August 9, 2013 

Attn: Ms. Susan Fairchild 

U.S. Environmental Protection Agency 

OAQPS/SPPD/MMG 

Mail Code D 243-04 

Research Triangle Park, NC 27711 

Subject: Follow-up to July 25, 2013 Meeting 

NESHAP for Mineral Wool Production 

Docket ID Number EPA-HQ-OAR-2010-1041 

Dear Ms. Fairchild: 

Thank you again for taking the time to meet with us regarding the proposed revisions to the 

NESHAP for Mineral Wool Production1 (hereinafter the “Proposed Rule”). We are submitting 

this letter as a follow-up to our meeting on July 25, 2013. 

Roxul USA Inc. (“Roxul”) is a new source in the mineral wool production category in the U.S. 

Roxul participated in the public comment process for this rulemaking through our industry 

group, the North American Insulation Manufacturer’s Association (NAIMA). However, as we 

discussed during our meeting there is a specific concern regarding demonstration of compliance 

with the startup and shutdown provisions, particularly for Carbonyl Sulfide (COS), due to our 

melting furnace design constraints. The alternative that we discussed for demonstration of 

compliance consisted of monitoring the air and oxygen introduced to the melting furnace. By 

maintaining an oxidizing environment during melting (as indicated by an oxygen content 

greater than 21%), the formation of COS would be greatly inhibited. Upon further review, we 

have determined that, in addition to air and oxygen, fuel input must also be considered. As 

described further below, monitoring the air-fuel equivalence ratio or lambda (λ) will provide the 

best indication of an oxidizing environment as a method for demonstration of compliance. 

Per your request, this letter also documents our suggestions regarding the other topics 

discussed during our meeting. 

 

1 78 F.R. 22369, April 15, 2013
Ms. Susan Fairchild 

U.S. EPA Docket ID No. EPA–HQ–OAR–2010–1041 

Page 2 of 5 

Roxul Design and Melting Conditions 

Although the Roxul melting furnace design can be differentiated from that of a traditional 

cupola, the furnace at its basic premise meets the current NESHAP Subpart DDD definition of a 

cupola (i.e., a large, water-cooled metal vessel to which a mixture of fuel, rock and/or slag, and 

additives is charged and heated to a molten state for later processing). Per the Proposed Rule 

definition, the Roxul melting furnace would be considered an open-top cupola.2 

The Roxul furnace design requires an oxidizing or “fuel-lean” combustion environment for 

melting to occur. In other words, the furnace is designed to operate with more oxygen than 

required for complete combustion of fuel to occur. This design parameter is expressed as the 

air-fuel equivalence ratio or lambda (λ) shown below. 

Where, 

λ = Ratio of O2 actually present in combustion chamber divided by O2 that should be present to 

obtain complete combustion of fuel. 

Oxygen Available = Actual quantity of O2 introduced. 

Fuel Demand for Oxygen = Required quantity of O2 for stoichiometric combustion of the quantity 

of fuel present. 

Lambda is equal to 1.00 when oxygen and combustible demand for oxygen are in balance – the 

perfect stoichiometric point. If there is excess oxygen present for the amount of fuel (a lean 

mixture), lambda will be greater than 1.00. If a mixture contains too little oxygen for the 

amount of fuel (a rich mixture), lambda will be less than 1.00. 

Lambda is a parameter in the Roxul control system that is always greater than 1.00. Oxygen 

and fuel added to the furnace is regulated according to a specified set point (>1.00). Actual 

lambda will be calculated from real time monitoring of the quantity of oxygen and fuel 

introduced and the known oxygen demand of the fuel for complete combustion to occur. 

Melting conditions will affect the content of melting exhaust. For example, with a lean mixture 

of fuel-to-oxygen, sulfur that is present will oxidize to form sulfur dioxide (SO2), due to the 

excess oxygen available that has not been consumed during combustion. With a rich mixture of 

fuel-to-oxygen, sulfur is reduced to carbonyl sulfide (COS), a Hazardous Air Pollutant (HAP) in 

the Proposed Rule revisions. A traditional cupola operates with a “fuel-rich” environment by 

combusting continuous layers of rock and coke. Even with oxygen enrichment systems that aid 

 

2

 “Open-top cupola means a cupola that is open to the outside air and operates with an air flow rate that is unrestricted and at 

low pressure.” [Proposed 78 F.R. 22369, April 15, 2013]. NAIMA comments dated May 30, 2013 suggested deletion 

of the phrase “and at low pressure.”

Fuel demand for Oxygen

Oxygen available

 λ(Lambda) =
Ms. Susan Fairchild 

U.S. EPA Docket ID No. EPA–HQ–OAR–2010–1041 

Page 3 of 5 

in increasing combustion efficiency, a traditional cupola design will always contain more fuel 

than available oxygen, creating a reducing environment. 

Demonstrating Compliance During Startup and Shutdown 

Carbonyl Sulfide (COS) 

In July 2013, Roxul collected Tedlar bag samples during the startup of a melting furnace at a 

sister plant in Europe. A sample was collected every ten minutes over the course of a ~90 

minute startup for a total of nine samples. The samples were analyzed for COS using a GC-MS 

and the results indicated that COS was present below the detection limit of less than 1 ppmv in 

all samples. An emission rate of 0.006 lb COS/ton melt or 0.06 lb COS/hr would be equivalent 

to 1 ppmv COS for this startup. Because only low-sulfur gaseous fuels are used during 

shutdown, which further limits COS emissions, COS emissions during shutdown would be less 

than those tested for startup. In addition, the air-fuel equivalence ratio (or lambda) is 

maintained at greater than 1.00 during shutdown. 

Roxul supports the COS limits for open-top cupolas in the Proposed Rule. As we discussed in 

our meeting, we would like to offer a compliance demonstration alternative in addition to the 

one presented in the Proposed Rule3. For demonstrating compliance with emission limits 

during periods of startup and shutdown, Roxul proposes to add the following to §63.1197(e), 

“...For demonstrating compliance with the COS emission limits during periods of 

startups and shutdowns you may keep records showing that the open or closed-top 

cupola operated with a fuel-lean environment, as indicated by an air-fuel equivalence 

ratio of greater than 1.00.” 

The definition for air-fuel equivalence ratio would read as follows, 

 

“Air-fuel Equivalence Ratio (or lambda) means the ratio of oxygen actually present in the 

cupola melting chamber divided by the oxygen required to obtain complete combustion 

of the actual quantity of fuel input based on stoichiometry.” 

As described above, the Roxul melting furnace will operate and maintain an air-fuel 

equivalence ratio, or lambda, of greater than 1.00 at all times, including periods of startup and 

shutdown. This value will be recorded as demonstration of compliance during these periods. 

COS testing has also been performed during normal operation at another melting furnace in 

Europe. The testing was conducted in accordance with EPA methods and indicated that COS 

 

3

Proposed Rule 40 CFR §63.1197(e), “During periods of startups and shutdowns you may demonstrate compliance with the 

emission limits in §63.1178 by keeping records showing that your emissions were controlled using air pollution control devices 

operated at the parameters established by the most recent performance test that showed compliance with the standard.”
Ms. Susan Fairchild 

U.S. EPA Docket ID No. EPA–HQ–OAR–2010–1041 

Page 4 of 5 

emissions were well below the lb/ton limitation for open-top cupolas in the Proposed Rule. 

That said, the proposed alternative would also be appropriate for demonstration of compliance 

during normal melting furnace operations. This alternative would not preclude the proposed 

initial and periodic compliance demonstration of performance testing. 

Other Meeting Discussion Points 

Hydrogen Fluoride (HF) & Hydrogen Chloride (HCl) 

The November 25, 2011 version of the Proposed Rule indicated monitoring of incinerator or 

RTO firebox temperature as a demonstration of continuous compliance with the proposed limits 

for HF and HCl4, which we do not understand the intent of. Another option would be the use 

of a flue gas desulfurization (FGD) system that may already be in place for the control of SO2

emissions. This approach is similar to the one described in the Mercury and Air Toxics 

Standards (MATS) for power plants5. The MATS rule preamble6 states that in FGD systems, HF 

and HCl will be removed more rapidly and readily from flue gas than SO2. This is due to the 

ability of HF and HCl to more easily react with caustic sorbents and also due to their water 

soluble nature. Compliance with the HF and HCl limits in the Proposed Rule could then be 

demonstrated through monitoring of continuous injection of sorbent material. 

Definitions 

In our meeting, we discussed clarifications to the definitions of startup and shutdown in the 

Proposed Rule. Roxul is in support of either the Proposed Rule definition of startup (with one 

minor exception) or the version proposed by NAIMA in their rule comments - assuming that the 

compliance demonstration alternative discussed herein for COS is accepted. In the Proposed 

Rule definition of startup, Roxul would prefer to replace “coke interspersed with layers of rock 

and/or slag and other mineral products” with “fuel and rock and/or slag and other mineral 

products”. 

Roxul proposes the following language for the definition of shutdown, 

“Shutdown begins when the feed of raw materials is stopped. Shutdown ends when the 

cupola is empty.” 

Please note that Roxul also supports the comment made by NAIMA with regard to the 

definition of open-top cupola (i.e., removal of the phrase, “and at low pressure.”). 

 

4

 See §63.1182(a),(b) of Proposed Rule. 

5

 Found at 40 CFR Part 63 Subpart UUUUU--National Emission Standards For Hazardous Air Pollutants: CoalAnd Oil-Fired Electric Utility Steam Generating Units.

6

 76 F.R. 24976, May 3, 2011
Ms. Susan Fairchild 

U.S. EPA Docket ID No. EPA–HQ–OAR–2010–1041 

Page 5 of 5 

* * * 

We are available by teleconference or for an in person meeting with you and your team should 

the need arise. In the meantime, please contact me at (905) 875-9304 or 

bent.jorgensen@roxul.com with any questions. 

Sincerely, 

Bent Jorgensen 

Vice President of Operations 

Cc: Ken Cammarato – Roxul, Inc. 

 Elisa Rosenbohm – Rockwool International 

Sid Trant – Bradley Arant Boult Cummings, LLP 

 Jeff Twaddle, P.E. – Environmental Resources Management