Power Generation and Plant Operation

Course Contents

Energy Sources, Steam Power Plants, Boilers, Condensers, Water

conditioning, Combustion, Cooling Water Supply, Turbines, Gas

Turbine , Nuclear Power Reactors, Steam Generators, Nuclear Safety

Generators, Sub-station equipments etc.

Energy Sources

• Fuels Solids – Coal, Coke, Anthracite etc. Liquids – Petroleum and its derivates Gases – Natural gas, blast furnace gas

• Energy stored in water• Nuclear Energy• Wind Power• Solar Energy• Tidal Power• Geothermal Energy etc.

Fuels A chemical fuel is a substance which release heat energy

on combustion. Carbon & Hydrogen are the principal combustible elements.

Types of Fuel Natural PreparedSolid Wood Coal , Coke

Peat CharcoalLignite Coal Anthracite

Liquid Petroleum GasolineKerosene

Gaseous Natural Gas Coal GasCoke Oven

Blast Furnace

Solid FuelsCoal – its main components are Carbon, Hydrogen Nitrogen,

Sulphur, moisture and ash. Pass through different stages like

Peat, Lignite – Brown Coal Semi-bituminous coal –

Bituminous Coal, Semi Anthracite – Anthracite Properties of Coal :- 1. Energy Content of heating value2. Sulphur Content 3. Burning Characteristics4. Grindability5. Ash

A good Coal should have:i. Low ash content and high calorific valueii. Small percentage of Sulphuriii. Burning characteristics etc.

Grading of Coal:-Grading is done on the following basis:i. Size ii. Heating valueiii. Ash Content iv. Ash Softening temperaturev. Sulphur Content.A grade written as (5 – 10 cm, 500-A8-F24-S1.6)

Liquid FuelsPetroleum :- Heavy oil or crude oil is refined in

refineries, which gives most important product called petrol. Composition of some liquid fuels is as under:-

Fuel Carbon Hydrogen Sulphur Ash

Petrol 85.5 14.4 0.1 -Benzene 91.7 8.0 0.3 -Kerosene 86.3 13.6 0.1 -Diesel Oil 86.3 12.8 0.9 -Light Fuel 86.2 12.4 1.4 -Heavy Fuel 88.3 9.5 1.2 1.0

Important properties of Liquid Fuels

i. Specific gravity ii. Flash Pointiii. Volatility iii. Ash contentiv. Sulphur Content v. Corrosive propertyvi. Heating valueLiquid fuels should have:i. Low ash Contentii. High heating valueiii.Less corrosive tendencyiv.Less Sulphur content

Gaseous FuelsNatural Gas: The main components of natural gas are

Methane (CH4) and Ethane (C2H6). It has calorific value nearly 21000 kJ/m3 .Natural gas is used alternately of simultaneously with oil for internal combustion.

Coal Gas: Hydrogen, Carbon monoxide, hydro-carbons. Prepared by carbonization of coal. Used in boilers and for commercial purpose.

Coke Oven Gas: It is obtained during the production of coke by heating the bituminous coal

Blast Furnace gas: It is produced during smelting operation in which air is forced through layers of coke and iron ore.

Advantages : i. Cleanliness ii. Better Control of combustioniii.No problem of storage iv.Much less excess air is required for complete

combustionv. More efficiency of furnace operationComposition of gaseous Fuels:

H2, CO, CH4, C2H4, C2H6, C4H8 , CO2 , O2 , N2

Energy Stored in Water• The energy stored in flowing streams of water contain

Mechanical Energy. It may exist as the kinetic energy of a moving stream or as a potential energy of water (dam).Water power is quite cheap where water is available in abundance.Capital Cost of hydroelectric power plant is higher.Operating cost is low.

Nuclear EnergyNuclear power is cheaper as compared to other energy

sources.i. 1 kg of Uranium = 4500 tones coal = 2000 tones of

oil

The capital cost is higher and there is safety factor is also involved and problem of disposal of radio- active material is also there.

Wind EnergyThe expense of installation and variability of operation

have tend to limit the use of wind mills. i. No fuel provision and transport are requiredii. Non pollutingiii. No maintenance is required over a long periodiv. Working life is about 20-25 years.Disadvantages:Noisy , Large area is required to build a wind form,

Irregular source

Solar Energy• 1014 KW energy is being received by the surface of

earth, however this amount of energy is not easily convertible.

• not constantly available• Capital investment is high for the conversion

apparatus.

Tidal And Geothermal Energy

Rise and Fall of tides offer a mean for storing water at the rise.

• water Head is very low• Power generation is not continuous • Favorable sites are limited• Geothermal Energy • 10,715 (MW) of geothermal power is online in 24

countries.

STEAM POWER PLANTS

• Using Coal, Gas or Oil or Nuclear Fission to generate steam in boilers/steam generators.

• Steam is utilized to drive the turbines which are coupled to generator to get electricity.

• This type of plant may contain several other heat saving devices, like water heaters,

A thermal power station is a power plant

in which the prime mover is steam

driven. Water is heated, turns into steam

and spins a steam turbine which drives

an electrical Generator. After it passes

through the turbine, the steam is

condensed in a condenser and recycled

to where it was heated; this is known as

a Rankine cycle. The greatest variation

in the design of thermal power stations is

due to the different fuel sources.

Thermal Power Plant

The conversion from coal to electricity takes place in three stages.

Stage 1The first conversion of energy takes place in the boiler. Coal is burnt in the boiler furnace to produce heat. Carbon in the coal and Oxygen in the air combine to produce Carbon Dioxide and heat.

Stage 2The second stage is the thermodynamic process. The heat from combustion of the coal boils water in the boiler to produce steam. In modern power plant, boilers produce steam at a high pressure and temperature. The steam is then piped to a turbine. The high pressure steam impinges and expands across a number of sets of blades in the turbine. The impulse and the thrust created rotates the turbine. The steam is then condensed to water and pumped back into the boiler to repeat the cycle.

Stage 3In the third stage, rotation of the turbine rotates the generator rotor to produce electricity based of Faraday’s Principle of electromagnetic induction

1. Cooling tower 2. Cooling water pump 3. Transmission line

4. Unit transformer (3-phase) 5. Electric generator (3-phase)

6. Low pressure turbine 7. Boiler feed pump 8. Condenser 9.

Intermediate pressure turbine 10. Steam governor valve 11.

High pressure turbine 12. Deaerator 13. Feed heater 14.

Coal conveyor hopper 15. Coal 16. Pulverized fuel mill 17.

Boiler drum 18. Ash hopper 19. Superheater 20. Forced

draught fan (3-phase) 21. Reheater 22. Air intake 23.

Economizer 24. Air preheater 25. Precipitator 26. Induced

draught fan 27. Chimney Stack

Components of a modern steam power plant

1. Reliability 2. Minimum Capital Cost

3. Minimum operating and maintenance cost4. Capacity to meet peak load effectively 5. Minimum losses of energy in transmission6. Low cost of energy supplied to the consumer7. Reserve capacity to meet future demand.

Essential Requirements of steam power station design

Selection of site for Power Plant

1. Availability or raw material2. Nature of land 3. Cost of land4. Availability of water 5. Transport facilities 6. Ash disposal facilities7. Availability of labour 8. Size of the plant9. Load centre 10. Public problems11. Future extensions etc.