**[Mercury Emissions Monitoring Program for Coal-Fired
Boilers]{.underline}**

**[under the Clean Air Mercury Rule]{.underline}**

**[Status Report]{.underline}**

**August 2006**

**Introduction**

The Clean Air Mercury Rule (CAMR) requires affected electric utility
units to continuously monitor mercury (Hg) mass emissions, using
technically-feasible, compliance-capable technologies. To ensure that
the Hg emission reduction goals of CAMR are met, these monitoring
technologies will be subject to rigorous certification and quality
assurance/quality control (QA/QC) requirements under 40 CFR Part 75. The
U.S. Environmental Protection Agency (EPA) continues to work with the
regulated community, the monitoring equipment and software vendors,
academia, and other organizations to ensure timely implementation of a
technically sound, effective CAMR mercury monitoring program.

This paper updates the February 2006 status report on the mercury
emissions monitoring program under the CAMR. The paper discusses the
results of the mercury emission monitoring demonstration and method
validation tests to date and the remaining challenges to be overcome.
The paper also discusses capacity issues associated with the
availability and installation of the required monitoring systems within
the required CAMR deadlines.

**Background**

Over the past two years, EPA, the Electric Power Research Institute
(EPRI), industry and monitoring equipment vendors have conducted field
demonstration and validation tests of continuous mercury emission
monitoring systems (CEMS) and sorbent trap monitoring systems at a
number of coal-fired utility boilers. EPA and the National Institute of
Standards and Technology (NIST) have also been working together to
develop NIST-traceable mercury calibration gas standards and protocols
necessary to ensure the accuracy of the mercury monitoring systems. As a
result of these tests, system design changes have been made to improve
the performance and reliability of the monitoring systems. Most notably,
design changes have been made to reduce probe plugging and calibration
drift, particularly under wet stack environments. Additionally, the
precision between different CEM systems has improved dramatically.

Working with EPRI, NIST, and industry, most of the major issues have
been successfully addressed, and now the focus of future field tests and
laboratory analyses is on resolving the remaining issues. These include:
(1) developing a viable instrumental reference method (IRM) for mercury;
(2) finalizing NIST traceability protocols for Hg calibration gas
cylinders and gas generators; and (3) improving CEMS performance in
daily calibration error tests and system integrity checks (especially in
low temperature, low concentration, high moisture stack environments).

EPA is also working with industry and other groups to develop an
alternative reference method using sorbent trap technology. However, the
Agency still considers a workable instrumental reference method for
mercury to be the best alternative to the currently-required Ontario
Hydro wet-chemistry reference method.

**Hg CEMS and Sorbent Trap Hardware**

Mercury monitoring technologies continue to advance at a rapid pace and
are on-track to meet the QA/QC requirements required under CAMR.
However, continued commitment from all parties is essential to maintain
this pace and ensure that CAMR requirements are met.

Approximately, twelve Hg CEMS and sorbent trap vendors are currently
developing new and improved monitoring systems. EPA, EPRI and monitoring
system vendors will continue to conduct tests demonstrating these
improvements at various coal-fired power plants in the United States. Hg
CEMS manufactured by Tekran, Horiba, Durag, Opsis, Thermo, Ohio Lumex,
Forney/Genesis, and GE/PS Analytical are currently being field tested.
Most manufacturers have made significant improvements to or refinements
of their monitors as a direct result of EPA and EPRI's field
demonstration tests. For example, several new CEMS probe designs have
been developed, some of which reduce plugging and may reduce system
calibration drift in low concentration, high moisture stack
environments. Other more streamlined probe designs are being developed
by equipment vendors to facilitate sample traversing[^1]during IRM
testing. Vendors are also working to integrate Hg calibration gas
generating systems into their CEMS.

Mercury sorbent trap monitoring systems continue to perform well at the
EPA and EPRI field test sites. Remaining developmental efforts for these
systems will include: (1) testing of a variety of sorbent materials and
sample conditioning systems; and (2) development of alternatives to the
lengthy process of sending Hg samples to a laboratory for analysis.
Promising alternatives that allow for rapid, on-site sample analysis
include thermal desorption and direct combustion methods, both of which
are based on sample heating/combustion to release mercury. Industry is
also working to improve the Hg detection capabilities of sorbent trap
systems in low-concentration stack environments.

**Instrumental Reference Method Evaluation and Validation**

EPA has drafted a conceptual mercury IRM to provide an alternative to
the lengthy and complex Ontario Hydro reference method currently
required by CAMR. EPRI and industry will continue to provide IRM
development assistance to EPA through the assessment of its feasibility
and challenges. Issues associated with the implementation and validation
of the conceptual IRM are currently being addressed at the EPA North
Carolina and the EPRI Kentucky test sites. Also, IRM development was one
of the primary areas of focus at the recent Pennsylvania/Lehigh
University field test, and is currently a primary area of focus at a
Texas lignite field test site. The principal objective of these field
tests is to demonstrate the practicality and effectiveness of the draft
IRM procedures in a variety of stack environments. EPA and EPRI are
examining the length of time required to perform the procedures and the
efficacy of pre- and post-test dynamic spiking, as well as the
possibility of using SO~2~ stratification test results as an indicator
of Hg stratification in the stack. Equipment manufacturers are also
exploring equipment design modifications to improve sample conditioning,
reference method probe mobility, and the integrity of the instruments
during transport.

**Field Demonstrations**

Field demonstration tests currently in progress include a continuation
of EPA's work at a coal-fired power plant in North Carolina and EPRI's
work at a field test site in Kentucky. Substantial improvements in Hg
CEMS and sorbent trap operation and performance have been achieved at
these two test sites. Testing was recently completed at a coal-fired
power plant in Pennsylvania in collaboration with Lehigh University, and
additional testing has commenced at a lignite coal-fired facility in
Texas. The following paragraphs describe these tests in more detail.

[North Carolina Site Testing]{.underline}: At this dry stack location,
EPA ORD has installed and operated a Tekran CEMS since December 2004. In
addition to the Tekran system, the test team has evaluated Hg CEMS
manufactured by Thermo, Horiba, GE/PS Analytical, Forney/Genesis, Durag
and Ohio Lumex. These evaluations include multiple certification and
relative accuracy tests as well as long-term daily calibration error
tests and weekly system integrity checks. Results of the testing effort
include improvements in instrument reliability as evidenced through
increased data availability. More recently, the North Carolina site has
been used to demonstrate and optimize tools and approaches for
implementing the conceptual IRM, including the refinement of approaches
for dynamic spiking. The North Carolina test site is also being used to
evaluate new and innovative probes that can be used to meet the
traversing requirements of the IRM.

[Kentucky Site Testing]{.underline}: As mentioned in the February 2006
status report, the Kentucky test site is now serving as an equipment and
software development location for Hg CEMS vendors and is considered to
be representative of the most challenging measurement environment found
among well-controlled boilers (i.e., it represents low temperature, low
Hg concentration, and high moisture flue gas conditions). EPRI has
evaluated the performance and reliability of CEMS manufactured by GE,
Thermo, and Tekran at this site, as well as sorbent trap systems made by
Frontier Geosciences. Remaining CEMS and sorbent trap performance issues
continue to be addressed.

Participating equipment vendors are also developing and testing suitable
probes for the wet stack conditions encountered at the Kentucky site.
One manufacturer is testing two probe types simultaneously. Each of
these new probes has shown promise, and has significantly reduced the
occurrence of plugging. On-going efforts are being made to continue to
improve probe reliability and reduce the amount of required maintenance
and repair. The Agency expects that industry and vendors will have
reliable probes within the next few months.

Other outstanding CEMS issues that have been identified at the Kentucky
test site include: (1) the need to reduce calibration drift; (2) the
need for front-end humidification to allow for dynamic spiking and daily
calibration at the probe; and (3) the need to optimize the position of
the Hg converter in the sampling system (i.e., nearer to or farther away
from the probe). EPRI and industry experts are addressing these issues,
however, the same high level of commitment and support provided up to
this point needs to be maintained by all parties to ensure that these
issues are satisfactorily resolved.

[Lehigh Field Study]{.underline}: With support from EPA, EPRI, the
Italian government, several utility companies and others, the Lehigh
University Energy Research Center (ERC) organized a field test where
reference methods for mercury, heavy metals and particulate, which have
been developed in the U.S. and the European Union (EU), were compared.
The field testing was begun in late June 2006 and was completed in July
2006. Testing was conducted by a joint U.S. and European Union team at a
power plant in Pennsylvania. Western Kentucky University (WKU) provided
a mobile mercury test laboratory for the project.

As part of the Lehigh field study, EPA was able to satisfactorily
perform many of the procedures in EPA's draft conceptual IRM, including
dynamic spiking, calibration error, and system integrity tests. The test
team performed IRM test procedures on Hg CEMS manufactured by Thermo
Electron, Tekran, GE/PS Analytical and Ohio Lumex. In addition, Frontier
Geosciences and CONSOL/Clean Air performed Appendix K sorbent trap
monitoring. The Lehigh study provided a valuable opportunity to assess
the amount of time required to perform the IRM pretest activities and
sample runs, and to develop and optimize the dynamic spiking procedures.
Due to time and resource constraints, only limited traverse and
stratification tests (using SO~2~ as a surrogate) were undertaken. These
issues will be addressed more fully in future field tests. The results
of the conceptual IRM testing from the Lehigh study will be compared to
those obtained with paired Ontario Hydro trains.

[We Energies Michigan Field Study]{.underline}:

We Energies has been working with the Department of Energy on a mercury
control technology demonstration project at a Michigan test site,
involving a ®TOXECON baghouse and activated carbon injection to control
mercury emissions from three electric generating units. Hg CEMS
manufactured by Thermo have been installed on the inlet and outlet of
the baghouse and have been operating without any significant problems
for several months. Baseline stack tests were conducted in February
using the Ontario Hydro reference method and the Appendix K sorbent trap
method. In addition, CEMS relative accuracy and IRM evaluation testing
are scheduled to be performed later this summer or in the fall.

[Texas Lignite Field Study:]{.underline}

WKU, in conjunction with EPRI, is conducting three field tests on Tekran
and Thermo CEMS at a lignite-fired utility plant in Texas. The tests are
scheduled to be completed later this summer. Both relative accuracy and
IRM evaluation testing will be conducted. Stratification tests, using
SO~2~ as a surrogate for Hg, will also be performed during one of the
field tests.

[Additional Field Tests:]{.underline}

EPRI and the U.S. Department of Energy performed relative accuracy tests
of a Hg CEMS and a sorbent trap monitoring system at another field site
in Pennsylvania. IRM evaluation tests were also performed. The IRM tests
were conducted using batch-type dynamic spiking.

Field tests of Thermo and Tekran CEMS and two sorbent trap monitoring
systems have also been performed at an Indiana power plant. These tests
are part of EPA's Environmental Technology Verification (ETV) program.
The verification testing included two relative accuracy tests, the first
of which was conducted in mid-June 2006 and the second in mid-July 2006.
IRM evaluation testing was not done at this site.

**Availability of Mercury Monitoring Systems**

Approximately 1100 electric generating units (EGUs) are affected by
CAMR. EPA estimates that between 800 and 1000 mercury monitoring systems
(i.e., Hg CEMS and sorbent trap systems) must become commercially
available between now and 2008, to ensure that the affected EGUs will be
able to meet the continuous emission monitoring requirements of CAMR.
The exact number of Hg monitoring systems that will be needed to
implement CAMR is somewhat uncertain, because: (1) some of the affected
units are in common stack configurations; and (2) at least 100 to 200 of
the affected units are expected to qualify as low mass emission (LME)
units under Part 75 (§75.81(b)), and the owners of these units may elect
to perform periodic Hg emission testing rather than installing mercury
monitoring systems.

The manufacturers of Hg CEMS have indicated that beginning in 2007 they
will, collectively, be able to produce well over 1000 CEMS per year. One
vendor plans to produce 600 Hg CEMS per year, and a second vendor plans
to produce 60 CEMS per month. A number of other monitoring equipment
manufacturers also plan to increase their production capabilities to
meet the monitoring demands of CAMR. Based on these projections, there
will be more than enough Hg CEMS and sorbent trap systems available to
meet the requirements of CAMR, and there should be sufficient time for
facilities to install and certify the monitoring systems before the
January 1, 2009 compliance deadline.

Thus, EPA is confident that the CAMR monitor certification deadline will
be met. The Agency will continue to work with industry and with the
equipment vendors to ensure that the CAMR emissions monitoring program
is implemented on schedule.

**NIST- Traceable Hg Calibration Standards**

NIST continues to provide assistance in developing Hg reference
standards for elemental and oxidized mercury. The existence of such
reference standards is the first step in developing the NIST-traceable
Hg standards for use under Part 75. EPA ORD and NIST are collaborating
to develop calibration procedures for mercury gas generators and
cylinders. Gas generators calibrated by these procedures are expected to
be available for field tests during the fall of this year. These
calibration procedures will serve as the basis for drafting traceability
protocols for elemental and oxidized mercury. The Agency also expects
that NIST-traceable gas standards and protocols will be available in
fiscal year 2007 for use in certifying CEMS and sorbent trap monitoring
systems.

**Rulemaking Changes to Hg Monitoring Provisions in Part 75**

EPA has proposed minor technical and procedural changes to the Hg
monitoring provisions of Part 75. The proposed changes were published in
the Federal Register on 22 August 2006 and are expected to be finalized
by early summer 2007. These changes include adding EPA Method 29 (with
additional QA provisions consistent with the Ontario Hydro method) as an
alternative reference method. Method 29 is similar to Ontario Hydro, but
is more familiar to stack testers. The method would be an option for
relative accuracy and LME tests.

The rule change proposal also addresses the testing and reporting
requirements of mercury LME units and provides changes to the common
stack provisions. EPA will also solicit comment on how to equitably
apply the LME provision to units which, in addition to coal, burn fuels
that have very low Hg content. The rule currently assumes that only coal
is burned in these units.

[^1]: In order to make measurements of its concentration in the stack,
    sampling at multiple points is generally required. "Traversing" is
    the act of moving the probe to reach the individual sampling points.