Steam_Cycle_Power_Plant.pptx

8/11/2019 Steam_Cycle_Power_Plant.pptx

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Working Of A Power Plant Boiler

Boiler in a power plant has two functions:

The Combustion system converts energy in coal to Heat

Water and steam system converts the heat to steam at high pressures and temperatures

Details: The higher the furnace temperature, the faster the steam production. The

saturated steam thus produced can then either be used immediately to producepower via a turbine or else may be further superheated to a higher temperature;this notably reduces suspended water content making a given volume of steamproduce more work.

Any remaining heat in the combustion gases can then either be evacuated ormade to pass through an economiser, the role of which is to warm the feed waterbefore it reaches the boiler


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Type of Boiler(Power Generation)

According to flow of water & hot gases:

Water tube (4,500 - 20,000 kg/hour of steam)

Fire tube (8000 - 12000 kg/hour of steam)
http://en.citizendium.org/images/d/d8/Fire-tube_Boiler.png


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Water vs Fire tube boilers

Fire tube boilers have low initial cost & are more compact

But they are more likely to explosion, water volume is large & due to poor

circulation they cannot meet quickly the change in steam demand

For the same output the outer shell of fire tube boilers is much larger than the

shell of water-tube boiler

Water tube boilers require less weight of metal for a given size, are less liable to

explosion, produce higher pressure, are accessible and can respond quickly to

change in steam demand

The efficiency of water-tube boilers is more.


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Design of steam powerplant


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Major Components & their function

Economiser

Most of the sensible heat is absorbed in the Economiser. These are a set of coilsmade from steel tubes located in the tail end of a boiler. The hot gases leaving theboiler furnace heat the water in the coils. The water temperature is slightly less

than the saturation temperature. From the economiser the water is fed to the'drum'.

Air pre-Heating:

The hot gases coming out of the economizer is used to preheat the airbefore supplying it to the combustion chamber. An increase in airtemperature of 20 degrees can be achieved by this method. The preheated air is used for combustion and also to dry the crushed coal beforepulverizing


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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. Soot blowers control the

formation of soot and reduce its corrosive effects. The advantages are that

they are placed far away from the high temperature zone, they concentrate

the cleaning through a single large nozzle rather than many small nozzles and

there is no concern of nozzle arrangement with respect to the boiler tubes.


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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 steamchamber of the superheater header and is fed into the steam pipe to the

cylinders. Superheated steam is more expansive.

Reheater

The reheater functions 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.


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http://www.brighthubengineering.com/power

-plants/23879-how-does-a-power-plant-

boiler-work-water-and-steam-system/#

http://en.wikipedia.org/wiki/Steam-

electric_power_station
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Steam_Cycle_Power_Plant.pptx

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