poiiution formation and control

A SEMINAR REPORT
Submitted by
Haidar majeed hachim
In partial fulfillment for the award of the degree
Of
MASTER OF POWER PLANT
IN
MECHANICAL ENGINEERING
PRO. Dr NAFIZ KAHRMAN


 The rise in civilization is closely related to the
improvement is transportation. In the development of
transportation, internal combustion engine play an
important role of petrol and diesel engine. This problem
is increasing day by day with increasing pollution So our
aim is to find out the air pollutant from petrol as well as
diesel engine and control those. - Undesirable emissions
in internal combustion engines are of major concern
because of their negative impact on air quality, human
health, and global warming. Therefore, there is a
concerted effort by most governments to control them.
Undesirable emissions include unburned hydrocarbons
(HC), carbon monoxide (CO), nitrogen oxides (NOx), and
particulate matter (PM
ABSTRACT


 The life of a human being is precious. Certainly, to
live a comfortable life you need to have good
surrounding. At least all the basic needs like air,
water, food. -the emissions are very harmful to
human beings and all these emissions should be
controlled
INTRODUCTION


 Air pollution: is defined as the addition of any material
which have a dangerous effect of our plant to our
atmosphere
 Emissions”: is a collective term that is used to describe the
undesired gases and particles which are released into the
air or emitted by various sources
 Criteria Pollutants: The U.S. Environmental Protection
Agency (EPA) is primarily concerned with emissions that
are or can be harmful to the public at large. EPA considers
carbon monoxide (CO), lead (Pb), nitrogen dioxide (NO2),
ozone (O3), particulate matter (PM), and sulphur dioxide
(SO2) as the pollutants of primary concern,.


Point sources, which include facilities such as
factories and electric power plants.
- Mobile sources, which include cars and trucks
but also lawn mowers, airplanes, and anything
else that moves and releases pollutants into the
air .
Biogenic sources, which include trees and
vegetation, gas seeps, and microbial activity.
- Area sources, which consist of smaller
stationary sources such as dry cleaners and
degreasing operations
Types of pollutions source


typical emissions contain primary greenhouse
gases Like(carbon Monoxides(CO2)),(methan
(CH4)),(nitrous oxides(NO2))
 - criteria pollutants like(carbon
monoxide(CO)),(total nitrogen
oxides(NOX)),(sulpher dioxide(SO2)),(non
methane volatile organic
compounds(NMVOC),(particulate
matter(PM)),(lead(Pb)
Pollution gases :divide in
to


 Fuel is burned in the internal combustion engine and
the air/gasoline residuals are emitted through the
tailpipe
 Heat causes fuel to evaporate throughout the fuel
system. Hot, sunny days and engines warmed by
running provide heat to vaporize fuel into the air
 Refueling at the service station where gasoline
vapors escape into the air
Pollutants are released
when…..


 carbon monoxide(CO)
 carbon dioxide (CO2)
 nitrogen oxides (NOX)
 hydrocarbons (HC)
 particulate matter (PM)
Some kind of air pollution
gases


 The pollutants in vehicle emissions are known to damage lung
tissue
 Motor vehicle pollution also contributes to the formation of acid
rain and adds to the greenhouse gases that cause climate
change
 On warm, sunny days, hydrocarbons react with oxides of
nitrogen to create a secondary pollutant, ozone. In many urban
areas, motor vehicles are the single largest contributor to
ground-level ozone which is a common component of smog.
Ozone causes coughing, wheezing and shortness of breath
 carbon monoxides (CO)reduce the flow of oxygen in the blood
stream and is particularly dangerous to person with heart
disease
Effect of pollution


 engine design modification
 cleaner fuel : ( methanol, ethanol, bio-diesel and
CNG (Compressed natural Gas)
 - post combustion control devise
 -inspection and maintenance devices
 - Zero-emission vehicles include battery-electric
vehicles, plug-in hybrid-electric vehicles, and
hydrogen fuel-cell-electric vehicles
Solutions


 - reduce pollution from our vehicles by driving less,
improving our driving habits, keeping our vehicles
in good running order
 Make sure tires are properly inflated
 Make sure the gasoline cap fits properly
 Drive at steady, moderate speeds
 Increase the green land
Solutions


 Non Dispersive Infrared Analysed (NDIR): detectors
are the industry standard method of measuring the
concentration of carbon oxides (CO & CO2)
 Absorption bands of common gases: The flame
ionisation detector (FID) is the industry standard
method of measuring hydrocarbon (HC)
concentration
 Chemi-luminescence detector (CLD): It is the
industry standard method of measuring nitric oxide
(NO) concentration
Measurement techniques
used to measure pollutants


 To reduce atmospheric pollution, two different
approaches are followed:
 1-To reduce the formation of pollutants in the
emission by redesigning the engine system, fuel
system, cooling system and ignition system
 2-By destroying the pollutants after these have been
formed
Control of Emission In Ic
Engine


 HYDROCARBONS(HC): Hydrocarbon emissions result
when fuel molecules in the engine do not burn or burn
only partially(tail pipe emission)
 NITROGEN OXIDES (NOx): Under the high pressure and
temperature conditions in an engine, nitrogen and oxygen
atoms in the air react to form various nitrogen oxides,
collectively known as NOx.
 CARBON MONOXIDE(CO): Carbon monoxide (CO) is a
product of incomplete combustion and occurs when
carbon in the fuel is partially oxidized rather than fully
oxidized to carbon dioxide
Pollutants formation


 CARBON DIOXIDE(CO2): Carbon dioxide does not
directly impair human health, but it is a “greenhouse
gas” that traps the earth’s heat and contributes to the
potential for global warming
 Evaporative Emissions(HC)(not tail pipe emissions):
Hydrocarbon pollutants also escape into the air
through fuel evaporation and evaporative losses can
account for a majority of the total hydrocarbon
pollution
Pollutants formation


 a- DIURNAL: Gasoline evaporation increases as the
temperature rises during the day, heating the fuel tank
and venting gasoline vapors
 B- RUNNING LOSSES: The hot engine and exhaust
system can vaporize gasoline when the car is running
 C-HOT SOAK: The engine remains hot for a period of
time after the car is turned off, and gasoline evaporation
continues when the car is parked
 D-REFUELING: Gasoline vapours are always present in
fuel tanks. These vapours are forced out when the tank is
filled with liquid fuel
Evaporative emissions
occur several ways:


 S.I. engine emissions are divided into three
categories:
 1- exhaust emission
 2- evaporative emission .
 3- crank case emission
 The major constituents which contribute to air
pollution are CO, NOx, and HC
Si engine emissions


 The relative amounts depend on engine design and
operating conditions but are of order:
 1- NOx -> 500-1000 ppm (20 gm/kg of fuel )
 2- CO -> 122% (200gm/kg of fuel)
 3- HC -> 43000 ppm (25 gm/kg of fuel)
 Fuel evaporation from fuel tank and carburettor
exists even after engine shut down and these are
unburned hydrocarbons.
Si engine emissions


 most important variables in determining S.I.
emission is the fuel air equivalence ratio
 Exhaust gas recirculation (EGR). Method is used
with stoichiometric mixtures in many engines to
reduce emissions but in the same time deteriorates
combustion quality
Si engine emissions


 Emissions formed as a result of burning the
heterogeneous air/fuel mixture depend on:
 1- the prevailing conditions not only during combustion,
but also during the expansion and especially prior(befor)
to the exhaust valve opening
 2- Mixture preparation during the ignition delay
 3- fuel ignition quality
 4- residence time at different combustion temperatures
 5- expansion duration
 6- general engine design features
CI engine emissions


 -Incomplete combustion products formed in the early
stages of combustion may be oxidized later during the
expansion stroke
 Mixing of unburned hydrocarbons with oxidizing gases,
high combustion chamber temperature, and adequate
residence time for the oxidation process permit more
complete combustion
 In most cases, once nitric oxide (NO) is formed it is not
decomposed, but may increase in concentration during
the rest of the combustion process if the temperature
remains high
CI engine emissions


 1-Crankcase Emission Control (PCV System): A small amount
of charge in the cylinder leaks past piston rings into crankcase
of the reciprocating engines. A significant part of charge stored
in the piston- ring-cylinder crevice leaks into the crankcase.
These gases are known as ‘crankcase blow by’
 . in the uncontrolled engines The crankcase blow by gases
ventilated to atmosphere under the effect of pressure difference
occurring naturally between the crankcase and atmosphere
 . In control of crankcase emissions, the blow by gases are
recycled back to the engine assisted by a positive pressure drop
between the crankcase and intake manifold
 When engine is running and intake charge is throttled the
intake manifold is at a lower pressure than the crankcase. The
blow-by gases mix with the intake charge
Control of emission from
SI engines:


SI engines:


 -about 20% of HC emitted by uncontrolled car from
this source
 -in (PVC) one way valve is used to control the flow
of blow by gases
SI engines:


 2-Evaporative Emission Control(HC)
 -this source emitted about 20% of HC
 -this system is a fully closed system
 This system consists of a device to store fuel vapours
produced in the fuel A canister containing activated
charcoal is used to store the fuel vapours. The vapours
produced in the fuel tank normally collect in the fuel tank
itself and are vented to the charcoal canister when fuel
vapour pressure becomes excessive The fuel vapours
from the tank and carburettor led to and adsorbed into
the charcoal When engine is running-----
SI engines:


 -----the vacuum created in the intake manifold is
used to draw fuel vapours from the canister into the
engine. Purging air is sucked through the canister
which leads the fuel vapours from canister to the
engine
 -Employment of refuelling vapour recovery (ORVR)
system to prevent evaporation fuel escape during the
refueling
 -A sealed fuel tank filler cap is used and a stable fuel
tank pressure is maintained by the purging process
of the canister
SI engines:


 sealed fuel tank is kept under vacuum to prevent
permeation of fuel through walls of a polymer fuel
tank and leakage of fuel vapours through filler cap.
Fuel tubing made of high density polymer or steel to
reduce/prevent fuel permeation
SI engines:


 3-Exhaust Gas Recirculation: The heat capacity of the
exhaust gas is higher than the air as it contains significant
amount of tri-atomic gases CO2 and water vapours.
Therefore, addition of exhaust gas to fresh intake charge
has a higher effect in lowering the combustion
temperatures
 EGR is defined as a mass per cent of total intake flow-
 EGR=[ṁEGR /ṁi](100) Where “i” is the total mass flow
into engine
 EGR systems are made to operate mostly in the part-load
range-
SI engines:


 Typically, only about 5 to 10 % EGR rates are
employed
 At higher EGR rates, frequency of partial and
complete misfire cycles increases resulting in
unacceptably higher HC emissions and loss in fuel
economy and power
 An EGR control valve is used to regulate flow of
EGR depending upon engine operating conditions.
The intake manifold pressure or exhaust back
pressure may be used to control EGR rate as these
parameters vary with engine load
SI engines:


 EGR is deactivated at engine idle, because large
amount of residual gas is already present in the
cylinder
 - EGR rate is controlled by the engine electronic
control unit. A pressure sensor in the exhaust or
intake provides signal to the electronic control
SI engines:


 4- Water Injection
 -Water addition to intake charge is another form of charge
dilution to reduce combustion temperatures and that led
to reduce NOX
 -Water has been directly injected into intake manifold or
used as water-fuel emulsion. Emulsifying chemicals in
about 2 per cent by volume are added to form water-
gasoline emulsions
 -With water addition ranging from 10 to 30% by volume
of gasoline, large reductions in NOx are possible
However; high increase in HC is observed although only
a slight increase in CO occurs
SI engines:


 -small amount of water improve the (BSFC)brake
specific fuel consumption
 -large amount of water→increase the
(BSFC)→reducing the NOX→ Increase HC→increase
CO→corrosion of engine components
SI engines:


 Hydrocarbons, carbon monoxide and oxides of nitrogen
are created during the combustion process and are
emitted into the atmosphere from the tail pipe
 An oxygen sensor was installed in the exhaust system and
would measure the fuel content of the exhaust stream. It
then would send a signal to a microprocessor, which
would analyse the reading and operate a fuel mixture or
air mixture device to create the proper air/fuel ratio
 PM emissions from stationary diesel engines are more of
a concern
diesel engine:


 Several emission control technologies exist for diesel
engine:
 1- PM control
 2- Oxidation or lean- NOx catalyst→reduce diesel
emissions and PM
 3- diesel particulate filter systems →reduce PM and
diesel emissions
 4- special ceramic coatings applied to the combustion
zone surfaces of the piston crown, valve faces, and
head→reduce PM and NOX
diesel engine


 -ceramic coatings can be used by themselves or combined
with an oxidation catalyst to give even greater reduction
of PM
 - Ceramic engine coatings change the combustion
characteristics such that less dry, carbon soot, is produced
 - ceramic coatings+ oxidation catalyst ceramic coatings
allow retarding of the engine to reduce NOx, while CO
and particulates are maintained at low levels
 The selection of an emission control technology for
gaseous emissions depends not only on the targeted
pollutants but also the engine type and operating mode,
i.e. speed and load
diesel engine


 1-Catalyst Control Technologies :The principle behind a
catalyst for control of the gaseous emissions of a
stationary IC engine is that the catalyst causes chemical
reactions without being changed or consumed
 a-Non selective Catalytic Reduction (NSCR) and Three-
way Catalysts :
 NSCR has been used to control NOx emissions from rich-
burn engines
 The systems have demonstrated the ability to achieve
greater than 98 percent reduction
Gaseous Emission Control
of Stationary IC Engines:


 . Over 3000 rich burn IC engines have been equipped
with NSCR technology .Engines in excess of 250 hp
have been equipped with NSCR.
 In the presence of CO and NMHC in the engine
exhaust, the catalyst converts NOx to nitrogen and
oxygen, NSCR reduces NOx, CO, and NMHC
emissions
 if an engine is operated stoichiometrically. NSCR
used in this manner is defined as a three-way
conversion catalyst


 In order for conversion efficiencies to remain high.
 -the air to fuel ratio must remain within a fairly
narrow window of the stoichiometric point (ë=1)
 -NOx conversion efficiency drops dramatically when
the engine is run in the lean regime, while NMHC
and CO conversion efficiency also declines
somewhat


 b-Selective Catalytic Reduction (SCR):SCR is a method of
controlling NOx emissions from lean-burn stationary IC
engines. Lean-burn engines are characterized by an
oxygen-rich exhaust, thereby making the reduction of
Nox
 . first introducing a reducing agent such as ammonia,
urea, or others makes the necessary chemical reactions
possible. The reactions that occur over the catalyst bed
using ammonia can reduce by greater than 90%.This
approach is called selective catalytic reduction (SCR)
because with the reducing agent present, the catalyst
selectively targets NOx reduction alone


 The amount of reagent injected is calibrated by measuring the
NOx concentration. or by its predicted concentration knowing
the engine's operating parameters
 -Both precious metal and base metal catalysts have been used in
SCR systems. Base metal catalysts, typically vanadium and
titanium, areused for exhaust gas temperatures between 450EF
and 800EF. For higher temperatures (675EF to 1100EF), zeolite
catalysts may be used. Both the base metal and zeolite catalysts
are sulphur tolerant for diesel engine exhaust. Precious metal
SCR catalysts are useful for low temperatures (350EF to 550EF).
When using precious metal SCR catalysts, attention should be
paid to the fuel sulphur content and the appropriate
formulation selected.




 2-Oxidation Catalysts
 Oxidation catalysts have been used on off-road mobile
source lean-burn engines. Oxidation catalysts contain
precious metals impregnated onto a high geometric
surface area carrier and are placed in the exhaust stream.
 They are very effective in controlling CO and NMHC
emissions. CO can be reduced by greater than 98 per cent
and NMHC emissions can be reduced by over 90 per cent.
They are also used to reduce particulate emissions of
diesel engines by oxidizing the soluble organic fraction of
the particulate reductions of over 30 per cent can be
achieved


 Oxidation catalysts also serve to eliminate the
characteristic odour associated with diesel exhaust
by oxidizing the aldehyde and acrogenic emissions .
 DOCs also play an important role in continually
removing soot from the DPF. This occurs by
oxidizing some of the NO to NO2 which serves to
oxidize the soot or by generating heat through the
oxidation of CO and HC to raise the DPF
temperature above the soot oxidation temperature


 3-Particulate Emission Control of Stationary IC Engines:
 -Diesel particulate emissions are composed of a variety of
compounds from fuel and lube oil combustion, as well as
engine wear and sulphate from diesel fuel sulphur
 -The majority of the particulate consists of carbon and the
soluble organic fraction (SOF) consisting of unburned fuel
and unburned lube oil
 -Both oxidation catalysts and diesel particulate filters can
be used to substantially reduce diesel PM emissions


 a-Diesel Oxidation Catalysts:
 that catalysts will reduce 90 per cent of the SOF
resulting in a 40 to 50 per cent reduction in total PM
emissions.
 the sulphur content of diesel fuel is critical to
applying catalyst technology. Catalysts used to
oxidize the SOF of the particulate can also oxidize
sulphur dioxide to form sulphates, which is counted
as part of the particulate.


 Catalyst formulations have been developed which
selectively oxidize the SOF while minimizing
oxidation of the sulphur dioxide. However, the
lower the sulphur content in the fuel, the greater the
opportunity to maximize the effectiveness of
oxidation catalyst technology


 b-Diesel Particulate Filters (DPF) or Trap Oxidizer
System:
 The trap oxidizer system consists of a filter
positioned in the exhaust stream designed to collect
a significant fraction of the particulate emissions
while allowing the exhaust gases to pass through the
system
 Since the volume of PM generated by a diesel engine
is sufficient to fill up and plug a reasonably sized
DPF over time


 . some means of disposing of this trapped particulate
must be provided. The most promising means of disposal
is to burn or oxidize the particulate in the trap, thus
regenerating, or cleansing, the DPF of collected
particulate. A complete trap oxidizer system consists of
the filter and the means to facilitate the regeneration
 filter material
 1-ceramic monoliths 2-woven silica fibre coils
 3-ceramic foam 4-mat-like ceramic fibres
 5-wire mesh 6-sintered metal substrates


-Collection efficiencies of
these filters range from 50
per cent to over 90 percent


 4-Exhaust gas recirculation(EGR) and retarding injection
timing:Both techniques will reduce NOx emissions of
diesel engines by more than 40 per cent. However, both
techniques are accompanied by secondary effects:
 a-Injection timing retard, while decreasing NOx emissions
substantially, increases the emissions of CO, NMHC, and
PM and reduces fuel economy. The increase in the other
exhaust emissions, however, can be offset with either
oxidation catalyst or diesel particulate filter technology.
Ceramic engine coatings have been found to offset the
fuel economy


 b-Employing EGR to diesel engines introduces
abrasive diesel particulate into the air intake which
could result in increased engine wear and fouling.
Using EGR after a diesel particulate filter would
supply clean EGR and effectively eliminate this
concern


 5-Closed crankcase ventilation technology
 : is being installed on a heavy duty trucks equipped with
turbocharged diesel engine to eliminate crankcase
emissions
 Crankcase emissions vented to the engine compartment
have been found to enter cabin air and can be a significant
source of driver and passenger PM exposure
 These systems capture particulate generated in the
crankcase and return them to the lubricating system of the
engine.

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