Method to control air pollution

1. Presented
By-
Registration no.-
M.Tech (Env. Engg.)
Presented to-
Dr. R.C. Vaishya

2. Contents
 Introduction
 Major air pollutants
 Sources of air pollution
 Effects of air pollution
 Air pollution control methods
 Particulate pollution control
 Gaseous pollution control
 Conclusion
 References

3. Introduction
 Air pollution is a situation in which the outdoor atmosphere
contains materials in concentrations which are harmful to people and
their environment.

4. Major air pollutants
 Particulate matter
 Ozone
 Carbon monoxide
 Nitrogen dioxide
 Sulfur dioxide
 Lead
 Toxic air pollutants
 Greenhouse gases

5. Sources of air pollution

6. Effects of air pollution

7. Air pollution control methods
1. Dilution :
dilution of contaminants in the atmosphere can be
accomplished through the use of tall stacks.
2. Control at source :
a) Substitution of raw materials
b) Process modification
c) Modification of existing equipment
d) Maintenance of equipment
e) Pollution control equipment

8. Particulate pollution control
Devices for particulate pollutant control:
a) Gravitational settling chamber-
 For removal of particles > 50µ
 Simple in design and operation.
 Settling chamber use the force of
gravity to remove solid particles.
 Efficiency of removal is < 50%.

9. b) Centrifugal collectors /cyclones-
 Centrifugal force is utilized to
separate the particulate matter.
 It can remove particle of size 5
to 25µm.
 Efficiency of removal is 50 to
90 %.
 Used mostly in industries such
as feed and grain mills, cement
plants etc.

10. c) Electrostatic precipitators
 Works on the principle of
electrical charging of particulate
matter (-ve) and collecting it in
a (+ve) charged surface.
 It can remove particle of size >
1µ.
 Removal efficiency is 95 to
99%.

11. d)Wet collectors or scrubbers
 Particulate matters are incorporated into liquid droplets and removed
from the gas stream.
 Collection efficiency is a function of the energy consumed in the air
to water contact process.
 Types of scrubbers-
 Spray tower
 Venturi scrubber
 Cyclone scrubber

12. Spray towers
 Water is introduced by means
of spray nozzle.
 As the polluted gas flows
upwards, the particulates
present collide with the water
droplets being sprayed, then
under the influence of
gravitational force, liquid
droplets containing the
particulates settle to the bottom
of spray tower.

13. Venturi scrubbers
 Submicron particulates (size 0.5 to
5µm) associated with smokes and
fumes are effectively removed.
 At a velocity from 60 to 180m/s, the
contaminant gas passes through a duct
that has a venturi shaped throat
section.
 A coarse water spray is injected into
the throat, where it is atomized by the
high gas velocities.
 The liquid droplets collide with the
particles in the gas stream, and the
particles get entrained in the droplets
and fall down to be removed later on.

14. Cyclone scrubbers
 High pressure spray nozzles
generate a fine spray that
intercepts the small particles
entrained in the swirling gases.
 Particulate matter thrown to the
wall by centrifugal force is then
drained to the collection sump.
 For droplets of 100µm,
efficiency approaches 100%,
and 90 to 98% removal is
achieved for droplets between 5
and 50µm.

15. e)Fabric filters (Baghouse filters)
 In this device, the particulate
laden gas stream passes
through a woven fabric that
filters out the particulate matter
and allows the gas to pass
through.
 After a dust mat has formed on
the fabric, more efficient
collection of submicron
particles (99+percent) is
accomplished by sieving.

16. Gaseous pollution control
Methods of control include:
a) Adsorption-
 Surface phenomenon
 Adsorption towers use adsorbents to
remove the impurities from the gas
stream.
 The impurities can bind either
physically or chemically to the
adsorbing material.
 It can remove low concentration of
impurities from the flue gas stream.
 The most commonly used adsorbent is
activated carbon.

17. b) Absorption
 In this process, gaseous pollutants
removed by dissolution into a
liquid solvent/absorbent such as
water.
 The amount of gas that dissolves in
a solvent depends upon the
properties of both the gas and the
solvent.
 Absorbents used to remove sulfur
dioxide, oxides of nitrogen,
hydrogen sulfide, chlorine,
ammonia, hydrogen chloride and
hydrocarbons.

18. c)Condensation
 Condensation is the process of converting a gas or vapor to liquid.
Any gas can be reduced to liquid by lowering its temperature and/or
increasing its pressure.
 Condensers are typically used as pretreatment devices. They can be
used ahead of adsorbers, absorbers, and incinerators to reduce the
total gas volume.
 Removal efficiency of condensers typically range from 50% to more
than 95% depending upon design and applications.

19. d) Combustion
This method used for the removal of VOCs since they can
be decomposed to CO2 and H2O.
The combustion equipment is designed to push oxidation
reactions as close as possible to completion, leaving a
minimum of unburned compounds.
For efficient combustion to occur ,it is necessary to have
proper combination of four basic elements: oxygen,
temperature, turbulence, and time.

20. Conclusion
 Air pollution is a major environmental issue .It can affect health and
life support systems as well.
 Since clear air is an essential factor of life for respiration, it is
necessary to prevent the sources of air pollution.
 Using appropriate controlling devices and processes, the pollutants in
the air can be removed.
 There are five processes for the removal of particulate matters.
Settling chambers, cyclone, electrostatic precipitators, wet scrubber,
fabric filters.
 For gaseous matters, adsorption, absorption, condensation, and
combustion processes are used.

21. References:
 Peavy, H.S., Rowe, D.R. and Tchobanoglous, G. (1985)
Environmental Engineering. McGraw-Hill Book Company, New
York, 696.
 https://www.yourarticlelibrary.com/air-pollution/5-effective-
methods-to-control-air-pollution-explained-with-diagram/28360

22. THANK YOU