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

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Presentation on theme: "Gas Turbine Technologies for Electric Generation by Rob Shepard, P.E."— Presentation transcript:

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

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

3 3 Gas Turbine Applications Simple Cycle Combined Cycle Cogeneration

4 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 for Quick Start-Up Designed to Efficient, Cost-Effective Operation Typically Has Ability to Operate in SC Mode

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

6 6 Brayton Cycle – Gas Turbine Cycle

7 7 Thermodynamic Fundamentals Pressure Ratio & CT Components

8 8 Combustion or Gas Turbine

9 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.

10 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%.

11 11 Gas Turbine Applications Simple Cycle Link to picture

12 12 Simple Cycle Power Plant Westinghouse 501D5 – 340 MW

13 13 Combined Cycle Power Plant

14 14 Combined Cycle Plant Design

15 15 Gas Turbine Components Compressor – Combustor - Turbine

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

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

18 18 GE Combustion Turbine Comparisons

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

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

21 21 Gas Turbine Barrier Inlet Filter Systems

22 22 Gas Turbine Pulse Inlet Filter System

23 23 Inlet Guide Vanes

24 24 Inlet Guide Vanes

25 25 Gas Turbine Compressor Rotor Assembly

26 26 6B Gas Turbine

27 27 Gas Turbine Cut Away Side View

28 28 Gas Turbine Combustor Arrangement

29 29 Frame 5 GT

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

31 31 FT4 Gas Turbine

32 32 FT4 Gas Turbine – Gas Generator (Compressor)

33 33 FT4 Gas Turbine – Gas Generator (Compressor)

34 34 FT4 Gas Turbine – Free Turbine

35 35 FT4 Gas Turbine – Free Turbine Gas Path

36 36 FT4 Gas Generator Performance

37 37 FT4 Free Turbine Performance

38 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

39 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

40 40 Typical Peaking Plant Components Lube Oil System GSUGenerator Fire ProtectionStarting Engine Switchgear / MCC

41 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

42 42 Picture courtesy of Nooter/Eriksen How does a Combined Cycle Plant Work?

43 43 Combined Cycle Heat Balance

44 44 Combined Cycles Today Plant Efficiency ~ 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

45 45 Combined Cycle Efficiency Simple cycle efficiency (max ~ 44%*) Combined cycle efficiency (max ~58-60%*) Correlating Efficiency to Heat Rate (British Units) = 3412/(Heat Rate) --> 3412/ = 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) = 3600/(Heat Rate) --> 3600/ = 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

46 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 NO x control Relative Humidity

47 47 Altitude Correction

48 48 Humidity Correction

49 49 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

50 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

51 51 Heat Recovery Steam Generator (HRSG)

52 52 Steam Turbine GE D11

53 53 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) Heat Rejection Equipment - Condenser

54 54 Questions? Rob Shepard Neel-Schaffer, Inc.


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