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Thermal power station - Wikipedia, the free encyclopediaHelp us provide free
content to the world by donating today!Thermal power station
From Wikipedia, the free encyclopedia
Jump to: navigation, search

A thermal power station near Sofia, Bulgaria
Mohave Generating Station, a 1,580 MW thermal power station near Laughlin,
Nevada fuelled by coal
Geothermal power station in IcelandEnergy portal
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; 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 electrical energy. However, power plant is the
most common term in the United States, while power station prevails in many
Commonwealth countries and especially in the United Kingdom.
Almost all coal, nuclear, geothermal, solar thermal electric, and waste
incineration plants, as well as many natural gas power plants are thermal.
Natural gas is frequently combusted in gas turbines as well as boilers. The
waste heat from a gas turbine can be used to raise steam, in a combined cycle
plant that improves overall efficiency.
Such power stations are most usually constructed on a very large scale and
designed for continuous operation.
Contents [hide]
1 History
2 Efficiency
3 Diagram of a typical coal-fired thermal power station
4 Steam generator
4.1 Boiler furnace and steam drum
4.2 Fuel preparation system
4.3 Fuel firing system and igniter system
4.4 Air path
4.5 Auxiliary systems
4.5.1 Fly ash collection
4.5.2 Bottom ash collection and disposal
4.5.3 Boiler make-up water treatment plant and storage
5 Steam turbine-driven electric generator
5.1 Barring gear (or Turning gear)
5.2 Condenser
5.3 Feedwater heater
5.4 Superheater
5.5 Deaerator
5.6 Auxiliary systems
5.6.1 Oil system
5.6.2 Generator heat dissipation
5.6.3 Generator high voltage system
6 Other systems
6.1 Monitoring and alarm system
6.2 Battery supplied emergency lighting and communication
7 Transport of coal fuel to site and to storage
8 See also
9 References
10 External links


[edit] History
Reciprocating steam engines have been used for mechanical power sources since
the 18th Century, with notable improvements being made by James Watt. The very
first commercial central electrical generating stations in New York and London,
in 1882, also used reciprocating steam engines. As generator sizes increased,
eventually turbines took over due to higher efficiency and lower cost of
construction. By the 1920s any central station larger than a few thousand
kilowatts would use a turbine prime mover.
[edit] Efficiency
The electric efficiency of a conventional thermal power station, considered as
saleable energy produced at the plant busbars compared with the heating value of
the fuel consumed, is typically 33 to 48% efficient, limited as all heat engines
are by the laws of thermodynamics (See: Carnot cycle). The rest of the energy
must leave the plant in the form of heat. This waste heat can be disposed of
with cooling water or in cooling towers. If the waste heat is instead utilized
for e.g. district heating, it is called cogeneration. An important class of
thermal power station are associated with desalination facilities; these are
typically found in desert countries with large supplies of natural gas and in
these plants, freshwater production and electricity are equally important
co-products.
Since the efficiency of the plant is fundamentally limited by the ratio of the
absolute temperatures of the steam at turbine input and output, efficiency
improvements require use of higher temperature, and therefore higher pressure,
steam. Historically, other working fluids such as mercury have been
experimentally used in a mercury vapour turbine power plant, since these can
attain higher temperatures than water at lower working pressures. However, the
obvious hazards of toxicity, and poor heat transfer properties, have ruled out
mercury as a working fluid.
[edit] Diagram of a typical coal-fired thermal power station

Typical diagram of a coal-fired thermal power station 1. Cooling tower10.
Steam control valve19. Superheater
2. Cooling water pump11. High pressure steam turbine20. Forced draught
(draft) fan
3. Three-phase transmission line12. Deaerator21. Reheater
4. Step-up transformer13. Feedwater heater22. Combustion air intake
5. Electrical generator14. Coal conveyor23. Economiser
6. Low pressure steam turbine15. Coal hopper24. Air preheater
7. Boiler feedwater pump16. Coal pulverizer25. Precipitator
8. Surface condenser17. Boiler steam drum26. Induced draught (draft) fan
9. Intermediate pressure steam turbine18. Bottom ash hopper27. Flue gas
stack

[edit] Steam generator

Schematic diagram of typical coal-fired power plant steam generator highlighting
the air preheater (APH) location. (For simplicity, any radiant section tubing is
not shown.)The steam generating boiler has to produce steam at the high purity,
pressure and temperature required for the steam turbine that drives the
electrical generator. The generator includes the economizer, the steam drum, the
chemical dosing equipment, and the furnace with its steam generating tubes and
the superheater coils. Necessary safety valves are located at suitable points to
avoid excessive boiler pressure. The air and flue gas path equipment include:
forced draft (FD) fan, air preheater (APH), boiler furnace, induced draft (ID)
fan, fly ash collectors (electrostatic precipitator or baghouse) and the flue
gas stack.[1][2][3]
For units over about 200 MW capacity, redundancy of key components is provided
by installing duplicates of the FD fan, APH, fly ash collectors and ID fan with
isolating dampers. On some units of about 60 MW, two boilers per unit may
instead be provided.
[edit] Boiler furnace and steam drum
Once water inside the boiler or steam generator, the process of adding the
latent heat of vaporization or enthalpy is underway. The boiler transfers energy
to the water by the chemical reaction of burning some type of fuel.
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 the downcomers to the lower inlet waterwall
headers. From the inlet headers the water rises through the waterwalls and is
eventually turned into steam due to the heat being generated by the burners
located on the front and rear waterwalls (typically). As the water is turned
into steam/vapor in the waterwalls, the steam/vapor once again enters the steam
drum. 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
the water droplets from the steam and the cycle through the waterwalls is
repeated. This process is known as natural circulation.
The boiler furnace auxiliary equipment includes coal feed nozzles and igniter
guns, soot blowers, water lancing and observation ports (in the furnace walls)
for observation of the furnace interior. Furnace explosions due to any
accumulation of combustible gases after a trip-out are avoided by flushing out
such gases from the combustion zone before igniting the coal.
The steam drum (as well as the superheater coils and headers) have air vents and
drains needed for initial startup. The steam drum has internal devices that
removes moisture from the wet steam entering the drum from the steam generating
tubes. The dry steam then flows into the superheater coils.
Geothermal plants need no boiler since they use naturally occurring steam
sources. Heat exchangers may be used where the geothermal steam is very
corrosive or contains excessive suspended solids. Nuclear plants also boil water
to raise steam, either directly passing the working steam through the reactor or
else using an intermediate heat exchanger.
[edit] 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
pulverizers may be ball mills, rotating drum grinders, or other types of
grinders.
Some power stations burn fuel oil rather than coal. The 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.
[edit] Fuel firing system and igniter system
From the pulverized coal bin, coal is blown by hot air through the furnace coal
burners at an angle which imparts a swirling motion to the powdered coal to
enhance mixing of the coal powder with the incoming preheated combustion air and
thus to enhance the combustion.
To provide sufficient combustion temperature in the furnace before igniting the
powdered coal, the furnace temperature is raised by first burning some light
fuel oil or processed natural gas (by using auxiliary burners and igniters
provide for that purpose).
[edit] Air path
External fans are provided to give sufficient air for combustion. The forced
draft fan takes air from the atmosphere and, first warming it in the air
preheater for better combustion, injects it via the air nozzles on the furnace
wall.
The induced draft fan assists the FD fan by drawing out combustible gases from
the furnace, maintaining a slightly negative pressure in the furnace to avoid
backfiring through any opening. At the furnace outlet, and before the furnace
gases are handled by the ID fan, fine dust carried by the outlet gases is
removed to avoid atmospheric pollution. This is an environmental limitation
prescribed by law, and additionally minimizes erosion of the ID fan.
[edit] Auxiliary systems
[edit] Fly ash collection
Fly ash is captured and removed from the flue gas by electrostatic precipitators
or fabric bag filters (or sometimes both) located at the outlet of the furnace
and before the induced draft fan. The fly ash is periodically removed from the
collection hoppers below the precipitators or bag filters. Generally, the fly
ash is pneumatically transported to storage silos for subsequent transport by
trucks or railroad cars.
[edit] Bottom ash collection and disposal
At the bottom of every boiler, a hopper has been provided for collection of the
bottom ash from the bottom of the furnace. This hopper is always filled with
water to quench the ash and clinkers falling down from the furnace. Some
arrangement is included to crush the clinkers and for conveying the crushed
clinkers and bottom ash to a storage site.
[edit] Boiler make-up water treatment plant and storage
Since there is continuous withdrawal of steam and continuous return of
condensate to the boiler, losses due to blow-down and leakages have to be made
up for so as to maintain the desired water level in the boiler steam drum. For
this, continuous make-up water is added to the boiler water system. The
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).
A DM plant generally consists of cation, anion and mixed bed exchangers. The
final water from this process consists essentially of hydrogen ions and
hydroxide ions which is the chemical composition of pure water. The DM water,
being very pure, becomes highly corrosive once it absorbs oxygen from the
atmosphere because of its very high affinity for oxygen absorption.
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 water in the tank to avoid contact with atmospheric 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
deaerated, with the dissolved gases being removed by the ejector of the
condenser itself.
[edit] Steam turbine-driven electric generator

Rotor of a modern steam turbine, used in a power stationMain article: Turbo
generator
The steam turbine-driven generators have auxiliary systems enabling them to work
satisfactorily and safely. The steam turbine generator being rotating equipment
generally has a heavy, large diameter shaft. The shaft therefore requires not
only supports but also has to be kept in position while running. To minimise the
frictional resistance to the rotation, the shaft has a number of bearings. The
bearing shells, in which the shaft rotates, are lined with a low friction
material like Babbitt metal. Oil lubrication is provided to further reduce the
friction between shaft and bearing surface and to limit the heat generated.
[edit] Barring gear (or Turning gear)
Barring gear is the term used for the mechanism provided for rotation of the
turbine generator shaft at a very low speed (about one revolution per minute)
after unit stoppages for any reason. Once the unit is "tripped" (i.e., the
turbine steam inlet valve is closed), the turbine starts slowing or "coasting
down". 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 deflection
is because the heat inside the turbine casing tends to concentrate in the top
half of the casing, thus making the top half portion of the shaft hotter than
the bottom half. The shaft therefore warps or bends by millionths of inches,
only detectable by monitoring eccentricity meters.
But this small amount of shaft deflection would be enough to cause vibrations
and damage the entire steam turbine generator unit when it is restarted.
Therefore, the shaft is not permitted to come to a complete stop by a mechanism
known as "turning gear" or "barring gear" that automatically takes over to
rotate the unit at a preset low speed.
If the unit is shut down for major maintenance, then the barring gear must be
kept in service until the temperatures of the casings and bearings are
sufficiently low.
[edit] Condenser
Main article: Surface condenser

Diagram of a typical water-cooled surface condenser.[2][3][4][5]The surface
condenser is a shell and tube heat exchanger in which cooling water is
circulated through the tubes.[6][7][8][2] The exhaust steam from the low
pressure turbine enters the shell where it is cooled and converted to condensate
(water) by flowing over the tubes as shown in the adjacent diagram. Such
condensers use steam ejectors or rotary motor-driven exhausters for continuous
removal of air and gases from the steam side to maintain vacuum.
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. Since the condenser temperature can almost always be kept significantly
below 100 oC 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. Plants operating in
hot climates may have to reduce output if their source of condenser cooling
water becomes warmer; unfortunately this usually coincides with periods of high
electrical demand for air conditioning.
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.

“册”、“分册”，“电气主接线”
"List", "division", "Electrical Connection"

Thermal power station - Wikipedia, the free encyclopediaHelp us provide free
content to the world by donating today!Thermal power station
From Wikipedia, the free encyclopedia
Jump to: navigation, search

A thermal power station near Sofia, Bulgaria
Mohave Generating Station, a 1,580 MW thermal power station near Laughlin,
Nevada fuelled by coal
Geothermal power station in IcelandEnergy portal
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; 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 electrical energy. However, power plant is the
most common term in the United States, while power station prevails in many
Commonwealth countries and especially in the United Kingdom.
Almost all coal, nuclear, geothermal, solar thermal electric, and waste
incineration plants, as well as many natural gas power plants are thermal.
Natural gas is frequently combusted in gas turbines as well as boilers. The
waste heat from a gas turbine can be used to raise steam, in a combined cycle
plant that improves overall efficiency.
Such power stations are most usually constructed on a very large scale and
designed for continuous operation.
Contents [hide]
1 History
2 Efficiency
3 Diagram of a typical coal-fired thermal power station
4 Steam generator
4.1 Boiler furnace and steam drum
4.2 Fuel preparation system
4.3 Fuel firing system and igniter system
4.4 Air path
4.5 Auxiliary systems
4.5.1 Fly ash collection
4.5.2 Bottom ash collection and disposal
4.5.3 Boiler make-up water treatment plant and storage
5 Steam turbine-driven electric generator
5.1 Barring gear (or Turning gear)
5.2 Condenser
5.3 Feedwater heater
5.4 Superheater
5.5 Deaerator
5.6 Auxiliary systems
5.6.1 Oil system
5.6.2 Generator heat dissipation
5.6.3 Generator high voltage system
6 Other systems
6.1 Monitoring and alarm system
6.2 Battery supplied emergency lighting and communication
7 Transport of coal fuel to site and to storage
8 See also
9 References
10 External links

[edit] History
Reciprocating steam engines have been used for mechanical power sources since
the 18th Century, with notable improvements being made by James Watt. The very
first commercial central electrical generating stations in New York and London,
in 1882, also used reciprocating steam engines. As generator sizes increased,
eventually turbines took over due to higher efficiency and lower cost of
construction. By the 1920s any central station larger than a few thousand
kilowatts would use a turbine prime mover.
[edit] Efficiency
The electric efficiency of a conventional thermal power station, considered as
saleable energy produced at the plant busbars compared with the heating value of
the fuel consumed, is typically 33 to 48% efficient, limited as all heat engines
are by the laws of thermodynamics (See: Carnot cycle). The rest of the energy
must leave the plant in the form of heat. This waste heat can be disposed of
with cooling water or in cooling towers. If the waste heat is instead utilized
for e.g. district heating, it is called cogeneration. An important class of
thermal power station are associated with desalination facilities; these are
typically found in desert countries with large supplies of natural gas and in
these plants, freshwater production and electricity are equally important
co-products.
Since the efficiency of the plant is fundamentally limited by the ratio of the
absolute temperatures of the steam at turbine input and output, efficiency
improvements require use of higher temperature, and therefore higher pressure,
steam. Historically, other working fluids such as mercury have been
experimentally used in a mercury vapour turbine power plant, since these can
attain higher temperatures than water at lower working pressures. However, the
obvious hazards of toxicity, and poor heat transfer properties, have ruled out
mercury as a working fluid.
[edit] Diagram of a typical coal-fired thermal power station

Typical diagram of a coal-fired thermal power station 1. Cooling tower10.
Steam control valve19. Superheater
2. Cooling water pump11. High pressure steam turbine20. Forced draught
(draft) fan
3. Three-phase transmission line12. Deaerator21. Reheater
4. Step-up transformer13. Feedwater heater22. Combustion air intake
5. Electrical generator14. Coal conveyor23. Economiser
6. Low pressure steam turbine15. Coal hopper24. Air preheater
7. Boiler feedwater pump16. Coal pulverizer25. Precipitator
8. Surface condenser17. Boiler steam drum26. Induced draught (draft) fan
9. Intermediate pressure steam turbine18. Bottom ash hopper27. Flue gas
stack

[edit] Steam generator

Schematic diagram of typical coal-fired power plant steam generator highlighting
the air preheater (APH) location. (For simplicity, any radiant section tubing is
not shown.)The steam generating boiler has to produce steam at the high purity,
pressure and temperature required for the steam turbine that drives the
electrical generator. The generator includes the economizer, the steam drum, the
chemical dosing equipment, and the furnace with its steam generating tubes and
the superheater coils. Necessary safety valves are located at suitable points to
avoid excessive boiler pressure. The air and flue gas path equipment include:
forced draft (FD) fan, air preheater (APH), boiler furnace, induced draft (ID)
fan, fly ash collectors (electrostatic precipitator or baghouse) and the flue
gas stack.[1][2][3]
For units over about 200 MW capacity, redundancy of key components is provided
by installing duplicates of the FD fan, APH, fly ash collectors and ID fan with
isolating dampers. On some units of about 60 MW, two boilers per unit may
instead be provided.
[edit] Boiler furnace and steam drum
Once water inside the boiler or steam generator, the process of adding the
latent heat of vaporization or enthalpy is underway. The boiler transfers energy
to the water by the chemical reaction of burning some type of fuel.
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 the downcomers to the lower inlet waterwall
headers. From the inlet headers the water rises through the waterwalls and is
eventually turned into steam due to the heat being generated by the burners
located on the front and rear waterwalls (typically). As the water is turned
into steam/vapor in the waterwalls, the steam/vapor once again enters the steam
drum. 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
the water droplets from the steam and the cycle through the waterwalls is
repeated. This process is known as natural circulation.
The boiler furnace auxiliary equipment includes coal feed nozzles and igniter
guns, soot blowers, water lancing and observation ports (in the furnace walls)
for observation of the furnace interior. Furnace explosions due to any
accumulation of combustible gases after a trip-out are avoided by flushing out
such gases from the combustion zone before igniting the coal.
The steam drum (as well as the superheater coils and headers) have air vents and
drains needed for initial startup. The steam drum has internal devices that
removes moisture from the wet steam entering the drum from the steam generating
tubes. The dry steam then flows into the superheater coils.
Geothermal plants need no boiler since they use naturally occurring steam
sources. Heat exchangers may be used where the geothermal steam is very
corrosive or contains excessive suspended solids. Nuclear plants also boil water
to raise steam, either directly passing the working steam through the reactor or
else using an intermediate heat exchanger.
[edit] 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
pulverizers may be ball mills, rotating drum grinders, or other types of
grinders.
Some power stations burn fuel oil rather than coal. The 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.
[edit] Fuel firing system and igniter system
From the pulverized coal bin, coal is blown by hot air through the furnace coal
burners at an angle which imparts a swirling motion to the powdered coal to
enhance mixing of the coal powder with the incoming preheated combustion air and
thus to enhance the combustion.
To provide sufficient combustion temperature in the furnace before igniting the
powdered coal, the furnace temperature is raised by first burning some light
fuel oil or processed natural gas (by using auxiliary burners and igniters
provide for that purpose).
[edit] Air path
External fans are provided to give sufficient air for combustion. The forced
draft fan takes air from the atmosphere and, first warming it in the air
preheater for better combustion, injects it via the air nozzles on the furnace
wall.
The induced draft fan assists the FD fan by drawing out combustible gases from
the furnace, maintaining a slightly negative pressure in the furnace to avoid
backfiring through any opening. At the furnace outlet, and before the furnace
gases are handled by the ID fan, fine dust carried by the outlet gases is
removed to avoid atmospheric pollution. This is an environmental limitation
prescribed by law, and additionally minimizes erosion of the ID fan.
[edit] Auxiliary systems
[edit] Fly ash collection
Fly ash is captured and removed from the flue gas by electrostatic precipitators
or fabric bag filters (or sometimes both) located at the outlet of the furnace
and before the induced draft fan. The fly ash is periodically removed from the
collection hoppers below the precipitators or bag filters. Generally, the fly
ash is pneumatically transported to storage silos for subsequent transport by
trucks or railroad cars.
[edit] Bottom ash collection and disposal
At the bottom of every boiler, a hopper has been provided for collection of the
bottom ash from the bottom of the furnace. This hopper is always filled with
water to quench the ash and clinkers falling down from the furnace. Some
arrangement is included to crush the clinkers and for conveying the crushed
clinkers and bottom ash to a storage site.
[edit] Boiler make-up water treatment plant and storage
Since there is continuous withdrawal of steam and continuous return of
condensate to the boiler, losses due to blow-down and leakages have to be made
up for so as to maintain the desired water level in the boiler steam drum. For
this, continuous make-up water is added to the boiler water system. The
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).
A DM plant generally consists of cation, anion and mixed bed exchangers. The
final water from this process consists essentially of hydrogen ions and
hydroxide ions which is the chemical composition of pure water. The DM water,
being very pure, becomes highly corrosive once it absorbs oxygen from the
atmosphere because of its very high affinity for oxygen absorption.
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 water in the tank to avoid contact with atmospheric 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
deaerated, with the dissolved gases being removed by the ejector of the
condenser itself.
[edit] Steam turbine-driven electric generator

Rotor of a modern steam turbine, used in a power stationMain article: Turbo
generator
The steam turbine-driven generators have auxiliary systems enabling them to work
satisfactorily and safely. The steam turbine generator being rotating equipment
generally has a heavy, large diameter shaft. The shaft therefore requires not
only supports but also has to be kept in position while running. To minimise the
frictional resistance to the rotation, the shaft has a number of bearings. The
bearing shells, in which the shaft rotates, are lined with a low friction
material like Babbitt metal. Oil lubrication is provided to further reduce the
friction between shaft and bearing surface and to limit the heat generated.
[edit] Barring gear (or Turning gear)
Barring gear is the term used for the mechanism provided for rotation of the
turbine generator shaft at a very low speed (about one revolution per minute)
after unit stoppages for any reason. Once the unit is "tripped" (i.e., the
turbine steam inlet valve is closed), the turbine starts slowing or "coasting
down". 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 deflection
is because the heat inside the turbine casing tends to concentrate in the top
half of the casing, thus making the top half portion of the shaft hotter than
the bottom half. The shaft therefore warps or bends by millionths of inches,
only detectable by monitoring eccentricity meters.
But this small amount of shaft deflection would be enough to cause vibrations
and damage the entire steam turbine generator unit when it is restarted.
Therefore, the shaft is not permitted to come to a complete stop by a mechanism
known as "turning gear" or "barring gear" that automatically takes over to
rotate the unit at a preset low speed.
If the unit is shut down for major maintenance, then the barring gear must be
kept in service until the temperatures of the casings and bearings are
sufficiently low.
[edit] Condenser
Main article: Surface condenser

Diagram of a typical water-cooled surface condenser.[2][3][4][5]The surface
condenser is a shell and tube heat exchanger in which cooling water is
circulated through the tubes.[6][7][8][2] The exhaust steam from the low
pressure turbine enters the shell where it is cooled and converted to condensate
(water) by flowing over the tubes as shown in the adjacent diagram. Such
condensers use steam ejectors or rotary motor-driven exhausters for continuous
removal of air and gases from the steam side to maintain vacuum.
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. Since the condenser temperature can almost always be kept significantly
below 100 oC 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. Plants operating in
hot climates may have to reduce output if their source of condenser cooling
water becomes warmer; unfortunately this usually coincides with periods of high
electrical demand for air conditioning.
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.

1. Coal Supply
• Coal from the mine is delivered to the coal hopper, where it is crushed to five centimetres (2 inches) in size.
• The coal is processed and delivered by a conveyor belt to the generating plant.
2. Pulverizer
• The coal is then pulverized, or crushed, to a fine powder, mixed with air and blown into the boiler, or furnace for combustion.
3. Boiler
• The coal / air mixture ignites instantly in the boiler.
• Millions of litres of purified water are pumped through tubes inside the boiler.
• Intense heat from the burning coal turns the purified water in the boiler tubes into steam, which spins the turbine (see number four) to create electricity.
4. Precipitator, stack
• Burning coal produces carbon dioxide (CO2), sulphur dioxide (SO2) and nitrogen oxides (NOx).
• These gases are vented from the boiler.
• Bottom ash, which is made of coarse fragments that fall to the bottom of the boiler, is removed.
• Fly ash, which is very light, exits the boiler along with the hot gases.
• An electrostatic precipitator (a huge air filter) removes 99.4 per cent of fly ash before the flue gases are dispersed
into the atmosphere.
5. Turbine, generator
• Water in the boiler tubes picks up heat from the boiler and turns into steam.
• The high-pressure steam from the boiler passes into the turbine (a massive drum with thousands of propeller blades).
• Once the steam hits the turbine blades, it causes the turbine to spin rapidly.
• The spinning turbine causes a shaft to turn inside the generator, creating an electric current.
6. Condensers and the cooling water system
• Cooling water is drawn into the plant and circulated through condensers, which cools steam discharged from the turbine.
• Steam from the turbine also passes through the condensers in separate pipes from cooling water.
• The cold water is warmed by the steam, which condenses back into pure water and circulates back to the boiler to begin the process of generating electricity again.
• Cooling water, now warm from the heat exchange in the condensers, is released from the plant.
7. Water treatment plant: water purification
• To reduce corrosion, water must be purified for use in the boiler tubes.
• Other wastewater systems within the plant collect water used to clean pipes and other equipment, and sludge from the water purification process and other processes.
• Waste water is pumped out of the plant and into the holding ponds.
8. Precipitator, Ash systems
• Ash that builds up on the precipitator's plates is vibrated off and collected in large hoppers or bins.
• Fly ash and bottom ash are removed from the plants and hauled to disposal sites or ash lagoons.
• Depending on the market demand, fly ash produced from TransAlta's three plants is sold to the cement industry for construction.
9. Substation, transformer, transmission lines
• Once the electricity is generated, transformers increase the voltage so it can be carried across the transmission lines.
• Once electricity is delivered to substations in cities and towns, the voltage flowing into the distribution lines is reduced, and then reduced again to distribute electricity to customers.

Power is the driving force for a variety of energy into electric energy plants. On the basis of the use of energy in the form of coal-fired power plants can be divided into, water power plants, atomic energy power plants, geothermal power, wind power, and so on.

Thermal power plant referred to as thermal power plants using coal, oil, natural gas and other fuels to produce chemical energy of the plant. According to their function can be divided into two categories, namely, condensing steam power plants and power plant. The former only to the user power supply, and power plant in addition to the supply of electricity users, but also to hot steam and hot water supply users, the so-called "combined heat and power production."

The capacity of thermal power plants of different sizes, in the form of concrete may differ from each other on their production process is similar to the term. On the map is condensing steam coal-fired power plant diagram of the production process.

Coal-fired, coal from the coal belt to transport coal field in the fighting. Large-scale coal-fired power plants to enhance the efficiency of coal combustion are. As a result, coal bucket of coal to the first ground into pulverized coal in coal. Ground hot air to carry coal from the Powder ranked by the fan into the boiler furnace burning inside. After the formation of coal combustion heat boiler flue gas along the level of flue and flue movement of the tail, giving off heat, dust to enter the final, after the burning of coal ash will be separated. Clean the flue gas in the role of the induced draft fan through the chimney into the atmosphere. Used by the combustion air blower into the installation of flue at the rear of the air preheater, the use of hot air gas heating. In this way, so that on the one hand, in addition to the boiler into the air temperature has increased, easy-to-fire and the burning of coal, on the other hand, can reduce exhaust gas temperature to increase the utilization of geothermal energy. From the air pre-heater exhaust hot air into two: one to dry coal and coal transportation, and another directly into the combustion chamber. The burn coal ash falling into the furnace slag of the following fight, and dust from the isolated small gray water together with red mortar to the pumping station, then pumping mortar to gray market.

Deaerator water tank in the water after a water pump to boost after the adoption of high-pressure heaters into the economizer. In the economizer, hot water heating gas, and then enter the boiler at the top of the drum inside. In the boiler furnace clouds around the water pipes, known as the water wall. Water wall and down both ends of the pipe through the box connectivity with the drum, the drum of water constantly circulating through the water wall, absorbing the love of coal combustion to release heat. Some cold water in the wall is heated in boiling water into steam after vaporization, the saturated steam from the drum into the upper part of the outflow in the superheater. Saturated steam superheater in the absorption of heat to continue to become superheated steam. Superheated steam high pressure and temperature, so there are a lot of heat energy. Have the potential heat pipe by the introduction of superheated steam turbine, heat will be converted into kinetic energy. To promote high-speed flow of steam turbine rotor rotation, the formation of mechanical energy.
The steam turbine generator rotor and the rotor shaft through even-linked. When the steam turbine rotor rotation when driven generator rotor rotation. At the other end of the generator rotor with a small DC generator, called exciter. Exciter issued to the DC generator rotor coil, so that the rotor electromagnet into the surrounding magnetic field generated. When the generator rotor rotation, is also a rotating magnetic field, the generator stator wire cutting will have a magnetic induction current line. In this way, then steam turbine generators of electrical energy into mechanical energy. By the power transformer to step-up voltage, the electricity transmission line to the user.

Heat energy released from the steam turbine from the lower part of the exhaust emission of the mouth, called the lack of steam. Lack of steam in the condenser circulating water pump was sent to the condenser cooling water cooling, condenses into water from the new, condensed water into the water. Condensate from the condensation water into the low-pressure heaters and eventually return to the deaerator, the completion of a cycle. In the course of the cycle is hard to avoid the disclosure of soft drinks, that is, the loss of soft drinks, so appropriate to the circulatory system in a number of water supply in order to ensure the normal cycle. High pressure heater at the end of the cycle is to increase the thermal efficiency of the device used, deaerator to remove oxygen-containing water to reduce corrosion of pipes and equipment.

Although the above analysis is more complicated, but from the point of view of energy conversion is very simple, that is, the chemical fuel to heat the steam → → potential energy to mechanical energy →. In the boiler of the total, the chemical energy of fuel into the steam heat; in the steam turbine, steam heat into mechanical energy of the rotating wheels; in the generator in electrical energy into mechanical energy. Furnace, machine, electricity is the main power plant equipment, also known as the host of the three. And the three host complement the work of the equipment into or auxiliary aids. Host and its auxiliary equipment connected to the pipeline, known as the Line, and other systems. The main power plant combustion system, soft drinks, electrical systems and so on.

In addition to the main system, power plant and some other auxiliary production systems, such as the coal transportation systems, chemical treatment of water systems, drainage systems, such as the mortar. These systems work in coordination with the main system, they complete each other's energy production. Large-scale thermal power plants to ensure the normal operation of these devices, thermal power plants with a large number of instruments used to monitor the operation of equipment, as well as set up in the automatic control device, in a timely manner in order to the main Des conditioning equipment. Modernization of thermal power plants, has adopted advanced computer distributed control system. These systems can control the entire production process control and automatic adjustment, according to the different situations of various facilities to coordinate the work of the situation, the entire plant automation level reached a new height. Automatic devices and systems in power plants has become an indispensable part.

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