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Gas Turbine Technologies for Electric Generation

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Presentation on theme: "Gas Turbine Technologies for Electric Generation"— Presentation transcript:

1 Gas Turbine Technologies for Electric Generation
by Rob Shepard, P.E.

2 Gas Turbine Basics Gas Turbines Types How They Work Applications
Components of Plant Flow Paths Operation 2

3 Gas Turbine Applications
Simple Cycle Combined Cycle Cogeneration 3

4 Types of Gas Turbine Plants
Simple Cycle Operate When Demand is High – Peak Demand Operate for Short / Variable Times Designed for Quick Start-Up Not designed to be Efficient but Reliable Not Cost Effective to Build for Efficiency Combined Cycle Operate for Peak and Economic Dispatch Designed to Efficient, Cost-Effective Operation Typically Has Ability to Operate in SC Mode 4

5 Principles of Operation
Open Cycle Also referred to as simple cycle) 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

6 Brayton Cycle – Gas Turbine Cycle

7 Thermodynamic Fundamentals
Pressure Ratio & CT Components 7

8 Combustion or Gas Turbine

9 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. 9

10 Principles of Operation Overall Energy Transformations (Thermal Efficiency)
Useful Work = Energy released in turbine minus energy absorbed by compressor. The compressor requires typically approximately 50% of the energy released by the turbine. Overall Thermal Efficiency = Useful Work/Fuel Chemical Energy *100 Typical overall thermal efficiencies of a combustion turbine are 20% - 40%. 10

11 Gas Turbine Applications
Simple Cycle Link to picture 11

12 Simple Cycle Power Plant Westinghouse 501D5 – 340 MW

13 Combined Cycle Power Plant

14 Combined Cycle Plant Design

15 Gas Turbine Components Compressor – Combustor - Turbine

16 Gas Turbine Components & Systems (cont’d)
Exhaust System Simple Cycle Stack Transition to HRSG Generator Open-Air cooled TEWAC Hydrogen Cooled Starting Systems Diesel Motor Static Combustion System Silo, Cannular, Annular Water, Steam, DLN Turbine Multiple Shaft, Single Shaft Number of Stages Material and Manufacturing Processes Paper Towel thru compressor 16

17 Combustion Turbine Fuels
Conventional Fuels Natural Gas Liquid Fuel Oil Nonconventional Fuels Crude Oil Refinery Gas Propane Synthetic Fuels Chemical Process Physical Process 17

18 GE Combustion Turbine Comparisons

19 Gas Turbine Types Advanced Heavy-Duty Units
Advanced Aeroderivative Units 19

20 Gas Turbine Major Sections
Air Inlet Compressor Combustion System Turbine Exhaust Support Systems 20

21 Gas Turbine Barrier Inlet Filter Systems

22 Gas Turbine Pulse Inlet Filter System

23 Inlet Guide Vanes 23

24 Inlet Guide Vanes 24

25 Gas Turbine Compressor Rotor Assembly

26 6B Gas Turbine 26

27 Gas Turbine Cut Away Side View

28 Gas Turbine Combustor Arrangement

29 Frame 5 GT 29

30 GE LM2500 Aeroderivative Gas Turbine
Power Turbine Section Compressor Turbine Section Compressor 30

31 FT4 Gas Turbine 31

32 FT4 Gas Turbine – Gas Generator (Compressor)

33 FT4 Gas Turbine – Gas Generator (Compressor)

34 FT4 Gas Turbine – Free Turbine

35 FT4 Gas Turbine – Free Turbine Gas Path

36 FT4 Gas Generator Performance

37 FT4 Free Turbine Performance

38 Aeroderivative Versus Heavy Duty Combustion Turbines
Aeroderivatives 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 38

39 Typical Simple Cycle CT Plant Components
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 39

40 Typical Peaking Plant Components
Lube Oil System GSU Generator Switchgear / MCC Starting Engine Fire Protection 40

41 Combining the Brayton and Rankine Cycles
Gas Turbine Exhaust used as the heat source for the Steam Turbine cycle Utilizes the major efficiency loss from the Brayton cycle Advantages: 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 High fuel costs Uncertain long term fuel source Output dependent on ambient temperature 41

42 How does a Combined Cycle Plant Work?
The first question that should be answered is how does a combined cycle work. A combined cycle plant generates power by the use of both steam and heated air. Air is drawn into the combustion turbine and compressed. The compressed air is heated, which forces it to expand and turn the rotor blades of the turbine. Since, the turbine, compressor, and generator share the same shaft, the energy imparted to the turbine also generates the mechanism for turning the generator, which generates electricity. The remaining energy in the flue gas is exhausted from the combustion turbine as waste energy. The waste energy exhausted from the combustion turbine is channeled through the heat recovery steam generator (HRSG) and is absorbed by the heating surface to produce steam for generating power or for use in process applications. Picture courtesy of Nooter/Eriksen 42

43 Combined Cycle Heat Balance

44 Combined Cycles Today Plant Efficiency ~ 58-60 percent
Biggest losses are mechanical input to the compressor and heat in the exhaust Steam Turbine output Typically 50% of the gas turbine output More with duct-firing Net Plant Output (Using Frame size gas turbines) 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 Larger capacity units utilize the additional drums to gain efficiency at the expense of higher capital costs 44

45 Combined Cycle Efficiency
Simple cycle efficiency (max ~ 44%*) Combined cycle efficiency (max ~58-60%*) Correlating Efficiency to Heat Rate (British Units) h= 3412/(Heat Rate) --> 3412/h = Heat Rate* Simple cycle – 3412/.44 = 7,757 Btu/Kwh* Combined cycle – 3412/.58 = 5,884 Btu/Kwh* Correlating Efficiency to Heat Rate (SI Units) h= 3600/(Heat Rate) --> 3600/h = Heat Rate* Simple cycle – 3600/.44 = 8,182 KJ/Kwh* Combined cycle – 3600/.58 = 6,207 KJ/Kwh* Practical Values 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 45

46 Gas Turbine Generator Performance
Factors that Influence Performance Fuel Type, Composition, and Heating Value Load (Base, Peak, or Part) Compressor Inlet Temperature Atmospheric Pressure Inlet Pressure Drop Varies significantly with types of air cleaning/cooling Exhaust Pressure Drop Affected by addition of HRSG, SCR, CO catalysts Steam or Water Injection Rate Used for either power augmentation or NOx control Relative Humidity 46

47 Altitude Correction 47

48 Humidity Correction 48

49 Good applications for combined cycle plants
Cogeneration Plant A Cogeneration Plant Power generation facility that also provides thermal energy (steam) to a thermal host. Typical thermal hosts 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 Require both steam and electrical power 49

50 Major Combined Cycle Plant Equipment
Combustion Turbine (CT/CTG) Steam Generator (Boiler/HRSG) Steam Turbine (ST/STG) Heat Rejection Equipment Air Quality Control System (AQCS) Equipment Electrical Equipment 50

51 Heat Recovery Steam Generator (HRSG)

52 Steam Turbine GE D11 Aries – ½ of exhaust hood, Downward exhaust 52

53 Heat Rejection Equipment - Condenser
Same Function as discussed earlier in Session 9 Usually utilizes a cooling tower to reject heat to the atmosphere Rarely uses once through cooling (retrofit applications or ocean) 53

54 Questions? Rob Shepard Neel-Schaffer, Inc.

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