POWER March 2012 - 22

ever, at that flow rate, water droplets
were being carried by the inlet air past
the inlet air filter and impacting the
compressor blades. The fix was to reduce
the flow rate to 150 gpm. This
fixed the droplet issue but lowered the
cooling, so in 1998, Watson installed a
Mee Industries fogging system on each
turbine to work in tandem with the
evaporative coolers.
" An evaporative cooler is a crude
device in comparison to a fogging system, "
says Ingistov. " Evaps are simple
and reliable, but especially when the air
is cool and there is high relative humidity,
evaporative cooling is doing next to
nothing, but fogging is still efficient. "
Instead of going with the standard
Mee package, Watson Cogen ordered
a custom system, which included advanced
instrumentation, a pressure vessel,
and a submicron filter for the water.
The plant uses reclaimed water from a
local municipal district. Although Mee
had recommended using demineralized
water for the fogging system, Watson
decided to just filter the water. This
turned out to be a problem.
" Because we did not have the right
PM_USA_MultiDisc_11,58_19,05.qxp:Layout 1 27.06.2011 12:06 Uhr Seite 1
water, the water was plugging the
nozzle filters and the pumps were running
against a dead end, " says Ingistov.
" Once we changed to clean water, as
Mee suggested from day one, it reduced
maintenance problems by 90%. "
Initially, the nozzles were installed
upstream of the silencers, but he found
that the fog washed off the dirt that had
collected on the silencers and carried
it into the compressor, where it fouled
the blades, so they were subsequently
moved downstream of the silencers.
" Our biggest enemy now is the trash
Geiger
MultiDisc®
Screen
> Fish Friendly - EPA 316b
Compliant Screens
> Eliminates Condenser
Fouling from Debris
Carryover
> Easily Retrofit
> Low Maintenance Design
> Single Chain
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or Shafts
> Integral Spray Pump
screen, which is about 10 to 15 feet
upstream of the compressor inlet, " says
Ingistov. " In that position, it minimizes
foreign object damage, but when
fog strikes the screen, the fine particles
agglomerate and, when heavy enough,
fall down and are carried by the air
stream. "
Those large particles can produce a
mild erosion of the leading edge of the
first-stage compressor blades. Rather
than removing the trash screen, Watson
Cogen installed applied an erosion-resistant
coating to the leading edge of
the first-stage blades.
" We have been doing that for years,
and we are significantly arresting the
erosion losses, " says Ingistov.
Only When It Is Hot
Ingistov aggressively manages his fogging
system to get the greatest output
from his generators. The turbines operate
8,000 hours per year, and he uses
fog whenever the temperatures are
above 60F, producing an extra 2.5 MW
per turbine.
But not everyone needs to maximize
For more Info
Contact: dlanderson@passavant-geiger.us
Or call: 631 239 4121
Passavant-Geiger GmbH
Hardeckstrasse 3
76185 Karlsruhe · Germany
www.passavant-geiger.de
CIRCLE 13 ON READER SERVICE CARD
22
www.powermag.com
POWER | March 2012
the efficiency and output. Harbor Cogen,
which in 1992 was one of the first
power plants to use fogging, only uses
it on hot summer days. The plant has a
GE Frame 7 combined cycle system, but
it is no longer used as a cogen plant.
Instead, the once-through boiler that
was used for cogen is used to provide
steam to a pair of 10-MW steam turbines,
and the plant sells all its power
to Edison and the California Independent
System Operator. The plant mainly
operates during the summer months.
Plant Supervisor Ron Hoffard says that
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POWER March 2012

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