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Methodology for Assessing FGD Corrosion Risk for Bromine-based Mercury Control Technologies Gary Blythe and Ben Bayer, URS Corporation John Grocki, Advantage Resources Consulting, LLC Casey Smith, Lower Colorado River Authority

Methodology for Assessing FGD Corrosion Risk for Bromine ... 2014/Methodology for... · 3 Methodology for Assessing FGD Corrosion Risk for Bromine-based Mercury Control Technologies

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Page 1: Methodology for Assessing FGD Corrosion Risk for Bromine ... 2014/Methodology for... · 3 Methodology for Assessing FGD Corrosion Risk for Bromine-based Mercury Control Technologies

Methodology for Assessing FGD Corrosion Risk for Bromine-based Mercury Control Technologies

Gary Blythe and Ben Bayer, URS Corporation

John Grocki, Advantage Resources Consulting, LLC

Casey Smith, Lower Colorado River Authority

Page 2: Methodology for Assessing FGD Corrosion Risk for Bromine ... 2014/Methodology for... · 3 Methodology for Assessing FGD Corrosion Risk for Bromine-based Mercury Control Technologies

2

Methodology for Assessing FGD Corrosion Risk for Bromine-based Mercury Control Technologies

• LCRA was considering technologies for MATS Hg control

compliance at the Fayette Power Project station

–Three PRB-fired units, 450-610

gross MW, C-ESP, wet FGD

–Native Hg oxidation ~50%

• Candidate technologies were

tested at full scale in 2011:

–Br addition with coal

–Injection of brominated powdered activated carbon (PAC)

–Br addition with coal plus injection of non-Br PAC

Background

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Methodology for Assessing FGD Corrosion Risk for Bromine-based Mercury Control Technologies

• Potential corrosion in bunkers, coal feeders

• Air heater basket corrosion

• Increased pitting and/or crevice corrosion of wet FGD alloys of construction

–Station operates with zero liquid discharge

–Units 1 and 2 FGD use mostly Stebbins Tile and C-276; some lesser alloys in wetted areas

○ Closed-loop water balance

–Unit 3 FGD uses 316L with Potential Adjustment Protection, 317 LM, Alloy 2205

○ Relatively open-loop water balance

–Large reclaim water system ties the FGD systems together

○ Cl- purge water from Unit 3 used as makeup for Units 1 and 2

Balance-of-Plant Impact Concerns for Bromine-based Technologies

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4

Methodology for Assessing FGD Corrosion Risk for Bromine-based Mercury Control Technologies

• Inventory of water at station and closed water loop

on Units 1 and 2 FGD make testing for steady-

state Br concentrations impractical

–Months of testing would be required

• Substantial industry experience with Cl- and FGD

alloys, but little experience

with Cl-/Br- mixtures to

determine safe limits

Technical Issue – How to Assess Increased Risk to FGD Alloys from Br-based Hg Controls

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Methodology for Assessing FGD Corrosion Risk for Bromine-based Mercury Control Technologies

• Developed spreadsheet-based mass balance tool

–Process flow diagrams, water balance, Cl and Br balances

• LCRA data available to develop tool:

–Multiple years of coal data

–Existing station-wide water balance

○ But represented annual averages; not tied to specific coal, or unit operating conditions

–Measurements of Br in FGD inlet flue gas during 2011 Hg control option testing

–Process water Cl- and Br- concentration data collected over several months (summertime drought conditions)

–However, did not have Br in coal or makeup water

Technical Approach – FGD Water/Halide Mass Balance + Metallurgical Evaluation

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6

Methodology for Assessing FGD Corrosion Risk for Bromine-based Mercury Control Technologies

• Established baseline:

–Adapted station water balance to spreadsheet

–Converted average flows to process-based rates where possible (based on unit load, coal S, etc.)

–Used plant process water halide data to develop Cl-, Br- balances (educated guess on coal, makeup water Br-)

–Adjusted process flow diagram, flow rates to achieve good closures

• Developed predictive balances for Hg control conditions

–Used 2011 Hg control test data for future Br- input to FGD

–Let mass balance spreadsheets predict steady-state Cl-, Br- in FGD systems

Part 1: Developing Balance Cases

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Methodology for Assessing FGD Corrosion Risk for Bromine-based Mercury Control Technologies

Example Water Balance Process Flow Diagram

173 0

143

2

70

4 7

2

173 310

3

15

109 2

146

22 81

22 3

0

88% closure 100% closure

3

28 0

122

451 229 0

0

4

100% 170 86

321 33 closure 0

33

100% closure 108

136

100% closure

142 11 1 0

86 98

100% closure 58

432 0

11

0 36

3 27

54 76

328 38

51 12

31

43 41

95% closure

5 63 57

62 2

LS SYSTEM FLUSH FROM RECIRC C 0

WATER SUPPLY

MISTELIMINATORS

ABSORBERWASHDOWN

LIMESTONE PREP

PUMP & AGITATORSEALS

UNIT #3 FGDSYSTEM

UNIT #2 FGDSYSTEM

UNIT #1 FGDSYSTEM

THICKENER

EVAPORATIONTO ATM.

FILTER FEED TANK C

FILTER FEED TANK B

VACUUM FILTER

RECIRC WATER TANK B

RECIRC WATER TANK C

RECLAIM WATER SYSTEM

MISC. INFLOWS

GYPSUMHYDRATION

EVAPORATIONTO ATM.

EVAPORATIONTO ATM.

GYPSUMHYDRATION

GYPSUMHYDRATION

GYPSUM TO COMBUSTION

BYPRODUCTS LANDFILL

FROM CBL

EVAPORATIONTO ATM.

SPRAY EVAPORATION TO ATM.

SEWAGETREATMENT

ASH TRUCK WASHDOWN/ SUPPPRESSION (ASH)

RAIN

RAIN

EVAP.

WATER SUPPLY

PLANT COOLINGWATER

LIMESTONE PREP

WASHDOWN

DEWATERING AREA

WASHDOWN

RAIN VIA U1 & U2 ASH UNLOADING

RAIN

U3 FLYASHTRANSPORT WASHDOWN

U3 BOILERSEAL SYSTEM

U3 BOILERSUMP

U1 & U2 BOILERSEAL SYSTEMS

U1 & U2 ASH AREA SUMPS

DUST SUPPRESSION

(COAL)

WATER SUPPLY

WATER SUPPLY

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8

Methodology for Assessing FGD Corrosion Risk for Bromine-based Mercury Control Technologies

Example Br Balance Process Flow Diagram

0.2 0.0

1.0

0.01

0.1

0 0.0

0.0

0.2 0.0

0.0

0.2 0.1

0.1 0.0

2.1

0.2 2.0

0.3 0.0

0.0

88% closure 111% closure

COAL 0.8 0.0

9.7 0.0

46.6

0.0 1.6 0.0

COAL 1.2

0.0

0.0

101% 0.0

0.4 16.3 closure 0

0.2

88% closure 34.1 0.6

16.8

101% closure

17.6 0.0 34.0 0.0

0.6 0.0

102% closure 0.0

0.0 0.0

COAL 1.1 3.9

0 0.0

0.0 0.2

0.4 0.1

0.4 20.3

0.4 0.1

0.2

0.1 0.0

105% closure

0.0 0.0 0.1

0

0.0 0.1

WATER SUPPLY

MISTELIMINATORS

ABSORBERWASHDOWN

LIMESTONE PREP

PUMP & AGITATORSEALS

UNIT #3 FGDSYSTEM

UNIT #2 FGDSYSTEM

UNIT #1 FGDSYSTEM

THICKENER

EVAPORATIONTO ATM.

FILTER FEED TANK C

FILTER FEED TANK B

VACUUM FILTER

RECIRC WATER TANK B

RECIRC WATER TANK C

RECLAIM WATER SYSTEM

MISC. INFLOWS

GYPSUMHYDRATION

EVAPORATIONTO ATM.

EVAPORATIONTO ATM.

GYPSUMHYDRATION

GYPSUMHYDRATION

COMBUSTION BYPRODUCTS LANDFILL

FROM CBL

EVAPORATIONTO ATM.

SPRAY EVAPORATION TO ATM.

SEWAGETREATMENT

+

ASH TRUCK WASHDOWN/ SUPPPRESSION (ASH)

RAIN

RAIN

EVAP.

WATER SUPPLY

LIMESTONE PREP

WASHDOWN

DEWATERING AREA

WASHDOWN

RAIN VIA U1 & U2 ASH UNLOADING

RAIN

U3 FLYASHTRANSPORT WASHDOWN

U3 BOILERSEAL SYSTEM

U3 BOILERSUMP

U1 & U2 BOILERSEAL SYSTEMS

U1 & U2 ASH AREA SUMPS

DUST SUPPRESSION

(COAL)

PLANT COOLINGWATER

WATER SUPPLY

WATER SUPPLY

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Methodology for Assessing FGD Corrosion Risk for Bromine-based Mercury Control Technologies

• Established baseline

–Materials of construction of all FGD components

–Operating history (pH, Cl- conc., etc.)

–Current condition

○ Schedule did not allow for assessment inspections

–Develop Cl- limits for existing materials

• Estimated Br- effects on materials

–Limited data available for FGD conditions

–Relative effects of Br- vs. Cl- are alloy specific

○ Steen, et al. (short-term pitting potential measurements)

○ Sherlyn (defined a critical temperature which impacts relative Br-

vs. Cl- corrosivity, and which correlates with PREN values)

Part 2: Predicting Br- Impacts on FGD Materials

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Methodology for Assessing FGD Corrosion Risk for Bromine-based Mercury Control Technologies

• Developed alloy-specific halide relationships:

[Total Halide] = [Cl-] + X * [Br-]

–X establishes the relative weighting of Br- versus Cl-

concentrations on potential for pitting and crevice

corrosion

–X can vary from alloy to alloy

–Total Halide limits are then set using industry experience

with Cl- for each alloy

–With limited data available, considerable professional

judgment was required to establish X values

Part 2: Predicting Br- Impacts on FGD Materials (continued)

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Methodology for Assessing FGD Corrosion Risk for Bromine-based Mercury Control Technologies

• Total Halide limits not represented by single values

–pH, temperature, presence of scale and duration of

exposure all must be considered

–All of these variables impact recommended time between

component inspections

–Must consider the probability of simultaneous excursions

of multiple variables outside of “normal” range (e.g., high

Total Halides and low pH)

• Total Halide limits must consider lowest alloy installed

in FGD systems

Part 2: Predicting Br- Impacts on FGD Materials (continued)

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Methodology for Assessing FGD Corrosion Risk for Bromine-based Mercury Control Technologies

Example pH, Temperature, Scaling and Total Halide Relationship

• All parameters in blue - minimal halide

corrosion risk

• One parameter in yellow range –

moderate halide corrosion risk

• One parameter in red or two or more in

yellow – high risk of halide corrosion;

inspect soon

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Methodology for Assessing FGD Corrosion Risk for Bromine-based Mercury Control Technologies

• Units 1 and 2 FGD systems are more sensitive to Hg

control system selection in spite of higher alloys of

construction

–Closed-loop operation leads to elevated Total Halide

concentrations (outside of “blue box”)

• Based on 2011 test data, brominated PAC poses less of a

materials risk than Br addition with coal + non-Br PAC

(@2011 addition rates)

–Future testing with state-of-the-art PAC, optimized addition

rates may change these results

–Mass balances can predict steady-state Total Halogens at

future addition rates

Results

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Methodology for Assessing FGD Corrosion Risk for Bromine-based Mercury Control Technologies

• Implement brominated PAC injection as a near-term MATS compliance technology

–Determine optimal injection rates

–Consider Br with coal plus non-Br PAC later

• Monitor halide concentrations in FGD systems on a bi-weekly frequency, use Cl- and Br- specific analytical methods to apply “X” factor

• Update FGD component inspection frequencies as needed

–Use alloy-specific relationships, and

–Actual experience for Total Halide concentration, pH, temperature, scaling and duration of exposure

Recommendations