air and noise pollution environmental protection and control

JNTUK syllabus
Air Pollution control
equipments and
methods
• For particulate matter
1. Settling chambers
2. Fabric filters
3. Scrubbers
4. Cyclones
5. Electrostatic
precipitators
• For Gaseous
pollutants
1. Absorption
2. Adsorption
3. Combustion

Source correction methods
Raw material changes
Process changes
Equipment modification & replacement

Objectives of control equipment
o Prevention of nuisance
o Prevention of physical damage to property
o Elimination of health hazards to plant personnel
o Recovery of valuable waste product
o Minimization of economic losses
o Improvement of product quality

Particulate control equipment
o Gravitational settling chambers
o Fabric filters
o Scrubbers
o Cyclone separator
o Electrostatic precipitators

o Efficiency of a separating device
η= quantity of particulates collected from gas/
quantity of particulates present initially

Gravitational settling chamber
o Used to remove particles with size greater than 50
μm.
o Velocity of flue gas reduced in large chamber.
o Particles settle under gravitational force.

Vs= hV/ L ----------- (i)
L= length of chamber
V= horizontal velocity of carrier gas
Vs= settling velocity of particulates
h= height through which particulates travel before
settling down

By stokes law
Vs= g( p- )D2/18μ --------- (ii)
D= dia of particle
g= acceleration due to gravity
ρp= density of particle
ρ = density of gas
μ= viscosity of gas

From eq- i and ii
D= [18Vhμ/ Lg ( p- )]1/2
D = is minimum size of particle that can be
removed in a settling chamber

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

Application
o Industrial application is limited.
o Used widely for removal of large solid
particulates from draft furnace, kilns.
o Sometimes used in process industry, food and
metallurgical industry.
o Used as pre-cleaners for high efficiency
collectors.

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

Dp, min= [9 μ B/ V Nt( p- )] ½
Dp, min= dia of smallest particles that can be
removed cm
μ = viscosity of the fluid
B= width of cyclone inlet duct
V= avg. inlet velocity
Nt= no of turns made by gas stream in cyclone
p = density of particles
= density of fluid

o Design factor having greatest effect on
collection efficiency is cyclone diameter.
o Smaller dia, higher is efficiency, because
centrifugal action increase with decreasing radius
of rotation.
o Cyclone efficiencies > 90 % with particle dia of
10 μ
o > 95 % with particle dia 20 μ.

Efficiency
o Conventional efficiency
o High efficiency- smaller body dia to create
greater separating force.
o Increase collection efficiency, if increase in dust
particle size, dust particle density, gas inlet
velocity, inlet dust loading, cyclone body length
(no of gas revolutions)
o Decrease collection efficiency due to increase in
gas viscosity, cyclone dia, gas outlet dia, inlet
width, and inlet area

Operating problems
o Erosion
o Corrosion
o Material build up

Advantages
o Low initial cost.
o Require less floor area.
o Simple construction and maintenance.
o Can handle large volume of gas at high temp.
o No moving parts
Disadvantages
o Requires large head room.
o Less efficiency for smaller particles (<10μm).
o Sensitive to variable dust load and flow rate.

Applications
o Control gas borne particulates from industries
like cement, feed and grain processing, food and
beverage processing, mineral processing, paper
and textile industries and wood working
industries.
o Used in recovery of catalyst ducts in petroleum
industry and reduction of fly ash emission.

Electrostatic precipitators
o Works on the principle of electrical charging
of particulate Matter (-ve) and collecting it in a
(+ve) charged surface.
o 99% efficiency.
o Can remove particle size range of 0.1 μm to 1
μm.

Six major components
o A source of high voltage
o Discharge electrodes and collecting electrodes
o Inlet and outlet for gas
o A hopper for disposal of collected material
o An electronic cleaning system
o An outer casing to form an enclosure around
electrodes

Principles
o Gas stream passed two electrodes.
o High potential difference is maintained.
o Out of two electrodes, one is discharging other
collecting.
o Potentials of 100 kv are used.
o Ionization creates active glow zone called
“corona”.
o Gas ionization is dissociation of gas molecules
into free ions.

o As particulates pass through field, they get
charged and migrate to oppositely charged
electrode.
o Particles deposited on collecting electrodes, lose
charge and removed mechanically by rapping.,
vibration or washing to a hopper.

Single stage and two stage precipitators
o Single stage gas ionization and particulate
collection in a single stage.
o Two stage, particle ionized in first chamber and
collected in second chamber.
o Industrial precipitators single stage design.
o Two stage used for lightly loaded gases.
o Single stage for more heavily loaded gas streams.

Efficiency
o General collection efficiency is high, nearly
100%
o Installations operate 98 and 99% efficiency.
o Acid mist and catalyst recovery efficiencies in
excess of 99%.
o Carbon black, because of agglomeration
tendency collection efficiency less than 35%.

E= 1- e -Ut
f
E= collection efficiency
f= specific collecting area of precipitator,
expressed as sq m of collecting electrode area
per cubic m of gas handled per s.
Ut= migration velocity of particle towards
collection electrode
e= napierian log base

Design parameter
o Volumetric flow rate
o Composition
o Temperature
o Dew point
o Dust particle conc.
o Size of particle
o Bulk density
o Tendency of allgomorate

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

Application
o Cement factories
o Pulp and paper mills
o Steel plants
o Non- ferrous metal industry
o Chemical industry
o Petroleum industry
o Carbon black industry
o Electric power industry

Fabric filters or cloth filters
o Flue gas is allowed to pass through a woven
fabric, which filters out particulate matter.
o Small particles are retained on the fabric.
o Consists of numerous vertical bags 120-400
mm dia and 2-10 m long.
o Remove particles up to 1 μm.
o Its efficiency up to 99%.

Factors affecting efficiency
Efficiency decrease due to
o Excessive filter ratio:- ratio of carrier gas vs
gross filter area
o Improper selection of filter media:- temp.
resistance, resistance to chemical attack and
abrasion resistance taken into consideration.

Operating problems
o Cleaning
o Rupture of cloth
o Temperature
o Bleeding
o Humidity
o Chemical attack

Filter cleaning
o Rapping
o Shaking
o Back wash
o Pulse jet

Filter medium
o Carrier gas temp.
o Carrier gas composition
o Gas flow rate
o Size and shape of dust particles

Fabric Max.
operatin
g temp.
(˚ C)
Acid
resistance
Alkali
resistance
Abrasion
resistance
Tensile
strength
Kg/cm2
Cotton 82 Poor Good Very good 4920
Wool 93 Very good Poor Fair to
good
1755
Nylon 93 Poor to
fair
Excellent Excellent 5625
Dacron 135 Good Good Very good 5625
Polypropyl
ene
93 Excellent Excellent Excellent 7730
Fiber glass 290 Fair to
good
Fair to
good
Fair 14,060
Physical properties of bag filters

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

Application
o Metallurgical industry
o Foundries
o Cement industry
o Chalk and lime
o Brick works
o Ceramic industry
o Flour mills

Scrubbers or wet collectors
o Particulate matters are incorporated into liquid droplets
and removed from the gas stream.
o Flue gas made to push up against a down falling water
current.
o Particulate matter mix up with water thus falls down
and gets removed.

Collection mechanism
o Impingement
o Interception
o Diffusion
o Condensation

Types of scrubbers
o Spray towers
o Venturi scrubbers
o Cyclone scrubbers
o Packed scrubbers
o Mechanical scrubbers

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

Choice of equipment
1. Particulate size
2. Particulate loading
3. Efficiency required
4. Properties of carrier gas
1. Composition 6. Humidity
2. Temp. 7. Combustibility
3. Pressure 8. Reactivity
4. Viscosity 9. Toxicity
5. Density 10. Electrical property

5. Flow characteristics of carrier gas
1. Flow rate
2. Variation in flow rate
6. Specific property of contaminant
1. Composition 6.Toxicity
2. Contaminant phase 7. Hygroscopicity
3. Solubility 8. Agglomerating
characteristics
4. Combustibility 9. Electrical and sonic
properties
5. Reactivity 10. Catalyst poisoning

7. Allowable pressure drop
8. Contaminate disposal
9. Capital and operating cost of equipment
10. Ease of maintenance and reliability

Economical aspects
1. Cyclones:- cheap to install, power consumption
moderate, maintenance cost normal.
2. Filters:- expensive to install, power consumption
moderate. Maintenance cost high.
3. Electrostatic precipitators:- most expensive regarding
installation, power consumption moderate to low as
pressure drops. Maintenance cost moderate
4. Scrubbers :- installation cost moderate, maintenance
cost not high, high rate of power consumption.

Control of gaseous contaminants
Methods of control include:
o Absorption
o Adsorption
o Secondary combustion

Absorption
o Effluent gas passed through absorbers
(scrubbers), which contain liquid absorbent.
o Efficiency depends on
1. Amount of surface contact between gas and liquid
2. Contact time
3. Conc. of absorbing medium
4. Speed of reaction between the absorbent and gases
o Absorbents used to remove SO2, H2S, SO3, F
and oxides of nitrogen.

Equipments using principles of absorption for
removal of gaseous pollutants
o Packed tower
o Plate tower
o Bubble cap plate tower
o Spray tower
o Liquid jet scrubber absorbers

Gaseous
pollutants
Common absorbents used in solution form
SO2 Dimethylaniline, ammonium sulphite,
ammonium sulphate, sodium sulphide, calcium
sulphite, alkaline water,
H2S NaOH and phenol mix (3:2), tripottasium
phosphate, sodium alamine, sodium
thioarsenate, soda ash
HF Water, NaOH
NOX Water, aqueous nitric acid

Adsorption
o Surface phenomenon, require large solid surface
o Adsorption towers use adsorbents to remove the
impurities from the gas stream.
o The impurities bind either physically or chemically to
the adsorbing material.
o The impurities can be recovered by regenerating the
adsorbent.
o Adsorption towers can remove low concentrations of
impurities from the flue gas stream.

Construction and Operation
o Adsorption towers consist of cylinders packed with the
adsorbent.
o The adsorbent is supported on a heavy screen
o Since adsorption is temperature dependent, the flue gas
is temperature conditioned.
o Vapor monitors are provided to detect for large
concentrations in the effluent. Large concentrations of
the pollutant in the effluent indicate that the adsorbent
needs to be regenerated.

Advantages of Adsorption Towers
o Very low concentrations of pollutants can be removed.
o Energy consumption is low.
o Do not need much maintenance.
o Economically valuable material can be recovered during
regeneration.

Gaseous pollutants Adsorbents used in solid form
SO2 Pulverized limestone or
dolomite, alkalized alumina
H2S Iron oxide
HF Lump limestone, porous sodium
fluoride pellets
NOX Silica gel
Organic solvent vapours Activated carbon

Secondary combustion
o Flame or catalytic combustion can be utilized
when gases or vapors to be controlled.
o Fume and vapor incinerators
o After burners
o Flares, either with steam injection or venturi
flare

o After burners on incinerators met with varying
success depending on kind of after burner used
and type of incinerator.
o Flare design for smokeless combustion gases of
variable composition and wide range of flow
rates.
o Venturi flares, mix air with gases in proper ratio
prior to ignition to achieve smokeless burning.

o When conc. of combustible portion of gas
stream below flammable range, catalytic
combustion process used.
o Used to control effluent gases, fumes and odors
from refineries, burning waste, cracking gases,
chemical plants, paint and enamel ovens.

Method is expensive when
1. Fuel values of gaseous discharge low
2. Moisture content of discharge is high
3. Exhaust volume is extremely large

Factors considered in design of incinerators are
1. Sufficient air for combustion reaction
2. Adequate temp.
3. Adequate retention time

o Incineration equipment, single combustion
chamber.
o Combustion chamber proportioned that gas
velocity, gas flow patterns, established produce
adequate retention time.
o Avg. retention time 0.2-0.3 s at temp. 650 ˚C and
higher.

Contents
• Noise
• Noise Standards
• Sources of Noise Pollution
• Causes of Noise Pollution
• Effects of Noise Pollution
• Control of Noise Pollution
• IS14000

What is Noise?
• In simple terms, noise is unwanted sound. Sound is a form
of energy which is emitted by a vibrating body and on
reaching the ear causes the sensation of hearing through
nerves.
• Sounds produced by all vibrating bodies are not audible.
The frequency limits of audibility are from 20 HZ to 20,000
HZ.
• Sounds of frequencies less than 20 HZ are called infrasonics
and greater than 20,0000 HZ are called ultrasonics.

A noise problem generally consists of three inter-related
elements
1. The source,
2. The transmission path and
3. The receiver.
This transmission path is usually the atmosphere
through which the sound is propagated, but can include the
structural materials of any building containing the receiver

How it is computed?
• The intensity of sound is measured in sound pressure
levels (SPL) and common unit of measurement is decibel,
dB.
• If the sound levels are measured in terms of pressure,
then, sound pressure level, LP is given by,
The LP is measured against a standard reference
pressure
, which is equivalent to zero decibels.

Day-night equivalent noise levels (Ldn):
The day night equivalent noise levels of a community
can be expressed as
where,
Ld = day-equivalent noise levels (from 6AM - 9 PM), dB
Ln = night equivalent noise levels (from 9 PM - 6 AM), dB

Characteristics of Noise
• Sound pressure
• Frequency
• Duration
• Time of the day
• Location

Kinds of Noise
• Continuous
• Variable
• Impulse or Impact
• Chemical Noise
• Instrumental Noise

Variable Noise
Impulse Noise
Continuous Noise

Sources of Noise Pollution
• Household Sources
• Social Events
• Commercial and Industrial Activities
• Transportation

Household Sources
• Food Mixer
• Grinder
• Vacuum Cleaner
• Washing machine and Dryer
• Air Conditioner
• Cooler
• TV
• Loud speaker

Social Events
• Places of Worship
• Discos and Functions
• Political Parties
• Markets where people sell goods with
loudspeaker.
When these events are not often, they can be
termed as nuisance rather than noise pollution.

Commercial and Industrial Activities
• Printing Presses
• Manufacturing Industries
• Construction Sites

Sources of Construction Noise
• Pneumatic Hammers
• Air Compressors
• Bulldozers
• Loaders
• Dump Trucks
• Pavement breakers

Sources of Industry Noise
• Fans
• Motors
• Compressors mounted outside

Transportation
• Road Traffic Noise
• Aircraft Noise
• Noise from Rail Roads

Causes of Noise Pollution
• Poor Urban Planning
• Sounds from Motor Vehicles
• Sounds from Musical Instruments
• Car Alarms
• Office Equipment
• Factory Machinery
• Construction Work
• Barking Animals
• Appliances
• Audio Instruments
• Loud Speakers
• Noise Created by People

Effects of Noise Pollution
• Effects on Human
• Effects on Animals
• Effects on Environment

Effects on Human
• Hearing Impairment
• Interference with Spoken Communication
• Decrease in Efficiency
• Lack of Concentration
• Fatigue
• Sleep Disturbances
• Cardiovascular Disturbances
• Disturbance in Mental Health
• Impaired Task Performance
• Negative Social Behavior and Annoyance reactions
• Abnormal Fetus
• Temporary or Permanent Deafness

Diseases Caused by Noise Pollution
• High Blood Pressure
• Heart Attack
• Deafness
• Stress

Effect on Animals
• Damages Nervous system
• They become Dangerous and Attacking
• Raise Metabolism
• Death of Certain Species
• Genetic and Evolutionary Problems

Effects on Environment
• Breakage of Earth Barrier
• Damages Buildings, bridges and Monuments

Control of Noise Pollution
1. Control at Source
2. Control in the Transmission Path
3. Using Protective Equipment (Receiver)

Control at Source
• Reducing the Noise Levels from Domestic
Sectors
• Maintenance of Automobiles
• Use of Economic instruments
• Control over Vibrations
• Low Voice Speaking
• Prohibition on Usage of loudspeakers
• Selection of Machinery
• Maintenance of Machines

Control in the Transmission Path
• Installation of Barriers
• Installation of Panels and Enclosures
• Green Belt development

Using Protection Equipment
• Job Rotation
• Exposure Reduction
• Hearing Protection
• Protection at the Receiver End

Noise Control Techniques
• Sound insulation
• Sound Absorption
• Vibration Damping
• Vibration Isolation
• Urban Planning
• Public Education and Awareness

IS14000
• ISO 14000 is a family of standards related to environmental
management that exists to help organizations
1. minimize how their operations (processes, etc.) negatively
affect the environment (i.e., cause adverse changes to air,
water, or land)
2. comply with applicable laws, regulations, and other
environmentally oriented requirements
• ISO 14000 is similar to ISO 9000 quality management in
that both pertain to the process of how a product is
produced, rather than to the product itself.

ISO 14000 refers to a series of standards on environmental
management tools and systems. ISO 14000 deals with a
company's system for managing its day-to-day operations
and how they impact the environment.
1. The Environmental Management System and
Environmental Auditing address a wide range of issues
to include the following:
2. Top management commitment to continuous
improvement, compliance, and pollution prevention.
3. Creating and implementing environmental policies,
including setting and meeting appropriate targets.
4. Integrating environmental considerations in operating
procedures.

5. Training employees in regard to their environmental
obligations.
6. Conducting audits of the environmental management
system.

air and noise pollution environmental protection and control

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