Multimedia Impacts of
Halogen Injection for
Mercury Control in CoalFired Boilers
Connie Senior, Ken Baldrey,
Will Morris, Sharon Sjostrom
Presented at EUEC
January 30, 2012
ADA: Innovate, Develop, Commercialize
Motivation for This Presentation
• Adding halogens increases Hg oxidation, native
capture, and removal efficiency of ACI
• You’ll hear a lot about halogens at EUEC…
• …sometimes perspective is useful
Why Add Halogens?
• Adding halogens to fuel or flue gas:
– Halogen content of US coals varies widely
http://ugs.utah.gov/emp/mercury/index.htm
Why Add Halogens?
• Adding halogens to fuel or flue gas:
– Halogen content of US coals varies widely
• Bromine content typically 1% to 4% of chlorine content
Eastern Interior (Illinois Basin)
60
Br, ug/g
50
40
y = 0.0482x
R² = 0.1319
30
20
10
0
0
Source: USGS COALQUAL database
50
100
150
Cl, ug/g
200
250
300
Why Add Halogens?
• Adding halogens to fuel or flue gas:
HX in gas, ppmv, 3% O2 dry
– 500 ug/g Cl in coal = ~40 ppmv HCl in flue gas
– 500 ug/g Br in coal = ~17 ppmv HBr in flue gas
100
80
HCl
60
HBr
40
20
0
0
200
400
600
800
Halogen in Coal, µg/g dry
1,000
Why Add Halogens?
– Halogen content of
US coals varies
widely
– Oxidation of Hg and
capture of Hg on fly
ash enhanced with
additions of
halogens, like Cl and
Br
100
NaCl
MgCl2
CaCl2
HCl
CaBr2
%Oxidized Hg at Air Preheater
Outlet
• Adding halogens to
fuel or flue gas:
Halogen addition at various
full-scale PRB boilers
80
60
40
20
0
0
500
1000
1500
2000
Halogen in Coal, ppmw dry
Source: Dombrowski et al., 2006
2500
3000
Why Add Halogens?
• Adding halogens to
fuel or flue gas:
80%
Hg Removal across FGD
– Halogen content of US
coals varies widely
– Oxidation of Hg and
capture of Hg on fly
ash enhanced with
additions of halogens,
like Cl and Br
– Many plants’ APCDs
can take advantage of
native capture
100%
60%
40%
20%
0%
10
100
1,000
Coal Chlorine, ppm dry
Source: 1999 ICR
10,000
Why Add Halogens?
• Adding halogens to activated carbon increases
the ability to capture elemental Hg in lowhalogen flue gas (subbituminous or lignite)
100
Brominated Carbon
90
% Vapor-phase Hg Removal
80
NonBrominated
Carbon
70
60
50
40
Meramec 2, Darco Hg-LH
Meramec 2, Darco Hg
Stanton 1, Darco Hg-LH
Stanton 1, B-PAC
Stanton 1, Darco Hg
30
20
10
0
0
2
4
6
Sorbent (lb/MMacf)
8
10
Summary: Why Add Halogens?
• Adding halogens to fuel or flue gas:
– Halogen content of US coals varies widely
– Oxidation of Hg and capture of Hg on fly ash
enhanced with additions of halogens, like Cl and Br
– Many plants’ APCDs can take advantage of native
capture
• Adding halogens to activated carbon increases
the ability to capture elemental Hg in lowhalogen flue gas
How Effective Are Halogens?
Removal of Hg across FGD
• Halogens increase 100%
oxidized mercury:
Br more effective 80%
than Cl
60%
• Increased Hg
40%
removal across
scrubbers
Dry FGD, FF
Wet FGD
20%
0%
0%
20%
40%
60%
Fraction Hg2+ at Inlet
Source: DOE/EPRI sampling campaigns
80%
100%
How Effective Are Halogens?
Total Hg Removal (coal-to-stack)
• Halogens increase
oxidized mercury:
Br more effective
than Cl
• Increased Hg
removal across
scrubbers
Monticello: PRB/lignite,
ESP, wet FGD
100%
Chlorine addition
Bromine injection
90%
80%
70%
60%
50%
40%
30%
20%
10%
0%
1
10
100
1000
Halogen in coal, ug/g
10000
How Effective Are Halogens?
100
80
Hg Removal
• Halogens increase
oxidized mercury:
Br more effective
than Cl
• Increased Hg
removal across
scrubbers
• Halogens increase
effectiveness of
PAC
60
Plant Hardin: SCR/SDA/FF
KNX + 0.14 lb/MMacf PAC
KNX
40
20
0
0%
20%
40%
Percent recommended KNX rate
Source: DOE/EPRI sampling campaigns
60%
Effect of SCRs on Added Halogens
• Catalysts drive reactions toward equilibrium
– Results will be catalyst-specific
• Adding Br to the fuel makes the shift to Hg2+ take
place at higher temperatures (than Cl)
100%
%Oxidized Hg
80%
Equilibrium
modeling of
Plant Miller data
of Berry et al.
60%
Baseline
+ 3 ug/g Br
+ 18 ug/g Br
+ 33 ug/g Br
+ 328 ug/g Br
40%
20%
0%
600
700
800
o
Temperature, F
900
Effect of SCRs on Added Halogens
• Catalysts drive reactions toward equilibrium
– Results will be catalyst-specific
• Adding Br to the fuel makes the shift to Hg2+ take
place at higher temperatures (than Cl)
Hg0, ug/dNm3
9
8
SCR Inlet
7
SCR Outlet
6
Equilibrium
5
4
3
2
1
0
0
100
200
300
Added Br, ug/g coal equivalent
400
Comparison of
Plant Miller data
of Berry et al.
with calculated
equilibrium
Effect of SCRs on Added Halogens
– Results will be
catalyst-specific
– Subbituminous
(low-chlorine)
coals only
Equilibrium at 720oF
4.5
4.0
3.5
Hg0, ug/dNm3
• Bromine is more
efficient (equal
mass basis) than
chlorine at
oxidizing Hg
across SCRs
Subbituminous Coals
3.0
2.5
2.0
1.5
1.0
Bromine
0.5
Chlorine
0.0
0
100
200
300
Halogen, ug/g coal equivalent
400
Fate and Impacts of Halogens
• What are the potential impacts of halogen
addition on the boiler, APCDs, and emissions?
–
–
–
–
Corrosion
Fly ash
Stack emissions
Scrubber interactions
Fuel
Stack
Boiler
Burners
Coal
Pulverization
Air
SCR Heater
Particulate
SO2 Induced
Collector Scrubber Draft
Fan
Coal
Supply
Corrosion in Flue Gas
• Chlorine corrosion in furnaces can occur for very
high levels of chlorine in coal (> 2000 µg/g)
– Bromine addition at much lower concentrations
Corrosion loss, mm
• Indirect evidence that HBr
might be more corrosive
than HCl at flue gas
temperature
• No direct comparison, but
HBr corrosion higher than
baseline (no HBr) in
simulated flue gas
(6-month study)
0.12
Baseline
0.1
51 ppmv HBr
0.08
0.06
0.04
0.02
0
0
100
200
300
Temperature, oF
Zhuang et al., 2009
400
Bromine Addition: Fly Ash Impacts
8
7
6
5
4
3
2
1
0
11/1/05
Br in fly ash
Br injected
350
300
Br addedm µg/g coal
Br, µg/g
• Bromine additive or brominated PAC results in
increase in Br in fly ash
• Example: Br injection at Monticello (C-ESP)
250
200
150
100
50
0
11/15/05
11/29/05
12/13/05
Bromine injection at Monticello (EERC, URS data)
Bromine Addition: Fly Ash Impacts
Br in Fly Ash
Fly Ash, µg/g
12
Br in Leachate
10
8
0.4
0.3
0.2
6
4
0.1
2
0
0.0
0
20
40
60
Added Br, µg/g coal equivalent
Dombrowski et al., 2008
Leachate, mg/L
14
• Bromine additive or brominated PAC results in
increase in Br in fly ash
• Example: Br injection at Plant Miller (PRB, C-ESP)
• According to the authors:
• Hg concentration in fly ash
didn't increase with Br
injection
• 1% of Br captured by fly ash
• 50% of Br on fly ash leached
in SPLP test
Chlorine Emission from APCDs
Source: 2010 ICR
Bromine Emission from APCDs
PIPP
FF
Meramec
C-ESP
Boiler 1
C-ESP
Boiler 2
C-ESP
Boiler 3
C-ESP
0%
50%
100%
Percent of added halogen emitted in stack
All boilers are pulverized coal, burning subbituminous coal
Brominated
PAC injection
Fuel
addition
Chlorine Emission from APCDs
Source: 2010 ICR
Halogens in Wet Scrubbers
• Adding halogens (Cl or Br) increases oxidized Hg,
which increase capture of Hg in scrubber
• Wet FGD scrubbers remove halogens efficiently
– Average Cl removals for wet FGDs (2010 ICR): 81% for
subbituminous, 97% for bituminous
– Removal of Br at Plant Miller wet FGD: 94-96%
(Dombrowski et al., 2008)
• Halogens build up in wet scrubber liquor
Halogens in Wet Scrubbers
• Halogens build up in wet scrubber liquor…
slowly, depending on scrubber design
Hg in FGD liquor
Br injected
350
300
400
Br addedm µg/g coal
Br, mg/L, Hg, µg/L
500
Br in FGD liquor
250
300
200
200
150
100
100
0
11/1/05
50
0
11/15/05
11/29/05
12/13/05
Bromine injection at Monticello (EERC, URS data)
Halogens and Wet Scrubbers
• Increased Cl, Br concentration in scrubber liquor
can decrease Hg re-emission
• Recent observations (Air Quality VIII) that Br
addition to the fuel increases Se in scrubber liquor
Data from bituminous site with C-ESP, wet FGD
Se in fly % Se capture Se in FGD
ash, µg/g by fly ash liquor, µg/L
Baseline
24
70%
300
Br addition
10
20%
4900
(Dombrowski et al., 2011)
– Less uptake of Se by fly ash means more Se enters
FGD
Summary
• Halogen fuel/flue gas additives OR halogenated PAC
• Where do halogens go?
• Some removal in
particulate control
devices
• Efficient removal in FGDs
• Br is “new kid on the
block” – information
needed:
Fuel
Stack
Emission
Halogen
Injection
Boiler
Stack
SCR Air
Heater
Burners
Halogenated
Carbon
Injection
• Corrosion
• Multi-media fate
Coal
Pulverization
• Trace metal interactions
Particulate
SO 2 Induced
Collector Scrubber Draft
Fan
Fly
Ash
Coal
Supply
Scrubber
Blowdown
Questions?
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