                                                                               
MEMORANDUM


DATE:	December 2019

SUBJECT:	Technology Review for Surface Coating Operations in the Metal Coil Category

FROM:	Eastern Research Group, Inc.

TO:		Paula Hirtz, OAQPS/SPPD/MMG


1.0	INTRODUCTION

Section 112 of the CAA requires the U.S. Environmental Protection Agency (EPA) to establish technology-based standards for listed source categories of hazardous air pollutants (HAP). These technology-based standards are often referred to as maximum achievable control technology (MACT) standards. The Surface Coating of Metal Coil NESHAP (40 CFR part 63, subpart SSSS), hereafter referred to as the Metal Coil NESHAP, regulates HAP emissions from facilities that are major sources of HAP and are engaged in the surface coating of metal coil. The final NESHAP was promulgated on June 10, 2002, and a technical correction was published on March 17, 2003.

Pursuant to 40 CFR 63.5090(c), the rule requires the use of MACT to reduce HAP emissions from a coil coating line on which more than 15 percent of the metal coil coated, based on surface area, is equal to or greater than 0.15 millimeter (0.006 inch) thick. If the facility also has a coating line that is subject to 40 CFR part 63, subpart JJJJ (NESHAP for Paper and Other Web Coating), then the facility can demonstrate compliance with subpart JJJJ by demonstrating compliance with subpart SSSS for all coating lines under certain circumstances. 

Section 112 also contains provisions requiring the EPA to periodically revisit these standards. Specifically, section 112(d)(6) states:

      (6) REVIEW AND REVISION.  -  The Administrator shall review, and revise as necessary (taking into account developments in practices, processes, and control technologies), emissions standards promulgated under this section no less often than every 8 years.

To comply with this CAA requirement, the EPA conducted a technology review for the Metal Coil NESHAP standard for major sources. This memorandum addresses the technology review for metal coil surface coating operations.

For the purposes of this review, the EPA considers a "development" in practices, processes, and control technologies to be:

 Any add-on control technology or other equipment that was not identified and considered during MACT standard development;
 Any improvements in add-on control technology or other equipment (that was identified and considered during MACT standard development) that could result in additional emission reduction;
 Any work practice or operational procedure that was not identified and considered during development of the original MACT standard; 
 Any process change or pollution prevention alternative that could be broadly applied to the industry that was not identified and considered during MACT standard development; and
 Any significant changes in the cost (including cost effectiveness) of applying controls (including controls the EPA considered during the development of the original MACT standards).

Section 2 of this memorandum presents a summary of the sources of data that were used to conduct the technology review and Section 3 presents the coil coating process description, the existing level of MACT control and control measures identified for the technology review for metal coil surface coating operations. 
2.0	SOURCES OF AVAILABLE CONTROL TECHNOLOGY INFORMATION

To identify any developments in practices, processes, or control technologies that could be applicable to surface coating operations in the metal coil industry, we consulted the following sources of data: RACT/BACT/LAER Clearinghouse, the California Statewide Best Available Control Technology (BACT) Clearinghouse, regulatory actions promulgated for other surface coating NESHAP subsequent to the Metal Coil NESHAP, state regulations and operating permits, site visits, and industry information from individual facilities and the industry trade association. Our findings are discussed in the following sections. 

2.1	RACT/BACT/LAER Clearinghouse Database

Under the EPA's New Source Review (NSR) program, if a company is planning to build a new plant or modify an existing plant such that criteria air pollution emissions will increase by a certain amount, then the company must obtain an NSR permit. The NSR permit is a construction permit which generally requires the company to minimize air pollution emissions by modifying the process to incorporate pollution prevention measures and/or installing air pollution control equipment. 

The terms "RACT," "BACT," and "LAER" are acronyms for different program requirements relevant to the NSR program.  RACT, or Reasonably Available Control Technology, is required on existing sources in areas that are not meeting national ambient air quality standards (non-attainment areas). BACT, or Best Available Control Technology, is required on new or modified major sources in clean areas (attainment areas). LAER, or Lowest Achievable Emission Rate, is required on new or modified major sources in non-attainment areas. 

BACT and LAER (and sometimes RACT) are determined on a case-by-case basis, usually by state or local permitting agencies. The EPA established the RACT/BACT/LAER Clearinghouse, or RBLC, to provide a central database of air pollution technology information (including past BACT and LAER decisions contained in NSR permits) to promote the sharing of information among permitting agencies and to aid in future case-by-case determinations. However, data in the RBLC are not limited to sources subject to RACT, BACT, and LAER requirements. Noteworthy pollution prevention and control technology decisions and information on cost effectiveness may be included even if they are not related to past RACT, BACT, or LAER decisions. 

The RBLC contains over 5,000 air pollution control permit determinations that can help identify appropriate technologies to mitigate most air pollutant emission streams. It was designed to help permit applicants and reviewers make pollution prevention and control technology decisions for stationary air pollution sources, and includes data submitted by U.S. territories and all 50 states on over 200 different air pollutants and 1,000 industrial processes. 

The RBLC provides several options for searching the permit database on-line to locate applicable control technologies. On December 29, 2016, we conducted a search of the RBLC.  Our search specified processes in the metal coil surface coating category, with permits dating back to 1970. The search results included the following data fields:
 
       RBLC ID;
       Facility Name, and State;
       Permit Date;
       Process name;
       Pollutant;
       Control technology; and
       Percent efficiency of control.

A search conducted on September 19, 2017, revealed that the EPA's RBLC and the state of California's BACT clearinghouse have no records specific to coil coating operations.  The EPA's RBLC had no records specific to the coil coating process code (except for an erroneous entry for dip coating the copper wire coils used in electric motors), and no records were found for a search on the key words "coil," "roll coating," or "roller coating." The search of the state of California's BACT clearinghouse did not result in a BACT determination for the only known major source metal coil coating facility in California. We also collected and conducted a comprehensive review of state operating permits, discussed in Section 2.3 of this report.

2.2	Subsequent Regulatory Actions

Regulatory actions promulgated subsequent to the March 10, 2002, NESHAP were identified for similar surface coating operations. These regulatory actions, listed in Table 1, were reviewed for developments in practices, processes and control technologies.

Table 1. Subsequent Regulatory Actions for Sources Similar to Metal Coil Coating Operations

                             Major Source Standard
                                    Subpart
                               Date Promulgated
           Practices, Processes, and Control Technologies Evaluated
                      Surface Coating of Large Appliances
                                     NNNN
                                   7/23/2002
Emission limit as mass HAP per volume solids used. Controls include low-HAP coatings, permanent total enclosures and add-on controls (carbon adsorbers, condensers, thermal and catalytic oxidizers).
                          Paper and Other Web Coating
                                     JJJJ
                                   12/4/2002
Emission limit as wt % HAP reduction, wt % HAP in coating, mass HAP emitted per mass solids used, and thermal oxidizer outlet concentration. Controls include low solvent, waterborne, UV-cure, hot melt, and reactive resin coatings; oxidizers (thermal and catalytic), carbon adsorbers, condensers.
          Printing, Coating, and Dyeing of Fabrics and Other Textiles
                                     OOOO
                                   5/29/2003
Coating and Printing: Emission limit as mass HAP per mass solids used. Controls include low solvent, waterborne, UV-cure, hot melt, and reactive resin coatings; oxidizers (thermal, regenerative thermal, and catalytic); and carbon adsorbers.
           Surface Coating of Miscellaneous Metal Parts and Products
                                     MMMM
                                   1/2/2004
Emission limit as mass HAP per volume solids used. Controls include low-HAP coatings, ultraviolet (UV) curable electron beam (EB) curable coatings, powder coatings, add-on controls.
                 Surface Coating of Plastic Parts and Products
                                     PPPP
                                   4/19/2004
Emission limit as mass HAP per mass solids used. Controls include low-HAP coatings, UV and EB curable coatings, add-on controls.
             Surface Coating of Automobiles and Light-Duty Trucks
                                     IIII
                                   4/26/2004
Emission limit as mass HAP per volume solids deposited. Develop and implement a work practice plan to minimize organic HAP. Controls include low-HAP coatings, high efficiency application methods, and add-on controls.
                      Technology Review of MACT Standard
                                    Subpart
                               Date Promulgated
   Practices, Processes, and Control Technologies Identified as Developments
                                 Magnetic Tape
                                      EE
                                   4/7/2006
                                No developments
                            Printing and Publishing
                                      KK
                                   4/21/2011
          Permanent total enclosures installed on controlled presses.
                         Shipbuilding and Ship Repair
                                      II
                                  11/21/2011
 Concentrator/RTO installed on spray booths to achieve 95% control efficiency.
                         Wood Furniture Manufacturing
                                      JJ
                                  11/21/2011
RTO; Lower VOC coating limits based on California regional rules; more efficient spray guns; limit formaldehyde emission to 400 lb per rolling 12-month period. Bans conventional spray guns except when the overspray is routed to a control device.
                 Aerospace Manufacturing and Rework Facilities
                                      GG
                                   12/7/2015
                                No developments

Developments identified in the regulatory actions listed in Table 1 are discussed in more detail in Section 3 (Technology Review for Surface Coating Operations).

2.3 State Regulations and Operating Permits

Using a collection of data sources, including the EPA's Enforcement and Compliance History Online (ECHO) and the National Emission Inventory (NEI) databases, a total of 54 facilities from 21 states were identified as metal coil coating operations.

Because there were no RBLC records for coil coating, we conducted a comprehensive review of the state operating permits that were available on-line. In total, 39 permits were collected. The permit review revealed that 37 of the 39 facilities had add-on controls and 3 of the 39 facilities had only partial control (i.e., not all coil coating lines had control). 

The VOC emission limits in the state permits have various units of measure. Several permits restrict the emission rate (e.g., lb/hr, ton/yr) to avoid major source status while others are linked to VOC content delivered to the coater head. No permit had a VOC limit lower than the Metal Coil NSPS published in 1982 (40 CFR 60, subpart TT). 

Eight states and one local jurisdiction listed in the table below were identified that had regulations that control VOC emissions from metal coil coating. All of the eight states require the 2.6 lb VOC/gallon coating (less water and exempt volatiles) limit included in the 1977 EPA CTG (Pennsylvania specifies an equivalent limit in lb VOC /gallon coating solids). Chicago, IL, specifies a VOC content limit more stringent than the CTG limit. Five rules (Chicago, MO, OH, SC, and WI) also define the performance expectations for control systems.

Table 2. State and Local VOC Regulations

                          State or Local Jurisdiction
                                       
                                   Citation
                                       
                              VOC Content Limits*
                                       
                               Additional Limits
Chicago, Illinois
35 IAC 218.204(d)
1.7 lb/gallon 
Restricts VOC emissions over time (8.0 lb/hr). As an emission limit alternative, a capture/control system must provide 81% reduction and the control device must have 90% efficiency.
Indiana
326 IAC 8-2-4
2.6 lb/gallon
None
Missouri
10 CSR 10-5.330
2.6 lb/gallon
Limits can be achieved with low solvent technology and add-on control. A control system must have 90% efficiency or greater.**
New Jersey
N.J.A.C. 7:27-16.7(c)1
2.6 lb/gallon
-
Ohio
OAC 3745-21-09(B)(3)(n)(6) and 
OAC 3745-21-09(E)


2.6 lb/gallon
If a control system is employed, the limit is 4.0 lb VOC/gallon solids.
A control system must provide no less than 81% reduction of overall emissions and an efficiency of no less than 90%.
Pennsylvania
25 Pa. Code §129.52
4.02 lb/gallon coating solids
Restricts VOC emissions over time (3.0 lb/hr; 15 lb/day; 2.7 ton/yr).
South Carolina
61-62.5, Standard No. 5, Section II(F)(2)(b)
2.6 lb/gallon
Ways to meet the limit: 1) low solvent technology; 2) incineration that oxidizes 90% of non-methane VOC; 3) others approved case-by-case.
Texas
30 TAC Chapter 115
2.6 lb/gallon
None
Wisconsin
NR 422.06(2)
2.6 lb/gallon

Cleaning:
0.42 lb/gallon *** (beginning 3/1/2013)
Incineration or catalytic oxidation must oxidize 90% of non-methane compounds [see NR 422.04(2)(c)].

Cleaning operations also have work practice requirements.
*    Unless noted otherwise, all VOC content limits are in units of pounds VOC per gallon coating, less water and
       exempt volatiles. The Pennsylvania limit is equivalent to 2.6 lb/gallon coating.
**   State regulation control system efficiency calculations do not consider gas capture efficiency. 
*** The WI rule is not clear whether this is less water and exempt solvents. However, it is not unusual to have  
       VOC limits for cleaning solvents that do not exclude water and exempt solvents because many cleaning 
       solvent alternatives are water-based and they are not designed to leave behind a solid film on the cleaned
       equipment.

The operating permits for three facilities listed in Table 3 below include a limit on individual HAP. While the NESHAP restricts the total HAP relative to the amount of coating solids used, the three permits limit the HAP emissions released over time (i.e., lb/hr or tons/year). The individual HAP were formaldehyde, methanol, cresols and cresylic acid. 

Table 3. Operating Permits with Individual HAP Limits

                                   Facility
                                     State
                                  Permit Date
                                   Pollutant
                                     Limit
Agfa Corp.
                                      NJ
                                  10/21/2013
                                   Methanol
                             Cresols/Cresylic Acid
                                2.00 tons/year
                                0.12 tons/year
Precoat Metals
                                      WV
                                  8/26/2008*
                                 Formaldehyde
                                 0.04 lb/hour
Jupiter Aluminum Corp.
                                      WV
                                  11/10/2012
                                 Formaldehyde
                                 0.26 lb/hour
                               (0.37 tons/year)
* This permit remains active; the renewal application was submitted prior to the due date.

The EPA also identified four facilities, all from the same company, that are sources of hexavalent chromium (Cr-VI) from coil coating operations, according to the 2011 NEI. We found no operating permits that included a limit on Cr-VI. Industry information indicated that for the past 20 years, the coil coating producers have worked unsuccessfully to replace the hexavalent chromate ion with more benign corrosion-inhibiting species that give the same long-term protection to metals. The EPA contacted representatives from the National Coil Coaters Association (NCCA) and the company reporting the Cr-VI to ask about the specific emissions and emission sources. The company reporting the chromium compound emissions reported that it had always assumed that a small percentage of the chromium compounds deposited on the metal coil during the coil pretreatment and the curing of the prime coat were emitted as aerosolized chromium but did not provide a mechanism to explain why that would happen and did not have the analytical data to support the claim. The EPA reviewed all studies related to Cr-VI and did not find a study on the aerosolization of chromium from processes similar to the coil coating processes. The industry representatives also reported that they had communicated with the pretreatment process and coating vendors, who all reported that the chromium compounds in the pretreatment process and in the coatings should not enter the atmosphere because they are not volatilized at the temperatures of the curing ovens or the thermal oxidizers used as controls. 

2.4 Site Visits

The EPA conducted two site visits to metal coil surface coating facilities in support of this technology review. These facilities were: Precoat Industries located in Columbia, South Carolina and Alcoa Warrick Operations located in Evansville, Indiana. Site visit reports for these facilities are included in the Metal Coil docket (Docket ID No. EPA-HQ-OAR-2017-0685).

2.5 Industry Information

Industry Background

We gathered industry background information from a variety of sources to support the coil coating technology review including the National Coil Coaters Association (NCCA) and the American Coatings Association's (ACA) Industry Market Analysis (9[th] edition). The NCCA is the industry's trade association. It lists 73 members on its web site, some of which are coating manufacturers and material suppliers to the industry and are not coil coaters.  

The ACA market analysis of the coil coating industry is concentrated in Chapter 14 titled "Metal Building Products for Aluminum Extrusions and Siding." The ACA market analysis noted that about 75 percent of coil coated metal is used in metal building products for sidewalls, siding, roofing, garage doors, and entry doors; 11 percent of coil coated metal is used to construct appliances and metal office furniture; 9 percent of coil coated metal is used by the transportation sector for side panels for trailers and numerous automotive parts; and the remaining 5 percent of coil coated metal is used in miscellaneous applications. Pre-coated coil substrate provides an alternative to in-house painting by facilities that manufacture the metal products (original equipment manufacturers or OEMs) because coil coating eliminates OEM paint lines and the resulting HAP and VOC emissions. The ACA market analysis reported that using coil coating as an alternative to in-house liquid coatings for OEMs has grown, particularly during the 2010-2012 period. 

The market analysis reported that in 2014, coil and extrusion coatings accounted for 28.7 million gallons worth $908 million and described the coil coating market as a mature market. Some products, such as cementitious board, stucco, vinyl siding, and structural plastic substrates, compete with coil coated metal as a building product and the use of OEM powder coating competes with coil coated metal in the home appliances market. However, the growth in metal roofs could lead to increased demand for coil coated metal. The market analysis also reported that coil coaters have put an emphasis on thinner film coatings, and this practice has contributed to flat volume growth of coil coating consumption.

The market analysis reported that three coating companies supply 80 percent of the market with coil coatings and that 75 percent of coil coated metal, by area, is steel and the remainder is aluminum.

Coating Chemistry Background

The ACA market analysis reported that a variety of unique coating chemistries with special properties (formability, durability, weatherability, damage resistance, and corrosion, chemical and stain resistance) are used in the coil coating market. The coatings used for coil coating are often determined by the original equipment manufacturers (OEMs) who fabricate products from the coated metal and bring them to market. These coatings include:

 Polyester coatings especially engineered for appliance needs require properties for appearance, stain resistance, and resistance to damage during shipping. 
 Weatherable polyester coatings dominate the industry among non-architectural coatings, such as the sidewalls of truck trailers. Other common coating types include epoxies, epoxyacrylics, and acrylics.
 Fluropolymer coatings, such as polyvinylidenedifluoride (PVDF), have excellent weatherability characteristics and provide 20- to 40-year or lifetime warranties. These coatings are typically used on exterior metal cladding and roofing in commercial and residential applications and are more expensive than non-fluorinated resins.
 Siliconized polyesters are also used on exterior construction panels. They are intermediate in price between PVDF coatings and weatherable polyester coatings. 
 Plastisol coatings, based on polyvinyl chloride, are used in construction applications where chemical resistance is needed, such as chemical plants, smelting operations, and agricultural animal containment.
 Chromated coatings, such as primers containing strontium chromate (hexavalent chromium) are used for their corrosion protection properties.
      
The ACA market analysis notes that coil coaters have been working for the past 20 years to replace primers that contain hexavalent chromium (associated with strontium chromate) with primers that have the same performance in long term protection of metal. The analysis noted that this has been an issue in Europe and could also become an issue in the Asia Pacific region. 
         
Waterborne coatings are seldom used and powder coatings are not used for coil coating applications. The ACA market analysis stated that less than 1 percent of all coil coatings were waterborne coatings in 2014. The analysis predicted that the use of waterborne coatings was not likely to increase because they do not have the same properties as solvent borne coatings and require greater heat to drive off water and cure than solvent borne coatings. Powder coatings are not feasible for coil coating because they require slower line speeds, and film thickness is harder to control, compared to liquid coatings, according to the ACA market analysis.

Background on Control of Emissions

The ACA market analysis reported that U.S. coil coating facilities generally have thermal oxidizers to control VOC and HAP emissions, which agrees with our permit review. State operating permits showed that all but two facilities were equipped with a thermal oxidizer on at least one coil production line. The thermal oxidizers use the organic paint solvent vapors as a fuel supplement and return the heat to their curing ovens or use the heat elsewhere in the facility. The ACA market analysis also noted that because the solvent emissions are already controlled, coil coaters have little incentive to convert to waterborne coatings. Similarly, the coil coaters have little interest in ultraviolet or electron beam cured coating technologies because coil coaters believe that the energy costs would be higher than with thermally cured coatings.

3.0	TECHNOLOGY REVIEW FOR SURFACE COATING OPERATIONS

Process Description and Emission Sources

The metal coil coating process is a continuous operation that begins with a roll or "coil" of bare sheet metal and ends with a coated roll or coil of sheet metal that has a surface finish on one or both sides. Coil coated metals (generally steel and aluminum) are used in the manufacturing of products that require bending and stretching the coated metal into the appropriate shape for the final product with little or no cracking of the coating.

A typical coil coating line consists of an inlet station, where the metal strip is unrolled from the coil and enters the process; a metal cleaning and pretreatment section, where the metal is prepared for the coating application; a coating section, which may consist of a single coating station and curing oven or may consist of a prime coating station and curing oven and a finish coating station and curing oven; and an exit station, where the finished metal strip is repackaged into a roll or coil.

The normal technique by which coatings are applied in the coil coating industry is roll coating. In this technique, a roller picks up the coating and transfers the coating to the moving metal strip. Roll coating is considered to have 100 percent transfer efficiency. Coil coatings are applied in two main steps: prime coat and finish coat. Prime coat and finish coat operations both contribute to VOC and HAP emissions.

The VOC and HAP emissions result from the evaporation of organic solvents from the applied coating during the drying process. These coatings generally contain organic solvents such as ketones, esters, ethers, and aromatics. The major HAP emitted from the metal coil coating process, according to the 2011 and 2014 NEI, include xylenes (isomers and mixtures), glycol ethers, toluene, naphthalene, isophorone. ethyl benzene, and methyl isobutyl ketone. Methyl ethyl ketone (MEK) is also used as a solvent in these coatings, but MEK was removed from the list of HAP in December of 2005. It is unlikely that this delisting impacted the list of major sources, pursuant to 40 CFR 63.5130(a), because the compliance date for existing metal coil surface coating sources was June 10, 2005, before the MEK delisting date. 

3.1	Summary of Existing MACT Level of Control

The Metal Coil NESHAP promulgated first in 2002 limits emissions of HAP from major sources that coat metal coil. The portions of the metal coil coating line to which the emission limits apply are the coating application stations and associated curing ovens. The wet section/pretreatment and quench operations are part of the metal coil coating line but are not subject to the emission limitations. A coil coating line does not include ancillary operations such as mixing/thinning, cleaning, wastewater treatment, and storage of coating material.

The Metal Coil NESHAP provides options for limiting organic HAP emissions to one of the following specified levels (these compliance options apply to an individual coil coating line, to multiple lines as a group, or to the entire affected source):

 Use only individually compliant coatings with an organic HAP content that does not exceed 0.046 kg/liter of solids applied. 
 Use coatings with an average organic HAP content of 0.046 kg/liter of solids on a rolling 12-month average. 
 Either a capture system and add-on control device to reduce emissions by 98 percent or use a 100 percent efficient capture system and an oxidizer to reduce organic HAP emissions to no more than 20 ppmv as carbon.
 Use a combination of compliant coatings and control devices to maintain an average equivalent emission rate of organic HAP not exceeding 0.046 kg/liter of solids on a rolling 12-month average basis.

Capture systems are designed to collect solvent-laden air and direct it to a control device. When an entire emission source is enclosed such that 100 percent of the emissions and ventilation air is directed to a control device, the capture system is called a permanent total enclosure (PTE). EPA Method 204 outlines the criteria for the design and operation of a PTE. 

A 98-percent facility-wide coating line overall control efficiency (i.e., the PTE capture efficiency multiplied by the HAP destruction efficiency) was determined to be the MACT floor for both existing and new coil coating sources. Most facilities had installed thermal oxidizers to control emissions of VOC per NSPS (40 CFR Part 60 subpart TT) requirements prior to MACT development (see Section 3.3.1 for a more comprehensive breakdown of exiting controls). The thermal oxidizers use the organic solvent vapors from the paint as a fuel supplement and return the heat to curing ovens or use the heat elsewhere in the facility. When developing the Metal Coil NESHAP, the EPA determined whether existing thermal oxidizers would need to be upgraded or replaced according to their remaining useful life and the associated costs and emission reductions. In this analysis for existing sources, the EPA estimated a cost effectiveness of approximately $4,500 to remove each ton of HAP. 

The standard also sets operating limits for capture systems and add-on control devices. These limits are presented in Table 1.  

Table 1. Subpart SSSS Operating Limits for Capture Systems and Add On Control Devices

Control Device
                                Operating Limit
1. Thermal oxidizer
a. The average combustion temperature in any 3-hour period must not fall below the combustion temperature limit established according to §63.5160(d)(3)(i).

Note: Per the U.S. EPA's Applicability Determination Index Control Number M040025, for facilities using thermal incinerators, the MACT subpart SSSS effluent gas monitoring requirements may be streamlined with the similar NSPS subpart TT monitoring requirements.
2. Catalytic oxidizer
a. The average temperature measured just before the catalyst bed in any 3-hour period must not fall below the limit established according to §63.5160(d)(3)(ii); and either

b. Ensure that the average temperature difference across the catalyst bed in any 3-hour period does not fall below the temperature difference limit established according to §63.5160(d)(3)(ii); or

c. Develop and implement an inspection and maintenance plan according to §63.5160(d)(3)(ii).
3. Emission capture system
Develop a monitoring plan that identifies operating parameters to be monitored and specifies operating limits according to §63.5150(a)(4)

The rule does not specify work practice standards to minimize organic HAP emissions. 

To collect data for the MACT floor, the EPA sent a total of 110 companies performing metal coil surface coating surveys in 1996 and 1997 with questions on HAP use and emission controls in metal coil surface coating operations. A total of 89 coil coating facilities representing 105 coil coating lines returned completed questionnaires. All of the 105 coating lines had some sort of add-on emissions control, as follows:

 79 had thermal oxidizers;
 24 had catalytic oxidizers;
 2 had condenser/scrubber systems.

In addition, 45 of the coating lines were reported to be fitted with PTE to capture emissions. Following the survey, the EPA conducted a study to confirm the quality of capture and control efficiency data. Based on the verified data, the EPA determined at proposal that the MACT floor was the use of a PTE and a thermal oxidizer capable of achieving at least 98 percent organic HAP destruction efficiency, for an overall capture and control efficiency of 98 percent. The EPA could not identify any control technologies more stringent than the MACT floor technology. The EPA did not revise the MACT determination in the final rule as a result of any new information received in public comments.  

3.2	Identified Control Measures for Surface Coating Operations

The practices, processes, and control technologies evaluated for rules promulgated subsequent to the Metal Coil NESHAP (the area source rules and NESHAP listed in Table 2 above) and their applicability to metal coil coating are discussed in the following sections. 

3.2.1	Add-On Control Technology or Other Measures Not Identified and Considered During MACT Development 

The following measures were identified and considered during MACT development, but were not considered to be feasible, based on industry comment or on information that was gathered about the coil coating process from industry publications and from various EPA background documents and publications. Therefore, we do not consider these measures to represent a development under CAA section 112(d)(6).

Waterborne coating: Waterborne coatings generally produce lower levels of organic emissions, as compared to uncontrolled solvent borne coatings, but they are not available in formulations that are suitable for all coil coating end-product applications.  Furthermore, coil coaters themselves generally have solvent destruction systems in place, which enables them to use organic paint solvents as a fuel supplement. 

Low energy electron beam/ultraviolet (EB/UV) cured coatings: Since the early 1990s (when commercial scale UV/EB surface coating technology production lines began operation) technical advancements in acrylate functional polymer chemistry have increased. These advancements improved weathering characteristics and film adhesion and the use of UV/EB technology.  Compared with conventional hot air drying and curing methods, EB/UV curing may eliminate the need for large thermal ovens and solvent incinerators, and could reduce energy needs. However, US coil coating facilities generally believe that the cost of the energy required to cure UV and or EB coating would be higher than current costs associated with conventional thermally cured coatings.
      
Powder Coating: Powder coating is not used on U.S. coil coating lines. Coil powder coating would require slower line speeds and would not provide coil coaters the ability to control film thickness and edge overlap.[,] [,] 

Carbon Adsorption: Although technologically feasible, the 1998 NESHAP survey confirmed that no U.S. coil coaters used carbon adsorption. The high temperature of the oven exhaust would inhibit adsorption of volatile organic compounds on activated carbon in the adsorber beds. Adsorption is usually used only for coating application exhaust streams at temperatures below and no higher than approximately 100°F. Desorption using heated air or steam, to remove bound pollutants and regenerate the adsorber beds, begins at about 250°F. 

Subsequent NESHAPs:

The following subsequent surface coating NESHAP identified PTE and RTO as developments in add-on control technology. The Metal Coil NESHAP already includes a compliance option involving the use of a PTE and an add-on control device and these were considered in the development of the Metal Coil NESHAP, so they do not represent a development in control technology under CAA section 112(d)(6).

Printing and Publishing: The EPA examined the option of retrofitting permanent total enclosures (PTE) onto controlled presses that do not already have PTEs. A PTE improves the capture of solvent HAP from inks and delivers the additional captured solvent HAP to a control device. 

Shipbuilding and Ship Repair: The EPA identified an add-on control device, a concentrator/RTO, installed in 2009 at one shipbuilding and ship repair facility in California. The control device consisted of rotary concentrators followed by RTOs on five large, custom-built spray booths to control volatile organic emissions from some of the coating operations. The system is capable of achieving 95 percent control efficiency for the VOHAP emissions captured by the spray booths (which were estimated to capture 90 percent of the VOHAP emissions). 

Wood Furniture Manufacturing: The technology review identified the use of a RTO on a spray booth as a development for the coating of flat panels using an automated high-speed coating process. The technology review identified one facility using this control and fewer than five facilities that could install this technology. 

3.2.2	Improvements in Add-On Control Technology or Other Equipment for Organic HAP Emissions That Were Identified and Considered During MACT Development

In addition to the review of regulatory actions promulgated subsequent to the Metal Coil NESHAP, other data sources were considered, including the RBLC, state regulations, and industry information, as discussed in sections 2 and 3. Our review concluded that there are no improvements in add-on control technology or other equipment. The add-on controls that are now available have essentially the same emission reduction performance (i.e., 98 percent volatile organic compound destruction efficiency) as those that were available when the NESHAP was proposed and promulgated. 

3.2.3	Work Practices and Procedures Not Identified and Considered During MACT Development

No additional work practices or procedures were identified that could be applied to the affected source that were not already identified and considered during MACT development. The facility survey, conducted during MACT development, revealed that several types of work practices and housekeeping techniques were being used. 

Identified procedures included:

 Improving substrate pretreatment methods to control the amount of chemicals being discarded.
 Optimizing production run scheduling to generate long production runs per color to reduce color changeovers.
 Keeping all containers covered at all times except during filling and emptying operations.
 Cleaning coating rolls and pans inside enclosed coating booths to ensure that emissions are captured and controlled.
 Keeping all solvent soaked rags in closed containers.
 Reducing paint spillage when filling totes.
 Improving paint inventory systems by tracking and recording paint consumption on a revised manufacturing order which facilitates the prioritization of drums of paint such that the shelf life is not exceeded, thus reducing the amount of hazardous waste resulting from degraded paint.
 Conducting employee training and awareness programs to aid in the implementation of process changes designed to minimize paint-related waste generation.
 Conducting training and department housekeeping inspections.

The facility survey identified the following work practices for coating line cleanup
operations:
 Cleaning solvent is typically transferred into closed containers which are then used to dispense the solvent at the production line.
 Soak tanks used for cleaning rollers or other miscellaneous parts removed from the line are typically equipped with covers.
 Containers that are typically used to collect liquid waste are equipped with covers.
 Solvent-soaked rags are stored in closed containers or are compressed to remove free solvent before storage.

However, the final rule applied only to the coating application stations and the associated curing ovens (i.e., the affected source). The final rule did not apply to coating storage and mixing/thinning operations and did not apply to the equipment cleaning operations which are the primary operations to which the work practices would have been applied. No other work practices or procedures were included in the final rule. 

3.2.4	Any process change or pollution prevention alternative that could be broadly applied that was not identified and considered during MACT development.

Pollution prevention (P2) alternatives, including coating product reformulations, are currently used by the metal coil industry and were considered during the MACT floor development, specifically high solids and waterborne coatings. Cleaning is excluded from the definition of a coil coating line in the Metal Coil NESHAP, and cleaning operations are not regulated. It should be noted that all subsequent NESHAP, listed above in Table 1, contain P2 measures. Because P2 measures were considered in development of the Metal Coil NESHAP, they do not represent a development in control technology under CAA section 112(d)(6). It should also be noted that any P2 measures that have to do with cleaning would not apply to the coil coating NESHAP since that activity is excluded from the rule. The NESHAP survey data showed that parts and equipment cleaning contribute approximately four percent of HAP emissions from coil coating operations. 


 Any significant changes in the cost (including cost effectiveness) of applying controls (including controls the EPA considered during the development of the original MACT standards). 

As discussed above, a 98-percent facility-wide coating line overall control efficiency was determined to be the MACT floor for both existing and new coil coating sources. Most facilities had installed thermal oxidizers to control emissions of VOC per NSPS (40 CFR Part 60 subpart TT) requirements prior to MACT development. When developing the Metal Coil NESHAP, the EPA determined whether existing thermal oxidizers would need to be upgraded or replaced according to their remaining useful life and the associated costs and emission reductions. In this analysis for existing sources, the EPA estimated a cost effectiveness of approximately $4,500 to remove each ton of HAP. 

The information collected for this technology review has confirmed that the majority of facilities continue to comply with the emission limits by using thermal oxidizers. It was also confirmed that the thermal oxidizers use the organic solvent vapors from the paint as a fuel supplement and return the heat to curing ovens or use the heat elsewhere in the facility. These cost savings have not been documented but would result in a lower cost effectiveness if they could be quantified. 

The EPA did not identify any developments in processes, practices or control technologies for the metal coil source category as a result of this technology review. Therefore, we did not re-evaluate the cost (or cost-effectiveness) of applying additional add-on controls.  

