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- ------- 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. ------- 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. ------- 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 ^NA^X U-S-OFFICIAL MAt * f _- Official Business Penalty for Private Use $300 EPA/600/S7-86/038 0000329 PS U S ENVIR PROTECTION AGfNCY ------- |