4. A Rankine cycle with a two-stage steam turbine and
a single feed water heater.
5. BANDEL THERMAL POWER
STATION
OVERVIEW:-
Situated on the western bank of Bhagirathi River, Bandel Thermal Power Station is just 1 Km from
the Assam Road and connected with a heavy duty metal lead road 3 km off the Grand trunk
Road, NH2. Bandel Thermal Power Station’s nearest railhead is Tribeni on the Bandel-Katwa-
Azimgunj Line under Eastern Railways.
Successfully meeting the power sector demand for the State for more than four decades, Bandel
Thermal Power Station still remains a prominent player in the states power supply chain. Bandel
Thermal Power Station’s fifth unit with a capacity of 210 MW installed in 1982, was first of its kind
in Eastern India & fifth in India. Today, with five operational units the total installed capacity of the
station stands at 450 MW.
SI
NO
UNITS CAPACITY(MW)
1 UNIT-I 60
2 UNIT-II 60
3 UNIT-III 60
4 UNIT-IV 60
5 UNIT-V 210
TOTAL
CAPACITY-
450
UNIT SYNCHRONI
SATION
COD
1 04.09.1965 04.09.1965
2 18.10.1965 18.10.1965
3 17.02.1966 17.02.1966
4 03.08.1966 03.08.1966
5 08.10.1982 20.03.1983
6. WHAT IS THERMAL POWER PLANT ?
A thermal power station is a power station in which heat energy is
converted to electric power. In most of the places in the world
the turbine is steam-driven. Water is heated,& it turns into steam
and spins a steam turbine which drives an electrical alternator. After
it passes through the turbine, the steam is condensed in
a condenser and recycled to where it was heated; this is known as
a Rankine cycle. The greatest variation in the design of thermal
power stations is due to the different heat sources; fossil
fuel dominates here, although nuclear heat energy and solar heat
energy are also used. Some prefer to use the term energy
centre because such facilities convert forms of heat energy into
electrical energy. Certain thermal power stations are also designed
to produce heat energy for industrial purposes, or district heating,
or desalination of water, in addition to generating electrical power.
8. 1.COAL HANDLING PLANT
The function of coal
handling plant is automatic
feeding of coal to the
boiler furnace.
Coal handling plant
consists of a few systems-
• Coal.
• Unloading system.
• Conveyor system.
• Crushing system.
• Feeding system.
• Stacking system.
• Magnetic separator/metal
detector.
• Bin/chute vibratory system.
• Coal weighment.
• Coal sampling.
• Fire fighting system.
• Dust suppression system.
• Dust extraction system.
9. 2.PULVERISING PLANT
In modern thermal power plant , coal is pulverised i.e. ground
to dust like size & carried to furnace in a stream of hot air .
Pulverising is a mean of exposing a large surface area to the
action of oxygen & consequently helping combustion.
Pulverising mills are further classified as-
• Contact mill.
• Ball mill.
• Impact mill.
10. 3.DRAFT SYSTEM
The circulation of air is caused by a
difference in pressure , known as draft.
Draft is differential pressure between
atmosphere & inside the boiler . It is
necessary to cause the flow of gases
through the boiler setting . It may be –
• Natural draft.
• Mechanical draft.
11. 4.BOILER
A boiler or steam generator is a
closed vessel in which water
under pressure , is converted
into steam. It is one of the major
components of the thermal
power plant . It is always
designed to absorb maximum
amount of heat released in the
process of combustion.
Boilers are of two types-
• Fire tube boiler.
• Water tube boiler.
12. 5.SUPERHEATERS & REHEATERS
Most of the modern boilers are having superheater & reheater arrangement.
• SUPERHEATERS:
Superheater is a component of a steam-generating unit in which steam , after it has
left the boiler drum , is heated above its saturation temperature. The amount of
superheat is added to the steam is influenced by the location , arrangement, &
amount of superheater surface installed , as well as the rating of the boiler. The
superheater may consist of one or more stages of tube banks arranged to effectively
transfer heat from the products of combustion. Superheaters are classified as
convection , radiant or combination of these.
• REHEATERS:
Some of the heat of the superheated steam is used to rotate the turbine where it
loses some of its energy. Reheater is also steam boiler component in which heat is
added to this intermediate-pressure steam , which has given up some of its energy in
expansion through the high-pressure turbine. The steam after reheating is used in to
rotate the second steam turbine where the heat is converted to mechanical energy.
This mechanical energy is used to run the alternator , which is coupled to turbine ,
thereby generating electrical energy.
13. 6.TURBINE
A steam turbine converts heat energy
of steam into mechanical energy &
drives the generator. It uses the
principle that steam when issuing
from a small opening attains a high
velocity. This velocity attained during
expansion depends on initial & final
heat content of the steam. This
difference between initial & final
heat content represents the heat
energy converted into kinetic energy
. These are of two types-
• Impulse turbine.
• Reaction turbine.
14. 7.ASH HANDLING PLANT
The percentage of ash in coal
varies from 5% in good quality
coal to about 40% in poor
quality coal. Power plants
generally use poor quality coal,
thus amount of ash produced
by it is pretty large. The stations
use some conveyor
arrangement to carry ash to
dump sites directly for carrying
& loading it to trucks & wagons
which transport it to the site of
disposal.
15. 8.CONDENSER
Steam after rotating steam turbine comes to condenser. Condenser refers
here to the shell & tube heat exchanger(or surface condenser)installed at the
outlet of every steam turbine in Thermal power stations of utility companies
generally. These condensers are heat exchangers which convert steam from
its gaseous state to its liquid state, also known as phase transition. In so
doing, the latent heat of steam is given out inside the condenser. The purpose
is to condense the outlet(or exhaust) steam from steam turbine to obtain
maximum efficiency & also to get the condensed steam in the form of pure
water, otherwise known as condensate, back to the steam generator or
(boiler)boiler feed water.
16. 9.COOLING TOWERS & PONDS
A condenser needs huge quantity of water to condense
the steam. Most plants use a closed cooling system
where warm water coming from condenser is cooled &
reused. Small plants use spray ponds & medium & large
plants use cooling towers. Cooling tower is a steel or
concrete hyperbolic structure having a reservoir at the
base for storage of cooled water.
17. 10.FEED WATER HEATER
Advantages of heating water before feeding back to the boiler-
a) Feed water heating improves overall plant efficiency.
b) The dissolved oxygen & carbon dioxide which would
otherwise cause boiler corrosion are removed in feed water
heater.
c) Thermal stresses due to cold water entering the boiler drum
are avoided.
d) Quantity of steam produced by the boiler is produced.
e) Some other impurities carried by the steam & condensate,
due to corrosion of boiler & condenser are precipitated
outside the boiler.
Hence we use feed water heater.
18. 11.ECONOMISER
Flue gases coming out of boiler carry lot of heat. An
economiser extracts a part of heat from flue gases
& uses it for heating feed water. This use of
economiser results in saving coal consumption &
higher boiler efficiency.
19. 12.AIR PREHEATER
After flue gases leave economiser, some further heat can be
extracted from them & used to heat incoming water. Cooling of
flue gases by 20 degree centigrade increases the plant efficiency
by 1%.
Air preheaters may be of three types-
Plate type.
Tubular type.
Regenerative type.