POWER October 2013 - 39

Top planTs
tor delivers main steam at ~3,800 psia and
1,055F at the superheater and reheater outlets.
The steam generators are sliding pressure,
balanced draft units with spiral-wound
furnace wall construction. The tube materials
were selected to accommodate the use of
high-sulfur Illinois Basin coals. The state-ofthe
art emissions controls were designed and
furnished by Siemens Power Generation Inc.
to remove 98% of SO2, 90% NOx, and more
than 99% of particulate matter, the most
common emissions. PSEC takes native Illinois
coal that contains more than 9 pounds of
SO2 per million Btu and reduces emissions
to just 0.182 pounds of SO2 per million Btu.
This results in emissions that are less than
one-fifth the national average for existing
coal-fueled plants.
The air quality control equipment arrangement
begins with low-NOx burners, followed
by a selective catalytic reduction system for
NOx control, an activated carbon injection
system for mercury control, a hydrated lime
injection system for hydrofluoric acid removal,
a dry electrostatic precipitator (ESP) for
particulate control, wet flue gas desulfurization
for SO2 control, and a wet ESP for aerosol
control. PSEC reportedly spent ~$1 billion on
its air quality control systems alone.
Toshiba International Corp. supplied the
steam turbine-generators, nominally rated at
877 MW at an exhaust pressure of 3.0 inches
of mercury. Each steam turbine is a 3,600rpm,
extraction condensing, reheat type
unit with eight stages of steam extraction
for feedwater heating and feedwater pump
supply. The electric generators are rated at
1,020 kVA and are direct-driven, two-pole,
hydrogen-cooled machines with secondary
water cooling.
Steam turbine exhaust steam is condensed
in a two-shell, single-pressure, water-cooled
surface condenser with stainless steel tubes.
Cooling water is circulated through the condensers
and cooled by mechanical draft cooling
towers. The circulating water system for
each unit uses three 33%-capacity circulating
water pumps, and one auxiliary 100%-capacity
cooling water pump. Makeup water is supplied
from the Kaskaskia River located about
15 miles west of the plant. A storage pond has
an on-site 30-day backup water supply.
Express Delivery
Coal from the mine is conveyed to PSEC and
placed on the coal storage pile at a rate of
2,600 tons per hour via conveyor system. In
the normal course of business, sufficient coal
to operate the plant for 24 hours is delivered to
the plant in 10 hours. Coal is reclaimed from
the coal pile at 2,600 tons per hour to surge
hoppers located near each steam generator.
The active coal pile holds approximately 10
days of fuel under normal operating conditions.
Space on the plant site has also been allocated
for an inactive coal pile that can store
fuel for up to 60 days under full-load operation.
Rail service to the plant was configured
so that external supplies of coal, of a quality
specified in the plant's air permit, could be
procured should there be an extended disruption
in coal deliveries from the mine.
Bottom and fly ash from the boiler and
air quality control systems are collected
and combined with the wastes produced
by the flue gas desulfurization systems and
conveyed to the coal combustion residuals
(CCRs) storage area. Wastewater produced
by the plant, such as boiler and cooling tower
blowdown, is reused in the ash-handling
and flue gas desulfurization systems. Rail
service is also used for delivery of lime1.
Convenient coal. Coal conveyed from the mine is placed on the coal storage pile at a
rate of 2,600 tons per hour. Courtesy: Prairie State Generating Co., Ltd.
stone and disposal of CCRs. PSEC disposes
its CCRs in the newly constructed Near
Field, a monofill built to Illinois Environmental
Protection Agency standards that sits
directly adjacent to the power plant. CCRs
are transported to Near Field via conveyor,
further reducing the need for rail transportation.
PSGC also maintains Jordan Grove, a
fully lined and managed monofill 12 miles
south of the campus.
Revised and Amended
PSEC, like any controversial power generation
project, experienced delays caused by
permitting legal challenges and construction
delays. Bechtel Power Corp. and Prairie
State Generating Co., LLC originally
entered into a time and material engineering-procurement-construction
(EPC) agreement
with a targeted completion date, price,
and other performance requirements. In July
2010, a revised and amended EPC agreement
with a guaranteed completion schedule
was reached that fixed the total cost of
the project to PSEC at $3.999 billion, not
including the cost of the mine development.
According to Fitch, the rating agency for a
majority of the ownership group, the additional
project cost was mitigated by the additional
protection provided by the amended
construction contract.
The project cost is certainly higher than
originally envisaged in the early 2000s
for a coal plant of this magnitude but still
much cheaper than for integrated gasification
combined cycle-the only other option
for combusting the available Illinois Basin
coal-whose U.S. projects now under construction
have experienced massive cost
overruns and missed schedules.
However, now that the plant is operational,
plant owners are enjoying reliable electricity
with little fuel price risk for the next 30 years.
In addition, ownership of the asset decreases
each owner's exposure to the unpredictable
electricity spot market and to rising prices for
long-term bulk power purchases.
The ownership group is taking the long
view its investment-the price of natural
gas, coal, and the cost to transport coal will
steadily rise into the future while PSEC's
costs are under the owner's control, unlike
most plants. I expect the owners' investment
in PSEC will pay handsome dividends for
many years to come.
Both units have been performance tested
and each unit is now being dispatched at
higher than its nameplate capability: Unit 1
at 812 MW and Unit 2 in excess of 809 MW.
The tested net plant heat rate was reported by
PSEC as ~1% better than guarantee. ■
-Dr. Robert Peltier, PE is POWER's consulting
editor.
October 2013 | POWER
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