POWER January 2014 - 64

PRBCUG AWARDS
3. Comprehensive upgrades. North Omaha Station completed a multi-year upgrade of
its coal-handling system in 2012, from the point fuel arrives at the plant through the coal bunkers
on each boiler. Courtesy: OPPD
Tripper Room
Transfer House
Crusher House
safety, all combustible construction materials
were removed from the Tripper
Room walls, Transfer House walls, and the
Shaker House curbs. Walls were painted
for easy maintenance in all the materialhandling
zones.
Shaker House
■ Five carbon monoxide monitors were
installed in the coal bunkers, and an additional
four monitors were added to the
Shaker House. Data collected from these
monitors is logged by the Pi data-logger
located in the control room so that trends
in CO concentrations can be closely
watched and alarmed. When the concentration
of CO reaches a predetermined
level, an alarm sounds in the control room
and an email is sent directly to operations
supervisors.
The Crusher House and the Shaker House
were originally designed with last-generation
dust collection systems, each of which
included a collector, blower, disposal system,
and long lengths of ducting and many
high-maintenance isolation valves. Both dust
collection systems were removed from service
as part of the project, thus eliminating
a potential explosion hazard. In their place,
Martin Engineering installed insertable dust
filter systems in 12 high-dust zones. Instead
of conveying dust-laden air to a central dust
collector, the insertable system filters the air
at the transfer point so the dust can be immediately
returned to the conveying system. The
dust is captured on a pleated fiber filter that
is periodically cleaned using compressed air
injected against the reverse side of the filter.
Each filter system has two filter elements so
that one filter remains in service during the
staggered cleaning cycles. Unlike standard
filter elements, the filter material is impregnated
with carbon fibers so that a buildup of
static electricity is not possible (Figure 4).
The plant's coal chutes had also taken a
beating over the years, with several areas
where severe erosion had resulted in openings
that allowed coal leaks. The chutes were
relined as part of the upgrade project.
A " belt and suspenders " approach was
taken when designing the new dust collection
system. In addition to the new filter systems,
Martin also installed its Dust Fighter foam
system to further improve fugitive dust collection.
The foam system automatically mixes
and applies a thin film of dust collection foam
to the conveyed coal without increasing the
coal's moisture content. Each automated foam
system consists of a single mixing station that
prepares foam for up to eight nozzles installed
on the coal conveying chutes.
There were many other upgrades and improvements
to the NOS coal-handling system
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completed as part of the project. For example:
■ A water wash-down system was installed in
the Tripper Room and Tripper Room tunnel.
A water deluge system was installed in
the Transfer House, and the Shaker House
basement. Both systems were installed in
the Crusher House, Transfer House, and at
the transfer and mag belts.
■ To decrease housekeeping and improve
4. Efficient dust collection. The problematic
centralized dust collection systems were
retired and replaced by individual insertable dust
filter systems at the point of collection. The
self-cleaning system returns the collected dust
directly back into the enclosed conveying systems.
The top photo shows the original dust collection
tap placed just above the conveyor. The
new insertable dust collection system is shown
on the bottom. Courtesy: OPPD
■ Firefighting equipment was also procured
and staged outside the Tripper Room, including
a piercing rod kit and an F-500
cart with eductor and hoses.
■ Fugitive emissions from the coal pile were
reduced by properly grooming the coal
pile into a dome shape and by reducing
steep pile slopes.
■ A belt slippage protection system was
incorporated to the conveying systems to
prevent large spills of coal and to prevent
catastrophic belt failures.
The plant survey also carefully reviewed
the electrical area classifications and all
the changes and upgrades required to fully
comply with Class II, Division 1, Group F
classification were completed as part of the
project.
The work of the Coal Handling group at the
plant played an important role in receiving this
award. The group stepped up and took on new
responsibilities with respect to housekeeping.
In the process they created a culture of
excellence, both in operations and safety. The
group's safety record over the past years has
been impressive, having recently completed
20 years without a lost-time injury.
Upgrading the skills and capabilities of the
plant staff was also an important part of the
program. For example, new evacuation plans
were formulated in conjunction with the community
fire department and bunker firefighting
training was completed. Onsite fire fighting
drills with piercing rods in bunker fires and
open area fires were conducted with community
first responders to improve skills, communications,
and teamwork. A plant safety
video and a PRB combustible dust video were
also produced to further hone the skills of the
plant staff and contractors on the peculiarities
of safely handling PRB coal as part of an ongoing
safety training program. ■
-Dr. Robert Peltier, PE is POWER's
consulting editor.
POWER | January 2014

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POWER January 2014

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