A Presentation On steam power plant BABA HIRA SINGH BHATTAL INSTITUTE OF ENGINEERING AND TECHNOLOGY LEHRAGAGA-148031 DISTT.SANGRUR (Pb.) By :- Rakesh kumar Assistant professor Electrical Engineering Department.
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1. steam power plant BABA HIRA SINGH BHATTAL INSTITUTE OF
ENGINEERING AND TECHNOLOGY LEHRAGAGA- 148031 DISTT.SANGRUR (Pb.) By
:- Rakesh kumar Assistant professor Electrical Engineering
Department.
2. Essentials of Steam Power Plant Equipment A steam power
plant must have following equipment : (a) A furnace to burn the
fuel. (b) Steam generator or boiler containing water. Heat
generated in the furnace is utilized to convert water into steam.
(c) Main power unit such as an engine or turbine to use the heat
energy of steam and perform work. (d) Piping system to convey steam
and water.
3. The flow sheet of a thermal power plant consists of the
following four main circuits : (a) Feed water and steam flow
circuit. (b) Coal and ash circuit. (c) Air and gas circuit. (d)
Cooling water circuit.
4. A steam power plant using steam as working substance works
basically on Rankine cycle. Steam is generated in a boiler,
expanded in the prime mover and condensed in the condenser and fed
into the boiler again.
5. The different types of components used in steam power plant
(a) High pressure boiler. (b) Prime mover . (c) Condensers and
cooling towers . (d) Coal handling system . (e) Ash and dust
handling system . (f) Draught system . (g) Feed water purification
plant . (h) Pumping system . (i) Air preheater, economizer, super
heater, feed heaters.
6. Types of steam Generators Horizontal vertical or inclined.
Fire tube or water tube. Externally fired or internally fired.
Forced circulation and natural circulation. High pressure or low
pressure boiler.
7. Daltons law The partial pressure pressure of each
constituent is that pressure which the gas would exert if it
occupied alone that volume occupied by the mixture at the same
temperature.
8. Factors that should be considered while selecting the boiler
Working pressure and quality of steam required. Steam generation
rate. Floor area available. The portable load factor. Erection
facilities.
9. Properties of good steam generators It should be absolutely
reliable. It should occupy minimum space. It should be light in
weight. Capable of quick starting. Erection of boiler should be
simple.
10. Steam Power Plants are Classified as 1.By fuel. 2.By prime
mover. 3. By cooling tower.
11. Steam Power Plants are also Classified as; Central
stations; the electrical energy available from these stations is
meant for sale to the consumers who wish to purchase it.
Industrial/ captive power stations; this type of power station is
run by the manufacturing company for its own use and its output is
not available for general sale.
12. Jet condenser; low manufacturing cost. Low upkeeps,
requires small floor space and more auxiliary power required.
surface condenser; high manufacturing cost. high upkeeps, requires
large floor space and less auxiliary power required.
13. Feed water heating improves overall plant efficiency.
Quantity of steam produced by the boiler is increase. Thermal
stress due to cold water entering the boiler drum are avoided.
Chance of boiler corrosion are decrease.
14. Dust collectors are Classified as; Mechanical dust
collectors; (a) Wet type(scrubbers). Spray type, packed type and
impingement type. (b) Dry type. Gravitational separators, cyclone
separators, electrical dust collectors; Rod type and plate
type.
15. DIFFERENT TYPES OF BOILERS USED IN STEAM POWER PLANTS
horizontal, vertical or inclined. fire tube and water tube .
Externally or internally fired. Forced or natural circulation. High
pressure or low pressure. Stationary or portable. Single-tube and
multi-tube.
16. Working diagram Thermal power station.
17. C saturated water hot gases Steam Turbine Gen compressed
water superheated steam Condenser Pump cooling water saturated
steam Steam Generator (Boiler / Furnace) Steam Turbine Power
Plant
18. Schematic arrangement of equipment of a steam power
station. Coal received in coal storage yard of power station is
transferred in the furnace by coal handling unit. Heat produced due
to burning of coal is utilized in converting water contained in
boiler drum into steam at suitable pressure and temperature. The
steam generated is passed through the superheater.
19. Superheated steam then flows through the turbine. After
doing work in the turbine the pressure of steam is reduced. Steam
leaving the turbine passes through the condenser which is
maintained the low pressure of steam at the exhaust of
turbine.
20. Steam pressure in the condenser depends upon flow rate and
temperature of cooling water and on effectiveness of air removal
equipment. Water circulating through the condenser may be taken
from the various sources such as river, lake or sea. If sufficient
quantity of water is not available the hot water coming out of the
condenser may be cooled in cooling towers and circulated again
through the condenser. Bled steam taken from the turbine at
suitable extraction points is sent to low pressure and high
pressure water heaters.
21. Air taken from the atmosphere is first passed through the
air pre-heater, where it is heated by flue gases. The hot air then
passes through the furnace. The flue gases after passing over
boiler and superheater tubes, flow through the dust collector and
then through economiser, air pre-heater and finally they are
exhausted to the atmosphere through the chimney.
22. Disadvantage of steam power plant Maintenance and operating
cost are high. Long time required for erection and putting into
action . Large quantity of water is required. Great difficulty
experienced in coal handling . Efficiency decreases rapidly below
about 75 percent load.
23. Mechanical equipment in Thermal power station. BOILER
ECONOMISER TURBINE SUPER HEATER AIR PREHEATER CONDENSER
24. Superheater The superheater consists of a superheater
header and superheater elements. Steam from the main steam pipe
arrives at the saturated steam chamber of the superheater header
and is fed into the superheater elements. Superheated steam arrives
back at the superheated steam chamber of the superheater header and
is fed into the steam pipe to the cylinders. Superheated steam is
more expansive.
25. Advantages of superheated steam Capacity to do work is
increased without increasing its pressure. High temperature of
super heated steam results in an increase in thermal efficiency.
Heat losses due to condensation of stem on cylinder walls are
avoided to a great extent. Does not produce corrosion effect on
turbine.
26. Superheater It is a heating device. It is used to raise
temp of steam at const pressure. It removes even last traces of
moisture.
27. Classification of super heater Convection. Radiation.
Combination of convection and radiation.
28. Reheater The function of reheater is similar to the
superheater in that it serves to elevate the steam temperature.
Primary steam is supplied to the high pressure turbine. After
passing through the high pressure turbine, the steam is returned to
the steam generator for reheating (in a reheater) after which it is
sent to the low pressure turbine. A second reheat cycle may also be
provided.
29. Soot Blowers The fuel used in thermal power plants causes
soot and this is deposited on the boiler tubes, economizer tubes,
air pre heaters, etc. This drastically reduces the amount of heat
transfer of the heat exchangers. Soot blowers control the formation
of soot and reduce its corrosive effects. The types of soot blowers
are fixed type, which may be further classified into lane type and
mass type depending upon the type of spray and nozzle used.
30. Condenser The use of a condenser in a power plant is to
improve the efficiency of the power plant by decreasing the exhaust
pressure of the steam below 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 reduce the water
softening capacity to a considerable extent. A condenser is one of
the essential components of a power plant.
31. Functions of Condensers The main purposes of the condenser
are to condense the exhaust steam from the turbine for reuse in the
cycle and to maximize turbine efficiency by maintaining proper
vacuum. As the operating pressure of the condenser is lowered
(vacuum is increased), the enthalpy drop of the expanding steam in
the turbine will also increase. This will increase the amount of
available work from the turbine (electrical output).
32. Cooling Tower The importance of the cooling tower is felt
when the cooling water from the condenser has to be cooled. The
cooling water after condensing the steam becomes hot and it has to
be cooled as it belongs to a closed system. The Cooling towers do
the job of decreasing the temperature of the cooling water after
condensing the steam in the condenser.
33. Cooling Towers have one function : Remove heat from the
water discharged from the condenser so that the water can be
discharged to the river or re-circulated and reused.
34. A cooling tower extracts heat from water by evaporation. In
an evaporative cooling tower, a small portion of the water being
cooled is allowed to evaporate into a moving air stream to provide
significant cooling to the rest of that water stream.
35. Cooling Towers are commonly used to provide lower than
ambient water temperatures and are more cost effective and energy
efficient than most other alternatives. The smallest cooling towers
are structured for only a few litres of water per minute while the
largest cooling towers may handle upwards of thousands of litres
per minute. The pipes are obviously much larger to accommodate this
much water in the larger towers and can range up to 12 inches in
diameter.
36. Advantages of regenerative cycle Improve overall plant
efficiency. Protect boiler corrosion. Avoid the thermal stresses
due to cold water entering the boiler . Increased the quantity of
steam produced by boiler.
37. Function of economizer To extract a part of heat from the
fuel gas coming out of the boiler. To use heat for heating feed
water to the boiler. To increases the efficiency of boiler.
38. The economizer is a feed water heater, deriving heat from
the flue gases. The justifiable cost of the economizer depends on
the total gain in efficiency. In turn this depends on the flue gas
temperature leaving the boiler and the feed water inlet
temperature.
39. Air Pre-heater The flue gases coming out of the economizer
is used to preheat the air before supplying it to the combustion
chamber. An increase in air temperature of 20 degrees can be
achieved by this method. The pre heated air is used for combustion
and also to dry the crushed coal before pulverizing.
40. Advantages of mechanical handling Higher reliability. Less
labour required. Operation is easy and smooth. Economical for large
capacity plant. Losses in transport are minimised. Easily
started.
41. Disadvantages of mechanical handling Need continuous
maintenance and repair. Capital cost of plant is increased.
42. Working diagram Thermal power station.
43. Side view Thermal power station.
44. C saturated water Gen compressed water superheated steam
cooling water Pump Steam Turbine Condenser Steam Generator Steam
Turbine Power Plant saturated steam hot gases Heat Workout Total
Workin in Total Loss??? Where???
45. R. Shanthini 15 Aug 2010 According to the 2nd Law of
Thermodynamics when heat is converted into work, part of the heat
energy must be wasted Power generation type Unit size (MW) Energy
wasted (MW) Diesel engine 10 - 30 7 22 Gas Turbine 50 - 100 36 78
Steam Turbine 200 - 800 120 560 Combined (ST & GT) 300 - 600
150 380 Nuclear (BWR & PWR) 500 - 1100 330 760
46. The Simple Ideal Rankine Cycle 9-1 The McGraw-Hill
Companies, Inc.,1998
47. How can We Increase the Efficiency of the Rankine cycle?
Rankine cycle efficiency can be increased by increasing average
temperature at which heat is transferred to the working fluid in
the boiler or decreasing the average temperature at which heat is
rejected from the working fluid in the condenser. That is, the
average fluid temperature should be as high as possible during heat
addition and as low as possible during heat rejection.
48. The three ways by which efficiency of the Rankine cycle can
be increased are : (a) Lowering the condenser pressure. (b)
Superheating the steam to high temperatures. (c) Increasing the
boiler pressure.
49. The thermal efficiency of the Rankine cycle can be
increased by increasing the average temperature at which heat is
added to the working fluid and/or by decreasing the average
temperature at which heat is rejected to the cooling medium. The
average temperature during heat rejection can be decreased by
lowering the turbine exit pressure.
50. Consequently, the condenser pressure of most vapor power
plants is well below the atmospheric pressure. The average
temperature during heat addition can be increased by raising the
boiler pressure or by superheating the fluid to high temperatures.
There is a limit to the degree of superheating, however, since the
fluid temperature is not allowed to exceed a metallurgically safe
value.
51. Superheating has the added advantage of decreasing the
moisture content of the steam at the turbine exit. Lowering the
exhaust pressure or raising the boiler pressure, however, increases
the moisture content. To take advantage of the improved
efficiencies at higher boiler pressures and lower condenser
pressures, steam is usually reheated after expanding partially in
the high- pressure turbine.
52. This is done by extracting the steam after partial
extraction in the high-pressure turbine, sending it back to the
boiler where it is reheated at constant pressure, and returning it
to the low-pressure turbine for complete expansion to the condenser
pressure.
53. The average temperature during the reheat process, and thus
the thermal efficiency of the cycle, can be increased by increasing
the number of expansion and reheat stages. As the number of stages
is increased, the expansion and reheat processes approach an
isothermal process at maximum temperature. Reheating also decreases
the moisture content at the turbine exit.
54. Another way of increasing the thermal efficiency of the
Rankine cycle is by regeneration. During a regeneration process,
liquid water (feed water) leaving the pump is heated by some steam
bled off the turbine at some intermediate pressure in devices
called feed water heaters.
55. The two streams are mixed in open feed water heaters, and
the mixture leaves as a saturated liquid at the heater pressure. In
closed feed water heaters, heat is transferred from the steam to
the feed water without mixing.
56. The production of more than one useful form of energy (such
as process heat and electric power) from the same energy source is
called cogeneration. Cogeneration plants produce electric power
while meeting the process heat requirements of certain industrial
processes.
57. This way, more of the energy transferred to the fluid in
the boiler is utilized for a useful purpose. The faction of energy
that is used for either process heat or power generation is called
the utilization factor of the cogeneration plant.
58. The overall thermal efficiency of a power plant can be
increased by using binary cycles or combined cycles. A binary cycle
is composed of two separate cycles, one at high temperatures
(topping cycle) and the other at relatively low temperatures.
59. The most common combined cycle is the gas- steam combined
cycle where a gas-turbine cycle operates at the high-temperature
range and a steam-turbine cycle at the low- temperature range.
Steam is heated by the high-temperature exhaust gases leaving the
gas turbine. Combined cycles have a higher thermal efficiency than
the steam- or gas- turbine cycles operating alone.
60. Selection of plant site The selection of plant site for
thermal power plant compared with hydro-power plant is more
difficult as it involves number of factors to be considered for its
economic justification. A few important factors to be considered
for the selection of thermal power plants.
61. Selection of plant site AVAILABILITY OF COAL. Huge quantity
of coal is required for large thermal plants. ASH DISPOSAL
FACILITIES. SPACE REQUIREMENT. NATURE OF LAND. AVAILABILITY OF
WATER.
62. Selection of plant site TRANSPORT FACILITYIES. AVAILABILITY
OF LABOUR. PUBLIC PROBLEMS. SIZE OF THE PLANT.
63. Nowadays, the environment protection has become a crucial
problem and the authorities are requested to set increasingly more
stringent limits , one of which is the emissions from the
industrial plants of solid particulate and other gaseous
pollutants. ABOUT ELECTROSTATIC PRECIPITATOR
64. ABOUT ELECTROSTATIC PRECIPITATOR Electrostatic precipitator
(ESP) is a widely used device in so many different domains to
remove the pollutant particulates, especially in industrial plants.
What is ESP
65. HOW ESP WORKS Generally, the processes of electrostatic
precipitator are known as three main stages: particle charging,
transport and collection. Main process of ESP
66. Schematic of wire-plate ESP Schematic of wire-plate
electrostatic precipitator
67. Mechanism of ESP Mechanism of electrostatic
precipitator
68. PROCESS OF Particle charging Particle charging is the first
and foremost beginning in processes. As the voltage applied on
precipitator reach threshold value, the space inside divided into
ionization region and drift region.
69. The electric field magnitude around the negative electrode
is so strong that the electrons escape from molecule. Under the
influence of electric field, the positive ions move towards the
corona, while the negative ions and electrons towards the
collecting plates.
70. Particle transport In the moving way, under the influence
of electric field, negative ions cohere and charge the particles,
make the particles be forced towards collecting-plate.
71. Particle collection As soon as the particles reach the
plate, they will be neutralized and packed by the succeeded ones
subsequently. The continuous process happens, as a result,
particles are collected on the collecting plate.
72. 72 What is a Boiler? Introduction Vessel that heats water
to become hot water or steam At atmospheric pressure water volume
increases 1,600 times Hot water or steam used to transfer heat to a
process
73. The boiler is a rectangular furnace about 50 feet (15 m) on
a side and 130 feet (40 m) tall. Its walls are made of a web of
high pressure steel tubes about 2.3 inches (58 mm) in
diameter.
74. A boiler should fulfill the following requirements
(a)Safety : The boiler should be safe under operating conditions.
(b) Accessibility : The various parts of the boiler should be
accessible for repair and maintenance. (c) Capacity : The boiler
should be capable of supplying steam according to the
requirements.
75. (d) Efficiency : To permit efficient operation, the boiler
should be able to absorb a maximum amount of heat produced due to
burning of fuel in the furnace. (e) It should be simple in
construction and its maintenance cost should be low. (f) Its
initial cost should be low. (g) The boiler should have no joints
exposed to flames. (h) The boiler should be capable of quick
starting and loading.
76. Introduction BURNER WATER SOURCE BRINE SOFTENERS CHEMICAL
FEED FUEL BLOW DOWN SEPARATOR VENT VENTEXHAUST GAS STEAM TO PROCESS
STACK DEAERATOR PUMPS Figure: Schematic overview of a boiler room
BOILER ECO- NOMI- ZER
77. Types of Boilers 1. Fire Tube Boiler 2. Water Tube Boiler
3. Packaged Boiler 4. Fluidized Bed (FBC) Boiler 5. Stoker Fired
Boiler 6. Pulverized Fuel Boiler 7. Waste Heat Boiler 8. Thermic
Fluid Heater (not a boiler!) What Type of Boilers Are There?
78. The boilers can be classified according to the following
criteria. According to flow of water and hot gases : (a) Water tube
(b) Fire tube.
79. Type of Boilers 1. Fire Tube Boiler Relatively small steam
capacities (12,000 kg/hour) Low to medium steam pressures (18
kg/cm2) Operates with oil, gas or solid fuels
80. Type of Boilers 2. Water Tube Boiler Used for high steam
demand and pressure requirements Capacity range of 4,500 120,000
kg/hour Combustion efficiency enhanced by induced draft provisions
Lower tolerance for water quality and needs water treatment
plant
81. 3. Packaged Boiler Oil Burner To Chimney Comes in complete
package Features High heat transfer Faster evaporation Good
convective heat transfer Good combustion efficiency High thermal
efficiency Classified based on number of passes
82. Working of power plant Pulverized coal is air-blown into
the furnace from fuel nozzles at the four corners and it rapidly
burns, forming a large fireball at the center. The thermal
radiation of the fireball heats the water that circulates through
the boiler tubes near the boiler perimeter.
83. The water circulation rate in the boiler is three to four
times the throughput and is typically driven by pumps. As the water
in the boiler circulates it absorbs heat and changes into steam at
700 F (371 C) and 3,200 psi
84. The water enters the boiler through a section in the
convection pass called the economizer. From the economizer it
passes to the steam drum. Once the water enters the steam drum it
goes down to the lower inlet water wall headers.
85. From the inlet headers the water rises through the water
walls and is eventually turned into steam due to the heat being
generated by the burners located on the front and rear water walls
(typically). As the water is turned into steam/vapor in the water
walls, the steam/vapor once again enters the steam drum.
86. The steam/vapor is passed through a series of steam and
water separators and then dryers inside the steam drum. The steam
separators and dryers remove water droplets from the steam and the
cycle through the water walls is repeated. This process is known as
natural circulation.
87. super heater Fossil fuel power plants can have a super
heater and/or re-heater section in the steam generating furnace. In
a fossil fuel plant, after the steam is conditioned by the drying
equipment inside the steam drum, it is piped from the upper drum
area into tubes inside an area of the furnace known as the super
heater,
88. which has an elaborate set up of tubing where the steam
vapor picks up more energy from hot flue gases outside the tubing
and its temperature is now superheated above the saturation
temperature. The superheated steam is then piped through the main
steam lines to the valves before the high pressure turbine.
89. Condenser The condenser condenses the steam from the
exhaust of the turbine into liquid to allow it to be pumped. If the
condenser can be made cooler, the pressure of the exhaust steam is
reduced and efficiency of the cycle increases.
90. For best efficiency, the temperature in the condenser must
be kept as low as practical in order to achieve the lowest possible
pressure in the condensing steam.
91. Since the condenser temperature can almost always be kept
significantly below 100 C where the vapor pressure of water is much
less than atmospheric pressure, the condenser generally works under
vacuum. Thus leaks of non-condensible air into the closed loop must
be prevented.
92. The condenser generally uses either circulating cooling
water from a cooling tower to reject waste heat to the atmosphere,
or once-through water from a river, lake or ocean.
93. The condenser tubes are made of brass or stainless steel to
resist corrosion from either side. Nevertheless they may become
internally fouled during operation by bacteria or algae in the
cooling water or by mineral scaling, all of which inhibit heat
transfer and reduce thermodynamic efficiency.
94. Many plants include an automatic cleaning system that
circulates sponge rubber balls through the tubes to scrub them
clean without the need to take the system off-line.
95. Re heater Power plant furnaces may have a re heater section
containing tubes heated by hot flue gases outside the tubes.
Exhaust steam from the high pressure turbine is rerouted to go
inside the re heater tubes to pickup more energy to go drive
intermediate or lower pressure turbines.
96. Non toxic dust Sulphurous anhydride Carbon monoxide
Nitrogen dioxide Soot (fly ash) Hydrogen sulphide Pollution can be
define as the contamination of soil, air and water with undesirable
amount of material and heat. Main pollutants from a power
system
97. Acid rain; the rain which contain acid as its constituents,
brings all the acid down from high above the environment.
Contaminant; it is the another name of pollution. It is undesirable
substances which may be physical, chemical or biological.
Pollutant; these are undesirable substances present in the
environment these can be NO2, SO2, CO2,smoke,salt, bacteria.
98. Lot of heat is injected into biosphere from thermal power
plant, through exhaust gases and waste water. The major problem is
the effect of discharge of large quantity of heated wasted water
into natural water basins. Hot water raises the temperature and
disturbs the natural ecological balance Bad effects of thermal
pollution
99. Greater reliability of supply to the consumers. Avoid
complete shut down. The overall cost of energy per unit of an
interconnected system is less. There is a more effective use of
transmission line facilities. Less capital investment required.
Less expenses on supervision, operation and maintenance. Advantages
of combined operation of plants
100. Due to limited generating capacity diesel power stations
is not suitable for base load plants. Nuclear power stations is not
suitable for peak load plants. Incremental rate curve shows that as
output power increases, cost of plant also increases.