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MEMORANDUM

Date: December 7, 2012

Subject: Summary of the December 6, 2012 Meeting with Representatives of the 

Wool Fiberglass Industry and NAIMA

Wool Fiberglass Manufacturing RTR and Area Source Rule

RTI Project No. 0213199.001.007

From: Dave Reeves, RTI International

To: Susan Fairchild

OAQPS/SPPD/NRG (D243-02)

U.S. Environmental Protection Agency

Research Triangle Park, NC 27711

I. Introduction

A meeting with representatives of the North American Insulation Manufacturer’s Association 

(NAIMA) and the wool fiberglass manufacturing industries was held at the Hilton Garden Inn in 

Kansas City, KS on December 6, 2012. The purpose of the meeting was to discuss chromium and 

hexavalent chromium emissions from glass-melting furnaces at wool fiberglass facilities. This 

memorandum summarizes the major topics discussed during the meeting.

II. Attendees

See Attachment 1 for a list of attendees. 

III. Discussion

A meeting agenda was prepared and distributed by Mr. Angus Crane (NAIMA) and is included as 

Attachment 2. The purpose of this meeting was for NAIMA and industry representatives to 

present additional information on chromium and hexavalent chromium emissions from the four 

primary types of glass-melting furnaces used in the wool fiberglass industry. 

There was discussion on each furnace type related to chrome content of refractories in the 

different areas of the furnace, operating temperatures, and types of emission controls – see below. 

Additional details on each type of furnace were provided in facility site visits conducted earlier in 

the week. Many of the details specific to those furnaces are considered to be confidential business 

information (CBI) and are included in separate addendums to this memo. 

a. Oxy Gas or Oxy Fuel

- Attachment 3 has a diagram of a typical oxy gas furnace used in this industry;

- Refractories above glass line have high(er) chromium content because of the 

significantly higher temperatures;
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- Furnace crown refractories typically do have high Cr content, but not always;

- Furnace design, economics (cost), and safety are all critical

- Chrome emissions are primarily Cr+6 due to the higher temperatures and interaction 

with the volatiles from the batch (glass);

- Burner temperature = ~5,300° F and furnace environment temperature = ~3,000° F;

- Batch impurities such as sodium, boron, and other alkali earth metals can volatilize and 

corrode/erode the furnace walls;

- Boron is highly reactive and is a critical part of fiberglass insulation;

- Corrosive gases and the velocity of those gases inside the furnace cause erosion of the 

refractories – significant chemical interactions at these high temperatures; and 

- Materials trapped in the glass can be volatilized and emitted also.

b. Air Gas 

- Attachment 4 has a diagram of a typical air gas furnace used in this industry;

- Burner temperature = ~3,560° F; and

- Lower furnace temperatures (compared to oxy gas) so Cr refractories not needed in 

furnace super structure  lower Cr emissions.

c. Electric Melt (also called “Cold Top”) 

- Attachment 5 has a diagram of a typical electric melt furnace used in this industry;

- Temperature inside furnace above the glass = <250° F (measured 24” above batch);

- Lower furnace temperatures so Cr refractories not needed above the glass line;

- Wet or damp batch (raw materials) are added on top of the molten glass and serve as a 

crust or cover on the molten glass (in-process air pollution control technique); and

- Glass heated by metal electrodes positioned from the bottom of the furnace – except for 

startup when gas firing is used until enough melt is generated to contact the electrodes.

d. Steel Shell 

- Attachment 6 has a diagram of a typical steel shell furnace used in this industry;

- Temperature inside furnace above the glass = <200° F;

- Lower furnace temperatures so Cr refractories not needed above the glass line;
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- Top of furnace is a steel dust cover (not refractories); and

- Steel shell contains (recirculated) water jacket to help control temperature. 

The next discussion topic involved modeling and remodeling results. Three companies (Owens 

Corning, Guardian, and Saint Gobain/CertainTeed) conducted risk modeling based on the 

modeling information included in the project docket and provided results showing reduced risk 

from each of their fiberglass manufacturing facilities. Copies of the risk reports will be forwarded 

to the U.S. EPA risk modelers for review. 

The last discussion topic was startup and shutdown provisions being considered for both the area 

source rule and the RTR amendments being finalized for subpart NNN. Keith Barnett discussed 

various approaches being considered, including work practice standards to demonstrate 

compliance with emission limits applicable during periods of startup and shutdown. There was 

additional discussion about each type of furnace and procedures used by each company.