1

MEMORANDUM

DATE: June 22, 2015

SUBJECT: Section 112(d)(6) Technology Review for the Final Wool F iberglass NESHAP

FROM: Susan Fairchild, EPA/OAQPS/SPPD/MMG

TO: Docket EPA-HQ-OAR-2010-1042

1.0 Introduction

This memorandum presents the results of a review on the developments in practices, processes, and control technologies that apply to wool fiberglass man ufacturing, and specifically to sources subject to the national emission standards for hazardous air pollutants (NESHAP) for Wool Fiberglass Production (40 CFR 63, subpart NNN). This analysis is part of the U.S. Environmental Protection Agency’s (EPA’s) review efforts in accordance with section 112(d)(6) of the Clean Air Act (CAA). Section 2 of this memoran dum provides background information on the requirements of section 112(d)(6) of the CAA, the wool fiberglass source category, and the requirements of the Wool Fiberglass NESHAP. Section 3 discusses the review of information on developments in practices, processes, and control techno logies that have occurred since the original development of this NESHAP. Section 4 summariz es the technology review findings.

2.0 Background

2.1 Requirements of Section 112(d)(6) of the CAA

Section 112 of the CAA requires the EPA to establish techn ology-based standards for sources of hazardous air pollutants (HAP). These technology-based s tandards are often referred to as maximum achievable control technology, or MACT, standards. Section 112 also contains provisions requiring the EPA to revisit these standards. Spe cifically, CAA section 112(d)(6)

states:

(6) REVIEW AND REVISION. – The Administrator shall r eview, and revise as necessary (taking into account developments in practices , processes, and control technologies), emission standards promulgated under this sec tion no less often than every 8 years.

For the purpose of this technology review, a “developmen t” was considered to be any of the following:

• Any add-on control technology or other equipment that was not identified and considered during the development of the NESHAP;

• Improvements in add-on control technology or other equipm ent that were not identified and considered during NESHAP development that could result i n significant additional HAP emissions reductions;2

• Work practice or operational procedure that was not identifi ed and considered during NESHAP development; and

• Process change or pollution prevention alternative that could be broadly applied that was not identified and considered during the development of the NESHAP.

2.2 Description of Source Category and NESHAP Requirements 1

Wool fiberglass manufacturing is the high-temperature co nversion of various raw materials into a homogeneous melt, followed by the fabrication of this m elt into glass fibers. Wool fiberglass production can be segmented into three phases: raw materi als handling, glass-melting, and wool glass fiber forming and finishing. The primary component of glass fiber is sand, but it also includes varying quantities of feldspar, sodium sulfate, anhydr ous borax, boric acid, and many other materials. In the glass-melting furnace, the raw materials are heated to a high temperature and are transformed through a sequence of chemical reacti ons to molten glass. Although there are many furnace designs, furnaces are generally large, sh allow, and well-insulated vessels that are heated from above. In operation, raw materials are introduced continuously on top of a bed of molten glass, where they slowly mix and dissolve. Mixing is effected by natural convection, gases rising from chemical reactions, and, in some opera tions, by air or oxygen injection into the bottom of the bed. Oxygen is also used as a fuel and repl aces air at some furnaces.

Glass-melting furnaces vary in fuel source and method of heat application into four types: recuperative, regenerative, unit, and electric melter. Pr ior to 1999, the recuperative, regenerative, and unit melter furnaces could be fueled by either gas or oi l and could supplement those fuels with oxygen. Current industry technology no longer shows the use of oil as a fuel for glassmelting furnaces. Recuperative furnaces use a steel heat e xchanger, recovering heat from the exhaust gases by exchange with the combustion air. Regene rative furnaces use a lattice of brickwork to recover waste heat from exhaust gases. Elect ric furnaces melt glass by passing an electric current through the melt. Electric furnaces ar e either cold-top or steel shell. Cold top furnaces operate during normal production using only electricity , but during startup use natural gas to heat the empty furnace before it is filled with cullet. These furnaces use internal cullet at startup because it melts readily and a molten batch can be established readily in the furnace. Cold-top furnaces then establish a damp crust of raw mate rials, and convert to all electricity during the remainder of the furnace life. Cold-top furna ces are open above the level of the raw material; they do not have furnace walls or a crown. S teel shell furnaces are similar, but they have steel walls and top surrounding the melt.

Wool fiberglass is generally produced for insulation and is formed into continuous mats that are

cut into sections called “batts”. Some facilities also produce loose wool and other specialty products. During the formation of fibers into a wool fiberg lass mat (the process known as "forming" in the industry), glass fibers are made from molten glass and if the product is “bonded”, a chemical binder is simultaneously sprayed on th e fibers as they are created. Historically, the binder was a thermosetting resin th at holds the glass fibers together. Although the binder composition varies with product type, typically the binder consists of a solution of phenol-formaldehyde resin, water, urea, lignin, silane, an d ammonia. However, most facilities

1 AP 42 Compilation of Air Pollutant Emission Factors. O ffice of Air Quality Planning and Standards. Fifth Edition. Vol. I. Chapter 11.13: Glass Fiber Manufacturing. http://www.epa.gov/ttnchie1/ap42/ch11/final/c11s13.pdf.3

have begun to use phenol-formaldehyde free resins, some of which do not require heat for curing in a thermosetting process. Of the 30 wool fiberglass fa cilities currently operating in the US, 20 have completely phased out phenol/formaldehyde binders on RS lines.

Two methods of creating fibers are used by the industry; rota ry spin (RS) and flame attenuation. (FA). In the RS process, centrifugal force causes molte n glass to flow through small holes in the wall of a rapidly rotating cylinder to create fibers tha t are broken into flexible strands in an air stream. In the FA process, molten glass flows by gravity from the furnace through numerous

small orifices to create threads that are then atten uated (stretched to the point of breaking) by high-velocity hot air and/or a flame. After the glass fibers are created (by either process) and sprayed with the binder solution (if bonded), they are col lected by gravity on a conveyor belt in the form of a mat. If a thermoset bonded product is being produced, the conveyor carries the newly formed wool fiberglass through a large oven to cure the thermosetting binder and then through a cooling section where ambient air is drawn down th rough the mat. The wool fiberglass is then cooled before trimming. This curing process is not performed if the product is not bonded or if the resin is not one requiring the thermosetting pro cess. A summary of emission units as regulated under the subpart NNN for wool fiberglass facilit ies is included in Table 1.

Table 1. Summary of Wool Fiberglass Production Emission Units Emission Unit Regulated Process Description HAP Emitted Glass-Melting

Furnace Furnace where raw material is melted. Metals, HF, HCl

RS Lines RS lines that produce bonded building insulation

products (includes forming, curing, and collection processes). Formaldehyde, methanol, and phenol (from bonded products that use phenol/ formaldehyde binder) FA Lines FA lines that produce bonded pipe insulation and

heavy density products (includes forming, curing, and collection processes).

The current Wool Fiberglass NESHAP was promulgated on June 14, 1999 and applies to new and existing glass-melting furnaces, each new and existing F A manufacturing line producing a bonded pipe product or a bonded heavy density product, and each n ew and existing RS manufacturing line producing a bonded wool fiberglass building insulation product.

3.0 Practices, Processes, and Control Technologies for Wool Fib erglass Production

To determine developments in practices, processes, and con trol technologies, we examined the control technologies considered during NESHAP development and control technologies and advances identified through the data and information collect ion activities taken to support the Residual Risk and Technology (RTR) amendments, direct cor respondence with the industry, and through searches of the EPA’s RACT/BACT/LAER Clearingh ouse and the Internet.

3.1 Control Technologies Considered for the 1999 NESHAP

For the purpose of this exercise, a “development” was co nsidered to be:4 • Any add-on control technology or other equipment (e.g., f loating roofs for storage tanks) that was not identified and considered during MACT devel opment,

• Any improvements in add-on control technology or other e quipment (that was identified and considered during MACT development) that could result in significant additional emission reduction,

• Any work practice or operational procedure that was not i dentified and considered during MACT development,

• Any pollution prevention alternative that could be broadly applied that was not identified and considered during MACT development, and

• Any process change that could be broadly applied that was not identified and considered during MACT development.

Table 2 summarizes the practices, processes, and control technologies considered during the development of the 1999 MACT standard.

Table 2. Summary of Practices, Processes, and Control Tech nologies Identified and Considered During Wool Fiberglass Production 1999 MACT Developme nt 2

Emission Source Practices, Processes, and Control Technologie s
Furnaces Fabric filter, dry and wet ESP, batch wetting

3.2 Technology Developments After Promulgation of the 1999 NESHAP 3,4

Since development of the NESHAP in the 1990’s, the metho ds for controlling emissions from furnaces are the same, but some technologies have devel oped that can affect the emissions of wool fiberglass production. We evaluated our technology re view on all furnaces in the source category, which included furnaces at both area and major so urces. At the time the MACT standard was promulgated in 1999, all wool fiberglass facilit ies were major sources. However, due to the phase out of phenol/formaldehyde binder, most facil ities in the source category have changed status from major to area source. However, th is change in status did not affect the furnace (i.e., furnaces at major and area sources are of the same design and size). Therefore, we believe it is appropriate to consider all furnaces in the technology review for this process.

3.2.1 PM Emissions

For our technology review under CAA section 112(d)(6), the EPA reviewed furnace emissions data provided by facilities and found that current PM emissi on rates achieved by the majority of glass-melting furnaces are significantly lower than the 1999 MACT limit. We identified advances in control measures for PM emissions (as a sur rogate for metal HAP) including improvements in control technology (e.g., increased capt ure efficiency) and application of

2 Wool Fiberglass Insulation Manufacturing. Background Info rmation for Proposed Standards. December 1983.

3 Meeting Notes. Conversation between Carlos Davis, Ce rtainTeed, Kansas City, KS and Susan Fairchild, Environmental Scientist, US Environmental Protection Agency. April 14, 2011.

4 Meeting and Site Visit Notes. Conversation between C arlos Davis, CertainTeed, Kansas City, KS and Hugh McCullough, Environmental Scientist, Region 7, US Environme ntal Protection Agency. 2011.5

electrostatic precipitators that had been made since pro mulgation of the 1999 NESHAP. We also

found that PM emissions from electric furnaces are als o low due to the use of baghouses, designs other than cold-top electric furnaces, and batch wetting o f the crust above the molten glass in cold-top furnaces. These electric furnace designs are not new and were also used at many wool fiberglass manufacturing facilities at development of t he 1999 MACT standard. The EPA grouped PM emission rate data by control device (see Figure 1) and found that the control technology that achieves the best PM reduction when prope rly operated and maintained is a fabric filter (or baghouse).

In the air gas furnace, ambient air is drawn into the fur nace through ports located directly above the natural gas ports. Because only the oxygen portion of a ir is used in the combustion process,

the remainder of the volume of air is available for c hemical and physical interactions in the furnace environment. Dry raw minerals, which are fed into the inlet of the furnace, are heated and melted by the natural gas and oxygen portion of the air . The air gas furnace reaches just over 3500° F. Particulate resulting from portions of the raw mi nerals with higher melting points become entrained in the gases that exit the furnace, an d the particulate is emitted along with the remaining volume of gases.

When oxyfuel furnaces are used in place of the air gas furna ces, the melting temperature over 5000°F is reached. Because in the oxyfuel furnace, only oxygen is used with natural gas, the gas volume is reduced as compared to a similar air-gas furnace by about 80%. The oxygen is consumed in the combustion process. When the melting t emperature of the raw minerals is reached, the gases trapped within the crystalline structure of the minerals are liberated. The furnace gases that are emitted from the oxyfuel furnace originate mostly from the raw minerals. When cullet is used in place of raw minerals, the gases exiting the oxyfuel furnace are near zero. The lower the furnace gas volume and raw mineral content of the furnace, the lower the PM

emissions in the furnace exhaust. The PM emissions ar e indirectly proportional to the raw

mineral content of the furnace and the volume of air e ntering the furnace. 5

Electric furnaces both use electrodes embedded within the m elt to produce molten glass during normal operation, and have low PM emissions as a resul t of the furnace design and raw material wetting.

5 For the same reasons, total emissions of NOx are lo wer in the oxyfuel furnace than in the air gas furnace. The concentration of CO2 in the exhaust gases of the oxyfuel fur nace are higher than in the air gas furnace due to the lower total gas volume of the oxyfuel furnace.6 Figure 1. Furnace PM Emission Rate by Control Device

3.2.2 Chromium Compound Emissions

Subsequent to the November 2011 notice, we issued a CAA sect ion 114 ICR to collect emissions data and other information on glass-melting furnaces in or der to regulate area sources in a future action. This ICR resulted in a near complete dataset f or emissions test data on all wool fiberglass furnaces, with the only exceptions being furnaces at faci lities that were closed or that were shut down at the time of the 2012 testing. Additionally, in an e ffort to evaluate the various types of furnaces used in the production of wool fiberglass, the EPA project team visited several wool fiberglass facilities in 2012, and industry representatives provided detailed information on each type of furnace. After analyzing all of the data received, the EPA identified refractories having a high content of chromium, and their use in wool fiberg lass furnaces, as a new development affecting the emissions of chromium compounds from source s subject to the standard. We reviewed the use of chromium refractories (as compared t o non-chromium refractories), the use

of caustic scrubbers to reduce chromium in the furnace e xhaust, and the current industry practices used to reduce chromium emissions from the furnac e emissions. We analyzed the technical feasibility and the estimated impacts (e.g., costs, emissions reductions, risk reductions) of applying these developments.

In our technology review under CAA section 112(d)(6) for chr omium, we found that, while the furnaces and control technologies are generally the same as those used at promulgation of the MACT standard in 1999, there have been some developments in furnace design and preference in control equipment. Air-gas furnaces, once widely use d throughout this industry, have been mostly phased out due to high nitrogen oxide (NOx) and PM emis sions. In place of the air-gas furnace, oxyfuel furnaces are being constructed because they are more energy efficient, and 0 0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.4 0.45PM (lb/ton) 

### PM (lb/ton glass pulled)

**Emission Rates By Control Device Type**

PM Baghouses and Fabric

Filters Batch

Wetting Baghouse + Secondary

Control

ESP

Furnace7

because they emit NOx and PM at very low levels. Revie w of the industry literature 6,7,8,9,10 and public comments indicate that once a source of industri al oxygen is sited in the vicinity of a wool fiberglass manufacturer, that facility is likely to conv ert from air-gas or electric to oxyfuel technology.

We also found that while chromium refractories were use d prior to 1999, the manufacturers of these products had not overcome some significant problems ( such as spalling from thermal shock in certain high temperature applications). As a result, their use was confined to limited areas of the furnace that experience low thermal shock or areas in which furnace repairs and refractory replacement could be performed readily.

Developments in refractory technology and in furnace de sign are inextricably linked. Oxyfuel furnaces were not widely used prior to 1999 in the wool fibe rglass industry, due to a number of factors, especially refractory degradation in the wool fi berglass furnace environment. The then new technology of the oxyfuel furnace constructed using co nventional refractories available at the time (e.g., alumina-silicate, zirconium) limited th e furnace life to 4 or 5 years. As a result, air-gas and electric furnaces predominated in the industry pr ior to 1999.

With the advent of new refractory technology, new oxyfue l furnaces were constructed since the 1999 NESHAP that could be expected to have a longer service l ife. With the industry focus upon new furnace designs and technology, the research to devel op refractories that could withstand high temperatures, thermal shock and corrosive materials yielded the development of new types of chromium refractory products (such as fused-cast chromi um refractories and cast-in-place chromium refractories) that are used for construction of the high-temperature oxyfuel furnace. As a result, the wool fiberglass industry began a trend to ward oxyfuel furnaces constructed using high-chromium refractory products, a trend that is expect ed to continue into the future. The increased use of high-chromium refractory led to the incr eased chromium emissions as a result of both wool fiberglass raw material formulation (corros ivity) and associated refractory degradation (i.e., furnace wear).

Oxy-fuel furnaces have replaced all but three air gas fur naces and are expected to replace the remaining air gas furnaces over the next 10 years due to ove rall economic and production advantages. Oxy-fuel furnaces are fired using industrial-grade oxygen and natural gas to heat the furnace. They operate with higher temperatures above the melted glass (inside the furnace) than air gas furnaces due to the high temperature of oxygen combusti on. This also results in low PM and NOx emissions because there are no excess gases in the furnace (as is the case for air-gas furnaces).

6 U.S. DOE Energy Efficiency and Renewable Energy, Indus trial Technologies Program, Final Technical Report. “Compressive Creep and Thermophysical Performance of Re fractory Materials”. Oak Ridge National Laboratories.

June 2006.

7 Oxygen-Enhanced Combustion, Chapter 7. Baukal, Charles E., Jr. 1998.

8 “Advances in Oxyfuel Fired Glass-Melting Technology”. His ashi Kobayashi. January 2004.

9 “When does oxy-fuel make sense?” Russell Hewertson, Mana ger of Combustion Technology, Air Products and Chemicals, Inc., 2005.

10 Diagnostics And Modeling Of High-Temperature Corrosion Of Superstructure Refractories In Oxyfuel Glass

Furnaces: Extended Superstructure Refractory Life Will Enhance Oxyfue l Firing Process. Elliott Levine, Office of Industrial Technologies Energy Efficiency and Renewable Energy, U.S. Department of Energy, December 2000.8

Studies indicate that, under normal industrial temperatures and oxidizing conditions, trivalent chromium, which is present in the refractory, can oxid ize to hexavalent chromium. 11 It was found that uncombined and available oxides were responsible f or a higher yield of hexavalent chromium. Consequently, an increasing concentration of oxides in the oxy-fuel glass-melting

furnace environment increases the formation of chromium f rom the trivalent state to hexavalent state. The condition of high oxides in the oxy-fuel glas s-melting furnace environment is one characteristic of the highest emitting glass-melting f urnace. 12

Moreover, while the degradation of the glass-melting furn ace refractory indicates increasing chromium emissions, that process does not necessarily follow a normal and predictable pattern. The degradation of refractories within the glass-meltin g furnace is a function of numerous factors, including temperature, time, stress, and the com posite effects of aging and creep response. These processes are highly nonlinear, so the tra ditional equations that assume steadystate deformation rates are not appropriate. 13

We have also found that as the refractories of the gas -fired glass-melting furnaces degrade, the

chromium of those refractories at and above the metal /glass line is emitted as particulate to the

outside air. Chromium from the refractories below th e metal/glass line is absorbed into the molten glass and becomes vitrified with the other raw m inerals. Industry commented that refractory loss from degradation of the refractory wal ls in use is approximately 20,000 pounds of refractory annually. 14 However, much of the loss occurs below the glass mel t line. The chromium released below the glass melt line is believ ed to stay in the glass.

We determined that chromium emissions tend to increase wit h furnace age based on emissions test data for a facility with the highest-emitting gla ss-melting furnace (an oxy-fuel furnace) collected over a 7-year period for state inventory report ing. Table 3 shows the annual chromium compound emissions estimates calculated using the test resu lts and permitted production rates. The table shows that in 2004, chromium emissions were es timated to be less than five pounds annually. By 2010, the estimated emissions for the furnace i ncreased to 540 pounds per year. The emissions testing conducted in 2010 also showed that that 93 pe rcent of the total chromium was

in the hexavalent state.

11 Lee, Y., Nassaralla, CL., Minimization of Hexavalent Chromium in Magnesite-chrome Refractory. Metallurgical and Materials Transactions, 1998.

12 EPA Region 7 Notes on CertainTeed Kansas City Plant. June 30, 2011. EPA-HQ-OAR-2010-1042-0067.

13 Compressive Creep and Thermophysical Performance of Re fractory Materials. U.S. Department of Energy and Oak Ridge National Laboratory. June 2006 pp. 63.

14 Minutes of EPA Meeting with Representatives of the Woo l Fiberglass Industry and NAIMA. August 31, 2011.9 Table 3. Summary of Chromium Emissions from 2004 – 2010

Year Chromium Emissions (pounds per year)

2004 <5

2005 30

2008 114

2010 540

This glass-melting furnace was not reconstructed during this 7-year period covered by the chromium testing which indicates that a degradation of t he chromium refractory resulted in a significant increase in chromium emissions during this per iod. We believe that this high-emitting glass-melting furnace clearly demonstrates a potential for increased chromium emissions for glass-melting furnaces where the chromium containing ref ractory is exposed to high temperatures. While this glass-melting furnace is located a t a major source, we note, as discussed in Section 3.2, there is no difference in design and oper ation of a glass-melting furnaces at major

and area sources.

Electric furnaces do not emit chromium at the levels o f gas-fired furnaces. Test data collected on wool fiberglass furnaces in 2010 and 2012 show that the average chromium emissions from electric furnaces are approximately two orders of magnitude lower than the average chromium emissions from gas-fired furnaces. The electric furna ces having the highest chromium emission rate emitted at levels similar to the gas-fired furnaces emitting chromium at the lowest measured rates. Electric furnaces produce glass at lower production rates (averaging is about 50 tons per day), as compared to gas-fired furnaces (averaging about 250 to ns per day).

Gas-fired furnaces have higher chromium emission potenti al for compared to electric glassmelting furnaces, due to differences in design and operation of gas-fired glass-melting furnaces. A chromium refractory product has the greatest resistanc e to heat and wear of any refractory in use today. The temperatures above the melt in gas-fired glass-melting furnaces range from 2500 ◦

to 4500 ◦ F, while the temperatures in electric glass-melting furna ces are a few hundred degrees. Electric furnaces are constructed using chromium refract ory at and below the glass/metal line,

and a much smaller total surface area of chromium refra ctory is available for degradation and ensuing emission to the furnace stack as a result. Due to their higher operating temperatures, gasfired glass-melting furnaces are constructed using chromiu m refractories at various parts of the glass-melting furnace that are above the molten glass , including the crown. The presence of chromium above the glass melt line, high temperatures, and corrosive environment are factors influencing an increased chromium emission potential emis sions from gas-fired furnaces. In addition, the high temperatures result in more of the c hromium being converted to its hexavalent state compared to electric furnaces.

In summary, because of the advantages of oxy-fuel glass-m elting furnaces over other wool fiberglass glass-melting furnace technology described in the preceding discussions, we expect oxy-fuel glass-melting furnaces constructed of chromium refractories to replace many existing10

wool fiberglass glass-melting furnaces of other designs, par ticularly as sources of industrial oxygen are sited near wool fiberglass facilities. 15,16

3.3 Correspondence with Industry

To identify new emission control technologies in use, a voluntary information request was sent to all U.S. wool fiberglass manufacturing facilities. To identify new technologies, facilities were asked to identify any controls that did not fall under the following categories: electrostatic precipitator (ESP), scrubber, mechanical collector, fabri c filter, thermal incinerator, high velocity air filter (HVAF), mist eliminator, or ventilation sys tem. Facilities did not list any control devices that were not previously identified. At least one w ool fiberglass facility was identified as having a scrubber and dry ESP combination for controls on a furnace. Information from similar source categories showed that a sodium hydroxide (NaOH) sc rubber could be used on hightemperature gas-fired furnaces to reduce acid gas emissions as well as chromium compounds

emissions.

Additionally, as noted in Section 3.2.2, the EPA sent o ut a CAA section 114 ICR in 2011 that required PM, chromium, and hexavalent chromium testing o f furnaces to help determine the current levels of control at which existing technologies are currently operating. The ICR also required facilities to provide detailed information on the chromium contents of furnace refractories and their use of binders. The EPA has partici pated in several meetings with industry representatives and the wool fiberglass trade associati on (the North American Insulation Manufacturers Association, NAIMA) regarding current pra ctices and technologies used at wool fiberglass plants.

3.4 Search for Other Applicable Technology Developments

In addition to the information discussed above, search es of the RACT/BACT/LAER Clearinghouse and the Internet were conducted to identify other technologies or developments that could be applied to wool fiberglass production. The res ults of these searches are described in the following paragraphs.

3.4.1 RACT/BACT/LAER Clearinghouse 17

Under EPA’s New Source Review (NSR) program, if a company is planning to build a new plant or modify an existing plant such that air pollution emis sions will increase by a large amount, the company must obtain an NSR permit. The NSR permit is a c onstruction permit which requires the company to minimize air pollution emissions by changi ng the process to prevent air pollution and/or installing air pollution control equipment.

15 Letter from A. Crane, NAIMA to S. Fairchild, US EPA , dated January 28, 2013.

16 Baukal, Charles, et al, Oxygen-Enhanced Combustion . Boca Raton: CRC Press, 1998.

17 Technology Transfer Network, Clean Air Technology Cente r - RACT/BACT/LAER Clearinghouse. http://cfpub.epa.gov/rblc/index.cfm?action=Search.BasicSe arch&lang=eg11

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

new or modified sources in non-attainment areas.

BACT and LAER (and sometimes RACT) are determined on a c ase-by-case basis, usually by State or local permitting agencies. The EPA established th e RACT/BACT/LAER Clearinghouse, or RBLC, to provide a central database of air pollution t echnology information (including past BACT and LAER decisions contained in NSR permits) to pro mote 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, BA CT, and LAER requirements. Noteworthy prevention and control technology decisions and information are included even if they are not related to past RACT, BACT or LAER decisio ns.

The RBLC contains over 5,000 air pollution control permit de terminations 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 a nd control technology decisions for stationary air pollution sources, and includes data submitte d by several U.S. territories and all 50 States on over 200 different air pollutants and 1,000 industria l processes.

To identify technologies appropriate for wool fiberglass pro duction, searches of the RBLC were made using the Process Type Code: 99.033–Wool Fiberglass. Al l records from 1999 to 2011 were searched. In all cases, the control devices and me thods identified through the RBLC search do not represent new technologies for controlling HAP emi ssions.

3.4.2 Internet Search

A general search of the Internet was conducted for info rmation on control technologies for wool fiberglass furnaces, and RS and FA manufacturing lines. T he Internet search did not identify any new practices, processes, or technologies that have n ot already been considered in this review.

4.0 Technology Review Findings

4.1 Bonded Lines

For our technology review for the bonded lines under CAA se ction 112(d)(6) for the Wool Fiberglass Manufacturing source category in the 2011 proposa l (76 FR 72803), we conclude that emissions of formaldehyde, methanol and phenol have been significantly reduced since promulgation of the 1999 NESHAP due to the phasing out of phenol -formaldehyde binders. We did not receive any information or data during the public c omment period for the 2011 proposal or for the 2013 or 2014 supplemental proposals that warranted re vising our technology review for bonded lines. As discussed in section V.H of preamble to the final rule, we have issued a CAA section 114 ICR to wool fiberglass facilities to obta in updated formaldehyde, methanol, and phenol emissions and process data for RS manufacturin g lines we will conduct the12

technology review and evaluate RTR limits for these so urces, based on the CAA section 114 ICR data, at a future date.

4.2 Glass-Melting Furnaces

4.2.1 PM Emissions

Based on our technology review conducted under CAA section 112( d)(6), we conclude that that have been improvements in existing control technologies and advances in developments in control technologies and furnace design and operation th at have achieved PM emissions levels that are below the level established by the 1999 NESHAP. In order to reflect current achievable levels (as shown in Figure 1) , the EPA is reducing the M ACT floor limit for PM. In the November 2011 proposal, a PM limit was set under technolog y review, but the PM limit was erroneously calculated using an upper predictive limit (UPL) MACT floor methodology which was not appropriate. In order to determine a PM limit th at reflects current practices, the EPA gathered all PM emission rates from furnace emission t esting at major sources and calculated the emission rate that could be met by 99 percent of the sourc es for which the EPA had data. PM emissions rate data was available for 44 furnaces at maj or and area sources and the 99 th
percentile of the 44 furnaces was 0.33 pounds of PM per ton of glass pulled. Therefore, the EPA is finalizing a PM limit of 0.33 lb PM/ton for existing and new glass-melting furnaces in order to

reflect current achievable PM emission levels.

4.2.2 Chromium Emissions

Our technology review for chromium emissions from furna ces found that the use of highchromium refractories to construct entire gas-fired gla ss-melting furnaces for wool fiberglass manufacturing is a new development that began after prom ulgation of the 1999 NESHAP and that the increased use of high-chromium refractories h as led to an increase in emissions of chromium compounds since the 1999 NESHAP was established.

Figure 2 shows chromium emissions from gas-fired furnaces . These data, collected in 2010 and 2012, show that most gas-fired furnaces emit chromium compoun ds below 1 x 10- 4 lb/ton. Three furnaces which were tested in 2010 were repaired or rebuilt , and retested for the 2012 test request. In each case, chromium emissions decreased as a result of the rebuild / repair. Chromium emissions testing indicates that the highest well-performing furnace emits at

2.0 x 10 -4 lb/ton and that well-performing furnaces emit below 2.5 x 10 -4 lb/ton, Furnaces that measured higher than this level have already been rebuil t, but not retested.

Figure 2. Furnace Chromium Emission Rates by Furnace Type13