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Status of Alternative Reference Methods for Mercury Emission Measurements – Part 1 Scott Hedges, USEPA, CAMD EPRI CEM Users Group Meeting Phoenix, AZ May 9 - 11, 2007. Need for Alternative Reference Methods.

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Status of Alternative Reference Methods for Mercury Emission Measurements – Part 1Scott Hedges, USEPA, CAMDEPRI CEM Users Group MeetingPhoenix, AZMay 9 - 11, 2007
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
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)
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