EXPERIMENT NO. 2 AIM: To study coal based thermal power plant including (a). Site selection (b). Classification (c). Merits and demerits (d). Environmental impacts (e). Basic layout (f). Various parts (g).Working THEORY: WHAT IS THERMAL POWER STATION? A thermal power station is a power plant in which the prime mover 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 fuel sources. Some prefer to use the term energy center because such facilities convert forms of heat energy into electricity. Some thermal power plants also deliver heat energy for industrial purposes, for district heating, or for desalination of water as well as delivering electrical power. Installed thermal power capacity The installed capacity of Thermal Power in India, as of October 31, 2012, was 140206.18 MW which is 66.99%of total installed capacity. Current installed base of Coal Based Thermal Power is 120,103.38 MW which comes to 57.38% of total installed base. Current installed base of Gas Based Thermal Power is 18,903.05 MW which is 9.03% of total installed capacity. Current installed base of Oil Based Thermal Power is 1,199.75 MW which is 0.57% of total installed capacity. The state of Maharashtra is the largest producer of thermal power in the country. In thermal power stations, mechanical power is produced by a heat engine that transforms thermal energy, often from combustion of a fuel, into rotational energy. Most thermal power stations
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EXPERIMENT NO. 2
AIM: To study coal based thermal power plant including (a). Site selection (b). Classification
(c). Merits and demerits (d). Environmental impacts (e). Basic layout (f). Various parts
(g).Working
THEORY:
WHAT IS THERMAL POWER STATION?
A thermal power station is a power plant in which the prime mover 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 fuel sources. Some prefer to use the term energy center because such
facilities convert forms of heat energy into electricity. Some thermal power plants also deliver heat
energy for industrial purposes, for district heating, or for desalination of water as well as deliver ing
electrical power.
Installed thermal power capacity
The installed capacity of Thermal Power in India, as of October 31, 2012, was 140206.18 MW
which is 66.99%of total installed capacity.
Current installed base of Coal Based Thermal Power is 120,103.38 MW which comes to
57.38% of total installed base.
Current installed base of Gas Based Thermal Power is 18,903.05 MW which is 9.03% of
total installed capacity.
Current installed base of Oil Based Thermal Power is 1,199.75 MW which is 0.57% of total
installed capacity.
The state of Maharashtra is the largest producer of thermal power in the country.
In thermal power stations, mechanical power is produced by a heat engine that transforms thermal
energy, often from combustion of a fuel, into rotational energy. Most thermal power stations
produce steam, and these are sometimes called steam power stations. Not all thermal energy can
be transformed into mechanical power, according to the second law of thermodynamics. Therefore,
there is always heat lost to the environment. If this loss is employed as useful heat, for industr ia l
processes or district heating, the power plant is referred to as a cogeneration power plant or CHP
(combined heat-and-power) plant. In countries where district heating is common, there are
dedicated heat plants called heat-only boiler stations. An important class of power stations in the
Middle East uses by-product heat for the desalination of water.
CLASSIFICATION OF THERMAL POWER PLANT
By fuel
• Fossil-fuel power stations may also use a steam turbine generator or in the case of natural
gas-fired plants may use a combustion turbine. A coal-fired power station produces electricity by
burning coal to generate steam, and has the side-effect of producing large amounts of sulfur dioxide
which pollutes air and water and carbon dioxide, which contributes to global warming. About 50%
of electric generation in the USA is produced by coal-fired power plants
• Nuclear power plants use a nuclear reactor's heat to operate a steam turbine generator.
About 20% of electric generation in the USA is produced by nuclear power plants.
• Geothermal power plants use steam extracted from hot underground rocks.
• Biomass-fuelled power plants may be fuelled by waste from sugar cane, municipal solid
waste, landfill methane, or other forms of biomass.
• In integrated steel mills, blast furnace exhaust gas is a low-cost, although low-energy-
density, fuel.
• Waste heat from industrial processes is occasionally concentrated enough to use for power
generation, usually in a steam boiler and turbine.
• Solar thermal electric plants use sunlight to boil water and produce steam which turns the
generator.
By prime mover
• Steam turbine plants use the dynamic pressure generated by expanding steam to turn the
blades of a turbine. Almost all large non-hydro plants use this system. About 90% of all electric
power produced in the world is by use of steam turbines.
• Gas turbine plants use the dynamic pressure from flowing gases (air and combustion
products) to directly operate the turbine. Natural-gas fuelled (and oil fueled) combustion turbine
plants can start rapidly and so are used to supply "peak" energy during periods of high demand,
though at higher cost than base-loaded plants. These may be comparatively small units, and
sometimes completely unmanned, being remotely operated. This type was pioneered by the UK,
Prince town being the world's first, commissioned in 1959.
• Combined cycle plants have both a gas turbine fired by natural gas, and a steam boiler and
steam turbine which use the hot exhaust gas from the gas turbine to produce electricity. This greatly
increases the overall efficiency of the plant, and many new base load power plants are combined
cycle plants fired by natural gas.
• Internal combustion reciprocating engines are used to provide power for isolated
communities and are frequently used for small cogeneration plants. Hospitals, office buildings,
industrial plants, and other critical facilities also use them to provide backup power in case of a
power outage. These are usually fuelled by diesel oil, heavy oil, natural gas, and landfill gas.
By duty
Power plants that can be dispatched (scheduled) to provide energy to a system include:
• Base load power plants run nearly continually to provide that component of system load
that doesn't vary during a day or week. Base load plants can be highly optimized for low fuel cost,
but may not start or stop quickly during changes in system load. Examples of base-load plants
would include large modern coal-fired and nuclear generating stations, or hydro plants with a
predictable supply of water.
• Peaking power plants meet the daily peak load, which may only be for a one or two hours
each day. While their incremental operating cost is always higher than base load plants, they are
required to ensure security of the system during load peaks. Peaking plants include simple cycle
gas turbines and sometimes reciprocating internal combustion engines, which can be started up
rapidly when system peaks are predicted. Hydroelectric plants may also be designed for peaking
use.
• Load following power plants can economically follow the variations in the daily and
weekly load, at lower cost than peaking plants and with more flexibility than base load plants.
ADVANTAGES OF THERMAL POWER
1. The fuel used is quite cheap.
2. Less initial cost as compared to other generating plants.
3. It can be installed at any place irrespective of the existence of coal. The coal can be
transported to the site of the plant by rail or road.
4. It requires less space as compared to Hydro power plants.
5. Cost of generation is less than that of diesel power plants.
6. They can be located very conveniently near the load centers.
7. Does not require shielding like required in nuclear power plant
8. Unlike nuclear power plants whose power production method is difficult, for thermal
power plants it is easy.
9. Transmission costs are reduced as they can be set up near the industry.
10. The portion of steam generated can be used as process steam in different industries.
11. Steam engines and turbines can work under 25% of overload capacity.
12. Able to respond changing base loads without difficulty.
DISADVANTAGES OF THERMAL POWER
1. It pollutes the atmosphere due to production of large amount of smoke and fumes.
2. Large amounts of water are required.
3. Takes long time to be erected and put into action.
4. Maintenance and operating costs are high.
5. With increase in pressure and temperature, the cost of plant increases.
6. Troubles from smoke and heat from the plant, disposal of ash.
7. The following list corers most of the factors that should be studied and considered in
selection of proper sites for power plant construction:
a) Transportation network: Easy and enough access to transportation network is
required in both power plant construction and operation periods.
b) Gas pipe network: Vicinity to the gas pipes reduces the required expenses.
c) Power transmission network: To transfer the generated electricity to the
consumers, the plant should be connected to electrical transmission system.
Therefore the nearness to the electric network can play a roll.
d) Geology and soil type: The power plant should be built in an area with soil and
rock layers that could stand the weight and vibrations of the power plant.
e) Earthquake and geological faults: Even weak and small earthquakes can damage
many parts of a power plant intensively. Therefore the site should be away enough
from the faults and previous earthquake areas.
f) Topography: It is proved that high elevation has a negative effect on production
efficiency of gas turbines. In addition, changing of a sloping area into a flat site for
the construction of the power plant needs extra budget. Therefore, the parameters
of elevation and slope should be considered.
g) Rivers and floodways: Obviously, the power plant should have a reasonable
distance from permanent and seasonal rivers and floodways.
h) Water resources: For the construction and operating of power plant different
volumes of water are required. This could be supplied from either rivers or
underground water resources. Therefore having enough water supplies in defined
vicinity can be a factor in the selection of the site.
i) Environmental resources: Operation of a power plant has important impacts on
environment. Therefore, priority will be given to the locations that are far enough
from national parks, wildlife, protected areas, etc.
j) Population centers: For the same reasons as above, the site should have an enough
distance from population centers.
SCHEMATIC DIAGRAM OF THERMAL POWER PLANT
Fig. Typical diagram of a coal-fired thermal power station
1. Cooling tower 10. Steam Control valve 19. Superheater
2. Cooling water pump 11. High pressure steam turbine 20. Forced draught (draft) fan
3. transmission line (3-phase) 12. Deaerator 21. Reheater