Stress- -Assisted Corrosion (SAC) in Assisted Corrosion (SAC) in Stress Boiler Tubes Boiler Tubes Preet M. Singh* and Steve J. Pawel Pawel @ @ Preet M. Singh* and Steve J. * Georgia Institute Technology, Atlanta, GA * Georgia Institute Technology, Atlanta, GA @ Oak Ridge National Laboratory, Oak Ridge, TN @ Oak Ridge National Laboratory, Oak Ridge, TN DOE Project #DE- -FC07 FC07- -01ID1443 01ID1443 DOE Project #DE
Project Background Project Background Industrial Boilers Industrial Boilers Boiler Boiler To stack To stack Superheater Superheater Electrostatic Electrostatic precipitator precipitator Screen Tubes Screen Tubes Economizer Economizer Air delivery: Air delivery: Tertiary Tertiary (Fuel) (Fuel) Secondary Secondary Primary Primary Smelt! Smelt!
Stress Assisted Corrosion in Waterwall Tubes Stress Assisted Corrosion in Waterwall Tubes Welded Plate/Joint Welded Plate/Joint Stress Assisted Corrosion/ Cracking Stress Assisted Corrosion/ Cracking Boilers can experience SAC from waterside in in Boilers can experience SAC from waterside � Floor � Floor � Economizers Economizers � � � Waterwalls Waterwalls � Floor � Floor- -to Sidewall Seals to Sidewall Seals � Screens � Screens � Smelt Box Attachments Smelt Box Attachments � � � Roof Roof � Port Attachments � Port Attachments
Waterside Cracks in Waterwall Tube Near Waterside Cracks in Waterwall Tube Near Attachment Weld Attachment Weld
SAC in Recovery Boiler Tubes SAC in Recovery Boiler Tubes
Industrial Boilers and SAC Industrial Boilers and SAC SAC is Experienced in Various Industrial Boilers SAC is Experienced in Various Industrial Boilers � Water Leak in Some Industrial Boilers � Water Leak in Some Industrial Boilers AGRICULTURE AGRICULTURE can Potentially Cause Explosion can Potentially Cause Explosion 1% 1% � Numerous Accidents Reported � Numerous Accidents Reported AUTOMOTIVE AUTOMOTIVE STEEL STEEL UTILITY UTILITY 4% 4% 1% 1% � � Some were Fatal Some were Fatal 7% 7% CHEMICALS CHEMICALS PETROCHEMICAL 4% FOOD PETROCHEMICAL 4% FOOD � Project Benefits Project Benefits � 16% 16% 1% 1% � ~25 Trillion BTUs by 2020 ~25 Trillion BTUs by 2020 � MINING MINING 4% 4% � Cost Savings of ~ $133 � Cost Savings of ~ $133 Millon Millon/Year /Year MANUFACTURING PULP & PAPER MANUFACTURING PULP & PAPER � Safety Safety � 4% 58% 4% 58% Survey Data from Hercules- -BetzDearborn BetzDearborn Survey Data from Hercules
Project Objective Project Objective � � To Clarify Mechanisms Involved in Stress Assisted To Clarify Mechanisms Involved in Stress Assisted Corrosion (SAC) of Boiler Tubes Corrosion (SAC) of Boiler Tubes � Determine K Determine Key Parameters in its Mitigation and Control ey Parameters in its Mitigation and Control � � Microstructure Microstructure � � � Water Chemistry Water Chemistry � � Stress Stress � � Residual Stresses Due to Welding Residual Stresses Due to Welding � Operational Stresses � Operational Stresses
Project Team Project Team � Oak Ridge National Laboratory � Oak Ridge National Laboratory - - Dr. Steve J. Dr. Steve J. Pawel Pawel � Georgia Institute of Technology � Georgia Institute of Technology - - Dr. Preet M. Singh Dr. Preet M. Singh � Others Others � � Lawrence Livermore National Laboratory Lawrence Livermore National Laboratory - - Dr. Mike Quarry Dr. Mike Quarry � � Industrial Partners � Industrial Partners Dr. W.B.A. Sharp– – MeadWestvaco MeadWestvaco Mr. John Hainsworth Hainsworth – – B&W B&W Dr. W.B.A. Sharp Mr. John Mr. Steve Lukezich Mr. Steve Lukezich – – MeadWestvaco MeadWestvaco Dr. Ray Vasudevan Dr. Ray Vasudevan - - International International Mr. Paul B. Desch Mr. Paul B. Desch - - ONDEO ONDEO- - Nalco Nalco Paper Paper Dr. Peter Gorog Dr. Peter Gorog - - Weyerhaeuser Weyerhaeuser Mr. Mike Cooper Mr. Mike Cooper – – Longview Longview Company Inspections Company Inspections Mark Labell Labell – – Ahlstrom Ahlstrom Mark � Other Project Advisors Other Project Advisors � Mr. Mel Mr. Mel Esmacher Esmacher - - GE Specialty GE Specialty Dr. Barry Dooley – – EPRI EPRI Dr. Barry Dooley Materials Materials Dr. Jim Keiser - Dr. Jim Keiser - ORNL ORNL Mr. Karl Morency Morency – – Georgia Pacific Georgia Pacific Mr. Karl
Main Project Tasks Main Project Tasks � Task 1: Task 1: Laboratory Simulation of SAC Laboratory Simulation of SAC � � IPST IPST- -GTech GTech � � Task 2: Task 2: Material Characterization Material Characterization � � � [ORNL and IPST [ORNL and IPST- -GTech GTech] ] � Task 3: Task 3: Evaluation of Stress Effects Evaluation of Stress Effects � � [ORNL] � [ORNL] � Task 4: Task 4: Evaluation of Environmental Effects Evaluation of Environmental Effects � � [IPST [IPST- -GTech GTech and ORNL] and ORNL] � � Task 5: Task 5: Communication to US Industry Communication to US Industry � � � [IPST [IPST- -GTech GTech and ORNL] and ORNL]
Laboratory Simulation of SAC Laboratory Simulation of SAC Task 1 Task 1 � Develop Facilities to Simulate Boiler Tube Develop Facilities to Simulate Boiler Tube � Environment in Laboratory Environment in Laboratory � Capable of Controlling Water Capable of Controlling Water- -Chemistry Chemistry � Variables Variables � Dissolved Oxygen � Dissolved Oxygen � � pH pH � Cl Cl - , SO 4 , and Other Ions � - , SO 4- -2 2 , and Other Ions � � Conductivity Conductivity
Test Autoclave with Recirculation Loop Test Autoclave with Recirculation Loop Makeup Water Makeup Water Storage Tank Storage Tank Pressure Pressure Reducer Reducer Sensors for pH, ORP, Sensors for pH, ORP, O 2 , Conductivity, etc. , Conductivity, etc. Cooling Chamber Cooling Chamber Test Test High Pressure High Pressure Cooling Chamber Cooling Chamber N Pump Pump Autoclave Autoclave N 2 2 + + 2 320 o C, 320 C, O 1500 1500 Heating Chamber Heating Chamber 2 psi psi � � Test Capabilities Test Capabilities � � Temperature up to 350 o C, Pressure up to 3500 Temperature up to 350 C, Pressure up to 3500 psi psi � Electrochemical Tests � Electrochemical Tests � AC Impedance AC Impedance � � Stressed Samples for SAC � Stressed Samples for SAC � � Special Fixture for Constant Extension Rate Tests Special Fixture for Constant Extension Rate Tests
Autoclave with Recirculation Loop Autoclave with Recirculation Loop � � 100 Liter Makeup Tank 100 Liter Makeup Tank � � Heat Exchangers to Conserve Heat and Achieve Steady State Easily Heat Exchangers to Conserve Heat and Achieve Steady State Easily � � High Pressure Pump for Recirculation High Pressure Pump for Recirculation � � Continuous Water Chemistry Monitoring Continuous Water Chemistry Monitoring
Evaluation of Environmental Effects Evaluation of Environmental Effects Task 4 Task 4 Effect of Environment on Magnetite Growth and Effect of Environment on Magnetite Growth and Properties Properties
Boiler Environment and Magnetite Film on Boiler Environment and Magnetite Film on Tube Surface Tube Surface 3 Fe + 4 H 2 O → Fe Fe 3 O 4 + 4 H 2 3 Fe + 4 H 2 O → 3 O 4 + 4 H 2 Eh (Volts) Fe - H2O - System at 320.00 C 2.0 1.5 Fe2O3 1.0 FeO2(-a) 0.5 0.0 Fe(+2a) Fe3O4 -0.5 -1.0 -1.5 Fe H2O -2.0 0 2 4 6 8 10 12 14 C:\HSC5\EpH\Fe320.iep pH ELEMENTS Molality Pressure Fe 1.000E+00 1.112E+02 Above ~ 230 o C, Magnetite Film Forms on Carbon C, Magnetite Film Forms on Carbon Above ~ 230 Steel in Slightly Alkaline Oxygen- -free Water free Water Steel in Slightly Alkaline Oxygen
Stress Assisted Corrosion and Oxide Stress Assisted Corrosion and Oxide Scale Morphology Scale Morphology
Magnetite Film Growth and Morphology Magnetite Film Growth and Morphology Under Boiler Conditions Under Boiler Conditions � � SA 210 Carbon Steel Tube Samples SA 210 Carbon Steel Tube Samples � � Electrically Isolated Samples Electrically Isolated Samples � Samples Attached to Large Cathodes with Different Areas � Samples Attached to Large Cathodes with Different Areas � � Pure Water Pure Water (Double (Double- -Deionized Deionized) ) � � With and Without N With and Without N 2 Purge or O 2 Scavenger 2 Purge or O 2 Scavenger � 250 � 250 o o C to 320 C to 320 o o C C � X X- -Ray Diffraction of Sample Surface and Ray Diffraction of Sample Surface and � Metallography to Characterize Film Metallography to Characterize Film � Atomic Force Microscopy (AFM) for Film Morphology Atomic Force Microscopy (AFM) for Film Morphology � and Properties and Properties
Atomic Force Microscopy Atomic Force Microscopy Unexposed SA- -210 Carbon Steel Surface 210 Carbon Steel Surface Unexposed SA 10 8 30 20 6 10 nm µm 0 4 -10 -20 2 -30 0 0 2 4 6 8 10 µm Max. Roughness = 10 nm Max. Roughness = 10 nm Topography Scan Topography Scan
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