Experience with Mercury Compliance

Gary Blythe, Katherine Dombrowski, Gwen Eklund, Mandi Richardson

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Presentation Outline

• Overview of the MATS rule • Lessons learned from Mercury compliance/testing

– Bromine addition – FGD co-benefit capture/re-emissions control – PAC injection – Other issues (startup/shutdown, target control levels, coal

variability) • Overview of other relevant rules

– Draft Effluent Limitations Guidelines (ELGs) – Coal Combustion Residues (CCR) rule

• How MATS compliance can impact compliance with these other rules 2

MATS Rule Overview

Emission Limits for Hg, FPM, Acid Gases

Work Practice Standards for

Organics

Notification, Recordkeeping, and

Reporting

Initial and Continuous Compliance

April 16, 2015-April 16, 2016

40 CFR Part 63 Subpart UUUUU (5U) Citations: 63.9980 through 63.10042

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MATS Emission Standards Existing Coal Units, >8,300 Btu/lb

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Pollutant Compliance Options Heat Input Standard Output Standard

Hg Hg 1.2 lb/TBtu 0.013 lb/GWh

Acid Gas HCI or

Acid Gases*

0.002 lb/MMBtu 0.2 lb/MMBtu

0.02 lb/MWh 1.5 lb/MWh

Particulate FPM or

Total Metals ** or

Individual Metals **

0.03 lb/MMBtu 50 lb/TBtu Good Luck!

0.3 lb/MWh 0.5 lb/GWh

*Unit must have FGD and SO2 CEMS **Sb, As, Be, Cd, Cr, Co, Pb, Mn, Ni, Se

LESSONS LEARNED FROM MERCURY CONTROL IMPLEMENTATION

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Hg Emissions (mainly Hg0)

Hg in Coal

Volatilized Hg (mainly Hg0)

Hg Oxidation Across SCR Hg0 Hg+2

Bromide Addition

ACI Hg Oxidation and

Hg Removal Across AH Hg0 Hg+2

Hg in Fly Ash Hg in Gypsum and Wastewater

Hg Removal Across PCD

Removal of Hg+2 Across FGD

Hg0 = Elemental Hg (insoluble in water) Hg+2 = Oxidized Hg (soluble in water)

Hg Oxidation Across SCR, AH, PCD

Hg+2 Removal by FGD

/ACI

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Bromide addition enhances mercury removal of ACI, fly ash, and wFGD by converting Hg0 to Hg+2

Corrosion is most frequently observed bromine balance-of-plant (BOP) effect EPRI Bromine BOP Study – 71 units participating • Fly ash sales - no effects observed • Opacity - increase at one plant with SCR/FF/FGD • FGD effluent - potential areas of concern

– Increase in Hg, Se, Br, brominated organics

• Corrosion – 36 units reported corrosion

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Bromide Addition

36 of 71 surveyed units had corrosion: All fired low-sulfur coals; all but two had air heater corrosion

Location of Corrosion # of Units Reported Corrosion Coal Handling 3 Boiler Tube 1 Air Heater 34 Air Heater Outlet Duct 3 ESP 2 ID Fan 4 FGD 2

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Air heater parts – constructed from carbon steel

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Rotor (axle) Diaphragm (spokes) Two Baskets

Seal

Elements

Diaphragm plate

Cold-end baskets most likely AH part to corrode Air Heater Part # Units Reporting Corrosion Cold-end baskets (plane outlined) 32 Cold-end basket bars 4 Diaphragm plate 2 Cold-end radial seal (attached to each diaphragm plate) 8

Courtesy Alstom Power

Hot-end radial seals

Cold-end radial seals

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Corrosion most likely in coldest parts of air heater; Estimate cold-end metal temperature

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Estimated Average Cold-End Metal Temperature =

Average of Air Inlet and Flue Gas Outlet Temperature

Minimum metal temperatures can be 50°F lower than average → closer to HBr condensation temp

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HBr Condensation Temperature

Some PRB units with low Br have corrosion; Bituminous units not corroding, despite higher Br

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PRB Units Bituminous Units

Units with Corrosion Units with No Corrosion

Minimizing risk of corrosion

• Enamel coating of AH • Minimize bromine released for Hg control • Operational changes to AH

– Monitor air heater temperatures – Pre-heat air – Soot blowing – Move carbon injection downstream of AH

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Measuring Hg oxidation upstream of FGD is important for diagnosing Hg emissions excursions

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Wet FGD Flue gas

Hg2+ = 3

Hg0 = 3

HgT = 3 (nearly all as Hg0)

Flue gas

Hg2+ re-emitted as Hg0

HgT = 6 Hg2+ = 5

Hg0 = 1 Hg2+ captured

Insufficient Hg oxidation by Br

Bromide Addition

Measurements may over-predict Hg oxidation • Methods not validated for use in the presence of Br in flue gas.

– CEMs, App K, 30B traps, speciated sorbent traps, Ontario Hydro

• Upstream of FGD, Hg measurement susceptible to bias – Measure artificially high Hg oxidation, low total Hg – Observed with the commercial Hg CEMS, speciated sorbent traps

• Downstream of FGD, measurement bias less likely – Br is scrubbed by FGD

• Common observations in bromide test programs – High Hg oxidation measured at FGD inlet – Yet, Hg emissions measured at FGD outlet remain high – Plants assume Hg re-emissions, but measurement bias is more likely

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FGD Co-benefit Capture of Hg

• Oxidized mercury (Hg2+) is scrubbed at high efficiency, elemental mercury (Hg0) is insoluble and generally not scrubbed

• Once scrubbed by the flue gas, oxidized mercury can be chemically reduced in the scrubber back to the elemental form – Elemental mercury formed is released into the stack flue gas

• The Oxidation-Reduction Potential (ORP) at which the FGD absorber operates has a major role in whether re-emissions occur – ORP represents a new parameter that should be monitored in

scrubbers used for co-benefit mercury capture

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Effect of ORP on Percent of Hg in Absorber Slurry Remaining in Liquor

• Forced oxidation, low ORP – little Hg remains in liquor – Re-emission typically

minimal or none

• Forced oxidation, high ORP – most of Hg remains in liquor – Significant re-

emission levels likely

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0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

-100 0 100 200 300 400 500 600 700

% o

f Mer

cury

in S

lurr

y Li

quor

ORP, mV

Forced Oxidation Systems Inhibited/Low Oxidation Systems

Effects of Load Cycling on ORP, Re-emissions

High Load

• Sulfur input to scrubber is near design level

• O2 in flue gas low • Operating near design levels

for L/G ratio, forced oxidation air O:SO2 ratio

• ORP should be in the low range

• Re-emissions are hopefully minimal

Low Load • Sulfur input to scrubber is

much lower than design level

• O2 in flue gas is high • L/G ratio is much higher

than design level – Increased O2 pickup from flue

gas • O:SO2 ratio is higher than

design level • ORP increases • Re-emissions occur

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How to Deal with Re-emissions

• Tune scrubber operation to lower ORP into ideal range – Decrease oxidation air rate, particularly at low load – Run fewer recycle pumps, particularly at low load – Increase pH set point slightly, if possible

• Use re-emission additives – Additives that contain reduced sulfur (organic or inorganic

base) • Work by producing an insoluble mercuric sulfide precipitate • Are only effective at lower ORP • Additives themselves can lower ORP

– PAC addition to scrubber slurry • Work by adsorbing Hg from FGD slurry liquor • Do not impact ORP, performance not affected by ORP

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Powdered Activated Carbon Injection Startup Issues • Equipment corrosion

– In silo – Feeder hoppers and valves – Transport headers

• Poor activated carbon distribution – Vendors should model gas/particle flow through entire

injection system, not just at lance injection point • Model should be rigorous enough to model powdered

carbon as a second, solid phase instead of as a gas – Particulate control device hopper sampling may be

required to determine carbon distribution 21

Coal Hg Variation Impacts on Hg Concentrations in Flue Gas – Example Data

Effects of Coal Hg Variation Case Study

• Two large coal-fired units on East Coast; equipped with SCR, ESP, wet scrubbers

• Plant tested a low Hg Columbian coal, among others, to see which would bring units into Hg compliance with co-benefit capture – When firing Columbian coal (0.05 ppm Hg) stack Hg emissions were

<1 lb/Tbtu – Plant signed multi-year contract for supply of this coal as a MATS

compliance strategy • Later shipments of Columbian coal contain up to 0.08 ppm

Hg – Units cannot achieve MATS compliance with the higher Hg coal – Plant now has a large stockpile of high Hg coal they cannot fire and

maintain compliance – Plans to test Br addition and/or re-emission additives

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Coal Hg Variation Case Study (cont’d)

• This is a good example of how coal Hg variations can cause MATS compliance issues

• It’s an even better example of the risk of taking an “empirical” approach to achieving MATS compliance: – Tried control approaches for short periods (~1 week each in

this case) – Only measured stack mercury concentrations, picked whatever

worked • Did not conduct upstream measurements to determine Hg removal

with fly ash, to measure Hg oxidation at FGD inlet, or to detect if re-emissions were occurring

• Now having to test additional approaches while trying to maintain compliance

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Unit Startup Impacts on Mercury Measurement

• Mercury emissions can spike during startup • Utilities have concerns about how these spikes impact

the 30-day rolling average • Separate trap monitoring systems have been installed at

many plants to supplement the compliance traps (which may be weekly runs) – Measure the impact of spikes in mercury emissions during

startup

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What Level to Control Stack Hg to Ensure MATS Compliance?

Normal Stack Hg Control Level, lb/TBtu

Uncontrolled Hg at Stack, lb/TBtu

Hours of Upset (no Hg Control) allowed to stay below 1.2 lb/Tbtu in 30-day Average

1.1 8.0 10

1.0 8.0 20

0.9 8.0 30

0.8 8.0 40

0.7 8.0 49

0.6 8.0 58

0.5 8.0 67

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OTHER RELEVANT REGULATIONS/DRAFT REGULATIONS

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COMPANY CONFIDENTIAL

Draft Effluent Limitation Guidelines – History

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New Final Action Date: September 2015, Permit Implementation beginning ~ late 2018

COMPANY CONFIDENTIAL

Consider all the Options (Existing) – EPA Preferred

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Current Conditions

Option 3a Option 3b Option 3 Option 4a

FGD Wastewater (including gypsum wash water)

Included as Low Volume Wastes T = Impoundment L: TSS & Oil and Grease

BPJ determination (technology and limits)

T: Chemical Precipitation(CP) a and Biological Treatment (BT) for facilities ≥ 2000 MW scrubbed capacity; BPJ determination <2000 MW L: Hg, As, Se and nitrate-nitrite ≥ 2000 MW scrubbed capacity; BPJ determination <2000 MW

T: CPa and BT L: Hg, As, Se and nitrate-nitrite

Fly Ash Transport Water

T: Impoundment L: TSS & Oil and Grease

T: Dry handling b L: Zero discharge

Bottom Ash Transport Water

T: Impoundment L: TSS & Oil and Grease

T: Impoundment L: Equal to BPT (no change from current rule)

T: Dry handling/ closed loop c for units >400 MW; Impoundment ≤ 400 MW L: Zero discharge for units >400 MW; Equal to BPT ≤ 400 MW

Increasing Pollutant Reduction

Must meet the limits established, do not need to use the preferred technology

COMPANY CONFIDENTIAL

Consider all the Options (Existing) – EPA Preferred

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Current Conditions Option 3a Option 3b Option 3 Option 4a

Coal Combustion Residual Leachate

Included as Low Volume Wastes T = Impoundment L: TSS & Oil and Grease

T: Impoundment L: Equal to BPT

(no change from current rule)

FGMC Wastewater (Activated Carbon Injection)

Included as Low Volume Wastes but common practice is no discharge

T: Dry handling b L: Zero discharge (current practice)

Nonchemical Metal Cleaning Wastes*

Included in Metal Cleaning Wastes BPT for Cu and Fe

T: CP L: Cu, Fe

Increasing Pollutant Reduction

*Nonchemical metal cleaning wastes exemption: if previously permitted as LVW without copper and iron limits (up to 27% of plants)

Activated carbon injection upstream of FGD should not be subject to FGMC Wastewater limits

COMPANY CONFIDENTIAL

Comparison of Proposed Limits to Existing Limits

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FGD Wastewater (all dischargers; approximately 311 plants) 1982 - Daily Max 1982 - Monthly

Average Daily Max Monthly Average

Arsenic, total 8 µg/l 6 µg/l

Mercury, total 242 ng/l 119 ng/l

Selenium, total 16 µg/l 10 µg/l

Nitrate/Nitrite as N 0.17 mg/l 0.13 mg/l

Total Suspended Solids

100.0 mg/l 30.0 mg/l 100.0 mg/l 30.0 mg/l

Oil and Grease 20.0 mg/l 15.0 mg/l 20.0 mg/l 15.0 mg/l

Combustion Residual Leachate (“new” leachate only) 1982 - Daily Max 1982 - Monthly

Average Daily Max Monthly Average

Arsenic, total 8 µg/l 6 µg/l

Mercury, total 242 ng/l 119 ng/l

Total Suspended Solids

100.0 mg/l 30.0 mg/l 100.0 mg/l 30.0 mg/l

Oil and Grease 20.0 mg/l 15.0 mg/l 20.0 mg/l 15.0 mg/l

Previously only limited for BPT as Low Volume

Wastes

Previously only limited for BPT as Low Volume Wastes

Final CCR Rule – Preamble: Pages 1 (21302) to 167 (21467) – Final Rule: Pages 167 (21467) to 201 (21501)

Perspective from the EPA on the Preamble “The final definition makes extremely clear the impoundments that are covered by the rule, so an owner or operator will be able to easily discern whether a particular unit is a CCR surface impoundment.” [Final CCR Rule, Page 57 (21357)]

EPA’s CCR Rule

• Comprehensive set of requirements for the safe disposal of coal combustion residuals (CCRs) in landfills and surface impoundments under subtitle D of RCRA, based on environment and public health studies; the rule also addresses beneficial use.

• These regulations address the risks from coal ash disposal -- leaking of contaminants into ground water, airborne fugitive dust, and failures of coal ash surface impoundments.

• The CCR rule sets out recordkeeping and reporting requirements as well as the requirement for each facility to establish and post specific information to a publicly-accessible website.

CCR Rule Compliance – Potential Requirement Elements to Consider Increased Hg in Impoundments, Landfills & Use

Requirement Deadline to Comply Description of Requirement

Air Criteria (257.80) October 19, 2015 - Prepare a fugitive dust control plan

Run-on & Run-off Controls (257.82)

October 17, 2016 - Prepare an initial run-on and run-off control plan

Groundwater Monitoring and Corrective Action (257.90-257.98)

October 17, 2017 - Install the groundwater monitoring system; develop the groundwater sampling & analysis program; initiate the detection monitoring program; and begin evaluating the groundwater monitoring data for statistically significant increases

Closure and Post-Closure Care (257.103-257.104)

October 17, 2016 - Prepare written closure and post-closure plans

Beneficial Use - keep records to show that that environmental releases to groundwater, surface water, soil and air will be at or below relevant regulatory and health-based benchmarks for human and ecological receptors during use.

Groundwater Monitoring and Corrective Action

Applicability • All CCR landfills (except inactive landfills that are not subject to the CCR Rule)

• All surface impoundments and lateral expansions (except inactive surface impoundments that will close within 36 months of the Rule)

Overview • Within 30 months of publication

- Install groundwater monitoring system - Conduct 8 monitoring events (must account for seasonal and spatial variability)

• Semiannual detection monitoring can trigger assessment monitoring (one statistical failure of Appendix III)

• If Assessment monitoring identifies presence of Appendix IV constituent above Groundwater Protection Standards (GWPS), then an Assessment of Corrective Measure is triggered.

• Leads to Implementation of Corrective Action Program

Install GW Monitoring

System

Detection Monitoring

Assessment Monitoring

Corrective Measures

Corrective Action Program Appendix III Constituents

Boron

Calcium

Chloride

Fluoride

pH

Sulfate

Total dissolved solids (TDS)

Appendix IV Constituents Antimony Arsenic Barium Beryllium Cadmium Chromium Cobalt Fluoride Lead Lithium Mercury Molybdenum Selenium Thallium Radium 226 and 228 combined

Effects of MATS Compliance on ELG Compliance

• Br Addition – – Additional Br in wastewater may trigger tri-halomethane concerns for

downstream municipal water supplies – Possible increase in Se in FGD wastewater

• PAC Injection upstream of Particulate Control Device – – No significant impacts, particularly if handling fly ash dry

• Re-emission additives – reduced sulfur additives – – For high ORP FGD systems, lower ORP w/additive can benefit Se oxidation,

additive can lower liquor-phase Hg – For low ORP FGD systems, very low liquor-phase Hg may be achieved, but

possible increases in liquor-phase Se and As • PAC injection to slurry for re-emission control –

– Lower Hg in FGD liquor (not as low as with reduced-sulfur additives) and lower peroxodisulfate concentrations (affects nitrate and Se removal)

– No impact on ORP, liquor Se or As

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Possible CCR Rule Risks from MATS Compliance

• Higher mercury concentrations in CCR impoundments, CCR landfills or CCRs for beneficial uses

• If EPA’s regulatory limits for mercury in groundwater, surface water, soil or air emissions are exceeded, closure and corrective action may be triggered (not likely based on AECOM experience)

• Higher mercury concentrations of mercury or the additional constituents added by mercury control technology (e.g., bromine or carbon) may affect relevant byproduct specifications, regulatory standards or design standards – The only evidence of this to date for AECOM has been Hg

concentration limits for FGD gypsum used for wallboard production