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Update on Mercury Emission Measurement Reference Methods, Gas Standards and Traceability Protocols Scott Hedges USEPA, CAMD CAIR/CAMR Implementation Workshop EPA Region V Chicago, Illinois June 7, 2007. Background.

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Update on Mercury Emission Measurement Reference Methods, Gas Standards and Traceability ProtocolsScott HedgesUSEPA, CAMDCAIR/CAMR Implementation WorkshopEPA Region V Chicago, IllinoisJune 7, 2007

background
Background
  • The Clean Air Mercury Rule (CAMR) requires sources to install and certify mercury monitoring systems by January 1, 2009
  • Affected sources have begun ordering monitoring and data acquisition systems
  • Vendors have expressed a high level of confidence that continuous mercury emission monitoring systems will be available to meet industry needs and CAMR requirements
background3
Background
  • Development of the CAMR monitoring program has been a collaborative effort between EPA (OAQPS, ORD, CAMD), NIST and industry (EPRI, RMB, WRI, EERC and others)
  • EPA continues its full commitment to working with utilities, vendors, academia, NIST, and other organizations to successfully develop all aspects of the CAMR mercury monitoring program
  • Most major technical issues are behind us but some challenges remain
mercury monitoring next steps
Mercury Monitoring – Next Steps
  • Promulgate instrumental and sorbent-based mercury reference methods
  • Develop NIST-traceable calibration gases and protocols
  • Develop training materials and conduct training for EPA Regions, States and sources
  • Ordering, installation and certification of monitors by sources
  • Collect, quality assure, and report data
need for alternative reference methods
Need for Alternative Reference Methods
  • Reference methods will significantly help in performing RATAs of the mercury CEMS and sorbent trap monitoring systems required by CAMR
  • The currently-available reference method – Ontario Hydro – uses wet chemistry techniques and typically requires 2-3 weeks of laboratory analysis before the test results are known
  • The alternative reference methods should allow for RATA results to be known while the test team is on-site.
  • As such, timely alternatives to the lengthy and complex Ontario Hydro reference method are strongly desired
  • In fact, these alternative reference methods are needed as soon as possible
    • Most Hg CEMS and sorbent trap monitoring systems will need RATAs in 2008 to meet 1/1/2009 deadline
    • Many utilities are also planning RATAs this year
evaluation and validation of alternative reference methods
Evaluation and Validation of Alternative Reference Methods
  • EPA and industry (EPRI and others) are completing remaining field validation tests for the instrumental and sorbent trap-based reference methods
  • An instrumental reference method (IRM) that provides timely RATAs with immediate, real-time results is easier to implement than OH and is consistent with NOX and SO2 trading programs
  • A sorbent trap reference method is considered another viable alternative method. When it combines thermal desorption / direct combustion techniques, it allows for onsite analysis
  • EPA and EPRI are currently completing sorbent trap method comparison studies using a modified EPA Method 301 which compares existing data from sorbent trap systems against data from the Ontario Hydro reference method.
    • Body of sorbent trap data has been favorable (i.e., good agreement with Ontario Hydro)
availability of alternative reference methods
Availability of Alternative Reference Methods

EPA is preparing a rule package for both the instrumental and sorbent-based reference methods

  • Process being expedited through direct final rule making effort
  • Final rule tentatively scheduled for early August publication in the Federal Register
  • Would become final in October if no adverse comments are received
  • Methods will be made available at www.epa.gov/ttn/emc

- Pre-proposal drafts of these methods are tentatively planned to be posted in about a week to the above website with links to the CAMD website

mercury instrumental reference method irm
Mercury Instrumental Reference Method (IRM)
  • Timely (real-time)
  • Performance-based
    • Amenable to multiple and new technologies
    • Test program-specific verification of data quality
    • Agency committed to performance-based methods (Federal Register Notice of Intent 62 FR 52098, 10/6/97)
  • Consistent w/ SOx & NOx instrumental methods
  • Key elements
    • Calibration error/linearity
    • System integrity/conversion efficiency
    • System response time
    • Interference test
    • Dynamic spiking (gaseous method of standard additions)
mercury irm development
Mercury IRM Development
  • Used Methods 6C (SO2) and 7E (NOx) as starting point and factored in lessons learned from Hg CEMS demonstrations
  • Drafted Conceptual IRM and posted 2/28/06 at: www.epa.gov/ttn/emc/
  • Evaluated in field by EPA/ORD, EPRI, and others
planned modifications to 2 28 06 version of irm
Planned Modifications to 2/28/06 Version of IRM
  • Requiring only pre-test dynamic spiking and making optional until 1/1/09
  • Relaxing Hg0 calibration error criteria
  • Simplifying Hg2+ calibration to a system integrity check
  • Relaxing drift criteria
  • Making interference test optional
  • Waiving Hg stratification testing until 1/1/09 and adding a “low emitter cutoff”
sorbent trap reference method for mercury
Sorbent Trap Reference Method for Mercury
  • Performance-based
    • Amenable to new sorbents, equipment, and analytical technologies
      • Lab verification of sorbent performance and analysis
      • Test program-specific verification of data quality
  • Capability for timely results
  • Description
    • Known volume of stack gas is sampled through paired, in-stack 2-section sorbent traps (e.g., iodated carbon)
    • Analysis by any suitable system that can meet performance criteria (e.g., leaching, digestion, thermal desorption/direct combustion coupled with UV AF, UV AA, XRF)
sorbent trap reference method for mercury cont
Sorbent Trap Reference Method for Mercury, cont.
  • Key QA Elements
    • Laboratory
      • Matrix interference test (for wet digestion analyses)
      • Minimum sample mass determination
      • Analytical bias test (Hg0 and Hg2+)
    • Field (for each test)
      • Paired train agreement (assess precision)
      • Sorbent trap second section breakthrough
      • Field recovery test (assess bias)
proposed monitoring changes to part 75
Proposed Monitoring Changes to Part 75
  • Proposed Part 75 rule changes published August 22, 2006
    • Comment period closed in October 06
    • Reference Method 29 proposed as an alternative Ontario Hydro reference method
    • Minor technical/procedural changes proposed to Subpart I of Part 75 including adding multiple/common stack heat input procedures
    • Solicited comments relating to the development of reference method based on sorbent trap technology
    • Received comments were not extensive - essentially supportive of changes
    • Rule expected to become final late summer
additional hg related part 75 changes being considered
Additional Hg-Related Part 75 Changes being Considered
  • Possible changes to Subpart B (Monitoring Provisions) and Appendix K being considered for inclusion in the Alternative Reference Method Rule Package
    • Providing minor clarifications to the Hg monitoring and measurement provisions
    • Requiring same type of sorbent material used during an Appendix K RATA also be used during daily operation
    • Allowing smaller sorbent traps to be used during an Appendix K RATA than used during daily operation
      • will reduce the required sampling time per run
    • Removing spike recovery normalization correction to sorbent trap monitoring systems
    • Providing alternatives to dry gas meters in Appendix K (e.g., allowing the use of thermal mass flow meters)
nist traceable hg calibration standards
NIST-Traceable Hg Calibration Standards
  • EPA and NIST continue their collaborative work to provide NIST traceability for elemental and oxidized mercury calibration standards
  • We are expecting to have NIST-traceability protocol documents this year for use in certifying CEMS and sorbent trap monitoring systems
  • A working draft traceability protocol has been prepared for elemental mercury gas generators
    • Will incorporate user-friendly uncertainty calculation spreadsheets into the draft
hg gas standard traceability
Hg Gas Standard Traceability
  • CAMR requires “NIST Traceable” elemental and oxidized Hg gas standards
  • A "NIST-traceable" Hg gas generator is one that has been compared and certified directly (without intermediate standards) to another Hg gas generator that has been certified by NIST at its laboratories
  • Gas standards must be traceable to a measured, not theoretical, concentration
how traceability protocol works
How Traceability Protocol Works …
  • NIST Standard and NIST-Traceable Reference Materials (SRMs and NTRMs) are gas standards used by vendors to:

- generate the gas standards used in the field by industry

- calibrate instrumentation to establish the concentrations of the field gases sold

  • EPA Traceability Protocol provides guidance on how to establish the uncertainty of the gases used, traceable to the NIST reference materials
how protocol process works for elemental hg generators
How Protocol Process Works for Elemental Hg Generators
  • NIST certifies vendor-prime generators using ID-ICP/MS
  • NIST calibrates individual set points that are used to certify vendor-prime generators
  • EPA traceability protocol uses qualification and certification tests to establish traceability of field generators (user-primes) to NIST-certified generators (vendor-primes)
  • Protocol includes quarterly QC check procedures to evaluate continuous performance of generators in the field
  • It is the responsibility of the vendor to qualify and certify their field generators using the guidance in the protocol
  • It is the responsibility of the end user to perform the quarterly QC checks once their generators have been placed into field operation
qualification tests for establishing traceability
Qualification Tests for Establishing Traceability
  • Qualification tests have been designed to examine representative generators for potentially significant operating variables (e.g., back pressure, temperature and flow control, operating environment temperature and voltage, drift, etc) and their effect on candidate generator output performance

- To qualify for certification, the output of a candidate generator must be repeatable

- Qualification tests designed to demonstrate that the candidate generator output is repeatable over an appropriate range for each variable likely to change between the time and place of certification and its subsequent use

- Focus is given to variables that may impact performance in the field

qualification tests for establishing traceability21
Qualification Tests for Establishing Traceability
  • The objectives of the qualification tests are to demonstrate thata candidate generator's concentration output is repeatable within ±1% relative
  • The relationship between the output and the variable needs to be quantified during the qualification tests
  • Repeatability must be within ± 1 percent relative for each variable that may change between the point of certification and the point of use
  • Repeatability tests are based on a series of single point comparisons made between the candidate generator and a stable gaseous mercury calibration standard at six or more different concentrations on each of six or more different days
certification tests for establishing traceability
Certification Tests for Establishing Traceability
  • Certification tests have been designed to establish a quantitative relationship between each field generator and the local vendor-prime generator
  • Tests are comparable to the NIST certification procedures/method for vendor-prime generators, the difference is that additional statistical / mathematic expressions are being developed that predict mercury concentrations over the entire calibration range of the generator within a known level of uncertainty
  • These quantitative relationships will be available in easy-to-use spreadsheet software that vendors can use to enter generator set point vs measured concentration
  • The spreadsheet will then establish the predictive relationship of generator set point to output concentration with a known uncertainty as a relative function of concentration
  • It is anticipated that the equation will be simply added to the software of each generator so that set point and true concentration agree
certification tests for establishing traceability23
Certification Tests for Establishing Traceability
  • Certification requires the measurement of at least 6 comparisons between the candidate generator and a vendor-prime generator at each of no less than 6 NIST-certified concentrations
  • These comparisons must cover the full range of Hg concentrations (0.2 to 40 µg/m3) and must be spaced equally across at least two days (e.g., 3 comparisons on Day 1 and 3 comparisons on Day 2)
  • Certification tests are used to establish the 6 comparisons over two days (to determine inter and intra-day repeatability)
  • Statistical analyses are used to determine output uncertainty
  • Combined (extended) uncertainty must be within ± 3 percent
  • We plan to allow a combined uncertainty of ± 5 percent until January 9, 2009 for intra- and inter-day repeatability testing of generators to be completed and interpreted
certification tests for establishing traceability24
Certification Tests for Establishing Traceability

EPA is working on an alternate procedure to allow field certification of candidate generators at three specific concentrations by direct nose-to-nose comparison with the identical concentrations from a vendor-prime generator. The same combined (extended) uncertainty acceptance criterion that is applicable for the six-concentration approach will also apply to the three-concentration approach.

traceability of elemental mercury gas cylinders
Traceability of Elemental Mercury Gas Cylinders
  • Combined overall uncertainty target is currently ± 3 percent
  • Currently elemental mercury gas cylinders are prepared/certified according to the Green Book (the existing EPA traceability protocol for gas standards)
  • Shelf life and stability will be assessed by NIST and EPA with input from vendors and WRI
  • Cylinders will play a valuable quality assurance role including their use:

- in evaluating the field performance of gas generators, and

- as stand alone gas standards

nist traceable hg calibration standards27
NIST-Traceable Hg Calibration Standards

To date EPA:

  • Has prepared working draft elemental mercury gas generator traceability protocol
  • Working draft has been sent to vendors
  • Is preparing oxidized mercury gas traceability protocol
nist traceable hg calibration standards28
NIST-Traceable Hg Calibration Standards

To date NIST:

  • Has developed draft certification procedures for elemental and oxidized mercury gas generators (vendor-prime generators)
  • Invited generator vendors to come in and begin certifying elemental mercury gas generators