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Findings from Field Tests of PEMS and Portable Analyzers

Findings from Field Tests of PEMS and Portable Analyzers. John Schakenbach, USEPA Scott Shanklin, Karen Wesson, Penny Kellar The Cadmus Group, Inc. Electric Power Research Institute CEM Users Group Conference Savannah, GA May 6, 2005. What’s a PEMS?. Predictive Emissions Monitoring System

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Findings from Field Tests of PEMS and Portable Analyzers

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  1. Findings from Field Tests of PEMS and Portable Analyzers John Schakenbach, USEPA Scott Shanklin, Karen Wesson, Penny Kellar The Cadmus Group, Inc. Electric Power Research Institute CEM Users Group Conference Savannah, GA May 6, 2005

  2. What’s a PEMS? • Predictive EmissionsMonitoring System • Asetof mathematical models that develops a numerical relationship between a unit’s operating parameters and a pollutant • Does not directly measure emissions

  3. History of PEMS • PEMS used for emissions since 1980 • EPRI studied PEMS in the mid-90s • PEMS have been approved: • for gas-fired boilers (<250 mmBtu/hr) under NSPS subpart Db by several states • for gas-fired turbines by Texas TNRCC rule • PEMS allowed under final CAM Rule (10/97) • Three Part 75 NOx PEMS conditionally approved on gas-fired turbines and boiler

  4. Types of PEMS • First principles • material balances, thermodynamics, reaction kinetics • Regression • establishes statistical relationship • Neural network • iterative process using weighting factors • Hybrid

  5. Potential Part 75 PEMS Users • Gas-fired (possibly oil-fired) turbine where NOx CEMS will be replaced • Low mass emitters • Existing App. E peaking units transitioning to baseload operation • Possibly 100-200 new turbines would use PEMS

  6. Field Test • Host site: Dominion Chesterfield #8 in VA, gas-fired, GE Frame 7F turbine, 160MW, unfired HRSG, steam injection for NOx control • 8 month duration to capture summer, fall, winter ambient temperature and humidity variations • 1 PEMS was compared to Part 75-certified NOx CEMS, using Subpart E • Quarterly RATAs • Test sensor failure • Determine appropriate QA/QC

  7. Field Test • Host site: KUA, Cane Island, Unit 2 in FL, gas-fired, GE Frame 7EA turbine, 80 MW, unfired HRSG, with dry low NOx • 7 month duration to capture summer, fall, winter temperature and humidity • 1 PEMS and 4 portable NOx analyzers were compared to Part 75-certified NOx CEMs, RM 7E & Subpart E criteria • Quarterly RATAs • Test sensor failure • Determine appropriate QA/QC

  8. Findings • PEMS inputs must stay within operating envelope • Abbreviated Subpart E statistical tests when coupled with 3-level initial RATA appear to provide adequate initial QA • Certain statistical test allowances should be made for low emitting and/or low emission variability sources • PEMS can be accurate for gas-fired combustion turbines where NOx is controlled by either water or steam injection or by dry-low-NOx if proper training and QA are performed

  9. Findings • Compared to contracting out, purchasing portable analyzer for PEMS QA can be accurate and lower cost • PEMS can be a lower cost alternative to CEMS for certain applications • PEMS were unable to successfully predict NOx emissions during startup or shutdown

  10. Example Turbine PEMS Operating Envelope

  11. Subpart E Test Results Chesterfield Unit 8* *Mean NOx concentration is about 21 ppm. ** No startups or shutdowns

  12. Subpart E Test Results KUA Unit 2* *Mean NOx concentration is about 8 ppm. **Actually “Yes”. Subpart E requires t-test only be applied to data at normal load. Therefore, because data w/o startups and shutdowns passed t-test, all data sets passed t-test.

  13. PEMS Relative Accuracy Results • At Chesterfield, 1,255 9-run rolling RATAs • Startups and shutdowns excluded • 98% met alt spec of ± 0.020 lb/mmBtu mean dif • 75% met 10% RA • At KUA, 851 9-run rolling RATAs • Startups and shutdowns excluded • 100% met alt spec of ± 0.020 lb/mmBtu mean dif • 52% met 10% RA

  14. Initial Certification for NOx PEMS

  15. Initial Certification for NOx PEMS *Mean reference value during RATA or RAA is ≤0.200 lb NOx/mmBtu

  16. Initial Certification for NOx PEMS *If reference method sd <3% span or 5 ppm, either of these values may be used when calculating F. **When reference method mean < 5 ppm for an operating level, that operating level may be removed from the correlation analysis.

  17. Hints for Using Portable Electrochemical Analyzers • When performing stability check for 3 cells, purge with ambient air between gas injections to reduce degradation of cell performance • For low NOx sources, analyzers must provide readings to 0.1 ppm • For low NOx sources, provide an alternative perf spec of ± 1 ppm difference from reference value • Analyzer should have a minimum calibration threshold appropriate to stack gas concentration being measured

  18. Modified ASTM Method D6522-00

  19. Modified ASTM Method D6522-00

  20. Portable NOx Analyzer Results KUA Unit 2* *Mean NOx concentration is about 8 ppm. **All meet the alt perf spec of ±0.015 lb NOx/mmBtu of reference mean ***Chemiluminescence

  21. Portable NOx Analyzer Results KUA Unit 3* *Mean NOx concentration is about 4 ppm. **All meet the alt perf spec of ±0.015 lb NOx/mmBtu of reference mean ***Chemiluminescence

  22. Ongoing NOx PEMS QA/QC Tests *Mean reference value during RATA or RAA is ≤0.200 lb NOx/mmBtu

  23. Ongoing NOx PEMS QA/QC Tests *Mean reference value during RATA or RAA is ≤0.200 lb NOx/mmBtu

  24. Ongoing NOx PEMS QA/QC Tests

  25. Capital Cost Estimates for CEMS and PEMS

  26. Estimated Annual Costs for CEMS and PEMS

  27. For a Copy of Presentation www.epa.gov/airmarkets, click on Recent Additions or John Schakenbach Phone: 202-343-9158 schakenbach.john@epa.gov

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