POWER November 2014 - 46

EMISSIONS
Boosting Efficiency with a
Sootblowing Optimization System
Too-frequent sootblowing can damage boiler components and place a big load
on plant efficiency, but not enough of it can be just as big a problem. A
sootblowing optimization system can help you find the " sweet spot. "
Neel Parikh, Peter Rogge, and Kenneth Luebbert
W
ith the increasing demands placed
on today's coal-fired power plants
worldwide, operators are continuously
looking for the best options to increase
their efficiency and maintain process optimization-all
while watching the bottom line.
A big part of this is complying with evertightening
emissions regulations.
In the U.S., for example, the Environmental
Protection Agency is in the process
of developing and implementing new
standards requiring the power sector to cut
carbon emissions by 30% by 2030, and the
industry is looking to comply by the most
efficient means possible. Fortunately, for
coal-fired plants looking to achieve optimization
without costly modifications, there
are economical alternative technologies that
can be considered.
In coal-fired power plants, optimizing any
process can be demanding. Operators at the
Kansas City Power & Light (KCP&L) Hawthorn
Generating Station recently accepted
the challenge of optimizing their sootblowing
process. Located in Jackson County,
Mo., and situated on the south bank of the
Missouri River, Hawthorn Unit 5 is a 594MW,
wall-fired, water-cooled boiler that fires
100% Powder River Basin subbituminous
coal (Figure 1).
Beyond Ad-Hoc Sootblowing
Today's coal-fired plants are increasingly
expected to operate at varying loads while
simultaneously dealing with operational influences
such as fuel-quality variations and
air quality-control requirements. For the
most part, these plants still utilize traditional
sootblowing technology to remove soot deposits.
However, these traditional patterns
can present challenges to optimal plant operation.
If there is insufficient sootblowing,
the transfer of heat from flue gas to steam is
impeded, resulting in decreased boiler efficiency.
Large soot deposits can also restrict
flue gas draft, requiring additional fan power
46
and further reducing efficiency. On the other
hand, too-frequent cleaning causes heating
surface erosion and related unit outages,
high steam and metal temperatures, as well
as increased spray flows that will reduce efficiency
on most units.
Typical sootblower equipment uses jets
of steam, water, or air to remove deposits on
heating surface tubes. Sootblowing increases
power generation costs, both from expenses
associated with the cleaning medium as well
as the parasitic power required to drive compressors
and pumps.
The sootblower activation cycle is usually
based on the operator's experience and
recommendations from the boiler manufacturer.
This generally results in a simplistic
solution based on continuous sootblowing
at fixed intervals or individual operator
judgment. Sootblowing at fixed intervals
cleans the boiler and avoids hard-to-remove
buildup, but it can also mean that sootblowing
occurs when it isn't truly necessary and
it can cause undesirable process parameter
fluctuations during load variations and other
dynamic operating conditions. Sootblowing
on individual operator judgment leads to
inconsistent sootblowing patterns and requires
continuous operator intervention on a
24-hour basis, which burdens operators and
usually results in suboptimal sootblowing
activities.
Optimization Challenges
In 2000, as part of rebuilding work after an
accident in 1999, Hawthorn Unit 5's sootblowing
system was reconstructed, and engineers
encountered the traditional problems
detailed above. Substantial engineering hours
were spent developing sequences over the
years that would accommodate the varying
operating conditions. The system was functional
but certainly not optimized.
There were several specific operational
challenges with the existing sequence-based
sootblowing control system at Hawthorn.
www.powermag.com
POWER | November 2014
Catalyst Temperature Limitations.
Economizer exit gas temperature (EEGT)
is constrained by selective catalytic reduction
(SCR) catalyst temperature limitations.
Hawthorn had been forced to reduce load on
several occasions when this EEGT constraint
was encountered. EEGT is dependent on fuel
type, combustion parameters, and cleanliness
of the boiler surfaces. Specific sootblowing
activity is known to help EEGT in certain
conditions, but it needs to be carefully executed
and relies on manual blower intervention
when using sequence-based controls.
Reheater. Managing reheater cleanliness
is especially challenging. There is a
delicate balance between a clean reheater,
which causes excessively high reheat temperatures
(and maximum attemperation
1. Clean-up time. Kansas City Power &
Light's (KCP&L's) Hawthorn Generating Station
recently implemented a comprehensive
improvement in its sootblowing processes.
Courtesy: KCP&L
http://www.powermag.com
POWER November 2014

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