Furnace Fume Extraction System By Whizz Engineering Services Pvt. Ltd.

Dust/Fume Extraction System:
In thermal
power stations, Metal Industry, Coal/material conveying is one of the
most important steps. Coal/Material handling system mainly consists of
unloading, screening, crushing, stacking, reclaiming and bunker feeding
equipment arranged in an optimum configuration. Coal or bulk solids are
received at site either by ships or by rail-wagons or by trucks. It is
then conveyed for screening and crushing. For smaller capacity plants,
either conveyor with traveling tripper or conveyor with telescopic chute
is generally used for stacking the crushed coal andreclaimed using
bridge type scraper reclaimer or underground reclaim hopper with
suitable capacity dozers.

Dust generation in a plant:
Loading
point, Unloading point of belt conveyor, Discharge Chutes: Dust from
the operation of belt conveyors originates mainly at the trail pulley
where material is received and at the head pulley where material is
discharged. Dust generation depends on belt width, speed, height of fall
of coal.

Bunker Feeding Point: Crushed coal either
directly from crushers or from the crushed coal stockyard is conveyed to
boiler bunkers through traveling trippers or reversible shuttle
conveyors. Dust is generated while loading the bunkers, spreading of
which is controlled to some extent by conveyor sealing arrangement, and
needs to be extracted from bunkers.

Crusher area: Crushers
are used for size reduction in the coal or other particle. The huge
gyratory or roller crushers are used for primary size reduction, while
jaw or gyratory crushers are used for secondary size reduction. Large
side hoods are used for dust extraction.

Process:

The
arrangement for dust extraction system for bunkers consists of eight
Suction points, four on either side of Tripper Conveyor. The Tripper
Conveyor feeds only two feeding points out of the eight, at a time. Thus
for those two feed points, corresponding two suction hoods sucks dust
laden gas in the system. While other six feeding points are closed using
belt sealing arrangement. This dust laden gas is carried to the bag
filer through interconnecting ducting.The gas is filtered through the
bags due to the entrapment of dust particles into filter media. Each row
of the bags, receives periodic pulses of compressed air, thus pulsing
the bags, thereby dislodging the dust to the hopper. The pulsejet system
is provided with a pressure switch to control the maximum pressure in
the air header. The pressure drop across the bag house is measured by a
Differential pressure Indicator or by a water tube manometer. In case of
the excessive pressure drop, a Differential pressure switch comes into
operation and provides a signal, which would be interlocked with Control
Panel. The dislodged dust is collected in the hopper and discharged
through the RAV. RAV is provided with zero speed switches to ensure
overload protection of Geared motor. To improve the flow characteristics
or to avoid chocking, rat holing, arching of dust in the hopper,
Pneumatic knockers are provided on the hopper.

In order to
control maximum level of dust in the hopper, a Level switch is provided.
The level switch is to be interlocked with the control panel so that
the dust level in the hopper should not rise above the set level. Coal
dust is combustible and tends to form dust clouds, hence precautions for is taken by providing vent, to reduce the risks of
property damage and personal injury. The Fan provided develops the
necessary draft. The draft control of the Fan is carried by VFD. The VFD
is provided with PID controller. The PID controller receives the signal
from Differential pressure transmitter across the Flow measuring
device, and gives controlling signal to VFD, to maintain necessary RPM
of fan thereby maintaining necessary draft in the system. The clean air
is discharged at the outlet of I.D. Fan.