TM 5-810-15
chute back plates. Impact type liners or bars will be
the hopper. There is no "live" reclaim ability with
installed at material discharge impact points.
this method.
d. Construction. Headchutes and transfer chutes
c. Drawdown hopper. A more expensive method
will be totally enclosed to reduce spillage and
of reclaiming coal is with the use of a vibrating
fugitive dust. Rubber dust curtains and seals will be
drawdown hopper or pile discharger. The draw-
provided around the conveyor belt as it enters and
down hopper is located directly under the coal
exits the headchute. Conveyor headchutes will have
storage pile and is designed to operate on a timed
at least 2 inches clearance between the edge of the
cycle basis, which transmits controlled vibration
head pulley and the inside of the chute. For belt
energy into the coal pile, generating fracture lines,
widths up to 42-inch and 48-inch through 72-inch
causing the control column of flow to be drawn
clearance will be 3-inch. Headchute construction
down into the hopper and onto the conveyor belt.
should have provisions to remove the entire pulley
This method of coal reclaim can provide the plant
assembly and frame so maintenance can be done in
with a certain amount of "live" reclaim from the
the shop. Chutework will be flanged and bolted
coal pile minimizing the use of mobile coal moving
design with externally mounted bearings and hinged
machinery.
access doors for ease of maintenance. Provide
hinged, access doors on both sides or front (above
5-19.
Wet and dry dust control.
material impact point) of headchutes.
a. General. Whenever a dry material such as coal
is moved or changes its direction during a process,
chute detector will be furnished at each transfer
the result is fugitive airborne dust. Fugitive dust
point to protect the conveyor from damage. Pres-
emissions can be significantly reduced by the
sure or resistance type plug chute switches are not
addition of an effective dry dust collection system,
as reliable as the tilt type switches and will not be
wet suppression system or combination of both.
used.
With the evolution of more stringent air pollution
control regulations, coal handling systems are being
5-18.
Coal reclaim.
required to meet these standards for the
a. General. Reclaim systems can be classified
geographical area they are located in. Federal, State
into two categories, below grade and above grade
or local clean air codes can rule out the use of one
coal reclaim systems. Small size steam plants
or the other types of dust control systems.
b. Wet dust suppression system. Wet dust sup-
usually cannot economically justify the types of
reclaim systems employed by the larger power
pression system is usually used where the dust
plants such as the above grade reclaimers, bucket
producing area is complex, large and unconfined,
wheels, boom mounted bucket wheels, barrel and
such as stockpiles or track hoppers.
bridge reclaimers, and the below grade system such
(1) This type of system uses a proprietary
as V-shaped slot bunkers, glory holes and
water soluble, surface active, proportioned chemi-
underground reclaim tunnels with vibratory or
cal additive, to dampen and agglomerate fugitive
rotary plow devices. These type of reclaim devices
dust particles at the source making them too heavy
require a very large capital outlay. Smaller plants
to be airborne.
usually employ a combination of both the above
(2) The effectiveness of wet suppression sys-
and below grade systems.
tems can range from total suppression in warm
b. Reclaim hopper. This is the cheapest and
weather to questionable operation in cold subfreez-
simplest form of reclaiming coal from long term
ing temperatures. Additional moisture can cause
storage. In this method an above ground bulldozer
coal to stick together complicating the flow charac-
moves coal from the storage pile to a below grade
teristics of the material being conveyed, and can
reclaim hopper. The hopper will be approximately
reduce the burning characteristics of the coal and
12 foot square and covered with a steel grizzly or
are only as effective as the amount of dust that is
grillage with maximum 6-inch square openings. The
contacted by the suppressing agent.
hopper and grillage will be designed for a fully
(3) A wet suppression system is a simple
loaded hopper and the weight of a bulldozer, front-
solution to dust control, that does not require the
end loader or truck. A vibrating apron or belt
use of costly or elaborate enclosures or hoods, are
feeder under the hopper outlet and a manually
cheaper to install and require far less space than a
adjustable strike off gate on the hopper regulate the
dry dust collection system. Changes or alterations
amount of coal loaded onto the reclaim conveyor.
required after startup can be made with the
This method of coal reclaim is solely dependent on
minimum of expense and system downtime.
the front-end loader or bulldozer to move coal to
5-12
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