POWER March 2012 - 39

PLANT DESIGN
by clean-up quantities, frequencies, and difficulties.
Consider how the selected design
reduces the cost of manual labor otherwise
needed for clean-up to help financially justify
a decision.
Vacuum systems are an effective alternative
to shoveling large spills when crushed
coal is dry. Truck-mounted systems are
often employed when an abnormal event
occurs and the services of a contractor is
a logical response. At plant locations that
are within reasonable distance of a coalhandling
system dust collector or scrubber,
a permanent central vacuuming system is
usually an economical choice. Portable
units can be added to plant tools where
a central system is not available. Keep in
mind, however, that portable vacuum systems
are essentially dust collection systems
and entail all the hazards associated
with contained dust.
With any washdown system, an important
consideration is disposal of sludgeladen
wash water. Sometimes concrete
floors can be resloped to drains using
a layer of thinset mortar, but this is not
critical. Workers can also hose down dust
accumulations, " walking " them to the collecting
basin, and follow up with a wide
floor squeegee to help move puddles.
Tunnels will normally slope to a belowgrade
vault, which is often fitted with a
sump pump. It may be necessary to upgrade
the design to handle increased water
flow, higher solids flow, and larger particles.
A slurry pump in an agitated sump
should be considered.
For above-grade floors, collection basins
fitted with a grating cover should be
connected to large-diameter downspouts or
nearly vertical drain pipes. The washdown
water will be saturated with silt and larger
particles that mass into a muddy mess in
shallow slopes, where velocities are too
low to maintain the sludge in suspension.
Naturally, elbows should not be used, but
cleanout provisions at any bend should.
Inspect Bulk Coal Storage
Coal is subject to spontaneous heating
as it absorbs oxygen from the air, often
within the first 90 to 120 days. Freshly
mined coal absorbs oxygen more rapidly
and spontaneously heats quicker than coal
that has been mined and stored. Moisture
aids spontaneous heating by assisting oxidation.
Water used in fighting a coal pile or
silo fire may aggravate the problem if sufficient
water does not reach the core of the
fire to adequately cool and quench it.
To reduce the potential for stockpile
heating and the progression of events to a
hazard, coal should not be simply stacked
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March 2012 | POWER
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39
from an elevated discharge into a gravityformed
pile. Coal fines will naturally accumulate
in the center of the pile, while
the largest particles roll down the surface
to the perimeter base, creating voids at the
perimeter base of the stockpile. Winds entering
the crevices promote oxidation and
fan the flames. It is better to stack coal in
layers and contour and compact it with
mobile equipment, especially for longerterm
storage. This also allows rainfall to
be more easily shed from the surface, so it
can be collected in perimeter ditches.
Finally, hot coal should not be reclaimed
RS PM ad 013012_Layout 1 1/31/12 8:52 AM
from a storage pile. This introduces an ignition
source into the coal-handling system.
Any smoldering coal should be segregated
from the main stockpile and extinguished. ■
-Daniel Mahr, PE (danmahr@energy-pc
.com) is a project manager with Energy Associates
PC. Michael A. Schimmelpfennig,
PE (mschimmelpfennig@ameren.com) is a
consulting engineer for Power Operations
Services, Ameren Missouri.
1970 Dodge Super Bee
Do you have flows up to
1,400 US GPM (320 m
3
/hr),
heads up to 3,400 feet
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RS Series
(-30˚C to 149˚C), and
up to 3,500 RPM? Then you need Carve
Designed for moderate to high pressure pu
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the RS ideally suited for Industrial and Pro
Pressure Boost Systems, Boiler Feed, Reve
and Mine Dewatering. Whatever your appl
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2415 Park Avenue
Muscatine, IA 52761
563.263.3410
Fax: 563.262.0510
www.carverpump.com
http://www.carverpump.com http://www.powermag.com
POWER March 2012

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