PM 2.5 and CPM Emission Measurements Understanding the Limitations and Implications

Transcription

1 PM 2.5 and CPM Emission Measurements Understanding the Limitations and Implications Vipin Varma and Ashok Jain NCASI AWMA Louisiana Section A Multi-Media Forum October 30, 2013

2 Outline PM 2.5 Definitions and Measurement Methods Filterable PM 2.5 EPA Method 201A Condensable PM EPA Method 202 Regulatory Background and Significance Measurement Method Limitations M201A Train blanks, Sources with entrained moisture M202 Train blanks, Method artifacts Modeling PM 2.5 Emissions Impacts Summary 2

3 PM 2.5 Components and Test Methods PM 2.5 Component Test Method Filterable PM 2.5 Method 201A Condensable PM (CPM) Method 202 Filterable PM 2.5 Solid or liquid material at stack temperature Condensable PM Vapor or gas at stack temperature Condenses to liquid or solid at stack exit Expected to be stable in the atmosphere and collected on ambient samplers 3

4 EPA Method 201A 4

5 EPA Method 202 (version pre-2010) Front-half Catch Back-half Catch 5

6 Current EPA Method 202 (Promulgated December 2010) 6

7 Regulatory Background Prevention of Significant Deterioration (PSD) Review PSD review is triggered at existing major source if: Net emission increase due to contemplated project equals to or exceeds applicable major modification significant emission rates (SER) SERs established both for criteria and non-criteria pollutants PSD reviews include BACT analysis Air quality analysis, including ambient air impact modeling Assessments of existing (baseline) and projected impacts 7

8 Regulatory Background Removal of the PM10 Surrogacy Policy EPA issued final rule in May 2011 repealing the grandfathering provision for PM 2.5 in the federal PSD permit program Grandfathering provision allowed use of PM10 as a surrogate for PM 2.5 in PSD reviews for permit applications submitted before July 15, 2008 The use of PM10 as a surrogate for state PSD programs also ended in May

9 Regulatory Significance PSD Significant Emission Rate (SER) Thresholds Pollutant SER Components PM 25 T/yr Filterable PM Only PM T/yr Filterable PM 10 + Condensable PM (CPM)* PM T/yr Filterable PM CPM * Now included in the definition PSD considerations SER thresholds have reduced even as the PM components considered have expanded CPM can be 2 to 3 times filterable PM 2.5 The new SER for PM 2.5 (along with definition to include CPM) has significant impacts 9

10 EPA Method 201A Limitations Cannot be used on sources with entrained moisture (wet ESPs, wet scrubbers, etc.) For wet sources EPA recommends reporting total filterable PM as filterable PM 2.5 Alternate method currently being evaluated by EPA may be granted Other Test Method (OTM) status Train blank correction is not permitted (although EPA reported train blanks 0.9 mg) Can lead to positive bias on sources emitting low levels of filterable PM 2.5 Forces longer sampling times when collected PM mass is very small (to minimize this bias) 10

11 Filterable PM 2.5 Emissions from Natural Gas Combustion A case of positive biasrs Run No. PM 2.5 Mass, mg Train Blank, mg Average True PM Mass, mg = 0.67 mg; Test Duration = 24 hr 11

12 Impact of Train Blank on Filterable PM 2.5 Emission Estimates from Natural Gas Boiler Run Time, hrs True Value* PM 2.5 (mg) Reported Value** Bias, Percent Actual Estimated * True Value for 1, 3, 5 & 10-hour run times estimated from 24-hour runs ** Reported Value = (True Value mg measured train blank) 12

13 Current EPA Method 202 Limitations Train blank correction limitation of 2.0 mg results in significant positive bias Typical blanks range from 5 to 7 mg Affects low emitters and requires extremely long test periods Artifact CPM formation has not been fully eliminated and may be increased due to extremely long test periods Conversion of SO 2 to sulfate (and accounted as CPM) Impacts due to capture of NH 3 in the impinger 13

14 Train Blanks with EPA Method 202 Results from NCASI Studies Blank ID* Inorganic Organic Total CPM LRFR A1STR A2STR BBHR CBHR A11PBR ALK3R Averages * Field train blanks collected by multiple individuals under varying field conditions 14

15 Significance of Train Blank in Source Testing with M202 Natural Gas Boiler (24-hour sampling run) Run No. CPM Mass, mg Average Maximum Allowed Train Blank Reported CPM Mass Measured CPM Train Blank True CPM Mass 2.0 mg mg 5.39 mg mg 15

16 Impact of Train Blank on CPM Emission Estimates for Natural Gas Combustion Run Time, hrs CPM, mg Bias, Percent True Value* Measured Value** Reported Value*** *True Value for 1, 3, 5 & 10-hour run times estimated from 24-hour test results **Measured Value = True Value mg actual train blank ***Reported Value = Measured Value 2 mg allowed train blank 16

17 lb/mmbtu Impact of Sampling Time and Train Blank on PM 2.5 Emissions from Natural Gas-Fired Boiler 8.00E E E E E E E E E+00 1-hour run 3-hour run 5-hour run 10-hour run 24-hour, 3-run average Adjustment (0, 2) Actual Train Blank Adjustment (0.28, 5) 17 AP-42

18 Method 202 Artifact Formation Sulfate Content of CPM in Gas-Fired Boilers Run No. Reported CPM 1, mg True CPM 2, mg SO 4 2- Content, mg Averag e Reported CPM = Measured CPM minus 2.0 mg blank correction 2 True CPM = Measured CPM minus 5.39 mg train blank 18

19 Components of Kraft Recovery Furnace PM and CPM Analyte PM Mass, mg CPM Carbonate Chloride Nitrate Sulfate Ammonium Potassium Sodium Total Mass by IC (mg)

20 Impacts of SO 2 and NH 3 on Reported CPM Levels Components of CPM in various sources Sulfate (SO 4 2- ) the major component in natural gas-fired boiler Chloride, carbonate and sulfate - anions in kraft recovery furnace (RF) Ammonium - major cation in the recovery furnace Questions: Was SO 2 captured in CPM impinger solution during long test runs and converted to SO 4 2-? Was NH 3 captured in CPM impingers reacting with acid gases to form ammonium? Was HCl captured as CPM (measured as chloride)? 20

21 NCASI Modified Train Blank Study Extensive train blank data obtained in summer 2013 using a full sampling train Comprising of laboratory-cleaned and baked glassware/ equipment Exposed to stack conditions and subjected to all sampling and sample recovery steps except actual stack gas sampling 21

22 NCASI Modified Train Blank Study Results Train Blank ID Filterable PM 2.5 Blank Values, mg CPM PB PB PB PB PB PB PB PB Mean Std. Dev % CI

23 Results of SO 2 Oxidation Inhibition Study a Sample ID Alcohol Added None Ethanol Ethanol Ethanol Units Alcohol Concentration (%) Sulfate at t=0 hours (mg/l) 7.0 <0.5 <0.5 <0.5 Sulfate at t=1 hour (mg/l) 13.5 <0.5 <0.5 <0.5 Sulfate at t=3 hours (mg/l) < Sulfate at t=24 hours (mg/l) < Sulfate at t= hours (mg/l) 76.2 (120 hrs) 11.7 (104 hrs) a 120 ppm SO 2 bubbled for 1-hour 23

24 EPA Method 202 Potential Fixes for Method Bias Issues Allow for a train blank correction based on modified train blank tests Permit the use of ethanol in CPM impingers to minimize SO 2 oxidation As an alternative, advance the evaluation and use of Method CTM-039 (dilution method) for CPM measurements 24

25 EPA s position on Test Methods We do not believe that sources and states should be limited to Federal Register test methods for developing their emissions inventories, for developing applicable requirements, and for demonstrating compliance with applicable requirements. Accordingly, we believe that it is appropriate for sources and states to use other test methods, even if there is a Federal Register test method, as long as the test method used is a reliable indicator of the emissions performance for the regulated pollutant. Federal Register, May 18, 2011, p

26 Summary EPA Methods 201A and 202 subject to positive bias Bias due to train blanks increases as sampling time decreases Bias due to artifact formation may increase as sampling time increases Some chemical interaction and artifact formation issues in the new Method 202 train are unresolved 26