Mercury Issues for Coal-Fired Power Plants: Emissions, Fate and Health Effects, Controls George Offen Technical Executive Emissions/Combustion Product

Mercury Issues for Coal-Fired Power Plants: Emissions, Fate and Health Effects, Controls

George OffenTechnical ExecutiveEmissions/Combustion Product Mgmt

with material from Ramsay Chang, Paul Chu, Leonard Levin, Naomi Goodman

Indiana Society of Mining and ReclamationJasper, IndianaDecember 7, 2004

2 Copyright © 2004 Electric Power Research Institute, Inc. All rights reserved.

Regulatory Status

• Two alternative approaches proposed 12/15/03– MACT - compliance by 2008-9

• Bituminous – 2 #/TBtu

• Sub-bit – 5.8 #/TBtu

• Lignite – 9.2 #/TBtu

• New source standards – more stringent

– Cap-and-trade• Co-benefits by 2010, 15 TPY (70% ΔHg by 2018)

• Allocations by states

– Possible to “opt” out in one option

• Final rule delayed until 3/15/05

• Hg rule + Clean Air Interstate Rule Clear Skies Act

• States considering/adopting stringent limits


Mercury Global Anthropogenic EmissionsAnthropogenic Emissions ~ 1/3rd – 1/2 Total Emissions

United States155

U.S. utilities 48South & Central

America194

Europe560

Africa271

Oceania53

rest of North America71

Asia1231

Global total2535 tons per year


U.S. mercury deposition from non-U.S. sources

% contribution by non-U.S. sources, 2004


Annual deposition of mercury for 2004 Base Case

g/m2-y


Annual deposition of mercury for 2020 Cap & Trade Scenario

g/m2-y


Drop in Mercury Exposure by Most-Sensitive Women (child-bearing age, high blood Hg level), 2020 Cap & Trade


How Mercury DEPOSITING in the U.S. Changes If Utility EMISSIONS Change

Total Coal Plant Mercury EMISSIONS, (U.S.) tons/yr

% Difference in Mercury EMISSIONS from Base Case

Total Mercury DEPOSITION in the U.S. [wet + dry, Hg(tot)], T/yr, ALL MERCURY SOURCES

% Difference in all U.S. Mercury DEPOSITION from Base Case

Net Present Value of COSTS to Attain Stated Emissions Levels

CURRENT CONDITIONS (2004 Base Case)

46.6 − 164 −

2020 MACT SCENARIO

30.2 - 35% 156 - 5% $10 billion

2020 CAP & TRADE SCENARIO

14.9 - 68% 153 - 7% $2 billion


Mercury “Basics”

• Mercury emission levels very low– ppb or lb/TBtu levels– ~250 lb/yr for 500 MW unit

• Generally a gas at ESP/fabric filter inlet– Elemental (metallic, Hg0), – Ionic (oxidized, Hg+2), or– Particulate (HgP)

• Typical speciation– Powder River Basin (PRB): 75-90% Hg0

– E. Bituminous: 60-90% Hg+2

• Speciation affects controls and transport• FGD captures only Hg+2

– Some captured Hg+2 may be converted to Hg0 and re-emitted


Indiana Coals < Mercury than all E.Bit* Median = 0.07 ppm or ~5.4 #/TBtu need 63% ΔHg95% = 0.15 ppm need 83% ΔHg

0

10

20

30

40

50

60

70

80

90

100

0 0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.4 0.45

Mercury Concentration (mg/kg)

Perc

entil

e

Eastern Bit. (n = 18,000)

Indiana Bit (n = 1,400)

Source: 1999 EPA ICR

Indiana

All Eastern Bit.

* Also < chlorine


Sorbent Injection

Scrubber

BoilerStack

ESP/FFCoal Cleaning

Additives

SCR, Hg catalyst, corona

Power Plant Mercury Control Options – Overview

Polishing Filter(TOXECON™)

Fixed adsorption structures


SCR + FGD Co-benefits

• SCR – NOx control

• FGD – SO2 control– Also captures Hg+2

• SCRs may increase Hg+2 and improve overall Hg control– Removals of ~80-90+% possible for

bituminous coals

– ~40-60% without SCR

• FGD chemistry may impact Hg+2 to Hg0 conversion “re-emission”

• ~8 power plants with SCR/FGD to be tested in 2004


SCR + FGD Provide Hg Co-benefit on Bituminous Coal Plants (PRB site has baghouse)

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

S11 S2 - 1 S4 - 1 S5 S4 - 2 S10 C5

Site

Hg

Rem

ov

al

(%)

With SCR

Without SCR

PRB


SCR + FGD Likely to Achieve Proposed MACT Limit for Existing Facilities; ? for New Facilities

0.0

0.5

1.0

1.5

2.0

2.5

S4 -1

S4 -2

S4 -3

C5 C6 C7 S11 S10 S2 -1

S5 S2 -2

S2 -3

C8 C9 C10 C1 C2 S7

Site, FGD Design

Hg

Em

iss

ion

s (

lb/T

Btu

)

Proposed MACT for New Bituminous Plants

Proposed MACT for Existing Bituminous Plants FGD Bypass

Venturi Scrubber

Limestone - Forced Oxidation

Limestone - Inhibited Oxidation Mg Lime

Spray Dryer Fabric Filter

PRB


Field Results – ACI Hg Removal w/ ESPs

0

10

20

30

40

50

60

70

80

90

0 5 10 15 20 25 30

Injection Concentration (lb/Macf)

Hg

Rem

ova

l (%

)

Full-Scale Test (Lo S Bit)

Full-Scale Test (Hi S Bit)

Pilot Sites (8)

$3.5M/yr for 500MW

Full-Scale Test (PRB)

Full-Scale Test (ND Lig)

-Which line is correct?-Is this performance sustainable?-What are the impacts?-Are there lower-cost sorbents?


Halogen Additives Improved ΔHg by AC Across SD-BH for Western Coals

0

10

20

30

40

50

60

70

80

90

100

0 1 2 3 4 5 6 7

Injection Rate (lb/M acf)

Hg

Re

mo

va

l (%

)

Stanton CTCPRB 04

Stanton CTClignite 04

Sunflower CTC04

Earlier FGD FieldData

Earlier IAC FieldData

All short-term data (≤ 30 days); many questions!• Corrosion• Secondary emissions


TOXECON™ - An Option to ESP Injection

• Injection between ESP and polishing baghouse– Much less sorbent

– No ash impacts

– $45-55/kW projected

Ash Carbon/Hg


TOXECON™ Long-term Results

86% average removal at injection rate that maintains 1.5 p/b/h


Mercury Measurements

• Ontario Hydro Method

– ~2 hour flue gas sample

– Chemical solutions to capture Hg

– ASTM; used in EPA “ICR” study

• Continuous mercury monitors (CMMs) - also “SCEM”

– Still developmental

– Measurement every 2 to 5 minutes

– Must convert Hg+2 to Hg0 before analyses

• QuickSEMTM – EPRI development

– Basis for EPA “draft” method 324

– Integrated sample over hours to week+

– Uses a solid sorbent (carbon)

– Simpler, more accurate, but not instantaneous readout


Questions?


Indiana Coals Tend to Have Less ChlorineMay produce Less Oxidized Hg? Emissions data?

0

10

20

30

40

50

60

70

80

90

100

0 500 1000 1500 2000 2500 3000 3500 4000

Chlorine Concentration (mg/kg)

Perc

en

tile

Eastern Bit (n = 18,000)

Indiana Bit. (n = 1,400)

Source: 1999 EPA ICR

Indiana

All Eastern Bit.


Sorbent Injection

• Activated carbon injection (ACI)– Hg adsorbs onto carbon capture

by ESP/BH

– Most developed technology

– Variety of carbons

– Potential issues• Ability to extrapolate from few test

sites to full boiler population and fuels

• Can you sell your fly ash?

• Is the ash hazardous waste?

• Impact on ESP performance?

• Baghouse size, bag life?


Sorbent Injection (concl.)

• Chemically-treated carbons new, appear promising– May be most applicable to W.

coals

– Early, short-term tests show 80-90+% ΔHg at ¼ to 1/3rd sorbent injection rate

• Halogen injection into boiler + std. AC ~ performance?

• Same questions as AC + potential release of halogen

• Non-carbon sorbents/reagents being developed– Amended silicates

– Sodium tetrasulfide


0.0

1.0

2.0

3.0

4.0

5.0

6.0

7.0

8.0

6/7 6/8 6/9 6/10 6/11 6/12 6/13 6/14 6/15 6/16 6/17 6/18 6/19 6/20 6/21 6/22 6/23 6/24 6/25 6/26 6/27

Calendar Date

Ave

rage

Mer

cury

Con

cen

trat

ion

, u

g/m

3Hg Emissions Can Be VariableComparison of Hourly and Daily Averages for 1 month

Hourly Averages

Daily Average

Documents

Mercury Issues for Coal-Fired Power Plants: Emissions, Fate and Health Effects, Controls George Offen Technical Executive Emissions/Combustion Product