thermal engineering - rankine cycle

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THERMALENGINEERING FOR 500 MW BOILER

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Thermal Engineering - Rankine Cycle

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  • THERMALENGINEERING FOR 500 MW BOILER

  • The laws of thermodynamics describe the transport of heat and work in thermodynamic processes. These laws have become some of the most important in all of physics and other types of science associated with thermodynamics.Laws of thermodynamics The four laws of thermodynamics:The zeroth law of thermodynamics, which underlies the basic definition of temperature. The first law of thermodynamics, which mandates conservation of energy, and states in particular that the flow of heat is a form of energy transfer.

    The second law of thermodynamics, which states that the entropy of an isolated macroscopic system never decreases, or (equivalently) that perpetual motion machines are impossible.

    The third law of thermodynamics, which concerns the entropy of a perfect crystal at absolute zero temperature, and which implies that it is impossible to cool a system all the way to exactly absolute zero.

  • Zeroth law of thermodynamicsIf two thermodynamic systems are each in thermal equilibrium with a third, then they are in thermal equilibrium with each other.First law of thermodynamicsEnergy can be neither created nor destroyed. It can only change forms.In any process in an isolated system, the total energy remains the same.For a thermodynamic cycle the net heat supplied to the system equals the net work done by the system.The first law can be expressed as the fundamental thermodynamic relation:

    Heat supplied to a system = increase in internal energy of the system + work done by the system

    Increase in internal energy of a system = heat supplied to the system - work done by the system

    This is a statement of conservation of energy: The net change in internal energy (dU) equals the heat energy that flows in (TdS), minus the energy that flows out via the system performing work (pdV).

  • Second law of thermodynamics

    In a few words, the second law states "spontaneous natural processes increase entropy overall." Another brief statement is "heat can spontaneously flow from a higher-temperature region to a lower-temperature region, but not the other way around." Nevertheless, energy can be transferred from cold to hot, for example, when a refrigerator cools its contents while warming the surrounding air, though still all transfers as heat are from hot to cold.Third law of thermodynamics

    As temperature approaches absolute zero, the entropy of a system approaches a constant minimum.

    Briefly, this postulates that entropy is temperature dependent and results in the formulation of the idea of absolute zero.

  • The specific definition, which comes from Clausius, is as shown in equation 1 below. S = Q/T Equation 1

    In equation 1, S is the entropy, Q is the heat content of the system, and T is the temperature of the system. So, entropy in classical thermodynamics is defined only for systems which are in thermodynamic equilibrium.

    As long as the temperature is therefore a constant, it's a simple enough exercise to differentiate equation 1, and arrive at equation 2. S = Q/T Equation 2

    Here the symbol " " is a representation of a finite increment, so that S indicates a "change" or "increment" in S, as in S = S1 - S2, where S1 and S2 are the entropies of two different equilibrium states, and likewise Q.

  • A thermodynamic process is that when there is some sort of energetic change within the system, generally associated with changes in pressure, volume, internal energy, temperature, or any sort of heat transferAdiabatic process - a process with no heat transfer into or out of the system.

    Isochoric process - a process with no change in volume, in which case the system does no work.

    Isobaric process - a process with no change in pressure.

    Isothermal process - a process with no change in temperature.

    An adiabatic process is a thermodynamic process in which there is no heat transfer (Q) into or out of the system. In other words Q = 0. An isentropic process occurs at a constant entropy. For a reversible process this is identical to an adiabatic process.An isenthalpic process introduces no change in enthalpy in the system Thermodynamic Process

  • Thermodynamic cycle

    A thermodynamic cycle is a series of thermodynamic processes transferring heat and work, while varying pressure, temperature, and other state variables, eventually returning a system to its initial state. A thermodynamic cycle is a closed loop on a P-V diagram. A P-V diagram's Y axis shows pressure (P) and X axis shows volume (V). The area enclosed by the loop is the work (W) done by the process:

    This work is equal to the balance of heat (Q) transferred into the system:

  • Thermodynamic power cycles are the basis for the operation of heat engines, which supply most of the world's electric power and run almost all motor vehicles. Power cycles can be divided according to the type of heat engine they seek to model. The most common cycles that model internal combustion engines are the Otto cycle, which models gasoline engines and the Diesel cycle, which models diesel engines. Cycles that model external combustion engines include the Brayton cycle, which models gas turbines, and the Rankine cycle, which models steam turbines.

  • Types of thermodynamic cycles

    thermodynamic cycle can (ideally) be made out of 3 or more thermodynamic processes (typical 4). The processes can be any of these: isothermal process (at constant temperature, maintained with heat added or removed from a heat source or sink) isobaric process (at constant pressure) isometric / isochoric process (at constant volume) .adiabatic process (no heat is added or removed from the working fluid) isentropic process, reversible adiabatic process (no heat is added or removed from the working fluid - and the entropy is constant) isenthalpic process (the enthalpy is constant)

  • Carnot cycle The Carnot cycle is a cycle composed of the totally reversible processes of isentropic compression and expansion and isothermal heat addition and rejection. The thermal efficiency of a Carnot cycle depends only on the temperatures in kelvins of the two reservoirs in which heat transfer takes place, and for a power cycle is:where TL is the lowest cycle temperature and TH the highest. Thermodynamic power cycles

    Types of thermodynamic cycles

    Carnot cycle Ideal cycle Otto cycle Diesel cycle Scuderi cycle Stirling cycle Joule or brayton cycleRankine cycle

  • CARNOT ENGINE1-2 - Isothermal Expansion at T1K2-3 - Adiabatic Expansion up to T2K3-4 - Isothermal Compression at T2K4-1 - Adiabatic Expansion up to T1K

    For Carnot Cycle = 1 - T2 T1 T1 = Temp. of heat source where T2 = Temp. of heat sink Carnot Cycle gives maximum possible thermal efficiency which can be obtained between any two given temperature limits.

    11234STT1T2

  • Ideal cycle An illustration of an ideal cycle heat engine (arrows clockwise).An ideal cycle is constructed out of:TOP and BOTTOM of the loop: a pair of parallel isobaric processes LEFT and RIGHT of the loop: a pair of parallel isochoric processes

    Ideal cycle

  • Rankine cycle The Rankine cycle is a cycle which converts heat into work. The heat is supplied externally to a closed loop, which usually uses water. This cycle generates about 80% of all electric power used throughout the world,[1] including virtually all solar thermal, biomass, coal and nuclear power plants. It is named after William John Macquorn Rankine, a Scottish polymath.

  • A Rankine cycle describes a model of steam operated heat engine most commonly found in power generation plants. Common heat sources for power plants using the Rankine cycle are the combustion of coal, natural gas and oil, and nuclear fission.

    The Rankine cycle is sometimes referred to as a practical Carnot cycle as, when an efficient turbine is used, the TS diagram begins to resemble the Carnot cycle. The main difference is that heat addition and rejection are isobaric in the Rankine cycle and isothermal in the theoretical Carnot cycle. A pump is used to pressurize liquid instead of gas. This requires a very small fraction of the energy compared to compressing a gas in a compressor (as in the Carnot cycle).

  • The efficiency of a Rankine cycle is usually limited by the working fluid. Without the pressure reaching super critical levels for the working fluid, the temperature range the cycle can operate over is quite small: turbine entry temperatures are typically 565C (the creep limit of stainless steel) and condenser temperatures are around 30C. This gives a theoretical Carnot efficiency of about 63% compared with an actual efficiency of 42% for a modern coal-fired power station. This low turbine entry temperature (compared with a gas turbine) is why the Rankine cycle is often used as a bottoming cycle in combined cycle gas turbine power stations.

    The working fluid in a Rankine cycle follows a closed loop and is re-used constantly. The water vapor with entrained droplets often seen billowing from power stations is generated by the cooling systems (not from the closed loop Rankine power cycle) and represents the waste heat that could not be converted to useful work. Note that cooling towers operate using the latent heat of vaporization of the cooling fluid. The white billowing clouds that form in cooling tower operation are the result of water droplets which are entrained in the cooling tower airflow; they are not, as commonly thought, steam. While many substances could be used in the Rankine cycle, water is usually the fluid of choice due to its favorable properties, such as nontoxic and unreactive chemistry, abundance, and low cost, as well as its thermodynamic properties.

  • Processes of the Rankine cycle There are four processes in the Rankine cycle, these states are identified by number in the diagram to the right.

    Process 1-2: The working fluid is pumped from low to high pressure, as the fluid is a liquid at this stage the pump requires little input energy. Process 2-3: The high pressure liquid enters a boiler where it is heated at constant pressure by an external heat source to become a dry saturated vapor. Process 3-4: The dry saturated vapor expands through a turbine, generating power. This decreases the temperature and pressure of the vapor, and some condensation may occur.

  • Process 4-1: The wet vapor then enters a condenser where it is condensed at a constant pressure to become a saturated liquid. In an ideal Rankine cycle the pump and turbine would be isentropic, i.e., the pump and turbine would generate no entropy and hence maximize the net work output. Processes 1-2 and 3-4 would be represented by vertical lines on the T-S diagram and more closely resemble that of the Carnot cycle. The Rankine cycle shown here prevents the vapor ending up in the superheat region after the expansion in the turbine which reduces the energy removed by the condensers.

  • Q1-Q2 W Useful work = ------- = --- = --------------- Q1 Q Heat supplied

    Rejected Heat = 1 - -------------------- Useful Heat

    T1 - T2 T2 Carnot = -------- = 1 - --- T1 T1To achieve more efficiency T2 should be as low as possible and T1 should be as high as possible

    THERMAL EFFICIENCY OF CARNOT CYCLE

  • Selection of Optimum Boiler PressurePressure, MPahTmax = 450 oC

    Chart1

    0.3534656959

    0.3535791061

    0.3630267273

    0.3785054357

    0.3888337305

    0.3956885262

    0.4006685769

    0.4022179496

    0.403546982

    0.4046856506

    0.4056319259

    0.4064299594

    0.4070856329

    Efficiency

    Sheet1

    ph1h2h3h4Pump workTurbine WorkNet WorkHeat InputEfficiencyx 4Overall Eff

    3.973209.3213.3333122254110611023117.70.3530.84590.2990

    4209.3213.3333022244110611023116.70.3540.84530.2989

    5209.3214.3331621855113111263101.70.3630.82930.3011

    7.5209.3216.9328021137.611671159.43063.10.3790.79880.3024

    10209.3219.43241205610.111851174.93021.60.3890.77520.3014

    12.5209.3221.93200200912.611911178.42978.10.3960.75530.2989

    15209.3224.431561966.315.11189.71174.62931.60.4010.73740.2955

    16209.3225.431381950.416.11187.61171.52912.60.4020.73070.2939

    17209.3226.431191934.617.11184.41167.32892.60.4040.72410.2922

    18209.3227.431001919.418.11180.61162.52872.60.4050.71770.2904

    19209.3228.430801904.219.11175.81156.72851.60.4060.71130.2885

    20209.3229.530601889.420.21170.61150.42830.50.4060.70510.2866

    21209.3230.530391874.521.21164.51143.32808.50.4070.69890.2845

    pEfficiency

    3.9730.353

    40.354

    50.363

    7.50.379

    100.389

    12.50.396

    150.401

    160.402

    170.404

    180.405

    190.406

    200.406

    210.407

    px 4

    3.9730.8459

    40.8453

    50.8293

    7.50.7988

    100.7752

    12.50.7553

    150.7374

    160.7307

    170.7241

    180.7177

    190.7113

    200.7051

    210.6989

    pOverall Eff

    3.9730.2989966321

    40.2988804184

    50.3010580649

    7.50.302350142

    100.3014239079

    12.50.2988635439

    150.2954530086

    160.2939006558

    170.2922083696

    180.2904428915

    190.2885259889

    200.2865737644

    210.2845121488

    Sheet1

    3.973

    4

    5

    7.5

    10

    12.5

    15

    16

    17

    18

    19

    20

    24.05

    Efficiency

    Sheet2

    0

    0

    0

    0

    0

    0

    0

    0

    0

    0

    0

    0

    0

    Sheet3

    0

    0

    0

    0

    0

    0

    0

    0

    0

    0

    0

    0

    0

    x 4

  • Chart2

    7.465

    7.127

    6.921

    6.769

    6.646

    6.448

    6.212

    6.075

    5.881

    5.753

    5.554

    5.407

    Pressure, MPa

    Entropy, kJ/kg K

    Pressure Vs Entroy

    Sheet1

    17.46530.22767640887.4653096.59367.465326423280.306617.270.8975

    27.12733.30628144787.1273080.510267.127324822220.151216.420.8535

    36.92135.02529786196.9213063.510736.921323121580.115.90.8267

    46.76936.23830625316.7693046.511046.769321421100.07315.520.8068

    56.64637.1471025266.6463028.511256.646319620710.057815.210.7908

    76.44838.42166861736.4482990.511496.448315820090.039914.720.765

    106.21239.64486938716.2122928.511616.212309619350.0246114.130.7343

    126.07540.19420842736.0752883.511596.075305118920.021113.780.7164

    155.88140.71237756015.8812807.511435.881297518320.0156513.30.6912

    175.75340.93801127075.7532750.511265.753291817920.0130212.980.6745

    205.55441.08658743635.5542650.510895.554281817290.0099412.480.6485

    225.40741.04259871625.4072570.510555.407273816830.00825312.110.6294

    Sheet1

    00

    00

    00

    00

    00

    00

    00

    00

    00

    00

    00

    Pressure (MPa)

    h, Kj/kg

    Pressure Vs Enthalpy

    Sheet2

    00

    00

    00

    00

    00

    00

    00

    00

    00

    00

    00

    Entropy, kJ/kg K

    h, KJ/kg

    Entropy Vs Enthalpy

    Sheet3

    00

    00

    00

    00

    00

    00

    00

    00

    00

    00

    00

    00

    Pressure, MPa

    Qin & Wt (kJ/kg)

    Pressure Vs Q & W

    0

    0

    0

    0

    0

    0

    0

    0

    0

    0

    0

    0

    Pressure, Mpa

    Eff, %

    Pressure Vs Eefficiency

    00

    00

    00

    00

    00

    00

    00

    00

    00

    00

    00

    00

    Entropy

    Q or W

    Entropy Vs Q & W

    0

    0

    0

    0

    0

    0

    0

    0

    0

    0

    0

    0

    Entropy

    Entropy Vs Efficiency

    00

    00

    00

    00

    00

    00

    00

    00

    00

    00

    00

    00

    Pmax, MPa

    h3 & h4

    Optimaization of Boiler Pressure

    0

    0

    0

    0

    0

    0

    0

    0

    0

    0

    0

    0

    Pressure, MPa

    Entropy, kJ/kg K

    Pressure Vs Entroy

  • Chart1

    0.3824540803

    0.3971486762

    0.4060601925

    0.4141263458

    0.4218885718

    0.4296013824

    0.4373888602

    0.4454158136

    Maximum Temperature C

    Efficiency

    Effect of Maximum Temperature

    Sheet1

    Tmax = 450 C

    ph1h2h3h4Pump workTurbine WorkNet WorkHeat InputEfficiencyx 4Overall Eff

    3.973209.3213.3333122254110611023117.70.3530.84590.2990

    4209.3213.3333022244110611023116.70.3540.84530.2989

    5209.3214.3331621855113111263101.70.3630.82930.3011

    7.5209.3216.9328021137.611671159.43063.10.3790.79880.3024

    10209.3219.43241205610.111851174.93021.60.3890.77520.3014

    12.5209.3221.93200200912.611911178.42978.10.3960.75530.2989

    15209.3224.431561966.315.11189.71174.62931.60.4010.73740.2955

    16209.3225.431381950.416.11187.61171.52912.60.4020.73070.2939

    17209.3226.431191934.617.11184.41167.32892.60.4040.72410.2922

    18209.3227.431001919.418.11180.61162.52872.60.4050.71770.2904

    19209.3228.430801904.219.11175.81156.72851.60.4060.71130.2885

    20209.3229.530601889.420.21170.61150.42830.50.4060.70510.2866

    21209.3230.530391874.521.21164.51143.32808.50.4070.69890.2845

    pEfficiency

    3.9730.353

    40.354

    50.363

    7.50.379

    100.389

    12.50.396

    150.401

    160.402

    170.404

    180.405

    190.406

    200.406

    210.407

    px 4

    3.9730.8459

    40.8453

    50.8293

    7.50.7988

    100.7752

    12.50.7553

    150.7374

    160.7307

    170.7241

    180.7177

    190.7113

    200.7051

    210.6989

    pOverall Eff

    3.9730.2989966321

    40.2988804184

    50.3010580649

    7.50.302350142

    100.3014239079

    12.50.2988635439

    150.2954530086

    160.2939006558

    170.2922083696

    180.2904428915

    190.2885259889

    200.2865737644

    210.2845121488

    Sheet1

    0

    0

    0

    0

    0

    0

    0

    0

    0

    0

    0

    0

    0

    Efficiency

    Sheet2

    0.2989966321

    0.2988804184

    0.3010580649

    0.302350142

    0.3014239079

    0.2988635439

    0.2954530086

    0.2939006558

    0.2922083696

    0.2904428915

    0.2885259889

    0.2865737644

    0.2845121488

    Sheet3

    0.8459

    0.8453

    0.8293

    0.7988

    0.7752

    0.7553

    0.7374

    0.7307

    0.7241

    0.7177

    0.7113

    0.7051

    0.6989

    x 4

    TCh1h2h3h4Pump workTurbine WorkTCNet WorkvmaxvminMEPHeat InputTCEfficiencyTCx 4TCOverall Eff

    100419434.63156222315.6933100917.41.3370.001037100686.69566447572721.41000.33710590141000.79921000.2694

    90376.9392.23156217415.398290966.71.8580.00102990520.57894280522763.8900.349772053900.7871900.2753

    80334.9350.23156212415.31032801016.72.640.00102380385.26292574742805.8800.3623565472800.7748800.2808

    70293308.23156207315.21083701067.83.8450.00101770277.78478728962847.8700.3749561065700.7625700.2859

    60251.1266.33156202015.21136601120.85.7540.00101160194.82046636972889.7600.3878603315600.7501600.2909

    50209.3224.43156196615.11190501174.98.8730.00100550132.42793757212931.6500.4007709101500.7374500.2955

    40167.5182.63156191115.11245401229.914.150.0010014086.92487715922973.4400.4136342234400.7246400.2997

    30125.8140.83156185515130130128623.40.00099783054.95960849133015.2300.4265057044300.7115300.3035

    2083.9498.923156179714.981359201344.0240.350.00099512033.30986732713057.08200.4396417496200.6981200.3069

    0

    0

    0

    0

    0

    0

    0

    0

    0

    Tc

    Eff

    Condenser Temperature Vs Efficiency

    0

    0

    0

    0

    0

    0

    0

    0

    0

    Tc

    x4

    Condenser Temperature Vs Quality

    0

    0

    0

    0

    0

    0

    0

    0

    0

    Tc

    X4.Eff

    00

    00

    00

    00

    00

    00

    00

    00

    00

    0

    0

    0

    0

    0

    0

    0

    0

    0

    Tc

    p, kPa

    Mean Effective Pressure

    Tmaxh3h4

    342.226101698342.29122384.6342.20.3824540803342.20.6248342.20.23895730947.518342.2121.308858739

    4002975188340010922749.64000.39714867624000.70224000.27887780048.45400129.2307692308

    4503156196645011902930.64500.40606019254500.73744500.29942878598.872450134.1298467087

    5003309203250012773083.65000.41412634585000.7655000.31680665469.205500138.7289516567

    5503449208955013603223.65500.42188857185500.78895500.33282789439.492550143.2785503582

    6003582214060014423356.66000.42960138246000.81036000.34810600019.75600147.8974358974

    6503712218765015253486.66500.43738886026500.82996500.36298901519.985650152.7290936405

    7003840223070016103614.67000.44541581367000.84827000.377801693110.21700157.6885406464

    209.3

    214.3

    2802

    1945

    857

    116.6861143524

    301948.658109685

    583.430571762

    202532.088681447

    0.3292499131

    181695.198

    360.56

    0.3534586733

    47684.06

    169.1523944661

    1324

    75.5287009063

    32024.16918429

    1191600

    235479.881

    67977

    0.3295361096

    4.2639921722

    0.8100301126

    977.75

    102.2756328305

    266571.209409358

    Maximum Temperature C

    Efficiency

    Effect of Maximum Temperature

  • pmax=10MPa

    Chart7

    121.308858739

    129.2307692308

    134.1298467087

    138.7289516567

    143.2785503582

    147.8974358974

    152.7290936405

    157.6885406464

    Tmax, C

    MEP, kPa

    Effect of Maximum Temperature

    Sheet1

    Tmax = 450 C

    ph1h2h3h4Pump workTurbine WorkNet WorkHeat InputEfficiencyx 4Overall Eff

    3.973209.3213.3333122254110611023117.70.3530.84590.2990

    4209.3213.3333022244110611023116.70.3540.84530.2989

    5209.3214.3331621855113111263101.70.3630.82930.3011

    7.5209.3216.9328021137.611671159.43063.10.3790.79880.3024

    10209.3219.43241205610.111851174.93021.60.3890.77520.3014

    12.5209.3221.93200200912.611911178.42978.10.3960.75530.2989

    15209.3224.431561966.315.11189.71174.62931.60.4010.73740.2955

    16209.3225.431381950.416.11187.61171.52912.60.4020.73070.2939

    17209.3226.431191934.617.11184.41167.32892.60.4040.72410.2922

    18209.3227.431001919.418.11180.61162.52872.60.4050.71770.2904

    19209.3228.430801904.219.11175.81156.72851.60.4060.71130.2885

    20209.3229.530601889.420.21170.61150.42830.50.4060.70510.2866

    21209.3230.530391874.521.21164.51143.32808.50.4070.69890.2845

    pEfficiency

    3.9730.353

    40.354

    50.363

    7.50.379

    100.389

    12.50.396

    150.401

    160.402

    170.404

    180.405

    190.406

    200.406

    210.407

    px 4

    3.9730.8459

    40.8453

    50.8293

    7.50.7988

    100.7752

    12.50.7553

    150.7374

    160.7307

    170.7241

    180.7177

    190.7113

    200.7051

    210.6989

    pOverall Eff

    3.9730.2989966321

    40.2988804184

    50.3010580649

    7.50.302350142

    100.3014239079

    12.50.2988635439

    150.2954530086

    160.2939006558

    170.2922083696

    180.2904428915

    190.2885259889

    200.2865737644

    210.2845121488

    Sheet1

    Efficiency

    Sheet2

    Sheet3

    x 4

    TCh1h2h3h4Pump workTurbine WorkTCNet WorkvmaxvminMEPHeat InputTCEfficiencyTCx 4TCOverall Eff

    100419434.63156222315.6933100917.41.3370.001037100686.69566447572721.41000.33710590141000.79921000.2694

    90376.9392.23156217415.398290966.71.8580.00102990520.57894280522763.8900.349772053900.7871900.2753

    80334.9350.23156212415.31032801016.72.640.00102380385.26292574742805.8800.3623565472800.7748800.2808

    70293308.23156207315.21083701067.83.8450.00101770277.78478728962847.8700.3749561065700.7625700.2859

    60251.1266.33156202015.21136601120.85.7540.00101160194.82046636972889.7600.3878603315600.7501600.2909

    50209.3224.43156196615.11190501174.98.8730.00100550132.42793757212931.6500.4007709101500.7374500.2955

    40167.5182.63156191115.11245401229.914.150.0010014086.92487715922973.4400.4136342234400.7246400.2997

    30125.8140.83156185515130130128623.40.00099783054.95960849133015.2300.4265057044300.7115300.3035

    2083.9498.923156179714.981359201344.0240.350.00099512033.30986732713057.08200.4396417496200.6981200.3069

    Tc

    Eff

    Condenser Temperature Vs Efficiency

    Tc

    x4

    Condenser Temperature Vs Quality

    Tc

    X4.Eff

    Tc

    p, kPa

    Mean Effective Pressure

    Tmaxh3h4

    342.226101698342.29122384.6342.20.3824540803342.20.6248342.20.23895730947.518342.2121.308858739

    4002975188340010922749.64000.39714867624000.70224000.27887780048.45400129.2307692308

    4503156196645011902930.64500.40606019254500.73744500.29942878598.872450134.1298467087

    5003309203250012773083.65000.41412634585000.7655000.31680665469.205500138.7289516567

    5503449208955013603223.65500.42188857185500.78895500.33282789439.492550143.2785503582

    6003582214060014423356.66000.42960138246000.81036000.34810600019.75600147.8974358974

    6503712218765015253486.66500.43738886026500.82996500.36298901519.985650152.7290936405

    7003840223070016103614.67000.44541581367000.84827000.377801693110.21700157.6885406464

    209.3

    214.3

    2802

    1945

    857

    116.6861143524

    301948.658109685

    583.430571762

    202532.088681447

    0.3292499131

    181695.198

    360.56

    0.3534586733

    47684.06

    169.1523944661

    1324

    75.5287009063

    32024.16918429

    1191600

    235479.881

    67977

    0.3295361096

    4.2639921722

    0.8100301126

    977.75

    102.2756328305

    266571.209409358

    Maximum Temperature C

    Efficiency

    Effect of Maximum Temperature

    Tmax, C

    Quality, x

    Effect of Maximum Temperature

    Tmax, C

    x. eff

    Effect of Maximum Temperature

    Tmax, C

    Wnet & Qin

    Effect of Maximum Temperature

    Tmax, C

    MEP, kPa

    Effect of Maximum Temperature

  • DPNLSHTRPlaten SHTRSCREEnLTSHESPAPHID fanChimneyEconomiserBottom AshDowncomerDrum waterwallFireball Gooseneck Reheater

  • Steam generation principleSteam power plants operate on Rankine Cycle, DM water as working fluid.Sensible heat is added in economiser +furnaceSteam generation takes place in waterwall.Typical furnace efficiency is 45% approx. Heat transfer in furnace and enclosed superheater takes place thru radiation. condenserCEPLPHBFPHPH+Ecow/wSHHPTIPTRHLPT

  • Superheater & ReheaterHeat associated with the flue gas is used in superheaters & Reheater, LTSH, economiser.Maximum steam temperature is decided by the operating drum pressure and metallurgical constraints of the turbine blade material.Reheating is recommened at pressure above 100 ksc operating pressure. Reheating is done at 20-25% of the operating pressure.Carbon steel, alloy steel & SS used for tubing of SH & RH.

    condenserCEPLPHBFPHPH+Ecow/wSHHPTIPTRHLPT

  • Principle of circulationDensity water and steam changes with pressure as shown.At higher pressure, density difference reduces.Flow establishment in down comer, waterwall and drum is due to density difference and height of water column (i.e. waterwall) at lower pressure.225ksc185 ksc165 kscPressure (KSC) Sp. gravity

  • Type of CirculationNatural circulation (upto 165 ksc)

    Forced/ assisted circulation (185-190 ksc)Once thru boiler1. Sub critical2. Supercritical

    Density difference & height of water columnAssisted by external circulating pump (CC/ BCW pump)

    Below 221.5 bar240-360 bar

  • Circulation ratioIt may be defined as ratio of feed water flow thru down comers to the steam generated in water wall.Ratio of the weight of 2-phase mixture to the weight of dry steam in waterwall.Ratio of the total fluid contained to the weight of the dry steam in waterwall.

    CR = 30-35 Industrial boilersCR = 6-8 Natrual cir. BoilersCR = 2-3 Forced cri. BoilersCR = 1 Once thru boilers (Sub critical)CR = 1 Supercritical boilers

  • Representation of steam/ water parameters on T-S diagram321Sub critical parameterCritical parameter, (225.65 ksc/ 374.16oC)Supercritical parameterTemperature Entropy 374.16oC

  • *