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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Official Business
Penalty for Private Use $300
EPA/600/S7-86/038
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