Power plant engineering

By

polayyaTPIST

INTRODUCTION A power plant is assembly of systems or subsystems to generate

electricity, i.e., power with, economy and requirements The power plant itself must be useful economically and

environmental,friendly to the society. A power plant may be defined as a machine or assembly of equipment that

generates and delivers, a flow of mechanical or electrical energy. The main equipment for the generation of electric power is generator. When coupling it to a prime mover runs the generator, the

electricity is generated. The major power plants, which are discussed in this

Subject, are,1. Steam power plant2. Diesel power plant3. Gas turbine power plant4. Nuclear power plant5. Hydro electric power plantThe Steam Power Plant, Diesel Power Plant, Gas Turbine Power

Plant and Nuclear Power Plants, are called THERMAL POWER PLANT, because these convert heat into electric energy.

CLASSIFICATION OF POWER PLANTS

POWER DEVELOPMENT IN INDIA The history of power development in India dates back to 1897 when a 200 kW

hydro-station was,first commissioned at Darjeeling. The first steam station was set up in Calcutta in 1899

By the end of,1920, the total capacity was 130 mW, comprising. Hydro 74 mW, thermal 50 mW and diesel 6 mW.

In1940, the total capacity goes to 1208 mW. There was very slow development during 1935-1945 due to,Second World War.

The total generation capacity was 1710 mW by the end of 1951. The development

really started only after 1951 with the launching of the first five-year plan. During the First Plan, construction of a number of Major River Valley Projects

like Bhakra-Nangal, Damodar Valley, Hira Kund and Chambal Valley was taken up. These projects resulted in the,stepping up of power generation. At the end of the First Plan, generation capacity stood at 34.2 lakh kW.

Emphasis in Second Plan (1956-61) was on development of basic and heavy industries andrelated need to step up power generation. Installed capacity at the end of Second Plan reached 57 lakhkw. comprising 3800 mW thermal and 1900 MW hydel.

POWER DEVELOPMENT IN INDIA During the Third Plan period (1961-66), emphasis was on

extending power supply to rural areas. Fourth Plan envisaged need for central participation in expansion

of power generation programmes at strategic locations to supplement activities in the State Sector. Progress during the period coveringThird Plan, three Annual Plans and Fourth Plan was substantial with installed capacity rising to 313.07lakh kW compression; 113.86 lakh kW from Hydro-electric Projects, 192.81 lakh kW from Thermal, Power Projects and balance of 6.4 lakh kW from Nuclear Projects at the end of the Fifth Plan.

During the Sixth Plan, total capacity addition of 196.66 lakh kW comprising Hydro 47.68 lakhkW, Thermal 142.08 lakh kW and Nuclear 6.90 lakh kW was planned

Eighth Plan has recommended a capacity addition programme,of 38,369 mW for the Eighth Plan period,

PRESENT POWER POSITION IN INDIAThe present power position in India is alarming as there

are major power shortages in almost all, states of the country leading to crippling of industries and hundreds of thousands of people losing jobs, and a heavy loss of production

The overall power scene in the country shows heavy shortages almost in all states. The situation, is going to be aggravated in coming years as the demand is increasing and the power industry is not keeping pace with the increasing demand.

Many of the states in India depend to a large extent on hydro generation. The increase in demand has far outstripped the installation of new plants. Also there is no central grid to distribute excess energy from one region to another. The experience in the operation of thermal plants is inadequate. All these have led to heavy shortages and severe hardship to people.

POWER CORPORATIONS IN INDIANATIONAL THERMAL POWER CORPORATION:

National Thermal Power Corporation (NTPC) was incorporated in November, 1975, as a public sector undertaking with main objective of planning, promoting and organizing integrated development of Thermal Power in the Country. The Authorized Capital of the corporation is Rs. 6,000 crore.

NATIONAL HYDRO-ELECTRIC POWER CORPORATION:The National Hydroelectric Power Corporation (NHPC) was incorporated in November 1975,with objectives to plan, promote and organize an integrated development of hydroelectric Power in the12 POWER PLANT ENGINEERING Central Sector.RURAL ELECTRIFICATION CORPORATION:The Rural Electrification Corporation (REC) was set up in July, 1969, with the primary objective of promoting rural electrification by financing rural Electrification Schemes and Rural Electric Cooperatives in the states.

CENTRAL POWER RESEARCH INSTITUTE (CPRI), BANGALORE:The Central Power Research Institute, which was set up in 1960 as a subordinate office under the erstwhile Central Water and Power Commission (Power Wing), was reorganized and registered as society under the Karnataka Societies Act, 1960, with effect from January, 1978

DAMODAR VALLEY CORPORATION:Damodar Valley Corporation (DVC) was established in 1948 under an Act of Parliament for,unified development of Damodar Valley covering an area of 24,235 sq km in Bihar and West Bengal.

NORTH-EASTERN ELECTRIC POWER CORPORATION LIMITED:The North-Eastern Electric Power Corporation Ltd., was constituted in 1976 under the Companies, Act under the aim of developing the large electric power potential of the North-Eastern Region.

BHAKRA BEAS MANAGEMENT BOARD AND BEAS CONSTRUCTION BOARDUnder the Punjab Reorganization Act. 1966, Bhakra Management Board thereto managed management of Bhakra Darn and reservoirs and works appurtenant. The construction of Beas Project was undertaken by the Beas Construction Board. After completion of works of Beas Project, management of the project was taken over by Bhakra Management Board redesignated as Bhakra Beas Management Board (BBMB).

POWER ENGINEERS TRAINING SOCIETY (PETS):The Power Engineers Training Society (PETS) was formed in 1980 as a autonomous body to, function as an Apex National Body for meeting the training requirements of Power Sector in the Country

NATHPA, JHAICRI POWER CORPORATION LIMITED:24, 1988, for execution of Nathpa Jhakri Power Project (6 × 250 mW) with equity participation in the ratio of 3 : 1. The corporation has an authorized Share Capital of Rs 1,000 crore. It will also execute other Hydro-electric Power Projects in the region with consent of the state government.

Introduction to steam power plantWorks on Rankine CycleSteam produced in boiler (usually by burning coal) is

expanded in the prime mover (ie; steam turbine)Condensed steam is fed back to boiler againThe steam turbine drives the alternator produces

electricitySteam power plants contribute about 65% of total electrical

energy generated in India

India is one of the world’s largest consumer of energy

Conventional sources: Thermal, Hydro and Nuclear.

Non- conventional: Wind, solar, Geothermal, tidal.Installed capacity – 1,61,352MW

Thermal = 95151.74MWNuclear = 4,120MWHydro = 36877.76MWRES = 13242.41MW

Annual power production – 68o billion KWH

Break up of PowerThermal Power Plants – 75%Hydro Electric Power Plants - 21%Nuclear Power Plants - 4%Installed wind power Generation – 9655MW30% to 40% of electrical power is lost in

transmission and distribution

General Layout of Steam Power Plant

Main CircuitFuel And Ash CircuitAir And Gas CircuitFeed Water And Steam CircuitCooling Water Circuit

Fuel And Ash CircuitFuel stored and fed to the boiler through

conveyor belts. Broken down into proper shape for complete burning.

Ash thus generated after burning is removed from the boiler through ash handling equipment

Air And Gas CircuitAir is required for combustion of fuel and is

supplied through fansAir is passed through air preheater to extract

energy from flue gases for proper burning of the fuel

Flue gases have ash and several gases which are passed through the precipitator(dust collector) and go to atmosphere through chimney.

Feed Water And Steam CircuitSteam Converted to water by condenser.Water is demineralized & hence not wasted to

have better economic operation of the plant.Some part of steam and water is lost while

passing through different parts.Boiler feed pump feeds water into the boiler

drum where it is heated to form steam.Wet steam is again heated in super heater

before passing through the turbineSteam is expanded in the turbine to run it. After

which again it goes to boiler for reheating

Cooling Water Circuit

To condensate the steam, large quantity of cooling water is required which is taken from river or pondage

After passing through the condenser, it is fed back to the river or Pondage

Boiler

Turbine

Turbine – Full View

Layout of Steam Power PlantThe schematic arrangement of a modern steam

power station can be divided into the following stages:

Coal and ash handling plantSteam generating plantSteam turbineAlternatorFeed waterCooling arrangement

Coal and Ash handling plantCoal is transported to power station by rail or

road and stored in coal storage plant and then pulverised

Pulverised coal is fed to fed to the boiler by belt conveyers

Coal gets burned in the boiler and ash produced is removed to the ash handling plant and then delivered to ash storage plant for disposal

A 100MW station operating at 50% LF may burn about 20000tons of coal per month and produce 3000 tons of ash

Coal handling plant

ASH HANDLING PLANT

The Ash from the boiler is collected in two forms:1. Bottom Ash(Slurry):It’s a waste which is dumped into a Ash Pond2. Fly ash: Fly ash is separated from Flue Gases in ESP(Electro static

Precipitator).

Fly Ash & Flue Gases

Economizer ESP

Bottom ash(wet ash)

Ash Pond

Boiler

Cylo

Chimney

Fly ash

Flue Gases

Cement Factory

Steam generating plantThe steam generating plant consists of a boiler

for the production of steam and other auxiliary equipment for the utilization of flue gases

1) Boiler: The heat of combustion in the boiler is utilized to convert water into steam at high temperature and pressure

Boiler at Kota Thermal Power Station

Steam generating plant2) Superheater: The steam produced in boiler

is wet and is passed through a superheater where it is dried and superheated. Increases efficiency

Steam generating plant3) Economiser: It’s essentially a feed water heater and derives heat from the flue gases

Steam generating plant4) Air Preheater: Increases the temperature

of the air supplied for coal burning by deriving heat from flue gases. Air is drawn from the atmosphere by a forced drought fan and is passed through air preheater before supplying to the boiler furnace.

Steam TurbineDry and superheated steam from superheater

is fed to the steam turbine.The heat energy of steam when passing over

the blades of turbine is converted into mechanical energy.

After giving energy to the turbine, the steam is exhausted to the condenser which condenses the exhausted steam by means of cold water circulation

Turbine – Full View

BoilerWater tube boilerFire tube boiler

Boiler

Firetube boilerhot gases pass through the tubes, feed water

surrounds them

Watertube boilersteam and water circulate through drums

and small diameter tubes, gases of combustion pass around them

more commonly used, lighter, occupies less space and has increased efficiency (higher pressure and temperature)

Watertube boiler

Watertube boilermain boilerdonkey (auxiliary) boilerlow, intermediate, high pressure b.single-drum b., two-drum b., three-drum b.vertical b., horizontal b.single-flow b., double-flow b.

Superheaterconsists of headers and superheater tubesconverts saturated steam into dry steam

Turbinesteam is admitted to the turbineheat energy is converted into mechanical

energy – useful workhigh pressure turbinelow pressure turbine

AlternatorSteam turbine is coupled to an alternator

which converts the mechanical energy to electrical energy

The electrical output of the alternator is delivered to the bus bars through transformer, circuit breakers and isolators.

Feed WaterThe condensate from the condenser is used

as feed water to the boiler.The water that may be lost in the cycle is

made up from the external sourceThe feed water on its way to boiler gets

heated up by water heaters and economiser.This helps to improve the overall efficiency of

the plant

Water in a Power Plant is used for1.Production of Steam- for rotating turbine.2.Cooling Purpose- For cooling of various equipment

3% of water is wasted during this process. Appx 4 cubic mt water is lost /day/MW

Cooling ArrangementCondenser condenses the steam exhausted

from the turbineWater is drawn from natural sources like

river, lake, canals…Circulating water takes up the heat and itself

gets heated upThis hot water can be discharged away or

used again by using a cooling tower