| Mohammed Kabiruddin

UNIVERSITY OF

PETROLEUM &

ENERGY STUDIES

VARIOUS COMPONENTS OF

POWER PLANT

Various Components of Power Plant

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Mohammed Kabiruddin, MS-ES, UPES

Contents

Boiler

Turbine

Deaerator

Heat Exchangers

Super Heater

Economizers

Condenser

Feed water heater

Electrical generator

Bibliography

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Mohammed Kabiruddin, MS-ES, UPES

Thermal Power Station

1. Boiler

A boiler is an enclosed vessel that provides a means for combustion heat

to be transferred into water until it becomes heated water or steam. The hot

water or steam under pressure is then usable for transferring the heat to a

process. Water is a useful and cheap medium for transferring heat to a

process. When water is boiled into steam its volume increases about 1,600

times, producing a force that is almost as explosive as gunpowder. This causes

the boiler to be extremely dangerous equipment that must be treated with

utmost care.

The process of heating a liquid until it reaches its gaseous state is called

evaporation. Heat is transferred from one body to another by means of

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Mohammed Kabiruddin, MS-ES, UPES

(1) Radiation, which is the transfer of heat from a hot body to a cold

body without a conveying medium,

(2) Convection, the transfer of heat by a conveying medium, such as air

or water and

(3) Conduction, transfer of heat by actual physical contact, molecule to

molecule.

A. Boiler Systems

The boiler system comprises of: feed water system, steam system and

fuel system. The feed water system provides water to the boiler and regulates

it automatically to meet the steam demand. Various valves provide access for

maintenance and repair.

The steam system collects and controls the steam produced in the

boiler. Steam is directed through a piping system to the point of use.

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Mohammed Kabiruddin, MS-ES, UPES

Throughout the system, steam pressure is regulated using valves and checked

with steam pressure gauges.

The fuel system includes all equipment used to provide fuel to generate

the necessary heat. The equipment required in the fuel system depends on the

type of fuel used in the system. A typical boiler room schematic is shown in

Figure.

The water supplied to the boiler that is converted into steam is called

feed water. The two sources of feed water are:

(1) Condensate or condensed steam returned from the processes and

(2) Makeup water (treated raw water) which must come from outside the

boiler room and plant processes. For higher boiler efficiencies, the feed water

is preheated by economizer, using the waste heat in the flue gas.

There are virtually infinite numbers of boiler designs but generally they fit into

one of two categories:

1. Fire tube or "fire in tube" boilers; contain long steel tubes through which

the hot gasses from a furnace pass and around which the water to be

converted to steam circulates. Fire tube boilers, typically have a lower

initial cost, are more fuel efficient and easier to operate, but they are

limited generally to capacities of 25 tons/hr and pressures of 17.5

kg/cm2

.

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Mohammed Kabiruddin, MS-ES, UPES

2. Water tube or "water in tube" boilers in which the conditions are

reversed with the water passing through the tubes and the hot gasses

passing outside the tubes. These boilers can be of single- or multiple-

drum type. These boilers can be built to any steam capacities and

pressures, and have higher efficiencies than fire tube boilers.

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Mohammed Kabiruddin, MS-ES, UPES

2. Turbine

Turbine, rotary engine that converts the energy of a moving stream of water,

steam, or gas into mechanical energy. The basic element in a turbine is a wheel

or rotor with paddles, propellers, blades, or buckets arranged on its

circumference in such a fashion that the moving fluid exerts a tangential force

that turns the wheel and imparts energy to it. This mechanical energy is then

transferred through a drive shaft to operate a machine, compressor, electric

generator, or propeller. Turbines are classified as hydraulic, or water, turbines,

steam turbines, or gas turbines. Today turbine-powered generators produce

most of the world's electrical energy. Windmills that generate electricity are

known as wind turbines.

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Mohammed Kabiruddin, MS-ES, UPES

3. Deaerator

A deaerator is a device that is widely used for the removal of air and

other dissolved gases from the feed water to steam generating boilers. In

particular, dissolved oxygen in boiler feedwaters will cause serious corrosion

damage in steam systems by attaching to the walls of metal piping and other

metallic equipment and forming oxides (rust). It also combines with any

dissolved carbon dioxide to form carbonic acid that causes further corrosion.

Most deaerators are designed to remove oxygen down to levels of 7 ppb by

weight (0.0005 cm³/L) or less.

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Mohammed Kabiruddin, MS-ES, UPES

4. Heat Exchangers

Heat exchangers are equipment that transfers heat from one medium

to another. The proper design, operation and maintenance of heat exchangers

will make the process energy efficient and minimize energy losses. Heat

exchanger performance can deteriorate with time, off design operations and

other interferences such as fouling, scaling etc. It is necessary to assess

periodically the heat exchanger performance in order to maintain them at a

high efficiency level.

Heat exchangers may be classified according to their flow arrangement.

In parallel-flow heat exchangers, the two fluids enter the exchanger at the

same end, and travel in parallel to one another to the other side. In counter-

flow heat exchangers the fluids enter the exchanger from opposite ends. The

counter current design is most efficient, in that it can transfer the most heat.

See countercurrent exchange. In a cross-flow heat exchanger, the fluids travel

roughly perpendicular to one another through the exchanger.

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Mohammed Kabiruddin, MS-ES, UPES

For efficiency, heat exchangers are designed to maximize the surface

area of the wall between the two fluids, while minimizing resistance to fluid

flow through the exchanger. The exchanger's performance can also be affected

by the addition of fins or corrugations in one or both directions, which increase

surface area and may channel fluid flow or induce turbulence.

The driving temperature across the heat transfer surface varies with

position, but an appropriate mean temperature can be defined. In most simple

systems this is the log mean temperature difference (LMTD). Sometimes direct

knowledge of the LMTD is not available and the NTU method is used.

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Mohammed Kabiruddin, MS-ES, UPES

5. Super Heater

A super heater is a device in a steam engine that heats the steam generated by

the boiler again, increasing its thermal energy and decreasing the likelihood

that it will condense inside the engine. Super heaters increase the efficiency of

the steam engine, and were widely adopted. Steam which has been

superheated is logically known as superheated steam; non-superheated steam

is called saturated steam or wet steam.

Super heaters were applied to steam locomotives in quantity from the early

20th century, to most steam vehicles, and to stationary steam engines

including power stations.

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Mohammed Kabiruddin, MS-ES, UPES

6. Condenser

The surface condenser is a shell and tube heat exchanger in which

cooling water is circulated through the tubes. 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.

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Mohammed Kabiruddin, MS-ES, UPES

Thus leaks of non-condensable 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.

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7. Economizers

Economizers, or in British English economisers, are mechanical devices

intended to reduce energy consumption, or to perform another useful function

like preheating a fluid. The term economizer is used for other purposes as well.

In simple terms, an economizer is a heat exchanger.

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Mohammed Kabiruddin, MS-ES, UPES

8. Feed water heater

In the case of a conventional steam-electric power plant utilizing a drum

boiler, the surface condenser removes the latent heat of vaporization from the

steam as it changes states from vapour to liquid. The heat content (btu) in the

steam is referred to as Enthalpy. The condensate pump then pumps the

condensate water through a feed water heater. The feed water heating

equipment then raises the temperature of the water by utilizing extraction

steam from various stages of the turbine.

Preheating the feedwater reduces the irreversibilities involved in steam

generation and therefore improves the thermodynamic efficiency of the

system. This reduces plant operating costs and also helps to avoid thermal

shock to the boiler metal when the feedwater is introduced back into the

steam cycle.

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Mohammed Kabiruddin, MS-ES, UPES

9. Electrical generator:-

In electricity generation, an electrical generator is a device that converts

mechanical energy to electrical energy, generally using electromagnetic

induction. The reverse conversion of electrical energy into mechanical energy

is done by a motor, and motors and generators have many similarities.

A generator forces electric charges to move through an external

electrical circuit, but it does not create electricity or charge, which is already

present in the wire of its windings. It is somewhat analogous to a water pump,

which creates a flow of water but does not create the water inside. The source

of mechanical energy may be a reciprocating or turbine steam engine, water

falling through a turbine or waterwheel, an internal combustion engine, a wind

turbine, a hand crank, the sun or solar energy, compressed air or any other

source of mechanical energy.

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10. Bibliography

1. http://en.wikipedia.org/wiki/Thermal_power_station

2. http://en.wikipedia.org/wiki/Deaerator

3. http://en.wikipedia.org/wiki/Economiser

4. http://en.wikipedia.org/wiki/Regenerative_heat_exchanger

5. http://www.tva.gov/power/coalart.htm

6. http://images.google.co.in/images?um=1&hl=en&q=feed+water+heater

&start=18&sa=N&ndsp=18