February 2007
Environmental Technology
Verification Report
APEX INSTRUMENTS
SORBENT-BASED MERCURY SAMPLING SYSTEM
Prepared by
Battelle
Baireiie
Business of IiMicwa
Under a cooperative agreement with
imJlrr\ U.S. Environmental Protection Agency
ET1/ET1/ET1/
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February 2007
Environmental Technology Verification
Report
ETV Advanced Monitoring Systems Center
APEX INSTRUMENTS
SORBENT-BASED MERCURY SAMPLING SYSTEM
by
Thomas Kelly
Jan Satola
Zachary Willenberg
Amy Dindal
Battelle
Columbus, Ohio 43201
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Notice
The U.S. Environmental Protection Agency (EPA), through its Office of Research and
Development, has financially supported and collaborated in the extramural program described
here. This document has been peer reviewed by the Agency. Mention of trade names or
commercial products does not constitute endorsement or recommendation by the EPA for use.
This report was prepared by Battelle to summarize testing supported in part by the Illinois
Department of Commerce and Economic Opportunity through the Office of Coal Development
and the Illinois Clean Coal Institute (ICCI). Neither Battelle nor any of its subcontractors nor the
Illinois Department of Commerce and Economic Opportunity, Office of Coal Development, the
ICCI, nor any person acting on behalf of either:
(a) Makes any warranty of representation, express or implied, with respect to the accuracy,
completeness, or usefulness of the information contained in this report, or that the use of
any information, apparatus, method, or process disclosed in this report may not infringe
privately-owned rights; or
(b) Assumes any liabilities with respect to the use of, or for damages resulting from the use
of, any information, apparatus, method or process disclosed in this report.
Reference herein to any specific commercial product, process, or service by trade name,
trademark, manufacturer, or otherwise, does not necessarily constitute or imply its endorsement,
recommendation, or favoring; nor do the views and opinions of authors expressed herein
necessarily state or reflect those of the Illinois Department of Commerce and Economic
Opportunity, Office of Coal Development, or the ICCI.
Notice to Journalists and Publishers: If you borrow information from any part of this
report, you must include a statement about the state of Illinois' support of the project.
11
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Foreword
The U.S. Environmental Protection Agency (EPA) is charged by Congress with protecting the
nation's air, water, and land resources. Under a mandate of national environmental laws, the
Agency strives to formulate and implement actions leading to a compatible balance between
human activities and the ability of natural systems to support and nurture life. To meet this
mandate, the EPA's Office of Research and Development provides data and science support that
can be used to solve environmental problems and to build the scientific knowledge base needed
to manage our ecological resources wisely, to understand how pollutants affect our health, and to
prevent or reduce environmental risks.
The Environmental Technology Verification (ETV) Program has been established by the EPA to
verify the performance characteristics of innovative environmental technology across all media
and to report this objective information to permitters, buyers, and users of the technology, thus
substantially accelerating the entrance of new environmental technologies into the marketplace.
Verification organizations oversee and report verification activities based on testing and quality
assurance protocols developed with input from major stakeholders and customer groups
associated with the technology area. ETV consists of six environmental technology centers.
Information about each of these centers can be found on the Internet at http://www.epa.gov/etv/.
Effective verifications of monitoring technologies are needed to assess environmental quality
and to supply cost and performance data to select the most appropriate technology for that
assessment. Under a cooperative agreement, Battelle has received EPA funding to plan,
coordinate, and conduct such verification tests for "Advanced Monitoring Systems for Air,
Water, and Soil" and report the results to the community at large. Information concerning this
specific environmental technology area can be found on the Internet at http://www.epa.gov/etv/
centers/center 1 .html.
in
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Acknowledgments
The authors wish to acknowledge the support of all those who helped plan and conduct the
verification test, analyze the data, and prepare this report. This verification was funded in part by
the Illinois Clean Coal Institute (ICCI) under Project No. 04-1/3.2D-1; we appreciate the
involvement and support of Dr. Francois Botha, Project Manager for the ICCI. We acknowledge
the contribution of the Northern Indiana Public Service Company (NIPSCo, a NiSource
company) in hosting this verification at the R. M. Schahfer Generating Station and, in particular,
the efforts of Craig Myers, Bert Valenkamph, and Gary Logan of NIPSCo in support of the field
testing. We also thank Eric Ginsburg and William Grimley of U.S. EPA for their assistance in
setting up a Site Access Agreement among EPA, Battelle, and NiSource. Finally, we would like
to thank Robin Segall of U.S. EPA, Ernest Bouffard of the Connecticut Department of
Environmental Protection, Francois Botha of ICCI, and Craig Myers of NIPSCo for their review
of this verification report.
IV
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Contents
Page
Notice ii
Foreword iii
Acknowledgments iv
List of Abbreviations vii
Chapter 1 Background 1
Chapter 2 Technology Description 2
Chapter 3 Test Design and Procedures 5
3.1 Introduction 5
3.2 Test Facility 6
3.3 Test Procedures 7
3.3.1 Relative Accuracy 7
3.3.2 Data Completeness 8
3.3.3 Operational Factors 8
3.4 Verification Schedule 8
Chapter 4 Quality Assurance/Quality Control 10
4.1 OH Reference Method 10
4.1.1 OH Reproducibility 10
4.1.2 OH Blank and Spike Results 11
4.2 Audits 12
4.2.1 Performance Evaluation Audit 12
4.2.2 Technical Systems Audit 13
4.2.3 Data Quality Audit 14
4.3 QA/QC Reporting 14
4.4 Data Review 14
Chapters Statistical Methods 15
5.1 Relative Accuracy 15
5.2 Data Completeness 15
Chapter 6 Test Results 16
6.1 Relative Accuracy 16
6.1.1 Relative Accuracy: Uncorrected Data 17
6.1.2 Relative Accuracy: Spike-Corrected Data 18
6.2 Data Completeness 18
6.3 Operational Factors 19
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Chapter 7 Performance Summary 20
Chapters References 21
Figures
Figure 2-1. Apex XC-60 Gas Sampling Consoles 3
Figure 2-2. Apex SGC 4000 Hg Stirling Gas Conditioner 3
Figure 2-3. Apex Dual Trap Sampling Probe and Heated Line 4
Tables
Table 3-1. Operating and Stack Gas Conditions at Schahfer Station Unit 17 7
Table 3-2. Schedule of OH Method Sampling in the Week of July 10, 2006 8
Table 4-1. OH Results from July 10-13,2006, Sampling Period 11
Table 4-2. Summary of PE Audit Results 13
Table 6-1. Apex System HgT Results 17
Table 6-2. Data Used for Comparison of OH and Apex HgT Results 18
Table 6-3. Data Used for Comparison of OH and Spike-Corrected Apex HgT Results 19
VI
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List of Abbreviations
agl
AMS
ASTM
CEM
cm3/min
EPA
ETV
°F
FGD
H202
H2S04
Hg
HgCl2
Hg°
HgT
Hgox
HNO3
ICCI
KC1
klb/hr
KMnO4
L/min
MW
ug/dscm
ug/mL
mL
NIPSCo
NIST
NOX
OH
ppm
PE
QA
QC
QMP
RA
above ground level
Advanced Monitoring Systems
American Society for Testing and Materials
continuous emission monitor
cubic centimeter per minute
U.S. Environmental Protection Agency
Environmental Technology Verification
degrees Fahrenheit
flue gas desulfurization
hydrogen peroxide
sulfuric acid
mercury
mercuric chloride
elemental mercury
total mercury
oxidized mercury
nitric acid
Illinois Clean Coal Institute
potassium chloride
thousands of pounds per hour
potassium permanganate
liters per minute
megawatt
microgram per dry standard cubic meter
microgram per milliliter
milliliter
Northern Indiana Public Service Company
National Institute of Standards and Technology
nitrogen oxides
Ontario Hydro
part per million
performance evaluation
quality assurance
quality control
quality management plan
relative accuracy
vii
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RD relative deviation
SC>2 sulfur dioxide
ISA technical systems audit
Vlll
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Chapter 1
Background
The U.S. Environmental Protection Agency (EPA) supports the Environmental Technology
Verification (ETV) Program to facilitate the deployment of innovative environmental
technologies through performance verification and dissemination of information. The goal of the
ETV Program is to further environmental protection by accelerating the acceptance and use of
improved and cost-effective technologies. ETV seeks to achieve this goal by providing high-
quality, peer-reviewed data on technology performance to those involved in the design,
distribution, financing, permitting, purchase, and use of environmental technologies.
ETV works in partnership with recognized testing organizations; with stakeholder groups
consisting of buyers, vendor organizations, and permitters; and with the full participation of
individual technology developers. The program evaluates the performance of innovative
technologies by developing test plans that are responsive to the needs of stakeholders,
conducting field or laboratory tests (as appropriate), collecting and analyzing data, and preparing
peer-reviewed reports. All evaluations are conducted in accordance with rigorous quality
assurance (QA) protocols to ensure that data of known and adequate quality are generated and
that the results are defensible.
The EPA's National Exposure Research Laboratory and its verification organization partner,
Battelle, operate the Advanced Monitoring Systems (AMS) Center under ETV. The AMS Center
recently evaluated the performance of the Apex Instruments Sorbent-Based Mercury Sampling
System for determining mercury in stack gas at a coal-fired power plant. This evaluation was
carried out in collaboration with the Illinois Clean Coal Institute and with the assistance of the
Northern Indiana Public Service Company.
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Chapter 2
Technology Description
The objective of the ETV AMS Center is to verify the performance characteristics of
environmental monitoring technologies for air, water, and soil. This report provides results for
the verification testing of the Apex system. The following is a description of the system, based
on information provided by the vendor. The information provided below was not verified in this
test.
The Apex system tested in this program consisted of two Apex Instruments Model XC-60 Gas
Sampling Consoles, an SGC 4000 Hg Stirling Gas Conditioner, and a 9-foot-long dual trap
mercury sampling probe with a 25-foot-long heated sample line. Each XC-60 console
incorporated a dry gas meter, rotameter flow meter, manual sample flow control valves,
temperature indicators, vacuum gauge, and sampling pump. These consoles allow simultaneous
sampling with two sorbent traps through the single probe, maintaining a constant sampling flow
of about 500 cubic centimeters per minute (cmVmin) through each trap. Pre- and post-run leak
checks were conducted in each run. Sample gas drawn through the sorbent traps in the probe tip
was transported through the heated sample line to the SGC 4000 Hg Stirling Gas Conditioner,
where moisture was removed by condensation before the gas entered each XC-60 console.
Sampling data were recorded manually every 15 minutes during each run and included stack,
probe, console, and Stirling chiller temperatures; sample flow rates; and vacuum and pressure
readings. Barometric pressure was documented for each run and used to correct results to
standard conditions. Figure 2-1 shows the two XC-60 consoles, Figure 2-2 the SGC 4000 Hg
Gas Conditioner, and Figure 2-3 the Apex sampling probe and heated line.
The cost of the Apex system as tested (i.e., a manually operated dual system) is $10,000 to
$15,000, depending on options. As used in this test, the cost per sorbent trap sample was $205,
consisting of $55 for the trap, $60 for pre-spiking with mercury, and $90 for analysis after
sampling. The sorbent traps used with the Apex system in this test were prepared and analyzed
by OhioLumex, Inc., of Twinsburg, Ohio.
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Figure 2-1. Apex XC-60 Gas Sampling Consoles
Figure 2-2. Apex SGC 4000 Hg Stirling Gas Conditioner
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Figure 2-3. Apex Dual Trap Sampling Probe and Heated Line
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Chapter 3
Test Design and Procedures
3.1 Introduction
This verification test was conducted according to procedures specified in the Test/QA Plan for
Verification of Continuous Emission Monitors (CEMs) and Sorbent-Based Samplers for Mercury
at a Coal-Fired Power Plant.^ Appendix K in Chapter 40 of the Code of Federal Regulations,
Part 75 (40 CFR Part 75)(2) establishes sorbent-based sampling systems as an acceptable
approach for determining mercury in the stack gas of utility generating stations. Such sorbent-
based systems collect integrated samples of mercury from stack gas onto selective sorbent
materials over extended time periods (from a few hours to several days). The collected samples
are then analyzed for mercury and the stack gas mercury concentration is calculated. Appendix K
defines procedures for use of such systems to collect total vapor phase mercury in combustion
source emissions, and requires the use of multi-stage sorbent traps pre-spiked with mercury as a
quality assurance (QA) measure. In the test reported here, the Apex system was verified for
measurement of total vapor-phase mercury (HgT), which is the sum of elemental mercury (Hg°)
and oxidized mercury (Hgox) (which is primarily mercuric chloride [HgCb]) vapors. Note that
the Apex system is a sample collection system; the mercury results shown from the system in
this report resulted from use of the system with sorbent traps prepared and subsequently analyzed
for mercury by Ohio Lumex, Inc.
The Apex system was verified by evaluating the following parameters:
• Relative accuracy (RA)
• Data completeness
• Operational factors such as ease of use, maintenance and data output needs, power and other
consumables use, reliability, and operational costs.
Verification of the system was conducted during part of a field test that lasted from June 12 to
July 25, 2006, and that included two separate four-day periods of reference mercury
measurements carried out by ARCADIS Inc., under subcontract to Battelle, using American
Society for Testing and Materials (ASTM) D 6784-02, the "Ontario Hydro" (OH) method.(3)
Specifically, the Apex system was used to sample stack gas from July 10 through July 13, 2006
and RA was determined by comparing the Apex vapor-phase mercury results to simultaneous
results from 12 two-hour sampling runs with the OH method. Data completeness was assessed as
the percentage of maximum data return achieved by the Apex system over its test period.
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Operational factors were evaluated by means of operator observations and records of needed
maintenance, vendor activities, and expendables use.
The sorbent traps used with the Apex system were prepared for this test by Ohio Lumex.
The traps included three sections of sorbent; the third section of each trap was spiked with
60 nanograms (ng) of mercury in the preparation process. After sampling, the sorbent traps were
shipped to Ohio Lumex for analysis for mercury by an approach in which individual sorbent
sections were pyrolyzed in a Lumex RP-91C pyrolysis attachment, thereby driving the collected
mercury vapor into a Lumex RA-915+ Mercury Analyzer. The minimum reporting limit was
10 ng of mercury per sorbent section with this analytical approach, equivalent to approximately
0.15 micrograms per dry standard cubic meter of stack gas (ug/dscm) based on the sampling rate
of 500 cnrVmin.
3.2 Test Facility
The host facility for the Apex system verification was the R.M. Schahfer Generating Station,
located near Wheatfield, Indiana, approximately 20 miles south of Valparaiso, Indiana. The
Schahfer plant consists of four units (designated 14, 15, 17, and 18), with a total rated capacity of
about 1,800 megawatts (MW). The Apex system verification was conducted at Unit 17, which
burns pulverized Illinois sub-bituminous coal and has an electrostatic precipitator and a wet flue
gas desulfurization (FGD) unit. Unit 17 has a typical capacity of about 380 MW. The unit was
operated near this capacity for most of the test period, although the typical daily pattern of
operation was to reduce load substantially for a few hours between late evening and early
morning.
Flue gas from Unit 17 feeds into a free-standing concrete chimney with an internal liner. The top
of the stack is 499 feet above ground level (agl). Emission test ports and penetrations in the
concrete chimney and liner are located at a platform approximately 8 feet wide that encircles the
outside of the stack at 370 feet agl. The stack diameter at the platform level is 22 feet 6 inches, so
the total flow area is 397.6 square feet. The last flow disturbance is at the FGD connection to the
stack liner at 128 feet agl. Thus, the emission test ports were over 10 stack diameters down-
stream from the last flow disturbance and nearly six diameters upstream from the stack exit. Four
emission test ports were located at 90° intervals around the circumference of the stack about
4 feet above the platform at 370 feet agl and were standard 4-inch ports with #125 flanges. No
traversing was done during sampling; both the OH method and the Apex sampled from a single
fixed point one meter inside the inner liner of the stack at their respective port locations. This
arrangement was justified by the absence of stratification observed for sulfur dioxide (802) and
nitrogen oxides (NOx) at this sampling location.
Table 3-1 summarizes key operating and stack gas conditions that characterize Schahfer Unit 17
during the field period, showing the range and average values of key parameters and
constituents. Stack gas pressure was slightly positive at the sampling location.
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Table 3-1. Operating and Stack Gas Conditions at Schahfer Station Unit 17
Parameter Average Range
Unitl7Loada 334 MW 140-391
Coal Feed Rate3 297 klb/hrc 140-374
Temperature3 130°F 118-140
Moistureb 16.2% 15.7-16.7
NOxa 97ppmd 61-165
SO2a 193ppm 104-316
Total mercury vaporb 1.01 ug/dscme 0.79-1.22
a: Values calculated from hourly data recorded by R.M. Schahfer staff June 12 to July 25, 2006.
b: Values based on measurements made during OH reference sampling periods July 10-13, 2006.
c: klb/hr = thousands of pounds per hour.
d: ppm = parts per million.
e: ug/dscm = micrograms per dry standard cubic meter.
3.3 Test Procedures
Following are the test procedures used to evaluate the Apex system.
3.3.1 Relative A ccuracy
The RA of the Apex system was evaluated by comparing its HgT results to simultaneous results
obtained by sampling stack gas with the OH method. The OH method is the currently accepted
reference method for mercury measurements in stack gas, and employs dual impinger trains
sampling in parallel through a common probe to determine oxidized and elemental vapor-phase
mercury by means of appropriate chemical reagents.(3) Over the period of July 10 to 13, 2006
ARCADIS conducted a series of 12 OH runs on the Unit 17 stack, each two hours in duration,
using paired OH trains. The HgT concentration determined by the OH reference method was
compared to the corresponding result from paired Apex traps sampled over exactly the same time
period as the OH run.
The OH trains were dismantled for sample recovery in the field by ARCADIS staff, and all
collected sample fractions were logged and stored for transfer to the ARCADIS analytical
laboratory. All sample handling, quality assurance/quality (QA/QC) activities, and mercury
analyses were conducted by ARCADIS. Subsequent to mercury analysis, ARCADIS reviewed
the data and reported final mercury results from all trains in units of ug/dscm. The results from
the paired OH trains were checked relative to the duplicate precision criterion required of the OH
method,(4) and qualified OH results were averaged to produce the final reference data. The paired
sorbent trap samples collected using the Apex system were sent to Ohio Lumex, in Twinsburg,
Ohio, for mercury analysis. The mercury results from the paired Apex sorbent traps were
reviewed for spike recovery and duplicate precision relative to Appendix K requirements.(2) RA
was calculated as described in Section 5.1, and in addition the average of all Apex sorbent
system results was compared to the average of all OH results.
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3.3.2 Data Completeness
No additional test procedures were carried out specifically to address data completeness of the
Apex sorbent system. This parameter was assessed by comparing the overall data return to the
total possible data return.
3.3.3 Operational Factors
Operational factors such as maintenance needs, data output, consumables use, and ease of use
were evaluated based on observations by Battelle and Schahfer facility staff. Examples of
information used to assess operational factors were the use or replacement of any consumables,
the effort or cost associated with maintenance or repair, vendor effort (e.g., time on site) for
repair or maintenance, the duration and causes of any down time or data acquisition failure, and
observations about ease of use of the Apex system.
3.4 Verification Schedule
The Apex system was verified in a field effort that also evaluated two mercury CEMs and one
other sorbent-based system. The Apex system was installed at the Unit 17 stack on July 9 and
removed on July 13, 2006, during which period it was operated by a vendor representative.
Twelve successive OH reference method runs were carried out in this period for comparison to
the Apex results.
Table 3-2 shows the actual schedule of OH reference method sampling completed by ARCADIS
between July 10 and 13, 2006. The OH sampling proceeded efficiently, with three runs
conducted on each of four successive days. In all cases the Apex vendor representative was
informed of the planned start time of each OH run, and in a few instances the start time of a run
was delayed slightly to assure that the technologies being tested were fully ready to obtain data
during the OH run. All OH runs were of exactly two hours duration.
Table 3-2. Schedule of OH Method Sampling in the Week of July 10, 2006
Run Number
1
2
3
4
5
6
7
8
9
10
11
12
Date
7/10/06
7/10/06
7/10/06
7/11/06
7/11/06
7/11/06
7/12/06
7/12/06
7/12/06
7/13/06
7/13/06
7/13/06
Start Time
9:00
11:50
14:55
8:30
11:15
14:00
8:30
11:40
14:15
8:20
11:10
13:45
End Time
11:00
13:50
16:55
10:30
13:15
16:00
10:30
13:40
16:15
10:20
13:10
15:45
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Following the field sampling effort, all sorbent trap samples were turned over by Apex
Instruments to Ohio Lumex for analysis. Ohio Lumex returned an analysis data file that included
results for collected mercury on the first two sorbent sections of each trap, the spike recovery
from the third section, and the spike-corrected stack gas mercury results for both individual traps
and paired trap averages. Battelle staff used information from this analysis file also to calculate
stack gas mercury concentrations uncorrected for mercury spike recovery.
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Chapter 4
Quality Assurance/Quality Control
QA/QC procedures were performed in accordance with the quality management plan (QMP) for
the AMS Center(5) and the test/QA plan for this verification test.(1) QA/QC procedures and
results are described below.
4.1 OH Reference Method
This verification test included a comparison of Apex sorbent sampler results to those of the OH
reference method for flue gas mercury.(3) The quality of the reference measurements was assured
by adherence to the requirements of the OH method, including requirements for solution and
field blanks, spiked samples, and initial and continuing blanks and calibration standards. In
addition, all OH reference measurements were made with paired trains, and the percent relative
deviation (%RD) of each data pair was required to be < 10% (at mercury levels >1.0 ug/dscm) or
< 20% (at mercury levels < 1.0 ug/dscm) (%RD = difference between the paired train results
divided by sum of those results, expressed as a percentage).(4) Data not meeting this criterion
were excluded from comparison with the Apex results. The following sections present key data
quality results from the OH method.
4.1.1 OH Reproducibility
The mercury results of the OH stack gas samples are shown in Table 4-1 for the July 10-13
period of OH method sampling. The table indicates the OH run number, and lists the average
vapor phase Hgox, Hg°, and total Hg results from the paired OH trains in each run, and the
percent relative deviation of each pair of results. All mercury results are in micrograms of
mercury per dry standard cubic meter (ug/dscm).
Inspection of Table 4-1 shows that HgT in the Unit 17 stack ranged from 0.787 to 1.215 ug/dscm
in the OH runs conducted in the July 10-13 period. The average HgT value was 1.008 ug/dscm
(note that one OH result for HgT is excluded from the average because of inadequate dual train
precision, as described below). Hg° comprised the great majority of the HgT, consistent with the
scrubbing of the Schahfer Unit 17 flue gas. Hgox never exceeded about 0.09 ug/dscm, and was
typically about 5% of the HgT.
10
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Table 4-1. OH Results from July 10-13, 2006, Sampling Period
Mercury Concentration (ug/dscm) and %RD of Paired Train Results3
OH Run
1
2
3
4
5
6
7
8
9
10
11
12
Hgox
0.033
0.037
0.040
0.066
0.029
0.038
0.028
0.084
0.090
0.093
0.092
0.037
%RD
10.1
2.9
3.7
52.3
11.6
2.0
5.7
7.2
6.3
0.6
0.9
22.7
Hg°
0.902
0.823
0.929
0.886
0.757
1.018
1.055
0.997
1.126
0.982
1.014
1.015
%RD
0.8 (
1.4 (
1.1 (
1.4 (
0.3 (
6.5
1.2
12.6
0.7
0.1
2.0
0.6
HgT
).935
).860
).969
).952
).787
.056
.083
.081
.215
.074
.107
.053
%RD
0.4
1.2
0.9
4.9
0.1
6.4
1.3
11.0
0.2
0.1
1.8
0.2
a: %RD = difference between paired train results divided by sum of paired train results.
Table 4-1 shows generally close agreement between the paired OH train results for all three
mercury fractions. The %RD values in Table 4-1 are less than 7% in all 12 runs for both Hg° and
Hgx, with the exception of Run 8, for which %RD exceeded 10% for both HgT and Hg°. The
%RD values for Hgox are slightly higher, with four values exceeding 10%, probably due to the
low Hgox concentrations. The only %RD values in Table 4-1 which do not meet the acceptance
criteria for paired OH results are the value of 11.0% RD for HgT in run 8, and the values of 22.7
and 52.3 %RD for Hgox in Runs 12 and 4, respectively. Because of the %RD value, the HgT
result from Run 8 is excluded from calculation of the RA of the Apex system.
4.1.2 OH Blank and Spike Results
Analyses were conducted on ten total samples collected at the Schahfer site from the blank
reagents used in the OH method in the July 10-13 period. Only two of those samples showed
detectable mercury, with concentrations of 0.003 and 0.006 microgram per liter (ug/L),
respectively. This blank reagent concentration is negligible in comparison to the mercury in
impinger solutions recovered from trains after stack sampling. Those recovered sample
concentrations were typically about 0.1 ug/L, 0.2 ug/L, and 4 ug/L in potassium chloride (KC1)
solution, hydrogen peroxide (H2O2) solution, and potassium permanganate (KMnO/t) solution,
respectively.
Blank OH sampling trains were prepared and taken to the sampling location on the Unit 17 stack
on three occasions in the period of OH sampling, and were then returned for sample recovery
without exposure to stack gas. These blank OH trains provide additional assurance of the quality
of the train preparation and recovery steps. For the July 10-13 sampling period, the total amounts
of mercury recovered from the three blank trains range from 0.193 to 0.250 ug, equivalent to
approximately 10 percent of the typical total amount of mercury recovered from a train after
stack sampling at the Schahfer plant. Those blank train results correspond to stack gas mercury
concentrations of less than 0.1 ug/dscm under typical sampling conditions in this verification.
11
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All initial and continuing blank and calibration values from laboratory analysis of the OH
samples met the requirements of the OH method. The recovery of mercury spiked into each
reagent solution recovered from blank and sampled OH trains was also evaluated during
laboratory analysis. Those spike recoveries ranged from 88 to 117%, and averaged 100%. The
recovery of mercury spiked into blank train samples as part of the performance evaluation (PE)
audit also met the prescribed criteria, as described in Section 4.2.1.
4.2 Audits
Three types of audits were performed during the verification test: a performance evaluation (PE)
audit of the OH reference method, a technical systems audit (TSA) of the verification test
performance, and a data quality audit. Audit procedures are described further below.
4.2.1 Performance Evaluation Audit
PE audits of the OH method were carried out through procedures implemented at the Schahfer
plant during the field period. Table 4-2 summarizes the procedures and results of the PE audits of
the OH reference method, showing the parameter audited, the date of the audit, the OH and
reference values, the observed agreement, and the target agreement. The OH method
incorporates dual sampling trains, and the equipment used by ARCADIS to carry out the OH
sampling included dual Model 522 Source Sampler meter boxes (Apex Instruments, Fuquay-
Varina, North Carolina) designated by their serial numbers as #2007 and #2008. As a result, for
some parameters Table 4-2 includes results for both meter boxes, or for both of the dual OH
trains. Note that most of the PE audit procedures were carried out in the initial period of OH
sampling conducted four weeks before the OH measurements against which the Apex results
were compared.
Four PE audits were conducted:
• A Fluke Model 52 II digital thermometer (Serial No. 80730162) was used to audit the probe
temperature measurements made by the #2007 meter box and the stack temperature measure-
ments made by the #2008 meter box. For this comparison, the appropriate thermocouple was
disconnected from the meter box and connected to the Fluke thermometer.
• A BIOS International Corporation DryCal National Institute of Standards and Technology-
(NIST)-traceable flow measurement standard (Model DC2-B, Serial No. 103777, vendor-
calibrated on May 9, 2006) was used to audit the sample gas flow rate with each of the two
OH meter boxes.
• A set of weights (Rice Lake Weight Set, Serial No. 1JXA) calibrated to ASTM Class 3
standards was used to audit the electronic balance (AND FP-6000, Serial No. 6402118) used
for weighing the OH method impingers.
• Recovery of mercury from OH trains was audited by spiking impingers containing KC1,
H2O2/nitric acid (HNOs), and KMnOVsulfuric acid (H2SO/t) reagents in two blank OH
impinger trains, with 1 milliliter (mL) of a prepared mercury solution, in each of the two
separate periods of OH sampling. The mercury spiking solution was 2.5 ug/mL Hg in 1%
and was prepared by dilution of a NIST-traceable 1,000-ppm (i.e., 1,000-ug/mL)
12
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standard (Aa34n-l, Accustandards, Inc.). In the first week of OH sampling, Impingers 2, 4,
and 5 of Blank Trains 8L and 8R were spiked; and, in the final week of OH sampling,
Impingers 2, 4, and 6 of Blank Trains 7L and 7R were spiked.
Table 4-2 shows that all the PE audit results were within the target tolerances set in the test/QA
plan.(1)
Table 4-2. Summary of PE Audit Results
Parameter
OH temperature
measurement
OH sample flow
measurement
Impinger weighing
Mercury spike
recovery
Date
6/14/06
probe T
stack T
7/11/06
6/14/06
6/14/06
train 8L
imp 2
imp 4
imp 5
train 8R
imp 2
imp 4
imp 5
7/12/06
train 7L
imp 2
imp 4
imp 6
train 7R
imp 2
imp 4
imp 6
OH Result
228 °Fa
127 °Fb
15.02L/mina
14.58 L/minb
199.72
499.27
2.48 ug
2.02 ug
2.08 ug
2.47 ug
1.97ug
2.10ug
2.24 ug
2.12ug
2.38 ug
2.27 ug
2.33 ug
2.39 ug
Reference
Value
230°F
129°F
14.56 L/min
14.35 L/min
200 grams
500 grams
2.5 ug
2.5 ug
2.5 ug
2.5 ug
2.5 ug
2.5 ug
2.5 ug
2.5 ug
2.5 ug
2.5 ug
2.5 ug
2.5 ug
Observed
Agreement
0.29%
0.31%
3.2%
1.6%
0.14%
0.15%
0.8%
19.2%
16.8%
1.2%
21.2%
16.0%
10.4%
15.2%
4.8%
9.2%
6.8%
4.4%
Target
Agreement
2% absolute T
5%
Greater of 1%
or 0.5 gram
25%
25%
25%
25%
25%
25%
25%
25%
25%
25%
25%
25%
a: #2007 meter box.
b: #2008 meter box.
L/min = liters per minute; T = temperature; imp = impinger.
4.2.2 Technical Systems A udit
A Battelle Quality Management representative conducted a TSA at the Schahfer test site on
June 14 to ensure that the verification test was being conducted in accordance with the test/QA
plan(1) and the AMS Center QMP.(5) As part of the TSA, test procedures were compared to those
specified in the test/QA plan,(1) and data acquisition and handling procedures, as well as the
reference standards and method were reviewed. The Quality Management representative
observed OH method sampling and sample recovery processes, interviewed ARCADIS
personnel, and observed the PE audit procedures noted above, except for the OH sample flow
and second OH train spiking audits, which were conducted at a later date. Observations and
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findings from the TSA were documented and submitted to the Battelle Verification Test
Coordinator for response. None of the findings of the TSA at the Schahfer site required
corrective action. In addition, an internal TSA was conducted in the laboratory charged with
analyzing the OH samples. This TSA was conducted by the ARCADIS independent QA Officer
in the laboratory on-site at EPA in Research Triangle Park, North Carolina, on July 19 and
July 27, 2006. None of the findings of this laboratory TSA required corrective action. Records
from both TSA efforts are permanently stored with the Battelle Quality Manager.
4.2.3 Data Quality Audit
At least 10% of the data acquired during the verification test were audited. Battelle's Quality
Manager traced the data from the initial acquisition, through reduction and statistical analysis, to
final reporting to ensure the integrity of the reported results. All calculations performed on the
data undergoing the audit were checked.
4.3 QA/QC Reporting
Each audit was documented in accordance with Sections 3.3.4 and 3.3.5 of the QMP for the ETV
AMS Center.(5) Once the audit reports were prepared, the Battelle Verification Test Coordinator
ensured that a response was provided for each adverse finding or potential problem and imple-
mented any necessary follow-up corrective action. The Battelle Quality Manager ensured that
follow-up corrective action was taken. The results of the TSA were submitted to the EPA.
4.4 Data Review
Records generated in the verification test received a one-over-one review before these records
were used to calculate, evaluate, or report verification results. Data were reviewed by a Battelle
technical staff member involved in the verification test. The person performing the review added
his/her initials and the date to a hard copy of the record being reviewed.
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Chapter 5
Statistical Methods
The statistical methods used to evaluate the quantitative performance factors listed in Section 3.1
are presented in this chapter. Qualitative observations were also used to evaluate verification test
data.
5.1 Relative Accuracy
The RA of the Apex system with respect to the OH reference method results was assessed as a
percentage, using Equation 1:
d
•t
'n-l
RA = _ ^n xlOO% (1)
x
where Prefers to the difference between the OH reference mercury concentration and the Apex
result over the OH sampling period, and x corresponds to the OH reference mercury
concentration. Sd denotes the sample standard deviation of the differences, while tan_i is the t
value for the 100(1 - a)th percentile of the distribution with n-l degrees of freedom. The RA was
determined for an a value of 0.025 (i.e., 97.5% confidence level, one-tailed). RA was calculated
only for total vapor-phase mercury. All paired OH data meeting the method quality criteria were
eligible for inclusion in the calculation of RA. All 12 OH runs met the quality criterion and were
included in the RA calculation for the Apex system. A RA of less than 20% is considered
acceptable.(2) Alternatively, when the mean reference mercury level is less than 5.0 jig/dscm (as
in this test), agreement of the overall average Apex value within 1.0 jig/dscm of the mean OH
value is also considered acceptable.(2)
5.2 Data Completeness
Data completeness was calculated as the percentage of the total possible data return that was
achieved by the Apex system over its several days of operation in the field. The primary form of
data completeness was the number of OH runs (out of 12) for which the Apex system produced
valid data. In addition, any down time when the Apex system would not have been available to
carry out a measurement was judged as incomplete data. The causes of any substantial
incompleteness of data were established from operator observations or vendor records.
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Chapter 6
Test Results
The results of the verification tests of the Apex system are presented below for each of the
performance parameters.
6.1 Relative Accuracy
The RA of the Apex system with respect to the OH results for HgT was calculated using
Equation 1 in Chapter 5. The primary calculation of RA was conducted using the data from all
collected Apex sorbent samples. In addition, RA was calculated after applying the acceptance
criteria and spike recovery correction required under Appendix K(2) to the Apex sorbent trap
results. These additional calculations were made to illustrate the impact on RA results if these
criteria were applied.
Table 6-1 summarizes the results obtained from the Apex system. Table 6-1 lists the date, run
number, and trap number of each Apex sorbent sample; the HgT concentration in stack gas
determined by analysis of the first sorbent stage of each trap; and the corresponding average
concentration of each pair of traps. Also shown are the spike recovery percentage found by
analysis of the third stage of each trap, which was spiked with nominally 60 ng of mercury; the
Hgx concentration that results from applying the spike recovery correction to each trap as
indicated in Appendix K;(2) the corresponding average spike-corrected concentration of each pair
of traps; and the percent relative difference of the spike-corrected paired trap results. It should be
noted that several of the sorbent traps were broken during sampling. For four such traps, the first
sorbent stage could not be recovered, resulting in no measurement of stack gas mercury.
However, for three of those traps, the third sorbent stage was recovered, allowing determination
of spike recovery. Also, because of the breakage of traps, only a single trap was available for use
in the 12th sampling run.
Table 6-1 shows that the HgT results from paired sorbent traps were generally closely similar.
Table 6-1 also shows the spike recovery percentage for each trap, and indicates that this
percentage was always within the acceptable range of 75 to 125%. The analysis of the sorbent
traps had a minimum reporting limit of 10 ng of mercury per section of sorbent, and this value of
< 10 ng was reported for the second sorbent section (i.e., the backup sampling section) in every
trap. The maximum mass of mercury collected on any of the first sorbent sections was about
80 ng, so this reporting limit amounted to at least 12 percent of the mercury found on the first
section. As a result, it was not possible to determine whether mercury breakthrough from the first
to the second section was within the 5% limit stated in Appendix K.(2)
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Table 6-1. Apex System HgT Results
Date/Run/Trap
7/10/06 Rl Tl
7/10/06 Rl T2
7/10/06 R2 Tl
7/10/06 R2 T2
7/10/06 R3 Tl
7/10/06 R3 T2
7/1 1/06 R4T1
7/1 1/06 R4T2
7/1 1/06 R5T1
7/1 1/06 R5T2
7/1 1/06 R6T1
7/1 1/06 R6T2
7/12/06 R7 Tl
7/12/06 R7 T2
7/12/06 R8 Tl
7/12/06 R8 T2
7/12/06 R9 Tl
7/12/06 R9 T2
7/13/06 RIO Tl
7/13/06 RIO T2
7/13/06 R11T1
7/1 3/06 R11T2
7/13/06 R12 Tl
7/13/06 R12 T2
HgT
(jig/dscm)
1.146
1.113
1.059
c
1.083
1.082
1.127
c
1.269
1.312
1.320
0.956
1.138
1.172
1.027
1.114
1.036
1.254
1.305
1.260
1.233
f
Pair Avg
HgT
(jig/dscm)
1.130
1.059
1.083
1.127
1.269
1.316
1.047
1.099
1.075
1.254
1.283
1.233
% Spike
Recovery
105
105
95
90
103
97
113
113
e
113
123
108
88
90
110
95
100
100
95
103
105
95
105
Spike-
Corrected HgT
(jig/dscm)a
1.092
1.060
1.115
c
1.048
1.119
0.994
c
1.120
1.064
1.219
1.082
1.265
1.065
1.081
1.114
1.036
1.213
1.243
1.327
1.174
Pair Avg Spike-
Corrected HgT
(jig/dscm)
1.076
1.115
1.084
0.994
1.120
1.141
1.174
1.073
1.075
1.213
1.285
1.174
%RDb
1.5
d
3.3
d
d
6.8
7.8
0.7
3.6
d
3.3
d
a: Spike-corrected result = (HgT/% Spike Recovery) x 100.
b: %RD (percent relative deviation) = 100 x absolute value of (T1-T2)/(T1+T2).
c: Trap broken, first sorbent stage not recovered.
d: Only one valid result, %RD not calculated.
e: Trap broken, third (spiked) sorbent stage not recovered.
f: Only one trap available for this run.
6.1.1 Relative Accuracy: Vncorrected Data
Table 6-2 lists the HgT results in ug/dscm from the OH method (see Table 4-1) and the Apex
sorbent sampler (see Table 6-1, third column), for OH runs 1 through 12. Table 6-2 also notes
which five Apex results are from a single trap, as opposed to the average of paired traps. The RA
of the Apex sorbent sampler based on 11 runs (OH Run 8 is excluded, as noted in Section 4.1.1)
using the uncorrected data is 26.6%. Also for these 11 runs, the overall average HgT value from
the OH reference method is 1.008 jig/dscm, whereas the uncorrected Apex average is
1.171 jig/dscm, a difference of 0.162 jig/dscm.
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Table 6-2. Data Used for Comparison of OH and Apex HgT Results
Date
7/10/06
7/10/06
7/10/06
7/11/06
7/11/06
7/11/06
7/12/06
7/12/06
7/12/06
7/13/06
7/13/06
7/13/06
OH Run OH HgT
No. (jig/dscm)
1 0.935
2 0.860
3 0.969
4 0.952
5 0.787
6
7
8
g
10
11
12
.056
.083
.081a
.215
.074
.107
.053
Apex HgT
(jig/dscm)
1.130
1.059b
1.083
1.127b
1.269b
1.316
1.047
1.099
1.075
1.254b
1.283
1.233b
a: This ran excluded from RA calculation because %RD outside limits.
b: This result from a single trap; all others from paired traps.
6.1.2 Relative Accuracy: Spike-Corrected Data
Table 6-3 lists the HgT results in ug/dscm from the OH method (see Table 4-1) and the spike-
corrected results in ug/dscm from the Apex system (see Table 6-1, sixth column), for OH runs 1
through 12. Table 6-3 also notes which five Apex results are from a single trap, as opposed to the
average of paired traps. The RA of the Apex system based on 11 runs (OH Run 8 is excluded, as
noted in Section 4.1.1) using the spike-corrected data is 20.3%. Also for these 11 runs, the
overall average HgT value from the OH reference method is 1.008 ug/dscm, whereas the spike-
corrected Apex average is 1.132 jig/dscm, a difference of 0.124 jig/dscm.
The paired trap precision requirement of <10% RD stated in Appendix K(2) was met in the seven
Apex runs in which paired traps were recovered (see Table 6-1, last column). However, eight
runs is below the nine values needed to calculate RA, so that calculation was not done using only
the spike-corrected paired trap results.
6.2 Data Completeness
The Apex sampler was operated during all 12 of the OH runs conducted July 10-13, 2006.
However, as noted in Section 6.1 and described below in Section 6.3, the recovery of sorbent
traps for analysis was incomplete. Both of the paired sorbent traps were recovered and analyzed
for seven of the 12 OH runs, and one trap was recovered and analyzed in four other runs. In the
remaining run, only one sorbent trap was used because the Apex representative had exhausted
his supply of traps and did not have a second trap to install in the sampling probe. Treating those
runs with only one trap recovered as one-half of a complete sampling run, the overall data
completeness for the Apex sampler is calculated to be 79.2%.
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Table 6-3. Data Used for Comparison of OH and Spike-Corrected Apex HgT Results
Date
7/10/06
7/10/06
7/10/06
7/11/06
7/11/06
7/11/06
7/12/06
7/12/06
7/12/06
7/13/06
7/13/06
7/13/06
OH Run OH HgT
No. (jig/dscm)
1 0.935
2 0.860
3 0.969
4 0.952
5 0.787
6
7
8
g
10
11
12
.056
.083
.081a
.215
.074
.107
.053
Spike-Corrected Apex
HgT (jig/dscm)
1.076
1.115b
1.084
0.994b
1.120b
1.141
1.174
1.073
1.075
1.213b
1.285
1.174b
a: This ran excluded from RA calculation because %RD outside limits.
b: This result from a single trap; all others from paired traps.
6.3 Operational Factors
Apex Instruments had originally intended that the system verified in this test would use a new
product, a dual-train digital meter box. However, shortly before the field period, Apex personnel
concluded that the dual digital unit was not quite ready for field evaluation. As a result, the
system tested used two Apex Model XC-60 manual meter boxes, along with a SGC 4000 Hg
Stirling cooler to remove moisture from the sample gas, and a 9-foot long dual sampling probe.
The greatest limitation of the Apex system was the poor quality of the sorbent traps used. The
traps were very fragile, and the glass tubing used for the traps was of inconsistent diameter. With
some traps the glass tubing was slightly small in diameter, so that it was difficult to tighten the
Teflon® ferrule enough to achieve an adequate seal; with other traps the tubing was slightly too
large, so that the ferrule and corresponding nut could not even slide on over the tube. This
inconsistency made installation and retrieval of the traps difficult, and coupled with the relatively
thin wall of the glass tubing led to frequent breakage of the traps. The Apex representative had
brought 30 sorbent traps to the Schahfer site, more than enough to conduct 12 runs with dual
traps. However, in only seven of those 12 runs were both traps recovered for analysis, and in four
others only one trap could be recovered. For the final OH sampling interval, only a single usable
sorbent trap was available for the Apex system. It should be noted that this limitation due to the
traps is not related to the Apex sampling technology itself, i.e., improvements in the quality of
the sorbent traps should translate directly into improved performance of the entire system.
An additional limitation of the Apex system was the relatively heavy sampling probe used with
the system. This probe was very difficult for one operator to handle, and in fact the Apex
operator suffered a burn from contacting the hot probe while attempting to withdraw the probe
after an early sampling run. For safety, assistance was provided to the Apex operator in inserting
and removing the probe for subsequent sampling runs. Development of a simpler, lighter
sampling probe would be a valuable improvement to the Apex system.
19
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Chapter 7
Performance Summary
The RA of the Apex system for determining Hgx based on 11 OH runs was 26.6%, when the
comparison was based on Apex results uncorrected for mercury spike recovery. For those
11 runs, the overall average Hgx value from the OH reference method was 1.008 jig/dscm,
whereas that from the Apex system was 1.171 jig/dscm, a difference of 0.162 jig/dscm. When
comparing Apex results corrected for mercury spike recovery, the RA for 11 runs was 20.3%,
and the OH and Apex average values were 1.008 jig/dscm and 1.132 jig/dscm, respectively, a
difference of 0.124 jig/dscm.
The Apex sampler was operated during all 12 OH runs conducted over four days with no delays
or sampling interruptions. However, the recovery of sorbent traps for analysis was incomplete
due to breakage of traps. Both paired sorbent traps were recovered for seven of the 12 OH runs,
one trap was recovered for four runs, and in the remaining run only one usable sorbent trap was
available. Treating those five runs with only one trap recovered as one-half of a complete
sampling run, the overall data completeness for the Apex sampler is calculated to be 79.2%.
The greatest limitation of the Apex system was the poor quality of the sorbent traps used. The
traps were fragile, and the glass tubing used for the traps was of inconsistent diameter. This made
installation and retrieval of the traps difficult and led to frequent breakage of the traps. It should
be noted that this limitation due to the traps is not related to the Apex sampling technology itself,
i.e., improvements in the quality of the sorbent traps should translate directly into improved
performance of the entire system. An additional limitation of the Apex system was the relatively
heavy sampling probe used with the system, which was very difficult for one operator to handle
alone.
The approximate cost of the Apex system as tested (i.e., a manually operated dual system) is
$10,000 to $15,000, depending on options. The cost of each sorbent trap sample was $205,
including pre-spiking of the trap and analysis for mercury after sampling.
20
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Chapter 8
References
1. Test/QA Plan for Verification of Continuous Emission Monitors and Sorbent-Based
Samplers for Mercury at a Coal-Fired Power Plant, Battelle, Columbus, Ohio, May 18,
2006.
2. Code of Federal Regulations, 40 CFR part 75, including Appendices A through K, July
2005.
3. Standard Test Method for Elemental, Oxidized, Particle-Bound and Total Mercury in Flue
Gas Generated from Coal-fired Stationary Sources (Ontario Hydro Method)., ASTM D
6784-02, American Society for Testing and Materials, West Conshohocken, PA, June 2002.
4. Performance Specification 12A - Specifications and Test Procedures for Total Vapor Phase
Mercury Continuous Emission Monitoring Systems in Stationary Sources, 40 CFR Part 60
Appendix B, July 2005.
5. Quality Management Plan (QMP) for the ETV Advanced Monitoring Systems Center,
Version 6.0, U.S. EPA Environmental Technology Verification Program, Battelle,
Columbus, Ohio, November 2005.
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