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Jagan Steam Power Plant

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    steam power plant

    BABA HIRA SINGH BHATTAL INSTITUTE OF

    ENGINEERING AND TECHNOLOGY LEHRAGAGA-

    148031 DISTT.SANGRUR (Pb.)

    By :-Rakesh kumar

    Assistant professor

    Electrical Engineering Department.

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    Essentials of Steam Power Plant Equipment

    A steam power plant must have following equipment :

    (a) A furnace to burn the fuel.(b) Steam generator or boiler containing water.

    Heat generated in the furnace is utilized to

    convert water into steam.

    (c) Main power unit such as an engine or

    turbine to use the heat energy of steam and

    perform work.

    (d) Piping system to convey steam and water.

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    The flow sheet of a thermal power plant

    consists of the following four main circui ts :(a) Feed water and steam flow circuit.

    (b) Coal and ash circuit.

    (c) Air and gas circuit.(d) Cooling water circuit.

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    A steam power plant using steam as working

    substance works basically on Rankine cycle.

    Steam is generated in a boiler, expanded in theprime mover and condensed in the condenser

    and fed into the boiler again.

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    The different types of components used in steam

    power plant

    (a) High pressure boiler.

    (b) Prime mover .

    (c) Condensers and cooling towers .

    (d) Coal handling system .

    (e) Ash and dust handling system .

    (f) Draught system .

    (g) Feed water purification plant .(h) Pumping system .

    (i) Air preheater, economizer, super heater, feed

    heaters.

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    Types of steam Generators Horizontal vertical or inclined.

    Fire tube or water tube.

    Externally fired or internally fired.

    Forced circulation and natural circulation.

    High pressure or low pressure boiler.

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    Daltons law The partial pressure pressure of each

    constituent is that pressure which the gas

    would exert if it occupied alone that volumeoccupied by the mixture at the sametemperature.

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    Factors that should be considered while

    selecting the boiler Working pressure and quality of steam

    required.

    Steam generation rate.

    Floor area available.

    The portable load factor.

    Erection facilities.

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    Properties of good steam generators It should be absolutely reliable.

    It should occupy minimum space.

    It should be light in weight.

    Capable of quick starting.

    Erection of boiler should be simple.

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    Steam Power Plants are Classified as

    1.By fuel.

    2.By prime mover.3.By cooling tower.

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    Steam Power Plants are also Classified as;

    Central stations; the electrical energy available fromthese stations is meant for sale to the consumers who

    wish to purchase it.

    I ndustr ial/ captive power stations; this type of

    power station is run by the manufacturing company for

    its own use and its output is not available for general

    sale.

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    Jet condenser; low manufacturing cost. Lowupkeeps, requires small floor space and more

    auxiliary power required.

    surface condenser; high manufacturing cost.high upkeeps, requires large floor space and less

    auxiliary power required.

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    Feed water heating improves overall plant

    efficiency.

    Quantity of steam produced by the boiler isincrease.

    Thermal stress due to cold water entering the

    boiler drum are avoided.Chance of boiler corrosion are decrease.

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    Dust collectorsare Classified as;

    Mechanical dust collectors;

    (a)Wet type(scrubbers).Spray type, packed type and impingement type.

    (b) Dry type.

    Gravitational separators, cyclone separators,electricaldust collectors;Rod type and plate type.

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    DIFFERENT TYPES OF BOILERS USED IN

    STEAM POWER PLANTS

    horizontal, vertical or inclined.

    fire tube and water tube .

    Externally or internally fired.

    Forced or natural circulation.

    High pressure or low pressure.

    Stationary or portable.

    Single-tube and multi-tube.

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    or ng agram ermapower station.

    S T bi P Pl

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    C

    saturatedwater

    hot gases

    SteamTurbine

    Gen

    compressedwater

    superheatedsteam

    Condenser

    Pump

    cooling watersaturatedsteam

    Steam Generator(Boiler / Furnace)

    Steam Turbine Power Plant

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    Superheated steam then flows through the

    turbine. After doing work in the turbine the

    pressure of steam is reduced. Steam leavingthe turbine passes through the condenser

    which is maintained the low pressure of

    steam at the exhaust of turbine.

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    Steam pressure in the condenser depends uponflow rate and temperature of cooling water andon effectiveness of air removal equipment.

    Water circulating through the condenser may be

    taken from the various sources such as river, lakeor sea. If sufficient quantity of water is notavailable the hot water coming out of thecondenser may be cooled in cooling towers andcirculated again through the condenser.

    Bled steam taken from the turbine at suitableextraction points is sent to low pressure and highpressure water heaters.

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    Air taken from the atmosphere is firstpassed through the air pre-heater, where it is

    heated by flue gases. The hot air then passesthrough the furnace.

    The flue gases after passing over boiler andsuperheater tubes, flow through the dust

    collector and then through economiser, airpre-heater and finally they are exhausted tothe atmosphere through the chimney.

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    Disadvantage of steam power plant

    Maintenance and operating cost are high.

    Long time required for erection and putting into

    action . Large quantity of water is required.

    Great difficulty experienced in coal handling .

    Efficiency decreases rapidly below about 75percent load.

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    Mechanical equipment in Thermal

    power station.

    BOILER

    ECONOMISER

    TURBINE

    SUPER HEATER

    AIR PREHEATER

    CONDENSER

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    SuperheaterThe superheater consists of a superheater

    header and superheater elements. Steam from

    the main steam pipe arrives at the saturated

    steam chamber of the superheater header and is

    fed into the superheater elements.

    Superheated steam arrives back at the

    superheated steam chamber of the superheaterheader and is fed into the steam pipe to the

    cylinders. Superheated steam is more expansive.

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    Advantages of superheated steamCapacity to do work is increased without

    increasing its pressure.

    High temperature of super heated steamresults in an increase in thermal efficiency.

    Heat losses due to condensation of stem on

    cylinder walls are avoided to a great extent.

    Does not produce corrosion effect on

    turbine.

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    Superheater It is a heating device.

    It is used to raise temp of steam at const

    pressure.

    It removes even last traces of moisture.

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    Classification of super heaterConvection.

    Radiation.

    Combination of convection and radiation.

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    ReheaterThe function of reheater is similar to the

    superheater in that it serves to elevate the

    steam temperature. Primary steam is suppliedto the high pressure turbine.

    After passing through the high pressure

    turbine, the steam is returned to the steam

    generator for reheating (in a reheater) after

    which it is sent to the low pressure turbine. A

    second reheat cycle may also be provided.

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    Soot BlowersThe fuel used in thermal power plants causes

    soot and this is deposited on the boiler tubes,

    economizer tubes, air pre heaters, etc.

    This drastically reduces the amount of heat

    transfer of the heat exchangers. Soot blowers

    control the formation of soot and reduce its

    corrosive effects.

    The types of soot blowers are fixed type, which

    may be further classified into lane type and

    mass type depending upon the type of spray and

    nozzle used.

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    Condenser

    The use of a condenser in a power plant is toimprove the efficiency of the power plant by

    decreasing the exhaust pressure of the steam

    below atmosphere.

    Another advantage of the condenser is that the

    steam condensed may be recovered to provide a

    source of good pure feed water to the boiler and

    reduce the water softening capacity to a

    considerable extent. A condenser is one of the

    essential components of a power plant.

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    Functions of Condensers

    The main purposes of the condenser are to

    condense the exhaust steam from the turbine

    for reuse in the cycle and to maximize turbine

    efficiency by maintaining proper vacuum. As the operating pressure of the condenser is

    lowered (vacuum is increased), the enthalpy

    drop of the expanding steam in the turbine willalso increase. This will increase the amount of

    available work from the turbine (electrical

    output).

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    Cooling TowerThe importance of the cooling tower is felt

    when the cooling water from the condenser has

    to be cooled.

    The cooling water after condensing the steam

    becomes hot and it has to be cooled as it

    belongs to a closed system. The Cooling towersdo the job of decreasing the temperature of the

    cooling water after condensing the steam in the

    condenser.

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    Cooling Towers have one function :

    Remove heat from the water discharged

    from the condenser so that the water can bedischarged to the river or re-circulated and

    reused.

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    A cooling tower extracts heat from water by

    evaporation. In an evaporative cooling

    tower, a small portion of the water beingcooled is allowed to evaporate into a moving

    air stream to provide significant cooling to

    the rest of that water stream.

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    Cooling Towers are commonly used to

    provide lower than ambient watertemperatures and are more cost effective and

    energy efficient than most other alternatives.

    The smallest cooling towers are structured foronly a few litres of water per minute while the

    largest cooling towers may handle upwards of

    thousands of litres per minute. The pipes are

    obviously much larger to accommodate this

    much water in the larger towers and can

    range up to 12 inches in diameter.

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    Advantages of regenerative cycle Improve overall plant efficiency.

    Protect boiler corrosion.

    Avoid the thermal stresses due to cold water

    entering the boiler .

    Increased the quantity of steam produced by

    boiler.

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    Function of economizer To extract a part of heat from the fuel gas

    coming out of the boiler.

    To use heat for heating feed water to theboiler.

    To increases the efficiency of boiler.

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    The economizer is a feed water heater,

    deriving heat from the flue gases. The

    justifiable cost of the economizer depends onthe total gain in efficiency. In turn this

    depends on the flue gas temperature leaving

    the boiler and the feed water inlettemperature.

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    Air Pre-heater

    The flue gases coming out of the economizer

    is used to preheat the air before supplying itto the combustion chamber. An increase in

    air temperature of 20 degrees can be

    achieved by this method. The pre heated airis used for combustion and also to dry the

    crushed coal before pulverizing.

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    Advantages of mechanical handlingHigher reliability.

    Less labour required.

    Operation is easy and smooth.

    Economical for large capacity plant.

    Losses in transport are minimised.

    Easily started.

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    Disadvantages of mechanical handlingNeed continuous maintenance and repair.

    Capital cost of plant is increased.

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    Working diagram Thermal

    power station.

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    Side view Thermal power station.

    Steam Turbine Power PlantTotal

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    C

    saturatedwater

    Gen

    compressedwater

    superheatedsteam

    cooling water

    PumpSteamTurbine

    Condenser

    Steam Generator

    Steam Turbine Power Plant

    saturatedsteam

    hot gases

    Heat

    WorkoutTotal

    Workin

    in

    Total

    Loss???Where???

    A di t th

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    R. Shanthini 15Aug 2010

    According to the2ndLaw of Thermodynamics

    when heat is converted into work,part of the heat energy must be wasted

    Power generation

    type

    Unit size

    (MW)

    Energy wasted

    (MW)

    Diesel engine 10 - 30 7 22

    Gas Turbine 50 - 100 36 78

    Steam Turbine 200 - 800 120

    560Combined (ST & GT) 300 - 600 150 380

    Nuclear (BWR & PWR) 500 - 1100 330 760

    9-1

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    The Simple Ideal Rankine Cycle

    The McGraw-Hill Companies, Inc.,1998

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    How can We Increase the Efficiency of the

    Rankine cycle?

    Rankine cycle efficiency can be increased by

    increasing average temperature at which

    heat is transferred to the working fluid inthe boiler or decreasing the average

    temperature at which heat is rejected from

    the working fluid in the condenser. That is,

    the average fluid temperature should be as

    high as possible during heat addition and as

    low as possible during heat rejection.

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    The three ways by which eff iciency of the

    Rankine cycle can be increased are :

    (a) Lowering the condenser pressure.

    (b) Superheating the steam to high

    temperatures.

    (c) Increasing the boiler pressure.

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    The thermal efficiency of the Rankine cyclecan be increased by increasing the averagetemperature at which heat is added to the

    working fluid and/or by decreasing theaverage temperature at which heat isrejected to the cooling medium. The averagetemperature during heat rejection can be

    decreased by lowering the turbine exitpressure.

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    Consequently, the condenser pressure of most

    vapor power plants is well below theatmospheric pressure. The average

    temperature during heat addition can be

    increased by raising the boiler pressure or bysuperheating the fluid to high temperatures.

    There is a limit to the degree of superheating,

    however, since the fluid temperature is notallowed to exceed a metallurgically safe value.

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    Superheating has the added advantage of

    decreasing the moisture content of the steam at

    the turbine exit. Lowering the exhaust pressure

    or raising the boiler pressure, however, increases

    the moisture content. To take advantage of the

    improved efficiencies at higher boiler pressures

    and lower condenser pressures, steam is usually

    reheated after expanding partially in the high-

    pressure turbine.

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    This is done by extracting the steam after

    partial extraction in the high-pressure

    turbine, sending it back to the boiler whereit is reheated at constant pressure, and

    returning it to the low-pressure turbine for

    complete expansion to the condenser

    pressure.

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    The average temperature during the reheatprocess, and thus the thermal efficiency ofthe cycle, can be increased by increasing thenumber of expansion and reheat stages. As

    the number of stages is increased, theexpansion and reheat processes approach anisothermal process at maximum

    temperature. Reheating also decreases themoisture content at the turbine exit.

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    Another way of increasing the thermal

    efficiency of the Rankine cycle is by

    regeneration. During a regeneration process,

    liquid water (feed water) leaving the pump

    is heated by some steam bled off the turbine

    at some intermediate pressure in devices

    called feed water heaters.

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    The two streams are mixed in open feed

    water heaters, and the mixture leaves

    as a saturated liquid at the heaterpressure. In closed feed water heaters,

    heat is transferred from the steam to

    the feed water without mixing.

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    The production of more than one usefulform of energy (such as process heat and

    electr ic power) f rom the same energy source

    is cal led cogeneration. Cogeneration plantsproduce electric power while meeting the

    process heat requirements of certain

    industr ial processes.

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    This way, more of the energy

    transferred to the fluid in the boiler

    is utilized for a useful purpose. Thefaction of energy that is used for

    either process heat or power

    generation is called the utilization

    factor of the cogeneration plant.

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    The overall thermal efficiency of a powerplant can be increased by using binary

    cycles or combined cycles. A binary cycle

    is composed of two separate cycles, one athigh temperatures (topping cycle) and the

    other at relatively low temperatures.

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    The most common combined cycle is the gas-steam combined cycle where a gas-turbinecycle operates at the high-temperature rangeand a steam-turbine cycle at the low-temperature range. Steam is heated by thehigh-temperature exhaust gases leaving the

    gas turbine. Combined cycles have a higherthermal efficiency than the steam- or gas-turbine cycles operating alone.

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    Selection of plant site

    The selection of plant site for thermal power

    plant compared with hydro-power plant is

    more difficult as it involves number offactors to be considered for its economic

    justification.

    A few important factors to be considered forthe selection of thermal power plants.

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    Selection of plant site

    AVAI LABI L I TY OF COAL.

    Huge quantity of coal is required for

    large thermal plants.ASH DI SPOSAL FACIL I TI ES.

    SPACE REQUIREMENT.

    NATURE OF LAND.

    AVAI LABI L I TY OF WATER.

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    Selection of plant site

    TRANSPORT FACIL I TYIES.

    AVAI LABI L I TY OF LABOUR.

    PUBLIC PROBLEMS.SIZE OF THE PLANT.

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    Nowadays, the environment protection has

    become a crucial problem and theauthorities are requested to set increasingly

    more str ingent l imits , one of which is the

    emissions from the industr ial plants of solidparticulate and other gaseous pollutants.

    ABOUT ELECTROSTATIC

    PRECIPITATOR

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    ABOUT ELECTROSTATIC PRECIPITATOR

    Electrostatic precipitator (ESP) is a widely

    used device in so many different domainsto remove the pollutant particulates,

    especially in industr ial plants.

    What is ESP

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    HOW ESP WORKS

    Generally, the processes of

    electrostatic precipitator are known as

    three main stages: particle charging,

    transport and collection.

    Main process of ESP

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    Schematic of wire-plate ESP

    Schematic of wire-plate electrostatic

    precipitator

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    Mechanism of ESP

    Mechanism of electrostatic precipitator

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    PROCESS OF Particle charging

    Particle charging is the first and

    foremost beginning in processes.

    As the voltage applied on precipitator

    reach threshold value, the space inside

    divided into ionization region and driftregion.

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    The electric field magnitude around thenegative electrode is so strong that the

    electrons escape from molecule.

    Under the influence of electric field, the positive

    ions move towards the corona, while the

    negative ions and electrons towards thecollecting plates.

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    Particle transport

    I n the moving way, under the inf luence ofelectr ic field, negative ions cohere and charge the

    particles, make the particles be forced towards

    collecting-plate.

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    Particle collectionAs soon as the particles reach the plate,

    they will be neutralized and packed by

    the succeeded ones subsequently. Thecontinuous process happens, as a result,

    particles are collected on the collecting

    plate.

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    72

    What is a Boiler?

    Introduction

    Vessel that heats water to become hot water

    or steam

    At atmospheric pressure water volume

    increases 1,600 times

    Hot water or steam used to transfer heat to aprocess

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    The boiler is a rectangular furnaceabout 50 feet (15 m) on a side and 130 feet

    (40 m) tall. Its walls are made of a web ofhigh pressure steel tubes about 2.3 inches

    (58 mm) in diameter.

    http://en.wikipedia.org/wiki/Furnacehttp://en.wikipedia.org/wiki/Furnace
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    A boiler should ful f i l l the fol lowing requi rements

    (a)Safety : The boiler should be safe under

    operating conditions.

    (b) Accessibility : The various parts of the

    boiler should be accessible for repair and

    maintenance.

    (c) Capacity : The boiler should be capable of

    supplying steam according to the requirements.

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    (d) Efficiency : To permit efficient operation, the boiler

    should be able to absorb a maximum amount of heatproduced due to burning of fuel in the furnace.

    (e) It should be simple in construction and its

    maintenance cost should be low.

    (f) Its initial cost should be low.

    (g) The boiler should have no joints exposed to flames.

    (h) The boiler should be capable of quick starting and

    loading.

    I t d ti

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    Introduction

    BURNERWATER

    SOURCE

    BRINE

    SOFTENERSCHEMICAL FEED

    FUELBLOW DOWN

    SEPARATOR

    VENT

    VENTEXHAUST GASSTEAM TOPROCESS

    STACK DEAERATOR

    PUMPS

    Figure: Schematic overview of a boiler room

    BOILER

    ECO-

    NOMI-

    ZER

    T f B il

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    Types of Boilers

    1. Fire Tube Boiler

    2. Water Tube Boiler

    3. Packaged Boiler4. Fluidized Bed (FBC) Boiler

    5. Stoker Fired Boiler

    6. Pulverized Fuel Boiler7. Waste Heat Boiler

    8. Thermic Fluid Heater (not a boiler!)

    What Type of Boilers Are There?

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    The boilers can be classif ied according to the

    following cr iter ia.According to flow of water and hot

    gases :

    (a) Water tube(b) Fire tube.

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    Type of Boilers

    1. Fire Tube Boiler

    Relatively small steam

    capacities (12,000 kg/hour)

    Low to medium steam

    pressures (18 kg/cm2)

    Operates with oil, gas or solid

    fuels

    T f B il

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    Type of Boilers

    2. Water Tube Boiler

    Used for high steam demand

    and pressure requirements

    Capacity range of 4,500

    120,000 kg/hour

    Combustion efficiency

    enhanced by induced draft

    provisions Lower tolerance for water

    quality and needs water

    treatment plant

    3. Packaged Boiler

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    Oil

    Burner

    To

    Chimney

    Comes in complete package Features

    High heat transfer

    Faster evaporation

    Good convective heattransfer

    Good combustion efficiency

    High thermal efficiency

    Classified based on number ofpasses

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    Working of power plant

    Pulverized coal is air-blown into thefurnace from fuel nozzles at the four

    corners and it rapidly burns, forming a

    large fireball at the center. The thermal

    radiation of the fireball heats the waterthat circulates through the boiler tubes near

    the boiler perimeter.

    http://en.wikipedia.org/wiki/Coal_dusthttp://en.wikipedia.org/wiki/Coal_dusthttp://en.wikipedia.org/wiki/Thermal_radiationhttp://en.wikipedia.org/wiki/Thermal_radiationhttp://en.wikipedia.org/wiki/Thermal_radiationhttp://en.wikipedia.org/wiki/Thermal_radiationhttp://en.wikipedia.org/wiki/Thermal_radiationhttp://en.wikipedia.org/wiki/Coal_dusthttp://en.wikipedia.org/wiki/Coal_dusthttp://en.wikipedia.org/wiki/Coal_dusthttp://en.wikipedia.org/wiki/Coal_dusthttp://en.wikipedia.org/wiki/Coal_dusthttp://en.wikipedia.org/wiki/Coal_dusthttp://en.wikipedia.org/wiki/Coal_dusthttp://en.wikipedia.org/wiki/Coal_dusthttp://en.wikipedia.org/wiki/Coal_dusthttp://en.wikipedia.org/wiki/Coal_dusthttp://en.wikipedia.org/wiki/Coal_dusthttp://en.wikipedia.org/wiki/Coal_dust
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    The water circulation rate in the boileris three to four times the throughput and

    is typically driven by pumps. As the

    water in the boilercirculates it absorbsheat and changes into steam at 700 F

    (371 C) and 3,200 psi

    http://en.wikipedia.org/wiki/Boilerhttp://en.wikipedia.org/wiki/Boiler
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    The water enters the boiler through a

    section in the convection pass called the

    economizer. From the economizer it

    passes to the steam drum. Once thewater enters the steam drum it goes down

    to the lower inlet water wall headers.

    http://en.wikipedia.org/wiki/Economizerhttp://en.wikipedia.org/wiki/Steam_drumhttp://en.wikipedia.org/wiki/Steam_drumhttp://en.wikipedia.org/wiki/Steam_drumhttp://en.wikipedia.org/wiki/Steam_drumhttp://en.wikipedia.org/wiki/Economizer
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    From the inlet headers the water rises

    through the water walls and is eventuallyturned into steam due to the heat being

    generated by the burners located on the

    front and rear water walls (typically). As

    the water is turned into steam/vapor in the

    water walls, the steam/vapor once again

    enters the steam drum.

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    The steam/vapor is passed through a series of

    steam and water separators and then dryersinside the steam drum.

    Thesteam separatorsand dryers remove

    water droplets from the steam and the cyclethrough the water walls is repeated. This process

    is known as natural circulation.

    http://en.wikipedia.org/wiki/Steam_separatorhttp://en.wikipedia.org/wiki/Natural_circulationhttp://en.wikipedia.org/wiki/Natural_circulationhttp://en.wikipedia.org/wiki/Steam_separator
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    super heaterFossil fuel power plants can have a super

    heaterand/or re-heater section in the steam

    generating furnace. In a fossil fuel plant,after the steam is conditioned by the drying

    equipment inside the steam drum, it is piped

    from the upper drum area into tubes insidean area of the furnace known as the super

    heater,

    http://en.wikipedia.org/w/index.php?title=Super_heater&action=edit&redlink=1http://en.wikipedia.org/w/index.php?title=Super_heater&action=edit&redlink=1http://en.wikipedia.org/w/index.php?title=Super_heater&action=edit&redlink=1http://en.wikipedia.org/w/index.php?title=Super_heater&action=edit&redlink=1http://en.wikipedia.org/w/index.php?title=Super_heater&action=edit&redlink=1http://en.wikipedia.org/w/index.php?title=Super_heater&action=edit&redlink=1http://en.wikipedia.org/w/index.php?title=Super_heater&action=edit&redlink=1http://en.wikipedia.org/w/index.php?title=Super_heater&action=edit&redlink=1http://en.wikipedia.org/w/index.php?title=Super_heater&action=edit&redlink=1http://en.wikipedia.org/w/index.php?title=Super_heater&action=edit&redlink=1http://en.wikipedia.org/w/index.php?title=Super_heater&action=edit&redlink=1http://en.wikipedia.org/w/index.php?title=Super_heater&action=edit&redlink=1
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    which has an elaborate set up of tubing where

    the steam vapor picks up more energy from

    hot flue gases outside the tubing and itstemperature is now superheated above the

    saturation temperature. The superheated

    steam is then piped through the main steam

    lines to the valves before the high pressure

    turbine.

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    Condenser

    The condenser condenses the steam from the

    exhaust of the turbine into liquid to allow it

    to be pumped. If the condenser can be madecooler, the pressure of the exhaust steam is

    reduced and efficiency of the cycleincreases.

    http://en.wikipedia.org/wiki/Rankine_cyclehttp://en.wikipedia.org/wiki/Rankine_cycle
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    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.

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    Since the condenser temperature can almost

    always be kept significantly below 100 C

    where the vapor pressureof water is muchless than atmospheric pressure, the condenser

    generally works under vacuum. Thus leaksof non-condensible air into the closed loop

    must be prevented.

    http://en.wikipedia.org/wiki/Vapor_pressurehttp://en.wikipedia.org/wiki/Vacuumhttp://en.wikipedia.org/wiki/Vacuumhttp://en.wikipedia.org/wiki/Vapor_pressurehttp://en.wikipedia.org/wiki/Vapor_pressurehttp://en.wikipedia.org/wiki/Vapor_pressure
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    The condenser generally uses either

    circulating cooling water from a cooling

    tower to reject waste heat to theatmosphere, or once-through water from a

    river, lake or ocean.

    http://en.wikipedia.org/wiki/Cooling_towerhttp://en.wikipedia.org/wiki/Cooling_towerhttp://en.wikipedia.org/wiki/Cooling_towerhttp://en.wikipedia.org/wiki/Cooling_towerhttp://en.wikipedia.org/wiki/Cooling_towerhttp://en.wikipedia.org/wiki/Brass
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    The condenser tubes are made of brass

    or stainless steel to resist corrosionfrom either side. Nevertheless they may

    become internally fouled during operation

    by bacteria or algae in the cooling water or

    by mineral scaling, all of which inhibit heat

    transfer and reduce thermodynamicefficiency.

    http://en.wikipedia.org/wiki/Brasshttp://en.wikipedia.org/wiki/Stainless_steelhttp://en.wikipedia.org/wiki/Thermodynamic_efficiencyhttp://en.wikipedia.org/wiki/Thermodynamic_efficiencyhttp://en.wikipedia.org/wiki/Thermodynamic_efficiencyhttp://en.wikipedia.org/wiki/Thermodynamic_efficiencyhttp://en.wikipedia.org/wiki/Thermodynamic_efficiencyhttp://en.wikipedia.org/wiki/Stainless_steelhttp://en.wikipedia.org/wiki/Stainless_steelhttp://en.wikipedia.org/wiki/Stainless_steelhttp://en.wikipedia.org/wiki/Brass
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    Many plants include an automatic

    cleaning system that circulates sponge

    rubber balls through the tubes to scrub

    them clean without the need to take the

    system off-line.

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    Re heaterPower plant furnaces may have a re heater

    section containing tubes heated by hot flue

    gases outside the tubes. Exhaust steam fromthe high pressure turbine is rerouted to go

    inside the re heater tubes to pickup more

    energy to go drive intermediate or lower

    pressure turbines.

    M i ll t t f t

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    Nontoxic dust

    Sulphurous anhydride

    Carbon monoxide

    Nitrogen dioxide

    Soot (fly ash)

    Hydrogen sulphide

    Pollution can be define as the contamination of soil ,

    air and water with undesirable amount of mater ial and

    heat.

    Main pollutants from a power system

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    Acid rain; the rain which contain acid as itsconstituents, brings all the acid down from high

    above the environment.

    Contaminant; it is the another name of

    pollution. It is undesirable substances whichmay be physical, chemical or biological.

    Pollutant; these are undesirable substancespresent in the environment these can be NO2,SO2, CO2,smoke,salt, bacteria.

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    Lot of heat is injected into biosphere from

    thermal power plant, through exhaust gases

    and waste water. The major problem is theeffect of discharge of large quantity of

    heated wasted water into natural water

    basins. Hot water raises the temperature

    and disturbs the natural ecological balance

    Bad effects of thermal pollution

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    Greater reliability of supply to the consumers.

    Avoid complete shut down.

    The overall cost of energy per unit of an

    interconnected system is less.

    There is a more effective use of transmission

    line facilities.

    Less capital investment required.

    Less expenses on supervision, operation and

    maintenance.

    Advantages of combined operation of plants

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    Due to limited generating capacity diesel

    power stations is not suitable for base load

    plants.Nuclear power stations is not suitable for

    peak load plants.

    I ncremental rate curve shows that asoutput power increases, cost of plant

    also increases.

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