POWER August 2011 - 32

PLANT OF THE YEAR
water is collected and pumped to the plant
using 10,000-gpm pumps, with a maximum
of 14,500 gpm possible. By taking this approach
to collect makeup water, the entire
matter of water withdrawals avoids the expected
requirements of the upcoming revisions
to the Clean Water Act Section 316(b).
Makeup water is subsequently clarified and
used as supply water to the wet FGD or goes
through further treatment before being used
as boiler makeup water.
Air Quality Control Systems. On the
exhaust gas side of the plant, similarly sized
air quality systems supplied by Alstom Power
were installed on both Iatan units. NOx
emission limits are based on a 30-day rolling
average, giving the plant some operating
flexibility. The boilers have proven capability
to operate with NOx
The wet FGD systems, using the same size
vessel on both units, routinely operate at 99%
removal, producing SO2
levels in the 0.055
lb/million Btu range, well within the permit
limit of 0.070 lb/million Btu (see Table 3).
The plant has experienced little problem with
ammonia slip.
The baghouses on both units are essentially
identical, although Iatan 2 uses 25,000
bags while Iatan 1 uses slightly fewer and is
outfitted with four fewer compartments than
Iatan 2. Opacity permit limits are set at 15%,
although the plant has operated reliably in the
1% to 3% range.
4. Combined stack. The two units' wet scrubber vessels are located on opposite sides of
the new combined stack. Note that the SCR system is integrated into the structure of Iatan 2,
unlike at Iatan 1, shown in Figure 2. Courtesy: KCP&L
gas well below the 0.06 lb/million Btu permit
limit. Each vessel is equipped with five
recycle pumps but usually runs only three or
four, depending on operating conditions.
There are other common systems at the
plant, such as the wet FGD reagent preparation
equipment. In addition, the stack was
constructed to enclose the stack gas exhausts
from both units (Figure 4). The ammonia
preparation system, common to both
units, uses truck-delivered normal aqueous
ammonia and a common large storage tank.
Another common system is the No. 2 diesel
fuel system used for boiler startup; adding
another system for Iatan 2 triggered new and
expensive requirements, so the single system
does double duty.
Steam Turbine System. A unique feature
of Iatan 2's design is the ability to peak
the output of the plant while not burning any
additional fuel. The steam turbine system is
designed with five feedwater heaters on the
low-pressure side and three on the high-pressure
side (Figure 5). The top feedwater heater
on the high-pressure side is designed to be
closed, thereby taking the feedwater heater
out of service. In this circumstance, the turbine
extraction steam instead travels through
the steam turbine to produce more power, up
to 40 MW.
However, this additional power doesn't
5. Supercritical steam turbine. Toshiba supplied the 930-MW (gross), 850-MW (net)
steam turbine. A unique feature of Iatan 2 is the ability to valve out the top feedwater heater to
produce an additional 40 MW at the penalty of about 100 Btu/kWh in heat rate. Courtesy: KCP&L
come without a cost. The additional steam
flow to the condenser, after passing through
the steam turbine, produces lower feedwater
temperatures and therefore suboptimal performance
conditions at a constant fuel flow.
This off-design operation results in a reduction
in the plant heat rate of 100 Btu/kWh.
No question this is cheap peaking power-a
motor-operated valve costs much less than a
40-MW gas turbine.
Challenges Overcome
Downey believes that KCP&L's oversight of
the project played a key role in the successful
and on-time completion of Iatan 2. The
project team was augmented by experienced
project consultant Burns & MacDonnell and
an executive oversight committee (EOC)
joined by experts from the law firm of Schiff
Hardin, specialists in energy law; construction
contracting; and management of large,
complex construction projects. The project
team was responsible for the overall integrated
project schedule and tight management of
contractors on the job site.
The EOC, also with representatives on the
job site, served as an independent voice reporting
directly to Downey. The EOC, augmented
by the company's legal, regulatory,
32
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levels in the exhaust

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POWER August 2011

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