4th Yr Final Proj Ppt

AN ENERGY AND EXERGY BASED ANALYSIS OF A TURBINE CYCLE IN A 500MW COAL BASED THERMAL

POWER PLANT

Submitted by :SAYANTAN MANDALSAYANTAN BISWASKOUSHIK GHOSH

Under the guidance ofProf. Malay Kanti Naskar

HOD,Mechnical Engineering Dept.

INTRODUCTIONThe energy supply to demand narrowing down day by day around the world, the growing demand of power has made the power plants of scientific interest, but most of the power plants are designed by the energetic performance criteria based on first law of thermodynamics only. The real useful energy loss cannot be justified by the fist law of thermodynamics, because it does not differentiate between the quality and quantity of energy. Exergy is never in balance for real processes. Energy is a measure of quantity but Exergy is a measure of quality and quantity. Power plants are normally examined using energy analysis but, as pointed out previously, a better understanding is attained when a more complete thermodynamic view is taken, which uses the second law of thermodynamics in conjunction with energy analysis via exergy methods.

PROJECT SUMMARYThe objective of the present work is to energy & exergy based analysis based on operating data of a 500MW thermal power plant at different unit load like 100%, 80%, 60% to design a model which helps us to determine different losses and irreversibility of different components of the turbine cycle. Based on these determinations, it is possible to take different measures to increase the efficiency the turbine cycle. For this purpose, Mejia Thermal Power Station of Damodar Valley Corporation is taken into consideration.

REVERSIBLE WORK AND IRREVERSIBILITY

As a closed system expands, some work needs to be done to push the atmospheric air out of the way (Wsurr).

For constant-volume systems, the total actual and useful works are identical (Wu = W).

The difference between reversible work and

actual useful work is the irreversibility.

Reversible work Wrev: The maximum amount of useful work that can be produced (or the

minimum work that needs to be supplied) as a system undergoes a process between the

specified initial and final states.

EXERGY: WORK POTENTIAL OF ENERGY• The useful work potential of a given amount of energy at some

specified state is called exergy, which is also called the availability or available energy.

• Exergy represents the upper limit on the amount of work a device can deliver without violating any thermodynamic laws.

The immediate surroundings of a hot potato are simply the temperature gradient zone of the air next to the potato.

The atmosphere contains a tremendous amount of energy, but no exergy.

EXERGY ASSOCIATED WITH KINETIC AND POTENTIAL ENERGY

The work potential or

exergy of potential energy

is equal to the potential energy

itself.

Exergy of kinetic energy:

Exergy of potential energy:

The exergy of kinetic and potential energies are equal to themselves, and they are entirely available for work. Unavailable energy is

the portion of energy that cannot be

converted to work by even a reversible heat

engine.

Thermodynamic Analysis

Mass balance:

Energy balance:

Exergy balance:

Irreversibity rate or Exergy destruction rate:

0 outin mm

ininoutout hmhmWQ

ImmWX ininoutoutheat

genSTI 0

Specific exergy of a flowing stream of matter is calculated as :

There is no change of the chemical compositions of the working fluid in the turbine cycle. The change of the kinetic and potential exergies are negligible, only the physical exergy is considered.

where

Total exergy rate of a fluid steam becomes

chemepekphy ..

phy

)( 000 ssThhphy

)( 000 ssThhmmX

Thermodynamic Analysis

PROCESS FLOW DIAGRAM OF A THERMAL POWER PLANT

TABLE 1: FLOW AND THERMODYNAMIC PROPERTY DATA AT 500MWE, 0% MAKE UP WATER AND 0.1033ATM. BACK PRESSURE FOR THE PLANT OPERATING AT 60% LOAD

FLOW PRESSURE TEMP DRYNESS FRACTION

MASS FLOW RATE

(ṁ)

SPECIFIC ENTHALPY

(h)

SPECIFIC ENTROPY

(s)

SPECIFIC EXERGY

(ɛ)

ENERGY FLOW RATE

(Ė)

EXERGY FLOW RATE

( Ėx) bar °c x kg/s kJ/Kg kJ/Kg-K kJ/Kg MW MW1 170.00 537.00 250.73 3392.35 6.40 1489.65 850.58 373.512 28.09 332.70 229.67 3055.78 6.67 1073.51 701.81 246.553 28.09 322.70 20.14 3055.78 6.67 1072.62 61.53 21.604 25.32 537.00 229.66 3544.83 7.42 1337.27 814.12 307.125 4.53 292.10 194.69 3049.52 7.48 823.87 593.72 160.406 10.99 413.70 12.41 3292.08 7.46 1073.50 40.85 13.327 4.53 292.10 23.01 3049.52 7.48 823.87 70.18 18.968 0.10 0.94 171.98 2446.13 7.70 155.28 420.69 26.719 0.23 0.96 4.79 2531.98 7.60 271.68 12.13 1.30

10 0.97 135.70 11.67 2748.37 7.56 499.99 32.06 5.8311 1.80 194.00 6.45 2859.68 7.53 620.24 18.44 4.0012 27.36 321.90 20.14 3055.72 6.69 1067.93 61.53 21.5013 10.62 413.40 12.46 3292.00 7.48 1067.48 41.03 13.3114 4.26 291.80 10.58 3049.61 7.51 816.60 32.25 8.6415 0.23 0.97 4.79 2526.74 7.62 261.37 12.11 1.2516 0.93 135.50 11.67 2748.33 7.58 493.98 32.06 5.7617 1.74 193.80 8.12 2859.60 7.55 614.58 23.21 4.9918 187.39 187.40 20.14 804.62 2.19 157.54 16.20 3.1719 187.39 150.30 32.54 645.00 1.83 105.64 20.99 3.4420 26.15 98.90 6.45 416.36 1.29 35.66 2.68 0.2321 26.15 64.20 18.11 270.88 0.88 12.51 4.91 0.2322 26.15 62.40 23.05 263.36 0.86 11.87 6.07 0.2723 0.10 46.10 207.61 193.03 0.65 2.94 40.08 0.6124 26.15 46.60 207.61 197.39 0.66 5.68 40.98 1.1825 26.15 61.40 207.61 259.18 0.84 13.36 53.81 2.7726 26.15 95.70 207.61 402.89 1.26 33.04 83.65 6.8627 26.15 113.70 207.61 478.80 1.46 49.11 99.41 10.2028 4.11 143.90 250.73 605.97 1.78 80.17 151.94 20.1029 187.39 147.60 250.73 633.51 1.80 102.20 158.84 25.6330 187.39 147.60 26.39 633.51 1.80 102.20 16.72 2.7031 187.39 147.60 224.34 633.51 1.80 102.20 142.12 22.9332 187.39 185.20 224.34 795.05 2.17 154.16 178.36 34.5933 187.39 230.80 224.34 997.66 2.59 231.23 223.82 51.8834 3.91 291.30 12.44 3049.50 7.55 804.96 37.93 10.0135 0.11 0.97 12.44 2503.13 7.87 161.47 31.13 2.01

DEAD STATE

Temperature (oC)

Specific enthalpy (kJ/kg)

Specific entropy (kJ/kg-K)

Dead state 25.00 104.93 0.37

A system is said to be in the dead state when it is in thermodynamic equilibrium with the environment it is in.

A system that is in equilibrium with its environment is said to be at the dead state.

At the dead state, the useful work potential (exergy) of a system is zero.

Rate of Exergy Destruction

2nd Law Efficiency

Turbines

Pumps

Heaters

Condenser

Deaerator

turbineoutinturbine WXXI

pumpoutinpump WXXI

outinheater XXI

outincondenser XXI

outindearator XXI

outin

turbineturbineII XX

I

1,

pump

pumppumpII W

I

1,

in

heaterheaterII X

I

1,

in

condensercondenserII X

I

1,

in

dearatordearatorII X

I

1,

Rate of exergy destruction and exergy efficiency of the components in the turbine cycle

DATA ANALYSIS

GRAPHICAL ANALYSIS OF IRREVERSIVILITY

BFPCEP

HPTIP

TLP

TLP

H-1

LPH-2

LPH-3

HPH-1

HPH-2

CONDENSER

DEARETOR02

4

68

1012

1416

1820

IRREVERSIBILITY

IRREVERSIBILITY

GRAPHICAL ANALYSIS OF EXERGY EFFICIENCY

BFPCEP

HPTIP

TLP

TLP

H-1

LPH-2

LPH-3

HPH-1

HPH-2

CONDENSER

DEARETOR0

20

40

60

80

100

120

80.14

63.33

82.41

95.5690.15

76.1

38.05

68.21

94.3889.42

43.95

90.22

2ND LAW EFFICIENCY(%)

2ND LAW EFFICIENCY(%)

GRASSMAN DIAGRAM FOR EXERGY FLOW THROUGH THE TURBINE CYCLE AT 60% OF RATED

UNIT LOAD

CONCLUSION

In this study an energy and exergy analysis of design and off design condition of a 500MW coal fired thermal power plant has been carried out based on mass, energy and exergy balance equation. The thermodynamic states of the plant components are shown in Table1. Exergy destruction, exergy and energy efficiency of the boiler components are presented in Table2. It has been found that maximum exergy destruction occurs due to combustion process. It has also been found that exergy efficiency is lower than energy efficiency. According to the table-2 we get LPH-2 exergy efficiency or 2nd law efficiency 38% which is really poor. To overcome this problem some precaution should be taken and these are air venting and retubing. After doing all this operation if we did not get our desired efficiency then we have to replace the heater, but it will increase the overall cost. The performance can be improved maintaining an optimum excess air level and also with change in ambient temperature.

THE END ? NO …!!!BECAUSE…

THIS IS JUST THE BEGINNING As we know this types of project is new to India so there are a lot

of scope to improve power plant efficiency by doing energy and exergy analysis of a thermal power plant.

Thank you very much to the project supervisor and the presentation attendees, we wish good luck for the carrier of all classmates. Thank you to the department of mechanical engineering, Netaji Subhash Engineering College to unleash our potentials and let us prepare for the participation in the professional industry .

THANK YOU

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