MEMORANDUM

SUBJECT: Chromium Emissions and Furnace Age

DATE: August 14, 2014

FROM: Susan Fairchild

Office of Air Quality Planning and Standards

TO: Docket ID No. EPA

- HQ

- OAR

- 2010

- 1042

The EPA collected information on furnace age, refractory chromium content, and chromium emissions from each glass

- melting furnace in the wool fiberglass industry ( located at both major and area sources). T he information was collected in two phases: a voluntary industry survey conducted in 2010 and a Section 114 information collection request sent out by EPA in 2012. After the results of the 2010 voluntary industry survey were obtained
, source testing revealed high chromium emissions from a few furnac es. During this same time period, s ome companies rebuilt or repaired some glass

- me l ting furnaces which resulted in reduce d chromium emissions. For the 2012 Section 114 information request, companies were required to provide information on the chromium
cont ent of their furnace refractories, furnace age, dates of furnace repairs and rebuilds, and conduct emissions testing on furnaces 1 at all facilities producing wool fiberglass. The data from both the 2010 and the 2012 collection efforts were compiled into a project database from which all analyses for the rule development were conducted.

Most glass

- melting furnaces with chromium emissions that exceed the proposed existing

source emission limit (based on production throughput) are more than 10 years old, with ages ranging from less than 1 year up to 23 years. The median age of furnace s among both major and area sources that exceed the limit is 12 years and the average age is 11 years. The median age of furnaces that meet the chromium limit is 10 years and the average age is 8.5 years. We considered these data and without the ability to extract specific furnace design elements, note that furnaces emitting chromium at or below the limit are generally 2 to 3 years younger than the furnaces emitting chromium at lev els exceeding the limit. Chart 1 ( below ) shows the compiled chromium compounds emissions data for gas

- fired (oxyfuel and air

- gas) glass

- melting furnaces by age.

1 Every gas

- fired furnace was required to be tested and every unique furnace at every f acility was required to be tested regardless of whether i t was electric or gas

- fired.Review of the furnace information and emissions test data show that serial testing was

conduc ted at three furnaces in the industry: one series of four tests on the K2 furnace located at Certainteed facility in Kansas City, KS; and two series of tests conducted on the MT1 and MT2 furnaces at the Certainteed facility in Mountaintop, PA (these were
t ested over two different furnace campaigns).

The K2 furnace was constructed in 2002, began normal operations in 2003 and underwent testing in 2004, 2005, 2008, 2010, and 201 1 . The company applied by permit to increase their production rate at the K2 furnace in 2008, and the 2008 test was conducted to determine the PM and chromium emissions at the new production rate. Testing conducted in 2004

- 2008 sampled PM and total chromium compounds; testing conducted in 2010 and 2011 analyzed for both hexavalent chromium and total chromium compounds. The 2010 testing showed CrVI was 93% of the total chromium compounds emitted by the K2 furnace. Analytical problems 2 with t he 201 1 test (including the loss of

2 The 2011 testing was conducted properly, however the calculations done during the reporting phase were not correct, thus the reported numbers were incorrectly low. The corrected values presented by the test contractor were appropriate (and much higher than their original report). There remains the issue of discarded filters that

were re quired under the method to be analyzed for hexavalent chromium; this step was not conducted and contributed to the low measured hexavalent emissions. While there appears to be no further reasons to discard the 2010 data (after corrections and assumptions o f the level of hexavalent chromium that the discarded filter may have contained), the corrected 2011 report confirms emissions of the same order of magnitude, though slightly lower than the 2010 testing. This lower value may be attributed to the discarded filter.

10 11 11

7.5 10 7

10 12 12

12

<1 <1

8

-1E-04 1.2E-18 0.0001 0.0002 0.0003 0.0004 0.0005 0.0006

Air Gas Air Gas Oxy Fuel Oxy Fuel Air Gas Oxy Fuel Oxy Fuel Oxy Fuel Oxy Fuel Oxy Fuel Oxy Fuel Oxy Fuel Oxy Fuel lb Cr/ton Chart 1. Chromium Emissions of Gas Fired Furnaces by Age

Old Test Data

2012 Test Data

6.00E-05 Area Sources 2

Major Sourcescollected chromium compounds which were not analyzed as r equired by the method)

influenced our decision to use only the 2010 test to quantify this source’s emissions of chromium. . This furnace is responsible for the highest measured hexavalent and total chromium emissions in the industry, as shown in Table 1 be low.
Table1. Certainteed K2 Furnace chromium emission testing.

Year K2 Chromium emissions at permitted production rate, pounds per year 2004 <5 2005 30 2008 114 2010 540

The second series of tests were conducted at the Certainteed facility in Mountaintop, PA. The ESP outlet controlling the MT1 and MT2 furnaces was first tested in 1991 and 1995. The test conducted in 1991 showed emissions at 10.5 lb/year. Four years later, the same furnace showed that chromium emissions had doubled. That furnac e was then rebuilt and retested. The second set of chromium emission tests were then conducted on the rebuilt furnace in 1998 and 2003. These two tests measured chromium emissions at 4.9 lb/year and 5.3 lb/year, respectively. Chromium emissions doubled ove r four years in the first furnace campaign, and increased an average of less than 2% per year over the second furnace campaign, an increase that is not statistically significant. While the two different test sets show increasing chromium emissions with fur nace age, they also show that other factors, potentially including differences in furnace designs, chromium content of refractories, and internal furnace chemistry as a result of the wool fiberglass raw material composition, may account for significant dif ferences in chromium emissions.
Table 2. Serial testing of unaltered furnaces.
Incremental Total Chromium Emissions from Oxy

- Fuel Furnaces (lb/yr)
Furnace K2 MT1 MT1 First test emissions (lb/yr) <5 10.5 4.9 Last test emissions (lb/yr) 540 20.9 5.3
Time Period 6 yrs 4 yrs 5 yrs
Annual Incremental Emission Rate (%/yr) 1,473 50 <2

Annual Incremental Emission Rate (lb/yr) 72.8 2.6 <0.1Other Factors Influencing Chromium Emission s

The rate of c hromium emi ssions is influenced by the size of the furnace, chromium content of the refractor ies , position with in the furnace, available boron from the glass melt, chemistry of the melt , and glass pull rate. Changes in these factors can reduce or increase the rate of chromium emissions f rom wool fiberglass furnaces.
Most of the furnace design and operating parameters as well as the glass chemistry are proprietary to each company and held in strict confidence, making them largely unknown for r egulatory development . We obtained information in our Section 114 information collection from all wool fiberglass companies on furnace age, first construction date, and most recent rebuild dates. Section 114 furnace construction data and i ndustry statements 2,3 obtained after submittal of the Section 114 information collection and during site visits indicate the following:

 all gas

- fired wool fiberglass furnaces are constructed using high chromium refractories,

 chromium refractories are chiefly responsible for the higher chromi um emissions

 the use of chromium refractories in the construction of gas

- fired furnaces is an essential component of the wool fiberglass manufacturing process.

Gas

- fired furnaces typically operate around 2
, 800 ◦ F and oxyfuel furnaces operate between 3,500 and 4
, 000 ◦ F

. Borides , which are used in the wool fiberglass formulation for attenuat ion of the fibers durin g the production process
, introduce a highly corrosive and reactive component to the wool fiberglass furnace chemistry. Both the tempe rature and corrosivity of the furnace environment cause wear on the inside of the furnace lining. Wool fiberglass gas

- fired furnaces are constructed using refractories that are high in chromium to withstand both the thermal and chemical demands of the int erior of the wool fiberglass furnace.
The refractory materials typically include oxides of silica, magnesium, alumina and two types of chromium

- bearing materials: Cr 2 O 3 (from the chromium

- bearing ores chromite and magnesiochromite) and Cr3O4 (chromic oxid e, a pigment). The increasing chromium emission rate with refractory wear is substantiated by industry studies, published papers symposia and other sources available in the technical literature

. 5,6,7,8,14
Based on the available information, chromium emissions increase with furnace age, and may increase exponentially for certain furnace designs and glass formulations. However,

w e are not at this time able to predict chromium emission rate due to the absence of complete data on the many influencing factors.

Mechanism of Chromium EmissionsT he refractory bricks and blocks are installed having even and level smooth sides. Over

the life of the furnace, the hot furnace gases react with any available oxides (including those in the refractory materials), causing degradation of t he refractor y mater ials . The refractory wear pattern is semi

- spherical

. A s the corrosive gases of the wool fiberglass furnace continue to erode the refractory lining over the life of the furnace, the spherical wear pattern is enlarged.
The volume of a sphere is calculated as :

V = 4
3 ∏r 3

The volume of a hemisphere is half that of a sphere, or:

V = ( 4
3 ∏r 3 ) / 2
As the corrosive gases of the wool fiberglass furnace continue to erode the refractory lining over the life of the furnace, the spherical wear pattern is enlarged. Thus, as the furnace interior is continually corroded/eroded in semispherical manner, the su rface area exposed to the corrosive environment enlarges exponentially. We believe t his phenomenon is the reason that the chromium emission s for the K2 furnace increased exponentially over time and is illustrated by the K2 emissions testing in Table 1. Con sequently, we believe that chromium emission rate s for gas

- fired furnaces have the potential to increase exponentia l l y over time.
We considered whether the known principles of refractory degradation could be applied to the life expectancy of the furna ce to determine at what point the chromium emissions would be expected to approach the chromium emission limit. However, the data are insufficient at this time for development of a predictive pattern of anticipated future chromium emissions. We proposed in both November 25, 2011 and the April 15, 2013 Federal Register for the Wool Fiberglass RTR and Area Source Rules that owner / operators of Wool Fiberglass furnaces would be required to conduct chromium testing periodically. Future compliance emissions tes ting compiled from wool fiberglass facilities may add to the existing data to improve our understanding of the correlation between increasing furnace age and accelerated chromium

.R eferences

1. Section 114 and ICR Responses. Dataset for the Wool Fiberglass RTR and Area Source Rule. U.S. Environmental Protection Agency, Office of Air Quality Planning and Standards. CBI file. 2013. 2. Industry

- EPA Meetings. March 19, 2012 ; August 31, 2011 ; November 16, 2011. 3. Wool fiberglass manufacturer ’ s facility s ite v isits to Certainteed and Owens

- Corning U.S. sites. CBI Office project number 481, USEPA/OAQPS/SPPD. December 2012. 4. Saint

- Gobain Ceramic Materials. Chromium Oxides. Saint

- Gobain Websites, 2012. 5. “Formation of hexavalent chromium by reac t ion between slag and magnesi te

- chrome refractory”. Lee, Y., Nasaralla, C.L. Metallurgical and Materials Transactions, B: Process Metallurgy and Materials Processing Sciences . Vol 29: 2. April 1998. 6. Corrosion of Chromium Rich Oxide Refractories in Molten Waste Glasses . Gan, Hao; Lu, Xiaodong; Buechele, Andrew C.; Paul, M. Catherine; and Pegg, Ian L. Catholic Univ. America, for U.S. Dept. of Energy. March 2002. 7. Compressive Creep and Thermophysical Performance of Refractory Materials . Ferber, M.K.; Weresczak, A.A.; Hemrick, J.G. Oak Ri dge Nat’l. Lab. for U.S. Dept. of Energy. Energy Efficiency and Renewable Energy. Document No. ORNL/TM

- 2005/134. June 2006. Contract No. DE

- AC05

- 00OR22725. 8. “Hexavalent chromium in refractories”. Khoroshavin, L.B.; Deryabin, V.A.; Perepelitsyn, V.A.; and L apteva, T.N. Refractories and Industrial Ceramics . Vol. 34. No. 9

- 10. Pp. 457

- 462. 1993. 9. “NYS Governor’s Awards for Pollution Prevention

- Owens Corning, Delmar Plant”. Dept. of Env. Cons. NY State Press Release. Jan 30. 2013. 10. Oxygen

- Enhanced Combustion . Ch apter 7. “Glass”. Eleazer, P.B. and Hoke, B.C., Jr. pp. 215

- 236. 1988. Ed. Baukal, Charles E. 11. Refractory Insulation and Fire Brick. Glass Furnace. Refractory Insulation and Fire Brick Website, 2012. 12. Saint

- Gobain SEFPRO. Sintered High Chromium Oxide. Saint

- Gobain websites, 2012. 13. Refractories for Industrial Processing: Opportunities for Improved Energy Efficiency

. Hemrick, James G.; Hayden H. Wayne; Angelini, Peter; Moore, Robert E.; and Headrick, William L. for Oak Ridge Nat’l. Labs. January 2005. 14. “Environme ntal Issues Affecting Raw Material Selection” . GMIC Workshop, Columbus, OH. Oct 20, 2011. Ross, Philip C. www.GlassIndustryConsulting.com.