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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 Fiber Glass Furnaces

Dear Ms. Fairchild:

INTRODUCTION

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

opportunity to provide work practices employed by fiber glass 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 for reducing emissions during startup and shutdown for fiber glass furnaces. NAIMA 

and its members would be willing to elaborate or expand on the information set fort h 

herein. The work practices described herein reflect input from all of NAIMA’s fiber glass 

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 furnace and emissions control equipment. Not all work 

practices are or could be employed at every facility.

Because of the subtle proprietary differences in the same types of furnaces operated by different 

manufacturers, NAIMA’s response to Question 1 summarizes the operational practices of all of 

its members to achieve reduced emissions during startup and shutdown of their fiber glass 

insulation furnaces. NAIMA believes that additional specificity can be obtained , where 

necessary, while protecting the proprietary differences in these furnaces.
Ms. Susan Fairchild

August 6, 2014

Page 2

QUESTION 1

Question: “What work practices or housekeeping measures are used by fiber glass 

companies to keep particulate matter (“PM”) (including chrome) emissions low 

during startup and shutdown for the following furnace types?”

 Oxy-Fuel: The only times that an oxy-fuel furnace is started up are after: 1) its initial 

construction; 2) it has been shut down and rebuilt at the end of its safe operating life; or 3) it 

has been idled due to weakness in the market. All oxy-fuel furnaces use only natural gas for 

startup and shutdown. Please note that a typical life span of an oxy-fuel furnace is 6 to 10

years.

For startup, the following work practices are observed:

1. The furnace is slowly heated with external natural gas fired sources (heat-up burners); the 

use of natural gas and slow heating process help to lower emissions.

2. During this initial heating, good combustion practices are followed to minimize 

emissions associated with the products of combustion.

3. After the furnace reaches a specific temperature, the dedicated furnace energy sources are 

initiated.

4. At the appropriate point during the startup process, glass cullet is introduced into the 

preheated furnace.

5. The furnace emission control equipment is brought online at the appropriate time during 

the startup process, prior to introducing batch, to control emissions.

6. As the control equipment is brought online, its operation is monitored to assure that it is 

operating within predetermined ranges that assure its proper operation.

7. When the furnace achieves the required steady state level of operation and control 

equipment is determined to be operating properly, the furnace exhaust gases are routed 

through the control device and batch raw materials are fed into the furnace to achieve a 

normal glass level and operating parameters.

For oxy-fuel furnace shutdowns, the following work practices are observed:

1. The introduction of glass raw material (batch) into the furnace is halted.

2. The input energy is reduced to a level to keep the glass molten; the lowered energy input 

reduces emissions.

3. Good combustion practices are maintained to minimize emissions associated with the 

products of combustion.

4. Emission control devices are taken offline when operating conditions permit or are 

required to preserve the control device.

5. The melter is drained.

6. Energy to the furnace is discontinued and the furnace is allowed to cool.
Ms. Susan Fairchild

August 6, 2014

Page 3

 Air-Gas: The only times that an air-gas furnace is started up are: 1) after its initial 

construction or after it has been shut down; 2) it has been rebuilt at the end of its safe 

operating life; or 3) it has been idled due to weakness in the market. All air-gas furnaces use 

only natural gas for startup and shutdown. Please note that the normal life span of an air-gas 

furnace is 6 to 9 years.

For startup, the following work practices are observed:

1. The furnace is slowly heated with natural gas fired sources. The use of natural gas and 

graduated increases in heat help to lower emissions.

2. During the initial heating process, good combustion practices are followed to minimize 

emissions associated with the products of combustion.

3. After the furnace reaches a specific temperature, glass cullet is introduced into the 

furnace.

4. The furnace emission control equipment is brought online at the appropriate time during 

the startup process, prior to introducing batch, to control emissions.

5. The control equipment is monitored to assure that it is operating within predetermined 

ranges that assure its proper operation.

6. When the furnace achieves the required steady state level of operation and control 

equipment is determined to be operating properly, batch raw materials are fed into the 

furnace to achieve a normal glass level and operation parameters.

For shutdown, the following work practices are observed:

1. Introduction of glass raw material (batch) to the furnace is halted.

2. The input energy into the furnace is reduced to the level required to maintain the glass in 

a molten state to allow removal of as much of the glass as possible from the furnace.

3. Good combustion practices are maintained to minimize emissions associated with the 

products of combustion.

4. Emission control devices are taken offline when operating conditions permit or are 

required to preserve the control device. Depending on the design, this may occur before 

or after the draining is complete.

5. The furnace is drained and all furnace power is shut off after the glass is finished 

draining.

6. Energy to the furnace is discontinued and the furnace is allowed to cool.

 Cold-Top Electric: Because cold-top electrics are all electric, there is no combustion. For 

cold-top electrics, furnace rebuilds are typically every 4 to 7 years. Cold-top electric 

furnaces have inherently low PM and chromium emissions. Typically, the only times that a 

cold-top furnace is started up are after: 1) its initial construction; 2) it has been shut down 

and rebuilt at the end of its safe operating life; or 3) it has been idled due to weakness in the 

market. All cold-top furnaces are electrically heated except during a portion of the startup 

process prior to batch introduction.
Ms. Susan Fairchild

August 6, 2014

Page 4

For startup, the following work practices are observed:

1. Temporary gas burners are used to slowly heat up the furnace to a specific temperature 

and operating state.

2. Good combustion practices are followed to minimize emissions associated with the 

products of combustion.

3. Plant cullet (glass previously produced at the plant) is fed into the furnace to be remelted; use of this type of cullet lowers melting temperature requirements and helps to 

reduce emissions.

4. Electric heating replaces the temporary gas startup heaters as the sole source of energy

for the furnace.

5. When required operating conditions are achieved, batch is fed into the furnace and a crust 

or cover is established over the molten glass.

6. Emission control equipment is turned on at the appropriate time depending on the type of 

control equipment being used and is monitored to assure that it is operating within 

predetermined ranges that assure its proper operation. Typically, a batch cover must be 

established to get the inlet to the control device below the maximum safe operating 

temperature of the control device.

For furnace shutdowns, the following work practices are observed:

1. Glass raw material (batch) introduction to the furnace is halted.

2. The input energy is reduced to a level to keep the glass molten.

3. Emission control devices are taken offline when operating conditions permit or are 

required to preserve the control device. Depending on the design, this may be before or 

after draining is complete.

4. The furnace is drained.

5. The furnace electrode power is shut off.

6. Temporary gas burners are engaged to facilitate the removal of the remaining molten 

glass from the furnace.

7. Good combustion practices are followed to minimize emissions associated with the 

products of combustion.

8. Energy to the furnace is discontinued and the furnace is allowed to cool.

 Steel-Shell Melters: The only times that a steel-shell melter is started up are after: 1) its 

initial construction; 2) after it has been shut down and rebuilt at the end of its safe operating 

life; or 3) it has been idled due to weakness in the market. All steel-shell melters are 

electrically heated except possibly during part of the startup process. All steel-shell melters 

operate on electricity, so emissions are inherently lower; this is a clean fuel as a heat source. 

Please note that the order of steps described for steel-shell melters may vary for each 

manufacturer.

For startup, the following work practices are observed:
Ms. Susan Fairchild

August 6, 2014

Page 5

1. In some facilities, temporary gas burners are used to slowly heat up the furnace to a 

specific temperature and operating state. In other facilities, the startup begins with

electrical power.

2. Good combustion practices are followed to minimize emissions associated with the 

products of combustion.

3. Plant cullet (glass previously produced at the plant) is fed into the furnace to be remelted; use of this type of cullet lowers melting temperature requirements and helps to 

reduce emissions.

4. Electric heating replaces the temporary gas startup heaters as the sole source of energy

for the furnace.

5. Emission control equipment is turned on at the appropriate time depending on the type of 

control equipment being used and is monitored to assure that it is operating within 

predetermined ranges that assure its proper operation. Typically, a batch cover must be 

established to get the inlet to the control device below the maximum safe operating 

temperature of the control device.

6. When required operating conditions are achieved, batch is fed into the furnace and a crust 

or cover is established over the molten glass.

For furnace shutdowns, the following work practices are observed:

1. The introduction of glass raw material (batch) into the furnace is halted.

2. The input energy into the furnace is reduced to the level required to maintain the glass in 

a molten state to allow removal of as much of the glass as possible from the furnace.

3. Emission control devices are taken offline when operating conditions permit or are 

required to preserve the control device, which may be before or after the energy is 

discontinued and the unit is drained, depending on design.

4. Energy to the furnace is discontinued and the furnace is allowed to cool.

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. 57) – EPA believes that there may be 

variations in emissions from fiber glass plants during startup and shutdown. If 

variations occur, are the variations attributable to furnace type? What other 

factors might explain variations?”

NAIMA agrees that emissions of some pollutants likely are higher during the startup period than 

at normal steady state operations, and emissions of other pollutants likely are lower. NAIMA 

also agrees that emissions from fiber glass plants during startup and shutdown vary from plant to 

plant just as they do during normal steady state operation and that although some of those 

variations are attributable to the different furnaces used in the various plants that there are other 
Ms. Susan Fairchild

August 6, 2014

Page 6

reasons for those differences in emissions. See NAIMA’s comments on behalf of the Wool Fiber 

Glass Manufacturers regarding EPA’s Proposed Rule National Emissions Standards for 

Hazardous Air Pollutants: Mineral Wool Production and Wool Fiberglass Manufacturing, dated 

February 3, 2012, pages 57-58.

Other factors that likely contribute to those differences in emissions are:

 Differences in the proprietary design and construction of the furnace.

 Differences and variations in the batch materials and the sources of those batch materials.

 Differences in the emission control equipment used at the plants and variations in operating 

parameters.

 Differences in how the furnaces are operated.

QUESTION 3

Question: “How are emissions monitored during startup and shutdown? What issues might 

be detected during monitoring? Does the monitoring inform you about specific 

actions that need to be taken to modify the emissions?”

For all furnace types, there is no direct, formal monitoring of actual emissions from the furnace 

during all phases of startup and shutdown. Emissions testing using prescribed testing protocols 

cannot be conducted during startup and shutdown because of the unique operating conditions 

present during those times. In fact, EPA standard reference methods only allow for performance 

testing to be conducted during steady state operations, which do not exist during startup and 

shutdown. During periods of startup and shutdown, when control equipment is operational, the 

control equipment is monitored to determine that it is operating normally. At times when control 

equipment is not operating or cannot be relied upon because of the nuances of the startup and 

shutdown process, the manufacturers have come to rely upon operating procedures and work 

practices that have been developed over the years that appear to produce fewer emissions than 

others that have been tried. The items identified in response to Question 1 are representative of 

those work practices and procedures that experience has identified as things that reduce 

emissions during startup and shutdown.

Specific examples of monitoring include:

 Fuel/oxygen ratios are monitored to ensure good combustion practices are followed.

 Normal operating parameters of both the furnace and control device are monitored.

 Baghouse inlet temperature would be monitored to determine the point at which to start the 

fan, as would differential pressure across the baghouse.

 Generally, the same procedure in reverse would be followed on shutdown.

 Monitoring conducted pursuant to specific permit requirements. 
Ms. Susan Fairchild

August 6, 2014

Page 7

QUESTION 4

Question: “What measures (work practices or housekeeping measures) are undertaken by 

companies to make certain that emissions levels are maintained throughout the 

startup and shutdown period?”

In addition to the answers set forth above for each furnace type in Question 1, these additional 

work practices are also relevant:

 Follow startup and shutdown checklists specific to the particular furnace.

 Cleaning and maintaining of all emissions control equipment according to manufacturers’ 

recommendations.

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

equipment.

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

vendors by company employees.

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