The document discusses several methods for controlling particulate contaminants, including their working principles: 1) Gravity separators and centrifugal separators remove larger particles (>50 μm) from gas streams using gravitational settling or centrifugal forces. 2) Electrostatic precipitators ionize particles and collect them on oppositely charged plates, achieving high removal efficiencies of over 90% for particles over 1 μm. 3) Fabric filters and wet scrubbers like particulate scrubbers can remove over 90% of particles less than 10 μm using filtration through fabric or liquid contact. Selection depends on factors like contaminant properties, space, and costs.

1. CONTROL OF PARTICULATE CONTAMINANTS
1. Factors affecting Selection of Control
Equipment
2. Gas Particle Interaction – Working principle
3. Gravity Separators - Working principle
4. Centrifugal separators - Working principle
5. Fabric filters - Working principle
6. Particulate Scrubbers - Working principle
7. Electrostatic Precipitators - Working principle

2. Factors affecting Selection of Control Equipment
The following factors are considered for selecting a
particular air pollution control equipment.
• Environment
• Engineering
• Economic
Environmental :
• equipment location, availability space, ambient
conditions, availability of adequate utilities and
ancillary system facilities.
• Maximum allowable emissions.
• Contribution of air pollution control system to waste
water and solid waste.
• Contribution of air pollution control system to plant
noise levels.

3. Engineering:
• Design and performance characteristics of the
particular control system(size and weight)
• Pressure drop, reliability and dependability,
temperature limitation, maintenance
requirement.
• Contaminant characteristics(physical and
chemical) properties,concentration, particulate
shape and size distribution in the case of
particulates.
• Gas stream characteristics (volume, flow rate,
temperature, pressure, humidity, composition,
reactivity, corrosiveness and toxicity).

4. Economic:
• Capital cost (equipment, installation, engineering
etc)
• Operating cost (utilities, maintenance etc)
• expected equipment lifetime and salvage value.

5. • PM stands for particulate matter - particle
pollution
• It is a mixture of solid particles and liquid
droplets found in the air - Some particles, such as
dust, dirt, soot, or smoke.
• Fine particulate matter (PM2.5) is an air pollutant
- when levels in air are high.
• PM2.5 are tiny particles in the air that reduce
visibility and cause the air to appear hazy when
levels are elevated.
• Exposure to such particles can affect both your
lungs and your heart.

6. Types of particulate matter
• Inhalable coarse particles - found near
roadways and dusty industries, they are larger
than 2.5 micrometers and smaller than 10
micrometers in diameter.
• Fine particles - found in smoke and haze, and
are 2.5 micrometers in diameter and smaller.

7. steps to Reduce Exposure to Indoor PM
• Vent all fuel-fired combustion appliances to the
outdoors (including stoves, heaters and furnaces)
• Install and use exhaust fans vented to the
outside when cooking.
• Avoid the use of unvented stoves, fireplaces or
space heaters indoors.
Measurement Method :
• The most accurate measurements is gravimetric
(weighing) method. Air is drawn through a
preweighed filter, and particles collect in the
filter.

8. Gas Particle Interaction –Working
principle - Gravity Separators
• Gravitational settling chambers used to remove large particles
usually > 50 µm from gas stream.
• Particles settle under gravitational force.
• This device consists of huge rectangular chambers in which
the velocity of the carrier gas is decreased so that particles in
the gas settle down by gravity.
• The gas stream polluted with particulates is allowed to enter
from one end..
• The horizontal velocity of the gas stream is kept low in order
to give sufficient time for the particle to settle by gravity.
• The particulates having higher density obey stoke’s law and
settle at the bottom of the chamber from where they are
removed ultimately.
• Several horizontal shelves or trays improve the collection
efficiency by shortening the settling path of the particles.

9. Advantages :
Low initial cost
Easy to design
Low pressure drop
 low maintenance
cost
Disadvantages
Require large space
Less collection efficiency
Only larger size particles can be
collected

10. Cyclone separators
• A simple cyclone separator consists of a cylindrical shell,
conical base, dust hopper and an inlet. An out let for
discharging the particulates is present at the base of the
cone.
• Through an inlet, the dust laden gas enters tangentially.
where the gas receives a rotating motion and generates a
centrifugal force.
• Under the influence of the centrifugal force generated by
the spinning gas, the solid particulates are thrown to the
cyclone walls as the gas spirals upwards inside the cone.
• The particulates slide down the walls of the cone and into
the hopper and are discharged from the outlet.
• It can remove 10 to 50 µm particle size.

12. Disadvantages:
• Requires large head room
• Less efficiency for smaller particles
• Sensitive to variable dust load and flow rate.
Advantages :
1. Low initial cost
2. Require less floor area
3. Simple construction and maintenance

13. Electrostatic precipitator
• Electrostatic precipitator are used in removal of fly ash dust particles
from electric utility boiler emissions.
• The dust laden gas is passed between oppositely charged
conductors.
• Then it becomes ionized as the voltage applies between the
conductors.
• As the dust laden gas is passed through those highly charged
electrodes, both negative and positive ions are formed.
• The ionized gas is further passed through the collecting units.
• Which consist of a set of vertical metal plates.
• Alternate plates are positively charged and earthed.
• As the alternate plates ate earthed high intensity electrostatic field
applies a force on oppositely charged dust particles and drives them
toward the grounded plates.
• The deposited dust particles are removed from the plates by giving
the shaking motion of the plates with the help of external means.
• The dust removed from the plates with the help of shaking motion is
collected in the dust hoppers.

15. Advantages:
1.high collection efficiency
2. particles may be collected dry or wet
3. can be operated at high temperature.
4. Maintenance is normal
5. few moving parts
Disadvantages:
• High initial cost
• Require high voltage
• Collection efficiency reduce with time
• Space requirement is more

16. Centrifugal Separator
• The centrifugal separator features an inlet, outlet,
and separator. The separator produces a spinning
vortex, which leads to the filtration of solids from
liquids. The separated solids are collected at the
bottom of the separator, and they are removed
from there.
• centrifugal separator is the most effective
• least expensive method for PM control.
• More than 90% dust removal efficiency

18. Fabric filter
• Fabric filter remove partcles upto 1μm. FFs are typically
referred to as baghouses.
• When the flue gas is allowed to pass through a fabric,
which filters out particulate matter.
• Dust laden gas or air enters the baghouse through hoppers
then it is directed into the baghouse compartment.
• The gas is drawn through the bags, either on the inside or
outside depending on cleaning method.
• A layer of dust accumulates on the filter media surface
until air can no longer move through it.
• When sufficient pressure drop occurs, the cleaning
process begins.
• When the compartment is clean, normal filtering resumes.

20. Advantages
• Higher collection efficiency for smaller than 10
μm particle size.
• High removal yield for coarse and fine dust.
• Varying load does not influence pressure drop
and efficiency.
• Collected dust can possibly be re-used in the
process.
• Residual emissions are determined by incoming
concentrations.
• Relatively easy to use.

21. Disadvantages:
• High temperature gases need to be cooled
• High maintenance and fabric replacement cost
• Large size equipment
• Fabric is liable to chemical attack.

22. Particulate Scrubbers:
• Particulate scrubber is a low energy scrubber and is
the simplest wet scrubber used for particulate
control.
• A particulate scrubber is a scrubber in which a liquid
is mixed with the gas to collect solids.
• In particulate scrubbers, the liquid is dispersed into
the gas as a spray, and the liquid droplets are the
main collectors for the solid particles.
• It consists of an open vessel with one or more sets of
spray nozzles to distribute the scrubbing liquid.
• Typically, the gas stream enters at the bottom and
passes upward through the sprays.

23. • Devices called wet scrubbers trap suspended
particles by direct contact with a spray of water
or other liquid.