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 Production 1 (hereinafter the “Proposed Rule”). We are submitt ing this letter as a follow-up to our meeting on July 2 5, 2013.

Roxul USA Inc. (“Roxul”) is a new source in the min eral wool production category in the U.S. Roxul participated in the public comment process fo r 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 co ncern regarding demonstration of compliance with the startup and shutdown provisions, particula rly for Carbonyl Sulfide (COS), due to our melting furnace design constraints. The alternativ e that we discussed for demonstration of compliance consisted of monitoring the air and oxyg en 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 gr eatly 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 eq uivalence ratio or lambda ( λ ) will provide the best indication of an oxidizing environment as a me thod for demonstration of compliance.

Per your request, this letter also documents our su ggestions regarding the other topics discussed during our meeting.

1 78 F.R. 22369, April 15, 2013Ms. 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 di fferentiated 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 f or later processing). Per the Proposed Rule definition, the Roxul melting furnace would be cons idered 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 d esigned 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 O 2 actually present in combustion chamber divided by O 2 that should be present to obtain complete combustion of fuel. Oxygen Available = Actual quantity of O 2 introduced. Fuel Demand for Oxygen = Required quantity of O 2 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 o xygen present for the amount of fuel (a lean mixture), lambda will be greater than 1.00. If a m ixture contains too little oxygen for the

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

Lambda is a parameter in the Roxul control system t hat is always greater than 1.00. Oxygen and fuel added to the furnace is regulated accordin g 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 melti ng exhaust. For example, with a lean mixture of fuel-to-oxygen, sulfur that is present will oxid ize to form sulfur dioxide (SO 2 ), 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 sulfi de (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. Eve n 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.” Oxygen for demand Fuel available Oxygen 

### Lambda

= 

### ) ( 

# λMs. 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 environm ent.

Demonstrating Compliance During Startup and Shutdow n

**Carbonyl Sulfide (COS)** In July 2013, Roxul collected Tedlar bag samples du ring the startup of a melting furnace at a sister plant in Europe. A sample was collected eve ry ten minutes over the course of a ~90 minute startup for a total of nine samples. The sa mples were analyzed for COS using a GC-MS and the results indicated that COS was present belo w 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-s ulfur gaseous fuels are used during

shutdown, which further limits COS emissions, COS e missions during shutdown would be less than those tested for startup. In addition, the ai r-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 de monstration alternative in addition to the one presented in the Proposed Rule 3 . For demonstrating compliance with emission limit s during periods of startup and shutdown, Roxul propo ses to add the following to §63.1197(e),

“...For demonstrating compliance with the COS emissio n 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 in dicated 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 r atio of oxygen actually present in the cupola melting chamber divided by the oxygen requir ed to obtain complete combustion of the actual quantity of fuel input based on stoic hiometry.”

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 demonstra tion of compliance during these periods.

COS testing has also been performed during normal o peration at another melting furnace in Europe. The testing was conducted in accordance wi th EPA methods and indicated that COS

3 Proposed Rule 40 CFR §63.1197(e), “ **During periods of startups and shutdowns you may de monstrate compliance with the**  **emission limits in §63.1178 by keeping records show ing that your emissions were controlled using air p**  **ollution 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 a ppropriate for demonstration of compliance during normal melting furnace operations. This alt ernative would not preclude the proposed initial and periodic compliance demonstration of pe rformance 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 conti nuous compliance with the proposed limits

for HF and HCl 4 , which we do not understand the intent of. Anothe r option would be the use of a flue gas desulfurization (FGD) system that may already be in place for the control of SO 2 emissions. This approach is similar to the one des cribed in the Mercury and Air Toxics Standards (MATS) for power plants 5 . The MATS rule preamble 6 states that in FGD systems, HF and HCl will be removed more rapidly and readily fr om flue gas than SO 2 . This is due to the ability of HF and HCl to more easily react with cau stic sorbents and also due to their water soluble nature. Compliance with the HF and HCl lim its in the Proposed Rule could then be demonstrated through monitoring of continuous injec tion 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 P roposed Rule definition of startup (with one minor exception) or the version proposed by NAIMA i n their rule comments - **assuming** that the compliance demonstration alternative discussed here in for COS is accepted. In the Proposed Rule definition of startup, Roxul would prefer to r eplace “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 defin ition 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 ma de 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 Em ission Standards For Hazardous Air Pollutants: Coal

And Oil-Fired Electric Utility Steam Generating Uni ts.

6 76 F.R. 24976, May 3, 2011Ms. 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 per son 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 Manag ement