POWER October 2010 - 42

TOP PLANTS
new 600-MW Unit 2 was built. This approach
also ensured that the new Unit 1 reliably
replaced the energy produced by the
old plant before decommissioning.
Construction of the new Isogo Unit 1
began in 1998, and commercial operations
followed in April 2002. The two older
units were decommissioned in November
2001, and the project site was " scrapped "
by March 2004. Construction of the new
Unit 2 began in October 2005, and it entered
commercial service in July 2009.
When Isogo Unit 2 entered commercial
service, power generating capacity
was more than double what had been produced
by the original plant. In addition
to meeting Yokohama's generation needs,
Isogo was designed for maximum thermal
efficiency.
High efficiency requires high steam pressures
and temperatures. The main steam
pressure is ultrasupercritical (USC) at 25
MPa (3,626 psi) with a main steam temper1.
World-class performance. In the
ReACT multipollutant control system, flue
gas passes through activated carbon in the
desulfurization tower to adsorb sulfur oxides.
Spent activated carbon is sent to the
regeneration tower, where the SO2 is removed
and the activated carbon is reused.
The SO2 is recovered as a highly concentrated
sulfuric acid that has market value.
As a co-benefit, 20% to 40% of the NOx
and
up to 90% of both elemental and oxidized
forms of mercury are removed in the process.
Courtesy: J-POWER
ature of 600C (1,112F). Reheat is a blistering
620C (1,148F). Unit 1 operates with the
same steam conditions, except the reheat
temperature is just 10C less, at 610 C. The
mit level for Unit 2). Unit 2 regularly
operates with single-digit ppm levels of
SO2
, reflecting an almost 98% rate of
reduction.
The low levels of air emissions reached by
Isogo Unit 2 are, quite frankly, phenomenal
and set a new standard for coal-fired power
plant design that should interest plant designers
and regulators alike.
gross thermal efficiency of the new Unit 2
is 45% (LHV).
Clean Sweep
Isogo ranks as the cleanest coal-fired power
plant in the world in terms of emissions
intensity, with levels comparable to those
from a natural gas-fired combined-cycle
plant. The air quality control system on
Unit 2 is a multipollutant control system,
unlike the individual components found on
Unit 1 and on most coal-fired plants. Unit
2 uses a unique regenerative activated coke
dry-type technology (ReACT) that scrubs
SOx
mercury and NOx
■ ReACT removes up to 90% of both
elemental and oxidized forms of mercury
through adsorption using activated
coke.
■ By using an electrostatic precipitator,
soot and dust emissions were reduced
from 50 mg/Nm3
to an average of 7.5
mg/Nm3, and Unit 2 operates at less than
5 mg/Nm3
or 0.005 lb/mmBtu). This
performance equates to over 99.9% removal
efficiency. The flue gases are then
exhausted to the atmosphere through a
common 200-m stack.
from the flue gas but also removes
as a co-benefit (Figure
1). A thorough discussion of this new multipollutant
control technology appeared in
" ReACT Reduces Emissions and Water
Use " in the July issue of POWER, which
can be accessed at www.powermag.com.
Another very important advantage for
the ReACT technology is that it uses only
1% of the water required by conventional
wet flue gas desulfurization systems.
The low levels of air emissions reached
by Isogo Unit 2 are, quite frankly, phenomenal
and set a new standard for coal-fired
power plant design that should interest
plant designers and regulators alike:
■ Flue gas emissions are first treated by an
ammonia selective catalytic reduction deNOx
system
before entering the ReACT
system. Together, they reduce NOx
from
159 ppm to an average of about 16.5 ppm
(13 ppm is the permit level for Unit 2).
However, operating experience has found
that the plant typically operates in the
single-digit ppm levels. This equates to an
overall NOx
removal rate of about 92%.
■ ReACT reduces SOx from 60 ppm to an
average of 15 ppm (10 ppm is the per42
www.powermag.com
■
The improved plant thermal efficiency
reduced the amount of CO2
released
into the atmosphere by 17% on a lb/
kWh basis. J-POWER understands that
reducing CO2
reductions from coal-fired
plants begins by designing a plant with
the highest possible thermal efficiency.
Strong Market Plant
Demonstrated single-digit levels of emissions
could have a profound impact on
future permitting of coal-fired plants
worldwide, especially in the U.S. Certainly,
constructing a similar plant in the U.S.
would set the benchmark for emissions
permits for future coal-fired plants.
J-POWER has also announced that
" preparations for environmental impact
assessment " have begun for replacement
of the two units at the Takehara Thermal
Power Station. This 1,300-MW station,
built in 1967 and 1974, would remain in
service during construction of two likesized,
but much more efficient units with
much lower emissions. The two older units
would be retired after construction is completed
in 2020. Construction is estimated
to begin in 2014. ■
-Dr. Robert Peltier, PE is POWER's
editor-in-chief.
POWER | October 2010
http://www.powermag.com http://www.powermag.com
POWER October 2010

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