What are Dr. Seuss s favorite air pollutants?

Transcription

1 What are Dr. Seuss s favorite air pollutants? 1 NO x and SO x 2011 The Williams Companies, Inc. All rights reserved. GPA Presentation 1

2 NO x and Ambient Air Chemistry as it relates to the New NO 2 1-Hour Standard Jill Hecht, Williams Midstream Mark J. Bareta, Williams Midstream 2011 The Williams Companies, Inc. All rights reserved. GPA Presentation 2

3 NO 2 1-Hour Standard > EPA recently revised the primary NAAQS (National Ambient Air Quality Standards) to include a 100 ppb averaged hourly standard More stringent, more complicated standard More modeling required and more difficult to prove compliance > New and existing sources are required to show that they do not cause a significant contribution to a violation of NAAQS 2011 The Williams Companies, Inc. All rights reserved. GPA Presentation 3

4 NO x Introduction > Nitrogen Oxides (NO x ) are a family of gases formed during combustion and include: NO NO 2 N 2 O NO 3 N 2 O 3 N 2 O 4 N 2 O 5 > The majority of NO x however are in the form of NO and NO 2 > Most NO x combustion emissions are in the form of NO 2011 The Williams Companies, Inc. All rights reserved. GPA Presentation 4

5 NO x In-Stack Air Chemistry > Two major types of NO x Formation Primary source is thermal NO x Secondary source is fuel-bound NO x > Thermal NO x Formation N 2 + O N + O 2 N + OH NO + N NO + O NO + H 2NO + O 2 2NO The Williams Companies, Inc. All rights reserved. GPA Presentation 5

6 NO x Ambient Air Chemistry > NO and NO 2 react with a variety of constituents in ambient air > Three main reactions that reside in equilibrium: NO 2 hv NO + O NO 2 Photolysis O + O 2 O 3 Ozone Formation O 3 + NO NO 2 + O 2 Titration > These reactions are balanced and cyclic and help to explain the changing diurnal patterns seen in ambient air quality data 2011 The Williams Companies, Inc. All rights reserved. GPA Presentation 6

7 Concentration (PPB) Example Diurnal Pattern 60 Houston Aldine (Urban) June 2nd, :00 5:00 10:00 15:00 20:00 Hour (24:00 Format) NO NO2 O The Williams Companies, Inc. All rights reserved. GPA Presentation 7

8 NO x Ambient Air Chemistry, cont d > VOC s contribute significantly to ozone formation in the presence of sunlight > During the day, titration is balanced by photolysis, resulting in lower levels of NO and NO 2 hv O 3 + NO NO 2 + O 2 NO 2 NO + O > Important Notes: NO, NO 2 and ozone ambient air ratios shift and change throughout the day There are many reactions taking place, not just titration or photolysis NO and NO 2 are also removed from the air during natural processes, mainly through formation of HNO 3 through direct absorption into ground, PM or cloud droplets 2011 The Williams Companies, Inc. All rights reserved. GPA Presentation 8

9 Additional NO x Ambient Air Reactions 2 ROG + O + O 3 R + RCO + RO + OH OH + NO 2 HNO 3 OH + CO H + CO 2 H + O 2 HO 2 RO 2 + NO RO + NO 2 HO 2 + NO NO 2 + OH ROG + OH R + H 2 O R + O RO 2 RO 2 + NO RO + NO 2 RO + O 2 HO 2 + RCHO HO 2 + NO NO 2 + OH RO 2 + NO 2 ROONO 2 NO 2 + RCOO RCOONO The Williams Companies, Inc. All rights reserved. GPA Presentation 9

10 Ambient Air Quality Data Analysis > Examination of NO/NO 2 ratios in natural ambient air Denver, CO Welby Ambient Monitoring Station Seasonal Differences Houston, TX Houston Aldine and Lake Jackson Ambient Monitoring Stations Urban vs. Rural Comparison The Williams Companies, Inc. All rights reserved. GPA Presentation 10

11 Concentration (PPB) Temperature (F) Concentration (PPB) Temperature (F) Denver Data 2010 Welby January 1st, 2010 Welby June 1st, Hour (24:00 Format) Hour (24:00 Format) NO NO2 O3 TEMP NO NO2 O3 TEMP 2011 The Williams Companies, Inc. All rights reserved. GPA Presentation 11

12 Concentration (PPB) Concentration (PPB) Urban vs. Rural Texas Data 60 Houston Aldine (Urban) June 2nd, Lake Jackson (Rural) June 2nd, :00 5:00 10:00 15:00 20:00 Hour (24:00 Format) 0 0:00 5:00 10:00 15:00 20:00 Hour (24:00 Format) NO NO2 O3 NO NO2 O The Williams Companies, Inc. All rights reserved. GPA Presentation 12

13 Ambient NO 2 /NO x Ratios > Reviewed actual NO 2 /NO x ratios seen in natural ambient air monitoring data > Examined hourly data from three stations for NO 2 /NO x ratios San Juan, New Mexico monitoring station (Jan 2010 Dec 2010) Bloomfield, New Mexico monitoring station (Mar 2010 Jan 2011) Houston Aldine, Texas monitoring station (Jan 2010 Dec 2010) The Williams Companies, Inc. All rights reserved. GPA Presentation 13

14 Summary Table Maximum Minimum Average NO 2 /NO x Ratios by Area, All Data San Juan, NM Bloomfield, NM Houston (Aldine), TX Pollutant Concentration by Area NO 2 Concentration, ppb San Juan, NM Bloomfield, NM Houston (Aldine), TX NO Concentration, ppb San Juan, NM Bloomfield, NM Houston (Aldine), TX O 3 Concentration, ppb San Juan, NM Bloomfield, NM Houston (Aldine), TX The Williams Companies, Inc. All rights reserved. GPA Presentation 14

15 Data Points of Note Location Max Ratio Max NO 2 ppb Ratio Max NO 2 ppb San Juan Bloomfield Houston Aldine > Data supports idea of different chemistry occurring in air > Data supports that you can t apply a set ratio and have it be representative of what s actually happening > There s even less conversion happening in a plume 2011 The Williams Companies, Inc. All rights reserved. GPA Presentation 15

16 NO 2 /NO x Ratio Observations > Ambient air ratios of NO 2 and NO x vary Vary with time, concentration, and atmospheric conditions Annual data set with great variations is not representative of short term data and hourly conditions Average and median ratios of 0.75 reflect annual average air chemistry Of note, we see lower ratios and less conversion when NO 2 is higher in concentration Important because EPA is assuming that there s a high and uniform conversion When examining the highest NO2 concentrations, you should be applying lower conversion ratios 2011 The Williams Companies, Inc. All rights reserved. GPA Presentation 16

17 Comparison of Ambient Ratios to NO/NO 2 Conversion > High hourly conversion ratios (1.00) are most conservative but only seen when NO x levels are very low, and hardly seen when NO 2 concentrations are above 20 ppb > High annual conversion ratios ( ) are also conservative but are only truly indicative of annual average ambient conditions > Compliance model assumes one method of conversion; can t analyze additional reactions, including NO 2 removal processes > Current assumed conversion ratios ignore complexity of local factors and chemistry > No consistent ratio seen in ambient air quality data 2011 The Williams Companies, Inc. All rights reserved. GPA Presentation 17

18 Conclusion > Hourly ambient air chemistry is incredibly complex and cannot be accurately accounted for with simplified models and assumptions > Ambient air is well-mixed system in a quasi-equilibrium state where NOx chemistry is stable only over time > Long-term ambient conditions and ratios are not representative of shortterm plume concentrations and reactions The purpose of the research was to raise questions regarding compliance with the new 1-hour NO 2 standard. If an intern who doesn t even have her college degree yet can find weaknesses and questionable assumptions, then maybe, just maybe, there s something that needs to be further addressed The Williams Companies, Inc. All rights reserved. GPA Presentation 18

19 Thank you for your time! > Jill Hecht Williams Midstream NO x and SO x Our game is done, sir Thank you for a lot of fun, sir > Mark J. Bareta Williams Midstream Mark.Bareta@Williams.com The Williams Companies, Inc. All rights reserved. GPA Presentation 19

20 References 1. Seuss, Dr. Fox in Socks. < +in+socks+book&view =detail&id=15b0c6284a551799bda2c1d7d530bd50f8b834b6&first=1&form=idfrir>. 2. Alley, F.C. and C. David Cooper. Air Pollution Control: A Design Approach. 3 rd Ed. Long Grove: Waveland Press, Inc., Colorado Department of Public Health and the Environment. Real-Time Air Monitoring Sites. Air Pollution Control Division Technical Services Home. < ags.aspx>. 4. Texas Commission on Environmental Quality. GeoTAM Viewer. GeoTAM. < 5. New Mexico Environment Department. New Mexico Map: San Juan County. NMED Air Monitoring Website. < 6. Seuss, Dr. Dr. Seuss Sign Generator. RedKid.net. < The Williams Companies, Inc. All rights reserved. GPA Presentation 20