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ABSTRACT
In view of the present significance of the power crisis we endeavored to interpret this
Combined Cycle Power Plant. In this project we aimed to minimize the energy and exergy
losses. We have also briefed about the sophisticated and state of the art facilities such as Heat
Recovery Steam Generator in Combined Cycle Power Plant. We have chosen Octane and
Methane as fuels and plots have been drawn by varying input pressure and temperature
conditions. We have also embraced the performance of Combined Cycle Power Plant with
HRSG and without HRSG.
1 | P a g e
CHAPTER 1
1.1 AIM
1.2 INTRODUCTION
2 | P a g e
1.1 AIM:
To analyze the energy and exergy losses of combined cycle power plant with heat
recovery steam generator by Octane and Methane as fuels and to draw the variation of overall
efficiency for different temperature and pressure conditions.
3 | P a g e
AIM
Octane as fuel
Energy& Exergy losses
calculation
Methane as fuel
1.2 INTRODUCTION:
Rapid degradation of fuel resources questions the survival of human being on the earth.
Electricity is the greatest form of energy which is been interpreted in the lives of human.
Electricity is the only form of energy which is easy to produce, easy to transport, easy to use and
easy to control.
This is the only energy which can be easy for generation, easy for transmission and easy for
distribution. Electricity consumption per capita is the living standard of people of country.
Thermal power plants generate more than 80% of total electricity production in the world.
In order to satisfy the growing energy needs, a new technology combined cycle has been evolved
as the big source of power. Combined Cycle power plants are gaining wider acceptance due to
more and more availability of natural gas, now a days, because of their higher overall thermal
efficiencies, peaking two-shifting capabilities, fast start-up capabilities and lesser cooling water
requirements. The principle of combined cycle power plant is that the exhaust of one Heat engine
is used as the heat source for another, thus extracting more useful energy from the heat,
increasing the overall efficiency. In Gas turbine we need approximately 12000C as heat required
to generate the power. In this temperature of exhaust gases is 5000C. That is high amount of heat
is wasted through exhaust gases. We take this disadvantage as advantage by supplying exhaust
gases heat as input to the steam turbine.
Heat Recovery Steam Generator is used to recover exhaust heat from the gas turbines and to
generate superheated steam which operates Rankine cycle.
Gas turbines can use a variety of liquid and gaseous fuels (Conventional or non conventional
type). Conventional fuels, which are used regularly at gas turbine installations, are various grades
of oils, ranging from light petroleum naphtha to residual fuels. In this project we chose Octane
and Methane of Paraffin family as fuels. We have analyzed the energy and exergy losses of
CCPP by varying pressure and temperature conditions.
4 | P a g e
CHAPTER 2
2.1 RANKINE CYCLE
2.2 BRAYTON CYCLE
2.3 COMBINED CYCLE OF RANKINE CYCLE & BRAYTON CYCLE
2.4 HEAT RECOVERY STEAM GENERATOR
5 | P a g e
2.1. RANKINE CYCLE:
Saturated or superheated steam enters the turbine at state 1, where it expands isentropically
to the exit pressure at state 2. The steam is then condensed at constant pressure and temperature
to a saturated liquid, state 3. The heat removed from
the steam in the condenser is typically transferred to the cooling water. The saturated liquid then
flows through the pump which increases the pressure to the boiler pressure (state 4), where the
water is first heated to the saturation temperature, boiled and typically superheated to state 1.
Fig 2.1Circuit layout of diagram of rankine cycle
6 | P a g e
2.1.1. Steam power plant:
Power plants generate electrical power by using fuels like coal, oil or natural gas. A
simple power plant consists of a boiler, turbine, condenser and a pump. Fuel, burned in the boiler
and super heater, heats the water to generate steam. The steam is then heated to a superheated
state in the super heater. This steam is used to rotate the turbine which powers the generator.
Electrical energy is generated when the generator windings rotate in a strong magnetic field.
After the steam leaves the turbine it is cooled to its liquid state in the condenser. The liquid is
pressurized by the pump prior to going back to the boiler. Since the fluid undergoes a cyclic
process, there will be no net change in its internal energy over the cycle, and consequently the
net energy transferred to the unit mass of the fluid as heat during the cycle must equal the net
energy transfer as work from the fluid.
Fig 2.1.1 layout diagram of steam power plants
7 | P a g e
An important application of thermodynamics is the analysis of power cycles through which the
energy absorbed as heat can be continuously converted into mechanical work. A thermodynamic
analysis of the heat engine cycles provides valuable information regarding the design of new
cycles or for improving the existing cycles.
2.2. BRAYTON CYCLE:-
fig 2.2 idealized Brayton cycle
Brayton cycle is the air standard cycle for the gas turbine power plant. Here air is first
compressed reversibly and adiabatically, heat is added to it reversibly at constant pressure, air
expands in the turbine reversibly and adiabatically, and heat is then rejected from the air
reversibly at constant pressure to bring it to the initial state. The Brayton cycle consists of :
TWO REVERSIBLE ISOBARS
TWO REVERSIBLE ADIABATICS
ŋ = 1 – ( Q1/Q2 ) (or) ŋbrayton = 1 – 1 / ( rp )^(γ-1/γ) (5)
8 | P a g e
The efficiency of the Brayton cycle, therefore, depends upon either the compression ratio or the
pressure ratio. For the same compression ratio the Brayton cycle efficiency is equal to the Otto
cycle efficiency.
2.2.1. Gas turbine power plant:
A gas turbine, also called a combustion turbine, is a type of internal combustion engine. It
has an upstream rotating compressor coupled to a downstream turbine, and a combustion
chamber in-between.
Energy is added to the gas stream in the combustor, where fuel is mixed
with air and ignited. In the high pressure environment of the combustor, combustion of the fuel
increases the temperature. The products of the combustion are forced into the turbine section.
There, the high velocity and volume of the gas flow is directed through a nozzle over the
turbine's blades, spinning the turbine which powers the compressor and, for some turbines,
drives their mechanical output. The energy given up to the turbine comes from the reduction in
the temperature and pressure of the exhaust gas.
Energy can be extracted in the form of shaft power, compressed air or thrust or any combination
of these and used to power aircraft, trains, ships, generators, or even tanks.
9 | P a g e
fig 2.2.1 Layout diagram for Gas turbine power plant
2.3. COMBINED CYCLE POWER PLANT:
Combined Cycle power plants are those which have both gas and Steam turbines
supplying power to the network. Combined cycle power plants employ more than one
thermodynamic cycle – Rankine (steam) and Brayton (gas). In a combined cycle power plant, a
gas turbine generator generates electricity and the waste heat is used to make steam to generate
additional electricity through a steam turbine, which enhances the efficiency of electricity
generation. Additionally, combined cycles are characterized by flexibility, quick part-load
starting, suitability for both base-load and cyclic operation, and a high efficiency over a wide
range of loads.
10 | P a g e
Fig 2.3.Layout diagram for combined cycle power plant
Combined Cycle Power Plant assets need to be flexible to meet rapidly fluctuating demand
levels. As well, they need to remain reliable and demonstrate that every effort has been made to
minimize environmental impacts and maximize efficiency. Ensuring flexible, reliable operation
with minimum forced outages, implementing innovative strategies that reduce emissions and
dealing with volatile power markets while achieving the lowest operating costs possible are the
new industry reality.
11 | P a g e
2.4 HRSG (HEAT RECOVERY STEAM GENERATOR):
Fig 2.4.Combined cycle power plant with HRSG
The HRSG is designed to extract maximum recoverable heat from the exhaust gas of
the gas turbine. For this purpose the exhaust gas flow from the gas turbine is arranged in a
direction counter to the water/ steam circuit of HRSG. The exhaust gas from the gas turbine
enters HP ,IP & LP section of the Boiler .All the three section include the Secondary and primary
superheaters evaporators & Economizers., & finally through CPH module before exhausted to
the atmosphere by the stack.
The steam drum placed above the evaporators serves as a balancing vessel for water
and steam. It receives feedwater from the Economizer and maintains positive water supply to the
evaporator modules. Drum receives the mixture of steam and water from the evaporator modules
12 | P a g e
by the heat transfer. After separating water from the steam / water mixture at drum, the saturated
steam is supplied to the main steam line through Superheaters.
2.4.1 Scope of HRSG:
The heat recovery steam generator (HRSG) comes in numerous shapes, designs, configurations,
arrangements, etc. The HRSG here we are discussing is water tube (as opposed to a fired tube)
type heat recovery unit. This refers to the process fluid that is the steam or water being on inside
of the tube with the products of combustion being on the outside of the tube. The products of
combustion are normally at or close to atmospheric pressure, the shell side is generally not
considered to be a pressure vessel.
Fig 2.5.HRSG
13 | P a g e
2.4.2. Evaporator section:
Evaporation of pre-treated feed water (w) by motive steam(m) bled from the turbine is
often used where the boiler make-up water requirement is not large. Both evaporated water (v)
and condensed steam (c) exiting the evaporator are fed back as make-up in to the plant.
2.4.3. Super heater section:
The super heater section of the HRSG is used to dry the saturated vapor being separated
in the steam drum. In some units it may be heated to little above the saturation point where in
other units may be significant temperature for additional energy storage. The super heater section
is normally located in the hotter gas steam, in front of the evaporator.
2.4.4. Economizer section:
The economizer section, sometimes called a pre heated or preheat coil, is used to preheat
the feed water being introduced to the system to replace the steam(vapor)being removed from the
steam via the super heater or a stream outlet and the water loss through the blow down. It is
normally located in the colder gas downstream of the evaporator. Since the evaporator inlet and
outlet temperatures are both close to the saturation temperature for the system pressure, the
amount of heat that may be removed from the flue gas is limited due to approach to the
evaporator, known as pinch point which is discussed later, where as the economizer inlet
temperature is low allowing the flue gas temperature to be taken lower.
14 | P a g e
CHAPTER 3
3.1 EXERGY
3.2 OCTANE (C8H18) AS FUEL
3.3 METHANE (CH4) AS FUEL
15 | P a g e
3.1 EXERGY
The First law of Thermodynamics makes only quantitative analysis of system. It doesn’t
discriminate quality wise. It is the Second law which discriminate the quality of energy. The
exergy of a system is the maximum work obtainable as the system comes to equilibrium with the
surroundings (i.e. dead state). The higher the value of exergy, more is the work obtainable from
the system. This exergy is a composite property depending on the state of system and
surroundings. When the system is in thermal equilibrium with its surroundings is said to be at
dead state having zero exergy.
We know that energy can be conserved. But what is not conserved is exergy. Once the exergy is
wasted it can never be recovered. When we use electricity we are not destroying any energy, we
are converting it to less useful form that is from high exergy value to lower exergy value.
ENERGYin – ENERGYout = 0
EXERGYin – EXERGYout = EXERGY destroyed
ENERGY OF ISOLATED SYSTEM NEVER CHANGE,
ENTROPY OF ISOLATED SYSTEM NEVER DECREASE,
EXERGY OF ISOLATED SYSTEM NEVER INCREASE.
Below table shows the different grades of energy
High grade energy Low grade energy
Electrical Energy Heat or Thermal Energy
Mechanical work Heat derived from nuclear fission
Water power Heat derived from fossil fuels
Wind power
Tidal power
16 | P a g e
3.2 OCTANE (C8H18) AS FUEL:
Octane is a hydrocarbon of Paraffin family and an alkane with the chemical formula C8H18.
Octane has many structural isomers that differ by the amount and location of branching in the
carbon chain. Because of low-molecular weight hydrocarbons, octane and its isomers are very
flammable. Octane and its isomers are components of gasoline (petrol). Octane became well
known in American popular culture in the mid- and late-sixties, when gasoline companies
boasted of "high octane" levels in their gasoline advertisements. We have chosen Octane as a one
fuel to compare overall efficiency of the system.
The combustion reaction when Octane burned,
C8H18 + 12.5O2 8CO2 + 9H2O
(Reactants) (Products)
The properties of Octane are,
Calorific value of Octane: 44.43MJ/kg
Specific heat ratio of Octane: 1.33
Specific heat of Octane: 1.148 KJ/kg
Ratio of chemical exergy to enthalpy formation (Ѱ): 1.0725
17 | P a g e
3.2 METHANE (CH4) AS FUEL:
Generally, Methane gas is an ideal fuel for use in gas turbines because of its clean burning,
availability at a lower cost and practically free from solid residue. The Methane gas has high
calorific value relatively. Moreover Methane has little inherent sulfur content and is
environmentally acceptable because the resulting SO2 emissions are inherently low. This is the
cleanest of all fossil fuels. It is free from ash and mixes well with air to undergo complete
combustion producing very little smoke. It has high hydrogen content and produces as
considerable amount of water vapor when burned.
The combustion reaction when methane burned,
CH4 + 2O2 CO2 + 2H2O
(Reactants) (Products)
The properties of Methane are,
Calorific value of Methane: 55.50MJ/kg
Specific heat ratio of Methane: 1.32
Specific heat of Methane: 2.24 KJ/kg
Ratio of chemical exergy to enthalpy formation (Ѱ): 1.0977
18 | P a g e
CHAPTER 4
4.1 CALCULATION PROCEDURE OF COMBINED CYCLE POWER PLANT WITHOUT HRSG
4.2 CALCULATIONS FOR COMBINED CYCLE POWER PLANT WITH HRSG BY OCTANE AS FUEL
4.3 CALCULATIONS FOR COMBINED CYCLE POWER PLANT WITH HRSG BY METHANE AS FUEL
19 | P a g e
4.1. Calculation procedure of combined cycle power plant without HRSG:
INPUT PARAMETERS:
Gas turbine:
Pressure ratio of gas turbine : 7.5
Air inlet temperature : 15 0C
Maximum cycle temperature : 750 0C
Steam turbine:
Gas leaves the steam generator : 100 0C
Steam supplied to the turbine : 50 bar, 600 0C
Condenser pressure : 0.1 bar
Total power output of the plant : 200 MW
Calorific value of the fuel : 43.3 MJ/kg
Take for combustion gases Cpg= 1.11 kJ/kg K and γ= 1.33
For air Cpa= 1.005 kJ/kg K and γ= 1.4
Fig 4.1 Layout diagram for combined cycle power plant without HRSG
20 | P a g e
Solution:
For the gas turbine cycle:
T ₂T ₁ = ( P₂
P₁)( γ−1
γ) = (7.5)(0.4/1.4)
T2 = 2880×(7.5)2/7 = 512.165 K
T ₃T ₄
= ( P₃P₄
)( γ−1
γ) = (7.5)(0.33/1.33)
T4 = 1023/(7.5)(0.33/1.33) = 620.52 K
For the steam cycle, from Mollier chart,
ha = 3670, hb = 2305, hc = hd = 192 kJ/kg
(Wnet)GT = ma Cpg (T3-T4) - ma Cpa (T2-T1)
= ma {1.11× (1023-620.52) - 1.005× (512.65 - 288)}
= 221.47 ma
(WT)ST = ms(ha - hb) = ms(3670 - 2305) = 1365 ms
1365 ms +221.47 ma = 200×103 -------- (1)
Now, ma Cpg (T5-T6) = ms (ha-hc)
ma 1.11 (1023-373) = ms (3670-192)
msma
= 715/3478 = 0.2056 ------------- (2)
Substituting in Equation (1),
1365 ×0.2056 ma + 221.47 ma = 2,00,000
ma = (2,00,000/500.26) = 398.34 kg/s
ms = 0.2056×398.34 = 81.9 kg/s
(Wnet)GT = 221.47 ma = 221.47×398.34 = 88.22 MW
21 | P a g e
(WT)ST = 1365 ms = 1365×81.9 = 111.78 MW
Wnet = (Wnet)GT + (WT)ST
= 88.22 + 111.78 = 200 MW
Q1 = ma Cpg (T3 - T2 - T5 - T4)
= 398.34×1.11(1023 - 512.165 + 1023 - 620.52)
= 400.19 MW
Ƞthermal = WnetQin =
200400.19
= 50%
Power developed by Gas Turbine 88.22 MW
Power developed by Steam Turbine 111.78 MW
Mass flow rate of steam 81.9 kg/s
Mass flow rate of air 398.34 kg/s
Overall efficiency 50%
22 | P a g e
4.2. Calculation for combined cycle power plant with HRSG by Octane as fuel:
INPUT PARAMETERS
Inlet condition of air to the compressor : 1 bar, 25 0C
Pressure ratio of compressor : 8
Maximum gas temperature at inlet to the gas turbine : 900 0C
Pressure drop in the combustion chamber : 3%
Efficiency of the compressor : 0.88
Efficiency of the gas turbine : 0.88
Calorific value of liquid octane (C8H18) used as fuel : 44.43 MJ/kg
Specific heat of air : 1.006 kJ/kg K
Specific heat of gas : 1.148 kJ/kg K
Specific heat ratio of gas : 1.333
Specific heat ratio of air : 1.4
Condition of steam at inlet to the steam turbine : 40 bar, 425 0C
Condenser pressure : 0.04 bar
Feed water temperature to the HRSG : 170.4 0C
Efficiency of the steam turbine : 0.82
Pressure drop of gas in the HRSG : 5 kpa
Steam flow rate : 29.235 kg/s
Assume Ѱ= (∆G0)/(∆H0)=1.0401+0.1728(hc)
Where (h/c) is the mass ratio of hydrogen to carbon in the fuel.
23 | P a g e
Fig 4.2 Layout diagram for combined cycle power plant with HRSG
Solution:
Gas turbine plant:
P1= 1 bar, P2= 8 bar, T1= 298 K, Ƞc= 0.88
T ₂T ₁ = ( P₂
P₁)( γ−1
γȠc) = 80.4/(1.4×0.88) = 1.965
T2= 298×1.965= 586K = 313 0C
Combustor:
Pressure loss = 0.03×8 = 0.24 bar
P3 = 8 - 0.24 = 7.76 bar
Let the flow rate of combustion gas be 1 kg/s and that of fuel f kg/s.
The flow of air = (1 - f) kg/s
24 | P a g e
Therefore,
f×CV = 1.Cpg (T3 - T1) - (1 - f) Cpa(T2 - T1)
f×44,430 = 1×1.148 (900 - 25) - (1 - f)×1.006 (313 - 25)
= 1004.5 - 289.7 (1 - f)
f =714.8/44140.7 = 0.0162 kg/s
Air fuel ratio = (1−f )
f= 0.9838/0.0162= 60.73
Now, C8H18 + 12.5O2 = 8CO2 + 9H2O
Air fuel ratio for stoichiometric combustion = (12.5×32)/ (0.232×114) = 15.12
Excess air = (60.73-15.12)/15.12= 3.02 or 302%
Gas turbine:
P4= 1+0.05= 1.05 bar, T3= 1173 K
T ₃T ₄
= ( P₃P₄
)(
(γ−1) Ƞtγ
) = (7.76/1.05)(0.333×0.88)/1.333
= 1.5530
T4 = 11731.553 = 755 K = 482 0C
This is the turbine exhaust gas temperature.
HRSG:
Let the pinch point temperature difference (T5 - Tf) be 30 0C,
Tf = (Tsat) 40 bar = 250.40C
T5 = 250.4+30 = 2800C
Now, from steam tables, ha = 3272 kJ/kg and hf = 1087 kJ/kg.
According to energy balance equation we have,
mg cpg (T4 - T5) = ms (ha – hf)
1×1.148(482 – 80) = ms (3272 – 1087)
25 | P a g e
ms = 0.106 kg/s
The total heat transfer in the HRSG yields the stack temperature T6,
That is for 170.40C, he = 721 kJ/kg
1.148 (482 – T6) = 0.106(3272 – 721)
T6 = 2470C
Power output:
ha = 3272 kJ/kg
sa = 3.853 kJ/kg
sb1 = sf + xbs (sfg) = 0.4226 + xbs (8.052)
xbs = 0.7986
hb1 = hf + xbs (hfg) = 121.46 + 0.7986 (2432.9) = 2064.37 kJ/kg
By neglecting pump work, output of steam turbine is
WST = ms (ha – hb1) ȠT = 29.235(3272 – 2064)×0.82 = 28950 kW
Mass flow rate of gas in gas turbine
ma = 29.2350.106
= 275.8 kg/s
Air flow rate entering the compressor ma = (1- f) 275.8 = 0.9838×275.8 = 271.3 kg/s
Power output from the gas turbine WGT = 275.18×1.148 (900 – 482) – 271.3×1.006 (313-25)
= 53,744 kW
Total power output = WST + WGT = 82,607 Kw
Fuel mass flow rate, mf = 0.01662 × 275.8 = 4.466 kg/s
Overall efficiency of combined plant Ƞo = 82607
4.466 × 44430 = 41.63%
Efficiency of steam plant ȠST = h a−hbh a−he
= 38.8%
26 | P a g e
Efficiency of GT plant ȠGT = 53744
4.466 × 44430 = 27.09%
“Lost heat “coefficient in the exhaust stack XL = 275.8× 1.148(247−25)
4.466 × 44430 = 35.4%
Overall efficiency can also be calculated as Ƞo = ȠGT + ȠST - ȠGT ȠST - ȠST XL
= 0.271+0.388-0.271×0.388-0.388×0.354
= 0.417 = 41.7%
Thus, it is close to the value of 41.63% which is obtained earlier.
Exergy flux and irreversibilities:
Given, Ѱ = −∆Gₒ−∆ Hₒ
= 1.0401+0.1729(hc)
Where (h/c) is the mass ratio of hydrogen to carbon in the fuel.
For Octane (C8H18), Ѱ = 1.0401+0.1729(18 ×1)(8 ×12)
= 1.0725
−∆ Hₒ = mf×(CV)0 = 4.466×44,430 = 198,424 kW
−∆ Gₒ = −∆ Hₒ×Ѱ = 1.0725×198424 = 212810kW
Tₒ ∆Sₒ = ∆ Gₒ −∆ Hₒ = 212810 – 198424 = 14386 kW
Exergy destruction in various components
Compressor: Rate of irreversibility given as Ic = ma T0 (s2 – s1)
Where s2 – s1 = cpa ln (T ₂T ₁
) - Raln ( P ₂P ₁
)
= 1.006 ln (586298 )–
0.4 ×1.0061.4
ln 8
= 0.0818 kJ/kg K
27 | P a g e
Ic = 271.3×298×0.0818 = 6613 kW
Combustor: Rate of irreversibility is given by Icomb = T0 [(Sp) 3 – (SR) 2]
i.e., Icomb = T0 [{mgcpg ln (T ₃T ₁
)- mgRg ln ( P ₃P ₁
)} - { mgcpg ln (T ₂T ₁
)– maRa ln ( P ₂P ₁
)}] + T0 ∆S0
= 80,947 – 6672 + 14,386 = 88661 kW
Gas Turbine: Rate of energy dissipation is given by IGT = mg T0 (s4 – s3)
Where, s4-s3 = cpa ln (T ₄T ₃
) - Rg ln ( P ₄P ₃
)
= -0.5053+0.5740 = 0.0687 kJ/kg K
IGT = 275.8× 298(0.0687) = 5646 kW
HRSG: Rate of work lost in HRSG is
IHRSG = T0 [ms (sa – se) + (s6 – s4)]
Where sa – se = 6.853 – 2.046 = 4.807 kJ/kg K
s6 – s4 = cpa ln (T ₆T ₄
) - Rg ln ( P ₆P ₄
)
= -0.428+0.014 = -0.414 kJ/kg K
IHRSG = 298×29.235×4.807 – 275.8×298×0.414
= 41,789 – 34,026 = 7853 kW
Steam Turbine: Rate of energy dissipation is IST = ms (sb – sa)T0
sa = 60853kJ/kg K
sb = sf + xb (sfg) = 0.4226+0.89×8.052
= 7.589 kJ/kg K
IST = 29.235 (7.589-6.85)×298 = 6412 kW
28 | P a g e
Exhaust losses: Rate of exergy losses due to exhaust flue gases is
Iexh = ∫T ₆
Tₒ
[1−(TₒT )]dQ = mg cpg [(T6 – T0) – T0 ln (T ₆
T ₁)]
= 275.8×1.148 [(247-25) – 298 ln (520298 )] = 17,760 kW
Exergy balance:
Exergy input (kW) Power output(kW) Exergy losses(kW)
−∆ Gₒ= 212,810 WGT = 53,744 Compressor : 6,613
W ST = 28,950 Combustor : 88,661
Gas turbine : 5,646
HRSG : 7,853
Steam turbine : 6,412
Exhaust gases : 7,760
Input = 212,810 kW Total output = 82,607 kW Total losses = 1,32,945 kW
Exergy output + exergy destruction = 82,607 + 1, 32,945 = 2, 15,552 kW
This is 1.3% greater than the exergy input.
Exergetic (or) second law efficiency (or) measure of perfectness of the system
ȠII= Minimumexergy ¿ perform task ¿Actual exergy available ¿
perform thetask ¿ = 82,607212810
=
38.8%
29 | P a g e
4.3. Calculation for combined cycle power plant with HRSG by Methane as fuel:
INPUT PARAMETERS
Inlet condition of air to the compressor : 1 bar, 25 0C
Pressure ratio of compressor : 8
Maximum gas temperature at inlet to the gas turbine : 900 0C
Pressure drop in the combustion chamber : 3%
Efficiency of the compressor : 0.88
Efficiency of the gas turbine : 0.88
Calorific value of liquid methane (CH4) used as fuel : 55.5 MJ/kg
Specific heat of air : 1.006 kJ/kg K
Specific heat of gas : 2.24 kJ/kg K
Specific heat ratio of gas : 1.32
Specific heat ratio of air : 1.4
Condition of steam at inlet to the steam turbine : 40 bar, 425 0C
Condenser pressure : 0.04 bar
Feed water temperature to the HRSG : 170.4 0C
Efficiency of the steam turbine : 0.82
Pressure drop of gas in the HRSG : 5 kpa
Steam flow rate : 29.235 kg/s
Assume Ѱ= (∆G0)/(∆H0)=1.0401+0.1728(hc)
Where (h/c) is the mass ratio of hydrogen to carbon in the fuel.
30 | P a g e
Solution:
Gas turbine plant:
P1= 1 bar, P2= 8 bar, T1= 298 K, Ƞc= 0.88
T ₂T ₁ = ( P₂
P₁)( γ−1
γȠc) = 80.4/(1.4×0.88) = 1.965
T2= 298×1.965= 586K = 313 0C
Combustor:
Pressure loss = 0.03×8 = 0.24 bar
P3 = 8 - 0.24 = 7.76 bar
Let the flow rate of combustion gas be 1 kg/s and that of fuel f kg/s.
The flow of air = (1 - f) kg/s
Therefore,
f×CV = 1.Cpg (T3 - T1) - (1 - f) Cpa(T2 - T1)
f×55,500 = 1×2.24 (900 - 25) - (1 - f)×1.006 (313 - 25)
= 1960 - 289.7 (1 - f)
f = 0.03025 kg/s
Air fuel ratio = (1−f )
f= 0.96975/0.03025= 32.05
Now, CH4 + 2O2 = CO2 + 2H2O
Air fuel ratio for stoichiometric combustion = (2×32)/ (0.232×16) = 17.24
Excess air = (32.05 - 17.24)/17.24= 0.85 or 85%
Gas turbine:
P4= 1+0.05= 1.05 bar, T3= 1173 K
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T ₃T ₄
= ( P₃P₄
)(
(γ−1) Ƞtγ
) = (7.76/1.05)(0.333×0.88)/1.333
= 1.5530
T4 = 11731.553 = 755 K = 482 0C
This is the turbine exhaust gas temperature.
HRSG:
Let the pinch point temperature difference (T5 - Tf) be 30 0C,
Tf = (Tsat) 40 bar = 250.40C
T5 = 250.4+30 = 2800C
Now, from steam tables, ha = 3272 kJ/kg and hf = 1087 kJ/kg.
According to energy balance equation we have,
mg cpg (T4 - T5) = ms (ha – hf)
1×2.24(482 – 280) = ms (3272 – 1087)
ms = 0.2179 kg/s
The total heat transfer in the HRSG yields the stack temperature T6,
That is for 170.40C, he = 721 kJ/kg
2.24 (482 – T6) = 0.2179(3272 – 721)
T6 = 234.7 0C
Power output:
ha = 3272 kJ/kg
sa = 3.853 kJ/kg
sb1 = sf + xbs (sfg) = 0.4226 + xbs (8.052)
xbs = 0.7986
hb1 = hf + xbs (hfg) = 121.46 + 0.7986 (2432.9) = 2064.37 kJ/kg
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By neglecting pump work, output of steam turbine is
WST = ms (ha – hb1) ȠT = 29.235(3272 – 2064)×0.82 = 28950 kW
Mass flow rate of gas in gas turbine
mg = 29.2350.2179
= 134.17 kg/s
Air flow rate entering the compressor ma = (1- f) 134.17 = 0.969×134.16 = 130.10 kg/s
Power output from the gas turbine WGT = 134.17×2.24 (900 – 482) – 130.10×1.006 (313-25)
= 84,749.59 kW
Total power output = WST + WGT = 1, 13,699.74 kW
Fuel mass flow rate, mf = 0.03025 × 134.17 = 4.0583 kg/s
Overall efficiency of combined plant Ƞo = 1,13,699.74
4.0583 ×55,500 = 50.47%
Efficiency of steam plant ȠST = h a−hbh a−he
= 38.8%
Efficiency of GT plant ȠGT = 84,749.59
4.0583 ×55,500 = 37.62%
“Lost heat “coefficient in the exhaust stack XL = 134.17 ×2.24 (233−25)
4.0583 × 55,500 = 29.27%
Overall efficiency can also be calculated as Ƞo = ȠGT + ȠST - ȠGT ȠST - ȠST XL
= 0.3762+0.388-0.3762×0.388-0.388×0.2927
= 0.5048 = 50.48%
Thus, it is close to the value of 50.47% which is obtained earlier.
Exergy flux and irreversibilities:
Given, Ѱ = −∆Gₒ−∆ Hₒ
= 1.0401+0.1729(hc)
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Where (h/c) is the mass ratio of hydrogen to carbon in the fuel.
For Octane (C8H18), Ѱ = 1.0401+0.1729(4 × 1)(1 ×12)
= 1.0977
−∆ Hₒ = mf×(CV)0 = 4.0583×55,500 = 225,235.62 kW
−∆ Gₒ = −∆ Hₒ×Ѱ = 225235.62 ×1.0977 = 247,241.17 kW
Tₒ ∆Sₒ = ∆ Gₒ −∆ Hₒ = 247241.17 – 225235.62 = 22,005.52 kW
Exergy destruction in various components
Compressor: Rate of irreversibility given as Ic = ma T1 (s2 – s1)
Where s2 – s1 = cpa ln (T ₂T ₁
) - Raln ( P ₂P ₁
)
= 1.006 ln (586298 )–
0.4 ×1.0061.4
ln 8
= 0.0818 kJ/kg K
Ic = 130.10×298×0.0818 = 3240.52 kW
Combustor: Rate of irreversibility is given by Icomb = T0 [(Sp) 3 – (SR) 2]
i.e., Icomb = T0 [{mgcpg ln (T ₃T ₁
)- mgRg ln ( P ₃P ₁
)} - { mgcpg ln (T ₂T ₁
)– maRa ln ( P ₂P ₁
)}] + T0 ∆S0
= 1, 59,985.18 – 95,858.61 + 22,005.52 = 96,997.49 kW
Gas Turbine: Rate of energy dissipation is given by IGT = mg T0 (s4 – s3)
Where, s4-s3 = cpa ln (T ₄T ₃
) - Rg ln ( P ₄P ₃
)
= -0.5053+0.5740 = 0.0687 kJ/kg K
IGT = 134.17× 298(0.0687) = 15,264.24 kW
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HRSG: Rate of work lost in HRSG is
IHRSG = T0 [ms (sa – se) + (s6 – s4)]
Where sa – se = 6.853 – 2.046 = 4.807 kJ/kg K
s6 – s4 = cpa ln (T ₆T ₄
) - Rg ln ( P ₆P ₄
)
= -0.8776 + 0.01400 = -0.8626 kJ/kg K
IHRSG = 298×29.235×4.807 – 134.17×298×0.8626
= 7392.52 kW
Steam Turbine: Rate of energy dissipation is IST = ms (sb – sa)T0
……………… sa = 60853kJ/kg K
sb = sf + xb (sfg) = 0.4226+0.89×8.052
= 7.589 kJ/kg K
IST = 29.235 (7.589-6.85)×298 = 6412 kW
Exhaust losses: Rate of exergy losses due to exhaust flue gases is
Iexh = ∫T ₆
Tₒ
[1−(TₒT )]dQ = mg cpg [(T6 – T0) – T0 ln (T ₆
T ₁)]
= 134.17 ×2.24 [(233 - 25) – 298 ln (507298 )] = 16,524.48 kW
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Exergy balance:
Exergy input (kW) Power output (kW) Exergy losses (kW)
−∆ Gₒ= 247,241.17 W GT = 84,749.59 Compressor : 3240.52
WST = 28,950 Combustor : 86,132.08
Gas turbine : 15,264.24
HRSG : 7392.52
Steam turbine : 6,412
Exhaust gases : 16,524
Input = 247,241.17 kW Total output = 113,699.74 kW Total losses = 134,965.84 Kw
Exergy output + exergy destruction = 113,699.74 + 134,965.84 = 248,665.58 kW
This is 0.57% greater than the exergy input.
Exergetic (or) Second law efficiency (or) Measure of perfectness of the system
ȠII= Minimumexergy ¿ perform task ¿Actual exergy available ¿
perform thetask ¿ = 113,699.74247,241.17
= 45.98%
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CHAPTER 5
5. RESULTS AND DISCUSSIONS
5.1.RESULTS FOR COMBINED CYCLE POWER PLANT (Without HRSG)
5.2 RESULTS FOR COMBINED CYCLE POWER PLANT (With HRSG)
USING OCTANE AS FUEL
5.3. RESULTS FOR COMBINED CYCLE POWER PLANT (With HRSG)
USING METHANE AS FUEL
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5.1.RESULTS FOR COMBINED CYCLE POWER PLANT (Without HRSG)
5.1.1. Varying the inlet temperature of compressor
PARAMETERS
150C 250C 350C 450C
Mass flow rate of steam (kg/s) 81.89 83.19 84.53 85.9
Mass flow rate of air (kg/s) 398.32 404.62 411.13 417.85
Total heat input (MW) 403.82 402.21 400.56 398.86
Work done by gas turbine (kW) 88.22 86.45 84.52 82.73
Work done by steam turbine (kW) 111.77 113.55 115.38 117.25
Total power out (kW) 199.99 200 200 199.98
Thermal efficiency (%) 49.52 49.72 49.93 50.13
5.1.2. Varying the pressure ratios
PARAMETERS
6 bar 7.5 bar 9 bar 10.5 bar
Mass flow rate of steam (kg/s) 83.12 81.89 81.41 81.37
Mass flow rate of air (kg/s) 404.29 398.32 395.99 395.77
Total heat input (MW) 408.21 403.81 401.48 400.35
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Work done by gas turbine (kW) 86.54 88.22 88.86 88.93
Work done by steam turbine (kW) 113.46 111.78 111.12 111.07
Total power out (kW) 200 200 199.98 200
Thermal efficiency (%) 48.99 49.53 49.82 49.96
5.1.3. Varying the inlet temperatures of Gas turbine:
PARAMETERS
6000C 7500C 9000C 10500C
Mass flow rate of steam (kg/s) 94.29 81.97 72.5 64.99
Mass flow rate of air (kg/s) 458.59 398.68 352.65 316.08
Total heat input (MW) 434.87 404.17 380.61 361.85
Work done by gas turbine (kW) 71.29 88.11 101.13 111.28
Work done by steam turbine (kW) 128.71 111.89 98.96 88.71
Total power out (kW) 200 200 199.99 199.99
Thermal efficiency (%) 45.99 49.48 52.54 55.27
5.1.4. Varying the steam generation in the boiler:
PARAMETERS
40 bar 50 bar 60 bar 70 bar
Mass flow rate of steam (kg/s) 83.04 82.12 81.34 80.94
Mass flow rate of air (kg/s) 401.54 395.95 391.61 388.59
Total heat input (MW) 407.08 401.41 397.01 393.95
Work done by gas turbine (kW) 88.73 87.49 86.53 85.87
Work done by steam turbine (kW) 111.27 112.5 113.47 114.12
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Total power out (kW) 200 199.99 200 199.99
Thermal efficiency (%) 49.13 49.82 50.38 50.76
5.1.5. Varying the steam temperatures:
PARAMETERS
5000C 6000C 7000C 8000C
Mass flow rate of steam (kg/s) 89.87 82.12 75.29 69.63
Mass flow rate of air (kg/s) 404.83 395.95 387.14 380.47
Total heat input (MW) 410.41 401.41 392.48 385.71
Work done by gas turbine (kW) 89.46 87.49 85.55 84.07
Work done by steam turbine (kW) 110.54 112.5 114.44 115.93
Total power out (kW) 200 199.99 199.99 200
Thermal efficiency (%) 48.73 49.82 50.95 51.85
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5.2 RESULTS FOR COMBINED CYCLE POWER PLANT (With HRSG)
USING OCTANE AS FUEL:
5.2.1. Varying the inlet temperatures of compressor
PARAMETERS
15 0C 250C 350C 450C
Mass flow rate of steam (kg/s) 0.106 0.106 0.106 0.106
Mass flow rate of gas (kg/s) 275.8 275.8 275.8 275.8
Mass flow rate of fuel (kg/s) 4.578 4.467 4.33 4.19
Work done by gas turbine (kW) 56,494.84 53,734.51 51,239.04 48,464.91
Work done by steam turbine (kW) 28,863 28,863 28,863 28,863
Total power out (kW) 85,357.84 82,597.51 80,102.04 77,327.91
Overall efficiency (%) 41.51 41.63 41.61 41.96
5.2.2. Varying the pressure ratios.
PARAMETERS
8 bar 10 bar 12 bar 14 bar
Mass flow rate of steam (kg/s) 0.106 0.107 0.078 0.06
Mass flow rate of gas (kg/s) 275.8 273.2 406 487.2
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Mass flow rate of fuel (kg/s) 4.47 4.18 5.8 6.57
Work done by gas turbine (kW) 53,553.31 42,616.12 75,579.98 86,730.43
Work done by steam turbine (kW) 28,863 28,863 28,863 28,863
Total power out (kW) 82,416.31 71,479.12 1,04,442.98 1,15,593.43
Overall efficiency (%) 38.49 39.54 40.46 41.53
5.2.3. Varying the inlet temperature of Gas turbine
PARAMETERS
9000C 10000C 11000C 12000C
Mass flow rate of steam (kg/s) 0.106 0.14 0.174 0.208
Mass flow rate of gas (kg/s) 275.8 208.8 168 140.5
Mass flow rate of fuel (kg/s) 4.468 3.925 3.595 3.358
Work done by gas turbine (kW) 53,648.30 49,320.80 46,679.21 44,893.12
Work done by steam turbine (kW) 28,863 28,863 28,863 28,863
Total power out (kW) 82,511.30 78,183.50 75,542.21 73,756.12
Overall efficiency (%) 41.56 44.83 47.29 49.43
5.2.4. Varying the steam generation in the boiler:
PARAMETERS
30 bar 40 bar 50 bar 60 bar
Mass flow rate of steam (kg/s) 0.102 0.106 0.11 0.114
Mass flow rate of gas (kg/s) 286.62 275.8 265.77 256.45
Mass flow rate of fuel (kg/s) 4.643 4.468 4.305 4.154
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Work done by gas turbine (kW) 55,846.91 53,734.59 51,801.45 49,977.23
Work done by steam turbine (kW) 28,261.15 28,986.25 29,456.45 29,813.65
Total power out (kW) 84,108.06 82,720.84 81,257.90 79,790.80
Overall efficiency (%) 40.77 41.67 42.48 43.23
5.2.5. Varying the steam temperatures:
PARAMETERS
425 0C 525 0C 625 0C 725 0C
Mass flow rate of steam (kg/s) 0.106 0.096 0.087 0.072
Mass flow rate of gas (kg/s) 275.8 304.58 336.03 375.25
Mass flow rate of fuel (kg/s) 4.468 4.993 5.443 5.847
Work done by gas turbine (kW) 53,743.28 59,333.37 65,467.52 72,658.56
Work done by steam turbine (kW) 28,998.09 32,271.08 35,769.90 39,528.40
Total power out (kW) 82,741.37 91,604.45 1,01,237.42 1,12,548.05
Overall efficiency (%) 41.68 41.79 41.86 41.95
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5.3. RESULTS FOR COMBINED CYCLE POWER PLANT (With HRSG)
USING METHANE AS FUEL:
5.3.1. Varying the inlet temperatures of compressor
PARAMETERS
15 0C 25 0C 35 0C 45 0C
Mass flow rate of steam (kg/s) 0.217 0.217 0.217 0.217
Mass flow rate of gas (kg/s) 134.17 134.17 134.17 134.17
Mass flow rate of fuel (kg/s) 4.136 4.058 3.971 3.904
Work done by gas turbine (kW) 86,090.40 84,749.59 83,516.56 82,232.03
Work done by steam turbine (kW) 28,950 28,950 28,950 28,950
Total power out (kW) 1,15,040.55 1,13,699.74 1,12,466.71 1,11,182.18
Overall efficiency (%) 50.11 50.47 51.02 51.36
5.3.2. Varying the pressure ratios
PARAMETERS
8 bar 10 bar 12 bar 14 bar
Mass flow rate of steam (kg/s) 0.217 0.181 0.153 0.13
Mass flow rate of gas (kg/s) 134.16 160.72 190.85 224.53
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Mass flow rate of fuel (kg/s) 4.058 4.725 5.469 6.327
Work done by gas turbine (kW) 84,749.59 1,07,237.38 1,31,836.50 1,59,144.79
Work done by steam turbine (kW) 28,950 28,950 28,950 28,950
Total power out (kW) 1,13,699.74 1,36,187.53 1,60,786.65 1,88,094.94
Overall efficiency (%) 50.47 51.93 53.05 53.62
5.3.3. Varying the inlet temperatures of Gas turbine:
PARAMETERS
900 0C 1000 0C 1100 0C 1200 0C
Mass flow rate of steam (kg/s) 0.217 0.282 0.348 0.415
Mass flow rate of gas (kg/s) 134.17 103.7 83.36 70.39
Mass flow rate of fuel (kg/s) 4.058 3.55 3.216 2.984
Work done by gas turbine (kW) 84,749.59 74,338.24 66,782.33 61,649.39
Work done by steam turbine (kW) 28,950 28,950 28,950 28,950
Total power out (kW) 1,13,699.74 1,03,288.93 95,732.48 90,599.54
Overall efficiency (%) 50.47 52.42 53.73 54.77
5.3.4. Varying the steam generation in the boiler:
PARAMETERS
30 bar 40 bar 50 bar 60 bar
Mass flow rate of steam (kg/s) 0.206 0.217 0.209 0.21
Mass flow rate of gas (kg/s) 141.71 134.16 139.81 139.14
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Mass flow rate of fuel (kg/s) 4.286 4.058 4.229 4.208
Work done by gas turbine (kW) 92,876.26 84,749.59 91,629.37 91,190.34
Work done by steam turbine (kW) 25,171.33 28,950 26,369.37 27,328.28
Total power out (kW) 1,18,047.59 1,13,699.79 1,17,999.34 1,18,519.14
Overall efficiency (%) 49.62 50.47 50.27 50.84
5.3.5. Varying the steam temperatures:
PARAMETERS
425 0C 525 0C 625 0C 725 0C
Mass flow rate of steam (kg/s) 0.217 0.185 0.171 0.156
Mass flow rate of gas (kg/s) 134.17 157.26 170.76 186.32
Mass flow rate of fuel (kg/s) 4.058 4.57 5.165 5.636
Work done by gas turbine (kW) 84,749.59 1,03,061.68 1,11,919.26 1,22,112.5
Work done by steam turbine (kW) 28,950 29,965.89 33,082.32 36,678.23
Total power out (kW) 1,13,699.74 1,33,027.48 1,45,001.58 1,58,790.38
Overall efficiency (%) 50.74 50.46 50.58 50.76
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Discussion for the above cases:
The above tables represent the performance calculations of without & with HRSG in combined cycle power plant by Octane and Methane as fuels. The overall efficiency varied by varying the parameters like inlet temperature of compressor, gas turbine inlet temperature, pressure ratio.
5.4 Plots for the above results:
Graph 5.1.Inlet temperature vs Thermal efficiency
The above graph represents the variations in efficiency of CC plant with respect to inlet temperatures of compressor. It clearly conveys the efficiency will be improved with HRSG.
47 | P a g e
Ƞth
Inlet Temp
Inlet Temp vs Ƞth
Graph 5.2.Pressure ratio vs Thermal efficiency
The above graph represents variation of thermal efficiency with respect to pressure ratio of gas turbine. It is found that high efficiency can be obtained by with HRSG.
Graph 5.3.Maximum temperature vs Thermal efficiency
The above graph represents the variations in efficiency of CC plant with respect to maximum temperature of gas turbine. It clearly conveys the efficiency will be improved with HRSG.
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Pressure Ratio vs Ƞth
Ƞth
Pressure Ratio
Max Temp vs Ƞth
Ƞth
Max Temp
Graph 5.4.Steam turbine pressure vs Thermal efficiency
The above graph represents the variations in efficiency of CC plant with respect to pressure of boiler of steam turbine. It clearly conveys the efficiency will be improved with HRSG.
Graph 5.5.Steam turbine Temperature vs Thermal efficiency
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Steam Turbine Pressure vs ȠthȠth
Max Pressure
Steam Turbine Temp vs Ƞth
Ƞth
Max Temp
The above graph shows the variation of thermal efficiency with respect to maximum temperature reached in steam turbine. From above plots it is observed that combined cycle power plant gives high efficiency with Heat Recovery Steam Generator exceeding 50%.
5.5 RESULTS (OCTANE VS METHANE):
By taking Octane and Methane as fuels efficiency of Combined Cycle Power Plant with HRSG has been evaluated. The results plotted below.
Graph 5.6.Inlet temperature vs Thermal efficiency
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Inlet Temp vs Ƞo
Ƞo
Inlet Temp
Graph 5.7.Pressure ratio vs Thermal efficiency
Graph 5.8.Maximum temperature vs Thermal efficiency
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Pressure Ratio vs Ƞo
Ƞo
Pressure Ratio
Max Temp vs ȠoȠo
Max Temp
Graph 5.9.Maximum pressure in steam turbine vs Thermal efficiency
Graph 5.10.Maximum temperature in steam turbine vs Thermal efficiency
The above plots show that Methane shows immortal properties than that of Octane. Methane gave better results because of higher calorific value and specific heat. Fuel burning rate directly affects the power developed by Gas turbine. By varying various input parameters Methane gave better results.
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Ƞo
Steam Turbine Max Pressure vs Ƞo
Max Pressure
Steam Turbine Max Temp vs Ƞo
Ƞo
Max Temp
Below figure briefs the energy and exergy variations of CCPP with Octane and Methane as fuels.
However there are more losses with Methane as fuel, they can be neglected when compare to the efficiency. Second law efficiency is the measure of perfectness of the system. It shows the quality of the system. From above we can found that Methane fuel possesses high exergetic efficiency. Variation of fuel directly affects the power generated by Gas turbine.
PARAMETERS OCTANE METHANE
Power Developed By Gas Turbine 53,744 kW 84,749.59 kW
Power Developed By Steam Turbine 28,863 kW 28,950.15 kW
Total Power Developed 82,607 kW 1,13,699.74 kW
Efficiency Of Gas Turbine 27.09% 37.62%
Efficiency Of Steam Turbine 38.80% 38.81%
Overall Efficiency 41.63% 50.47%
Chemical Exergy 212,810 kW 247,241.17 kW
Change in Enthalpy Of Formation 198.424 kW 225,235.65 kW
Rate Of Exergy Loss In Combustion 14,386 kW 22,005.52 kW
EXERGY LOSSES:(kW)
1. Compressor 6,613 3,240.52
2. Combustor 88,661 86,132.08
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3. Gas Turbine 5,646 15,264.24
4. HRSG 7,856 7,392.52
5. Steam Turbine 6,412 6,412
6. Exhaust Losses 17,760 16,524.48
TOTAL LOSSES 1,32,945 kW 1,34,965.84 kW
SECOND LAW EFFICIENCY 38.80% 46.00
CONCLUSION:
To conclude, combined cycle power plant with HRSG can meet growing energy needs. Selection of best fuel can certainly improves the performance of the Combined Cycle Power Plant.
From the above results it is observed that
1. Combined Cycle power plant with Heat Recovery Steam Generator gives more efficiency.
2. Methane gas is the best fuel to improve the overall efficiency because of its high calorific value.
3. Change of fuel directly affects the work done by Gas turbine.
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REFERENCES:
1. Power plant engineering by P.K.Nag.
2. Engineering Thermodynamics by Cengel.
3. T. Srinivas1*, B. V.Reddy2, A. V. S. S. K. S. Gupta3:Parametric Simulation of Combined Cycle Power Pant by pp. 29-36, 2011 Int. J. of Thermodynamics ISSN 1301-9724 / e-ISSN 2146-1511
4. Thermal engineering by Rajput.
5. Manuel valdes, Jose L. Rapun : Optimization of heat recovery steam generators for combined cycle gas turbine power plants, Applied Thermal Engineering 21 (2001) 1149-1159.
6. Gas turbine combined cycle, http: // www.gepower.com
7. B.V. Reddy, G. Ramkiran, K. Ashok Kumar, P.K. Nag, Second law analysis of a waste heat recovery steam generator, International Journal of Heat and Mass Transfer 45 (2002) 1807–1814.
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8. Xiang, W., Chen, Y. (2007). Performance improvement of combined cycle power plant based on the optimization of the bottom cycle and heat recuperation. Journal of Thermal Science, 16(1), 84-89.
9. Engineering thermodynamics by P K Nag
10. Ravi kumar ,N.,rama Krishna, k., sita rama raju, A .V., Exergy analysis of gas turbine power plant with alternative configuration of regenerator proceedings on CD, 2nd international exergy energy environment symposium(IEEES2), kos,Greece, 2005,VI-13
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