Gas Turbine Technologies
for Electric Generation
by
Rob Shepard, P.E.
www.Neel-Schaffer.com
rob.shepard@neel-schaffer.com
Gas Turbine Basics
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Gas Turbines
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2
Types
How They Work
Applications
Components of Plant
Flow Paths
Operation
Gas Turbine Applications
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Simple Cycle
 Combined Cycle
 Cogeneration
3
Types of Gas Turbine Plants
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Simple Cycle
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Operate When Demand is High – Peak Demand
Operate for Short / Variable Times
Designed for Quick Start-Up
Not designed to be Efficient but Reliable
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Combined Cycle
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4
Not Cost Effective to Build for Efficiency
Operate for Peak and Economic Dispatch
Designed for Quick Start-Up
Designed to Efficient, Cost-Effective Operation
Typically Has Ability to Operate in SC Mode
Principles of
Operation
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Open Cycle
Also referred to as simple cycle)
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The energy contained in a flowing ideal gas
is the sum of enthalpy and kinetic energy.
Pressurized gas can store or release energy.
As it expands the pressure is converted to
kinetic energy.
Link to picture
5
Brayton Cycle – Gas Turbine Cycle
6
Thermodynamic Fundamentals
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Pressure Ratio &
CT Components
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Combustion or Gas Turbine
8
Principles of Operation
Compressor
 As air flows into the compressor, energy is transferred from its
rotating blades to the air. Pressure and temperature of the air
increase.
 Most compressors operate in the range of 75% to 85% efficiency.
Combustor
 The purpose of the combustor is to increase the energy stored in
the compressor exhaust by raising its temperature.
Turbine
 The turbine acts like the compressor in reverse with respect to
energy transformation.
 Most turbines operate in the range of 80% to 90% efficiency.
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Principles of Operation
Overall Energy Transformations (Thermal Efficiency)
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Useful Work = Energy released in turbine minus energy absorbed by
compressor.
The compressor requires typically approximately 50% of the energy released by
the turbine.
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Overall Thermal Efficiency =
Useful Work/Fuel Chemical Energy *100
Typical overall thermal efficiencies of a combustion turbine are 20% - 40%.
10
Gas Turbine Applications
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Simple Cycle
Link to picture
11
Simple Cycle Power Plant
Westinghouse 501D5 – 340 MW
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Combined Cycle Power Plant
13
Combined Cycle Plant Design
GT PRO 13.0 Drew Wozniak
12.54 p
90 T
30 %RH
944 m
4327 ft elev.
Net Power 95959 kW
LHV Heat Rate 7705 BTU/kWh
967.3 m
1X GE 6581B
149.2 p
684 T
Fogger
4.717 m
143.2 p
2072 T
2 X GT
73.85 %N2
13.53 %O2
3.233 %CO2+SO2
8.497 %H2O
0.8894 %Ar
12.93 p
1034 T
1934.6 M
33781 kW
12.39 p
68 T
948.7 m
30813 kW
Natural gas 18.58 m
LHV 369671 kBTU/h
77 T
122 T
292.6 M
122 T
850 p
950 T
248.6 M
96 T
1.694 p
120 T
222.1 M
17.19 p
220 T
292.6 M
29.65 M
29.58 M
0.1296 M
26.36 M
195.8 p 597 T
6.89 M
879.8 p 954 T
V4
183 p 375 T 70 M
120 T
V8
6.89 M
FW
LPB
IPE2
IPB
HPE2
IPS1
HPE3
IPS2
HPB1
HPS3
268 T
1934.6 M
1031 T
1934.6 M
17.19 p
220 T
29.65 M
268
203.6 p
373 T
292.6 M
326
p[psia], T[F], M[kpph], Steam Properties: Thermoflow - STQUIK
14
1512 10-13-2004 23:27:31 file=C:\Tflow13\MYFILES\3P 0 70.gtp
203.6 p 924.2 p
383 T 472 T
36.75 M 251.1 M
419
481
534
199.7 p 910.5 p
460 T 523 T
36.75 M 251.1 M
538
568
195.8 p 910.5 p
500 T 533 T
36.75 M 248.6 M
569
879.8 p
954 T
248.6 M
897
1031
Natural gas
0M
Gas Turbine Components
Compressor – Combustor - Turbine
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Gas Turbine Components & Systems (cont’d)
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Combustion System
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Multiple Shaft, Single
Shaft
Number of Stages
Material and
Manufacturing
Processes
Exhaust System
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Silo, Cannular, Annular
Water, Steam, DLN
Turbine
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Generator
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Simple Cycle Stack
Transition to HRSG
Open-Air cooled
TEWAC
Hydrogen Cooled
Starting Systems
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Diesel
Motor
Static
Paper Towel thru
compressor
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Combustion Turbine Fuels
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Conventional Fuels
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Nonconventional Fuels
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Crude Oil
Refinery Gas
Propane
Synthetic Fuels
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Natural Gas
Liquid Fuel Oil
Chemical Process
Physical Process
GE Combustion Turbine Comparisons
18
Gas Turbine Types
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Advanced Heavy-Duty Units
Advanced Aeroderivative Units
Parameter
Capital Cost, $/kW
Heavy Duty Aero-Derivative
Lower
Higher
10 - 330
5 – 100
Efficiency
Lower
Higher
Plan Area Size
Larger
Smaller
Maintenance Requirements
Lower
Higher
Technological Development
Lower
Higher
Capacity, MW
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Gas Turbine Major Sections
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Air Inlet
Compressor
Combustion System
Turbine
Exhaust
Support Systems
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Gas Turbine Barrier Inlet Filter Systems
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Gas Turbine Pulse Inlet Filter System
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Inlet Guide Vanes
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Inlet Guide Vanes
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Gas Turbine Compressor Rotor Assembly
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6B Gas Turbine
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Gas Turbine Cut Away Side View
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Gas Turbine Combustor Arrangement
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Frame 5 GT
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GE LM2500 Aeroderivative Gas Turbine
Compressor
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Compressor
Turbine
Section
Power
Turbine
Section
FT4 Gas Turbine
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FT4 Gas Turbine – Gas Generator (Compressor)
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FT4 Gas Turbine – Gas Generator (Compressor)
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FT4 Gas Turbine – Free Turbine
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FT4 Gas Turbine – Free Turbine Gas Path
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FT4 Gas Generator Performance
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FT4 Free Turbine Performance
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Aeroderivative Versus Heavy Duty Combustion
Turbines
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Aeroderivatives
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Higher Pressure Ratios and Firing Temperatures Result
in Higher Power Output per Pound of Air Flow
Smaller Chilling/Cooling Systems Required
Compressor Inlet Temperature Has a Greater Impact on
Output and Heat Rate
Benefits of Chilling/Cooling Systems are More
Pronounced
Typical Simple Cycle CT Plant Components
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Prime Mover (Combustion Turbine)
Fuel Supply & Preparation
Emissions Control Equipment
Generator
Electrical Switchgear
Generator Step Up Transformer
Starting System (Combustion Turbines)
Auxiliary Cooling
Fire Protection
Lubrication System
Typical Peaking Plant Components
Lube Oil System
Switchgear / MCC
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GSU
Generator
Starting Engine
Fire Protection
Combining the Brayton and Rankine Cycles
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Gas Turbine Exhaust used as the heat source for the Steam
Turbine cycle
 Utilizes the major efficiency loss from the Brayton cycle
 Advantages:
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Relatively short cycle to design, construct & commission
Higher overall efficiency
Good cycling capabilities
Fast starting and loading
Lower installed costs
No issues with ash disposal or coal storage
Disadvantages
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High fuel costs
Uncertain long term fuel source
Output dependent on ambient temperature
How does a Combined Cycle Plant Work?
Picture courtesy of Nooter/Eriksen
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Combined Cycle Heat Balance
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Combined Cycles Today
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Plant Efficiency ~ 58-60 percent
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Steam Turbine output
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up to 750 MW for 3 on 1 configuration
Up to 520 MW for 2 on 1 configuration
Construction time about 24 months
Engineering time 80k to 130k labor hours
Engineering duration about 12 months
Capital Cost ($900-$1100/kW)
Two (2) versus Three (3) Pressure Designs
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44
Typically 50% of the gas turbine output
More with duct-firing
Net Plant Output (Using Frame size gas turbines)
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Biggest losses are mechanical input to the compressor and heat in the
exhaust
Larger capacity units utilize the additional drums to gain efficiency at
the expense of higher capital costs
Combined Cycle Efficiency
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Simple cycle efficiency (max ~ 44%*)
Combined cycle efficiency (max ~58-60%*)
Correlating Efficiency to Heat Rate (British Units)
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--> 3412/h = Heat Rate*
– 3412/.44 = 7,757 Btu/Kwh*
– 3412/.58 = 5,884 Btu/Kwh*
Correlating Efficiency to Heat Rate (SI Units)
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h= 3412/(Heat Rate)
Simple cycle
Combined cycle
h= 3600/(Heat Rate)
Simple cycle
Combined cycle
--> 3600/h = Heat Rate*
– 3600/.44 = 8,182 KJ/Kwh*
– 3600/.58 = 6,207 KJ/Kwh*
Practical Values
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HHV basis, net output basis
Simple cycle 7FA (new and clean)
10,860 Btu/Kwh (11,457 KJ/Kwh)
Combined cycle 2x1 7FA (new and clean) 6,218 Btu/Kwh (6,560 KJ/Kwh)
*Gross LHV basis
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Gas Turbine Generator Performance
Factors that Influence Performance
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Fuel Type, Composition, and Heating Value
Load (Base, Peak, or Part)
Compressor Inlet Temperature
Atmospheric Pressure
Inlet Pressure Drop
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Exhaust Pressure Drop
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Affected by addition of HRSG, SCR, CO catalysts
Steam or Water Injection Rate
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Varies significantly with types of air cleaning/cooling
Used for either power augmentation or NOx control
Relative Humidity
Altitude Correction
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Humidity Correction
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Cogeneration Plant
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A Cogeneration Plant
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Typical thermal hosts
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paper mills,
chemical plants,
refineries, etc…
potentially any user that uses large quantities of
steam on a continuous basis.
Good applications for combined cycle plants
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Power generation facility that also provides
thermal energy (steam) to a thermal host.
Require both steam and electrical power
Major Combined Cycle Plant Equipment
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Combustion Turbine (CT/CTG)
Steam Generator (Boiler/HRSG)
Steam Turbine (ST/STG)
Heat Rejection Equipment
Air Quality Control System (AQCS) Equipment
Electrical Equipment
Heat Recovery Steam Generator (HRSG)
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Steam Turbine
GE D11
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Heat Rejection Equipment - Condenser
Same Function as
discussed earlier in
Session 9
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53
Usually utilizes a
cooling tower to
reject heat to the
atmosphere
Rarely uses once
through cooling
(retrofit applications
or ocean)
Questions?
Rob Shepard
Neel-Schaffer, Inc.
www.Neel-Schaffer.com
rob.shepard@neel-schaffer.com
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