The presentation gives the basic idea as to the environment, pollutions and laws, the governing bodies and the limits of the emmissions. Also specifically about the solid waste, liquid waste and the gas emmissions from the Thermal Power Plants.

1. ENVIRONMENT AND POLLUTION
CONTROL IN THERMAL POWER
STATIONS
Manohar Tatwawadi
total output power solutions
+91 9372167165
PUNE

2. GLOBAL ENVIRONMENT
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3. POWER PLANT & ENVIRONMENT
Thermal power stations are no exception in that
• They burn coal and release products of coal
combustion into air thereby polluting the
troposphere.
• Draw water from hydrosphere and generate
steam, use water for cooling purposes. Consume
water for domestic and other ancillary activities
• Land or lithosphere also has concern since
construction of power units, colony, ash bund etc.
require acquisition of land.
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4. LAWS PERTAINING TO ENVIRONMENT
PROTECTION
There are four laws/acts under which an industrial
unit has to operate. They are
• WATER POLLUTION CONTROL ACT,
• AIR POLLUTION CONTROL ACT,
• ENVIRONMENT PROTECTION ACT,
• HAZARDOUS WASTES (MANAGEMENT AND
HANDLING) RULES 1989,
• MANUFACTURE, STORAGE AND IMPORT OF
HAZARDOUS CHEMICALS RULES 1989.
The acts are being modified as the need felt.
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5. WATER POLLUTION CONTROL ACT
• Water Pollution control act is meant to prevent
pollution of water bodies. Water bodies include
rivers, lakes, surface drains and also ground
water.
• Discharge of domestic and industrial wastes on
land may flow into water bodies indicated above
either directly or indirectly.
• This may defeat the designated use of that source
either for drinking /industrial /agricultural
purposes by changing its natural composition.
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6. AIR POLLUTION CONTROL
• Air pollution control efforts by industries also are being
supervised by Pollution Control Board. They measure stack
emissions and if the values exceed 150 mg/m3 for particulate
matter or SO2 and NOx then the industry is being warned.
• It also has defined stack height calculation formula as
H = 14(Q)0.27, where Q is SO2 emission in kg/hr and that stack
height should not be less than 30m.
• If coal is the fuel, the stack height should be calculated by the
formula H(m)=74 x (Q)0.3 where Q is the particulate matter
emission rate in Kg/hour.
• The SPM limits may be reduced for the reduction in pollution.
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7. Handling of Hazardous Waste
• Hazardous Waste Rules include list of materials which have been
classified as hazardous. Such material includes inflammable,
corrosive, capable of producing highly acidic or alkaline
leachates or polluting waste water. Toxic or oily and tarry
material is also included.
• Pollution control boards visit and verify if an industry is
producing, storing, handling treating and transporting any of the
hazardous material. If yes, then verify if it is being carried out in
environmentally compatible manner or not. Then the board will
issue Authorization letter in which several conditions are
prescribed. This is to be renewed every two years.
• Sludge from ETP, chlorine gas, hydrochloric acid are examples of
hazardous material.
• Thermal Power Plant will have to comply with these rules/acts.
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8. Environmental Protection Rule
Parameters Standards
Condenser cooling water
PH 6.5 – 8.5
Temperature (For once through cooling
system)
Not more than 50C Higher than the intake water
temperature.
Free available chlorine 0.5
Boiler Blow down
Suspended Solids. 100
Oil & Grease 20
Copper 1.0
Iron 1.0
Cooling Tower Blow down
Free available chlorine 0.5
Zinc 1.0
Chromium 0.2
Phosphate 0.2
Other Corrosion Inhibiting Material Yet to be established
Ash Pond Effluent
PH 6.5 – 8.5
Suspended solids 100
Oil and Grease 20
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9. WATER QUALITY
Water is the next important
input other than coal during
thermal power generation.
Water quality and quantity is
decided as per the use to which
water is put to.
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10. WATER QUALITY REQUIREMENTS
USE QUALITY REQUIREMENT
1. Steam generation Demineralised water, conductivity less than 1.0
us, pH 8.9 – 9.2, silica 0 mg/L
2. Cooling water Hardness 0, Langelier Index +0.2.
3. Drinking water Wholesome; palatable, colourless, odorless,
transparent, without disease causing bacteria,
and without toxic elements, without algae.
4. Ash handling Raw or untreated water.
5. Fire fighting Raw or untreated water.
6. Coal handling plant
for quenching of
coal.
Raw or untreated water.
Following table gives a synopsis of water uses
and of water quality requirements.
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11. WATER SOURCES
• Out of three type of water sources (surface, ground
and oceans), surface sources are preferred since they
have less ionic loads & are replenished by rain water.
But they can be polluted and / or depleted due to ovel
abstraction during poor replenishment by rain.
• Water from surface sources needs treatment
1.For removal of suspended impurities,
2.Removal of dissolved solids for boiler and condenser
uses and
3.For removal of disease causing bacteria.
These impurities and method of their removal is given in
the next slide.
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12. WATER IMPURITIES & REMOVAL
Impurities Methods of Removal
Suspended Settle-able solids. Gravity settling in one day
reservoir.
Suspended colloidal & near
colloidal size particles.
Chemical treatment coagulation,
flocculation, settling, filtration.
Dissolved solids. Demineralization.
Cations – Calcium, magnesium,
sodium, potassium.
Cation exchanger.
Anions – Bicarbonate, sulphate
chloride, silica, etc.
Strong and weak base anion
exchanger.
Hardness causing calcium,
magnesium.
Cation exchanger on sodium
cycle.
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13. REMOVAL OF MICRO ORGANISMS
Bacteria Effect Method of Removal
Salmonella Typhi Typhoid fever. Disinfection by chlorine /
ozone / uv of water.
Salmonella paratyphi Paratyphoid ---- do -----
Salmonella SP Food poisoning. ---- do -----
Shigella dysenteric Bacillary dysentery ---- do -----
Vibrio choleac Cholera ---- do -----
Viral
Virus Infections
hepatitis/Jaundice
---- do -----
Polio virus Poliomyelitis ---- do -----
Coxsackie ECHO, adeno & rota. Gastroenteritis ---- do -----
Protozoan
Amoebic histolytic Dysentry ---- do -----
Giardiacysts Giardiasis ---- do -----
Endomocba Coli Gastroenteritis ---- do -----
Bacteria Effect Method of Removal
Salmonella Typhi Typhoid fever. Disinfection by chlorine /
ozone / uv of water.
Salmonella paratyphi Paratyphoid ---- do -----
Salmonella SP Food poisoning. ---- do -----
Shigella dysenteric Bacillary dysentery ---- do -----
Vibrio choleac Cholera ---- do -----
Viral
Virus Infections
hepatitis/Jaundice
---- do -----
Polio virus Poliomyelitis ---- do -----
Coxsackie ECHO, adeno &
rota.
Gastroenteritis ---- do -----
Protozoan
Amoebic histolytic Dysentry ---- do -----
Giardiacysts Giardiasis ---- do -----
Endomocba Coli Gastroenteritis ---- do -----
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14. Waste Water Sources in a Power
station.
S.N. Source Characteristics
1. Water Treatment Plant
Clarification/sedimentation. High concentrations of suspended solids
(SS).
Filter back wash High concentrations of suspended solids
(SS).
2. Demineralization Plant.
Regenerant washes from cation exchanger. Highly acidic, total dissolved solids (TDS)
Regenerant washes from anion exchanger Highly alkaline, total dissolved solids.
Regenerant washes from Softener Saline Water
3. Cooling tower Blow down High TDS, algae, pH
4. Boiler blow down. High S.S.
5. Colony waster / sewage. High organic matter, S.S., disease causing
organisms.
6. Ash Handling Plant (AHP) High S.S.
7. Coal Handling Plant (CHP) High S.S.
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15. EFFECTS OF WASTE WATER AND
TREATMENT METHODS
Sr. No. Waste Water
Source
Effects on Method of Treatment
Water Land
1 W.T.P. Addl. Turbidity. Water Logging Settling, decantation & reuse of
supernatant. Solids on sludge drying
beds.
2 D.M./Softener
Plants.
Increase in acidity/
alkalinity
Ground water
Contamination
Dilution, neutralization.
3 C.T. Pond blow-
down.
Increase in algae Water logging Destruction of algae /dilution &
reuse for ash handling.
4 AHP/ CHP Siltation Water Logging Settling, Decantation, and reuse of
supernatant for ash handling.
5 Sewage Biological pollution. Soil sickness, ground
water contamination
Biological treatment for removal of
organic matter, disinfection and
reuse for ash handling OR Dilution
and use for ash handling.
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16. SCHEME FOR REUSE & RECYCLE OF
WASTE WATER IN T.P.S.
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17. AIR POLLUTION
• Air pollution is the presence of one or more air contaminants e.g. dust,
fumes, gases, mist, odour, smoke. They should be present in sufficient
quantities, of such characteristics and of such duration so as to be or
likely to be injurious to plant & human life, animal life, property or may
interfere with the comfortable enjoyment of life.
• Concentrations of air pollutants can be expressed in ppm or μg/m3
which are related as under :
• There are three sources of air pollutants. They are mobile, stationary
and fugitive. Emissions from these are suspended particulate matter
(SPM), oxides of nitrogen ((NOx)), sulphur dioxide (SO2), respirable
particulate matter (RPM) and hydrocarbons. There is a perpetual
increase in concentrations of these pollutants.
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18. Computed global Pollutants increase
per year
Sr.
No.
Source CO SPM SO2 HC NOx Total Million
Tonnes/yr
1. Mobile 69.1 1.4 0.9 7.8 9.1 88.3
2. Stationary 2.1 1.4 19.0 0.2 10.6 33.3
3. Fugitive
Industrial
operations
5.8 3.7 3.8 10.8 0.7 24.8
Solid Waste
Disposal
2.2 0.4 0 0.6 0.10 3.3
Forest fire,
agriculture
burning.
6.2 0.9 0 2.4 0.2 9.7
Total 85.4 7.8 23.7 21.8 20.7 159.4
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19. Air Pollutants
There are two types of air pollutants as under :-
• Primary:- Emitted directly in atmosphere e.g. SPM, SO2, NOx, HC.
• Secondary:- O3, Peroxyacetyl Nitrate(PAN) Due to
photochemical reactions.
Examples of primary pollutants are :
• SPM - Dust, Smoke, fumes, fly ash, mist, spray
• Organic matter - benzene, methane, hexane
• Inorganic matter - CO, CO2 , SO2 , NOx , HF
Fly ash is finely divided into non-combustible particles arising along
with gases from coal combustion & has particle size between 1-
1000 micro meters and it can be airborne if it is less than 1-20
micrometer and settable particles are more than 10 micrometer.
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20. Effects of Air Pollutants
Name of
Pollutant
Effect
Particulate
matter
Visibility of air reduced, is more harmful in presence of
gaseous pollutants, and affects respiratory system.
Particles over 10 μm arrested by hair in the nose, between
2 & 10 μm arrested by cilia movement & lymphocytes and
phagocytes in lungs protect from particles of < 2 μm
Carbon
monoxide
CO in blood affects hemoglobin. Plants are insensitive
absorbed by lungs therefore oxygen carrying capacity of
blood stream is decreased and visual discrimination.
HC Photochemical smog, eye irritation.
Pb Anemia defects, brain effects
NOx Respiratory disorders.
Note:- Two pollutants together would be more harmful than an individual.
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21. Ambient Air Quality (AAQ)
• Ambient Air Quality (AAQ) has to be regularly and scientifically
monitored.
• Emissions from stack and fugitive sources in an industry have to be
measured, similarly contributions by mobile sources have to be
computed from standard emission factors for different vehicles and
from traffic density.
• Resultant AAQ is then compared with the National AAQ standards
to decide if air quality is affected or not.
• AAQ must be monitored within the premises and a record is being
maintained. This data is used to calculate Pollution Standard
Indices.
• Central Pollution Control Board has divided regions into Industrial,
Residential / Rural and sensitive area in which the criteria pollutants
should not exceed the limits given in following table in the next
slide.
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22. National Ambient Air Quality
Standards (NAAQS)
Pollutant
Time weighted
Averate
Concentration in Air (μg / m3 )
Industrial
Areas
Residential
Rural & Other
Areas
Sensitive
Areas
Oxides of Nitrogen (Nox) Annual Average 80.0 60.0 15.0
24 hrs. 120.0 80.0 30.0
Sulpher di oxide (SO2) Annual Average 80.0 60.0 15.0
24 hrs. 120.0 80.0 30.0
Suspended particulate
matter(SPM)
Annual Average 360.0 140.0 70.0
24 hrs. 500.0 200.0 100.0
Respirable particulate matter
(RPM) size < 10 μm
Annual Average 120.0 60.0 50.0
24 hrs. 150.0 100.0 75.0
Lead (Pb) Annual Average 1.0 0.75 0.50
24 hrs. 1.50 1.0 0.75
Carbon monoxide (CO) 8 Hours. 5000.0 2000.0 1000.0
24 Hours. 10000.0 4000.0 2000.0
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23. Pollution Standard Indices (PSI)
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24. Stack Emmissions
• Stack emissions or chimney emissions are being regularly
monitored by thermal power station (TPS) authorities by using
special kits.
• Emissions in (TPS) are being controlled by electrostatic
precipitators (ESPs) and some times by fabric filters.
• ESPs trap particles of size exceeding 1 micron with an efficiency
of above 99 percent. But these are costly and are sensitive to
duct load, flow rates and ash resistivity problems.
• Fabric filters have efficiency over 99 percent and can trap
particles of less than 1 micron size. It is sensitive to filtration
velocity, cooling of gases is required upto 100-1400 C.
• Humidity affects the performance since head loss can increase.
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25. Solid Wastes Management & Disposal
• Solid waste generation is intrinsic to both human and industrial activities.
• Whereas domestic solid wastes comprise of plastic, rags, paper, glass, metals etc.
Industrial solid waste includes scrap, boiler ash, sludges, packing materials, coal rejects
etc.
• Method of management of solid wastes depends on the source, characteristics
quantity.
• Incineration is a method in which solid waste with adequate calorific value is burnt in
presence of excess oxygen like coal in thermal power plant. The products of combustion
can be CO2 , SO2 , NOx etc. depending on composition of solid waste.
• Pyrolysis is a method in which solid waste is burnt/coalifield in limited supply of
oxygen. Products are coal and gases for example in coke oven battery of a steel plant
coal is converted to coke and gases like pyridine, benzene, xylene etc are recovered.
• Sanitary Land Fill by appropriate material is another method of disposal of solid waste
wherein low lying areas are filled with alternate layers of soil e.g. ash slurry is being
deposited over undulated land. Abandoned mine pits can be used for the purpose and
they can be converted into green land by plantation since fly ash contains essential
nutrients like N, P, K and also micro nutrients like copper, iron, zinc, manganese and
cobalt.
• Compositing of domestic refuse/garbage is being practiced by agriculturists.
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26. NOISE POLLUTION
• It is included as a environmental pollutant because it can lead
to hearing loss, hypertension and interference to
communication & sleep. These effects depend on the type of
exposer, to the noise level and individuals reactions.
• All modern Gadgets generate noise of different types. The
types of noises are continuous & sudden. Human response is
different to these noises.
• Intensity of noise is measured in terms of decibles dB(A).
• A decible is a unit of sound pressure equal to 20 time the log
(base 10) of the magnitude of a sound pressure P to the
reference sound pressure Pr. (Reference pressure in air is
0.00002 Newtons).
• Noise has frequency intensity, and pressure attributes.
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27. NOISE POLLUTION
• Higher the noise more is the decible readings on a
noise meter, which measure the sound level. It is
necessary to have a source of noise, a medium for
propagation of sound waves and a receptor for noise
pollution to occur.
• Modification of all these three or one is necessary to
control exposer to higher noise level e.g.
• An air condition unit can have split, compressor, and
cooling arrangement.
• Propagation of sound waves can be arrested by
absorbing media like wood, trees etc.
• Protect the receptor by ear mask.
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28. NOISE POLLUTION
• Some typical noise levels in T.P.S. are :-
• Permitted exposer levels.
• These levels will vary with acoustics of each power station.
dB Hrs.
T.G. Floor 90 - 92 dB 90 8 hrs.
Cooling Towers 80 – 85 dB 92 6 hrs.
Automobile Horns. @ 90 dB 95 4 hrs.
Auditorium @ 30 dB - -
Boiler steam blowing above 130 dB 115 < 15 min.
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29. Efforts towards Environmental
Management
• All T.P.S. shall provide arrangement for recycle & reuse of waste water
for ash handling to conserve fresh water.
• Extensive plantation is carried out within the premises.
• Performances of E.S.P. regularly monitored and stack emission is
controlled to the levels so as not to alter ambient air quality around
T.P.S.
• Extraneous Air pollution sources around T.P.S. to be identified and
removed. (Generally domestic coal shegadies used by the residents).
• Awareness programmes to be arranged for engineers and staff of
power stations to invite active participation of staff.
• Plantation on ash bunds can be thought off to arrest fugitive dust from
the bunds.
• Ground water potential around ash bunds can be reused as fresh water
for ash handling.
• Uses of Fly Ash to be increased.
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