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Modeling the New 1-Hour Nitrogen Dioxide (NO 2 ) and Sulfur Dioxide (SO 2 ) NAAQS Alan Dresser Research Scientist I October 14, 2011.

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Presentation on theme: "Modeling the New 1-Hour Nitrogen Dioxide (NO 2 ) and Sulfur Dioxide (SO 2 ) NAAQS Alan Dresser Research Scientist I October 14, 2011."— Presentation transcript:

1 Modeling the New 1-Hour Nitrogen Dioxide (NO 2 ) and Sulfur Dioxide (SO 2 ) NAAQS Alan Dresser Research Scientist I October 14, 2011

2 Overview of New NO 2 NAAQS 1-hr NO 2 = 100 ppb (189 ug/m3) Effective on April 12, 2010 Based on 98th percentile of annual distribution of daily max. 1-hour values Current NJ 1-Hour Background Levels: 37% to 67% of NAAQS

3 NO 2 1-Hour Modeling EPA Guidance Memos of June 28, 2010 and March 1, 2011: Interim SIL (7.5 ug/m 3 ) 3-Tiered NO to NO 2 conversion approach Treatment of intermittent emissions (limits modeling of start-up/shutdown, emergency equipment)

4 NO 2 1-Hour Modeling NJDEP Guidance: Interim SIL of 10 ug/m 3 (NESCAUM) July 29, 2011 memo – Emergency generator and fire pump exemptions from modeling 1-hour NO 2 /SO 2 impacts (specific to combined-cycle plants, case- by-case for others)

5 Example of 1-Hour NO 2 Modeling LS Power West Deptford Station 600 MW Combined-Cycle Plant Natural gas with 0.05% sulfur oil backup Modeled before EPA and NJDEP guidance memos (intermittent sources; emergency generator/fire pumps)

6 Scenarios of Interest Normal Operations (NOx natl. gas = 37 lb/hr, NOx oil = 70 lb/hr) Startup Operations (NOx = 323 lb/hr) Emergency Generator (NOx = 10 lb/hr) Fire Pump (NOx = 1.3 lb/hr)

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8 1-Hour NO 2 Impacts (Highest 98 th percentile / 8 th high concentration) Normal Operations (70 lbs/hr, oil) = 8.1 ug/m 3 Startup Operations (323 lbs/hr) = 42 ug/m 3 Emergency Equipment(11.3 lbs/hr) = 43 ug/m 3 (no testing during turbine startup/shutdown) (1-hour NO2 NAAQS = 189 ug/m 3 )

9 Lesson : Smaller sources with short stacks and transitional scenarios at large facilities can cause big 1-hr NO 2 impacts!

10 Overview of New SO 2 NAAQS 1-hr SO 2 = 75 ppb (196 ug/m3) Effective on August 23, 2010 Based on 99th percentile of annual distribution of daily max. 1-hour values Current NJ 1-Hour Background Levels: 18% - 47% of NAAQS

11 SO 2 1-Hour Modeling August 23, 2010 EPA Guidance Memos: Suggested interim SIL (7.8 ug/m 3 ) Methods of demonstrating NAAQS compliance, calculating background, etc. 24-hour and annual SO 2 NAAQS revoked Intermittent emissions not as important as with NO 2

12 Example of 1-Hour SO 2 Modeling Portland Power Plant Coal-fired Unit 1 – 160 MW / 1958 Unit 2 – 240 MW / 1962 No existing emission controls for SO 2 Average 2007 – 2010 annual emissions of 29,067 tons

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16 1-Hour SO 2 Modeling Conducted with Two EPA Models 1. AERMOD (guideline model) 2. CALPUFF (complex terrain model) Designed for locations with complex wind fields Must conduct a model validation showing it performs better for the given application than EPA’s guideline model (see June 2011 JAWM article)

17 CALPUFF – Allowable Emissions Max. Impact 1.4 times over 3-hr NAAQS

18 Summary of CALPUFF Results 1-Hour SO 2 NAAQS (196 ug/m 3 ) Meteorological Time Period Emissions Days Violating NAAQS % Over NAAQS 2002Allowable % (~ 17 x NAAQS) 2002 Actual (CEM data) % (~ 10 x NAAQS) (background not included)

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20 Summary of AERMOD Results 1-Hour SO2 NAAQS (196 ug/m 3 ) Meteorological Time Period Emissions Days Violating NAAQS % Over NAAQS Allowable % (~ 6 x NAAQS) Actual (avg. monthly)5 138 % (~ 1.4 x NAAQS) (No predicted violations of the 3-hour or 24-hour NAAQS, background not included)

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22 Columbia Lake SO 2 Monitor Data collected at Columbia Lake Monitor since Sept. 23, exceedances of the 1-hour SO 2 NAAQS of 75 ppb (196 ug/m 3 ) recorded since Sept. 23, 2010 Monitor located where both models predicted high impacts but not maximum

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24 Columbia Lake - Sept. 23, 2010 to Sept. 15, 2011

25 1-Hour SO 2 Modeling Conclusions SO 2 1-Hour NAAQS is much more easily violated than the 3 and 24-Hour NAAQS Columbia Lake monitoring confirms both CALPUFF and AERMOD predictions of 1- hour NAAQS violation at that location Principal sources of concern are older, large sources burning No. 6 oil or coal (especially after Sub. 9 Sulfur in Fuel Rule)

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