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.

121

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.

.