agenda corrosion in wet flue gas desulfurization (fgd...

AGENDA Corrosion in Wet Flue Gas Desulfurization (FGD) Systems

1st Supplemental Project Meeting Charlotte, North Carolina

EPRI Offices: Building 2 Auditorium January 27-28, 2011

TIME Activity Lead Thursday, January 27, 2011 – open meeting (prospective participants welcome) 8:00 am Breakfast All 8:30 am Welcome to EPRI G. Offen – EPRI 8:45 am Introductions & Goals for Meeting T. Hart (Utility

Chairman) -American Electric Power, C. Dene, J. Shingledecker - EPRI

9:00 am Review of Recent Industry Experience with Alloy 2205 in Wet FGD Systems

J. Shingledecker – EPRI

10:00 am Break 10:30 am Content of EPRI Supplemental Project –

Corrosion in Wet FGDs C. Dene, J. Shingledecker – EPRI

11:30 am Q/A about working with EPRI All 12:00 pm Lunch All 1:00 pm Characterizing Chemistry to Help

Understand Corrosion Issues C. Dene – EPRI G. Blythe, URS Corp.

1:45 pm Preliminary Results of Data Collection and Outline of EPRI Root Cause Analysis

B. Tossey – DNV, Columbus

2:30 pm Break All 3:00 pm Group discussion All 5:00 pm Adjourn 7:00 pm Dinner Friday January 28, 2011 – Closed Meeting (open to all funders of the ‘Corrosion in Wet FGDs’ Supplemental Project) 8:00 am Breakfast All 8:15 am Review of workscope, timelines, etc J. Shingledecker, C.

Dene 9:00 am Review of draft deliverable – FGD

Inspection Guideline M. Schwartzwalder – SES

10:00 am Break All 10:30 am Additional questions on root cause analysis B. Tossey – DNV,

Columbus 11:00 am Non Destructive Evaluation (NDE) S. Walker - EPRI 11:30 Other issues All 12:00 pm Lunch All 1:00 pm Wrap-up admin issues, next meetings, etc C. Dene, J.

Shingledecker – EPRI 2:00 pm Adjourn

Corrosion in Wet FGDs

EPRI Welcome

George Offen

Sr. Technical Executive

1st Project Meeting January 27-28, 2011

2© 2011 Electric Power Research Institute, Inc. All rights reserved.

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Run existing units better, comply with regulations, aid new build decisions

Antitrust Guidelines for EPRI Meetings

1st Corrosion in Wet FGD Systems Project Meeting

January 27-28, 2011


General Antitrust Rules for Meeting Conduct

• These Guidelines for the 2205 Alloy Meeting participants are not legal advice! They are intended to enhance compliance with the letter and spirit of the antitrust laws.

• No set of guidelines can guarantee immunity from legal problems, but observing the following rules should minimize the potential for straying into questionable antitrust territory.

• If a participant has a question, he or she should contact their own company counsel


2205 Alloy Meeting Antitrust Guidelines

Collaborative research to accelerate the competitive deployment of solutions to corrosion issues in wet FGD scrubbers

When and Where

These Guidelines apply before, during, and after the” 2205 Alloy” meetings, and in both formal and informal communications.

Meeting’s Purpose

Why Guidelines?

The antitrust laws apply to EPRI, its members, funders, contractors, and advisors; violations can lead to civil and criminal liability.


In any discussions of goods and services offered in the market by others, including competitors, suppliers, and customers.

2205 Alloy Meeting Antitrust Guidelines (cont’d)

We Will Not Recommend

Use of particular vendors, contractors, or consultants for non-EPRI projects; we will not promote commercial products or services of third parties.

Be Accurate, Objective, and

Factual

Pricing, production capacity, or cost information, market strategies, business plans, and/or other competitively sensitive information, unless that information is publicly available.

Do Not Discuss


2205 Alloy Meeting Antitrust Guidelines (concl.)

For advice from your own Legal Department if you have questions about these guidelines or about a particular situation or activity at EPRI.

Ask

Review and Understand

The “2205 Alloy Meeting” Antitrust Compliance Policy, available at 2205 Alloy meetings and from the EPRI Program Managers.

Do Not Agree With Others

To discriminate against, or refuse to deal with (i.e., “boycott”), a supplier; or to set price, divide markets, or allocate customers.

Corrosion in Wet Flue Gas Desulfurization Systems

Introductions and Meeting Goals

T. Hart Utility Chairman, American Electric Power C. Dene, J. Shingledecker EPRI1st Supplemental Project Meeting EPRI Offices - Charlotte, NC January 27-28, 2011


Safety: Evacuation Route Building 2

You are here

Restrooms

Assembly Area (Southeast Corner of Parking Lot)


Agenda – January 27, 2011

8:30 am Welcome to EPRI G. Offen – EPRI

8:45 am Introductions & Goals for Meeting T. Hart (Utility Chairman) - American Electric Power, C. Dene, J. Shingledecker - EPRI

9:00 am Review of Recent Industry Experience with Alloy 2205 in Wet FGD Systems

J. Shingledecker – EPRI

10:00 am Break

10:30 am Content of EPRI Supplemental Project – Corrosion in Wet FGDs

C. Dene, J. Shingledecker – EPRI

11:30 am Q/A about working with EPRI All

12:00 pm Lunch All

1:00 pm Characterizing Chemistry to Help Understand Corrosion Issues

C. Dene – EPRIG. Blythe, URS

1:45 pm Preliminary Results of Data Collection and Outline of EPRI Root Cause Analysis

B. Tossey – DNV, Columbus

2:30 pm Break All

3:00 pm Group discussion All

5:00 pm Adjourn


Agenda – January 28, 2011

8:00 am Breakfast All

8:15 am Review of workscope, timelines, etc J. Shingledecker, C. Dene

9:00 am Review of draft deliverable – FGD Inspection Guideline

M. Schwartzwalder – SES

10:00 am Break All

10:30 am Additional questions on root cause analysis B. Tossey – DNV, Columbus

11:00 am Non Destructive Evaluation (NDE) S. Walker - EPRI

11:30 Other issues All

12:00 pm Lunch All

1:00 pm Wrap-up admin issues, next meetings, etc C. Dene, J. Shingledecker – EPRI

2:00 pm Adjourn


Goals for Today

• Industry Alert: provide entire industry (not just EPRI members) with critical information on corrosion observations in alloy 2205 FGD absorber vessels

• Introduce and answer questions on a new EPRI supplemental project open to the industry: Corrosion in Wet FGDs

• Technical Presentations:– Role of process chemistry and monitoring– Preliminary results from industry survey

• Industrial Feedback and Discussion– What specific questions do we need to be asking to

address root cause in this project?– What are we missing and what do you need?


General Notes

• Attendee List• Presentations• Dinner (tonight – Ciro’s, walking distance from Hilton)• Internet access


Together…Shaping the Future of Electricity

Corrosion in Wet Flue Gas Desulfurization (FGD) Systems

Recent Industry Experience with Alloy 2205 Absorber Vessels & Components

J. Shingledecker Senior Project Manager, EPRI Fossil Materials and Repair Program (P87)1st Supplemental Project Meeting EPRI Offices - Charlotte, NC January 27-28, 2011


Acknowledgements

EPRI acknowledges the contributions of the following utilities and their personnel who shared their experience, knowledge, and ample visual examples of corrosion damage which made this presentation possible

• American Electric Power (AEP)• Duke Energy• WE Energies


Outline

• Materials of Construction in Modern Absorbers• Materials Selection Drivers for New Absorber Vessels• Corrosion Observations

– Proper inspection & nature of observations– Locations

• Welds, base metal, crevice corrosion– Improper fabrication practices– Summary

• Mitigation methods being tried– Alloys– Coatings and tiling– Potential adjustment


Where we were EPRI Report 1011913

• In 2005, EPRI completed a survey on the material performance for 12 components in 42 FGD systems including: ductwork, absorbers, recycle tanks, etc.

• For absorber vessels– 36 used stainless steel or carbon steel lined with stainless

steel or nickel-based alloys with few reported major problems• Minor issues with claddings• Corrosion in mixing zones• Metallics being considered as replacements for other organic liners or rubber

– First installation of 2205 was ~2004 (no experience prior)


Current Database of All North American FGD Absorber Vessels (360 units)

Materials Number % of Units

2205 Duplex 67 19.0

255 Duplex 13 3.7

31 Stainless 2 0.6

317L 3 0.8

317LM 3 0.8

317LMN 17 4.8

AL6XN 2 0.6

C-276 11 3.1

Flakeglass 15 4.2

FRP 18 5.1

Rubber Lined 3 0.8

Ceramic Tile 42 11.9

Vinyl Ester 2 0.6

Undetermined 155 43.9

All constructed from 2004 to

present

Stainless steels >30% of FGD Fleet

Source: EPRI FGD Material Database (Program 75)

Note: Not all stainless vessels have reported widespread corrosion


Why Duplex? – Cost Considerations

• Composition– 317LMN: Fe-19Cr-15Ni-4.5Mo-N (Austentic)– AL-6XN: Fe-21Cr-24.5Ni-6.5Mo-N (Superaustenitic)– 2205: Fe-22.5Cr-5.5Ni-3.2Mo-N (Duplex)– C276 Ni-15.5Cr-16Mo-5Fe-3.7W (Nickel-based)

• Nickel and Molybdenum– 500%+ raw

price fluctuation past 10 years

– Alloys can be 5-10X in cost compared to stainless

Nickel Prices 2003 to 2008 ($ per tonne)


Why Duplex? – Process Chemistry Considerations (Alloy Selection Chart 1of3)

• 2205– Moderate

Chlorides– Severe pH

• Improved performance compared to 317LMN

Source: Nickel Institute


Why Duplex? – Process Chemistry Considerations (Alloy Selection Chart 2 of 3)

• 2205– Mild Chlorides– Moderate pH

• Poorer performance compared to 317LMN

Adapted from: W.H.D. Plant. “The Cost-Effective Use of Nickel Alloys and Stainless Steels for Chimneys (Stacks) in Air Pollution Control Systems.” Corrosion 2000. Paper No. 00577.


Why Duplex? – Process Chemistry Considerations (Alloy Selection Chart 3 of 3)

Note pH 5.5-6.5

Flue Gas Desulfurization Materials Guidelines Update: Coating and High Alloys EPRI, Palo Alto, CA: 2001. 1004026

• Chloride Resistance Factor (CRF)

• 2205: 37.9– Moderate

Chlorides– Moderate

pH• Improved

performance compared to 317LMN


Summary of Duplex Materials Selection

• Cost compared to stainless steels, nickel-based alloys, or lined vessels– Drivers: alloy composition, raw materials price

fluctuations, thinner walls (higher strength for duplex)• Operational conditions

– Drivers: Moderate Chloride and pH design conditions– 2 out of 3 alloy selection charts show improved

behavior compared to 317LMN

2205 was the winner for alloy selection in 2004-2010


Proper Inspection Techniques are Essential to Locating Corrosion

• Draft EPRI Guideline on inspection of wet FGDs has been completed and is available to supplemental project funders

• Before inspection, deposits and scale must be removed to assess underdeposit corrosion

Example of Hard Tenacious Scale

¾” Thick Black Scale


Cleaned section of an absorber vessel


Scale removal is not enough

• Comparison of the same surface (grit blasted) under direct and indirect lighting

• Standard walkthrough could miss the corrosion

Indirect lighting with LED flashlight reveals corrosion

Direct lighting during typical visual inspection


Small surface indications may represent a larger issue (1 of 3)

• Comparison of visual examination and radiograph in same location

Corrosion extends from weld heat-affected-

zone (HAZ) subsurface into base metal



Extensive metal loss with minimal surface

penetration

• Pit size on surface is not a good indication of level of attack

• Pits can ‘wormhole’ through metal• Extreme example: through-wall vessel leak

initiated 12” (300mm) higher inside vessel than external leak location



• Pits are difficult to see• Most metal loss is subsurface• Images taken in base metal from two different units


Role of microstructure remains unclear

• Micrographs are from different units• Austenite = white, Ferrite = dark/gray

Preferential corrosion attack in ferrite

Preferential corrosion attack in austenite in 2205


Weld metal and heat affected zones are susceptible

Corrosion in weld heat-affected zone causing through wall

failure of 11/16” (17mm) thick vessel wall External view of through-

wall HAZ leaks


Weld metal and heat affected zones are susceptible

• Examples of weld pitting and corrosion after ~4 months of service


Base metal is susceptible

Extent of removed corrosion pits on absorber vessel walls after ~2 months of service (corrosion was ground out leaving divots)

General appearance of corrosion pits in base metals

Corrosion pit after ~11 months of service (vessel wall)


The damage is not restricted to weld metal heat-affected-zone (HAZ) or Alloy 2205

Corrosion in 2205 (lower wall)

Corrosion in 255 (upper wall)

Corrosion in 2205 HAZ extending into base metal


Multiple corrosion locations can be observed in the same vessel

• All images taken from multiple inspections on same 2205 absorber vessel (during first 12 months of operation)

Pitting on vertical seam (weld & HAZ)

Pitting in weld metal

Pitting on wall base metal (arrows indicate new pits during 2nd

inspection)

HAZ Pits


Floors and walls are both experiencing corrosion

Severe corrosion noted in heat- affected-zone of shell to floor

joint

Corrosion in floor also observed


Crevice locations are susceptible

Corrosion on Bobcat door

Corrosion at bolted

attachmentCorrosion at manway seal


Multiple designs are affected

Dye penetrate reveals extensive corrosion in weld seam of

spray tower

Corrosion in 2205 beam support for Jet Bubble Reactor (JBR)


Improper fabrication practices are contributing in some instances (1 of 2)

Corrosion pattern following apparent writing on vessel (improper use of markers)


Improper fabrication practices are contributing in some instances (2 of 2)

Corrosion pattern following grinding marks on floor

Iron Contamination

Improper welding sequence may have contributed to weld metal susceptibility (final pass should be on vessel interior)


Components beyond the absorber vessel constructed with 2205 can be affected

Weld Heat-Affected- Zone Corrosion in

Spray Header

Design modification to minimize deposition in

header and stresses on weldment

Deposition in 2205 Spray Header


Summary of Corrosion Observations

• Locating corrosion is only as good as your inspection techniques– Proper cleaning of scale and deposits– Serious corrosion may only be indicated with small surface

features• Role of microstructure is unclear• Corrosion is affecting:

– Weld metal and heat-affected-zones (HAZ)– Base metal– Regions of improper fabrication techniques– Multiple designs– Times as short as 2 months and through-wall leaks recorded

in less than 1 year of service• Mechanisms reported:

– Crevice corrosion, underdeposit corrosion, MIC (suggested for one case, dismissed by another)


Mitigation strategies currently being implemented by industry

• Relining the vessel with Stebbins tile• Weld Repair• Coatings• Potential

Adjustment (PAP)


Stebbins Tile Mock-up for 2205 Jet Bubble Reactor Vessel

Tile

Mortar

Intermediate layer coating for thermal expansion

2205 Vessel

Currently considered a ‘permanent’ fix


Weld Repair Options in Use Today

• Installation of plate work• Addition of external support (vessel integrity)• Issues

– New additional welds– Full removal of corrosion

products prior to welding

Plate work Repair

External support


Weld Repair

• One utility reported corrosion was so extensive:– 65% of horizontal welds repaired– 50% of vertical weld repaired– 3 leaks were discovered after welding

• Questions on weld repair– What filler metal?– How do you remove all corrosion

products?– What about the new heat-affected-zone?– When do I need to repair (i.e. how do I

know I’ve violated a minimum wall thickness? Corrosion on

repair weld


Potential Adjustment Protection (PAP) System

• Successful in other (older) FGD systems• Not applied to 2205 duplex until 2010• Utility application 2010

– Lab study suggested 2205 should be amenable to approach

– ~1Millions dollars for design & installation – 1 unit– Currently on 2 units


External view of PAP System

PAP system anode entry (1 of 6)

PAP system reference electrode (1 of 4)


Internal view of PAP System

PAP system center column, radial

supports, perforated deflectors,

six anode assemblies


Considerations & Preliminary Performance

• Considerations:– Removal of corrosion prior to installation– Limits accessibility for inspections– Maintenance

• Performance (3 months, 2 units)• Lower than expected reference readings in lower area

• Field testing has showed passivation• Field testing showed insufficient current density to fully passivate lower area of tower

• Evaluations continue• Exploring the use of additional anodes


Summary of Mitigation Methods in Use Today

• Shorter-term fixes:– Weld repair– Patch plate repair– Structural support (vessel integrity)– Coatings (still gathering data)

• Long-term solutions– Relining with Stebbin’s tile

• Not yet proven for lining of a metallic 2205 vessel with corrosion already present

– Cladding• Not yet used on large scale but has been used for local

protection in the past (same welding issues as short-term repair)– Potential Adjustment Protection (PAP)

• First installations on 2205 in 2010• Still on a learning curve: passivation has been realized but full

vessel passivation will require additional modifications


Overall Summary

• Duplex 2205 is being used extensively in many Wet FGD designs

• Significant corrosion has been observed by multiple utilities utilizing different designs

• Effected areas– Base metal, weld metal, heat-affected-zones, and

areas of improper fabrication– Not limited to absorber vessels– Proper inspection is critical to finding corrosion– Underdeposit corrosion, crevice corrosion, and MIC all

reported mechanisms• Short and long-term mitigation strategies are now being

implemented with varied success

Corrosion in Wet Flue Gas Desulfurization Systems

Content of EPRI Supplemental Project

C. Dene, J. Shingledecker EPRI1st Supplemental Project Meeting EPRI Offices - Charlotte, NC January 27-28, 2011


Background (Timeline)

• Widespread reports of corrosion in Wet FGD Systems constructed with duplex 2205

• At the request of the EPRI Generation Council (October 7- 8, 2010) EPRI convened a meeting with utility members in November 4, 2010 (Charlotte, NC)– 47 participants representing 15 members– Meeting goals

• Review industry experience with 2205

• Determine appropriate actions for EPRI & Industry


Key Takeaways from EPRI Member 2205 Meeting

• Clearly a widespread issue in 2205• The cost of inspections, temporary fixes, and potential longer-term

solutions is very high both from lost generation and cost of repair• Voice of the members:

– This is a safety issue: We need to alert the industry beyond EPRI membership

– The time for talk is over, (sharing experience can only get us so far) we need action

– We need to collect detailed data on operation, materials, construction practices, and corrosion observations

– Numerous unanswered questions exist and there was general consensus that EPRI should put together a project to address these issues


EPRI Actions

• Alert the industry: today’s meeting– 70+ participants – utilities, OEMs,

alloy manufacturers, consulting & inspection firms

• Data collection– Key stakeholders and EPRI rapidly developed and

distributed a 3-page spreadsheet (November)– 12 utilities responded (December) with 9 completed

sheets• Project

– Statement of Work (SOW) was developed by EPRI and reviewed by select utility members

– Supplement project notice (SPN) released and membership sign-up began in mid-December


(Some) Key Questions

• Is everyone doing an adequate job inspecting these units? • What is the cause of the corrosion?• Are alloys beyond 2205 in jeopardy?• Do we have consistent fabrication practices across the

industry? – Lots of questions on surface finish, welding, etc

• What are my options for repair and how do they perform?• What about coatings, alternate alloys, etc?

– Are there options for testing without large scale installation?


EPRI Response: Corrosion in Wet Flue Gas Desulfurization (FGD) Systems

• Supplemental project launched December 2010• Project Scope:

– Root cause analysis for corrosion found in alloy 2205 in wet FGD systems

– Fabrication guidelines for the use of alloy 2205 and other metallic alloys in wet FGD system

– Repair guidance for metallic FGD systems and components experiencing corrosion

– Corrosion behavior and performance of alternate materials and coatings for wet FGDs

– Information exchange through a Corrosion in FGD Materials Interest Group


Tasks

1. Root cause analysis for FGD corrosion in alloy 2205 - Year 1

2. Laboratory and/or field testing of materials, coatings, etc to support other tasks - Years 1 & 2

3. Fabrication guidelines for construction of metallic FGD systems (include welding guidance for duplex stainless steels) – Year 1

4. Repair Options & Guidance – Year 25. Corrosion behavior and performance of alternate

materials & coatings (includes task 2 results) – Year 26. Corrosion in FGD Materials Interest Group meetings –

Years 1 & 2


Task 1. Root cause analysis for FGD corrosion in alloy 2205 – Year 1

Subtasksa. Develop root cause analysis (RCA) procedureb. Collect data from industryc. Review of relevant literatured. RCA Report & recommendationse. Inspection techniques

Deliverables (Year 1)• Final Report: Inspection Techniques for Corrosion

Damage in Wet FGDs• Final Report: Root cause analysis of alloy 2205

corrosion in wet FGD systems


Task 1. Progress

a. Develop root cause analysis (RCA) procedure Presentation later today - we need this group to bring forward as many specific questions as possible to properly do a RCA

b. Collect data from industry Initial spreadsheet collection is complete and analysis is ongoing. Missing and additional information will be collected through site visits, assessments, phone calls, etc.

c. Review of relevant literature Initiated

d. RCA Report & recommendationse. Inspection techniques and guideline

Draft report complete, provided to project funders for review (Jan. 21, 2011)


Task 2. Laboratory and/or field testing of materials, coatings, etc to support other tasks – Year 1 & 2

• The task details will be developed based on input from root cause analysis findings and project funder needs

• Possible testing variables:– Materials– Surface preparation– Welds/weldments– Coatings

• Possible Approaches– Laboratory screening tests– Field trials

• Coupons in operating units (some work ongoing by utilities)• Test loop/chamber off existing unit(s)

• Progress: Task not yet initiated


Task 2. Laboratory and/or field testing of materials, coatings, etc to support other tasks – Year 1 & 2

• Progress: – Task not yet initiated– Task 1 Root Cause Analysis will assist in defining

areas where more information is needed

Deliverables (Year 2) – Included in Task 5 Report


Task 3. Fabrication guidelines for construction of metallic FGD systems – Year 1

• Provide consistent guidelines for proper fabrication practices– Avoid iron contamination– Ensure proper surface preparation

• Provide welding guidance for FGD construction (some conflicting guidance in industry today)– Duplex stainless steels– Stainless steels and nickel-based alloys– Clad construction– Heat input, thickness, welding sequence, filler metal

selection, post-weld inspection requirements


Task 3. Fabrication guidelines for construction of metallic FGD systems – Year 1

• Progress: – Task not yet initiated– First discussions with project funders Friday

Deliverables (Year 1)• Final Report: Fabrication guidelines for metallic FGD

systems


Task 4. Repair Options & Guidance (includes task 2 results) – Year 2

• Improved weld repair guidance– Post-corrosion cleaning and preparation– Filler metals and processes– Inspection

• Field experience with ‘stop-gap’ measures such as weld repairs and coatings

• Review of experience with Potential Adjustment Protection (PAP)

• Process chemistry/operational changes• Others?


Task 4. Repair Options & Guidance (includes task 2 results) – Year 2

• Progress: No action on workplan, currently monitoring these options as information is gained through Interest Group

Deliverables (Year 2)• Final Report: Repair options for corrosion in metallic FGD

systems


Task 5. Corrosion behavior and performance of alternate materials & coatings (includes task 2 results) – Year 2

• Laboratory and/or field test results from Task 2• Additional laboratory tests on coatings

– Adherence, thermal stability, embrittlement, surface preparation, etc.

• Progress: – No action yet– Begin to define potential coating solutions of interest

with project funders

Deliverables (Year 2)• Final Report: Corrosion behavior and performance of

alternative materials and coatings


Task 6. Corrosion in FGD Materials Interest Group meetings – Years 1 & 2

• Minimum of 2 meetings per year (aim for 3 in first year)• Conduct webcast/conference calls as appropriate for task

items or deliverables which require reviews• Meeting Dates

– 1st Meeting: January 27-28, 2011: EPRI Offices Charlotte, NC

– 2nd Meeting (after agreement with funders): June 20-21, 2011: Orlando, FL (prior to EPRI 2nd Int. Conference on Welding and Fabrication Technology for New Power Plant Components – Nuclear & Fossil)

– 3rd Meeting – Fall/winter 2011– 2012 TBD


Summary of Planned Project Deliverables

• Final Report: Inspection Techniques for Corrosion Damage in Wet FGDs Draft Report Available

• Final Report: Root cause analysis of alloy 2205 corrosion in wet FGD systems Work has initiated

• Final Report: Fabrication guidelines for metallic FGD systems

• Final Report: Repair options for corrosion in metallic FGD systems

• Final Report: Corrosion behavior and performance of alternative materials and coatings


Project Participation and Details

• Project Cost:– 50k/yr for 2 yrs (100k total)– EPRI members can use

tailored collaboration funds for up to 1/2 of the cost

• Membership:– Open to non-EPRI members– Current membership

• 11 participants committed• Conducting the project:

– With 7 funders Tasks 1 & 6 will be initiated– Additional tasks will initiate based on funding and as

directed and prioritized by project participants

Characterizing FGD Chemistry to Help Understand Corrosion Issues

Gary Blythe, URS Corporation

512-419-5321 / [email protected] Dene, EPRI 650-855-2425 / [email protected]

January 27, 2011

mailto:[email protected]


• Most of us understand the importance of chlorides, pH, and temperature in pitting corrosion

• Other parameters may also be important

– Manganese [Mn] concentrations by phase

– Oxidation-reduction potential (ORP)

• Direct measure of how chemically oxidizing or reducing is the aqueous environment in the reaction tank

• Can impact what phase Mn, other trace elements report to in FGD slurry (scaling potential)

Why Characterize FGD Chemistry?


Change in Mn Forms with pH, ORP (Pourbaix diagram in pure water)

• Mn changes from soluble Mn2+ to insoluble Mnx Oy(Mn4+) as ORP increases at FGD pH

• At a given ORP level, phase of Mn could change between absorber (soluble) and reaction tank (insoluble) with pH variation– Could contribute to

MnO2 scale formation in reaction tank over time


Full-scale Data for Mn Partitioning in Reaction Tank Slurry vs. ORP

R2 = 0.78

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

0 100 200 300 400 500 600 700

ORP, mV

% o

f E

lem

ent

in S

lurr

y L

iqu

or

% Mn in Liquor

% Mn in Liquor -Outliers:

Site H Unit 3

Site M Units 3 & 4


Full-scale Data for Mn Partitioning in Reaction Tank Slurry vs. ORP – for One Unit

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

0 50 100 150 200 250 300 350 400 450 500

ORP, mV

% o

f E

lem

ent

in S

lurr

y L

iqu

or

% Mn in Liquor


Where Does the Mn in FGD Slurry Come from?

• EPRI trace element balance data for 7 coal-fired units with limestone wet FGD systems:– Average Mn balance closure around units – 85%– Average calculated contribution of limestone to Mn

found in FGD output streams – 107%– Results suggest ~all Mn comes from limestone

• EPRI data for Mn concentrations in limestone from 8 LSFO wet FGD systems:– Range: 31 – 349 ppm– Average: 125 ppm– Standard Deviation: 99 ppm– Anecdotal data show even greater variability (3 ppm to

>1000 ppm)


What are Mn Concentrations in FGD Reaction Tank Slurry?

• Liquid phase (EPRI data from 8 LSFO systems):

– Range: 0.009 ppm (9 ppb) to 302 ppm– Average, standard deviation: 44 ppm ± 79 ppm– Cycles up like chloride due to evaporation, liquor return

from dewatering• Solid phase (same 8 systems):

– Range: 6 to 181 ppm– Average, standard deviation: 49 ppm ± 51 ppm– Tends to concentrate in fine solids, gets recycled to

absorber with hydroclone overflow return


Initial FGD Characterization

• FGD Recycle Slurry:– Slurry pH, temperature, wt% solids – ORP– Trace elements (solid and liquor phases)

• Mn in particular• Other redox active species (e.g., chromium, iron, vanadium)• Suggest ~20 element scans of slurry solid and liquid phase

– Chlorides, other halogens (fluoride, bromide, iodide) in liquor – Other major FGD liquor species (calcium, magnesium, sodium,

sulfite, sulfate, carbonate)– Concentrations of any additives used (DBA, formate, etc.)

• Limestone (raw rock or as ground), Makeup Water:– Mn and iron at a minimum– Suggest ~20 element scans


FGD Characterization

• Slurry pH, temperature – EPRI Methods A1, C1– Calibrate hand-held meter in lab

before measuring (pH 4, 7 buffers)– Measure in recycle pump suction,

scrubber bleed pump suction, pH meter pot, etc.

– Measure in flowing sample, with temp. compensation

– Don’t carry sample back to lab to measure!

• ORP – no EPRI method– Can use same meter as for pH if it

has a mV scale– Uses separate probe (can just replace

pH probe)– Same notes as above for pH apply


Additional Notes about ORP Measurement

• URS has had good luck with Beckman (BKA57197 [silver/silver chloride reference]) probe

• Measurements are relative to the reference electrode, so be sure to note reference electrode type with data

• Most meters do not have a calibration adjustment, but ORP standards are available– Zobell solution – 231 mV with Ag/AgCl– Thermo Orion standard – 215 mV with Ag/AgCl– Check before and after reading

• Measure at the same time, place as pH• Do not take reading until temp. readout is steady, matches temp.

during pH measurement– ORP reading may not ever steady out – just read value when

temp. readout is steady– Measurement is not exact, ±10-20 mV is adequate


Sampling for Trace Elements (including Mn)

• Sample at same location as pH, temperature, ORP measurements (and at the same time)

• Filter sample as soon as possible after collection to preserve partitioning (do not send whole slurry to off-site lab to analyze!)

– Recommend filtering through 0.45 µM pore size filter, dry at 60oC– Preserve liquor at plant lab to 1% HNO3 using Trace Metal Grade

acid (preserved sample requires HazMat shipping)– Collect slurry and ship acidified liquor sample in pre-cleaned EPA

sample bottles• 3rd party lab may provide bottles

– Collect and ship solid phase in clean, air-tight, sealed container


Sampling/Analysis Methods for Balance of FGD Samples (EPRI FGD Chemistry and Analytical Methods Handbook, 1013347)

Method TypeMethod

No. Method Description

Gravimetric Percent Solids/Percent Moisture Methods

F1 Gravimetric Method for Weight Percent Solids in Wet Scrubber Slurries

F3 Cassia Flask Density Method for Weight Percent Solids

F6 Thermogravimetric Determination of Solid Concentration and Gypsum Purity

Atomic Absorption (AA) Methods

H1 Calcium, Magnesium, Sodium, Potassium, Iron, Manganese, and Aluminum Analyses by Flame AA

Ion Chromatograph (IC) Methods

I2 Analysis by IC of Fluoride, Chloride, Sulfite, Sulfate, Thiosulfate, and Total Sulfur in Scrubber Liquors and Total Sulfur in Scrubber Solids

Calcium/Magnesium Methods

J1 Calcium and Magnesium Analysis in Limestone and Scrubber Solids by EDTA Titration

J2 Calcium and Magnesium Analysis in Scrubber Liquor by EDTA Titration


Sampling/Analysis Methods for Balance of FGD Samples (EPRI FGD Chemistry and Analytical Methods Handbook, 1013347)[continued]

Method TypeMethod No. Method Description

Sulfite Methods M2 Sulfite Analysis in Scrubber Liquors and Slurry Solids by Iodine-Thiosulfate Titration

Carbonate Methods N3 Alkalinity (Carbonate, Oxide, and Hydroxide) Measurement by Acid-Base Titration

N4 Coulometric Determination of Carbonate in Liquids and Solids

Chloride Methods O1 Chloride Analysis in FGD Liquors by Mercuric Nitrate Titration

O4 Chloride Analysis by Silver Nitrate Titration Using a Chloride Ion-Specific Electrode

O5 Extraction of Chloride from Gypsum, and pH and Percent Inerts Determination of Gypsum

Fluoride Methods P1 Fluoride Analysis in Solid and Liquid Samples by Ion Selective Electrode

Organic Acid Methods S1 Buffer Capacity Titration


Ongoing FGD Characterization (straw man)

• ORP measurement at same frequency as routine FGD pH instrument calibration (1-2 times/week; get data at varied unit load, coal S)

• Routine tracking of Mn in limestone (weekly at first?)– Consider submitting NIST SRM 1c limestone for QC

• Trace metals concentrations, partitioning in FGD slurry (Mn weekly, balance of elements monthly?)

• Chloride – most plants routinely measure to adjust blow down rates anyway

• Liquor-phase sulfite – may need to track (daily?) if lowering ORP to avoid Mn scale formation


Ongoing FGD Characterization (Table)

Analyte Frequency

ORP in FGD slurry 1-2/wk. (get data at varied load, coal S)

Mn in limestone 1/wk.

Mn in FGD slurry solids and liquor 1/wk.

Other trace elements in FGD slurry solids and liquor

1/mo.

Chloride in FGD liquor 2/wk.

Sulfite in FGD liquor 1-5/wk.

1st Supplemental Project Meeting

EPRI Root Cause Analysis

Brett Tossey (DNV)Gerry Koch (DNV)Arun Agrawal (DNV)

Corrosion in Wet Flue Gas Desulfurization (FGD) Systems

January 27th-28th, 2011


Outline

• EPRI Root Cause Analysis Workscope

• Preliminary review of collected spreadsheets

• Preliminary literature review

• Structure of root cause analysis/feedback


EPRI RCA Scope

• RCA: Alloy 2205 FGD corrosion (finish 2011)– Define expected outputs

• This will assist on choosing a RCA structure– Survey the industry (in progress by EPRI )

• Fabrication, operating conditions, and corrosion in 2205 absorber components

– Review state of the art• EPRI studies; public domain literature

– Report results of root cause analysis including: • Materials selection process• Corrosion observations and failure mechanisms• Operation variables• Fabrication variables• Knowledge gaps


Preliminary Glimpse of Industry Survey

• How DNV will manage the data?

• What might we find?

• Filling gaps and obtaining clarification– Streamline communication; company rep.

• When will the results be available?


Industry Data

• Managing data will require– Common language

• Both widely recognized amongst team members and software friendly

– Frequency plots

• Display large amounts of data that are difficult to interpret intabular form

• Shows the relative frequency of occurrence

• Quickly illustrates the data distribution

– Descriptive statistics

Scale color, surface prep, bulk solution parameter, feedstock,…


• What might we find?

• Trigger(s) for localized corrosion that explain the rate of attack

• Key decisions that led to this place• “We are only as good as the information we have”

• Identify inputs for acceptable mitigation strategies• % of attack, threshold OPEX

Industry Data


• Filling Gaps and Sharing Knowledge– Site visits, PC/phone interviews, then refining data– There will be a need to supplement the EPRI survey

data– Built in flexibility; expect the unexpected– Show the spreadsheet?

– EPRI has preliminary data on 54 scrubbers that employ 2205

– Detailed timelines for each absorber

Industry Data


Industry Data

• Detailed information gathered by EPRI

• Design and construction– In-service date, 2205 location, weld filler, typical coal, bulk

slurry chemistry, and more

• Metallurgical and corrosion-related– Location, type, severity, and distribution of corrosion

• Construction and fabrication – Post-fabrication cleaning, mechanical tool type, chemical

used


Review State of the Art

• Some important questions…that may already have answers– What analyses have been completed by utilities? Why?– What are the corrosion design criteria?– Is MIC a factor?– Is galvanic corrosion a factor near welds?– What conditions lead to corrosion rates > 250 mpy?– Should regular inspections be performed? On what interval?

• We will come back to this.

• State of the art– EPRI Report over the past 20+ years– Technical papers– Utility internal reports; lab data, field data, failure analysis


• 1. C. Kepner, B. Tregoe, “The Rational Manager” 2nd Edition, 1976• 2. J.P. Dimmer, R.A. Wood, D.N. Williams, W.E. Berry, J.H. Payer, “Failure-Cause Analysis - Fossil-Fired Power Parts” EPRI Report CS-2029 September 1981• 3. G. H. Koch, J. A. Beavers, T. K. Christman, “Evaluation of Flue Gas Desulfurization Materials in the Mixing Zone: R. D. Morrow Sr. Generating Station,” EPRI

Report CS-5476.• 4. G. H. Koch, N. G. Thompson, J. M. Spangler, “The Effect of SO2 Scrubber Environments on Alloy Corrosion,” EPRI Report CS-4697.• 5. G. H. Koch, J. A. Beavers, T. K. Christman, “Materials Testing in Synthetic FGD Environments,” EPRI Report CS-3740.• 6. H. S. Rosenberg, G. O. Davis, B. Hindin, A. K. Agrawal, W. J. Sheppard, G. H. Koch “Guidelines for FGD Materials Selection and Corrosion Protection,” EPRI

TR-100680 V2.• 7. G. H. Koch, N. G. Thompson, J. L. Means, “Effects of Trace Elements in Flue Gas Desulfurization Environments on the Corrosion of Alloys – A Literature

Review,” EPRI Report CS-4374.• 8. N. Sridhar, L.H. Flasche, J. Kolts, “ Corrosion and Mechanical Properties of Duplex Stainless Steel Weldments,” J. Metals 37, 1985.• 9. ASTM A923-06, “Standard Test Method for Detecting Detrimental Intermetallic Phases in Duplex Stainless Steel.”• 10. N. Sridhar, L.H. Flasche, J. Kolts , ”Effects of welding parameters on localized corrosion of a duplex stainless steel,” Material Performance, December 1984,

page 51.• 11. N. Sridhar, J. Kolts, “ Effects of Nitrogen on the Selective Dissolution of a Duplex Stainless Steel,” Corrosion Volume 43, No. 11, 1987.• 12. J.W. Fourie, F.P.A. Robinson, “Literature Review on the influence of weld-heat inputs on the mechanical and corrosion properties of duplex stainless steel,” J.

S. Afr. Inst. Min Metall, Volume 90, No. 3, 1990.• 13. Effect of electrolyte composition on the active to passive transition behavior in H2SO4/HCl solutions,” I-Hsuang Lo et al, Corrosion Science 48 (2006) 696-

708.• 14. A. Agrawal, G. Koch, R. Ross, “Corrosion Performance of Duplex and Austenitic Stainless Steels in Simulated SO2 Absorber Environments,” Corrosion 1996,

Paper 96449.• 15. D. C. Agarwal, “Alloy Selection Methodology and Experiences of the FGD Industry in Solving Complex Corrosion Problems; The last 25 years,” Corrosion

1996, Paper 96447.• 16. ASM Metals Handbook, Volume 13C, 2006.• 17. ASTM G48, “Standard Test Methods for Pitting and Crevice Corrosion Resistance of Stainless Steels and Related Alloys by Use of Ferric Chloride Solution.”• 18. R. E. Avery, W. L. Mathay, D. Gandy, “Material Performance in Flue Gas Desulfurization (FGD) Systems –Experience of 42 Fossil Fuel-Burning Plants,”

AIRPOL 2007, NACE.• 19. R. E. Avery, W. L. Mathay, W.H.D. Plant, “Utilization of Nickel-Containing Alloys for FGD Systems in N. America and Europe,” Corrosion 1996, Paper 96455.• 20. D. Caudill, G. Koch, “Corrosion of Carbon Steel Substrate Under C-276 Wallpaper,” Corrosion 1996, Paper 96450.• 21. DOE/NETL “Demonstration of Innovative Applications of Technology for the CT-121 FGD Process, A DOE Assessment,” Report 1177, 2002 (2002/1177).• 22. M. G. Fontana, Corrosion Engineering 3rd Ed., 1986.• 23. J. Grubb, J. Fritz, B. Parks, R. Polinski, “A 6% Mo Stainless Steel for Flue Gas Desulfurization,” Corrosion 2000, Paper 00583.• 24. K, Hjuler, K. Dam-Johansen, “Mechanism and Kinetics of the Reaction between Sulfur Dioxide and Ammonia in Flue Gas,” Industrial Eng. Chem. Res., V31,

Number 9, 1992.• 25. FGD Technology, National Research Council, 1980.• 26. J. Peultier, F. Barrau, J. Audouard, “Corrosion Resistance of Duplex and Super Duplex Stainless Steels for Air Pollution Control Process Systems,” Corrosion

2005, Paper 05316.• 27. B. S. Phull, W. L. Maythay, R. W. Ross, “Corrosion Resistance of Duplex and 4-6% Mo-Containing Stainless Steels in FGD Scrubber Absorber Slurry

Environments,” Corrosion 2000, Paper 00578.• 28. H. S. Rosenburg, H. M. Grotta, “NOx Influence on Sulfite Oxidation and Scaling in Lime / Limestone Flue Gas Desulfurization (FGD) Systems,” Environmental

Science and Tech., V14, Number 4, 1980.• 29. B. C. Syrett, “Corrosion Control in Electric Power Plants,” Corrosion Science, V35, Numbers 5-8, pp. 1189 – 1198, 1993.• 30. R. Zauter, T. L. Ladwein, “Recent Experiences with Stainless Steels in Flue Gas Desulfurization Plants,” Corrosion 2000, Paper 00579.



Structure of RCA

• Show RCA slides


RCA Outcome

• The RCA 2011 schedule is:– Literature review by the end of Q1 – Draft report by the end of Q2– Member comments incorporated by end of Q3– Final report and wrap up at the end of 2011

• The goal is to leverage experience to generate a complete, rapid response– Knowledge gaps need to be addressed quickly


Supplemental slides

• Modeling absorbers materials


Supplemental slides

Nondestructive Evaluation Possibilities

Stan M. Walker Sr. Project ManagerCorrosion in Wet Flue Gas Desulfurization (FGD) Systems January 27-28, 2011


FGD Absorber Vessel

• Concern With Corrosion Of Interior Of Vessel

• Corrosion Primarily Limited To Slurry Region

• Question Is How Best To Examine Large Surface Area Of Absorber Vessel For Corrosion

• Any Concerns With Corrosion Of Floor?


Interior Of Absorber Vessel

• Access To Interior Is Good After Cleaning

• Consider Real-Time Digital Radiography– Detector Inside– Source Outside– Synchronous Motion For Each

• Consider Ultrasonic Guided Waves


Real-Time Radiography

• Detector Could Be Suspended From Above Similar To Boiler Waterwall System

• X-Ray Source Place On Motion Device On Outside

• Synchronous Motion Allows Scanning At ~5 Feet (1.5 Meter) Per Minute


Use Of Digital Radiography

• Suspend Cables From Above In Absorber

• Motorized Motion For Detector Vertical & Horizontal

• White Stand Not Needed For Detector

• Current Source Has Motorized Motion Horizontal Only, With Manual Crank For Vertical

• Could Easily Incorporate Vertical Motion & Manual Lateral Movement


Ultrasonic Guided Waves

• Place Guided Wave Sensors On Outside Of Vessel

• No Cleaning• Guided Waves Directed

Vertically Or Circumferentially• Detection Of Damage Exceeding

2-5% Cross Section• Would Also Detect Various

Geometrical Anomalies– Welds, Attachments, Openings

• Might Be Feasible To Use Monitoring Mode– Sensors In Place & Measure

Changes


Potential Unknowns

• Radiography– Personnel Exclusion Zone Size– Mechanization Mods– May Only Detect Abrupt Changes

• Guided Waves– Affects Of Duplex Steel– Attaching Sensors– Determination Of Non-Damage Signals

• After Baseline Established, Very Easy– May Be Possible To Mount Sensors Vertically At 1 Location &

Examine 360° - 180° Each Direction

agenda corrosion in wet flue gas desulfurization (fgd...

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