NICMAR

ENVIRONMENTAL CHALLENGES IN POWER

PROJECTS

By

VAMSIMOHAN VOGETY, P51071

SURESH GUNDETI, P51066

OBEROY DEVABHAKTUNI, P51037

PGP- PEM 5th Batch2009-11

A Thesis submitted in partial fulfillment of the Academic requirements for the Post Graduate Programme in Project

Engineering and Management

(PGP PEM)

DECLARATION

We declare that the research thesis entitled “Environmental Challenges in Power Projects” is a

bonafide work carried out by us, under the guidance of Prof. A. K. Garg. Further we declare that

this has not previously formed the basis of award of any degree, diploma, associate-ship or other

similar degrees or diplomas, and has not been submitted anywhere else.

Date: 9th April 2010 Mr. Vamsi Mohan Vogety

Mr. Suresh Gundeti

Mr. Oberoy Devabhaktuni

PGP PEM 5th Batch (2009-2011)

NICMAR Pune

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CERTIFICATE

This is to certify that the research thesis entitled “Environmental Challenges in Power Projects”

is bonafide work of Mr. Vamsi Mohan Vogety, Mr. Suresh Gundeti, and Mr. Oberoy

Devabhaktuni in partial fulfillment of the academic requirements for the award of Post Graduate

Programme in Project Engineering and Management (PGP PEM). This work is carried out by

them, under my guidance and supervision.

Date: Prof. A. K. Garg

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ACKNOWLEDGEMENT

It is our sincere feeling of respect to express our gratitude to National Institute of Construction

Management and Research, PUNE for giving us an opportunity to carry out this project.

At the outset, we would like to thank Dr. Mangesh G. Korgaonker, Director, NICMAR PUNE

for giving us an opportunity to explore the implications of the course in real-time infrastructure

projects through mini thesis.

We would like to thank Prof. Vivek C Datey, Deputy Dean, PGP-PEM, and Prof. Deshpande,

Head, PGP-PEM, National Institute of Construction Management and Research, PUNE for

extending their complete support and encouraging us in every aspect related to mini-thesis that

enabled us to put our best efforts.

We wish to avail this opportunity to express our deep sense of gratitude to our guide Prof. A. K.

Garg, National Institute of Construction Management and Research, PUNE for sparing his

valuable time in providing suggestions and guiding us in carrying out research work.

Mr. Vamsi Mohan Vogety

Mr. Suresh Gundeti

Mr. Oberoy Devabhaktuni

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TABLE OF CONTENTS

ABSTRACT…………………………………………………………………………………......6

SECTIONS

1. Introduction…………………………………………………………...……………………...7

2. Process of power generation in coal based thermal power station…………………………...9

3. Emissions in power plant...………………………………………………………………….11

4. Impact of Emissions on Environment…………………...…………………………………..12

4.1. Nitrogen Oxides……………………………………………………….………………..12

4.2. Particulate Matter……………………………………………………………………….13

4.3. Sulphur Oxides…………………………………………………………………………14

4.4. Carbon Emissions……………………………………………………………………….14

5. How to deal with environmental challenges? ………………………………………………15

5.1. Advanced technologies…………………………………………………………………15

5.2. Improvising the process of generation by controlling the major pollutants…………....18

6. Capturing Emissions……………………………………………………………………........22

7. Power generation through renewable sources of energy…………………………………….24

8. Tables related to emissions……………………………………………………………..…....28

9. References…………………………………………………………………………………...32

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ABSTRACT

Today, world is facing lot of environmental challenges. The main reason for this is the increasing

activity of human in almost every activity on earth. This is being done in order to meet the

demand for basic needs of human. One such primary requirement for human and for carrying out

any activity on earth is the availability of power. Power is generated from power stations. Every

power station requires fuel for combustion and 70% of power stations in world use coal as fuel

which upon combustion releases potentially harmful emissions into the environment. Power

generation is a confluence of different technologies and processes. Various activities involved in

the process of generation release effluents into the environment which weren’t taken care of until

till recent times wherein pollution has reached alarming levels. At this juncture, we would like to

highlight the fact that power plants are one of the major contributors to environmental pollution.

Our thesis work is focused on what are the various challenges possessed by power plants. For

our thesis, we considered coal fired thermal power stations for explanation as other types of

power plants doesn’t release emissions as much as that by coal based thermal power stations. We

had also laid emphasis on how to reduce these emissions and what are various technologies

being adopted to reduce emissions.

In the end, we have given a comprehensive list of emission standards related to power plants that

are prescribed by International Energy Agency.

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1. INTRODUCTION

Today, India accounts for 3 – 4 % of global GHG emissions. It is estimated that coal power

plants are responsible for 93 percent of the sulfur dioxide and 80 percent of the nitrogen oxide

emissions generated by the electric utility industry. Therefore, saving environment has become

one of the primary tasks of any government/organization today. The Kyoto-protocol, the

Copenhagen meets, policies of IPCC (International Panel on Climate Change) are all concerned

about the same.

With heavy demand arising for the requirement of power in India, a huge expansion in power

projects is on its way. As per the projections, in India, an expansion of around 100000 MW is

envisaged in next 10 years. Assuming that the power expansion is as per projection or more,

rapid construction of mega power projects is on its way. Many of the projects are under

construction and many more are expected to start in few years. As already mentioned, power

plants are known to contribute a lot to environmental pollution and with heavy expansion

envisaged, there is an imminent need to direct our thought process on few questions which are

mentioned below:

a) What are the various hazardous emissions released from the power plants? What are its

effects on environment? How can they be controlled?

b) In India, almost 70% of power production is through coal based generation. With coal

running out of stock, how to meet with the shortage of materials esp. coal? What would

be the green alternatives?

c) Every organization is now concentrating on reducing emission targets and trying to keep

a limit on carbon dioxide, nitrogen oxides, sulfur dioxide, particulate matter and mercury

etc. To maintain the desired levels of targets, the companies may have to reduce the

production. Won’t this be paradoxical when a huge expansion is envisaged?

The above questions pose a challenge to the industry today. Organizations are facing catch-22

situation today. On one side, they want to expand the capacity heavily. On other hand, they

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pollution has already reached an alarming stage and therefore every organization is striving to

reduce pollution.

Fig 1: Carbon dioxide emissions by regions

Fig 2: Energy demand in Million ton of oil equivalent (1 toe = 11630KWHr)

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2. PROCESS OF POWER GENERATION IN COAL BASED THERMAL POWER STATION

In order to study on emissions, let us first understand the process of power generation through

coal based thermal power station. A diagram of typical coal-based thermal power station has

been shown as an attachment.

Description of components:

1. Cooling tower 10. Steam governor valve 19. Super heater

2. Cooling water pump 11. High pressure turbine 20. Forced draught fan

3. Transmission line (3-phase) 12. Deaerator 21. Reheater

4. Unit transformer (3-phase) 13. Feed heater 22. Air intake

5. Electric generator (3-phase) 14. Coal conveyor 23. Economizer

6. Low pressure turbine 15. Coal hopper 24. Air preheater

7. Boiler feed pump 16. Pulverized fuel mill 25. Precipitator

8. Condenser 17. Boiler drum 26. Induced draught fan

9. Intermediate pressure turbine 18. Ash hopper 27. Chimney Stack

Description of process from coal to electricity:

The process of a typical coal-fired thermal power plant is as described below:

Coal is conveyed (14) from an external stack and ground to a very fine powder by large

metal spheres in the pulverized fuel mill (16). There it is mixed with preheated air (24)

driven by the forced draught fan (20). The hot air-fuel mixture is forced at high pressure into

the boiler where it rapidly ignites.

Water of a high purity flows vertically up the tube-lined walls of the boiler, where it turns

into steam, and is passed to the boiler drum, where steam is separated from any remaining

water.

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The steam passes through a manifold in the roof of the drum into the pendant super heater

(19) where its temperature and pressure increase rapidly to around 200 bars and 570°C,

sufficient to make the tube walls glow a dull red.

The steam is piped to the high-pressure turbine (11), the first of a three-stage turbine process.

A steam governor valve (10) allows for both manual control of the turbine and automatic

setting.

The steam is exhausted from the high-pressure turbine and reduced in both pressure and

temperature and the steam is returned to the boiler reheater (21). The reheated steam is then

passed to the intermediate pressure turbine (9), and from there passed directly to the low

pressure turbine set (6).

The exiting steam, now a little above its boiling point, is brought into thermal contact with

cold water (pumped in from the cooling tower) in the condensor (8), where it condenses

rapidly back into water, creating near vacuum-like conditions inside the condensor chest.

The condensed water is then passed by a feed pump (7) through a Deaerator (12), and pre-

warmed, first in a feed heater (13) powered by steam drawn from the high pressure set, and

then in the economizer (23), before being returned to the boiler drum.

The cooling water from the condensor is sprayed inside a cooling tower (1), creating a highly

visible plume of water vapor, before being pumped back to the condensor (8) in cooling

water cycle.

The three turbine sets are coupled on the same shaft as the three-phase electrical generator

(5) which generates an intermediate level voltage (typically 20-25 kV). This is stepped up by

the unit transformer (4) to a voltage more suitable for transmission (typically250 – 500 kV)

and is sent out onto the three-phase transmission system (3).

Exhaust gas from the boiler is drawn by the induced draft fan (26) through an electrostatic

Precipitator (25) and is then vented through the chimney stack (27).

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3. EMISSIONS IN POWER PLANT

Combustion of coal in thermal power plants releases lot of pollutants. The emissions are

considered to be responsible for heating up the atmosphere, producing a harmful global

environment. For easy understanding, we have divided thermal power station into various units

and emissions released from each of the units have been mentioned.

Type of handling

system

Components

responsible for

emissions

Emissions from the components

BTG system Boiler Carbon dioxide (CO2), nitrogen oxides (NOx), sulphur

dioxide (SO2), particulates, carbon monoxide(CO),

dioxins, heavy metals, fly ash(contains mercury, a

potentially dangerous element)

CW system Cooling tower,

Condenser

Particulate matter(PM10), toxic air contaminant

(Legionella, a genus of bacteria that causes

legionnaire's disease, has been found in the drift

droplets) , hydro carbon emissions

Coal handling

plant

Coal yard, Mill

reject system

Particulate matter (PM), dust

Ash handling

plant

ESP, Flue gas

stack

Particulate matter (PM) and carbon soot, carbon

monoxide (CO), nitrogen oxides (NO, NO2), sulphur

oxides (SO2, SO3)

Fuel Diesel, mainly

HSD (high-

speed diesel)

and furnace oil

Sulphur dioxide (SO2), nitrogen oxides, carbon

monoxide (CO), nitrogen oxides (NOX), non-methane

hydrocarbons / voc, and diesel soot/ particulate matter

(PM10)

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4. IMPACT OF EMISSIONS ON ENVIRONMENT

Various emissions released from power plant can be categorized as following:

a) Nitrogen Oxides

b) Particulate matter

c) Sulphur Emissions

d) Carbon Emissions

4.1. Nitrogen Oxides

The release of nitrogen into our environment has more than doubled over the past century

contributing to problems such as ground level ozone, acid rain and other environmental

challenges. Emission from power plants is one of the largest sources of Nitrogen oxides. Power

Plants release millions of tons of Nitrogen Oxides into the air. 30% of emissions from power

plants are Nitrogen oxides.

4.1.1. Ill effects of Nitrogen oxides

1) Nitrogen dioxide causes respiratory ailments:

a. Nitrogen oxides are dangerous when inhaled. When they are released from power

plants into nearby neighborhoods, they are associated with respiratory side effects

such as asthma attacks.

b. Nitrogen oxides form small nitrate particles that are associated with serious health

impacts like heart attacks and result in hazy skylines in our cities and national

parks.

2) Nitrogen oxides contribute to unhealthy ozone levels:

a. Ozone pollution (ground level ozone or smog) is a very strong airborne oxidizing

agent. It is formed when nitrogen oxides reacts with hydrocarbons in the presence

of heat and sunlight. Ozone at ground level is linked with asthma attacks and even

birth defects and also retards growth of trees and crops.

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3) Nitrogen oxides contribute to dangerous fine particulate matter pollution. The effects of

particulate matter are discussed later.

4) Loss of species diversity and loss of balance of ecosystem: Nitrogen oxides lead to

pollution of soils, groundwater and estuaries. Nitrate particles can form nitric acids in the

atmosphere contributing to acid rain and overloading ecosystems with nitrogen,

effectively over-fertilizing them.

4.2. Particulate Matter

Particulate matter is usually defined as PM10 or PM25 which means diameter of particulate

matter is less than 10 or 25 micrometers respectively. Power plant usually releases PM10 or

PM25. Particulates are released chiefly because of sulphur burning.

Inhalation of particulate matter causes heavy damage to health and sometimes may prove to be

fatal. Particulate matter is composed of many chemical compounds. The main component of

particulate matter in power plant is fly ash. Various components of fly ash are:

SiO2 - 51.4% by weight

Al2O3 - 22.1% by weight

Fe2O3 - 17.2% by weight

Many toxic elements and heavy metals are highly enriched in the fly ash relative to the

original coal. For example, considerable amounts of Beryllium – Be (16.4ppm), Copper

– Cu (106ppm), Zinc – Zn (578ppm), Arsenic – As (40.4ppm), Cadmium – Cd

(2.6ppm), Mercury – Hg (18ppm), Lead – Pb (71ppm), and Uranium – Ur (21.8ppm) is

found in fly ash

The release of ash pond decant into the local water bodies - water dries up, dust nuisance,

increases turbidity, decreases primary productivity, affects fishes and other aquatic biota. When

fly ash comes into contact with water, it leaches into groundwater supplies which get polluted

and unsuitable for domestic use

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Large amount of land is used to dispose fly ash from the coal based plants. Due to this, there is

change in natural soil properties. It becomes more alkaline due to the alkaline nature of fly ash.

Soft bodied soil workers like earthworms will die out.

4.3. Sulphur Oxides

Oxides of sulphur are released from boiler, fuel burning, and ash handling plant. Power plants

burning coal transform sulphur in the fuel to sulphur oxides. The major chemical form emitted

by power plants is sulfur dioxide or SO2, sulfur trioxide SO3, another form of SOX constitutes

approximately 0.5% to 2% of the SOX.

The conversion of SO2 emissions to sulphate particles can contribute to the mass of fine particles

in the atmosphere.

The main concern of sulphur emissions is acid rain. However, increasing coal use or blending

Indian coal with imported coal of higher calorific value (further increasing electricity production)

needs to be carefully addressed through viable technological options. Average SO emissions per

unit of electricity are 0.0069 Gg. Total SO emissions from all the power plants in India are

estimated at 0.007 Teragrams (Tg) per day or 2.7 Tg per year.

4.4. Carbon Emissions

Carbon monoxide (CO) and Carbon dioxide (CO2) are the main emissions from coal combustion

at thermal power plants. Utilities burn mostly coal with approximately 10 – 30% excess air. The

total carbon is converted to CO after the reaction (combustion) is complete. Total CO emissions

from all the power plants in India are estimated at 1.1 Teragrams (Tg) per day or 397 Tg per

year. Average CO emission per unit of electricity is 1.04 Gig grams (Gg). Both CO and CO2

emissions are green house gases. These emissions are considered to be responsible for heating up

the atmosphere, producing a harmful global environment.

Ill effects of CO and CO2:

a) Carbon dioxide is the main green house gas responsible for global warming

b) Carbon monoxide when inhaled reacts with blood and forms carboxy haemoglobin which

blocks blood flow in the body causing death.

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5. HOW TO DEAL WITH ENVIRONMENTAL CHALLENGES?

A brief description has been mentioned about different emissions from thermal power plants

from where these emissions are generated and the ill effects of these emissions. The alarming

level of pollution reminds us about the importance of improving the efficiency of coal fired

power plants and the minimization of their environmental impacts, for both economic and

environmental reasons. A number of pollutants emitted from coal fired power plants require due

consideration, although effective means for their control already exist in some cases. For

instance, systems exist to control emissions of sulphur (SOX) and nitrogen oxides (NOX), or

particulates. Power plants emit large quantities of CO2. With few exceptions, however, CO2

control technologies have not been adopted. And yet, incentives can be introduced for deploying

technologies that lower, or even eliminate, CO2 emissions.

Once the ill effects of the emissions are understood, it is very important to understand how to

mitigate the risks or dangers associated with the emissions. It is clear that the emissions can’t be

reduced to zero levels. However, now that the emissions have reached an alarming stage, effort

has to be put in to reduce the emissions. Some of the ways through which the emissions can be

reduced are:

a) By using advanced technology

b) By improving the process of generation

c) By capturing the emissions and proper disposal/treatment of the emissions

d) By re-utilization of the emissions

e) By emphasizing usage of non-conventional sources of energy to generate power

5.1. Advanced technologies:

1. Clean coal technology: A range of technologies has been developed to minimize the

emission of a variety of undesirable substances emitted from coal-fired power plants. One

such technology is Clean Coal technology. CCT is a technology which, in an

economically viable manner, reduces plant emissions to enable the facility to meet or

exceed any emissions standards in force. CCTs are becoming increasingly important, as

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they provide a means for coal-fired plant to meet the requirements of the increasingly

stringent environmental legislation applied in many countries.

2. Pulverized Fuel: A number of types of coal-fired power plant technology are currently

deployed around the world. In terms of potential for further significant development in

future, efforts are focused largely on pulverized fuel (PF) and integrated gasification

combined cycle (IGCC) systems. In terms of both number of plants and installed

capacity, PF plants dominate the world electricity generating market. PF-based plant is

found throughout the world and is in widespread use in both developed and developing

nations. In operation, coal is burned in a boiler that raises high-pressure steam. This is

then passed through a steam turbine and used to generate electricity. Over the years,

many advances have been made to PF plant technology, including environmentally-

focused measures to minimize emissions of SO2, NOX and particulates, also the

application of advanced steam cycles that allow for greater plant efficiency. Typical PF

plant is characterized by overall thermal efficiencies of some 36% (Lower Heating Value

– LHV - basis), but in some developing nations this figure can be much lower. Plants

with higher steam temperatures and pressures can attain up to around 45% and, as further

developments take place, efficiencies of 50-55% may ultimately be achieved. The more is

the efficiency, the lesser is the release of emissions into the environment.

3. IGCC: In integrated gasification combined cycle (IGCC) plants, coal is reacted with

steam and oxygen in a gasifier, generating a fuel gas that consists predominantly of CO

and hydrogen. This gas is cleaned using a number of available techniques and burned in a

gas turbine. The exhaust heat is used to drive a steam cycle, producing additional

electricity. IGCC plants allow high efficiencies to be attained even when using low grade

coals.

4. FBC: Fluidized bed combustion (FBC) technology is the most important, being applied

often to niche markets for co-firing of coals with various waste streams. Of the FBC

variants employed, circulating FBC is most commonly encountered for power generation

purposes. There are a handful of pressurized (PFBC) plants in operation.

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A range of pollutants are generated from coal-fired power generating plants and some pollutants

are more specific to a particular unit/technology. Historically, attention has focused mainly on

controlling emissions of SO2, NOX and particulates. Numerous systems have been developed and

applied for their control. Some control specifically one type of pollutant, whereas others may

integrate several control systems, thus allowing for the control of two or more pollutants (e.g.

combinations of SO2, NOX and particulates). Here, a range of technologies are either being

demonstrated or applied commercially. Most on-going development work, for either one

pollutant or integrated control systems, is focused on increasing process efficiency and/or

reducing capital and operating costs, often through the adoption of simplified process design and

operation. To date, work has concentrated largely on controlling emissions of the more

traditional pollutants. However, emphasis has increased more recently on control strategies for a

range of other pollutant species that are present in lower concentrations.

When the addition of emissions control systems to a plant is being contemplated, a number of

issues require consideration in order to determine the most appropriate variant(s), and many will

reflect the configuration and age of the particular plant. Where, for instance, an ageing PF-fired

power plant is involved, there are several possible options that may be pursued. Clearly, if the

plant currently has little in the way of effective control systems, as may be the case in some of

the developing nations, an option is to retrofit off-the-shelf equipment, available on a turn-key

basis from many equipment vendors. But, if the plant is nearing the end of its working life and is

of low overall efficiency, it may be more cost-effective to re-power it with newer, more efficient

PF technology or a system based on fluidized bed combustion or IGCC technology; this is a

particularly attractive option for older plants and for those facing increasing power demands.

Such options can be effective for significantly increasing a plant’s efficiency, as well as reducing

its environmental impact. Where a newer, more efficient power plant is involved, it may be more

appropriate to upgrade or add to the existing emissions control systems, or to replace them with

more effective variants. Again, the replacement of the existing combustion plant may also be in

order. In most cases, the selection of appropriate emissions control systems will require

consideration on a case-by-case basis.

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5.2. Improvising the process of generation by controlling the major pollutants

a) Sulphur dioxide: This is a major precursor for acid rain formation and numerous

technical solutions have been developed and are widely applied today. Two basic

types of control system are used, one working internally and the other externally. In

both cases, these systems remove SO2 from combustion gases exiting the boiler. Some

flue gas desulphurization (FGD) systems operate within existing ductwork, primarily

in PF plant, and are capable of reducing SO2 emissions, typically by 50-70%. Where

larger plant is involved, FGD systems based on scrubber technologies are often used.

These are more efficient and can achieve reductions of up to more than 95%. The

extracted SO2 can be commercialized for use in producing gypsum. In some

countries, such as Germany, all major power plants are equipped with some form of

FGD systems. However, globally, application is patchy, especially in some of the

developing nations.

Fig 3: Large FGD unit fitted to a power plant in Japan

b) Nitrogen oxides (NOX):

Nitrogen oxides are also involved in the formation of acid rain, as well as

contributing to the formation of urban smog. In industrialized countries, NOXs from

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power plants are today captured on a broad scale. There are essentially three types of

techniques for controlling and minimizing NOX formation.

a. In the case of PF plant, NOX can be controlled through primary measures such

as air and fuel staging and other combustion modifications. Special designs of

low-NOX burners can be retrofitted, resulting in NOX reductions of up to some

60%.

b. A technique known as “re burning” can also be applied, whereby natural or

coal-derived gas is burned above the main combustion zone in such a way that

NOX is broken down into molecular nitrogen thus reduction levels of up to

70% can be attained.

c. There also exist several downstream NOX control measures which rely on the

injection of ammonia or urea into the flue gases. These are termed “selective

catalytic reduction” (SCR) and “selective non-catalytic reduction” (SNCR).

Such techniques can reduce NOX emissions by up to 90%, but they are more

expensive than other control measures.

c) Particulates:

Coal combustion inevitably produces small particles and as with other major

pollutants, numerous national and international limits are in force, limiting the levels

emitted into the atmosphere. Several main types of technology are used to control

particulate emissions from coal-fired power plants and large industrial processes.

These are described below.

a. Electrostatic precipitators (ESPs): These units rely on the transfer of an

electric charge to particles suspended in a gas stream and their subsequent

removal via an electric field to a suitable collecting electrode. They are widely

applied in power plants and are capable of achieving collection efficiencies of

more than 99.5%.

b. Fabric filters: Here, particles carried in a gas stream are retained as the

stream passes through multiple filter bags manufactured from high-

temperature synthetic fibers, usually at temperatures of up to some 300oC.

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Fabric filtration has found growing application for both utility and industrial

uses.

c. Wet particles scrubbers: A large number of variants (foam, film, spray

columns, etc) are available, most based on the use of a liquid medium to

collect flue gas particulates. They are used widely for industrial coal-fired

applications, but have also been used in high-temperature and pressure

applications, as in IGCC and pressurized fluidized bed combustion (PFBC)

plant. In some cases, particulate control may be combined with the removal of

other species such as SO2, HF and HCl.

d. Hot gas cleanup systems: This technology is considered to have significant

potential for application in some forms of advanced power generation.

Particles in the gas stream are trapped as the gas passes through a series of

porous filters (tubes, candles and other configurations) operating at 250-

400oC. These offer potential for significantly enhanced overall plant

efficiency. Several coal-fired IGCC plants have demonstrated treatment of

their gas streams using either porous ceramic or metallic hot gas filter units.

d) Control of other pollutants:

Efforts are being made, however, to control emissions of mercury, the element

currently of most concern. Coal-fired power plants and waste incinerators are

responsible for some 70% of global anthropogenic mercury emissions. Mercury is

difficult to control because, unlike other trace metals that tend to be present as

particulates, it is found in flue gas as a vapor (in either elemental or ionic form). As a

low concentration vapor (usually in the range 5-20 μg/m3), much of it passes through

particulate control devices such as fabric filters and ESPs. Although such

conventional control systems remove a certain percentage of mercury (ESPs can

remove roughly 24%, fabric filters roughly 28%), additional control measures are

required in order to achieve significant reductions.

Other emission control systems may also be effective in capturing some of the

mercury present. For instance, while FGD scrubbers are used to control SO2

emissions, there is also increasing interest in using these to remove simultaneously

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both SO2 and trace metals, including mercury (average mercury removal is around

34%).

A number of mercury capture methods are presently being deployed effectively on

waste incinerators. But, although new control systems are currently being developed

specifically for coal-fired power plant, these are not yet being deployed

commercially. For instance, through its Fossil Energy Program, the United States

Department of Energy is funding investigations into a range of technologies aimed at

developing more effective options that will reduce emissions by 90% by 2010.

Systems that show potential comprise: application of carbon filter beds (used for both

acid gas and mercury removal), use of special condensing heat exchangers located in

the flue gas stream, mercury capture based on the use of a noble metal, and carbon

injection. The latter involves direct injection of activated carbon into the flue gas

stream and it is the closest to commercialization.

e) Control of particulates:

Larger particulates can be controlled effectively by a variety of devices, but PM2.5 is

considerably more difficult to control. PM2.5 particles may often be a complex

mixture of pollutants emitted directly from combustion processes, whereas, in other

cases, gases like SO2, NOX and volatile organic compounds (VOCs) interact with

other compounds in the air to form fine particles. PM2.5s have been associated with a

number of harmful effects on human health and on ecosystems, also with contributing

to atmospheric haze and power plant plume opacity. The chemical and physical

properties of PM2.5s can vary significantly between regions, with particles often

containing varying levels of sulphate (from SO2), organic and elemental carbon,

nitrate and crustal materials derived from soil dust.

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6. CAPTURING EMISSIONS

Many systems for controlling the pollutants are already in widespread use in different parts of

the world. In parallel with the on-going drive for greater efficiency and lower costs for such

control systems, however, efforts are also being focused increasingly on the control and

minimization of CO2 emitted from coal-fired power plants

CO2 capture: The main approach to controlling CO2 emissions is to capture it from the

combustion flue gases. Some types of CO2 capture technologies (based on both chemical and

physical absorption) are well established and have been in use for several decades. The majority

of chemical-based methods rely on scrubbing systems that utilize amine solutions to remove CO2

from exhaust gases. Amine scrubbers have already been applied to different types of coal-fired

industrial process and power station. In most cases, the systems used are similar in concept and

configuration and usually employ a re-generable amine, such as mono-ethanolamine (MEA) as

the working solvent. Depending on the particular application and type of flue gas being treated,

such systems can recover up to 98% of the CO2 present, and produce a CO2 stream of up to 99%

purity. Historically, many processes have relied on MEA. Recently, however, more advanced

amines have been developed, for instance by Mitsubishi Heavy Industries (MHI), and are now

being applied commercially. Such new amines are claimed to suffer less degradation and to have

lower consumption rates and energy requirements than conventional MEA-based solvents;

significant improvements in performance have been reported. Here, technological developments

have been instrumental in both improving product quality and reducing operational costs.

A number of commercial-scale physical absorption-based technologies are also in use, generally

applied to systems operating at higher pressures. These rely on a range of solvents that include

methanol and propylene carbonate. For IGCC applications, processes based on the use of

proprietary solvents such as Union Carbide’s Selexol are considered to be the most applicable.

Such solvents are favored where high concentrations of CO2 are present in the flue gas stream.

They also impose low energy requirements on the system. In the United States, Selexol-based

systems have been demonstrated at the Texaco Cool Water IGCC plant and used commercially at

the Destec-based Plaquemine facility. In general, further development of physical solvent-based

systems would be advantageous in order to broaden their range of operating conditions.

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Alternative capture technologies that may also be applicable to coal-fired power plant in the

longer term include systems based on the application of specialized separation membranes and

cryogenic technologies. With the latter, CO2 can be separated from other gases through cooling

and condensation; cryogenic separation has been used widely for the purification of gas streams,

typically of high pressure and containing more than 90% CO2. The technology is less applicable,

however, to more dilute gas streams. Much further development will be required before such

systems can be considered for application to full-scale power generation facilities.

At this juncture, one should remember what the International Energy Agency has commented:

“Numerous technology solutions offer substantial CO2-reductions potential, including renewable

energies, fossil-fuel use with CO2 capture and storage, nuclear fission, fusion energy, hydrogen,

bio-fuels, fuel cells and efficient energy end use. No single technology can meet this challenge

by itself. Different regions and countries will require different combinations of technologies to

best serve their needs and best exploit their indigenous resources. The energy systems of

tomorrow will rely on a mix of different advanced, clean, efficient technologies for energy

supply and use.”

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7. POWER GENERATION THROUGH RENEWABLE SOURCES OF

ENERGY

Though our scope for mini-thesis is more on environmental challenges posed by power projects,

we would like to emphasize the usage of non-conventional sources to produce energy. Though

they require huge investments, over the time the cost per unit significantly reduces due to the

concept of “Learning Curves”. However, we have laid less emphasis to this topic in mini-thesis.

Naturally available resources like wind, sunlight, biomass, geothermal heat should be used to

generate power. Though the amount of energy generated by these resources is very less

compared to that from coal, government should take necessary steps to promote them.

a) Small scale industries should use the wastes generated to produce power through captive

power units. The more is the usage of captive units using wastes generated, the less is

their dependency on power and thus leading to reduction in demand, though minimal.

b) Power should be generated through Photo Voltaic cells. World Institute of Sustainable

Energy has mentioned that there is enough unutilized area available in India to generate

electricity sufficient for next 10 years. Government should ease policies and encourage

the use of renewable sources to generate electricity.

A recent development by Magenn power in power generation using wind is the MAGENN AIR

ROTOR SYSTEM. Magenn Power's MARS is a Wind Power Anywhere solution with distinct

advantages over existing Conventional Wind Turbines and Diesel Generating Systems including:

global deployment, lower costs, better operational performance, and greater environmental

advantages.

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Fig: Magenn Air Rotor System

MARS is a lighter-than-air tethered wind turbine that rotates about a horizontal axis in response

to wind, generating electrical energy. This electrical energy is transferred down the 1000-foot

tether for immediate use, or to a set of batteries for later use, or to the power grid. Helium

sustains MARS and allows it to ascend to a higher altitude than traditional wind turbines. MARS

captures the energy available in the 600 to 1000-foot low level and nocturnal jet streams that

exist almost everywhere.

The Advantages of MARS over Conventional Wind Turbines:

Wind Power Anywhere™ removes all placement limitations. Coast-line or off-shore locations

are not necessary to capture higher speed winds. Reaching winds at 1,000-feet above ground

level allow MARS to be installed closer to the grid. MARS is mobile and can be rapidly

deployed, deflated, and redeployed without the need for towers or heavy cranes. MARS is bird

and bat friendly with lower noise emissions and is capable of operating in a wider range of wind

speeds - from 4 mph to greater than 60 mph.

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The Advantages of a MARS combined Wind and Diesel Solution over a Diesel Generator-

only solution:

MARS can complement a diesel generator by offering a combined diesel-wind power solution

that delivers power below 20 cents per kWh. This compares to a wide range of 25 cents to 99

cents per kWh for diesel-alone, reflecting the high fuel and transportation costs in remote areas.

The MARS combined solution allows lower pollution and green house gas emissions. It also

results in lower handling, transporting, and storage costs.

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The Magenn Power Air Rotor System (MARS) is an innovative lighter-than-air tethered device

that rotates about a horizontal axis in response to wind, efficiently generating clean renewable

electrical energy at a lower cost than all competing systems. This electrical energy is transferred

down the tether to a transformer at a ground station and then transferred to the electricity power

grid. Helium (an inert non-reactive lighter than air gas) sustains the Air Rotor which ascends to

an altitude for best winds and its rotation also causes the Magnus effect. This provides additional

lift, keeps the device stabilized, keeps it positioned within a very controlled and restricted

location, and causes it to pull up overhead rather than drift downwind on its tether. This

technology is yet to take a dominant presence. MARS shows the potential of R & D.

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8. TABLES RELATED TO EMISSIONS

8.1 Emission standards of thermal power plants

Source Parameter Concentration limit not exceed, mg/l (except pH)

Condenser Cooling water

(cooling system)

pH

Temperature

Free available Chloride

6.5 to 8.5

Not more than 50C higher than the intake

0.5Boiler Blow

downSuspended solids

Oil & greaseCopper (Total)

Iron (Total)

100201.01.0

Cooling tower

Blow down

Free available chlorineZinc 

Chromium (Total)Phosphate

Other corrosion inhibiting material

0.51.00.25.0

Limit to be established on case by case basis by Central Board in case of Union Territories and

State Boards in case of StatesAsh pond effluent

pHsuspended solids

oil & grease

6.5 to 8.510020

Generation Capacity Pollutant Emission limitGeneration capacity 210 MW

or moreParticulate matter 150 mg/Nm3

Generation capacity less than 210 MW

Particulate matter 350 mg/Nm3

Depending upon the requirement of local situation, such as protected area, the State Pollution

Control Boards and other implementation agencies under the Environment (protection) Act 1986

may prescribe a limit of 150 mg/Nm3 irrespective of generation capacity of the plant

8.2 Thermal Power Plant: Stack Height/Limits

Generation Capacity Stack Height (meters)500 MW and above 275

200 MW/210 MW to 500MW 220Less than 200 MW/210 MW H=14(Q)03 where Q is emission rate of SO2

 in kg/hr, and H is Stack Height in meters.

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8.3. Options regarding the reduction of fine dust estimates in fossil fired large combustion

plants, excepting gas combustion plants

Thermal

combustion

Output

(MW)

Dust emission values(mg/Nm3)Options

achieving

these values

Hard coal Liquid boiler fuels

New

plants

Existing

plants

New

plants

Existing

plants

50-100 5-20 5-30 5-20 5-30 ESS or FF

100-300 5-20 5-25 5-20 5-25 ESS or FF in combination with

FGD (wet, hd or dai) for

SF,ESS or FF for FBF>300 5-10 5-20 5-10 5-20

Abbreviations:

1. Dai - Dry adsorbent injection

2. ESS - Electrostatic separator

3. FBF - Fluidized bed firing

4. FF - Fibrous filter

5. FGD - Flue gas desulphurization

6. Hd - Half-dry

7. SF - dust combustion

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8.4. Options regarding the reduction of SO2 emissions in coal combustion plants

Abbreviations:

1. CFBF - Circulating fluidized bed firing system

2. Dai - dry adsorbent injection

3. FBF- fluidized bed firing system

4. FGD - flue gas desulphurization

5. hd - half-dry

6. PFBF- Pressure fluidized bed firing system

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Thermal

combustion

Output

(MW)

SO2 emission values(mg/Nm3)

Option achieving these valuesHard and brown coal

New plants Existing plants

50-100

200-400

150-400

(FBF)

200-400

150-400Low-sulphur fuel or /and FGD

(dai) or FGD (hd) or FGD (wet)

(depending on the plant size).

Cleaners using seawater.

Combined process reducing NOX

and SO2 ,lime stone injection(FBF)

100-300 100-200 100-250

>300

20-150

100-200

(CFBF/PFBF)

20-200

100-200

(CFBF/PFBF)

8.5. NOx Emissions in hard Coal combustion plants using different combustion techniques

Thermal combustio

nOutput (MW)

Combustiontechnique

NOx emission values(mg/Nm3)

Option achieving these values

New plantsExisting plants

50-100

Grate firing 200-300 200-300Pm and /or SNCR

SF 90-300 90-300Combination of Pm and SNCR or

SCRSFBF&PFBF 200-300 200-300 Combination of Pm

100-300SF 90-200 90-200

Combination of Pm together with together with SCR or combined

processSFBF,CFBF&

PFBF100-200 100-200

Combination of pm together with SNCR

>300SF 90-150 90-200

Combination of pm together with SCR or combined process

SFBF,CFBF&PFBF

50-150 50-200 Combination of Pm

Abbreviations

1. CFBF - Circulating fluidized bed firing system2. PFBF - Pressure fluidized bed firing system3. Pm - Primary measures reducing the NOX

4. SF - Dust combustion5. SFBF - Stationary fluidized bed firing system6. SNCR - Selective non catalytic NOX reduction

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9. REFERENCES/BIBILOGRAPHY

[1] “Dew Journal” – A journal by Bentley infrastructure on news from power industry

[2] Article titled “Analysis of strategies for reducing multiple emissions from power plants”

published by Energy Information Administration, Department of Energy, Washington DC

[3] Article titled “Control and minimization of coal-fired power plant emissions” published

by Working party on fossil fuels, International Energy Agency

[4] Power plant performance reporting and improvement under the provision of the Indian

Energy Conservation Act as a part of Indo German Energy Program

[5] Article titled “Mid-west Nitrogen” by Clean Air Task Force

[6] Environmental Impact Assessment of Masinloc coal fired power plant project published

by Republic of Philippines

[7] Power plant engineering by Dr. P. K. Nag

[8] Environmental Engineering by Dr. A. K. Garg

[9] Websites:

[9.1] www.fossil.energy.gov

[9.2] www.enzenglobal.com

[9.3] www.wikipedia.org

[9.4] Electrical Power Research Institute, www.epri.com

[9.5] www.apgenco.gov.in

[9.6] Andhra Pradesh Pollution Control Board, www.appcb.ap.nic.in

[9.7] www.ntpc.co.in

[9.8] Central Power Ministry, www.powermin.nic.in

[9.9] Central Pollution Control Board, www.cpcb.nic.in

[9.10] Ministry of Environment and Forest, www.moef.nic.in

[9.11] Energy Information Administration, Department of Energy, US, www.eia.doe.gov

[9.12] International Energy Agency, www.iea.org

[9.13] Environmental Protection Agency, www.epa.gov

[9.14] Organization for Economic Cooperation and Development, www.oecd.org

[9.15] www.magenn.com

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