POWER October 2010 - 22

a relatively high speed (greater than 10 feet/
minute). When high-speed, brief contact with
the LN2
was made, the base metal temperature
dropped only between 9F and 18F on
average. This small temperature drop induced
no notable metal shrinkage and had no notable
influence on mechanical properties of
the base metal.
Case History at PPL Generation
LN2
cleanings were conducted at PPL Generation's
Montour Power Plant in Washingtonville,
Penn., and then at Brunner Island
Power Plant in York Haven, Penn. Both of
these plants use rotary regenerative Ljungström
APHs. Upstream of the APH are finned
tube steam coil air preheaters (Figure 3).
The finned tube air preheaters often
fouled after a few years of plant operation.
Additionally, cleaning of the rotary APH
located above caused debris to fall onto
the steam coil surface that must then be
cleaned. At PPL's Brunner Island Unit 3, a
760-MW coal-fired unit, the fouling was due
to fly ash deposits, dust/debris, and lube oil
that had formed a thick shell over the fin coil
surfaces. Because this unit is typically baseloaded,
PPL prefers to conduct APH maintenance
only during scheduled outages.
Previous APH cleaning with water,
chemicals, and detergents was ineffective
in removing tenacious deposits of fly ash
and oil (Figure 4). During operation, the
fouling restricted combustion airflow to
the boiler through both the " A " and " B "
sides. This reduced airflow through the air
heater often limited power output during
certain weather and other operating conditions.
As an outage approached for the
unit in spring 2010, the Conco NitroLance
system was evaluated by PPL engineers
and was then scheduled for cleaning the
fouled " B " side air preheater coils.
A site evaluation conducted by Conco
83,000
hours of product performance
testing each year
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5. Proper attire required. A Conco
technician, suited up with full-face respirators
(with external air), rubber boots, and cryogenic
insulated gloves, is cleaning the Brunner Island
Unit 3B steam coil air heater. Courtesy: Conco
engineers and plant personnel concluded
that installing a new access door in the
ducting adjacent to the air heater would
be beneficial. Scaffolding was placed directly
under the horizontal air preheater,
allowing clear access to the area to be
cleaned. Conco supplied two mobile LN2
units. Only one mobile unit is normally
required, but due to minimal time allocated
during the outage for cleaning, two
4. Fouled tubes. The " B " steam coil air
heater tubes in " as-found " condition prior to
cleaning. Courtesy: Conco
CIRCLE 15 ON READER SERVICE CARD
22
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POWER October 2010

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