POWER October 2015 - 25

TOP PLANT
in October 2012 (Figure 1). Early release of
long-lead components significantly reduced
project cost and schedule risks.
The design of the new AQCS provides for
significant reduction in emissions of mercury
(>90%), sulfur dioxide (SO2, >90%), and particulate
matter. First, mercury emissions are
reduced by a carbon injection system, a postcombustion
process that injects carbon particles
into the flue gas to facilitate capture of
mercury as a particulate. Second, a spray dryer
absorber (SDA) flue gas desulfurization system
reduces SO2 emissions. Finally, a pulse
jet fabric filter (PJFF) captures fine particulate
emissions and reduces sulfuric acid mist.
According to Bob Newell, Alliant Energy's
senior manager-strategic projects, " The
basic plan was to get the emissions of sulfur
and mercury down to about the 90% level of
what it had been over the past several years
[on each unit], and also to have minimal impact
on plant operations. "
New Gas Path
One of the major design challenges was arranging
the new AQCS equipment so that the
existing stacks could be used. Complicating
the arrangement was the fact that different
precipitators are used on each unit.
Unit 2 uses a " cold " electrostatic precipitator
(ESP), which means the ESP is placed
in the gas path after the air preheater (APH);
then gas passes through two induced draft
(ID) fans before entering the stack. After the
upgrade, flue gas leaving the ID fans enters a
common duct that evenly splits the gas flow
between two SDA modules, two PJFFs, and
two axial flow booster fans to compensate for
the added flue gas pressure drop. Activated
carbon injection occurs at the discharge of
the ID fans. The gas exiting each axial booster
fan is recombined into a single duct that
directs the gas to the existing stack.
Unit 1's gas path is similar, although it is
configured with a " hot " ESP (the ESP is placed
before the APH). The flow paths downstream
of the ID fans are otherwise identical.
Ash collected from the ESP on both units is
recycled and sold. Two SDA modules are used
on each unit because of individual module
size limitations. The AQCS additions at each
unit also include a reagent preparation system,
lime storage silos, scrubber solids handling
and conveying system, a truck-based lime delivery
station, and other ancillary equipment.
The equipment arrangement includes provisions
for future installation of lime delivery
and scrubber solids removal by rail.
Plan for Success
According to Jeff Kurtz, Black & Veatch vice
president and project director, energy, " Safety
was incorporated into every phase of the project
at the Columbia Energy Center, and as a
result, there were more than 1.9 million hours
worked without a single lost time incident. " A
site-specific, behavior-based safety program
focused on making safe behaviors a focus of
daily work practices to eliminate injuries at
every step of the project. " We brought all of
the contractor executives on site, having their
buy-in to what the safety program would be, "
1. Squeeze job. The air quality control system equipment and ducting for both units was
completed in time for the spring 2014 outages. New equipment for each unit included axial
booster fans, twin spray dryer absorber (SDA) modules, and a pulse jet fabric filter. The ducting
that makes its way to and from the original stack connection flange is seen on the right. The
two-module SDA configuration used by each unit is in the center. Courtesy: Black & Veatch
POWER POINTS
Winning Attributes
State-of-the-art emissions control
upgrades ensure long-term
viability of reliable baseload
power source
On-time or early completion of
every phase, while total project
costs were $38 million under
public utility commission-
approved cost
Stellar safety record, with no losttime
incidents
said Kurtz. Every safety committee included
representatives from Black & Veatch, Babcock
& Wilcox, Alliant Energy, and all major
subcontractors on the project.
Quality is another means to measure project
success. Black & Veatch used its Living
Quality Behaviors program, which is a behavior-based
initiative that promotes face-to-face
communications regarding quality issues.
Only 12 non-conformance reports were issued
on the project, all of which were resolved to
Alliant Energy's satisfaction. Change orders
on the project were less than 0.5% of the total
project cost, and final project costs came in at
$38 million under the authorized Public Service
Commission amount.
Schedule performance on this project
was outstanding by any measure. All critical
milestones were completed ahead of schedule,
despite extreme cold weather conditions
in Wisconsin endured during the winter of
2013/2014. Mechanical completion was 32
and 29 days early for Units 1 and 2, respectively,
and substantial completion was 38 and
33 days early. Ductwork connections that tiedin
the new AQCS equipment were completed
during the plant's normally scheduled spring
2014 outages, a short 42-day window during
which the work was completed early. Final
completion, which includes the contractually
required performance and emissions tests,
were successfully completed on February 5,
2015, almost two months in advance of the
contract-mandated completion date (April 1)
for each unit. The 60-day equipment reliability
demonstration tests were later passed with
excellent results: 99.0% and 99.7% for Units
1 and 2, respectively.
Not only will these upgrades save the
plant from being shut down, but they also
equip CEC to serve Wisconsin for many
more years. ■
-Dr. Robert Peltier, PE is POWER's
consulting editor.
October 2015 | POWER
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POWER October 2015

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