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1. SIGMA INSTITUTE OF ENGINEERING
VADODARA-19
Mechanical department
Class :m11
Semester : I
GUIDED BY :

2. PREPARED BY :
Khushwant Labana
Enrollment no:140500119048
Class:M 11
Sem 1

3. Air Pollution: causes
and control

4. AIR POLLUTION
Air is one of the vital part
of life .Air supplies with
oxygen is essential for
our bodies to live. Air is
99.9% nitrogen, oxygen,
water vapors and inert
gases. Due to man made
activities along with
some natural processes
many physical addition
of material that turn the
air impure or unclean.
That is called air
pollution.

5. AIR POLLUTION
Air pollution primarily
comes from burning
fossil fuels such as
natural gas, petroleum,
and coal. Humans are
the main cause of air
pollution. Industry,
including factories and
power plants, burn large
quantities of fuel. Burning
coal and petroleum
releases sulfur oxides and
nitrogen oxide into the air.
Airplanes, boats, and cars
burn petroleum, releasing
carbon monoxide and

6. Primary vs Secondary pollutants
• Not all of the pollutants found in the
atmosphere are the direct result of
emissions.
• Many pollutants arise from chemical
reactions in the atmosphere with other
substances or light (photochemical
reactions).
•Pollutant substances that are directly emitted
into the atmosphere = primary pollutants.
•Substances not directly emitted into the
atmosphere, formed by chemical reactions in
the atmosphere = secondary pollutants.

7. TYPES OF POLLUTION
 INDOOR POLLUTION
 Indoor air pollution occurs inside our homes, office and
schools.
 The main types of indoor pollutants are tobacco smoke,
gases from stoves and furnaces, household chemicals,
small fiber particles, and hazardous fumes given off by
building materials like insulation , glue, and paint .
 In high amounts it causes headache, eye irritation, etc.
 OUTDOOR POLLUTION
 Gases and particulates form of pollutants pour into the
atmosphere from the burning of fuel to motor vehicles, heat
buildings, business and industrial processes , burning of
garbage etc…
 Outdoor pollution make huge impacts on atmosphere and
the organisms
 Acid rain , global warming, etc are some of its
consequences .

8. TYPES OF POLLUTANTS
 Aerosols
 Particulates solid phase
 Dust
 Ash
 Fumes
 Solid and liquid
 Smoke (from combustion)
 Coastal aerosols
 Liquid
 Aggregate gases (sulfate, nitrate)
 Gases
COx
SOx
NOx
PAH

9. SIX PRIMARY OR “CRITERIA” AIR POLLUTANTS
 Carbon monoxide (CO)
 Sulfur oxides (SOx)
 Nitrogen dioxide (NO2)
 Ozone (O3)
 Hydrocarbons
 Particulate matter(PM2.5
_PM10)

10. Carbon Monoxide
•colorless, odorless, tasteless, non irritating
gas
•produced when carbon does not burn in fossil
fuels,ie incomplete combustion.
•Commonly present in automobile exhaust
•deprives body of O2 causing headaches,
fatigue, and impaired vision, it may lethal when
continually inhale concentration above
1000ppm over a period of 4 hours.

11. Sulfur Dioxide
•Colourless gas with penetrating and pungent
odour
•produced mainly when coal and fuel oil are
burned
•present in power plant exhaust
•narrows the airway, causing wheezing and
shortness of breath, especially in those with
asthma
The formation of SO2, SO3, and sulfuric
acid
S + O2 SO2
2 SO2 + O2 2SO3
SO3 + H2O H2SO4

12. Nitrogen Dioxide
•reddish, brown gas
•produced when nitric oxide combines
with oxygen in the atmosphere
•present in car exhaust and power
plants
•affects lungs and causes wheezing;
increases chance of respiratory failure.
•Smokers may readily develop lung disease as cigarettes
and cigars containing 330 to 1,500 ppm nitrogen oxides.
Prolonged exposure at 1 to3 ppm or even less may fatal.
•It also react with water to cause acid rain
4NO2+2H2O+O2 ------- 4HNO3

13. Control of Air
Pollutants
Methods of air pollution control can be divided into two
categories:
•THE CONTROL OF PARTICULATE EMISSIONS
•THE CONTROL OF GASEOUS EMISSIONS
The term particulate refers to tiny particles of
matter such as smoke, soot, and dust that are released
during industrial, agricultural, or other activities.
Gaseous emissions are industrial products such as
sulfur dioxide, carbon monoxide, and oxides of nitrogen
also released during various manufacturing operations.

14. THE CONTROL OF PARTICULATE
EMISSIONS
1. Particulates – Cyclones
 separation by centrifugation –
Cyclone utilise centrifugal force generated by a
spinning gas stream to separate the particulate matter
from the carrier gas.
The general principle of inertia separation is that the
particulate-laden gas is forced to change direction. As
gas changes direction, the inertia of the particles
causes them to continue in the original direction and
be separated from the gas stream.

15. 3.Particulates –
Filtration
Fibre bags commonly used for control
of particulate emissions with very
high dust loadings and smaller
particles.
• Filters consist of porous structure
composed of granular or fibrous
material which tends to retain the
particulate matter as the carrier
gas passes through the voids of the
filter.
• The dust is collected on the
inside of the bag surface and the

16. 4.Particulates – Wet
Scrubbers
 spray systems where fine water droplets are
sprayed at high velocity at right angles to the
emerging gas
 Most of the particles in the gas stream are
scavenged by the water droplets, which fall and
are collected along with the particles
 relatively low efficiencies (80-90%) and is usually
employed as a pre-cleaner to remove particles
larger than 5m

18. 5.Particulates – Electrostatic
Precipitators
 pass dirty gas through a series of fine wires
(coronas) charged with DC current – causes
particles to aggregate & precipitate
 Alternatively corona produces negative ions
that cause particles in the gas stream to
become negatively charged, and attracted to
positive terminal – where they aggregate and
fall into a collection hopper
 Large precipitators and low gas flow rates
give better results

20. charged electrodes
soot laden smoke
inlet
soot free gas escape
earth point
removal of soot particles

21. GASEOUS POLLUTANTS –
PROCESS MODIFICATIONS
 simplest and least expensive methods for the control of
gaseous pollutants
 fuel substitution e.g. low sulfur coal, or fuel oils in place of
cheaper coal can greatly reduce the amount of SO2
emissions at the source
 This type of source control is always the best approach
wherever possible
Gaseous pollutants - Combustion
 involves a series of complex chemical reactions in which
oxygen is combined with organic molecules, to form CO2
and H2O
 commonly referred to as incineration or afterburning

22. GASEOUS POLLUTANTS - ADSORPTION
 physical adsorption to solid surfaces
 Reversible - adsorbate removed from the adsorbent by
increasing temp. or lowering pressure
 widely used for solvent recovery in dry cleaning, metal
degreasing operations, surface coating, and rayon,
plastic, and rubber processing
 limited use in solving ambient air pollution problems –
with its main use involved in the reduction of odour
 Adsorbents with large surface area to volume ratio
(activated carbon) preferred agents for gaseous pollutant
control
 Efficiencies to 99%

23. GASEOUS POLLUTANTS - ABSORPTION
 Scrubbers remove
gases by chemical
absorption in a
medium that may be a
liquid or a liquid-solid
slurry
 water is the most
commonly used
scrubbing medium
 Additives commonly
employed to increase
chemical reactivity and
absorption capacity

24. CONTROL OF AIR POLLUTION
Minimize activities which are causes the pollution
like transportation and burning of fossil fuels.
Modification of Equipments.
By using the low sulphur coal in industries.
Removing the sulphur from coal (by washing with
the help of bacteria)
By using the biological and bio-scrubbers.
Plantation more trees.