant cancellations
that were caused by the public's
waning support for nuclear power following
the Fukushima disaster. The plant is located
on the mid-east coast of Korea on a 2.6 km2
plant site, of which 1 km2
is land reclaimed
from the ocean. The first phase consists of
two 550-MW units, with each unit comprising
two CFB boilers and a single Toshiba
steam turbine. Eventually, the plant will have
four 550-MW CFB units. When completed,
the 2,200-MW Samcheok Green Power Project
will become the largest CFB plant in the
POWER | November 2016

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POWER November 2016

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