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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
3 Copyright © 2004 Electric Power Research Institute, Inc. All rights reserved.
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
4 Copyright © 2004 Electric Power Research Institute, Inc. All rights reserved.
U.S. mercury deposition from non-U.S. sources
% contribution by non-U.S. sources, 2004
5 Copyright © 2004 Electric Power Research Institute, Inc. All rights reserved.
Annual deposition of mercury for 2004 Base Case
g/m2-y
6 Copyright © 2004 Electric Power Research Institute, Inc. All rights reserved.
Annual deposition of mercury for 2020 Cap & Trade Scenario
g/m2-y
7 Copyright © 2004 Electric Power Research Institute, Inc. All rights reserved.
Drop in Mercury Exposure by Most-Sensitive Women (child-bearing age, high blood Hg level), 2020 Cap & Trade
8 Copyright © 2004 Electric Power Research Institute, Inc. All rights reserved.
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
9 Copyright © 2004 Electric Power Research Institute, Inc. All rights reserved.
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
10 Copyright © 2004 Electric Power Research Institute, Inc. All rights reserved.
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
11 Copyright © 2004 Electric Power Research Institute, Inc. All rights reserved.
Sorbent Injection
Scrubber
BoilerStack
ESP/FFCoal Cleaning
Additives
SCR, Hg catalyst, corona
Power Plant Mercury Control Options – Overview
Polishing Filter(TOXECON™)
Fixed adsorption structures
12 Copyright © 2004 Electric Power Research Institute, Inc. All rights reserved.
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
13 Copyright © 2004 Electric Power Research Institute, Inc. All rights reserved.
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
14 Copyright © 2004 Electric Power Research Institute, Inc. All rights reserved.
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
15 Copyright © 2004 Electric Power Research Institute, Inc. All rights reserved.
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?
16 Copyright © 2004 Electric Power Research Institute, Inc. All rights reserved.
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
17 Copyright © 2004 Electric Power Research Institute, Inc. All rights reserved.
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
18 Copyright © 2004 Electric Power Research Institute, Inc. All rights reserved.
TOXECON™ Long-term Results
86% average removal at injection rate that maintains 1.5 p/b/h
19 Copyright © 2004 Electric Power Research Institute, Inc. All rights reserved.
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
20 Copyright © 2004 Electric Power Research Institute, Inc. All rights reserved.
Questions?
21 Copyright © 2004 Electric Power Research Institute, Inc. All rights reserved.
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.
22 Copyright © 2004 Electric Power Research Institute, Inc. All rights reserved.
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?
23 Copyright © 2004 Electric Power Research Institute, Inc. All rights reserved.
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
24 Copyright © 2004 Electric Power Research Institute, Inc. All rights reserved.
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
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