AIR POLLUTION lecture EnE203 updated.pdf

this is a lecture for air pollution lesson in the subject of Ene 203

1. AIR POLLUTION
EnE203 Lecture
Joseph Gerard T. Reyes, Ph.D.

2. Outline
•Definition
•Composition of atmospheric air
•Classification and sources of air pollutants
•Effects of air pollution
•Air pollution control methods, equipment and safety

3. What is Pollution?
•Change in background concentration
•Any substance introduced into the environment that adversely affects
the usefulness of a resource.
•Pollution happens because no process is 100% efficient; each process
produces waste, which can contribute to pollution.
•Air pollution -one or more contaminants or combinations in such
quantities and of such durations in atmospheric air which tend to be
injurious to biological life, or materials

4. The Earth’s Atmosphere: Composition
Note: The Earth’s atmosphere has been changing over
time due to natural and anthropogenic activities.

5. GasTypical Surface
Concentration
(ppm)
Lifetime Source
N
2
780,840 Biologicalcycle
O
2
209,840 Biological cycle
H
2
OVariable Hydrologic cycle
Ar9340 Inert
CO
2
355 7 y Fossilfuel combustion, deforestation
CH
4
1.72 7 y Wetlands, natural gas use,
agriculture
N
2
O0.31 120 yOceans, soils, combustion
CO0.10 1 monthMethane oxidation, combustion
O
3
0.04 Photochemistry
NH
3
10
-3
10 d Livestock, fertilizer, wildlife, oceans
NO/NO
2
10
-3
1 d High-temperature combustion
SO
2
10
-3
1 d Coal, combustion
CFCl
3
2.7 x 10
-4
50 y Refrigerant, solvent
ATMOSPHERIC CONSTITUENTS (Seinfeld and Pandis, 1998)

6. Pressure = 1,000
millibars at
ground level
Atmospheric pressure (millibars)
02004006008001,000
120
110
100
90
80
70
60
50
40
30
20
10
0
(Sea
Level)
–80–4004080120
Temperature (˚C)
Altitude (kilometers)
Altitude (miles)
75
65
55
45
35
25
15
5
Thermosphere
Heating via ozone
Mesosphere
Stratosphere
Ozone “layer”
Heating from the earth
Troposphere
Temperature
Pressure
Mesopause
Stratopause
Tropopause
The Structure of the Earth’s Atmosphere

7. Classification of Sources of Air Pollution
•Natural –e.g., pollen grains, volcanic eruptions, forest fires, dust
storms, spores, bacteria and other microorganisms.
•Man-made –e.g., industrial plants, thermal power plants,
automobile exhaust, fossil fuel burning, mining

8. Stationary and Mobile Sources of Emissions
•Stationary sources
•Point (major) source –a stationary single, major source of emissions; can be
pinpointed to a single location
•Area source -smaller-size facilities that release lesser quantities of toxic
pollutants into the air; mobile sources with indefinite routes
•Volume source –a three-dimensional source of pollutant emissions (includes
elevations from ground, e.g. emissions from roof vents of buildings);
emissions are often uncontrolled
•Line source –mobile sources with definite routes

11. Characteristics of Air Pollutants
•temporarily or permanently resident in the atmospheric air
•alter the environment leading to effects on health, the food chain,
and well-being of people
•pollutants can be solid (large or sub-molecular), liquid or gas
•originate from a natural or anthropogenic sources (or both)
•It is estimated that anthropogenic sources have changed the
composition of global air by less than 0.01%. This will still have a
significant impact on the climate, ecosystem and all species on the
planet.

12. CLASSIFICATION OF AIR POLLUTANTS
•primary pollutants, which are emitted directly from identifiable
sources
•secondary pollutants, which are produced in the atmosphere when
certain chemical reactions take place among primary pollutants.
Atmospheric phenomena influence the formation of secondary
pollutants

13. Major Primary Pollutants
•particulate matter (PM)
•sulfur dioxide
•nitrogen oxides
•volatile organic compounds (VOCs)
•carbon monoxide
•lead

16. Secondary Pollutants
•Some primary air pollutants react with one another or with other
chemicals to form secondary pollutants.
•Examples are
•Ozone
•Formaldehyde
•PAN (peroxyacetyl nitrate, C2H3NO5)
•smog (photochemical or smoke induced)
•acid mist
•sulfuric acid

18. •
Atmospheric sulfuric acid is one example of a
secondary pollutant –cause of acid rain
•
Air pollution in urban and industrial areas is
often called smog.
•
Photochemical smog, a noxious mixture of
gases and particles, is produced when strong
sunlight triggers photochemical reactions in
the atmosphere.
•
The major component of photochemical smog is
ozone.

19. Major Pollutants, Sources, and Effects
Carbon monoxide (CO)
•colorless, odorless, tasteless gas.
•No effect at normal conc. (0.1ppm) but higher
concentrations produce serious effects
•Volcanoes, natural gas emissions, seed germination
contribute to CO
•Transport sector account for up to 95% of CO
emissions in cities (US EPA 2008)
•Effects of CO poisoning: reduced oxygen carrying
capacity of blood, decrease in vision; cardio-vascular
disorders.

21. Major Pollutants, Sources, and Effects
Carbon dioxide (CO
2
)
•colorless, odorless, tasteless gas.
•a product of combustion, respiration or decomposition; can also
be a secondary pollutant
•emitted from natural and anthropogenic sources
•effects: nausea, headaches
•an atmospheric greenhouse gas

22. Major Pollutants, Sources, and Effects
Oxides of nitrogen (NO
x
)
•group that includes NO, NO
2
, N
2
O.
•sources include:
•fuel combustion in automobiles and industries; three types of production –
fuel NO
x
, thermal NO
x
, prompt NO
x
•agriculture
•lightning
•forest fires.
•natural ionizing radiations
•effects: Reduce blood carrying capacity; lung problems
•can react with other airborne compounds to produce nitric acids and
photochemical smog

23. Major Pollutants, Sources, and Effects
Oxides of sulfur(SO
x
)
•include SO
2
, SO
3
.
•67% SO
x
pollution due to volcanic activities and other natural
sources
•anthropogenic sources are fossil fuel burning, transportation,
industrial activities; sulfuris contained in fuel such as coal and
diesel
•effects: respiratory problems; materials such as marbles, cloth,
paper, leather also affected; impact on plants
•can react with airborne compounds to produce sulfuric acid

24. Major Pollutants, Sources, and Effects
Hydrocarbons (HC)
•include methane, ethylene,
acetylene, terpenes etc.
•sources include
•coal fields
•natural fires
•incomplete combustion
•forest fires
•Effects:
•carcinogenic
•lead to the formation of ozone and PAN
•affect plants and degrade materials
such as rubber, fabric and paint

25. Major Pollutants, Sources, and Effects
Particulate Matter (PM)
•particles of various substances suspended in the air (aerosols)
•in the form of solid particles and liquid droplets
•vary widely in size
•PM may be found in dust, smoke, fumes, mist, fog, fly ash etc.
•known sources of PM:
•diesel trucks and buses
•construction equipment
•power plants
•burning of solid fuels
•PM can also be a result of condensation of gases or reactions of air-borne
compounds

27. Effects of PM:
•premature death
•aggravated asthma
•acute respiratory symptoms
•chronic bronchitis
•decreased lung function (shortness of breath)
People with existing heart and lung disease, as
well as the elderly and children, are particularly at
risk.

28. Effects of air pollution on humans

29. •air pollution accounts for around 30-40% of cases of
asthma and 20-30% of all respiratory disease.
•Short-term effects: irritation to nose, eye, throat,
bronchitis, headache etc.
•Long-term effects: lung disease, chronic respiratory
problem, damage to heart, brain, eyes etc.
•eye irritation due exposure to NO
x
, O
3
, PAN, PM
•nose and throat ailments due to pollutants such as
SO
2
, NO
x

30. •gaseous pollutants like H
2
S, SO
2
, NO
2
and hydrocarbons
cause noxious odors
•irritation of respiration tract caused by SO
x
, NO
x
, CO, O
3
.
•exposure to high concentrations of SO
2
, NO
2
and SPM
causes bronchitis and asthma
•CO and NO react with hemoglobin and reduce O
2
carrying capacity of blood
•heavy metals like lead can cause poisoning; high
concentrations cause damage to liver and kidney.

31. Air Pollutant Factors Affecting Human Health
•nature of the pollutants
•concentration of the pollutants
•duration of exposure
•state of health of receptor
•age group of the receptor

32. Effects of air pollution on plants

33. •decreased yield in agriculture.
•suppressed growth of vegetables.
•leaf injury and damage to young plants.
•decreased growth rate and increased death rate

34. Some Effects of air pollution on materials
•corrosion of metals due to SO
2
in presence of oxygen
and moisture is converted into H
2
SO
4
; H
2
SO
4
reacts
with limestone, marble and other building materials
to cause deterioration.
•soiling and erosion of building materials.
•SO
2
, O
3,
H
2
S and aerosols damage protective coating
and paints of the surface
•O
3
and PAN causes cracking of rubber and various
electrical insulations
•deterioration of art work due to SPM.

35. Air pollution control
Cannot be fully prevented but can be controlled.
1.Preventive measures
2.Control measures using devices
Preventive measures (source control)
•selection of suitable fuel (e.g., low sulphur coal in
power plant, using of CNG)
•modifications in industrial processes
•selection of suitable sites; zoning for industrial
plants

36. Control measures using devices
•when source control is not possible
•control done by:
•collecting pollutants by using equipments
•reducing pollutants concentrations by thermal or
catalytic combustion
•converting the pollutants to less toxic forms
•releasing the pollutants using stacks for greater
dispersion.

37. Air pollution controlling equipment
•Gravitational settling chamber
•Used to remove particles with size greater than
50 μm.
•Velocity of flue gas reduced in large chamber.
•Particles settle under gravitational force.

38. Advantages
•Low initial cost.
•Easy to design.
•Low pressure drop.
•Low maintenance cost.
•Dry and continuous disposal of solid particulates.
Disadvantages
•Require large space.
•Less collection efficiency.
•Only larger size particles can be collected.

39. Cyclone separator
•Centrifugal force is utilized to
separate the particulate matter.
•It can remove 10 to 50 μm
particle size.
•Used mostly in industries.

40. Advantages
•Low initial cost.
•Require less floor area.
•Simple construction and maintenance.
•Can handle large volume of gas at high temp.
Disadvantages
•Requires large head room.
•Less efficiency for smaller particles (<10μm).
•Sensitive to variable dust load and flow rate.

41. Electrostatic precipitators
•works on the principle of electrical charging of
particulate matter (negative) and collecting it in
a positive-charged surface
•99% collection efficiency
•can remove particle size range of 0.1 μm to 1
μm.

43. Advantages
•High collection efficiency.
•Particles may be collected dry or wet.
•Can be operated at high temp. (300-450˚c).
•Maintenance is normal.
•Few moving parts.
Disadvantages
•High initial cost.
•Require high voltage.
•Collection efficiency reduce with time.
•Space requirement is more.
•Possible of explosion during collection of
combustible gases or particulates.

44. Fabric filters
•Flue gas is allowed to
pass through a woven
Fabric, which filters out
Particulate matter.
•Small particles are
retained on the fabric.
•Remove particles up to 1 μm.
•Its efficiency up to 99%.

45. Advantages
•Higher collection efficiency for smaller than
10μm particle size.
•Performance decrease becomes visible, giving
prewarning.
•Normal power consumption.
Disadvantages
•High temp. gases need to be cooled.
•High maintenance and fabric replacement cost.
•Large size equipment.
•Fabric is liable to chemical attack.

46. Scrubbers
•Particulate matters are incorporated into liquid
droplets and removed from the gas stream.
•Different types of scrubbers are-
-Spray tower
-Venturi scrubber
-Cyclone scrubber
•Flue gas made to push up against a down falling
water current.
•Particulate matter mix up with water thus falls
down and gets removed.

47. Spray tower
Cyclone scrubber

48. Advantages
•Simultaneously remove particulates and gaseous
pollutants.
•Hot gases can be cooled down.
•Corrosive gases can be recovered and neutralize.
Disadvantages
•Lot of waste waters produced.
•Poses freezing problem in cold countries.
•Maintenance cost is high when corrosive materials
are collected.

49. END OF LECTURE