SYMPOSIUM ON INDUSTRIAL APPLICATIONS OF GAS TURBINES

Transcription

1 20TH SYMPOSIUM ON INDUSTRIAL APPLICATIONS OF GAS TURBINES Inlet Fogging and Overspray Impact on Gas Turbine Life and Performance by Klaus Brun / Southwest Research Institute Rainer Kurz / Solar Turbines Inc. Marybeth Nored / Apache Corp. Joseph Thorp / Aramco Services Co. Presented at the 20th Symposium on Industrial Application of Gas Turbines (IAGT) Banff, Alberta, Canada - October 2013 The IAGT Committee shall not be responsible for statements or opinions advanced in technical papers or in symposium or meeting discussions.

2 INLET FOGGING AND OVERSPRAY IMPACT ON INDUSTRIAL GAS TURBINE LIFE AND PERFORMANCE DR. KLAUS BRUN SOUTHWEST RESEARCH INSTITUTE DR. RAINER KURZ SOLAR TURBINES MARYBETH NORED APACHE CORP JOSEPH THORP ARAMCO SERVICES COMPANY

3 BACKGROUND Twelve 12 GE 5002 C and D models operated in mountainous tropical climate to drive gas re injection compressors. Installation of inlet fogging and overspray systems were intended to increase power and efficiency of the gas turbines. Initially some performance increase was observed but a rapid decrease in performance occurred after less than 3 months on all units. One rotor was sent to overhaul after 22,000 hrs as degradation exceeded 10%. Visual rotor inspections showed significant compressor blade leading edge erosion, tip clearance opening, and corrosion pitting. Identify the causes of performance loss and blade degradation.

4 STUDY OVERVIEW Review the factors that affect performance of the gas turbines and identify the root cause of the corrosion and erosion in GT compressor: Perform visual blade inspection and geometry measurement to quantify blade erosion. Collect blade fouling deposits and chemically analyze them Analyze inlet air filter samples and water samples to identify sources of blade deposits Perform analysis and tests to determine impact of inlet cooling and overspray on performance. Review operation and maintenance practices : Inlet cooling Inlet Filtration Water washing

5 ASIDE: INLET POWER AUGMENTATION BACKGROUND Inlet Air Chillers: Heat exchanger cooling of inlet air using mechanical and absorption chillers with or without thermal energy storage Icehouses Refrigerant cycles Seawater cooling Evaporative Cooling: Direct reduction of inlet air by water evaporation Wetted media Fogging Wet compression Overspray Interstage injection

6 GT INLET TEMPERATURE

7 INLET FOGGING Inlet Filter Drain Pump Skid Water Gas Turbine - Up to 100% Relative Humidity (Saturation) Fogging - Above 100% Relative Humidity Overspray Courtesy Mee Industries

8 EVAPORATIVE COOLING Dry Bulb Thermometer Wet Bulb Thermometer 90 F 32 C Evap. Cooling Potential (20 F/11 C) 70 F 21 C air Wet cloth wick Courtesy Mee Industries

9 INLET COOLING % 60% Wet Bulb (F) 70 40% 20% HUMIDITY RATIO (Lbv/Lba) DRY BULB TEMPERATURE (F) Psychiometric Chart

10 POWER AUGMENTATION (GE) Courtesy General Electric

11 TYPICAL FOG NOZZLE ARRAY

12 TYPICAL SPRAY NOZZLES Impact Pin Orifice Filter

13 SITE PUMP SKID INSTALLATION High pressure feed lines (stainless steel tubes). Pump Skid with high-pressure pumps and Control Center

14 SOME CONSIDERATIONS FOR INLET POWER AUGMENTATION Concern Inlet icing FOD Casing distortion Corrosion Erosion Fouling Aerodynamic instability Mitigation Temperature shut off Inlet screen Spray Pattern Water quality Droplet Size Water quality Overspray, degradation

15 GE FRAME 5 DEGRADATION ANALYSIS (GE MS5002C/D) Rated Power kw Heat Rate kj/kwh Efficiency % Pressure Ratio Exhaust Flow kg/sec Turbine Speed RPM Exhaust Temperature C 20,340 12,

16 COMPRESSOR IMPACT ON GT PERFORMANCE Fouling Performance Loss 12 % GT Performance Decrease % Compressor Ratio Decrease Power Efficiency

17 COMPRESSOR DEGRADATION MECHANISMS Fouling: The deposition of particles on blades Surface Corrosion: Surface oxidation and material loss of blades LE/TE Erosion: Abrasive removal of material of blade leading and trailing edge Tip Clearances: Opening of blade tip clearances caused by rubbing and erosion Assembled Rotor that was Analyzed All negatively affect aerodynamic performance of compressor.

18 TYPICAL COMPRESSOR DEGRADATION AGENTS Type Cause Effect Sand Filter Openings Erosion Dirt/fines Filter/saturation Fouling Carbon/oil Exhaust Fumes Fouling Salt Atmospheric Salt Ocean Corrosion Salt Water injection Corrosion Sulfur Exhaust Fumes, Atmosphere Corrosion Calcium Water injection Fouling

19 COMPRESSOR DEGRADATION STUDY (22K HRS ROTOR)

20 BLADE VISUAL EXAMINATION Row 0: Severe erosion on leading edge Row 5: Shallow pitting/ erosion on suction side near leading edge Row 10: Pitting on suction side near trailing edge Row 15: Significant patches of pitting throughout

21 BLADE DEPOSIT CHEMICAL ANALYSIS Compressor Deposits in Row #1: Sand/Dirt Compressor Deposits in Row #4: Carbon/Oils

22 BLADE DEPOSIT CHEMICAL ANALYSIS Compressor Deposits in Row #11: Salt Compressor Deposits in Row #16: Salt/Sulfur

23 BLADE SURFACE CHEMISTRY Sodium Concentration Found in Deposit Analisys of Frame 5 Rotor at Different Rows Sodium Concentration 40 Concentration percentage (%) Row 1 Row 4 Row 11 Row 16 Concentration of Sodium in Different Compressor Rows

24 SALT FOULING REDEPOSIT

25 TESTED WATER QUALITY (FROM TREATMENT PLANT) Average Average Chlorides Chloride Concetration Concentration of the Water of Water Used for Fogging Average Concentration of Chlorides Getting into the Axial Compressor of the MS-5002C Units Concetration( m g /L ) Fall 06 Jul-02 Sep-02 Nov-02 Jan-03 Mar-03 May-03 Jul-03 Sep-03 Nov-03 Jan-04 Mar-04 May-04 Jul-04 Sep-04 Nov-04 Jan-05 Mar-05 May-05 Jul-05 Sep-05 Nov-05 Jan-06 Mar-06 May-06 Jul-06 Sep-06 Nov-06 Fall 03 Winter 03 Spring 04 Summer 04 Fall 04 Winter 04 Spring 05 Summer 05 Fall 05 Winter 05 Spring 06 Summer 06 Chlorides (g/month) Winter kg of Salt per Month

26 BLADE EXAMINATION SUMMARY FINDINGS

27 BLADE FOULING, EROSION, AND CORROSION MECHANISMS Salts Salts and other chlorides in combination with moisture are primarily responsible for metal surface pitting in gas turbine compressor Oils and Waxes Oils and waxes are residues from compressor washing or ambient air contamination Form a very thin surface film on the blades Oils and waxes act as binding agents for dirt or sand Carbon Carbon or Coke deposits on compressor blades indicate that exhaust gases from the gas turbine or other internal combustion engines are entering the axial compressor Dirt Sands Sand is a significant contributor to blade leading and trailing edge erosion and surface fouling Introduced into the gas turbine through the inlet filter and is an indication of inadequate inlet filtration or filter dirt saturation Corrosive Agents Foreign corrosive agents, such as sulfur compounds, vanadium, or heavy metals are introduced by pollutants in the ambient air

28 ASIDE: COMPRESSOR WASHING CONSIDERATIONS

29 INLET FILTRATION

30 INLET FILTER CONSIDERATIONS API Limit

31 INLET FILTER CONDITION Pressure testing and visual observation of the filters indicated filter dirt saturation. Chemical analysis of filters also showed salt penetration. Site 1 Filter Sample Site 2 Filter Sample

32 FILTER DIRT SATURATIONS PROCESS

33 INLET AIR FILTER DP TRENDING Average Differential Pressure Through Inlet Air Filter and Process Gas vs. Time for HP3 Unit MMCSFD DP (in-h2o) Process Gas Differential Pressure Through Inlet Air Filters (H20) and Process Gas May-2003 Jul-2003 Sep-2003 Nov-2003 Jan-2004 Mar-2004 May-2004 Jul-2004 Sep-2004 Nov-2004 Jan-2005 Mar-2005 May-2005 Jul-2005 Sep-2005 Nov-2005

34 INLET DP: PROBLEM IDENTIFICATION Trend Suddenly increasing filter dp Suddenly decreasing filter dp Slowly increasing Filter dp Slowly decreasing dp Cyclical dp Cause Dust saturation, water Filter break, inlet duct hole, blow in door Probably normal Flexible joint ripping, sensor drift, filter break Filter saturation / water

35 SUMMARY OF INSPECTION AND TEST OBSERVATIONS Rapid LE/TE edge and tip erosion of the compressor blades is attributed to over spraying. Fogging water has dissolved salts or other chlorides leading to fouling and corrosion pitting. Gas turbine is ingesting exhaust from other combustion machines On line and off line washing methods are not adequate for the application and cause re deposits in last stages of compressor. The inlet filters have inadequate rain protection resulting in dirt saturation and carry over.

36 PREDICTED PERFORMANCE: POWER AUGMENTATION Average Turbine Power Output Comparision MS-5002 C Units at Cusiana Power (HP) Fall 03 Winter 03 Spring 04 Summer 04 Fall 04 Winter 04 Spring 05 Summer 05 Fall 05 Winter 05 Spring 06 Summer 06 Fall 06 Winter 06 Turbine Power Output with Fogging Overspray Turbine Power Output without Fogging Turbine Power Output with Fogging

37 PREDICTED PERFORMANCE: EFFICIENCY Turbine Efficiency vs. Season MS-5002 C Units at Cupiagua Efficiency (%) Fall 03 Winter 03 Spring 04 Summer 04 Fall 04 Winter 04 Spring 05 Summer 05 Fall 05 Winter 05 Spring 06 Summer 06 Fall 06 Winter 06 Efficiency With Fogging Overspray Efficiency Without Fogging Efficiency With Fogging

38 PREDICTED PERFORMANCE: FOGGING EFFICIENCY INCREASE Increase of Turbine Efficiency due to Fogging Frame Increase of Effciency (%) Fall 03 Winter 03 Spring 04 Summer 04 Fall 04 Winter 04 Spring 05 Summer 05 Fall 05 Winter 05 Spring 06 Summer 06 Fall 06 Winter 06

39 ACTUAL PERFORMANCE (AT 22K HRS): CALCULATED LOSSES BY SOURCE Blade Surface Fouling Surface Corrosion/Pitting Relative Influence Power Loss (HP) 10% % 540 Blade Edge Erosion 35% 1,260 Rotor Clearances 30% 1,080 System Losses 10% 360 Recoverable Some Recovery Not Recoverable

40 NON-RECOVERABLE DEGRADATION RATE Average Gas Turbine Power Output vs. Time Ideal Power With Fogging Ideal Power Without Fogging Forecasted Power Degradation With Fogging Average Turbine Power Output (hp) Fogging Cross Over Overspray Cross Over Normal Operating Time (Hour)

41 COMPRESSOR DEGRADATION AERO- STABILITY Surge Margin versus Blade Degradation Blade Degradation % Surge Margin Surge Margin Safety Surge Margin Equivalent Chord Loss Equivalent Chord Loss Includes Aerodynamic Degradation

42 COMPRESSOR FOGGING & OVERSPRAY AERO-STABILITY Interstage Injection % Surge Margin % Saturation Stage 1 Stage 2 Stage 1 and 2

43 SUMMARY AND CONCLUSIONS

44 SUMMARY AND CONCLUSIONS

45 SUMMARY AND CONCLUSIONS

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49 SUMMARY AND CONCLUSIONS

50 Thank you very much. Questions, please.