power plant engg-Unit I.pptx

7/30/2019 power plant engg-Unit I.pptx

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Power plan t Eng ineering

UNIT-I


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POWER PLANT

A power station (also referred to as a generating

station, power plant, or powerhouse) is an

industrial facility for the generation ofelectric

power.

Power plantis also used to refer to the engine in

ships, aircraft and other large vehicles.
http://en.wikipedia.org/wiki/Electricity_generationhttp://en.wikipedia.org/wiki/Electric_powerhttp://en.wikipedia.org/wiki/Electric_powerhttp://en.wikipedia.org/wiki/Enginehttp://en.wikipedia.org/wiki/Enginehttp://en.wikipedia.org/wiki/Electric_powerhttp://en.wikipedia.org/wiki/Electric_powerhttp://en.wikipedia.org/wiki/Electricity_generation


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SOURCES OF POWER


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POWER TRANSMISSION TO HOUSE


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POWER TRANSMISSION TO HOUSE


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POWER PLANT


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CLASSIFIACTION OF POWER PLANT

Steam or thermal power plant. Hydroelectric power plant.

Nuclear power plant.

Diesel power plant. Gas turbine power plant.

Solar power plant.

Wind power plant. Tidal power plant.


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HYDRO ELECTRIC POWER PLANT

Principle: water is used as working fluid.

Potential energy of water stored at higher level is

converted into mechanical energy which is used forpower generation.

Water is allowed to flow under pressure from dam

which is used to run the turbine & electric power is

generated.

Potential energy Mechanical Energy Electrical

Energy


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Device Energy conversion

Dam Water potential energy.

Turbine Potential energy Mechanical

Energy.

Generator Mech.energy Electrical energy.


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PARTS OF HYDEL POWER PLANT

Dam

Spillway

Penstock and Tunnel

Surge Tank

Power Station


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DAM

Dams are structures built over rivers to stop the water flow and

form a reservoir. The reservoir stores the water flowing down the

river.

This water is diverted to turbines in power stations. The dams

collect water during the rainy season and stores it, thus allowing

for a steady flow through the turbines throughout the year.

Dams are also used for controlling floods and irrigation. The

dams should be water-tight and should be able to withstand the

pressure exerted by the water on it.

There are different types of dams such as arch dams, gravity damsand buttress dams. The height of water in the dam is called head

race.


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SPILLWAY A spillway as the name suggests could be called as a way for

spilling of water from dams.

It is used to provide for the release of flood water from a dam. It

is used to prevent over toping of the dams which could result in

damage or failure of dams.

Spillways could be controlled type or uncontrolled type. The

uncontrolled types start releasing water upon water rising above a

particular level.


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PENSTOCK AND TUNNEL Penstocks are pipes which carry water from the reservoir to the

turbines inside power station.

They are usually made of steel and are equipped with gate

systems.

Water under high pressure flows through the penstock. A tunnel

serves the same purpose as a penstock.

It is used when an obstruction is present between the dam and

power station such as a mountain


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SURGE TANK Surge tanks are tanks connected to the water conductor system.

It serves the purpose of reducing water hammering in pipes which

can cause damage to pipes.

The sudden surges of water in penstock is taken by the surge tank,

and when the water requirements increase, it supplies the collected

water thereby regulating water flow and pressure inside the

penstock.


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POWER STATION Power station contains a turbine coupled to a generator.

The water brought to the power station rotates the vanes of the

turbine producing torque and rotation of turbine shaft.

This rotational torque is transferred to the generator and is

converted into electricity.

The used water is released through the tail race


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TYPES OF HYDEL POWER PLANT

Stand alone

Pumped storage


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PUMPED STORAGE

This method produces electricity to supply high peak demands bymoving water between reservoirs at different elevations. At times

of low electrical demand, excess generation capacity is used to

pump water into the higher reservoir.

When there is higher demand, water is released back into the

lower reservoir through a turbine.

Pumped-storage schemes currently provide the mostcommercially important means of large-scale grid energy storage

and improve the daily capacity factorof the generation system
http://en.wikipedia.org/wiki/Reservoir_(water)http://en.wikipedia.org/wiki/Grid_energy_storagehttp://en.wikipedia.org/wiki/Capacity_factorhttp://en.wikipedia.org/wiki/Capacity_factorhttp://en.wikipedia.org/wiki/Grid_energy_storagehttp://en.wikipedia.org/wiki/Reservoir_(water)


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Advantages- Hydro electric power plant:

Waterthe working fluid is a natural & renewable

energy source available in plenty.

Life of the plant is very long.

Running cost of plant is low.

Maintenance & operation cost is low.

No ash disposal problem.

Less supervising staff.

No fuel transportation problem.

In addition to power generation these plants are useful

for irrigation and flood control.


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Disadvantages- Hydro electric power plant:

Initial cost is more high & more time required forerection.

Power generation depends on quantity of water available

Transmission losses are more high & cost is high.

Plants are situated away from load centers it requires

long transmission lines.


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BOILERS

Boiler is an apparatus to produce steam.

Thermal energy released by combustion of fuel is

transferred to water, which vaporizes and gets converted

into steam at the desired temperature and pressure


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APPLICATIONS OF BOILERS

(i) Producing mechanical work by expanding it in steam

engine or steam turbine.

(ii) Heating the residential and industrial buildings

(iii) Performing certain processes in the sugar mills,chemical and textile industries.


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REQUIREMENTS OF BOILERS

(i) Safety. The boiler should be safe under operating conditions.

(ii) Accessibility. The various parts of the boiler should be accessible for repair and

maintenance.

(iii) Capacity. The boiler should be capable of supplying steam according to the

requirements.

(iv) 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.

(v) It should be simple in construction and its maintenance cost should be low.

(vi) Its initial cost should be low.

(vii) The boiler should have no joints exposed to flames.(viii) The boiler should be capable of quick starting and loading.


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TYPES OF BOILERS

According to flow of water and hot gases.

1. Water tube.

2. Fire tube.

Water tube boilers are classified as follows.

1. Horizontal straight tube boilers

(a) Longitudinal drum (b) Cross-drum.

2. Bent tube boilers

(a) Two drum (b) Three drum

(c) Low head three drum (d) Four drum.


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Fire tube boilers are classified as follows.

l. External furnace:

(i) Horizontal return tubular

(ii) Short fire box

(iii) Compact. 2. Internal furnace:

(i) Horizontal tubular

(a) Short firebox (b) Locomotive (c) Compact (d) Scotch.

(ii) Vertical tubular.

(a) Straight vertical shell, vertical tube

(b) Cochran (vertical shell) horizontal tube.


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According to position of furnace.

(i) Internally fired (ii) Externally fired

According to the position of principle axis.

(i) Vertical (ii) Horizontal (iii) Inclined.

According to application.(i) Stationary (ii) Mobile, (Marine, Locomotive).

According to the circulating water.

(i) Natural circulation (ii) Forced circulation.

According to steam pressure.

(i) Low pressure (ii) Medium pressure (iii) Higher pressure.


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COCHRAN BOILER

This boiler consists of a cylindrical shell with its crown

having a spherical shape.

The furnace is also hemispherical in shape


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COCHRAN BOILER


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LANCASHIRE BOILER It is stationary fire tube, internally fired, horizontal, natural

circulation boiler.

This is a widely used boiler because of its good steaming quality

and its ability to burn coal of inferior quality.

These boilers have a cylindrical shell 2 m in diameters and itslength varies from 8 m to 10 m.

It has two large internal flue tubes having diameter between 80 cm

to 100 cm in which the grate is situated.

This boiler is set in brickwork forming external flue so that theexternal part of the shell forms part of the heating surface


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LANCASHIRE BOILER


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LOCOMOTIVE BOILER Locomotive boiler is a horizontal fire tube type mobile

boiler.

The main requirement of this boiler is that it shouldproduce steam at a very high rate.

Therefore, this boiler requires a large amount of heatingsurface and large grate area to burn coal at a rapid rate.


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LOCOMOTIVE BOILER


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BABCOCK WILCOX BOILER Babcock and Wilcox original model is a straight water

tube boiler.

The boiler shell known as water and steam drum is madeof high quantity steel.

It is connected by short tubes with the uptake header orriser and by longer tubes to the down take header


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BABCOCK WILCOX BOILER


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HIGH PRESSURE BOILERS In all modern power plants, high pressure boilers (> 100 bar) are

universally used as they offer the following advantages.

In order to obtain efficient operation and high capacity, forced

circulation of water through boiler tubes is found helpful.

I . The efficiency and the capacity of the plant can be increased as

reduced quantity of steam is required for the same power

generation if high pressure steam is used.

2. The forced circulation of water through boiler tubes provides

freedom in the arrangement of furnace and water walls, in additionto the reduction in the heat exchange area.

3. The tendency of scale formation is reduced due to high velocity

of water.


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HIGH PRESSURE BOILERS 4. The danger of overheating is reduced as all the parts

are uniformly heated.

5. The differential expansion is reduced due to uniform

temperature and this reduces the possibilityof gas and airleakages.


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LA MONT BOILER

A forced circulation boiler was first introduced in 1925

by La Mont.

These boilers have been built to generate 45 to 50 tonnes

of superheated steam at a pressure of 120 bar and

temperature of 500C.


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LA MONT BOILER


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BENSON BOILER The main difficulty experienced in the La Mont boiler is

the formation and attachment of bubbles on the inner

surfaces of the heating tubes.

The attached bubbles reduce the heat flow and steam

generation as it offers higher thermal resistance

compared to water film.


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FLUIDISED BED COMBUSTION (FBC) Burning of pulverised coal has some problems such as particle

size of coal used in pulverised firing is limited to 70-100 microns.

The pulverised fuel fired furnances designed to burn a particular

cannot be used other type of coal with same efficiency, the

generation of high temp. about (1650 C) in the furnace creates

number of problems like slag formation on super heater,

evaporation of alkali metals in ash and its deposition on heat

transfer surfaces, formation of SO2 and NOX in large amount.


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FLUIDISED BED COMBUSTION (FBC)


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CLASSIFICATION OF POWER PLANT CYCLE Power plants cycle generally divided in to the following

groups,

(1) Vapour Power Cycle

(Carnot cycle, Rankine cycle, Regenerative cycle,Reheat cycle, Binary vapour cycle)

(2) Gas Power Cycles

(Otto cycle, Diesel cycle, Dual combustion cycle, Gasturbine cycle.)


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CARNOT CYCLE It has high thermodynamics efficiency.

It is a standard of comparison for all other cycles. The thermal

efficiency () of Carnot cycle is as follows:

= (T1T2)/T1

where, T1 = Temperature of heat source

T2 = Temperature of receiver


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RANKINE CYCLE


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RANKINE CYCLE Efficiency of Rankine cycle

= (H1H2)/ (H1Hw2)

where,

Hl = Total heat of steam at entry pressure

H2 = Total heat of steam at condenser pressure

(exhaust pressure)

Hw2= Total heat of water at exhaust pressure


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REHEAT CYCLE


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REHEAT CYCLE Efficiency = {(H1H2) + (H3H4)}/{H1 + (H3H2)

Hw4}

H1 = Total heat of steam at 1

H2 = Total heat of steam at 2H3 = Total heat of steam at 3

H4 = Total heat of steam at 4

Hw4 = Total heat of water at 4


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REGENERATIVE CYCLE (FEED WATER HEATING)


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REGENERATIVE CYCLE (FEED WATER HEATING) m2 = Weight of bled steam at a per kg of feed water heated

m2 = Weight of bled steam at a per kg of feed water heated H1 = Enthalpies of steam and water in boiler

Hw1 = Enthalpies of steam and water in boiler

H2, H3 = Enthalpies of steam at points a and b

t2, t3 = Temperatures of steam at points a and b H4, Hw4 = Enthalpy of steam and water exhausted to hot well.

Work done in turbine per kg of feed water between entrance and a

= H1H2

Work done between a and b = (1 m2)(H2 H3)

Work done between b and exhaust = (1

m2

m3)(H3

H4)

Total heat supplied per kg of feed water = H1Hw2

Efficiency () = Total work done/Total heat supplied

= {(H1H2) + (1m2)(H2 H3) + (1m2m3)(H3 H4)}/(H1Hw2)


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REHEAT-REGENERATIVE CYCLE


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REFERENCES

Arora S.C. and Domkundwar.S-A Course in Power

Plant Engineering

Nag P.K.- Power Plant Engineering

R.K.Rajput-PowerPlant Engineering A.K.Raja-PowerPlant Engineering

Documents

power plant engg-Unit I.pptx