The Pursuit of Representative PM 2.5 Emission Factors for Gas-Fired Combustion Units

Transcription

1 The Pursuit of Representative PM 2.5 Emission Factors for Gas-Fired Combustion Units Presented by: Louis Corio Zephyr Environmental Corporation Presented at: EUEC 2015 February 17, 2015

2 Presentation Outline Description of particulate matter (PM) Background on PM measurement methods Recent EPA guidance for processing stack test measurements Background on traditional PM emission factors Alternate PM emission factors Data needed to develop factors Use of alternate factors by regulators and permit applicants Summary and concluding remarks

3 Description of PM Filterable PM Condensable PM e.g., H 2 SO 4 PM TSP PM 2.5 PM 10 PM 2.5 Fuel Combustion Source

4 Description of PM Filterable PM Condensable PM e.g., H 2 SO 4 PM TSP PM 2.5 PM 10 PM 2.5 PM Sampling Train Equipment Gas Flow Filterable (248 F) Condensable (85 F) Fuel Combustion Source

5 Background on PM Measurement Methods EPA s Test Methods for PM: PM TSP (filterable): Method 5, established in 1971 PM 10 (filterable): Method 201A, established in 1990 Condensable PM: Method 202, established in 1991 In Dec. 2010, EPA revised Methods 201A and 202: Method 201A: Added hardware to measure filterable PM 2.5 Method 202: Changed hardware and procedures for more accurate condensable PM measurement

6 Filtered stack gas (via Method 5 or Method 201A)

7 Background on PM Measurement Methods (cont d) For gas-fired units, very low level of PM mass is in the exhaust; could be near/at minimum detection level of measurement methods EPA acknowledges, but does not mandate, that longer test run times may be necessary to collect a sufficient weighable mass to increase method precision

8 Background on PM Measurement Methods (cont d) Any amount of error introduced during sampling or analysis could result in significant high bias and unrepresentatively high PM emissions from test results Factors resulting in high bias in measured PM emissions: Condensable PM artifact formation (not eliminated with Dec method revisions) Elevated background PM concentrations Contamination of sampling train hardware or sample recovery/analysis materials (e.g., reagents)

9 EPA s Interim Guidance for Treatment of Condensable PM Test Results EPA issued interim guidance on April 8, 2014, addressing the processing of Method 202 measurements for regulatory compliance purposes for PM 10 and PM 2.5 Intent is to reduce overestimation of condensable PM Focus of guidance is on treatment of field train blanks, which are used by testing firms to assess potential contamination and correct measurements

10 EPA s Interim Guidance for Treatment of Condensable PM Test Results (cont d) Revised Method 202 procedures allow subtraction of field train recovery blank mass of up to 2.0 mg from measured condensable PM sample mass Industry analysis of blank data showed that higher values are common; therefore, EPA petitioned to change the blank correction procedures EPA s current guidance for blanks: Use field train proof blank instead of field train recovery blank Proof blank correction as high as 5.1 mg can then be used to adjust condensable PM measurement EPA to issue Best Practices Handbook in 2015

11 Background on Traditional EPA AP-42 emission factors, or Vendors PM emissions guarantees PM Emission Factors Rely on the same test methods as used to develop AP-42 emission factors Emission factors based on upper confidence limits from statistical analysis of test results

12 Background on Traditional PM Emission Factors (cont d) AP-42 emission factors for natural gas-fired units: Boilers (Table 1.4-2): Filterable PM: lb/mmbtu Condensable PM: lb/mmbtu Total PM = lb/mmbtu Combustion turbines (Table 3.1-2a): Filterable PM: lb/mmbtu Condensable PM: lb/mmbtu Total PM = lb/mmbtu

13 Boilers: Filterable PM B rating ( above average ) Condensable PM D rating ( below average ) (Condensable PM factor based on four stack tests conducted earlier than the mid-1990s) Combustion turbines: Background on Traditional PM Emission Factors (cont d) Filterable PM C rating ( average ) Condensable PM C rating (Filterable and condensable PM factors based on three stack tests conducted at one facility in the mid-1990s)

14 The Need for More Representative PM Emission Factors EPA has been working in recent years to address the measurement/analysis issues regarding PM stack testing Nonetheless, emission factors (e.g., AP-42) based on historical test results are not likely to be representative

15 The Need for More Representative Relatively new PM 2.5 requirements necessitate the use of a more representative PM emission rate Air permit applicants: PM Emission Factors (cont d) 10 tpy PM 2.5 significant emission rate for PSD and NNSR applicability Compliance demonstration for restrictive PM 2.5 NAAQS Availability and cost of emission offsets (NNSR) State and other regulatory agencies need representative PM 2.5 emission inventories for SIP planning

16 Alternate PM Emission Factors: What s Needed to Develop the Factors? Actual compliance test results for existing gas-fired units (may not be easily accessible) and Solid technical support, such as research study results, e.g., New York State Energy Research and Development Authority/American Petroleum Institute (NYSERDA/API) research program

17 Alternate Emissions Factors (cont d): NYSERDA/API Research Studies - Background NYSERDA/API testing program sponsored by several government and private organizations, with GE Energy and Environmental Research Corporation providing lion s share of technical management PM emissions testing of natural gas-fired boilers, heaters, and combustion turbines occurred over the period (focus on fine PM) Well-controlled testing using EPA reference test methods (e.g., Method 202) and conditional test methods (e.g., dilution sampling method) with 6-hr test run times

18 Alternate Emission Factors (cont d): AP-42 Factors vs. NYSERDA/API Results PM 2.5 Emissions (lb/mmbtu) AP-42 NYSERDA/API: EPA Methods NYSERDA/API: Dilution SM NG Boilers/Heaters NG CC Turbines

19 Alternate Emission Factors (cont d): Revised PM Emissions for 2002 NEI In August 2005, EPA stated they would revise PM emissions in final 2002 National Emissions Inventory (NEI) because AP-42 emission factors for condensable PM were too high EPA based their adjustments on the NYSERDA/API research program results for gas-fired units EPA s alternate emission factors were 89-94% lower than AP-42 factors

20 Alternate Emission Factors (cont d): WRAP s Regional Haze Rule Analysis Western Regional Air Partnership (WRAP) Stationary Sources Joint Forum used EPA-adjusted NEI factors to develop baseline and future (2018) PM 10 and PM 2.5 emission inventories for regional haze rule assessments WRAP States regional haze SIPs submitted to and approved by EPA in timeframe

21 Alternate Emission Factors (cont d): Source Permitting Case Study New Mexico New Mexico Permitting Project: Application for new natural gas-fired simple cycle combustion turbine, aeroderivative ( aero ) type, submitted to NMED-AQB in 2010 Vendor-provided PM emission factor nearly equivalent to AP-42 factor; deemed unrepresentative NYSDERA/API research studies results used to bolster development of alternate total PM emission factor from stack test data for existing aero-type turbines

22 Alternate Emission Factors (cont d): Source Permitting Case Study New Mexico Key criteria for keeping test data in the analysis: No contamination noted in Method 202 analysis results Testing conducted in 2000 or later Extended run sampling times of 2 hours or greater Resulting alternate total PM emission factor is 39% lower than AP-42 emission factor NMED-AQB issued construction permit in June 2011

23 Summary and Concluding Remarks The regulated community as well as regulators recognize that AP-42 emission factors for PM are not the most representative factors for gas-fired combustion units Actual stack test data for similar gas-fired combustion units, supported by NYSERDA/API research program results, provide a solid basis for approvable alternate PM emission factors In some cases, EPA s April 2014 interim guidance can help to improve the representativeness of alternate emission factors when using Method 202 stack test data Further guidance (Best Practices Handbook) and revisions to Method 202 under development

24 Summary and Concluding Remarks (cont d) For permit applicants, developing and using an alternate, representative emission factor requires balancing: The need to demonstrate compliance with PM 2.5 NAAQS in the application, with the need to demonstrate compliance with emission limits in permit The need for careful testing under extended test run times for permit compliance demonstrations, with the associated higher cost of such testing

25 Thank you! Louis Corio Zephyr Environmental Corporation Phone: (410) Visit us at and