2. A thermal power station is a power plant 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, turns into
steam and spins a steam turbine which drives an electrical
generator. 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 center because such
facilities convert forms of heat energy into electrical energy.
3.
4.
5. The Rankine cycle is a model that is used to predict
the performance of steam turbine systems, though the
theoretical principle also applies to reciprocating
engines such as steam locomotives.
The Rankine cycle is an idealized thermodynamic
cycle of a heat engine that converts heat into
mechanical work while undergoing phase change.
The heat is supplied externally to a closed loop,
which usually uses water as the working fluid.
6. It is named after William John Macquorn Rankine, a
Scottish polymath and Glasgow University professor.
The Rankine cycle closely describes the process by
which steam-operated heat engines commonly found in
thermal power generation plants generate power.
7.
8.
9. 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 (aka h-s chart or Mollier
diagram), or numerically, using steam tables.
10. 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.
11. A boiler is a closed vessel in which water or
other fluid is heated. The fluid does not necessarily boil
The heated or vaporized fluid exits the boiler for use in
various processes or heating applications
including water heating, central heating, boiler-based
power generation, cooking, and sanitation.
12.
13. The turbine generator consists of a series of
steam turbines interconnected to each other and a
generator on a common shaft. There is usually a high-
pressure turbine at one end, followed by an
intermediate-pressure turbine, and finally one, two, or
three low-pressure turbines, and the generator.
As steam moves through the system and loses
pressure and thermal energy, it expands in volume,
requiring increasing diameter and longer blades at
each succeeding stage to extract the remaining
energy.
14.
15. The use of condensers in thermal power plant or steam
power plant improves the efficiency of the power plant
by decreasing the exhaust pressure of the steam below
the atmosphere.
Another advantage of the condenser is that the steam
condensed may be recovered to provide a source of
good pure feed water to the boiler and reduces the
water softening plant capacity to a considerable extent.
The use of condenser in steam power plant reduces the
overall cost of the generation by increasing the thermal
efficiency of the power plant.
16.
17. A boiler feedwater pump is a specific type of pump used
to pump feedwater into a steam boiler. The water may be
freshly supplied or returning condensate produced as a
result of the condensation of the steam produced by the
boiler.
These pumps are normally high pressure units that take
suction from a condensate return system and can be of
the centrifugal pump type or positive displacement type.
Feed water pumps range in size up to many horsepower and
the electric motor is usually separated from the pump body
by some form of mechanical coupling.
18.
19.
20. A rotary car dumper or wagon tippler is a mechanism
used for unloading certain railroad cars such
as hopper cars, gondolas or lorries
It holds the rail car to a section of track and rotates
the track and car together to dump out the contents.
Tippler is used for emptying the loaded wagons by
tipping it. Tippler retains wagon from top as well as
from side by using clamping devices provided on it.
21.
22. Belt Conveyors are very suitable means of
transporting large quantities of coal over large
distances.
Belt Conveyors consists of endless belt made of
rubber, canvas or balata running over a pair of end
drums or pulleys and supported by series of rollers
(known as idlers) provided at regular intervals. The
return idlers which support the empty belt are plain
rollers and are space wide apart.
23.
24. A pulverizer or grinder is a mechanical device for the
grinding of many different types of materials. For example,
a pulverizer mill is used to pulverize coal for combustion in
the steam-generating furnaces of fossil fuel power plants.
A ball mill is a pulverizer that consists of a horizontal
rotating cylinder, up to three diameters in length, containing
a charge of tumbling or cascading steel balls, pebbles, or
rods.
A tube mill is a revolving cylinder of up to five diameters in
length used for fine pulverization of ore, rock, and other
such materials; the material, mixed with water, is fed into
the chamber from one end, and passes out the other end as
a slurry.
25.
26. 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 a water demineralising treatment plant
(DM).
27. 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.
28.
29. In thermal power plants fuel oil play a vital role. Oil
burners besides initial lightining up are also used to
provide effective ignition of the coal associated with
P.F. burners and to stabilise the flame.
The burners can provide enough heat to carry on
boiling operations of the boilers for initial starting
period. It can provide 10-15% of the maximum load. At
lean periods or when it is desired to run the boilers at
off load condition oil burners are used.
30. In the boiler furnace the combustion of coal is
performed by hot air and produced heat is used to
generate the steam. After combustion of the coal air is
changed in ash and hot flue gases.
The exhaust from firing zone contains 40% of SO2,
CO2 and NO2 as impurities. This air is known as flue
gases.
The flue gases are now directed to the electrostatic
precipitators. On its way the gas is used in economizer
and several other places to increase its efficiency.
