poiiution formation and control

control Pollutant formation andA SEMINAR REPORT

Submitted byHaidar majeed hachim

In partial fulfillment for the award of the degreeOf

MASTER OF POWER PLANTIN

MECHANICAL ENGINEERINGPRO. 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

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

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:

-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


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-----


-----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


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


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-


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


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


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


-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


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

Control of emission from 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

Control of emission from 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

Control of emission from 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.


Gaseous Emission Control of

Stationary IC Engines:

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.


poiiution formation and control

Engineering

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