multimedia impacts of halogen injection for...

Multimedia Impacts of Halogen Injection for

Mercury Control in Coal-Fired 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

Source: USGS COALQUAL database

y = 0.0482xR² = 0.1319

0102030405060

0 50 100 150 200 250 300

Br, u

g/g

Cl, ug/g

Eastern Interior (Illinois Basin)

Why Add Halogens?

• Adding halogens to fuel or flue gas: – 500 ug/g Cl in coal = ~40 ppmv HCl in flue gas – 500 ug/g Br in coal = ~17 ppmv HBr in flue gas

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100

0 200 400 600 800 1,000

HX in

gas

, ppm

v, 3

% O

2dr

y

Halogen in Coal, µg/g dry

HCl

HBr

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

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20

40

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0 500 1000 1500 2000 2500 3000

Halogen in Coal, ppmw dry

%O

xidi

zed

Hg

at A

ir P

rehe

ater

O

utle

t

NaClMgCl2CaCl2HClCaBr2

Halogen addition at various full-scale PRB boilers

Source: Dombrowski et al., 2006

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

Source: 1999 ICR

0%

20%

40%

60%

80%

100%

10 100 1,000 10,000

Hg

Rem

oval

acr

oss

FGD

Coal Chlorine, ppm dry

Why Add Halogens?

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100

0 2 4 6 8 10

% V

apor

- pha

se H

g R

emov

al

Sorbent (lb/MMacf)

Meramec 2, Darco Hg-LH Meramec 2, Darco Hg Stanton 1, Darco Hg-LHStanton 1, B-PACStanton 1, Darco Hg

• Adding halogens to activated carbon increases the ability to capture elemental Hg in low-halogen flue gas (subbituminous or lignite) Brominated Carbon

Non-Brominated Carbon

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 low-halogen flue gas

How Effective Are Halogens?

• Halogens increase oxidized mercury: Br more effective than Cl

• Increased Hg removal across scrubbers

0%

20%

40%

60%

80%

100%

0% 20% 40% 60% 80% 100%

Rem

oval

of H

g ac

ross

FG

D

Fraction Hg2+ at Inlet

Dry FGD, FF

Wet FGD

Source: DOE/EPRI sampling campaigns




0%

10%

20%

30%

40%

50%

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100%

1 10 100 1000 10000

Tota

l Hg

Rem

oval

(co

al-to

-sta

ck)

Halogen in coal, ug/g

Chlorine additionBromine injection

Monticello: PRB/lignite, ESP, wet FGD




• Halogens increase effectiveness of PAC

Source: DOE/EPRI sampling campaigns

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100

0% 20% 40% 60%

Hg R

emov

al

Percent recommended KNX rate

KNX

KNX + 0.14 lb/MMacf PAC

Plant Hardin: SCR/SDA/FF

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)

0%

20%

40%

60%

80%

100%

600 700 800 900

%O

xidi

zed

Hg

Temperature, oF

Baseline+ 3 ug/g Br+ 18 ug/g Br+ 33 ug/g Br+ 328 ug/g Br

Equilibrium modeling of Plant Miller data of Berry et al.


• 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)

Comparison of Plant Miller data of Berry et al. with calculated equilibrium

0123456789

0 100 200 300 400

Hg0 ,

ug/d

Nm

3

Added Br, ug/g coal equivalent

SCR Inlet

SCR Outlet

Equilibrium


• Bromine is more efficient (equal mass basis) than chlorine at oxidizing Hg across SCRs – Results will be

catalyst-specific – Subbituminous

(low-chlorine) coals only

0.00.51.01.52.02.53.03.54.04.5

0 100 200 300 400

Hg0 ,

ug/d

Nm

3

Halogen, ug/g coal equivalent

Bromine

Chlorine

Equilibrium at 720oF

Subbituminous Coals

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

Boiler

Burners

Air Heater

Fuel

Coal Pulverization

Coal Supply

Particulate Collector

SO 2 Scrubber

Induced Draft Fan

Stack

SCR

Corrosion in Flue Gas

• 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)

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0.02

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0.1

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0 100 200 300 400

Corr

osio

n lo

ss, m

m

Temperature, oF

Baseline

51 ppmv HBr

• Chlorine corrosion in furnaces can occur for very high levels of chlorine in coal (> 2000 µg/g) – Bromine addition at much lower concentrations

Zhuang et al., 2009

Bromine Addition: Fly Ash Impacts

• Bromine additive or brominated PAC results in increase in Br in fly ash

• Example: Br injection at Monticello (C-ESP)

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350

012345678

11/1/05 11/15/05 11/29/05 12/13/05

Br ad

dedm

µg/

g coa

l

Br, µ

g/g

Br in fly ash Br injected

Bromine injection at Monticello (EERC, URS data)

Bromine Addition: Fly Ash Impacts

• 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

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0 20 40 60

Leac

hate

, mg/

L

Fly

Ash,

µg/

g

Added Br, µg/g coal equivalent

Br in Fly Ash

Br in Leachate

Dombrowski et al., 2008

Source: 2010 ICR

Chlorine Emission from APCDs

Meramec

PIPP FF

C-ESP

Brominated PAC injection

All boilers are pulverized coal, burning subbituminous coal

Bromine Emission from APCDs

0% 50% 100%

Boiler 3

Boiler 2

Boiler 1

Percent of added halogen emitted in stack

C-ESP

C-ESP

C-ESP

Fuel addition

Source: 2010 ICR

Chlorine Emission from APCDs

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

Bromine injection at Monticello (EERC, URS data)

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500

11/1/05 11/15/05 11/29/05 12/13/05

Br ad

dedm

µg/

g coa

l

Br, m

g/L,

Hg,

µg/

L

Br in FGD liquor Hg in FGD liquor Br injected

Halogens and Wet Scrubbers

• Increased Cl, Br concentration in scrubber liquor can decrease Hg re-emission

Data from bituminous site with C-ESP, wet FGD

Se in fly ash, µg/g

% Se capture by fly ash

Se in FGD liquor, µg/L

Baseline 24 70% 300Br addition 10 20% 4900(Dombrowski et al., 2011)

• Recent observations (Air Quality VIII) that Br addition to the fuel increases Se in scrubber liquor

– Less uptake of Se by fly ash means more Se enters FGD

Summary

Fly Ash

Boiler

Burners

Air Heater

Fuel

Coal Pulverization

Coal Supply

Particulate Collector

SO 2 Scrubber

Induced Draft Fan

Stack

SCR

Scrubber Blowdown

Stack Emission

Halogen Injection

Halogenated Carbon Injection

• 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: • Corrosion • Multi-media fate • Trace metal interactions

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