U.S. Environmental Protection Agency
•ificatio
ET
Mercury Continuous Emission Monitors (OEMs)
The U.S. EPA Environmental Technology Verification
(ETV) Program's Advanced Monitoring Systems (AMS)
Center, operated by Battelle under a cooperative agreement
with EPA, has verified the performance of seven continuous
emission monitors1 (CEMs) for measuring mercury
emissions (Figure 1). Four additional monitoring
technologies are currently in testing with reports to be final
in early 2007. To address the health effects caused by
mercury emissions from coal-fired plants, EPA recently
issued the Clean Air Mercury Rule (CAMR). This rule
requires coal-fired power plants, the largest remaining
unregulated source of human-generated mercury emissions
in the U.S., to reduce mercury emissions. The rule also will
require power plants to monitor their mercury emissions
using technologies like those verified by the ETV Program.
Technology Description
and Verification Testing
CEMs for mercury are a rela-
tively new technology
category. They offer an
advantage over conventional
laboratory techniques (e.g.,
^^! the Ontario Hydro method) in
^" that they can provide
continuous or frequent results
through sequential readings at
intervals of several minutes,
, labor, and cost associated
One of the test locations for
mercury CEM verification
Mercury and Its Regulatory
Background at a Glance
Mercury is a toxic, persistent pollutant mat,
after deposition from the atmosphere and
methylation bioaccumulates in the food
chain, particularly in fish. Mercury can cause
adverse neurological health effects,
particularly in young children and the unborn
children of mothers who eat food
with significant quantities of mercury.
The Clean Air Mercury Rule (CAMR), which
EPA issued on March 18, 2005, creates
a market-based cap-and-trade program that
will reduce nationwide utility emissions of
mercury. Under a cap-and-trade program, coal-
fired power plants that reduce emissions more
than is required receive allowances. They can
then trade these allowances to sources that are
unable to meet the requirement, or bank them
for future use.
A cap-and-trade program, like that under
the CAMR, must include reliable monitoring
of emissions to ensure that reductions occur,
allow for tracking progress, and lend
credibility to the trading component of the
program. Therefore, the CAMR requires coal-
fired utilities that emit more than 29 pounds of
mercury per year to collect mercury emission
data continuously. To collect these data, the
utilities can use either CEMs, like those
verified by the ETV Program, or another long-
term mercury sampling method, a sorbent trap
monitoring approach.
and thus, they avoid the delay
with laboratory methods.
The ETV-verified CEMs determine elemental mercury
vapor concentrations by atomic absorption (AA), atomic
fluorescence (AF), or plasma atomic emission (AE). The
CEMs use aqueous reagents or heated catalysts to reduce
oxidized forms of mercury to elemental mercury for
detection, allowing measurement of total vapor-phase
mercury. Although some CEMs only measure total vapor-phase mercury (i.e., the sum of elemental and
oxidized mercury vapor), others allow separate measurement of the elemental and oxidized forms. Table 1
summarizes some of the performance data for the verified technologies. Additional information on the
verification of mercury CEMs can be found at http://www.epa.gov/etv/verifications/vcenterl-ll.html.
The verification testing was conducted in two phases. In the first phase, four of the technologies were tested
under conditions simulating a) coal-fired flue gas, and b) municipal incinerator flue gas. The tests took place at
a pilot-scale incinerator in Research Triangle Park, North Carolina, over a three-week period. In the second
phase, five technologies (including two of the technologies tested in the first phase) were evaluated at a foil-
scale hazardous waste incinerator
in Oak Ridge, Tennessee. In
addition, the ETV Program is
currently conducting a third
phase of testing at a coal-fired
power plant. The box on the right
identifies CEMs and sorbent-
based sampling technologies
included in this third phase.
ETV Advanced Monitoring
Systems Center
Robert Fuerst, EPA
fuerst.robert (glepa.gov
Tel: (919) 541-2220
Amy Dindal, Battelle
dindala@battelle.org
Tel: (561) 422-0113
Mercury Monitoring Technologies
Included in the Third Phase of
ETV Verification
Tekran Instruments, Series 3300 Mercury CEM
Thermo Electron, Mercury Freedom System
Environmental Supply Company, HG-324
sorbent-based sampling system
Apex Instruments, mercury sorbent-based
sampling system
The ETV Program operates largely as a public-private partnership through competitive cooperative agreements with non-profit research institutes. The
program provides objective quality-assured data on the performance of commercial-ready technologies. Verification does not imply product approval or
effectiveness. ETV does not endorse the purchase or sale of any products and services mentioned in this document.
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Selected Outcomes of Verified
Mercury CEM Technologies
• Contributed to advancing mercury
monitoring technology and resulted in
improvements in monitors by the
participating vendors
• Helped inform the development of the
CAMR and could assist in future rule
refinements
• Helped small vendors compete in the
marketplace
• Verification of the mercury CEMs
involved significant collaboration
with state agencies (e.g.,
Massachusetts and Connecticut), the
Department of Energy and Illinois
Clean Coal Institute. These
collaborations resulted in the sharing
of scientific expertise among the
agencies and enabled smaller vendors
to participate in the tests.
Fig 1. ETV-Verified CEMs for Mercury (First Two Phases of Testing)
Envimetrics, Argus-Hg 1000 Mercury CEM:
Uses AE spectroscopy with a proprietary catalytic
converter that reduces molecular forms of
mercury to atomic mercury. Total mercury can be
measured during automatic operation, or both
total and elemental mercury can be measured
when manually operated.
Nippon Instruments Corporation, DM-6/
DM-6P Mercury CEM: Uses cold vapor
AA with a catalytic process to measure
total mercury.
Nippon Instruments Corporation, AM-2
Elemental Mercury CEM: Uses cold vapor
AA, with a distilled water scrubbing trap for
removal of any oxidized mercury species, to
measure elemental mercury.
OPSIS AB, HG-200 Mercury
CEM: Uses a double-beam pho-
tometer to measure total or ele-
mental mercury with a thermo-
catalytic converter that forms
elemental mercury from any
oxidized mercury compounds to
measure total mercury.
PS Analytical, Ltd., Sir Galahad II
Mercury CEM (verified in both
phases): Uses AF to provide
separate and continuous
measurement of elemental and total
mercury with a proprietary aqueous
reagent to convert oxidized mercury
to elemental mercury for total
mercury measurement.
Nippon Instruments Corporation, MS-1/
DM-5 Mercury CEM (verified in both
phases): Uses cojd vapor AA to provide
separate and continuous measurements of
elemental and oxidized mercury, which are
separated using a wet scrubbing and
chemical reaction system.
CEM: Uses cold vapor AA to provide
separate and continuous measure-
ments of elemental and total mercury,
with catalytic pyrolysis to decompose
oxidized mercury to elemental mercury
for total mercury measurement.
The price of the monitors ranged from $30,000 to $70,000 at the time of testing.
Table 1. Selected Performance of Verified CEMs for Mercury
Technology*
Average Relative
Accuracy, %
Relative
Precision, %
Response
Time (95%)
Bias, %
Correlation6
Slope
Intercept
r2
Data
Completeness
First Phase
A
B
C (Phase I)
D (Phase I)
58.2 to 71%
(total mercury)
14 to 23%
(elemental
mercury)
20.6 to 32.8%
(total mercury)
13.2 to 39.1%
(total mercury)
2.5 to 27%
3 to 40.3%
1.8 to 24.7%
3.7 to 23.9%
30 to 100
seconds
One 13-minute
cycle
One 5- to 6-
minute cycle
35 to 50 sec-
onds
-44.5 to -20.5%
7%
-4.9 to -0.3%
-7%
not re-
ported
0.885
0.681
0.607
not reported
-0.212
2.492
3.92
0.621
0.973
0.978
0.938
Not estimated
100%
100%
100%
Second Phase
C (Phase 1 1)
D (Phase II)
E
F
G
59.8%
(total mercury)
11.2%
(total mercury)
76.5%
(overall)
20.3%
(overall)
76.3%
(overall)
8.9 to 15.9%
9.2 to 17.3%
10.1 to 22.1%
9.1 to 10.9%
12. 5 to 43. 3%
One 5- to 6-
minute cycle
2 to 3 minutes
One7-minute
cycle
2 minutes
One5-minute
cycle
2.8 to 6.9%
0.0 to 6.6%
0.3 to 14.6%
0.0 to 13. 6%
Not
evaluated
0.4973
0.899
0.3404
0.8347
0.3559
6.8904
2.4969
9.4121
3.5033
8.1695
0.875
0.987
0.839
0.953
0.935
88.3%
97.7%
92.7%
97.5%
65.8%
A Because the ETV Program does not compare technologies, the performance results shown in this table do not identify the vendor associated with each result and are not in
the same order as the list of technologies in Figure 1 .
B Correlation data shown are for total mercury, except technology B, where results shown are for elemental mercury.
Note: In each phase of verification testing, the Ontario Hydro method was used as the reference method for establishing the performance of the tested technologies. The
performance parameters verified included the following: accuracy relative to the Ontario Hydro method, correlation with that method, precision (i.e., repeatability), bias, cali-
bration/zero drift, response time, interferences, data completeness, and other operational factors. The ETV Program found that the average relative accuracy for the monitors
ranged from 11. 2 to 76.5%. A result of 0% indicates perfect accuracy relative to the reference mercury concentration. The relative precision ranged from 1.8 to 43.3%. A
result of 0% indicates perfect precision. A higher r2 value indicates a h gher correlation with the standard test method over the range of concentrations tested.
References
U.S. EPA, Mercury, http://www.epa.gov/mercury/.
U.S. EPA, 2006. ETV Case Studies: Demonstrating Program Outcomes. Volume II.
EPA/600/R-06/082. September 2006. (Primary source)
U.S. EPA, ETV, http://wmv.epa.gov/etv/.
EPA/600/S-07/006
January 2007
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