APC Strategy for Mercury CEMSby Trey Lightsey

2010 Annual Meeting & Technical Conference A&WMA – Southern Section

Renaissance Riverview Plaza Hotel

Regulatory Overview – Timeline2000 – Clinton EPA will regulate mercury from coal-fired utility boilers under Section 112

of the CAA (Clean Air Act)2004 – Bush EPA decides that listing coal-fired utility boilers under Section 112 of the

CAA was ‘in error’2005 – Bush EPA issues CAMR (Clean Air Mercury Rule) delisting EGUs from Section

112 of the CAA and establishing a mercury trading program2008 – DC Court of Appeals vacates CAMR2009 – Obama EPA will develop emission standards for HAPs (Hazardous Air Pollutants)

under Section 112 of the CAA and announces an ICR (Info Collection Request) to collect HAP data from utility boilers

2011 – Per a consent decree, a draft of the HAPs Utility MACT (Maximum Achievable Control Technology) is due in March which will set final emission limits by November

2014 – All affected utilities must be in compliance with the HAPs Utility MACT by November (3 years post-submittal of the final rule)

APC Strategy for Mercury CEMS – Overview– 15 TMFS (Thermo Mercury Freedom Systems) Hg CEMS were

implemented at 6 coal-fired steam plants as part of the vacated CAMR.– 7 Hg CEMS were relocated to wet stacks with the addition of FGDs.– Each Hg CEMS was certified per the vacated CAMR which included a

cycle (response) time test, a 3 pt linearity, a 3 pt system integrity check, a calibration error test (7 day drift) and a RATA.

– Daily, weekly, quarterly and annual QA/QC (including 30B RATAs for annual recertification) is being performed.

– Efforts similar to the APC Strategy for Hg CEMS are necessary to advance source monitoring technology and to set realistic maintenance and budgeting expectations ahead of implementing new Utility MACTs and other monitoring requirements. There will be lessons learned from Hg CEMS that will apply to other HAPs monitoring.

APC Strategy for Mercury CEMS – TMFS

APC Strategy for Mercury CEMS – RATAs

– Method 30B– A known volume of flue gas is extracted from a stack/duct through paired, sorbent

media traps at a pre-determined flow rate; the traps are recovered from the sampling system and analyzed by any suitable determinative technique that can measure total vapor phase mercury and meet performance criteria

– Sampling– APC field services performs the sampling portion of the RATA using 2-bed, iodated,

activated carbon traps from Ohio Lumex– Sorbent trap sampling system is an Apex XC-6000EPC– Method 4 moisture determination using an Apex XC-40 console

– Analysis– APC field services using an Ohio Lumex RA-915+ Zeeman Mercury Spectrometer

with RP-M324 attachment– APC environmental test lab using a Leco AMA254 Mercury Analyzer

APC Strategy for Mercury CEMS – Sampling

Flue gasQuartz cotton 1

Quartz cotton 2

Sorbent bed 1Sorbent bed 2

APC Strategy for Mercury CEMS – Sampling

APC Strategy for Mercury CEMS – AnalysisMethod 30B Data Input

Train ID

Trap ID Date Time

Sec 1 Mass (ng)

Sec 2 Mass (ng)

Tot Mass (ng)

Break through (<10%)

Pair Trap Agree (<10%)

Spike Mass (ng) (50-150%)

Spike Conc (ng/L)

Field Recovery

FRT - 3 runs (85-115%)

M.4 Mois

Std Sample Vol (L)

Dry Basis Conc (ng/L)

Wet Basis Conc (ng/L)

Avg Wet Basis Conc (ng/L) Note

1A 63261 6/1/2010 7:29-7:59 107.00 0.00 107.00 0.0% 0 28.919 3.70 3.411B 63298 6/1/2010 7:29-7:59 113.00 0.00 113.00 0.0% 0 28.651 3.94 3.642A 63245 6/1/2010 8:09-8:39 117.00 0.00 117.00 0.0% 0 28.741 4.07 3.752B 63274 6/1/2010 8:09-8:39 110.00 0.00 110.00 0.0% 0 28.474 3.86 3.563A 61114 6/1/2010 8:51-9:21 236.00 0.00 236.00 0.0% 100 28.645 4.75 4.283B 63171 6/1/2010 8:51-9:21 128.00 0.00 128.00 0.0% 0 28.273 4.53 4.094A 61117 6/1/2010 9:31-10:01 242.00 0.00 242.00 0.0% 100 28.543 4.97 4.494B 63193 6/1/2010 9:31-10:01 134.00 0.00 134.00 0.0% 0 28.580 4.69 4.235A 61152 6/1/2010 10:11-10:41 266.00 0.00 266.00 0.0% 100 28.348 5.86 5.325B 63194 6/1/2010 10:11-10:41 167.00 0.00 167.00 0.0% 0 28.169 5.93 5.386A 61112 6/1/2010 11:14-11:44 271.00 0.00 271.00 0.0% 100 28.895 5.92 5.376B 63197 6/1/2010 11:14-11:44 167.00 0.00 167.00 0.0% 0 28.230 5.92 5.377A 61151 6/1/2010 11:56-12:26 257.00 0.20 257.20 0.1% 100 28.900 5.43 4.957B 63230 6/1/2010 11:56-12:26 156.00 0.00 156.00 0.0% 0 27.738 5.62 5.138A 63199 6/1/2010 1:08-1:38 162.00 0.10 162.10 0.1% 0 29.128 5.56 5.078B 63272 6/1/2010 1:08-1:38 159.00 0.00 159.00 0.0% 0 27.892 5.70 5.209A 63704 6/1/2010 1:57-2:27 156.00 0.00 156.00 0.0% 0 29.059 5.37 4.839B 63717 6/1/2010 1:57-2:27 154.00 0.00 154.00 0.0% 0 27.838 5.53 4.9710A 0.00 #DIV/0! 0 #DIV/0! #DIV/0!10B 0.00 #DIV/0! 0 #DIV/0! #DIV/0!11A 0.00 #DIV/0! 0 #DIV/0! #DIV/0!11B 0.00 #DIV/0! 0 #DIV/0! #DIV/0!12A 0.00 #DIV/0! 0 #DIV/0! #DIV/0!12B 0.00 #DIV/0! 0 #DIV/0! #DIV/0!

#DIV/0!

#DIV/0!

0.3%

1.2%

0.3%

0.9%

2.7%

3.1%

3.0%

2.9%

0.6%

#DIV/0!

#DIV/0!

#DIV/0!

10.09%

106.3%

108.2%

7.79%

9.75%

9.75%

94.5%

9.18%

8.82%

97.9%

3.71

3.79

3.45

3.46

3.27

5.35

5.37

5.04

9.18%

8.82%

100.1%

97.5%

7.79%

5.13

3.52

3.66

4.19

4.36

4.90

#DIV/0!

APC Strategy for Mercury CEMS – Analysis

APC Strategy for Mercury CEMS – Ex.1

• Ex.1 is an 800MW unit that burns mainly Columbian coal and is equipped with an SCR and FGD

• Initially, the Hg CEMS was located on an exterior duct leading to a single lined, dry stack downstream of an SCR

• The dry duct hourly Hg concentrations varied in the 2 – 8ug/scm range during the certified period (Jun 09’ – Sep 09’) and depended primarily upon operating variables (load, fan/flow, coal variations, PCD operation, etc.)

• There was 99+% data availability* during the certified period on the dry duct• The Hg CEMS is currently located in the annulus space of a single-lined wet stack

downstream of all PCDs (SCR and FGD) at an elevation of ~500’ft• The wet stack hourly Hg concentrations have varied in the 0.1 – 4ug/scm range

since certification in Jun 10’• Currently maintaining 99+% data availability* on the wet stack

*availability is based on hourly averages; an available hour is one in which a previous 24hr (daily calibration) was successful and there are at least 2 minutes of valid data in each of the 4 hourly quadrants

APC Strategy for Mercury CEMS – Ex.1RATA results - DRY performed on 6/17/09; FGD performed on 6/29/10

APC Strategy for Mercury CEMS – Ex.2

• Ex.2 is a 750MW unit that burns mainly Western PRB coal and is equipped with an SCR and FGD

• Initially, the Hg CEMS was located in the annulus space of a dual-lined dry stack downstream of an SCR

• The dry stack hourly Hg concentrations varied in the 2 – 12ug/scm range during the certified period (Aug 08’ – May 10’) and depended primarily upon operating variables (load, fan/flow, coal variations, PCD operation, etc.)

• There was 87+% data availability* during the certified period on the dry stack• The Hg CEMS is currently located in the annulus space of a dual-lined wet stack

downstream of all PCDs (SCR and FGD) at an elevation of ~500’ft• The wet stack hourly Hg concentrations have varied in the 2 – 6ug/scm range since

certification in May 10’• Currently maintaining 98+% data availability* on the wet stack

*availability is based on hourly averages; an available hour is one where a previous 24hr (daily calibration) was successful and there are at least 2 minutes of valid data in each of the 4 hourly quadrants

APC Strategy for Mercury CEMS – Ex.2

RATA Results – DRY performed on 7/28/09; FGD performed on 5/12/10

APC Strategy for Mercury CEMS – Ex.3

• Ex.3 is a 900MW unit that burns mainly Alabama coal and is equipped with an SCR and FGD

• Initially, the Hg CEMS was located on an exterior duct leading to a single lined, dry stack downstream of an SCR

• The dry duct hourly Hg concentrations varied in the 2 – 10ug/scm range during the certified period (June 08’ – Aug 09’) and depended primarily upon operating variables (load, fan/flow, coal variations, PCD operation, etc.)

• There was 85+% data availability* during the certified period on the dry duct• The Hg CEMS is currently located in the annulus space of a single-lined wet stack

downstream of all PCDs (SCR and FGD) at an elevation of ~500’ft• The wet stack hourly Hg concentrations have varied in the 0.1 – 5ug/scm range

since certification in Apr 10’• Currently maintaining 93+% data availability* on the wet stack

*availability is based on hourly averages; an available hour is one in which a previous 24hr (daily calibration) was successful and there are at least 2 minutes of valid data in each of the 4 hourly quadrants

APC Strategy for Mercury CEMS – Ex.3

RATA Results – DRY performed on 8/4/09; FGD performed on 3/31/10

APC Strategy for Mercury CEMS – Ex.4

• Ex.4 is comprised of (2) 300MW units that burn mainly Alabama coal and is equipped with an ESP (only)

• The Hg CEMS is located in the annulus space of a single-lined dry stack downstream of the ESP at an elevation of ~300’ft

• The dry stack hourly Hg concentrations have varied in the 10 – 30ug/scm range since certification in Jan 09’ and depend primarily upon load and coal variations

• Currently maintaining 90+% data availability* on the dry stack

*availability is based on hourly averages; an available hour is one in which a previous 24hr (daily calibration) was successful and there are at least 2 minutes of valid data in each of the 4 hourly quadrants

APC Strategy for Mercury CEMS – Ex.4Used =1 Not = 0 Run Time Date

RM 30B (ng/L)

Hg CEMS (ug/scm) Diff

0 1 0:00 1/0/1900 #DIV/0! #DIV/0! #DIV/0!1 2 7:39-8:09 7/13/2010 25.20 26.87 1.661 3 8:24-8:54 7/13/2010 26.62 26.45 0.171 4 9:05-9:35 7/13/2010 24.89 26.05 1.151 5 9:48-10:18 7/13/2010 24.35 24.69 0.341 6 10:29-10:59 7/13/2010 22.77 24.38 1.621 7 11:11-11:41 7/13/2010 21.41 23.21 1.801 8 11:57-12:27 7/13/2010 20.41 22.53 2.111 9 12:46-1:16 7/13/2010 21.54 22.50 0.971 10 1:25-1:55 7/13/2010 21.25 23.05 1.800 11 0:00 1/0/1900 #DIV/0! #DIV/0! #DIV/0!0 12 0:00 1/0/1900 #DIV/0! #DIV/0! #DIV/0!

Mean 23.16 24.41 1.29Std Dev 0.683Conf Coef 0.510Rel Accuracy 7.78%RATA Status PASSTvalue 2.306Bias 1.053

Lessons Learned, Challenges and Next Steps• Mercury removal (generally) occurs in the FGD (absorber solution) when gaseous phase Hg0 is oxidized to

Hg2+ by halogens present in/injected on the coal, by an SCR catalyst or through an air pre-heater ahead of the FGD

• Additionally, ACI (activated carbon injection), e.g. directly into an ESP, removes Hg from the flue via the same chemi-adsorption principles that bind Hg to the activated carbon in sorbent traps

• High SO2 and PM generally equates to more maintenance/issues for Hg CEMS; systems with PCDs (especially FGDs) generally require less maintenance

• Hg CEMS use N2 as a diluent requiring (>100psi) for N2 generation further necessitating either air compressors (and additional maintenance) or a greater burden on plant air

• Probes require high heat for Hg2+ conversion and to ensure that Hg will not bind to components making probes difficult/tedious/expensive to maintain

• Analyzers require high intensity UV lamps that continue to experience issues and present challenges• Probe controller components are very susceptible to lightning and power surges• Hg CEMS may experience considerable downtime and non-availability after maintenance/troubleshooting

while the system ‘settles out’• Calibrator traceability protocols were created to ensure accurate, NIST traceable, field reference calibrators• Currently, TMFS calibrators can achieve (down to) 2.5ug/scm limiting system ranges to 0-10ug/scm in

order to accommodate regulatory QA/QC• Vendors such as Ohio Lumex offer upgrades that will significantly lower MDLs for carbon trap analysis• Work continues on the development of a portable Hg CEMS and instrumental reference method (30A) that

will allow for real-time and direct comparison of Hg CEMS