Modeling Guidance and Examples for Commonly Asked Questions (Part II)
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Modeling Guidance and Examples for Commonly Asked Questions (Part II) Reece Parker and Justin Cherry, P.E. Air Permits Division Texas Commission on Environmental Quality Advanced Air Permitting Seminar 2014
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Modeling Guidance and Examples for Commonly Asked Questions (Part II). Reece Parker and Justin Cherry, P.E. Air Permits Division Texas Commission on Environmental Quality Advanced Air Permitting Seminar 2014. What Is Ozone?. Stratospheric Ozone. Good. sunlight. O + O. O 2. O + O 2. O 3. - PowerPoint PPT Presentation
Transcript of Modeling Guidance and Examples for Commonly Asked Questions (Part II)
Modeling Guidance and Examples for Commonly Asked Questions
(Part II)
Reece Parker and Justin Cherry, P.E.Air Permits Division
Texas Commission on Environmental QualityAdvanced Air Permitting Seminar 2014
What Is Ozone?
Good• Stratospheric Ozone
O2sunlight O + O
O + O2 O3
Bad• Ground-level Ozonesunlight
VOC + NOx O3 (and other products)
Ground-level Ozone Is:
• The main component of smog.
• Not emitted directly in the air but forms when emissions of precursors, including NOx and VOCs “cook” in the sun:
– Emissions from industrial facilities, electric utilities, motor vehicle exhaust, gasoline vapors, and chemical solvents are the major man-made sources of NOx
and VOCs.
• Mainly a summertime pollutant because sunlight and hot weather accelerate its formation.
Ozone levels can be high in both urban and rural areas, often due to transport of emissions of ozone precursors.
2008 Ground-level Ozone Standards
• Primary and secondary 8-hr ozone standards:
75 ppb*
*based on the 3-yr average of the annual fourth highest daily maximum
8-hr ozone concentration
Type of Application
Non-Attainment Review?
PSD Increment:• SO2
• PM10
Property Line:• SO2
• H2S
Health Effects:• Benzene
PSD Review?• SO2
• PM10
Property Line:• SO2
• H2S
Health Effects:• Benzene
Non-attainment vs. Attainment
Non-attainment Review
• Provide full documentation and details to reduce review time and mitigate potential issues
• Protocol document should resemble AQA without modeling results
Final product? Not exactly...
Ozone Impact Analysis not required.
Emissions offsets to improve air quality
PSD Review
• If project is major by itself or a major modification, a protocol is required:– For all criteria pollutants with an increase– Must be sent to EPA Region 6 for review– May include protocol for state-only requirements
• Items to include in protocol are listed in protocol checklist
• Consider all the items in the protocol check list before you start on your protocol document
An ozone impacts analysis is required when a project emits:
100 tpy or more of VOCs
and/or
100 tpy or more of NOx
Ozone Impacts Analysis
• Obtain representative monitoring data
• Determine whether the project area is VOC-limited or NOx-limited*
• Quantitative demonstration
• Qualitative demonstration
*Based on TCEQ’s own SIP photochemical modeling, most of the urban and rural areas of Texas are NOx-limited.
Quantitative Demonstration
• Photochemical modeling: Comprehensive Air Quality Model with extensions
(CAMx)
• Screening approach using AERMOD: Demonstration based on comments by EPA for NOx-
limited areas
Quantitative Demonstration (Cont.)
• Screening approach using AERMOD:
Conservative analysis based on NOx modeling:
– Determine if the project is NOx-limited or VOC-limited
– If VOC-limited, determine GLCmax at a distance of 10-11 km
– Assume 90% conversion of NOx to NO2
– Assume 3 ozone molecules per NOx molecule
– Add result to the representative monitored concentration
– Compare to the standard
Example of Quantitative Demonstration
Determine a representative monitor concentration
Project Location
Example (Cont.)
Determine a representative monitor concentration
Monitor Location
3-yr avg of 4th highest daily maximum 8-hr conc.
69 ppb
Example (Cont.)
Determine GLCmax 10-11 km from project sources
Example (Cont.)
Model Output
Converting model result to ppb:
2.96 µg/m3 x (100 ppb)/(188 µg/m3) = 1.57 ppb
Example (Cont.)
• Assume 90% conversion of NOX to NO2:
1.57 ppb x 0.9 = 1.413 ppb
• Assume 3 molecules ozone per molecule NOX:
3 x 1.413 ppb = 4.24 ppb
• Add result to monitored concentration:
69 ppb + 4.24 ppb = 73.24 ppb
• Compare to standard:
73.24 ppb < 75 ppb
Qualitative Demonstration
• Assessment of current air quality:– Ozone trends
– NOX trends
– VOC trends
• Analysis of the project’s potential ozone impact – Selection of Existing Photochemical Modeling Analyses:– Modeling simulation (Did photochemical modeling follow EPA
guidance?)
– Source characterization
– Meteorological parameters and regional transport
Example Qualitative DemonstrationOzone Trends BPA Area
BPA Area Ozone Design Values for all Monitoring Sites (1992-2013)0.105
0.100
0.095
0.090
0.085
0.080
0.075
0.070
0.065
0.060
Site ID: 482450009Site ID: 482450101Site ID: 4824510351997 8-hr Ozone NAAQS
2008 NAAQS Threshold
2008 8-hr Ozone NAAQS 1997 NAAQS Threshold
Site ID: 482450011Site ID: 482450102Site ID: 483611001
Site ID: 482450022Site ID: 482450628Site ID: 483611100
8-hr
Ozo
ne D
esig
n Va
lue
(ppm
)
Example (Cont.)
NOx Trends (BPA Area)
Summary of NOx Emissions Data in BPA Area (tons per day)
0
50
100
150
200
250
NO
x Em
issi
ons
(ton
s pe
r day
)
Nonroad
NonroadNonroad
Onroad
Area
PointPoint Point
Point
AreaArea
Area
OnroadOnroad
Onroad Nonroad
2005 NEI 2008 NEI 2011 NEI
Example (Cont.)NOx Trends (BPA Area)
Maximum BPA Area Annual Average NOX Concentration (1998-2013)
14.0
16.0
Annu
al N
Ox C
once
ntra
tion
(ppb
)
12.0
10.0
8.0
6.0
4.0
2.0
0.0
Example (Cont.)VOC Trends (BPA Area)
Summary of VOC Point and Area Emissions Data in BPA Area (tons per day)
Example (Cont.)VOC Trends (BPA Area)
Annual Average Level of Ethylene Measured in the BPA Area (1997-2013)
14.0
12.0
10.0
8.0
6.0
4.0
2.0
0.0
Annu
al A
vera
ge M
easu
rem
ents
(ppb
)
Ethylene Emissions
Range of Measured Annual Averages
Median of Measured Annual Averages
Year
Example (Cont.)VOC Trends (BPA Area)
Annual Average Level of Propylene Measured in the BPA Area (1996-2013)An
nual
Ave
rage
Mea
sure
men
ts (p
pb)
3.0
1.0
10.0
8.0
6.0
4.0
2.0
0.0
Propylene Emissions
Range of Measured Annual Averages
Median of Measured Annual Averages9.0
7.0
5.0
Year
Example (Cont.)Source Characterization
• Photochemical Modeling Project:– 24 Natural Gas-fired
Refrigeration Compressor Turbines
– 4 Acid Gas Vents– 1 Marine Flare– 2 Wet Gas Flares– 2 Dry Gas Flares– 2 Natural Gas-fired
Generator Turbines– 2 Emergency
Generators
• Proposed Project:– 6 Natural Gas-fired
Refrigeration Compressor Turbines
– 1 LNG Storage LP Flare– 1 Wet/Dry Gas Ground
Flare– 1 Auxiliary Boiler– 4 Thermal Oxidizers– 7 Diesel Generators– 1 Natural Gas-fired
Essential Generator– 1 Blowdown Vent
Example (Cont.)
Source Characterization
Photochemical ModelingPTE NOx Emissions
2,665.29 tpyPSD Increment:• SO2
• PM10
Property Line:• SO2
• H2S
Health Effects:• Benzene
Proposed ProjectPTE NOx Emissions
681.46 tpyPSD Increment:• SO2
• PM10
Property Line:• SO2
• H2S
Health Effects:• Benzene
Photochemical modeling approx. 4X more NOx than proposed project.
Example (Cont.)Meteorological Parameters and Regional Transport
BPA Area
Surface Pressure (HPA) Relative Humidity (%)
Example (Cont.)Meteorological Parameters and Regional Transport
BPA Area
Surface Roughness (m) Temperature (oC)
Example (Cont.)Meteorological Parameters and Regional Transport
BPA Area
Wind Vectors (knts) Wind Velocity (knts)
Example (Cont.)
Model Results
Photochemical modeling results in the BPA Area based on 4X as much NOx is between 0.1-0.5 ppb.
Questions?
Contact Information
• Justin Cherry, P.E.– Air Dispersion Modeling Team
– (512) 239-0955
• Reece Parker– Air Dispersion Modeling Team
– (512) 239-1348
Air Permits Division
(512) [email protected]
Justin Cherry
Air Permits Division
Reece Parker
(512) 239-1348
