Pulse Jet-Bag House Filter (Air Pollution Control Equipments)
ORIENT PCL
Cleaning the air for the better Returns
Regular Hopper Entry:
The
pulse jet bag filter in its most rudimentary form basically consists of the
filtration elements housed in a casing. Below this casing is a hopper with a
discharge valve, to continuously remove the dust that is collected on the bags.
The entire unit is supported from the ground on structural legs. A caged ladder
provides access to the top of the unit for maintenance. The dust laden air enters
through the hopper by suction (normally) or (positive pressure). The heavier
dust particles fall off at the entry itself, while the lighter dusts get
carried upward to the bags.
The
dust gets deposited on the outer surface of the bags and the clean air moves
upward from the centre of the bags through the outlet plenum to the top air
outlet. This is known as filtration. The dust collected on the
outer surface of the bags is removed in a pre-determined cycle by a momentary
pulse of high-pressure compressed air. The compressed air moves from an air reservoir
or compressed air header via the particular pulse valve into the compartment
manifold and thereon into the bags in the row beneath it. The pressurised entry
of compressed air through the venturis into the bags, inflate the latter. and
the dust cake formed on the bag surface slides down in the form of flakes. The
cages help the bags retain their original shape once the effect of the
compressed air is gone. This completes the cleaning process. The
dust slides down the hopper walls to the rotary air lock valve. The latter is a
rotating device which discharges the dust continuously, all the while
maintaining an air seal.
Orient
PCL range in above construction covers both completely standardized and
pre-engineered Bag Filters - the AJ / AP series – up to a particular size with
customized variations also available beyond this.
Flush Mounted- Insertable
Transfer
points involving two conveyors or from one conveyor to / from other material
handling equipment often involve isolated point(s) where free standing bag
filter(s) can be an expensive proposition. Space availability on ground is also
an issue at times. Typically, these insertable bag filters units are
devoid of any hopper. The unit can be suitably positioned on the conveyor
directly. On pulsing, dust falls back onto this conveyor, thus avoiding a need
for a separate dust discharge hopper.
Depending
on the height of fall of dust, two such insertable bag filters may be required
– one at the end of the discharging conveyor and one on the receiving conveyor.
When a single unit is used, it is normally on the receiving conveyor – as shown
in the adjoining figure – this being where generation of dust is higher due to
impact. These types of units are also optimal solutions for venting of bins /
silos / hoppers.
The
units in this construction are mostly standardized and pre-engineered, though
customized variations can be offered where necessary.
Flush Mounted - Circular
The
construction here is similar to an insertable bag filter; however, in this
case, the casing of the bag filter is circular instead of being rectangular.
The top cover could be a dished end – as in the adjoining figure – which is
used for high positive design pressure or vacuum, as is typically a situation
encountered for applications related to venting of silos / bins connected to pneumatic
conveying systems.
Casing Entry
Here
the dirty gas enters the casing – through the inlet cum- bypass damper in
boiler bag filters (as in the sketch alongside) – and flows into a central
chamber formed by perforated sheets. The gas flow towards the bags is partially
through the perforations and partially upward from below of the sheets,
ensuring better gas distribution and the separation of heavier dust
respectively.
The
lighter dust gets carried upward to the bags. This gets deposited on the outer
surface of the bags and is removed by a pre-determined cycle by a momentary
pulse of high
pressure
compressed air as in the case of a typical hopper entry type of bag filter.
Orient
PCL range in above construction is also completely standardized and
pre-engineered - the AJC / APC series - upto a particular size.
Circular- Tangential Entry
The
gas enters into the bag filter tangentially at the bottom of the casing. This
gives the dust laden gas a circular motion which helps in removing the heavy
& coarser particles that are present in the gas stream in a manner similar
to a cyclonic collector. These collected particles are directly discharged into
the hopper. It is only the very fine particles that get carried to and
collected
on
the bag surface. Thus, the total dust load on bags is reduced making it
possible to maintain lower pressure drop across bags. This also permits the use
of lesser frequency of bag pulsing, which in turn increases bag life.
Due
to its circular construction, these bag filters can withstand more +/- pressure
as compared to normal rectangular bag filters. The circular construction of bag
filter also ensures leak proof ness. The possibility of dust accumulation
inside casing (on edges etc.) is eliminated. Due to the arrangement of bag as
shown in the image alongside, each and every bag is exposed to the dust laden
gas. The swivelling arrangement shown enables the top cover to be pushed to on
one side and lifting of the same. Due to special top cover and outlet plenum
construction the entry of outside air is avoided.
Pre- Separator Extended Hopper
In
the Pre-separator extended hopper type of unit, the dirty gas enters in the
common inlet plenum formed as an aisle between the two filter modules resulting
in pre-separation of the dust laden gases.
From
there it flows to both the modules undergoing filtration as in a regular unit. The
cleaned gases travel back to the common outlet plenum from the individual clean
air plenums and then flow out through the outlet duct to the ID fan.
Pre- Separator Casing with Baffle-TKB
Series
The
phenomenal growth of the Cement Industry has seen the advent of plants of much
bigger size. The conventional bag filters have been found to be inadequate to
handle large gas flows in excess of 6,00,000 m3/hr. This is due to severe limitations
on aspects like high gas flow per bag, high velocity of gases through bag
filter, higher pressure drops across filters, high space requirement and high compressed
air consumptions.
To
overcome these limitations, Orient PCL has designed a new series of bag filters
– the TKB series.
Some
of the unique features incorporated in the TKB series are highlighted below.
A.
Low pressure air cleaning system:
The
TKB Pulse Jet Bag Filter (PJBF) long bag design incorporates a specialized low-pressure
cleaning system that offers following distinct advantages over conventional bag
filters with high pressure cleaning system:
1.
Lower pressure drop across the unit.
2.
Lower consumption of compressed air.
3.
Longer filter bag life.
4.
Lower noise levels during operation.
The
low-pressure cleaning system uses a special immersion type header mounted pulse
valve. This cleaning system is so effective that it achieves 25% more cleaning
pressure on the bag. The impulse is built in half the time it takes
conventional system.
· Effectively
flushes the bag & reduces re-deposition of fine dust.
· Can
clean bags up to 10 meters length.
· Cleans
the internal of the filter media to have lower longer-term pressure drops.
· The
filter media is not flexed as extensively as in the conventional cleaning,
thereby increasing media life.
B.
Unique gas flow path:
The
TKB series filters are specially designed for high inlet dust loads. The gases
enter the filter casing entry plenum behind a baffle and are directed upwards
by this specially designed baffle. The 90 degrees turn that the gases take on entry
helps in separating a lot of dust. This reduces the dust load on bags. The
unique gas flow path makes the gases enter the filter with an upward bias on
the velocity. This upward bias reduces impact of the dust particles on bag surface
enhancing the life of the bags.
C. Wider Pitch of Bags
The
bag pitch – the centre to centre distance between the bags – plays a very
important role in the performance of the bag filter. In order to address the
high gas flows and very high dust loads involved the TKB series filters has
adopted an increased spacing between bags – as much as 36%. This additional
clear space allows the high amount of dust load to fall by reducing gas
velocity between bags. This also reduces the sliding friction at bags enhancing
the life of the bags.
D.
Specially reinforced cages:
The
conventional cages cannot be used in bag filters as there is a tendency to bend
due to the excessive length. Higher thickness wires are used for cages when the
height of bag or cage is 6 m or more than that. This higher thickness ensures straightness
of the cage as this actually ensures the spacing between bags which are freely
suspended from the bag filter tube sheet. The above features of the Orient PCL
TKB bag filters have made this the most popular design in the Indian Cement
industry.
Bag/Cage/Venturi Arrangement
Cages
are wire frames placed inside pulse jet filter elements to provide support to
the fabric as flexing occurs during filtration and cleaning cycles. Configuration
of a frame generally follows the shape of the filter elements, i.e., circular,
oval, flat or starshaped.
Cages
for long filter elements are made in sections which snap together for easier
handling. Wear points on filter bags may develop at the horizontal supports. Cage
designs to reduce these points increase the number of vertical wires and reduce
the horizontal supports. Protective coatings on cages can extend the life of
the cage and the bag. Coatings such as vinyl, epoxy, zinc, and Teflon® may be
used.
Corporate Office:-
17,812/CT, Parsvnath City Centre,
Sector-III,Bhiwadi, Alwar,
Rajasthan- 301019
Mob:9460142333, 9460143333
Email: info@orientpcl.com
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