UNIT-III
1. Air Pollution Control: Industrial Air Pollution Controlling Devices,
Gravity Settling Chamber, Cyclone & Fabric Filter, Wet Scrubber &
Electrostatic Precipitator.
2. Gaseous Air Pollution Controlling Devices: Absorption, Adsorption &
Oxidation.
3. Automobile Exhaust.
4. Noise Pollution, Its Effects & Control.
Specific Learning Objectives of Unit-III: -
1) To understand various ways to control air pollution.
2) To understand industrial air pollution controlling technology.
3) To understand noise pollution and its control.
4) To understand automobile exhaust.
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Air Pollution Controlling Technology:-
Air pollutants pose a great danger to the environment.
A removal of air pollutants from flue gases by a proper technology has a greater
significance.
There are 3 broad approaches to the control of air pollutants:-
1) Control at source.
2) Control by using pollution control equipments.
3) Dilution in the atmosphere.
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1) Control at source:-
Most effective is to prevent emission at the source itself.
This can be achieved by investing various approaches at early stages of process
design and development,
Selecting those methods which do not contribute to air pollution or have the
minimum air pollution potential.
Control at source can be accomplished by:
a) Raw Material change
b) Process Change
c) Equipment Modification or Replacement
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a) Raw Material Change:-
Some raw materials are primarily responsible for causing air pollution.
Use of pure grade raw material is often beneficial and may reduce the formation of
undesirable impurities and by-products or may even eliminate the trouble some
effluents.
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b) Process Changes:-
Changing the process being used is still another important method of controlling
emission at their source.
Ex. Washing the coal before pulverization to reduce the fly ash emission.
Ex. Reduction of the formation of NOx in combustion chambers by low excess air
combustion in two stages, fuel gas recirculation and water injection.
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c) Equipment Modification or Replacement:-
Another approach of control of pollutants at the source involves the proper use of
existing equipments, modification and replacement of equipments.
Ex. The un-burnt CO & HC in the cylinders of an automobile engine can be burnt
by injecting into hot exhaust manifold of the engine.
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3) Dilution:-
Dilution of PM & gases can be accomplished by the use of tall stacks.
Pollution released from taller stacks disperse easily & hence low ground level
concentration are observed.
Thus, dilution is only a short term control measure & tends to bring about highly
undesirable long range effects.
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3) Control by using Pollution Control Equipments:-
1. Particulates Air Pollution Controlling Devices
2. Gaseous Air Pollution Controlling Devices
To remove the particulates from flue gases, various types of control equipments are
available.
Controlling devices are divided into five major groups:
1) Gravity Settling Chamber,
2) Cyclone,
3) Fabric Filter,
4) Wet Scrubber &
5) Electrostatic Precipitator.
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Selection of Equipments depends on:-
1) Quantity of gas & its variation.
2) Nature & concentration of particulates.
3) Temp. & pressure of the gas stream.
4) Quality of the treated effluent.
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Objectives of Air Pollution Controlling Equipment:-
1) Prevention of physical damage to property.
2) Elimination of health hazards.
3) Recovery of valuable waste product.
4) Improvement of product quality.
5) Prevention of nuisance.
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Gravitational settling Chamber:-
1) The force of gravity removes only large PM by allowing them to settle in the
chamber.
2) Gas stream enters a chamber where the velocity of gas is reduced to drop out the
large particles from the gas stream.
3) Settled large size PM are collected in hopper at the bottom.
4) Used in conjunction with a more efficient control devices because this chamber
removes only larger particles.
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Gravitational settling Chamber:-
1) Constructed as long horizontal box with inlet, outlet & dust collection hoppers.
2) Velocity of the particle laden gas stream is reduced in the chamber.
3) All the particles are subjected to the force of gravity.
4) At reduced gas velocity in the chambers, the larger particles > 40u are settled into
hoppers.
5) It mainly used as a pre-cleaner for other particle emission control devices to remove
very large particles.
> 100um --- 25cm/s
10um --- 0.3cm/s
1 um --- 0.003 cm/s
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Cyclones:-
1) Simple mechanical device.
2) Used to remove relatively large particles from gas streams
3) Used as pre-cleaner for more sophisticated air pollution control equipment. (ESP)
4) More efficient than settling chamber.
5) Forces are responsible for removal are centrifugal & gravitational.
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Cyclones:-
1) Shape of cyclones causes the gas stream to rotate in a spiral motion.
2) Larger particles move towards the outside of the wall by virtue of their momentum.
3) Particles loss kinetic energy there & are separated from the gas stream.
4) After this because of gravitational force it falls down to get collected.
5) > 25um
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Wet Collectors :- (Wet Scrubber)
1) In wet scrubbing processes, liquid or solid particles are removed from a gas stream
by transferring them to a liquid.
2) The liquid most commonly used as water.
3) PM collection efficiency over 95%.
4) Requires low energy.
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Wet Collectors :- (Wet Scrubber)
1) Consist of a open vessel with one or more sets of spray nozzles to distribute the
scrubbing liquid.
2) Gas stream enters at the bottom & passes upward through the sprays.
3) The most common high energy wet scrubber is the venturi scrubber.
4) Rain is the natural process of cleaning atmosphere or environment.
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Fabric Filter:- (Bag Filter or Baghouses)
1) It uses a filter material such as nylon or wool to removes particles from the dust laden
gases.
2) The particles retained on the fabric material, while clean gas passes through the
material.
3) Collected particles are then removed from the fabric filter by a cleaning mechanism
which is either the mechanical shaking or by use of air blast.
4) Removed particles are the stored in a collection hopper.
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Fabric Filter:- (Bag Filter or Baghouses)
1) Cyclones have lower collection efficiency than fabric filter.
2) Depending upon the design & choice of fabric, PM control efficiency can be more than
99%.
3) Fabric filter are better able to reduce fine PM when they are not overloaded with larger
PM.
4) Therefore best application of a bag filter includes a cyclone in a sequence.
5) Cyclone is good at removing larger particles, it complements the fabric filter well.
6) > 0.1um
7) Wet filter is better filter.
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Electro Static Precipitators :- (ESP)
1) Widely used in power plant.
2) PM is removed by the use of +vely charged & -vely charged electrodes.
(Electromagnetic field).
3) ESP have no moving parts.
4) Requires electricity.
5) Extremely effective in removing sub micron PM.
6) Expensive.
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Electro Static Precipitators :- (ESP)
1) At periodic intervals, the PM from charged plates are removed by rappers or
hammers or vibrators depending on the design & collected into the bottom hopper.
2) Collection efficiency more than 98% for PM10.
3) ESP can handle hot flue gases at temp. up to 5700C.
4) Compare to fabric filter ESP uses less energy & lower maintenance requirements.
5) Better separation efficiency.
6) > 0.1 um
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Control of Gaseous Pollutants :-
The control of gaseous pollutants from stack gases depends on their properties.
The methods of control include:
1) Combustion
2) Absorption
3) Adsorption
4) Condensation.
5) Bio-filter.
6) Advanced Oxidation by UV, O3, HPO,etc.
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Combustion :-
Organic compounds from different manufacturing operations are converted to
innocuous carbon dioxide & water.
Devices are designed to push oxidation reactions to leave minimum unburned
compounds.
Three methods of combustion commonly used in air pollution control are:-
1) Direct combustion
2) Thermal Combustion
3) Catalytic Combustion
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Direct Combustion :-
1) Gaseous air pollutants are burned directly in a combustor with or without aid of
additional fuel such as natural gas.
2) Combustion process should be designed in such a way that the flame burns at any wind
speed & any gas flow rate.
3) Mostly used in refineries & petrochemical plants.
4) Relatively safe method of highly combustible waste gases.
5) Economical only if the waste gases itself contribute more than 50% of total heating
value required for incineration.
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Thermal Combustion :-
1) When conc. Of combustible pollutants is below the lower explosive limit, thermal
incinerator is one of the choice for combustion.
2) This method is often used when the heating value of the waste gas in the range of 50-
750 KJ/m3.
3) Waste gas stream is preheated in a heat exchanger & then passed through the
combustion zone of a burner supplied with supplemental fuel.
4) Properly designed & operated incinerator can completely destroy the organic vapor
from the exist gases.
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Catalytic Combustion :-
Accelerates the rate of a chemical reaction
Waste gas stream need not to be heated to high temp. as in thermal incineration.
Catalytic oxidation proceed through:-
1) Adsorption of the gas on the active surface
2) Chemical reaction of combustible with oxygen
3) Desorption of reaction product from the surface
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Absorption :-
Effluent gases are passed through absorber (scrubber) which contain liquid
absorbents that remove one or more of the air pollutants.
Absorbent are being used to remove SO2, H2S, SO3, F & NOx.
Some of the absorbents are regenerative while other are of non-regenerative.
Some of the absorbing solution that are used in the removing different gaseous
pollutants from gas stream are:-
SO2 – Ammonia Sulphate, Alkaline Water, Calcium Sulphate
NOx -- Water, Nitric Acid
H2S -- NaOH & Phenol Mix
HF – Water & NaOH
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Absorption :-
Efficiency of process depends upon:-
1) Amount of surface contact between gas & liquid.
2) Contact time
3) Conc. Of the absorbing medium
4) Speed of reaction between absorbent & gases
Major Equipments:-
1) Packed Bed
2) Plate Tower
3) Bubble Cap Tower
4) Spray Tower
5) Liquid Jet Scrubber
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Adsorption :-
1) Effluent gases are passed through adsorbent which contain solids of porous structure
2) Commonly used adsorbent include Activated Carbon, Silica Gel, Activated Alumina,
Lithium Chloride, etc.
3) Adsorption is a surface phenomenon and requires very large solid surface area.
4) Adsorption equipment is generally the packed bed of some porous adsorbing material.
5) Efficiency of removal of gases depends on:-
Physical & chemical characteristics of the adsorbent.
The conc. & nature of the gas to be adsorbed.
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Adsorption :-
The commonly used adsorbent for removal of gases are:
1) SO2 --- Limestone
2) NOx --- Silica Gel
3) VOCs ---- Activated Carbon
4) H2S --- Iron Oxide
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Condensation :-
Process of converting a gas to liquid.
Any gas can be reduced to a liquid by lowering its temp. and/or increasing its
pressure.
Used as pretreatment device ahead of absorption, adsorption & combustion.
Condenser are of two types contact condenser & surface condenser.
1) Contact Condenser:- contact with cold liquid
2) Surface Condenser :- contact with cooled surface
Removal efficiency ranges from 50 to 95 % depending upon design & application.
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Bio-filter :- ( Biological Oxidation)
Used to destroy VOCs & odor by microbial oxidation of these problem compounds.
Most effective on water soluble material.
Polluted air passed is passed through a wetted bed, which support a biomass of
bacteria that adsorb & metabolize pollutants.
Efficiency over 98% are possible.
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Sound
Sound produced by continuous and regular vibrations.
Sound is produced by altering pressure changes in the air, caused by various reason.
Sound is vibrations that travel through the air or another medium and can be heard
when they reach a person's or animal's ear.
Sound
In physics, sound is a vibration that propagates as a typically audible
mechanical wave of pressure and displacement, through a medium such as air or
water.
Sound waves propagate in the form of sinusoidal path as shown in figure
1) The amplitude of the sound wave is measure in the units of pressure such as N/m2
2) Pressure waves which our ears detect and thus classified as audible sound, Range from
0.00002 N/m2 to 20 N/m2.
3) Sound becomes louder as pressure increases.
4) The pressure at which the sound first becomes audible is known as threshold of hearing
or beginning of feeling of sound.
5) Threshold of hearing for normal healthy ear is about 0.00002 N/m2 ie 20 uPa ie 0dB
6) Sound is measured in units called decibels (dB)
7) Decibel unit is approximately the smallest change of sound intensity which the human
ear is able to appreciate.
Sound Pressure Level (SPL) is ratio of two pressure.
SPL = 20 Log10 ( P / Pref)
Where, SPL = Sound Pressure level in dB
P = Pressure of sound in N/m2
Pref = Reference Pressure in N/m2= 0.00002N/m2
Threshold of hearing is usually taken as the standard reference pressure.
Que 1: If sound pressure is 0.02 Pa, what is the sound pressure level or sound in
dB?
SPL = 20 Log10 ( P / Pref)
Where, SPL = Sound Pressure level in dB
P = Pressure of sound in N/m2 = 0.02N/m2
Pref = Reference Pressure in N/m2= 0.00002N/m2
Que 1: If sound pressure is 0.02 Pa, what is the sound pressure level or sound in
dB?
SPL = 20 Log10 ( P / Pref)
Where, SPL = Sound Pressure level in dB
P = Pressure of sound in N/m2 = 0.02N/m2
Pref = Reference Pressure in N/m2= 0.00002N/m2
SPL = 20 Log10 ( P / Pref)
SPL = 20 Log10 ( 0.02 / 0.00002)
SPL = 60 dB
NOISE POLLUTION?
Unpleasant & unwanted sound which disrupts one’s quality of life is called as noise.
When there is lot of noise in the environment, it is termed as noise pollution.
Any sound may be noise if circumstances cause it to be disturbing
Noise as pollutant becomes a nuisance and affects the health of a person, his activities
and mental activity.
Sound pressure for known sounds
Approximate Speed of Sound in Common Materials
Medium
Sound Velocity
(ft/s)
Sound Velocity
m/s
Air, dry (0°C and 760 mm Hg) 1,100 330
Wood (soft - along the fibre) 11,100 3,400
Water (15°C) 4,700 1,400
Concrete 10,200 3,100
Steel 16,000 5,000
Lead 3,700 1,200
Glass 18,500 5,500
Hydrogen (0°C and 760 mm Hg) 4,100 1,26
Adding noise sources and subtracting background noise
10 log 2 = 3 dB
Types of Noise:-
Depending upon the duration noise can also be grouped in the following three types:-
1) Continuous Noise:-
Uninterrupted sound level that varies less than 5dB during the entire period of observation.
Ex. Running fan.
2) Intermittent Noise:-
Continues for more than one second and is then interrupted for more than one second.
Ex. Drilling machines used by dentist.
3) Impulse Noise:-
Change of sound pressure of at-least 40dB within 0.5 seconds.
Ex. Noise produced from firing of a weapon.
Noise Level in dB Effects
0 Threshold of hearing
120 Pain Threshold
190 Permanent damage if prolonged exposure
Effects of Noise Pollution on Human Health:-
1) Noise pollution adversely affects the health of millions of people.
2) Noise pollution can damage physiological and psychological (health).
3) High blood pressure.
4) Stress related illness.
5) Sleep disruption.
6) Hearing loss.
7) Productivity loss.
8) It can also cause memory loss, severe depression, and panic attacks.
9) Cause headach.
Effects of Noise Pollution on Human Health:-
10) Loss of concentration.
11) Influence on blood pressure.
12) Cause depression & emotional disturbance.
13) Can damage to heart, brain, kidney & lever.
14) Irritation, dis-satisfaction, disinterest & affects work performance.
15) Long exposure may increase threshold of hearing.
16) Prolonged exposure to the noise may result temporary deafness or nervous
breakdown.
17) Various body system can affect by noise are auditory, circulatory & nervous system.
Sources of Noise
I. Indoor Sources of Noise:-
Moving people, crying babies, radios, banging of door, etc.
II. Outdoor Sources od Noise:- Automobile traffic, railways, aeroplanes, loudspekers, machines in factory, etc.
1) Industrial Sources of Noise:- Various operation in industries.
2) Non-Industrial Sources of Noise:- Loudspeakers, automobiles, Aircraft, trains, radios, etc.
Sources of Noise Pollution
1. Transportation systems are the main source of noise pollution in urban areas.
2. Construction of buildings, highways, and streets cause a lot of noise, due to the
usage of air compressors, bulldozers, loaders, dump trucks, and pavement
breakers.
3. Industrial noise also adds to the already unfavorable state of noise pollution.
4. Loud speakers, plumbing, boilers, generators, air conditioners, fans, and vacuum
cleaners add to the existing noise pollution.
Other sources of noise pollution that need to be addressed
1. Boat noise
2. especially jet skis
3. Construction noise
4. Snow mobiles
5. Industry
Major transportation sources of noise pollution:
rail, road, and air
Control of Noise Pollution
1) Proper design, proper equipment operation & equipment maintenance can control noise.
2) Proper lubrication & better maintenance.
3) Installing noisy machines in sound proof chamber.
4) Reduce the noise by making layer of damping material like rubber beneath the machines.
5) Using silencer to control from automobiles.
6) Provide earplugs, earmuffs, noisy helmets, etc. to people working in noisy installation.
7) Noisy industrial area must be away from residential, educational & hospitals.
8) Planting green trees and shrubs along road, hospital, institutes, etc. help in reducing
noise. (10dB)
Control of Noise Pollution
9) Provide enclosure, shield and barriers so that some of the sound waves are cut off
from propagating.
10) By constructing glazed window or door with double or triple panels of glass and
filling the gaps with sound absorbing material.
11) Community development or urban management should be done with long-term
planning, along with an aim to reduce noise pollution.
12) Social awareness programs should be taken up to educate the public about the causes
and effects of noise pollution.
13) Strict legislative measures like:-
1) Minimum use of loud speakers
2) Banning pressure horns in automobiles.
3) Framing a separate noise pollution act.
Aesthetic noise barrier:
Highway in Melbourne, Australia
Roadway Noise - Solutions
Pavement type:
Certain asphalts, such as those containing rubber or stone, can be less noisy
than other pavements.
However, some studies have shown the reduction in noise is only a few
decibels, not enough to be significant.
More research is needed before pavement type can be an effective noise-
reducing technique
How Sound is Heard
Sound and human hearing:-
People generally hear sounds
between the “threshold of hearing”
and the “threshold of pain”
In terms of pressure,
this is 0.00002 N/m2 – 20 N/m2
The decibel scale was developed from this fact and makes numbers more
manageable
The decibel scale generally ranges from approximately 0 to 130
Human hearing and Frequency
0 16 Hz 20 kHz 5 MHz
UNIT-III1. Air Pollution Control: Industrial Air Pollution Controlling Devices,
Gravity Settling Chamber, Cyclone & Fabric Filter, Wet Scrubber &
Electrostatic Precipitator.
2. Gaseous Air Pollution Controlling Devices: Absorption, Adsorption &
Oxidation.
3. Automobile Exhaust.
4. Noise Pollution, Its Effects & Control.
84DTEL
AUTOMOBILE EXHAUST
Emission Sources in a Diesel Engine Powered Vehicle:-
Emission Sources Car
Introduction
1) Exhaust gas or flue gases is emitted as a result of the combustion of fuels such
as petrol, diesel or fuel oil.
2) Automobile exhaust system is responsible for transporting the burned exhaust,
or combustion gases, from its engine and out through the tail pipe.
3) An exhaust system is usually tubing used to guide reaction exhaust gases away
from a controlled combustion inside an engine .
(The entire system conveys burnt gases from the engine and includes one or more
exhaust pipes, depending on the overall system design.)
Definition:-
Exhaust system carries away the gases created when the fuel and air are
burned in the engine. These gases are harmful to humans and our life.
Oxygen sensor measure how much oxygen in the exhaust. It’s connect to computer to control the
correct mixture for fuel economy.
Automobile Emission:-
Types of Emission
1. Exhaust Emission
2. Evaporative Emission
Pollutants in Exhaust Gas:
1. Carbon monoxide(CO)
2. Oxides of Nitrogen(NOx)
3. Hydro Carbons(HC)
4. Smoke
5. Lead
6. Sulphuric Oxide
7. PM
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AUTOMOBILE EXHAUST
• 20 % Crankcase vapors
• 20% Fuel Vaporization
• 60% Exhaust
Air Pollutants from Automobile Exhaust:
1) CO (carbon monoxide): The main source of CO in cities is the internal
combustion engine, where it is produced by incomplete combustion.
2) NOx (nitrogen oxide): It forms when fuels are burned at high temperatures.
3) HC (hydrocarbons): Much of the hydrocarbon fuel passes through the process
unconsumed and is expelled into the atmosphere along with other exhaust
fumes.
4) Other pollutants such as C6H6 - Benzene and its derivatives and SO2 are also
emitted.
5) CO2 (carbon dioxide): The internal combustion engine contributes to the
increased concentrations of CO2 in the atmosphere.
Components of Automobile Exhaust System
The exhaust system may essentially consist of the following components:
Exhaust Manifold
Exhaust Pipes
Catalytic Converter
Muffler
The Tail Pipe
Automobile Exhaust System & Its Components:-
(Sound waves cancel each other)
Importance of Exhaust System
The exhaust system has three major functions:
1) To channel out the waste products of combustion out of the engine.
2) To reduce the noise generated by the engine.
3) To clean up the emissions that are harmful to the environment.
4) To reduce the pollution and to increase the efficiency of the engine.
Exhaust Manifold
An Exhaust Manifold is the upper end of the exhaust system.
It is attached directly to the side of the engine and
is the first part of the exhaust system to receive the burned
exhaust gases from the car's engine.
It takes all cylinders exhaust to one pipe. Made from steel, stainless steel or aluminum.
The exhaust manifold burns any fuel that was inadequately burned by the engine and
funnels it down into the main exhaust system.
Due to high temperatures, Excellent oxidation resistance, High-temperature strength,
Thermal fatigue properties are required.
Exhaust Pipes
The exhaust pipes are responsible for transporting the burned exhaust
gases from the engine though the exhaust manifold towards the car's
tailpipe.
It can be made up of metal (steel or stainless steel) or aluminum.
The pipes are used to create an effectively sealed pathway.
TYPES OF PIPES
There are basically two types:
■ Regular pipe
■ Flexible pipe
Regular exhaust pipe is solid, typically available in straightlengths, bent configurations and elbows.
Flexible exhaust pipe is flexible enough to bend with roadconditions and accommodate thermal expansion of the system.
The exhaust system may be sealed by welding joints or usingexhaust clamps as a simple, effective way to seal overlappingpipes.
Catalytic Converter
A device that uses a catalyst to convert
three harmful compounds in car
exhaust into harmless compounds.
1) Hydrocarbons - in the form of
unburned gasoline.
2) Carbon monoxide -formed by the
partly combustion of fuel.
3) Nitrogen oxides - created when the
heat in the engine forces nitrogen in
the air to combine with oxygen.
Different Catalysts
There are two different types of catalyst:
• Reduction Catalyst – (first stage)
It uses platinum and rhodium to help
reduce the NOx emissions.
Example:
2NO => N2 + O2 or 2NO2 => N2 + 2O2
• Oxidation Catalyst – (second stage)
It uses platinum and palladium to help
reduce the unburned hydrocarbons
and carbon monoxide by burning
(oxidizing) them.
Example: 2CO + O2 => 2CO2
Catalytic Converters
HC and COCO2 H2o
Catalytic Converter
Engine
Exhaust Flow from engine
through converter
Catalytic Converters
• This is a honey-comb block type catalytic converter.
• Exhaust gasses flow thru the honey-comb block
Muffler
A muffler or silencer is a device for reducing the amount of noise emitted
by the exhaust of an internal combustion engine.
The main muffler absorbs the noise of the exhaust gas and is composed of
an outer shell, inner plates, inner pipes, end plates and other components.
It contains a deceptively simple set of tubes that are finely tuned to reflect
the sound waves produced by an engine so that they cancel each other out.
Muffler
Vector Muffler - for larger diesel trucks, uses many concentric cones.
Spiral Baffle Muffler - for regular cars, uses a spiral-shaped baffle syste
TAIL PIPE
The tail pipe is end of the final length of exhaust pipe which ends with just a
straight or angled cut where it vents to open air.
Hydrocarbons:-
Hydrocarbons are produced because of incomplete fuel combustion or fuel evaporation.
High hydrocarbon emission are the results of a:
cylinder misfire.
Improper ignition timing
Worn cylinder rings (pumping oil into the combustion chamber
Hydrocarbons emission is considered a hazardous form of air pollution because of.
Eye.
Throat.
Lung irritation.
And possibility cancer.
Carbon Monoxide:-
Carbon monoxide emission are exhaust emission that is the result of partially
burned fuel.
A high carbon monoxide emission can be caused by a:
– Restricted or dirty air cleaner.
– Advance ignition timing.
– Clogged fuel injectors.
NOx :-
• Oxides of nitrogen, (NOx) are emission produced by extreme heat.
• Air consist of approximately 79% nitrogen and 21% oxygen
• When combustion chamber temperature reaches 2500 degrees F or 1370
degrees C, nitrogen and oxygen combine to produce oxide of nitrogen
(NOx)
Oxides of nitrogen is responsible for the dirty brown color is SMOKE.
NOx can cause eye & respiratory irritation.
Newer high compression, not proper air fuel mixture and hotter running
engine produces more NOx than earlier engine.
The same factors that increases NOx will tend to improve fuel mileage and
lower HC and CO2 production.
Fuel
Air
Exhaust
manifold
Catalytic
Converter
Fuel
Tank
Fuel
Pump
HC
CO
Solid particulate
FuelFuel
Vapors
Particulates:-
• A high concentration of particulate matter (PM) is manifested as visible
smoke in the exhaust gases.
• Solid carbon material.
• Condensed hydrocarbons and their partial oxidation products.
• Diesel particulates consist of solid carbon (soot) at exhaust gas temperatures
below 500oC.
• Burning crankcase oil will also produce smoke especially during engine warm
up where the HC condense in the exhaust gas.
Indian Automobile Industry
Largest three wheeler market in the world
2nd largest two wheeler market in the world
7th largest passenger car market in Asia & 10th Largest in the world
4th largest tractor market in the world
5th largest commercial vehicle market in the world
5th largest bus & truck market in the world
Control of Automobile Exhaust Gasses
Automotive manufactures agree the best way to lower exhaust emission is to burn all
the fuel entering the combustion chamber.
Modern engine have introduced several modification to ensure all fuel entering the
combustion chamber is burned.
Lower compression ratio, by lowering compression ratio vehicle can burn unleaded
fuel. The use of unleaded fuel allows for catalytic converters that help reduce HC
and CO emissions.
Lower compression ratio also lower combustion temperature reducing NOx
emission.
Smaller combustion chambers, allows for more heat to remain inside the combustion
chamber that can aid in the burning of fuel.
Reduce quench areas, the areas between the piston and the cylinder head is
the quench area. Modern engine are design to reduce high quench areas.
Combustion process:- advances in fuel injectors, oxygen sensors, and on-
board computers.
Optimizing the choice of operating parameters:- Two NOx control measures
that have been used in automobile engines are spark retard and EGR.
After treatment devices in the exhaust system:- catalytic converter.
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Control of Automobile Exhaust Gasses:-
Control of Automobile Exhaust:-
Reduce your driving speed: The best fuel economy for most vehicles is 60 km/h.
Reducing your speed from 100 km/h to 60 km/h improves fuel economy by 30% on
fuel consumption.
Avoid aggressive driving: Aggressive driving, rapid acceleration, or quick stops has
been shown to increase fuel use by about 39%, and saves about 4% of your time.
Avoid idling: Excessive idling pollutes. Turn off the engine whenever you can. If you
are stopped for more than ten seconds, turn it off. In the winter, the most effective way
to warm up a cold vehicle is to drive it. Idle for 30 seconds and then drive away for
optimum performance and fuel efficiency.
Reduce your number of trips: The best way to reduce fuel use and save money is
by planning activities and combining errands to reduce the number of trips.
Do you need a vehicle?: You could save yourself a lot of money and time by evaluating if
you even need a vehicle. Maybe you could take the bus? Or walk to your destinations?
What do I need the car for?: This would help you find out what kind of car you need. Do
you need a truck for work? Do you just need something small to get into town? Do you need
a van because you have a large family?
Should I buy a used car or a new car? Older cars can be less expensive, but can also be
bad for the environment and bad on fuel. New cars produce less emission and are more fuel
efficient.
Check tire pressure: 5% of under-inflation = 1% decrease in fuel efficiency. Under-
inflation of 20% will reduce the life of your tire by about 15%.
Regular tune-ups: A poorly tuned engine can consume an average of 10% more fuel.
One poorly tuned vehicle can emit pollutants equivalent to 20 properly tuned vehicles.
Clean or replace air filters and spark plugs: Clean filters and spark plugs help keep
fuel use and greenhouse gas emissions down.
Have your idle mixture and idle speed adjusted: Adjusting idle speed according to
vehicle specifications on pre-1988 vehicles can decrease greenhouse gas emissions during
idling.
Maintain braking systems: Dragging brakes can decrease fuel efficiency by up to 40%.
Minimize air conditioner use: Using air conditioning can increase fuel consumption
and greenhouse gas emissions by up to 21%.
Maintain wheel alignment: Make sure wheels are aligned and balanced, and ball joints
or constant velocity joints are lubricated.
Use overdrive and high gears: While driving, strive for the lowest engine rpm at a
given road speed by selecting the highest gear in which the vehicle will operate properly.
Operate overdrive automatic transmissions in the overdrive mode.
Have your oxygen sensor checked: Vehicles made in 1988 or after should have the
oxygen sensor checked regularly. When this sensor malfunctions, the computer could
increase the fuel ration to burn more fuel and thus increasing greenhouse gas emissions.
Replace or service the EGR valve: The exhaust gas recirculator (EGR) valve reduces a
variety of greenhouse gases.
Use a timed block heater: Improve fuel efficiency by 8 to 23% with a block heater at
below 0oC. Set timer for 2.5 hours before you leave.
Be aerodynamic: Reducing wind resistance on the highway by rolling up the windows
cuts fuel consumption.
Travel light: The heavier the vehicle, the more fuel it burns. Avoid unnecessary weight.
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Fuel Tank Vapor Recovery
• Does not allow gasoline to
evaporate from the gas tank to the
atmosphere.
• Gas tank is sealed and vapors
travel to a charcoal canister.
• The canister is purged of vapors by
the intake manifold and burned in
the engine.
Quiz
• The best way to decrease exhaust emission is to:
– A. Increase valve overlap.
– B. Increase compression Ratios.
– C. Increase combustion chamber size.
– D. Burn all fuel enter the combustion chamber.
Future:
• Hybrid cars.
• Gasoline fuel.
Questions Bank:-
1. List what are the various gaseous pollutants and in brief describe the various treatment
processes for their control.
2. Discuss the working mechanism of ESP with neat sketch.
3. What is Bag filter? Explain its working.
4. What is Cyclone? Explain its working with advantages & disadvantages.
5. What are the wet scrubbers? Explain working of any one of them?
6. Define Noise pollution? Discuss different effects of Noise pollution on health?
7. What are the types of Noise? Suggest control measures to reduce Noise pollution?
8. What are the levels of Noise pollution from different sources.
9. State and explain various types of Automobile emission.
10. Enlist and discuss the Automobile exhaust pollutants from diesel & petrol engines. How
reduction can be carried out.
11. Write a short note on :
a) Noise pollution & its control b) Control of Automobile emission.
.