United States
Environmental Protection
Agency
Air and Energy Engineering
Research Laboratory
Research Triangle Park NC 2771
Research and Development
EPA/600/S7-86/038 Jan.
SEPA Project Summary
Asphaltic Concrete Industry
Source Category Report
John S. Kinsey
The objective of this study was .to
develop particulate emission factors
based on cutoff size for inhalable
particles for the asphaltic concrete
industry. After review of available
information characterizing particulate
emissions from asphalt concrete
plants, the data were summarized and
rated in terms of reliability. Size spe-
cific emission factors were developed
from these data for each of the three
processes used in the manufacture of
asphalt concrete. A detailed process
description is presented, with emphasis
on factors affecting the generation of
emissions. A replacement for Section
8.1 (Asphalt Concrete Plants) of AP-
42 was prepared, containing the size
specific emission factors developed by
the program.
This Project Summary was devel-
oped by EPA's Air and Energy Engi-
neering Research Laboratory, Research
Triangle Park, NC, to announce key
findings of the research project that is
fully documented in a separate report
of the same title (see Project Report
ordering information at back).
Introduction
The purpose of this program was to
summarize the best available informa-
tion on emissions of inhalable particulate
matter in the asphalt concrete industry.
The main objective of the program was
to develop reliable size specific emission
factors for each of the three basic
processes used to produce asphalt
concrete. Both uncontrolled and con-
trolled emission factors are presented in
the report. The uncontrolled factors
represent emissions that would result if
the particulate control device (baghouse,
scrubber, etc.) were bypassed: the
controlled factors represent emissions
emanating from a particular type of
control system. The size-specific emis-
sion factors are generally based on the
results of simultaneous sampling con-
ducted at the inlet and outlet of the
control device(s), utilizing a variety of
particle sizing techniques. Other objec-
tives of this program were to present
current information on the asphalt
concrete industry as well as prepare a
replacement for Section 8.1 in AP-42, "A
Compilation of Air Pollutant Emission
Factors."
The above objectives were met by a
thorough literature search which
included the following sources:
Data from inhalable particulate char-
acterization program,
Fine Particle Emissions Inventory
System (FPEIS),
AP-42 background file at EPA's Office
of Air Quality Planning and Standards
(OAQPS),
MRI files, and
Various industry sources (e.g..
National Asphalt Pavement Associ-
ation.
The emission data contained in 27
reference documents were reviewed,
analyzed, summarized, and ranked
according to the criteria established by
OAQPS as published in the report,
"Technical Procedures for Developing
AP-42 Emission Factors and Preparing
AP-42 Sections," April 1980. After
ranking the data, emission factors were
calculated using the highest quality data
available. The quality of the data used
to develop each emission factor is
indicated by the emission factor rating.
Process and control system operating
data as well as general industry infor-
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mation were also obtained and summar-
ized as general background information.
It was not part of this program to provide
detailed engineering analyses, product
specifications, or detailed evaluations of
trends in the industry.
Results
Paniculate emissions are generated
from various activities at an asphalt
concrete plant including raw material
handling, aggregate drying, mixing, and
product handling. The dryer (or drum
mixer) potentially represents the largest
single contribution to process-related
particulate emissions in an asphalt
concrete plant. Fugitive dust emissions
from open sources (e.g., unpaved roads),
also a major contributor, are not specif-
ically treated in this report.
The size-specific emission factors in
Tables 1 and 2 represent controlled and
uncontrolled emissions from conven-
tional (batch or continuous mix) asphalt
concrete plants based on the type of
control device used. The emission factors
in Tables 3 and 4 represent controlled
and uncontrolled emissions from drum
mix asphalt plants. The emission factors
in Table 4 were developed from tests at
a single split-feed recycle plant equipped
with a baghouse collector. Size-specific
emission factors for other types of recycle
processes are not included in the report
because of insufficient data.
Traditionally, ducted and process
fugitive emissions from asphalt concrete
plants have been controlled by a cyclone
followed by a baghouse. Such control
systems may not be general practice at
present since the percentage of drum-
mix facilities, which generally have no
primary collector, has increased signif-
icantly since 1975. Wet dust suppression
is the most common technique used to
control open dust sources in asphalt
concrete plants.
Table 1. Emission Factors for Total
Paniculate from Conventional
Asphalt Concrete Plants*
(Emission Factor Rating: B)
Emission Factor
Type of Control
Uncontrolled?
Precleaner
High efficiency cyclone
Spray tower
Baffle spray tower
Multiple centrifugal
scrubber*
Orifice scrubber
Venturi scrubber"
Baghouse'
kg/Mg
22.5
7.5
0.85
0.20
0.15
0.035
0.02
0.02
0.01
Ib/ton
45.0
15.0
1.7
0.4
0.3
0.07
0.04
0.04
0.02
^Expressed in terms of emissions per unit
weight of asphalt concrete produced.
Includes both batch mix and continuous mix
processes.
''Almost all plants have at least a precleaner
following the rotary drier.
* Average from a properly designed, installed,
operated, and maintained scrubber, based on
a study to develop New Source Performance
Standards. Range of values = 0.004-0.0690
kg/Mg.
"Range of values = 0.013-0.0690 kg/Mg.
'Emissions from a properly designed,
installed, operated, and maintained
baghouse, based on a study to develop New
Source Performance Standards. Range of
values = 0.004-0.018 kg/Mg.
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Table 2. Summary of Size-Specific Factors for Conventional Asphalt Plants'
(Emission Factor Rating: D)
Cumulative Mass Equal to or
Less Than Stated Size (%)
Particle
Size
(umA)"
2.5
5.0
10.0
15.0
20.0
Uncon-
trolled
0.83
3.5
14
23
30
Cy-
clone
Collec-
tors
5.0
11
21
29
36
Multiple
Centri-
fugal
Scrub-
bers
67
74
80
83
84
Gravity
Spray
Towers
21
27
37
39
41
Bag-
house
Col-
lector
33
36
40
47
54
Cumulative Paniculate Emission Factor Equal to or Less Than Stated Size c
Uncontrolled
kg/Mg
0.19
0.78
3.1
5.3
6.8
Ib/ton
0.37
1.6
6.1
11
14
Cyclone
Collectors
kg/Mg Ib/ton
0.048 0.096
0.13 0.26
0. 18 0.36
0.25 0.50
0.30 0.60
Multiple
Centrifugal
Scrubbers
kg/Mg Ib/ton
0.023 0.046
0.026 0.052
0.028 0.056
0.029 0.058
0.030 0.060
Gravity
Spray
Towers
kg/Mg Ib/ton
0.041 0.082
0.053 0.11
0.073 0. 15
0.078 0.16
0.081 0.16
Baghouse
Collector*
kg/Mg Ib/ton
0.003 0.006
0.004 0.008
0.004 0.008
0.005 0.01
0.005 O.O1
Total mass emission factor
23
45
0.85 1.7
0.035 0.070 0.20 0.40 0.01 0.02
"Rounded to two significant figures.
"Aerodynamic diameter.
"Based on emission factors for total paniculate shown in Table 1. Expressed in terms of emissions per unit weight of asphalt concrete produced.
Mg 3 x 10"g; ton = 2,000 Ib.
"Rounded to one significant figure.
Table 4. Particle Size Distribution and Size-Specific Emission Factors for Drum Mix Asphalt
Plants Controlled by a Baghouse Collector*
Table 3. Total Paniculate Emission
Factors for Drum Mix Asphalt
Concrete Plants*
(Emission Factor Rating: B)
(Emission Factor Rating: D)
Emission Factor
Type of Control
Uncontrolled
Cyclone or multiclone
Low energy wet
scrubbing"
Venturi scrubber
kg/Mg
2.45
0.34
0.04
0.02
Ib/ton
4.9
0.67
0.07
0.04
'Expressed in terms of emissions per unit
weight of asphalt concrete produced. These
factors differ from those for conventional
asphalt concrete plants because the
aggregate contacts and is coated with asphalt
early in the drum mix process.
"Two types: (1) water droplets are sprayed into
the stack exit, or (2) water droplets are
sprayed onto the fan (dynamic scrubber).
Cumulative Mass Equal to
or Less Than Stated Size Cumulative Paniculate Emission Factors
Particle (Percent) Equal to or Less Than Stated Size'
Size Uncon-
(umA)" trolled
2.5 5.5
10.0 23
15.0 27
Total mass
Emission
Factor
Condensible
Organics"
Uncontrolled*
Controlled* kg/Mg
11 0.14
32 0.57
35 0.65
2.5
Ib/ton
0.27
1.1
1.3
4.9
Controlled*
10~3 kg/Mg
0.53
1.6
1.7
4.9
3.9
10'3 Ib/ton
1.1
3.2
3.5
9.8
7.7
'Rounded to two significant figures.
"Aerodynamic diameter.
"Includes data from two tests out of eight where ~ 30% recycled asphalt paving was processed
utilizing a split feed, direct flame process.
"Based on an uncontrolled emission factor of 2.45 kg/Mg (see Table 3).
'Calculated using an overall collection efficiency of 99.8% for a baghouse applied to an
uncontrolled emission factor of 2.45 kg/Mg.
^Expressed in terms of emissions per unit weight of asphalt concrete produced. Not generally
applicable to recycle processes. Mg = 10* g; ton = 2000 Ib.
"Determined at outlet of a baghouse collector while plant was operating with ~ 30% recycled
asphalt paving. Factors are applicable only to a direct flame heating process using a split
feed.
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J. S. Kinsey is with Midwest Research Institute, Kansas City, MO 64110.
Dale L. Harmon is the EPA Project Officer (see below).
The complete report, entitled "Asphaltic Concrete Industry Paniculate
Emissions: Source Category Report," (Order No. PB 87-119 574/AS; Cost:
$30.95, subject to change) will be available only from:
National Technical Information Service
5285 Port Royal Road
Springfield, VA22161
Telephone: 703-487-4650
The EPA Project Officer can be contacted at:
Air and Energy Engineering Research Laboratory
U.S. Environmental Protection Agency
Research Triangle Park, NC 27711
United States
Environmental Protection
Agency
Center for Environmental Research
Information
Cincinnati OH 45268
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Penalty for Private Use $300
EPA/600/S7-86/038
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U S ENVIR PROTECTION AGfNCY
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