Report of Rohit r Bhosale

7/29/2019 Report of Rohit r Bhosale

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POLLUTANT OF S.I ENGINE, C.I ENGINE, GAS TURBINE,

THERMAL POWER PLANT

BY:-ROHIT.R.BHOSALE


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SOURCES OF POLLUTANTS FROM SI ENGINE.

The following are the three main sources form which pollutants are emitted from the SI

engine:

The crankcase. Where piston blow-by fumes and oil mist are vented to the

atmosphere.

The fuel system. Where evaporative emissions from the carburetor or petrol

injection air intake and fuel tank are vented to the atmosphere.

The exhaust system. Where the products of incomplete combustion are expelled

from the tail pipe into the atmosphere.


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Crankcase Emission

The piston and its rings are designed to form a gas-tight seal between the sliding piston

and cylinder walls. However, in practice there will always be some compressed charge

and burnt fumes escape during compression and power stroke to crankcase. These

gases are usually unburnt air-fuel mixture hydrocarbons, or burnt (or partially burnt)

products of combustion, C02, H2O (steam) or CO. These products also contaminate the

lubricating oils.


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Evaporative Emission

Evaporative emissions account for 15 to 25% of total hydrocarbon emission from a

gasoline engine. The following are two main sources of evaporative emissions:

The fuel tank

The carburettor.

(i) Fuel tank losses. The main factors governing the tank emissions are fuel volatility

and the ambient temperature but the tank design and location can also influence the

emissions as location affects the temperature. Insulation of tank and vapour collection

systems have all been explored with a view to reduce the tank emission.

(ii) Carburettor losses. Although most internally vented carburettors have an external

vent which opens at idle throttle position, the existing pressure forces prevent outflow of

vapours to the atmosphere. Internally vented carburettor may enrich the mixture which

in turn increases exhaust emission.

EXHAUST EMISSION

The different constituents which are exhausted from S.I. engine and different factors

which will affect percentages of different constituents are discussed below:


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Hydrocarbons (HC)

The emission amount of HC (due to incomplete combustion) is closely related to

Design variables, Operating variables and engine condition. The Surface to volumeratio greatly

affects the HC emission. Higher the S/V ratio, higher the HC emission

irrespective of whether mixture is rich or lean. When the Mixture supplied is lean or rich,

the flame propagation becomes weak which causes in turn causes incomplete

combustion and results in HC emission.

Carbon Mono oxide (HC)

If the oxidation of CO to CO is not complete, CO remains in the exhaust. It can be said

theoretically that, the petrol engine exhaust can be made free from CO by operating it at

A/F ratio = 15. However, some CO is always present in the exhaust even at lean

mixture and can be as high as 1 per cent. CO emissions are lowest during acceleration

and at steady speeds. They are, however, high during idling and reach maximum during

deceleration.

Oxides of nitrogen (NO)

Oxides of nitrogen occur mainly in the form of NO and NO and are generally formed at

high temperature. The maximum NO levels are observed with A/F ratios of about 10

percent above stoichiometric. It has also been observed that NO increases withincreasing manifold pressure, engine load and compression ratio. This characteristic is

different from HC and CO emission which is nearly independent of engine load except

for idling and deceleration.

Lead emission

Lead emissions come only from S.I. engines. In the fuel, lead is present as antiknock

agents in SI Engine. It may not be possible to eliminate lead completely from all petrols

immediately because a large number of existing engines rely upon the lubricationprovided by a lead film to prevent rapid wear of exhaust valve seats.

SI ENGINE EMISSION CONTROL

The main methods, among various methods, for S.I. engine emission control are:


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Modification in the engine design and operating parameters.

Treatment of exhaust products of combustion.

Modification of the fuels.

Modification in the Engine Design and Operating Parameters

Modification of combustion chamber involves avoiding flame quenching zones

where combustion might otherwise be incomplete and resulting in high HC

emission. This includes: Reduction of surface to volume (SAT) ratio, Reduced

space around piston ring

Lower compression ratio: Lower compression ratio reduces the quenching effectby reducing

the quenching area, thus reducing HC.Lower compression ratio alsoreduces NO emissions due

to lower maximum temperature. Lower compression,however, reduces thermal efficiency and

increases fuel consumption.Treatment of exhaust products of combustion.The exhaust gas

coming out of exhaust manifold is treated to reduce JIC and COemissions. The devices used to

accomplish are After burner , Exhaust manifold reactorand Catalytic converter.After-burner: is a

burner where air is suppliedto the exhaust gases and mixture is burnt withthe help of ignition

system. The HC and COwhich are formed in the engine combustionbecause of inadequate 02

and inadequatetime to burn are further brunt by providing air in a separate box, known as

after-burner.Exhaust manifold reactor is a further development of after-burner where thedesign ischanged so as to minimize the heat loss and to provide sufficient time for mixing

ofexhaust and secondary air. 3. Catalytic converter:

A catalytic converter is a device which is placed in the vehicle exhaust system to reduceHC and

CO by oxidizing catalyst and NO by reducing catalyst.

Modification of the fuels

The ability of a fuel to burn in mixtures leaner than stoichiometric ratio is a rough

indication of its potential emission reducing characteristics and reduced fuel

consumption. If gasoline is changed to propane as engine fuel CO emission can

substantially be reduced with reduced HC and NO and in changing from propane to

methane the CO as well HC emission touch zero level and only the NO remains as a


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significant factor. From pollution point of view both methane and steam reformed

hexane are very attractive fuels but we are unable to use at present for want of

technological progress.

CONTROL OF OXIDES OF NITROGEN.

The concentration of oxides of nitrogen in the exhaust is closely related to the peak

cycle temperature. The following are the three methods (investigated so far) for

reducing peak cycle temperature and thereby reducing NO emission.

Exhaust gas recirculation (EGR)

Catalyst

Water injection.

EXHAUST GAS RECIRCULATION ( E G R )

This method is commonly used to reduce NOx in petrol as well as diesel engines. In S.Iengines,

about 10 percent recirculation reduces NOx emission by 50 percent. Unfortunately, the

consequently poorer combustion directly increases HC emission and callsfor mixture

enrichment to restore combustion regularity which gives a further indirect increase of both HC

and CO.exhaust gas recirculation (EGR) system. A portion(about 10 to 15%) of the exhaust gases

is re-circulated to cylinder intake charge, andthis reduces the quantity of O2 available for

combustion. The exhaust gas forrecirculation is taken through an orifice and passed through

control valve for regulationof the quantity of recirculation.The effect of A/F ratio of NOx

emission taking EGRparameter. It may be observedthat, maximum emission of NO takes place

duringlean mixture limits when gas recirculation is leasteffective. Whereas, for emission of

hydro carbon(HC) and carbon monoxide (CO) lean mixture ispreferred, 15 percent

recyclingreduces NOx by 80 percent but in creases HC and CO by 50 to 80%. These are

twoconflicting requirements of this emission control system and this problem has beensolved

by adopting package system which have both NO and HC/CO control devices.Catalyst. A few

types of catalysts have been tested to reduce the emission of NOx, acopper catalyst has been


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used in the presence of CO for this purpose. The research isgoing on to develop a good catalyst.

The research is on for newer good catalyst.

Water injection. It has been observed that the specific fuel consumption decreases a

few percent at medium water injection rate. Attempts have been made to use water as adevice

for controlling the N0x .This method, because of its complexity, is rarely used.

TOTAL EMISSION CONTROL PACKAGES

We know that any method which is used to decrease NO tries to increase HC and COand vice-

versa. Thus it is of paramount importance to develop a method/system whichshould reduce

emissions of NO HC, CO to a desired level simultaneously. After alongand detailed experimental

study of various possible systems, the following two

systems/packages have been developed to achieve the required results1. Thermal reactor package

2. Catalytic converter package.

Using this approach, the following are the three basic methods of emission control:

Thermal reactors, which rely on homogeneous oxidation to control CO and HC;

Oxidation catalyst for CO and HC;

Dual catalyst system (here a reduction catalyst for NO and an oxidation catalyst

for CO and HC are connected in series).

Thermal reactor package:

A thermal reactor is a chamber which is designed to provide adequate residence timefor

allowing appreciable oxidation of CO and HC to take place. For enhancing theconversion of CO

to CO2 the exhaust temperature is increased by retarding the spark.

Actual thermal reactor (made of high nickel steel) that is used on a car consists of two enlarged

exhaust manifolds which allow greater residence time for burning HC and CO with oxygen in the

pumped in air. For keeping aflame constantly burning (and there by assuming complete

combustion) a secondary airpump injects fresh air into the reactor; this reduces HC and CO.

About 10 to 75 percentof the gas is re-circulated after cooling in the intercooler to reduce the

formation of NOx

In this packing system are also included the following


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Enriched and stage carburettor temperature controls;

Crankcase valve to control blow-by gases;

Special evaporation control valves.

In this package emission of NOx,HC and CO are reduced to a required level but at the

cost of 20 per cent less power and 10 per cent more fuel consumption. This converter

can be employed for a run of 15000 km.

Catalytic Converter Package:

The working principle of this package is to control the emission levels of various

pollutants by changing the chemical characteristics of the exhaust gases. The catalytic

converter package as com pared to thermal reactor package requires non-leaded fuel

as lead reduces the catalytic action.

The major advantage of this converter (as compared to thermal reactor) is that it allows

a partial decoupling of emission control from engine operation in that the conversion

efficiencies for HC and CO are very high at normal exhaust temperatures.

Converters for HC and CO and NOxare arranged as shown in the figure. The NOx

catalyst is the first element in the gas flow path, does not cause release of any heat.

The next is HC/CO catalyst, which releases heat to such a great extent that may cause

overheating and burning of the element. This is taken care of by injecting air throughsecondaryair pump. A bypass valve ahead of converter is used to increase the

converter life. For better control of NOx, exhaust gas is circulated via an intercooler back

to air cleaner. For this system, the power loss is about 30% and the fuel consumption is

about 10% more than normal.EFFECT OF ENGINE EMISSION ON HUMAN HEALTH

The effects of different engine emissions on human health are discussed below:

1.Sulphur dioxide (SO2)

It is an irritant gas and affects the mucous membrane when inhaled. In the

presence of water vapour it forms sulphurous and sulphuric acids These acids

cause severe bronchospasma at very low levels of concentration.

Diseases like bronchitis and asthama are aggravated by a high concentration of


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SO2

2.Carbon-monoxide (CO):

It has a strong affinity (200 times) for combining with the haemoglobin of the

blood to form carboxyhaemoglobin. This reduces the ability of the haemoglobin

to carry oxygen to the blood tissues.

CO affects the central nervous system.

It is also responsible for heart attacks and a high mortality rate.

3.Oxides of nitrogen (NOx):

These are known to cause occupational diseases. It is estimated that eye and

nasal irritation will be observed after exposure to about 15 p.p.m. of nitrogen

oxide, and pulmonary discomfort after brief exposure to 25 p.p.m. of nitrogen

oxide.

It also aggrevates diseases like bronchitis and asthama.

Hydrocarbon vapours:

They are primarily irritating.

They are major contributors to eye and respiratory irritation caused by

photochemical smog

Compounds of Incomplete combustionExhaust discharge from IC engines carry compounds of incomplete combustion

(polycyclic organic compounds and aliphatic hydrocarbons), which act as

carcinogenic agents and are responsible for lungs cancer

4.Lead

Inorganic lead compounds (discharged from vehicles using leaded petrol) cause

a variety of human health disorders.

The effects include gastrointestinal damage, liver and kidney damage,abnormality in fertility and pregnancy etc.

5.Smoke

It is visible carbon particles.

It causes irritation in eyes and lungs, and visibility reduction. It also, causes other


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respiratory diseases.

Generally speaking, Susceptibility to the effects of exhaust emissions is greatest

amongst infants and the elderly. Those with chronic diseases of lungs or heart are

thought to be at great risk.

4 stroke I C engine is economical and less pollutant than 2 stroke engine Justify.

In two-stroke engine the charge has to be compressed outside for scavenging and

charging (this consumes some engine power). A part of this charge escapes directly

through exhaust ports (short circuiting). Thus power spent in compressing this fraction

of the charge is wasted. Particularly in S.I. engines the charge consists of air-fuel

mixture. This loss of power and charge is absent in 4-stroke engine. Therefore 4-stroke

engine is always economical than 2-stroke engine.

Further the loss of charge increases HC in the exhaust in case of two-stroke engines,

Hence 4-stroke engine is also less pollutant than 2-stroke engine.


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C.I ENGINE

POLLUTANT PRODUCED IN I.C ENGINE AND CAUSES

There has been a great concern, in recent years, that the I C Engines are responsible

for too much atmospheric pollution, which is detrimental to human health & environment.

Thus concerted efforts are being made to reduce the responsible pollutants emitted


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from the exhaust system without sacrificing power & fuel consumption.

Air pollution can be defined as an addition to our atmosphere of any material which will

have a deleterious effect on life upon our planet. Besides IC engines other sources

such as electric power stations, industrial and domestic fuel consumers also add

pollution.

MECHANISM OF POLLUTANTS FORMATION

(MAIN POLLUTANTS EMITTED BY PETROL ENGINE

Pollutants are produced by the incomplete burning of the air-fuel mixture in the

combustion chamber. The major pollutants emitted from the exhaust due to incomplete

combustion are:

Carbon monoxide (CO)

Hydrocarbons (HC)

Oxides of nitrogen (NO).

Other products produced are acetylene, aldehydes etc. If, however, combustion is

complete- - the only products being expelled from the exhaust would be water vapour

which is harmless, and carbon dioxide, which is an inert gas and, as such it is not

directly harmful to humans.CARBON MONOXIDE (CO) :

It is a colour less gas of about the same density as air. It is a poisonous gas which,

when inhaled, replaces the oxygen in the blood stream so that the bodys metabolism

can not function correctly. Small amounts of CO concentrations, when breathed in, slow

down physical and mental activity and produces headaches, while large concentration

will kill.

Mechanism of formation of CO:-

CO is intermediate product of combustion remains in exhaust if the oxidation of CO to

C02 is not complete. Theoretically , it can be said that petrol engine exhaust is free of

CO if the air fuel ratio is 15. However, some CO is always present in the exhaust even


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at lean mixture and can be as high as 1%. CO is generally formed when the mixture is

rich in fuel. The amount of CO formed increases the mixture becomes more and more

rich in fuel. A small amount of CO will come out of the exhaust even when the mixture

is slightly lean in fuel. This is due to the fact that equilibrium is not established when the

products pass to the exhaust. At the high temperature developed during the combustion,

the products formed are unstable, and the following reactions take place before the

equilibrium is established.

2H2O+ O2 2(1-y) H20 + 2yH2 + yO2

where, y is the fraction of H20 dissociated.

C+02 C02 + (1-x)CO2 +x CO + x/2 O2

As the products cool down to exhaust temperature, major part of CO reacts with oxygen

form CO2 However, a relatively small amount of CO will remain in exhaust, its

concentration creasing with rich mixtures.

2. HYDROCARBONS (HC):

The unburnt hydrocarbons emission is the direct result of incomplete combustion. The

emission amount of hydrocarbon is closely related to design variables and combustion

chamber design and operating variables such as A:F ratio, speed, load and mode of

operation as idling, running or accelerating. Surface to volume ratio and wall quenching

greatly affects in formation of HC. Hydrocarbons, derived from unburnt fuel emitted, by

exhausts, engine crankcase fumes and vapour escaping from the carburetor are also

harmful to health.

Mechanism of formation of HC

Due to existence of local very rich mixture pockets at much lower temperatures than

combustion chambers, unburnt hydrocarbons may appear in the exhaust.The

hydrocarbons also appear due to flame quenching near the metallic walls.

A significant portion of this unburnt hydrocarbon may burn during expansion and

exhaust strokes if the oxygen concentration and exhaust temperature is suitable for

complete oxidation Otherwise a large amount of hydrocarbon will go out with the


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exhaust gases.

3. OXIDES OF NITROGEN (NO):

Oxides of N2 generally occur mainly in the form of NO and N02 . These are generally

formed at high temperature. Hence high temperature and availability of 02 are the main

reason for the formation of N0 and NO2 .Many other oxides like N2O4, N2O, N2O3 ,N2O5

are also formed in low concentration but they decompose spontaneously at ambient

conditions of NO2. The maximum NOxlevels are observed with A:F ratios of about 10%

above stoichiometric. Oxides of nitrogen and other obnoxious substances are produced

in very small quantities and, in certain environments, can cause pollution, while

prolonged exposure is dangerous to health.

Mechanism of formation of nitric oxide (NO)

At high combustion temperatures, the following chemical reactions take place behind

the flame:

N2+ O2 2NO

N2+ 2H2 O 2NO+2H2

Chemical equilibrium calculations show that a significant amount of NO will be formed

the end of combustion. The majority of NO formed will however decompose at the low

temperature of exhaust. But due to very low reaction rate at the exhaust temperature apart of NO formed remains in exhaust. It is far in excess of the equilibrium composition

at that temperature as t formation of NO freezes at low exhaust temperatures. The NO

formation will be less in rich mixtures than in lean mixtures.

4. SMOKE OR PARTICULATE

Solid particles are usually formed by dehydrogenation, polymerisation and

agglomeration. In the combustion process of different hydrocarbons, acetylene (C2H2) is

formed as intermediate product. These acetylene molecules after simultaneous polymerizationdehydration produce carbon particles, which are the main constituent of the particulate.

5. ALDEHYDES: Due to very slow chemical reaction during delay period in the diesel

engines, aldehydes are formed as intermediate products. In some parts of the spray the

aldehydes will be left after the initial reactions. These aldehydes may be oxidised in the


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later part of the cycle, if the mixture temperature is high, and if there is sufficient oxygen.

At heavy loads, due to lack of oxygen, an increase in aldehyde emission in the exhaust

is observed.


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GAS TURBINE

3.1.1 General1

Gas turbines, also called combustion turbines, are used in a broad scope of applications

including electric power generation, cogeneration, natural gas transmission, and various

processapplications. Gas turbines are available with power outputs ranging in size from 300

horsepower (hp) toover 268,000 hp, with an average size of 40,200 hp.2 The primary fuels used

in gas turbines are naturalgas and distillate (No. 2) fuel oil.3

3.1.2 Process Description1,2

A gas turbine is an internal combustion engine that operates with rotary rather than

reciprocatingmotion. Gas turbines are essentially composed of three major components:

compressor, combustor, andpower turbine. In the compressor section, ambient air is drawn in

and compressed up to 30 times ambientpressure and directed to the combustor section where

fuel is introduced, ignited, and burned.

Combustorscan either be annular, can-annular, or silo. An annular combustor is a doughnut-

shaped, single, continuouschamber that encircles the turbine in a plane perpendicular to the air


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flow. Can-annular combustors aresimilar to the annular; however, they incorporate several can-

shaped combustion chambers rather than asingle continuous chamber. Annular and can-

annular combustors are based on aircraft turbine technologyand are typically used for smaller

scale applications. A silo (frame-type) combustor has one or morecombustion chambers

mounted external to the gas turbine body. Silo combustors are typically larger thanannular or

can-annular combustors and are used for larger scale applications.

The combustion process in a gas turbine can be classified as diffusion flame combustion, or

leanpremixstaged combustion. In the diffusion flame combustion, the fuel/air mixing and

combustion takeplace simultaneously in the primary combustion zone. This generates regions

of near-stoichiometricfuel/air mixtures where the temperatures are very high. For lean-premix

combustors, fuel and air arethoroughly mixed in an initial stage resulting in a uniform, lean,

unburned fuel/air mixture which isdelivered to a secondary stage where the combustion

reaction takes place. Manufacturers use differenttypes of fuel/air staging, including fuel

staging, air staging, or both; however, the same staged, lean-premixprinciple is applied. Gas

turbines using staged combustion are also referred to as Dry Low NOXcombustors. The majority

of gas turbines currently manufactured are lean-premix staged combustionturbines.

Hot gases from the combustion section are diluted with additional air from the compressor

sectionand directed to the power turbine section at temperatures up to 2600oF. Energy fromthe hot exhaust gases,which expand in the power turbine section, are recovered in the form of

shaft horsepower. More than50 percent of the shaft horsepower is needed to drive the internal

compressor and the balance of recoveredshaft horsepower is available to drive an external

load.2 Gas turbines may have one, two, or three shafts totransmit power between the inlet air

compression turbine, the power turbine, and the exhaust turbine. Theheat content of the

exhaust gases exiting the turbine can either be discarded without heat recovery (simplecycle);

recovered with a heat exchanger to preheat combustion air entering the combustor(regenerativecycle); recovered in a heat recovery steam generator to raise process steam, with

or without supplementaryfiring (cogeneration); or recovered, with or without supplementary

firing, to raise steam for a steam turbine.Rankine cycle (combined cycle or repowering).


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The simple cycle is the most basic operating cycle of gas turbines with a thermal efficiency

rangingfrom 15 to 42 percent. The cycle thermal efficiency is defined as the ratio of useful shaft

energy to fuelenergy input. Simple cycle gas turbines are typically used for shaft horsepower

applications withoutrecovery of exhaust heat. For example, simple cycle gas turbines are used

by electric utilities forgeneration of electricity during emergencies or during peak demand

periods.

A regenerative cycle is a simple cycle gas turbine with an added heat exchanger. The heat

exchanger uses the turbine exhaust gases to heat the combustion air which reduces the

amount of fuelrequired to reach combustor temperatures. The thermal efficiency of a

regenerative cycle is approximately35 percent. However, the amount of fuel efficiency and

saving may not be sufficient to justify the capitalcost of the heat exchanger, rendering the

process unattractive.

A cogeneration cycle consists of a simple cycle gas turbine with a heat recovery steam

generator(HRSG). The cycle thermal efficiency can be as high as 84 percent. In a cogeneration

cycle, the steamgenerated by the HRSG can be delivered at a variety of pressures and

temperatures to other thermalprocesses at the site. For situations where additional steam is

required, a supplementary burner, or ductburner, can be placed in the exhaust duct stream of

the HRSG to meet the sites steam requirements.A combined cycle gas turbine is a gas turbine with a HRSG applied at electric utility sites. Thegas

turbine drives an electric generator, and the steam from the HRSG drives a steam turbine which

alsodrives an electric generator. A supplementary-fired boiler can be used to increase the

steam production.

The thermal efficiency of a combined cycle gas turbine is between 38 percent and 60

percent.Gas turbine applications include gas and oil industry, emergency power generation

facilities,independent electric power producers (IPP), electric utilities, and other industrialapplications. Thepetroleum industry typically uses simple cycle gas turbines with a size range

from 300 hp to 20,000 hp.

The gas turbine is used to provide shaft horsepower for oil and gas production and

transmission.Emergency power generation sites also utilize simple cycle gas turbines. Here the


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gas turbine is used toprovide backup or emergency power to critical networks or equipment.

Usually, gas turbines under 5,000hp are used at emergency power generation sites.

Independent electrical power producers generate electricity for resale to larger electric

utilities.Simple, regenerative, or combined cycle gas turbines are used at IPP; however, most

installations usecombined cycle gas turbines. The gas turbines used at IPP can range from 1,000

hp to over 100,000 hp.

The larger electric utilities use gas turbines mostly as peaking units for meeting power demand

peaksimposed by large commercial and industrial users on a daily or seasonal basis. Simple

cycle gas turbinesranging from 20,000 hp to over 200,000 hp are used at these installations.

Other industrial applications forgas turbines include pulp and paper, chemical, and food

processing. Here, combined cycle gas turbines are used for cogeneration.

3.1.3 Emissions

The primary pollutants from gas turbine engines are nitrogen oxides (NOX), carbon

monoxide(CO), and to a lesser extent, volatile organic compounds (VOC). Particulate matter

(PM) is also aprimary pollutant for gas turbines using liquid fuels. Nitrogen oxide formation is

strongly dependent on the high temperatures developed in the combustor. Carbon monoxide,

VOC, hazardous air pollutants (HAP), and PM are primarily the result of incomplete combustion.

Trace to low amounts of HAP and sulfur dioxide (SO2) are emitted from gas turbines. Ash and

metallic additives in the fuel may also contribute to PM in the exhaust. Oxides of sulfur (SOX)

will only appear in a significant quantity if heavy oils are firedin the turbine. Emissions of sulfur

compounds, mainly SO2, are directly related to the sulfur content of the

fuel.

Available emissions data indicate that the turbines operating load has a considerable effect on

theresulting emission levels. Gas turbines are typically operated at high loads (greater than or

equal to 80percent of rated capacity) to achieve maximum thermal efficiency and peak

combustor zone flametemperatures. With reduced loads (lower than 80 percent), or during

periods of frequent load changes, thecombustor zone flame temperatures are expected to be

lower than the high load temperatures, yieldinglower thermal efficiencies and more incomplete

combustion. The emission factors for this sections arepresented for gas turbines operating


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under high load conditions. Section 3.1 background informationdocument and emissions

database contain additional emissions data for gas turbines operating undervarious load

conditions.

Gas turbines firing distillate oil may emit trace metals carried over from the metals content of

thefuel. If the fuel analysis is known, the metals content of the fuel ash should be used for flue

gas emissionfactors assuming all metals pass through the turbine.

If the HRSG is not supplementary fuel fired, the simple cycle input-specific emission

factors(pounds per million British thermal units [lb/MMBtu]) will also apply to

cogeneration/combined cyclesystems. If the HRSG is supplementary fired, the emissions

attributable to the supplementary firing mustalso be considered to estimate total stack

emissions.

3.1.3.1 Nitrogen Oxides -

Nitrogen oxides formation occurs by three fundamentally different mechanisms. The

principalmechanism with turbines firing gas or distillate fuel is thermal NOX, which arises from

the thermaldissociation and subsequent reaction of nitrogen (N2) and oxygen (O2) molecules in

the combustion air.

Most thermal NOX is formed in high temperature stoichiometric flame pockets downstream of

the fuelinjectors where combustion air has mixed sufficiently with the fuel to produce the peak

temperature fuel/air interface.

The second mechanism, called prompt NOX, is formed from early reactions of nitrogen

moleculesin the combustion air and hydrocarbon radicals from the fuel. Prompt NOX forms

within the flame and isusually negligible when compared to the amount of thermal NOX

formed. The third mechanism, fuel NOX, stems from the evolution and reaction of fuel-bound

nitrogen compounds with oxygen. Natural gas has negligible chemically-bound fuel nitrogen

(although some molecular nitrogen is present). Essentially all NOX formed from natural gas

combustion is thermal NOX. Distillate oils have low levels of fuel-bound


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nitrogen. Fuel NOX from distillate oil-fired turbines may become significant in turbines

equipped with ahigh degree of thermal NOX controls. Otherwise, thermal NOX is the

predominant NOX formationmechanism in distillate oil-fired turbines.

The maximum thermal NOX formation occurs at a slightly fuel-lean mixture because of

excess oxygen available for reaction. The control of stoichiometry is critical in achieving

reductions in thermal NOX. Thermal NOX formation also decreases rapidly as the temperature

drops below the adiabatic flame temperature, for a given stoichiometry. Maximum reduction of

thermal NOX can be achieved by control of both the combustion temperature and the

stoichiometry. Gas turbines operate with high overall levels of excess air, because turbines use

combustion air dilution as the means to maintain the turbine inlet temperature below design

limits. In older gas turbine models, where combustion is in the form of a diffusion flame, most

of the dilution takes place downstream of the primary flame, which does not minimize peak

temperature in the flame and suppress thermal NOX formation.

Diffusion flames are characterized by regions of near-stoichiometric fuel/air mixtures

wheretemperatures are very high and significant thermal NOX is formed. Water vapor in the

turbine inlet aircontributes to the lowering of the peak temperature in the flame, and therefore

to thermal NOX emissions.Thermal NOX can also be reduced in diffusion type turbines through

water or steam injection. The injectedwater-steam acts as a heat sink lowering the combustionzone temperature, and therefore thermal NOX.

\ Newer model gas turbines use lean, premixed combustion where the fuel is typically

premixed with morethan 50 percent theoretical air which results in lower flame temperatures,

thus suppressing thermal NOXformation.

Ambient conditions also affect emissions and power output from turbines more than from

externalcombustion systems. The operation at high excess air levels and at high pressures

increases the influenceof inlet humidity, temperature, and pressure.4 Variations of emissions of30 percent or greater have beenexhibited with changes in ambient humidity and temperature.

Humidity acts to absorb heat in the primaryflame zone due to the conversion of the water

content to steam. As heat energy is used for water to steamconversion, the temperature is the

flame zone will decrease resulting in a decrease of thermal NOXformation. For a given fuel


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firing rate, lower ambient temperatures lower the peak temperature in theflame, lowering

thermal NOX significantly. Similarly, the gas turbine operating loads affect NOXemissions.

Higher NOX emissions are expected for high operating loads due to the higher

peaktemperature in the flame zone resulting in higher thermal NOX.

3.1.3.2 Carbon Monoxide and Volatile Organic Compounds -

CO and VOC emissions both result from incomplete combustion. CO results when there

isinsufficient residence time at high temperature or incomplete mixing to complete the final

step in fuelcarbon oxidation. The oxidation of CO to CO2 at gas turbine temperatures is a slow

reaction compared tomost hydrocarbon oxidation reactions. In gas turbines, failure to achieve

CO burnout may result fromquenching by dilution air. With liquid fuels, this can be aggravated

by carryover of larger droplets fromthe atomizer at the fuel injector. Carbon monoxide

emissions are also dependent on the loading of the gasturbine. For example, a gas turbine

operating under a full load will experience greater fuel efficiencieswhich will reduce the

formation of carbon monoxide. The opposite is also true, a gas turbine operatingunder a light

to medium load will experience reduced fuel efficiencies (incomplete combustion) which

willincrease the formation of carbon monoxide.

The pollutants commonly classified as VOC can encompass a wide spectrum of volatile

organiccompounds some of which are hazardous air pollutants. These compounds are

discharged into theatmosphere when some of the fuel remains unburned or is only partially

burned during the combustionprocess. With natural gas, some organics are carried over as

unreacted, trace constituents of the gas, whileothers may be pyrolysis products of the heavier

hydrocarbon constituents. With liquid fuels, large dropletcarryover to the quench zone

accounts for much of the unreacted and partially pyrolized volatile organicemissions.Similar to

CO emissions, VOC emissions are affected by the gas turbine operating loadconditions. Volatile

organic compounds emissions are higher for gas turbines operating at low loads as vcompared

to similar gas turbines operating at higher loads.

3.1.3.3 Particulate Matter13 -


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PM emissions from turbines primarily result from carryover of noncombustible trace

constituentsin the fuel. PM emissions are negligible with natural gas firing and marginally

significant with distillate oilfiring because of the low ash content. PM emissions can be

classified as "filterable" or "condensable" PM.Filterable PM is that portion of the total PM that

exists in the stack in either the solid or liquid state andcan be measured on a EPA Method 5

filter. Condensable PM is that portion of the total PM that exists asa gas in the stack but

condenses in the cooler ambient air to form particulate matter. Condensable PMexists as a gas

in the stack, so it passes through the Method 5 filter and is typically measured by analyzingthe

impingers, or "back half" of the sampling train. The collection, recovery, and analysis of the

impingersis described in EPA Method 202 of Appendix M, Part 51 of the Code of Federal

Regulations. CondensablePM is composed of organic and inorganic compounds and is generally

considered to be all less than 1.0micrometers in aerodynamic diameter.

3.1.3.4 Greenhouse Gases5-11


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Carbon dioxide (CO2) and nitrous oxide (N2O) emissions are all produced during natural gas

anddistillate oil combustion in gas turbines. Nearly all of the fuel carbon is converted to CO2

during thecombustion process. This conversion is relatively independent of firing configuration.

Methane (CH4) isalso present in the exhaust gas and is thought to be unburned fuel in the case

of natural gas or a product ofcombustion in the case of distillate fuel oil.

Although the formation of CO acts to reduce CO2 emissions, the amount of CO produced

isinsignificant compared to the amount of CO2 produced. The majority of the fuel carbon not

converted toCO2 is due to incomplete combustion.

Formation of N2O during the combustion process is governed by a complex series of reactions

andits formation is dependent upon many factors. However, the formation of N2O is minimized


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whencombustion temperatures are kept high (above 1475oF) and excess air is kept to a

minimum (less than 1percent).

3.1.3.5 HAP Emissions -Available data indicate that emission levels of HAP are lower for gas turbines than for

othercombustion sources. This is due to the high combustion temperatures reached during

normal operation.

The emissions data also indicate that formaldehyde is the most significant HAP emitted from

combustionturbines. For natural gas fired turbines, formaldehyde accounts for about two-thirds

of the total HAPemissions. Polycyclic aromatic hydrocarbons (PAH), benzene, toluene, xylenes,

and others account for theremaining one-third of HAP emissions. For No. 2 distillate oil-firedturbines, small amount of metallicHAP are present in the turbines exhaust in addition to the

gaseous HAP identified under gas fired turbines.

These metallic HAP are carried over from the fuel constituents. The formation of carbon

monoxide duringthe combustion process is a good indication of the expected levels of HAP

emissions. Similar to COemissions, HAP emissions increase with reduced operating loads.

Typically, combustion turbines operateunder full loads for greater fuel efficiency, thereby

minimizing the amount of CO and HAP emissions.

3.1.4 Control Technologies12

There are three generic types of emission controls in use for gas turbines, wet controls using

steamor water injection to reduce combustion temperatures for NOX control, dry controls

using advancedcombustor design to suppress NOX formation and/or promote CO burnout, and

post-combustion catalyticcontrol to selectively reduce NOX and/or oxidize CO emission from

the turbine. Other recently developedtechnologies promise significantly lower levels of NOX

and CO emissions from diffusion combustion typegas turbines. These technologies are currently

being demonstrated in several installations.Emission factors in this section have been

determined from gas turbines with no add-on controldevices (uncontrolled emissions). For NOX

and CO emission factors for combustion controls, such aswater-steam injection, and lean pre-


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mix units are presented. Additional information for controlledemissions with various add-on

controls can be obtained using the section 3.1 database. Uncontrolled, leanpremix,and water

injection emission factors were presented for NOX and CO to show the effect ofcombustion

modification on emissions.

3.1.4.1 Water Injection -

Water or steam injection is a technology that has been demonstrated to effectively suppress

NOXemissions from gas turbines. The effect of steam and water injection is to increase the

thermal mass bydilution and thereby reduce peak temperatures in the flame zone. With water

injection, there is anadditional benefit of absorbing the latent heat of vaporization from the

flame zone. Water or steam istypically injected at a water-to-fuel weight ratio of less than one.Depending on the initial NOX levels, such rates of injection may reduce NOX by 60 percent

orhigher. Water or steam injection is usually accompanied by an efficiency penalty (typically 2

to 3 percent)but an increase in power output (typically 5 to 6 percent). The increased power

output results from theincreased mass flow required to maintain turbine inlet temperature at

manufacturer's specifications. BothCO and VOC emissions are increased by water injection,

with the level of CO and VOC increasesdependent on the amount of water injection.

3.1.4.2 Dry Controls -

Since thermal NOX is a function of both temperature (exponentially) and time (linearly), the

basisof dry controls are to either lower the combustor temperature using lean mixtures of air

and/or fuel staging,or decrease the residence time of the combustor. A combination of

methods may be used to reduce NOXemissions such as lean combustion and staged

combustion (two stage lean/lean combustion or two stagerich/lean combustion).

Lean combustion involves increasing the air-to-fuel ratio of the mixture so that the peak

andaverage temperatures within the combustor will be less than that of the stoichiometric

mixture, thussuppressing thermal NOX formation. Introducing excess air not only creates a

leaner mixture but it alsocan reduce residence time at peak temperatures.


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Two-stage lean/lean combustors are essentially fuel-staged, premixed combustors in which

eachstage burns lean. The two-stage lean/lean combustor allows the turbine to operate with an

extremely leanmixture while ensuring a stable flame. A small stoichiometric pilot flame ignites

the premixed gas andprovides flame stability. The NOX emissions associated with the high

temperature pilot flame areinsignificant. Low NOX emission levels are achieved by this

combustor design through cooler flametemperatures associated with lean combustion and

avoidance of localized "hot spots" by premixing the fueland air.

Two stage rich/lean combustors are essentially air-staged, premixed combustors in which

theprimary zone is operated fuel rich and the secondary zone is operated fuel lean. The rich

mixture produceslower temperatures (compared to stoichiometric) and higher concentrations

of CO and H2, because ofincomplete combustion. The rich mixture also decreases the amount

of oxygen available for NOXgeneration. Before entering the secondary zone, the exhaust of the

primary zone is quenched (to extinguishthe flame) by large amounts of air and a lean mixture is

created. The lean mixture is pre-ignited and thecombustion completed in the secondary zone.

NOX formation in the second stage are minimized throughcombustion in a fuel lean, lower

temperature environment. Staged combustion is identified through avariety of names,

including Dry-Low NOx (DLN), Dry-Low Emissions (DLE), or SoLoNOx.

3.1.4.3 Catalytic Reduction Systems -

Selective catalytic reduction (SCR) systems selectively reduce NOX emissions by

injectingammonium (NH3) into the exhaust gas stream upstream of a catalyst. Nitrogen oxides,

NH3, and O2 reacton the surface of the catalyst to form N2 and H2O. The exhaust gas must

contain a minimum amount of O2and be within a particular temperature range (typically 450oF

to 850oF) in order for the SCR system tooperate properly.

The temperature range is dictated by the catalyst material which is typically made from

noblemetals, including base metal oxides such as vanadium and titanium, or zeolite-based

material. The removalefficiency of an SCR system in good working order is typically from 65 to

90 percent. Exhaust gastemperatures greater than the upper limit (850oF) cause NOX and NH3


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to pass through the catalystunreacted. Ammonia emissions, called NH3 slip, may be a

consideration when specifying an SCR system.

Ammonia, either in the form of liquid anhydrous ammonia, or aqueous ammonia hydroxide

isstored on site and injected into the exhaust stream upstream of the catalyst. Although an SCR

system canoperate alone, it is typically used in conjunction with water-steam injection systems

or lean-premix systemto reduce NOX emissions to their lowest levels (less than 10 ppm at 15

percent oxygen for SCR and wetinjection systems). The SCR system for landfill or digester gas-

fired turbines requires a substantial fuelgas pretreatment to remove trace contaminants that

can poison the catalyst. Therefore, SCR and othercatalytic treatments may be inappropriate

control technologies for landfill or digester gas-fired turbines.

The catalyst and catalyst housing used in SCR systems tend to be very large and dense (in terms

ofsurface area to volume ratio) because of the high exhaust flow rates and long residence times

required forNOX, O2, and NH3, to react on the catalyst. Most catalysts are configured in a

parallel-plate, "honeycomb"design to maximize the surface area-to-volume ratio of the catalyst.

Some SCR installations incorporateCO catalytic oxidation modules along with the NOX

reduction catalyst for simultaneous CO/NOX control.

Carbon monoxide oxidation catalysts are typically used on turbines to achieve control of

COemissions, especially turbines that use steam injection, which can increase theconcentrations of CO andunburned hydrocarbons in the exhaust. CO catalysts are also being

used to reduce VOC and organic HAPsemissions. The catalyst is usually made of a precious

metal such as platinum, palladium, or rhodium.

Other formulations, such as metal oxides for emission streams containing chlorinated

compounds, are alsoused. The CO catalyst promotes the oxidation of CO and hydrocarbon

compounds to carbon dioxide(CO2) and water (H2O) as the emission stream passes through the

catalyst bed. The oxidation processtakes place spontaneously, without the requirement forintroducing reactants. The performance of theseoxidation catalyst systems on combustion

turbines results in 90-plus percent control of CO and about 85 to90 percent control of

formaldehyde. Similar emission reductions are expected on other HAP pollutants.


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3.1.4.4 Other Catalytic Systems14,15 -

New catalytic reduction technologies have been developed and are currently being

commerciallydemonstrated for gas turbines. Such technologies include, but are not limited to,

the SCONOX and theXONON systems, both of which are designed to reduce NOX and COemissions. The SCONOX system isapplicable to natural gas fired gas turbines. It is based on a

unique integration of catalytic oxidation andabsorption technology. CO and NO are catalytically

oxidized to CO2 and NO2. The NO2 molecules aresubsequently absorbed on the treated surface

of the SCONOX catalyst. The system manufacturerguarantees CO emissions of 1 ppm and NOX

emissions of 2 ppm. The SCONOX system does not requirethe use of ammonia, eliminating the

potential of ammonia slip conditions evident in existing SCR systems.Only limited emissions

data were available for a gas turbine equipped with a SCONOX system. This datareflected HAPemissions and was not sufficient to verify the manufacturers claims.

The XONON system is applicable to diffusion and lean-premix combustors and is currently

beingdemonstrated with the assistance of leading gas turbine manufacturers. The system

utilizes a flamelesscombustion system where fuel and air reacts on a catalyst surface,

preventing the formation of NOX whileachieving low CO and unburned hydrocarbon emission

levels. The overall combustion process consists ofthe partial combustion of the fuel in the

catalyst module followed by completion of the combustiondownstream of the catalyst. The

partial combustion within the catalyst produces no NOX, and thecombustion downstream of

the catalyst occurs in a flameless homogeneous reaction that produces almostno NOX. The

system is totally contained within the combustor of the gas turbine and is not a process

forclean-up of the turbine exhaust. Note that this technology has not been fully demonstrated

as of thedrafting of this section. The catalyst manufacturer claims that gas turbines equipped

with the XONONCatalyst emit NOX levels below 3 ppm and CO and unburned hydrocarbons

levels below 10 ppm.Emissions data from gas turbines equipped with a XONON Catalyst were

not available as of the draftingof this section.


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THERMAL POWER PLANT


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Thermal Power Plants have been found to affect Environmental segments of the surrounding

region very badly.Environmental deterioration is attributed to emission of large amount of SOx,

NOx & SPM & RSPM which disperse over 25Kms radius and cause respiratory and related

ailments to human beings and animal kingdom. It also affects photosynthesisprocess, balance

of minerals & micro and major nutrients in the plants, soil strata, structures & buildings get

affected due tocorrosive reactions.

INTRODUCTION

Power generating units are mega project, which require not only huge capital investment but

alsovarious natural resources like, fossil fuels and water, thus create an immeasurable &

everlasting impacts onthe environment and generate tremendous stress in the local eco-system

in spite of stringent governmentnorms to control and mitigate the damages to the environment

by the power plants.


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Environmental Impacts and cost-benefit analysis of Power stations like STPS, Chandrapur,

GandhiNagar, Gujarat, gas based power plant, Jhenor- Gandhar, Gujarat & STPS, Ramagundam,

Andhra Pradeshcarried out by Khan et al.1, (1990) is discussed below.

Out of reported SOx (3-37 g/m3), NOx (5-34 g/m3) & SPM (53-482 g/m3) the values of SPM

aremuch higher than the limits of NAAQ standards2. The maximum tolerable limits on annual

average basis areSO2 (60 g/m3), NOx (60 g/m3) & SPM (140 g/m3). The reported values of

SO2 and NOx lies within thelimits, however, they are toxic on long term basis. It is pertinent to

note that the values of the pollutantsreported are even after all the mitigative, modern and

state of the art preventive control equipments installedand working in all the Power Stations.

The SPM also includes RSPM (Respirable suspended particulate matters) and both types of

fineparticles normally spread over 25 Kms from the Thermal Power station. These pollutants

cause respiratoryand related aliments to human beings and animal kingdom. Because of

deposition of SPM on the plants,photosynthesis process of plants is affected very badly. These

particles penetrate inside the plants throughleaves & branches thereby creating imbalance of

minerals & micro and major nutrients in the plants. All these affect the plant growth very badly.

Due to this no big industrial zone is developed within 20 Kms

radius of the source and the habitations too are facing severe problems. Spreading &

deposition of SPM onsoil disturbs the contents of minerals, micro and major nutrients.Continuous and long term deposition ofSPM causes the fertile and forest land to be

unproductive for plants & farming.

Due to continuous & long lasting emission of SOx & NOx, which are the principal pollutants

coalbased plants, surrounding structures, buildings, monuments of historic importance &

metallic structures tooare affected very badly due to corrosive (Acid rain) reactions. Well

known example of this is the victimizedTajmahal of Agra which is being deteriorated due to

these toxic gases. It is also worth to note that very highamount of carbon dioxide (CO2)emission (0.9-0.95 kg/kwh) from thermal power plants contribute to globalwarming leading to

climate change.

Impact on water


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Water on earth, with the power of the sun, is in a continuous delicate circle. People supply

the water they need from this circle and after consuming they give it back tothe same system.

During this process, the contaminating substances which aremixed into the water change the

chemical and biological features ofit and this is called water pollution. Water pollution

adversely causes the water supply to change physically, chemically, biologically,

bacteriologically and of course ecologically. It is strongly believed that if a thermal power plant

(the center generating electricity from the heat in combustion) is opened near Village, it will do

great harm on the natural environment. These risks really worry the inhabitants of the village.

People who earn their livings on fishing or farming believe that they will possibly lose their

source of income because of the pollution if thermal power plant is established.

According to the results from the interviews with the people living in Village, it is

obvious that they are really uneasy about their health beacuse the power plant is


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planned to be built very close to their settled area. They think this will provide new

avenues for industry but on the other hand it means nothing for the ones who are

under the risk of losing their health.

How do the thermal power plants pollute the water ?

Only less than half of the energy generated by thermalpower plants can be converted into

electrical energy.Remaining part is called leakage energy and it comesout with radiation or is

plunged into the air in the form ofgas through the chimneys.

One of the most important environmental impacts ofthermal power plants is cooling water

and the need for cooling water is not as smallas it is regarded. Therefore, they are usually set

up very close to the natural watersources such as rivers, lakes or sea where cooling water canbe easily supplied andused. The dispose of waste materials into the sea or onto the land is a

veryirresponsible way that has been used for years. The most destructive andunfavourable

waste materials the thermal power plants release are the waste ofashes. They are spread

around the nature, into the air or underground by the windand rainfall. This, of course, causes

ground and water pollution.

Are the biological diversity in polluted water and human health in

danger ?

The balance of temperature around the receiving environment is lost because of

releasing a significant amount of waste water used for cooling, cleaning process and

so on in thermal power plants.The chemicals used in the process of waste water treatment

(e.g.removal oftemporary hardness / precipitation) before releasing into the receiving

environmentcause a wide range of contamination.

Discharges of waste heat and spread of thermal contamination such as SO2 into the seas,rivers

and lakes, have an important role which endangers the biological life in water. As aresult, many

species in water and their habitats will be faced with the danger of extinction.

Due to the disruption of ecological balance and decrease in diversity, all living

creaturesespecially human who has the most important role in this process will be suffering


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from theseadverse changes.Furthermore, the contaminants from thermal power plants ( SO2)

cause acid rainsand they will lead to great changes in the chemical features of air, land and

water.Poisonous elements such as copper (Cu) and lead(Pb) from acid rains will alsopollute our

drinking water.

The local people living in and around the place where the thermal power plant is planned

toestablish are directly under the threat of such consequences.

Is it possible to use environment-friendly renewable energy sources

instead of thermalpower plants ?

In order to protect the ecological balance, sources of energy have to be renewable. Being

sustainable does not mean beingrenewable. Sustainability is only possible as long as it can

berenewable. Renewable energy is energy which comes fromnatural resources (such as

sunlight, wind, rain, tides, andgeothermal heat) and which are naturally replenished.Therefore

the energy systems have to be sustainable but enegy sources have to be renewable.

The natural energy resources such as hydrolic, solar, geothermal and wind energyare not

only renewable but they are also non-polluting resources. The energy gotten from biomass and

biogas is also environment-friendly. Livableenvironment for whom live today and in future is

only possible by using such systems.

The water requirement for a coal-based power plant is about 0.005-0.18 m3/kwh. At STPS,

the water requirement has been marginally reduced from about 0.18 m3/kWh to 0.15 m3/kwh

after the installation of a treatment facility for the ash pond decant. Still the water requirement

of 0.15 m3/kwh = 150 Liters per Unit of electricity is very high compared to the domestic

requirement of water of a big city.

Ash pond decant contains harmful heavy metals like B, As, Hg which have a tendency to

leach out over a period of time. Due to this the ground water gets polluted and becomes

unsuitable for domestic use. At Ramagundam STPS leakage of the ash pond decants was

noticed into a small natural channel. This is harmful to the fisheries and other aquatic biota in

the water body. Similar findings were noted for Chandrapur.


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The exposure of employees to high noise levels is very high in the coal based thermal power

plant. Moreover, the increased transportation activities due to the operation of the power

plant leads to an increase in noise levels in the adjacent localities.

Impact on land

The land requirement per mega watt of installed capacity for coal, gas and hydroelectric

powerplants is 0.1-4.7 ha., 0.26 ha. and 6.6 ha. respectively. In case of coal based power plants

the landrequirement is generally near the area to the coal mines. While in the case of gas-based

it is any suitable landwhere the pipeline can be taken economically. Land requirement of

hydroelectric power plants is generallyhilly terrain and valleys. 321 ha., 2616 ha. and 74 ha. of

land were used to dispose flyash from the coalbased plants at Ramagundam, Chandrapur and

Gandhinagar respectively. Thus large area of land is requiredfor coal based thermal power

plant. Due to this, natural soil properties changes. It becomes more alkalinedue to the alkaline

nature of flyash.


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Biological & thermal impact

The effect on biological environment can be divided into two parts, viz. the effect on flora and

theeffect on fauna. Effect on flora is due to two main reasons, land acquisition and due to fluegas emissions.Land acquisition leads to loss of habitat of many species.

The waste-water being at higher temperature (by 4-5oC) when discharged can harm the local

aquaticbiota. The primary effects of thermal pollution are direct thermal shocks, changes in

dissolved oxygen, andthe redistribution of organisms in the local community. Because water

can absorb thermal energy with onlysmall changes in temperature, most aquatic organisms

have developed enzyme systems that operate in onlynarrow ranges of temperature. These

stenothermic organisms can be killed by sudden temperature changesthat are beyond thetolerance limits of their metabolic systems. Periodic heat treatments used to keep thecooling

system clear of fouling organisms that clog the intake pipes can cause fish mortality.

Socio-economic impact

The effect of power plants on the socio-economic environment is based on three parameters,

viz.Resettlement and Rehabilitation (R & R), effect on local civic amenities and work related

hazards toemployees of the power plants. The development of civic amenities due to the

setting up of any powerproject is directly proportional to the size of the project. The same has

been observed to be the highest forthe coal based plants followed by the natural gas based

plant and lastly the hydroelectric plant. The coalbased plant has the highest number of

accidents due to hazardous working conditions.

A similar study was undertaken by Agrawal & Agrawal3 (1989) in order to assess the impact of

airpollutants on vegetation around Obra thermal power plant (1550 MW) in the Mirzapur

district of UttarPradesh. 5 study sites were selected northeast (prevailing wind) of the thermal

power plant. Responses ofplants to pollutants in terms of presence of foliar injury symptoms

and changes in chlorophyll, ascorbic acidand S content were noted. These changes were

correlated with ambient SOx and suspended particulatematter (SPM) concentrations and the

amount of dust settled on leaf surfaces. The SOx and SPMconcentrations were quite high in the


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immediate vicinity of the power plant. There also exists a directrelationship between the

concentration of SPM in air and amount of dust deposited on leaf surfaces.

In a lichen diversity assessment carried out around a coal-based thermal power plant by Bajpai

et al.4,(2010) indicated the increase in lichen abundance. Distributions of heavy metals from

power plant wereobserved in all directions.

Manohar et al.5, (1989) have carried out the study on effects of thermal power plant emissions

onatmospheric electrical parameters, as emissions from industrial stacks may not only cause

environmental andhealth problems but also cause substantial deviation in the fair weather

atmospheric electric parameters.Observations of the surface atmospheric electric field, point

discharge current and wind in the vicinity of athermal power plant were found to be affected.

Warhate6 (2009) has studied the impact of coal mining on Air, Water & Soil on the surrounding

areaof coal mining at Wani dist. Yavatmal. Environmental segments namely air, water & soil in

this area areaffected within 10-15 Kms from the source. Human beings, animal kingdom, plants

& soil are extensivelyaffected within 5 Kms of the source.

CONCLUSION

Thermal Power Plant affects environmental segments of the surrounding region very badly.

Largeamount of SOx, NOx & SPM are generated which damage the environment and are highly

responsible fordeterioration of health of human beings, animal kingdom as well as plants.

Emission of SPM & RSPMdisperse over 25 Kms radius land and cause respiratory and related

aliments to human beings and animalkingdom.

SPM gets deposited on the plants which affect photosynthesis. Due to penetration of

pollutantsinside the plants through leaves & branches, imbalance of minerals, micro and major

nutrients in the plantstake place which affect the plant growth severely. Spreading & deposition

of SPM on soil, disturb the soilstrata thereby the fertile and forest land becomes less

productive. Because of continuous & long lastingemission of SOx & NOx, which are the principal

pollutants emitted from a coal based power plant, structures& buildings get affected due to

corrosive reactions.


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Report of Rohit r Bhosale

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