lesson7_steampowerplant.ppt

7/29/2019 Lesson7_SteamPowerPlant.ppt

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Lesson 7


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mechanical power is produced by a heatengine that transforms thermal energy (from

combustion of a fuel) into rotational energy

heat (generated in the furnace) is transmittedto the boiler where water forced into theboiler by the feed pump is converted intosteam


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steam drives turbine blades shaft


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the efficiency of a steam turbine is limited bythe maximum temperature of the steam

produced and is not directly a function of thefuel used (for the same steam conditions,coal, nuclear and gas power plants all havethe same theoretical efficiency)


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Operating pressure Boiler efficiency

Steaming hours Heating surface Generating surface Superheated steam


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Operating pressure the pressure at whichthe boiler is operated in service

Boiler efficiency -the ratio between thethermal energy actually absorbed by waterand the thermal energy available in fuel (80 90 %)


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Steaming hours -the time during which theboiler generates steam

Heating surface -the total surface of all partsexposed to combustion gases (tubes,superheater, economiser)


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FURNACE BOILER

SUPERHEATER TURBINE CONDENSER


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a chamber in which heat is produced combustion of fuel & generation of hot gases

burners break oil into fine particles toensure efficient combustion


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steam generator saturated & superheatedsteam

steam drum - a reservoir of water/steam atthe top end of the water tubes, it stores thesteam generated in the water tubes and actsas a separator for the steam/water mixture(difference in densities)

water circulation natural or forced


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watertube boiler firetube boiler


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hot gases pass through the tubes, feed watersurrounds them


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steam and water circulate through drums andsmall diameter tubes, gases of combustion

pass around them

more commonly used, lighter, occupies lessspace and has increased efficiency (higherpressure and temperature)


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main boiler donkey (auxiliary) boiler

low, intermediate, high pressure b. single-drum b., two-drum b., three-drum b. vertical b., horizontal b. single-flow b., double-flow b.


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consists of headers and superheater tubes converts saturated steam into dry steam


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steam is admitted to the turbine heat energy is converted into mechanical

energy

useful work high pressure turbine low pressure turbine


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heat exchanger tubes sea water

steam water (condensate) vacuum is created due to steam / condensate

volume difference vacuum is maintained by constant cool water

circulation through the tubes


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CONDENSATE COLLECTING TANK(HOTWELL)

MAIN CONDENSATE PUMP AIR EJECTOR DEAERATING FEED TANK MAKE UP TANK (EMERGENCY FEED TANK) FEED PUMP FEED HEATER ECONOMISER


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condensate collecting tank (hotwell) Main Condensate Pump

to pump water from the hotwell through themain air ejector to the deaerating feed tank


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to remove the oxygen from the system to heat the condensate

to be used as storage tank for heated feedwater


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Form: cylindrical tank in three sections

First section (the lowest)

storage space =beginning of the feed phase

Middle section: atomizing valve assembly torelease entrapped air from the water

Upper section: preheater compartment


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losses in cycle when the feed water level in the deaerating

tank drops to a minimum, make-up feedwater enters the system


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pump that forces feed water into the boiler


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preheats the feed water before it enters theboiler


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to improve the efficiency of the steam plantby using thermal energy, i.e. preheating the

feedwater before it passes into the boiler

water is heated under pressure to removedissolved air and vapour to minimize internalboiler corrosion


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double-bottom tank -> transfer pump ->settling tank -> daily (service) tank -> fuel oil

pressure pump -> strainer -> heater -> finemesh -> burner (recirculating connection)


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lesson7_steampowerplant.ppt

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