Document ID: EPA-HQ-OAR-2017-0685-0040
Agency: epa
Document Type: Supporting & Related Material
Title: 
Posted Date: 2019-06-04T04:00Z

MEMORANDUM
TO:		Paula Hirtz, U.S. EPA/OAQPS/SPPD
FROM:		Brian Palmer, Eastern Research Group, Inc.
DATE:		October 1, 2018
SUBJECT:	Summary of EPA Site Visit to the Alcoa Warrick Operations 
      The EPA visited the Alcoa Warrick Operations located at 4000 West State Road 66, Newburgh, Indiana on September 27, 2018 to collect background information for the risk and technology review for the Surface Coating of Metal Coil NESHAP (40 CFR part 63, subpart SSSS). The plant is a major source of HAP emissions and is therefore subject to the NESHAP. The site visit included a presentation and discussion about the coil coating operations and a facility tour that included the metal coil coating operations and the primary and secondary aluminum production operations. 
Attendees
Paula Hirtz, U.S. EPA/OAQPS/SPPD
Paul Versace, U.S. EPA/Office of General Council
Brian Palmer, ERG, Inc.
Scott Darling, EHS Manager, Alcoa Warrick Operations
Bruce Perkett, Coating Specialist, Alcoa Rigid Packaging, Alcoa Warrick Operations
Ken Hall, Alcoa Warrick Operations Manager of Fabricated Products
Nic Houghton, Alcoa Warrick Operations
Jill Mruk, Plant Systems Superintendent, Alcoa Warrick Operations
Shane Irvin, Alcoa Warrick Operations, Programs Coordinator
Will Richardson, Alcoa Warrick Operations, Air Programs
Background
      The Alcoa Warrick Operations facility is an integrated producer of coated aluminum coils. Located on the site is a coal fired electric power plant, a primary aluminum smelter, a secondary aluminum production facility, an aluminum hot rolling mill, and the coil coating facility. The facility first began operating in 1960 with the first primary aluminum production pot line. 
      The coil coating operations produce Food and Drug Administration (FDA) approved coated aluminum coils for aluminum cans and lids in the beverage, canned food, and pet food markets. The coated coil must be ready for contact with food because it is not washed before or after the can bodies and lids are formed and before it is in contact with the food or beverage. The beverage can bodies are made from uncoated aluminum coil and are washed after forming and before coating the interior and exterior of the cans. 
      The facility has three coating lines. Two are conventional liquid coating lines (CCL2 and CCL3) in which the coating is applied by metal rollers to both sides of the metal. The third line is an electrocoat line in which the coating is applied in an aqueous bath by a cathodic coating process. Each line is about 3,000 feet long. The coil coating lines run 24 hours per day, and 365 days per year, except during 2-day maintenance periods that occur about every 12 weeks. 
      The facility uses about 1.5 million gallons of coating per year.
Conventional Liquid Coating Lines
      The metal coils that are coated on CCL2 and CCL3 first go through a process on the line of trimming and flattening. The trimming is performed before the coating process so that the metal trimmings can be sent directly to the secondary aluminum production process, which can process only uncoated metal. 
      The metal strip is then pretreated with an acid washing and etching process using a solution of chromic, phosphoric, and hydrofluoric acids. The acid wash is sprayed on and then rinsed off with water. This acid wash primarily promotes adhesion of the final coating, and also provides protection from corrosion. The facility representatives reported that BPA-NI coatings (in which bisphenol-A is not intentionally added) did not perform well with pre-treatments that were free of chromic acid, especially for the metal used in can ends that have a pull tab opening. The facility representatives also reported that the HAP emissions from the acid wash process were minimal and offered to provide the stack testing results to EPA.
      The pretreated strip is then coated on both surfaces by separate sets of three rollers. In each set, the first metering roller is in a bath of coating. This metering roller transfers the coating to a second applicator roller that applies the coating to the metal strip, which is supported by a third backup roller. The second set of rollers coats the second side of the sheet. Both sets of rollers are located in a room enclosure, referred to as the H2 Room, with the operators who monitor the coating process and also clean the rollers when changing colors. The enclosure air is generally vented to a thermal oxidizer, except for air near the floor of the H2 Room, which is captured by floor sweeps and vented to the atmosphere.
      After coating, the metal strip passes to a heated bake oven with a temperature of 
650 degrees F. The metal strip is suspended on an air cushion as it passes through the heated bake oven and reaches a temperature of about 450 °F. A water spray quench is used to cool the metal after it comes out of the bake oven. The air from the bake oven is vented to the thermal oxidizer. Heat from the thermal oxidizer is recovered to help preheat the air in the bake oven.
      The facility representatives explained that because the air from the floor sweeps in the H2 Room is not sent to the thermal oxidizer, it does not qualify as a permanent total enclosure for compliance. However, the VOC captured by the floor sweeps and vented to the atmosphere on CCL2 and CCL3 represents only about 0.27 percent of the VOC used on CCL2 and CCL3 combined. The amount vented by the floor sweeps is based on a mass balance accounting of the amount of VOC in the coating, the amount of coating applied, and the amount of VOC measured at the inlet of the thermal oxidizers. The facility representatives noted that the cleaning operations that are performed inside the H2 Room are not part of the affected source covered by subpart SSSS, but most of the emissions from the H2 Room, excluding the emissions from the floor sweeps, are sent to the thermal oxidizer. So, even though the cleaning operations are not technically regulated by subpart SSSS, they are controlled.
      The H2 Room was built around the coater heads before subpart SSSS was proposed and promulgated. The room was built to reduce fire and explosion risk. The facility representatives may have some cost data for the construction of the H2 Room.
      Some of the coatings used on CCL2 and CCL3 are waterborne coatings, but water is not the only solvent. These coatings still contain some VOC and HAP solvents. Some of the coatings contain butyl cellosolve. Sherwin-Williams is the supplier for the CCL2 and CCL3. Methyl ethyl ketone (MEK) is used as a cleaning solvent and accounts for about 95 percent of the cleaning solvent use. Waterborne coatings are first cleaned from the equipment with water, and then MEK. The facility representatives noted that MEK is exothermically absorbed on activated carbon and can cause excessive heating if used with a carbon absorber air pollution control system.
Electrocoating Line
      The electrocoating line coats bare metal. It does not use the pretreatment process used on the conventional liquid coating lines CCL2 and CCL3. The metal coated on the electrocoating line is used exclusively for the tops of aluminum beverage cans. The two coatings used are FDA approved and are either clear or gold tinted with a relatively low percent of pigment. The coating is 30 percent solids as purchased but is 10 percent solids in the electrocoat bath.
      The clear coating is about 80 percent of the coatings applied on this line and has a HAP content of 0.006 kilograms HAP per liter of coating solids (kg/liter). The gold coating has a HAP content of 0.249 kg/liter.
      In order to maintain the same solids content in the bath and to remove low molecular weight compounds in the water, some water is constantly removed from the bath through microfiltration as coating is added and deposited on the metal. The result is that about 6-1/2 gallons of water is used for every 1 gallon of coating applied. The coating on the metal that leaves the bath is about 85 to 95 percent polymer and about 5 to 15 percent water. 
      The water that is removed from the bath is directed to a biological wastewater treatment facility that also treats the wastewater from CCL2 and CCL3.
      The electrocoating line is the only high speed line of its type in the United States and maybe the world. It was developed in close cooperation with the coating supplier PPG. The electrocoating advantages include the fact that all the coating is deposited on the metal, it is highly automated, there is minimal equipment cleaning, and because of the high flash point of the coating, it is safer than handling a solvent borne coating. 
      The metal is first washed, rinsed and then dried, and then submerged in the horizontal electrocoat bath. The metal acts as the anode while passing between a series of cathodes. After the bath, the metal is rinsed and then passes to the bake oven and reaches a temperature between 400 and 460 ℉. After the bake oven, the metal is cooled using an air quench. A thin layer of wax is applied to the coated metal to act as a lubricant as the can end is formed. 
Coating Storage and Mixing
      All of the coatings used are single component coatings and arrive ready to use, except for final adjustment of coating viscosity. The high volume coatings are delivered by tanker truck and are stored in an enclosed tank farm in which the tanks all have fixed roofs. The tank farm is subject to the Organic Liquids Distribution NESHAP, but the only compliance requirement is that the facility must certify that the coatings being stored are below the vapor pressure limits at which additional requirements would apply. The facility is not subject to any leak detection and repair requirements for the coating piping system.
      Coating viscosity is adjusted in the coating mixing room before the coating is delivered to the coaters. The facility representatives reported that emissions from the mixing room are minimal based on software used to estimate emissions from tanks and process vessels.
Compliance Performance
      The facility representatives reported that the latest overall removal efficiencies (ORE) considering both capture and control on CCL2 and CCL3 were measured at 99.77 percent and 99.56 percent. The thermal oxidizers are operated at 1350 °F and the minimum temperature during the most recent test was 1287 °F. The facility representatives reported that CCL2 and CCL3 usually achieve an emission rate between 50 and 75 percent of the limits in subpart SSSS. 
      The facility representatives use the ORE, coating usage, the coating information from the safety data sheets (SDS) for the coatings to calculate the VOC input to each coating line and to determine compliance. 
      The amount of coating on the finished coil is specified by the customer in units of milligrams per square inch of metal (mg/in[2]).
      The facility representatives reported that hourly variability in emissions is minimal and the only change in emissions is when they change to a different coating. Different coatings have different emission rates. They also reported that the ability to average across lines was an important tool for compliance and that the electrocoating line has helped their overall compliance through averaging.
Startup, Shutdown, and Malfunction
      The facility representatives discussed how they would handle an unplanned shutdown, if for example, the thermal oxidizer went off-line. The thermal oxidizer and the coating operations have an interlock such that if the thermal oxidizer loses power the coating head opens and coating application stops. A damper also closes the ventilation to the stack and the fans are automatically shut off. The H2 Room would be evacuated until the thermal oxidizer and the fans could be restarted. 
      If they have a planned shutdown of the thermal oxidizer, they remove all solvent from the H2 Room before the thermal oxidizer is shut down. The temperature on the thermal oxidizer is gradually lowered to 400 °F before it is completely shut down to allow for gradual cooling of the thermal oxidizer.