Thermal power plant

1. ENERGY ENGINEERING (THERMAL
POWER PLANT )
150 MARKS
Prof. Siraskar G.D.
Mechanical engineering department
PCCOE&R
Insem 30-endsem 70-TW 25- OR 25

2. I shall make electricity so cheap that
only rich can afford to burn
candles….Thomas Edison
After many experiments, first with carbon filaments and then with platinum and
other metals, Edison returned to a carbon filament.[46] The first successful test
was on October 22, 1879;[44]:186[47][48][33] it lasted 13.5 hours.[49] Edison
continued to improve this design and on November 4, 1879, filed for U.S.
patent 223,898 (granted on January 27, 1880) for an electric lamp using "a
carbon filament or strip coiled and connected to platina contact wires".[50] This
was the first commercially practical incandescent light.[51]

3. Unit 1: Introduction and Thermal Power Plant 6 hrs
A) Power Generation: Global Scenario, Present status of power
generation in India, in Maharashtra, Role of private and governmental
organizations, Load shedding, Carbon credits, Pitfalls in power reforms,
concept of cascade efficiency.
A) Thermal Power Plant
Introduction: General layout of modern power plant with different circuits,
working of thermal power plant, coal classification, coal, ash and dust
handling, selection of coal for Thermal Power Plant, FBC boilers, high
pressure boiler, Rankine cycle with reheat and regeneration, cogeneration
power plant
(with numerical)

4. Unit 2: Steam condenser and environmental of thermal power plan
A)Steam Condenser: Necessity of steam condenser, Classification, Cooling
water requirements, Condenser efficiency, Vacuum efficiency, Cooling towers, air
Leakage, Effects of Air Leakage on condenser performance, (Numerical
Treatment)
b) Environmental impact of thermal power plant
Different pollutant from thermal power plant, their effect on human health and
vegetation, methods to control pollutant such as particulate matter oxides of
sulphur, oxides of nitrogen, dust handling system, ESP , scrubber, water pollution,
thermal pollution, noise pollution from TPP and its control

5. Unit 3: Hydroelectric and Nuclear power plant 8 hrs
A)Hydroelectric Power Plant: Introduction, Site Selection, Advantages and
Disadvantages of HEPP,
Hydrograph , Flow duration curve ,Mass Curve, Classification of HEPP with layout.
B)Nuclear Power Plants: Elements of NPP, Nuclear reactor & its types, fuels
moderators, coolants,
control rod, classification of NPP, N-waste disposal
Unit 4: Diesel & Gas Turbine Power plant
Unit 5: Non-Conventional Power Plants
Unit 6: Instrumentation and Economics of Power Generation
B) Economics of Power Generation: Introduction, Cost of electric energy, Fixed and
operating cost, (with numerical treatment), Selection and Type of generation,
Selection of generation equipment,
Performance and operation characteristics of power plants and Tariff methods.

6. POWER GENERATION
Prof. Siraskar G.D.
Mechanical engineering department
PCCOE&R
Subject: Energy Engineering
Unit 1

7. Why electrical energy?
In the form of electricity?

8. Energy and power
Energy consumption as
measure of prosperity
a) Commercial energy sources
b) Non commercial energy sources
Power kW
Energy kWh

9. 9
• Electrical energy is most useful form of energy because it can be most
conveniently transformed into other forms of energy like heat light,
mechanical energy that we require in our day to day life.
• But electricity is not readily available and is required to be produced
(generated) in a factory called power station.
• Like any other manufacturing process, the production (generation) of
electricity also need some cost to be incurred - Plants and Equipment, Inputs
(water, fuel etc.), Ash smoke disposal systems, Personnel
• Cost of Transmission and Distribution to the large number of consumers of
various categories (viz. domestic, commercial, industrial, agricultural etc.)
• All these costs when added together constitutes the total cost of electricity
which in the consumers have to share according to the quantum of electricity
consumed taking into account the nature and time of use of electricity by each
category of consumers.
INTRODUCTION

10. • The question is how this cost of electricity is to determined in a transparent manner.
• Some standard principles have been evolved through ages of un & sell of electricity
become more and more complicated.
• Methods of calculation of cost of generation of electricity in a Thermal Power station in
terms of these basic principles.
• Cost of Electricity has two components – Fixed Cost and Variable Cost
The basic difference between power and energy –
Power –
It is the capacity to Generate or consume electricity. The term “Power” specifies the capacity
of generation or consumption in terms of Kilowatt (KW) or Megawatt (MW). One Megawatt as
we know in one thousand Kilowatt.
Energy –
It is the Power Generated or Consumed by utilizing the capacity for a duration of time. It one
kilowatt Power has been generated or distributed continuously for one hour, it is said that an
energy of One Kilowatt hour has been generated or used. Similarly if Five kilowatt of Power is
generated or consumed for Two hours, an energy of 10 ( = 5 X 2) kilowatt hour has been
generated or consumed and so on.
10
INTRODUCTION ……(contd.)

11. Types of energy
Renewable
Non renewable

13. India energy consumption
Coal: 192,971.5 MW (58.3%)
Large Hydro: 44,963.42 MW (13.6%)
Small Hydro: 4,389.55 MW (1.3%)
Wind Power: 32,700.64 MW (9.9%)
Solar Power: 14,771.69 MW (4.5%)
Biomass: 8,295.78 MW (2.5%)
Nuclear: 6,780 MW (2.0%)
Gas: 25,150.38 MW (7.6%)
Diesel: 837.63 MW (0.3%)
330000 MW India capacity
2017
330 GW

15. •The first demonstration of an electric light in
Calcutta (now Kolkata) was conducted on 24
July 1879 .
•India began utilizing grid management on a
regional basis in the 1960s
•India’s capacity 330 GW (2017)
• Maharashtra, Western India.[1] With a total
generation of 10,737 MW, it is the second
largest power producing company in India

16. Year India electricity
production
1947 1362 MW
2016 326840 MW
2018 340000 MW

17. As of December 2010, the installed power generation capacity of
India stood at 169 GW and is trying to add another 78 GW by 2012.
330 GW by 2016, The demand for electricity is expected to be
about 1,000 GW by 2030.

18. Per capita consumption is also indicator of growth

20. India has electrified 96% villages, but is still far from
taking power to all homes

21. India has one National Grid with an installed capacity of
330.86 GW as on 30 November 2017.. Wikipedia
Share of fossil energy 66.2%
Share of renewable energy 31.8%
GHG emissions from electricity generation (2015)
2066.01MtCO2
[2]
Average electricity use (2016-17) 1,122 kWh per capita
Transmission & Distribution losses (2015-16) 21.81
%Residential consumption = 24.32%[3]
Industrial consumption = 40.01%[3]
Agriculture consumption = 18.33%[3]
Commercial consumption = 9.22%[3]
Services
Share of private sector in generation 44% (October 17)

22. Maharashtra:
Thermal power plant Operational
1.Chandrapur Super Thermal Power Station - 3340 MW.
2.Koradi Thermal Power Station - 620 MW
3.Khaparkheda Thermal Power Station - 1340 MW
4.Bhusawal Thermal Power Station - 1420 MW
5.Nashik Thermal Power Station - 630 MW
6.Parli Thermal Power Station - 1130 MW
7.Paras Thermal Power Station - 500 MW
Planned / Under Development
Chandrapur Super Thermal Power Station Project U-8,9 - 2 X 500MW
Koradi Thermal Power Station Project U-8,9,10 - 3 X 660MW [5]
Parli Thermal Power Station Project U-8 - 1 X 250MW
Thermal Power Stations Gas based
Uran Gas Turbine Power Station - 4 X 108, 2 X 120 = 672 MW

23. Hydro Power Stations[edit]
Bhatghar- Dam
Bhatsa
Bhira - 80 MW
Dimbhe Dam
Ghatghar Pumped Storage Hydroelectric Power Plant - 250 MW
Kanher Dam
Koyna Hydroelectric Project - 1,956 MW
Manikdoh Dam
Panshet Dam
Pavana Dam
Surya Dam
Tillari Dam, Chandgad
Ujani Dam
Vaitarna Dam
Varasgaon Dam
Veer Dam
Warna Dam
Yeldari Dam

24. Global primary energy sources
Coal: 984 billion tons , USA has 25.4 %, Russia 15.9 % China 11.6 % , India
8.9 %
Petroleum oil: global 1147 billion barrels ( 1 barrel = 160 liters) Saudi has 23
%
Gas: 176 trillion cubic meter, Russian has 27 %
World reserve will lost oil 45 years gas 65 years , coal 200 years
Global consumption : 9741 billion tones of oil equivalent (Mtoe)
Developing country energy growth rate is 2.7 %
Oil use is 39 %
Natural gas 2.2 % use
Coal predominant
Co2 emission increase is 1.9 %
1 metric ton coal = 0.41 Mtoe

25. India: 17 % of population consume 3.5 % f world energy
India: energy
Type India Total Used In global Will last World
will
Coal 58.3
%
92 billion
tones
662 million
tons /year,
imports 730
m t
8.6 % (4th
)
230 years 192 years
Oil 36% 763.48
million
tones
36 MTs 0.4 % Top
10 in
world
82 %
imports
Gas 10% 1227.4
billion cu
m
31.90 BCM /
year
0.77
Nuclear
Power
2.4 70000 Mt 3310 MW

26. MW Coal Gas Diesel Total Nuclea
r
Hydro RES
total
Grand
total
India 196097 24867 837 221802 6780 45487 72012 346082
Maha 26960 3512 0 30473 690 3331 8759 43254
Power production scenario

28. ROLE OF PRIVATE SECTOR
 Electricity act 2003 private allowed
 Removed need of licenses for power generation
 Power plant having 1000 MW , no tax for 10 years
 Allowed 100 %FDI
 Selling bulk power to grid
 Less import duty for 1000 MW and more plant
equipment
 40 % by private sector

29. GOVERNMENT ORGANIZATION
 National thermal power corporation (NTPC) established in
1975
 45 % share in production and distribution
 Rural electrification corporation : some sate 100% (REC)
 Nuclear power corporation : it was se up in 1987 target
20000MW (NCP)
 National hydro power corporation (NHPC)
 Power grid corporation of India (PGCI)
 State Electricity Boards (SEB’s) :18

30. Load shedding:
During power shortage , some dispensable appliances are switched
off except the essential services like water supply and street lighting
This cause minor in convenience to consumer
Load shedding can also be done on the entire system simultaneously
or on different parts of the network in the city in rotation
In case of industries if load increases above certain maximum demand
circuit breaker switch off power which is installed at company premises
.
In case of more load, few non necessary equipment can be switch off.
•

31. A carbon credit is a generic term for any tradable certificate or permit
representing the right to emit one tonne of carbon dioxide or the mass of
another greenhouse gas with a carbon dioxide equivalent (tCO2e) equivalent to
one tonne of carbon dioxide.[1][2][3]
Carbon credits and carbon markets are a component of national and
international attempts to mitigate the growth in concentrations of greenhouse
gases (GHGs). One carbon credit is equal to one tonne of carbon dioxide, or in
some markets, carbon dioxide equivalent gases. Carbon trading is an
application of an emissions trading approach. Greenhouse gas emissions are
capped and then markets are used to allocate the emissions among the group
of regulated sources.

34. Carbon credit :
Co2, nox, cfc
Started in 1992 ..in brazil earth summit
1997 , : 160 country met in Japan Kyoto ,
now 184 countries accepted
2001 bush denies
2004 : 170 countries sign in germany
Even Russia sign in 2004
2005 force
2011 canada withdraw as china became major emitter …and usa not part..
But latar
Coal 1kwh = 1 ton of co2
If wind instead of coal reduce 1 ton = one carbon credit
Can sale such credit, one credit = $36
This money can be used for development of developing country

38. Cascade efficiency:
Cascade Energy. Cascade Energy focuses on industrial energy efficiency.
We help you do more with less energy, reducing energy costs, and increasing
productivity and profits. Cascade has special expertise in: Industrial
Refrigeration, Compressed Air, Fans and Pumps.

40. Thermal Power Plant:
Content:
•General information
•General layout of modern power
plant with different circuits,
•working of thermal power plant,
•coal classification,
• coal handling,
•Ash handling,
• dust handling,

41. Steam power plant:
Converts chemical energy of the fossil fuels (coal, oil gas) in
to mechanical energy.
Classification of steam power plant:
a) Central station (condensing type)
b) Industrial power station or captive power station. ( mostly
non condensing type)

42. Factors of steam power plant location selection
•Availability of raw material.. 1 MW requires 12 ton coal/day,
approx 400 mw requires 5000 to 5000 tonnes coal per day, so
near coal filed or railway station.
•Nature of land: should have good bearing capacity,
minimum bearing capacity must be 1 MN/m2
•Cost of land
•Availability of water
•Transport facility
•Ash disposal facility: for 400 Mw , requires 10 hectors/year
land for ash dumping height up to 6.5 meters
•Availability of labour
•Size of the plant
•Load center: near load center or near c.g. of load
•Public problem: away from towns.
•Future extension

43. Essential requirement of steam power plant:
•Reliability
•Minimum capital cost
•Minimum operating and maintenance cost
•Capacity to meet peak load effectively
•Minimum losses of energy in transmission
•Low cost of energy supplied to the consumer
•Reserve capacity to meet future demands

45. Thermal power plant

48. There are four processes in the Rankine cycle. These states are
identified by numbers (in brown) in the above T–s diagram.
Process 1–2: The working fluid is pumped from low to high pressure. As
the fluid is a liquid at this stage, the pump requires little input energy.
Process 2–3: The high-pressure liquid enters a boiler, where it is heated
at constant pressure by an external heat source to become a dry
saturated vapour. The input energy required can be easily calculated
graphically, using an enthalpy–entropy chart (h–s chart, or Mollier
diagram), or numerically, using steam tables.
Process 3–4: The dry saturated vapour expands through a turbine,
generating power. This decreases the temperature and pressure of the
vapour, and some condensation may occur. The output in this process
can be easily calculated using the chart or tables noted above.
Process 4–1: The wet vapour then enters a condenser, where it is
condensed at a constant pressure to become a saturated liquid.

49. Thermal power plant

50. a)Coal and Ash circuit
b)Air and gas circuit
c)Feed water and steam circuit
d)Cooling water circuit

52. Advantages and disadvantages of steam power plants
Advantages:
1) Fuel used is cheaper
2) They can respond quickly with changes in load on the plant
3) Space required is less compared to hydro power plant
4) A portion of steam can used as process steam for various
industries.
5) They can be overloaded up to 20 % without difficulty.
6) Cost of electric power generation and its initial cost is less compared
to diesel plant
7) Can be located near the load center conveniently thus reduces the
transmission line cost and loss of energy in transmission lines.
Disadvantages:
1) Operation and maintenance cost is high
2) Time needed for erection of plant is high before it is put to operation
3) Large quantity of water is needed
4) Coal and ash handling poses a serious problem
5) The part load efficiency is low pollution causes health problem to
workers and habitant near the thermal power plant

53. Coal classification:
Properties of Coal
Coal Classification Coal is classified into
three major types namely
a) Anthracite, (high grade 90 % C CV
36000 kJ/kg), semi anthracite
b)bituminous, (40 to 60% C) cv 32000
kj/kg) . semi 20 % volatile matter
c) lignite. (30 % carbon )
d) Peat (10 to 20 % Carbon, up to 90 %
moisture)

54. However there is no clear demarcation between them and
coal is also further classified as semi- anthracite, semi-
bituminous, and sub-bituminous. Anthracite is the oldest coal
from geological perspective. It is a hard coal composed
mainly of carbon with little volatile content and practically no
moisture. Lignite is the youngest coal from geological
perspective. It is a soft coal composed mainly of volatile
matter and moisture content with low fixed carbon. Fixed
carbon refers to carbon in its free state, not combined with
other elements. Volatile matter refers to those combustible
constituents of coal that vaporize when coal is heated. The
common coals used in Indian industry are bituminous and
sub-bituminous coal. The gradation of Indian coal based on
its calorific value is as follows:

56. Grade Calorific Value Range ( in kCal/kg)
A exceeding 6200
B – 6200 4940
C -5600 6200
D- 4940 3360
E -3360 4940
F -2400 -3360
G 1300 – 2400
Analysis of Coal There are two methods:
ultimate analysis and
proximate analysis.
The ultimate analysis determines all coal component elements,
solid or gaseous and
the proximate analysis determines only the fixed carbon, volatile
matter, moisture and ash percentages.
The ultimate analysis is determined in a properly equipped
laboratory by a skilled chemist, while proximate analysis can be
determined with a simple apparatus. It may be noted that
proximate has no connection with the word “approximate”.

59. Proximate Analysis Proximate analysis indicates the percentage by
weight of the Fixed Carbon, Volatiles, Ash, and Moisture Content in coal.
The amounts of fixed carbon and volatile combustible matter directly
contribute to the heating value of coal. Fixed carbon acts as a main heat
generator during burning. High volatile matter content indicates easy
ignition of fuel. The ash content is important in the design of the furnace
grate, combustion volume, pollution control equipment and ash handling
systems of a furnace. A typical proximate analysis of various coal is given
in the
TABLE 1.5 TYPICAL PROXIMATE ANALYSIS OF VARIOUS COALS (IN
PERCENTAGE)
Parameter Indian Coal Indonesian Coal South African Coal Moisture 5.98
9.43 8.5 Ash 38.63 13.99 17 Volatile matter 20.70 29.79 23.28 Fixed Carbon
34.69 46.79 51.22

60. Significance of Various Parameters in Proximate Analysis
a) Fixed carbon: Fixed carbon is the solid fuel left in the furnace after
volatile matter is distilled off. It consists mostly of carbon but also
contains some hydrogen, oxygen, sulphur and nitrogen not driven off
with the gases. Fixed carbon gives a rough estimate of heating value
of coal
b) Volatile Matter: Volatile matters are the methane, hydrocarbons,
hydrogen and carbon monoxide, and incombustible gases like carbon
dioxide and nitrogen found in coal. Thus the volatile matter is an index
of the gaseous fuels present. Typical range of volatile matter is 20 to
35%. Volatile Matter • Proportionately increases flame length, and
helps in easier ignition of coal. • Sets minimum limit on the furnace
height and volume. • Influences secondary air requirement and
distribution aspects. • Influences secondary oil support
c) Ash Content: Ash is an impurity that will not burn. Typical range is 5
to 40% Ash • Reduces handling and burning capacity. • Increases
handling costs. • Affects combustion efficiency and boiler efficiency •
Causes clinkering and slagging.

61. d) Moisture Content: Moisture in coal must be transported, handled
and stored. Since it replaces combustible matter, it decreases the heat
content per kg of coal. Typical range is 0.5 to 10% Moisture • Increases
heat loss, due to evaporation and superheating of vapour • Helps, to a
limit, in binding fines. • Aids radiation heat transfer.
e) Sulphur Content: Typical range is 0.5 to 0.8% normally. Sulphur •
Affects clinkering and slagging tendencies • Corrodes chimney and
other equipment such as air heaters and economisers • Limits exit flue
gas temperature.

62. Measurement of Moisture Determination
of moisture is carried out by placing a sample of powdered raw coal of
size 200-micron size in an uncovered crucible and it is placed in the oven
kept at 108 o C along with the lid. Then the sample is cooled to room
temperature and weighed again. The loss in weight represents moisture.
(15 minute to one hour and then in crucible kept in anhydrous calcium
chloride to absorb moisture )
Measurement of Volatile Matter Fresh sample / same previous of
crushed coal is weighed, placed in a covered crucible, and heated in a
furnace at 950o C, for 7 minutes. The sample is cooled and weighed. Loss
of weight represents moisture and volatile matter. The remainder is coke
(fixed carbon and ash)
Measurement of Carbon and Ash : (950o C for half hour) remaining will
be ash . The cover from the crucible used in the last test is removed and
the crucible is heated over the Bunsen burner until all the carbon is
burned. The residue is weighed, which is the incombustible ash. The
difference in weight from the previous weighing is the fixed carbon. In
actual practice Fixed Carbon or FC derived by subtracting from 100 the
value of moisture, volatile matter and ash.

63. Chemical Properties Ultimate Analysis: The ultimate analysis
indicates the various elemental chemical constituents such as
Carbon, Hydrogen, Oxygen, Sulphur, etc. It is useful in determining
the quantity of air required for combustion and the volume and
composition of the combustion gases. This information is required for
the calculation of flame temperature and the flue duct design etc.
Typical ultimate analyses of various coals are given in the
Parameter Indian Coal, % Indonesian Coal,
Moisture 5.98
Mineral Matter (1.1 x
Ash)
Carbon
Hydrogen
Nitrogen
Sulphur
Oxygen

74. Important properties of coal
Grindability
Weatherability
Swelling index
Heating value of coal
Ash softening temperature
Coal preparation (Beneficiation)
1) Sizing of coal: crushing
2) Removal of rocks of mine
3) Ash removal
4) Removal of minerals associated with sulphur: : by
crushing and by chemical washing (pyritic sulphur which
is chemically connected)
5) Removal of surface moisture by drying: centrifugal driers
6) Blending of different coal to achieve the required
properties of coal

76. Slurry or emulsion types of fuels: By using little
modification in existing system
1)Coal oil Mixture (COM)
2)Coal water mixture (CWM): work is going on 60
to 80 % coal
3)Coal methanol mixture (CMM) 50 % coal, 50 %
methanol: efficient , High heating value, easy to
transport
Advantages: it is cheaper than oil
Not required major change in plant
Can be used like oil
Less storage
Pollution is reduced
Low rank coal can be used
Reduces carbon loss

79. Coal transportation:
1)By river or sea
2)By rail
3)By road
4)By pipe line
Coal handling :
12 tom per MW power
means 12000 ton for
1000 MW power plant

80. 60 wagon per
train , each
carries 100 tons
means approx
6000 tons/ trip

82. Coal unloading
Wagon unloading
Grab crane for
unloading coal

83. Advantages: used when other arrangement not
possible, less power and maintenance, low
operating cost
Disadvantages: high initial cost
50 tonnes/hour

85. Lift trucks with scoop
Unloading bridges

86. Self unloading ship

89. Belt conveyor
100 tons/hour, 500 rpm, 20 degree inclination

90. Advantages:
•Low cost
•Smooth and clean
operation
•Low maintenance
•Controller rate of coal
transport
•Large quantity over large distance
•20 degree inclination
•60 to 100 meter /minute speed
•50 to 100 tons / hour capacity
•400 meter
•Used for medium and large power plant
•Disadvantages
•Not for greater height
and short distance
•For more height ,
length of conveyor
becomes excessive
Belt conveyor

92. Screw Conveyor:
•Endless helicoids screw fitted to shaft, driving mechanism is
connected to one end of the shaft and other end of the shaft
is supported in an enclosed ball bearing.
•Diameter of screw 15 to 50 cm
•Speed 70 to 120 rpm
•Maximum capacity 125 tonnes / hour

93. Screw conveyor:
Enclosed
Used for small distance 30 m
100 tons/hour
Speed 120 rpm
Can transport coal dust.
Advantages:
Cheap, dust tight, require less space
Disadvantages:
High power consumption per tons coal
transport
Wear and tear of screw, shorter life.

99. Coal storage:
Coal is storage at least 30 days (by train) to 45 days(by ship) requirement
and 10 to 15 days if near to mine
Advantages:
To avoid failure of supply , may be due to transport system, or may be
mine strike or any such reason
Coal storage will give us flexibility of purchase coal at low price, may lead
to get coal at cheaper rate
Disadvantage:
Risk of storage, due to combustion as coal stored in open space
Property coal may change deteriorate,
May loss due to rain , wind
Space required as well as manpower required for this
Inventory cost
Coal is stored : type
Dead storage
Live storage
In open space
Closed space storage

100. Dead storage: normally open
For longer time 15 days to 30 days, 10 % of annual
consumption
a)Storage in the piles (hip): 10 to 12 m
b) under water storage: to avoid spontaneous ignition
Disadvantage:
Coal dust due to wind,
Can be avoid by sprinkling
water or spray water
Due to rain coal get passed away.
Coal paste may be formed,

101. Live storage normally closed : short time like one or two days
Shed type: longitudinal
cover shed
Dome type; concrete
wall

102. Large silos: filling is
uniform due to gravity

108. Magnetic separators:

112. Solid fuel firing
1 hand firing system
2. Stoker firing

114. Coal Burning
1. Stoker firing
2. Pulverized fuel firing
1. stoker firing:
Stoker is powered by fuel feeding mechanism and grate
• Cheaper grade fuel can be used
• High efficiency
• Flexible operation
• Less space
• Small and large boilers
• Less possibility of explosions
• Less investment as compared to pulverizing plant
• Disadvantages:
• Complicated construction
• For large unit coat may be more than pulverizing plant

116. Stoker
Overfeed Under Feed
Traveling grate
stoker
Spreader
stoker
Single retro
stoker
Multi retro
stoker
Chain grate
stoker
Bar grate
stoker

118. Endless chain,
sprockets,
speed 15 to 50
cm /minute
Advantages:
simple, low cost,
maintenance, self
cleaning, HRR
controlled by chain
speed
DA: Preheated air temp limited to 180 Celsius,
clinkering, not for high capacity boiler 200 tones/hour

121. 2. Spreader stoker: Grate function is
only to support
coal, from
Hooper coal is
fed in to the path
of rotor by means
of a conveyer
and is thrown in
to furnace by
rotor
Secondary air , over fire , turbulence, un burnt coal and ash removed
periodically , used up to 140 toned /hour
A: any type of coal, high preheated
air possible, low operation cost,
clinkering reduced, volatile matter
easily burnt
DA: difficulty for varying size
of coal, fly ash is more, clinker
not removed,

124. Underfeed stokers:
Air entering through the holes in the grate comes in contact
with the raw coal, then it passes through incandescent coke,
where reaction like overfeed takes place, gases produced
passes through layer of ash, secondary air is supplied to
burn the combustible gases.
Multi retort underfeed stokers
It consist of series of sloping parallel trough formed by
tuyere stacks. These troughs are called retorts.
Under coal Hooper at the head end , feeding rams
reciprocates back and forth. With the ram in outer position
coal falls in gap, and inward stroke it forces coal into the
retort.

129. Pulverization of coal:
Unit system
Centralized system

130. Pulverized fuel firing:
•Coal is reduced to fine powder with the help of grinding mills
and then projected in to combustion chamber with the help of
hot air current.
•Amount of air required (secondary air) is supplied separately.
•Turbulence created
•Finesse is such that 70 % of coal pass through 2– mesh sieve
and 90 % through 50 mesh sieve
Advantages:
•Any grade coal
•Controlled rate of feed
•Complete combustion
•Good peak load capacity
•Free from sagging and clinker
troubles.
•Highly free heated secondary air
350 Celsius
•Small size furnace
DA: high capital cost
•Lot of Fly ash
•Coal burn like a gas explosion
possibility is more
• maintenance is more of
brickwork
•Special equipment, skilled
operator, separate coal
preparation

151. Impact hammer mill

155. Long / U flame Burner

170. The atomization of fuel can be accomplished by following methods
a) High pressure air or steam atomizing burner
B ) Mechanical burner
Spray nozzle burner

176. Mechanical ash handling system ;
Figure shows a mechanical ash handling system. In this
system ash cooled by water seal falls on the belt conveyor
and is carried out continuously to the bunker. The ash is
then removed to the dumping site from the ash banker with
the help of trucks.

178. Hydraulic ash handling system:
a)Low velocity Hydraulic ash handling system
Ash follows on channel ,
where low velocity (3 to 5
m/s) water streams carries
this ash to sump, capacity 50
t/hour, distance 500 m
b) High velocity Hydraulic ash handling system
Hopper below boiler are fitted with water nozzles, ash
follows from boiler will be carried away by high speed
jet water to sump, capacity 120 t/hr, distance 1km

179. Advantages of hydraulic system: high capacity, can
handle molten ash, clean and dust free.
Disadvantages: due to ash and water forms chemical,
and due to that ash handling equipment need to corrosive
resistance

180. Pneumatic ash handling system:

181. •Pneumatic system can handle abrasive ash and fine dust
•Ash from boiler falls into a crusher where large as particles are
divided in to small particle, a high velocity air stream created by
as exhauster carries all the ash and dust particle to primary
separator which works on cyclone principal. Ash is collected in
Hooper.
•The air with left over ash passes through the secondary ash
separator and air leaving this separator is passed through a
filter for removing dust particle. So washed/clean air passes to
exhauster.
•This is cheap, occupies less space, removes all the ash and
the ash handled is in dry state.
•Problem is that due to abrasive ash particle wear and tear is
more.

199. Electrostatic precipitator