Transcript Modeling the New 1-Hour Nitrogen Dioxide

Modeling the New 1-Hour
Nitrogen Dioxide (NO2)
and Sulfur Dioxide (SO2)
NAAQS
Alan Dresser
Research Scientist I
October 14, 2011
Overview of New NO2 NAAQS
 1-hr NO2 = 100 ppb (189 ug/m3)
 Effective on April 12, 2010
 Based on 98th percentile of annual
distribution of daily max. 1-hour values
 Current NJ 1-Hour Background Levels:
37% to 67% of NAAQS
NO2 1-Hour Modeling
EPA Guidance Memos of June 28, 2010
and March 1, 2011:
 Interim SIL (7.5 ug/m3)
 3-Tiered NO to NO2 conversion approach
 Treatment of intermittent emissions
(limits modeling of start-up/shutdown,
emergency equipment)
NO2 1-Hour Modeling
NJDEP Guidance:
 Interim SIL of 10 ug/m3 (NESCAUM)
 July 29, 2011 memo – Emergency
generator and fire pump exemptions from
modeling 1-hour NO2/SO2 impacts
(specific to combined-cycle plants, caseby-case for others)
Example of 1-Hour NO2 Modeling
LS Power West Deptford Station
 600 MW Combined-Cycle Plant
 Natural gas with 0.05% sulfur oil backup
 Modeled before EPA and NJDEP
guidance memos (intermittent sources;
emergency generator/fire pumps)
Scenarios of Interest
 Normal Operations
(NOx natl. gas = 37 lb/hr, NOx oil = 70 lb/hr)
 Startup Operations (NOx = 323 lb/hr)
 Emergency Generator (NOx = 10 lb/hr)
Fire Pump (NOx = 1.3 lb/hr)
1-Hour NO2 Impacts
(Highest 98th percentile / 8th high concentration)
 Normal Operations (70 lbs/hr, oil) = 8.1 ug/m3
 Startup Operations (323 lbs/hr) = 42 ug/m3
 Emergency Equipment(11.3 lbs/hr) = 43 ug/m3
(no testing during turbine startup/shutdown)
(1-hour NO2 NAAQS = 189 ug/m3)
Lesson : Smaller sources with short stacks and
transitional scenarios at large facilities can
cause big 1-hr NO2 impacts!
Overview of New SO2 NAAQS
 1-hr SO2 = 75 ppb (196 ug/m3)
 Effective on August 23, 2010
 Based on 99th percentile of annual
distribution of daily max. 1-hour values
 Current NJ 1-Hour Background Levels:
18% - 47% of NAAQS
SO2 1-Hour Modeling
August 23, 2010 EPA Guidance Memos:
 Suggested interim SIL (7.8 ug/m3)
 Methods of demonstrating NAAQS
compliance, calculating background, etc.
 24-hour and annual SO2 NAAQS revoked
Intermittent emissions not as important as with NO2
Example of 1-Hour SO2 Modeling
Portland Power Plant
 Coal-fired
1 – 160 MW / 1958
 Unit 2 – 240 MW / 1962
 Unit
 No existing emission controls for SO2
 Average 2007 – 2010 annual emissions of
29,067 tons
1-Hour SO2 Modeling Conducted
with Two EPA Models
1. AERMOD (guideline model)
2. CALPUFF (complex terrain model)

Designed for locations with complex
wind fields

Must conduct a model validation
showing it performs better for the given
application than EPA’s guideline model
(see June 2011 JAWM article)
CALPUFF – Allowable Emissions
Max. Impact 1.4 times
over 3-hr NAAQS
Summary of CALPUFF Results
1-Hour SO2 NAAQS (196 ug/m3)
Meteorological
Time Period
Emissions
Days
Violating
NAAQS
2002
Allowable
39
2002
Actual
(CEM data)
(background not included)
27
% Over
NAAQS
1662 %
(~ 17 x
NAAQS)
1019 %
(~ 10 x
NAAQS)
M
m
Summary of AERMOD Results
1-Hour SO2 NAAQS (196 ug/m3)
Meteorological
Time Period
Emissions
1993-94
Allowable
1993-94
Actual
(avg. monthly)
Days
Violating
NAAQS
42
615 %
(~ 6 x
NAAQS)
5
138 %
(~ 1.4 x
NAAQS)
(No predicted violations of the 3-hour or 24-hour NAAQS,
background not included)
% Over
NAAQS
Columbia Lake SO2 Monitor
 Data collected at Columbia Lake
Monitor since Sept. 23, 2010
 31 exceedances of the 1-hour SO2
NAAQS of 75 ppb (196 ug/m3)
recorded since Sept. 23, 2010
 Monitor located where both models
predicted high impacts but not
maximum
Columbia Lake - Sept. 23, 2010 to Sept. 15, 2011
1-Hour SO2 Modeling Conclusions
 SO2 1-Hour NAAQS is much more easily
violated than the 3 and 24-Hour NAAQS
 Columbia Lake monitoring confirms both
CALPUFF and AERMOD predictions of 1hour NAAQS violation at that location
 Principal sources of concern are older,
large sources burning No. 6 oil or coal
(especially after Sub. 9 Sulfur in Fuel Rule)