75th air base wing - iis7proceedings.ndia.org/jsem2007/4179_bennett.pdf75th air base wing 1...

75th Air Base Wing

1

Comparison of CALPUFF and OBODM for Open Burn/Open

Detonation Modeling

22 May 2007

Mark Bennett, Ph.D.CH2M Hill, Inc

Joint Services Environmental Management Conference and

Exposition Columbus, Ohio

2

7 5 T H A I R B A S E W I N G

Co-authors

Glenn Palmer – Hill Air Force Base, UT

Mitchell Lindsay – CH2M Hill, Inc

Andrea White – CH2M Hill, Inc

Chris Merrill – CH2M Hill, Inc

Sara Van Klooster – CH2M Hill, Inc

3


Outline

Background

Goal and Objective

Methods

Results

Conclusion

4


BackgroundHazardous waste combustors require a RCRA permit (40 CFR Part

264)Guidance provided in Final Human Health Risk Assessment Protocol for Hazardous Waste Combustion Facilities (HHRAP), EPA,September 2005HHRAP Chapter3: Air Dispersion and Deposition Modeling

Written primarily with application to incineratorsRecommends use of ISCST3Not appropriate for Open Burn/Open Detonation events (lacks buoyant area or volume source capabilities)Typically the Open Burn/Open Detonation Dispersion Model (OBODM)is used (an alternative EPA model)

5


Background – OBODM

OBODM is intended for use in evaluating the potential air quality impacts of the open-air burning and detonation (OB/OD) of obsolete munitions and solid propellants. OBODM uses cloud/plume rise, dispersion, and deposition algorithms taken from existing models (e.g., REEDM and the “original” ISC) for instantaneous and quasi-continuous sources to predict the downwind transport and dispersion of pollutants released by OB/OD operations. The model can be used to calculate peak concentration, time-mean concentration, dosage (time-integrated concentration), and particulate gravitational deposition for emissions from multipleOB/OD sources for either a single event or up to a year of sequential hourly source and meteorological inputs.

6


Background – OBODM

While OBODM has algorithms for OB and OD events, it does have some limitations:

Complex terrain option cannot be used when calculating concentration with gravitational deposition occurring or gravitational deposition for particulates with appreciable settling velocitiesolder, gravitational settling method used for dry depositioncannot calculate wet depositionlimited number of gridded receptorsdiscrete receptors must be entered by hand, thus greater opportunity for error

cont.

7


Background – CALPUFFCALPUFF is EPA preferred model for long-range transport (>50 km) and case-by-case for complex wind fields

Non-steady state Puff Model (CALPUFF)• causality• stagnation flows

Standard use with Diagnostic Meteorological Model (CALMET)• However, can be used with augmented “ISC” met file or AERMOD met

fileIncludes special option for time varying buoyant area sources (designed for forest fires)both wet and dry deposition

8


BackgroundOBODM and CALPUFF Lite used to evaluate the air concentration and deposition values from the detonation of representative Trident C4 motors at the UTTR. Two phases of analysis

Phase I: Use CALPUFF in screening mode and OBODM to model the Open Detonation (OD) of C4 with varying Net Explosive Weights (NEW)Phase II: Use CALPUFF in screening mode and OBODM to model OD events with varying particle size distributions

9


Goal

The goal of the present study was to evaluate CALPUFF as an alternative to OBODM for the air dispersion modeling for Open Burn/Open Detonation events.

10


Objectives

Use OBODM and CALPUFF to model the impacts of the emissions from open detonation events with parameters representative of the Thermal Treatment Unit (TTU) at Utah Test and Training Range (UTTR).

11


Methods – Meteorological DataSame met file will be used in both OBODM and CALPUFF Lite2004 meteorological data from the onsite TTU surface stationmost complete set of data available at this timeSince most interested in a comparison between the two models - filled in the missing onsite wind direction, wind speed, temperature, stability class, and mixing height data with Salt Lake City dataThe EPA PCRAMMET processor used to combine with upper air data from Salt Lake CityExtended records for use in CALPUFF

12


Methods – Meteorological DataISCMET.DAT (CALPUFF)

Hourly values (standard records)•wind speed, flow direction• temperature, stability class•mixing height for rural/urban

Hourly values (extended record)•surface friction velocity•Monin-Obukhov length•surface roughness•precipitation code and rate•others not used

13


Methods – Receptor Grid

20km by 20km with a 500 meter spacingAll of the vapor phase impacts will be evaluated using terrain-adjusted receptors for both modelsOBODM cannot model particle phase impacts with complex terrain or elevated terrain, therefore, for OBODM, all particle phase impacts will be evaluated in flat terrainCALPUFF Lite results for terrain adjusted receptors for both vapor and particle phase

14


Methods – Source TermsFOR BOTH OBODM & CALPUFF LITE

Detonation events can only occur between 10am and 4pmParticle phase pollutant will be modeled as Aluminum OxideVapor phase pollutant will be modeled as Carbon MonoxideHeat released during detonation of C4 motors calculated from POLU4WNCO and Al2O3 emission rates calculated from POLU4WNDetonation time of 2.5 seconds (default value for OBODM for detonation)CO emission rate: 1.4E-06 lbs of CO per lb of NEWAl2O3 emission rate: 0.4 lbs of Al2O3 per lb of NEW

15


Methods – OBODM Source Terms

OBODM Source Terms (entered directly)NEWs (lbs): 3,000; 17,000; 39,000; 81,000Heat content: 2448 cal/g from POLULocations (NAD 1927): UTMX 340866, UTMY 4554800Source Elevation: 1431 metersDimensions: 8 ft by 10 ft (only for burn)Events cannot occur when wind speeds are less than 1.3 m/s

16


Methods – CALPUFF Source Terms

CALPUFF Buoyant Area Source Emission File (BAEMARB.DAT)Area of the source – Based off of the observed initial plume radiusHorizontal radius of plume – Experimental data indicates that an 81,000 lb NEW detonation results in an initial horizontal radius of approx 150 meters. Assuming that the initial “puff” is a hemisphere, the corresponding volume was calculated. The plume volumes were scaled linearly by total mass and the effective radius was calculated for each NEW.Initial Vertical Spread – Vertical radius of the “puff” is approximately half the horizontal radiusDetonation Duration – For consistency, OBODM default of 2.5 seconds usedInitial Release Height – Midpoint of the initial vertical spread

17


Methods – CALPUFF Source Terms

CALPUFF Buoyant Area Source Emission File (BAEMARB.DAT) - continuedInitial Vertical Velocity – Initial “puff” vertical velocity was calculated using the plume buoyancy flux equation and the heat flux equation Emission Rate – Data from POLU4WN“Puff” Temperature – Final temperature of the “puff” calculated using heat balance between the “puff” before and after the entrainment of ambient air. Initial specific volume and temperature of the “puff” based on POLU4WN. Initial mass assumed stoichiometric combustion of the total NEW. The final volume was from observational data. The difference in the initial mass and the final mass was assumed to be from entrainment of ambient air.

18


Methods – Phase IIFive log-normal particle size distributions were chosen to span range of expected particle sizes

Minimum Diameter

(μm)

Maximum Diameter

(μm)

Average Diameter

(μm)

Geometric Standard Deviation

(μm)

Geometric Mass

Diameter (μm)

0.1 1.0 0.3 1.8 0.1

1.0 2.5 1.6 1.3 1.4

2.5 10 5.0 1.4 3.6

10 20 14 1.2 13

20 100 45 1.5 28

19


Results - General

Both sets of concentration contours consistent with windroses; however, show differences consistent with plume model vs puff modelLocation of maximums generally do not agreeGenerally, OBODM maximums greater than CALPUFF Lite maximumsCALPUFF Lite wet deposition approx twice CALPUFF Lite dry deposition

20


Results – Phase IRatio of OBODM / CALPUFF concentrations

Vapor Phase Particle Phase

17,000 lb 81,000 lb 17,000 lb 81,000 lb

1 hour 1.9 3.0 4.6 6.2

24 hour 2.7 3.9 9.1 9.6

Annual 3.3 4.6 5.0 10.2

Time-weighted average

21


Results – Phase I: Vapor Phase

22


Results – Phase I: Particle Phase

23


Results – Phase IComparison of Maximums for Dry and Wet Deposition

OBODM Dry / CALPUFF Dry

CALPUFF Wet / CALPUFF Dry

17,000 lb 81,000 lb 17,000 lb 81,000 lb

1 hour 1.6 2.3 3.0 4.9

24 hour 11 15 3.5 7.0

Annual 25 48 1.6 3.5


24


Results – Phase I: Dry Deposition

25


Results – Phase I: Wet vs Dry Deposition

26


Results – Phase IIRatio of Max Particulate Concentrations: OBODM / CALPUFF17,000 NEW


0.1 – 1.0 1.0 – 2.5 2.5 – 10 10 – 20 20 - 100

1 hour 4.8 4.7 4.6 4.4 4.5

24 hour 9.5 9.3 9.1 8.7 8.7

Annual 5.2 5.1 5.0 4.7 4.6

27


Results – Phase IIRatio of Max Particulate Concentrations: OBODM / CALPUFF81,000 NEW


0.1 – 1.0 1.0 – 2.5 2.5 – 10 10 – 20 20 - 100

1 hour 6.6 6.4 6.2 5.9 5.9

24 hour 10.1 9.9 9.6 9.1 9.2

Annual 10.7 10.4 10.2 9.5 9.8

28


Results – Phase IIRatio of Max Dy Deposition: OBODM / CALPUFF17,000 NEW


0.1 – 1.0 1.0 – 2.5 2.5 – 10 10 – 20 20 - 100

1 hour 4.5 5.5 1.6 1.9 3.0

24 hour 14.8 59.0 11.2 6.6 16.7

Annual 25.9 475.5 25.5 11.8 17.1

29


Results – Phase IIRatio of Max Dy Deposition: OBODM / CALPUFF81,000 NEW


0.1 – 1.0 1.0 – 2.5 2.5 – 10 10 – 20 20 - 100

1 hour 6.9 6.1 2.3 3.0 4.6

24 hour 22.6 75.6 15.8 9.8 18.1

Annual 51.3 818.2 48.4 24.3 33.3

30


Results – Phase IIRatio of Max Wet Deposition to Dry Deposition (CALPUFF Lite)17,000 NEW


0.1 – 1.0 1.0 – 2.5 2.5 – 10 10 – 20 20 - 100

1 hour 85.5 19.6 3.0 1.6 0.9

24 hour 47.4 35.0 3.5 0.9 0.6

Annual 17.0 57.7 1.6 0.3 0.2

31


Results – Phase IIRatio of Max Wet Deposition to Dry Deposition (CALPUFF Lite)81,000 NEW


0.1 – 1.0 1.0 – 2.5 2.5 – 10 10 – 20 20 - 100

1 hour 148.8 24.4 4.9 2.7 1.6

24 hour 103.0 63.6 7.0 1.9 1.3

Annual 37.9 111.5 3.5 0.7 0.5

32


Results – Phase II: OBODM

33


Results – Phase II CALPUFF Lite

34


Results – Phase II: Wet vs Dry

35


Conclusions

Even for small grid, refinement of puff model over plume model significantRefinement that allows terrain effects for particle phase also significantRefinement that allows wet deposition significant even for relatively dry climate

More realistic results likely justify slight increase in level of effort

36


Conclusions - continued

Variations in concentrations small as a function of particle sizesHowever, large variations in both wet and dry deposition

Impacts of further refinement to full CALPUFF worth examining

37


Questions?

75th air base wing - iis7proceedings.ndia.org/jsem2007/4179_bennett.pdf75th air base wing 1...

Documents