EBB 4043 ELECTRICAL AND ENERGY SYSTEM

LECTURE 2STEAM TURBINE

Objectives

To identify the main part of steam power plant.

To understand the working principle of steam power plant.

To understand the layout of steam power plant.

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Classification of Power Plant

Power plants using conventional (non-renewable) sources of energy• Steam power plant• Nuclear power plant• Diesel power plant• Gas power plant

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Classification of Power Plant

Power plants using Non-conventional(renewable) sources of energy• Hydro electric power plant• Solar thermal power plant• Wind powered generation(aerogeneration)• Wave power plant• Tidal power plant• Geothermal power plant• Bio-mass power plant• Oceanthermal power plant

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Steam Power Plant

Fuel : Coal / Gas /Oil Main parts : Boiler, Turbine, Generator

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Steam Turbine Combined Power Plant (Gas Turbine and

Steam Turbine) Gas Turbine Diesel Engine

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How is electric power produced using oil, coal or natural gas?

Principle of Steam Turbine

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Main parts of steam turbine

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Terminology

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Boiler

An important part of steam power production systems. The function of a boiler is to provide an enclosure in

which pressurized water can be heated to a high temperature to produce steam.

The heat from burning fossil is transferred to an area through which pressurized water flows - the water is converted to steam

The transfer of heat within a boiler utilizes the three methods of heat transfer: radiation, conduction and convection.

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Boiler The radiation method involves the movement of heat energy

from a warm area to a cool area, and is dependent upon temperature difference and the ability of materials to absorb heat.

The conduction method requires contact between the heat source and the heated area, and it relies upon the heat conductivity of the heated material.

Convection is the movement of heat from a hot area to a cooler area by means of an intermediate substance, such as gas.

Each of these three methods of heat transfer occurs in varying amounts, depending upon boiler design.

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Boiler A boiler must functions properly as the boiler operation determines the

quantity of steam available to produce the rotary motion of the turbine. When more power input for the generating process is required, because

of an increased load on the system, the boiler must deliver more steam to the turbine.

Boilers must be able to provide effective water circulation, efficient fuel combustion, and maximum heat transfer to the circulating water.

The boilers used in most steam power plants today are called water-tube boilers.

Their design consists of banks of tubes, separated by heat insulation where water is circulated through the tubes under high temperature and high pressure.

Boiler design is very important for an efficient steam power plant operation.

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Stocker Boiler

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Boiler Coal/Gas/Oil

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Boiler Gas / Oil

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Boiler Auxiliary Systems

There are several auxiliary systems used in a steam power plant to increase the operation and efficiency of the boilers.

Among them are • Economizer• Feedwater Heaters • Preheater • Superheater

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Economizer

Economizers utilize the hot exhaust gases from the fuel reactions within a boiler to preheat the cold feedwater that is pumped into the boiler.

Thus, the economizer uses the waste gases, which would otherwise be emitted through the exhaust stack, for an important purpose.

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Feedwater Heater and Preheater

Feedwater heaters and preheaters are used to increase the water temperature before its entry into the boiler.

These systems heat the pumped feedwater by means of steam, which is circulated through the unit.

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Superheater

These units consist of banks of tubes located at the hottest area of the boiler.

Steam flows through these tubes before its entry into the steam turbine.

The purpose of the superheater is to cause the steam to reach a higher temperature so as to produce more energy in the steam turbine.

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Turbine

After steam has been produced, a rotary motion must be developed.

This rotary motion is produced by a steam turbine.

The rotor is usually divided into two parts—the high pressure rotor and the low pressure rotor.

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Turbine

The low-pressure rotor is larger in diameter than the high-pressure rotor.

Steam is channelled to the high-pressure rotor, and it is then routed to the low-pressure rotor.

Steam turbines ordinarily achieve a maximum efficiency of less than 30 percent, but only when run at very high speeds.

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Turbine

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Expanded View of Turbine

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Turbine Generator

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Turbine Rotor

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Condenser Condensers are used to cool the used steam that

has passed through the steam turbine . Extraction turbines have a steam condenser

operating under a vacuum to condense the steam not extracted for other processes.

The condensate (condensed steam) is returned to the boilers to produce steam again.

The unused heat from the condensed steam is rejected to the lake.

Extraction turbines are able to meet variable steam load conditions and still maintain electrical production needs.

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Condenser

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Chimney – fly ash

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Cooling Tower

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Steam Power Plant Animation

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Pros and Cons

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Advantages of thermal power plant :• Low initial cost• Since located near the load centre, the cost of transmission and the losses due to

transmission are considerably reduced.• The construction and commissioning of thermal power plant takes lesser period.

Disadvantages of thermal power plant:• Fuel is a non-renewable source of energy.• Efficiency decreases with decreasing load.• Cost of power generation is high.• Smoke produced by burning the fuel causes air pollution.• Life of thermal power plant is 25 years. The efficiency decreases to less than 10%

after its life period.• Turbines has a high running speed of 3000 to 4000 rpm.