# Presentation: 655412

*Update on Mercury Emission Measurement Reference Methods, Gas Standards and Traceability Protocols*
- Scott HedgesUSEPA, CAMDCAIR/CAMR Implementation WorkshopEPA Region VII, Kansas City, KS
- August 16, 2007

## 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

## 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 

- Complete direct final rule package which includes instrumental and sorbent-based reference methods
- Complete NIST-traceable calibration gas certification procedures and protocols
- Continue field demonstration testing of reference method options
- Develop training materials and conduct training for EPA Regions, States and sources
- Already completed CAIR/CAMR implementation training workshops in Atlanta, Chicago and Dallas
- Will conduct workshops in Denver in October and in DC area in November

## Need for Alternative Reference Methods

- Reference method options 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 will 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
- Hg CEMS and sorbent trap monitoring systems will need RATAs in 2008 to meet 1/1/2009 deadline
- Many utilities are also planning preliminary RATAs this year

## 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)

## Alternative Reference Methods to be included in Direct Final Rule Package

- EPA is finalizing direct rule package for both the instrumental and sorbent trap-based reference methods
- Drafts of these methods were posted on OAQPS Emission Measurement Center website and linked to CAMD’s website (refer to Method 30A and 30B posted at:
- 		http://www.epa.gov/ttn/emc/prelim.html)
- This posting will help power plants and stack testers plan for upcoming certification tests
- Rule is expected to be signed this week and published in the Federal Register in late August/early September
- Rule would become final in late October/early November if no adverse comments are received

## 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

- Used Methods 6C (SO2) and 7E (NOx) as starting point and factored in lessons learned from Hg CEMS demonstrations
- Conceptual IRM posted on EPA EMC website in February 2006 (www.epa.gov/ttn/emc)
- Evaluated in field by EPA/ORD, EPRI, and others

## Modifications to Conceptual 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
- Improved guidance for stratification testing (temporal variation, low level cutoff)
- Waiving Hg stratification testing until 1/1/09

**Notes:**
Until 2009, testers can either use SO2 as a surrogate and perform stratification testing or assume minimal stratification and use the 3-point short measurement line.

In 2009, the waiver is no longer in effect and any stratification testing that is done to justify using fewer sampling points or a different measurement line must be Hg stratification testing, performed in accordance with the Method 30A procedure.  

"low emitter cutoff" means that for very low Hg concentrations (TBD), we are considering waiving stratification testing altogether at test locations  where it would normally be needed  to justify fewer sampling points or a different measurement line (e.g., after a wet scrubber).

## IRM Advancements - Update on Demonstration Testing

- More portable IRM equipment are now available (e.g., 25 pound probes as compared to 150 pound probes or higher just a year ago)
- We can traverse, conduct tracer gas flow measurements and conduct dynamic spiking with latest IRM sampling equipment
- We are working with vendors to optimize their equipment
- These new equipment will be used for upcoming Hg stratification testing
- Stratification testing is our highest remaining priority for IRM verification testing

## 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.

- 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)

##  Advancements in Sorbent Trap Method - Update on Demonstration Testing

- EPA has successfully demonstrated the efficacy and timeliness of the sorbent trap reference method during recent (May 07) demonstration tests
- Good spike recoveries (within ± 15% of complete recovery)
- Reduced quantity of Hg needed for analysis (about 20 ng minimum sampling mass)
- Reduced sampling time (one hour or less)
- We will conduct additional sorbent trap testing within the next few months to verify performance on a wet stack with elevated SO3
- Tests to be run at different flow rates and with different sorbent materials

## Proposed Monitoring Changes to Part 75

- Proposed changes to Part 75 were published August 22, 2006 (comment period was closed in October 06)
- Proposed rule includes
- a “re-engineered” Part 75 data collection and processing system incorporating a user-friendly XML format
- minor technical/procedural changes to Subpart I of Part 75 (Hg Mass Emission Provisions) including adding multiple/common stack heat input procedures
- Proposed rule solicited comments relating to the development of reference method based on sorbent trap technology
- Comments received were not extensive - essentially supportive of changes
- Rule expected to become final late summer

## Additional Hg-Related Part 75 Changes in Direct-Final Rule 

- The following changes to Subpart B (Monitoring Provisions) and Appendix K are being included 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)

## 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

## 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

## 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

- 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 periodic 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 QC checks once their generators have been placed into field operation

## 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

**Notes:**

The protocol certification 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 mathematical expressions will be available in easy-to-use spreadsheet software that vendors can use to enter generator set point vs measured concentration and the spreadsheet will then establish the predictive relationship of generator setpoint to output concentrtaion with a known uncertainty as a relative function of concentration.  calculate the hg concentration(s).   I do not have a specific example.  However, it is anticipated that the equation will be simply added to the software of each generator so that setpoint and true concentration agree.

The 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) 

## Certification Tests for Establishing Traceability

- Certification tests have been designed to establish quantitative relationships between each field generator and the local vendor-prime generator
- 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 establish the predictive relationship of generator set point to output concentration with a known uncertainty as a relative function of concentration

## Update on NIST-Traceable Hg Calibration Gas Standards

- EPA prepared a working draft traceability protocol for elemental mercury gas generators and submitted it to vendors, EPRI, NIST and RMB for review
- Comments have been addressed and incorporated into a revision to the working draft that will be provided to vendors and protocol collaborators for feedback
- Future drafts will also incorporate user-friendly uncertainty calculation spreadsheets
- As part of the revised working draft protocol, we developed a full-range and a fixed-point procedure for certifying Hg generators and procedures for conducting field QC checks

## Update on NIST-Traceable Hg Calibration Gas Standards (Cont.)

- NIST has completed certification testing for their NIST primary gas generator and are conducting test to certify the “vendor-prime” generators
- EPA is developing a draft protocol for certifying oxidized Hg gas generators
- We are also working with Western Research Institute, NIST and vendors to conduct variability/uncertainty testing of mercury gas generators and cylinders

##  Update on Elemental Mercury Gas Cylinder Traceability   

- Elemental mercury gas cylinder traceability procedures will be added to the existing Green Book (the existing EPA traceability protocol for SO2/NOx calibration gas standards)
- Shelf life and stability of mercury gas cylinders will be assessed by NIST and EPA with input from vendors and Western Research Institute

## Questions???

		Comments??

Thank You!!

- 		Comments??
- Thank You!!