August9,2013

Attn: Ms. SusanFairchild 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 NumberEPA-HQ-OAR-2010-1041

Dear Ms. Fairchild: Thankyou againfor taking the time to meetwith us regarding the proposed revisions to the NESHAP for Mineral Wool Production! (hereinafter the "Proposed Rule/l). We are submitting this letter as a follow-up to our meeting onJuly 25, 2013. Roxul USA Inc. ("Roxul/l) is a new source inthe mineral wool production category inthe U.S. Roxul participated in the public commentprocess for this rulemaking through our industry group, the NorthAmerican Insulation Manufacturer's Association (NAIMA). However, as we discussed during our meeting there is a specific concern regarding demonstration ofcompliance with the startup and shutdownprovisions, particularly for Carbonyl Sulfide (COS), due to our melting furnace design constraints. The alternative that we discussed for demonstration of compliance consisted ofmonitoring 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 ofCOS 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, monitoringthe air-fuel equivalence ratio orlambda (A) will providethe best indication ofan OXidizing environment as a method for demonstration ofcompliance.
Peryour request, this letter also documents our suggestions regarding the other topics discussed during ourmeeting.

1 78 F.R. 22369, April 15, 2013

420 Bronte Street, Milton, Ontario 19T OH9 1-800-265-6878 or (905) 878-8474 www.roxul.comMs. Susan Fairchild U.S. EPA Docket ID No. EPA-HQ-OAR-2010-1041 Page 2 of5 

### RoxulDesign andMelting Conditions Although the Roxul melting furnace design canbe differentiated from that of a traditional cupola, the furnace atits basic premise meets the current NESHAP Subpart DDD definition ofa cupola (i.e., a large, water-cooled metal vessel to which a mixture offuel, rock and/or slag, and additives is charged and heated to a molten state for later processing). Per the Proposed Rule definition, the Roxul meltingfurnace wouldbe considered anopen-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 offuel to occur. This design parameter is expressed as the air-fuel equivalence ratio or lambda (A) shownbelow. 

# A(Lambda) 

## = Oxygen available Fuel demandfor Oxygen Where, A = Ratio of02 actually present in combustionchamber divided by 02that should be present to obtain complete combustion offuel. Oxygen Available Actual quantity of02 introduced. Fuel Demand for Oxygen = Required quantity of02 for stoichiometric combustion ofthe quantity of fuel present. Lambda is equal to 1.00 when oxygen and combustible demand for oxygen are inbalance

- the perfect stoichiometricpoint. If there is excess oxygen present for the amount offuel (a lean mixture), lambda will be greater than 1.00. If a mixture contains too little oxygen for the amount offuel (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 ofthe quantityofoxygen and fuel introduced and the known oxygen demand ofthe fuel for complete combustion to occur. Melting conditions will affect the content ofmelting exhaust. For example, with a lean mixture offuel-to-oxygen, sulfur that is present will oxidize to form sulfur dioxide (S02), due to the excess oxygen available thathas 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" environmentby combusting continuous layers ofrock and coke. Even withoxygen enrichment systems that aid

2 "Open-top cupola means acupola that is open to the outside airand operates with an air flow rate that is unrestrictedandat low pressure." [Proposed 78 F.R 22369, April 15, 2013]. NAIMA comments dated May 30, 2013 suggested deletion ofthephrase "and at low pressure."Ms. SusanFairchild U.S. EPA Docket ID No. EPA-HQ-OAR-20l0-1041 Page 3 ofS in increasing combustionefficiency, 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 ofa melting furnace at a sister plantinEurope. A sample was collected every tenminutes over the course of a -90 minute startup for a total ofnine samples. The samples were analyzed for COS using a GC-MS and the results indicated that COS was presentbelow the detection limit ofless than 1 ppmv in all samples. An emission rate of 0.0061b COS/tonmelt or 0.061b COS/hr wouldbe equivalent to 1 ppmv COS for this startup. Because only low-sulfur gaseous fuels are used during shutdown, whichfurther limits COS emissions, COS emissions during shutdown wouldbeless 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 additionto the one presented inthe 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 indicatedby an air-fuel equivalence ratio ofgreater 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 presentinthe cupola melting chamber dividedby the oxygenrequired to obtain complete combustion ofthe actual quantity offuel inputbased**on-stoichlometry~-~-~~- .--~-~-**  As described above, the Roxul melting furnace will operate and maintain an air-fuel equivalence ratio, or lambda, ofgreater than 1.00 at all times, including periods of startup and shutdown. This value will be recorded as demonstration ofcompliance during these periods. COS testing has also beenperformed during normal operation at another melting furnace in Europe. The testing was conducted in accordance with EPA methods and indicated that COS

3 Proposed Rule40 CFR §63.1197(e}, "Duringperiods of startups and shutdowns you may demonstrate compliance with the emission limits in §63.1178 by keeping records showing thatyouremissions were controlled using airpollution control devices operated at the parameters established by the most recentperformance test that showed compliance with the standard./IMs. SusanFairchild U.S. EPA Docket ID No. EPA-HQ-OAR-2010-1041 Page4of5 emissions were well below the lb/tonlimitation for open-top cupolas in the Proposed Rule. That said, the proposed alternative would also be appropriate for demonstration ofcompliance during normal melting furnace operations. This alternative would not preclude the proposed initial and periodic compliance demonstration ofperformance testing. OtherMeetingDiscussion Points 

### Hydrog-en Fluoride (HF) & 

### Hydrog-en Chloride (HCZ) The November 25, 2011 version ofthe Proposed Rule indicated monitoring ofincinerator or RTO firebox temperature as a demonstration ofcontinuous compliance with the proposed limits for HF and HCI4, which we do not understand the intent of. Another optionwouldbe the use of a flue gas desulfurization (FGD) system that may alreadybe inplace for the control of**S~** emissions. This approachis similar to the one described in the Mercury and Air Toxics Standards (MATS) for power plantsS• The MATS rule preamble6 states that in FGD systems, HF and HCI will be removed morerapidly and readily from flue gas than

### 502. This is due to the ability ofHF and HCI to more easilyreact with caustic sorbents and also due to their water soluble nature. Compliance with the HF and HCllimits inthe Proposed Rule could thenbe demonstrated throughmonitoring ofcontinuous injection of sorbent material. Definitions In our meeting, we discussed clarifications to the definitions of startup and shutdownin the Proposed Rule. Roxul is in support ofeither the Proposed Rule definition of startup (with one minor exception) or the version proposedby NAIMA in their rule comments

- 

### assuming that the compliance demonstration alternative discussed herein for COS is accepted. Inthe Proposed Rule definition of startup, Roxul would prefer to replace"coke interspersed with layers ofrock and/or slag and other mineral products" with "fuel androck and/or slag and other mineral products". Roxul proposes the following language for the definition of shutdown, "Shutdownbegins when the feed ofraw materials is stopped. Shutdownends when the cupola is empty." Please note that Roxul also supports the comment madeby NAIMA withregard to the definition of open-top cupola (Le., removal ofthe phrase, "and at low pressure.").

4 See §63.1182(aMb) ofProposed Rule. S Found at 40 CFR Part 63 Subpart UUUUU--National Emission Standards For Hazardous Air Pollutants: Coal­ And Oil-Fired Electric Utility Steam Generating Units. 6 76 F.R. 24976, May 3, 2011Ms. SusanFairchild U.S. EPA Docket lD No. EPA-HQ-OAR-2010-1041 PageS of5 

### *** We are available by teleconference or for aninperson meeting with you and your team should the need arise. In themeantime, please contactme at (905) 875-9304 or bent.jorgensen@roxul.com with any questions. Sincerely,

Cc: Ken Cammarato Roxul, Inc. Elisa Rosenbohm Rockwool International Sid Trant

- Bradley Arant Boult Cummings, LLP JeffTwaddle, P.E. Environmental Resources Management

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