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TO: PROJECT FILES 

FROM: SUSAN FAIRCHILD, US EPA 

DATE: 22 SEPTEMBER 2014 

RE: SITE VISIT TO ROXUL MINERAL WOOL PRODUCTION FACILITY, BYHALIA, MS 

AUGUST 6-7, 2014 

1 PURPOSE 

In telephone conversations with Roxul, Inc. (a subsidiary of Rockwool International) representatives and contractors 

during the course of the first and supplemental proposals, the EPA learned that Rockwool International was constructing 

a new mineral wool production facility in Mississippi. This new facility would use a process which is different in certain 

respects from the other U.S. production facilities. Rockwool International operated several such facilities in Europe. 

The EPA’s goal for this site visit is to understand Roxul’s production processes, how they differ or are similar to other U.S. 

facilities’ mineral wool production processes, the HAP emitted by the new processes, and to understand the regulatory 

issues arising from the advent of the new processes. 

2 ATTENDEES 

Persons from the EPA, Roxul, ERM (a contractor to Roxul) and the State of Mississippi attended the site visit. 

The following attended from EPA:

Susan Fairchild, Sr. Environmental Scientist

Keith Barnett, Group Leader, Minerals and Manufacturing Group

The following attended from Roxul:

Bent S. Jorgensen, Vice President, Operations

Ken Cammarato, Vice President General Counsel and General Manager, USA Operations

Tony Borden, Health and Safety Manager

Sharon Taylor, Environmental Manager

The following attended from ERM:

Jeffrey H. Twaddle, P.E.

Kasey Harrington
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The following attended from Mississippi Department of Environmental Quality (DEQ):

Preston Bridges, EEIT

3 BACKGROUND 

Section 112 of the Clean Air Act (CAA) outlines the statutory requirements for the EPA’s stationary source air 

toxics program. Section 112 requires EPA to set maximum achievable control technology (MACT) standards for 

source categories listed for regulation of hazardous air pollutants (HAP). The MACT standards for Mineral 

Wool Production (Part 63, Subpart DDD were promulgated in June 1999.

The Risk and Technology Review (RTR) is a combined effort to evaluate both risk and technology as required 

by the Clean Air Act (CAA) after the application of the MACT standards. Section 112(f)(2) directs EPA to 

conduct risk assessments on each source category subject to MACT standards, and to determine if additional 

standards are needed to reduce residual risks. Section 112(d)(6) of the CAA requires EPA to review and revise 

MACT standards, as necessary, taking into account developments in practices, processes and control 

technologies. The Agency is conducting both these reviews at once under the RTR review. In addition to the 

requirements of the RTR review, EPA is also reviewing the standards to determine whether any HAP or HAPemitting processes exist which were not regulated by the 1999 MACTs and whether emission limits for 

surrogates in the rule should be corrected or replaced by the original listed HAP.

The EPA first proposed the RTR for Mineral Wool on November 25, 2011. The first supplemental proposal was published 

on April 15, 2013, and announced several changes to the first proposal, including changes to the emission limits for

combined collection and curing, and to startup and shutdown provisions. The second supplemental proposal is 

expected to be signed by the Administrator on October 15, 2014, and published in the Federal Register shortly 

thereafter. 

4 FACILITY OVERVIEW 

Roxul, a Rockwool International Company headquartered in Toronto, Ontario, Canada sought permits and 

began site preparation for this new mineral wool production facility in 2012. The Roxul facility currently operates

one production line consisting of raw material preparation, transfer and storage; melting; fiber formation, collection and 

curing; cutting, packaging and storage. Roxul is permitted to begin construction on a second line. Roxul is also

permitted for fabrication processes for the manufacture of other products. 

4.1 PRODUCTS 

Roxul is planned to be capable of manufacturing a variety of bonded and loose-fill (non-bonded) products, including 

insulation for both residential and non-residential applications, sound-proofing, ceiling tile and asphalt roofing. 

This facility is currently capable of manufacturing a variety of mineral wool products, including:

 Residential insulation

 Commercial/ Institutional insulation

 Industrial insulation

 Marine & Offshore
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 Soundproofing and Acoustical barriers 

Roxul’s products are manufactured in thicknesses from one to 8 inches on the single operating production line. 

Roxul is planning to significantly expand the production capacity at the Byhalia plant. A second production line is 

planned and permitted which will double capacity. 

The new production line is planned as a mirror image of the current line, with additional capability for production of 

ceiling tile and asphalt roofing in addition to the additional capacity for mineral wool insulation products. When the 

second production line is completed, Roxul plans to simultaneously complete an industrial oxygen plant on site which 

will supply the compressed gas for both cupolas (melting furnaces).

4.2 EXISTING PRODUCTION PROCESSES 

4.2.1 Raw Material Loading, Preparation, Transfer and Storage Processes 

Fuels used for production at Roxul include compressed industrial oxygen, coal and natural gas. Raw materials include 

basalt, slag (from iron and steel electric arc furnaces), mineral additives, internal recycled mineral wool and 

phenol/formaldehyde binder. 

Compressed oxygen is currently transported in tanks and stored onsite. Basalt and slag are received from a quarry and 

steel plant, respectively, and are received as grain size, and sieved onsite to ensure proper sizing. Rod crushing is used 

for any materials out of size specification. All fuels and raw materials are stored onsite in silos (coal) and bins (other 

mineral products).

4.2.2 Startup 

The cupola is started empty using only clean fuels (natural gas) for 2-5 minutes until it reaches temperatures sufficient to 

begin melting the mineral mixture, approximately 3200° F. At that point the coal burners start and feed material is 

introduced. This phase of startup lasts 10-15 minutes. At this point (12 – 20 minutes) the melting furnace is capable of 

producing usable melt. Steady state production is reached in less than 90 minutes.

4.2.3 Melting Process 

The Roxul process differs from other US mineral wool production facilities in the melting process. The Roxul process uses 

a melting furnace fired with coal and natural gas, rather than a cupola fired with coke. 

Coal, slag, and basalt from hoppers and silos are measured and weighed onto charging belts; mineral additives are used 

to achieve the correct chemistry of the melt, and the raw material mixture is blended and fed as a continuous stream 

into the cupola. The melting furnace operates continuously for a 2 week period under the melting furnace maintenance

schedule. 

4.2.4 Shutdown 

The melting furnace is shut down for maintenance every two weeks, and is a process that requires about 15 minutes to 

complete, excluding cooling of the melting furnace. All air pollution control devices (APCD) operate continuously, 

including during shutdown, and therefore should continue to capture and control any emissions during the shutdown 

process. 
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4.2.5 Fiber Formation, Collection and Curing Process 

As molten mineral mixture exits the melting furnace, the melt enters the spinners, forming fibers; phenol-formaldehyde 

binder is sprayed continuously as the fibers are formed and collected. The combined collection and curing processes at 

Roxul are considered Vertical Design as the area where the fibers are collected is vertically oriented. 

The collected fibers form a wooly fleece which is spread onto a moving conveyor to a pendulum device which lays the 

fiber fleece to the desired thickness. The formed mat then enters the curing oven which heats and sets the 

phenol/formaldehyde resin. These processes are automated and are similar to the processes at other mineral wool 

production facilities. 

4.2.6 Cooling Process 

As the formed mat exits the curing oven, it is cooled before cutting and packaging. When the ceiling tile and asphalt 

roofing fabrication processes are added at a future date, cooled mineral wool bats will be transferred to those 

manufacturing processes. 

4.2.7 Fabrication (future) Processes 

Production of ceiling tile and asphalt roofing, products which are fabricated from mineral wool products, is also planned. 

The production of ceiling tile and asphalt roofing are not regulated under subpart DDD, Mineral Wool Production.

4.2.8 Cutting, Packaging, Storage, and Shipping 

After the mineral wool produced to the desired thickness, it is cut to size. All cutting and packaging operations are 

automated and robotic are operated from a central location. Rollers transfer the product from the cooling section 

through the cutters, into the bagging section and then to storage until the product is shipped to the customer.

4.3 AIR POLLUTION CONTROL EQUIPMENT 

Pollutants emitted from the melting furnace are controlled using several sets of devices installed in series. The emissions 

from the melting furnace are first sent to an integrated SNCR for destruction of nitrogen oxides (NOx) and secondary 

combustion chamber for destruction of CO, then to a baghouse for PM and HAP metals removal. The emission stream is 

next directed to a semi- dry lime scrubber for adsorption of sulfur oxides (SOx) in series with a second fabric filter for 

removal of the lime, then melting furnace emissions are directed to the furnace stack. Emissions from the collection 

process are sent first to a filter for fiber removal and then to the Wet Electrostatic Precipitator (WESP) for removal of

filterable and condensable particulate matter (due to phenol-formaldehyde binder). Emissions of organics, including

phenol, formaldehyde and methanol from the curing oven are first sent to an afterburner and then to a filter for 

removal of both organics and fibers. Post-control emissions from the collection and curing processes enter separate 

stacks which run alongside one another and are adjoining at the outlet of the second stack. Particulate (fiber) emissions 

from the cooling zone are directed to a filter in series with the WESP. All emission control collection material from the 

furnace is returned to the raw material input bins for reincorporation into the process with the exception of the sorbent 

material used in the SO2 scrubber. A schematic of the Roxul manufacturing process entitled, “Process Overview” is 

available in the Appendix to this report. 

4.4 PROJECTED EMISSIONS ESTIMATES (COMMISSIONING PHASE UNDERWAY) 

Roxul has provided to the permitting authorities projections of expected emissions estimates from the mineral wool 

production lines, as shown in Table 4-1 below. These emissions estimates are based upon production at the European 

and Canadian facilities, not on emissions testing, material balance, or emission factor-derived estimates.

Table 4-1: Pollutants and Significant Emissions Rates for the Roxul US Facility
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Pollutant Significant Emissions Rate (tons/yr) PTE Exceeds SER?

Carbon monoxide * 100 Yes

Nitrogen oxides * a 40 Yes

Sulfur dioxide * b 40 Yes

Particulate matter *(PM) 25 Yes

PM10 * 15 Yes

PM2.5 * c 10 Yes

Ozone (VOC) * 40 (of VOCs or NOx) Yes

Lead * 0.6 No

Asbestos 0.007 No

Beryllium 0.0004 No

Mercury 0.1 No

Vinyl chloride 1 No

Fluorides (excluding hydrogen fluoridee) d 3 Noe

Sulfuric acid mist 7 Yes

Hydrogen sulfide (H2S) 10 No

Total Reduced sulfur compounds (including 

H2S) (excluding COSe)

10 No

Arsenic f Any emission rate Yes

* Criteria Pollutants

a Nitrogen dioxide is the compound regulated as a criteria pollutant; however, significant emissions are based on the sum of all 

oxides of nitrogen.

b Sulfur dioxide is the measured surrogate for the criteria pollutant sulfur oxides.

c 10 tpy of direct PM2.5 emissions; 40 tpy of sulfur dioxide emissions; 40 tpy of nitrogen oxide emissions unless demonstrated not to 

be a PM2.5 precursor under paragraph (b)(50) of this section.

d Total fluorides means elemental fluorine and all fluoride compounds as measured by reference methods specified in §60.195 or by 

equivalent or alternative methods (see §60.8(b)). [40 CFR 60.191]

e HF and COS are HAPs and not included in the Fluoride or Total reduced Sulfur Compounds pollutant category. See Section 3.1.1 

and §52.21(b)(50)(v) for further explanation.

f Significant emission rates have not been promulgated for these pollutants, and until such time, any emissions by a new major 

sources or any increase in emissions at an existing major source due to modification, are "significant."

4.5 OPERATING AND MAINTENANCE SCHEDULE 

Roxul operates for 2 week periods on a 24-hour schedule followed by melting furnace maintenance. Additionally, every 

8 weeks additional maintenance and rebuilding of the melting furnace downspout is conducted, along with any other 

maintenance required downstream of the melting furnace.

4.6 REGULATORY ISSUES 

4.6.1 Issues regarding regulation of melting furnace emissions 

Though the melting furnace process at Roxul is very different from any other mineral wool cupola now in operation, it

meets the definition in DDD of a cupola, and would thus be subject to the cupola emissions limits. Roxul does not expect 

this to raise any compliance issues for any of the pollutants except for the demonstration of compliance with CO. 

The MACT standard of 1999 requires CO be measured as a surrogate to COS, and CO reductions of 99% are required 

under that rule. In order to determine percent reduction, measurements of the pollutant must be taken both before and 
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after the APCD. Due to both the design and extreme temperatures (both unique to Roxul among mineral wool producers 

in the U.S.), the percent reduction cannot be measured. Because the CO limits are required by the existing MACT 

standard for this industry, and because CO remains the surrogate for COS until the RTR is finalized, as a legal matter, the 

CO limits cannot be dismissed. The EPA representatives recommended that Roxul pursue an alternative compliance 

demonstration for the Mineral Wool MACT CO limits. 

Limited testing at the Byhalia facility also showed COS emissions below the method detection limit. Because the Roxul 

melting furnace design has an oxidizing atmosphere, compared to the standard mineral wool cupola design which has a 

reducing atmosphere, all the raw material and fuel sulfur is converted to SO2 rather than some being converted to COS. 

Emissions of other pollutants (SO2), NOx, HF and HCl are controlled and are expected to be low. 

Emission testing was conducted at sister sites in Europe on processes that are identical to the processes in place in the 

commissioning phase at Byhalia. The available representative testing shows COS also tested below the detection level of 

the method. 

4.6.2 Issues Regarding Startup / Shutdown Work Practices 

Periods of startup and shutdown for this process are approximately 12-20 minutes. Given this short startup/shutdown 

times, and the fact that the emission test methods for the pollutants of concern typically require a full day to collect 

three valid test runs, the EPA representatives noted it would appear that emission testing is not practicable. Therefore,

Roxul was requested to provide to EPA any work practices used to minimize emissions during periods of startup and 

shutdown, and contact us to discuss and follow up on the potential work practices used for the unique cupola operated 

at this facility. 

4.6.3 Issues Regarding New/Existing Source Status 

As described in the Background section of this report, three proposals issued over the 3-year period (November 2011 to 

October 2014) pertain to the Mineral Wool Production Source Category. Roxul began actual construction of the facility 

in Byhalia, Mississippi in May of 2013, which was after the first and second proposal but before subsequent October 

2014 supplemental proposal. Roxul representatives stated that they would have been considered a new site, not an 

existing site under the originally proposed version of the rule.