all4 inc awma re-entrainment
TRANSCRIPT
www.all4inc.com | Philadelphia | Atlanta | Houston | Washington DC
Re-entrainment Evaluations: Not Your Father’s Air Dispersion Modeling
Amanda Essner | [email protected] | 610.933.5246 x 129
Dustin Snare| [email protected] | 610.933.5246 x 126
Sharon Sadler | [email protected] | 571.392.2595
June 7, 2017
Presented to the Air & Waste Management Association’s 110th Annual Conference & Exhibition by All4 Inc.
2 Your environmental compliance is clearly our business.
Agenda
Introduction
Methodology
Case Study
AIR QUALITY MODELING
3 Your environmental compliance is clearly our business.
What is entrainment?
An atmospheric event that occurs when suspended particles or compounds that are exhausted in a plume are carried back into a plume of air
Introduction
4 Your environmental compliance is clearly our business.
Re-Entrainment
Emissions source(ex: Emergency Generator, Hot Water Boiler, Combined Heat and Power Unit)
Exhaust from emissions source containing CO, NOX, SO2, VOC, etc.
Rooftop mounted air handling unit or fresh air intake
Potential location for exhaust plume
to be entrained into the building
through an intake
Pollutants in plume can become re-entrained due to effects of buildings
5 Your environmental compliance is clearly our business.
Not traditionally required under Federal or state air quality regulation
• American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE) or Indoor Air Quality (IAQ) guidelines
Prompted by either a consideration during the designphase of a capital project or in response to comments about odor in an existing facility
Who Cares?
• Especially for healthcare facilities, where the same people may occupy them 24-hours per day and for extended periods of time.
• Sensitive populations in a concentrated area (ex. patients, students)
6 Your environmental compliance is clearly our business.
Utilize air quality modeling to predict the concentration of pollutants of concern at air intakes around a facility
Compare the predicted concentrations with published health guidelines
• National Ambient Air Quality Standards (NAAQS)
• Occupational Safety and Health Administration (OSHA)
• American Conference of Governmental Industrial Hygienists (ACGIH)
• National Institute for Occupational Safety and Health (NIOSH)
The How
7 Your environmental compliance is clearly our business.
Methodology
U.S. EPA’s AERMOD
• Allows the user to input building dimensions and tiers to account for building downwash
• Receptors can be set at flagpole heights to represent air intake locations
• Model single sources and the combination of multiple sources
• Meteorological data is readily available through the National Weather Service (NWS) online to process
8 Your environmental compliance is clearly our business.
Emissions sources – point sources, stack parameters
Buildings – dimensions, height, tiers
Receptors – air intake locations
Develop emissions rates – either manufacture guarantees or utilize published emissions factors
Model Inputs
9 Your environmental compliance is clearly our business.
1-hour and 8-hour maximum modeled concentrations at receptors (intakes)
Apply screening factor to 1-hour concentrations to evaluate 15-minute averaging periods
Compare results with published health guidelines
Refine model
• Apply NOX refinements (ARM, ARM2)
• Raise stack heights or change stack locations
Model Outputs
10 Your environmental compliance is clearly our business.
New hospital
Central utility plant
▪ 2 emergency generators (ULSD)
▪ 2 domestic hot water heaters (natural gas)
▪ 1 steam boiler (natural gas)
▪ 3 hot water boilers (natural gas with propane back-up)
7 air intake locations
Case Study
11 Your environmental compliance is clearly our business.
Modeled sources at full capacity, operating simultaneously at worst-case conditions
Modeled concentrations of CO resulted in no exceedances of health guidelines or NAAQS
Modeled concentrations of NOX resulted in exceedances
• Design phase, change configuration:
• (1) with the stacks closest to the building [problem]
• (2) with the stacks farther from the building (i.e., turning the equipment to face away from the building) [no problem]
The Strategy – Part 1
12 Your environmental compliance is clearly our business.
Engineering company did not want to change configuration, so….
NOX refinements – utilize Ambient Ratio Method (ARM)
• Refine amount of NOX emitted that is converted to NO2
Modeling iterations:
• 2 EGENs @ 100% load
• 1 EGEN @ 100% load
• 2 EGENs @ 50% load
• 2 EGENs @ 25% load
The Strategy – Part 2
13 Your environmental compliance is clearly our business.
Other Considerations
Debug options in AERMOD to evaluate how plume is being affected by building downwash
Evaluate travel time of plume to receptor (intake) locations for understand NOX conversion rate
Wind tunnel modeling – comprehensive but expensive
14 Your environmental compliance is clearly our business.
Other Considerations
www.all4inc.com | Philadelphia | Atlanta | Houston | Washington DC
Thank you!Questions?
Amanda Essner | [email protected] | 610.933.5246 x 129
Dustin Snare| [email protected] | 610.933.5246 x 126
Sharon Sadler | [email protected] | 571.392.2595
June 7, 2017
www.all4inc.com/resources www.all4inc.com/training