REDUCTION OF HIGHLY REACTIVE VOLATILE ORGANIC COMPOUNDS

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REDUCTION OF HIGHLY REACTIVE VOLATILE ORGANIC
COMPOUNDS VARIABLE EMISSIONS IN
HOUSTON/GALVESTONMONITORING, MODELING,
MEASURING, RULEMAKING

• David Allen
• Department of Chemical Engineering, and
• Center for Energy and Environmental Resources
• University of Texas
• (512-471-0049 allen_at_che.utexas.edu)

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The Houston-Galveston area is a severe ozone
non-attainment area costs and benefits of
controls have been estimated to be 5
billion/yr The current EPA approved State
Implementation Plan (SIP, approved in 2000) calls
for significant NOx emission reductions
(approximately 70 of the 2007 inventory 90
for point sources) SIP also called for some VOC
emission reductions Proposed new plan adds
emission reductions for highly reactive VOCs from
industrial facilities and applies 80, rather
than 90 industrial NOx emission reductions



















































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Outline

• Why focus on Highly Reactive Volatile Organic
  Compounds (HRVOCs)? Why are we considering
  variability in emissions? This presentation will
  provide an overview of the scientific basis for
  decision-making
• Impact of scientific findings on air quality
  policy and current direction of technical
  analyses impacting policy decisions

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Focus on HRVOCs emerged out of the Texas Air
Quality Study -2000(TEXAQS - 2000)

• (www.utexas.edu/research/ceer/texaqs/)
  (www.utexas.edu/research/ceer/texaqsarchive)

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TEXAQS - 2000 Study overview

• Study conducted from approximately August 15 -
  September 15
• Approximately 300 investigators
• 5 aircraft
• 5 major ground chemistry sites
• Coordinated with Houston fine particulate matter
  Supersite sampling intensive

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TexAQS and other research programs address key
areas of uncertainty

• Emission inventories
• Chemical and physical processes in the
  atmosphere, particularly those leading to rapid
  and efficient ozone formation (a.k.a. ozone
  spikes)
• Regional air quality modeling/air quality
  policies

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Chemical and physical processes in the
atmosphere Rapid ozone formation events
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TexAQS data have played a crucial role in
understanding these events Physical insights
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Hydrocarbon Reactivities
Top 10 of samples exhibit reactivities that are
4x the mean value. For the most part the highest
reactivities are geographically associated with
industries in the Ship Channel.
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Apportionment of reactivity for high reactivity
samples

• For the high reactivity samples, low molecular
  weight alkenes (propene, ethene and butenes) are
  a major source of hydrocarbon reactivity for
  ozone formation.

Twin Otter VOC Samples Average for 26 samples
with kgt10 s-1
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TexAQS showed us that HRVOCs are important, but
what is relative importance of short, episodic
releases vs. continuous, steady emissions?
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HRVOC emissions

• HRVOCs defined as ethylene, propylene, butylenes
  and 1,3-butadiene
• Continuous emissions to be addressed with a CAP
  (and trade?) program
• Emission events to be handled through a short
  term cap

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Conceptual issue
In most of US, industrial emissions are
relatively constant or are small enough that
meteorology is cause of worst conditions In
Houston, both meteorology and emissions are cause
of worst conditions
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Conceptual issue
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Estimating variability for continuous emissions
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Event Emissions and their impact on ozone
formation in the Houston Galveston Area
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Key Questions

• Are the magnitudes of emission events, singularly
  and collectively, significant relative to routine
  emissions?
• What are the characteristics of the events in
  terms of time, space, and composition?
• How do the events influence ozone formation?

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• TCEQ event database, established in early 2003
• First 11 Months of reporting
• NOx emission event emissions are small compared
  to annual average emissions
• At specific times and locations, VOC and HRVOC
  emissions can be large relative to annual average
  emissions

Average hourly emissions of all point sources
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VOCs 4,000,000 lb

• Total mass of over 4 millions pounds (2000 tons)
  contributes 4 to the 45,000 tons of VOC emitted
  over a single year from point sources in the four
  counties.
• 14 times (18 hours) during the eleven-month
  period, event emissions exceed the annual average
  for all facilities in the region.

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HRVOCs 1,650,000 lb

• Total mass of over 1.6 millions pounds (830 tons)
  is 12 of the 6800 tons of HRVOC emitted over a
  single year from point sources in the four
  counties.
• 29 times (115 hours) during the eleven-month
  period, event emissions exceed the annual
  average.

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1,3-Butadiene 50,000 lb
Propene 500,000 lb
Butenes 100,000 lb
Ethene 1,000,000 lb
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What are the characteristics of the events in
terms of time, space, and composition?
Less than 24 hours
Daily
2-3 times per week
Most HRVOC events last less than a day, many last
less than an hour Largest number of events is
from events of 100-1000 lb, but most of the mass
is associated with events greater than 1000 lb,
which occur, on average, several times per week
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Conceptual model

• Events with emissions of more than 1000 pounds of
  HRVOCs occur several times per week, on average
  events with emissions of more than 10,000 pounds
  of HRVOCs occur several times per month, on
  average
• Many are relatively short (well under one hour in
  duration)
• Among the HRVOCs, ethene and propene dominate
• Events occur primarily in Harris and Brazoria
  counties at chemical manufacturing facilities

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What are the consequences for ozone formation?

• Example of worst case scenario Monitoring data
  from a 6700 lb, 30 minute ethylene release at
  LaPorte

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10,000 lb ethylene release at LaPorte, (6700 lb
between 11 and 1125 AM) 3/27/2002
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Short term ozone enhancements of up to 100 ppb
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Add Event to Air Quality Model(most recent
version with 1-km resolution)
Without Event
With Event
Layer One 149.9 ppb vs203.0 ppb
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Outline

• Why Highly Reactive Volatile Organic Compounds
  (HRVOCs)? Why are we considering variability in
  emissions? An overview of the scientific basis
  for decision-making
• Impact of scientific findings on air quality
  policy and current direction of technical
  analyses impacting policy decisions

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Actions taken by the TCEQ and current technical
analyses

• Based on the data from TexAQS, which indicate
  that VOC emissions from industrial facilities are
  responsible for rapid and efficient ozone
  formation, new rules have been proposed for
  emissions of highly reactive volatile organic
  compounds (HRVOCs) from flares, cooling towers
  and fugitive sources
• Balance between NOx and HRVOC emission controls
  reevaluated, balance between short term and
  annual HRVOC emissions being evaluated focus of
  work at UT is on short term releases and on
  characterizing scientific uncertainties

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Summary

• Overview of major findings from TexAQS Shift in
  focus to reactive hydrocarbons
• Impact of findings on air quality policy Shift in
  focus to reactive hydrocarbons with a focus on
  most reactive hydrocarbons caps on HRVOC
  emissions
• Current direction of technical analyses impacting
  policy decisions (Highly Reactive Volatile
  Organic Compounds, HRVOCs) Relative importance of
  annual and short term limits on HRVOC emissions