Chhabra Thermal Power plant Report by Chandramohan lodha

AIETM/CE/2016-17/P.T.I.V.
A
Practical Training and Industrial Visit Report
On
CHHABRA THERMAL POWER PLANT”
Submitted Partial Fulfilment for the award of the degree of
Bachelor of Technology
In
Civil Engineering
2016-2017
(1 June 2016 – 25 July 2016)
Submitted to:- Submitted by:-
Mr Gori ShankarSoni Chandra Mohan Lodha
Head of Department Roll No. : 13EAOCE016
Department of Civil Engineering Class : 4th year(7th sem.)
DEPARTMENT OF CIVIL ENGINEERING

ARYA INSTITUTE OF ENGINEERING TECHNOLOGY &
MANAGEMENT
OMAXE CITY, AJMER ROAD, JAIPUR, RAJASTHAN
RAJSTHAN TECHNICAL UNIVERSITY, KOTA

ARYA INSTITUTE OF ENGINEERING TECHNOLOGY &
MANAGEMENT
CERTIFICATE
(Session 2016- 2017)
This is to certify that the work, which is being presented in the project on “Chhabra
Thermal Power Plant Ash Dyke” submitted by Mr Chandra Mohan
Lodha(13EAOCE016), a student of fourth year (7th
Sem.) B. Tech. in Civil Engineering in
partial fulfilment for the award of degree of Bachelor of Technology is a record of student’s
work carried out and found satisfactory for submission.
Mr Gori Shankar Soni Ms Geetanjali Ganguly
Head of department Seminar Co-ordinator
Department of Civil Engineering Department of Civil Engineering

CONTENTS
1. Power plant 10
1.1 Introduction 11
1.2 Purpose of power plant 12
2. Ash Dyke/pond 13
2.1 Introduction 14
2.2 Purpose 16
2.3 Ash pond layout 16
3. Construction of ash dyke 17
3.1 Machinery used in construction 17
3.2 Material used in construction 17
3.3 Preparation of base 17
3.4 Maintenance of ash pond 17
3.5 Construction of trench beam 19
3.6 Construction of sloping walls 20
3.7 Construction of bad 21
3.8 Construction of bund 22
3.8.1 Upstream construction method 23
3.8.2 Downstream construction method 24
4. Construction of drainage system 25
4.1 Drain 25
4.2 Water drainage tank 27
5. Fly ash 29
5.1 Introduction 29

5.2 Generation of fly ash 30
5.3 Composition of fly ash 32
5.4 Properties of fly ash 33
5.4.1 Physical 33
5.4.2 Chemical 34
5.5 Classification fly ash 35
5.5.1 Class c fly ash 35
5.5.2 Class f fly ash 36
5.6 Fly ash hazardous 36
5.7 Management of fly ash 37
5.7.1 Recycling of fly ash 38
5.7.2 Difficulties in handling of fly ash 38
5.7.3 Problems associated with fly ash disposal 39
6. Handling/Collection of Fly Ash 40
6.1 Introduction 41
6.2 Collection system 42
6.3 Dumping process ofdry fly ash 43
6.4 Dumping process ofwet fly ash 45
6.5 Bottom ash handling system 46
7. Special features 47
Conclusion 48
Reference 49

LIST OF FIGURE
SR.NO. NAME PAGE NO.
1.1 Chhabra Thermal Power Plant 11
2.1 Ash pond Plan 13
2.3 Ash Pond Layout 15
3.3 Preparation of Base 17
3.5 Plan of Trench Bem 19
3.6.A Cutting of Sloping Wall 20
3.6 B Construction of Sloping Wall 21
3.7 Construction of bed 22
3.8.1 Upstream Construction Method 23
3.8.2 Down Stream Construction Method 24
4.1.A Drain Plan 26
4.1.B Construction of Drain 27
4.2 Water Drainage tank 28
5.2 Production of Fly Ash In dry bottom
utility
31
5.3 Ash Generation from Coal Fired Boiler 32
5.4.1 Class c Fly ash 35
5.4.2 Class f fly ash 36
6.2.1 Fly ash slurry system 42
6.3.A Dumping Process 43
6.3.B Fly Ash Vessel 44
6.3.C Fly Ash Silo 45

LIST OF TABLES
SR. NO. NAME PAGE NO.
5.2 Fly Ash utilization Statics 31
5.4.1 Engg. Properties of Fly Ash 33
5.7.1 Fly Ash Construction Related
Application
38

CHAPTER 1. POWER PLANT
1.1 Introduction
Chhabra Thermal Power Plant is one of Rajasthan coal fired power plant. It is located at
Chowki Motipura (Village) of tehsil Chhabra in Rajasthan Baran district.
The planned capacity of power plant is 2650MW at the end of 12th Five year plan.
The first and 2nd unit at Chhabra super thermal power plant was set up at a cost of Rs2,350
crore. Chhabra is all set to become a power generation hub in the state as in the second phase two
more units with a capacity of 250 MW each will be installed.
Rajasthan Rajya Vidyut Utpadan Nigam Limited (RVUN) has been entrusted with the job of
development of power projects under state sector, in the state along with operation &
maintenance of state owned power stations. Government of Rajasthan constituted the Rajasthan
Rajya Vidyut Utpadan Nigam Ltd. (RVUN) under Companies Act-1956 on 19th July, 2000. The
Nigam is since playing lead role in giving highest priority to the power generation for manifold
and rapid development of the state.
The generating Stations of RVUN have acquired a distinctive reputation in the country for their
efficient and economic power generation.
Chhabra Thermal Power Station is a 1000-megawatt (MW) coal-fired power station in
Rajasthan state, India.
A 1320 MW expansion of the power station is under construction.
Installed capacity
Unit 1 - 250 MW - Operating (commissioned October 30, 2009)
Unit 2 - 250 MW - Operating (commissioned May 4, 2010)
Unit 3 - 250 MW - Operating (commissioned September 14, 2013)
Unit 4 - 250 MW - Operating (commissioned 30 June 2014)
Unit 5 - 660 MW - Construction
Unit 6 - 660 MW - Construction

1.2 Purpose of powerplant
In thermal power stations, mechanical power is produced by a heat engine , which transforms
Thermal Energy, often from Combustion of a fuel into rotational energy. Most thermal power
stations produce steam, and these are sometimes called steam power stations. About 86% of all
electric power is generated by use of steam turbines. Not all thermal energy can be transformed
to mechanical power, according to the second law of thermodynamic.
Therefore, there is always heat lost to the environment. If this loss is employed as useful heat, for
industrial processes or district heating, the power plant is referred to as a cogeneration power
plant or CHP (combined heat-and-power) plant. In countries where district heating is common,
there are dedicated heat plants called heat-only boiler stations. An important class of power
stations in the Middle East uses by product heat for desalination of water.
Fig.1.1 Chhabra Thermal Power Plant

CHAPTER 2 ASH DYKE
2.1 Introduction
Fly ash is a very fine material produced by burning of pulverized coal in a thermal power
plant, and is carried by the flue gas and is collected by the electrostatic precipitators or
cyclones. The high temperatures of burning coal turns the clay minerals present in the coal
powder into fused fine particles mainly comprising aluminum silicate. Fly ash produced thus
possesses both ceramic and pozzolanic properties. The problem with fly ash lies in the fact
that not only does its disposal requires large quantities of land, water and energy, its fine
particles, if not managed well, by virtue of their weightlessness, can become air-borne.
Currently, 100 million tons of fly ash being generated annually in India, with 65000 acres of
land being occupied by ash ponds. Such a huge quantity does pose challenging problems, in
the form of land usage, health hazards, and environmental dangers. Both in disposal, as well
as in utilization, utmost care has to be taken, to safeguard the interest of human life, wild life
and environment. The physical, geotechnical and chemical parameters to characterize fly ash
are the same as those for natural soils. The properties of ash are a function of several
variables such as coal source, degree of pulverization, design of boiler unit, loading and
firing conditions, handling and storing methods. A change in any of the above factors can
result in detectable changes in the properties of ash produced. The procedures for the
determination of these parameters are also similar to those for soils. An ash pond is an
engineered structure for the disposal of bottom ash and fly ash. The wet disposal of ash into
ash ponds is the most common ash disposal method, but other methods include dry disposal
in landfills. Dry-handled ash is often recycled into useful building materials. Wet disposal
has been preferred due to economic reasons, but increasing environmental concerns
regarding leachate from ponds has decreased the popularity of wet disposal. The wet method
consists of constructing a large "pond" and filling it with fly ash slurry, allowing the water to
drain and evaporate from the fly ash over time. Ash ponds are generally formed using a
ring embankment to enclose the disposal site. The embankments are designed using similar
design parameters as embankment dams, including zoned construction with clay cores. The
design process is primarily focused on handling seepage and ensuring slope stability.

Fig.2.1 Ash pond plan
2.2 Purpose of ash pond
Fly, a waste of thermal power plants, has its production per annum having crossed the 100
million tones limit is causing several challenges. The thermal power plants do not always pay
much attention towards the maintenance of ash ponds because of it being a waste. There are
various ways for disposing off the fly ash produced in thermal power plants. Out of these ways
disposing the fly ash in ash ponds in the form of slurry with water is one of the best alternatives.
Fly ash form the electrostatic precipitator and bottom ash from the bottom of the boiler are mixed
together and is subsequently mixed with water in a ratio varying from 1 part ash and 4 to 20 parts
of water. The slurry is then pumped into the ash ponds which are located within or outside the

thermal power plant. Depending on the distance and elevation difference, energy required for
pumping is very high and requires booster pumps at intermediate locations.
No well design procedure or codal provision exists for the ash pond construction and
maintenance. There are several examples of failures in ash ponds which resulted in leakage of fly
ash-water slurry into the surrounding areas including water bodies and creating environmental
hazard. The ash pond is designed economically and proper procedures are adopted to avoid any
kind of leakage from the ash ponds. Hydrostatic pressure over the full height of the bund is
minimized by decanting the water which travel away from the bund forming a sloping beech and
only the ash being settled close to the bund.
2.3 Ash pond layout
Following points should be considered while selecting the location and layout of an ash pond:-
 The ash pond area should be close enough to the thermal power plant to reduce the
Pumping cost.
 Provisions for vertical and horizontal expansions should be made considering the life of
the power plant.
 The area should be far away from any water bodies like river, lake etc. to avoid
environmental hazard due to any leakage of fly ash-water slurry.
 In coastal areas where the ground water is already saline, the water form ash pond should
be preferably drained through the bottom of the ash pond and this type of pond has
greater stability.
In interior areas, it is preferable to have a fairly impervious stratum to prevent migration of ash
water into the ground water to prevent its pollution.
In hilly terrain region, a suitable valley can be identified for forming the ash pond. In such case
the hill slopes will serve as the dyke for the pond and the cost would be less for construction.
In most of the ash ponds, the total area can be divided into compartments and while one is
operational other can be evacuated off the deposited ash for reuse.

The deposited fly ash can be used to increase the height of the embankment which ultimately
increases the amount of fly ash slurry containing capacity of the pond. If the area consists of a
single pond, it is not possible to increase the height while the pond is in operation. Each pond
should have a minimum area to ensure that there is adequate time available for settlement of ash
particles while the slurry travels from the discharge point to the outlet. This distance should be a
minimum of 200m to ensure that only clear water accumulates near the outlet point.
Fig.2.3 Ash pond layout

CHAPTER 3 CONSTRUCTION OF ASH POND
3.1 Machinery used in construction
There are following machineries are used in construction
 Hydra(jcb)
 Poke land
 Vibration roller
 Trucks
 Dozer
 Grader
3.2 Material used in construction
 Soil
 Cement
 Concrete ( grade M15,M7.5 )
 LDPE ( 75micron thick membrane )
 Black cotton ( black soil )
3.3 Preparation of base
The preparation of base for the ash pond construction is simplest process. Firstly survey of the all
area and test of field like soil test, ground water level of area .marked the area required for the
ash pond construction . After that dig the depth about 12meter depth all area by machinery used.
Finished the base surface clearly with 0 degree angles. The ash pond all sides having width 12 to
15 meter for vehicle travelling and transportation. The ash pond all walls having slope 60 degree.
Cutting the all walls with 60 degree slope and finish properly. Around the ash pond drainage
system must required so drainage base also cut by machines.Now base is complete for the ash
pond design process.

Fig. 3.3 Preparation of base
3.4 Maintenance of ash dyke
The following guidelines should be followed for the proper maintenance of the ash pond:-
1) Method of slurry discharge:-
For ash ponds, it is most important that the discharge points are uniformly distributed
over the entire perimeter of the ash dyke. The coarser particles settle near the discharge
point whereas the finer particles get carried away from the discharge point. Uniformly
distributing discharge points provides adequate bearing capacity to the dyke being
constructed on the existing segment of the ash pond. It is better that the discharge shall be
simultaneously made from all the discharge points for more uniform beach formation
along the perimeter. When the freeboard in the reservoir is less than 0.5m, then further
discharge should be diverted to the other pond which should be ready. A minimum of
50m beach should be formed to maintain the stability of the downstream slope.

2) Decanting system:-
The quality of the decanted water should be satisfactory with total suspended solids less than
100 ppm. If the elevation of the outlet is low, then the suspended solids will increase.
A delay in raising the outlet elevation will result in high concentration of ash. On the other
hand, early raising will result in increased area of decanted water pond and reduce the beach
length.
3) Raising of ash dyke:-
The pond already filled up with ash should be allowed to dry without any further discharge of
slurry for minimum 1 month till the construction work for raising the height of the dyke
hasn’t begun. This type of pond should be provided with water sprinklers at regular intervals
to prevent dust pollution. Too much of water spraying makes the surface of the ash pond
swampy.
4) Maintenance of ash dyke:-
Following aspects should be considered for maintenance of the ash dyke:-
 Wet patches on the downstream slope formed due to inadequate beach length or
choked drain should be prevented.
 Gulley formation on the slope due to rain should be prevented.
 Rat or animal holes should be covered.
 Growth of plants should be plugged.
 If the free board gets reduced due to erosion, then additional earth fill is provided on
the top of the dyke.
5) Other general recommendations:-
The area of the ash dyke should be provided with fencing and unauthorized entry should be
prohibited.

The entire dyke perimeter should have accessible roads. A site office should be
constructed with a full time engineer responsible for inspection and monitoring of the
dyke.
3.5 Construction of anchor trench
The construction of trench beam is located in the bottom of the ash dyke along the sloping walls.
The design of trench beam according to the drawing all the measurements used according to the
drawing. The trench beam located nearly the sloping wall base point. The beam having size
500mm height, 230 mm width (500*230) mm and concrete grade M7.5 used in the construction.
This is typically used for landfills and reservoirs. The geomembrane comes up from the side
slope and then runs over the top for a short distance. It then terminates vertically down into a
trench dug by a backhoe or trenching machine.
Fig.3.5 Plan of trench beam

3.6 Construction of sloping walls
Firstly sloping wall of the ash dyke properly cut by the machineries with proper angle.
After cut the walls with proper angle the wall upper surface leveled with the 75mm soil. And soil
covered by the 150 micron thin black LDPE.
The design of sloping walls of ash dyke required technical specifications. Design according to
the given drawing.
The concrete used in the sloping wall construction is M15.Construction of sloping walls is as
follows given dimensions. Length 9m, width 3m, thickness 75mm.
The water cement ratio in the M15 grade concrete is using different because sloping wall so the
water is less used in the concrete.
Fig.3.6 a. Cutting of sloping wall

Fig.3.6 b. Construction of sloping wall
3.7 Construction of bed
The construction of ash dyke bed is similar process as like dams bad process.
The width of bad is equal to 15metere with flat surface. It is also used for transportation in the
construction time. It is increase the depth of dyke.
It is made up of sand with compaction; compaction should be completed by the vibration roller.
The length of bad is depends upon the size of dyke.

Fig.3.7 Construction of bed
3.8 Construction of bund
The cost of construction of a single ash pond is generally high. But this cost can be reduced by
constructing the ash pond in stages by various methods like
a) Upstream construction method,
b) Downstream construction method
c) Centre line construction method
Each stage has an increasing or incrementing height of 7-9m. The above methods are described
in brief and their advantages & disadvantages:-

3.8. 1 upstream construction method
This is the best design of raising the height of the dyke since it involves the least earthwork
quantity. The above construction method has the minimum cost involved in it.
Fig.3.8.1 upstream construction method
Following are the disadvantages of upstream construction method:-
Since the total weight of the new construction is supported by the deposited ash, the ash
deposition should be perfect in order to have adequate load bearing capacity.
As the height of the pond increases, the area of the ash pond goes on decreasing and
beyond certain stage; it becomes uneconomical to raise further height of the dyke.
The drain at the upstream face should be well connected to the drain of the earlier
segment; else ineffective drainage can result in reducing the stability of the slope.
The ash pond cannot be operational while raising the height of the dyke by this method of
construction. The pond needs to be dried to initiate the construction work.

3.8.2 Downstream construction method
After the pond gets filled up to the first stage, the pond height is increased by depositing the fly
ash or earth on the downstream face of the dyke as shown in the figure. The advantage of this
method of construction of ash pond is that the height of the dyke can be raised even if the pond
is operational.
Fig.3.8.2 Downstream construction method
After the pond gets filled up to the first stage, the pond height is increased by depositing the fly
ash or earth on the downstream face of the dyke as shown in the figure. The advantage of this
method of construction of ash pond is that the height of the dyke can be raised even if the pond
is operational.
Disadvantage of this method is that it involves approximately the same cost and amount of
construction as in single stage construction.

CHAPTER 4 CONSTRUCTION OF DRAINAGE SYSTEM
The construction of drainage system for the side water disposal which comes by the rain and
present around the ash dyke. So protect the ash pond walls from the rain water the proper
drainage system must be required.
4.1 Drain
 Drain a fixture that provides an exit-point for waste water or water that is to be re-circulated.
 Drainage, the natural or artificial removal of surface and sub-surface water from a given
area.
 Storm drain, a system of collecting and disposing of rain water in an urban area.
The drainage system of ash dyke is outer side of the dyke. The construction of ash dyke with
special supervision and according to the given drawing. The drainage system base completed by
using of concrete M7.5 and walls having dimensions height 800mm, width 350mm and length
depends upon the drain length. The slope between starting point of wall and end point of wall is
1:0.5.The drain walls constructed by the cement, sand, bricks with proper ratio of cement sand
and water.
The ancient Indus of sewerage and drainage that were developed and used in cities
throughout the civilization were far more advanced than any found in contemporary urban cities
in the Middle East and even more efficient than those in some areas of the Indian Subcontinent
today.
The civil engineer is responsible for drainage in construction projects. They set out from the
plans all the roads, street gutters, drainage, culverts and sewers involved
in construction operations. During the construction process he/she will set out all the necessary
levels for each of the previously mentioned factors.
Civil engineers and construction managers work alongside architects and supervisors,
planners, quantity surveyors, the general workforce, as well as subcontractors. Typically, most

jurisdictions have somebody of drainage law to govern to what degree a landowner can alter the
drainage from his parcel.
Drainage options for the construction industry include:
 Point drainage, which intercepts water at gullies (points). Gullies connect to drainage pipes
beneath the ground surface and deep excavation is required to facilitate this system.
Support for deep trenches is required in the shape of planking, strutting or shoring.
 Channel drainage, which intercepts water along the entire run of the channel. Channel
drainage is typically manufactured from concrete, steel, polymer or composites. The
interception rate of channel drainage is greater than point drainage and the excavation
required is usually much less deep .
Fig. 4.1.a Drain plan

Fig.4.1.b Construction of drain
4.2 Water drainage tank
The water drainage tank is located near the outside of ash dyke which collect the drain water and
the disposal of collected water. The drainage tank collect the rain water from drain 1, 2, 3 and
another tank is collect the rain water from drain 4, 5, 6.
A water tank is a container for storing liquid. The need for a water tank is as old as civilization,
to provide storage of water for use in many applications, drinking

water, irrigate agriculture, fire suppression, agricultural farming, both for plants and
livestock, chemical manufacturing, food preparation as well as many other uses. Water tank
parameters include the general design of the tank, and choice of construction materials, linings.
Various materials are used for making a water
tank: plastics (polyethylene, polypropylene), fiberglass, concrete, and stone, steel (welded or
bolted, carbon, or stainless). Earthen pots also function as water storages. Water tanks are an
efficient way to help developing countries to store clean water.
Fig. 4.2 Water drainage tank

CHAPTER 5 FLY ASH
5.1 Introduction
Fly ash is a very fine material produced by burning of pulverized coal in a thermal power plant,
and is carried by the flue gas and is collected by the electrostatic precipitators or cyclones. The
high temperatures of burning coal turns the clay minerals present in the coal powder into fused
fine particles mainly comprising aluminum silicate. Fly ash produced thus possesses both
ceramic and pozzolanic properties. The problem with fly ash lies in the fact that not only does its
disposal requires large quantities of land, water and energy, its fine particles, if not managed
well, by virtue of their weightlessness, can become air-borne. Currently, 100 million tons of fly
ash being generated annually in India, with 65000 acres of land being occupied by ash ponds.
Such a huge quantity does pose challenging problems, in the form of land usage, health hazards,
and environmental dangers. Both in disposal, as well as in utilization, utmost care has to be
taken, to safeguard the interest of human life, wild life and environment.
The World Bank has cautioned India that by 2015, disposal of coal ash would require 1000
square kilometers or 1 square meter of land per person. Since coal currently accounts for 75% of
power production in the country, the bank has highlighted the need for new and innovative
methods for reducing impact on the environment.
The physical, geotechnical and chemical parameters to characterize fly ash are the same as those
for natural soils, e.g., specific gravity, grain size, atterberge limits, compaction characteristics,
permeability coefficients, shear strength parameters and consolidation parameters. The properties
of ash are a function of several variables such as coal source, degree of pulverization, design of
boiler unit, loading and firing conditions, handling and storing methods. A change in any of the
above factors can result in detectable changes in the properties of ash produced. The procedures
for the determination of these parameters are also similar to those for soils.

5.2 Generation of fly ash
Fly ash is produced as a by-product in coal fired thermal power plants. Pulverized coal, when
blown into the boiler, it is ignited and generates heat and is self converted to a molten residue.
The heat is then extracted by the tubes of the boiler and the molten residue is thus cooled to form
ash. The finer ash particles are carried away by the flue gas to the electrostatic precipitators and
are referred as fly ash, whereas the heavier ash particles fall to the bottom of the boiler and are
called as bottom ash. Different types of coal fired boilers are (a) Dry bottom boilers, (b) Wet
bottom boilers and (c) Cyclone furnaces. Dry bottom boilers produce 80% ash as fly ash and
20% as bottom ash. Wet bottom boilers produce 50% each as fly ash and bottom ash
respectively. Lastly, cyclone furnaces produce 20% as fly ash and 80% as bottom ash. In India
coal/lignite based thermal power plants account for more than 55% of the electricity installed
capacity and 65% of electricity generation. The ash content of the coal used at the thermal power
plants ranges from 30-40%, with the average ash content around 38%. Since low ash, high grade
coal is reserved for metallurgical industries. The thermal power plants have to use high ash, low
grade coal. The thermal power plants ash generation has increased from about 40 million tons
during 1993-94, to 120 million tons during 2005-06, and is expected to be in the range of 175
million tons per year by 2012.

Fig.5.2 Production of fly ash in a dry bottom utility boiler with electrostatic precipitator.
Table 5.2 fly ash generation and utilization statistics

5.3 Composition of fly ash
Depending upon the source and makeup of the coal being burnt, the composition of fly ash and
bottom ash vary considerably. Fly ash includes substantial amounts of silicon dioxide and
calcium oxide which are the main ingredients of many coal bearing rocks.
Toxic constituents of fly ash depend upon the specific coal bed makeup, but may include one or
more of the following elements in quantities or trace amounts to varying percentages: Arsenic,
molybdenum, selenium, cadmium, boron, chromium, lead, manganese, mercury, strontium,
thallium, vanadium, beryllium along with dioxins. Fly ash is a fine, glass powder recovered from
the gases of burning coal during the production of electricity.
The micron-sized earth elements consist of primarily of silica, alumina and iron. When mixed
with lime and water, the fly ash forms a cementious compound with properties very similar to
that of Portland cement.
Properties of fly ash are like SiO2, Al2O3, Fe2O3, CaO.
Fig. 5.3 Ash generation from coal fired boiler

5.4 Properties of fly ash
5.4.1 Physical properties
Fly ash consists of fine, powdery particles that are predominantly spherical in shape, either solid
or hollow, and mostly glassy (amorphous) in nature.
The carbonaceous material in fly ash is composed of angular particles.
The particle size distribution of most bituminous coal fly ashes is generally similar to that of silt
(less than a 0.075 mm or No. 200 sieve). Although sub bituminous coal fly ashes are also silt-
sized, they are generally slightly coarser than bituminous coal fly ashes. The particle size
distribution of raw fly ash is very often fluctuating constantly, due to changing performance of
the coal mills and the boiler performance.
The specific gravity of fly ash usually ranges from 2.1 to 3.0, while its specific surface area
(measured by the Blaine air permeability method) may range from 170 to 1000 m2/kg.
Table 5.4.1 Engineering properties of fly ash parameter

The color of fly ash can vary from tan to gray to black, depending on the amount of unburned
carbon in the ash. The lighter the color, the lower the carbon content. Lignite or sub bituminous
fly ashes are usually light tan to buff in color, indicating relatively low amounts of carbon as well
as the presence of some lime or calcium. Bituminous fly ashes are usually some shade of gray,
with the lighter shades of gray generally indicating a higher quality of ash.
5.4.2 Physical properties
The chemical properties of fly ash are influenced to a great extent by those of the coal burned
and the techniques used for handling and storage. There are basically four types, or ranks, of
coal, each of which varies in terms of its heating value, its chemical composition, ash content,
and geological origin. The four types, or ranks, of coal are anthracite, bituminous, sub
bituminous, and lignite. In addition to being handled in a dry, conditioned, or wet form, fly ash is
also sometimes classified according to the type of coal from which the ash was derived.
The principal components of bituminous coal fly ash are silica, alumina, iron oxide, and calcium,
with varying amounts of carbon, as measured by the loss on ignition (LOI). The LOI for fly ash
should be less than 6 %. Lignite and sub bituminous coal fly ashes are characterized by higher
concentrations of calcium and magnesium oxide and reduced percentages of silica and iron
oxide, as well as lower carbon content, compared with bituminous coal fly ash. Very little
anthracite coal is burned in utility boilers, so there are only small amounts of anthracite coal fly
ash.
They consist mostly of silicon dioxide (SiO2), which is present in two forms: amorphous, which
is rounded and smooth, and crystalline, which is sharp, pointed and hazardous;
Aluminum oxide (Al2O3) and iron oxide (Fe2O3) Chemical composition of fly ash is as
follows: SiO2, 59.38; Fe2O3, 6.11; CaO, 1.94; MgO, 0.97; SO3, 0.76; alkalis, 1.41; and unburnt
sulphur and moisture, 3.74%. Fly ash contain following toxic metals Hg, 1; Cd, Ga, Sb, Se, Ti
and V, 1-10; As, Cr, La, Mo, Ni, Pb, Th, U and Zn, 10-100; and B, Ba, Cu, Mn and Sr, 100-1000
mg/kg. Heavy metals like (As, Mo, Mn and Fe) show leaching with concentration above
permissible limits.

5.4 Classification of fly ash
Two classes of fly ash are defined by ASTM C618: Class F fly ash and Class C fly ash. The
chief difference between these classes is the amount of calcium, silica, alumina, and iron content
in the ash. The chemical properties of the fly ash are largely influenced by the chemical content
of the coal burned (i.e., anthracite, bituminous, and lignite).
5.4.1 Class c fly ash
Fly ash produced from the burning of younger lignite or sub bituminous coal, in addition to
having pozzolanic properties, also has some self-cementing properties.
Fig.5.4.1 Class C fly ash
In the presence of water, Class C fly ash will harden and gain strength over time. Class C fly ash
generally contains more than 20% lime (CaO). Unlike Class F, self-cementing Class C fly ash
does not require an activator. Alkali and sulfate (SO4) contents are generally higher in Class C
fly ashes. Class C fly ash can be identified from its light brownish color.
5.4.2 Class f fly ash
The burning of harder, older anthracite and bituminous coal typically produces Class F fly ash.
This fly ash is pozzolanic in nature, and contains less than 10% lime (CaO). Possessing

pozzolanic properties, the glassy silica and alumina of Class F fly ash requires a cementing
agent, such as Portland cement, quicklime, or hydrated lime, with the presence of water in order
to react and produce cementitious compounds. Alternatively, the additions of a chemical
activator such as sodium silicate (water glass) to a Class F ash can lead to the formation of a
geopolymer. Class F fly ash can be identified by its dark brownish color.
Fig. 5.4.2 Class F fly ash
5.6 Fly ash hazardous
Fly ash is a very fine powder and tends to travel far in the air. When not properly disposed, it is
known to pollute air and water, and causes respiratory problems when inhaled. When it settles on
leaves and crops in fields around the power plant, it lowers the yield. The conventional method
used to dispose off both fly ash and bottom ash is to convert them into slurry for impounding in
ash ponds around the thermal plants. This method entails long term problems.
The severe problems that arise from such dumping are:-

The construction of ash ponds requires vast tracts of land. This depletes land available
for agriculture over a period of time.
When one ash pond fills up, another has to be built, at great cost and further loss of
agricultural land.
Huge quantities of water are required to convert ash into slurry.
During rains, numerous salts and metallic contents in the slurry can leach down to the ground
water and contaminate it.
5.7 Management of fly ash
5.7.1 Recycling of fly ash
In 1996, approximately 14.6 million metric tons (16.2 million tons) of fly ash were used. Of this
total, 11.85 million metric tons (13.3 million tons), or approximately 22 percent of the total
quantity of fly ash produced, were used in construction-related applications.
Between 1985 and 1995, fly ash usage has fluctuated between approximately 8.0 and 11.9
million metric tons (8.8 and 13.6 million tons) per year, averaging 10.2 million metric tons (11.3
million tons) per year.
Fly ash is useful in many applications because it is a pozzolan, meaning it is a siliceous or
alumino-siliceous material that, when in a finely divided form and in the presence of water, will
combine with calcium hydroxide (from lime, Portland cement, or kiln dust) to form cementious
compounds.

Table 5.7.1 Fly ash construction related applications (recycling)
5.7.2 Difficulties in handling of fly ash
Many challenges are to be faced in the handling and utilization of fly ash. Some of these
Difficulties include:-
The composition of fly ash depends on the quality of coal utilizers. So the costumer
cannot be sure of the quality of fly ash available form a particular source.
The unavailability of testing, labeling & packing facilities of fly ash results in
unnecessary expenses to the costumers.
The location of thermal power plants in remote areas creates difficulties in transportation
and lifting for the user industries.

5.7.3 Problem associated with fly ash disposal
Primarily, the fly ash is disposed of using either dry or wet disposal schemes. In dry disposal, the
fly ash is transported by truck, chute, or conveyor at the site and disposed of by constructing a
dry embankment (dyke). In wet disposal, the fly ash is transported as slurry through pipe and
disposed off in impoundment called “ash pond”. Most of the power plants in India use wet
disposal system and when the lagoons are full, four basic options are available:-
Constructing new lagoons using conventional construction material.
Hauling of fly ash from the existing lagoons to another disposal site.
Raising the existing dyke using conventional construction material and
Raising the dyke using fly ash excavated from the lagoon (ash dyke).
The option of raising the existing dyke is very cost effective because any fly ash used for
constructing dyke would, in addition to saving the earth filling cost, enhance disposal capacity of
the lagoon.
An important aspect of design of ash dyke is the internal drainage system. The seepage discharge
from the internal surfaces must be controlled with filters that permit water to escape freely and
also to hold particles in place and the peizometric surface on the downstream of the dyke. The
internal drainage system consists of construction of rock toe, 0.5 meter thick sand blanket and
sand chimney. After completion of the final section including earth cover the turfing is
developed from sod on the downstream slope.

CHAPTER 6 HANDLING/COLLECTION OF FLY ASH
6.1 Introduction
The sample collection of different types of ashes such as fly ash, bottom ash and pond ash has
different procedures. The fly ash and the bottom ashes are generated at the power plant and can
be collected directly from the discharge points. In most of the power plants sampling pipes are
provided at places near the discharge point or near the storage point for collection of ash
samples. The sample can be directly collected into a bucket or any other container and can be
suitably packed for transportation. The sample used in this study was fly ash collected from the
bottom of the electrostatic precipitator of NTPC Kaniha, Talcher, Orissa.
When the Coal combustion takes place in the boiler, some part of the coal remains unburnt and
that un-burnt particles are called the Ash, which is approximately 26% to 40% of the total coal
undergoing combustion. Basically this is nothing but the residual part of the coal. This ash will
be extracted out in the form of Bottom Ash & Fly Ash according to the places of collection after
the combustion.
If we calculate the ash percentage in any plant, then it will be as following:
 Total Ash = 40% of the coal combusted
 Bottom ash = 20% of the total ash
 Fly ash = 80% of the total ash
Below mentioned values are the ash consumption in a 135 MW Sub-critical Boiler in terms of
Metric Tons (MT). The coal consumption in a 135 MW Sub-critical boiler is around 2000 MT
(Approx.) and compared to that the ash generation will be as follows.
For a 135 MW Bottom Ash Disposal (in 24 Hours) 134 MT (Approx.)
For a 135 MW Fly Ash Disposal (in 24 Hours) 537 MT
(Approx.)
So whatever the Ash generated during the combustion process has to be sent out of the plant as it
is of no use in the plant processes. Also Now-a-days the Government Norms are very strict as far
as the environmental issues are concerned. So we have to handle the Ash in a proper manner in

order to avoid any environmental issues. Generally most of the power plants have a tie-up with
the Cement making companies and the power plants supply the Fly Ash to those Cement making
companies for making cement from the Fly ash and coming to the bottom ash, which is not
having any fine particles as compared to the Fly Ash. So we use it for road filling and for making
Fly Ash bricks.
6.2 Collection system
Ash Handling System mainly consists of the transportation of Fly ash and Bottom ash from
boiler to the respective storing points and the system adopts transporting methods such as
Systems for Bottom Ash:
Bottom Ash Transportation with SSC (Submersed Scrapper Conveyor)
Bottom Ash Transportation with High Pressure Water or Jet Pumps
Systems for Fly Ash:
Fly Ash Slurry Transportation with the bottom ash
Fly Ash Dry Pneumatic Transportation
In Fly Ash Handling System, the major objective is to collect and transport the fly ash from the
ash hoppers of the ESP to the Fly ash silo or to the Ash Slurry making tank. Generally the power
plants prefer Dry Fly ash Disposal instead of making Ash Slurry from the Fly ash and the reason
is that the fly ash collected from the ESP Bottom Hopper is very fine and suitable for Cement
making, if we are making slurry of it then it will not be suitable for Cement making and
economically also it is very good if you are selling the Ash to the Cement Plants. So these are the
reasons why most of the plants are going for Fly ash Disposal instead of Slurry Disposal (Ash
Water).
6.2.1 Slurry Type Fly Ash Disposal System:
This is one of the simplest system for ash disposal from ESP hopper to the slurry pond.High
Pressure water and fly ash is mixed below the ESP hopper and below in the diagram you can see
that tapping for mixing of water is provided.

Fig.6.2.1 fly ash slurry system
6.2.2 Dry Type Fly Ash Disposal System:
Fly Ash from the ESP Hoppers is collected in the Ash Vessels and from there it is transported to
the Fly Ash Silos by the help of Compressed air and from the Ash Silos, the ash is transported to
the Bulkers(Sealed Vessel Trucks).

6.3 Dumping process of dry fly ash
Fig. 6.3.a Dumping process of fly ash
ESP Hopper:
Hopper is a large conical type container used for dust or ash collection. After the field charging
in ESP we go for hammering of collecting plates and the fly ash deposited on the collecting
plates gets stored in the hopper. To ensure free flow of ash into the ash vessels from the hopper,
the lower portions of the hoppers are provided with electric heaters. Because if the temperature
of the ash falls below the ash fusion temperature then the ash will form big clusters and may
choke the entire conveying system.
Dome valve:
It is situated between the ESP hopper and Ash vessel; it is a special type of valve which is highly
leak proof. It consists of a dome type structure with a rubber seal which is continuously getting
supply from the compressed air.
Air Vent Line:
To remove the trapped air from the vessel, we use vent line and due to this line air from the
vessel is transported to Hopper and ash come down. It basically does two things, first of all by

removing the air from the vessel, it is removing the back-pressure from the Vessel and
simultaneously it is pressurizing the ash hopper.
Compressor:
A compressed air station is set up in the plant. The compressed air station provides air for the
pneumatic conveying system and purging of fabric filters as we already explained in ESP. After
compressing the air, we have to remove all the moisture content from the air. To remove the
moisture from air we use Adsorbent Air Drier (AAD) and Refrigeration Air Drier (RAD).The
pressure of the compressor is depended on the system design.
Ash Vessels:
Ash vessels are present just below the ESP hoppers with the Dome Valve assembly. They are
supposed to contain the fly ash for a certain amount of time which will be carried to the fly ash
silos. Their ash holding capacity is depended on the conveying capacity of the ash line to the Ash
Silos.
Fig.6.3.b Fly ash vessels

Fly Ash Silo: Fly Ash Silos store the fly ash generated by the Boiler in the maximum continuous
operating conditions (BMCR).The bottom of each fly ash silo is equipped with two ash
discharging chutes. One ash discharging chute is used for discharging the comprehensively used
dry fly ash and the other one is connected with a wet mixer, discharging the wet fly ash. The wet
ash mixer is just a back-up for the dry ash disposal system. Each fly ash silo is equipped with the
bag filters and bag filter cleaning facilities with exhaust fans.
Fig.6.3.c Fly ash silo

 Air extraction fan: It is used to create a negative pressure inside the vessel of the silo
and the air goes out through the bag filters.
 Extractor: It is used to evacuate the Air from the Bulkers (Closed Vessel Truck), which
is connected to the ash disposal chute and the discharge is connected to ash vessel.
 Diverting and dump valve: If one ash silo will not work we divert the line into another
silo with the help of diverting valve and to dump the ash into ash silo dump valve is used.
6.4. Dumping process ofwet fly ash
Wet Fly Ash Disposal System:
Up to the hopper part it is same as that of Dry Fly Ash handling system. After the hopper instead
of going into the vessel, the ash gets mixed with a high Pressure water and this mixture goes to a
slurry tank for further pumping. The slurry formed is further pumped through a series of pumps
or a single GEVO pump for dumping in the Ash yard. For mixing of fly ash with water, a
tapping is provided for High Pressure water below the hopper.
6.5 Bottom ashhandling system
The bottom ash quantity is around 20% of the total Ash generation and there are mainly two
types of bottom ash disposal systems.
 Dry Type Bottom Ash Disposal
 Wet Ash Slurry Disposal
Dry Type Bottom Ash Disposal: First of all we will discuss about the Dry type bottom ash
disposal system.
Slurry Type Bottom Ash Disposal: Here the bottom ash from the 2nd pass of the Boilers goes
to the Clinker Grinder in the 1st pass by the help of high pressure water and from the Clinker
Grinder all the ash goes to a slurry sump for further pumping.

CHAPTER 7 SPECIAL FEATURE OF ASH DYKE
Use of LDPE (175 micron thick membrane) to protect underground water. Use of trench beam
to maintain black cotton (Black Soil). Use of sloping walls with concrete to protect seepage of
water. Use of proper drainage system around the ash dyke.
Low-density polyethylene (LDPE) is a thermoplastic made from the monomer ethylene. It was
the first grade of polyethylene, produced in 1933 by Imperial Chemical Industries (ICI) using a
high pressure process via free radical polymerization. Its manufacture employs the same method
today. The EPA estimates 5.7% of LDPE (recycling number 4) is recycled. Despite competition
from more modern polymers, LDPE continues to be an important plastic grade.
Use of the concrete sloping walls.

CONCLUSION
The generation, composition, properties and classification of fly ash were studied in this report.
Different recycling methods along with the difficulties in handling and disposal problems of fly
ash were discussed which comes under the management of fly ash
The design of an ash pond involved mathematical approach towards dam construction which is
out of the scope of this report. So the aspects to be considered during layout and design of an ash
pond are provided in the report.
But the experiment conducted for the determination of optimum concentration of polymer is at
low scale and the optimum concentration determined has lesser effect on the settling of fly ash in
industrial scale. The above concentration used in the determination of settling rate signifies a
very small difference in the rate of settling as compared to the usual settling process in thermal
power plants

REFERENCE
1. Ram Avatar Meena AEN of civil department in CTPP power plant.
2. Yogesh Momaya Project Manager in radix infra projects pvt.ltd.
3. Subhal giri & Prabhakar Singh site engineer of ash dyke in radix infra projects pvt.ltd.
during training period.
4. www.google.com/ash pond construction
5. www.google.com/fly ash

Chhabra Thermal Power plant Report by Chandramohan lodha

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