height and then was impacting on
shallow chute surfaces of the
collection hopper. The stream was also
spread-out instead of being
concentrated. DEM analysis showed
that, when handling fine and moist
waste coal, parts of the stream
impacting on valleys would slow
down significantly and start building
up. Furthermore, coal impacting on
the shallow surface of the collection
hopper slowed down on account of
the chute surface not being steep and
smooth enough. The throat area of
the chute (outlet of the collection
hopper) was therefore presented
with a large amount of
slow‑moving coal. The throat was
not big enough to handle this coal
at lower velocities at the given
throughput rate. Thus, coal would
start to accumulate in the chute. A
converging chute, full with
material, acts essentially like a
hopper, where arching problems
can occur. Test results indicated
that, if the chute was full with coal,
arching was likely to occur near
the throat leading to choking of the
chute.
Based on this analysis, working
with the layout and equipment
constraints, J&J provided
recommendations for modification
of the chute configuration. This
included providing appropriate
steepness and smoothness to the
chute surface, and increasing the
throat area. Plugged-chute
detectors, instruments to detect
occurrence of plugging inside
chutes, were also repositioned
away from the direct coal stream.
Based on the recommended
chute design provided by J&J,
SAS Global Corp. detailed the
chute components and fabricated
the new chute pieces. During a
planned outage in Autumn 2013,
the chute modifications were
installed (Figures 7 and 8). The
installation work was performed
by TEC-Industrial and took about
two weeks to complete.
Performance results
After the modifications, the crusher
discharge chutes, as well as the
RC2 and RC3 to RC4/RC5 chutes,
have performed well. The reliability of
the coal transfer operation has
increased significantly. Before the
modifications, operators had to
constantly keep an eye on these chutes
to catch any flow issues before the
problems became serious. Now these
operators can focus on their work
without worrying about the chute
pluggage problems. Plant personnel
are satisfied with these modifications.
In the words of the Operations
Manager for the plant, Shane Young,
“Prior to the new chute design, we
had employees stationed at virtually
all inspection points to assist the flow
of material. Once the new chutes were
installed we were able to focus on
other process improvements as chute
plugging in these two areas has
virtually been a non issue”. As a result
of this positive experience, Dominion
is currently changing other transfer
chutes at the Virginia City Hybrid
Energy Center.
When Sasol Synfuels in South
Africa had problems with dust and
spillage at their coal processing
plant in Secunda, they knew to
contact Martin. The new conveyor
products from Martin were able
to contain the fugitive material,
minimized safety hazards
and lost production time, and
significantly reduce maintenance
and wash water usage.
“We’re very happy
with the upgrades,”
stated
Koos Meyer
, Divisional Manager
of the Eastern and Western plants.
“The equipment is
performing well, and
the installation was
neat and professional.”
In fact, Martin Engineering
technicians have started work on
a nearly identical project at Sasol’s
East Coal Processing Plant.
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OUR TAGLINE,
IT’S WHAT WE DO.
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