This document describes and compares four common particulate control devices: settling chambers, electrostatic precipitators, bag filters, and cyclones. Settling chambers use gravity to remove larger particles by passing gas through a long, rectangular chamber. Electrostatic precipitators ionize particles and capture them on oppositely charged plates, achieving over 99% collection efficiency. Bag filters use fabric bags to trap particles in a dust cake, while cyclones use centrifugal force to separate particles from gas in a vertically-mounted cylinder. Each device has advantages like low cost or efficiency, and disadvantages like size, temperature, or particle size removal limits.

1. Settling chamber or gravity settler.
• It is also known as gravity settling chamber, gravity collector,
expansion chamber and outfall chamber.
• It is generally used in removing larger size partial.
• It is generally build in the form of long, horizontal, rectangular
chamber with an inlet at one end and outlet at other end.
• Flow through the chamber is uniform.
• Hopper are used to collect the settled out materials, through
drag scrapper.
• The dust removal system must be sealed to prevent air leaking
into the chember.

2. Cont…
• There are two types of settling chember.
(a)The expansion chamber.
(b)The multiple-trey chamber.
• In the expansion chamber, the velocity of gas stream is reduced
as the gas expand in large chamber and this reduced velocity
allows larger particle to settled out of gas stream.
• In multiple trey chember, a number of thin treys are closely
spaced within the chember which allows the gas to flow
horizontally between them.
• Gas velocity increased as compared to expansion chember, so it
is used for collection of smaller particle( less than 15µ)

4. Advantages
• Low capital cost
• Very low energy cost
• No moving part
• Few maintenance requirement
• Low operating cost
• Excellent reliability
• Low pressure drop through device
• Dry collection and disposal.

5. Disadvantages
• Relatively low particulate matter collection efficiencies.
• Unable to handle sticky materials.
• Large physical size.
• Treys in multiple trey settling chamber may warp.

6. Electrostatic precipitator
• ESP is a large, industrial emission control unit that utilized
electrical energy directly to removed particulate matter.
• It is designed to trap and remove dust from all kinds of gases
with very high efficiency.
• It is generally used in power or electric industry, cement,
chemical, metal and paper.
• It collects most of the dust and clean gas released to atmosphere
through stack.
• Precipitator collect 99.9% or more dust from gas stream.

7. Principle:
ESP removes particles from the exhaust gas stream.
There are six activities that takes place:
• Ionization- Charging of particles.
• Migration-Transporting the charged particles to the collecting
surfaces.
• Collection- Precipitation of the charged particles into the
collecting surfaces.
• Charge dissipation- Neutralizing the charged particles on the
collecting surfaces.
• Particle dislodging-Removing the particles from the collecting
surface to the hopper.
• Particle removal-Conveying the particles from the hopper to a
disposal point or return to the process.

9. Working:
• As air enter the ESP, the particle pass through an electrical
field that gives charge to the particle.
• The charge particles pass through a series of alternately charge
collector plate.
• Particles are repelled by plates with the same polarity and
attracted to plate with opposite polarity.
• Dual stage ESP ,includes two parts:
charging and collecting sections.
• In charging section, the incoming smoke, mist and particulates
pass by ionizer wires which imparts positive charge on these.
• It is then transfer to collector section which contains secondary
electric field with negative charge aluminum plate.
• It get attract and removing from air stream.

12. Advantages
• High collection efficiency.
• Particle as small as 0.1μm can be removed.
• Low maintenance and operating cost.
• Cleaning is easy by removing different parts of unit.

13. Disadvantages
• High initial cost.
• Space required is more because of large size of equipment.
• The poisonous gas like ozone is produced during ionization.

14. Bag filter
• It is the most common type of fabric collector consist of tabular
bags.
• A bag house filter consist of numerous bags 120-140mm dai and
2-10m long.
• They are suspended with open ends attached to a manifold and
the hopper at bottom for collection of the dust.
• The gas entering through the inlet pipe strikes a baffle plate,
which causes larger particle to fall into hopper due to gravity.
• The carrier gas flows upward through fabric bag leaving
particulate matter as a cake inside the bags.
• Initially efficiency is low but after the formation of cake it get
increased about 99%.

15. • The cake usually formed in a minute or sometimes even
seconds.
• The accumulation of dust increases the air resistance of the filter
and therefore filter bags have to be periodically cleaned.
• It can be cleaned by rapping, shaking or vibration or reverse air
flow, causing the filter cake to be loosened and fall into the
hopper.

17. Advantages
• High collection efficiency for all particle size specially particle
smaller than 10µ.
• Simple construction and operation.
• Collection and disposal of particulate in dry form.
• Nominal power consumption.
• Low pressure drop.

18. Disadvantages
• Large size of equipment.
• High temperature in between 250-3000c.
• High maintenance and operation cost.

19. Cyclone
• It is defined as a structure without moving parts in which
velocity of an inlet gas stream is transported into vortex from
which centrifugal force drive suspended particle on the wall of
cyclone body.
• It consist of vertically placed cylinder with inverted cone
attached to the base.
• The particulate gas stream enter through inlet. The outlet pipe
for purified gas is at the top and dust particulates are collected at
bottom of storage hopper.

20. Working:
• The gas path generally follows a double-vortex.
• At the starting the gas spirals downwards at the outer periphery
of cylindrical portion continues through conical portion and
reaches the bottom.
• The gas stream then moves upward in narrow inner spiral and
leaves through the outlet pipe.
• Due to rapid spiral movement of gas, the dispersion are
projected towards the wall by centrifugal force and drop by
gravity to the bottom and collected in hopper.
• It is used for collection of wide range of size and concentration.

21. Application:
• It is used for control of gas borne particulate in industrial
operation as cement manufacture, paper industry.
• Cyclone are also used to separate dust in disintegration, such as
rock crushing, sand conditioning in industries.
• It is also used in recovery of catalyst dust in petroleum industry
and reduction in fly ash emission.

23. Advantages
• Low initial cost
• Simple construction and operation
• Low pressure drop
• Low maintenance requirement
• It has no moving parts.
• They can be constructed of any material which will meet the
temperature.

24. Disadvantages
• Low collection efficiency for particles below 5-10μ in
diameter.
• Equipment is subjected to serve abrasive deterioration.
• Decreasing collection efficiencies for decreasing concentration
in the gas stream.