POWER November 2015 - 49

SAFETY
Table 1. Dust levels in controlled flow chutes. This
table shows controlled flow chute dust level improvements at the tail
end of receiving conveyors. Source: Basin Electric Power Cooperative
Average
Chute location
Conveyor 3 to 5
Conveyor 3 to 6
Conveyor 4 to 5
Conveyor 4 to 6
Conveyor 5 to 7
Conveyor 6 to 8
Crusher 1 to 9
Crusher 1 to 18a
Crusher 2 to 10
Crusher 2 to 19
before chute
replacement
(mg/m3)
5.5
5.5
5.5
5.5
4.8
4.8
NM
NM
NM
NM
Notes: NA = not applicable, NM = not measured.
eas-one by more than 75% (Table 1).
Not only did the changes decrease dust levels, but the chutes also
improved conveyor capacity by more centrally loading the coal. The
new chutes plug less frequently, reducing coal spillage and eliminating
the need for one of the existing dust collectors while also being
easier to maintain.
" This project would not have been as successful without the diligence
and patience of the Plant Techniques personnel. They were
able to accomplish incredible things in very short hot-work periods, "
Larson said. " The new transfer points met all the goals, and Laramie
River Station plans to install more in the coming years. "
Improving Dust Collection
Although controlled flow chutes and foam suppression reduced dust
creation, the focus team still saw the need to address dust collection,
both through baghouses and washdown. Nearly all of LRS's existing
baghouses were indoors and lacked internal fire suppression. Fortunately,
an already-completed major dust collection improvement
served as the basis for all other coal yard baghouse modifications.
In 2011, a new Air-Cure dust collector was installed at the rotary
car dumper to pneumatically convey the dust almost one mile through
a 6-inch line to the main plant silos. With this design, the vast majority
of dust collected at the dumper is only handled once before it is
fed into the pulverizers.
The focus team decided to replace four of the coal yard dust collectors
with modern, fully equipped Air-Cure baghouses that discharge
the dust into the pneumatic line. This project will put a stop
to handling the same dust at different transfer points and decrease
dust levels throughout the system. Project construction is planned for
completion in 2016.
Regardless of the dust control equipment, dust cleanup through
washdown is still an essential facet of a clean coal system. Currently,
coal yard personnel perform all washdown activities manually at
LRS. To address this, the focus team developed a three-year plan to
install an automated washdown system throughout the coal system.
The project is scheduled in three phases beginning in 2016 with completion
expected in 2018. Drainage modifications are under way in
the main plant cascades and other areas to accommodate the higher
effluent volumes generated by the new system.
Automatic washdown will allow rapid cleaning in tight time windows,
permitting the coal yard to direct its manpower to other acNovember
2015 | POWER
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CIRCLE 21 ON READER SERVICE CARD
49
Average
after chute
replacement
(mg/m3)
2.2
1.3
2.5
1.8
2.3
2.6
0.4
0.4
0.4
0.6
Percent
improvement
59%
77%
54%
68%
53%
46%
NA
NA
NA
NA
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POWER November 2015

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