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August 6, 2014

Ms. Susan Fairchild

Sector Policies and Programs Division

Metals and Minerals Group (D243-02)

Office of Air Quality Planning and Standards

U.S. Environmental Protection Agency

4930 Old Page Road

Durham, NC 27703

RE: NAIMA’s Responses To EPA’s Questions – Work Practices For Startup and 

Shutdown of Mineral Wool Cupolas

Dear Ms. Fairchild:

INTRODUCTION

The North American Insulation Manufacturers Association (“NAIMA”) appreciates the 

opportunity to provide work practices employed by mineral wool insulation manufacturers 

during startup and shutdown. As NAIMA stated in its written comments, emissions data are not 

available for startup and shutdown, and the work practices set forth herein provide a sound 

approach to keeping emissions low during startup and shutdown for mineral wool cupolas.

NAIMA and its members would be willing to elaborate or expand on the information set f orth 

herein. The work practices described herein reflect input from NAIMA’s mineral wool 

companies.

The work practices and related information are organized herein by providing aggregated 

responses to four questions that were posed to member companies by NAIMA, as suggested by

conversations with the Environmental Protection Agency (“EPA”). These work practices set 

forth herein may not be used at all facilities. The work practices vary by company depending on 

the particular design of each facility’s process and emissions control equipment. Not all work 

practices are or could be employed at every facility.

QUESTION 1

Question: What work practices or housekeeping measures are used by mineral wool 

companies to keep particulate matter (“PM”) and carbonyl sulfide (“COS”) 

emissions low during startup and shutdown?
Ms. Susan Fairchild

August 6, 2014

Page 2

 Cupola (furnace) emissions are generally controlled with some form of drop out section 

that separates heavy particulate – a thermal oxidizer or combustor – in which any

combustible gases are ignited and burned, and a baghouse or other particulate control

may be used. Natural gas burners provide the ignition source and any necessary

supplemental fuel for the oxidizer. Oxidizer exhaust typically goes through a heat 

exchanger to preheat cupola combustion air (combustion “blast” air) to 900-1000°F. 

Many facilities also inject oxygen into the cupola for combustion (oxygen enrichment).

 Some facilities inject dry sorbent or lime into the area immediately after the combustor 

and before the baghouse to control sulfur emissions. Other facilities may limit the sulfur 

content of the fuel (typically coke) to control sulfur emissions.

 Use of preheat and oxygen enrichment reduces the fuel (typically coke) required in the 

cupola.

 Facilities that use a cupola generally close the stack cap to route the cupola emissions 

through the control devices either prior to or within five minutes of lighting the cupola, 

depending on how well the oxidizer handles the thermal shock of the cap closure.

 During shutdown, the oxidizer and the other controls are in use until oxygen enrichment 

and blast air are removed from the cupola. At that point, the oxidizer is bypassed and 

shutdown, and the cupola is drained after that point.

 During scheduled startups and shutdowns, facilities typically have additional personnel 

and necessary supervision to ensure startup procedures are followed.

 Operators insure all equipment is operational by visually checking electronics and

computer screens, as well as the equipment.

QUESTION 2

Question: Based on this statement from NAIMA’s comments – ‘emissions of some 

pollutants likely are higher during the startup period than at normal steady-state 

operations, and emission of other pollutants likely are lower . . .’ (see NAIMA’s 

February 3, 2012 comments to EPA on p. 49) – EPA believes that there may be 

variations in emissions from rock and slag wool plants during startup and 

shutdown. If variations occur, what are the variations attributable to? What other 

factors might explain variations?

Emissions of some pollutants presumably are higher during the startup period than at normal, 

steady-state operations. For example, emissions of COS and CO likely are higher than usual 

during startup and shutdown because only fuel (typically coke) is being burned initially. 

Emissions of other pollutants likely are lower, for example, because the batch has not yet melted 

during startup. Given the emission limits are on a pound per ton of melt basis, the emissions are 

almost certainly higher on that basis, given the lack of melt, independent of the relative level of 

absolute emissions.
Ms. Susan Fairchild

August 6, 2014

Page 3

Emissions control equipment may not be as effective during startup and shutdown periods as it is 

during steady-state operations. There are numerous reasons why a source might not always 

meet, during periods of startup or shutdown, the emission limitations established based on 

performance during steady-state operation, even if the control devices used are started up before 

the process units and are operational during the shutdown phase of a process. For example, a 

control device may be less efficient until it reaches its design operating temperature, or it may be 

less efficient when the pollutant concentrations in the gases to be treated are lower than during 

steady-state operation (as they often will be when a process is starting up or shutting down).1 

For instance, even if an oxidizer is operational prior to cupola lighting, the inlet temperature of 

the oxidizer will rapidly rise as the hotter gases enter it and then level off. Depending on how 

the temperature controls of the oxidizer respond, the control efficiency can easily fluctuate. On 

the other hand, until a manufacturing process reaches steady-state operation, that process may

generate higher emissions, either on a total mass basis or on a mass per unit of production basis.2

The startup and shutdown periods are very brief, representing a small portion of the overall 

operating cycle, and that brevity therefore undercuts any potentially perceived need for new or 

different requirements during these periods. Cupolas typically operate for a one- to two-week 

period, (this is not representative of all facilities) and the startup period for a cupola generally is 

1 to 2 hours and the shutdown period ranges from 0.5 to 2 hours. Assuming that the combined 

startup and shutdown period is 4.0 hours, these combined periods are roughly 2 percent of an 

approximately one-week production run and 1 percent of an approximately two-week production 

run. These time frames are averages, not precisely applicable to all facilities. Further, control 

devices are operational on at least the majority of the startup and shutdown periods.

There could be higher emissions for the very short period that the oxidizer is being bypassed 

after the cupola is lit (both PM and COS) than during normal operations. But even in these 

instances, the oxidizer is brought up to the required destruction temperature before the cupola is 

lit. Because it takes a while to obtain melt, on a pound per ton basis, the emissions remain higher 

than normal for a period even after the oxidizer is put on line, even though absolute emissions 

should no longer be elevated. Not all cupolas (furnaces) are designed to bypass oxidizers and 

filters.

These additional details provide further explanation on reasons for possible variations:

 During cupola startup, at some facilities, only the fuel (typically coke) is burning until a 

sufficient "coke bed" is established in the bottom of the cupola. Then raw materials are 

placed on top.

 Products of fuel (typically coke) combustion would be evident in emissions on startup.

 Products of fuel (typically coke) combustion and raw material melting would be evident 

in emissions during startup as well as shutdown conditions.

 

1

See, e.g., 68 Fed. Reg. 1,276, 1,287-88 (Jan. 9, 2003).

2

See, e.g., 76 Fed. Reg. 63,878, 63,883 (Oct. 14, 2011).
Ms. Susan Fairchild

August 6, 2014

Page 4

 In many facilities, pollution control equipment would be running the majority of the time 

in each of these conditions.

 Equipment malfunction emergencies may also cause variations in emissions, although 

malfunctions are outside the scope of the questions posed.

QUESTION 3

Question: For emissions during startup and shutdown:

 Are emissions monitored during startup and shutdown currently?

Emission levels are not measured during startup or shutdown. EPA standard emission testing 

methods require testing be conducted during steady-state operating conditions, which do not 

occur during the startup and shutdown period. Control device parameters and the equipment 

itself are monitored. In some cases, opacity is monitored visually.

 What issues might be detected during monitoring?

Insufficient air flow, pressure readings, motors not running, water not flowing, oxygen not 

flowing, insufficient temperature in control devices, etc.

 Does the monitoring inform you about specific actions that need to be taken to 

reduce the emissions?

Operators are trained on the entire cupola melting operation. Standard procedures specify 

specific actions to be taken during the startup and shutdown periods. Experienced supervisors 

are present during the startup and shutdown periods as well.

QUESTION 4

Question: What additional measures (work practices or housekeeping measures) can be 

undertaken by companies to make certain that emissions levels are maintained 

throughout the startup and shutdown period?

 Follow company startup and shutdown procedures.

 Prior to startup after extended down times (not counting cupola drops), cupolas 

(furnaces) and all associated environmental abatement and control systems are inspected, 

cleaned, maintained, and work performed documented as set forth in a preventive 

maintenance program or operation, maintenance, and monitoring plan.

 Facilities maintain logs that record routine regular inspections of operating components 

of emissions control equipment.
Ms. Susan Fairchild

August 6, 2014

Page 5

 During a portion of the startup, some facilities use clean fuel (natural gas) to heat up 

afterburners, raw materials, and eventually ignite the fuel source.

 Routine observation of working equipment to assure proper function of emissions control 

equipment.

 During startup, melting cupolas (furnace) and abatement equipment are monitored by 

temperature controls, air pressure and flow gauges within a specific operational range to 

ensure optimal and safe operations and low emissions.

 Raw material quality is monitored via certificates of analysis when received from outside 

vendors.

 If a malfunction occurs during startup, trained operators will quickly rectify the problem 

or move the cupola (furnace) into relief mode (pause startup and tap furnace). When 

problems have been rectified, startup can continue from where it was aborted.

If you have any questions, please do not hesitate to contact me.

Sincerely,

Angus E. Crane

Executive Vice President, General Counsel

cc: Mr. Keith W. Barnett

Group Leader, Office of Air Quality and Planning Standards

Sector Policies and Programs Division, Mineral and Manufacturing Group

U.S. Environmental Protection Agency

4930 Old Page Road

Durham, NC 27703