Prof. arvind kumar_air_pollution

The Atmosphere
Gas Concentration, % by volume
Nitrogen 78.1
Oxygen 21.0
Argon 0.9
Carbon dioxide* 3.3 x 10-2
Hydrogen 5 x 10-5
Ozone 1 x 10-6
Methane* 2 x 10-4
9/20/2014 AIR POLLUTION
3

Air Pollution: Sources,
Effects & Remediation
Fresh air is good if you do not take too much of it; most of the achievements
and pleasures of life are in bad air.
Oliver Wendell Holmes
Definition: contamination of the air by noxious gases and minute particles
of solid and liquid matter (particulates) in concentrations that endanger
health-Air pollution only occurs outdoors
9/20/2014 AIR POLLUTION 2

Criteria Air Pollutants: Air Quality Index (AQI)
 Do we have a way to determine local air quality? AQI/PSI (formerly
Pollutants Std Index)
 Assigns numerical rating to air quality of six criteria pollutants
(TSP, SO2, CO, O3, NO2, and TSP*SO2)
API Value Air Quality Descriptor
0-50 Good
51-100 Moderate
101-199 Unhealthful
200-299 Very unhealthful
300 Hazardous
8

Sources of Air Pollution
Natural Sources
(Biogenic sources)
 Volcanoes
 Coniferous forests
 Forest fires
 Pollens
 Spores
 Dust storms
 Hot springs
Anthropogenic
 Fuel combustion - Largest
contributor
 Chemical plants
 Motor vehicles
 Power and heat generators
 Waste disposal sites
 Operation of internal-combustion
engines

Sources of Outside Air Pollution
 Combustion of gasoline and
other hydrocarbon fuels in
cars, trucks, and airplanes
 Burning of fossil fuels (oil,
coal, and dinosaur bones)
 Insecticides
 Herbicides
 Everyday radioactive fallouts
 Dust from fertilizers
 Mining operations
 Livestock feedlots

Physical Forms of an Air Pollutant
 Gaseous form
o Sulfur dioxide
o Ozone
o Hydro-carbon vapors
 Particulate form
o Smoke
o Dust
o Fly ash
o Mists

CLASSICAL AIR POLLUTANTS
Nitrogen dioxide
Ozone and other photochemical oxidants
Particulate matter
Sulfur dioxide

 A major form of air pollution is emissions
given off by vehicles.

What’s in smog
 particulates (especially lead)
 nitrous oxides
 potassium
 Carbon monoxide
 Other toxic chemicals

Sources of Indoor pollution
 Efficient insulation
 Bacteria
 Molds and mildews
 Viruses
 animal dander and cat saliva
 plants
 house dust
 Mites
 Cockroaches
 pollen

Effects on the environment
 Acid rain
 Ozone depletion
 Global warming
 In human population- respiratory
problems, allergies, strengthens
lugs, and a risk for cancer

Comparative Photos Showing Yuschenko Immediately Prior To And
Immediately Following Dioxin Poisoning
http://en.wikipedia.org/wiki/Viktor_Yushchenko (Note: this is an extreme case
of dioxin poisoning)
18

= NO3
H+ SO4
http://www.umac.org/ocp/4/info.html
-

Acid rain
 contains high levels of sulfuric or nitric acids
 contaminate drinking water and vegetation
 damage aquatic life
 erode buildings
 Alters the chemical equilibrium of some soils

Strategies
 Air Quality Management Plan
 Development of new
technology- electric cars,
cleaner fuels, low nitrogen
oxide boilers and water
healers, zero polluting paints
 Use of natural gas
 Carpooling
 Follow the laws enacted

Urban Emissions
•There are small emissions of NOx from industrial processes
•The main emissions are from combustion.
•There is negligible nitrogen in gasoline or diesel fuels so the
nitrogen oxides arise from the N2 and O2 in the air.
•Sulphur dioxides arise from the sulphur present in most fuels.
•Particulate matter describes matter below 10μm aerodynamic
diameter.

Role of Engines and Fuel
 Different engines and fuel combinations
give out different emissions in different
quantities.
 Some engines have catalysts which
effectively remove part of the harmful
gases.

Catalytic Converters and
Particle Traps
 Catalytic converters can be fitted to cars to reduce NOx
emissions.
CO + HC + NOx H2O + N2 + CO2
Platinum Honeycomb
 Particle traps can be used to reduce PM10 and NOx, but
the effectiveness is severely reduced if the fuel the
vehicle burns has a high sulphur content.
 The major target in the battle for cleaner cities is diesel.

STRATEGIE
The Clean Air approach:
 Based on scientific knowledge Using best
available, quality-controlled real-world data
With close involvement of stakeholders:
1. Project future emissions and air quality resulting from full
implementation
2. Explore scope and costs for further measures
3. Analyze cost-effective policy scenarios
4. Estimate benefits of policy scenarios

Main pollutants used in the CAFE
assessment

Particulate Matter (PM ) Pollution
- Traffic emissions including diesel engines
- Small combustion sources burnng coal and wood
- Reductions of SO2, N0x, NH3 and VOC

Ground level ozone
- VOC control to reduce ozone in cities
- N0x reduction from traffic
- Control of N0x emissions from ships
- Methane reduction

Ozone Formed

Climate Problems/Global Change/Air
Pollution 21st Century
 Greenhouse gases: global warming
(CO2, CFCs, NOx, CH4, H20)
 Air pollution: NOx, SO2, haze, aerosols,
O3, heavy metals (Hg, Pb, Cd), organic
compounds
 Ozone depletion: O3

Industrial Pollution Control System
Solution of the Pollution is Dilution

Particulate Matter
Pollutant
Particulate Matter (PM10)
Particulate Matter (PM2.5)

 Two possible fates
 Factors affecting fate
 Aerodynamic properties
 Physiological behavior
Methods of Deposition
Impaction*
Interception*
Diffusion*
Electrostatic Attraction
Gravitational Settling

INCINERATOR
 organic compounds from process
industries are destroyed at high
temperature (590 and 650oC & 1800
to 2200oF for most hazardous waste)
 Oxidizing organic compounds
containing sulfur or halogens produce
unwanted pollutants such as sulfur
dioxide, hydrochloric acid,
hydrofluoric acid, or phosgene

SRCUBBERS

Control Techniques
 Gravity settling chamber
 Mechanical collectors
 Particulate wet scrubbers
 Electrostatic precipitators
 Fabric filters

Fabric Filter
 High collection Efficiency over a broad
range of particles sizes
 Application: Cement kiln, Foundries,
Steel furnaces and Grain handling plants

GRAVITY SETTLING CHAMBERS
 The removal of larger-sized
particles, e.g., 40–60μm in
diameter
 Velocities (in the range of
1–10 ft/s)

CYCLONES
 Large diameter cyclones have good
collection efficiencies for particle 40-
50μm dia
 <23 cm diameter cyclones have good
collection efficiencies for particle 15-
20μm dia

Device Min.
Particle
size μm
Efficiency
%
(mass
basis)
Advantage Disadvantages
Gravitational
settler
>50 <50 •Low pressure loss,
•Simplicity of design
•maintenance
•Much space required
•Low collection efficiency
Centrifugal
collector
5-25 50-90 •Simplicity of design and
maintenance
•Little floor space required
•Dry continuous disposal
of collected dusts
•Low to moderate
pressure loss
•Handles high dust
loadings
•Temperature independent
•Much head room required
•Low collection efficiency for
small particles
•Sensitive to variables dust
loading and flow rates

ELECTROSTATIC PRECIPITATORS
 Extremely efficient for wide
range of particle sizes; even
submicron size

Wind Rose
 how wind speed and direction are typically
distributed at a particular location
 The directions of the rose with the longest
spoke show the wind direction with the
greatest frequency

Applications
 Urban Planning
 Siting of industrial locations including chimney & other air polluting source
 Industrial zoning & industrial estate planning
 Air pollution modeling.
 Disaster Management
 Street layout
 Ventilation of urban, industrial and housing
 Environmental Impact Assessment study.
 Oceanography
 Wind Energy
 Agriculture Engineering
 Ambient Air Monitoring
 Noise Impact Modeling

Parameters Affecting
Dispersion
wind speed
As the wind speed increases, the plume becomes longer and narrower; the
substance is carried downwind faster but is diluted faster by a larger
quantity of air.

ground conditions
 Ground conditions affect the mechanical mixing at the surface and the wind
profile with height.
 Trees and buildings increase mixing, whereas lakes and open areas
decrease it.

height of the release above ground level
The release height significantly affects ground-level concentrations.
As the release height increases, ground-level concentrations are
reduced because the plume must disperse a greater distance
vertically.

momentum and buoyancy of the
initial material released
The buoyancy and momentum of the
material released change the effective
height of the release.

Gases cool as they Neutral
mix and dilute with COOl air . Neutral Buoyancy
Smokestack plume demonstrating initial buoyant rise of hot gases
97

Calculation of effective stack height
 Using following data
a) Physical stack is 203 m tall with 1.07m diameter
b) Wind velocity is 3.56 m/s
c) Air temperature is 13 oC
d) Barometric pressure is 1000 millibars
e) Stack gas velocity is 9.14 m/s
f) Stack gas temperature is 149oC.

Atmospheric stability
Atmospheric stability relates to vertical mixing of the air.
During the day, the air temperature decreases rapidly with
height, encouraging vertical motions. At night the
temperature decrease is less, resulting in less vertical motion.

Atmospheric stability …
Dry adiabatic lapse rate (stable, neutral atmosphere)
dT  
- 1 C 100 m
dZ
dA
P
Pd + P
dZ
Natural balance between
hydrostatic head,  g dA
dZ, and pressure forces

Dry adiabatic lapse rate (dry adiabat, DALR or unsaturated lapse
rate): lapse rate of unsaturated air (i.e., air with a relative humidity
of less than 100%)
Wet adiabatic lapse rate (wet adiabat, saturated lapse rate, SALR,
moist adiabatic lapse rate or MALR) : the air parcel is saturated and,
because of the release of the heat of vaporization, the rate of
cooling will decrease to what is known as the wet adiabatic lapse
rate.
Environmental lapse rate (ELR, prevailing lapse rate or ambient
lapse rate) : The actual real-world profile of temperature versus
altitude that exists at any given time and in any given geographical
location is called the environmental lapse rate

the atmospheric stability can be characterized by these four categories
 A very stable atmosphere is one that has very little, if any, vertical motion of the
air.
 A stable atmosphere is one that discourages vertical motion but does have some
motion of the air.
 An unstable atmosphere is one that encourages continual vertical motion of the
air, upwards or downwards.
 A neutral atmosphere is one that neither discourages nor encourages vertical
motion of the air and is often referred to as conditionally stable.

Lapse Rate Effect
ELR > 0
1
the atmospheric temperature increases with
altitude. There is essentially no vertical turbulence
and the atmosphere is said to be very stable or
extremely stable.
ELR> – 5.5 K/km
2
some small amount of vertical turbulence and the
atmosphere is said to be stable. It is also referred
to as being sub-adiabatic.
MALR> ELR> DALR
3
the atmosphere is said to be neutral. *U.S.
Standard Atmosphere of – 6.5 K/km in most cases
ELR < DALR
4
there turbulence in the atmosphere and it is said to
be unstable. It is also referred to as being super-adiabatic
.
ELR= 0 the atmosphere would be in an isothermal
condition (no change of temperature with altitude)
and would be also be said to be very stable.

A “buoyant” atmosphere
et aR espaL
t hgi e H
Super-adiabatic lapse rate:
t hgi e H
t hgi e H
001
l art ueN
0
001
22 12 02
cit abai dA yr D
cit abai dar epuS
meT
t hgi e H
er ut ar ep meT
gni pooL

er ut ar ep meT
t hgi e H
Sub-adiabatic lapse rate:
t hgi e H
t hgi e H
t hgi e H
t hgi e H
er ut ar ep meT
er ut ar ep meT
gni nnaF
gni no C
gni pooL
er ut ar ep meT
t hgi e H
t hgi e H
001
0
001
22 12 02
l a mr eht osI
0
0
001
22 12 02
l art ueN
001
22 12 02
cit abai dabuS
22 12 02
er ut ar ep meT
er ut ar ep meT

atmosphere’s dispersive capability = maximum mixing depth*the
average wind speed. This product is known as the ventilation
coefficient (m2/s) . Values of ventilation coefficient less than about
6000 m2/s are considered indicative of high air pollution potential

10000
1000
100
10
A
B
C
D
E
F
z, m
0.1 1 10 100
Downwind distance, km
y, m
1000 A
100
10
1
B
C
D
E
F
0.1 1 10 100
Downwind distance, km
A= Extremely unstable; B-moderately unstable; C-Slightly unstable;
D-Neutral; E-Slightly stable; F- Moderately stable

Pasquill Stability classes A - F
A= Extremely unstable; B-moderately unstable; C-Slightly unstable;
D-Neutral; E-Slightly stable; F- Moderately stable


1
Gaussian concentration distribution
H
1
Q
x,y σ
H
1




Plume centre line Concentration

exp
Q






x, 0 π u σ σ
σ
Q
x, 0 π u σ σ
Location Maximum concentration










 


 

 
2
2
z y z
C
Effective stack height is zero
z y
C 





 

 




 

 

 
2
y
2
z y z
y
2
exp
σ
2
exp
π u σ σ
C
H
2
z  
131

The maximum ground level concentration along the x axis
can be calculated







σ
2Q
max σ

  
z
y
2
r
e π u H
C

Determining Max. ground
level concentration:
A power plant burns 5.45 tonnes of coal/hr
and discharges the combustion products
through a stack that has an effective
height of 75 m. The coal has sulfur
content of 4.2 %, and the wind velocity
at the top of the stack is 6 m/s. The atm
conditions are moderately to slightly
stable.
Determine
 Max. ground level concentration of SO2
and the distance from the stack at which
the maximum occurs
 Determine the ground-level
concentrations at a distance of 3 km
downwind at the centre line of the plume
and at a crosswind distance of 0.4 km on
either side of the centerline.

Thank you for kind attention
Thank you for kind attention

Prof. arvind kumar_air_pollution

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