                                                                               
DRAFT MEMORANDUM
DATE:	September 8, 2020
TO:		Korbin Smith, U.S. EPA OAQPS/SPPD/MMG
FROM:	SC&A Incorporated
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SUBJECT:	Industry Characterization for Carbon Black Production NESHAP                          
1.0 Purpose and Introduction	
The purpose of this memorandum is to provide an industry characterization for the carbon black production source category. This characterization is based on data/information gathered for the EPA's proposed Carbon Black Production Residual Risk and Technology Review (RTR), as well as historic information included in documents prepared in support of the 2002 National Emissions Standards for Hazardous Air Pollutants (NESHAP) promulgated for carbon black production major sources. 
Data/information gathered for purposes of the Carbon Black Production RTR includes data/information provided to the Agency through the Office of Enforcement and Compliance (OECA), Enforcement and Compliance History Online (ECHO) website, and the International Carbon Black Association (ICBA), of which 13 Carbon Black Production facilities are members. Based on this information, the EPA has determined that there are 15 Carbon Black Production facilities in the U.S., all of which are major sources of hazardous air pollutants (HAP) subject to the Carbon Black Production NESHAP. 
Section 2.0 of this memorandum describes the type and purpose of products covered by the carbon black production source category. Section 3.0 summarizes the manufacturing processes that produce the materials of the carbon black production source category. Section 4.0 details the emissions characteristics of carbon black production source category emission sources. 
2.0 Carbon Black Production Industry Characterization
Carbon black is used for a wide variety of applications, including reinforcing, pigments, conductivity, heat dissipation, and many others. Carbon black is used in the production of tires, belts, hoses, wire & cable sheathing, rubber & plastic moldings, roofing materials, seals & gaskets, toners, printing inks, paint and colorants, refractories, and all types of plastics. Approximately 90% of the produced carbon black is used in rubber applications, primarily automotive tires, with 9% used as a colorant for inks, paints, plastics, and paper, and the remainder used for hundreds of other diverse applications.
Carbon black production facilities included as part of the source category are facilities that produce carbon black via any of the three processes: furnace black, thermal black, or acetylene decomposition. Carbon black production is covered by the Standard Industrial Classification (SIC) code 2895 and the North American Industrial Classification System (NAICS) code is 325182. Two other production processes, the lamp black and bone black processes, are classified under SIC code 2816 (Inorganic Pigments) and are not included in the carbon black production source category.
The 15 identified carbon black production major source facilities are owned by 5 companies across 6 states, with facilities being primarily located in Texas and Louisiana, but also located in Kansas, Alabama, Oklahoma, and Ohio.[2]
3.0 Carbon Black Production Process
Carbon black is produced through partial oxidation or thermal decomposition of hydrocarbon substances. Many processes for carbon black production have been developed and are distinguished either by process (e.g., furnace black, lamp black, thermal black) or by raw material (e.g., acetylene black or bone black). The major components of carbon black production process unit include (1) a feedstock and raw materials section consisting primarily of feedstock storage tanks, (2) a production unit section consisting of one or more reactors, (3) a separation section that includes the filters, (4) a pelletization and densification section consisting of wet or dry pelletization equipment and densification, (5) a packaging and storage section that includes final product silos and packaging for pellets and powder, and (6) a shipping section that consists of storage and shipment of bags and bulk storage. Below is a brief description of each of the three carbon black production processes included in the carbon black source category (i.e., furnace black process, thermal black process, acetylene black process).
3.1 Furnace Black Process
The furnace black process is the process by which carbon black is produced via thermal-oxidative decomposition in a closed system. The furnace black process (representing 98 percent of carbon black production) involves the injection of a heavy petroleum-based feedstock into a closed reactor to atomize the feedstock oil under controlled conditions that primarily converts the feedstock into carbon black and hydrogen gas. The temperature within the reactor ranges from 1,300 to 1,700℃ and is rapidly quenched to about 1,000℃ to protect the carbon black product. The product stream then proceeds through heat exchanges to preheat the primary combustion air. Once the stream cools to about 270℃, the carbon black product is collected in a baghouse in a continuous process. Residual gas from the process is used as fuel (to produce heat, steam, or electric power), or redirected to a combustion device. 
Collected carbon black is transported to a micro-pulverizer, where it is further processed. The pulverized carbon black is conveyed to a cyclone and into the surge tank, which accumulates the product and serves as a reservoir to maintain a steady supply to the pelletizers. A non-HAP, water based liquid is added to the carbon black at the pelletizer to allow easier handling. Newly formed pellets are sent to a rotary dryer heated by natural gas and/or gas from the reactor. Dried product is then moved to storage tanks for shipment. Figure 1 presents a process flow diagram of the furnace black process.
3.2 Thermal Black Process
The thermal black process generally utilizes a natural gas feedstock, consisting primarily of methane or heavy aromatic oils, and two refractory lined furnaces that alternate on a cycle between production, preheating, and carbon black production. The feedstock is injected into one of the hot refractory lined furnaces, where in the absence of air, the heat from the refractory material decomposes the natural gas into carbon black and hydrogen. The product stream from the reaction between the two tanks is collected, cooled with water, and the carbon black is removed by a bag filter. The exiting carbon black may be further processed to remove impurities, pelletized, screened, and then packaged for shipment. The hydrogen off-gas is burned in air to preheat the second furnace.

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                        Figure 1. Furnace Black Process

                                       


3.3 Acetylene Black Process
The acetylene black process relies on the exothermic decomposition of acetylene at high temperatures, which is an attractive feedstock due to its high carbon content. Separation of the carbon black is similar to the furnace black process. However, the acetylene black process typically utilizes one reactor, as it is a continuous process. The reaction continuously occurs at 800 to 1000℃ in a refractory-lined, water-cooled metal retort. The decomposition is initialized by burning acetylene to bring the temperature to the desired level. Once the reaction temperature has been reached, the air supply is cut off to allow for decomposition of acetylene into carbon and hydrogen. The acetylene black process does not include a pelletization process. 
4.0 Emissions Characteristics
The primary HAP emitted by carbon black production facilities include carbon disulfide, carbon sulfide, lead, mercury, and hydrogen cyanide. Process vent emissions consist of tailgas from the reactors. The primary emission sources for these pollutants are the main unit filter (MUF) process vents. 
The 2002 Carbon Black Production NESHAP established maximum achievable control technology (MACT) emission limits for the MUF process vents. Main unit filter process vents with HAP > 260 parts per million (ppm) are required to use a flare or reduce HAP by 98 weight percent or to 20 ppm by volume (ppmv), whichever is less stringent, by venting through a closed vent system to any combination of control devices. Facilities routing emissions through a closed vent system to a control device/flare are required to conduct initial/annual leak inspections (and meet repair requirements when leaks detected) in accordance with Method 21 of 40 CFR part 60, appendix A.
Historically, the majority of facilities in the carbon black production industry utilized flares to control emissions from process vents. Due to State/Federal government and industry consent decree agreements that require additional control of criteria pollutants (particulate matter (PM)) from carbon black production facilities, all but one facility are transitioning from flares to incinerators.
Hazardous air pollutant emissions from process vents after the MUF were not regulated under the 2002 Carbon Black Production NESHAP because HAP emissions from these vents were considered insignificant.
The EPA's evaluation of equipment leaks under the 2002 Carbon Black Production NESHAP also found that leaks were not a significant source of HAP emissions for the carbon black production source category. One of the reasons for this is the low vapor pressures of the raw materials used in the production process (i.e., the typical carbon black feedstock is less than 0.05 kilopascals).
Similarly, the EPA's evaluation of the potential for HAP emissions from storage vessels indicated that they were not a significant source of emissions from carbon black production facilities. This is because the typical feedstock oil used in the carbon black production process is heavy fuel oil, which, because of its low vapor pressure, is not likely to be emitted to the atmosphere under normal operating conditions. In addition, the feedstock oil is nearly solid under standard pressure and temperature and typically needs to be heated to (and maintained at) 120 degrees Fahrenheit to allow it to flow as a liquid.
Lastly, the EPA did not identify any wastewater emissions of consequence as a result of the carbon black production process. The process uses a quench tower to capture the product, and the effluent guidelines applicable to this source category require that there be no discharge of process wastewater to navigable waters from carbon black production facilities.

