ESTIMATION OF THE IMPORTANCE
OF CONDENSED PARTICULATE MATTER
TO AMBIENT PARTICULATE LEVELS
PEDCo ENVIRONMENTAL
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ESTIMATION OF THE IMPORTANCE
OF CONDENSED PARTICULATE MATTER
TO AMBIENT PARTICULATE LEVELS
Prepared by
PEDCo Environmental, Inc.
505 South Duke Street, Suite 503
Durham, North Carolina 27701-3196
Contract No. 68-02-3512
Task Order No. 37
PN 3525-37
Task Manager
Harold G. Richter, Ph.D
Prepared for
U.S. ENVIRONMENTAL PROTECTION AGENCY
OFFICE OF AIR QUALITY PLANNING AND STANDARDS
RESEARCH TRIANGLE PARK, NORTH CAROLINA 27711
April 1983
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ESTIMATION OF THE IMPORTANCE
OF CONDENSED PARTICIPATE MATTER
'TO AMBIENT PARTICULATE LEVELS
Prepared by
PEDCo Environmental, Inc.
505 South Duke Street, Suite 503
Durham, North Carolina 27701-3196
Contract No. 68-02-3512
Task Order No. 37
PN 3525-37
Task Manager
Harold G. Richter, Ph.D
Prepared for
U.S. ENVIRONMENTAL PROTECTION AGENCY
OFFICE OF AIR QUALITY PLANNING AND STANDARDS
RESEARCH TRIANGLE PARK, NORTH CAROLINA 27711
April 1983
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DISCLAIMER
This report was prepared for the U.S. Environmental Protection Agency
by PEDCo Environmental, Inc., Cincinnati, Ohio, under Contract No. 68-02-3513,
Work Assignment No. 37. The contents of this report are reproduced herein as
received from the contractor. The opinions, findings, and conclusions ex-
pressed are those of the author and not necessarily those of the U.S. Environ-
mental Protection Agency.
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CONTENTS
Figures v
Tables v1
Acknowledgment vii
Executive Summary viii
1. INTRODUCTION 1
1.1 Purpose of this study 1
1.2 Approach 2
2. CHARACTERIZATION OF CONDENSED PARTICULATE MATTER 3
2.1 Definition of condensed particulate matter 3
2.2 Properties that characterize condensed particulate matter 4
2.3 Reference points for condensed particulate data comparison 4
3. CONDENSED PARTICULATE MATTER FROM STATIONARY SOURCES 7
3.1 Estimation of condensed particulate matter by source category 7
3.2 Estimation of condensed particulate matter as primary sulfate
emissions 18
3.3 Test methods for stationary sources 19
3.4 Control of condensed particulate matter from stationary
sources 22
4. CONDENSED PARTICULATE MATTER FROM MOBILE SOURCES 27
4.1 Light-duty vehicles 27
4.2 Heavy-duty vehicles 28
4.3 Test methods for mobile sources 29
4.4 Mobile source impact in an urban situation 29
4.5 Future mobile source trends 30
5. CASE STUDIES OF POTENTIAL CONDENSED PARTICULATE MATTER EMISSIONS
IN THREE CITIES 32
5.1 Houston, Texas 32
5.2 Philadelphia, Pennsylvania 36
5.3 Portland, Oregon 36
m
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CONTENTS (continued)
Page
6. EFFECT OF CONDENSED PARTICIPATE ON AMBIENT PM1Q 41
6.1 Primary and secondary participates studies 41
6.2 Visibility impairment 44
6.3 Impact based on National emissions data reports 47
6.4 Recommendations for future study 47
REFERENCES 51
GLOSSARY 55
Appendix A Formation of condensed particulate matter A-l
Appendix B Filterable vs. condensed particulate matter and
adjusted emission factors B-l
Appendix C Discussions of EPA Methods 5 and 17, modi fed Method 5,
and the stack dilution sampling system C-l
Appendix D Control techniques for condensed particulates D-l
Appendix E Test methods for mobile sources including data summary
and correction factor E-l
IV
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FIGURES
Number Page
1 Average Number, Surface Area, and Volume Distributions
of Los Angeles Smog 5
2 Summary of Relative Source Contributions for Sites 20
3 Eight-day Average of Daytime Fine- and Coarse-fraction
Mass Concentrations Apportioned by Chemical Species in
Houston from September 11 to 19, 1980 46
4 Contributions to the Mean Daytime Light Extinction
Coefficient in Detroit 47
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TABLES
Number Page
1 Potential Stationary Sources of Condensed Particulate 8
2 EPA Method 5 Test Results—Ratio of Front Half (Filterable)
to Back Half Particulates by Source Type 10
3 Estimated Percents of Ambient Sulfate Levels Due to PSE
for Different Geographical Regions of the U.S. 21
4 Examples of Process Modifications to Reduce Condensed
Particulate 24
5 Estimated Total Cost of Reducing Condensed Particulate
Emissions (September 1982 dollars) 26
6 1973 Stationary Source Particulate Matter, Estimated
Condensed Particulate, and Estimated Total Particulate
Emissions from Source Types in the Houston-Galveston Urban
Area that Generate Greater than 100 tons/year (tons/year) 33
7 Stationary Source Particulate Matter, Estimated Condensed
Particulate, and Estimated Total Particulate Emissions
in the Houston-Galveston Urban Area Based on TACB Permit
Applications after 1973 (tons/year) 35
8 Total Stationary Source and Estimated Condensed Particulate
Emissions in Philadelphia Neighborhood Scale Study
(tons/year) 37
9 Estimated Total Particulate Emission Rates in Portland
Airshed 39
10 Relative Contribution of Condensed Particulate Matter to
Fine Particulate in Portland 40
11 Major Selected Source Categories of Condensed Particulate 48
12 Stationary Source Categories Accounting for Two Percent or
More of 1978 Actual Particulate Emissions 49
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ACKNOWLEDGMENT
This report was prepared for the U.S. Environmental Protection Agency
by PEDCo Environmental, Inc., Cincinnati, Ohio. Dr. Harold G. Richter was the
EPA Project Officer. Mr. William G. DeWees served as the Project Director,
and Mr. Vinson Hellwig was the Project Manager. The principal authors at PEDCo
were Mr. Vinson Hellwig, Mr. Joseph Steigerwald, and Mrs. Barbara Allen. Sec-
tions of this report were authored by Dr. Joseph Sickles, Research Triangle
Institute, and Dr. Guy Oldaker, Entropy Environmentalists, Inc. The authors
thank Dr. Richter for his overall guidance, direction, and comments on this
study. The authors also thank the California Air Resources Board, Pennsylvania
Department of Environmental Resources, and the South Coast Air Quality Manage-
ment District for making available unpublished data for this study.
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EXECUTIVE SUMMARY
Condensed particulate matter3 results from chemical reactions as well as
physical phenomena. The findings of this report indicate that whereas inorganic
species form condensed particulate matter by physical condensation, chemical
reactions, agglomeration, and nucleation, organic species from stationary and
mobile sources form condensed particulate matter primarily by physical conden-
sation. Almost all condensed particulate matter is formed in the <10 micron
range, referred to as PMjQ.
PEDCo gathered test data for 60 stationary source categories to determine
the ratio of condensed particulate (assumed to be represented by the back half
of the Method 5 sampling train) to filterable particulate (represented by the
& Stail) ^"Cf t> ?
front half of the EPA Methods 5 and 17 sampling trains). "Twer-be-,limited data,
this relationship was the best available means of estimating the significance
of condensed particulate matter for a large number of stationary sources.
This technique, however, overestimates some source categories while underesti-
mating others. Therefore, the data estimates are suitable for program guidance
only and should not be considered as actual contributions.
Based on this relationship, PEDCo then conducted several analyses to
evaluate the existing data base on particulate emissions from several station-
ary source categories. The following summarize the results of this evaluation.
o A review of the 10 major stationary source contributors of
particulate emissions determined by a 1978 OAQPS study indicated
that the current estimated particulate emissions would have to ,
be increased by 27 percent to account for condensed particulate,
if only these source categories were considered.
o A review of the 10 major stationary source contributors of par-
ticulate emissions in a 1978 DSSE study (67.3% of total emissions)
indicated that the current estimate of particulate emissions would
have to be increased by 30 percent to account for condensed partic-
ulate.
aA definition of condensed particulate is presented in Section 2.1 of this
report.
v i i i
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o Condensed particulate accounted for 30 percent, 48 percent,
and 22 percent of the total primary stationary source partic-
ulate emissions in the Houston, Texas; Philadelphia, Pennsyl-
vania; and Portland, Oregon areas, respectively. All of these
studies were smaller in size than their respective Air Quality
Control Region. (AQCR).
The above impacts account only for the contribution from stationary sources;
the percentages do not represent the total impact on PM,0- The total impact
on ambient air would be significantly less on a percentage basis since back-
ground sources contribute little condensed particulate matter and some cate-
gories such as mobile sources account for condensed particulate matter in
emissions inventories.
A review of studies conducted in Houston and Detroit indicated that fine
particulate can impair visibility by creating a highly visible plume. Since
condensed particulate forms mostly fine particulate, it should have a similar
effect. Although the total impact could not be estimated using the available
data, sufficient evidence exists to indicate the need for further investigation
of this problem.
Methods available for control of condensed particulates from stationary
sources fall into three categories: 1) process or raw materials modifications
that remove or reduce the amounts of the species present, 2) process modifica-
tions that would cause a shift in the size of particles in the effluent to
particles greater than 10 ym in diameter, and 3) collection of the condensed
particulate with control devices. Although some modifications to process and
raw materials are feasible for reducing condensed particulate, in some cases,
this might only delay the eventual formation of PM1Q through secondary par-
ticulate formation. Control technology exists for many sources of condensed
particulate; however, the cost per pound of particulate collected is generally
much greater for condensed particulate than for filterable particulate.
This study also included an assessment of the test methods currently
being developed for use on stationary sources to measure condensed particulate.
A state-of-the-art condensed particulate matter sampling system has been
developed by EPA's Industrial Environmental Research Laboratory (IERL), but
thus far it has had limited field use. The principles of dilution and sample
collection by lERL's Stack Dilution Sampling System (SDSS) have been confirmed
in part by a similar sampling system used on mobile sources by the Environmental
Sciences Research Laboratory (ESRL). The mobile source sampling system has
had extensive evaluation and field use.
ix
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This study also evaluated the results of various ambient sampling
studies to determine the impact of condensed particulates on ambient air
quality. An analysis of these sampling studies indicates that in more
heavily industrialized urban areas, up to half of the PM,n is primary sulfate,
3
secondary sulfate, and nitrate, and up to one-fourth is condensed particulate.
The data base that was developed and researched for this report did not
provide an adequate foundation to establish the exact contribution of condensed
particulate matter to PM1Q. Unfortunately, most total suspended particulate
(TSP) or PM,Q studies do not relate the stationary source contributions directly
to the ambient monitoring results. This analysis indicates a need for further
study"to address current test methods for measuring particulate matter emissions
and to resolve the question regarding primary and secondary particulate forma-
tion at the receptor site.
It should be noted that a significant portion of the findings in this
report are based only on estimates. The indications of the results, however,
indicate clearly that further studies should be undertaken to provide accurate
data acquisition techniques and to conduct ambient studies to determine whether
State and local agencies must consider condensed particulate in the develop-
ment of their control strategies for attaining current or revised TSP National
Ambient Air Quality Standards (NAAQS). As additional data are acquired, the .
resulting data bases and emission factors should be updated accordingly.
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SECTION 1
INTRODUCTION
Section 109(d) of the Clean Air Act as amended in 1977 requires the U.S.
Environmental Protection Agency (EPA) to review the air quality criteria for
the total suspended particulate (TSP) National Ambient Air Quality Standards
(NAAQS) by December 31, 1980, and at 5-year intervals thereafter. As a result
of these reviews, the EPA may revise the air quality criteria and promulgate
new NAAQS in accordance with Sections 108 and 109(b) of the Clean Air Act.
Since the promulgation of the TSP NAAQS in 1971, the need for promulgation
of a NAAQS for size-specific particulate matter has been of considerable con-
5
cern to EPA. Because of this concern, EPA has committed a substantial
research effort toward studying the sources, effects, and transport of those
particulate matter size fractions believed to have the greatest impact on
health and welfare.
The EPA is now in the process of reviewing the current TSP NAAQS with re-
gard to the requirements in the Clean Air Act as amended in 1977. As part of
this review, the Agency has collected, analyzed, and evaluated a wide variety
of data on health and welfare effects and on emissions and ambient air quality.
Some of these data provide information on condensed particulate matter.
1.1 PURPOSE OF THIS STUDY
Because of the manner by which particulate matter is measured in stack
gases, the mass of the condensed particulate matter is generally not included
in calculations of particulate matter emission factors. Moreover, if the con-
densed particulate matter is a significant fraction of TSP and particulate
matter with an aerodynamic particle size diameter of 10 urn or less (PM1Q),
strategies to reduce ambient levels of TSP or PM,Q may be less effective than
estimated initially. If the States are to develop effective control strategies
for PM,Q, EPA must ascertain the importance of condensed particulate matter
to ambient levels of PM1Q. The objectives of this study were 1) to obtain
1
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engineering and emission data on potential stationary sources of condensed
participate matter and 2) to estimate the impact of condensed participate mat-
ter on ambient TSP and PM,g air quality and on visibility. In addition, if
condensed particulate matter was determined to be a major contributor to ambi-
ent air quality, control techniques and emission testing methods were then
reviewed and discussed. Wherever possible, potential modifications to existing
data bases and emission factors are also discussed.
The ultimate goal of the study is to estimate the impact of condensed
particulate matter on ambient TSP and PM,Q levels and to identify those sta-
tionary sources that may be the major contributors of condensed particulate
matter in the United States.
1.2 APPROACH
Although no source tests were performed or special ambient studies con-
ducted as part of this effort, a number of source test reports were reviewed
and the data were evaluated to determine the potential impact of condensed
particulate. Data from ambient studies dealing with condensed particulate
•matter and unpublished source test data from the files of the EPA Emissions
Measurement Branch and the States of California, Pennsylvania, and North
Carolina, were also reviewed and evaluated in an effort to summarize the
available information on condensed particulate matter.
A literature search was conducted to establish a comprehensive list of
studies dealing with condensed particulate matter. These studies were then
reviewed, and pertinent data were extracted and analyzed. Because the data
on condensed particulate matter are limited, much of this report is based on
extrapolated data and/or good engineering judgment.
In addition to summarizing all available data on condensed particulate
matter, PEDCo selected three urban areas for case studies to estimate the
potential impact of condensed particulate matter emissions on ambient air
quality: Houston, Texas; Philadelphia, Pennsylvania; and Portland, Oregon.
Relative PM1Q contributions from several source categories were estimated on
the basis of available data for these areas, and adjustments were made to par-
ticulate matter emission inventories to account for estimated condensed
particulate.
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SECTION 2
CHARACTERIZATION OF CONDENSED PARTICULATE MATTER
The term "condensed participate matter" has been used in various contexts
without a widely accepted definition. Since the main goal of this study is
to determine the significant stationary source contributors of condensed par-
ticulate matter, the definition pertains only to stationary source emissions
and excludes all filterable particulate matter collected by EPA Method 5.
2.1 DEFINITION OF CONDENSED PARTICULATE MATTER
Condensed particulate matter is defined in this report as material that
is a gas or a vapor at the stack temperature at the sampling location which
transforms into a liquid or solid from immediately after the sample location
to within a few seconds after it leaves the stack or duct. The two major
requirements for formation of condensed particulate matter are 1) the stack
effluent is diluted with the ambient air approximately tenfold, and 2) the
mixed stack effluent quickly comes to ambieat temperature. In most cases both
of these requirements will be met within a few seconds and a few hundred feet
after exiting the process or stack. The condensed particulate matter can form
both in or out of the stack as a result of cooling. When the filtration temp-
erature (usually 250°F) of the EPA Method 5 is less than the stack temperature,
a portion of the filterable particulate may be condensed particulate matter.
However, this portion of condensed particulate matter is not included in this
report since it is currently regulated as particulate and is included in the
emissions inventory.
In contrast, secondary particulate is a product of atmospheric chemical
reactions and requires several minutes, hours, or days to form. Because the
definitions allow some slight overlap between what is considered to be con-
densed particulate matter and what is considered to be secondary particulate,
a refined definition of particulate must describe temperature, pressure, and
other factors of collection techniques. Therefore, particulate collected by
reference method condensed particulate matter train must exactly define "con-
densed particulate matter" in terms of the previously mentioned parameters.
3
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2.2 PROPERTIES THAT CHARACTERIZE CONDENSED PARTICIPATE MATTER
Chemical and physical mechanisms influence aerosol formation and growth.
Chemical reactions produce a compound that may convert from gas to form a
particulate, and such reactions may occur in or on the particle. To a large
extent, nucleation, condensation, absorption, adsorption, coagulation, and
sedimentation determine the size distribution of aerosols.
Particulate matter exists in various sizes, both at the source and in the
atmosphere. Size distributions of aerosols can be based on number, surface
area, and volume (or mass). Figure 1 shows the number, surface area, size,
and volume distributions of Los Angeles smog. '
In ambient air, the volume (or mass) distribution is usually bimodal,
with a demarcation between fine and coarse particles occurring between 2 and
3 ym particle diameter. Coarse particulate matter typically originates from
natural and anthropogenic mechanical processes and comprises approximately
two-thirds of the aerosol mass. Fine particles typically originate from com-
bustion sources and the condensation of chemical or photochemical reaction
products.
Fine particles may show two surface area modes. ' The first mode (at
approximately 0.02 urn) results from direct emissions of combustion products.
The second (between 0.1 and 0.5 urn) results from the coagulation of primary
particles or the condensation of reaction products or water on primary parti-
cles. The latter is known as the "accumulation mode," because aerosols that
grow into this range by coagulation and condensation tend to remain in this
range.
By number, most of the particles are smaller than 0.1 urn. Particles of
this size are produced by nucleation in combustion sources and by gas-to-
particle conversion processes such as occur in urban atmospheres; this is
known as the "nucleation" mode. A more detailed discussion of particle
formation is presented in Appendix A.
2.3 REFERENCE POINTS FOR CONDENSED PARTICULATE DATA COMPARISON
Strategies for the control of particulate matter from stationary sources
currently focus on emissions of primary particulate matter and their relation-
ship to measured ambient particulate matter levels. Ideally, the cause-and-
effect relationship between emitted particulate and particulate matter
4
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.001
SUB- /r>
RANGES ( I
.1 I 10
PARTICLE DIAMETER, MICRONS
100
MOST
NUMBER.
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measured at ambient conditions could be established by simply determining
participate matter emissions from the stationary sources. Although data are
available on particulate matter emissions for many stationary source categories,
these data cannot necessarily be used in a straightforward way to estimate
the total particulate matter emissions. According to 40 CFR 60, the current
definition of particulate matter is any solid or liquid matter collected by
the EPA Reference Methods 5 and 17, but this definition applies only to fil-
terable particulate. Actual emissions from sources would consist of both
filterable and condensed particulate matter. The total impact on the ambient
particulate level from any source would be some portion of the primary (fil-
terable and condensed) and the secondary particulate matter that is formed
later as a result of atmospheric reactions. The impact is a function of both
the particle size distribution of the primary particulate and the conversion
rate and ratio of the secondary particulate formation.
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SECTION 3
CONDENSED PARTICIPATE MATTER FROM STATIONARY SOURCES
A variety of stationary sources emit gaseous vapors that condense in the
ambient air to become particulate matter. Condensed particulate emissions
form from both organic and inorganic compounds and are generated by fossil
fuel combustion, incineration, and various industrial processes. Table 1
presents a list of potentially significant stationary sources of condensed
particulate.
3.1 ESTIMATION OF CONDENSED PARTICULATE MATTER BY SOURCE CATEGORY
EPA Method 5 source test data from the Emission Measurement Branch (EMB)
of the EPA and the States of California, Pennsylvania, and North Carolina were
reviewed to estimate the condensed particulate levels from stationary sources.
The "front half" (or filterable portion) of each test and the "back half" (or
impinger catch) were tabulated to determine their contribution to the total
sample. For the purpose of this analysis, the condensed particulate was
assumed to be the particulate present in the impinger catch.
By use of Method 5 data from various sources and the tabulation of data
as "back-half" versus "filterable," the relative contribution of condensed par-
ticulate from source categories was estimated. The data bases were limited,
however, and no allowance was made for artifact formation in the impingers or
particle size distribution of the collected sample.
Table 2 summarizes the EPA Method 5 results used in this study. It pre-
sents the ratio of filterable particulates and back-half catch to total par-
ticulate collected in Method 5 tests of 60 process source categories. These
data represent one or more source tests.
All data collected are shown in Appendix B. Appendix B also contains a
table presenting emissions estimates based on adjusted AP-42 emission factors
for selected process source categories. The AP-42 emission factors were ad-
justed to account for increased particulate wherever the appropriate source
categories could be matched with the data in Table 2. This increase would be
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TABLE 1. POTENTIAL STATIONARY SOURCES OF CONDENSED PARTICIPATE
Alfa fa dryers
Anode baking furnaces
Asphalt plants
Asphalt roofing
Felt saturating
Asphalt blowing
Boilers/other combustion
Bagasse
Coal
Lignite
Oil
Wood/bark
Charcoal kilns
Chemical production
Boric acid
Phosphoric acid
Potassium still
Zinc sulfate
Citrus peel dryers
Coke plants
Corn processing
Wet milling
Syrup manufacturing
Elemental phosphorus
Electric arc furnace
Expanded vinyl
Ferroalloy mills
Fertilizer plants
Ammonium nitrate
Diammonium phosphate
Fiberboard
Dryer
Press
Fiberglass and mineral wood
Curing ovens
Blow chambers
Glass plants
Grain dryers
Gray iron foundries
Incinerators
Iron and steel mills
Sinter plant
Electric arc furnace
Basic oxygen furnace
Open hearth furnace
Sand blasting
Heat treating
Scrap steel melting
Kraft pulp and paper mills
Recovery boilers
Lime kiln
Smelt dissolve tank
Blow tank/hot water accumulator
Lime kiln
Manure dryers
Mineral products
Gypsum
Clay dryers
Feldspar dryers
Clay kilns
(continued)
8
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TABLE 1 (continued)
Petroleum refineries
FCC
Catalytic regenerator
Heaters
Petroleum coke
Portland cement plants
Kiln
Finish mill
Primary nonferrous smelters
Al Soderberg furnace
Cu converter
Cu electric furnace
Cu fluid fed roaster
Pb sinter line
Pb blast furnace
Mo roasters
Zn ore briquet dryer
Zn sweat kiln
Zn fume kiln
Residential heating
Oil
Wood
Rubber curing press
Rubber incineration
Secondary metal smelters
Al scrap furnace
Al dross furnace
Brass and bronze furnaces
Cu furnace
Pb furnaces
Pb02 mills
Pb grid coating
Pb remelt pot
Other metal furnaces
Sewage sludge incinerators
Silicon carbide furnaces
Spray paint booths
Sulfite pulp mill
Recovery boiler
MME blow tanks
Textile
Nylon polymerization
Melt polymer spinning
Tenter frame
Dye beck
Heat set
Texturizing
Latex backing
Tire buffing operations
Wood products
Veneer plant dryer
Resawing
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TABLE 2. EPA METHOD 5 TEST RESULTS—RATIO OF FRONT HALF (FILTERABLE)
TO BACK HALF PARTICULATES BY SOURCE TYPE3
Source type
Anode baking furnace
Asphalt plants
Boiler/coal (industrial)
(utility)
Boiler/oil
Boiler/wood
Brick and tile kilns
Chemical production
Potassium still
Chrome oxide kiln
Boric acid
Electric arc furnaces
BOF
Open hearth
Coke ovens
Sandblast
Heat treating
Elemental phosphorous
Fiberboard dryer
Glass plant
Grain dryers
Incinerators
Municipal
Industrial
Sewage sludge
Iron and steel
Iron foundries
Iron and steel sinter plants
Kraft pulp
Recovery boilers
Lime kiln
Smelt dissolve tank
Lime kiln
Particulates, %
Filterable
65.8
67.9
90.1
55.6
42.7
84.0
72.2
65.3
94.3
44.1
62.9
77.3
71.7
68.2
69.9
46.0
57.5
73.0
74.5
69.7
35.3
61.8
76.4
70.8
85.7
60.9
83.8
89.6
Back half
34.2
32.1
9.9
44.4
57.3
16.0
27.8
34.7
5.7
55.9
37.1
22.7
28.3
31.8
30.1 '
54.0
42.5
27.0
25.5
30.3
64.7
38.2
23.6
29.2
14.3
39.1
16.2
10.4
Number of
test reports
7
17
10
15
27
14
9
1
1
2
3
3
4
2
2
1
2
14
3
4
1
2
6
14
10
6
6
3
(continued)
10
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TABLE 2 (continued)
Source type
Mineral products
Gypsum
Clay dryer
Feldspar dryer
Clay kiln
Mineral wool
Petroleum refineries
Heaters
FCC
Catalytic regenerator
Portland cement
Kiln (gas-fired)
(coal-fired)
(wet-process)
(dry- process)
(process not specified)
Finish mill (wet-process)
Primary nonferrous smelters
Zinc sweat kiln
Zinc fume kiln
Zinc ore briquet dryer
Lead sinter line
Lead blast furnace
Copper converter
Copper converter, electric arc
furnace, and fluid bed
roaster
Copper reverberatory furnace
Copper roasters
Molybdenum roasters
Roofing
Saturated felt
Asphalt blowing
Particulates, %
Filterable
87.3
0.5
11.6
87.4
60.7
45.6
76.1
46.6
90.1
73.8
65.5
37.9
46.4
81.1
82.9
48.0
73.6
24.7
86.6
82.7
95.6
37.7
69.5
39.8
44.5
99.0
97.0
55.7
56.8
Back half
12.7
99.5
88.4
12.6
39.3
54.4
23.9
53.4
9.9
26.2
34.5
62.1
53.5
18.9
17.1
52.0
26.4
75.3
13.4
17.3
4.4
62.3
30.5
60.2
55.5
1.0
2.9
44.3
43.2
Number of
test reports
1
1
1
2
3
1
2
3
1
1
8
1
1
1
1
1
3
1
1
1
2
1
1
1
1
1
1
2
4
(continued)
1.1
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TABLE 2 (continued)
Source type
Secondary metal smelters
Aluminum dross furnace
Aluminum furnace
Lead furnace
Lead mill
Lead grid casting
Lead remelt pot
Nonferrous metal reclamation
furnace
Silicon carbide furnaces
(Acheson furnace)
Spray paint booths
Textile
Dryers
Tenter frame
Wood products
Sanding
. Resawing
Parti culates, %
Filterable
11.1
33.7
44.2
47.2
52.3
89.8
64.5
68.3
62.2
24.7
14.1
73.4
91.7
Back half
88.9
66.3
55.8
52.8
47.7
10.2
35.5
31.7
37.8
75.3
85.9
26.6
8.3
Number of
test reports
1
1
7
1
4
1
3
4
4
1
4
3
2
Test results reflect emissions after air pollution control equipment.
12
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more indicative of the true total participate impact on the TSP ambient air
quality levels. For the emission factors for a size-specific particulate
matter standard, the filterable particulate portion would need to be reduced
to include only the regulated particle size range of each test. The adjust-
ment for particle size distribution was beyond the scope of this task.
In addition to the data available from the Method 5 tests, information
on condensed particulate was also available for the following source cate-
gories as discussed below:
o Kraft pulp and paper
o Portland cement plants
o Primary nonferrous smelters
o Textile industry.
3.1.1 Kraft Pulp and Paper
Investigations of out-of-stack aerosol formation as a result of emissions
from kraft pulp mills have indicated that these emissions are significant
8 9
sources of cloud condensation nuclei (CCN). ' One study indicated that a
q
large portion of these emissions is less than 1 urn. The assumption was
made that these particles might be the products of SCL-NH.-I^O (liquid) reac-
tions. Also, a portion of the CCN was attributed to sulfuric acid (HLSO.),
sodium sulfate (Na^SC*), sodium hydroxide (NaOH), and sodium sulfite (Na2S03),
all of which were believed to have condensed in the ambient air.
A review of phase diagrams, published literature, and computer simulation
models indicates that a significant amount of sodium chloride (NaCl) and hydro-
gen chloride (HC1) may be produced by the combustion of black liquor contain-
ing chlorine. The amount of chlorine in the liquor determines the relative
amounts of NaCl and HC1 in the gas stream. Because of the high vapor pressure
of NaCl and elevated furnace temperatures, the material is lost from the smelt,
Maximum loss rate occurs at a liquor chlorine concentration of 1% percent by
weight. At this liquor concentration the fume may contain up to 30 percent
NaCl. If the black liquor contains 3 percent chlorine, the gas stream can
contain up to 300 ppm HC1. Chlorine enters the kraft system through several
sources: 1) storage of logs in brackish or salt water, 2) contamination in
makeup chemicals such as saltcake, and 3) recycling of waste chlorine bleach
13
-------
liquors. The recycling of bleach liquors appears to be the major source of
chlorine. The amount of chlorine in black liquor has increased significantly
since mills are recycling effluent streams and normal outlets have been re-
duced; i.e., the equilibrium in the system has shifted.
Also, the increased use of low-odor recovery boilers has resulted in an
increase in the weight of sodium sulfate lost from the boilers. In low-odor
boilers, total reduced sulfur is reduced by shifting the chemical equilibrium
to form sodium sulfate instead of SOp- As a result of this shift, a higher
amount of Na^SO. is emitted. Because of the higher flue gas temperature
(-218 C), a portion of the material is in the vapor phase when it exits the
electrostatic precipitator (ESP). Because of the increased amount of sodium
sulfate and sodium chloride in the fume, the particle size is reduced.
3.1.2 Portland Cement Plants
The portland cement industry is a good example of a potential condensed
particulate emitter that was studied to determine the cause of these emissions.
One such study was prompted by a problem resulting from the formation of a
bluish-white detached plume at a portland cement plant stack in Glens Falls,
New York. This plume, which occurred intermittently and only during humid
and cool weather conditions, did not appear to be a typical water vapor plume.
Under an EPA grant, the University of Denver performed an extensive investi-
gation of the Glens Falls cement kiln to evaluate the condensed particulate
12
formation in the plume. The Glens Falls plant, which is a dry process
plant (raw material crushing and mixing), uses an ESP for particulate control.
The ESP was originally designed for a wet process plant; however, rather than
replacing it, the plant installed a water injection system downstream of the
kiln and upstream of the ESP to condition and cool the exhaust gases to the
ESP.
The results of the study showed that the plume contained various species
of sulfates: ammonium sulfate, ammonium bisulfate, and sulfuric acid. Stack
tests (12 runs) performed on the facility showed that the stack gases con-
tained an average of 171 ppm of ammonia and 204 ppm of sulfur oxides (in the
13
gaseous state) and 20 percent moisture content.
After laboratory research and analysis of the condensed plume, the fol-
lowing mechanism for formation of the ammonium sulfate compounds was proposed:
14
-------
the S02 dissolves in the condensed water vapor along with NH3; the NH- shifts
the pH of the system and forces the reaction SCL + H?0 -*• HSCL~ + H+; further
= +
shifts in the pH forces the reaction HSCL -> SO- + H . Because the pH has
shifted and the SCL has converted to HS03~ and S03~, it is more easily oxi-
dized than SCL. The predominant resulting reaction is:
3NH3 + 2S02 + 3H20 + h$2 •
Because some sulfuric acid is also present in the system, the condensed par-
ticul.
acid.
ticulate consists of ammonium sulfate, ammonium bisulfate, and some sulfuric
12
Raw materials that are used in the manufacture of portland cement con-
tain varying amounts of volatile alkali compounds. When exposed to the in-
tense heat of the calcining kiln, this material volatilizes and combines with
water, SCL, and chlorides in the gas stream. The species formed include
NaOH, Na2S04, NaCl , KOH, KC1, K2S04, and S03~. Relative amounts of each species
vary depending on feed rate, relative amounts of feed alkali, temperature, and
kiln conditions. As these species exit the kiln, they either condense as fine
particles and penetrate farther into the last fields of the ESP and are emitted
or condense on larger particles in the gas stream. Selective removal of large
particles (CaO, CaCCL, SiCL) in the inlet fields results in a particle size
shift to fine alkali compounds in the exit gas stream. The method of condensa-
tion (as fine particles or as coating on large particles) is determined by the
relative concentration of particles in the hot gas stream, the predominant
chemical species, and the rate of cooling.
This detached plume phenomenon has been observed at several other port-
land cement plants, therefore, this problem, is not unique.
3.1.3 Primary Nonferrous Smelters
Sources of condensed particulate emissions from pyrometallurgical smelt-
ing include lead sintering operations, copper roasters, and furnaces. Both
copper and lead smelting have two processes that emit condensed particulate.
Some of this particulate is in the form of sulfuric acid and sulfates formed
from the SCL in the lead sinter line off-gases and copper roasters, but most
of it is emitted in the form of a metallic oxide fume from the furnaces (i.e.,
arsenic trioxide).
15
-------
Arsenic emission rates from copper smelters equipped with pollution con-
trols range from 0.1 to 36.5 kg/h (0.3 to 80.4 Ib/h) in the United States.
Much of the arsenic leaves the control equipment in a vapor state and con-
denses in the ambient air, unless gas cooling is performed before the control
14
device.
3.1.4 Textile Industry
Organic materials are used in all processing steps in the textile indus-
try. Oils are applied during spinning, throwing, and knitting to reduce
friction and minimize yarn damage; detergents are used as scouring aids; the
dyeing process and the dyes themselves include the use of softeners, anti-
foaming agents, and dye accelerants or carriers; and finishing may include
treatment with water-repellent, flame-retardant, soil-resistant, antistatic,
and crease-resistant materials. Drying and heat treatment of fabrics play an
important role in textile processing, and the relationship between the retained
and/or process-vehicle organic material on the fabric or yarn and the drying
of heat-treatment conditions largely defines the potential for condensed
organic emissions.
Three studies were conducted on various textile finishing operations in
plants in North Carolina. ' ' One study determined the manner and amount
of organic carrier emitted to the atmosphere during the dyeing of polyester
fabric in dye becks open to the atmosphere. The data indicate that the car-
rier, biphenyl, was emitted at a rate equal to 42 to 50 percent of the initial
charge during the dye cycle. The dye beck is maintained at 100°C (212°F) after
the charge and during the dyeing process and the boiling point of biphenyl is
256.1°C (493.0°F).16
A modified EPA Method 5 sampling train was used to test the emissions.
The biphenyl was collected in the impingers and analyzed by gas chromatography.
The tested emission rate was 586 kg/Mg (1,171 Ib/ton) of charged biphenyl for
the dye beck. All of the biphenyl collected was in the back half of the
sampling train and was considered condensed particulate.
The second study was a source test (similar to the first one for biphenyl)
performed on a loop dryer at a different plant in North Carolina. The loop'
dryer was used to dry cloth after the dyeing process was complete. Two tests
were conducted with a modified EPA Method 5 sampling train. The biphenyl was
16
-------
collected in the back half of the train and analyzed by gas chromatography.
The resulting biphenyl emissions were 8.4 kg/Mg (16.8 Ib/ton) of cloth or for
the two drying lines, 33.7 kg/h (74.3 Ib/h) of biphenyl (condensable organic
compound).
The third study was an analysis of ambient pollutant particulate data
18
collected near two textile finishing plants. The organic particulate matter
was extracted from ambient filters with benzene, and the benzene extract was
analyzed by gas chromatography.
Gas chromatographic analyses of suspected organic compounds and stearic
and palmitic acids (used in the process at one plant) were compared with the
extracted organic material from the ambient filters. The resulting chromato-
graphic retention times on the same column and at the same conditions were
3
identical. The organic fraction on this filter exceeded 78 ug/m .
A similar analysis for suspected organic compounds (stearic, palmitic,
and oleic acids) used in the process at the second plant was compared with
the extracted organic material from the ambient filters. The resulting re-
tention times on the same column and at the same conditions were identical.
3
The organic fraction of this sample was 146 ug/m .
No attempt was made in this study to determine the ratio of condensed
particulate matter to noncondensed organic emissions, nor was a measurement
made of the efficiency of the collection of these compounds on the filter
media.
Additional data indicate that the curing of latex backing on drapery and
upholstery fabrics results in the loss of substantial amounts of organic frac-
tions. The emission is primarily composed of stearic acid, oleic acid, and
palmitic acid. The rate of emission and the visible opacity are related to
usage rates in the chemical formulation and curing temperature. Reported
rates were 2 to 3.6 kg/1000 kg of fabric processed.
With the exception of a minor amount of fiber lost (-0.45 kg/h), all of
the particulate emissions from textile processing is in the form of a hydro-
carbon aerosol. The condensation temperature for most processes is between
49°C (120°F) and 121°C (250°F).
17
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3.2 ESTIMATION OF CONDENSED PARTICIPATE MATTER AS PRIMARY SULFATE EMISSIONS
Sulfates account for a significant portion of the TSP in urban areas.
Because a major fraction of urban atmospheric sulfate is contained in parti-
cles smaller than 2 urn in diameter, sulfates are a major constituent in the
ambient PM1Q. Based on the data available, it appears that primary sulfate
emissions (PSE) from coal and oil combustion may account for 50 percent or
more of ambient sulfate levels in certain Air Quality Control Regions (AQCR's).
Uncontrolled combustion of residual oil in utility boilers results in a
mean conversion of 4.45 percent of the fuel sulfur to primary sulfates. Of
this primary sulfate, approximately 36 percent is particulate sulfate; the
remainder is comprised of gaseous sulfur trioxide, sulfuric acid, and sulfuric
acid mist. Uncontrolled combustion of pulverized bituminous coal in utility
boilers results in a mean conversion of only 1.41 percent of the fuel sulfur
to primary sulfates. The sulfate is distributed approximately equally between
particulate and gaseous/mist phases. The EPA reference method collects the
particulate sulfate and some of the acid mist and may convert and collect some
of the gaseous sulfur compounds. Although all of the acid mist and gaseous
pollutants generally would be considered as condensed particulate matter, the
condensed particulate matter portion that is collected with the filterable
particulate is regarded as filterable particulate for this study and in the
emission inventories.
Despite the significance of both primary and secondary sulfates, neither
is specifically regulated on either a source or ambient basis, with a few
minor exceptions. The relative contributions of primary and secondary sulfates
will vary from region to region, depending upon emission patterns and the
amount of SO." formed in, transported into, and removed from the regional
ambient air. Man-made contributions to ambient sulfates are composed of three
sources: (1) regional primary sulfate emissions, (2) regional secondary sul-
fate formation, and (3) extra-regional contributions attributed to long-range
transport and transformation of sulfur oxides. Anthropogenic primary sulfate
emissions can be characterized as arising from combustion, transportation, or
areawide sources. The relative contribution of each source type can vary sub-
stantially in different localities. The rate of regional formation of sul-
fates by local atmospheric conversion of SOp is dependent upon atmospheric
conditions in the region. High humidity and the presence of catalysts such
18
-------
as nitrates, olefins, sulfates and chlorides of iron and manganese, and ammonia
can increase the conversion rate of SCL to sulfate by several orders of mag-
nitude from the rate in clean air. The importance of regional secondary sul-
fate formation hinges not only on the rate of conversion of S02 to sulfate,
but on the amount of time locally-generated SOp resides in the regional air
environment before it is transported into other regions. Ambient sulfates
resulting from long-range transport of primary and secondary sulfates can
comprise an important fraction of total ambient sulfates in regions which are
not meteorologically isolated from other regions. Combustion source emissions,
rather than area or transportation source emissions, would be expected to be
transported far from the source because they are emitted at greater heights
4
above the ground.
A cursory examination of the factors noted above can be made to give
estimates of the percent of total ambient sulfates which are primary sulfates
in certain regions of the U.S. For example, in eastern cities (e.g., New
York), the ratio of PSE to total sulfur emissions is high due in great part
to oil-fired combustion sources. But while the amount of regional secondary
sulfate formation is probably average, the extraregional contributions of sul-
fate (both primary and secondary) are quite high. Here the percentage of
ambient sulfates due to PSE is probably about 50 percent. In nonurban areas
of the East, emission densities are less, but extraregional contributions to
the ambient sulfate level from both primary and secondary sulfates are still
high. In these cases, PSE probably contributes only 20 to 50 percent of the
total ambient sulfates. Isolation of a region can prevent extraregional con-
tributions of sulfate. So in isolated regions, local PSE generally comprise
a larger proportion of ambient sulfate levels. Table 3 summarizes regional
4
data on the contributions of PSE to total ambient sulfate. Figure 2 gives
the contribution of sulfate compared to the other major contributors of a
typical urban and nonurban ambient particulate concentration. These are given
for both coarse and fine particulate.
3.3 TEST METHODS FOR STATIONARY SOURCES
Although several methods are currently available for measuring particulate
matter mass concentrations within stationary source effluent streams, not all
of these methods will produce results that are representative of primary
19
-------
<2.5 um
2.5 - 30 ym
URBAN
<2.5
2.5 - 30 ym
NONURBAN
Figure 2. Summary of relative source contributions
for sites.
20
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TABLE 3, ESTIMATED PERCENTS OF AMBIENT SULFATE LEVELS DUE TO
PSE FOR DIFFERENT GEOGRAPHICAL REGIONS OF THE U.S.3
Region
Percent of ambient SO." due to PSE
East and midwest east of Mississippi
River, urban
West, urban; also other isolated
urban sites
Los Angeles Basin
East and midwest, nonurban
West, nonurban
Up to 50%
50% or more
20 to 50% (only 10 to 40% of ambient
S04~ due to regional coal and oil
combustion in stationary sources)
20 to 40%
Not meaningful due to very low emis-
sions and transport factors
As used here, PSE include primary sulfates from all regional and extra-
regional sources, not merely regional coal and oil combustion. The true
percentage will depend on local PSE patterns and the relative contribution
of combustion, area, and transportation sources.
particulate matter emissions. Some methods are intended for quantifying levels
of filterable particulate matter, whereas others can produce results that more
accurately approximate the contributions of both filterable and condensed par-
ticulate matter.
The most widely used test methods for particulate emissions from stationary
sources are EPA Methods 5 and 17. Both methods rely on a filter media to trap
the particulate matter for measurement. Appendix C contains discussions of
Methods 5 and 17, a modified Method 5 (including impinger catch), and a stack
dilution sampling system (SDSS) to provide a general understanding of how the
test results from each are related to the formation of condensed particulate
matter in the effluent stream.
Technically valid interpretations of data on particulate matter mass
concentrations require an understanding of the method used to obtain the data.
This requirement is particularly important with regard to the problem of pre-
dicting primary particulate matter emission factors from available data.
Thus, the available data base can be used effectively for the purpose of this
study if the user understands how well the data obtained from the sampling
methods account for the condensed particulate portion of the effluent sample.
21
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Based upon the current level of understanding that has been briefly sum-
marized, a general hierarchy can be formulated that shows how the results of
commonly available methods and the levels of primary and filterable particu-
late matter relate to each other. Accordingly, when the condensed particulate
phenomenon exists, the mass concentrations of particulate matter may be ex-
pected to take the following order:
Filterable = Particulate <_ Particulate < Particulate = Primary <_ Particulate
particulate matter deter- matter deter- matter deter- particulate matter deter-
matter mined by Ref- mined by Ref- mined by Stack matter mined by modl-
erence Method 17 erence Method 5 Dilution Sampling3 fled Reference
Method 5a
3.4 CONTROL OF CONDENSED PARTICULATE MATTER FROM STATIONARY SOURCES
Methods available for control of condensed particulates from stationary
sources fall into three main categories: 1) modifications to processes and
raw materials to remove or reduce the amounts of the species present, 2) pro-
cess modifications that result in a particle size shift in the effluent to
larger fractions, and 3) collection of the condensed particulate matter in
add-on control devices. The formation of secondary plumes outside the source
stack represents a separate and complex control methodology and is discussed
separately.
3.4.1 Process Modifications
Most condensed particulate matter results from the introduction of a raw
material or contaminant into a high-temperature industrial process. The
volatilization of the species results in the selective loss of the material
in the effluent stream as a gas and the condensation of a compound as the
gas stream temperature is reduced. The point of condensation may be within
the ductwork, stack, or outside the stack, depending on the chemical species
and/or the gas stream temperature. The condensed material may be solid or
liquid, depending on chemical composition and temperature. Removal or reduc-
tion of the volatile components in the process feed is an effective method
of reducing condensed aerosol emissions. Examples of processes in which this
technique has been applied are asphalt concrete plants, expanded vinyl curing,
fiberboard dryers, fiberglass and mineral wool curing ovens, electric arc
aSee Appendix C for discussion of SDSS and modified Method 5.
22
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furnaces, kraft pulp recovery boilers and lime kilns, expanded aggregate kilns,
municipal incinerators, Portland cement finish mills and kilns, secondary
metal furnaces (aluminum, brass, copper, lead), and textile operations (melt
polymer spinning, heat setting, texturing latex backing curing). Table 4 lists
source emissions and specific process changes that have been used to reduce
aerosol formation.
Process modifications also may include the use of chemicals that change
volatile components to a less volatile form. The use of oil treatments,
which poison the vanadium in residual oils and reduce its action in the forma-
tion of SO- aerosol, is an example of this method. These applications also
include chemical reactions that cause an element to be removed as a result
of high volatility. Selective injection of CaCK to a portland cement kiln
shifts the equilibrium to form KC1 instead of KOH or I^SO^. The volatility
of KC1 allows the species to be withdrawn through the alkali bypass system
and collected. This reduces the loss of KOH and K^SO. from the tower ESP.
Chemical treatment is used less frequently and must be applied on a case-by-
case basis, depending on process chemistry and product requirements.
Process modifications also may be made that allow the condensation of
particles to occur on the surface of larger particles in the gas stream. The
control of gas stream temperature, concentration of particles, and rate of
cooling is necessary to prevent the condensation of the condensed particulate
matter. Interferences such as particle polarity and gas stream moisture also
have an influence on particle partitioning. It appears that since the number
of particles in the gas stream is reduced as a result of higher collection
efficiencies (fabric filters and ESP's), heavy metals condense as separate
aerosols. These aerosols form high-opacity plumes of low mass (i.e., very
small particles), which have become evident in coal- and oil-fired boilers,
cement kilns, and primary smelter operations.
Gas streams that contain volatile species may pass through conventional
control devices before the particulate matter can condense to a solid or liquid
droplet. A process control modification that allows the gas stream to be
cooled before entering the control device has been proven to be an effective
control option. Serious technical problems arise in the process if the gas
stream contains high concentrations of water vapor or corrosive gases (SO-,
HCl, HF), or when the condensed particulate matter is composed of hydrocarbon
23
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TABLE 4. EXAMPLES OF PROCESS MODIFICATIONS TO REDUCE CONDENSED PARTICULATE
Source category
Aerosol
Process change
Asphalt plant (drum mix)
Expanded vinyl
Fiberboard dryers
Fiberglass curing ovens
Mineral wool blow chamber
Electric arc furnace (secondary
steel)
Kraft pulp (recovery boiler)
Kraft pulp (lime kiln)
Portland cement (finish mills)
Portland cement (kilns)
Municipal Incinerators
Secondary metal furnaces
Textile plants heat setting
Latex curing
Texturing
Melt spinning
Residual fuel boilers
Hydrocarbon (oils)
Hydrocarbon (plastlclzer)
Hydrocarbon (wax, resin)
Hydrocarbon (resin)
Hydrocarbon (oils)
Hydrocarbon (oil)
Condensed fume (Nad, S03)
Condensed fume (Na20)
Hydrocarbon
Condensed fume (alkali)
Condensed fume (hydrocarbon)
Hydrocarbons
Hydrocarbons
Hydrocarbons
Hydrocarbons
Hydrocarbons
Acid aerosol
Move asphalt Injection point; use lower vola-
tility asphalt; reduce aggregate temperature.
Change plastlclzer formulation; Improve low
volatility component; reduce curing temperature.
Use higher melting paint wax; change thermo-
plastic resin; reduce dryer temperature; elimi-
nate hot spots In gas stream.
Change resin formula; reduce curing temperature.
Change point of Injection of annealing oil; use
less volatile annealing oil; reduce usage rate.
Reduce percentage of oil In turnings; segregate
poor quality scrap (zinc, paint); use optimum
charge technique; Improve burning above charge.
Reduce Cl content of black liquor; reduce
excess air.
Improve lime mud washing.
Reduce use of grinding aids.
Reduce alkali recycle In Insufflated dusts; use
alkali bypass; change raw feed composition.
Recycle waste and segregate before burning to
remove plastics, metals, etc.; Improve combustion.
Improve combustion; reduce oil/plastic content
of charge; pre-burn charge.
Pre-scour cloth; reduce fabric temperature.
Improve purity of chemical agents; reduce usage;
reduce curing temperature; change chemical formula.
Lower setting temperature; use oil of lower vola-
tility; reduce usage.
Use less spin finish; change formula to reduce
volatility; reduce temperature.
Reduce vanadium content of oil; reduce boiler
excess air; Improve soot blowing practices.
-------
materials that are sticky or that agglomerate on the collection surface.
Proper selection of abatement controls and careful management of gas stream
and control device conditions can eliminate major problems in this area. Con-
strucing ductwork control devices and waste systems from corrosion-resistant
materials (fiber-reinforced plastic, Hastelloy) is one way to eliminate cor-
rosion problems. Gas stream cooling has been applied effectively to several
processes, including textiles, municipal incinerators, boilers, primary metals,
specialty metals, and cement, kraft pulp, and refractory kilns.
3.4.2 Add-On Control Devices
Several add-on control options are available for collecting condensed
aerosols (primary particulate and liquid aerosols). These include positive
corona two-stage ESP's, ionizing wet scrubbers, high-energy venturi scrubbers,
fabric filters, mist eliminators, dry ESP's, wet ESP's, and fume incinerators
(direct-fired and catalyst). The application of each depends on process con-
ditions, chemical species, separation of elements, particle size distribution,
water vapor content, corrosive gases, and condensation temperature of aerosol.
The principles and application of some of these control devices are described
in detail in Appendix E.
3.4.3 Comparative Cost of Control Devices for Condensed Particulates
Table 5 presents the estimated costs of reducing condensed particulate
emissions in five industries. These estimates are broad and may vary from
plant-specific values.
25
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TABLE 5. ESTIMATED TOTAL COST OF REDUCING CONDENSED PARTICULATE EMISSIONS
(September 1982 dollars)
Description
Filterable
PM
Condensed
PM
Coal-fired utility power plants
$/kW
$/acfm.
Efficiency, %
Wood-fired steam boiler
$/acfm
Efficiency, %
Sinter stand (wind box)
$/ton-year
$/acfm
Efficiency, %
Veneer dryers
$/ft2
$/acfm
Efficiency, %
Cement kiln
$/ton-year
$/acfm
Efficiency, %
50.00
14.00
99.7
2.00
90.0
4.00
15.00
99.0
0.0
0.0
N/A
4.40
15.00
99.0
150.00
43.00
95.0
20.00
90.0
7.50
30.00
95.0
190.00
5.00
95.0
8.40
30.00
90.0
26
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SECTION 4
CONDENSED PARTICIPATE MATTER FROM MOBILE SOURCES
Some constituents of gaseous emissions from mobile sources condense to
form particulate matter when cooled by dilution with ambient air. These emis-
sions, consisting primarily of soluble organic fraction (SOF), vary substan-
tially with engine type, fuel, and operating conditions, and are generally
presented as a percentage of the total particulate mass. Mobile source emis-
sion factors currently used by EPA include condensed particulate. Soluble
organics account for 10 to 60 percent of the total particulate mass emitted
from mobile sources and occur predominantly in the respirable particulate size
range (<10 ym). Emission inventories show that mobile source exhaust
contribute from 2.5 to 5.0 percent of calculated yearly particulate emissions.
Most studies concerning mobile source emissions categorize vehicles into
two weight classes: light-duty and heavy-duty. Light-duty vehicles are those
whose gross vehicle weight (GVW) is 8500 pounds or less; heavy-duty vehicles
are those whose GVW exceeds 8500 pounds. Some studies reviewed for the pur-
pose of this study also include a medium-duty class consisting of vehicles
whose GVW ranges from 8500 to 10,000 pounds.
4.1 LIGHT-DUTY VEHICLES
The vast majority of light-duty vehicles are gasoline-powered. However,
because diesels achieve higher MPG at the same vehicle weight than gasoline-
powered vehicles, they are increasing in popularity. Unfortunately, diesel
engines emit considerably more particulate matter than gasoline engines.
For light-duty vehicles using unleaded gas, the SOF varies from 5 to 23
percent; for vehicles using leaded gas the SOF varies from 9 to 30 percent,
23 24
and for vehicles using diesel the SOF varies from 10 to 60 percent. ' It
should be noted, however, that these percentages can be misleading since the
numbers indicate the condensed fraction of the total particulate emitted rather
than the actual amount emitted. In fact, leaded gasoline engines emit from
3 to 10 times more total particulate matter per kilometer traveled than unleaded
27
-------
gasoline engines, while diesel engines emit approximately 20 times the amount
23 24
of participate matter per kilometer traveled as unleaded gasoline engines. '
The amount of condensed particulate emitted per kilometer is the product of
the percent SOF and the particulate emissions, specifically, 0.0015 to 0.0030
g/km for unleaded fuel, 0.013 to 0.050 g/km for leaded fuel, and 0.03 to 0.11
g/km for diesel fuel.20' 23"25
Experiments have been conducted recently to measure the effect of chang-
ing parameters such as engine load and mileage accumulation on the percent
SOF. Generally, as the load increases, the total amount of material emitted
increases, but the percent SOF drops for all types of engines. As mileage
accumulates on light-duty diesel engines, the percent SOF increases for the
first 32,200 km (20,000 miles) and gradually levels off for an indeterminate
20
number of kilometers. Data are
accumulation on gasoline engines.
20
number of kilometers. Data are not available on the effect of mileage
4.2 HEAVY-DUTY VEHICLES
Diesel engines presently power half of the heavy-duty vehicles and are
preferred over gasoline engines because of their greater MPG and longer life,
attributes that are expected to increase the number of diesel engines in this
category faster than in the light-duty category. This increase also will be
partly due to conversions from gasoline to diesel for compliance with 1983
heavy-duty gaseous emission standards. These emission standards may result in
the use of catalytic converters on heavy-duty gasoline engines, which will in
turn reduce the cost difference between gasoline and diesel engines and
increase the use of diesel engines.
As mentioned earlier, although diesel engines give better mileage, they
also emit substantially more total particulate matter than gasoline engines.
The percent SOF for gasoline-powered heavy-duty engines is low, usually around
10 percent; the percent SOF for light- and heavy-duty diesel engines, on the
or pc
other hand, can range from 10 to more than 60 percent. ' For example,
light-duty and heavy-duty diesels emit approximately 0.3 g/km and 1.0 g/km
of total particulate matter, respectively. If 40 percent of this is assumed
to be condensed particulate, this calculates to 0.12 g/km and 0.40 g/km of
condensed particulate, respectively. When compared with the condensed
28
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participate emissions from light-duty gasoline engines (0.003 g/km), condensed
participate emissions from heavy-duty diesel engines become significant. These
vehicles contribute an estimated 50 percent of the mobile source TSP, whereas
they account for only 4 percent of the vehicle miles traveled in an urban
area.
Several studies have been made on the effects of varying loads and fuel
types on particulate emissions from heavy-duty diesel engines. In a study
conducted by Dietzmann, Parness, and Bradow, three types of fuel were tested:
oc
minimum, average, and premium grades. The results indicated that condensed
particulate emissions changed as the grade of fuel changed; the emissions were
0.24 g/km, 0.26 g/km, and 0.29 g/km for minimum, average, and premium grades,
respectively. The effect of varying driving conditions on particulate emis-
sions was also tested and indicated that freeway driving conditions produced
40 to 55 percent of the total particulate emissions. In another study, a test
of the effect of load on emissions demonstrated that as the load increased the
28
percent SOF of the particulate matter decreased.
4.3 TEST METHODS FOR MOBILE SOURCES
It should again be noted that the current EPA mobile source emission
factors include condensed particulate matter. The testing program for mobile
sources is discussed in more detail in Appendix E. The principle of this
sampling system is similar to that of the SDSS. Of all the sampling parameters,
the amount of dilution air used and the temperature of the collection filter
have the greatest effect on the formation of condensed particulate matter.
Any dilution in excess of 10 parts dilution air to 1 part source effluent
provides reproducible results. The filter temperature affects sampling since
the greater the filter temperature, the lower the condensed particulate matter.
4.4 MOBILE SOURCE IMPACT IN AN URBAN SITUATION
Established methodologies exist for modeling mobile source emissions
from specific points or roadways. Attempting to model mobile source emis-
sions in a large urban area is more complex, however, and less well defined.
A large percentage of mobile source emissions occur in urban areas. Typical
TSP contributions from mobile sources in a central business district average
29
-------
10 to 11 ug/m , of which an estimated 25 percent represents condensed particu-
28
late matter. Additional information is needed on the concentration distri-
bution of condensed participate matter and its impact on the urban area.
Bradow conducted a particulate exposure analysis in which 1985 exposures
were calculated in St. Louis, Missouri, by using the Gaussian-plume multiple-
29
source air quality algorithm (RAM) model. St. Louis was selected for this
analysis because extensive data were available as a result of EPA's Regional
Air Pollution Study (RAPS). The RAM model predicted TSP contributions of
3
13 ug/m from mobile sources in the central city area, which decreased to 6
3 3
ug/m and 2 ug/m in residential and suburban areas, respectively. When com-
paring these data to a 1977 emission inventory, Bradow concluded that mobile
sources contribute approximately 15 percent of the fine fraction of ambient
aerosols in St. Louis. It should be noted that diesel engines are currently
the principal source of fine particulate and that the number of diesels is
slowly increasing.
Although the areawide contribution of mobile sources is small compared
with the contribution of other source categories, the air quality impact on
a limited geographic area is significant. Because mobile sources emit their
pollutants in proximity to population centers, the local concentration of
fine particulate matter from mobile sources can reach levels close to 100
3 29
ug/m under adverse meteorological conditions.
4.5 FUTURE MOBILE SOURCE TRENDS
Over the last several years regulations have been promulgated that specify
the average miles per gallon light-duty vehicles must achieve and their allow-
able emissions. These regulations are based on current available technology,
economic feasibility, and forecasts of future trends in vehicle use and
technology. Assuming constant emissions per vehicle, the forecasts indicate
a substantial increase in condensed particulate matter emissions in the
future.
Projections indicate that 25 percent of the vehicles produced by one
American corporation in 1985 will be light-duty diesels, and by 1995, diesel
engines will comprise 25 percent of the total U.S. sales. Several factors
could affect these estimates and result in ranges of diesel sales from 10 to
50 percent. Factors such as technological feasibility and regulatory changes
30
-------
will determine the exact amount of the growth of this class and type of vehi-
cle. Light-duty diesel engines produce approximately 20 times more condensed
organics per vehicle kilometer than light-duty unleaded-gasoline engines. As
diesel-powered vehicles increase in number and replace gasoline-powered vehi-
cles, the emissions of condensed organics will increase significantly. Assum-
ing that the emissions per vehicle remain constant, nationwide annual condensed
3
organic emissions from light-duty diesels will increase from 0.1 x 10 to
38.9 x 103 Mg/yr in 1995.22
Heavy-duty vehicles, currently half gasoline-powered and half diesel-
22
powered, are projected to become totally diesel-powered by 1995. Currently,
heavy-duty diesels emit 29.4 x 10 Mg/yr of condensed organics, whereas
3
heavy-duty gasoline engines emit 5.9 x 10 Mg/yr. Emissions from a heavy-duty
diesel can be as much as 10 times higher than those from a heavy-duty gasoline
25
engine, but this value varies considerably. Therefore, assuming that 100
percent of the heavy-duty vehicles are converted to diesel engines, condensed
particulate emissions from the heavy-duty vehicles category could potentially
increase to 58.8 x 10 Mg/yr.
If both of the previous predictions are accurate (i.e., the nationwide
conversion of 25 percent of light-duty vehicles and 100 percent of heavy-duty
vehicles to diesels), condensed particulate emissions could increase from
67.9 x 103 to 97.7 x 103 Mg/yr.
31
-------
SECTION 5
CASE STUDIES OF POTENTIAL CONDENSED PARTICIPATE MATTER
EMISSIONS IN THREE CITIES
As part of this study, three urban areas (Houston, Texas; Philadelphia,
Pennsylvania; and Portland, Oregon) were analyzed to determine the increase
in primary particulate emissions when condensed particulate matter was included
in the emissions inventories of heavy population centers. The primary criterion
for selection of the three study areas was data availability, which also deter-
mined the extent of detail of the analyses. Emission inventories were examined,
and calculated condensed particulate emission factors (from Section 4 of this
report) were applied to the various categories. The generated values were
presented earlier in Table 2.
5.1 HOUSTON, TEXAS
Data from EPA's 1980 visibility and characterization experiment in
Houston were analyzed to determine the potential effect of condensed particu-
late emissions on the Houston-Galveston urban area. Sources emitting 100
tons/yr or more of particulate matter were tabulated from a 1973 NEDS inventory.
The Texas Air Control Board (TACB) then determined the maximum emission poten-
tial of each source type according to permit applications for point sources
with the potential to emit at least 200 tons/yr.
Fluid crackers in the petroleum industry accounted for 23 percent of
total 1973 particulate emissions, followed by natural gas combustion at 19
percent. Since 1973, a large increase in emissions from fuel oil combustion
has been permitted, along with substantial increases in emissions from natural
gas combustion. These source categories are believed to contribute significant
condensed particulate emissions to the ambient air. Condensed particulate
matter forms in the respirable size range, generally with diameters less than
1 urn. Table 6 presents the 1973 NEDS point source inventory data for the
Houston-Galveston urban area, along with estimates of potential condensed par-
ticulate emissions extrapolated from the back half emission factors calculated
32
-------
TABLE 6. 1973 STATIONARY SOURCE PARTICULATE MATTER, ESTIMATED CONDENSED
PARTICIPATE, AND ESTIMATED TOTAL PARTICULATE EMISSIONS FROM SOURCE
TYPES IN THE HOUSTON-GALVESTON URBAN AREA THAT GENERATE GREATER
THAN 100 TONS/YEAR
(tons/year)
Source type
Fluid catalytic crackers
Natural gas combustion (including boil-
ers, process heaters, cement kilns)
Fertilizer production
Rock handling— quarries, (including
storage, crushing, grinding, etc.)
General sintering— iron production
Grain handling
Wood bark boiler
Electric arc furnace— steel production
Residual oil boilers
General polymer production
Recovery boilei — sulfate pulping
Ferromanganese furnace
Oil petroleum process heater
Distillate oil boilers
Liquor oxidation tower — sulfate pulping
Miscellaneous industrial incinerators
Material handling— cement manufacturing
Iron — direct reduction
Silico— manganese ferroalloy open
furnace
Miscellaneous crude fractionation and
aromatic recovery
Material handling— brick manufacturing
Sulfuric acid contact
Flare
1973 PM
emissions
11,017
8,997°
3,337
2,898
2,349
l,973b
1,910
1,315
1,141
,l,116b
1,034
890°
846
827
820b
742
681
641
K
621°
564b
554
513b
430b
Estimated emissions
Condensed
PM
3,460
NDAC
2,466
NC
969
NDA
365
310
1,531
NDA
170
NDA
1,009
1,110
NDA
1,362
NCd
151
NDA
NDA
NC
NDA
NDA
Total
PM
14,477
-
5,803
2,898
3,318
-
2,275
1,625
2,672
-
1,207
-
1,855
1,937
-
2,104
681
792
-
-
554
_
-
(continued)
33
-------
TABLE 6 (continued)
Source type
Blast furnace fugitive emissions
General PVC production
Asphalt applications
Coke quenching
Calcining— time production
Sulfate pulping
Tin blast furnace
Tetraethyl lead manufacturing
Saw mill
Calcining
PVC calendaring
Coal crushing/handling
Lime kilns—sulfate pulping
.Smelt dissolving tank--sulfate pulping
Totals
1973 PM ,
emissions
340
314b
253
238b
228
210
175b
154b
153
146b
132b
106
106
102
30,790
Estimated emissions
Condensed
PM
80
NDA
120
NDA
26
53
NDA
NDA
14
NDA
NDA
NC
68
20
13,287
Total
PM
420
372
254
263
167
106
174
123
44,083
From 1973 NEDS emission inventory.
5Not included in total since no data were available.
'NDA = no data available.
NC = no condensed particulate.
34
-------
in Section 4 of this report. Table 7 presents the maximum potential for
emissions based on post-1973 permit data. Both studies were of the urban
area only and may not represent the AQCR.
TABLE 7. STATIONARY SOURCE PARTICULATE MATTER, ESTIMATED CONDENSED
PARTICULATE, AND ESTIMATED TOTAL PARTICULATE EMISSIONS IN THE
HOUSTON-GALVESTON URBAN AREA, BASED ON TACB PERMIT APPLICATIONS
AFTER 1973 (tons/year)
Source type
Fuel oil combustion
Natural gas combustion (including
boilers, process heaters, cement
kilns)
Coal combustion
Trench burners
Olefins production
Fluid crackers
Vinyl chloride production
Continuous casting—steel
Hydro forming
Rock crushing
Totals
Maximum PM
emissions
13,674
5,109
2,509
2,496b
l,410b
1,183
440b
438b
298b
201
22,676
Estimated emissions
Condensed
PM
18,349
563
277
NDA
NDA
372
NDA
NDA
NDA
NC
19,561
Total
PM
32,023
5,672
2,786
1,555
201
42,237
Includes point sources with potential to emit at least 200 tons/yr.
'Emissions are not included in the total since no data were available.
In the categories for which it was possible to make estimates, the total
condensed particulate matter is estimated to be 13,287 tons/yr, as shown in
Table 6.
Based on 1973 data, the total particulate emissions from stationary
sources in the Houston-Galveston urban area increased 30 percent when the
estimated condensed particulate sources were included in the inventory; the
29
TACB study shows an increase of about 46 percent.
Unfortunately, the data were inadequate to relate air quality to the
emission estimates on a source-specific basis, i.e., to estimate the impact
30
on a particular monitoring site.
.35
-------
5.2 PHILADELPHIA, PENNSYLVANIA
To determine the potential effect of condensed participate emissions on
the Philadelphia airshed, a summary of point source emissions from the NEDS
inventory was analyzed by using the emission factor technique discussed earlier
in this section. These data were summarized as part of a neighborhood-scale
study of inhalable and fine suspended particulate matter conducted in Phila-
31
delphia in 1980. Table 8 presents these neighborhood emission data, esti-
mated condensed particulate emissions, and total particulate emissions includ-
ing the condensed particulate portion. (This neighborhood-scale study may not
represent the AQCR.) If insufficient information was available concerning the
actual source type (e.g., chemical production), no emission factor was applied
to that source category. Table 8 shows that in the categories for which it
was possible to make such an estimate, the total condensed particulate is esti-
mated to be 3873 tons/yr. This value is probably biased high in relation to
the impact on TSP because of the major categories for which condensed particu-
late emissions are estimated. Most of these sources are subject to artifact
formation in the modifed Method 5 test on which the emission factors are
32
based. However, residual oil combustion—the primary source category in the
Philadelphia airshed—accounts for 21 percent of the total NEDS source category
emission ra-tes that are greater than 5 tons/yr.
The estimates of total particulate emissions for stationary sources in
the Philadelphia neighborhood-scale study increased 48 percent when potential
condensed particulate sources were included in the inventory. Unfortunately,
as noted in Section 5.1, the data were inadequate to relate air quality to
the emissions estimate on a source-specific basis.
5.3 PORTLAND, OREGON
The Portland Aerosol Characterization Study (.PACS) identifies major
sources of both TSP and respirable particulate (<1 um) in the Portland-
Vancouver interstate air quality maintenance area.
The methodology of PACS was to analyze the ambient particulate matter
collected and attempt to account for the original source rather than esti-
mating the impact on the ambient monitor. The contributions of condensed
particulate, although not identified, were accounted for in PACS because of
the methodology applied.
36
-------
TABLE 8. STATIONARY SOURCE AND ESTIMATED CONDENSED PARTICIPATE
EMISSIONS IN PHILADELPHIA NEIGHBORHOOD SCALE STUDY
(tons/year)
Source type
Residual oil combustion
Refinery oil heater
Municipal incinerators
Anthracite coal combustion
Coke oven
Feed and grain handling
Chemical preparation
Mineral handling
Copper smelting
Sugar cane processing
Natural gas combustion
Can label coating oven
Cargo handling
Paint production
Asphaltic roofing materials products
Forest products
Zinc galvanizing
Carpet making
Carbon black furnace
Aluminum melting furnace
Lead smelting
Totals
Inhalable and
fine particulate
emissions
study9
987
726
705
651
466
404
109C
108
96C
94C
51
50C
44
44C
41
34C
29C
23C
12C
7
5C
4319
Estimated emissions
Condensed
PM
1748
866
306
723
184
NC
NDA
NC
NDA
NDA
NDA
NDA
NC
NDA
32
NDA
NDA
NDA
NDA
14
NDA
3873
Total
PM
2735
1592
1011
1374
650
404
-
108
-
-
-
-
44
-
73
-
-
-
-
21
-
8012
Sum of all NEDS emission rates greater than 5 tons/yr within a source cate-
gory from Philadelphia and Camden Counties. (Reference 31)
3NC = no condensed PM emitted; NDA = no data available.
*
'Emissions are not included in totals since no data were available.
37
-------
Available data for Portland identified about 90 percent of the sources
of TSP and only 65 percent of the sources of respirable particulate. Back-
ground sources contribute 40 percent of Portland's TSP and 49 percent of the
33
respirable particulate. Table 9 lists the major sources of locally gener-
ated TSP. This study was of the Air Quality Maintenance Area (AQMA) and may
not represent the AQCR. Condensed particulate contributions are calculated
by using the emission factor technique described in Section 5.1. The source
inventory, although not used quantitatively in the study, was used qualitatively
to identify candidates for characterization and inclusion for the receptor
model. Table 10 presents the PACS estimate of fine particulate matter emissions
in the Portland airshed by source category.
In stationary source types for which it was possible to make an estimate,
the total condensed particulate is estimated to be 1349 tons/yr. When compared
with the total of all other primary particulates (11,046 tons/yr), this value
indicated that the data base should have accounted for an additional 11 per-
cent of condensed particulate. The same condensed particulate value, when
compared with the fine particulate (<10 ym) data base (Table 10), indicated
that the stationary source was emitting an additional 18 percent condensed
particulate matter. This increase in the fine particulate data base seems to
be very low, and the impact on fine particulate would be expected to be at
least twice the value shown in Table 10. The Portland data are believed to
be biased low because some of the sources were not included in the inventory.
Among those sources not accounted for are hog fuel boilers and aluminum smel-
ters, which are believed to be significant contributors of condensed particu-
late. Also, the major source of Portland's locally generated TSP is geological
dust (e.g., road dust), which accounted for 24 percent of the TSP in 1977-1978.
No condensed particulate emissions are expected from this source category.
Potential industrial sources of condensed particulate contributed only 2 per-
cent of the TSP in downtown Portland. Stationary sources contributed about
half of the total annual emissions in Portland. Therefore, the impact on
annual emissions from stationary sources would be increased only by 22 percent
by the inclusion of condensed particulate. This percentage of condensed par-
ticulate contribution is low compared with the 30 percent and 48 percent in
Houston and Philadelphia, respectively.
Since the particle cut size varied between studies for fine particulate, the
particle size will be given for each fine particulate study.
38
-------
TABLE 9 . ESTIMATED TOTAL PARTICIPATE EMISSION RATES
IN PORTLAND AIRSHED3
Source category
Geological
Transportation6
Fossil fuel
Vegetative burning
Forest product industry
Vegetative
Aluminum industry
Iron industry
Miscellaneous stationary
sources
Totals
Annual b
emissions,
tons/yr
4,411
3,688
815
488
3,255
568
1,650
261
1,807
16,913
Percent of
total in
Portland0
26.1
21.8
4.8
2.9
19.1
3.4
9.8
1.5
10.7
-
Annual
condensed PM
emissions, d
tons/yr
22
-
857
-
183
187
-
52
48
1,349
Total
emissions,
tons/yr
4,433
3,688
1,672
488
3,408
755
1,650
313
1,855
18,262
aPACS.
Based on reference method test data.
Percentage does not include condensed particulate.
Represents condensed particulate from stationary sources only.
eThe condensed particulate is part of the mobile source emissions data.
39
-------
TABLE 10. RELATIVE CONTRIBUTION OF CONDENSED PARTICULATE MATTER
TO FINE PARTICULATE IN PORTLAND
Source category
Geological
Transportation
Fossil fuel
Vegetative burning
Forest product industry
Vegetative
Aluminum industry
Iron industry
Miscellaneous stationary
sources
Totals
Annual
emissions,
tons/yr
495
1,938
78f
395
2,197C
271C
1,023C
211C
1,312C
8,623
Percent of
total
emissions
5.7
22.5
9.1
4.6
25.5
3.1
11.9
2.4
15.2
-
Annual
condensed PM
emissions,
tons/yr
22
-
857
-
183
187
-
52
48
1,349
Total
emissions,
tons/yr
517
1,938
1,638
395
2,380
458
1,023
263
1,360
9,972
°PACS.
Condensed particulate matter not shown because the test method accounted
for it.
cTotal emissions for process where relationship with condensed particulate
matter is known.
Emissions estimated from DEQ report.
40
-------
SECTION 6
EFFECT OF. CONDENSED PARTICIPATE ON AMBIENT PM1Q
It is difficult to establish a quantitative impact of condensed particu-
late on PM,Q. Because condensed particulates form in the submicrometer
particle size range, these particulates would have an impact on an ambient
monitoring site, but at this time it is difficult, if not impossible, to
differentiate between primary and secondary particulates when analyzing ambi-
ent monitoring site results.
An additional effect of condensed particulates on the atmosphere is the
impairment of visibility. Although the extent of this visibility impairment
is unknown, some preliminary work in Houston and Detroit lends itself to a
qualitative discussion.
6.1 PRIMARY AND SECONDARY PARTICULATES STUDIES
. Studies of the particulates released by coal combustion have shown the
34 35
existence of two distinct size modes on a mass basis. ' The first occurs
at particle sizes of 0.1 urn in diameter and the second at particle sizes
larger than 0.5 ym. The mode at the 0.1 ym diameter size apparently results
from volatilization of ash components during combustion and subsequent nuclea-
tion, coagulation, and condensation of the volatilized components as the com-
bustion gases cool. This is borne out by the preferential concentration of
the more volatile elements measured on the smaller sized particles.
Other studies of power plant plumes have shown that 90 percent of a unit's
primary sulfate emissions were in the entrained scrubber liquor. In this
study, primary sulfates accounted for 4 to 17 percent of total sulfates
measured downwind in the plume.
Once released, primary pollutants are subject to atmospheric chemical
and physical processes in their transformation to secondary pollutants. The
percentage of gas-to-particle conversion product.that forms new particles
(nucleation) has been reported to average between 5 and 10 percent for power
37 38
plant plumes. ' Thus, condensation apparently accounts for most of the
41
-------
particle growth in power plant plumes. Conversion of SO^ to secondary par-
ticulate sulfate in these plumes ranges from 0 to 10 percent per hour, depend-
ing on a number of variables. ' ' This conversion rate appears to be
heavily influenced by photochemical processes.
A recent study estimating the primary sulfate formation from fossil fuel-
40
fired combustion sources was performed by oxygen isotope ratio measurements.
18 16
This study compared the oxygen isotope ratios ( O/ 0) in sulfate compounds
40
found in the atmosphere with isotope ratios in the boiler stacks. The basis
for the ratio estimates is that the sulfates formed from combustion gases is
18
higher in 0 than sulfates formed in the atmosphere as a result of atmospheric
reactions of the SOp emitted from the source. This study estimated that 10
to 40 percent of the sulfates emitted from the sources tested were primary
40
sulfate. It should be noted that the authors of this study defined primary
sulfate as that sulfate formed only from gases exiting the combustion sources.
Unlike the definition of primary sulfate used in this report, their definition
did not allow for sulfates formed with entrained air immediately after leaving
the stack (Section 2). Based on this referenced study, it could be concluded
.that more than 10 to 40 percent of the ambient sulfate particulate matter
was emitted as a primary sulfate from a combustion source rather than a sec-
ondary conversion to sulfur dioxide. This analytical method may find appli-
cation for estimating primary and secondary sulfate formation for fossil fuel-
fired steam generators in general.
6.1.1 Ambient Studies
On the average, 30 percent of the aerosol mass in Los Angeles results
41
from gas-to-particle conversion in the atmosphere. Estimates of 15 to 20
percent primary and 30 to 40 percent secondary organic carbon have been made
14
at Pasadena, Pomona, and Riverside. During a severe photochemical episode
in Pasadena, secondary material (organics, nitrates, and sulfates) has
39
accounted for 95 percent of the total aerosol mass.
Primary organics include linear and branched alkanes and alkenes, sub-
stituted benzenes and styrenes, quinones, acridines, quinolines, phenols,
cresols, phthalates, fatty acids, carbonyl compounds, some pesticides, and
polycyclic aromatic hydrocarbons (PAH's). Secondary organics are too numer-
ous to mention, but most are difunctional in nature, which results in a marked
decrease in the vapor pressure of the secondary organic relative to that of a
42
-------
precursor primary organic of similar carbon number. This also probably accounts
for the efficient aerosol formation capability of secondary organics.
In both ambient air and power plant plumes a major portion of sulfates
is found in the fine particle fraction (0.5 urn). Ambient suburban samples
have shown that 85 to 90 percent of aliphatic acids, 90 to 95 percent of
carboxylic acids, and 95 to 98 percent of PAH are found on particles with
42
diameters of less than 3 urn. Seventy-five and 85 percent of the mass of
the two PAH's, benzo(a)pyrene and coronene, were found to be associated with
43
particles with diameters of less than 0.26 ym. Thus, in ambient air, a
substantial portion of both sulfates and particulate organic carbon is found
in the fine particle fraction below 0.5 ym in diameter.
6.1.2 Models
Source-oriented atmospheric dispersion modeling has been used to attri-
44 45
bute ambient pollutant concentrations to source emissions. ' Using high-
quality emission inventories and representative meteorological information,
these models have often been able to make adequate predictions of the specific
sources of nonreacting gaseous pollutant concentrations at receptors. These
source models have proved to be inadequate for predicting particulate matter
concentration, however, for the following reasons:
o Particulate emissions are widely dispersed (arising from both
point and area sources) and difficult to quantify.
o Transport of particulate matter is strongly dependent on
particle size.
o Standard source models are not equipped to deal with the com-
plexities of aerosol chemistry and physics.
Whereas source-oriented models begin with measurements at the source
and estimate ambient concentrations, receptor-oriented models begin with ambi-
ent concentrations and estimate source contributions to them. The receptor
model relies on properties of the aerosol that are common to source and recep-
tor and are unique to specific source types, such as composition, size dis-
tribution, and variability (due to variation at the source and to meteorologi-
cal transport). Currently used receptor models can be classified as chemical-
mass-balance, multivariate, microscopic, and hybrid source/receptor. Regard-
less of the type of receptor model used, however, aerosol composition, size,
43
-------
and variability data are needed at both source and receptor for these models
to work. Lack of adequate source sampling and characterization appears to be
the major limitation to advancing the application of receptor modeling.
Since neither source nor receptor models are entirely satisfactory for
defining the source-receptor relationship of particulate pollutants, distin-
guishing primary from secondary particulates would appear to present an even
more formidable task. For example, transformation rates may differ for dif-
ferent sources (given particulate species may exist within an airshed as both
primary and secondary particulate), and certain sources may not be associated
with unique secondary particulates. This suggests that except on a case-by-
case'basis where a special field study has been carried out, it would be
difficult to take ambient particulate data (such as HIVOL), separate the
primary from the secondary particulates, and then reconcile them to their
respective sources.
6.2 VISIBILITY IMPAIRMENT
Although the mechanisms of human perception and the fundamentals of
atmospheric visibility impairment are understood reasonably well, some uncer-
tainties remain. Visibility impairment results from light scattering and
absorption by particles (mostly fine) and, to a lesser extent, NCL. Princi-
pal categories of impairment include 1) plume blight near sources, 2) bands
or layers of discoloration or veiled haze, and 3) widespread regionally
homogeneous haze. Important causes of impairment include natural sources
(blue sky scatter, fog, dust, forest fires, volcanoes, sea spray, and biologic
sources) and manmade sources of sulfur oxides, particulates, nitrogen oxides,
and volatile organics. Important source categories of visibility impairment
include utilities, industrial fuel combustion, smelters, pulp mills, urban
plumes, fugitive dust, and managed fires. A number of empirical techniques
have been developed for identifying sources of observed impairment. Visibility
models are being validated and should be used to evaluate the impact of point
sources at distances of up to 150 km from the sources. Regional models are
useful for analyses, but they require further refinement before regulatory
application.
44
-------
Condensed participate matter contributes to visibility impairment for
several reasons. First, condensed participate forms in the submicrometer size
range and scatters or absorbs light. Second, some reactions taking place in
the atmosphere lead to secondary product formation from some condensed par-
ticulate, such as sulfuric acid mist, which forms more light scattering or
47
absorbing products. Therefore, the potential for visibility impairment is
present where there are sources of condensed particulate. Because this report
is oriented toward the urban situation, the discussion of visibility impair-
ment centers on urban visiblity.
Visibility impact in urban areas varies with source composition, meteor-
ology", location, and season. The principal sources of primary and secondary
fine aerosols are 1) major stationary source emissions of sulfur oxides,
organics, and primary particulate matter, 2) mobile source emissions, and
3) space heating. Many of these sources also emit nitrogen oxides.
Among the point sources potentially important to visibility impairment
are utilities, industrial fuel combustion pulp mills, and smelters. These
point sources are significant contributors to condensed particulate, and the
condensed particulate, in turn, is related to visibility impairment. Studies
on the effect of visibility impairment by aerosol formation and fine particu-
48 49
late were conducted in Houston, Texas, and Detroit, Michigan. ' Although
these studies did not differentiate condensed particulate from other fine
particulate, they did identify some chemical species that could have
originated as condensed particulate.
Figure 3 shows the makeup of the fine fraction (<2.5 yg) of particulate
48
matter found in the Houston study. The largest portion (sulfates) was
found to be associated predominantly with ammonium sulfate mixed with 19 per-
48
cent sulfuric acid in the day and 7 percent at night. It was also concluded
14
from C data that 60 +_ 15 percent of the carbon in the fine fraction origi-
nated from fossil fuel combustion. The apportionment of mean daytime light
extinction coefficient (a measure of visibility impairment) was as follows:
4.7 percent by nitrogen dioxide gas, 32 percent by sulfate and related cations,
17 to 24 percent by carbon, 5 percent by other species, 16 percent by water
evaporated from these particles, 13 +_ 7 percent by bound water, and 5.6 per-
48
cent by the ambient air (normal molecular makeup).
45
-------
TRACE ELEMENT
CRYSTAL
Cl, Na
CARBON
OTHER
SULFATE AND
CATIONS
1.9%
= 2.9%
= 0.8%
= 0.6%
= 18%
= 22%
= 54%
Figure 3. Eight-day average of daytime fine- and coarse-fraction
mass concentrations apportioned by chemical species in Houston
from September 11 to 19, 1980.
The quantitative estimate of condensed particulate contributing to
visibility impairment in Houston could not be determined, but a qualitative
statement can be made to the effect that a large portion of the species was
probably condensed particulate in origin.
49
The Detroit study found visibility impairment to be due to the same
48
chemical species as those found in the Houston study. As would be expected,
the proportions of the chemical species were comparable, but not the same,
because the source contributors are different in the two areas. Figure 4
shows the contribution to the mean daytime light extinction coefficient. In
the Detroit study, the dominant chemical species was ammonium sulfate, which
49
accounted for about 50 percent of the fine particulate. This study also
showed that sulfates are the most efficient light-scattering fine particles
49
per unit mass of dry weight.
As in the Houston study, it was not possible to arrive at a quantitative
estimate of the condensed particulate contributing to visibility impairment
in Detroit, but a qualitative statement can be made to the effect that a
large portion of the species was probably condensed particulate in origin.
46
-------
RAYLEIGH SCATTER = 7%
N02 = 4%
OTHER FINE
PARTICULATE MATTER = 4%
CARBON = 20%
SULFATE AND WATER = 65%
Figure 4. Contributions to the mean daytime light extinction
coefficient in Detroit (July 15 to 21, 1981).
6.3 IMPACT BASED ON NATIONAL EMISSIONS DATA REPORTS
In Section 5, the impact of total primary particulate from selected sta-
tionary sources was estimated to be 30 percent condensed particulate in
Houston, Texas; 48 percent in Philadelphia, Pennsylvania; and 22 percent in
Portland, Oregon. Two data reports were adjusted to estimate the percent
contribution of condensed particulate to primary particulate emissions on a
national basis. Table 11 shows the 10 major contributors to TSP as reported
by OAQPS and the corresponding source-specific condensed particulate emissions.
These adjusted results indicate that condensed particulate would contribute
about 27 percent of the total primary particulate impact on TSP. Table 12
shows the 10 largest stationary source particulate emitters as reported by
DSSE in 1978. These adjusted results indicate that condensed particulate
would contribute about 30 percent of the total primary particulate impact on
TSP from stationary sources only. This computation is based on various assump-
tions that may not be valid, but it does serve as an estimate.
6.4 RECOMMENDATIONS FOR FUTURE STUDY
There are two basic weaknesses in the data used in this report. The
first weakness deals with the use of data from the back half of the EPA
Method 5 source tests. As noted previously, Method 5 tests are subject to
artifact formation and other errors that make it difficult to use these data
47
-------
TABLE 11. MAJOR SELECTED SOURCE CATEGORIES EMITTING CONDENSED PARTICULATE
Source category
Integrated iron and steel plants
and coke ovens
Portland cement plants
Coal-fired electric utility boilers
Coal -fired industrial boilers
Kraft pulp and paper mills
Asphalt batching plants
Primary nonferrous smelters
Grey iron foundries
Lime plants
Total
TSP,
[x 103 tons]
3388
981
966
831
297
164
142
134
168
70716
Condensed
particulate,
[x 103 tons]
1164. Ob
271. 4C
768.3
91.6
89. 7b
77.4
56. 9d
41.4
15.3
2576
Total ,
[x 103 tons]
4552.0
1252.4
1734.3
922.6
386.7
241.4
198.9
175.4
183.3
9647
Includes emissions from material handling and storage piles.
Average of aggregate emissions.
cWeighted average (25% wet process; 75% dry process).
Weighted average based on production (54% Cu; 19% Pb; 22% Zn; 5% other).
eOAQPS data file of Nationwide Emissions, 1978, was adjusted for revised iron
and steel emission factors projected to 1979 on basis of GNP growth.
48
-------
TABLE U. STATIONARY SOURCE CATEGORIES ACCOUNTING FOR TWO PERCENT
OR MORE OF 1978 ACTUAL PARTICULATE EMISSIONS
Source category
Coal -fired steam electric power
plants
Stone and rock processors
Portland cement plants3
Coal -fired industrial boilers
Iron and steel mills and coke plants
Grain elevators and mills
Forest fires and prescribed burning
Solid waste disposal
Brick and tile plants
Primary copper smelters
Total
Percent of
total actual
emissions
19.1
10.9
6.3
5.6
6.7
5.5
4.2
3.5
2.9
2.6
67.3%
Percent after
>;- adjustment*-. .
for condensed PM
34.4
10.9
10.7
6.2
9.6
7.4
4.2
5.0
4.0
4.3
96.7%
Weighted average (25% wet process; 75% dry process).
""Condensed particulate concentration was unknown; therefore it is not
included.
49
-------
to estimate condensed particulate. The second weakness deals with the current
ambient air quality data and the ability to relate emissions to air quality.
With regard to the first weakness, more source testing needs to be per-
formed on stationary sources to establish more reliable emission factors for
condensed particulate matter. This testing should be conducted using the SDSS
train discussed in Appendix E of this report.
With regard to the second weakness, the relationship between primary and
secondary sulfate formation should be more closely investigated. In the
cities of Detroit and Houston more than 50 percent of the fine particulate
matter (<2.5 ym) was made up of sulfate compounds. Additional studies similar
40
to that conducted by Holt on fossil fuel-fired steam generators and primary
sulfate formation are recommended. Once the relationship between primary and
secondary sulfate formation has been established, a dispersion model such as
the Industrial Source Complex-Short Term (ISC-ST) can be used with the appro-
priate conversion rates for secondary sulfate formation to estimate the impact
of condensed particulate matter on air quality. Receptor modeling techniques
should also be developed to consider condensed particulate matter.
Finally, a coordinated program to relate receptor modeling to ambient
air quality analyses should be implemented. Monitoring networks should be
established based on the projected impact from selected sources. Tracer
studies or the oxygen isotope ratio method described in Section 6.1 (for com-
bustion sources only) can be used to determine the condensed particulate
matter contribution at the established receptor locations. The monitoring
program should be designed to provide information on the amount of particu-
late formed as a result of primary and secondary formation.
50
-------
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3. Blagun, B., and D. Dunbar. Compilation of Ambient Particulate Matter
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7. Husar, R. B., and K. T. Whitby. Growth Mechanisms and Size Spectra of
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11. Personal communication from R. Hawks, PEDCo Environmental, Inc., Durham,
North Carolina, October 1, 1982.
12. Armstrong, J. A., et al. Balloon-Borne Particulate Sampling of the Glen
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13. Grotecloss, G., et al. NH3 Effects in Cement Kiln Plume Formation and in
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17. North Carolina Department of Natural and Economic Resources, Division of
Environmental Management, Air Quality Section. Biphenyl Emission Test
Report for Loop Dryer #3, Wake Finishing Plant, Burlington Industries.
July 22 and 24, 1975.
18. Hawks, R. L. Ambient Air Study of Benzene Soluble Organic Particulates
Near Textile Wet Processing Facilities. Final Report. North Carolina
Department of Natural and Economic Resources, Division of Environmental
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19. Plee, L. S., and J. S. MacDonald. Some Mechanisms Affecting the Mass of
Diesel Exhaust Particulate Collected Following a Dilution Process. SAE
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20. Gibbs, R. E., J. D. Hyde, and S. M. Byer. Characterization of Particu-
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801372. 1980.
21. Ingalls, M. N., and R. L. Bradow. Particulate Trends with Increasing
Dieselization. Presented at the 1981 Air Pollution Control Association
Annual Meeting, Philadelphia, Pennsylvania.
22. Chapter 5: National Impact of Motor Vehicle Particulate Emissions.
23. Hare, C. T., and F. M. Black. Motor Vehicle Particulate Emission Factors.
Presented at the Air Pollution Control Association 74th Meeting and Expo-
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24. Lang, J. M., et al. Characterization of Particulate Emissions from In-
Use Gasoline-Fueled Motor Vehicles. SAE Technical Paper. No. 811186.
1981.
25. Dietzmann, H. E., M. A. Parness, and R. L. Bradow. Emissions from
Gasoline and Diesel Delivery Trucks by Chassis Transient Cycle. ASME
No. 81-DGP-6, 1981.
52
-------
26. Dietzman, H. E., M. A. Parness, and R. L. Bradow. Emissions From Trucks
by Chassis Version of 1983 Transvent Procedures. SAE Technical Paper
No. 801371. 1980.
27. Personal communication with R. Bradow, U.S. Environmental Protection
Agency, Research Triangle Park, North Carolina, March 9, 1982.
28. Black,, F. and L. High. Methodology for Determining Particulate and
Gaseous Diesel Hydrocarbon Emissions. SAE Technical Paper No. 790422.
1979.
29. Bradow, R. L. Diesel Particulates Emissions. Bull. New York Acad.
Med., Vol. 56, No. 9, November-December 1980.
30. Dzubay, T. G., et al. Visibility and Aerosol Composition in Houston,
Texas. Environ. Sci. and Tech., 16:(8)514-525, 1982.
31. Chow, J. C., et al. A Neighborhood Scale Study of Inhalable and Fine
Suspended Particulate Matter Source Contributions to an Industrial Area
in Philadelphia. Paper No. 81-14.1, presented at the 1981 Air Pollution
Control Association Annual Meeting, Philadelphia, Pennsylvania.
32. Oldaker, G. B. Condensible Particulate and Its Impact on Particulate
Measurements. Entropy Environmentalists, Inc., U.S. EPA Contract No.
68-01-4148, Task No. 69. May 1980.
33. Cooper, J. A., and J. G. Watson. Portland Aerosol Characterization
Study. Final Report. Oregon Graduate Center, Beaverton, Oregon.
July 31, 1979.
34. Flagan, R., and-S. K. Friedlander. Recent Developments in Aerosol Science.
D. Shaw (ed.). Wiley-Interscience, New York. 1978.
35. McElroy, M. W., R. C. Carr, D. S. Ensor, and G. R. Markowski. Size
Distribution of Fine Particles From Coal Combustion. Science, 215:13-19,
1982.
36. Balfour, W. D., L. P. Edwards, and G. K. Tannahill. Secondary Forma-
tion Products in Power Plant Plumes. EPA-600/S7-81-092, 1981.
37. Hegg, D. A., and P. V. Hobbs. Measurements of Gas-to-particle Conver-
sion in the Plumes From Five Coal-fired Electric Power Plants. Atmos-
pheric Environment, 14:99-116, 1980.
38. Whitby, K. T., B. K. Cantrell, and D. B. Kittelson. Nuclei Formation
Rates in a Coal-fired Power Plant Plume. Atmospheric Environment, 12:
313-321, 1978.
39. Grosjean, D. Ozone and Other Photochemical Oxidants. National Academy
of Sciences. Washington, D. C. 1977.
53
-------
40. Holt, B. D., R. Kumar, and P. T. Cunningham. Primary Sulfates in Atmo-
spheric Sulfates: Estimation by Oxygen Isotope Ratio Measurements.
Science, 217:51-53, 1982.
41. Friedlander, S. K. Recent Developments in Aerosol Science. D. Shaw (ed.)
Wiley-Interscience, New York, New York, 1978.
42. Vaeck, L. V., and K. V. Canwenberghe. Cascade Impactor Measurements of
the Size Distribution of the Major Classes of Organic Pollutants in
Atmospheric Particulate Matter. Atmospheric Environment, 12:2229-2239,
1978.
43. Miguel, A. H., and S. K. Friedlander. Distribution of Benzo(A)Pyrene and
Coronene With Respect to Particle Size in Pasadena Aerosols in the Sub-
micron Range. Atmospheric Environment, 12:2407-2413, 1978.
44. Duval, M. M., and S. K. Friedlander. Source Resolution of Polycyclic
Aromatic Hydrocarbons in the Los Angeles Atmosphere. Report prepared
for U.S. Environmental Protection Agency (Grant No. R806YOY-0251) by
the University of California, Los Angeles, California. 1981.
45. Watson, J. G. Receptor Models Relating Ambient Suspended Particulate
Matter to Sources. EPA-600/2-81-039, 1981.
46. U.S. Environmental Protection Agency. Protecting Visibility. An EPA
Report to Congress. EPA-450/5-79-008, October 1979.
47. U.S. Environmental Protection Agency. Workbook for Estimating Visibility
Impairment. EPA-450/4-80-031, November 1980.
48. Dzubay, T. G., et al. Environmental Science and Technology, 16: (2)514-
525, 1982.
49. Wolff, et al. The Relationships Between the Chemical Composition of
Fine Particles and Visibility in the Detroit Metropolitan Area. Paper
No. 82-11M.2, presented at the 1982 Air Pollution Control Association
Annual Meeting, New Orleans, Louisiana.
54
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GLOSSARY
Aerosol - Fine solid or liquid matter suspended in gas or air.
Back half - Particulate matter collected in the impingers and all sample-
exposed glassware after the filter of either EPA Methods 5 or 17.
Detached plume - Occurrence of a visible plume forming after the exit of a
stack with a clear space between the stack and first observance of plume
formation.
Filterable particulate - Particulate matter determined by EPA Reference
Method 5. For some sources, the amount of "filterable" material collected
is a function of the probe and filter temperature.
Fine particulate - Particulate matter with an aerodynamic particle size of
usually 2.5 ym or less.
Front half - Particulate matter collected in either EPA Methods 5 or 17 on the
filter front half of the probe lines, probe fitting, and probe nozzle.
Inhalable particulate - Respirable particulate matter. The aerodynamic par-
ticle size limitation will be defined by EPA upon proposal of the
applicable regulation.
PM,Q - Particulate matter with an aerodynamic particle size of 10 ym (50%
cutoff diameter) and less.
Primary particulate - Particulate matter that is formed by the process either
prior to or after the control equipment or within the stack or immediately
after the stack.
Pseudo particulate/artifact - Particulate matter that would not form in the
ambient air but is formed as the result of the conditions and confine-
ment in the sampling train.
Secondary particulate - Particulate matter formed in the ambient air as the
result of chemical reactions in the atmosphere.
Soluble organic fraction (SOF) - The portion of the particulate sample extracted
by dichloromethane in the mobile source test procedure.
Total particulate - Particulate matter including both the front and back halves
of EPA Methods 5 or 17.
55
-------
APPENDIX A
FORMATION OF CONDENSED PARTICIPATE MATTER
A-l
-------
For the purposes of this study condensed particulate matter is defined
as matter emitted in a gas phase at higher than ambient temperature which then
forms particulate matter in the ambient air. As ambient air is entrained, the
temperature of the plume drops which causes condensation of some pollutants.
The nature of the particulate formed will depend on the source of the emissions.
For example, a primary nonferrous smelter emits metallic oxide fumes that con-
dense into inorganic particulate, whereas a textile tenter frame operation
emits organic chemicals that condense into organic particulate.
Primary condensed particulate is defined in this study as particulate
formed by the physical phenomenon of condensation (or some other mechanism),
which is complete before or at a 10:1 dilution ratio in the plume. Gaussian
diffusion equations have been applied to determine the distance within which
a dilution of 10:1 or greater is achieved. The results indicate that this
occurs within 5 meters downwind of the stack. This determination of the plume
center!ine concentration is based on an assumed windspeed of 1 m/s (the mini-
• mum value used in modeling), a stack height of 90 m, and a gas temperature
of 436 K. The equations yielded a concentration of less than 2 percent 5
meters downwind of the stack. According to the equation, the desired dilution
ratio (10:1) occurred within 1 meter downwind of the stack. Since the equa-
tions are not at a limited distance downwind from the source, accuracy of the
estimates cannot be assumed as exact. Also, the Gaussian diffusion equations
do not consider entrainment and microscale turbulence. Stack parameters such
as gas temperature, exit velocity, stack diameter, and stack orifice config-
uration will have a great effect on the amount of turbulence occurring at the
. mouth of the stack. All of this leads to a breakdown of the equations within
a meter or so of the source. Nevertheless, it is safe to assume the 10:1
dilution ratio occurs within 5 meters downwind of the emission point.
Particles in the atmosphere may be primary or secondary in nature.
Primary particulates are those that are emitted in particulate form directly
from sources or those that enter the particulate state shortly after their
release. Primary particulates are produced directly in the physical or
chemical processes peculiar to an emission source. Sources vary, they in-
clude those of natural origin, such as volcanoes, forest fires, and wind, as
A-2
-------
well as those of anthropogenic origin, such as diesel engines, coal combustion,
and gravel crushing. Whereas primary particulates may occur in all sizes,
secondary particles are usually quite small (<1 urn in diameter).
Secondary particulates are those produced from gases and vapors by chemi-
cal and physical processes occurring in the atmosphere after the release of
the gases and vapors from their respective sources. Secondary particulates
may result from natural events such as the conversion of sulfur dioxide (SOL)
to sulfate formation downwind in an SC^-laden volcanic plume or from anthro-
pogenic activity such as the gas-to-particle conversion that occurs in smoggy,
urban environments.
Both primary and secondary particulates may originate from the same
source. For example, coal-fired power plants release large quantities of
primary particulate in the form of fly ash. In these same power plants, sul-
fur impurities in the combustion boiler fuel are oxidized to SC^, which is
subsequently released to the atmosphere and oxidized to secondary particulate
(sulfate).
A single compound can act as both primary and secondary particulate
matter. Power plant emissions again provide a convenient example. In the
boiler, sulfur trioxide (SO,) and sulfate salts are formed along with S02 gas
and fly ash. Generally, about 1 percent of the sulfur present in the flue
4
gas exists as SCL. As the flue gas cools, water vapor can condense and the
SO-j-HpO mixture can form sulfuric acid droplets. These sulfuric acid droplets,
along with any sulfate salts present in the plume, are considered primary sul-
fates; whereas, the sulfates that form downwind as a result of gas-to-particle
conversion of the gaseous SOp are considered secondary sulfates. Reconcilia-
tion of primary and secondary sulfates on the basis of ambient sampling is
quite difficult.
Condensed particulate (as defined in this study) is formed in the ambi-
ent air by one of three physical mechanisms:
1) Nucleation
2) Condensation
3) Coagulation.
These three mechanisms may form particulate matter, mostly in the submicron
range, after the gases exit an air pollution source.
A-3
-------
Nucleation
Nucleation is the process in which molecules become physically associated
3 4
in such a manner as to form a new parcel in a stable liquid phase. ' This
process may occur between molecules of the same species or between molecules
of different species. The latter process, heteromolecular nucleation, is
beyond the scope of the current treatment. Nucleation in the current context
is that which occurs between like molecules.
Condensation
Condensation is the physical process in which molecules leave the gas or
vapor"phase and enter the liquid phase. This process is responsible for most
of the gas-to-particle conversion that occurs in the atmosphere. An important
parameter controlling condensation is the concentration of the condensing
species. Transfer of molecules to the liquid phase occurs only when the vapor
concentration exceeds the saturation vapor pressure at existing temperature
and pressure conditions. Under supersaturated conditions, condensation will
occur to relieve this excess vapor pressure until a saturation ratio of unity
is achieved.
Equilibrium thermodynamics provide information on the vapor pressures of
particles and droplets and on the conditions at which condensation can occur.
The vapor pressure/temperature curves shown in Figure A-l for two different
compounds illustrate factors that could influence the ambient phase distri-
bution of emitted compounds. Based on Figure A-l it can be determined that:
o The termination of the vapor pressure curve represents the
critical point for the substance under consideration. A
pure gas at a temperature above its critical temperature can-
not be liquified regardless of the degree of compression.
Thus, compounds with critical temperatures less than 300 K
are always gases at ambient temperatures. In the current
effort, such species represent noncondensing species (e.g.,
He, H2, Ne, NZ, 02, NO, CO, CH4, and C2H4).
o A compound having a vapor pressure in excess of the baro-
metric pressure at a given temperature will be in the
vapor state and can immediately be classified as volatile.
Thus, Compound B will always be in the vapor state at one
atmosphere of pressure as long as its temperature exceeds
Ti (Figure A-l). In addition, it is also apparent from
Figure A-l that at atmospheric conditions Compound A is
volatile and Compound B is condensable.
A-4
-------
o:
o
c/>
t/7
LU
Q£
O-
o
Q_
Compound A Compound B
Critical Points
Liquid Phase
Side of Curves
Process
Conditions
Atmospheric
Conditions
'1
Temperature
Figure A-l.
Vapor pressure curves indicating reversible
adiabatic expansion of stack gas from process
conditions to atmospheric conditions. Conden-
sation of a compound occurs when its vapor
pressure curve is intersected.
A-5
-------
o Within an industrial process, the pressure and temperature
may be elevated to such a degree that the compound will be
in the gaseous state at process conditions, regardless of
its phase distribution at ambient conditions. Figure A-l
shows an example of this for Compound B at the point
labeled "process conditions." If the compound is emitted
into atmospheric conditions via reversible adiabatic ex-
pansion or by mixing with cooler air at a lower concentra-
tion, a portion of the compound will condense into a fine
aerosol. This occurs when the gas-phase concentration of
the species exceeds its gas phase saturation concentration.
The distribution of components between phases is governed by thermody-
3 4
namic equilibrium. ' Supersaturation of a vapor mixture produced by cool-
ing or chemical reaction is relieved by formation of a liquid phase. Conden-
sation usually takes place on the curved surface of a droplet. As the droplet
diameter becomes smaller than 1 urn, fewer molecules are adjacent to the sur-
face than for a flat surface. This permits liquid molecules on the surface
of the droplet to escape more easily, which increases the vapor pressure over
a droplet with decreasing droplet diameter. This is known as the Kelvin effect
and is described by Equation (1):
p
P~~ = exp [oTF] Equation (1)
where
P, = the equilibrium vapor pressure over particle diameter d
P = the partial pressure at a flat surface
a = the surface tension
v = the molecular volume
k = Boltzman's constant.
The Kelvin effect suggests that condensation will not occur on small par-
ticles unless the vapor pressure of the condensing species substantially exceeds
the saturation vapor pressure. Condensation becomes "easier" with increasing
particle diameter, as the importance of the Kelvin effect diminishes. Thus,
the Kelvin effect sets a lower limit on the particle size of a polydisperse
aerosol that can serve as condensation nuclei.
In contrast, the presence of a nonvolatile solute in a solvent solution
tends to reduce the vapor pressure of the solvent to an extent dependent upon
A-6
-------
the nature and concentration of the solute. Thus, because vapor pressure
lowers as a result of the presence of a solute, a solution droplet can grow
via condensation in an atmosphere that is not saturated in either component.
Expressions describing the rate at which condensation occurs (F) depend
to a large extent on the particle size under consideration and are presented
3 4
in Table A-l. ' When the Kelvin effect is important, the partial pressure
driving force in the expressions in the table must be corrected to account
for the increased equilibrium vapor pressure resulting from particle curvature.
As discussed above, gas-to-particle conversion can occur by both nuclea-
tion and condensation. In addition, chemical reactions occurring within the
droplet or upon the surface of the particle can also result in gas-to-particle
conversion. Growth laws are expressions for the change in particle volume or
particle diameter with time. Growth laws for condensation and for chemical
reaction are presented in Table A-2. Comparison of measured results with
these theoretical expressions can be used to gain insight on the gas-to-particle
conversion mechanism that occurs. By matching data with growth laws it is
possible to identify mechanisms that are consistent with data and to exclude
those that are inconsistent. This approach has been used by McMurry and Wil-
son (1982) to suggest that droplet phase reactions were important in account-
ing for growth of aerosols measured under humid ambient conditions in the
Great Smokey Mountains, because condensation was an important growth mecha-
nism in low-humidity smog-chamber experiments.
Nucleation generates high concentrations of very small particles, whereas
the number of particles is a factor in the growth of particles by condensation.
Criteria for determining which process controls gas-to-particle conversion
3 7
have been developed by Friedlander (1977) and McMurry and Friedlander (1979).
These criteria are complex and beyond the scope of this study. Husar and
o
Whitby (1973) have presented data that suggest nucleation may be important
2 3
for aerosol surface area concentrations below 500 ym /cm , however, condensa-
tion may be important above this value. For .most sources it is likely that
pre-existing aerosol in the stack and near stack plume will be sufficient to
promote condensation as the primary gas-to-particle mechanism.
A-7
-------
TABLE A-l. RATE EXPRESSIONS FOR CONDENSATION0
Pa rt i c 1 e
size,
ym
d » 0.1
d ^ 0.1
d « 0.1
Knudsen
number
Kn « 1
Kn ~ 1
Kn » 1
Regime
Continuum
Transition
Free molecule
Rate expression
p _ 2-rrDd , }
F kT ("TV
r _ o-n-nj/n n \ l+Kn
r - e."uu\n*~nij n
1 a l+1.71Kn+1.333KrT
d2Pl(PrPd)
r 2mkT
Equation
(2)
(3)
(4)
In these expressions, D is the gaseous diffusitivity; nd is the concentration
and P. is the partial pressure in equilibrium with the surface; n, is the bulk
concentration and P, is the bulk partial pressure; and Kn is Knudsen number
(Kn = 2 liters/d = ratio of the mean free path of the condensing species to
the particle radius.
TABLE A-2. THEORETICAL GROWTH LAWS
Mechanism
controlled by
Condensation
Continuum
Transition
Free molecule
Surface reaction
Volume reaction
Volume
growth rate
a d
a d, f(Kn)
ad2
ad2
ad3
Diameter
growth rate
a d f(Kn)
ad°
ad°
a d
A-8
-------
Coagulation
Coagulation is the process in which particles come into contact with one
3 9
another and coalesce. ' Because coagulation is a mass-conserving process,
it only acts on an aerosol system to modify its size distribution. Coagula-
tion is governed by the Brownian motion of particles and by their interaction
at very short distances. The rate of coagulation is approximated by the
number of particle collisions per unit time per volume. For an initially
monodisperse aerosol system, the number of particles per unit volume, N, is
diminished by coagulation at a rate described by Equation (5):
-K N
^r= °2 Equation (5)
The coagulation constant, K , is equivalent to S^dD or 8kT/3u or 6 x 10"
3
cm /s,
where
D = particle diffusivity
U = the gas viscosity.
In this system, the initial diameter will be the minimum, and over time
coagulation will increase both the mode and the breadth of the size distribu-
tion. This does not continue indefinitely, because for a polydisperse system,
the highest rate of coagulation on a per-particle basis occurs on particles
at opposite ends of the size distribution. The smallest particles combine
with the largest at a faster rate than with any other size. The addition of
a small particle does not significantly alter the size of the large particle.
The apparent effect of coagulation on an aerosol system is the removal of
small particles from the distribution with no overall change in mass. Coagu-
lation can therefore be thought of qualitatively as acting to establish and
maintain a particle size distribution of moderate breadth.
CHEMICAL COMPOSITION OF CONDENSED PARTICULATE MATTER
Very little direct data were found on the chemical composition of con-
densed particulate matter; however, based on the chemical and physical
properties of organic and inorganic compounds, certain hypotheses indicate
that certain classes of compounds will form condensed particulate.
A-9
-------
Organic Compounds
Generally speaking, any organic compound that is emitted from an air pol-
lution source to the atmosphere in the vapor state and is normally a solid at
ambient temperatures will condense once the critical temperature and pressure
are reached for a given compound. This condensation is a physical phenomenon.
In tests conducted on mobile sources, it was found that condensation occurred
most readily with C,5 and greater organic species.
Higher-molecular-weight organic compounds such as polycyclic organic
matter (POM) have been collected from stationary sources with a modified EPA
Method 5 sampling train. Part of the collected POM passed through the filter
portion of the train and was trapped by condensation, however, the exact por-
12
tion was not reported.
Inorganic Compounds
The behavior of inorganic compounds with respect to condensation appears
to be less predictable than that of organic compounds because of the flue gas
temperatures or the reactions taking place with the species present in many
stationary source stack gas effluent streams.
Vaporous species of inorganic compounds such as Si02> MgO, heavy metal
oxides, Na2$04, KpS04, NaCl, and PbO have been found in the flue gas from coal
combustion. Compounds such as Si09, Na9SO/i, and K^SO, generally condense
L. L. T" £ T1 1-5
in the stack, but other species such as PbO may remain in the vapor state.
It has been suggested that some of the materials with higher condensation temp-
eratures, such as Si02, might be condensing on the surface of other particles
as they leave the combustion zone, but before they exit to the atmosphere.
Therefore, whether they formed homogeneous or heterogeneous condensation pro-
ducts, the metallic oxides would generally follow thermodynamic predictions
for condensation when the condensation temperatures were above 1300 K.
At sources such as primary nonferrous smelters and large fossil fuel-
fired combustion units, some inorganic species do have significant vapor pres-
sure at typical stack temperatures. Typical metallic oxides found in the
flue gas of coal combustion sources are metals such as As, Mn, Ni, Pb, V, and
14
Se, and in lesser amounts, Cd. At elevated temperatures, most of these
species have a vapor pressure that allows some of the material to remain gas-
eous. This material will subsequently condense when the temperature approaches
A-10
-------
ambient conditions. Arsenic trioxide, for example, has a high vapor pressure
(100°C) relative to other metal oxides. This high vapor pressure means that
at least some of the arsenic trioxide will escape as a vapor. At 100°C, one
estimate of arsenic trioxide vapor concentration in a gas stream is 4.30 x
ID'3 g/m3.15
Sulfate compounds make up the largest category of inorganic condensable
emissions. Sulfates are formed as the result of the sulfur content of either
the raw material being processed or the fuel being burned. The sulfur is con-
verted to SCL and SO., by oxidation, and it reacts with other compounds or ele-
ments, either in the combustion or process zone or in the stack gases. As
discussed earlier, sulfates formed some distance from the source are considered
secondary particulate and are not included in this study.
Sulfuric acid mist is a condensed particulate (for the purposes of this
study) formed in flue gases of combustion sources. The reactants, S03 and
HpO, are present in flue gas from sources that burn fuel containing sulfur.
Sulfuric acid is not a filterable material, and a modified EPA Method 6 is
required to test for sulfuric acid emissions from combustion sources.
Ammonia plays a very significant role in the production of sulfates.
This common gas is generated primarily as a result of soil bacteria decompos-
ing amino acids in the natural environment. Estimates of the amount of natural
ammonia generated yearly range-from 1169 to 5900 million tons. Industrial
sources, primarily fossil fuel combustion, contribute about 4 million tons/year.
The residence time for ammonia has been estimated to be about 7 days, and it
is the primary source of gaseous alkaline emissions. It serves to neutralize
acidic compounds such as sulfur dioxide and nitrogen dioxide.
Evidence suggests that ammonia reacts with sulfur oxides and forms am-
is i Q ?n
monium sulfoxide compounds. Whitby (1978),10 Friend (1974),iy Roesler (1965),
21 2?
Kircher (1977), and Husar (1978) report evidence that many of these
23
ammonium sulfoxide compounds exist as ammonium sulfate. Eatough (1978)
suggests that a considerable fraction of the observed ambient aerosol sulf-
oxides may be inorganic sulfites, which are relatively stable. These sul-
fites appear to be oxidized to sulfate very slowly, with half-lives measured
in years.
A-ll
-------
Some possible ammonium sulfoxide compounds that are stable at ambient
temperatures include ammonium sulfate ((NH4)2S04), ammonium bisulfate
(NH4HS04), ammonium sulfite ((NH4)2S03'H20), ammonium bisulfite (NH4HS03),
sulfamic acid (NH3S03), ammonium sulfamate (NH4S03NH2), ammonium dithionate
((NH4)2S2Og), and ammonium persulfate ((NH4)2S2Og). Combinations of these
salts, with substituted cations forming complex salts, are also possible.
The stability of such compounds, as indicated by the ammonia vapor pressure
that they exert, is apparently very sensitive to trace contaminants and acidic
24
impurities (see Scott 1979). Pure ammonium sulfate, however, is a stable
solid at temperatures up to 950 F. Pure ammonium bisulfate boils at about
900° F,17
The oxidation of sulfur dioxide in aqueous systems is very sensitive to
25
catalysis and pH. Ammonia is believed to be one of the most effective agents
for promoting these reactions. One of the first reported studies of ammonia-
catalyzed S0« oxidation in water droplets was conducted by van den Heuvel
26
(1963). The researchers observed extremely rapid oxidation, on the order
of 10 percent per minute, under laboratory conditions. Much slower, but very
27
significant rates for natural systems, have been described by McKay (1971)
28
and Adamowicz (1979). The presence of ammonia and sulfur dioxide in water
droplets results in rapid oxidation and formation of ammonium sulfoxide com-
pounds. Relatively high concentrations of ammonia are expected to promote
very rapid formation of aerosol particles; however, these rapid reactions
take place only if an aqueous phase is present. Gas phase reactions between
ammonia and sulfur dioxide proceed much more slowly. In the natural environ-
ment, formation of fog, rain, or other precipitation is expected to enhance
significantly the reactions between natural ammonia sources and sulfur
dioxide.17
The absorption of sulfur dioxide in water has been studied in detail
by Carmichael and Peters (1979). The chemical reactions of sulfur dioxide
in aqueous solutions presented in this report apply to rain drops, surface
water bodies, or stack sampling impingers. They present an equilibrium dis-
tribution of sulfur species in the plus-four oxidation state S(IV) as illu-
strated in Figure A-2. Dilute sulfur dioxide going into solution exists
primarily as bisulfite ions. The initial pH of a raindrop in a sulfur dioxide
atmosphere is about six. The pH changes rapidly to between 4 to 5 as more
A-12
-------
T=25°C
o
UJ
Q.
CO
u.
o
UJ
1.0
0.8
0.6
0.4
0.2
/ SO,
14
Figure A-2. Distribution of S(IV) species concentrations as a function of
solution pH.29
A-13
-------
sulfur dioxide enters the system. The reduced pH drives the equilibrium
toward the SCL'HUO species.
Since the presence of ammonia promotes SOZ formation in an aqueous sys-
tem (that readily oxidizes to SOT), it may be one of the primary factors in
the formation of condensable sulfate particulate. It also chemically combines
with the SO^ to form particulate such as NH4HS04 and (NH^SO^, common sulfate
species.
A-14
-------
REFERENCES
1. U.S. Environmental Protection Agency. User's Guide for MPTER. EPA-
600/8-80-016, April 1980.
2. User's Guide for PTPLU. Aerocomp, Inc. U.S. EPA Contract No. 68-02-3442.
May 1982.
3. Friedlander, S. K. Smoke, Dust, and Haze. Wiley-Interscience, New
York. 1977.
4. Friedlander, S. K. Recent Developments in Aerosol Science. D. Shaw (ed.)
Wiley-Interscience, New York. 1978.
5. Green, H. L., and W. R. Lane. Particulate Clouds: Dusts, Smokes and
Mists. E and F. N. Spon Ltd., London. 1964.
6. McMurry, P. H., and J. C. Wilson. Growth Laws for the Formation of
Secondary Ambient Aerosols: Implications for Chemical Conversion
Mechanisms. Atmospheric Environment, 16:121-134, 1982.
7. McMurry, P. H., and S. K. Friedlander. New Particle Formation in the
Presence of an Aerosol. Atmospheric Environment, 13:1635-1651, 1979.
8. Whitby, K. T., R. B. Husar, and B. Y. Liu. The Aerosol Size Distribution
of Los Angeles Smog. Journal of Colloid and Interface Science, 39:177-
204, 1972.
9. Smoluchowsky, M. V. Mathematical Theory of the Kinetics of the Coagu-
lation of Colloidal Solutions. Z Phys Chem, 92:129-137, 1917.
10. Metcalfe, H. C., J. E. Williams, and J. F. Castka. Modern Chemistry,
Holt, Rinehart, and Winston, Inc. 1966.
11. Personal communication from R. Bradow, U.S. Environmental Protection
Agency, Research Triangle Park, North Carolina, March 9, 1982.
12. U.S. Environmental Protection Agency. Preliminary Assessment of the
Sources, Control and Population Exposure to Airborne Polycyclic Organic
Matter (POM) as Indicated by Benzo(a)Pyrene (BaP). Final Report.
November 10, 1978.
13. McWallan, J. J., G. J. Yurek, and J. F. Elliot. Combustion and Flame.
Volume 42:45-60. 1981.
14. Radian Corporation. Trace Metals and Conventional Combustion Sources.
U.S. EPA Contract No. 68-02-2608. April 1980.
A-15
-------
15. Hellwig, G. V., and T. Mappes. Extended Source Survey Report for Arsenic.
PEDCo Environmental, Inc. U.S. EPA Contract No. 68-02-3173, Task No. 34.
May 1982.
16. Cheney, J. L., and J. T. Chehaske. Measurement of Primary Sulfates
with an Acid Condensation System. Paper No. 82-58.9, presented at the
1982 Air Pollution Control Association Annual Meeting.
17. Chadbourne, J. F., et al. Reactive Plumes - Sampling and Opacity Concerns
for Cement Kilns. Paper No. 80-12.4, presented at the 1980 Air Pollution
Control Association Annual Meeting, Montreal, Canada.
18. Whitby, K. T., et al. Nuclei Formation Rates in a Coal-Fired Power
Plant Plume. Atmospheric Environment, 12:313-321, 1978.
19. Friend, J. P. Formation of Atmospheric Aerosols by Gas to Particle
Conversions. AICHE Symposium, Sat., 701:267-220. 1974.
20. Raesler, J. F., H. J. R. Stevenson, and J. S. Nader. Size Distribution
of Sulfate Aerosols in Ambient Air. Journal of Air Pollution Control
Association, 15:576-579. 1965.
21. Kircher, J. F., et al. A Survey of Sulfate, Nitrate, and Acid Aerosol
Emissions and Their Control. EPA-600/7-77-04. NTIS PB-267 588.
22. Husar, R. B., J. P. Lodge Jr., and D. J. Moore. Sulfur in the Atmosphere.
Atmospheric Environment, 12:7-23, 1978.
23. Eatough, D. J., et al. The Formation and Stability of Aerosol Sulfate
Species in Aerosols. Atmospheric Environment, 12:263-271, 1982.
24. Scott, W. D., and F. C. R. Cattell. Vapor Pressure of Ammonium Sulfates.
Atmospheric Environment, 13:307-317, 1979.
25. Fuller, E. C., and R. H. Gist. The Rate of Oxidation of Sulfite Ions
by Oxygen. J. Am. Chem. Soc. 63:1644-1650, 1941.
26. Van den Heuvel, A. P., and B. J. Mason. The Formation of Ammonium
Sulfate in Water Droplets Exposed to Gaseous Sulfur Dioxide and Ammonia.
Quart J. Roy. Meteorol. soc., 89:271-275, 1963.
27. McKay, H. A. C. The Atmospheric Oxidation of Sulfur Dioxide in Water
Droplets in the Presence of Ammonia. Atmospheric Environment, 5:7-14,
1971.
28. Adamowicz, R. F. A Model for the Reversible Washout of Sulfur Dioxide,
Ammonium and Carbon Dioxide From a Polluted Atmosphere and the Pro-
duction of Sulfates in Raindrops. Atmospheric Environment, 13:105-121,
1979.
29. Carmichael, G. R., and L. K. Peters. Some Aspects of S02 Absorption by
Water - Generalized Treatment. Atmospheric Enviornment, 13:1505-1513,
1979.
A-16
-------
APPENDIX B
FILTERABLE VS. CONDENSED PARTICULATE MATTER
AND ADJUSTED EMISSION FACTORS
B-l
-------
EPA METHOD 5 TEST RESULTS—RATIO OF FILTERABLES TO BACK HALF
CATCH, BY SOURCE CATEGORYa
Category/subcategory
Anode baking furnace
_
Asphalt plants
Boiler/coal
(industrial)
Filterables,
%
97.32
58.46
98.63
74.94
33.66
47.80
49.53
75.7
68.6
32.5
21.5
48.8
20.6
85.3
20.6
86.1
95.0
92.3
97.6
88.6
97.3
87.5
97.14
88.91
88.45
88.35
96.91
88.60
81.22
90.97
98.70
81.50
Back half,
%
2.68
41.54
1.37
25.06
66.33
52.19
50.47
24.3
31.4
67.5
78.5
51.2
79.4
14.7
79.4
13.9
5.0
7.7
12.4
10.9
2.6
12.5
2.86
11.09
11.55
11.65
3.09
11.40
18.78
9.03
1.30
18.50
Back half,
mean, %
34.2
32.1
9.93
Back half,
a, %
23.4
29.3
5.77
(continued)
B-2
-------
EPA Method 5 Test Results (continued)
Category/subcategory
Boiler/coal
(utility)
Boiler/oil
(continued)
Filterables,
%
16.07
0.71
80.00
83.72
83.33
51.09
94.52
86.11
58.07
97.57
7.33
27.25
23.40
76.70
50.80
61.38
64.65
68.82
63.75
44.95
75.69
60.07
16.03
31.78
32.46
50.53
45.20
56.97
14.70
22.40
20.43
49.05
25.31
25.77
24.34
46.89
35.67
41.27
26.59
36.05
19.19
45.38
Back half,
%
83.93
99.29
20.00
16.28
16.67
48.91
5.49
13.89
41.93
2.43
92.67
72.75
77.60
23.50
49.20
38.62
35.35
31.18
36.25
55.05
24.31
39.93
83.97
68.22
67.54
49.47
54.80
33.02
85.30
76.60
79.57
50.95
74.69
74.23
75.66
53.11
56.41
30.69
73.41
63.95
80.18
54.62
Back half,
mean, %
44.30
57.30
Back half,
a, %
33.44
18.38
B-3
-------
EPA Method 5 Test Results (continued)
Category/subcategory
Boiler/ wood
Brick and tile plant kilns
Chemical production
Potassium still
Chrome oxide kiln
Boric acid
Boric acid
Elemental phosphorous
Fiberboard dryer
Filterables,
%
25.82
85.02
91.72
100.00
100.00
82.80
66.60
89.90
92.00
88.90
80.80
79.20
96.80
94.90
92.57
99.54
95.45
91.86
64.78
82.36
36.38
31.18 -
55.85
65.32
94.31
16.17
70.94
46.0
95.59
19.36
Back half,
%
74.18
14.98
8.28
0.00
0.00
17.20
33.40
10.10
8.00
10.10
19.20
20.80
3.20
5.10
7.43
0.46
4.55
8.14
35.22
17.64
63.62
68.82
44.15
34.68
5.61
83.83
29.06
54.0
4.41
80.64
Back half,
mean, %
16.04
27.80
42.5
Back half,
a, %
18.34
24.70
38.1
(continued)
B-4
-------
EPA Method 5 Test Results (continued)
Category/subcategory
Glass plants
Grain dryers
Incinerators
Municipal
Industrial
Sewage sludge
Iron foundries
Filterables,
%
8.85
85.53
83.72
85.31
74.62
53.52
56.10
90.00
92.70
94.20
85.60
63.80
67.10
80.40
74.29
95.43
53.88
4.17
93.55
85.00
96.20
35.26
79.14
44.40
93.47
90.20
65.20
65.10
49.90
93.50
Back half,
%
91.15
14.47
16.28
14.69
25.38
46.48
43.90
10.00
7.30
5.80
14.40
36.20
32.90
19.60
25.71
4.56
46.12
95.83
6.45
15.00
3.80
64.74
20.86
55.60
6.53
9.80
33.80
34.90
50.10
6.50
Back half,
mean, %
27.0
25.5
30.27
38.23
23.6
Back half,
a, %
21.8
17.0
38'. 10
17.40
16.9
(continued)
B-5
-------
EPA Method 5 Test Results (continued)
Category/subcategory
Iron and steel sinter plant
_
Electric arc furnaces
Basic oxygen furnace
Open hearth
Coke ovens
Filterables,
%
9.55
88.43
79.80
85.50
92.50
57.80
63.40
86.80
99.70
57.70
66.80
45.30
81.50
76.40
59.38
51.90
97.79
98.13
97.47
97.99
66.5
30.0
92.3
55.51
90.41
49.72
43.10
68.75
91.53
83.40
Back half,
%
90.45
11.57
20.20
14.50
7.50
42.20
36.50
13.20
0.30
42.30
33.20
54.70
18.40
23.60
40.62
48.10
2.21
1.87
2.52
2.01
33.5
70.0
7.7
44.49
9.59
14.04
56.90
31.25
8.47
16.60
Back half,
mean, %
29.2
19.1
37.1
22.7
28.3
Back half,
a, %
22.6
20.8
25.6
15.5
18.4
(continued)
B-6
-------
EPA Method 5 Test Results (continued)
Category/subcategory
Sand blast (steel )
Heat treat (steel)
Kraft pulp and paper mills
Recovery boilers
Lime kiln
Smelt dissolve tank
Lime kiln
Filterables,
%
36.96
99.67
45.47
93.23
99.55
97.14
76.80
89.00
92.50
93.80
45.70
92.10
89.50
85.20
72.00
94.80
54.50
75.10
31.60
37.30
66.60
62.70
97.40
89.60
93.00
93.70
94.97
79.64
94.20
Back half,
%
63.04
0.32
54.53
6.77
4.45
2.86
23.20
11.00
7.50
6.20
54.30
7.90
10.50
14.80
28.00
5.20
45.50
24.90
68.40
62.70
33.40
37.30
2.50
10.50
7.00
6.30
5.03
20.36
5.80
Back half,
mean, %
14.3
39.1
16.2
10.4
Back half,
a, %
14.4
22.1
13.8
7.1
B-7
-------
EPA Method 5 Test Results (continued)
Category/subcategory
Mineral products
Gypsum
Clay dryer
Feldspar dryer
Clay products kiln
_
Mineral wool
Petroleum refineries
Heaters
FCC
Catalytic regenerator
Portland cement
Kiln (gas -fired)
Kiln (coal -fired)
Kiln (wet-process)
I f+mn + *i mi t s\A \
Filterables,
%
87.28
0.49
11.60
80.80
94.10
45.40
99.16
38.37
45.6
97.6
54.8
43.2
69.9
26.6
90.08
73.84
69.0
58.5
47.7
48.0
53.2
58.7
96.1
92.6
Back half,
%
12.72
99.51
88.40
19.20
5.90
54.60
1.64
61.63
54.4
2.6
45.2
56.8
30.1
73.4
9.92
26.16
31.0
41.5
52.3
52.0
46.8
41.3
3.9
7.4
Back half,
mean, %
12.6
39.29
23.9
53.4
34.5
Back half,
a, %
6.6
26.80
21.3
17.8
17.9
B-8
-------
ERA Method 5 Test Results (continued)
Category/subcategory
Kiln (dry process)
Kiln (process not
specified)
Finish mill (wet-process)
.
Primary nonferrous smelters
Zinc sweat kiln
Zinc fume kiln
Zinc ore briquet dryer
Lead sinter line
Lead blast furnace
Copper converter
Copper converter, electric
furnace, and fluid bed
roaster
Copper reverberatory
furnace
Copper roasters
Molybdenum -roasters
Roofing
Saturated felt
(continued)
Filterables,
%
37.90
46.43
81.10
82.90
48.00
66.5
63.2
91.0
24.73
86.57
82.68
99.9
91.3
37.7
69.5
39.77
44.50
99.00
97.04
65.6
45.8
Back half,
%
62.10
53.57
18.90
17.10
52.00
33.5
36.8
9.0
75.27
13.43
17.32
0.1
8.7
62.3
30.5
60.23
55.50
1.00
2.96
34.4
54.2
Back half,
mean, %
26.4
4.4
44.3
Back half,
a, %
12.4
4.3
9.9
B-9
-------
€PA Method 5 Test Results (continued)
Category/subcategory
Asphalt blowing
Secondary metal smelters
Aluminum dross furnace
Aluminum furnace
Lead furnace
Pb02 mills
Lead grid casting
Lead remelt pot
Nonferrous metal
reclamation furnace
Si li cone carbide furnaces
(Acheson furnace)
Filterables,
%
14.62
12.71
100.00
100.00
11.11
33.73
88.58
71.70
23.50
27.80
18.70
5.80
63.00
47.19
34.90
42.95
54.48
81.74
89.83
85.00
11.90
96.60
17.80
89.12
83.82
82.40
Back half,
%
85.38
87.27
0.00
0.00
88.89
66.26
11.42
18.30
76.50
72.20
81.30
94.20
37.00
52.81
65.10
57.05
45.52
18.26
10.17
15.00
88.10
3.40
82.20
10.88
16.18
17.60
Back half,
mean, %
43.2
55.8
47.7
35.5 '
31.7
Back half,
a, %
43.2
30.6
16.0
37.5
29.2
(continued)
B-10
-------
EPA Method 5 Test Results (continued)
Category/subcategory
Spray paint booths
Textile
Dryers
Tenter frame
Wood products
Sanding
Resawing
Filterables,
%
46.09
63.49
72.23
66.90
24.65
9.1
18.5
4.2
23.9
26.62
94.04
99.41
83.65
99.69
Back half,
%
53.91
36.51
27.77
33.10
75.34
90.1
81.5
95.8
76.1
73.38
5.96
0.59
16.35
0.31
Back half,
mean, %
37.8
85.9
26.6
8.3
Back half,
a, %
9.8
7.6
40.6
8.0
Test results reflect emissions after air pollution control equipment.
B-ll
-------
ADJUSTED EMISSION FACTORS
[g/Mg (lb/ton)]
Source category
Anode baking furnace
Uncontrolled
Asphalt plants
Venturi scrubber
Baghouse
Boiler - coal
Industrial
Uncontrolled
Utility
Uncontrolled
Boiler - oil
Utility.
kg/10% liters
(lb/10J gal)
Industrial
kg/103-liters
(lb/lb
1.5 (3.0)
0.15 CO. 3)
0.05 (0.1)
6.5 (13A)
8A (16A)
1 (8)
2.75 (23)
2.5-7.5 (5-15)
0.3 (0.6)
0.5A (1A)
N/A
N/A
0.3 (0.6)
1 (2)
3 (6)
Emission factor
adjusted for
condensables
2.3 (4.6)
0.2 (0.4)
0.07 (0.13)
6.6A (13. 2A)
8.4A (16. 8A)
2.3 (18.7)
6.4 (54)
3.0-8.9 (6.0-17.8)
0.4 (0.8)
0.7A (1.4A)
0.5 (1.0)
1.4 (2.8)
4.0 (8.0)
Quantity
attributable
to condensable
in IP range
0.8 (1.6)
0.05 (0.1)
0.02 (0.03)
0.1A (0.2A)
0.4A (0.8A)
1.3 (10.7)
3.7 (31)
0.5-1.4(1.0-2.8)
0.1 (0.2)
0.2A (0.4A)
0.2 (0.4)
0.4 (0.8)
1.0 (2.0)
B-12
-------
Adjusted Emission Factors (continued)
Source category
Incinerators
Municipal
Uncontrolled
Industrial
Uncontrolled
Sewage sludge
Uncontrolled
Iron foundries
Uncontrolled
Iron and steel
Sinterplant
Uncontrolled
Electric arc
furnace
Uncontrolled
BOF
Uncontrolled
Open hearth
Uncontrolled
Coke ovens
coking cycle
Kraft pulp & paper
Recovery boilers
Untreated and
uncontrolled
Lime kiln
Uncontrolled
Smelt dissolve tank
Uncontrolled
Lime kiln
Uncontrolled
( rnn-h T nnorl ^
Unadjusted
emission,
factor3 'D
15 (30)
3.5 (7.0)
50 (100)
8.5 (17)
10 (20)
3.5-5.3(7.0-10.6)
16-43 (32-86)
2.9-6.0(5.8-12.0)
0.05 (0.1)
75 (150)
22.5 (45)
2.5 (5)
100 (200)
Emission factor
adjusted for
condensables
15.5 (30)
3.7 (7.4)
52 (104)
8.7 (17.4)
10.3 (20.6)
3.6-5.4(7.2-10.8)
16.7-44.8(33.4-89.6)
3.0-6.1(6.0-12.2)
0.07 (0.14)
76.1 (152.2)
23.4 (46.8)
3.0 (6)
101 (202)
Quantity
attributable
to condensable
in IP range
0.5 (1.0)
0.2 (0.4)
2 (4)
0.2 (0.4)
0.3 (0.6)
0.1 (0.2)
0.7-1.8(1.4-3.6)
0.1 (0.2)
0.02 (0.04)
1.1 (2.2)
0.9 (1.8)
0.5 (1)
1 (2)
B-13
-------
Adjusted Emission Factors (continued)
Source category
Mineral Products
Gypsum
Uncontrolled
Clay dryer
Uncontrolled
Mineral wool cupola
Petroleum refining
Heaters
kg/10%liters
(lb/10J bbl) of oil
burned)
FCC (uncontrolled)
kg/103, liters
(lb/l(T bbl) of
fresh feed)
Portland cement
Kiln (wet-process)
Kiln (dry-process)
Primary nonferrous
smelters
Pb s interline
Downdraft,
uncontrolled
Lead blast furnace
Copper converter
Copper roaster
Roofing
Saturated felt
Blowing
(continued)
Unadjusted
emission,
factor*'13
45 (90)
35 (70)
11 (22)
2.4 (840)
0.695(242)
114 (228)
122 (245)
106.5(213.0)
180.5(361.0)
30 (60)
22.5 (45)
1 (2)
1.25 (2.5)
Emission factor
adjusted for
condensables
45.6 (91.2)
38.9 (77.8)
18 (49)
4.0 (1384)
0.913 (318)
174 (348)
323 (646)
106.9 (213.8)
478 (957)
43 (86)
22.7 (45.4)
1.4 (2.8)
2.24 (4.48)
Quantity
attributable
to condensable
in IP range
0.6 (1.2)
3.9 (7.8)
7 (27)
1.6 (544)
0.218 (76)
60 (120)
201 (402)
0.4 (0.8)
298 (596)
13 (26)
0.2 (0.4)
0.4 (0.8)
0.99 (1.98)
B-14
-------
Adiusted Emission Factors (continued)
Source category
Secondary metal
smelters
Aluminum dross
furnace
Uncontrolled
Controlled
Aluminum furnace
Reverberatory
Uncontrolled
Controlled
Lead furnace
Uncontrolled
Lead remelt pot
Uncontrolled
Unadjusted
emission.
factor3 'D
7.25 (.14.5)
1.65 (3.3)
2.15 (4.3)
0.65 (.1.3)
96.5 (193)
0.4 (0.8)
Emission factor
adjusted for
condensables
8.0 (16.0)
14.85 (29.7)
2.29 (4.58)
1.08 (2.16)
100.5 (201.0)
0.90 (1.8)
Quantity
attributable
to condensable
in IP range
13.2 (26.4)
13.2 (26.4)
1.28 (2.56)
1.28 (2.56)
4.0 (8.0)
0.5 (1.0)
A = percent ash.
3N/A = not available,
B-15
-------
APPENDIX C
DISCUSSIONS OF EPA METHODS 5 AND 17, MODIFIED
METHOD 5, AND THE STACK DILUTION SAMPLING
SYSTEM
C-l
-------
The following paragraphs discuss standard participate testing methods
and their relationship to measuring primary particulates. The discussions are
arranged in order of increasing capability for measuring primary particulate
matter. For each method the following points are emphasized: a) the purpose
associated with the method's use and what the method is intended to quantify;
b) the component parts of the method's sampling train that figure prominently
in the actual collection of particulate matter (e.g., probes, filters, and
impingers); and c) the method's limitations from the standpoint of artifact
formation and other biases.
EPA REFERENCE METHOD 17
Reference Method 17 is the most commonly applied of a group of similar
methods, all of which entail an in situ filtration technique for the determi-
nation of particulate matter mass concentrations. [The other methods are the
o
American Society for Mechanical Engineers (ASME) Power Test Code 27 and the
American Society for Testing and Materials (ASTM) D 3685-78 (Method A).3]
Figure C-l illustrates the Reference Method 17 sampling train. For the pur-
poses of this discussion, the important components of the train are 1) the
sampling nozzle and 2) the in-stack filter holder, which contains the filter
during sampling.
Reference Method 17 is used to test particulate matter control equipment
when it can be shown that results will equal those obtained by Reference
Method 5. The stated criterion for the use of Reference Method 17 is that
the particulate matter mass concentration associated with the subject effluent
stream show no temperature dependence. (Since particulate matter is defined
essentially in terms of Reference Method 5, however, both the preceding applic-
ability statements have the same meaning.)
From a technical standpoint, results of Reference 17 should strictly
represent the filterable particulate matter portion of the sampled effluent
stream. Nevertheless, artifact-forming mechanisms can be postulated because
the particulate matter is concentrated at the filter. Accordingly, one of
C-2
-------
INPINGER TRAIN OPTIONAL. MAY BE REPLACED
BY AN EQUIVALENT CONDENSER
TEMPERATURE
SENSOR
NOZZLE
THERMOMETER
RESERVE-TYPE
PITOT TUBE
VACUUM LINE
VACUUM PUMP
Figure C-l. Reference Method 17 sampling train.
C-3
-------
the general principles of chemical reactivity indicates that rates increase as
the concentrations of reactants increase. This argument applies to effluent
streams from combustion processes. For example, effluent streams from coal-
fired boilers contain alkaline fly ash and acidic gases (e.g., sulfur trioxide);
when these alkaline and acidic components react, the result would be an increase
in fly ash (i.e., particulate matter) mass. Because the formation of artifacts
resulting from filtration-concentration reactivity has not been investigated,
the impact of this postulated phenomenon on filterable particulate matter
determinations is unknown. This phenomenon, however, is general; therefore,
artifact formation via concentration effects are possible for all methods that
entail filtration for separating particulate matter from reactive effluent
sample streams. Concentration effects are also possible and have been observed
on methods that entail the collection of particulate matter by impingement in
water. (This subject is discussed further under EPA Reference Method 5.)
It should be recognized that the issue of "concentration artifacts" is a
reflection of the inability of the in-stack method to duplicate (or simulate)
the particulate matter removal processes that are common to the plume.
EPA REFERENCE METHOD 5
4
Reference Method 5 is the method used most frequently to determine
mass concentrations of particulate matter within stationary source effluent
streams. Method 5 is specified for assessing the performance of particulate
matter control equipment installed at sources subject to New Source Perform-
ance Standards. The Reference Method 5 sampling train is illustrated in Fig-
ure C-2.
For this discussion, the important features of the sampling train are
1) the heated probe and 2) the out-of-stack filter enclosed within a heated
box. These two components of the sampling train are commonly referred to
together as the "front half," a term that distinguishes this section of the
train from the "back half," which is the term applied to the set of impingers
that follow the filter. (The back half is further discussed later in this
section.) During sampling, the probe and the box that houses the filter are
both heated to ensure that filtration occurs at 248 _+ 25°F (120 +_ 14°C).
C-4
-------
o
I
TEMPERATURE SENSOR
IMPINGER TRAIN OPTIONAL, MAY BE REPLACED
BY AN EQUIVALENT CONDENSER
CHECK
VALVE
VACUUM
LINE
THERMOMETER
FILTER HOLDER
HEATED AREA
THERMOMETER
TEMPERATURE
SENSOR
PITOTTUBE
PROBE
STACK
— WALL
TYPE S
PITOT TUBE
PITOT MANOMETER
ORIFICE
MAIN VALVE
VACUUM
GAUGE
THERMOMETERS
DRY GAS METER
AIRTIGHT
PUMP
Figure C-2. Reference Method 5 sampling train.
-------
The following is the Reference Method 5 definition of participate matter
as the term applies to stationary sources subject to NSPS:
"Particulate matter" means any finely divided solid or liquid
material, other than uncombined water, as measured by Method 5 of
Appendix A to this part or an equivalent or alternative method.
The out-of-stack filtration technique is in accordance with a reference
method approach to assessing performance because all particulate matter
determinations effectively fall within a consistent (i.e., reference)
temperature range of collection. The specified controlled temperature is a
critical parameter because the formation of condensed particulate matter is
sensitive to temperature.
EPA did not intend to include sulfuric acid as part of the filterable
particulate for Subparts D and Da. Accordingly, higher filtration temperatures
(< 320°F (<_ 160°C)) are permitted when Reference Method 5 is applied at fossil
fuel-fired steam generators having high concentrations of sulfuric acid mist
within their effluent streams. This variation to Method 5 is an important
issue because it illustrates the limitations of particulate matter measurements
as viewed from two conceptual levels. First, the characterization of partic-
ulate matter in chemical terms (e.g., sulfuric acid) is noteworthy here.
Because particulate matter is invariably characterized only in physical terms,
particulate matter measurement is rarely interpreted in light of filterable
and condensable components; these are best distinguished on the basis of an
understanding of chemical composition. This limitation is general for all
the methods that are used to determine gross particulate matter.
Second, the variation noted above underscores a limitation of Reference
Method 5 sampling for determining the quantity of condensed particulate mat-
ter. The measured filterable particulate matter may contain a large portion
of condensed particulate matter. Thus, a significant temperature difference
may exist between the effluent stream at the measurement point and the effluent
stream at the point of filtration. If such a temperature difference exists
and if the effluent stream contains condensable components, it is possible
for these components to condense and be quantified in the front half of the
Reference Method 5 sampling train. To ensure reproducibility of emission
measurement results, the probe and filter temperatures are specified by the
applicable regulation. Comparative results from concurrent particulate
C-6
-------
matter sampling by Reference Methods 5 and 17 sampling trains at fossil fuel-
8 9
fired steam generators and at portland cement plants have shown that such
condensed participate matter is not only possible, but may be significant.
Recent studies have been conducted on several source categories that involve
the combustion of fossil fuel to determine the portion of the filterable par-
ticulate that is condensed particulate matter in the form of sulfates. The
findings have not been published.
Other factors affect the interpretation of Reference Method 5 results with
regard to how well they represent mass concentrations of filterable particulate
matter. For example, additional particulate may form within the sampling probe
if temperatures drop below 250°F (121°C). The results of sampling train per-
formance evaluations have shown that significant cooling may occur during
traversing when considerable lengths of the probe are exposed to ambient temp-
eratures. The impact of such cooling, however, has not been quantified.
PROPOSED EPA REFERENCE METHOD 5
12
When Reference Method 5 was proposed in 1971, particulate matter was
determined from the material captured in both the front half of the sampling
train (probe and out-of-stack filter) and the back half of the train (impingers
which contained water). The designation of the back half catch as particulate
matter became a controversial issue, and the promulgated sampling method
entailed only front half measurements. Thus, the major difference between
the proposed and promulgated Reference Method 5 is that the proposed method
entails quantification of material captured in the impingers, whereas the
promulgated method does not. The sampling trains, however, are identical.
Although it is not included with the federally prescribed methods for
assessing source performance, the proposed Reference Method 5 sampling method-
ology is applied by several state air pollution control agencies; consequently,
some particulate matter emission data reflect the contribution of back half
particulate matter.
Since the front half of the proposed Reference Method 5 is identical to
that of the promulgated method, the arguments pertaining to the impacts of
condensed particulate matter and artifacts are the same.
C-7
-------
The effluent sample that exits the filter contains essentially no partic-
ulate matter; however, when the sample leaves the heated box, it cools, and
depending on the source, particulate matter may condense as a consequence of
this temperature drop. Indeed, on occasion, sulfuric acid mist condensation
has been observed at this position within the sampling train. The material
that condenses after the filter is included with the impinger catch during
sampling train cleanup operations.
The greatest potential for condensation, however, exists as the effluent
sample passes through the water contained within the impingers. The water
medium effectively cools the effluent sample to temperatures that correspond
roughly to ambient conditions. The use of this medium for particulate matter
collection is artificial, however, because the particulate matter in this pro-
cess is highly concentrated on the filter and in the impinger solution where
the condensate is collected, as opposed to the plume where it is highly diluted.
It should be noted that similar arguments regarding the representativeness of
particulate matter measured in the impingers were central to the controversy
that ultimately led to the omission of the back half catch from the promulgated
Reference Method 5.14'15
Two aspects of the impinger collection technique warrant discussion
because of their potential to effect condensation in addition to those that
would occur as a natural consequence of plume cooling. First, the water it-
self is capable of reacting with components of the effluent that condense or
dissolve. This condensation has been observed in special cases when the
effluent sample stream contained reactive gaseous species. The second criti-
cal aspect of the technique relates to the fact that the water concentrates
the effluent sample stream. Thus, as noted earlier in the case of filtration
techniques in general, chemical reaction rates increase with concentration;
this concentration process is in direct opposition to the dispersion and dilu-
tion processes that characterize plume behavior.
Artifact formation also may occur up to and including the analytical
phase of the back half sample. Thus, artifact-forming reactions are not limited
to the sampling phase of the particulate matter determination, but may con-
tinue over significant periods of time. In short, if artifact-forming
reactions are occurring, their effect will generally be magnified.
C-8
-------
Very little information pertinent to these condensation artifacts is
currently available. This state-of-the-art reflects the fact that chemical
characterization is necessary before any generalizations can be made regarding
the origin of the material captured in the impingers. Chemical characteriza-
tions are expensive; also, they are seldom germane to sampling operations.
It should be noted that the importance of back half characterization with
regard to the interpretation of particulate matter measurement results is
emphasized within ASTM D3685-78 (Method B).3
STACK DILUTION SAMPLING SYSTEM (SDSS)
The Stack Dilution Sampling System (SDSS) ' is a method for determining
mass concentrations of particulate matter within stationary source effluent
streams. The SDSS was developed for quantifying primary inhalable particu-
late (IP) matter emissions which implicitly include IP of condensed particu-
late origin. The SDSS is distinguished from the methods discussed earlier by
its ability to characterize particle size distribution and, through simulated
formation, to provide measurements of condensed particulate matter. This
sampling system has not been extensively field validated.
The SDSS is illustrated in Figure C-3. The important features of the
system are 1) two (in series) in-stack cyclones which separate and collect
two particle size fractions and which pass particles with aerodynamic sizes
less than 2.5 urn, 2) a dilution chamber which simulates particulate matter
formation in the source's plume at controlled conditions by mixing the efflu-
ent sample with filtered, humidified air, and 3) a hi-vol impactor and/or
filter.
As indicated by the name, the essential feature of this measurement
method is the dilution chamber which is designed to simulate the production
of condensed particulate matter in the plume as it cools and mixes with the
atmosphere. This simultation ability is a feature that distinguishes the
SDSS from the other described methods which are not intended strictly for
use in quantifying the condensed particulate matter fraction of stationary
source primary particulate matter emissions. Thus, the SDSS has the potential
capability of characterizing the particle size distribution of the primary
particulate matter.
C-9
-------
HI VOL IMPACTOR
ANO/OR FILTER
PROCESS STREAM
SAMPLING
CYCLONE
o
i
/ \
TO HEATERS. BLOWERS
TEMPERATURE SENSORS
JL
8 @@
EXHAUST BLOWER
DILUTION
/ CHAMBER
11 . T(
' ft
SI
FILTER
3 1 1 . .<
MAIN CONTROL
TO ORIFICE
PRESSURE TAPS
FT
FLOW. PRESSURE
MONITORS
TO ULTRAFINE
PARTICLE SIZING
SYSTEM (OPTIONAL)
/DILUTION AIR
HEATER
CONDENSER
• DILUTION AIR
BLOWER
ICE BATH
Figure C-3. Diagram of stack dilution sampling system.
-------
The performance of the SDSS has been evaluated at several stationary
sources, including a coal-fired power plant, kraft recovery boilers, and a
continuous drum-mix asphalt plant. The results of all of these tests are in
substantive agreement with predictions. For example, results from particle
size characterizations of the diluted effluent samples were consistent with
the formation of sulfuric acid aerosol, the existence of which was predicted
from independent determinations of the precursor compound, sulfur trioxide.
Although the SDSS currently appears to be the most attractive method for
quantifying primary particulate matter emissions from stationary sources, the
accuracy of this method has not been established. This shortcoming is not
necessarily a drawback, however, because in principle the SDSS can be applied
in a reference method fashion.
Tests were performed with the SDSS train at two kraft pulp mill recovery
boilers, a drum-mix asphalt plant, and a coke quench operation. Table C-l
presents the average condensed particulate matter expressed as the percentage
of the total catch for each test, along with the average results from Method 5
tests at similar sources.
A comparison of the available data tends to confirm the fact that
Method 5 collects condensed particulate matter in the filterable particulate
catch. By removing some of the condensed particulate matter in the front
half of the train, the back half catch is less proportioned than the measured
condensed particulate portion of the SDSS.
Drum-mix asphalt plants are the only source category for which an emis-
sion factor (0.008 Ib of condensed organics per ton of asphalt paving pro-
duct) has been reported. The emission factor calculated for the purpose of
this report (0.03 Ib of condensed material per ton of asphalt paving produced)
18
was based on EPA emission factors (AP-42) and an average of .Method 5 test
results. The method used to calculate this emission factor was based on only
two SDSS source tests; however, if a calculation is made by applying the per-
cent condensed particulate matter reported in the SDSS tests to the Method 5
data collected, the result is an emission factor of 0.03 Ib of condensed
material per ton of asphalt paving produced. This emission factor is the
same as the one calculated by using Method 5 back half data and AP-42.
C-ll
-------
TABLE C-l. COMPARISON OF CONDENSED PARTICULATE TEST RESULTS
BY SDSS AND METHOD 5
Process
Kraft recovery boiler (with direct
contact evaporation)
Kraft recovery boiler (no direct
contact evaporation)
Drum-mix asphalt plant
Coke quenching
% Condensable
SDSS
33.15
81.8
45.45
34.2
Method 5a
No data
14.3
32.1
No data
Results represent back half or impinger catch percentage
C-12
-------
REFERENCES
1. Federal Register. Vol. 43, No. 37 - Thursday, February 23, 1978.
2. American Society of Mechanical Engineers. Determining Dust Concentration
in a Gas Stream. Performance Test Code 27-1957. New York, New York.
3. American Society for Testing and Materials. Standard Test Method for
Particulates Independently or for Particulates and Collected Residue
Simultaneously in Stack Gases. ASTMD 3685-78. 1980.
4. Federal Register. Vol. 36, No. 247, Thursday, December 23, 1971.
5. Code of Federal Regulations, Title 40, Part 60, Subpart A, Section 60.2.
6. Federal Register. Vol. 37, No. 55 - Tuesday, March 21, 1972.
7. Federal Register. Vol. 40, No. 194 - Monday, October 1975.
8. Kendall, D. R. Recommendations on a Preferred Procedure for the Deter-
mination of Particulate in Gaseous Emissions. JAPCA, 26:871, 1976.
9. Hower, J. E., Jr., R. N. Pesut, and W. M. Henry. Evaluation of Stationary
Source Particulate Measurement Methods. Volume I, Portland Cement
Plants. EPA-600/2-75-051a, June 1975.
10. Vollaro, R. F. An Evaluation of the Current EPA Method 5 Filtration
Temperature Control Procedure, in Stack Sampling Technical Information,
A Collection of Monographs and Papers. Vol. IV. EPA-450/2-78-042d,
October 1978.
11. Peters, E. T., and J. W. Adams. Evaluation of Stationary Source Particu-
late Measurement Methods. Volume III. Gas Temperature Control During
Method 5 Sampling. EPA-600/2-79-115, June 1979.
12. Federal Register. Vol. 36, p. 15704, August 17, 1971.
13. Hemeon, M. C. L., and A. W. Black. Stack Dust Sampling: In-Stack Filter
or EPA Train. JAPCA, 22:516, 1972.
14. Hillenbrand, L. J., R. B. Engdahl, and R. E. Barrett. Chemical Composi-
tion of Particulate Air Pollutants From Fossil-Fuel Combustion Sources.
U.S. EPA Report. March 1, 1973.
C-13
-------
15. Kowalczyk, J., et al. Source Test Procedure for Determination of Particu-
late Emissions From Veneer Driers. Publication of the Control Agency
Directors - Eight-Source Test Committee, Pacific Northwest International
Section, Air Pollution Control Association. September 1972.
16. Williamson, A. D., J. D. McCain, W. B. Smith, and D. B. Harris. A Stack
Dilution Sampling System for the Measurement of Condensible Vapors in
Process Emissions. Presented at the Third Symposium on Advances in
Particulate Sampling and Measurement, Daytona Beach, Florida, October
1981.
17. Heinsohn, R. J., J. W. Davis, and K. T. Knapp. Dilution Source Sampling
System. Environmental Science and Technology, 14:1205, 1980.
18. U.S. Environmental Protection Agency. Compilation of Air Pollutant Emis-
sion Factors. AP-42.
C-14
-------
APPENDIX D
CONTROL TECHNIQUES FOR CONDENSED PARTICIPATES
D-l
-------
The following are more detailed descriptions of add-on control devices
that can be used to remove condensed participate.
POSITIVE-CORONA TWO-STAGE ELECTROSTATIC PRECIPITATOR
The positive-corona two-stage electrostatic precipitator (ESP) is com-
monly used to collect organic aerosols in low-temperature gas streams. The
gas stream is cooled to between 90° to 120°F (32° to 49°C) by evaporative
cooling (direct contact), indirect heat exchangers, or dilution air. The con-
densed particles are charged in the first stage of the ESP by use of a wire
electrode and high current. The particles are then placed in a high-potential
field in the second stage and collected on metal plates. Because the aerosol
is liquid and is spread over the collection surface, it forms a film of viscous
organic material which is continuously drained from the plates. When the par-
ticulate matter to be collected is sticky, water spray, detergents, and perio-
dic steam cleaning are used to form an emulsion that will drain from the surface,
These collectors can effectively reduce visible emissions from 100 to <5 per-
cent opacity. Removal efficiency may be as high as 99.5 percent. The col-
lection is not particle size selective, and regeneration of particles does
not occur from the plates. The effectiveness of control is limited only by
the inlet gas temperature.
The only serious problems with these control devices are that they 1) are
generally small (<30,000 acfm), 2) require precleaners to remove solid par-
ticulates, and 3) are subject to fires. Typical applications are in the
textiles, rubber, vinyl, asphalt roofing, printing, grain drying, and food
industries.
WET ELECTROSTATIC PRECIPITATORS
The major problem in controlling condensed particulate in dry collection
devices is that the gas stream usually must be cooled below the moisture or
acid dew point, which causes collection surface fouling, bag blinding, and
corrosion. The wet ESP is manufactured from corrosion-resistant materials
or has resistant surface coatings such as epoxy or rubber. The collection
surfaces are constantly flooded with a film of water, which prevents material
from coating the collection surface and fouling the collection. Also, because
D-2
-------
particles are wetted when they reach the collection surface, the possibility
of particle reentrainment does not exist. These properties make the wet ESP
an ideal device for collecting condensed participate. The gas stream may be
cooled to near-ambient conditions, and sticky or tacky materials may be col-
lected. Emulsifying agents may be added to the water to reduce fouling in
the waste handling systems. Typical applications include anode baking furnaces,
mineral wool cupolas, sulfite and kraft recovery furnaces, chemical waste
incinerators, steel sinter plants, elemental phosphorus furnaces, and chemical
waste incinerators. Test data indicate outlet grain loadings of 0.005 to
0.03 gr/dscf, and removal efficiencies as high as 99.9 percent. Gas volumes
range-between 800 and 100,000 acfm per unit. Multiple modules may be used
for higher gas volumes.
IONIZING WET SCRUBBERS
The collection efficiency of a packed-bed scrubber may be increased for
the collection of condensed particulate by the addition of an ionizing sec-
tion before the packed bed. Ionizing scrubbers are generally two-stage with
a presaturation section. Units fabricated out of corrosion-resistant materi-
als (FRP, Hastalloy) have been used to collect condensed particulate plumes
containing ammonium bisulfite, H^SO,, HCl, and HF. Opacities have been re-
duced from 100 to 10 percent, and outlet grain loading is as low as 0.005
gr/dscf. The scrubber cannot be applied, though, to sources containing
appreciable amounts of primary particulate that would foul the packed bed.
HIGH ENERGY VENTURI
Condensed particulate may be collected by a high-energy venturi (45 to
60 in. H20) when the condensed particulate forms ahead of the venturi throat.
A major drawback to the system is that most installations do not presaturate
the gas stream, and the particles condense after the venturi throat. Also,
flashing of water containing dissolved solids in the gas stream may produce
condensed particulate in the submicrometer range. High-energy venturi scrub-
bers have been used on a wide range of process operations, including coke
oven pushing, steel basic oxygen furnaces, sinter plants, lime kilns, boilers,
recovery boilers, elemental phosphorus furnaces, and fertilizer processes.
D-3
-------
Removal efficiencies vary from 40 to 99 percent, depending on scrubber design
and process conditions.
FABRIC FILTERS
Fabric filters have been proven to be an effective method for controlling
condensed participate. The application of the units, however, must be limited
to sources that are operated above the moisture and acid dewpoints, thus pre-
venting the gas stream from being reduced in temperature sufficiently to allow
condensation of many species. Due to this limitation, the control option may
be employed only on dry gas streams where the particulate is not sticky or
tacky. Removal efficiencies are high (>99%) where the air-to-cloth ratio,
gas stream temperature, and filter maintenance are properly controlled. Fabric
filters have been applied to condensed plumes such as glass furnaces, steel
sinter plants, boilers, asphalt concrete plants, ferroalloy mills, fertilizer
plants, fiberboard plants, grain dryers, gray iron foundaries, lime kilns,
mineral products, incinerators, portland cement plants, secondary metal (cop-
per, aluminum, lead, zinc) operations, tire buffing, and wood product industries.
MIST ELIMINATORS
Fiber pad mist eliminators have been used successfully to remove organic
aerosols from gas streams for process use and as air pollution control devices.
The gas stream must be cooled to allow condensation of the aerosol. The aero-
sol is formed through a tightly packed fiberglass mat, which results in parti-
cle agglomeration and coating of the liquid on the fiber structure. Collected
liquors are drained from the mat by gravity and transferred to waste. The
collection efficiency of the system is limited by the inlet gas temperature
and the filter superficial velocity. Problems with the application of this
control method are similar to that discussed under positive-corona ESP's.
Fouling of the fibers and fire are major concerns. Removal efficiencies of
99.9 percent are not uncommon, and opacities may be reduced from 100 to <5
percent.
INCINERATION
Condensed organic emissions may be controlled by incineration. The
application of furnaces, flares, and catalytic combustion have been widely
D-4
-------
used for some time to control organic compound emissions. Incineration
destroys organic emissions by oxidizing them to carbon dioxide and water vapor.
Incineration is the most universally applicable control method for organics;
given the proper conditions, any organic compound will oxidize. Oxidation
proceeds more rapidly at higher temperatures and higher organic pollutant
content. Incinerators (also called afterburners) have been used successfully
for many years on a variety of sources ranging in size from <1000 acfm to
>40,000 scfm.
The use of existing boilers and process heaters to destroy organic emis-
sions provides a possible means of pollution control with small capital cost
and little or no fuel cost. However, this option is severely limited in its
application because: 1) the heater must be operated whenever the pollution
source is operated; 2) the fuel rate to the burner cannot be allowed to fall
below that required for effective combustion; 3) temperature and residence
time in the heater firebox must be sufficient for combustion; 4) the volume
of polluted exhaust gas must be much smaller than the burner air requirement;
and 5) the source of the gas must be close to the process heater. Unfortu-
ately, few boilers or heaters will meet all these conditions.
Noncatalytic add-on incinerators (sometimes called thermal or direct-
flame incinerators) may be used in some applications. In this type of in-
cinerator, a portion of the polluted gas may be passed through the burner(s)
in which auxiliary fuel is fired. Gases exiting the burner(s) in excess of
2000°F (1093°C) are blended with the bypassed gases and held at temperature
until reaction is complete. The equilibrium temperature of mixed gases is
critical to effective combustion of organic pollutants.
A temperature of 1400° to 1500°F (760° to 816°C) at a residence time of
0.3 to 0.5 seconds is sufficient to achieve 90 percent oxidation of most
2
potentially condensable organic material.
CATALYTIC INCINERATION
The use of a catalyst in an incinerator reportedly enables satisfactory
oxidation rates at temperatures in the range of 500 to 600 F (260 to 315 C)
at the inlet and 750° to 1000°F (399° to 538°C) at the outlet. If heat recov-
ery is not practiced, significant energy savings are possible by use of a
D-5
-------
catalyst. The fuel savings become less as primary and secondary heat recovery
are added. Because of the lower temperatures, materials of construction sav-
ings are possible for heat recovery and for incineration.
Catalysts are specific in the types of reactions they promote; however,
some available oxidation catalysts will work on a wide range of organic com-
pounds. Common catalysts are platinum or other metals on either an alumina
pellet or honeycomb support; metal catalysts also can be used.
The effectiveness of a catalyst depends on the accessibility of "active
sites" to reacting molecules. Every catalyst will begin to lose its effec-
tiveness as soon as it is put into service. This must be compensated for
either by overdesigning the amount of catalyst in the original charge or by
raising the temperature in the catalyst to maintain the required efficiency.
At some time, however, activity declines to a point where the catalyst must be
cleaned or replaced. Catalysts can be deactivated by normal aging, being used
at excessively high temperatures, coating with particulates, or poisoning.
Catalyst lifetime of greater than one year is considered acceptable.
Catalyst material can be lost from the support by erosion, attrition, or
vaporization. These processes increase with temperature. For metals on
alumina, if the temperature is less than 100°F (38°C), life will be 3 to 5
years if no deactivation mechanisms are present. At 1250° to 1300°F (677?
to 704°C), life drops to one year. Even short-term exposure to 1400° to
1500°F (760° to 816°C) can result in near total loss of catalytic activity.3
CONDENSATION
Any component of a condensable mixture can be condensed if brought to
equilibrium at a low enough temperature. The temperature necessary to achieve
a given vapor concentration is dependent on the vapor pressures of the com-
pounds.
Condensation will begin when a temperature is reached at which the vapor
pressure of the volatile component is equal to its partial pressure. The
point where condensation first occurs is called the dew point. As the vapor
is cooled, condensation continues and the partial pressure stays equal to the
vapor pressure. The less volatile a compound (i.e., the higher the normal
boiling point), the lower will be the amount that can remain vapor at a given
temperature.
D-6
-------
ABSORPTION (SCRUBBING)
Absorption, as an air pollution control process, involves dissolving a
soluble gas component in a relatively nonvolatile liquid. The absorption step
is only the collection step. After the gas is dissolved, it must be recovered
or reacted to an innocuous form.
Common absorbents for organic vapors are water, nonvolatile organics, and
aqueous solutions. Absorption is increased by lower temperatures, higher gas
solubility, higher gas concentrations, higher liquid-to-gas ratios, lower gas
concentrations in the liquid, and greater contacting surface. Absorption has
been widely used as a product recovery step in the petroleum and petrochemical
industry, where concentrations are typically very high. These products are
generally recovered either by heating to lower the solubility or by distillation,
If a chemical oxidizer is present in the liquid stream, organics can be
oxidized in the stream. This technique has been used to convert low concen-
trations of odorous compounds to less odorous forms. The expense of the oxi-
dizing chemical, however, prevents its use where concentrations greater than
a few parts per million are present.
The absorption-regeneration approach for organic solvents is severely
limited by the low concentrations and consequent low solubilities of most
organic gases in the absorbent.
Direct contact with water may be used as a cooling method for removal of
high boiling compounds to avoid-opacity problems in the exhaust, but in most
cases, the materials do not go into solution to any appreciable extent. If
water is used for condensation in this way, water treatment may be necessary
before discharge.
Except in a few specialized cases, absorption is not applicable to con-
trol of organic emissions except as a preliminary step.
CARBON ADSORPTION
Carbon adsorption is applicable to most organic-emitting industries but
it may be of limited use in the control of a broad range of condensed organic
particulates. Carbon adsorption uses a physical phenomenon to separate organic
vapors from a gas stream and to concentrate these vapors to a more manageable
D-7
-------
form. The term "sorption" applies to two types of phenomena: 1) where vapor
molecules are concentrated by adsorption on the surface, and 2) where vapors
are concentrated by absorption of the vapor molecules into the mass of the
sorbent. Adsorption is accomplished by the use of four different types of
materials: 1) chemically reactive adsorbents, 2) polar adsorbents, 3) molec-
ular sieves, and 4) nonpolar adsorbents.
When adsorption is not accompanied by chemical reaction, the process is
termed physical adsorption. Preferentially, polar adsorbents adsorb polar
molecules (e.g., water) and nonpolar adsorbents adsorb nonpolar molecules
(e.g., hydrocarbon). Molecules of any solid are attracted to each other, and
the surface, molecules of the adsorption medium are subject to unbalanced
forces that cause vapor or liquid molecules to be attracted to the surface.
Adsorption takes place through a combination of molecular attraction (Van der
Waals forces) and capillary condensation of the vapors being adsorbed in the
pores provided by the extended surface of the adsorbent. Although activated
carbon does not enter into chemical reaction with the adsorbed vapors, it
does catalyze hydrolysis and degradation reactions of certain organic solvents
such as ketones.
Activated carbon is the only physical adsorbent currently in widespread
use for organic vapor collection. It is a nonpolar adsorbent although it
has some adsorptivity for water.
For concentrations greater than a few parts per million, carbon must be
used many times for economic reasons. Regeneration is required to remove
adsorbed vapors and reuse the carbon. Regeneration, which is the removal of
adsorbed organics from the carbon, is accomplished by bringing the bed to
near equilibrium by increasing the temperature. Typical regenerants are steam,
hot air, and hot inert gas. The hotter the regenerant and the longer the
the regeneration period, the more adsorbed solvent that will be removed (de-
sorbed) from the carbon bed. There is an economic optimum where adequate
desorption occurs at reasonable energy cost. The residual organic compound in
the bed after regeneration is called the "heel," and the "working capacity"
is the difference between full capacity and the heel. Regeneration is
typically about 50 percent complete for each cycle under proper (or economic)
operation.
D-8
-------
The reasons for limited applicability are the possible boiling points of
the adsorbed organic compounds and the energy required to regenerate the car-
bon bed. It is possible that some condensed organic material may not be
desorbed because of the high energy and temperature requirements for desorp-
tion. Polymerization reactions may produce tar-like products that will con-
dense at the operating temperatures of carbon adsorbers and not be desorbed,
which causes fouling.
Another disadvantage of carbon adsorption is its adsorption of moisture.
The relative humidity must be kept below 50 percent. Water formed by fuel
combustion must be considered in calculating the humidity level of the gas
stream.
COMBINATION CONTROL SYSTEMS
A combination of control technologies, together with the introduction of
cooling air, has been applied to primary nonferrous smelters for the control
of the condensed particulate arsenic trioxide (ASpO-). Because As^O., has a
higher vapor pressure than either oxides of selenium or vanadium, this combi-
nation of control technologies should also be effective in controlling these
condensed particulates.
At a primary copper and lead smelter in Sweden, the arsenic emissions
from multi hearth roasters are condensed by a cooling tower before they enter
the ESP's. A scrubber system is planned for the metal -producing furnaces,
which is expected to reduce furnace arsenic emissions alone from 10 to 5
4
tons/yr. No other details regarding these systems were available.
Arsenic emissions from a gold smelter in Ontario, Canada, are controlled
by a "hot ESP/cold bag" system, which has been evaluated for technology trans-
fer to other types of smelters. Because this smelter processes only 2400 kg/h
of ore concentrates, adaptation to other primary nonferrous smelters would in-
volve a large scaleup of the control equipment. Figure D-l presents a flow
5
diagram of the smelter and the overall control system. .
Figure D-2 shows the roasting and gas cleaning operations at this smelter.
Gases pass through two banks of process cyclones and into the hot ESP; after-
wards, off-gases from the ESP are mixed with ambient air to lower the tempera-
ture and to condense the As907. Particulates, some as a vapor, pass through
D-9
-------
FROM MINE
COARSE ORE
STORAGE
I
CRUSHING
CIRCUIT
I
PINE ORE
STORAGE
1
GRINDING
CIRCUIT
ROASTER
AIR
COOLING
AIR
COOLING.
AIR
FLOTATION
I
TABLING
FLUID BED
ROASTERS
CYCLONES
HOT
ELECTROSTATIC
PRECIPITATOR
DILUTION
COOLER
FLOTATION TAILS
TO CYANIOATION
UNDERFLOW TO
AMALGAMATION
COLD
BAGHOUSE
GASES
TO STACK
,A»2O3 TO UNDERGROUND
STORAGE
Figure EM. Gold smelter flow diagram.
D-10
-------
AIR
7.4 i
(260 scfm)
REACTOR
NO. 2
500-525»C
(925-975*F)
CYCLONES
400«C
(750*F)
REACTOR
NO. 1
540-565'C
(1000-1050
CONCENTRATES
2400 kg/h
(5400 lb/h)
SOLIDS AS
BOS SLURRY
ELECTROSTATIC
PRECIPITATOR
(2 IN PARALLEL)
370'C (700'F)
COOLING
AIR ,
300 nT/mln
(10.650 scfm)
50
(1730 scfn)
AIR
26
(940 scfm)
MIXING
CHAMBER
107«C (225*F)
CALCINES
TO CVANIOATION
2157 kg/h
(4750 lb/h)
STACK
GAS
395 m3/m1n
(13.930 scfm)
STACK
BAGHOUSE
(2 BANKS OF 2)
A$203 TO
UNDERGROUND
STORAGE
253 ko/h
(560 lb/h)
Figure D-2. Gold smelter roasting and gas-cleaning operations.
-------
the hot ESP to the mixer-cooler and then to a four-chamber fabric filter,
where they are collected. The As203 dust from the fabric filter is removed
periodically and conveyed to underground storage. The reheat stack burner
just prior to the stack (see Figure D-2) is not required in normal operation.
Electrically heated air is circulated between the double walls of the
ESP to prevent condensation of As203 on the inner walls. Two chambers are
located in each of two parallel banks, but only one transformer-rectifier
(T-R) set serves all four chambers.
The walls of the mixer-cooler used to condense As2CL in the gas stream
from the ESP are heat-traced and insulated up to the mixing chamber to prevent
condensation on the duct walls. Ambient air is fed into the center of the
mixer-cooler, and hot gases from the ESP are fed tangentially to create a
swirling action. Ideally, As^Oo condenses in the gas stream of the mixing
chamber at about 107 C. The four-chamber fabric filter is insulated and the
stack is double-walled to avoid wall condensation.
Capture efficiencies for total arsenic were 15 percent for the ESP and
99.8 percent for the ESP and fabric filter. The emission rate of arsenic was
179 kg/h at the ESP inlet and 0.20 kg/h at the outlet of the fabric filter,
which yielded an overall control efficiency of 99.9 percent for arsenic emis-
sions.
D-12
-------
REFERENCES
1. U.S. Environmental Protection Agency. Control of Volatile Organic
Emissions From Existing Stationary Sources - Volume I: Control Methods
for Surface-Coating Operations. Office of Air Quality Planning and
Standards, Research Triangle Park, North Carolina. EPA-450/1-76-028,
November 1976.
2. Shell Development Company. After Burner Systems Study. Emeryville,
California. EPA-R2-72-062, August 1972.
3. MSA Corporation. Package Sorption Study. Evans City, Pennsylvania.
EPA-R2-73-202, April 1973.
4. Lindau, L. Emissions of Arsenic in Sweden and Their Reduction. U.S.
Department of Health, Education, and Welfare. Public Health Service.
National Institute of Health. Environmental Health Perspectives, 19:(8)
25-29, 1977.
5. U.S. Environmental Protection Agency. Second Symposium on the Transfer
and Utilization of Particulate Control Technology. Vol. III. Particu-
late Control Devices. Denver, Colorado. EPA-600/9-80-039c, July 1979.
pp. 484-507.
D-13
-------
APPENDIX E
TEST METHODS FOR MOBILE SOURCES INCLUDING
DATA SUMMARY AND CORRECTION FACTOR
E-l
-------
TEST METHODS FOR MOBILE SOURCES
Sampling emissions from mobile sources is difficult because the sampling
equipment is stationary but the source is not. This problem is overcome by
operating the source in a stationary position on a dynamometer and attaching
the sampling apparatus to the exhaust pipe. Figure E-l illustrates a sampling
system approved by Federal Testing Procedures (FTP). The exhaust gas enters
the dilution chamber and is mixed with ambient air. A sample is then taken by
a particulate probe and a heated probe to determine the total hydrocarbon
emissions. The sample taken by the particulate probe leads to two sets of
primary and backup filters which are used to determine the amount of particu-
late-bound organics present in the gaseous stream. The cool particle test,
the procedure for determining particulate-bound organics, is as follows: the
emissions are collected on Teflon-coated glass fiber filters and extracted by
methylene chloride extraction. The solution is then concentrated and analyzed
by gas chomatography to determine the composition.
The primary and backup filters also aid in determining an acceptable
level of collection efficiency. If backup filter weight gain is less than 5
percent of the combined primary and backup filter weight gain, then only the
primary filter weight gain is used in the emission rate calculation. If the
value is greater than 5 percent, the total weight gain of both filters must be
used.
Several methods of exhaust dilution are commonly used in mobile source
emission testing procedures. Figure E-2 illustrates the baffle mixing system
and Figure E-3 shows the turbulent-flow tunnel. The difference between these
two methods is primarily the technique for diluting exhaust gas. The baffle
mixing system contains a baffle arrangement to mix the exhaust with ambient
air, whereas the turbulent-flow tunnel mixes the gases with turbulent flow. A
small amount of particulate (6 percent) is lost when using the baffle system.
Both systems, however, result in complete mixing of the gases.
Mobile source sampling systems have many problems including sample
validity when using standard dilution tunnel techniques and the necessary
filter material for accurate pollutant collection. The latter is only a
minor problem, and will be discussed only briefly. The problem of primary
concern is the validity of samples.
E-2
-------
m
AMBIENT AIR INLET
OrilONAl FOR
PAHTICULATF.
BACKGROUHO READING
ZERO AIR
INTEGRATOR
COUNTERS
TO BACKGROUND SAMPLE BAG
HEAD BACKGROUND IAG
DILUTION TUNNEL
HEATED PROBE
JfAHTICUIATE PROBE
MIXING ORIFICE
IICIE EXHAUST INLET
PRIMARY FILTER (PHASE I AND II
BACK UP FILTER (PHASE I AND 31
NOTE: THREE FILTER HOLDERS
(ONE FOR EACH PHASEI
ARE ALSO ACCEPTABLE
PRIMARY FILTER (PHASE 21
BACK-UP FILTER
(PHASE 2)
TO PUMP. HOIOUETER
AND GAS MEIER
MANOMETER
DISCHARGE
Figure E-l. Federal emissions certification sampling system.
1
-------
FARTICULATE: °*» *•"'•''?«
ANALYSIS: MC- CO- NO«.
FOUR l-«i. OIAM. COj
EXHAUST—»"
FIFE
MIXING HOT FID
BAFFLES THC ANALYSIS
2
Figure E-2. Baffle mixing system.
GAS ANALYSIS'
•FARTICULATE: ScCO.NO, '
ANALYSIS: CO,
FOUR 1-i«. DIAM. .
FROBES
EXHAUST FIFf
ORIFICE MIXING FLATE HOT *•">. DIA. '
FID
THC
ANALYSIS
2
Figure E-3. Turbulent-flow-tunnel.
The two main problems affecting the validity of samples collected from-
dilution tunnels are the variations in the dilution ratio and the general in-
ability of dilution systems to correctly simulate atmospheric conditions.
The use of constant-volume-sampling dilution systems, in which the total flow
is constant (i.e., changes in the exhaust emission rate changes the amount of
dilution air added), results in large variations in the dilution ratio and
mixture temperature.
When Black and High tested the effects of the changing dilution ratio on
a heavy-duty diesel engine, they found SOF increased from 31.3 percent to 32.9
2
with an increase of dilution ratio from 10:1 to 275:1. When a similar test
at a dilution ratio of 20:1 showed 29.0 percent SOF, they concluded that there
was no statistical significance in increased condensed particulate from a
dilution ratio of 10:1 to 275:1. MacDonald et al. demonstrated that as the
temperature is increased while maintaining a constant dilution ratio, the
amount of condensed material collected drops. The increased filter tempera-
ture causes evaporation/desorption and prevents condensation/adsorption of
the organic compounds which decreases the percentage collected. Federal test-
ing procedures specify that the temperature at the sample probe should be at
or below 125 F (52°C), but the significance of this temperature has not been
3
demonstrated.
E-4
-------
The method for sampling participates emitted by motor vehicles involves
dilution of the total exhaust flow with filtered ambient air prior to collec-
tion. Undiluted exhaust is not sampled because the results may be biased, in
that both physical and chemical properties of the emissions are affected by
temperature and dilution.
Dilution with ambient air permits particle-particle and particle-gas
interactions similar to those that occur under actual driving conditions;
however, these interactions are only approximations. The dilution of vehicle
2
exhaust cannot be simulated in the lab. Tests conducted at the University of
Minnesota indicate that the dilution ratio 2.5 meters behind a vehicle moving
at low speed is approximately 200:1, at 8 meters behind the vehicle, the ratio
4
reaches 1000:1. The dilution ratios most commonly used in mobile source
sampling, though, are less than 50:1. The use of larger, more representative
dilution ratios would require prohibitively long sampling periods to get
concentrations compatible with existing sampling analytical technology.
After the exhaust is diluted with ambient air, it passes through the
filter material for particle collection. Particles are collected by diffusion
deposition, direct interception, gravitational deposition, electrostatic
deposition, deposition by molecular forces, and inertia! deposition. The
importance of these individual mechanisms varies, depending on the filter
type, the gas velocity, the particle shape, and the characteristics of the
material being collected.
The two basic types of filters are membrane and fiber filters. In mem-
brane filters, gas flows through pore-like passages in a thin membranous
material, whereas in fiber filters, gas flows through a deep filament network
of fiberous material. The primary mechanism of collection in membrane filters
is direct interception. The primary mechanism for collection in fiber
filters is diffusion deposition until a "clogged" state is reached (character-
ized by an increase in the pressure drop across the filter), at which time
direct interception becomes the dominant process.
Two basic types of fiber filters are generally used today: 1) glass and
2) Teflon-coated glass fiber filters. Glass filters, which have been used for
many years, are currently being replaced with Teflon-coated glass fiber filters
because the latter have the advantages of being less hygroscopic, more mechan-
ically sound, and easier to handle. In addition, glass filters were found to
E-5
-------
adsorb some gaseous organic pollutants. This was demonstrated by Black and
High when they tested glass and Teflon coated glass fiber filters and found
that the glass filters adsorbed 25 to 32 percent of the gaseous organics
2
collected in tests on diesel engines.
DATA SUMMARY AND CORRECTION FACTOR
The filter temperature affects the amount of condensed material col-
lected; as the temperature increases, the collection efficiency drops.
MacDonald, et al. tested the effects of increasing filter temperature while
4
maintaining a constant dilution ratio. A 46 percent decrease in the percent
SOF was observed as the filter temperature increased from 35 to 100°C. In
addition, the amount of total particulate collected decreased 13 percent.
Table E-l presents the results of this experiment. Table E-2 presents a sum-
mary of emissions collected in several recent studies. This table includes
the study referenced, vehicle type, fuel type, percent SOF, emissions, and the.
temperature at which the emission sample was collected, along with the appro-
priate correction factor and the corrected emissions. The two tables cannot
be directly compared because they are products of different experiments on
light-duty diesel engines and, as previously stated, organic emissions can
5 o
vary from 10 to 60 percent. At a filter temperature of 52 C, 95 percent of .
the condensed material was collected. These data support the establishment of
a correction factor, 1/0.95 or 1.05, to correct for increased filter tempera-
tures.
E-6
-------
TABLE E-l. EFFECTS OF VARYING FILTER TEMPERATURE ON EXTRACTABLE
ORGANIC COLLECTION3
Filter
temperature, C
100
90
80
70
60
52
50
45
40
35
Extractable
organics, %
20.0
24.2
27.7
30.8
33.4
35.0
35.4
36.2
36.8
37.0
Collection efficiency compared with per-
cent collected at 35°C, %
54
65
75
83
90
95
96
98
99
100
E-7
-------
TABLE E-2. SUMMARY OF DATA ON CONDENSED PARTICULATE EMISSIONS FROM MOBILE SOURCES
Reference
I.D. No.
24a
24a
24a
24a
24a
24a
24a
24a
25a
25a
23a
23a
5
6
26a
Vehicle
typeb
LD (FTP)
LD (FTP)
LD (HWFET)d
LD (HWFET)
LD (FTP)
LD (HWFET)
HD
HD
HD
HD
LD
HD
LD
HD
HD
Fuel
type
Leaded
Unleaded
Leaded
Unleaded
Diesel
Diesel
Unleaded/
1 eaded
gasoline
Diesel
Diesel
Leaded
gasoline
Diesel
Diesel
Diesel
Diesel
Diesel
Soluble
organics,
%
21
45
9
45
26
23
2-7
10-53
62
5-17
15
12-50
14-59
11-58
13-63
Condensed
particulate
emissions,
g/km
0.013
0.003
0.015
0.005
0.08
0.05
0.009-0.02
0.12 -0.33
0.27
0.030
0.047
0.12-0.50
0.03-0.11
_ —
0.18-0.36
Collection
temperature,
°C
£52
£52
£52
£52
£52
£52
£52
£52
52
52
£52
£52
£52
£52
52
Correction
factor
1.05C
1.05C
1.05C
1.05C
1.05C
1.05C
1.05C
1.05C
1.05
1.05
1.05C
1.05C
1.05C
1.05C
1.05
Corrected
emissions,
g/km
0.014
0.003
0.016
0.005
0.084
0.053
0.009-0.021
0.13 - 0.35
0.28
0.032
0.049
0.13 -0.53
0.032-0.12
—
0.19 -0.38
00
aI.D. No. refers to main text reference numbers (preceding the appendices).
bLD = light-duty; HD = heavy-duty.
Signifies that this factor is a maximum of 1.05. The exact factor depends on the exact temperature
of the filter at the time the sample was taken.
Highway Federal Emissions Test.
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REFERENCES
1. Black, F., and L. High. Methodology for Determining Participate and
Gaseous Diesel Hydrocarbon Emissions. SAE Technical Paper No. 790422.
1979.
2. Black, F., and L. Doberstein. Filter Media for Collecting Diesel Particu-
late Matter. Environmental Sciences Research Laboratory, U.S. EPA. March
1981.
3. MacDonald, J. S., et al. Experimental Measurements of the Independent
Effects of Dilution Ratio and Filter Temperature on Diesel Exhaust
Particulate Samples. SAE Technical Paper No. 800185. 1980.
4. Plee, L. S., and J. S. MacDonald. Some Mechanisms Affecting the Mass of
Diesel Exhaust Particulate Collected Following a Dilution Process. SAE
Technical Paper No. 800186. 1980.
5. Gibbs, R. E., J. D. Hyde, and S. M. Byer. Characterization of Particu-
late Emissions From In-Use Diesel Vehicles. SAE Technical Paper No.
801372. 1980.
6. Hare, C. T. and R. L. Bradow. Characterization of Heavy-Duty Diesel
Gaseous and Particulate Emissions, and Effects of Fuel Composition.
SAE Technical Paper No. 790490. 1979.
E-9
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