training report of suratgarh thermal power plant, rajasthan ,india

1. ABSTRACT
The Suratgarh Super Critical Thermal Power Station is an electricity production
project that is maintained by the Rajasthan Rajya Vidhyut Nigam Limited. It is
Rajasthan’s foremost super thermal power station.
This station has been successful in controlling pollution and maintaining balance
of atmospheric emissions in the environment. The Union Ministry of Power has
awarded this power station with the Golden Shield Award.
The resinous project of Rajasthan, the Super Thermal Power Station, and
Suratgarh is situated near village Thukrana about 27 km. from Suratgarh city in
Sriganganagar district. The site was considered an ideal location for setting up a
thermal power station due to availability of land, water, transmission line and
cheap labour.
Suratgarh Super Thermal Power Station has reached such dizzying heights of
success that its sixth unit. In this unit, maximum capacity on coal firing was
attained in less than 10 hours and the phenomenal completion of the project in
less than two years is a ground breaking achievement for the nation. Besides the
philanthropic organization also has a social conscience. The organization plants
nearly 3.5 Lakhs saplings every year, digs up dykes and water bodies and
monitors the effusion of effluent materials and ambient air quality in order to
check the pollution level.

2. INTRODUCTION
Suratgarh Super Thermal Power Station
STPS is situated near village Thukrana about 27Km south east of Suratgarh town
is Shri Ganaganager Distt. Suratgarh was considered an ideal location for setting
up a thermal power station in the state having regards to the availability of land,
water, transmission network proximity to broad gauge railway and being an
important load centre for north-west Rajasthan. Water and coal required in a
large amount. Coal is received here from coal-fields of MP areas through
railways and water requirement will be 121.824 MLD and would be sourced
from the INDIRA GANDHI CANAL through a pipeline at a distance of about 23
kms from the project. The supply of coal is from MP, Jharkhand by rail. About
18000 tonne coal required per day for whole unit and each unit consumes
150tonnes coal per day. About 2x3 km2 area covered by plant and approximately
1800 employees works in a plant including chief engineer to labour. The supply
electricity to the northern Rajasthan, Ratangarh, Bikaner, Ganganagar.
Suratgarh super thermal power project is an existing 1500 MW coal based
thermal power plant promoted and operated by Rajasthan Rajya Viduth Utpadan
Nigam Ltd. at Shriganganagar in Rajasthan, India.
The four units of 660 MW have been proposed. The proposal is for expansion by
addition of 2×660 MW Coal Based Thermal Power Plant at village Thukrana, in
Suratgarh Tehsil, in Sri Ganganagar Distt., in Rajasthan.
The existing plants are of capacity 2×250 MW (Stage I) ; 2×250 MW (Stage II) ;
1×250 MW (Stage III) ;and 1×250 MW (Stage IV). Land requirement will be
400 hectares, which comprises of 338 ha single crop agricultural land; And 22 ha
waste land. Out of total land required, about 360 ha will be used for main plant;
And 40 ha will be used for township.
Coal requirement will be 6.5 MTPA and both will be domestic and imported.
Domestic coal will be obtained from Parsa East & Kante Basan Coal Block for

3. which environmental clearance has been obtained on 21.12.2011. Domestic coal
and imported coal will be blended in a ratio of 70:30 respectively.
Ash content in domestic coal will be 35% and imported coal will be 16%. About
1.5236 MTPA fly ash and 0.3809 bottom ash will be generated. Stack height will
be 275m.
Cost of the project will be Rs 7920.00 Crores. (Include stage 5)
The techno-economic clearance for the prefect was issued by CEA in June1991.
The planning commission accorded investment sanction for the project in Nov.
1991 for a total estimated cost of Rs. 1253.31 Crores on prices prevailing in
Sept.1990. The updated cost of the project is estimates at Rs. 2300 Crores of
including IDC.
 Unit 1st
of STPS was commissioned on coal firing on 4.10.1998 and
commercial operation of the unit was declared from 1.2.1999. The unit was
dedicated to the Nation by Hon’ble Chief Minister of Rajasthan Shri Ashok
Gehlot on 3.10.1999.
 The foundation stone for Unit 3rd
and 4th
STPS stage-II was laid by
Hon’ble Chief Minister of Rajasthan Shri Ashok Gehlot on 3.10.1999.
 250MW Unit of STPS was commissioned on 28.3.2000 and was put on
commercial operation from 16.7.2000. It saved Rs. 80 Crores due to early
start of generation. The Unit was dedicated to the Nation by Hon’ble Dy.
Leader of Opposition, Lok-Sabha Smt. Sonia Gandhi on 13.10.2000.
 The foundation stone 250MW Unit 5th
under STPS stage-III was laid by
Hon’ble Union Minister of Power Shri Suresh P.Prabhu on 12.2.2001.
 250MW Unit 3rd
of STPS was commissioned on oil 29.10.2001 and was
put on commercial from 15.1.2002. The unit was dedicated to the Nation
by Hon’ble Dy. Leader of Opposition, LokSabha Shri ShivrajV.Patil on
17.3.2002.

4.  250MW Unit 4th
of STPS was commissioned on oil 25.3.2002 and has
been put on commercial operation from 31.7.2002. The unit was dedicated
to the Nation by Hon’ble Leader of Opposition, Rajya Sabha Dr.
Manmohan Singh on 10.8.2002. With the commissioning of Unit 4th
of
250MW at STPS it became FRIST SUPER THERMAL POWER
STATION OF RAJASTHAN.
 250MW Unit 5th
& Unit 6th
of STPS was commissioned on oil 25.3.2002
and has been put on commercial operation from 31.7.2002. The unit was
dedicated to the Nation by Hon’ble Leader of Opposition, Rajya Sabha Dr.
Manmohan Singh on 10.8.2002. With the commissioning of Unit 4th
of
250MW at STPS it became FRIST SUPER CRITICAL THERMAL
POWER STATION OF RAJASTHAN.
INSTALLED CAPACITY
Following is the unit wise capacity of the plant:
Installed Capacity of SSTPS
Stage
Unit
Number
Installed Capacity (MW)
Date of
Commissioning
Status
Stage I 1 250 May, 1998 Running
Stage I 2 250 March, 2000 Running
Stage II 3 250 October, 2001 Running
Stage II 4 250 March, 2002 Running
Stage III 5 250 June, 2003 Running
Stage IV 6 250 March, 2009 Running

5. Stage
Unit
Number
Installed Capacity (MW)
Date of
Commissioning
Status
Stage V 7 660 2016
Work in
progress
Stage V 8 660 2016
Work in
progress
Approved Capacity 2820 MW
Installed
Capacity
1500 MW
Location Suratgarh,Rajasthan
Water Source INDIRA GANDHI
CANAL
Fuel Coal
Beneficiary
Place
northernRajasthan,
Ratangarh, Bikaner,
Ganganagar.
Fuel requiremnt 6.5 MILLION TONNES
PER ANNUM
Sourse of fuel M.P ,JHARKHAND.
Total Area 5020 BIGHA
Approved Investment 2300 crores

6. SELECTION OF SITE FOR THERMAL POWER PLANTS
The following factor should be considered while selecting a site for a steam
power plant for economical and efficient generation:-
SUPPLY OF WATER
A large quantity of water is required in steam power plants. It is required:
i. It raises the steam in the boiler.
ii. For cooling purposes such as in condensers.
iii. As a carrying medium such as in disposal of ash.
iv. For drinking purposes.
The efficiency of direct cooled plant is about 0.5% higher than that of the plant in
which cooling towers are used. This means a saving of about Rs. 7.5 Lakhs per
year in fuel cost for a 2000 MW station.
Huge amounts of coal is required for raising the steam (20,000 tonnes per day for
a 2,000 MWs). Since the Government policy is to use only low grade coal with
30 to 40% ash content for the power generation purpose, the steam power plant
should be located near the coal mines to avoid the transport of coal and ash.
REQUIREMENT OF LAND
The land is required not only for setting up of the plant but also for other
purposes such as staff colonies, coal storage, ash disposal etc. Cost of land adds
to the final cost of plant. So it should be available at a reasonable cost. Land
should be good bearing capacity since it has to withstand about 7Kg. /Sq. Cm.
Moreover, land should be reasonably level. It should not be low lying.
As the cost of the land adds up to the final cost of the plant, it should be available
at a reasonable price. Land should be also available for future extension.
LABOUR SUPPLIES Skilled and unskilled labourers should be available at
reasonable rates near the site of power plant.

7. TRANSPORTATION FACILITY
The land and rail connections should be proper and capable of taking heavy and
over dimensioned loads of machines etc. To carry coal, oil etc. Which are daily
requirements, we need these transport linkages.
The facilities must be available for transportation of heavy equipment and fuels
e.g. near railway station
ASH DISPOSAL
Ash is the main waste product of the steam power plant. Hence some suitable
means for disposal of ash should be applied. Ash can be purchased by building
contractors, cements manufacturers or it can be sued for brick making near the
plant site. Otherwise wasteland should be available near the plant site for
disposal of ash.
DISTANCE FROM THE POPULATED AREA
Since most of the modern generating stations employ pulverized fuel residues
and fumes from them are quite harmful. Therefore the site for the plant should be
away from the populate area.
The factors to be considered while selecting a site for a steam power plant for the
efficient generation are:
NEARNESS OF THE LOAD CENTRE
The power plant should be as near as possible to the centre of load so that the
transmission cost and losses are minimum. This factor is most important when dc
supply system is adopted.

8. PLANT FAMILIARIZATION
Thermal Power Plant Layout
Coal Handling System Equipment
• Wagon Tippler
• Conveyor Belt
• Pulleys
• Take Ups
• Skirt Board
• Scrappers
• Magnetic Separator
• Vibrating Screen
• Crushers

9. Conveyor Belts
• Made of different layers or piles of fabric duck protected by a rubber cover
on both sides & edges.
• Fabric duck are designed to withstand tension created in carrying the load.
Nylon rubber cover protect the fabric duck.
o Material: Fire resistant grade.
o Belt Width: 1600 mm.
o Strength: 1000/1250 KN.
o Belt speed: 3.2-3 m/s.
o Belt length: 20km.
Drive Unit
• Motors coupled to reduction gear with the help of flexible/fluid coupling
on the high speed shaft of the gear box.
• Flexible coupling on the input side.
Pulleys
• Made of mild steel.
• Rubber coating is used to increase friction
• Factor of friction between belt & pulley (rubber lagging)
• Shell dia-500mm.
• Shaft dia-1400mm.
• Pulley length-1800mm.
• Shaft length-2350mm (bearing center to center.
Take Up Pulleys
Take up pulleys facilitate:
• Necessary tension for the drive to operate the belt.
• Sag at a point where required horse power is minimum so that the load
will move with ease.
• Disturbance over idlers.

10. Skirt Board
• Used with chutes at trail end.
• Guides material centrally on the belt while loading until it has settle down
on the belt.
Scrappers
• Placed at discharge pulley in order to clean the carrying side of belt.
• It avoids the wear of return idlers due to build-up of material.

11. TURBINE
Introduction
The steam turbines and their auxiliaries installed have been manufactured by
BHEL. The turbines are three cylinders, compound 3000 rpm, double flow
exhaust type reheat units with initial parameters of 13 Kg/cm2. And five low
pressure heaters are fed. The high pressure cylinder comprises of two curt is
wheels as a regulation stage. Intermediate pressure cylinders comprise of twelve
stages and each of the double flow section of the L.P. cylinder consists of four
stages.
Operation
There are two live steam lines connecting the boiler to the turbine. The
superheated steam enters the H.P. turbine and strikes its blades hence heat energy
of steam is converted into mechanical energy. The steam from H.P. turbine is
reheated in reheater and reheated steam is sent to L.P. turbine through hot steam
lines. Here second stage of energy conversion is takes place. Then steam is sent
to L.P. turbine from where it is ejected by vacuum ejectors and condensed. Here
are low cold reheaters and two hot reheat lines connecting the reheater and
turbine. In each of the two steam lines one electrically operated isolating valve,
one water separator and one quick closing stop valve are mounted. The direction
of revolution of turbine is clockwise when looking at turbine from front bearing
pedestal. For the oil lubrication of bearings and for governing, the main oil pump
driven shaft is assembled into the front bearing pedestal of turbine itself.

12. COMPONENTS OF TURBINE

13. CASING OR CYLINDERS:
A casing is essentially a pressure vessel which must be capable of withstanding
the maximum working pressure and temperature that can be produced within it.
The working pressure aspects demand thicker and thicker casing and the
temperature aspects demand thinner and thinner casings.
STEAM TURBINE
“A steam turbine is a device that extracts thermal energy from pressurized
steam and uses it to do mechanical work on a rotating output shaft”
OPERATING PRINCIPLE
A steam turbine has two main parts:
• Cylinder (stator)
• Rotor
The cylinder or rotor is a steel or cast iron housing usually divided at the
horizontal center line. Its halves are bolted together for easy access. The
cylinder contains fixed blade carried by rotor. Each fixed blade set is mounted
on a diaphragm located in front of each disc on the rotor or directly in the
casing. A disc and diaphragm pair form a turbine stage. Steam turbine can have

14. HIGH PRESSURE TURBINE
• Single steam flow of two shell (casing) design.
• Outer casing is of barrel type and has neither an axial or radial flange. Due
to the perfect symmetric design of the outer casing and uniform wall
thickness at all sections mass concentration is prevented which could have
caused high thermal stresses and this helps it remain leak proof during
quick changes in temperature during start up and shut down.
• The inner casing is axially split and is almost cylindrical in shape as the joint
flanges are relieved by higher pressure acting from outside.
Casing is made of creep resistant chromium-molybdenum-vanadium (Cr-Mo-V)
steel casting.
• The turbine has 2 main stop valves (MSV) and 2 control valves (CV) located
symmetrically to the right and left of the casing. The valves are arranged in
pairs with one stop valve and one control valve in a common body. Each
MSV and CV has a dedicated hydraulic servomotor.
• The steam lines from ESV & CV are connected to the inlet connections of
the outer casing by breech nuts.
• The exhaust end of HPT has a single out let connection from bottom.
• HPT Moving and Stationary Blades:
1) HPT blading consists of 25 reaction stages with single flow 50% reaction
2) Blades have three main parts:
i) Aero foil: It is the working part of the blade where steam expansion takes
place.

15. ii) Root: It is the portion of the blade which is held with rotor or casing.
iii) Shrouds: End portion of blades are held together.
3) The stationary and moving blades of all stages are provided with inverted t-
roots. All these blades are provided with integral shrouds which after
installation form a continuous shroud.
4) The moving and stationary blades are inserted into the corresponding
grooves in the shaft and inner casing. The insertion slot in the shaft is closed by
a locking blade which is fixed by grub screws.
5) Sealing strips are caulked into the inner casing and the shaft to reduce
leakages losses at the blade tips.
6) H P Turbine Steam Inlet/outlet pressure -150 Kg/Cm²/39.69 Kg/Cm²
A inlet/outlet Temperature - 537*C/346*C
Intermediate Pressure Turbine
• The Intermediate Pressure Turbine is of double flow construction with two
horizontally split casings (Inner & Outer casing).
• The hot reheated steam enters the inner casing at the mid-section from
top and bottom and expands in opposite side in two blade sections and
compensates axial thrust.
• The inner casing carries the stationary blading
• The 2 stop and control valves are supported on the foundation cover plate
below el 17.00 m floor in front of turbine – gen unit.
• Casing is made of creep resisting Cr-Mo-V steel casting.
• The shaft is made of high creep resistance Cr-Mo-V steel forging.
• IPT Moving and Stationary Blades:
1) IPT blading consists of 17 reaction stages per flow with 50 % reaction. &single
flow
2) The stationary and moving blades of all stages are provided with inverted t-
roots. All these blades are provided with integral shrouds which after
installation form a continuous shroud.
3) The moving and stationary blades are inserted into the corresponding
grooves in the shaft and inner casing. The insertion slot in the shaft is closed by
a locking blade which is fixed by grub screws.

16. 4) Sealing strips are caulked into the inner casing and the shaft to reduce
leakages losses at the blade tips.
5) I P Turbine Steam Inlet pressure - 35.64 Kg/Cm²
a. Outlet pressure - 6.83 Kg/Cm²
b. Exhaust Temp. - 305*C
Low Pressure Turbine
• Low Pressure Turbine casing consists of double flow unit and has a triple
shell welded casing.
• The outer casing consists of front and rear walls, two lateral longitudinal
support beams and the upper dome; connected to condenser by welding.
• The inner-inner & inner-outer casing carries the turbine guide blades and
diffuser.
• Steam admitted to the LPT inner casing from IPT from both left and right
side horizontally. Expansion joints are installed in the steam piping to
prevent any undesirable deformation of the casings due to thermal
expansion of the steam piping.
• LPT Moving and Stationary Blades:
1) LPT blading consists of 8 reaction stages per flow with 50 % reaction & double
flow
2) The stationary and moving blades of first three stages are provided with
inverted t-roots. All these blades are provided with integral shrouds which after
installation form a continuous shroud. First three guide blades are mounted on
inner-inner casing.
3) LP Turbine Steam Inlet pressure - 6.83 Kg/Cm²
a. Exhaust Temp. - 49*C

17. GENERATOR
Mechanical energy is converted into electric power the stator winding of
generator by the interaction of rotating magnetic field. Rotating magnetic field
is created by field winding mounted on rotor shaft with the help of excitation
system. When the shaft is rotated at 3000 RPM by the coupled turbine electric
power is generated at a voltage 16.5 KV and 50 Hz frequency. Generator is filled
with hydrogen gas for cooling its winding which in turn is cooled by circulating
water. The voltage of such generated electricity is step up to 220 KV or 400 KV
through transformer and power transmitted to ratangarh GSS for northern Grid,
and different areas of Rajasthan. 6.0 million units energy is generated in 250
MW unit in a single day, out of this about ten percent is consumed in unit itself
for running its auxiliary equipment like pumps, fans etc. about 3300 metric tons
of coal is consumed in one 250 MW unit in a day.
THEORY:
Turbo generator manufactured by BHEL in co-operate with most
modern design concept and constructional features which ensures
reliability, easy and constructional and operational aconomicity. There is a
provision for cooling water in order to maintain a constant temperature of
coolant (hydrogen) which controls the temp. of wdg., core etc. as per load.
TECHNICAL DATA
Apparent power - 294 MVA
Active power - 250 MW
Current - 10290 Amp
Voltage - 16.5KV +/-825 V
Speed - 3000rpm
Power factor - 0.85
Hydrogen pressure - 3.0 bar
Rated field current - 2386Amp

18. COAL HANDLING PLANT
Wagon tippler has rated unloading capacity of twelve box wagon per hour.
Including shunting and spotting time of haulage equipment. For vibrating
feeders of capacity 350 tons/hr. each have been provided in crusher house to
receive coal and distribute it through manually operated rake and pinion gate to
three vibrating screens of 675 tons/hr. capacity each coal above 200mm size
passes granular for crushing and reduction in size. Coal below 20 mm size passes
granular and discharged on to crushed coal conveyor belt.
Following permutation and combination of operation are possible with installed
system. To transfer all crushed coal received coal from crusher house to live
storage pipe. To transfer part of received from crusher coal to plant and to
balance to storage yard. To deliver the raw coal bunkers part and received
crushed coal mixed with balanced coal from the live storage pipe. To transfer
the plant crushed coal at 750tons/hr from the reclaim live pile and
simultaneously stock. The vibrating ones as stated above can be obtained by the
use of flap gates which are installed on various chute and two vibrating feeders,
installed on tower. The coal carried on various conveyor shall be main
monitored to ensure proper loading and distributing weightless and vibrating
feeders

19. The main equipments of CHP are:
1. Wagon trippler: - A tripler is a equipment that is used for unloading the
coal from box by lifting and tilting the box.
2. Side arm charger: - It is used for pushing or carrying the loaded or empty
boxes.
3. Conveyors: - Different sized and diff. Capacity conveyors are installed for
feeding the coal from Tripler to bunkers.
4. Crusher: - Crushers are provided for crushing the coal in desired sizes.
5. Primary crusher : 2
6. Secondary crusher : 8
7. Stacker cum re-claimer : 2
8. Stacker/Reclaimer: - The stored coal is stacked or reclaimed by the
stacker/reclaimer.
9. Bunkers: - Crushed coal is led to the mills via canonical shaped bunkers.
10.Coal feeder:- Coal feeder delivers the coal from the bunkers to the mill.
11. Pulverization of coal:- Pulverizing mills In modern TPS’s coal is pulverized
i.e. ground to dust likesize. Pulverization is a means of exposing a large
surface area to the action oxygen and consequently helping the combustion.
mill used for one unit in which one standby. Mill is 4.7met in dia. &7.2 met in
length.
GRADE U.H.V
A >6200 Kcal/kg
B 5600-6200 kcal/kg
C 4940-5600 kcal/kg
D 4200-4940 kcal/kg
E 3360-4200 kcal/kg
F 2400-3360 kcal/kg

21. BOILER
Introduction
the boiler is the main part of any thermal power plant. It converts the fuel
energy into steam energy. The fuel may be furnace oil, diesel oil, natural gas or
coal. The boiler may be fired from the multiple fuels.
The boiler is installed in SSTPS are made by BHEL. Each of the boilers are
single drum, tangential fired water tube naturally circulated over hanged,
balanced draft, dry bottom reheat type and is designed for pulverizing coal firing

22. with a max. Continuous steam output of 375 tons/hour at 138 Kg/cm2
pressure
and 540℃ temperature. The thermal efficiency of each boiler at MCR is 86.8%.
Four number of bowl mills have been installed for each boiler. Oil burners are
provided for initial start-up and stabilization of low load. Two E.S.P. (One for
each boiler) is arranged to handle flue gases from the respective boilers. The
gases from E.S.P. Are discharged through 180 meters high chimney. I.D. fan and
a motor is provided near the chimney to induce the flue gases. The boiler is
provided with a balanced draft consisting of tow forced draft fans and two
induced draft fans. Flue gases are utilized to heat the secondary air for
combustion tin the tubular type air heaters installed in the boilers. Since the
boiler furnace is maintained at t negative pressure, to avoid atmospheric air
entering the furnace a hydraulic pressure is maintained at the furnace bottom.
The water filled in the stainless steel seal through the hydraulic seal between the
furnace ash hoppers and the water wall ring heater. Adequate clearance is also
provided for the downward expansion of the furnace. Ash is formed by the result
of burning of coal inside furnace. A small quantity of ash is collected in the
bottom ash hopper and considerable amount of ash is collected in the E.S.P. and
magnetic separator hopper.
This collected ash is extract and disposed of in as slurry from in the ash disposal
arc.
For the central steam power plants o large capacity water tube are used. Water
tube boilers essentially consist of drums and tubes. The tubes are always external
to drum. In comparison to fire tube boilers the drum in such boilers do not
contain any tubular heating surface, so they can be built in smaller diameters and
consequently they will withstand high pressure. The water tube boilers have got
following advantages over the fire tube boilers.

23. The selection of the size and type of boiler depends upon –
i. The output required in terms of amount of steam per hour, operating
temperature and pressure.
ii. Availability of fuel and water.
iii. The probable load factor.
iv. Space requirement and availability.
type, no external pumping device is used for the movement of the fluid.
The difference in densities in contents of fluids in down comers from the
drum and risers in the furnaces is used to effect the movement of fluids.
This type of circulation is employed in most of the utility boiler. The
movement of the steam and water will increase with increased heat input to
a maximum value or so called end point, after which further increase in
heat absorption will result in a decrease in flow.
Internal Structure of Boiler

24. One of the characteristics of natural circulation is its tendency to provide
the highest flow in the tubes with the greatest heat absorption.
MILLING PLANT
• Pulverized coal system:
For steam generation, there is basically system of pulverization normally in
SSTPS plant used is direct firing system
• Direct firing system:
1. Hot primary system: In this system the fan is located before the pulverized
and handles complete primary air required for drying a transporting the
coal. Disadvantages are that the fan is required to handle high temperature
air resulting in high a fan power. Separate sealing air fans are required to
seal the mill and journal bearings.
2. Cold primary air system: The primary air fan handles clean cold air either
from FD fan discharge or taking suction from atmosphere. The advantages
are saving in fan power and maintenance. The only disadvantages is the
cost increase due to additional duct work and air heater.
3. Suction system: In this system the mill operates under negative pressure
suction being created by an exhauster placed after the mill. The exhauster
handles all the coal air mixture and forces it into the burners. The advantage
of suction system is that the plant can be maintained clean. The
disadvantage of this system is that at high speed exhauster has to handle
coal air mixture and tends to wear more as the pulverised size increase.
4. Pressurised exhauster system: In this system the mills operate under
positive pressure with exhauster provided at exit of pulverise to boost the
pulverized coal into the pressurised furnace. Since the pulverised operates
with lesser pressure than forced draft fan pressure.
# In the plant tube type of pressurised mill is used.

25. DRUM/TUBE MILLS;-
This type mills is slow speed type.
They operate at a speed of 17-20 rev/min and formerly were designed as
suction mills. The mill drum carrying the ball charge rotate in the
antifriction bearings. Raw- coal is fed to the drum through the inlet elbow
and gets crushed to power inside the drum and solved to fall down. Due to
the impact of the balls on coal particles and side over each other and also
over the liners, the coal gets crushed. Hot flue gases are used for drying and
transporting the pulverized coal from the mill to the classifier. As a result of
this high availability in a tube-ball mill installation, it is not normal to
provide standby milling capacity. This helps to reduce the overall capital
cost of the paint. Power requirements have also to reduce, but they are still
much greater than those for medium speed limits.
Advantage:
• High output possible, up to 50 tonnes per hour
• No maintenance over long periods
• High availability
• Because of high availability no stand by capacity is required
• No mill rejects, no problems with ‘tramp’ iron
• Reserve of fuel within mill makes output more stable
Disadvantages:
• High power consumption.
• Some problem with control of coal level within the mill.
• Virtually constant power consumption at all loads; low load operation of
therefore not economical.
• With high moisture content fuels a high primary air temperature is required
because of the low air/fuel ratio

26. • Unplanned stops leave the mill full of coal which, under unfavourable
conditions, can ignite. This coal has to be quenched and even dug out
otherwise the mill cannot be restarted.
COAL FEEDER:-
Coal feeder deliver the coal from the bunker to the mill. Since the amount
of coal delivered determiners the output of the mill, if feeder that the coal
flow, through the coal feeder has to be controlled. This is normally
achieved either by control of feeder speed or by control of the position of a
scraper knife or plough.
# In plant drag link coal feeder’s type of coal feeder is used.
In suratgarh thermal power plant there are three fans:
1. F.D FAN(Forced fan)
2. I.D FAN(Induced fan)
3. P.A FAN(Primary fan)
• Forced draft fan: In the axial reaction fans (Type AP) the major
part of (about 80%) energy transferred is converted into static
pressure in the impeller itself. The rest of the energy is converted
into static pressure in the diffuser. These fans are generally driven
at constant speed. The flow is converted by varying the angle of
incidence of impeller blades.it therefore becomes possible by this
process to achieve high efficiencies even during part load
operation.
The blade pitching operation is performed by mechanical linkages
connected to a hydraulic servomotor which if flanged to the
impeller
Technical Data:
Application : forced draft fan
No. of : 2

27. Medium handled : Atmospheric air
Orientation : Vertical Suction and Horizontal
Delivery
Capacity : 105.2 m3
/sec
Temp. : 45 0
c
Speed : 1480rpm
Coupling : Rig flex coupling
Driving motor rating : 700 KW
Fan weight : 8 tones
Type of fan regulating : Blade Pitch Control
INDUCTION DRAFT FAN: - radial fans manufactured are single stage,
single/double suction, simply supported/overhung centrifugal machine which can
be used to handle fresh air as well as hot gases in power plant application.
In this the medium handled enters the impeller axially and after passing through
the impeller leaves radially. A large part of the energy transferred to the medium
is converted into kinetic energy as the medium passes through the impeller. The
spiral casing converts part of the kinetic energy in the medium to pressure
energy. These fans are generally driven by constant speed motors. The output of
the fan is usually controlled by inlet dampers or inlet guide vanes or by varying
the speed of the by suitable speed control device.
Technical Data:
Application : induced draft fan
No. of : 3
Type : NDZV 33 S
Medium handled : Flue Gas
Orientation : 450 top incl. Suction Bottom Horizontal Delivery

28. Capacity : 2505 m3
/sec
Temp. Of medium : 1540
c
Speed : 740 rpm
Coupling : Hydraulic Coupling
Drive motor rating : 1750 KW
Fan weight : 52.7 tones
PRIMARY AIR FAN: - PA fan is sane as forced draft fan only the difference
is that in this fan there are two stages AP fan (Axial profile fan) the two impeller
are connected by means of a link rod with this w can operate both the impeller
blades synchronously.
TECHANICAL DATA
Application : primary air fan
No. of : 3
Type : AP 217/12
Medium handled : Atmospheric air

29. BOILER FURNACES
A boiler furnace is a chamber in which fuel is burnt to liberate the heat energy. It
provides support and enclosures for the combustion equipment’s. The boiler
furnace walls are made of refractory materials such as fire clay, silica, kaolin etc.
Such materials have the property of resisting change of shape, weight or physical
properties at high temperatures. The construction of boiler furnace varies from
plain refractory walls to completely water cooled walls, depending upon
characteristics of fuel used and ash produced, firing method, nature of load
demand, combustion space required, excess air used, operating temperature,
initial and operating costs.
The plain refractory walls are suitable for small plants where the furnace
temperature may not be high. For larger plants, where the furnace temperature is
quite high, refractory walls are made hollow and air is circulated through hollow
space to keep the temperature of the furnace walls low.
The recent development is to use water walls. Water walls are built of tubes of
diameters ranging from 25mm to 100mm variously spaced with or without fins
or studs and bare or with different thickness of mouldable refractory on the inner
face. Heat transfer rates run from 0.5x106
to 104x106
Kilo-calories per cubic
metre of surface. To meet these requirements of heat transmission, circulation on
the water side must be adequate obtained by convection or by pumps. This type
is suitable for pulverised fuel fired boilers and high steaming rates can be
maintained.
Super-heater and Re-heater
A Super-heater is a device which removes the last traces of moisture from the
saturated steam leaving the boiler tubes and also increases its temperature above
the saturation temperature. For this purpose, the heat of combustion gases from

30. the furnace is utilised. Super-heaters consists of groups of tubes made of steel
(carbon steel for steam temperature up to 950℉, carbon-molybdenum steel for
steam temperatue of 1,050 ℉ and stainless steel for steam temperature of
1,200℉) with an outside diameter ranging from 25mm to 64mm. The super-
heater tubes are heated by the heat of combustion gases during their passage from
the furnace to the chimney.
Super-heaters are classified into two parts.
Radiant Super-Heater:- It is located in the furnace between the furnace water-
walls and absorbs heat from the burning fuel through radiation. It has two main
disadvantages firstly, owing to high furnace temperature; it may get overhead
and therefore, requires a careful design. Secondly it gives drooping
characteristics i.e. the temperature of superheat falls with the increase in steam
output, because with the increases in steam output and radiant heat transfer being
a function of furnace temperature increases slowly with steam flow or the steam
temperature falls.
Convection Super-Heater:- It is located well back in the boiler tube bank,
receives its heat entirely from fuel gases through convection. It gives rising
characteristics i.e. the temperature of superheat increases with the increase in

31. steam output because with the increase in steam output both gas flow over the
super-heater tubes and steam flow within the tubes increase with causes increase
in the rate of heat transfer and mean temperature difference. Convection super-
heaters are more commonly used.
The function of the re-heater is to re-superheat the partly expanded steam from
the turbine. This is done so that the steam remains dry as far as possible through
the last stage of the turbine. Modern plants have re-heaters as well as super-
heaters in the same gas passage of the boiler. They can also be of combination
type using both radiant and convective heating.
Economiser
When the combustion gases leave the boiler after giving most of their heat to
water tubes, super-heater tubes and reheater tubes, they still possess lot of heat
which if not recovered by means of some devices, would go waste. Economiser
and air pre-heater are such devices which recover the heat from the flue gases on
their way to chimney and raise the temperature of feed water and air supplied for
combustion respectively.
Economiser raises boiler efficiency (by10-12%), causes saving in fuel
consumption and reduces temperature stresses in boiler joints because of higher
temperature of feed water, but involves extra cost of installation, maintenance
and regular cleaning and additional requirement of space. Economiser tubes are
made of steel either smooth or covered with fins to increase the heat transfer
surface area. The tubes can be arranged in parallel continuous loops welded to
and running between a pair of water headers or in return bend design with
horizontal tubes connected at their ends by welded or gasket return bends outside
the gas path. The feed water flow through the tubes and the flue gases outside the
tubes across them. The heat transfer from flue gases to feed water is by
convection. The feed water should be sufficiently pure not to cause forming of
scales and cause internal corrosion and under boiler pressure. The temperature of

32. feed water entering the economiser should be high enough so that moisture from
the flue gases does not condense on the economiser tubes, which may absorb
S02and CO2 from the flue gases and form acid to corrode the tubes. The
temperature of the feed water entering the economiser is usually kept above 84℃.
In a modern economiser, the temperature of feed water is raised from about
247℃ to 276℃.
Air preheater
Air preheaters are employed to recover the heat from the flue gases leaving the
economiser and heat the incoming air required for combustion. This raises the
temperature of the furnace gases, improves combustions rates and efficiency, and
lowers the stack temperature, thus improving the overall efficiency of the boiler.
It has been found that a drop of 20-22c in the fuel gas temperature increases the
boiler efficiency by about 1%. An air pre-heater should have high thermal
efficiency, reliability of operation, less maintenance charges, should occupy
small space, should be reasonable in initial cost and should be accessible.
Air preheater are two types –
Recuperative air preheater: - These types of air preheater are continuous in
action while the regenerative type is discontinuous in action and operates on
cycle. In recuperative type of heaters, the two fluids ate separated by heat transfer
surface, one fluid flowing constantly on one side and the other fluid on the other
side of the surface. In the recuperative type of heaters, the rate of heat transfer is
low, space occupied in large and cleaning of surface is difficult. The plate type
recuperative heater consists of rectangular flat plates spaced from 12.5mm to
25mm apart, leaving alternate air and gas passages.
Regenerative air preheater: - It consists of a rotor made up of corrugated
elements. The rotor is placed in a drum which has been divided into two
compartments, air and gas compartments. To avoid leakage from one
compartment to the other seals are provided. The rotor rotates at a very slow

33. speed of 3-4rpm. As the rotor rotates, it alternately passes through flue gases and
air zones. The rotor elements are heated by the flue gases in their zone and
transfer this heat to air when they are in air zone.
SPECIFICATION
1. Heating element – hot end, hot intermediate, cold end
Materials –carbon& carbon steel
2. Rotor main drive motor – 11KW, 1450rpm, 50 Hz
3. Guide bearing – spherical roller bearing
Support bearing – spherical roller thrust
Thermostat –burling thermostat
4. Oil capacity
Guide bearing housing – 25 litre
Supporting bearing housing- 150 litre
5. Number of steam coil APH – 2 no’s per boiler
6. Installed position –vertical
7. Design pressure – 20 kg/ cm2
8. Design temp – 2500 0
c
9. Weight of one steam coil APH- 1950kg

34. CONDENSER
1. To provide lowest economic heat rejection temperature from the steam thus
saving on steam required per unit of electricity
2. To convert exhaust steam to water for reuse this saving on feed water
required.
3. DE aeration of make-up water introducing in the condenser.
4. To form a convenient point for introducing makes up water
Surface condenser:
This type is generally used for modern steam turbine installations. Condensation
of exhaust steam takes place on the outer surface of the tubes, which are cooled
by water flowing inside them.
The condenser essentially consist of a shell, which enclose the steam space.
Tubes carrying cooling water pass through the steam space. The tubes are
supplied cooling water from inlet water box on one side and discharged, after
taking away heat from the steam, to the outlet water box on the other side.
Instead of one inlet and one outlet water boxes, each supplying cooling water to a
separate bundle of tubes. This enables cleaning and maintenance of part of the
tubes while turbine can be kept running on a reduced load.
Description of condenser
Steam, after expansion through the prime mover, goes through the condenser
which condenses the exhaust steam and also removes air and other non-
condensable gases from steam while passing through them. The recovery of
exhaust steam in the condenser reduces the make-up feed water that must be
added to the system, from 100% when exhausted to atmosphere, to about 1-5%
and thereby reduces considerably the capacity of water treatment plant. The
exhaust pressure may be lowered from the standard atmospheric pressure to
about 25mm of Hg absolute and thereby permitting expansion of steam, in the
prime mover, to a very low pressure and increasing plant efficiency operation.
Any leakage of air into the condenser destroys the vacuum and causes

35. i. An increase in the condenser pressure which limits the useful heat
drop in the prime mover.
ii. A lowering of the partial pressure of the steam and of the saturation
temperature along with it. This means that the latent heat increases
and there- fore, more cooling water is required.
Condenser

36. EVAPORATOR
Evaporators ate employed for supplying pure water as make-up feed water in
steam power plants. In an evaporator raw water is evaporated by using extracted
steam and the vapours so produced may vex condensed to give a supply of
distilled or pure feed water. These vapours can be condensed in feed water
heaters by the fee water or in separate evaporator condensers using teed water as
the cooling medium.
There are two main types of evaporators-
Film or Flash Type Evaporator: -In this kind of evaporators, there are tubes or
coils through which the steam is passed. Raw water is sprayed by means of
nozzles on the surface of these tubes and some of the raw water will be converted
into vapours. These vapours ate collected from the evaporator and are condensed
to give pure and distilled water for boilers.
Submerged Type Evaporator: - In this kind of evaporators, the tubes through
which the steam is passed are submerged in raw water. The vapours rising from
the raw water are collected and condensed to provide a supply of pure make-up
feed water. Because of continuous operation of raw water, concentration of
impurities goes on increasing, so periodic blowing down of raw water is
essential. Scales formed on the surface of the tubes will retard the heat transfer
rate and so its removed is very necessary. This is removed by draining the raw
water from the shell and then spraying the tubes with cold water while the tubes
are kept hot by flow of steam through them. The scale is cracked off and is
washed away by the spray.
Feed Water Heater
These heaters are used to heat the feed water by means of bled steam before
it is supplied to the boiler. Necessity of heating feed water before feeding it back
to the boiler arises due to the following reasons:
i. Overall power plant efficiency is improved.

37. ii. Thermal stresses due to cold water entering the drum of boiler are
avoided.
iii. There is an increase in the quantity of steam produced by the boiler.
iv. The dissolved oxygen and carbon dioxide which would otherwise cause
boiler corrosion are removed in the feed water heaters.
v. Some other impurities carried by steam and condensate, due to
corrosion in the boiler and condenser, ate precipitated outside the
boiler.
Feed water heaters are two types:
Open or Contact Heaters:- These are usually constructed to remove non-
condensable gases from water and steam along with raising the feed water
temperature. Such heaters are also called the deaerator. The amount of gas
dissolved in water depends upon its temperature. This decreases sharply with the
increasing temperatures and falls to almost zero at the boiling point. Such feed
water heaters are used in small power plants.
Closed or Surface Heaters:- These heaters consist of closed shell in which
there are tubes or coils through which either steam or water is circulated.
Usually, the water is circulated through the tubes and the steam and water may
flow either in the same direction or in opposite directions. Such heaters may be
the temperature of steam. For maintaining a high overall heat transfer for the

38. heater, the water velocity should be high but pumping costs limit the velocity to
about 1-2.5m/s.

39. COOLING TOWERS
A cooling tower is a wooden or metallic rectangular structure inside of which is
packed with baffling devices. The hot water is led to the tower top and falls down
through the tower and is broken into small particles while passing over the
baffling devices. Air enters the tower from the bottom and flows upward. The air
vaporises a small percentages of water, thereby cooling the remaining water. The
air gets heated and leaves the tower at the top. The cooled water falls down into a
tank below the tower from where into small droplets, the drought provided by the
tower and the large evaporating surface help to cool water very quickly
practically during the time while it is descending. Although eliminators are
provided at the top of the tower to prevent escape of water particles with air but
even then there is a loss of water to the extent of around 5% and this loss has to

40. made up by water drawn from well or any other source. Air can be circulated in
cooling towers through draught.
Cooling water pump:
The motor of the CWP has following specification;
Type : Y1600-16/2150
Output power : 16000KW
Stator voltage : 6.6KV
Speed : 372rpm
Frequency : 50Hz
Stator rated current : 182A
Stator connection : 2Y
Internal Structure of Cooling Tower

41. Ambient temperature : 50 o
c
Insulation class : B
Weight : 17500Kg
CW pump
Pump is single stage double suction centrifugal pump
Type : 1400S25-1
Capacity : 1600m3
/h
Speed : 370 rpm
Power : 1600 KW
Weight : 35000kg
Head : 25m
NPSHR : 8.5m
Manufacturer : B.H.E.L. , Haridwar
Rating : 3550KW
Speed : 1492rpm
Electricity supply : 6.6KV, 3-phase, 50 Hz

42. TURBO ALTERNATOR
In a central power station, the system turbine and alternator are directly coupled
to avoid transmission losses. Turbo-alternators are high speed machines (3,000 or
5,000RPM) for 50 Hz systems. These machines have horizontal configurations
and smooth cylindrical (or non-salient pole) type field structure wound usually
for 2 or 4 poles. To reduce the peripheral speed (maximum peripheral speed
should not exceed 175 m/s) the diameter of the rotor is kept small and axial
length is increased. The ratio of diameter to axial length ranges from 1/3 to ½.
Due to high peripheral speed, the rotating part of the turbo-alternator is subjected
to high mechanical stresses. As a result the rotor of large turbo-alternator is
normally built from solid steel forging. Chromium-nickel-steel or special
chrome-nickel-molybdenum steel is used for rotors of turbo-alternators. The coils
are held in place by steel or bronze wedges and the coil ends are fastened by
metal rings. Normally two-third of the rotor is slotted for the field winding and
one-third is left without slots so as to form the pole faces.500 MW units
generally use hollow stator conductor. The short-circuit ratio is 0.4 to 0.6
The non-salient field structure used in turbo-alternators has the following special
features:
i. They are of smaller diameter (maximum 1m in 2-pole machine) and of very
long axial length.
ii. Robust construction and noiseless operation.
iii. Less wind age (air-resistance) loss.
iv. Better in dynamic balancing.
v. High operating speed (3,000 or 1,500).
vi. Nearly sinusoidal flux distribution around the periphery, and therefore,
gives a better emf waveform than obtainable with salient pole field
structure.

43. vii. There is no need of providing damper windings (except in special cases to
assist in synchronising) because the solid field poles themselves act as
efficient dampers.
.

44. FUEL HANDLING AND FEED WATER
Fuel Handling
Coal can be handled manually or mechanically. Mechanical adopted as it is
reliable, expeditious and economical. Owing to large quantity of coal required to
be handled every day, mechanical handling has become absolutely necessary.
The main required of a coal handling plant are reliability, soundness and
simplicity requiring a minimum of operatives and minimum of maintenance.
Besides, the plant should be able to deliver the required quantity of coal at
destination during peak hours.
Transportation or Delivery of Coal
There are three ways of transporting coal from coal mines to the site of power
plant i.e. by sea or river, by road and by rail. If the power plant is situated on the
bank of a river or near the sea-shore, it is often economical to transport coal in
boats or barges, unload mechanically by cranes or grab buckets and place in the
storage yard or directly to the conveyor system to be carried to the power plant.
Transportation by road is possible for small and medium size plants only. The
chief advantage of this system is possibility of carrying coal directly into the
power house up to the point of consumption. Moreover due to less traffic
restrictions it is considered better system in comparison to rail transport.
Transportation of coal by rail, particularly for station located interior, is still the
most important mean of transportation in common use.
Methods of Coal Handling
Irrespective of the method of transportation of coal adopted, the coal has to be
carried to the boiler stokers or the coal preparation plant in the case of pulverised
fuel firing. The various stages in coal handling are:

45. Unloading Stage:-The coal is unloaded from the point of delivery by means of
i. coal shakers or coal accelerators
ii. rotary car dumpers or wagon tipplers and
iii. grab buckets
The choice equipment will depended upon the method of transportation adopted.
The main equipment employed for taking the coal from the unloading site to the
dead storage are belt conveyors, screw conveyors, bucket elevators, skip hoist,
grab bucket conveyors and flight conveyors.
Reclamation: It is the process of taking coal from dead storage for preparation
or further feeding to hoppers or live storage.
Live storage: It consists of about one day requirement of coal of power plant and
is usually a covered storage in the power station near the boiler furnace. It can be
provided with bunkers and coal bins.
Input handling: refers to handling of coal between the live storage and firing
equipment. In case of simple stoker firing only chutes may be required to feed
the coal from storage bunkers to the firing units.
Coal weighing enables: one to have an idea of total quantity of coal delivered at
the site and also whether or not proper quantity has been burnt as per load on the
plant. It can be accomplished by
i. weighing bridge,
ii. belt scale and
iii. Automatic recording system.
The wagon can be unloaded either manually or by using rotary wagon tipplers.

46. Feed Water
The system coming out the turbine is condensed and the condensate is feedback
to the boiler as feed water. Some water may be lost due to blow-down, leakage
etc. and to make up these losses additional water, called the make-up water, is
required to be fed to the boiler. The make-up water in a modern thermal plant is
about 1-4%.
The sources of boiler feed water is generally a river or lake which may contain
suspended and dissolved impurities, dissolved gases etc.
It is necessary to heat and purify the water before feeding to the boiler.
The heating of feed water
i. improves the overall efficiency of the plant
ii. removes dissolved oxygen and carbon-die-oxide
iii. causes precipitation of other impurities carried by steam and condensate
outside the boiler
iv. Avoids thermal stresses owing to entry of cold water into the boiler.
The water is treated for removal of suspended and soluble solids and removal of
gases.
The various methods used for water treatment are:
i. Mechanical (sedimentation and filtration)
ii. Thermal (distillation and deaerate heating)
iii. Chemical (lime treatment, soda treatment, lime soda treatment, zeolite
treatment and demineralisation).
Lime treatment is suitable for the treatment of carbonate hardness, carbon-die-
oxide in the water, either in a free state or in bicarbonate combination. In the
process lime is taken up in hydrated form and relatively insoluble precipitate of
calcium carbonate and magnesium hydroxide and formed. The process is best
carried on in large tanks from the treating plant.

47. ASH HANDLING AND DRAUGHT SYSTEM
Ash Handling: -Coal contains a considerable amount of ash. The percentage of
ash in the coal varies from about 5% in good quantity coals to about 40% in poor
quantity coals. Generally poor quality coal is used in steam power plants and,
therefore, a system power plant produces hundreds of tonnes of ash daily (a
modern 2,000 MW steam power plant produces about 5,000 tonnes of ash daily).
For removal of ash from the boilers and its disposal to the suitable site is quite
difficult and quite elaborate equipment is required. Ash handling comprises the
following operations:
i. Removal of ash from the furnace ash hoppers.
ii. Transfer of this ash to a fill or storage and
iii. disposal of stored ash
The ash can be disposed of in the following ways.
i. Waste land sites may be reserved for the disposal of ash.
ii. Building contractors may utilise it to fill the low lying areas.
iii. Disused quarries within reasonable distance of the power plant may be
employed for dumping the ash into the evacuated land.
iv. Deep ponds may be and the ash can be dumped into these ponds to fill
them completely. When such ponds are completely filled, they may be
covered with soil and seeded with grass.
v. When seaborne coal is used, barges may take the ash to sea for disposal
into a water grave.

48. Dust Collection
The exhaust gases leaving the boiler contain particles of solid matter in
suspension-smoke, dust, soot, flyash or carbon as material called “cinder”. The
quantity of these solid particles largely depends upon the method of fuel firing.
Flue dust is greatest with pulverised fuel and spreader stoker firing systems are
much less with underfeed stoker systems. In case of pulverized fuel firing, 60 to
80 percent of the total ash produced in the furnace, escapes through the chimney
as fuel dust.
Gas cleaning devices make use of certain physical electrical properties of the
particular matter of the gas stream. Basically gas cleaning devices called the dust
collectors may be classified into mechanical and electrical ones (electrostatic
precipitators).
Mechanical dust collectors can be further classified as wet and dry dust
collectors. In wet type units, dust is washed away from the flue gases by spraying
water on it. This system is usually not used because it need large amount of
water.
Draught System
In a boiler the combustions of the fuel requires supply of sufficient quantity of air
and removal of exhaust gases and this is achieved by draught system.
The circulation of air is caused by a difference in pressure, known as draught.
Thus be draught is the difference in pressure between the two points i.e.
atmosphere and inside the boiler.
Natural Draught: - The natural draught is provided by the action of chimney or
stack and is used only in small boilers. Its intensity depends upon the average
temperature (difference between the flue gases within the chimney and the
outside air (the gases within the chimney are at as higher temperature than that of

49. the surrounding air) and also on the height of the chimney above the level of the
furnace grate.
Mechanical Draught: -Artificial or mechanical draught is provided when the
natural draught caused by a chimney is not sufficient or where a certain draught
is required to be maintained irrespective of weather conditions or boiler operating
conditions. In case of large steam boilers where economisers and air pre-heaters
are employed, the exit temperature of the flue gases is sufficiently lowered and
also the volume of air required is tremendously high. In such cases the height of
the chimney to cause the required draught may be excessive in height and cost.
In a mechanical draught system, the movement of air is due to the action of a fan.
A mechanical draught may consist of induced draught or forced draught or both.

50. STEAM POWER PLANT CONTROLS
In case of large power plant the various controls used to be accomplished
manually on the basis of instrument reading. Now the various controls involved
in the power plant operation have been completely automated resulting in
i. Increased labour productivity
ii. Improvement in the safety of operation and reliable functioning of the
various instruments and equipment
A number of controls, such at the boiler, turbine and generator unit are provided
in a steam power plant so as to maintain the best conditions at all loads. Turbine
governing is affected by throttling the steam at the main valve or by reducing
only the steam mass flow by cutting off one or more nozzles through which the
seam enters the blades. The first method of governing, known as throttle
governing or qualitative governing is used in case of small turbines and the
second method of governing, known as nozzle governing or cut-off governing or
quantitative governing, is used of large turbines. Maintenance of proper vacuum
in the condenser, enough circulating water, a number of pumps, oil pressure for
control of circuits, steam bleeding if any and the heater and feed water control
are other requirement of the turbine.
In case of an isolated generating unit, increase in load causes reduction in the
speed of the unit and hence reduction in frequency. However, in case of
generating connected to infinite bus bars the load shared by the unit can be
adjusted the turbine speed. In this case frequency remains constant.
In general, centralized control is employed for modern steam power plants, the
boiler and turbine control being at one place in the turbine room and the
generator and feeder controls in the control room, in some cases all controls are
centralized in one room, called the control room.

51. THERMAL POWER PLANT AUXILIARIES
The equipment’s which help in the proper functioning of the plant are called
plant auxiliaries. The various plant auxiliaries can be grouped under the
subheading of boiler auxiliaries, coal and ash auxiliaries, turbo-alternator
auxiliaries and miscellaneous ones.
Boiler make-up water treatment plant and storage
Since there is continuous withdrawal of steam and continuous return
of condsate to the boiler, losses due to blow down and leakages have to be made
up to maintain a desired water level in the boiler steam drum. For this,
continuous make-up water is added to the boiler water system. Impurities in the
raw water input to the plant generally consist of calcium and magnesium salts
which impart hardness to the water. Hardness in the make-up water to the boiler
will form deposits on the tube water surfaces which will lead to overheating and
failure of the tubes. Thus, the salts have to be removed from the water, and that is
done by water demineralising treatment plant (DM). A DM plant generally
consists of cation, anion, and mixed bed exchangers. Any ions in the final water
from this process consist essentially of hydrogen ions and hydroxide ions, which
recombine to form pure water. Very pure DM water becomes highly corrosive
once it absorbs oxygen from the atmosphere because of its very high affinity for
oxygen.
The capacity of the DM plant is dictated by the type and quantity of salts in the
raw water input. However, some storage is essential as the DM plant may be
down for maintenance. For this purpose, a storage tank is installed from which
DM water is continuously withdrawn for boiler make-up. The storage tank for
DM water is made from materials not affected by corrosive water, such as PVC.
The piping and valves are generally of stainless steel. Sometimes, a steam
blanketing arrangement or stainless steel doughnut float is provided on top of the

52. water in the tank to avoid contact with air. DM water make-up is generally added
at the steam space of the surface condenser (i.e., the vacuum side). This
arrangement not only sprays the water but also DM water gets de-aerated, with
the dissolved gases being removed by a de-aerator through an ejector attached to
the condenser.
Fuel preparation system
In coal-fired power stations, the raw feed coal from the coal storage area is first
crushed into small pieces and then conveyed to the coal feed hoppers at the
boilers. The coal is next pulverized into a very fine powder. The pulverisers may
be ball mills, rotating drum grinders, or other types of grinders.
Oil must kept warm (above its pour point) in the fuel oil storage tanks to prevent
the oil from congealing and becoming unpumpable. The oil is usually heated to
about 100 °C before being pumped through the furnace fuel oil spray nozzles.
Boilers in some power stations use processed natural gas as their main fuel.
Other power stations may use processed natural gas as auxiliary fuel in the event
that their main fuel supply (coal or oil) is interrupted. In such cases, separate gas
burners are provided on the boiler furnaces.
Barring gear
Barring gear (or "turning gear") is the mechanism provided to rotate the turbine
generator shaft at a very low speed after unit stoppages. Once the unit is
"tripped" (i.e., the steam inlet valve is closed), the turbine coasts down towards
standstill. When it stops completely, there is a tendency for the turbine shaft to
deflect or bend if allowed to remain in one position too long. This is because the
heat inside the turbine casing tends to concentrate in the top half of the casing,
making the top half portion of the shaft hotter than the bottom half. The shaft
therefore could wrap or bend by millionths of inches.
This small shaft deflection, only detectable by eccentricity meters, would be
enough to cause damaging vibrations to the entire steam turbine generator unit

53. when it is restarted. The shaft is therefore automatically turned at low speed
(about one percent rated speed) by the barring gear until it has cooled sufficiently
to permit a complete stop.
Oil system
An auxiliary oil system pump is used to supply oil at the start-up of the steam
turbine generator. It supplies the hydraulic oil system required for steam turbine's
main inlet steam stop valve, the governing control valves, the bearing and seal oil
systems, the relevant hydraulic relays and other mechanisms.
At a preset speed of the turbine during start-ups, a pump driven by the turbine
main shaft takes over the functions of the auxiliary system.
Generator cooling
While small generators may be cooled by air drawn through filters at the inlet,
larger units generally require special cooling arrangements. Hydrogen gas
cooling, in an oil-sealed casing, is used because it has the highest known heat
transfer coefficient of any gas and for its low viscosity which
reduces windage losses. This system requires special handling during start-up,
with air in the generator enclosure first displaced by carbon dioxide before filling
with hydrogen. This ensures that the highly flammable hydrogen does not mix
with oxygen in the air.
The hydrogen pressure inside the casing is maintained slightly higher
than atmospheric pressure to avoid outside air ingress. The hydrogen must be
sealed against outward leakage where the shaft emerges from the casing.
Mechanical seals around the shaft are installed with a very small annular gap to
avoid rubbing between the shaft and the seals. Seal oil is used to prevent the
hydrogen gas leakage to atmosphere.
The generator also uses water cooling. Since the generator coils are at a potential
of about 22 kV, an insulating barrier such as Teflon is used to interconnect the

54. water line and the generator high-voltage windings. Demineralised water of low
conductivity is used.
Generator high-voltage system
The generator voltage for modern utility-connected generators ranges from 11
kV in smaller units to 22 kV in larger units. The generator high-voltage leads are
normally large aluminium channels because of their high current as compared to
the cables used in smaller machines. They are enclosed in well-grounded
aluminium bus ducts and are supported on suitable insulators. The generator
high-voltage leads are connected to step-up transformers for connecting to a
high-voltage electrical substation (usually in the range of 115 kV to 765 kV) for
further transmission by the local power grid.
The necessary protection and metering devices are included for the high-voltage
leads. Thus, the steam turbine generator and the transformer form one unit.
Smaller units may share a common generator step-up transformer with individual
circuit breakers to connect the generators to a common bus.
Monitoring and alarm system
Most of the power plant operational controls are automatic. However, at times,
manual intervention may be required. Thus, the plant is provided with monitors
and alarm systems that alert the plant operators when certain operating
parameters are seriously deviating from their normal range.
Control Rooms: -The control room is the nerve centre of a power station. The
various controls performed from here are voltages adjustment, load control,
emergency tripping of turbines etc. and the equipment and instruments housed in
a control room are synchronising equipment, voltages regulators, relays,
ammeters, voltmeters, wattmeter’s, kWh meters, kVARh meters, temperature
gauges, water level indicators and other appliances, as well as a mimic diagram
and suitable indicating equipment to show the opened or closed position of
circuit breakers, isolators etc.

55. Fig.10 Control Room of Thermal Power Plant

56. EFFICIENCY AND SUPER- CRITICAL TECHNOLOGY
Efficiency of Thermal Power Plants
The thermal efficiency of thermal power plants, defined as the ratio of the heat
equipment of the mechanical energy transmitted to the turbine shaft and the heat
of combustion is quite low (about 30%). Overall efficiency of the power plant,
defined as the ratio of heat equipment of electrical output to the heat of
combustion, is about 29%. The overall efficiency is determined by multiplying
the thermal efficiency of power plant by the efficiency of generation.
Table2: Efficiency of Installed Plant Capacity
Advantages of Thermal Power Plants
• They can respond to rapidly changing loads without difficulty
• A portion of the steam generated can be used as a process steam in
different industries
• Steam engines and turbines can work under 25 % of overload
continuously
• Fuel used is cheaper
• Cheaper in production cost in comparison with that of diesel power
stations
Installed Plant Capacity Average Overall Thermal Efficiency
Up to 1MW 4%
1MW to 10MW 12%
10MW to 50MW 16%
50MW to 100MW 24%
above 100MW 27%

57. Disadvantages of Thermal Power Plant
• Maintenance and operating costs are high
• Long time required for erection and putting into action
• A large quantity of water is required
• Great difficulty experienced in coal handling
• Presence of troubles due to smoke and heat in the plant
• Unavailability of good quality coal
• Maximum of heat energy lost
• Problem of ash removing
Super Critical Technology
At a temperature of about 600℃ and pressure of 30N/mm2
, water enters a
supercritical phase and has properties between those of liquid and gas. Water in
supercritical stage can dissolve a number of organic compounds and gases and on
addition of hydrogen peroxide and liquid oxygen combustion process starts. The
steam power plants operating on this principle are called supercritical plats.
The advantages of such plants are that low grade fossil fuels (e.g. lignite) can be
used, NO2 emissions are completely eliminated and SO2 emission are reduced
and complete burning of coal occurs. So the plant has no need of
desulphurisation and equipment and soot collector. With this system the cost of
processing flue gas emissions (electrostatic precipitator etc.) is eliminated and
cooling water requirements are also reduced, so the system becomes more
economical and efficient. Supercritical power plants, these days have an overall
efficiency of just over 40%. With the use of temperature around 700℃ (known as
ultra supercritical condition), the overall efficiency of the system may be
improved to around 50%.

58. TECHNICAL GAINS
After completing my training, I have not only developed the skill of practically
applying my conceptual knowledge into use but I have understood the rigorous
hard work that requires to be put in, in an actual industry that no book can ever
teach me. Moreover, I have understood various topics in depth and can answer
questions such as:
• Why the theoretical knowledge imparted to us during our courses
is useless without an exposure to the industries?
• How does a power plant system works?
• What are measures to prevent plant accident and emergency?
• What procedure to follow in case of an emergency?
• What various practical reasons are behind many things followed in
an Industry?
• Effects on environment through modern power plant as compared
to old power plant.
• The various steps that are taken in an industry towards waste-
management

59. REFERENCE
• "Suratgarh Super Thermal Power Station"Rajasthan
RajyaVidyutUtpadan Nigam Ltd
• A course in Electrical Power By J.B.Gupta
• Babcock & Wilcox Co. (2005). Steam: Its Generation and Use (41st
edition ed.)ISBN 0-9634570-0-4.
• Thomas C. Elliott, Kao Chen, Robert Swanekamp (coauthors)
(1997). Standard Handbook of Powerplant Engineering (2nd edition
ed.). McGraw-Hill Professional. ISBN 0-07-019435-1
• Maury Klein, The Power Makers: Steam, Electricity, and the Men Who
Invented Modern America Bloomsbury Publishing USA, 2009 ISBN 1-
59691-677-X
• J.C. Hensley (Editor) (2006). Cooling Tower Fundamentals (2nd Ed.
ed.). SPX Cooling Technologies.
• Power plant engineering by R.K Rajput